JPH0753816B2 - High gloss rubber modified polystyrene composition - Google Patents

Description

TECHNICAL FIELD The present invention relates to a high-gloss rubber-modified polystyrene composition having an excellent overall quality balance.

For example, rubber-modified polystyrene is often used for parts of household electric appliances, but compared with conventional ABS resin,
They had the drawbacks of poor impact strength and low gloss on the surface of the molded product. Recently, the demand for the appearance of an improved rubber-modified polystyrene that is close to the characteristics of ABS resin has been intensified from the market due to cost reduction and thinning tendency.

The resin composition of the present invention exhibits an excellent overall quality balance of impact strength, gloss, tensile strength and heat resistance in injection molded products, extruded sheets, extrusion vacuum molded products and the like. Since it is possible to replace expensive ABS resin and make the product thinner, it has great value as an economical resin that can reduce costs.

(Prior Art and Its Problems) Rubber-modified polystyrene has been used industrially in many cases, but its dispersed rubber particle size is generally about 1.0 to 5.0 microns (μ), which is as small as 1.0 μ or less. In the case of rubber particle size, a preferable resin has not been obtained. Also,
In rubber-modified polystyrene, the ratio of gel component and rubber component is usually 3.5 or more. (Encyclopedia of Polymer s
On page 401 of cience and Technology Vol13, the gel component is 3-10% of the rubber component of rubber modified polystyrene.
It is stated to be 10-40%. ) Further, the ratio of the gel component and the rubber component of the commercially available rubber-modified polystyrene is based on the Journal of Applied Polymer Science Vol.
Shown on pages 3 and 354, 4.1, 3.6, 1.6,
3.5 and most are over 3.5.

In addition, a resin composition composed of a rubber-modified styrenic resin and an organic polysiloxane is described in Modern Plastics November 1972 114.
Pp. 116, Plastics Age Vol. 20, 1974, May issue, p. 107, JP-A-55-3494, JP-A-53-12465
61, JP-A-57-187345, JP-A-57-187346
Although it is described in the prior art documents such as Japanese Patent Laid-Open Publication No. JP-A No. 2003-187, when a rubber-modified polystyrene having a small rubber particle diameter is used, a preferable resin composition has not been obtained.

In order to meet the market demand for the improved rubber-modified polystyrene having an excellent overall quality balance mentioned above, the improved rubber-modified polystyrene having an excellent quality balance of impact strength, gloss, tensile strength and heat resistance is required. Will be needed. It is an object of the present invention to obtain an inexpensive high-gloss rubber-modified polystyrene having an excellent quality balance of impact strength, gloss, tensile strength and heat resistance.

(Means for Solving Problems) The present invention comprises a rubber-modified polystyrene having a specific microstructure, which is not common in the prior art, and a specific polydimethylsiloxane among organic polysiloxanes.

That is, the present invention provides a rubber-modified polystyrene composition in which a rubber polymer is dispersed in the form of particles, wherein (A) the dispersed particles have an average particle diameter in the range of 0.20 to 1.00 micron, and (B) the composition The ratio of the gem component and the rubber component contained is in the range of 2.0 to 3.3, and (C) the composition contains 0.005% of polydimethylsiloxane.
The rubber-modified polystyrene composition contains ~ 0.8% by weight.

The present invention succeeds in obtaining a high-gloss rubber-modified polystyrene composition having a very good quality balance by combining all of the requirements (A), (B), and (C).

The rubber-modified polystyrene used in the present invention can be produced by a bulk polymerization method or a bulk suspension polymerization method in which an aromatic monovinyl monomer is polymerized in the presence of a rubbery polymer.
Further, the rubber-modified polystyrene can be produced by controlling the state of stirring in the polymerization step, the mixed state at the time of producing rubber particles, and the like. Aromatic monovinyl monomers include styrene and o-methylstyrene, p-methylstyrene, m-methylstyrene, 2,4-
Nuclear alkyl-substituted styrenes such as dimethyl styrene, ethyl styrene and p-tert-butyl styrene, and α-alkyl substituted styrenes such as α-methyl styrene and α-methyl-p-methyl styrene are used. The rubber-like polymer may be polybutadiene, styrene-butadiene copolymer or the like, and the polybutadiene may be high cis polybutadiene having a high cis content or low cis polybutadiene having a low cis content.

The produced rubber-modified polystyrene needs to have a specific microstructure, the rubber-like polymer is dispersed in particles, and the average particle size thereof is 0.20 to 1.00 micron, preferably 0.20 to It should be in the 0.70 micron range, most preferably in the 0.30 to 0.60 micron range. If the average particle size is smaller than 0.20 micron, the impact strength will be reduced, and if it is larger than 1.00 micron, the gloss and tensile strength will be deteriorated and a resin having a good overall quality balance cannot be obtained.

