JPH0236373B2 - PURASUCHITSUKUSEIKEIHOHO - Google Patents

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention provides a method for applying a conductive film and a radio wave absorbing film formed on the surface of a plastic molded article, or a radio wave absorbing film and a radio wave absorbing film formed thereon. The present invention relates to a plastic molding method for forming a multilayer coating consisting of a conductive coating. More specifically, the present invention relates to a method for obtaining a plastic molded body having the purpose of shielding electromagnetic waves, preventing static electricity, etc.

(Prior art) In recent years, it has become clear that electromagnetic waves and static electricity are the cause of malfunctions in electronic devices that use semiconductor devices, and in Western countries, malfunctions are caused by electromagnetic waves and static electricity.
The current regulations regarding electronic devices that incorporate IC and LSI elements are beginning to become law, and the electronic device industry is urgently required to take countermeasures.

Currently, one of the methods to shield these sources of interference electromagnetic waves is to knead conductive powder into plastic and then mold it, giving the plastic molded body itself a conductive function (for example, Japanese Patent Publication No. 35-9643 )It has been known. however,
Although 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 an electrical conductor, resulting in a decrease in the physical strength of the plastic after molding, an increase in weight, and It has not been put into practical use much because of various other drawbacks such as problems in molding.

Another known shielding 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 against shape damage and discoloration caused by organic solvents contained in conductive paints, as well as undercoat measures to improve paint film adhesion strength and prevent paint film peeling. There were problems such as odor caused by solvent volatilization, adverse effects on the human body, and danger of 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 coating. has also been proposed (for example, Special 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 problems with the work, 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 increase 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, even in the field of molding, a powder coating containing a small amount of normal color pigments is heated and applied to the inner surface of a pressure mold 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 FRP surface is known (for example, Japanese Patent Publication No. 58-44459,
JP-A-57-181823, JP-A-58-124610).

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

On the other hand, conductive films have the problem of having the ability to reflect electromagnetic waves but not absorbing them, and moreover, are not effective in shielding electromagnetic waves in the high frequency range (low wavelength).

Furthermore, since conductive coatings are conductive, if they are exposed inside an electronic device housing, there is a high risk of electric shock or leakage due to contact with internal devices carrying current. This can also be cited as one of the problems.

(Problems to be Solved by the Invention) The present invention solves safety and hygiene problems caused by organic solvent volatilization, and problems such as scattering of powder paint, adhesion to the outside of the mold, and uneven film thickness. By solving this problem, a powdered resin composition containing a high concentration of conductive fine powder can be efficiently and uniformly attached to the plastic surface.
It is an object of the present invention to provide a method for molding a plastic molded article having electrical conductivity and a surface resistance value of about 10 ² ohms/□ or less.

Furthermore, it is an object of the present invention to provide a plastic molding method for forming a multilayer coating having a radio wave absorbing coating that absorbs electromagnetic waves in a high frequency range and, in some cases, has a function of preventing electric shocks and leakage accidents caused by conductive coatings.

(Means for Solving the Problems) That is, the present invention provides a plastic molding method in which first, a powdery resin composition of either a conductive powdery resin composition or a radio wave absorbing powdery resin composition is used. After applying the powdered resin composition into the mold by electrostatic coating, and then applying the other powdered resin composition among the powdered resin compositions by electrostatic coating, the plastic is molded, and a conductive film and an insulating film are formed. The present invention relates to a plastic molding method in which a multilayer film consisting of a film is brought into close contact with the surface of a plastic molded body.

(Specific Description of the Invention) The conductive powder resin composition used in the method of the present invention is a thermosetting or thermoplastic resin composition containing conductive fine powder.

Examples of the thermosetting resin include acrylic resin, polyester resin, epoxy resin, alkyd resin,
Urethane resin, epoxy modified polyester resin,
An example is 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.

Various types of thermosetting resins can be used, such as a self-curing type and a curing agent (crosslinking agent) curing type.

Examples of the curing agent for the thermosetting resin include dicyandiamide, acid anhydride, imidazole derivative, aromatic diamine, boron trifluoride amine complex compound, hydrazide, decamethylene dicarboxylic acid, blocked isocyanate compound, amino resin, etc.
Those normally used for thermosetting powder coatings can be used.

Further, as the thermoplastic resin, known ones such as acrylic resin, epoxy resin, polyester resin, polyethylene resin, polypropylene resin, styrene polymer, vinyl chloride polymer, polyamide resin, butyral resin, cellulose resin, and petroleum resin are used. Can be mentioned.

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.

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

The softening point was measured by Kofler's method, and the melting point was measured by Durran's method.

