GB2399521A - Composite coating film having excellent anti-chipping properties - Google Patents

Abstract

A composite coating film is produced by forming an electrocoated film on a substrate, and then successively applying an intermediate paint, a base paint and a clear paint in a wet-on-wet manner, followed by baking and curing the applied three layers at once, wherein ```said intermediate paint contains, on the basis of a resin solid content, <SL> <LI>(a) 5 to 30% by weight of a urethane-modified polyester resin having a number average molecular weight of 1,500 to 3,000, obtained by reacting an aliphatic isocyanate compound with a hydroxy group-containing polyester resin having a glass transition point (Tg) of 40 to 80{C, the polyester being obtained by polycondensation of an acid component containing 80 mol% or more of isophthalic acid and a polyhydric alcohol, <LI>(b) 30 to 60% by weight of a polyolefin elastomer having an acid group and/or a hydroxy group, and <LI>(c) 10 to 30% by weight of a blocked isocyanate compound. The method provides with a coated composite film excellent in anti-chipping property by a three-coat one-bake method. </SL>

Description

239952 1

METHOD FOR COATED COMPOSITE FILM

FIELD OF THE INVENTION

l0001l The present invention relates to a method for forming a coated composite film and, more particularly, to a method for forming a coated composite film by a three-coat one-bake method.

BACKGROUND OF THE INVENTION

0002 There are two methods for forming a coated composite film. One is a method in which every coated film is baked and cured after coating. The other is a method in which a coated composite film is formed by coating two or more paints without curing and then cured one time. For example, two-coat one-bake method is generally performed for forming a metallic coating. JP-A No.11-114489 discloses a method for forming a coated composite film which comprises successively forming a color base coating film, a metallic base coating film and a clear coating film, and then baking and curing the three layers at the same time, in order to enhance film appearance.

100031 When an intermediate coating film, a base coating film and a clear coating film are formed by a three-coat one-bake method, a baking oven for curing the intermediate coating can be eliminated. Accordingly, consumed energy and operation time are reduced, and there is great advantage in economical view and environment pollution. However, the three-coat one-bake method has, for example, the following problems.

100041 Peeling of coating film occurs in some cases by so-called chipping where a running vehicle snaps up pebbles and the pebbles collide with a coating film. In the conventional coated composite film formation method such :: \ as baking every application of respective paints and a two-coat one-bake method, an undercoating film and an intermediate coating film are baked and cured, independently. Therefore, strategy for chipping could be adopted by forming an anti-chipping coating film on or beneath an intermediate coating film, or forming an intermediate coating film in which chipping is not recognized, by adjusting the brightness of a topcoating film and the brightness of an intermediate coating film.

100051 For example, JP-A No.2002-249699 and JP-A No.9-208882 describe a chipping primer coating composition, and formation of an anti-chipping coating film in a coated composite film.

[000y In addition, in JP-A No.6-256714 or JP-A No.6-254482, improvement in the anti-chipping property is studied from a viewpoint of a composition of an intermediate paint, but a level of improvement is insufficient for using in a three-coat one-bake method.

1 71 Further, a body of an automobile has many concave and convex,and there is a problem that, when a whole surface of the body is coated by a three-coat one-bake method, deteriorated appearance such as popping and miscibility of layers is easily caused depending on a portion thereof.

OBJECT OF THE INVENTION

[00081 The present invention solves the aforementioned conventional problems, and an object of the present invention is to provide a method of forming a coated composite film excellent in the anti-chipping property by a three-coat one-bake method.

SUMMARY OF THE INVENTION

9] The present invention provides a method for producing a coated r r composite film, comprising forming an electrocoated film on a substrate, and then successively applying an intermediate paint, a base paint and a clear paint in a wet-on-wet manner, followed by baking and curing the applied three layers at once, wherein the intermediate paint contains, on the basis of a resin solid content, (a) 5 to 30% by weight of a urethane-modified polyester resin having a number average molecular weight of 1,500 to 3,000, obtained by reacting an aliphatic isocyanate compound with a hydroxy group-containing polyester resin having a glass transition point (Tg) of 40 to 80 C, the polyester being obtained by polycondensation of an acid component containing 80 mol% or more of isophthalic acid and a polyhydric alcohol, (b) 30 to 60% by weight of a polyolefin elastomer having an acid group and/or a hydroxy group, and (c) 10 to 30% by weight of a blocked isocyanate compound.

DETAILED DESCRIPTION OF THE INVENTION

00101 Intermediate coating film In the coating film formation method of the present invention, an intermediate paint used for forming an intermediate coating film contains a urethane-modified polyester resin (a) , a polyolefin elastomer (b) and a blocked isocyanate compound (c). The intermediate paint may further contain a melamine resin (d), a nonaqueous dispersion resin having a core-shell structure (e) and a flake shape pigment (f), if necessary.

[00111 The urethane-modified polyester resin (a) can be obtained by reacting a hydroxy group-containing polyester resin with an aliphatic isocyanate compound. - l)

[001y Generally, a polyester resin can be prepared by polycondensing an acid component such as carboxylic acid, acid anhydride and acid chloride, and a monohydric or polyhydric alcohol. The hydroxy group-containing polyester resin used in the present invention contains isophthalic acid in an acid component used in a polycondensation reaction, at 80 mol% or more on the basis of a total mole number of an acid component. When an amount of isophthalic acid in an acid component is lower than 80 mol%, a glass transition point (Tg) of the resulting hydroxy group-containing polyester resin becomes lower than the desired range, being not preferable.

100131 Examples of an acid component other than is,ophthalic acid include phthalic acid, phthalic acid anhydride, tetrahydrophthalic acid, tetrahydrophtalic acid anhydride, hexahydrophthalic acid, hexahydrophthalic acid anhydride, methyltetrahydrophthalic acid, methyltetrahydrophthalic acid anhydride, himic acid anhydride, trimellitic acid, trimellitic acid anhydride, pyromellitic acid, pyromellitic acid anhydride, terephthalic acid, maleic acid, maleic acid anhydride, fumaric acid, itaconic acid, adipic acid, azelaic acid, sebacic acid, succinic acid, succinic acid anhydride, dodecenylsuccininc acid, dodecenylsuccininc acid anhydride and the like. Alternatively, as an acid component, acids other than polyvalent carboxylic acid and acid anhydride, which are usually used in preparation of a polyester resin may be contained. Examples of such acid include monocarboxylic acid and hyroxycarboxylic acid. As an acid used for preparing the hydroxy group- containing polyester resin, isophthalic acid may be used alone, or may be used by mixing with other acid.

[00141 Examples of the polyhydric alcohol include ethylene glycol, diethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, polypropylene

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glycol, neopentyl glycol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,4-cyclohexanediol, 2,2-dimethyl-3-hydroxypropyl-2,2-dimethyl-3-hydroxypropionate, 2,2,4-trimethyl-1,pentanediol, polytetramethylene ether glycol, polycaprolactone polyol, glycerin, sorbitol, annitol, trimethylolethane, trimethylolpropane, trimethylolbutane, hexanetriol, pentaerythritol, dipentaerythritol and the like.

lO0151 In preparation of the hydroxy group-containing polyester resin, other components which can be reacted with these components may be used in addition to the aforementioned acid components and polyhydric alcohols.

Examples of such other components include acid chloride, acid derivatives of lactones, an epoxide compound, and a drying oil and a semidrying oil and fatty acid derivatives thereof. Lactones can form a graft chain by ring-opening addition to polyester resin of polyvalent carboxylic acid and polyhydric alcohol.

Examples of lactones includes p-propiolactone, dimethylpropiolactone, butyllactone, y-valerolactone, s-caprolactone, y-caprolactone, ycapryllactone, crotolactone, 6-valerolactone, 6-caprolactone and the like. In particular, E-caprolactone is most preferable. Specitc examples include monoepoxide compound such as Carjula E (manufactured by Shell Chemical Co., Ltd.), and lactones.