The average particle size referred to here is calculated by the following formula by taking a transmission electron micrograph of a rubber-modified polystyrene by an ultrathin section method and measuring the particle size of 1000 rubber-like polymer particles in the photo. is there.

(Here, ni is the number of rubber-like polymer particles having a particle diameter Di.) The average particle diameter of the rubber-like polymer particles is the stirring strength at the time of polymerization,
It depends on the solution viscosity of the rubber-like polymer used, and can be adjusted by changing these.

The ratio of the gel component and the rubber component contained in the rubber-modified polystyrene used in the present invention is 2.0 to 3.3, preferably 2.
It must be in the range of 3 to 3.0. When the ratio of the gel component and the rubber component is less than 2.0, the impact strength is lowered, and when the ratio is more than 3.3, the gloss, the coloring property and the rigidity are lowered and a resin having an excellent overall quality balance cannot be obtained.

The amount of the gel component referred to here is obtained by dissolving and dispersing rubber-modified polystyrene in toluene, separating insoluble matter by centrifugation and decantation, removing the torune, and then measuring the weight. Is. The rubber component can be calculated from the ratio of the rubber and the monomer used during the polymerization, or can be analyzed by a method such as infrared spectrum analysis.

The ratio of the gel component and the rubber component can be controlled by, for example, a method of adding polystyrene before or during the initiation of the polymerization of the solution in which the rubbery polymer is dissolved in the aromatic monovinyl monomer. As a preferred method for producing the rubber-modified polystyrene used in the present invention, a polymerization solution obtained by polymerizing a solution comprising a rubber-like polymer and an aromatic monovinyl monomer and an aromatic monovinyl monomer are polymerized. There is a method in which the obtained polymerization solution is mixed under a high shearing force and the polymerization is further advanced.

The polydimethylsiloxane used in the present invention is It is necessary to have a structural unit represented by.
In the case of the rubber-modified polystyrene having a small rubber particle size as in the present invention, a preferable resin composition cannot be obtained with an organic polysiloxane other than polydimethylsiloxane as described in the prior art documents. More preferably, the polydimethylsiloxane also has a viscosity at 25 ° C of 10 to 10.0
It is in the range of relatively low molecular weight of 00 centistokes.

Further, the content of polydimethylsiloxane in the rubber-modified polystyrene composition is in the range of 0.005 to 0.8% by weight. When the content is less than 0.005% by weight, the impact strength is reduced, and when it exceeds 0.8% by weight, the colorability and the secondary processability of the resin molded product (chemical adhesion, printability, paintability, etc.) are improved. Not preferable. Although the reason why the coloring property and the secondary processability are deteriorated when the amount added is large is not clear, it is considered that it is because the compatibility of the polydimethylsiloxane in the rubber-modified polystyrene is lowered. From such a point, the content of polydimethylsiloxane is important for obtaining a preferable rubber-modified porstyrene composition.

The method for producing the rubber-modified polystyrene composition of the present invention is not particularly limited, and for example, polydimethylsiloxane may be added to a styrene monomer to carry out polymerization, or rubber-modified polystyrene and polydimethylsiloxane may be used. Melt mixing may be performed using an extruder or the like. Further, a master pellet having a high polydimethylsiloxane concentration may be produced from polydimethylsiloxane and polystyrene, and the master pellet and rubber-modified polystyrene may be mixed to obtain a molded article.

In the rubber-modified polystyrene composition of the present invention, a metal salt of a higher fatty acid, for example, zinc stearate, calcium stearate, etc., a amide of a higher fatty acid, or a combination of lubricants such as ethylene bis-stearamide, is used, Good results are obtained in terms of impact strength and gloss. The amount of lubricant used is 0.01-1.0% by weight, preferably 0.0
It is 1 to 0.2% by weight.

Further, additives such as a face wash, a lubricant, a filler, a release agent, a plasticizer and an antistatic agent can be added to the rubber-modified polystyrene composition of the present invention as required.

(Effect) The resin composition of the present invention is excellent in overall quality balance in physical properties such as impact strength, gloss, tensile strength and heat resistance. These points are close to the characteristics of ABS resin, the economic effect as an alternative to ABS resin is great, and it is possible to sufficiently meet the demand of the market aiming for thinning. .

The resin composition of the present invention can be used as a molded article in the fields of light electric appliances, sundries, toys and the like.

(Example) An example is shown below. The data shown in the examples are measured according to the following method.

Izod impact strength: According to ASTM D 256.

Tensile strength: ASTM D 638 gloss; ASTM D 638 dumbbell test pieces were measured for the glossiness (incident angle 60 °) of the gate part and end gate part and averaged.

