JPH02208311A - Production of impact-resistant aromatic vinyl resin - Google Patents

Abstract

PURPOSE:To obtain the title resin of excellent gloss by polymerizing an aromatic vinyl compound in the presence of a styrene/butadiene block copolymer of a specified structure and adjusting the diameter of the copolymer particles dispersed in the obtained resin to be in a specified range. CONSTITUTION:An aromatic vinyl compound (e.g. styrene) is polymerized in the presence of a styrene/butadiene block copolymer having a ratio of the weight-average MW in terms of PS to the number-average MW in terms of PS >=1.20, a ratio of the peak MW determined by GPC to the weight-average MW in terms of PS >=1.02, a viscosity (at 25 deg.C) of a 5wt.% styrene solution of 200-2000cP, a total styrene content of 3-20wt.%, a block styrene content >=60% based on the total styrene content, and a vinyl bond content in the butadiene part of 13-30% and a mean particle diameter of the copolymer particles dispersed in the obtained resin is adjusted to 0.4-2.5mum.

Description

Detailed Description of the Invention a. Industrial Application Field The present invention is used as a molding material for various molded products that require excellent impact resistance and good gloss, such as electrical products, furniture, and building materials. The present invention relates to a method for producing an impact-resistant aromatic vinyl resin.

b. Conventional technology and problems Impact-resistant aromatic vinyl resins have excellent moldability and other various physical properties in addition to impact resistance, so they are widely used as molding materials for molded products that require impact resistance. However, in order to expand its uses and improve the quality of products obtained from the impact-resistant polystyrene resin, it is desired that it have excellent impact resistance and good gloss.

Generally, in order to improve the gloss of an impact-resistant aromatic vinyl resin, it is necessary to use a raw material rubber with a low solution viscosity.

However, when a raw material rubber with a low solution viscosity is used, a problem arises in that the impact resistance of the resulting impact-resistant aromatic vinyl resin is reduced. In this way, in impact-resistant aromatic vinyl resins, gloss and impact resistance are contradictory properties,
It has been difficult to obtain an impact-resistant aromatic vinyl resin with good gloss without reducing impact resistance.

Problems to be Solved by the C9 Invention In view of the above circumstances, the inventors of the present invention have conducted intensive studies with the aim of obtaining an impact-resistant aromatic vinyl resin with a high balance of impact resistance and gloss. , an aromatic vinyl compound is radically polymerized in the presence of a styrene-butadiene block copolymer having a specific solution viscosity and a specific structure, and the rubber particles dispersed in the resulting resin are adjusted to a specific particle size range. The inventors have discovered that the above technical problem can be solved by doing so, and have arrived at the present invention.

60 Means for Solving the Problems The present invention provides a method for polymerizing an aromatic vinyl compound in the presence of a styrene-butadiene block copolymer.
The above styrene-butadiene block copolymer has a ratio of weight average molecular weight (Mw) to number average molecular weight (Mn) in terms of polystyrene (M w / M n ) of 1.2.
0 or more, ■ Gel permeation chromatography (GPC)
) and the weight average molecular weight (M w ) in terms of polystyrene (P M /
M w ) is 1.02 or more; ■ The viscosity of a 5% styrene solution measured at 25°C is 200 to 2000 centipoise; ■ The total styrene content is 3 to 20% by weight; ■ The blocked styrene content is 60% of the total styrene content. % or more, ■ A styrene-butadiene block copolymer having a vinyl bond content of 13 to 30% in the butadiene moiety is used, and the average particle diameter of the block copolymer particles dispersed in the resulting resin is 0.4%. The present invention provides a method for producing an impact-resistant aromatic vinyl resin, which is characterized in that the impact-resistant aromatic vinyl resin is adjusted to a range of 2.5 μm.

The present invention will be explained in detail below.

Conventionally, when styrene and butadiene are block-polymerized in a hydrocarbon solvent using an organolithium-based catalyst by a commonly used batch polymerization method or continuous polymerization method, the Mw/Mn and PM limited in the present invention are
/Mw cannot be obtained. Usually, in batch polymerization, Mw/Mn is 1.1 to 1.3, PM/M
w is 0°9~. 1.0, and in continuous polymerization, M w
/Mn is 1°8~2.6, PM/Mw is 0.7~0
．． It is 8.

