JPH0987333A - Aromatic vinyl copolymer and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an aromatic vinyl copolymer whose oligomer content is as low as 1.5wt.% or less and which brings about a resin molded item having the surface with less bleeding and makes a mold less soiled. SOLUTION: This aromatic vinyl copolymer is an aromatic vinyl copolymer obtained by continuous mass polymerization of a monomer mixture of 20 to 90wt.% aromatic vinyl monomer, 0 to 60wt.% vinyl cyanide monomer, 0 to 80wt.% (meth)acrylic ester monomer, and 0 to 60wt.% other vinyl monomer copolymerizable with these wherein the content of the oligomer having a molecular weight of 100 to 1,000 is 1.5wt.% or less and the reduced viscosity is 0.2 to 0.8dl/g. When the monomer mixture is subjected to continuous mass polymerization, it is carried out in such manner that in a first polymerization vessel the polymerization temperature T1 is such that 110 deg.C<=T1<=130 deg.C and the polymerization reaction rate is 40 to 65wt.%, and in a lower part of a second polymerization vessel the polymerization temperature T2 is such that 150 deg.C<=T2<=175 deg.C and the polymerization reaction rate is 70 to 90wt.%.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aromatic vinyl copolymer produced by a continuous bulk polymerization method, which has a low content of oligomers and has little bleeding on the surface of a resin molded product and mold stains, and the aromatic vinyl copolymer. The present invention relates to a method for efficiently producing a vinyl-based copolymer by a bulk polymerization method.

[0002]

2. Description of the Related Art Conventionally, as a method for producing a copolymer composed of an aromatic vinyl monomer and a vinyl cyanide monomer, a suspension polymerization method, an emulsion polymerization method, a solution polymerization method, a bulk polymerization method, etc. Are known, and these production methods may be selected depending on the use of the resulting copolymer, but generally, the heat of the polymerization reaction is removed and the handling of a viscous substance that increases with the polymerization reaction is generally restricted. The current situation is that they have been selected. The suspension polymerization method, the emulsion polymerization method and the solution polymerization method are advantageous manufacturing methods in that there are relatively few restrictions due to the above-mentioned viscous substances, but on the other hand, the contamination of impurities by the auxiliary raw material used and the waste water for separating water. Environmental pollution due to load,
There was also a problem in terms of energy loss due to solvent separation.

On the other hand, the bulk polymerization method is free from problems such as mixing of impurities, environmental pollution and energy loss, but is largely restricted by viscous substances. Therefore, as a method for solving such a problem, an efficient bulk polymerization method using a two-tank continuous bulk polymerization apparatus has been proposed (Japanese Patent Publication No. 49-26).
711, Chemical Engineering, 48 (6), 415-420
P. (1984)). However, in the continuous bulk polymerization method, the restriction due to the viscous substance is solved, but in order to facilitate the handling of the viscous substance generated as the polymerization reaction progresses, the melting point of the copolymer obtained as a product is 20
It was necessary to polymerize at a polymerization temperature as high as ℃ or more. Therefore, the aromatic vinyl-based copolymer obtained by continuous bulk polymerization using a two-tank continuous bulk polymerization apparatus has an oligomer content of 2.0 wt% with a molecular weight of 100 to 1000 by-produced at high temperature.
Higher than above, continuous due to the oligomer bleeding onto the surface of the resin molded product. There was a problem that the mold was heavily soiled during shaping.

Further, since the copolymer is produced at a high polymerization temperature, there is a problem that carbide is generated and the color tone is deteriorated due to thermal deterioration of the copolymer inside the polymerization tank, and stable continuous operation cannot be performed for a long period of time.

[0005]

SUMMARY OF THE INVENTION The present invention has been achieved as a result of studying to solve the problems in the prior art described above. Therefore, the object of the present invention is to
Aromatic vinyl copolymer produced by continuous bulk polymerization method with low oligomer content and less bleeding on the surface of resin molded product and mold stain, and efficiency of this aromatic vinyl copolymer by bulk polymerization method The present invention is to provide a method of manufacturing the same.

