JPH0770240A - Production of alpha-methylstyrene-arylonitrile-based - Google Patents

Abstract

PURPOSE:To obtain the subject copolymer useful as various molded articles, having a low content of residual monomer, excellent mechanical strength, transparency and heat resistance by copolymerizing alpha-methylstyrene with acrylonitrile using a specific polymerization initiator. CONSTITUTION:alpha-Methylstyrene is copolymerized with acrylonitrile using an organic peroxide having 5-20 repeating units of the formula as a polymerization initiator and further copolymerized with a copolymerizable monomer to give the objective copolymer. In obtaining the copolymer, the amount of the organic peroxide used is 0.1-3.0wt.%, preferably 0.2-2.0wt.% based on the whole amount of the monomers.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an .alpha.-methylstyrene-acrylonitrile copolymer which has a small amount of residual monomers and is excellent in mechanical strength, transparency and heat resistance.

[0002]

2. Description of the Related Art As a method for producing an .alpha.-methylstyrene-acrylonitrile copolymer having excellent mechanical strength and heat resistance, organic peroxides such as t-butylperoxyacetate, t-butylperoxybenzoate and benzoyl peroxide are used. Known to be used. For example, in JP-A-62-141313, a method of polymerizing a large amount of the above-mentioned organic peroxide as a polymerization initiator (hereinafter referred to as an initiator) is described, and JP-A-2-46603 and JP-A-2-46603. -49330 discloses the use of polyfunctional initiators such as t-butylperoxyhexahydrophthalate.

[0003]

Generally, since the method for producing a copolymer is practically useful, it is necessary that the polymerization conversion rate is high under normal conditions and that the degree of polymerization is not difficult to control. is there. However, when the above-mentioned known peroxides are used, it is necessary to use a very large amount of the initiator regardless of the polymerization temperature due to the low activity of the initiator, and thus the obtained copolymerization The degree of polymerization of the coalescence was extremely low, and the strength was low as a molding material, so that it was not useful. Then, in order to increase the degree of combined polymerization, it is necessary to reduce the amount of the initiator used, but in this case, so-called dead end polymerization occurs, and the polymerization rate decreases. That is, when it is attempted to obtain a high conversion rate, the polymerization time becomes extremely long and the productivity is remarkably reduced.

It is already known to polymerize styrene by using a polymeric peroxide having a plurality of peroxide bonds in the molecule. However, when using polyterephthaloyl peroxide or the like, a satisfactory resin was not obtained.

In addition to the above method, JP-A-57-65735
The publication discloses a method for producing an α-methylstyrene-acrylonitrile-based copolymer at a high conversion rate by emulsion polymerization. The copolymer produced by this method contains a salting-out agent and an emulsifier, and thus heat resistance and weather resistance are reduced,
There are restrictions on the fields of use.

[0006]

DISCLOSURE OF THE INVENTION The present inventors have found that an α-methylstyrene-acrylonitrile copolymer, which has a small amount of residual monomers and is excellent in mechanical strength, transparency and heat resistance, can be industrially used. As a result of the research for the purpose of developing a method superior to the known method, the present invention has been completed.

That is, the present invention provides a polymerization initiator in the production of an α-methylstyrene-acrylonitrile copolymer by copolymerizing α-methylstyrene and acrylonitrile, and optionally a monomer copolymerizable with these compounds. Is the general formula,

[Chemical 2] And the number of repeating units is 5
.Alpha.-, which is an organic peroxide of .about.20.
It is a method for producing a methylstyrene-acrylonitrile-based copolymer.

In the present invention, the organic peroxide having the repeating unit represented by the chemical formula 1 is, for example, polymeric diacyl peroxyside obtained by reacting azelaic acid chloride with hydrogen peroxide in the presence of alkali. Here, when the number of repeating units is n, n is 5 to 20. When n is less than 5, the effect of the invention is small, and n is 20.
If it exceeds, the solubility in the monomer tends to decrease, which is not preferable. It is also possible to modify the terminal by adding a monofunctional carboxylic acid chloride such as lauric acid chloride or 3,3,5-trimethylhexanoic acid chloride to the reaction system.

