JPH0192416A - Heat-bondable conjugate fiber having excellent heat-bonding property and bulkiness - Google Patents

Abstract

PURPOSE:To obtain the titled conjugate fiber, consisting of a specific polyester as a core layer, propylene based polymer as an intermediate layer and olefinic polymer having a lower melting point than that of the intermediate layer as the outermost layer and having excellent adhesive properties, bulkiness and elastic recovery. CONSTITUTION:The aimed conjugate fiber which is a sheath-core type conjugate fiber, consisting of three layers of an intermediate layer 2 around a core layer 1, the outermost layer 3 placed in at least part of the outer periphery of the intermediate layer 2 and having a polyester containing >=80mol% ethylene terephthalate as the above-mentioned core layer and a propylene based polymer which is a homopolymer, copolymer or terpolymer consisting of >=85wt.% propylene as the afore-mentioned intermediate layer and an olefinic polymer, such as high-density polyethylene, having a lower melting point that that of the above-mentioned intermediate layer as the afore-mentioned outermost layer and suitable as a material for nonwoven fabrics.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a thermoadhesive composite material 41 which has excellent thermal adhesiveness and bulkiness and is particularly suitable as a material for nonwoven fabrics.

(Prior art) Heat-adhesive composite fibers made of two components with different melting points can be bonded between fibers without using an adhesive, so there is no need for drying as with adhesive bonding, and energy saving is required. It is economical because it has a small amount of YI, and is widely used today as a fiber material for various nonwoven fabrics including sanitary materials that avoid the inclusion of substances harmful to the human body such as formalin. In particular, for example, Japanese Patent Publication No. 50-4767, Japanese Patent Publication No. 52
As seen in Japanese Patent Publication No. 12830 or Japanese Patent Publication No. 55-483, polyolefin composite fibers in which polypropylene and polyethylene are arranged in a parallel type or core-sheath type do not contain harmful substances and can be used at relatively low temperatures. Can be thermally bonded
This type of thermal adhesive is most commonly used for various nonwoven fabrics because it has a soft texture and excellent chemical resistance.

(Problems to be Solved by the Invention) However, conventional heat-adhesive composite fibers are not necessarily satisfactory in terms of bulk and elastic recovery properties. When producing textured nonwoven fabrics.

A nonwoven fabric with improved strength by subjecting a carded web or random web of heat-adhesive composite fibers to hot air processing or embossing roll processing to melt only the low-melting point components of the composite fibers and bonding between the fibers. However, the resulting nonwoven fabric has poor bulkiness compared to the web before thermal bonding. Then, the nonwoven fabric after the above thermal bonding process is usually rolled up into a paper tube! For example, when the above-mentioned rolled product shipped after storage is unwound for use, the elastic recovery force is small, so the bulkiness is significantly impaired compared to before winding. The situation is as follows.

As a way to improve such bulkiness and elastic recovery, it is possible to use polyester instead of polypropylene as the core component in conventional heat-adhesive composite fibers that use polypropylene as the core component and polyethylene as the sheath component. In such heat-adhesive composite fibers, the chemical affinity between polyethylene and polyester is extremely poor, so the adhesive strength of the interfiber bonding points formed by melt adhesion of the polyethylene components is extremely low9. The tensile strength of the nonwoven fabric made by this method is low.

Depending on the application, it may not be suitable for use.

(Means for Solving the Problems) The heat-adhesive fiber according to the present invention is a core-sheath type composite fiber consisting of three layers including a core layer, an intermediate layer around the core layer, and an outermost layer around at least a part of the outer periphery. the layer is made of polyester of which at least 80 mole percent is ethylene terephthalate;
It is a thermoadhesive composite fiber in which the middle layer is made of a propylene polymer and the outermost layer is made of an olefin polymer with a lower melting point than the middle layer, and the bulkiness and elasticity of the nonwoven fabric is improved by placing polyester in the core layer. By improving the recovery property and disposing the propylene polymer in the intermediate layer, the chemical affinity with the low melting point olefin polymer is increased, and the yi interfiber adhesive strength in nonwoven fabrics (adhesion is increased by melting of the olefin polymer) is improved. formation).

The polyester used as the core layer polymer of the heat-adhesive composite fiber of the present invention contains at least 80 mol% of ethylene terephthalate, and contains a copolymer component such as ethylene isophthalate within an amount not exceeding 20 mol%. Good too. The propylene polymer used as the intermediate layer component is a homopolymer, copolymer, or terpolymer consisting of 85% by weight of propylene. Examples of the olefin polymer used in the outermost layer include high density polyethylene, medium density polyethylene, low density polyethylene, and ethylene/vinyl acetate copolymer.