[00161 The hydroxy group-containing polyester resin has a glass transition point (Tg) of 40 to 80 C, preferably 45 to 75 C. When the glass transition point (Tg) is lower than 40 C, a film hardness is reduced. When the point is higher than 80 C, the anti-chipping performance is reduced.

O017] Examples of the aliphatic isocyanate compound include hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, cyclohexane-1,4diisocyanate, dicyclohexylmethane-4,4-diisocyanate, methylcyclohexane diisocyanate and isopholone diisocyanate.

l0018l In particular, it is preferable from a viewpoint of the antichipping performance and the weather resistance of a coating film that hexamethylene diisocyanate or trimethylhexamethylene diisocyanate is used. Buret, isocyanurate and adduct of them may be used.

[00191 A reaction of the hydroxy group-containing polyester resin and the aliphatic isocyanate compound can be performed by the method known to a person skilled in the art. , l0020l The urethane-modified polyester resin (a) has a number average molecular weight (Mn) of 1,500 to 3,000, preferably 1,700 to 2,500. When the molecular weight is smaller than 1500, coating workability and curability are not sufficient. When the molecular weight exceeds 3,000, a nonvolatile fraction becomes too low at applying, and coating workability becomes deteriorated conversely. Herein, a number average molecular weight is determined by a GPC method using polystyrene as a standard.

l0021l The urethane-modified polyester resin (a) has a hydroxy-group value (OHV) of preferably 30 to 180, more preferably, 40 to 160. When a hydroxy group value exceeds 180, water resistance of a coating film is reduced. When the hydroxy group value is smaller than 30, curing ability of a coating film is reduced. In addition, the resin has an acid value (AV) of preferably 3 to 30 mgKOH/g, more preferably 5 to 25 mgKOH/g. When an acid value exceeds 30 mgKOH/g, water resistance of a coating film is reduced. When an acid value is smaller than 3 mgKOH/g, curing ability of a coating film is reduced.

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[00221 An amount of the urethane-modified polyester resin (a) contained in an intermediate paint is, on the basis of a weight of a resin solid content, 5 to 30% by weight, preferably 10 to 30% by weight. When an amount is smaller than 5% by weight, anti-chipping performance becomes insufficient. When a component exceeds 30% by weight, hardness of a coating film is reduced.

tO023l It is considered that, by inclusion of the urethane-modified polyester resin as a component for an intermediate paint, elasticity of a coating film is improved, and anti-chipping property of a coating film is also improved.

[00241 The polyolefin elastomer (b) is generally a polyolefin-based graft polymer. The polyolefin elastomer (b) is prepared, for example, copolymerizing a polyolefin-based macro monomer and an ethylenic unsaturated compound.

[00251 The polyolefin-based macro monomer refers to a high-molecular monomer having an ethylenic unsaturated group on a polyolefin chain and at a terminal thereof. The polyolefin-based macro monomer is obtained, for example, by reacting polyolefin having a hydroxy group with an acid or an acid anhydride having an ethylenic unsaturated group.

[00261 Examples of polyolefin having a hydroxy group include polyolefinbased resin such as polyethylene, polypropylene, polybutadiene, hydrogenated polybutadiene, polyisoprene, hydrogenated polyisoprene, EPDM and the like, which have a hydroxy group at both terminals. It preferably has a number average molecular weight of 200 to 5000, more preferably 500 to 4000.

[00271 Examples of commercially available polyolefin having a hydroxy group include the following:

[00281 [Table 1] 1 : ::

Trade name Manufacturer Compound Mn G-1000 Nippon Soda Co., Ltd. a,a,polybutadiene glycol about 1,500 G-2000 Nippon Soda Co., Ltd. a,c,polybutadiene glycol about 2,000 G-3000 'Nippon Soda Co., Ltd. a,aapolybutadiene glycol about 2,900 Gl-1000 Nippon Soda Co Ltd. a,c,hydrogenated about 1,500 polybutadene glycol Gl-2000 Nippon Soda Co., Ltd. a,a3-hydrogenated about 2,100 polybutadiene glycol Gl-3000 Nippon Soda Co., Ltd. a,a,-hydrogenated about 3,000 polybutadene glycol R- 15HT Idemitsu Petrochemical a,-polybutadiene glycol about 1,200 R45HT Idemitsu Petrochemical a,c-polybutadiene glycol about 2,800 LIR- 506 Kuraray Co., Ltd. Polyisoprene pentaol about [00291 Examples of acid anhydride having an ethylenic unsaturated group include maleic anhydride, itaconic anhydride, succinic anhydride and the like.

Among them, it is particularly preferable to use maleic anhydride.

100301 A reaction of polyolefin having a hydroxy group with acid or acid anhydride having an ethylenic unsaturated group can be performed by the method known to a person skilled in the art.

l0031l The polyolefin-based macro monomer may be obtained by reacting polyolefin having a hydroxy group, a diisocyanate compound and an alcohol having an ethylenic unsaturated group. Examples of the alcohol having an ethylenic unsaturated group include hydroxy group-containing acryl monomer.

1003y As the diisocyanate compound, aliphatic diisocyanate which is used for preparing an urethane-modified polyester resin can be used. Particularly preferable is isophorone diisocyanate.

10033] As the hydroxy group-containing acryl monomer, for example, hydroxyethyl methacrylate (HEMA), hydroxyethyl acrylate (HEA), hydroxypropyl methacrylate (HPMA), hydroxypropyl acrylate (HPA) and hydroxybutyl acrylate (MBA) can be used. These can be used alone or by mixing two or more.

Among these hydroxy group-containing acryl monomers, hydroxyethyl(meth) acrylate is particularly preferably used.

[00341 A reaction of the polyolefin having a hydroxy group, the diisocyanate compound and the alcohol having an ethylenic unsaturated group can be performed by the method known to a person skilled in the art.

100351 The ethylenic unsaturated compound to be copolymerized with.the polyolefin-based macro monomer include an ethylenic unsaturated monomer, an unsaturated acryl resin, an unsaturated polyester resin and the like.

100361 Examples of the ethylenic unsaturated monomer include acryl monomer, such as methyl acrylate, methyl methacrylate, acrylic acid, methacrylic acid, hydroxyethyl acrylate, hydroxyethyl methacrylate, nbutyl acrylate and n-butyl methacrylate and the like. These acryl monomers may be used alone or by mixing two or more. Further, other monomers which can be copolymerized with the acryl monomers such as styrene and vinyl acetate may be used.

100371 The unsaturated acryl resin is such that an unsaturated bond is introduced in an acrylic resin. For example, the unsaturated acryl resin can be obtained by adding glycidyl methacrylate to a carboxyl group of an acryl resin, by adding acid anhydride having an unsaturated bond to a hydroxyl group of an acryl resin, or by adding carboxylic acid having an unsaturated bond to an oxirane group of an acryl resin.

00381 As the unsaturated acryl resin, it is preferable that an acid value is O to ! : :' mgKOH/g, more preferably 0 to 150 mgKOH/g, a hydroxy group value is 10 to 300, more preferably 10 to 200, a number average molecular weight is 1000 to 50000, more preferably 2000 to 5000, and an iodine value is 0.5 to 100, more preferably 0.5 to 70.

100391 The unsaturated polyester resin can be obtained by a conventional method, for example, by a reaction of a polyol compound and a polybasic acid compound having an unsaturated group.

100401 In the unsaturated polyester resin, it is preferable that an acid value is 0 to 200 mgKOH/g, more preferably 0 to 150 mgKOH/g, a hydroxy group value is to 300, more preferably 10 to 200, a number average molecular weight is 1000 to 5000, more preferably 1000 to 4000, and an iodine value is 0.5 to 100, more preferably 0.5 to 70.

