JPH03287834A - Acrylic flameproofed textile fabric - Google Patents

Abstract

PURPOSE:To obtain the subject fabric, composed of acrylic flameproofed fiber having many openings with an unspecial shape in the cross section of the fiber and the respective openings forming nearly parallel strawy voids in the longitudinal direction of the aforementioned fiber and reducing the weight thereof. CONSTITUTION:The objective fabric obtained by adding preferably 10-15% polyalkylene glycol having preferably 10000-20000 average molecular weight to a spinning raw material consisting essentially of >=60wt.% acrylonitrile and up to 40wt.% ethylenic monomer copolymerizable with the aforementioned acrylonitrile, aging the prepared solution preferably for 6-10hr, spinning the resultant spinning solution, heat-treating the formed fiber at 200-400 deg.C in an oxidizing atmosphere, providing acrylic flameproofed fiber having many openings of an unspecial shape in the cross section and the respective openings forming streaky (strawy) voids with >=60mum length nearly parallel to the longitudinal direction of the above-mentioned fiber, crimping the prepared fiber, then spinning the crimped fiber and weaving the aforementioned spun fiber, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a fabric made of flame-resistant acrylic fiber useful as a raw material for flame-resistant products, a heat-resistant material, and a reinforcing material.

(Prior art) Flame-resistant fibers are intermediate products in the carbon fiber manufacturing process that uses acrylonitrile fibers, cellulose fibers, phenol fibers, pitch fibers, etc. as raw materials. It is known that it can be obtained by heat treatment in the temperature range of 200 to 400°C (for example, Japanese Patent Application Laid-open No. 59-30914).

This acrylic flame-resistant fiber has potential flame resistance,
Due to its high heat resistance, it has been attracting attention in various fields in recent years, and is useful as a raw material for flameproof products and as a heat-resistant material. Furthermore,
It is also attracting attention as a raw material for composite materials.

Furthermore, fabrics made of acrylic flame-resistant fibers, such as woven fabrics, knitted fabrics, non-woven fabrics, and felts, are also known (Japanese Patent Laid-Open No. 57
-82585).

[Problem to be solved by the invention]

However, conventionally known flame-retardant fibers have a high density and are heavy when worn on the body, such as fire-retardant products such as firefighting suits, and are too heavy for workers when worn for long periods of time. It is a burden. Furthermore, when using it as a raw material for composite materials, there is a demand for a special product that is lighter and has a greater reinforcing effect.

Under these circumstances, as the demand for flame-resistant fibers increases in recent years, there is a strong demand for fabrics that are lightweight, have excellent reinforcement characteristics, and have excellent flame-resistant performance.

Conventional flame-resistant fibers cannot fully meet this demand.

The present invention provides a fabric made of flame-resistant acrylic fiber, which has flame resistance and physical properties comparable to those of conventional flame-resistant fibers, is lighter, and has a special feature that is excellent as a reinforcing material.

[Means to solve the problem]

The present inventors previously filed a patent application for an acrylic fiber with a novel fiber structure and a method for producing the same (Japanese Patent Application Laid-Open No. 63-328891). The present invention was completed based on the discovery that flame-resistant acrylic fibers with excellent fiber properties can be obtained.

That is, the present invention has a large number of openings having an unspecified shape in the cross section of the fiber, and each of the openings has a length of 60μ or more approximately parallel to the length direction of the fiber inside the fiber. This fabric is made of flame-resistant acrylic fibers that form striation-like (straw-like) voids.

Hereinafter, the fabric made of the acrylic flame-resistant fiber of the present invention will be explained in more detail.

The acrylic flame-resistant fiber constituting the fabric of the present invention has a cross section cut perpendicular to the length direction of the fiber (hereinafter referred to as
It has a large number of openings having an unspecified shape in its cross section (referred to as a cross section), and the openings are characterized in that they form streak-like (straw-shaped) voids inside the fibers.

