JP4980941B2 - Stretch material and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an elastic material having proper elasticity and excellent in touch feeling. <P>SOLUTION: The elastic material comprising a nonwoven fabric is produced by heating and crimping a fiber web with high temperature steam, which comprises a conjugate fiber having a phase structure formed with plural resins of different heat shrinkage factors. The conjugate fiber of the elastic material is oriented almost in parallel to the plane direction and almost uniformly crimped in the thickness direction with 20-200 &mu;m average radius of curvature, and has &ge;20 N/50 mm breaking strength of at least one direction in the plane direction and &ge;0.2 N/50 mm 25% recovery stress in recovery behavior after 50% elongation. The conjugate fiber comprises a polyalkylene arylate-based resin and a modified polyalkylene arylate-based resin and may be a parallel or eccentric sheath-core structure. The elastic material is suitable for mask ear loop elements and sanitary material elastic elements. <P>COPYRIGHT: (C)2009,JPO&amp;INPIT

Description

  The present invention relates to an elastic material that is made of a nonwoven fabric, has excellent elasticity, and is suitable for an ear hook member for a mask, an elastic member for a paper diaper, and the like, and a method for producing the same.

  Conventionally, rubber having excellent stretchability has been used to fix fabrics and papers to the human body in sanitary materials such as masks and diapers, hats, clothes and socks. However, since rubber has a strong contraction force, it often causes a sense of discomfort and pain to the skin in applications that directly touch delicate parts of the body, such as sanitary materials, or applications that are worn for a long time. In particular, when the ear hooking member of the mask is made of rubber, since the rubber directly hits the base of the ear, pain and discomfort are likely to occur. Therefore, in recent masks, disposable masks or the like have been proposed that use an extension force of a nonwoven fabric as an ear hook member.

For example, Japanese Patent Application Laid-Open No. 2007-50192 (Patent Document 1) has a basis weight of 80 to 130 g / m ² , 75 to 25% by weight of a polyolefin-based crimped composite fiber, and a polyester-based crimped composite fiber 25 to 75. The crimped conjugate fiber is mechanically entangled to maintain the nonwoven fabric form, the elongation stress at 50% elongation is 0.02 to 0.04 N / mm ² , and An ear hook member for a mask having an initial elongation rate of 2 to 10% at 50% elongation is disclosed. In this mask hook member, after the crimped composite fiber is entangled with water flow from a plurality of orifices to maintain the nonwoven fabric form, the dehydrated and dried fiber web is heat-treated at a temperature at which the fibers are not welded. Crimp is expressed. This document does not describe the heating method, but describes the dry heat shrinkage of the latent crimped fibers.

  However, in this mask hook member, the crimp of the latent crimp fiber is not uniform in the thickness direction, so that the stretchability is not sufficient. Moreover, since the cushioning property or flexibility is low due to the non-uniformity, the touch is bad. Furthermore, the stretchability is easily reduced by repeated stretching and the durability is not sufficient.

  Furthermore, utilization of the nonwoven fabric which has air permeability and a softness | flexibility is also examined also in the expansion-contraction member of a paper diaper (disposable diaper). For example, Japanese Patent Application Laid-Open No. 2006-348461 (Patent Document 2) discloses a copolymer of propylene, 1-butene and an α-olefin having 5 to 12 carbon atoms, and the composition of each component is 15 to 15 propylene. Fiber of olefin copolymer having 70 mol%, 1-butene 5 to 50 mol% and 5 to 12 carbon atoms α-olefin 15 to 70 mol%, and a melt flow rate of 10 to 2000 g / 10 min. It is disclosed that the non-woven fabric formed in (1) is used as a stretchable member for sanitary materials such as paper diapers. This document also describes a method for forming a nonwoven fabric by interlacing a crimped fabric with a method such as hot embossing, water jet, hot air through, needle punching, etc. as a method for producing a stretchable nonwoven fabric.

  However, the fiber treated with a method such as hot embossing, water jet, needle punching, etc. is oriented in the thickness direction, and entangled within the nonwoven fabric surface, resulting in poor touch and high strength and elasticity. It is also difficult. Moreover, according to the hot air through treatment, heat fusion near the center in the thickness direction becomes insufficient, and it is difficult to obtain high strength and stretchability. In addition, the feel of the olefin copolymer itself used is poor. Furthermore, when fibers are fixed together by means of fusing such as hot embossing, hot air through, melt blow, or binder, the stress generated by complicated movement during use cannot be relieved by the interlocking of the fibers, so Is likely to occur, and the skin may be uncomfortable.

  Further, 2007-230180 (Patent Document 3) discloses a stretchable laminated member comprising a core material having a nonwoven fabric bonded to at least one surface, the core material containing 15 to 45% styrene. The nonwoven fabric is continuously bonded to the core material, and when the laminated member is stretched 100%, it peels off or breaks from the core material before and after the stretching. In addition, it is disclosed that an elastic laminate member having a stress of 50% or less when the nonwoven fabric is stretched is 3 N / 25 mm or less in the CD direction is used for a disposable diaper. This document describes a nonwoven fabric obtained by a spunbond method or a spunlace method as the nonwoven fabric.

However, since this stretchable member is laminated on both sides with a nonwoven fabric manufactured by the spunbond method or the spunlace method, the recovery property at the time of extension is low, liquid leakage is likely to occur, and the touch is also poor.
JP 2007-50192A (Claim 1, paragraphs [0019] [0021] [0023] [0024]) JP 2006-348461 A (Claim 1, paragraphs [0001] [0116]) JP 2007-230180 A (Claim 1, paragraphs [0001] [0030] [0023] [0024])

  Accordingly, an object of the present invention is to provide a stretchable material having an appropriate stretchability and excellent in touch and a method for producing the same.

  Another object of the present invention is to provide a stretchable material in which a decrease in stretchability is suppressed even when repeatedly stretched and a method for producing the same.

  Still another object of the present invention is to provide a stretchable material that has air permeability, does not contain harmful components, and has little skin irritation and a method for producing the same.

  Another object of the present invention is to provide a stretchable material having a large recovery force when stretched and capable of firmly fixing a cloth, paper, or the like to the body and a method for producing the same.

  As a result of intensive studies to achieve the above-mentioned problems, the present inventors have found that a nonwoven fabric obtained by entanglement of a fiber having a potential for heat-crimping with a high-temperature steam to develop a three-dimensional crimp is suitable. The present invention has been completed by finding out that it has elasticity and is excellent in touch.

  That is, the elastic material of the present invention is an elastic material composed of a nonwoven fabric including a composite fiber having a phase structure formed of a plurality of resins having different thermal shrinkage rates, and the composite fiber is substantially in the plane direction. 25 in the recovery behavior after 50% elongation, with parallel orientation and an average curvature radius of 20 to 200 μm, crimped substantially uniformly in the thickness direction, a breaking strength in at least one direction in the plane direction of 20 N / 50 mm or more. % Recovery stress is 0.2 N / 50 mm or more. The softening point or melting point of the resin constituting the composite fiber may be 100 ° C. or higher, and the resin exposed on the surface of the composite fiber may be a non-wet heat adhesive resin. The composite fiber is composed of a polyalkylene arylate resin and a modified polyalkylene arylate resin, and may have a parallel type or an eccentric core-sheath type structure. In the stretchable material, the proportion of the composite fiber may be 80% by mass or more. The stretchable material of the present invention may have a 25% recovery stress of about 0.3 to 1.5 N / 50 mm in a recovery behavior after 50% elongation. Further, the breaking strength in at least one direction in the plane direction may be 40 N / 50 mm or more. Furthermore, the elongation at break in at least one direction in the plane direction may be 100% or more (particularly about 150 to 350%). The stretchable material of the present invention has a surface that can come into contact with the body, and is suitable as a stretchable material for sanitary materials (particularly, an ear hook member for a mask or a stretchable member for a paper diaper). The present invention also includes a sanitary material provided with the elastic material (particularly, a mask provided with the mask hook member and a mask provided with a paper diaper elastic material.

  The present invention includes the step of forming a fiber including a composite fiber having a phase structure formed of a plurality of resins having different thermal shrinkage rates, and the step of crimping the fiber web by heating with high-temperature steam. Also included are methods of manufacturing the material.

  The stretchable material of the present invention has an appropriate stretchability because the composite fiber is uniformly crimped and entangled in the thickness direction, and also has a soft and appropriate cushioning property, so that the touch is also excellent. Moreover, even if it expands and contracts repeatedly, the fall of a stretching property is suppressed and it is excellent in durability. Moreover, since it has a nonwoven fabric structure, it is excellent in air permeability. Furthermore, since it is mechanically entangled using high temperature steam without using a binder component, it does not contain harmful components and has little skin irritation. Therefore, the stretchable material of the present invention is suitable for applications that come into contact with the body such as sanitary materials.