[0006]

To achieve the above object, the aromatic vinyl copolymer of the present invention comprises 20 to 90% by weight of an aromatic vinyl monomer and a vinyl cyanide monomer. Continuous bulk polymerization of a monomer mixture consisting of 0 to 60% by weight, 0 to 80% by weight of a (meth) acrylic acid ester-based monomer, and 0 to 60% by weight of another vinyl-based monomer copolymerizable therewith. An aromatic vinyl-based copolymer obtained by
The content of the oligomer having a molecular weight of 100 to 1000 is 1.5% by weight or less, and the reduced viscosity is 0.2 to 0.8 dl / g.

Further, the method for producing an aromatic vinyl copolymer of the present invention comprises 20 to 90% by weight of an aromatic vinyl monomer,
A unit consisting of 0 to 60% by weight of a vinyl cyanide monomer, 0 to 80% by weight of a (meth) acrylic acid ester type monomer, and 0 to 60% by weight of another vinyl monomer copolymerizable therewith. When performing continuous bulk polymerization of the monomer mixture using a two-tank continuous bulk polymerization apparatus, the polymerization temperature T1 in the first polymerization tank is 110 ° C. ≦ T1 ≦ 130 ° C., and the polymerization reaction rate is 40 to
65% by weight, and the polymerization temperature T in the lower part of the second polymerization tank
2 is 150 ° C. ≦ T2 ≦ 175 ° C., the polymerization reaction rate is 80 to 9
It is characterized by being 0% by weight.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Although the aromatic vinyl copolymer of the present invention is obtained by continuous bulk polymerization,
Compared with an aromatic vinyl-based copolymer obtained by a conventional bulk polymerization method, the content of oligomers having a molecular weight of 100 to 1000 is 1.5% by weight or less, and particularly 1.2% by weight or less. It has an excellent performance that there is little bleeding on the surface of and the mold stain.

The aromatic vinyl copolymer of the present invention has a reduced viscosity ηsp / c of 0.2 to 0.8 dl /
g, particularly preferably in the range of 0.3 to 0.7 dl / g, and if it is less than 0.2 dl / g, mechanical properties such as impact resistance and chemical resistance become insufficient, so 0.8 dl / g If it exceeds the above range, the moldability is deteriorated, which is not preferable. The reduced viscosity ηsp / c as used herein is a value calculated by the following formula after dissolving 0.2 g of an aromatic vinyl copolymer in 50 ml of methyl ethyl ketone and measuring the flowing time at 30 ° C. using a viscosity tube. is there. Reduced viscosity ηsp / c = [(t1 / t0) -1] / C In the formula, t1: downflow time in the sample solution (seconds) t0: downflow time of the blank solution (seconds) C: resin concentration of the measurement sample ( g / 100 ml) The method for producing the aromatic vinyl copolymer of the present invention having the above characteristics will be described below. First, the monomer component forming the aromatic vinyl copolymer of the present invention will be described.

The aromatic vinyl copolymer used in the present invention is an aromatic compound having a polymerizable double bond,
Specific examples include styrene, α-methylstyrene, p-methylstyrene, vinyltoluene, propylstyrene, butylstyrene and cyclohexylstyrene. These aromatic vinyl monomers are used alone or as a mixture of two or more. Among these aromatic vinyl monomers, styrene and α-methylstyrene are particularly preferably used.

The vinyl cyanide monomer used in the present invention is a compound having a polymerizable double bond and a cyano group, and specific examples thereof include acrylonitrile and methacrylonitrile. These vinyl cyanide monomers are used alone or as a mixture of two or more. Among these vinyl cyanide-based monomers, acrylonitrile is particularly preferably used.

Specific examples of the (meth) acrylic acid ester-based monomer used in the present invention include methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, glycidyl methacrylate, hydroxyethyl methacrylate and acrylic acid. Butyl and the like can be mentioned. These (meth) acrylic acid ester-based monomers are
It is used in one kind or a mixture of two or more kinds. Of these (meth) acrylic acid ester-based monomers, methyl methacrylate is particularly preferably used.

Specific examples of other vinyl monomers used in the present invention include N-phenylmaleimide, N-cyclohexylmaleimide, methyl-substituted N-phenylmaleimide, maleic anhydride, acrylic acid and methacrylic acid. Of these, N-phenylmaleimide is particularly preferably used.

