JPH10251355A - Production of rubber-modified styrene-based resin composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce the subject composition, excellent in balance between good flexural elastic modulus with planar impact strength by dissolving a butadiene-based rubber in a solution of a styrene monomer and polymerizing the styrene monomer at a specified temperature with a specific polymerization initiator. SOLUTION: (B) A butadiene-based rubber having 20-200cP solution viscosity (SV) and a Mooney viscosity (ML) satisfying 20×log(SV)>ML is dissolved in a solution composed of (i) a styrene monomer (ii) a solvent and, an necessary, (iii) other monomers, having a conjugated C-C double bond and copolymerizable with the component (i), an additive, etc., and the polymerization is carried out by using (C) a polymerization initiator composed of (iv) a polyfunctional organic peroxide having 75-95 deg.C 10-hr half-life temperature in an amount of 0.0001-0.0006 equiv. based on the component (i) and (v) a monofunctional organic peroxide having 110-130 deg.C 10hr half-life temperature in an amoung of 0.00005-0.0003 equiv. based on the component (i) and regulating the temperature until the conversion rate of the component (i) attains 30% to the 10-hr half-life temperature of the component (iv) +40 deg.C or below.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a rubber-modified styrenic resin composition. More specifically, the present invention relates to a method for producing a rubber-modified styrenic resin composition having an excellent balance of physical properties such as surface impact strength, rigidity, fluidity and the like in a short residence time in a polymerization apparatus.

[0002]

2. Description of the Related Art Rubber-modified styrene resin compositions represented by HIPS (high impact polystyrene, high impact polystyrene) are excellent in impact resistance and rigidity in addition to moldability and dimensional stability. It has been used in various fields such as home appliances, office equipment, and industrial parts.

[0003] In recent years, in these fields, as products have become larger, thinner and have high cycle molding, a balance between impact resistance and rigidity, and further improved fluidity have been demanded. It has become There is an increasing demand for surface impact strength among impact resistances. In order to increase the impact resistance of the rubber-modified styrenic resin composition, it is effective to increase the content of the rubbery polymer in the resin composition, but on the other hand, there is a problem that rigidity and fluidity are reduced. Was. For this reason, in order to improve the balance and flowability between the impact resistance and rigidity of the rubber-modified vinyl aromatic resin composition, it is important to achieve high impact resistance using as little of the rubbery polymer as possible. there were.

[0004] As is well known, HIPS is generally prepared by dissolving a rubbery polymer in styrene and polymerizing in the presence of shear. With the progress of polymerization, a part of styrene is grafted on the rubber-like polymer, and then the rubber-like polymer is dispersed as particles having a size of 0.5 to 10 μm through phase inversion. Obtained by removal under vacuum.

With a smaller amount of rubbery polymer, high impact H
Various methods have been proposed to obtain IPS. For example, HIPS using a polybutadiene rubber having a ratio of cis-1,4 bonds in a butadiene unit chain of 90 mol% or more as a rubbery polymer (Japanese Patent Laid-Open No. 52-864).
No. 44), however, the particle size and the form of the particles are not sufficiently specified, and the balance between impact strength and rigidity is insufficient.

Japanese Patent Laid-Open No. 7-53 filed earlier by the present inventors
The technique described in Japanese Patent No. 642 is excellent as a technique for solving these problems, however, in some applications requiring higher surface impact strength, impact resistance such as blending of a thermoplastic elastomer is used. It was necessary to further enhance the properties and increase the wall pressure of the molded product. Further, since only a production method under a specific range of polymerization rate is disclosed, efficient production may be prevented in some cases. That is, if a large amount of initiator is used to improve productivity, the grafting reaction cannot be appropriately controlled, and a technology capable of producing a rubber-modified styrenic resin composition having satisfactory physical properties at a sufficiently high productivity is eventually obtained. Was not disclosed.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to provide a rubber-modified styrenic resin composition which has an excellent balance between good flexural modulus and surface impact strength and can shorten the residence time in a polymerization apparatus. The point is to provide a manufacturing method.

