JPH05279428A - Rubber-modified styrenic resin composition having excellent balance of physical property and its production - Google Patents

Abstract

PURPOSE:To obtain a rubber-modified styrenic resin composition having extremely improved appearance of molded article, especially luster and excellent impact strength. CONSTITUTION:In dispersed rubber particles of rubber-modified styrenic resin composition, particles having a salami structure are made into particles having small particle diameter and blended with particles having a single occlusion structure. A particle diameter distribution has three peaks and the average particle diameter is 0.2-0.8mu. Further the particle diameter distribution is wider than a conventional one and the ratio of 5% value and 95% value of cumulative distribution of particle diameters of volume standard of rubbery polymer particles is 3-45.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rubber-modified styrenic resin composition having a high gloss, which is excellent in the balance between the appearance of molded articles and impact resistance, and a method for producing the same.

[0002]

2. Description of the Related Art ABS resin is a resin having a good balance between the appearance of a molded article and impact strength, and is widely used in household electric appliances, electronic devices and the like. Recently, the trend toward cost reduction of these products has increased, the use of rubber-modified styrenic resins in place of ABS resins has increased, and they are also used for molded products having large and more complicated shapes and thin thickness. It became so. Under such circumstances, there has been a demand for a rubber-modified styrenic resin having good gloss, excellent moldability, and high impact strength.

The rubber-modified styrenic resin is obtained by dispersing rubber particles in a styrene-based resin, and the particle size of the dispersed rubber particles has an important influence on the product performance. The smaller the size, the better the gloss of the molded product. Usually, the rubber particle size (average particle size, the same applies hereinafter) in the rubber-modified styrene-based resin is about 1.0 to 5.0 μm, but recently, in order to improve the gloss of the molded product, it is 1.0 μm.
Resins in which rubber particles of m or less are dispersed have also been developed.
However, in the rubber-modified styrenic resin, when the rubber particle diameter is 1.0 μm or less, the impact strength is usually remarkably lowered, and therefore there is a limit to improving the gloss while maintaining the impact strength of the molded product. In order to improve these problems, a method of blending a rubber-modified styrene resin in which rubber particles of 1.0 μm or less are dispersed with a rubber-modified styrene resin in which particles of 1.0 μm or more are dispersed is disclosed in JP-B-4.
6-41467, JP-A-59-1519, JP-A-63-
241053, U.S. Pat. No. 4,146,589, and the like. However, these methods have problems that the gloss is not yet sufficient and that the balance between impact strength and gloss is not good.

On the other hand, when a styrene monomer having a styrene-butadiene block copolymer having a high styrene content dissolved therein was polymerized as a rubber component, rubber particles of 0.5 μm or less having a single occlusion structure were dispersed in polystyrene. It is well known that they are formed in a state (eg Angew. Makromol. Chem. 58/59.
P175-198 (1977)). Utilizing this, a method for producing a rubber-modified styrene resin having excellent gloss and transparency of a molded article is disclosed in Japanese Patent Publication No. 48-18594, Japanese Patent Publication No. 61-500497, Japanese Patent Publication No. 63-48317, and Japanese Patent Publication No. 63-48317. It is proposed in Kaisha 64-74209. According to these methods, the surface gloss and the transparency of the molded product are remarkably improved as compared with the conventional rubber-modified styrene resin. However, although improvements in impact strength have been attempted, they have not been sufficient.

Further, a rubber-modified styrene resin in which rubber particles having a single occlusion structure formed by using the above styrene-butadiene copolymer rubber are dispersed, and a usual rubber particle in which a small amount of rubber particles having a salami structure are dispersed are used. By blending rubber-modified styrenic resin and making the particle size distribution curve of dispersed rubber particles into a bimodal shape (distribution curve having two maximum values), impact resistance while maintaining the gloss of the molded product at a high level Attempts to improve U.S. Pat. No. 4,493,92
2, found in JP-A-63-112646. In these methods, although the impact strength is certainly improved, the gloss is still insufficient, and the impact strength is insufficient, so that it is necessary to add polydimethylsiloxane or the like to the resin. there were.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide a rubber-modified styrene-based resin which has a markedly improved appearance of a molded article and is excellent in impact strength as compared with conventional rubber-modified styrene-based resins, and the production thereof. To provide a method.

Another object of the present invention is, for example, a rubber-modified styrenic resin suitable as a resin material for a large-sized, thin-walled, molded article having a complicated shape, which is molded by an injection molding method,
And a method for manufacturing the same.

