JP2011226002A - Composite fiber of crypto-irregular sheath core and non-woven fabric comprising the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a non-woven fabric which has a high effect of improving touch feeling, draping, soft and bulkiness feeling as well as diffusing water (high spreading), and a sheath core type composite fiber having a wide range of fineness.SOLUTION: A composite fiber of crypto-irregular sheath core is a composite fiber comprising: a sheath part made from a resin composition (A) comprising a polyolefin resin (a) and a noncrystalline resin (b); and a core part comprising a thermoplastic resin (B) in which a melting point of the polyolefin resin (a) is lower than that of the thermoplastic resin (B) and a glass transition point (Tg) of the noncrystalline resin (b) is higher than that of the polyolefin resin (a), and the irregular shape on the surface of the sheath part can be formed by heat treatment of the composite fiber.

Description

  The present invention provides a latent concavo-convex sheath-core composite fiber capable of forming a concavo-convex shape on the surface of a sheath portion by heat treatment, a nonwoven fabric having concavo-convex on the fiber surface using the same, and the latent concavo-convex sheath-core composite fiber. The present invention relates to an effective manufacturing method.

  Since a nonwoven fabric can generally be manufactured directly from fibers without passing through a spinning process or a twisting process, the manufacturing process is simpler than that of a woven fabric or a knitted fabric. Nonwoven fabrics having such advantages are widely used for sanitary materials and daily necessities. Among these nonwoven fabrics, polypropylene-based nonwoven fabrics are used, for example, as surface materials for paper diapers and napkins, simple wipers, separators for secondary batteries, filters (filter materials), and the like. In such a nonwoven fabric, a composite fiber having a sheath-core structure, for example, a sheath-core composite fiber having a polypropylene resin as a core material and a polyethylene resin as a sheath material is used. The sheath-core composite fiber is usually subjected to a stretching treatment in order to increase the strength.

In addition, as a method for producing a short fiber nonwoven fabric, a thermal bonding composite fiber is aligned using a card machine, laminated and entangled so as to have a predetermined basis weight, and then heat treated to fuse the fibers together. Thus, a method of forming a nonwoven fabric is known.
The heat-adhesive conjugate fiber can be made into a nonwoven fabric relatively easily by hot air or heat from a heat roller without using an adhesive. As such a heat-adhesive conjugate fiber, various types have been developed so far, for example, a heterogeneous polymer sheath-core type conjugate fiber such as a polyethylene-polypropylene conjugate fiber and a polyethylene-polyethylene terephthalate conjugate fiber, and a copolyester. -Various fibers have been developed, such as homogeneous polymer sheath-core composite fibers such as polyethylene terephthalate composite fibers. Moreover, when obtaining the nonwoven fabric which uses a heat bondable sheath-core type composite fiber as a material, the hot-air fusion method and the hot roll fusion method are properly used depending on the use of the nonwoven fabric. That is, the hot air fusion method is generally employed when emphasizing the tactile sensation and texture of the obtained nonwoven fabric, and the hot roll fusion method is employed when emphasizing the strength of the obtained nonwoven fabric.
By the way, the most commonly used nonwoven fabric made of polyethylene-polypropylene-based sheath-core type composite fibers has a problem that it has a peculiar slip feeling and a tactile sensation and a texture that is not good. A good non-woven fabric is required.

  Conventionally, it has been proposed to provide irregularities on the fiber surface for the purpose of improving the touch and texture of woven and non-woven fabrics, soft feeling, and swelling. For example, (1) a polyester composition containing 20 to 50% by mass of a poly (meth) acrylate-based resin and a polyester substantially free of a poly (meth) acrylate-based resin having a mass ratio of 3:97 to 40:60 The composite spinning is carried out at a rate of 3,500 m / min or less, and the obtained undrawn yarn is drawn to a maximum draw ratio of 0.62 to 0.91 times at a drawing temperature of 55 to 95 ° C. (2) A non-woven fabric composed of a composite long fiber composed of at least a non-elastomeric resin and an elastomer resin, wherein the composite long fiber is The composite long fiber has a non-elastomeric resin / elastomeric resin volume ratio (%) in the range of 30/70 to 5/95, and has a fineness of the composite long fiber. An elastic long-fiber nonwoven fabric characterized by being dTex or less (see, for example, Patent Document 2), (3) Polyester [A] having a melt viscosity of 100 Pa · s or more when discharging a spinning stock solution from a spinneret is a sheath component Polyester [B] of 20 Pa · s or less is used as a core component, and the difference in melt viscosity between the polyesters [A] and [B] is greater than 100 Pa · s and less than 350 Pa · s, and is due to the thickness of the core. A multifilament yarn made of a composite fiber that is thick and thin, and a special spotted yarn (see, for example, Patent Document 3) having a fineness portion of 15 pieces / m or more in the length direction of the yarn is disclosed. ing.