The reason why 80% or more of polyester is required for the core layer is that 180% polyester is required to withstand the heating temperature during thermal bonding.
This is to have a melting point of ℃ or higher and to improve elastic recovery properties.

In order to avoid unfavorable effects such as heat shrinkage and softening of the core layer and intermediate layer during thermal bonding processing of fiber aggregates and nonwoven fabrics using thermally bonded composite fibers made of these three components, the olefin polymer in the outermost layer is It is desirable that the melting point of the intermediate layer is at least 20° C. lower than the melting point of the propylene polymer constituting the intermediate layer.

As shown in the cross-sectional view of FIG. 1, the composite fiber of the present invention has an intermediate layer 2 around a core layer 1, and an outermost layer 3 around the core layer 1.
It will be arranged. The outermost layer 3 is not limited to covering the entire circumference of the intermediate layer 2; for example, as shown in FIG. 2, the outermost layer 3' may be provided so that a portion of the outer circumference of the intermediate layer 2 is exposed. .

The fibers of the present invention may be used alone as a fiber material for nonwoven fabrics, or may be mixed with other types of fibers, but in order to obtain a thermal bonding effect, it is preferable to blend the fibers in an amount of 30% by weight or more.

(Function) The thermoadhesive composite fiber of the present invention has an outermost layer made of an olefin polymer with a low melting point, and an intermediate layer made of a propylene polymer. The interfiber bonding strength formed by the melting of the coalesce is much higher than that of fibers using polyester instead of propylene polymer, and since polyester is used as the core layer, the fibers are bulky. Excellent elasticity after recovery.

(Example) Examples 1 and 2 and Specimen Examples 1 and 2 The core layer was polyethylene terephthalate with a melting point of 260° and [η] (measured in Q-RIU enol) of 0.68. The middle layer is made of polypropylene with a melt flow rate of 17 at 167°C and 230°C, and the outermost layer is made of polypropylene with a melting point of 132°C and a melt index of 18. Using high-density polyethylene with a density of 0.955, these were separately supplied to three extruders to perform melt extrusion, and from a composite spinneret (number of nozzles: 52) having an outer diameter of 0.5+x+* nozzle holes. By spinning, a three-component core-sheath type composite fiber having a composite ratio (cross-sectional area ratio) of core layer: intermediate layer: outermost layer = 1: 1: 1 and a fiber cross section as shown in FIG. Ta. Next, this core-sheath type composite fiber is heated and stretched,
After applying mechanical crimping using a stuffer box type crimping machine and relaxing heat treatment at 1-10°C for 25 minutes,
It was cut into a length of 11II11 to make a staple fiber.

On the other hand, as a comparative example, the core layer was made of the polypropylene, and the outermost layer was made of the high-density polyethylene.

A core-sheath type composite fiber with no intermediate layer was spun. The composite ratio of core layer:outermost layer is 1=1. This is also heated and stretched in the same manner as above, mechanically tS-shrinked using a stuffer box crimper, and then subjected to relaxing heat treatment 8! It was then cut into staple fibers.

Further, as Comparative Example 2, a core-sheath type composite fiber was spun, in which the core layer was made of the polyester, the outermost layer was made of the high-density polyethylene, and the intermediate layer was omitted. Composite ratio is core layer: 1 & outer layer: 1
:1.

This was treated in the same manner as in Comparative Example 1 to form stable fibers.

A web obtained by supplying these stable fibers to a roller card is heated at 140 ° C. for 1 minute with a hot air penetration type thermal processing machine under no load to melt the polyethylene component,
A nonwoven fabric (fabric weight approximately 40 g/♂) in which the fibers were adhesively bonded was obtained. The results are shown in Table 1.

Example 3. and Comparative Examples 3 and 4 The core layer was made of polyethylene terephthalate with a melting point of 260°C [η] of 0.65, and the melting point was 167°C.

The middle layer is polypropylene with a melt flow rate of 20 at 230°C, and the outermost layer is an ethylene/vinyl acetate copolymer (vinyl acetate content: 6% by weight) with a melting point of 104°C and a melt index of 20. The material was supplied to three extruders for melt extrusion, and the outer diameter was 0.5.
Composite spinneret with mm nozzle holes (52 nozzles)
The composite ratio is core N: intermediate layer: outermost layer = I: 1.
A three-component core-sheath type composite fiber having a fiber cross section as shown in FIG. 1 of I was obtained. This fiber was stretched 3.5 times at 60°C and mechanically crimped using a 2-stuffer box crimper.
After relaxing heat treatment at 60°C for 15 minutes, 51 n+i
It was cut into lengths to make stable fibers.

