JPS63105012A - Production of acrylonitrile-based polymer - Google Patents

Abstract

PURPOSE:To obtain the titled polymer capable of giving acrylic fiber of outstanding transparency and flame-retardancy, by incorporating specified amounts of 2-acrylamide-2methylpropane sulfonic acid (salt) in the reaction system in the production of the titled polymer by aqueous suspension polymerization. CONSTITUTION:In the production of the objective acrylonitrile-based polymer containing 45.5-65.5wt% of acrylonitrile and 33.0-52.0wt% of vinylidene chloride by aqueous suspension polymerization, >=3.0wt% (on a 2-acrylamide-2- methylpropane solfonic acid basis), based on the whole monomer, of 2- acrulamide-2-methylpropane sulfonic acid (salt) is incorporated in the polymerization system. The polymerization is preferably carried out at 30-40 deg.C and pH 2.0-3.5, using, as initiators, an oxidizing agent such as ammonium persulfate and a reducing agent such as acid sodium sulfite. The above-mentioned process is capable of polymerizing large quantities of vinylidene chloride even without using surfactant.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention is a novel method for producing an acrylonitrile polymer suitable for producing acrylic fibers having excellent transparency and high flame retardancy.

[Conventional technology]

Acrylic fibers made of acrylonitrile-based polymers have properties similar to wool, such as excellent bulk, texture, and color clarity, and are used in a wide range of applications. However, acrylic fibers, like many natural fibers, inherently have the disadvantage of being easily flammable.

BACKGROUND ART In recent years, living environments have become more exposed to disasters such as fire, and there has been an increasing demand for flame retardant textile products. In particular, flame retardancy is becoming an essential condition for interior products such as curtains and carpets that require flame retardancy.

As a method to make acrylic fiber flame retardant, (1) sb,
(2) A method of blend-spinning a flame-retardant polymer such as a vinyl chloride polymer and an acrylonitrile polymer; (3) A method of blend-spinning a flame-retardant polymer such as a vinyl chloride polymer and an acrylonitrile polymer; Many methods have been proposed, including methods for copolymerizing polymers.

Among these methods, copolymerization with flame-retardant monomers is a method that can impart flame retardancy semi-permanently to fibers without damaging the original physical properties, texture, etc. of acrylic fibers. The method is excellent and widely used.

Examples of these flame-retardant monomers include halogen-containing vinyl monomers, such as vinyl chloride, vinylidene chloride, and vinyl bromide. However, acrylic fibers made by spinning polymers obtained by copolymerizing these flame-retardant monomers do not possess all of the excellent performance originally possessed by acrylic fibers, and are still not fully satisfied. I cannot say that I am in a position to do so. Moreover, in order to have excellent flame retardant performance, it is necessary to contain a large amount of these monomers, but this results in the loss of the original excellent properties of acrylic fibers. In particular, it significantly reduces dyeing clarity and devitrification prevention properties, which poses a major problem that impairs commercial value. The reason for this is thought to be that most acrylic fibers containing a large amount of halogen-containing vinyl monomers are manufactured by wet spinning, which tends to create fine voids within the fiber structure.

Therefore, in order to improve the devitrification properties of acrylic fibers containing large amounts of halogen-containing vinyl monomers, it is especially important to prevent the formation of fine voids within the fiber structure in the coagulation bath. There is. As a method of improving such devitrification and imparting sufficient dyeability to copolymers containing halogen-containing monomers, strong acid groups (which serve as dyeing sites for dyes) have been used.
-8O3) is widely used.

In such a method, an acrylonitrile/vinyl chloride or vinylidene chloride copolymer containing a large amount of a sulfonic acid group-containing vinyl monomer is mixed with a flame-retardant acrylonitrile/vinyl chloride or vinylidene chloride copolymer,
It has been proposed to produce flame-retardant fibers with good devitrification prevention properties by blend spinning (% Kosho 53-93
No. 00).

