PACKAGING UNIT HAVING IMPROVED SEALING AND A METHOD OF FORMING A PACKAGING UNIT HAVING IMPROVED SEALING

Abstract

A packaging unit for hygiene articles is formed from a sheet of material having an inner surface and an outer surface. The inner surface includes an edge zone including an inner edge portion and an outer edge portion. The sheet has at least one folding axis dividing the sheet into a first region and a second region. The inner edge portion and the outer edge portion of the edge zone of the first region is provided with adhesive, and the other of the inner edge portion and the outer edge portion of the edge zone of the first region is adhesive-free. Further, one of the inner edge portion and the outer edge portion of the edge zone of the second region is provided with adhesive, and the other is adhesive-free in a complementary manner to the edge zone of the first region.

Description

TECHNICAL FIELD

The present invention relates to a packaging unit for hygiene articles, the unit being formed from a sheet of material, the sheet having an inner surface and an outer surface, the inner surface comprising an edge zone comprising an inner edge portion and an outer edge portion, the sheet having two folding axes, the folding axes dividing the sheet into a first region, a second region and a third region, wherein the packaging unit may be folded along the folding axes with the first, second and third regions in an overlapping configuration. The present invention also relates to a method of forming a packaging unit for hygiene articles from a sheet of material, a web of material for forming packaging units, as well as to a method of forming a web of material for forming packaging units.

BACKGROUND OF THE INVENTION

Disposable hygiene articles, such as sanitary napkins and panty liners, are normally packaged individually in e.g. an easy wrap or a single wrap. Individual packages facilitate hygienic carrying of single articles for future use, e.g. in a handbag. The edges of the individual packages are often sealed by means of ultrasonic welding or heat welding. Further, the packaging units are often used both as a means for packaging an unused article and for disposal of the used article.

It is desirable that used articles of this kind can be disposed of discretely and hygienically.

This may be particularly important when the user lacks the possibility to dispose of the used article immediately after the used article has been replaced, e.g. when there is no waste bin available in the toilet area. In this case, the user may need to put the used article in e.g. the handbag or backpack, which requires that the package is tightly sealed in order to avoid staining and odour.

The disposal problem has been an object of quite an intensive investigation, and several solutions have been suggested.

GB 2 153 779 discloses a wrapper sheet that may be provided with a pouch formed by overlaying at least a portion of the wrapper with a sheet of liquid impermeable material which is affixed to the wrapper on three sides. The pouch is used to receive the soiled article. Such a wrapper suffers from disadvantages of requiring an additional amount of material, and not being able to form a tight disposal package.

Another common solution for disposing of used hygiene articles is disclosed in e.g. WO 94/14396. This document discloses a fold and wrap package comprising a wrapper comprising a single strip of material having a flap panel, a central panel and an end panel, and a tape tab for securing the wrapper in a disposal configuration. A major disadvantage of such a wrapper is that it is not possible to form a tightly sealed package when the article is to be disposed of.

WO 88/10219 discloses a packaging unit which is formed by folding an elongated sheet of material provided along the mutually parallel edges thereof with a continuous or broken narrow coating of pressure-sensitive adhesive by means of which the container part is held together, with adhesive surfaces lying against and bonding to adhesive surfaces. The packaging unit further comprises a lid coated at least partially with a pressure-sensitive adhesive so as to enable the lid to be refastened to the outside of the container part. Such a packaging unit thus has very strongly sealed side seams where the adhesive-coated surfaces are in contact with each other, and a resealable lid providing a tightly sealed disposal package. However, since the adhesive-coated surfaces are in contact with each other, it is impossible to unfold the sheet completely for positioning of a used item, which thus has to be inserted into the rather limited container part. This may be disadvantageous, since a used hygiene article often becomes more bulky than before use, making it difficult to insert it into the container part.

US H 1454 discloses a reclosable sheet for packaging and disposal of hygiene articles. The sheet comprises edge adhesive strips positioned such that when the sheet is folded, the adhesive-coated areas do not come into contact with each other. In order to serve its purpose, the folding of the sheet has to be initiated from the adhesive-free transverse edge of the sheet. If the folding is initiated from the adhesive-coated transverse edge, two layers of adhesive will overlap each other, and the adhesive-free transverse edge will be positioned at the outer position of the package, i.e. the package will not be tightly sealed.

A conventional type of packaging unit intended for packaging single articles comprises an elongated rectangular sheet of material which is folded to form a bag-like package with a folded-over lid, also called e-folding. These known packaging units are welded along the edges by means of heat or ultrasound, and are opened by tearing along the welded seams at the edges, so that the package may be unfolded to expose the contents of the package.

The main drawback of welded packaging units of this kind is that they cannot be used satisfactorily as disposal bags since, once opened, the packages cannot be resealed and therefore do not allow a used article to be packaged in an acceptable manner with regard to hygiene. Furthermore, the unfolded packaging sheet has non-aesthetic appearance, since the broken welds are often uneven and frilly.

Hence there is a need for a packaging unit which can be used both for packaging a new hygiene article and for sanitary keeping and disposing of a used hygiene article, which is easily opened and securely resealed, and which is aesthetically appealing.

SUMMARY OF THE INVENTION

The present invention provides a packaging unit which can be used both for packaging a new hygiene article and for safe and sanitary disposing of a used hygiene article. The packaging unit of the present invention provides a possibility of forming a tight package both for a new and a used article, thus keeping the new article sanitary and clean prior to use, and eliminating the risk of staining and odour when a used article is packaged. The packaging unit is easy to unfold and reseal, and is aesthetically appealing.

As used herein, the term “inner surface” refers to the surface of the packaging unit facing the product positioned inside the packaging unit, and the term “outer surface” refers to the surface opposite to the inner surface, i.e. the surface facing the ambient.

By the term “edge zone” is meant a portion of the packaging unit adjacent to the edges of the packaging unit. The width of an edge zone may be varied.

The term “inner edge portion” refers to the portion of the edge zone positioned towards the centreline of the packaging unit.

