JPH09302171A - Resin composition containing star-type polystyrene - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a styrene resin composition, free from the losses of rigidity and heat resistance, excellent in fluidity, mechanical strength and forming processability, and suitable for producing a thin-wall formed article, etc., by compounding a specific anion polymerization polystyrene component with a specific rubber-modified vinyl aromatic polymer, etc., at a specific ratio. SOLUTION: This styrene resin composition is obtained by compounding (A) 1-50wt.%, preferably 10-50wt.% of a polystyrene component obtained by anionic polymerization and having a weight average molecular weight(Mw) of 100,000-500,000 and (B) 99-50wt.%, preferably 90-50wt.% of a rubber-modified vinyl aromatic polymer or a styrene polymer obtained by a radical polymerization. The polystyrene component in the anionic polymer is a mixture of a linear component having Mw of 40,000-200,000 and a branched component having Mw of 120,000-600,000.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The styrenic resin composition of the present invention has an unprecedented balance of high fluidity and mechanical strength, so that it is a resin material for large-sized thin-walled molded products and injection-molded products with complicated shapes. Can be preferably used as.

[0002]

2. Description of the Related Art Rubber-modified polystyrene represented by HIPS is inexpensive, excellent in processability, and has excellent impact resistance and electrical insulation properties, so that it is used in a wide variety of fields such as home appliances, office equipment, industrial parts, and daily necessities. It is used. Recently, in these fields, there has been a rapid progress in the movement of production plants overseas, especially for home appliance manufacturers, and for the remaining domestic production, ultra-large and wide-screen TVs have become the mainstream as TV cabinet materials, and thin and large There is an increasing demand to develop easily moldable materials such as low pressure molding materials that can be molded using aluminum metal molds because of the ultra high flow materials that can be molded and the reduction in injection molding costs.

Generally, this rubber-modified polystyrene is obtained by radically polymerizing styrene in the presence of a rubber-like polymer. The rubber-modified polystyrene thus obtained has a form in which a rubber-like polymer is present as a dispersed phase in a resin continuous phase composed of linear polystyrene. As is well known, in order to increase the impact strength of rubber-modified polystyrene, it is effective to increase the content of the rubber-like polymer in the resin composition, but on the other hand, there is a problem that the rigidity and fluidity are lowered. is there. For this reason, in order to improve the balance between impact strength and rigidity of rubber-modified polystyrene and the fluidity, it is important to use as little rubber-like polymer as possible to give high impact resistance, and to maintain a certain rubber-like weight. There is a demand for a method for further enhancing the balance between impact resistance and fluidity under the combined content. In addition, various methods have been studied for controlling the molecular weight and the molecular weight distribution of the polystyrene portion of the continuous phase in order to enhance the balance between impact resistance and fluidity, but the satisfactory effect has not been obtained yet.

[0004]

DISCLOSURE OF THE INVENTION The present invention provides a styrene resin composition which retains fluidity and mechanical strength without impairing the rigidity and heat resistance of the styrene resin and has good moldability. The task is to do.

[0005]

Means for Solving the Problems As a result of intensive studies conducted by the present inventors in order to achieve the above-mentioned object, the present inventors have found that a star-shaped branched polystyrene-based polymer having a weight average molecular weight of 120,000 to 600,000 obtained by anionic polymerization is used. A resin composition obtained by blending a mixture of a polymer and a polystyrene-based polymer having a linear structure with a weight average molecular weight of 40,000 to 200,000 obtained by anionic polymerization having a lower molecular weight than this, and polystyrene (PS) obtained by ordinary radical polymerization. The product exhibits extremely good fluidity, and mechanical properties such as impact resistance and rigidity and thermal properties such as heat resistance are the same as those of ordinary radical polymerization impact resistant polystyrene (HIP).
The present invention has been completed by finding that it has remarkably excellent characteristics as compared with S).

In the present invention, the continuous phase is PS by radical polymerization.
And a branched PS made by anionic polymerization of a specific structure and a PS obtained by anionic polymerization of a linear structure having a specific molecular weight, and other polystyrene such as linear PS having a different molecular weight in radical polymerization. Or a mixture of anionic polymerization linear PS and linear radical polymerization PS cannot be achieved. The star polymer having a specific structure synthesized by anionic polymerization as referred to in the present invention is a living state prepolymer having a linear molecular weight obtained by anionic polymerization, which is a low molecular weight polyfunctional compound (coupling agent) or a small amount of divinylbenzene. Obtained by reacting with polyfunctional monomers. Further, it can be synthesized by using a polyfunctional anionic polymerization initiation catalyst synthesized from a polyfunctional vinyl monomer.

