JP2000080244A - Rubber-modified styrenic resin composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a rubber-modified styrenic resin composition giving molded products having excellent surface glosses and excellent mechanical properties such as impact resistance. SOLUTION: This rubber-modified styrenic resin composition comprises 100 pts.wt. of a rubber-modified styrenic resin and 0.001-3.0 pts.wt. of a silicone elastomer powder having a rubber hardness of <50 regulated by JIS K6253. Molded products having surface glosses and mechanical properties in good balance are obtained by the action of the silicone elastomer powder.

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 capable of obtaining a molded article having excellent appearance such as surface gloss and mechanical properties such as impact resistance.

[0002]

2. Description of the Related Art In order to improve the impact resistance of hard and brittle polystyrene resin, an impact resistance using an unvulcanized rubber such as polybutadiene rubber or styrene-butadiene rubber as a toughening agent is used. Polystyrene resin is inexpensive and has excellent processability and various physical properties.
Widely used. However, recent demands for impact-resistant polystyrene resins require not only balance between impact resistance and rigidity, but also balance including appearance such as surface gloss, and even translucency. It is difficult to completely satisfy these requirements by a conventional method using an unvulcanized rubber.

As a method for improving properties including the surface gloss, a method which requires the addition of an organic silicon-based additive is disclosed. For example, JP-A-57-170
No. 950 discloses a composition in which an organic polysiloxane is added to a rubber-modified styrenic resin using a specific rubber, and JP-A-61-85461 discloses a rubber-modified styrene resin having a specific rubber dispersed particle diameter. A composition in which polydimethylsiloxane having a specific viscosity is added to a styrene resin is disclosed.
However, these methods are not sufficiently effective,
In particular, the method disclosed in JP-A-57-170950 has a problem that the impact strength is not sufficiently improved.

Another method is disclosed in Japanese Patent Laid-Open No. 3-263.
No. 415 discloses a composition comprising two-component dispersed rubber particles of a small particle component having an average particle size of 0.1 to 0.4 μm and a large particle component having an average particle size of 0.8 to 2.0 μm. Is disclosed. However, this method has a problem that the production cost is high because two or more rubber components are used.

An object of the present invention is to provide a rubber-modified styrenic resin composition which overcomes the problems of conventional impact-resistant polystyrene resins and has a good balance of various properties including surface gloss and impact resistance. Aim. Another object of the present invention is to provide a molded article obtained from the rubber-modified styrene resin composition.

[0006]

Means for Solving the Problems The present inventors add a specific amount of a specific silicone elastomer powder to a rubber-modified polystyrene-based resin to achieve a good balance of various properties such as surface gloss and impact resistance. In addition, they have found that they can be improved synergistically, and have completed the present invention.

That is, the present invention relates to a rubber-modified styrenic resin 1
00 parts by weight and a silicone elastomer powder having a rubber hardness of less than 50 specified in JIS K6253.
Provided is a rubber-modified styrenic resin composition containing 001 to 3.0% by weight. Further, the present invention provides a molded article obtained from the rubber-modified styrene resin composition.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The rubber-modified styrenic resin used in the present invention comprises: a styrenic resin forming a matrix;
It consists of soft component particles (rubber-like polymer) dispersed in a resin and is obtained by polymerizing a styrene monomer and a copolymerizable vinyl monomer in the presence of a rubber-like polymer. is there.

Examples of the styrene monomer include styrene, alkylstyrene (eg, o-, m- and p-methylstyrene, p-ethylstyrene, p-isopropylstyrene, butylstyrene, p-tertiary butylstyrene) Various α-alkylstyrenes (eg methylstyrene, ethylstyrene); various alhalostyrenes (eg o-, m- and p-chlorostyrene, bromostyrene, fluorostyrene); various di, tri, tetra or Penta-substituted chlorostyrene, bromostyrene, fluorostyrene; one selected from various α- or β-halo-substituted styrenes (eg, α-chlorostyrene, α-bromostyrene, β-chlorostyrene, β-bromostyrene)
More than species can be mentioned.

Examples of the copolymerizable vinyl monomer include acrylic acid, methacrylic acid or esters thereof, unsaturated nitriles such as acrylonitrile, maleic acid, and maleic anhydride.