The term “outer edge portion” refers to the portion of the edge zone positioned towards the edge of the packaging unit.

By the term “single ply” is meant a packaging unit comprising a single ply of a coherent material. The examples of a single ply packaging unit may be a plastic film, such as a polyethylene film, a nonwoven material, a metallic foil or the like. A single ply material may be a non-homogenous material such as a plastic film material comprising integrated layers or a nonwoven material having varying fibre composition in different parts of the material. A single ply material as used herein does not comprise materials having separable layers.

By the term “laminate” is meant a packaging unit comprising at least two united separable plies of material that can be the same or different. In the context of the present invention, the laminate may for example be constituted of two separable plies of plastic film, a film and nonwoven, two plies of nonwoven, or the like.

By the term “transverse cutting zone” is meant an area of the web of material where an incision is made in order to separate a piece of the web of material, thus forming a sheet for forming a packaging unit of the present invention.

By the term “release agent” is meant a substance being able to adjust the adhesive strength of an adhesive.

By the term “resealable adhesive” is meant an adhesive that provides a non-permanent adhesive bond between two adherent surfaces, i.e. a bond that may be broken by applying a pulling force to the adherent, and recreated by applying a pressing force to the adherent.

The present invention provides a packaging unit for hygiene articles and a method of forming a packaging unit, which substantially eliminate the drawbacks of the packaging units discussed above.

The packaging unit for hygiene articles according to the present invention is formed from a sheet of material having an inner surface and an outer surface, the inner surface comprising an edge zone comprising an inner edge portion and an outer edge portion. The sheet has two folding axes, i.e. a first folding axis and a second folding axis, the folding axes dividing the sheet into a first region, a second region and a third region, such that the packaging unit may be folded along the folding axes with the first, second and third regions in an overlapping configuration. The packaging unit according to the present invention is characterized in that one of the inner edge portion and the outer edge portion of the edge zone of the second region is provided with resealable adhesive, and the other of the inner edge portion and the outer edge portion of the edge zone of the second region is adhesive-free and is provided with a release agent. The release agent is provided in order to be able to control the adhesive strength of the resealable adhesive used in the present invention.

Further, one of the inner edge portion and the outer edge portion of the edge zone of the first region and one of the inner edge portion and the outer edge portion of the edge zone of the third region are provided with resealable adhesive in a complementary manner to the edge portion being provided with resealable adhesive in the second region such that a chessboard pattern of resealable adhesive is formed along the edge zone. Moreover, the other of the inner edge portion and the outer edge portion of the edge zone of the first region and the other of the inner edge portion and the outer edge portion of the edge zone of the third region are free from resealable adhesive and from release agent. When the sheet is folded about the first folding axis, the edge portion carrying resealable adhesive in the first region is brought in contact with the edge portion carrying release agent in the second region, and the edge portion carrying resealable adhesive in the second region is brought in contact with the adhesive-free edge portion in the first region, thus forming a pocket. When the packaging unit is folded around the second folding axis, the edge portion carrying resealable adhesive in the third region is brought in contact with the outer surface of the packaging unit in the first region, thus forming a lid. Such a folding of a packaging unit is commonly referred to as e-folding.

It has been discovered that providing release agent on one of the edge portions of the second region, while keeping the adhesive-free edge portions of the first and the third region free from release agent, provides a packaging unit having advantageous properties when considering adhesive strength and reclosability of the packaging unit.

A suitable resealable adhesive to be used with the packaging unit of the present invention is pressure-sensitive hotmelt adhesive, e.g. PT231 F from Savaré having an unlimited open time, meaning that the adhesive can bond to another substrate at any time. The total weight of the resealable adhesive in the first, second and third regions may be 0.05-0.1 g.

The pressure-sensitive adhesive used with the packaging unit is one which has a very high self-adhesion but which can be readily separated or released from other materials, such as plastic materials or paper which has been treated with a release agent. A major advantage of the packaging unit according to the present invention is that it can be completely unfolded when a new hygiene article is about to be taken out. In contrast thereto, prior art packages having adhesively sealed edges with adhesive-coated edge portions being in contact with each other have too high adhesive strength of the adhesively sealed edges, and any attempt to completely unfold the package would lead to tearing and breakage of the packaging unit, making it unusable for discrete and hygienic disposal of the used article. As the adhesive-coated edge portions of the packaging unit of the present invention are not in contact with each other when the packaging unit is folded, the packaging unit can be readily opened and resealed, providing a tight disposal package. At the same time, due to the presence of release agent in the second region, tensile strength of the adhesively sealed edges of the pocket of the packaging unit using the adhesive pattern of the present invention is sufficient to provide a tight package for both a new and a used article, and low enough to provide a readily-opened package.

Using a release agent in the second region of the packaging unit permits the provision of a packaging unit comprising an adhesive having adequate strength to keep the packaging unit tightly sealed prior to opening, while the packaging unit may still be opened without using unduly high forces, potentially destroying the packaging unit and making it unsuitable for disposal purposes, and at the same time strength sufficient to form a tight packaging unit when the packaging unit is resealed.

Moreover, addition of the release agent prevents migration of the adhesive, which means that the adhesive remains in its original position when the packaging unit is opened, rather than being transferred to the surface being with contact with the edge portion carrying adhesive when the packaging unit is sealed. Such a migration of adhesive is undesirable, since it increases the pulling force needed to open the packaging unit, and deteriorates the reclosability of the packaging unit when the packaging unit is resealed, since the migrated adhesive may form lumps, thus reducing the adhesive area available for formation of the resealed adhesive bond.

The release agent may form a coating covering the entire adhesive-free edge portion of the second region of the packaging unit. Also, the release agent may be applied in a pattern throughout the entire length of the adhesive-free edge portion of the second region. The pattern may be continuous, such as spiral, wave, zigzag, helix, or intermittent, such as lines, dots, crosses, stars, squares. Further, it is conceivable that the release agent is arranged on a section of the adhesive-free edge portion of the second region. The area of the section covered with a release agent may constitute 10-90% of the total area of the adhesive-free edge portion of the second region, preferably 20-85%, more preferably 60-75% of the total area of the adhesive-free edge portion of the second region.

