JP2005298729A - Coating composition for conductive primer and coating method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a coating composition for a conductive primer that has excellent adhesion to a plastic material and can give excellent conductivity in electrostatic coating, and a coating method using the same.
(A) Chlorinated polyolefin resin, or chlorinated polyolefin resin and non-chlorinated polyolefin resin,
It consists of (B) blocked polyisocyanate and (C) conductive carbon, (A) / (B) has a solid content mass ratio of 50/50 to 90/10, and (C) has a resin solid content of 100 mass. The coating composition for conductive primer is 3 to 30 parts by mass with respect to parts.
[Selection figure] None

Description

  The present invention relates to a coating composition for a conductive primer that has excellent adhesion to a plastic material and can provide excellent conductivity in electrostatic coating when the top coating is electrostatically coated on the plastic material. And a coating method using the same.

It is a well-known technique to use a conductive primer coating composition for the purpose of imparting conductivity as an undercoat for electrostatic coating of a top coating on a plastic material. Existence of a functional pigment is also widely known.
A problem in the conductive primer coating composition is the adhesion between the plastic material, in particular, a polyolefin resin material such as polypropylene resin, and the primer coating.

In order to solve this adhesion, 100 parts by mass of chlorinated polyolefin resin (A) and 30 to 150 parts by weight of inorganic filler (B) surface-treated with a cationic polymer and an antistatic agent are included. A semiconductive chlorinated polyolefin resin composition and a molded body comprising the same are known (for example, Patent Document 1). In this patent document, calcium carbonate or the like is used as an inorganic filler, and acetylene black and ketjen black, which are conductive fillers, are used as comparative examples. However, these coating compositions have good adhesion to plastic materials, but do not exhibit good electrical conductivity immediately after coating containing a solvent, and have the drawback that they develop after the solvent evaporates. .

In addition, the primer coating composition composed of chlorinated polyolefin resin and conductive filler not only exhibits good conductivity immediately after coating with a solvent, but also the conductivity of the coating film when using a coating immediately after production. However, when coated with a paint after long-term storage, there was a drawback in storage stability related to conductivity that the conductivity of the coating film was inferior.
In addition, as a primer for a plastic material that forms an excellent coating film such as adhesion and recoat adhesion, “a chlorine content is 16 to 22% by weight, a melting point is 80 ° C. or less, and a weight average molecular weight is 30000 to 120,000. A certain chlorinated polyolefin resin (A), an isocyanurate type aliphatic and / or alicyclic polyisocyanate blocked with a malonic acid dialkyl ester and an acetoacetate block, and a polyisocyanate (B) and a polyol resin (C). Is known (for example, Patent Document 2). However, this primer for plastic material has a drawback that it has poor adhesion to the plastic material due to the reaction between the polyol resin and the block polyisocyanate.

  Furthermore, as a primer for a polyolefin resin that forms a film having excellent adhesion to a polyolefin resin as an object to be coated and an adjacent top coat film, "cyclohexyl acrylate, cyclohexyl methacrylate, isobutyl acrylate, isobutyl methacrylate, n-butyl" An acrylic resin having a number average molecular weight of 1000 to 40000 and a hydroxyl value of 10 to 200 obtained by polymerizing a monomer component containing 30 to 95% by weight of at least one selected from acrylate and n-butyl methacrylate ( A primer for polyolefin resin characterized by containing a curing agent (E) such as a block polyisocyanate compound in A) and chlorinated or non-chlorinated polyolefin resin (B) is known (for example, patent document). 3). However, even in this patent, there was a drawback that the adhesion to the polyolefin resin material was inferior due to the reaction between the acrylic resin having a hydroxyl group and the blocked polyisocyanate.

JP-A-2002-194158 Claim 1 JP-A-2002-121462 Claim 1 JP-A-2003-313332 Claims 1 to 3 and paragraph [0033] of the specification

In addition to good adhesion to plastic materials, there is no paint composition for conductive primer that gives good conductivity immediately after painting and maintains good conductivity even after long-term storage of the paint. It was.

  As a result of intensive research to solve the above-mentioned problems, the present inventors have required chlorinated polyolefin resin, or chlorinated polyolefin resin and non-chlorinated polyolefin resin, blocked polyisocyanate, and conductive carbon. It came to complete the coating composition for conductive primers used as a component. A feature of the present invention is that the isocyanate group of the blocked polyisocyanate does not need to react with a resin containing a hydroxyl group.

