JPS61266651A - Nonwoven fabric - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a high-strength nonwoven fabric suitable for various uses such as sanitary materials, packaging materials, filtration materials, rug base materials, and core materials.

(b) Conventional technology Cellulose fibers and various synthetic fibers have traditionally been used as materials for nonwoven fabrics, but in recent years, synthetic fibers have been used to make paper using a wet method using ordinary circular or fourdrinier paper machines. Techniques for producing dry nonwoven fabrics using nonwoven fabrics, cards, random webs, etc. are gradually developing, and the amount of these nonwoven fabrics used is increasing year by year. In the above nonwoven fabric manufacturing method, the production speed is 100 m in the wet nonwoven fabric manufacturing method.
/111n, and although the production speed is slow in the dry nonwoven fabric manufacturing method, thick materials such as hard cotton can be easily manufactured. However, in all of these nonwoven fabric manufacturing methods, the binder is usually used after forming the nonwoven fabric, followed by dipping, spraying, coating, etc., drying and heat treatment to bond the fibers together, or blending binder fibers and heat treatment.
Strength is imparted to nonwoven fabrics by a method of melting binder fibers and bonding between fibers, as well as other methods such as a needle punch method and a water jet method.

Generally speaking, the higher the strength, the better it is for the product and is desirable. In order to increase the strength of a non-woven fabric, basically, in addition to using high-strength fibers as constituent fibers of the non-woven fabric, it is also necessary to increase the amount of intertwining between the fibers, and to firmly bond the fibers to each other, especially at the points where the fibers are intertwined. Specifically, it is necessary to increase the amount of binder attached, increase the blending ratio of binder fibers, increase the heat treatment temperature, and increase the needle density, but all of these methods are costly. This is undesirable as it may adversely affect other properties such as making the fibers stiffer and becoming rougher and harder.Especially in the case of nonwoven fabrics made of constituent fibers such as polyester and nylon, the cross-sectional shape of the fibers is usually circular, so the fibers may The contact at the intertwined point is point-like or linear, and even if a binder is used, the strength is low if only that point is bonded.In order to increase the strength, a large amount of binder is used to cover a wide area near the intertwined point of the fibers. In addition, locations other than the intertwining points must also be bonded via a binder, which is thought to cause problems such as roughness and hardness as described above.

(c) Problems to be Solved by the Invention The present invention provides a high-strength nonwoven fabric that can be produced without changing conventional nonwoven fabric production conditions, such as the amount of binder added, the blending ratio of binder fibers, the heat treatment temperature, and the needle density. This is what we are trying to provide.

(d) Means and action for solving the problems The present invention includes:
5% by weight or more of the constituent fibers are composed of irregular cross-section synthetic fibers having a multilobed radial shape of four or more lobes and a concave cross-section between adjacent lobes, and in the cross-sectional shape of the irregular cross-section synthetic fibers, The radius R of an inscribed circle that touches at least three of the concave parts between adjacent lobes of a radial multilobed shape with four or more lobes, and the length from the center of the inscribed circle to the tip of the multilobed ratio L
The nonwoven fabric is characterized in that at least three of /R are 1.2 or more.

The nonwoven fabric of the present invention can be produced by any conventionally known wet or dry method. After forming a web and further needle bunching if necessary, a binder is applied by dipping, spraying, coating, etc. It can be produced by applying it by drying and heat treatment, or by mixing binder fibers into the web in advance and heat treatment to bond the fibers together.

The most important point in the nonwoven fabric of the present invention is that, as mentioned above, 5% by weight or more of the constituent fibers have a radial cross-sectional shape of four or more lobes, and the irregular cross-section is concave between adjacent lobes. This is a point occupied by synthetic fibers, and by being at least partially composed of synthetic fibers with such a multilobal cross-sectional shape,
The nonwoven fabric of the present invention has higher strength than ordinary nonwoven fabrics made of circular or trilobal synthetic fibers, and has a good texture and an elegant luster. However, if the number of leaves becomes 9 or more, the shape becomes close to round (therefore, the effect of increasing strength tends to weaken), and up to 8 leaves are preferable.

FIG. 1 is a cross-sectional view showing an example of a radial four-lobed cross-section fiber of the irregular cross-section synthetic fibers. That is, radially 4
convex leaves (11, +21. (31, (4)) and four concave parts (al, (b
It shows a shape consisting of l, (C1, (d+).5
The basic pattern is the same for multilobed forms that are larger than leaves.

As is clear from the cross-sectional shape, the irregular cross-section synthetic fibers have four or more grooves in the longitudinal direction of the fiber surface corresponding to the number of leaves, so when a nonwoven web is formed,
The contact area between fibers is large at intertwined points, and when a certain amount of binder is applied, a relatively large amount of binder accumulates in the concave grooves on the fiber surface at the contact points with fibers or intertwined points. It is thought that the adhesive fixation between the fibers becomes strong, resulting in a nonwoven fabric with high strength and good texture.

The basic cross-sectional shape of the irregular cross-section synthetic fiber used in the nonwoven fabric of the present invention is as described above, but in order to increase the strength of the nonwoven fabric, it is necessary that the shape satisfies the following conditions. That is, the ratio L/R of the radius R of the inscribed circle that touches at least three of the concave parts of the radial multilobal shape and the length from the center 0 of the inscribed circle to the tip of the multilobular part. , at least three leaves are 1.2 or more. In addition, in a multilobal shape of four or more leaves, if multiple inscribed circles can be drawn, the inscribed circle is the smallest one. By satisfying the above conditions, the concave grooves on the fiber surface will have sufficient depth to accumulate the binder required to exhibit high adhesive strength.

