GB2408046A - Cationic coating composition - Google Patents

Cationic coating composition Download PDF

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Publication number
GB2408046A
GB2408046A GB0420965A GB0420965A GB2408046A GB 2408046 A GB2408046 A GB 2408046A GB 0420965 A GB0420965 A GB 0420965A GB 0420965 A GB0420965 A GB 0420965A GB 2408046 A GB2408046 A GB 2408046A
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Prior art keywords
coating film
cationic
coating composition
coating
film
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GB0420965A
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GB0420965D0 (en
GB2408046B (en
Inventor
Shigeo Nishiguchi
Akihiko Shimasaki
Hideki Iijima
Koji Kamikado
Tadayoshi Hiraki
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Kansai Paint Co Ltd
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Kansai Paint Co Ltd
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    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
    • C08L63/00—Compositions of epoxy resins; Compositions of derivatives of epoxy resins
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G18/00—Polymeric products of isocyanates or isothiocyanates
    • C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
    • C08G18/28—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen characterised by the compounds used containing active hydrogen
    • C08G18/40—High-molecular-weight compounds
    • C08G18/64—Macromolecular compounds not provided for by groups C08G18/42 - C08G18/63
    • C08G18/6415—Macromolecular compounds not provided for by groups C08G18/42 - C08G18/63 having nitrogen
    • C08G18/643—Reaction products of epoxy resins with at least equivalent amounts of amines
    • 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
    • B05D7/52—Two layers
    • B05D7/54—No clear coat specified
    • B05D7/546—No clear coat specified each layer being cured, at least partially, separately
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G18/00—Polymeric products of isocyanates or isothiocyanates
    • C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
    • C08G18/08—Processes
    • C08G18/0804—Manufacture of polymers containing ionic or ionogenic groups
    • C08G18/0809—Manufacture of polymers containing ionic or ionogenic groups containing cationic or cationogenic groups
    • C08G18/0814—Manufacture of polymers containing ionic or ionogenic groups containing cationic or cationogenic groups containing ammonium groups or groups forming them
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G18/00—Polymeric products of isocyanates or isothiocyanates
    • C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
    • C08G18/70—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen characterised by the isocyanates or isothiocyanates used
    • C08G18/72—Polyisocyanates or polyisothiocyanates
    • C08G18/80—Masked polyisocyanates
    • C08G18/8061—Masked polyisocyanates masked with compounds having only one group containing active hydrogen
    • C08G18/807—Masked polyisocyanates masked with compounds having only one group containing active hydrogen with nitrogen containing compounds
    • C08G18/8077—Oximes
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G18/00—Polymeric products of isocyanates or isothiocyanates
    • C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
    • C08G18/70—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen characterised by the isocyanates or isothiocyanates used
    • C08G18/81—Unsaturated isocyanates or isothiocyanates
    • C08G18/8141—Unsaturated isocyanates or isothiocyanates masked
    • C08G18/815—Polyisocyanates or polyisothiocyanates masked with unsaturated compounds having active hydrogen
    • C08G18/8158—Polyisocyanates or polyisothiocyanates masked with unsaturated compounds having active hydrogen with unsaturated compounds having only one group containing active hydrogen
    • C08G18/8175—Polyisocyanates or polyisothiocyanates masked with unsaturated compounds having active hydrogen with unsaturated compounds having only one group containing active hydrogen with esters of acrylic or alkylacrylic acid having only one group containing active hydrogen
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
    • C09D163/00—Coating compositions based on epoxy resins; Coating compositions based on derivatives of epoxy resins
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
    • C09D175/00—Coating compositions based on polyureas or polyurethanes; Coating compositions based on derivatives of such polymers
    • C09D175/04—Polyurethanes
    • C09D175/12—Polyurethanes from compounds containing nitrogen and active hydrogen, the nitrogen atom not being part of an isocyanate group
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
    • C09D5/00—Coating compositions, e.g. paints, varnishes or lacquers, characterised by their physical nature or the effects produced; Filling pastes
    • C09D5/44—Coating compositions, e.g. paints, varnishes or lacquers, characterised by their physical nature or the effects produced; Filling pastes for electrophoretic applications
    • C09D5/4419—Coating compositions, e.g. paints, varnishes or lacquers, characterised by their physical nature or the effects produced; Filling pastes for electrophoretic applications with polymers obtained otherwise than by polymerisation reactions only involving carbon-to-carbon unsaturated bonds
    • C09D5/443—Polyepoxides
    • C09D5/4453—Polyepoxides characterised by the nature of the curing agent
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D13/00—Electrophoretic coating characterised by the process
    • C25D13/22—Servicing or operating apparatus or multistep processes
    • 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
    • B05D1/00—Processes for applying liquids or other fluent materials
    • B05D1/007—Processes for applying liquids or other fluent materials using an electrostatic field
    • 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
    • B05D3/00—Pretreatment of surfaces to which liquids or other fluent materials are to be applied; After-treatment of applied coatings, e.g. intermediate treating of an applied coating preparatory to subsequent applications of liquids or other fluent materials
    • B05D3/02—Pretreatment of surfaces to which liquids or other fluent materials are to be applied; After-treatment of applied coatings, e.g. intermediate treating of an applied coating preparatory to subsequent applications of liquids or other fluent materials by baking
    • B05D3/0209—Multistage baking
    • 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
    • B05D3/00—Pretreatment of surfaces to which liquids or other fluent materials are to be applied; After-treatment of applied coatings, e.g. intermediate treating of an applied coating preparatory to subsequent applications of liquids or other fluent materials
    • B05D3/02—Pretreatment of surfaces to which liquids or other fluent materials are to be applied; After-treatment of applied coatings, e.g. intermediate treating of an applied coating preparatory to subsequent applications of liquids or other fluent materials by baking
    • B05D3/0254—After-treatment
    • 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
    • B05D3/00—Pretreatment of surfaces to which liquids or other fluent materials are to be applied; After-treatment of applied coatings, e.g. intermediate treating of an applied coating preparatory to subsequent applications of liquids or other fluent materials
    • B05D3/06—Pretreatment of surfaces to which liquids or other fluent materials are to be applied; After-treatment of applied coatings, e.g. intermediate treating of an applied coating preparatory to subsequent applications of liquids or other fluent materials by exposure to radiation
    • B05D3/061—Pretreatment of surfaces to which liquids or other fluent materials are to be applied; After-treatment of applied coatings, e.g. intermediate treating of an applied coating preparatory to subsequent applications of liquids or other fluent materials by exposure to radiation using U.V.