The amount of the organic peroxide of the present invention used with respect to the monomer is 0.1 to 3.0 based on the total amount of the monomer.
%, Preferably 0.2 to 2.0% by weight,
If it is less than 1% by weight, there is no substantial effect, and if it exceeds 3.0% by weight, not only the reaction becomes difficult to control, but also the degree of polymerization of the polymer is extremely lowered and the mechanical strength is greatly lowered. Further, the organic peroxide in the present invention can be used in combination with other organic peroxides or in combination with an azo polymerization initiator.

The copolymerizable monomer used in the present invention is, for example, styrene, paramethylstyrene, parachlorostyrene, para-t-butylstyrene, acrylic acid ester, methacrylic acid ester and the like.

The monomers used in the present invention are 10-80% by weight of α-methylstyrene, 20-90% by weight of acrylonitrile, and 0-70% of monomers copolymerizable with these compounds.
% By weight.

The polymerization method may be suspension polymerization, bulk polymerization, or a combination thereof.

The polymerization temperature in the present invention is usually 60 to 1.
A range of 30 ° C is used. When the polymerization temperature is lower than 60 ° C, the polymerization rate becomes slow, which is economically disadvantageous. Also, 13
If the temperature exceeds 0 ° C, not only is the polymerization rate increased, it becomes difficult to control the heat of polymerization, but also the degree of polymerization is reduced, the mechanical strength is reduced, and the coloration of the polymer is unfavorable. The polymerization temperature may be constant, or the polymerization may be carried out continuously or stepwise while raising the temperature.

[0014]

EFFECTS OF THE INVENTION According to the method of the present invention, an α-methylstyrene-acrylonitrile copolymer having less residual monomer and excellent mechanical strength, transparency, and heat resistance as compared with the conventional method is practically excellent. It became possible to manufacture under the conditions.

[0015]

EXAMPLES The present invention will be specifically described below with reference to Examples and Comparative Examples. The methods for measuring the physical properties in Comparative Examples were as follows. (1) Polymerization conversion rate: Determined from the residual monomer in the polymer. (2) Polymerization average molecular weight: measured by GPC. (3) Surface condition of molded product: Occurrence of defective molding such as flash mark phenomenon and flow mark phenomenon was ranked as follows by visual observation. Molded product surface condition ○ Very good, △ Good, ×
Poor molding (4) YI (yellowness): Performed according to JIS K7103. (5) Heat distortion temperature: Performed according to JIS K-7207. (6) Impact strength: Measured according to JIS K-6871. Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples. As a reference example, a synthesis example of a specific peroxide in the present invention will be shown.

Reference Example 1 4 with a capacity of 200 ml equipped with a stirrer, a thermometer, and a dropping funnel.
To a one-necked flask, 7.3 g of 50% hydrogen peroxide and 80.3 g of 11% caustic soda were added. 22.5 g of azelaic acid chloride was added dropwise thereto while maintaining the temperature at 10 ° C. After reacting for 30 minutes, it was filtered and washed with water repeatedly until the pH reached 7. It was vacuum dried to obtain 14.7 g of white powder. As a result of analyzing this powder, it was found to be an organic peroxide represented by the structural formula of Chemical formula 3.

[Chemical 3] This is hereinafter referred to as Az-1.

Reference Example 2 In the same manner as in Reference Example 1 except that 20.6 g of azelaic acid chloride and 23.6 g of azelaic acid chloride and 3.6 g of 3,3,5-trimethylhexanoic acid chloride were mixed and used. 15.2 g of white powder was obtained. As a result of analyzing this powder, it was found to be an organic peroxide represented by the structural formula of Chemical formula 4.

[Chemical 4] This is hereinafter referred to as Az-2.

Example 1 A capacity of 5000 having a stirrer, a cooler, and a nitrogen gas introducing pipe
Pure water (2 kg) and tricalcium phosphate (20 g) were added to a ml autoclave, and the mixture was sufficiently stirred while blowing nitrogen gas. After 1.4 kg of α-methylstyrene, 0.6 kg of acrylonitrile and 18.6 g of Az-1 were added thereto, the system was replaced with nitrogen. The autoclave was heated and the content was heated from 70 ° C to 140 ° C at 10 ° C / h and polymerized for 7 hours. The obtained suspension polymerization liquid was neutralized with hydrochloric acid, dehydrated and then dried at 70 ° C. to obtain a granular polymer.
The polymerization conversion rate was 99.7%. The molecular weight determined by GPC was 72100. This polymer was pelletized by using an ordinary extrusion molding machine, and various physical properties were measured. The results are shown in Table 1.

