WO2012105602A1 - Actualized crimped composite short fiber and process for production thereof, fiber assembly, and sanitary article - Google Patents

Abstract

A composite short fiber comprising a first component and a second component, wherein the first component (1) comprises a linear polyethylene having a density of 0.90-0.94 g/cm³ and a low-density polyethylene, the second component (2) contains 50 mass% or more of a polyester having a melting point that is higher by 40°C or more than the melting point of the linear polyethylene that constitutes the first component, the first component (1) makes up at least 20% of the surface of the fiber in the cross section of the fiber, and the two components are arranged in such a manner that the position of the gravity center of the second component (2) is deviated from the position of the gravity center of the fiber. In this manner, an actualized crimped composite short fiber having at least one crimping form selected from a wavy crimping form and a spiral crimping form can be produced.

Description

Revealed crimpable composite short fiber and method for producing the same, fiber assembly and sanitary article

The present invention is an excellent crimpable composite short fiber excellent in spinnability and workability (particularly high-speed card property), and has a good surface feel and flexibility in the thickness direction, and The present invention relates to a fiber assembly having excellent elasticity and a hygiene article using the fiber assembly.

Various types of composite fibers have been proposed that are composed of two or more components that are composed of polyethylene as a main component so as to occupy at least a part of the surface of the composite fiber. About such a composite fiber, the improvement is repeated for the purpose of improving more the tactile feeling and softness | flexibility of the product (especially nonwoven fabric) obtained from a fiber, and improving the thermal adhesiveness by polyethylene more.

For example, Patent Document 1 (Japanese Patent Laid-Open No. 2008-264473) discloses that the first component is a component containing linear polyethylene polymerized using a metallocene catalyst, the second component is 50% by mass or more of polytrimethylene terephthalate. A composite fiber comprising polyester, wherein the center of gravity of the second component is deviated from the position of the center of gravity of the composite fiber, and the composite fiber has at least one kind of crimp selected from wave-shaped crimp and spiral crimp Proposed crimped conjugate fiber. The composite fiber proposed in Patent Document 1 is very soft because the second component is mainly composed of polytrimethylene phthalate, and exhibits an excellent initial bulk recovery rate.

Patent Document 2 (Japanese Patent Application Laid-Open No. 63-105111) discloses a composite heat-bonding fiber in which two components having different melting points are arranged concentrically or in parallel, and one of the components is linearly low in high-density polyethylene. It is composed of a low melting point component to which 2 to 20% of density polyethylene or low density polyethylene is added, and the other component is a resin having a fiber forming ability higher than the low melting point component by 20 ° C. or more as a high melting point component. Proposed composite heat-fusible fibers. The composite fiber described in this document has a wide range of proper fusing conditions, and it is possible to obtain a non-woven fabric having a stable fusing strength and texture even with fluctuations in production conditions and outside air conditions. .

Patent Document 3 (Japanese Patent Application Laid-Open No. 11-350255) discloses a sheath made of a polyethylene resin (A) having a high melting point and a low melting point, and the low melting point being at least 5 ° C. lower than the high melting point, A core-sheath type composite fiber composed of a core part composed of a high melting point resin (B) having a melting point higher by 10 ° C. or more than the highest melting point, or a polyethylene resin part composed of a polyethylene resin (A); A side-by-side type composite fiber composed of a high melting point resin portion made of a melting point resin (B) is proposed. The composite fiber described in this document can widen the proper processing temperature, thereby preventing the winding of the roll and the poor fusion when the web made of the fiber is entangled by hot embossing. , Excellent heat embossing property.

Patent Document 4 (Patent No. 4315663) discloses a polyester, a polyethylene obtained by mixing a first polyethylene obtained by a metallocene polymerization catalyst and a second polyethylene obtained by a Ziegler-Natta polymerization catalyst. The polyester is arranged on the core, and the polyethylene is arranged on the sheath. The core-sheath-type composite spinning hole is supplied and melt-spun so that the core is made of the polyester and the sheath is made of the polyethylene. The cross-sectional shape of the core-sheathed composite continuous fiber is not substantially changed in the fiber axis direction, and the sheath thickness is nonuniform and randomly changing in the fiber axis direction and the fiber circumferential direction. After that, a method for producing a nonwoven fabric characterized by accumulating the core-sheath composite long fibers is proposed. According to this production method, a long fiber nonwoven fabric having excellent flexibility and heat sealability due to the fact that the fiber diameter of the long fibers is not constant can be obtained.

JP 2008-264473 A JP 63-105111 A Japanese Patent Laid-Open No. 11-350255 Japanese Patent No. 4315663

Fiber products (especially non-woven fabrics) composed of composite fibers composed of polyethylene as the main component occupying at least part of the composite fiber surface are widely used as surface materials for sanitary articles such as sanitary napkins and disposable diapers. Has been. Since the surface material of a hygiene article is in direct contact with a delicate part of the human body or animal, it is strongly required that the surface material itself has an excellent tactile sensation. Such demands are increasing in recent years. Specifically, the tactile sensation required for the surface material is not only good surface tactile sensation (smoothness when touching the surface), but also soft and fluffy sensation in the thickness direction, ie, bulkiness and thickness direction. A property that is easily deformed when a force is applied, that is, flexibility in the thickness direction, and a cushion-like feel that gives a feeling of return when a force is applied in the thickness direction, that is, a bulk recovery property is required. Yes.

Also, when manufacturing textile products from fibers as well as the surface material of sanitary articles, it is desired to produce them as efficiently as possible. One index of production efficiency is the high-speed card property when manufacturing nonwoven fabrics. The high-speed card property is a web production speed (1) in the production of a nonwoven fabric when a web is produced by opening a short fiber with a card machine without causing nep or formation unevenness. As expressed in meters per minute). In the non-woven fabric mass production site, for example, a high-speed card property of 100 m / min may be required.

It is not easy to obtain a composite short fiber having a good tactile sensation and excellent in high-speed card properties. For example, the actual crimpable conjugate fiber described in Patent Document 1 has a problem that it is inferior in high-speed card property because it is flexible. Since the fibers described in Patent Documents 2 and 3 use polyethylene having a high melting point, the fibers are not necessarily flexible, and a fiber aggregate obtained using the fibers does not exhibit good tactile sensation (particularly surface tactile sensation). Patent Document 4 achieves flexibility by obtaining a long-fiber nonwoven fabric having a special shape. However, when a fiber with a non-constant fiber diameter is made into a short fiber, for example, and the card is passed, the condition of the fiber becomes the card. It cannot pass well, leading to the occurrence of Nep and uneven formation.

The present invention has been made in view of such circumstances, and has been made for the purpose of obtaining a composite fiber having good tactile sensation and excellent in high-speed card properties.

The present invention
A composite short fiber comprising a first component and a second component,
The first component includes linear polyethylene having a density of 0.90 g / cm ³ to 0.94 g / cm ³ and low density polyethylene,
In the first component, the low density polyethylene is included so as to occupy 5% by mass to 25% by mass of the total mass of the linear polyethylene and the low density polyethylene,
The second component contains 50% by mass or more of polyester having a melting point 40 ° C. or higher than the melting point of the linear polyethylene constituting the first component,
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,
The composite short fiber has at least one kind of crimp selected from a wave crimp and a spiral crimp,
An actual crimpable composite short fiber is provided.

The present invention provides a method for producing crisp crimpable composite staple fibers. That is,
A method for producing a composite short fiber comprising a first component and a second component,
5% by mass of the total mass of the linear polyethylene and the low density polyethylene, the linear polyethylene having a density of 0.90 g / cm ³ to 0.94 g / cm ³ and the low density polyethylene. A first component occupying ~ 25% by weight;
A second component containing 50% by mass or more of a polyester having a melting point of 40 ° C. or higher than the melting point of the linear polyethylene constituting the first component;
In the fiber cross section, the first component occupies at least 20% of the fiber surface, and melt spinning to obtain a spun filament so that the center of gravity of the second component deviates from the center of gravity of the fiber,
The spinning filament is at a temperature within the range of Tg ₂ ° C. to 95 ° C. (where Tg ₂ is the glass transition temperature of the polymer component having the highest glass transition temperature among the polymer components contained in the second component). Stretching up to 5 times,
Applying mechanical crimps to the filaments after drawing in the range of 5 crimps / 25mm to 25 threads / 25mm,
Performing an annealing treatment at a temperature within a range of 50 to 115 ° C .;
Provided is a method for producing a composite short fiber having at least one kind of crimp selected from wave-shaped crimps and spiral crimps, which comprises cutting an annealed filament into a length of 1 mm to 100 mm.

The present invention also provides a fiber aggregate containing 20% by mass or more of the above-described actual crimpable composite short fiber. The fiber aggregate is preferably a non-woven fabric, and more preferably a heat-bonded non-woven fabric heat-bonded with the first component.

