WO2008156125A2 - Multilayer coating film-forming method - Google Patents

Multilayer coating film-forming method Download PDF

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Publication number
WO2008156125A2
WO2008156125A2 PCT/JP2008/061176 JP2008061176W WO2008156125A2 WO 2008156125 A2 WO2008156125 A2 WO 2008156125A2 JP 2008061176 W JP2008061176 W JP 2008061176W WO 2008156125 A2 WO2008156125 A2 WO 2008156125A2
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WO
WIPO (PCT)
Prior art keywords
resin
paint
group
acid
coating film
Prior art date
Application number
PCT/JP2008/061176
Other languages
French (fr)
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WO2008156125A8 (en
WO2008156125A3 (en
Inventor
Yoshiyuki Yukawa
Original Assignee
Kansai Paint Co., Ltd.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Kansai Paint Co., Ltd. filed Critical Kansai Paint Co., Ltd.
Priority to CN200880021056.8A priority Critical patent/CN101687220B/en
Priority to JP2009553848A priority patent/JP4991883B2/en
Publication of WO2008156125A2 publication Critical patent/WO2008156125A2/en
Publication of WO2008156125A3 publication Critical patent/WO2008156125A3/en
Publication of WO2008156125A8 publication Critical patent/WO2008156125A8/en

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D7/00—Processes, other than flocking, specially adapted for applying liquids or other fluent materials to particular surfaces or for applying particular liquids or other fluent materials
    • B05D7/50—Multilayers
    • B05D7/56—Three layers or more
    • B05D7/57—Three layers or more the last layer being a clear coat
    • B05D7/572—Three layers or more the last layer being a clear coat all layers being cured or baked together
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D2202/00—Metallic substrate
    • B05D2202/10—Metallic substrate based on Fe
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D7/00—Processes, other than flocking, specially adapted for applying liquids or other fluent materials to particular surfaces or for applying particular liquids or other fluent materials
    • B05D7/50—Multilayers
    • B05D7/56—Three layers or more
    • B05D7/57—Three layers or more the last layer being a clear coat
    • B05D7/577—Three layers or more the last layer being a clear coat some layers being coated "wet-on-wet", the others not

