JP2014033802A - Cushioning material and composite short fiber for cushioning material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cushioning material having excellent bulk recoverability, reducing permanent-set, and having proper resiliency, and composite short fiber capable of providing such a cushioning material.SOLUTION: The cushioning material includes a first component 1 and a second component 2, and also includes a composite short fiber 10 for revealing at least solid curling. In the cushioning material, the first component 1 includes at least one kind of linear low-density polyethylene (LLDPE) by 60 mass% or more, and density of the whole linear low-density polyethylene included in the first component 1 is 0.88 g/cm-0.918 g/cm, and in a fiber cross section, the first component 1 occupies at least 20% of a fiber surface, and a gravity center position of the second component 2 is dislocated from a gravity center position of the fiber, and at least a part of the mutual fibers is thermally adhered by at least a part of the first component 1.

Description

  The present invention relates to an excellent bulk recovery property, a cushion material in which the bulk is not easily reduced even after repeated compression, and a composite short fiber constituting the cushion material of the present invention.

  Conventionally, urethane foam has been widely used as a cushioning material for various seats including automobile seats, bedding such as mattresses and bed mats, and clothing pads such as brassiere pads and shoulder pads. Yes. However, from the viewpoint of safety, impact on the environment at the time of disposal, and lack of air permeability, the use of a nonwoven fabric containing crimped conjugate fibers as a cushioning material in place of urethane foam has been studied.

  As such a composite fiber, for example, Patent Document 1 (Japanese Patent Application Laid-Open No. 2008-274473) includes, as a first component, linear polyethylene polymerized using a metallocene catalyst, and 50% by mass of polytrimethylene terephthalate. A crimped conjugate fiber containing the above-described polyester as a second component is disclosed. In the crimped conjugate fiber disclosed in Patent Document 1, when viewed from the fiber cross section, the first component occupies at least 20% of the surface of the conjugate fiber, and the center of gravity of the second component is from the center of gravity of the conjugate fiber. This conjugate fiber is an apparently crimped conjugate fiber characterized by having at least one kind of crimp selected from wave-shaped crimps and spiral crimps. When such an actual crimpable conjugate fiber is used, a fiber aggregate (for example, non-woven fabric) having a large initial bulk can be obtained, and the bulk reduction (sagging) at the time of heat processing is small, and the bulk at a high temperature. Since the recoverability is also good, it can be used as a field where heat resistance is required, for example, a vehicle cushion material.

JP 2008-274473 A

  However, recently, in the nonwoven fabric or cushioning material using such a composite fiber, further improved excellent bulk recovery properties have been demanded, and the nonwoven fabric produced using the fiber disclosed in Patent Document 1 Or in the cushion material, the bulk recovery property is inadequate, the said request | requirement cannot be satisfied, and there was room for the further improvement.

  The present invention has been made in view of such circumstances, and further has a superior bulk recovery property, and has a low elasticity and a moderate elasticity, and a composite capable of obtaining these. It was made for the purpose of providing short fibers.

As a result of diligent research, the present inventors have found that the density of linear polyethylene contained in the first component of the composite staple fiber contained in the nonwoven fabric to be used as a cushioning material, particularly a heat-bonded nonwoven fabric, and exhibiting steric crimps. If the fiber is high, mechanical strength such as fiber hardness and flexural modulus will increase, and if such a fiber is bent and fixed with a large force, its shape will be memorized, and it will try to remove the load and return it to its original shape. It was also found that a large force is required, and the nonwoven fabric or cushioning material containing such fibers is difficult to recover in bulk and is likely to remain deformed as repeated compressive residual strain. Therefore, the present inventors blended linear low density polyethylene into the first component in an amount of 60% by mass or more as the linear polyethylene contained in the first component of the composite short fiber, and the first component. by the density of the entire linear low density polyethylene and 0.88 g / cm ³ or more 0.918 g / cm less than ³ contained in the strain repeated compressive residual nonwoven or cushioning material is reduced, excellent bulk recovery properties Has been found, and the present invention has been completed.

Therefore, the present invention is a nonwoven fabric or cushion material comprising a composite short fiber containing a first component and a second component and at least expressing steric crimps,
The first component contains 60% by mass or more of at least one linear low density polyethylene (LLDPE),
The density of the entire linear low-density polyethylene contained in the first component is less than 0.88 g / cm ³ or more 0.918 g / cm ^3,
In the fiber cross section, the first component occupies at least 20% of the fiber surface, the center of gravity of the second component is deviated from the center of gravity of the fiber,
Provided is a cushioning material in which at least a part of the fibers are thermally bonded by at least a part of the first component.
Further, the present invention is a composite short fiber comprising a first component and a second component, and expressing at least steric crimps,
The first component contains 60% by mass or more of at least one linear low density polyethylene (LLDPE),
The density of the entire linear low-density polyethylene contained in the first component is less than 0.88 g / cm ³ or more 0.918 g / cm ^3,
In the fiber cross section, the first component occupies at least 20% of the fiber surface, and the gravity center position of the second component is deviated from the fiber gravity center position.
Provided is a composite short fiber for a cushioning material.

The composite short fiber constituting the nonwoven fabric or cushion material of the present invention is a fiber that includes a first component and a second component, and that develops at least steric crimp, and the first component is at least one linear type. the low density polyethylene comprises 60 wt% or more, yet, by the density of the entire linear low-density polyethylene contained in the first component and 0.88 g / cm ³ or more 0.918 g / cm less than ^3, repeated compression residual A nonwoven fabric or a cushioning material having reduced strain and excellent bulk recovery can be provided.

FIG. 1 shows a form of mechanical crimping. 2A to 2C show crimped forms of composite short fibers according to an embodiment of the present invention. FIG. 3 shows a crimped form of the composite short fiber according to another embodiment of the present invention. FIG. 4 shows a fiber cross section of a composite short fiber according to an embodiment of the present invention.

The present invention provides a nonwoven fabric or cushion material having a low repeated compressive residual strain and excellent bulk recovery, and composite short fibers constituting these. The composite short fiber of the present invention includes a first component and a second component, and is a fiber that expresses at least steric crimp, and the first component includes at least one linear low-density polyethylene (LLDPE ( linear comprises low density polyethylene)) 60 wt% or more, the density of the entire linear low-density polyethylene contained in the first component and less than 0.88 g / cm ³ or more 0.918 g / cm ³ . When a cushion material made of a nonwoven fabric is produced using composite short fibers containing the first component having such a density, a cushion material having excellent bulk recovery can be obtained by reducing the repeated compressive residual strain of the cushion material. be able to. The term “short fiber” (or staple) used in the present invention is a term used to distinguish from “long fiber” (or filament). In the present invention, the fiber length is 1 mm to 100 mm. Means fiber.

  Here, the term “three-dimensional crimp” used in the present invention is used to distinguish it from a mechanical crimp in which the peak of the crimp as shown in FIG. 1 is an acute angle. Specifically, the three-dimensional crimp includes, for example, a crimp having a peak portion curved as shown in FIG. 2A (wave shape crimp), and a crimp having a peak portion curved as shown in FIG. 2B (spiral shape). 2C, a crimp in which a wave shape crimp and a spiral crimp are mixed, an acute crimp of the mechanical crimp shown in FIG. 1 as shown in FIG. 3, and FIG. 2A. As shown in FIG. Of course, the crimp may be a mixture of the mechanical crimp shown in FIG. 1, the wave crimp shown in FIG. 2A, and the spiral crimp shown in FIG. 2B. The three-dimensional crimp may be a three-dimensional crimp expressed by heat treatment or the like in the latent crimpable conjugate fiber, or may be a three-dimensional crimp expressed in the manifest crimped conjugate fiber. Here, the latent crimpable conjugate fiber means that the three-dimensional crimp or the stronger three-dimensional crimp is not developed at the fiber stage, or has developed a weak three-dimensional crimp and is subjected to heat treatment. It is a fiber that develops crimps. The actual crimpable conjugate fiber is a fiber that has developed a three-dimensional crimp at the fiber stage, and the state of the three-dimensional crimp does not change even when it is subjected to heat treatment, or the degree of the change is small. . The composite short fiber of the present invention is preferably an actual crimpable composite fiber, or depending on the combination of the first component and the second component and the composite form of the first component and the second component, Can only be obtained.

  Hereinafter, the first component and the second component of the composite short fiber contained in the nonwoven fabric or cushion material of the present invention will be described in detail.

