JPH08319315A - Styrene-based random copolymer and method for producing the same - Google Patents

Abstract

PURPOSE: To obtain a styrene-based random copolymer comprising a styrene- based compound unit and a bismaleimide compound unit in a specific ratio, excellent in impact resistance, tension in melting, heat resistance and an external appearance of a molding. CONSTITUTION: This copolymer comprises (A) 99-99.95wt.%, preferably 99.5-99.95wt.% of a styrene-based compound unit and (B) 1-0.05wt.%, preferably 0.5-0.05wt.% of a bismaleimide compound unit of the formula (R<1> is H or methyl; R<2> is a bifunctional organic group) and has 200,000-1,000,000 weight-average molecular weight. Styrene, α-methylstyrene, p-methylstyrene, etc., may be cited as the component A. N,N'-m-Phenylenebismaleimide or N,N'-4,4'- methylenediphenylene)dimaleimide may be preferably cited as the component B. The copolymer is obtained by adding 0.05-1wt.%, preferably 0.05-0.5wt.% of the component B to the component A.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a styrene-based random copolymer excellent in impact resistance, tension upon melting and heat resistance, and excellent in appearance of a molded article, and a method for producing the same.

[0002]

2. Description of the Related Art Styrenic resins are rigid, have excellent dimensional stability, and are inexpensive, so
Widely used in extrusion foaming applications. Particularly for injection molding applications, higher molecular weight has been required in recent years in order to improve impact resistance, but in general, there is a drawback that fluidity decreases when the molecular weight is increased. On the other hand, in order to improve the fluidity, methods such as lowering the molecular weight and adding a plasticizer such as mineral oil can be considered, but the addition of mineral oil causes a decrease in heat resistance. By the way, shortening of the molding cycle is mentioned as a problem required for injection molding applications along with impact resistance, but for that purpose it has high fluidity during injection and solidifies at high temperature during cooling, that is, heat resistance Need to be excellent.

As a method for satisfying the heat resistance and impact strength of the resin while maintaining the fluidity as described above, a method of broadening the molecular weight distribution of the resin has been proposed, for example, Japanese Patent Publication No. 57-30843 and Japanese Patent Publication No. Kosho 62-612
Japanese Patent No. 31 discloses a method of obtaining a resin composition having a wide molecular weight distribution by blending a high molecular weight polystyrene and a low molecular weight polystyrene or by using a multistage polymerization method. However, this method has a problem in that the manufacturing process becomes complicated and the manufacturing cost increases, which is not preferable from the viewpoint of industrial implementation.

Further, JP-A-2-170806 discloses a method of broadening the molecular weight distribution of the obtained resin by using a compound having a plurality of vinyl groups such as divinylbenzene during the polymerization reaction. There is. However, in this method, the molecular weight may be rapidly increased during the polymerization to partially generate a gel insoluble matter, and in the method of continuously adding the styrene compound to the reaction system, that is, in the so-called continuous bulk polymerization method, For example, divinylbenzene, which has a low boiling point of 200 ° C., is easily vaporized, and gel deposits are likely to occur in the reaction tank and the degassing tank. Further, the obtained polymer has a problem that the extruded products such as films and sheets have poor transparency.

On the other hand, there is a method of copolymerizing a compound represented by N-phenylmaleimide with styrene for the purpose of improving heat resistance.
It has the disadvantage that the impact strength is significantly reduced.

[0006]

In such a situation,
The problem to be solved by the present invention is excellent in impact strength, tension during melting and heat resistance, and therefore, it is possible to shorten the molding cycle, and there is a risk of cross-linking gelation during polymerization or during injection extrusion molding. Styrene-based polymer and a method for producing the same.

[0007]

That is, in the first aspect of the present invention, the styrene compound unit is 99 to 99.9.
5% by weight and a bismaleimide compound unit represented by the following general formula in an amount of 1 to 0.05% by weight, and a weight average molecular weight of 200,000 to 1,000,000. Is provided. (In the formula, R ¹ represents hydrogen or a methyl group, and R ² represents a divalent organic group.)

