JPS62212115A - Plastic molding method - Google Patents

Abstract

PURPOSE:To realize the uniform coating of an antistatic film having a specified resistance without scattering of powder and adhering of powder outside a mold by a method wherein the amount of fine electrically-conductive powder contained in powdered resin composition lies within a specified range. CONSTITUTION:Powdered resin composition containing 1-95wt% of fine electrically-conductive powder is electrically charged and then spread on the interior of a mold. After that, plastic material is filled into the mold and molded under the respective predetermined temperature and/or pressure. Thus, the powdered resin composition in the mold is anchoringly and tightly bonded with the surface of a molded plastic by the heat of plastic material and/or molding heat and the like, thus obtaining a plastic molded body with uniform electrically- conductive film on its surface and antistatic property, the surface resistance of which is larger than 10<13>ohm/square and not more than 10<11>ohm/square. When electrically-conductive carbon is used as fine electrically-conductive pow der, its preferable content lies within the range of 1-50wt%. When fine electrically-conductive powder other than the above-mentioned carbon is used, its preferable content lies within the range of 30-95wt%.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a plastic molding method for forming an antistatic coating on the surface of a plastic molded article.

Specifically, the present invention relates to a method for obtaining a plastic molded body having the purpose of removing static electricity, preventing static electricity, preventing corona discharge, etc.

(Prior Art) In recent years, malfunctions of electronic devices using semiconductor devices have become a problem in various fields.

These causes include not only electromagnetic waves, but also electric shock current that flows when static electricity charged on the human body due to friction is discharged through an electrical conductor, which can cause static electricity to build up on insulating materials near high-voltage areas such as televisions. is charged, and when it reaches a critical voltage or higher and discharges, an excessive current flows temporarily and electromagnetic waves are generated at the same time as the discharge, causing the semiconductor device to malfunction or be destroyed.

Therefore, in order to prevent malfunctions of electronic devices and the like, it is necessary to remove static electricity that accumulates on plastic housings and the like for self-defense.

Currently, one known method for eliminating these charging phenomena is to knead conductive powder into plastic and then mold it to give the plastic molded body itself an antistatic function (for example, Japanese Patent Publication No. 35-9643). It is being However, while this method has the advantage of being easy to work with, it requires the inclusion of a large amount of conductive powder in order to obtain a good electrical conductor, which results in a decrease in the physical strength of the plastic after molding and an increase in weight. , problems in molding, and other various drawbacks, so it is not put into practical use much.

Another known antistatic method is to apply a solvent-soluble conductive paint to the inner surface of an electronic device housing with a brush or spray.

In this method, it is necessary to take measures such as damage to the plastic shape and discoloration caused by the organic solvents contained in the conductive paint, as well as measures against undercoating to improve the adhesion strength of the paint film and prevent paint film peeling. There were problems such as odor due to continuous failure of organic solvents, negative effects on the human body, and dangers such as fire.

Recently, a method has been developed in which a solvent-soluble conductive paint is applied with a brush or a spray gun into a mold for electronic device housings, and then the plastic is molded within the mold to integrate the plastic molded body and the conductive film. has also been proposed (for example, Japanese Patent Publication No. 48-25061). According to this method, a grease-like composition is applied inside a mold, a conductive powder such as graphite is sprayed on top of the composition, and then a liquid synthetic resin is injected and cured to make predetermined areas conductive. A method has been proposed for obtaining an insulating molded body with high properties. However, this method has the fundamental problem that the conductive powder has weak adhesion at points other than the points of contact with the grease-like composition, so careful attention is required when injecting the resin, and in addition, the injection speed is also limited. There were operational problems such as the fact that it was extremely slow.

Therefore, this method cannot be applied to high-speed molding methods such as injection molding methods.

In addition, the above-mentioned known example also describes a method of using a synthetic resin adhesive before resin injection in order to strengthen the adhesion of the conductive powder, but if this method is adopted, the aforementioned solvent can be removed. None of the problems associated with applying a melt-molded conductive paint after molding have been solved.

In general, as a means to solve the above-mentioned problems of solvent-soluble paints, it is conceivable to use, for example, powder paints that do not contain any solvent at all.