  On the other hand, Patent Document 4 discloses that, in the case of a modified cross-section fiber having a continuous groove in the vertical direction, a capillary phenomenon appears in the groove and the effect of diffusing water (large bleeding) is increased. Yes.

JP 2001-164428 A JP 2004-250795 A JP-A-8-188925 WO2009 / 150745 pamphlet

However, the composite fiber having irregularities on the surface described in Patent Document 1 does not use a polyolefin-based resin for both the core component and the sheath component, and is made of a polyester-based resin composition. This is a technique that regulates the draw ratio with respect to the temperature and the maximum draw ratio, and causes the sheath component to exhibit irregularities.
The elastic long-fiber non-woven fabric described in Patent Document 2 is a composite fiber composed of an elastomer resin such as styrene-ethylene-butylene-styrene block copolymer (SEBS) and a non-elastomeric resin such as a polypropylene resin. And a non-elastomeric resin / elastomer resin volume ratio of the composite fiber, a fineness of the composite fiber of 5 dTex or less, and a composite long fiber having a helical structure and an uneven structure formed on the surface. It is the comprised nonwoven fabric.
Further, the special patch described in Patent Document 3 has polyester [A] having a melt viscosity defined as a sheath component, polyester [B] as a core component, and the melt viscosity of polyesters [A] and [B]. It is a multifilament yarn made of a composite fiber that has a difference due to the thickness of the core portion and is caused by the thickness of the core.
In these techniques, all are techniques for forming irregularities on the surface of the composite fiber itself, and high-speed spinning is essential, can only be applied to thin fibers, and the resulting irregularities are relatively small. It was a thing.

The technique described in Patent Document 4 includes a sheath-core type polyester fiber of 20% by mass or more, and the polyester fiber contains ethylene glycol in the sheath part, and is a variant that defines the mass ratio of the sheath part / core part. This is a technique for providing a water-absorbing quick-drying woven or knitted fabric using cross-sectional fibers. And, in the case of a modified cross-section fiber having a continuous groove in the longitudinal direction, a capillary phenomenon appears in the groove, and the woven or knitted fabric using the modified cross-section fiber has a large effect of diffusing water (large bleeding). It is disclosed.
However, when producing a non-woven fabric using this modified cross-section fiber, it is preferably a heat-bonded composite fiber. It turns out that the nozzle for manufacturing is expensive and leads to high costs, and the sheath component melts and aggregates at the time of heat fusion, so it is difficult to form a sharp shape, and the capillarity manifesting power of the obtained nonwoven fabric is relatively small It was.

  The present invention has been made under such circumstances, and improves the tactile sensation, texture, soft feeling and swelling feeling, and can provide a non-woven composite having a great effect of diffusing water (large bleeding). An object of the present invention is to provide a fiber, a nonwoven fabric obtained therefrom, and an effective method for producing the sheath-core type composite fiber.

As a result of intensive studies to achieve the above object, the present inventor obtained the following knowledge. (1) As the sheath-core type composite fiber, the sheath portion is composed of a resin composition including a polyolefin resin and an amorphous resin, the core portion includes a thermoplastic resin, and the melting point of the polyolefin resin. When the amorphous resin has a glass transition point (Tg) and a melting point of the thermoplastic resin satisfying a specific relationship, the composite fiber has an irregular shape on the surface of the sheath by heat treatment. It can be formed, that is, it is a latent concavo-convex sheath-core composite fiber, (2) The latent concavo-convex sheath-core composite fiber has a wide range of fineness of about 1 to 5000 dTex because the principle is clear. (3) Heat treatment of the nonwoven fabric obtained from the latent concavo-convex sheath-core composite fiber yields a nonwoven fabric having a concavo-convex shape on the surface of the sheath portion, which can be adapted to the above-mentioned purpose. (4 The nonwoven fabric having the uneven shape can obtain the same effect as the water-absorbing quick-drying woven or knitted fabric described in Patent Document 4, for example, by attaching a surfactant having a high water absorption rate to form a paper diaper (configuration of paper diaper: top / medium / When used as a second sheet (bottom = top sheet / second sheet / absorber), the urine diffusion performance is improved, and the urine can be efficiently diffused and absorbed by the absorber disposed on the lower surface. (5) Since the conventional round cross-section nozzle can be used as it is for spinning the latent uneven sheath-core composite fiber, it is advantageous in cost. (6) The latent uneven sheath-core composite fiber is the above (1). It has been found that production can be efficiently carried out by using the indicated raw materials and subjecting to a specific melt spinning step and a hot drawing step.
The present invention has been completed based on such findings.