A second aspect of the present invention is a method for producing a styrene-based random copolymer by copolymerizing a styrene-based compound and a bismaleimide compound represented by the following general formula: The present invention provides a method for producing a styrene-based random copolymer, characterized in that the bismaleimide compound is added in a proportion of 0.05 to 1% by weight with respect to the system compound. (In the formula, R ¹ represents hydrogen or a methyl group, and R ² represents a divalent organic group.)

The present invention will be described in detail below. The styrene-based random copolymer of the present invention is a styrene-based random copolymer having a weight average molecular weight of 200,000 to 1,000,000 composed of a styrene-based compound unit and a bismaleimide compound unit represented by the above general formula.

Examples of the compound constituting the styrene compound unit include α such as styrene and α-methylstyrene.
-Substituted alkyl styrene, nuclear substituted alkyl styrene such as p-methyl styrene, and the like can be mentioned. Further, together with the styrene compound, a compound copolymerizable with the styrene compound, such as acrylonitrile, methacrylonitrile,
Ester derivatives such as methacrylic acid and methyl methacrylate, and maleic anhydride, maleimide, and nucleus-substituted maleimide typified by phenylmaleimide may be used in combination.

The bismaleimide compound used in the present invention is
It is a compound having the following structural formula. In the formula, R ¹ represents hydrogen or a methyl group, preferably hydrogen, and R ² is a divalent organic group, preferably Represents

Specific examples of the bismaleimide compound include N, N'-ethylenedimaleimide, N, N'-tetramethylenedimaleimide, N, N'-m-phenylenebismaleimide, N, N'-p. -Phenylene bismaleimide, N, N '-(4,4'-methylenediphenylene)
Examples thereof include dimaleimide, N, N′-oxypropylene dimaleimide, and N, N′-oxydiethylene dimaleimide. Among these, N, N'-m-phenylene bismaleimide and N, N '-(4,4'-methylenediphenylene) dimaleimide are preferable.

In the styrene random copolymer of the present invention, the styrene compound unit is 99 to 99.95% by weight, preferably 99.5 to 99.95% by weight, and the bis represented by the above general formula. The maleimide compound unit is 1 to 0.
It is a styrene-based random copolymer composed of 05% by weight, preferably 0.5 to 0.05% by weight, and having a weight average molecular weight of 200,000 to 1,000,000, preferably 200,000 to 600,000. If the content ratio of the bismaleimide compound is too small, the impact strength and the tension at the time of melting are inferior, while if it is too large, the solubility in the styrene compound is poor, and there is a risk of cross-linking gelation and fluidity. Inferior. The content ratio of the bismaleimide compound can be quantified by pyrolysis gas chromatography or the like. If the weight average molecular weight is too small, the impact strength and the tension during melting are poor,
On the other hand, if it is too large, the liquidity is poor.

The styrene-based random copolymer of the present invention is
With respect to the styrene compound and the styrene compound,
It is produced by adding 0.05 to 1% by weight, preferably 0.05 to 0.5% by weight, of the above bismaleimide compound.

The styrene random copolymer of the present invention is
The polymerization method is not particularly limited, and for example, either a batch suspension polymerization method or a continuous bulk polymerization method may be used. Further, either a thermal polymerization method or a polymerization method using a polymerization initiator can be used, and various radical polymerization initiators can be used as the polymerization initiator.

In the batch suspension polymerization method, for example, tricalcium phosphate or the like can be used as a dispersant. As the surfactant, for example, sodium dodecylbenzene sulfonate, polyvinyl alcohol, etc. can be used. The styrene compound and the bismaleimide compound are uniformly mixed, and the mixture and a polymerization initiator such as benzoyl peroxide are put into a polymerization tank at one time. At a polymerization temperature of 80 to 110 ° C, a conversion rate is usually 50 to 90% by weight. %, Preferably 70-90% by weight,
Then, the polymerization temperature is raised to 130 to 150 ° C. to complete the polymerization, and the target styrene-based random copolymer is obtained.

