JPH10310670A - Styrene-based resin composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a styrene-based resin composition that can give moldings having excellent persistent antistatic effect, good appearance and excellent impact strength, by compounding a rubber-modified styrene-based resin with a potassium-containing ethylene/unsaturated carboxylic acid copolymer ionomer, a styrene-based thermoplastic elastomer and an ethylene/methyl methacrylate copolymer. SOLUTION: The rubber-modified styrene-based resin is exemplified by an acrylonitrile/butadiene rubber/styrene copolymer. The ethylene/unsaturated carboxylic acid copolymer ionomer is desirably one having a structure derived by neutralizing part or all of the carboxyl groups of an ethylene/unsaturated carboxylic acid random copolymer with potassium ions and having a potassium ion content in the range of 0.4-4 mol/kg. The thermoplastic styrene elastomer used is desirably a block copolymer of styrene with e.g. butadiene. The ethylene/ methyl methacrylate copolymer is desirably one containing 10-50 wt.% methyl methacrylate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a styrenic resin composition, and more particularly to a styrenic resin composition having excellent appearance of a molded article, good balance of physical properties, and sustained antistatic properties.

[0002]

2. Description of the Related Art Plastics generally have a high electrical insulation property and are easily charged by friction and the like, so that dust and dirt adhere to the plastic to impair the appearance of the molded product surface or cause malfunctions of electronic equipment. have.

[0003] In order to improve such disadvantages, conventionally,
A method of preventing static charge of plastic molded articles by kneading an antistatic agent composed of various surfactants into a resin has been adopted.However, low molecular weight surfactants are washed with water on the molded article surface or There is a problem that the antistatic effect is lost due to short-term use because it is removed by performing a treatment such as wiping with a cloth.

It is also known that ionomers of an ethylene / unsaturated carboxylic acid copolymer using an alkali metal as an ion source are excellent in non-charging properties, and such non-charging ionomers are blended in a polymer. It is also known to prevent charging of polymer compositions. However, the surface resistivity of such a composition has a large temperature dependency, and the antistatic effect in a low humidity atmosphere is insufficient.

As a means for solving the above problems, Japanese Patent Application Laid-Open No. 8-134295 discloses that a compound having a molecular weight of 400 or less having three or more hydroxyl groups in a molecule is blended into an alkali metal ionomer, and this is mixed with a resin. A method of kneading is disclosed.

[0006]

The method disclosed in Japanese Patent Application Laid-Open No. 8-134295 provides a good antistatic effect even in a low-humidity atmosphere and is excellent in persistence, but the molded product is not delaminated. There is a problem that appearance is spoiled because it is easily caused, and there is a problem that impact strength is low.

[0007] Under such circumstances, an object of the present invention is to provide a styrene resin composition having excellent antistatic effect, preventing appearance defects due to delamination, and having good impact resistance. .

[0008]

The present inventors have conducted intensive studies to solve the above-mentioned problems. As a result, (a) a rubber-modified styrenic resin was added to (b) ethylene / ethylene resin using potassium as an ion source.
By blending the ionomer of an unsaturated carboxylic acid copolymer, (c) a styrene-based thermoplastic elastomer, and (d) an ethylene / methyl methacrylate copolymer, appearance defects can be prevented, and the impact strength is excellent. The inventors have found that a styrene-based resin composition capable of maintaining antistatic properties can be obtained, and have completed the present invention.

[0009]

DETAILED DESCRIPTION OF THE INVENTION The styrene resin composition of the present invention comprises (a) a rubber-modified styrene resin, (b) an ionomer of an ethylene / unsaturated carboxylic acid copolymer using potassium as an ion source, and (c) It is characterized in that a styrene-based thermoplastic elastomer and (d) an ethylene / methyl methacrylate copolymer are essential components. (A) a rubber-modified styrenic resin, (b) an ionomer of an ethylene / unsaturated carboxylic acid copolymer using potassium as an ion source,
A styrenic resin composition having excellent appearance of molded articles, good balance of physical properties, and sustained antistatic properties by using (c) a styrene-based thermoplastic elastomer and (d) an ethylene / methyl methacrylate copolymer in combination. Can be obtained.

