JP2848220B2 - Injection molded product made of rubber-modified polystyrene resin composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection molded article comprising a rubber-modified polystyrene resin composition.
More specifically, the present invention relates to an injection molded article comprising a rubber-modified polystyrene resin composition having excellent impact strength, rigidity and surface gloss.

[0002]

2. Description of the Related Art A rubber-modified polystyrene resin composition obtained from a polystyrene resin and a rubbery polymer is a so-called high impact polystyrene (High Impact P).
polystyrene (HIPS). Such impact-resistant polystyrene is useful as a resin having improved impact strength while maintaining the rigidity of ordinary polystyrene.

[0003] Incidentally, rubber-modified polystyrene resin compositions are widely used for injection molded products such as OA equipment and home electric appliances. The resin composition used in such applications is required to have excellent mechanical properties such as impact resistance and rigidity, and have excellent surface gloss, that is, excellent appearance properties. And such demands have reached an increasingly high level in recent years.

However, the rubber-modified polystyrene-based resin composition is not always satisfactory in view of sufficiently satisfying all the above requirements.

[0005]

An object of the present invention is to provide an injection-molded article comprising a rubber-modified polystyrene resin composition having excellent impact resistance, rigidity and surface gloss.

[0006]

That is, the present invention provides a rubber-modified polystyrene resin composition comprising a polystyrene resin forming a matrix and soft component particles dispersed in the resin. The present invention relates to an injection-molded product comprising a rubber-modified polystyrene resin composition satisfying the conditions of A) to (D). (A) The length average particle diameter (D ₁ ) of the soft component particles represented by the following formula is 0.15 to 0.29 μm. D ₁ = 1ni · Di / Σni (where ni is the particle diameter D
i is the number of soft component particles, and Σ represents the total for i. (B) The ratio (D ₄ / D) of the weight average particle diameter (D ₄ ) of the soft component particles represented by the following formula and the length average particle diameter (D ₁ ).
The value of D ₁ ) is 1.00 to 1.25. D ₄ = Σni · Di ⁴ / Σni Di ³ (C) The toluene swelling degree of the soft component particles is 10.0 to 1
5.0 (D) The content of the soft component particles in the rubber-modified polystyrene resin composition is 20.0 to 35.0% by weight.

The details will be described below. The rubber-modified polystyrene-based resin composition of the present invention is a rubber-modified polystyrene-based resin composition comprising a polystyrene-based resin forming a matrix and soft component particles dispersed in the resin.

[0008] Styrene is generally used as the styrene compound monomer constituting the polystyrene resin.
Alkyl-substituted styrenes such as o-methylstyrene, m-methylstyrene and p-methylstyrene can also be used.

As the rubbery polymer, a butadiene polymer, a styrene-butadiene copolymer, an isoprene polymer, a styrene-isoprene copolymer and the like can be used. Further, a styrene-butadiene copolymer and a butadiene polymer can be used in combination. As the butadiene polymer, either so-called high cis polybutadiene having a high cis content or so-called middle cis polybutadiene having a cis content of about 35% can be used.

In the present invention, the soft component particles represented by the following formula have a length average particle diameter (D ₁ ) of 0.15 to 0.2.
9 μm, preferably 0.15 to 0.25 μm.

D ₁ = Σni · Di / Σni (where n
i is the number of soft component particles having a particle diameter Di, and Σ represents the sum of i. )

When D ₁ is too small, the impact strength is poor, while when D ₁ is too large, the rigidity and / or surface gloss are poor.

In the present invention, the value of the ratio (D ₄ / D ₁ ) between the weight average particle diameter (D ₄ ) of the soft component particles represented by the following formula and the above length average particle diameter (D ₁ ) is as follows: 1.00-1.
25.

D ₄ = Σni · Di ⁴ / Σni Di ³

If the value of the ratio is excessive, the rigidity and / or surface gloss are poor. Note that the value of the ratio does not become 1 or less.

In order to determine the above Di and ni, transmission electron micrographs of ultrathin sections of the rubber-modified polystyrene resin composition were taken, and the soft component particles 200 to 5 in the photographs were taken.
The particle size (Di) and the number of particles (ni) of 00 particles
Should be observed. When the particles are not perfectly circular, the average value of the maximum diameter and the minimum diameter is defined as the particle diameter.

In the present invention, the degree of swelling of the soft component particles in toluene is 10.0 to 15.0. When the degree of swelling is too small, the impact strength is poor, while when the degree of swelling is too high, the surface gloss is poor.