<First component>
The first component is at least one linear low density polyethylene (LLDPE), based on the total mass of the first component, 60% by mass or more, preferably 70% by mass to 100% by mass, more preferably 75% by mass. Contains ~ 95% by mass. Moreover, the density of the whole linear low density polyethylene contained in a 1st component is 0.88 g / cm < ³ > or more and less than 0.918 g / cm < ³ >. That the density of the whole linear low density polyethylene satisfies the above range means that if one kind of linear low density polyethylene is included, the density of the linear low density polyethylene satisfies the above range, When the first component contains two or more types of linear low density polyethylene, the density of each linear low density polyethylene and the mass of all the linear low density polyethylenes contained in the first component are 100%. Sometimes it can be determined from the proportion of each linear low density polyethylene. Preferably the density of the entire linear low-density polyethylene contained in the first component is a ^{0.89g / cm 3 ~0.917g / cm 3} , If it is 0.90g / cm ³ ~0.917g / cm 3 and even more ^preferably from If it is 0.902cm ³ ~0.916g / cm 3.

In the present invention, the density of the entire linear low-density polyethylene contained in the first component is within the range of less than 0.88 g / cm ³ or more 0.918 g / cm ^3, the first component impairs spinnability It will have moderate elasticity and flexibility, and the composite short fiber will be flexible and easily return to its original shape against deformation. Therefore, the nonwoven fabric or cushioning material containing the composite short fiber of the present invention repeatedly exhibits a reduced compressive residual strain and can exhibit excellent bulk recovery properties.

  In this invention, the composite short fiber which has the said characteristic can be easily obtained as content in the 1st component of a linear low density polyethylene is 60 mass% or more. When the proportion is less than 60% by mass, the composite short fiber does not exhibit the flexibility due to the linear low density polyethylene because the proportion of the linear low density polyethylene in the first component decreases, and the resulting composite short There is a risk that the fiber and the nonwoven fabric or cushion material using the fiber are hard, the bulk recovery property is poor, and the strain due to compression tends to increase.

Further, in the present invention, the linear low density polyethylene overall density contained in the first component is within the range of less than 0.88 g / cm ³ or more 0.918 g / cm ^3, the first component is spinnable The composite short fiber is flexible and easily returns to its original shape with respect to deformation. Therefore, the nonwoven fabric or cushioning material containing the composite short fiber of the present invention repeatedly exhibits a reduced compressive residual strain and can exhibit excellent bulk recovery properties.

  The linear low density polyethylene that can be used in the present invention refers to a copolymer obtained by copolymerizing ethylene and an α-olefin. The α-olefin is generally an α-olefin having 3 to 12 carbon atoms. Specific examples of the α-olefin having 3 to 12 carbon atoms include propylene, butene-1, pentene-1, 4-methylpentene-1, hexene-1, 4-methylhexene-1, heptene-1, Mention may be made of octene-1, nonene-1, decene-1, dodecene-1 and mixtures thereof. Among these, propylene, butene-1, 4-methylpentene-1, hexene-1, 4-methylhexene-1 and octene-1 are particularly preferable, butene-1 and hexene-1 are more preferable.

  The α-olefin content in the linear low density polyethylene is preferably 1 mol% to 10 mol%, and more preferably 2 mol% to 5 mol%. If the α-olefin content is low, the flexibility of the fiber may be impaired. When the content of α-olefin is increased, the crystallinity is deteriorated, and the fibers may be fused during fiber formation.

The linear low density polyethylene that can be used in the first component is not necessarily limited to a low density (generally 0.925 g / cm ³ or less), and the density is, for example, 0.85 g / cm ^{3 to} 0.945 g. / cm ^3, preferably ^{0.89g / cm 3 ~0.93g / cm 3} , more preferably ^{0.90g / cm 3 ~0.925g / cm 3} , even more preferably 0.902g ^/ cm 3 ~0. was 920 g / cm ^3, if it is possible to make the density of the entire linear low-density polyethylene contained in the first component in the range of less than 0.88 g / cm ³ or more 0.918 g / cm ^3, particularly its density There is no limitation. If the density of the linear low-density polyethylene contained in the first component is less than 0.85 g / cm ³ , the linear low-density polyethylene has properties close to that of an elastomer. There is a possibility that so-called spinnability is lowered due to frequent wear. In this case, the first component of the composite short fiber becomes soft, and there is a possibility that sufficient bulkiness and bulk recoverability may not be obtained when the nonwoven fabric or cushion material is used. On the other hand, when the density of the linear low-density polyethylene is higher than 0.945 g / cm ³ , the surface feel and the flexibility in the thickness direction tend to be inferior when the nonwoven fabric or the cushion material is used. Further, in that case, the first component of the composite short fiber becomes hard as a whole, and when deformed for a long time or repeatedly compressed, the deformation is likely to remain. There is a risk of problems such as “swelling” becoming larger.

In the present invention, the density of the entire linear low-density polyethylene contained in the first component is less than 0.88 g / cm ³ or more 0.918 g / cm ^3, since the structure is not particularly limited, different the density It is used in combination of two or more linear low density polyethylene, the density of the entire linear low-density polyethylene contained in the first component in the range of less than 0.88 g / cm ³ or more 0.918 g / cm ³ You may adjust. In the present invention, it is preferable to use a combination of two or more types of linear low-density polyethylenes having different densities because the repeated compressive residual strain of the resulting cushion material can be further reduced. The reason for this is that two or more types of linear low density polyethylenes with different physical properties such as density and copolymer and their ratio and molecular weight distribution are mixed and used as the first component. -Like low-density polyethylene is dispersed throughout the first component, and the lower-density linear low-density polyethylene gives flexibility to the entire first component and brings flexibility and flexibility to the composite short fiber. As a result, higher density linear low-density polyethylene gives elasticity and stiffness to the entire first component, and gives elasticity to the composite short fiber. Both are uniform throughout the first component. Although it is presumed that the fiber properties are improved by being dispersed in the fiber, it is not bound by such a theory.

When used in combination with different linear low density polyethylene having a density of two or more, linear low density polyethylene overall density of less than 0.88 g / cm ³ or more 0.918 g / cm ³ contained in the first component If it can be adjusted within the range, the density of the linear low density polyethylene to be combined is not particularly limited, and the linear low density polyethylene having a density exceeding the upper limit of the density of the first component, and the density of the first component You may use it in combination with the linear low density polyethylene below the minimum of a density. In the present invention, a linear low-density polyethylene having a high density and a linear low-density polyethylene having a low density are used in combination, and the density of the whole linear low-density polyethylene contained in the first component is 0.00. it is preferably adjusted to 88 g / cm ³ or more 0.918 g / cm ³ less than the range. At this time, the density of the higher-density linear low-density polyethylene (sometimes referred to herein as “first linear low-density polyethylene (LLDPE ₁ )”) is, for example, 0.908 g. / cm ³ or more 0.94 g / cm ³ or less, preferably 0.91 g ^/ cm 3 ～0.94G / cm ^3, more preferably ^{0.912g / cm 3 ~0.935g / cm 3} . Further, the density of the linear low-density polyethylene having a lower density (sometimes referred to as “ _second linear low-density polyethylene (LLDPE ₂ )” in this specification) is, for example, 0.85 g / cm ³ or more 0.908 g / cm less than ^3, preferably 0.88g ^/ cm 3 ~0.908g ^/ cm less than ^3, more preferably ^{0.89g / cm 3 ~0.906g / cm 3} .

When using a combination of a high density linear low density polyethylene (LLDPE ₁ ) and a low density linear low density polyethylene (LLDPE ₂ ), the higher density linear low density polyethylene (LLDPE _1). ) Is used, based on the total mass of the first component, when the total mass of the first component is 100% by mass, for example, 3% by mass to 97% by mass, preferably 5% by mass to 95% by mass, More preferably, it is 8 mass%-92 mass%. The amount of linear low density polyethylene (LLDPE ₂ ) having the lower density is, for example, 3 masses when the total mass of the first component is 100 mass% based on the total mass of the first component. % To 97% by mass, preferably 5% to 95% by mass, and more preferably 8% to 92% by mass. However, this time, the density of the entire linear low-density polyethylene contained in the first component must be in the range of less than 0.88 g / cm ³ or more 0.918 g / cm ^3. Moreover, the sum total of LLDPE ₁ and LLDPE ₂ does not exceed 100 mass%.

In the present invention, a linear low density polyethylene (LLDPE ₁ ) having a high density and a linear low density polyethylene (LLDPE ₂ ) having a low density are used in combination, and the linear low density contained in the first component is used. By setting the density of the whole polyethylene within the range of 0.88 g / cm ³ or more and less than 0.94 g / cm ³ , the resulting non-woven fabric or cushion material has a repeated compressive residual strain of less than 14%, preferably less than 12%, more Preferably, it can be less than 10%, can achieve remarkably reduced repeated compressive residual strain, has excellent bulk recovery, and has little sag and moderate elasticity or A cushion material can be obtained.