Examples of the rubbery polymer include a butadiene polymer and a styrene-butadiene copolymer. As the butadiene polymer, high cis polybutadiene having a high cis content and low cis polybutadiene having a low cis content can be used. As the styrene-butadiene copolymer rubber, either a complete block type or a taper block type can be used.
One in which a part of the styrene unit in the 3-butadiene block copolymer rubber is replaced with a monovinyl aromatic compound unit copolymerizable with styrene, and one of the 1,3-butadiene units in the styrene-butadiene copolymer rubber. Part is replaced by a diolefin unit other than 1,3-butadiene, styrene unit in the styrene-butadiene copolymer rubber and 1,1,
Examples thereof include those in which a part of the 3-butadiene unit is replaced by a monovinyl aromatic compound unit copolymerizable with styrene and a diolefin unit other than 1,3-butadiene.

The proportion of the rubbery polymer in the rubber-modified styrenic resin is preferably 4 to 12% by weight in order to prevent the rigidity and the surface gloss from lowering and to prevent the impact resistance from lowering.

The volume average particle diameter of the rubbery polymer is preferably 0.1 to 2.0 μm in order to suppress a decrease in surface gloss.
m, particularly preferably 0.1 to 1.0 μm. The volume average particle diameter was determined by taking a transmission electron micrograph of a molded article obtained from the composition using an ultra-thin section method, measuring the particle diameter in circle of 1,000 rubber-like polymers, It is a value calculated from. Volume average particle diameter = (ΣniDi ⁴ ) / (ΣniDi ³ ) (ni represents the number of rubbery polymers having a circle-converted particle diameter Di (μm)).

The rubber-modified styrene resin may be a mixture of a styrene resin and a styrene-butadiene copolymer, or a mixture of a styrene resin, a styrene-butadiene copolymer, and a graft-type rubber-modified styrene resin. Furthermore, polyolefin, polycarbonate, polyamide,
Melting point of polyester, polyether, etc. is 100 to 300
A thermoplastic resin having a temperature of ° C. may be blended, and a compatibilizer may be added as necessary.

The rubber-modified styrenic resin can be produced by applying a conventional polymerization method. For example, it can be produced by a bulk-suspension two-stage polymerization method or a bulk polymerization method in which a rubber-like polymer is dissolved in a styrene-based monomer, then bulk-polymerized, and further subjected to suspension polymerization. During the bulk polymerization reaction, it is usually preferable to stir until the polymerization rate of the styrene monomer becomes about 30% by weight, but it is preferable to reduce the stirring thereafter.

At the time of polymerization, a molecular weight regulator such as α-methylstyrene dimer, mercaptans, terpenes, and halogen compounds, a solvent, a polymerization initiator and the like can be added. Examples of the solvent include at least one of aromatic hydrocarbons such as toluene, xylene, and ethylbenzene, aliphatic hydrocarbons, and dialkyl ketones. The amount of the solvent used is preferably 0.1 to 50% by weight in order to keep the polymerization rate at an appropriate level and facilitate the recovery of the solvent. As the polymerization initiator, a general initiator such as an organic peroxide such as a peroxide or an azo compound can be used.

The silicone elastomer powder used in the present invention has a rubber hardness of 5 specified in JIS K6253.
0, preferably having a rubber hardness of 0.1 to 3
0. When the rubber hardness is less than 50, the impact resistance of the molded article can be improved.

The silicone elastomer powder used in the present invention has a volume average particle size of 0.1 to 25.0 μm.
m, preferably from 0.1 to 20.0 μm. When the volume average particle diameter is within the above range, it is possible to prevent a decrease in heat resistance and rigidity of the molded body and a decrease in surface gloss without impairing the fluidity of the composition. The volume average particle diameter is measured by a particle counter.

As such a silicone elastomer powder, JP-A No. 10-67900, page 4, right column, bottom 10 lines to page 6, left column 8 lines, page 6, left column, bottom 16 lines to right column, bottom 9 lines (However, excluding silicone resin powder). That is, one or more selected from silicone rubber powder and silicone composite powder obtained by curing oily silicone can be used. Among them, silicone rubber powder and silicone composite powder are preferable, and silicone composite powder is particularly preferable.

The silicone rubber powder is preferably one obtained by subjecting (a) a vinyl group-containing organopolysiloxane and (b) an organohydrogenpolysiloxane to an addition reaction and curing.

