LINER-PROVIDED CAP AND CAP-PROVIDED THREADED CONTAINER
Provided is a liner-provided cap for sealing the mouthpiece of a threaded container, which includes the cap shell 4 consisting of the top plate 2 and the tubular peripheral wall section 3 that hangs from the peripheral edge of the top plate 2, and the synthetic resin liner 5 provided on the inner surface of the top plate 2. The liner 5 includes the disk-shaped rigid sheet 5a disposed in contact with the inner surface of the top plate 2, and the soft layer 5b that is laminated to the rigid sheet 5a and is more flexible than the rigid sheet 5a. The soft layer 5b is concentric with the rigid sheet 5a and is formed in an annular or disk shape with a diameter smaller than that of the rigid sheet 5a so that the soft layer 5b can be brought into contact with at least the mouthpiece.
1. Field of the Invention
The present invention relates to a liner-provided cap and a cap-provided threaded container excellent in openability, sealing property, and suitability for liner setting.
The present invention also relates to a liner-provided cap and a cap-provided threaded container excellent in openability, sealing property, and gas-barrier property.
2. Description of the Related Art
In general, a cap (container lid) used for such as a glass bottle, a PET bottle, and an aluminum bottle provided with a synthetic resin liner is in a wide use. In the case of a metallic cap, there are various methods for producing the same. Examples of such methods include a disk insertion method in which both sides of a sheet such as aluminum thin sheet, tin thin sheet, and chromium plating thin sheet (TFS: tin-free steel) are repeatedly coated several times, punched out, and molded into a cap shell (cap shell body) to thereby insert a previously molded disk-like molded one (disk-like molded body) thereto; a disk insertion and adhesion method in which a disk-like molded body is heat-adhered in the center after the insertion of the disk-like molded body; a lining method in which a liner material such as vinyl chloride sol (PVC paste) is flowed into a cap shell for adhesion while subjecting to a gelatinization by heating at the same time; and an in-shell mold method in which a molten resin is put into a cap shell, heat-adhered, and embossed.
These methods are disadvantageous in that although manufacturing facilities for use in the disk insertion method or the disk insertion adhesion method are relatively inexpensive, a produced cap often exhibits inferior oxygen barrier property because of a, single layered liner. In addition, since a disk-like liner is punched out from the sheet, the punched waste of the liner is generated, resulting in unfavorable poor yield rates from the material. These liners can be recycled, however, when the liners already used are mixed and used for food application, a part of the recycled liners contacts the surface in contact with a liquid. Hence, from the viewpoint of sanitation, a punched waste is typically not reused for the same liner production. In addition, since the liner has a sheet configuration, the central portion of the layer, where it is not involved in sealing property, cannot be reduced, resulting in a weight increase of the liner.
On the other hand, in the lining method, although a liner material can be placed at the seal portion only, sanitation may be poor because the main material is vinyl chloride sol (PVC paste). The in-shell mold method has a relatively high efficiency for the amount of the liner material used, and is suitable for mass production, whereas it is not appropriate for low-volume production. Since the liner material is extruded from an extruder and cut in a semi-molten state, a material having poor extrusion moldability cannot be used, whereby the available material is limited. Furthermore, since an opening torque value is generally high, a lubricant tends to be often used.
To deal with these problems, Patent Documents 1 to 4 conventionally disclose a liner material having a multilayer structure. In the liner material, a high hardness resin is attached to a low hardness resin, so that advantageous punching property and cap insertability are obtained due to the high hardness resin. In addition, shape retainability after the cap is sealed and low opening torque when the cap is opened are provided, and sealing property is provided due to the low hardness resin. In other words, the liner material can provide advantageous sealing property and openability. For example, Patent Document 1 discloses a liner made of PP (polypropylene) resin and elastomer laminated at a constant rate.
Patent Document 5 discloses a packing in which a synthetic resin liner is attached to an aluminum-punched sheet that has been subjected to drawing. However, this method includes many steps such as applying a liner adhesion coating material onto an aluminum sheet; punching out the resulting sheet; subjecting to a drawing process; and heat-adhering the liner material (heat-adhesion of liner and shell), which increase cost and is thereby not practical. Also, compared to resin (such as PP resin), recycling of the punched waste of an aluminum sheet is not easy.
The liner material is used for many of metallic caps or plastic caps used for glass bottles, aluminum bottle cans, polyethylene terephthalate (PET) bottles, or the like. In particular, a liner is essential for the metallic cap, synthetic resin is widely used for the liner. For the metallic cap, the in-shell mold method in which both sides of a sheet such as aluminum thin sheet, tin thin sheet, and chromium plating thin sheet (TFS) are repeatedly coated several times, punched out, and molded into a cap shell to put a molten resin into a cap shell for embossing is common.
In addition to above, there are other methods for inserting an expanded PE (polyethylene) disk, and for heat-molding a cast vinyl chloride sol (PVC paste), which are disadvantageous in cost and sanitation, and are thereby limited in use. A method for molding a plastic shell has substantially the same problem. The in-shell mold method has a high efficiency for the amount of the liner used and can produce a liner having an advantageous sealing property. However, since the liner material is completely adhered to a cap shell, the friction force between the mouth and the cap shell of the container when the cap is opened is relatively large. Consequently, a torque required for opening is high, which occasionally causes difficulty in opening.
For this reason, a lubricant mainly made of fatty acid amide is added to most of the liner material. It is designed such that the lubricant is bled out onto the surface of the liner to thereby reduce the friction between the liner and the mouth of the container so that the cap can be opened with a low torque. However, it is difficult to control the amount of bleeding of the lubricant. When the amount of bleeding is too small, the lubricant cannot work sufficiently, resulting in high torque required for opening. When the amount of bleeding is too much, the lubricant may fall into the content, which is likely to be regarded as a foreign substance.
To eliminate these problems, a two-layer liner to be described below has been proposed. For the two-layer liner, a high hardness resin and a soft resin are laminated to each other, whereby sealing property is maintained by the soft resin layer, and an appropriate torque when the cap is opened is produced by the friction between the hard resin layer and the cap shell. Although the two-layer sheet liner exhibits advantageous sealing property, it does not have sufficient sealing property with respect to the content required for a long-term storage. This is mainly for the sake that gas such as oxygen passes out through the liner to contribute the degradation of the content.
Although the harder plastic typically exhibits better gas-barrier property, some degree of flexibility is required as a liner material in order to maintain sealing property between the container and the cap shell. For this reason, among the common plastics, a material having inferior gas-barrier property is used as the liner material. Undesirably, a material having particularly poor gas-barrier property must be used for a cap liner for high temperature filling goods or a liner for retort treatment. Since a material having flexibility must be used for the liner material, a method or a material for improving gas-barrier property of a liner material has conventionally been proposed.
For example, the techniques described in Patent Documents 2, and 6 to 12 have conventionally been proposed.
However, the techniques described in these Patent Documents have several disadvantages for the liner material. For example, the liner material described in Patent Document 6 has a multilayer structure composed of a barrier layer and a soft layer such that a thin film-deposited polyethylene terephthalate film such as silicon oxide is in contact with the bottle mouth. With this arrangement, the irregularities of the bottle mouth cannot be covered sufficiently because of the hardness of the deposited layer, whereby sufficient sealing property cannot be obtained.
For a synthetic resin cap provided with a metatarsal packing, Patent Document 7 discloses a method for inserting, adhering, depositing, applying a barrier material into a cap shell or a metatarsal packing. This method can be employed for production but results in high cost. For example, a manufacturing apparatus of a large-scale is required for insert molding, and the production speed is significantly reduced, which leads to an expensive cap. Likewise, adhesion, application, and deposition are also costly. In addition, these cap liners cannot withstand retort treatment.
Patent Document 8 discloses a container lid having gas-barrier property and heat resistance. This technique discloses a cap in which an elastomer consisting of a butyl rubber, PP resin, and liquid paraffin, which have been crosslinked, is used for the liner material so as to be retortable. Hence, the smell of the crosslinking agent emanates from the liner, which is not suitable for food application. Also, because of poor slidability, such liner is not suitable for the liner of the cap being rotated and opened such as a ROPP (roll on pilfer proof) cap.
Furthermore, for the liner material consisting of a sliding layer and a sealing layer, Patent Document 9 discloses a method for applying a non-volatile liquid between the sliding layer and the cap shell to achieve complete adhesion between the cap shell and the liner to thereby prevent gas such as oxygen from being passed out therethrough. In this method, the liner is in intimate contact with the cap shell in a state where an internal pressure of nitrogen or carbon dioxide is applied to the container, resulting in advantageous sealing property. Further, the liner is also in contact with the cap shell through the nonvolatile liquid, and thereby rotates freely, whereby the cap can be opened with a low torque. However, when the container is at a normal pressure or a reduced pressure, the intimate contact fails between the cap shell and the liner, thereby introducing the problem of not acquiring the barrier effect of the nonvolatile liquid.
Also, a polyolefin liner mainly composed of polyethylene is used for the liner material for an aluminum cap for use in bottle cans, glass bottles, or PET bottles. Styrene elastomer is often used for the liner material required for heat resistance such as retort treatment. These liner materials are often molded by the in-shell mold method. Since these liner materials are molded by the in-shell mold method, they have a reduced material loss compared to a sheet liner, which leads to excellent cost efficiency. However, as described above, the liner is fully adhered to the cap shell, which has the disadvantage of high opening torque.
Even when styrene elastomer or olefinic elastomer liner material is in-shell molded into a cap shell made of synthetic resin such as PP resin, opening torque tends to be increased in a similar way. To overcome this problem, it is common to employ a method in which the frictional resistance between the container and the cap is reduced to thereby reduce an opening torque by adding a lubricant to a liner material to bleed out the lubricant onto the surface of the liner so as to obtain lubricity. In this method, it is difficult to control the amount of bleeding of the lubricant. When the amount of bleeding is too small, the opening torque becomes high as described above. When the amount of bleeding is too much, the lubricant that has bled out onto the surface of the liner may fall into the content, which will be regarded as a foreign substance.
To eliminate these problems, the two-layer sheet liner disclosed in Patent Document 2 has been proposed for example. As in Patent Document 9, the liner is composed of a soft sealing layer and a hard sliding layer which are laminated to each other. The liner is designed such that the sliding layer and the cap's top surface are slid to each other when the cap is opened so as to provide low torque. The liner material exhibits advantageous sealing property and openability. However, the liner material has insufficient oxygen barrier property with respect to the content required for a long-term commodity cycle since the liner is not in intimate contact with the cap's top surface and thereby gas such as oxygen passed out through the liner causes the content to degrade.
PRIOR ART DOCUMENTS[Patent Document 1] Japanese Unexamined Patent Application Publication No. 2006-76575
[Patent Document 2] Japanese Unexamined Patent Application Publication No. 2007-119059
[Patent Document 3] Japanese Unexamined Patent Application Publication No. 2007-161331
[Patent Document 4] Japanese Unexamined Patent Application Publication No. 2007-161332
[Patent Document 5] Japanese Unexamined Patent Application Publication No. 2003-321040
[Patent Document 6] Japanese Unexamined Patent Application Publication No. 2000-344269
[Patent Document 7] Japanese Unexamined Patent Application Publication No. 2001-192057
[Patent Document 8] Japanese Unexamined Patent Application Publication No. 2002-160759
[Patent Document 9] Japanese Unexamined Patent Application Publication No. 2008-50031
[Patent Document 10] Japanese Unexamined Patent Application Publication No. 2003-12013
[Patent Document 11] Japanese Unexamined Patent Application Publication No. 2008-174249
[Patent Document 12] Japanese Unexamined Patent Application Publication No. 2004-1862
SUMMARY OF THE INVENTION Problems to be Solved by the InventionThe following problems still remain in the conventional techniques described above.
Among the methods of manufacturing a liner for a cap, a molding method in which a molten liner material is placed in a shell for embossing by an extruder is in common practice. However, an adhesion coating material applied to the inner surface of the shell and a liner material are adhered to each other over their entire surface. At this time, if the liner material is not adhered to the inner surface of the shell, a liner resin is adhered to an embossed mold, and the liner material does not remain in the shell, so that the liner cannot be formed in the cap. Hence, in the case of a metallic cap, a coating material for adhering to the liner material is applied. When the cap is capped to the container in a state where the liner material is adhered over its entire surface, the liner is difficult to move, so that it may be difficult to fit the shape of the container, resulting in insufficient sealing property. Therefore, it is desirable that the liner material of the portion in contact with the container mouth be flexible, in other words, non-adhesive.
