JP2001064565A - Conductive paint composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a conductive paint composition which is excellent in storage stability and forms a coating film having excellent adhesion to an object to be coated and an overcoat film and excellent conductivity. SOLUTION: A resin containing 2 to 20% by weight of a cellulose ester derivative obtained by ring-opening graft polymerization of a cyclic ester to a cellulose ester having a hydroxyl group is 7%.
5 to 85 parts by weight and conductive carbon black 40 to 6
A conductive paint composition comprising a conductive pigment composed of a mixture of 0% by weight and flake graphite of 60 to 40% by weight in a proportion within a range of 15 to 25 parts by weight.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a conductive coating composition. More specifically, a conductive pigment comprising a mixture of a conductive coating resin and a conductive carbon black and a flaky graphite containing a cellulose ester derivative obtained by ring-opening graft polymerization of a cyclic ester to a cellulose ester having a hydroxyl group; And a conductive coating composition comprising:

[0002]

2. Description of the Related Art Conventionally, conductive paints have been applied in the following manner.
A conductive coating composition is applied to a non-conductive coating object such as inorganic or plastic, and after imparting conductivity to the surface of the non-conductive coating object, a top coating composition is electrostatically applied to the coating. This is commonly done.

The conductive coating composition includes, for example, resins such as aminoalkyd resins and aminoacrylic resins; metal powders such as stainless steel, tin, copper, and aluminum; metal oxides such as zinc oxide; There are known those in which a conductive pigment such as a conductive filler such as titanium-coated mica, silicon, and cobalt sulfide is mixed and dispersed.

[0004] However, the metal powder itself has low electric resistance and therefore can be used in a small amount, but is not practical because of its high price. In addition, since this product has a large specific gravity, it separates from the resin component during the storage of the paint, and settles and agglomerates at the bottom of the container. Dispersion becomes difficult, and as a result, a coating film containing little metal powder pigment is formed, and there is a disadvantage that the conductivity of the coating film is poor.

On the other hand, since the metal oxide itself has a higher electric resistance than the metal powder itself, the amount of the metal oxide used increases in an attempt to obtain a coating film having the same conductivity as that of the metal powder.
As a result, there is a disadvantage that the storage stability of the paint, the physical properties of the coating film, and the like are deteriorated. It is also difficult to obtain a coating film having excellent conductivity by reducing the amount of the conductive filler used.

[0006] It is known that conductive pigments such as conductive carbon and carbon-based conductive pigments such as flaky graphite also enhance the conductivity. This conductive carbon is usually ball mill,
It is mixed and dispersed in the paint using a disperser such as a sand mill. In this dispersion, if the conductive carbon is dispersed to near the primary particles, a coating film with less contact between the conductive carbon particles is formed. Therefore, there is a disadvantage that the conductivity of the coating film is deteriorated, and when the amount of the conductive carbon is increased to increase the conductivity, the physical properties of the coating film are deteriorated. On the other hand, if a large amount of conductive carbon aggregated particles are present without sufficiently dispersing the conductive carbon particles, there is a drawback that the storage stability of the paint is deteriorated and the finished appearance of the coating film is poor.

Further, flaky graphite can form a coating film having excellent conductivity even when used in a small amount as compared with conductive carbon. Is inferior in adhesion to

[0008]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned problems, and forms a conductive film having excellent adhesion and conductivity to an object to be coated and a top coat, and excellent storage stability. It is an object of the present invention to provide a conductive coating composition.

[0009]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, a cellulose ester obtained by subjecting a cyclic ester to ring-opening graft polymerization on a cellulose ester having a hydroxyl group has been studied. A coating composition containing a resin containing a derivative as an essential component, and a conductive pigment formed by using a specific ratio of conductive carbon black and flaky graphite is excellent in storage stability, and furthermore, an object to be coated and a top coat The inventors have found that a coating film having excellent adhesion to the coating film and excellent conductivity is formed, and the present invention has been completed.

