JPH04122474A - Coating of vehicular outer panel part - Google Patents

Abstract

PURPOSE:To form a coating film excellent in pitching resistance in the same process by a method wherein, after assembly of metal and plastic members, the water barrier coat having a specific composition and character is applied, followed by an intermediate coat and then a top coat. CONSTITUTION:The metal members are electrodeposited with a cation type electrodeposition paint and assembled with plastic members to build an integral vehicle outer panel part. Water barrier coat is then applied to the surface of the outer panel part by spraying, brushing or other means, followed by drying. This barrier coat material is a water paint comprising the olefin resin of the acid radical-containing polymer consisting of chlorinated polypropylene and maleic acid and the composition consisting of urethane resin as a vehicle component. An intermediate coat is applied as required. A top coat is also applied. By this coating method, the coating film having the good color compatibility and improved pitching resistance, corrosion resistance and clearness can be obtained in a single process.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method of painting an outer panel of an automobile formed by assembling a metal member and a plastic member.

(Prior art and its problems) In recent years, automobile exterior panels such as automobile bumpers, facias, fenders, door panels, panel hoods, panel roofs, and panel trunk lids have been mostly made of metal materials. Some or all of these parts are being replaced by plastic parts. For example, bumpers and fascia parts made of plastic, such as polyurethane and polyfluoropylene, are now used in most passenger cars, with the exception of large trucks and taxis.

Furthermore, cases in which the lower parts of fenders, door panels, etc. are replaced with plastics such as the above-mentioned plastics, polycarbonate, ABS, and SMC are becoming more noticeable.

In the future, it is inevitable that the range of plastics used in automobile exterior panels will further increase, and this trend is actually being observed in panel roofs, panel trunk lids, etc. This is because the use of plastics not only reduces vehicle weight and fuel consumption, but also improves the corrosion resistance and impact resistance of the vehicle body (and can be molded into any shape). This is because the advantages of processing, such as the ability to make a new car, match the needs for fashion and differentiation of car bodies, which have become important in recent years.

However, despite this current situation, there is no established method for painting the exterior panels of automobiles, which are made up of metal and plastic parts. After applying different types of paints that were suitable for each on separate painting lines, both parts were assembled onto the exterior of the car. According to this method, because the paints (especially colored base coats) used for both parts are different, it is extremely difficult to make the color tone of both parts the same when assembled and integrated, and furthermore, the painting process and subsequent This has the disadvantage that the assembly process of parts is complicated.

Furthermore, in the field of automobile coatings, durability is a problem, particularly the peeling phenomenon of coating films due to the impact of pebbles thrown up by wheels or the like while the automobile is running, that is, depping. The reason for this is that if the impact flaking caused by pebbles or the like affects the steel surface, the problem will be expanded to include rusting and corrosion due to the exposure of the metal surface.

In particular, in cold regions such as Europe and the United States, the progress of rust and corrosion is significantly accelerated by the influence of rock salt that is spread on automobile roads to prevent freezing, so there is a strong desire to improve the chipping resistance of paint films. There is.

In order to prevent this chipping and the progression of corrosion caused by it, various studies have been conducted on chemical conversion treatments on the surface of the external metal base of the car body, electrodeposited brimers, intermediate coats, and top coats. A solution has not yet been found.

On the other hand, regarding the painting of steel plate parts, an elastic film-forming paint containing a modified Boolefin resin as a main component is applied between the electrodeposited film and the intermediate coat and/or top coat. Although there have been attempts to improve chipping properties, there have been problems with the finished appearance of the painted surface, such as a lack of smoothness and sharpness. Furthermore, since the solid content ratio in the paint is about 5 to 10% by weight, a large amount of organic solvent evaporates into the atmosphere during painting, drying, and other processes, which does not satisfy environmental conservation issues. Currently, concrete measures for environmental conservation internationally are moving from consideration to implementation in various fields, and it is imperative that all concerned parties work together to protect the earth from pollution. Must be.

(Means for Solving the Problem) In view of this situation, the inventors of the present invention have developed an automobile exterior panel made by assembling a metal member and a plastic member by painting both parts the same color in a simplified process. We have conducted extensive research with the aim of providing a method for forming a paint film that can be finished with a paint film appearance that is equal to or better than conventional methods, has excellent chipping resistance, and is also environmentally friendly. It is.

As a result, after the metal and plastic parts are assembled and combined, a water-based barrier coat having a specific composition and properties is applied to both parts, and then an intermediate coating is applied as needed. By applying a two-coat paint, the above-mentioned drawbacks can be overcome and the object of the present invention has been achieved.

That is, the present invention is a method for painting an automobile exterior panel consisting of a metal member and a plastic member, which comprises assembling a metal component and a plastic component coated with a cationic electrodeposition paint in advance to form an automobile exterior panel; A water-based barrier coat whose main vehicle component is a composition consisting of an olefin resin and a urethane resin is applied to both parts, and then, if necessary, an intermediate coat is applied, and then a top coat is applied. The present invention relates to a method for painting an automobile exterior panel, characterized by the following.

A feature of the present invention is that when applying an intermediate coat paint and a top coat paint to an automobile exterior panel made by assembling and combining metal members and plastic members, a specific composition and property is preliminarily applied to the intermediate and top coat paints. A barrier coat having the following properties is applied to the outer panel. As a result, it has become possible to paint the metal and plastic parts of automobile exterior panels with a single intermediate coat and top coat, thereby eliminating the inconsistency in color tone between the two parts. Moreover, the chipping resistance of the formed coating film,
Corrosion resistance and physical performance are also significantly improved. In addition, the finished appearance, such as smoothness and sharpness, is improved, and the organic solvent content of the barrier coat is significantly reduced compared to conventional barrier coats, so there are great environmental conservation benefits.

The aqueous barrier coats 1 to 1 of the present invention are more flexible than conventional intermediate coating films, and have unique viscoelasticity based on polyolefin resins and polyurethane resins. If such a coating film is applied in advance to the entire surface of the metal and plastic parts of an automobile's exterior panels, the intermediate coating film and topcoat coating that occur due to physical differences such as thermal elasticity and flexibility between the two parts can be applied in advance. Since most or all of the "strain" between the film and the film is absorbed into the barrier coat film, it is almost possible to prevent the "strain" from spreading to the intermediate coat and top coat. . As a result, it has become possible to apply a single-composition intermediate coating paint and a "coat paint" to the entire surface of both parts of the exterior panel of an automobile, and it has become possible to finish both parts in the same color tone. Furthermore, even if a strong impact force is applied by rock salt, pebbles, etc. to the surface of the coating film consisting of the intermediate coating and top coating formed through the barrier coating film, most or all of the impact energy is absorbed by the barrier coating film. Since the paint film is absorbed into the interior, there is almost no impact peeling of the paint film, and most of the occurrence of physical damage to the top coat film has been eliminated, so there is no chance of peeling off of both the top coat and intermediate coat due to chipping, and occurrences on metal parts. Rust, corrosion, etc. could be prevented.

