JPH04266915A - Rubber modified vinyl aromatic resin composition and production thereof - Google Patents

Abstract

PURPOSE:To obtain the title composition having excellent luster, impact resistance, moldability and surface hardness by dispersing butadiene-based polymer particles to a matrix of a polymer having a specific composition. CONSTITUTION:First, (C) a butadiene-based polymer which is an S B2 type block copolymer composed of a polymer block B consisting essentially of butadiene and a polymer block S consisting essentially of styrene, having 20-40wt.% block S content is dissolved in a mixture of (A) a vinyl aromatic monomer and (B) an unsaturated nitrile monomer. Then reaction is carried out while controlling content of the component B in a copolymer of the components A and B, formed before phase transition and particle formation of the component C, <=10%, a given amount of the component B is additionally added and the polymerization is completed to give the objective composition wherein particles of the component C having 0.1-0.7mum weight-average particle diameter and capsule structure of single layer and/or multiple layer are dispersed into a matrix of a polymer comprising 95-75% component A and 5-25% component B.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rubber-modified resin composition excellent in gloss, impact resistance, moldability and rigidity, and a method for producing the same. More specifically, the present invention relates to a rubber-modified vinyl aromatic resin composition having a specific rubber particle morphology and excellent gloss, impact resistance, moldability, rigidity, and surface hardness, and a method for producing the same.

0002

[Prior Art] Rubber-modified vinyl aromatic resins, typified by high-impact polystyrene, are used in a wide variety of applications including home appliances and OA equipment because of their excellent moldability, dimensional stability, and impact resistance. However, the gloss of the molded product was inferior to that of ABS resin. In recent years, these impact-resistant polystyrenes have been required to have high gloss properties similar to those of ABS resins. As a conventional method for achieving this purpose, it is known to reduce the particle size of a rubbery polymer dispersed in a rubber-modified vinyl aromatic resin. When the thickness is less than microns, there is a drawback that the impact strength is significantly reduced.

On the other hand, as a recent attempt to improve the balance between impact strength and gloss, a rubber-like polymer is dispersed in polystyrene in the form of particles, and the dispersed particles are divided into two mountains, a small particle portion and a large particle portion. Rubber-modified polystyrene has been proposed, which exhibits a distribution consisting of a small particle portion with an average particle size of 0.1 to 0.6 microns and a large particle portion with an average particle size of 0.7 to 2.0 microns. (Unexamined Japanese Patent Publication No. 63-1
12646, JP 1-261444, JP 1-275649). Rubber-modified polystyrene produced using this method has a much better balance of gloss and impact strength than conventional rubber-modified polystyrene.
Although it was one step closer to the quality of ABS resin,
The problem remained that it was inferior in rigidity and surface hardness compared to resin.

[0004] Also, West German Patent Publication DE360337
5A1 includes a resin phase of 50 to 95% by weight consisting of 98 to 50% by weight of styrene and 2 to 50% by weight of acrylonitrile, and a soft styrene-butadiene block polymer consisting of 50 to 95% by weight of styrene and 50 to 5% by weight of butadiene. A rubber modified resin composition comprising 50 to 5% by weight of a phase is disclosed. Although the resin composition according to the present invention had excellent transparency, it had low tensile properties, especially low elongation, and poor practical impact strength.

On the other hand, in JP-A-63-207803 and JP-A-63-207804, styrene 90
~55% by weight, a resin phase of 65 to 95% by weight consisting of 10 to 45% by weight of acrylonitrile, and an SB type or SBS type block polymer consisting of 10 to 30% by weight of styrene and 90 to 70% by weight of butadiene, with an average particle size of 0. .05～
Rubber-modified resin compositions comprising 5 to 35 weight percent of a 0.5 micron soft phase are disclosed. Although the resin composition according to the present invention has excellent impact strength, there remains room for improvement in gloss.

