JP2000080131A - Preparation of rubber-modified styrenic resin - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a preparative process for a rubber-modified styrenic resin which is capable of giving a molded article excellent gloss and mechanical properties such as impact resistance. SOLUTION: A preparative process for a rubber-modified styrenic resin contains the steps: a step of polymerizing a rubbery polymer and an aromatic vinyl monomer to such an extent that the rubbery polymer does not become dispersed particulates, a step of polymerizing the rubbery polymer and the aromatic vinyl monomer until the rubbery polymer has changed into dispersed particulates, and a step of the deaeration to remove unnecessary matters in the polymerization reaction liquid. In this process, an emulsion of silicone powder-water system is added prior to the deaeration step.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a rubber-modified styrene resin which is particularly useful as a raw material for producing 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 silicone oil is added to a rubber-modified styrenic resin using a specific rubber. However, this method has a problem that the impact strength is not sufficiently improved.

Further, examples of a composition in which a specific silicone oil compound is added to a rubber-modified styrenic resin having a specific rubber-dispersed particle diameter are disclosed in JP-B-3-76388, JP-B-5-11142 and JP-B-5-11142. Fair 5-1114
JP-B-3, JP-B5-45624, JP-B7-5
3816, JP-A-3-179046, JP-B-63-30948, JP-B-63-56895, JP-A-9-183887, JP-A-9-18
3888 and JP-A-9-124885. However, even with these techniques, there has not yet been obtained one having a good balance between surface gloss and impact resistance.

The present invention overcomes the problems of the conventional impact-resistant polystyrene resin and provides a rubber-modified styrene-based resin composition capable of obtaining a molded article having various properties including surface gloss and impact resistance in a well-balanced manner. It is an object of the present invention to provide a method for producing the same.

[0006]

SUMMARY OF THE INVENTION The present invention comprises a step of polymerizing a rubber-like polymer and an aromatic vinyl monomer to such an extent that the rubber-like polymer does not become dispersed particles. In a method for producing a rubber-modified styrenic resin including a devolatilization step of removing unnecessary substances in a polymerization reaction solution and a step of polymerizing until a styrene-based resin is produced, a silicone powder aqueous emulsion is added before the devolatilization step. Provide a way.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The production method of the present invention comprises a step of polymerizing a rubber-like polymer to such an extent that the rubber-like polymer does not become dispersed particles (hereinafter referred to as a "first polymerization step"), (Hereinafter referred to as “second polymerization step”) and a devolatilization step of removing unnecessary substances in the polymerization reaction solution. Before and after each step, a known production step of a rubber-modified styrene resin is performed. It can be added as appropriate. Further, as the polymerization method, a bulk polymerization method, a solution polymerization method, a conventional method such as a suspension polymerization method can be applied,
The bulk polymerization method is preferable from the viewpoint of improving productivity.

[0008] In the first polymerization step, the rubbery polymer and the aromatic vinyl-based monomer are mixed to the extent that the rubbery polymer does not become dispersed particles, that is, the rubber phase is a continuous phase and the styrene-based resin phase is dispersed. Polymerizes to the extent that it remains as a phase.

The rubbery polymer used in the first polymerization step includes butadiene polymer, styrene-butadiene copolymer and the like. As a 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-based copolymer rubber, either a complete block type or a taper block type can be used,
For example, styrene-1,3-butadiene block copolymer rubber in which part of the styrene unit is replaced by a monovinyl aromatic compound unit copolymerizable with styrene, 1,3 in styrene-butadiene copolymer rubber One in which a part of butadiene units is replaced by a diolefin unit other than 1,3-butadiene, and a part of styrene units in the styrene-butadiene copolymer rubber and a part of 1,3-butadiene units are each styrene. And those substituted with a monovinyl aromatic compound unit copolymerizable with a diolefin unit other than 1,3-butadiene.

