JPS62276014A - Production of acrylonitrile yarn having high strength and high modulus of elasticity - Google Patents

Abstract

PURPOSE:To obtain the titled yarn without forming large oil drops even by no use of a dispersion stabilizer, by polymerizing an acrylonitrile polymerizable unsaturated monomer by the use of azobis(cyanopentanoic acid) as a polymerization initiator, spinning and drawing. CONSTITUTION:A polymerizable unsaturated monomer containing >=80wt% acrylonitrile is polymerized by the use of 4,4'-azobis(4-cyanopentanoic acid) as a polymerization initiator preferably by suspension polymerizatoon method or by emulsion polymerization method to give an acrylonitrile polymer having >=5 reduced viscosity, which is spun and drawn to give the aimed yarn. Methyl (meth)acrylate, etc., may be cited as other monomers to be copolymerized with acrylonitrile and the amount of the monomer is preferably <=10wt% in the case of production of precursor for carbon yarn.

Description

Detailed Description of the Invention V. Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a method for producing high performance acrylonitrile fibers, particularly high strength and high modulus acrylonitrile fibers.

[Conventional technology]

Although acrylonitrile fibers have excellent hydrolysis resistance, solvent resistance, and weather resistance, the strength of currently developed fibers is slightly inferior to that of condensed fibers such as polyester and polyamide, so they are not suitable for industrial use. It is only used as a precursor for carbon fiber production. However, in recent years, the performance requirements for precursors for producing carbon fibers have become higher, and in consideration of their use as industrial materials, the appearance of acrylonitrile fibers with even improved mechanical properties is awaited. As one means of achieving this, a method has been considered to increase the degree of polymerization of the acrylonitrile polymer used for fiber shaping. For example, a method of increasing the degree of polymerization of a polymer obtained by carrying out polymerization using a mixed solvent of dimethylformamide, dimethylacetamide, dimethylsulfoxide, and water, which is a poor solvent for polyacrylonitrile polymers, is disclosed in Japanese Patent Publication No. 56-10996. Publication No., Special Publication No. 48-364
30, JP-A No. 52-47088, etc., and another method is a method of polymerization using a reaction product of an alkali metal salt of a carboxylic acid and trialkylaluminium as a polymerization catalyst, as disclosed in Japanese Patent Publication No. 52-47088. 47-26978
It has been proposed in the Publication No.

[Problem that the invention seeks to solve]

However, the reduced viscosity of the polymers obtained by polymerization using the above mixed solvent as a polymerization medium is 2.0 or less, and the viscosity of the polymerization system is abnormally low at a relatively low polymerization rate. There is a strong tendency for the polymerization rate to increase, and the polymerization system cannot be stirred, making it difficult to control the polymerization system, which poses a problem in terms of polymer productivity. In addition, although the method described in Japanese Patent Publication No. 47-26978 yields an acrylonitrile polymer with a high degree of polymerization, the polymerization reaction system is anionic polymerization, and water as a commonly used polymerization medium cannot be used in the polymerization operation. However, there are problems in terms of polymerization equipment and industrialization.

Therefore, the present inventors conducted extensive studies in view of the current state of the production method for highly polymerized acrylonitrile polymers, and found that a highly polymerized acrylonitrile polymer was obtained by using a specific polymerization initiator. The inventors have discovered that a high-strength, high-elastic acrylonitrile fiber can be obtained by spinning a polymer, leading to the present invention.

[Means for solving problems]

The present invention is acrylonitrile, which has a reduced viscosity of 5 or more and is obtained by polymerizing a polymerizable unsaturated monomer containing 80% by weight or more using 4,4'-azobis(2-cyanopentanoic acid) as a polymerization initiator. The acrylonitrile polymer is spun,
This is a method for producing high-strength, high-modulus acrylonitrile fibers, which is characterized by stretching.

The starting material used in carrying out the present invention is acrylonitrile alone, or acrylonitrile in 80 parts by 1 part.
% or more of polymerizable unsaturated monomers. Other polymerizable unsaturated monomers that can be copolymerized with acrylonitrile include methyl acrylate, ethyl acrylate,
Acrylic acid such as butyl acrylate, propyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, hexyl methacrylate, esters of methacrylic acid, 710-gen vinylides such as vinyl chloride, vinyl bromide, vinyl chloride, acrylic acid,
Acids such as methacrylic acid, itaconic acid, crotonic acid, styrene sulfonic acid, vinyl sulfonic acid, and their salts, or maleic acid imide, phenylmaleimide, acrylamide, methacrylamide, styrene, α-methylstyrene, vinyl acetate, etc. to name a few. Can be done. These monomers can be used alone or in combination of two or more, but the copolymerization ratio is 2 as described above.
It is preferably less than 0% by weight, and more preferably 10% by weight or less when considering the production of precursors for producing carbon fibers.