The present invention further provides a surface material for a hygiene article comprising the fiber assembly. The present invention still further provides a hygiene article incorporating the surface material.

The apparently crimpable composite short fiber of the present invention comprises a first component containing linear polyethylene having a density of 0.90 g / cm ³ to 0.94 g / cm ³ and a predetermined amount of low density polyethylene. However, it contains 50% by mass or more of polyester, the second component is decentered, and has at least one kind of crimp selected from wave crimps and spiral crimps. The actual crimpable composite short fiber is excellent in card passing property and gives an excellent card web, and a fiber aggregate (particularly non-woven fabric) containing this fiber gives a good surface feel, It is excellent in bulkiness, flexibility in the thickness direction, and bulk recovery. Furthermore, this actual crimpable composite short fiber makes it possible to carry out a heat bonding treatment in a wide temperature range when producing a heat bonded nonwoven fabric by using two types of polyethylene. Therefore, the actual crimpable composite short fiber is suitable for constructing a product that is in direct contact with a delicate part of a human body or an animal, such as a surface material of a hygiene article, and the product with high productivity. Makes it possible to manufacture.

The fiber aggregate (particularly non-woven fabric) containing composite short fibers obtained by the method for producing an actual crimpable composite fiber of the present invention gives good surface feel and is bulky, flexible in the thickness direction and bulk recovery. Excellent in properties. Therefore, according to the manufacturing method, it is possible to manufacture with high productivity composite short fibers suitable for constituting a product that is in direct contact with a delicate part of a human body or an animal, such as a surface material of a hygiene article. It becomes.

FIG. 1 shows a fiber cross section of an actual crimpable composite short fiber according to an embodiment of the present invention. FIGS. 2A-C show the crimped form of the manifest crimpable composite staple fiber in one embodiment of the present invention. FIG. 3 shows a form of conventional mechanical crimping. FIG. 4 shows the crimped form of the manifest crimpable composite staple fiber in another embodiment of the present invention.

In order to achieve the above object, the present inventors have ensured that the low melting point component ensures the flexibility and thermal adhesiveness of the fiber, and the high melting point component increases the bulkiness and bulk recoverability of the nonwoven fabric. We thought it necessary to provide sufficient rigidity to withstand high-speed cards. Therefore, an investigation was made to obtain an apparently crimped conjugate fiber in which the low melting point component is composed of linear polyethylene giving a good surface feel, the high melting point component is composed of polyester, and steric crimps are expressed. However, such fibers are excellent in terms of surface tactile sensation, but are not necessarily sufficient in terms of high-speed card properties, bulkiness when made into a nonwoven fabric, flexibility in the thickness direction, and bulk recovery properties. Therefore, it was studied to modify the low melting point component within a range that does not impair the surface feel derived from the linear polyethylene.

As a result of the study, by adding a small amount of low-density polyethylene to linear polyethylene having a density of a predetermined value or more, it is excellent in high-speed card properties without impairing the good surface feel of linear polyethylene, and non-woven fabric It was found that composite short fibers exhibiting excellent bulkiness, flexibility in the thickness direction, and bulk recoverability when obtained. Therefore, the actual crimpable composite short fiber of the present invention is
The first component includes linear polyethylene having a density of 0.90 g / cm ³ to 0.94 g / cm ³ and low density polyethylene,
In the first component, the low density polyethylene is included so as to occupy 5% by mass to 25% by mass of the total mass of the linear polyethylene and the low density polyethylene,
The second component contains 50% by mass or more of polyester having a melting point 40 ° C. or higher than the melting point of the linear polyethylene constituting the first component,
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,
The composite short fiber has at least one kind of crimp selected from a wave crimp and a spiral crimp,
It is an actual crimpable composite short fiber. Hereinafter, the first component and the second component constituting the composite short fiber will be described.

The first component includes linear polyethylene having a density of 0.90 g / cm ³ to 0.94 g / cm ³ and low density polyethylene. Linear polyethylene (also referred to as “LLDPE (Linear Low Density Polyethylene)”), the linear polyethylene used in the present invention is not necessarily limited to low density (generally 0.925 g / cm ³ or less). Refers to a copolymer obtained by copolymerizing ethylene and 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, heptene-1, octene-1, nonene-1, Decene-1, dodecene-1 and mixtures thereof may be mentioned. Of 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 polyethylene is preferably 1 mol% to 10 mol%, 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 polyethylene used in the first component has a density of 0.90 g / cm ³ to 0.94 g / cm ³ . When the density is less than 0.90 g / cm ³ , the first component becomes soft, and when it is made into a nonwoven fabric, sufficient bulkiness and bulk recovery are not obtained, and it is inferior in terms of high-speed card properties. May not be obtained. On the other hand, when the density of the linear polyethylene is higher than 0.94 g / cm ³ , the bulkiness and bulk recovery of the nonwoven fabric are improved when it is made into a nonwoven fabric, but the surface feel and flexibility in the thickness direction of the nonwoven fabric are improved. Tend to be inferior. Thus, linear polyethylene is preferably ^{0.90g / cm 3 ~ 0.935g / cm} 3, more preferably ^{0.91g / cm 3 ~ 0.935g / cm} 3, even more preferably 0.913 g / cm ^It has a density of ³ to 0.935 g / cm ³ .

The linear polyethylene preferably has a melting point before spinning in the range of 110 ° C to 125 ° C. The melting point of the linear polyethylene is preferably higher than the melting point of the low density polyethylene to be added. If the melting point of the linear polyethylene is too high, a non-woven fabric having a strength that can withstand practical use may not be obtained when a thermobonding nonwoven fabric is produced by performing a thermal bonding treatment at a low temperature. If the melting point of the linear 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 good nonwoven fabric cannot be obtained. By making the melting point of the linear polyethylene higher than the melting point of the low density polyethylene added to it, in the nonwoven fabric, the linear polyethylene functions as a skeleton polymer and the low density polyethylene serves as a softening agent. Appropriate flexibility can be obtained in the fiber and the fiber assembly obtained therefrom.

The linear polyethylene having the above density and melting point can be easily obtained by copolymerizing ethylene and α-olefin using a metallocene catalyst. However, linear polyethylene is limited to those polymerized using a metallocene catalyst as long as it has a density of 0.90 g / cm ³ to 0.94 g / cm ³ and preferably has the melting point described above. Instead, for example, a polymerized with a Ziegler-Natta catalyst may be used.

The melt index (MI) of linear polyethylene is preferably in the range of 1 g / 10 min to 60 g / 10 min in consideration 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 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 preferred.

The ratio (Q value: Mw / Mn) between the weight average molecular weight (Mw) and the number average molecular weight (Mn) in the linear polyethylene is preferably 5 or less. The Q value is more preferably 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 polyethylene has a narrow width. By using a linear polyethylene satisfying this Q value range as the first component. Thus, it is possible to obtain a composite short fiber excellent in actual crimpability.

The flexural modulus of linear polyethylene is in the range of 65 MPa to 850 MPa in consideration of the properties of the actual crimpable conjugate fiber obtained, the tactile feel of the fiber aggregate using the actual crimpable conjugate fiber, and the bulkiness. It is preferable that it exists in. Here, the flexural modulus is measured according to JIS K 7171 (2008). The actual crimpable conjugate fiber of the present invention has a soft tactile sensation due to the linear polyethylene that is the main component of the first component, but simply being flexible does not cause the fiber to be stiff and the card passing property is reduced. In some cases, it is difficult to obtain a fiber aggregate that is bulky and has a high bulk recovery property. Therefore, it is preferable that the linear 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). Specifically, the bending elastic modulus is 65 MPa or more. Are preferred. If the flexural modulus of the linear 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 from 120 MPa to 750 MPa, particularly preferably from 180 MPa to 700 MPa, and most preferably from 250 MPa to 650 MPa.

The hardness of the linear polyethylene is 45 to 75 in consideration of the properties of the actual crimpable conjugate fiber obtained and the tactile sensation, bulkiness and bulk recovery of the fiber aggregate using the actual crimpable conjugate fiber. It is preferable to be within the range. Here, the hardness of linear polyethylene refers to durometer hardness (HDD) measured using a type D durometer in accordance with JIS K 7215 (1986). If the linear polyethylene, which is the main component of the first component, is too soft, the stiffness of the fiber is lost, the fiber cardability may be reduced, and a bulky fiber aggregate may be difficult to obtain. In addition, the bulk recoverability of the fiber assembly may be reduced. Therefore, it is preferable that the linear polyethylene has a certain degree of hardness, specifically 45 or more. If the linear polyethylene has a too high hardness, the soft tactile sensation may be lost. Therefore, it is preferably 75 or less. More specifically, the hardness of the linear polyethylene is more preferably 48 to 70, particularly preferably 50 to 65, and most preferably 50 to 62.