The component (a) has at least two vinyl groups bonded to a silicon atom in one molecule, and preferably has one or both terminals of a vinyl group. Examples of the organic group bonded to a silicon atom other than a vinyl group include an alkyl group such as a methyl group, an ethyl group, a propyl group, a butyl group, a hexyl group and a dodecyl group, an aryl group such as a phenyl group, a β-phenylethyl group, and a β-phenylethyl group. And aralkyl groups such as -phenylpropyl group, and halogen-substituted hydrocarbon groups such as chloromethyl group and 3,3,3-trifluoropropyl group. Among these, the component (a) is preferably one in which 90 mol% or more of the organic groups bonded to the silicon atom is a methyl group because the effect of improving the impact resistance is large. The component (a) is represented by the general formulas (1), (2) and (3) described on page 5, right column, line 6 to left column, bottom eight lines.
Is preferably represented by

The component (b) has at least two hydrogen atoms bonded to a silicon atom in one molecule. As the organic group bonded to the silicon atom, the same organic group as the component (a) can be mentioned, but a methyl group is preferable because the effect of improving impact resistance is large. The component (b) is preferably represented by the general formulas (4), (5) and (6) described in the above publication, from page 5, right column, bottom line, line 4 to page 6, left column, line 5, line.

The silicone composite powder is obtained by coating the surface of silicone rubber fine particles with a silicone resin. This silicone composite powder is prepared by putting spherical silicone rubber powder and methyltrichlorosilane or methyltrimethoxysilane into a reaction vessel, hydrolyzing and condensing methyltrichlorosilane, etc., so that the surface of the silicone rubber powder is polymethylsilsesquiscane. It can be produced by a method such as coating with oxane.

The content of the silicone elastomer powder is based on 100 parts by weight of the rubber-modified styrene resin.
0.001 to 3.0 parts by weight, preferably 0.05 to 1.
0 parts by weight. When it is 0.01 part by weight or more, sufficient impact resistance can be obtained, and when it is 3.0 parts by weight or less, a decrease in surface gloss can be prevented.

The method for producing the composition of the present invention is not particularly limited, since the dispersibility of the silicone elastomer powder is extremely excellent. For example, a method of performing polymerization by suspending a silicone elastomer powder in a styrene-based monomer liquid, a method of adding a silicone elastomer powder before the devolatilization step after the polymerization reaction or after the devolatilization step, and the like can be applied. it can. Further, a method in which a rubber-modified styrene resin and a silicone elastomer powder are dry-blended and melt-kneaded with a single-screw or twin-screw extruder can also be applied.

The rubber-modified styrenic resin composition of the present invention may contain, if necessary, a lubricant, a plasticizer, a release agent, a flame retardant, an ultraviolet absorber, an antioxidant, an antistatic agent, a coloring agent, and a filler. And the like.

The molded article of the present invention is obtained by molding the above rubber-modified styrenic resin composition into a desired shape. The molding method is not particularly limited, and injection molding, extrusion molding, etc. may be used. Can be.

When the injection molding method is applied, the injection molding conditions are set to an injection molding temperature of 180 to 280 ° C., an injection molding pressure of 5
0-140kg / cm ² · G, screw rotation speed 50-300
The selection is appropriately performed in the range of rpm. When the extrusion molding method is applied, a method of extruding from a T-die after melting by an extruder, a method of extruding into a sheet from an extruder, and a method of biaxial stretching by a tenter method or an inflation method can be exemplified. . The stretching in this case may be uniaxial stretching, simultaneous biaxial stretching, or biaxial stretching by an inflation method.

[0029]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples. In addition, the measurement and evaluation methods are as follows.

(1) Impact strength (Izod impact strength) Measured according to JIS K7710. (2) Drop weight impact strength Measured according to ASTM-D1709. (3) Tensile strength Measured in accordance with JIS-K7113-1981. (4) Flexural strength Measured in accordance with ASTM-D790. (5) Surface gloss Measured according to JIS-Z-8741.

