JPH03287818A - Thermally bondable fiber and nonwoven fabric - Google Patents

Abstract

PURPOSE:To obtain the title fiber providing nonwoven fabric having soft handle and high strength arranging a first component comprising a specific PE and a second component composed of crystalline PP in a specific conjugate ratio into a sheath core type to give undrawn conjugate fiber and drawing. CONSTITUTION:(A) A first component comprising a PE having >=0.930g/cm<3> density and 5-35, preferably 8-30 melt flow index (g/10 minutes at 190 deg.C) and (B) a second component composed of crystalline PP in a conjugate ratio (component A/B) of (65-35)/(35-65) are arranged in sheath core type or side-by-side type to give undrawn conjugate yarn, which is drawn at 1.5-3.0, preferably 1.8-2.5 draw ratio to give the objective fiber.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to thermally bondable fibers and nonwoven fabrics.

More specifically, the present invention relates to thermoadhesive fibers and nonwoven fabrics that yield nonwoven fabrics with a soft texture and high strength.

[Conventional technology]

In the production of nonwoven fabrics, methods for adhering fibers to each other include methods such as needle punching that involve intertwining between fibers;
There are methods using various adhesives, methods using heat-adhesive fibers, etc. When heat-adhesive fibers are used, the bonding method can be roughly divided into an air-through method using a SAXILON band dryer, a SAXILON drum dryer, etc., and a point bonding method using a hot roll.

The fibers used in the point bond method are widely used, such as polyolefin fibers such as polypropylene fibers, polyethylene fibers, and polyethylene-polypropylene composite fibers, or synthetic fibers such as polyester fibers and polyamide fibers. JP-A No. 132-2Ei3321 for polyolefin heat-adhesive fibers, JP-A-1913 for polyolefin fibers containing benzophenone compounds, method for producing nonwoven fabric by heat-bonding with suction drum and then heat-bonding with emboss roll. as Japanese Patent Publication No. 1-30942, and as a self-adhesive nonwoven fabric of a specific weight containing sheath-core type fibers made of high-density polyethylene/polypropylene, Japanese Patent Application Laid-open No. 1349/1986.
[I9 Publication, Japanese Patent Publication No. 12830/1983, etc. are known as nonwoven fabrics made from fibers having no latent crimp properties made of specific polyethylene/polypropylene.

[Problem to be solved by the invention]

These nonwoven fabrics are required to have properties such as a soft texture and high strength, but when conventional polyethylene-polypropylene composite fibers are used, the strength of the nonwoven fabric increases as the thermal bonding temperature increases, but the texture is significantly impaired. On the other hand, if the thermal bonding temperature is low, the texture will be soft but the strength of the nonwoven fabric will be weak, and it is difficult to satisfy both.

[Means to solve the problem]

As a result of intensive research in order to improve the above-mentioned drawbacks of conventional polyethylene-polypropylene composite fibers, the present inventors have discovered that the first component consists of polyethylene having a density of 0.930 g/cm or more and a melt flow index of 5 to 35. and a second component consisting of crystalline polypropylene at a composite ratio (first component/
2nd component) A thermoadhesive fiber obtained by drawing a composite undrawn yarn of 65-35/35-65 in a sheath-core type or parallel type, and stretching it at a rate of 1.5-3.0. The present invention was completed after learning that the initial objective could be achieved by using a nonwoven fabric made by thermally bonding heat-adhesive fibers.

The density of the polyethylene used in the present invention is 0.930g
/cm" or more, and ordinary high-density polyethylene, linear low-density polyethylene, and mixtures thereof can be used. If the density is less than 0.930 g/cm", the friction on the fiber surface will be high and the card will not pass through. Problems arise such as the properties of the nonwoven fabric deteriorate, and after processing the nonwoven fabric, it becomes slimy and the smoothness of the surface is impaired. Moreover, the melt flow index of polyethylene is 5-35, preferably 8-30.

If the groove is not 5, thread breakage is likely to occur during spinning (if the groove is over 35, the adhesive point strength of the nonwoven fabric is weak and it is likely to break.Polypropylene can be selected as appropriate from those used for general fibers, but polypropylene and It is necessary to use a material having an appropriate melt viscosity in consideration of the fiber cross-sectional shape when composited.

The composite ratio of polyethylene and polypropylene (polyethylene/polypropylene) is 65-35/35-65. When the component ratio of polyethylene exceeds 65%, the strength of the composite fiber decreases, so that after thermal bonding, the nonwoven fabric will break even if the strength at the bonding point is strong. Moreover, if it is less than 35%, the bonding point will not have sufficient strength due to the small amount of the fusion bonding component, which is not suitable.

The composite undrawn yarn obtained by melt-spinning in a sheath-core type or parallel type under the above conditions is stretched at a draw ratio of 1.5 to 3.0, preferably 1.8 to 2.5. The thermoadhesive conjugate fiber of the invention can be obtained. Stretching ratio is 1
．． If it is less than 5, the adhesive point strength after thermal bonding processing is strong but the strength of the fiber itself is weak, and if it exceeds 3.0, the fiber strength is sufficient but the adhesive point strength is weak, so it is difficult to obtain a high-strength nonwoven fabric. Can not.

