KR100556619B1 - Thermoplastic Styrene Resin Composition for Gas Assist Injection Molding - Google Patents

Abstract

The present invention (A) 89.5 to 92 parts by weight of a styrene compound; (B) 8 to 10.5 parts by weight of polybutadiene rubber; (C) 1.0 to 3.5 parts by weight of liquid paraffinic mineral oil having a viscosity of 54 to 76 centistokes at room temperature with respect to 100 parts by weight of the base resin; (D) 0.1 to 0.5 parts by weight of polydimethylsiloxane having a viscosity of 10 to 1,000 centistokes at room temperature; (E) 0.01 to 0.1 parts by weight of zinc-stearate, which is a metal salt of a higher fatty acid; (F) 0.02-0.08 parts by weight of t-dodecyl mercaptan as a molecular weight regulator; (G) 0.04 to 0.12 parts by weight of tertiary butyl peroxyacetate as a polymerization initiator; And it is to provide a styrene-based thermoplastic resin composition comprising an optional (H) antioxidant.

Description

Styrene-based thermoplastic resin composition suitable as a gas injection molding material {Thermoplastic Styrene Resin Composition for Gas Assist Injection Molding}             

Field of invention

The present invention relates to a thermoplastic styrene resin composition, and more particularly, to a gas injection molding material, and capable of injection at low temperature, low pressure, and low speed, the structure is complicated, and a thin molding and a super large (50 inch or more) C- The present invention relates to a styrene-based thermoplastic resin composition suitable for molding a TV housing and having excellent flowability in which heat resistance, impact resistance and low temperature impact resistance (minus 20 ° C) are harmonized.

Background of the Invention

Rubber modified polystyrene resin (HIPS) is widely used as a housing for electrical and electronic products due to its good physical properties such as impact resistance, heat resistance and fluidity. In particular, as consumers' preference for super-large products has increased recently, home appliance makers are increasing the production of extra-large products, and at the same time, resin manufacturers are developing resins with improved flowability for molding these products.

As the size of C-TV moldings is increased in size, thickness, and weight, injection molding technology is rapidly shifting to a gas-assist injection molding method. However, the conventional general rubber modified polystyrene resin (HIPS) has low fluidity, so that when the ultra-large C-TV molding is manufactured by using the gas injection molding method, it is practically not applicable due to the problem of unfilled molding and the bursting of the molding due to excessive injection pressure. It was impossible. In addition, injection at a high temperature is not good because it increases the possibility that the resin is decomposed to generate gas, which is a direct cause of the appearance defects of injection products such as flow marks and black lines.

In order to solve the above problems, the present inventors have been developed a styrene-based thermoplastic resin composition suitable for the gas injection method at low temperature, low pressure and low speed, excellent flowability in combination with heat resistance and impact resistance and low temperature impact resistance It is early.

SUMMARY OF THE INVENTION An object of the present invention is to provide a styrene-based thermoplastic resin composition which is suitable for gas injection molding materials at low temperature, low pressure and low speed, and has a complicated structure and is used for molding thin molded articles and ultra-large C-TV housings.

Another object of the present invention is to provide a styrene-based thermoplastic resin composition having excellent fluidity in combination with heat resistance, impact resistance and low temperature impact resistance.

The above and other objects of the present invention can be achieved by the present invention described below. Hereinafter, the content of the present invention will be described in detail.

Styrene-based thermoplastic resin composition suitable as the gas injection molding material of the present invention (A) 89.5 to 92 parts by weight of the styrene compound; (B) 8 to 10.5 parts by weight of polybutadiene rubber; (C) 1.0 to 3.5 parts by weight of mineral oil based on 100 parts by weight of the base resin; (D) 0.1-0.5 weight part of polydimethylsiloxane; (E) 0.01 to 0.1 parts by weight of zinc-stearate, which is a metal salt of a higher fatty acid; (F) 0.02-0.08 parts by weight of t-dodecyl mercaptan as a molecular weight regulator; (G) 0.04 to 0.12 parts by weight of tertiary butyl peroxyacetate as a polymerization initiator; And an optional (H) antioxidant. In the present invention, the above components are subjected to bulk continuous polymerization, and as a result, a styrene-based thermoplastic resin composition having a weight average molecular weight of 130,000 to 170,000 is provided. Hereinafter, the components of the resin composition of the present invention will be described in detail.