The release agent useful in the present invention may be a silicone-based release agent, or low-adhesion backsize coating (known as LAB coatings), exemplified by, but not limited to, those disclosed in WO99/11683, U.S. Pat. No. 5,571,586 or U.S. Pat. No. 7,004,320. In general, the invention is carried out by coating paper or plastic film with a nonstick coating, sometimes termed a release coating, such as a silicone polymer coating or a polysiloxane. Polysiloxanes are particularly useful non-stick coatings, and both solvent-based and solvent-free polysiloxanes can be used. The polysiloxanes are cured either thermally or by radiation.

In order to provide a packaging unit having an optimal compromise between the adhesive strength when the packaging unit is sealed, and the pulling force needed to open the packaging unit, an intensive investigation has been carried out, as will be described in greater detail below. It has been found that the user perceives the packaging unit as securely sealed prior to opening, and at the same time find the packaging unit to be easily opened when the total adhesive force between the inner edge portion in the first region and the inner edge portion in the second region, and between the outer edge portion in the first region and the outer edge portion in the second region, i.e. the adhesive strength of the pocket, is 0.5-2.5 N, preferably 1.5-2 N.

Preferably, the adhesive force between the edge portion carrying adhesive in the third region and the outer surface of the first region, i.e. the adhesive strength of the lid, is the same or sufficiently the same as the adhesive strength of the pocket, which makes the packaging unit to be perceived as being opened smoothly and evenly. Thus, the adhesive force between the edge portion in the third region being provided with adhesive and the outer surface of the first region may be 0.5-2.5 N, preferably 1.5-2 N. However, the adhesive strength of the lid may be different from the adhesive strength of the pocket.

The prevailing shape of the sheet of material for forming a packaging unit is square or rectangular. Such a sheet according to the present invention has side edges, referred to herein as longitudinal edges, transverse edges and corner portions, the edge zones of the first and second regions of the sheet of material being arranged along the longitudinal edges. The edge portions covered with adhesive, the adhesive-free portions and the portions carrying a release agent are thus positioned along the longitudinal edges. In order to avoid that the edges of the sheet curl up or crinkle when the packaging unit is opened, the adhesive provided on the outer edge portions may be positioned at a distance from the longitudinal edges. This distance may be between 0.5-5 mm, preferably between 1-3 mm.

The width of the adhesive-covered edge portions may be varied depending on the adhesive strength desired. The wider the adhesive-covered edge zones, the stronger the sealing. The width of the adhesive-covered edge portions may be same or different in the different regions. Moreover, the amount of the resealable adhesive may be same or different in different regions.

The length of the adhesive-covered edge portions in each region may be equal to the length of each region, or may be 0.1-1 millimetres shorter than the length of each region.

Preferably, the length of the adhesive-covered edge portions in each region is equal to the length of each region.

Further, at least one of the transverse edges of the packaging unit according to the present invention is preferably provided with adhesive. In order to facilitate opening, at least one of the corner portions may be free from adhesive such that a gripping tab is formed.

The sheet for forming a packaging unit may be a single ply sheet of any suitable material known to the person skilled in the art, such as polyethylene film or nonwoven. The sheet may also be a laminate comprising at least two distinct layers. Laminates suitable for packaging of hygiene articles are assumed to be known to the person skilled in the art, and are not in any way limiting for the present invention.

If desired, the sheet for forming a packaging unit according to the present invention may be opaque in order to disguise the contents of the packaging unit, which is particularly important if the used article wrapped into the packaging unit of the present invention cannot be disposed immediately after replacement. Further, the sheet may comprise print, which may be beneficial for attracting the user's attention and improving the user's mood.

The sheet of material forming a packaging unit according to the present invention may comprise an odour-inhibiting or odour-neutralising substance. Such a substance may be applied in any suitable manner known to the person skilled in the art, e.g. as coating, activatable microcapsules, impregnated patches or the like.

It is conceivable that the sheet for forming a packaging unit according to the present invention may be stretchable or expandable, which may be advantageous if the hygiene article is greatly deformed during use, and may thus be difficult to wrap without deforming the packaging unit.

The packaging unit for hygiene articles according to the present invention may is formed by a method comprising the steps of:

• • a) providing a sheet having an inner surface and an outer surface, the inner surface comprising an edge zone comprising an inner edge portion and an outer edge portion, the sheet having two folding axes dividing the sheet into a first region, a second region, and a third region;
  • b) providing one of the inner edge portion and the outer edge portion of the edge zone of the second region with resealable adhesive, such that the other of the inner edge portion and the outer edge portion of the edge zone of the second region is adhesive-free;
  • c) providing one of the inner edge portion and the outer edge portion of the edge zone of the first region and one of the inner edge portion and the outer edge portion of the edge zone of the third region with resealable adhesive in a complementary manner to the edge portion of the second region being provided with resealable adhesive; such that a chessboard pattern of resealable adhesive is formed along the edge zone; and such that the other of the inner edge portion and the outer edge portion of the edge zone of the first region and the other of the inner edge portion and the outer edge portion of the third region are adhesive-free;
  • d) providing the adhesive-free edge portion of the edge zone of the second region with a release agent;
  • e) folding the sheet about the first folding axis, such that the edge portion carrying resealable adhesive in the first region is brought in contact with the edge portion carrying release agent in the second region; and the edge portion carrying resealable adhesive in the second region is brought in contact with the adhesive-free edge portion in the first region;
  • f) folding the sheet about the second folding axis, such that the edge portion carrying resealable adhesive in the third region is brought in contact with the outer surface of the first region.

