JPH0849156A - Production of polybenzazole fiber nonwoven fabric - Google Patents

Abstract

PURPOSE:To easily produce a polybenzazole nonwoven fabric excellent in heat resistance, flame resistance and abrasion resistance at a low cost. CONSTITUTION:This method for producing a nonwoven fabric is to melt a spinning dope comprising polybenzazole and polyphosphoric acid, extrude the dope into a noncoagulating gas, pull the extruded fiber by a stress separating device or an aspirator run by using a liquid stream, collect the fiber on a net conveyor as a nonwoven fabric, wash and dry the fabric and obtain the objective nonwoven fabric.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a high-strength, high-modulus polybenzoxazole-based nonwoven fabric. More specifically, the present invention relates to a yarn manufacturing method that significantly facilitates the method for manufacturing a nonwoven fabric.

[0002]

2. Description of the Related Art Polybenzazole fiber has a strength and elastic modulus more than twice that of polyparaphenylene terephthalamide fiber, which is a typical super fiber currently on the market. Therefore, it is expected as a next-generation super fiber.
It is known to manufacture fibers from polyphosphoric acid solutions of polybenzazole polymers. For example, there are US Pat. No. 5,296,185 and US Pat. No. 5,294,390 for the spinning method, and US Pat. No. 5,288,445 for the heat treatment method.
No. has been proposed. However, as far as the inventors know, there is no prior art on a method for producing a nonwoven fabric of polybenzazole fiber.

[0003]

Polybenzazole fiber nonwovens can be made off-line in a conventional manner using long or short polybenzazole fibers made by a conventional method. Further, as in the case of a non-woven fabric which is generally formed by wet spinning, it is possible to produce the non-woven fabric by introducing the coagulated fiber or the dried fiber to the non-woven fabric production process. However, even if the polybenzazole fiber is produced by an efficient manufacturing method, the washing and drying steps are long, and if the washing and drying steps can be passed as a nonwoven fabric, it can be washed and dried efficiently without reducing the spinning speed. It is extremely economical because it can be done. That is,
Although it is unprecedented as a method for manufacturing non-woven fabrics using wet spinning, if the process of directly collecting spun yarn on a net conveyor and making it into a non-woven fabric can be applied like the process of producing non-woven fabrics of polyester or propylene, the non-woven fabric can be used for spinning speed. The process transfer speed can be extremely slow. On the contrary, the processes that require a long time, such as extraction, washing with water, drying, and heat treatment, become easier with a nonwoven fabric. Therefore, a nonwoven fabric of polybenzazole fiber may be manufactured at a low cost. The problem with polybenzazole fibers is that the dope consisting of polybenzazole polymer and polyphosphoric acid has a very high viscosity and a high spinning tension, so that the extension of the discharge dope cannot be achieved at all by drawing by gas. The present invention overcomes such technical difficulties and provides a novel production method for industrially obtaining a polybenzazole nonwoven fabric.

[0004]

[Means for Solving the Problems] The inventors of the present invention have conducted intensive studies and found a solution to the problem, for the purpose of facilitating the production of a polybenzazole nonwoven fabric. That is, a spinning dope composed of polybenzazole and polyphosphoric acid is spun from a spinneret. The discharged yarn has an extremely high extension viscosity and cannot easily give a draft. Then, after applying a constant speed to the yarn with a godet roll, it is taken up by a fluid (liquid or gas) aspirator. Or give a draft with an aspirator using a liquid flow. The yarn and fluid discharged from the aspirator are collected on the conveyor net. It was found that a non-woven fabric composed of yarn bundles after collection can be coagulated and / or extracted and further dried to easily obtain a polybenzazole non-woven fabric. The purpose of the present invention is its manufacturing method.

The present invention will be described in detail below. The polybenzazole fiber in the present invention means a fiber made of polybenzazole polymer, and polybenzazole (PBZ)
The term "polybenzoxazole (PBO) homopolymer, polybenzothiazole (PBT) homopolymer and random, sequential or block copolymers of PBO and PBT". Here, polybenzoxazole, polybenzothiazole and their random, sequential or block copolymers are, for example, described in "Liquid Crystalline Polymer C" by Wolfe et al.
ompositions, Process and Products "US Patent No. 47
03103 (October 27, 1987), "Liquid C
rystall-ine Polymer Compositions, Process and Prod
ucts ”US Pat. No. 4,533,692 (August 6, 1985)
Sun), "Liquid Crystalline Poly (2,6-Benzothiazole)
Composition, Process and Products "US Patent No. 45
No. 33724 (August 6, 1985), "Liquid Cryst
alline Polymer Compositions, Process and Products
US Pat. No. 4,533,693 (August 6, 1985)
Sun), Evers' Thermooxidative-ly Stable Articula
ted p-Benzobisoxazole and p-Benzobisthiazole Polym
res ”US Pat. No. 4,539,567 (November 16, 1982), Tasi et al.,“ Method for making Heterocyclic ”.
Block Copolymer "US Pat. No. 4,578,432 (19
March 25, 1986), etc. The structural unit contained in the PBZ polymer is preferably selected from lyotropic liquid crystal polymers. The monomer unit consists of the monomer units described in structural formulas (a) to (h), and more preferably, essentially, structural formulas (a) to (h).
It consists of monomer units selected from (c).