The coating method of the present invention will be specifically explained below.

Automobile outer panel (object to be coated): The automobile outer panel is an outer panel made by assembling and combining metal members and plastic members. For example, it may be a bumper, a fascia, a fender, a door panel, a panel foot, a panel roof, a panel trunk lid, or a combination of two or more of these. In other words, the individual parts themselves may be made up of a plastic part and a metal part, or the part made of a metal part and a part made of a plastic part may be combined and integrated. Further, the metal part is mainly made of iron, copper, aluminum, zinc, or an alloy containing these, and the plastic part is made of, for example, polyurethane, polypropylene, polycarbonate, or the like.

In the present invention, the term "automobile" in the outer panel of an automobile is not limited to only so-called passenger cars, but also includes motorcycles, trucks, safari cars, and the like.

Of the above-mentioned two members, it is preferable that the metal member is previously subjected to a chemical conversion treatment using zinc nonate, iron phosphate, or chromate according to a conventional method, if necessary, and then coated with a cationic electrodeposition paint.

On the other hand, the plastic part undergoes solvent vapor degreasing, polishing, acid treatment,
It is preferable to perform surface treatment by corona discharge or the like.

Cationic electrodeposition paint - A known electrodeposition paint for coating the above metals can be used. The cationic electrodeposition paint uses a basic water-dispersed resin that can be neutralized with an organic or inorganic acid, such as an epoxy resin, an acrylic resin, or a polybutadiene resin that has a large number of amine groups in the resin skeleton. Water-based paint 4 (resin is not limited to these), the resin includes a neutralizing agent, pigments (coloring pigments, extender pigments, anti-foil pigments, etc.), a hydrophilic solvent, water, and if necessary, a curing agent and a crosslinking agent. It is made into a paint by conventional methods by blending it with additives, etc. Examples of neutralizing agents for neutralizing and water-soluble (dispersing) the above basic water-dispersible resin (usually used by dissolving it in a hydrophilic solvent) include acetic acid, hydroxyl acetic acid, propionic acid, butyric acid, lactic acid, glycine, etc. Organic acids such as sulfuric acid, hydrochloric acid, phosphoric acid, and other inorganic acids can be used. The amount of neutralizing agent is
A neutralization equivalent range of 01 to 04 is suitable for the base number of the above resin (approximately 50 to 200). The solid content concentration is about 5-4
Dilute to 0% by weight with deionized water and adjust pH to 55.
The steel plate is electrodeposited using a conventional method while maintaining the molecular weight within the range of .about.80. The thickness of the electrodeposition coating film is not particularly limited, but it is preferably 10 to 40 LL for a cured coating film, and about 14 LL.
The coating is cured by heating to 0 to 210°C.

Furthermore, a block polyisocyanate compound can be used as the curing agent.

Furthermore, an epoxy resin having an average of two or more epoxy group-containing functional groups per molecule, which is formed by bonding an epoxy group to an alicyclic skeleton and/or a bridged alicyclic skeleton, can also be used as a curing agent. The group-containing functional group consists of an alicyclic skeleton and/or a bridged alicyclic skeleton and an epoxy group, and the alicyclic skeleton is a 4- to 10-membered, preferably 5- to 6-membered saturated carbocyclic ring or The epoxy group contains a condensed ring in which two or more of the epoxy groups / \
C<) One of the carbon atoms in the xy group is directly bonded to the ring carbon atom in the alicyclic skeleton or bridged alicyclic skeleton "For example, the following formula (a), (b)@teru" or, two carbon atoms of the epoxy group and two adjacent carbon atoms constituting the ring in the alicyclic skeleton or bridged alicyclic skeleton [for example, the following formula (C), (D)] is important.

Specific examples of such epoxy group-containing functional groups include those represented by the following formulas (a) to (d). and Rz each represent H, CH3 or C2H5,
And R1, R8 and R9 each represent H or CH3.

The above-mentioned epoxy resin curing agent is described in detail in British Published Patent No. 356,970 by the present applicant, and is also applicable to the present invention.

In the present invention, the electrodeposited metal member and plastic member are assembled to form an integrated automobile exterior panel, and then a barrier coating is applied to the entire surface of both parts.

Barrier coat, barrier coat used in the present invention
- is a water-based paint whose vehicle component is a composition consisting of an olefin resin and a urethane resin.

The olefin resin used in the barrier coat of the present invention is a polymer containing an olefin monomer and/or a diene monomer as an essential monomer component.

Specifically, propylene-ethylene copolymer, chlorinated polypropylene, EPDM (ethylene-propylene-diene copolymer), polybutadiene, styrene-bucdiene copolymer, acrylonitrile pucdiene copolymer, etc. Examples include acid group-containing polymers obtained by polymerizing acid group-containing polymerizable unsaturated monomers such as maleic acid, maleic anhydride, acrylic acid, and meccrylic acid. Among them, the acid group-containing polymer obtained by polymerizing chlorinated polypropylene and (anhydrous) maleic acid has a particularly superior chlorinated polypropylene (preferably chlorination rate of 20 to 30% by weight) component compared to propylene base materials. This material has the advantage that it exhibits excellent adhesion properties to the topcoat film and has excellent water resistance, etc., resulting in less adhesion deterioration due to its (anhydrous) maleic acid component. It is desirable to use it. When using the (anhydrous) maleic acid component, it is usually 05 to 1 based on the acid group-containing polymer.
0% by weight, preferably in the range of about 1-5% by weight.

The olefin resin has a number average molecular weight of about 3000 to
50,000, preferably in the range of about 10,000 to 30,000. If the molecular weight is less than about 3,000, the coating film will tend to stick, attracting foreign matter such as dust and dirt, and the appearance of the final topcoat film will deteriorate, and the plastic substrate after the water resistance test will deteriorate. It is not preferable because it has the disadvantage that the electrodepositability of the electrodeposited material is deteriorated.

On the other hand, if the molecular weight is greater than about 50,000, it is not preferred because a coating film with excellent smoothness cannot be obtained.