[0008]

Means for Solving the Problems The inventors of the present invention have made extensive studies in view of the importance of the above object, and as a result, in a rubber-modified styrene-based resin composition, (1) a rubber particle having a salami structure having a small particle size. (2) The rubber particles having a single occlusion structure are made into a dispersed state, the particle size distribution is made into a three-peaked shape, and the volume average diameter is 0.
The range is from 2 to 0.8 μm, and (3) the particle size distribution is made wider than before, which is completely different from the conventional knowledge, and is 5% of the cumulative distribution of the volume-based particle size of rubber-like polymer particles and 95%. By finding a special index called the value of the ratio of% value and controlling it, when this rubber-modified styrene resin is used in a molded article, the appearance of the molded article,
In particular, they have found that the gloss is remarkably improved and the impact strength is also excellent, and the present invention has been completed.

That is, the present invention relates to a rubber-modified styrene resin composition obtained by dispersing rubber-like polymer particles in a homopolymer or copolymer of a styrene-based monomer, wherein (a) the rubber-like polymer particles The volume average diameter is in the range of 0.2 to 0.8 μm, the shape of the volume-based particle size distribution curve of the rubber-like polymer particles (b) is composed of three peaks, and (c) the rubber-like polymer particles The value of the ratio of the 5% value and the 95% value of the cumulative distribution of the particle diameter on a volume basis is in the range of 3 to 45, and (d) the 5 wt% styrene solution viscosity is 20 to 50 centipoise and the styrene content is 25.
% To 50% by weight of styrene-butadiene block copolymer (I) and 5% by weight styrene solution having a viscosity of 20 to 50
It is composed of a styrene-butadiene block copolymer (II) having a styrene content of 5 wt% to 20 wt% in centipoise, and the weight ratio of (I) to (II) is (I) / (II) = 95 /
A rubber-modified styrene resin composition having an excellent balance of physical properties, characterized in that a rubber-like polymer of 5 to 40/60 is used as a raw material for forming rubber-like polymer particles, and the rubber-like polymer particles have a salami structure. And particles having a single occlusion structure, the particles having a salami structure have a volume average diameter of 0.3 to 2.0 μm, and the particles having a single occlusion structure have a volume average diameter of 0.1 to 1.0 μm. And the ratio of the number of particles having a single occlusion structure to the total number of particles is 30 to 99%, and the ratio of the number of particles having a salami structure is 70 to 1%.

The present invention also provides a rubber-modified styrenic resin composition according to claim 1, which comprises polymerizing a solution of the rubbery polymers (I) and (II) dissolved in a styrenic monomer or a mixture thereof. The amount of styrene-based polymer in the reaction vessel for granulating the rubber-like polymer is X% by weight, the total amount of the rubber-like polymer is Y% by weight, and the styrene content of the rubber-like polymer (I) is Is Z% by weight, and the conversion rate of the styrene-based monomer or the mixture thereof is set to a range satisfying the following formula (III) 42 ≦ X + 2.33 × Y + (Z-40) ≦ 52 (III). A method for producing a rubber-modified styrene-based resin composition having an excellent balance of physical properties, which is 0 per 100 parts by weight of a solution of an organic peroxide in which a rubber-like polymer is dissolved when the rubber-like polymer is made into particles. .000
5 to 0.007 parts by weight is included.

The styrene-based monomer referred to in the present invention is a side chain alkyl-substituted styrene such as styrene, α-methylstyrene, α-ethylstyrene, vinyltoluene, vinylxylene, ot-butylstyrene, p-styrene. Nuclear alkyl-substituted styrenes such as t-butylstyrene and p-methylstyrene, halogenated styrenes such as monochlorostyrene, dichlorostyrene, tribromostyrene and tetrahydrostyrene, and p-hydroxystyrene, o-methoxystyrene and the like. , Particularly preferably styrene,
α-methylstyrene and p-methylstyrene.
The styrene-based monomer may be used alone or in combination of two or more.

The rubber-like polymer particles are the above-mentioned rubber-like polymer, that is, the above-mentioned styrene-based monomer added with a predetermined amount of the styrene-butadiene block copolymers (I) and (II) or the same monomer. The mixture is polymerized to form a dispersion in a styrene polymer.