The star polymer of the present invention is a star po defined in p432 of the New Edition High Polymer Dictionary (Asakura Shoten).
say lymer. In the case of the present invention, it is a radial type polymer in which n vinyl aromatic polymers are bonded mainly to polyfunctional low molecular weight compound residues or polyvinyl aromatic residues.
Here, the base compound of the polyfunctional compound residue or the polyvinyl compound residue is a low molecular weight compound having a molecular weight of about 2000 or less. The number of branched polymers is 3-8. The star polymer may be, for example, a mixture of 3-branched and 4-branched polymers.

Further, the linear polystyrene polymer synthesized by anionic polymerization used together with these star polymers is a relatively low molecular weight polymer having a weight average molecular weight of 40,000 to 200,000 and imparts fluidity to the composition. It is added for the purpose. The linear polymer can be added by adjusting the coupling rate in the coupling reaction when synthesizing the star-shaped polymer, or by separately blending the linear polymer adjusted to the target molecular weight by anionic polymerization. In order to impart fluidity while preventing the mechanical strength of the composition from decreasing, it is important that the weight average molecular weight of the polymer is within a specific range and the addition amount is within a specific range.

The content ratio of the linear polymer in the component (A) of the present invention is 1 to 50% by weight. The linear polymer in the component (A) is a low molecular weight component, and it is preferable to add a small amount of it to impart high fluidity, but the weight average molecular weight is 4
If it is less than 10,000, the deterioration of physical properties is not preferable. Further, if the weight average molecular weight exceeds 200,000, the effect of imparting fluidity becomes small, which is not preferable. The upper limit of the content of the linear polymer in the component (A) is 50% by weight in order to increase the amount of the branched polymer of the component (A), and the content of 1% or more is required to impart fluidity to the composition. is there.

The weight average molecular weight (Mw) of the component (A) of the present invention is in the range of 100,000 to 500,000.
When the weight average molecular weight of the component (A) is 100,000 or less, the molecular weight is too low and mechanical strength is insufficient, and the weight average molecular weight is 50.
If it is more than 10,000, the fluidity is greatly reduced, which is outside the scope of the present invention.

In the anionic polymerization, the molecular weight is usually adjusted by adjusting the amount of organolithium used as a catalyst with respect to the amount of charged monomers, but the branched polymer of the present invention causes the molecular weight to jump depending on the number of branches by the coupling reaction. In the case of the present invention, the weight average molecular weight (Mw) of the branched polymer component after the coupling reaction is in the range of 120,000 to 600,000. It is more preferably 150,000 to 500,000, and even more preferably 150,000 to 400,000. If the weight average molecular weight of the branched polymer is lower than 120,000, the molecular weight becomes too low and the mechanical strength becomes insufficient.
On the other hand, when it exceeds 600,000, the fluidity is largely reduced, which is outside the scope of the present invention. The preferable molecular weight distribution (weight average molecular weight Mw / number average molecular weight Mn) is 1.8 or less, preferably 1.6 or less.

Specifically, a method for synthesizing a star-shaped branched polymer by an anionic polymerization method will be described. An active one-terminal vinyl aromatic polymer obtained by polymerizing a vinyl aromatic monomer with an organic lithium compound in a hydrocarbon solvent. It can be obtained by subjecting the combined product to a coupling reaction with a low molecular weight polyfunctional compound. Examples of the organolithium compound of the above method include n-propyllithium, iso-propyllithium, n-butyllithium,
iso-butyllithium, sec-butyllithium, t
Examples thereof include ert-butyllithium and phenyllithium. The polyfunctional compound used in the coupling reaction is a low molecular weight compound having 3 to 8 functional groups capable of reacting with an active lithium terminal to form a bond.

Examples of these low molecular weight compounds include polyhalogen compounds, polyepoxy compounds, polycarboxylic acid ester compounds, polyketone compounds and polycarboxylic acid anhydrides. Some specific examples are silicon tetrachloride, di (trichlorosilylyl) ethane, 1,3,5-tribromobenzene, methyltrichlorotin, epoxidized soybean oil, tetraglycidyl 1,3-bisaminomethylcyclohexane. , Dimethyl oxalate, tri-2-ethylhexyl trimellitate, pyromellitic dianhydride, diethyl carbonate and the like.