The urethane resin, which is a vehicle component used in combination with the olefin resin, is obtained by reacting (1) a component containing an average of two or more active hydrogens per molecule and (2) a polyisocyanate component. It is a urethane bomber obtained by reacting a urethane polymer or a fluoropolymer obtained by reacting components (1) and (2) with a chain extender component. Further, these urethane resins may contain acid groups.

Component (1) can be used without any limitation as long as it contains an average of two or more active hydrogens (preferably hydroxyl groups) in one molecule. Specifically, the following can be mentioned.

i) Diols such as ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, 1.2-butylene glycol, 1.3-butylene glycol, 2.3-butylene glycol, 1.4-
Butylene glycol, 1.5-pentadiol, neopentyl glycol, 1.6-hexane glycol, 2.5
Hexanediol, dipropylene glycol, 2 2
4-trimethyl-1,3-pentadiol, tricyclodecane dimetatool, 1,4-cyclohexane dimetatool, etc.

(11) Polyether diol: For example, one obtained by ring-opening polymerization or ring-opening copolymerization (block or random) of an alkylene oxide adduct, alkylene oxide, cyclic ether (tetrahydrofuran, etc.) of the diol (1), e.g. Polyethylene glycol, polypropylene glycol, polyethylene-propylene (
block or random) glycol, dioxytetramethylene glycol, dioxyheximethylene glycol, dioxytetramethylene glycol, etc.

(iii) Polyester diols: (anhydrous) dicarboxylic acids (e.g. adipic acid, succinic acid, sebacic acid, glutaric acid, maleic acid, fumaric acid, fucuric acid, etc.) and glycols [e.g. ethylene glycol, propylene glycol, 1,4- Butanediol, 16-hexanediol, 1,8-octamethyleneshiol, neopentyl glycol, bishydroxymethylcyclohexane, bishydroxyethylbenzene, alkyl dialkanolamine, m-xylylene glycol, l 4-bis(2-
hydroxyethoxy)benzene, 4,4'-bis(2-
hydroxyethoxy)diphenylpropane, etc.], such as polyethylene adipate, polybutylene adipate, polyhexamethylene adipate, polyethylene/propylene adipate, bishydroxymethylcyclohexane and 04 to C8 linear dicarboxes. Polyester diols consisting of acid mixtures (e.g. K I N G Industries Inc C
o, Noni-FLEX-148, 188), polylactone diols (for example, polycaprolactone diols and mixtures of two or more thereof), and the like.

(1v) Polyether ester diol, ether group-containing diol (such as the above-mentioned polyether diol, diethylene glycol, triethylene glycol, dipropylene glycol) or a mixture of these and other glycols with the dicarboxylic acid or (anhydrous) dicarboxylic acid Those obtained by reacting with compounds (phthalic anhydride, maleic anhydride, etc.) and alkylene oxides, such as poly(polyoxytetramethylene) adipate.

(V) Polycarbonate diol General formula]) %Formula% (1) (In the formula, R is a residue of a C1 to C1□ saturated aliphatic diol, and X represents the number of repeating units in the molecule, usually 5 to 50. (which is an integer) etc. The compound is a saturated aliphatic diol (1,4-butanediol, 1,5-bentanediol, 1,6-hexanediol, polyethylene glycol such as diethylene glycol, polypropylene glycol) in such a proportion that both ends have OH groups. , oxyethylene oxypropylene copolymerized diol, etc.) and substituted carbonates (diethyl carbonate, diphenyl carbonate-1, etc.)
It can be obtained by a transesterification method in which the saturated aliphatic diol is reacted with phosgene, a method in which the saturated aliphatic diol is reacted with phosgene, or a method in which the saturated aliphatic diol is further reacted if necessary.

The diols described in (i) to (V) above can be used alone or in combination of two or more.

Also, among the diols described in (i) to (V) above, those described in (i) to (iii) are preferred, and more preferably the number average molecular weight is about 5000 or less, preferably about 100.
Examples include those in the range of 0 to 3000.

In addition to the diols mentioned above, (vi) a low molecular weight polyol containing three or more hydroxyl groups in one molecule (preferably a number average molecular weight of 500 or less) can be blended.

When the low molecular weight polyol (vl) is used, for example, the molecular skeleton of the urethane resin has branching properties to form a three-dimensional structure in the urethane resin, thereby improving the water dispersion stability of the polyurethane particles, and improving the formation of polyurethane particles. It has the advantage of improving the water resistance and chemical resistance of the coating film.

As the (vl) low molecular weight polyol, for example, 1-
Limethylolpropane, trimethylolethane, glycerin, tris-2-hydroxyedyl isocyanurate, penquerythritol, and the like can be used. The (vl) low molecular weight polyol can be blended in an amount of about 0.1 mol or less per 1 mol of the diol component. If the amount is more than about 0] mol, it is not preferable because the storage stability of the aqueous compound may deteriorate or the physical properties of the coating film may deteriorate.

As the polyisocyanate component (2) to be reacted with the component (1), a compound containing an average of two or more isocyanate groups in one molecule can be used. Specifically, as aliphatic diisocyanate compounds, aliphatic diisocyanates having 1 to 12 carbon atoms, such as hexamethylene diisocyanate, 2.2.4-trimethylhexane diisocyanate, lysine diisocyanate, etc., and as alicyclic diisocyanate compounds, carbon Alicyclic diisocyanates of numbers 4 to 18, such as 1,4-cyclohexane diisocyanate, ]-]isocyanato 3 isocyanatomethyl 3.
5.5-1-limethylcyclohexane (isophorone diisocyanate), 4,4'-dicyclohexylmethane diisocyanate, methylcyclohexylene diisocyanate, isopropylidene dicyclohexyl 4,4'-diisocyanate, etc.; As aromatic isocyanate, tolylene diisocyanate , 4,4'-diphenylmethane diisocyanate, xylylene diisocyanate, metaxylylene diisocyanate, etc., as well as modified products of these diisocyanates (carposiimide, uretdione, uretimine-containing modified products, etc.), and mixtures of two or more of these. can be mentioned.

Any conventional method can be used to introduce acid groups into the urethane resin, but for example, dimethylolalkanoic acid may be replaced with part or all of the glycol components described in (1) to (IV) above. By introducing a carboxy group into polyether thiol, polyester diol, polyether ester diol, etc. in advance, or by using a mixture of the diol component (i) or (V) and dimethylolalkanoic acid. A method of introducing an acid group is preferred. Examples of such dimethylolalkanoic acids include dimethylol acetic acid, dimethylol propionic acid, dimethylol acetic acid, and dimethylol valeric acid.

