JPS63308012A - Production of styrene-maleimide copolymer emulsion - Google Patents

Abstract

PURPOSE:To obtain the titled emulsion capable of being stably subjected to emulsion polymerization and readily coagulating and recovering a copolymer useful as interior automative trim with an inorganic acid, by blending a monomer mixture with a surface active agent containing soap of fatty acid type, adjusting the blend into a proper pH and subjecting to emulsion polymerization. CONSTITUTION:(A) 100pts.wt. monomer mixture consisting of (i) 30-98wt.% styrenic monomer, (ii) 2-70wt.% maleimide monomer and (iii) 0-40wt.% another vinyl monomer copolymerizable with these monomers is blended with (B) 0.2-4pts.wt. surface active agent which comprises (iv) soap of fatty acid type and (v) soap of sodium sulfonate type and the weight ratio of the component iv and the component v of 10:90-95:5, the aqueous solution is adjusted to pH5-9 and emulsion polymerization is carried out to give the emulsion.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides a styrene-maleimide copolymer with excellent heat resistance and processability that is useful as a base material for automobile interior materials, OA equipment housing materials, etc. The present invention relates to a method for stably producing a styrene-maleimide copolymer emulsion, in particular a method for stably producing a styrene-maleimide copolymer emulsion, in which the copolymer can be easily coagulated and recovered from a copolymer emulsion with an inorganic acid. The present invention relates to a method for producing a polymer emulsion.

[Prior Art] Conventionally, in order to improve the heat resistance of polystyrene, it has been common practice to copolymerize styrene with α-methylstyrene, an unsaturated carboxylic acid anhydride, or a maleimide monomer. However, although α-methylstyrene can improve the heat resistance of polystyrene,
If the amount used increases, not only the polymerization rate will drop significantly, but also the thermal stability of the resulting copolymer will be extremely poor. In addition, when unsaturated carboxylic acid anhydride is used as a copolymerization component, in the same way as when α-methylstyrene is used,
A product with good thermal stability cannot be obtained. Furthermore, if a maleimide monomer is used as a copolymerization component, the heat resistance of polystyrene can be increased without reducing the thermal stability or polymerization rate. Because maleimide monomers are easily hydrolyzed with alkali, when copolymerizing maleimide monomers with styrene in emulsion polymerization, alkaline type surfactants such as fatty acid soaps (e.g., sodium rosinate) are used. The problem is that it cannot be done. Additionally, relatively neutral surfactants consisting of strong acids and strong bases such as sodium sulfonate are commonly used to coagulate and recover copolymers from emulsions. Inorganic acids cannot be used, and large amounts of metal salts must be used. Use of a large amount of metal salt not only increases cost and is not economical, but also causes various problems in the physical properties of the copolymer.

[Problems to be Solved by the Invention] The purpose of the present invention is to overcome the drawbacks of the conventional styrene-maleimide copolymer production method and to stably produce a styrene-maleimide copolymer emulsion. It is an object of the present invention to provide a method for producing a styrene-maleimide copolymer emulsion, which allows the copolymer to be easily coagulated and recovered from the copolymer emulsion using an inorganic acid.

[Means for Solving the Problems] The present invention provides a method for producing a styrene-maleimide copolymer emulsion that can achieve the above objects.

That is, the present invention contains 30 to 98% by weight of styrenic monomer,
A styrene-maleimide copolymer is obtained by emulsion polymerization of a monomer mixture consisting of 2 to 70% by weight of a maleimide monomer and 0 to 40% by weight of another vinyl monomer copolymerizable with these monomers. A method for producing an emulsion comprising (a) fatty acid turquoise soap and (b) sulfonic acid sodium soap, and the weight ratio of (a) to (b) is 10:90 to 95.
0.2 to 4 parts by weight of a surfactant having a ratio of 5 to 5 is used per 100 parts by weight of the monomer mixture, and the pI of the aqueous solution is 5 to 9.
The present invention relates to a method for producing a styrene-maleimide copolymer emulsion, which is characterized by carrying out emulsion polymerization in a styrene-maleimide copolymer emulsion.