In carrying out the above-mentioned anionic polymerization method,
The lithium compound is added in an amount of 0.05 to 0.5 parts by weight based on the vinyl aromatic monomer. Further, the above polyfunctional compound is added in an amount of 0.5 to 1.5 times equivalent to the amount of organolithium and reacted. The reaction proceeds very rapidly and is usually complete in minutes to tens of minutes. As a solvent for the above reaction, cyclohexane, n-hexane, benzene, toluene, ethylbenzene or the like is used. The reaction temperature for carrying out the polymerization based on the anionic polymerization method is -30 to
It is carried out in the range of 150 ° C. The polymerization time is usually several seconds to several hours, although it depends on the hydrocarbon solvent concentration and the polymerization temperature. Either a batch system or a continuous system can be applied to these reactions, but the batch system gives a narrower molecular weight distribution.

Separately from the above coupling reaction, a vinyl aromatic monomer is polymerized in a hydrocarbon solvent using an organolithium compound as an initiator, and a one-terminal active vinyl aromatic polymer present in the living room after completion of the polymerization is obtained. It is possible to synthesize a multi-branched vinyl aromatic polymer by adding a small amount of a polyfunctional vinyl aromatic monomer (for example, divinylbenzene) as an initiator and polymerizing. In this method, the ratio of the polyfunctional vinyl aromatic monomer added to the organolithium compound used as the polymerization initiator is 0.1 to 0.1 in terms of molar ratio.
It is in the range of 1.0. By this method, it is possible to synthesize a multi-branched polymer having a slightly wide molecular weight distribution, which is substantially close to a star polymer.

The star-branched polystyrene thus obtained and the polystyrene having a linear structure obtained by anionic polymerization having a specific molecular weight and containing no known rubber-modified vinyl aromatic polymer described below or rubber obtained by radical polymerization are contained. By blending polystyrene, the styrene resin composition of the present invention can be obtained. When the composition of the present invention is a rubber-modified vinyl aromatic polymer composition containing branched and linear anion-polymerized polystyrene, the rubber-like polymer in the composition is diluted with the anion-polymerized polystyrene. It is important to increase the content of the rubber-like polymer in the rubber-modified vinyl aromatic polymer.

The HIPS to be blended depends on the impact strength and rigidity of the rubber modified vinyl aromatic resin composition of interest.
The content of the rubber-like polymer is generally in the range of 6 to 30% by weight. The rubber-modified vinyl aromatic polymer of the component (B) of the present invention is styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, ethylstyrene, P-tert-butylstyrene in the presence of a rubber-like polymer. ,
In a continuous phase of a linear vinyl aromatic polymer obtained by polymerizing a single or a mixture of two or more kinds of nuclear alkyl-substituted styrenes such as α-alkylstyrenes such as α-methylstyrene A polymer in which a rubber-like polymer is present as dispersed particles. Typically, in addition to rubber-modified polystyrene known as HIPS, a rubber-modified styrene-based resin composition in which a styrene unit in the polystyrene phase is replaced with a vinyl aromatic monomer unit other than the above-mentioned styrene can be mentioned. For the purpose of the present invention, the branched and linear vinyl aromatic polymer as the component (A) and the rubber-modified vinyl aromatic polymer as the component (B) are preferably composed of the same vinyl aromatic monomer.

The rubber-like polymer in the above component (B) is
It has a glass transition temperature of −30 ° C. or lower. Specific examples include polybutadiene, styrene-butadiene rubber (SBR), acrylonitrile-butadiene rubber (NB
R) and other diene rubbers, ethylene-propylene-diene rubber (EPDM), acrylic rubber and the like. As the polybutadiene rubber, both high cis rubber and low cis rubber can be preferably used. Further, the above polybutadiene rubber, SBR, and NBR can be preferably used in which some or all of the unsaturated double bonds are hydrogenated.