  In addition, the stretchable material of the present invention has a large recovery force when stretched by uniform crimping, and can firmly fix cloths, papers, and the like to the body. Therefore, the stretchable material of the present invention is particularly suitable for applications that must be fixed in close contact with the body, such as mask ear hook members (stretchable members) and paper diaper stretchable members. Intrusion of particles and leakage of liquid can be suppressed.

  In the present specification, the hygiene material means a disposable material composed of fabric or paper (especially paper) among materials worn on the body in relation to health such as medical care or nursing care. . Specifically, sanitary materials include masks, gloves, bandages, gauze or absorbent cotton, adhesive bandages, poultices, surge tapes, diapers, sanitary napkins, and the like. Furthermore, in the present specification, fabric and paper are not strictly distinguished, and any sheet-like product composed of natural fiber or synthetic fiber is applicable, and woven fabric, non-woven fabric, plain paper, Includes synthetic paper. The fabric or paper may be a material combined with another constituent material (for example, a plastic film or a metal foil).

[Elastic material]
The stretchable material of the present invention is composed of a nonwoven fabric including fibers in which a phase structure is formed of a plurality of resins having different thermal shrinkage rates (or thermal expansion rates), and this composite fiber is mainly oriented in the plane direction. The coil is crimped along the orientation axis with an average radius of curvature of 20 to 200 μm. As will be described in detail later, the nonwoven fabric causes high temperature (overheated or heated) water vapor to act on the web containing the composite fiber to develop crimps on the composite fiber without causing the fibers to fuse (mechanical). ) Obtained by entanglement.

(Nonwoven fabric material)
A composite fiber is a fiber (latently crimped fiber) having an asymmetric or layered (so-called bimetal) structure that causes crimping by heating due to the difference in thermal shrinkage rate (or thermal expansion rate) of a plurality of resins. A plurality of resins usually have different softening points or melting points. The plurality of resins include, for example, polyolefin resins (low density, medium density or high density polyethylene, poly C _2-4 olefin resins such as polypropylene), acrylic resins (acrylonitrile units such as acrylonitrile-vinyl chloride copolymer) Acrylonitrile-based resin, etc.), polyvinyl acetal resin (polyvinyl acetal resin, etc.), polyvinyl chloride resin (polyvinyl chloride, vinyl chloride-vinyl acetate copolymer, vinyl chloride-acrylonitrile copolymer, etc.), polychlorinated Vinylidene resins (vinylidene chloride-vinyl chloride copolymer, vinylidene chloride-vinyl acetate copolymer, etc.), styrene resins (heat-resistant polystyrene, etc.), polyester resins (polyethylene terephthalate resin, polytrimethylene terephthalate resin, polybutylene) Poly C _2-4 alkylene arylate resins such as terephthalate resin and polyethylene naphthalate resin), polyamide resins (polyamide 6, polyamide 66, polyamide 11, polyamide 12, polyamide 610, polyamide 612, etc. aliphatic polyamide resins) , Semi-aromatic polyamide resins, polyphenylene isophthalamide, polyhexamethylene terephthalamide, poly-p-phenylene terephthalamide and other aromatic polyamide resins), polycarbonate resins (bisphenol A type polycarbonate, etc.), poly p-phenylene benzo You may select from thermoplastic resins, such as a bisoxazole resin, a polyphenylene sulfide resin, a polyurethane-type resin, and a cellulose resin (cellulose ester etc.). Further, each of these thermoplastic resins may contain other copolymerizable units.

  Among these resins, in the present invention, a non-wet heat adhesive resin (or heat-resistant hydrophobic resin having a softening point or melting point of 100 ° C. or higher is not melted or softened even when heat-treated with high-temperature steam and the fibers are not fused. Resin or non-aqueous resin), for example, polypropylene resin, polyester resin, and polyamide resin are preferable. In particular, aromatic polyester resin and polyamide resin are preferable from the viewpoint of excellent balance of heat resistance and fiber forming property. preferable. In the present invention, the resin exposed on the surface of the composite fiber is preferably a non-wet heat adhesive fiber so that the fibers constituting the nonwoven fabric are not fused even if they are treated with high-temperature steam.

  The plurality of resins constituting the composite fiber may have different heat shrinkage rates, and may be a combination of resins of the same system or a combination of different resins.

  In this invention, it is preferable that it is comprised with the combination of resin of the same type | system | group from the point of adhesiveness. In the case of a combination of resins of the same system, a combination of a component (A) that forms a homopolymer (essential component) and a component (B) that forms a modified polymer (copolymer) is usually used. In other words, the homopolymer that is an essential component is crystallized more than the homopolymer by, for example, copolymerizing and modifying a copolymerizable monomer that lowers the crystallinity, melting point, or softening point. The melting point or the softening point may be lowered as compared with the homopolymer. Thus, a difference may be provided in the thermal shrinkage rate by changing the crystallinity, melting point or softening point. The difference in melting point or softening point may be, for example, about 5 to 150 ° C, preferably about 50 to 130 ° C, and more preferably about 70 to 120 ° C. The ratio of the copolymerizable monomer used for the modification is, for example, 1 to 50 mol%, preferably 2 to 40 mol%, more preferably 3 to 30 mol% (particularly 5 to 5 mol%) with respect to all monomers. 20 mol%). The composite ratio (mass ratio) of the component forming the homopolymer and the component forming the modified polymer can be selected according to the structure of the fiber. For example, the homopolymer component (A) / modified polymer component (B) = 90/10 to 10/90, preferably 70/30 to 30/70, more preferably about 60/40 to 40/60.

In the present invention, the composite fiber is a combination of an aromatic polyester resin, particularly a polyalkylene arylate resin (a) and a modified polyalkylene arylate resin (b) because it is easy to produce latent crimpable conjugate fibers. It may be a combination. The polyalkylene arylate resin (a) is composed of an aromatic dicarboxylic acid (such as symmetric aromatic dicarboxylic acid such as terephthalic acid or naphthalene-2,6-dicarboxylic acid) and an alkanediol component (such as ethylene glycol or butylene glycol such as C _{3- 6} alkanediol etc.) and a homopolymer. Specifically, poly C _2-4 alkylene terephthalate resins such as polyethylene terephthalate (PET) and polybutylene terephthalate (PBT) are used, and generally a general PET having an intrinsic viscosity of about 0.6 to 0.7. PET used for fibers is used.

On the other hand, in the modified polyalkylene arylate resin (b), the melting point or softening point of the polyalkylene arylate resin (a), which is an essential component, is a copolymer component that lowers the crystallinity, such as an asymmetric aromatic dicarboxylic acid. Further, a dicarboxylic acid component such as alicyclic dicarboxylic acid or aliphatic dicarboxylic acid, an alkanediol component having a chain length longer than the alkanediol of the polyalkylene arylate resin (a) and / or an ether bond-containing diol component can be used. These copolymerization components can be used alone or in combination of two or more. Among these components, as dicarboxylic acid components, asymmetric aromatic carboxylic acids (isophthalic acid, phthalic acid, 5-sodium sulfoisophthalic acid, etc.), aliphatic dicarboxylic acids (C _6-12 aliphatic dicarboxylic acids such as adipic acid, etc.) ) such as is commonly, as the diol component, alkane diol (1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, etc. C _3-6 alkanediol such as neopentyl glycol), polyoxyalkylene Glycols (polyoxy C _2-4 alkylene glycols such as diethylene glycol, triethylene glycol, polyethylene glycol, polytetramethylene glycol, etc.) are widely used. Among these, asymmetric aromatic dicarboxylic acids such as isophthalic acid, polyoxy C _2-4 alkylene glycol such as diethylene glycol, and the like are preferable. Further, the modified polyalkylene arylate resin (b) may be an elastomer having C _2-4 alkylene arylate (ethylene terephthalate, butylene terephthalate, etc.) as a hard segment and (poly) oxyalkylene glycol as a soft segment. .

  In the modified polyalkylene arylate resin (b), as the dicarboxylic acid component, the ratio of the dicarboxylic acid component (for example, isophthalic acid) for lowering the melting point or the softening point is, for example, relative to the total amount of the dicarboxylic acid component, It is 1-50 mol%, Preferably it is 5-50 mol%, More preferably, it is about 15-40 mol%. The ratio of the diol component (for example, diethylene glycol) for reducing the melting point or the softening point as the diol component is, for example, 30 mol% or less, preferably 10 mol% or less (for example, 0 mol%) with respect to the total amount of the diol component. .About 1 to 10 mol%). When the proportion of the copolymer component is too low, sufficient crimps are not expressed, and the form stability and stretchability of the nonwoven fabric after crimps are reduced. On the other hand, if the proportion of the copolymer component is too high, the crimping performance will be high, but it will be difficult to spin stably.