Definitions

  • This invention relates to a multilayer coating film -forming method which can reduce the use amount of solvent and shorten the process steps, and yet excels in coating workability and finished appearance.
  • VOC volatile organic solvent
  • the outer panel portions of car bodies are normally coated with multilayer coating film comprising undercoating film of cationic electrodeposition paint, intermediate coating film and top coating film, for the purpose of imparting corrosion resistance and favorable appearance.
  • JP Sho 61 (1986)"141969A discloses a metallic finishing method comprising applying onto a coating object an organic solvent-based or non-aqueous dispersion type thermosetting paint which contains a neutralization product of polyvalent carboxylic acid resin and amino resin but is free of metallic pigment, adjusting the viscosity of the coated paint to at least 10 poises (20 0 C), applying thereonto a thermosetting water-based metallic paint, further applying thereonto a transparent thermosetting paint, and curing thus formed three-layered coating film simultaneously by heating.
  • thermosetting water-based metallic paint even when the viscosity of the organic solvent-based or non- aqueous dispersion type thermosetting paint is adjusted to the above-specified range according to the above method, still such defects as degradation in finished appearance or occurrence of cracks in the coating film after application of a thermosetting water-based metallic paint may take place, for example, under highly humid condition in which the viscosity control becomes insufficient to disturb uniform orientation of metallic pigment in the thermosetting water-based metallic paint applied thereon.
  • JP Hei 11 (l999)-197592A proposes a multilayer coating film-forming method characterized in that the metallic pigment-free organic solvent-based or non-aqueous dispersion type thermosetting paint contains specific gelled fine polymer particles.
  • the effect of this method to prevent the aforesaid defects is still insufficient and, in particular, the problem remains that cracks may occur under high humidity condition.
  • the object of the present invention is to provide a method which realizes reduction in use amount of solvent and shortening of the process steps, and which can form multilayer coating film with excellent coating workability and finished appearance even under high humidity condition.
  • a multilayer coating film-forming method comprising applying a base coating paint, successively applying onto the uncured coated surface a water-based coloring paint and a clear paint, and then heating the three-layered coating film formed of the base coating paint, water-based coloring paint and clear paint to cure them simultaneously, in which a paint containing a specific tertiary amino group -containing resin and specific crosslinking agent is used as the base coating paint, and come to complete the present invention.
  • the present invention provides a multilayer coating film-forming method comprising applying base coating paint (A) onto a coating object, successively applying onto the so formed uncured coated surface water-based coloring paint (B) and clear paint (C), and then heating to simultaneously cure the three-layered coating film composed of the paints (A), (B) and (C), the method being characterized in that the base coating paint (A) contains
  • tertiary amino group -containing resin which is obtained by copolymerizing tertiary amino group -containing unsaturated monomer Or I), polyoxyalkylene group -containing nonionic unsaturated monomer (b"2) and other unsaturated monomer (b-3), and
  • the base coating paint (A) contains carboxyl group- and hydroxyl group -containing resin (a) and tertiary amino group -containing resin (b).
  • a structure which may be regarded as pseudo-crosslinkage caused by acid-base interaction between the carboxyl groups in the resin (a) and the tertiary amino groups in the resin (b) is formed to exhibit viscosity-raising effect, which leads to favorable viscous effect in the two-layered coating film formed by subsequent application of the water-based coloring paint (B).
  • the base coating paint (A) which is first applied onto a coating object is a paint containing a carboxyl group- and hydroxyl group -containing resin (a), tertiary amino group -containing resin (b), and crosslinking agent (c) reactable with hydroxyl group.
  • any resin which contains carboxyl groups and hydroxyl groups in its molecules can be used as the resin (a), without any particular limitation.
  • resins for example, acrylic resin, polyester resin, polyether resin, polycarbonate resin, polyurethane resin and the like can be named.
  • Carboxyl groups in resin (a) brings about viscosity-developing effect at the coated film of base coating paint (A), by forming a pseudo-crosslinked structure due to the acid-base interaction with tertiary amino groups of resin (b). Also hydroxyl groups in resin (a) contribute to cure the coating film, upon reaction with the crosslinking agent (c).
  • the resin (a) can have an acid value within a range of generally 2 - 100 mgKOH/g, preferably 5 - 80 mgKOH/g, inter alia, 5 — 65 mgKOH/g.
  • the carboxyl group- and hydroxyl group -containing resin (a) can have a hydroxyl value within a range of generally 20 - 200 mgKOH/g, preferably 35 - 180 mgKOH/g, inter alia, 50 - 150 mgKOH/g.
  • carboxyl group- and hydroxyl group -containing resin (a) As preferred examples of the carboxyl group- and hydroxyl group -containing resin (a), carboxyl group- and hydroxyl group -containing acrylic resin, carboxyl group- and hydroxyl group -containing polyester resin, and carboxyl group- and hydroxyl group -containing polyurethane resin can be named.
  • Carboxyl group- and hydroxyl group -containing acrylic resin can be synthesized by, for example, copolymerizing carboxyl group -containing unsaturated monomer (M- 1), hydroxyl group -containing unsaturated monomer (M- 2) and other copolymerizable unsaturated monomer (M- 3), according to the accepted practice.
  • Carboxyl group -containing unsaturated monomer (M- 1) encompasses those compounds having at least one carboxyl group and one unsaturated bond per molecule, examples of which include acrylic acid, methacrylic acid, crotonic acid, itaconic acid, maleic acid and maleic anhydride. These may be used either alone or in combination of two or more.
  • Hydroxyl group -containing unsaturated monomer (M-2) encompasses those compounds having at least one hydroxyl group and one unsaturated bond per molecule, the hydroxyl groups acting chiefly as the functional group as the functional in the reaction of the carboxyl group- and hydroxyl group -containing acrylic resin with the crosslinking agent (c) which is reactable with hydroxyl group.
  • hydroxyl group-containing unsaturated monomer (M"2) monoesterification products of (meth)acrylic acids with C2-io dihydric alcohols are particularly preferred, specific examples including hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth) aery late and the like.
  • (meth)acrylate means acrylate or methacrylate.
  • hydroxyl group -containing unsaturated monomer (M"2) for example, compounds obtained by further ring-opening polymerization of hydroxyalkyl (meth) acrylate such as 2-hydroxyethyl (meth) acrylate with ⁇ -caprolactone or the like, such as PLACCEL FA-I, PLACCEL FA-2, PLACCEL FA- 3, PLACCEL FA-4, PLACCEL FA-5, PLACCEL FM-I, PLACCEL FM-2, PLACCEL FM-3, PLACCEL FM-4, PLACCEL FM-5 (tradename, Daicel Chemical Industries, Ltd.) and the like can be conveniently used.
  • hydroxyalkyl (meth) acrylate such as 2-hydroxyethyl (meth) acrylate with ⁇ -caprolactone or the like
  • hydroxyl group -containing unsaturated monomer (M-2) furthermore, polyethylene glycol mono(meth)acrylate, polypropylene glycol mono(meth)acrylate, 2-hydroxy3-phenoxypropyl (meth)acrylate, 2-hydroxy-3"butoxypropyl (meth)acrylate, monohydroxyethyl (meth) acrylate phthalate and the like can also be used.
  • copolymerizable unsaturated monomers include those compounds having one unsaturated bond per molecule, other than above-named carboxyl group -containing unsaturated monomer (M- 1) and hydroxyl group -containing unsaturated monomer (M-2), and as their specific examples, those listed in the following (l) - (6) can be named: (l) monoesterified products of (mett ⁇ acrylic acid with Ci-20 monohydric alcohol- for example, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, irbutyl (meth)acrylate, iso-butyl (meth) acrylate, tert-butyl (meth)acrylate, 2-ethylhexyl (meth) acrylate, cyclohexyl (meth)acrylate, lauryl (meth)acrylate, isobornyl (meth) acrylate, tridecyl (meth) monoesterified
  • aromatic unsaturated monomers f or example, styrene, crmethylstyrene and vinyltolueneJ
  • glycidyl group-containing unsaturated monomers ' - compounds containing at least one each of glycidyl group and unsaturated bond per molecule for example, glycidyl acrylate and glycidyl methacrylate;
  • unsaturated bond-containing amide compounds for example, acrylamide, methacrylamide, dimethylacrylamide, N,N-dimethylpropyl acrylamide, N-butoxymethyl acrylamide, N-methylol acrylamide, N-methylol methacrylamide and diacetonacrylamide ;
  • unsaturated bond-containing nitrile compounds-' for example, acrylonitrile and methacrylonitrile.
  • the carboxyl group- and hydroxyl group -containing acrylic resin can have an acid value within a range of generally 5 — 100 mgKOH/g, preferably 20 - 80 mgKOH/g, inter alia, 35 - 65 mgKOH/g. Where the acid value of the resin is less than 5 mgKOH/g, there are occasions in which the viscosity-developing effect due to the resin's interaction with tertiary amino group -containing resin (b) is reduced. Whereas, when it exceeds 100 mgKOH/g, water resistance of the coating film may deteriorate.
  • the carboxyl group- and hydroxyl group -containing acrylic resin can also have a hydroxyl value within a range of generally 20 - 150 mgKOH/g, preferably 35 - 120 mgKOH/g, inter alia, 50 — 100 mgKOH/g.
  • a hydroxyl value of the resin is less than 20 mgKOH/g, curability may become insufficient, and when it exceeds 150 mgKOH/g, water resistance of the coating film may deteriorate.
  • the carboxyl group- and hydroxyl group -containing acrylic resin can have a number- average molecular weight within a range of generally 2,000 - 100,000, preferably 3,000 - 50,000, inter alia, 4,000 — 20, 000.
  • the number- average molecular weight of a resin is a value converted of the number-average molecular weight measured with gel permeation chromatograph, HLC8120GPC (tradename, Tosoh Corporation), based on the number- average molecular weight of standard polystyrene.
  • Carboxyl group- and hydroxyl group -containing polyester resin can be prepared by per se known reaction, for example, through esterification reaction of polybasic acid with polyhydric alcohol.
  • Polybasic acid is a compound having at least two carboxyl groups per molecule, examples of which include phthalic acid, isophthalic acid, terephthalic acid, succinic acid, adipic acid, azelaic acid, sebacic acid, tetrahydrophthalic acid, hexahydrophthalic acid, maleic acid, fumaric acid, itaconic acid, trimellitic acid, pyromellitic acid and anhydrides thereof.
  • Polyhydric alcohol is a compound having at least two hydroxyl groups per molecule, examples of which include diols such as ethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 2,2-diethyl-l,3-propanediol, neopentyl glycol, 1,9-nonanediol, 1,4-cyclohexanediol, hydroxypivalic acid neopentyl glycol ester, 2-butyl-2-ethyM,3-propanediol, 3-methyM,5-pentanediol, 2,2,4-trimethylpentanediol and hydrogenated bisphenol A; at least trivalent polyols such as trimethylolpropane, trimethylolethane, glycerine and pentaeryth
  • These compounds may also be forming ethers with lower alcohols. It is also permissible to react a monoepoxy compound such as ⁇ -olefin epoxide, e.g., propylene oxide, butylene oxide or the like, CARDURA ElO (tradename, Japan Epoxy Resin Co., glycidyl ester of synthetic highly branched saturated fatty acid) or the like, with an acid and introduce such a compound into polyester resin.
  • Carboxyl groups can be introduced into polyester resin by such method as carrying out the above esterification reaction using excessive polybasic acid; or, after an esterification reaction of polybasic acid with polyhydric alcohol, further reacting the product with polybasic acid such as trimellitic acid or anhydride thereof.
  • the carboxyl group- and hydroxyl group -containing polyester resin may be a fatty acid-modified polyester resin which is modified with (semi)drying oil fatty acid such as linseed oil fatty acid, coconut oil fatty acid, safflower oil fatty acid, soybean oil fatty acid, sesame oil fatty acid, perilla oil fatty acid, hempseed oil fatty acid, tall oil fatty acid, dehydrated castor oil fatty acid and the like. It is generally adequate that the modification amount with these fatty acid is not more than 30 mass% in terms of oil length.
  • the carboxyl group- and hydroxyl group -containing polyester resin may also be one which is partially reacted with monobasic acid such as benzoic acid.
  • the carboxyl group- and hydroxyl group -containing polyester resin can have an acid value within a range of generally 5 - 70 mgKOH/g, preferably 15 - 55 mgKOH/g, inter aha, 25 - 45 mgKOH/g.
  • acid value of the resin is less than 5 mgKOH/g, there are occasions in which the viscosity-developing effect due to the resin's interaction with tertiary amino group -containing resin (b) is reduced.
  • it exceeds 70 mgKOH/g water resistance of the coating film may deteriorate.
  • the carboxyl group- and hydroxyl group -containing polyester resin can have a hydroxyl value within a range of generally 30 - 200 mgKOH/g, preferably 50 - 180 mgKOH/g, inter alia, 70 - 150 mgKOH/g. Where hydroxyl value of the resin is less than 30 mgKOH/g, curability may become insufficient, and when it exceeds 200 mgKOH/g, water resistance of the coating film may deteriorate.
  • the carboxyl group- and hydroxyl group -containing polyester resin can have a number-average molecular weight within a range of generally 300 - 50,000, in particular, 500 - 20,000, inter alia, 1,000 - 10,000. Where number- average molecular weight of the resin is less than 300, the coating film may exhibit insufficient weatherability, while smoothness of the coated surface may be impaired when it exceeds 50,000.
  • Carboxyl group- and hydroxyl group -containing polyurethane resin-' Carboxyl group- and hydroxyl group -containing polyurethane resin can be obtained, for example, by reacting polyol which contains carboxyl group-containing polyol, with polyisocyanate according to the accepted practice.
  • carboxyl group -containing polyol for example, 2,2-dimethylolpropionic acid, 2,2-dimethylolbutanoic acid and the like can be named, 2,2-dimethylolpropionic acid being particularly preferred.
  • a minor amount of a solvent such as N-methylpyrrolidone may be used for accelerating the reaction.
  • polyols which do not contain carboxyl groups include dihydric alcohols such as ethylene glycol, diethylene glycol, propylene glycol, butylene glycol, hexamethylene glycol and the like; and trihydric alcohols such as trimethylolpropane, glycerine, pentaerythritol and the like.
  • dihydric alcohols such as ethylene glycol, diethylene glycol, propylene glycol, butylene glycol, hexamethylene glycol and the like
  • trihydric alcohols such as trimethylolpropane, glycerine, pentaerythritol and the like.
  • high molecular weight for example, polyetherpolyol, polyesterpolyol, acrylpolyol, epoxypolyol and the like can be named.
  • polyetherpolyol for example, polyethylene glycol, polypropylene glycol, polytetramethylene glycol and the like can be named.
  • polyester polyol for example, polycondensation products of alcohols such as aforesaid dihydric alcohol, dipropylene glycol, 1,4-butanediol, 1,6-hexanediol, neopentyl glycol and the like, with dibasic acid such as adipic acid, azelaic acid, sebacic acid and the like; lactone-derived ring-opening polymer polyol such as poly cap rolactone, polycarbonatediol and the like can be named.
  • polyisocyanate to be reacted with above polyol for example, aliphatic polyisocyanates such as hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, dimeric acid diisocyanate, lysine diisocyanate and the like and biuret type adducts or isocyanurate ring adducts of these polyisocyanates; alicyclic diisocyanates such as isophorone diisocyanate, 4,4'-methylenebis(cyclohexylisocyanate), methylcyclohexane-2,4- or 2,6-diisocyanate, 1,3- or l ⁇ -diGsoeyanatomethyOcyclohexane, 1,4-cyclohexane diisocyanate, 1,3-cyclopentane diisocyanate, 1,2-cyclohexane diisocyanate and the like and biuret type adducts or isocyan
  • aromatic diisocyanate compounds such as xylylene diisocyanate, metaxylylene diisocyanate, tetramethylxylylene diisocyanate, tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 1,5 -naphthalene diisocyanate, 1,4- naphthalene diisocyanate, 4,4'toluidine diisocyanate, 4,4'-diphenylether diisocyanate, m- or p-phenylene diisocyanate, 4,4'-biphenylene diisocyanate, 3 ) 3'-dimethyl-4,4'-biphenylene diisocyanate, bis(4-isocyanatophenyl)sulfone, isopropylidenebis- (4-phenylisocyanate) and the like and biuret type adducts or isocyanurate ring adducts of these polyisocyan
  • the carboxyl group- and hydroxyl group -containing polyurethane resin can have an acid value within a range of generally 2 - 50 mgKOH/g, preferably 5 - 40 mgKOH/g, inter alia, 5 - 20 mgKOH/g.
  • acid value of the resin is less than 2 mgKOH/g, there are occasions in which the viscosity-developing effect due to the resin's interaction with tertiary amino group -containing resin (b) is reduced.
  • it exceeds 50 mgKOH/g water resistance of the coating film may deteriorate.
  • the carboxyl group- and hydroxyl group -containing polyurethane resin can have a number- average molecular weight within a range of generally 1,000 - 3,000,000, in particular, 10,000 - 2,000,000, inter alia, 20,000 - 1,000,000. Where number- average molecular weight of the resin is less than 1,000, the coating film may exhibit insufficient weatherability, while smoothness of the coated surface may be impaired when it exceeds 3,000,000.
  • secondary monoamines such as diethylamine, diethanolamine, drn- or diisopropanolamine, N-methylethanolamine, N-ethylethanolamine and the like; tertiary monoamines such as N,N'dimethyl- ethanolamine, trimethylamine, triethylamine, triisopropylamine, methyldiethanolamine and the like; and polyamines such as diethylenetriamine, hydroxyethylaminoethylamine, ethylaminoethylamine, methylaminopropylamine and the like. These can be used either alone or in combination of two or more.
  • Suitable use rate of the basic substance for the neutralization is normally 0.1 - 1.0 equivalent, in particular, 0.2 — 0.8 equivalent to the carboxyl groups in the resin (a).
  • Tertiary amino group -containing resin (b) encompasses, in particular, tertiary amino group-containing acrylic resin which is obtained by copolymerizing tertiary amino group -containing unsaturated monomer Otrl), polyoxyalkylene group -containing, nonionic unsaturated monomer (b-2) and other unsaturated monomer (b-3).
  • Tertiary amino group -containing unsaturated monomer (b-l) Tertiary amino group -containing polymerizable unsaturated monomer (b-l) is the monomeric component for introducing tertiary amino groups into the tertiary amino group -containing resin (b), and has a tertiary amino group and unsaturated group per molecule.
  • N,N-dialkylaminoalkyl (meth)acrylates such as N,N-dimethylaminoethyl (meth)acrylate, N,N-diethylaminoethyl (mettOacrylate, N,N-dimethylaminopropyl (meth)acrylate, N,N-di-t-butylaminoethyl (meth)acrylate, N,N-dimethylaminobutyl (meth)acrylate and the like
  • N,N-dialkylaminoalkyl (meth)acrylamides such as N,N-dimethylaminoethyl (meth)acrylamide, N,N-diethylaminoethyl (meth)acrylamide, N,N-dimethylaminopropyl (meth)acrylamide and the like.
  • These monomers can be used either alone or in combination of two or more.
  • N,N-dialkylaminoalkyl (meth)acrylates in particular, N,N'dimethylaminoethyl (meth)acrylate, are preferred as tertiary amino group -containing polymerizable unsaturated monomers.
  • tertiary amino groups introduced into tertiary amino group -containing resin (b) by such tertiary amino group -containing polymerizable unsaturated monomer (b- l) act for expressing viscosity of coated paint attributable to pseudo-crosslinkage forming effect by the acid-base interaction with the carboxyl groups in resin (a).
  • Polyoxyalkylene group -containing nonionic unsaturated monomer (b"2) is the monomeric component for introducing polyoxyalkylene groups into tertiary amino group -containing resin (b) to impart hydrophilicity to the tertiary amino group-containing resin (b) and to inhibit excessive interaction between the resins (a) and (b), which has polyoxyalkylene group and unsaturated group per molecule.
  • polyoxyalkylene group polyoxyethylene group, polyoxypropylene group, groups having polyoxyethylene- polyoxypropylene block structure and the like can be named.
  • Polyoxyalkylene group preferably has a molecular weight within a range of generally 200 - 3,000, in particular, 300 - 2,500.
  • R 1 stands for hydrogen or methyl
  • R 2 stands for hydrogen or Ci-4 alkyl
  • m is an integer of 4 - 60, preferably 6 - 50
  • n is an integer of 2 or 3, preferably 2, wherein the m oxyalkylene units (CnEbnO) may be the same or different can be named.
  • Such monomer (b-2) include tetraethylene glycol (meth)acrylate, methoxytetraethylene glycol (meth)acrylate, ethoxytetraethylene glycol (meth)acrylate, n-butoxytetraethylene glycol (meth)acrylate, tetrapropylene glycol (meth)acrylate, methoxytetrapropylene glycol (meth)acrylate, ethoxytetrapropylene glycol (meth)acrylate, n-butoxytetrapropylene glycol (meth)acrylate, polyethylene glycol (meth)acrylate, polypropylene glycol (meth)acrylate, methoxypolyethylene glycol (meth)acrylate, ethoxypolyethylene glycol (meth)acrylate and the like. Of these, particularly polyethylene glycol (meth)acrylate and polypropylene glycol (meth)acrylate are preferred. These monomers can be used either alone or in combination of two or more.
  • Still other unsaturated monomer (b-3) includes unsaturated monomers other than the above-described monomers (Vl) and (b-2), which are copolymerizable with these monomers (b-l) and (b-2) and are suitably selected according to the properties desired for the tertiary amino group -containing resin (b).