In fact, in the field of molding as well, powder coatings containing a small amount of ordinary colored pigments are heated and applied to the inner surface of a pressure mold in advance by a fluidized bed or spray, and then compression molded using SMC or BMC. A method of forming a protective or colored film on the surface of FRP is known (for example, Japanese Patent Publication Nos. 44459/1982, 181823/1982, and 124610/1982).

However, even with these methods, there are problems such as powder scattering, adhesion to the outside of the mold, and uneven film thickness.

(Problems to be Solved by the Invention) The present invention solves safety and hygiene problems caused by organic solvent volatilization, as well as problems such as powder scattering, adhesion to the outside of the mold, and uneven film thickness. The powdered resin composition containing the conductive fine powder is efficiently and uniformly adhered to the plastic surface, and the surface resistance value is greater than 103 ohms/□.
The object of the present invention is to provide a method for molding plastic molded products having antistatic properties of less than 'ohm/□.

That is, the present invention provides a plastic composition in which a powdered resin composition containing conductive fine powder is applied into a mold by electrostatic coating, and then the plastic is molded to form an antistatic coating on the surface of the plastic molded body. This relates to a molding method.

(Means for Solving the Problems) The powdered resin composition used in the method of the present invention is a thermosetting or thermoplastic resin composition containing conductive fine powder at a concentration of 1 to 95% by weight. It is.

The conductive fine powder includes conductive metal oxides such as conductive zinc oxide, tin oxide, antimony oxide, and indium oxide; mixtures containing at least one of the above oxides; and/or
or a solid solution; a mixture of a colored pigment and the conductive oxide;
Compounds such as colored pigments whose surface is coated with the conductive oxide; or electrically conductive carbon such as crystalline carbon such as graphite carbon, or conductive carbon such as amorphous carbon powder such as acetylene black or Ketjen black. fine powder with an average particle size of 100μ or less, preferably 0.05
It is about ~50μ. These powders can be used alone or in combination of two or more.

In the method of the present invention, the conductive fine powder is contained in the powdered resin composition in an amount of 1 to 95% by weight.

In particular, in the present invention, when conductive carbon is used as the conductive fine powder, its content is in the range of 1 to 50% by weight, and when other conductive fine powders are used, the content is 30% by weight. It is preferably in the range of ~95% by weight.

In the present invention, the powdered resin composition containing conductive fine powder includes a composition in which conductive fine powder is encapsulated in each individual resin powder, and a resin powder in which most of the conductive fine powder is encapsulated. It also means a mixture of a small amount of conductive fine powder (provided that the total amount of conductive fine powder is within the above range). In the latter case, it is natural that the electrical resistance in the powder state must be high enough to allow electrostatic coating.

If the content of the conductive fine powder in the powdered resin composition is less than 70% by weight, it will not be possible to form a good antistatic coating on the surface of the plastic molded product, while if it exceeds 95% by weight, Both are unfavorable because they make it difficult to perform electrostatic coating efficiently.

In addition, when using conductive carbon, if its content exceeds 50% by weight, it tends to become difficult to disperse in the powdered resin composition due to oil absorption, which is not very preferable.

As the resin used as a color vehicle in the powdered resin composition of the present invention, any thermosetting or thermoplastic resin commonly used in powdered plastics, powder coatings, etc. can be used.

Examples of the thermosetting resin include acrylic resin, polyester resin, epoxy resin, alkyd resin, urethane resin,
Examples include epoxy modified polyester resin and acrylic modified polyester resin. In particular, acrylic resins, polyester resins, and epoxy resins are preferred from the viewpoint of storage stability and conductivity of the coating film.

The thermosetting resin may be of various types, such as a self-curing type, a hardening agent/crosslinking agent hardening type, and the like.

Examples of curing agents for the thermosetting resin include dicyandiamide, acid anhydrides, imidazole derivatives, aromatic diamines, boron trifluoride amine complexes, hydrazides, decamethylene dicarboxylic acid, blocked isocyanate compounds, amino resins, etc. Those normally used for thermosetting powder coatings can be used.

Further, as the thermoplastic resin, polyester resin,
Acrylic resin, epoxy resin, polyethylene resin, polypropylene resin, styrene polymer, vinyl chloride polymer,
Known resins include polyamide resin, butyral resin, cellulose resin, and petroleum resin.

The thermosetting resin and the thermoplastic resin can be used individually or as a mixture, or if necessary, the thermosetting resin and the thermoplastic resin can be used in combination.

