JP2545248B2 - Stretchable non-woven fabric - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of use] The present invention relates to a non-woven fabric having excellent stretchability, which is used as a base fabric, a bandage, etc. for a patch.

[Prior art and its problems]

A non-woven fabric made by adhering two low melting point components of a thermo-adhesive composite fiber composed of two types of thermoplastic resins having different melting points to each other by heat-sealing is hygienic and smooth to the touch. Therefore, it is often used as a surface material for masks or paper diapers. As a method of imparting elasticity to such a nonwoven fabric, a method of using a thermoadhesive conjugate fiber that causes crimping of the fiber during heat treatment for heat fusion (Japanese Patent Laid-Open No. 59-211668) is known. ing. However, in such a method, the fibers shrink with the occurrence of crimp during heat treatment,
There were problems such as non-uniform thickness and density of the non-woven fabric.

[Means for solving problems]

As a result of earnest research for obtaining a homogeneous nonwoven fabric having excellent stretchability, the present inventors have found that a mixed fiber of a highly shrinkable conjugate fiber (A) and a low shrinkage and heat-adhesive conjugate fiber (B) is used. The inventors have completed the present invention by knowing that the intended purpose can be achieved by fixing the contact points of the fibers as a web by fixing the adhesive components of the composite fiber (B).

In the present invention, high shrinkage means a case where the shrinkage rate of the fibers accompanying crimping generated during the heat treatment described below exceeds 40%, and low shrinkage means a case where the shrinkage rate is 20% or less. To do.

The low-shrinkage and heat-adhesive polyolefin-based composite fiber (B) used in the present invention is crystalline polypropylene (melting point 16).
5 ° C / high density polyethylene (melting point 132 ° C), crystalline polypropylene (melting point 165 ° C) / ethylene / vinyl acetate copolymer (melting point 18 ° C), etc. Of these, the low melting point thermoplastic resin (hereinafter sometimes referred to as the adhesive component) is 50% of the fiber surface.
% Or more, it is a composite yarn spun into a parallel type or a sheath-core type, and in order to have a low shrinkage, the sheath-core type may be used. (For example, as shown in JP-B-52-37097 and JP-A-52-4653) or sufficient annealing treatment can be easily carried out. If the content of the composite fiber (B) in the mixed fiber is less than 10% by weight, the bonding points of the fibers are insufficient, resulting in insufficient strength and insufficient elongation recovery rate. It is not preferable because of insufficient elongation.

The highly shrinkable polyolefin composite fiber (A) used in the present invention is crystalline polypropylene (melting point 165 ° C.) / High density polyethylene (melting point 132 ° C.), crystalline polypropylene (melting point 165 ° C.) / Ethylene / propylene copolymer ( Melting point 1
It can be obtained by composite spinning of two types of polyolefin resins with different melting points such as 32 ° C) into a parallel type or an eccentric sheath core type.
As the low melting point component of the composite fiber (A), a polyolefin resin having a melting point lower than the melting point of the low melting point component of the composite fiber (B) by 5 ° C. or more is used. Although the shrinkage rate varies depending on the spinning / drawing conditions, generally, high shrinkability can be obtained by drawing at 1.5 to 2.5 times at low temperature. However, in the heat treatment described below, the thermoplastic resin used for the composite fiber (A) is higher than the above adhesive component by 5 ° C. or more in order to fuse the contact points of the fibers with only the adhesive component of the composite fiber (B). Select one with a melting point.

When the content of the composite fiber (A) in the mixed fiber is less than 50% by weight, the resulting nonwoven fabric has poor elasticity and insufficient elongation recovery rate, and when it exceeds 90% by weight, shrinkage unevenness occurs, which is not preferable.

In the present invention, other fibers can be mixed and used as long as the composite fibers (A) and the composite fibers (B) do not exceed the above contents. Such other fibers may be fibers that do not shrink or deteriorate by the heat treatment described later, and examples thereof include natural fibers such as cotton and wool, and synthetic fibers such as rayon, nylon, polyester, and polyolefin. . A mixture of the above fibers is formed into a web having a desired weight per unit area using a known device such as a card machine or a random webr, and the melting point of the composite fiber (B) is higher than the melting point of the adhesive component (low melting point resin) of the composite fiber (B). The heat treatment for forming a nonwoven fabric is performed at a temperature lower than the melting points of both components of the resin and the composite fiber (A). The heat treatment can be performed by a known method such as infrared heating, a hot air dryer, a heating roll.

〔Example〕

The present invention will be described more specifically with reference to Examples and Comparative Examples. The test method used in each example is as follows.