The low-density polyethylene (also referred to as “LDPE”) contained in the first component is a soft polyethylene with many branches, and is also referred to as a high-pressure polyethylene due to its production method. In the present invention, by adding a small amount of low-density polyethylene to the first component, the manifestation of crimp is improved, and the bulkiness and bulk recovery properties and the high-speed card properties when made into a nonwoven fabric are improved. It becomes possible. In addition, since low density polyethylene is softer than linear polyethylene, for example, it is possible to ensure surface texture that tends to decrease when using high density linear polyethylene. It is.

Density of the low density polyethylene is preferably ^{0.91g / cm 3 ~ 0.93g / cm} 3. Since the density of low density polyethylene tends to depend on the MI (190 ° C) of the polymer, considering the spinnability, the density of low density polyethylene should be 0.915 g / cm ³ to 0.92 g / cm ^3. Is preferred.

The melting point of the low density polyethylene 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, the actual crimp can be expressed more favorably, the thermal processing temperature range during the production of the nonwoven fabric can be widened, and a flexible nonwoven fabric is obtained after heat treatment be able to. 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 melting point of the low density polyethylene is preferably lower than the melting point of the linear polyethylene. The melting point of the low density polyethylene is more preferably 5 ° C. or more lower than the melting point of the linear polyethylene, and even more preferably 10 ° C. or more lower than the melting point of the linear polyethylene.

The melt index (MI) of 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. The Q value is more preferably 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 polyethylene and the low density polyethylene are composed of 95% to 75% by mass of the linear polyethylene when the combined mass is 100% by mass. It is preferable that they are mixed so as to occupy 5% by mass to 25% by mass. More preferably, the linear polyethylene accounts for 90% by mass to 80% by mass, and the low density polyethylene accounts for 10% by mass to 20% by mass. If the proportion of linear polyethylene is too large, the effect of adding low-density polyethylene is difficult to obtain, and the nonwoven fabric is inferior in bulk when made into a nonwoven fabric. If the proportion of linear polyethylene is too small, a nonwoven fabric with high strength cannot be obtained 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. Therefore, the bulkiness of the nonwoven fabric containing this fiber is 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 polyethylene molecules with few branches, distortion during stretching is likely to occur, so steric crimps are likely to occur. Estimated. However, the present invention is not limited by this estimation. In addition, since low density polyethylene functions as a softening agent, when low density polyethylene is included in the above range, for example, when a high-density linear polyethylene is used, the resulting nonwoven fabric is excellent in the thickness direction. 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. Can do.

The first component contains other polymer components in addition to the linear polyethylene and the low-density polyethylene as long as a steric crimp is sufficiently developed in the composite short fiber and a non-woven fabric giving a good tactile sensation is provided. Good. For example, the first component is high density polyethylene, polypropylene, polybutene, polybutylene, polymethylpentene resin, polybutadiene, propylene copolymer (for example, propylene-ethylene copolymer), ethylene-vinyl alcohol copolymer, ethylene- Polyolefin resins such as vinyl acetate copolymer, ethylene- (meth) acrylic acid copolymer, or ethylene- (meth) methyl acrylate copolymer, polyethylene terephthalate, polybutylene terephthalate, polytrimethylene terephthalate, polyethylene naphthalate Polyester resins such as phthalate, polylactic acid, polybutylene succinate and copolymers thereof, polyamide resins such as nylon 66, nylon 12 and nylon 6, acrylic resins, polycarbonate, polyacetate Lumpur, engineering plastics such as polystyrene and cyclic polyolefin, mixtures thereof, and is selected from such as those elastomeric resin may include one or more polymer components.

The first component preferably includes 50% by mass or more, more preferably 75% by mass or more as a polymer component, and more preferably 75% by mass or more. More preferred.

The first component is a component other than the 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, an antioxidant, and an ultraviolet ray. Additives such as absorbents and crystal nucleating agents 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.

The second component is a component containing 50% by mass or more of a polyester having a melting point 40 ° C. or more higher than the melting point of the linear polyethylene constituting the first component as the polymer component. The second component preferably contains 50% by mass or more of polyester as the polymer component, more preferably 75% by mass or more, and most preferably 100% by mass.

Polyester is preferably used because it is less expensive than other polymers, has high rigidity, and gives the fiber stiffness. Examples of the polyester include polymers or copolymers such as polyethylene terephthalate, polybutylene terephthalate, polytrimethylene terephthalate, polyethylene naphthalate, and polylactic acid. The melting point of the polyester is 40 ° C. or more higher than the melting point of the linear polyethylene constituting the first component. The preferable melting point of polyester is a temperature higher by 50 ° C. or more than the melting point of linear polyethylene.

Among the polyesters, polyethylene terephthalate and polybutylene terephthalate have high rigidity compared to polytrimethylene terephthalate and give the fiber stiffness, so that the high-speed card property of the resulting crimped composite short fiber can be improved. Make good. In particular, polyethylene terephthalate is most preferably used because of its high rigidity. Polyethylene terephthalate also has high crystallinity and is less susceptible to heat shrinkage by adjusting the drawing conditions during fiber production as appropriate, so that it does not show latent crimps or shows only slight crimps. Functional composite staple fibers can be provided. 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 is 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 fiber gives the nonwoven fabric which gives a favorable tactile sense, it is not specifically limited. 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 deteriorate the high-speed card property of the resulting fiber. Therefore, it is preferably not used in the actual crimpable composite short fiber of the present invention.

The second component is a component other than the 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 softening agent, an antioxidant, and an ultraviolet ray. Additives such as absorbents and crystal nucleating agents 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 actual crimpable composite short fiber of the present invention, (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. When a nonwoven fabric is produced with the actual crimpable fiber of the present invention, the second component mainly contributes to the bulkiness and bulk recovery of the nonwoven fabric, and the first component mainly contributes to the nonwoven fabric strength and the nonwoven fabric softness. . 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, so that the bulk recoverability tends to deteriorate.

In the actual crimpable composite of the present invention, the position of the center of gravity of the second component is shifted from the position of the center of gravity of the fiber in the fiber cross section. FIG. 1 shows a fiber cross section of a composite short fiber according to an embodiment of the present invention. 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) is 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 ratio of the deviation (hereinafter sometimes referred to as eccentricity). 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 fiber cross section of the actual crimpable composite fiber (10) When the center of gravity (4) is Cf and the radius (5) of the fiber cross section of the actual crimpable conjugate fiber (10) is rf, the numerical value shown by the following formula is used.
Eccentricity (%) = [| Cf−C1 | / rf] × 100

The fiber cross section where the center of gravity (3) of the second component (2) is displaced from the center of gravity (4) of the fiber is preferably an eccentric core-sheath type or a parallel type as shown in FIG. 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 fiber cross section is preferable in that desired wave shape crimps and / or spiral crimps can be easily expressed. The eccentricity of the eccentric core-sheath type composite short fiber is preferably 5% to 50%. A more preferable eccentricity is 7% to 30%. In addition to the circular shape, the shape of the second component in the fiber cross section may be elliptical, Y-shaped, X-shaped, well-shaped, polygonal, star-shaped, or the like, and the fiber cross section of the composite short fiber (10). In addition to the circular shape, the shape may be elliptical, Y-shaped, X-shaped, well-shaped, polygonal, star-shaped, or hollow.

FIG. 2 shows a crimped form of an actual crimpable composite short fiber 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. A crimp in which a wave shape crimp and a spiral crimp as shown in FIG. 2C are mixed is also included in the present invention. In the case of ordinary mechanical crimping as shown in FIG. 3, if the so-called serrated crimp has a sharp crest, 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 also includes a crimp in which the sharp crimp of the mechanical crimp as shown in FIG. 4 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 crimps including the wave shape crimp and the spiral crimp shown in FIG. 2C are mixed in terms of achieving both the card passing property and the initial bulk and bulk recovery properties.

The actual crimpable composite short fiber of the present invention can be produced by the following procedure. First, a first component containing linear polyethylene and low density polyethylene, and a second component containing, for example, 50% by mass or more of polyethylene terephthalate and / or polybutylene terephthalate, the first component is at least on the fiber surface in the fiber cross section. Using a composite nozzle that occupies 20% and the center of gravity of the second component deviates from the center of gravity of the fiber, for example, an eccentric core-sheath composite nozzle, the second component is spun at 240 ° C. to 330 ° C., The first component is melt-spun at a spinning temperature of 200 ° C. to 300 ° C. and taken up at a take-up speed of 100 m / min to 1500 m / min to obtain a spun filament.