[00411 Copolymerization of the polyolefin-based macro monomer and the ethylenic unsaturated compound can be performed by a method known to a person skilled in the art. For example, according to a solution polymerization method, the polyolefin-based macro monomer is dissolved in a suitable solvent, a temperature is risen and, thereafter, the ethyhlenic unsaturated compound together with a suitable polymerization initiator is added dropwise while stirring.

l0042l Examples of a suitable solvent used in a reaction include aliphatic hydrocarbons such as kerosine, ethylcyclohexane and Shelizole TH (trade name, manufactured by Shell Japan Co., Ltd.), aromatic hydrocarbons such as toluene, xylene and Swazole100 (trade name, manufactured by Maruzen Petrochemical Co., Ltd.), esters such as butyl acetate and Uca Ester EEP (trade name, manufactured by Union Carbide), and alcohols such as butanol, isobutanol and ethylene glycol, monobutyl ether.

10043] Examples of the polymerization initiator include peroxides such as t-butylperoxy-2-ethyl hexanoate, benzoyl peroxide and diphthal peroxide, and azo-based initiators such as azo bisisobutyronitrile and 2,2'-azobis(2,4dimethylvaleronitrile).

[00441 A reaction temperature is generally adjusted 60 to 1 60 C, preferably 80 to 140 C. An end point of a reaction is determined by steady viscosity of a reaction solution.

100451 The resulting polyolefin elastomer has a number average molecular weight of 3,000 to 200,000, preferably 10,000 to 100,000. When a number average molecular weight is smaller 3,000, appearance of a coated composite film is deteriorated. On the other hand, when a number average molecular weight exceeds 200,000, the solubility of the polyolefin elastomer in a solvent is deteriorated.

l0046l Further, it is preferable that the polyolefin elastomer has a hydroxy group and/or a carboxyl group. More preferably, the polyolefin elastomer has both of a hydroxy group and a carboxyl group. By using the polyolehn elastomer containing one or more of these functional groups, the physical property and the anti-chipping property of the resulting coated composite film can be further improved.

100471 An acid value of the polyolefin elastomer is preferably 1 to 50 mgKOH/g, more preferably 5 to 30 mgKOH/g. When an acid value exceeds 50 mgKOH/g, water resistance of the resulting coated composite film is reduced. In addition, a hydroxy group value of the polyolefin elastomer is preferably 1 to 200, more preferably 50 to 150. When a hydroxy group value exceeds 200, water resistance of the resulting coated composite film is reduced. :,

10048] An amount of the polyolefin elastomer (d) contained in an intermediate paint is 30 to'60% by weight, preferably 30 to 40% by weight based on a weight of a resin solid content. When an amount is smaller than 30%, improvement in physical property values of the resulting coated composite film and appearance of a coating film are not seen. When an amount exceeds 60%, compatibility of a paint is reduced, leading to unevenness.

0049] By inclusion of the polyolefin elastomer as a component of an intermediate paint, an elongation rate of a coating film is improved, and the anti-chipping property of a coating film is also improved. In addition, since the compatibility between an intermediate coating film arid a topcoating film is reduced, and a base coating film or a clear coating film does not permeate into a wet intermediate coating film, phase mixing is prevented, and appearance, in particular, gloss appearance is improved.

100501 The blocked isocyanate compound (c) is a component for curing the urethane-modified polyester resin (a) and the polyolefin elastomer (b).

100511 The blocked isocyanate compound can be obtained by adding a blocking agent to aliphatic isocyanate or a derivative thereof. When the blocked isocyanate compound is heated, a blocking agent is dissociated to generate an isocyanate group, which is then reacted with a hydroxy group in the urethane-modified polyester resin to cure the material.

[00521 Examples of the aliphatic isocyanate and a derivative thereof include compounds which are used upon preparation of the urethanemodified polyester resin. Examples of the blocking agent include compounds having an active methylene group such as acetyl acetone, ethyl acetoacetate and ethyl malonate. By using the blocking agent, elasticity of a film is improved, and anti-chipping property of a film is also improved.

[00531 The blocked isocyanate compound is commercially available, for example, as active methylene-type blocked isocyanate UDuranate MF-K60X from Asahi Chemical Industry Co., Ltd. 00541 An amount of the blocked isocyanate compound (c) contained in an intermediate coating paint may be 10 to 30% by weight, preferably 15 to 25% by weight on the basis of a weight of a resin solid content. When an amount is smaller than 10% by weight, the curability becomes insufficient. When an amount exceeds 30% by weight, a cured film becomes too hard, and brittle.

100551 The melamine resin (d) is not particularly limited, but a methylated melamine resin, a butylated melamine resin or a methyl-butyl mixed type melamine resin can be used. Examples include "Cymel-303", "Cymel 254, turban 128n and "Urban 20N60 sold by Mitsui Toatsu Co., Ltd., and "Sumimar Series" sold by Sumitomo Chemical Co., Ltd. l0056l An amount of the melamine resin (d) contained in an intermediate coating paint is 20% by weight at maximum, more preferably 5 to 15% by weight on the basis of a resin solid content weight. When an amount of the melamine resin exceeds 20% by weight, a cured film becomes too hard, and brittle.

[00571 The non-aqueous dispersion resin (e) having a core-shell structure can be prepared by copolymerizing a dispersion stable resin and a copolymerizable monomer in a mixed solution with an organic solvent, to obtain the resin as a non-cross-linked resin particle which is insoluble in the mixed solution. A monomer to be copolymerized in the presence of the dispersion stable resin for obtaining a non-cross-linked resin particle is not particularly limited as far as it is a radicalpolymerizable unsaturated monomer.

l0058l In order to synthesize the aforementioned dispersion stable resin and a non-aqueous dispersion, it is preferable to use a polymerizable monomer having a functional group because the non-aqueous dispersion having a functional group can react with the curing agent together with the dispersion stable resin containing a functional group to form a threedimensionally cross-linked coating film.

[00591 The dispersion stable resin is not particularly limited as far as the non-aqueous dispersion can be stably synthesized in an organic solvent.

Specifically, it is preferable to use an acryl resin, a polyester resin, a polyether resin, a polycarbonate resin, polyurethane resin and the like, which have a hydroxyl group value of 10 to 250, preferably 20 to 180, an acid value of 0 to mgKOH/g, preferably 0 to 50 mgKOH/g, and a number average molecular weight of 800 to 100,000, preferably 1,000 to 20,000. When above parameters exceed upper limits, the handling property of the resin is reduced, and the handling property of the non-aqueous dispersion itself is also reduced. When parameters below lower limits, there is a possibility that the resin is desorbed and the stability of a particle is reduced when formulated into a coating film.

l0060l A method of synthesizing the aforementioned dispersion stable resin is not particularly limited, but include preferably a method of obtaining the resin by radical polymerization in the presence of a radical polymerization initiator, and a method of obtaining the resin by condensation method or an addition reaction.

Further, a monomer which is used for obtaining the aforementioned dispersion stable resin can be appropriately selected depending on the property of the resin, but it is preferable to use monomers having a functional group such as a hydroxyl group, an acid group and the like which are possessed by polymerizable monomers described later which are used for synthesizing the non-aqueous dispersion and, further if needed, monomers having a functional group such as a glycidyl group, an isocyanate group and the like may be used.

l0061l In addition, a component ratio of the aforementioned dispersion stable resin and the aforementioned polymerizable monomer can be arbitrarily selected depending on the purpose. For example, it is preferable that the dispersion stable resin is 3 to 80% by weight, particularly S to 60% by weight, and the polymerizable monomer is 97 to 20% by weight, particularly 95 to 40% by weight on the basis of a total weight of both components. Further, the total concentration of the dispersion stable resin and the polymerizable monomer in an organic solvent is preferably 30 to 80% by weight, particularly 40 to 60% by weight on the basis of a total weight.

l0062l The aforementioned non-aqueous dispersion can be obtained by polymerizing a radical polymerizable monomer in the presence of the dispersion stable resin. In the non-aqueous dispersion, it is preferable that a hydroxy group value is 50 to 400, preferably 100 to 300, an acid value is 0 to 200 mgKOH/g, preferably 0 to 50 mgKOH/g, and an average particle diameter (D50) is 0.05 to 10 Em, preferably 0.1 to 2 Em. When parameters are below lower limits, a particle shape can not be maintained. When parameters exceed upper limits, the stability is reduced when dispersed in a paint.

