JPH0411059A - Stretchable nonwoven fabric - Google Patents

Abstract

PURPOSE:To obtain the title nonwoven fabric composed of a copolymer fiber of polymer block consisting essentially of an aromatic vinyl compound and specific polymer block, having low modulus and highly stretchable property as well as excellent weather resistance and useful for poultice pad base, etc. CONSTITUTION:The aimed nonwoven fabric composed of a fiber of block copolymer consisting of (A) a polymer block A consisting essentially of 10-50wt.% aromatic vinyl compound and (B) polymer block B consisting essentially of recurring units expressed by formula I and formula II (arbitrary one or two in R<1> to R<6> are methyl and the remainder are H). Furthermore, basic pattern is preferably triblock (the components A-B-A).

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to thermoplastic elastomer nonwoven fabrics.

More specifically, it has low modulus, high elasticity, and excellent weather resistance.
In particular, the present invention relates to a nonwoven fabric made of a thermoplastic elastomer that is suitable for applications that require elasticity, such as a poultice base fabric.

[Prior Art 1] There has been a strong demand for stretchable nonwoven fabrics in the nonwoven fabric industry, and various types have been proposed. For example, stretchable nonwoven fabrics that utilize fiber crimping are available as poultice base fabrics, but they are insufficient in terms of elongation and elastic recovery. Polyamide, polyolefin, and polyester elastomers are available as polymers, but they do not provide sufficient extensibility. Above all, nonwoven fabrics made of polyurethane have good elasticity (Japanese Patent Application Laid-Open No. 59-223347). However, when used as a poultice base fabric, it has drawbacks such as its rough texture making it difficult to apply poultices, and its slightly high modulus making it unsuitable for this purpose, poor weather resistance, and yellowing.

[Problems to be Solved by the Invention] An object of the present invention is to obtain an elastomeric nonwoven fabric with low modulus, high elasticity, and excellent weather resistance.

[Means for Solving the Problems] The present invention comprises a polymer block A mainly composed of 10 to 50% by weight of an aromatic vinyl compound and the following [N formula and 0 to 20 mol% of [I[] formula] This is a stretchable nonwoven fabric made of fibers of a block copolymer consisting of a polymer block B mainly composed of the repeating units shown below.

(However, any one or two of R+, ..., R4 are methyl groups, and the rest are hydrogen atoms.) Such a block copolymer consists of eight polymer blocks mainly composed of aromatic vinyl compounds. A block copolymer consisting of a polymer block B mainly composed of a conjugated diene compound is hydrogenated, and 80% of the aliphatic double bonds based on the conjugated diene are
% or more by hydrogenation.

As the aromatic vinyl compound referred to in the present invention, styrene is the most preferable in terms of cost. Furthermore, examples of conjugated dienes include 1,3-butadiene, isoprene, pentadiene, hexadiene, etc., and imprene is suitable for the purpose of the present invention.

Hydrogenated block copolymer (hereinafter referred to as 5) used in the present invention
The styrene content of the EPS (abbreviated as EPS) ranges from 10 to 50% by weight. If the styrene content is less than 10%, moldability and heat resistance will be poor. Styrene content is 50% by weight
If it is more than that, the elasticity and flexibility will be reduced, making it impossible to achieve the object of the present invention.

In the 5EPS used in the present invention, 80% or more, preferably 90% or more of the isoprene double bonds based on conjugated double bonds must be hydrogenated.

If it is less than this, thermal deterioration is likely to occur during melt molding, and the resulting nonwoven fabric also has poor weather resistance, which is a problem.

Although there are various polymer forms of the block copolymer, linear block forms, particularly ABA type triblocks, are preferred. These 5EPS are obtained by anionic polymerization using an organic lithium compound or metallic sodium as an initiator in a hydrocarbon solvent. The hydrogenation reaction can be carried out using a noble metal such as platinum or palladium, an organic nickel compound, an organic cobalt compound, or a composite catalyst of these compounds and other organic metal compounds. The hydrogenation rate is
It can be calculated by the iodine value measurement method.

The thermoplastic elastomer used in the present invention has the above-mentioned 5EPS as an essential component, but if necessary, hydrogenated substances such as paraffin oil can be added to improve flow processability. . Furthermore, various additives can be added to further improve the heat resistance, weather resistance, flame retardance, and other functions of the polymer.

The stretchable nonwoven fabric of the present invention is produced using the above-mentioned composition by a direct molding method usually called melt-blowing, that is, by melt-spinning a thermoplastic resin, making it into a fiber stream with high-speed gas, and collecting it in a sheet form. Nonwoven fabrics can be produced by various methods proposed in Japanese Patent Application Laid-open Nos. 49-10258, 49-48921, and 50-121570.