As the aromatic vinyl monomer used in the first polymerization step, styrene, alkylstyrene (for example, o
-, M- and p-methylstyrene, p-ethylstyrene, p-isopropylstyrene, butylstyrene, p-
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; various α- or β-halo-substituted styrenes (eg, α-chlorostyrene, α-bromostyrene, β-chlorostyrene, β-bromomostyrene) and the like In addition to one or more selected from styrene-based monomers, acrylic acid, methacrylic acid or esters thereof,
1 selected from unsaturated nitriles such as acrylonitrile and copolymerizable vinyl monomers such as maleic acid and maleic anhydride;
More than species can be mentioned.

The amounts of the rubbery polymer and the aromatic vinyl monomer are determined by the amount of the rubber-modified styrene-based resin in order to prevent the rigidity and surface gloss of the molded article from decreasing and to prevent the impact resistance from decreasing. It is preferable to adjust so that the content of the rubbery polymer is 1 to 30% by weight.

In the first polymerization step, 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.

As the solvent, aromatic hydrocarbons such as toluene, xylene and ethylbenzene, aliphatic hydrocarbons,
One or more dialkyl ketones can be mentioned.
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.

Examples of the polymerization initiator include ketone peroxides such as cyclohexanone peroxide, 3,3,5-trimethylcyclohexanone peroxide, methylcyclohexanone peroxide, 1,1-bis (t-butylperoxy) cyclohexane, n Peroxyketals such as -butyl-4,4-bis (t-butylperoxy) valerate, cumene hydroperoxide, diisopropylbenzene peroxide, 2,5-dimethylhexane-2,5-dihydroperoxide, t-butylcumyl peroxide, α, α'-bis (t-butylperoxy-m-isopropyl) benzene, 2,5-dimethyl-
2,5-di (t-butylperoxy-m-isopropyl)
Dialkyl peroxides such as benzene, 2,5-dimethyl-2,5-di (t-butylperoxy) hexyne-3,
Diacyl peroxides such as decanoyl peroxide, lauroyl peroxide, benzoyl peroxide, and 2,4-dichlorobenzoyl peroxide; peroxycarbonates such as bis (t-butylcyclohexyl) peroxydicarbonate; Organic peroxides such as oxybenzoate, peroxyesters such as 2,5-dimethyl-2,5-di (benzoylperoxy) hexane, and 2,2-azobis (2-methylbutyronitrile), 1,1 One or more selected from azo compounds such as' -azobis (cyclohexane-1-carbonitrile) can be mentioned.

The reaction temperature in the first polymerization step is preferably 90 to 170 ° C. when no polymerization initiator is used, and 90 to 14 ° C. when a polymerization initiator is used.
It is preferred to carry out the reaction at 0 ° C. Further, the treatment in the first polymerization step is preferably performed with stirring, and the degree of stirring in that case is preferably 0.5 to 20 s ^-1 as a shear rate.

In the second polymerization step, polymerization is performed until the rubbery polymer is dispersed into particles, that is, the styrene resin phase is a continuous phase and the rubber phase is a dispersed phase. The treatment in the second polymerization step is preferably performed in a tower reactor, and the reaction temperature is preferably 90 to 160 ° C.

After the second polymerization step, a devolatilization step for removing unreacted monomers, solvents, and other unnecessary substances in the polymerization reaction solution is performed. In the present invention, the devolatilization step is performed before the devolatilization step. Then, an aqueous silicone powder emulsion is added to the polymerization reaction solution.

The silicone powder contained in the aqueous silicone powder emulsion is disclosed in JP-A-10-67.
No. 900, page 4, right column, bottom 10 lines to page 6, left column 8 lines, 6
What is described from 16 lines from the lower left column to 9 lines from the lower right column of the page can be mentioned. That is, 1 is selected from silicone rubber powder, silicone resin powder and silicone composite powder obtained by curing oily silicone.
More than one kind can be used, and among these, silicone rubber powder and silicone composite powder are preferable, and silicone composite powder is particularly preferable.

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

The component (a) has at least two vinyl groups bonded to a silicon atom in one molecule, and preferably has one or both ends 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 silicon atoms 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.