The method for producing the styrene-maleimide copolymer emulsion of the present invention will be described below.

Examples of the styrenic monomer used as the first component in the monomer mixture in the present invention include styrene, α-methylstyrene, p-methylstyrene, and halogenated styrene. Two or more styrenic monomers may be used in combination. The amount of these styrene monomers used is 30 to 98% by weight, preferably 35 to 95% by weight in the monomer mixture.
Weight%.

The amount of styrenic monomer used is 30ff in the monomer mixture
If it is less than 1%, the processability, which is an inherent characteristic of styrenic resins, will deteriorate, which is undesirable, and if it is more than 98% by weight, the heat resistance will hardly be improved.

In addition, maleimide monomers used as the second component in the monomer mixture in the present invention include maleimide, N-phenylmaleimide, N-cyclohexylmaleimide, N-cyclohexylmaleimide, and N-phenylmaleimide.
-(o-chlorophenyl)maleimide, N-(o-methoxyphenyl)maleimide, N-(p-hydroxyphenyl)maleimide, N-isopropylmaleimide, and the like. Two or more types of maleimide monomers may be used in combination. The amount of these maleimide monomers used is 2 to 70%, preferably 5 to 5% in the monomer mixture.
It is 0% by weight. If the amount of maleimide monomer used is less than 2% by weight in the monomer mixture, a copolymer with excellent heat resistance cannot be obtained, and if it is more than 70% by weight, processability may decrease. Not only does this become noticeable, but also the mechanical strength etc. decreases, which is undesirable.

Other vinyl monomers that can be copolymerized with the styrene monomer and maleimide monomer used as needed in the present invention include unsaturated nitriles such as acrylonitrile and methacrylonitrile, methyl ( meta) acrylate,
(meth)acrylic acid esters such as ethyl (meth)acrylate, butyl (meth)acrylate, hydroxyethyl (meth)acrylate, glycidyl (meth)acrylate, unsaturated carboxylic acids such as acrylic acid, methacrylic acid, itaconic acid, etc. can give. Two or more of these other vinyl monomers can also be used in combination. The amount of other vinyl monomers used is 0 to 40% by weight, preferably 0 to 35% by weight in the monomer mixture. The amount of other vinyl monomers used is 4% in the monomer mixture.
If the amount is more than 0%, the original properties of the styrenic resin will be lost, which is not preferable.

The surfactants used in emulsion polymerization of the monomer mixture are (a) fatty acid soap and (b) sodium sulfonate soap.

Examples of the fatty acid quartzite of the component (a) include sodium rosin acid, sodium laurate, sodium palmitate, sodium stearate, sodium myristate, and sodium oleate. Examples of the sodium sulfonate soap of component (b) include sodium alkylbenzenesulfonates such as sodium dodecylbenzenesulfonate, and sodium alkylnaphthalenesulfonates. The ratio of component (a) to component (b) used is within the range of 10:90 to 95:5, preferably 20:80 to 90:IO, by weight. If the usage ratio of component (a) to component (b) is less than 10/90, that is, the amount of component (a) used is less than 10;
b) If the amount of component used is more than 90%, it is extremely difficult to recover the styrene-maleimide copolymer by coagulating it with an inorganic acid from the copolymer emulsion obtained by emulsion polymerization. be. On the other hand, the usage ratio of component (a) to component (b) is 95
If the amount of component (a) used is more than 95, and if the amount of component (b) used is less than 5, the emulsifying effect will decrease and the emulsion will be destroyed during polymerization, resulting in poor emulsion polymerization. become unable to complete.

