JPS6172010A - Production of acrylonitrile copolymer - Google Patents

Abstract

PURPOSE:A specifically composed monomer mixture consisting of acrylonitrile, vinylidene chlorine and so on is subjected to continuous suspension polymerization in an aqueous medium under special conditions to enable industrially advantageous polymerization of the titled polymer which gives flame-retardant acrylic fibers with high resistance to clarity loss. CONSTITUTION:A monomer mixture consisting of (A) acrylonitrile, (B) vinylidene chloride and (C) a vinyl monomer bearing sulfonic group such as allylsufonic acid is polymerized in an aqueous medium using a bisulfite sat as a reducing agent for a water-soluble redox initiator so that the equivalent ratio of the reducing agent to the oxidizing agent becomes 1-4 to give the objective polymer containing 40-75wt% of component A, 30-58wt% of component B and 0.5-1.5wt% of component C. In order to improve the polymerization utility of component B, the use of an anionic surfactant is recommended in an amount of 0.8-2wt% based on the total monomers.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention is a novel method for producing an acrylonitrile polymer suitable for producing flame-retardant acrylic fibers.

[Conventional technology]

Acrylic fibers have properties similar to wool, such as bulkiness, texture, and color clarity, and are used in a wide range of applications.

However, acrylic fibers, like many natural fibers, have the disadvantage of being easily flammable. In recent years, living environments have become more exposed to the risk of 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 for making acrylic fibers flame retardant (method of containing or attaching nonflammable substances such as 11Sb, O, etc. to the fibers, (2) blending a flame retardant polymer such as polyvinyl chloride and an acrylonitrile polymer) Many methods have been proposed, including (3) copolymerization of flame-retardant monomers.Among these methods, semi-permanently imparting flame retardancy to fibers has been proposed. Copolymerization with flame-retardant monomers is an excellent and widely used method that allows for the production of acrylic fibers without damaging the original physical properties, texture, etc. of acrylic fibers.

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,
It does not have all the excellent properties that acrylic fibers inherently have, and it cannot be said that it is still in a fully satisfactory state. Moreover, in order to have excellent flame retardant performance, it is necessary to contain a large amount of these monomers.
On the contrary, this results in the loss of the original properties of the acrylic fiber. In particular, it significantly reduces dyeing clarity and devitrification prevention, 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. ing.

As a method of improving such devitrification and imparting sufficient dyeability to copolymers containing rogen-containing monomers, strong acidic groups (-so, -"
) is widely used. Vinyl monomers containing these sulfonic acid groups include allylsulfonic acid, metaallylsulfonic acid, styrenesulfonic acid, and salts thereof. However, these monomers have poor reactivity with acrylonitrile, and a large amount of these monomers is required in order to sufficiently contain these monomers in the polymer. Furthermore, since these monomers are water-soluble and have high boiling points, they can only be recovered using very sophisticated methods, which significantly increases the cost of producing copolymers containing halogen-containing vinyl monomers. It has increasing drawbacks.

In recent years, a method of incorporating a vinyl monomer containing a sulfonic acid group into a flame-retardant acrylonitrile copolymer has been studied, and the devitrification prevention properties of flame-retardant fibers are being improved. Such a method involves blending and spinning acrylonitrile/vinyl chloride or vinyl chloride copolymer containing a large number of vinyl monomers containing sulfonic acid groups with a flame-retardant acrylonitrile/vinyl chloride or vinylidene chloride copolymer. Japanese Patent Publication No. 53-9300 proposes a method for producing flame-retardant fibers with good devitrification prevention properties by doing so.

