JP3160352B2 - Ultra-high gloss rubber-modified styrenic resin composition and method for producing the same - Google Patents

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 high gloss and excellent balance between appearance and impact resistance of a molded product and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, in the fields of household electric appliances and electronic equipment, ABS resins capable of obtaining molded articles having a good balance between appearance and impact strength have been widely used. However, recently, there has been an increasing demand for cost reduction of these products, and there has been a demand for a molded product having a large, complicated shape and a small thickness. A rubber-modified styrene resin composition is used. Under such circumstances, the rubber-modified styrenic resin composition is required to have good gloss, excellent moldability, and high impact strength.

In a rubber-modified styrenic resin composition, the particle size of the dispersed particles of the rubbery polymer (hereinafter abbreviated as rubber particles) has an important effect on product performance,
The smaller the particle size of the rubber particles, the higher the gloss of the molded product.
Usually, the particle size of the rubber particles in the rubber-modified styrenic resin composition is about 1.0 to 5.0 μm, but recently, in order to improve the gloss of a molded product, a resin having a rubber particle diameter of 1.0 μm or less has been used. Has also been developed. However, in the rubber-modified styrene resin composition, when the rubber particle diameter is 1.0 μm or less, the impact strength is significantly reduced. Therefore, there is a limit to improving the gloss while maintaining the impact strength of the molded product. . In order to solve such a problem, a rubber-modified styrenic resin composition having rubber particles having a particle size of 1.0 μm or less and a rubber-modified styrenic resin composition having rubber particles having a particle size of 1.0 μm or more are blended. The method is described in JP-B-46-41467, JP-A-59-1519, JP-A-63
-241033, and U.S. Pat. No. 4,146,589. In these methods, there have been problems such as insufficient gloss or poor balance between impact resistance and gloss.

On the other hand, when a rubber-modified styrene resin composition is polymerized using a styrene-butadiene block copolymer having a high styrene content as a rubber component, the particle size having a single occlusion structure is 0.5 μm or less. It is well known that rubber particles are formed (eg, Angew.
58/59, pp. 175-198, 1977), and a method for producing a rubber-modified styrenic resin composition having excellent gloss and transparency of a molded product by using these is disclosed in JP-B-48-185.
94, JP-A-61-500977, JP-A-63-483
17, disclosed in JP-A-64-74209. According to these methods, although the gloss and transparency of the molded product have been remarkably improved as compared with the conventional rubber-modified styrenic resin composition, sufficient physical properties are still obtained for the impact strength. Did not.

Further, a rubber-modified styrenic resin composition having rubber particles having a single occlusion structure formed using the styrene-butadiene copolymer rubber, and a general rubber-modified resin having a small amount of rubber particles having a salami structure Blend with styrenic resin composition and adjust particle size distribution of dispersed rubber particles to 2
Attempts to improve the impact resistance while maintaining the gloss of the molded article at a high level by forming a mountain are disclosed in US Pat.
493,922 and JP-A-63-112646. In these methods, although the impact strength is improved, the gloss is still insufficient, so that it is necessary to add polydimethylsiloxane or the like to the resin.

[0006]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a rubber-modified styrenic resin composition having a significantly improved appearance and a superior impact strength as compared with conventional rubber-modified styrenic resins. And a method for manufacturing the same.

Another object of the present invention is to provide a rubber-modified styrenic resin composition suitable as a resin material having a large, thin, and complicated shape formed by, for example, injection molding, and a method for producing the same. It is in.

[0008]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies in view of the importance of the above object, and have found that, in a rubber-modified styrenic resin composition, (1) rubber particles having a salami structure have a small particle size. (2) rubber particles having a single occlusion structure having a larger particle size than conventional particles are mixed, the particle size distribution is made three peaks, the average particle size is in the range of 0.2 to 0.8 μm, and ( 3) To make the particle size distribution wider than before and control a new index not found in the prior art, that is, the ratio of 5% value to 95% value of the volume-based cumulative particle size distribution of rubber particles. As a result, it was found that the appearance of the molded product, particularly the gloss, was remarkably improved and the impact strength was also excellent, and the present invention was completed.