The styrene-butadiene block copolymer of the present invention is
It can be obtained by the method shown below in a hydrocarbon solvent using an organolithium catalyst, but even if there is a method other than this, as long as the styrene-butadiene block copolymer having the above specific structure can be obtained, Any method can be used, including polymerization or a mixture of two or more different block copolymers.

One of the preferred methods for producing the styrene-butadiene block copolymer is to sequentially block copolymerize butadiene and styrene in a hydrocarbon solvent using an organolithium compound as an initiator. or 10803 groups (K represents a potassium metal atom), and (ii) general formula: CH2=C=CHR (wherein, R
represents a hydrogen atom or an alkyl group containing 1 to 3 carbon atoms. ) is a method in which one or more of the 1,2-diene compounds represented by the following are co-present.

According to this production method, a 1,2-diene compound and -SO
By adjusting the amount of anionic surfactant having a group in
/Mn and PM/Mw can be obtained.

- Peat The solvent is not particularly limited, but aliphatic, alicyclic and aromatic hydrocarbon compounds which are liquid under the polymerization conditions can be used. Preferred hydrocarbon solvents include pentane, n-hexane, n-hebutane, isooctane, n-decane, cyclohexane, methylcyclopentane, benzene, diethylbenzene, etc., and these include not only one type but also two or more types. It may also be a mixture of the two.

In addition, the organic lithium initiator described in "2" is one in which at least one lithium atom is bonded to a hydrocarbon, such as methyllithium, ethyllithium, n-propyllithium, n-butyllithium, 5ec-butyllithium, t
-butyllithium, n-hexyllithium, cyclohexyllithium, lithium benzene, lithium naphthalene,
1,4 dilithiobutane, 1,5-dilithiopentane, 1
．． Examples include 10-dilithiodecane and 1,3.5-1 lylithiocyclohexane, and preferred examples include monolithium hydrocarbon compounds such as n-butyllithium, 5ec-butyllithium, and t-butyllithium.

In the above manufacturing method, an ether or a tertiary amine compound can be added as long as the amount of vinyl bond in the butadiene moiety in the block copolymer to be manufactured does not exceed 30%. Specific examples of ethers and tertiary amines include ethyl ether, tetrahydrofuran, dioxane, ethylene glycol methyl ether, diethylene glycol dimethyl ether, triethylamine,
Examples include pyridine, NNN'N'-tetramethylethylenediamine, and the like. Based on the above -803 or -
Examples of anionic surfactants having a 0803K group include the following compounds.

(a) Potassium alkylaryl sulfonate; dodecylbenzene sulfonate, tetradecylbenzene sulfonate, hexadecylbenzene sulfonate, octadecylbenzene sulfonate, dibutylnaphthalene sulfonate, n-hexylnaphthalene sulfonate, Dibutylphenyl sulfonate, formalin condensate of naphthalene sulfonate, etc.

Preferred among these are potassium dodecylbenzenesulfonate, potassium tetradecylbenzenesulfonate, potassium hexadecylbenzenesulfonate and potassium octadecylbenzenesulfonate.

(b) Sulfonic acid potassium salt having an amide bond; N-
Methyl-N-oleyl taurate, N-methyl-N-lauryl taurate, N-phenyl-N-stearyl taurate, N-methyl-N-methanesulfonate laurylamide, and the like.

Preferred among these is potassium N-methyl-N methanesulfonate laurylamide.

(C) Sulfonic acid potassium salt having an ester bond; salt of a condensate of oxyethanesulfonic acid and oleic acid (C
, 7H38COOCH2SO3K), sulfosuccinate dioctyl salt, sulfomaleate dioctyl salt, etc.

Preferred among these is the potassium salt of dioctyl sulfosuccinate.

(d) Potassium salt of higher alcohol sulfate ester; lauryl alcohol sulfate ester salt, oleic alcohol sulfate ester salt, stearyl alcohol sulfate ester salt, etc.

Preferred among these is the potassium salt of the sulfuric ester of lauryl alcohol.

(e) Potassium salt of sulfate ester having an ester bond; lauroyltrimethylene glycol sulfate salt (C
41H23COOCH2CH2CH20SO3K), caproyl ethylene glycol sulfate salt (Cs H
11C00CH2CH2O803K) etc.

In addition, various sulfate ester salts and sulfonates such as a sulfate ester salt of polyoxyethylene alkyl ether and a sulfate ester salt of polyoxyethylene alkylphenyl ether can be used.

Preferred among these is the potassium salt of lauroyl trimethylene glycol sulfate.