The component (B) is generally prepared by subjecting the vinyl aromatic monomer to bulk, bulk / suspension, or emulsion polymerization in the presence or absence of the above rubbery polymer. The method using lumps or lumps / suspension is economically superior. In the case of bulk polymerization, a small amount of an inert solvent such as ethylbenzene or toluene may be added. According to the above method, when the component (B) is a rubber-modified vinyl aromatic polymer, the vinyl aromatic monomer is polymerized in the presence of the rubber-like polymer, so that the vinyl polymer is surrounded by the rubber-like polymer particles. A part of the aromatic polymer is grafted, and a dispersed phase having a structure in which some of the particles of the vinyl aromatic polymer are included inside the rubber-like polymer particles is formed.

The weight of the dispersed phase of the rubber-modified vinyl aromatic polymer is higher than the weight of the rubber-like polymer because the graft component and the encapsulated vinyl aromatic polymer particles are contained in the dispersed phase. The ratio of the weight of the dispersed phase to the weight of the rubber-like polymer is a value in the range of about 1.5 to 3.5 in bulk, bulk / suspension polymerization. The dispersed phase can be separated and collected by dissolving in a good solvent of the vinyl aromatic polymer constituting the continuous phase of the rubber-modified vinyl aromatic resin composition, for example, methyl ethyl ketone, and centrifuging. The weight average molecular weight of the vinyl aromatic polymer constituting the continuous phase of the component (B) may be in the range of 150,000 to 300,000 according to the standard method. (B)
The average particle diameter of the dispersed phase formed by the rubber-like polymer of the component is 0.1
It is adjusted in the range of ˜4.0 μm. A more preferable particle size range is 0.4 to 3 microns. The swelling index (Swe) for toluene, which is a measure of the degree of crosslinking of the dispersed phase particles,
llingIndex) is adjusted in the range of 6 to 14.

In the case of the composition of the present invention, a vinyl aromatic polymer containing no rubber component obtained by radical polymerization is contained as the component (B), but in this case, the finally obtained composition contains no rubber component. Therefore, it has no impact resistance, but has excellent transparency, rigidity, and heat resistance. In order to maintain the balance between fluidity and mechanical strength, which is the object of the present invention, the weight average molecular weight of the rubber-free vinyl aromatic polymer of component (B) is preferably in the range of 200,000 to 500,000. . Foamed sheets and transparent polystyrene sheets are major applications of the composition comprising the component (B) and the component (A) containing no rubber component. Since the polystyrene foam sheet is excellent in heat retention and lightweight, it is used as a food container, an instant noodle donburi container, a heat insulating material and a cushioning material.

The properties required of the styrenic polymer for the foam are that the surface of the foam has a good appearance, the surface is smooth and the printability is good, the extrusion stability during foam extrusion is good, and the productivity is good. In addition, it is possible to increase the expansion ratio. A transparent polystyrene sheet is widely used as a lightweight container for storing food, a stationery, and a packaging material for miscellaneous goods because of its rigidity and transparency and its excellent moldability. Polystyrene sheets are molded into various lightweight containers by vacuum molding, pressure molding, etc., but the required properties of the material are to improve the moldability by adding plasticizers to shorten the molding cycle and to improve the toughness of molded products. For example, it imparts crack prevention during trimming. The composition of the present invention having a good balance of fluidity and mechanical strength can be suitably used for these applications.

The components (A) and (B) may be mixed by melt kneading with a known device such as a kneader, Banbury mixer, single-screw or twin-screw extruder. In addition to the above, for example, anionic polymerization is carried out, and a polymerization solution containing a star-branched polymer synthesized by deactivating living anions by a coupling reaction and a polymerization solution of component (B) in the course of bulk polymerization are mixed. Then, the polymerization of the component (B) is continued for a desired time, and after the polymerization is completed, the residual monomer and the inert solvent such as ethylbenzene are removed by a devolatilizer to obtain the styrene resin composition of the present invention.

The mixing ratio of the components (A) and (B) is in the range of 1 to 50% by weight of the component (A) and 99 to 50% by weight of the component (B). The higher the proportion of the component (A) in the continuous phase of the composition, the more the balance between the fluidity and the physical properties tends to be improved. In the case of using the component (B) prepared under the manufacturing conditions of, 50% by weight or more is required.

In the styrene resin composition of the present invention, if necessary, stabilizers such as higher fatty acids, higher fatty acid metal salts, polydimethylsiloxane, hindered phenols, pigments,
Additives such as a plasticizer and an antistatic agent can be added.

[0026]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to examples, but these do not limit the scope of the present invention.