The blending ratio of each of the above-mentioned monomer components is 20 to 90% by weight, particularly 60 to 90% by weight of the aromatic vinyl monomer, and 0 to 60% by weight of the vinyl cyanide monomer. 1
It is selected from the range of 0 to 40% by weight, 0 to 80% by weight of the (meth) acrylic acid ester-based monomer, and 0 to 60% by weight of the other vinyl-based monomer copolymerizable therewith. Here, if the amount of the aromatic vinyl-based monomer is less than 20% by weight, the molding processability is remarkably deteriorated, and if the amount of the vinyl cyanide-based monomer exceeds 60% by weight, the resulting copolymer is markedly colored. And the heat resistance is also lowered, which is not preferable. In addition, the (meth) acrylic acid ester-based monomer is 80
If the content exceeds 100% by weight, the mechanical strength of the molded product will decrease significantly,
Further, if the amount of the other vinyl-based monomer exceeds 60% by weight, the molding processability and the mechanical strength also deteriorate, which is not preferable.

The monomer mixture used for the bulk polymerization is
Among them, aromatic vinyl monomers, especially styrene 60 to 9
0% by weight, vinyl cyanide-based monomer, especially 10-40% by weight of acrylonitrile, (meth) acrylic acid ester-based monomer, especially 0-80% by weight of methyl methacrylate It is suitable.

In the present invention, mercaptans such as n-dodecyl mercaptan and t-dodecyl mercaptan, which are added as a polymerization regulator during ordinary radical polymerization, to the above-mentioned monomer mixture, organic compounds such as carbon tetrachloride, etc. Halides, disulfides and the like may be added, and if necessary, initiators usually used in radical polymerization, for example, azobisisobutyronitrile, azo-based initiators such as azobiscyclohexanenitrile, Benzoyl peroxide, lauryl peroxide, cumene hydroperoxide, t-butyl perbenzoate, 1,1-
Organic peroxides such as di (t-butyl-3-oxy) -3,3,5-trimethylhexane may be used.
Further, in the present invention, a solvent having a boiling point in the range of −15 to + 5 ° C. with respect to the boiling point of the aromatic vinyl monomer used, for example, dipropyl ketone, ethylbenzene, xylene, valeronitrile, butyl ether, etc. 2 may be added to the polymerization tank.

The continuous bulk polymerization of the present invention is carried out using a two-tank continuous bulk polymerization apparatus divided into two stages. here,
A specific example of a typical two-tank type continuous bulk polymerization apparatus used for carrying out the present invention will be described below with reference to FIG. As shown in FIG. 1, the two-tank continuous bulk polymerization apparatus manufacturing apparatus used in the present invention comprises a first polymerization tank A, a second polymerization tank B, and a devolatilization apparatus C.
Then, the first polymerization tank A has a stirring device 1, a heating mechanism 2, and a cooling device which are a complete mixing tank in order to narrow the molecular weight distribution and the composition distribution of the polymer as much as possible and continuously take out a uniform polymer. The mechanism 3 and the pressure control mechanism 4 are provided, the pressure of the gas phase part is controlled by the pressure control mechanism 4 to control the internal temperature, and the evaporating monomer vapor is condensed by the cooling mechanism 3 to form the water separator 5. It is necessary to separate the water by the method described above, and to return the recovered monomer to the reaction system by the reflux monomer pump 6.

The polymerization liquid that has passed through the first polymerization tank A is then continuously supplied to the second polymerization tank B by a gear pump 7 or the like. The polymerization liquid supplied to the second polymerization tank B has a polymer concentration of 40-
Since it is polymerized up to 65%, the melt viscosity is high, and when it is polymerized in the second polymerization tank, the solution viscosity increases. Therefore, in the second polymerization tank B, it is difficult to perform complete mixing and to uniformly control the temperature of the polymerization liquid, like the first polymerization tank A. Therefore, in the second polymerization tank B, a mixing method that allows the plug flow type movement such that the polymerization liquid in the polymerization tank is mixed in the horizontal direction but not in the vertical direction, In addition, a multi-step heat insulation mechanism 9 that keeps the heat by providing a jacket in which the wall of the polymerization tank is divided into multiple steps
It is necessary to adopt.