That is, the present invention
(A) chlorinated polyolefin resin, or chlorinated polyolefin resin and non-chlorinated polyolefin resin,
It consists of (B) blocked polyisocyanate and (C) conductive carbon, (A) / (B) has a solid content mass ratio of 50/50 to 90/10, and (C) has a resin solid content of 100 mass. The coating composition for conductive primers is provided in an amount of 3 to 30 parts by mass with respect to parts.

In the conductive primer coating composition, the chlorine content of the chlorinated polyolefin resin is 5 to 50% by mass, the melting point is 50 to 90 ° C., and the weight average molecular weight is 1,000 to 100, The conductive primer coating composition is 000.
Further, the present invention provides the conductive primer coating composition according to claim 1, wherein the non-chlorinated polyolefin resin has a weight average molecular weight of 1,000 to 150,000 in the conductive primer coating composition. .

The present invention also provides the coating composition for a conductive primer, wherein the solid content mass ratio between the chlorinated polyolefin resin and the non-chlorinated polyolefin resin is 100/0 to 50/50 in the above-described conductive primer coating composition. To do.
Furthermore, the present invention is to apply the above-described conductive primer coating composition on the surface of a plastic material to form a conductive primer coating, and then apply a top coating to the surface of the conductive primer coating. Provided is a painting method characterized by painting.

Obtaining a coating composition for a conductive primer that has good adhesion to a plastic material, imparts good conductivity immediately after coating, and maintains good conductivity even after long-term storage of the coating I was able to. In particular, good conductivity immediately after painting means that the primer can be electrostatically coated in a wet state, and the interval between the conductive primer coating and the top coating is shortened. Conventionally, a coating line that requires a long distance for drying can be shortened, and productivity can be improved in terms of time and space.

Below, the coating composition for conductive primers and the coating method in this invention are explained in full detail.
Specific applications in the present invention include automobile parts such as passenger cars, trucks, motorcycles, buses, and industrial products such as personal computers and mobile phones, and the materials thereof include various thermosetting moldings. The material and various thermoplastic synthetic resin molding materials can be mentioned.
Examples of the thermosetting molding material include unsaturated polyester resins, epoxy resins, phenol resins, and melamine resins.
Examples of the thermoplastic synthetic resin molding material include polypropylene resin and polypropylene resin-based alloy material. A polypropylene resin-based alloy material is a composite material in which a polypropylene resin and one or more polymers are physically mixed, and is known as a material having a synergistic effect on overall practical performance.

  Although it does not specifically limit as a polypropylene resin-type alloy material, The polymer alloy which consists of 5-95 mass% of polypropylene resins and 95-5 mass% of other resin is mentioned. As a polypropylene resin-based alloy material that easily exhibits the effect of the present invention, polypropylene resin is 50 to 95% by mass, more preferably 60 to 95% by mass, and other resin for alloy 50 to 5% by mass, more preferably A polymer alloy composed of 40 to 5% by mass is exemplified. Other resins for alloy include polyamide resin, polyethylene terephthalate resin, polybutylene terephthalate resin, polyvinyl chloride resin, ethylene-propylene-diene monomer copolymer rubber (EPDM), ethylene-propylene copolymer rubber (EPR) Typical examples include thermoplastic elastomers. The other resin for alloy can be used 1 type or in combination of 2 or more types.

These other resins for alloys can be partially modified for compatibilization and dispersion, or can be used in combination with a compatibilizing agent. Examples of the thermoplastic resin molding material suitably used in the present invention include polypropylene resin, polypropylene resin-based alloy material, polystyrene resin, polyphenylene ether resin, and ABS resin. Such a thermosetting resin molding material or thermoplastic resin molding material is, for example, an ultraviolet absorber, an antioxidant, a release agent, an antistatic agent, a colorant, One or more flame retardants, plasticizers, fiber reinforcing agents such as glass fibers, inorganic fillers and the like can be contained.