The degree of swelling of the soft component particles in toluene is as follows:
It is measured by the method. That is, the rubber-modified po
About 1.0 g of the styrene resin composition is precisely weighed and collected,
At room temperature (about 23 ° C.), a toluene solvent 50
Dissolve in ml. Next, the insoluble matter during the dissolution was centrifuged.
(Approximately 10,000 revolutions / minute x 2 hours) and decantation
Weight of isolate isolated by toluene and swollen by toluene
(W_Three) Is measured. In addition, the isolated
After adding 0.5 ml, the mixture is dried, and the weight after drying (W _Four)
Measure. The toluene swelling degree of the soft component particles is (W_Three-W
_Four) / W_FourRequired by

In the present invention, the content of the soft component particles in the rubber-modified polystyrene resin composition is from 20.0 to 3
5.0% by weight. When the content of the soft component particles is too small, the impact strength is poor, while when the content of the soft component particles is too large, the rigid surface gloss is poor.

The content of the soft component particles in the rubber-modified polystyrene resin composition is measured by the following method. Specifically, about 0.5 g of a rubber-modified polystyrene resin composition as a sample was precisely weighed (weight: W ₁ ), and the sample was mixed at room temperature (about 23 ° C.) with a mixed solvent of methyl ethyl ketone-methanol (volume ratio of methyl ethyl ketone / methanol =
10/1) Dissolve in 50 ml. Next, the insoluble matter during the dissolution is isolated by centrifugation and decantation, and the insoluble matter is dried and its weight (W ₂ ) is measured. Content of the soft component particles in the rubber-modified polystyrene resin composition is obtained by _{W 2 / W 1 × 100%} .

In the present invention, the soft component particles are constituted by a core portion, which is a single continuous phase composed only of a polystyrene resin, and a shell portion composed of a rubber-like polymer containing the core portion (occlude). Further, it is preferable to have a single occlusion structure (also referred to as a core / shell structure or a capsule structure). Generally, the structure of the soft component particles in the rubber-modified polystyrene-based resin composition includes a single occlusion structure and a plurality of small particles of polystyrene-based resin dispersed in a continuous phase composed of a rubber-like polymer. There is a so-called salami structure. The observation of the structure of the soft component is performed using a transmission electron microscope as in the measurement of the average particle diameter described above.

The method for producing the rubber-modified polystyrene-based resin composition of the present invention includes a usual method of obtaining polystyrene, that is, a method of polymerizing a styrene-based compound (monomer) in the presence of a rubber-like polymer. I can give it. Here, the polymerization reaction method includes a bulk polymerization method or a bulk-suspension two-stage polymerization method. The distribution characteristics of the particle diameter of the soft component particles, the degree of swelling of the soft component particles in toluene,
The structure of the soft component particles in the rubber-modified polystyrene resin composition can be controlled by adjusting the type and amount of the rubbery polymer to be added, the stirring speed during the polymerization reaction, the temperature, the amount of the chain transfer agent, and the like.

The method for obtaining an injection-molded article using the rubber-modified polystyrene resin composition of the present invention is not particularly limited, and a usual method can be used.

The thus obtained injection molded article comprising the rubber-modified polystyrene resin composition of the present invention is excellent in impact resistance, rigidity and surface gloss. For example, it is suitably used for OA equipment and home electric appliances.

[0025]

Next, the present invention will be described by way of examples. The measurement and evaluation methods are as follows. Items other than those described below were performed as described above. (1) Impact strength (Izod impact strength) Measured according to JIS K7110. However, the standard for the thickness of the notched sample of 6.4 mm was adopted. (2) Rigidity (rigidity) Measured in accordance with JIS K7203. (3) Surface gloss (surface appearance) A flat plate with a thickness of 2 mm is injection molded, and the central part is JIS
It was measured according to the standard of K7105 45 degree specular gloss measurement method. The molding machine used was Toshiba IS-150E,
Mold temperature 40 ° C, sample shape 150 × 90 × 2mmt
And

Example 1 80% by weight of styrene monomer, 12% by weight of styrene-butadiene copolymer,
A mixture consisting of 3% by weight of mineral oil and 3% by weight of mineral oil was sent, and at a temperature of 140.degree.
The polymerization was carried out to a conversion of 37.5%. Subsequently, the obtained mixture is polymerized to a conversion of 79% using a liquid-filled polymerization tank, and then volatile components are removed in a degassing tank at 240 ° C. to obtain a pellet-shaped rubber-modified polystyrene resin composition. Was.

Examples 2 to 4 Several types of styrene-butadiene copolymer rubbers and corresponding polymerization temperatures, stirring speeds, conversions,
The rubber-modified polystyrene resin composition in the form of pellets of Examples 2 to 3 was obtained by changing the temperature of the degassing layer and further changing the amount of the chain transfer agent. Further, the sample of Example 2 and the general-purpose polystyrene containing no rubber particles were mixed at a weight ratio of 70%.
/ 30 was blended with a normal extrusion-type granulator to obtain a pellet-shaped rubber-modified polystyrene resin composition of Example 4.