  Modified polyalkylene arylate resin (b) is used in combination with polyvalent carboxylic acid components such as trimellitic acid and pyromellitic acid, and polyol components such as glycerin, trimethylolpropane, trimethylolethane, and pentaerythritol as necessary. And may be branched.

  The cross-sectional shape of the composite fiber (cross-sectional shape perpendicular to the length direction of the fiber) is a general solid cross-sectional shape such as a round cross-section or an irregular cross-section [flat shape, elliptical shape, polygonal shape, 3-14 leaf shape, It is not limited to T-shape, H-shape, V-shape, dogbone (I-shape), etc.], and may be a hollow cross-section, but is usually a round cross-section.

  As a cross-sectional structure of the composite fiber, a phase structure formed in a plurality of resins, for example, a core-sheath type, a sea-island type, a blend type, a parallel type (side-by-side type or multilayer bonding type), a radial type (radial bonding type) ), Hollow radiation type, block type, random composite type and the like. Among these cross-sectional structures, the structure in which the phase portions are adjacent (so-called bimetal structure), or the structure in which the phase structure is asymmetrical, for example, an eccentric core-sheath type, in parallel, because it is easy to develop spontaneous crimping by heating. A mold structure is preferred.

  If the composite fiber has a core-sheath type structure such as an eccentric core-sheath type, the core portion is not damaged if it has a heat shrinkage difference with the non-wet heat adhesive resin of the sheath portion located on the surface. Consists of wet heat adhesive resin (for example, vinyl alcohol polymers such as ethylene-vinyl alcohol copolymer and polyvinyl alcohol) and thermoplastic resin having a low melting point or softening point (for example, polystyrene, low density polyethylene, etc.) May be.

  The average fineness of the composite fiber can be selected from a range of, for example, about 0.1 to 50 dtex, preferably 0.5 to 10 dtex, and more preferably 1 to 5 dtex (particularly 1.5 to 3 dtex). If the fineness is too thin, it is difficult to produce the fiber itself, and it is difficult to secure the fiber strength. Moreover, it becomes difficult to express a beautiful coiled crimp in the step of expressing crimp. On the other hand, if the fineness is too thick, the fiber becomes stiff and it is difficult to express sufficient crimp.

  The average fiber length of the composite fiber can be selected from a range of, for example, about 10 to 100 mm, preferably 20 to 80 mm, and more preferably about 25 to 75 mm (particularly 40 to 60 mm). If the fiber length is too short, it becomes difficult to form a fiber web, and in addition, in the step of developing crimps, entanglement between fibers becomes insufficient, and it becomes difficult to ensure strength and stretchability. In addition, if the fiber length is too long, it becomes difficult to form a fiber web with a uniform basis weight, and a lot of fibers are entangled at the time of web formation, which interferes with each other when crimping occurs. This makes it difficult to develop stretchability. Furthermore, in the present invention, when the fiber length is in the above range, some of the fibers crimped on the nonwoven fabric surface are appropriately exposed on the nonwoven fabric surface, so that the self-adhesiveness of the nonwoven fabric described later can be improved.

  By applying heat treatment to this composite fiber, crimp is developed (appears) and becomes a fiber having a substantially coiled (spiral or helical spring-shaped) three-dimensional crimp.

  The number of crimps before heating (mechanical crimp number) is, for example, about 0 to 30 pieces / 25 mm, preferably about 1 to 25 pieces / 25 mm, and more preferably about 5 to 20 pieces / 25 mm. The number of crimps after heating is, for example, 30 pieces / 25 mm or more (for example, 30 to 200 pieces / 25 mm), preferably about 35 to 150 pieces / 25 mm, and more preferably about 40 to 120 pieces / 25 mm. It may be about 45 to 120 pieces / 25 mm (especially 50 to 100 pieces / 25 mm).

  The stretchable material of the present invention has a substantially uniform crimp in the thickness direction because the latent crimpable conjugate fiber constituting the nonwoven fabric is crimped with high-temperature steam so that the crimp of the conjugate fiber oriented substantially parallel to the surface direction is uniform. It has the characteristic of being expressed in Specifically, in the cross section in the thickness direction, the number of fibers forming one or more coil crimps in the central portion (inner layer) of each region divided in three in the thickness direction is, for example, 5 ~ 50 / 5mm (surface direction length) · 0.2mm (thickness), preferably 10-50 pieces / 5mm (surface direction) · 0.2mm (thickness), more preferably 20-50 pieces / 5mm ( (Surface direction) · 0.2 mm (thickness). In the present invention, most crimped fiber axes are oriented in the plane direction, and the number of crimps is uniform in the thickness direction. Even if it does not contain an agent, it has practical strength. In addition, in this-application specification, "the area | region divided into three equal to the thickness direction" means each area | region which sliced in the direction orthogonal to the thickness direction of a nonwoven fabric, and was divided into three equal parts.

  Furthermore, in the stretchable material of the present invention, the fact that the crimps are uniform in the thickness direction can also be evaluated by the uniform fiber curvature. The fiber curvature is a ratio (L2 / L1) of the fiber length (L2) to the distance (L1) between both ends of the fiber (crimped fiber), and the fiber curvature (particularly in the central region in the thickness direction). Fiber curvature) is, for example, 1.3 or more (for example, 1.35 to 5), preferably 1.4 to 4 (for example, 1.5 to 3.5), and more preferably 1.6 to 3 ( In particular, it is about 1.8 to 2.5). In addition, in this invention, in order to measure a fiber curvature based on the electron micrograph of a nonwoven fabric cross section so that it may mention later, the said fiber length (L2) stretches | stretches the fiber crimped three-dimensionally and is linear. It does not mean the actual fiber length (actual length), but refers to a fiber length (fiber length on the photograph) obtained by stretching the two-dimensionally crimped fibers shown in the photograph into a straight line. That is, the fiber length (fiber length on the photograph) in the present invention is measured shorter than the actual fiber length.

  Furthermore, in the present invention, the crimp is expressed substantially uniformly in the thickness direction, so that the fiber curvature is uniform in the thickness direction. In the present invention, the uniformity of the fiber curvature rate can be evaluated by comparing the fiber curvature rates in the respective layers that are divided into three equal parts in the thickness direction in the cross section in the thickness direction. That is, in the cross section in the thickness direction, the fiber curvature rate in each region divided into three equal parts in the thickness direction is in the above range, and the ratio of the minimum value to the maximum value of the fiber curvature rate in each region (minimum value / maximum value) ) (Ratio of the minimum region to the region with the maximum fiber curvature) is, for example, 75% or more (for example, 75 to 100%), preferably 80 to 99%, more preferably 82 to 98% (especially 85 to 98%). 97%).

  As a specific method for measuring the fiber curvature and its uniformity, a method is used in which a cross section of the nonwoven fabric is taken with an electron micrograph and the fiber curvature is measured for a region selected from each region divided into three equal parts in the thickness direction. It is done. The area to be measured is measured in an area of 2 mm or more in the length direction for each of the surface layer (surface area), inner layer (center area), and back layer (back area) divided into three. Further, the thickness direction of each measurement region is set so that each measurement region has the same thickness width in the vicinity of the center of each layer. Furthermore, each measurement region includes 100 or more (preferably about 300 or more, more preferably about 500 to 1000) fiber pieces that are parallel in the thickness direction and capable of measuring the fiber curvature in each measurement region. Set as follows. After setting each of these measurement regions, after measuring the fiber curvature rate of all the fibers in the region, calculating the average value for each measurement region, the region showing the maximum average value and the minimum average value The uniformity of the fiber curvature is calculated by comparison with the region shown.

  As described above, the crimped fiber constituting the nonwoven fabric has a substantially coil-shaped crimp after the crimp is developed. The average curvature radius of a circle formed by the coil of crimped fibers can be selected from a range of about 10 to 250 μm, for example, for example, 20 to 200 μm (for example, 50 to 200 μm), preferably 50 to 160 μm (for example, 60 to 150 μm), more preferably about 70 to 130 μm. Here, the average radius of curvature is an index representing the average size of the circle formed by the coil of crimped fibers, and when this value is large, the formed coil has a loose shape, in other words It means having a shape with a small number of crimps. Further, when the number of crimps is small, the entanglement between the fibers is also reduced, which is disadvantageous for exhibiting sufficient stretch performance. Conversely, when a coiled crimp having an average radius of curvature that is too small is manifested, the fibers are not sufficiently entangled, making it difficult to ensure web strength, and also exhibiting such a crimp. Production of latent crimped fibers is also very difficult.