The conductive fine powder refers to metal powder or alloy powder such as gold, platinum, palladium, silver, copper, or nickel; or the surface of inorganic powder or plastic powder that is an electrically poor conductor such as nickel-coated mica powder. It is a fine powder with good electrical conductivity, such as one coated with a metal that is a good electrical conductor, and has a particle size range of 0.5 to 100 μm, preferably about 1 to 50 μm. These powders can be used alone or in combination of two or more.

Dendritic metal fine powder is particularly effective for the purpose of the present invention, that is, to obtain a film with good conductivity and excellent adhesion.

The conductive fine powder is preferably 70 to 95% by weight, more preferably 75% by weight in the conductive powder resin composition.
It is contained in the range of ~90% by weight.

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

The amount of conductive fine powder in the conductive powder resin composition is
If it is less than 70% by weight, it will not be possible to form a good conductive film on the surface of the plastic molded object, while if it exceeds 95% by weight, it will be difficult to perform electrostatic coating efficiently. , I don't really like either of them.

The conductive powdery resin composition used in the method of the present invention can be obtained by a known method for producing powder coatings and the like.

For example, after heating and melting and mixing the resin and conductive powder, and other necessary hardening agents, additives, etc.,
After using a mechanical pulverization method of cooling, pulverizing, and sieving, or dispersing the resin, conductive fine powder, and other necessary hardening agents, additives, etc. in a solvent, the obtained dispersion is immersed in heated air. Dry spray method etc. can be applied.

Therefore, when obtaining a composition containing conductive fine powder at a higher concentration, when using a resin with a low melting point, or when considering prevention of agglomeration of a powdered resin composition, the following wet granulation method is used. A manufacturing method using a method is preferred.

For example, water-soluble solvents such as alcohols, ethylene glycol derivatives, diethylene glycol derivatives, esters, and ketones (preferably 20
A liquid composition obtained by dissolving the resin in a solution with a solubility in water of 10 to 30% by weight at °C, and then mixing the resin, conductive fine powder, and other necessary curing agents, additives, etc. A substance (hereinafter referred to as a dispersion) is emulsified and dispersed in an amount of water (approximately 3 to 40 times the amount of the dispersion) in which all the water-soluble solvents contained in the dispersion are dissolved. 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 stirring or mixing with a line mixer is
This process is continued until the solvent in the emulsified fine particles migrates into the 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, the particles are adjusted using a ball mill, pot mill, sand mill, etc., and then dried to prevent the resin particles from agglomerating, preferably by freeze drying, vacuum drying, etc., and if necessary, sieved to obtain the conductive powder of the present invention. A resin composition is obtained. Such a manufacturing method is described, for example, in Japanese Patent Application Laid-open No. 48-52851, Japanese Patent Publication No. 54-5832, and Japanese Patent Publication No. 54-54.
-26250, 54-31492, 56-5796, 56
It is detailed in the -29890 publication.

Furthermore, the particle size range of the conductive powder resin composition used in the method of the present invention is about 0.5 to 100 μm,
Preferably it is about 1 to 50 μm.

On the other hand, the electromagnetic absorbing powder resin composition used in the method of the present invention is a thermosetting or thermoplastic resin composition containing radio wave absorbing fine powder.

The resin as a color vehicle used in the electromagnetic wave absorbing powder resin composition of the present invention may be any thermosetting or thermoplastic resin similar to that used in the conductive powder resin composition. Can be used. In addition, as a method for producing a radio wave absorbing powdered resin composition,
The same method as the method for obtaining the conductive powdery resin composition can be applied.

In particular, when obtaining a resin composition containing a high concentration of radio wave absorbing fine powder, or when considering prevention of agglomeration of the radio wave absorbing powder resin composition, the production method using the wet granulation method is preferable. .

The softening point and melting point of the resin used in the electromagnetic wave absorbing powder resin composition, as well as the particle size of the resin composition, are preferably within the same range as in the case of the conductive powder resin composition.

The radio wave absorbing fine powder used in the radio wave absorbing powder resin composition has the general formula M ²⁺ O (Fe ₂ O ₃ ) [M represents a divalent metal such as Ni, Zn, Mn, etc. ] Preferably, spinel-type ferrite particles are represented by the following formula.

Such particles include, for example, NiFe ₂ O ₄ ,
ZnFe ₂ O ₄ , MnFe ₂ O ₄ , CuFe ₂ O ₄ , Fe ₃ O ₄ ,
CoFe ₂ O ₄ etc., or Ni−Zn, Ni−Mn, Mn−
Examples include composite ferrites such as Zn. These may be used alone or as a mixture of two or more.