Urethane resins with acid groups introduced can be dispersed in water without the use of surfactants or with a reduced amount of surfactants, which has the advantage of improving the water resistance of the coating film. be. The content of acid groups is about 25 to 50, preferably about 30 to 100, as the acid value of the urethane resin.
More preferably, the range is about 50 to 80. If the acid value is less than about 25, the water dispersibility will be poor. On the other hand, if the acid value is more than about 150, the water resistance of the coating film may be poor, which is not preferable.

Urethane resin usually has a number average molecular weight of 10,000 to
100,000, preferably about 20,000 to 50,000,
More preferably, one having a molecular weight of 25,000 to 35,000 can be used. By the reaction of the components (1) and (2), the urethane prepolymer (usually number average molecular weight 10
00 to 3000), the molecular weight may be adjusted to the above range by chain elongation. If the number average molecular weight of the urethane resin is less than about 10,000, water resistance, flexibility, etc. may deteriorate, while if it is greater than 100,000, this may cause sedimentation, aggregation, etc. during paint storage.
It may cause defects such as spots on the paint film, or
This is not preferred because the smoothness of the coating film may deteriorate.

The chain extension method of the urethane prepolymer may be carried out according to a known method. For example, water, water-soluble polyamines, glycols, etc. may be used as the chain extender component, and the urethane prepolymer and chain extender component may be reacted. If necessary, a reaction catalyst may also be used. As the water-soluble polyamine, a primary amino group and/or a secondary amino group]
A polyamine compound having two or more polyamines can be used, for example, water-soluble polyamines such as ethylenecyamine, heramethylenediamine, xylylenediamine, xylylenediamine, diethylenetriamine, triethylenetetramine, etc. Water-soluble alicyclic polyamines such as piperazine and mixtures thereof can be suitably used.

As glycols, for example, ethylene glycol, propylene glycol, ethylene glycol, triethylene glycol, butanediol, hexanediol, trimethylolpropane, etc. can be suitably used.

As reaction catalysts, trialkylamines such as trimethylamine, triethylamine, triisopropylamine, tri-n-propylamine, tri-n-butylamine: N-alkylmorpholine, such as N-methylmorpholine, N-ethylmorboline, N-dialkylalkanolamine , e.g. N-dimethylethanolamine, N-
Diethylethanolamine: N-alkylvinylpyrrolidone and mixtures of two or more thereof.

The method for making the olefin resin and urethane resin water-based may be any conventionally known method, but for example: After that, a surfactant and/or neutralizing agent is added and dispersed in water.

■ After mixing the urethane resin raw materials (1) and (2) with the olefin resin, the (1) and (2)
) A method of reacting the components (so that they are substantially free of isocyanate groups), then adding a surfactant and/or a neutralizing agent, and dispersing them in water.

■ A surfactant and/or neutralizing agent is added to an olefin resin and dispersed in water, and a surfactant and/or neutralizing agent is added to a urethane resin (substantially not containing incyanate groups). A method in which the agent is added and dispersed in water.

■ NCO group-containing urethane prepolymer (Toruga, NGO
10H equivalent ratio in the range of 11 to 19) is mixed with an olefin resin, dispersed in water, and simultaneously subjected to a chain extension reaction. In this method, a chain extender other than water may be added at the same time, and if necessary, a chain extender catalyst,
Surfactants, neutralizing agents, etc. may also be added.

■ After mixing the urethane resin raw materials (1) and (2) with the olefin resin, the (1) and (2)
) components to obtain a mixture of NCO group-containing urethane prepolymer (NC○10H equivalent ratio of about 1.1 to 19) and olefin resin, and then water dispersion and chain elongation in the same manner as in (1) above. A method in which the reactions are carried out at the same time, (1) a method in which the NCO group-containing urethane prepolymer is subjected to a chain extension reaction in the same manner as in (2) above, and simultaneously dispersed in water, and (2) a method in which the olefin resin described in (1) is dispersed in water. A mixing method etc. can be suitably applied.

The neutralizing agent is used when acid groups are present in the urethane resin, olefin resin, urethane prepolymer, etc., and the same neutralizing agent as the above-mentioned chain extension reaction catalyst can be used. Among these, preferred are trialkylamines,
N-alkylvinylpyrrolidone is particularly preferred, and triethylamine is particularly preferred. The amount of neutralization is about 0.5 to 20 equivalents, preferably 1 to 20 equivalents per equivalent of carboxyl group.
The amount may be about 1.5 equivalents.

Examples of surfactants include higher alcohols, alkylphenols, arylphenols, nonionic surfactants such as ethylene oxide adducts such as polyoxypropylene glycol, and sulfate ester salts of ethylene oxide adducts such as alkylphenols and higher alcohols. , anionic surfactants such as alkylbenzene sulfonates, and mixtures thereof are preferred. Further, from the viewpoint of coating film water resistance, the blending ratio of the surfactant is preferably about 10 parts by weight or less, preferably about 5 parts by weight or less, based on 100 parts by weight of the resin solid content.

Among the above, using those obtained by chain extension reaction can help water dispersion of polyolefin resin, stabilize the resin particles, and have water resistance and
It has the advantage of producing a coating film with excellent performance such as appearance. The polyurethane polymer obtained by carrying out the chain extension reaction is preferably one containing acid groups.

The blending ratio of the olefin resin and the urethane resin, which are the vehicle components of the coating composition of the present invention, is about 5 to 40% by weight, preferably about 10 to 30% by weight, and about 95 to 60% by weight of the latter, both calculated in terms of resin solid content. % by weight, preferably about 90-70
A weight percent range is desirable. Polyolefin resin is about 5
If the olefin resin is less than about 40% by weight or the urethane resin is more than about 95% by weight, the adhesion to the plastic substrate will decrease, while if the olefin resin is more than about 40% by weight or the urethane resin is about 60% by weight. If the amount is less, the adhesion to the top coat, water resistance, storage stability of the paint, etc. will deteriorate, which is not preferable.

In the composition obtained by making it water-based by the above-mentioned methods ① to ②, the urethane resin component is used as a component to assist in the water dispersion of the olefin resin and to stabilize the olefin resin particles. Further, an aqueous dispersion of a urethane resin can be mixed with the aqueous olefin resin as a component having a function of improving coating performance.

As the aqueous dispersion of urethane resin used to improve coating film performance, the same aqueous dispersion of urethane resin as described in the above-mentioned aqueous conversion method can be used.