    • B05D3/065—After-treatment
    • B05D3/067—Curing or cross-linking the coating
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P20/00—Technologies relating to chemical industry
    • Y02P20/50—Improvements relating to the production of bulk chemicals
    • Y02P20/582—Recycling of unreacted starting or intermediate materials

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  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Engineering & Computer Science (AREA)
  • Health & Medical Sciences (AREA)
  • Medicinal Chemistry (AREA)
  • Polymers & Plastics (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Wood Science & Technology (AREA)
  • Materials Engineering (AREA)
  • Electrochemistry (AREA)
  • Metallurgy (AREA)
  • Manufacturing & Machinery (AREA)
  • Molecular Biology (AREA)
  • Application Of Or Painting With Fluid Materials (AREA)
  • Paints Or Removers (AREA)

Abstract

A cationic coating composition comprises (A) a blocked polyisocyanate crosslinking agent modified with an unsaturated group obtained by reacting (a) an unsaturated compound with a hydroxyl group, (b) a blocking agent, and (c) a polyisocyanate, (B) a cationic epoxy resin, and (C) a photopolymerisation initiator. The unsaturated compound may be hydroxyethyl (meth)acrylate and the blocking agent may be an oxime, such as methyl ethyl ketoxime. A method is also described, wherein the composition is used to produce an electrodeposition coating film, which is subjected to irradiation and heating to form a cured mono-layer film. A method of forming a multi-layer coating film is also disclosed, which comprises the steps of coating the composition onto a substrate to form a cationic coating film, irradiating the coating film, coating an intercoat and/or topcoat composition to form a intercoat and/or topcoat film, and simultaneously heating and curing the cationic coating film and the intercoat and/or topcoat film.

Description

Cationic Coating Compo.sitlon and Coating Eilm-Forming Method
Background of the Invention:
Field of the Invention:
The present Invent ices relates to a Gal ionic coat sing composition, curable by both irradiation and heating, a coating filrm-formirlg method anct a coated product.
Description of Background Art: _.
In the field of the automobile coating, various kinds of developments and app:roa--eC; have been proposed from the standpoint s of an optimization of a production cost arch a measure to c ope W1 th tic env1 r Foment.
In the productJor- cost oE:tirnizatlorl, for the purpose of providing a cheap product to a user, approaches to improvements in prcducticir cost, for example, reviews of automobile body production steps filch as reduction in steels, energy saving, recluc t ion in spar e, tact up, an integrated coating of a plastic part and steel plate and the like, reduction in a starting material cost and the like, have been proposed.
As measures to cope with the environment, studies In the production environment, t:or example, provision of a water based or powder intercoat coating composition and topcoat coating composition, and deletion of the intercoat coating 1 composition for the purpose of reducing an exhaust gas, gum and soot from a drying oven, and reducing a volatile organic compound have been made, and in the case of the product environment, provision of an electrodeposition coating film free of a harmful metal such as lead, tin and the like has been promoted.
A coating composition containing an acrylic resin having a functional group reactive with light, and a heat- curable curing agent is disclosed in Japanese Patent Application Laid- Open No. 11169/89 (Patent Reference 1).
However, the above coating composition can not be subjected to an electrodeposition coating and may result unsatisfactory corrosion resistance due to the use of the acrylic resin.
Japanese Patent Application Laid-Open No. 241533 discloses a photocurable putty used in an automobile repair, containing bisphenol A type epoxy di(meth)acrylate and capable of forming a cured coating film by a photopolymerization reaction (Patent Reference 2). However, a satisfactory curing can not be achieved by photo-curing only, resulting in unsatisfactory properties in finish properties and corrosion resistance.
International Patent Application Laid-Open No. 99/125660 discloses a coating method which comprises coating a cationic electrodeposition coating composition, followed by coating an intercoat coating composition by a wet on wet coating method for the purpose of reduction in steps and energy savings (Patent Reference 3). - 2
However, the wet on wet coating of the intercoat coating composition onto the cationic electrodeposition coating film develops mixing between the electrodeposition coating film and the intercoat coating film, resulting in reducing finish properties and corrosion resistance.
Japanese Patent Application Laid-Open No. 2002-265822 (Patent Reference 4) discloses a novel cationic electrodeposition coating composition containing, as a coating film-forming resin, a resin composition having sulfonium group and propargyl group, and a coating film- forming method which comprises subjecting the cationic electrodeposition coating composition to electrodeposition coating, followed by photopolymerizing to form a cured coating film for the purpose of making possible a low temperature curing and short time curing. However, Patent Reference 4 may result a volatilization of sulfur (S) in the sulfonium group into the air on heat curing, and an eluation thereof from the coating film on recycling a coating substrate, resulting in providing heavy loads onto environment.