It should be noted that steps b) and c) may be performed simultaneously. Further, step d) may be performed after step a), thus giving an alternative method for forming a packaging unit for hygiene articles according to the present invention, wherein the method comprises the steps of:

• • a) providing a sheet having an inner surface and an outer surface, the inner surface comprising an edge zone comprising an inner edge portion and an outer edge portion, the sheet having two folding axes dividing the sheet into a first region, a second region, and a third region;
  • b) providing one of the inner edge portion and the outer edge portion of the edge zone of the second region with a release agent;
  • c) providing the other one of the inner edge portion and the outer edge portion of the edge zone of the second region being free from release agent with resealable adhesive;
  • d) providing one of the inner edge portion and the outer edge portion of the edge zone of the first region and one of the inner edge portion and the outer edge portion of the edge zone of the third region with resealable adhesive in a complementary manner to the edge portion of the second region being provided with resealable adhesive; such that a chessboard pattern of resealable adhesive is formed along the edge zone; and such that the other of the inner edge portion and the outer edge portion of the edge zone of the first region and the other of the inner edge portion and the outer edge portion of the third region are adhesive-free;
  • e) folding the sheet about the first folding axis, such that the edge portion carrying resealable adhesive in the first region is brought in contact with the edge portion carrying release agent in the second region; and the edge portion carrying resealable adhesive in the second region is brought in contact with the adhesive-free edge portion in the first region;
  • f) folding the sheet about the second folding axis, such that the edge portion carrying resealable adhesive in the third region is brought in contact with the outer surface of the first region.

It should be noted that steps c) and d) may be performed simultaneously.

Consequently, when a packaging unit comprising two folding axes is folded, the adhesive-covered edge portions of the first region are brought into contact with the edge portions of the second region carrying release agent, and the adhesive-covered portions of the second region are brought into contact with the adhesive-free portions of the first region, thus forming a pocket. The subsequently folded third region is folded over the outer surface of the first region and the adhesive-covered edge portions of the third region are brought into contact with the adhesive-free outer surface of the first region, thus forming a lid. The folding order may be reversed, i.e. the adhesive-covered edge portions of the second region are brought in contact with the adhesive-free portions of the third region, and the adhesive-covered portions of the third region are brought in contact with the portions of the second region carrying the release agent. The lid may be formed by folding the first region over the outer surface of the third region. The adhesive pattern according to the present invention thus has the advantage of giving the user the possibility to fold the packaging unit in any order when resealing the packaging unit, and still obtain a liquid- and odour-tight package, ensuring that the used article is disposed of in a discrete and hygienic manner. Further, when the packaging unit of the present invention is used for disposal, the user may choose to roll the packaging unit instead of folding it.

The present invention also relates to a web of material for forming packaging units for hygiene articles, wherein the packaging units are formed by cutting the web into sheets of appropriate size. The web of material of the present invention has a longitudinal direction running along a longitudinal central axis and a transverse direction perpendicular to the longitudinal direction, and comprises a plurality of transverse cutting zones arranged along a respective central cutting axis running in the transverse direction of the web. The transverse cutting zones are positioned at a distance from each other in the longitudinal direction of the web. Each of said transverse cutting zones comprises a central portion and a first and a second peripheral portion arranged on either side of the central portion in the transverse direction. At least a section of the central portion of each of the transverse cutting zones of the web is provided with a release agent.

The release agent may be provided along the entire length of the central portion of the transverse cutting zone, or may be provided at a section of the central portion of the transverse cutting zone, as described above.

Of course, each of the transverse cutting zones may be provided with resealable adhesive in at least a section of the transverse cutting zone being free from release agent, such that the section provided with a resealable adhesive in the central portion of the transverse cutting zone is displaced in the longitudinal direction in relation to the sections provided with a resealable adhesive in the first and the second peripheral portions of the transverse cutting zone. In other words, a chessboard pattern of resealable adhesive is formed along each of the transverse cutting zones.

The web according to the present invention may be made of any material suitable for manufacturing packaging units, i.e. a plastic film, a nonwoven, a laminate, or any other material known to the person skilled in the art.

The dimensions of a web of material of the present invention may vary depending on the size of the packaging units to be manufactured. Most typically, the web of material is in the form of a roll having a length of several hundred meters in the longitudinal direction, and a width in the transverse direction of 10-50 cm, preferably 15-40 cm, more preferably 20-30 cm.

The dimensions of the transverse cutting zone may vary depending on the size of the packaging unit to be manufactured, and on the adhesive strength required. The transverse cutting zone may have a width in the longitudinal direction of the web of 0.5-5 cm, preferably 1-4 cm, more preferably 2-3 cm. The length of the transverse cutting zone in the transverse direction of the web equals the width of the web of material in the transverse direction of the web.

The present invention further relates to a manufacturing method for providing a web of material for forming packaging units for hygiene articles, comprising the steps of:

• • a) providing a web of material having a longitudinal direction running along a longitudinal central axis and a transverse direction perpendicular to the longitudinal direction, the web running in machine direction (MD) such that the longitudinal direction of the web coincides with the MD, the web comprising a plurality of transverse cutting zones, each of the transverse cutting zones being arranged along a central cutting axis running in the transverse direction of the web, the transverse cutting zones being positioned at a distance from each other in the longitudinal direction of the web; each of the transverse cutting zones comprising a central portion and a first and a second peripheral portion arranged on either side of the central portion in the transverse direction of the web;
  • b) providing at least a section of the central portion of each of the transverse cutting zones of the web with a release agent in the transverse direction of the web;
  • c) providing at least a section of the remaining portion of each of the transverse cutting zones of the web with resealable adhesive in the transverse direction of the web; such that the section provided with a resealable adhesive in the central portion of the transverse cutting zone is displaced in the longitudinal direction in relation to the sections provided with a resealable adhesive in the first and the second peripheral portions of the transverse cutting zone;
  • d) cutting the web through the transverse cutting zones along the central cutting axes.