9. In addition to the above-mentioned components, if necessary, components such as anti-sag agents, hardening accelerators, antioxidants, pigments, etc., which are generally used in powdered plastics and powder coatings, may be added to the powdered resin composition. , can also be mixed.

The powdered resin composition used in the method of the present invention can be obtained, for example, from a known powder coating manufacturing method.

For example, a mechanical pulverization method in which the conductive fine powder, resin, and other necessary hardening agents, additives, etc. are heated, melted, mixed, cooled, crushed, and sieved; A dry spray method, etc., in which additives and the like are dispersed in a solvent and then the resulting dispersion is sprayed into heated air, can be applied.

Therefore, when obtaining a composition containing a conductive fine powder with a higher concentration, or when considering the shape and maintenance of the conductive fine powder, prevention of clumping of the powdered resin composition, etc., the following wet granulation method is recommended. The manufacturing method according to is particularly preferred.

For example, the resin is dissolved in a water-soluble solvent such as alcohols, ethylene glycol derivatives, diethylene glycol derivatives, esters, and ketones (preferably having a solubility in water of 10 to 30% by weight at 20°C), and then A liquid composition (hereinafter referred to as a dispersion liquid) obtained by dispersing conductive fine powder and mixing a curing agent, additives, etc. as necessary, is prepared in an amount that dissolves all the water-soluble solvent contained in the dispersion liquid ( Emulsify and disperse in water (approximately 3 to 40 times the volume of the dispersion). Emulsification is carried out by dropping, pouring, or spraying the dispersion into water under vigorous stirring, or by mixing water and the dispersion using a line mixer.

The above-mentioned stirring or mixing using a line mixer is carried out until the solvent in the emulsion fine particles is transferred into water and particles are formed.

In this way, the solvent in the emulsion fine particles is extracted into water, and resin particles are obtained.

The resin particles are separated from the water-solvent mixture by filtration or centrifugation, and if necessary, water washing and separation are repeated a necessary number of times to obtain resin particles in the form of a slurry or a water-containing cake. Then, if necessary, use a ball mill, pot mill,
After granulation with a sand mill or the like, the resin particles are dried, preferably freeze-dried, vacuum-dried, or smoked to prevent agglomeration, and if necessary, sieved to obtain the powdered resin composition of the present invention. Such a manufacturing method is described, for example, in Japanese Patent Application Laid-open No. 48-
No. 52851, Special Publication No. 54-5832, No. 54-26
250, No. 54-31492, No. 56-5796, and No. 56-29890.

In this way, it is possible to obtain a powdered resin composition containing conductive fine powder and having a relatively nearly spherical shape while maintaining the shape of the powder.

The resin used in the powdered resin composition in the present invention has a softening point of 40 to 160°C and a melting point of 60 to 180°C, preferably a softening point of 60 to 130°C and a melting point of about 70 to 160°C.

The softening point was measured by Kof Ier's method, and the melting point was measured by Du'rran's method.

Further, the particle size range of the powdered resin composition used in the method of the present invention is 100μ or less, preferably 0.05 to 50μ.
It is about μ.

On the other hand, there are no particular restrictions on the molding methods to which the method of the present invention can be applied, and commonly used molding methods such as compression molding, transfer molding, lamination molding, and injection molding (reaction and liquid injection molding methods are also applicable). ), blow molding method, vacuum molding method, etc.

In addition, the plastic materials used in these molding methods include unsaturated polyester resin, phenolic resin,
Commonly used for molding such as epoxy resins, urea and melamine resins, styrene resins, acrylic resins, vinyl resins, polyethylene resins, silicone resins, ABS resins, nylon resins, polyacecool resins, polycarbonate resins, polyphenylene oxide resins, polypropylene resins, etc. thermosetting or thermoplastic resins, and these resins are kneaded with reinforcing fibers, fillers, curing agents, stabilizers, colorants, thickeners, mold release agents, foaming agents, flame retardants, etc. Resin composition, further sheet molding compound (SM
C), bulk molding compound (BMC), etc. can be used.

Next, the molding method of the present invention will be explained.

The conductive fine powder obtained as described above is 1 to 95% heavy weight.
The powdered resin composition containing the powder is coated with an electrostatic powder coater or the like.
Charge it to 60 to -9QKV and apply it inside the mold. The coating film thickness etc. is determined as necessary, but it is usually 10 to 200μ.
That's about it.

