Gather and sanitary material containing the same

Abstract

To provide a gather and a sanitary material which hardly leave a mark when worn, and which hardly become displaced when a wearer moves.SOLUTION: Provided is a gather in which a ratio between a 50% elongation stress in an elongation rate 2000% / min and the 50% elongation stress in the elongation rate 200% / min is 1.05 or higher and 3.00 or lower, and the sanitary material containing the gather. The gather preferably contains at least thermoplastic polyurethane elastic fibers and non-woven fibers.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to gathers and sanitary materials containing the same.

Background Art

[0002] Conventionally, gathers having elasticity have been arranged at the waist and legs of disposable diapers to prevent displacement during wearing and to prevent leakage of urine and the like. Such gathers generally have a non-woven fabric and elastic fibers such as rubber and polyurethane, and the elastic fibers are adhered to the non-woven fabric by a hot melt adhesive or the like in an extended state during the production of the gathers, imparting elasticity to the gathers. Generally, gathers of sanitary materials such as disposable diapers are required to have, in addition to elasticity, resistance to displacement and resistance to leaving marks. For example, in Patent Document 1 below, by specifying the physical properties of a gather in which elastic fibers are arranged at regular intervals between two sheets, a pants-type diaper that is less likely to be displaced during wearing and can suppress rubber marking has been proposed.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, it cannot be said that the pants-type diaper described in Patent Document 1 can sufficiently suppress displacement of the diaper against the intense movements of the wearer.

[0005] In view of the problems of the above prior art, the problem to be solved by the present invention is to provide a gather and a sanitary material that are less likely to leave marks during wearing and are also less likely to be displaced when the wearer moves.

Means for Solving the Problems

[0006] As a result of intensive studies and repeated experiments to solve the above problems, the inventor of the present application unexpectedly discovered that a gather in which the ratio of the 50% elongation stress at an elongation rate of 2000% / min to the 50% elongation stress at an elongation rate of 200% / min is 1.05 or more and 3.00 or less can solve the above problems, and thus completed the present invention. That is, the present invention is as follows.

[0007] [1] A gather in which the ratio of the 50% elongation stress at an elongation rate of 2000% / min to the 50% elongation stress at an elongation rate of 200% / min is 1.05 or more and 3.00 or less. [2] The gather according to [1] above, comprising at least a thermoplastic polyurethane elastic fiber and a nonwoven fabric. [3] The gather according to [2] above, further comprising a hot melt adhesive. [4] The gather according to [2] or [3] above, wherein the distance between hard domains measured by a small-angle X-ray scattering apparatus of the thermoplastic polyurethane elastic fiber is 10.0 nm or more and 30.0 nm or less, and the full width at half maximum of the peak of the azimuthal angle distribution is 50° or more and 130° or less. [5] The gather according to any one of [2] to [4] above, wherein the number of filaments of the thermoplastic polyurethane elastic fiber is 10 or more and 150 or less. [6] The gather according to any one of [2] to [5] above, wherein the single-filament fineness of the thermoplastic polyurethane elastic fiber is 5 dtex or more and 20 dtex or less. [7] The gather according to any one of [2] to [6] above, wherein the total fineness of the thermoplastic polyurethane elastic fiber is 150 dtex or more and 1500 dtex or less. [8] The gather according to any one of [2] to [7] above, wherein the thermoplastic polyurethane elastic fiber contains a polyurethane synthesized from a polymer polyol, MDI, and 1,4-butanediol. [9] The gather according to any one of [2] to [8] above, wherein the molecular weight of the hard segment of the thermoplastic polyurethane elastic fiber is 750 or more and 1500 or less.

[10] The gather according to any one of [2] to [9] above, wherein the thermoplastic polyurethane elastic fiber does not substantially have a crosslinking containing an allophanate bond.

[11] The gather according to any one of [3] to

[10] above, wherein the content of the hot melt adhesive is 0.02 g / m or more and 0.10 g / m or less with respect to the elongation length per one thermoplastic polyurethane elastic fiber.

[12] The gather according to any one of [3] to

[11] above, wherein the hot melt adhesive is a styrene block copolymer selected from the group consisting of a block copolymer of a vinyl aromatic hydrocarbon and a conjugated diene compound and a hydrogenated product thereof.

[13] The basis weight of the nonwoven fabric is 8 g / m 2 or more and 50 g / m 2 or less, and the gather according to any one of [2] to

[12] above.

[14] The gather according to any one of [1] to

[13] above, wherein the elongation rate at the elongation limit of the gather is 50% or more and 250% or less.

[15] A sanitary material comprising the gather according to any one of [1] to

[14] above. [Advantages of the Invention]

[0008] The gather and the sanitary material of the present invention are less likely to leave marks during wearing and are also less likely to shift even when the wearer moves. [Modes for Carrying Out the Invention]

[0009] Hereinafter, modes for carrying out the present invention (hereinafter referred to as "the present embodiment") will be described in detail. The present invention is not limited to the following present embodiment, and can be variously modified and implemented within the scope of the gist thereof.

[0010] In the gather of the present embodiment, the ratio of the 50% elongation stress at an elongation rate of 2000% / min to the 50% elongation stress at an elongation rate of 200% / min is 1.05 or more and 3.00 or less.

[0011] [Gather] The gatherer of this embodiment has a ratio of the 50% elongation stress at an elongation rate of 2000% / min to the 50% elongation stress at an elongation rate of 200% / min (hereinafter, also referred to as the "speed response ratio") of 1.05 or more and 3.00 or less, more preferably 1.06 or more and 2.90 or less, still more preferably 1.07 or more and 2.80 or less, still more preferably 1.10 or more and 2.50 or less, still more preferably 1.15 or more and 2.20 or less, and most preferably 1.20 or more and 2.0 or less.

[0012] By setting the speed response ratio of the gatherer of this embodiment to 1.05 or more, when the wearer moves and the gatherer is stretched at high speed, the stress becomes particularly high, so the resistance to displacement when the wearer moves is exhibited. Further, by setting the speed response ratio to 3.00 or less, the gatherer does not become too high in stress when stretched at high speed, and it becomes difficult to leave marks during wearing.

[0013] The gatherer of this embodiment is a stretchable member having a large number of pleats and is stretchable in at least one direction. There are no particular restrictions on the material constituting the gatherer or the method of manufacturing the gatherer, and it can be produced by a conventionally known method in the manufacturing process of ordinary paper diapers, sanitary products, etc. Generally, it can be produced by a method in which elastic fibers are adhered to a non-woven fabric or the like using hot melt or the like in a stretched state. Specific examples of the method for manufacturing the gatherer include a process in which elastic fibers are unwound from a wound body, a process in which elastic fibers are stretched through guides or rollers, a process in which a hot melt adhesive is directly applied in a state where the elastic fibers are stretched, a process in which elastic fibers are pressed and adhered to a non-woven fabric with a pressure roll, and a process in which the elastic member is contracted.

[0014] From the perspective of improving the stretchability and recovery property, the gather of this embodiment is preferably one in which a thermoplastic polyurethane elastic fiber and a nonwoven fabric are adhered. As a method of adhering the thermoplastic polyurethane elastic fiber and the nonwoven fabric, for example, a method of using a hot melt adhesive, or a method of melting and adhering part or all of the thermoplastic polyurethane elastic fiber and / or the nonwoven fabric by heat can be mentioned. Among them, the gather of this embodiment is preferably one in which the thermoplastic polyurethane elastic fiber and the nonwoven fabric are adhered by a hot melt adhesive from the perspective of improving the stretchability and recovery property. The thermoplastic polyurethane elastic fiber and the nonwoven fabric may be adhered to the entire surface continuously in the longitudinal direction of the thermoplastic polyurethane elastic fiber, or may be adhered partially intermittently in the longitudinal direction of the polyurethane elastic fiber. Also, within a range that does not inhibit the object of the present invention, materials other than the nonwoven fabric and the polyurethane elastic fiber may be inserted, attached, or coated.