  • Such monomers (b-3) include Ci-24 straight chain or cyclic alkyl (meth)acrylate monomers such as methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, lauryl (meth)acrylate, stearyl (meth)acrylate, cyclohexyl (meth) aery late, isobornyl (meth)acrylate, tridecyl (mettOacrylate and the like!
  • hydroxyl group -containing unsaturated monomers such as 2-hydroxyethyl (meth) aery late, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate and the like; acrylamide, methacrylamide; oxetane ring-containing (meth)acrylates such as 3-ethyl-3-(meth)acryloyloxymethyloxetane, 3-methyl-3-(meth)- acryloyloxymethyloxetane, 3-butyl-3-(meth)acryloyloxymethyloxotane and the like!
  • aromatic vinyl compounds such as styrene, crmethylstyrene, vinyltoluene and the like; (meth)acrylonitrile, vinyl acetate, and the like.
  • unsaturated monomers can be used either alone or in combination of two or more.
  • the tertiary amino group -containing resin (b) preferably contains functional groups reactable with the crosslinking agent (c).
  • the functional groups reactable with the crosslinking agent (c) hydroxyl group is preferred.
  • the monomer (b-3) preferably contains, as at least a part of its component, a hydroxyl group -containing unsaturated monomer.
  • hydroxyl group -containing unsaturated monomer examples include monoesterified products of polyhydric alcohols with (meth)acrylic acid, such as 2-hydroxyethyl
  • 4-hydroxybutyl (meth)acrylate, polyethylene glycol mono(meth)acrylate, and the compounds formed by ring-opening polymerization of monoesterified product of polyhydric alcohol with (meth)acrylic acid, with ⁇ -caprolactone are preferred in respect of reactivity. These compounds can be used either alone or in combination of two or more.
  • the tertiary amino group -containing resin (b) can be obtained by copolymerizing the tertiary amino group -containing unsaturated monomer OrI), polyoxyethylene group -containing nonionic unsaturated monomer (b-2) and still other unsaturated monomer (b-3).
  • the use ratio of such monomers (b-l), (b"2) and 0r3) is not strictly limited, but is variable depending on physical properties desired for the tertiary amino group -containing resin.
  • the monomer (b-l) can be within a range of generally 1 - 25 mass%, preferably 3 — 20 mass%, inter alia, 5 — 15 mass%; the monomer (b ⁇ 2), within a range of generally 5 — 40 mass%, preferably 7 - 35 mass%, inter alia, 10 — 30 mass%; and the monomer (b"3), within a range of generally 35 - 94 mass%, preferably 45 — 90 mass%, inter alia, 55 - 85 mass%.
  • hydroxyl group -containing unsaturated monomer is preferably used within a range of generally 3 — 30 mass%, in particular, 5 — 25 mass%, based on the total amount of monomers (b-l), (b-2) and (b-3).
  • Copolymerization of those monomers (b-l), (b"2) and (b-3) can be carried out by the processes known per se, for example, by solution polymerization in organic solvent.
  • the copolymerization by solution polymerization process can be carried out, for example by dissolving or dispersing a mixture of the monomers (b-l), (b-2) and (b-3) with radical polymerization initiator in the organic solvent, and heating the solution or dispersion usually at about 80°C — about 200 0 C, for around 1 - 10 hours under stirring to effect the polymerization.
  • organic solvent for such solution polymerization use of hydrophilic organic solvent such as of propylene glycol type or dipropylene glycol type is preferred.
  • the tertiary amino group -containing resin (b) preferably has an amine value within a range of generally 3 - 100 mgKOH/g, in particular, 10 - 80 mgKOH/g, inter alia, 15 - 60 mgKOH/g, for favorable viscosity-expressing effect.
  • the tertiary amino group -containing resin (b) also preferably has a hydroxy value within a range of generally 10 - 130 mgKOH/g, in particular, 20 - 100 mgKOH/g, inter alia, 30 — 70 mgKOH/g, in respect of water resistance and curability of the coating film, and in consideration of smoothness of the coated surface and weatherability of resulting coating film, preferably has a number- average molecular weight within a range of generally 500 - 20,000, in particular, 1,000 - 10,000, inter alia, 3,000 - 7,000.
  • the monomer (b'l) component constituting the tertiary amino group -containing resin (b) contributes to viscosity expression of coated paint due to pseudo-crosslinkage-forming effect with the carboxyl group- and hydroxyl group -containing resin (a), and the monomer (b"2) component constituting the tertiary amino group -containing resin (b) contributes to formation of coating film having excellent finished appearance, as it suppresses excessive formation of the pseudo-crosslinked structure.
  • Crosslinking agent (c) reactable with hydroxyl group- The crosslinking agent (c) used in the present invention is subject to no particular limitation so long as it is a compound reactable with hydroxyl group and, for example, following melamine resin, blocked polyisocyanate compound, water- dispersible blocked polyisocyanate compound and the like can be conveniently used.
  • melamine resin examples include di-, tri-, tetra-, penta- and hexa-methylolmelamines and their alkyletherified products with alcohol (examples of the alkyl including methyl, ethyl, propyl, isopropyl, butyl, isobutyl, 2-ethylhexyl and the like) and their condensates.
  • melamine resin also include, for example, Nihon Cytec Industries, Inc.'s Cymel 303, Cymel 323, Cymel 325, Cymel 327, Cymel 350, Cymel 370, Cymel 380, Cymel 385, Cymel 212, Cymel 251, Cymel 254 and Mycoat 776 (all tradenames); Monsanto Chemical Co's Regimin 735, Regimin 740, Regimin 741, Regimin 745, Regimin 746 and Regimin 747 (all tradenames); Sumitomo Chemicals Co.'s Sumimal M55, Sumimal M30W and Sumimal M50W (all tradenames); and Mitsui Chemicals, Inc.'s U-VAN series such as U-VAN 20SB (tradename).
  • melamine resin those having mononuclear body content of at least 30 mass%, in particular, at least 40 mass%, inter alia, at least 45 mass%, are preferred.
  • alkyletherified melamine resin methoxyetherified or methoxybutoxy mixed etherified melamine resins in which the ratio of methoxy group is high, such that the mol ratio of methoxy group and butoxy group (methoxy group/butoxy group) is within a range of normally 100/0 - 60/40, in particular, 100/0 - 70/30, are preferred.
  • Specific examples of such melamine resin include Cymel 325, Cymel 327, Cymel 350, Cymel 212, Cymel 251, Mycoat 212 and Mycoat 776 (all tradenames, made by Nihon Cytec Industries, Inc.).
  • sulfonic acid such as paratoluenesulfonic acid, dodecylbenzenesulfonic acid, dinonylnaphthalene sulfonic acid and the like, or salts of these acids with amine can be used as catalyst.
  • Those melamine resins can be used either alone or in combination of two or more.
  • Blocked polyisocyanate compounds are the polyisocyanate compounds having at least two free isocyanate groups per molecule, whose isocyanate groups are blocked with blocking agent.
  • polyisocyanate compounds forming such blocked polyisocyanate compounds include aliphatic polyisocyanates such as hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, dimeric acid diisocyanate, lysine diisocyanate and the like, and biuret type adducts and isocyanurate adducts of these polyisocyanates; alicyclic diisocyanates such as isophorone diisocyanate, 4,4'-methylenebis(cyclohexylisocyanate), methylcyclohexane-2,4- or 2,6-diisocyanate, 1,3" or l,4-di(isocyanatomethyl)cyclohexane, 1,4-cyclohexane diisocyanate, 1,3-cyclopentane diisocyanate, 1,2-cyclohexane diisocyanate and the like, and biuret type adducts and isocyanur
  • the blocking agent is a compound which blocks free isocyanate groups upon reacting with isocyanate groups in a polyisocyanate compound. Normally such blocked polyisocyanate compound releases the blocking agent when heated to, for example, at least 100 0 C, preferably at least 130°C, to regenerate the free isocyanate groups which can react with hydroxyl groups.
  • the reaction of a blocking agent with a polyisocyanate compound can be carried out by a method known per se.
  • blocking agent examples include phenolic compounds such as phenol, cresol, xylenol, nitrophenol, ethylphenol, hydroxydiphenyl, butylphenol, isopropylphenol, nonylphenol, octylphenol, methyl hydroxybenzoate and the like! lactams such as ⁇ -caprolactam, ⁇ -valerolactam, ⁇ -butyrolactam, ⁇ -propiolactam and the like; aliphatic alcohols such as methanol, ethanol, propyl alcohol, butyl alcohol, amyl alcohol, lauryl alcohol and the like?
  • ethers such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, propylene glycol monomethyl ether, methoxymethanol and the like; benzyl alcohol; glycolic acid!
  • glycolic acid esters such as methyl glycolate, ethyl glycolate, butyl glycolate and the like; lactic acid; lactic acid esters such as methyl lactate, ethyl lactate, butyl lactate and the like; alcohols such as methylolurea, methylolmelamine, diacetone alcohol, 2 -hydroxy ethyl acrylate, 2-hydroxyethyl methacrylate and the like; oximes such as formamidoxime, acetamidoxime, acetoxime, methylethylketoxime, diacetylmonoxime, benzophenoxime, cyclohexanoxime and the like; active methylenes such as dimethyl malonate, diethyl malonate, ethyl acetoacetate, methyl acetoacetate, acetylacetone and the like; mercaptans such as butyl mercaptane, t-butyl mercaptane, he
  • blocked polyisocyanate compound those polyisocyanate compounds as named above, whose isocyanate groups are blocked with hydroxymonocarboxylic acid-containing blocking agent and which are rendered water-dispersible by the carboxyl groups introduced into the blocked polyisocyanate compounds by the hydroxymonocarboxylic acids can also be used.
  • the blocking agent those similar to the abve-named can be used.
  • the hydroxymonocarboxylic acid include 2 ⁇ hydroxy acetic acid, 3-hydroxypropanoic acid, 12-hydroxy-9"octadecanoic acid (ricinoleic acid), 3-hydroxy-2,2"dimethylpropanoic acid (hydroxypivalic acid), dimethylolpropionic acid (DMPA) and the like. Of these,
  • 3-hydroxy-2,2-dimethylpropanoic acid (hydroxypivalic acid) is preferred.
  • the solvent used for the blocking reaction preferably is not reactive with isocyanate groups, and hence, for example, ketones such as acetone, methyl ethyl ketone and the like! esters such as ethyl acetate; and N-methylpyrrolidone (NMP) are preferred.
  • catalyst for accelerating urethanation reaction such as organotin compound can be used.
  • preferred content ratio of the resin (a), resin (b) and crosslinking agent (c) is: based on the total solid contents of these three components, resin (a), within a range of generally 20 - 80 mass%, in particular, 30 — 70 mass%, inter alia, 40 - 60 mass%; resin (b), within a range of generally 5 - 35 mass%, in particular, 10 - 30 mass%, inter alia, 15 — 25 mass%; and crosslinking agent (c), within a range of generally 15 - 45 mass%, in particular, 20 - 40 mass%, inter alia, 25 - 35 mass%.
  • Fine polymer particles (d)'- The base coating paint (A) can further contain fine polymer particles (d) for improving thickening effect and after tack resistance.
  • fine polymer particles (d) for example, polymer particles obtained by emulsion polymerization of a monomer (d"l) which contains at least two unsaturated groups per molecule and other unsaturated monomer (d-2) in the presence of an allyl group -containing reactive emulsifier.
  • Such fine polymer particles are disclosed, for example, in JP Hei 3 (1991)-6677OA.
  • the monomer (d- 1) containing at least two unsaturated groups per molecule for example, unsaturated monocarboxylic acid ester of polyhydric alcohol, unsaturated alcohol ester of polybasic acid, and aromatic compound substituted with at least two unsaturated groups can be named.
  • ethylene glycol diacrylate ethylene glycol dimethacrylate, triethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, 1,3-butylene glycol dimethacrylate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, 1,4-butanediol diacrylate, neopentylglycol diacrylate, 1,6-hexanediol diacrylate, pentaerythritol diacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, pentaerythritol dimethacrylate, pentaerythritol trimethacrylate, pentaerythritol tetramethacrylate, glycerol dimethacrylate, glycerol diacrylate, glycerol allyloxydimethacrylate, 1,1,1- tri
  • those carboxyl group -containing unsaturated monomer (M- 1), hydroxyl group -containing unsaturated monomer (M ⁇ 2) and other copolymerizable unsaturated monomer (M- 3) as exemplified as to the carboxyl group- and hydroxyl group -containing resin (a) can be similarly used.
  • nitrogen-containing alkyl (meth)acrylate such as dimethylaminoethyl (meth)acrylate
  • diene compounds such as butadiene, isoprene and the like!
  • alkoxysilane group -containing monomers such as vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris(2-methoxyethoxy)silane, ⁇ -methacryloxypropyl- trimethoxysilane, vinyl triacetoxysilane and the like can also be used. These monomers can be used either alone or in combination of two or more.
  • the use ratio of above monomers (d"l) and (d-2) is not strictly limited, but is variable depending on physical properties desired of the fine polymer particles, which can be, based on the total amount of the monomers (d"l) and (d-2), such that the monomer (d"l) is within a range of generally 1 - 60 mass%, preferably 1 - 50 mass%, inter alia, 1 - 40 mass%, and the monomer (d'2), within a range of generally 40 - 99 mass%, preferably 50 — 99 mass%, inter alia, 60 — 99 mass%.
  • Copolymerization of the monomers (d"l)and (d'2) can be carried out by emulsion polymerization thereof by the means known per se in the presence of an allyl group -containing reactive emulsifying agent, using a polymerization initiator.
  • an allyl group -containing reactive emulsifier any of anionic, cationic or nonionic reactive emulsifiers can be used so long as they are allyl group -containing reactive emulsifiers, anionic allyl group -containing reactive emulsifiers being particularly preferred.
  • anionic allyl group -containing reactive emulsifier examples include ammonium salts of sulfonic acid compounds containing allyl groups, specifically, for example, anionic emulsifiers whose basic structure is p olyoxy ethylene alkyl ether sulfate salt, into which radical-polymerizable allyl group as a part of its hydrophobic groups is introduced.
  • anionic emulsifiers which are commercially available, for example, Aqualon KH" 10 (tradename, Daiichi Kogyo Seiyaku Co., Ltd.), Latemul S- 180A (tradename, Kao Corporation), SR-1025 (tradename, Asahi Denka Co., Ltd.) and the like can be named.
  • Adequate use rate of the reactive emulsifier is, to the total quantity of the monomers (d-l) and (d-2), normally 0.1 - 10 mass%, preferably 1 — 5 mass%.
  • anionic surfactant, nonionic surfactant, amphcrionic surfactant and the like other than the above reactive emulsifier may be concurrently used as the emulsifier.
  • anionic surfactant fatty acid, alkylsulfate salt, alkylbenzenesulfonic acid salt, alkylphosphoric acid salt and the like
  • nonionic surfactant polyoxyethylene alkyl ether, polyoxy ethylene alkylallyl ether, polyoxyethylene derivatives, sorbitan fatty acid ester, polyoxyethylenesorbitan fatty acid ester, polyoxyethylene alkylamine, alkylalkanolamine and the like
  • ampho-ionic surfactant alkylbetaine and the like.
  • Adequate use amount of these optionally added emulsifiers is, based on the combined quantity of the monomers (d"l) and (d"2), normally within a range of 0.1 - 10 mass%, preferably 1 — 5 mass%.
  • polymerization initiator for example, peroxide represented by ammonium persulfate, potassium persulfate, ammonium peroxide and the like; "redox" initiators in which these peroxides are combined with reducing agents such as sodium hydrogensulfite, sodium thiosulfate, Rongalit, ascorbic acid and the like; and azo compounds such as 4,4'-azobis(4-cyanobutanoic acid) and the like can be named.
  • azo compounds in particular, water-soluble azoamide compounds can be suitably used.
  • Water-soluble azoamide compounds are known per se (e.g., see JP Sho 61 (1986)-218618A, JP Sho 61 (1986)-63643A), and concrete examples of commercial products include VA Series (tradename, Wako Pure Chemical Industries, Ltd.).
  • the use ratio of the polymerization initiator is, based on the combined quantity of the monomers (d-l) and (d"2), normally within a range of 0.01 - 10 mass%, preferably 0.1 - 5 mass%.
  • Suitable concentration of total unsaturated monomers during the emulsion polymerization reaction is normally within a range of 0.1 - 50 mass%, preferably 0.5 - 30 mass%.
  • the reaction temperature of the emulsion polymerization differs depending, for example, on the kind of polymerization initiator used, but normally it can be 60 - 90 0 C, and the reaction time, normally 5 — 10 hours.
  • the fine polymer particles (d) can have a hydroxyl value within a range of generally 0 - 70 mgKOH/g, preferably 0 - 60 mgKOH/g, inter alia, 0 — 50 mgKOH/g.
  • the fine polymer particles (d) can have an acid value within a range of generally 0 - 90 mgKOH/g, preferably 0 - 70 mgKOH/g, inter alia, 0 - 50 mgKOH/g.
  • the fine polymer particles (d) can furthermore have particle diameters within a range of generally 10 - 500 nm, preferably 20 - 250 nm, inter alia, 30 - 150 nm.
  • the particle diameter measurement is made with COULTER N4 Model submicron particle analyzer (Nikkaki Bios Co., Ltd.).
  • the fine polymer particles (d) may be neutralized with basic compound, where necessary.
  • the neutralizer for the fine polymer particles (d) those basic substances exemplified as to neutralization of the carboxyl group- and hydroxyl group -containing resin (a) can be similarly used.
  • the fine polymer particles (d) are used preferably in an amount within a range of generally 0 - 40 mass%, in particular, 0 - 30 mass%, inter alia, 0 — 20 mass%, based on the total solid content of the resin (a), resin (b) and crosslinking agent (c).
  • the base coating paint (A) can be formulated by mixing the above-described resin (a), resin (b), crosslinking agent (c) and optionally the fine polymer particles (d), together with a solvent.
  • the base coating paint (A) may be either water-based or hydrophilic organic solvent-based, while generally hydrophilic organic solvent-based type is preferred.
  • hydrophilic organic solvent signifies organic solvent at least 20 g of which is soluble in 100 g of water.
  • hydrophilic organic solvent for example, ester type, ether type, alcoholic, amide type and ketone type solvents meeting the above condition can be used.
  • hydrophilic organic solvents can be used either alone or in combination of two or more.
  • such hydrophilic organic solvents as ethylene glycol monomethyl ether acetate, diethylene glycol monomethyl ether acetate, diethylene glycol monoethyl ether acetate, dioxane, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol diethyl ether, diethylene glycol monobutyl ether, propylene glycol monoethyl ether, dipropylene glycol monomethyl ether, methyl alcohol, ethyl alcohol, allyl alcohol, n-propyl alcohol, isopropyl alcohol, tert-butyl alcohol,
  • the hydrophilic organic solvent also encompasses hydrophilic organic solvent-water mixed system which is formed by substituting a part of above-described hydrophilic organic solvent with deionized water or the like.
  • hydrophilic organic solvent-water mixed system normally adequate ratio ranges, per the total solvent present in the base coating paint (A), the hydrophilic organic solvent, 50 — 100 mass%; and water, 0 - 50 mass%.
  • the base coating paint (A) contains fine polymer particles (d)
  • the fine polymer particles (d) can be added in the form of an aqueous dispersion as it is, or when the base coating paint (A) is hydrophilic organic solvent-based, they may be first converted to a form as dispersed in a hydrophilic organic solvent before the addition.
  • aqueous dispersion of the fine polymer particles (d) to a dispersion in a hydrophilic organic solvent can be effected by, for example, a method comprising adding solvent such as xylene, butyl alcohol, butyl acetate, methyl ethyl ketone, toluene or the like to an aqueous dispersion of fine polymer particles (d), removing water by azeotropy of water and the solvent(s), and dispersing the fine polymer particles (d) in the hydrophilic organic solvent; or a method comprising evaporating water off from an aqueous dispersion of fine polymer particles (d) by spray drying system or simple drying and thereafter re-dispersing the particles in hydrophilic organic solvent.
  • solvent such as xylene, butyl alcohol, butyl acetate, methyl ethyl ketone, toluene or the like
  • solvent such as xylene, butyl alcohol, butyl a
  • Pigment may also be blended in the base coating paint (A).
  • the pigment for example, inorganic and organic coloring pigments such as titanium dioxide, zinc flower, Carbon Black, red iron oxide, Phthalocyanine blue, Prussian blue, Cobalt Blue, azo pigment, phthalocyanine pigment, quinacridone pigment, isoindoline pigment, vat pigment and perylene pigment; extenders such as talc, clay, kaoline, baryta, barium sulfate, barium carbonate, calcium carbonate, silica and alumina white!
  • pigments such as aluminum powder, mica powder, titanium dioxide -coated mica powder, micaceous iron oxide, silver-plated glass flakes, titanium -coated graphite, metal titanium flakes, phthalocyanine flakes and the like can be conveniently used. These pigments can be used either alone or in combination of two or more.
  • Adequate blend ratio of pigment is, based on the total solid content of the resin (a), resin (b) and crosslinking agent (c), generally within a range of 0 - 250 mass%, in particular, 0.1 - 150 mass%.
  • the base coating paint (A) can further be suitably blended with, where necessary, various paint additives such as curing catalyst, dispersant, antisettling agent, defoaming agent, thickener, UV absorber, light stabilizer, surface regulator, antioxidant and the like.
  • various paint additives such as curing catalyst, dispersant, antisettling agent, defoaming agent, thickener, UV absorber, light stabilizer, surface regulator, antioxidant and the like.
  • Concentration of the non-volatile component in the base coating paint (A) at its application time can be normally within a range of 20 - 65 mass%, it being preferred to adopt high-solid type in which the organic solvent content is reduced and the non-volatile component's concentration is adjusted to fall within a range of normally 30 - 60 mass%, in particular, 40 - 60 mass%, for preventing atmospheric pollution and resources saving.
