LAMINATED FABRIC

- KURARAY CO., LTD.

To provide a laminated fabric having an air permeability and a filtering capability, the laminated fabric includes a supporting layer and a protective layer bonded together. The protective layer includes a stretchable nonwoven fabric comprises an ultra-fine fiber. This laminated fabric has an air permeability of 2 cc/cm2/sec. or higher and a 1 μm quartz dust collecting efficiency of 90% or higher. The laminated fabric may also have a water resistant layer which is positioned on the protective layer so that the protective layer is employed as an intermediate layer between the water resistant layer and the supporting layer.

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Description
CROSS REFERENCE TO THE RELATED APPLICATIONS

This application is based on and claims Convention priority to Japanese application No. 2007-066496, filed Mar. 15, 2007, the entire disclosure of which is herein incorporated by reference as a part of this application.

FIELD OF THE INVENTION

The present invention relates to a laminated fabric (or a multi-layered fabric) having a sufficient strength, an air permeability and a filtering capability, and more particularly, to the laminated fabric of a kind capable of being easily reduced in volume at a low cost.

BACKGROUND ART

In order to protect human bodies from harmful and/or hazardous substances such as dust harmful to human bodies, contagions and viruses, and/or in order to avoid secondary infection resulting from infected mediums having one or some of the hazardous substances adhering thereto, various protective materials are utilized. Such protective materials are required to have not only a filtering capability for effectively removing the harmful and/or hazardous substances, but also an air permeability to minimize the discomfort which the user may feel when the protective material is brought into direct contact with the user's body. However, since the filtering capability and the air permeability are properties incompatible with each other, and therefore, it is difficult to fulfill both the filtering capability and the air permeability at the same time.

By way of example, Patent Document 1 listed below discloses a composite nonwoven fabric as a protective clothing material, which comprises a nonwoven fabric having a water vapor permeability and a water proofing property, a porous fabric, and a thermally bondable nonwoven fabric. In the composite nonwoven fabric, the thermally bondable nonwoven fabric is interposed between the water vapor permeable and water resistant nonwoven fabric and the porous fabric, and three of them are laminated together. However, this conventional composite nonwoven fabric is incapable of being increased in air permeability as a composite nonwoven fabric in its entirety because the nonwoven fabric and the porous fabric are bonded to the thermally bondable nonwoven fabric which is distorted in a flexible film shape.

In addition, disposal of the protective materials contaminated with those substances being harmful to human bodies has now come to be a controversial issue. By way of example, the protective materials of the kind referred to above are generally utilized as a disposable material and are heaped up as hazardous wastes in a plastic bag after one-time use. Then, the used protective materials are to be disposed of by waste disposers. However, if the protective materials are bulky, such a problem arises that increase in transportation cost as well as disposal cost of those protective materials, and therefore, demands have been made to reduce the costs by reducing the volume of those protective materials.

One way to reduce the volume of the protective materials may include a method of reducing the pressure inside the bags or compressing those bags, a method of reducing the volume of the bags by means of heating such as dry heating or wet heating, and the like. But the method to reduce the volume by way of reduction of the pressure inside the bags is considered undesirable because it may emit contaminants to air being exhausted.

Further, as one of the volume reduction methods by way of compression of the bags, there has been suggested an equipment designed to heat the contaminated wastes so that the wastes can be caked in a block form to thereby reduce the volume, or an equipment designed to pulverize the wastes to thereby reduce the volume. Both of them are currently available in the commercial market, such equipments, however, are undesirable because of being extremely expensive and large in scale. Also, the reduction of the volume by means of the dry heat treatment requires heat resistant bags and is therefore costly to perform.

A method of and an apparatus for reducing the volume of infectious medical wastes by means of, for example, hot water has been suggested (See, for example, Patent Document 2 listed below.). Patent Document 2 pertains to a method of and an apparatus for treating infectious medical wastes, characterized in that a mixture of infectious medical wastes (A) which are made of a hydrophilic resin insoluble in a water having a temperature of not higher than 50° C., and water (B), which mixture has a mixing ratio (A)/(B) of 70/30 to 20/80, is treated at a temperature within the range of 70 to 150° C. so that the infectious medical wastes (A) can be solidified with their volume reduced. Although the apparatus disclosed in Patent Document 2 appears to be compact in size, but has required a special device to achieve the volume reduction.

[Patent Document 1] JP Laid-open Patent Publication No. 2003-336155

[Patent Document 2] JP Laid-open Patent Publication No. 2003-073498

DISCLOSURE OF THE INVENTION

An object of the present invention is to provide a laminated fabric having both of incompatible properties of air permeability and filtering capability (collecting capability).

Another object of the present invention is to provide a laminated fabric which can be integrated without the air permeability being degraded.

A further object of the present invention is to provide a laminated fabric which is effective to maintain the filtering capability even after it has been loaded.

A still further object of the present invention is to provide a laminated fabric, the volume of which can be reduced at a reduced cost and without requiring the use of any special equipment.

As a result of intensive studies conducted by the inventors of the present invention in an attempt to accomplish those and other objects of the present invention, it has been found that if a laminated or layered fabric is prepared by bonding a stretchable nonwoven fabric as a protective layer to a supporting layer (or holding layer), the laminated fabric can have both of the air permeability and the filtering capability, which have hitherto been incompatible with each other, and can hold the filtering capability even when some burden is placed on the laminated fabric.

It has further been found that in the case where a volume reducible supporting layer (A layer) is used as the supporting layer and the volume reducible supporting layer is prepared from fibers capable of shrinking 5 to 90% when at least one layer is immersed in a hot water of not lower than 60° C.; the laminated fabric and a protective material prepared therefrom can be obtained that can be readily reduced in volume at a reduced cost without requiring the use of any special equipment.

In other words, the present invention provides a laminated fabric which comprises: a supporting layer; and a protective layer comprising a stretchable nonwoven fabric formed from an ultra-fine fiber, the protective layer bonded to the supporting layer; whereby the laminated fabric having an air permeability of 2 cc/cm2/sec or higher and also having an efficiency of 90% or higher when collecting quartz particles 1 μm in size.

The ultra-fine fibers referred to above may comprise a thermoplastic elastomer, for example, a heat resistant thermoplastic elastomer. The thermoplastic elastomer that can be employed in the practice of the present invention may comprise a thermoplastic elastomer selected from the group consisting of, for example, SEPS, SEBS, a polyurethane series thermoplastic elastomer, a polyester series thermoplastic elastomer and a polyamide series thermoplastic elastomer. The stretchable nonwoven fabric forming the protective layer may be of a kind having, for example, a stretch of 30% or higher at break. This stretchable nonwoven fabric preferably comprises an ultra-fine fiber in the form of, particularly, a nanofiber having a fiber diameter within the range of 10 to 1000 nm and also having a weight within the range of 0.01 to 10 g/m2.

On the other hand, a part of the fibers forming the supporting layer may be a volume reducible fiber. By way of example, the volume reducible fibers may comprise a polyvinyl alcohol fiber. In other words, the present invention may encompass a laminated fabric having its volume capable of being reduced with a hot water. Such a volume reducible laminated fabric may be of a kind capable of shrinking 5 to 90% when immersed in a hot water of 60° C. or higher.

Also, the laminated fabric of the present invention may include a water resistant layer which is positioned on the protective layer so that the protective layer is employed as an intermediate layer between the water resistant layer and the supporting layer. In such case, the laminated fabric may have a withstanding pressure within the range of about 300 to 1500 mmH2O.

Furthermore, the present invention also encompasses a protective material, particularly, a protective clothing. The protective material may comprise the laminated fabric referred to above. Where the laminated fabric has a volume reducing capability, the present invention also includes a method of reducing the volume of the laminated fabric by placing the laminated fabric into a sealable vessel and supplying a hot water of 60° C. or higher to the laminated fabric.

As hereinabove discussed, the laminated fabric of the present invention can have the filtering capability and the air permeability simultaneously when the laminated fabric comprises the supporting layer and the unique protective layer. In particular, since the protective layer has a stretchability, it can exhibit an excellent follow-up characteristic to any other layers. Accordingly, without the air permeability being degraded, not only can the integrity of the laminated fabric be improved, but the filtering capability of the laminated fabric can be maintained even after a predetermined burden has been applied thereto.

Specifically, where the nanofiber nonwoven fabric is used as the protective layer, both a high air permeability and a high filtering capability can be realized.

Also, where a volume reducible material is used as the supporting layer, the laminated fabric of the present invention can, after its volume has been reduced with the use of hot water, be transported and/or disposed of easily and, therefore, the cost incurred in transportation and/or disposal can be reduced advantageously.