Next, among the polymer components contained in the second component, the draw ratio is 1. at a stretching temperature not lower than the melting peak temperature of the linear polyethylene, not less than the glass transition point (Tg ₂ ) of the polymer component having the highest glass transition point. Stretching is performed at 8 times or more. 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 95 ° C, and a particularly preferable upper limit of the stretching temperature is 90 ° 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 stretching temperature is equal to or higher than the melting peak temperature of the linear polyethylene, the fibers are fused, which is not preferable.

A more preferred lower limit of the draw ratio is 2 times, a particularly preferred lower limit of the draw ratio is 2.2 times, and a most preferred lower limit of the draw ratio is 2.4 times. The upper limit of the more preferable draw ratio is 5 times, the upper limit of the particularly preferable draw ratio is 4.0 times, and the upper limit of the draw ratio is most 3.5 times. If the draw ratio is less than 1.8 times, the draw ratio is too low, so that it is difficult to obtain a fiber in which corrugated crimps and / or spiral crimps are expressed, and the bulkiness of the nonwoven fabric is reduced. In addition, since the rigidity of the fiber itself is reduced, the nonwoven fabric processability such as card passing property tends to be inferior or the bulk recovery property tends to be lowered. Further, if necessary, an annealing treatment may be performed in an atmosphere of dry heat, wet heat, steam, etc. at a temperature at which fibers at 50 ° C. to 115 ° C. are not fused before and after stretching.

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, if 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 that after the crimping is performed by the crimping machine, an annealing treatment is performed in an atmosphere of dry heat, wet heat or steam at 50 ° C. to 115 ° C. By the annealing treatment, the expression of steric crimps can be promoted in the actual crimpable composite short fibers. Specifically, the process can be simplified if the fiber treatment agent is applied and then crimped by a crimping machine, and the drying treatment is performed simultaneously with the annealing treatment in a dry heat atmosphere at 50 ° C. to 115 ° C. 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, an actual crimpable composite staple fiber in which steric crimp is expressed is obtained.

In the actual crimpable composite short fiber of the present invention thus obtained, the number of crimps (three-dimensional crimp number) is 12 threads / It is preferably 25 mm to 18 peaks / 25 mm. Further, when the number of crimps and the crimp rate are measured according to JIS L 1015 (2010), the ratio of the crimp rate to the crimp number (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 actual crimpable composite short fiber of the present invention are not particularly limited, and are selected according to the application. For example, the actual crimpable composite staple fiber of the present invention, as described later, is used for manufacturing a heat-bonded nonwoven fabric in which fibers are thermally bonded after producing a web by a card machine (or other means), It is preferable to use short fibers having a fineness of 1.1 to 15 dtex and a fiber length of 1 to 100 mm. For example, when the actual crimpable composite short fiber of the present invention is used as a surface material of a sanitary material, the fineness is preferably 1.5 dtex to 3.5 dtex. Needless to say, these finenesses and fiber lengths may be used when producing non-woven fabrics other than heat-bonded non-woven fabrics. Specifically, the actual crimpable composite short fiber of the present invention is suitable for a dry nonwoven fabric (for example, an air-through nonwoven fabric, a spunlace nonwoven fabric, a needle punched nonwoven fabric, etc.) manufactured by producing a fiber web using a card machine. It may have a fiber length (fiber length 15 mm to 80 mm, more preferably 32 mm to 64 mm), a fiber length suitable for manufacturing wet nonwoven fabrics (fiber length 1 mm to 20 mm, more preferably 3 mm to 15 mm), or airlaid It may have a fiber length (1 mm to 30 mm, more preferably 5 mm to 25 mm) suitable for producing a nonwoven fabric. 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 actual crimpable composite short fiber of the present invention described above contains 20% by mass or more in the fiber assembly, so that the surface feel is good, the bulkiness, the flexibility in the thickness direction, and the bulk recovery property. To form an excellent fiber aggregate. Examples of the fiber aggregate include woven and knitted fabrics and nonwoven fabrics.

Subsequently, a non-woven fabric will be described together with its production method as a specific example of the fiber assembly of the present invention. The non-woven fabric is made by integrating the fibers by a method in which a fiber web is prepared so as to contain 20% by mass or more of the actual crimpable composite short fibers, and then the fibers are entangled and / or thermally bonded. It is obtained by making it. When other fibers are used, examples of the other fibers include natural fibers such as cotton, silk, wool, hemp, and pulp, regenerated fibers such as rayon and cupra, and acrylic, polyester, polyamide, and polyolefin. One type or a plurality of types of fibers can be selected from synthetic fibers such as polyurethane and polyurethane according to the purpose of use. Other fibers may be used by mixing with the actual crimpable composite staple fiber of the present invention, or may be used by being laminated with a fiber web comprising the actual crimpable composite staple fiber of the present invention.

Examples of the fiber web used in manufacturing 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 manufacturing a nonwoven fabric using the actual crimpable composite short fiber of the present invention, a nonwoven fabric is obtained in the form of a heat-bonded nonwoven fabric in which fibers are thermally bonded to each other by heat-treating the fiber web. Is preferred. This is because the heat-bonded nonwoven fabric remarkably exhibits the effects (flexibility in the thickness direction, bulk recoverability and bulk recoverability) brought about by the actual crimpable 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 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 so much applied to the fiber web, such as a hot air penetration type heat treatment machine, a hot air blowing type heat treatment machine and an infrared heat treatment machine, is 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 joined at the contact point or intersection, and the three-dimensional crimp generated in the actual crimpable composite short fiber is not destroyed. Select such conditions. For example, the heat treatment temperature is the melting peak temperature before spinning of the linear polyethylene (if a plurality of linear polyethylene is included in the first component, the melting of the linear polyethylene having the highest melting peak temperature). The temperature is preferably Tm ° C. to (Tm + 40) ° C. when the peak temperature is Tm. A more preferable heat treatment temperature range is (Tm + 5) ° C. to (Tm + 30) ° C.

The heat-bonded nonwoven fabric produced in this way has a good surface feel and high bulkiness and bulk recovery. Furthermore, this heat bondable nonwoven fabric exhibits high flexibility in the thickness direction of the nonwoven fabric. The flexibility in the thickness direction of the nonwoven fabric can be expressed by an index “bulk after compression”. When comparing nonwoven fabrics having the same thickness, the smaller the bulk after compression, the easier the nonwoven fabric to collapse in the thickness direction. "It's flexible. The flexibility in the thickness direction of the nonwoven fabric can also be expressed by an index “bulk change rate”. The bulk change rate is indicated by the ratio of the change amount of the bulk (thickness) due to compression to the original nonwoven fabric bulk (thickness), and the larger the bulk change rate, the more flexible the nonwoven fabric is in the thickness direction. It is preferable that the bulk change rate of the thermobonding nonwoven fabric containing the actual crimpable composite short fiber of the present invention is 85% or more. More preferably, it is 88% or more.

Also, the heat-bonded nonwoven fabric can be evaluated by the bulk recoverability after compression in the thickness direction (bulk recovery after compression). The post-compression recovery bulk shows bulk recoverability in the thickness direction of the nonwoven fabric, and it can be said that the larger the recovery bulk, the richer the cushioning property (elasticity). When used as a surface material for sanitary articles, for example, a nonwoven fabric rich in cushioning properties follows the movement of the body and has improved adhesion to the skin. Bulk recovery after compression is the ratio of the nonwoven fabric bulk (thickness) before compression to the nonwoven fabric bulk (thickness) after a certain time has elapsed after removing the load from the compressed state, and the greater the bulk recovery after compression, , Exhibit greater cushioning properties. It is preferable that the bulk recovery rate of the thermobonding nonwoven fabric containing the actual crimpable composite short fiber of the present invention is 60% or more. More preferably, it is 65% or more, and particularly preferably 68% or more.

KES (Kawabata Evaluation System) is one of the methods to measure the texture of the fabric and to objectively evaluate the surface touch and thickness direction flexibility, bulkiness, and bulk recovery (elasticity) of the heat-bonded nonwoven fabric. Can be measured and evaluated based on The surface tactile sensation of the heat-bonded nonwoven fabric can be evaluated by measuring the characteristic value of surface friction defined by KES. The thickness direction flexibility, bulkiness, and bulk recovery (elasticity) of the heat-bonded nonwoven fabric are as follows: It can be evaluated by measuring a compression characteristic value obtained from the behavior of a load-displacement curve at the time of a compression test defined by KES. Specifically, the average friction coefficient (hereinafter also referred to as MIU) and the variation of the average friction coefficient (sometimes referred to as the average deviation of the friction coefficient μ, hereinafter also referred to as MMD) are measured as the characteristic values of the surface friction. The MIU represents the difficulty (or ease of slipping) of slipping on the surface, and the larger the value, the more difficult it is to slip. MMD shows the dispersion | variation in friction, and it shows that the surface is so rough that this is large. The surface of the heat-bonding nonwoven fabric containing the actual crimpable composite short fiber of the present invention tends to have a high MIU but a small MMD. Such a non-woven fabric feels resistance when touched by hand, but also gives a unique touch feeling called “smooth feeling” and “moist feeling” because it also feels smooth. The equipment for measuring the surface friction characteristic value is not particularly limited as long as the equipment can measure the surface friction based on KES. The characteristic value of the surface friction can be measured by using, for example, a KES-SE friction tester, KES-FB4-AUTO-A automated surface tester (both manufactured by Kato Tech Co., Ltd.) and the like.