However, since this method uses an organic solvent as a 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, making it an industrially advantageous method. It can not be said. On the other hand, aqueous suspension polymerization using water as a medium is superior in that it has a fast polymerization rate, easy recovery of unreacted monomers, and easy temperature control during polymerization. Because it is easy to polymerize, it is widely used in the production of acrylic fibers. However, suspension polymerization using water as a medium has various disadvantages, especially when copolymerizing a monomer with extremely low solubility in water with acrylonitrile, the disadvantage is that the polymerization utility of the monomer is reduced. have. 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 shortcomings,
By adding a surfactant to No. 916 and dispersing the water-insoluble halogen-containing vinyl monomer in water, the polymerization utility of the halogen-containing monomer is greatly improved. A method for obtaining an acrylonitrile-based copolymer containing a large amount of acrylonitrile has been proposed. This method is
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. , which has the disadvantage of further reducing the polymerization utility of the monomer, which has low reactivity towards acrylonitrile.

As a method for improving the drawbacks of aqueous suspension polymerization in which these surfactants are added and further improving the devitrification prevention properties of flame-retardant acrylic fibers, JP-A-57-10613
Using sulfonic acid group-containing vinyl monomers having a reactivity ratio of 1 or more with respect to the reactivity ratio of acrylonitrile in No. 1, and adding the sulfonic acid group-containing vinyl monomers to the reaction system A method for producing an acrylonitrile polymer that has good flame retardancy and good devitrification prevention properties by controlling the amount of devitrification has been proposed.

Sulfonic acid group-containing vinyl monomers that are relatively reactive to acrylonitrile include methacryloyloxypropylsulfonic acid, styrene sulfonic acid, vinylbenzyl sulfonic acid, and their salts, but they are expensive and difficult to manufacture. It has the following disadvantages. In addition, the method of regulating the addition time of the sulfonic acid-containing vinyl monomer is widely used in the molding method of acrylonitrile polymers (it is difficult to apply it to the currently used aqueous suspension continuous polymerization method; This method cannot be said to be the most advantageous industrially since it is not possible to produce a polymer.

The production of acrylonitrile polymers containing a large amount of halogen-containing vinyl monomers by the industrially advantageous aqueous suspension continuous polymerization method has the following drawbacks.

Halogen-containing monomers that have flame retardancy are generally low boiling point substances, and when the temperature inside the polymerization reactor exceeds the boiling point of the monomer, the halogen-containing vinyl monomer evaporates and disperses from the polymerization reaction system. Polymerization availability decreases. When copolymerizing such low-boiling monomers, a method is adopted in which the pressure inside the polymerization tank is maintained to prevent the monomer from evaporating and dispersing. Continuous polymerization requires a very sophisticated method for maintaining the polymer, and it is not an industrially advantageous method because it significantly impairs the operability of the polymerization reaction, the process stability, and the quality stability of the produced polymer. . When continuous polymerization, which maintains the quality of the polymer produced in this way, is adopted for the copolymerization of flame-retardant acrylonitrile/halogen-containing vinyl monomer, it is necessary to It is necessary to carry out the polymerization at a high temperature, which further results in a decrease in the polymerization utility of the sulfonic acid group-containing vinyl monomer.

[Problem that the invention seeks to solve]

In producing acrylonitrile-based polymers containing a large amount of halogen-containing vinyl monomers, the problem with the aqueous suspension continuous polymerization method is that it improves the polymerization utilization of halogen-containing vinyl monomers, which are water-insoluble. Due to constraints such as the need to add a surfactant to achieve this, and the need for low-temperature polymerization to prevent evaporation and dispersion of halogen-containing vinyl monomers, which are low-boiling substances, sulfonic acid group-containing vinyl monomers are This is a trap that significantly reduces the polymerization availability of polymers. For this reason, it is not possible to provide a polymer with sufficient sulfonic acid groups to prevent devitrification of acrylonitrile fibers having flame retardancy.

The object of the present invention is to solve the problems of such a water-based suspension continuous polymerization system and to provide an industrially advantageous method for producing acrylonitrile polymers having flame retardancy.