Of course, steps b) and c) may be carried out in any order, i.e. the web of material may first be provided with a resealable adhesive, and then with the release agent on the sections of the central portion of the transverse cutting zones being free from the resealable adhesive.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will now be described by way of example only and with reference to the accompanying drawings, of which:

FIG. 1 shows a packaging unit according to the present invention;

FIG. 2 depicts the packaging unit depicted in FIG. 1 in a folded state;

FIGS. 3 and 4 illustrate a web of material for manufacturing packaging units according to the present invention;

FIG. 5 shows a graphic representation of the glue amount on different samples of the packaging units;

FIG. 6 shows a graphic representation of the adhesive force of the pocket of different samples of the packaging units;

FIG. 7 shows a graphic representation of the adhesive force of the lid of different samples of the packaging units;

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The packaging unit 1 depicted in FIG. 1 is a rectangular sheet comprising a first folding axis 9 and a second folding axis 9′ dividing the packaging unit into a first region 10, a second region 11 and a third region 12. Each of the regions comprises an inner edge portion 5, 5′, 5″ and an outer edge portion 6, 6′, 6″. As shown in FIG. 1, the outer edge portions 6, 6″ of the first and third regions respectively are provided with resealable adhesive 7, while the inner edge portions 5, 5″ of the first and third regions respectively are adhesive-free. The adhesive pattern of the second region 11 is complementary to the adhesive pattern of the first and third regions 10, 12, thus forming a chessboard pattern. In other words, the inner edge portion 5′ of the second region 11 is provided with resealable adhesive 7, and the outer edge portion 6′ of the second region 11 is adhesive-free and is provided with a release agent 22. This in turn means that, when the sheet is e-folded about the first and second folding axes 9, 9′ as shown in FIG. 2, the outer edge portions 6 of the first region 10 or the outer edge portions 6″ of the third region 12 carrying resealable adhesive 7 are brought in contact with the outer edge portions 6′ carrying the release agent 22 in the second region 11, depending on which of the first and the third regions 10, 12 is brought in contact with the second region 11. Consequently, the inner edge portions 5′ carrying resealable adhesive 7 in the second region 11 are brought into contact with the adhesive-free inner edge portions 5 of the first region 10 or the adhesive-free inner edge portions 5″ of the third region 12. As can be seen from FIG. 2, the width of the sealing area corresponds to the sum of the widths of the adhesive portions 5′, 6. It should be noted that the order in which the packaging unit is folded is irrelevant. For example, the packaging unit may be folded around the second folding axis 9′, bringing the third region 12 in contact with the second region 11, sealing the outer edge portions 6″, 6′ and the inner edge portions 5″, 5′ and forming a pocket. The packaging unit is subsequently folded around the first folding axis 9, bringing the first region 10 in contact with the outer surface of the third region 12, thus forming a lid and sealing the packaging unit (FIG. 2). The folding order may also be reversed. This is a great advantage, since when the packaging unit of the present invention is used for disposal, the user does not have to fold the packaging unit in any particular order to be able to obtain a tightly sealed package. The packaging unit will provide a tight and hygienic package regardless of the folding order. Also, the user may choose to roll the packaging unit rather than folding it.

The packaging unit depicted in FIG. 1, wherein the release agent is provided in the edge zone of the second region only, has the advantage of having an optimal adhesive strength and reclosability, which will be discussed in greater detail below.

In order to obtain a tight package, the transverse edges 4′ and 4* of the packaging unit 1 are provided with resealable adhesive 7. When both transverse edges 4′ and 4* are provided with adhesive, the folding order is irrelevant, as described above. It is also conceivable to provide only one of the transverse edges 4′, 4* with resealable adhesive 7. In this case, the folding must be initiated around the folding axis being positioned closest to the adhesive-free transverse edge, such that the region comprising the adhesive-covered transverse edge portion forms a lid and such that the resealable adhesive positioned at the transverse edge portion seals the packaging unit.

In order to facilitate the opening of the package, the adhesive-covered portions may be positioned such that at least one of the corner portions 21 of the packaging unit 1 is adhesive-free, thus forming a gripping tab that is gripped by the user upon opening the package. Moreover, the adhesive-free corner portion 21 serves as an evacuation opening when the packaging unit is sealed (FIG. 2).

FIG. 3 depicts a web of material 501 suitable for manufacturing packaging units according to the present invention after step b) of the manufacturing method for providing a web of material for forming packaging units for hygiene articles. The web of material has a longitudinal direction running along a longitudinal central axis 508 and a transverse direction perpendicular to the longitudinal direction. The web 501 comprises a plurality of transverse cutting zones 502, each being arranged along a respective central cutting axis 503 running in the transverse direction of the web. The transverse cutting zones 502 are positioned at a distance from each other in the longitudinal direction of the web 501. Each of the transverse cutting zones comprises a central portion 505 and a first and a second peripheral portion 504, 504′ arranged on either side of the central portion 505 in the transverse direction of the web. As shown in FIG. 3, the central portion 505 of the transverse cutting zone 502 is provided with a release agent.

FIG. 4 illustrates the web of material 501 after the resealable adhesive has been applied to the web of material 501, i.e. after step c) of the manufacturing method for providing a web of material for forming packaging units for hygiene articles. The web of material 501 is provided with resealable adhesive in sections of the transverse cutting zone 602 being free from release agent, such that a chessboard pattern of is formed in a manner described above. Thus, section 511 of the central portion 505 of the transverse cutting zone 502, as well as sections 506 and 506′ of the first and the second peripheral portions 504, 504′ of the transverse cutting zone 502 are provided with adhesive. When the web of material 501 is cut along the central cutting axes 503, the packaging units similar to the ones depicted in FIG. 1 are formed.

Method for Measuring the Adhesive Force of the Packaging Unit

The method is intended to determine the force required to open the packaging unit when the edge portions described above have been sealed by means of the resealable adhesive. Adhesive force is specified as the Average Load between Extension Limits, the force required to separate glue-to-release agent or glue-to-material of a packaging unit. Measurements have been made both on newly produced and aged packaging units.