The spinel type ferrite fine particles can be produced by a generally known method, for example, the method described in "Powder and Powder Metallurgy", Vol. 29, No. 6, Page 12.

The radio wave absorbing fine particles used in the method of the present invention have a particle size of about 0.05 to 10 μm, and the particles are preferably 50 μm in diameter in the radio wave absorbing powder resin composition.
Contains about 95% by weight.

In the above range, if the radio wave-absorbing fine particles are less than 50% by weight, the effect of absorbing electromagnetic waves in the high frequency range cannot be expected to be very good.On the other hand, if the content exceeds 95% by weight, it becomes difficult to obtain a uniform coating. I don't like it.

The radio wave absorbing powdered resin composition of the present invention is
A composition in which all of the radio wave absorbing fine powder is encapsulated in each individual resin powder, and a mixture of a resin powder containing most of the radio wave absorbing fine powder and a small portion of the radio wave absorbing fine powder (however, a composition in which the radio wave absorbing fine powder is contained in each resin powder) This means that the total amount of absorbent fine powder falls within the above range.

In addition to the above-mentioned components, components generally used in powder coatings, such as anti-sag agents, curing accelerators, antioxidants, extender pigments, etc., may be added to the radio wave-absorbing powdered resin composition as necessary. You can also do that.

Furthermore, the particle size range of the radio wave absorbing powdered resin composition is about 0.5 to 100 μm, preferably 1 to 50 μm.
It is about m.

On the other hand, there are no particular restrictions on the molding method 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) (including yon molding method), blow molding method, vacuum molding method, etc.

Plastic materials used in these molding methods include unsaturated polyester resins, phenolic resins, epoxy resins, urea and melamine resins, styrene resins, acrylic resins, vinyl resins, polyethylene resins, silicone resins, and ABS.
Thermosetting or thermoplastic resins commonly used for molding, such as resins, nylon resins, polyacetal resins, polycarbonate resins, polyphenylene oxide resins, polypropylene resins, etc., and reinforcing fibers, fillers, Resin compositions kneaded with curing agents, stabilizers, colorants, thickeners, mold release agents, foaming agents, flame retardants, etc., as well as sheet molding compounds (SMC), bulk molding compounds (BMC), etc. Available for use.

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

In the method of the present invention, either a conductive powder resin composition or a radio wave absorbing powder resin composition is electrostatically coated into a mold, and then the powder resin composition is applied onto the mold. The other powdered resin composition of the compositions is electrostatically applied.

In other words, (1) when a radio wave absorbing powder resin composition is applied as the first layer, a conductive powder resin composition is applied as the second layer, and (2) a conductive powder resin composition is applied as the first layer. When a radio wave absorbing powdered resin composition is applied, the radio wave absorbing powdered resin composition is applied as a second layer.

It is a matter of course that a composite layer of two or more layers can be obtained, and in that case, it is sufficient to apply a different type of powdered resin composition from the previously applied powdered resin composition.

Furthermore, a colored or transparent powdered resin composition containing or not containing a colored pigment is applied as a powdered resin composition to be applied on the second layer to exhibit an aesthetic or protective function. is also possible.

As a typical example of the present invention, the method for the case (1) will be described in detail below.

First, the radio wave-absorbing powdered resin composition obtained as described above was coated with an electrostatic powder coater or the like at a temperature of -30 to -
Charge it to 90KV and apply it inside the mold. The coating film thickness etc. is determined depending on the need, but it is usually 10 to 200 μm.
That's about it.

Then, the conductive powder resin composition is electrostatically applied thereon at -30KV to -90KV in the same manner as described above. The film thickness is preferably about 10 to 200 μm.

Finally, fill the mold with plastic material,
Each is molded at a predetermined temperature and/or pressure.
In this way, each 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 body having a uniform radio wave absorbing and conductive coating on the surface is formed. can get.

The method (1) 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.
FIG. 3 is an enlarged view of the dotted line portion of the process, and FIG. 3 is an enlarged view of the main part of the obtained plastic molded article.

As shown in FIG. 1, in the pre-process A, a masking material 5 is fixed to unnecessary parts of the fixed mold 3a.

In the coating step B, the electrostatic coating machine 6 coats the electromagnetic wave absorbing powdered resin composition 2a on the surface of the fixed mold 3a. Next, in a coating step D, the electroconductive powder resin composition 4a is coated with the electrostatic coating machine 6' to coat the electromagnetic absorbing powder resin composition coating 2a.
Apply on top.

Finally, the masking material is removed and, if necessary, heated in a heating step E to plasticize the applied powdered resin compositions 2a and 4a.