[0015] In the gather of this embodiment, when a plurality of thermoplastic polyurethane elastic fibers are adhered to the nonwoven fabric, the polyurethane elastic fibers may be adhered to the nonwoven fabric in a state of being parallel to each other and arranged, or may be arranged in an arc shape, a parabolic shape, a zigzag shape, a sine wave shape, etc., or may be arranged in combination thereof.

[0016] From the perspective of increasing the speed response ratio, the elongation rate of the gather of this embodiment at the breaking point of elongation is preferably 50% or more and 250% or less. By setting the elongation rate of the gather at the breaking point of elongation to 50% or more, the stretching of the nonwoven fabric can be prevented, and the speed response ratio of the thermoplastic polyurethane elastic fiber is likely to be reflected in the gather, so that the speed response ratio of the gather can be increased. By setting the elongation rate of the gather at the breaking point of elongation to 250% or less, the number of folds of the gather can be reduced, and the speed response ratio of the thermoplastic polyurethane elastic fiber is likely to be reflected when the gather is stretched, so that the speed response ratio of the gather can be increased. The method of setting the elongation rate of the gather at the breaking point of elongation to 50% or more and 250% or less is not particularly limited, but for example, a method of manufacturing the gather by controlling the magnification of stretching of the thermoplastic polyurethane elastic fiber before adhering it to the nonwoven fabric is preferably used.

[0017] [Thermoplastic polyurethane elastic fibers contained in the gathers] The gathers of this embodiment can contain thermoplastic polyurethane elastic fibers. The thermoplastic polyurethane elastic fibers preferably contain 80 wt% or more, more preferably 85 wt% or more, still more preferably 90 wt% or more, and most preferably 95 wt% or more of thermoplastic polyurethane. As the thermoplastic polyurethane, it suffices if it has thermoplasticity. For example, it is not particularly limited as long as it has a structure polymerized from diisocyanate, polymer polyol, low molecular weight diol, low molecular weight diamine, etc. Also, the polymerization method thereof is not particularly limited. As the thermoplastic polyurethane, for example, a polyurethane (hereinafter also referred to as "polyurethane urea") polymerized from diisocyanate, polymer polyol, and a low molecular weight diamine as a chain extender composed of an active hydrogen compound may be used, or a polyurethane (hereinafter also referred to as "polyurethane urethane") polymerized from diisocyanate, polymer polyol, and a low molecular weight diol as a chain extender composed of an active hydrogen compound may also be used. Glycols or isocyanates having a functionality of 3 or more may be used as long as they do not prevent the desired effects of the present invention. In the present specification, "thermoplasticity" means having a reversible property of being able to melt by heating below the decomposition temperature, showing plastic flow while in the molten state, and solidifying by cooling. Generally, the polyurethane resin starts to decompose at 230°C or higher.

[0018] Examples of the polymer polyol include, but are not limited to, polymer diols such as polyether-based diols, polyester-based diols, and polycarbonate diols. From the viewpoint of hydrolysis resistance, the polymer polyol is preferably a polyether-based polyol, and more preferably a polyether-based diol.

[0019] Examples of the polyether polyol include polyethylene oxide, polyethylene glycol, polyethylene glycol derivatives, polypropylene glycol, polytetramethylene ether glycol, copolymer diol composed of tetrahydrofuran (THF) and neopentyl glycol, and copolymer diol composed of THF and 3-methyltetrahydrofuran. These polyether polyols may be used alone or in combination of two or more. Further, the number average molecular weight of the polymer diol is preferably 1000 or more and 8000 or less. By using the polymer diol within this range, elastic fibers excellent in elongation, stretch recovery, and heat resistance can be easily obtained. From the viewpoint of photo-degradability, the polyether polyol is preferably polytetramethylene ether glycol, copolymer diol which is a copolymer of THF and neopentyl glycol, and polyol blended with these.

[0020] Examples of the diisocyanate include aromatic diisocyanate, alicyclic diisocyanate, and aliphatic diisocyanate. Examples of the aromatic diisocyanate include, but are not limited to, diphenylmethane diisocyanate (hereinafter also referred to as "MDI"), tolylene diisocyanate, 1,4-diisocyanate benzene, xylylene diisocyanate, 2,6-naphthalene diisocyanate, and the like. Examples of the alicyclic diisocyanate and aliphatic diisocyanate include methylene bis(cyclohexyl isocyanate) (hereinafter also referred to as "H12MDI"), isophorone diisocyanate, methylcyclohexane 2,4-diisocyanate, methylcyclohexane 2,6-diisocyanate, cyclohexane 1,4-diisocyanate, hexahydroxylylene diisocyanate, hexahydrotoluene diisocyanate, octahydro 1,5-naphthalene diisocyanate, and the like. These diisocyanates may be used alone or in combination of two or more. In particular, from the viewpoint of the stretch recovery of the elastic fiber, the diisocyanate is preferably an aromatic diisocyanate, and more preferably MDI.

[0021] As the chain extender composed of an active hydrogen compound, it is preferably at least one selected from the group consisting of low molecular weight diamines and low molecular weight diols. In addition, as the chain extender, those having both a hydroxyl group and an amino group in the molecule, such as ethanolamine, may be used. From the viewpoint of obtaining a thermoplastic polyurethane suitable for melt spinning, the active hydrogen compound is preferably a low molecular weight diol.

[0022] The low molecular weight diamine as the chain extender composed of an active hydrogen compound is not limited to the following, and examples include hydrazine, ethylenediamine, 1,2-propanediamine, 1,3-propanediamine, 2-methyl-1,5-pentanediamine, 1,2-diaminobutane, 1,3-diaminobutane, 1-amino-3,3,5-trimethyl-5-aminomethylcyclohexane, 2,2-dimethyl-1,3-diaminopropane, 1,3-diamino-2,2-dimethylbutane, 2,4-diamino-1-methylcyclohexane, 1,3-pentanediamine, 1,3-cyclohexanediamine, bis(4-aminophenyl)phosphine oxide, hexamethylenediamine, 1,3-cyclohexyldiamine, hexahydrometaphenylenediamine, 2-methylpentamethylenediamine, bis(4-aminophenyl)phosphine oxide, etc.

[0023] Examples of the low molecular weight diol as the chain extender composed of an active hydrogen compound include ethylene glycol, 1,3-propanediol, 1,4-butanediol, bis(hydroxyethoxy)benzene, bis(hydroxyethylene)terephthalate, 1-methyl-1,2-ethanediol, 1,6-hexanediol, etc. These low molecular weight diols may be used alone or in combination of two or more. From the viewpoint of the stretch recovery of the elastic fiber, the low molecular weight diol is preferably a diol having a molecular weight of 60 or more and 120 or less, and more preferably 1,4-butanediol.