Unfortunately, even in this case, the liner material slides between the container and the liner during opening since it is firmly adhered to the cap. In this case, since the contact between the container and the liner is strong, a large force (high opening torque) is required for opening the cap (slide between the liner and the container mouth). Hence, a lubricant is usually added to the liner material to interpose the lubricant onto the surface of the liner material to thereby reduce the opening torque. When the amount of lubricant added is too small, the lubricant does not provide sufficient lubricity. When the amount of lubricant added is too much, the lubricant that has been floated onto the surface of the liner may fall into the content, which will be regarded as a foreign substance. For this reason, the use of lubricant in appropriate amounts is required, however, it is difficult to determine the appropriate amount since it is affected by various conditions. Consequently, the opening torque becomes too high, or the lubricant floats on the content, or the both problems may occur simultaneously.
To overcome these problems, a liner material composed of a multilayer sheet as shown in the above Patent Document has been proposed. The multilayer sheet liner material is arranged such that a hard and lubricative sliding layer (rigid layer) is disposed on the side where the liner is in contact with the cap shell, and a sot sealing layer (soft layer) is disposed on the other side where the liner is in contact with the container mouth. The liner material is slid between the sliding layer and the cap shell during opening, whereby the cap can be opened with a low force. Since no or a small amount of lubricant is required for use at the portion in contact with the container mouth, the disadvantage of the float of the lubricant does not occur.
However, in order to prevent the multilayer sheet liner from falling off after being inserted into the cap shell or when the cap is opened, the multilayer sheet liner is set to a size as close to the inner diameter of the cap shell as possible, and the soft sealing layer compressed during sealing overhangs to the side surface. Consequently, a overhung soft sealing layer may be in contact with the inside surface of the cap shell, resulting in undesirably high torque when the cap is opened. Even if the outer diameter of the liner is as small as possible, the liner is offset from the center of the cap shell during capping to cause a portion of the liner to contact the shell, whereby a phenomenon occurs in that the opening torque is undesirably increased.
In the case of a liner using an aluminum sheet as shown in Patent Document 5, the end of the liner is bent and then engaged with the cap shell, which requires bending and results in a disadvantageous increase in manufacturing cost. Furthermore, because the strength of an aluminum sheet is strong, drawing of the cap shoulder during capping is difficult. As a result, it is difficult to seal the side surface of the cap, and thereby the problems occur in that sufficient sealing property cannot be obtained.
The present invention has been made in view of the aforementioned circumstances, and an object of the present invention is to provide a liner-provided cap, a method for manufacturing the same, and a cap-provided threaded container excellent in openability, sealing property, and suitability for liner setting.
As described above, a metallic cap such as aluminum or tin is always provided with a liner to completely seal the space between the cap and the container mouth. A resin cap requiring high sealing property is also provided with a liner. Some degree of flexibility is required for these liner materials in order to completely seal fine irregularities formed on the mouth of the container (glass bottle, PET bottle, bottle can, or the like). When the flexibility is required for a plastic or elastomer, the plastic or elastomer with greater flexibility (soft) generally tends to exhibit poor gas-barrier property and reduce heat resistance.
The reduction in gas-barrier property promotes oxidation degradation of the content, whereby a long shelf life cannot be taken. In addition, a liner which cannot withstand retort treatment may have limited application for use.
Moreover, a flexible liner material has poor sliding property. Hence, in a case where the cap is rotated and opened, the opening torque becomes high, which will be a major source of complaint. To overcome the problems, a lubricant is added to the liner material as described above, thus increasing its slidability and reducing its opening torque.
However, in this case, since the control of the lubricant fails, the use of the lubricant still leads to high opening torque or the lubricant may fall into the content because the amount thereof is too much, which will be the source of complaint. On the other hand, to overcome the problems, Patent Document 6 discloses a multilayer sheet liner material. This is designed such that the liner material is divided into a sliding layer and a sealing layer to allow them to join each other, a hard resin such as PP resin as the sliding layer is in contact with a cap shell, and a soft resin such as elastomer as the sealing layer is in contact with a bottle mouth so as to maintain sealing property.
In this case, since an opening can be achieved by the slide between the cap shell and the sliding layer of the liner, there is no need to add a lubricant into a liner material, which is free from the problem in terms of a lubricant for controlling an opening torque. However, in this method, the liner is not in intimate contact with the cap shell because the cap is slid between the cap shell and the liner. Consequently, gas such as oxygen is passed out from the cap shell and the liner through the liner top surface so as to degrade the content. Hence, such liner is not suitable for a long-term storage.
As one of the improvements; Patent Document 9 discloses a method for applying a non-volatile organic liquid between a cap shell and a liner. This method is characterized in that the liner is in intimate contact with the cap shell, and the cap is slid between the cap shell and the liner when being opened, whereby a stable opening torque value can be obtained. In this method, good results can be obtained when a content filled into a container such as glass bottle or PET bottle is in an internal pressure state such that the liner is constantly pushed to the cap shell from the inside. However, as described above, when the filled container is at a normal pressure or a reduced pressure, a gap will occur between the shell and the liner, which promotes the degradation of the content due to gas permeation from the top surface.
Patent Document 10 discloses a liner having a structure wherein a test material having low oxygen permeability such as nylon as an oxygen barrier sheet is disposed between a packing material and a cap shell. With this method, a barrier material such as nylon having poor slidability is in direct contact with the cap shell, resulting in high opening torque. If a barrier layer is uncoated as described above, sufficient performance cannot be obtained due to degradation of gas-barrier property and physical property caused by the contact of a barrier material with moisture.
Although the two-layer liner (including sheet mold liner) in which a sliding layer and a sealing layer are adhered to each other as disclosed in Patent Document 2 exhibits excellent openability, it is not sufficient as a cap's liner material requiring for high gas-barrier property as described above. The cause that can be considered may lie in a structure such that the cap is slid between the sheet mold liner and the cap shell when being opened. Such a structure causes gas such as oxygen to permeate between the cap shell and the liner to further permeate the liner material, therefore leading to the degradation of the content.
Hence, a sliding layer having a certain gas-barrier property has been proposed. For example, Patent Document 11 discloses a container lid having a structure consisting of an air barrier material that serves as an oxygen barrier sheet such as EVOH resin (ethylene-vinyl alcohol copolymer resin) or nylon; and an elastic resin material, i.e., packing material such as polyethylene. However, a barrier material such as EVOH resin or nylon absorbs moisture, resulting in a reduction of gas-barrier property. Since most of these air barrier materials exhibit poor slidability, it is difficult to control sliding when these are used for the sliding layer of the two-layer sheet. Therefore, it is difficult to set an opening torque within a certain desired value.
In addition, these air barrier materials must be completely adhered to a packing material. However, sufficient adhesive force cannot generally be obtained between an air barrier material such as EVOH resin, nylon, or the like and polyethylene or elastomer used as a packing material (sealing layer). Thus, a conventional method in which an air barrier material is formed of a barrier material and a packing material is formed of polyethylene has numerous difficulties in producibility, cost, and practicability in practical application.
Patent Document 12 discloses a method for improving gas-barrier property by blending a certain amount of a barrier resin such as EVOH resin with an olefin resin of the inside plug of a resin cap. The method is effective for a container with high dimensional accuracy of the bottle mouth such as PET bottle to some degree, but is not sufficiently effective for a container with insufficient accuracy of the bottle mouth such as glass bottle or resealed can.
For an inside plug type liner, the accuracy of the inner diameter of the bottle mouth is critical. However, the accuracy of the inside plug for a glass bottle, resealed can, and the like cannot be made as high as that of a PET bottle for manufacturing reasons. On the other hand, a gas barrier resin such as EVOH resin has high hardness. When such resin is blended with resin such as polyethylene, it becomes harder. Consequently, in spite of an enhancement of its own gas-barrier property, sealing property (to seal fine irregularities) as a packing is significantly reduced, which is undesirable for use as a packing material for a normal container.
The present invention has been made in view of the aforementioned circumstances, and an object of the present invention is to provide a liner-provided cap and a cap-provided threaded container which are excellent in openability, sealing property, and gas-barrier property as well as excellent in producibility and practicability.
Means for Solving the ProblemsThe present invention employs the following arrangements in order to solve the above problems. In other words, the liner-provided cap of the present invention is a liner-provided cap for sealing the mouth of a threaded container, including a cap body consisting of a top plate and a tubular peripheral wall section that hangs from the peripheral edge of the top plate, and a synthetic resin liner provided on the inner surface of the top plate, wherein the liner includes a disk-shaped rigid sheet disposed in contact with the inner surface of the top plate, and a soft layer that is laminated to the rigid sheet is more flexible than the rigid sheet, and wherein the soft layer is concentric with the rigid sheet, and is formed in an annular or disk shape with a diameter smaller than that of the rigid sheet so that the soft layer can be brought into contact with at least the mouth.
In the liner-provided cap, the soft layer is concentric with the rigid sheet and is formed in an annular or disk shape with a diameter smaller than that of the rigid sheet so that the soft layer can be brought into contact with at least the mouth. Hence, even if the soft layer deforms due to pressure during capping, an excellent openability can be obtained because the end of the soft layer is set apart from the inside surface of the cap shell and the liner stopping protrusion and thus an opening torque value does not increase by the contact of the end with them. Since the synthetic resin liner has less rigidity compared with a conventional liner using an aluminum sheet, a plane-shaped synthetic resin liner can still be readily engaged with the cap shell, and the drawing of a cap shoulder can also be readily performed. In the present invention, the liner end is formed of a rigid sheet only and has less rigidity, the liner can be readily engaged with a cap shell compared with the case where the entire liner has the two-layer structure of the rigid sheet and the soft layer. Furthermore, since the soft layer portion is less than the rigid sheet, the total weight of the liner can be reduced compared with the case where the entire liner has the two-layer structure of the rigid sheet and the soft layer.
Also, since the liner has a multilayer structure composed of the soft layer and the rigid sheet, high sealing property can be obtained by the soft layer, and excellent openability and drop impact resistance can be obtained by the free rotation of the liner with respect to the cap body with the help of the rigid sheet having high lubricity and low frictional resistance compared to that of the soft layer, whereby there is no need to add a large volume of lubricant.
The liner-provided cap of the present invention is characterized in that the rigid sheet is formed of polypropylene resin and the soft layer is formed of styrene elastomer. In other words, since the rigid sheet is formed of polypropylene resin and the soft layer is formed of styrene elastomer, the liner-provided cap has particularly excellent sealing property, heat resistance, and adhesive property to the rigid sheet and the soft layer.
The liner-provided cap of the present invention is characterized in that t×f is set to 150 or more when the thickness of the rigid sheet is set as t(mm) and the flexural modulus is set as f(MPa). In other words, by setting t×f to 150 or more when the thickness of the rigid sheet is set as t(mm) and the flexural modulus is set as f(MPa), such setting can secure the liner-provided cap against extraction from the liner stopping protrusion due to the significant flexural capacity of the rigid sheet when the adhesion of the soft layer to a mold punch or the mouth of a container causes the soft layer to be pulled and thereby the rigid sheet abuts against the liner stopping protrusion.
The liner-provided cap of the present invention is characterized in that the tubular peripheral wall section includes a liner stopping protrusion protruding toward the interior thereof and supporting the liner from the underside thereof, and when the inner diameter of the tubular peripheral wall section is set as D0 and the protruded length of the liner stopping protrusion is set as w, the outer diameter D1 of the rigid sheet is set in a range of D0≧D1>D0−2w, and when the central diameter of the mouth is set as R1, the outer diameter d1 of the soft layer is set in a range of D0−2w>d1>R1. In other words, in the liner-provided cap, since the outer diameter of the rigid sheet and the outer diameter of the soft layer are set in the range described above, the liner can be prevented from falling off by the engagement of the rigid sheet to the liner stopping protrusion. In addition, since the soft layer is not in contact with the liner stopping protrusion while being in contact with the mouth, an increase in opening torque can be prevented while maintaining high sealing property.
The liner-provided cap of the present invention is characterized in that a non-volatile organic liquid is applied between the top plate and the liner. In other words, in the liner-provided cap, a non-volatile organic liquid is applied between the top plate and the liner, whereby the adhesion and gas-barrier property of liner can be improved.