In view of the above background, provision of a
cationic coating composition, and a multi-layer coating film- forming method using an intercoat coating composition and/or a topcoat coating composition in addition to the cationic coating composition, which make possible the optimization of a production cost, for example, reduction in steps and energy savings by omission of heating and drying oven and heating - 3 step, and providing reduced loads onto environment and showing good properties in finish properties and corrosion resistance, has been demanded.
Summary of the Invention:
It is an object of the present invention to provide a cationic coating composition, and a method of forming a mono layer electrodeposition coating film or a multi-layer coating film by use of the cationic coating composition.
Preferred embodiments may be capable of achieving one or more of reduction in steps, energy saving, reduction in space, and reduction in loads onto environment, for example, reduction in an exhaust gas, gum soot from a drying oven.
The present inventors made intensive studies for the purpose of solving the problems in the art to find out a cationic coating composition containing an unsaturated group- modified blocked polyisocyanate crosslinking agent (A), a cationic epoxy resin (B) and a photopolymerization initiator (C), an unsaturated group-modified cationic epoxy resin (A), a blocked polyisocyanate crosslinking agent (B) and a photopolymerization initiator (C), a mono-layer coating film- forming method which comprises subjecting a cationic coating film to irradiation and heating to obtain a cured mono-layer coating film, and a multi-layer coating film-forming method, which comprises subjecting a cationic coating film to irradiation only, followed by coating an intercoat coating composition and/or a topcoat coating composition, and simultaneously heating and curing the resulting multi-layer coating film, resulting in accomplishing the present invention.
That is, the present invention provides 1. A cationic coating composition containing (A) an unsaturated group- modified blocked polyisocyanate crosslinking agent obtained by reacting a hydroxyl group containing unsaturated compound (a), a blocking agent (b) and a polyisocyanate compound (c), (B) a cationic epoxy resin, and (C) a photopolymerization initiator, 2. A cationic coating composition as defined in paragraph 1, wherein an unsaturated group concentration of the unsaturated groupmodified blocked polyisocyanate crosslinking agent (A) is in the range of 0.25 to 4.5 moles/kg on the basis of the solid content of the crosslinking agent (A), 3. A cationic coating composition as defined in paragraph 1 or 2, wherein the cationic coating composition further contains a polymerizable unsaturated group-containing compound (D), 4. A mono-layer coating film-forming method, which comprises subjecting a cationic electrodeposition coating composition as the cationic coating composition as defined in any one of paragraphs 1 to 3 to electrodeposition coating to form an electrodeposition coating film, followed by subjecting the electrodeposition coating film to both irradiation and heating to form a cured mono-layer coating film, 5. A multi-layer coating film-forming method which comprises the following successive steps (1) to (4): a step (1) of coating the cationic coating composition as defined in any one of paragraphs 1 to 3 onto a coating substrate to form a cationic coating film, a step (2) of subjecting the cationic coating film formed in the step (1) to irradiation, a step (3) of coating an intercoat coating composition and/or a topcoat coating composition to form an intercoat coating film and/or a topcoat coating film, and a step (4) of simultaneously heating and curing the cationic coating film, and the intercoat coating film and/or the topcoating film, 6. A multi-layer coating film-forming method as defined in paragraph 5, wherein the cationic coating film formed by the step (1) in paragraph 5 is preheated at a temperature of 60 to 120 C, 7. A multi-layer coating film-forming method as defined in paragraph 5, wherein the cationic coating composition is a cationic electrodeposition coating composition, and 8. A coated product obtained by any one of the methods as defined in paragraphs 4 to 7.
Detailed Description of the Invention:
The present invention provides a coating film-forming method, which uses a cationic coating composition curable by irradiation and heating, and which makes possible reduction in steps, energy saving, reduction in space, reduction in production cost and reduction in loads onto environment, for example, reduction in exhaust gas, gum and soot from a drying oven, and provides a coated product showing good properties in finish properties and water resistance.
The present invention also provides a multi-layer coating film-forming method which comprises subjecting a cationic coating film to irradiation only, followed by coating an intercoat coating composition and/or a topcoat coating composition to form an intercoat coating film and/or a topcoat coating film, and simultaneously heating and curing the resulting multi-layer coating film.
Cationic Coating Composition The cationic coating composition of the present invention contains an unsaturated group-modified blocked polyisocyanate crosslinking agent (A), a cationic epoxy resin (B) and a photopolymerization initiator (C), and preferably a polymerizable unsaturated group-containing compound (D).
Unsaturated group-modified blocked polyisocyanate crosslinking agent (A): The unsaturated group-modified blocked polyisocyanate crosslinking agent (A) is an addition reaction product of a hydroxyl group-containing unsaturated compound (a), a blocking agent (b) and a polyisocyanate compound (c). The use of the hydroxyl group-containing unsaturated compound (a) makes possible to introduce an unsaturated group into the crosslinking agent by reaction of the hydroxyl group with the polyisocyanate compound. Examples of the hydroxyl group - 7 - -at containing unsaturated compound may include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4- hydroxybutyl (meth)acrylate, an addition product of 2- hydroxyethyl (meth)acrylate with caprolactone, for example, Placcel FA-2, FM-3, etc. (trade names, marketed by Daicel Chemical Industries, Ltd.) and the like. These may be used alone or in combination.
The blocking agent is such that addition of the blocking agent to an isocyanate group in the polyisocyanate compound blocks the isocyanate group, and a resulting blocked polyisocyanate compound is stable at normal temperatures, but heating at a heat-curing temperature usually in the range of about 100 C to 200 C may dissociate the blocking agent to regenerate a free isocyanate group.