[00631 Representative polymerizable monomers having a functional group used for synthesizing the aforementioned non-aqueous dispersion are as follows.

Examples of monomers having a hydroxyl group include hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, hydroxybutyl (meth)acrylate, : I: hydroxymethyl tmeth)acrylate, allyl alcohol, and adduct of hydroxyethyl (meth)acrylate and s-caprolactone.

00641 On the other hand, examples of monomers having an acidic group include polymerizable monomers having a carboxyl group, a sulfonic acid group or the like. Examples of monomers having a carboxyl group include (meth)acrylic acid, crotonic acid, ethacrylic acid, propylacrylic acid, isopropylacrylic acid, itaconic acid, maleic acid anhydride, fumaric acid and the like. Examples of polymerizable monomers having a sulfonic acid group include t-butylacrylamide sulfonic acid and the like. When polymerizable monomer having an acidic group is used, it is preferable that a part of an acidic group is a carboxylic group.

100651 In addition, examples of polymerizable monomers having a functional group include a glycidyl group-containing unsaturated monomer such as glycidyl (meth)acrylate, and an isocyanate group-containing unsaturated monomer such as m-isopropenyl+,oc-dimethylbenzylisocyanate, isocyanatoethyl acrylate and the like.

100661 Examples of other polymerizable monomers include (meth)acrylic acid alkyl ester such as methyl (meth)acrylate, ethyl (meth)acrylate, isopropyl (meth)acrylate, n-propyl (meth)acrylate, n-butyl (meth)acrylate, t-butyl (meth)acrylate, isobutyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, noctyl (meth)acrylate, lauryl (meth)acrylate, stearyl (meth)acrylate, and tridecyl (meth)acrylate, addition reaction products of oil fatty acid and acrylic acid or methacrylic acid ester monomer having an oxirane structure (e.g., addition reaction product of stearic acid and glycidyl methacrylate etc.) addition reaction product of an oxirane compound containing a C3 or higher alkyl group and acrylic acid or methacrylic acid, styrene, amethylstyrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, ptbutylstyrene, benzyl (meth)acrylate, itaconic acid ester (di methyl itaconate) , maleic acid ester (di methyl maleate) , fumaric acid ester (dimethyl fumarate), as well as other polymerizabie monomers such as acrylonitrile, moth acrylonitrile, methylisopropenyl ketone, vinyl acetate, Veoba Monomer (manufactured by Shell Chemical Co., Ltd., trade name), vinyl propionate, vinyl pivalate, ethylene, propylene, butadiene, N,N-dimethylaminoethyl acrylate, N,N-dimethylaminoethyl methacrylate, acrylamide, and vinyl pyridine.

100671 It is preferable that a polymerization reaction for obtaining theaforementioned non-aqueous dispersion is performed in the presence of a radical polymerization initiator. Examples of the radical polymerization initiator include azo-based initiators such as 2,2'azobisisobutyronitrile, and 2,2'-azobis(2,4-dimethylvaleronitrile), benzoyl peroxide, lauryl peroxide, t-butyl peroctoate and the like. It is desirable that an amount of these initiators is 0.2 to 10 parts by weight, preferably 0.5 to 5 parts by weight per a total of 100 parts by weight of a polymerizable monomer. It is preferable that a polymerization reaction for obtaining a non-aqueous dispersion in an organic solvent containing a dispersion stable resin is generally performed in a temperature range of about to 160 C for 1 to 15 hours.

100681 In addition, the aforementioned non-aqueous dispersion is a particle component in a paint different from a cross-linked polymer particle, but has the characteristic that it does not form a particle structure in a coating film. That is, the non-aqueous dispersion is different from a cross-linking polymer particle in that since there is no cross-linking site in a particle, a particle shape is changed :: in a baking process, and this can be a resin component.

9] Further, for example, a resin particle called NAD (Non Aqueous Dispersion) which is described in Coloring Material, vol.48 (1975), pp.2834 and is used in a NAD paint, can be also used.

t0070l An amount of a non-aqueous dispersion resin (a) contained in an , intermediate paint is 15% by weight at maximum, preferably 5 to 12% by weight on the basis of a weight of a resin solid content. When an amount exceeds 15% by weight, anti-chipping performance is reduced.

[00711 By using the non-aqueous dispersion resin (e), prevention of miscibility between coating layers becomes easy, and appearance is improved.

l0072l As the flake shape pigment (0 mica, alumina, talc and silica can be used and it is preferable from a viewpoint of the chipping performance that talc is used.

100731 It is preferable that the flake shape pigment (0 has a size of a long diameter of 1 to 10 Am and a number average particle diameter of 2 to 6 tom.

When a long diameter is outside the aforementioned range, appearance of a film is inferior, and the sufficient anti-chipping performance is not obtained.

When a number average particle diameter is outside the aforementioned range, similarly, appearance of a coating film is inferior and the sufficient antihipping performance is not obtained.

100741 A content of the flake shape pigment (fly is 0.4 to 2 parts by weight based on 100 parts by weight of a resin solid content. A content of 0.5 to 1.5 parts by weight is more preferable. When a content is outside the aforementioned range, since the adhesion property with an undercoating film is reduced, the sufficient chipping performance is not obtained.

10075] Other resins which can be contained are not particularly limited, but examples thereof include an acryl resin, a polyester resin, an alkyd resin, an epoxy resin and the like. These resins may be used alone or in combination of two or more.

[00761 Examples of the coloring pigment include an azo chelate-based pigment, an insoluble azo-based pigment, a fused azobased pigment, a phthalocyanine-based pigment, an indigo pigment, a perinone-based pigment, a perylene-based pigment, a dioxane-based pigment, a quinacridone-based pigment, an isoindolinone-based pigment, a metal complex pigment and the like as an organic base. As an inorganic base, chrome yellow, yellow iron oxide, iron oxide red, carbon black, titanium dioxide and the like can be used. In addition, as an extender pigment, calcium carbonate, barium sulfate, aluminum powder, kaolin and the like can be used.

[007n A gray-based coloring pigment containing carbon black and titanium dioxide as a main pigment is generally used. Further, a coloring pigment having a hue compatible with that of a top coating, and a combination of various pigments may be also used.

8] In addition, in order to prevent miscibility with a top coating film and maintain coating workability, a theological agent can be added to the aforementioned intermediate paint. Examples of the theological agent include materials which generally exhibit thixotropic properties, for example, polyamide-based agents such as a swollen dispersion of fatty acid amide, amide fatty acid, phosphate of long chain polyaminoamide and the like, polyethylene-based agents such as a colloidal swollen dispersion of polyethylene oxide and the like, organic bentonite-based agents such as organic acid smectite clay, montmorillonite and the like, inorganic pigments such as aluminum "silicate, barium sulfate and the like, flake shape pigments developing viscosity depending on a shape of a pigment, a cross-linked resin particle and the like.

10079] A total amount of a solid content of an intermediate paint used in the present invention at applying is 20 to 80% by weight, preferably 25 to 65% by weight. When the amount is outside this range, paint stability is reduced.

When the amount exceeds an upper limit, a viscosity is too high and appearance of a coating film is reduced. When the amount is below a lower limit, a viscosity is too low, deteriorated appearance such as miscibility of layers and ununiformity occurs.

10080] In addition to the aforementioned components, other additives which are usually added to a paint, for example, a surface adjusting agent, an anti-oxidant, an anti-foaming agent and the like may be incorporated in the intermediate paint used in the present invention. An amount of them to be incorporated is within a range known to a person skilled in the art.

100811 In addition, other resin may be contained in the urethane-modified polyester resin. Such a resin is not particularly limited, but include an acryl resin, a polyester resin, an alkyd resin, an epoxy resin and the like. These resins may be used alone or in combination of two or more.