That is, the first aspect of the present invention is to provide a cellulose ester derivative (a) obtained by subjecting a cyclic ester to ring-opening graft polymerization to a cellulose ester having a hydroxyl group.
20% by weight and 98-80% by weight of resin for coating (b)
(The total of (a) and (b) is 100% by weight.) 75 to 85% by weight of a conductive coating resin (A), 40 to 60% by weight of a conductive carbon black (c), and scales. Graphite (d) 60 to 40% by weight ((c)
And the sum of (d) is 100% by weight. The present invention provides a conductive paint composition which is blended at a ratio of 25 to 15% by weight (the total of (A) and (B) is 100% by weight). I do. A second aspect of the present invention is the conductive paint according to the first aspect, wherein the cellulose ester having a hydroxyl group is at least one selected from the group consisting of cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, and cellulose nitrate. A composition is provided. Third of the present invention
Provides the conductive coating composition according to the first or second aspect of the present invention, wherein the cellulose ester having a hydroxyl group is a cellulose acetate having an acetyl group substitution degree of 1 to 2.9. A fourth aspect of the present invention provides the conductive coating composition according to any one of the first to third aspects of the present invention, wherein the cyclic ester is ε-caprolactone. A fifth aspect of the present invention is the conductive material according to any one of the first to fourth aspects, wherein the cellulose ester derivative (a) is obtained by graft-polymerizing 1 to 50 mol of ε-caprolactone per glucose unit of a hydroxyl group-containing cellulose ester. A paint composition is provided. Sixth Embodiment
Provides the conductive coating composition according to any one of the first to fifth aspects of the present invention, wherein the weight average molecular weight of the cellulose ester derivative (a) is 50,000 to 1,000,000.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described below. The resin (A) for a conductive paint used in the present invention comprises 2 to 20% by weight, preferably 5 to 15% by weight of a cellulose ester derivative (a) obtained by ring-opening graft polymerization of a cyclic ester to a cellulose ester having a hydroxyl group. weight%,
And 98 to 80% by weight, preferably 9% by weight of the coating resin (b).
5 to 85% by weight (the total of (a) and (b) is 100% by weight
It is. )). When the content of the cellulose ester derivative (a) is less than 2% by weight or less, it is difficult to increase the conductivity of the dried coating film or the undried coating film, and the application efficiency of the top coating material is deteriorated. On the other hand,
If the content is more than 20% by weight, the compatibility with the coating resin (b) is reduced, and the storage stability of the coating composition is unfavorably deteriorated.

The cellulose ester having a hydroxyl group according to the present invention refers to a cellulose ester in which the hydroxyl group of cellulose is esterified with an acid such as fatty acid or nitric acid while leaving a part of the hydroxyl group. Acetate, cellulose acetate propionate,
Cellulose acetate butyrate, cellulose acetate phthalate, cellulose esters such as cellulose nitrate can be exemplified, among these cellulose acetate,
Cellulose acetate propionate and cellulose acetate butyrate are preferred, and cellulose acetate is particularly useful. The average number of ester bonds composed of a fatty acid or the like and the hydroxyl group of the glucose unit of cellulose is 1 to 2.9 per glucose unit, that is, the degree of substitution is 1 to 2.9.
Therefore, the average number of residual hydroxyl groups per glucose unit is preferably 0.1 to 2, particularly preferably 0.2 to 1.3.

The cyclic ester according to the present invention is not particularly limited as long as it can undergo ring-opening polymerization.
For example, β-propiolactone, δ-valerolactone,
ε-caprolactone, α, α-dimethyl-β-propiolactone, β-ethyl-δ-valerolactone, α-methyllactone, β-methyl-ε-caprolactone, γ-methyl-ε-caprolactone, 3,3 5-trimethyl-
Lactones such as ε-caprolactone, 3,5,5-trimethyl-ε-caprolactone, enantholactone, and cyclic esters such as glycolide and lactide. The cyclic ester according to the present invention is not limited to a single type, but may be a combination of a plurality of the above various types. In addition, as the cyclic ester,
In particular, ε-caprolactone, which is easily available industrially, is relatively inexpensive, and has excellent compatibility with the cellulose ester according to the present invention, such as cellulose acetate, is particularly preferred.

There is no particular limitation on the charging ratio of the cellulose ester having a hydroxyl group and the cyclic ester for obtaining the cellulose ester derivative according to the present invention, and it can be appropriately selected according to the use form of the conductive coating composition. However, in order to carry out graft polymerization of a cyclic ester onto a cellulose ester having a hydroxyl group, generally, the former 1 to 85 w
The ratio of the latter is preferably 15 to 99 wt% with respect to t%. When the charging ratio of the cellulose ester having a hydroxyl group exceeds 85 wt%, the viscosity of the reaction system becomes extremely high,
It becomes difficult to handle. Conversely, if it is less than 1 wt%, characteristics of cellulose ester such as heat resistance are lost, which is not preferable. When the viscosity is too high, it is difficult to handle, and as a third component, an organic solvent that does not have active hydrogen having good compatibility with cellulose acetate and cyclic ester is added to lower the viscosity of the system to facilitate the reaction. Is also possible.