That is, the present invention relates to a rubber-modified styrenic resin composition comprising a styrenic polymer and a rubbery polymer, wherein (a) the rubbery polymer has a 5% styrene solution viscosity of 2%.
0-50 centipoise, styrene content 25% by weight
A rubbery polymer 1 comprising a styrene-butadiene block copolymer having a styrene content of 5 to 50% by weight and a styrene content of 5% by weight;
A rubbery polymer 2 composed of a styrene-butadiene block copolymer having a viscosity of 30 to 90 centipoise and a rubbery polymer 3 composed of a polybutadiene having a viscosity of 30 to 90 centipoise. The weight ratio of rubbery polymer 2 is rubbery polymer 1 / rubbery polymer 2 = 9
5/5 to 40/60, and the sum of the rubber-like polymer 1 and the rubber-like polymer 2 and the weight ratio of the rubber-like polymer 3 are (rubber-like polymer 1 + rubber-like polymer 2) / rubber-like polymer 3 = 99 / 1-7
0/30, and the rubber-like polymer is dispersed as dispersed particles in the rubber-modified polystyrene in the composition,
The (b) volume average diameter of the dispersed particles of the rubbery polymer is 0.
(C) the volume-based particle size distribution is composed of three peaks, and (d) the ratio between the 5% value and the 95% value of the volume-based cumulative particle size distribution is 3 to 0.8 μm. 45 is a rubber-modified styrenic resin composition characterized by being in the range of 45.

In the present invention, among the dispersed particles of the rubber-like polymer, the dispersed particles having a salami structure have a volume average diameter of 0.3.
To 2.0 μm, the volume average diameter of the dispersed particles having a single occlusion structure is in the range of 0.1 to 1.0 μm, and the number of dispersed particles having a single occlusion structure is the total number of particles. And the number of dispersed particles having a salami structure is 70 to 99% with respect to the total number of particles.
The rubber-modified styrenic resin composition is 1%.

The present invention also relates to a process for producing a rubber-modified styrenic resin composition by dissolving rubbery polymers 1, 2 and 3 in a styrene monomer and polymerizing the solution. Assuming that the proportion of the styrene-based polymer in the reaction vessel for forming particles is X% by weight, the proportion of the rubbery polymer is Y% by weight, and the styrene content of the rubbery polymer 1 is Z% by weight, X, Y, Z
Is the following formula,

[0012]

The method for producing the rubber-modified styrenic resin composition, wherein the following formula is satisfied: 42 ≦ X + 2.33Y + (Z−40) ≦ 52

In the present invention, when the rubber-like polymer is formed into particles, the organic peroxide is dissolved in a solution 100 in which the rubber-like polymer is dissolved.
The method for producing the above rubber-modified styrene resin composition, wherein 0.0005 to 0.007 parts by weight is used per part by weight.

Hereinafter, the present invention will be described in detail.

The styrene-based polymer referred to in the present invention is a polymer selected from one or more of the following styrene-based monomers and homopolymerized or copolymerized.

Styrene monomers include side-chain alkyl-substituted styrenes such as styrene, α-methylstyrene and α-ethylstyrene, vinyl toluene, vinyl xylene, o
-T-butylstyrene, pt-butylstyrene, p-
Nuclear alkyl-substituted styrenes such as methylstyrene, halogenated styrenes such as monochlorostyrene, dichlorostyrene, tribromostyrene, and tetrahydroxystyrene, and p-hydroxystyrene, o-methoxystyrene, and the like. Among them, styrene, α-methylstyrene and p-methylstyrene are particularly preferred.

In the present invention, the ratio of the rubbery polymer 1 to the rubbery polymer 2 is rubbery polymer 1 / rubbery polymer 2 = 9.
It is necessary to be in the range of 5/5 to 40/60. 95/5
If it exceeds 300, the impact strength decreases, and if it is less than 40/60, the gloss decreases. The sum of the rubbery polymer 1 and the rubbery polymer 2;
The ratio of the rubbery polymer 3 needs to be in the range of (rubbery polymer 1 + rubbery polymer 2) / rubbery polymer 3 = 99/1 to 70/30. If it is less than 70/30, the gloss is reduced and 9
If it exceeds 9/1, the impact strength decreases.

In the present invention, a rubber-modified styrenic resin composition containing the rubbery polymer 1, a rubber-modified styrenic resin composition containing the rubbery polymer 2 and a rubbery polymer 3 are separately produced. Although it may be blended by an extruder or the like, preferably, the rubbery polymer 1, the rubbery polymer 2, and the rubbery polymer 3 are previously placed in a polymerization reaction tank prior to copolymerization with the styrene-based polymer. It is preferable to mix them.