Furthermore, the liner-provided cap of the present invention is characterized in that when the area of the liner is set as S(cm2) and the coating amount of the non-volatile organic liquid is set as Y(mg), the coating amount of the non-volatile organic liquid is represented as the relationship of Y=αS, where α falls within a range of 0.01 to 1.00. In other words, in the liner-provided cap, the coating amount of the non-volatile organic liquid is set in the range described above, an appropriate coating amount without bleeding out corresponding to the area of the liner and excellent gas-barrier property can be obtained.
The liner-provided cap of the present invention is characterized in that the non-volatile organic liquid is silicone oil or glycerin. In other words, in the liner-provided cap, the non-volatile organic liquid is silicone oil or glycerin, which significantly improves gas-barrier property. The selection of glycerin as the non-volatile organic liquid can readily adjust the kinematic viscosity of the non-volatile organic liquid by the addition of water.
The threaded container of the present invention is characterized in that the threaded container includes a liner-provided cap and the liner-provided cap is the liner-provided cap of the present invention.
In other words, since a soft layer with a diameter smaller than that of a rigid sheet is formed on the rigid sheet, these liner-provided cap and the cap-provided threaded container exhibit excellent openability and sealing property as described above.
The present invention employs the following arrangements in order to solve the above problems. In other words, the liner-provided cap of the present invention is a liner-provided cap for sealing a mouth of a threaded container body and is characterized in that the liner-provided cap includes a cap body consisting of a top plate and a tubular peripheral wall section that hangs from the peripheral edge of the top plate; and a liner provided on the inner surface of the top plate, wherein the liner includes a sliding layer disposed in contact with the inner surface of the top plate; a sealing layer that is laminated to the sliding layer and is more flexible than the sliding layer; an intermediate layer disposed between the sliding layer and the sealing layer and having gas-barrier property; and an adhesive layer disposed between the intermediate layer and the sliding layer or the sealing layer to adhere to each other.
Since the liner-provided cap includes the intermediate layer having gas-barrier property and the adhesive layer disposed between the intermediate layer and the sliding layer or the sealing layer to adhere to each other, a good adhesive property can be obtained by bringing the intermediate layer into contact with the sealing layer even when a sufficient adhesive strength cannot be obtained by the direct adhesion between the intermediate layer and the sealing layer for example.
In addition, a high hardness resin is disposed as the sliding layer that contacts with the inner surface of the cap shell, an elastic body that is completely in close contact with the sliding layer is disposed as the sealing layer (mainly, elastomer), and the intermediate layer that serves as the gas barrier layer is interposed between the sliding layer and the sealing layer, whereby the liner having excellent gas-barrier property can be obtained. In other words, the liner is a multilayer that is sequentially composed of the sliding layer, the intermediate layer, the adhesive layer, and the sealing layer, and the intermediate layer has gas-barrier property, whereby liner material excellent in sealing property, gas-barrier property, openability, and retort resistance can be provided. As long as the intermediate layer is disposed between the sealing layer and the sliding layer and is adhered via the adhesive layer, the sliding layer may be multilayered and the intermediate layer may be inserted therein via the adhesive layer.
The liner-provided cap of the present invention is characterized in that the intermediate layer is formed of a metal foil. In other words, in the liner-provided cap, the intermediate layer is formed of a metal foil such as an aluminum foil, whereby very high gas-barrier property can be obtained.
The liner-provided cap of the present invention is characterized in that the intermediate layer is formed of a gas barrier resin. In other words, in the liner-provided cap, since the intermediate layer is formed of a gas barrier resin such as EVOH resin, the intermediate layer can be formed by extrusion, resulting in low cost and excellent producibility.
The liner-provided cap of the present invention is characterized in that the intermediate layer is a material of which an adhesive strength to the sealing layer is lower than that to the sliding layer, and the adhesive layer is formed of the same material as that of the sliding layer. In other words, in the liner-provided cap, the adhesive layer is formed of the same material as that of the sliding layer having a good adhesive property to the intermediate layer, so that it is easy to manufacture a laminated liner and the cost can be reduced.
The liner-provided cap of the present invention is characterized in that the sealing layer is molded. In other words, in the liner-provided cap, since the sealing layer is molded, various shapes of the sealing layer corresponding to the mouth shape of the threaded container body can be easily obtained.
The liner-provided cap of the present invention is characterized in that the sealing layer is formed of a styrene elastomer. In other words, in the liner-provided cap, since the sealing layer is formed of a styrene elastomer which is a blend of a low MFR SEBS (styrene-ethylene-butylene-styrene), PP resin, and liquid paraffin, a retortable liner can be obtained.
The cap-provided threaded container of the present invention is a threaded container including a cap and is characterized in that the cap is the above-described liner-provided cap of the present invention. In other words, in the cap-provided threaded container, the cap is the above-described liner-provided cap of the present invention, thereby having excellent openability and sealing property as well as excellent gas-barrier property and producibility.
According to the present invention, the following effects are provided.
In other words, for the liner-provided cap and the cap-provided threaded container according to the present invention, the soft layer is concentric with the rigid sheet and is formed in an annular or disk shape with a diameter smaller than that of the rigid sheet so that the soft layer can be brought into contact with at least the mouth. Hence, even if the soft layer is deformed during capping, the soft layer does not contact with the inside surface of the cap shell, whereby excellent openability can be obtained while maintaining low opening torque. The liner can be readily engaged with the cap shell, and high sealing property and suitability for liner setting can be obtained.
For the liner-provided cap and the cap-provided threaded container according to the present invention, an adhesive layer disposed between the intermediate layer having gas-barrier property and the sliding layer or the sealing layer to adhere to each other is provided, whereby a good adhesive property of the intermediate layer via the adhesive layer can be obtained, and excellent producibility can be obtained by openability due to the sliding layer, sealing property due to the sealing layer, improved gas-barrier property due to the intermediate layer, and high adhesive property due to the adhesive layer.
Hereinafter, an embodiment of the liner-provided cap and the cap-provided threaded container according to the present invention will be described with reference to
As shown in
The cap shell 4 is machined from a sheet made of, for example, aluminum or aluminum alloy, and the sheet used is a coated sheet of which the inner and outer surfaces are coated (inner surface: size varnish+top coating, outer surface: size coating+top coating (gloss varnish)). Various lubricant-added type solution is used for the top coating of the inner and outer surfaces as required. For example, a coating material made of a resin such as epoxy phenol to which polyolefin wax is added as lubricant is baking-applied onto the inner surface of the top plate 2.
The liner 5 has a multilayer structure including the disk-shaped rigid sheet 5a disposed in contact with the inner surface of the top plate 2, and the soft layer 5b that is laminated to the rigid sheet 5a by a mold and is more flexible than the rigid sheet soft layer 5a so as to provide the sealing effect to the cap shell 4.
For a material of the rigid sheet 5a, synthetic resin, PP (polypropylene) resin, HDPE (high density polyethylene), PA (polyamide, generally known as nylon), PC (polycarbonate), PET (polyethylene terephthalate), PBT (polybutylene terephthalate), PAN (polyacrylonitrile), PVC (polyvinyl chloride), and the like may be employed.
For a material of the soft layer 5b, TPS (styrene elastomer, TPO (olefin elastomer), TPU (urethane elastomer), TPEA (polyamide elastomer), TPEE (polyester elastomer), PVC-TPE (polyvinyl chloride-based elastomer), and the like may be employed.
Examples of the material combination of the rigid sheet 5a and the soft layer 5b adhereable in an in-shell mold include as follows.
In particular, a preferable material combination is such that the rigid sheet 5a is formed of polypropylene resin and the soft layer 5b is formed of styrene elastomer. In other words, a PP (polypropylene) resin is best suited for the material of the rigid sheet 5a which serves as the sliding layer because of inexpensive cost and excellent heat resistance. Also, a TPS (styrene elastomer) is best suited for the material of the soft layer 5b because of excellent adhesive property to the PP resin and advantageous retort-resistant performance.
The rigid sheet 5a is set such that t×f is 150 or more when the thickness of the rigid sheet 5a is set as t(mm) and the flexural modulus is set as f(MPa). The thickness of the rigid sheet 5a is set in a range of from 0.1 mm to 1.0 mm and more preferably from 0.2 mm to 0.8 mm.
Furthermore, the soft layer 5b is set such that the thickness of the portion in contact with the mouthpiece 7 of the bottle 6 is thicker than those of the other portions. In the soft layer 5b, the thickness of the portion in contact with the mouthpiece 7 is set in a range of from 0.1 mm to 0.9 mm.
Also, the soft layer 5b is concentric with the rigid sheet 5a and is formed in an annular or disk shape with a diameter smaller than that of the rigid sheet 5a so as to be brought into contact with at least the mouthpiece 7. The soft layer 5b may be formed in an annular shape with a diameter smaller than that of the rigid sheet 5a.
The tubular peripheral wall section 3 includes a knurl 8, a liner stopping protrusion 9, a perforated line 10, a bead 11, and a skirt 12. The liner stopping protrusion 9 is a triangular cross-section or semicircular shape which is concave toward the inside of the tubular peripheral wall section 3, and a plurality of the liner stopping protrusions 9 each having an inward protrusion are disposed and spaced circumferentially. As described above, the liner stopping protrusion 9 functions to support the liner 5 from the underside thereof and substantially serves as a flushing port. The liner stopping protrusion 9 may be formed inward in a strip shape in the peripheral direction.
A plurality of the liner stopping protrusions 9 are formed substantially at evenly-spaced intervals, and their positions are set in a range from the top surface to the thickness of the rigid sheet 5a or additional 1.0 mm.
When the inner diameter of the tubular peripheral wall section 3 is set as D0 and the projected length (pressed amount) of the liner stopping protrusion 9 is set as w, the outer diameter D1 of the rigid sheet 5a is set in a range of D0≧D1>D0−2w. When the central diameter of the mouthpiece is set as R1, the outer diameter d1 of the soft layer 5b is set in a range of D0−2w>d1>R1.
A non-volatile organic liquid is applied between the top plate 2 and the liner 5. The preferred non-volatile organic liquid is silicone oil or glycerin.
When the area of the liner 5 is set as S(cm2) and the coating amount of the non-volatile organic liquid is set as Y(mg), the coating amount of the non-volatile organic liquid is represented as the relationship of Y=αS, where α falls within a range of 0.01 to 1.00.
The cap 1 is placed on a bottle body 13 such as a glass bottle, a resin bottle such as PET bottle, and a bottle so-called bottle can molded from a metal such as aluminum alloy, and is subjected to a capping treatment so as to be seamed and attached to the mouthpiece 7. Such arrangement is referred to as cap-provided threaded container, for example, cap-provided bottle (hereinafter referred to simply as “bottle”) 6.
The capping treatment process is carried out using a capping device consisting of a pressure block, a thread roller, a skirt roller, and the like.
In other words, the capping treatment is performed as follows: the top plate 2 of the cap 1 placed on the mouthpiece 7 is pushed in the direction of the bottom of the bottle using a pressure block and subjected to drawing by a pressure block with this condition to thereby form a stepped portion 14 at the shoulder of the cap 1. In addition, a thread portion 7a is formed by the thread roller with this condition to wind up the skirt 12 to the turnip portion 7b of the mouthpiece 7 by a skirt roller.
In this manner, the cap 1 is wound onto the mouthpiece 7, whereby the liner 5 that is the inner surface of the top plate 2 of the cap 1 is pressed upon the mouthpiece 7. As a result, the content of the bottle 6 is sealed. The filling of the content is, of course, performed immediately before the cap 1 is placed on the bottle 6.
On the other hand, when the bottle 6 is opened, the cap 1 is unscrewed to cut along the perforated line 10, whereby the cap 1 is removed from the mouthpiece 7. Consequently, the mouthpiece 7 is opened so as to remove the content.
Then, the cap 1 that has been removed is reinserted into the mouthpiece 7, so that the bottom 6 can be closed again.
The cap 1 may be formed of a synthetic resin. In such a case, the cap 1 is configured such that a liner is inserted into a cap shell mainly made of a synthetic resin material such as polypropylene or polyethylene which has been molded by injection molding or compression molding. For a cap shell made of a synthetic resin, a thread portion, knurl, and PP band (pilfer-proof band) are often formed during molding. The cap 1 may be perforated in a post processing.