[0006]

[Means for Solving the Problems] As a result of intensive studies to solve the above problems, the present inventors have found that a specific particle size range of a specific particle size in a vinyl aromatic polymer matrix of a specific composition It has been discovered that a rubber-modified vinyl aromatic resin composition having a structure in which butadiene polymer particles having a particle structure are dispersed effectively solves the above problems,
The present invention has now been completed.

That is, the present invention comprises 95 to 75% by weight of vinyl aromatic monomer units and 5 to 2% by weight of unsaturated nitrile monomer units.
A rubber-modified vinyl aromatic resin composition comprising butadiene-based polymer particles dispersed in a polymer matrix of 5% by weight, wherein the butadiene-based polymer particles have a weight average particle diameter of 0.1%. A vinyl aromatic resin composition, which is a single-layer and/or multi-layer capsule structure particle in the range of ~0.7 microns, and a butadiene-based polymer are mixed with a vinyl aromatic monomer and an unsaturated nitrile monomer. A rubber-modified vinyl aromatic resin composition is obtained by dissolving the mixed monomer and, if necessary, adding a solvent, and polymerizing the butadiene-based polymer with stirring or in the presence of shearing force until the butadiene-based polymer becomes particles. When producing, 1) the butadiene-based polymer is an SB2 type block copolymer or an SBS3 type block copolymer consisting of a polymer block B mainly composed of butadiene and a polymer block S mainly composed of styrene; , and the content of polymer block S in the block copolymer is 20 to 4
0% by weight, and 2) unsaturated nitrile monomer units in the copolymer of the vinyl aromatic monomer and unsaturated nitrile monomer produced before the butadiene polymer undergoes phase inversion and becomes particles. 3) Then, a desired amount of unsaturated nitrile monomer is further added to complete the polymerization. The present invention provides a method for producing a resin composition.

[0008] The contents of the present invention will be explained in order below. In addition to styrene, the vinyl aromatic monomer referred to in the present invention includes o-methylstyrene, m-methylstyrene, p-methylstyrene, 2,4-dimethylstyrene, and ethylstyrene.
Nuclear alkyl-substituted styrenes such as p-tert-butylstyrene, α-methylstyrene, α-methyl-p-
It refers to α-alkyl substituted styrene such as methylstyrene, but typical examples include styrene alone or a monomer mixture in which a portion of styrene is replaced with the above-mentioned vinyl aromatic monomer other than styrene.

[0009] The unsaturated nitrile monomer referred to in the present invention refers to acrylonitrile, methacrylonitrile, etc., and a typical example is acrylonitrile. As mentioned above, the resin composition of the present invention contains 95 to 75% by weight of vinyl aromatic monomer units and 5% by weight of unsaturated nitrile monomer units.
This is a rubber-modified vinyl aromatic resin composition in which butadiene polymer particles having a specific particle size and a specific structure are dispersed in a polymer matrix of ~25% by weight. If the content of unsaturated nitrile monomer units in the polymer matrix is less than 5% by weight, the resin composition will have poor rigidity and surface hardness, and if it exceeds 25% by weight, the resin composition will have poor fluidity. is inferior and does not fall within the scope of the present invention. A more preferable range is 10 to 20% by weight.

[0010]Although there is no particular restriction on the molecular weight of the polymer matrix, it is preferably 0.4 expressed in reduced viscosity.
It is in the range of 0 to 0.80 dl/g. Next, the butadiene polymer particles need to be single-layer and/or multi-layer capsule structure particles having a weight average particle diameter in the range of 0.1 to 0.7 microns. The above-mentioned single-layer or multi-layer capsule structure particles refer to particles in which the outermost portion of the butadiene-based polymer particle, which is composed mainly of butadiene, forms an unbranched closed layer (or shell). Particles having such a structure can be distinguished from the fact that the outermost part consisting of a component mainly composed of butadiene is recognized as a single closed loop in a transmission electron micrograph taken using an osmic acid staining method.