[0024] Thermoplastic polyurethane can use known polyurethane-forming reaction technologies and can be produced by either the one-shot method or the prepolymer method. In the case of the prepolymer method, under a nitrogen purge, a polymer polyol and a diisocyanate are added to a reaction tank equipped with a warm water jacket and a stirrer, preferably in a molar ratio of 1.0:1.8 to 3.0, more preferably 1.0:2.0 to 2.5, and the prepolymer reaction is preferably carried out at 40°C or higher and 100°C or lower, more preferably 50°C or higher and 80°C or lower, to obtain a prepolymer with isocyanate groups at both ends. Next, an active hydrogen compound is added to this prepolymer with isocyanate groups at both ends in an equivalent amount approximately equal to the number of functional groups of the isocyanate end groups, and a chain extension reaction is carried out. As the equivalent ratio, it is preferably 0.95 or more and 1.1 or less, more preferably 0.99 or more and 1.05 or less, with respect to the isocyanate end groups. Thereafter, solid-phase polymerization is carried out to obtain a polyurethane with a predetermined molecular weight. As the method of the chain extension reaction and the solid-phase polymerization, an active hydrogen compound is preferably added to a batch reaction vessel containing the prepolymer at 40°C or higher and 100°C or lower as it is, and then discharged, and the solid-phase polymerization is preferably carried out at 60°C or higher and 200°C or lower, more preferably 70°C or higher and 150°C or lower, to obtain pelletized chip-shaped polymer. After uniformly mixing the prepolymer and the active hydrogen compound, the cylinder temperature of the polymerization zone is preferably set at 160°C or higher and 240°C or lower using a cylindrical pipe form or a twin-screw extruder, and after obtaining the polymer continuously or semi-continuously, the solid-phase polymerization may be carried out at 60°C or higher and 220°C or lower, more preferably 70°C or higher and 150°C or lower.

[0025] Regarding the spinning method for producing thermoplastic polyurethane elastic fibers, there is no particular limitation as long as the desired physical properties can be obtained. For example, in addition to the method of putting polyurethane elastic chips into an extruder, heating them, and melt-spinning, there are methods of melting the polyurethane elastic chips and then mixing and spinning a polyisocyanate compound, and methods of adding a reaction product of a prepolymer with isocyanate groups at both ends and an active hydrogen compound to the prepolymer with isocyanate groups at both ends and continuously spinning without going through the chip-forming process.

[0026] The thermoplastic polyurethane introduced into the extruder is metered by a metering pump and introduced into the spinning head. If necessary, after removing foreign substances by filtration using a wire mesh, glass beads, etc. in the spinning head, it is discharged from the die, air-cooled in a cold air chamber, and if necessary, a treatment agent is applied, and then wound up via godet rolls.

[0027] In the spinning process, the temperature of the die, the cold air velocity, the cold air temperature, the convergence position, and the spinning speed are adjusted, and the temperature profile and spinning tension of the fiber are precisely controlled. The temperature of the die is preferably 180°C to 220°C, more preferably 200°C to 210°C. For the cold air, a general cooling method for melt spinning such as blowing the cold air vertically from directly below the spinning nozzle in the running direction of the yarn is used. The cold air velocity is preferably 0.2 m / s to 2.0 m / s, more preferably 0.5 m / s to 1.2 m / s, and the cold air temperature is preferably 5°C to 20°C, more preferably 7°C to 15°C. As a method for converging multifilaments, a method of installing a false twister between the die and the godet roll, propagating the twist from the lower part according to the strength of the twist, converging the filaments with each other, and controlling the height of the convergence point can be mentioned. As the false twisting method, a general method can be selected, and an air false twister using an air nozzle, a ring false twister in contact with a rotating ring, etc. can be used.

[0028] The thermoplastic polyurethane elastic fiber may be coated with a treatment agent such as an oil agent from the viewpoints of spinnability, processability, etc. Examples of the treatment agent include, but are not limited to, silicone-based oils such as dimethyl silicone, mineral oil-based oils, and combinations thereof. The application method of the treatment agent is not particularly limited, and for example, a method of applying it with an oiling roller, etc. can be mentioned.

[0029] When the weight average molecular weight (Mw) of the thermoplastic polyurethane elastic fiber is measured according to polystyrene standards by GPC, it is preferably 80,000 or more and 800,000 or less, more preferably 80,000 or more and 500,000 or less, and still more preferably 100,000 or more and 300,000 or less.

[0030] When the number average molecular weight (Mn) of the thermoplastic polyurethane elastic fiber is measured by GPC using polystyrene standards, it is preferably 40,000 or more and 400,000 or less, more preferably 40,000 or more and 250,000 or less, and still more preferably 50,000 or more and 150,000 or less.

[0031] When the polydispersity (Mw / Mn) of the thermoplastic polyurethane elastic fiber is measured by GPC using polystyrene standards, it is preferably 1.5 or more and 3.0 or less, more preferably 1.5 or more and 2.5 or less.

[0032] The thermoplastic polyurethane elastic fiber may contain polymers other than polyurethane, and additives such as antioxidants, light stabilizers, ultraviolet absorbers, gas discoloration inhibitors, dyes, activators, matting agents, lubricants, etc., as long as the desired effects of the present invention are not lost.

[0033] From the perspective of expressing the velocity response ratio of gathers, the distance between hard domains measured by a small-angle X-ray scattering device (hereinafter referred to as "SAXS") for the thermoplastic polyurethane elastic fiber is preferably 10.0 nm or more and 30.0 nm or less, more preferably 10.0 nm or more and 27.0 nm or less, still more preferably 10.0 nm or more and 25.0 nm or less, even more preferably 10.5 nm or more and 20.0 nm or less, and most preferably 11.0 nm or more and 15.0 nm or less. And the full width at half maximum of the azimuthal distribution is preferably 50° or more and 130° or less, more preferably 60° or more and 120° or less, still more preferably 60° or more and 110° or less, and most preferably 80° or more and 100° or less. By setting the distance between hard domains to be 10.0 nm or more and 30.0 nm or less, it becomes easier to manufacture gathers with an appropriate velocity response ratio, and it is possible to achieve both the resistance to displacement of the gathers when the wearer moves and the suppression of marks during wearing. The reason for the correlation between the distance between hard domains and the velocity response ratio is not yet clear, but the inventor estimates as follows. The greater the difference between the structural change of the hard domains of the thermoplastic polyurethane elastic fiber when the gather is stretched at high speed and the structural change of the hard domains of the thermoplastic polyurethane elastic fiber when stretched at low speed, the greater the velocity response ratio is considered to be. When a gather containing thermoplastic polyurethane elastic fibers with a long distance between hard domains and a large hard domain size is stretched at high speed, compared with when stretched at low speed, the structure of the hard domains of the polyurethane elastic fiber is greatly destroyed, and the physical properties are improved by the stress of the destruction, and the velocity response ratio can be increased. By setting the full width at half maximum to be 50° or more and 130° or less, it becomes easier to manufacture gathers with a velocity response ratio of 1.05 or more, and the resistance to displacement of the gathers when the wearer moves can be demonstrated. The reason why it becomes easier to manufacture gathers with a velocity response ratio of 1.05 or more by setting the full width at half maximum to be 50° or more and 130° or less is not yet clear, but the inventor estimates as follows. When a gather containing thermoplastic polyurethane elastic fibers with an orientation degree such that the full width at half maximum is 50° or more is stretched at high speed, compared with when stretched at low speed, the structure of the hard domains of the polyurethane elastic fiber is greatly destroyed, and the physical properties are improved by the stress of the destruction, and the velocity response ratio can be increased.A gather containing thermoplastic polyurethane elastic fibers with an orientation degree such that the full width at half maximum is 130° or less has little change in the structure of the hard domains when stretched at a low speed, and the difference from the change in structure when stretched at a relatively high speed becomes large, resulting in a large speed response ratio.