[0008]

Means for Solving the Problems In order to solve the above-mentioned problems, the present inventors have conducted intensive studies and found that a butadiene rubber is dissolved in a monomer solution containing styrene as a main component and polymerized. In the method for producing a styrenic resin composition, a 10-hour half-life temperature of 75 to 95 ° C. is used as a polymerization initiator.
Of the polyfunctional organic peroxide is 0.00
When a monofunctional organic peroxide having a range of 01 to 0.0006 equivalents and a 10-hour half-life temperature of 110 to 130 ° C is used in a range of 0.00005 to 0.0003 equivalents to the total amount of the monomers, Not only can a rubber-modified styrenic resin composition be efficiently produced with a short residence time in a polymerization apparatus,
Surprisingly, they have found that the balance between contradictory physical properties such as surface impact strength, rigidity, and fluidity is remarkably improved, and have completed the present invention.

That is, the present invention relates to a method for polymerizing a rubber-modified styrene resin composition by dissolving a butadiene rubber in a solution of a styrene monomer to prepare a stock polymerization solution and adding a polymerization initiator. The polyfunctional organic peroxide (a) having a 10-hour half-life temperature of 75 to 95 ° C. is added in an amount of 0.0001 to 0.0006 equivalent to the styrene monomer.
The monofunctional organic peroxide (b) having a time half-life temperature of 110 to 130 ° C. is added to the styrene monomer in an amount of 0.00005 to 0.1.
Using 0003 equivalents, the polymerization until the conversion of styrene reaches 30% is carried out at a 10-hour half-life temperature of the polyfunctional organic peroxide (a) having a 10-hour half-life temperature of 75 to 95 ° C. + 40 ° C. or less. A method for producing a rubber-modified styrene resin composition.

Hereinafter, the present invention will be described in detail. In the method for producing the rubber-modified styrenic resin composition of the present invention, a 10-hour half-life temperature of 75 to 95 ° C. is used as a polymerization initiator.
Of the polyfunctional organic peroxide (a) in an amount of 0.0001 to 0.0006 equivalents based on the total amount of the styrene monomer, and 10
The monofunctional organic peroxide (b) having a time half-life temperature of 110 to 130 ° C is used in an amount of 0.0000 with respect to the total amount of the styrene monomer.
It must be used in the range of 5 to 0.0003 equivalents.

The solution of the styrene monomer in the present invention includes styrene, and, if necessary, another monomer having a conjugated C--C double bond copolymerizable therewith, a solvent, and a small amount of an additive. Consisting of a styrene-based monomer solution. Examples of other monomers having a conjugated CC double bond copolymerizable with styrene include substituted styrenes such as α-methylstyrene, p-methylstyrene, and bromostyrene; methacrylic acid and methyl methacrylate;
Methacrylates such as butyl methacrylate,
Examples include acrylic acid and acrylic acid esters such as methyl acrylate and butyl acrylate, and maleic acid derivatives such as methacrylonitrile, acrylonitrile, maleic anhydride, and N-phenylmaleimide.

Examples of the solvent used in the present invention include ethylbenzene, mixed xylene, aromatic hydrocarbons such as toluene, ketones such as methyl ethyl ketone, and halogenated hydrocarbons such as tetrachloroethane. Ethylbenzene is most suitable for the purpose of the present invention of efficiently producing a resin composition in a closed system without using the same.

For the same purpose, the amount of the solvent used is preferably small, preferably about 15% by weight or less, more preferably 10% by weight or less. Examples of the additives used in the present invention include a chain transfer agent, an antioxidant, a mineral oil, and a silicone oil.
And (b) may be used together.

The butadiene rubber in the present invention means, in addition to polybutadiene, butadiene-containing copolymer rubbers such as styrene-butadiene copolymer rubber and butadiene-isoprene copolymer rubber, and hydrogen at some double bonds of polybutadiene. Refers to modified polybutadiene rubbers such as rubber to which is added. Solution viscosity (SV) of rubber in the present invention
Is the value of a 5% styrene solution at 25 ° C.
00 centipoise, preferably 30-100
More preferably, it is less than centipoise. If the solution viscosity is too high, it takes time to pulverize and dissolve the rubber, and it is difficult to feed the liquid at high speed due to pressure loss, which is not preferable because of high productivity which is one of the objects of the present invention. Conversely, if the solution viscosity is too low, it becomes difficult to control the particle size, and as a result, sufficient impact resistance may not be provided.