  The linear low-density polyethylene has a melting point before spinning, for example, a melting point of 130 ° C. or lower, and a melting point in the range of 85 ° C. to 128 ° C., preferably 90 ° C. to 125 ° C. More preferably, it is within the range. If the melting point of the linear low-density polyethylene is too high, a non-woven fabric having a strength that can withstand practical use may not be obtained when a heat-bonding nonwoven fabric is produced by heat bonding at a low temperature. When the melting point of the linear low density polyethylene is low, when the heat-bonding nonwoven fabric is manufactured by applying the heat-bonding treatment at a high temperature, the surface touch of the nonwoven fabric may be deteriorated, or the high-speed card property is inferior. , A nonwoven fabric with good formation may not be obtained. Moreover, in this invention, a 1st component contains 60 mass% or more of such linear low density polyethylene whose melting | fusing point is 130 degrees C or less, for example, It is preferable to contain 70 mass%-100 mass%. By setting the content of the linear low density polyethylene having a melting point of 130 ° C. or less in the above range, the first component has appropriate elasticity and flexibility without impairing the spinnability. It is supple and has an effect of being easy to become a fiber that easily returns to its original shape against deformation.

The linear low density polyethylene having the above density and melting point can be easily obtained by copolymerizing ethylene and α-olefin using a metallocene catalyst. However, the density of the entire linear low-density polyethylene contained in the first component becomes 0.88 g / cm ³ or more 0.918 g / cm less than ^3, preferably be linear low density polyethylene has the melting point As long as the linear low density polyethylene is not limited to one polymerized using a metallocene catalyst, for example, one polymerized using a Ziegler-Natta catalyst may be used.

  The melt index (MI) of the linear low density polyethylene is preferably in the range of 1 g / 10 min to 60 g / 10 min in view of spinnability. Here, the melt index (MI) is measured according to JIS K 7210 (1999) (conditions: 190 ° C., load 21.18 N (2.16 kgf)). The larger the MI, the slower the rate of solidification of the sheath component during spinning, and the more easily the fibers are fused. On the other hand, if the MI is too small, fiberization becomes difficult. More specifically, the MI of the linear low-density polyethylene is preferably 2 g / 10 min to 40 g / 10 min, more preferably 3 g / 10 min to 35 g / 10 min, and 5 g / 10 min to 30 g / 10 min. Even more preferably.

  The ratio (Q value: Mw / Mn) between the weight average molecular weight (Mw) and the number average molecular weight (Mn) in the linear low density polyethylene is preferably 5 or less. A more preferable Q value is 2 to 4, and even more preferably 2.5 to 3.5. When the Q value is 5 or less, it can be said that the molecular weight distribution of the linear low density polyethylene is narrow, and the linear low density polyethylene satisfying this Q value range is used as the first component. By using it, a composite short fiber excellent in steric crimping property can be obtained.

  The bending elastic modulus of the linear low density polyethylene is preferably in the range of 25 MPa to 850 MPa in consideration of the properties of the obtained composite short fibers, the touch of the resulting nonwoven fabric or cushion material, and the bulkiness. Here, the flexural modulus is measured according to JIS K 7171 (2008). The composite short fiber of the present invention has a soft tactile sensation due to the linear low-density polyethylene which is the main component of the first component, but the fiber is not firm only by being soft and the card passing property is lowered. In some cases, it is difficult to obtain a nonwoven fabric that is bulky and rich in bulk recovery. Therefore, it is preferable that the linear low density polyethylene is not easily deformed to some extent with respect to bending (that is, it is preferable that the deformation with respect to bending is somewhat high), and specifically, the bending elastic modulus is high. The thing of 25 Mpa or more is preferable. If the flexural modulus of the linear low density polyethylene is too large, the soft tactile sensation may be lost. Therefore, it is preferably 850 MPa or less. More specifically, the flexural modulus of linear polyethylene is more preferably 130 MPa to 600 MPa, particularly preferably 35 MPa to 400 MPa, and most preferably 40 MPa to 300 MPa.

  The hardness of the linear low density polyethylene is preferably in the range of 35 to 70 in consideration of the properties of the obtained composite short fibers and the touch, bulkiness, and bulk recoverability of the resulting nonwoven fabric or cushioning material. . Here, the hardness of linear low density polyethylene refers to durometer hardness (HDD) measured using a type D durometer in accordance with JIS K 7215 (1986). If the linear low-density polyethylene, which is the main component of the first component, is too soft, the stiffness of the fiber will be lost, and the card passing property of the fiber may be reduced, or it may be difficult to obtain a bulky nonwoven fabric. In some cases, the bulk recovery of the nonwoven fabric may be reduced. Therefore, the linear low density polyethylene preferably has a certain degree of hardness, specifically a hardness of 35 or more. If the hardness of the linear low density polyethylene is too large, the soft touch may be lost, so it is preferably 70 or less. More specifically, the hardness of the linear low density polyethylene is more preferably 40 to 63, particularly preferably 43 to 60, and most preferably 45 to 60.

  The first component contains a polymer component in addition to the linear low-density polyethylene as long as a steric crimp is sufficiently developed in the composite short fiber of the present invention and a non-woven fabric giving a good tactile sensation is provided. You can leave. For example, the first component further includes low density polyethylene, high density polyethylene, polypropylene, polybutene, polybutylene, polymethylpentene resin, polybutadiene, propylene-based copolymer (for example, propylene-ethylene copolymer), ethylene-vinyl alcohol. Polyolefin resins such as copolymers, ethylene-vinyl acetate copolymers, ethylene- (meth) acrylic acid copolymers, or ethylene- (meth) acrylic acid methyl copolymers, modified products thereof, polyethylene terephthalate, Polyester resins such as polybutylene terephthalate, polytrimethylene terephthalate, polyethylene naphthalate, polylactic acid, polybutylene succinate and copolymers thereof, modified products thereof, polys such as nylon 66, nylon 12 and nylon 6 One or more polymer components selected from amide resins, modified products thereof, acrylic resins, polycarbonate, polyacetal, engineering plastics such as polystyrene and cyclic polyolefin, mixtures thereof, and elastomer resins May include.

  In the present invention, the amount of the polymer component other than the linear low-density polyethylene that may be blended with the first component is such that the density of the first component is within the above range and 40% by mass of the first component. Preferably, it is selected so as not to exceed. For example, when the total mass of the linear low density polyethylene and the other polymer is 100% by mass, the content of the other polymer component is 3% by mass to 40% by mass, preferably 5% by mass. -25% by mass, more preferably 5% by mass to 20% by mass.

  In this invention, it is preferable that a 1st component contains a low density polyethylene as other polymer components other than a linear low density polyethylene.

  Low density polyethylene (also called “LDPE” (Low Density Polyethylene)) that may be contained in the first component is a soft polyethylene with many branches, and is also called a high-pressure polyethylene due to its production method. . In the present invention, if necessary, low-density polyethylene is added to the first component in a small amount so that steric crimps, in particular, actual crimps, can be expressed more satisfactorily to obtain bulkiness and bulk recovery. And high-speed card performance can be improved. Also, since low density polyethylene is softer than linear low density polyethylene, for example, low-density polyethylene ensures surface texture that tends to decrease when using high-density linear low-density polyethylene. It is also possible to do.

The density of the low density polyethylene is preferably 0.91 g / cm ^{3 to} 0.93 g / cm ³ . Since the density of the low density polyethylene tends to depend on the MI (190 ° C.) of the polymer, in view of spinnability, the density of the low density polyethylene ^is 0.915g / cm ³ ~0.92g / cm 3 Is preferred. In addition, the density of the low density polyethylene may be higher than the upper limit of the density that the whole linear low density polyethylene contained in the first component should have. May be.

  The melting point of the low density polyethylene before spinning is preferably 90 ° C to 120 ° C. In the present invention, low-density polyethylene having a low melting point is preferably used. By using low-density polyethylene with a low melting point, steric crimps, particularly manifested crimps, can be expressed more favorably, the thermal processing temperature range during the production of the nonwoven fabric can be widened, and after heat treatment A flexible nonwoven fabric can be obtained. More specifically, the melting point of the low density polyethylene is more preferably 95 ° C to 115 ° C, and particularly preferably 100 ° C to 110 ° C.

  The melt index (MI) of the low density polyethylene is generally preferably in the range of 1 g / 10 min to 60 g / 10 min in view of spinnability. Here, the melt index (MI) is measured according to JIS-K-7210 (1999) (conditions: 190 ° C., load 21.18 N (2.16 kgf)). This is because the larger the MI, the slower the solidification rate of the sheath component during spinning, and the more easily the fibers are fused. On the other hand, if the MI is too small, fiberization becomes difficult. More specifically, the MI of the low density polyethylene is preferably 3 g / 10 min to 50 g / 10 min, more preferably 5 g / 10 min to 50 g / 10 min, and 10 g / 10 min to 50 g / 10 min. Is even more preferred.

  The Q value in the low density polyethylene is preferably 10 or less. A more preferable Q value is 4 to 9, and even more preferably 5 to 8. If the Q value exceeds 10, a good crimped shape may not be obtained, and the adhesive strength tends to be low.

