JP2710832B2 - Styrene resin composition with excellent antistatic properties - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a styrenic resin composition having excellent antistatic properties, improved moldability and hot water resistance.

[Conventional technology]

Generally, styrene-based resins have excellent electrical insulation properties and are widely used for electric and electronic parts because of their properties. On the other hand, it has a good balance of mechanical strength, heat resistance, and moldability, and is widely used in applications that do not necessarily require electrical insulation. In these fields that do not require electrical insulation,
On the contrary, styrene-based resins are disadvantageous in that they have good electrical insulation properties, such as being easily charged by friction and adsorbing dust, causing damage to the appearance and causing electrostatic breakdown of ICs and the like.
Further, in recent years, as the density of magnetic recording media has increased, so-called dropout phenomenon has occurred due to dust adsorption due to electrification of the recording medium container, which has become a serious problem in the field.

To solve the above problem, kneading the antistatic agent, which is a conventional low molecular surfactant, into the styrene resin,
Alternatively, the method has been applied by lowering the surface resistivity by applying it to the surface of a molded product.

[Problems to be solved by the invention]

However, since the styrene resin generally has a glass transition temperature higher than room temperature, the antistatic agent present on the surface of the molded product is removed by washing the surface of the molded product with water or wiping with a cloth or the like, and the antistatic performance is significantly reduced. I do.

Furthermore, in order to achieve a predetermined antistatic performance, it is necessary to knead or apply a relatively large amount of an antistatic agent, which causes stickiness on the surface of a molded product. In order to solve such a problem, there has been proposed a resin composition in which a styrene-based polymer contains polyethylene oxide having a specific molecular weight and a sulfonate having a specific structure (Japanese Patent Application No. Hei.
53721) Although practically used, there is a problem that whitening occurs when exposed to hot water for a long time. In a field where hot water resistance is required, a solution to this problem as soon as possible is desired.

[Means for solving the problem]

The present inventors have conducted intensive studies in view of such a problem, and as a result, have found that a styrene-based polymer containing polyethylene oxide and a sulfonate has a styrene-
The inventors have found that this problem can be solved by a resin composition containing a maleic anhydride copolymer and an alkali metal salt of acetic acid, and have reached the present invention.

That is, the present invention relates to 100 parts by weight of a styrene polymer and polyethylene oxide 3 having a number average molecular weight of 50,000 to 1,000,000.
To 35 parts by weight and 100 parts by weight of a resin composition comprising 0.5 to 5 parts by weight of sodium dodecylbenzenesulfonate, 0.05 to 0.5 parts by weight of a sodium or lithium salt of acetic acid and a content of maleic anhydride of 25 to 40 mol%. A styrene-based resin composition having excellent antistatic properties, containing 1 to 15 parts by weight of a certain styrene-maleic anhydride copolymer.

The styrenic polymer in the present invention comprises a polymer of a styrenic monomer. Styrene-based 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, trichlorostyrene, and the like. Bromostyrene,
Examples thereof include halogenated styrenes such as tetrabromostyrene, and particularly preferred are styrene and α-methylstyrene, and at least one of such styrene-based monomers is used. Further, if desired, acrylonitrile, methacrylonitrile, acrylonitrile-based monomers such as fumaronitrile, maleimide, N-methylmaleimide, maleimide-based monomers such as N-phenylmaleimide,
Acrylic ester monomers such as methyl acrylate and methyl methacrylate 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. Polymers, butadiene-acrylic acid ester 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 as islands when observed by electron micrographs, and the continuous phase exists as a sea.

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 parts by weight, preferably 5 to 100 parts by weight of the styrene polymer.
~ 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 styrenic 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.

The content of sodium dodecylbenzenesulfonate is
It is 0.5 to 5 parts by weight, preferably 0.7 to 3 parts by weight, per 100 parts by weight of the styrenic polymer. When the amount is less than 0.5 part by weight, the antistatic property is insufficient. On the other hand, when the amount exceeds 5 parts by weight, the resin composition undergoes heat history in an extruder, a molding machine, etc. Undesirably.

The content of sodium acetate or lithium acetate as a component of the present invention is 0.05 to 0.5 part by weight per 100 parts by weight of the resin composition comprising the styrenic polymer, polyethylene oxide and sodium dodecylbenzenesulfonate. When the content is less than 0.05 parts by weight, there is no effect of improving the hot water resistance, which is the object of the present invention, and whitening occurs upon contact with hot water. On the other hand, if the content exceeds 0.5 parts by weight, silver tends to be generated on the surface of the molded product, which is not preferable.

The styrene-maleic anhydride copolymer is a copolymer of a styrene monomer and a maleic anhydride monomer, and the styrene monomer is the styrene monomer used for the styrene polymer. Although it is composed of a body, particularly preferred are styrene and α-methylstyrene, and at least one of such styrene monomers is used. If desired, an acrylonitrile-based monomer, a maleimide-based monomer, an acrylate-based monomer or the like can be used in combination with the styrene-based monomer. The water lily-maleic anhydride copolymer can be modified with a rubbery polymer.

The maleic anhydride content in the styrene-maleic anhydride copolymer is 25 to 40 mol%, and when less than 25 mol%,
There is no effect of improving the hot water resistance. On the other hand, if it exceeds 40 mol%, silver is generated on the surface of the molded product, and the object of the present invention cannot be achieved.