Further, Mooney viscosity (ML) is one of that of rubber.
It is a value at 00 ° C., and preferably satisfies 20 × log (SV)> ML in relation to the common logarithm of the solution viscosity (SV). When this is satisfied, a resin molded product having higher impact strength and excellent appearance can be obtained. If it is not satisfied, the particle size distribution tends to be wide, and the appearance of the resulting resin molded product may be impaired.

Next, the polymerization initiator will be described. In the present invention, two kinds of organic peroxides having different decomposition temperatures and valences are used as polymerization initiators. The 10-hour half-life temperature referred to in the present invention is a temperature at which the concentration can be expected to be halved in 10 hours when heated in a 0.1 mol / L benzene solution under a nitrogen atmosphere. Can be obtained by interpolation from the experimental data of.

The organic peroxide is C—O—O— in the molecule.
A compound having a bond of C or a bond of C—O—O—H, which is a peroxyketal, a dialkyl peroxide, a diacyl peroxide, a peroxydicarbonate, a peroxyester, a ketone peroxide. And hydroperoxides.

The valence is the number of oxygen-oxygen bonds contained in one molecule. The monofunctionality means that the valence is 1, and the polyfunctionality means that the valence is 2 or more. Specifically, the polyfunctional organic peroxide (a) having a 10-hour half-life temperature of 75 to 95 ° C. includes 1,1-bis (t-butylperoxy) cyclohexane and 1,1-bis (t-butylperoxy). Oxy) 3,3,5-trimethylcyclohexane and the like. Examples of the monofunctional organic peroxide (b) having a 10-hour half-life temperature of 110 to 130 ° C. include dicumyl peroxide, t-butylcumyl peroxide, -T-butyl peroxide and the like, and one or more of these are used.

In the method for producing the rubber-modified styrenic resin composition of the present invention, the amount of the polymerization initiator used is such that the polyfunctional organic peroxide (a) having a 10-hour half-life temperature of 75 to 95 ° C. is a styrene monomer. In the range of 0.0001 to 0.0006 equivalents with respect to the total amount of
Is in the range of 0.00005 to 0.0003 equivalents to the total amount of the monomers.

When the ratio is less than the above ratio, or when only one of the organic peroxides (a) and (b) is used, the surface impact strength of the obtained resin is insufficient,
It is not preferable because productivity is lowered. When the amount of the organic peroxide to be used is larger than the above range, the surface impact strength of the obtained resin may be insufficient, or in an extreme case, a runaway reaction may occur, resulting in an uncontrollable state. Not preferred.

A more preferred amount of the polymerization initiator is a polyfunctional organic peroxide (a) having a 10-hour half-life temperature of 75 to 95 ° C.
However, the monofunctional organic peroxide (b) having a 10-hour half-life temperature of 110 to 130 ° C. is 0.00008 to 0.0002 equivalent. The method for producing the rubber-modified styrenic resin composition of the present invention comprises a polyfunctional organic peroxide (a) having a 10-hour half-life temperature of 75 to 95 ° C.
May be first mixed with other raw materials and heated, or may be added to other pre-heated raw materials when the conversion of styrene does not exceed 5%. It can be diluted with a part of the solvent or diluted with a part of the additive that does not react with the organic peroxide.

If the addition time is later than this, it becomes difficult to control the rubber particles to a desired size, and eventually the physical properties of the obtained resin composition become insufficient. The method for producing the rubber-modified styrenic resin composition of the present invention has a 10-hour half-life temperature of 11
The monofunctional organic peroxide (b) at 0 to 130 ° C. may be mixed with other raw materials first and then heated, but a part or all of the polymerization liquid after the rubber particles are dispersed It is more preferable to add 10 hours half-life temperature is 110-13
Since the monofunctional organic peroxide (b) at 0 ° C. has a higher decomposition temperature than the polyfunctional organic peroxide (a) having a half-life of 10 to 75 ° C. to 95 ° C. The rate of decomposition in the latter half is high, and it can be expected that it acts on rubber particles after phase inversion, but it seems to work more effectively by adding it to the polymerization liquid after rubber particles are dispersed. .

Further, a part or all of the polyfunctional organic peroxide (a) having a 10-hour half-life temperature of 75 to 95 ° C. is added to the stock polymerization solution or the polymerization solution at a stage before the conversion of styrene reaches 5%. In addition, it is preferable to add a part or all of the monofunctional organic peroxide (b) having a 10-hour half-life temperature of 110 to 130 ° C. to the polymerization liquid after the rubber particles are dispersed.