[Means for solving problems]

That is, the gist of the present invention is that acrylonitrile 4
0-75% by weight, 30-58% by weight vinylidene chloride and 0.5-1.5% vinyl monomer containing sulfonic acid groups.
% by weight using a water-soluble redox initiator in water as a medium, acidic sulfite or its salt is used as a reducing agent, and the equivalent ratio of reducing agent/oxidizing agent is 1 to 4. In order to produce an acrylonitrile-based copolymer, preferably, 0.8 to 2% by weight of an anionic surfactant is added to the polymerization system based on the total amount of monomers to be supplied. It provides a raw material that makes it possible to produce flame-retardant acrylic fibers with excellent anti-permeation properties.

The present invention will be explained in detail below.

The first requirement in the present invention is that the composition of the acrylonitrile-based polymer containing a nitrogen-containing monomer is 40 to 75%.
It is an acrylonitrile polymer mainly containing 30 to 58 weight % of acrylonitrile and 30 to 58 weight % of vinylidene chloride.

The content of acrylonitrile must be 40 to 75% by weight; if it is less than 40% by weight, the excellent fiber performance inherent to acrylonitrile-based synthetic fibers cannot be maintained, and if it exceeds 75% by weight, the acrylic Although the performance as a synthetic fiber can be easily obtained, it is difficult to provide high flame retardant performance. The content of vinyl chloride IJden needs to be 30 to 58% by weight, and vinyl chloride,
If the content of IJ Den is less than 30% by weight, high flame retardant performance cannot be obtained, and if it exceeds 58% by weight, not only will the fiber performance inherent to 7crylonitrile synthetic fibers not be retained, but the polymerization The polymer produced in the reaction vessel becomes fine particles, making it difficult to separate the polymer from the aqueous polymer solution.

In the present invention, chloride and =lJdene were selected as the flame-retardant halogen monomer because vinylidene chloride has a relatively high boiling point among halogen-containing monomers (and is most advantageous for aqueous suspension continuous polymerization). It's for a reason.

Further, the acrylonitrile polymer used in the present invention is acrylonitrile and vinylidene chloride.

In addition to the sulfonic acid group-containing vinyl monomer, a small amount of monoolefinic monomer copolymerizable with these monomers may be included (the composition of the copolymer is not restricted in any way. Examples of 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 the flame-retardant acrylonitrile polymer produced in the present invention is polymerized by an aqueous suspension continuous polymerization method using a redox initiator, an acidic reducing agent must be used. Sulfurous acid or its salt is used, and the equivalent ratio of reducing agent/oxidizing agent supplied to the reaction system is 1 or more and 4
The purpose is to do the following. Reducing agents generally used as redox initiators include sulfite, thiosulfate or their salts, iron sulfate, nitric acid or its salts, etc. However, the present invention specifies sulfite or its salts as the reducing agent. Hydrogen sulfite radicals generated by the redox reaction of the initiator remain in the polymer as terminal groups and provide sulfonic acid groups, and these terminal sulfonic acid groups are effective in preventing devitrification of flame-retardant acrylic fibers. This is because it acts on

Although it is possible to blow sulfur dioxide gas into the polymerization reaction system to supply acidic sulfite or its salt, this method does not affect the present invention in any way. In addition, the reason why the equivalent ratio of reducing agent/oxidizing agent is specified to be 1 or more and 4 or less is that if it is less than 1, the generation rate of radicals generated by redox reaction will decrease and the polymerization reaction efficiency will decrease, so this is not an industrially advantageous method. This is because it cannot be said. In addition, when the concentration exceeds 4, the concentration of hydrogen sulfite radicals generated increases, but conversely, the two radicals react with each other and are deactivated, reducing the polymerization rate. This is because it not only makes it difficult to produce a polymer with a certain degree of polymerization, but also promotes non-uniformity of the polymerization reaction.