  In the composite fiber crimped into a coil shape, the average pitch of the coil is, for example, about 0.03 to 0.5 mm, preferably about 0.03 to 0.3 mm, and more preferably about 0.05 to 0.2 mm.

  The nonwoven fabric (fiber web) may contain other fibers (non-composite fibers) in addition to the composite fibers. Non-composite fibers include, for example, the above-described non-wet heat-adhesive resin or wet heat-adhesive resin, cellulosic fibers [for example, natural fibers (cotton, wool, silk, hemp, etc.), semi-synthetic fibers. (Acetate fiber such as triacetate fiber), regenerated fiber (rayon, polynosic, cupra, lyocell (for example, registered trademark name: “Tencel”, etc.), etc.)] and the like. The average fineness and average fiber length of the non-composite fibers are the same as those of the composite fibers. These non-conjugated fibers can be used alone or in combination of two or more. Of these non-composite fibers, recycled fibers such as rayon, semi-synthetic fibers such as acetate, polyolefin fibers such as polypropylene and polyethylene, polyester fibers, and polyamide fibers are preferable. In particular, from the viewpoint of blendability and the like, it may be the same type of fiber as the composite fiber. For example, when the composite fiber is a polyester fiber, the non-composite fiber may also be a polyester fiber.

  The ratio (mass ratio) of the conjugate fiber and the non-conjugated fiber can be selected from the range of about conjugate fiber / non-conjugated fiber = 70/30 to 100/0, for example, 80/20 to 100/0 (for example, 80 / 20 to 99.5 / 0.5), preferably 90/10 to 100/0 (for example, 90/10 to 99/1), and more preferably about 95/5 to 100/0. By blending non-composite fibers, the balance between strength and stretchability or flexibility of the nonwoven fabric can be adjusted. However, if the proportion of the composite fiber (latently crimped fiber) is too small, the crimped fiber expands and contracts after the onset of crimping, and the non-composite fiber becomes a resistance to the contraction particularly when contracted after the expansion. It is difficult to ensure stress.

  Nonwoven fabrics (fiber webs) are further made of conventional additives such as stabilizers (heat stabilizers such as copper compounds, UV absorbers, light stabilizers, antioxidants, etc.), antibacterial agents, deodorants, perfumes, It may contain a colorant (such as a dye / pigment), a filler, an antistatic agent, a flame retardant, a plasticizer, a lubricant, and a crystallization rate retarder. These additives can be used alone or in combination of two or more. These additives may be carried on the surface of the fiber or may be contained in the fiber.

(Characteristics of stretch material)
The stretchable material of the present invention is not constrained by the individual fibers constituting the nonwoven fabric, but the crimping of the composite fiber is manifested and the shape changes into a coil shape, so that the fibers are intertwined with each other and restrained. Or it has a latched structure. The external shape is usually a plate shape or a sheet shape. Furthermore, although the planar shape of the plate-like nonwoven fabric can be selected according to the use, it is usually a rectangular sheet shape such as a tape shape or a belt shape, a circle or an ellipse shape, or a shape obtained by combining these shapes according to the use. (For example, a rectangular sheet shape or a combination of an elliptical shape and a belt shape).

  In the stretchable material of the present invention, it is desirable that most (most) fibers constituting the nonwoven fabric (axial core direction of the coiled crimped fiber) are oriented substantially parallel to the nonwoven fabric surface (sheet surface). . In the present specification, “orientated substantially parallel to the surface direction” means, for example, a large number of fibers locally (axial direction of the coiled crimped fibers), such as entanglement by a needle punch. Means a state where portions oriented along the thickness direction do not exist repeatedly.

  The stretchable material of the present invention is composed of composite fibers oriented in the surface direction (length direction) of the nonwoven fabric and crimped in a coil shape, and adjacent or intersecting composite fibers are entangled with each other in the crimped coil portion. is doing. Moreover, the composite fiber is slightly entangled even in the thickness direction (or oblique direction) of the nonwoven fabric. In particular, in the present invention, in the composite fiber web, the composite fiber is entangled in the process of contracting into a coil shape, and the fiber is restrained by the entangled coil portion. Therefore, a nonwoven fabric expand | extends largely in a surface direction (longitudinal direction) by the coil part which entangles rather than the width direction or the thickness direction. Furthermore, since it is oriented in the surface direction and the longitudinal direction, when tension is applied in the longitudinal direction, the entangled coil portion expands and tries to return to the original coil shape, so that it has high elasticity in the surface direction and the longitudinal direction. have. Furthermore, also in the thickness direction of the nonwoven fabric, the entangled coil portions exhibit cushioning properties and flexibility in the thickness direction.

  On the other hand, when there are many fibers oriented in the thickness direction (perpendicular to the sheet surface) without substantially fusing the fibers constituting the nonwoven fabric, these fibers also form a coiled crimp. Therefore, the fibers are entangled with each other extremely complicatedly. As a result, other fibers are restrained or fixed more than necessary, and further the expansion and contraction of the coil constituting the fibers is inhibited, so that the stretchability of the nonwoven fabric is reduced. Therefore, it is desirable to orient the fibers as parallel as possible to the sheet surface.

  Thus, in the stretchable material of the present invention, since the coiled fibers are oriented substantially parallel to the surface direction, the nonwoven fabric has stretchability in the surface direction. On the other hand, when the fiber is stretched in the thickness direction, the fiber is easily unwound, and thus does not exhibit stretchability (shrinkage) as seen in the surface direction. Such fiber orientation can be easily confirmed by such stretchability observation even when the fibers are dense and it is difficult to visually observe the orientation.

Density of the nonwoven fabric (bulk density) is, for example, can be selected from 0.01 to 0.5 g / cm ³ in the range of about, for example, 0.03~0.4g / cm ^3, preferably 0.05~0.3g / Cm ³ , more preferably about 0.08 to 0.25 g / cm ³ (particularly 0.1 to 0.2 g / cm ³ ).

  The stretch material of the present invention may have one or more holes in the surface direction (or longitudinal direction) from the viewpoint of further improving air permeability. In the case of having a plurality of holes, the holes may be arranged or oriented periodically or regularly. The area occupied by the pores is, for example, 50% or less (for example, 1 to 50%), preferably 3 to 40%, and more preferably about 5 to 30% with respect to the total area of the nonwoven fabric surface. If the area of the hole is too large, the stretchability and strength as a stretchable material may not be exhibited.

The basis weight of the nonwoven fabric (nonwoven fabric after heating) can be selected, for example, from a range of about 10 to 300 g / m ² , preferably 20 to 250 g / m ² , and more preferably about 30 to 200 g / m ² . The thickness of a nonwoven fabric can be selected from the range of about 0.1-10 mm, for example, is 0.2-5 mm, for example, Preferably it is 0.3-3 mm, More preferably, it is about 0.4-1.5 mm. When the weight per unit area and thickness are in this range, the balance between the stretchability and flexibility or cushioning properties of the nonwoven fabric is improved.

  The elastic material of the present invention has a breaking strength of at least 20 N / 50 mm (for example, 20 to 150 N / 50 mm) in at least one direction in the plane direction (for example, in the case of a belt, both in the length direction and the width direction), preferably It is about 23 to 120 N / 50 mm, more preferably about 25 to 100 N / 50 mm (particularly 28 to 80 N / 50 mm). This breaking strength can be selected according to the application. For example, when it is used for an ear hook member for a mask, it may be about 20 N / 50 mm or more. However, when it is used for an elastic member such as a paper diaper, it has a relatively strong breaking strength. For example, it may be 40 N / 50 mm or more (for example, 40 to 150 N / 50 mm), preferably about 50 to 100 N / 50 mm. In this invention, since it has such a breaking strength, it is excellent in elasticity, and even if it is used repeatedly, it can suppress that it fractures | ruptures or a elasticity falls. In particular, when the stretchable material has a strip shape and is used by being stretched and contracted in the length direction, it is preferable that the range of the breaking strength is satisfied in the length direction.

  Moreover, when manufacturing a strip | belt-shaped member using the elastic material of this invention, it is necessary to process a nonwoven fabric according to the width | variety and length required for a strip | belt-shaped member, but this process normally uses a slitter rewinder. Can be easily processed. Therefore, in the present invention, it is preferable that the breaking strength is in the above range in the length direction of the nonwoven fabric from the viewpoint of ensuring good productivity.