The process for producing the rubber-modified styrenic resin composition of the present invention is characterized in that the polyfunctional organic peroxide (a) having a 10-hour half-life temperature of 75 to 95 ° C. until the conversion of styrene reaches at least 30%. It is necessary that the operating conditions be such that the polymerization is performed within a range of not exceeding 10 hours half-life temperature +40 degrees. When the polymerization is carried out at a high temperature exceeding the above temperature, the initiator of the polyfunctional organic peroxide (a) having a 10-hour half-life temperature of 75 to 95 ° C. is decomposed all at once in a short time, and the control becomes difficult. However, the balance of physical properties of the obtained resin is also lowered, which is not preferable.

Further, until the conversion of styrene exceeds 60%, the temperature of the polymerization liquid is raised to a temperature at which the monofunctional organic peroxide (b) has a 10-hour half-life temperature of 110 to 130 ° C., which is 10-hour half-life temperature + 10 ° C. or more. It is preferable to increase the value, and it is preferable because the physical property balance and productivity of the obtained resin are improved. The method for producing the rubber-modified styrenic resin composition of the present invention comprises:
A high polymerization rate of 15% / hr or more can be achieved at a monomer conversion rate. Further, it is possible to obtain a rubber-modified styrene-based resin composition having an excellent balance of physical properties, particularly, a balance between fluidity and surface impact strength.

The reason why a rubber-modified styrenic resin composition having a high polymerization rate and an excellent balance of physical properties can be obtained is not clear, but the styrenic polymer grafted to the disperse phase by using a specific polymerization initiator in combination is not clear. The amount of coalesced chains,
It is considered that the relationship between the chain length distribution and the molecular weight distribution of the styrene-based polymer forming the continuous phase is in a range suitable for the expression of a balance of physical properties including fluidity and surface impact strength.

Although it is not clear why the organic peroxide (a) is effective when it is polyfunctional, it is probable that when the first functional group is decomposed and the styrene-based polymer grows therefrom, This is probably because the second and subsequent functional groups do not cause a graft reaction to polybutadiene because they are unevenly distributed in the polystyrene phase, so that only the polymerization rate can be increased without excessive graft reaction. .

The polymerization system may be a batch system, a continuous system, or a combination of these systems, but a more preferable system is a continuous system, and the high productivity aimed at by the present invention can be easily obtained.
The method for producing the rubber-modified styrenic resin composition of the present invention can be suitably used as a polymerization apparatus, such as a complete mixing type, a plug flow type, or a plug flow type equipped with a circulation device. In this case, it is necessary to use at least two or more polymerization apparatuses connected in series.

The impact strength can be further increased by adding polydimethylsiloxane, mineral oil, metal salts of higher fatty acids and amides of higher fatty acids to the rubber-modified styrenic resin composition obtained in the present invention. . Furthermore,
In the rubber-modified styrenic resin composition obtained in the present invention,
Dyes and pigments, lubricants, fillers, release agents, plasticizers, antistatic agents,
Additives such as flame retardants and inorganic fillers can be added as needed.

The rubber-modified styrenic resin composition obtained by the present invention is blended with another thermoplastic resin, for example, a polyphenylene ether resin or a polyolefin resin,
A thermoplastic resin composition having a higher heat distortion temperature and higher chemical resistance can also be used.

[0031]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described specifically with reference to examples. (1) The following butadiene rubber was used. Low cis polybutadiene rubber (hereinafter PB-1): Residual unsaturated bond is 1,4-cis 36%, 1,4-trans 52%, 1,2-vinyl 12%, Mooney viscosity at 100 ° C (ML) Of 35% styrene at 25 ° C. (SV) of 90 centipoise.

Low-cis polybutadiene rubber (hereinafter referred to as P
B-2): Residual unsaturated bond is 1,4-cis 36%, 1,
4-trans 52%, 1,2-vinyl 12%, Mooney viscosity 55, 5% Styrene solution viscosity 165 centipoise. Low cis polybutadiene rubber (PB-3): Residual unsaturated bond is 33% 1,4-cis, 49% 1,4-trans, 18% 1,2-vinyl and Mooney viscosity is 6%.
8. A 5% styrene solution having a viscosity of 93 centipoise.