That is, the present invention
[1] A composite fiber composed of a sheath part made of a resin composition (A) containing a polyolefin resin (a) and an amorphous resin (b) and a core part containing a thermoplastic resin (B). The melting point of the polyolefin resin (a) is lower than the melting point of the thermoplastic resin (B), and the glass transition point (Tg) of the amorphous resin (b) is higher than the melting point of the polyolefin resin (a). A latent concavo-convex sheath-core composite fiber capable of forming a concavo-convex shape on the surface of the sheath by heat-treating the composite fiber,
[2] The latent uneven sheath-core composite fiber according to [1], wherein the thermoplastic resin (B) is crystalline polypropylene and the polyolefin resin (a) is high-density polyethylene,
[3] The latent uneven sheath-core composite fiber according to [1] or [2], wherein the amorphous resin (b) is a cyclic olefin copolymer and / or polycarbonate.
[4] The latent uneven sheath-core composite fiber according to [3], wherein the amorphous resin (b) is a cyclic olefin copolymer,
[5] In the above [1] to [4], the content ratio of the polyolefin resin (a) and the amorphous resin (b) in the resin composition (A) is 97: 3 to 70:30 by mass ratio. The latent uneven sheath-core composite fiber according to any one of the above,
[6] A non-woven fabric obtained from the latent uneven sheath-core composite fiber according to any one of [1] to [5] is heat-treated to express unevenness on the surface of the sheath portion. Nonwoven fabric,
[7] The nonwoven fabric according to [6], wherein the heat treatment is performed at a temperature equal to or higher than the melting point of the polyolefin resin (a) and at or near the glass transition point (Tg) of the amorphous resin (b). And [8] a polyolefin-based resin comprising a sheath part made of a resin composition (A) containing a polyolefin resin (a) and an amorphous resin (b), and a core part containing a thermoplastic resin (B). A resin composition (A) having a melting point of the resin (a) lower than the melting point of the thermoplastic resin (B) and the glass transition point (Tg) of the amorphous resin (b) is used as a sheath, and the thermoplastic resin (B) A step of melt-spinning the sheath-core composite fiber with the core as the core, and heat-stretching at a temperature not lower than the Tg of the polyolefin resin (a) and not higher than the melting point, and not higher than the Tg of the amorphous resin (b). A process for producing a latent concavo-convex sheath-core composite fiber, comprising:
Is to provide.

  INDUSTRIAL APPLICABILITY According to the present invention, a latent concavo-convex sheath-core composite fiber having a wide range of fineness capable of producing a non-woven fabric that improves tactile sensation, texture, soft sensation, and swell sensation and has a large effect of diffusing water (large bleeding) In addition, it is possible to provide an effective method for producing the nonwoven fabric obtained therefrom and the latent concavo-convex sheath-core composite fiber.

2 is a SEM photograph of a sheath-core composite unstretched fiber in Example 1. 2 is a SEM photograph of a sheath-core composite drawn fiber in Example 1. It is a SEM photograph of the sheath core conjugate fiber which constitutes the hot air fusion nonwoven fabric in Example 1. 4 is an SEM photograph of sheath core composite unstretched fiber in Example 2. 4 is a SEM photograph of a sheath-core composite drawn fiber in Example 2. It is a SEM photograph of the sheath core conjugate fiber which constitutes the hot air fusion nonwoven fabric in Example 2. It is a transmission optical microscope photograph of the sheath-core composite fiber which comprises the hot air fusion | melting nonwoven fabric in Example 2. FIG. 3 is a SEM photograph of a sheath core composite unstretched fiber in Comparative Example 1. 4 is a SEM photograph of a sheath-core composite stretched fiber in Comparative Example 1. It is a SEM photograph of the sheath core composite fiber which constitutes the hot air fusion nonwoven fabric in comparative example 1. It is an optical microscope photograph of the sheath-core composite fiber which comprises the hot air fusion nonwoven fabric in the comparative example 3.

First, the latent uneven sheath-core composite fiber of the present invention will be described.
The latent concavo-convex sheath-core composite fiber of the present invention includes a sheath portion made of a resin composition (A) containing a polyolefin resin (a) and an amorphous resin (b), and a core containing a thermoplastic resin (B). The melting point of the polyolefin resin (a) is lower than the melting point of the thermoplastic resin (B), and the glass transition point (Tg) of the amorphous resin (b) is the polyolefin resin. It is higher than the melting point of (a), and is characterized in that an uneven shape is formed on the surface of the sheath portion by heat-treating the composite fiber.