Equipment

• • Tensile tester, 20 N load cell, crosshead speed 500 mm/min

Distance between clamps	25	mm
Crosshead movement	80	mm
Clamps for tensile tester	60	mm wide
The calculation of Average Load between Extension	15-65	mm
Limits from the tensile curve is done between

• • Heat cupboard 40±3° C.
  • Pieces of paper, approx. 60×30 mm.
  • Double-sided tape, approx. 5 mm wide.

Sample Preparation

The adhesive must be allowed to stabilize before the tests are conducted.

• • For measurements on newly produced samples, the samples should be stored for at least one week from the production occasion at room temperature.
  • Alternatively, for measurement on newly produced samples, the samples should be stored for 24±1 hours in a heat cupboard at 40° C. The samples should be allowed to acclimatize to the ambient temperature for at least one hour prior to measurements.
  • Aging is simulated by storing the samples in a heat cupboard at 40° C. for four weeks; analogous to the above, the samples should be allowed to acclimatize to the ambient temperature for at least one hour prior to measurements.

Procedure

The pre-tension is between −0.100 N and +0.100 N in both pull tests.

Pull 1, testing of the first product opening, i.e. opening of the region forming the lid according to the above:

• • Put double-sided tape along one of the longitudinal edges of a piece of paper;
  • Attach the tape carrying the piece of paper to the inner surface of the packaging unit at the central portion of the transverse edge;
  • Center and secure the product in the lower clamp. Secure the piece of paper in the upper clamp;
  • If necessary, adjust the pre-tension to the correct level by changing the position of the piece of paper in the clamp;
  • Perform Pull 1 test.

Pull 2, testing of the second product opening, i.e. opening of the region forming the pocket according to the above:

• • Open the remaining section of the lid such that the packaging unit is unfolded around the second folding axis, and fold the lid such that the transverse edge of the lid is parallel to the second folding axis;
  • Insert the folded lid of the packaging unit and the hygiene article arranged inside the packaging unit into the lower clamp, such that the upper edge of the lower clamp is aligned with the second folding axis, and secure it;
  • Open the transverse adhesive seam of the packaging unit only up to the remaining glued seams in the second and third regions of the packaging unit;
  • Secure the released transverse edge of the packaging unit in the upper clamp without securing any part of the hygiene article;
  • Adjust the pre-tension; e.g. by manually folding away the sections of the secured product that press against the upper clamping yoke;
  • Perform Pull 2 test.

Method for Measuring Reclosability

This method relates to visual evaluation of how many packaging units remain sealed after a given time interval from the occasion of placing a used hygiene article in the packaging unit and sealing the edge portions. A dark-colored (black) cylinder is placed in the packaging unit and the edge portions are sealed by a pressing unit. The samples are checked visually after a given time, and the number and/or percentage of samples that are still sealed is reported.

Equipment

• • Foam cylinders made of polyurethane foam, with outer diameter=25 mm, and length=60 mm
  • Timer, accuracy ±0.3 sec
  • Pressing unit equipped with:
    • Pressing plate, 50×25 mm ±0.5 mm;
    • Anvil, 70×25 mm ±0.5 mm
  • Plate and anvil covered with foam and Teflon tape.
  • Pressure force 100 N ±5 N
  • Pressing time 3 seconds ±1 sec
  • Stretching tool, each fork pin being 8×1.5 mm ±1 mm
  • Digital dynamometer with load cell >100 N, type Mecmesin AFTI or equivalent

Procedure

Before the test starts, check that the pressure force as well as pressure time of the pressing unit is according to the specifications.

It is recommended to test 75 samples in each sample group.

• • Gently open the packaging unit, remove the hygiene article, and make sure that the packaging unit is not damaged. Gently spread out the packaging unit on a flat surface making sure that the packaging unit doesn't wrinkle.
  • Place the cylinder at the transverse edge of the packaging unit. Make sure that the cylinder is placed at the same transverse edge for all the samples.
  • Wrap the cylinder in the packaging unit by rolling the cylinder, making sure that the longitudinal edge portions do not wrinkle or fold. Perform this step on all the samples before sealing the edges.
  • Divide the samples into 5 samples groups.
  • Place the tip of the fork pins of the stretching tool inside the opening formed at one of the transverse edges of the packaging unit.
  • Stretch out as many of the wrinkles as possible, and pre-seal the opening by manually gently pressing the transverse edges together.
  • Repeat the procedure on the other transverse edge of the packaging unit.
  • Place one of the pre-sealed transverse edges between the pressing plates. It is desirable to press as much of the packaging unit material as possible without squeezing the foam cylinder inside. The transverse edge of the packaging unit should at maximum be aligned with the inner edge of the pressing plate.
  • Press the start button and wait until the pressing unit has performed one complete cycle. Turn around the sample immediately and seal the other transverse edge.

Start a timer set to 10 minutes (tolerance −1/+2 min). After 10 minutes check the status of the sealed edges. The status is checked according to the following procedure:

• • Lift each of the samples and inspect both transverse edges by slightly twisting and turning the sample around. Be careful not to disturb the sealed edges.
  • If the cylinder is visible at any of the transverse edges when making a quick overview, the sample is considered to be open and is rejected from further inspection.
  • Note the result, replace the sample at the table and start a timer set to 50 minutes (tolerance ±5 min). Repeat the 60 minutes status check of the sealed edges, discard the samples that are already open.
  • Report the number of samples that remained closed after 10 and 60 minutes versus the number of tested samples.
  • Calculate the amount of closed samples in percentage (%), by whole numbers

$\%=\frac{{\mathrm{Samples}}_{\mathrm{closed}}}{{\mathrm{Samples}}_{\mathrm{total}}}·100$

Results

All the samples have the chess-board adhesive pattern depicted in FIG. 1. The amount of adhesive is varied in the different regions. Thus, in the first region 10 and the third region 12, the adhesive amount at the outer edge portions 6 and 6″ is 18 gsm, while the adhesive amount is 10 gsm at the inner edge portions 5′ of the second region, and 20 gsm at the transverse edge portions 4′ and 4*. The total amount of adhesive does not differ significantly between different samples (FIG. 5). Hence, the adhesive amount should not influence the adhesive force or reclosability results.