The amount of the surfactant consisting of fatty acid soap and sodium sulfonate soap is 0.2 to 4 parts by weight, preferably 0.3 to 3 parts by weight, based on 100 parts by weight of the monomer mixture. If the amount of surfactant used is less than 0.2 parts by weight, emulsion polymerization cannot be carried out in a stable manner. Furthermore, if the amount of surfactant used is more than 4 parts by weight, not only will it be difficult to recover the styrene-maleimide copolymer from the copolymer emulsion, but also the surfactant will be added to the copolymer. This is not preferable because the amount of the styrene-maleimide copolymer that is mixed in increases, and the thermal properties and mechanical properties of the resulting styrene-maleimide copolymer are impaired.

When preparing an aqueous solution by dissolving a surfactant consisting of a fatty acid soap and a sodium sulfonate soap in water, and performing emulsion polymerization of a monomer mixture in this aqueous solution, the p of the aqueous solution is
It is necessary to adjust H in advance to 5-9, preferably 6-8. When emulsion polymerization of a monomer mixture is carried out in an aqueous solution with a pH+ of less than 5, the maleimide monopods in the monomer mixture will undergo hydrolysis, and
Fatty acid soaps become completely insoluble in water and no longer serve as surfactants. On the other hand, p of the aqueous solution
If ++ is higher than 9, the maleimide monomer in the monomer mixture will be easily saponified, which is not preferred. Any inorganic acid, organic acid, inorganic base, or organic base may be used to adjust the pH of the aqueous solution. In order to adjust the pH to the above range, it is preferable to dilute these acids and bases beforehand.

As the polymerization initiator, reducing agent, etc. used in carrying out the present invention, those used in general emulsion polymerization can be used. Further, the polymerization temperature is preferably in the range of 40 to 90°C.

The styrene-maleimide copolymer emulsion obtained by the method of the present invention can be easily coagulated with an inorganic acid, and the styrene-maleimide copolymer can be easily recovered from the emulsion.

Examples of inorganic acids include hydrochloric acid, sulfuric acid, nitric acid, and phosphoric acid. These inorganic acids can be used alone or in combination of two or more.

[Examples] The present invention will be explained in more detail below with reference to Examples and Comparative Examples.

In addition, the Vicat softening point in the examples is JIS
Measured according to K-7206-1982. Also,
MFI was measured at a temperature of 250° C. and a load of 5 kg according to JIS K-7210-1976.

Example 1 After preparing an aqueous surfactant solution by dissolving 1.2 parts by weight of sodium sulfonate and 0.8 parts by weight of sodium dodecylbenzenesulfonate in 200 parts by weight of water, dilute hydrochloric acid was added to this aqueous surfactant solution. The mixture was stirred and mixed.

The pH of the resulting aqueous solution was 7.5. This aqueous solution 1
After charging 50 parts by weight, 0.01 parts by weight of ferrous sulfate, and 0.5 parts by weight of dextrose into a reaction vessel and raising the temperature to 70°C while passing N2 gas, 75 parts by weight of styrene, N-
Monomer mixture 1 consisting of 25% by weight of phenylmaleimide
0 parts by weight and the remaining surfactant aqueous solution.
, 3 parts by weight of cumene hydroperoxide were continuously injected over 3 hours.

After the injection, the reaction was further carried out at 70°C for 1.5 hours. The emulsification state was good, and a styrene-N-phenylmaleimide copolymer emulsion could be stably obtained.

The resulting emulsion was soaked in warm water with 5 parts of sulfuric acid dissolved in advance.
When added to 0 parts by weight, the styrene-N-phenylmaleimide copolymer was easily coagulated and the copolymer could be easily recovered. The Vicat softening point of the resulting copolymer was 125°C. Also, MFI is 1.5 g/
It was 10 minutes.

Example 2 Emulsion polymerization was carried out in the same manner as in Example 1, except that a monomer mixture consisting of 60% by weight of styrene, 20% by weight of acrylonitrile, and 20% by weight of N-phenylmaleimide was used. The emulsification state was good, and the obtained copolymer emulsion could be easily coagulated with sulfuric acid. The Vicat softening point of the resulting copolymer was 130°C. Also, M
FI was 0.7 g:/10 min.