100821 A process for preparing a paint composition used in the present invention including the process described later is not particularly limited, but all processes which are well known to a person skilled in the art such as kneading and dispersing of a blend of a pigment using a kneader, a roll and a SO mill can be used.

3] Base coating film The base paint used in the coating film formation methods of the present invention is used for constituting a top coating film with a clear paint.

This base paint contains a film forming resin, a curing agent, a coloring pigment and, if necessary, a metallic pigment and the like.

[00841 The film forming resin contained in the aforementioned base paint is not particularly limited, but preferable examples thereof include an acryl resin, a polyester resin, an alkyd resin, an epoxy resin, an urethane resin and the like.

These resins can be used alone or in combination of two or more.

lO085] The aforementioned film forming resin can be used by combining with a curing agent. From a viewpoint of the various performances and the cost of the resulting coating film, an amino resin and/or a blocked isocyanate resin are preferably used.

l0086l A content of the aforementioned curing agent is preferably 20 to 60% by weight, more preferably 30 to 50% by weight, based on a weight of a solid content of the film forming resin. When a content is smaller than 20% by weight, curability becomes insufficient. When a content is higher than 60% by weight, a cured film becomes too hard, and brittle.

100871 In addition, as the aforementioned coloring pigment, for example, coloring pigments exemplified for the aforementioned intermediate paint can be contained.

l0088l A shape of metallic pigment optionally contained in the aforementioned base paint is not particularly limited. The metallic pigment may be colored.

For example, a metallic pigment having an average particle diameter (D50) of 2 to 50 m, and a thickness of 0.1 to 5 1lm is preferable. In addition, a metallic : :: pigment having an average particle diameter in a range of 10 to 35 Em is excellent in luster appearance, and is suitably used. The pigment concentration (PWC) of the metallic pigment in the aforementioned paint is generally 20.0% by weight or less. The concentration is preferably 0.01 to 18.0% by weight, more preferably 0.1 to 15.0% by weight. When an amount of the metallic pigment exceeds 20.0% by weight, appearance of a film is reduced.

l0089l Examples of the aforementioned metallic pigment include noncolored or colored metal metallic pigments of metals or alloys such as aluminum, copper, zinc, iron, nickel, tin and aluminum oxide, and a mixture thereof. Further, an interfering mica pigment, a white mica pigment, a graphite and other colored or non-colored flake shape pigments may be used jointly.

100901 The total pigment concentration (PWC) of the metallic pigment and other all pigments in a paint is 0.1 to 50% by weight, preferably 0.5 to 40% by weight, more preferably 1.0 to 30% by weight. When the concentration exceeds an upper limit, appearance of a coating film is reduced.

l0091l Further, as in the aforementioned intermediate paint, in order to maintain coating workability' it is preferable to add a theological agent to the base paint.

A theological agent is used for forming a film having no ununiformity and sag and, generally, agents exhibiting thixotropic properties may be contained. As such an agent, for example, agents exemplified for the aforementioned intermediate paint can be contained.

l0092l In addition to the aforementioned components, additives which are generally added to a paint such as a surface adjusting agent, a theological agent, an antioxidant, an ultraviolet inhibitor and an antifoaming agent may be incorporated into the base paint used in the present invention. An amount of them to be incorporated is within a range known to a person skilled in the art.

100931 An amount of a total solid substance of the base paint used in the present invention at applying is 10 to 60% by weight, preferably 15 to 50% by weight. When the amount is above an upper limit or below a lower limit, stability of a paint is reduced. When the amount exceeds an upper limit, a viscosity is too high, and appearance of a coating film is reduced. When the amount is below a lower limit, a viscosity is too low, and deteriorated appearance such as miscibility of layers and ununiformity occurs.

00941 Clear coating film For forming the clear coating film, a clear paint is used. The clear paint is not particularly limited, but clear paints containing a film forming thermosetting resin and a curing agent can be utilized. As a form of the clear paint, a solution type, an aqueous type and a powder type are exemplified.

10095] From a viewpoint of transparency and resistance to acid etching, preferable examples of the solution-type clear paint include a combination of an acryl resin and/or a polyester resin and an amino resin, a combination of an acryl resin and/or a polyester resin and an isocyanate compound, and an acryl resin and/or a polyester resin having carboxylic acid-epoxy curing system.

100961 In addition, examples of the aqueous type clear paint include paints containing a resin obtained by neutralizing the film forming resin contained in the aforementioned exemplified solution-type clear paints with a base so that paints become aqueous. The neutralization can be performed by adding tertiary amine such as dimethylethanolamine and triethylamine before or after polymerization.

009n On the other hand, as the powder-type clear paint, conventional powder P. : paints such as thermoplastic and thermosetting powder paints can be used.

Since coating films having the better physical properties are obtained, thermosetting powder paints are preferable. Embodiments of the thermosetting powder paints include epoxy-based, acryl-based and polyester resin-based powder clear paints, but acryl-based powder clear paints having the better weather resistance are particularly preferable.

1009Y As the powder type clear paint used in the present invention, epoxycontaining acryl resin/polyvalent carboxylic acid-based powder paints are particularly preferable because there is no volatile material at curing, better appearance is obtained and yellowing is scarcely caused.

1 99] Further, as in the intermediate paint, in order to keep coating workability, it is preferable that a theological agent is added to the clear paint. As a theological agent, agents exhibiting thixotropic properties can be generally contained. As the agent, for example, agents exemplified for the intermediate paint can be contained. If necessary, a curing catalyst, a surface adjusting agent and the like can be contained.

01001 Substrate The coating film formation method of the present invention can be advantageously used in various substrates, for example, metals, plastics, foamed materials and the like, in particular, the metal subrace and cast articles.

The method can be particularly suitably used in metal products which can be cation electrocoated.

101011 Examples of the aforementioned metal products include iron, copper, aluminum, tin, zinc and the like and alloys containing these metals.

Embodiments include vehicle bodies and parts of an automobile, a truck, a motorbike, a bus and the like. It is particularly preferable that the metals are suRace-treated with phosphate, chromate or the like in advance.

[01021 In addition, in a substrate used in the metallic coating film formation method of the present invention, an electrodeposition coating film may be formed on a chemical-treated steel plate. As an electrodeposition paint for forming an electrodeposition coating film, cation type and anion type may be used, and a cation type electrodeposition paint composition is preferable because it gives a coated composite film excellent in corrosion resistance.

01031 Coating film formation method In the coating film formation method of the present invention, successively, an intermediate coating film is formed with an intermediate paint, a base coating film is formed with a base paint, and a clear coating film is formed with a clear paint, on a substrate, in a wet-on-wet manner.

101041 When an automobile body is coated with an intermediate paint in accordance with the present invention, in order to enhance appearance, a film can be formed by a multi-stage coating, preferably 2 stage by air electrostatic spray coating, or a coating method of a combination of air electrostatic spray coating with a rotation atomizing electrostatic coating machine called as "I (micro micro) bel", p (micro) bel" orUmetabel.

101051 A thickness of a dried coating film formed of an intermediate paint in the present invention varies depending on the desired utility. In many cases, a thickness of 10 to 60 Am is useful. When a thickness exceeds an upper limit, sharpness of image is reduced, disadvantage such as ununiformity and sagging occurs at coating in some cases and, when a thickness is below a lower limit, the surface can be hidden and uneven coating occurs.

- :: i

101061 In the coating film formation method of the present invention, further, a base paint and a clear paint are coated on an uncured intermediate coating film in a wet-on-wet manner, to form a base coating film and a clear coating film.

101071 A base paint used for forming a base coating film in the method the present invention can be coated by electrostatic spray coating or with a rotation atomizing electrostatic coating machine such as a metabel, a,ul1 bel, a bel and the like. A dried thickness of the coating film can be set to be 5 to 35 m, preferably 7 to 25,um. When a thickness of a base coating film exceeds 35 Em, sharpness of image is reduced, and ununiformity or sagging occurs in some cases. When a thickness is less than 5 m, the surface hiding property becomes insufficient and uneven coating (state of discontinuous film) occurs in some cases, both being not preferable.