  The chlorine content of the chlorinated polyolefin resin used in the present invention is preferably 5 to 50% by mass, more preferably 15 to 35% by mass, and further preferably 18 to 25% by mass. If the chlorine content of the chlorinated polyolefin resin exceeds 50% by mass, the solvent resistance and weather resistance of the coating film may be poor, and if it is less than 5% by mass, the dissolving power in the solvent decreases. However, there is a problem that a stable solution cannot be obtained. Examples of the chlorinated polyolefin resin used in the present invention include those obtained by chlorinating a non-chlorinated polyolefin resin, which will be described later. Suitable examples include, for example, chlorinated polyethylene resin, chlorinated polypropylene resin, chlorinated ethylene- Examples thereof include a propylene copolymer and a chlorinated ethylene-vinyl acetate copolymer.

The chlorinated polyolefin resin used in the present invention may be modified by copolymerizing an acid anhydride such as maleic anhydride. However, since the chlorinated polyolefin resin used in the present invention does not react with isocyanate, it is not necessary to contain a hydroxyl group, and it is preferable that the hydroxyl group content is small. The hydroxyl value of the chlorinated polyolefin resin is preferably 9 mgKOH / g or less, more preferably 5 mgKOH / g or less, still more preferably 2 mgKOH / g or less, and particularly preferably no hydroxyl group.
The weight average molecular weight of the chlorinated polyolefin resin used in the present invention is preferably 1,000 to 100,000, more preferably 5,000 to 90,000, and still more preferably 10,000 to 80,000. is there. If the weight average molecular weight exceeds 100,000, a problem such as poor coating workability occurs. If the weight average molecular weight is less than 1,000, the resin itself has insufficient cohesive force, so that a normal coating film cannot be obtained. Occurs.

The non-chlorinated polyolefin resin used in the present invention is a non-chlorinated polyolefin resin, and specifically, selected from olefins having 2 to 10 carbon atoms such as ethylene, propylene, butylene and hexene. It is a polymer or copolymer obtained by polymerizing one kind or two or more kinds. Non-chlorinated polyolefin resins include (meth) acrylic acid, maleic acid, fumaric acid and other unsaturated carboxylic acids, (meth) acrylic acid alkyl esters, styrene, acrylonitrile and other polymerizable monomers. A polyolefin resin copolymerized according to a known method or modified by graft polymerization is also included, but the content of polymerized units of olefin is preferably 50% by mass or more, particularly preferably 70% by mass or more. However, since the non-chlorinated polyolefin resin used in the present invention does not react with isocyanate, it is not necessary to contain a hydroxyl group, and it is preferable that the hydroxyl group content is small. The hydroxyl value of the chlorinated polyolefin resin is preferably 9 mgKOH / g or less, more preferably 5 mgKOH / g or less, still more preferably 2 mgKOH / g or less, and particularly preferably no hydroxyl group.

The weight average molecular weight of the non-chlorinated polyolefin resin is preferably 1,000 to 150,000, more preferably 5,000 to 130,000, and still more preferably 10,000 to 12,000. If the weight average molecular weight exceeds 150,000, the problem of poor coating workability occurs. If the weight average molecular weight is less than 1,000, the resin itself has insufficient cohesive force, so that a normal coating film cannot be obtained. Occurs.
In the present invention, a chlorinated polyolefin resin can be used alone, or a chlorinated polyolefin resin can be used in combination with a non-chlorinated polyolefin resin. A preferred ratio of the chlorinated polyolefin resin and the non-chlorinated polyolefin resin is a mass ratio of solid content, preferably 100/0 to 50/50, more preferably 100/0 to 60/40, and particularly preferably. Is 100/0 to 70/30. When the proportion of the non-chlorinated polyolefin resin exceeds 50% by mass, the conductivity is lowered.

In the present invention, other resins having a hydroxyl value of 9 mgKOH / g or less, preferably 5 mgKOH / g or less, more preferably 2 mgKOH / g or less, and particularly preferably no hydroxyl group can be contained. As other resin having a hydroxyl value of 9 mgKOH / g or less, an epoxy resin containing two glycidyl groups in one molecule having a hydroxyl value of 9 mgKOH / g or less is preferable. This epoxy resin can further improve the adhesion to the plastic material. This epoxy resin preferably does not contain a hydroxyl group having an epoxy equivalent of 170 to 1000, and more preferably a liquid at normal temperature that does not contain a hydroxyl group having an epoxy equivalent of 170 to 300.
The blocked polyisocyanate in the present invention is obtained by non-releasing an isocyanate group of a polyisocyanate compound having two or more isocyanate groups in one molecule with a blocking agent.