The styrene-butadiene block copolymer (I) has a styrene content of 25 to 50% by weight,
The viscosity of the 5 wt% styrene solution is 20 to 50 centipoise. The styrene-butadiene block copolymer (II) has a styrene content of 5 to 20% by weight,
The viscosity of the 5 wt% styrene solution is 20 to 50 centipoise.

In the present invention, the rubber-like polymer particles formed as described above have a volume average particle size of 0.2 to 0.
It must be 8 μm. The volume average particle diameter here is measured as follows. That is, an electron micrograph of a resin by an ultra-thin section method is taken, and the minor and major diameters of 500 to 700 rubber particles in the photograph are measured, and the average is defined as the particle diameter, which is averaged by the following formula. is there.

Volume average particle diameter = ΣnD ⁴ / ΣnD ³ (where n is the number of rubber particles having a particle diameter D μm). When the volume average particle diameter is less than 0.2 μm, the obtained rubber modification The impact strength of styrene resin is low, and
If it exceeds 8 μm, the appearance of the molded article, especially the surface gloss, is deteriorated, which is not preferable.

In the present invention, the shape of the distribution curve of the rubber-like polymer particles needs to have three peaks.

The fact that the shape of the distribution curve of the rubber-like polymer particles in the present invention consists of three peaks means that the horizontal axis is 0.1.
When the particle diameter based on volume is plotted in μm units and the frequency is plotted on the vertical axis, the distribution has five inflection points where the sign (positive or negative) of the tangent slope changes.

When the shape of the distribution curve is two peaks, the impact strength is improved, but the appearance of the molded product is inferior, and the gloss gradient is particularly large. The distribution of the present invention is adjusted by the molecular weight distribution of the rubber-like polymer used, the ratio of the rubber-like polymer to be mixed, and the like. In the present invention, the gloss gradient means a difference in gloss due to a difference in the distance from a gate in a molded article for injection molding, a portion where the wall thickness changes or a corner-shaped portion where the flow state greatly changes during injection molding and a standard. It indicates the difference in gloss from the specific area.

Further, in the present invention, the number is cumulatively counted from particles having a larger volume-based particle diameter of the rubber-like polymer particles, and the cumulative distributions are respectively 5% and 95%. Value of ratio of particle size, ie 5% of cumulative distribution
Value to 95% value (hereinafter referred to as distribution coefficient)
The range is 45. Preferably in the range of 3.5-40,
It is particularly preferably in the range of 4-35. When it is less than 3, the effect of improving the impact strength is low, and when it exceeds 45, the appearance of the molded product is inferior and particularly the gloss gradient becomes large. The amount is adjusted by the molecular weight distribution of the rubber-like polymer used, the amount ratio of the rubber-like polymer to be mixed, the stirring strength during the polymerization, the residence time and the like.

In the present invention, the ratio of the rubber-like polymer (I) to the rubber-like polymer (II) is (I) / (II) = 9.
It should be in the range of 5/5 to 40/60. 95/5
If it exceeds, the impact strength will decrease, and if it is less than 40/60, the gloss will decrease.

The rubber-modified styrenic resin according to the present invention in which the rubber-like polymers (I) and (II) are dispersed is, for example, a rubber-modified styrene-based resin composition containing the rubber-like polymer (I) and a rubber-like composition. A method of separately producing a rubber-modified styrene-based resin containing a polymer (II), and blending with an extruder or the like;
The rubber-like polymers (I) and (II) can be obtained by, for example, preliminarily mixing them in a polymerization reaction tank at the time of polymerizing the styrene resin. The rubber-like polymers (I) and (II) can be used in the polymerization reaction tank. The method of mixing by mixing is preferable.

The present invention includes the case where the rubber-like polymer particles are particles having a salami structure and a single occlusion structure.

The salami structure in the present invention means the structure of particles having a plurality of occlusions in one rubber particle when an electron micrograph of a resin is taken by an ultra-thin section method and observed. The single occlusion structure means a structure of particles having only one occlusion in one rubber particle.

In the present invention, among the rubber-like polymer particles, the particles having a salami structure have a volume average diameter of 0.3 to 2.
In the range of 0 μm, the volume average diameter of the particles having a single occlusion structure is set to a range of 0.1 to 1.0 μm, and the ratio of the particles having a single occlusion structure to the total number of particles is set to a range of 30 to 99%. The ratio of the number of particles having a salami structure is preferably in the range of 70 to 1%. In this case, the volume average diameter of the rubber-like polymer particles is 0.2
Care must be taken to be in the range of ~ 0.8 μm.