BRIEF DESCRIPTION OF THE DRAWINGS

In any event, the present invention will become more clearly understood from the following description of preferred embodiments thereof, when taken in conjunction with the accompanying drawings. However, the embodiments and the drawings are given only for the purpose of illustration and explanation, and are not to be taken as limiting the scope of the present invention in any way whatsoever, which scope is to be determined by the appended claims. The drawings are not necessarily to scale, and emphasis has instead been placed upon illustrating the principles of the invention. In the accompanying drawings, like reference numerals are used to denote like parts throughout the several views, and:

FIG. 1 is a schematic diagram of an apparatus for manufacturing a protective layer which is a nanofiber layer containing tangled and deposited nanofibers, showing an example of a laminated fabric according to a preferred embodiment of the present invention; and

FIG. 2 is a schematic sectional view showing an example of the structure of the laminated fabric (a laminate) according to a preferred embodiment of the present invention.

 BEST MODE FOR CARRYING OUT THE INVENTION

The laminated fabric of the present invention is a laminated fabric (layered fabric) of a structure having a protective layer and a supporting layer bonded together, in which the protective layer includes a stretchable nonwoven fabric prepared from ultra-fine fibers. The laminated fabric of the present invention has an air permeability of 2 cc/cm2/sec. or higher and also has an efficiency of 90% or higher when collecting quartz particles 1 μm in size.

[Supporting Layer]

The supporting layer employed in the laminated fabric of the present invention is provided for the purpose of retaining the protective layer. The supporting layer may not be specifically limited to a particular one, as long as the laminated fabric as a whole can exhibit a specific air permeability. The supporting layer may be employed in the form of a woven fabric, a knitted fabric, or a nonwoven fabric.

The supporting layer referred to above may be prepared from either natural fibers such as, for example, animal or vegetable fibers, or various synthetic fibers, depending on the purpose of use of the laminated fabric. Those fibers may be employed singly or in combination.

The synthetic fibers used to form the supporting layer may be polyvinyl alcohol fibers; ethylene-vinyl alcohol fibers; polyamide fibers (including, for example, aliphatic polyamide fibers comprising, for example, nylon 6, nylon 66, nylon 46, nylon 610, nylon 11 and/or nylon 12, alicyclic polyamide fibers, aromatic polyamide fibers such as aramid fibers, and semi-aromatic polyamide fibers consisting of an aromatic dicarboxylic acid and an aliphatic alkylenediamine); polyolefinic fibers (including, for example, polyethylene fibers, polypropylene fibers and composite fibers of polypropylene and polyethylene); polyester fibers (including, for example, polyethylene terephthalate fibers); acrylic fibers (including, for example, polyacrylonitrile fibers and polymethyl methacrylate fibers); polyurethane fibers; cellulose fibers (including, for example, rayon fibers and acetate fibers); halogen-containing fibers (including, for example, vinyl chloride fibers, vinylidene chloride fibers, polyvinyl fluoride fibers, polyvinylidene fluoride fibers and fibers made of a copolymer of polyvinylidene fluoride and hexafluoropropylene); polyimide fibers; polybenzimidazole fibers; polyarylate fibers; or polyphenylene sulfide fibers.

Of those fibers enumerated above, the polyvinyl alcohol fibers, the ethylene vinyl alcohol fibers, the polyamide fibers or the polyester fibers are preferred as a material for the synthetic fibers employed in the supporting layer.

The fineness of the fibers forming the supporting layer may be of any value that can be chosen as desired depending on the texture or feeling which is required to the laminated fabric, but may be within the range of, for example, about 0.1 to 1000 dtex, and preferably within the range of about 1 to 400 dtex. Also, where the supporting layer is a woven fabric, warps and wefts of the woven fabric may have respective finenesses, which may be either the same or different from each other, but the ratio of the fineness of the wefts relative to the fineness of the wasp (i.e., the warp fineness/weft fineness) may be within the range of about 10/1 to 1/10, and preferably within the range of about 5/1 to 1/5.

The weight of the supporting layer per unit area may be of any value that can be chosen as desired depending on the form of the supporting layer, and not specifically limited to a particular value so long as the air permeability and the collecting capability both required in the practice of the present invention are satisfied. The weight of the supporting layer per square meter may be within the range of about 5 to 100 g/m2 and, preferably, within the range of about 10 to 90 g/m2.

The supporting layer may be in the form of a woven fabric, a knitted fabric, a nonwoven fabric or a synthetic paper, and may not be specifically limited to a particular form as long as the eventually formed laminated fabric can have a predetermined or required air permeability and collecting capability. In any event, the woven fabric, the knitted fabric, the nonwoven fabric or the synthetic resin referred to above may be prepared in any known or customarily practiced method.

Of the various forms of the supporting layer, the nonwoven fabric is preferred for the supporting layer in terms of the collecting capability and the air permeability.

The method of making the supporting layer using the nonwoven fabric is not specifically limited to a particular method, and any of a spun bonding method, a meltblown method, a spun lacing method, a thermal bonding method, a chemical bonding method, an airlaid method and a needle punching method can be employed therefor.

(Volume Reducible Supporting Layer)

Further, in terms of the volume reducing capability, the supporting layer of the present invention, may be a volume reducible supporting layer (A layer) prepared from fibers capable of shrinking 5 to 90% after immersion of the fibers in a hot water of 60° C. or higher. In other words, when the laminated fabric of the present invention is used under the working environment of 50° C. or lower, the laminated fabric can exhibit a satisfactory protective function against dust, contagions and/or viruses without shrinking due to moisture such as sweat. On the contrary, at the time it is desired to be disposed of, the laminated fabric is immersed in a hot water of 60° C. or higher, and the shrinkage of a portion of the fibers forming the laminated fabric results in reduction of the laminated fabric entirely in volume.

Where such a feature as discussed above is possessed in the laminated fabric of the present invention, even if a layer (B layer) incapable of undergoing shrinkage in a water of 50° C. or lower is used, when the B layer is bonded to the volume reducible supporting layer (A layer) prepared from the fibers capable of undergo 5 to 90% shrinkage when immersed in the hot water of 60° C. or higher, the resultant protective laminated fabric as well as a protective clothing prepared therefrom will have an excellent volume reducing capability as will be discussed in detail later.

In the practice of the present invention, in order to reduce the volume of the laminated fabric for a protective clothing on the whole, at least a part of the fibers forming the supporting layer may be a volume reducible fiber capable of undergoing shrinkage when immersed in a hot water.

The volume reducible fibers referred to above are preferably hydrophilic fibers, more specifically, fibers of a water soluble synthetic polymer, and particularly PVA (polyvinyl alcohol) fibers comprising a vinyl alcohol polymer. The PVA fiber has a biodegradability and is, therefore, excellent in terms of low impacts on the environments during underground disposal.

The kind of vinyl alcohol polymers used for the PVA fibers that can be suitably employed in the A layer in accordance with the present invention may not be specifically limited to a particular type, and the preferred vinyl alcohol polymers may be the one having a viscosity-average degree of polymerization of 1,000 or higher, and particularly 1,500 or higher in terms of the practical mechanical performance; or 5,000 or lower in terms of the spinning capability and cost. Also, by the same reason, the preferred vinyl alcohol polymers may be the one having a degree of saponification of 50 mole % or higher, preferably 65 mole % or higher and, more preferably 80 mole % or higher.

The vinyl alcohol polymer may be copolymerized with any other monomer, and the examples of a copolymerizing component include ethylene, vinyl acetate, itaconic acid, vinyl amine, acrylamide, vinyl pivalate, maleic anhydride, a sulfonic acid-containing vinyl compound, and the like.

In terms of the practice mechanical performance, the vinyl alcohol polymer preferably contains a vinyl alcohol unit in a quantity of 70 mole % or higher of the total constituent unit. Also, so long as the effects of the present invention are not lost, the fibers may contain one or more polymers, other than the vinyl alcohol polymer, and any additive(s). In terms of the fiber performance, the content of the vinyl alcohol polymer preferably exceeds 30 mass % per fibers and, more preferably 50 mass % per fibers.

There will now be described a method of making the PVA fibers, which can be suitably employed in the A layer in accordance with the present invention. When the fibers are prepared with a spinning liquid in which a water soluble PVA polymer is dissolved in water or an organic solvent by a method as will be described later, the fiber excellent in mechanical characteristics can be efficiently manufactured. Nevertheless, so long as the effects of the present invention are not lost, the spinning liquid may contain one or more additives and any other polymer. The solvent forming a part of the spinning liquid includes, for example, water; a polar solvent such as dimethylsulfoxide (DMSO), dimethylacetamide, dimethylformamide or N-methylpyrrolidone; a polyvalent alcohol such as glycerin or ethylene glycol; a mixture of one of those solvents with a swellable metal salt such as rhodan salt, lithium chloride, calcium chloride or zinc chloride; a mixture of those solvents; or a mixture of one of those solvents with water. Among those solvents, water or DMSO is most preferred in terms of the solubility at a low temperature, low toxicity and low corrosive properties.

The concentration of the polymer contained in the spinning liquid may vary depending on the liquid components, the degree of polymerization or the solvent to be used, and is preferably within the range of 8 to 40 weight percent. The liquid temperature of the spinning liquid at the time of extrusion is within a range enough to avoid gelling, decomposing and coloring of the spinning liquid, and is specifically preferably within the range of 50 to 150° C.