For the above reasons, the second polymerization tank B contains
An agitator 8 with a scraping blade that causes less vertical mixing, specifically, an agitator 8 having several blades for scraping the wall surface is used, which is equipped with this agitator 8. , Short pass and back mixing can be suppressed. Further, in the second polymerization tank B, like the first polymerization tank A, a cooling mechanism 3, a pressure control mechanism 4, a water separator 5, a reflux monomer pump 6 and the like are provided to condense evaporating monomers and the like. Can be refluxed to the reaction system.

The polymerized product discharged from the second polymerization tank B is sent to a devolatilizer unit C which vaporizes and separates unreacted monomers, a solvent and water. As the devolatilizer unit C, a multistage vent is particularly used. The use of extruders is preferred. This multi-stage vent extruder C
The unreacted monomers and the solvent vaporized in step 1 can be purified and separated by the water separator 5 and the reflux monomer pump 6 or the like, and reused by returning them to the second polymerization tank B as a mixed solution. More preferable.

The heating temperature in the devolatilizer C is preferably set to about 200 to 280 ° C.
The strand-shaped polymer continuously extruded from the devolatilizer may be cut into pellets for use in the next molding step, or may be directly continuously molded into a sheet or a pipe.

In the method for producing an aromatic vinyl copolymer of the present invention, when the continuous bulk polymerization is carried out using the above-mentioned two-tank continuous bulk polymerization apparatus, the initiator polymerization or the thermal polymerization is carried out in the first polymerization tank A. The reaction rate is 40 to 65% by weight,
In particular, after reacting the supplied monomer to 50 to 60% by weight, the polymerization reaction is performed in the second polymerization tank B until the reaction rate becomes 70 to 90% by weight, particularly 80 to 90% by weight,
Next, the unreacted monomer is removed by the devolatilizer C and the polymer is taken out.

In the present invention, the molecular weight is 100 to 100.
In order to reduce the oligomer content of 0, the reaction temperature T1 of the first polymerization tank A is set to 110 to 130 ° C, particularly 115 to 125 ° C.
While controlling the temperature to ℃, the lower temperature T of the second polymerization tank B
It is important to control 2 to 150 to 175 ° C., particularly 155 to 170 ° C., which is lower than the conventional temperature. Then, in order to lower the lower temperature T2 of the second polymerization tank B to 175 ° C. or lower, it is necessary to set the reaction rate in the first polymerization tank A to 40% or more. Therefore, the reaction temperature T1 of the first polymerization tank is set to 110-
It needs to be 130 ° C.

That is, if the reaction temperature T1 of the first polymerization tank A is less than 110 ° C., a polymerization solution having a reaction rate of 40% or more cannot be obtained, and if it exceeds 130 ° C., the reaction rate is 65%.
% Or more, and the melt viscosity of the reaction solution increases too much, which is not preferable. Further, the lower temperature T2 of the second polymerization tank B is 150
If the temperature is lower than ℃, the melt viscosity of the reaction solution is too high, and it is difficult to stir and mix. If the temperature exceeds 175 ° C, the oligomer content increases and the generation of carbides remarkably increases, which is not preferable.
Then, the reaction rate of the polymerization liquid discharged from the second polymerization tank B is 70% by weight.
If the amount is less than 100%, the volatile matter removal by the devolatilizer C becomes insufficient, and if it exceeds 90% by weight, the melt viscosity of the reaction liquid is too high, and stirring and mixing are difficult, which is not preferable.

According to the above method, it is possible to increase the number of continuous operation days before the operation is stopped due to an increase in carbide.
Stable continuous bulk polymerization can be continued for a long time,
Extremely efficient.

Thus, the aromatic vinyl-based copolymer efficiently obtained by the method of the present invention has a molecular weight of 100 to 1000, though it is obtained by continuous bulk polymerization.
Has an oligomer content of 1.5% by weight or less, which is lower than the conventional one, and its reduced viscosity ηsp / c is 0.2 to 0.
It is in the range of 8 dl / g, and exhibits excellent performance in that there is little bleeding on the surface of the resin molded product and stains on the mold.

[0027]

The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. The percentages and parts used in this example are% by weight and parts by weight, respectively. Further, the oligomer content, injection mold stain, pellet MI value, pellet color tone YI value and carbide were evaluated by the following methods.

[Oligomer content] It was measured by a gel permeation chromatograph (GPC) manufactured by Waters.