The cross-sectional shape of the opening in the cross-section of the void has an unspecified shape. Figure 1 is an electron micrograph (4000x magnification) showing the cross-sectional structure of acrylic flame-resistant fibers (hereinafter referred to as flame-resistant fibers) constituting the fabric of the present invention.
It is. As shown in FIG. 1, the cross-sectional shape of the opening of the flame-resistant fiber of the present invention may be approximately circular, flat, sharply curved, large or small in cross-section, etc. The flame-resistant fiber of the present invention, whose shape is not constant and irregular, is characterized by having a large number of voids of unspecified shape.

Next, each of the openings is arranged inside the flame-retardant fiber.
Almost parallel strip-like (straw-like) voids are formed along the length of the fibers. There is no particular limit to the length of the void along the length of the fiber (hereinafter simply referred to as length), but the longer it is, the more hollow the flame-resistant fiber becomes, and the lighter it is, the more it can be used as a reinforcing material. In this case, it is preferable because it can provide a resilient composite material. Particularly preferred is a length of 60μ or more.

In order to achieve special properties when used as such a reinforcing material, the length of the void is preferably 60 μm or more.

Next, although the number of voids in the cross section of the flame-resistant fiber depends on the size of the pore diameter of the voids, it is generally preferable that there be 100 or more voids. If the number of voids is small, the weight is insufficient.

Furthermore, when used as a reinforcing material, excellent elasticity cannot be imparted to the composite material.

As described above, the flame-resistant fiber of the present invention is characterized by the shape, number, and length of the openings in the cross section of the fiber, and the combination of these requirements makes it lightweight and suitable as a reinforcing material. It is something that can express its characteristics. These characteristics of the flame-resistant fiber of the present invention are new characteristics not found in conventionally known flame-resistant fibers.

Next, the method for producing the flame-resistant fiber of the present invention will be described in detail.

The acrylic fiber (hereinafter referred to as raw material acrylic fiber) used to produce the flame-resistant fiber of the present invention has a novel fiber structure that has not been previously known.

That is, the raw material acrylic fiber has a large number of openings having an unspecified shape in the cross section of the fiber, and each of the openings has 60 parallel openings along the fiber length direction inside the fiber.
It is an acrylic fiber that forms streak-like (straw-like) voids having a length of μ or more.

FIG. 2 is an electron micrograph (4000x magnification) showing the cross-sectional structure of the raw material acrylic fiber. As shown in Figure 2, there are many openings with unspecified shapes in the cross section of the raw acrylic fibers, some of which are approximately circular, some are flat, and others have sharp edges. Its shape, such as those with repeated bends, large or small cross sections,
The size is not constant and is irregular.

Figure 3 is an electron micrograph (4,000 mm
times). As shown in Figure 3, inside the fiber, there are stripes (straw-like) that are almost parallel to the fiber length direction.
It forms a void.

The length of the void along the length of the fiber (hereinafter simply referred to as length) is preferably 60μ or more, and if the length of the void is shorter than 60μ, flame-resistant fibers may be used as a reinforcing material. When used, composite materials become unsuitable for fields that require flexibility and elasticity.

If the length of the void is 60 μm or more, it is most preferable that the void be continuous over substantially the entire length of the fiber, since the longer the void is, the more easily the fiber will be split. The raw material acrylic fiber is a polymer of at least 60% by weight of acrylonitrile (the following percentages indicate weight unless otherwise specified) and up to 40% of an ethylene-based polymer copolymerizable with acrylonitrile, or at least two polymers. It is made of a mixture of acrylic polymers.

Ethylene monomers that can be copolymerized with acrylonitrile include conventionally known monomers, such as acrylic acid, methacrylic acid, and their esters (methyl acrylate, ethyl acrylate, methyl methacrylate, methacrylic acid (ethyl etc.), vinyl acetate, vinyl chloride, vinylidene chloride, acrylamide, methacrylamide, methacrylonitrile, allylsulfonic acid, methallylsulfonic acid,
Styrene sulfonic acid, vinylpyridine, 2-methyl-5
-vinylpyridine, N,N-dimethylaminoethyl methacrylate, and the like.