Next, plastic materials are filled into the molds and molded at predetermined temperatures and/or pressures.

In this way, the powdered resin composition in the mold is anchored and adhered to the molded plastic surface by the heat of the plastic material and/or the heat of molding, etc., and a plastic molded article having a uniform conductive coating on the surface is obtained.

The method of the present invention will be explained with reference to drawings regarding a typical injection molding method. FIG. 1 is a schematic diagram showing the method of the present invention, and FIG. 2 is an enlarged view of the dotted line portion of step C in FIG. 1. , FIG. 3 is an enlarged view of the main part of the obtained plastic molded body.

As shown in FIG. 1, in the pre-process A, the fixed mold 3a
The masking material 4 is fixed on unnecessary parts.

In coating step B, the electrostatic coating machine 5 coats the powdered resin composition 2a on the surface of the fixed mold 3a. Next, remove the masking material and heat it in heating step C if necessary.
The applied powdered resin composition 2a is plasticized.

Next, in the molding process, a plastic mold 3 is placed on the fixed mold 3a.
b is placed and the mold is closed, and the gap in the mold is filled with molten plastic material through the filling hole 3b' and molded, and at the same time, the antistatic coating film 2 is anchored and adhered to the surface of the plastic molded product 1.

In the demolding process E, a coating film 2 with an antistatic function is formed on the surface.
The plastic molded body l having the following properties is opened and taken out. In this way, a plastic molded article having an antistatic coating of uniform thickness can be efficiently obtained.

In addition, in the molding method of the present invention, the mold may be preheated in advance, or in the case of a mold at room temperature or a mold with a low preheating temperature, it may be heated with hot air, electricity, infrared rays, etc. after applying the powdered resin composition. preferable.

By doing so, it is possible to prevent scattering of the powdered resin composition adhered only by electrostatic force by electrostatic coating.

In particular, in injection molding, blow molding, or vacuum forming methods in which plastic material is injected under pressure or moves during molding, the preheating temperature of the mold and the resin content in the powdered resin composition are particularly important. It is preferable that the softening point and melting point of (melting point +10°C)≧mold preheating temperature≧softening point.

If the mold preheating temperature is lower than the softening point of the resin, the adhesion between the mold and the powdered resin composition will be low, leading to the movement of the plastic material due to the pressure applied to the plastic material during molding and the injection speed during injection. The powdered resin composition moves or scatters due to pressure and the like, making it difficult to obtain a uniform coating. In addition, the heat temperature of the mold is (melting point of resin + 10℃)
If it exceeds this, the powdered resin composition will melt after being applied, exhibit fluidity, and will move due to movement of the plastic material, injection speed, pressure, etc., as described above, making it difficult to obtain a uniform coating. Particularly in injection molding methods, undesirable problems may occur, such as a striped coating or a molded product having no coating at all, especially near the injection port (nozzle).

As described above, according to the method of the present invention, safety and hygiene problems caused by organic solvent volatilization, problems such as powder paint scattering, adhesion to the outside of the mold, and uneven film thickness are resolved. , the powdered resin composition containing the conductive fine powder can be efficiently and uniformly adhered to the plastic surface.

Hereinafter, the present invention will be explained in detail with reference to Examples.

"Part" or "%" is expressed as "heavy weight" or "heavy weight %". Prior to Examples, a powdered resin composition was manufactured using the formulation shown below.

[Formulation 1] Epoxy resin 30% white conductive fine powder 30% flow aid
1% methyl ethyl ketone
The 39% epoxy resin is Shell Chemical @ product name Epico) 11002 (epoxy equivalent 600-700, melting point 83 °C, softening point 57 °C), and the white conductive fine powder is Mitsubishi Metals white conductive powder, trade name W-1 [Fine powder whose titanium oxide surface is coated with a tin-based conductive agent (average particle size 0.2μ)
)] and the flow aid was Modaflow, a product of Monsando Co., Ltd., respectively.

The composition consisting of the above formulation was dispersed in a magnetic pot mill for 2 hours to obtain a liquid composition.