  In the first component, the linear low-density polyethylene and the low-density polyethylene are such that the linear low-density polyethylene occupies 95% to 75% by mass when the combined mass is 100% by mass. It is more preferable that the low density polyethylene is mixed so as to occupy 5% by mass to 25% by mass. Even more preferably, the linear low density polyethylene accounts for 90 mass% to 80 mass% and the low density polyethylene accounts for 10 mass% to 20 mass%. If the proportion of the linear low density polyethylene is too large, it is difficult to obtain the effect of adding the low density polyethylene, and when the nonwoven fabric is used, the nonwoven fabric may be inferior in bulkiness. If the proportion of linear low-density polyethylene is too small, the strength of the nonwoven fabric may be reduced when a heat-bonded nonwoven fabric is obtained.

  When the low density polyethylene is contained within the above range, the composite short fiber exhibits good steric crimps, reduces variation in the expressed crimps, and increases the fiber crimp rate. Can do. Therefore, the bulkiness of the nonwoven fabric containing this fiber can be improved. The reason why steric crimps are likely to appear is not clear, but since long branches of low-density polyethylene are entangled with linear low-density polyethylene molecules with few branches, distortion in stretching is likely to occur, so that steric crimps appear. It is estimated that it becomes easy. However, the present invention is not limited by this estimation. In addition, since the low density polyethylene functions as a softening agent, when the low density polyethylene is included in the above range, for example, when a high density linear low density polyethylene is used, the resulting nonwoven fabric has a thickness direction. Excellent flexibility and surface tactile sensation. Furthermore, when low-density polyethylene is included in the above range, the processing temperature range of the nonwoven fabric can be widened, and a nonwoven fabric having a substantially constant and flexible texture can be obtained regardless of the processing temperature when manufacturing the heat-bonding nonwoven fabric. Is preferable.

  The first component, based on the total mass of the first component, preferably contains 70% by mass or more, and contains 75% by mass or more of the linear low density polyethylene and the low density polyethylene as the polymer component. More preferably, 80% by mass or more is further included, and it is more preferable that only the linear low density polyethylene and the low density polyethylene are included as the polymer component. Further, in the first component, the total amount of the linear low density polyethylene and the low density polyethylene may be 100% by mass.

  In this invention, it is also preferable that a 1st component contains polar group containing modified polyolefin as other polymer components other than a linear low density polyethylene. The first component is a polymer component other than the linear low-density polyethylene, and includes a polar group-containing modified polyolefin, so that the thermal adhesion between fibers becomes stronger, the nonwoven fabric of the present invention, and other materials This is because the adhesiveness can be improved.

  The polar group-containing modified polyolefin that may be contained in the first component refers to a polyolefin resin containing a carboxyl group, a hydroxyl group, a sulfonic acid group, and the like, and specific examples include ethylene-ethylenically unsaturated carboxylic acid. . Ethylene-ethylenically unsaturated carboxylic acid refers to a copolymer containing ethylene and unsaturated carboxylic acid, including a copolymer of ethylene and ethylenically unsaturated carboxylic acid, ethylene and ethylenically unsaturated carboxylic acid, Furthermore, it refers to a copolymer obtained by copolymerizing other copolymer components. There are no particular limitations on the method of obtaining a copolymer of ethylene and an ethylenically unsaturated carboxylic acid, or a copolymer containing ethylene and an ethylenically unsaturated carboxylic acid, and further copolymerized with other copolymerization components. Random copolymers, block copolymers, graft copolymers, and the like obtained by copolymerization can be used. The ethylenically unsaturated carboxylic acid constituting the ethylene-ethylenically unsaturated carboxylic acid is not particularly limited, and examples thereof include acrylic acid, methacrylic acid, ethacrylic acid, fumaric acid, maleic acid, itaconic acid, monomethyl maleate, and maleic acid. Examples thereof include monoethyl acid, maleic anhydride, itaconic anhydride, and esters of these acids. Specific examples of the ethylene-ethylenically unsaturated carboxylic acid copolymer include ethylene-acrylic acid ester-glycidyl methacrylate (GMA) copolymer, ethylene-acrylic acid ester-maleic anhydride copolymer, and ethylene-acrylic. Acid copolymer (EAA), ethylene-methacrylic acid copolymer (EMAA), ethylene-ethacrylic acid copolymer, ethylene-maleic acid copolymer, ethylene-fumaric acid copolymer, ethylene-itaconic acid copolymer , Ethylene-maleic anhydride copolymer, ethylene-itaconic anhydride copolymer, and the like. Among them, ethylene-acrylic acid ester-glycidyl methacrylate (GMA) copolymer, ethylene-acrylic acid ester-maleic anhydride copolymer, ethylene-acrylic acid copolymer, ethylene-methacrylic acid copolymer, and ethylene-maleic acid A copolymer is preferable, and an ethylene-acrylic acid ester-glycidyl methacrylate (GMA) copolymer, an ethylene-acrylic acid ester-maleic anhydride copolymer, an ethylene-acrylic acid copolymer, and an ethylene-methacrylic acid copolymer are used. More preferably, an ethylene-acrylic acid ester-glycidyl methacrylate (GMA) copolymer and an ethylene-acrylic acid ester-maleic anhydride copolymer are even more preferable.

  Specific examples of the polar group-containing modified polyolefin that may be included in the first component of the present invention include “LOTADER (registered trademark)” (Arkema Japan), which is an ethylene-acrylic ester-glycidyl methacrylate (GMA) copolymer. ), “BONDINE (trade name)” which is an ethylene-acrylic acid ester-maleic anhydride copolymer (manufactured by Arkema Japan), and “Nuclele (registered trademark)” (Mitsui, Ltd.) which is an ethylene-methacrylic acid copolymer. DuPont Polychemical Co., Ltd.) and "Modic (registered trademark)" (Mitsubishi Chemical Co., Ltd.) which is an olefin-maleic acid copolymer.

  In the first component, the linear low density polyethylene and the polar group-containing modified polyolefin are 97% by mass to 70% by mass of the linear low density polyethylene when the combined mass is 100% by mass. It is preferable to occupy, and it is more preferable that the polar group-containing modified polyolefin is mixed so as to occupy 3% by mass to 30% by mass. Even more preferably, the linear low density polyethylene accounts for 95% to 75% by mass and the polar group-containing modified polyolefin accounts for 5% to 25% by mass. If the proportion of linear low-density polyethylene is too large, the effect of adding the polar group-containing modified polyolefin is difficult to obtain, and when it is made into a nonwoven fabric, in the tensile strength of the nonwoven fabric and the adhesion to other materials, There is a possibility that a difference from a fiber not containing a polar group-containing modified polyolefin as one component is not recognized. If the proportion of the linear low-density polyethylene is too small, the bulk-recoverability and bulkiness of the nonwoven fabric may be lost when it is made into a heat-bonded nonwoven fabric.

  The first component, based on the total mass of the first component, preferably contains 70% by mass or more, and 75% by mass or more, as a polymer component, including linear low-density polyethylene and polar group-containing modified polyolefin. More preferably, it is more preferable to contain 80% by mass or more, and it is more preferable that only the linear low density polyethylene and the polar group-containing modified polyolefin are included as the polymer component. In the first component, the linear low density polyethylene and the polar group-containing modified polyolefin may be 100% by mass.

  In this invention, it is also preferable that a 1st component contains a low density polyethylene and a polar group containing modified polyolefin as other polymer components other than a linear low density polyethylene. In addition to the low-density polyethylene and the polar group-containing modified polyolefin as a polymer component other than the linear low-density polyethylene, the first component can improve the crimp development and flexibility of the fiber, and This is because thermal adhesion becomes stronger and adhesion between the nonwoven fabric of the present invention and other materials is improved. In the case where the first component contains low-density polyethylene and a polar group-containing modified polyolefin as other polymer components other than the linear low-density polyethylene, preferred low-density polyethylene and polar group-containing modified polyolefin are each independently Since it is as having demonstrated the case where it contains in one component, the detailed description is abbreviate | omitted here.

  When the first component includes linear low-density polyethylene, low-density polyethylene, and polar group-containing modified polyolefin, when the combined mass is 100% by mass, the linear low-density polyethylene is 94% by mass to It is preferable that 70% by mass is mixed, low density polyethylene accounts for 3% by mass to 27% by mass, and polar group-containing modified polyolefin accounts for 3% by mass to 27% by mass. More preferably, the linear low density polyethylene accounts for 90 mass% to 75 mass%, the low density polyethylene accounts for 5 mass% to 20 mass%, and the polar group-containing modified polyolefin accounts for 5 mass% to 20 mass%. Mixed to occupy.