The catalyst used in the graft polymerization reaction of a cellulose ester having a hydroxyl group with a cyclic ester, particularly a lactone, according to the present invention includes a catalyst usually used for a ring opening reaction of a cyclic ester, that is, sodium,
Derivatives such as alkali metals such as potassium and alkoxides thereof, alkylaluminum and derivatives thereof represented by triethylaluminum, alkoxytitanium compounds represented by tetrabutyl titanate, tin octylate, organic metals or metal complexes such as dibutyltin laurylate, Metal halides such as organotins are mentioned. The preferred catalyst used for producing the cellulose ester derivative according to the present invention is tin octylate.

In order to obtain the above-mentioned cellulose ester derivative (a) which is the graft polymer according to the present invention, a conventional reactor equipped with a stirrer and a reflux condenser (with a drying tube) is used. Machines are preferably used. The polymerization temperature for obtaining the above-mentioned derivative according to the present invention is usually preferably the temperature applied to ring-opening polymerization of a cyclic ester, and is preferably from 100 to 210 ° C. Further, the polymerization reaction time, the type of cellulose ester having a hydroxyl group and the cyclic ester, the charging ratio, the type and amount of the catalyst,
The reaction temperature varies depending on the reaction apparatus, and is not particularly limited, but is preferably 1 hour to 8 hours.

In obtaining the graft polymer according to the present invention, it is desirable that the raw materials, nitrogen, reactor, and the like used in the polymerization reaction are sufficiently dried. Further, the water content of the reaction system is 0.1 wt% or less, preferably 0.1 wt%.
01 wt% or less, more preferably 0.001 wt% or less.

The cellulose ester derivative (a), which is an average graft polymer obtained by polymerizing the cellulose ester having a hydroxyl group and the cyclic ester at the charged ratio, has an ε-
Caprolactone has a structure formed by addition polymerization of 1 to 50, preferably 3 to 30, more preferably 5 to 20 mol.

The molecular weight of the cellulose ester derivative (a) thus obtained also depends on the molecular weight of the starting cellulose ester having a hydroxyl group and the type of the cyclic ester to be grafted. Weight average molecular weight (GP
C: Measured using a calibration curve of standard polystyrene in chloroform. ) Is preferably in the range of 50,000 to 1,000,000, more preferably 80,000 to 800,000.
If the weight average molecular weight is less than 50,000, the strength of the coating film of the conductive coating composition tends to be insufficient. On the other hand, if it exceeds 1,000,000, the viscosity of the graft polymer is too high, and the smoothness of the coating film becomes low, so that problems in coating tend to occur.

As the coating resin (b) used in combination with the cellulose ester derivative, conventionally known coating resins can be used. For example, chlorinated polypropylene resin, maleated chlorinated polypropylene resin, ethylene-acrylic acid copolymer, EP
Polyolefin-based resins such as DM (terpolymer of ethylene-diene monomer); polybutadiene-based resins; and the above-mentioned polyolefin-based resins or polybutadiene-based resins and radically polymerizable unsaturated monomers such as (meth) acrylates and styrene. Graft copolymer obtained by graft reaction; thermoplastic resin such as epoxy-fatty acid ester resin, alkyd resin, acrylic resin; acrylic resin, polyester resin, alkyd resin, epoxy resin and urethane resin Such as base resin and crosslinking agent (amino resin, blocked polyisocyanate compound)
And a room temperature-curable resin comprising the base resin and a crosslinking agent (polyisocyanate compound).

The conductive pigment (B) used in the present invention is in the range of 40 to 60% by weight, preferably 45 to 55% by weight, of the conductive carbon black (c), in the form of flaky graphite (d).
60 to 40% by weight, preferably 55 to 45% by weight
(The total of (c) and (d) is 100% by weight.) The compounding ratio of the conductive carbon black is less than 40% by weight, and the compounding ratio of the flaky graphite is less than 40% by weight. If the content exceeds 60% by weight, the adhesion to the object to be coated and the top coat is undesirably reduced. On the other hand, if the compounding ratio of the conductive carbon black is more than 60% by weight and the compounding ratio of the flaky graphite is less than 40% by weight, the physical properties of the coating film are undesirably reduced.

The conductive carbon black (c) used in the present invention is a powder containing carbon as a main component,
It can be appropriately selected from those known per se, for example, those obtained by a production method of thermal black, furnace black, lamp black, contact black (channel black, roll black, disk black) and the like.