[0034] The method of setting the distance between hard domains of the thermoplastic polyurethane elastic fiber to be 10.0 nm or more and 30.0 nm or less, and the full width at half maximum of the peak of the azimuthal angle distribution to be 50° or more and 130° or less is not particularly limited. For example, in the production of gathers, a method of controlling the heat history applied to the thermoplastic polyurethane elastic fiber in the step of bonding the thermoplastic polyurethane elastic fiber and the non-woven fabric using a hot melt adhesive, or in the step after bonding, is preferably used. Specifically, since the distance between hard domains tends to increase due to heat, a method using a heating roll in the step of bonding the thermoplastic polyurethane elastic fiber and the non-woven fabric using a hot melt adhesive can be mentioned. Also, since the full width at half maximum of the peak of the azimuthal angle distribution tends to increase as the cooling rate after heating increases, a method of blowing cold air onto the gather immediately after bonding the thermoplastic polyurethane elastic fiber and the non-woven fabric using a hot melt adhesive can be mentioned.

[0035] From the viewpoint of expressing the speed response ratio of the gather, the number of filaments of the thermoplastic polyurethane elastic fiber is preferably 10 or more and 150 or less, more preferably 10 or more and 120 or less, and still more preferably 20 or more and 120 or less. The reason why the speed response ratio can be increased by setting the number of filaments to be 10 or more and 150 or less is not yet clear, but the inventor estimates as follows. Thermoplastic polyurethane elastic fibers manufactured so that the number of filaments is 10 or more have higher physical properties of the raw yarn, so it becomes easier to reflect the speed response ratio of the raw yarn in the gather. Thermoplastic polyurethane elastic fibers manufactured so that the number of filaments is 150 or less can make the cooling of single filaments uniform in the cooling process in the melt spinning step, so the variation in physical properties between single filaments can be reduced, and it becomes easier to increase the speed response ratio of the raw yarn, and it becomes easier to reflect the speed response ratio of the raw yarn in the gather.

[0036] From the perspective of expressing the speed response ratio of the gather, the denier per filament of the thermoplastic polyurethane elastic fiber is preferably 5 dtex or more and 20 dtex or less, more preferably 7 dtex or more and 16 dtex or less. Although the reason why the speed response ratio can be increased by setting the denier per filament to 5 dtex or more and 20 dtex or less is not yet clear, the inventor presumes as follows. The thermoplastic polyurethane elastic fiber manufactured so that the denier per filament is 5 dtex or more can make the cooling between single filaments uniform during the cooling process in the melt spinning process, so the variation in physical properties between single filaments can be reduced, it becomes easier to increase the speed response ratio of the raw yarn, and it becomes easier to reflect the speed response ratio of the raw yarn in the gather. The thermoplastic polyurethane elastic fiber manufactured so that the denier per filament is 20 dtex or less is easily cooled during the cooling process in the melt spinning process, the variation in physical properties between single filaments can be reduced, it becomes easier to increase the speed response ratio of the raw yarn, and it becomes easier to reflect the speed response ratio of the raw yarn in the gather.

[0037] From the perspective of expressing the speed response ratio of the gather, the total denier of the thermoplastic polyurethane elastic fiber is preferably 150 dtex or more and 1500 dtex or less. Although the reason why the speed response ratio can be increased by setting the total denier of the thermoplastic polyurethane elastic fiber to 150 dtex or more and 1500 dtex is not yet clear, the inventor presumes as follows. The thermoplastic polyurethane elastic fiber manufactured so that the total denier is 150 dtex or more has high physical properties of the raw yarn, so it becomes easier to reflect the speed response ratio of the raw yarn in the gather. The thermoplastic polyurethane elastic fiber manufactured so that the total denier is 1500 dtex or less can make the cooling uniform during the cooling process in the melt spinning process, so the variation in physical properties in the yarn length direction can be reduced, it becomes easier to increase the speed response ratio of the raw yarn, and it becomes easier to reflect the speed response ratio of the raw yarn in the gather.

[0038] From the viewpoint of increasing the speed response ratio of the gather, the thermoplastic polyurethane elastic fiber preferably contains a polyurethane synthesized from polymer polyol, MDI, and 1,4-butanediol. Although the reason why the speed response ratio can be exhibited by the thermoplastic polyurethane elastic fiber contained in the gather of the present embodiment containing a polyurethane synthesized from polymer polyol, MDI, and 1,4-butanediol is not yet clear, the inventor presumes as follows. It is considered that the greater the difference between the structural change of the hard domain of the thermoplastic polyurethane elastic fiber when the gather is stretched at high speed and the structural change of the hard domain of the thermoplastic polyurethane elastic fiber when it is stretched at low speed, the greater the speed response ratio. The thermoplastic polyurethane elastic fiber synthesized from polymer polyol, MDI, and 1,4-butanediol has a strong hydrogen bonding force in the hard domain, and when stretched at high speed, the structure of the hard domain is greatly destroyed, but when stretched at low speed, the structure of the hard domain is hardly destroyed, and the speed response ratio can be increased.

[0039] From the perspective of expressing the speed response ratio of the gather, the molecular weight of the hard segment of the thermoplastic polyurethane elastic fiber is preferably 750 or more and 1500 or less, more preferably 800 or more and 1300 or less, and still more preferably 850 or more and 1200 or less. By setting the molecular weight of the hard segment of the thermoplastic polyurethane elastic fiber contained in the gather of the present embodiment to 750 or more and 1500 or less, it becomes easier to make the speed response ratio 1.05 or more and 3.00 or less. Although the reason why it becomes easier to make the speed response ratio 1.05 or more and 3.00 or less by setting the molecular weight of the hard segment to 750 or more and 1500 or less is not yet clear, the inventor estimates as follows. When the molecular weight of the hard segment is 750 or more and 1500 or less, when the gather containing the thermoplastic polyurethane elastic fiber is stretched at high speed, the degree of structural destruction of the hard domain of the polyurethane elastic fiber becomes appropriate, and the speed response ratio is controlled within the range of 1.05 or more and 3.00 or less. The manufacturing method of the thermoplastic polyurethane elastic fiber in which the molecular weight of the hard segment is 750 or more and 1500 or less is not particularly limited. For example, a method of manufacturing a thermoplastic polyurethane elastic fiber from a thermoplastic polyurethane polymerized by controlling the molar number of isocyanate with respect to the polymer polyol is preferably used. Generally, when the molar number of isocyanate with respect to the polymer polyol is increased, the molecular weight of the hard segment can also be increased.

[0040] From the perspective of further enhancing the effect of improving the resistance of gathers to displacement when the wearer moves, it is preferable that the thermoplastic polyurethane elastic fiber substantially has no crosslinking containing allophanate bonds in which urethane bonds are crosslinked by isocyanate groups. The reason why the speed response ratio can be increased by not having crosslinking containing allophanate bonds is not yet clear, but the inventor presumes as follows. It is considered that the greater the difference between the structural change of the hard domain of the thermoplastic polyurethane elastic fiber when the gather is stretched at high speed and the structural change of the hard domain of the thermoplastic polyurethane elastic fiber when it is stretched at low speed, the greater the speed response ratio. When a gather containing a thermoplastic polyurethane elastic fiber without a crosslinked structure is stretched at high speed, the structure of the hard domain is easily destroyed during high-speed stretching, the speed response ratio increases, and the resistance of the gather to displacement when the wearer moves is exerted. The method for producing a thermoplastic polyurethane elastic fiber having no crosslinking containing allophanate bonds is not particularly limited. For example, a method for producing a thermoplastic polyurethane elastic fiber by controlling the total molar number of a chain extender composed of a polymer polyol and an active hydrogen compound to be equal to or more than the molar number of isocyanate and then polymerizing is preferably used.

[0041] [Hot-melt adhesive contained in the gather] From the perspective of increasing the speed response ratio of the gather, the amount of the hot-melt adhesive contained in the gather of the present embodiment is preferably 0.02 g / m or more and 0.10 g / m or less, more preferably 0.03 g / m or more and 0.08 g / m or less, with respect to the elongation length per thermoplastic polyurethane elastic fiber.