Since this method uses an organic solvent as the polymerization medium, the polymerization rate is slow, and there are many operational difficulties such as recovery of unreacted monomers and a significant increase in viscosity after the polymerization reaction, so it is difficult to find an industrially advantageous method. I can not say. On the other hand, aqueous suspension polymerization using water as a medium has advantages such as high polymerization rate, easy recovery of unreacted monomers, and ease of temperature control during polymerization.Moreover, continuous polymerization is possible. Because it is easy, it is widely used in the production of acrylic fibers.

However, tragic polymerization, which prefers water, also has various disadvantages.
In particular, when a monomer having extremely low solubility in water is copolymerized with acrylonitrile, the polymerization utility of the monomer is reduced. In particular, halogen-containing vinyl monomers having flame retardant properties fall under such monomers because they have extremely low solubility in water.

As a way to solve these drawbacks, by adding a surfactant and dispersing the water-insoluble halogen-containing vinyl monomer in water, the polymerization utility of the halogen-containing monomer can be greatly improved, and the halogen It has been proposed to produce an acrylonitrile copolymer containing a large amount of vinyl monomer (Japanese Patent Publication No. 33916/1983).

Although the addition of a surfactant improves the polymerization utility of water-insoluble monomers, it has the disadvantage of decreasing the polymerization utility of water-soluble sulfonic acid group-containing vinyl monomers. , has the disadvantage of further reducing the polymerization availability of monomers with low reactivity toward acrylonitrile.

As a method for improving the drawbacks of aqueous suspension polymerization in which these surfactants are added and further improving the devitrification spinnability of flame-retardant acrylic fibers, the reactivity ratio to acrylonitrile is 1 or more. By using reactive sulfonic acid group-containing vinyl monomers and regulating the time during which these sulfonic acid group-containing vinyl monomers are added to the reaction system, flame retardance with good devitrification prevention properties can be achieved. It has been proposed to produce an acrylonitrile polymer having the following properties (JP-A-57-10613).

However, the method of regulating the addition time of the sulfonic acid-containing vinyl monomer is difficult to apply to the aqueous suspension continuous polymerization method that is widely used in the production of acrylonitrile polymers. It is not possible to produce a composite, and it cannot be said to be an advantageous method in industrial terms.

[Problem that the invention seeks to solve]

When producing acrylonitrile-based polymers containing a large amount of halogen-containing vinyl monomers, the problems with the aqueous suspension continuous polymerization method are that the halogen-containing vinyl monomers are water-insoluble and the sulfonic acid is hydrophilic. The aim is to efficiently copolymerize a group-containing monomer with acrylonitrile in the same reaction system.

The purpose of the present invention is to solve the problems of the aqueous suspension system and to develop an industrial acrylonitrile polymer suitable for producing acrylic fibers with excellent flame retardancy and transparency. The objective is to provide an advantageous manufacturing method.

[Means for solving problems]

The gist of the present invention is that acrylonitrile 45.5 to 64.5
When producing an acrylonitrile polymer containing 33.0 to 52.0% by weight of vinylidene chloride using water as a medium, 2-acrylamido-2methylpropanesulfonic acid or a salt thereof is supplied to the reaction system. A method for producing an acrylonitrile polymer, which comprises supplying 3.0% by weight or more of 2-acrylamido-2methylpropanesulfonic acid to the total monomers and reacting without adding a surfactant. It is in.

The present invention makes it possible to produce highly flame-retardant acrylic fibers with excellent transparency by not adding surfactants, which were previously thought to be essential in producing copolymers. .

The present invention will be explained in detail below.

The first requirement in the present invention is that the composition of the acrylonitrile polymer containing the nitrogen-containing monomer is 45.5 to 6.
4.5% by weight acrylonitrile and 33.0~sz,o
ti% vinylidene chloride as the main ingredient.