In the case of a synthetic resin cap, a general method for plugging is that the cap 1 is seamed to the mouthpiece 7 while being rotated after the cap 1 is placed on the mouthpiece 7. At this time, the PP band (pilfer-proof band) is engaged with the turnip (an outwardly projecting annular beed) portion 7b of the mouthpiece 7. By unscrewing the cap 1 in the opposite direction to the direction when the cap 1 is plugged, the cap 1 is opened along the screw of the mouthpiece 7. Since the PP band (pilfer-proof band) is attached to the turnip portion 7b of the mouthpiece 7, it is cut from the perforated line, and thereby the opening of the bottle 6 is explicitly shown. The bottom 6 can also be re-closed again as required.
Next, a method for producing a liner-provided cap 1 of the present embodiment will be described in the case of a metallic cap with reference to
For example, to produce an aluminum cap shell 4 for a 38 PP cap (pilfer-proof cap), a coating material is applied to the inner and outer surfaces of an aluminum sheet 21 with a thickness of 0.25 mm as shown in
Next, a method for producing the liner 5 will be described with reference to
Conventionally, when a liner material is produced, for example, a sheet is formed by an extruder, punched into a disk-like shape, and put in a mold so as to produce an insert-molded elastomer using an injection molding machine.
Alternatively, a method for molding a rigid layer and an elastomer layer alternately using a two-color molding machine and laminating them is used. It is common to insert a liner molded by the method into a cap shell by aligning with a hopper.
When a cap is produced by the method, the production cost of a liner is increased. In addition, a special mold and a special producing machine (such as two-color molding machine) are required, resulting in a significant slower production speed. Furthermore, an apparatus for adjusting the two faces of a molded liner for alignment is required.
In contrast, the production method of the present embodiment exhibits excellent producibility and cost efficiency as follows. In the production method of the present embodiment, a PP single layer sheet 27 that serves as the rigid sheet 5a is firstly extruded from the extruder 25 provided with the T die 24 as shown in
The liner stopping protrusion 9 is formed into the cap shell 4, so that the disk-like rigid sheet 5a is less likely to be pulled out once it is inserted. The thickness of the rigid sheet 5a is set in a range of 0.1 to 1.0 mm and preferably in a range of 0.2 to 0.8 mm. When the thickness is less than 0.1 mm, the rigid sheet 5a exhibits insufficient properties. A process of inserting the disk into the cap shell 4 may be performed before a slit (knurl 8) or a hook (liner stopping protrusion 9) is formed onto the cap shell 4. In this case, there is no possibility that a disk is scratched by a hook or defective insertion occurs.
A certain amount of soft resin such as molten elastomer that has been extruded from the extruder 25 at the next in-shell mold process is put into the cap shell 4 to which the rigid sheet 5a is inserted so as to form a certain liner-shaped soft layer 5b by using an immediately-cooled die. As described above, the shape of the soft layer 5b has concentric circles with a diameter smaller than the outer diameter of the rigid sheet 5a. In the case of molding the resin, complete adhesion of the rigid sheet 5a and the soft layer 5b made of elastomer can be achieved by means of material selection. When the adhesion strength is low, the surface of the sheet may be subjected to surface treatment such as corona discharge treatment, glow discharge treatment, plasma treatment, anchor coat treatment, frame treatment, adhesive application, or the like after the sheet is molded. In this case, a surface treatment is only applied to a surface to be adhered to such elastomer.
When the thickness of the rigid sheet 5a is less than 0.1 mm, the resin of the soft layer 5b is not detached from the mold punch after the rigid sheet 5a is bonded with the soft layer 5b made of an in-shell molded soft resin, and thereby a phenomenon occurs in that the resin of the soft layer 5b is pulled out from the cap shell 4 together with the rigid sheet 5a. Also, the thickness and hardness of the rigid sheet 5a are important. When the thickness of the rigid sheet 5a is set as t and its flexural modulus is set as f, the value of t×f is preferably 150 or more. If the value of t×f is less than 150, the following phenomenon occurs. That is, when a molten soft material is placed onto the rigid sheet 5a and stamped by a mold punch, the soft member of the soft layer 5b is attached to the punch, whereby the soft member may be lifted up from the cap shell 4 together with the rigid sheet 5a. In addition, the soft member may be left in the mouthpiece 7 or dropped off from the cap shell 4 when the cap is opened.
If the thickness of the rigid sheet 5a is greater than 1.0 mm, it does not serve as a liner for capping. In general, the punched waste 28 of the rigid sheet 5a is immediately comminuted to chips by a chopper for use as a recycled material, so that the punched waste 28 is recycled again as the rigid sheet 5a.
In the case of a resin cap shell, the cap shell is substantially the same of the metallic cap shell 4, and a female screw which engages with a male screw provided at the bottle mouth is provided beforehand at the inside of the cap shell. The resin cap shell is molded by injection molding or compression molding, and then subjected to perforated line process, vent hole process, or outer surface printing process as required. As in the aluminum cap described above, after insertion of the rigid sheet 5a, a molten soft liner material is supplied onto the rigid sheet 5a, and embossed by a cooled punch to thereby form the soft layer 5b, so that the cap of the present invention can be provided.
Since the liner 5 and the cap shell 4 are flexible in a rotational direction, the opening torque when the cap 1 begins to turn is only a resistance between the rigid sheet 5a of the liner 5 and the cap shell 4 when the cap 1 is opened from the bottle body 13. In this case, by contrast with the soft layer 5b in contact with the mouthpiece 7, the rigid sheet 5a has low frictional resistance, whereby an appropriate opening torque value with a smaller temperature dependence can be obtained.
For opening the cap 1 of the present embodiment, the cap 1 is firstly slid between the rigid sheet 5a which serves as the liner rigid layer and the cap shell 4. Thereafter, the cap shell 4 rotates without the rotation of the liner 5 and thereby the liner 5 is pulled up by the liner stopping protrusion 9. In this case, since a force that lifts the liner 5 from the mouthpiece 7 is obtained by the rotation of the cap shell 4, very low rotation torque is sufficient. In this case, a large volume of lubricant needs not be added to the soft layer 5b, a problem such as bleeding out of the lubricant from the liner 5 to thereby fall into the content is not generated.
In the case of a conventional liner composed of a multilayer sheet consisting of a hard member and a soft member, oxygen permeation from the liner top surface occurs in spite of high sealing property between the mouthpiece 7 and the liner, so that a sufficient oxygen barrier property as a cap may not be obtained. To enhance barrier property of the liner composed of a multilayer sheet, a resin having high barrier property is laminated between the hard member and the soft member because of low barrier property of the soft member. Such method results in a large-scale apparatus and is therefore not practical. In this case, a punched waste cannot be recycled.
In contrast, the present embodiment can provide a cap having enhanced gas-barrier property by laminating or depositing a barrier film or an inorganic film such as DLC (diamond-like hard carbon film) onto the rigid sheet 5a, punching the resulting sheet into a disk-like shape, inserting it into the cap shell 4, and molding the soft layer 5b composed of a soft member thereon. Alternatively, a material with barrier property such as nylon, PET, PAN, and EVOH may be used for the rigid sheet 5a.
A beverage filled into the bottle 6 is attached to the inner surface of the cap 1 when the bottle 6 is opened after being filled and capped. Consequently, a beverage attached to the inner surface of the cap 1 falls at the same time as opening, and the problem entailed the contamination of clothing thereby occurs. In the case of an in-shell molded type liner, measures are taken such that a certain shape such as groove or ridge extending from the center of the liner in a radial or parallel manner is formed to gather a beverage attached to the inner surface of the cap 1 in one place to prevent the beverage in a bulk mass from falling. However, in the case of a multilayer sheet liner, a flattened surface makes it difficult to provide various shapes on the liner surface. On the other hand, in the present embodiment, it is easy to impart a certain shape onto the liner surface when the soft layer 5b is molded.
In a conventional sheet liner, a punched sheet is directly inserted into a cap shell. In contrast, since the liner 5 of the present embodiment has a relatively thin thickness compared with the conventional sheet liner, a nonvolatile liquid (preferably silicone oil or glycerin) is applied onto the inner surface of the cap shell 4 before a sheet is punched and inserted, whereby the adherability of the liner 5 that has been punched and inserted can be improved and the opening torque value of the cap 1 can be reduced. In addition, the liner 5 is brought into intimate contact with the cap's top surface, resulting in improved gas-barrier property as the cap 1. As shown in
The required coating amount of the nonvolatile liquid is proportional to the diameter of the cap. When the coating amount is too small, barrier property becomes insufficient. When the coating amount is too much, it causes the bleeding out of the liquid between the liner 5 and the cap shell 4, resulting in the phenomenon that the liquid is attached to the bottle mouth when the cap 1 capped to a bottle can is opened. The coating amount thereof may slightly differ depending on the surface conditions of the liner 5, but is preferably approximately proportional to the diameter of the cap.
In a conventional sheet liner, a sheet is punched into a disk-like shape at normal temperatures and inserted into the cap shell 4 without any special heat treatment. In contrast, in the present embodiment, since a molten soft liner material is placed onto the rigid sheet 5a after the insertion of the rigid sheet 5a and immediately press-molded to thereby form the soft layer 5b, the surface of the rigid sheet 5a is in a complete sterile condition and thereby the cap 1 exhibiting excellent hygiene can be supplied.
Furthermore, in a conventional in-shell molded type liner, it is difficult to print on a liner. In contrast, in the present embodiment, the rigid sheet 5a is printed before being punched into a disk-like shape, and inserted into the cap shell 4. Then, a molten soft liner material is supplied thereon, and immediately press-molded to thereby form the soft layer 5b, whereby the cap 1 provided with the printed liner 5 can be supplied. The printed surface of the liner 5 of the cap 1 is not in direct contact with the content, which is excellent in hygiene. This printing may be useful when adapted for a prize cap.
In the conventional multilayer sheet liner, a sheet is punched into a disk for insertion but it is very difficult to recycle a punched waste because a plurality of materials are laminated thereon. On the other hand, in the production method of the present embodiment, since the punched waste 28 from the hard portion (punched waste 28 of rigid sheet 5a) of the liner material is only generated, it is easy to chip and recycle the punched waste 28 into pellet form. The punched waste 28 can also be directly recycled depending on the conditions. Therefore, in the production method of the present embodiment, 100% of the liner material for the rigid sheet 5a can be theoretically used for production.
According to the present embodiment, the cap 1 having excellent handling ability such as drop impact resistance can be provided. For example, assume that a filled and capped bottle is inverted and dropped so as to impact the cap. In the conventional in-shell molded type liner, a phenomenon occurs which the liner material is detached from the bottle when the displacement between the bottle and the cap due to impact is large. On the other hand, in the present embodiment, since the liner 5 and the cap shell 4 can be moved freely, the percentage of the liner 5 in intimate contact with the mouthpiece 7 being dragged by the displacement of the cap shell 4 is small when the cap is subjected to impact, resulting in advantageous drop impact resistance.
Also, when the liner 5 of the present embodiment is opened, the inner top surface of the cap shell 4 and the sliding layer (rigid sheet 5a) of the liner 5 are firstly slid, so that there is no need for the sealing layer (soft layer 5b) to slide. Thus, there is no need to add the amount of lubricant required for the sliding of the sealing layer, so that the falling of the bled lubricant into the content does not occur. The characteristic smell of lubricant also does not transfer to the content. It should be noted that a small amount of antiblocking agent or lubricant may be used for the sealing layer in order to improve detachability between the sealing layer and the bottle mouth.
In the present embodiment as described above, the soft layer 5b is concentric with the rigid sheet 5a and is formed in an annular or disk shape with a diameter smaller than that of the rigid sheet 5a so that the soft layer 5b can be brought into contact with at least the mouthpiece 7. Hence, even if the soft layer 5b deforms due to pressure during capping, an excellent openability can be obtained because the end of the soft layer 5b is set apart from the inside surface of the cap shell 4 and the liner stopping protrusion 9 and thus an opening torque value does not increase by the contact of the end with them.
Since the synthetic resin liner 5 has less rigidity compared with a conventional liner using an aluminum sheet, a plane-shaped synthetic resin liner 5 can still be readily engaged with the cap shell 4, and the drawing of the cap shoulder can also be readily performed. The end of the liner 5 is formed of the rigid sheet 5a only and has less rigidity, the liner 5 can be readily engaged with the cap shell 4 compared with the case where the entire liner has the two-layer structure of the rigid sheet 5a and the soft layer 5b. Furthermore, since the soft layer 5b portion is less than the rigid sheet 5a, the total weight of the liner can be reduced compared with the case where the entire liner has the two-layer structure of the rigid sheet 5a and the soft layer 5b.