Example 3 Sodium laurate was used instead of sodium zinate, 75% by weight of styrene and N-phenylmaleimide 2
40% by weight of styrene, 15% by weight of α-methylstyrene, 20% by weight of acrylonitrile and 25% by weight of N-cyclohexylmaleimide instead of a monomer mixture consisting of 5% by weight.
Emulsion polymerization and coagulation were carried out in the same manner as in Example 1, except that a monomer mixture consisting of % by weight was used and hydrochloric acid was used instead of sulfuric acid. The emulsification state was good, and the obtained copolymer emulsion could be easily coagulated with hydrochloric acid. The Vicat softening point of the copolymer produced is 145
It was °C. Moreover, MFI was 0.4 g/10 minutes.

Example 4 Emulsion polymerization was carried out in the same manner as in Example 1, except that a monomer mixture consisting of 55% by weight of styrene, 15% by weight of methyl methacrylate and 30% by weight of N-(para-hydroxyphenyl)maleimide was used. Ta. The emulsification state was good, and the resulting copolymer emulsion could be easily coagulated with sulfuric acid. The Vicat softening point of the copolymer produced is 15
The temperature was 7°C.

Comparative Example 1 1.2 parts of sodium zinate and 0.8 parts of sodium dodecylbenzenesulfonate were added to 200 fflffl of water.
Emulsion polymerization was carried out in the same manner as in Example 1, except that the aqueous surfactant solution of PT (10) obtained by dissolving the monomer in Thirty minutes after starting the injection of the mixture and initiator, the emulsification broke down and a copolymer emulsion could not be obtained.

Comparative Example 2 Emulsion polymerization was carried out in the same manner as in Example 1, except that an aqueous surfactant solution with a pH of 11 consisting of 2.0 parts by weight of sodium zinate and 200 parts by weight of water was used as it was without adjusting the pH. I did this. Immediately after starting polymerization, the emulsified state became unstable and polymerization was not possible.

Comparative Example 3 The pH of an aqueous surfactant solution consisting of 2.0 parts by weight of sodium dodecylbenzenesulfonate and 200 parts by weight of water was adjusted to pH 7 or 8 with sodium hydroxide. Emulsion polymerization was carried out in the same manner as in Example 1 except that this aqueous solution was used. Although the emulsification state was good, when an attempt was made to coagulate the obtained copolymer emulsion with sulfuric acid, the copolymer could not be coagulated and the copolymer could not be recovered.

Comparative Example 4 The pH of an aqueous surfactant solution consisting of 2.0 parts by weight of sodium zinate and 200 parts by weight of water was adjusted to pH 7.1 with dilute hydrochloric acid. Emulsion polymerization was carried out in the same manner as in Example 1 except that this aqueous solution was used. As a result, sodium rosinate precipitated and emulsion polymerization could not be carried out.

[Effects of the Invention] According to the present invention, a monomer mixture can be stably emulsion polymerized, and the resulting emulsion can be easily processed with an inorganic acid to form a styrene-maleimide system with excellent heat resistance and processability. The copolymer can be coagulated and recovered.

Claims (1)

[Claims] A monomer mixture consisting of 30 to 98% by weight of a styrene monomer, 2 to 70% by weight of a maleimide monomer, and 0 to 40% by weight of another vinyl monomer copolymerizable with these monomers. A method for producing a styrene-maleimide copolymer emulsion by emulsion polymerization, comprising (a) a fatty acid soap and (b) a sodium sulfonate soap, and (a)
A surfactant having a weight ratio of 10:90 to 95:5 is used in an amount of 0.2 to 4 parts by weight per 100 parts by weight of the monomer mixture, and the pH of the aqueous solution is adjusted to 5 to 9. A method for producing a styrene-maleimide copolymer emulsion, which comprises emulsion polymerization.