Next, in the molding process F, the movable mold 3b is placed on the fixed mold 3a and the mold is closed, and a filling hole 3 is formed in the gap in the mold.
The molten plastic material is filled and molded from b', and the conductive coating 4 and the radio wave absorbing coating 2 are anchored and adhered to the surface of the plastic molded body 1.

In the demolding step G, the molded plastic body 1 having the coating 2 having a conductive function and the coating 4 having a radio wave absorbing function on its surface is opened and taken out.

In this way, a plastic molded article having a conductive coating and a radio wave absorbing 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.

Note that the preheating of the mold refers to a case where the mold temperature is higher than room temperature due to heat applied from the outside or heat during molding of a plastic material.

Further, the heating after applying the powdered resin composition refers to heating after applying the radio wave absorbing powdered resin composition and/or heating after applying the conductive powdered resin composition,
It is preferable that the resin in the resin composition partially softens and melts to such an extent that the powder particles adhere to each other.

In the method of the present invention, in particular, injection molding methods, blow molding methods in which the plastic material is injected under pressure or the plastic material moves during molding,
Alternatively, in a vacuum forming method, etc., the mold preheating temperature and the softening point and melting point of the resin in the powdered resin composition may be within the range of (melting point + 10°C) ≧ mold preheating temperature ≧ softening point. Particularly preferred.

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. Additionally, if the mold preheating temperature exceeds (resin melting point + 10°C), the powdered resin composition will completely melt after application.
It becomes fluid and moves due to movement of the plastic material, injection speed, pressure, etc., as described above, making it difficult to obtain a uniform coating. Particularly in the injection molding method, undesirable problems may occur, such as a striped coating or a molded product having no coating at all, especially near the injection port (nozzle).

(Effects of the Invention) As described above, according to the method of the present invention, safety and hygiene problems due to organic solvent volatilization, powder paint scattering, adhesion to the outside of the mold, uneven film thickness, etc. can be avoided. This problem has been solved, and the powdered resin composition containing a high concentration of conductive fine powder can be efficiently and uniformly attached to the plastic surface.
It can absorb electromagnetic waves in the high frequency range, and when a radio wave absorbing layer is provided as the outermost layer, it is possible to prevent electric shocks and leakage accidents that would occur if only a conductive film was used.

Hereinafter, the present invention will be explained in detail with reference to Examples.
"Parts" or "%" are expressed as "parts by weight" or "% by weight." Prior to Examples, powdered resin compositions were manufactured using the formulations shown below.

Production of radio wave absorbing powdered resin composition [Formulation 1] Epoxy resin 45% Dicyandiamide 4% Mn-Zn ferrite particles (average particle size approximately 1 to 2 μm)
m) 50% Flow aid 1% The epoxy resin is manufactured by Ciel Chemical Co., Ltd. under the trade name Epicote #1004 (epoxy equivalent: 875-975, melting point: 98°C,
Softening point: 70°C) was used, and Modaflow (trade name, manufactured by Monsanto) was used as a flow aid.

The composition of Formulation 1 is mixed and kneaded at 110°C or less using a heated roller, the kneaded mixture is cooled and pulverized by a pulverizer, and the portion that passes through a 100-mesh sieve is processed into radio wave absorbing powder. Resin composition (A-
1) was created.

[Formulation 2] Epoxy resin 10% Methyl ethyl ketone 50% Ni-Zn ferrite particles (average particle size approx. 0.5-1μ
m) 40% The epoxy resin is manufactured by Ciel Chemical Co., Ltd. under the trade name Epicote #1002 (epoxy equivalent: 600-700, melting point: 83°C,
A mixture of #1004 (melting point: 92°C, softening point: 65°C) at a ratio of 1:1 was used.

The composition consisting of Formulation 2 was dispersed for 2 hours using a magnetic pot mill to obtain a liquid composition. Next, the liquid composition was sprayed into 3000 parts of water at a temperature of 20° C. or less under high speed stirring 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 finely pulverized by dispersion using a ball mill to obtain a slurry-like powdered resin composition. After repeating water washing three times or more,
The mixture was filtered, dried under dry air at a temperature of 20° C. or lower, pulverized, and sieved (100 meshes) to prepare a radio wave absorbing powdered resin composition (A-2).

[Formulation 3] Polyester resin 10% Mn-Zn ferrite particles (average particle size approximately 1-2μ
m) 50% Methyl ethyl ketone 40% The above polyester resin is a trade name manufactured by Nippon U-Pica Co., Ltd.
GV-110 (melting point 85°C, softening point 65°C) was used.