The volume average diameter in the present invention is determined as follows. That is, an electron micrograph is taken by an ultra-thin section method of the resin, the short diameter and the long diameter of each of the 500 to 700 rubber particles in the photograph are measured, and the average value is determined as the particle diameter. Ask.

[0020]

[Equation 3] Volume average diameter = ΣnD ⁴ / ΣnD ³ (where n is the number of rubber particles having a particle diameter of D μm.) When the volume average diameter is less than 0.2 μm, the impact strength of the rubber-modified styrenic resin is reduced. On the other hand, if it exceeds 0.8 μm, the appearance of the molded product, particularly the surface gloss, is undesirably reduced.

The volume-based particle size distribution of the rubber particles is 3
It needs to be a mountain. That is, when the volume average diameter is plotted in 0.1 μm units on the horizontal axis and the frequency is plotted on the vertical axis, the distribution has five inflection points where the sign (positive or negative) of the slope of the tangent changes. The particle size distribution is adjusted by the molecular weight distribution of the rubbery polymer, the mixing ratio of the rubbery polymer, and the like.

When the distribution is two peaks, as in the prior art, the impact strength is improved, but the appearance of the molded product is inferior.
In particular, the gloss gradient increases. Gloss gradient is injection molding,
This is the difference in gloss depending on the part of the molded product obtained by transfer molding or the like. Here, the difference in gloss due to the distance from the injection gate and the difference in gloss between the part where the flow state changes significantly during injection molding, such as a part where the wall thickness changes or a corner-shaped part, and a part where the flow state is standard are shown. Point.

Further, the volume-based particle diameter of the rubber particles is counted from the larger particle and counted, and the ratio D1 / D2 (hereinafter referred to as D1 / D2) of particle diameter D1 at which the cumulative distribution is 5% and particle diameter D2 at which the cumulative distribution is 95% is obtained. , Distribution coefficient) in the range of 3 to 45. It is preferably in the range of 3.5 to 40, more preferably in the range of 4 to 35. If it is less than 3, the effect of improving the impact strength is low, and if it exceeds 45, the appearance of the molded product is inferior, and particularly the gloss gradient becomes large. The distribution coefficient is adjusted by the molecular weight distribution of the rubber-like polymer, the mixing ratio of the rubber-like polymer, the stirring intensity during polymerization, the residence time, and the like.

In the present invention, among the dispersed particles of the rubbery polymer, the volume average diameter of the rubber particles having a salami structure is set in the range of 0.3 to 2.0 μm, and the volume average diameter of the rubber particles having a single occlusion structure is adjusted. The diameter is in the range of 0.1 to 1.0, the ratio of rubber particles having a single occlusion structure to the total number of particles is 30 to 99%, and the ratio of the number of rubber particles having a salami structure is 70 to It must be in the range of 1%. If the volume average diameter of the rubber particles having a salami structure is larger than 2.0 μm, the appearance of the molded product is inferior,
In particular, the gloss gradient increases. On the other hand, if it is less than 0.3 μm, the impact strength will be low. When the volume average diameter of the rubber particles having a single occlusion structure is larger than 1.0 μm, the gloss is reduced, and when it is smaller than 0.1 μm, the impact strength is reduced.
Further, when the number of rubber particles having a single occlusion structure is less than 30% of the total number of particles, the gloss is reduced or the gloss gradient is increased. Conversely, if it is more than 99%, the impact strength is reduced.

The salami structure referred to in the present invention means, when an electron micrograph is taken and observed by an ultra-thin section method of a resin,
It refers to the structure of particles having multiple occlusions within one rubber particle. Also, the single occlusion structure is
Refers to particles having only one occlusion within one rubber particle.

In the present invention, the composition ratio of the rubbery polymer and the styrene-based polymer is preferably in the range of rubbery polymer / styrene-based polymer = 3/97 to 25/75. 3/97
If it is less than 30%, the molded article has excellent gloss but the impact strength is reduced. If it is more than 25/75, the impact strength is improved but the gloss is reduced or the gloss gradient is increased.

The process of the present invention comprises the steps of
Is obtained by bulk polymerization or bulk-suspension two-stage polymerization of a solution prepared by dissolving a styrene monomer in a styrene monomer. Assuming that the amount of the coalescing is X% by weight, the total amount of the rubbery polymer is Y% by weight, and the styrene content of the rubbery polymer 1 is Z% by weight, the values of the following two formulas become 42 or more and 52 or less. It is necessary to adjust the addition rate of the styrene monomer.