Hereinafter, the present invention will be described specifically. The rubber-modified styrenic resin (a) used in the present invention includes:
Acrylonitrile / butadiene rubber / styrene copolymer, methyl methacrylate / butadiene rubber / styrene copolymer, acrylonitrile / ethylene / propylene rubber / styrene copolymer, acrylonitrile / acrylic rubber / styrene copolymer, butadiene rubber / Styrene copolymer and the like.

The ionomer of (b) an ethylene / unsaturated carboxylic acid copolymer using potassium as an ion source, which is used in the present invention, is characterized in that some or all of the carboxyl groups of the ethylene / unsaturated carboxylic acid random copolymer are potassium. It has a structure neutralized with ions. The ethylene / unsaturated carboxylic acid random copolymer has an ethylene component of 60
-95% by weight, especially 70-90% by weight, unsaturated carboxylic acid component in 5-40% by weight, especially 10-30% by weight, other unsaturated monomer component in 0-30% by weight, especially 0-20% It is preferred that they are copolymerized in a proportion of weight%. Such a copolymer can be obtained by random copolymerization of each polymerization component under high temperature and high pressure. In addition, examples of the unsaturated carboxylic acid component in the ionomer include acrylic acid, methacrylic acid, fumaric acid, maleic acid monomethyl ester, maleic acid monoethyl ester, and maleic anhydride.
The content of potassium ions in the ionomer is desirably in the range of 0.4 to 4 mol, preferably 0.6 to 2 mol, per kg of the ionomer from the viewpoint of non-charging properties. Further, it is preferable to use one having a degree of neutralization with potassium (average degree of neutralization when two or more ionomers are used) of 60 mol% or more, particularly 70 mol% or more. In the ionomer component in the present invention, a plasticizer for improving antistatic performance and processability, for example, a polyoxyalkylene polyol, a polyvalent hydroxy compound such as glycerol or trimethylolpropane, etc., per 100 parts by weight of the polymer component,
0.1 to 20 parts by weight, preferably 0.5 to 10 parts by weight may be added. When the addition amount is less than 0.1 part by weight,
The effect of improving the antistatic property is not sufficiently obtained. On the other hand, when the amount is more than 20 parts by weight, it becomes difficult to adjust the composition, and the surface contamination by bleed is liable to occur.

The (c) styrene-based thermoplastic elastomer used in the present invention is a block copolymer composed of an aromatic vinyl monomer and a conjugated diene monomer, or a conjugated diene monomer part is partially hydrogenated. Block copolymer. Styrene is most preferred as the aromatic vinyl monomer constituting the block copolymer, and 1,3-butadiene, isoprene and the like are preferred as the conjugated diene monomer. In the block structure of the block copolymer, a polymer block composed of an aromatic vinyl monomer is represented by S, and a polymer block composed of a conjugated diene and / or a partially hydrogenated unit thereof is represented by B. In this case, a linear block copolymer of SB, S (BS) _n (where n is an integer of 1 to 3), S (BSB) _m (where m is an integer of 1 to 2), or (SB) _p X (However, p
Is an integer of 3 to 6, and X is a star block copolymer having a bonding center at the B portion represented by a coupling agent residue such as silicon tetrachloride, tin tetrachloride, or a polyepoxy compound. Is preferred. Above all, type 2 of SB, SBS
And the SBSB type 4 linear block copolymer are preferred. In particular, the styrene thermoplastic elastomer (c) used in the present invention includes styrene-butadiene.
It is preferably a styrene block copolymer. The butadiene content in the block copolymer is 30 to 80% by weight, preferably 50 to 70% by weight. When the butadiene content is in the range of 30 to 80% by weight, the block copolymer is present at the interface between the styrene resin and the ionomer resin, and the compatibility of both resins can be enhanced.

The ethylene-methyl methacrylate copolymer (d) used in the present invention has a methyl methacrylate content of preferably 10 to 50% by weight, more preferably 20 to 40% by weight. Methyl methacrylate (MM
When the content of A) is in the range of 10 to 50% by weight, coordination to the vicinity of the surface of the ionomer resin can be enhanced.