The above-mentioned spinning liquid can be suitably allowed to subject to a wet spinning, a dry spinning or a dry-jet wet spinning after extruding of the spinning liquid from a nozzle, and the spinning liquid may be extruded into a coagulating bath capable of solidifying the PVA polymer. In particular, where the spinning liquid is extruded through multiple holes, the use of the wet spinning process is preferred rather than the dry-jet wet spinning process because conglutination of the fibers can be avoided during the extrusion of the spinning liquid. It is to be noted that the wet spinning process referred to above is a process, in which the spinning liquid can be extruded from a nozzle directly into a coagulating bath (solidifying bath), whereas the dry-jet wet spinning process is a process, in which the spinning liquid is first extruded from a nozzle into the atmosphere full of air or inert gas and then introduced into a coagulating bath.

The coagulating liquid used in the practice of the present invention varies depending on whether the solvent in the spinning liquid is an organic solvent or whether it is water. In the case of the spinning liquid utilizing the organic solvent, the use is preferred of a mixed liquid containing the coagulating liquid and the spinning liquid solvent in order to improve the eventually obtained fiber strength or the like. The coagulating liquid used in the mixed solution may be an organic solvent such as an alcohol (including, for example, methanol and ethanol), or a ketone (including, for example, acetone and methyl ethyl ketone), which solvent is of a kind having a solidifying capability to the PVA polymer. In particular, an organic solvent containing methanol and DMSO is preferred, which are preferably mixed in a mixing ratio (methanol)/(DMSO) of 55/45 to 80/20 in terms of the productivity and the solvent recovery. Also, the temperature of the coagulating liquid is preferably 30° C. or lower, and particularly for achieving a uniform gelatinization upon cooling, it is preferably 20° C. or lower, and more preferably 15° C. or lower. On the other hand, in the case where the spinning liquid is used in the form of an aqueous solution, the coagulating bath includes an aqueous solution of mineral salts having a solidifying capability to the PVA polymer. For example, mirabilite, sodium chloride or carbon hydrate can be suitably employed for the solidifying solvent forming a part of the coagulating liquid. As a matter of course, the coagulating liquid referred to above may be either acidic or alkaline.

Thereafter, the solvent in the spinning liquid is removed by extraction from extruded filaments to solidify the filaments. It is preferred that the filaments can be stretched in the bath during the extraction step, not only because conglutination of the fibers during drying can be suppressed, but also because the eventually obtained fibers can have an increased strength. The degree of stretching is preferably within the range of 1.5 to 6 times. The extraction of the solvent is carried out generally by passing the extruded filaments through a plurality of extraction baths. For the extraction baths, the coagulating liquid singly or a mixture of the coagulating liquid with the solvent for the spinning liquid can be employed, and the extraction baths may have a temperature within the range of 0 to 80° C.

Then, the filaments are dried to obtain PVA fibers. At this time, an oiling agent may be applied as required during the drying process. The drying temperature is preferably 210° C. or lower. In particular, the use of a multi-stage drying is preferred, which may be carried out in such a manner that the drying is performed at a temperature equal to or lower than 160° C. at the initial stage of drying, and at the later stage of drying, the drying is performed at a higher temperature. Further, a dry heat stretching and, if required a dry heat shrinking, are preferably carried out to orient and crystallize PVA molecular chains to thereby increase the tenacity of the fibers. When the fibers are used to form structures such as nonwoven fabrics, if the tenacity of the fibers is too low, reduction in in-process transportability may be readily expected. In order to increase the mechanical performance of the fibers, the dry heat stretching is preferably carried out under a temperature condition within the range of 120 to 280° C.

The fineness of the PVA fibers that can be obtained by the manufacturing method described hereinabove is not specifically limited to a particular value, and the PVA fibers may have a fineness selected from a large range, for example, within the range of 0.1 to 1,000 dtex, and preferably 1 to 400 dtex. The fineness of the fibers may be suitably adjusted depending on the diameter of the nozzle and/or the stretching ratio. Also, the fibers may have a length which is not specifically limited to a particular value, and may be suitably selected in consideration of the purpose of use.

It is to be noted that the fibers that can undergo 5 to 90% shrinkage when immersed in a hot water of a temperature equal to or higher than 60° C. may be employed as a part of the A layer, not necessarily employed in the entirety of the A layer. Where a part of the A layer comprises those shrinkable fibers capable of undergoing 5 to 90% shrinkage when immersed in the hot water of 60° C. or higher, the shrinkage percentage may be lowered as compared with the case, in which the A layer in its entirety is prepared from the shrinkable fibers. However, even if only a part of the A layer comprises those shrinkable fibers; the laminated fabric in its entirety can be shrunken 5 to 90% when the material and the composition ratio are suitably selected.

[Protective Layer]

The protective layer employed in the laminated fabric of the present invention includes a stretchable nonwoven fabric prepared from ultra-fine fibers in terms of the capability of collecting microparticles. The stretchable nonwoven fabric substantially retains a fibrous shape as a nonwoven fabric, without being transformed into a film in the laminated fabric, for the purpose of securing the air permeability. For this reason, while the laminated fabric of the present invention has a high filtering performance enough to have an efficiency of 90% or higher when collecting quarts particles of 1 μm in size, it also ensures an air permeability as high as 2 cc/cm2/sec concurrently. Also, since the protective layer has a stretchability, it can exhibit a good follow-up characteristic with both the supporting layer and a water resistant layer as will be described later. Accordingly, when the laminate fabric is used for wearing as a protective clothing, the protective layer will hardly break. Accordingly, reduction in filtering capability of the laminated fabric as a whole can be suppressed advantageously, even when a predetermined loading such as stretching is imposed on the laminated fabric.

The ultra-fine fibers employed in the practice of the present invention may not be specifically limited to a particular type as long as it provides stretchability to the non-woven fabric. The frequently employed ultra-fine fibers are formed from a thermoplastic elastomer in view of the elasticity and fiber forming properties.

Examples of the thermoplastic elastomer includes a styrene series thermoplastic elastomer, a urethane series thermoplastic elastomer, an olefinic thermoplastic elastomer, a vinyl chloride series thermoplastic elastomer, a polyester series thermoplastic elastomer, a polyamide series thermoplastic elastomer, and the like. Those thermoplastic elastomers may be employed singly or in combination. Also, the thermoplastic elastomer referred to above may be a polymer blend of thermoplastic elastomer, in which the thermoplastic elastomer is combined with a polymer material for the synthetic fibers (for example, olefinic polymers) discussed previously under the heading of the supporting layer. In addition, if required, one or more kind of organic or inorganic powders may be mixed in the thermoplastic elastomer referred to above.

The urethane series thermoplastic elastomer comprises a hard segment comprising a low molecular weight glycol and a diisocyanate, and a soft segment comprising a high molecular weight diol and diisocyanate.

The low molecular weight glycol includes, for example, C1-10 diols such as ethylene glycol, 1,4-butane diol and 1,6-hexane diol, whereas the high molecular weight diol includes, for example, poly(1,4-butylene adipate, poly(1,6-hexane adipate), polycaprolactone, polyethylene glycol, polypropylene glycol and polyoxytetramethylene glycol. The diisocyanate referred to above includes, for example, tolylene diisocyanate, 4,4-diphenylmethane diisocyanate, hexamethylene diisocyanate and isophorone diisocyanate.

The styrene series thermoplastic elastomer includes, for example, SBS (styrene/butadiene/styrene block copolymer), SIS (styrene/isoprene/styrene block copolymer), SEBS (styrene/ethylene/butadiene/styrene block copolymer) and SEPS (styrene/ethylene/propylene/styrene block copolymer).

The olefinic thermoplastic elastomer comprises a polyethylene or a polypropylene as a hard segment and SEBS or an ethylene/propylene copolymer as a soft segment.

The vinyl chloride series thermoplastic elastomer comprises a crystalline polyvinyl chloride as a hard segment and a non-crystalline polyvinyl chloride or acrylonitrile as a soft segment.

The polyester series thermoplastic elastomer comprises a saturated polyester as a hard segment and an aliphatic polyether or aliphatic polyester as a soft segment.

The polyamide series thermoplastic elastomer comprises a polyamide as a hard segment and, as a soft segment, a polyester or a polyether that is non-crystalline and has a low glass transition temperature.

Of those thermoplastic elastomers referred to above, SEPS, SEBS, the urethane series thermoplastic elastomer, the polyester series thermoplastic elastomer or the polyamide series thermoplastic elastomer can be advantageously employed in terms of the heat resistance.

This kind of the heat resistant and stretchable nonwoven fabric does not transform into a film even when the protective layer and the supporting layer are integrated together by means of a thermo compression bonding to form the laminated fabric, and, therefore, a predetermined air permeability can be secured in the laminated fabric.

