JPH08158229A - Production of nonwoven fabric - Google Patents

Abstract

PURPOSE: To obtain flexible nonwoven fabric having good touch feeling by promoting separation of thermally separable conjugate fiber. CONSTITUTION: A fiber web containing >=30wt.% of a thermally separable conjugate fiber using a thermoplastic resin whose melting point (T1 deg.C) is within the range of 130 deg.C<T1 <350 deg.C as the first component and using a thermoplastic resin having a melting point lower than that of the first component and having large heat shrinkage factor as the second component is subjected to heat treatment at a temperature lower than the melting point of the first component to afford a thermally bonding nonwoven fabric, which is then subjected to calendering. Thereby, separation of a thermally separable conjugate fiber is promoted to provide the objective nonwoven fabric in which many ultra-fine fibers are formed.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a surface material for absorbent articles,
The present invention relates to a method for producing a nonwoven fabric suitable for wipers and filters.

[0002]

2. Description of the Related Art Conventionally, there has been proposed a fiber capable of being divided into ultrafine fibers by heat treatment, that is, a heat-splittable composite fiber, without depending on a physical impact treatment such as a high-pressure water stream or a chemical treatment such as a solvent. .

For example, in Japanese Patent Laid-Open No. 169720/1990, a heat splitting type composite fiber composed of a high melting point component and a low melting point component and capable of being split by heat treatment at a temperature higher than the melting point of the low melting point component, and this Nonwoven fabrics made of fibers have been proposed.

The present applicant has also found that the heat-separability of the first component and the second component having a melting point of 20 ° C. or more lower than that of the first component and having a heat shrinkability of 50% or more at a temperature near the melting point. A composite fiber has been previously proposed (see JP-A-6-73613).

Since these heat-splittable composite fibers are split by heat, using them makes it possible to economically produce a soft and tactile non-woven fabric composed of ultrafine fibers without using a large-scale apparatus for high-pressure water stream treatment. Can be produced.

[0006]

However, the above-mentioned fibers have the following problems. First, Japanese Patent Laid-Open No. 2-1697
The fiber proposed in No. 20 is heat-treated at a temperature equal to or higher than the melting point of the low-melting point component to be divided, and thus the formed ultrafine fibers are easily joined by melting of the low-melting point component to form a bundle. It was hard to say that the obtained nonwoven fabric sufficiently exhibited the properties peculiar to the ultrafine fibers.

On the other hand, in the heat-separable conjugate fiber proposed by the applicant, even if the heat treatment is performed at a temperature higher than the melting point of the second component, the second component is thermally shrunk and then melts, so that the fibers are partially separated. Therefore, the ultrafine fibers are not joined together in a wide range to form a bundle. However, the separation by heat treatment has a problem that the degree of separation is smaller than that by physical impact. That is, when the heat treatment is applied, the fibers are certainly separated into the respective constituent components, but the separated constituent components are not dispersed as one independent fiber,
After separation, they are still dense and retain their shape as a single fiber. Therefore, although a non-woven fabric using this fiber exhibits better flexibility and tactile sensation than the conventional heat-bonded non-woven fabric, it is inferior in flexibility and the like as compared with the one in which the ultrafine fibers are formed by being divided by the high pressure water flow. I couldn't deny it.

In view of these circumstances, the present invention has been made for the purpose of obtaining a nonwoven fabric which is softer and has a better tactile feel by using the heat-separable conjugate fiber.

[0009]

That is, the present invention is based on the melting point (T
The first component is a fiber-forming thermoplastic resin having a temperature of ₁ ° C.) in the range of 130 <T ₁ <350, and the melting point of the first component is 20.
A thermoplastic resin having a heat shrinkage of 50% or more at a temperature near the melting point, which is lower than ℃, is used as the second component, and 30% by weight of the heat-separable composite fiber in which each component is partially exposed on the fiber surface.
The short fiber web containing the above is heat-treated at a temperature higher than the melting point of the second component and lower than the melting point of the first component to form a heat-bonded nonwoven fabric, and then calendered. It is about. The contents will be described below.

The first component constituting the heat-separable conjugate fiber used in the present invention is a thermoplastic resin having a melting point in the range of 130 to 350 ° C. Examples of such resins include polyesters such as polyethylene terephthalate and polybutylene terephthalate, nylon 6, nylon 66, nylon 610, nylon 11, nylon 12, nylon M.
Conveniently used are homopolymers, copolymers, graft-transformed organisms and polymer alloys of polyamides such as XD6 (trade name: manufactured by Mitsubishi Gas Chemical Co., Inc.), polyolefins such as polymethylpentene, polypropylene and ethylene vinyl alcohol copolymer. To be Among them, polyester, polyamide and polymethylpentene are particularly preferably used.