The conductive carbon black (c) has a DBP (dibutyl phthalate) oil absorption of 70 to 250.
ml / 100 g, preferably 100-200 ml / 10
It is preferable to use one having an electrical resistivity of 1 Ω · cm or less, preferably 0.1 Ω · cm or less, within a range of 0 g. If the DBP oil absorption is smaller than 70 ml / 100 g, a large amount of conductive carbon black is required to increase the conductivity of the coating film, and thus the physical properties of the coating film may be undesirably reduced. On the other hand, the DBP oil absorption is 250 ml / 10
If it is larger than 0 g, the storage stability of the paint tends to decrease, and the finish appearance of the overcoat tends to decrease, which is not preferable. On the other hand, if the electric resistivity is larger than 1 Ω · cm, the amount of the resin used increases, and the storage stability of the paint and the physical properties of the coating film tend to deteriorate, which is not preferable.

Preferred examples of the conductive carbon black (c) include, for example, Vulcan XC as a trade name.
-72 (Cabot Corp.), CONDUCTEX900,
CONDUCTEXT 975 (Columbiam Chemicals
Company) and Denka HS-100 (manufactured by Denki Kagaku Kogyo Co., Ltd.).

The above-mentioned DBP oil absorption and electric resistivity are values measured by the following test methods. DBP oil absorption:
Accurately weigh 1.00 ± 0.01 g of the dried sample, transfer it to a smooth glass plate or stone plate of about 300 × 300 mm or more, and if it is granular, apply moderate pressure with a spatula to break the particles. . About 1/2 of DBP required from burette
Is gently poured onto a glass plate or a stone plate, the DBP is spread evenly in a circle, and then the sample is transferred little by little onto the DBP and dispersed, and carefully kneaded by a spatula to draw a small circle. The sample attached to the spatula is removed by another spatula, and about 1/3 to 1/4 of DBP is added, and the same operation is repeated to make the mixture uniform. One drop is added when approaching the end point, and 1/2 drop is added when approaching the end point. The point where the whole becomes one tight mass is defined as the end point. This operation is completed in 10 to 15 minutes. After 3 minutes have passed after the operation is completed, the amount of DBP dropped in the burette is read, and the oil absorption amount is calculated by the following equation. OA = (V / W) × 100 Here, OA: oil absorption (ml / 100 g), V: amount of oil used up to the end point (ml), W: weight of dried sample (g).

Electric resistivity: About 0.25 g of a dry sample is packed in an insulating cylindrical container, and the amount of the sample is adjusted so that the height of the sample when compressed at a pressure of 50 ± 1 kg / cm ² becomes 10 ± 0.5 mm. Is increased or decreased, and the electrical resistivity (Ω · cm) is calculated from the potential difference between both ends under this pressure, the current, the filling height of the sample, and the cross-sectional area by the following formula. ρ = (S / L) × R where R = V / A ρ: electric resistivity (Ω · cm), S: cross-sectional area of the sample (cm ² ), L: filling height of the sample (cm), R: electric resistance (Ω), V: potential difference (V), A: current (A).

The flaky graphite (d) is in the form of a powder and has a thickness of 0.5 μm or less and an average particle size of 0.5 μm.
Thickness in the range of １５15 μm, preferably 1-7 μm is good. If the thickness is more than 0.5 μm, the amount used is increased, and the storage stability of the paint and the physical properties of the coating film tend to decrease, which is not preferable. When the average particle size is smaller than 0.5 μm, the conductivity of the coating film is not sufficient, and when the average particle size is larger than 15 μm, the workability of spray coating tends to decrease,
In addition, the adhesion to the object to be coated and the overcoat film tends to decrease, which is not preferable.

Preferred examples of the flaky graphite (d) include, for example, graphite powder SP-1 as a trade name.
0, SP-20, HAG-15, HAG-150, HA
G-300 (above, manufactured by Nippon Graphite Co., Ltd.), artificial graphite PO
G-2, POG-10, POG-20 (all manufactured by Sumitomo Chemical Co., Ltd.) and the like.

The above-mentioned resin (A) for conductive paint and conductive pigment (B) are used in an amount of 75 to 85% by weight, preferably 78 to 82% by weight, of resin (A) for conductive paint. B) 25 to 15% by weight, preferably 22 to 18% by weight
(The sum of (A) and (B) is 100% by weight). When the compounding amount of the conductive coating resin (A) is less than 75% by weight and the compounding amount of the conductive pigment (B) is more than 25% by weight, the physical properties of the coating film are reduced,
It is not preferable because the adhesion between the object to be coated and the top coat is reduced. On the other hand, the compounding amount of the resin (A) for the conductive paint is 8
If the amount exceeds 5% by weight and the amount of the conductive pigment (B) is less than 15% by weight, it is not preferable because a coating film having excellent conductivity cannot be formed.