The above-mentioned anionic surfactant contains a polar compound such as alcohol, amine, carboxylic acid, or phosphoric acid in an amount of 0.1 to 2.0 times mole relative to K in order to increase its solubility in hydrocarbon solvents. It can be added and used.

Further, the general formula to be used simultaneously with the anionic surfactant having these -SO3K groups or -OSO3K groups is: %Formula% (In the formula, R represents a hydrogen atom or an alkyl group containing 1 to 3 carbon atoms. ) Examples of the 1,2-diene compound represented by these include propadiene, 1,2-butadiene, and the like.

Next, the styrene-butadiene block copolymer having a specific structure of the present invention will be described.

As the styrene-butadiene block copolymer of the present invention, an AB type block copolymer is preferably used. Mw/Mn of the styrene-butadiene block copolymer of the present invention is 1.2 or more, preferably 1.2 to
1.9, more preferably 1°3 to 1.7. Mw
If /Mn is less than 1.2, the resulting resin will have poor impact resistance. In addition, the peak molecular weight (PM) obtained by GPC of the styrene-butadiene block copolymer of the present invention
and the weight average molecular weight (M w ) (P M / M
w) is 1°02 or more, preferably 1.04 to 1.3
0, more preferably 1.05 to 1.25. PM
/Mw is less than 1.02, the resulting resin has poor impact resistance.

The Mooney viscosity of the styrene-butadiene block copolymer of the present invention is preferably 80 to 180, more preferably 100 to 150. If it is less than 80, the diameter of the dispersed rubber particles in the obtained resin may become small and the impact resistance may be deteriorated, which is undesirable.If it exceeds 180, the particle diameter of the dispersed rubber particles will be uneven, making it difficult to obtain a resin. Poor gloss.

2 of the styrene-butadiene block copolymer of the present invention
The viscosity of a 5% by weight styrene solution at 5°C is 200-2
000 centipoise, preferably 300 to 1500 centipoise, more preferably 500 to 1500 centipoise, particularly preferably 500 to 1300 centipoise. If it is less than 200 centipoise, impact resistance is poor.

When it exceeds 2000 centipoise, the particle system of the dispersed rubber particles becomes irregular and the resulting resin has poor gloss.

The total styrene content of the styrene-butadiene block copolymer of the present invention is 3 to 20% by weight, preferably 5 to 18% by weight. If it is less than 3% by weight, the resulting resin will have poor gloss. If it exceeds 20% by weight, the resulting resin will have poor impact resistance.

The block styrene content of the styrene-butadiene block copolymer of the present invention is 60% of the total styrene content.
That's all. If it is less than 60%, there will be many random bonds between styrene and butadiene, and the resulting resin will have poor impact resistance.

The amount of vinyl bond in the styrene-butadiene block copolymer of the present invention is 13 to 30%, preferably 14 to 25%.
It is. If it is less than 13%, the resulting resin will have poor impact resistance and gloss. When it exceeds 30%, the gloss is good but the impact resistance is poor.

In the present invention, at the same time as using the specific styrene-butadiene block copolymer described above, the average particle diameter of the block copolymer particles dispersed in the resin obtained is 0.4 to 2.5 μm. It is necessary to adjust the particle size within the range of 0.5 to 2.0 μm, preferably within the range of 0.5 to 2.0 μm.If the average particle diameter is less than 0.4 μm, the Izot impact strength will be poor;
If it exceeds 2.5 μm, only a surface with poor gloss can be obtained. Adjustment of the particle size of block copolymer particles is
The shape of the stirrer in the polymerization tank, the rotation speed of the stirrer, the stirring time,
Although it is influenced by various factors such as polymerization temperature and cannot be determined unambiguously, the particle size can generally be adjusted under conditions that place stress on the rubber during stirring during graft polymerization, such as by increasing the rotational speed. This can be done by reducing .

The method of the present invention uses the above-mentioned specific styrene-butadiene block copolymer and graft-polymerizes an aromatic vinyl compound thereto.

Examples of the aromatic vinyl compound include styrene, α-methylstyrene, p-methylstyrene, vinyltoluene, vinylnaphthalene, vinylethylbenzene, vinylxylene, etc., but preferably styrene,
α-methylstyrene and p-methylstyrene, more preferably styrene.