  The stretchable material of the present invention has a breaking elongation of at least one direction in a plane direction (for example, in the case of a belt-like shape, both in the length direction and the width direction) of 100% or more (for example, 100 to 1000%), preferably 150%. Above (for example, 150 to 500%), more preferably about 200 to 400% or more (for example, 220 to 300%), usually about 150 to 350%. When the elongation at break is within this range, the stretchability is high, and for example, it expands and contracts without breaking even when stretched and used as an ear hook member for a mask or a telescopic member for paper diapers.

  The elastic material of the present invention may have a recovery rate after 50% elongation (50% elongation recovery rate) of 70% or more (eg, 70 to 100%) in at least one direction, for example, 75 to 100%. , Preferably 80 to 100%, more preferably about 85 to 100% (especially 90 to 100%). When the elongation recovery rate is in this range, the followability to elongation is improved, and for example, the shape of the place of use can be sufficiently followed, and appropriate fixing and tightening with an elastic material is possible. In particular, it is useful in applications where it is necessary to directly touch and fix the body, such as sanitary materials such as masks and paper diapers. In particular, in a paper diaper expansion / contraction member having such a high elongation recovery rate, the paper diaper can be firmly attached to the body and leakage of urine can be suppressed.

  The elastic material of the present invention has a 25% recovery stress in a recovery behavior after 50% elongation in a 50% elongation recovery behavior in at least one direction in the plane direction (for example, in the case of a belt, in both the length direction and the width direction). The return stress is, for example, 0.2 N / 50 mm or more (for example, 0.3 to 1.5 N / 50 mm), preferably 0.4 to 1 N / 50 mm, more preferably 0.5 to 0.8 N / 50 mm. (Especially 0.55 to 0.7 N / 50 mm). This value can be selected as necessary. For example, when used for an ear hook member for a mask, it is, for example, about 0.2 to 0.5 N / 50 mm, preferably about 0.22 to 0.45 N / 50 mm. When used for an elastic member for paper diapers, the thickness is about 0.4 to 1.0 N / 50 mm, preferably about 0.45 to 0.9 N / 50 mm, and more preferably about 0.5 to 0.8 N / 50 mm.

  Furthermore, the ratio between the stress at 25% elongation [elongation stress (X)] in the initial 50% elongation behavior and the return stress [recovery stress (Y)] at 25% elongation in the return behavior after 50% elongation ( Y / X) is, for example, about 0.01 to 0.5, preferably about 0.05 to 0.4, and more preferably about 0.1 to 0.35 (particularly 0.2 to 0.3). In this invention, since recovery stress is comparatively low with respect to extension stress in this way, moderate stretchability is shown. In other words, when used as an elastic material such as a mask or diaper, this characteristic does not cause large permanent distortion with a slight movement of the body due to moderately high stress, and the form does not hinder the movement of the body. On the other hand, after being deformed once by the movement of the body, it exhibits excellent characteristics such as tightening to the extent that it does not become a resistance to the movement of the body, and maintaining the form and adhesion.

  The elastic material of the present invention usually has anisotropy between the flow direction (MD) and the width direction (CD direction) in the manufacturing process, as well as the anisotropy between the surface direction and the thickness direction. . That is, the stretchable material of the present invention is not limited in that the axial direction of the coiled crimped fiber is substantially parallel to the surface direction in the course of production, but also the axis of the coiled crimped fiber oriented substantially parallel to the surface direction. The core direction tends to be substantially parallel to the flow direction. As a result, when a rectangular nonwoven fabric is produced, the stretch properties and breaking properties, particularly the breaking strength, have anisotropy between the flow direction and the width direction in the nonwoven fabric production. When used as a belt-like member, a member having high stretchability in the length direction can be obtained by using the flow direction in the length direction.

  The stretch material of the present invention preferably has water repellency. This is because it is possible to prevent water from adhering and penetrating into the human body, particularly when used for applications that come into contact with the human body, such as masks and diapers. The expression of water repellency is that the fibers are exposed to water or water vapor in the manufacturing process described later, so that hydrophilic substances attached to the fibers are washed away, and the original properties of the resin are expressed on the surface of the fibers. by. Specifically, the water repellency is preferably 3 points or more (preferably 3 to 5 points, more preferably 4 to 5 points) in the JIS L1092 spray test.

  Further, the skin oil irritation of the stretchable material of the present invention is also reduced by washing away the fiber oil adhering to the fiber by the cleaning effect of water or water vapor.

The air permeability of the stretchable material of the present invention is 0.1 cm ³ / (cm ² · sec) or more as measured by the Frazier method, for example, 1 to 500 cm ³ / (cm ² · sec), preferably 5 to 5 cm. It is about 300 cm ³ / (cm ² · sec), more preferably about 10 to ²⁰⁰ cm ³ / (cm ² · sec). Since the stretchable material of the present invention has high air permeability, it is suitable for use in human bodies such as masks and diapers.

[Method of manufacturing elastic material]
The method for producing an elastic material of the present invention includes a step of forming a fiber containing the composite fiber into a web, and a step of crimping the composite fiber web by heating with high-temperature steam.

  First, in the step of forming a fiber into a web, the fiber containing the composite fiber is formed into a web. As a method for forming the web, a conventional method, for example, a direct method such as a spun bond method or a melt blow method, a card method using melt blow fibers or staple fibers, a dry method such as an air array method, or the like can be used. Among these methods, a card method using melt blown fibers or staple fibers, particularly a card method using staple fibers is widely used. Examples of the web obtained using staple fibers include a random web, a semi-random web, a parallel web, and a cross-wrap web.

  Next, the obtained fiber web is subjected to a step of heating and crimping, whereby the composite fibers are oriented substantially parallel to the surface direction, and are crimped substantially uniformly in the thickness direction with a specific curvature radius. Although a crimped nonwoven fabric is obtained, in the present invention, in the step of crimping by heating with high-temperature steam, some of the fibers of the obtained fiber web are obtained from the point that the fibers are appropriately crimped and entangled. It is preferable to go through a preliminary entanglement step. In such an entanglement step, the entanglement method may be a method of mechanically entanglement, but a method of entanglement by spraying or spraying (spraying) water is preferable. Entangling the fibers with a water flow can increase the density of the entanglement due to crimping in the heating process, can make the web wet, and can more uniformly propagate water vapor into the web. The water to be sprayed or sprayed may be sprayed from one side of the fiber web or from both sides. From the viewpoint of efficiently performing strong entanglement, it is preferable to spray from both sides.

  That is, the water ejection pressure in this step is, for example, 2 MPa or more (for example, 2 to 15 MPa), preferably 3 to 12 MPa, more preferably 4 to 10 MPa (particularly 5 to 5 MPa) so that the fiber entanglement is in an appropriate range. 8 MPa). In addition, the temperature of water is 5-50 degreeC, for example, Preferably it is 10-40 degreeC, for example, is 15-35 degreeC (normal temperature) grade.

  The method for spraying water is not particularly limited as long as it is a method that can be uniformly entangled with the fibers of the fiber web, but from the viewpoint of simplicity, using a nozzle having a regular spray area or spray pattern, A method of spraying water by spraying or the like is preferable. In addition, in order to suppress scattering of the fiber due to the jet of water, the fiber web may be wetted with a small amount of water in advance.

  Specifically, the fiber web obtained in the fiber web forming step is sent to the next step by a belt conveyor, and then sprayed with water in a state of being placed on the conveyor belt. The conveyor belt may be water-permeable, and water may be sprayed on the surface and both surfaces by passing water-permeable conveyor belt from the back side of the fiber web and spraying water on the web.

  The nozzle for spraying water may be arranged using a plate or a die in which predetermined orifices are continuously arranged in the width direction so that the orifices are arranged in the width direction of the fiber web to be supplied. There may be one or more orifice rows, and a plurality of rows may be arranged in parallel. A plurality of nozzle dies having a single orifice array may be installed in parallel.

  In the case of using a nozzle with an orifice in the plate, the thickness of the plate may be about 0.5 to 1.0 mm. The diameter and pitch of the orifice are not particularly limited as long as the fiber can be entangled so that the shrinkability and mechanical properties are moderate, but the diameter of the orifice is usually 0.01 to 2 mm, preferably Is about 0.05 to 1.5 mm, more preferably about 0.1 to 1.0 mm. The pitch of the orifices is usually about 0.1 to 2 mm, preferably about 0.2 to 1.5 mm, and more preferably about 0.3 to 1 mm. If the orifice diameter is too small, the processing accuracy of the nozzle becomes low and the processing becomes difficult, and the operational problem that clogging is likely to occur easily occurs. Moreover, since the amount of flowing water falls, the fiber of a fiber web may be unable to move. Conversely, if it is too large, it will be difficult to obtain a sufficient water pressure. On the other hand, if the pitch is too small, the nozzle holes become too dense and the strength of the nozzle itself is reduced. In addition, it is inevitably necessary to reduce the pore diameter, and the amount of water cannot be secured. On the other hand, if the pitch is too large, there will be cases where the water flow does not sufficiently hit the fiber web, resulting in insufficient fiber entanglement.