Examples of the styrene compound (A) used in the present invention include styrene, α-methylstyrene, α-ethylstyrene, and ρ-methylstyrene.

The polybutadiene-based rubber (B) in the present invention is mixed with 10 to 30% by weight of rubber component (I) and 90 to 70% by weight of rubber component (II). Here, the rubber component (I) is a polybutadiene-based rubber having a 1,4-cis content of 45% by weight or less, a solution viscosity of 190 parts by weight to 5 parts by weight of polybutadiene rubber in 95 parts by weight of styrene monomer, and a level of 190 to 250 centipoise. The rubber component (II) is a polybutadiene rubber having a 1,4-cis content of 99% by weight or less and a solution viscosity of 140 parts by weight to 5 to 5 parts by weight of polybutadiene rubber in 95 parts by weight of the styrene monomer.

The polybutadiene-based rubber (B) is used in an amount of 8 to 10.5 parts by weight based on 100 parts by weight of the base resin consisting of (A) + (B). If it is used in excess of 10.5 parts by weight, heat resistance, fluidity and tensile strength are inferior. In addition, the average particle diameter of the rubbery material dispersed on the styrene-based thermoplastic resin composition should be 0.8 to 2.0 μm. If the average particle diameter is less than 0.8 μm, the impact resistance is lowered. Will fall.

The mineral oil (C) used in the present invention is a liquid paraffinic mineral oil having a viscosity of 54 to 76 centistokes at room temperature, and 1.0 to 3.5 weight parts based on 100 parts by weight of the base resin consisting of (A) + (B). Used as wealth. If the mineral oil (C) is used in less than 1.0 parts by weight fluidity is lowered, when used in excess of 3.5 parts by weight is not good because the heat resistance is lowered.

The polydimethylsiloxane (D) having the following structural formula used in the present invention has a structural unit represented by-(-Si-O-)-and has a viscosity of 10 to 1,000 centistokes at room temperature:

Wherein R represents a methyl group and n is an integer representing a polysiloxane unit.

The polydimethylsiloxane (D) is used in 0.1 to 0.5 parts by weight based on 100 parts by weight of the base resin consisting of (A) + (B), if less than 0.1 parts by weight of injection mold release properties and low temperature impact resistance, 0.5 Excessive use in excess of parts by weight does not improve the low temperature impact resistance.

The zinc-stearate (E), which is a metal salt of a higher fatty acid used in the present invention, is preferably used in an amount of 0.01 to 0.1 parts by weight based on 100 parts by weight of the base resin consisting of (A) + (B), if 0.01 parts by weight If it is added below, the releasability is insufficient, and if it is added at 0.1 parts by weight or more, the problem of gas generation occurs, which is not preferable.

The t-dodecyl mercaptan (F) used as the molecular weight regulator is preferably added in an amount of 0.02 to 0.08 parts by weight based on 100 parts by weight of the base resin consisting of (A) + (B). This is not easy.

In addition, the tertiary butyl peroxyacetate (G) used as a polymerization initiator in the present invention is preferably added in an amount of 0.04 to 0.12 parts by weight based on 100 parts by weight of the base resin consisting of (A) + (B), and if 0.04 parts by weight If it is added below, the graft ratio of the polymer is lowered, and the impact resistance is lowered. If it is added in excess of 0.12 parts by weight, the polymerization reaction occurs rapidly, and the polymerization temperature cannot be controlled, which is dangerous.

Antioxidant (H) optionally used in the present invention includes triethylene glycol-bis-3- (3-t-butyl-4-hydroxy-5-methylphenyl) propionate, etc., which is added at 0.05 parts by weight. desirable.