The urethane resin C (hereinafter referred to as urethane resin A) contained in the aqueous mixture of the urethane resin and olefin resin obtained in the above steps 1 to 3, and the urethane resin added to this aqueous mixture to improve coating film performance. A preferred combination of the urethane resin (hereinafter referred to as urethane resin B) in the water dispersion of is a monomer having good compatibility with the olefin resin, such as an aliphatic or alicyclic polyol as the component (1). , a urethane resin obtained by using an aliphatic or alicyclic diisocyanate compound as the component (2) is used as the urethane resin A, and a urethane that uses a large amount of monomers with excellent physical properties, such as aromatic diisocyanates as the component (2). system resin with a number average molecular weight of 20,000 or more, preferably 30,000 to 100
A combination of using a urethane resin of No. 000 as the urethane resin B is mentioned. In addition, the blending ratio of these is such that the ratio of olefin resin/urethane resin A/urethane resin B is approximately 5% based on the solid content of these resins.
~40wt%/15-60wt% 10-80wt%, preferably about 10-30wt%/20-50wt%/20
The content may be 70% by weight.

In addition, the aqueous compound used in the barrier coating of the present invention has a coating composition of about 0.00000
It is desirable to have an average particle size of 1 to 5 pm, preferably about 0.05 to 2.0 .mu.m.

In addition, in order to improve the electrostatic coating on Plus Deck members, a conductive substance is added to the barrier coat to lower the volume resistivity of the coating film to 107 ΩCm or less, especially 103 to 105
It is preferable to adjust it to Ωcm. Examples of the conductive substance include powders of conductive carbon, graphite, silver, copper, nickel, aluminum, zinc oxide, tin dioxide, and tungsten oxide, composite metal powders made of tin oxide and antimony oxide, and furthermore, It is possible to use materials such as mica, titanium oxide, potassium titanate, etc., which are coated with a conductive material on the surface of a material having a characteristic shape.

The amount of these compounds is preferably within a range that does not impair the physical performance of the barrier coat film and the finished appearance of the coated surface, and specifically, the resin solid content of the barrier coat is 10
It is preferably 100 parts by weight or less per 0 parts by weight.

In the barrier coat of the present invention, coloring pigments, extender pigments, coated surface conditioners, anti-wrinkle agents, fluidity conditioners, anti-cissing agents, plasticizers and the like can be added as necessary.

The barrier coat of the present invention is usually adjusted to have a solid content of about 20 to 50% by weight and a viscosity of about 500 to 3000 centipoise (B type viscometer, rotation speed 6 RPM).

In the present invention, these barrier coats are applied to the surfaces of metal parts and plastic parts coated with cadion type electrodeposition, but the coating method is not limited, and examples include spray painting, brush painting, dipping painting, melt painting, There are electrostatic coatings, etc., and the coating film thickness is 5 to 20μ, depending on the coating film formed.
Particularly preferred is 10 to 15μ. And this coating film is at room temperature ~
Drying can be performed at 16o'C, preferably in the range of about 80-120C.

Intermediate paint, a paint to be applied to the above-mentioned barrier coated surface, which can be a known intermediate paint with excellent adhesion, smoothness, sharpness, overbake resistance, weather resistance, etc. Specifically, an organic solution-type thermosetting intermediate coating material whose vehicle main components are a short oil having an oil length of 30% or less, an ultra-short oil alkyd resin, or an oil-free polyester resin and an amine resin can be mentioned. These alkyd resins and polyester resins have a hydroxyl value of 60 to 140 and an acid value of 5.
~20, and preferably uses an unsaturated oil (or unsaturated fatty acid) as the modified oil, and suitable amine resins include alkyl (1 to 5 carbon atoms) etherified melamine resins, urea resins, benzoguanamine resins, etc. . The blending ratio of these is 65 to 85% of alkyd resin and/or oil-free polyester resin based on solid content weight.
, especially 70-80%, amine resin 35-15%, especially 3
It is preferably 0 to 20%. Furthermore, the above amino resin can be replaced with a polyisocyanate compound, a blocked polyisocyanate compound, or a polyisocyanate compound. In addition, the form of the intermediate coating is most preferably an organic chemical liquid type, but it may also be a non-water liquid type, a high solid type, a water-containing liquid type, an aqueous dispersion type, etc. using the above-mentioned vehicle components. do not have. In the present invention, the hardness (pencil hardness) of the intermediate coating film is 3B to 2H (
The temperature is preferably in the range of 20°C (based on the grinding method). Furthermore, extender pigments, coloring pigments, other paint additives, and the like can be added to the intermediate paint as necessary.

In the present invention, the intermediate coating paint can be applied to the barrier coat surface in the same manner as for the barrier coat, and the thickness of the coating film is preferably in the range of 10 to 50 jL based on the cured film. The curing temperature can be arbitrarily selected depending on the vehicle components and the material of the Plus Deck (subject to be coated), and for example, room temperature to 180°C is suitable.

In the present invention, it is also possible to omit the application of the intermediate paint.

Top coat 2 A paint applied to the above-mentioned barrier coated surface (intermediate coating omitted) or intermediate coated surface, which imparts cosmetic properties to the object to be coated. Specifically, the finished appearance (sharpness, smoothness, gloss, etc.), weather resistance (gloss retention, color retention, chalking resistance, etc.), chemical resistance, water resistance, moisture resistance, hardenability, etc. Paints which are known per se and which form a coating film with excellent properties can be used, such as paints whose main vehicle component is an amine-acrylic resin, an amino-alkyd resin, an amino-polyester resin, or the like. The form of these paints is not particularly limited, and organic solution type, non-aqueous dispersion type, water-soluble (dispersion) wave type, powder type, high solid type, etc. can be used.

The coating film is formed by drying with heat, heat drying, irradiation with active energy rays, etc. In the present invention, the coating film formed by these top coats has a pencil hardness of 2B to 3H (2B to 3H).
0°C, according to the Zurikis method). Furthermore, the above amino resin can be replaced with a polyisocyanate compound or a blocked polyisocyanate compound.

The top coating used in the present invention is classified into enamel paint, which is a paint using the above-mentioned vehicle main component mixed with metallic pigments and/or colored pigments, and clear paint, which contains no or almost no of these pigments. As a method of forming a top coat film using these paints, for example, ■ Applying metallic pigments, metallic paints mixed with colored pigments as necessary, or solid color paints mixed with colored ready-to-dry paints. , heat cured (metallic or solid color finish using 1 coat 1 beta method).

■Paint with metallic paint or solid color paint,
After heating and curing, clear coating 1 is further applied and heating and curing is performed again (metallic or solid color finish using 2-coat, 2-bake method).