It is to be noted that if the supporting layer is a volume reducible supporting layer (A layer) capable of undergoing shrinkage when immersed in a hot water, such a supporting layer may be bonded to a layer (B layer) of a kind, which does not undergo shrinkage in a water having a temperature of not higher than 50° C., to provide a laminated fabric, and the resultant laminated fabric will be a volume reducible laminated fabric capable of undergoing shrinkage in a hot water of a temperature equal to or higher than 60° C.

In such case, the fabric material, the weight and the thickness of the B layer may not be specifically limited to a particular one or particular values and may be arbitrarily chosen in consideration of an object to be protected, but the B layer preferably has a water resistance sufficient to substantially avoid shrinkage in contact with a moisture component such as, for example, sweats when it is used under the working environment of 50° C. or lower.

The ultra-fine fibers forming the stretchable nonwoven fabric referred to above has an average fiber diameter preferably not greater than, for example, 10 μm (for example, within the range of about 10 nm to about 8 μm), and more preferably not greater than 5 μm because the eventually formed laminated fabric has both the air permeability and the filtering capability. The ultra-fine fibers of this kind can be prepared in any known manner such as a meltblown process.

Specifically, in view of the necessity to increase the air permeability and the protecting capability, the ultra-fine fibers employed in the practice of the present invention may be nanofibers having an average fiber diameter within the range of 10 to 1,000 nm (preferably within the range of about 15 to 800 nm and, more preferably, within the range of about 25 to 600 nm).

In order to strike a delicate balance between the protecting capability and the air permeability of the laminate fabric, the important point should be how the pressure loss of the fabric is minimized and how harmful microparticles can be collected by the fabric. In view of the above point, the nanofibers are considered to be suitable from the viewpoint of striking a balance between the protecting capability and the air permeability partly because they can exhibit the Slip Flow effect enough to reduce the pressure loss during the filtration and partly because they have a high air permeability. (Takeyuki Kawaguchi, “Kodo Sangyo Hakkutsu Senryaku (Strategy of Advanced Industrial Structure Development Using Nanofiber Technology)” (Supervising Editor: Tatsuya Motomiya), Chapter 10, pp. 373)

It is to be noted that the fiber diameter herein referred to in connection with the present invention means a diameter of the transverse section of fibers that can be measured from an electron micrograph taken of a fiber aggregation at a magnification of ×5,000, and is an average value obtained by measuring the fiber diameters of randomly chosen 50 fibers.

The weight of the stretchable nonwoven fabric per unit area employed in the practice of the present invention is not specifically limited to a particular value as long as the laminated fabric of the present invention satisfies the air permeability and the collecting ability both defined in the present invention, but may be chosen in consideration of the average fiber diameter of the ultra-fine fibers.

By way of example, in the case where the average fiber diameter of the ultra-fine fibers exceeds 1 μm, the weight of the stretchable nonwoven fabric is preferably within the range of about 1 to 20 g/m2, and more preferably within the range of about 5 to 15 g/m2.

Also, by way of example, if the average fiber diameter of the ultra-fine fibers is not greater than 1 μm, the weight of the stretchable nonwoven fabric is preferably within the range of about 0.01 to 10 g/m2, more preferably within the range of about 0.03 to 8 g/m2, and further preferably within the range of about 0.05 to 6 g/m2.

If the weight of the non-woven fabric is too large for the average fiber diameter, it may occur that the air permeability discussed previously will be lowered below 2 cc/cm2/sec. although the laminate fabric has an improved protecting capability from passage of microparticles such as, for example, asbestos hazardous to the human body. In particular, in the case of the nanofibers, increase in cost will occur with an increased proportion to the nanofibers in the fabric, and therefore, it is not preferable. On the other hand, if the weight of the non-woven fabric is too small, the air permeability will improve, but it is not preferable because it would be difficult to uniformly distribute over the entire supporting layer, and as a result, the efficiency of collecting the 1 μm quartz particles will be lowered below 90%.

Since the protective layer comprises the stretchable nonwoven fabric as hereinabove described, it is possible to increase the stretch at break (%) as compared with the non-stretchable nonwoven fabric. By way of example, the stretch (%) of the stretchable nonwoven fabric at break may be of a value equal to or higher than, for example, 30% (for example, within the range of about 30 to 200%) and, preferably, within the range of about 35 to 180%, when an oblong test piece thereof having a width of 15 mm is measured in accordance with JIS P8113.

The stretchable nonwoven fabric can be prepared by the method of making the nonwoven fabric, described hereinbefore under the heading of the supporting layer, using ultra-fine fibers. Also, in the case of the ultra-fine fibers being nanofibers, the nonwoven fabric prepared from the nanofibers may be manufactured by the use of the following process.

In the first place, the nanofibers referred to above may be prepared by the use of, for example, the following method. As a polymer spinning liquid (or spinning liquid), either a dissolved polymer solution in which a polymer is dissolved in a solvent capable of dissolving such polymer, or a melted polymer solution in which the polymer is melted by heating, can be suitably employed. Then, nanofibers are laminated or conjugated as the previously described B layer by means of an electrostatic spinning process using the spinning liquid. For the electrostatic spinning process, a method can be employed, in which while a high voltage is applied to an electroconductive member capable of dispensing the spinning liquid, nanofibers can be deposited on a counter electroconductive member (or electrode) that is grounded to the earth. By this method, the spinning liquid that is extruded from a spinning liquid supply unit can be electrified (or charged) to split the droplets from the spinning liquid; fibers are then continuously drawn from one point of the liquid droplets under the influence of an electric field; and the split and divided fibers are diffused, and finally being deposited on a collecting belt or sheet disposed at a location spaced a few to tens centimeters from the spinning liquid supply unit. The fibers are slightly conglutinated simultaneously with deposition to inhibit movement of those fibers and a dense sheet can be obtained when ultra-fine fibers are successively deposited on the moving collecting belt or sheet.

In other words, referring to FIG. 1, the spinning liquid in which the polymer is dissolved is measured and transmitted by a metering pump 1, and is distributed under a uniform pressure and flow by a distributing and rectifying block 2. Then the distributed spinning liquid is supplied to a nozzle unit 3. The nozzle unit 3 has spinnerets 4 each fitted thereto so as to protrude the spinnerets 4 having a respective hole of a hollow needle configuration, and leakage of electricity over the nozzle unit 3 is prevented by electrically insulating members 5. The protruding spinnerets 4, each made of an electroconductive material, are fitted to the nozzle unit 3 so as to be vertically downwardly oriented and juxtaposed relative to each other in a direction perpendicular to the direction of travel of a sheet take-up apparatus 7, which may be in the form of an endless conveyor. An output terminal of a high voltage DC generating unit is fitted to each of the projecting spinnerets 4 so that application to those spinnerets 4 can be made possible through a conducting wire. The endless conveyor in the sheet take-up apparatus 7 has a grounded electroconductive member 8 fitted thereto so that the applied potential can be neutralized. The spinning liquid supplied under pressure from the nozzle unit 3 to the projecting spinnerets 4 is electrified to split, fibers are then continuously drawn from one point of liquid droplets under the influence of an electric field, and then the nanofiber scaffolds deposited on the electroconductive member fitted to the sheet take-up apparatus 7. The deposited nanofibers, in which slight conglutination proceeds, are moved with the movement of the sheet take-up apparatus 7, and simultaneously with the movement of the endless conveyor, another deposition ejected from the spinnerets 4 is placed onto the next to the former deposition in the endless conveyor. As a result, a dense and uniform sheeting can be formed by repeating deposition of ultra-fine fibers.

[Laminated Fabric]

The laminated fabric comprises the protective layer and the supporting layer which are bonded together. The method of bonding the supporting layer and the protective layer together to provide the laminated fabric may not be specifically limited to a particular one. By way of example, where the nonwoven fabric is used, thermal bonding, chemical bonding, needle punching, hydroentangling or any other method can be suitably employed. Also, coating of the protective layer to the supporting layer by means of a method such as, for example, spun bonding, meltblowing, and electro-spinning may be suitably employed with no problem.

Also, where no affinity exists between the supporting layer and the protective layer, a bonding layer (for example, a layer to be used for bonding with a binder or for bonding resulting from thermal fusion) having an affinity to respective compositions of those layers may be inserted in between those layers. For example, where a thermally fusible bonding layer is employed therebetween, the relationship between the softening point (TB) of the fibers forming the stretchable nonwoven fabric (the protective layer) and the softening point (TH) of the thermally fusible bonding layer may be TH<TB, preferably about TH+5≦TB and more preferably about TH+10≦TB.

Also, in the practice of the present invention, in order to increase the water resistance of the laminated fabric, a water resistant layer may be further positioned or laminated on the protective layer so that the protective layer is employed as an intermediate layer between the water resistant layer and the supporting layer. The use of the water resistant layer so laminated is effective to inhibit the reduction of the collecting capability and the air permeability of the protective layer resulting from deposition of water components, even when the laminated fabric is used under high humidity or under the environment susceptible to deposition of the water components.