The content of acrylonitrile in the composition of the polymer of the present invention was specified to be 45.5 to 64.5 mi%.
This is because if it is less than 64% by weight, the excellent fiber performance inherent to acrylic fibers cannot be maintained.
This is because if it exceeds 5% by weight, the performance as an acrylic fiber can be easily obtained, but it is difficult to provide high flame retardant performance. The content of vinylidene chloride was specified as 33.0 to 52.0% by weight because the content of vinylidene chloride was 33.0% by weight.
This is because if the amount is less than 52.0% by weight, high flame retardant performance cannot be obtained, and if it exceeds 52.0% by weight, the fiber performance inherent to acrylic fibers cannot be maintained. In the present invention, vinylidene chloride was selected as the flame-retardant halogen-containing monomer because vinylidene chloride has a relatively high boiling point among halogen-containing monomers and is most suitable for aqueous cloudy continuous polymerization.

In addition to acrylonitrile, vinylidene chloride, and a sulfonic acid group-containing vinyl monomer, the acrylonitrile polymer used in the present invention may also contain a small amount of a monoolefinic monomer that can be copolymerized with these. It does not restrict the composition in any way. Examples of these copolymerizable monoolefin monomers include acrylic acid, methacrylic acid and their esters, acrylamide, vinyl acetate, and styrene.

Next, the second requirement of the present invention is that when producing an acrylonitrile polymer that satisfies the first requirement of the present invention by an aqueous suspension polymerization method, 2-acrylamido-2methylpropanesulfonic acid or a salt thereof The purpose is to supply 3.0% by weight or more of 2-acrylamido-2methylpropanesulfonic acid to the total monomers supplied to the reaction system.

2-Acrylamido-2-methylpropanesulfonic acid or its salt is copolymerized with acrylonitrile and vinylidene chloride to introduce a sulfonic acid group into the resulting copolymer, and the flame retardant product is obtained by spinning the polymer. Not only does it give excellent transparency to acrylic fibers, but it also has appropriate reactivity with acrylonitrile and vinylidene chloride, so it produces fine polymers in the polymerization reaction system. This fine polymer contains a large amount of sulfonic acid groups and has high hydrophilicity, and since it contains acrylonitrile and vinylidene chloride, it also has lipophilicity. For this reason, it has the same effect as a surfactant, and the reactivity of water-insoluble vinylidene chloride is increased even without the addition of a surfactant. Such 2-acrylamide-
The effect of 2-methylpropanesulfonic acid is thought to be due to its appropriate reactivity with acrylonitrile and vinyl chloride, and generally, sulfonic acid groups with a benzene ring such as vinylbenzenesulfonic acid have high reactivity. Even if the containing monomer is copolymerized with acrylonitrile or vinylidene chloride, the above-mentioned fine polymer will not be produced and the reactivity of vinylidene chloride cannot be increased. Conversely, 2-
The same applies to those having lower reactivity than acrylamide-2-methylpropanesulfonic acid.

If the amount of 2-acrylamide-2-methylpropanesulfonic acid or its salt is 3.0% by weight or more based on the total monomers supplied to the reaction system, if it is less than 3.0% by weight, the polymerization reaction will occur. This is because, depending on the conditions, it may not be possible to produce a fine polymer, and it may not be possible to introduce sufficient sulfonic acid groups to impart transparency to acrylic fibers made by spinning the polymer.

The third requirement of the present invention is that no surfactant is added to the polymerization reaction system. The surfactant defined here is a compound having both a generally defined hydrophilic group and a lipophilic group, and is not to be interpreted in a narrow sense. As a result of intensive studies by the present inventors regarding the devitrification properties of fibers made by spinning acrylonitrile-vinylidene chloride copolymer, it was found that the surfactant is present in the polymer that satisfies the first requirement of the present invention. It has been found that the transparency of the fibers obtained by spinning the coalescence is impaired. In particular, nonionic surfactants with polyethylene glycol chains have good solubility in acrylonitrile and vinylidene chloride, so they are incorporated into the resulting polymer, making it difficult to remove them sufficiently during the washing process and impairing the transparency of the fibers. This results in significant damage.