  As long as the polyisocyanate compound is conventionally used for coating applications, various polyisocyanates can be used without any particular limitation. As such polyisocyanate, various polyisocyanates, such as aromatic polyisocyanate and aliphatic or alicyclic polyisocyanate, can be used, for example. Examples of such polyisocyanates include toluene diisocyanate (TDI), 4,4′-diphenylmethane diisocyanate (MDI), xylene diisocyanate (XDI), hexamethylene diisocyanate (HDI), lysine diisocyanate (LDI), and 2-isocyanate. Preferable examples include ethyl-2,6-diisocyanate caproate (LTI), isophorone diisocyanate (IPDI), trimethylhexamethylene diisocyanate (TMDI), hydrogenated xylene diisocyanate (H6XDI) and the like. Such polyisocyanate may be used individually by 1 type, or may be used as a mixture thereof. The polyisocyanate may be used in the form of a burette type, adduct type, isocyanurate type or the like as a prepolymer. From the viewpoint of weather resistance, it is preferable to use an aliphatic polyisocyanate.

Normally, those used as a blocking agent for a polyisocyanate compound are appropriately selected depending on the dissociation temperature, but the polyisocyanate compound used in the present invention is not expected to react with a hydroxyl group. An oxime known as a blocking agent, an active methylene compound, a malonic acid dialkyl ester, an acetoacetate ester, ε-caprolactam, a β diketone, or the like may be used. However, since the conductivity of the coating film applied after long-term storage of the paint is reduced, those containing no amine are preferred.
In the present invention, the solid content mass ratio of (A) chlorinated polyolefin resin, or chlorinated polyolefin resin and non-chlorinated polyolefin resin, and (B) blocked polyisocyanate is 50/50 to 90/10, preferably Is 60/40 to 90/10, more preferably 65/35 to 89/11, and particularly preferably 70/30 to 85/15. When the proportion of the blocked polyisocyanate exceeds 50% by mass, the adhesion to the material is lowered, and when it is less than 10% by mass, the conductivity immediately after coating is not sufficient.

The conductive carbon used in the present invention is a pigment obtained by coating carbon black with a conductive metal oxide such as antimony oxide. As the conductivity of the cured coating film, the surface resistance value is preferably, for example, 1 × 10 ³ to 1 × 10 ⁹ Ω · cm, and particularly preferably 1 × 10 ⁴ to 1 × 10 ⁶ Ω · cm.
3-30 mass parts is preferable with respect to 100 mass parts of resin solid content, as for the compounding quantity of conductive carbon, More preferably, it is 4-25 mass parts, Most preferably, it is 5-20 mass parts. When the blending amount of the conductive carbon is less than 3 parts by mass, the conductivity is not sufficient immediately after coating, and when it exceeds 30 parts by mass, the dispersion is poor.
Here, resin solid content means solid content of resin, such as (A) component, (B) component, and other resin whose hydroxyl value is 9 mgKOH / g or less.

In the present invention, the coating method of the conductive primer coating composition is not particularly limited, and for example, it can be applied by air spray coating, airless spray coating, low-pressure atomizing spray coating (HVLP), or the like. Although there is no restriction | limiting in particular also in the thickness of a coating film, In order to make a coating film exhibit electroconductivity, it is preferable that cured coating film thickness is 5-15 micrometers.
The top coat applied on the conductive primer coating obtained by applying the conductive primer coating composition of the present invention may be a solid color paint or a combination of a metallic base coat paint and a clear paint. There may be.
Polyurethane resin paint is generally used as the resin for solid color paint, but other thermosetting materials such as acrylic-melamine resin paint can be used as long as they can be cured at a temperature that does not deform the material. Mold resin composition may be used.

The pigments for solid color paints include titanium oxide, carbon black, yellow lead, ocher, yellow iron oxide, Hansa Yellow, Pigment Yellow, Chrome Orange, Chrome Vermillion, Permanent Orange, Amber, Permanent Red, Brilliant Carmine, Fast There are violet, methyl violet lake, ultramarine blue, bitumen, cobalt blue, phthalocyanine blue, pigment green, naphthol green and the like, and various additives can be used in the top coat as necessary.
The resin used for the metallic base coat paint and the clear paint is the same as the solid color paint, and a polyurethane resin paint is generally used. However, if the resin can be cured at a temperature that does not deform the material, acrylic-melamine is used. Other thermosetting resin compositions such as resin-based paints may be used.