  The belt conveyor to be used is not particularly limited as long as it can be conveyed without disturbing the form of the fiber web used for processing, but an endless conveyor is preferably used. In addition, a general independent belt conveyor may be sufficient, and if necessary, another belt conveyor may be combined and conveyed by sandwiching the fiber web between both belts. In particular, in the next heating step of fixing to the final form of the fiber web, the fiber web may be sandwiched using a set of belts to adjust the density of the fiber web. By conveying in this way, when processing a fiber web, it can suppress that the form of the conveyed web deform | transforms by external forces, such as the water for entangling, high temperature steam, and the vibration of a conveyor. When using a pair of belts, the distance between the belts may be appropriately selected depending on the basis weight of the fiber web and the target density. For example, it is 1 to 10 mm, preferably 1 to 8 mm, more preferably about 1 to 5 mm. It is.

  The endless belt used for the conveyor is not particularly limited as long as it does not hinder the conveyance of the web or the high-temperature steam treatment, but if it is a net, a net roughly coarser than 90 mesh (for example, a net of about 10 to 80 mesh) is preferable. . A fine net with a mesh larger than this has low air permeability, and it becomes difficult for water for entanglement and water vapor in the next process to pass through. The material of the belt is not particularly limited, but the material of the belt used in the heating step is metal, heat-treated polyester-based resin, polyphenylene sulfide-based resin, polyarylate-based resin (totally aromatic Heat resistant resins such as aromatic polyester resins) and aromatic polyamide resins. The belt used for the conveyor may be the same in the preliminary entanglement process using a water flow or the like and the heating process using high-temperature steam. However, since adjustment is required for each process, a separate conveyor is usually used. Is used.

  Finally, the fiber web in which the fibers are appropriately entangled is sent to the next process by a belt conveyor, and is crimped by heating with high-temperature steam. In the method of treating with high-temperature steam, the fiber web sent by the belt conveyor is exposed to a high-temperature or heated steam (high-pressure steam) flow, and crimps are developed in the composite fiber (latent crimped fiber) to thereby produce the present invention. An elastic material is obtained. In other words, in the present invention, the composite fiber moves while changing its shape into a coil shape due to the expression of the crimp, and the three-dimensional entanglement between the fibers is expressed. In particular, since the fiber web in the present invention has air permeability, even if the treatment is performed from one direction, high-temperature water vapor penetrates into the inside, and a substantially uniform crimp is developed in the thickness direction. The fibers are entangled with each other.

  Specifically, in the present invention, the fiber web entangled with running water is subjected to high-temperature steam treatment on a belt conveyor, but the fiber web shrinks simultaneously with the high-temperature steam treatment. Therefore, it is desirable that the fiber web to be supplied is over-feed according to the size of the target nonwoven fabric immediately before being exposed to high-temperature steam. The ratio of overfeed is about 110 to 300%, preferably about 120 to 250%, with respect to the length of the target nonwoven fabric.

  In order to supply water vapor to the fiber web, a conventional water vapor jet apparatus is used. As this steam spraying device, a device capable of spraying steam substantially uniformly over the entire width of the web at a desired pressure and amount is preferable. When two belt conveyors are combined, a water vapor spraying device is mounted in one of the conveyors, and water vapor is supplied to the web through a water-permeable conveyor belt or a conveyor net placed on the conveyor. A suction box may be attached to the other conveyor. Excess water vapor that has passed through the fiber web may be sucked and discharged by the suction box, but in order to cause the water vapor to adhere sufficiently to the fiber web and to more efficiently express the fiber crimp that is generated by this heat. Since it is necessary to keep the web as free as possible, it is preferable to supply water vapor without suction and discharge by a suction box. Further, in order to subject the front and back of the fiber web to water vapor treatment at a time, further on the opposite side of the conveyor to which the water vapor spraying device is mounted, the downstream portion from the portion where the water vapor spraying device is mounted Another steam spraying device may be installed in the conveyor. In the case where there is no downstream steam injection device, when it is desired to steam-treat the front and back of the nonwoven fabric, the front and back of the fiber web that has been treated once may be reversed and passed through the treatment device again.

  Since the high-temperature steam sprayed from the steam spraying device is an air stream, unlike the hydroentanglement process or the needle punch process, the fibers in the fiber web that is the object to be processed enter the inside of the fiber web without largely moving. . It is considered that the water vapor flow effectively covers the surface of each fiber existing in the fiber web and allows uniform heat crimping by the invasion action of the water vapor flow into the fiber web. Moreover, since heat can be sufficiently conducted to the inside of the fiber web as compared with the dry heat treatment, the degree of crimping in the surface and the thickness direction becomes substantially uniform.

  The nozzle for injecting high-temperature steam is also a plate or die in which predetermined orifices are continuously arranged in the width direction, and the orifice in the width direction of the fiber web to be supplied is the same as the nozzle for water entanglement. May be arranged in a line. There may be one or more orifice rows, and a plurality of rows may be arranged in parallel. A plurality of nozzle dies having a single orifice array may be installed in parallel.

  In the case of using a nozzle with an orifice in the plate, the thickness of the plate may be about 0.5 to 1.0 mm. The orifice diameter and pitch are not particularly limited as long as the target crimp expression and the fiber entanglement associated with this expression can be efficiently realized, but the orifice diameter is usually 0.05 to 2 mm, Preferably it is 0.1-1 mm, More preferably, it is about 0.2-0.5 mm. The pitch of the orifices is usually 0.5 to 5 mm, preferably 1 to 4 mm, and more preferably about 1 to 3 mm. If the diameter of the orifice is too small, an operational problem that clogging is likely to occur is likely to occur. On the other hand, if it is too large, it will be difficult to obtain a sufficient water vapor injection force. On the other hand, if the pitch is too small, the hole diameter is also small, and the amount of high-temperature steam is reduced. On the other hand, if the pitch is too large, there are cases where high-temperature steam does not sufficiently hit the fiber web, making it difficult to ensure strength.

  The high-temperature steam to be used is not particularly limited as long as the desired fiber crimp expression and appropriate fiber entanglement can be realized, and may be set depending on the material and form of the fiber to be used. It is about 0.1 to 2 MPa, preferably about 0.2 to 1.5 MPa, and more preferably about 0.3 to 1 MPa. If the water vapor pressure is too high or too strong, the fibers forming the web may move more than necessary, resulting in turbulence, or the fibers may be entangled more than necessary. In extreme cases, the fibers are fused together, making it difficult to ensure the desired stretchability. In addition, when the pressure is too weak, it becomes impossible to impart the amount of heat necessary for expressing the crimp of the fiber to the web that is the object to be processed, or water vapor cannot penetrate the fiber web, and the expression of the crimp of the fiber in the thickness direction is exhibited. It tends to be uneven. In addition, it is difficult to control the uniform ejection of water vapor from the nozzle.

  The temperature of the high-temperature steam is, for example, about 70 to 150 ° C, preferably about 80 to 120 ° C, and more preferably about 90 to 110 ° C. The processing speed of the high temperature steam is, for example, 200 m / min or less, preferably 0.1 to 100 m / min, and more preferably about 1 to 50 m / min.

  After the crimping of the composite fiber in the fiber web is expressed in this way, moisture may remain in the nonwoven fabric, and the nonwoven fabric may be dried as necessary. As for drying, it is necessary that the fibers on the surface of the non-woven fabric in contact with the heating element for drying do not adhere to the heat of drying to reduce the stretchability, and a conventional method can be used as long as the stretchability can be maintained. For example, a large dryer such as a cylinder dryer or tenter used for drying nonwoven fabrics may be used, but the remaining moisture is very small and can be dried by a relatively light drying means. Therefore, a non-contact method such as far-infrared irradiation, microwave irradiation, electron beam irradiation, or a method of blowing or passing hot air is preferable.

  The obtained non-woven fabric is wetted with water in the production process and exposed to a high-temperature steam atmosphere. That is, since the nonwoven fabric of the present invention is subjected to the same treatment as that of washing, the adhering matter to the fibers such as spinning oil is washed. Therefore, the stretch material of the present invention is hygienic and exhibits high water repellency.