Further, in the continuous bulk polymerization method, specifically,
The styrene compound and the bismaleimide compound are uniformly mixed, the mixture is continuously supplied to a polymerization tank, and the final conversion is usually 60% by weight or more, preferably 70% by weight or more at a polymerization temperature of 140 to 200 ° C. To 200 ° C. to 280 ° C., followed by passing through a vacuum degassing tank at 200 ° C. to 280 ° C. to recover unreacted monomers and to obtain the target styrene-based random copolymer. obtain.

The polymerization tank is not particularly limited. For example, a complete mixing type stirring polymerization tank, a plug flow type full-filling type polymerization tank, a static mixing tube type polymerization tank, or a combination of these polymerization tanks. You may use. Further, the method of adding the bismaleimide compound and the polymerization initiator is not particularly limited, for example, together with a styrene compound, a method of adding to the reaction system once or in several batches, styrene. Any method of continuously adding to the reaction system together with the system compound and the like may be used.

In order to improve the impact resistance of the resulting styrene-based random copolymer, it may be of HIPS type. For example, a rubber-like substance such as polybutadiene may be dissolved in a raw material monomer, and after polymerization, a polymerized product may be obtained. You may mix in. Examples of the rubbery substance include polybutadiene, acrylonitrile-butadiene copolymer rubber, diene rubber such as styrene-butadiene copolymer rubber, polybutyl acrylate, ethylene-propylene-diene rubber and the like.

The styrene-based random copolymer of the present invention is
Films, sheets, foams with excellent balance of flowability and impact strength without impairing heat resistance, high tension during melting and no risk of cross-linking gelation during molding, and excellent appearance of molded products It can be effectively used as an extruded product such as a plastic container, an injection processed product such as a home electric appliance.

[0021]

EXAMPLES The present invention will be specifically described below with reference to examples and comparative examples, but the present invention is not limited to the examples. The evaluation method was as follows.

(1) Weight average molecular weight (Mw) and number average molecular weight (Mn) Gel permeation chromatography (GPC) (manufactured by JASCO Corporation) equipped with a differential refractometer as a detector was used. Measured. (2) Melt Flow Rate (MFR) (Fluidity) Based on JIS K7210, the resin temperature was 200 ° C., and the load was 5 kg. (3) Falling ball impact strength, except that the polymer was press molded into a size of 50 × 50 × 2 mmt at 200 ° C. and the weight of the ball was 28.2 g.
It carried out according to JIS K7211, and measured the value of 50% breaking height. The higher the value, the higher the impact strength. (4) Melt tension (tension during melting) Using a melt tension tester manufactured by Toyo Seiki Co., Ltd.
200 ° C, extrusion speed 20 mm / min, winding speed 50 rpm
It was measured at. (5) Vicat Softening Point (Heat Resistance) Based on JIS K7206, the load was measured at 5 kg. (6) Appearance of molded product A 90 × 150 × 2 mmt flat plate was injection molded at a resin temperature of 220 ° C., and the appearance was visually judged. ○ The surface is smooth and transparent, and ○ is the one with rough skin or fogging.
And

Examples 1 and 2 In an autoclave having an internal volume of 20 L, 8 kg of water, 8 kg of styrene monomer, and 0.3.
2 kg, sodium dodecylbenzene sulfonate 0.3
g, and the polymerization initiator and N, N'-m shown in Table 1 were used.
-Phenylene bismaleimide (Sumitomo Chemical Co., Ltd.)
Sumifine BM (registered trademark) was added at the same time at the start of polymerization to carry out suspension polymerization at the polymerization temperature and polymerization time shown in Table 1 to obtain a styrene-based random copolymer (polystyrene beads). Next, the beads were washed, dehydrated, dried, and then pelletized at 210 ° C. with a 40 mmφ extruder.
Table 1 shows the evaluation results.

Examples 3 to 4 Styrene monomer 8k was placed in an internal volume of 20 L autoclave.
g and N, N′-m-phenylene bismaleimide shown in Table 1 were charged and subjected to bulk thermal polymerization at 120 ° C. for 2 hours. After that, after lowering the temperature once to make it open system, 8 kg of water,
Suspension polymerization was carried out at a polymerization temperature and a polymerization time shown in Table 1 by adding 0.2 kg of tricalcium phosphate as a dispersant, 0.4 g of sodium dodecylbenzenesulfonate, and a polymerization initiator shown in Table 1. A random copolymer (polystyrene beads) was obtained. Next, the beads are washed, dehydrated and dried, and then 2 with a 40 mmφ extrusion granulator.
Pelletized at 10 ° C. Table 1 shows the evaluation results.