A radio wave absorbing powdered resin composition (A-3) was prepared by using the composition of Formulation 3 in the same manner as Formulation 2.

[Formulation 4] Acrylic resin 9% Ni-Zn ferrite particles (average particle size approximately 0.5-1μ
m) 51% Methyl ethyl ketone 40% The acrylic resin is manufactured by Dainippon Ink and Chemicals Co., Ltd.
Product name A-224S (melting point: 114°C, softening point: 70°C) was used.

A radio wave absorbing powdered resin composition (A-4) was prepared by using the composition of Formulation 4 in the same manner as Formulation 2.

Manufacture of conductive powder resin composition [Formulation 5] Epoxy resin 12% Dendrite-shaped copper powder 48% Flow aid (same as Formulation 1) 1% Methyl ethyl ketone 39% The epoxy resin is manufactured by Ciel Chemical Co., Ltd. under the trade name Epicote #1002 was used as the dendrite-shaped copper powder, and electrolytic copper powder trade name MD-1 manufactured by Mitsui Mining & Smelting Co., Ltd. [more than 80% passing through 325 mesh (opening 44 μm)] was used.

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

Next, the liquid composition was sprayed into 3000 parts of water at a temperature of 20° C. or less under high speed stirring 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 powdered resin composition. After repeating water washing three times or more, filter, dry in dry air at 20℃ or less, crush,
Sieve (150 mesh) and conductive powder/resin =
80/20 (weight ratio) conductive powder resin composition (B
-1) was created.

[Formulation 6] Epoxy resin 9% Dendrite-shaped copper powder 51% Flow aid (same as Formulation 1) 1% Methyl ethyl ketone 39% Epoxy resin is manufactured by Ciel Chemical Co., Ltd. under the trade name Epicote #1001 (epoxy equivalent 450-500, melting point 69℃, softening point 50℃), and the dendrite-shaped copper powder is electrolytic copper powder manufactured by Mitsui Mining & Mining Co., Ltd. under the trade name MD-1 and MF-D _2.
(weight average particle diameter: 8 μm) were mixed in a 1:1 ratio by weight.

After making the liquid composition in the same way as formulation 5,
A conductive powder resin composition (B-2) having a conductive fine powder/resin ratio of 85/15 (weight ratio) was prepared in the same manner.

[Formulation 7] Epoxy resin 6% Dendrite-shaped copper powder 54% Flow aid (same as Formulation 1) 1% Methyl ethyl ketone 39% Epoxy resin is manufactured by Ciba Geigy Co., Ltd. under the trade name Araldite 6097 (epoxy equivalent 900-1000, melting point 100°C) ,
The dendrite-shaped copper powder used was electrolytic copper powder (trade name MF-D ₂ , manufactured by Mitsui Mining & Mining Co., Ltd.).

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

Next, after creating a conductive powdered resin composition in the same manner as in Formulation 5, a hardening agent for imidazole-based epoxy resins [trade name: Kyuazol C ₁₁ Z, manufactured by Shikoku Kasei Kogyo Co., Ltd.] was added as a fine powder. as4phr
Dry mix in the ratio of conductive fine powder/resin = 90/
A conductive powder composition (B-3) having a weight ratio of 10 (weight ratio) was prepared.

[Formulation 8] Epoxy resin 12% Nickel powder 48% Methyl ethyl ketone 40% Epoxy resins are manufactured by Ciel Chemical Co., Ltd. under the trade name Epicote #1002, #1004, and #1007 (epoxy equivalent
1750-2200, melting point 128℃, softening point 85℃) 1:
Mixed at a ratio of 1:1 (weight ratio) (melting point approx.
107℃, softening point 65℃), and the nickel powder is Inco's product name #123 (average particle size of about 3 to 7 μm) and #255 (average particle size of about 2 to 3 μm) in a 1:1 (weight ratio). ) were used.

The composition consisting of the above formulation was dispersed in the same manner as Formulation 5 to create a liquid composition.

Next, in the same manner as in Formulation 5, a conductive powdery resin composition (B-4) having a conductive fine powder/resin ratio of 80/20 (weight ratio) was prepared from the liquid composition.

[Formulation 9] Epoxy resin 9% Nickel powder (same as formulation 8) 51% Methyl ethyl ketone 40% Epoxy resins are manufactured by Ciel Chemical Co., Ltd. under the trade name Epicote #1002, #1004, #1007, and #1009 (epoxy equivalent 2400-3300) (melting point: about 148°C, softening point: 90°C) in a ratio of 1:1:2:2 (weight ratio) (melting point: about 135°C, softening point: 75°C) was used.