  • Single coating film of the base coating paint (A) is normally of colored and non-transparent or colored and transparent solid tone, or of metallic tone.
  • the non- transparent coating film signifies a coating film whose percent transmission is less than 5%, as measured with a 20 ⁇ rthick cured coating film made of the base coating paint alone,' and transparent coating film is one having percent transmission of 5% or higher, as measured with a 20 ⁇ rthick cured coating film made of the base coating paint alone.
  • the coating objects to which the method of the invention is applicable are not particularly limited, and, for example, sheet steel such as cold-rolled sheet steel, zinc-plated sheet steel, zinc alloy-plated sheet steel, stainless steel sheet and tin-plated sheet steel; metal substrates such as aluminum plate and aluminum alloy- plate; and various plastic materials can be used. They may also be bodies of various vehicles such as automobiles, two-wheeled vehicles and container cars formed thereof.
  • the coating objects may also be metallic surfaces of metal substrates or of car bodies, which have been given a surface treatment such as phosphate treatment, chromate treatment or complex oxide treatment. Furthermore, the coating objects may be given an undercoating (e.g., cationic electrodeposition coating) in advance and depending on the occasion, further coating such as intermediate coating may be applied where necessary.
  • a surface treatment such as phosphate treatment, chromate treatment or complex oxide treatment.
  • the coating objects may be given an undercoating (e.g., cationic electrodeposition coating) in advance and depending on the occasion, further coating such as intermediate coating may be applied where necessary.
  • the base coating paint (A) is applied onto a coating object.
  • Application of the base coating paint (A) can normally be effected by the steps of adjusting coating viscosity of the base coating paint (A) with, for example, diluting solvent or the like, to normally 13 - 60 seconds, preferably 15 - 40 seconds using Ford cup No. 4 at 20 0 C, and applying the same by such means as air spray, airless spray, rotary atomizing coating or the like, optionally applying static electricity where necessary, to a cured film thickness of generally about 5 — about 25 ⁇ m, in particular, about 10 — about 20 ⁇ m.
  • so formed base coating film (A) without curing so formed base coating film (A) by heating, and optionally after allowing it to stand at ambient temperature for about 1 - 20 minutes or further preheating the coated surface at about 60 — about 80 0 C for around 3 — 10 minutes, where necessary, water-based coloring paint (B) is applied onto the uncured coated surface.
  • Water-based coloring paint (B) is applied onto the uncured coated surface.
  • Water-based coloring paint (B) is a water-based liquid paint to be coated onto a surface coated with uncured base coating paint (A), which can generally be formulated by mixing a base resin (B-I), crosslinking agent (B-2) and coloring pigment (B-3) into, and dispersing in, water.
  • A uncured base coating paint
  • the base resin (B" l) for example, carboxyl group- and hydroxyl group -containing acrylic resin, carboxyl group- and hydroxyl group -containing polyester resin and the like can be named.
  • the base resin (B"l) preferably has an acid value within a range of generally 10 — 150 mgKOH/g, in particular, 30 - 100 mgKOH/g.
  • the base resin (B-I) preferably has a hydroxyl value within a range of generally 10 - 150 mgKOH/g, in particular, 30 - 100 mgKOH/g.
  • the acrylic resin as the base resin (B- 1) preferably has a number-average molecular weight within a range of generally 3,000 - 100,000, in particular, 5,000 - 50,000; and the polyester resin, generally 500 - 50,000, in particular, 3,000 - 30,000.
  • the base resin (B- 1) those explained as to the carboxyl group- and hydroxyl group -containing resin (a) used in the base coating paint (A) can be similarly used.
  • the acrylic resin those produced by emulsion polymerization in the presence of an aqueous solution of dispersion stabilizer can also be used.
  • Such acrylic resin produced by the emulsion polymerization preferably has a number-average molecular weight of generally at least 100,000, in particular, within a range of 200,000 - 2,000,000. '
  • aqueous resins such as acrylic resins having an acid value within a range of 10 - 150 mgKOH/g and a number-average molecular weight within a range of 5,000 - 30,000 can be conveniently used.
  • the emulsion polymerization can be carried out by those means known p_er se.
  • acrylic emulsions produced by multistage polymerization process using carboxyl group -containing unsaturated monomers are preferred, as they can give water-based coloring paint excelling in coating workability.
  • the basic substance used for the neutralization those basic substances exemplified in relation to the resin (a) in the base coating paint (A) can be similarly used. Its adequate use amount is normally within a range of 0.1 - 1.5 equivalent, in particular, 0.3 - 1.2 equivalent, to the carboxyl groups in the acrylic emulsion produced by the above multistage polymerization process.
  • crosslinking agent (B"2) at least one selected from those hydroxyl group -reactable crosslinking agents exemplified in relation to the crosslinking agent (c) in the base coating paint (A) can be used.
  • Suitable use ratio of the base resin (B-I) and crosslinking agent (B-2) is- based on the combined amount of the two components, the base resin (B-I), within a range of generally 50 — 90 mass%, in particular, 60 - 85 mass%, inter alia, 65 - 80 mass%; and the crosslinking agent (B-2), generally 10 - 50 mass%, in particular, 15 - 40 mass%, inter alia, 20 - 35 mass%.
  • the coloring pigment (B'3) is for coloring the coating film of water-based coloring paint (B), and the film may be colored and transparent, or colored and non-transparent.
  • coloring pigment (B"3) those exemplified as to the base coating paint (A) can be similarly used. Coloring pigments can be used either alone or in combination of two or more.
  • the water-based coloring paint (B) can be formulated, for example, by mixing base resin (B-I), crosslinking agent (B-2) and coloring pigment (B'3) into water and dispersing them.
  • base resin (B-I) crosslinking agent
  • B-2 crosslinking agent
  • B'3 coloring pigment
  • the water-based coloring paint may further be blended with extender and the like, as necessity requires.
  • paint additives such as curing catalyst, dispersant, antisettling agent, defoamer, thickener, UV absorber, light stabilizer, surface regulating agent, antioxidant and the like may be suitably used.
  • Preferred non-volatile component content in the water-based coloring paint (B) at its application time is normally within a range of 15 — 65 mass%.
  • Coating film of the paint (B) alone can be a non- transparent or transparent solid tone or metallic tone coating film.
  • the non-transparent coating film signifies a film made of the water-based coloring paint alone, which has a % transmission less than 5% at its cured thickness of 20 ⁇ m
  • the transparent coating film signifies a film as above which has a % transmission of at least 5% at its cured thickness of 20 ⁇ m.
  • the water-based coloring paint (B) is applied onto an uncured coated surface with the base coating paint (A) which has been allowed to stand at ambient temperature for 1 — 20 minutes, where necessary, and further preheated at about 60°C - about 80 0 C for about 3 - 10 minutes, again where necessary.
  • water-based coloring paint (B) can be carried out after adjusting its coating viscosity to normally 15 — 60 seconds, preferably 20 - 50 seconds at 20 0 C with, for example, Ford cup No. 4, by such means as air spray, airless spray, rotary atomizing coating or the like, under impression of static electricity where necessary, to a film thickness referring to cured coating film of about 5 — about 40 ⁇ m, in particular, about 10 — about 35 ⁇ m,
  • the water-based coloring paint (B) is coated on uncured coated surface with the base coating paint (A), and then a clear paint (C) is coated.
  • a clear paint (C) is coated.
  • the two-layered coating film formed of the base coating paint (A) and water-based coloring paint (B) may be preliminarily dried at temperatures of about 50 - about 100 0 C. Upon this pre-drying, the most of the volatile components in the two-layered coating film such as organic solvent, water and the like are evaporated.
  • the coating film is dried and solidified upon volatilization of the volatile components under the pre-drying, when the clear paint (C) is applied onto the coated surface and the solvent, low molecular weight resin component and the like which are contained in the clear coating film infiltrate and diffuse in the two-layered coating film, viscosity drop of the two-layered coating film can be inhibited. In consequence, re-flowing of metallic pigment can be suppressed when metallic pigment is used, to prevent occurrence of metallic unevenness.
  • thermosetting resin composition used in the clear paint include, for example, compositions composed of base resin such as acrylic resin, polyester resin, urethane resin and the like having crosslinkable functional groups such as hydroxyl group, and crosslinking agent such as melamine resin, (blocked) polyisocyanate compound and the like; and acid-epoxy crosslinking resin compositions comprising acid group -containing resin and epoxy group -containing resin as the constituent components.
  • base resin such as acrylic resin, polyester resin, urethane resin and the like having crosslinkable functional groups such as hydroxyl group, and crosslinking agent such as melamine resin, (blocked) polyisocyanate compound and the like
  • acid-epoxy crosslinking resin compositions comprising acid group -containing resin and epoxy group -containing resin as the constituent components.
  • water-based type can be favorably used from the standpoint of solvent reduction.
  • coloring pigment, extender pigment or the like can be used to an extent not impairing transparency.
  • coloring pigment and extender pigment for example, those exemplified in relation to the base coating paint (A) can be used.
  • the coloring pigments and extender pigments can be used each alone or in combination of two or more.
  • the clear paint (C) can further suitably contain, where necessary, such paint additives as curing catalyst, defoamer, thickener, UV absorber, light stabilizer, antioxidant, surface regulating agent, dispersant, antisettling agent and the like.
  • Preferred non-volatile component concentration of the clear paint (C) at its application time is normally within a range of 30 — 70 mass%.
  • the clear paint (C) is coated on the two-layered coating film formed of base coating paint (A) and water-based coloring paint (B).
  • the clear paint (C) is applied, after it is adjusted to have an adequate coating viscosity with solvent and/or water, by those methods known per se, such as airless spray, air spray, rotary atomizing coating or the like. Its coating may be carried out under impression of static electricity.
  • Suitable coated film thickness is, based on the cured coating film, normally within a range of about 25 - about 50 ⁇ m, in particular, about 30 - about 45 ⁇ m.
  • the resulting three-layered coating film formed of the base coating paint (A), water-based coloring paint (B) and clear paint (C) is simultaneously cured by heating, to form a multilayer coating film.
  • the three-layered coating film may be preliminarily dried at about 50 - about 100 0 C for about 1 - 10 minutes, where necessary to accelerate evaporation of the volatile components mainly in the coating film of the clear paint (C). This pre-drying evaporates off the most of the volatile components such as organic solvent, water and the like that are present in the three -layered coating film.
  • Heat-curing of the three-layered coating film can be effected by heating at temperatures of normally about 100 - about 18O 0 C, preferably about 120 - about 170 0 C, normally for about 5 - 60 minutes, preferably about 10 — 40 minutes.
  • the heating and optional pre-drying can be effected by heating means known per se. Specifically, they can be effected with drying oven such as hot air oven, electric oven, infrared induction heating oven and the like.
  • the above-described multilayer coating film-forming method enables reduction in use amount of solvent and shortening of process steps, and provides multilayer coating film excelling in coating workability and finished appearance even under high humidity conditions.
  • the method can be advantageously used as a multilayer coating film -forming method applicable to intermediate paint and top paint coating steps in car coating.
  • part and % are invariably based on mass, and thickness of coating film is invariably based on the cured coating film.
  • PLACCEL FM-3 is a tradename (Daicel Chemical Industries Ltd.) of ⁇ -caprolactone-modified hydroxyethyl methacrylate (modified at a ratio of 3 mols of ⁇ -caprolactone per mol of hydroxyethyl methacrylate).
  • each of the products was aged at 95°C for 2 hours under nitrogen gas passage, cooled to 60°C, and diluted with 15 parts of ethylene glycol, monobutyl ether, to provide solutions of respective tertiary amino group-containing resins OrI) - (b'3) having a solid content of 50 mass%.
  • the solid mass concentrations (%) and resinous parameters of the resulting resin (b-l) - (b-3) solutions are shown in the following Table 2.
  • MPEG 2000 MA (tradename) is a methoxypoly ethylene glycol 2000 methacrylate
  • MPEGlOOO MA (tradename) is a methoxypolyethylene glycol 1000 methacrylate, both being the monomers made by Degussa Japan Co., Ltd.
  • the active component of MPEG 2000 MA is 50%.
  • a four-necked flask equipped with a stirrer, thermometer, cooling tube and mantle heater was charged with 355 parts of deionized water and 4 parts of LATEMUL S- 120A (tradename, a sulfosuccinic acid-derived allyl group -containing anionic reactive emulsifier, KAO Corporation, solid content 50%), of which temperature was raised to 90 0 C under stirring. Then 20% of an aqueous solution of 1.25 parts of VA-086 (tradename, a water-soluble azoamide polymerization initiator, 2,2'-azobis[2-methyl-N-(2- hydroxyethyl)-propionamide], Wako Pure Chemical Industries, Ltd.) in 50 parts of deionized water was added.
  • VA-086 tradename, a water-soluble azoamide polymerization initiator, 2,2'-azobis[2-methyl-N-(2- hydroxyethyl)-propionamide], Wako Pure Chemical Industries, Ltd.
  • a monomeric mixture (a mixture of 48 parts of styrene, 22 parts of methyl methacrylate, 22 parts of n-butyl acrylate and 8 parts of 1,6-hexanediol diacrylate) was added, followed by 30 minutes' stirring. Then dropwise addition of the remaining monomeric mixture and the remaining aqueous polymerization initiator solution was started. The dropping of the monomeric mixture required 3 hours, and that of the aqueous polymerization initiator solution required 3.5 hours, respectively, and the polymerization temperature was maintained at 90°C in the meantime. After the end of dropping the aqueous polymerization initiator solution, the reaction mixture was aged at 90 0 C for 30 minutes. Cooling the same to room temperature and filtering through 200-mesh Nylon cloth, an aqueous fine polymer particle dispersion having a solid content of 20% was obtained.
  • a monomeric mixture a mixture of 48 parts of styrene, 22 parts of methyl methacrylate, 22 parts of n-
  • the resulting aqueous dispersion of fine polymer particles was dried on a stainless steel vat in an electric hot air drier at 6O 0 C to remove water.
  • solid was re-dispersed in 6O 0 C ethylene glycol monomethyl ether to provide a dispersion (d-l) of fine polymer particles having a solid content of 20%.
  • An aqueous dispersion of acrylic resin (i) was produced as follows, as a resin dispersion to be used for a water-based coloring paint (B).
  • a reactor equipped with a thermometer, thermostat, stirrer, reflux condenser and a dropping device was charged with 145 parts of deionized water and 1.2 parts of Newcol 562SF (Note 3), which were stirred and mixed in nitrogen gas current. Raising the temperature to 80 0 C, 5% of the total amount of the following monomeric emulsion (l) and 5.2 parts of 3% aqueous ammonium persulfate solution were introduced into the reactor and maintained at 80 0 C for 20 minutes. Then the remaining monomeric emulsion (l) was added into the reactor dropwise over 3 hours, followed by 30 minutes' aging. Then the following monomeric emulsion (2) was added dropwise over 1.5 hours.
  • the reaction mixture was aged for 2 hours, and cooled to 30 0 C under gradual addition of 89 parts of 1.5% aqueous N,N-dimethylethanolamine solution into the reactor. Discharging the reaction mixture through lOOmesh Nylon cloth, an aqueous dispersion of acrylic resin (i) having a solid content of 25% was obtained.
  • the acrylic resin (i) had a hydroxyl value of 22 mgKOH/g, an acid value of 30 mgKOH/g and an average particle size of 100 nm.
  • Newcol 562SF tradename, Nippon Nyukazai Co., Ltd., ammonium polyoxyethylene alkylbenzenesulfonate, active ingredient, 60%.
  • Monomeric emulsion (l) By mixing under stirring 94.3 parts of deionized water, 17 parts of methyl methacrylate, 80 parts of n-butyl acrylate, 3 parts of allyl methacrylate and 1.2 parts of Newcol 562SF, monomeric emulsion (l) was obtained.
  • Monomeric emulsion (2) By mixing under stirring 37.3 parts of deionized water, 15.4 parts of methyl methacrylate, 2.9 parts of n-butyl acrylate, 5.9 parts of hydroxyethyl acrylate, 5.1 parts of methacrylic acid, 0.5 part of Newcol 562SF and 1.7 parts of 3% aqueous ammonium persulfate solution, monomeric emulsion (2) was obtained.
  • Pigment-dispersed paste 1 was obtained by mixing 33.3 parts of the acrylic resin (a-l) as obtained in Production Example 1, 1 part of CARBON MA- 100 (tradename, Carbon Black, Mitsubishi Chemical Co.), 40 parts of JR-806 (tradename, titanium white, Tayca
  • BARIACE B-32 (tradename, barium sulfate, Sakai Chemical Industry Co., Ltd.), 1.6 parts of N,N-dimethylethanolamine and 24.1 parts of ethylene glycol monobutyl ether, and dispersing the mixture in a paint shaker for 30 minutes.
  • Production Example 10 was repeated except that the acrylic resin (a-l) solution was replaced by acrylic resin (a-2) solution, to provide pigment-dispersed paste 2.
  • Production Example 12 was repeated except that the acrylic resin (a-l) solution was replaced by acrylic resin (a-2) solution, to provide pigment-dispersed paste 2.
  • Production Example 10 was repeated except that the acrylic resin (a-l) solution was replaced by acrylic resin (a-3) solution, to provide pigment-dispersed paste 3.
  • Production Example 10 was repeated except that the acrylic resin (a-l) solution was replaced by acrylic resin (a-4) solution, to provide pigment-dispersed paste 4.
  • Examples 1 - 6 and Comparative Example 1 Test panels were prepared as follows, using as the base coating paint (A) each of the base coating paints (A'l) - (A- 7) as obtained in Production Examples 14 — 20, and as the water-based coloring paint (B), the water-based coloring paint (B-I) as obtained in Production Example 21.
  • PALBOND #3020 (tradename, Nippon Parkerizing Co., a zinc phosphate treating agent)-applied cold-rolled steel sheet
  • ELECRON GT-IO (tradename, Kansai Paint Co., a cationic electrodeposition paint) was electrocoated and cured by heating at 170 0 C for 30 minutes to form a 20 ⁇ rthick coating film.
  • each of the base coating paints (A-l) through (A- 7) was applied as would provide a 20 ⁇ rthick coating film with Minibell G (tradename, Japan Ransburg Co., a rotary atomizing electrostatic coater) under the conditions of temperature 25°C and humidity 80%, allowed the coated surfaces to stand for 7 minutes, onto which the water-based coloring paint (B- 1) was applied as would provide a 25 ⁇ rthick coating film, with REA (tradename, Japan Ransburg Co., an electrostatic air spray coater), allowed the coated surfaces to stand for 3 minutes, and preheated them at 70°C for 5 minutes.
  • Minibell G tradename, Japan Ransburg Co., a rotary atomizing electrostatic coater
  • a clear paint (C) (KINO# 1200TW, tradename, Kansai Paint Co., acid/epoxy curing type acrylic resin derived clear paint, with its viscosity adjusted to 25 seconds at 20 0 C as measured with Ford cup No. 4) was coated as would provide a 35 ⁇ rthick film, with Minibell G.
  • the three -layered films formed of the base coating paint (A), water-based coloring paint (B-l) and clear paint (C) were cured by heating them in an electric hot air drying oven at 140 0 C for 30 minutes, to provide the test panels (multilayer films).
  • Long Wave value is an index of amplitude of surface roughness of the wavelength ranging about 1.2 - 12 mm, and can evaluate the condition of medium wave texture of coated film surface.
  • Short Wave value is an index of amplitude of surface roughness of the wavelength ranging about 0.3 - 1.2 mm, and can evaluate the condition of fine texture of coated film surface.
  • less measured values indicate higher smoothness of the coating film surface.
  • SW values less than 15 as measured with Wave Scan indicate favorable coated surface smoothness.
  • IV value IV values were measured with a laser metallic effect measuring device (ALCOPE LMR-200, tradename, Kansai Paint Co.). IV is an index of whiteness of metallic coating film. The higher the degree of uniform orientation of metallic pigment in parallel with the coated surface, the higher the degree of whiteness and the better the metallic effect. Higher IV values indicate higher whiteness.
  • Metallic unevenness ACOPE LMR-200, tradename, Kansai Paint Co.
  • test panels were mounted on a test piece support in Suga Test Instruments Co., Ltd.'s flying stone tester JA-400 Model (tradename, a chipping test device), and 50 g of crushed granite rock of particle size No. 7 was blown at the coated surface with compressed air of 0.392 MPa (4 kgf/cm 2 at -2O 0 C).
  • the extent of thereby incurred damage on the coated film was visually observed and evaluated : O: size of the damage was small and the electrocoated surface or the substrate steel sheet were not exposed; A' size of the damage was small but the electrocoated surface and substrate steel sheet were exposed! X • size of the damage was considerably large and the substrate steel sheet was broadly exposed.