The blocking agent to satisfy the above requirements may include, for example, a lactam based compound such as 6- caprolactam, y-butylolactam and the like; an oxime compound such as methylethylketoxime, cyclohexanoneoxime and the liked phenol based compound such as phenol, p-t-butylphenol, cresol and the like; aliphatic alcohols such as n-butanol, 2- ethylhexanol and the like; aromatic alkyl alcohols such as phenyl carbitol, methylphenyl carbitol and the like; and ether alcohol compounds such as ethylene glycol monobutyl ether, ethylene glycol monoethyl ether and the like.
The polyisocyanate compound (c) may include, for example, aromatic, aliphatic or alicyclic polyisocyanate compound such as tolylene diisocyanate, xylene diisocyanate, - 8 - phenylene diisocyanate, diphenylmethane-2,4'-diisocyanate, diphenylmethane-4,4-diisocyanate (or MDI), crude MDI, bis(isocyanatomethyl)cyclohexane, tetramethylene diisocyanate, hexamethylene diisocyanate, methylene diisocyanate, isophorone diisocyanate and the like; a cyclic polymerization product of these polyisocyanate compounds, isocyanate biuret type adducts, a terminal isocyanate-containing compound obtained by reacting an excess amount of these polyisocyanate compounds with a low molecular active hydrogencontaining compound such as ethylene glycol, propylene glycol, trimethylolpropane, hexane trial, castor oil and the like, and the like. These may be used alone or in combination.
The unsaturated group concentration of the unsaturated group-modified blocked polyisocyanate crosslinking agent (A) is in the range of 0.25 to 4.5 moles/kg on the basis of the solid content of the crosslinking agent (A).
When outside the above range, an unbalance between coating film curing due to irradiation and coating film curing due to heating may cause a nonuniform crosslinking, resulting in reducing finish properties and anticorrosive properties.
Cationic epoxy resin (B): The epoxy resin used in the cationic epoxy resin (B) may preferably include, from the standpoint of corrosion resistance of the coating film, an epoxy resin prepared by reaction of a polyphenol compound with an epihalohydrin such as epichlorohydrin.
The polyphenol compound used for obtaining the epoxy resin may include ones known in the art, for example, bis(4- hydroxyphenyl)-2,2-propane (bisphenol A), 4,4- dihydroxybenzophenone, bis(4-hydroxyphenyl)methane (bisphenol F), bis(4-hydroxyphenyl)-1,1-ethane, bis(4-hydroxyphenyl)1,1-isobutane, bis(4-hydroxy-tert-butyl-phenyl)-2, 2-propane, bis(2-hydroxynaphthyl)methane, tetra(4-hydroxyphenyl)- 1,1,2,2-ethane, 4,4-dihydroxydiphenylsulfone (bisphenol S), phenol novolak, cresol novolak, and the like.
The epoxy resin obtained by the reaction of the polyphenol compound with epichlorohydrin may particularly include ones derived from bisphenol A and represented by the following formula: H2C-HO-H2C-O< :HO-CH2-8H-CH2OlH:O-CH2-CH-CH2 where n is O to 8.
The epoxy resin has an epoxy equivalent in the range of to 2,500, preferably 200 to 2,000, more preferably 400 to 1,500, and a number average molecular weight in the range of at least 200, particularly 400 to 4,000, more particularly 800 to 2,500.
Examples of commercially available trade names of the epoxy resin may include Epikote 828 EL, Epikote 1002, Epikote 1004 and Epikote 1007 (trade names marketed by Japan Epoxy Resin Co., Ltd. ).
The cationic group-containing compound in the cationic epoxy resin (B) is a compound containing a cationic group - 10 such as amino group, ammonium salt group, sulfonium salt group, phosphonium salt group and the like. Of these, amino- group is preferable from the standpoint of water dispersibility. The amino group may be introduced into the epoxy resin by addition of the amino group-containing compound to the epoxy resin.
The amino group-containing compound is a cationic properties-imparting component which introduces amino group into the epoxy resin base and cationizes the epoxy resin, and may include one having at least one active hydrogen to react with epoxy group.
The amino group-containing compound used for the above purpose may include, for example, mono- or di-alkylamine such as monomethylamine, dimethylamine, monoethylamine, diethylamine, monoisopropylamine, diisopropylamine, monobutylamine, dibutylamine and the like; alkanolamine such as monoethanolamine, diethanolamine, mono(2- hydroxypropyl)amine, di(2-hydroxypropyl)amine, tri(2- hydroxypropyl)amine, monomethylaminoethanol, monoethylaminoethanol and the like; alkylene polyamine such as ethylenediamine, propylenediamine, butylenediamine, hexamethylenediamine, tetraethylenepentamine, pentaethylenehexamine, diethylaminopropylamine, diethylenetriamine, triethylenetetramine and the like, and a ketiminized product of these polyamines; an alkyleneimine such as ethyleneimine, propyleneimine and the like; a cyclic amine such as piperazine, morpholine, pyrazine and the like, - 11 - and the like.
A mixing ratio of the cationic group-containing compound as a reaction component relative to the epoxy resin is not specifically limited and may arbitrarily be varied depending on uses of the coating composition, but is preferably such that the epoxy resin is in the range of 60 to by weight, preferably 65 to 90% by weight, and the cationic group-containing compound is in the range of 5 to by weight, preferably 10 to 35' by weight based on a total solid content of the epoxy resin and the cationic group-containing compound.
The above addition reaction may be carried out in a suitable solvent under the conditions of about 80 C to about 170 C, preferably about 90 C to about 150 C and 1 to 6 hours, preferably about 1 to 5 hours. The above solvent may include, for example, hydrocarbons such as toluene, xylene, cyclohexane, n-hexane and the like; esters such as methyl acetate, ethyl acetate, butyl acetate and the like; ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, methyl amyl ketone and the like; amides such as dimethyl formamide, dimethyl acetamide and the like; alcohols such as methanol, ethanol, n- propanol, iso-propanol and the like, and mixtures thereof.