The coating composition of the present invention is preferably used as a solvent type coating material using an organic solvent as a medium or a non-aqueous solvent dispersion coating material. Any organic solvent can be used without particular limitation as long as it can dissolve or disperse the resin. Specific examples thereof include aromatic hydrocarbons such as benzene, toluene, and xylene; and fats such as hexane, heptane, octane, and decane. Group hydrocarbons; chlorinated hydrocarbons such as trichloroethylene, perchlorethylene, dichloroethylene, dichloroethane, dichlorobenzene; ketone solvents such as methyl ethyl ketone and diacetone alcohol; alcohol solvents such as ethanol, propanol and butanol Agents: Cellosolve solvents such as methyl cellosolve, butyl cellosolve, cellosolve acetate and the like can be mentioned.

The coating composition of the present invention may contain other pigments other than the above-mentioned conductive pigment. The other pigments are not particularly limited as long as they are commonly used for paints, and the following are roughly classified into inorganic pigments and organic pigments.

Examples of the inorganic pigments include white: phosphates such as titanium oxide, zinc oxide, basic lead carbonate, basic lead sulfate and zinc phosphate, and molybdates such as calcium molybdate; black: carbon black; Pine smoke, graphite, iron black, etc .;
Yellow: yellow, synthetic iron oxide yellow, transparent iron oxide, titanium yellow, zinc yellow, strontium chromate, etc .; red: iron oxide, transparent iron oxide, lead red, molybdate orange, cuprous oxide, basic chromic acid Lead, lead cyanamide, etc .; green: chromium oxide, chrome green, etc .; blue: navy blue, ultramarine, cobalt blue, etc .; extender pigment: calcium carbonate, barium sulfate, talc, clay, mica, silica, gypsum, etc .; Metal powder: aluminum powder, oxidized lead powder, etc. whose surface is oxidized; and other pearl content.

As the organic pigment, azo lake type:
β-naphthol, β-oxynaphthoic acid, naphthol AS, acetoacetic anilide, etc .; insoluble azo: β
-Naphthol, naphthol AS, acetoacetic anilide, pyrazolone, etc .; condensed azo: naphthol AS
Polycyclic pigments: anthraquinone type, phthalocyanine, quinacridone, isoindolinone, dioxazine, perylene, perinone, thioindigo, pyrocholine, fluorbin, quinophthalone; and other metal complex types.

Further, the coating composition of the present invention may optionally contain a plasticizer, a dispersant, a coating surface adjuster, a flow adjuster, an ultraviolet absorber, an ultraviolet stabilizer, an antioxidant, a crosslinking reaction accelerator, a crosslinking reaction inhibitor. For example, various known additives can be used. The method for producing the coating composition of the present invention using the above-mentioned components may be based on the same apparatus and process as the conventional method for producing a coating composition. For example, using a suitable dispersing machine such as a ball mill, a sand mill, a roll mill, or the like, a pigment is dispersed in a mixture of a binder and a solvent to prepare a pigment paste, and then, necessary components are further added and uniformly mixed with a disper or the like. It can be made into a paint by a method.
The coating composition of the present invention can be applied to a non-conductive material or a material having conductivity or a material whose conductivity is desired to be further enhanced. Specific examples of these materials include a plastic material, a reinforced plastic material, and an inorganic material. Materials and the like can be mentioned.

The coating composition of the present invention can be applied by a conventional coating method. That is, a paint diluted to a viscosity suitable for coating with a solvent can be applied by means of air spray coating, airless spray coating, various electrostatic coatings, dip coating, roll coating, brush coating, or the like. The coating film thickness is usually in the range of about 5 to 40 μm, preferably about 10 to 25 μm based on the dry film thickness. The coating is dried at room temperature or forcibly until the surface resistance of the target coating reaches about 1 × 10 6 Ω / cm.

The coating film formed from the conductive coating composition of the present invention can be used as an electromagnetic shielding coating film or as an undercoat coating film for electrostatic coating of an intermediate coating or top coating.