For example, as the water resistant layer, a moisture permeable and water resistant nonwoven fabric may be employed. The moisture permeable and water resistant nonwoven fabric referred to above can be formed by applying a water repellent or water resistant coating to the nonwoven fabric formed by the use of the various fibers previously discussed under the heading of the supporting layer, but in terms of securement of the air permeability of the supporting layer, the water resistant layer is preferably formed with hydrophobic fibers. The hydrophobic fibers may be exemplified with polyolefinic fibers or polyester series fibers, both of which have been discussed previously under the heading of the supporting layer, and two of them, the polyolefinic fibers are preferred therefor. As a process of laminating the water resistant layer, any of the method discussed under the method of laminating the supporting layer and the protective layer together can be employed. The water resistant layer has a weight, which may be so chosen as to be within the range of, for example, about 5 to 50 g/m2 and, preferably, within the range of about 10 to 45 g/m2 in order to impart water resistant property.

Also, in the laminated fabric, the total of the respective weights of the supporting and protective layers (plus that of the water resistant layer that is employed if desired) may be arbitrarily chosen depending on the characteristics of the supporting layer and/or those of the protective layer and may be within the range of, for example, about 30 to 100 g/m2 and, preferably within the range of about 40 to 90 g/m2.

Specifically, in the case where the supporting layer has a volume reducing capability in view of reducing the volume of laminate fabric in its entirety, the thickness of the protective layer (plus the thickness of the water resistant layer that is employed if desired) relative to the thickness of the supporting layer may be not larger than about twice of the thickness of the supporting layer, and preferably not larger than about 1.5 times the thickness of the supporting layer.

It is to be noted that if required, a film may be bonded to a part of the supporting layer. Even in such case, a method of bonding the film to the fibers may not specifically limited, but such bonding may be accomplished by means of the use of a binder or a thermal fusion.

Also, if required, in order for the resultant sheeting comprising the film to be utilizable in any of various applications, any post-treatment may be performed. By way of example, a calendering treatment for densification, a treatment to impart a hydrophilic property, a water repellent treatment, and/or a surfactant depositing treatment may be performed.

The laminated fabric for a protective clothing according to the present invention is preferably subjected to an electret treatment. The electret treatment referred to above means a material capable of semipermanently retaining electric polarization even in the absence of any external electric field and forming an electric field in the surrounding, and the electret treatment can be performed with an easily chargeable material such as, for example, a polypropylene.

That is because since when the electret treatment is performed, a collecting function by means of the electrostatic force can be added, the efficiency of collecting the microparticles can be drastically increased without altering the air permeability. With respect to the electret treatment, various systems such as, for example, a thermal electret, an electroelectret, a photoelectret, a radioelectret, a magnetelectret, a mechanoelectret are available, and any of them can be suitably employed.

In terms of the protecting capability, the laminated fabric manufactured in the manner described hereinabove has an efficiency of 90% or higher, preferably 93% or higher, and more preferably 96% or higher, when collecting quartz particles 1 μm in size.

Dust particles, contagions and viruses, all harmful to human bodies, have varying particle sizes. Asbestos, which are an exemplary harmful dust, are made up of an aggregation of fibrous matters of a length within the range of a few μm to some tens μm. The sizes of bacteria and fungi, which are a kind of contagions, are 2 to 3 μm in most cases. Although viruses themselves have sizes of 0.01 to 0.1 μm, the route of infection is in most cases by way of a droplet infection caused by patients' coughing, and the sizes of the droplets are 2 μm or greater in most cases. Considering the above mentioned sizes, it can be expected that if the efficiency of collecting the 1 μm quarts particles is 90% or higher, those dusts, contagions and viruses can be substantially almost completely protected.

On the other hand, if the efficiency of collecting the 1 μm quartz particles is lower than 90%, it is indeed undesirable in terms of the protecting capability discussed above.

The laminated fabric of the present invention has an air permeability of 2 cc/cm2/sec. or higher in order to secure an amenity to the human body. If the air permeability is lower than 2 cc/cm2/sec., one will feel uncomfortable with humid and, therefore, it is not desirable. The air permeability of the laminated fabric is preferably not lower than 3 cc/cm2/sec. and more preferably within the range of 3.5 cc/cm2/sec. to 10 cc/cm2/sec. As for the relationship between the air permeability and the 1 μm quartz particle collecting efficiency discussed previously, increase of the protecting capability lowers the air permeability, accompanied by increase of the humidity. As a result, the usage characteristics, for example, the amenity of wearing will be lowered. In order to prevent such an undesirable result, the protecting capability and the air permeability are desired to fall within the respective ranges of performance discussed hereinbefore.

In the present invention, since the stretchable nonwoven fabric is used for the protective layer, the follow-up characteristic of the protective layer with any other layers, that is, the supporting layer or the protective layer is excellent. Accordingly, even after a predetermined loading has been imposed, it is possible to keep the integrity of the laminated fabric as a whole, and any undesirable reduction in filtering capability can also be avoided. The laminated fabric of the present invention, even when being washed five times and dried in a manner according to, for example, the JIS L1096 B.23.1 A method, may have a 1 μm quarts particle collecting efficiency of 90% or higher (preferably 93% or higher and, more preferably, 95% or higher).

If the laminated fabric has a water resistance, the withstanding pressure of the laminated fabric, when measured according to a low water pressure method stipulated in JIS L1092 may be within the range of about 300 to 1,500 mmH2O, and preferably within the range of 400 to 1,000 mmH2O. If the withstanding pressure is too low, it will not play a role of protecting the protective layer from water, but if the withstanding pressure is too high, there is a possibility that the laminated fabric as a whole will have an air permeability departing from the predetermined value.

Also, where the laminated fabric has a volume reducing capability, the volume reducible laminated fabric may undergo about 5 to 90% shrinkage in a hot water of 60° C. or higher (for example, 60° C. or higher, but lower than 70° C.), and when a disposal space is considered, it may undergo about 10 to 92% shrinkage, and preferably about 20 to 94% shrinkage. In particular, in terms of increase in the rate of shrinkage, the laminated fabric may undergo 30 to 95% shrinkage and, preferably 40 to 90% shrinkage when held in a hot water of 70° C. or higher (for example, 70° C. or higher, but lower than 80° C.).

It is to be noted that the rate of shrinkage herein referred to means a value calculated according to the method described later under the heading of the rate of shrinkage (%) of the fabric in a hot water.

[Method of Reducing the Volume of Volume Reducible Laminated Fabric]

Where the laminated fabric of the present invention has a volume reducing capability, the volume of the laminated fabric can easily be reduced with no use to any special equipment and at a reduced cost.

By way of example, reduction in volume of the laminated fabric can be accomplished by putting the volume reducible laminated fabric (and the protective material prepared form such fabric) into a suitable vessel (for example, a plastic container or a plastic bag) and supplying a hot water of 60° C. or higher to the laminated fabric. A method of supplying the hot water is not particularly limited to a specific method, and the hot water may be filled in the vessel before the laminated fabric is put therein; or after water is filled in a sealable vessel, such water may be heated to a predetermined temperature in the vessel.

For example, for heating, any suitable method may be employed, as long as the water within the vessel can be heated to a temperature equal to or higher than 60° C. There may be suitably employed for this purpose, for example, a method of applying a hot air from the outside of the vessel, a method of immersing the vessel itself into a hot water, or a method of heating water in the vessel by the means of an induction heating apparatus such as, for example, an electronic oven.

The proportion of the hot water relative to the laminated fabric is not specifically limited to a particular value as long as the volume of the laminated fabric can be reduced, and relative to 100 parts by weight of the laminated fabric, 200 parts by weight or larger (for example, within the range of about 250 to 500 parts by weight), and preferably 300 parts by weight or larger (for example, within the range of about 350 to 450 parts by weight) of the hot water may be employed.

Where the vessel used to achieve the volume reduction is employed in the form of a plastic bag, reduction of the volume of the protective clothing can be achieved by putting 200 parts by weight or larger of water relative to 100 parts by weight of the laminated fabric constituting the protective clothing into the plastic bag; sealing the plastic bag; and then heating the plastic bag from the outside of the bag with a heater or heating the inside of the bag by means of an induction heating apparatus such as, for example, an electronic oven, to thereby reduce the volume of the protective clothing. The plastic bag referred to herein may not be particularly limited to a specific one as long as it will be neither melted or decomposed at a temperature of use thereof, and may be of a kind having a moisture resistance and a water resistance effective to avoid leakage of water.

It is to be noted that a method of sealing the plastic bag may also not be specifically limited to a particular method, and any of a method of tightly tying itself, a method of closing the mouth of the bag with the use of a fastening tool and a method of heat sealing the bag may be employed.

The protective clothing utilizing the volume reducible laminated fabric can be transported or disposed of after the volume thereof has been reduced subsequent after use. As a result, the cost, which will be incurred in transportation and disposal, can be reduced advantageously.

Hereinafter, the present invention will be demonstrated by way of examples and comparative examples, which are not intended to limit the scope of the present invention, but are only for illustrative purpose.