Comparative Example 1 Polymerization and granulation were carried out in the same manner as in Example 1 except that N, N'-m-phenylene bismaleimide was not added. Table 2 shows the evaluation results.

Comparative Example 2 Polymerization and granulation were carried out in the same manner as in Example 1 except that the amount of N, N'-m-phenylene bismaleimide added was 1.2% by weight. Table 2 shows the evaluation results.

Comparative Examples 3 to 4 Instead of N, N'-m-phenylene bismaleimide,
Polymerization and granulation were performed in the same manner as in Example 1 except that divinylbenzene (purity 55% by weight, manufactured by Tokyo Kasei Kogyo Co., Ltd.) shown in Table 2 was added. Table 2 shows the evaluation results.

Comparative Example 5 An autoclave having an internal volume of 20 L was charged with 10 kg of water, 4.75 kg of styrene monomer, 0.2 kg of tribasic calcium phosphate as a dispersant, and 0.3 g of sodium dodecylbenzenesulfonate, and the polymerization initiator shown in Table 3 was used. And 0.25 kg of N-phenylmaleimide (registered trademark Imirex-P manufactured by Nippon Shokubai Co., Ltd.) were added simultaneously at the start of polymerization to carry out suspension polymerization at the polymerization temperature and the polymerization time shown in Table 3 to obtain a styrene-based random copolymer. (Polystyrene beads) were obtained. Next, granulation was performed in the same manner as in Example 1. The evaluation results are shown in Table 3.

Comparative Example 6 Polymerization and granulation were carried out in the same manner as in Example 3 except that N, N'-m-phenylene bismaleimide was not added. The evaluation results are shown in Table 3.

The results show the following. Examples 1 to 4 satisfying the conditions of the present invention, without impairing the heat resistance,
The result shows an excellent balance between fluidity and impact strength, and the tension during melting is high. On the other hand, Comparative Example 1 and Comparative Example 6 in which N, N′-m-phenylene bismaleimide was not added
Is excellent in fluidity but inferior in impact strength and has low tension during melting. Comparative Example 2 in which the amount of N, N′-m-phenylene bismaleimide added was excessive was insoluble in the methylethylketone / methanol = 10/1 mixed solvent and gelled. In Comparative Example 3 and Comparative Example 4 in which divinylbenzene was used instead of N, N′-m-phenylene bismaleimide, the weight average molecular weight increased sharply despite the small addition amount, and Comparative Example 3 therein Poor liquidity. Although Comparative Example 4 has a good balance between fluidity and impact resistance, the appearance of the molded product is poor. Comparative Example 5 containing N-phenylmaleimide had a low weight average molecular weight contrary to Comparative Examples 3 to 4, was inferior in impact strength, and had a low final conversion rate, and a monomer remained, so that an accurate copolymer was obtained. The fluidity and heat resistance of the material itself could not be measured.

[0031]

[Table 1] ────────────────────────────────── Actual example 1 2 3 4 ────── ───────────────────────────── Comonomer (% by weight) N, N'-m-phenylene bismaleimide 0.3 0.1 0.3 0.1 Divinylbenzene − − − − N-phenylmaleimide − − − − Polymerization initiator (ppm by weight) Benzoyl peroxide 2300 2300 2000 2000 t-butyl peroxybenzoate 750 750 1000 1000 Polymerization temperature / hour (hr) 90 ° C. 4 4 3 3 140 ℃ 2 2 2 2 Final conversion ^{* 1} (%) 99.8 99.8 99.8 99.8 Weight average molecular weight (10,000) 29.8 24.1 37.3 29.5 Polydispersity (Mw / Mn) 3.1 2.4 3.1 2.5 Melt flow rate (g / 10min) 3.4 5.8 3.0 4.8 Falling ball impact strength (cm) 41.9 39.5 44.3 39.5 Melt tension (g) 17.0 7.9 22.7 12.5 Vicat softening point (℃) 103 102 103 102 Appearance of molded product ○ ○ ○ ○ ─── ───────────────────────────────