The cationic epoxy resin (B) may also be plasticized and modified. An epoxy resin-plasticizing modifier may include ones having a good compatibility with the epoxy resin and hydrophobic properties. - 12
An amount of the modifier used for plasticization must be in a minimum amount necessary for plasticization, and is in the range of 3 to 40 parts by weight, preferably 5 to 30 parts by weight per 100 parts by weight of the epoxy resin.
The modifier may preferably include, for example, ones having reactivity with epoxy group such as xylene formaldehyde resin, polycaprolactone polyol and the like.
The cationic epoxy resin (B) may also be unsaturated group-modified.
An unsaturated group may be introduced into the epoxy resin by addition of an unsaturated group-containing compound to the epoxy resin.
The unsaturated group-containing compound may include, for example, a carboxyl group-containing unsaturated monomer such as acrylic acid, methacrylic acid, crotonic acid, itaconic acid, maleic acid, fumaric acid and the like; a hydroxyl group-containing unsaturated monomer such as 2hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, adducts of 2-hydroxyethyl (meth)acrylate with caprolactone, for example, Placcel FA-2, Placcel FM-3 (trade names, marketed by Daicel Chemical Industries, Ltd., respectively) and the like, and an adduct thereof with a diisocyanate compound such as tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, xylylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, 4,4'methylenebisayclohexyl isocyanate and the like. Of these, the mono-adduct with the diisocyanate - 13 compound is preferable from the standpoint of a degree of freedom on synthesis.
An unsaturated group concentration of the cationic epoxy resin (B) is preferably in the range of O to 1.0 mol/kg based on a solid content of the cationic epoxy resin (B). A concentration outside the above range may reduce storage stability.
A mixing ratio of the unsaturated group-modified blocked polyisocyanate crosslinking agent (A) and the cationic epoxy resin (B) is such that the crosslinking agent (A) is 10 to 50 by weight, preferably 15 to 40 by weight, and the cationic epoxy resin (B) is 50 to 90% by weight, preferably 60 to 85 by weight based on a total solid content of the unsaturated group-modified blocked polyisocyanate crosslinking agent (A) and the cationic epoxy resin (B) respectively.
Photopolymerization Initiator (C): The photopolymerization initiator (C) in the cationic coating composition may include, for example, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isobutyl ether, diethoxyacetophenone, 2-hydroxy-2-methyl-1- phenylpropane-1-on, 2-benzyl-2-dimethylamino-1-(4- morpholinophenyl)-butanone, 2,4,6-trimethylbenzoylphenyl- phosphine oxide, 2, 4,6-trimethylbenzoylphenylethoxyphosphine oxide, benzophenone, methyl, o-benzoyl benzoate, hydroxybenzophenone, 2-isopropyl-thioxanthone, 2,4dimethylthioxanthone, 2,4-diethylthioxanthone, 2,4 - 14 dichlorothioxanthone, 2, 4,6-tris(trichloromethyl)-S-triazine, 2-methyl-4, 6-bis(trichloro)-s-triazine, 2-(4-methoxyphenyl)4,6-bis(trichloromethyl)-s-triazine and the like.
Specifically, trade names of the photopolymerization initiator may include, for example, Cyracure W I-6970, Cyracure W I-6g74, Cyracure W I6g90, Cyracure W I-6950 (marketed by USA Union Carbide Corp., trade names respectively), Irgacure 184, Irgacure 819, Irgacure 261 (marketed by Ciba Specialty Chemicals K.K., trade names respectively), SP- 150, SP-170 (marketed by Asahi Denka Co., Ltd., trade names respectively), CG-24-61 (marketed by Ciba Specialty Chemicals K.K., trade name), CI-2734, CI-2758, CI- 2855 (marketed by Nippon Soda Co., Ltd., trade names respectively), PI- 2074 (marketed by Rhone-Poulenc S A., trade name, pentafluorophenylborate toluylcumyl iodonium salt), FFC509 (marketed by 3M Co., Ltd., trade name), BBI102 (marketed by Midori Kagaku Co., Ltd., trade name) and the like.
These photopolymerization initiators may be used alone or in combination. A mixing amount of the photopolymerization initiator (C) is preferably in the range of 0.1 to 15% by weight, preferably 0.2 to 10% by weight based on a total solid content of the unsaturated group- modified blocked polyisocyanate crosslinking agent (A) and the cationic epoxy resin (B) from the standpoint of photocurability.
The photopolymerization initiator (C) may be used in - 15 combination with a photosensitized for the purpose of promoting the photopolymerization reaction. The photosensitized used in combination may include, for example, a tertiary amines such as triethylamine, triethanolamine, methyldiethanolamine, methyl 4-dimethylaminobenzoate, ethyl 4-dimethylaminobenzoate, isoamyl 4-dimethylaminobenzoate, (2dimethylamino)ethyl benzoate, Michler's ketone, 4,4'diethylaminobenzophenone and the like; alkylphosphines such as triphenylphosphine and the like, thioethers such as p- thiodiglycol and the like, and the like.
The photosensitizers may be used alone or in combination. A mixing amount of the photosensitized is in the range of O to 5% by weight based on a total solid content of the unsaturated group-modified blocked polyisocyanate crosslinking agent (A) and the cationic epoxy resin (B).
Polymerizable Unsaturated Group-Containing Compound (D): The cationic coating composition may further contain a polymerizable unsaturated groupcontaining compound (D). The polymerizable unsaturated group-containing compound (D) is a compound having at least one radically polymerizable unsaturated group in one molecule, preferably at least two from the standpoint of curing properties.