Also, since the liner 5 has a multilayer structure composed of the soft layer 5b and the rigid sheet 5a, high sealing property can be obtained by the soft layer 5b, and excellent openability and drop impact resistance can be obtained by the free rotation of the liner 5 with respect to the cap shell 4 with the help of the rigid sheet 5a having high lubricity and low frictional resistance compared to that of the soft layer 5b, whereby there is no need to add a large volume of lubricant.
Also, the soft layer 5b is formed onto the rigid sheet 5a by resin molding, a large volume of punched waste when the rigid sheet 5a is punched into a disk-like shape is composed of a single layer and thereby can be reused (recycled). In addition, when the resin molding is performed after the insertion of the rigid sheet 5a into the cap shell 4, there is no need to select which side of the punched rigid sheet 5a is the front and back when inserted into the cap shell 4 because there is no distinction therebetween.
Furthermore, since only the soft layer 5b is formed by resin molding, the soft layer 5b can be obtained in various shapes and the amount of the material used can be reduced by uniquely setting a sectional thickness as required. Since a molten soft material is placed onto the rigid sheet 5a and is formed by resin molding, the surface of the rigid sheet 5a is in a complete sterile condition and thereby the cap exhibiting excellent hygiene can be obtained. Even when the rigid sheet 5a is subjected to pre-printing, the printed surface is covered by the soft layer 5b so as not to be in direct contact with the content, which is excellent in hygiene.
Since the outer diameter of the rigid sheet 5a and the outer diameter of the soft layer 5b are set in the range described above, the liner can be prevented from falling off by the engagement of the rigid sheet 5a to the liner stopping protrusion 9. In addition, since the soft layer 5b is not in contact with the liner stopping protrusion 9 while being in contact with the mouthpiece 7, an increase in opening torque can be prevented while maintaining high sealing property.
When the rigid sheet 5a is formed of polypropylene resin and the soft layer 5b is formed of styrene elastomer, such liner is particularly excellent in sealing property, heat resistance, and adhesive property between the rigid sheet 5a and the soft layer 5b.
Furthermore, by setting t×f to 150 or more when the thickness of the rigid sheet is set as t(mm) and the flexural modulus is set as f(MPa), such setting can secure the liner against extraction from the liner stopping protrusion 9 due to the significant flexural capacity of the rigid sheet 5a when the adhesion of the soft layer 5b to a mold punch or the mouthpiece 7 causes the soft layer 5b to be pulled and thereby the rigid sheet 5a abuts against the liner stopping protrusion 9.
By setting the thickness of the portion in contact with the mouthpiece 7 of the soft layer 5b is thicker than those of the other portions, high sealing property can be obtained. In addition, a portion other than the portion in contact with the mouthpiece 7 can be made to be thin, so that the amount of the soft material used may be reduced, resulting in cost reduction.
A non-volatile organic liquid is applied between the top plate 2 and the liner 5, whereby the adhesion and gas-barrier property of liner 5 can be improved. In particular, the coating amount of the non-volatile organic liquid is set in the range described above, an appropriate coating amount without bleeding out corresponding to the area of the liner 5 and excellent gas-barrier property can be obtained. Furthermore, the non-volatile organic liquid is silicone oil or glycerin, which significantly improves gas-barrier property. Note that the selection of glycerin as the non-volatile organic liquid can readily adjust the kinematic viscosity of the non-volatile organic liquid by the addition of water.
It should be understood that the present invention should not be limited to the embodiments described above but variously modified and changed without departing from the spirit of the invention.
Next, the liner-provided cap and the cap-provided threaded container according to the present invention will be specifically described with reference to actually produced Examples.
The cap shell 4 is produced in the following procedure. First, a coating material such as epoxy phenol or polyester is baking-applied two or more times with the thickness of 1 to 10 μm onto the inner and outer surface of an aluminum alloy sheet, and the coated aluminum alloy sheet is punched into a cap-like shape by pressing. Then, the perforation 10, the knurl 8, and the liner stopping protrusion 9 are machined onto the side wall of the cap. This machined cap is the cap shell 4.
The corresponding liner 5 is produced in the following procedure. First, a hard synthetic resin (e.g., HDPE, PP, various nylons, PAN, PET, PBT, and PC, etc.) is extruded into the single layer sheet 27 for the rigid sheet 5a using the extruder 25 and the T die 24. The thickness of the single layer sheet 27 is preferably in the range of from 0.1 to 1.0 mm and more preferably in the range of from 0.2 to 0.8 mm. The synthetic resin requires a certain rigidity, and the flexural modulus is preferably 400 MPa or more depending on the thickness thereof. The surface of the rigid sheet 5a may be subjected to corona discharge treatment as required. An adhesive component may be laminated or applied onto the rigid sheet 5a so as to adhere to the soft layer 5b.
The single layer sheet 27 is punched into a disk-like rigid sheet 5a to insert into the cap shell 4. The diameter of the rigid sheet 5a must be greater than the inner diameter of the liner stopping protrusion 9, and be capable of free rotation in the cap shell 4. The punched waste 28 may be immediately molded into a chip for an immediate use as a raw material of hard member.
For the cap shell 4 into which the rigid sheet 5a has been inserted, at the next step, a certain amount of a molten resin used for the soft layer 5b, which has been extruded from the mold liner extruder 29, is cut, placed into the center of the rigid sheet 5a, and immediately pressed by a cold punch to form the soft layer 5b of a certain shape. For the soft layer 5b, a blend of various elastomers or resins and an elastomer shows a good result. Examples of such elastomer include olefin elastomer, styrene elastomer, polyamide elastomer, polyester elastomer, polyurethane elastomer, vinyl chloride elastomer, and the like.
A soft member used for the soft layer 5b preferably has a JIS hardness of 50 (hardness D) or less and more preferably of 45 (hardness D) or less. The thickness of the formed sealing layer (soft layer 5b) is preferably from 0.1 to 0.8 mm and more preferably from 0.2 to 0.6 mm at least at the portion in contact with the mouthpiece 7.
Example 1Next, the results of the comparative test carried out for confirming the effects of the present invention will now be described.
In this test, an aluminum alloy sheet with a thickness of 0.25 mm with its inner and outer surfaces painted was molded into a cap shell 4 for 38-mm PP cap (pilfer-proof cap). For the cap shell 4, an aluminum sheet of which the inner surface was baking-applied with a polyolefin lubricant-containing epoxy phenol coating material at the rate of 50 mg/dm2 was used. Then, a polypropylene sheet formed by an extruder 25 and T die 24 was punched into a 37.8 mm rigid sheet 5a, and the rigid sheet 5a was inserted into the cap shell 4 having an inner diameter φ of 38.05 mm. In the cap shell 4, the 12 liner locking hooks (liner stopping protrusion 9) protruding toward the interior with a length of 1.0 mm extending substantially horizontally along the top surface was formed. The position of the hook was 1.5 mm in height from the cap's top surface. An automatic liner insertion machine was used for insertion.
Several kinds of the rigid sheet 5a made of polypropylene having different thickness were produced by changing the interval of the thickness of the T die and the interval of the pressure roller. For the cap shell 4 into which the rigid sheet 5a has been inserted, a certain amount of a melting elastomer, which has been extruded from the extruder 25, was supplied, and immediately pressed by a cold punch to form the shape of the soft layer 5b. The elastomer was formed such that the sum of the thickness of the PP sheet (polypropylene sheet) and the elastomer becomes about 1.0 mm. For the aforementioned elastomer, PP, liquid paraffin, and styrene elastomer blended with a styrene-ethylene/propylene-styrene block copolymer (SEPS) were used. The central portion of the soft layer 5b, where it is not involved in sealing property of the mouthpiece 7, was formed as thin as possible.
To examine the characteristics of the cap 1, an aluminum bottle with a content of 275 g (total amount 338 ml) was filled with water, air was substituted with nitrogen by adding liquid nitrogen dropwise at the headspace portion, and the bottle was sealed with a test cap. A single-head capper was used for sealing. A pressure block used had a drawing diameter φ of 35.6 mm with a drawing depth of 1.6 mm. A head pressure for capping was 1000 N.
This capped bottle was subjected to retort treatment at 121° C. for 20 minutes. After allowed to stand at room temperature for one week, an opening torque value was measured. Also, suitability for setting (suitability for liner setting) when these liners 5 were inserted by an automatic insertion machine was also evaluated. These liners 5 were also evaluated for detachment when the cap is opened. These evaluation results are shown in the following Table 1.
As Comparative Examples, a sliding layer (rigid sheet) and sealing layer (soft layer) were co-extruded, laminated into a two-layer sheet, and punched into a certain diameter disk, and inserted into the cap shell 4. The thickness of the sliding layer and the sealing layer tested was substantially the same as that in the present Examples.
This result indicates that the liner of the present invention is excellent in suitability for liner setting to a cap shell compared to a conventional two-layer sheet even if the thickness of the sliding layer (rigid sheet) is the same. In addition, it is found that the maximum value of the opening torque of the conventional two-layer sheet is large, resulting in an increase in average.
Example 2The liner of the present invention was produced as in Example 1, and compared with a conventional two-layer liner material as a Comparative Example. In the present invention, a sliding layer (rigid sheet) having a different outer diameter size was produced. After the insertion into a cap shell, a sealing layer (soft layer) was formed by the in-shell mold method. The size of the prototype sliding layer (rigid sheet) was estimated considering the upper limit and the lower limit of the present invention, and the prototype sliding layer was inserted into the cap shell. These were evaluated in the same manner as in Example 1. A conventional two-layer sheet was tested as a Comparative Example. The sheets of Comparative Examples were produced by extruding and laminating PP and styrene elastomer as in Example 1 from the two-layer extruder and the T die of a sheet molding machine, adjusting the thickness thereof by a cold roller, cutting them to a certain width. After cutting, the sheets were punched into a disk-like shape in accordance with the size of each outer shape, and inserted into cap shells.
This result indicates that the liner of the present invention is excellent in suitability for liner setting compared with a conventional two-layer sheet liner when the height and length of the hook is kept certain, and the liner is appropriately set into the cap shell for sufficient sliding even if the sliding layer (rigid sheet) has an inner diameter substantially identical to the inner diameter of the cap shell.
In the conventional two-layer sheet liner, the sealing layer (soft layer) and the sliding layer (rigid sheet) have the same outer diameter. Hence, when the liner having an outer diameter close to the inner diameter of the cap shell is set to the cap shell, stable liner insertability may not be obtained due to thickness of the liner.
In the conventional two-layer sheet liner, since the sealing layer (soft layer) is brought into contact with the side surface of the hook (liner stopping protrusion) or cap shell when the cap is opened after sealing, some of the liners indicate high opening torque value (larger maximum), leading to high average. Although a liner disengagement may occur when the outer diameter of the sliding layer (rigid sheet) is small, the liner of the present invention has a smaller degree of liner fallout compared to that of the conventional two-layer sheet liner.
The settable size D1 of the outer diameter of the liner is D1>D0−2w. In this case, since D0=38.05 and w=1.5, D1>35.05 (mm).
Example 3In this test, an aluminum alloy sheet with a thickness of 0.25 mm with its inner and outer surfaces painted was molded into a cap shell of a 38-mm PP cap (pilfer-proof cap). For the cap shell, an aluminum sheet of which the inner surface was baking-applied with a polyolefin lubricant-containing epoxy phenol coating material at the rate of 50 mg/dm2 was used. This aluminum sheet was punched out by pressing, and molded into a 38-mm PP cap (pilfer-proof cap) shell. To the cap shell, silicone oil or glycerin as non-volatile organic liquid was used and applied to the central inner surface of the cap shell by varying the amount of the organic liquid.
A polypropylene sheet shaped by the T die extruder was punched into a rigid sheet with a diameter of 37.6 mm, and inserted into a cap shell. The rigid sheet inserted into the cap shell was produced such that the surface thereof was less affected by a cold roller during molding. A sheet with a different thickness was also molded by changing molding conditions. To the cap shell into which the rigid sheet was inserted, a certain amount of melting elastomer extruded from the extruder was supplied, and immediately pressed by a cold punch to mold into the shape of the soft layer for adhesion.