Abstract

This invention provides a multilayer coating film-forming method comprising applying base coating paint (A) onto a coating object, successively applying onto the so formed uncured coated surface water-based coloring paint (B) and clear paint (C), and then heating to simultaneously cure the three-layered coating film composed of the paints (A), (B) and (C), in which the base coating paint (A) contains carboxyl group- and hydroxyl group-containing resin; tertiary amino group -containing resin which is obtained by copolymerizing tertiary amino group -containing unsaturated monomer, polyoxyalkylene group -containing nonionic unsaturated monomer and other unsaturated monomer (b-3); and crosslinking agent reactable with hydroxyl group.

Description

DESCRIPTION
Multilayer Coating Film-forming Method
Technical Field This invention relates to a multilayer coating film -forming method which can reduce the use amount of solvent and shorten the process steps, and yet excels in coating workability and finished appearance.
Background Art
Great concerns are drawn to environmental problems on global scale in these years, and also in car industries, attempts for environmental improvement in the manufacturing steps are positively advanced. Problems such as global warming, generation of industrial waste and discharge of volatile organic solvent (VOC) take place in the process of car manufacture. Particularly as to VOC, the greatest part thereof is generated in coating steps and effective countermeasures are urgently required.
Also from the viewpoints of improving productivity and reducing energy consumption, a coating process which dispenses with heat-curing in coating steps has been in demand and proposals therefor are made.
The outer panel portions of car bodies are normally coated with multilayer coating film comprising undercoating film of cationic electrodeposition paint, intermediate coating film and top coating film, for the purpose of imparting corrosion resistance and favorable appearance.
For VOC reduction, adoption of water-based paints is promoted also for intermediate coat and top coat. Whereas, because the chief ingredient of solvent for water-based paint is water and the solvent is evaporated from coated film more difficultly compared with organic solvent-based paints, they are subject to such shortcomings as higher tendency to cause sagging of coating film and deterioration in finished appearance as influenced by temperature and humidity of coating environment. As a multilayer coating film -forming method which can reduce VOC and allow omission of heat- curing step of coated film, for example, JP Sho 61 (1986)"141969A discloses a metallic finishing method comprising applying onto a coating object an organic solvent-based or non-aqueous dispersion type thermosetting paint which contains a neutralization product of polyvalent carboxylic acid resin and amino resin but is free of metallic pigment, adjusting the viscosity of the coated paint to at least 10 poises (200C), applying thereonto a thermosetting water-based metallic paint, further applying thereonto a transparent thermosetting paint, and curing thus formed three-layered coating film simultaneously by heating. However, even when the viscosity of the organic solvent-based or non- aqueous dispersion type thermosetting paint is adjusted to the above-specified range according to the above method, still such defects as degradation in finished appearance or occurrence of cracks in the coating film after application of a thermosetting water-based metallic paint may take place, for example, under highly humid condition in which the viscosity control becomes insufficient to disturb uniform orientation of metallic pigment in the thermosetting water-based metallic paint applied thereon.
As a metallic finishing method preventing such defects, for example, JP Hei 11 (l999)-197592A proposes a multilayer coating film-forming method characterized in that the metallic pigment-free organic solvent-based or non-aqueous dispersion type thermosetting paint contains specific gelled fine polymer particles. The effect of this method to prevent the aforesaid defects is still insufficient and, in particular, the problem remains that cracks may occur under high humidity condition.
Disclosure of the Invention
The object of the present invention is to provide a method which realizes reduction in use amount of solvent and shortening of the process steps, and which can form multilayer coating film with excellent coating workability and finished appearance even under high humidity condition. In consequence of accumulation of concentrative studies, we have now discovered that the above object can be accomplished by a multilayer coating film-forming method comprising applying a base coating paint, successively applying onto the uncured coated surface a water-based coloring paint and a clear paint, and then heating the three-layered coating film formed of the base coating paint, water-based coloring paint and clear paint to cure them simultaneously, in which a paint containing a specific tertiary amino group -containing resin and specific crosslinking agent is used as the base coating paint, and come to complete the present invention. Thus the present invention provides a multilayer coating film-forming method comprising applying base coating paint (A) onto a coating object, successively applying onto the so formed uncured coated surface water-based coloring paint (B) and clear paint (C), and then heating to simultaneously cure the three-layered coating film composed of the paints (A), (B) and (C), the method being characterized in that the base coating paint (A) contains
(a) carboxyl group- and hydroxyl group -containing resin,
(b) tertiary amino group -containing resin which is obtained by copolymerizing tertiary amino group -containing unsaturated monomer Or I), polyoxyalkylene group -containing nonionic unsaturated monomer (b"2) and other unsaturated monomer (b-3), and
(c) crosslinking agent reactable with hydroxyl group. In the multilayer coating film-forming method of the present invention, the base coating paint (A) contains carboxyl group- and hydroxyl group -containing resin (a) and tertiary amino group -containing resin (b). Hence, in the coating film formed after application of the base coating paint (A) a structure which may be regarded as pseudo-crosslinkage caused by acid-base interaction between the carboxyl groups in the resin (a) and the tertiary amino groups in the resin (b) is formed to exhibit viscosity-raising effect, which leads to favorable viscous effect in the two-layered coating film formed by subsequent application of the water-based coloring paint (B). Due to this effect, even in situations tending to induce layer mixing in two-layered coating film, such as under high humidity condition, layer mixing can be inhibited and very excellent coating workability is exhibited. Because the steric hindrance at the polyoxyalkylene group side chain moieties derived from the monomer (b"2) in the resin (b) inhibits excessive pseudo-crosslinked structure formation between the resin (a) and resin (b), furthermore, an effect is achieved that the base coating paint (A) is free from deterioration in smoothness caused by aggregation and in consequence a multilayer coating film of extremely superior finished appearance can be formed. Hereinafter the multilayer coating film-forming method of the present invention is explained in further details.
Embodiments for Working the Invention
Base coating paint (A)- According to the method of the present invention, the base coating paint (A) which is first applied onto a coating object is a paint containing a carboxyl group- and hydroxyl group -containing resin (a), tertiary amino group -containing resin (b), and crosslinking agent (c) reactable with hydroxyl group.
Carboxyl group- and hydroxyl group -containing resin (a)-
Any resin which contains carboxyl groups and hydroxyl groups in its molecules can be used as the resin (a), without any particular limitation. As specific kinds of resins, for example, acrylic resin, polyester resin, polyether resin, polycarbonate resin, polyurethane resin and the like can be named.
Carboxyl groups in resin (a) brings about viscosity-developing effect at the coated film of base coating paint (A), by forming a pseudo-crosslinked structure due to the acid-base interaction with tertiary amino groups of resin (b). Also hydroxyl groups in resin (a) contribute to cure the coating film, upon reaction with the crosslinking agent (c).
From the viewpoint of having the carboxyl group- and hydroxyl group -containing resin (a) to exhibit the viscosity-developing effect . caused by the interaction with the tertiary amino group -containing resin Ob), the resin (a) can have an acid value within a range of generally 2 - 100 mgKOH/g, preferably 5 - 80 mgKOH/g, inter alia, 5 — 65 mgKOH/g. Also in consideration of curability or water resistance of the coating film to be obtained, the carboxyl group- and hydroxyl group -containing resin (a) can have a hydroxyl value within a range of generally 20 - 200 mgKOH/g, preferably 35 - 180 mgKOH/g, inter alia, 50 - 150 mgKOH/g.
As preferred examples of the carboxyl group- and hydroxyl group -containing resin (a), carboxyl group- and hydroxyl group -containing acrylic resin, carboxyl group- and hydroxyl group -containing polyester resin, and carboxyl group- and hydroxyl group -containing polyurethane resin can be named.
Carboxyl group- and hydroxyl group -containing acrylic resin- Carboxyl group- and hydroxyl group -containing acrylic resin can be synthesized by, for example, copolymerizing carboxyl group -containing unsaturated monomer (M- 1), hydroxyl group -containing unsaturated monomer (M- 2) and other copolymerizable unsaturated monomer (M- 3), according to the accepted practice.
Carboxyl group -containing unsaturated monomer (M- 1) encompasses those compounds having at least one carboxyl group and one unsaturated bond per molecule, examples of which include acrylic acid, methacrylic acid, crotonic acid, itaconic acid, maleic acid and maleic anhydride. These may be used either alone or in combination of two or more.
Hydroxyl group -containing unsaturated monomer (M-2) encompasses those compounds having at least one hydroxyl group and one unsaturated bond per molecule, the hydroxyl groups acting chiefly as the functional group as the functional in the reaction of the carboxyl group- and hydroxyl group -containing acrylic resin with the crosslinking agent (c) which is reactable with hydroxyl group. As the hydroxyl group-containing unsaturated monomer (M"2), monoesterification products of (meth)acrylic acids with C2-io dihydric alcohols are particularly preferred, specific examples including hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth) aery late and the like.
In the present specification, "(meth)acrylate" means acrylate or methacrylate.
Also as the hydroxyl group -containing unsaturated monomer (M"2), for example, compounds obtained by further ring-opening polymerization of hydroxyalkyl (meth) acrylate such as 2-hydroxyethyl (meth) acrylate with ε-caprolactone or the like, such as PLACCEL FA-I, PLACCEL FA-2, PLACCEL FA- 3, PLACCEL FA-4, PLACCEL FA-5, PLACCEL FM-I, PLACCEL FM-2, PLACCEL FM-3, PLACCEL FM-4, PLACCEL FM-5 (tradename, Daicel Chemical Industries, Ltd.) and the like can be conveniently used. As the hydroxyl group -containing unsaturated monomer (M-2), furthermore, polyethylene glycol mono(meth)acrylate, polypropylene glycol mono(meth)acrylate, 2-hydroxy3-phenoxypropyl (meth)acrylate, 2-hydroxy-3"butoxypropyl (meth)acrylate, monohydroxyethyl (meth) acrylate phthalate and the like can also be used.
Other copolymerizable unsaturated monomers (M- 3) include those compounds having one unsaturated bond per molecule, other than above-named carboxyl group -containing unsaturated monomer (M- 1) and hydroxyl group -containing unsaturated monomer (M-2), and as their specific examples, those listed in the following (l) - (6) can be named: (l) monoesterified products of (mettύacrylic acid with Ci-20 monohydric alcohol- for example, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, irbutyl (meth)acrylate, iso-butyl (meth) acrylate, tert-butyl (meth)acrylate, 2-ethylhexyl (meth) acrylate, cyclohexyl (meth)acrylate, lauryl (meth)acrylate, isobornyl (meth) acrylate, tridecyl (meth)acrylate, stearyl (meth)acrylate and butoxyethyl (meth)acrylateJ
(2) aromatic unsaturated monomers: for example, styrene, crmethylstyrene and vinyltolueneJ
(3) glycidyl group-containing unsaturated monomers'- compounds containing at least one each of glycidyl group and unsaturated bond per molecule, for example, glycidyl acrylate and glycidyl methacrylate;
(4) unsaturated bond-containing amide compounds- for example, acrylamide, methacrylamide, dimethylacrylamide, N,N-dimethylpropyl acrylamide, N-butoxymethyl acrylamide, N-methylol acrylamide, N-methylol methacrylamide and diacetonacrylamide ;
(5) other unsaturated compounds: for example, vinyl acetate, vinyl propionate, vinyl chloride, and versatic acid vinyl esters such as Veo Va 9 and Veo Va 10 (tradename, Japan Epoxy Resin Co.);
(6) unsaturated bond-containing nitrile compounds-' for example, acrylonitrile and methacrylonitrile.
These other unsaturated monomers (M- 3) can be used either alone or in combination of two or more. The carboxyl group- and hydroxyl group -containing acrylic resin can have an acid value within a range of generally 5 — 100 mgKOH/g, preferably 20 - 80 mgKOH/g, inter alia, 35 - 65 mgKOH/g. Where the acid value of the resin is less than 5 mgKOH/g, there are occasions in which the viscosity-developing effect due to the resin's interaction with tertiary amino group -containing resin (b) is reduced. Whereas, when it exceeds 100 mgKOH/g, water resistance of the coating film may deteriorate. The carboxyl group- and hydroxyl group -containing acrylic resin can also have a hydroxyl value within a range of generally 20 - 150 mgKOH/g, preferably 35 - 120 mgKOH/g, inter alia, 50 — 100 mgKOH/g. When the hydroxyl value of the resin is less than 20 mgKOH/g, curability may become insufficient, and when it exceeds 150 mgKOH/g, water resistance of the coating film may deteriorate.
The carboxyl group- and hydroxyl group -containing acrylic resin can have a number- average molecular weight within a range of generally 2,000 - 100,000, preferably 3,000 - 50,000, inter alia, 4,000 — 20, 000. When the resin has a number- average molecular weight less than 2,000, the coating film may come to have insufficient weatherability, while its molecular weight exceeding 100,000 may invite degradation in smoothness of the coated surface. In the present specification, the number- average molecular weight of a resin is a value converted of the number-average molecular weight measured with gel permeation chromatograph, HLC8120GPC (tradename, Tosoh Corporation), based on the number- average molecular weight of standard polystyrene.
Carboxyl group- and hydroxy group -containing polyester resin:
Carboxyl group- and hydroxyl group -containing polyester resin can be prepared by per se known reaction, for example, through esterification reaction of polybasic acid with polyhydric alcohol.
Polybasic acid is a compound having at least two carboxyl groups per molecule, examples of which include phthalic acid, isophthalic acid, terephthalic acid, succinic acid, adipic acid, azelaic acid, sebacic acid, tetrahydrophthalic acid, hexahydrophthalic acid, maleic acid, fumaric acid, itaconic acid, trimellitic acid, pyromellitic acid and anhydrides thereof. Polyhydric alcohol is a compound having at least two hydroxyl groups per molecule, examples of which include diols such as ethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 2,2-diethyl-l,3-propanediol, neopentyl glycol, 1,9-nonanediol, 1,4-cyclohexanediol, hydroxypivalic acid neopentyl glycol ester, 2-butyl-2-ethyM,3-propanediol, 3-methyM,5-pentanediol, 2,2,4-trimethylpentanediol and hydrogenated bisphenol A; at least trivalent polyols such as trimethylolpropane, trimethylolethane, glycerine and pentaerythritoL" and polyhydroxycarboxylic acids such as 2,2-dimethylolpropionic acid, 2,2-dimethylolbutanoic acid, 2,2-dimethylolpentanoic acid, 2,2-dimethylolhexanoic acid and 2,2-dimethyloloctanoic acid. These compounds may also be forming ethers with lower alcohols. It is also permissible to react a monoepoxy compound such as α-olefin epoxide, e.g., propylene oxide, butylene oxide or the like, CARDURA ElO (tradename, Japan Epoxy Resin Co., glycidyl ester of synthetic highly branched saturated fatty acid) or the like, with an acid and introduce such a compound into polyester resin. Carboxyl groups can be introduced into polyester resin by such method as carrying out the above esterification reaction using excessive polybasic acid; or, after an esterification reaction of polybasic acid with polyhydric alcohol, further reacting the product with polybasic acid such as trimellitic acid or anhydride thereof. The carboxyl group- and hydroxyl group -containing polyester resin may be a fatty acid-modified polyester resin which is modified with (semi)drying oil fatty acid such as linseed oil fatty acid, coconut oil fatty acid, safflower oil fatty acid, soybean oil fatty acid, sesame oil fatty acid, perilla oil fatty acid, hempseed oil fatty acid, tall oil fatty acid, dehydrated castor oil fatty acid and the like. It is generally adequate that the modification amount with these fatty acid is not more than 30 mass% in terms of oil length. The carboxyl group- and hydroxyl group -containing polyester resin may also be one which is partially reacted with monobasic acid such as benzoic acid. The carboxyl group- and hydroxyl group -containing polyester resin can have an acid value within a range of generally 5 - 70 mgKOH/g, preferably 15 - 55 mgKOH/g, inter aha, 25 - 45 mgKOH/g. Where acid value of the resin is less than 5 mgKOH/g, there are occasions in which the viscosity-developing effect due to the resin's interaction with tertiary amino group -containing resin (b) is reduced. Whereas, when it exceeds 70 mgKOH/g, water resistance of the coating film may deteriorate. The carboxyl group- and hydroxyl group -containing polyester resin can have a hydroxyl value within a range of generally 30 - 200 mgKOH/g, preferably 50 - 180 mgKOH/g, inter alia, 70 - 150 mgKOH/g. Where hydroxyl value of the resin is less than 30 mgKOH/g, curability may become insufficient, and when it exceeds 200 mgKOH/g, water resistance of the coating film may deteriorate.
The carboxyl group- and hydroxyl group -containing polyester resin can have a number-average molecular weight within a range of generally 300 - 50,000, in particular, 500 - 20,000, inter alia, 1,000 - 10,000. Where number- average molecular weight of the resin is less than 300, the coating film may exhibit insufficient weatherability, while smoothness of the coated surface may be impaired when it exceeds 50,000. Carboxyl group- and hydroxyl group -containing polyurethane resin-' Carboxyl group- and hydroxyl group -containing polyurethane resin can be obtained, for example, by reacting polyol which contains carboxyl group-containing polyol, with polyisocyanate according to the accepted practice.
As carboxyl group -containing polyol, for example, 2,2-dimethylolpropionic acid, 2,2-dimethylolbutanoic acid and the like can be named, 2,2-dimethylolpropionic acid being particularly preferred. When these polyols are used, a minor amount of a solvent such as N-methylpyrrolidone may be used for accelerating the reaction.
It is also permissible to concurrently use polyols which do not contain carboxyl groups. Examples of low molecular weight polyols free of carboxyl group include dihydric alcohols such as ethylene glycol, diethylene glycol, propylene glycol, butylene glycol, hexamethylene glycol and the like; and trihydric alcohols such as trimethylolpropane, glycerine, pentaerythritol and the like. As those of high molecular weight, for example, polyetherpolyol, polyesterpolyol, acrylpolyol, epoxypolyol and the like can be named. As the polyetherpolyol, for example, polyethylene glycol, polypropylene glycol, polytetramethylene glycol and the like can be named. As the polyester polyol, for example, polycondensation products of alcohols such as aforesaid dihydric alcohol, dipropylene glycol, 1,4-butanediol, 1,6-hexanediol, neopentyl glycol and the like, with dibasic acid such as adipic acid, azelaic acid, sebacic acid and the like; lactone-derived ring-opening polymer polyol such as poly cap rolactone, polycarbonatediol and the like can be named.
As polyisocyanate to be reacted with above polyol, for example, aliphatic polyisocyanates such as hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, dimeric acid diisocyanate, lysine diisocyanate and the like and biuret type adducts or isocyanurate ring adducts of these polyisocyanates; alicyclic diisocyanates such as isophorone diisocyanate, 4,4'-methylenebis(cyclohexylisocyanate), methylcyclohexane-2,4- or 2,6-diisocyanate, 1,3- or l^-diGsoeyanatomethyOcyclohexane, 1,4-cyclohexane diisocyanate, 1,3-cyclopentane diisocyanate, 1,2-cyclohexane diisocyanate and the like and biuret type adducts or isocyanurate ring adducts of these polyisocyanates! aromatic diisocyanate compounds such as xylylene diisocyanate, metaxylylene diisocyanate, tetramethylxylylene diisocyanate, tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 1,5 -naphthalene diisocyanate, 1,4- naphthalene diisocyanate, 4,4'toluidine diisocyanate, 4,4'-diphenylether diisocyanate, m- or p-phenylene diisocyanate, 4,4'-biphenylene diisocyanate, 3)3'-dimethyl-4,4'-biphenylene diisocyanate, bis(4-isocyanatophenyl)sulfone, isopropylidenebis- (4-phenylisocyanate) and the like and biuret type adducts or isocyanurate ring adducts of these polyisocyanantesl polyisocyanates having at least three isocyanate groups per molecule such as triphenylmethane-4,4'-4"-triisocyanate, 1,3,5-triisocyanatobenzene, 2,4,6-triisocyanatotoluene, 4,4'-dimethyldiphenylmethane- 2,2',5,5Hetraisocyanate and the like and biuret type adducts or isocyanurate ring adducts of these polyisocyanates can be named. The carboxyl group- and hydroxyl group -containing polyurethane resin can have an acid value within a range of generally 2 - 50 mgKOH/g, preferably 5 - 40 mgKOH/g, inter alia, 5 - 20 mgKOH/g. Where acid value of the resin is less than 2 mgKOH/g, there are occasions in which the viscosity-developing effect due to the resin's interaction with tertiary amino group -containing resin (b) is reduced. Whereas, when it exceeds 50 mgKOH/g, water resistance of the coating film may deteriorate.
The carboxyl group- and hydroxyl group -containing polyurethane resin can have a number- average molecular weight within a range of generally 1,000 - 3,000,000, in particular, 10,000 - 2,000,000, inter alia, 20,000 - 1,000,000. Where number- average molecular weight of the resin is less than 1,000, the coating film may exhibit insufficient weatherability, while smoothness of the coated surface may be impaired when it exceeds 3,000,000.
It is desirable to neutralize carboxyl groups in the carboxyl group- and hydroxy! group- containing resin (a). It is furthermore desirable to carry out the neutralization before mixing the carboxyl group- and hydroxy 1 group -containing resin (a) with tertiary amino group -containing resin (b), crosslinking agent (c) and the like. Examples of basic substance useful for the neutralization include ammonia! primary monoamines such as ethylamine, propylamine, butylamine, benzylamine, monoethanolamine, neopentanolamine, 2-aminoρropanol, 3-aminopropanol and the like! secondary monoamines such as diethylamine, diethanolamine, drn- or diisopropanolamine, N-methylethanolamine, N-ethylethanolamine and the like; tertiary monoamines such as N,N'dimethyl- ethanolamine, trimethylamine, triethylamine, triisopropylamine, methyldiethanolamine and the like; and polyamines such as diethylenetriamine, hydroxyethylaminoethylamine, ethylaminoethylamine, methylaminopropylamine and the like. These can be used either alone or in combination of two or more.
Suitable use rate of the basic substance for the neutralization is normally 0.1 - 1.0 equivalent, in particular, 0.2 — 0.8 equivalent to the carboxyl groups in the resin (a).
Tertiary amino group -containing resin (b):
Tertiary amino group -containing resin (b) encompasses, in particular, tertiary amino group-containing acrylic resin which is obtained by copolymerizing tertiary amino group -containing unsaturated monomer Otrl), polyoxyalkylene group -containing, nonionic unsaturated monomer (b-2) and other unsaturated monomer (b-3).
Tertiary amino group -containing unsaturated monomer (b-l): Tertiary amino group -containing polymerizable unsaturated monomer (b-l) is the monomeric component for introducing tertiary amino groups into the tertiary amino group -containing resin (b), and has a tertiary amino group and unsaturated group per molecule.
As specific examples, N,N-dialkylaminoalkyl (meth)acrylates such as N,N-dimethylaminoethyl (meth)acrylate, N,N-diethylaminoethyl (mettOacrylate, N,N-dimethylaminopropyl (meth)acrylate, N,N-di-t-butylaminoethyl (meth)acrylate, N,N-dimethylaminobutyl (meth)acrylate and the like; and N,N-dialkylaminoalkyl (meth)acrylamides such as N,N-dimethylaminoethyl (meth)acrylamide, N,N-diethylaminoethyl (meth)acrylamide, N,N-dimethylaminopropyl (meth)acrylamide and the like. These monomers can be used either alone or in combination of two or more.
Of these monomers, N,N-dialkylaminoalkyl (meth)acrylates, in particular, N,N'dimethylaminoethyl (meth)acrylate, are preferred as tertiary amino group -containing polymerizable unsaturated monomers.
The tertiary amino groups introduced into tertiary amino group -containing resin (b) by such tertiary amino group -containing polymerizable unsaturated monomer (b- l) act for expressing viscosity of coated paint attributable to pseudo-crosslinkage forming effect by the acid-base interaction with the carboxyl groups in resin (a).
Polyoxyalkylene group -containing nonionic unsaturated monomer (b-2):
Polyoxyalkylene group -containing nonionic unsaturated monomer (b"2) is the monomeric component for introducing polyoxyalkylene groups into tertiary amino group -containing resin (b) to impart hydrophilicity to the tertiary amino group-containing resin (b) and to inhibit excessive interaction between the resins (a) and (b), which has polyoxyalkylene group and unsaturated group per molecule.
As the polyoxyalkylene group, polyoxyethylene group, polyoxypropylene group, groups having polyoxyethylene- polyoxypropylene block structure and the like can be named.
Polyoxyalkylene group preferably has a molecular weight within a range of generally 200 - 3,000, in particular, 300 - 2,500.
As typical examples of the monomer (b-2), for example, the compounds represented by the following formula (l): CH2 = C(R1)COO(CnH2nO)m-R2 (D in which R1 stands for hydrogen or methyl, R2 stands for hydrogen or Ci-4 alkyl, m is an integer of 4 - 60, preferably 6 - 50, and n is an integer of 2 or 3, preferably 2, wherein the m oxyalkylene units (CnEbnO) may be the same or different can be named.
Specific examples of such monomer (b-2) include tetraethylene glycol (meth)acrylate, methoxytetraethylene glycol (meth)acrylate, ethoxytetraethylene glycol (meth)acrylate, n-butoxytetraethylene glycol (meth)acrylate, tetrapropylene glycol (meth)acrylate, methoxytetrapropylene glycol (meth)acrylate, ethoxytetrapropylene glycol (meth)acrylate, n-butoxytetrapropylene glycol (meth)acrylate, polyethylene glycol (meth)acrylate, polypropylene glycol (meth)acrylate, methoxypolyethylene glycol (meth)acrylate, ethoxypolyethylene glycol (meth)acrylate and the like. Of these, particularly polyethylene glycol (meth)acrylate and polypropylene glycol (meth)acrylate are preferred. These monomers can be used either alone or in combination of two or more.
