JP2636970C - - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a styrene-based polymer, and more particularly, to a molding material for a high-quality molded article which can be produced without reducing productivity. The present invention relates to a method for producing a styrenic polymer suitable for a method. 2. Description of the Related Art Conventionally, high-molecular-weight polystyrene has been produced in order to increase the strength of polystyrene. However, when trying to increase the molecular weight of polystyrene, the reaction rate must be suppressed, and there has been a problem that productivity is extremely reduced. In order to solve this problem, methods using organic peroxides or polyfunctional compounds or methods using special reactors have been proposed, but these methods are not enough to increase the reaction rate, A suitable method for producing high-quality, high-molecular-weight polystyrene without reducing productivity has not yet been developed, such as a problem with the quality of polystyrene. For example, Japanese Patent Publication No. 41-19511 discloses a technique for producing polystyrene using a specific organic peroxide. However, since the amount of the organic peroxide used is too large, the molecular weight of the organic peroxide is reduced. There was a drawback that only low polystyrene was obtained and the impact strength was poor. In order to improve the impact strength and the molecular weight distribution, see JP-A-2-170806.
Japanese Patent Application Laid-Open Publication No. H11-176,086 describes a method for producing a styrene-based polymer by adding and polymerizing a polyfunctional vinyl compound, but the degree of haze of the molded product is not sufficient. Japanese Patent Application Laid-Open No. Sho 64-70507 describes that a special reactor is used for producing a styrene resin having a high molecular weight in a continuous bulk polymerization method.
There was a problem that the reaction rate was not sufficiently improved. [0004] Therefore, there has been a demand for the development of a method for producing a high-molecular-weight styrene-based polymer useful as a material for molded articles having excellent haze and impact strength without reducing productivity. The present inventors have intensively studied to develop a manufacturing method from such a viewpoint. As a result, 10 to 450 ppm by weight of a specific organic peroxide is added to a compound whose component is a styrene-based monomer (aromatic vinyl-based monomer). It has been found that a styrene-based polymer having desired properties can be produced by the polymerization, and the above object can be achieved. The present invention has been completed based on such findings. That is, the present invention provides a compound having a styrene monomer as a component, which is represented by the following general formula (I): [Where R is a tertiary alkyl group or a tertiary aralkyl group, and R ¹ and R ² are each an alkyl group having 1 to 2 carbon atoms. The organic peroxide represented by the formula (1) was added in a total amount of 10 to 450 ppm by weight in the initial stage of polymerization, or divided in the initial stage and during the polymerization and added in a total amount of 10 to 450 ppm by weight to form a series connection. ~ 6
The weight average molecular weight is from 30 × 10 ⁴ to 30 × 10 ⁴ , wherein the reaction temperature is 90 to 200 ° C. and the reaction temperature difference between the reactors is set within 40 ° C. to carry out continuous bulk polymerization. 70 × 10 ⁴ , and a weight average molecular weight (Mw) and a number average molecular weight (M
The present invention provides a method for producing a styrenic polymer wherein the ratio (Mw / Mn) of n) is 2.0 to 3.0. The styrene monomer (ie, aromatic vinyl monomer) used in the present invention includes α-substituted alkylstyrene such as styrene, α-methylstyrene, α-ethylstyrene, and α-isopropylstyrene. And nucleus-substituted alkylstyrenes such as p-methylstyrene, m-methylstyrene, and 2,5-dimethylstyrene; nucleus-substituted halogenated styrenes such as p-chlorostyrene, p-bromostyrene, and dibromostyrene; and mixtures thereof. be able to. Therefore, the styrene polymer produced by the method of the present invention is a homopolymer or copolymer (random, graft, etc.) of a styrene monomer selected from the above styrene and substituted styrene. The organic peroxide used in the present invention is represented by the general formula (I). Here, R is a tertiary alkyl group (that is, tertiary butyl group, tertiary amyl group, tertiary octyl group, etc.) or a tertiary aralkyl group (cumyl group,
R ¹ and R ² are each an alkyl group having 1 to 2 carbon atoms (that is, a methyl group or an ethyl group). Specific examples of the organic peroxide include 2,2-bis (4,4-ditertiarybutylperoxycyclohexyl) propane; 2,2-bis (4,4-ditertiaryamylperoxycyclohexyl) propane; 2,2-bis (4,4-dicumylperoxycyclohexyl) propane; 2,2-bis (4,4-ditert-butylperoxycyclohexyl) butane, and the like. Among them, two or two
-Bis (4,4-ditert-butylperoxycyclohexyl) propane is preferred. These may be used as a mixture. The addition amount of this organic peroxide is
It is selected at a ratio of 10 to 450 ppm by weight based on the styrene monomer. If this amount is less than 10 ppm by weight, there is no substantial effect of addition, and 450 parts by weight pp
