JPH0459847A - Thermoplastic resin composition - Google Patents

Abstract

PURPOSE:To obtain the subject composition, composed of a polystyrene-based resin, a polyolefinic resin and a hydrogenated modified block copolymer in a specific proportion, excellent in impact and oil resistance, capable of providing molded products with a sharp shape and useful as household appliances, automotive parts, etc. CONSTITUTION:The objective composition is composed of (A) 30-70wt.% polystyrene-based resin (e.g. polystyrene), (B) 10-65wt.% polyolefinic resin (e.g. polyethylene) and (C) 5-20wt.% hydrogenated modified block copolymer, having at least one vinyl-substituted aromatic compound polymer block (A) and containing >=0.5wt.% any of organic acids, acid anhydrides and ester groups with at least 70wt.% saturated double bonds.

Description

[Detailed description of the invention] <Industrial application field> The present invention has excellent impact resistance, chemical resistance, oil resistance, and rigidity.
The present invention also relates to a polystyrene resin composition that provides a molded article, particularly a foamed molded article, having a sharp shape.

<Conventional technology> Polystyrene resin is rigid and has good dimensional stability, and is widely used for molding applications, but it lacks impact resistance and has poor chemical and oil resistance, so it is not suitable for many applications. expansion is being hindered.

Also, although the shape is sharp in foam molding,
Lacks softness and shock absorption.

In order to compensate for the drawbacks of the polystyrene resins, attempts have been made to combine them with polyolefin resins. Polystyrene resins and polyolefin resins have poor compatibility, so even if they are mechanically melted and mixed, only a product with poor rigidity and impact resistance can be obtained. Therefore, in order to improve the compatibility between the two, a specific styrene-conjugated diene block copolymer,
Compositions containing hydrogenated block copolymers or ethylene-vinyl acetate copolymers have been proposed. For example, Japanese Patent Publication No. 62-12812 and Japanese Patent Publication No. 62-34
No. 782, JP-A No. 1-174550, etc. G is a hydrogenated styrene-butadiene-styrene pronoc copolymer or a hydrogenated (styrene-butadiene) n-block copolymer with a polystyrene resin and a polyolefin resin. discloses a technique for use as a compatibilizer for However, Japanese Patent Publication No. 62-12812 and Japanese Patent Publication No. 1-17
The invention described in Japanese Patent No. 4550 does not sufficiently improve the impact resistance even when compared to the polystyrene resin used in PACE, and problems remain in practical use. Although the composition disclosed in Japanese Patent Publication No. 62-34782 has excellent impact resistance and oil resistance,
It lacks the rigidity and sharpness of molded products that polystyrene resin has. As described above, a resin composition for molding applications that has the properties of polystyrene resin and polyolefin resin in a well-balanced manner has not yet been obtained.

<Problems to be Solved by the Invention> In view of this situation, the present invention has excellent impact resistance and oil resistance,
The object of the present invention is to obtain a polystyrene resin composition that has a certain degree of rigidity and provides a molded article with a sharp shape.

Means for Solving the Problems> The thermoplastic resin composition of the present invention is conjugated with at least one of (a) a polystyrene resin, (b) a polyolefin resin, and (c) a vinyl-substituted aromatic compound polymer block A. The block copolymer has at least one diene polymer block B, and contains 0.5% by weight or more of an organic acid, acid anhydride, or ester group in the block copolymer, and contains at least 70 of the double bonds in the block copolymer. % saturated hydrogenated block copolymer, and wherein component (a) is saturated at 70 to 3%.
0% by weight, 10-65% by weight of component (b), component (c)
It is characterized by consisting of 5 to 20% by weight.

(a) Polystyrene resins include polystyrene, rubber-modified polystyrene, 7-acrylonitrile-styrene copolymer, acrylonitrile-lostadiene-tyrene copolymer, methyl methacrylate-styrene copolymer, and conjugated diene-styrene copolymer. It is a resin consisting of a vinyl-substituted aromatic compound such as a polymer.

(b) The polyolefin resin is a homopolymer of a-olefin, a copolymer of α-olefin or vinyl acetate, or a mixture thereof. Examples include polyethylene, polypropylene, polymethylpentene, ethylene-propylene ethylene-vinyl acetate copolymer, and the like.

(c) The hydrogenated modified block copolymer has at least one vinyl-substituted aromatic compound polymer block A and at least one conjugated diene polymer block B, and has an organic acid, acid anhydride, or ester group. 0 during block copolymerization
．． It is a hydrogenated block copolymer containing 5% by weight or more, and at least 70% of the double bonds in the block copolymer are saturated. The vinyl-substituted aromatic compound polymer floc A is a homopolymer or copolymer of styrene, α-methylstyrene, p-methylstyrene, and 2,4-dimethylstyrene.

Conjugated diene polymer block B is a homopolymer of 1,3-butadiene and isoprene or a copolymer thereof.

The molecular weight of block A of the above block copolymer is 5ooo
10% by weight of the block copolymer
That's all. Even if a block copolymer outside the above range is used, the compatibility between the polystyrene resin and the polyolefin resin will not be improved, nor will the impact resistance of the resin composition be improved.

Although resin compositions using the block copolymers that have not been modified with organic acids, acid anhydrides, or ester compounds have improved impact resistance and oil resistance, the microscopic morphology of the compositions is quite large. - It becomes an island structure, and this structure varies depending on the composition and crosstalk conditions, making it impossible to obtain stable physical properties.