For the aforementioned elastomer, PP, liquid paraffin, and styrene elastomer blended with a polymer SEPS were used. The thickness of the elastomer was changed corresponding to the thickness of the sheet. The central portion of the soft layer, where it is not involved in sealing property of the mouthpiece, was formed as thin as possible. An aluminum bottle with a content of 275 g (total amount 340 ml) was capped with the cap. Water with a certain amount of vitamin C was used for the contents The headspace volume was kept at 40 ml, and the headspace portion was substituted with nitrogen gas for capping.
All drawing depths were 1.6 mm and the head pressure was 1000 N. After the capped bottle was subjected to retort treatment at 121° C. for 20 minutes, the opening torque, drop impact performance, and retention of vitamin C were evaluated. After the opening torque was measured, the cap was visually observed with regard to the degree of bleeding out of nonvolatile liquid to the cap.
Likewise, the 33 PP cap (pilfer-proof cap) (aluminum sheet thickness 0.23 mm, outer diameter of liner 32.8 mm) and 28 PP cap (pilfer-proof cap) (aluminum sheet thickness 0.22 mm, outer diameter of liner 27.4 mm) with its inner and outer surfaces coated was also evaluated in a similar way. The interior content and total content of the container are substantially the same as those of the 38 PP cap (pilfer-proof cap).
As can be seen from the Tables 3, 4, and 5, a liner consisting of the PP sheet (polypropylene sheet) and the in-shell molded elastomer exhibits improved oxygen barrier property by the application of a certain amount of a nonvolatile liquid such as silicone oil, which does not cause reduction in sealing property and drop impact resistance but causes reduction in openability. For the liner consisting of the sheet and the in-shell molded elastomer, the improvements in oxygen barrier property by the application of a nonvolatile liquid such as silicone oil between the sheet and the cap shell are small when the coating amount thereof is too small. On the other hand, when the coating amount thereof is too much, it may cause bleeding of the nonvolatile liquid at the inside of the cap shell after capping and retort treatment. An appropriate coating amount Y(mg) stands in a relationship of Y=αS which is proportional to a liner area S(cm2), a value of α is preferably from 0.01 to 1 and more preferably from 0.02 to 0.9. When no coating is applied, barrier property slightly increases by thickening the PP layer, however, drop impact performance may deteriorate due to thickening.
Example 4Using a polypropylene resin cap with an outer diameter of 42 mm, water-vapor permeability was compared between a cap with the liner of the present invention inserted and a cap with a two-layer sheet liner inserted as a Comparative Example. In other words, a sheet for testing the resin cap was inserted, and a glass bin containing a certain amount of calcium chloride was capped with the cap. The tightening torque for capping was 350 N·cm. These capped glass bins were placed in a desiccator in a 95% humidity, and the weight changes were measured after one month. The opening torques were measured after one month. The sample size for each group was 10.
Insertability and liner fall-off were evaluated while holding the inner diameter of the cap's liner section of 38.8 mm and changing the outer diameter of the liner by varying the size of the sliding layer (rigid sheet). At this time, the inner diameter of the hook (liner stopping protrusion) was 37.8 mm and the hook height was 1.5 mm. The hooks were circumferentially and continuously formed. A certain amount of silicone oil was applied between the cap shell and the liner.
This result indicates that moisture permeability amount can be kept at low level when silicone oil is applied between the cap shell and the liner. The opening torque is stable compare to that of a conventional two-layer sheet under substantially the same condition. In some conventional two-layer sheets, the sealing layer (soft layer) is brought into contact with the side surface of the cap shell, resulting in higher maximum value and larger variations.
Example 5In this test, an aluminum alloy sheet with a thickness of 0.25 mm with its inner and outer surfaces painted was molded into a cap shell of a 38-mm PP cap (pilfer-proof cap). For the cap shell, an aluminum sheet of which the inner surface was baking-applied with a Teflon (registered trademark) lubricant-containing epoxy phenol coating material at the rate of 50 mg/dm2 was used. A polypropylene sheet molded by the T die extruder was punched into a rigid sheet (37.8 mm in thickness) and inserted into the cap shell. Several kinds of rigid sheets having different thicknesses were produced by changing the slit width of the T die.
For the cap shell into which the rigid sheet has been inserted, a certain amount of a melting elastomer, which has been extruded from the extruder, was supplied, and immediately pressed by a cold punch to form the soft layer of a certain shape. The elastomer used was PP, liquid paraffin, and styrene elastomer blended with a polymer SEPS. Several kinds of caps were produced such that the seal portions (portion where the liner contacts with the mouthpiece) of the soft layers are different in thickness. The central portion of the soft layer 5b, where it is not involved in sealing property of the mouthpiece, was formed as thin as possible.
To examine the characteristics of the cap 1, an aluminum bottle with a content of 275 g (total amount 338 ml) was filled with water, and sealed with a test cap. A single-head capper was used for sealing. A pressure block used had a drawing diameter φ of 35.6 mm with a drawing depth of 1.8 mm. A head pressure for sealing was 1100 N.
The headspace volume was kept at 63 ml, and the headspace portion was substituted with nitrogen gas for sealing. Then, the capped bottle was subjected to retort treatment at 121° C. for 20 minutes. Sealing property immediately after the retort treatment, opening torque value after allowed to stand at room temperature, and drop impact performance were evaluated. These evaluation results are shown in the following Table 7. As Comparative Examples, the evaluation results for the in-shell molded type caps are also shown in Table 7.
As can be seen from the above table, the liner consisting of the PP sliding layer (rigid sheet) with a thickness of 0.2 mm or more and the TPS sealing layer (soft layer) exhibits excellent openability and drop impact resistance compared to an in-shell molded liner made from TPS alone. When the sliding layer (rigid sheet) is too thin, slipping-out occurs during in-shell mold method. On the contrary, when the sliding layer (rigid sheet) is too thick, the drop impact resistance becomes inferior. However, even in such a case, the liner still has excellent openability, and the punched waste of the rigid sheet can be beneficially reused.
Example 6The liner of Example 6 was produced as in Example 5, and its producibility was compared with a two-layer liner of Comparative Examples. In Example 6, a PP sheet (polypropylene sheet) was punched to form a rigid sheet as in Example 5. A punched waste was milled, mixed with a PP member, and reused as sheet material. In a sheet of Comparative Examples, PP and styrene elastomer were extruded and laminated by the two-layer extruder and the T die, i.e., a sheet molding machine, adjusted the thickness by a cold roller, and cut in bars with a certain width. Then, the resulting bar was punched into a disk-like shape with a diameter of 37.8 mm and inserted into a cap shell. Punching was performed with an arrangement such that the maximum number of rigid sheets can be obtained from a sheet. In this state, their performance as a cap and production efficiency of a liner were compared. Note that the total evaluation criteria is different from that in Example 5. The results are shown in Table 8.
As can be seen from the results shown in the Table 8, the material efficiencies of the two-layer sheets in Comparative Examples were roughly 50%, whereas the material efficiencies of the liners in Example 6 were close to 90%. Although there was no difference in the opening torque, the two-layer sheet exhibited inferior sealing property, when the sliding layer (rigid sheet) for the two-layer sheet was too thick. Leakage was observed due to drop impact.
Example 7In Example 7, a 38-mm PP cap (pilfer-proof cap) shell was molded as in Example 5, and the coating material for a cap shell was substantially the same as that in Example 5. Resin sheets, which were different each other in thickness, molded by the T die extruder were punched into disk-like rigid sheets with a diameter of 37.8 mm, and each sheet was inserted into the cap shell. For the cap shell into which the rigid sheet has been-inserted, a certain amount of melting elastomer, which has been extruded from the extruder, was supplied, and immediately pressed by a cold punch to form a soft layer as in Example 5. The elastomer used was the same as that in Example 1. To examine the slipping-out resistance, the flexural modulus and thickness of the rigid sheet were measured for each material.
In order to examine the characteristics of the cap, the cap was evaluated in the same way as in Example 5. Specifically, an aluminum bottle with a content of 275 g (total amount 338 ml) was filled with 85° C. hot water, and sealed with a test cap. A single-head capper was used for sealing. A pressure block used had a drawing diameter φ of 35.6 mm with a drawing depth of 1.8 mm. A head pressure for sealing was 1100 N. The headspace volume was kept at 63 ml, and the headspace portion was substituted with nitrogen gas for sealing. Then, sealing property immediately after treatment, opening torque value after allowed to stand at room temperature, and drop impact performance were evaluated. These evaluation results are shown in the following Table 9.
As can be seen from the Table 9, when the value of t×f is 150 or more in the Examples of the present invention where the flexural modulus is set as f(MPa) and the thickness of the rigid sheet is set as t (mm), slipping-out phenomenon does not occur when the soft layer is formed on the rigid sheet.
Second EmbodimentHereinafter, an embodiment of the liner-provided cap and the cap-provided threaded container according to the present invention will be described with reference to
As shown in
As shown in
The cap shell 106 is formed of resin such as polyolefin resin or polystyrene or is machined from an aluminum or aluminum alloy sheet.
The liner 107 includes a sliding layer 107a disposed in contact with the inner surface of the top plate 104; a sealing layer 107b that is laminated to the sliding layer 107a and is more flexible than the sliding layer 107a; an intermediate layer 107c disposed between the sliding layer 107a and the sealing layer 107 and having gas-barrier property; and an adhesive layer 107d disposed between the intermediate layer 107c and the sealing layer 107b to adhere to each other. In other words, the sealing layer 107b is laminated to the sliding layer 107a via the intermediate layer 107c and the adhesive layer 107d.
The intermediate layer 107c is made of a material having a lower adhesive strength to the sealing layer 107b than the sliding layer 107a, and having gas-barrier property higher than that of the sliding layer 107a and the sealing layer 107b. Example of such material include a metal foil or a gas barrier resin.
The adhesive layer 107d is preferably formed of the same material as that of the sliding layer 107a.
The sealing layer 107b is preferably molded and formed of styrene elastomer.
In other words, preferred barrier materials to be inserted as the intermediate layer 107c include an organic gas-barrier resin such as EVOH resin (ethylene-vinyl alcohol copolymer resin), PA (nylon), and PAN (polyacrylonitrile). A metal sheet (metal foil) such as aluminum, iron, and tin may also be used. When a metal sheet is employed as the intermediate layer 107c, baking coating material such as PET film, PP film, or epoxy phenol with heat resistance is suitable for double-sided lamination. Since the surface at the mouthpiece 103 side is adhered to the sealing layer 107b, it is preferable that the adhesive layer 107d be formed of a PP film.
A synthetic resin coating material such as epoxy phenol as the adhesive layer 107d may be applied onto a metal sheet such as aluminum, iron, and tin employed as the intermediate layer 107c. In this case, in order to cause the intermediate layer 107c to adhere to the sealing layer 107b, it is preferable that the adhesive layer 107d made of a coating material which can adhere to the sealing layer 107b or a coating material in which an adhesive component was added be formed on the surface of the mouthpiece 103 side.
Various elastomers are suitable for the sealing layer 107b. However, from the viewpoints of price, heat resistance, adhesiveness to sliding layer, moldability, and the like, olefin elastomer or styrene elastomer is preferable. In particular, in consideration of retort treatment, styrene elastomer which is a blend of styrene block copolymer, PP resin, and a flexible material such as liquid paraffin is preferred as described above.
SBC (styrene-hydrogenated conjugated diene block copolymer rubber) for use in the elastomer is SEBS (styrene-ethylene-butylene-styrene: styrene-hydrogenated butadiene block copolymer rubber) or SEPS (styrene-hydrogenated isoprene block copolymer rubber utilizing styrene-ethylene-propylene-styrene: isoprene polymer block) with low MFR (0.01 g/10 min or less at 230° C. in 5 kg). Other SBCs such as SIS (styrene-isoprene-styrene block copolymer), SBS (styrene-butadiene-styrene block copolymer), and SIBS (styrene-isobutylene-styrene block copolymer) cannot endure retort treatment due to insufficient heat resistance. A flexible material for use in retortable styrene elastomer is typically liquid paraffin, however, polybutene may also be used.
Next, an example of the method for manufacturing the liner 107 and the cap 101 of the present embodiment will be described.