Colorability: A certain amount of black face wash was added to 100 parts by weight of resin to give a black colored product, which was a molded piece (vertical 89 mm, width 50 mm,
Thickness 2.5mm). As a control sample, 9% by weight
A black molded piece made by adding dyes and pigments to the high-impact polystyrene containing the polybutadiene rubber is prepared, and the color tone and texture are compared and ranked.

25 per 1 Kg of natural high-impact polystyrene
Black colored molded pieces prepared by adding dyes and pigments equivalent to yen, 20 yen, and 15 yen are referred to as control samples A, B, and C, respectively.

Reference Example 1 Production of rubber-modified polystyrene As a first flow, at a feed rate of 2 / hour, 10% by weight of polybutadiene, 80% by weight of styrene, 10% of ethylbenzene
A mixture consisting of 100 parts by weight of a solution of 100% by weight and 0.045 parts by weight of 1,1 bis (t-butylperoxy) 3,3,5-trimethylcyclohexane is continuously fed into the first polymerization machine. The temperature of the first polymerization machine is 105 ° C. 1 / as the second flow
A mixed solution of 90% by weight of styrene and 10% by weight of ethylbenzene is fed into a second polymerization machine at a temperature of 120 to 140 ° C at a feeding rate of time. The first flow and the second flow are mixed in the mixer under a shearing force with a shear rate of 200 sec ^-1 .

Further, after feeding into a third polymerization machine at a temperature of 110 to 130 ° C. and a fourth polymerization machine at a temperature of 135 to 160 ° C. to proceed polymerization, unreacted monomers and solvent are removed under reduced pressure to form a pelletized rubber. A modified polystyrene is obtained.

According to the above method, the polybutadiene content is 9% by weight, the average particle size of the dispersed rubber particles is in the range of 0.17μ to 1.20μ, and the ratio of the gel component and the rubber component is in the range of 1.8 to 3.2. Seven types of rubber-modified polystyrene were obtained.

Reference Example 2 Production of Rubber Modified Polystyrene 100 parts by weight of a solution consisting of 7% by weight of polybutadiene, 83% by weight of styrene and 10% by weight of ethylbenzene, and 1,1 bis (t
-Butylperoxy) 3,3,5-trimethylcyclohexane (0.045 parts by weight) was continuously fed to the first polymerization machine and the polymerization was continued with stirring, and then the second polymerization machine and the third polymerization machine were used. After further advancing the polymerization with a machine, the unreacted monomer and the solvent are removed under reduced pressure to obtain a pellet-shaped rubber-modified polystyrene.

According to the above method, two kinds of rubber-modified polystyrene having a polybutadiene content of 9% by weight, an average particle diameter of dispersed rubber particles of 0.52μ and 0.55μ, and a gel component / rubber component ratio of 3.5 and 4.0 were prepared. Obtained.

Examples 1 to 4 and Comparative Examples 1 to 5 0.1% by weight of polydimethylsiloxane having a viscosity of 500 centistokes was added to each of the rubber-modified polystyrenes obtained in Reference Example 1 and Reference Example 2 and kneaded in an extruder. A resin composition was obtained and evaluated for Izod impact strength, tensile strength, gloss and colorability. The results are shown in Table-1. If the average particle size is less than 0.20μ, the Izod impact strength will decrease, and
It can be seen that when it exceeds 1.00 μ, gloss and tensile strength decrease. Further, it can be seen that when the ratio of the gel component and the rubber component is less than 2.0, the Izod impact strength decreases, and when it exceeds 3.3, the gloss, colorability and tensile strength decrease. It can be seen that it is preferable that the average particle size is in the range of 0.20 to 1.00 μ and the ratio of the gel component and the rubber component is in the range of 2.0 and 3.3.

Examples 5 to 7 and Comparative Examples 6 to 7 Polydimethylsiloxane used in Example 1 in the rubber-modified polystyrene obtained in Reference Example 1 having an average particle size of 0.50 μ and a gel component to rubber component ratio of 2.8, and A resin composition was obtained in the same manner as in Example 1 with the addition amounts of zinc stearate shown in Table 2, and the physical properties were evaluated. The results are shown in Table-2.
It was shown to. When the amount of polydimethylsiloxane added is as small as 0.002% by weight, the Izod impact strength decreases. If the amount of polydimethylsiloxane added is more than 0.8% by weight, the coloring property is deteriorated, which is not preferable.

Claims (1)

[Claims] 1. A rubber-modified polystyrene composition in which a rubber-like polymer is dispersed in the form of particles, wherein (A) the dispersed particles have an average particle size in the range of 0.20 to 1.00 micron, and (B) in the composition. The ratio of the gel component and the rubber component contained is in the range of 2.0 to 3.3, and (C) the composition contains polydimethylsiloxane in an amount of 0.005 to
High gloss rubber modified polystyrene composition characterized by containing 0.8% by weight