As the silicone resin powder, polymethylsilsesquioxane powder is preferable. This polymethylsilsesquioxane is described in the above publication, page 6, left column 9
According to the reaction formula described in the line from the right to the right column, line 8, methyltrichlorosilane or methyltrialkoxysilane is hydrolyzed in water and condensed.

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 aqueous silicone powder emulsion is
A silicone powder produced by emulsion polymerization can be used as it is, and a silicone powder emulsified and dispersed in water using an emulsifier can be used.

The solid content of the aqueous silicone powder emulsion is preferably 1 to 70% by weight, particularly preferably 1 to 30% by weight, and further preferably 1 to 10% by weight. When the solid content is within the above range, the dispersibility with the rubber-modified styrenic resin is good, so that mechanical properties such as impact resistance can be enhanced.

The addition amount of the aqueous silicone powder emulsion is based on 100 parts by weight of the aromatic vinyl monomer.
It is preferably 0.001 to 20.0 parts by weight, particularly preferably 0.001 to 5.0 parts by weight. When the amount is 0.001 part by weight or more, sufficient impact resistance can be imparted to the molded article, and when the amount is 20.0 parts by weight or less, a decrease in the surface gloss of the molded article can be prevented.

The volume average particle diameter of the rubbery polymer contained in the rubber-modified styrenic resin of the present invention is preferably 0.1 to 2.0 μm, particularly preferably 0.1 to 2.0 μm, in order to suppress a decrease in surface gloss. １．０1.0 μm. The volume average particle size was determined by taking a transmission electron micrograph of a molded product obtained from the composition using an ultrathin section method,
This is a value calculated by measuring the particle diameter of 0 circles and calculating from the following equation. 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 styrenic resin of the present invention can be molded by applying a known molding method such as injection molding or extrusion molding. In that case, if necessary, lubricant,
Plasticizers, release agents, flame retardants, UV absorbers, antioxidants,
Additives such as an antistatic agent, a colorant, and a filler can be blended.

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.

[0030]

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) Bending strength Measured according to ASTM-D790. (4) Tensile strength Measured in accordance with JIS-K7113-1981. (5) Surface gloss Measured according to JIS-Z-8741.

Example 1 A 10-liter reactor equipped with stirring blades was charged with 6636 g of styrene monomer, low-cis polybutadiene (Dien 55, 364 g of Asahi Kasei), and 350 g of ethylbenzene, followed by purging with nitrogen. Thereafter, polymerization was carried out to a polymerization rate of 35% at a reaction temperature of 110 ° C. and a rotation speed of the stirring blade of 30 rpm. Next, the reaction solution was transferred into a tower reactor, and the reaction temperature was 130 ° C.
At a polymerization rate of 85%. Thereafter, the reaction solution was taken out of the tower reactor, and an aqueous silicone powder emulsion (BY29-119, manufactured by Toray Dow Corning Co., solid content concentration: 10% by weight, added amount: 67 g) was added. Unreacted monomers and ethylbenzene were removed under reduced pressure to obtain a rubber-modified styrene resin. Each of the above measurements was performed on this resin. Table 1 shows the results.

Example 2 The procedure of Example 1 was repeated, except that the addition amount of the aqueous silicone powder emulsion was changed to 335 g. Each of the above measurements was performed on this resin. Table 1 shows the results.

Example 3 A 10 liter reactor equipped with stirring blades was charged with 6636 g of a styrene monomer, low-cis polybutadiene (Dien 55, 364 g of Asahi Kasei), and 350 g of ethylbenzene, followed by purging with nitrogen. Thereafter, polymerization was carried out to a polymerization rate of 35% at a reaction temperature of 110 ° C. and a rotation speed of the stirring blade of 30 rpm. Next, the reaction solution was transferred into a tower reactor, and the reaction temperature was 130 ° C.
At a polymerization rate of 85%. Thereafter, the reaction solution was taken out of the tower reactor, and an aqueous silicone powder emulsion (BY29-122, manufactured by Toray Dow Corning Co., solid content concentration: 10% by weight, added amount: 67 g) was added. Unreacted monomers and ethylbenzene were removed under reduced pressure to obtain a rubber-modified styrene resin composition. Each of the above measurements was performed on this resin. Table 1 shows the results.

