JPH0731953B2 - Method for manufacturing conductive plastic molded product - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Field of Industrial Application> The present invention relates to a method for producing a conductive plastic molded product having excellent abrasion resistance.

<Prior art> When plastics are applied to members such as semiconductor wafer storage containers, electronic and electrical members, etc., which require antistatic performance, they are conventionally molded by kneading carbon black powder, metal fibers, etc. into resin. Was there. However, in these methods, the molded product is opaque and the contents cannot be seen through. In order to improve this point, a paint containing a tin oxide-based conductive powder has been developed, and a method of applying it on a plastic sheet has been studied. Further, since the coating film containing the conductive powder is soft, a method of using a scuff resistant coating is also under study. For example, in JP-A-60-61258,
A method of sequentially laminating a hard coat layer and a conductive layer on a plastic sheet is disclosed.

Further, Japanese Patent Application Laid-Open No. 60-181177 describes a method for producing a conductive plastic sheet in which a silicon-based thermosetting resin film containing conductive powder is provided on the plastic sheet.

<Problems to be Solved by the Invention> In recent years, transparency has been particularly required in a semiconductor wafer storage container, a partition of a semiconductor manufacturing plant, etc., which requires antistatic properties, but conventional methods do not always provide sufficient charging. Preventability and transparency could not be achieved.

In the methods disclosed in JP-A-60-61258 and JP-A-60-181177, a coating agent containing a conductive powder is applied on a plastic sheet. The surface of the film is likely to have irregularities, so that the gloss of the obtained sheet becomes poor and the transparency and surface hardness also decrease.

The present inventors have earnestly studied and achieved the present invention for the purpose of forming a coating film having excellent conductivity and transparency on a plastic molded product without generating irregularities on the coating film surface.

<Means for Solving Problems> The present invention contains a conductive powder containing tin oxide as a main component in the surface layer of a plastic molded article when the molded article is molded using a casting polymerization mold or a molding die. The present invention relates to a method for producing a conductive plastic molded product having excellent surface smoothness, which comprises integrally forming a scratch-resistant coating inside the casting polymerization mold or the molding mold.

The feature of the present invention is that when forming an antistatic scuff resistant cured coating on the surface of plastic molded articles such as plastic sheets and various plastic molded articles, in order to smooth the surface at a high level, casting The surface of the polymerization mold or the molding die is coated with a polymerizable composition for forming a scratch-resistant film containing a conductive powder containing tin oxide as a main component, and the mixture is polymerized and cured to have a conductive scratch-resistant film. To form
Then, in contact with the scratch-resistant coating, a polymerizable monomer is cast-polymerized or a molten resin is molded to form a plastic molded article, and the scratch-resistant coating is transferred to the surface of the plastic molded article. Especially.

In addition, a method in which the polymerizable composition is applied in the above-mentioned method, a polymerizable monomer is cast, and a scratch-resistant coating film is formed by polymerization curing as well as polymerization curing of a raw material for a plastic molded article can be used.

The casting polymerization method to which the present invention can be applied is not particularly limited, for example, a so-called cast weight in which a methyl methacrylate monomer containing a partial polymer called syrup is injected into a glass casting polymerization mold to polymerize and cure. There is legality. In this case, the inner surface of the glass mold is coated with a polymerizable composition for forming a conductive scratch-resistant coating, which is then polymerized and cured to previously form a conductive scratch-resistant coating, and then the inside of the glass mold is formed. In, the cast polymerization of methyl methacrylate syrup can be performed. The glass casting polymerization type consisting of this glass plate is a soft polyvinyl chloride, ethylene-vinyl acetate copolymer, between two glass plates with excellent surface smoothness.
It is assembled by inserting polyethylene, an ethylene-methyl methacrylate copolymer, etc. as a cushioning material and stopping with a clamp.

As a method of continuously performing cast polymerization, a method of casting polymerization of methyl methacrylate or the like between two steel belts is known. In this case, the abrasion-resistant coating is formed on the surface of the steel belt. Thus, the method of the present invention can be carried out.

It can also be applied to injection molding, where a polymerizable composition for forming a conductive scratch-resistant coating is applied to the inner surface of a preforming mold, and then polymerized and cured to form a conductive scratch-resistant coating. Then, a methyl methacrylate resin, a styrene resin, an acrylonitrile-styrene copolymer resin, a polycarbonate resin and the like are melted and injection-molded.

The polymerizable component used in the polymerizable composition for forming a scratch-resistant film used in the present invention is not particularly limited, but a preferable example thereof is a molecular weight of 150 or more and at least two acryloyloxy groups and / or methacryloyloxy groups. Crosslinkable compounds having 30 or 30
Examples thereof include a mixture with another copolymerizable monomer which is contained in an amount of at least wt%, a condensate obtained by (co) hydrolyzing an alkoxysilane, colloidal silica and the like.