The compound (D) specifically may include, for example, as a monofunctional polymerizable monomer, styrene, methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, cyclohexyl (meth) acrylate, cyclohexenyl (meth)acrylate, 2 - 16 hydroxyl (meth)acrylate, hydroxypropyl (meth)acrylate, tetrahydro-furfuryl (meth)acrylate, c- caprolactone-modified tetrahydrofurfuryl (meth)acrylate, phenoxyethyl (meth)acrylate, phenoxy-polyethylene glycol (meth)acrylate, dicyclopentenyl (meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate, isobornyl (meth)acrylate, benzyl (meth)acrylate, s-caprolactone-modified hydroxyethyl (meth)acrylate, polyethylene glycolmono (meth)acrylate, polypropylene glycolmono (meth)acrylate, 2-hydroxy-3- phenoxypropyl (meth)acrylate, 2-hydroxy-3-butoxypropyl (meth)acrylate, monohydroxyethyl phthalate (meth)acrylate, Aronix MllO (trade name, marketed by Toagosei Chemical Industry Co., Ltd.), N- methylol (meth)acrylamide, N-methylol (meth)acrylamide butyl ether, acryloylmorpholine, dimethylaminoethyl (meth)acrylate, N-vinyl-2-pycrolidone and the like; as bifunctional polymerizable monomer, for example, ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, dipropylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, bisphenol A ethylene oxide-modified di(meth)acrylate, bisphenol A propylene oxide-modified di(meth)acrylate, 2-hydroxy-1acryloxy-3-methacryloxypropane, tricyclodecanedimethanol di(meth)acrylate, di(meth)acryloyloxy-ethyl acid phosphate, Kayarad HX-220, 620, R-604, MANDA (trade name, marketed by - 17 Nippon Kayaku Co., Ltd., respectively) , Photomer (trade name, marketed by Cognis Japan Ltd., epoxy oligomer), and the like; and as tri- or higher functional polymerizable monomer, for example, trimethylolpropane tri(meth)acrylate, trimethylolpropane ethylene oxide-modified tri(meth)acrylate, trimethylolpropane propylene oxide-modified tri(meth)acrylate, glycerin tri(meth)acrylate, glycerin ethylene oxide-modified tri(meth)acrylate, glycerin propylene oxidemodified tri(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, isocyanuric acid ethylene oxidemodified triacrylate, dipentaerythritol, hexa(meth)acrylate, and the like. These compounds may be used alone or in combination.
A mixing amount of the polymerizable unsaturated group- containing compound (D) is such that the polymerizable unsaturated group- containing compound (D) is in the range of O to 45% by weight based on a total solid content of the unsaturated group-modified blocked polyisocyanate crosslinking agent (A) and the cationic epoxy resin (B).
The cationic coating composition may preferably include a cationic electrodeposition coating composition obtained by a method, which comprises mixing the unsaturated group- modified blocked polyisocyanate crosslinking agent (A), the cationic epoxy resin (B), the photopolymerization initiator (C), preferably the polymerizable unsaturated group- containing compound (D) and additives with sufficient agitation, followed by neutralizing with a water-soluble acid - 18 in a water based medium to make water-soluble or water- dispersible.
Preferable examples of the acid used for neutralization may include an organic carboxylic acid such as acetic acid, formic acid and the like, preferably mixtures thereof. Use of the organic carboxylic acid for neutralization may improve finish properties and throwing power properties resulting from the coating composition, and coating composition stability.
The cationic coating composition of the present invention may contain a bismuth compound as an anticorrosive agent. The bismuth compound may not be particularly limited, but may include an inorganic bismuth compound such as bismuth oxide, bismuth hydroxide, basic carbonate bismuth, bismuth nitrate, bismuth silicate and the like. Of these, bismuth hydroxide is preferable.
The bismuth compound may also include an organic acid bismuth salt prepared by reacting at least two organic acid, at least one of which is aliphatic hydroxyearboxylic acid, with the above bismuth compound.
An organic acid used in preparation of the organic acid bismuth salt may include, for example, glycol acid, glycerin acid, lactic acid, dimethylolpropionic acid, dimethylol butyric acid, dimethylol valeric acid, tartaric acid, malic acid, hydroxymalonic acid, dihydroxysuccinic acid, trihydroxysuccinic acid, methyl malonic acid, benzoic acid, citric acid and the like. - 19
These inorganic bismuth compounds and organic acid bismuth salts may be used alone or in combination.
A mixing amount of these bismuth compounds in the cationic coating composition of the present invention may not be particularly limited and may widely be varied depending on performances required for the coating composition, but is such that a bismuth content is in the range of O to 10 parts by weight, preferably 0.05 to 5 parts by weight per 100 parts by weight of the resin solid content in the coating composition.
The cationic coating composition of the present invention may optionally contain a tin compound as a curing catalyst. The tin compound may include, for example, an organic tin compound such as dibutyltin oxide, dioctyltin oxide and the like; aliphatic or aromatic carboxylic acid salt of dialkyltin, for example, dibutyltin dilaurate, dioctyltin dilaurate, dibutyltin diacetate, dioctyltin dibenzoate, dibutyltin dibenzoate and the like. Of these dialkyltin aromatic carboxylic acid salt is preferable.
A mixing amount of the above tin compounds in the cationic coatingcomposition of the present invention may not particularly be limited and may widely be varied depending on performances required for the coating composition, but is such that a tin content is in the range of 0.01 to 8. 0 parts by weight, preferably 0.05 to 5.0 parts by weight per 100 parts by weight of a resin solid content in the coating composition. -
The cationic coating composition may optionally and preferably contain a modifying resin such as a xylene resin, acrylic resin and the like, and may optionally contain a coating composition additive such as a color pigment, extender pigment, anti-corrosive pigment, organic solvent, pigment dispersant, surface controlling agent and the like.