[0011] If the weight average particle diameter of the butadiene polymer particles is less than 0.1 micron, the impact strength of the resin composition is insufficient, and if it exceeds 0.7 micron, the resin composition has insufficient impact strength. The gloss becomes inferior. A more preferable range of weight average particle diameter is 0.2 to 0.5 micron. Furthermore, if the structure of the butadiene polymer particles is not a single-layer and/or multi-layer capsule structure, the balance between gloss and impact strength in the resin composition will be poor.

[0012] In the above, the structure of the butadiene polymer particles can be confirmed by a transmission electron micrograph taken by an ultra-thin section method of the resin composition, and the weight average particle diameter can be confirmed by the transmission electron micrograph taken by the ultrathin section method of the resin composition. The particle diameter of 500 to 1000 butadiene polymer particles in a microscopic photograph was measured and calculated using the following formula. Weight average particle diameter = Σni・Di4/Σni・Di3 (where ni=number of butadiene polymer particles with particle size Di) The content of the butadiene polymer in the resin composition is calculated based on the butadiene equivalent in the resin composition. The rubber content is adjusted to be in the range of 5 to 35% by weight. The rubber content in terms of butadiene referred to herein is the product of the butadiene polymer content in the resin composition and the butadiene content in the butadiene polymer.

A rubber-modified vinyl aromatic resin composition that satisfies the above requirements comprises a vinyl aromatic monomer and an unsaturated nitrile monomer in the presence of a butadiene polymer having a specific composition and structure described later. The mixture can be obtained by graft polymerization under specific conditions. In the above, the butadiene-based polymer is a polymer block B mainly composed of butadiene (hereinafter abbreviated as polymer block B),
An SB2 type block copolymer or an SBS3 type block copolymer consisting of a polymer block S mainly composed of styrene (hereinafter abbreviated as polymer block S), and a polymer block in the block copolymer. S content is 20
~40% by weight is required.

In the above, polymer block B is 1,3
- 90% by weight or more of butadiene monomer units and 10% by weight of other monomer units copolymerizable with 1,3-butadiene monomer
It is a polymer block consisting of: Examples of other monomers copolymerizable with the above-mentioned 1,3-butadiene include styrene and isoprene. Polymer block B is preferably polybutadiene. The polymer block S includes 90% by weight or more of styrene monomer units and 10% by weight of other monomer units copolymerizable with the styrene monomer.
The polymer block consists of less than % by weight. Other monomers copolymerizable with the styrene monomer include α-methylstyrene. The polymer block S is preferably polystyrene.

[0015] The butadiene polymer needs to be an SB2 type block copolymer or an SBS3 type block copolymer. In the case of a block copolymer having a structure other than this, such as an SBSB4 type block copolymer or a (SB)n [n is an integer of 3 or more] star-shaped block copolymer in which the bonding center is the B block, The structure of the butadiene-based polymer particles obtained by the graft polymerization described below does not have the above-mentioned monolayer and/or multilayer capsule structure, and the object of the present invention cannot be achieved.

[0016] Also, when the content of the polymer block S in the above-mentioned SB2 type block copolymer or SBS3 type block copolymer is less than 20% by weight or more than 40% by weight, the structure of the butadiene polymer particles However, it is difficult to form the above-mentioned capsule structure, which is not preferable. A more preferable composition and structure of the block copolymer is that the content of the polymer block S is 25
~35% by weight styrene-butadiene type 2 block copolymer.

The above SB2 type block copolymer or SBS3 type block copolymer includes a portion where the composition gradually decreases or gradually increases between the polymer block S and the polymer block B. It may also be what is known as a block copolymer. Although there is no particular restriction on the molecular weight of the above-mentioned butadiene-based polymer, it is preferable that the viscosity of a 5% by weight styrene solution at 25°C is in the range of 10 to 50 centipoise.

The butadiene polymer satisfying the above requirements is
It can be obtained by a known anionic polymerization method using a lithium-based catalyst. The resin composition of the present invention is obtained by dissolving a butadiene-based polymer that meets the above requirements in a liquid containing a mixed monomer consisting of a vinyl aromatic monomer and an unsaturated nitrile monomer, and a solvent added as necessary. can be efficiently obtained by bulk polymerization, bulk suspension polymerization, or solution polymerization under specific conditions described below.