In the present invention, “to form irregularities on the surface of the sheath” means to form irregular irregularities on the surface of the sheath. This irregular unevenness appears due to the fact that the thickness of the sheath part is nonuniform in the fiber axis direction and the fiber circumferential direction, and randomly changes. About the thickness of a sheath part here, also about the location where a sheath part does not exist, ie, the location where the core part is exposed, thickness is included as zero. Therefore, when irregularities are formed, the fiber diameter of the sheath-core composite fiber is such that the diameter of the core portion is L ₀ and the fiber diameter of the portion where the thickness of the sheath portion is maximum is L _1. The direction changes randomly in the range of L _{0 to} L ₁ . Moreover, the radius of the core is "L _0/2", the fiber radius of the portion where the thickness of the sheath is the largest and "L _1/2", in the fiber circumferential direction, of the sheath-core composite fibers fiber radius varies randomly in the range of "L ₀ / 2~L _1/2".
In addition, although the case where the cross section of a core part and a sheath core composite fiber is circular was demonstrated here, these cross sections do not need to be circular. When the cross-section of the core and sheath-core composite fiber is non-circular, the diameter of the core and the fiber diameter of the sheath-core composite fiber can be interpreted as the diameter and fiber diameter of a virtual circle corresponding to the cross-sectional area. Good.

[Material for sheath]
In the latent concavo-convex sheath-core composite fiber of the present invention, a polyolefin resin (a) and an amorphous resin (b) are used as a material constituting the sheath (hereinafter sometimes referred to as a sheath material). The resin composition (A) formed in combination is used.
(Polyolefin resin (a))
The polyolefin resin (a) used as one component of the sheath material has a melting point lower than that of the thermoplastic resin (B) used as the material constituting the core portion, and is used in combination as a component of the sheath material. It needs to be lower than the glass transition point (Tg) of the amorphous resin (b). When the melting point of the polyolefin-based resin (a) does not satisfy the above-mentioned conditions, it is difficult to obtain a sheath-core composite fiber having thermal adhesiveness, and it is difficult to produce a nonwoven fabric by a hot-air fusion method. However, irregular irregularities are hardly formed on the surface of the sheath.
The polyolefin-based resin (a) is not particularly limited as long as it has the properties described above. For example, an ethylene-based polymer such as high-density, medium-density, low-density polyethylene or linear low-density polyethylene, A copolymer of propylene and another α-olefin, specifically, a non-crystalline propylene-based heavy polymer such as propylene-butene-1 random copolymer, propylene-ethylene-butene-1 random copolymer, or soft polypropylene. Examples thereof include polymer and poly-4-methylpentene-1. These polyolefin resin (a) may be used individually by 1 type, and may be used in combination of 2 or more type.
Among these, high-density polyethylene (melting point of about 130 ° C.) is preferable in consideration of spinnability and cost.

(Amorphous resin (b))
As a component of the sheath material, the amorphous resin (b) used in combination with the polyolefin resin (a) described above has a glass transition point (Tg) higher than the melting point of the polyolefin resin (a) described above. It takes a thing. The reason is as described in the polyolefin resin (a).
Examples of the amorphous resin (b) include cyclic olefin polymers and polycarbonate.
Examples of the cyclic olefin polymer include a cyclic olefin copolymer that is a copolymer of ethylene and norbornene [manufactured by Polyplastics Co., Ltd., registered trademark “TOPAS”, Tg of 5013 = 134 ° C.], a copolymer of ethylene and cyclic olefin. Cyclic olefin copolymer as a polymer [Mitsui Chemicals, registered trademark “Apel”, APL5014DP Tg = 135 ° C.], cycloolefin polymer obtained by metathesis ring-opening polymerization of norbornene derivative [manufactured by Nippon Zeon, registered trademark “ ZEONEX ”, Tg of 480R = 138 ° C.], cycloolefin polymer having a tricyclodecane structure [manufactured by JSR, registered trademark“ ARTON ”, Tg = 171 ° C.] and the like.
In the present invention, the amorphous resin (b) may be used singly or may be used in combination of two or more, and in particular, a cyclic olefin copolymer and / or polycarbonate is used from the viewpoint of performance. preferable.

  In the latent uneven sheath-core composite fiber of the present invention, in the resin composition (A) used as the sheath material, the content ratio of the polyolefin resin (a) and the amorphous resin (b) described above is From the viewpoint of forming irregular irregularities on the sheath surface by heat treatment of the composite fiber, the mass ratio is preferably 97: 3 to 70:30, more preferably 95: 5 to 85:15. .