Due to steric hindrance at the polyoxyethylene group side chain moieties which are introduced into tertiary amino group -containing resin (b) by the monomer (b-2), excessive formation of pseudo-crosslinked structure between the resins (a) and (b) is inhibited, and in consequence multilayer coating film of excellent finished appearance can be obtained without deterioration in smoothness caused by aggregation of the base coating paint (A).
Other unsaturated monomer (b-3)'-
Still other unsaturated monomer (b-3) includes unsaturated monomers other than the above-described monomers (Vl) and (b-2), which are copolymerizable with these monomers (b-l) and (b-2) and are suitably selected according to the properties desired for the tertiary amino group -containing resin (b).
Specific examples of such monomers (b-3) include Ci-24 straight chain or cyclic alkyl (meth)acrylate monomers such as methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, lauryl (meth)acrylate, stearyl (meth)acrylate, cyclohexyl (meth) aery late, isobornyl (meth)acrylate, tridecyl (mettOacrylate and the like! hydroxyl group -containing unsaturated monomers (typically hydroxyalkyl (meth)acrylate monomers) such as 2-hydroxyethyl (meth) aery late, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate and the like; acrylamide, methacrylamide; oxetane ring-containing (meth)acrylates such as 3-ethyl-3-(meth)acryloyloxymethyloxetane, 3-methyl-3-(meth)- acryloyloxymethyloxetane, 3-butyl-3-(meth)acryloyloxymethyloxotane and the like! aromatic vinyl compounds such as styrene, crmethylstyrene, vinyltoluene and the like; (meth)acrylonitrile, vinyl acetate, and the like. These unsaturated monomers can be used either alone or in combination of two or more.
From the viewpoint of coated film performance, the tertiary amino group -containing resin (b) preferably contains functional groups reactable with the crosslinking agent (c). As the functional groups reactable with the crosslinking agent (c), hydroxyl group is preferred. In that case, the monomer (b-3) preferably contains, as at least a part of its component, a hydroxyl group -containing unsaturated monomer.
Specific examples of the hydroxyl group -containing unsaturated monomer include monoesterified products of polyhydric alcohols with (meth)acrylic acid, such as 2-hydroxyethyl
(meth)acrylate, hydroxypropyl (meth) aery late, 2,3-dihydroxybutyl (meth)acrylate, 4-hydroxybutyl (mettOacrylate, polyethylene glycol mono(meth)acrylate and the like; and the compounds formed by ring'opening polymerization of those monoesterified products of polyhydric alcohol with (meth)acrylic acid with ε-caprolactone. Of those, 4-hydroxybutyl (meth)acrylate, polyethylene glycol mono(meth)acrylate, and the compounds formed by ring-opening polymerization of monoesterified product of polyhydric alcohol with (meth)acrylic acid, with ε-caprolactone are preferred in respect of reactivity. These compounds can be used either alone or in combination of two or more.
The tertiary amino group -containing resin (b) can be obtained by copolymerizing the tertiary amino group -containing unsaturated monomer OrI), polyoxyethylene group -containing nonionic unsaturated monomer (b-2) and still other unsaturated monomer (b-3).
The use ratio of such monomers (b-l), (b"2) and 0r3) is not strictly limited, but is variable depending on physical properties desired for the tertiary amino group -containing resin. Whereas, based on the total amount of the monomers (b-l), (b-2) and (b-3), the monomer (b-l) can be within a range of generally 1 - 25 mass%, preferably 3 — 20 mass%, inter alia, 5 — 15 mass%; the monomer (b~2), within a range of generally 5 — 40 mass%, preferably 7 - 35 mass%, inter alia, 10 — 30 mass%; and the monomer (b"3), within a range of generally 35 - 94 mass%, preferably 45 — 90 mass%, inter alia, 55 - 85 mass%.
Also the hydroxyl group -containing unsaturated monomer is preferably used within a range of generally 3 — 30 mass%, in particular, 5 — 25 mass%, based on the total amount of monomers (b-l), (b-2) and (b-3).
Copolymerization of those monomers (b-l), (b"2) and (b-3) can be carried out by the processes known per se, for example, by solution polymerization in organic solvent. Specifically, the copolymerization by solution polymerization process can be carried out, for example by dissolving or dispersing a mixture of the monomers (b-l), (b-2) and (b-3) with radical polymerization initiator in the organic solvent, and heating the solution or dispersion usually at about 80°C — about 2000C, for around 1 - 10 hours under stirring to effect the polymerization. As the organic solvent for such solution polymerization, use of hydrophilic organic solvent such as of propylene glycol type or dipropylene glycol type is preferred.
The tertiary amino group -containing resin (b) preferably has an amine value within a range of generally 3 - 100 mgKOH/g, in particular, 10 - 80 mgKOH/g, inter alia, 15 - 60 mgKOH/g, for favorable viscosity-expressing effect. The tertiary amino group -containing resin (b) also preferably has a hydroxy value within a range of generally 10 - 130 mgKOH/g, in particular, 20 - 100 mgKOH/g, inter alia, 30 — 70 mgKOH/g, in respect of water resistance and curability of the coating film, and in consideration of smoothness of the coated surface and weatherability of resulting coating film, preferably has a number- average molecular weight within a range of generally 500 - 20,000, in particular, 1,000 - 10,000, inter alia, 3,000 - 7,000. The monomer (b'l) component constituting the tertiary amino group -containing resin (b) contributes to viscosity expression of coated paint due to pseudo-crosslinkage-forming effect with the carboxyl group- and hydroxyl group -containing resin (a), and the monomer (b"2) component constituting the tertiary amino group -containing resin (b) contributes to formation of coating film having excellent finished appearance, as it suppresses excessive formation of the pseudo-crosslinked structure.
Crosslinking agent (c) reactable with hydroxyl group- The crosslinking agent (c) used in the present invention is subject to no particular limitation so long as it is a compound reactable with hydroxyl group and, for example, following melamine resin, blocked polyisocyanate compound, water- dispersible blocked polyisocyanate compound and the like can be conveniently used.
Melamine resin:
Specific examples of melamine resin include di-, tri-, tetra-, penta- and hexa-methylolmelamines and their alkyletherified products with alcohol (examples of the alkyl including methyl, ethyl, propyl, isopropyl, butyl, isobutyl, 2-ethylhexyl and the like) and their condensates.
Specific examples of the melamine resin also include, for example, Nihon Cytec Industries, Inc.'s Cymel 303, Cymel 323, Cymel 325, Cymel 327, Cymel 350, Cymel 370, Cymel 380, Cymel 385, Cymel 212, Cymel 251, Cymel 254 and Mycoat 776 (all tradenames); Monsanto Chemical Co's Regimin 735, Regimin 740, Regimin 741, Regimin 745, Regimin 746 and Regimin 747 (all tradenames); Sumitomo Chemicals Co.'s Sumimal M55, Sumimal M30W and Sumimal M50W (all tradenames); and Mitsui Chemicals, Inc.'s U-VAN series such as U-VAN 20SB (tradename).
As the melamine resin, those having mononuclear body content of at least 30 mass%, in particular, at least 40 mass%, inter alia, at least 45 mass%, are preferred. Also in consideration of finished appearance and storage stability, as alkyletherified melamine resin, methoxyetherified or methoxybutoxy mixed etherified melamine resins in which the ratio of methoxy group is high, such that the mol ratio of methoxy group and butoxy group (methoxy group/butoxy group) is within a range of normally 100/0 - 60/40, in particular, 100/0 - 70/30, are preferred. Specific examples of such melamine resin include Cymel 325, Cymel 327, Cymel 350, Cymel 212, Cymel 251, Mycoat 212 and Mycoat 776 (all tradenames, made by Nihon Cytec Industries, Inc.).
Also when the melamine resin is used as crosslinking agent, sulfonic acid such as paratoluenesulfonic acid, dodecylbenzenesulfonic acid, dinonylnaphthalene sulfonic acid and the like, or salts of these acids with amine can be used as catalyst.
Those melamine resins can be used either alone or in combination of two or more.
Blocked polyisocyanate compound-
Blocked polyisocyanate compounds are the polyisocyanate compounds having at least two free isocyanate groups per molecule, whose isocyanate groups are blocked with blocking agent.
Examples of the polyisocyanate compounds forming such blocked polyisocyanate compounds include aliphatic polyisocyanates such as hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, dimeric acid diisocyanate, lysine diisocyanate and the like, and biuret type adducts and isocyanurate adducts of these polyisocyanates; alicyclic diisocyanates such as isophorone diisocyanate, 4,4'-methylenebis(cyclohexylisocyanate), methylcyclohexane-2,4- or 2,6-diisocyanate, 1,3" or l,4-di(isocyanatomethyl)cyclohexane, 1,4-cyclohexane diisocyanate, 1,3-cyclopentane diisocyanate, 1,2-cyclohexane diisocyanate and the like, and biuret type adducts and isocyanurate ring adducts of these polyisocyanate s>' aromatic diisocyanate compounds such as xylylene diisocyanate, metaxylylene diisocyanate, tetramethylxylylene diisocyanate, tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 1,5-naphthalene diisocyanate, l,4"naphthalene diisocyanate, 4,4'-toluidine diisocyanate, 4,4'-diphenylether diisocyanate, m' or p-phenylene diisocyanate, 4,4'-biphenylene diisocyanate, 3,3'-dimethyl-4,4'-biphenylene diisocyanate, bis(4-isocyanatophenyl)- sulfone, isopropylidenebis(4-phenylisocyanate) and the like, and biuret type adducts and isocyanurate ring adducts of these polyisocyanates; polyisocyanates having at least three isocyanate groups per molecule such as triphenylmethane-4,4',4"-triisocyanate, 1,3,5-triisocyanatobenzene, 2,4,6-triisocyanatotoluene, 4,4''dimethyldiphenylmethane-2,2',5,5'-tetraisocyanate and the like, and biuret type adducts and isocyanurate ring adducts of these polyisocyanatesj urethanation adducts formed by reacting polyol such as ethylene glycol, propylene glycol, 1,4-butylene glycol, dimethylolpropionic acid, polyalkylene glycol, trimethylolpropane, hexanetriol and the like, with polyisocyanate compound at a ratio that the isocyanate groups in the latter become excessive to the hydroxyl groups of the former, biuret type adducts and isocyanurate ring adducts of these polyisocyanates. These polyisocyanate compounds can be used either alone or in combination of two or more.
The blocking agent is a compound which blocks free isocyanate groups upon reacting with isocyanate groups in a polyisocyanate compound. Normally such blocked polyisocyanate compound releases the blocking agent when heated to, for example, at least 1000C, preferably at least 130°C, to regenerate the free isocyanate groups which can react with hydroxyl groups. The reaction of a blocking agent with a polyisocyanate compound can be carried out by a method known per se. Examples of such blocking agent include phenolic compounds such as phenol, cresol, xylenol, nitrophenol, ethylphenol, hydroxydiphenyl, butylphenol, isopropylphenol, nonylphenol, octylphenol, methyl hydroxybenzoate and the like! lactams such as ε-caprolactam, δ-valerolactam, γ-butyrolactam, β-propiolactam and the like; aliphatic alcohols such as methanol, ethanol, propyl alcohol, butyl alcohol, amyl alcohol, lauryl alcohol and the like? ethers such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, propylene glycol monomethyl ether, methoxymethanol and the like; benzyl alcohol; glycolic acid! glycolic acid esters such as methyl glycolate, ethyl glycolate, butyl glycolate and the like; lactic acid; lactic acid esters such as methyl lactate, ethyl lactate, butyl lactate and the like; alcohols such as methylolurea, methylolmelamine, diacetone alcohol, 2 -hydroxy ethyl acrylate, 2-hydroxyethyl methacrylate and the like; oximes such as formamidoxime, acetamidoxime, acetoxime, methylethylketoxime, diacetylmonoxime, benzophenoxime, cyclohexanoxime and the like; active methylenes such as dimethyl malonate, diethyl malonate, ethyl acetoacetate, methyl acetoacetate, acetylacetone and the like; mercaptans such as butyl mercaptane, t-butyl mercaptane, hexyl mercaptane, t-dodecyl mercaptane, 2-mercaptobenzothiazole, thiophenol, methylthiophenol, ethylthiophenol and the like,' acid amides such as acetanilide, acetanisidide, acetotoluide, acrylamide, methacrylamide, acetamide, stearamide, benzamide and the like; imides such as succinimide, phthalimide, maleimide and the like; amines such as diphenylamine, phenylnaphthylamine, xylidine, N-phenylxylidine, carbazole, aniline, naphthylamine, butylamine dibutylamine, butylphenylamine and the like; imidazole compounds such as imidazole, 2-ethylimidazole and the like; pyrazoles such as 3,5'dimethylpyrazole; urea compounds such as urea, thiourea, ethyleneurea, ethylenethiourea, diphenylurea and the like; carbamic acid esters such as phenyl N-phenylcarbamate; imines such as ethyleneimine, propyleneimine and the like; and sulfites such as sodium bisulfite, potassium bisulfite and the like. These blocking agents can be used either alone or in combination of two or more.
Water'dispersible blocked polyisocyanate compound-'
As the blocked polyisocyanate compound, those polyisocyanate compounds as named above, whose isocyanate groups are blocked with hydroxymonocarboxylic acid-containing blocking agent and which are rendered water-dispersible by the carboxyl groups introduced into the blocked polyisocyanate compounds by the hydroxymonocarboxylic acids can also be used. As the blocking agent, those similar to the abve-named can be used. Examples of the hydroxymonocarboxylic acid include 2 ^hydroxy acetic acid, 3-hydroxypropanoic acid, 12-hydroxy-9"octadecanoic acid (ricinoleic acid), 3-hydroxy-2,2"dimethylpropanoic acid (hydroxypivalic acid), dimethylolpropionic acid (DMPA) and the like. Of these,
3-hydroxy-2,2-dimethylpropanoic acid (hydroxypivalic acid) is preferred. The solvent used for the blocking reaction preferably is not reactive with isocyanate groups, and hence, for example, ketones such as acetone, methyl ethyl ketone and the like! esters such as ethyl acetate; and N-methylpyrrolidone (NMP) are preferred.
When a blocked polyisocyanate compound is used as the crosslinking agent, catalyst for accelerating urethanation reaction such as organotin compound can be used.
In the base coating paint (A), preferred content ratio of the resin (a), resin (b) and crosslinking agent (c) is: based on the total solid contents of these three components, resin (a), within a range of generally 20 - 80 mass%, in particular, 30 — 70 mass%, inter alia, 40 - 60 mass%; resin (b), within a range of generally 5 - 35 mass%, in particular, 10 - 30 mass%, inter alia, 15 — 25 mass%; and crosslinking agent (c), within a range of generally 15 - 45 mass%, in particular, 20 - 40 mass%, inter alia, 25 - 35 mass%.
Fine polymer particles (d)'- The base coating paint (A) can further contain fine polymer particles (d) for improving thickening effect and after tack resistance. As fine polymer particles (d), for example, polymer particles obtained by emulsion polymerization of a monomer (d"l) which contains at least two unsaturated groups per molecule and other unsaturated monomer (d-2) in the presence of an allyl group -containing reactive emulsifier. Such fine polymer particles are disclosed, for example, in JP Hei 3 (1991)-6677OA.
As the monomer (d- 1) containing at least two unsaturated groups per molecule, for example, unsaturated monocarboxylic acid ester of polyhydric alcohol, unsaturated alcohol ester of polybasic acid, and aromatic compound substituted with at least two unsaturated groups can be named. Specific examples include ethylene glycol diacrylate, ethylene glycol dimethacrylate, triethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, 1,3-butylene glycol dimethacrylate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, 1,4-butanediol diacrylate, neopentylglycol diacrylate, 1,6-hexanediol diacrylate, pentaerythritol diacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, pentaerythritol dimethacrylate, pentaerythritol trimethacrylate, pentaerythritol tetramethacrylate, glycerol dimethacrylate, glycerol diacrylate, glycerol allyloxydimethacrylate, 1,1,1- trishy droxy- methylethane diacrylate, 1, 1,1-trishydroxymethylethane triacrylate, 1,1,1 - trishy droxymethy lethane dimethacrylate , 1,1,1 -trishy droxy - methylethane trimethacrylate, 1,1,1-trishydroxymethylpropane diacrylate, 1,1,1-trishydroxymethylpropane triacrylate, 1,1,1 - trishy droxymethy lpropane dimethacrylate, 1,1,1-trishydroxymethylpropane trimethacrylate, triallyl cyanurate, triallyl isocyanurate, triallyl trimellitate, diallyl terephthalate, diallyl phthalate, divinylbenzene and the like. These monomers can be used either alone or in combination of two or more.
As other unsaturated monomer (d"2), those carboxyl group -containing unsaturated monomer (M- 1), hydroxyl group -containing unsaturated monomer (M~2) and other copolymerizable unsaturated monomer (M- 3) as exemplified as to the carboxyl group- and hydroxyl group -containing resin (a) can be similarly used. Again, nitrogen-containing alkyl (meth)acrylate such as dimethylaminoethyl (meth)acrylate; diene compounds such as butadiene, isoprene and the like! and alkoxysilane group -containing monomers such as vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris(2-methoxyethoxy)silane, γ-methacryloxypropyl- trimethoxysilane, vinyl triacetoxysilane and the like can also be used. These monomers can be used either alone or in combination of two or more.
The use ratio of above monomers (d"l) and (d-2) is not strictly limited, but is variable depending on physical properties desired of the fine polymer particles, which can be, based on the total amount of the monomers (d"l) and (d-2), such that the monomer (d"l) is within a range of generally 1 - 60 mass%, preferably 1 - 50 mass%, inter alia, 1 - 40 mass%, and the monomer (d'2), within a range of generally 40 - 99 mass%, preferably 50 — 99 mass%, inter alia, 60 — 99 mass%. Copolymerization of the monomers (d"l)and (d'2) can be carried out by emulsion polymerization thereof by the means known per se in the presence of an allyl group -containing reactive emulsifying agent, using a polymerization initiator. As the allyl group -containing reactive emulsifier, any of anionic, cationic or nonionic reactive emulsifiers can be used so long as they are allyl group -containing reactive emulsifiers, anionic allyl group -containing reactive emulsifiers being particularly preferred. Concrete examples of anionic allyl group -containing reactive emulsifier include ammonium salts of sulfonic acid compounds containing allyl groups, specifically, for example, anionic emulsifiers whose basic structure is p olyoxy ethylene alkyl ether sulfate salt, into which radical-polymerizable allyl group as a part of its hydrophobic groups is introduced. As such emulsifiers which are commercially available, for example, Aqualon KH" 10 (tradename, Daiichi Kogyo Seiyaku Co., Ltd.), Latemul S- 180A (tradename, Kao Corporation), SR-1025 (tradename, Asahi Denka Co., Ltd.) and the like can be named.
Adequate use rate of the reactive emulsifier is, to the total quantity of the monomers (d-l) and (d-2), normally 0.1 - 10 mass%, preferably 1 — 5 mass%. Where necessary, anionic surfactant, nonionic surfactant, amphcrionic surfactant and the like other than the above reactive emulsifier may be concurrently used as the emulsifier. Specific examples include^ as anionic surfactant, fatty acid, alkylsulfate salt, alkylbenzenesulfonic acid salt, alkylphosphoric acid salt and the like; as nonionic surfactant, polyoxyethylene alkyl ether, polyoxy ethylene alkylallyl ether, polyoxyethylene derivatives, sorbitan fatty acid ester, polyoxyethylenesorbitan fatty acid ester, polyoxyethylene alkylamine, alkylalkanolamine and the like; and as ampho-ionic surfactant, alkylbetaine and the like. Adequate use amount of these optionally added emulsifiers is, based on the combined quantity of the monomers (d"l) and (d"2), normally within a range of 0.1 - 10 mass%, preferably 1 — 5 mass%.
As the polymerization initiator, for example, peroxide represented by ammonium persulfate, potassium persulfate, ammonium peroxide and the like; "redox" initiators in which these peroxides are combined with reducing agents such as sodium hydrogensulfite, sodium thiosulfate, Rongalit, ascorbic acid and the like; and azo compounds such as 4,4'-azobis(4-cyanobutanoic acid) and the like can be named. Of these, azo compounds, in particular, water-soluble azoamide compounds can be suitably used. Water-soluble azoamide compounds are known per se (e.g., see JP Sho 61 (1986)-218618A, JP Sho 61 (1986)-63643A), and concrete examples of commercial products include VA Series (tradename, Wako Pure Chemical Industries, Ltd.).
The use ratio of the polymerization initiator is, based on the combined quantity of the monomers (d-l) and (d"2), normally within a range of 0.01 - 10 mass%, preferably 0.1 - 5 mass%.
Suitable concentration of total unsaturated monomers during the emulsion polymerization reaction is normally within a range of 0.1 - 50 mass%, preferably 0.5 - 30 mass%.
The reaction temperature of the emulsion polymerization differs depending, for example, on the kind of polymerization initiator used, but normally it can be 60 - 900C, and the reaction time, normally 5 — 10 hours. From the viewpoint of water resistance of the resulting coating film, the fine polymer particles (d) can have a hydroxyl value within a range of generally 0 - 70 mgKOH/g, preferably 0 - 60 mgKOH/g, inter alia, 0 — 50 mgKOH/g. Again, in consideration of water dispersibility, the fine polymer particles (d) can have an acid value within a range of generally 0 - 90 mgKOH/g, preferably 0 - 70 mgKOH/g, inter alia, 0 - 50 mgKOH/g. The fine polymer particles (d) can furthermore have particle diameters within a range of generally 10 - 500 nm, preferably 20 - 250 nm, inter alia, 30 - 150 nm. In the present specification, the particle diameter measurement is made with COULTER N4 Model submicron particle analyzer (Nikkaki Bios Co., Ltd.).
The fine polymer particles (d) may be neutralized with basic compound, where necessary. As the neutralizer for the fine polymer particles (d), those basic substances exemplified as to neutralization of the carboxyl group- and hydroxyl group -containing resin (a) can be similarly used.
The fine polymer particles (d) are used preferably in an amount within a range of generally 0 - 40 mass%, in particular, 0 - 30 mass%, inter alia, 0 — 20 mass%, based on the total solid content of the resin (a), resin (b) and crosslinking agent (c).
The base coating paint (A) can be formulated by mixing the above-described resin (a), resin (b), crosslinking agent (c) and optionally the fine polymer particles (d), together with a solvent.
The base coating paint (A) may be either water-based or hydrophilic organic solvent-based, while generally hydrophilic organic solvent-based type is preferred.
In the present specification, hydrophilic organic solvent signifies organic solvent at least 20 g of which is soluble in 100 g of water.
As the hydrophilic organic solvent, for example, ester type, ether type, alcoholic, amide type and ketone type solvents meeting the above condition can be used. These hydrophilic organic solvents can be used either alone or in combination of two or more. In particular, such hydrophilic organic solvents as ethylene glycol monomethyl ether acetate, diethylene glycol monomethyl ether acetate, diethylene glycol monoethyl ether acetate, dioxane, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol diethyl ether, diethylene glycol monobutyl ether, propylene glycol monoethyl ether, dipropylene glycol monomethyl ether, methyl alcohol, ethyl alcohol, allyl alcohol, n-propyl alcohol, isopropyl alcohol, tert-butyl alcohol, ethylene glycol, 1,2-propylene glycol, 1,3-butylene glycol, 2,3-butylene glycol, hexylene glycol, hexanediol, dipropylene glycol, acetone, diacetone alcohol and the like can be suitably used.
The hydrophilic organic solvent also encompasses hydrophilic organic solvent-water mixed system which is formed by substituting a part of above-described hydrophilic organic solvent with deionized water or the like. In such hydrophilic organic solvent-water mixed system, normally adequate ratio ranges, per the total solvent present in the base coating paint (A), the hydrophilic organic solvent, 50 — 100 mass%; and water, 0 - 50 mass%. Where the base coating paint (A) contains fine polymer particles (d), the fine polymer particles (d) can be added in the form of an aqueous dispersion as it is, or when the base coating paint (A) is hydrophilic organic solvent-based, they may be first converted to a form as dispersed in a hydrophilic organic solvent before the addition. The conversion of aqueous dispersion of the fine polymer particles (d) to a dispersion in a hydrophilic organic solvent can be effected by, for example, a method comprising adding solvent such as xylene, butyl alcohol, butyl acetate, methyl ethyl ketone, toluene or the like to an aqueous dispersion of fine polymer particles (d), removing water by azeotropy of water and the solvent(s), and dispersing the fine polymer particles (d) in the hydrophilic organic solvent; or a method comprising evaporating water off from an aqueous dispersion of fine polymer particles (d) by spray drying system or simple drying and thereafter re-dispersing the particles in hydrophilic organic solvent. Pigment may also be blended in the base coating paint (A). There is no particular limitation concerning the pigment and, for example, inorganic and organic coloring pigments such as titanium dioxide, zinc flower, Carbon Black, red iron oxide, Phthalocyanine blue, Prussian blue, Cobalt Blue, azo pigment, phthalocyanine pigment, quinacridone pigment, isoindoline pigment, vat pigment and perylene pigment; extenders such as talc, clay, kaoline, baryta, barium sulfate, barium carbonate, calcium carbonate, silica and alumina white! and effect pigments such as aluminum powder, mica powder, titanium dioxide -coated mica powder, micaceous iron oxide, silver-plated glass flakes, titanium -coated graphite, metal titanium flakes, phthalocyanine flakes and the like can be conveniently used. These pigments can be used either alone or in combination of two or more.
Adequate blend ratio of pigment is, based on the total solid content of the resin (a), resin (b) and crosslinking agent (c), generally within a range of 0 - 250 mass%, in particular, 0.1 - 150 mass%.
The base coating paint (A) can further be suitably blended with, where necessary, various paint additives such as curing catalyst, dispersant, antisettling agent, defoaming agent, thickener, UV absorber, light stabilizer, surface regulator, antioxidant and the like.
Concentration of the non-volatile component in the base coating paint (A) at its application time can be normally within a range of 20 - 65 mass%, it being preferred to adopt high-solid type in which the organic solvent content is reduced and the non-volatile component's concentration is adjusted to fall within a range of normally 30 - 60 mass%, in particular, 40 - 60 mass%, for preventing atmospheric pollution and resources saving.