[0028]

X + 2.33Y + (Z−40) 2 Particle formation is possible outside the above range, but abnormal particles are generated in that case. When the value of the above equation is less than 42, when the obtained product is observed with an electron microscope, rubber particles that look like rods are generated, and both gloss and impact strength are reduced. on the other hand,
When the value of the above formula exceeds 52, giant particles are generated, and the gloss is reduced. In order to satisfy the above two formulas, specifically, when granulating the rubber-like polymer, when the amount Y of the rubber-like polymer in the reaction tank is large and / or when the rubber-like polymer 1 contains styrene, When the amount Z is large, the conversion of the styrene-based monomer is adjusted so that the amount X of the styrene-based polymer in the reaction tank increases, and when the amount Z is large, the amount of the styrene-based polymer in the reaction tank is adjusted. X
The conversion of the styrene monomer is adjusted so as to reduce the amount of the styrene monomer.

The conversion of the styrene monomer is determined by the polymerization temperature,
The type and concentration of the polymerization initiator, the polymerization time, and in the case of the continuous polymerization method, can be adjusted by a known method for adjusting the residence time and the like.

In the method of the present invention, it is not necessary to use a polymerization initiator when granulating the rubber-like polymer. It is preferable to use 0.0005 to 0.007 parts by weight based on parts. If it is used in an amount of more than 0.007 parts by weight, one part of giant particles is formed, and the gloss is reduced.
Also, if necessary, hindered phenolic antioxidants,
Antioxidants such as phosphorus antioxidants and sulfur antioxidants, fluidity improvers such as mineral oil, and release agents such as stearic acid, zinc stearate, and organic polysiloxane are used as a raw material solution or during or during polymerization. May be added at the end of the process.

[0031]

The present invention will be described in more detail with reference to the following examples, which do not limit the present invention.
The evaluation of physical properties was performed in the following manner. (1) Izod impact strength: Measured according to JISk-6871. (2) Evaluation of practical impact strength: FIG.
A falling weight impact strength test was performed on three portions, a portion 1, a portion 2 and a portion 3 of the molded article having the shape shown in FIG. Tip of falling weight R = 6.4m / m, inner diameter of loading platform 25m
/ M. In FIG. 1, a portion 1 is a portion where the thickness changes, a portion 2 is a portion near a corner, and a portion 3 is a standard portion. (3) Gloss: Measured at three sites, site 1, site 2 and site 3, of the molded article having the shape shown in FIGS. 1A and 1B according to JIS8741 (incident angle 60 °).

Tables 1 and 2 show the results of the evaluation of the physical properties of the rubber-modified styrenic resin compositions produced in the following Examples and Comparative Examples.

Example 1 A rubber-modified styrenic resin composition was produced using a continuous bulk polymerization apparatus in which three series reactors each having a stirrer were connected to a preheater at the outlet and then connected to a vacuum tank. 42% styrene content as a rubbery polymer 1 in a first reaction vessel with a stirrer,
4.0% by weight of a styrene-butadiene block copolymer having a viscosity of 32 centipoise in a 5% styrene solution, and a rubbery polymer 2 as a styrene-butadiene block copolymer 1 having a styrene content of 15% and a 5% styrene solution having a viscosity of 30 centipoise 0.7 parts by weight, as a rubbery polymer 3, 0.3% polybutadiene having a 5% styrene solution viscosity of 45 centipoise.
Parts by weight, 15 parts by weight of ethylbenzene, 79 parts by weight of styrene, and 1,1-bis (t-butylperoxy) 3,3,5-trimethylcyclohexane as an organic peroxide 0.0
A raw material liquid consisting of 05 parts by weight was continuously supplied. The stirring speed of the first stirrer is 250 rpm and the reaction temperature is 14
At 4 ° C., the residence time was 1.0 hour. The second group had a reaction temperature of 145 ° C. and a residence time of 2 hours, and the third group had a reaction temperature of 145 ° C. and a residence time of 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 set at 40 Torr.

Example 2 A rubber-modified styrenic resin composition was produced under the same conditions as in Example 1 except that the first stirring speed was 180 rpm.