Conventionally, it has been an economical method to obtain a rubber-modified resin composition by dissolving a butadiene-based polymer in a vinyl monomer mixture containing a vinyl aromatic monomer as a main component and polymerizing the mixture while stirring. It has been adopted as a method. In this method, at the initial stage of polymerization, a phase consisting of the butadiene polymer and the vinyl monomer mixture (hereinafter referred to as the rubber phase) forms a continuous phase, and the polymer of the vinyl monomer mixture forms a continuous phase. A phase consisting of a vinyl monomer mixture (hereinafter referred to as the resin phase) forms a dispersed phase, and as the polymerization progresses, the volume of the resin phase increases and eventually exceeds the volume of the rubber phase. The resin phase becomes a continuous phase and the rubber phase becomes a dispersed particle, resulting in a so-called phase inversion phenomenon.

Whether or not the polymerization liquid has completed phase inversion is determined by using a solvent that is a poor solvent for the butadiene polymer and a good solvent for the vinyl monomer mixture polymer, for example. It can be easily determined by adding it to dimethylformamide. In other words, in the case of a polymerization solution before phase inversion, a precipitate is formed when added to dimethylformamide, whereas
The polymerization liquid after phase inversion forms a milky white dispersion.

The rubber-modified vinyl aromatic resin composition of the present invention can only be obtained by using a butadiene polymer that satisfies the above requirements and controlling the polymerization conditions before and after the above phase inversion. That is, the rubber-modified vinyl aromatic resin composition of the present invention is obtained by adding the above-mentioned butadiene polymer to a mixed monomer consisting of a vinyl aromatic monomer and an unsaturated nitrile monomer, and a solvent as necessary. The unsaturated nitrile in the copolymer of the vinyl aromatic monomer and the unsaturated nitrile monomer that is produced before the butadiene-based polymer undergoes phase inversion and becomes particles when dissolved in a liquid and polymerized. It can be efficiently produced by controlling the average monomer content to 10% by weight or less, then adding a desired amount of unsaturated nitrile monomer, and completing the polymerization. In the above, the average content of the unsaturated nitrile monomer in the copolymer of the vinyl aromatic monomer and the unsaturated nitrile monomer produced before the butadiene-based polymer undergoes phase inversion and becomes particles. 1
If it exceeds 0% by weight, the butadiene-based polymer particles will not have the above-mentioned capsule structure but will have a cell or salami structure, making it impossible to achieve the object of the present invention.

In a preferred embodiment of the present invention, a butadiene polymer that satisfies the above requirements is added to a monomer containing styrene and acrylonitrile in a weight ratio of 98:2 to 93:7, respectively, and ethylbenzene as necessary. The average number of acrylonitrile units in the styrene-acrylonitrile copolymer produced by dissolving it in a solution containing a solvent such as toluene and polymerizing it with stirring or in the presence of shearing force until the butadiene-based polymer becomes particles. The content of acrylonitrile in the matrix of the final resin composition is controlled to be 10% by weight or less, and then the content of acrylonitrile in the matrix of the final resin composition is
Polymerization is completed by adding a desired amount of acrylonitrile (divided into multiple portions if necessary) so that the amount is 25% by weight.

There are no particular restrictions on the above polymerization method, and either a batch method or a continuous method may be used as long as the above requirements are satisfied. In the polymerization, a radical polymerization initiator such as an organic peroxide can also be used. The polymerization temperature is carried out in the conventional range of 80 to 180°C. After the polymerization is completed, unreacted monomers and solvent are removed according to a conventional method to obtain the desired rubber-modified vinyl aromatic resin composition.

The impact strength of the rubber-modified vinyl aromatic resin composition of the present invention can be further increased by adding polydimethylsiloxane, metal salts of higher fatty acids, and amides of higher fatty acids. Furthermore, additives such as dyes and pigments, lubricants, fillers, mold release agents, plasticizers, antistatic agents, and flame retardants can be added to the resin composition of the present invention as necessary. Hereinafter, the present invention will be specifically explained with reference to Examples.