10108] In the coating film formation method of the present invention, a clear coating film which is coated after formation of the base coating film, when the irregularities resulting from the base coating film and a metallic pigment are contained, is formed for protecting the film by hiding fine projections generated therefrom. As a coating method, it is preferable to form a film with the aforementioned rotation atomizing electrostatic coating machine, such as a pp bel, a bel and the like.

10109] A dry thickness of a clear coating film formed of the clear paint is preferably around 10 to 80 m, more preferably about 20 to 60 Am. When a thickness exceeds an upper limit, disadvantage such as popping and sagging occurs at application in some cases. When a thickness is below a lower limit, sharpness of image is reduced.

01101 Thus obtained coated composite films are subjected to coating film formation by simultaneous curing, so-called three-coat one-bake. In this case, a baking and drying oven can be omitted for the intermediate coating film and therefore is preferable from a viewpoint of economical properties and environment suitablity. The process, however, may require so-called pre-heating which is a step of removing volatile materials in the wet film with heat and wind between coating steps. For example, the heat can be imparted at 40 to 1 00 C for about 1 to 5 minutes.

1] By setting a curing temperature of the coated composite films at 100 to 1 80 C, preferably 130 to 1 60 C, the cured coating film having a high- crosslinking degree is obtained. When a temperature is higher than an upper limit, a coating film becomes hard and brittle. When a temperature is lower than a lower limit, curing is not sufficient. Curing time varies depending on a curing temperature, but it is suitable to cure at 130 to 160 C for 10 to 30 minutes.

[01121 Afilm thickness of a coated composite film formed in the present invention is generally 30 to 300 m, preferably 50 to 250 m. When it exceeds an upper limit, film properties such as temperature cycle test and the like are reduced. When it is below a lower limit, strength of a film is reduced.

l0113l According to the present invention, a coated composite film excellent in anti-chipping performance and appearance of a coating film can be obtained even when a coated composite film is formed by a threecoat one-bake method of successively forming an intermediate coating film, a base coating film and a clear coating film in a wet-on-wet manner and, thereafter, curing coating films at once.

0114l The composition of the intermediate coating paint of the present :: invention makes it possible to impart repulsion force against impact at chipping and properly Of converting impact energy into heat energy to coatings. Thus, a coated composite film obtained by the present invention has excellent anti-chipping properties which show small peeling area and less peeling frequency even when receives severe chipping.

10115] The coated composite film formation method of the present invention of successively forming an intermediate coating film, a base coating film and a clear coating film in a wet-on-wet manner is excellent in economical properties and environment suitability, since a baking and drying oven step for an intermediate coating can be eliminated. The present invention, accordingly, can provide the resulting coated composite film with many advantages, such as excellent anti-chipping property, enhanced physical property and good appearance.

EXAMPLES

101161 The present invention will be explained in detail by way of Examples below, but the present invention is not limited by the following Examples.

Hereinafter, "part' and "%" are based on weight.

[01171 Preparation ExamoIe 1 Preparation of urethane-modified polyester resin (a) 440 Parts of isophthalic acid, 20 parts of hexahydrophthalic acid, 40 parts of azelaic acid, 300 parts of trimethylolpropane and 200 parts of neopentyl glycol were placed into a 2L reaction vessel equipped with a nitrogen introducing tube, a stirrer, a temperature adjuster, an addition funnel and a cooling tube equipped with a decanter and, when raw materials were dissolved by heating and stirring became possible, 0.2 part of dibutyl tin oxide was placed therein, stirring was initiated and a reaction layer temperature was gradually risen from 180 to 220 C for 3 hours. Produced condensation water was distilled off from the system. When a temperature reached 220 C, a temperature was retained for 1 hour, 20 parts of xylene was gradually added to a reaction layer, and a condensation reaction was allowed to proceed in the presence of a solvent. When a resin acid value reached 10 mgKOH/g, the material was cooled to 1 00 C, and 100 parts of hexamethylene diisocyanate was gradually added over 30 minutes. Further, a temperature was retained for 1 hour, 200 parts of xylene and 200 parts of butyl acetate were added, to obtain an urethane-modified polyester resin having a solid content of 70%, a number average molecular weight of 2000, an acid value of 8 mgKOH/g, a hydroxy group value of 120 and resin Tg of 60 C.

[011 al Preparation Example 2 Preparation of nolvolefin elastomer (b-1) 650 Parts of a,-hydrogenated polybutadiene glycol "Gl-1000" manufactured by Nippon Soda Co., Ltd. and 650 parts of toluene were placed into a suitable reaction vessel equipped with a thermometer, a stirrer, a cooling tube, a nitrogen introducing tube and an addition funnel, and a temperature was risen to 50 C. To the reaction vessel was added dropwise a solution of 96 parts of isopholone diisocyanate and 96 parts of toluene over 1 hour, and a temperature was retained at 50 C for 1 hour. Then, a temperature of the reaction vessel was risen to 85 C, a solution of 56 parts of hydroxyethyl methacrylate and 56 parts of toluene was added dropwise over 1 hour, which was retained at 85 C for 1 hour, and cooled to obtain a polyolefin-based macro monomer solution (solid content 50%). .

9] 25.6 Parts of a polyolefinbased- macro monomer solution and 83.2 parts of toluene wede placed into a suitable reaction vessel, and a temperature was risen to 110 C. Separately, 20.0 parts of butyl acrylate, 29.0 parts of butyl methacrylate, 2.2 parts of hydroxybutyl methacrylate and 1.5 parts of t-butylperoxy-2-ethyl hexanoate were mixed to obtain a solution, which was . added dropwise to a reaction vessel over 3 hours while stirring the interior thereof. Thereafter, the reaction vessel was retained at 11 0 C for 30 minutes.

A solution of 0.5 part of t-butylperoxy-2-ethyl hexanoate and 5.0 parts of toluene was added dropwise over 30 minutes. After stirring was continued for 90 minutes, the material was cooled to obtain a polyolefin elastomer (b-1) solution (solid content 40%).

[01 201 The resulting polyoletn elastomer (b-1) had the physical property values of a number average molecular weight of 20,000 and a hydroxy group value of 20.

01211 Preparation Example 3 Preparation of nolvolefin elastomer (b-2) 650 Parts ofa,a,-hydrogenated polybutadiene glygol GI-1000" manufactured by Nippon Soda Co., Ltd., 692.1 parts of toluene and 42.1 parts of maleic acid anhydride were placed into a suitable reaction vessel equipped with a thermometer, a stirrer, a cooling tube, a nitrogen introducing tube and an addition funnel. The reaction vessel was pressurized, and was risen to 1 30 C.

A temperature was retained until a peak (1780 cop) of acid anhydride disappeared as measured by FT-IR and, at a disappearance time, the material was cooled to obtain a polyolefin-based macro monomer solution (solid content so%).

l0122l 102.9 Parts of a polyolefin-based macro monomer and 103.0 parts of toluene were placed into a suitable reaction vessel, and a temperature was risen to 110 C. Separately, 9.3 parts of butyl acrylate, 10.0 parts of butyl methacrylate, 10.0 parts of maleic acid, 9.0 parts of hydroxyethyl acrylate, 10.0 parts of hydroxybutylmethacrylate, 3.2 parts of methacrylic acid and 1.5 parts of t-butylperoxy-2-ethyl hexanoate were mixed to prepare a solution, and the solution were added dropwise over 3 hours while stirring the reaction solution.

Thereafter, the reaction vessel was retained at 11 0 C for 30 minutes. To this was added dropwise a solution of 0.5 part of t-butylperoxy-2-ethyl hexanoate and 5.0 parts of toluene over 30 minutes. After stirring was continued for 90 minutes, the material was cooled to obtain a polyolefin elastomer (b-2) solution (solid content 40%).

[01231 The resulting polyolefin elastomer (b-2) had the properties of a number average molecular weight of 40000, a hydroxy group value of 100 and an acid value of 20 mgKOH/g.