If the volume average particle diameter of the particles having a salami structure is larger than 2.0 μm, the appearance of the molded product is poor, and especially the gloss gradient is large, and if it is less than 0.3 μm, the impact strength is low. On the other hand, when the volume average particle size of the particles having a single occlusion structure is larger than 1.0 μm, the gloss becomes low,
If it is less than 0.1 μm, the impact strength will be low. When the number of particles having a single occlusion structure is less than 30%,
The gloss decreases and the gloss gradient increases. If it exceeds 99%, the impact strength will decrease.

The ratio of the rubber-like polymer to the styrene-based polymer in the rubber-modified styrene-based resin composition according to the present invention satisfying the above conditions is preferably in the range of 3/97 to 25/75.
When it is less than 3/97, the molded article has excellent gloss, but the impact strength is low. When it is more than 25/75, the impact strength is improved but the gloss is lowered or the gloss gradient is increased.

As the method for producing the rubber-modified styrene resin composition of the present invention, the rubber-like polymers (I) and (II) are used.
Is obtained by polymerizing a solution of styrene-based monomer in bulk polymerization or bulk-suspension two-stage polymerization method. In either case, styrene in a reaction tank for granulating a rubber-like polymer is used. When the amount of the system polymer is X% by weight, the total amount of the rubbery polymer is Y% by weight, and the styrene content of the rubbery polymer (I) is Z% by weight, the value of the following formula (IV) is 42 to 52. It is necessary to adjust the conversion rate of the styrene-based monomer so that it falls within the range.

X + 2.33 × Y + (Z-40) (IV) Particle formation is possible outside this range, but in that case abnormal particles occur. When it is less than 42, rubber particles that look like rods are formed when the obtained product is observed with an electron microscope.
The gloss and impact strength are low. On the other hand, when it exceeds 52, huge particles are generated and the gloss is lowered. Setting the above formula (IV) to a predetermined value specifically means that when the amount of the rubber-like polymer in the reaction tank for granulating the rubber-like polymer is large, or when the rubber-like polymer (I) is When the styrene content is high, the conversion rate of the styrene-based monomer is adjusted so that the amount of the styrene-based polymer in the reaction tank for granulating the rubber-like polymer is increased,
In the opposite case, it means adjusting the conversion rate of the styrene-based monomer so that the amount of the styrene-based polymer in the reaction tank for granulating the rubber-like polymer is reduced.

In the present invention, the conversion of the styrene-based monomer is adjusted by a known method, for example, the polymerization temperature, the kind and concentration of the polymerization initiator to be used, the polymerization time, and the residence time in the case of the continuous polymerization method. To be done.

In the present invention, it is not necessary to use a polymerization initiator when the rubber-like polymer is made into particles, but a solution 1 in which an organic peroxide is dissolved in the rubber-like polymer as a polymerization initiator.
It is preferable to use 0.0005 to 0.007 parts by weight with respect to 00 parts by weight. If it is used in an amount of more than 0.007 parts by weight, a large amount of giant particles may be generated, which may reduce the gloss. The rubber-modified styrenic resin of the present invention may optionally contain a hindered phenolic antioxidant, a phosphorus antioxidant, an antioxidant such as a sulfur antioxidant, a fluidity improver such as mineral oil, and stearic acid. A release agent such as zinc stearate or organic polysiloxane may be added to the raw material solution or during the polymerization or at the time when the polymerization is completed.

[0031]