If it exceeds m, the molecular weight of the obtained polymer decreases. There are various methods for adding this organic peroxide to the reaction system, and there is no particular limitation. Usually, it is sufficient to add the entire amount at the initial stage of the polymerization or to add the organic peroxide separately during the initial stage and during the polymerization. In the method of the present invention, the above-mentioned organic peroxide is used, but if necessary, a usual polymerization initiator can be used in combination. Here, as such a polymerization initiator, tertiary butyl hydroperoxide; ditertiary butyl peroxide; cumene hydroperoxide; dicumyl peroxide, benzoyl peroxide; 1,1-bis (tertiary butyl peroxy) Cyclohexane;
Organic peroxides such as 1,1-bis (tert-butylperoxy) -3,3,5-trimethylcyclohexane and azobisisobutyronitrile; azobis-2,4
Azo compounds such as dimethylvaleronitrile; azobiscyclohexanecarbonitrile; methyl azobisisobutyrate; azobiscyanovaleric acid; and other polymerization initiators can also be used. These polymerization initiators are used alone or in combination of two or more depending on the situation. The polymerization in the method of the present invention is usually carried out by continuous bulk polymerization, but may be carried out by batch polymerization. The method of continuous bulk polymerization is carried out as follows. That is, two to six reactors of complete mixing type and / or plug flow type and one or more monomer deaerators are connected in series to supply a monomer (styrene-based monomer). Here, the reaction temperature is 90 to 20.
0 ° C. is preferred. Further, the difference between the reaction temperatures of the respective reactors is preferably within 40 ° C. As described above, the organic peroxide of the general formula (I) may be added in its entirety at the beginning of the polymerization, or may be added separately at the beginning and during the polymerization. Ethylbenzene,
A small amount of a solvent such as xylene may be added. The reaction rate R is not particularly limited and may be selected according to the situation, but is preferably set to 5 to 15% / hour. In particular,
When the weight average molecular weight of the final reactor outlet and _{Mw 0, Mw 0 ≧ (75-3} × R) ×
It is preferably 10 ⁴ from the viewpoint of productivity. In addition, the conversion of the final reactor is 40
~ 90 wt% is preferred. The polymer (styrene polymer) that exited the final reactor was
Residual monomers are removed by a monomer deaerator and pelletized. Examples of the monomer deaerator include a thin film evaporator, a flash drum, and the like.
It is operated at 300 ° C. and 1 to 600 Torr. The residual monomer at the outlet of the degassing device is usually at most 5,000 ppm by weight, preferably at most 1,000 ppm by weight, more preferably at most 500 ppm by weight. When pelletizing, an antioxidant,
Additives such as an internal lubricant, an external lubricant, a release agent, a weathering agent, a flame retardant, and a coloring agent may be added. In the method of the present invention, the polymerization conditions such as the amount of the organic peroxide of the general formula (I) and the reaction temperature of each reactor in the multistage continuous polymerization (or batch polymerization) are changed to change the weight average molecular weight. (Mw) is 30 × 10 ⁴ to 70 × 10 ⁴ , preferably 30 × 10 ^{4 to} 60 × 10 ⁴
And a styrene polymer having a weight average molecular weight (Mw) and a number average molecular weight (Mn) ratio (Mw / Mn) (measured by gel permeation chromatography) of 2.0 to 3.0. . If the weight average molecular weight of this styrene polymer is less than 30 × 10 ⁴ , the impact resistance of the molded article is insufficient, and if the weight average molecular weight exceeds 70 × 10 ⁴ , the haze of the molded article (haze) Worsens. Further, the styrene-based polymer produced by the method of the present invention has a weight average molecular weight (
Mw) and the number average molecular weight (Mn), that is, Mw / Mn needs to be 2.0 to 3.0. When Mw / Mn exceeds 3.0, the degree of haze deteriorates, and the object of the present invention cannot be achieved. Next, the present invention will be described in more detail with reference to Examples and Comparative Examples. % In Examples
And ppm are all by weight. The weight-average molecular weight, number-average molecular weight, impact strength and haze of the molded article were measured by the following methods. Table 1 shows the results. Molecular Weight Measurement Method Gel Permeation Chromatography (GPC)
The measurement was performed using ALC / GPC (150-C type) manufactured by rs Co., Ltd., and a GPC column (TSK-GEL GMH6, TSK-GEL HM) manufactured by Toyo Soda Kogyo Co., Ltd. Impact strength Unnotched Izod impact strength was measured according to JIS K7110. Haze was measured according to JIS K7105 (haze measurement method). Example 1 A continuous bulk polymerization apparatus in which a complete mixing tank reactor having a capacity of 23 liters, two tower reactors having a capacity of 33 liters, and two degassing tanks were connected in series was provided. Screw (4
12.5 of styrene obtained by dissolving 400 ppm of 4-di-tert-butylperoxycyclohexyl) propane (trade name: Percadox 12 manufactured by Kayaku Akzo).