Examples of the above-mentioned irregular cross-section synthetic fibers include various synthetic fibers such as polyester, polyamide, polyacrylonitrile, polyolefin, and polyvinyl alcohol, and various additives such as matting agents and antistatic agents may be added as necessary. It may be contained, and any fineness in the range of 0.3 to 200 d can be used.

In the nonwoven fabric of the present invention, it is necessary that the above-mentioned irregular cross-section synthetic fibers are used in a uniform mixture of 5% or more by weight of the constituent fibers, including when used alone, and if it is less than 5% by weight, it is said to be high strength. Other fibers to be blended with the above-mentioned irregular cross-section synthetic fibers, which should preferably be blended in an amount of 20% by weight or more in order to obtain a sufficient effect if the intended purpose cannot be achieved, may be natural fibers or regenerated fibers as necessary. Any fibers such as synthetic fibers or low melting point binder fibers can be selected.

(E) Examples Example 1゜ Fineness is 1.4d, cross-sectional shape is 5-lobed, 8-lobed, 9-lobed, L
For each of four types of drawn polyester fibers having a fiber length of 51 m1 and having an average value of /R of 1.22 to 1.24, the fiber was 60% by weight and the fineness was 4d.

40% by weight of low-melting point polyester binder fibers with a circular cross section and a fiber length of 5 l are dispersed in water to a fiber concentration of 0.01% by weight, and paper is made using a square paper machine with a wire mesh of 25C11 x 25CI11. After reducing the moisture content of the paper stock to approximately 15%, use a drum-type rotary dryer to reduce the moisture content to 15%.
Heat treatment was performed at 40°C for 100 seconds to obtain a wet-laid nonwoven fabric with a basis weight of 40 g/m.

As a comparative example, the same method as the above example was used, except that a normal drawn polyester fiber with a circular cross section and a drawn polyester fiber having a trilobal shape and an average value of L/R of 1.20 were used instead of the drawn polyester fiber with an irregular cross section. A wet-laid nonwoven fabric was produced using exactly the same method under nine conditions.

Table 1 shows the tensile strength and gloss of each wet-laid nonwoven fabric obtained.

The nonwoven fabric of the present invention had higher strength, deeper luster, and better texture than the nonwoven fabric of the comparative example, which had a circular and trilobal cross section.

Table 1 * (Note) Tensile strength: Using a constant speed extension type tensile tester,
Sample width: 15n, sample length: 180mm.

Measured at a tensile speed of 20/sin Ta.

Example 2 The fineness is 1.25 d, the cross section has a radial six-lobed shape, the average value of L/R of the six leaves is 1.15, and the L/R of at least three leaves is 1.2 or more, and the L/R of the six leaves is 1.15. Fiber length 4 of four types of drawn polyester fibers with average R values of 1.2, 1.3 and 1.6
For each of 4B, 80% by weight of the fibers and 20% by weight of low melting point polyester binder fibers having a circular cross section with a fineness of 4d and a fiber length of 51mm were mixed, a carded web was prepared using a sample roller card, and the carded web was Heat treatment was performed for 100 seconds at a temperature of 140° C. using a drum-type rotary dryer to obtain a dry nonwoven fabric having a basis weight of 40 g/rrf.

As a comparative example, a dry nonwoven fabric was produced using the same method and conditions as in the example, except that ordinary drawn polyester fibers with a circular cross section were used in place of the drawn polyester fibers with irregular cross sections.

Table 2 shows the tensile strength and gloss of each of the obtained dry nonwoven fabrics.

Table 2 * (Note) Tensile strength: Using a constant speed extension type tensile tester,
Sample width 25f1. Sample length 100fl.

Measured at a tensile speed of 50 cm/sin. Ta.

The nonwoven fabric of the present invention has higher strength, better gloss, and better texture than the nonwoven fabric of the comparative example.
/R average value of 1.2 or more was excellent.

(f) Effects of the invention As mentioned above, the nonwoven fabric of the present invention has 5% by weight of the constituent fibers.
Since the above fibers are made of multi-lobed irregular cross-section fibers with four or more radial leaves, the bond between the fibers by the binder is strong and strong, and the appearance has an elegant luster unique to irregular cross-section fibers, and the texture is also good. It has good properties and can be used for commercial purposes such as sanitary materials, packaging materials, filtration materials, rug base materials, core materials, and other industrial materials.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an example of the cross-sectional shape of the modified cross-section synthetic fiber used in the present invention.

Claims (1)

[Claims] (1) At least 5% by weight of the constituent fibers are composed of irregular cross-section synthetic fibers having a multilobed shape with four or more radial leaves and a concave cross-section between adjacent lobes, and the cross section of the irregular cross-section synthetic fibers In terms of shape, the radius R of an inscribed circle that touches at least three of the concave parts between adjacent lobes of a multilobed shape with four or more radial leaves, and the length from the center of the inscribed circle to the tip of each leaf. A nonwoven fabric characterized in that at least three of the ratios L/R to L are 1.2 or more.