Then, the liquid composition was heated to a water temperature of 20°C under high speed stirring.
The following liquid composition was sprayed into 3000 parts of water to emulsify the liquid composition and extract the solvent into the water to form resin particles. Thereafter, filtration and water washing were repeated to obtain resin particles with an average particle diameter of about 100 μm. After adjusting the water content to around 50%, the resin particles were further finely pulverized to obtain a slurry-like powder resin composition. Furthermore, after repeating water washing three times or more, it is filtered, dried under dry air at 20°C or less, crushed, and sieved (150 meshes) to obtain conductive fine powder/resin = 5
A powdered resin composition (1) having a weight ratio of 0.0150 (weight ratio) was prepared.

[Formulation 2] Epoxy resin 24% Transparent conductive fine powder 36% Flow aid (same as Formulation 1) 1% Methyl ethyl ketone
The 39% epoxy resin is Shell Chemical's 0-gradient product name Epicoat #1001 (epoxy equivalent 450-500, melting point 69°C, softening point 50°C), and the transparent conductive fine powder is Mitsubishi Metals QI product name-1 [ Conductive fine powder*) mainly composed of tin oxide was used.

A liquid composition was prepared in the same manner as in Formulation 1, and then a powdered resin composition (2) having a conductive fine powder/resin ratio of 60/40 (weight ratio) was prepared in the same manner.

[Formulation 3] Epoxy resin 27% conductive zinc oxide powder 33% flow aid (same as formulation 1) 1% methyl ethyl ketone
The 39% epoxy resin is Ciba Geigi (!Kiku product name Araldite 6097 (epoxy equivalent: 900~
1000, melting point: 100° C., softening point: 80° C.), and Hakusui Chemical Industry Co., Ltd. product name 23-K (average particle size: 0.4 to 0.7 μm) was used as conductive zinc oxide powder.

The composition having the above formulation was dispersed in a paint shaker for 1 hour to obtain a liquid composition.

Next, after creating a powdered resin composition in the same manner as Formulation 1, an imidazole-based epoxy resin curing agent [Shikoku Kasei Kogyo Junsei brand name: Kikoazole CzZ] was added as a fine powder at a rate of 4 phr. A powder composition (conductive fine powder/resin = 45155 (weight ratio)) was dry mixed (
3) was created.

[Formulation 4] Epoxy resin 30% conductive zinc powder 30% flow aid (same as formulation 1) 1% methyl ethyl ketone
The 39% epoxy resins are manufactured by Shell Chemical ■ under the trade name Epicote 01001, $11002, and 111004 (epoxy equivalent weight 875-975, melting point 98°C, softening point 70°C).
) in a ratio of 1:1 to 1 (weight ratio) (
The conductive zinc powder is manufactured by Honjo Chemical under the trade name FX-C (average particle size 3.2μ).
)] were used respectively.

The composition consisting of the above formulation was made into a liquid composition in exactly the same way as Formulation 3, and a powdered resin composition (4) of conductive fine powder/resin -50150 (weight ratio) was created in the same manner as Formulation 1. did.

[Formulation 5] Epoxy resin 18% transparent conductive powder (same as formulation 2) 36% titanium oxide (rutile type) 6% methyl ethyl ketone
The 40% epoxy resin was prepared by mixing 40% epoxy resin (Meiko Pico) tt1002, $11004, tt1007 manufactured by Shell Chemical Co., Ltd. with poxy resin (H1750-2200, melting point 128°C, softening point 85°C) in a ratio of 1:1:1 (weight ratio). (melting point: about 107°C, softening point: 65°C) was used.

The composition consisting of the above formulation was dispersed in the same manner as Formulation 3 to create a liquid composition.

Next, in the same manner as in Formulation 1, a powdered resin composition (5) having a conductive fine powder/(resin+nonconductive pigment) = 60/40 (gravity ratio) was prepared from the liquid composition.

[Formulation 6] Epoxy resin 26% Transparent conductive fine powder 30% Azo red pigment
4% methyl ethyl ketone
40% epoxy resin is manufactured by Shell Chemical Product name Epicor) #1002, tt1004, #1007 and #10
09 (epoxy equivalent 2400-3300, melting point 148
°C, softening point 90 °C) in a ratio of 1:1:2:2 (weight ratio) (melting point approximately 135 °C, softening point 75 °C).
The transparent conductive fine powder is manufactured by Catalysts & Chemicals Industry @ Cloth name E
L COM-T L20 [scaly conductive powder mainly composed of tin oxide (width 0.1 μ, major axis 2 μ, minor axis 1 μ)] was used.