The mixing ratio of the styrene-butadiene block copolymer and the aromatic vinyl compound is such that the former is 3 to 25% by weight, preferably 5 to 15%, and more preferably 7 to 13% by weight.
, the latter is 97 to 75% by weight, preferably 95 to 85% by weight, and more preferably 93 to 87% by weight. The amount of styrene-butadiene block copolymer used is 3% by weight.
If it is less than 25% by weight, the impact resistance of the resulting resin will decrease, making it difficult to achieve the purpose of the present invention, and if it exceeds 25% by weight, the viscosity of the graft polymerization solution will become extremely high, making it difficult to carry out graft polymerization in practice. becomes.

The method of radical copolymerization of an aromatic vinyl compound to the specific styrene-butadiene block copolymer is not particularly limited, but for example, an aromatic vinyl compound in which the styrene-butadiene block copolymer is dissolved is used. It can be carried out by bulk polymerization or radical polymerization by combining bulk polymerization and suspension polymerization.

When a styrene-butadiene block copolymer and an aromatic vinyl compound are radically polymerized by bulk polymerization, the styrene-butadiene block copolymer is dissolved in the aromatic vinyl compound, and then a molecular weight regulator is added as necessary. Add.

As the molecular weight regulator, for example, α-methylstyrene dimer, n-decyl mercaptan, tert-F decyl mercaptan, 1-phenylbutene, 2-fluorene, mercaptans such as dipentene and chloroform, terpenes, and halogen compounds are used.

Furthermore, a lubricant is added to improve the moldability of the resulting resin. For example,
Ester-based lubricants such as butyl stearate and butyl phthalate, mineral toils, paraffin wax, and other lubricants used in conventional resin processing can be used.

After dissolving these molecular weight regulators and lubricants in the polymer solution, initiators such as benzoyl peroxide, lauroyl peroxide, cumene hydroperoxide, methyl ethyl ketone peroxide, dicumyl peroxide, diisopropyl peroxydicarbonate, tertiary -Butyl peroxyacetate, tertiarybutyl diperoxyisophthalate, 2
゜5-dimethyl-2,5-di(t-butylperoxy)
Add hexane or azobisisobutyronitrile, etc., and raise the reaction temperature to 60 to 200 ml under an inert gas atmosphere.
℃ and complete the reaction while stirring. Moreover, when carrying out thermal polymerization without a catalyst, the heating polymerization is usually carried out at 100 to 200°C to complete the reaction.

During the bulk polymerization reaction, it is generally preferable to carry out effective stirring until the polymerization rate of the aromatic vinyl compound reaches about 30%. In particular, in the present invention,
It is necessary to adjust the stirring so that the particle size of the block copolymer is within the range of the present invention. On the other hand, after the polymerization rate of the aromatic vinyl compound exceeds about 30%, it is preferable to ease the stirring.

At this time, a hydrocarbon solvent such as 1.luene, ethylbenzene, or xylene may be added in order to reduce the viscosity of the polymerization system.

After the polymerization is completed, the monomer and solvent are recovered by removing the monomer and the solvent using a vent-type router or steam stripping.

When radical polymerization is carried out by a combination of bulk polymerization and suspension polymerization, the bulk polymerization is first carried out until about 10 to 45% by weight of the monomer (aromatic vinyl compound) is converted into a polymer, and then the reaction solution is mixed with polyvinyl alcohol. ,
It is dispersed in an aqueous solution containing a suspension stabilizer such as polymethacrylate or tricalcium phosphate, and the reaction temperature is raised to 60 to 160°C while maintaining the suspension state to complete polymerization.

After the polymerization is completed, the suspension stabilizer is thoroughly washed away with water, and after drying, the aromatic vinyl resin is recovered.

In addition, when performing radical polymerization by the bulk polymerization or bulk-suspension polymerization, it is preferable that 50% by weight or more of the monomer used is the aromatic vinyl compound, and less than 50% by weight of the monomer is acrylonitrile other than the above compound. , methacrylonitrile, acrylic acid, methyl acrylate, methyl methacrylate, and other aliphatic vinyl compounds may be substituted.