A conductive powdery resin composition (B-5) having a conductive fine powder/resin ratio of 85/15 (weight ratio) was prepared using the composition having the above formulation in the same manner as in Formulation 5.

[Formulation 10] Epoxy resin 11% Silver powder 48% Methyl ethyl ketone 40% Dicyandiamide 1% The epoxy resin was Epicoat #1007, and the silver powder was conductive silver powder (average particle size approximately 1 μm) manufactured by Fukuda Metal Foil & Powder Industries Co., Ltd. used each.

A liquid composition was prepared using the composition described above in the same manner as in Formulation 5, 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 parts).
conductive powder resin composition with conductive fine powder/resin = 80/20 ⁽ weight ratio) (B-6) was created.

[Formulation 11] Polyester resin (same as formulation 3) 12% Dendrite-shaped copper powder (same as formulation 5) 48% Methyl ethyl ketone 40% The composition consisting of the above formulation was dispersed in a magnetic pot mill for 1.5 hours to form a liquid composition. From the liquid composition, conductive fine powder/
A conductive powdery resin composition (B-7) with resin=80/20 (weight ratio) was prepared.

[Formulation 12] Acrylic resin (same as formulation 4) 9% Nickel powder (same as formulation 8) 51% Methyl ethyl ketone 40% A composition consisting of the above formulation was prepared in the same manner as formulation 5, and conductive fine powder/resin = 85/ A conductive powdery resin composition (B-8) having a weight ratio of 15 (weight ratio) was prepared.

Example 1 After masking the unpainted part in a fixed mold that had been preheated to 80°C, electrostatically applied the radio wave absorbing powdered resin composition (A-1) under a voltage of -80KV to form a coating film. I forced it.

Then, in order to finally measure the surface resistance value of the conductive coating, a portion of the masking corresponding to both ends of the molded article was removed.

After that, the conductive powdered resin composition (B-1) was electrostatically applied under a voltage of -40KV to form a coating film, the remaining masking was removed, and the stationary mold and movable mold were sealed. did.

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/cm ² .

Thus, the film thickness is 40 μm and the surface resistance value is 0.81 ohm/
A heat-resistant polystyrene molded body having a uniform and highly conductive coating □ and a 60 μm radio wave absorbing coating thereon was obtained.

Example 2 The unpainted part of the fixed mold, which had been preheated to 70°C, was masked and a radio wave absorbing powdered resin composition (A-
2) was electrostatically coated under a voltage of -70 KV to form a coating film, and then a part of the masking was removed in the same manner as in Example 1.

Next, the conductive powder resin composition (B-2) was electrostatically applied under a voltage of -40 KV to form a coating film, and then the remaining masking was removed.

After that, the movable mold and movable mold are sealed, and the resin temperature is
PVC resin liquid at 180℃ is injected at a pressure of approximately 750Kg/
When injection molded in cm ² , a vinyl chloride resin molded product was obtained which had a uniform and highly conductive film with a film thickness of 60 μm and a surface resistance value of 0.55 ohm/□, and a radio wave absorbing film with a film thickness of 40 μm on top of it. It was done.

Example 3 The non-painted parts in a mold preheated to 90°C were masked, and then the radio wave-absorbing powdered resin composition (A-1) was coated with an electrostatic coating device under a voltage of -65 KV. After coating the painted portion within the mold to form a coating film, a portion of the masking was removed in the same manner as in Example 1.

Next, the conductive powder resin composition (B-3) was electrostatically applied under a voltage of -40 KV to form a coating film, and then the remaining masking was removed. After that, the hard vinyl chloride sheet was heated to 125 mm using a heating heater.
℃ to soften it, fix it to the mold with a clamp frame, and then use a vacuum pump to suck out the air inside the mold at a vacuum level of 720 mmHg.
When the sheet was closely attached to the mold surface and molded, the film thickness was 60μ
A hard vinyl chloride resin molded body was obtained, which had a uniform and highly conductive coating with a surface resistance value of 0.47 ohm/□ and a radio wave absorbing coating with a thickness of 40 μm thereon.

Example 4 The non-painted parts of the fixed mold, which had been preheated to 70°C, were masked and a conductive powdered resin composition (B-
4) was electrostatically coated under a voltage of -60KV to form a coating film, and then the radio wave absorbing powdered resin composition (A
-2) was electrostatically coated under a voltage of -40KV to form a coating film, and then the masking was removed.

After that, the fixed mold and the movable mold are sealed, and a polyethylene resin liquid with a resin temperature of 220°C is injected at a pressure of approximately 1100°C.
When injection molded at Kg/cm ² , a polyethylene resin molded product was obtained that had a uniform, highly conductive coating with a thickness of 60 μm and a surface resistance value of 1.0 ohm/□ on a radio wave absorbing coating with a thickness of 40 μm. .