As compression characteristic values, compression hardness (sometimes referred to as linearity of compression characteristics, hereinafter also referred to as LC), compression energy (sometimes referred to as compression work, hereinafter also referred to as WC (gf · cm 2 / cm 2). ² )), compression resilience (also referred to as compression recovery and compression recovery rate, hereinafter also referred to as RC (%)), T ₀ (thickness when load is 0.5 gf / cm ² (mm) )), T _M (load refers to a thickness of 50 gf / cm ² (mm)), compression ratio (the above T ₀ , T _M , 100 × (T ₀ −T _M ) / T ₀ Hereinafter, it is also referred to as EMC (%)). LC shows compressibility with a small force, and the larger this is, the harder it is to compress. WC indicates the work of compression. The larger this is, the softer in the thickness direction, the easier it is to compress. RC shows elasticity (recoverability, resilience) against compression, and the greater this, the easier it is to rebound against compression, i.e., cushioning. The EMC indicates the rate of change in thickness when two predetermined types of loads are applied, and the larger this is, the softer and bulkier it is, and the larger the deformation occurs when a load is applied. The heat-bonded nonwoven fabric containing the actual crimpable composite short fiber of the present invention has a high compressibility, so that it has a high initial bulk and is not only bulky, but also has a small compressibility and a large compressive energy. It is easy to be compressed in the direction and is flexible. The heat-bonded nonwoven fabric containing the actual crimpable composite short fiber of the present invention has a high compression resilience, and is therefore elastic against compression and exhibits a good cushioning property. The instrument for measuring the compression characteristic value obtained from the behavior of the load-displacement curve at the time of the compression test is not particularly limited as long as the instrument can measure the compression characteristic value based on KES. The compression characteristic value can be measured by using, for example, a KES-G5 handy compression tester or a KES-FB3-AUTO-A automated compression tester (both manufactured by Kato Tech Co., Ltd.).

The surface characteristics, that is, the surface friction of the heat-bonded nonwoven fabric, is that the measurement surface is the surface to which hot air is blown in the production of the nonwoven fabric, the measurement direction is the vertical direction (also referred to as MD direction), the static load is 25 gf, and the moving speed of the friction element is It can be measured as 1 mm / sec. The compression characteristic value, that is, the compression characteristic value obtained from the behavior of the load-displacement curve in the compression test of the heat-bonded nonwoven fabric, is the surface to which the hot air is blown in the production of the nonwoven fabric, and the circular area with an area of 2 cm ² is used as the compressor. Using a pressure plate, the speed can be measured as 0.02 cm / sec, the upper limit load is 50 gf / cm ² , and the DEF sensitivity is 20.

The heat-bonding nonwoven fabric containing the manifest crimpable composite short fiber of the present invention is characterized by a smooth and soft feel. In order to feel the smoothness and softness when touched, the average friction coefficient (MIU) and the variation of the average friction coefficient (MMD) are important among the characteristic values of the surface friction based on the KES. In the heat-bonded nonwoven fabric containing the actual crimpable composite short fibers of the present invention, the average friction coefficient MIU on the surface of the heat-bonded nonwoven fabric is preferably 0.3 or more and 0.6 or less. The average friction coefficient is 0.3 or more, that is, the friction is somewhat large compared to the conventional nonwoven fabric, and when the thermal adhesive nonwoven fabric touches the skin, appropriate friction and catching are created between the thermal adhesive nonwoven fabric and the skin, The tactile sensation feels “smooth” and “moist”. When the average friction coefficient is 0.6 or less, the average friction coefficient of the heat-bonded nonwoven fabric becomes too large, and the tactile sensation becomes worse (for example, the feeling of sticking to the skin or the tactile sensation due to excessive friction) Does not occur). The average friction coefficient (MIU) is more preferably from 0.3 to 0.5, and particularly preferably from 0.32 to 0.45. Next, it is preferable that the fluctuation | variation (MMD) of the average friction coefficient of the heat bonding nonwoven fabric surface containing the actual crimpable composite staple fiber of this invention is 0.016 or less. When the variation of the average friction coefficient is 0.016 or less, the surface of the nonwoven fabric is not rough, and the average friction coefficient MIU satisfies the above range, so that the heat-bonded nonwoven fabric is smooth and soft, It has a unique “feel of slimy”. The variation in the average friction coefficient is more preferably 0.015 or less. The lower limit of the average friction coefficient variation (MMD) is not particularly limited and is preferably closer to 0, but may be 0.001 or more.

The heat-bonding nonwoven fabric containing the actual crimpable composite short fiber of the present invention not only has a large initial bulk, but is soft and easily compressed when a load is applied. And when a load is removed or when a load becomes small, it repels and it has the characteristics that the bulk of a heat bondable nonwoven fabric recovers rapidly. In order to show these characteristics at the time of compression and compression release, LC, WC, RC, and EMC are important among the compression characteristic values based on the KES. In the heat-bonded nonwoven fabric containing the actual crimpable composite short fiber of the present invention, the compression hardness (LC) is preferably 0.64 or less. When the compression is 0.64 or less, there is no hardness during compression and a soft tactile sensation is obtained. The compression hardness (LC) is preferably 0.62 or less, and particularly preferably 0.6 or less. The lower limit value of the compression hardness (LC) is not particularly limited, but may be 0.15 or 0.2. The degree of compression (LC) is affected by the basis weight (g / m ² ) of the nonwoven fabric to be measured, and the nonwoven fabric with a larger basis weight may have a greater degree of compression. Therefore, even if it evaluates using the value which divided the value of compression hardness (LC) by the basis weight, ie, the compression hardness (LC) per unit basis weight (g / m < ² >), as a compression characteristic value of a heat bondable nonwoven fabric. Good. In the heat-bonded nonwoven fabric containing the actual crimpable composite short fibers of the present invention, the compression hardness (LC) per unit weight (g / m ² ) is preferably 0.013 or less, and more preferably 0.012 or less.

In the heat-bonded nonwoven fabric containing the actual crimpable composite short fiber of the present invention, the compression energy (WC) is preferably 1.0 gf · cm ² / cm ² or more. When the compression energy (WC) is 1.0 gf · cm ² / cm ² or more, the nonwoven fabric is greatly deformed when a load is applied, and the soft feeling is increased. The compression energy (WC) is more preferably 2.5 gf · cm ² / cm ² or more, particularly preferably 4.5 gf · cm ² / cm ² or more, and most preferably 5.1 gf · cm ² / cm ² or more. The upper limit of the compression energy is not particularly limited, but if it is greater than 8.0 gf · cm ² / cm ² , other compression characteristics may be affected, so it is preferably 8.0 gf · cm ² / cm ² or less. Preferably it is 6.0 gf · cm ² / cm ² or less.

In the heat-bonded nonwoven fabric containing the actual crimpable composite short fiber of the present invention, the compression resilience (RC) is preferably 58% or more. When the compression resilience is 58% or more, the heat-bonding nonwoven fabric is excellent in resilience, and when the load is reduced or the load is removed, the nonwoven fabric recovers the bulk following the load. In particular, by satisfying the preferable range of compression hardness (LC) and satisfying the preferable range of compression resilience (RC), it deforms softly with respect to compression and reduces the load to its original bulk, that is, the original shape. Try to return. For this reason, the thermal bonding nonwoven fabric becomes a nonwoven fabric that easily follows changes in the uneven parts of the body, and when this is used as a surface material for various sanitary materials, the surface material follows the changes in body movement and posture and compresses and recovers bulk. Therefore, it is easy to adhere to the body and brings about an advantage that a fit can be obtained. The upper limit of the compression resilience (RC) is not particularly limited, and may be 100%, 90%, or 85%.

In the heat-bonded nonwoven fabric containing the actual crimpable composite short fiber of the present invention, the compressibility (EMC) is preferably 70% to 98%. Here, the compression ratio, and _{T 0} is the thickness when the load is 0.5 gf / cm ^2, load using _{T M} is the thickness of the case of ^{50gf / cm 2, EMC (%} ) = 100 This is a compression characteristic value obtained by x (T ₀ -T _M ) / T ₀ . When the compression ratio is smaller than 70%, not only is the initial bulk small, but it is also difficult to deform against compression. When a load is applied to the heat-bonded nonwoven fabric, there is a proportion that can be deformed with an increase in load. There is a risk that the tactile sensation is small and intuitional. If the compression ratio is greater than 98%, it will be deformed too much when a load is applied, so that not only the shape maintainability tends to deteriorate, but also the heat-bonded nonwoven fabric will be crushed even with a small load, and a flat thin sheet shape There is a risk of becoming. In the heat-bonded nonwoven fabric using the actual crimpable composite short fiber of the present invention, the compressibility (EMC) is more preferably 72% to 95%, particularly preferably 75% to 90%, 78% Most preferred is ˜85%.