A powdered resin composition (6) having a conductive fine powder/(resin+non-conductive pigment)=50150 (weight ratio) was prepared using the composition consisting of the above formulation in the same manner as in Formulation 3.

[Formulation 7] Epoxy tree 1 effect 27.4% graphite carbon powder 12% methyl ethyl ketone 60% dicyandiamide
0.6% epoxy resin is Epicoat #1007
The graphite carbon powder used was CX-3000 (trade name, manufactured by Shin-etsu Graphite Industries Co., Ltd. (median particle size: about 3 μm)).

A liquid composition was prepared using the composition described above in the same manner as in Formulation 1, and then diluted by adding 50 parts of methyl ethyl ketone to 100 parts of the composition, followed by spray drying (air flow rate: 20 m2). conductive fine powder/resin -30/70
A powdered resin composition (7) of (weight ratio) was prepared.

[Formulation 8] Epoxy resin (same as formulation 4) 32% amorphous conductive carbon fine powder 8% flow aid Same as formulation 1) 0.596 methyl ethyl ketone
The 59.5% amorphous conductive carbon fine powder is Ketjen Black EC (average particle size 3
0μ) was used.

A powdered resin composition (8) with conductive fine powder/resin=20/80 (weight ratio) was prepared by using the composition consisting of the above formulation in the same manner as in Formulation 3.

[Formulation 9] Polyester resin 18% Conductive white powder (same as Formulation 1) 42% Methyl ethyl ketone
The 40% polyester resin is manufactured by Dainippon Ink Chemical under the trade name Finedic M-8000 (melting point 1
23°C, softening point 75°C).

The composition consisting of the above formulation was mixed with a magnetic po/ ) mill for 1
A liquid composition was prepared by dispersing for half an hour, and from the liquid composition in the same manner as in Formulation 1, conductive fine powder/resin = 70/3.
A powdered resin composition (9) having a weight ratio of 0 (weight ratio) was prepared.

[Formulation 10] Polyester resin (same as formulation 9) 15.7% transparent conductive powder (same as formulation 2) 36% titanium oxide fine powder (
Same as formulation 5) 8% methyl ethyl ketone
40% dianediamide 0.
A powdered resin composition σQ having a conductive fine powder/(resin+non-conductive pigment)-60/40 (weight ratio) was prepared using a composition consisting of the above-mentioned 3% composition in the same manner as in Formulation 7.

[Formulation 11] Polyester resin 27% conductive zinc oxide (same as formulation 3) 33% methyl ethyl ketone 40% polyester resin manufactured by Nippon Yubika, product name G-110 < melting point 85°C, softening point 65°C
) was used.

A powdered resin composition (10) having the above-mentioned formulation was prepared in the same manner as Formulation 9, with conductive fine powder/resin=55/45 (weight ratio).

[Formulation 12] Acrylic resin 24% Conductive white fine powder 36% Methyl ethyl ketone 40% Acrylic resin is manufactured by Dainippon Ink Chemical under the trade name Δ-2243 (melting point 114°C, softening point 70°C)
), the conductive white fine powder is manufactured by Titanium Industry ■, product name: ECT
-52 [mixed conductive fine powder of titanium oxide and tin oxide (average particle size 0.44μ)] was used.

A powdered resin composition 02) having the conductive fine powder/resin=60/40 (weight ratio) was prepared by using the composition having the above formulation in the same manner as in Formulation 5.

Example 1 After masking the unpainted part in a fixed mold preheated to 70°C, the powdered resin composition (1) was electrostatically applied under a voltage of -80 KV to form a coating film, and then masked. was removed, and the fixed mold and movable mold were sealed.

Then, a heat-resistant polystyrene resin liquid with a resin temperature of 270° C. was injection molded at an injection pressure of about 900 kg/c111.

In this way, a heat-resistant polystyrene molded body having a uniform antistatic coating with a film thickness of 40 μm and a surface resistance value of 7.5×10 6 ohms/□ was obtained.

Example 2 The non-painted parts of the fixed mold, which had been preheated to 60°C, were masked, and the powdered resin composition (2) was electrostatically applied under a voltage of -70 KV to form a coating film. I removed the masking. Next, the fixed mold and the movable mold are sealed, and a vinyl chloride resin liquid with a resin temperature of 180°C is injected at a pressure of about 750 k.
When injection molded with g/CffI, a vinyl chloride resin molded product having a uniform antistatic coating with a film thickness of 60 μm and a surface resistance value of 5×10′ ohm/□ was obtained.