The main examples of the compound having a molecular weight of 150 or more and having at least two acryloyloxy groups and / or methacryloyloxy groups are trimethylolpropane tri (meth) acrylate and trimethylolethanetri (meth).
Acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, glycerin tri (meth) acrylate, dipentaerythritol tri (meth) acrylate, dipentaerythritol tetra (meth) acrylate, dipentaerythritol penta (meth) Acrylate, dipentaerythritol hexa (meth) acrylate, tripentaerythritol tetra (meth) acrylate, tripentaerythritol penta (meth) acrylate, pentaerythritol di (meth) acrylate, 2,2-bis (4-acryloxydiethoxyphenyl) ) Propane, 2,
2-bis (4-methacryloxyethoxyphenyl) propane, diethylene glycol di (meth) acrylate,
Poly (meth) acrylate of polyhydric alcohol such as triethylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, tripentaerythritol hexa (meth) acrylate, tripentaerythritol hepta (meth) acrylate, malonic acid / Trimethylolethane / (meth) acrylic acid, malonic acid / trimethylolpropane / (meth) acrylic acid,
Malonic acid / glycerin / (meth) acrylic acid, malonic acid / pentaerythritol / (meth) acrylic acid, succinic acid / trimethylolethane / (meth) acrylic acid, succinic acid / trimethylolpropane / (meth) acrylic acid,
Succinic acid / glycerin / (meth) acrylic acid, succinic acid / pentaerythritol / (meth) acrylic acid, adipic acid / trimethylolethane / (meth) acrylic acid, adipic acid / trimethylolpropane / (meth) acrylic acid, adipine Acid / pentaerythritol / (meth) acrylic acid, adipic acid / glycerin / (meth) acrylic acid, glutaric acid / trimethylolethane / (meth) acrylic acid, glutaric acid / trimethylolpropane / (meth) acrylic acid, glutaric acid / Pentaerythritol /
(Meth) acrylic acid, glutaric acid / glycerin / (meth) acrylic acid, sebacic acid / trimethylolethane /
(Meth) acrylic acid, sebacic acid / trimethylolpropane / (meth) acrylic acid, sebacic acid / glycerin /
(Meth) acrylic acid, sebacic acid / pentaerythritol / (meth) acrylic acid, fumaric acid / trimethylolethane / (meth) acrylic acid, fumaric acid / trimethylolpropane / (meth) acrylic acid, fumaric acid / glycerin / ( (Meth) acrylic acid, fumaric acid / pentaerythritol / (meth) acrylic acid, itaconic acid / trimethylolethane / (meth) acrylic acid, itaconic acid / trimethylolpropane / (meth) acrylic acid, itaconic acid / glycerin / (meth ) Acrylic acid, itaconic acid / pentaerythritol / (meth) acrylic acid, maleic anhydride / trimethylolethane / (meth) acrylic acid, maleic anhydride / trimethylolpropane / (meth) acrylic acid,
Saturated or unsaturated polyester poly (meth) acrylate, tolylene diisocyanate, xylylene diisocyanate by a combination of compounds such as maleic anhydride / glycerin / (meth) acrylic acid, maleic anhydride / pentaerythritol / (meth) acrylic acid, Diphenylmethane diisocyanate, isophorone diisocyanate,
Hexamethylene diisocyanate, dicyclohexylmethane diisocyanate, or diisocyanate compounds obtained by hydrogenating aromatic isocyanates among these diisocyanate compounds (for example, hydrogenated xylylene diisocyanate, diisocyanate compounds such as hydrogenated diphenylmethane diisocyanate), triphenylmethane triisocyanate An acrylic monomer having an active hydrogen and an isocyanate-containing compound such as a polyisocyanate compound obtained by polymerizing a divalent or trivalent polyisocyanate compound or a diisocyanate compound such as isocyanate or dimethylenetriphenyltriisocyanate, for example. 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2-hydro Shi-3-methoxy-propyl (meth)
Urethane (meth) acrylates obtained by reacting acrylates, N-methylol (meth) acrylamides, N-hydroxy (meth) acrylamides, and the like, and other tri (meth) acrylates of tris 2-hydroxyethyl isocyanuric acid and the like. it can. Although these resins can be used as they are, methyl (meth) acrylate, ethyl (meth) acrylate,
It may be diluted with a polymerizable monomer such as butyl (meth) acrylate or propyl (meth) acrylate, or a solvent such as xylene, toluene, cellosolve, or ethyl acetate.

Polymerization and curing of these resin raw materials is performed by hot air heating, infrared heating,
It is carried out by a method such as photopolymerization by irradiation with ultraviolet rays, but a method of photopolymerization by irradiation with ultraviolet rays is preferable because of the simplicity of a curing device.