(2) After applying metallic paint or solid color paint, and subsequently applying clear paint, both coats are cured simultaneously by heating (2': Metallic or solid color finish by J-to-1 bake method).

These top coat paints are preferably applied by spray painting, electrostatic painting, etc. In addition, the coating film thickness is based on the dry coating film, 25 to 4011 for the above (■), and 10 to 4,011 for the above (■) and (2) for metallic paints and solid color paints.
3011 and clear paint preferably have a volume of 25 to 50 rl. The heating conditions can be arbitrarily selected depending on the vehicle components and the material of the plastic (subject to be coated). For example, from room temperature to
A range of 180°C is suitable.

In the present invention, the reason why the inconsistency in color tone between the two parts was resolved in the case of coating film formation on the metal and plastic parts of an automobile's outer panel is that a specific composition was applied in advance before the intermediate coating was applied. A barrier coat with the following properties is applied to both parts. As a result, the "strain" between the intermediate coating film and the intermediate coating film, which occurs due to the difference in physical performance such as thermal elasticity and flexibility, between the two components is absorbed by the barrier coating film, This is because it is possible to prevent contaminants from spreading to the intermediate coating film and the top coating film, and it is now possible to apply intermediate coating paint and top coating paint of the same composition to both components.

Furthermore, since the barrier coating film has the effect of absorbing impact energy applied from the outside, it is possible to provide a coating film that is excellent in chipping resistance and rich in corrosion resistance. The ability to absorb this impact energy and the above-mentioned "strain" is thought to depend on the viscoelasticity of the olefin resin or polyurethane resin component that forms the barrier coating film.

In addition, the reason why the topcoat finish, especially the image clarity, is improved compared to when a conventional barrier coat is applied is that the solvent resistance of the barrier coat film is improved by the combination of the polyurethane component and the olefin component alone. This is nothing but an improved result. That is, the barrier coat film is not eroded by the thinner component contained in the intermediate coat or top coat, and provides a coated surface with excellent smoothness. Furthermore, since the barrier coat is a paint with a low content of Ariiso-nin, it has the advantage of significantly improving the conventional level from the viewpoint of environmental conservation.

Mitsubishi V and Kari As described above, the metal parts and plastic parts coated with cationic electrodeposition paint were assembled and combined, and a barrier coat, intermediate coat paint, and top coat paint were applied to the outer panel of the automobile. The coating film had good color in several areas between the metal and plastic parts, and was also significantly improved in chipping resistance, corrosion resistance, physical performance, and image clarity.

Next, examples and comparative examples related to the present invention will be described.

■ Sample (1) Metal component: Galvanized steel sheet chemically treated with Bonderite #3030 (manufactured by Nippon Barker Rising ■, zinc phosphate system) (size 300 x 90 x 0.8 mm) (2) Plastic component: Polyamide vapor degreased with nitric chlorethane. Resin board (size 300x90x0.8m
m) (3) Cationic electrodeposition paint Nireclone #9200 (
(manufactured by Kansai Paint ■, epoxy polyamide cationic electrodeposition paint, gray color) (4) Water-based barrier coat First, the emulsion (
a-1) to (a-3), (b-1) and (b-
2), and production examples of resin solutions (A-1), (A-2) and (13-1) will be explained, and then production of barrier coats (E-1) to (E-5) will be explained. .

In addition, both parts and percentages are based on weight in principle.

Example number average molecule of urethane prepolymer A-1: 12
225 parts of polybutylene adipate with a number average molecular weight of 2000, 375 parts of polycaprolactone diol with a number average molecular weight of 2000, 1
．． Raw material consisting of 266 parts of 4-cyclohexane dimetatool, 604 parts of dimethylolpropionic acid, and 313 parts of inphorone diisocyanate (NGO10H=157)
was charged into a polymerization container and heated in a nitrogen gas atmosphere with stirring for 50 min.
After raising the temperature to ℃, 0.05 part of dibutyltin oxide was added as a polymerization catalyst, and the reaction was then carried out at 70℃ for 1 hour to form a urethane prepolymer with terminal NGO groups and an NCO group content of 3% ( A-1) was obtained. Number average molecular weight is 2150
There was.

Production side of urethane tree emulsion (a-1) 350 parts of the urethane prepolymer (A-1), 11 parts of acetone
After charging 5 parts of N-methylvinylpyrrolidone and 35 parts of N-methylvinylpyrrolidone into a reaction vessel and uniformly dissolving them at 50°C, 14.5 parts of triethylamine was added while stirring, and 550 parts of deionized water was added while maintaining the temperature at 50°C. The mixture was added and stirred for 2 hours to complete the water extension reaction.

Further, vacuum distillation is performed at 80°C or less, and the distillate is 115%
The acetone was distilled off to give 950 parts of urethane resin emulsion (a-1) with a solid content of 37%. The number average molecular weight is 32,000, and the average particle size is olpm.
Met.

Production example of urethane tree (A-2) 256 parts of the above polybutylene adipate, 427 parts of the above botcaprolactone diol, 30 parts of 1,4-cyclohexane dimetatool, 68 parts of dimethylolpropionic acid,
and 219 parts of isophorone diisocyanate (NGO10H=0.975) were charged into a polymerization container,
Heating was carried out while stirring and filling with nitrogen gas, and when the temperature reached 50°C, 0.005 parts of dibutyltin oxide was added.
The reaction was carried out at 0°C for 4 hours. After that, the temperature was lowered to 60°C and 50 parts of methanol was added to inactivate unreacted NGO groups. Then, 345 parts of acetone and 105 parts of N-methyl-vinylpyrrolidone were added and stirring was continued until uniformly dissolved i-1
A urethane resin (A-2) having a solid content of 67% was obtained. The number average molecular weight was 25,000.

Production side of urethane tree emulsion (a-2) 528.5 parts of the urethane resin (A, -2) was charged into a reaction container,
While stirring at 50°C, 14.5 parts of triethylamine was added, and while maintaining the temperature at 50°C, 620 parts of deionized water was gradually added, and stirring was continued for an additional hour. then 70
Acetone and methanol were distilled off by vacuum distillation at "C", and when the distillate reached 139 parts, the vacuum distillation was stopped, and the solid content was 35% and the organic solvent content was 14.6 parts.
A PHR urethane resin emulsion (a2) was obtained. The average particle size was 0.05 part m.