[0042] The hot melt adhesive preferably contains a thermoplastic elastomer as a main component, specifically, the thermoplastic elastomer is preferably contained in an amount of 60 wt% or more, more preferably 65 wt% or more, still more preferably 70 wt% or more, and most preferably 75 wt% or more. Examples of the hot melt adhesive containing a thermoplastic elastomer as a main component include a rubber-based hot melt adhesive made of a block copolymer of a vinyl aromatic hydrocarbon and a conjugated diene compound and a hydrogenated product thereof, a rubber-based hot melt adhesive made of a polyolefin copolymer, and a hot melt adhesive made of a copolymer having ethylene as a main chain (such as ethylene-vinyl acetate copolymer (EVA), ethylene-ethyl acrylate copolymer (EEA), ethylene-n-butyl copolymer (EnBA), etc.). Among these, from the viewpoint of increasing the speed response ratio of the gather, the hot melt adhesive contained in the gather of the present embodiment is preferably a styrene-based block copolymer composed of a block copolymer of a vinyl aromatic hydrocarbon and a conjugated diene compound and a hydrogenated product thereof. The reason why the speed response ratio can be increased by using a styrene-based block copolymer composed of a block copolymer of a vinyl aromatic hydrocarbon and a conjugated diene compound and a hydrogenated product thereof as the hot melt adhesive contained in the gather is not yet clear, but the inventor presumes as follows. The intermolecular force acting on the aromatic part contained in the hard domain of the thermoplastic polyurethane elastic fiber becomes stronger with the aromatic hydrocarbon of the hot melt adhesive, and the adhesive force between the thermoplastic polyurethane elastic fiber and the non-woven fabric becomes stronger, so that the speed response ratio of the yarn is more likely to be reflected in the gather.

[0043] Examples of the styrenic block copolymer comprising a block copolymer of a vinyl aromatic hydrocarbon and a conjugated diene compound and a hydrogenated product thereof include, specifically, non-hydrogenated products of block copolymers such as styrene-isoprene-styrene block copolymer (SIS) and styrene-butadiene-styrene block copolymer (SBS); hydrogenated products such as styrene-butadiene / butylene-styrene block copolymer (SBBS), styrene-ethylene / butylene-styrene block copolymer (SEBS), styrene-ethylene / propylene-styrene block copolymer (SEPS), and styrene-ethylene-ethylene / propylene-styrene block copolymer (SEEPS). These styrenic block copolymers may be used alone or in combination of two or more.

[0044] The hot melt adhesive may contain additives such as an antioxidant, a light stabilizer, an ultraviolet absorber, a lubricant, a plasticizer, and a slip agent, as long as the desired effects of the present invention are not lost.

[0045] In the production of the gather of the present embodiment, there is no particular limitation on the adhesion method using the hot melt adhesive, and a conventionally known method can be applied. Generally, the hot melt adhesive is heated and melted in a heating and melting tank before being applied to various adherends. Examples of the coating method for the heated and melted hot melt adhesive include coating with a caulking gun, a surelap, a bead, a summit, a spiral, a pattern coat, etc., typified by a V slit.

[0046] The melt viscosity of the hot melt adhesive is not particularly limited, but is preferably 1,000 mPa·s or more and 30,000 mPa·s or less at 150°C. When the melt viscosity of the hot melt adhesive at 150°C is 1,000 mPa·s or more, the adhesiveness by the hot melt adhesive is improved and the polyurethane elastic fiber is not peeled off from the nonwoven fabric. When the melt viscosity of the hot melt adhesive at 150°C is 30,000 mPa·s or less, the texture of the gather is improved.

[0047] [Nonwoven fabric contained in the gather] There is no particular limitation on the type of nonwoven fabric used for the gather of this embodiment. It may be a long fiber nonwoven fabric such as a spunbond nonwoven fabric, a meltblown nonwoven fabric, a flash spun nonwoven fabric, an electrospun nonwoven fabric, a wet spun nonwoven fabric, etc., or it may be a short fiber nonwoven fabric obtained by a wet papermaking method. However, a long fiber nonwoven fabric is preferred, and particularly a spunbond nonwoven fabric is preferred. There is no limitation on the basis weight of the nonwoven fabric. However, from the viewpoint of increasing the speed response ratio of the gather, it is preferably 8 g / m 2 or more and 50 g / m 2 or less. Regarding the reason why the speed response ratio can be increased by setting the basis weight of the nonwoven fabric contained in the gather to 8 g / m 2 or more and 50 g / m 2 or less, it is not yet clear. However, the inventors presume as follows. By setting the basis weight of the nonwoven fabric to 8 g / m 2 or more, when the thermoplastic polyurethane elastic fiber and the nonwoven fabric are adhered with a hot melt adhesive, it is possible to suppress the hot melt adhesive from soaking into the nonwoven fabric, and the adhesive strength between the hot melt adhesive and the thermoplastic polyurethane elastic fiber can be increased, and the speed response ratio of the yarn is likely to be reflected in the gather. Further, by setting the basis weight of the nonwoven fabric to 50 g / m 2 or less, a soft gather can be obtained, and the gather is likely to be stretched following the yarn, and the speed response ratio of the yarn is likely to be reflected in the gather.

[0048] There is no particular limitation on the fibers constituting the nonwoven fabric. They may be polyolefin fibers such as polyethylene and polypropylene, polyester fibers, polyamide fibers, cellulose fibers, polyurethane fibers, etc., or may be a mixture thereof. However, polyolefin fibers are preferred. Two or more nonwoven fabrics made of different fibers may be used in combination. As the polyolefin-based fibers, for example, fibers made of resins such as polyethylene, polypropylene, and copolymers of these monomers and other α-olefins can be used. Among these, since the strength is strong and it is difficult to break, and it is excellent in dimensional stability when manufacturing stretchable materials, it is preferable to use polypropylene-based fibers made of polypropylene and / or polypropylene copolymer.

[0049] The non-woven fabric preferably has high flexibility. In order to impart high flexibility to the non-woven fabric, when bonding the fiber web to form a non-woven fabric, it is preferable to adopt a partial thermocompression bonding method as the bonding means, and the smaller the partial thermocompression bonding area ratio, the better. Further, the average single fiber fineness of the fibers constituting the non-woven fabric is preferably 0.5 dtex or more and 3.0 dtex or less. In order to obtain good flexibility, the non-woven fabric may be subjected to profiling processing of unevenness. As the shape of the profiling processing, straight lines, curves, corners, circles, pear skin patterns, and other continuous and discontinuous ones can be applied, but from the viewpoint of the flexibility effect, a tortoiseshell pattern is preferable. Furthermore, in order to obtain good flexibility, an ester compound of a polyol having 3 to 6 valences and a monocarboxylic acid may be contained in the non-woven fabric. The ester compound may be contained by mixing it with the raw material resin before spinning, or may be imparted and contained after manufacturing the non-woven fabric.

[0050] The non-woven fabric may contain a hydrophilic agent. Further, the fibers constituting the non-woven fabric may be blended with a nucleating agent, a flame retardant, an inorganic filler, a pigment, a colorant, a heat stabilizer, an antistatic agent, etc. within a range that does not inhibit the object of the present invention.

[0051] [Hygienic material] The hygienic material including the gathers of the present embodiment is also an aspect of the present invention. Specific examples of the hygienic material include absorbent articles typified by disposable diapers and sanitary products. In disposable diapers, the gathers of the present embodiment are preferably used in the waist part and the leg part.