In the present invention, the first component is the density of the entire linear low-density polyethylene contained in the first component is not particularly limited as long as it is less than 0.88 g / cm ³ or more 0.918 g / cm ^3, linear low density polyethylene overall density of less than 0.88 g / cm ³ or more 0.918 g / cm ^3, and density of the first component is even 0.88 g / cm ³ or less than 0.918 g / cm ³ or more may not, but preferably preferably a density less than even 0.88 g / cm ³ or more 0.918 g / cm ³ of the first component. When it is within the range density of less than 0.88 g / cm ³ or more 0.918 g / cm ³ of the first component, the first component is to have appropriate elasticity and flexibility, composite short fibers is supple, This is because the fibers tend to return to their original shape with respect to deformation, and the cushion material of the present invention is repeatedly reduced in compressive residual strain and exhibits excellent bulk recovery. Preferably the density of the first component is a ^{0.89g / cm 3 ~0.917g / cm 3} , more preferable to be ^{0.90g / cm 3 ~0.917g / cm 3} , 0.902cm 3 ~0. Even more preferred is 916 g / cm ³ .

  The first component is a component other than the above polymer component, such as antistatic agent, pigment, matting agent, heat stabilizer, light stabilizer, flame retardant, antibacterial agent, lubricant, plasticizer, softener, antioxidant An additive such as an agent, an ultraviolet absorber, and a crystal nucleating agent may be included. Such an additive is preferably contained in the first component so as to occupy an amount of 10% by mass or less of the entire first component.

<Second component>
In the present invention, the second component contained in the composite short fiber is not particularly limited as long as it is a polymer component such as a resin capable of forming the composite short fiber together with the first component, and preferably included in the first component. A polymer component having a melting point higher than that of the linear low density polyethylene. The second component is, for example, polypropylene, polybutene-1, polymethylpentene resin, polybutadiene, propylene-based copolymer (for example, ethylene-propylene copolymer), ethylene-vinyl alcohol copolymer, ethylene-vinyl acetate copolymer. Polyolefin resins such as polymer, ethylene- (meth) acrylic acid copolymer, or ethylene- (meth) acrylic acid methyl copolymer, polyethylene terephthalate, polybutylene terephthalate, polytrimethylene terephthalate, polyethylene naphthalate, polylactic acid Polyester resins such as polybutylene succinate and copolymers thereof, polyamide resins such as nylon 66, nylon 12 and nylon 6, acrylic resins, polycarbonate, polyacetal, polystyrene and rings Engineering plastics, such as polyolefins, mixtures thereof, and is selected from such as those elastomeric resin may include one or more polymer components.

  The second component is preferably a component containing 50% by mass or more of a polyester that can have a melting point that is 40 ° C. or higher higher than the melting point of the linear low-density polyethylene that can constitute the first component. The second component contains, as a polymer component, polyester, preferably 50% by mass or more, more preferably 75% by mass or more, and most preferably 100% by mass, based on the total mass of the second component.

  Polyester can be preferably used because it is cheaper than other polymers, has high rigidity, and can give the fiber stiffness. Examples of the polyester include polymers such as polyethylene terephthalate, polybutylene terephthalate, polytrimethylene terephthalate, polyethylene naphthalate, polylactic acid, and copolymers thereof. The melting point of the polyester is 40 ° C. or more higher than the melting point of the linear low density polyethylene constituting the first component. The melting point of the polyester is preferably 50 ° C. higher than the melting point of the linear low density polyethylene.

  Among the polyesters, polyethylene terephthalate and polybutylene terephthalate have higher rigidity than polytrimethylene terephthalate and can give the fiber stiffness, thereby improving the high-speed card property of the resulting composite short fiber. be able to. In particular, polyethylene terephthalate (PET) is most preferably used because of its high rigidity. Polyethylene terephthalate also has high crystallinity and is difficult to heat shrink by appropriately adjusting the stretching conditions during fiber production, so that it does not show steric crimp, especially latent crimp, or very little. The actual crimpable composite staple fibers shown in FIG. When a non-woven fabric produced using such an actual crimpable composite short fiber is prepared, when the web is subjected to heat treatment, the web does not shrink or slightly shrinks, and the manufacturing process is caused by the web shrinkage. Management complexity can be eliminated or reduced.

  When the second component contains polyethylene terephthalate and / or polybutylene terephthalate as a preferred polyester and another polymer component other than that, the other polymer component sufficiently exhibits steric crimps in the composite short fiber. And as long as the nonwoven fabric which can give a good tactile sense can be given, it will not specifically limit. For example, other polyester resins, specifically, polyethylene naphthalate, polylactic acid, and polytrimethylene terephthalate may be mixed. However, as described above, polytrimethylene terephthalate is flexible and tends to reduce the high-speed card property of the resulting fiber. Therefore, it is preferably not used in the composite short fiber of the present invention.

  The second component is a component other than the above polymer component, such as an antistatic agent, a pigment, a matting agent, a heat stabilizer, a light stabilizer, a flame retardant, an antibacterial agent, a lubricant, a plasticizer, a softener, and an antioxidant. An additive such as an agent, an ultraviolet absorber, and a crystal nucleating agent may be included. Such an additive is preferably contained in the second component so as to occupy an amount of 10% by mass or less of the entire second component.

  In the composite short fiber of the present invention, the ratio of the first component to the second component (second component / first component) is preferably 8/2 to 3/7 (volume ratio). More preferably, it is 7/3 to 35/65, and most preferably 6/4 to 4/6. The second component mainly contributes to the bulkiness and bulk recoverability of the nonwoven fabric, and the first component mainly contributes to the strength of the nonwoven fabric and the softness of the nonwoven fabric. When the composite ratio is 8/2 to 3/7, the strength and softness of the nonwoven fabric and the bulk recoverability can be compatible. As the composite ratio increases, the strength of the nonwoven fabric increases, but the resulting nonwoven fabric becomes harder and the bulk recovery tends to be worse. On the other hand, when the amount of the second component is too large, the adhesion point is too small, and the strength of the nonwoven fabric is decreased.

In the composite short fiber of the present invention, the center of gravity of the second component is preferably deviated from the center of gravity of the fiber in the fiber cross section. FIG. 4 shows a fiber cross section of a composite short fiber according to an embodiment of the present invention. In FIG. 4, the first component (1) is disposed around the second component (2), and the first component (1) occupies at least 20% of the surface of the fiber (10) in the fiber cross section. Thereby, the surface of the first component (1) can be melted at the time of thermal bonding. In the fiber cross section, the gravity center position (3) of the second component (2) is deviated from the gravity center position (4) of the fiber (10), and the deviation ratio (hereinafter sometimes referred to as the eccentricity ratio). The cross section of the composite short fiber is magnified by an electron microscope or the like, the center of gravity (3) of the second component (2) in the fiber cross section is C1, and the center of gravity of the fiber in the fiber cross section of the composite short fiber (10) ( When 4) is Cf and the radius (5) of the fiber cross section of the composite short fiber (10) is rf, it is a numerical value represented by the following formula.
Eccentricity (%) = [| Cf−C1 | / rf] × 100

  As the fiber cross section in which the center of gravity (3) of the second component (2) deviates from the center of gravity (4) of the fiber, the eccentric core-sheath type shown in FIG. 4 (in this case, the first component (1) is the sheath component). The second component (2) is a core component) or a parallel type (side-by-side type) is a preferred form, and an eccentric core-sheath type is a more preferred form. Depending on the case, even a multi-core type may be used in which multi-core portions are gathered and are shifted from the center of gravity of the fiber. In particular, an eccentric core-sheath type fiber cross section is preferred in that a desired crimp and / or a three-dimensional crimp such as a spiral crimp can be easily expressed. The eccentricity ratio of the eccentric core-sheath type composite short fiber is preferably 5% to 50%. A more preferable eccentricity is 7% to 30%.

  FIG. 2 shows a crimped form of crimped composite short fibers according to an embodiment of the present invention. The corrugated crimp referred to in the present invention refers to a curved crest as shown in FIG. 2A. Spiral crimp refers to a crimped crest as shown in FIG. 2B. Crimps in which corrugated crimps and spiral crimps are mixed as shown in FIG. 2C can also be included in the present invention. In the case of ordinary mechanical crimping as shown in FIG. 1, if the crimped crest is an acute angle, that is, a so-called serrated crimp, the bulk recoverability of the nonwoven fabric cannot be increased. Furthermore, it is inferior to the surface elasticity against compression, the so-called spring effect, and in particular, sufficient bulk recovery is not obtained. Further, the present invention may also include a crimp in which the sharp crimp of the mechanical crimp as shown in FIG. 3 and the corrugated crimp shown in FIG. 2A are mixed. In the present invention, the term “three-dimensional crimp” is used to distinguish it from mechanical crimps, including wavy crimps and spiral crimps.

  In the present invention, it is particularly preferable that the wave shape crimp and the spiral crimp shown in FIG. 2C are mixed in that both the card passing property and the initial bulk and bulk recovery properties can be achieved.