Example 2 18.2 g of Az-2 instead of 18.6 g of Az-1
Was performed in the same manner as in Example 1 except that was used. The polymerization conversion rate was 99.8%. The molecular weight determined by GPC is 7
It was 3900. Various physical properties are shown in Table 1.

Comparative Example 1 18.0 g of azelaic acid polymeric peroxide having 3 repeating units instead of 18.6 g of Az-1
The same procedure as in Example 1 was carried out except that it was used. The polymerization conversion rate was 99.8%. The molecular weight determined by GPC is 65.
It was 400. Various physical properties are shown in Table 1.

Comparative Example 2 18.0 g of (Chemical formula 1) was used instead of 18.6 g of Az-1.
Was carried out in the same manner as in Example 1 except that azelaic acid polymeric peroxide having 21 repeating units represented by was used. The polymerization conversion rate was 99.9%. Also G
The molecular weight determined by PC was 74100. Various physical properties are shown in Table 1.

Comparative Example 3 The procedure of Example 1 was repeated except that 80.2 g of lauroyl peroxide was used instead of 18.6 g of Az-1. The polymerization conversion rate was 99.7%. The molecular weight determined by GPC was 54500. Various physical properties are shown in Table 1.

Comparative Example 4 The procedure of Example 1 was repeated except that 48.4 g of benzoyl peroxide was used instead of 18.6 g of Az-1. The polymerization conversion rate was 95.8%. The molecular weight determined by GPC was 55600. Since the polymerization conversion rate was small and obviously impractical, the physical properties were not measured.

Comparative Example 5 The procedure of Example 1 was repeated except that 16.4 g of terephthaloyl peroxide was used instead of 18.6 g of Az-1. The polymerization conversion rate was 95.1%. The molecular weight determined by GPC was 75100. Since the polymerization conversion rate was small and the practicality was poor, the physical properties were not measured.

Comparative Example 6 The procedure of Comparative Example 5 was repeated, except that the polymerization was carried out at 140 ° C. for 2 hours. The polymerization conversion rate was 99.6%. The molecular weight determined by GPC was 76500. Various physical properties are shown in Table 1.

[Table 1]

Example 3 1.4 kg of α-methylstyrene, acrylonitrile of 0.2.
Example 1 was repeated except that 1.0 kg of α-methylstyrene, 0.6 kg of acrylonitrile and 0.4 kg of styrene were used instead of 6 kg. Polymerization conversion rate is 9
It was 9.5%. The molecular weight determined by GPC is 1187.
It was 00. Various physical properties are shown in Table 2.

Comparative Example 7 Lauroyl peroxide 16.0 instead of Az-1
The same procedure as in Example 3 was carried out except that 0 g was used. The polymerization conversion rate was 99.3%. The molecular weight determined by GPC was 85500. Various physical properties are shown in Table 2.

[Table 2] As is clear from the results, even if the repeating unit represented by (Chemical Formula 1) is included, the mechanical strength is lowered when the number of the units is small as in Comparative Example 1, and the unit is as in Comparative Example 2. When the number is large, both mechanical strength and MI value decrease. By using a specific organic peroxide having 5 to 20 repeating units, the impact strength and thermal deformation of the copolymer are higher than those when using the conventional initiators of Comparative Examples 3, 4 and 7. It can be seen that the temperature is excellent. Further, when the polymeric peroxides of Comparative Examples 5 and 6 were used as the initiator, the conversion was not sufficiently increased under the same polymerization conditions. By extending the polymerization time, the molecular weight, impact strength, and heat distortion temperature were similar to those in Examples 1 and 2. However, it is understood that when the polymerization time is not extended, the residual monomer is not reduced, and the resulting molded product is colored.

Claims (1)

[Claims] 1. In the production of an α-methylstyrene-acrylonitrile-based copolymer in which α-methylstyrene and acrylonitrile or a copolymerizable monomer is copolymerized, the polymerization initiator is represented by the general formula: And the number of repeating units is 5
.Alpha.-, which is an organic peroxide of .about.20.
A method for producing a methylstyrene-acrylonitrile-based copolymer.