Example

[0052] The present invention will be specifically described by the following examples and comparative examples, but the scope of the present invention is not limited by the examples. First, the evaluation methods used in the following examples will be described.

[0053] (1) Speed response ratio of gathers Using a tensile testing machine (EZ-SX AUTOGRAPH manufactured by Shimadzu Corporation), in an atmosphere of 20°C and 65% RH, cut out the gather into a size of 2 cm in width, set it on the tensile testing machine so that it has no deflection, an initial length of 5 cm, and an initial load of 0 cN, and extend it to 100% elongation at elongation rates of 200% / min and 2000% / min, and measure the stress (cN) at 50% elongation. Here, let the maximum stress at an elongation rate of 200% / min be R and the maximum stress at an elongation rate of 2000% / min be R', and use the following calculation formula: Speed response ratio = R' / R From this, the speed response ratio of the gather was calculated. Note that the tensile tests at elongation rates of 200% / min and 2000% / min are each performed using separate samples.

[0054] (2) Content of hot melt adhesive in the gather Cut out a sample from the gather containing 1 thermoplastic polyurethane elastic fiber so that the length is 10 cm, measure its weight X (g) after storing it in an environment of 20°C and 65% RH for 24 hours. Immerse the sample in 100 mL of cyclohexane for 10 minutes to dissolve and remove the hot melt adhesive, take out the non-woven fabric and the thermoplastic polyurethane elastic fiber, place them on filter paper so that they are each without tension, and dry them in an environment of 20°C and 65% RH for 12 hours. Measure the total weight Y (g) of the dried non-woven fabric and thermoplastic polyurethane elastic fiber and the length Z (m) of the non-woven fabric. Here, the length Z (m) of the non-woven fabric refers to the length in the direction parallel to the direction in which the thermoplastic polyurethane elastic fiber was inserted. Use the following calculation formula: Amount of hot melt adhesive (g / m) = (X - Y) / Z From this, the amount of hot melt adhesive (g / m) applied to the thermoplastic polyurethane elastic fiber was calculated. The measurement was performed 4 times and the average value was taken.

[0055] (3) Elongation rate of elongation cut-off of the gather Using the length Z (m) of the non-woven fabric obtained in (2) above, use the following calculation formula: Elongation rate of elongation cut-off (%) = (10×Z - 1)×100 From this, the elongation rate (%) of the extension of the gather was calculated. The measurement was performed four times, and the average value was taken.

[0056] (4) Total fineness of the thermoplastic polyurethane elastic fibers contained in the gather The length of the thermoplastic polyurethane elastic fiber in the relaxed state (hereinafter, also referred to as "relaxed length") taken out from the gather by the method described in (2) above and its sample weight (g) were measured. From the following calculation formula, the total fineness (dtex) of the thermoplastic polyurethane elastic fiber in the relaxed state was calculated. The measurement was performed four times, and the average value was taken. Note that the "relaxed state" refers to a state in which the thermoplastic polyurethane elastic fiber taken out from the gather is left unloaded for 2 hours or more. Total fineness A (dtex) = sample weight (g) × 10000 / relaxed length (m)

[0057] (5) Number of filaments of the thermoplastic polyurethane elastic fibers contained in the gather The cross-section of the thermoplastic polyurethane elastic fiber taken out from the gather by the method described in (2) above was observed using an electron microscope JSM-6510 manufactured by JEOL Ltd., and the number of its single filaments was measured as the number of filaments.

[0058] (6) Single filament fineness of the thermoplastic polyurethane elastic fibers contained in the gather Using the total fineness A (dtex) and the number of filaments obtained in (4) and (5) above, the following calculation formula: Single filament fineness (dtex) = A / number of filaments From this, the single filament fineness (dtex) of the thermoplastic polyurethane elastic fiber was calculated.

[0059] (7) Distance between hard domains and full width at half maximum of the peak of the azimuthal angle distribution of the thermoplastic polyurethane elastic fiber The sample stage was set so that the fiber axis of the thermoplastic polyurethane elastic fiber taken out from the gather by the method described in (2) above was in the horizontal direction. X-rays were irradiated perpendicular to the fiber, and measurement was performed using SAXS under the following conditions. Measuring device: NANOPIX manufactured by Rigaku Corporation Incident X-ray wavelength λ: 0.154 nm Detector: 2D detector "Hypix-6000" Measurement time: 15 minutes Camera length: 1312 mm Optical system: Point collimation: 1st slit: 0.55 mm φ, guard slit: 0.35 mm φ High Resolution Mode Beam stopper: 2 mm φ

[0060] With the 12 o'clock direction of the 2D SAXS pattern I(2θ,φ) obtained by the 2D detector defined as 0° and the azimuth angle θ defined clockwise, the following formula:

Equation

Equation

[0061] Next, the hard domain spacing was calculated from the peak position q c obtained by fitting the vicinity of the peak of the one-dimensional scattering intensity I max with a Gaussian function. Note that q is the absolute value of the scattering vector.

Equation

[0062] Subsequently, for q s <q < q e (q s = q max - 0.1 nm -1 , q e = q max + 0.1 nm -1 ), the azimuthal distribution of the scattered light intensity is given by the following equation: [Mathematics] {where I sample (q, φ) is the two-dimensional scattering pattern of the sample, and I empty (q, φ) is the two-dimensional scattering pattern of the empty cell} was calculated.

[0063] The obtained azimuthal distribution I(φ) was normalized by the following equation: [Mathematics] After normalization, for the azimuthal distribution I

[0064] (φ), the full width at half maximum was calculated from the peak closest to the azimuthal angle φ = 90° under the following conditions. N Analysis software: Igor Pro 8.00 manufactured by Wavemetrics Analysis software: Igor Pro 8.00 manufactured by Wavemetrics Fitting method: Multi-peak Fit of Igor Pro 8.00 The baseline was set as a constant, and the constant connecting both ends of the peak base was used as the initial value. Also, the constant of the baseline was set as a variable in the fitting. A Gaussian function was used as the fitting function, and the Location, Width, and Height of the peak in the Multi-peak Fit were set as variables, with their initial values being 90°, 50°, and 1, respectively. The fitting range was set as both ends of the peak base closest to the azimuthal angle φ = 90°.

[0065] (8) Qualitative analysis of the components of the thermoplastic polyurethane contained in the gatherer and measurement of the molecular weight of the hard segment A sample collected from the thermoplastic polyurethane elastic fiber taken out from the gatherer by the method described in (2) above and a predetermined amount of internal standard dimethyl sulfoxide were measured, and NMR was measured under the following conditions to identify the structure and molar ratio of the polymer polyol, chain extender, and diisocyanate. The structures of the diisocyanate and the chain extender can be determined from the peak positions by NMR measurement. Measuring device: Bruker Biospin Avance600 Measured nucleus: 1H Resonance frequency: 600 MHz Number of integrations: 256 times Measurement temperature: Room temperature Solvent: Deuterated dimethylformamide Measurement concentration: 1.5 wt% Chemical shift standard: Dimethylformamide (8.0233 ppm)

[0066] The molecular weight of the hard segment of the thermoplastic polyurethane elastic fiber contained in the gatherer is calculated by solving the simultaneous equations of the following formulas (1) and (2). Mh = {Mda(N1 - 1) + Mdi×N0} / (N1 - N0 - 1) + 2Mdi … Formula (1) N0 = 0.03806N1 4 -0.3997N1 3 +1.617N1 2 -2.144N 1 +0.8795 … Formula (2) Mda: Molecular weight of the chain extender (number average molecular weight in the case of using a mixture of two or more types) Mdi: Molecular weight of the isocyanate N0: Molar ratio of unreacted isocyanate to polymer polyol N1: Molar ratio of isocyanate to polymer polyol Mh: Molecular weight of the hard segment