The commonly used emulsion polymerization method, solution polymerization method, and suspension polymerization method can be applied as the polymerization method when carrying out the present invention.
From the viewpoint of obtaining a polymer with a high degree of polymerization, it is preferable to use a suspension polymerization method or an emulsion polymerization method, and in addition, considering the production of precursors for carbon fiber production, polymerization can be performed without using auxiliary agents such as emulsifiers. Suspension polymerization is preferred. When carrying out suspension polymerization, a so-called aqueous suspension polymerization method using water as a polymerization medium is preferred, but a mixed system of water and an organic solvent can also be used if necessary. The organic solvent used here is preferably a solvent that can be used as a spinning solvent for acrylonitrile polymers, such as dimethylformamide, dimethylacetamide, dimethyl sulfoxide, ethylene carbonate, and γ-butyrolactone.
).

Further, in the present invention, it is important to use 4,4'-azobis(2-cyanopenta/acid) as a polymerization initiator. By using this initiator, even without using a dispersion stabilizer in the polymerization system, coarse oil droplets that cause the formation of coarse polymer particles when carrying out suspension polymerization are not generated at all, and the present invention can be stably carried out. An acrylonitrile polymer having a reduced viscosity of 5 or more and good solubility in a spinning solvent can be produced. The appropriate amount of the initiator to be used is usually 0.01 to 1% by weight based on the monomer mixture.

Next, a known method can be applied to the spinning method of the polymer obtained as described above.In the present invention, the acrylonitrile-based polymer obtained as described above is spun with dimethylformamide,
The entire spinning stock solution dissolved in an organic solvent such as dimethylacetamide is spun using a conventional wet or dry-wet spinning method, and the yarn coagulated in a coagulation bath is washed, stretched, dried and densified using a conventional method. High strength and high modulus acrylonitrile fibers can be used.

〔Example〕

Hereinafter, the present invention will be explained in more detail with reference to Examples. Note that "parts" in the text indicate parts by weight.

The breaking strength and breaking elongation in this example were determined using a Tensilon Summer type tensile tester at a test length of 20 mm and a tensile speed of 20 I.
+1/min, measurement atmosphere was 20C, 565% RH.

Also, the reduced viscosity of the polymer is 0.59 and dimethylformamide 100m7! It was dissolved in water and measured at 25tZ'.

250 ml of water was added to a flask equipped with a stirrer and a reflux condenser.
parts, 4.4'-azobis(4-cyanopentanoic acid) 0.
After charging 5 parts of the flask and purging the entire flask with nitrogen, the temperature inside the flask was raised to '175C, and 49 parts of acrylonitrile and 1 part of methacrylic acid were fed over about 90 minutes to carry out polymerization. After the supply was completed, stirring was continued for 1 hour at 75 U to complete the polymerization. The polymerization rate of the obtained polymer was 725X and the reduced viscosity was 1
It was 8.4.

The above polymer was dissolved in dimethylformamide to prepare a spinning stock solution having the concentrations shown in Table 1. These spinning stock solutions were discharged from a nozzle with a nozzle diameter of 0.2 and 500 holes into an 80% dimethylformamide aqueous solution at a temperature of -4C, and spun at a take-up speed of 15 m/min to obtain an undrawn yarn.

The obtained undrawn yarn was stretched 8 times in hot water and evaluated.

Table 1 Examples-2 to 4, Comparative Example-1 Examples by changing the amount of initiator charged as shown in Table 2-
Polymerization was carried out in the same manner as in 1, and the reduced viscosity was 16.4.12.8.
Four types of polymers of 10.2.3.7 were obtained. These polymers were dissolved in dimethylformamide to prepare a spinning stock solution. These spinning stock solutions were spun in the same manner as in Example-1. The evaluation results of the obtained drawn yarn are shown in Table 2.

Table 2

Claims (1)

[Claims] 4,4'-azobis(4-
A method for producing high-strength, high-elastic acrylonitrile fibers, which comprises spinning and drawing an acrylonitrile polymer having a reduced viscosity of 5 or more obtained by polymerizing using cyanopentanoic acid (cyanopentanoic acid).