On the other hand, as a polymerization method for producing the resin composition of the present invention, it is particularly preferable to use a bulk continuous polymerization method, because it is possible to easily produce a product having low production cost and uniform physical properties by mass production.

The graft rate of the final polymer produced by the above method is preferably 125 to 200%, and if the graft rate of the final polymer is less than 125%, the impact resistance is lowered and the impact resistance is lowered even if it exceeds 200%.

The weight average molecular weight (Mw) of the final polymer is preferably adjusted to 130,000 to 170,000 by adjusting the amount of the molecular weight regulator and the polymerization initiator, the polymerization temperature and the reaction time, and when the weight average molecular weight is less than 130,000, the impact resistance and stiffness are inferior. If it exceeds 170,000, the fluidity is lowered.

The thermoplastic resin composition of the present invention can be more clearly understood by the following examples, and the following examples are merely illustrative purposes of the present invention and are not intended to limit the scope of the invention.

Example

Example 1

8 parts by weight of polybutadiene rubber (10 parts by weight of rubber component (I) and 90 parts by weight of rubber component (II)) in 92 parts by weight of styrene, 3.5 parts by weight of liquid paraffinic mineral oil having a viscosity of 54 to 76 centistokes at room temperature. Parts, 0.1 parts by weight of polydimethylsiloxane having a viscosity of 10 to 1,000 centistokes at room temperature, and triethylene glycol-bis-3- (3-t-butyl-4-hydroxy-5-methylphenyl) propionate as an antioxidant 0.05 parts by weight and 0.02 parts by weight of zinc-stearate are added to the metal salt of a higher fatty acid, 0.12 parts by weight of tertiary butyl peroxyacetate as a polymerization initiator and 0.02 parts by weight of t-dodecylmercaptan as a molecular weight regulator are added by mass continuous polymerization. A polymer having a rubber particle average particle diameter of 2.0 탆, a graft ratio of a final polymer of 200%, and a weight average molecular weight of 170,000 was prepared. After injection into an injection molding machine to produce a test specimen for physical properties, the physical properties were measured under the following conditions, and the results are shown in Table 1.

Properties Measuring conditions Izod impact strength ASTM D258 (Sample Thickness: 1/8 inch) Vicat Softening Point ISO R306B (Rate: 50 ℃ / hr) The tensile strength ASTM D638 (TEST SPEED: 20mm / min) liquidity ASTM D1238 (200 ° C, 5kg) Low Temperature Izod Impact Strength ASTM D258 (-20 ℃, Specimen Thickness: 1/8 inch)

Example 2

9.5 parts by weight of polybutadiene rubber (20 parts by weight of rubber component (I) and 80 parts by weight of rubber component (II)), 90.5 parts by weight of styrene, 1.8 parts by weight of liquid paraffinic mineral oil, 0.3 parts by weight of polydimethylsiloxane, higher fatty acid In the same manner as in Example 1, except that 0.02 parts by weight of zinc-stearate as a metal salt, 0.04 parts by weight of tertiary butyl peroxyacetate as a polymerization initiator, and 0.08 parts by weight of t-dodecylmercaptan as a molecular weight regulator are used. Was carried out. As a result, a polymer having an average particle diameter of 1.5 μm in rubber phase, a graft ratio of 155% in a final polymer, and a weight average molecular weight of 150,000 was prepared, and the results of the measurement are shown in Table 1 below.

Example 3

10.5 parts by weight of polybutadiene rubber (30 parts by weight of rubber component (I) and 70 parts by weight of rubber component (II)) in 89.5 parts by weight of styrene, 1.0 part by weight of liquid paraffinic mineral oil, 0.5 part by weight of polydimethylsiloxane, and higher fatty acids. Example 2 except that 0.02 parts by weight of zinc-stearate as a metal salt, 0.08 parts by weight of tertiary butyl peroxyacetate as a polymerization initiator, and 0.05 parts by weight of t-dodecylmercaptan as a molecular weight regulator are used. It was. As a result, a polymer having an average particle diameter of 0.8 μm in rubber, a graft rate of 125%, and a weight average molecular weight of 130,000 was prepared, and the physical properties thereof were shown in Table 1 below.