High cis polybutadiene rubber (hereinafter P
B-4): 1,4-cis 96%, 1,1,
4-trans 2%, 1,2-vinyl 2%, Mooney viscosity of 29, 5% styrene solution viscosity of 39 centipoise. (2) Polyfunctional organic peroxide having a 10-hour half-life temperature of 75 ° C to 95 ° C (a): 1,1, -bis (t-butylperoxy) cyclohexane (hereinafter referred to as PO-1) 1,1, -bis (T-butylperoxy) 3,3
5-trimethylcyclohexane (hereinafter PO-2). (3) Monofunctional organic peroxide (b) having a 10-hour half-life temperature of 110 ° C to 130 ° C: dicumyl peroxide (hereinafter PO-3) di-t-butyl peroxide (hereinafter PO-4) (4) A monofunctional organic peroxide having a 10-hour half-life temperature of 98 ° C .: t-butylperoxyisopropyl carbonate (hereinafter referred to as PO-5) was used for comparison.

The analysis and the measurement of physical properties were carried out by the following methods. (5) Flexural modulus (kgf / cm ² ): ASTM D7
Measured according to No. 90. (6) Melt flow rate (g / 10 min): ISO
-1133 (No. 12 conditions). (7) Surface impact strength (kgf · cm): Injection molded 15
Using 50 flat test pieces of cm × 15 cm × 2 mm, 1
30mm at the tip with variable load from the height of m
Was dropped, and the breaking energy was determined from the load at which the test piece showed 50% destruction (Asahi Kasei method). (8) Vicat softening point (° C.): based on ASTM-D648.

[0035]

Example 1 Low-cis polybutadiene (hereinafter PB-1)
In styrene, followed by ethylbenzene, α-methylstyrene dimer as a chain transfer agent, and octadecyl-3- (3,5-di-t-butyl-4- as an antioxidant).
(Hydroxyphenyl) propionate was added, and finally a polymerization stock solution having the following composition was prepared (unit is% by weight, shown as Wt% in the table).

PB-1 4.4 4.4 Styrene 77.1 Ethylbenzene 14.0・ PO-2 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ 0.03 ・ PO-4 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ 0.01 ・ α-methylstyrene dimer ・ ・ ・ ・ ・ ・ ・ ・ ・ ・0.14 Mineral oil 4.2 Octadecyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate 0.1 PO-2 Is 0.03% by weight based on styrene.
This corresponds to 027 equivalents, and 0.01% by weight of PO-4 corresponds to 0.00009 equivalents to styrene.

The above polymerization stock solution was mixed with 8.5 parts of each internal volume.
The liquid was continuously fed at a rate of 3.0 liter / HR to a polymerization apparatus comprising three in-line reactors equipped with a stirrer of 7.0 liters, 7.0 liters and 7.0 liters. A circulation line is provided from the first reactor outlet to the first reactor inlet, and the reflux ratio is 25%.
At reflux. The solid concentration at the outlet of the first reactor is 30 to 35
The temperature inside the machine was controlled so as to be in the range of weight%. Next, the temperature in the tank was adjusted so that the solid concentration at the outlet of the second reactor and the outlet of the third reactor were 55 to 60% by weight and 78 to 82% by weight, respectively. Although the conversion of styrene at the outlet of the first reactor is 30% or more, the temperature in the first reactor is kept consistently lower than 130 ° C. of 90 ° C. + 40 ° C., which is the half-hour temperature of PO-2 for 10 hours. Was.

The rubber particle diameter of the resin finally obtained as determined by Coulter Multisizer is 1.8 to 2.2.
The number of stirring in the first reactor was adjusted to be μm. Next, the mixture was fed into a devolatilizer at 220 ° C. under vacuum to remove unreacted styrene and ethylbenzene, and the mixture was granulated with an extruder to obtain a pellet-shaped rubber-modified styrene resin composition. Table 1 shows the composition of the polymerization stock solution.

Next, test pieces were prepared from the obtained pellets of the rubber-modified styrene resin composition at a molding temperature of 220 ° C. using an injection molding machine, and the physical properties were measured. Table 2 shows the results.