The nonwoven fabric of the present invention uses the thermally bonded composite fiber of the present invention,
The web is sized using a card machine, and then thermally bonded using a relatively low-temperature heat roll. This processing temperature means that the nonwoven fabric is processed at a relatively lower temperature than the conventional processing temperature. This thermal bonding processing temperature is set higher if the roll speed is faster. More specifically, in linear low-density polyethylene whose outer skin, which serves as the bonding point, has a density of 0.930 g/am,
115-130'C, density 0.970 g/c
120 to 140°C is preferable for high-density polyethylene with a temperature of 120°C to 140°C. If the processing temperature is higher than the set temperature, the nonwoven fabric will have strong adhesive point strength but will have a weak texture. Conversely, if the processing temperature is lower than the set temperature, the nonwoven fabric will have a weak texture. Although it has a soft texture, the adhesive point strength of the nonwoven fabric is weak.

The strength of the nonwoven fabric obtained by the point bond method is
It is governed by the strength of the bonding point and the strength of the fibers connecting the bonding points. The thermally bonded composite fiber of the present invention has strong adhesion point strength when processed into a nonwoven fabric using the point bond method.
Moreover, the fiber itself is characterized by having appropriate strength, and furthermore, compared to conventional polyethylene-polypropylene composite fibers, it can be processed using low-temperature hot rolls, so it can be made into a nonwoven fabric with a soft texture.

〔Effect of the invention〕

Since the heat-adhesive fiber of the present invention is a composite fiber made of a specific polyethylene and a specific blending ratio, the fiber itself had appropriate strength.

When conventional polyethylene-polypropylene composite fibers are thermally bonded at relatively low temperatures, they do not have sufficient bonding point strength. However, since the heat-adhesive fiber of the present invention has low stretching, even when heat-adhesively processed at a relatively low temperature, the adhesive point strength was strong and the nonwoven fabric strength was high.

Furthermore, when the heat-adhesive fiber of the present invention is made into a nonwoven fabric, it has a strong adhesion point strength even when heat-bonded at a relatively low temperature, so it can be heat-bonded at a low temperature. Because of this relatively low-temperature thermal bonding process, the nonwoven fabric made of the thermally bondable fibers of the present invention had a soft texture.

As described above, since the heat-adhesive fiber of the present invention is a specific composite fiber that has been subjected to low stretching, it is possible to form the desired web using a carding machine and then perform ribbon bond processing using a relatively low-temperature heat roll or the like. can. For this reason, the thermal bonding fiber was able to produce a nonwoven fabric that had all of the characteristics of the fiber itself having appropriate strength, high strength adhesiveness, and a soft texture, which had been difficult to achieve in the past.

The thermoadhesive fibers and nonwoven fabrics of the present invention can be widely used as surface materials for sanitary materials such as sanitary napkins and disposable diapers, or for medical purposes such as surgical gowns.

〔Example〕

The present invention will be explained using Examples and Comparative Examples.

The following physical property evaluation method was used on each side.

Spinnability: Feed polypropylene and polyethylene to a composite spinning extruder and use a sheath-core type or parallel type spinneret with 350 holes to produce approximately 150 g/min.
The number of yarn breakages per hour when spinning at an extrusion rate of is evaluated based on the following criteria.

O: 0 times, △: 1 to 3 times, ×: 4 times or more Fiber fineness 1 Strength, elongation: The physical properties of the spun undrawn yarn and the fibers drawn at the draw ratio listed in Table 2 were determined according to JIS 1015 (
Measure according to the chemical fiber staple test method).

Non-woven fabric strong crab sample Heat-adhesive fiber was sized using a miniature card machine, and the obtained web of approximately 20 g/m was heated to a predetermined temperature, diameter 185 ms, pressure 20 kg/c.
mO') Eim/m between gold WA rolls (top: embossing roll with 25% convex area, bottom: flat roll)
It is made into a non-woven fabric by thermal bonding at a speed of in. The bowing strength of the obtained sample nonwoven fabric in a width of 5 cm was measured in the mechanical flow direction (hereinafter abbreviated as Ml) and in the direction perpendicular thereto (hereinafter abbreviated as CD).

Feel: The feel of the sample nonwoven fabric is judged by a sensory test conducted by five panelists.

5 people judged the texture to be soft, smooth, and smooth, while 0°2Å or less was judged to be slimy or hard.

Items judged to be slimy or hard with a thickness of 3 Å or more are marked with an x.

When conventional polyethylene-polypropylene composite fibers are used, as in Comparative Example 7, the nonwoven fabric has sufficient strength when thermally bonded at high temperatures, but the feel is hard, which is a practical problem. Although the feel is good as in Example 5, the nonwoven fabric lacks strength and cannot satisfy both requirements. Comparative Example 6 with a low stretching ratio, Comparative Example 1 and Comparative Example 2 that do not satisfy the polyethylene ratio, and Comparative Example 3 that does not satisfy the melt flow index, have insufficient nonwoven fabric strength and Comparative Example 4 that does not satisfy the polyethylene specific gravity. The nonwoven fabric has a slimy feel and lacks strength.

Claims (1)

[Claims] 1) The density is 0.930 g/cm^3 or more and the melt flow index (g/10 min, 190°C) is 5 to 35.
A first component consisting of polyethylene and a second component consisting of crystalline polypropylene are combined at a composite ratio (first component/second component).
65-35/Thermoadhesive fiber obtained by stretching composite undrawn yarn obtained by arranging 35-65 in a sheath-core type or parallel type at a stretching ratio of 1.5 to 3.0. 2) A nonwoven fabric obtained by thermally bonding the thermally bondable fiber of claim 1.