In the reference samples the packaging unit is free from release agent. In the samples S1-S3, the outer edge portion 6′ in the second region 11 is provided with release agent. The area of the outer edge portion 6′ of the second region 11 being provided with release agent is 25% in sample S1, 60% in S2, and 75% in S3.

Pull 1

The release agent added to S1-S3 should not influence the adhesive force of the lid, since the release agent applied at the inner surface of the second region does not affect the adhesive force between the adhesive in the third region and the outer surface of the first region of the packaging unit.

The results, shown in FIG. 6, confirm this assumption, even though there are some differences within each of the groups of samples, which most likely depend on migration of the adhesive.

Pull 2

The release agent added to S1-S3 should influence the adhesive force of the pocket. The release agent arranged at the outer edge portions 6′ in the second region will be in contact with the adhesive at the outer edge portions 6 in the first region, or the adhesive at the outer edge portion 6″ in the third region, depending on whether the packaging unit is folded around the first or the second folding axis.

Further, it is assumed that the adhesive force of the lid is somewhat lower compared to the adhesive force of the pocket, given the fact that the pocket is formed by adhering two edge portions carrying resalable adhesive, wherein the adhesive edge portion will be positioned adjacent to each other when the packaging unit is folded, while the lid is formed by adhering only one edge portion carrying adhesive. As was mentioned above, the adhesive strength of the adhesively sealed seam depends on the total width of the adhesive seam, which in turn is a sum of the widths of the adjacent adhesive-carrying edge portions.

The results are depicted in FIG. 7, wherein it is clearly seen that the reference samples has the highest adhesive force, while samples S1-S3 show a significantly lower adhesive force. Analogous with the values in Pull 1-tests, the major contributor to variations within each of the groups of samples is probably adhesive migration. Also, when comparing the results shown in FIGS. 6 and 7, it may be seen that the adhesive force of the pocket is higher than the adhesive force of the lid, in line with the assumption above. As mentioned earlier, it is desirable to provide a packaging unit having the values of adhesive forces of the lid and the pocket as close to each other as possible, such that the opening of the packaging unit is perceived as smooth and even by the user.

	TABLE 1
	Silicone	Adhesive force (N)	Reclosability (%)	Adhesive
Sample	area (%)	Pull 1	Pull 2	10 min	1 h	weight (g)
Ref	0	0.72	3.38	60	44	0.071
S1	25	0.75	1.92	60	36	0.069
S2	60	0.70	2.11	88	28	0.070
S3	75	0.62	2.00	80	64	0.070

As may be seen in Table 1, the Pull 1 values, indicating the adhesive strength of the lid, are substantially the same for all the samples, which confirms the assumption that the release agent arranged at the inner surface of the second region does not affect the adhesive strength of the lid being attached to the outer surface of one of the first and the third regions, as discussed above.

Pull 2 values shown in Table 1 clearly indicate that the adhesive strength of the pocket, i.e. adhesive strength between the inner surface of the edge portion of the second region and the inner surface of the edge portion of one of the first and the third regions, is significantly lower for samples S1-S3 compared to the reference samples. The conclusion that may be drawn from these results is that the addition of the release agent to one of the edge portions of the second region lowers the adhesive force of the pocket, which in turn facilitates opening of the pocket. Moreover, since the adhesive force of the lid (Pull 1) and the adhesive force of the pocket (Pull 2) do not differ as much in samples S1-S3 as in the reference samples, the opening of the packaging unit is perceived by the user as being even and smooth.

Another important factor to consider when assessing the adhesive force of the pocket and the lid is reclosability, i.e. the ability of the packaging unit to become and remain sealed after the user has placed a used hygiene article in the packaging unit. As may be seen in

Table 1, 60% of the reference and S1-samples remained sealed after 10 min. A significantly higher fraction of samples S2 and S3 remained sealed after 10 min, 88% and 80%, respectively. A possible explanation of this result is that the addition of a higher amount of release agent prevents migration of the adhesive, which means that the adhesive remains in its original position when the packaging unit is opened for the first time, rather than being transferred to the surfaces being in contact with the adhesive when the packaging unit is sealed. Such a transfer of the adhesive causes an uneven distribution of the adhesive, which in turn deteriorate reclosability.

Comparing now the reclosability results for 1 h, it may be concluded that the addition of the highest amount of release agent provides the best results regarding the ability of the resealed packaging unit to remain sealed. Thus, 64% of samples S3 remained sealed after 1 h, compared to 44% for the reference samples, 36% for S1 and 28% for S2. This confirms the assumption that the higher amount of the release prevents adhesive migration thus improving reclosability.

Although the present invention has been described with reference to various embodiments, those skilled in the art will recognise that changes may be made without departing from the scope of the invention. It is intended that the detailed description be regarded as illustrative and that the appended claims including all the equivalents are intended to define the scope of the invention.

Claims

1-22. (canceled)

23. A packaging unit for hygiene articles, the unit being formed from a sheet of material, said sheet having an inner surface and an outer surface, said inner surface comprising an edge zone comprising an inner edge portion and an outer edge portion, said sheet having two folding axes, dividing said sheet into a first region, a second region and a third region, wherein said packaging unit may be folded along said folding axes with said first, second and third regions in an overlapping configuration, wherein

one of said inner edge portion and said outer edge portion of said edge zone of said second region is provided with resealable adhesive, and the other of said inner edge portion and said outer edge portion of said edge zone of said second region is adhesive-free and is provided with a release agent;

one of said inner edge portion and said outer edge portion of said edge zone of said first region and one of said inner edge portion and said outer edge portion of said edge zone of said third region are provided with resealable adhesive in a complementary manner to said edge portion being provided with adhesive in said second region such that a chessboard pattern of resealable adhesive is formed along said edge zone; and

the other of said inner edge portion and said outer edge portion of said edge zone of said first region and the other of said inner edge portion and said outer edge portion of said edge zone of said third region are free from resealable adhesive and from release agent.