In the present invention, (a) a rubber-modified styrenic resin component and (b) ethylene
The preferred compounding ratio of the ionomer of the unsaturated carboxylic acid copolymer, (c) the styrene-based thermoplastic elastomer, and (d) the ethylene / methyl methacrylate copolymer is as follows:
Component (b) is 1 to 15 parts by weight, component (c) is 1 to 10 parts by weight, and component (d) is 1 to 10 parts by weight based on 100 parts by weight of component (a).
Parts by weight. More preferred compounding ratio is (a) component 10
Component (b) is 3 to 10 parts by weight with respect to 0 parts by weight, and (c)
Component is 1 to 5 parts by weight, and component (d) is 1 to 5 parts by weight. If the amount of the component (b) is less than 1 part by weight, the antistatic effect is not sufficient. If the amount is more than 15 parts by weight, the inherent properties of the styrene resin, such as rigidity and moldability, are impaired and foaming due to an increase in moisture absorption. The phenomenon becomes easier to appear.
If the amount of the component (c) is less than 1 part by weight, the effect of improving the impact resistance is not sufficient, and delamination tends to occur. If the amount is more than 10 parts by weight, the inherent properties of the styrene-based resin such as rigidity and moldability. Is impaired. When the amount of the component (d) is less than 1 part by weight, the antistatic effect is not sufficient, and when the amount is more than 10 parts by weight, impact resistance is deteriorated.

In the present invention, by further containing (e) an anionic surfactant, a styrene resin composition having more excellent antistatic performance can be obtained. Representative examples of the anionic surfactant include an alkyl sulfonate, an alkylbenzene sulfonate, a higher alcohol sulfate, a higher alcohol phosphate, and the like, and these may be used alone or in combination of two or more. Can be used. The addition amount is 0.5 to 5 parts by weight based on 100 parts by weight of the rubber-modified styrene resin (a).
Preferably, it is 1 to 3 parts by weight. When the amount is less than 0.5 part by weight, the effect of improving the antistatic property is small, and when the amount is more than 5 parts by weight, bleeding tends to cause surface contamination.

The styrenic resin composition of the present invention can be produced by a commonly used mixing method, for example, mixing by a roll, a Banbury mixer, a Henschel mixer, a single screw extruder, a twin screw extruder, or the like.

The styrenic resin composition of the present invention may optionally further contain known antioxidants, heat stabilizers, ultraviolet absorbers, lubricants, flame retardants, foaming agents, dyes and pigments, if necessary. it can.

[0018]

EXAMPLES Examples of the present invention will be described below in more detail, but the present invention is not limited to these examples.

Examples 1-4, Comparative Examples 1-3 (a) rubber-modified styrene resin, (b) ionomer of ethylene / unsaturated carboxylic acid copolymer using potassium as ion source, (c) styrene-based heat Plastic elastomer,
(D) Ethylene methacrylate copolymer and (e) anionic surfactant were melt-kneaded at a cylinder temperature of 200 ° C. using a twin-screw extruder at a ratio shown in Tables 1 and 2, and pelletized. . Then, each test piece was molded by an injection molding machine, and the properties of each test piece were evaluated. Evaluation of each physical property value and the like were performed by the following methods.

(1) Specific surface resistivity Test piece (120 × 120 × 2 m) prepared by injection molding
m) The surface resistivity on the side opposite to the gate was measured within one hour after molding in a constant temperature and humidity room at 23 ° C. and 55% RH using a high resistivity meter (HIRESTA-IP) manufactured by Mitsubishi Yuka. After molding, condition at 23 ° C and 55% RH for 24 hours, immerse in tap water with a few drops of detergent (trade name: Mama Lemon), rub the surface 10 times with a sponge, test with tap water and distilled water After washing the pieces and blowing off water drops with air,
After being left in a constant temperature and humidity room of 1% RH for one day, the surface specific resistivity on the side opposite to the gate was measured.

(2) Appearance of Molded Article The appearance of the test piece was visually observed to determine whether or not the surface was rough. A sample having good appearance without any rough skin was rated as "O", and a sample having rough skin was rated as "x".

(3) Delamination of molded article The end of the above-mentioned test piece was bent.
Those with laminar exfoliation were evaluated as x.

(4) DuPont impact strength A 2 mm thick test piece produced by injection molding was subjected to 23 ° C. and 50% RH.
After aging for 24 hours in the test piece, the tip R
And a weight having a different load was dropped from a predetermined height to cause 50% destruction, and the impact energy (kg · cm) was calculated.

(5) Izod impact strength Measured according to ASTM D-256 (notched, 1/4 inch thickness).