Single coating film of the base coating paint (A) is normally of colored and non-transparent or colored and transparent solid tone, or of metallic tone. Here the non- transparent coating film signifies a coating film whose percent transmission is less than 5%, as measured with a 20 μπrthick cured coating film made of the base coating paint alone,' and transparent coating film is one having percent transmission of 5% or higher, as measured with a 20 μπrthick cured coating film made of the base coating paint alone. Coating objects
The coating objects to which the method of the invention is applicable are not particularly limited, and, for example, sheet steel such as cold-rolled sheet steel, zinc-plated sheet steel, zinc alloy-plated sheet steel, stainless steel sheet and tin-plated sheet steel; metal substrates such as aluminum plate and aluminum alloy- plate; and various plastic materials can be used. They may also be bodies of various vehicles such as automobiles, two-wheeled vehicles and container cars formed thereof.
The coating objects may also be metallic surfaces of metal substrates or of car bodies, which have been given a surface treatment such as phosphate treatment, chromate treatment or complex oxide treatment. Furthermore, the coating objects may be given an undercoating (e.g., cationic electrodeposition coating) in advance and depending on the occasion, further coating such as intermediate coating may be applied where necessary.
According to the method of the present invention, first the base coating paint (A) is applied onto a coating object. Application of the base coating paint (A) can normally be effected by the steps of adjusting coating viscosity of the base coating paint (A) with, for example, diluting solvent or the like, to normally 13 - 60 seconds, preferably 15 - 40 seconds using Ford cup No. 4 at 200C, and applying the same by such means as air spray, airless spray, rotary atomizing coating or the like, optionally applying static electricity where necessary, to a cured film thickness of generally about 5 — about 25 μm, in particular, about 10 — about 20 μm. Without curing so formed base coating film (A) by heating, and optionally after allowing it to stand at ambient temperature for about 1 - 20 minutes or further preheating the coated surface at about 60 — about 800C for around 3 — 10 minutes, where necessary, water-based coloring paint (B) is applied onto the uncured coated surface. Water-based coloring paint (B)
Water-based coloring paint (B) is a water-based liquid paint to be coated onto a surface coated with uncured base coating paint (A), which can generally be formulated by mixing a base resin (B-I), crosslinking agent (B-2) and coloring pigment (B-3) into, and dispersing in, water.
As the base resin (B" l), for example, carboxyl group- and hydroxyl group -containing acrylic resin, carboxyl group- and hydroxyl group -containing polyester resin and the like can be named. From the viewpoint of water dispersibility, the base resin (B"l) preferably has an acid value within a range of generally 10 — 150 mgKOH/g, in particular, 30 - 100 mgKOH/g. In respect of curability, the base resin (B-I) preferably has a hydroxyl value within a range of generally 10 - 150 mgKOH/g, in particular, 30 - 100 mgKOH/g. Further in respect of weatherability, the acrylic resin as the base resin (B- 1) preferably has a number-average molecular weight within a range of generally 3,000 - 100,000, in particular, 5,000 - 50,000; and the polyester resin, generally 500 - 50,000, in particular, 3,000 - 30,000. As the base resin (B- 1), those explained as to the carboxyl group- and hydroxyl group -containing resin (a) used in the base coating paint (A) can be similarly used. Also as the acrylic resin, those produced by emulsion polymerization in the presence of an aqueous solution of dispersion stabilizer can also be used. Such acrylic resin produced by the emulsion polymerization preferably has a number-average molecular weight of generally at least 100,000, in particular, within a range of 200,000 - 2,000,000. '
As the dispersion stabilizer useful for the emulsion polymerization, besides nohionic surfactants' or anionic surfactants, aqueous resins such as acrylic resins having an acid value within a range of 10 - 150 mgKOH/g and a number-average molecular weight within a range of 5,000 - 30,000 can be conveniently used.
The emulsion polymerization can be carried out by those means known p_er se. In particular, acrylic emulsions produced by multistage polymerization process using carboxyl group -containing unsaturated monomers are preferred, as they can give water-based coloring paint excelling in coating workability. That is, an acrylic emulsion obtained by first polymerizing a monomeric mixture containing no or little carboxyl group -containing unsaturated monomer (normally no more than 3 mass% of the total monomers), and then continuing the polymerization reaction using a monomeric mixture containing carboxyl group -containing unsaturated monomer (normally 5 - 30 mass% of the total monomers) exhibits viscosity-developing effect upon neutralization with a basic substance, to provide water-based coloring paint excelling in coating workability such as sagging resistance and, therefore, is preferred. As the basic substance used for the neutralization, those basic substances exemplified in relation to the resin (a) in the base coating paint (A) can be similarly used. Its adequate use amount is normally within a range of 0.1 - 1.5 equivalent, in particular, 0.3 - 1.2 equivalent, to the carboxyl groups in the acrylic emulsion produced by the above multistage polymerization process.
As the crosslinking agent (B"2), at least one selected from those hydroxyl group -reactable crosslinking agents exemplified in relation to the crosslinking agent (c) in the base coating paint (A) can be used.
Suitable use ratio of the base resin (B-I) and crosslinking agent (B-2) is- based on the combined amount of the two components, the base resin (B-I), within a range of generally 50 — 90 mass%, in particular, 60 - 85 mass%, inter alia, 65 - 80 mass%; and the crosslinking agent (B-2), generally 10 - 50 mass%, in particular, 15 - 40 mass%, inter alia, 20 - 35 mass%.
The coloring pigment (B'3) is for coloring the coating film of water-based coloring paint (B), and the film may be colored and transparent, or colored and non-transparent. As such coloring pigment (B"3), those exemplified as to the base coating paint (A) can be similarly used. Coloring pigments can be used either alone or in combination of two or more.
The water-based coloring paint (B) can be formulated, for example, by mixing base resin (B-I), crosslinking agent (B-2) and coloring pigment (B'3) into water and dispersing them. Similarly to the case of base coating paint (A), the water-based coloring paint may further be blended with extender and the like, as necessity requires. Also where necessary, paint additives such as curing catalyst, dispersant, antisettling agent, defoamer, thickener, UV absorber, light stabilizer, surface regulating agent, antioxidant and the like may be suitably used.
Preferred non-volatile component content in the water-based coloring paint (B) at its application time is normally within a range of 15 — 65 mass%. Coating film of the paint (B) alone can be a non- transparent or transparent solid tone or metallic tone coating film. Here the non-transparent coating film signifies a film made of the water-based coloring paint alone, which has a % transmission less than 5% at its cured thickness of 20 μm, and the transparent coating film signifies a film as above which has a % transmission of at least 5% at its cured thickness of 20 μm.
The water-based coloring paint (B) is applied onto an uncured coated surface with the base coating paint (A) which has been allowed to stand at ambient temperature for 1 — 20 minutes, where necessary, and further preheated at about 60°C - about 800C for about 3 - 10 minutes, again where necessary.
Application of the water-based coloring paint (B) can be carried out after adjusting its coating viscosity to normally 15 — 60 seconds, preferably 20 - 50 seconds at 200C with, for example, Ford cup No. 4, by such means as air spray, airless spray, rotary atomizing coating or the like, under impression of static electricity where necessary, to a film thickness referring to cured coating film of about 5 — about 40 μm, in particular, about 10 — about 35 μm,
According to the method of the present invention, the water-based coloring paint (B) is coated on uncured coated surface with the base coating paint (A), and then a clear paint (C) is coated. Where necessary, however, preceding application of the clear paint (C), the two-layered coating film formed of the base coating paint (A) and water-based coloring paint (B) may be preliminarily dried at temperatures of about 50 - about 1000C. Upon this pre-drying, the most of the volatile components in the two-layered coating film such as organic solvent, water and the like are evaporated.
As the coating film is dried and solidified upon volatilization of the volatile components under the pre-drying, when the clear paint (C) is applied onto the coated surface and the solvent, low molecular weight resin component and the like which are contained in the clear coating film infiltrate and diffuse in the two-layered coating film, viscosity drop of the two-layered coating film can be inhibited. In consequence, re-flowing of metallic pigment can be suppressed when metallic pigment is used, to prevent occurrence of metallic unevenness.
Clear paint (C)
As the clear paint (C), normally those useful in car coating can be used, for example, organic solvent-based or water-based clear paint containing thermosetting resin composition. Such thermosetting resin composition used in the clear paint include, for example, compositions composed of base resin such as acrylic resin, polyester resin, urethane resin and the like having crosslinkable functional groups such as hydroxyl group, and crosslinking agent such as melamine resin, (blocked) polyisocyanate compound and the like; and acid-epoxy crosslinking resin compositions comprising acid group -containing resin and epoxy group -containing resin as the constituent components. As the clear paint, water-based type can be favorably used from the standpoint of solvent reduction. In the clear paint (C), furthermore, coloring pigment, extender pigment or the like can be used to an extent not impairing transparency. As such coloring pigment and extender pigment, for example, those exemplified in relation to the base coating paint (A) can be used. The coloring pigments and extender pigments can be used each alone or in combination of two or more.
The clear paint (C) can further suitably contain, where necessary, such paint additives as curing catalyst, defoamer, thickener, UV absorber, light stabilizer, antioxidant, surface regulating agent, dispersant, antisettling agent and the like. Preferred non-volatile component concentration of the clear paint (C) at its application time is normally within a range of 30 — 70 mass%.
The clear paint (C) is coated on the two-layered coating film formed of base coating paint (A) and water-based coloring paint (B). The clear paint (C) is applied, after it is adjusted to have an adequate coating viscosity with solvent and/or water, by those methods known per se, such as airless spray, air spray, rotary atomizing coating or the like. Its coating may be carried out under impression of static electricity. Suitable coated film thickness is, based on the cured coating film, normally within a range of about 25 - about 50 μm, in particular, about 30 - about 45 μm.
After coating the clear paint (C), the resulting three-layered coating film formed of the base coating paint (A), water-based coloring paint (B) and clear paint (C) is simultaneously cured by heating, to form a multilayer coating film.
After coating the clear paint (C) and before conducting the heat-curing, the three-layered coating film may be preliminarily dried at about 50 - about 1000C for about 1 - 10 minutes, where necessary to accelerate evaporation of the volatile components mainly in the coating film of the clear paint (C). This pre-drying evaporates off the most of the volatile components such as organic solvent, water and the like that are present in the three -layered coating film.
Heat-curing of the three-layered coating film can be effected by heating at temperatures of normally about 100 - about 18O0C, preferably about 120 - about 1700C, normally for about 5 - 60 minutes, preferably about 10 — 40 minutes.
In the method of the present invention, the heating and optional pre-drying can be effected by heating means known per se. Specifically, they can be effected with drying oven such as hot air oven, electric oven, infrared induction heating oven and the like.
The above-described multilayer coating film-forming method enables reduction in use amount of solvent and shortening of process steps, and provides multilayer coating film excelling in coating workability and finished appearance even under high humidity conditions. Thus the method can be advantageously used as a multilayer coating film -forming method applicable to intermediate paint and top paint coating steps in car coating.
Hereinafter the present invention is more specifically explained, referring to working Examples and Comparative Examples, it being understood that the invention is not limited thereto. Hereafter "part" and "%" are invariably based on mass, and thickness of coating film is invariably based on the cured coating film.
Examples
Production of carboxyl group- and hydroxyl group -containing acrylic resin (a)
Production Examples 1 — 4
A four-necked flask equipped with a stirrer, thermometer, cooling tube and nitrogen gas inlet was charged with 37.5 parts of isopropanol of which temperature was then raised to 85°C under nitrogen gas passage. After it reached 85°C, nitrogen gas supply was stopped and into the flask each of the monomeric mixtures having the blended composition of the monomers and polymerization initiator as shown in the following Table 1 was added drop wise over 3 hours.
(The system assumed weak refluxing condition at the initial stage of the dropwise addition, but the refluxing condition ceased as the dropping was continued.) The reaction system was aged for further 2 hours at 850C while passing nitrogen gas, and cooled to 6O0C. Diluting the product with 29 parts of methoxypropanol, solutions of respective carboxyl group- and hydroxyl group-containing acrylic resins (a-l) - (a-4) having a solid content of 60 mass% were obtained. The solid mass concentrations (%) and resinous parameters of the resulting resin (a- 1) - (a-4) solutions are shown in the following Table 1.
In the Table 1, PLACCEL FM-3 is a tradename (Daicel Chemical Industries Ltd.) of ε-caprolactone-modified hydroxyethyl methacrylate (modified at a ratio of 3 mols of ε-caprolactone per mol of hydroxyethyl methacrylate). TABLE 1
Figure imgf000036_0001
(Note l) polymerization initiator
Production of tertiary amino group -containing resin (b) Production Examples 5 - 7
A four-necked flask equipped with a stirrer, thermometer, cooling tube and nitrogen gas inlet was charged with 20 parts of ethylene glycol monobutyl ether whose temperature was raised to 95°C under nitrogen gas passage. After it reached 950C, nitrogen gas supply was stopped and into the flask each of the monomeric mixtures having the blended composition of the monomers, solvent and polymerization initiator as shown in the following Table 2 was added dropwise over 3 hours. Then each of the products was aged at 95°C for 2 hours under nitrogen gas passage, cooled to 60°C, and diluted with 15 parts of ethylene glycol, monobutyl ether, to provide solutions of respective tertiary amino group-containing resins OrI) - (b'3) having a solid content of 50 mass%. The solid mass concentrations (%) and resinous parameters of the resulting resin (b-l) - (b-3) solutions are shown in the following Table 2.
In the Table 2, MPEG 2000 MA (tradename) is a methoxypoly ethylene glycol 2000 methacrylate, and MPEGlOOO MA (tradename) is a methoxypolyethylene glycol 1000 methacrylate, both being the monomers made by Degussa Japan Co., Ltd. The active component of MPEG 2000 MA is 50%.
TABLE 2
Figure imgf000037_0001
(Note 2) polymerization initiator
Production of fine polymer particles (d)
A four-necked flask equipped with a stirrer, thermometer, cooling tube and mantle heater was charged with 355 parts of deionized water and 4 parts of LATEMUL S- 120A (tradename, a sulfosuccinic acid-derived allyl group -containing anionic reactive emulsifier, KAO Corporation, solid content 50%), of which temperature was raised to 900C under stirring. Then 20% of an aqueous solution of 1.25 parts of VA-086 (tradename, a water-soluble azoamide polymerization initiator, 2,2'-azobis[2-methyl-N-(2- hydroxyethyl)-propionamide], Wako Pure Chemical Industries, Ltd.) in 50 parts of deionized water was added. Fifteen (15) minutes thereafter, 5% of a monomeric mixture (a mixture of 48 parts of styrene, 22 parts of methyl methacrylate, 22 parts of n-butyl acrylate and 8 parts of 1,6-hexanediol diacrylate) was added, followed by 30 minutes' stirring. Then dropwise addition of the remaining monomeric mixture and the remaining aqueous polymerization initiator solution was started. The dropping of the monomeric mixture required 3 hours, and that of the aqueous polymerization initiator solution required 3.5 hours, respectively, and the polymerization temperature was maintained at 90°C in the meantime. After the end of dropping the aqueous polymerization initiator solution, the reaction mixture was aged at 900C for 30 minutes. Cooling the same to room temperature and filtering through 200-mesh Nylon cloth, an aqueous fine polymer particle dispersion having a solid content of 20% was obtained.
The resulting aqueous dispersion of fine polymer particles was dried on a stainless steel vat in an electric hot air drier at 6O0C to remove water. Thus obtained solid was re-dispersed in 6O0C ethylene glycol monomethyl ether to provide a dispersion (d-l) of fine polymer particles having a solid content of 20%.
Production of aqueous dispersion of acrylic resin (i) for water-based coloring paint (B) Production Example 9
An aqueous dispersion of acrylic resin (i) was produced as follows, as a resin dispersion to be used for a water-based coloring paint (B).
A reactor equipped with a thermometer, thermostat, stirrer, reflux condenser and a dropping device was charged with 145 parts of deionized water and 1.2 parts of Newcol 562SF (Note 3), which were stirred and mixed in nitrogen gas current. Raising the temperature to 800C, 5% of the total amount of the following monomeric emulsion (l) and 5.2 parts of 3% aqueous ammonium persulfate solution were introduced into the reactor and maintained at 800C for 20 minutes. Then the remaining monomeric emulsion (l) was added into the reactor dropwise over 3 hours, followed by 30 minutes' aging. Then the following monomeric emulsion (2) was added dropwise over 1.5 hours. The reaction mixture was aged for 2 hours, and cooled to 300C under gradual addition of 89 parts of 1.5% aqueous N,N-dimethylethanolamine solution into the reactor. Discharging the reaction mixture through lOOmesh Nylon cloth, an aqueous dispersion of acrylic resin (i) having a solid content of 25% was obtained. The acrylic resin (i) had a hydroxyl value of 22 mgKOH/g, an acid value of 30 mgKOH/g and an average particle size of 100 nm. (Note 3) Newcol 562SF: tradename, Nippon Nyukazai Co., Ltd., ammonium polyoxyethylene alkylbenzenesulfonate, active ingredient, 60%.
Monomeric emulsion (l): By mixing under stirring 94.3 parts of deionized water, 17 parts of methyl methacrylate, 80 parts of n-butyl acrylate, 3 parts of allyl methacrylate and 1.2 parts of Newcol 562SF, monomeric emulsion (l) was obtained.
Monomeric emulsion (2): By mixing under stirring 37.3 parts of deionized water, 15.4 parts of methyl methacrylate, 2.9 parts of n-butyl acrylate, 5.9 parts of hydroxyethyl acrylate, 5.1 parts of methacrylic acid, 0.5 part of Newcol 562SF and 1.7 parts of 3% aqueous ammonium persulfate solution, monomeric emulsion (2) was obtained.
Production of base coating paint (A) Production Example 10
Pigment-dispersed paste 1 was obtained by mixing 33.3 parts of the acrylic resin (a-l) as obtained in Production Example 1, 1 part of CARBON MA- 100 (tradename, Carbon Black, Mitsubishi Chemical Co.), 40 parts of JR-806 (tradename, titanium white, Tayca
Corporation), 25 parts of BARIACE B-32 (tradename, barium sulfate, Sakai Chemical Industry Co., Ltd.), 1.6 parts of N,N-dimethylethanolamine and 24.1 parts of ethylene glycol monobutyl ether, and dispersing the mixture in a paint shaker for 30 minutes.
Production Example 11
Production Example 10 was repeated except that the acrylic resin (a-l) solution was replaced by acrylic resin (a-2) solution, to provide pigment-dispersed paste 2. Production Example 12
Production Example 10 was repeated except that the acrylic resin (a-l) solution was replaced by acrylic resin (a-3) solution, to provide pigment-dispersed paste 3.
Production Example 13
Production Example 10 was repeated except that the acrylic resin (a-l) solution was replaced by acrylic resin (a-4) solution, to provide pigment-dispersed paste 4.
Production Examples 14 - 20
The solutions of acrylic resins (a-l) — (a-4) as obtained in Production Examples 1 - 4, those of tertiary amino group -containing resins (b"l) - (b"3) as obtained in Production Examples 5 - 7, pigment-dispersed pastes 1 — 4 as obtained in Production Examples 10 - 13, Cymel 325 (tradename, Mitsui Cytec Co., methylated melamine resin, solid content 80%), dispersion of fine polymer particles (d"l) as obtained in Production Example 8, and N,N-dimethylethanolamine were mixed by stirring at the blend ratios as shown in the following Table 3, and further ethylene glycol monomethyl ether was added to adjust viscosity of each of the mixtures to 30 seconds at 200C as measured with Ford cup No. 4. Thus base coating paints (A-l) - (A- 1)' were, obtained. In each of the base coating paints, the neutralization equivalent by
N,N-dimethylethanolamine to the carboxyl groups in the acrylic resins (a) was invariably 0.5. TABLE 3
Figure imgf000041_0001
Production of water-based coloring paint (B) Production Example 21
To 37.5 parts of Cymel 325, 50 parts of SETAL 6306 (tradename, Akzo Co., water-soluble polyester resin, solid content, 60%), and 160 parts of the aqueous dispersion of acrylic resin (i) as obtained in Production Example 9 were added under stirring by the order stated. Then Alumipaste GX180A (tradename, Asahi Chemical Industry Co., Ltd., aluminium flake paste) of an amount of 20 parts in terms of the aluminium pigment was added under stirring and mixed and dispersed. Further N,N-dimethylethanolamine and deionized water were added to adjust the pH to 8.0 and the viscosity to 30 seconds at 20°C as measured with Ford cup No. 4. to provide a water-based coloring paint (B- 1).
Formation of multilayer coating film (preparation of test panels) Examples 1 - 6 and Comparative Example 1 Test panels were prepared as follows, using as the base coating paint (A) each of the base coating paints (A'l) - (A- 7) as obtained in Production Examples 14 — 20, and as the water-based coloring paint (B), the water-based coloring paint (B-I) as obtained in Production Example 21.
Onto a PALBOND #3020 (tradename, Nippon Parkerizing Co., a zinc phosphate treating agent)-applied cold-rolled steel sheet, ELECRON GT-IO (tradename, Kansai Paint Co., a cationic electrodeposition paint) was electrocoated and cured by heating at 1700C for 30 minutes to form a 20 μπrthick coating film.
Then each of the base coating paints (A-l) through (A- 7) was applied as would provide a 20 μπrthick coating film with Minibell G (tradename, Japan Ransburg Co., a rotary atomizing electrostatic coater) under the conditions of temperature 25°C and humidity 80%, allowed the coated surfaces to stand for 7 minutes, onto which the water-based coloring paint (B- 1) was applied as would provide a 25 μπrthick coating film, with REA (tradename, Japan Ransburg Co., an electrostatic air spray coater), allowed the coated surfaces to stand for 3 minutes, and preheated them at 70°C for 5 minutes. Further leaving the panels to stand for 6 minutes, a clear paint (C) (KINO# 1200TW, tradename, Kansai Paint Co., acid/epoxy curing type acrylic resin derived clear paint, with its viscosity adjusted to 25 seconds at 200C as measured with Ford cup No. 4) was coated as would provide a 35 μπrthick film, with Minibell G. Leaving the panels to stand for the following 10 minutes, the three -layered films formed of the base coating paint (A), water-based coloring paint (B-l) and clear paint (C) were cured by heating them in an electric hot air drying oven at 1400C for 30 minutes, to provide the test panels (multilayer films).
Results of performance tests
Thus obtained test panels were given performance tests. The performance test results were as shown in later- appearing Table 4. Cracking in water-based coloring coat:
Occurrence of cracking in the coating films after application of the water-based coating film (B) was evaluated by visual observation, according to the following standard:
O: no cracking occurred in the water-based coloring coat
(metallic coating film) which was good; X : cracking occurred in the water-based coloring coat (metallic coating film) which was inferior.
Finished appearance:
Measured with BYK Gardner's Wave Scan (tradename) which measured Long Wave value (LW) and Short Wave value (SW). Long Wave value is an index of amplitude of surface roughness of the wavelength ranging about 1.2 - 12 mm, and can evaluate the condition of medium wave texture of coated film surface. Short Wave value is an index of amplitude of surface roughness of the wavelength ranging about 0.3 - 1.2 mm, and can evaluate the condition of fine texture of coated film surface. As to both of the Wave Scan values, less measured values indicate higher smoothness of the coating film surface. By way of a yardstick, generally SW values less than 15 as measured with Wave Scan indicate favorable coated surface smoothness. IV value: IV values were measured with a laser metallic effect measuring device (ALCOPE LMR-200, tradename, Kansai Paint Co.). IV is an index of whiteness of metallic coating film. The higher the degree of uniform orientation of metallic pigment in parallel with the coated surface, the higher the degree of whiteness and the better the metallic effect. Higher IV values indicate higher whiteness. Metallic unevenness:
The extent of occurrence of metallic unevenness in the test panels was evaluated by visual observation'-
O: metallic unevenness scarcely recognized; Δ: a little metallic unevenness recognized;
X '■ much metallic unevenness recognized.
Chipping resistance:
Each of the test panels was mounted on a test piece support in Suga Test Instruments Co., Ltd.'s flying stone tester JA-400 Model (tradename, a chipping test device), and 50 g of crushed granite rock of particle size No. 7 was blown at the coated surface with compressed air of 0.392 MPa (4 kgf/cm2 at -2O0C). The extent of thereby incurred damage on the coated film was visually observed and evaluated: O: size of the damage was small and the electrocoated surface or the substrate steel sheet were not exposed; A' size of the damage was small but the electrocoated surface and substrate steel sheet were exposed! X • size of the damage was considerably large and the substrate steel sheet was broadly exposed.
TABLE 4
Figure imgf000044_0001