[Material for core]
In the latent concavo-convex sheath-core composite material of the present invention, a thermoplastic resin (B) is used as a material constituting the core portion (hereinafter sometimes referred to as a core portion material).
The thermoplastic resin (B) needs to have a melting point higher than that of the polyolefin resin (a) described above. For example, crystalline polypropylene, crystalline polyester such as polyethylene terephthalate or polybutylene terephthalate, polyamide (nylon) ), Aromatic polyester resins (liquid crystal polymers) and the like, and these may be used alone or in combination of two or more. Among these, crystalline polypropylene is preferable from the viewpoint that irregular irregularities can be suitably formed on the surface of the sheath by heat treatment.

  As this crystalline polypropylene, an isotactic polypropylene resin is preferably used. Among them, those having an isotactic pentad fraction (IPF) of preferably 85% or more, more preferably 90% or more are advantageous. The Q value (weight average molecular weight / number average molecular weight Mw / Mn ratio), which is an index of molecular weight distribution, is 6 or less, and the melt flow rate MFR (temperature 230 ° C., load 21.18 N) is in the range of 3 to 50 g / 10 min. Is preferred. If the IPF is less than 85%, the stereoregularity is insufficient and the crystallinity is low, and the physical properties such as strength of the resulting composite fiber are poor.

The isotactic pentad fraction (IPF) (generally also referred to as mmmm fraction) is a side chain with respect to the main chain of carbon-carbon bonds composed of any five consecutive propylene units. This shows the proportion of the three-dimensional structure in which two methyl groups are located in the same direction. Pmmmm (5 propylene units are isotactic) in the isotope carbon nuclear magnetic resonance spectrum ( ¹³ C-NMR). From the absorption intensity derived from the methyl group of the third unit at the bonded site and Pw (absorption intensity derived from all methyl groups of the propylene unit), the formula IPF (%) = (Pmmmm / Pw) × 100
Can be obtained.

Further, the polypropylene may be a propylene homopolymer or a copolymer of propylene and an α-olefin (for example, ethylene, butene-1, etc.).
That is, as crystalline polypropylene, for example, isotactic propylene homopolymer having crystallinity, ethylene-propylene random copolymer having a small ethylene unit content, homo-part consisting of propylene homopolymer and ethylene unit content A propylene block copolymer composed of a copolymer part composed of an ethylene-propylene random copolymer having a relatively large amount of each of the above-mentioned propylene block copolymers, and each homo part or copolymer part in the propylene block copolymer further includes butene-1, etc. Examples thereof include crystalline propylene-ethylene-α-olefin copolymers formed by copolymerizing α-olefins.
In the present invention, the resin composition (A), which is the sheath material, and the thermoplastic resin (B), which is the core material, include various additives such as weathering agents and heat stabilizers as necessary. , Flame retardants, colorants, deodorants, antibacterial agents, fragrances and the like can be included.

[Manufacturing method of latent uneven sheath-core composite fiber]
Although there is no restriction | limiting in particular in the method of manufacturing the latent uneven | corrugated sheath-core composite fiber of this invention, For example, according to the method of this invention shown below, it can manufacture efficiently.
The production method of the present invention comprises a sheath part made of a resin composition (A) containing a polyolefin resin (a) and an amorphous resin (b), and a core part containing a thermoplastic resin (B), A resin composition (A) in which the melting point of the polyolefin resin (a) is lower than the melting point of the thermoplastic resin (B) and the glass transition point (Tg) of the amorphous resin (b) is used as a sheath, and a thermoplastic resin ( B) melt-spinning the sheath-core composite fiber with the core as the core, and heat at a temperature not lower than the Tg of the polyolefin resin (a) and not higher than the melting point and not higher than Tg of the amorphous resin (b). A step of stretching.

(Melt spinning process)
The step of melt spinning the sheath-core composite fiber in the production method of the present invention can be a known method conventionally used in the production of sheath-core composite fibers. For example, by using the above-mentioned sheath component and core component, a composite having a sheath-core structure is obtained by melt spinning at a spinning temperature of about 200 to 300 ° C. by a composite spinning apparatus equipped with two extruders and a sheath-core type fiber nozzle. Fiber is obtained. The core / sheath cross-sectional area ratio in the thus obtained sheath-core type composite fiber is usually selected in the range of 40/60 to 80/20.

(Heat drawing process)
In the production method of the present invention, the sheath-core composite fiber obtained in the melt spinning step is subjected to a heat stretching process. This heat stretching treatment is performed at a temperature not lower than Tg and not higher than the melting point of the polyolefin resin (a) and not higher than Tg of the amorphous resin (b).
In the thermal stretching step, a conventionally known thermal stretching treatment method, for example, contact heating stretching using a generally known metal heating roll or metal heating plate, or hot water, water vapor of about normal pressure to about 0.2 MPa. A method such as heating fluid such as hot air or non-contact heating using a heat ray such as far-infrared rays, or a combination thereof can be applied. In applications such as paper diapers where texture is required, the draw ratio is usually about 2 to 6 times, preferably 3 to 5 times. The single yarn fineness in the obtained composite drawn fiber is usually about 2 to 10 dTex, preferably 3 to 5 dTex.