Since the fiber assembly of the present invention, particularly the nonwoven fabric, more particularly the heat-bonded nonwoven fabric, has good surface touch, flexibility and cushioning properties, the surface material of sanitary articles such as sanitary napkins and diapers, wet tissues, wipers, Suitable for applications such as cosmetic materials, female bra pads, shoulder pads, vehicle cushioning materials, flooring flooring backing materials, cushioning materials, and packaging materials.

In particular, the heat-bonding nonwoven fabric of the present invention is suitable for a surface material of a sanitary article, and the present invention can also be provided as a sanitary article in which the heat-bonding nonwoven fabric of the present invention is used as a surface material. The hygiene article is a product including an absorbent that can absorb blood, body fluid, feces, and urine discharged from the human body or animal, and refers to products such as disposable diapers, sanitary napkins, and urine leak pads. Also called. Since the surface material of these products is directly attached to a delicate part of the human body or animal, it is required to have superior characteristics not only on the surface touch but also on the flexibility and cushioning properties in the thickness direction. . As described above, the heat-bonded nonwoven fabric of the present invention is excellent in surface tactile sensation, flexibility, and bulk recovery property, and thus is suitable for constituting a sanitary article together with other members as a surface material.

When the heat-bonded nonwoven fabric of the present invention is used as the surface material of a sanitary article, the basis weight is preferably 10 g / m ² to 70 g / m ² , more preferably 15 g / m ² to 60 g / m ^2. . However, the basis weight may be outside these ranges depending on the type of sanitary article. Moreover, when using the thermobonding nonwoven fabric of this invention for another use, the fabric weight is suitably selected according to the use.

When the heat-bonded nonwoven fabric of the present invention is used as a surface material of a sanitary article, it is preferable to contain the sensible crimped composite short fiber in an amount of 20% by mass or more, more preferably 50% by mass or more, and more preferably 80% by mass or more. It is particularly preferable to contain it. When the ratio of the actual crimpable composite short fibers is within the above range, the surface material has not only surface touch, but also excellent flexibility and cushioning in the thickness direction, and functions required for the surface material such as rough skin prevention. It can be demonstrated.

[Examples 1 to 13, Comparative Examples 1 to 6]
(First ingredient)
The following were prepared as linear polyethylene (LLDPE), low density polyethylene (LDPE) and high density polyethylene (HDPE).
LLDPE-1: linear 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 118 ° C, hexene copolymerization, flexural modulus 280 MPa, hardness (HDD) 52)
LLDPE-2: linear polyethylene polymerized with a metallocene catalyst (manufactured by Ube Maruzen Polyethylene Co., Ltd., trade name “Umerit® 631J”, density 0.931 g / cm ³ , Q value 3.0, MI = 20 g / 10 min, melting point 120 ° C., hexene copolymerization, flexural modulus 600 MPa, hardness (HDD) 60)
LLDPE-3: linear polyethylene polymerized by metallocene catalyst (trade name “ASPUN® 6835A” manufactured by Dow Chemical Co., Ltd.), density 0.950 g / cm ³ , Q value 3.5, MI = 17 g / 10 min , Melting point 126 ° C., octene copolymerization)
LLDPE-4: Linear polyethylene polymerized by 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 g) / 10min, melting point 86 ° C, hexene copolymerization, flexural modulus 62MPa, hardness (HDD) 40)
LLDPE-5: linear polyethylene polymerized by Ziegler-Natta catalyst (manufactured by Nippon Polyethylene Co., Ltd., trade name “NOVATEC (registered trademark) UJ370T”, density 0.921 g / cm ³ , Q value 4.2, MI = 22 g / 10 min, melting point 121 ° C., hexene copolymerization, flexural modulus 180 MPa, hardness (HDD) 50)

LDPE-1: manufactured by Nippon Polyethylene Co., Ltd., trade name “NOVATEC (registered trademark) LJ802”, density 0.918 g / cm ³ , Q value 5.3, MI = 22 g / 10 min, melting point 106 ° C.
LDPE-2: “Novatec (registered trademark) LJ902” manufactured by Nippon Polyethylene Co., Ltd., density 0.915 g / cm ³ , Q value 5.3, MI = 45 g / 10 min, melting point 102 ° C.
LDPE-3: manufactured by Nippon Polyethylene Co., Ltd., “Novatech (registered trademark) LC720”, density 0.922 g / cm ³ , Q value 5.1, MI = 9.4 g / 10 min, melting point 110 ° C.
LDPE-4: manufactured by Ube Maruzen Polyethylene Co., Ltd., trade name “J2516”, density 0.916 g / cm ³ , MI = 25 g / 10 min, melting point 106 ° C.
LDPE-5: manufactured by Ube Maruzen Polyethylene Co., Ltd., trade name “J3519”, density 0.916 g / cm ³ , MI = 35 g / 10 min, melting point 108 ° C.
HDPE: manufactured by Nippon Polyethylene Co., Ltd., trade name “NOVATEC (registered trademark) HE481”, density 0.956 g / cm ³ , Q value 5.6, MI = 12 g / 10 min, melting point 133 ° C., flexural modulus 900 MPa, hardness (HDD) 64

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

Using the polymers shown in Table 1-1 to Table 1-3 as the first component (mixing ratio (mass) in parentheses), and using the above trade name “T200E” as the second component, Using an eccentric sheath / core composite nozzle (600 holes) as the component, the composite ratio (volume ratio) of the first component / second component is 55/45, the spinning temperature of the sheath component is 260 ° C., and the spinning temperature of the core component is Melt extrusion was performed at 300 ° C. and a nozzle temperature of 290 ° C. to obtain a spun filament having an eccentricity of 25% and a fineness of 6.8 dtex. During melt extrusion, the discharge rate was 250 g / min, and the take-up speed was 615 m / min.

The obtained spinning filament was drawn 2.6 times in hot water at 80 ° C. to obtain a drawn filament having a fineness of about 3.3 dtex. Next, 0.3% by mass of an oil agent obtained by blending a C8 alkyl phosphate potassium salt and a C12 alkyl phosphate potassium salt in a ratio of 35:65 was added as a fiber treatment agent, and then the stretched filament was machined with a stuffing box type crimper. Crimps were applied to 12 pieces / 25 mm. And the annealing process and the drying process were simultaneously performed in the relaxed state for about 15 minutes with the hot air spraying apparatus set to 100 degreeC. Thereafter, the filament was cut into a fiber length of 51 mm to obtain an actual crimpable composite short fiber.
In any of Examples and Comparative Examples, the spinnability and stretchability were good.

A fiber web having a basis weight of about 50 g / m ² was produced from the obtained fiber using a roller type card machine. This fiber web was subjected to heat treatment for 10 seconds using a hot air spraying device set at a temperature 10 ° C. higher than the melting point of LLDPE (only HDPE in Comparative Example 6) constituting the first component of each fiber, The components were melted to obtain a heat bonded nonwoven fabric. However, in Example 2, Example 6 and Comparative Example 1, nonwoven fabrics heat-treated at 123 ° C. and 138 ° C. were also produced.

The following evaluation was implemented about the actual crimpable composite staple fiber and the heat bonding nonwoven fabric which were obtained.
[Crimp expression]
The fibers after annealing were observed for crimping and evaluated according to the following criteria.
A: A good three-dimensional crimp is recognized.
B: Corrugated crimp with a large crimp depth is observed.
C: A wave-shaped crimp is observed, but the length between the peaks is larger than the crimp depth.
D: Only serrated crimps imparted by mechanical crimps are observed.

[Number of crimps, crimp ratio]
It measured according to JIS L 1015 (2010).

[Nonwoven fabric bulk]
The thickness of 10 sheets of samples obtained by cutting a nonwoven fabric into a size of 100 mm × 100 mm was measured without applying a load, and this was defined as the bulk of the nonwoven fabric.

[Bulk after compression]
The thickness was measured at the time when a load of 5 kgf (49 N) was applied and 10 minutes passed after a sample of 10 sheets of nonwoven fabric cut to a size of 100 mm × 100 mm was applied, and this was taken as the bulk after compression.

[Bulk change rate]
Based on the measured volume of nonwoven fabric and volume after compression, the volume change rate (%) = [(volume of nonwoven fabric−volume after compression) / volume of nonwoven fabric)] × 100 was calculated.