In addition, known antioxidants, such as 2,6-tert-butyl-4-methylphenol, 2'-(1-methylcyclohexyl)-
4,6-dimethylphenol, 2,2'-methylene-bis(4-ethyl-6-tert-butylphenol),
4.4'-Thiobisu(6-tert-butyl-3-methylphenol)
, dilaurylthiodipropionate, tris(di-nonylphenyl)phossuite, wax; known UV absorbers such as p-tertbutylphenyl salicylate, 2,2'-dihydroxy-4-methoxybenzophenone, 2-(2hydroxy -4'-n-octoxyphenyl)benzothiazole; known lubricants such as paraffin wax, stearic acid, hydrogenated oils, stearamide,
Methylene bisstearamide, n-butyl stearate, ketone wax, octyl alcohol, lauryl alcohol, hydroxystearic acid triglyceride; known flame retardants such as antimony oxide, aluminum hydroxide, zinc borate, tricresyl phosphate, chlorinated paraffins , tetrabromobutane, hexabromobenzene, tetrabromobisphenol A; known antistatic agents, such as stearamidopropyldithyl-β-hydroxyethylammonium nitrate; known colorants, such as titanium oxide, carbon black, other inorganic or organic content; known fillers such as calcium carbonate, clay,
Silica, glass fiber, glass spheres, carbon fiber, etc. can be added as necessary.

e. Examples Hereinafter, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited to these Examples.

In the examples, unless otherwise specified, parts and % indicate parts by weight and % by weight.

Moreover, the data shown in the examples were measured according to the following method.

The microstructure of the styrene-butadiene block copolymer was measured by an infrared method (Morello method), and the styrene solution viscosity was measured by a Cannon-Fenske viscometer.

The amount of bound styrene in the styrene-butadiene block copolymer was determined by measuring the intensity of the infrared absorption peak due to the phenyl group at a wave number of 699 cm-', and using a preliminarily calculated calibration curve.

In addition, the molecular weight distribution of the styrene-butadiene block copolymer was determined by Toyo Soda Kogyo's HL (-802A type GP).
The measurement was carried out using C under the following conditions.

Column: 2 columns GMHXL manufactured by Toyo Soda Kogyo ■ Mobile phase: Tetrahydrofuran sample concentration: 0.1% by weight Measurement temperature: 40°C Detector: Differential refractometer M w / M n and P M / M w are converted into standard polystyrene. MwSMn SPM was determined and calculated. The amount of block styrene in the styrene-butadiene block copolymer is determined by +H-NMR.
, Chem, Tech,, 54.885 (19
81).

The physical properties of the impact-resistant polystyrene resin were measured according to the following method.

Izotsu impact strength (1 part 4 inches, with notch): 8o
The obtained molded product was molded using a Z injection molding machine at a cylinder temperature of 200° C. and was measured in accordance with ASTM D-256.

Tensile strength: Using an 8oz injection molding machine, cylinder temperature 2
For molded products obtained by molding at 00°C, ASTM
Measured according to D-638.

Gloss: Using an 8oz injection molding machine, cylinder temperature 200
For molded products obtained by molding at °C, ASTM D
-523, the reflection gloss at 60° was measured.

Median particle size measurement of dispersed rubber particles: Resin pellet 1~
Place 2 tablets in about 50 ml of dimethylformamide and add about 3
After standing for a while, this dimethylformamide solution was added to the electrolytic solution (ISOTON ■■), and the appropriate particle concentration was measured using a Coulter counter. From the obtained particle size distribution, the 50% median diameter was calculated. It was determined by

When the particle size was 0.4 μm or less, the dimethylformamide solution was measured using a Coulter N4 type submicron particle analyzer.

Example 1 18 kg of cyclohexane, 2.7 kg of butadiene, 1.3 g of tetrahydrofuran, 0.4 g of 1,2-butadiene, and 0.35 g of potassium dodecylbenzenesulfonate were charged into a reactor equipped with a jacket and a stirrer with an internal volume of 502 mm, and the temperature was lowered. After adjusting to 45°C, n-butyllithium 1
．． 2g was added and polymerized. 10 after reaching maximum temperature
After a few minutes, 0.3 kg of styrene was added, and the polymerization was continued for an additional 30 minutes. Add 2 to this polymer solution as a stabilizer.
After adding 6-tert-butyl-4-methylphenol at a ratio of 0.5% to the polymer, the solvent was removed by steam stripping, and the block polymer was dried with a heated roll at 100°C. Obtained. Table 1 shows the properties of the obtained polymer. This block polymer 7
A mixture of 93 parts of styrene and 93 parts of styrene was stirred at room temperature for 8 hours to uniformly dissolve the mixture.