[01241 Preparation ExamoIe 4 Preparation of non-anueous dispersion (a) Preparation of dispersion stable resin Parts of butyl acetate was placed into a vessel equipped with a stirrer, a temperature controller and a refluxing condenser. Then, 20 parts from a solution having the following composition:

[Table 2]

Methyl mathacrylate 38.9 parts Stearyl mathacrylate 38.8 parts 2-Hydroxyethyl acrylate _ 22.3 parts Azobisisobutyronitrile 5.0 parts was added, and a temperature was risen by heating while stirring. 85 Parts of . : the reminder of the aforementioned mixed solution was added dropwise at 11 0 C for 3 hour, and then, a solution of 0.5 part of azobisisobutyronitrile and 10 parts of butyl acetate was added dropwise over 30 minutes. The reaction solution was stirred to reflex for further 2 hours to increase a rate of change to a resin, and the reaction was completed to obtain an acryl resin having a solid content of 50% a number average molecular weight of 5600 and a SP value of 9.5.

0126l (b) Preparation of non-aqueous dispersion Parts of butyl acetate and 60 parts of the acryl resin obtained in the aforementioned (a) Preparation of a dispersion stable resin were placed into a vessel equipped with a stirrer, a condenser and a temperature controller. Then, a solution having the following composition:

012n [Table 3]

Styrene 7.0 parts Methacrylic acid 1.8 parts Methyl mathacrylate 12.0 parts Ethyl acrylate 8.5 parts 2-Hydroxyethyl acrylate 40.7 parts Azobisisobutyronitrile 1.4 parts was added dropwise at 1 00 C for 3 hours and, then, a solution of 0.1 part of azobisisobutyronitrile and 1 part of butyl acetate was added dropwise over 30 minutes. Stirring of the reaction solution was further continued for 1 hour, to obtain an emulsion having a solid content of 60% and a particle diameter of 180 nm. This emulsion was diluted with butyl acetate to obtain a core-shell type butyl acetate dispersion having a non-aqueous dispersion content of 40%, a viscosity of 300 cps (25 C) and a particle diameter of 1 80nm. This non-aqueous dispersion resin had TO of 23 C, a hydroxy group value of 162 and a SP value of 11.8, and a difference in SP values of all or a core part of this non-aqueous dispersion resin was 2.3.

0128l Example 1

Intermediate paint 1 14.3 Parts of the urethane-modified polyester resin obtained in the previous Preparation Example 1, 500 parts of BOR-904 (polyolefin elastomer manufactured by Sakai Chemical Industry Co., Ltd., ethylene/propylene copolymer, solid content 10%, acid value 4 mgKOH/g), 66.7 parts of Duranate MF-K60X (blocked isocyanate manufactured by Asahi Chemical Industry Co., Ltd., solid content 60%), 95 parts of CR-97 (titanium oxide manufactured by Ishihara Sangyo Kaisha, Ltd.), 5 parts of MA-100 (carbon black pigment manufactured by Mitsubishi Chemical Co., Ltd. ), and 0.1 part of Disparon 4200-20 (anti-settle agent manufactured by Kusumoto Chemicals, Ltd.) were placed into a 1 L vessel, and mixed with a disper, the same weight as that of the mixture of GB503M (glass beads having a particle diameter of 1.6 mm) was added, and dispersed at room temperature for 2 hours using a desk size SO mill. A particle size at completion of dispersion with a grind gauge was 5 1lm or less. Filtration of glass beads afforded an intermediate paint. This paint was diluted to 20 seconds/20 C with a mixed solvent of toluene/Swazole-100 (aromatichydrocarbon solvent manufactured by Exon) = 1/1 using a No.4 Ford cup. A solid content of the diluted paint was 25%, and the pigment concentration (PWC) was 50%.

[01291 Base paint An acrylmelamine-based metallic base pigment UOrga TO H600 1 8J Green Metallic" manufactured by Nippon Paint Co., Ltd. was diluted to 17 second/20 C with a mixed solvent of ethoxyethyl propionate/S-100 (aromatic hydrocarbon solvent manufactured by Exon) /toluene = 1/1/2 using a No.3 Ford cup. A non-volatile fraction of a paint at application was 31%. A non-volatile fraction at deposition was 65%.

[01301 Clear paint An acid epoxy curing-based clear pains Smack 0-1600 Clear" manufactured by Nippon Paint Co., Ltd. was diluted to 26 seconds/20 C with a mixed solvent of ethoxyethyl propionate/S-100 (aromatic hydrocarbon solvent manufactured by Exon) = 1/1 using a No.4 Ford cup. A non-volatile fraction of a paint at application was 50%. In addition, a non-volatile fraction at deposition was61%.

0131l Coatina film formation method A cationic electrodeposition paint UPower Top V-20" (manufactured by Nippon Paint Co., Ad.) was electrodeposition-applied on a SPC steel plate having a thickness of 0.8 mm, a length of 30 cm and a width of 10 cm which had been treated with zinc phosphate, so that a dry film thickness became 20 am, followed by baking at 160 C for 30 minutes, to prepare a coated plate.

Then, this was adhered to a moving body, the aforementioned intermediate paint was coated with "microbe!" (rotation atomizing type electrostatic coating machine) while moving, so that a dry film thickness became 20 1lm and, after application, setting was performed at intervals of 10 minutes.

[01321 Then, the aforementioned base paint was applied with a "microbe!" and a Umetabel" at 2 stage so that a dry film thickness became 15 m. Between two applications, an interval of 2.5 minutes was taken. After the second application, setting of 8 minutes was performed. Then, the aforementioned clear paint was coated with a "microbell" at 1 stage so that a dry film thickness became 35 ram, and 7 minutes setting was performed. Then, the resulting coated plate was baked at 1 40 C for 30 minutes in a dryer.

[01 By Method of film assessment Regarding the resulting coated plate, appearance of a coated composite film was assessed using WS-DOI (film appearance measuring equipment manufactured by Bick Chemie). By WS-DOI, assessment of appearance of a coating film, in particular, assessment of gloss appearance can be expressed by a Wa value. As a Wa value grows smaller, there is gloss appearance, and appearance is better.

lO134] Further, the anti-chipping property of the resulting coated plate was assessed as follows: Using a glabero tester (manufactured by Suga Test Instrument Co., Ltd.), 300 pieces of No.7 ground stones were collided to a film at an angle of 45 from a distance of 35 cm at an air pressure of 3.0 kgf/cm2.

After washing with water and drying, a peeling test was performed using an industrial gummed tape manufactured by Nichiban and, thereafter, a degree of peeling of a film in terms of a peeling diameter and the number of peelings was observed and assessed with naked eyes.

lO135] An elongation rate of an intermediate coating film was assessed as follows: An intermediate paint was applied on a polypropylene plate having a thickness of 3 mm so that a dry film thickness became 40 to 60 Elm, setting was performed for about 20 minutes, followed by baking drying at 1 40 C for 20 minutes. The resulting film was cut so that an effective part became length 5 cm x width 1cm, and this was peeled from a polypropylene plate to obtain a free film having no support. Regarding this free film, an elongation rate was measured with a tensile tester (Tension" manufactured by Toyo Boldwin) at a tensile rate of'10 mm/mint under the environment of 20 C.

0136l The above results are shown in Table 4.