Next, a method for producing the raw material acrylic fiber will be described.

The above polymer may be a conventionally known acrylic polymer solvent, such as an organic solvent such as dimethylformamide, dimethylacetamide, or dimethyl sulfoxide, a concentrated aqueous solution of an inorganic salt such as rhodan salt, zinc chloride, or nitric acid, or an inorganic acid. A spinning stock solution is prepared by dissolving it in a concentrated aqueous solution. In this case, the optimum concentration of the polymer varies depending on the type of solvent, but is preferably approximately 10 to 30%.

Next, polyalkylene glycol is added to the spinning dope. The above polyalkylene glycol contains ethylene oxide and propylene oxide in a weight ratio of 80:
20-20: 80 random type copolymer or block type copolymer, the number average molecular weight is 5,00
0 to 50.000, preferably 10.000 to 20
,000. If the number average molecular weight is less than 5.000, continuous voids cannot be obtained in the length direction of the fiber,
On the other hand, when the number average molecular weight exceeds so, ooo, the fiber becomes a microporous fiber with a microscopic, approximately spherical cavity. The fiber has at most several tens of cavities in its surface.In particular, fibers with a number average molecular weight of 10,000
~20,000, fibers are obtained that are fine along the length of the fiber and have elongated voids of unspecified cross-sectional shape in the cross section of the fiber.

Further, the spinning dope prepared by dissolving the polyalkylene glycol as described above is then aged for at least 4 hours.

Here, aging refers to, for example, leaving the spinning stock solution prepared by dissolving the acrylic polymer and polyalkylene glycol as it is without vigorous stirring or vibration, or gently moving the spinning stock solution. This refers to, for example, slowly transporting liquid through piping.

That is, by aging the spinning solution for more than 4 hours, agglomeration of polyalkylene glycol occurs, and when the spinning solution passes through the tube and is spun from the spinneret into the coagulation medium, shearing force acts on the spinning solution. Due to the difference in coagulation properties, fine streaks of polyalkylene glycol are formed and the acrylic polymer coagulates while polyalkylene glycol does not coagulate.
There is no particular upper limit to the aging time at which the complex-shaped voids described above are thought to occur due to the phase separation of both polymers, but there is no particular upper limit as long as it is 4 hours or more.
10 hours is preferred. The amount of polyalkylene glycol added is 5 to 20%, preferably 10 to 15%, based on the acrylic polymer. If it is less than 5%, the number of voids in the cross section of the fiber will be small, and a fiber with a large number of voids, for example 100 or more, will not be obtained;
If the amount added exceeds 20%, the number of openings will increase, but if it becomes too large, the fibers may split during the fiber manufacturing process.
Problems arise, such as that spinning cannot be performed stably.

When the amount of polyalkylene glycol added is 10 to 15%, the number of openings, spinning stability, etc. are most balanced.

This spinning dope is extruded through a spinneret into a coagulating medium of the spinning dope, and after passing through steps such as water washing, stretching, and drying, it is further heat-set as required.

For the steps after spinning, conventionally known methods for producing acrylic synthetic fibers can be adopted as they are.

Next, a method for producing the flame-resistant fiber of the present invention will be explained.

As a method for producing flame-resistant fibers, conventionally known methods can be used as they are.

That is, the flame-resistant fiber of the present invention can be produced by heat-treating the raw material acrylic fiber at a temperature range of 200 to 400° C. for several minutes to several hours in an oxidizing atmosphere such as air. During the heat treatment, it is preferable to hold the raw acrylic fiber under tension.

Next, a method for manufacturing the fabric of the present invention will be explained.