  The composite staple fiber of the present invention, in particular, the actual crimpable composite staple fiber, can be produced, for example, by the following procedure. The composite short fiber of the present invention may be a latent crimp fiber or an actual crimp fiber, and is preferably an actual crimp fiber, but is limited to an actual crimp fiber. Is not to be done. First, a first component containing linear low-density polyethylene and, if necessary, low-density polyethylene, and a second component containing, for example, 50% by mass or more of polyethylene terephthalate and / or polybutylene terephthalate are first in the fiber cross section. Using a composite nozzle in which the component occupies at least 20% of the fiber surface and the center of gravity of the second component deviates from the center of gravity of the fiber, such as an eccentric core-sheath composite nozzle, the second component is spun at the spinning temperature. A spinning filament can be obtained by melt-spinning the first component at a spinning temperature of 200 ° C. to 300 ° C. at 240 ° C. to 350 ° C. and drawing at a take-up speed of 100 m / min to 1500 m / min.

Next, among the polymer components contained in the second component, the draw ratio is a stretch temperature not less than the glass transition point (Tg ₂ ) of the polymer component having the highest glass transition point and less than the melting peak temperature of the linear low density polyethylene. Stretching is performed in the range of 1.5 times to 5.0 times. A more preferable lower limit of the stretching temperature is a temperature 10 ° C. higher than Tg ₂ . A more preferable upper limit of the stretching temperature is 90 ° C., and a particularly preferable upper limit of the stretching temperature is 85 ° C. If the stretching temperature is lower than Tg ₂ , the second component is less likely to crystallize, so the thermal shrinkage of the second component in the resulting fiber increases, or the bulk recovery of the nonwoven fabric made from the resulting fiber decreases. A trend is observed. If the drawing temperature is equal to or higher than the melting peak temperature of the linear low density polyethylene, the fibers are not fused, which is not preferable.

  A more preferred lower limit of the draw ratio is 1.8 times, a particularly preferred lower limit of the draw ratio is 2.0 times, and a most preferred lower limit of the draw ratio is 2.2 times. A more preferred upper limit of the draw ratio is 4.5 times, a particularly preferred upper limit of the draw ratio is 4.0 times, and a most preferred upper limit of the draw ratio is 3.8 times. When the draw ratio is less than 1.8 times, the draw ratio is too low, so it is difficult to obtain a fiber in which three-dimensional crimps such as corrugated crimps and / or spiral crimps are expressed. Not only does the bulkiness become small, but also the rigidity of the fiber itself becomes small, so that it tends to be inferior in non-woven fabric processability such as card passing property or the bulk recovery property is lowered. Moreover, you may perform an annealing process in atmosphere, such as dry heat, wet heat, and steam, at the temperature which 50 to 115 degreeC fibers do not melt | fuse before and after extending | stretching as needed.

  Next, before or after applying the fiber treatment agent as necessary, a crimp of 5/25 mm to 25/25 mm is applied using a known crimping machine such as a stuffing box type crimping machine. The crimped shape after passing through the crimper may be a serrated crimp and / or a corrugated crimp. When the number of crimps is less than 5 pieces / 25 mm, the card passing property tends to deteriorate, and the bulkiness and bulk recoverability of the nonwoven fabric tend to deteriorate. On the other hand, when the number of crimps exceeds 25 pieces / 25 mm, the number of crimps is too large, so the card passing property is lowered, and not only the formation of the nonwoven fabric is deteriorated, but also the initial volume of the nonwoven fabric may be reduced. .

  Furthermore, it is preferable to perform an annealing treatment in an atmosphere of dry heat, wet heat, or steam at 50 ° C. to 115 ° C. after the crimp is applied by the crimper. By the annealing treatment, the expression of steric crimps of the composite short fiber of the present invention can be promoted. Specifically, after applying the fiber treating agent, crimping is performed with a crimping machine, and the drying process is performed simultaneously with the annealing process in a dry heat atmosphere at 50 ° C. to 115 ° C., thereby simplifying the process. This is preferable because it is possible. If the annealing treatment is less than 50 ° C., the dry heat shrinkage of the resulting fiber tends to increase, and the resulting nonwoven fabric may be disturbed or the productivity may be reduced. Further, when the annealing step also serves as the drying step, if the annealing temperature is less than 50 ° C., the drying of the fibers may be insufficient. By such a method, it is possible to obtain a composite short fiber in which steric crimp is expressed, that is, an actual crimpable composite short fiber.

  In the composite short fiber of the present invention thus obtained, the number of crimps (three-dimensional crimp number) is 10/25 mm to 18 in consideration of the card passing property of the fiber and the bulkiness of the nonwoven fabric. (In the case where the composite short fiber of the present invention is a latent crimped fiber, the number of crimps is, for example, 5 ° C. lower than the melting point of the linear low-density polyethylene of the first component) This refers to the number of crimps of three-dimensional crimps that develop when a fiber is subjected to heat treatment in a free state at a temperature). Further, when the number of crimps and the crimp rate are measured in accordance with JIS L 1015 (2010), the ratio of the crimp rate to the number of crimps (crimp rate / crimp number). ) Is preferably 0.7 to 1.2, more preferably 0.85 to 1. The crimp rate indicates the fixity of the crimp (hardness of crimp), and if the crimp rate / crimp number satisfies the above range, the crimp is difficult to stretch, and the waveform and / Or since it has spiral crimps, the card passing property is good, the web after passing the card maintains the bulkiness, and the nonwoven fabric after the heat treatment can maintain the elasticity.

  The fineness and fiber length of the composite short fiber of the present invention are not particularly limited, and are selected according to the nonwoven fabric production method and the nonwoven fabric application. For example, as described later, the composite short fiber of the present invention has a fineness when it is used for manufacturing a heat-bonded nonwoven fabric in which fibers are thermally bonded after a web is produced by a card machine (or other means), for example. Is preferably 1.1 to 50 dtex and the fiber length is 10 to 100 mm. For example, when the composite short fiber of the present invention is used as a cushioning material, the fineness thereof may be 2.2 to 30 dtex, more preferably 3.3 to 20 dtex, and particularly preferably 5.6 to 18 dtex. Specifically, the composite short fiber of the present invention has a fiber length (fiber) suitable for a dry nonwoven fabric (for example, an air-through nonwoven fabric, a spunlace nonwoven fabric, a needle punched nonwoven fabric, etc.) produced by producing a fiber web using a card machine. When producing an air laid nonwoven fabric, the fiber length (10 mm to 32 mm, more preferably 12 mm to 28 mm) suitable for the production of the air laid nonwoven fabric may be used. It may have a fineness suitable for the method (fineness of 2.2 to 30 dtex, more preferably 3.3 to 20 dtex). The fineness can be adjusted as desired by adjusting the fineness and draw ratio of the spun filament. A fiber having a predetermined length is obtained by cutting the fiber after the annealing treatment.

  The composite short fiber of the present invention described above forms a fiber aggregate excellent in bulkiness, flexibility in the thickness direction and bulk recoverability by being contained in the fiber aggregate by 20% by mass or more. Can do. Examples of the fiber aggregate include woven and knitted fabrics and nonwoven fabrics. Moreover, when the composite short fiber of the present invention is a nonwoven fabric, particularly a heat-bonded nonwoven fabric, the surface of the composite short fiber of the present invention, preferably at least a part of the first component is a heat-bonding component, and at least a part of the fibers are combined. It is preferable to perform heat bonding. In the present invention, the second component may be partially melted. Further, the composite short fiber of the present invention may be a latent crimpable fiber or an actual crimpable fiber, but an actual crimpable fiber is particularly preferable.

  Then, a nonwoven fabric is demonstrated with the manufacturing method as a specific example of a fiber assembly. The non-woven fabric of the present invention is produced by producing a fiber web so as to contain 20% by mass or more of the composite short fiber of the present invention, and subsequently entangle the fibers and / or thermally bond them to each other. Can be obtained by integrating them. In addition to the composite short fiber of the present invention, other fibers may be used. In that case, as the other fibers, for example, natural fibers such as cotton, silk, wool, hemp, and pulp, rayon, and cupra are regenerated. One or more types of fibers can be selected from fibers and synthetic fibers such as acrylic, polyester, polyamide, polyolefin and polyurethane. Other fibers may be used by mixing with the composite short fiber of the present invention, or may be used by laminating with a fiber web comprising the composite short fiber of the present invention.

  Examples of the fiber web used when producing the nonwoven fabric include card webs such as parallel web, semi-random web, random web, cross web, and Chris cross web, airlaid web, wet papermaking web, and spunbond web. It is done. Two or more different types of fiber webs may be laminated.

  When producing a nonwoven fabric using the composite short fiber of the present invention, a nonwoven fabric is obtained in the form of a heat-bonded nonwoven fabric in which the fiber web is subjected to heat treatment to at least partially heat-bond the fibers with the first component. Is preferred. This is because the heat-bonded nonwoven fabric remarkably exhibits the effects (flexibility in the thickness direction, bulkiness, and bulk recovery) brought about by the composite short fibers of the present invention. In order to entangle the fibers, the fiber web may be subjected to entanglement treatment such as needle punch treatment or hydroentanglement treatment before and / or after the heat treatment, if necessary.