[0040]

Embodiments 2 to 4 PB-1 of Embodiment 1 is replaced with PB-2 and PB-2.
The ratio was changed to B-3 and PB-4, and the ratios of the other components were as shown in Table 1.
Polymerization, deaeration, and pelletization were performed in the same manner as in Example 1 except that the composition was changed as described above to obtain three types of rubber-modified styrene resin compositions. A test piece was prepared in the same manner as in Example 1, and the physical properties were measured. Table 2 shows the results.

[0041]

Example 5 The composition of the stock polymerization solution was changed as shown in Table 1, and the following steps were carried out while increasing the solution sending rate to 3.75 liter / HR to obtain a rubber-modified styrene resin composition and evaluate its physical properties. did. The polymerization conditions are shown in Table 1, and the evaluation results are shown in Table 2.

[0042]

Comparative Example 1 A 10-hour half-life temperature of a polymerization initiator was 110 ° C.
Polymerization, deaeration, and pelletization were carried out in the same manner as in Example 1 by changing the composition of the polymerization stock solution not containing the monofunctional organic peroxide (b) at ~ 130 ° C to obtain a rubber-modified styrene resin composition,
Physical properties were measured. Table 1 shows the composition of the polymerization stock solution, and Table 2 shows the evaluation results.

[0043]

Comparative Examples 2 to 4 PB-2 as polybutadiene rubber
Using PB-3 or PB-4 and changing the composition of the polymerization stock solution containing no polymerization initiator of the monofunctional organic peroxide (b) having a half-life temperature of 110 ° C. to 130 ° C. for 10 hours, Similarly, polymerization, degassing, and pelletization were performed to obtain three types of rubber-modified styrene resin compositions, and the physical properties were measured.

Table 1 shows the composition of the polymerization stock solution, and Table 2 shows the results of the evaluation. FIG. 1 shows the relationship between the flexural modulus and the surface impact strength described in Table 2. It can be seen that the rubber-modified styrenic resin compositions of Examples obtained by the production method of the present invention have a good balance.

[0045]

[Table 1]

[0046]

[Table 2]

[0047]

The process for producing the rubber-modified styrenic resin composition of the present invention is characterized in that a styrene-based resin composition having an unprecedented excellent flexural modulus and surface impact strength is prepared by polymerizing a styrene-based resin composition in a polymerization apparatus. The residence time in the inside can be shortened, and efficient production can be achieved.

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between flexural modulus and surface impact strength of a rubber-modified styrenic resin composition.

[Explanation of symbols]

 : Examples (numbers in parentheses are numbers of examples) □: Comparative examples (numbers in parentheses are numbers of comparative examples)

Claims (3)

[Claims] 1. A method for polymerizing a rubber-modified styrene resin composition by dissolving a butadiene rubber in a solution of a styrene monomer to prepare a stock polymerization solution and adding a polymerization initiator, wherein the polymerization initiator is reduced by 10 hours and a half. The polyfunctional organic peroxide (a) having a temperature of 75 to 95 ° C. is added to the styrene monomer in an amount of 0.
0001-0.0006 equivalent and 10 hour half-life temperature is 11
The monofunctional organic peroxide (b) at 0 to 130 ° C. is used in an amount of 0.00005 to 0.0003 equivalent relative to the styrene monomer, and the polymerization is carried out until the conversion of styrene reaches 30%.
A method for producing a rubber-modified styrene resin composition, which is carried out at a 10-hour half-life temperature of the polyfunctional organic peroxide (a) having a 0-hour half-life temperature of 75 to 95 ° C. + 40 degrees or less. 2. A part or all of the polyfunctional organic peroxide (a) having a 10-hour half-life temperature of 75 to 95 ° C. is added to a polymerization stock solution or a polymerization solution at a stage before the conversion of styrene reaches 5%. 2. The method according to claim 1, further comprising adding a part or all of the monofunctional organic peroxide (b) having a 10-hour half-life temperature of 110 to 130 [deg.] C. to the polymerization solution after the rubber particles are formed.
A method for producing the rubber-modified styrenic resin composition according to the above. 3. A solution viscosity (SV) of a butadiene rubber is 20 to 200 centipoise, and a Mooney viscosity (ML) is 20 in relation to a common logarithm of the SV.
The method for producing a rubber-modified styrene resin composition according to claim 1, wherein the butadiene rubber satisfies xlog (SV)> ML.