  The nonwoven fabric thus obtained is usually plate-shaped or sheet-shaped. The sheet-like non-woven fabric may be used as an elastic material as it is, but is usually cut by processing depending on the shape of the target elastic material (for example, the shape of the hook member of the mask or the overall shape of the mask). Can be processed into a desired shape. The obtained plate-like or sheet-like molded product is obtained by conventional thermoforming, for example, compression molding, pressure forming (extrusion pressure forming, hot plate pressure forming, vacuum pressure forming, etc.), free blow molding, vacuum forming, bending. You may process by a process, matched mold shaping | molding, hot plate molding, wet heat press molding, etc.

  The elastic material of the present invention is not particularly limited as long as it is a member that uses expansion and contraction, and can be used in a wide range of applications as a substitute for rubber. Furthermore, since the stretch material of the present invention has a good touch, excellent flexibility, and air permeability, it is used for fixing fabrics and papers to the human body (for example, sanitary materials such as masks and diapers, Hats, clothes, socks, etc.).

  Especially, since the elastic material of the present invention is hypoallergenic to the skin, hygiene materials (for example, masks, gloves, bandages, gauze, absorbent cotton, Suitable for bandages, poultices, surge tapes, diapers, sanitary napkins, etc.) Furthermore, since the stretchable material of the present invention has high breathability and good touch, the sanitary material itself may be composed of the stretchable material of the present invention, but since it also has high stretchability, it is used as a stretchable member in the sanitary material. Also good. In particular, the stretchable material itself is in direct contact with the human body and is particularly useful for stretchable members in mask ear hook members and paper diapers, for example, where high stretchability is required.

  As a specific form of use of the mask ear hook member, the shape of the mask is not particularly limited, and the mask ear hook member may be formed of the stretchable material of the present invention and may be combined with other fabrics to form the mask. Alternatively, the entire mask including the ear hook member may be formed of the stretchable material of the present invention and combined with a filter.

  When the elastic material of the present invention is used as an ear hook member for a mask, the shape is usually a belt shape, but the width is, for example, about 3 to 50 mm, preferably about 5 to 30 mm, and more preferably about 10 to 25 mm. . Further, the mask ear hook member made of the stretchable material of the present invention may be used in combination with other rubber strings if necessary.

  The elastic member in the paper diaper is a member for fixing the paper diaper to the body. Usually, it extends from the upper part of both sides of the back side of the paper diaper to a length that can be attached to the front surface when attached to the body. It is a belt-shaped member. This stretchable member is required to be breathable because it contacts the skin at both sides of the waist when worn on the body. The sticking mechanism with the front surface of the paper diaper is not particularly limited, and an adhesive, a hook-and-loop fastener, or the like may be used. However, since the stretch material of the present invention has crimped fibers on the surface, the stretch material It itself has a function as a loop-like engagement element of the hook-and-loop fastener. Therefore, as a concrete form of use of the elastic member for paper diapers, the elastic member of the paper diaper is composed of the elastic material of the present invention, and the hook-like engagement element is provided at the attachment portion of the elastic member on the front surface of the paper diaper. A paper diaper provided with a hook-and-loop fastener may be used.

  Even when the stretchable material of the present invention is used as a stretchable member for paper diapers, the shape thereof is usually a belt shape, and the width is, for example, 5 to 150 mm, preferably 10 to 100 mm, more preferably 15 to 80 mm (particularly 20 ˜60 mm). Furthermore, if necessary, the elastic member for paper diapers constituted by the elastic material of the present invention may be used in combination with other rubber strings or elastomers.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples. In addition, each physical-property value in an Example was measured with the following method. In the examples, “%” is based on mass unless otherwise specified.

(1) Number of crimps Evaluated according to JIS L1015 “Testing method for chemical fiber staples” (8.12.1).

(2) Weight per unit (g / m ² )
Measured according to JIS L1913 “Testing method for general short fiber nonwoven fabric”.

(3) Thickness (mm), apparent density (g / cm ³ )
The thickness was measured according to JIS L1913 “Test method for general short fiber nonwoven fabric”, and the density was calculated from this value and the basis weight value.

(4) Average curvature radius Using a scanning electron microscope (SEM), a photograph in which the cross section of the nonwoven fabric was magnified 100 times was taken. Among the fibers shown in the photograph of the cross-section of the nonwoven fabric, for the fibers forming one or more spirals (coils), the radius of the circle when drawing a circle along the spirals (from the coil axis direction) The radius of the circle when the contracted fiber was observed was determined, and this was defined as the radius of curvature. In addition, when the fiber has drawn the spiral in the ellipse shape, 1/2 of the sum of the major axis and the minor axis of the ellipse was used as the radius of curvature. However, in order to exclude the case where the crimped fiber does not exhibit sufficient coil crimping or the case where the spiral shape of the fiber is reflected as an ellipse, the major axis and minor axis of the ellipse Only the ellipses whose ratio (major axis / minor axis) falls within the range of 1.2 or less were measured. In addition, the measurement was performed with respect to an SEM image taken for an arbitrary cross section, and was shown as an average value of n number = 100.

(5) Fiber curvature and uniformity thereof An electron micrograph (magnification × 100 times) in the cross section of the nonwoven fabric was photographed, and the surface layer, inner layer, and back layer 3 in the thickness direction at the projected portion of the photographed fiber. The measurement area was set so as to be divided into three equal parts, and in the vicinity of the center of each layer, the length direction was 2 mm or more and 500 or more measurable fiber pieces were included. For these regions, the end-to-end distance (shortest distance) between one end of the fiber and the other end was measured, and the fiber length of the fiber (fiber length on the photograph) was measured. That is, when the end portion of the fiber is exposed on the nonwoven fabric surface, the end portion is used as it is as an end portion for measuring the distance between the end portions, and when the end portion is embedded in the nonwoven fabric, The boundary part (end part on the photograph) buried in was used as an end part for measuring the distance between the end parts. At this time, among the photographed fibers, a fiber image that cannot be confirmed to be continuous over 100 μm or more was excluded from measurement. And fiber curvature was computed from ratio (L2 / L1) of the fiber length (L2) of the fiber with respect to the distance (L1) between edge parts. In addition, the measurement of fiber curvature calculated the average value for every surface layer, inner layer, and back layer divided into three equal to the thickness direction. Furthermore, the uniformity in the thickness direction of the fiber curvature was calculated from the ratio between the maximum value and the minimum value of each layer.

  In FIG. 1, the schematic diagram about the measuring method of the image | photographed fiber is shown. FIG. 1A shows a fiber in which one end is exposed on the surface and the other end is buried inside the nonwoven fabric. In the case of this fiber, the end-to-end distance L1 is from the end of the fiber to the inside of the nonwoven fabric. It becomes the distance to the boundary part buried in. On the other hand, the fiber length L2 is a length obtained by two-dimensionally stretching the fiber of the portion where the fiber can be observed (the portion from the end of the fiber until it is buried in the nonwoven fabric) on the photograph.

  FIG. 1B shows a fiber in which both ends are buried in the nonwoven fabric. In the case of this fiber, the end-to-end distance L1 is the distance between both ends (both ends on the photograph) in the portion exposed on the nonwoven fabric surface. Become. On the other hand, the fiber length L2 is a length obtained by two-dimensionally stretching the fiber exposed on the nonwoven fabric surface on the photograph.

(6) Breaking strength and breaking elongation It measured according to JIS L1913 "General short fiber nonwoven fabric test method". The breaking strength and breaking elongation were measured in the flow (MD) direction and the width (CD) direction of the nonwoven fabric.

(7) 50% elongation recovery rate Measured according to JIS L1096 “General Textile Test Method”. However, in the evaluation in the present invention, the recovery rate was uniformly 50%, and after extending 50%, after returning to the original position, the next operation was started without waiting time. In addition, the measurement was performed about the flow (MD) direction and the width (CD) direction of the nonwoven fabric.

(8) 25% recovery stress, 25% recovery / elongation stress ratio In accordance with JIS L1096 “General Textile Test Method”, the nonwoven fabric was stretched to 50% elongation, and immediately at the same speed (with the load removed at the same speed) ) Reverted. In the first elongation process in this elongation recovery test, the elongation stress when the elongation is 25% is defined as elongation stress (X), and the return stress when the elongation is returned to 25% elongation in the return process after 50% elongation is the recovery stress ( Y). Y / X was calculated from the measurement results. In addition, the measurement was performed about the flow (MD) direction and the width (CD) direction of the nonwoven fabric.

(9) Air permeability Measured by the fragile method according to JIS L1096.