(Crimping)
In the present invention, the composite drawn fiber thus obtained is usually crimped. There is no restriction | limiting in particular as this crimping method, The method conventionally used for the crimping process of the polyolefin-type composite stretched fiber can be used. For example, the composite stretched fiber is subjected to mechanical crimping at a crimp number of about 10 to 18 pieces / 2.5 cm, preferably 12 to 16 pieces / 2.5 cm, by a conventional method. can get.

Next, the nonwoven fabric of this invention is demonstrated.
[Nonwoven fabric]
The non-woven fabric of the present invention is characterized in that the non-woven fabric obtained from the latent concavo-convex sheath-core composite fiber is heat-treated so that the concavo-convex shape is expressed on the surface of the sheath portion.
(Nonwoven fabric manufacturing method)
The nonwoven fabric of this invention can be manufactured by the following method, for example.
First, the crimped composite stretched fiber obtained by the above-described crimping process is usually cut into 15 to 80 mm, preferably 25 to 60 mm, in accordance with a conventional method to obtain a latent-concave uneven sheath-core composite fiber. Subsequently, a nonwoven fabric is produced using this short fiber latent uneven sheath-core composite fiber.

Non-woven fabric production methods include a heat fusion method, a heat roll method, a span lace method, a needle punch method, etc. In the present invention, it is advantageous to employ a heat fusion method, particularly a hot air fusion method. is there. This is because when the nonwoven fabric is produced by this hot-air fusion method, irregular irregularities appear on the surface of the sheath portion of the sheath-core composite fiber simultaneously with the production of the nonwoven fabric, and a desired nonwoven fabric can be easily obtained.
There is no restriction | limiting in particular as a manufacturing method of the nonwoven fabric by this hot-air melt | fusion method, The method conventionally used in manufacture of the nonwoven fabric by a hot-air melt | fusion process can be used. For example, the latent uneven sheath-core composite fiber of short fibers obtained as described above is carded with a roller card machine to produce a web with a desired basis weight, and then a hot-air fusion method such as an air-through method The said nonwoven fabric is obtained.
At this time, it is important that the hot air fusion is performed at a temperature equal to or higher than the melting point of the polyolefin resin (a) and near or below the glass transition point (Tg) of the amorphous resin (b).

EXAMPLES Next, although an Example demonstrates this invention further in detail, this invention is not limited at all by these examples.
Example 1
(1) Production of sheath-core composite unstretched fiber As a sheath material, high-density polyethylene [manufactured by Keiyo Polyethylene Co., Ltd., trade name “S6932”, MFR (190 ° C., 21.18 N) = 20 g / 10 min, melting point: about 130 C., Tg: about −120 ° C.) and a cyclic olefin copolymer [polyplastics, registered trademark “TOPAS 5013”, Tg = 134 ° C.] in a mass ratio of 95: 5, As a material, homopolypropylene [manufactured by Prime Polymer Co., Ltd., trade name “Y2005GP”, MFR (230 ° C., 21.18 N) = 20 g / 10 min, melting point: 161 ° C.] was used. A sheath spinning core having a single fiber fineness of 13.8 dTex, spun under the conditions shown in Table 1 by a composite spinning device having a composite fiber nozzle having 1200 holes of 4 mm. The case undrawn fiber was produced.

(2) Production of sheath-core composite stretched fiber The sheath-core composite unstretched fiber obtained in (1) above was stretched under the conditions shown in Table 1, and the single yarn fineness at a stretch ratio of 4 was 3. A sheath-core composite drawn fiber having 7 dTex was produced.
(3) Production of short-fiber sheath-core composite fiber The sheath-core composite stretched fiber obtained in (2) above was subjected to mechanical crimping. Then, the short core sheath core composite stretched fiber was produced by cutting to about 50 mm length with a rotary cutter.

(4) Fabrication of non-woven fabric Using the short-core sheath-core composite fiber obtained in (3) above, the hot air fusion method was used to achieve fusion conditions of a temperature of 135 ° C., a wind speed of 2.7 m / s, and a treatment time of 5 seconds. Thus, a hot-air fused nonwoven fabric having irregular irregularities on the surface of the sheath portion was produced.
FIG. 1 shows a scanning electron microscope (SEM) photograph of the sheath-core composite unstretched fiber, FIG. 2 shows an SEM photograph of the sheath-core composite stretched fiber, and FIG. 3 shows an SEM photograph of the sheath-core composite fiber constituting the hot-air fused nonwoven fabric. Indicates.
As can be seen from FIGS. 1 to 3, the surface of the sheath part of the sheath-core composite unstretched fiber has no irregularities, but the surface of the sheath part of the sheath-core composite stretched fibers is slightly uneven. Further, unevenness is considerably observed on the surface of the sheath portion of the sheath-core composite fiber constituting the hot-air fused nonwoven fabric. These irregularities are also summarized in Table 1.