[0032]

[Table 2] ────────────────────────────────── Comparative Examples 1 2 3 4 ────── ───────────────────────────── Comonomer (% by weight) N, N'-m-phenylene bismaleimide-1.2 --- Divinylbenzene − − 0.06 0.03 N-phenylmaleimide − − − − Polymerization initiator (ppm by weight) Benzoyl peroxide 2300 2300 2300 2300 t-Butylperoxybenzoate 750 750 750 750 Polymerization temperature / hour (hr) 90 ° C 4 4 4 4 140 ℃ 2 2 2 2 Final conversion ^{* 1} (%) 99.8 99.8 99.8 99.8 Weight average molecular weight (10,000) 22.1 Ge 78.1 33.1 Polydispersity (Mw / Mn) 2.3 l 5.1 3.1 Melt flow rate (g / 10min) 6.1 0.3 3.4 Falling ball impact strength (cm) 34.0 Measurement −45.0 Melt tension (g) 2.7 Constant −18.0 Vicat softening point (° C) 102 Not 102 102 Molded product appearance ○ Performance × × ───── ────────────────────────────

[0033]

[Table 3] ─────────────────────────── Comparative Example 5 6 ──────────────── ──────────── Comonomer (% by weight) N, N'-m-phenylene bismaleimide --- divinylbenzene --- N-phenylmaleimide 5-Polymerization initiator (ppm by weight) Benzoyl peroxide 2500 2000 t-Butyl peroxybenzoate 500 1000 Polymerization temperature / hour (hr) 90 ℃ 5.5 3 140 ℃ 12 Final conversion rate ^{* 1} (%) 97.3 99.8 Weight average molecular weight (10,000) 15.6 24.5 Polydispersity (Mw / Mn) 2.1 2.1 Melt flow rate (g / 10 minutes) 28 ^{* 2} 4.0 Falling ball impact strength (cm) 25.5 36.0 Melt tension (g) 1.5 ^{* 2} 5.2 Vicat softening point (° C) 90 ^{* 2} 102 Appearance of molded product ○ ○ ─── ────────────────────────

* 1 Final conversion rate: 0.5 g of the polystyrene beads obtained were weighed and 20 m of dimethylformamide was added.
It was dissolved in 1 and 1 ml of trimethylbenzene was added as an internal standard to prepare a solution, and the residual styrene concentration (percentage / bead) was measured by gas chromatography. The final conversion was calculated by (100-residual styrene concentration). * 2 Regarding the melt flow rate, melt tension, and Vicat softening point in Comparative Example 5, accurate data inherent to the resin could not be obtained because there were many residual monomers.

[0035]

As described above, according to the present invention, the heat resistance is not impaired, the fluidity and the impact strength are well balanced, and the tension during melting is high so that there is no risk of cross-linking gelation during molding. A styrene-based random copolymer can be provided. Therefore, since the copolymer has an excellent appearance of a molded article, it can be widely and effectively used as a material in the field of injection molding or extrusion molding. Further, the method for producing a styrene-based random copolymer of the present invention is easy to adjust the molecular weight,
It is possible to provide a production method in which gel insoluble matter is not generated and gel deposits are less likely to be generated in the reaction tank or the degassing tank.

Claims (2)

[Claims] 1. A styrene compound unit is 99 to 99.95.
%, And a bismaleimide compound unit represented by the following general formula in an amount of 1 to 0.05% by weight, and a weight average molecular weight of 200,000 to 1,000,000. (In the formula, R ¹ represents hydrogen or a methyl group, and R ² represents a divalent organic group.) 2. A method for producing a styrene random copolymer by copolymerizing a styrene compound and a bismaleimide compound represented by the following general formula, wherein the bismaleimide compound is added to the styrene compound. To 0.05
A method for producing a styrene-based random copolymer, characterized in that the styrene-based random copolymer is added in an amount of 1 to 1% by weight. (In the formula, R ¹ represents hydrogen or a methyl group, and R ² represents a divalent organic group.)