When performing polymerization by ultraviolet rays, it is preferable to add 0.1 to 20 parts by weight of a photosensitizer having a sensitizing action in the wavelength range of 400 nm or less to 100 parts by weight of the resin raw material.
It is more preferable to add 10 parts by weight. If the amount of the photosensitizer is less than 0.1 parts by weight, the curing rate will be slow, and if it exceeds 20 parts by weight, the weather resistance of the film after polymerization and curing will be poor.

As the photosensitizer, benzoin, benzoin ethyl ether, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1-hydroxycyclohexylphenyl ketone, azobisisobutyronitrile, benzoylpanoxide, and other generally known compounds. Photosensitizers.

As a condensate obtained by co-hydrolyzing alkoxysilane, colloidal silica, etc., a general formula R ¹ Si (OR ² ) ³ , Si (O
A condensate obtained by (co) hydrolyzing at least one selected from the group consisting of compounds represented by R ² ) ₄ and RnSiX _4-n (n: 1 to 3) as a raw material. In the above general formula, R ¹ represents an alkyl group such as a methyl group, an ethyl group and a butyl group; a phenyl group; a vinyl group; an unsaturated hydrocarbon group such as an allyl group; an epoxy group; an amino group. R ² represents an alkyl group such as a methyl group or an ethyl group, or an acyl group such as an acetyl group. X is a halogen group. As the raw material, methyltrimethoxysilane, methyltriethoxysilane, phenyltriethoxysilane or the like is used alone. In addition, methyltriethoxysilane and phenyltriethoxysilane, tetraethoxysilane and methyltrimethoxysilane, and methyltrimethoxysilane and methyltriethoxysilane may be used in combination.

These condensates may be used as they are, but may also be used by blending acrylate polymers, alcohols such as ethanol, propanol, butanol and the like.

Various additives conventionally used may be added to these scratch-resistant film-forming resin raw materials. Examples of the additives include dyes, pigments, antioxidants, ultraviolet absorbers, stabilizers, flame retardants, plasticizers and antistatic agents.

The conductive powder used in the present invention is preferably one containing tin oxide having a particle diameter of 0.2 μm or less as a main component. Particle size is 0.2 μm
When it becomes larger, the transparency of the methacrylic resin plate obtained is deteriorated because visible light is scattered. The amount of the conductive powder used is preferably 60 to 80% by weight in the resin raw material before the scratch-resistant film-forming resin raw material is diluted with the solvent.

If it is less than 60% by weight, the electrical conductivity of the plastic molded article will be poor, and if it is more than 80% by weight, the transparency will be significantly reduced and the formation of the coat layer will be difficult.

A syrup containing a monomer containing methyl methacrylate as a main component or a small amount of a polymer is used as a raw material of a plastic molded article to which the present invention can be preferably applied, and a methyl methacrylate is a main component as a resin raw material. Examples include homopolymers, copolymers, polystyrene, acrylonitrile-styrene copolymers, vinyl chloride resins, and polycarbonates. Among these, a methyl methacrylate resin-based plastic molded product is more preferably used in terms of strength (surface hardness) and aesthetics (transparency and colorability).

Here, in a syrup containing a monomer containing methyl methacrylate as a main component or a small amount of a polymer, in addition to methyl methacrylate, acrylic acid such as methyl acrylate, ethyl acrylate, propyl acrylate, and butyl acrylate is used. Examples thereof include esters, methacrylic acid esters such as cyclohexyl methacrylate, phenyl methacrylate and benzyl methacrylate, and aromatic vinyl compounds such as styrene, α-methylstyrene and p-methylstyrene. When the methyl methacrylate monomer partially contains a polymer, the polymer may be dissolved in the monomer, or the monomer may be partially polymerized.

The method for applying the polymerizable composition for forming a scuff resistant coating containing conductive powder to a casting polymerization mold or a molding die is not particularly limited, and brush coating, flow coating, or spray coating can be applied. When coating on a glass plate or a stainless plate in the casting polymerization method, a coating method such as roll coating or bar coating can be used.

In the present invention, the scuff resistant coating containing conductive powder is applied in a thickness of 0.5 to 100 μm, preferably 1 to 30 μm.
When the film thickness is 0.5 μm or less, it is not possible to secure sufficient surface hardness and antistatic property when transferred to the base plastic molding, and when it is more than 100 μm, the adhesion of the coating to the base plastic molding deteriorates. It causes cracks.

<Effects of the Invention> By carrying out the method of the present invention, it is possible to produce a plastic molded article having extremely excellent surface smoothness, surface hardness, transparency and antistatic property.

<Examples> Examples are shown below, but the present invention is not limited thereto. The evaluation methods for the plastic molded products described in the following examples are as follows.