[Surface feel]
The surface of the nonwoven fabric was touched and evaluated according to the following evaluation criteria.
A: Very smooth.
B: I feel a little rough.
C: It is rough.

[Shrinkage / formation]
Fabricate a fiber web of 30g / m ² with a vertical and horizontal width of 200mm x 200mm using a roller card machine, and set it to a temperature 10 ° C higher than the melting point of LLDPE constituting the first component of each fiber. Using the hot air spraying apparatus, heat treatment was performed for 1 minute, the vertical and horizontal dimensions of the web after the heat treatment were measured, and the web area shrinkage was determined according to the following formula.

Furthermore, the formation of the web after heat treatment was observed and evaluated according to the following criteria together with the web area shrinkage.
A: The shrinkage ratio of the web area was less than 3%, and the web surface (surface on which hot air was blown) was also smooth.
B: The shrinkage ratio of the web area was 5% or less, and the web surface (the surface on which the hot air was blown) was slightly uneven.
C: The web area shrinkage rate exceeded 5%, and the unevenness was conspicuous on the web surface (the surface on which the hot air was blown).

[Bulk recovery]
A load of 5 kgf (49 N) was applied to a stack of 10 samples obtained by cutting the nonwoven fabric into a size of 100 mm × 100 mm and left for 12 hours, and the thickness after 10 minutes of dewetting was measured. Furthermore, the bulk recovery rate was calculated from the obtained thickness and the nonwoven fabric bulk according to the formula: bulk recovery rate (%) = (thickness after dewetting / nonwoven fabric bulk) × 100.

[Strong nonwoven fabric]
The width of the specimen is measured using a constant speed tension type tensile tester in accordance with JIS L 1096 (2010) 6.12.1 A method (strip method), with the horizontal direction (CD direction) of the nonwoven fabric as the tensile direction. A tensile test was performed under the conditions of 5 cm, gripping interval 10 cm, and tensile speed 30 ± 2 cm / min, and the load value at the time of cutting was measured.

The performance of the fibers and nonwoven fabrics obtained in each Example and each Comparative Example is shown in Table 1-1 to Table 1-3.

As shown in Table 1-1 to Table 1-3, non-woven fabrics made of composite short fibers whose sheath component is composed only of linear polyethylene or composite short fibers whose sheath component is composed only of high-density polyethylene (Comparative Example 1 In all of 3 to 6), the bulk change rate was small, and the flexibility in the thickness direction was inferior. The nonwoven fabric composed of the composite short fibers of Comparative Example 6 was also inferior in surface tactile sensation. When linear low density polyethylene having a density of less than 0.90 g / cm ³ or exceeding 0.94 g / cm ³ is used, low density polyethylene is mixed to form a composite short fiber. Even so, the non-woven fabric produced therefrom did not give a good surface feel (Comparative Example 4), or did not show satisfactory properties in terms of bulkiness and bulk recovery rate (Comparative Example 5).

Any non-woven fabric made of composite short fibers in which a sheath component is formed by mixing linear low density polyethylene having a density in the range of 0.90 g / cm ³ to 0.94 g / cm ³ with low density polyethylene, It was bulky and exhibited good flexibility (small bulk change rate) in the thickness direction (Examples 1 to 13). In Examples 1 and 9, the evaluation of shrinkage / formation was low because the mixing ratio of the low density polyethylene was small, but in other respects it showed good characteristics and was sufficiently practical for some applications Met.

From the comparison between Example 6 and Comparative Example 2, the addition of low-density polyethylene not only contributes to the improvement in bulkiness, flexibility in the thickness direction, and bulk recovery, but also contributes to the improvement in the surface feel of the nonwoven fabric. You can see that This indicates that the low density polyethylene functions as a flexible component that contributes to an improvement in tactile feel of the linear polyethylene having a relatively high density.

For the nonwoven fabric of Example 5, the nonwoven fabric liquid absorption and liquid passage performance were measured by the following methods in order to confirm the effect as a surface material.

[Run-off]
(1) A nonwoven fabric is cut | disconnected so that a vertical direction (machine direction) x horizontal direction may be 18 cm x 7 cm, and a sample is prepared.
(2) This sample is placed on a support base having a substantially vertical isosceles triangle cross section having a slope whose vertical direction and horizontal plane form an angle of 45 degrees, and “Kim Towel” (registered by Nippon Paper Crecia Co., Ltd.) First, a stack of four "trademarks""is laid, and a nonwoven fabric sample is placed thereon and fixed.
(3) From the position of the upper end of the nonwoven fabric surface, 6 g of physiological saline is dropped at a rate of 1 g / 10 sec with a microtube pump or burette, and all the poured physiological saline is absorbed by the nonwoven fabric, and the physiological saline The position at which the water droplet disappeared from the nonwoven fabric surface is measured, and the distance between the position and the position at which the physiological saline solution is dropped on the nonwoven fabric surface is determined.

[Liquid absorption speed, liquid remaining amount, reversal amount]
(1) In order to measure the liquid absorption speed, the remaining liquid amount, and the return amount, the following articles were prepared.
Absorbent: 2 sets of Kim Towel (registered trademark) Plate with injection cylinder (inner diameter 1 cm below the cylinder)
Artificial menstrual blood (viscosity 8MPa ・ s)
Filter paper (ADVANTEC (registered trademark) No. 2 manufactured by Toyo Filter Paper Co., Ltd.) 10cm x 10cm
Weight (5kg, 287g x 2)
(2) Method The liquid absorption speed, the remaining liquid amount, and the reverse amount were measured according to the following procedure.
(I) A nonwoven fabric sample is placed on two sets of Kim Towel (registered trademark), a plate with an injection tube is placed thereon, and weights of 287 g are placed on both ends of the plate.
(Ii) Inject 5 ml of artificial menstrual blood from the tube. At this time, the time (liquid absorption time) until artificial menstrual blood becomes invisible from the nonwoven fabric surface (artificial menstrual blood is no longer confirmed as a liquid) is measured, and this is defined as the liquid absorption speed.
(Iii) Remove the plate and let stand for 10 minutes.
(Iv) After 10 minutes, sandwich the nonwoven fabric with filter paper (8 sheets), suck the artificial menstrual blood remaining on the nonwoven fabric into the filter paper, and weigh the mass of the filter paper (filter paper and artificial menstrual blood before absorbing artificial menstrual blood) The difference in the mass of the filter paper after absorbing water corresponds to the remaining liquid amount).
(V) Return the nonwoven fabric to the absorbent body, and newly place a filter paper (8 sheets) on the nonwoven fabric and place a 5 kg weight for 10 seconds. Thereafter, the mass of the filter paper is measured (the difference in mass between the filter paper before being placed on the non-woven fabric and the filter paper after placing the weight on the non-woven fabric corresponds to the reverse amount).
(Vi) Return to (i) above and perform the second measurement.

Table 2 shows the measured liquid absorption speed, liquid remaining amount, and reverse return amount.

As shown in Table 2, the nonwoven fabric of Example 5 has a function of allowing artificial menstrual blood to pass through and absorbing it under the absorbent body, and also in terms of liquid residue and liquid return, the surface of the sanitary article. It was a practical material.

[Surface characteristics and compression characteristics Evaluation by KES]
Using the fibers obtained in Examples 2 and 6 and Comparative Examples 1 and 6, fiber webs having a basis weight of about 50 g / m ² were produced with a roller card machine. The obtained card web is 10 ° C. higher than the melting point of LLDPE or HDPE constituting the first component of each fiber (Example 2: 128 ° C., Example 6: 130 ° C., Comparative Example 1: 128 ° C., Comparison) Example 6: Using a hot air spraying device set at 140 ° C., the hot air treatment was performed for 1 minute, and the first component was melted to obtain a heat-bonded nonwoven fabric.

In order to evaluate the surface touch and thickness direction flexibility, bulkiness, and bulk recovery (elasticity) of each obtained heat-bonded nonwoven fabric, surface properties and compression properties based on KES (Kawabata Evaluation System) Measurement and evaluation were performed.

Specifically, in order to evaluate the surface characteristics, a surface friction test of the heat-bonded nonwoven fabric was performed, and the average friction coefficient (MIU) and the average friction coefficient fluctuation (MMD) were measured as the surface characteristic values. A KES-SE® friction tester manufactured by Kato Tech Co., Ltd. was used for the test and measurement of surface friction on the heat-bonded nonwoven fabric. At the time of measurement, the measurement surface is a surface to which the hot-bonded nonwoven fabric is blown with hot air during manufacture, a static load is applied to the friction element, 25 gf, the friction element is parallel to the vertical direction of the nonwoven fabric, and the moving speed is 1 mm / sec. It was moved under conditions to measure MIU and MMD of the heat-bonding nonwoven fabric.