In order to improve the devitrification prevention properties of fibers spun from flame-retardant acrylonitrile polymers, it is necessary to uniformly perform the coagulation process in the spinning bath. It is effective to keep the Although the reason why the present invention has such an excellent effect is not clear, it is possible to uniformly introduce sulfonic acid groups into the terminals of the polymer when a rogen-containing monomer and acrylonitrile form a copolymer. It is thought that the sulfonic acid group at the end of the polymer has the effect of keeping the coagulation rate of the polymer uniform.

The present invention is to make an acrylonitrile polymer contain at least 0.5 to 1.5 weight percent of a vinyl monomer containing a sulfonic acid group. If the content of the sulfonic acid group-containing monomer is less than 0.5% by weight, the fiber obtained by spinning the polymer will not only have insufficient devitrification prevention properties (the excellent inherent properties of acrylonitrile fibers) This is to reduce the vividness of dyeing.Also, if the amount exceeds 2% by weight, the sulfonic acid groups with low reactivity will be copolymerized unevenly during polymerization of flame-retardant acrylonitrile-based polymers, and conversely, the fiber This is because not only does it impair the devitrification-preventing property, but also a polymer containing a relatively large amount of sulfonic acid groups is produced, and this polymer falls off in the spinning bath during spinning, impairing the operability of spinning.

Vinyl monomers containing sulfonic acid groups used in the present invention include, for example, allyl sulfonic acid, methalylsulfonic acid, vinylbenzenesulfonic acid, or their salts, which are industrially less expensive. It is advantageous to use monomers that are

In the present invention, it is preferable to supply the anionic surfactant in an amount of 0.8 to 2% by weight based on the total amount of monomers to be supplied. Halogen-containing vinyl monomers such as vinylidene chloride are generally insoluble in water, and when producing monomers with such properties using water as a polymerization medium and a redox initiator, Addition of surfactants is necessary to improve polymerization availability.

Surfactants are classified into anionic, nonionic, and cationic surfactants. As surfactants used in the present invention, anionic surfactants are defined as nonionic surfactants, while cationic surfactants have a poor emulsifying power for vinylidene chloride, so oil droplets of unreacted monomers are used in the polymerization reaction system. This is because the resulting polymer cannot be uniformly dispersed, resulting in non-uniform composition of the resulting polymer. By supplying a large amount of nonionic surfactant, it is possible to uniformly disperse unreacted monomer oil droplets to a certain extent in the polymerization reaction system, but the resulting aqueous polymer solution may take on an emulsified state and cause polymerization. It becomes difficult to separate the aggregates, and furthermore, washing is insufficient, resulting in many operational problems such as surfactants remaining in the produced polymer and falling off in the spinning bath during spinning.

The amount of anionic surfactant added needs to be 0.8 to 2% by weight based on the total amount of monomers supplied, and
．． If it is less than 8% by weight, the emulsifying power for vinylidene chloride is poor and monomer oil droplets cannot be uniformly dispersed, and if it is less than 2% by weight,
If the temperature is exceeded, the produced polymer will take on an emulsified state, which not only makes it difficult to separate the polymer from an aqueous polymer solution, but also reduces the polymerization utility of the water-soluble sulfonic acid group-containing vinyl monomer. Therefore, it is undesirable. Examples of the anionic surfactant include alkylbenzene sulfonate salts and alkyl alcohol sulfate salts, but there is no problem as long as the anionic surfactant is generally used in emulsion polymerization.

The oxidizing agent used in the present invention can be selected from water-soluble oxidizing agents commonly used in radical polymerization. For example, potassium persulfate.

Examples include persulfates such as ammonium persulfate, chlorates such as sodium chlorate, and the like.

In addition to the cholera catalyst, it is also possible to add a small amount of a metal salt such as iron sulfate to promote the polymerization reaction.