Comparative Example 1

9 parts by weight of polybutadiene rubber (40 parts by weight of rubber component (I) and 60 parts by weight of rubber component (II)), 91 parts by weight of styrene, 0.5 parts by weight of liquid paraffinic mineral oil, 0.6 parts by weight of polydimethylsiloxane, and higher fatty acids. In the same manner as in Example 1, except that 0.02 parts by weight of zinc-stearate as a metal salt, 0.05 parts by weight of tertiary butyl peroxyacetate as a polymerization initiator, and 0.04 parts by weight of t-dodecylmercaptan as a molecular weight regulator were used. Was carried out. As a result, a polymer having an average particle diameter of rubber phase of 3.0 μm, a graft ratio of 140% of a final polymer, and a weight average molecular weight of 140,000 was prepared, and the results of the measurement are shown in Table 1 below.

Comparative Example 2

7.0 parts by weight of polybutadiene rubber (50 parts by weight of rubber component (I) and 50 parts by weight of rubber component (II)) in 93 parts by weight of styrene, 3.5 parts by weight of mineral oil of liquid paraffin, 1.0 part by weight of polydimethylsiloxane, high quality As in Example 1, except that 0.02 parts by weight of zinc-stearate as a metal salt of fatty acid, 0.12 parts by weight of tertiary butyl peroxyacetate as a polymerization initiator, and 0.01 parts by weight of t-dodecyl mercaptan as a molecular weight regulator are used. Was carried out. As a result, a polymer having an average particle diameter of rubber phase of 0.6 μm, a graft ratio of 210% of a final polymer, and a weight average molecular weight of 190,000 was prepared, and the results are shown in Table 1 below.

Comparative Example 3

18.5 parts by weight of polybutadiene rubber (70% by weight of rubber component (I) and 30% by weight of rubber component (II)), 3.5 parts by weight of liquid paraffinic mineral oil, and zinc stearate as a metal salt of higher fatty acid It carried out similarly to Example 1 except having added 0.02 weight part, tertiary butyl peroxy acetate which is a polymerization initiator, and 0.03 weight part of t-dodecyl mercaptans which are molecular weight regulators. As a result, a polymer having an average particle diameter of rubber phase of 2.7 μm, a graft ratio of 110% of a final polymer, and a weight average molecular weight of 160,000 was prepared. The results of the measurement are shown in Table 1 below.

division Example Comparative Example One 2 3 One 2 3 Component (parts by weight) Styrene (A) 92 90.5 89.5 91 93 88.5 Polybutadiene rubber (B) 8.0 9.5 10.5 9.0 7.0 11.5 Mineral Oil (C) 3.5 1.8 1.0 0.5 3.5 3.5 Polydimethylsiloxane (D) 0.1 0.3 0.5 0.6 1.0 0 Zinc Stearate (E) 0.02 0.02 0.02 0.02 0.02 0.02 t-dodecyl mercaptan (F) 0.02 0.08 0.05 0.04 0.01 0.03 Tertiary Butyl Peroxy Acetate (G) 0.12 0.04 0.08 0.05 0.12 0.02 Properties Average Particle Diameter of Rubber Shape (㎛) 2.0 1.5 0.8 3.0 0.6 2.7 Graft Rate (%) 200 155 125 140 210 110 Weight average molecular weight (only) 17 15 13 14 19 16 Izod impact strength (kgcm / kg) 14.2 15.7 16.4 12.3 11.6 17.1 Vicat Softening Point (℃) 86.9 88.9 88.5 89.2 88.2 80.5 Tensile strength (kg / cm²) 278 267 246 258 288 225 Fluidity (g / 10min) 16.5 14.8 15.4 13.5 15.8 12.5 Low temperature (-20 ℃) Izod impact strength (kgcm / kg) 11.2 12.9 13.8 9.1 8.6 11.2