[0067] (9) Determination of the presence or absence of crosslinking containing allophanate bonds in the thermoplastic polyurethane elastic fibers contained in the gathers Thermoplastic polyurethane elastic fibers that dissolved in the following DMAc dissolution test and for which allophanate bonds could not be confirmed by the following NMR measurement were determined to be those having "no crosslinking containing allophanate bonds" in the terminology of this specification. Thermoplastic polyurethane elastic fibers that did not dissolve in the following DMAc dissolution test or that dissolved in the following DMAc dissolution test but for which allophanate bonds could be confirmed by the following NMR measurement were determined to be those having "crosslinking containing allophanate bonds". <DMAc Dissolution Test> Precisely weigh 0.2 g of the thermoplastic polyurethane elastic fibers taken out from the gathers by the method described in (2) above, immerse them in 10 g of DMAc, and stir at 20°C for 48 hours. After stirring, if no polymer lumps with a diameter of 1 mm or more could be visually confirmed, it was determined that it had dissolved in DMAc. <NMR Measurement (Qualification of Allophanate Bonds)> Weigh a predetermined amount of the polyurethane elastic fibers taken out from the gathers by the method described in (2) above and dried under a vacuum of -0.1 MPa at 80°C for 5 hours and the internal standard dimethyl sulfoxide, and measure NMR under the following conditions. By this measurement, the ratio of allophanate bonds to urethane bonds was confirmed. The ratio of allophanate bonds to the urethane bonds can be calculated by comparing the integral values of the respective hydrogens, and when this ratio is less than 0.05%, it is defined that no allophanate groups are contained. Generally, the hydrogen signal of allophanate bonds is often observed at 10.5 to 11.0 ppm, but this is not the limit. [NMR Measurement Conditions] Measuring device: ECS400 manufactured by JEOL Measuring nucleus: 1 H Resonance frequency: 400 MHz Number of integrations: 256 times Measuring temperature: Room temperature Solvent: Deuterated dimethylformamide Measuring concentration: 1.5 wt% Chemical shift standard: Dimethylformamide (8.0233 ppm)

[0068] (10) Qualitative analysis of the chemical structure of the hot melt adhesive contained in the gather The hot melt adhesive solution eluted from the gather by the method described in (2) above was concentrated and dried to dryness with an evaporator to obtain a sample. A predetermined amount of the sample was weighed and NMR was measured under the following conditions to identify the chemical structure. Measuring device: Bruker Biospin Avance600 Measured nucleus: 1H Resonance frequency: 600 MHz Number of integrations: 256 times Measuring temperature: Room temperature Solvent: Deuterated chloroform Measuring concentration: 1.5 wt% Chemical shift standard: Chloroform (7.24 ppm)

[0069] (11) Areal density of the nonwoven fabric contained in the gather The nonwoven fabric taken out from the gather by the method described in (2) above was cut into 0.5 cm × 10 cm, and the weight (g) of the nonwoven fabric was measured. Using the following calculation formula: Areal density of nonwoven fabric (g / m 2 ) = Weight of nonwoven fabric (g) / 0.0005 (m 2 ) The areal density of the nonwoven fabric (g / m 2 ) contained in the gather was calculated. The measurement was performed 10 times and the average value was taken.

[0070] (12) Resistance of the gather to displacement during operation The gather prepared above was left standing for 1 day in an unextended state to sufficiently relax the stress of the elastic fiber. Thereafter, a ring with a length of 50 cm was made from the relaxed gather. Ten subjects with a waist length of 75 cm to 80 cm wore this ring at the waist part and the number of people who felt it was difficult to displace was measured when worn for 8 hours. It can be said that the gather is more difficult to displace as the number of people who feel it is difficult to displace is larger in the above sensory evaluation. In this example, a gather in which the number of people who felt it was difficult to displace was 5 or more was regarded as qualified.

[0071] (13) Ease of leaving marks when wearing gathers The gathers prepared above were left in an unextended state for one day to sufficiently relax the stress of the elastic fibers. Then, a ring with a length of 50 cm was made from the relaxed gathers. Ten subjects with a waist length of 75 cm to 80 cm wore this ring at the waist part for 8 hours, and the number of people who did not leave marks when wearing was measured. Although it can be said that the more people who did not leave marks in the above sensory evaluation, the less likely the gathers are to leave marks, in this example, the gathers with 5 or more people who did not leave marks were regarded as qualified.

[0072] [Example 1] 2400 g of polytetramethylene ether glycol with a number average molecular weight of 1800 and 775.78 g of 4,4'-diphenylmethane diisocyanate were reacted under stirring at 60°C for 3 hours in a dry nitrogen atmosphere to obtain a polyurethane prepolymer capped with terminal isocyanate. 162.01 g of 1,4-butanediol was added to this polyurethane prepolymer and stirred for 15 minutes to obtain a thermoplastic polyurethane with a viscosity of 2000 poise (30°C). Then, it was poured out onto a Teflon (registered trademark) tray, and while the thermoplastic polyurethane was in the tray, it was annealed in a hot air oven at 110°C for 19 hours to obtain a thermoplastic polyurethane resin. The weight average molecular weight of this thermoplastic polyurethane resin was 200,000 in GPC.

[0073] The thermoplastic polyurethane resin thus obtained was pulverized into powder of about 3 mm using a pulverizer UG-280 type manufactured by Horai Co., Ltd. After drying the pulverized chips in a dehumidifying dryer to a moisture content of 100 ppm under the temperature condition of 110 °C, the thermoplastic polyurethane resin powder was charged from a hopper and melted in an extruder. It was metered and pressurized by a gear pump installed in the head, filtered through a filter, and then discharged from a nozzle with a diameter of 0.23 mm and 60 holes at a rate of 31 g / min. Thereafter, cold air was blown out from a cold air chamber where the length of the cold air and the cold air wind speed were adjusted, and melt spinning was carried out by applying it perpendicular to the fiber. Thereafter, using a ring type false twister, twist was propagated to the multifilament, and while applying a treatment agent mainly composed of polydimethylsiloxane and mineral oil, it was wound around a paper tube to obtain a wound body of thermoplastic polyurethane elastic fiber of 620 dtex / 60 filaments.

[0074] Five thermoplastic polyurethane elastic fibers were arranged in parallel at an interval of 7 mm, stretched to a length 2.0 times the original length, and a hot melt adhesive (765E manufactured by Henkel Japan Co., Ltd.) melted at 150 °C was continuously applied with a V slit. The polyurethane elastic fiber coated with the hot melt adhesive was continuously sandwiched between two non-woven fabrics (Eltasguard (registered trademark) manufactured by Asahi Kasei Corporation) with a width of 30 cm and a basis weight of 17 g / m 2 While being continuously pressed by an air cylinder (CQ2WB100-50DZ manufactured by SMC Corporation) supplying an air pressure of 0.5 MPa while being pushed in by a pair of heating rollers with an outer diameter of 16 cm and a width of 40 cm, with the surface temperature of one roller set to 80 °C and the surface temperature of the other roller set to room temperature, cold air with a cold air wind speed of 0.6 m / s and a cold air temperature of 16 °C was blown out from a cold air chamber with a cold air length of 300 mm at a distance of 300 to 600 mm below the crimping, and the cold air was applied perpendicular to the gather to produce a gather.