Example 3 A rubber-modified styrene resin composition was produced under the same conditions as in Example 1 except that the first stirring speed was 400 rpm.

Comparative Example 1 Example 1 was repeated except that the first stirring speed was 80 rpm.
A rubber-modified styrenic resin composition was produced under the same conditions as described above. The volume average diameter of the rubber-like polymer particles in the obtained product was as large as 1.10 μm, and the gloss was low.

Comparative Example 2 A rubber-modified styrenic resin composition was produced under the same conditions as in Example 1 except that the first stirring speed was 550 rpm. The average particle size of the rubber-like particles in the obtained product is 0.1
As small as 8 μm, the impact strength was low.

COMPARATIVE EXAMPLE 3 Rubbery polymer 1 was added to 6 parts by weight, and rubbery polymers 2 and 3 were used.
Rubber particles having a single occlusion structure under the same conditions as in Example 1 except that the first reaction temperature was 142 ° C., the residence time was 1.5 hours, and the stirring speed was 300 rpm, Then, a rubber-modified styrenic resin composition A having a small average particle diameter of 0.35 μm was produced. Separately, without using the rubbery polymers 1 and 2, 6 parts by weight of a polybutadiene having a 5% styrene solution viscosity of 50 centipoise was used as the rubbery polymer 3, and the first reaction temperature was 142 ° C.
A rubber-modified styrene resin composition in which the rubber particles have a salami structure and a large average particle diameter of 1.15 μm under the same conditions as in Example 1 except that the residence time is 1.5 hours and the stirring speed is 300 rpm. Material B was produced. The rubber-modified styrenic resin compositions A and B are mixed at a ratio of 85/15,
The product was obtained by melt-kneading with an extruder. The particle size distribution of the rubber particles dispersed in the resin composition was two peaks, and the gloss gradient of the molded product was large.

Comparative Example 4 A rubber-modified styrene resin composition was produced under the same conditions as in Example 1 except that the first reaction temperature was 148 ° C. and the residence time was 40 minutes. In the obtained product, the distribution coefficient of the cumulative particle size distribution was as large as 53, and the gloss gradient of the molded product was large.

Comparative Example 5 A rubber-modified styrene resin composition was produced under the same conditions as in Example 1 except that the first reaction temperature was 148 ° C. and the residence time was 3 hours. The obtained product had a small distribution coefficient of the cumulative particle size distribution of 2.7 and low impact strength.

Example 4 The same as Example 1 except that the rubbery polymer 1 was 4.05 parts by weight, the rubbery polymer 2 was 0.45 parts by weight, and the rubbery polymer 3 was 1.5 parts by weight. A rubber-modified styrenic resin composition was produced.

Example 5 Same as Example 1 except that the rubbery polymer 1 was 2.65 parts by weight, the rubbery polymer 2 was 3.23 parts by weight, and the rubbery polymer 3 was 0.12 parts by weight. A rubber-modified styrenic resin composition was produced.

Comparative Example 6 The rubber-modified styrenic resin composition A produced in Comparative Example 3 was directly molded and evaluated for physical properties. The gloss was high, but the impact strength was low.

Comparative Example 7 Same as Example 1 except that rubbery polymer 1 was 1.78 parts by weight, rubbery polymer 2 was 4.16 parts by weight, and rubbery polymer 3 was 0.06 parts by weight. A rubber-modified styrenic resin composition was produced under the following conditions. The gloss was low.

Example 6 A rubber-modified styrene resin composition was produced under the same conditions as in Example 1 except that the reaction temperature was changed to 140 ° C.

Example 7 A rubber-modified styrene resin composition was produced under the same conditions as in Example 1 except that the reaction temperature was changed to 150 ° C.

Example 8 A rubber-modified styrene resin composition was produced under the same conditions as in Example 1 except that the reaction temperature was 146 ° C. and no organic peroxide was used.

Comparative Example 8 A rubber-modified styrene resin composition was produced under the same conditions as in Example 1 except that the reaction temperature was changed to 136 ° C. The conversion of the first styrene monomer was 30%. When observing the product with an electron micrograph, stick-shaped rubber particles are seen.
Gloss and impact strength were low.

Comparative Example 9 A rubber-modified styrene resin composition was produced under the same conditions as in Example 1 except that the reaction temperature was changed to 154 ° C. The conversion of the first styrene monomer was 48%. Observation of the product with electron micrographs reveals huge particles,
The gloss was low.