Raw Materials Used (a) Daicel Styrol R81 (high impact polystyrene) manufactured by Daicel Chemical Industries, Ltd. as rubber-modified styrene resin, and (b) ethylene-unsaturated carboxylic acid copolymer using potassium as an ion source. Ethylene as ionomer
An ionomer composition comprising 91% by weight of 82% neutralized potassium salt (metal cation content: 1.2 mol / kg (ionomer)) of methyl methacrylic acid copolymer (12.5% by weight of methacrylic acid) and 9% by weight of glycerol, (c) SBS manufactured by Nippon Synthetic Rubber Co., Ltd. as a styrene-based thermoplastic elastomer
Grade TR2003 (rubber content 53% by weight), (d) Acryft WM403 (MMA content 38% by weight) manufactured by Sumitomo Chemical Co., Ltd. as an ethylene / methyl methacrylate copolymer, and (e) Hoechst as an anionic surfactant SAS93 manufactured by Japan KK was used.

[0026]

[Table 1]

[0027]

[Table 2]

As shown in Table 1, all of the samples obtained in Examples 1 to 4 have low specific resistivity, their effects are not changed even after washing with water, and all of them have excellent impact strength as well as high impact strength. It has the appearance of a molded product.

On the other hand, as shown in Table 2, when the (c) styrene-based thermoplastic elastomer of Comparative Examples 1 and 3 was not added, delamination occurred in the molded product, and the impact resistance was extremely low. Become.

When the ethylene-methyl methacrylate copolymer (d) of Comparative Example 2 is not added, the antistatic performance after water washing does not decrease, but the antistatic performance varies greatly depending on molding conditions and the like. Further, (c) of Comparative Example 3
When the styrene-based thermoplastic elastomer is not added, the specific resistance is low and good antistatic performance is exhibited, but the impact strength is not improved.

Therefore, (a) a rubber-modified styrenic resin,
The desired object of the present invention cannot be achieved if any of the components (b) ionomer, (c) styrene-based thermoplastic elastomer, and (d) ethylene / methyl methacrylate copolymer are missing. Further, by adding (e) an anionic surfactant, the antistatic performance can be further improved.

[0032]

According to the present invention, (a) a rubber-modified styrene resin is added to (b) an ethylene
The combined use of an ionomer of an unsaturated carboxylic acid copolymer, (c) a styrene-based thermoplastic elastomer and (d) an ethylene / methyl methacrylate copolymer prevents delamination and appearance deterioration accompanying the use of an antistatic agent. A styrene resin composition having excellent antistatic performance and mechanical strength can be provided.

Claims (6)

[Claims] 1. A rubber-modified styrenic resin, (b)
An ionomer of an ethylene / unsaturated carboxylic acid copolymer using potassium as an ion source, (c) a styrene-based thermoplastic elastomer, and (d) an ethylene / methyl methacrylate copolymer as essential components. Styrene resin composition. 2. (b) 1 to 15 parts by weight of an ionomer of an ethylene / unsaturated carboxylic acid copolymer using potassium as an ion source, and (c) styrene based on 100 parts by weight of a rubber-modified styrene resin. 1 to 10 parts by weight based thermoplastic elastomer, (d) ethylene / methyl methacrylate copolymer 1
The styrenic resin composition according to claim 1, wherein the amount is from 10 to 10 parts by weight. 3. (a) 3 to 10 parts by weight of an ionomer of an ethylene / unsaturated carboxylic acid copolymer using potassium as an ion source, and (c) styrene based on 100 parts by weight of a rubber-modified styrene resin. 1 to 5 parts by weight of a thermoplastic elastomer, (d) ethylene / methyl methacrylate copolymer 1
The styrenic resin composition according to claim 1 or 2, wherein the amount is from 5 to 5 parts by weight. 4. The ionomer according to claim 1, wherein the potassium ion content in the ionomer is in the range of 0.4 to 4 mol per kg of the ionomer, and the degree of neutralization with potassium is 60 mol% or more. Item 4. The styrene resin composition according to item 1. 5. The styrene resin composition according to claim 1, wherein (c) the styrene thermoplastic elastomer is a styrene / butadiene / styrene block copolymer. 6. The styrenic resin composition according to claim 1, further comprising (e) an anionic surfactant.