[0025]

[Examples and Comparative Examples] In the following Examples and Comparative Examples, styrene-butadiene block polymers or polybutadiene shown in Table 1 were used. 1) Polystyrene block. 2) 5% styrene solution viscosity at 25°C.

3) Star-shaped block with B block as the center of connection. In the following description, the composition of the polymerization solution is in parts by weight unless otherwise specified.

[0027]

[Example 1] A polymerization stock solution having the following composition was continuously fed at a flow rate of 2.3 liters/hour to a laminar flow three-stage reactor each having an internal volume of 6 liters and equipped with a devolatilization device and a stirrer. The solution was drained and polymerization was carried out while controlling the internal temperature.・Butadiene polymer B1
:12.0・Styrene
:71.9・Acrylonitrile :
3.1.Ethylbenzene
: 13.0・n-dodecyl mercaptan : 0.02 The stirring number of the first stage reactor is 180 rpm, the solid content concentration of the polymerization liquid at the outlet of the first stage reactor is 40% by weight, and the butadiene-based polymer is It had become particulate. Further, the polymerization solution was reprecipitated with methanol, and the acrylonitrile content in the produced styrene-acrylonitrile copolymer was determined by infrared spectrophotometry, and was found to be 7% by weight.

Next, the polymerization liquid discharged from the first stage reactor was introduced into the second stage reactor to continue polymerization. Acrylonitrile was additionally added from the upper stage of the second stage reactor at a flow rate of 0.12 liters/hour. The solid content concentration of the polymerization liquid at the outlet of the second stage reactor was 57% by weight. Next, the polymerization liquid discharged from the second stage reactor was introduced into the third stage reactor to continue polymerization. The solid content concentration of the polymerization liquid at the outlet of the third stage reactor was 75% by weight. Subsequently, the polymerization liquid discharged from the third stage reactor is led to the devolatilization equipment,
Unreacted monomers and solvent were removed to obtain pellets of a rubber modified resin composition. Next, the rubber modified resin composition was dispersed in methyl ethyl ketone, and insoluble matter was removed by centrifugation.
After re-precipitating the solution containing soluble components in methanol and drying,
The acrylonitrile content in the styrene-acrylonitrile copolymer matrix was determined to be 10% by weight by infrared spectrophotometry. The weight average particle diameter of the butadiene polymer particles was 0.25 microns, and they had a single-layer or multi-layer capsule structure.

The pellets of the obtained rubber modified resin composition were molded using an injection molding machine (cylinder temperature: 230°C, mold temperature: 60°C).
A test piece was prepared at 30°F (°C) and its physical properties were measured. The results are shown in Table 2. Note that the physical properties were measured by the following method.・Izod impact strength: Based on ASTM D256. - Flexural modulus: Based on ASTM D790.

- Melt flow rate: Based on ISO-R1133. - Vicat softening point: Based on ASTM D1525.・Gloss: ASTM D638 dumbbell test piece game
The average value of the gloss values of the top part and the end part was determined. In addition to the conventional 60 degree incident angle, measurements were also made at a light source incidence angle of 20 degrees. (The smaller the angle of incidence, the smaller the gloss, allowing for more precise comparison.) Rockwell hardness: Based on ASTM D785. (L scale)

[0031]

[Comparative Example 1] In Example 1, the composition of the polymerization stock solution was as follows, the amount of acrylonitrile added to the upper stage of the second stage reactor was 0.10 liters/hour, and the polymerization solution at the outlet of the third stage reactor was Pellets of a rubber modified resin composition were obtained in the same manner except that the solid content concentration was changed to 63% by weight.