[Shrinkage Rate of Fabric in Hot Water (%)]

The fabric is cut into a sample of 10×10 cm in size, which sample is then immersed for 2 minutes in a hot water in a free state. After the immersion, the fabric is removed from the hot water and the removed fabric is drained off lightly. Then respective dimensions (cm) of the fabric in a longitudinal direction (X) and a transverse direction (Y) are measured so that the rate of shrinkage can be calculated by the following equation:


Shrinkage Rate(%)={[(10−X)/10]+[(10−Y)/10]}/2×100

[Dust Collecting Efficiency (%)]

In accordance with the testing for particulate respirators stipulated in JIS T8151, the dust collecting efficiency was measured using a “Mask Tester: Model AP-6310FP” manufactured by and available from Shibata Scientific Technology Ltd. For the dust, quartz particles of 1 μm in particle size were used and the measurement was carried out under a condition of the wind velocity of 8.6 cm/min at measurement.

Further, after 5 times washing in accordance with the method stipulated in JIS L1096 B.23.1A, the dust collecting efficiency of the dried sample fabric was measured in a manner similar to that described above.

[Air Permeability (cc/cm2/sec.)]

The air permeability was measured with the use of the FRAZIER TYPE AIR PERMEABILITY TESTER (manufactured by and available from Toyo Seiki Seisaku-sho, Ltd.).

[Stretch of Protective Layer at Break (%)]

The stretch of protective layer at break was measured according to the method stipulated in JIS P8113, with the use of an oblong test piece of 1.5 cm in width.

[Tensile Strength (N/5 cm)]

The tensile strength was measured according to the method stipulated in JIS L1906, with the use of an oblong test piece of 5 cm in width.

Example 1

(1) Using crimped PVA fibers, which has a polymerization degree of 1,750, saponification degree of 98.5 mole %, 2.2 dtex in single fiber fineness, 51 mm in fiber length and 5 cN/dtex in strength (tradenamed “WN7” manufactured by and available from Kuraray Co., Ltd.: 6% in shrinkage rate in 60° C. hot water, 65% shrinkage rate in 70° C. hot water and dissolvable at 75° C.), a random web comprised of 100 parts by mass of the crimped PVA fibers and having a weight of 35 g/m2 was prepared.

(2) Then, a nonwoven fabric was produced with the web obtained under (1) above in the following manner, a so-called foam bonding process. More specifically, onto the web obtained under (1) above, was applied a foam prepared by beating a 10% aqueous solution of PVA which has a polymerization degree of 1,750 and a saponification degree of 98.5 mole % by a commercially available bubble machine. Then, the resultant web was squeezed to spread the PVA resin foam uniformly over the web by means of a mangle, and the resultant was dried to obtain the nonwoven fabric. Thus obtained nonwoven fabric was used as a supporting layer. It is to be noted that the rate of shrinkage of this supporting layer was 15% in a hot water of 60° C. and 70% in a hot water of 70° C.

(3) On the other hand, the protective layer and the water resistant layer were prepared in the following manner.

SEPTON (tradenamed under “SEPTON 2002” manufactured by and available from Kuraray Co., Ltd.) and polypropylene (tradenamed under “NOVATEC PP” manufactured by and available from Japan Polychem Corporation) were melted and kneaded together in a mixing ratio of 60/40 (mass ratio), and subsequently a layer was formed by means of a meltblowing process to provide a SEPTON/polypropylene blended nonwoven fabric having a weight of 10 g/m2, which fabric was used as the protective layer.

Also, as the water resistant layer, a nonwoven fabric having a weight of 20 g/m2 was prepared by the meltblowing process, using polypropylene (tradenamed under “NOVATEC PP” manufactured by and available from Japan Polychem Corporation).

(4) Thereafter, the supporting layer, the protective layer and the water resistant layer were overlapped one above the other in this specific order, followed by bonding together by means of a calendering process (carried out under calendering conditions of 130° C. in temperature, 0.1 MPa in contact pressure, and 5 m/min. in processing velocity) to thereby provide a layered body having such a sectional structure as shown in FIG. 2. It is to be noted that in FIG. 2, A represents the supporting layer, B represents the protective layer and C represents the water resistant layer.

(5) The performance of the fabric consisting of the layered body, which has been manufactured in the manner described in (4), is shown in Table 1. The fabric so obtained was found to have a weight of 65 g/m2, a tensile strength of 120 N/5 cm×100 N/5 cm (MD direction×CD direction), an air permeability of 2.1 cc/cm2/sec., a 1 μm quartz dust collecting efficiency of 97.3%, and a 1 μm quartz dust collecting efficiency after 5 times washing of 97.1%. The fabric was also found to have both of an air permeability and a filtering capability as the laminated fabric and to be excellent in integrity enough to exhibit the required filtering capability even after it has been loaded by means of, for example, washing. Therefore, the laminated fabric has a performance sufficient to allow it to be used as a fabric for a protective clothing. Also, when the laminated fabric was immersed in a hot water of 60° C., 12% shrinkage occurred, and when it was immersed in a hot water of 70° C., 61% shrinkage occurred.

Example 2

(1) Using crimped PVA fibers of a kind, which has a polymerization degree of 1,750, a saponification degree of 98.5 mole %, 2.2 dtex in single fiber fineness, 51 mm in fiber length and 5 cN/dtex in strength (tradenamed “WN7” manufactured by and available from Kuraray Co., Ltd.), a random web comprised of 100 parts by mass of the crimped PVA fibers and having a weight of 35 g/m2 was prepared and was subsequently subjected to an embossing process to provide an embossed nonwoven fabric. The embossing process was carried out under conditions of 12% in the ratio of embossing area, 180° C. in temperature, 40 kgf/cm in line pressure and 15 m/min. in processing velocity. This nonwoven fabric was used as the supporting layer.

(2) On the other hand, the protective layer and the water resistant layer were prepared in the following manner:

After placing polyurethane (tradenamed under “KURAMIRON 1190-000” manufactured by and available from Kuraray Co., Ltd.) in a vessel containing dimethylformamide (DMF) so that the concentration of polyurethane was 10 mass %, the mixture was agitated at 90° C. to dissolve the polyurethane, and the completely dissolved solution was then cooled down to ambient temperatures to thereby provide a spinning liquid. Using the spinning liquid so prepared in the manner described above, an electrostatic spinning was carried out with the spinning apparatus shown in FIG. 1. For the spinnerets 4, needles each 0.9 mm in diameter were used. Also, the spinnerets 4 and the sheet take-up apparatus 7 were spaced at a distance of 12 cm from each other. It is to be noted that in the sheet take-up apparatus 7, a polypropylene nonwoven fabric (the water resistant layer) having a weight of 20 g/m2, which was prepared from the polypropylene (tradenamed under “NOVATEC PP” manufactured by and available from Japan Polychem Corporation) in the same way as in Example 1 by means of the meltblowing process, was wound beforehand.

Thereafter, while the conveyor was driven at a velocity of 0.1 m/min., the spinning liquid was extruded from the spinnerets in a predetermined supply rate, and a 25 kV voltage was applied to the spinnerets to form a laminate comprising a polyurethane nanofiber layer which had a weight of 1.0 g/m2 laminated over the water resistant layer which was pre-wound around the sheet take-up apparatus 7.

(3) The supporting layer, prepared in the manner described in (1) above, and the protective layer and the water resistant layer, both prepared in the manner described in (2) above, were overlapped with the protective layer forming an interlayer, and were then calendered in a manner similar to that described under Example 1 to thereby provide a layered body.

(4) The fabric prepared from this layered body was found to have a weight of 56 g/m2, a tensile strength of 64 N/5 cm×54 N/5 cm (MD direction×CD direction), an air permeability of 5.7 cc/cm2/sec., a 1 μm quartz dust collecting efficiency of 99.9%, and a 1 μm quartz dust collecting efficiency after 5 times washing of 99.8%, as shown in Table 1. The fabric was also found to have both of an air permeability and a filtering capability as the laminated fabric and to be excellent in integrity enough to exhibit the required filtering capability even after it has been loaded by means of, for example, washing. For the reason discussed above, the laminated fabric has a performance sufficient to allow it to be used as a fabric for a protective clothing. Also, when the laminated fabric was immersed in a hot water of 60° C., 11% shrinkage occurred, and when it was immersed in a hot water of 70° C., 58% shrinkage occurred.

Example 3

(1) Using crimped PVA fibers of a kind, which has a polymerization degree of 1,750, a saponification degree of 98.5 mole %, 2.2 dtex in single fiber fineness, 51 mm in fiber length and 5 cN/dtex in strength (tradenamed “WN7” manufactured by and available from Kuraray Co., Ltd.: 6% in shrinkage rate in 60° C. hot water, 65% shrinkage rate in 70° C. hot water and dissolvable at 75° C.), a random web comprised of 100 parts by mass of the crimped PVA fibers and having a weight of 35 g/m2 was prepared.