[Dirt of injection molding die] The inner surface of the die after continuous 1000 shots of injection molding was visually observed and evaluated according to the following criteria. ⊚: No dirt adhered ∘: A very small amount of dirt adhered, but no problem was found.

[MI value of pellets] The melt index (MI value) was measured under the conditions of 220 ° C. and 6 kg using a melt indexer manufactured by Toyo Seiki.

[Yellow value of pellet color tone] The yellow index (YI value) was measured using a color difference meter manufactured by Suga Test Instruments.

[Carbide] A 10 × 10 square plate was formed,
100 g by visually counting foreign matter of 0.2 mm ² or more
It was converted to the number per hit.

Example 1 Using the two-tank continuous bulk polymerization apparatus shown in FIG. 1, 72 parts of styrene, 28 parts of acrylonitrile and 1,1-di (t-
Butylperoxy) -3,3,5 trimethylhexane (DBTH) (0.01 part) and n-dodecyl mercaptan (0.2 part) were supplied to the monomer mixture, and the polymerization temperature T
1 was controlled at 118 ° C. to polymerize the reaction rate to 60%.
This reaction solution was continuously supplied to the second plug-flow type polymerization tank, and the pressure in the polymerization tank was controlled so that the temperature T2 at the bottom of the polymerization tank became 165 ° C. At this time, the reaction rate of the reaction liquid discharged from the second polymerization tank was 85%.

Further, the reaction solution is continuously supplied to a devolatilization apparatus to volatilize and separate unreacted monomers, then extruded in a strand shape and cut with a cutter to obtain styrene-acrylonitrile copolymer pellets. It was The obtained pellet had ηsp / c of 0.50, and the molecular weight distribution was measured using a gel permeation chromatograph.
The oligomer content of 0 to 1000 was 1.0%, and as a result of observing the mold after continuous 1000 shots of injection molding,
There was very little dirt.

The number of continuous operation days of the bulk polymerization under these conditions was 180 days. The number of continuous operation days in this case means that the operation was stopped due to an increase in carbides in the copolymer pellets obtained when 180 days had elapsed. M of copolymer pellets during continuous operation
The I value was 11 g / 10 minutes, the YI value was 4, and the number of carbides of 0.2 mm ² or more was 2 pieces / 100 g, which was excellent in color tone and pellets containing little carbide were obtained.

Example 2 Using the same polymerization apparatus as in Example 1, 72 parts of styrene, 28 parts of acrylonitrile, n-
A monomer mixture liquid containing 0.16 parts of dodecyl mercaptan was supplied to the first polymerization tank, the polymerization temperature T1 was controlled at 130 ° C., and the reaction rate was polymerized to 55%. When the lower temperature T2 of the second polymerization tank was controlled to be 170 ° C., the reaction rate of the discharge from the second polymerization tank was 85%. Obtained styrene-
Ηsp / c of acrylonitrile copolymer pellets is 0.
50, the oligomer content was 1.4%, and the mold stain was slightly higher than in Example 1. Further, the number of continuous operation days of the bulk polymerization under these conditions was 150 days, the MI value of the obtained copolymer pellets was 11 g / 10 minutes, the YI value was 5, and the number of carbides was 3 pieces / 100 g.

Example 3 Using the same polymerization apparatus as in Example 1, 72 parts of styrene, 28 parts of acrylonitrile, 1,
A monomer mixture liquid consisting of 0.01 part of 1-di (t-butylperoxy) -3,3,5 trimethylhexane (DBTH) and 0.1 part of n-dodecyl mercaptan was supplied to the first polymerization tank, Control the polymerization temperature at 118 ° C to control the reaction rate at 60
Polymerized to%. Next, when the lower temperature T2 of the second polymerization tank was controlled to be 165 ° C., the reaction rate of the discharge from the second polymerization tank was 83%. The obtained styrene-acrylonitrile copolymer pellets had an ηsp / c of 0.7 and an oligomer content of 1.0%, and the mold fouling was almost the same as in Example 1. The number of continuous operation days of bulk polymerization under these conditions was 170 days, the MI value of the obtained copolymer pellets was 3 g / 10 minutes, the YI value was 4, and the number of carbides was 2 pieces / 100.
g.