-Butadiene polymer B2
: 7.0・Styrene
:74.7・Acrylonitrile :
3.3 Ethylbenzene
:15.0・n-dodecylmercaptan: 0.02・1,
1-bis(t-butylperoxy)3,3,5-trimethylcyclohexane: 0.015 The solid content concentration of the polymerization liquid at the outlet of the first stage reactor was 37% by weight, and the butadiene-based polymer was not granulated. was. The acrylonitrile content in the produced styrene-acrylonitrile copolymer was 7% by weight. The composition of the copolymer matrix, the particle size and particle morphology of the butadiene-based polymer were analyzed in the same manner as in Example 1. The particle size was 0.28 microns and had a salami structure. Then, the physical properties were measured in the same manner as in Example 1. The results are shown in Table 2.

[0033]

[Comparative Examples 2 and 3] Polymerization was carried out in the same manner as in Example 1, except that B3 and B4 were used instead of butadiene polymer B1. The solid content concentrations of the polymerization liquid at the outlet of the first stage reactor were 37% by weight and 38% by weight, respectively, and the butadiene polymer was particulate. The acrylonitrile content in the produced styrene-acrylonitrile copolymer is 7.
% by weight. The composition of the copolymer matrix, the particle size and particle morphology of the butadiene-based polymer were analyzed in the same manner as in Example 1. The particle diameters were 0.28 and 0.35 microns, respectively, and both had a salami structure. Then, the physical properties were measured in the same manner as in Example 1. The results are shown in Table 2.

[0034]

[Comparative Example 4] In Example 1, the composition of the polymerization stock solution was as follows, the amount of acrylonitrile added to the upper stage of the second stage reactor was 0.10 liters/hour, and the polymerization solution at the outlet of the third stage reactor was Pellets of a rubber modified resin composition were obtained in the same manner except that the solid content concentration was changed to 73% by weight.

-Butadiene polymer B5
:16.0・Styrene
:67.0・Acrylonitrile :
3.0 Ethylbenzene
:14.0・n-dodecyl mercaptan: 0.01 The solid content concentration of the polymerization liquid at the outlet of the first stage reactor is 37% by weight,
The butadiene polymer was found to be particulate. The acrylonitrile content in the produced styrene-acrylonitrile copolymer was 7% by weight. The composition of the copolymer matrix, the particle size and particle morphology of the butadiene-based polymer were analyzed in the same manner as in Example 1. The particle size is 0.05 micron,
It had a punctate shape. Then, the physical properties were measured in the same manner as in Example 1. The results are shown in Table 2.

[0036]

Comparative Example 5 A rubber-modified resin composition was obtained in the same manner as in Example 1, except that acrylonitrile was not additionally added to the upper stage of the second stage reactor. The composition of the copolymer matrix, the particle size and particle morphology of the butadiene-based polymer were analyzed in the same manner as in Example 1. The particle size is 0.25 microns,
It had a capsule structure. Then, the physical properties were measured in the same manner as in Example 1. The results are shown in Table 2.

[0037]

[Comparative Example 6] In Example 1, the composition of the polymerization stock solution was as follows, the stirring number of the first stage reactor was 200 rpm, the solid content concentration of the polymerization solution at the outlet of the third stage reactor was 62% by weight, and A rubber-modified resin composition was obtained in the same manner except that acrylonitrile was not additionally added to the upper stage of the two-stage reactor.

-Butadiene polymer B1: 9.
8.Styrene: 68
．． 8. Acrylonitrile: 6.4
・Ethylbenzene: 15.0・n
-Dodecyl mercaptan: 0.01 The solid content concentration of the polymerization liquid at the outlet of the first stage reactor was 37% by weight, and the butadiene polymer was particulate. The acrylonitrile content in the produced styrene-acrylonitrile copolymer is 1
It was 3% by weight. The composition of the copolymer matrix, the particle size and particle morphology of the butadiene-based polymer were analyzed in the same manner as in Example 1. The particle size was 0.45 microns and had a salami-like structure.

Next, the physical properties were measured in the same manner as in Example 1. The results are shown in Table 2.