Even anionic surfactants that are highly hydrophilic and have low C solubility in acrylonitrile and vinylidene chloride have an effect on fiber transparency.For the above reasons, the first requirement of the present invention is satisfied. It is particularly important to remove the surfactant in order to improve the transparency of the fibers produced by spinning the polymer.

The initiator used in the present invention can be selected from oxidizing agents and reducing agents commonly used when producing acrylonitrile polymers by aqueous suspension polymerization. Examples include a combination of an oxidizing agent such as a persulfate such as potassium persulfate or ammonium persulfate, or a chlorate such as sodium chlorate, and a reducing agent such as sulfite or a salt thereof.

Although any ratio of reducing agent/oxidizing agent is possible, it is preferable to set the equivalent ratio of oxidizing agent/reducing agent to 1 to 4 in order to advance the polymerization more efficiently.

The polymerization reaction temperature is preferably 30 to 40°C. The reason for this is that when the polymerization temperature exceeds 40°C, vinylidene chloride having a low boiling point evaporates and is dispersed outside the reaction system, thereby reducing the polymerization conversion rate of vinylidene chloride. Moreover, if it is lower than 30°C, the polymerization rate decreases, resulting in not only a decrease in productivity but also a loss in polymerization stability. Although it is possible to raise the polymerization temperature under pressure by shielding the polymerization reactor and preventing the evaporation and dissipation of vinylidene chloride, it is difficult to maintain a constant pressure inside the polymerization reactor in a continuous polymerization method, making it difficult to maintain a constant pressure in the reactor. I can't say it's a good idea.

It is preferable to use ion-exchanged water as the polymerization medium in the present invention. Further, the ratio of ion-exchanged water to monomer (hereinafter referred to as water/monomer ratio) can be any ratio, but preferably the water/monomer ratio is 1.0 to 5.
．． A range of 0 is selected. This is because if the water/monomer ratio is less than 1.0, the viscosity of the aqueous solution of the monomer increases, resulting in incomplete stirring and worsening of the temperature controllability of the X-combination.

Moreover, if the water/monomer ratio is 5.0 or more, the polymerization efficiency decreases and it cannot be said to be industrially advantageous. The average residence time of the monomers in the polymerization reactor is not particularly specified, and is preferably the time that is usually determined during the production of an acrylonitrile polymer by an aqueous suspension polymerization method. The hydrogen ion concentration in the polymerization reactor may be within a range where the catalyst used can quickly cause an oxidation/reduction reaction, preferably at a pH of 2.0 to 3.
．． 5 is good. A polymerization terminator is added to the polymer discharged from the polymerization vessel to stop the reaction. There is no problem with the terminator for the polymerization reaction, as long as it is one that is normally used when producing an acrylonitrile polymer in an aqueous suspension. After a polymerization terminator is added to the aqueous polymer solution, unreacted monomers are recovered. Methods for recovering unreacted monomers include direct distillation of the aqueous polymer solution, and methods of once dehydrating and washing to separate unreacted monomers from the polymer, followed by distillation, and both methods can be employed. In the latter case, a rotary vacuum p-filtration machine, a centrifugal dehydration machine, etc., which are known p-super-dehydration machines, are usually used. When separating a polymer from an aqueous polymer solution using these devices, in order to do it more efficiently, flocculants such as sodium sulfate or aluminum sulfate are added, or the temperature of the aqueous polymer solution is raised to promote coagulation of the polymer. You can also perform operations such as Any water remaining in the polymer is removed by conventional drying methods.

〔Example〕

EXAMPLES The present invention will be specifically described below with reference to Examples. Parts represent parts by weight.

Transparency was evaluated using the following method.

The obtained fibers were sufficiently opened and a felt of 20×10 cm and a basis weight of 250//m' was made using a needle punching machine. The created felt was cut into 9×40 U, placed in a 10-sized glass cell, immersed in benzyl alcohol, and the transmittance at a wavelength of 490.5 parts m was measured.