Example 4 Using the same polymerization apparatus as in Example 1, 24 parts of styrene, 4 parts of acrylonitrile, 72 parts of methyl methacrylate, azobisisobutyronitrile of 0.
A monomer mixture liquid consisting of 03 parts of t-dodecyl mercaptan and 0.2 parts of t-dodecyl mercaptan was supplied to the first polymerization tank, and the polymerization temperature T1 was adjusted to 11
The temperature was controlled to 7 ° C. and the polymerization was performed up to a reaction rate of 50%. next,
When the lower temperature T2 of the second polymerization tank was controlled to be 165 ° C., the reaction rate was 85%.

The styrene-acrylonitrile-methyl methacrylate terpolymer pellets thus obtained had an ηsp / c of 0.33 and an oligomer content of 1.1%, and the mold fouling was almost the same as in Example 1. there were. The number of continuous operation days of the bulk polymerization under these conditions was 160 days, the MI value of the obtained copolymer pellets was 16 g / 10 minutes, the YI value was 1, and the number of carbides was 3 pieces / 100 g.

Comparative Example 1 Using the same polymerization apparatus as in Example 1, 72 parts of styrene, 28 parts of acrylonitrile, 1,
A monomer mixture liquid consisting of 0.01 part of 1-di (t-butylperoxy) -3,3,5 trimethylhexane (DBTH) and 0.2 part of n-dodecyl mercaptan was supplied to the first polymerization tank, The polymerization temperature T1 was controlled to 105 ° C., and the polymerization was continued until the reaction rate reached 38%. Next, when the lower temperature T2 of the second polymerization tank is controlled to 190 ° C., the reaction rate becomes 85.
%Met. The obtained styrene-acrylonitrile copolymer pellets had an ηsp / c of 0.50 and an oligomer content of 2.4%, and the amount of mold fouling was clearly higher than those of Examples 1 to 4. The number of continuous operation days of bulk polymerization under these conditions was 40 days, the MI value of the obtained copolymer pellets was 11 g / 10 minutes, the YI value was as high as 11, and the number of carbides was as large as 42 g / 100 g.

Comparative Example 2 Using the same polymerization apparatus as in Example 1, 72 parts of styrene, 28 parts of acrylonitrile, n-
A monomer mixture solution containing 0.16 parts of dodecyl mercaptan was supplied to the first polymerization tank, and the polymerization temperature T1 was controlled at 120 ° C. to perform polymerization until the reaction rate reached 47%. Next, when the lower temperature T2 of the second polymerization tank was controlled to be 187 ° C., the reaction rate was 85%. The obtained styrene-acrylonitrile copolymer pellets had ηsp / c of 0.5.
0, the oligomer content was 2.3%, and the mold stain was obviously higher than in Examples 1-4. The number of continuous operation days of the bulk polymerization under these conditions was 50 days, the MI value of the obtained copolymer pellets was 11 g / 10 minutes, the YI value was as high as 12, and the number of carbides was as many as 36/100 g. .

Comparative Example 3 Using the same polymerization apparatus as in Example 1, 72 parts of styrene, 28 parts of acrylonitrile, 1,
A monomer mixture liquid consisting of 0.01 part of 1-di (t-butylperoxy) -3,3,5 trimethylhexane (DBTH) and 0.1 part of n-dodecyl mercaptan was supplied to the first polymerization tank, The polymerization temperature T1 was controlled to 105 ° C., and the polymerization was continued until the reaction rate reached 39%. Next, when the lower temperature T2 of the second polymerization tank is controlled to 188 ° C., the reaction rate is 83
%Met. The obtained styrene-acrylonitrile copolymer pellets had an ηsp / c of 0.7 and an oligomer content of 2.2%, and the amount of mold fouling was obviously higher than those of Examples 1 to 4. The number of continuous operation days of bulk polymerization under these conditions was 55 days, the MI value of the obtained copolymer pellets was 3 g / 10 minutes, the YI value was as high as 11, and the number of carbides was as many as 38/100 g. .