<Synthesis of Rubber-Modified Styrenic Resin> A styrene monomer 6 was placed in a 10-liter reactor equipped with stirring blades.
636 g, low-cis polybutadiene (Asahi Kasei diene 55, 364 g) and 350 g of ethylbenzene were charged. Next, after the inside of the reactor was replaced with nitrogen, polymerization was performed to a polymerization rate of 35% at a rotation speed of the stirring blade of 30 rpm, and the reaction solution was further transferred into a tower-type reactor, where polymerization was performed to a polymerization rate of 95%.
After that, the reaction solution was taken out from the tower reactor, and 200
Unreacted monomers were removed at a reduced pressure of 10 hPa at a temperature of 10 ° C. to obtain a rubber-modified styrene resin. The volume average particle diameter of the obtained rubber-modified styrene resin was 1.0 μm. Also,
As a result of measuring the molecular weight by GPC, the Mw of the obtained rubber-modified styrene resin composition was 200,000.

Examples 1 to 8 A silicone elastomer powder having a rubber hardness of 30.0 and a volume average particle size of 3.0 μm (B manufactured by Toray Dow Corning Co., Ltd.) was added to 100 parts by weight of the synthesized rubber-modified styrene resin.
Y29-119) at the ratio shown in Table 1 to obtain a rubber-modified styrene resin composition. Using this composition, 2
After re-granulation by a screw extruder (PCM30 type manufactured by Ikegai Iron Works Co., Ltd.), each test piece was prepared using an injection molding machine, and each measurement was performed. Table 1 shows the results. Each test piece was translucent.

Examples 9-16 Silicone elastomer powder having a rubber hardness of 7.0 and a volume average particle diameter of 3.0 μm (BY manufactured by Toray Dow Corning Co., Ltd.) was added to 100 parts by weight of the synthesized rubber-modified styrene resin.
29-122) at the ratio shown in Table 1 to obtain a rubber-modified styrene resin composition. Using this composition, after re-granulating by a twin-screw extruder (PCM30 type manufactured by Ikegai Iron Works Co., Ltd.), each test piece was prepared using an injection molding machine, and each measurement was performed. Table 1 shows the results. Each test piece was translucent.

[0034]

[Table 1]

The examples had a good balance of mechanical properties such as surface gloss and impact resistance.

Comparative Example 1 After the synthesized rubber-modified styrene resin was re-granulated by a twin-screw extruder (PCM30, manufactured by Ikegai Iron Works Co., Ltd.), each test piece was prepared using an injection molding machine. A measurement was made. Table 2 shows the results.

Comparative Examples 2 to 4 A silicone elastomer powder having a rubber hardness of 70.0 and a volume average particle diameter of 3.0 μm (Trefle E605 manufactured by Toray Dow Corning Co., Ltd.) was added to 100 parts by weight of the synthesized rubber-modified styrene resin. The composition was obtained at the ratio shown in FIG. Using this composition, after re-granulating by a twin-screw extruder (PCM30 type manufactured by Ikegai Iron Works Co., Ltd.), each test piece was prepared using an injection molding machine, and each measurement was performed. Table 2 shows the results.

Comparative Examples 5 to 7 A rubber hardness of 7 was added to 100 parts by weight of the synthesized polystyrene resin.
0.0, a silicone elastomer powder having a volume average particle size of 70.0 μm (Trefil E850 manufactured by Dow Corning Toray Co., Ltd.) was added at the ratio shown in Table 2 to obtain a composition. Using this composition, after re-granulating by a twin-screw extruder (PCM30 type manufactured by Ikegai Iron Works Co., Ltd.), each test piece was prepared using an injection molding machine, and each measurement was performed. Table 2 shows the results. Each test piece was opaque.

[0039]

[Table 2]

The comparative example was particularly inferior in impact strength.

[0041]

The rubber-modified styrenic resin composition of the present invention contains a silicone rubber elastomer powder having a specific hardness, so that it has excellent surface gloss and excellent mechanical properties such as impact resistance. Can be obtained.

Claims (3)

[Claims] 1. A rubber-modified styrenic resin of 100 parts by weight, and a silicone elastomer powder having a rubber hardness of less than 50 specified in JIS K6253 of 0.001 to 0.001.
A rubber-modified styrenic resin composition containing 3.0 parts by weight. 2. The rubber-modified styrenic resin composition according to claim 1, wherein the silicone elastomer powder has a volume average particle size of 0.1 to 25.0 μm. 3. A molded article obtained from the rubber-modified styrenic resin composition according to claim 1.