EXAMPLES The present invention will be specifically described below with reference to examples, but these do not limit the scope of the present invention. Evaluation of physical properties (1) Izod impact strength: measured according to JIS K-6871 (2) Evaluation of practical impact strength: Figure 1 by injection molding
A falling weight impact strength test was conducted on three parts of the molded article 1 having the shape shown in (a) and FIG. 1 (b), that is, part (1), part (2), and part (3). Tip of falling weight R =
The inner diameter of the carrier was 6.4 m / m, and the inner diameter was 25 m / m. The part (1) is a part whose thickness changes, the part (2) is a part near the corner, and the part (3) is a standard part. (3) Gloss: According to JIS 8741 (incident angle 60 °), the molded article 3 having the shape shown in FIGS. 1 (a) and 1 (b)
The measurement was carried out on a single site, site (1), site (2), and site (3). Example 1 A rubber-modified styrenic resin was produced using a continuous bulk polymerization apparatus in which a preheater was connected to the outlets of three reactors equipped with a stirrer in series, and then a vacuum tank was connected. The first reaction vessel equipped with a stirrer had a styrene content of 40% as rubbery polymer (I), and
% Styrene solution viscosity 35 centipoise styrene-butadiene block copolymer 4.2 parts by weight, as a rubber-like polymer (II), styrene content 15%, 5% styrene solution viscosity 30 centipoise styrene-butadiene block copolymer 1.8 parts by weight, ethylbenzene 15 parts by weight,
A raw material liquid consisting of 79 parts by weight of styrene and 0.005 parts by weight of 1,1-bis (t-butylperoxy) 3,3,5-trimethylcyclohexane as an organic peroxide was continuously supplied. The stirring of the first stirrer was 250 rpm, the reaction temperature was 144 ° C., and the residence time was 1.0 hour. Second
Basically, the reaction temperature is 145 ° C, the residence time is 2 hours, and the third
In the base, the reaction temperature was 148 ° C. and the residence time was 2.5 hours. The temperature of the preheater was maintained at 210 to 240 ° C., and the degree of vacuum in the vacuum chamber was 40 Torr. The results are shown in Tables 1 and 2. Example 2 It carried out on the same conditions as Example 1 except having set the 1st stirring to 180 rpm. Example 3 The conditions were the same as in Example 1 except that the first stirring was 400 rpm. Comparative Example 1 The conditions were the same as in Example 1 except that the first stirring was 80 rpm. The rubber-like polymer particles in the obtained product had a large average particle size of 1.00 μm and had low gloss. Comparative Example 2 The same conditions as in Example 1 were carried out except that the first stirring was 550 rpm. The rubber-like polymer particles in the obtained product had a small average particle size of 0.17 μm and had a low impact strength. Comparative Example 3 The rubber-like polymer (I) in Example 1 was 6 parts by weight,
The rubbery polymer (II) was not used, and the stirring of the first base was 30
Under the same conditions as in Example 1 except that 0 rpm, the reaction temperature was 142 ° C., and the residence time was 1.5 hours, a rubber-like polymer particle with a small particle size having a single occlusion structure having an average particle size of 0.35 μm was obtained. A rubber-modified styrene resin (A) was produced. Separately in Example 1, the rubbery polymers (I) and (I
Instead of I), 6 parts by weight of a polybutadiene having a viscosity of 50 centipoise in a 5% styrene solution was used, the first stirring was 300 rpm, the reaction temperature was 142 ° C., and the residence time was 1.5.
Under the same conditions as in Example 1 except that the time was changed, a rubber-modified styrene resin (B) having a large particle diameter and a salami structure having an average particle diameter of the rubber-like polymer particles of 1.15 μm was produced. The rubber-modified styrenic resins (A) and (B) were mixed at a ratio of 85/15 and melt-kneaded with an extruder to obtain a product. The particle size distribution of the rubber-like polymer had two peaks, and the gloss gradient of the molded product was large. Comparative Example 4 In Example 1, the first reaction temperature was 148 ° C.,
The conditions were the same as in Example 1 except that the residence time was 40 minutes. The obtained product had a large distribution coefficient of 51 and a large gloss gradient of the molded product. Comparative Example 5 In Example 1, the first reaction temperature was 140 ° C.,
The conditions were the same as in Example 1 except that the residence time was 3 hours. The obtained product had a small distribution coefficient of 2.7 and low impact strength. Example 4 5.4 parts by weight of the rubber-like polymer (I) in Example 1,
The conditions were the same as in Example 1 except that (II) was changed to 0.6 part by weight. Example 5 2.7 parts by weight of the rubber-like polymer (I) in Example 1,
The conditions were the same as in Example 1 except that the amount of (II) was 3.3 parts by weight. Comparative Example 6 The rubber-modified styrenic resin (A) produced in Comparative Example 3 was molded as it was and the physical properties were evaluated. High gloss, but low impact strength. Comparative Example 7 1.8 parts by weight of the rubber-like polymer (I) in Example 1,
The conditions were the same as in Example 1 except that the amount of (II) was 4.2 parts by weight. The gloss was low. Example 6 In Example 1, it carried out on the conditions similar to Example 1 except having set the reaction temperature to 140 degreeC. The conversion rate of the first styrene monomer was 36.7%. Example 7 The procedure of Example 1 was repeated except that the reaction temperature was changed to 150 ° C. The conversion rate of the first styrene monomer was 45.6%. Example 7 Example 1 was repeated except that the reaction temperature was 147 ° C. and no organic peroxide was used. Comparative Example 8 The procedure of Example 1 was repeated, except that the reaction temperature was 136 ° C. The conversion rate of the first styrene monomer was 33%. Electron micrograph observation of the product revealed rod-shaped particles with low gloss and impact strength. Comparative Example 9 The procedure of Example 1 was repeated except that the reaction temperature was changed to 154 ° C. The conversion rate of the first styrene monomer was 50.5%. Electron micrograph observation of the product revealed that there were large particles and the gloss was low. Comparative Example 10 The procedure of Example 1 was repeated except that the reaction temperature was 141 ° C. and the organic peroxide was 0.01 part by weight. Conversion rate of the first styrene monomer is 43%
Met. Electron micrograph observation of the product revealed that there were large particles and the gloss was low.