Example 1
Side-by-side composed of polyethylene terephthalate resin (component A) having an intrinsic viscosity of 0.65 and a modified polyethylene terephthalate resin (component B) copolymerized with 20 mol% isophthalic acid and 5 mol% diethylene glycol as latent crimpable fibers Type composite staple fiber (manufactured by Kuraray Co., Ltd., “PN-780”, 1.7 dtex × 51 mm length, mechanical crimp number 12 pieces / 25 mm, 130 ° C. × 62 minutes after heat treatment for 1 minute, 62 pieces / 25 mm) Got ready. Using 100% by mass of the side-by-side type composite staple fiber, a card web having a basis weight of 38.2 g / m ^{2 was} obtained by a card method.

  Next, the card web was preliminarily wetted with a small amount of water while being transferred to a belt conveyor equipped with a 76 mesh, 500 mm wide resin endless belt, and then an orifice having a diameter of 0.1 mm was formed in the width direction of the web. Nozzles provided in a row at 0.6 mm intervals were used in two rows on the front and back sides, and water was ejected from the nozzles to interlace the fibers. The water pressure was sprayed at 2 MPa on the front and back surfaces of the front nozzle row, and sprayed at 4 MPa on the front and back surfaces of the rear nozzle row.

  Next, this fiber web was transferred to the next water vapor treatment step while overfeeding the web to about 150% so as not to inhibit the shrinkage in the next water vapor treatment step. In addition, the same belt was equipped in the upper part of the belt of this belt conveyor, each rotated in the same direction at the same speed, and the belt conveyor which can adjust the space | interval of these both belts arbitrarily was used.

  Next, the card web is introduced into a water vapor jetting device provided on the belt conveyor, and 0.4 MPa of water vapor is jetted perpendicularly to the card web from the water vapor jetting device to perform the water vapor treatment, so that a coil of latent crimped fibers is obtained. While producing crimps, the fibers were entangled to obtain a nonwoven fabric. In this steam spraying device, a nozzle was installed in one conveyor so as to spray steam toward the web via a conveyor belt, and a suction device was installed in the other conveyor. However, this suction was not activated. In addition, the hole diameter of the steam spray nozzle is 0.3 mm, and an apparatus in which the nozzles are arranged in a line at a pitch of 2 mm along the conveyor width direction was used. The processing speed was 10 m / min, and the distance between the nozzle and the conveyor belt on the suction side was 5 mm.

The obtained nonwoven fabric had a basis weight of 82.0 g / m ² . Although this nonwoven fabric does not contain a rubber component, it stretches well in both the MD and CD directions, and after lightly stretching by hand to the extent that it does not break, it immediately returns to its original shape when the stress is released. Returned to. The evaluation results of the obtained nonwoven fabric are shown in Table 1.

  The strength and elongation recovery behavior of the obtained nonwoven fabric in the MD direction had physical properties that can be suitably used as a stretchable member for paper diapers. Furthermore, the strength in the CD direction and the elongation recovery behavior of the nonwoven fabric had physical properties at a level that can be suitably used as an ear hook member for a mask.

Example 2
A nonwoven fabric was obtained in the same manner as in Example 1 except that the mesh of the conveyor net at the time of hydroentanglement was 22 × 24 mesh (22 mesh / 25 mm in the length direction and 24 mesh / 25 mm in the width direction). . The results are shown in Table 1. In the obtained nonwoven fabric, an elliptical hole having a major axis of 1 mm × minor axis of 0.5 mm was formed. Moreover, the strength and elongation recovery behavior in the MD direction of the obtained nonwoven fabric had physical properties at a level that can be suitably used as a stretchable member for paper diapers. Furthermore, the strength in the CD direction and the elongation recovery behavior of the nonwoven fabric had physical properties at a level that can be suitably used as an ear hook member for a mask.

Example 3
A nonwoven fabric was obtained in the same manner as in Example 1 except that the basis weight of the card web was adjusted to 20.4 g / m ² . The results are shown in Table 1. Compared with the nonwoven fabric obtained in Example 1, the obtained nonwoven fabric became a nonwoven fabric with a low intensity | strength because of a low basis weight. The strength and elongation recovery behavior of this nonwoven fabric in the MD direction had physical properties at a level that can be suitably used as an ear hook member for a mask.

Example 4
A nonwoven fabric was obtained in the same manner as in Example 1 except that the basis weight of the card web was adjusted to 54.8 g / m ² . The results are shown in Table 1. The obtained nonwoven fabric was higher in strength than the nonwoven fabric obtained in Example 1, and thus the nonwoven fabric was high in strength and also high in stress at 50% elongation recovery. Both the MD direction and the CD direction of this nonwoven fabric had physical properties at a level that can be suitably used as an elastic member for paper diapers.

Example 5
A nonwoven fabric was obtained in the same manner as in Example 1 except that the pressure when the web was entangled with water spray was 4 MPa in the former stage and 6 MPa in the latter stage. The results are shown in Table 1. Although the obtained nonwoven fabric became stronger in fiber entanglement and higher in strength than the nonwoven fabric obtained in Example 1, the elongation recovery rate was slightly lower. The strength and elongation recovery behavior of the obtained nonwoven fabric in the MD direction had physical properties that can be suitably used as a stretchable member for paper diapers. Further, the strength in the CD direction and the elongation recovery behavior of the nonwoven fabric had physical properties that can be suitably used as an ear hook member for a mask.

Comparative Example 1
Instead of treating the web after the water entanglement treatment with water vapor, it was heat-treated in a hot air dryer at 130 ° C. for 10 seconds to develop crimps to obtain a nonwoven fabric. Although the obtained nonwoven fabric had elasticity, the return stress was clearly low. The results are shown in Table 1.

  As is clear from the results in Table 1, the stretchable materials of the examples have high breaking strength and breaking elongation, and have appropriate stretchability. On the other hand, the stretchable material of the comparative example is low in both breaking strength and breaking elongation and is not sufficiently stretchable.

FIG. 1 is a schematic diagram showing a method for measuring fiber curvature in the present invention.

Claims (15)

An elastic material composed of a nonwoven fabric including a composite fiber in which a phase structure is formed of a plurality of resins having different thermal shrinkage rates,
A step of forming a fiber including a composite fiber having a phase structure formed of a plurality of resins having different heat shrinkage rates, and an average curvature by heating the fiber web with water vapor at a temperature of 70 to 150 ° C. and a pressure of 0.1 to 2 MPa. Obtained by a manufacturing method including a step of crimping to a radius of 20 to 200 μm,
The composite fibers are oriented substantially parallel to the plane direction and crimped substantially uniformly in the thickness direction with an average curvature radius of 20 to 200 μm,
The breaking strength in at least one direction in the plane direction is 20 N / 50 mm or more,
And the elastic material whose 25% recovery stress in the recovery behavior after 50% elongation is 0.2 N / 50 mm or more.   The stretchable material according to claim 1, wherein the softening point or melting point of the resin constituting the composite fiber is 100 ° C or higher, and the resin exposed on the surface of the composite fiber is a non-wet heat adhesive resin.   The stretchable material according to claim 1 or 2, wherein the composite fiber is composed of a polyalkylene arylate resin and a modified polyalkylene arylate resin, and has a parallel type or an eccentric core-sheath type structure.   The stretch material according to any one of claims 1 to 3, wherein the proportion of the composite fiber is 80% by mass or more.   The elastic material according to any one of claims 1 to 4, wherein a 25% recovery stress in a recovery behavior after 50% elongation is 0.3 to 1.5 N / 50 mm.   The stretchable material according to any one of claims 1 to 5, wherein the breaking strength in at least one direction in the plane direction is 40 N / 50 mm or more.   The elastic material according to any one of claims 1 to 6, wherein the elongation at break in at least one direction in the plane direction is 100% or more.   The stretchable material according to any one of claims 1 to 7, wherein the elongation at break in at least one direction in the plane direction is 150 to 350%.   The elastic material in any one of Claims 1-8 which has a surface which can contact a body.   It is an expansion-contraction member for sanitary materials, The expansion-contraction material in any one of Claims 1-9.   The elastic member according to claim 10, wherein the hygienic elastic member is a mask ear hook member or a paper diaper elastic member. A sanitary material comprising the stretchable material according to any one of claims 1 to 11 .   A mask comprising the mask hook member according to claim 11.   A paper diaper comprising the elastic member for a paper diaper according to claim 11. A step of forming a fiber including a composite fiber having a phase structure formed of a plurality of resins having different thermal shrinkage rates, and the fiber web is crimped by heating with water vapor at a temperature of 70 to 150 ° C. and a pressure of 0.1 to 2 MPa. The manufacturing method of the elastic material in any one of Claims 1-11 including the process to do.

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