JP2795451B2 - Resin composition - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a resin composition having excellent antistatic properties and good moldability.

[Conventional technology]

In general, styrene resins have a large electric resistance and are widely used in various applications including electric and electronic parts because of their excellent electric insulation and mechanical properties.

However, in a field that does not require electrical insulation, it is easily charged by friction, adsorbs dust and impairs appearance, and causes various troubles such as causing electrostatic breakdown of ICs and the like.

In recent years, as the density of magnetic recording media has increased, so-called dropout phenomenon has been caused due to dust adsorption due to electrification of a housing of a recording medium or the like, which has become a serious problem.

In order to solve the above-mentioned problem, a conventional method of internally kneading an antistatic agent, which is a low-molecular surfactant, into a styrene-based resin or a method of applying an antistatic agent to the surface of a molded product is used.

[Problems to be solved by the invention]

However, the method using internal kneading loses the antistatic performance by removing the antistatic agent present on the surface of the molded product by washing with water, wiping with a cloth, or the like. In addition, the method of surface coating has a similar problem and also has a problem that processing cost is increased.

In addition, in the case of internal kneading, a relatively large amount of an antistatic agent is required to achieve a predetermined antistatic performance only with the antistatic agent, and as a result, dust adheres to a mold surface during molding. In addition, frequent wiping is required, which causes various problems such as a decrease in productivity.

[Means for solving the problem]

The present inventors have conducted intensive studies in view of such a problem, and as a result, solved the problem by a resin composition containing a styrene-based polymer containing polyethylene oxide having a specific molecular weight and a sulfonate having a specific structure. And reached the present invention.

That is, the present invention relates to 100 parts by weight of a styrene polymer, 3 to 35 parts by weight of a polyethylene oxide having a number average molecular weight of 50,000 to 1,000,000, (Wherein, R ₁ R ₂ represents hydrogen or an alkyl group having 12 or less carbon atoms, and X represents an arbitrary atom selected from the group consisting of Na, Li, and K). It is a resin composition having an excellent antistatic property by containing parts by weight.

The styrenic polymer in the present invention comprises a polymer of a styrenic monomer. Styrene monomers include side-chain alkyl-substituted styrenes such as styrene, α-methylstyrene and α-ethylstyrene, core alkyl-substituted styrenes such as vinyltoluene and p-methylstyrene, monochlorostyrene, dichlorostyrene, and trichlorostyrene. Examples thereof include halogenated styrenes such as bromostyrene and tetrabromostyrene. Particularly preferred are styrene and α-methylstyrene, and at least one of such styrene monomers is used. If desired, acrylonitrile, methacrylonitrile, acrylonitrile monomers such as fumaronitrile, maleimide monomers such as maleimide, N-methylmaleimide, N-phenylmaleimide, and acrylate esters such as methyl acrylate and methyl methacrylate A monomer such as a maleic acid monomer such as maleic acid or maleic anhydride can also be used in combination with the styrene monomer.

The styrenic polymer can be modified with a rubbery polymer. Examples of the rubbery polymer include polybutadiene, styrene-butadiene copolymer, butadiene-acrylonitrile copolymer, and ethylene-propylene-diene copolymer. Examples thereof include polymers, butadiene-acrylate copolymers, and the like.

The rubbery polymer in the rubber-modified styrenic resin is dispersed in the form of particles and forms a dispersed phase (called a microgel).
On the other hand, a polymer of a styrenic monomer or a copolymer with another monomer as required constitutes a continuous phase.

The microgel also contains a styrene polymer in a grafted or occluded form. The microgel exists in an island shape when observed by an electron micrograph, and the continuous phase exists in a sea shape.

The styrene-based polymer can be obtained by a known method such as a bulk polymerization method, a suspension polymerization method, and an emulsion polymerization method.

The content of polyethylene oxide is 3 to 35 polymer parts per 100 parts by weight of the styrenic polymer, preferably 5 to
~ 20 parts by weight.

If the amount of the polyethylene oxide is less than 3 parts by weight, sufficient antistatic properties cannot be obtained, and the particles are undesirably charged by friction and cause dust adsorption.

On the other hand, when it exceeds 35 parts by weight, the mechanical strength of the resin composition is significantly reduced.

In particular, the impact resistance is remarkably reduced, and it is difficult to maintain practical strength, and the resin composition cannot be used for large molded products such as electric and electronic parts.

Polyethylene oxide has a number average molecular weight of 50,000 to 100
It preferably has a molecular weight of 10,000, more preferably 10
10,000 to 500,000.

When the number average molecular weight is less than 50,000, the compatibility with the stellenic polymer is good, but the antistatic effect is poor.
If it exceeds 1,000,000, the compatibility with the styrenic polymer is poor, and the molded article is delaminated, resulting in a decrease in mechanical strength and a decrease in antistatic performance.

The method for producing polyethylene oxide is not particularly limited, and commercially available polyethylene oxide having a number average molecular weight in the above range may be used.

When other polyalkylene oxides or derivatives thereof (for example, polypropylene glycol, methoxypolyethylene glycol, polyethylene glycol monooctyl ether, polyethylene glycol monostearate, polyethylene glycol monolaurate, etc.) are used instead of polyethylene oxide, the antistatic property Is poor, and the desired effect cannot be obtained.

Sulfonates which are components of the present invention include benzene, toluene, ethylbenzene, propylbenzene,
Isopropylbenzene, n-butylbenzene, isobutylbenzene, sec-butylbenzene, t-butylbenzene, pentylbenzene, dodecylbenzene, xylene,
Examples thereof include alkali metal salts of sulfonic acids of ethyltoluene, cymene, t-butyltoluene, and diethylbenzene. The alkali metal salt can be arbitrarily selected from the group consisting of Na, Li, and K.