The pigments used in metallic base coat paints include aluminum flakes, vapor-deposited aluminum, and aluminum oxide, and the light interference pigments include flake-like mica, titanium oxide-coated mica, and iron oxide-coated mica. Various additives can be used as necessary.
By sequentially applying the metallic base coat paint and the clear paint by wet on wet, the design properties, finished appearance, weather resistance, chemical resistance, water resistance, moisture resistance and the like of the coating film can be further improved.

There are no particular restrictions on the method of applying these top coats, and for example, it can be applied by air spray coating, airless spray coating, electrostatic coating, etc., and can be obtained by coating the conductive primer coating composition of the present invention. In the case of coating on the surface of the conductive primer coating film, electrostatic coating is preferably used. The thickness of the top coat is not particularly limited, but the cured coat thickness is 20 to 60 μm in the case of a solid color paint, 10 to 30 μm in the case of a metallic base coat paint, and in the case of a clear coat. It is preferable that it is 15-50 micrometers.
These top coats can also be cured and dried at room temperature. However, in order to sufficiently cure the coating film, it is preferable to heat to a curing temperature of 70 to 150 ° C. If the curing temperature is less than 70 ° C, curing may not proceed sufficiently. When the curing temperature exceeds 150 ° C., the physical properties of the coating film may be deteriorated such as deformation of the material, yellowing of the coating film, and the coating film becoming hard and brittle. The curing time varies depending on the curing temperature, and 30 to 60 minutes is appropriate at a curing temperature of 70 to 150 ° C.

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.
In the examples and comparative examples, the coating film was evaluated by the following method.
≪Test method and evaluation≫

(Conductivity)
A commercially available aluminum tape is wrapped around each end of a plastic material having a length of about 15 cm, and the positions of the terminals are marked in advance so that the distance between the terminals of the measuring device is 10 cm. Next, a masking tape is wound around the aluminum tape leaving about 3 to 5 mm between the material and the conductive primer coating composition is applied by air spray. Immediately after painting, the masking tape is quickly peeled off, and terminals of “3-range insulation resistance meter model 3301” manufactured by Kyoritsu Electric Instruments Co., Ltd. are attached to the aluminum tape portions at both ends, and the conductivity is measured. The unit of the measured value is “× 10 ⁶ Ω” (see FIG. 1).
In addition, the measurement result of the coating film was expressed as “WET” immediately after coating (0 to 30 seconds after coating), and “DRY” after completely drying at 80 ° C. for 30 minutes. In addition, the storage stability of the conductive primer coating composition was compared between immediately after the coating was manufactured and stored at 40 ° C. for 7 days. The evaluation criteria for the WET coating film conductivity were “◯” when the WET coating film conductivity was less than 1,000 × 10 ⁶ Ω.

(Adhesion with the material)
In order to obtain 100 squares with an interval of 2 mm in the top-coated film, 11 cuts in length and width are made with a cutter knife, and the peeled state is evaluated with a cellophane tape. The evaluation results were as follows.
○: No peeling of coating film (100/100 in crosscut notation)
(Triangle | delta): The state which has peeling in a part of coating film (85-99 / 100 in a cross-cut notation)
X: State in which there is peeling in most of the coating film (0-84 / 100 in cross-cut notation)

(Gasoline resistance)
The top-coated paint plate is placed in a container filled with gasoline, the lid is closed and immersed for 10 minutes, then removed and left at room temperature for 5 minutes. The immersion and room temperature drying steps are defined as one cycle, and 10 cycles are performed to evaluate the state of the coating film. The evaluation results were as follows.
○: State in which there is no abnormality in the coating film △: State in which a part of the coating film has swelling or peeling ×: State in which the coating film has swelling or peeling

(Production Example 1)
In a dispersion container, a chlorinated polypropylene resin solution (trade name “Hardlen CY9122”, manufactured by Toyo Kasei Co., Ltd., maleic anhydride-modified chlorinated polypropylene resin, chlorine content 22 mass%, weight average molecular weight 50,000-60,000 , 400 mass parts of heating residue) and 5 mass parts of conductive carbon (trade name "Ketjen Black EC", manufactured by Ketjen Black International Co., Ltd.) Let When the desired particle size is reached, the dispersion is stopped and removed, and the removed dispersion base contains blocked polyisocyanate (trade name “Desmodule BL3157”, manufactured by Sumika Bayer Urethane Co., Ltd., HDI isocyanurate blocked with oxime, 26.7 parts by mass of NCO (11.2% by mass, heating residue 75% by mass) were weighed, added while stirring little by little, and sufficiently stirred to obtain a coating composition for conductive primer of Production Example 1. In Table 1, the composition of the resin raw material represented by resin solid content and the compounding ratio of conductive carbon are shown.