(1) Scratch resistance # 1000 Scratch test with steel wool A: No scratches even with strong rubbing B: Slight scratches with strong rubbing C: Slight scratches with light rubbing D: Even with slight rubbing Significantly scratched (2) Transparency (cloudiness) Measured according to ASTM D1003.

(3) Adhesion Cross-cut cellophane tape peeling test …… Put 11 film cutting lines in each length and width to reach the base material at 1 mm intervals, make 100 1mm ² meshes, and stick cellophane tape on it Peel it off quickly. This cellophane tape operation was repeated 3 times at the same location, and the number of unpeeled cells is shown.

(4) Surface resistivity Measured with a super insulation resistance meter (manufactured by Toa Denpa).

(5) Half-life It was measured with a static Honest meter (made by Shishido Shokai).

Example 1 Synthesis of Polyfunctional Urethane Acrylate A glass reactor equipped with a stirrer, a thermometer, and a dropping funnel was charged with 242 g of trimethylolpropane diacrylate and 0.25 g of hydroquinone monomethyl ether, and the temperature was kept at 60 ° C. Into it, 85 g of 2,4-tolylene diisocyanate was added dropwise over 1 hour. The mixture was stirred at the same temperature for 1 hour, 0.05 g of dibutyltin diacetate was added, the reaction was continued for another 2 hours to complete the reaction, and 325 g of a polyfunctional urethane acrylate was obtained. The isocyanate content of this product was 0.03%.

Preparation of UV-curing hard coating agent 300 g of dipentaerythritol hexaacrylate, 300 g of the above polyfunctional urethane acrylate, 150 g of butyl acetate and 30 g of 1-hydroxycyclohexyl phenyl ketone were thoroughly mixed to prepare a UV curing hard coating agent.

Preparation of Conductive Hard Coat Agent 150 g of the above UV curable hard coat agent, 350 g of commercially available tin oxide powder (manufactured by Mitsubishi Metals Co., Ltd.), and oleic acid as a dispersant
It was prepared by adding 10 g and mixing with a ball mill for 20 hours.

Manufacture of methyl methacrylate partial polymer 200g of methyl methacrylate polymer (Sumipex BMH Sumitomo Chemical Co., Ltd.) and 800g of methyl methacrylate are placed in a glass flask of No. 2 and stirred at 60 ° C for 4 hours to dissolve, and polymer is contained. A 20% methyl methacrylate partial polymer was produced.

On a 300 × 300 × 10 mm glass plate, the conductive hard coat agent is diluted twice with a 1/1 mixture solution of ethyl acetate / xylene, coated with a bar coater to a thickness of 3 μ, and allowed to stand for 20 minutes. The glass plate was irradiated with ultraviolet rays from a distance of 250 mm for 120 W for 20 seconds using a high-pressure mercury lamp (I-cure UE021-403C, 500VH02-L41 (2) manufactured by Eye Graphics Co., Ltd.) in the air.
The thus obtained two glass plates were cured, and the membrane was used as an inner surface to sandwich a gasket made of ethylene-vinyl acetate copolymer having a width of 3 m / m to assemble a cell.

The methyl methacrylate partial polymer (300 g) and lauroyl peroxide (0.3 g) that had been sufficiently mixed and dissolved in a glass flask were poured into a cell assembled with the glass plate and polymerized at 80 ° C in a water bath. Then, the conductive hard coat film was transferred.

The physical properties of the obtained polymer are shown in Table 1.

Examples 2 and 3 and Comparative Example 1 In the same manner as in Example 1, a polymer was obtained by changing the film thickness of the conductive hard coat layer, and its physical properties were measured and shown in Table 1.

Comparative Example 2 Methyl methacrylate resin plate (SUMIPEX 000 thickness 2mm
(Sumitomo Chemical Co., Ltd.) and the conductive hard coat obtained in Example 1.
Coating agent with a bar coater to a film thickness of 3μ, and it is polymerized and cured.
Thus, a conductive methacrylic resin plate was obtained.

The characteristics of the resin plate thus obtained were evaluated and are shown in Table 1.

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Claims (3)

[Claims] 1. When molding a plastic molded product using a casting polymerization mold or a molding die, a polymerizable composition for forming a scuff resistant coating containing a conductive powder containing tin oxide as a main component is cast. A method for producing a conductive plastic molded product, which comprises applying the composition onto a surface of a polymerization mold or a molding mold, polymerizing and curing the same, and then molding a plastic. 2. The method for producing a conductive plastic molded product according to claim 1, wherein the plastic molded product is a cast polymerization molded product containing methyl methacrylate as a main component. 3. The content of the conductive powder containing tin oxide as a main component in the polymerizable composition for forming a scratch-resistant coating is 60 to 80% by weight. Term or 2
A method for producing a conductive plastic molded article according to the item.