A coating method to form a coating film may include a cationic electrodeposition coating method, spray coating method, electrostatic coating method and the like.
The cationic electrodeposition coating may be carried out under conditions of a solid content concentration of about 5 to 409 by weight by diluting with deionized water, a pH in the range of 5.5 to 9.0, an electrodeposition coating bath temperature of 15 to 35 C and a loading voltage of 100 to 400 V. A cationic electrodeposition coating film thickness may not particularly be limited, but generally is in the range of to 40 am, particularly 15 to 35 Em as a cured coating film.
Curing and drying of the coating film may be carried out by the following methods, that is, (1) a method of subjecting a coating film to irradiation followed by heating, (2) a method of subjecting a coating film to heating followed by irradiation, (3) a method of subjecting a coating film to irradiation and heating simultaneously, and (4) a method of subjecting a coating film to irradiation only, followed by heating the resulting coating film, and an intercoat coating film and/or a topcoat coating film simultaneously. - 21
Curing by irradiation of the coating film may be carried out by irradiation of an ultraviolet light having a wave length of 200 to 450 nm. On irradiation of the ultraviolet light, an irradiation source having a highly sensitive wave length may be selected depending on a kind of the photopolymerization initiator. An irradiation source of the ultraviolet light may include, for example, high pressure mercury lamp, ultrahigh pressure mercury lamp, xenone lamp, carbon arc, metal halide lamp, sunlight and the like.
Conditions of ultraviolet light irradiation onto the coating film are such that an irradiation dose is in the range of 100 to 5,000 mj/cm2, preferably 500 to 3,000 mj/cm2. An irradiation time of about several minutes makes it possible to cure the coating film.
Heat curing conditions are such that a surface temperature of the coating film is in the range of about 120 to about 200 C, preferably about 130 to about 180 C, and a heat curing time is about 5 to 60 minutes, preferably about to 30 minutes.
Heat curing may also be carried out by a multi-layer coating film-forming method which comprises heat curing a cationic coating film or the cationic electrodeposition coating film, and an intercoat coating film and/or a topcoat coating film simultaneously.
Multi-Layer Coating Film-Forming Method A multi-layer coating filmforming method, which comprises heat curing a cationic coating film, and an - 22 intercoat coating film and/or a topcoat coating film simultaneously, is explained hereinafter.
That is, the multi-layer coating film-forming method comprises the following successive steps (1) to (4): a step (1) of coating the cationic coating composition as defined in any one of paragraphs 1 to 5 onto a coating substrate to form a cationic coating film, a step (2) of subjecting the cationic coating film formed in the step (1) to irradiation, a step (3) of coating an intercoat coating composition and/or a topcoat coating composition to form an intercoat coating film and/or a topcoat coating film, and a step (4) of simultaneously heating and curing the cationic coating film, and the intercoat coating film and/or the topcoating film.
The above steps (1) to (4) are explained more in detail hereinafter.
The step (1) is a step of coating a cationic coating composition to form a cationic coating film. In the case where the cationic coating composition is a cationic electrodeposition coating composition, a cationic electrodeposition coating may be applied onto a coating substrate, for example, an automobile body, parts, electrical products, architectural material and the like, made of iron, aluminum, tin, zinc, alloys thereof and the like. These electrically conductive coating substrates are preferably subjected to a surface treatment with a zinc phosphate prior 23 to coating the cationic electrodeposition coating composition from the standpoint of improving corrosion resistance.
The cationic electrodeposition coating film formed by the electrodeposition coating is washed with water, preferably followed by subjecting to preheating at a temperature of 60 to 120 C, setting at room temperature, air blowing and the like from the standpoints of improvements in finish properties and corrosion resistance.
The step (2) is a step of subjecting the cationic coating film to irradiation for crosslinking. The cationic coating film is crosslinked and cured by irradiation of an ultraviolet light having a wave length of 200 to 450 nm. On irradiation of the ultraviolet light, an irradiation source having a highly sensitive wave length may be selected depending on a kind of the photopolymerization initiator. An irradiation source of the ultraviolet light may include, for example, high pressure mercury lamp, ultrahigh pressure mercury lamp, xenone lamp, carbon arc, metal halide lamp, sunlight and the like. Conditions of ultraviolet light irradiation onto the coating film are such that an irradiation dose is in the range of 100 to 5,000 mj/cm2, preferably 500 to 3,000 mj/cm2. An irradiation time of about several minutes makes it possible to cure the coating film.
The step (3) is a step of coating an intercoat coating composition and/or a topcoat coating composition to form an intercoat coating film and/or a topcoat coating film. The intercoat coating composition and the topcoatcoating - 24 composition may include a water based, powder or organic solvent based ones comprising a base resin and a crosslinking agent respectively. However, from the standpoint of measures to environment, a water based coating composition comprising a water dispersion on emulsion of an acrylic resin or polyester resin containing carboxyl group and hydroxyl group respectively is preferable. Nevertheless a water based intercoat coating composition and a water based topcoat coating composition are usually an anionic coating composition, curing of the cationic coating film by irradiation can prevent mixing or agglomeration between the cationic coating film, and the intercoat coating film and/or the topcoat coating film, resulting in making it possible to form an intercoat coating film and/or a topcoat coating film showing improved finish properties.