Example 3 The non-painted parts of a mold that had been preheated to 90°C were masked, and then the powdered resin composition (3) was applied to the painted parts of the mold using an electrostatic coating device under a voltage of 155 KV. After painting and forming a paint film, the masking was removed. Then, a hard vinyl chloride sheet is heated using a heater.
The sheet was heated to 25°C to soften it, and was fixed to the above-mentioned mold using a clamp frame. Then, the air inside the mold was sucked out with a vacuum level of 72 QmmHg using a vacuum pump, and when the sheet was tightly attached to the mold surface and molded, the film thickness was determined. A hard vinyl chloride resin molded body having a uniform antistatic coating with a surface resistance of 60 μm and a surface resistance of 3×10′ ohm/□ was obtained.

Example 4 The non-painted parts of the fixed mold preheated to 65°C were masked in advance, and the powdered resin composition (4) was electrostatically applied under a voltage of -5QKV to form a coating film, and the masking was removed. did. Next, the fixed mold and the movable mold are sealed, and the resin temperature is set to 22.
Injection pressure of 0℃ polyethylene resin liquid is 1100kg/
When injection molded using cnf, a polyethylene resin molded body having a uniform antistatic coating with a film thickness of 50 μm and a surface resistance value of 1.2×10 7 ohms/□ was obtained.

Example 5 Masking the non-painted part in the fixed mold at a temperature of 60°C,
After applying the powdered resin composition (5) electrostatically under a voltage of -70 KV, the masking was removed and the mold was heated to 95° C. with an infrared heater to form a coating film. Next, the fixed mold and the movable mold are sealed, and ABS resin liquid with a resin temperature of 230°C is injected at a pressure of 1000 kg/an! Injection molded with
An ABS resin molded body having a uniform antistatic coating with a thickness of 60 μm and a surface resistance value of 3.5×10′ ohm/□ was obtained.

Example 6 The unpainted part of the inner surface of the mold, which had been preheated to 87°C, was masked, and the powdered resin composition (6) was applied to the coated part of the inner surface of the mold under a voltage of -60 KV using an electrostatic powder coating device. After painting and removing the masking, the inner surface of the mold was heated with an infrared heater to form a coating film.The polypropylene extruded into a tube at 195°C was inserted into the mold, and 3.5 kg/ctd of polypropylene was placed inside the tube. When the polypropylene was expanded by blowing compressed air into the mold and molded, the film thickness was 60 μm and the surface resistance value was 3.5.
A polypropylene resin molded article having a uniform antistatic coating of 106 ohms/square was obtained.

Example 7 The non-painted part in a mold preheated to 125°C was masked, and the powdered resin composition (7) was applied to the painted part in the mold under a voltage of 173 KV using an electrostatic powder coating device. After painting and molding the coating film, the masking was removed and phenol resin powder preheated to 116℃ was put into the molds.
Close the mold and heat to 155℃ to 180kg/c++f
When the mold was compressed at a pressure of 1, a phenolic resin molded article having a uniform antistatic coating with a thickness of 50 μm and a surface resistance of 2.5×10′ ohm/□ was obtained.

Example 8 The unpainted part of the inner surface of the mold preheated to 80° C. was masked, and the powdered resin composition (8) was applied to the coated part of the inner surface of the mold under a voltage of -5 QKV using an electrostatic powder coating device. After coating and forming a coating film, the masking was removed. Then, the fixed mold and the movable mold are sealed, and the resin temperature is set to 25.
When polybutylene terephthalate (PBT) resin reinforced with glass fiber at 0°C was injection molded at an injection pressure of 1000kg/c+f, the film thickness was 45μ and the surface resistance was 3.7X.
A glass fiber-reinforced PBT resin molded body having a uniform antistatic coating of 10' ohm/□ was obtained.

Example 9 The unpainted parts of the entire mold, which had been preheated to 120°C, were masked, and the powdered resin composition (9) was electrostatically applied under a voltage of -70 V to form a coating film. I removed the masking. Then, the fixed mold and the movable mold are sealed, and the resin temperature is set to 26.
Injection pressure of 0℃ polycarbonate resin liquid was 1500℃.
A polycarbonate resin molded body having a uniform antistatic coating with a thickness of 40 μm and a surface resistance value of 8.5×IQ′ ohm/□ was obtained by injection molding at a weight of 1.5 kg/cut.