24. The packaging unit according to claim 23, wherein the area of said adhesive-free edge portion of said second region being covered with the release agent constitutes 10-90% of said adhesive-free edge portion of said second region.

25. The packaging unit according to claim 23, wherein a release agent is provided along the entire length of said adhesive-free edge portion of said second region.

26. The packaging unit according to claim 23, wherein the release agent is applied in a continuous pattern or as a coating.

27. The packaging unit according to claim 23, wherein the release agent is applied in an intermittent pattern.

28. The packaging unit according to claim 23, wherein the total adhesive force between said inner edge portion in said first region and said inner edge portion in said second region, and between said outer edge portion in said first region and said outer edge portion in said second region is 0.5-2.5 N.

29. The packaging unit according to claim 23, wherein the total weight of said resealable adhesive in said first, second and third regions is 0.05-0.1 g.

30. The packaging unit according to claim 23, wherein the release agent is a silicone polymer or a polysiloxane.

31. The packaging unit according to claim 23, wherein said packaging unit is of substantially rectangular shape and comprises longitudinal edges, transverse edges and corner portions, said edge zones of said first, second and third regions of said sheet of material being arranged along said longitudinal edges.

32. The packaging unit according to claim 23, wherein said packaging unit comprises transverse edge zones and wherein at least a portion of one of said transverse edge zones is provided with resealable adhesive, while the remaining portion of said transverse edge zone is adhesive-free.

33. The packaging unit according to claim 32, wherein at least a section of said adhesive-free transverse edge portion is provided with a release agent.

34. The packaging unit according to claim 23, wherein said resealable adhesive is a pressure-sensitive hotmelt adhesive with unlimited open time.

35. The packaging unit according to claim 23, wherein said packaging unit is reclosable.

36. A series of packaging units according to claim 23, wherein said packaging units have been reclosed, and wherein 50%-100% of said reclosed packaging units in said series of reclosed packaging units remain sealed after 10 min from the reclosing occasion.

37. A method of forming a packaging unit for hygiene articles from a sheet of material, comprising the steps of:

providing a sheet having an inner surface and an outer surface, said inner surface comprising an edge zone comprising an inner edge portion and an outer edge portion, said sheet having two folding axes, said folding axes dividing said sheet into a first region, a second region, and a third region;

providing one of said inner edge portion and said outer edge portion of said edge zone of said second region with a release agent;

providing the other one of said inner edge portion and said outer edge portion of said edge zone of said second region being free from said release agent with resealable adhesive;

providing one of said inner edge portion and said outer edge portion of said edge zone of said first region and one of said inner edge portion and said outer edge portion of said edge zone of said third region with resealable adhesive in a complementary manner to said edge portion of said second region being provided with resealable adhesive; such that a chessboard pattern of resealable adhesive is formed along said edge zone; and such that the other of said inner edge portion and said outer edge portion of said edge zone of said first region and the other of said inner edge portion and said outer edge portion of said third region are adhesive-free;

folding the sheet about said first folding axis, such that the edge portion carrying resealable adhesive in said first region is brought in contact with the edge portion carrying release agent in said second region;

folding the sheet about said second folding axis, such that the edge portion carrying resealable adhesive in said third region is brought in contact with the outer surface of said first region.

38. A web of material for forming packaging units for hygiene articles, said web of material having a longitudinal direction running along a longitudinal central axis and a transverse direction perpendicular to the longitudinal direction, said web comprising a plurality of transverse cutting zones, each of said transverse cutting zones being arranged along a respective central cutting axis running in said transverse direction of said web, said transverse cutting zones being positioned at a distance from each other in said longitudinal direction of said web, each of said transverse cutting zones comprising a central portion and a first and a second peripheral portion arranged on either side of said central portion in said transverse direction of said web, wherein

a section of each of said central portion, said first and said second peripheral portion of each of said transverse cutting zones of said web are provided with a release agent, and

each of said transverse cutting zones is provided with resealable adhesive in a section of each of said central portion, said first and said second peripheral portion of said transverse cutting zone being free from release agent, such that said section provided with a resealable adhesive in said central portion of said transverse cutting zone is displaced in said longitudinal direction in relation to the said sections provided with a resealable adhesive in said first and said second peripheral portions of said transverse cutting zone, such that a chessboard pattern of resealable adhesive is formed along each of the transverse cutting zones.

39. The web of material according to claim 38, wherein said material is a plastic film, a nonwoven web or a laminate.

40. The web of material according to claim 38, wherein said web of material has a width in said transverse direction of 10-50 cm.

41. The web of material according to claim 38, wherein said transverse cutting zone has a width in said longitudinal direction of said web of 0.5-5 cm.

42. A manufacturing method for providing a web of material for forming packaging units for hygiene articles, comprising the steps of:

a) providing a web of material having a longitudinal direction running along a longitudinal central axis and a transverse direction perpendicular to the longitudinal direction, said web running in machine direction (MD) such that said longitudinal direction of said web coincides with said MD, said web comprising a plurality of transverse cutting zones, each of said transverse cutting zones being arranged along a central cutting axis running in said transverse direction of said web, said transverse cutting zones being positioned at a distance from each other in said longitudinal direction of said web, each of said transverse cutting zones comprising a central portion and a first and a second peripheral portion arranged on either side of said central portion in said transverse direction of said web;

b) providing a section of said central portion, said first and said second peripheral portion of each of each of said transverse cutting zones of said web with a release agent in said transverse direction of said web;

c) providing a section of each of said central portion, said first and said second peripheral portion of the remaining portion of each of said transverse cutting zones of said web being free from release agent with resealable adhesive in said transverse direction of said web, such that said section provided with a resealable adhesive in said central portion of said transverse cutting zone is displaced in said longitudinal direction in relation to the said sections provided with a resealable adhesive in said first and said second peripheral portions of said transverse cutting zone, such that a chessboard pattern of resealable adhesive is formed along each of the transverse cutting zones.

d) cutting said web through said transverse cutting zones along said central cutting axes, wherein steps b) and c) are carried out in any order.