The content of the styrene-maleic anhydride copolymer is a resin composition 10 comprising the styrene polymer, polyethylene oxide and sodium dodecylbenzenesulfonate.
It is 1 to 15 parts by weight per 0 parts by weight. If the content is less than 1 part by weight, there is no effect of improving hot water resistance, while if it exceeds 15 parts by weight, silver is undesirably generated on the surface of the molded product. Most preferably, it is 3 to 10 parts by weight.

In place of maleic anhydride monomer, copolymerization of unsaturated dicarboxylic acid monomer such as maleic acid, fumaric acid, citraconic acid, metaconic acid, glutaconic acid, methylene succinic acid, allylmalonic acid and styrene monomer Even if the coalescence is used, the desired improvement effect cannot be obtained.

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

As a method for producing the styrene resin composition of the present invention, for example, the specific styrene resin of the present invention and polyethylene oxide, sodium dodecylbenzenesulfonate, sodium acetate or lithium acetate and a styrene-maleic anhydride copolymer are monoaxially mixed. It is manufactured by a method such as melting and mixing with a mixer such as an extruder, a twin-screw extruder, and a Banbury mixer.

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

In addition, ordinary plasticizers, release agents, light stabilizers, acid value inhibitors,
The combined use of additives such as a flame retardant, a colorant and a stabilizer does not hinder the effects of the present invention.

〔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.

Nippon Yushi "PEG 20000"100,000; Meisei Chemical Co., Ltd. "Alcox R-150"200,000; Meisei Chemical Co., Ltd. "Alcox R-1000"500,000; Meisei Chemical Co., Ltd. Cox E-30 1,000,000; Meisei Chemical Co., Ltd. "Alcox E-60" 1.5 million; Meisei Chemical Co., Ltd. "Alcox E-75" Nippon Yushi "Nurex Powder F" is used as sodium dodecylbenzenesulfonate did.

As sodium acetate and lithium acetate, reagents manufactured by Junsei Chemical were used.

The following styrene-maleic anhydride copolymer was used.

Maleic anhydride copolymer content: 20 mol%; "SMA4000" manufactured by Sartomer (SARTOMER) 25 mol%; "SMA3000" manufactured by Sartomer (SARTOMER) 33 mol%; "SMA2000" manufactured by Sartomer (SARTOMER) 50 mol%; Various tests on "SMA 1000" resin composition manufactured by SARTOMER were performed by the following methods.

1) Surface resistivity: injection molding (cylinder temperature 220
(4 ° C., mold temperature 40 ° C.), a plate having a thickness of 4 cm × 4 cm × 2 mm was measured under the following conditions using an SM-10E ultra-insulation meter (manufactured by Toa Denpa Kogyo Co., Ltd.). .

(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, remove water on the surface and remove 50%
The humidity was measured at 23 ° C. for 24 hours and measured.

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

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

4) Hot water resistance: A sample formed into a 4 cm x 4 cm x 2 mm thick plate (cylinder temperature 220 ° C, mold temperature 40 ° C) is immersed in hot water at 60 ° C for 2 hours to whiten the surface of the sample. Observe presence,
The hot water resistance was evaluated.

Example 1 Styrene-based polymer ("Santac 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, 2 parts by weight of sodium dodecylbenzenesulfonate (" Nurex Powder F "manufactured by NOF Corporation), and a total amount of styrene polymer, polyethylene oxide and sodium dodecylbenzenesulfonate of 100
5 parts by weight of a styrene-maleic anhydride copolymer ("SMA 2000" manufactured by Sartomer Co.) containing 0.2 parts by weight of sodium acetate and 33 mol% of maleic anhydride were blended with a tumbler for 15 minutes with respect to parts by weight, and after blending, biaxially It was melt-mixed with an extruder (“AS-30” manufactured by Nakatani), pelletized, and provided as a sample.

About this sample, after drying at 80 ° C. for 3 hours, the surface resistivity, Izod impact strength, appearance of the molded product,
Table 1 shows the results of measuring the hot water resistance.

Examples 2 and 3 and 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 and 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 and 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.

Examples 8 and 9 and Comparative Examples 7 and 8 A resin composition was obtained and evaluated in the same manner as in Example 1 except that the ratio of sodium acetate was changed.

The results are shown in Table 1.

Example 10 and Comparative Examples 9 and 10 A resin composition was obtained and evaluated in the same manner as in Example 1 except that styrene-maleic anhydride copolymers having different maleic anhydride contents were used. The results are shown in Table 1.

Examples 11 and 12 and Comparative Examples 11 and 12 A resin composition was obtained and evaluated in the same manner as in Example 1 except that the ratio of the styrene-maleic anhydride copolymer was changed. The results are shown in Table 1.

〔The invention's effect〕

As is clear from the results shown in Table 1, the resin composition of the present invention has excellent antistatic properties, and has improved moldability and hot water resistance.

────────────────────────────────────────────────── (5) Continuation of the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical indication location C08L 35:06) (56) References JP-A-59-206444 (JP, A) JP-A-60 −155259 (JP, A) JP 52-12216 (JP, B1)

Claims (1)

(57) [Claims] 1. A composition comprising 100 parts by weight of a styrene-based polymer, 3 to 35 parts by weight of polyethylene oxide having a number average molecular weight of 50,000 to 1,000,000 and 0.5 to 5 parts by weight of sodium dodecylbenzenesulfonate. Antistatic consisting of 100 parts by weight of a resin composition, 0.05 to 0.5 part by weight of a sodium or lithium salt of acetic acid, and 1 to 15 parts by weight of a styrene-maleic anhydride copolymer having a maleic anhydride content of 25 to 40 mol%. Styrenic resin composition with excellent properties.