As the above-mentioned intermediate coating, a known intermediate coating having excellent adhesion, smoothness, sharpness, weather resistance and the like can be used. Specifically, a thermosetting intermediate coating material containing a short oil or a long and short oil alkyd resin having an oil length of 30% or less or an oil-free polyester resin and an amino resin as main components of a vehicle is used. These alkyd resins and polyester resins have a hydroxyl value of 60 to 140 mgK.
OH / g, an acid value of 5 to 200 mgKOH / g, and those using unsaturated oil (or unsaturated fatty acid) as a denatured oil are preferable, and the amino resin is an alkyl (preferably having 1 to 5 carbon atoms). What is suitable is etherified melamine resin, urea resin, benzoguanamine resin and the like. The mixing ratio of these two resins is based on the weight of the solid content, and the alkyd resin and / or the oil-free polyester resin 6
5 to 85% by weight, especially 70 to 80% by weight, amino resin 3
It is preferably from 5 to 15% by weight, particularly preferably from 30 to 20% by weight. Further, at least a part of the amino resin can be replaced with a polyisocyanate compound or a blocked polyisocyanate compound.

As the form of the intermediate coating, conventionally known ones such as an organic solvent type, a non-aqueous dispersion type, a high solid type, an aqueous solution type, an aqueous dispersion type, and a powder type using the above-mentioned vehicle component can be used. Can be used. Further, extender pigments, coloring pigments, other paint additives, and the like can be added to the intermediate coating paint as needed.

These intermediate coatings are coatings to be applied to the surface of the conductive coating film of the present invention, and the coating can be performed in the same manner as the conductive coating. It is preferable to be in the range of 10 to 50 μm based on the coating film of, the curing temperature of the coating film depends on the vehicle component,
60-160 ° C., especially 80-150 when cured by heating
It is preferred to heat at a temperature in the range of ° C.

The above top coating is a coating applied to the surface of the conductive coating film or the surface of the intermediate coating film, and imparts aesthetic properties to the object to be coated. Specifically, finished appearance (sharpness, smoothness, gloss, etc.), weather resistance (gloss retention, color retention, whitening resistance, etc.), chemical resistance, water resistance, moisture resistance, curability, etc. Known coatings that form excellent coatings can be used, and examples thereof include amino-acrylic resins, amino-alkyd resins, amino-polyester resins, and other coatings containing a vehicle as a main component. A coating in which a part or all of the amino resin is replaced with a polyisocyanate compound or a blocked polyisocyanate compound can also be applied.

The form of these top coats is not particularly limited, and any form such as an organic solvent type, a non-aqueous solvent dispersion type, an aqueous (dispersion) liquid type, a powder type, and a high solid type can be used. . Drying or curing of the coating film is performed by drying at room temperature, drying by heating, irradiation with active energy rays, or the like. The topcoat paint used in the present invention is any type of enamel paint in which a metallic pigment and / or a color pigment is blended with the paint containing the above-mentioned vehicle as a main component, and a clear paint containing no or little of these pigments. You may.

As a method of forming a top coat using these paints, the following method is exemplified. (1) A method of applying a metallic paint containing a metallic pigment and, if necessary, a color pigment, or a solid color paint containing a color pigment, followed by heating and curing (metallic or solid color by one coat and one bake method) Finish). (2) A method in which a metallic paint or a solid color paint is applied and cured by heating, and then a clear paint is further applied and then heated and cured again (metallic or solid color finish by a two-coat two-bake method). (3) A method in which a metallic paint or a solid color paint is applied, and then a clear paint is applied, and then the two paint films are simultaneously cured by heating (metallic or solid color finish by a two-coat one-bake method). It is preferable to apply these top coatings by spray coating, electrostatic coating or the like.

The coating film thickness is determined based on the dry coating film.
In the above (1), the range is 25 to 40 μm, in the above (2) and (3), the metallic paint and the solid color paint are in the range of 10 to 30 μm, and the clear paint is 25 to 50 μm.
m is each preferable. Heat curing conditions can be arbitrarily selected depending on the material of the object to be coated, vehicle components, etc.
Generally at 60-160 ° C, especially at 100-150 ° C
Heating for 40 minutes is preferred.