Example 10 All non-painted parts in the mold preheated to 150°C were masked, and the powdered resin composition αQ was electrostatically coated under an electrostatic voltage of -60 V to form a coating film, and then masked. I removed it. Then, the fixed mold and the movable mold are sealed, and the resin temperature is set to 3.
PPO (polyphenylene oxide) resin at 30℃ is injection molded at an injection pressure of 1500 kg/cffl.
A PO resin molded body was obtained.

The antistatic coating had some unevenness on the coating surface near the nozzle that injects the resin, but the average coating thickness was 40μ and the surface resistance was 5.
．． It was an antistatic coating of 5×105 ohm/□.

Example 11 The unpainted part of the inner surface of a mold that had been preheated to 90°C was masked, and the powdered resin composition was applied to the painted part of the mold using an electrostatic powder coating device, and then the masking was removed and the coating was applied. A polyethylene resin formed into a film and extruded into a tube at 175° C. was inserted into the mold, and 3.
When 2 kg/Crd of compressed air was blown into the tube and the tube was tightly attached to the inner surface of the mold, the film thickness was 60μ.
A polyethylene resin molded article having a uniform antistatic coating with a surface resistance value of 1.5×10 5 ohms/□ was obtained.

Example 12 All unpainted parts of the mold, which had been preheated to 105°C, were masked, and the powdered resin composition was electrostatically coated at a voltage of -80 KV to form a coating film, and then the masking was removed.

Then, the fixed mold and the movable mold are sealed, and the resin temperature is set to 240℃.
injection pressure of polypropylene resin liquid of 1500 kg/Cl
Injection molded with 11, film thickness 60μ, surface resistance value 1.8X
A polypropylene resin molded body having a uniform antistatic coating of 106 ohm/□ was obtained.

[Brief explanation of drawings]

Step C in FIG. 1 is a process schematic diagram showing an injection molding method which is an example of the method of the present invention. Figure 2 is an enlarged view of the dotted line in process C in Figure 1;
The figure is an enlarged sectional view of a plastic molded article obtained by the method of the present invention. 1... Plastic molded body, 2... Antistatic coating, 3... Molding mold, 4... Masking material, 5...
Electrostatic coating! Machine A. Maichi JP 62-212115 (If) Figure 2 Figure 3

Claims (8)

[Claims] (1) In a plastic molding method, a powdered thermosetting or thermoplastic resin composition containing conductive fine powder in a range of 1 to 95% by weight is applied into a mold by electrostatic coating, and then the plastic material is Filling and molding is performed, and the powdered resin composition is plasticized and compressed using the heat of the filling material and/or the heat during molding to form a thermosetting or thermoplastic resin film in close contact with the surface of the molded plastic. 10^3 ohm on the surface of the plastic molded object/10^1 larger than □
A plastic molding method that forms an antistatic coating of ＾1 ohm/□ or less. (2) The plastic molding method is an injection molding method, a blow molding method, or a vacuum forming method.
1) Plastic molding method described in section 1). (3) The plastic molding method according to claim (1) or (2), wherein the mold is a preheated mold. (4) A patent claim in which a powdered thermosetting or thermoplastic resin composition is applied inside a mold by electrostatic coating, and then the powdered resin composition is fused or cured by heating and then molded. The plastic molding method according to scope item (1), item (2), or item (3). (5) The melting point and hardening point of the resin component used in the powdered resin composition and the mold preheating temperature have a relationship of (melting point + 10°C) ≧ mold preheating temperature ≧ softening point. (3
The plastic molding method described in ). (6) The powdered resin composition is obtained by dispersing, granulating, and solvent extracting a liquid composition consisting of a water-soluble solvent, the water-insoluble and solvent-soluble resin, and a conductive fine powder in water, and then separating the liquid composition. The plastic molding method according to claim 1, which is a powdered resin composition obtained by drying wet granulation. (7) The powdered resin composition contains 1 to 50 conductive carbon.
% by weight of the plastic molding method according to claim (1). (8) The plastic molding method according to claim (1), wherein the powdered resin composition contains 30 to 95% by weight of conductive fine powder other than conductive carbon.