Example 1 Ion-exchanged water (p
357 parts of H=3), 56.9 parts of acrylonitrile, 40.0 parts of vinylidene chloride, and 3.1 parts of 2-acrylamide-2methylpropanesulfonic acid.
Ammonium persulfate 0.70 parts, sodium acid sulfite 0.84 parts, ferrous sulfate (FeSO4.7HzO) 4
．． Each of them was dissolved in ion-exchanged water in an amount of 4 x 10 parts, and continuous feeding was started. Further, ion-exchanged water was separately supplied so that the total amount of ion-exchanged water was 200 parts. The polymerization temperature was maintained at 35° C., the pH within the reaction system was maintained at 2.9, and sufficient stirring was performed continuously to conduct the reaction for an average of 120 minutes. An aqueous polymer solution was continuously taken out from the overflow port of the reactor, and 0.49 parts of sodium oxalate was added to it.
Ethylenediaminetetraacetate disodium salt 0.
07 parts, a polymerization terminator aqueous solution prepared by dissolving 1.82 parts of sodium bicarbonate in 100 parts of ion-exchanged water was added at a rate of 0.2 parts, and after further adding ion-exchanged water, unreacted was removed using a rotary vacuum filter. The monomer and excess polymerization aid were removed.

The aqueous polymer solution from which unreacted monomers and excess polymerization aid were removed was dehydrated using a centrifugal dehydrator to obtain a wet polymer containing about 50% water by weight. The obtained wet polymer was molded into pellets using a screw extruder and then dried using an aerated dryer to obtain the polymers shown in Table 1.

To confirm the presence of fine polymers, collect the polymer suspension and use NctSF.
After filtration, paper was used and washed with about 10 times the amount of washing water as compared to the combined suspension. The obtained furnace liquid was cloudy, and was collected and dried with a polyethylene hollow fiber to obtain a fine polymer. Furthermore, analysis of the composition of the obtained polymer revealed that vinylidene chloride was 20% by weight, and the sulfonic acid group in the polymer was 5.8X.
10 mol/p, 2-acrylamide-2
Methylpropanesulfonic acid content') It was a multi-polymer.

25 parts of the obtained polymer was dissolved in 75 parts of dimethylacetamide, spun into a 55% dimethylacetamide aqueous solution (30°C) through a 100-hole 0.13mm diameter spinneret, stretched 5 times, and then steamed at 115°C. Setting was performed to obtain a fiber having a denier of 14.8, a strength of 2.81/d, an elongation of 37.0%, and no devitrification. Moreover, the flame retardancy of the obtained fiber was LOI (limiting oxygen index) of 28.5, which was an extremely excellent flame retardant performance.

Example 2 Using the same equipment as in Example 1, acrylonitrile 52.3
The same conditions as in Example 1 were carried out, except that a monomer mixture of 45.0 parts of vinylidene chloride was supplied, and 0.45 parts of ammonium persulfate and 0.90 parts of sodium acid sulfite were each dissolved in ion-exchanged water. An aqueous polymer solution was obtained. The same reaction terminator as in Example 1 was added to the polymer aqueous solution taken out from the reactor overflow port, and after dehydration and washing with a centrifugal dehydrator, a wet polymer containing approximately 60% water by weight was obtained. . This wet polymer was dried at 70°C.

The obtained polymer was spun in the same manner as in Example 1.15.
A fiber with no devitrification was obtained, having a denier of 0 denier, a strength of 2.5 P/d, and an elongation of 36.0%. Furthermore, the flame retardancy of the obtained fiber was LOI 31.5, which showed very excellent flame retardancy.

Example 3 56.8 parts of acrylonitrile, 2-acrylamide-2
Other than supplying 4.0 parts of methylpropanesulfonic acid,
A polymer was obtained in the same manner as in Example 1.

The obtained polymer was spun in the same manner as in Example 1, and 15
．． A fiber with no devitrification was obtained, having a denier of 0 denier, a strength of 2.9 P/d, and an elongation of 36.0%. The flame retardant performance of this fiber is LO
It showed excellent performance with I29.0.