As can be seen in Table 1, in Comparative Example 1 compared with Examples 1 to 3 showing that the resin composition is polymerized within the desired content of each component of the present invention to improve heat resistance, impact resistance and low temperature impact resistance. Component (C) was used at less than 1.0 part by weight, resulting in low fluidity, and component (D) was used in excess of 0.5 parts by weight, but the low temperature impact resistance was not significantly improved. In Comparative Example 2, the component (B) was used in less than 8 parts by weight to significantly reduce the impact resistance, and the component (F) used as the molecular weight regulator was used in less than the preferred content of the resin having a target weight average molecular weight or more The composition was prepared and such a high weight average molecular weight resulted in lowered fluidity. In addition, in Comparative Example 3, the heat resistance, fluidity, and tensile strength were decreased due to the component (B) used outside the preferred content range of each component of the present invention, and the graft ratio was lowered due to the component (G), resulting in a lower impact resistance. Showed.

The present invention is suitable for gas injection molding materials at low temperature, low pressure, and low speed, and is used for forming a complicated structure, thin molding, and ultra-large C-TV housing, and combining heat resistance, impact resistance, and low temperature impact resistance (less than 20 ° C). It has the effect of providing the styrenic thermoplastic resin composition having excellent fluidity.

Simple modifications or changes of the present invention can be easily carried out by those skilled in the art, and all such modifications or changes can be seen to be included in the scope of the present invention.

Claims (7)

(A) 89.5-92 weight part of styrene compounds; (B) 8 to 10.5 parts by weight of polybutadiene rubber; (C) 1.0 to 3.5 parts by weight of mineral oil based on 100 parts by weight of the base resin; (D) 0.1-0.5 weight part of polydimethylsiloxane; (E) 0.01 to 0.1 parts by weight of zinc-stearate, which is a metal salt of a higher fatty acid; (F) 0.02-0.08 parts by weight of t-dodecyl mercaptan as a molecular weight regulator; (G) 0.04 to 0.12 parts by weight of tertiary butyl peroxyacetate as a polymerization initiator; And an optional (H) antioxidant. A styrene-based thermoplastic resin composition suitable for a gas injection molding material. The styrene-based thermoplastic resin composition according to claim 1, wherein the polybutadiene-based rubber (B) is dispersed on the resin composition, and the average particle diameter of the rubber phase is 0.8 to 2.0 µm. The styrene-based thermoplastic resin composition according to claim 1, wherein the graft ratio of the styrene-based thermoplastic resin composition is 125 to 200%. The styrene-based thermoplastic resin composition according to claim 1, wherein the weight average molecular weight (Mw) of the styrene-based thermoplastic resin composition is 130,000 to 170,000. According to claim 1, wherein the polybutadiene-based rubber (B) is made of a mixture of 10 to 30% by weight of the rubber component (I) and 90 to 70% by weight of the rubber component (II), wherein the rubber component ( I) is a polybutadiene-based rubber having a 1,4-cis content of 45% by weight or less and a solution viscosity of 190 parts by weight to 5 parts by weight of 5 parts by weight of polybutadiene rubber in 95 parts by weight of a styrene monomer. ) Is a styrene-based thermoplastic resin composition having a 1,4-cis content of 99% by weight or less, and a solution viscosity of 5 parts by weight of polybutadiene rubber to 95 parts by weight of the styrene monomer is 140 to 170 centipoise. The styrene-based thermoplastic resin composition according to claim 1, wherein the mineral oil (C) is a liquid paraffin-based mineral oil having a viscosity of 54 to 76 centistokes at room temperature. The styrene-based thermoplastic resin composition according to claim 1, wherein the polydimethylsiloxane (D) has a viscosity of 10 to 1,000 centistokes at room temperature and has the following structural formula:

Wherein R represents a methyl group and n is an integer representing a polysiloxane unit.