Example 5 After masking the unpainted part in the fixed mold at a temperature of 80°C and electrostatically painting the radio wave absorbing powdered resin composition (A-1) under a voltage of -70KV, the same procedure as in Example 1 was carried out. Part of the masking was removed.

Next, the conductive powdered resin composition (B-5) was electrostatically applied under a voltage of -40KV to form a coating film, the remaining masking was removed, and the mold was heated to 95°C using an infrared heater. A coating film was formed. After that, the fixed mold and the movable mold are sealed, and ABS resin liquid with a resin temperature of 230℃ is injected at a pressure of approximately 1000Kg/cm ²
An ABS resin molded article was obtained by injection molding using a uniform and highly conductive film having a thickness of 60 μm and a surface resistance value of 0.60 ohm/□, and a radio wave absorbing film having a thickness of 50 μm thereon.

Example 6 The unpainted part of the inner surface of the mold, which had been preheated to 87°C, was masked, and the radio wave absorbing powdered resin composition (A-4) was applied using an electrostatic powder coating device.
After the painted portion of the inner surface of the mold was painted under a voltage of 60 KV, a portion of the masking was removed in the same manner as in Example 1.

Then, after electrostatically coating the conductive powder resin composition (B-4) under a voltage of -30 KV, the remaining masking was removed, and the inner surface of the mold was heated with an infrared heater to bring the temperature of the mold to 100°C.

Thereafter, the polypropylene extruded into a tube shape at 195℃ was inserted into the mold, and 3.5Kg/cm ² of compressed air was blown into the tube to expand it.
When polypropylene was adhered to the inner surface of the mold and molded, a polypropylene resin molded product was obtained, which had a uniform, highly conductive film with a film thickness of 60 μm and a surface resistance value of 0.10 ohm/□, and a radio wave absorbing film with a film thickness of 50 μm on top of that. Obtained.

Example 7 Masking was applied to the non-painted parts in a mold that had been preheated to 70°C, and a conductive powder resin composition (B
-6) was applied to the painted area in the mold under a voltage of -70KV using an electrostatic powder coating device to form a coating film, and then the radio wave absorbing powdered resin composition (A-
1) was electrostatically coated under a voltage of -40KV to form a coating film, and then the masking was removed.

After that, phenolic resin powder preheated to 116°C was placed in the mold, the mold was closed, heated to 155°C, and the mold was compressed at a pressure of 180 kg/ ^cm2 , resulting in a film with a thickness of 50 μm. The film thickness on the radio wave absorbing film
A phenolic resin molded article having a uniform and highly conductive coating with a surface resistance of 0.15 ohms/□ at 60 μm was obtained.

Example 8 The unpainted parts of the mold, which had been preheated to 750°C, were masked and a radio wave absorbing powdered resin composition (A-
2) was electrostatically coated under a voltage of -70 KV to form a coating film, and then a part of the masking was removed in the same manner as in Example 1.

Next, the conductive powder resin composition (B-7) was electrostatically applied under a voltage of -40 KV to form a coating film, and then the remaining masking was removed. After that, the fixed mold and the movable mold were sealed, and a polycarbonate resin liquid with a resin temperature of 260°C was injection molded at an injection pressure of 1500 kg/cm ² to form a film with a film thickness of 40 μm and a surface resistance value of 1.1 ohm/cm.
□ Uniform and highly conductive film with a film thickness of 50μ on top
A polycarbonate resin molded body having a radio wave absorbing coating of m was obtained.

Example 9 The non-painted part in the mold, which had been preheated to 85°C, was masked, and the radio wave-absorbing powdered resin composition (A
-1) was electrostatically coated under a voltage of -60 KV to form a coating film, and then a part of the masking was removed as in Example 1 above.

Then, after electrostatically coating the conductive powder resin composition (B-8) under a voltage of -40 KV, the remaining masking was removed. After that, the fixed mold and the movable mold were sealed, and PPO (polyphenylene oxide) resin with a resin temperature of 330°C was injection molded at an injection pressure of 1500 kg/ ^cm2 , with an average film thickness of 50 μm and a surface resistance value of 0.95 ohm. /
A PPO resin molded body was obtained which had a highly conductive film □ and a radio wave absorbing film with a thickness of 40 μm thereon.

Example 10 The unpainted part of the inner surface of a mold that was preheated to 80°C was masked, and the radio wave absorbing powdered resin composition (A-3) was applied to the mold using an electrostatic powder coating device. After painting the area, a portion of the masking was removed in the same manner as in Example 1.