Example 2
In Example 1 (1), the mass ratio of the high density polyethylene “S6932” (supra) and the cyclic olefin copolymer “TOPAS 5013” (supra) was changed to 90:10, The same operation as in Example 1 was performed except that the single yarn fineness was 14.4 dTex and the single-core fineness of the sheath-core composite drawn fiber was 3.7 dTex.
FIG. 4 shows an SEM photograph of the sheath-core composite unstretched fiber, FIG. 5 shows an SEM photograph of the sheath-core composite stretched fiber, and FIG. 6 shows an SEM photograph of the sheath-core composite fiber constituting the hot-air fused nonwoven fabric. Further, FIG. 7 shows a transmission optical micrograph of the sheath-core composite fiber constituting the hot-air fused nonwoven fabric.
As can be seen from FIG. 4 to FIG. 7, no irregularities are observed on the sheath surface of the sheath-core composite unstretched fiber, but irregularities are observed on the sheath surface of the sheath-core composite stretched fiber. Large irregularities are observed on the surface of the sheath portion of the sheath-core composite fiber constituting the nonwoven fabric.

Example 3
As the sheath material, high density polyethylene [manufactured by Keiyo Polyethylene Co., Ltd., trade name “S6932”, MFR (190 ° C., 21.18 N) = 20 g / 10 min, melting point: about 130 ° C., Tg: about −120 ° C.] Polyethylene terephthalate [Kanebo Co., Ltd.] with a resin composition containing cyclic olefin copolymer [polyplastics, registered trademark “TOPAS 5013”, Tg = 134 ° C.] in a mass ratio of 90:10 Product name "K101
”, Relative viscosity 0.6, melting point: 264 ° C.], using a composite spinning apparatus including two single-screw extruders and a composite fiber nozzle having 1200 holes with a diameter of 0.4 mm. Spinning and drawing were performed under the conditions shown in the table, and the single yarn fineness of the sheath-core composite unstretched fiber was 8.75 dTex, and the single-fiber fineness of the sheath-core composite drawn fiber was 3.0 dTex. The operation was performed. As a result, large irregularities were observed on the surface of the sheath part of the sheath-core composite fiber constituting the hot-air fused nonwoven fabric.

Comparative Example 1
In Example 1 (1), only the high density polyethylene “S6932” (described above) is used as the sheath material, the single yarn fineness of the sheath core composite unstretched fiber is 13.9 dTex, and the single yarn fineness of the sheath core composite stretched fiber The same operation as in Example 1 was performed except that is 3.7 dTex.
FIG. 8 shows an SEM photograph of the sheath-core composite unstretched fiber, FIG. 9 shows an SEM photograph of the sheath-core composite stretched fiber, and FIG. 10 shows an SEM photograph of the sheath-core composite fiber constituting the hot-air fused nonwoven fabric.
As can be seen from FIGS. 8 to 10, the sheath surface of the sheath core composite unstretched fiber, the sheath surface of the sheath core composite stretch fiber, and the sheath surface of the sheath core composite fiber constituting the hot-air fused nonwoven fabric are No irregularities are observed.

Comparative Example 2
(1) Production of sheath-core composite unstretched fiber As sheath material, high-density polyethylene “S6932” (supra) and cyclic olefin copolymer [manufactured by Polyplastics, registered trademark “TOPAS 8007”, Tg = 78 ° C.] Using a homopolypropylene “Y2005GP” (supra) as a core material, and using two uniaxial extruders and 1200 holes having a diameter of 0.4 mm. Was spun under the conditions shown in Table 1 to produce a sheath-core composite unstretched fiber having a single yarn fineness of 7.9 dTex.

(2) Production of sheath-core composite stretched fiber The sheath-core composite unstretched fiber obtained in the above (1) is stretched under the conditions shown in Table 1, and the single yarn fineness with a draw ratio of 3.7 is 2. A sheath-core composite drawn fiber having a diameter of 6 dTex was produced.
(3) Production of short-fiber sheath-core composite fiber The sheath-core composite stretched fiber obtained in (2) above was subjected to mechanical crimping. Then, the short core sheath core composite stretched fiber was produced by cutting to about 50 mm length with a rotary cutter.