Firstly, a sheet in which both sides of an EVOH resin that serves as the intermediate layer 107c, are sandwiched together with a PP (polypropylene) resin which serves as the sliding layer 107a and the adhesive layer 107d is formed by coextruding. At this time, a modified olefin resin as an adhesive for adhering the EVOH resin and PP resin is inserted to form a sheet. Hence, the sheet is configured as PP resin (sliding layer 107a)/adhesive/EVOH resin (intermediate layer 107c)/adhesive/PP resin (adhesive layer 107d).
This arrangement is also applicable when a gas barrier layer that serves as the intermediate layer 107c is made of PA or PAN.
In the present embodiment, the thickness of the sheet is set to 0.4 mm for example. This sheet is punched into a disk with a diameter of 37.6 mm, inserted into the cap shell 106 of an aluminum PP cap (pilfer-proof cap) with a nominal diameter of 38 mm. Then, as the sealing layer 107b, the above styrene elastomer is molded onto the sheet inserted into the cap shell 106 by a liner molding machine of the in-shell mold method.
In other words, a testing liner is extruded into a molten strand from an extruder, cut down a certain amount, fallen into an approximately central portion of the sheet disk inserted into the cap shell 106, and immediately embossed into a certain shape in a cooled mold to thereby form the liner 107.
When the intermediate layer 107c is an aluminum foil with a thickness of 100 μm, an epoxy phenol coating material as the sliding layer 107a and the adhesive layer 107d is baking-applied onto the both sides of the intermediate layer 107c. For the application to the one side which serves as the adhesive layer 107d, a coating material with a modified polyolefin added is used in order to allow it to adhere to a PP resin which serves as the sliding layer 107a. Likewise as described above, this sheet is punched into a disk with a diameter of 37.6 mm, inserted into the cap shell 106 of an aluminum PP cap (pilfer-proof cap) with a nominal diameter of 38 mm. Then, the above styrene elastomer as the sealing layer 107b is molded onto the sheet inserted into the cap shell 106 by a liner molding machine of the in-shell mold method.
Thus, since the cap 101 of the present embodiment includes the adhesive layer 107d that is disposed between the intermediate layer 107c having gas-barrier property and the sliding layer 107a or the sealing layer 107b to adhere to each other, a good adhesive property can be obtained by bringing the intermediate layer 107c into contact with the sealing layer 107b via the adhesive layer 107d even when a sufficient adhesive strength cannot be obtained by the direct adhesion between the intermediate layer 107c and the sealing layer 107b for example.
In addition, a high hardness resin is disposed as the sliding layer 107a that contacts with the inner surface of the cap shell, an elastic body that is completely in close contact with the sliding layer 107a is disposed as the sealing layer 107b, and the intermediate layer 107c which serves as a gas barrier layer is interposed between the sliding layer 107a and the sealing layer 107b, whereby a liner having excellent gas-barrier property can be obtained. In other words, the liner 107 is a multilayer that is sequentially composed of the sliding layer 107a, the intermediate layer 107c, the adhesive layer 107d, and the sealing layer 107b, which allows the intermediate layer 107c to have gas-barrier property, whereby a liner material excellent in sealing property, gas-barrier property, openability, and retort resistance can be provided. As long as the intermediate layer 107c is disposed between the sealing layer 107b and the sliding layer 107a and is adhered via the adhesive layer 107d, the sealing layer 107b or the sliding layer 107a may be multilayered and the intermediate layer 107c may be inserted therein via the adhesive layer 107d.
When the intermediate layer 107c is formed of a metal foil such as an aluminum foil, very high gas-barrier property can be obtained.
When the intermediate layer 107c is formed of a gas barrier resin such as EVOH resin, the intermediate layer 107c can be formed by molding, resulting in low cost and excellent producibility.
Furthermore, the adhesive layer 107d is formed of the same material as that of the sliding layer 107a having a good adhesive property to the intermediate layer 107c, so that it is easy to manufacture a laminated liner and the cost reduction can be realized.
Since the sealing layer 107b is molded, various shapes of the sealing layer 107b corresponding to the shape of the mouth (mouthpiece 103) of the bottle body 102 can be easily obtained.
Furthermore, since the sealing layer 107b is formed of a styrene elastomer which is a blend of SEBS (styrene-ethylene-butylene-styrene) and the like, the retortable liner 107 can be obtained.
Hence, the bottle 108 provided with the cap 101 has excellent openability and sealing property as well as excellent gas-barrier property and producibility.
Next, the results of evaluation of the actually produced examples of the liner for capping, the cap, and the cap-provided threaded container according to the present invention will be specifically described.
As an example of the present invention, the liner-provided cap according to the present embodiment was produced as follows.
Example 8, Comparative Example 8An aluminum alloy sheet with a thickness of 0.24 mm of which the inner and outer surfaces have been baking-applied with a synthetic resin was molded into a cap shell of a so-called 38-mm PP cap (pilfer-proof cap). As the sliding layer, intermediate layer, and adhesive layer of a liner, three-layer (five-layer to be precise because of the adhesive between the EVOH resin and the PP resin) sheet consisting of the PP resin, EVOH resin, and PP resin (PP resin is disposed on both sides of the EVOH resin) was molded with a thickness of 500 μm. Furthermore, a sheet of TPS (styrene elastomer) with a thickness of 300 μm was laminated to the sheet as the sealing layer. The resulting sheet was punched into a disk with a diameter of 37.6 mm and inserted into a cap shell. The resulting cap was defined as Example 8-1.
As an another Example, the three-layer sheet was punched into a disk with a diameter of 37.6 mm and inserted into a cap shell. Then, TPS (styrene elastomer) as the sealing layer is molded onto the sheet inserted into the cap shell by a liner molding machine of the in-shell mold method. The resulting caps were defined as Example 8-2 and Example 8-3.
In addition to these, caps in which an aluminum foil and MX nylon were used for the intermediate layer having gas-barrier property were tested as Example 8-4 and Example 8-5, respectively. As used herein, the phrase “intermediate layer having gas-barrier property” refers to the state in which the gas (e.g., oxygen) permeability of the intermediate layer is lower that the gas permeability of the sliding layer.
As used herein, MX nylon is collectively refers to as polyamides (manufactured by MITSUBISHI GAS CHEMICAL COMPANY, INC.) using Meta-xylenediamine (MXDA). Nylon MXD6 which is one of such polyamides is represented in the following chemical formula.
The gas-barrier property of MX nylon is preferably 10−14 cm3*cm/(cm2*s*Pa) or less of oxygen permeability coefficient (20° C. when dried). As used herein, cm3*cm/(cm2*s*Pa) means the amount of oxygen (cm3) to be permeated through an object having a width of 1 cm and an area of 1 cm2 to which the pressure of 1 Pa is applied for one second.
As Comparative Examples, a cap in which a sliding layer is a PP single layer and a sealing layer is a laminated TPS sheet (Comparative Example 8-1), a cap in which a sliding layer is a PP single layer and a sealing layer is a molded TPS (Comparative Example 8-2), a cap in which a sliding layer is a EVOH single layer and a sealing layer is a molded TPS (Comparative Example 8-3), a cap having only a molded TPS sealing layer (Comparative Example 8-4), and a cap having only a molded olefin elastomer TPO sealing layer (Comparative Example 8-5) were tested.
A bottle can (with a volume of 340 ml) with a diameter of 38 mm, which was filled with 275 ml of aqueous solution containing about 400 ppm of vitamin C, was capped with each of these caps of Examples and Comparative Examples. A head pressure of 1000 N was applied for capping. Liquid nitrogen was added dropwise to the headspace portion immediately before capping to adjust the internal pressure to about 0.1 MPa. These capped bottles were subjected to retort treatment at 123° C. for 20 minutes, stored in a temperature-controlled room at 55° C. to perform an evaluation test as follows.
In the liners of the present Examples and Comparative Examples, 0.5% or less of titanium oxide as coloring material, 0.1% or less of hindered phenol stabilizer as stabilizer, and 1% or less of lubricant such as fatty acid amide are added as required.
<Method of Evaluation Test> (Oxygen Barrier Property)In order to examine the reduced amount of vitamin C due to oxygen permeation as gas-barrier property, in particular, oxygen barrier property, these capped bottles were left to stand in a temperature-controlled room at 55° C. for two months, and the amount of change of vitamin C was examined by an automatic potentiometric titrimeter.
(Evaluation Criteria)(In all evaluation criteria in the following, A, B, and C are determined as good and D is determined as no good. If any one of characteristics is evaluated as D, such cap is determined as no good.)
A=reduction rate <3%
B=reduction rate ≧3 to <6%
C=reduction rate ≧6 to <10%
D=reduction rate ≧10%
(sample size for each group was 3)
(Sealing Property)For filled bottles can subjected to retort treatment, an internal pressure before and after the retort treatment was measured to confirm the presence or absence of leakage. Furthermore, for a bottle that no leakage was confirmed, the bottle was inverted and dropped vertically from the height of 30 cm and 10 cm onto the iron sheet with an angle of 10°, then the presence or absence of leakage was confirmed by solution leakage and variation of internal pressure.
(Evaluation Criteria)A=no leakage when dropped from 30 cm
B=no leakage when dropped from 10 cm but leakage occurred when dropped from 30 cm
C=no leakage during retort treatment but leakage occurred when dropped from 10 cm
D=leakage occurred during retort treatment (Sample size for each group was 10)
(Opening Torque)After allowed to stand in a temperature-controlled room at 50° C. for one month, the above filled bottle cans subjected to retort treatment were taken out to measure an opening torque. A torque value (first torque) required to rotate the cap was measured. A torque value (second torque) when an aluminum bridge is cut-off is excluded. There is an appropriate range for the opening torque. When it is too high, opening becomes difficult, whereas when it is too low, such cap may be loosened during transportation and/or handling, leading to leakage.
(Evaluation Criteria)A=50 to 150 N·cm (most appropriate torque value)
B=150 to 200 N·cm (slightly high torque value)
B=30 to 50 N·cm (slightly low torque value)
D=>200 N·cm (too high torque value)
D=<30 N·cm (too low torque value)
The detailed structures of the respective Examples and Comparative Examples, and their evaluation results are shown in the following.
Structure and Evaluation of Example 8-1
Sliding layer/intermediate layer/adhesive layer=three-layered structure sheet made of PP resin (200 μm)/EVOH resin (20 μm)/PP resin (200 μm). The PP resin also contains an adhesive. The value within parenthesis denotes the thickness of the structure.
Sealing layer=TPS(a) (400 μm)=sheet of styrene elastomer (a blend of PP resin, liquid paraffin, and SEPS (styrene-ethylene-propylene-styrene)). Note that the MFR of SEPS is 0.0 g/10 min (200° C.-5 kg).
(Evaluation Result): advantageous oxygen barrier property, sealing property, and openability.
The above MFR (melt flow rate) is measured under testing conditions based on JIS K 7210 condition H (a test temperature of 200° C. and a nominal load of 5.00 kg). In this case, the notation (200° C.-5 kg) is used.
Structure and Evaluation of Example 8-2
Sliding layer/intermediate layer/adhesive layer=the same structure as that of Example 8-1.
Sealing layer=TPS(a) (400 μm)=the same material as that of Example 8-1. Provided that the sheet was produced by the in-shell mold method. The thickness denotes the thickness in contact with the mouth of the container. The thickness of the central portion not involved in sealing property becomes thin. (In the following in-shell mold method of the sealing layer, the thickness and structure are the same as that of the present Example.)
(Evaluation Result): advantageous oxygen barrier property, sealing property, and openability.
Structure and Evaluation of Example 8-3
Sliding layer/intermediate layer/adhesive layer=three-layered structure sheet made of PP resin (180 μm)/EVOH resin (40 μm)/PP resin (180 μm). The PP resin also contains an adhesive. The value within parenthesis denotes the thickness of the structure.
Sealing layer=TPS(b) (400 μm)=sheet of styrene elastomer (a blend of PP resin, liquid paraffin, and SEBS (styrene-ethylene-butylene-styrene)). Provided that the sheet was produced by the in-shell mold method. Note that the MFR of SEBS is 0.0 g/10 min (200° C.-5 kg).
(Evaluation Result): advantageous oxygen barrier property, sealing property, and openability.
Structure and Evaluation of Example 8-4
Sliding layer/intermediate layer/adhesive layer=three-layered structure sheet made of PP resin (100 μm)/Al(20 μm)/PP resin (100 μm). The PP resin also contains an adhesive. Al is an aluminum foil.
Sealing layer=TPS(a) (400 μm)=the same material as that of Example 8-1. Provided that the sheet was produced by the in-shell mold method.