Example 4 56.3 parts of acrylonitrile, 40 parts of vinylidene chloride,
rnnhibinyl 20 parts, 2-acrylamide)'-2,)
Polymerization was carried out in the same manner as in Example 1, except that 3.5 parts of propane sulfonic acid was supplied to obtain a polymer.

The obtained polymer was spun in the same manner as in Example 1, and 14
．． A fiber with a denier of 8 denier, a strength of 2.9 p/a, and an elongation of 36% was obtained which was free from devitrification.

Example 5 A polymer was produced in the same manner as in Example 1, except that 0.45 parts of sodium chlorate and sulfuric acid were supplied as oxidizing agents to maintain the pH of the reaction system at 2.5. The fibers were obtained by spinning. The obtained fiber has a denier of 15.0 and a strength of 2
．． A transparent fiber with 8 P/d and an elongation of 36% was obtained.

When the LOI of this fiber was measured, it was 28.5, showing excellent flame retardant performance.

Comparative example 1 2-acrylamide-2methylpropanesulfonic acid 3
．． Polymerization was carried out in the same manner as in Example 1 except that 3.1 parts of sodium styrene sulfonate was supplied instead of 1 part of sodium styrene sulfonate.

After the polymerization started and reached a steady state, the polymer suspension became viscous and the 1-polymer conversion rate was as low as 67%. In addition, the formation of fine polymers was confirmed in the same manner as in Example 1, but the filtrate did not become cloudy and no formation was confirmed.

23 parts of the obtained polymer was dissolved in 77 parts of dimethylacetamide, spun into a 55% dimethylacetamide aqueous solution (30°C) through a 100-hole 0.013nφ spinneret, and after stretching 5 times, it was steam-set at 115°C. 15
．． A fiber with a denier of 0, a strength of 3.1 p/d, and an elongation of 34% was obtained. Although the obtained fiber was a fiber without devitrification, its flame retardancy was insufficient at LOI of 24.5.

Comparative Example 2 Acrylonitrile 57.0 parts, vinylidene chloride 40.0 parts
Polymerization was carried out in the same manner as in Example 1, except that 3.0 parts and 3.0 parts of sodium allylsulfonate were supplied. Similar to Comparative Example 1, the polymer suspension had a high viscosity and a polymerization conversion rate of 6.
It was at a low level of 0%. The presence or absence of fine polymers was confirmed using the same method as in Example 1, but no formation was observed.

As a result of shaping the obtained copolymer into a dense fiber in the same manner as in Comparative Example 1, the fiber did not have sufficient transparency and its flammability was LO.
The I24.0 was insufficient.

Comparative Example 3 Acrylonitrile 58.0 parts, vinylidene chloride 40.0 parts
Polymerization was carried out in the same manner as in Example 1, except that 2.0 parts of 2-acrylamido-2-methylpropanesulfonic acid were supplied. As in Comparative Example 1, the polymer suspension became viscous, and the polymerization conversion rate was at a low level of 58%. The formation of fine polymers was confirmed in the same manner as in Example 1, but ν
The liquid was clear and no formation was observed.

The obtained polymer was spun in the same manner as in Comparative Example 1, but
The obtained fiber lacks transparency and flame retardant performance is LOI23,
5, which was insufficient.

Comparative Example 4 A monomer mixture of 56.9 parts of acrylonitrile and 40.0 parts of vinylidene chloride, 3.1 m of 2-acrylamido-2methylpropanesulfonic acid, /ionic surfactant (C+z Ht
s-<L)0(CHz CHtO)nHn x 13
), 1.2 parts of ammonium, 0.66 parts of ammonium, 0.79 parts of sodium acid sulfite, ferrous sulfate (F@S0,7H,O
) 4.4 x 10 parts of each were dissolved in ion-exchanged water and continuous feeding was started.

Further, ion-exchanged water was separately supplied so that the total amount of ion-exchanged water was 200 parts. The polymerization temperature was kept at 35°C and the pH of the reaction system was kept at 3.0, and sufficient stirring was carried out continuously.
The reaction was carried out for 0 minutes. 26 parts of the continuously obtained polymer was treated in the same manner as in Example 1 to obtain a polymer.