[0006]

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[0007]

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Suitable solvents for forming the dope of PBZ polymer include cresol and non-oxidizing acids capable of dissolving the polymer. Examples of suitable acid solvents include polyphosphoric acid, methanesulfonic acid and concentrated sulfuric acid or mixtures thereof. Further suitable solvents are polyphosphoric acid and methanesulfonic acid. The most suitable solvent is polyphosphoric acid.

The polymer concentration in the solvent is preferably at least about 7% by weight, more preferably at least 1%.
It is 0% by weight, most preferably at least 14% by weight. The maximum concentration is limited by practical handling characteristics such as the solubility of the polynose and the viscosity of the dope. Due to these limiting factors, the polymer concentration is usually 20% by weight.
Never exceeds.

Suitable polymers, copolymers or dopes are synthesized by known methods. For example, Wolfe et al., US Pat. No. 4,533,693 (August 6, 1985), Sy.
U.S. Pat. No. 4,772,678 to Bert et al. (September 2, 1988)
Day 0, Harris U.S. Pat. No. 4,847,350 (198).
It is synthesized by the method described in July 11, 1997). PB
Z polymers are described in US Pat. No. 5,089,591 to Gregory et al.
According to the publication (February 18, 1992), it is possible to achieve a high molecular weight at a high reaction rate in a dehydrating acid solvent under relatively high temperature and high shear conditions.

The dope thus polymerized is supplied to the spinning section and discharged from the spinneret at a temperature of usually 100 ° C. or higher. A plurality of die holes are usually arranged in a circumferential shape or a lattice shape, but other arrangements may be used. The number of spinneret pores is not particularly limited, but the array of spinneret pores on the spinneret surface must be maintained at a pore density that does not cause fusion between the discharge yarns.

Next, the gist of the present invention is that the dope discharged from the spinneret (the yarn in the state before extracting polyphosphoric acid) is a stress isolation device or a swingable aspirator using a liquid flow. Stretches with a higher tension. It is effective to provide a so-called quench chamber for cooling the yarn with cooling air between the stress isolator or the liquid flow aspirator and the spinneret in order to obtain a high spinning speed.

The stress isolation device generally uses a so-called godet roll or the like. It is desirable that the roll is made of a corrosion-resistant material, and that the surface has excellent releasability such as Teflon. When a stress isolation device is used, an aspirator for producing a nonwoven fabric is provided downstream thereof, and the aspirator is used to collect the yarn in a nonwoven fabric collection device such as a net conveyor. When the aspirator is a gas, by adjusting the temperature of the gas, fusion occurs between the single fibers of the collected non-woven fabric to obtain an appropriate entanglement, which is desirable for some applications. The gas supplied to the aspirator is preferably air, an inert gas such as nitrogen gas, carbon dioxide gas, or a mixed gas thereof. A jet flow of about 20 to 300 m / sec is ejected from the aspirator exit.

In the case of an aspirator using a liquid flow without using a stress isolation device, the yarn is directly collected by a non-woven fabric collecting device such as a net conveyor. The liquid stream used may be a coagulating liquid such as water or a non-coagulating liquid. The flow velocity is preferably 20 m / sec at the latest.

The collecting atmosphere as the nonwoven fabric may be liquid or gas, but the nonwoven fabric captured by a net conveyor or the like is subsequently coagulated and / or extracted, and finally the phosphoric acid contained in the yarn is 99.0 in the extraction bath. % Or more, preferably 99.5% or more. The liquid used as the extraction medium in the present invention is not particularly limited, but water, methanol or the like, which is not substantially compatible with polybenzoxazole, is preferable. Alternatively, the extraction bath may be separated into multiple stages to reduce the concentration of the phosphoric acid aqueous solution in sequence and finally washed with water. Further, the non-woven fabric is neutralized with an aqueous solution of sodium hydroxide and then washed with water.

The non-woven fabric after washing with water is dried by a dryer using high temperature air together with a collecting device such as a belt conveyor. The single fibers constituting the non-woven fabric thus obtained have a sufficient strength of 25 g / d or more and a sufficiently high elastic modulus of about 700 g / d. However, the non-woven fabric may be heat treated immediately or separately at 350 ° C. or more. By applying it, the elastic modulus of the single fiber is improved to 1500 g / d or more.

If necessary, the nonwoven fabric is subjected to an adhesive treatment, an entanglement treatment such as needle punching or water punching, or a calendaring treatment.

The obtained non-woven fabric has excellent heat resistance and excellent tear strength, and is not found in non-woven fabrics obtained from other fibers as a heat resistant protective material, heat insulating protective material, wear resistant protective material or flame resistant protective material. It has excellent characteristics.