  In order to obtain a heat-bonding nonwoven fabric, the fiber web is preferably subjected to heat treatment by a known heat treatment means. As the heat treatment means, a heat treatment machine in which pressure such as wind pressure is not applied to the fiber web, such as a hot air through heat treatment machine, a hot air blowing type heat treatment machine, and an infrared heat treatment machine, can be preferably used. The heat treatment conditions such as the heat treatment temperature are such that the first component is sufficiently melted and / or softened so that the fibers are bonded to each other at the contact point or intersection, and the steric crimp generated in the composite short fiber of the present invention is not collapsed. It is preferable to carry out by selecting various conditions. For example, the heat treatment temperature is the melting peak temperature before spinning of the linear low density polyethylene (the linear chain having the highest melting peak temperature when a plurality of linear low density polyethylenes are included in the first component). When the melting peak temperature of the low-density polyethylene is Tm, the temperature is preferably (Tm−15) ° C. to (Tm + 40) ° C. A more preferable heat treatment temperature range is (Tm−10) ° C. to (Tm + 30) ° C.

  In addition, in the heat-bonded nonwoven fabric of the present invention, repeated compression residual strain measured by the method B of JIS K6400-4, 4.5.2 (repetition of compression with a test piece thickness of 50% was repeated 80,000 times continuously. After that, the thickness after being left for 30 minutes is preferably 14% or less. When the repeated compressive residual strain is 14% or less, the heat-bonded nonwoven fabric of the present invention has a reduced volume caused by repeated compression, so-called “sagging” is small, and deterioration of the fiber or nonwoven fabric due to compression is suppressed. It shows that the bulk recovery and durability are excellent. If the repeated compressive residual strain exceeds 14%, the “sag” generated in the nonwoven fabric becomes prominent when the nonwoven fabric is repeatedly compressed. Therefore, when used as a cushioning material or a pad for clothing, the feeling of use deteriorates due to the sag or deformation. There is a fear. The repeated compressive residual strain is preferably 13% or less, more preferably 12% or less, and even more preferably 10% or less. The lower limit of the repeated compressive residual strain is not particularly limited because it is preferably as it approaches 0%, but may be 1% or more, 3% or more, or 5% or more.

In the nonwoven fabric containing the composite short fiber of the present invention, particularly in the thermal bonding nonwoven fabric, the density is, for example, 2 kg / m ^{3 to} 100 kg / m ³ , preferably 5 kg / cm ^{3 to} 80 kg / m ³ , more preferably 10 kg / m. ^{3 to} 40 kg / m ³ . If the density of the nonwoven fabric is within the above range, the nonwoven fabric containing the composite short fiber of the present invention can be used, for example, cushion materials used for various seats typified by automobiles, clothing pads, bedding products, etc. In applications, it exhibits moderate hardness, elasticity and cushioning properties, and an effect such as excellent bulk recovery of the nonwoven fabric can be obtained. However, the density may be outside these ranges depending on the type of the heat-bonding nonwoven fabric. Moreover, when using the thermobonding nonwoven fabric of this invention for another use, the density may be suitably selected according to the use.

  Moreover, in the nonwoven fabric containing the composite short fiber of this invention, especially the thermobonding nonwoven fabric, the thickness is 2 mm or more, for example, Preferably it is 5 mm-500 mm, More preferably, it is 5 mm-300 mm. If the thickness of the non-woven fabric is within the above range, the non-woven fabric containing the composite short fiber of the present invention is processed into a non-woven fabric suitable for the intended use from the above thickness range. Appropriate hardness and cushioning will be exhibited. The thickness of the non-woven fabric varies depending on the intended use, so the upper limit is not particularly limited. The thickness of the nonwoven fabric containing the composite short fiber of the present invention may be 800 mm or less, 600 mm or less, or 500 mm or less. However, the thickness may be outside these ranges depending on the type of the heat-bonding nonwoven fabric. Moreover, when using the thermobonding nonwoven fabric of this invention for another use, the thickness may be suitably selected according to the use.

  The nonwoven fabric of the present invention, particularly the heat-bonded nonwoven fabric, repeatedly has a low residual compressive strain, hardly deforms when the load is removed after the load is applied, and is excellent in bulk recovery. For example, a cushion material (for example, an automobile) In absorbent materials such as cushion materials used for general, office seats, sanitary napkins, disposable diapers and nursing diapers Including cushions placed under the face sheet), clothing pads (for example, female bra pads, shoulder pads, elbow pads, knee pads), bedding (for example, beds, futons, beds) Mats, mattresses, pillows, etc.), and because they are bulky, elastic, and bulk-recoverable, Heated material is suitable for applications such as heat insulating material.

If the thermal bonding nonwoven fabric of the present invention the cushion material, the density is more preferable to ^{5kg / m 3 ~80kg / m 3} , It is more preferable that the thickness of the 5Mm～500mm. However, the density and thickness may be outside these ranges depending on the type of cushioning material. Moreover, when using the thermobonding nonwoven fabric of this invention for another use, the density and thickness can be suitably selected according to the use.

  When the heat-bonded nonwoven fabric of the present invention is used as a cushioning material, the composite short fiber of the present invention is preferably contained in an amount of 20% by mass or more, more preferably 25% by mass or more, and particularly preferably 30% by mass or more. preferable. Moreover, 100 mass% of a nonwoven fabric or a cushion material may be comprised with the composite staple fiber of this invention. When the ratio of the composite short fiber of the present invention is within the above range, a bulky nonwoven fabric is easily obtained due to the three-dimensional crimp expressed by the composite short fiber of the present invention. The nonwoven fabric is rich in elasticity and cushioning. In addition, when the nonwoven fabric is manufactured, heat treatment is performed at an appropriate temperature, so that the composite short fibers of the present invention uniformly dispersed throughout the nonwoven fabric cause thermal bonding between the fibers at the portion where the fibers are in contact with each other. In addition to increasing the durability of the nonwoven fabric, it is possible to exert functions required for the cushion material, such as the elasticity of the fibers being thermally bonded to each other, thereby increasing the elasticity.

[Examples 1 to 5, Comparative Example 1]
(First ingredient)
The following were prepared as linear low density polyethylene (LLDPE) and low density polyethylene (LDPE).

LLDPE A: linear low density polyethylene polymerized with a metallocene catalyst (manufactured by Ube Maruzen Polyethylene Co., Ltd., trade name “420SD”, density 0.918 g / cm ³ , Q value 3.0, MI = 7 g / 10 min, Melting point 116 ° C., hexene copolymerization, flexural modulus 270 MPa, hardness (HDD) 52)
LLDPE B: linear low density polyethylene polymerized with a metallocene catalyst (manufactured by Nippon Polyethylene Co., Ltd., trade name “Kernel (registered trademark) KS560T”, density 0.898 g / cm ³ , Q value 3.1, MI = 16.5 g / 10 min, melting point 90 ° C., hexene copolymerization, flexural modulus 62 MPa, hardness (HDD) 40)
LLDPE C: linear low-density polyethylene polymerized with a metallocene catalyst (trade name “613A” manufactured by Ube Maruzen Polyethylene Co., Ltd., density 0.913 g / cm ³ , MI = 30 g / 10 min, melting point 97 ° C. and 113 ° C. Two-stage peak, flexural modulus 230 MPa, hardness (HDD) 50)

LDPE a: Low density polyethylene (Ube Maruzen Polyethylene Co., Ltd., trade name “J2516”, density 0.916 g / cm ³ , MI = 25 g / 10 min, melting point 106 ° C., hardness (HDD) 45)

(Second component)
As a polymer constituting the second component, polyethylene terephthalate (PET) (manufactured by Toray Industries, Inc., trade name “T200E”, melting point 250 ° C., intrinsic viscosity value (IV value) 0.64) was prepared.

  As the first component, the polymers shown in Table 1 below (the density of the first component and the density of each polymer contained in the first component are as described in Table 2 below) are the mixing ratios shown in Table 1 ( %) And using the above-mentioned trade name “T200E” (PET) as the second component, using these two components using an eccentric sheath-core composite nozzle (nozzle hole number 600 holes), The composite ratio (volume ratio) of the first component (sheath component) / second component (core component) is 55/45, the spinning temperature of the first component is 290 ° C, the spinning temperature of the second component is 310 ° C, and the nozzle temperature Was melt-extruded at 300 ° C., and the spun filament was taken up at a predetermined speed (200 m / min. To 280 m / min.) Shown in Table 1 below, and a predetermined fineness (20.8 dtex or 28 dtex) shown in Table 1 below, Eccentric It obtained 25% of the spinning filament. In Table 1 below, the conditions (drawing speed (m / min), unstretched fineness (that is, fineness before stretching) (dtex)) during production of the spun filament are shown in more detail. At this time, the spinning property of the filament was evaluated. As evaluation criteria for spinnability, ◎ indicates that no yarn breakage occurs during melt spinning, and that there is no variation in the fusion between fibers or the fineness of unstretched fibers. Although there is variation in the fineness, there is no problem in production, and fusion between fibers or yarn breakage does not occur.