Urethane tree emulsion (a-3 manufacturing side molecular weight 20
00 polytetraoxymethylene glycol 476 parts, molecular weight 435) K -F T-, E Xl 88 (
K.I.N.G. Industries Inc.
Co., Ltd., cyclohexane dimetatool-terminated linear polyester) 130 parts,], ]4-cyclohexane diisocyanate 26 parts dimethylolpropionic acid 63 parts
parts, 35 parts of glycerin, tolylene diisocyanate (T
DI) 184 parts, and isophorone diisocyanate (I
PDI) 11.7 parts of raw material (OH/NGO=1.
33) into a polymerization container, prepolymer (A, -1,
), terminal NC○ with an NCO group-containing group content of 3%
A urethane prepolymer with groups was obtained. Next, a urethane resin emulsion (a-1) with a solid content of 38% was prepared in exactly the same manner as emulsion (a-1) except that this prepolymer was used.
-3) was obtained. The molecular weight was 43,000, and the average particle size was 0.07 part m.

Olefin tree, emulsion (manufacturing example of b-1 Maleated chlorinated polypropylene with average molecular weight 10,000 (chlorination rate 25%, maleic anhydride content 20%)
A reaction vessel was charged with 500 parts of n-hebutane, 150 parts of n-hebutane, and 50 parts of N-methylvinylpyrrolidone, and the mixture was stirred at 70° C. under a nitrogen gas atmosphere to uniformly dissolve the olefin resin solution (B-1). Thereafter, after cooling the inside of the system to 50°C, 10.6 parts of triethylamine and Neugen EA-
After adding 5 parts of 140 (polyethylene glycol noniphenyl ether, nonionic surfactant, HLB 14th - Kogyo Yakuhin) and stirring for 1 hour, add 2000 g of deionized water.
1 part was gradually added, and stirring was continued for an additional hour. Next 7
The solvent was removed under reduced pressure at 0°C, and n-hebutane and water were distilled off until the distillate amounted to 600 parts, resulting in a solid content of 23.
A 6% olefin resin emulsion (b-1) was obtained. The average particle diameter was 0.8P.

Acrylic resin modified salt PP emulsion (b-λLq
Chlorinated polypropylene resin (number average molecular weight (
Mn, ) 5800, chlorine content 26%) solid content 50
% toluene solution and 350 parts of butyl cellosolve were charged and heated to 100°C.

Next, a mixture of 52 parts of acrylic acid, 130 parts of styrene, 468 parts of n-butyl acrylate, 69 parts of 75% penzoyl peroxide, and 50 parts of isopropanol was added dropwise to the chlorinated polypropylene resin solution over 3 hours. , aged at the same temperature for 1 hour, and then a solution of 325 parts of azobisisovaleronitrile dissolved in 50 parts of butyl cellosolve was added dropwise over 1 hour to this product, maintained at the same temperature for 1 hour, and further heated to 110 The temperature was raised to °C, and unreacted monomer, water, isopropanol, and toluene were removed under reduced pressure to obtain a resin liquid (B-2) with a resin acid value of 405.

Next, while stirring (B-2), dimethylethanolamine was added in an amount equivalent to 10% of the carboxyl groups in the resin solution, and then 20% of deionized water was added.
75 parts was added to create an emulsion (b
-21 was obtained. The average particle diameter was Q, 5pTn.

Barrier Coat (E-1) 208 parts of the urethane resin emulsion (a-1) and 106 parts of the olefin resin emulsion (bl) were thoroughly mixed at 25°C in a stirring vessel to obtain a solid content of 31.8% (maleic chlorinated olefin/ Urethane resin = 25/75), organic solvent content 12.5PHH (a, -1,), (b
-1) A mixed emulsion (c-1) was obtained.

Emulsion (c-1) 404 parts, Dentol WK-2
Barrier coat (El) was obtained by thoroughly kneading 60 parts of 00B (Otsuka Chemical (gradient, tin oxide conductive agent). (Volume resistivity value 3. I x 10297 cm) Barrier coat (E-2) 1.20 parts of the urethane resin (A-2) and 35 parts of the olefin resin solution (B-) were charged into a reaction vessel, and while stirring the system was kept at 50°C, 31 parts of triethylamine and Neugen EA were added. -1400.25 parts was added and stirring was continued for 1 hour, and 1274 parts of deionized water was added over 1 hour. The solvent was removed under reduced pressure at 70°C until the distillate (acetone, methanol) reached 296 g. , nonvolatile content 39.0% (maleated chlorinated polypropylene/polyurecne ratio = 25/75), organic solvent content 17.4PH
An emulsion of H (c-2) was obtained. The average particle diameter is 0.
It was 28 pages. 256 parts of this emulsion (c-2) and 60 parts of WK-200B were thoroughly kneaded to obtain a barrier coat (E-2). Volume specific resistance value 2.4xlO2Ω
/Cm) Barrier coat (E-3) 214.2 parts of the urethane resin emulsion (a-2) and 105 parts of the olefin resin emulsion (b-1,)
．． Mix 9 parts well at 25°C in a stirring container until the solid content is 3.
2.2% (maleated chlorinated polypropylene/urethane resin = 25/75), organic solvent content 1.6PHR (
a-2) (b-1) A mixed emulsion (c-3) was obtained.

320 parts of this emulsion (c-3) and 30 parts of Printex Shi-6 (manufactured by Degussa, conductive carbon) were thoroughly kneaded to obtain a barrier coat (E-3). (Volume resistivity 8.2 x 102 Ω/cm) Barrier coat (E-4 Maleated polyethylene-polypropylene with a number average molecular weight of 30,000, with a maleic anhydride content of 2% by weight and an ethylene to polypropylene ratio of 40 parts/60 parts) Copolymer resin 70
1 part, 70 parts of N-methyl-vinylpyrrolidone, and 70 parts of toluene were stirred in a reaction vessel at 100°C for 1 hour to obtain a uniform olefin resin solution (B-3). Next, the temperature inside the reaction vessel was lowered to 75°C and stirring was continued, then 280 parts of the urethane prepolymer (A-1) and 70 parts of methyl ethyl ketone were charged, and after neutralization with 145 parts of triethylamine, the temperature was lowered to 75°C. While maintaining the temperature, 700 parts of deionized water was added, and the reaction was allowed to proceed for 2 hours to complete the water extension reaction. Furthermore, methyl ethyl ketone was distilled off by vacuum distillation, and the solid content was 2
9.3% (maleated ethylene-propylene copolymer/
Polyurethane resin = 20/80), solvent content 39.5
A PHR emulsion (b-3) was obtained. The average particle size of this emulsion was 0.5 μm. 170.6 parts of this emulsion and the urethane resin emulsion (a
-3) Mix 131.5 parts and further add WK-200B.
60 parts were thoroughly kneaded to obtain a barrier coat (E-4). (Volume resistivity 4.2xlO2Ω/cm) Barrier coat (E-5 177.3 parts of emulsion (b-3), emulsion (
a-1) 135.1 parts, W-1-P (-Rhishi Metal ((1)
and 100 parts of a tin oxide-based conductive pigment) were thoroughly kneaded to obtain a barrier coat (E-5). (Volume specific resistance value 41×1
02Ω/cm) Koi↓1dan2bori- 4237 parts of polyolefin resin emulsion (b-1) and 60 parts of WK200B were thoroughly kneaded to form a paint (E-
6) was obtained. (Volume specific resistance value 2.5 x 102Ω/cm
) 1 column" 1 420 parts of the polyolefin resin solution (B-3), 30 parts of triethylamine, and Neugen EA-140 (manufactured by Daiichi Kogyo Yakuhin ■, polyethylene glycol) nylphenyl ether, nonionic surfactant, HL81.4)3
．． 0 parts and 280 parts of R-free water are thoroughly mixed to obtain an emulsion (b-4). Its particle size was 25μ.