In the present invention, when the conductive carbon black (c) and the flaky graphite (d) are blended at a specific ratio, the conductive carbon black (c) forms a structure having a chain structure or a chain structure, Since the flaky graphite (d) is present in the coating composition in an agglomerated form, there is no risk that these conductive pigments (B) are separated from the conductive coating resin (A) or settle. It has an excellent effect on long-term storage stability. And, since the conductive carbon black and the flaky graphite in the coating film formed from this have the same structure as described above, since these are connected to each other, the conductivity of the coating film is increased. The effect can be reproduced efficiently. The action of the cellulose ester derivative (a) obtained by ring-opening graft polymerization of a cyclic ester with a cellulose ester having a hydroxyl group is not clear, but the scale-like graphite (d) is converted into a scale-like graphite (d) during the coating film drying step. It is presumed that the effect is enhanced by the action of orienting the flat surface so as to face the surface to be coated. As a result, the scales are often in contact with each other, and the conductive carbon black (c) and the scale-like graphite (d) are used.
The effect of increasing the conductivity of the coating film can be exhibited by the connection with.

[0045]

The present invention will be described more specifically with reference to Synthesis Examples, Examples and Comparative Examples, but the present invention is not limited thereto. “Parts” and “%” in Synthesis Examples, Examples and Comparative Examples are based on weight.

Synthesis Examples 1 and 2 (Synthesis of Cellulose Ester Derivative) In a reactor equipped with a stirrer, a thermometer, and a reflux condenser (with a drying tube at the top), absolutely dried cellulose acetate (manufactured by Daicel Chemical Industries, Ltd.) Acetification degree 55%, substitution degree 2.45, described as cotton wool in Table 1), purified ε-caprolactone were added at the weight ratio shown in Table 1, and the water concentration in the reaction system was 0.1 wt.
% Or less, heated to 180 ° C., and stirred to uniformly dissolve the cellulose acetate. After confirming dissolution, 0.24 parts of tin octylate (II value) was added dropwise as a catalyst, and after reacting for 4 hours, the graft was taken out of the reactor.

[0047]

[Table 1]

[Examples 1 to 3 and Comparative Examples 1 to 5] (Production Examples of Coatings A to H) Coatings A to H were prepared according to the formulations shown in Table 2.

[0049]

[Table 2]

Numerical values in the table indicate parts. -Sparklon S-822: trade name, chlorinated polyolefin manufactured by Nippon Paper Industries, 20% solids toluene solution-Oil-free polyester: isophthalic acid / tetrahydrophthalic acid / trimethylolpropane / neopentyl glycol, solid content 70% Xylene solution (OH value 50m
gKOH / g resin, acid value 9 mg KOH / g resin) Uban 222: trade name, urea melamine resin manufactured by Mitsui Chemicals, Inc., solid content 60% n-butanol solution Denka HS-100: trade name, Denki Kagaku Kogyo ( Co., Ltd., conductive carbon black (DBP oil absorption 115ml / 1
00g, electrical resistivity 0.24Ω · cm) Vulcan XC-72: trade name, Cabot. Corp
Conductive carbon black (DBP oil absorption 175ml /
100 g, electric resistivity 0.1 Ω · cm or less) Scale-like graphite (graphite powder) POG-2: trade name
Kyowa Carbon Co., Ltd. artificial graphite (average particle size 2
μm) ・ Scaly graphite (graphite powder) SP-5: trade name, graphite manufactured by Nippon Graphite Industry Co., Ltd. (average particle size: 45 μm)
m) ・ JR-600A: Trade name, titanium white made by Teikoku Chemical Co., Ltd.

(Preparation of test plate) Size 70 × 150 × 3
The material a (polypropylene plate: manufactured by Mitsubishi Yuka Co., Ltd.) and the material b (RIM-polyurethane plate: manufactured by Nippon Test Panel Co., Ltd.) adjusted to mm were exposed to trichlorethane vapor for 1 minute to obtain a degreased plate. The paints A to H were spray-coated so as to have a dry film thickness of 20 μm, dried under the conditions shown in Table 3, and then overcoated (SOFLEX #
1200 white: Electrostatic coating of Aminopolyester resin paint (Kansai Paint Co., Ltd.) (Turbo G minibell)
15000 rpm, shaving pressure 1
kg / cm ² , applied voltage -90 kV, distance between the object to be coated and the tip of the gun 30 cm, discharge rate 200 ml / min, conveyor speed 3 m / min.
The sample was dried at 20 ° C. for 30 minutes and used for the test.