(Evaluation Result): advantageous oxygen barrier property, sealing property, and openability.
Structure and Evaluation of Example 8-5
Sliding layer/intermediate layer/adhesive layer=three-layered structure sheet made of PP resin (180 μm)/MXNy (50 μm)/PP resin (180 μm). The PP resin also contains an adhesive. MXNy is MX nylon.
Sealing layer=TPS(a)=the same material as that of Example 8-1. Provided that the sheet was produced by the in-shell mold method.
(Evaluation Result): advantageous oxygen barrier property, sealing property, and openability.
Structure and Evaluation of Example 8-6
Sliding layer/intermediate layer/adhesive layer=three-layered structure sheet made of E/P(a) (5 μm)/Al (100 μm)/E/Pb (5 μm). Al is an aluminum foil. The E/P(a) layer is a baking coating material made from epoxy phenol. The E/P(b) layer is a baking coating material made from epoxy phenol to which a PP-base adhesive component is added at a ratio of 5% of solid matter.
Sealing layer=TPS(a)=the same material as that of Example 8-1. Provided that the sheet was produced by the in-shell mold method.
(Evaluation Result): advantageous oxygen barrier property, sealing property, and openability.
Structure and Evaluation of Example 8-7
Sliding layer/intermediate layer/adhesive layer=three-layered structure sheet made of PP resin (20 μm)/Al (100 μm)/E/Pb (5 μm). The PP resin also contains an adhesive. Al is an aluminum foil. E/P(b) is a baking coating material made from epoxy phenol to which a PP-base adhesive component is added at a ratio of 5% of solid matter.
Sealing layer=TPS(a) (400 μm)=the same material as that of Example 8-1. Provided that the sheet was produced by the in-shell mold method.
(Evaluation Result): advantageous oxygen barrier property, sealing property, and openability.
Structure and Evaluation of Example 8-8
Sliding layer/intermediate layer/adhesive layer=the same structure as that of Example 8-1.
Sealing layer=TPS(c) (400 μm)=the same styrene elastomer as that of Example 8-1. Note that the MFR of SEPS used is 1.0 g/10 min (200° C.-5 kg) and the sealing layer was molded by the in-shell mold method.
(Evaluation Result): advantageous oxygen barrier property and openability but slightly inferior sealing property.
Structure and Evaluation of Example 8-9
Sliding layer/intermediate layer/adhesive layer=the same structure as that of Example 8-1.
Sealing layer=TPO(a) (400 μm)=olefin elastomer (a blend of LLDPE (linear low-density polyethylene) and EPR (ethylene-propylene rubber) 20%) was used. Note that the MFR of LLDPE used is 1.0 g/10 min (200° C.-5 kg) with a density of
0.928 and the sealing layer was molded by the in-shell mold method.
(Evaluation Result): slightly advantageous openability but slightly inferior sealing property. Favorable oxygen barrier property.
Structure and Evaluation of Comparative Example 8-1
Sliding layer=PP (600 μm) single-layer sheet. The value within parenthesis denotes the thickness of the structure.
Sealing layer=TPS(a) (400 μm)=styrene elastomer sheet (a blend of PP resin, liquid paraffin, and SEPS). Note that the MFR of SEPS is 0.0 g/10 min (200° C.-5 kg). The sliding layer and the sealing layer were simultaneously molded by co-extrusion.
(Evaluation Result): advantageous sealing property and openability but inferior oxygen barrier property.
Structure and Evaluation of Comparative Example 8-2
Sliding layer=PP (400 μm) single-layer sheet. The value within parenthesis denotes the thickness of the structure.
Sealing layer=TPS(a) (400 μm)=styrene elastomer (a blend of PP resin, liquid paraffin, and SEPS). Note that the MFR of SEPS is 0.0 g/10 min (200° C.-5 kg). The sealing layer was molded by the in-shell mold method.
(Evaluation Result): advantageous sealing property and openability but inferior oxygen barrier property.
Structure and Evaluation of Comparative Example 8-3
Sliding layer=EVOH (300 μm) single-layer sheet. Note that a modified olefin resin was applied onto the surface to be adhered with the sealing layer. The thickness also includes the thickness of the adhesive.
Sealing layer=TPS(a) (400 μm)=the same styrene elastomer as that of Example 8-1. The sealing layer was molded by the in-shell mold method.
(Evaluation Result): advantageous oxygen barrier property and openability but unstable sealing property.
Structure and Evaluation of Comparative Example 8-4
Liner=TPS(a) (700 μm) single liner produced by the in-shell mold method.
(Evaluation Result): slightly advantageous oxygen barrier property, advantageous sealing property, but high opening torque.
Structure and Evaluation of Comparative Example 8-5
Liner=TPO(a) (700 μm) single liner produced by the in-shell molded.
(Evaluation Result): inferior oxygen barrier property and too low opening torque.
Example 9Next, by using a cap provided with the same liner as that of the above Example 8, the same evaluation was performed by varying the filling and sterilization conditions.
(Filling Method)As in Example 8, a bottle can (with a maximum volume of 340 ml) with a nominal diameter of 38 mm was filled with 290 ml of aqueous solution at 85° C. containing about 400 ppm of vitamin C in the same way, and was then capped. A head pressure of 1000 N was applied for capping. Liquid nitrogen was added dropwise to the headspace portion immediately before capping to adjust the internal pressure to about 0.1 MPa. These capped bottles were stored in a temperature-controlled room at 55° C. to perform an evaluation test as follows. As Comparative Examples, the same liners as those of Comparative Examples in the above Example 8 were used.
<Method of Evaluation Test> (Oxygen Barrier Property)In order to examine the reduced amount of vitamin C due to oxygen permeation as, in particular, oxygen barrier property among gas-barrier properties, these capped bottles were left to stand in a temperature-controlled room at 55° C. for two months, and the amount of change of vitamin C was examined by an automatic potentiometric titrimeter. The capped bottle immediately after filling was measured as control.
(Evaluation Criteria)A=reduction rate <3%
B=reduction rate ≧3 to <6%
C=reduction rate ≧6 to <10%
D=reduction rate ≧10%
(sample size for each group was 3)
(Sealing Property)For filled bottle cans subjected to heat treatment, an internal pressure before and after the heat treatment was measured to confirm the presence or absence of leakage. Furthermore, for a bottle that no leakage was confirmed, the bottle was inverted and dropped vertically from the height of 30 cm and 10 cm onto the iron sheet with an angle of 10°, then the presence or absence of leakage was confirmed by solution leakage and variation of internal pressure.
(Evaluation Criteria)A=no leakage when dropped from 30 cm
B=no leakage when dropped from 20 cm but leakage occurred when dropped from 30 cm
C=no leakage during heat treatment but leakage occurred when dropped from 20 cm
D=leakage occurred during heat treatment (Sample size for each group was 10)
(Opening Torque)After allowed to stand in a temperature-controlled room at 55° C. for one month, the above filled bottle cans subjected to heat treatment were taken out to measure an opening torque. The bottle cans were measured and evaluated in the same way as in Example 8.
Examples 9-1 to 9-7: advantageous oxygen barrier property, sealing property, and openability.
Examples 9-8 to 9-9: advantageous oxygen barrier property but slightly low sealing property and opening torque.
Comparative Examples 9-1 to 9-2: inferior oxygen barrier property.
Comparative Example 9-3: advantageous oxygen barrier property but inferior opening torque.
Comparative Example 9-4: inferior oxygen barrier property and high opening torque.
Comparative Example 9-5: inferior oxygen barrier property.
As shown in the above evaluation, in Comparative Examples, any one of the properties such as oxygen barrier property, sealing property, and openability is no good, whereas in the present Examples, good results are obtained for all of oxygen barrier property, sealing property, and openability.
It should be understood that the present invention should not be limited to the embodiments and Examples described above but variously modified and changed without departing from the spirit of the invention.
REFERENCE NUMERALS1. cap (liner-provided cap), 2, 104. top plate, 105. tubular peripheral wall section, 106. cap shell (cap body), 5, 107. liner, 5a. hard sheet, 5b. soft layer, 7, 103. mouthpiece (mouth), 6, 108. cap-provided bottle (cap-provided threaded container), 9. liner stopping protrusion, 13, 102. bottle (threaded container) body, 101. cap, 107a. sliding layer, 107b. sealing layer, 107c. intermediate layer, 107d. adhesive layer
Claims
1. A liner-provided cap for sealing a mouth of a threaded container, comprising:
- a cap body consisting of a top plate and a tubular peripheral wall section that hangs from the peripheral edge of the top plate; and
- a synthetic resin liner provided on the inner surface of the top plate, the liner comprising: a disk-shaped rigid sheet disposed in contact with the inner surface of the top plate; and a soft layer that is laminated to the rigid sheet and is more flexible than the rigid sheet,
- wherein the soft layer is concentric with the rigid sheet and is formed in an annular or disk shape with a diameter smaller than that of the rigid sheet so that the soft layer can be brought into contact with at least the mouth.
2. The liner-provided cap according to claim 1, wherein the rigid sheet is formed of polypropylene resin and the soft layer is formed of styrene elastomer.
3. The liner-provided cap according to claim 1, wherein t×f is set to 150 or more when the thickness of the rigid sheet is set as t(mm) and the flexural modulus is set as f(MPa).
4. The liner-provided cap according to claim 1, wherein the tubular peripheral wall section includes a liner stopping protrusion protruding toward the interior thereof and supporting the liner from the underside thereof,
- when the inner diameter of the tubular peripheral wall section is set as D0 and the protruded length of the liner stopping protrusion is set as w, the outer diameter D1 of the rigid sheet is set in a range of D0≧D1>D0−2w, and
- when the central diameter of the mouth is set as R1, the outer diameter d1 of the soft layer is set in a range of D0−2w>d1>R1.
5. The liner-provided cap according to claim 1, wherein a non-volatile organic liquid is applied between the top plate and the liner.
6. The liner-provided cap according to claim 5, wherein when the area of the liner is S(cm2) and the coating amount of the non-volatile organic liquid is set as Y(mg), the coating amount of the non-volatile organic liquid is represented as the relationship of Y=αS, where α falls within a range of 0.01 to 1.00.
7. The liner-provided cap according to claim 5, wherein the non-volatile organic liquid is silicone oil or glycerin.
8. A threaded container having a liner-provided cap, wherein the liner-provided cap is the liner-provided cap according to claim 1.
9. A liner-provided cap for sealing a mouth of a threaded container body, comprising:
- a cap body consisting of a top plate and a tubular peripheral wall section that hangs from the peripheral edge of the top plate; and
- a liner provided on the inner surface of the top plate, the liner comprising: a sliding layer disposed in contact with the inner surface of the top plate; a sealing layer that is laminated to the sliding layer and is more flexible than the sliding layer; an intermediate layer disposed between the sliding layer and the sealing layer and having gas-barrier property; and an adhesive layer disposed between the intermediate layer and the sliding layer or the sealing layer to adhere to each other.
10. The liner-provided cap according to claim 9, wherein the intermediate layer is formed of a metal foil.
11. The liner-provided cap according to claim 9, wherein the intermediate layer is formed of a gas barrier resin.
12. The liner-provided cap according to claim 9, wherein the intermediate layer is a material of which an adhesive strength to the sealing layer is lower than that to the sliding layer, and the adhesive layer is formed of the same material as that of the sliding layer.
13. The liner-provided cap according to claim 9, wherein the sealing layer is molded.
14. The liner-provided cap according to claim 9, wherein the sealing layer is formed of styrene elastomer.
15. A cap-provided threaded container, wherein the cap is the liner-provided cap according to claim 9.
16. A threaded container having a liner-provided cap, wherein the liner-provided cap is the liner-provided cap according to claim 2.
17. A threaded container having a liner-provided cap, wherein the liner-provided cap is the liner-provided cap according to claim 3.
18. A threaded container having a liner-provided cap, wherein the liner-provided cap is the liner-provided cap according to claim 4.
19. A cap-provided threaded container, wherein the cap is the liner-provided cap according to claim 10.
20. A cap-provided threaded container, wherein the cap is the liner-provided cap according to claim 11.
Type: Application
Filed: Nov 5, 2015
Publication Date: Feb 25, 2016
Inventors: Tatsuya Hanafusa (Gotemba-shi), Hideyasu Muto (Gotemba-shi)
Application Number: 14/933,454