This solution was transferred to a reactor with an internal volume of 1 (l) equipped with a jacket and a stirrer, 0.02 part of tert-dodecyl mercaptan was added, and polymerization was carried out at 110°C until the polymerization rate of styrene reached approximately 30%. , stirring at this time is 500 pp
The rotation speed was m. Next, 0.05 part of cumyl peroxide was added per 100 parts of this polymerization solution, and 3 parts of tribasic calcium phosphate was added as a suspension stabilizer, and 0.0 parts of sodium dodecylbenzenesulfonate was added as a surfactant.
150 parts of water containing 0.005 parts were added and the solution was suspended with stirring. This suspension mixture was heated to 120°C with stirring for 4 hours.
Polymerization was carried out by heating at 140° C. for 4 hours. The obtained bead-shaped resin was separated from each other, washed with water, dried with hot air, and then pelletized using an extruder. The impact-resistant styrene resin thus obtained was injection molded to provide test pieces for measuring physical properties. Table 2 shows the measurement results for each physical property.

Example 2 The same method as in Example 1 was carried out except that n-butyllithium was changed to 0.9 g and potassium dodecylbenzenesulfonate was changed to 0.24 g. The properties of the polymer are shown in Table 1, and the physical properties of the obtained resin are shown in Table 2.

Comparative Example 1 In Example 1, butadiene was added to 2. The same method as in Example 1 was carried out except that 85 kg, n-butyllithium was changed to 1.65 g, potassium dodecylbenzenesulfonate was changed to 0.48 g, and styrene was changed to 0.15 g. The properties of the polymer are shown in Table 1, and the physical properties of the obtained resin are shown in Table 2.

Examples 3 to 5, Comparative Examples 2 to 5 Polymers were obtained using the amounts of the respective chemicals in Example 1 as shown in the following table, and their physical properties were measured. The results are shown in Table-1, Table-
Shown in 2.

When the base polymers of Examples 1 to 5 are used, they exhibit an excellent balance between impact resistance and gloss, and also have good tensile strength.

Comparative Example 1 has a low solution viscosity, resulting in a small rubber particle size and poor impact resistance, and Comparative Example 2 has a styrene content outside the range of the present invention, resulting in poor impact resistance. Comparative Example 3 has poor impact resistance because the vinyl content is outside the range of the present invention;
Since the ratios of Mw/Mn and P M /M w are outside the range of the present invention, the gloss is inferior. Comparative Example 5 has a poor balance between impact resistance and gloss because the styrene block rate is outside the range of the present invention.

f9 Effects of the Invention According to the present invention, it is possible to obtain an impact-resistant aromatic vinyl resin with excellent impact resistance and gloss, which can be used for parts of household appliances such as televisions, refrigerators, air conditioners, and washing machines. It is useful for parts for office equipment such as computers and word processors, building materials, and miscellaneous goods.

Patent applicant: Japan Synthetic Rubber Co., Ltd.

Claims (2)

[Claims] (1) In the method of polymerizing an aromatic vinyl compound in the presence of a styrene-butadiene block copolymer, as the styrene-butadiene block copolymer, [1] Weight average molecular weight in terms of polystyrene (@Mw@) and Ratio of number average molecular weight (@Mn@) (@Mw@/@Mn@)
is 1.20 or more, [2] Gel permeation chromatography (GP
The peak molecular weight (PM) obtained by C) and the polystyrene equivalent weight average molecular weight (@Mw@
) ratio (PM/@Mw@) is 1.02 or more, [3] the viscosity of a 5 wt% styrene solution measured at 25°C is 200 to 2000 centipoise, [4] the total styrene content is 3 to 20 wt% , [5] Block styrene content is 60% of total styrene content
As mentioned above, [6] A styrene-butadiene block copolymer having a vinyl bond content of 13 to 30% in the butadiene moiety is used, and the average particle diameter of the block copolymer particles dispersed in the resulting resin is 0.4%. A method for producing an impact-resistant aromatic vinyl resin, the method comprising adjusting the particle size to a range of 2.5 μm. (2) When the above styrene-butadiene block copolymer is subjected to sequential block copolymerization of butadiene and styrene using an organolithium compound as an initiator in a hydrocarbon solvent, (i) -SO_3K group or -OSO_3K group ( K represents a potassium metal atom), and (ii) the general formula: CH_2=C=CHR (wherein R is a hydrogen atom or 1 to 3 carbon atoms); The method according to claim 1, wherein the styrene-butadiene block copolymer is produced in the coexistence of one or more 1,2-diene compounds represented by Method.