The second component constituting the heat-separable conjugate fiber is
It is a thermoplastic resin whose melting point is lower than that of the first component by 20 ° C. or more and whose heat shrinkage rate is 50% or more at a temperature near the melting point. As such a resin, ethylene-propylene copolymer,
Examples thereof include propylene copolymers such as ethylene-butene-1-propylene terpolymer. Also, an isophthalic acid component or a metal sulfonic acid group-containing polyester copolymer can be used, and when this is used, wet heat separation is also possible.

When polyester, polyamide or polymethylpentene is used as the first component, the second component has an ethylene-propylene copolymer and / or a melting point (T ₂ ° C.) in the range of 110 <T ₂ ≤140. Alternatively, it is preferable to use an ethylene-butene-1-propylene terpolymer.

As shown in FIG. 1, FIG. 2 and FIG. 3, both the first component and the second component are divided into two or more of the first component (1) by the second component (2) in the fiber cross section. Each component becomes a constituent component of the fiber cross section, each constituent unit is adjacent to a constituent unit of a different component, and all constituent units are arranged so that part of them is exposed on the fiber surface. Is desirable. With such a structure, the heat treatment causes the second component to remarkably shrink and become a lump and separate from the composite fiber, and only the first component remains in the fiber form to form ultrafine fibers. When the heat treatment temperature is set to a temperature equal to or higher than the melting point of the second component, the second component melts after contracting, and thus acts as a heat-adhesive component.

If the heat separation property is not impaired, the first
There may be components other than the component and the second component. For example, the structure of the fiber cross section as shown in FIG. 4 may be adopted, and the first component (1) may be composed of two kinds of components, an A polymer and a B polymer.

In any cross-sectional structure, it is desirable that the composite ratio (volume ratio) of both components is 20:80 to 80:20 for the first component and the second component in consideration of spinnability and the like.

In the present invention, a fiber web containing 30% by weight or more of the above-mentioned heat-separable conjugate fiber is preferably used. This is because if the proportion of the heat-separable conjugate fiber is less than 30% by weight, the characteristics of the ultrafine fiber nonwoven fabric cannot be exhibited.

The form of the web is not particularly limited, and can be arbitrarily selected from a long fiber web, a web formed by wet papermaking, a random web composed of staple fibers, a semi-random web, a cross web, a parallel web and the like. Further, the basis weight and the like may be determined according to the intended use of the nonwoven fabric finally obtained. However, it should be noted that calendering, which will be described later, reduces the thickness.

The web containing the heat-separable conjugate fiber is heat-treated at a temperature higher than the melting point of the second component of the heat-separable conjugate fiber and lower than the melting point of the first component. By this heat treatment, the second component shrinks and the heat-separable conjugate fiber is separated, and at the same time, the constituent fibers are partially bonded by the melting of the second component. At this stage, although the heat-separable conjugate fiber is separated into its constituent components, it is just 1
It is in a state in which a large number of deep grooves are carved in the fibers of the book, and the formed ultrafine fibers are bundled and still maintain the shape as one fiber.

Next, the heat-bonded nonwoven fabric is calendered. The purpose of calendering is to loosen the ultrafine fibers in the bundled state as described above into individual fibers so that the ultrafine fibers are more separated and present. Calendering should be performed at room temperature. When heated, the nonwoven fabric obtained by remelting the second component becomes hard, which is not preferable. The pressure needs to be appropriately set according to the basis weight of the nonwoven fabric. For example, a nonwoven fabric having a basis weight of about 40 g / m ² can sufficiently achieve the above object even with a linear pressure of 20 kg / cm. A combination of metal rolls, hard rubber rolls, cotton rolls, etc. is used for processing. Also,
In addition to the flat roll, an embossing roll may be used, and the processing with the embossing roll promotes the separation of the ultrafine fibers only at the embossed portion.

[0020]

In the present invention, the heat-separable conjugate fiber is separated into a bundle-shaped ultrafine fiber group, and this ultrafine fiber group is separated into individual fibers by calendering to give the nonwoven fabric excellent flexibility and feel. . Further, the heat-shrinkable component, which is the second component, also plays the role of the heat-adhesive component, and thus allows the nonwoven fabric to be formed only by the heat treatment.

The calendering process has the effect of promoting the separation of the ultrafine fiber group in a bundled state and making the above heat-bonded non-woven fabric softer and more tactile.

[0022]

EXAMPLES The present invention will be described below with reference to examples.