[0019]

EXAMPLES Examples will be shown below, but the present invention is not limited to these examples. Example 1 Polybenzoxazole 1 having an intrinsic viscosity of 24.4 dL / g measured with a methanesulfonic acid solution at 30 ° C., obtained by the method described in US Pat. No. 4,533,693.
A spinning dope made of polyphosphoric acid having a content of 4.0 (weight)% and a phosphorus pentoxide content of 83.17% was used for spinning. The dope was passed through a metal mesh filter material, then kneaded and defoamed with a biaxial kneading device, and then the pressure was raised to maintain the polymer solution temperature at 170 ° C., using the device shown in FIG. Number 33
Spinning at 170 ° C from a spinneret having 4 and a temperature of 60 ° C
After the discharged yarn was cooled by using the cooling air of No. 1, the yarn was wound on a godet roll whose surface was treated with Teflon to give a yarn speed of 200 m / min. Then, it was pulled by an aspirator using compressed air as a supply fluid and collected by a net conveyor.
The transfer speed of the net conveyor is 20 cm / min. Next, the collected non-woven fabric is put together with the net conveyor at a temperature of 22 ± 2.
It was introduced into an extraction bath consisting of a 10% phosphoric acid aqueous solution kept at ° C. Subsequently, the non-woven fabric as it was collected on the net conveyor was further washed with ion-exchanged water in the second extraction bath to be immersed in a 0.1 N sodium hydroxide solution for neutralization. After further washing with a washing bath, the non-woven fabric is dried for 5 minutes in an air drying room kept at 190 ° C.
A nonwoven fabric having a moisture content of 5 g / m ² and a water content of 0.8% was obtained. Twenty single fibers were arbitrarily taken out from the nonwoven fabric and the strength and elongation were measured. The average value was a fineness of 1.5 denier, the strength was 35 g / d, the elastic modulus was 800 g / d, and the elongation was 4.5%. This non-woven fabric was further entangled with a water punch. The obtained non-woven fabric had a good appearance, and no change in morphology was observed even after heating in an oven at 400 ° C. for 5 hours.

<Example 2> Polybenzbisoxazole fibers were extruded from the spinneret under the same spinning conditions as in Example 1 except that the cooling air temperature was 80 ° C. As shown in FIG. 2, unlike Example 1, the discharged yarn was stretched by an aspirator using a water stream without using a godet roll, and the yarn was directly shaken off on a net conveyor. The collected nonwoven fabric was extracted, neutralized, washed with water, and dried as in Example 1, and wound up as a web. Twenty single fibers were arbitrarily taken out from the non-woven fabric and measured for strength and elongation, the average value was 2.5 denier, the strength was 33 g / d, and the elastic modulus was 800 g.
/ D and the elongation was 4.4%. This non-woven fabric was further entangled with a needle punch. The obtained non-woven fabric had a good appearance, and no change in morphology was observed even after heating in an oven at 400 ° C. for 5 hours.

Comparative Example 1 Except that an aspirator using compressed air is used instead of the aspirator using water flow,
An experiment was conducted under exactly the same conditions as in Example 2, but an aspirator using gas could not obtain sufficient traction force, a non-woven fabric made of continuous fibers could not be obtained, and the aspirator was clogged with dope at the same time as yarn breakage, and It was not possible to make a non-woven fabric.

[0022]

According to the present invention, a polybenzazole non-woven fabric having excellent heat resistance, flame resistance and abrasion resistance can be manufactured easily and at low cost as compared with the conventional method.

[Brief description of drawings]

FIG. 1 is a schematic diagram of an apparatus according to a first embodiment of the present invention.

FIG. 2 is a schematic diagram of an apparatus according to a second embodiment of the present invention.

[Explanation of symbols] 1: Spinning head, 2: Quench chamber, 3: Teflon coated godet roll, 4: Compressed air aspirator, 5: Non-woven fabric collection net conveyor, 6: Coagulation bath net conveyor, 7: Extraction bath net conveyor, 8: Neutralization bath net conveyor, 9: Wash bath net conveyor, 10: Dryer, 11: Winder, 14: Liquid flow aspirator

Claims (4)

[Claims] 1. A spinning dope composed of polyphosphoric acid and polybenzazole is extruded from a spinneret, and then the obtained dope filament is pulled by an aspirator using a liquid flow to disperse and deposit on the collecting surface. A method for producing a polybenzazole fiber nonwoven fabric. 2. A spinning dope composed of polyphosphoric acid and polybenzazole is extruded from a spinneret, and the obtained dope filament is given a constant yarn speed with a godet roll, and then an aspirator using a liquid flow or a gas flow. A method for producing a polybenzazole fiber non-woven fabric, which comprises pulling and dispersing and depositing on a collecting surface. 3. A polybenzazole fiber non-woven fabric, characterized in that the dope filament pulled by the aspirator according to claim 1 or 2 is collected on a net conveyor, and then polyphosphoric acid is washed off and dried on the net conveyor. Manufacturing method. 4. The method for producing a polybenzazole fiber non-woven fabric according to claim 1, wherein the polybenzazole fiber non-woven fabric is entangled.