(4) Fabrication of non-woven fabric Using the short-core sheath-core composite fiber obtained in (3) above, the hot air fusion method was used to achieve fusion conditions of a temperature of 135 ° C., a wind speed of 2.7 m / s, and a treatment time of 5 seconds. Thus, a hot air fusion nonwoven fabric was produced.
When the sheath-core composite fiber constituting the hot-air fused nonwoven fabric was observed with an SEM, the surface of the sheath portion did not show any unevenness.

Comparative Example 3
(1) Production of sheath-core composite unstretched fiber As sheath material, high-density polyethylene “S6932” (supra) and cyclic olefin copolymer [manufactured by Polyplastics, registered trademark “TOPAS 8007”, Tg = 78 ° C.] Using a homopolypropylene “Y2005GP” (supra) as a core material, and using two uniaxial extruders and 1200 holes with a diameter of 0.4 mm. Was spun under the conditions shown in Table 1 to produce a sheath-core composite unstretched fiber having a single yarn fineness of 4.6 dTex.

(2) Production of sheath-core composite stretched fiber The sheath-core composite unstretched fiber obtained in (1) above is stretched under the conditions shown in Table 1, and the single yarn fineness with a draw ratio of 1.8 is 2 A sheath-core composite drawn fiber having a diameter of 9 dTex was produced.
(3) Production of short-fiber sheath-core composite fiber The sheath-core composite stretched fiber obtained in (2) above was subjected to mechanical crimping. Then, the short core sheath core composite stretched fiber was produced by cutting to about 50 mm length with a rotary cutter.

(4) Fabrication of non-woven fabric Using the short-core sheath-core composite fiber obtained in (3) above, the hot air fusion method was used to achieve fusion conditions of a temperature of 135 ° C., a wind speed of 2.7 m / s, and a treatment time of 5 seconds. Thus, a hot air fusion nonwoven fabric was produced.
FIG. 11 shows an optical micrograph of the sheath-core composite fiber constituting the hot-air fused nonwoven fabric. As can be seen from FIG. 11, no irregularities are observed on the surface of the sheath portion of the sheath-core composite fiber constituting the hot-air fused nonwoven fabric.

  The latent uneven sheath-core composite fiber of the present invention has a wide range of fineness, improves tactile sensation, texture, softness and swelling, and gives a non-woven fabric having a large effect of diffusing water (large bleeding) Can do.

Claims (8)

  A composite fiber comprising a sheath part made of a resin composition (A) containing a polyolefin resin (a) and an amorphous resin (b) and a core part containing a thermoplastic resin (B), the polyolefin fiber The melting point of the resin (a) is lower than the melting point of the thermoplastic resin (B), and the glass transition point (Tg) of the amorphous resin (b) is higher than the melting point of the polyolefin resin (a). A latent concavo-convex sheath-core composite fiber capable of forming a concavo-convex shape on the surface of the sheath by heat-treating.   The latent uneven sheath-core composite fiber according to claim 1, wherein the thermoplastic resin (B) is crystalline polypropylene and the polyolefin resin (a) is high-density polyethylene.   The latent uneven sheath-core composite fiber according to claim 1 or 2, wherein the amorphous resin (b) is a cyclic olefin copolymer and / or a polycarbonate.   The latent uneven sheath-core composite fiber according to claim 3, wherein the amorphous resin (b) is a cyclic olefin copolymer.   The latent ratio according to any one of claims 1 to 4, wherein a content ratio of the polyolefin resin (a) and the amorphous resin (b) in the resin composition (A) is 97: 3 to 70:30 by mass ratio. Uneven type sheath-core composite fiber.   A nonwoven fabric obtained by heat-treating a nonwoven fabric obtained from the latent uneven sheath-core composite fiber according to any one of claims 1 to 5 to develop an uneven shape on the surface of the sheath portion.   The nonwoven fabric according to claim 6, wherein the heat treatment is performed at a temperature equal to or higher than the melting point of the polyolefin resin (a) and near or below the glass transition point (Tg) of the amorphous resin (b).   A polyolefin resin (a) and a non-crystalline resin (b) are composed of a sheath portion made of a resin composition (A) and a core portion containing a thermoplastic resin (B). The sheath is composed of the resin composition (A) having a melting point lower than the melting point of the thermoplastic resin (B) and the glass transition point (Tg) of the amorphous resin (b), and the thermoplastic resin (B) as the core. A step of melt spinning the core composite fiber, and a step of hot drawing at a temperature not lower than the melting point Tg of the polyolefin resin (a) and not higher than the melting point and not higher than Tg of the amorphous resin (b). A method for producing a latent uneven sheath-core composite fiber characterized by