Comparative Examples 1 to 6 Several types of styrene-butadiene copolymer rubbers and the amounts of initiator, polymerization temperature, stirring speed, conversion, deaeration layer temperature, and chain transfer agent amount according to each type Was changed to obtain pellet-shaped rubber-modified polystyrene resin compositions of Comparative Examples 1 to 6.

The results are shown in Tables 1 and 2. From these results, the following can be understood. All examples according to the present invention show satisfactory results in all evaluation items. On the other hand, each comparative example lacking the requirements of the present invention is inconvenient as follows. Comparative Example 1 in which the degree of toluene swelling is too small, Comparative Example 2 in which the content of the soft component particles is too small, and Comparative Example 3 in which the length average particle diameter of the soft component particles is too small are all inferior in impact resistance. Comparative Example 4, in which the length average particle diameter of the soft component particles is excessively large and the ratio of the length average particle diameter to the weight average particle diameter is excessive, is inferior in surface gloss. Comparative Example 5, in which the ratio between the length average particle diameter and the weight average particle diameter is excessive, is inferior in rigidity and surface gloss. Comparative Example 6, in which the degree of toluene swelling is excessive, is inferior in surface gloss.

[0030]

Table 1 Structure of soft component particle * 1 OOOOD ₁ μm 0.180 0.185 0.206 0.185 D ₄ μm 0.195 0.211 0.238 0.211 D ₄ / D ₁ 1.083 1.140 1.155 1.140 Toluene swelling 13.5 11.2 12.5 11.1 Content of soft component particles wt% 26.7 30.0 27.9 21.1 Evaluation Impact strength kg ・ cm / cm 6.4 6.7 6.8 4.8 Flexural modulus kg / cm ² 19800 19000 18900 22200 Surface gloss% 101.8 103.0 103.0 103.4 −−−−−−−−−−−−−−−−−−−−−−−−−−−−−

[0031]

[Table 2]--------------------------------------Comparative Example 1 2 3 4 5 6 Soft Structure of component particles * 1 OOOOOOD ₁ μm 0.180 0.170 0.142 0.306 0.207 0.195 D ₄ μm 0.195 0.206 0.159 0.465 0.269 0.233 D ₄ / D ₁ 1.083 1.212 1.112 1.520 1.300 1.195 Toluene swelling 8.1 14.2 14.7 14.1 13.4 18.1 Content of soft component particles wt% 26.7 16.8 24.7 24.5 28.0 24.2 Evaluation Impact strength kg ・ cm / cm 3.1 2.4 2.6 6.0 7.0 7.2 Flexural modulus kg / cm ^{2 20} 100 23 ^{200 20} 600 18600 16400 18400 Surface gloss% 101.5 102.3 102.4 96.9 98.7 95.4 −−−−− −−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−

* 1 Structure of Soft Component Particles O: Single Occlusion Structure

[0033]

As described above, according to the present invention, an injection-molded article comprising a rubber-modified polystyrene resin composition excellent in impact strength, rigidity and surface gloss can be provided.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-5-320272 (JP, A) JP-A-4-227711 (JP, A) JP-A-3-197522 (JP, A) JP-A-63- 122720 (JP, A) JP-A-63-122718 (JP, A) JP-A-60-130614 (JP, A) JP-A-60-130613 (JP, A) Special table 61-500497 (JP, A) (58) Field surveyed (Int. Cl. ⁶ , DB name) C08F 251/00-292/00

Claims (2)

(57) [Claims] 1. A rubber-modified polystyrene-based resin composition comprising a polystyrene-based resin forming a matrix and soft component particles dispersed in the resin, and satisfying the following conditions (A) to (D): An injection molded article comprising a rubber-modified polystyrene resin composition. (A) The length average particle diameter (D ₁ ) of the soft component particles represented by the following formula is 0.15 to 0.29 μm. D ₁ = 1ni · Di / Σni (where ni is the particle diameter D
i is the number of soft component particles, and Σ represents the total for i. (B) The ratio (D ₄ / D) of the weight average particle diameter (D ₄ ) of the soft component particles represented by the following formula and the length average particle diameter (D ₁ ).
The value of D ₁ ) is 1.00 to 1.25. D ₄ = Σni · Di ⁴ / Σni Di ³ (C) The toluene swelling degree of the soft component particles is 10.0 to 1
5.0 (D) The content of the soft component particles in the rubber-modified polystyrene resin composition is 20.0 to 35.0% by weight. 2. A soft component particle comprising a core portion, which is a single continuous phase composed only of a polystyrene resin, and a shell portion composed of a rubber-like polymer that includes the core portion (occlude). An injection molded article comprising the rubber-modified polystyrene resin composition according to claim 1, which has an occlusion structure.