[0040]

Example 2 A rubber-modified resin composition was obtained in the same manner as in Example 1, except that the amount of acrylonitrile added to the upper stage of the second stage reactor was changed to 0.25 liters/hour. The composition of the copolymer matrix, the particle size and particle morphology of the butadiene-based polymer were analyzed in the same manner as in Example 1. Next, Example 1
The physical properties were measured in the same manner. The results are shown in Table 3.

[0041]

[Examples 3 and 4] In Example 1, the following composition was used as the polymerization liquid, and the amount of acrylonitrile added to the upper stage of the second stage reactor was 0.12 liters/hour and 0.30 liters/hour, respectively.
A rubber modified resin composition was obtained in the same manner except that the volume was changed to liter/hour.・Butadiene polymer B1: 12.0 ・Styrene
: 72.7・Acrylonitrile : 2.3・Ethylbenzene : 13.0・n-dodecylmercaptan: 0.015 The composition of the copolymer matrix, the particle size of the butadiene-based polymer,
The particle morphology was analyzed. Then, the physical properties were measured in the same manner as in Example 1. The results are shown in Table 3.

[0042]

[Example 5] In Example 1, butadiene-based polymer B
A rubber modified resin composition was obtained in the same manner except that B6 was used instead of B6. The composition of the copolymer matrix, the particle size and particle morphology of the butadiene-based polymer were analyzed in the same manner as in Example 1. The particles had a capsule structure.

Next, the physical properties were measured in the same manner as in Example 1. The results are shown in Table 3.

[0044]

[Table 1]

[0045]

[Table 2]

[0046]

[Table 3]

[0047]

Effects of the Invention The resin composition of the present invention has butadiene polymer particles having a unique structure dispersed in a vinyl aromatic polymer matrix, which improves impact strength, gloss, and
It has favorable properties of excellent rigidity and surface hardness. Because of these properties, it is highly preferred as a resin for obtaining injection molded products such as telephones and vacuum cleaners, as well as molded products that require a particularly clear appearance.

[0048] Furthermore, in the method of the present invention, the above resin composition is prepared by polymerizing a vinyl aromatic monomer and an unsaturated nitrile monomer under specific conditions in the presence of a butadiene polymer having a specific structure. It can be obtained efficiently and has great economic value.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a single-layer or multi-layer capsule structure particle according to the present invention.

FIG. 2 is a transmission electron micrograph of the rubber modified resin composition of Example 1.

FIG. 3 is a transmission electron micrograph of the rubber-modified resin composition of Comparative Example 6.

Claims (2)

[Claims] Claim 1: 95 to 75% by weight of vinyl aromatic monomer units
and a rubber-modified vinyl aromatic resin composition comprising butadiene polymer particles dispersed in a polymer matrix comprising 5 to 25% by weight of unsaturated nitrile monomer units,
The butadiene polymer particles have a weight average particle diameter of 0.1
A rubber-modified vinyl aromatic resin composition characterized by having single-layer and/or multi-layer capsule structure particles in the range of ~0.7 microns. [Claim 2] A butadiene-based polymer is dissolved in a liquid containing a mixed monomer consisting of a vinyl aromatic monomer and an unsaturated nitrile monomer, and a solvent is added as necessary, so that the butadiene-based polymer is When producing a rubber-modified vinyl aromatic resin composition by polymerizing with stirring or in the presence of shearing force until it becomes particles, 1) the butadiene-based polymer is polymerized with polymer block B mainly composed of butadiene and styrene. It is an SB2 type block copolymer or an SBS3 type block copolymer consisting of a polymer block S mainly composed of, and the content of the polymer block S in the block copolymer is 20 to 40% by weight, ) The average content of unsaturated nitrile monomer units in the above-mentioned copolymer of vinyl aromatic monomer and unsaturated nitrile monomer produced before the butadiene polymer undergoes phase inversion and becomes particles. 3) Control the content to 10% by weight or less.
The method for producing a rubber-modified vinyl aromatic resin composition according to claim 1, characterized in that a desired amount of unsaturated nitrile monomer is then added to complete the polymerization.