[0052]

[Table 3]

The evaluation test methods and results in Table 3 are shown below. (1) Storage stability of paint: Put paint in a closed container made of polyethylene, leave it at 40 ° C for one month, and then examine the pigment for sedimentation state and abnormalities such as viscosity change. did. ：: No abnormality, Δ: Pigment sedimentation, ×: Pigment sedimentation and viscosity rise are remarkable. (Manufactured by Kasei Co., Ltd.). Film resistance is 1 × 108Ω / cm
The above items were measured using a Hioki 3110 battery-type insulation resistance meter (manufactured by Hioki Electric Co., Ltd.). (3) Coating rate: In the preparation of the test plate, a tin plate having the same size as the raw material a and the raw material b was used. The overcoating and drying were performed in the same manner as in the preparation of the test plate, and the coating rate was determined by the following formula. (Weight of the top coat applied to the material a or the material b / weight of the top coat applied to the tin plate) x 100 (4) Visual appearance: The indoor coating was coated under a condition of daylight fluorescent lamp of 500 lux or more. The glossiness, smoothness, and the presence or absence of abnormalities were determined in the stages of ○ to ×. ：: No abnormality, Δ: Slightly poor, ×: Poor (5) Sharpness: Image Clarity Meter (HA-IC)
H, manufactured by Suga Test Instruments Co., Ltd.). (6) Adhesion: A cross-cut cellophane tape peeling test was performed according to JIS K5400, and evaluated on a scale of Δ ×.は indicates no peeling, and × indicates overall peeling. (7) Bending resistance: A test plate was cut into a size of 20 × 150 mm, and was wound in a -20 ° C. atmosphere around a cylinder (steel) having a coating surface of 25.4 mm in diameter with the coated surface facing outward.
Bending at 0 °, depending on the degree of peeling, cracking, etc.
The evaluation was made at the stage of ×. ○: No abnormality at all, △: Cracked, ×
Is cracked and peeling is recognized. (8) Chipping resistance: Tester: QGR gravelometer (Q panel company product) Stone to be sprayed: crushed stone having a diameter of about 15 to 20 mm Volume of stone to be sprayed: about 500 ml Spraying air pressure: about 4 kg / Temperature at the time of cm ² test: about −20 ° C. A test piece was attached to a test piece holding table, and about 500 ml of crushed stone was fired on the test piece with a blowing air pressure of about 4 kg / cm ^2. Evaluation was based on criteria. ：: A part of the top coating film is slightly damaged by the impact. Δ: The damage caused by the impact and the peeling of the coating film reach the undercoat film. X: The coating film is significantly damaged by the impact. (9) Moisture resistance: A test piece was placed in an atmosphere of 50 ° C. and 98% RH or more for 10 days, and then a cross-cut adhesion test was performed. .

[0054]

The conductive coating composition of the present invention, which contains conductive carbon black and flaky graphite in a specific ratio, has a long-term storage stability without fear that these conductive pigments may separate and settle from the resin component. It exhibits excellent effects, and since these are connected to each other, the effect of increasing the conductivity of the coating film can be efficiently reproduced. In addition, by using a cellulose ester derivative obtained by ring-opening graft polymerization of a cyclic ester to a cellulose ester having a hydroxyl group, a large number of flaky contacts will be performed, and the conductive carbon black and the flaky flakes described above will be formed. The effect of increasing the conductivity of the coating film can be obtained by coupling with graphite, and a coating film having excellent adhesion and conductivity to an object to be coated and a top coat can be formed.

Claims (6)

[Claims] 1. A cellulose ester having a hydroxyl group is subjected to ring-opening graft polymerization of a cyclic ester with a cellulose ester derivative (a) in an amount of 2 to 20% by weight and a coating resin (b) in an amount of 98 to 80% by weight ((a ) And (b) is 100% by weight.) 75 to 85% by weight of a conductive coating resin (A), 40 to 60% by weight of a conductive carbon black (c), and flaky graphite ( d) 60 to 40% by weight (the sum of (c) and (d) is 10
0% by weight. (B) a conductive pigment comprising a mixture of
A conductive coating composition which is blended at a ratio in the range of 25 to 15% by weight (the total of (A) and (B) is 100% by weight). 2. A cellulose ester having a hydroxyl group,
The conductive coating composition according to claim 1, wherein the composition is at least one selected from the group consisting of cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, and cellulose nitrate. 3. A cellulose ester having a hydroxyl group,
3. The conductive coating composition according to claim 1, which is cellulose acetate having an acetyl group substitution degree of 1 to 2.9. 4. The conductive coating composition according to claim 1, wherein the cyclic ester is ε-caprolactone. 5. The conductive coating composition according to claim 1, wherein the cellulose ester derivative (a) is obtained by graft-polymerizing 1 to 50 mol of ε-caprolactone per glucose unit of a hydroxyl group-containing cellulose ester. . 6. The conductive coating composition according to claim 1, wherein the weight average molecular weight of the cellulose ester derivative (a) is 50,000 to 1,000,000.