[Comparative Example 4] Using the same polymerization apparatus as in Example 1, 24 parts of styrene, 4 parts of acrylonitrile, 72 parts of methyl methacrylate, azobisisobutyronitrile.
A monomer mixture liquid consisting of 03 parts of t-dodecyl mercaptan and 0.2 parts of t-dodecyl mercaptan was supplied to the first polymerization tank, and the polymerization temperature T1 was adjusted to 11
The temperature was controlled to 0 ° C., and polymerization was performed until the reaction rate reached 40%.
Next, when the lower temperature T2 of the second polymerization tank was controlled to be 185 ° C., the reaction rate was 85%. Ηsp / c of the obtained pellets is 033, and the content of oligomers is 2.3%.
Therefore, the mold stain was obviously more than in Examples 1 to 4. The number of continuous operation days of the bulk polymerization under these conditions was 60 days, the obtained styrene-acrylonitrile-methyl methacrylate terpolymer copolymer pellets had an MI value of 16 g / 10 minutes and a YI value of 5. It was higher than in Example 4, and the number of carbides was as high as 29/100 g.
These results are summarized in Table 1.

[0044]

[Table 1] As is clear from the results shown in Table 1, the aromatic vinyl-based copolymers (Examples 1 to 4) obtained by the method of the present invention were the aromatic vinyl-based copolymers obtained by the method lacking the conditions of the present invention. Compared with the polymers (Comparative Examples 1 to 4), the oligomer content was low, the number of continuous operation days was long, and the mold stain was small.
The color tone is also excellent.

[0045]

INDUSTRIAL APPLICABILITY The aromatic vinyl copolymer of the present invention is obtained by continuous bulk polymerization, but the content of oligomers having a molecular weight of 100 to 1000 is as low as 1.5% or less, and the resin It has the excellent characteristics that there is little bleeding on the surface of the molded product and less dirt on the mold during continuous molding. Further, according to the method for producing an aromatic vinyl-based copolymer of the present invention, it is possible to increase the number of continuous operation days until the number of carbides increases and the operation is stopped, and stable continuous bulk polymerization is continued for a long period of time. It is capable and extremely efficient.

[Brief description of drawings]

FIG. 1 is a schematic view showing an example of an apparatus for continuous bulk polymerization of an aromatic vinyl copolymer of the present invention.

[Explanation of Codes] A First polymerization tank B Second polymerization tank C Devolatilizer 1 Stirrer 2 Heating mechanism 3 Cooling mechanism 4 Pressure controller 5 Water separator 6 Reflux monomer pump 7 Gear pump 8 Scraped blade impeller with perforated plate Device 9 Multi-stage heat retention mechanism

Claims (5)

[Claims] 1. Aromatic vinyl-based monomer 20 to 90% by weight, vinyl cyanide-based monomer 0 to 60% by weight, (meth)
Aromatic vinyl-based copolymerization obtained by continuous bulk polymerization of a monomer mixture consisting of 0 to 80% by weight of an acrylate-based monomer and 0 to 60% by weight of another vinyl-based monomer copolymerizable therewith. The combined content of oligomers having a molecular weight of 100 to 1000 is 1.5% by weight or less, and the reduced viscosity is 0.2.
Aromatic vinyl-based copolymer, characterized in that it is 0.8 dl / g. 2. The aromatic vinyl-based copolymer according to claim 1, wherein the single polymer mixture is composed of 60 to 90% by weight of styrene and 10 to 40% by weight of acrylonitrile. 3. 20 to 90% by weight of an aromatic vinyl monomer, 0 to 60% by weight of a vinyl cyanide monomer, (meth)
A monomer mixture consisting of 0 to 80% by weight of an acrylate-based monomer and 0 to 60% by weight of another vinyl-based monomer copolymerizable therewith is continuously bulked using a two-tank continuous bulk polymerization apparatus. In the polymerization, the polymerization temperature T1 in the first polymerization tank is 110 ° C. ≦ T1 ≦ 130 ° C., and the polymerization reaction rate is 4
The polymerization temperature T2 in the lower part of the second polymerization tank is 150 ° C. ≦ T2 ≦ 175 ° C., and the polymerization reaction rate is 70%.
A method for producing an aromatic vinyl-based copolymer, characterized in that the content of the aromatic vinyl copolymer is about 90% by weight. 4. The method for producing an aromatic vinyl-based copolymer according to claim 3, wherein the single polymer mixture is composed of 60 to 90% by weight of styrene and 10 to 40% by weight of acrylonitrile. 5. The styrene-based copolymer according to claim 3, wherein the first polymerization tank of the two-tank type polymerization apparatus is a complete mixing type and the second polymerization tank is a plug flow type. Manufacturing method.