Reference Example 1 (Branched polystyrene A1 to A2
Preparation) The autoclave was charged with 14.0 kg of styrene and 60 kg of cyclohexane, and the internal temperature was controlled to 50 ° C. Then, a 10% cyclohexane solution containing 11.2 g of n-butyllithium was injected to start the reaction. After 4 minutes, the internal temperature rose to 78 ° C. When the reaction solution was sampled and the molecular weight was measured by gel permeation chromatography (GPC), the weight average molecular weight at this point was 1
It was 22,000 and the number average molecular weight was 1173,000. Next, the autoclave was raised to 80 ° C. and tetraglycidyl 1,3-bisaminomethylcyclohexane (hereinafter TED
20% cyclohexane solution containing 10.0 g was added in two portions, and a coupling reaction was carried out. After stirring for 20 minutes, the polymer was precipitated with methanol,
The branched polymer A1 was recovered.

The GPC chart of this product was a mixture of 3- and 4-branched polystyrene containing 15.8% of uncoupled low molecular weight. This compound had a weight average molecular weight of 372,000 and a molecular weight distribution (Mw / Mn) of 1.3.
It was 3. TED is a tetrafunctional coupling agent, but the fact that the tri-branched polymer produced 60% or more is considered to be because the styryllithium at the active terminal is difficult to react with the fourth epoxy group due to steric hindrance. By partially changing the synthesis conditions for A1 of Reference Example 1 and treating in the same manner, an uncoupled linear polymer 17.1 having a weight average molecular weight of 142,000.
%, A 3- and 4-branched polymer mixture A2 containing 78% of a 3-branched polymer having a weight average molecular weight of 482,000 and a molecular weight distribution of 1.62 was synthesized. Table 1 shows the analysis results and the melt flow rate (MFR).

Reference Example 2 (4-branched polystyrene A3, A
Preparation of 4) 60 kg of cyclohexane and 10.0 kg of styrene monomer were charged into the autoclave, and the internal temperature was controlled at 50 ° C. Then, a 10% cyclohexane solution containing 6.3 g of n-butyllithium was injected to initiate polymerization.
After 5 minutes, the internal temperature rose to 80 ° C. When a part of the reaction liquid was sampled and subjected to GPC analysis, it was a polymer having a weight average molecular weight of 150000 and a molecular weight distribution of 1.03.
Then, the temperature inside the autoclave was raised to 80 ° C., and 2.8 g of di (trichlorosilylyl) ethane was used as a coupling agent.
10% cyclohexane solution containing was added. 20
The reaction was carried out with stirring for a minute. The reaction solution was treated in methanol to recover a branched polymer of A3.

The product had a weight average molecular weight of 51,000,000, a molecular weight distribution of 1.21, and was an approximately 4-branched polymer containing 20.0% of uncoupled linear polymer. Di (trichlorosilylyl) ethane used as a coupling agent is a hexafunctional coupling agent, but TE
Similar to the case of D, it worked only as a tetrafunctional compound due to steric hindrance. By adjusting the addition amounts of the catalyst and the coupling agent, the same treatment is carried out to contain 23.2% of an uncoupled linear polymer having a weight average molecular weight of 600,000 and a weight average molecular weight of 161,000 with a molecular weight distribution of 1.25. A branched polymer A4 was obtained.

Reference Example 3 (Preparation of 6-branched polystyrene and 8-branched polystyrene A5, A6) Cyclohexane 60 kg and styrene monomer 10.0 kg were charged in an autoclave at an internal temperature of 50 ° C. and 10% containing n-butyllithium 10.2 g. Polymerization was carried out by adding a catalyst in a cyclohexane solution. A polymer having a weight average molecular weight of 95,000 and a molecular weight distribution of 1.03 at this point was prepared, and a 10% cyclohexane solution containing 35 g of p-divinylbenzene was added to the polymer. After reacting for 20 minutes, the reaction solution was poured into a large amount of methanol to precipitate the polymer, thereby obtaining a branched polymer. The GPC analysis of this product showed that it was a branched polymer having a weight average molecular weight of 57,000 and a molecular weight distribution of 1.65, and having an average of 6 branches, which was nearly star-shaped.