Of the above sulfonates, sodium dodecylbenzenesulfonate is most preferred from the viewpoint of antistatic properties.

The content of the sulfonate is 100
It is 0.5 to 5 parts by weight, preferably 0.7 to 3 parts by weight per part by weight. If the sulfonic acid salt is less than 0.5 part by weight, the antistatic property is insufficient, while if it exceeds 5 parts by weight, the resin composition undergoes heat history in an extruder, a molding machine, etc., causing discoloration and molding. This is not preferable because silver is generated on the surface of the object.

The method for producing the styrenic resin composition of the present invention is not particularly limited. For example, the specific styrenic resin of the present invention is mixed with polyethylene oxide and a sulfonate using a single-screw extruder, a twin-screw extruder, or a Banbury mixer. It is manufactured by a method such as melting and mixing in a machine.

The resin composition of the present invention may contain a cationic, anionic, nonionic or other antistatic agent to further improve the antistatic properties.

Further, the combined use of ordinary additives such as a plasticizer, a mold release agent, a lightfast agent, an antioxidant, a flame retardant, a colorant, and a stabilizer does not hinder the effects of the present invention at all.

〔Example〕

Next, the present invention will be specifically described with reference to Examples and Comparative Examples.

"Santac" manufactured by Mitsui Toatsu Chemicals as a styrene polymer
ST-42 "was used.

 The following polyethylene oxide was used.

Number average molecular weight 20,000: Nippon Yushi "PEG 20000" 100,000: Meisei Chemical "Alcox R-150" 200,000: Meisei Chemical "Alcox R-1000" 500,000: Meisei Chemical "Alcox R-1000" Cox E-30 ”1,000,000:“ Alcox E-60 ”manufactured by Meisei Chemical Industry 1.5 million:“ Alcox E-75 ”manufactured by Meisei Chemical Industry“ Nurex Powder F ”(dodecylbenzene sulfone) manufactured by NOF Corporation as a sulfonate Acid) was used.

Various tests on the resin composition were performed by the following methods.

1) Surface resistivity: injection molding (cylinder temperature 220)
℃, mold temperature 40 ℃) to make a 4cm × 4cm × 2mm plate,
The measurement was performed using an SM-10E ultra-insulation meter (manufactured by Toa Denpa Kogyo KK) under the following conditions.

(1) Immediately after molding: Immediately after molding, after sufficient washing with distilled water, moisture on the surface was removed, and humidity was measured at 50% RH and 23 ° C. for 24 hours to measure.

(2) After leaving for 150 days; After leaving for 50 days at 50% RH and 23 ° C. after molding, thoroughly wash with distilled water and remove water on the surface
% RH was measured at 23 ° C for 24 hours.

2) Izod impact strength; measured (notched) according to ASTM D-256.

3) Appearance of molded product: In an injection molding machine (cylinder temperature 240
C.) for 3 minutes and formed into a 4 cm × 4 cm × 2 mm plate, and the surface was observed to confirm the degree of discoloration and generation of silver.

(Example 1) Styrene-based polymer ("Santak ST" manufactured by Mitsui Toatsu Chemicals, Inc.)
-42 ") 100 parts by weight and a polyethylene oxide having a number average molecular weight of 200,000 (" Alcox R-10 "manufactured by Meisei Chemical Co., Ltd.)
00 ") 8 parts by weight and 2 parts by weight of sodium dodecylbenzenesulfonate (" Nurex Powder F "manufactured by NOF Corporation) are blended by a tumbler for 15 minutes, and further melted by a twin screw extruder (" AS-30 "manufactured by Nakatani). It mixed, pelletized, and used for the sample.

This sample was dried at 80 ° C. for 3 hours, and the surface resistivity, Izod impact strength, and appearance of the molded article were measured by the above-described methods. Table 1 shows the results.

Examples 2 and 3 Comparative Examples 1 and 2 A resin composition was obtained and evaluated in the same manner as in Example 1 except that the number average molecular weight of polyethylene oxide was changed. The results are shown in Table 1.

Examples 4 and 5 Comparative Examples 3 and 4 A resin composition was obtained and evaluated in the same manner as in Example 1 except that the ratio of polyethylene oxide was changed. The results are shown in Table 1.

Examples 6 and 7 Comparative Examples 5 and 6 A resin composition was obtained and evaluated in the same manner as in Example 1 except that the ratio of sodium dodecylbenzenesulfonate was changed. The results are shown in Table 1.

[Effects of the Invention] As is clear from the results shown in Table 1, the resin composition of the present invention has excellent antistatic properties and improved moldability.

Continuation of the front page (56) References JP-A-59-206444 (JP, A) JP-A-60-206865 (JP, A) JP-A-54-45380 (JP, A) JP-A-60-94432 (JP) , A) JP 52-12216 (JP, B2) (58) Fields investigated (Int. Cl. ⁶ , DB name) C08L 25/00-25/18 C08L 71/02 C08K 5/42

Claims (1)

(57) [Claims] A. Essentially, A. 100 parts by weight of a styrenic polymer and B. 3 to 35 parts by weight of a polyethylene oxide having a number average molecular weight of 50,000 to 1,000,000; (Wherein, R ₁ R ₂ represents hydrogen or an alkyl group having 12 or less carbon atoms, and X represents an arbitrary atom selected from the group consisting of Na, Li, and K). A resin composition having excellent antistatic properties characterized by containing parts by weight.