In order to evaluate the compression characteristics of the heat-bonded nonwoven fabric, specifically, a compression test is performed on the heat-bonded nonwoven fabric, and the compression hardness (LC), compression energy (WC), and compression are calculated from the load-displacement curve. Resilience (RC), T ₀ (thickness at a load of 0.5 gf / cm ² ), T _M (thickness at a load of 50 gf / cm ² ), and compressibility (EMC) were measured. A KES-G5 handy compression tester manufactured by Kato Tech Co., Ltd. was used for the compression test and measurement of the compression characteristic value for the heat-bonded nonwoven fabric. At the time of measurement, a circular pressure plate having an area of 2 cm ² is used as a compressor, SENS is set to 2, and DEF sensitivity is set to 20, so that the compression speed of the compressor is 0.02 cm / sec with respect to the heat-bonded nonwoven fabric. And compressed until the load reached 50 gf / cm ² . After the load reached 50 gf / cm ² , the compression characteristic value was measured by removing compression so that the moving speed of the compressor was 0.02 cm / sec. Table 3 shows the measurement results.

In the results of the surface characteristics and compression characteristics based on KES shown in Table 3, when comparing the compression characteristics of Example 2 and Example 6 with Comparative Example 6, the nonwoven fabrics of Examples 2 and 6 have an LC of Comparative Example 6. It is smaller and RC and EMC are larger than the nonwoven fabric of the comparative example 6. This is because the first component of the actual crimpable composite short fiber used in Examples 2 and 6 contains linear polyethylene having a bending elastic modulus smaller than that of high-density polyethylene as a resin component. By using linear polyethylene, a thermobonding nonwoven fabric that has a small LC and is softly deformed with respect to the load can be obtained. Moreover, since the bending elastic modulus of linear polyethylene is small, in order to deform | transform more largely with respect to a load, it is thought that EMC became large. That is, it is considered that the non-woven fabric containing the actual crimpable composite short fiber of the present invention is softly deformed with respect to the load in the thickness direction and has a large amount of deformation, so that it becomes a heat-bonding non-woven fabric having a soft feeling. In addition, the heat-bonding nonwoven fabric composed of the actual crimpable composite short fiber composed of a resin component containing a large amount of linear polyethylene as the first component (including Comparative Example 1) has a RC higher than that of Comparative Example 6. Since it is large, linear polyethylene itself is more elastic than high-density polyethylene, and is presumed to be a flexible resin.

Comparing the nonwoven fabric of Example 2 and Example 6 with the nonwoven fabric of Comparative Example 1, the nonwoven fabric of Comparative Example 1 has an RC equivalent to that of Example 6 that is considered to be affected only by linear polyethylene. , LC is increased, and WC and EMC are smaller than those in Examples 2 and 6. Since the nonwoven fabric of Comparative Example 1 has a small specific volume, that is, a nonwoven fabric having a small initial volume and a large density, it is presumed that the nonwoven fabric has a soft feeling without being deformed with respect to compression in the thickness direction. .

Comparing the surface properties of the nonwoven fabrics of Example 2 and Example 6 and the nonwoven fabrics of Comparative Examples 1 and 6, the nonwoven fabrics of Examples 2 and 6 have a large MIU representing the difficulty of slipping on the surface of the nonwoven fabric. The surface is difficult to slip. On the other hand, the MMD representing the roughness of the nonwoven fabric surface is smaller in the nonwoven fabrics of Examples 2 and 6. From this result, the nonwoven fabric using crimped composite short fibers composed of a resin component containing linear polyethylene and low density polyethylene satisfying a specific density range of the first component has a large MIU on the surface of the nonwoven fabric, MMD is small. For this reason, this non-woven fabric has an appropriate friction against the skin, and when the skin touches, the frictional force works between the non-woven fabric and gives the sensation that the non-woven fabric sticks to the skin. That is, since there is no roughness, the tactile sensation becomes smooth and gives a unique and comfortable tactile sensation (smoothness and moist feeling).

In the nonwoven fabrics of Comparative Examples 1 and 6, the average friction coefficient MMD is large. MMD, that is, the roughness of the surface of the nonwoven fabric is not only influenced by the surface of the fibers constituting the surface of the nonwoven fabric, but also the ease of movement of the fibers when the skin or friction tester moving on the surface of the nonwoven fabric (ease of deformation) ) Is also affected. Therefore, it is considered that the more difficult the fibers are to be deformed, the less the fibers on the surface move with respect to the movement of the skin and the friction element, and the greater the force required for the skin and the friction elements to move and move the fibers. The nonwoven fabric of Comparative Example 6 is a fiber that is difficult to deform, in which the first component of the actual crimpable composite short fiber that the nonwoven fabric comprises is composed of high-density polyethylene having a large flexural modulus, thereby preventing skin and friction It is presumed that the force required for movement momentarily increases and the MMD increases. Further, the nonwoven fabric of Comparative Example 1 is presumed to be a fiber that easily deforms because the first component of the actual crimpable composite short fiber constituting the nonwoven fabric is composed of linear polyethylene. Since the nonwoven fabric has a small specific volume (in other words, a high density), the number of fibers constituting the nonwoven fabric surface is increasing. Therefore, when the skin and friction elements are moved in the nonwoven fabric of Comparative Example 1, many fibers are present in the skin and friction elements compared to the nonwoven fabrics of Examples 2 and 6 (the specific volume is larger and the density is smaller). It is estimated that the MMD has increased because the force necessary for moving the skin and the frictional momentary momentary increases.

The actual crimpable composite short fiber of the present invention is flexible and excellent in processability (especially high-speed card property). When made into a nonwoven fabric, the nonwoven fabric has a good surface feel, bulkiness and thickness direction. Gives flexibility and bulk recovery. Therefore, the actual crimpable composite short fiber of the present invention is particularly suitable for constituting the surface material of a hygiene article, and other fiber products such as wet tissue, wipers, cosmetic materials, and female bra pads. Suitable for constituting shoulder pads, vehicle cushioning materials, flooring flooring backing materials, cushioning materials, and packaging materials.

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 (9)

1. A composite short fiber comprising a first component and a second component,
   The first component includes linear polyethylene having a density of 0.90 g / cm ³ to 0.94 g / cm ³ and low density polyethylene,
   In the first component, the low density polyethylene is included so as to occupy 5% by mass to 25% by mass of the total mass of the linear polyethylene and the low density polyethylene,
   The second component contains 50% by mass or more of polyester having a melting point 40 ° C. or higher than the melting point of the linear polyethylene constituting the first component,
   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,
   The composite short fiber has at least one kind of crimp selected from a wave crimp and a spiral crimp,
   Obvious crimpable composite staple fiber.
2. 2. The actual crimpable composite short fiber according to claim 1, wherein the linear polyethylene is polymerized using a metallocene catalyst.
3. 3. The actual crimpable composite short fiber according to claim 1 or 2, wherein a melting point of the linear polyethylene before spinning is higher than a melting point of the low density polyethylene before spinning.
4. When measuring the number of crimps and the crimp rate according to JIS L 1015 (2010) in the composite short fiber, the ratio of the crimp rate to the number of crimps (crimp rate / crimp number) is 1.2 or less. The actual crimpable composite staple fiber according to any one of claims 1 to 3, wherein
5. A method for producing a composite short fiber comprising a first component and a second component,
   5% by mass of the total mass of the linear polyethylene and the low density polyethylene, the linear polyethylene having a density of 0.90 g / cm ³ to 0.94 g / cm ³ and the low density polyethylene. A first component occupying ~ 25% by weight;
   A second component containing 50% by mass or more of a polyester having a melting point of 40 ° C. or higher than the melting point of the linear polyethylene constituting the first component;
   In the fiber cross section, the first component occupies at least 20% of the fiber surface, and melt spinning to obtain a spun filament so that the center of gravity of the second component deviates from the center of gravity of the fiber,
   The spinning filament is at a temperature within the range of Tg ₂ ° C. to 95 ° C. (where Tg ₂ is the glass transition point of the polymer component having the highest glass transition point among the polymer components contained in the second component). Stretching up to 5 times,
   Applying a mechanical crimp to the stretched filament in the range of 5/25 mm to 25/25 mm
   Performing an annealing treatment at a temperature within a range of 50 to 115 ° C .;
   A method for producing a composite short fiber having at least one kind of crimp selected from corrugated crimps and spiral crimps, comprising cutting an annealed filament into a length of 1 mm to 100 mm.
6. A fiber assembly containing 20% by mass or more of the actual crimpable composite short fiber according to any one of claims 1 to 4.
7. The fiber assembly according to claim 6, which is a non-woven fabric in which fibers are thermally bonded to each other by the first component of the actual crimpable composite short fiber.
8. A sanitary article surface material comprising the fiber assembly according to claim 6 or 7.
9. A sanitary article comprising the surface material according to claim 8.

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