(Production Examples 2 to 18)
Except that part of the blocked polyisocyanate was replaced with epoxy resin (trade name “Epicoat # 828”, Japan Epoxy Resin Co., Ltd., bisphenol A type liquid epoxy resin, epoxy equivalent 190, heating residue 100% by mass) The conductive primer coating composition of Production Example 2 was obtained in the same manner as in Production Example 1. As in Production Example 1, Tables 1 to 3 show the composition of the resin raw materials represented by the resin solid content and the blending ratio of conductive carbon. Similarly, the coating compositions for conductive primers of Production Examples 3 to 18 were obtained at the ratio of the resin raw materials shown in Tables 1 to 3.

(Production Examples 19 to 21)
A part of the chlorinated polypropylene resin solution was mixed with an acrylic resin varnish containing a hydroxyl group (trade name “LB-0115”, manufactured by NOF BASF Coatings Co., Ltd., hydroxyl value 150 mgKOH / g, weight average molecular weight 2,000 to 4). In the same manner as in the above Production Example, except that the heating residue was replaced by 65% by mass), the coating compositions for conductive primers of Production Examples 19 to 21 were obtained at the blending ratios shown in Table 4. . In addition, Table 4 is the composition of the resin raw material represented by resin solid content, and the compounding rate of conductive carbon like Table 1.
The raw materials indicated by abbreviations in Tables 1 to 4 are as follows.

A-1: Hardren CY9122 (trade name, manufactured by Toyo Kasei Co., Ltd., maleic anhydride-modified chlorinated polypropylene resin, chlorine content 22 mass%, weight average molecular weight 50,000-60,000, heating residue 20 mass %)
A-2: Super Clon 842LM (trade name, manufactured by Nippon Paper Chemical Co., Ltd., maleic anhydride-modified chlorinated polypropylene resin, chlorine content 20 mass%, weight average molecular weight 50,000-60,000, heating residue 20 mass%)
A-3: Supercron 892L (trade name, manufactured by Nippon Paper Chemical Co., Ltd., maleic anhydride-modified chlorinated polypropylene resin, chlorine content 22 mass%, weight average molecular weight 60,000 to 70,000, heating residue 20 mass%)
B-1: Unistor P401AM (trade name, manufactured by Mitsui Chemicals, specially modified non-chlorinated polyolefin resin, weight average molecular weight 80,000 to 100,000, heating residue 11% by mass)

C-1: Desmodur BL3175 (trade name, manufactured by Sumika Bayer Urethane Co., Ltd., HDI isocyanurate blocked with oxime, containing NCO 11.2% by mass, heating residue 75% by mass)
C-2: Death module BL4265 (trade name, manufactured by Sumika Bayer Urethane Co., Ltd., IPDI isocyanurate blocked with oxime, containing NCO 8.1 mass%, heating residue 65 mass%)
C-3: Desmodur TPLS2957 (trade name, manufactured by Sumika Bayer Urethane Co., Ltd., HDI isocyanurate blocked with ε-caprolactam, containing NCO 10.2% by mass, heating residue 75% by mass)
C-4: Desmodur BL3475 (trade name, manufactured by Sumika Bayer Urethane Co., Ltd., HDI isocyanurate blocked with β-diketone, containing NCO 8.2 mass%, heating residue 75 mass%)

C-5: Duranate MFK60X (trade name, manufactured by Asahi Kasei Co., Ltd., HDI isocyanurate blocked with active methylene, containing NCO 6.6% by mass, heating residue 60% by mass)
C-6: Duranate MFB60X (trade name, manufactured by Asahi Kasei Corporation; HDI isocyanurate blocked with oxime, containing NCO 8 mass%, heating residue 60 mass%)
D-1: Acrylic resin LB-0115 containing a hydroxyl group (trade name, manufactured by NOF BASF Coatings Co., Ltd., hydroxyl value 150 mgKOH / g, weight average molecular weight 2,000 to 4,000, heating residue 65% by mass )
E-1: Epicoat # 828 (trade name, manufactured by Japan Epoxy Resin Co., Ltd., bisphenol A type liquid epoxy resin, epoxy equivalent 190, hydroxyl value 0 mgKOH / g, heating residue 100% by mass)
P: Ketjen Black EC (trade name, manufactured by Ketjen Black International Co., Ltd., conductive carbon)