Similarly to this reference example, the weight average molecular weight was changed to 5 by changing the addition amounts of n-butyllithium and divinylbenzene.
An average 8-branched polymer having a molecular weight distribution of 68,000 and a molecular weight distribution of 1.80 was obtained. When a branched polymer is obtained using divinylbenzene, the number of branches is adjusted by the amount of added divinylbenzene, but the molecular weight distribution is wider than when a coupling agent is used, and the polymer has a structure substantially similar to that of a star polymer. Was obtained and almost no unreacted linear polymer was contained.

Reference Example 4 (Preparation of linear monodisperse polystyrene A7, A8) 60 kg of cyclohexane and 10.0 kg of styrene monomer were charged into an autoclave at an initial reaction temperature of 50 ° C. and n-
A cyclohexane solution containing 8.0 g of butyllithium was injected to carry out the polymerization reaction. After reacting for 20 minutes, the polymer was precipitated in methanol to obtain a linear monodisperse polymer A7. The weight average molecular weight of this product is 167,000,
The polymer had a number average molecular weight of 16200,000, which was close to monodisperse. Similarly, a linear polymer A8 having a weight average molecular weight of 105,000 and a number average molecular weight of 101,000 was obtained.

Reference Example 5 (Preparation of Rubber Modified Polystyrene B1) Polybutadiene (Nihon Zeon Co., Ltd., Nipol 1220)
SL) was dissolved in styrene, and then ethylbenzene and a small amount of t-butylperoxyisopropyl carbonate were added to prepare a polymerization stock solution having the following composition. (Unit parts by weight) ・ Polybutadiene 9.8 ・ Styrene 76.8 ・ Ethylbenzene 13.0 ・ t-Butylperoxyisopropyl carbonate 0.04 ・ α-Methylstyrene dimer 0.02 ・ Polydimethylsiloxane 0.10

The above-mentioned polymerization stock solution was continuously fed at a rate of 2.2 liters / hr to a 3-tank reactor equipped with a stirrer of 6.2 liters. Solids concentration of the 1st tank reactor outlet is 3
The temperature inside the reactor was controlled so as to be 8% by weight. At the same time, the temperature inside the reactor was adjusted so that the solid content concentration at the outlet of the final tank reactor was 80% by weight. Then, it was sent to a devolatilizer under vacuum at 230 ° C. to remove unreacted styrene and ethylbenzene, and granulated with an extruder to obtain pellet-shaped rubber-modified polystyrene B1. The proportion of polybutadiene in B1 was 12.3% by weight. Next, the weight average molecular weight and the number average molecular weight of the continuous phase obtained by gel permeation chromatography of the methyl ethyl ketone soluble component of A1 were 254,000 and 92,000, respectively. The average particle size of the dispersed phase was 1.5 μm, and the swelling index in toluene was 9.8.

The measurements in Examples and Comparative Examples were according to the methods described below. (1) Izod impact test Measured at 23 ° C. by a method according to ASTM-D245. (2) DuPont Dirt Test Injection molded 10 cm × 7 cm × 2 cm flat plate test piece 5
Using 0 sheets, a missile having a constant tip load and a curvature of 6 mm was dropped at different heights, and the energy at which the test piece broke was determined. (3) Flexural modulus according to ASTM D790 (4) Melt flow rate (MFR) according to ISO-R1133 200 ° C., 5 kg / cm ²

(5) Measurement of number average molecular weight (Mn), weight average molecular weight (Mw) and Mw / Mn It was measured by gel permeation chromatography (GPC). GPC measurement conditions Measuring device: Tosoh HLC-8020 (built-in differential refractive index detector) Column: Using two Tosoh TSKgel-GMH ^XL Temperature: 38 ° C Solvent: Tetrahydrofuran (THF) Sample concentration: 0.1 wt / v % Sampling pitch: 1 / 0.4 (times / second) Molecular weight calculation: Calculated by creating a calibration curve using the relationship between the molecular weight of Tosoh TSKgel standard polystyrene and the elution time as a cubic regression curve. To calculate the degree of branching of polystyrene, Mw1 of the linear polymer before the coupling reaction is measured,
The degree of branching is calculated as Mw2 after the coupling reaction = Mw2 /
Calculated from Mw1.