[Production of heat-separable conjugate fiber] Melting point 260 ° C.
Polyethylene terephthalate resin of the first component (1),
A melting point of 136 ° C. An ethylene-propylene copolymer was used as the second component (2), and a conjugate fiber having a fiber cross section as shown in FIG. 2 was melt-spun at a spinning temperature of 300 ° C. Then this 9
After being stretched 3 times in hot water at 5 ° C., a mechanical crimp of 16 pcs / inch is given in a stuffing box while applying a fiber treatment agent, and dried for 15 minutes in a hot air through dryer at 110 ° C., It was cut into 2 denier, 38 mm staple fibers.

[Examples 1 and 2] A parallel web having a basis weight of about 40 g / m ² was prepared with a parallel card using only the above-mentioned heat-separable conjugate fiber. The web was heat-treated in a hot air penetrating type machine at 150 ° C. for about 30 seconds to obtain a heat-bonded nonwoven fabric. Next, this was calendered at a linear pressure shown in Table 1 using a processing machine composed of a metal flat roll and a cotton roll.

[Examples 3 to 4] A web was prepared in the same manner as in Examples 1 and 2, and after heat treatment, the area was 0.785.
Calendering was carried out with a linear pressure shown in Table 1 using a processing machine comprising a metal embossing roll and a cotton roll having 25 circular protrusions of mm ² per cm ² .

[Comparative Example 1] A non-woven fabric was prepared by the same method as in Example 1 and heat-treated as a comparative example.

Table 1 shows the physical properties of the nonwoven fabrics of Examples 1 to 4 and Comparative Example 1.

[0028]

[Table 1]

In Table 1, the physical properties of the nonwoven fabric were evaluated by the following methods.

[Strength, breaking length, elongation] JIS L 1
According to 096, a sample piece with a width of 5 cm and a length of 15 cm is grasped at a gripping interval of 10 cm and stretched at a pulling speed of 30 cm / min using a constant-speed extension type tensile tester, and the load value and extension rate at cutting are respectively set. Strength (kg / 5 cm) and elongation (%) were used. The breaking length was calculated from the breaking length (km) = strength (kg) / [sample width (m) x basis weight (g / m ² )].

[Drape Coefficient] JIS L 1096
Evaluation was performed using a drape tester in accordance with the above. Here, the surface that was in contact with the net conveyor in the hot air dryer was the "back" surface of the sample.

[Separated State] The surface of the nonwoven fabric is magnified 140 times with a microscope and the fibers are observed from the side,
The following criteria evaluated. 1 As seen from the side, separation is not observed, and ultrafine fibers are bundled to maintain the shape as one fiber. 2 Separated to form ultrafine fibers, one fiber is 2-3
It is observed that the fibers are separated into ultrafine fibers. 3 Separated to form ultrafine fibers, one fiber is 4-5
It is observed that the fibers are separated into ultrafine fibers.

[0033]

As described above, according to the method for producing a non-woven fabric of the present invention, the heat-separable conjugate fiber can be more easily promoted to be separated without impairing various properties such as strength of the heat-bonded non-woven fabric after heat treatment. A non-woven fabric having a good feel can be obtained. Also,
According to the manufacturing method of the present invention, since the heat-bonded nonwoven fabric is once calendered, the nonwoven fabric can be manufactured and calendered separately, which does not require major modification of existing equipment. Also, since the calendering is performed at room temperature, the production cost can be kept low.

[Brief description of drawings]

FIG. 1 is a fiber cross-sectional view of an example of a heat-separable conjugate fiber used in the present invention.

FIG. 2 is a fiber cross-sectional view of an example of the heat-separable conjugate fiber used in the present invention.

FIG. 3 is a fiber cross-sectional view of an example of the heat-separable conjugate fiber used in the present invention.

FIG. 4 is a fiber cross-sectional view of an example of the heat-separable conjugate fiber used in the present invention.

[Explanation of symbols]

 1st component 2nd component

Continuation of front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display location B01D 39/16 A D01D 5/36 D01F 8/04 Z D04H 1/42 KRT

Claims (1)

[Claims] 1. A melting point (T ₁ ° C.) of 130 <T ₁ <350.
The thermoplastic resin in the range of 1 is used as the first component, the thermoplastic resin having a melting point lower than that of the first component by 20 ° C. or more and the thermal shrinkage rate of 50% or more at the temperature near the melting point is the second component, and each component is A fiber web containing 30 wt% or more of heat-separable conjugate fibers, a part of which is exposed on the fiber surface, is heat-treated at a temperature higher than the melting point of the second component and lower than the melting point of the first component. A method for manufacturing a non-woven fabric, which comprises calendering the heat-bonded non-woven fabric.