Then, after electrostatically coating the conductive powder resin composition (B-7) under a voltage of -40 KV, the remaining masking was removed.

After that, the polyethylene resin extruded into a tube shape at 175℃ was inserted into the above mold, and 3.2Kg/
When compressed air of cm ² was blown into the tube and the tube was inflated and molded, it formed a uniform, highly conductive film with a film thickness of 60 μm and a surface resistance value of 0.67 ohm/□.
A polyethylene resin molded article having a radio wave absorbing coating with a thickness of 40 μm thereon was obtained.

Example 11 The non-painted parts of the mold were preheated to 105°C and masked, and the electromagnetic wave absorbing powdered resin composition (A-4) was electrostatically applied at a voltage of -80 KV to form a coating film. After that, a part of the masking was removed in the same manner as in Example 1 above.

Then, after electrostatically coating the conductive powder resin composition (B-8) under a voltage of -40 KV, the remaining masking was removed.

After that, the fixed mold and the movable mold are sealed, and a polypropylene resin liquid with a resin temperature of 240°C is injected at a pressure of 1500°C.
Injection molded at Kg/ ^cm2 , film thickness 60μm, surface resistance value
A uniform, highly conductive coating of 0.51 ohm/□,
A polypropylene resin molded body having a radio wave absorbing coating having a thickness of 40 μm thereon was obtained.

[Brief explanation of drawings]

FIGS. 1A to 1G are process schematic diagrams showing an injection molding method that is an example of the method of the present invention. FIG. 2 is an enlarged view of the dotted line in step E in FIG. 1, and FIG. 3 is an enlarged sectional view of a plastic molded article obtained by the method of the present invention. DESCRIPTION OF SYMBOLS 1... Plastic molded object, 2... Radio wave absorbing coating, 3... Molding mold, 4... Conductive coating, 5...
...Masking material, 6...Electrostatic coating machine.

Claims (1)

[Scope of Claims] 1 In the plastic molding method, first, a powdery resin composition, either a conductive powdery resin composition or a radio wave absorbing powdery resin composition, is applied into a mold by electrostatic coating. Then, after applying the other powdered resin composition of the powdered resin compositions on top of the powdered resin composition by electrostatic coating, a plastic material is filled and molded, and the powder is melted by the heat of the filling material and/or the heat during molding. 1. A plastic molding method for forming a multilayer coating on the surface of a plastic molded article, which method comprises plasticizing and compressing a resin composition to bring a thermosetting or thermoplastic resin coating into close contact with the surface of the molded plastic. 2 The conductive powder resin composition contains conductive fine powder.
Claim 1, which is a thermoplastic or thermosetting powdery resin composition containing in the range of 70 to 95% by weight.
Plastic molding method described in Section 1. 3. The plastic according to claim 1, wherein the radio wave absorbing powder resin composition is a thermoplastic or thermosetting powder resin composition containing radio wave absorbing fine powder in a range of 50 to 95% by weight. Molding method. 4. The plastic molding method according to claim 1, wherein the plastic molding method is an injection molding method, a blow molding method, a transfer molding method, or a vacuum molding method. 5. The plastic molding method according to claim 1, wherein the mold is a preheated mold. 6. The plastic molding method according to claim 1, wherein the conductive and/or radio wave absorbing powder resin composition is fused or hardened by heating before being filled with the plastic material. 7 The melting point and softening point of each resin component used in the conductive and radio wave absorbing powder resin composition and the mold preheating temperature are in the range of (melting point + 10 ° C) ≧ mold preheating temperature ≧ softening point. A plastic molding method according to claim 5. 8. The plastic molding method according to claim 1 or 2, wherein the conductive powder is a dendrite-shaped fine metal powder. 9. The plastic molding method according to claim 1 or 3, wherein the radio wave absorbing powder is spinel type ferrite powder. 10 The conductive powder resin composition is obtained by dispersing a liquid composition consisting of a water-soluble solvent, the water-insoluble and solvent-soluble resin, and conductive fine powder in water,
The plastic molding method according to claim 1, which is a powdered resin composition obtained by a wet granulation method in which the resin composition is granulated, extracted with a solvent, and then separated and dried. 11 The radio wave absorbing powdered resin composition is prepared by dispersing, granulating, and solvent extracting a liquid composition consisting of a water soluble solvent, the water insoluble and solvent soluble resin, and a radio wave absorbing fine powder in water, and then separating the composition. The plastic molding method according to claim 1, which is a powdered resin composition obtained by a wet granulation method in which the resin composition is granulated and dried.