[0032]

[Table 1]

[0033]

[Table 2]

[0034]

As described above, the rubber-modified styrenic resin obtained by the method of the present invention has an excellent balance of impact strength and appearance, particularly gloss, and is a component material for household electric appliances, electronic devices and the like. The industrial utility value is great in the use of.

[Brief description of drawings]

FIG. 1 is a plan view (a) and a sectional view (b) of an injection-molded test piece used for evaluation of practical impact strength and gloss.

[Explanation of symbols]

 1 molded product

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Kozo Ichikawa 1-6 Takasago, Takaishi-shi, Osaka Mitsui Toatsu Chemical Co., Ltd. (72) Inventor Akihiko Nakajima 1-6 Takasago, Takaishi-shi, Osaka Mitsui Toatsu Inside the Chemical Co., Ltd. (72) Masato Takahisa 1-6 Takasago, Takaishi City, Osaka Prefecture Mitsui Toatsu Chemical Co., Ltd.

Claims (4)

[Claims] 1. A rubber-modified styrenic resin composition obtained by dispersing rubber-like polymer particles in a homopolymer or copolymer of a styrene-based monomer, wherein (a) the volume average diameter of the rubber-like polymer particles. Is in the range of 0.2 to 0.8 μm, and (b)
The shape of the volume-based particle size distribution curve of the rubber-like polymer particles is composed of three peaks, and (c) the ratio of the 5% value to the 95% value of the cumulative distribution of the volume-based particle diameter of the rubber-like polymer particles. Value is 3 to 45
In the range of (d) 5% by weight styrene solution viscosity is 20
~ 50 centipoise styrene content 25% by weight ~ 50
Wt% styrene-butadiene block copolymer (I)
And a styrene-butadiene block copolymer (II) having a 5 wt% styrene solution viscosity of 20 to 50 centipoise and a styrene content of 5 wt% to 20 wt%, and the weight ratio of (I) to (II) is ( I) / (II) = 95 / 5-40 / 6
A rubber-modified styrene-based resin composition having an excellent balance of physical properties, characterized in that a rubber-like polymer of 0 is used as a raw material for forming rubber-like polymer particles. 2. The rubber-like polymer particles include particles having a salami structure and a single occlusion structure, and the volume average diameter of the particles having a salami structure is 0.3 to 2.0 μm.
The volume average diameter of particles having a single occlusion structure is 0.1 to 1.0 μm, and the ratio of the number of particles having a single occlusion structure to the total number of particles is 30 to
99%, the ratio of the number of particles having a salami structure is 70-
The rubber-modified styrene resin composition according to claim 1, which is 1%. 3. The rubber-modified styrene-based polymer according to claim 1, which is obtained by polymerizing a solution of the rubber-like polymers (I) and (II) according to claim 1 in a styrene-based monomer or a mixture thereof. In the method for producing a resin composition, the amount of the styrene-based polymer in the reaction vessel for granulating the rubber-like polymer is X% by weight, the total amount of the rubber-like polymer is Y% by weight, and the amount of the rubber-like polymer (I) is The styrene content is Z% by weight, and the conversion rate of the styrene-based monomer or the mixture thereof is in a range satisfying the following formula (III) 42 ≦ X + 2.33 × Y + (Z-40) ≦ 52 (III) A method for producing a rubber-modified styrene-based resin composition having an excellent balance of physical properties, which is characterized in that 4. The rubber according to claim 3, wherein 0.0005 to 0.007 parts by weight of an organic peroxide is added to 100 parts by weight of a solution in which the rubbery polymer is dissolved when the rubbery polymer is made into particles. A method for producing a modified styrene resin composition.