[0075] The obtained speed response ratio of the gather was 1.50, and the elongation rate at break was 100%. Also, the thermoplastic polyurethane elastic fiber contained in the gather was 620 dtex and 60 filaments, and it contained polyurethane synthesized from polytetramethylene ether glycol (PTMG), 4,4'-diphenylmethane diisocyanate (MDI), and 1,4-butanediol (BDO). The distance between hard domains was 12.0 nm, the full width at half maximum of the peak of the azimuthal angle distribution was 90°, the molecular weight of the hard segment was 1005, and it did not contain a crosslinked structure. Also, the hot melt adhesive was a styrene-butadiene-styrene block copolymer (SBS), the coating amount was 0.04 g / m, and the basis weight of the nonwoven fabric was 17 g / m 2 It was. The results are also shown in Table 1 below.

[0076] [Examples 2 to 9] In the manufacturing process of the gather, except that the temperature and air pressure of the heat roller for crimping were changed to control the distance between hard domains of the thermoplastic polyurethane elastic fiber and adjust the speed response ratio of the gather, the gather was produced in the same manner as in Example 1.

[0077] [Examples 10 to 16] In the manufacturing process of the gather, except that the cold air velocity and cold air temperature of the cold air chamber were changed to control the full width at half maximum of the peak of the azimuthal angle distribution of the thermoplastic polyurethane elastic fiber and adjust the speed response ratio of the gather, the gather was produced in the same manner as in Example 1.

[0078] [Examples 17 to 27] Except for using thermoplastic polyurethane elastic fibers with different numbers of filaments, single filament fineness, and total fineness, the gather was produced in the same manner as in Example 1.

[0079] [Examples 28 to 29] Except for using thermoplastic polyurethane elastic fibers in which the isocyanate component was 1,6-hexamethylene diisocyanate (HDI) (Example 28) and the chain extender was 1,3-propanediol (PDO) (Example 29), the gather was produced in the same manner as in Example 1.

[0080] [Examples 30 to 36] Gathers were produced in the same manner as in Example 1, except that thermoplastic polyurethane elastic fibers having different molecular weights of the hard segment were used.

[0081] [Example 37] Gathers were produced in the same manner as in Example 1, except that thermoplastic polyurethane elastic fibers having a crosslinked structure were used.

[0082] [Examples 38 to 42] Gathers were produced in the same manner as in Example 1, except that the coating amount of the hot melt adhesive was changed.

[0083] [Examples 43 to 47] Gathers were produced in the same manner as in Example 1, except that styrene-isoprene-styrene block copolymer (SIS) (Example 43), styrene-butadiene / butylene-styrene block copolymer (SBBS) (Example 44), styrene-ethylene / butylene-styrene block copolymer (SEBS) (Example 45), ethylene-ethyl acrylate copolymer (EEA) (Example 46), and ethylene-vinyl acetate copolymer (EVA) (Example 47) were used as the hot melt adhesive.

[0084] [Examples 48 to 51] Gathers were produced in the same manner as in Example 1, except that nonwoven fabrics having different basis weights were used.

[0085] [Examples 52 to 55] Gathers were produced in the same manner as in Example 1, except that the draw ratio of the thermoplastic polyurethane elastic fibers before being adhered to the nonwoven fabric was changed to change the elongation at break.

[0086] [Comparative Examples 1, 2] In the manufacturing process of the gathers, except that the temperature of the heat roller for crimping and the air pressure were changed to control the distance between the hard domains of the thermoplastic polyurethane elastic fibers and adjust the speed response ratio of the gathers, the gathers were produced in the same manner as in Example 1.

[0087] [Comparative Examples 3 and 4] In the manufacturing process of the gathers, except that the cold air velocity and cold air temperature in the cold air chamber were changed to control the full width at half maximum of the peak of the azimuthal angle distribution of the thermoplastic polyurethane elastic fibers and adjust the speed response ratio of the gathers, the gathers were produced in the same manner as in Example 1.

[0088] [Comparative Example 5] Except that the polyurethane elastic fibers produced by dry spinning were used, where the chain extender composed of an active hydrogen compound was ethylenediamine (EDA) and the molecular weight of the hard segment was 700, the gathers were produced in the same manner as in Example 1. The distance between the hard domains of the polyurethane elastic fibers extracted from the gathers was 9.0 nm, and the speed response ratio was 1.00.

[0089] [Comparative Example 6] In the manufacturing process of the gathers, except that the temperature of the heat roller for crimping was set to room temperature and the cold air chamber was not used, the gathers were produced in the same manner as in Example 1.

[0090] [Comparative Example 7] Except that the polyurethane elastic fibers produced by dry spinning were used, where the chain extender composed of an active hydrogen compound was ethylenediamine (EDA) and the molecular weight of the hard segment was 700, the gathers were produced in the same manner as in Comparative Example 6.

[0091] The manufacturing conditions, measurement results of each property of the obtained polyurethane elastic fibers and gathers, etc. in the above Examples and Comparative Examples are shown in Tables 1 to 5 below.

[0092]

Table 1

[0093]

Table 2

[0094]

Table 3

[0095]

Table 4

[0096]

Table 5

Industrial Applicability

[0097] The gather according to the present invention can be used as a member of a sanitary material such as an absorbent article typified by sanitary products and disposable paper diapers, so that an appropriate speed response ratio can be exhibited, and it is difficult to shift against the intense movements of the wearer, and a product that is difficult to leave marks can be obtained.

Claims

1. A gather in which the ratio of the 50% elongation stress at an elongation rate of 2000% / min to the 50% elongation stress at an elongation rate of 200% / min is 1.05 or more and 3.00 or less.

2. The gather according to claim 1, comprising at least a thermoplastic polyurethane elastic fiber and a nonwoven fabric.

3. The gather according to claim 2, further comprising a hot melt adhesive.

4. The gather according to claim 2 or 3, wherein the distance between hard domains measured by a small angle X-ray scattering apparatus of the thermoplastic polyurethane elastic fiber is 10.0 nm or more and 30.0 nm or less, and the full width at half maximum of the peak of the azimuthal angle distribution is 50° or more and 130° or less.

5. The gather according to claim 2 or 3, wherein the number of filaments of the thermoplastic polyurethane elastic fiber is 10 or more and 150 or less.

6. The gather according to claim 2 or 3, wherein the fineness per single filament of the thermoplastic polyurethane elastic fiber is 5 dtex or more and 20 dtex or less.

7. The gather according to claim 2 or 3, wherein the total fineness of the thermoplastic polyurethane elastic fiber is 150 dtex or more and 1500 dtex or less.

8. The gather according to claim 2 or 3, wherein the thermoplastic polyurethane elastic fiber contains a polyurethane synthesized from a polymer polyol, MDI, and 1,4-butanediol.

9. The gather according to claim 2 or 3, wherein the molecular weight of the hard segment of the thermoplastic polyurethane elastic fiber is 750 or more and 1500 or less.

10. The gather according to claim 2 or 3, wherein the thermoplastic polyurethane elastic fiber substantially does not have a crosslinking containing an allophanate bond.

11. The gather according to claim 3, wherein the content of the hot melt adhesive is 0.02 g / m or more and 0.10 g / m or less with respect to the elongation length per one thermoplastic polyurethane elastic fiber.

12. The gather according to claim 3, wherein the hot melt adhesive is a styrene-based block copolymer selected from the group consisting of a block copolymer of a vinyl aromatic hydrocarbon and a conjugated diene compound and a hydrogenated product thereof.

13. The basis weight of the nonwoven fabric is 8 g / m 2 or more and 50 g / m 2 or less. The gather according to claim 2 or 3

14. The gather according to any one of claims 1 to 3, wherein the elongation rate at break of the gather is 50% or more and 250% or less.

15. A sanitary material comprising the gather according to any one of claims 1 to 3.

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