[0038]

【Example】

Example 1 30 parts by weight of 3,4-branched mixed radial type branched polystyrene A1 prepared in Reference Example 1 and 70 parts by weight of a rubber-modified vinyl aromatic polymer B1 containing 12.3% of polybutadiene prepared in Reference Example 5. Were blended, melt-kneaded using a twin-screw extruder, and pelletized. The polybutadiene content of this product was 8.61%, and the composition of the matrix excluding the gel content was anion branched polymer / anion linear polymer / radical polydisperse polymer = 32.
It is 0 / 6.0 / 62.0. Next, using an injection molding machine, molding was performed at a resin temperature of 220 ° C. to prepare a test piece, and the physical properties shown in Table 2 were evaluated.

Example 2 Anion 3, which was synthesized in Reference Example 1 in the same manner as in Example 1,
30 parts by weight of the 4-branched polymer A2 and 70 parts by weight of the rubber-modified polystyrene B1 synthesized in Reference Example 5 are blended,
After extrusion molding, the physical properties of the same items as in Example 1 were evaluated. Table 2 shows the results.

Examples 3, 4 Example 1 was repeated with a 40/60 blending ratio of GP polystyrene and rubber modified polystyrene. Since the rubber component is small, the IZOD and Dupont impact strength is low, but the flexural modulus is high.

Examples 5-7 Example 1 was repeated using as radical B polydisperse GPPS free of rubber component as component B. It can be seen that the compositions of the examples have much better MFR and elastic modulus than the comparative examples.

Comparative Examples 1 and 2 Comparative compositions were prepared by matching the compositions of Examples 1 and 2 and Examples 3 and 4 with the rubber content. Comparative Example 1 is a composition containing no branched PS, and Comparative Example 2 is a radical polydisperse composition containing no anionically polymerized PS. It can be seen that the balance between MFR and impact strength is inferior to those in the examples. Comparative Example 3 Radical polymerization polydisperse GPPS. It can be seen that the MFR is extremely low regardless of the molecular weight.

[0043]

[Table 1]

[0044]

[Table 2]

[0045]

The styrene resin composition of the present invention is
(A) An anion-polymerized polystyrene component which is a mixture of a linear component and a component having a star-shaped branched structure, and (B)
A rubber-modified vinyl aromatic polymer or styrene-based polymer obtained by radical polymerization, and by adopting such a composition, without impairing rigidity and heat resistance,
A resin composition having a good balance between fluidity and mechanical strength and good moldability can be obtained.

Claims (7)

[Claims] 1. A polystyrene component having a weight average molecular weight (Mw) of 100,000 to 500,000 obtained by anionic polymerization (A) and a polystyrene component of the anionic polymer having a weight average molecular weight (Mw) of 40,000 to 200,000. 1B to 50% by weight of an anion-polymerized polystyrene component, which is a mixture of a linear component of 1) and a component having a branched structure with a weight average molecular weight (Mw) of 12,000,000 to 60,000, and (B) is obtained by radical polymerization. A styrene resin composition comprising 99 to 50% by weight of a rubber-modified vinyl aromatic polymer or styrene polymer. 2. The styrene resin composition according to claim 1, wherein the component (A) is 10 to 50% by weight and the component (B) is 90 to 50% by weight. 3. The styrene resin composition according to claim 1, wherein the weight average molecular weight (Mw) of the component (A) is 120,000 to 400,000. 4. The content of the linear polymer as the component (A) is 1 to 50% by weight, and the polymer having a branched structure is 99 to
The styrene resin composition according to claim 1, which is 50% by weight. 5. A vinyl aromatic in which the component (A) is a branched polymer centered on a polyfunctional low molecular weight compound residue and has a uniform molecular weight distribution (weight average molecular weight Mw / number average molecular weight Mn) of 1.5 or less. It has a star-shaped branched structure in which 3 to 8 polymers are bonded and has a weight average molecular weight (MW) of 120,000 to 60.
The weight average molecular weight (M)
(2) The styrene resin composition according to claim 1, which is a mixture of components having a linear structure of 40,000 to 150,000 and the polymer of the mixture has a weight average molecular weight of 100,000 to 500,000. 6. The styrene-based polymer according to claim 1, wherein the weight average molecular weight (Mw) of the vinyl aromatic polymer constituting the continuous phase of the rubber-modified vinyl aromatic polymer as the component (B) is 150,000 to 300,000. Resin composition. 7. The weight average molecular weight (Mw) of the vinyl aromatic polymer not containing the rubber component (B) is 20 to 5.
The styrene-based resin composition according to claim 1, which is 0,000.