As water as a polymerization medium in the method of the present invention, it is preferable to use ion-exchanged water. Further, the ratio of ion-exchanged water to the monomer (hereinafter referred to as water/monomer ratio) can be any ratio, but preferably the water/monomer ratio is 1 to 5.
The range is selected. If the water/monomer ratio is less than 1, the viscosity of the aqueous polymer solution will increase, making stirring difficult, making it difficult to control the temperature of polymerization, and causing non-uniformity of the polymerization reaction. On the other hand, if the water/monomer ratio exceeds 5, the polymerization efficiency decreases and it cannot be said to be industrially advantageous. The average residence time of the monomer in the polymerization reactor may be the time normally employed when producing 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 pH 2 to 3.5).

A polymerization termination agent is added to the polymer taken out from the polymerization vessel to terminate the reaction. The terminator for the polymerization reaction may be one that is normally used when producing acrylonitrile polymers by aqueous suspension polymerization.

After a polymerization terminator is added to the polymer aqueous solution, unreacted monomers are recovered. There are two ways to recover unreacted monomers: direct distillation of the aqueous polymer solution, and dehydration and washing to separate unreacted monomers from the polymer followed by distillation, but both methods can be used. be. In the latter case, a rotary vacuum filtration machine, a centrifugal dehydrator, etc., which are known temporary dehydrators, are usually used as the dehydrating/washing machine. 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.

Example-1 Ion-exchanged water (p
h = 3), a monomer mixture of 55 parts of acrylonitrile, 43 parts of vinylidene chloride, 2 parts of sodium metaallylsulfonate, 0.9 parts of sodium lauryl alcohol sulfate, 0.53 parts of ammonium persulfate, and sodium acid sulfite. 0.64 parts ferrous sulfate (FeSO
4H'ya,o) 4.4X10 parts, sulfuric acid 0.04
Each was dissolved in ion-exchanged water to make 8 parts, and continuous feeding was started. Furthermore, the total amount of ion exchange water is 250
ion-exchanged water was separately supplied so that the

The polymerization temperature was maintained at 35° C., continuous and sufficient stirring was performed, and the reaction was carried out for an average of 80 minutes. An aqueous polymer solution is continuously taken out from the overflow port of the reactor, and 0.49 parts of sodium oxalate and 0.0 parts of ethylenediaminetetraacetate are added to the solution.
7 parts of sodium bicarbonate and 1.82 parts of sodium bicarbonate dissolved in 100 parts of ion-exchanged water were added at a rate of 0.2 parts, and then ion-exchanged water was added. The polymer 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 a pellet shape using a single-screw extruder and then dried using an aerated dryer to obtain the polymers shown in Table 1.

25 parts of the obtained polymer was dissolved in 75 parts of dimethylacetamide, passed through a 1000-hole 0.07nφ spinneret, spun into a 55% dimethylacetamide aqueous solution (30°C), stretched 5 times, and then spun at 115°C. Perform steam heat setting, 3
．． 0 denier, strength 3. A fiber with Op/d and elongation of 35% and no devitrification was obtained. Furthermore, the flame retardancy of the obtained fiber was LOI (Limiting Oxygen Index) 30, and very excellent flame retardant performance was obtained.

Example 2 Using the same equipment as in Example 1, a monomer mixture of 48 parts of acrylonitrile and 50 parts of vinylidene chloride was supplied, and 0.48 parts of ammonium persulfate and 0.4 parts of sodium acid sulfite were added.
Polymer aqueous solutions were obtained by dissolving 58 parts of sulfuric acid and 0.44 parts of sulfuric acid in ion-exchanged water under the same conditions. The same reaction terminator as in Example 1 was added to the polymer aqueous solution taken out from the reactor overflow port, and 2 parts of sodium sulfate dissolved in ion-exchanged water was added, and the temperature was raised to 80°C to remove unreacted monomers. was evaporated and separated, and the polymer was agglomerated. The resulting aqueous polymer solution was dehydrated and washed using a centrifugal dehydrator to obtain a wet polymer containing about 60% water by weight.