Liter / hour, the temperature of the three reactors was increased to 110 ° C / 110 ° C / 120 ° C
Kept. The conversion at the outlet of the third reactor was 75.2%. After removing residual styrene in a degassing tank, the mixture was pelletized. The weight average molecular weight Mw of the obtained pellet was 45.2 × 10 ⁴ , and Mw / Mn was 2.64. After injection molding the pellets into a plate having a thickness of 3 mm, the Izod impact strength without notch and the degree of haze were measured. The results are shown in Table 1. Examples 2 to 5 In the same manner as in Example 1 except that the addition amount of 2,2-bis (4,4-ditert-butylperoxycyclohexyl) propane, the supply amount of styrene, and the reaction temperature were changed. Polymerized. The results are shown in Table 1. Comparative Example 1 Polymerization was carried out in the same manner as in Example 1 except that 2,2-bis (4,4-di-tert-butylperoxycyclohexyl) propane was not used and the supply amount of styrene was changed. The results are shown in Table 1. Comparative Example 2 Polymerization was carried out in the same manner as in Example 1 except that the amount of 2,2-bis (4,4-di-tert-butylperoxycyclohexyl) propane was changed to 700 ppm.
The results are shown in Table 1. Comparative Example 3 Polymerization was carried out in the same manner as in Example 1 except that the temperatures of the three reactors were 90 ° C./110° C./150° C. The results are shown in Table 1. Comparative Example 4 The temperature of the three reactors was set at 80 ° C./80° C./90° C., and the supply amount of styrene was 4.
Polymerization was carried out in the same manner as in Example 1 except that the amount was 0 liter / hour. The results are shown in Table 1. Comparative Example 5 Instead of 2,2-bis (4,4-di-tert-butylperoxycyclohexyl) propane, 1,1-bis (tert-butylperoxy) -3,3
5-Trimethylcyclohexane (trade name: Perhexa 3M, manufactured by NOF Corporation)
Polymerization was carried out in the same manner as in Example 1 except that ()) was used. The results are shown in Table 1. Comparative Example 6 Polymerization was carried out in the same manner as in Example 1 except that benzoyl peroxide was used instead of 2,2-bis (4,4-ditert-butylperoxycyclohexyl) propane. The results are shown in Table 1. [Table 1] [Table 2] [Table 3] As described above, according to the method of the present invention, a styrene-based polymer having a high molecular weight can be obtained without lowering the productivity. The impact strength is remarkably superior to the conventional one. Therefore, the styrene-based polymer produced by the present invention is effectively used as a molding material for various household articles, electric appliances and the like.

Claims (1)

[Claim 1] The compound which is a styrene monomer has the following general formula (I): [Where R is a tertiary alkyl group or a tertiary aralkyl group, and R ¹ and R ² are each an alkyl group having 1 to 2 carbon atoms. 2) connected in series by adding the organic peroxide represented by the formula (1) in a total amount of 10 to 450 ppm by weight in the initial stage of the polymerization, or by adding a total of 10 to 450 ppm by weight in the initial stage and during the polymerization. ~ 6
The weight-average molecular weight is 30 × 10 ⁴ to 40 to 200 ° C., wherein the reaction temperature is 90 to 200 ° C. and the reaction temperature difference between the reactors is set within 40 ° C. to carry out continuous bulk polymerization. 70 × 10 ⁴ , and a weight average molecular weight (Mw) and a number average molecular weight (M
A method for producing a styrenic polymer wherein the ratio (Mw / Mn) of n) is 2.0 to 3.0.