In this case, the polymer used in the present invention has excellent processability such as heat resistance and flowability, and can be molded with ease similar to polypropylene, which is a normal thermoplastic polymer, and has a high melt viscosity, polymer discharge rate, By varying the amount of jetting fluid, it is possible to obtain any desired nonwoven fabric.

[Examples] In order to explain the present invention more specifically and in detail, Examples of the present invention are shown below, but the content of the present invention is not limited to these Examples.

Example 1 In a pressure-resistant container with a stirrer, 3.000 g of cyclohexane
55 parts by weight of sufficiently dehydrated styrene and 0.7 parts by weight of n-butyllithium were added, polymerized at 60°C for 60 minutes, then 300 parts by weight of isoprene was added for 60 minutes, and then 55 parts by weight of styrene was added. Polymerize for 60 minutes,
Synthesize a styrene-isoprene-styrene type block copolymer. The styrene content of the obtained polymer was 27
% by weight.

Cyclohexane was added to this polymer solution to make the polymer concentration 10%, degassed under reduced pressure, replaced with hydrogen, and then
．． Add 5 wt%/polymer palladium catalyst to 10 k
The hydrogenation reaction was carried out in a hydrogen atmosphere of 1.5 g/cm'' to obtain a hydrogenated block copolymer with a hydrogenation rate of 98%.

This polymer was melted in an extruder and then fed into a die at 270°C. Using a melt-blown spinning device with 0.3 mm orifices arranged at l+n+u pitch and slits for jetting heated gas on both sides, 0.2 g per hole was used.
The polymer was discharged at a rate of 1, and air heated to 265° C. was injected in an amount 40 times the weight of the polymer to atomize it. This was collected on a wire mesh belt installed 15 cm below the nozzle and taken up by a winder at the rear.

The physical property values of the nonwoven fabric obtained in Example 1 are shown below.

Weight: 70g/+
e” Strength 3.6x 3.5
g/am/ g/m”30% modulus 0.7
3X O, 63g/cm/g/w" 100% elongation recovery rate 94% Filament diameter 5μ Weather resistance (fade tester) grade 5 or higher (discoloration and fading) This nonwoven fabric has a high fabric density and is stretchable under low stress. It has excellent properties and is ideal for use as a poultice base fabric.

Example 2 Using the polymer of Example 1, temperature, discharge amount, air amount,
The winding speed was changed and the nonwoven fabric was collected. Table 1 shows the conditions and physical property values.

Comparative Example 1 Polymers with a styrene content of 10% and 60% and a hydrogenation rate of 95% were produced by a polymerization method similar to Example 1, and each was made into fibers. However, with 10%, although it could be made finer, it stuck to the wire mesh and could not be made into a non-woven fabric. Also, 6
If it is 0%, the fluidity is poor and it is difficult to thin the fibers, and at the same time, the bonding force between the fibers is poor, and the elasticity is poor, so that the object of the present invention cannot be achieved.

Comparative Example 2 A polymer having a styrene content of 30% and a hydrogenation rate of 80% was obtained by a polymerization method according to Example 1. When this polymer was melt-blown, thermal decomposition occurred and only very weak fibers were obtained, which was not suitable for use as a non-woven fabric.

[Effects of the Invention] The polymer of the present invention is easily moldable into a nonwoven fabric, and it is possible to make a nonwoven fabric with an arbitrary structure. The obtained nonwoven fabric has high elasticity, high elasticity, and low modulus without vulcanization, so it can be used as a base fabric for poultices. In addition, it has superior weather resistance compared to urethane elastic fibers and is less prone to discoloration or yellowing during use, so it can be used for all purposes other than high-temperature use. It also has excellent low temperature properties.

Patent applicant RiRashi Co., Ltd. Representative Patent Attorney Ken Honda

Claims (2)

[Claims] (1) Polymer block A mainly composed of 10 to 50% by weight of an aromatic vinyl compound and the following formula [I] and 0 to 20
A stretchable nonwoven fabric made of fibers of a block copolymer consisting of a polymer block B mainly containing repeating units represented by the formula [II] in a range of mol %. ▲There are mathematical formulas, chemical formulas, tables, etc.▼ (However, in formulas [I] and [II], any one or two of R^1 to R^4 are methyl groups, and the rest are hydrogen atoms. ) (2) The basic type of block copolymer is triblock (A-
B-A) The stretchable nonwoven fabric according to item 1.