(2) Then, a nonwoven fabric was produced with the web obtained under (1) above in the following manner, a so-called foam bonding process. More specifically, onto the web obtained under (1) above, was applied a foam prepared by beating a 10% aqueous solution of PVA which has a polymerization degree of 1,750 and a saponification degree of 98.5 mole % by a commercially available bubble machine. Then, the resultant web was squeezed to spread the PVA resin foam uniformly over the web by means of a mangle, and the resultant was dried to obtain the nonwoven fabric. Thus obtained nonwoven fabric was used as a supporting layer. It is to be noted that the rate of shrinkage of this supporting layer was 15% in a hot water of 60° C. and 70% in a hot water of 70° C.

(3) For the water resistant layer, was prepared a polypropylene nonwoven fabric (water resistant layer) having a weight of 20 g/m2, which was prepared by the meltblowing process using the same polypropylene as that used in Example 1 (“NOVATEC PP” tradenamed polypropylene manufactured by and available from Japan Polychem Corporation).

(4) Thereafter, while the supporting layer was moved at a conveyor velocity of 50 m/min., a hot melt resin (tradenamed “INSTANTLOCK MP801” available from Nippon NSC Ltd.; melting point: about 140° C.) was uniformly applied to the supporting layer in a quantity of 2 g/m2 under conditions of 190° C. in nozzle temperature and 205° C. in hot air temperature to form a resin coating on the supporting layer, followed by cooling the coating once and winding around a take-up roll. Also, in a manner similar to the supporting layer, the hot melt resin referred to above was also applied to the water resistant layer referred to above in a quantity of 2 g/m2.

(5) On the other hand, the protective layer was prepared in the following manner.

After placing SEPTON (tradenamed under “SEPTON 2002” manufactured by and available from Kuraray Co., Ltd. and having a softening point of about 150° C.) in a vessel containing dimethylformamide (DMF) so that the concentration of SEPTON was 10 mass %, the mixture was agitated at 90° C. to dissolve the SEPTON, and the completely dissolved solution was then cooled down to ambient temperatures to thereby provide a spinning liquid. Using the spinning liquid so prepared in the manner described above, an electrostatic spinning was carried out with the spinning apparatus shown in FIG. 1. For the spinnerets 4, needles each 0.9 mm in diameter were used. Also, the spinnerets 4 and the sheet take-up apparatus 7 were spaced at a distance of 10 cm from each other. It is to be noted that the sheet take-up apparatus 7 was surrounded by the supporting layer coated with the hot melt resin which was obtained in (4) above, so that the surface of the hot melt resin was deposited with nanofibers.

Thereafter, while the conveyor was driven at a velocity of 0.1 m/min., the spinning liquid was extruded from the spinnerets, to the spinnerets a 20 kV voltage was applied, in a predetermined supply rate to obtain deposit or scaffold of 1.0 g/m2 of SEPTON nanofibers over the water resistant layer, and then the composite layer was wound around the sheet take-up apparatus 7.

(6) Further, the supporting layer, deposited with the SEPTON nanofiber layer, and the water resistant layer, coated with the hot melt resin as in (4) above, were overlapped one above the other with the hot melt resin coating on the water resistant layer held in contact with the SEPTON nanofiber layer, and then were bonded together by means of a calendering process (carried out under calendering conditions of 140° C. in temperature, 0.1 MPa in contact pressure, and 5 m/sec. in processing velocity) to thereby provide a layered body. The fabric prepared from this layered body was found to have a weight of 60 g/m2, a tensile strength of 93 N/5 cm×49 N/5 cm (MD direction×CD direction), an air permeability of 8.1 cc/cm2/sec., a 1 μm quartz dust collecting efficiency of 99.7%, and a 1 μm quartz dust collecting efficiency after 5 times washing of 99.7%, as shown in Table 1. The fabric was also found to have both of an air permeability and a filtering capability as the laminated fabric and to be excellent in integrity enough to exhibit the required filtering capability even after it has been loaded by means of, for example, washing. Accordingly, the laminated fabric has a performance sufficient to allow it to be used as a fabric for a protective clothing. Also, when the laminated fabric was immersed in a hot water of 60° C., 12% shrinkage occurred, and when it was immersed in a hot water of 70° C., 64% shrinkage occurred.

Example 4

(1) A nylon spun bonded nonwoven fabric having a weight of 30 g/m2 (tradenamed “ELTAS N01030” manufactured by and available from Asahi Kasei Corporation) was used as the supporting layer.

(2) A polypropylene nonwoven fabric having a weight of 20 g/m2 prepared from the same polypropylene (tradenamed “NOVATEC PP” manufactured by and available from Japan Polychem Corporation) as that used in Example 1 by means of the meltblowing process was used as the water resistant layer.

(3) Then, while the supporting layer was moved at a conveyor velocity of 50 m/min., a hot melt resin (tradenamed “INSTANTLOCK MP801” available from Nippon NSC Ltd.) was uniformly applied to the supporting layer in a quantity of 2 g/m2 under conditions of 190° C. in nozzle temperature and 205° C. in hot air temperature to form a resin coating on the supporting layer, followed by cooling the coating once and winding around a take-up roll. Also, in a manner similar to the supporting layer, the hot melt resin referred to above was also applied to the water resistant layer referred to above in a quantity of 2 g/m2.

(4) On the other hand, the protective layer was prepared in the following manner.

After placing polyurethane (tradenamed under “KURAMIRON 1190-000” manufactured by and available from Kuraray Co., Ltd.) in a vessel containing dimethylformamide (DMF) so that the concentration of polyurethane was 10 mass %, the mixture was agitated at 90° C. to dissolve the polyurethane and the completely dissolved solution was then cooled down to ambient temperatures to thereby provide a spinning liquid. Using the spinning liquid so prepared in the manner described above, an electrostatic spinning was carried out with the spinning apparatus shown in FIG. 1. For the spinnerets 4, needles each 0.9 mm in diameter were used. Also, the spinnerets 4 and the sheet take-up apparatus 7 were spaced at a distance of 12 cm from each other. It is to be noted that the sheet take-up apparatus 7 was surrounded by the supporting layer coated with the hot melt resin which was obtained in (3) above, so that the surface of the hot melt resin was deposited with nanofibers.

Thereafter, while the conveyor was driven at a velocity of 0.1 m/min., the spinning liquid was extruded from the spinnerets in a predetermined supply rate, and a 25 kV voltage was applied to the spinnerets to laminate 1.0 g/m2 of polyurethane nanofibers over the nonwoven layer.

(5) Further, the supporting layer, deposited with the polyurethane nanofiber layer, and the water resistant layer, coated with the hot melt resin as in (3) above, were overlapped one above the other with the hot melt resin coating on the water resistant layer held in contact with the polyurethane nanofiber layer, and then were bonded together by means of a calendering process (carried out under calendering conditions of 140° C. in temperature, 0.1 MPa in contact pressure, and 5 m/sec. in processing velocity) to thereby provide a layered body. The fabric prepared from this layered body was found to have a weight of 55 g/m2, a tensile strength of 105 N/5 cm×71 N/5 cm (MD direction×CD direction), an air permeability of 8.4 cc/cm2/sec., a 1 μm quartz dust collecting efficiency of 99.9%, and a 1 μm quartz dust collecting efficiency after 5 times washing of 99.8%, as shown in Table 1. The fabric was also found to have both of an air permeability and a filtering capability as the laminated fabric and to be excellent in integrity enough to exhibit the required filtering capability even after it has been loaded by means of, for example, washing. Accordingly, the laminated fabric has a performance sufficient to allow it to be used as a fabric for a protective clothing.

Example 5

Except for using a polyethylene terephthalate spun bonded nonwoven fabric (tradenamed “ELTAS E01030” manufactured by and available from Asahi Kasei Corporation) having a weight of 30 g/m2 as the supporting layer instead of the foam bonded PVA nonwoven fabric employed on the supporting layer in Example 3, a fabric was prepared in a manner similar to that in Example 3. As shown in Table 1, the fabric so prepared was found to have a weight of 55 g/m2, a tensile strength of 124 N/5 cm×77 N/5 cm (MD direction×CD direction), an air permeability of 9.1 cc/cm2/sec., a 1 μm quartz dust collecting efficiency of 99.6%, and a 1 μm quartz dust collecting efficiency after 5 times washing of 99.5% and was also found to have both of an air permeability and a filtering capability as the laminated fabric and to be excellent in integrity enough to exhibit the required filtering capability even after it has been loaded by means of, for example, washing.

Comparative Example 1

The polypropylene nonwoven fabric (the water resistant layer) and the nylon nonwoven fabric (the supporting layer) both obtained in (3) of Example 4 and applied with the hot melt resin were directly overlapped one above the other with the hot melt resin adhering thereto, with no protective layer intervening therebetween, and were subsequently subjected to a calendaring process in a manner similar to that in Example 4 to form a fabric. As shown in Table 1, this fabric was found to have a weight of 54 g/m2, a tensile strength of 101 N/5 cm×70 N/5 cm (MD direction×CD direction), an air permeability of 21 cc/cm2/sec., a 1 μm quartz dust collecting efficiency of 33.1%, and a 1 μm quartz dust collecting efficiency after 5 times washing of 32.8% and was also found to have an unacceptable filtering capability.