  The obtained spinning filament was drawn in a hot water tank adjusted to a predetermined temperature to obtain a drawn filament having a fineness of 9 dtex. Next, after applying a water-repellent fiber treatment agent (fiber treatment agent concentration of 5% by weight) as a fiber treatment agent to the drawn filament, 10 crimps / 25 mm of mechanical crimp is applied to the drawn filament using a stuffing box type crimper. It applied so that it might become -18 piece / 25mm. Then, an annealing process and a drying process were simultaneously performed in a relaxed state for 15 minutes using a hot air spraying apparatus set at a predetermined temperature shown in Table 1 below (also referred to as a heat treatment). Thereafter, the filament was cut into a fiber length of 64 mm to obtain an actual crimpable composite short fiber. The detailed production conditions (stretching bath temperature, stretching ratio, heat treatment temperature) of the composite short fiber are shown in Table 1 below. At this time, the crimper passage was evaluated. As evaluation criteria for crimper passage, ◎ indicates that the drawn tow is discharged cleanly from the crimper outlet and crimps are uniformly applied without unevenness. ○ indicates that the crimped shape is slightly uneven but produced It indicates that there is no problem in the discharge of drawn tow at the crimper outlet without any problems.

The obtained crimped composite short fiber is opened, and if there is a fiber to be blended, after sufficiently blending, a fiber web having a basis weight of about 75 g / m ² using a roller type card machine (roller type parallel card machine) Was made. At this time, card passability was evaluated. As an evaluation standard for card passability, ◎ indicates that a good card web is obtained and there is no generation of static electricity or fibers that do not apply to the card, ○ indicates that some fibers that do not apply to the card are generated, but production It indicates that the card web is in good condition without any problems. Ten fiber webs thus obtained were laminated to prepare a laminated card web having a basis weight of 750 g / m ² . The laminated card web is packed into a wooden frame of 200 mm × 200 mm so as to have a thickness of 25 mm, and is put into a constant temperature thermal processing machine set to a predetermined thermal bonding temperature shown in Table 1 below, and after 4 minutes, it is pulled up and down. Repeatedly, after that, heat treatment was performed for 6 minutes for a total of 10 minutes to melt at least a part of the first component to obtain a heat-bonded nonwoven fabric. Table 1 shows the thermal bonding temperature at this time in detail. The thickness of the obtained heat bonding nonwoven fabric was 25 mm, and the density was 30 kg / m ³ .

  About each obtained heat bonding nonwoven fabric, the compression residual strain (%) was measured repeatedly. The repeated compressive residual strain was measured based on the method of JIS K6400-4, 4.5.2 B (the test piece was continuously compressed 80,000 times, and then left for 30 minutes. Later measure the thickness). The results are shown in Table 1.

As shown in Tables 1 and 2, the heat-bonded nonwoven fabric of Comparative Example 1 uses only high-density linear low-density polyethylene (LLDPE A, density 0.918 g / cm ³ ) as the first component of the composite short fiber. The overall density of the linear low-density polyethylene is high (density: 0.918 g / cm ³ ), and as a result, the repeated compressive residual strain of the nonwoven fabric is as high as 14.3%, which is excellent. No bulk recovery was obtained. Moreover, when the heat-bonding nonwoven fabric of Comparative Example 1 was used as a cushioning material, the sag was large and an appropriate elasticity could not be obtained.

On the other hand, in the heat-bonded nonwoven fabrics of Examples 1 to 5 of the present invention, surprisingly, the density of the whole linear low-density polyethylene contained in the first component of the composite short fiber is 0.88 g / cm ³ or more and 0. By setting it within the range of less than .918 g / cm ³ , the repeated compressive residual strain of the nonwoven fabric was remarkably reduced to less than 14%, and excellent bulk recoverability could be obtained.

Further surprisingly, in the present invention, the total density of the linear low density polyethylene contained in the first component of the composite short fiber is 0.88 g / cm using a combination of linear low density polyethylene (LLDPE). ^By setting it within the range of ³ or more and less than 0.918 g / cm ³ (Example 1 and Examples 3 to 5), in particular, high-density linear low-density polyethylene (LLDPE A, density: 0.918 g / cm). ³ ) and low-density linear low-density polyethylene (LLDPE B, density: 0.898 / cm ³ ) in combination, the repeated compressive residual strain is reduced to less than 12%. In Example 1, it decreased to less than 10%, and very excellent bulk recoverability could be obtained.

  Thus, when the composite short fiber of this invention was used, it was able to provide the nonwoven fabric which has the outstanding bulk recovery property, and there is little sag and has moderate elasticity.

  The present invention can provide a non-woven fabric having excellent bulk recovery, low sag, and moderate elasticity, so that cushion materials (for example, for automobiles, aircraft, railway vehicles, In addition to cushion materials used for boat seats, cushion materials used for general household and office seats, and cushion materials placed under the top sheet in absorbent articles such as sanitary napkins, paper diapers, and nursing paper diapers Etc.), clothing pads (eg, female bra pads, shoulder pads, elbow pads, knee pads), bedding (eg, beds, futons, bed mats, mattresses, pillows, etc.) In addition to being bulky and elastic and bulk recovering, it is suitable for configuring sound absorbing materials, sound insulating materials, vibration insulating materials, vibration damping materials, heat insulating materials, heat insulating materials, etc. .

DESCRIPTION OF SYMBOLS 1 1st component 2 2nd component 3 Center of gravity position in fiber cross section of 2nd component 4 Center of gravity position in fiber cross section of composite short fiber 5 Radius in fiber cross section of composite short fiber 10 Composite short fiber

Claims (11)

A cushioning material comprising a composite short fiber comprising a first component and a second component, and at least expressing steric crimps,
The first component contains 60% by mass or more of at least one linear low density polyethylene (LLDPE),
The density of the entire linear low-density polyethylene contained in the first component is less than 0.88 g / cm ³ or more 0.918 g / cm ^3,
In the fiber cross section, the first component occupies at least 20% of the fiber surface, the center of gravity of the second component is deviated from the center of gravity of the fiber,
A cushion material in which at least a part of the fibers are thermally bonded by at least a part of the first component.   The cushion material according to claim 1 whose repetitive compression residual strain measured by B method of JIS K6400-4 and 4.5.2 is 14% or less.   The cushion material according to claim 1 or 2, wherein the first component includes at least two types of linear low-density polyethylene (LLDPE) having different densities. The first component, the density of 0.908 g / cm ³ or more 0.94 g / cm ³ or less of the first linear low density polyethylene (LLDPE _1), density of 0.85 g / cm ³ or more 0.908 g Second linear low-density polyethylene (LLDPE ₂ ) less than / cm ^3, and when the total mass of the first component is 100% by mass, LLDPE ₁ is included at 3% by mass to 97% by mass, The cushion material according to claim 3, wherein LLDPE ₂ is contained in an amount of ₃ to 97% by mass, and the total of LLDPE ₁ and LLDPE ₂ does not exceed 100% by mass.   The first component further includes low density polyethylene (LDPE), and the content of the low density polyethylene (LDPE) is based on the total mass of the linear low density polyethylene (LLDPE) and the low density polyethylene (LDPE). The cushion material according to any one of claims 1 to 4, wherein the cushion material is 5 mass% to 25 mass%. The density of the first component is less than 0.88 g / cm ³ or more 0.918 g / cm ^3, a cushion material according to claim 1.   The cushion material in any one of Claims 1-6 in which a 2nd component contains a polyethylene terephthalate.   The cushion material in any one of Claims 1-7 containing the said composite short fiber 20 mass% or more. A composite short fiber comprising a first component and a second component and expressing at least steric crimps,
The first component contains 60% by mass or more of at least one linear low density polyethylene (LLDPE),
The density of the entire linear low-density polyethylene contained in the first component is less than 0.88 g / cm ³ or more 0.918 g / cm ^3,
In the fiber cross section, the first component occupies at least 20% of the fiber surface, and the gravity center position of the second component is deviated from the fiber gravity center position.
Composite short fiber for cushioning material.   The composite short fiber for a cushion material according to claim 8, wherein the first component includes at least two types of linear low density polyethylene (LLDPE) having different densities. The first component, the density of 0.908 g / cm ³ or more 0.94 g / cm ³ or less of the first linear low density polyethylene (LLDPE _1), density of 0.85 g / cm ³ or more 0.908 g Second linear low-density polyethylene (LLDPE ₂ ) less than / cm ^3, and when the total mass of the first component is 100% by mass, LLDPE ₁ is included at 3% by mass to 97% by mass, The composite short fiber for a cushion material according to claim 10, wherein LLDPE ₂ is contained in an amount of ₃ to 97% by mass, and the total of LLDPE ₁ and LLDPE ₂ does not exceed 100% by mass.

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