Example 4 The procedure of Example 2 was repeated, except that the addition amount of the aqueous silicone powder emulsion was changed to 335 g. Each of the above measurements was performed on this resin. Table 1 shows the results.

Comparative Example 1 A 10 liter reactor equipped with stirring blades was charged with 6636 g of styrene monomer, low-cis polybutadiene (Diene 55, 364 g, manufactured by Asahi Kasei), and 350 g of ethylbenzene, followed by purging with nitrogen. Thereafter, polymerization was carried out to a polymerization rate of 35% at a reaction temperature of 110 ° C. and a rotation speed of the stirring blade of 30 rpm. Next, the reaction solution was transferred into a tower reactor, and the reaction temperature was 130 ° C.
At a polymerization rate of 85%. Thereafter, the reaction solution was taken out of the tower reactor, and unreacted monomers and ethylbenzene were removed at 200 ° C. under a reduced pressure of 10 mmHg to obtain a rubber-modified styrene resin composition. Each of the above measurements was performed on this resin. Table 1 shows the results.

Comparative Example 2 A 10-liter reactor equipped with stirring blades was charged with 6636 g of styrene monomer, low-cis polybutadiene (Dien 55, 364 g, manufactured by Asahi Kasei), and 350 g of ethylbenzene, followed by purging with nitrogen. Thereafter, polymerization was carried out to a polymerization rate of 35% at a reaction temperature of 110 ° C. and a rotation speed of the stirring blade of 30 rpm. Next, the reaction solution was transferred into a tower reactor, and the reaction temperature was 130 ° C.
At a polymerization rate of 85%. Thereafter, the reaction solution was taken out from the tower reactor, and a silicone powder aqueous emulsion solution (BY29-119, manufactured by Toray Dow Corning, solids concentration 63%, addition amount 11 g) was added, and after sufficient stirring,
Unreacted monomers and ethylbenzene were removed at 200 ° C. under a reduced pressure of 10 mmHg to obtain a rubber-modified styrene resin composition. Each of the above measurements was performed on this resin. Table 1 shows the results.

Comparative Example 3 The silicone powder added in Comparative Example 2 was BY2
Except having changed to 9-122, it carried out similarly to the comparative example 2.
Each of the above measurements was performed on this resin. Table 1 shows the results
Shown in

[0039]

[Table 1]

Examples 1 to 4 all had each property in a well-balanced manner. In Comparative Examples 2 and 3, since the solid content of the emulsion was too high, the dispersibility with the polymerization reaction liquid was poor, and the impact strength was particularly poor.

[0041]

According to the production method of the present invention, an aqueous emulsion of silicone powder is added, so that the surface gloss is excellent,
Moreover, a molded article having excellent mechanical properties such as impact resistance can be obtained.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4J002 BN141 CP032 CP042 CP142 FB092 FB112 FD010 FD020 FD050 FD070 FD090 FD100 FD130 FD160 FD170 4J026 AA17 AA68 AC10 AC11 AC16 AC32 AC36 BA05 BA06 BA08 BA25 DB27 BA27 DB31 DB35 DB31 DB32 DB38 EA02 EA03 GA08 GA09 4J100 GB05

Claims (2)

[Claims] 1. A step of polymerizing a rubber-like polymer and an aromatic vinyl monomer to such an extent that the rubber-like polymer is not dispersed into particles, a step of polymerizing the rubber-like polymer until the rubber-like polymer is dispersed into particles, and a polymerization reaction. A method for producing a rubber-modified styrene resin, which comprises a devolatilization step for removing unnecessary substances in a liquid, wherein a water-based silicone powder emulsion is added before the devolatilization step. 2. The method according to claim 1, wherein the aqueous silicone powder emulsion having a solid content of 1 to 70% by weight is added in an amount of 0.001 to 20.0 parts by weight based on 100 parts by weight of the aromatic vinyl monomer. A method for producing a rubber-modified styrenic resin.