When the composition of the polyolefin resin is 65% by weight or more,
The rigidity of the molded product is poor, and as a result of the molded product (shrinking), the shape (shape) is not sharp.If the block copolymer in the composition is less than 5% by weight, the impact resistance will not be improved, and if the content of the block copolymer is less than 20% by weight, the rigidity will be poor. Inferior.

As described above, the composition ratio of (a) polystyrene resin and (b) polyolefin resin in the resin composition of the present invention is 3.
0-70: 65-10 is preferred.

The manufacturing method, modification method, and hydrogenation of the block copolymer are not particularly limited.

The resin composition of the present invention may contain any filler if necessary. Examples include glass fiber, titanium white, carbon, silica, talc, mica, and zinc oxide. Furthermore, additives can be added as necessary. Examples include flame retardants, antioxidants, heat stabilizers, ultraviolet absorbers, lubricants, and antistatic agents.

The resin composition of the present invention is produced by melting (a) a polystyrene resin, (b) a polyolefin resin, and (c) a hydrogenated modified block copolymer using a known method such as a single-screw extruder or a twin-screw extruder. It can be manufactured by melting and kneading in a mixer.

The resin composition of the present invention can be molded using a commonly used molding machine. For example, injection molding, extrusion molding,
It is a resin composition that can be molded by blow molding or the like. Also, extrusion foam molding and bead foaming are possible. These molded products have excellent impact resistance, oil resistance, rigidity, and sharp shapes.

<Example> Examples are shown below. The present invention is not limited to these examples.

The data shown in the examples were measured based on the following method.

(1) Izot impact strength: JIS K7110
G followed.

(2) Flexural modulus: According to JIS K7203.

(3) Elongation at break: According to JIS K7113.

(4) Sink marks: The presence or absence of sink marks on injection molded products was visually determined.

○...with sink marks ×...with no sink marks Examples 1 to 4. Comparative Examples 1 to 4 (a) f. Polystyrene (hereinafter abbreviated as GPPS) was used as the listyrene-based resin, Nisbrite 7-62, manufactured by Sumima Kagaku Kogyo ■. MI = 6, density o, 9° (b
) Linear low-density polyethylene (hereinafter abbreviated as L-LDPE) as a polyolefin resin produced by Sumiya Kagaku Kogyo■
Manufactured by Sumikasen'-LGA401.

MI=20. Density 0.925° and ethylene-vinyl acetate copolymer (hereinafter abbreviated as EVA).
Manufactured by Sumitomo Chemical ■, Evatate 0D1032, MI
= 2, density Q, 92. Hinyl acetate content 5wt%.

(c) Shell chemistry department as a hydrogenated block copolymer,
901 (!: omitted), solution viscosity 6000. Density 0.
91. Styrene content 28 wt%.

Kraton G1651 (hereinafter abbreviated as 1651) solution viscosity 6000, density 0.91. Styrene content 29
wt% was used for each.

The resin composition of the present invention was melt-kneaded into pellets using a 40 m single-screw extruder. Thereafter, injection molding was performed to obtain a test piece.

The compositions and physical properties of Examples and Comparative Examples are shown in Table 1.

As shown in the examples, by using a hydrogenated modified block copolymer in a composition within the range described in the present invention, a resin composition with excellent impact resistance, rigidity, and oil resistance can be obtained. Also, foam molding is also good. On the other hand, unless a block copolymer is used, the impact resistance is not improved as shown in Comparative Example 1.

When an unmodified block copolymer is used, impact resistance is not sufficiently improved and oil resistance is also poor.

Comparative Example 3 is a composition containing a large amount of GPPS which is outside the claimed range of the present invention, but the impact resistance is insufficiently improved and the oil resistance is also poor. Comparative Example 4, which has a composition containing a large amount of EVA, has poor rigidity, has sink marks on the molded product, and does not have the characteristics of polystyrene.

<Effects of the Invention> The resin composition obtained by the present invention has the rigidity of a polystyrene resin, the sharpness of a molded product, the impact resistance and oil resistance of a polyolefin resin, and has excellent moldability. It is also suitable for foam molding.The field of use is wide-ranging, including home appliance parts, automobile parts, food packaging, etc.

Claims (1)

[Claims] 1. (a) polystyrene resin, (b) polyolefin resin, (c) at least one vinyl-substituted aromatic compound polymer block A and at least one conjugated diene polymer block B a hydrogenated modified block copolymer containing at least 0.5% by weight of an organic acid, acid anhydride, or ester group in the block copolymer and saturating at least 70% of the double bonds in the block copolymer. A composition comprising: and 70 to 3 of component (a).
0% by weight, 10-65% by weight of component (b), component (c)
A thermoplastic resin composition comprising 5 to 20% by weight of. 2. The thermoplastic resin composition according to claim 1, wherein the polystyrene resin (a) is one selected from polystyrene, rubber-modified polystyrene, acrylonitrile-styrene copolymer, and acrylonitrile-butadiene-styrene copolymer. 3. The thermoplastic resin composition according to claim 1 or 2, wherein the polyolefin resin (b) is polyethylene, polypropylene, ethylene-vinyl acetate copolymer, or a mixture thereof. 4. The thermoplastic resin composition according to claim 1, 2 or 3, wherein the conjugated diene compound of (c) the hydrogenated modified block copolymer is butadiene or isoprene. 5. (c) The thermoplastic resin according to claim 1, 2, 3 or 4, wherein the molecular weight of block A in the hydrogenated modified block copolymer is 5000 or more and is 10% by weight or more based on the block copolymer. Composition.