The obtained polymer was spun in the same manner as in Example 1, and 3.
A fiber with no devitrification of 1 denier, a strength of 2.9 P/d, and an elongation of 37% was obtained.Furthermore, the flame retardance of the obtained fiber was L.
It showed very excellent flame retardant performance with an OI of 33.

Example 3 Using the same equipment and method as in Example 1, 1.2 parts of sodium laurylbenzene sulfonate was used instead of 0.9 parts of sodium lauryl alcohol sulfate as a surfactant.
The polymers shown in Table 1 were obtained.

The obtained polymer was spun in the same manner as in Example 1, and 3.
A fiber with no devitrification was obtained, having a denier of 2 denier, a strength of 2.91/d, and an elongation of 36.0%. The flame retardant performance of this fiber is LOI2
It showed an excellent value of 9.5.

Example 4 The same equipment as in Example 1 was used, except that 0.85 parts of acidic sodium sulfite and 0.064 parts of sulfuric acid were dissolved in ion-exchanged water and supplied to the reaction vessel. Obtained union.

The resulting polymer was spun in the same manner as in Example 1 to obtain a fiber with no devitrification, and an excellent flame retardant performance with an LOI of 30.

Comparative Example 1 Example 1 except that 4.33 parts of dispersible sodium sulfite was supplied
The polymers shown in Table 1 were obtained in the same manner using the same equipment.

By spinning the obtained polymer in the same manner as in Example 1, it had a denier of 3.0, a strength of 2.67 P/d, and an elongation of 3.
Although a fiber with excellent flame retardancy of 5.0% and LOI of 29.5 was obtained, it was devitrified and lacked luster.

Comparative Example 2 In Example 1, a nonionic surfactant ((,
,H,,-0(CH,CH,0)n)t,13) in n
Example 1 except that 1.5 parts of ammonium persulfate, 0.86 parts of sodium acid sulfite, and 0.065 parts of sulfuric acid were each dissolved in ion-exchanged water and supplied.
Polymers shown in Table 1 were obtained in the same manner as above.

The obtained polymer was spun in the same manner as in Example 1, and 2.
9 denier, strength 3. I P/d, elongation 34.5%
of fibers were obtained. Although the flame retardance of the fiber showed an excellent value of LOI 30, it was a devitrified fiber with no luster.

Table 1 *Specific viscosity Measured at 25°C using a dimethylformamide solution with a concentration of 0.5 J'/100 mj.

*Devitrification status and gloss ◎Evaluation in 4 stages: Best, O Good, Δ Slightly Poor, × Poor *AN Acrylonitrile, VdC1 Vinylidene Chloride, MS Sodium Metaallylsulfonate [Effects of the Invention] Detailed explanation in Examples Although the polymer compositions of the acrylonitrile fibers are almost the same as described above, the fibers produced by spinning the flame-retardant acrylonitrile polymer produced by the present invention have no devitrification (shiny and shiny). This effect of the present invention lies in the homogenization of the polymer composition, and in particular uniform introduction of sulfonic acid groups into the polymer seems to be effective in preventing devitrification. The reason for this is that by making the polymer composition uniform, the coagulation process of the polymer during spinning is maintained uniformly, and fibers having a dense structure with few voids can be obtained.

Claims (1)

[Scope of Claims] 1. A copolymer consisting of 40 to 75% by weight of acrylonitrile, 30 to 58% by weight of vinylidene chloride, and 0.5 to 1.5% by weight of a vinyl monomer containing a sulfonic acid group is dissolved in water. Acrylonitrile-based acrylonitrile is produced using a water-soluble redox initiator as a medium, using acidic sulfite or its salt as a reducing agent, and setting the equivalent ratio of reducing agent/oxidizing agent to 1 to 4. Method for producing copolymer. 2. Anionic surfactant is supplied at 0% relative to the total amount of monomers.
．． The manufacturing method according to claim 1, characterized in that 8 to 2% by weight is supplied.