After the above-mentioned flame-resistant acrylic fiber is crimped and spun into a spun yarn, the spun yarn can be woven or knitted to obtain a woven or knitted fabric. Furthermore, a nonwoven fabric or felt can be obtained from the sliver obtained in the above spinning process. When obtaining a nonwoven fabric or felt from this sliver, it is preferable to use a commonly known adhesive.

The present invention will be explained in more detail below using examples.

Example 1 Acrylonitrile 95.0%, methyl acrylate 4.5%
% and 0.5% of sodium methallylsulfonate is a random copolymerized polyether of ethylene oxide and propylene oxide (number average molecular weight 10.00).
The ratio of 0 ethylene oxide and propylene oxide is 75:25') is dissolved in a 67% nitric acid aqueous solution,
A spinning dope having an acrylic polymer concentration of 16% and a random polymerization type polyether concentration of 2.4% was prepared. This spinning solution was allowed to stand for 4 hours, then extruded through a spinneret into a 37% nitric acid aqueous solution cooled to 0°C, washed with water, stretched 10 times in boiling water, and dried with hot air at 70°C. , 2.5d
fibers were produced and dried.

An electron micrograph (4000 times) of a cross section of this fiber is shown in FIG. 2, and an electron micrograph (4000 times) of a longitudinal section of this fiber is shown in FIG.

In FIG. 3, the black portions are voids, and it can be seen that the voids are continuous in a stripe shape substantially parallel to the length of the fiber.

Also, in Fig. 2, the black parts are openings,
There are many irregular openings with unspecified shapes, such as those with approximately circular cross-sections, those with flat shapes, those with repeated sharp bends at the edges, and those with large or small cross-sections. It can be seen that there is a mixture of

Next, this fiber (tow) is placed under tension in an air atmosphere for 23 minutes.
It was heated at 5°C for 2 hours and then at 255°C for 2 hours.

An electron micrograph (4000x magnification) of a cross section of the flame-resistant fiber thus obtained is shown in FIG. From FIG. 1, it can be seen that there are many voids of unspecified shape in the cross section of the flame resistant fiber.

Physical properties of flame-resistant fiber: tensile strength 1.3 g/d, tensile elongation 22%, 0.65% spinning oil was applied to this flame-resistant fiber, and after cutting to an average fiber length of 105 mm, the number of crimps was 9/ It was spun for 25 m and crimped at a crimp rate of 12%.

When this spun yarn was woven to form a heat insulating sheet,
It was approximately 35% lighter in weight than a conventionally known heat insulating sheet made of flame-resistant fibers with equivalent heat insulating performance.

Furthermore, this sheet did not burn even when exposed to the flame of a gas burner, and had sufficient flame resistance.

Example 2 In Example 1, the sliver obtained in the spinning process was stretched and spread, impregnated with a silicone resin face (manufactured by Shin-Etsu Chemical Co., Ltd.) emulsion solution (purity 35% by weight), and 1% by weight of the resin adhered. A nonwoven fabric was produced. The purpose of this nonwoven fabric was 300 g/nf. This nonwoven fabric was approximately 35% lighter in weight than a conventionally known heat insulating sheet made of flame-resistant fibers having equivalent heat insulating performance.

〔Effect of the invention〕

The fabric made of flame-resistant fibers of the present invention has a low apparent density because it uses hollow flame-resistant fibers that have many linear voids. For this reason, the present invention can provide a more lightweight insulation fabric.

[Brief explanation of the drawing]

Figure 1 is an electron micrograph showing an example of the cross-sectional structure of the flame-resistant fiber used in the fabric of the present invention, Figure 2 is an example of the cross-sectional structure of the raw material acrylic fiber, and Figure 3 is its longitudinal cross-section. It is an electron micrograph showing the structure of the surface.

Claims (1)

[Claims] The cross section of the fiber has a large number of openings having an unspecified shape, and each of the openings is in the form of a stripe having a length of 60μ or more that is substantially parallel to the longitudinal direction of the fiber inside the fiber. A fabric made of flame-resistant acrylic fibers that forms straw-like voids.