The obtained polymer was spun in the same manner as in Example 1.15.
A fiber with a denier of 0, a strength of 2.97/d, and an elongation of 34% was obtained. However, the obtained fibers were devitrified fibers with no luster.

Comparative Example 5 Instead of n kql 3 ), 0.4 parts of sodium lauryl sulfate was supplied, and 0.5 parts of ammonium persulfate was supplied.
A polymer was obtained under the same conditions as in Comparative Example 4, except that 3 parts and 0.64 parts of sodium acid sulfite were supplied.

The obtained polymer was spun in the same manner as in Example 1, and 15
．． A fiber with a denier of 0 denier, a strength of 3.1 //d, and an elongation of 35.0% was obtained. Although the obtained fibers were glossy, they were inferior in transparency compared to the fibers in each example.

Comparative Example 6 26 parts of the polymer obtained in Example 1, Nonion NK13)
0.05 parts of dimethylacetamide was dissolved in 74.0 parts of dimethylacetamide, and passed through a 100-hole, 0.13-nφ nozzle with a diameter of 55 mm.
% dimethylacetamide aqueous solution (30°C),
After double stretching, steam setting was performed at 115°C to obtain a fiber with a denier of 15.1, a strength of 2.9//a, and an elongation of 36%.
The fibers became dull.

Comparative Example 7 In the same manner as in Comparative Example 6, 0.01 part of sodium diuryl sulfate was added to 26 parts of the polymer obtained in Example 1 and 74.0 parts of dimethylacetamide, and dissolved. The fibers were obtained by spinning.

The obtained fibers were glossy fibers similar to Comparative Example 4, but the transparency was poor.

Table 1 shows the results of these Examples and Comparative Examples.

*Measurements were made at 25°C using a dimethylformamide solution with a specific viscosity concentration of 0.5//100-.

* Devitrification status and gloss were evaluated in 4 stages: ◎ most good, O good, △ slightly poor, and × poor.

* AN Acrylonitrile dC1 Vinylidene chloride V Vinyl acetate * SAG -so, - group in polymer (X 10' mol/P) Sample 1/ was dissolved in 59 ml of dimethylformamide and passed through an ion exchange resin to form a free acid, Measurement was carried out by neutralization titration with 0.0 IN potassium hydroxide methanol solution.

As shown in the above examples, the fibers obtained by spinning the polymer obtained according to the present invention have excellent transparency and a high degree of flame retardancy. As shown in Comparative Examples 6 and 7, when a surfactant is added when the polymer obtained in Example 1 is spun and shaped into fibers, the resulting fibers become more transparent. This effect can also be seen in anionic surfactants, which have relatively little effect.

〔Effect of the invention〕

In this way, not adding a surfactant is effective in imparting excellent transparency to acrylonitrile and vinylidene chloride copolymer, and in the present invention, 2-acrylamido-2methylpropanesulfonic acid or its salt is It has good reactivity with acrylonitrile and vinyl chloride, and can produce fine polymers by supplying a certain amount or more to the reaction system. Furthermore, this finely divided polymer has the effect of dispersing water-insoluble vinylidene chloride, and vinylidene chloride is efficiently incorporated into the copolymer without using a surfactant.

These effects of the present invention are due to the fact that the acrylonitrile-based polymer is suitable for producing acrylic fibers with excellent transparency and flame retardancy. The present invention has great industrial significance.

Claims (1)

[Claims] (1) When producing an acrylonitrile polymer containing 45.5 to 64.5% by weight of acrylonitrile and 33.0 to 52.0% by weight of vinylidene chloride using water as a medium, 2-acrylamide-2methylpropanesulfur Foonic acid or its salt is added to the total monomers supplied to the reaction system at a rate of 2
A method for producing an acrylonitrile polymer, which comprises supplying 3.0% by weight or more of -acrylamide-2methylpropanesulfonic acid and reacting without adding a surfactant.