01371 Examole 2 Intermediate paint 2 28.6 Parts of the urethane-modified polyester resin obtained in the previous Preparation Example 1,148 parts of PP-2001 (polypropylene-based elastomer manufactured by Mitsui Chemicals, Inc., solid content 27%, acid value 6.6 mgKOH/g, hydroxy group value 13.6),16.7 parts of U-128 (melamine resin manufactured by Mitsui Sitec, solid content 60%), 33.3 parts of MF-K60X (active methylene-type blocked isocyanate manufactured by Asahi Chemical Industry Co., Ltd., solid content 60%), 25 parts of the non-aqueous dispersion obtained in the previous Preparation Example 4, 39.2 parts of CR-97 (titanium oxide manufactured by Ishihara Sangyo Kaisha, Ltd.), 2.9 parts of MA-100 (carbon black pigment manufactured by Mitsubishi Chemical Co., Ltd.), 0.1 part of Disparon 4200-20 (anti-settle agent manufactured by Kusumoto Chemicals, Ltd.) and 0.8 part of LMS-300 (talc manufactured by Fuji Talc) were placed into a 1 L vessel, and mixed with a disper, the same amount as that of the mixture of GB503M (glass beads having a particle diameter of 1.6 mm) was added, followed by dispersion at room temperature for 2 hours using a desk size SO mill. A particle size at completion of dispersion with a grind gauge was 5,um or less. Filtration of glass beads afforded an intermediate paint. This paint was adjusted to 20 seconds/20 C with a mixed solvent of toluene/Suwazole-100 (aromatic hydrocarbon solvent manufactured by Exon) = 1/1 using a No.4 Ford cup. A solid content of the diluted paint was 46%, and the pigment - ^ concentration (PWC) in a paint was 30%.

l0138l According to the same manner as that of Example 1 except that the aforementioned intermediate paint 2 was used in place of the intermediate paint 1, a coated composite film was prepared, and assessed as described above.

The results are shown in Table 4.

0139l Example 3

Intermediate paint 3 4.3 Parts of the urethanmodified polyester resin obtained in the previous Preparation Example 1, 125 parts of the polyolefin elastomer (b-1) obtained in the previous Preparation Example 2, 66.7 parts of MF-K60X (blocked isocyanate manufactured by Asahi Chemical Industry Co., Ltd., solid content 60%), 95 parts of CR-97 (titanium oxide manufactured by Ishihara Sangyo Kaisha, Ltd.), 5 parts of MA-100 (carbon black pigment manufactured by Mitsubishi Chemical Co., Ltd.), and 0.1 part of Disparon 4200-20 (anti-settle agent manufactured by Kusumoto Chemicals, Ltd.) were placed into a 1 L vessel, and a pigment was prepared like the intermediate paint 1 of Example 1. A solid content of the resulting diluted paint was 51%, and the pigment concentration (PWC) in a paint was 50%.

l0140l According to the same manner as that of Example 1 except that the aforementioned intermediate paint 3 was used in place of the intermediate paint 1, a coated composite film was prepared, and similarly assessed. The results are shown in Table 4.

[01411 Example 4

Intermediate saint 4 28.6 Parts of the urethane-modified polyester resin obtained in the - À : previous Preparation Example 1, 99.9 parts of the polyolefin elastomer (b- 2) obtained in the previous Preparation Example 3, 16.7 parts of U-128 (melamine resin manufactured by Mitsui Sitec, solid content 60%), 33.3 parts of MF-K60X (active methy!ene-type blocked isocyanate manufactured by Asahi Chemical Industry Co., Ad., solid content 60%), 25 parts of the non-aqueous dispersion obtained in the previous Preparation Example 4, 39.2 parts of CR-97 (titanium oxide manufactured by Ishihara Sangyo Kaisha, Ltd.), 2.9 parts of MA-100 (carbon black pigment manufactured by Mitsubishi Chemical Co., Ltd.), 0.1 part of Disparon 4200-20 (anti-settle agent manufactured by Kusumoto Chemicals, Ad.), and 0.8 part of LMS-300 (talc manufactured by Fuji Talc) were placed into a 1 L vessel, and a paint was prepared like the intermediate paint 2 of Example 2. A solid content of the resulting diluted paint was 45%, and the pigment concentration (PWC) in a paint was 30%.

2] According to the same manner as that of Example 1 except that the aforementioned intermediate paint 4 was used in place of the intermediate paint 1, a coated composite film was prepared, and was similarly assessed. The results are shown in Table 4.

[01431 Comparative Example 1 Intermediate paint 5 107 Parts of the urethane-modified polyester resin varnish obtained in the previous Preparation Example 1, 280 parts of CR-97 (titanium oxide manufactured by Ishihara Sangyo Kaisha, Ltd.), 13 parts of MA-100 (carbon black pigment manufactured by Mitsubishi Chemical Co., Ltd.), 7 parts of LMS-100 (scaly talc manufactured by Fuji Talc), 47 parts of butyl acetate and 47 parts of xylene were placed into a 1 L vessel, and mixed with a disper, the same

-

weight as that of the mixture of GB503M (glass beads having a particle diameter of 1.6 mm) was added, followed by dispersion at room temperature for 3 hours using a desk size SG mill, to obtain a gray pigment paste. A particle size at completion of dispersion with a grind gauge was 5 Am or less. Filtration of glass beads afforded a pigment paste. To 100 parts of this pigment paste were added 24 parts of the urethane-modified polyester resin (a) in Preparation;: Example 1, 24 parts of MF-K60X (active methylene-type blocked isocyanate manufactured by Asahi Chemical Industry Co., Ltd., solid content 60%), and 24 parts of U-20N60 (melamine resin manufactured by Mitsui Sitec, solid content 60%). To this was added a mixed solvent of ethoxyethyl propionate/S-100 (aromatic hydrocarbon solvent manufactured by Exxon Co.) = 111, and the material was diluted to 19 seconds/20 C using a No.4 Ford cup. A solid content of the diluted paint was 49%, and the pigment concentration (PWC) in a paint was 30%.

101441 According to the same manner as that of Example 1 except that the aforementioned intermediate paint 5 was used in place of the intermediate paint 1, a coated composite film was prepared, and similarly assessed. The results are shown in Table 4.

014q Comparative Examole 2 CP-101 (chipping primer manufactured by Nippon Paint Co., Ltd.) was spray coated on a steel plate which had been electrodeposition-coated and baking-cured so as to have a film thickness of 5 Am before a coating film was formed using the intermediate paint 5 using in Comparative Example 1. After setting was performed for 5 minutes, an intermediate coating film was formed using the intermediate paint 5 described in Comparative Example 1. Then, using the base paint and the clear paint described in Example 1, a coated composite film was prepared as in Example 1, and was similarly assessed.

The results are shown in Table 4.

01461 Table 4]

Exampie Exampie Exampie Example Exampie Exampie Assessment of appearal Ice Diva 25 21 21 19 21 29 damm)eter 1.5 1.5 1.2 1.2 2.0 1.5 Number Antipeelings 10 8 10 9 20 10 p i n E I o n g a t- _ _ co at i n 7 0 100 8 0 10 0 3 0 3 0

Claims (5)

- - WHAT IS CLAIMED IS

1. A method for producing a coated composite film, comprising forming an electrocoated film on a substrate, and then successively applying an l intermediate paint, a base paint and a clear paint in a wet-on-wet manner, followed by baking and curing the applied three layers at once, wherein said intermediate paint contains, on the basis of a resin solid content, (a) 5 to 30% by weight of a urethane-modified polyester resin having a number average molecular weight of 1,500 to 3,000, obtained by reacting an aliphatic isocyanate compound with a hydroxy group-containing polyester resin having a glass transition point (Tg) of 40 to 80 C, the polyester being obtained by polycondensation of an acid component containing 80 mol% or more of isophthalic acid and a polyhydric alcohol, (b) 30 to 60% by weight of a polyolefin elastomer having an acid group and/or a hydroxy group, and (c) 10 to 30% by weight of a blocked isocyanate compound.

2. The method according to claim 1, wherein said intermediate paint further comprises, on the basis of a resin solid content, (d) up to 20 % by weight of a melamine resin.

3. The method according to claim1 or 2, wherein said intermediate paint further comprises, on the basis of a resin solid content, (e) up to 15% by weight of a non-aqueous dispersion resin having a core- shell structure.

4. The method according to any of claims 1 to 3, wherein said polyolefin elastomer (b) has an acid value of 1 to 50 mg KOH/g and/or a hydroxy group value of 1 to 200. 41 _

5. The method according to any of claims 1 to 4, wherein said blocked isocyanate compound is one of which isocyanate group is blocked with a compound having an active methylene group.