Condensation rate A parallel web of 25 cm in length and width is heated in a hot air oven at a specified temperature for 5 minutes, and the length in the longitudinal direction (a) after heating is measured, and (1-a / 25) x 100 = shrinkage rate Ask.

Initial elongation According to the tensile test method of JIS L 1085 (Nonwoven fabric test method), a test piece with a width of 5 cm and a length of 20 cm is gripped at a gripping interval of 10 c.
Draw a load-elongation curve at m and a pulling speed of 10 cm / min.
The elongation when the weight reaches 200 g is the initial elongation.

Elongation recovery rate According to the extension recovery rate measuring method (fixed length method) of JIS L 1096 (general woven fabric test method), the upper end of a test piece with a width of 5 cm and a length of 20 cm is clamped, and marks at intervals of 10 cm are lengthwise. Then
Extend the distance between marks to 12 cm, leave it for 1 minute, then remove the weight, and after 3 minutes, measure the length (L) between the marks.
(6-L / 2) × 100 = Calculated by the recovery rate.

Feeling A sensory test was conducted by 5 panelists, and when all were judged to be soft ○ When 3 or more were judged to be soft △ When 3 or more were judged to be lacking in softness Is displayed as ×.

Uniformity Place a transparent glass plate (5 mm in thickness, 10 cm in length and width) on a non-woven fabric (10 cm in length and width) on a black mount, and count the number of holes with a diameter of 1 mm or more when compressed by the weight of glass. Measure the number of holes is 0, ○, 1-2 is △, 3
Display more than one with x.

Examples 1 to 7 and Comparative Examples 1 to 6 Using the five types of fibers shown in Table 1, webs with various mixing ratios shown in Table 2 were prepared and heat treated in a hot air oven for 3 minutes to give nonwoven fabrics. Obtained. The basis weight, heat treatment temperature and physical properties of the non-woven fabric are also shown in Table 2.

Composite fiber (1): ethylene-propylene copolymer (melting point
138 ° C) and crystalline polypropylene (melting point 165 ° C) were spun in parallel at a composite ratio of 50/50 and drawn 2.7 times at 80 ° C to obtain a single fiber fineness of 3 denier and a fiber length of 51 mm. .

Composite fiber (2): a high-density polyethylene (melting point 132 ° C.) and crystalline polypropylene (melting point 165 ° C.), which were obtained by spinning a composite fiber in a parallel type at a composite ratio of 50/50 and stretching 4 times at 30 ° C. A composite fiber with a yarn fineness of 3 denier and a fiber length of 51 mm.

Composite fiber (3): Ethylene / vinyl acetate copolymer (melting point
108 ° C) as a sheath component, crystalline polypropylene (melting point 165
C.) as a core component, a composite fiber having a denier of 50 mm and a composite fiber of 3 denier and a fiber length of 51 mm, obtained by composite spinning into a sheath-core type at a composite ratio of 50/50 and stretching at 80.

Composite fiber (4): crystalline polypropylene (melting point 165 ° C)
And high-density polyethylene (melting point 132 ° C), so that the high-density polyethylene occupies 66% of the cross section of the fiber, the composite ratio is 50/5.
A composite fiber having a single yarn fineness of 3 denier and a fiber length of 51 mm, which was obtained by performing parallel spinning at 0 ° C. and stretching 4 times at 100 ° C.

PP fiber: A fiber having a single yarn fineness of 3 denier and a fiber length of 51 mm obtained by spinning a crystalline polypropylene alone.

As is clear from the results shown in Table 2, in the nonwoven fabric of the present invention, the contact points of the fibers are composite fibers (B) by heat treatment.
In addition to being firmly adhered by the low melting point resin, the composite fiber (A) tends to shrink during heat treatment, so that moderate stress acts between the fibers and it has excellent extensibility and elongation recovery. There is.

Claims (1)

(57) [Claims] 1. A shrinkage rate of 40% consisting of two components with different melting points
Highly shrinkable polyolefin-based composite fiber (A)
90% to 50% by weight, consisting of two components with different melting points
10% to 50% by weight of a polyolefin-based composite fiber (B) having a low shrinkage and a heat adhesive property of 20% or less, and the melting point of the low melting point component constituting the composite fiber (A) is the composite fiber ( The melting point of the adhesive component constituting B) is 5 ° C. or more, and the contact point between the fibers is fixed by fusion bonding of the adhesive component of the composite fiber (B), and the elongation recovery rate at 20% elongation is 90% or more. A polyolefin stretchable non-woven fabric characterized by being present.