Example 1
Two commercially available black polypropylene plates (length 70 mm, width 150 mm, thickness 3 mm) are prepared, and the surface is wiped with isopropyl alcohol to remove dirt and dust adhering to the object to be coated. Next, an aluminum tape and a masking tape are wound by the method described in the conductivity test method. The coating composition for the conductive primer of Production Example 1 whose viscosity was adjusted to 11 seconds under the conditions of Ford Cup # 4 and 20 ° C. with xylene was dried by air spray so that the dry coating thickness was 6 to 8 μm. Paint. One of the test pieces is immediately peeled off from the aluminum tape and the conductivity immediately after coating is measured. The remaining one test piece is dried for 30 minutes at 80 ° C. in a dryer, and then the conductivity is measured. Further, after the coating composition of Production Example 1 is stored at 40 ° C. for 7 days, the same test is performed. These measurement results are shown in Table 1.

(Examples 2 to 14)
In the same manner as in Example 1, the test was conducted by changing only the conductive primer coating composition shown in Tables 1 and 2. These measurement results are shown in Tables 1 and 2.
(Comparative Examples 1-4)
The test was conducted in the same manner as in Example 1, except that only the conductive primer coating composition shown in Table 3 was changed. These measurement results are shown in Table 3.

(Example 15)
A polypropylene plate (trade name “PX01A”, manufactured by Nippon Polychem, length 70 mm, width 150 mm, thickness 3 mm) is wiped with isopropyl alcohol to remove dirt and dust adhering to the object to be coated. Next, the coating composition for conductive primer of Production Example 1 whose viscosity was adjusted to 11 seconds under the conditions of Ford Cup # 4 and 20 ° C. with xylene was dried with an air spray so that the dry coating thickness was 6 to 8 μm. Paint to become. After setting for 2 minutes at room temperature, acrylic resin base coat paint (trade name “Primac No. 5600 Silver”, manufactured by Nippon Oil & Fats BASF Coatings Co., Ltd., metallic paint) has a dry coating thickness of 15 μm. Next, dry the acrylic resin-based clear paint (trade name “Primac No. 5900 Clear”, manufactured by Nippon Oil & Fats BASF Coatings Co., Ltd.) with wet-on-wet. Electrostatic coating was performed so that the coating thickness was 30 μm, and a temperature of 120 ° C. was kept for 20 minutes with a dryer to obtain a coating test plate.
Using this test plate, adhesion to the material and gasoline resistance were tested. The test results are shown in Table 4.

(Examples 16 to 17, Comparative Examples 5 to 7)
A test plate was prepared and tested in the same manner as in Example 15 except that only the conductive primer coating composition shown in Table 4 was replaced. The test results are shown in Table 4.

It is the schematic which showed the measuring method of electroconductivity.

Claims (5)

(A) chlorinated polyolefin resin, or chlorinated polyolefin resin and non-chlorinated polyolefin resin,
It consists of (B) blocked polyisocyanate and (C) conductive carbon, (A) / (B) has a solid content mass ratio of 50/50 to 90/10, and (C) has a resin solid content of 100 mass. 3 to 30 parts by mass with respect to parts, A conductive primer coating composition. The coating composition for a conductive primer according to claim 1, wherein the chlorine content of the chlorinated polyolefin resin is 5 to 50 mass%, the melting point is 50 to 90 ° C, and the weight average molecular weight is 1,000 to 100,000. The conductive primer coating composition according to claim 1, wherein the non-chlorinated polyolefin resin has a weight average molecular weight of 1,000 to 150,000.   The coating composition for a conductive primer according to claim 1, wherein the solid content mass ratio between the chlorinated polyolefin resin and the non-chlorinated polyolefin resin is 100/0 to 50/50. The conductive primer coating composition according to any one of claims 1 to 4 is applied to the surface of a plastic material to form a conductive primer coating, and then the surface of the conductive primer coating is overcoated. A painting method characterized by electrostatically painting a paint.

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