Comparative Example 10 A reaction was carried out under the same conditions as in Example 1 except that the reaction temperature was 141 ° C. and 0.01 parts by weight of an organic peroxide was used. The conversion of the first styrene monomer was 40%. Observation of the product with electron micrographs reveals huge particles,
The gloss was low.

[0051]

[Table 1]

[0052]

[Table 2]

[0053]

As described above, the rubber-modified styrenic resin composition according to the present invention has an excellent balance of impact strength and physical properties such as appearance and, in particular, gloss, and is useful as a material for parts of home electric appliances and electronic equipment. The industrial value of use is great.

[Brief description of the drawings]

FIG. 1A is a plan view of an injection-molded test piece used for evaluation of practical impact strength and gloss, and FIG. 1B is a cross-sectional view taken along line AA ′.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kozo Ichikawa 1-6-6 Takasago, Takaishi City, Osaka Prefecture Inside Mitsui Toatsu Chemicals Co., Ltd. (72) Inventor Akihiko Nakajima 1-6-6 Takasago, Takaishi City, Osaka Prefecture Mitsui Toatsu In Chemical Co., Ltd. (72) Inventor Masato Takaku 1-6-6 Takasago, Takaishi-shi, Osaka Mitsui East Pressure Chemical Co., Ltd. (56) References JP-A-4-88006 (JP, A) JP-A-2-34613 ( JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C08L 51/04 C08F 279/02 C08F 287/00

Claims (4)

(57) [Claims] 1. A rubber-modified styrenic resin composition comprising a styrenic polymer and a rubbery polymer, wherein (a) the rubbery polymer has a 5% styrene solution viscosity of 20 to 50 centipoise and a styrene content of 25% to 50% by weight
A rubber-like polymer 1 comprising a styrene-butadiene block copolymer, having a 5% styrene solution viscosity of 20 to 50 centipoise and a styrene content of 5% to 20% by weight
The rubbery polymer 2 comprising a styrene-butadiene block copolymer and a 5% styrene solution having a viscosity of 30 to 90
It is composed of a rubbery polymer 3 composed of polybutadiene having a centipoise, and the weight ratio of the rubbery polymer 1 and the rubbery polymer 2 is rubbery polymer 1 / rubbery polymer 2 = 95/5 to 40
/ 60, and the weight ratio of the sum of the rubbery polymer 1 and the rubbery polymer 2 and the rubbery polymer 3 is (rubbery polymer 1 + rubbery polymer 2) / rubbery polymer 3 = 99/1. And the rubber-like polymer is dispersed as dispersed particles in the rubber-modified polystyrene in the composition, and the (b) volume average diameter of the dispersed particles of the rubber-like polymer is 0.1. 2-0.8μ
m, (c) the volume-based particle size distribution is composed of three peaks, and (d) the 5% value of the volume-based cumulative particle size distribution and 9
A rubber-modified styrenic resin composition having a ratio of 5% to a range of 3 to 45. 2. Among the dispersed particles of a rubber-like polymer, the dispersed particles having a salami structure have a volume average diameter of 0.3 to 2.0 μm.
m, the volume average diameter of the dispersed particles having a single occlusion structure is in the range of 0.1 to 1.0 μm, and the number of dispersed particles having a single occlusion structure is based on the total number of particles. The rubber-modified styrenic resin composition according to claim 1, wherein the composition is 30 to 99%, and the number of dispersed particles having a salami structure is 70 to 1% based on the total number of particles. 3. A method for producing a rubber-modified styrenic resin composition comprising dissolving rubbery polymers 1, 2 and 3 in a styrene monomer and polymerizing the solution, granulating the rubbery polymer. X percentage by weight of the styrenic polymer in the reaction vessel
Assuming that the proportion of the rubbery polymer is Y% by weight and the styrene content of the rubbery polymer 1 is Z% by weight, X, Y and Z are as follows.
3. The method for producing a rubber-modified styrenic resin composition according to claim 1, wherein the following expression is satisfied: 42 ≦ X + 2.33Y + (Z−40) ≦ 52. 4. When the rubbery polymer is formed into particles, the organic peroxide is used in an amount of 0.0005 to 0.007 parts by weight based on 100 parts by weight of the solution in which the rubbery polymer is dissolved. A method for producing the rubber-modified styrenic resin composition according to claim 3.