540 parts of this emulsion (b-4) and WK-200B
60 parts were thoroughly kneaded to obtain a paint (E7). (Volume resistivity 3.6XX102Ω/cm) Maleated polyethylene-polymer with a number average molecular weight of 80,000, containing 2% by weight of maleic anhydride and an ethylene to polypropylene ratio of 30 parts/70 parts. Brobylene copolymer resin 10
0 part was dissolved in 900 parts of toluene heated to 100°C, then cooled to 20°C, and Dentol WK-20
The mixture was thoroughly kneaded with 60 parts of 0B to obtain a paint (E-8).

(Volume resistivity value 36 x 102 Ω/cm) For paints (E-1,) to (E-7), the viscosity was 500 to 600 centipoise with deionized water (B-type viscometer, 20
°C) and then used for painting.

For paint (E-8), photo cup # with toluene
The viscosity was adjusted to 4 and 12 seconds (20°C) and used for coating.

Furthermore, among (E-1) to (E-8), (E6) to (E
-8) is a barrier coat for comparison.

(5) Intermediate paint Amirac N-2 Sealer (Kansai Paint (white product, amine polyester resin intermediate coat) (6) Top coat (A) Amirac White (manufactured by Kansai Paint, amino alkyd resin top coat, White paint for 1 coat and 1 bake, pencil hardness HB) CB) ・Magiclon Silver (manufactured by Kansai Paint (1), aminoacrylic resin top coat paint, silver metallic paint for 2 coats and 1 bake, pencil hardness H) ( C): Magikron Clear (Kansai Paint (manufactured by Kiki), amino acrylic resin topcoat paint, clear paint for 2 coats and 1 bake, pencil hardness H) (D): Soflex #140
0 Silver Metallic (Kansai Paint (made by Kiki, metallic paint for plastic, amine polyester) (E)
Suflex #500 Clear (manufactured by Kansai Paint ■, clear paint for plastics, urethane acrylic type) ++ Examples and Comparative Examples Cationic electrodeposition paint Nireclone #92 on the above metal parts
00 was applied by a conventional method and cured by heating at 170'C for 30 minutes (cured coating thickness: 20LL).

Next, the metal member coated with the cationic electrodeposition paint in this way is combined with the plastic member to be coated, and then an intermediate coat and a second coat of paint are electrostatically applied using air spray as a barrier coat. Each was painted as shown in Table 1.

Furthermore, in Table 1, (1) All film thicknesses are based on dry and cured coatings.

(2) The top coats of Example 2.4.6 and Comparative Example 2.4.5 were both wet-on-wet with 2 coats and 1 coat.
It is a bake system, and the top coat (B) or (D
), leave it at room temperature for 15 minutes, then apply the top coat (C).
) or (E) was painted and baked.

(3) In Examples 1 to 6 and Comparative Examples 1 to 3.5, a single barrier coat, intermediate coat, and top coat were applied to both sides of the metal member and plastic member, and in Comparative Example 4, a cadion type coating was applied to the metal member. Electrodeposition paint, intermediate coat paint, and top coat paints (B) and (C) were applied, and the plastic members were coated with paints (D) and (E).

III Performance Test Results A coating film performance test was conducted using the coated plates coated in the above Examples and Comparative Examples. The results are shown in Table 2.

Test method (Sai)) Image C1arity Meter (H△-
Measured using ICH and Suga Test Iso ((η)).

(*2) Impact resistance Testing was conducted in an atmosphere at 0°C in accordance with JIS K5400-19796.13.3B method. Weight 500g
Damage to the paint film was examined by dropping a weight from a height of 50 cm.

(*3) Chipping resistance l! I: (1) Test 1 (Usage: Q-G-R gravelometer (product of Q Panel Company) Capacity: Approximately 500 J (4) Blowing air pressure: Approximately 4 kg/cm2 (5) Temperature during test: Approximately 20°C The test piece was attached to a holding stand, and the air pressure was approximately 500 J when blowing approximately 4 kg/cm2. After blasting crushed stone particles onto a test piece, the coating surface condition and salt spray resistance were evaluated.

The state of the painted surface was visually observed and evaluated using the following criteria. For salt spray resistance, test pieces were subjected to a salt spray test for 240 hours in accordance with JIS22371, and the presence or absence of estrus from the impacted area and the state of corrosion were observed. .

O (Good) Only a few scratches due to impact were observed on a part of the top coat, and no peeling of the electrodeposited coating was observed at all.

△ (slightly poor) Many scratches due to impact were observed on the second coat and intermediate coat, and peeling of the electrodeposition coating was also observed here and there.

× (Poor) Most of the top coat and intermediate coat have peeled off, and the electrodeposition coating on the impact area including the impact area and its surrounding area has peeled off.

(*4) Color difference The color difference between the metal member and the plastic member was measured according to JIS 28730.

In the table, S is the performance of the coating film formed on the metal member, and P is the performance of the coating film formed on the plastic member.

(*5) Organic solvent content Harriero prepared for spraying Contained in paints The theoretical value of the amount of organic solvent used is Resin solid content 100 weight Calculated on a per unit basis.

Claims (1)

[Claims] A method for painting an automobile exterior panel consisting of a metal component and a plastic component, in which a metal component and a plastic component coated in advance with a cationic electrodeposition paint are assembled to form an automobile exterior panel, and both components are coated with olefin. A water-based barrier coat whose main vehicle component is a composition consisting of a polyurethane resin and a urethane resin is applied, then an intermediate coat is applied as needed, and then a top coat is applied. How to paint the board.