Claims

1. A multilayer coating film-forming method comprising applying base coating paint (A) onto a coating object, successively applying onto the so formed uncured coated surface water-based coloring paint (B) and clear paint (C), and then heating to simultaneously cure the three-layered coating film composed of the paints (A), (B) and (C), the method being characterized in that the base coating paint (A) contains
(a) carboxyl group- and hydroxyl group -containing resin,
(b) tertiary amino group -containing resin which is obtained by copolymerizing tertiary amino group -containing unsaturated monomer (b-l), polyoxyalkylene group-containing nonionic unsaturated monomer (b'2) and other unsaturated monomer (tr3), and
(c) crosslinking agent reactable with hydroxyl group.
2. A method according to Claim 1, in which the resin (a) has an acid value within a range of 2 — 100 mgKOH/g and a hydroxyl value within a range of 20 - 200 mgKOH/g.
3. A method according to Claim 1, in which the resin (a) is selected from the group consisting of carboxyl group- and hydroxyl group -containing acrylic resin, carboxyl group- and hydroxyl group -containing polyester resin, and carboxyl group- and hydroxyl group -containing polyurethane resin.
4. A method according to Claim 1, in which the monomer (b"l) contains N,N-dialkyldiaminoalkyl (meth)acrylate as a constituent component.
5. A method according to Claim 1, in which the monomer (b"2) is a compound represented by the following formula (l)'-
CH2 = C(R1)COO(CnH2nO)m-R2 (D in which R1 stands for hydrogen or methyl, R2 stands for hydrogen or C1-4 alkyl, m is an integer of 4 — 60, and n is an integer of 2 or 3, wherein the m oxyalkylene units (CnlHbnO) may be the same or different
6. A method according to Claim 1, in which the resin (b) has an amine value within a range of 3 — 100 mgKOH/g and a hydroxyl value within a range of 10 - 130 mgKOH/g.
7. A method according to Claim 1, in which the crosslinking agent (c) is selected from the group consisting of melamine resin, blocked polyisocyanate compound and water-dispersible blocked polyisocyanate compound.
8. A method according to Claim 1, in which the base coating paint (A) contains, based on the total solid content of the resin (a), resin (b) and crosslinking agent (c), 20 — 80 mass% of resin (a), 5 — 35 mass% of resin (b) and 15 - 45 mass% of crosslinking agent (c).
9. A method according to Claim 1, in which the base coating paint (A) further contains (d) fine polymer particles which are obtained by emulsion polymerizing monomer (d- 1) which contains at least two unsaturated groups per molecule and other unsaturated monomer (d-2) in the presence of an allyl group -containing reactive emulsifier.
10. A method according to Claim 9, in which the base coating paint (A) contains 0 - 40 mass% of fine polymer particles (d), based on the total solid content of the resin (a), resin (b) and crosslinking agent (c).
11. A method according to Claim 1, in which the base coating paint (A) is a hydrophilic organic solvent-based base coating paint.
12. Articles coated by the method as described in any one of Claims 1 - 11.
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JP6921669B2 (en) * 2016-08-05 2021-08-18 花王株式会社 Three-dimensional object precursor treatment agent composition
JP6929130B2 (en) * 2016-08-09 2021-09-01 楠本化成株式会社 Mixed layer control agent

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20020046950A1 (en) * 2000-10-19 2002-04-25 Klausjoerg Klein Concentrate suitable for the preparation of cathodic electrodeposition coating compositions
WO2003070781A1 (en) * 2002-02-15 2003-08-28 Ppg Industries Ohio, Inc. Thermosetting compositions containing alternating copolymers of isobutylene type monomers
US20060121204A1 (en) * 2004-02-06 2006-06-08 Yasukiho Nakae Water-based intercoating composition and method of forming multilayered coating film

Family Cites Families (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS61141969A (en) * 1984-12-17 1986-06-28 Kansai Paint Co Ltd Metallic finishing method
JPH01266126A (en) * 1988-04-19 1989-10-24 Dainippon Ink & Chem Inc Curable resin composition
JP2513161B2 (en) * 1995-01-11 1996-07-03 大日本インキ化学工業株式会社 Resin composition for low temperature dry paint
JP4736144B2 (en) * 1997-04-16 2011-07-27 日本ペイント株式会社 High corrosion resistance, high weather resistance, cationic electrodeposition coating composition
JP2004211015A (en) * 2003-01-08 2004-07-29 Nippon Paint Co Ltd Weak solvent system one-can type coating composition and method producing the same
JP4099142B2 (en) * 2003-12-22 2008-06-11 亜細亜工業株式会社 Two-component curable aqueous coating composition and method for producing aqueous emulsion
JP5198718B2 (en) * 2004-12-22 2013-05-15 関西ペイント株式会社 Thermosetting water-based paint and coating film forming method

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20020046950A1 (en) * 2000-10-19 2002-04-25 Klausjoerg Klein Concentrate suitable for the preparation of cathodic electrodeposition coating compositions
WO2003070781A1 (en) * 2002-02-15 2003-08-28 Ppg Industries Ohio, Inc. Thermosetting compositions containing alternating copolymers of isobutylene type monomers
US20060121204A1 (en) * 2004-02-06 2006-06-08 Yasukiho Nakae Water-based intercoating composition and method of forming multilayered coating film

Non-Patent Citations (3)

* Cited by examiner, † Cited by third party
Title
DATABASE WPI Week 198948 Thomson Scientific, London, GB; AN 1989-353785 XP002514727 & JP 01 266126 A (DAINIPPON INK & CHEM KK) 24 October 1989 (1989-10-24) *
DATABASE WPI Week 199602 Thomson Scientific, London, GB; AN 1996-017461 XP002514728 & JP 07 292314 A (DAINIPPON INK & CHEM INC) 7 November 1995 (1995-11-07) *
DATABASE WPI Week 200553 Thomson Scientific, London, GB; AN 2005-515073 XP002514729 & JP 2005 179573 A (ASIA KOGYO KK) 7 July 2005 (2005-07-07) *

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2009146317A1 (en) * 2008-05-30 2009-12-03 E. I. Du Pont De Nemours And Company Process for the production of a dark-color multi-layer coating
WO2009146318A1 (en) * 2008-05-30 2009-12-03 E. I. Du Pont De Nemours And Company Process for the production of a dark-color multi-layer coating
US8835008B2 (en) 2008-05-30 2014-09-16 Axalta Coating Systems Ip Co., Llc Process for the production of a dark-color multi-layer coating
CN102019292A (en) * 2010-11-11 2011-04-20 东北大学 Preparation method of titanium-steel composite plate thin strip
CN102019292B (en) * 2010-11-11 2012-09-05 东北大学 Preparation method of titanium-steel composite plate thin strip
DE102012106145A1 (en) * 2012-07-09 2014-01-09 Baumeister Chemicals & Consulting Gmbh & Co. Kg Additives for coating color
WO2015090443A1 (en) * 2013-12-20 2015-06-25 Basf Coatings Gmbh Method for producing formulations containing a pigment and a filler
US9914840B2 (en) 2013-12-20 2018-03-13 Basf Coatings Gmbh Process for preparing pigment and filler containing formulations
US11326020B2 (en) 2016-08-05 2022-05-10 Kao Corporation Composition for treating three-dimensional object precursor

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