Comparative Example 2

(1) A nylon spun bonded nonwoven fabric having a weight of 30 g/m2 (tradenamed “ELTAS N01030” manufactured by and available from Asahi Kasei Corporation) was used as the supporting layer.

(2) A polypropylene nonwoven fabric having a weight of 20 g/m2 prepared from the same polypropylene (tradenamed “NOVATEC PP” manufactured by and available from Japan Polychem Corporation) as that used in Example 1 by means of the meltblowing process was used as the water resistant layer.

(3) Then, while the supporting layer was moved at a conveyor velocity of 50 m/min., a hot melt resin (tradenamed “INSTANTLOCK MP801” available from Nippon NSC Ltd.) was uniformly applied to the supporting layer in a quantity of 2 g/m2 under conditions of 190° C. in nozzle temperature and 205° C. in hot air temperature to form a resin coating on the supporting layer, followed by cooling the coating once and winding around a take-up roll. Also, in a manner similar to the supporting layer, the hot melt resin referred to above was also applied to the water resistant layer referred to above.

(4) On the other hand, the protective layer was prepared in the following manner.

After placing polyacrylonitrile (manufactured by and available from Sigma Aldrich Co.; weight average molecular weight: 150,000) in a vessel containing dimethylformamide (DMF) so that the concentration of polyacrylonitrile is 11 mass %, the mixture was agitated at 90° C. to dissolve the polyacrylonitrile and the completely dissolved solution was then cooled down to ambient temperatures to thereby provide a spinning liquid. Using the spinning liquid so prepared in the manner described above, an electrostatic spinning was carried out with the spinning apparatus shown in FIG. 1. For the spinnerets 4, needles each 0.9 mm in diameter were used. Also, the spinnerets 4 and the sheet take-up apparatus 7 were spaced at a distance of 10 cm from each other. It is to be noted that the sheet take-up apparatus 7 was surrounded by the supporting layer coated with the hot melt resin which was obtained in (3) above, so that the surface of the hot melt resin was deposited with nanofibers.

Thereafter, while the conveyor was driven at a velocity of 0.1 m/min., the spinning liquid was extruded from the spinnerets in a predetermined supply rate, and a 18 kV voltage was applied to the spinnerets to laminate 1.0 g/m2 of polyacrylonitrile nanofibers over the nonwoven layer.

(5) Also, the supporting layer, laminated with the polyacrylonitrile nanofiber layer, and the water resistant layer, coated with the hot melt resin as in (3) above, were overlapped one above the other with the hot melt resin coating on the water resistant layer held in contact with the polyacrylonitrile nanofiber layer and were bonded together by means of a calendering process (carried out under calendering conditions of 140° C. in temperature, 0.1 MPa in contact pressure, and 5 m/sec. in processing velocity) to thereby provide a layered body. The fabric prepared from this layered body was found to have a weight of 55 g/m2, a tensile strength of 104 N/5 cm×70 N/5 cm (MD direction×CD direction), an air permeability of 7.5 cc/cm2/sec., a 1 μm quartz dust collecting efficiency of 99.6%, and a 1 μm quartz dust collecting efficiency after 5 times washing of 84.1%, as shown in Table 1. The fabric was also found to have lost an integrity for the nonwoven fabric enough to fail to maintain the required filtering capability.

Comparative Example 3

As a comparison, when the performance of a commercially available fabric tradenamed “TYVEK SOFT” (having a weight of 41 g/m2) and manufactured by and available from E. I. du Pont de Nemours and Company, which is currently used as the standard protective base material, was evaluated, the tensile strength thereof was found to be 80 N/5 cm×94 N/5 cm (MD direction×CD direction) and the 1 μm quartz dust collecting efficiency was found to be so high as 98.5% as shown in Table 1. However, the air permeability of the commercially available fabric referred to above was found to be very low of 0.4 cc/cm2/sec. and no shrinkage was found occurring in a hot water of either 60° C. and 70° C.

TABLE 1 Com. Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Com. Ex. 1 Com. Ex. 2 Ex. 3 Supporting Material PVA PVA PVA Nylon PET Nylon Nylon “TYVEK Layer Form Foambond Emboss Foambond Spunbond Spunbond Spunbond Spunbond SOFT” Weight(g/m2) 35 35 35 30 30 30 30 Protective Material SEPTON/PP Polyurethane SEPTON Polyurethane SEPTON — PAN Layer Form Meltblowing Nanofiber Nanofiber Nanofiber Nanofiber — Nanofiber Weight(g/m2) 10 1 1 1 1 — 1 Stretch at 205 51 38 51 38 — 24 break (%) Water Material PP PP PP PP PP PP PP Resistant Form MB MB MB MB MB MB MB Layer Weight(g/m2) 20 20 20 20 20 20 20 Adhering Method Calender Calender Hot melt Hot melt Hot melt Hot melt Hot melt Total Weight 65 56 60 55 55 54 55 41 Tensile MD 120 64 93 105 124 101 104 80 Strength CD 100 54 49 71 77 70 70 94 (N/5 cm) Air Permeability 2.1 5.7 8.1 8.4 9.1 21 7.5 0.4 (cc/cm2/sec) Collecting Before 97.3 99.9 99.7 99.7 99.6 33.1 99.6 98.5 Efficiency Washing After 5 times 97.1 99.8 99.7 99.8 99.5 32.8 84.1 98.3 Washing Withstanding 1132 850 753 811 781 751 831 1005 Pressure (mmH2O) Shrinkage 60° C. water 12 11 12 0 0 0 0 0 Rate (%) 70° C. water 61 58 64 0 0 0 0 0

The laminated fabric of the present invention is advantageously used as a protective material for protecting human bodies from harmful and/or hazardous substances such as, for example, dust harmful to human bodies, contagions and viruses, and/or harmful and/or hazardous substances afloat in the atmospheric air. Such protective material is used not only as a protective clothing (such as, for example, protective clothes, masks, gloves and/or hats), but also sheeting, protectors and/or filters of a kind used under the environment, where the harmful and/or hazardous substances tend to stick thereto, to protect human bodies from the secondary infection of those harmful and/or hazardous substances.

Also, where the laminated fabric has a volume reducing capability, since the laminated fabric (or the protective material) can be reduced in volume and be then transported or disposed of after use, the cost incurred in transportation or disposal can be reduced advantageously.

Claims

1. A laminated fabric which comprises:

a supporting layer; and
a protective layer comprising a stretchable nonwoven fabric formed from an ultra-fine fiber, the protective layer bonded to the supporting layer;
whereby the laminated fabric having an air permeability of 2 cc/cm2/sec or higher and also having an efficiency of 90% or higher when collecting quartz particles 1 μm in size.

2. The laminated fabric as claimed in claim 1, in which the ultra-fine fiber comprises a thermoplastic elastomer.

3. The laminated fabric as claimed in claim 2, in which the thermoplastic elastomer comprises at least one thermoplastic elastomer selected from the group consisting of SEPS, SEBS, a polyurethane series thermoplastic elastomer, a polyester series thermoplastic elastomer and a polyamide series thermoplastic elastomer.

4. The laminated fabric as claimed in claim 1, in which the stretchable nonwoven fabric has a stretch of 30% or higher at break.

5. The laminated fabric as claimed in claim 1, in which the stretchable nonwoven fabric comprises an ultra-fine fiber being a nanofiber of 10 to 1,000 nm in fiber diameter and also have a weight within the range of 0.01 to 10 g/m2.

6. The laminated fabric as claimed in claim 1, in which at least a part of the fibers forming the supporting layer is a volume reducible fiber.

7. The laminated fabric as claimed in claim 6, in which the volume reducible fiber comprises a polyvinyl alcohol fiber.

8. The laminated fabric as claimed in claim 1, further comprising a water resistant layer, the water resistant layer being positioned on the protective layer so that the protective layer is employed as an intermediate layer between the water resistant layer and the supporting layer.

9. The laminated fabric as claimed in claim 8, which has a withstanding pressure within the range of 300 to 1,500 mmH2O.

10. The laminated fabric as claimed in claim 1, in which 5 to 90% shrinkage takes place when immersed in a hot water of 60° C. or higher.

11. A protective material, in which at least a part thereof comprises a laminated fabric as defined in claim 1.

12. A volume reducing method which comprises placing a laminated fabric as defined in claim 1 into a sealable vessel and supplying a hot water of 60° C. or higher to the laminated fabric.

Patent History
Publication number: 20100024136
Type: Application
Filed: Mar 6, 2008
Publication Date: Feb 4, 2010
Applicant: KURARAY CO., LTD. (Kurashiki-shi, Okayama)
Inventors: Masatoshi Takenoiri (Okayama), Keisuke Takishima (Osaka), Junichi Sugino (Osaka), Shinya Inada (Okayama)
Application Number: 12/530,466