On the other hand, as Comparative Example 3, a core-sheath type composite fiber was obtained by spinning in the same manner as in Example 3, with the polypropylene in the core layer, the ethylene/vinyl acetate copolymer in the outermost layer, and the intermediate layer omitted. (Composite core layer: outer layer = 1:1) This fiber was repeated in the same manner as in Example 3 to obtain a staple fiber.

Comparative Example 4 is a core-sheath type composite fiber in which the core layer is the polyester, the M outer layer is the ethylene-vinyl acetate copolymer, and the intermediate layer is omitted (composite ratio core layer: outer layer = 1:1).
was spun, and the same operations as in Comparative Example 3 were repeated to obtain stable fibers.

The web obtained by supplying these staple fibers to a roller card is heated at 120°C for 1 minute under no load using a hot air penetration type thermal processing machine to melt the ethylene and vinyl acetate components, thereby producing a nonwoven fabric in which the fibers are adhesively bonded. (Weight approx. 40 g
/wi”). The results are shown in Table 2.

(Margins below) Table 2 In Tables 1 and 2, "thickness of carded web" and "thickness of nonwoven fabric" are the values obtained by measuring under a load of 0.1 g/C112 at 40 g. /m" is the value obtained by converting to the basis weight, and the "thickness after removing weight" is vertical 15 C.
10 pieces of non-woven fabric cut to the size of IIX horizontal 151
The sheets were stacked, compressed to a thickness of 0.1+am per sheet, which corresponds to the thickness of nonwoven fabric based on a basis weight of 40 g/m'', left for one week, then deweighted, and left in that state for 24 hours. The thickness measured under a load of 0.1g/am2 is 40
g/m", and the tensile strength is the tensile strength at break of a strip of width 5 cm with a basis weight of 40 g.
/m” values are shown.

(Effects of the Invention) As described above, the heat-adhesive composite fiber of the present invention has a specific polymer in the core layer, middle layer, and outermost layer, and the bulkiness of the carded web and nonwoven fabric after heat-adhesion processing is improved. The elasticity of the nonwoven fabric is high, and the elasticity recovery of the nonwoven fabric is large. For example, when a nonwoven fabric wound into a roll is cut into a length, a remarkable recovery of bulkiness is observed.

Therefore, nonwoven fabrics obtained by using the heat-adhesive composite fibers of the present invention alone or by blending them with other fibers are suitable as surface materials for sanitary materials that require bulkiness, and if they are good, they have good unibody recovery properties. is particularly suitable as a surface material for an absorbent core material because it has the effect of preventing backflow of liquid in the absorbent core material.

Furthermore, since the heat-adhesive conjugate fiber of the present invention is rich in elastic recovery, even if it is stored for a long period of time while being wound around a paper tube during the manufacturing process of nonwoven fabric, its bulkiness will be restored when it is sized out.
This helps eliminate the inconvenience that bulkiness is reduced due to compression winding.

In addition, the polyester (core layer) and the olefin polymer (outermost layer) do not come into direct contact within the fiber, and polypropylene, which has a high chemical affinity with the olefin polymer, exists as an intermediate layer, making it possible to heat-fuse the fiber. The interfacial adhesion between the olefin polymer and polypropylene after deposition is strong.

Therefore, a nonwoven fabric thermally bonded using the fibers of the present invention has a high interfiber bonding strength, so that high tensile strength can be obtained.

The thermoadhesive composite fiber of the present invention has excellent adhesiveness, bulkiness, and elastic recovery, and is therefore suitable for use not only in nonwoven fabrics for sanitary materials but also in textile products in various fields.

[Brief explanation of the drawing]

The drawing is an enlarged cross-sectional view of the composite fiber of the present invention. (1) is a core layer, (2) is an intermediate layer, and (3) and (3) are outermost layers.

Claims (1)

[Claims] A core-sheath type composite fiber consisting of three layers, an intermediate layer surrounding a core layer, and an outermost layer around at least a portion of the outer periphery of the intermediate layer, wherein the core layer is made of polyester of which at least 80 mol% is ethylene terephthalate, A thermoadhesive composite fiber with excellent thermal adhesiveness and bulk, characterized in that the intermediate layer is made of a propylene polymer and the outermost layer is made of an olefin polymer with a lower melting point than the intermediate layer.