The base resin in the above water based coating composition may include any ones containing hydroxyl group and carboxyl group as known in the art, for example, polyester resin, acrylic resin, fluorocarbon resin, siliconcontaining resin and the like. The base resin has a hydroxyl value of 30 to 200 mg KOH/g, particularly 50 to 150 mg KOH/g, an acid value of 10 to 100 mg KOH/g, particularly 15 to 75 mg KOH/g, a number average molecular weight of 1,000 to 100,000, particularly 5,000 to 50,000.
A crosslinking agent used in combination with the base resin may include, for example, melamine resin, urea resin, benzoguanamine resin, methyloled product thereof, etherified - 25 amino resin obtained by etherifying a part of all of the methyloled product with mono-alcohol having 1 to 8 carbon atoms, and blocked polyisocyanate.
The water based coating composition may optionally contain a color pigment, extender pigment, ultraviolet light absorber and the like. A mixing amount of the pigment is O to 150 parts by weight per 100 parts by weight of a total weight of the base resin and the crosslinking agent.
The intercoat coating composition and/or the topcoat coating composition are prepared by mixing and dispersing the base resin and the crosslinking agent with water respectively.
A mixing ratio to water may not particularly be limited, but mixing is preferably be carried out so that a solid content on coating can be in the range of 15 to 60 by weight. The topcoat coating composition may optionally contain a color pigment, metallic pigment, extender pigment, ultraviolet light absorber and the like.
The intercoat coating composition and/or the topcoat coating composition may be coated by at least one layer respectively by a coating method such as an air spray coating, airless spray coating, rotary spray coating or electrostatic coating and the like so as to a film thickness of about 10 to am.
The step (4) is a step of simultaneously heating and curing the cationic coating film, and the intercoat coating film and/or the topcoat coating film at a heating temperature of about 100 to 200C, preferably about 120 to 180.C for 1 to - 26 minutes, preferably 10 to 30 minutes.
A heating method may include a direct or indirect hot air drying method by use of an electric furnace, gas furnace and the like, a heating method by use of infrared rays and far infrared rays, a dielectric heating method by use of high frequency, and the like. As measures to refuse and dust, the multi-layer coating film comprising the cationic coating film, and the intercoat coating film and/or the topcoat coating film can be heated and cured by subjecting to the heating method by use of infrared rays and far infrared rays, followed by subjecting to the hot air drying method.
The present invention can provide the following particular effects.
In the case where the cationic electrodeposition coating composition is used as the cationic coating composition of the present invention, the combined use of both irradiation and heating in the crosslinking reaction of the electrodeposition coating film makes possible reduction in steps, energy savings and reduction in space, resulting in making it possible to reduce exhaust gas, gum and soot from the drying oven and to reduce loads onto environment, and resulting in reducing a heating loss, i.e. a weight loss after heat curing and drying of the electrodeposition coating film.
According to the conventional multi-layer coating film- forming method, which comprises coating a cationic electrodeposition coating composition as a cationic coating - 27 composition to form an uncured electrodeposition coating film, followed by coating onto the uncured electrodeposition coating film an intercoat coating composition and/or topcoat coating composition to form an intercoat coating film and/or topcoat coating film, and heat curing simultaneously, the resulting multi-layer coating film may show poor properties in finish properties and water resistance.
Contrary thereto, the multi-layer coating film-forming method of the present invention prevents mixing between the cationic coating film, and the intercoat coating film and/or the topcoat coating film, and makes possible improvements in finish properties and water resistance.
Example
The present invention will be explained more in detail by the following Examples and Comparative Examples, in which "part" and "a" mean "part by weight" and "% by weight" respectively. The present invention should not be limited thereto.
Preparation Example 1 Preparation of Crosslinking Agent No. 1 (for Example): A reactor was charged with 222 g of isophorone diisocyanate and 97 g of methyl isobutyl ketone, followed by heating up to 50 C, slowly adding 116 g of hydroxyethyl acrylate, 96 g of methyl ethyl ketoxime and 0.5 g of hydroquinone, heating up to 100 C, sampling with time while keeping at that temperature, and confirming that absorption of an unreacted isocyanate disappeared by an infrared - 28 absorption spectral measurement to obtain an unsaturated group-modified crosslinking agent No. 1 having an unsaturated group concentration of 2.9 mol/kg and a solid content of 80.
Preparation Example 2 Preparation of Crosslinking Agent No. 2 (for Example): A reactor was charged with 168 g of hexamethylene diisocyanate and 87 g of methyl isobutyl ketone, followed by heating up to 50 C, slowly adding 130 g of hydroxyethyl methacrylate, 96 g of methyl ethyl ketoxime and 0.5 g of hydroquinone, heating up to 100 C, sampling with time, while keeping at that temperature, and confirming that absorption of an unreacted isocyanate disappeared by an infrared absorption spectral measurement to obtain an unsaturated group-modified crosslinking agent No. 2 having an unsaturated group concentration of 2.6 mol/kg and a solid content of 80%.
Preparation Example 3 Preparation of Crosslinking Agent No. 3 (for Comparative
Example):
A reactor was charged with 222 g of isophorone diisocyanate and 99 g of methyl isobutyl ketone, followed by heating up to 50 C, slowly adding 174 g of methyl ethyl ketoxime, heating up to 70 C, sampling with time, while keeping at that temperature, and confirming that absorption of an unreacted isocyanate disappeared by an infrared absorption spectral measurement to obtain a crosslinking agent No. 3 having a solid content of 80%.
Preparation Example 4 - 29 Preparation of cationic epoxy resin No. 1: A mixture of 1010g of Epikote 828EL (trade name, marketed by Japan Epoxy Resin Co., Ltd., epoxy resin), 390g of bisphenol A and 0.2g of dimethylbenzylamine was reacted at 130 C so as to be an epoxy equivalent of 800, followed by adding 160g of diethanolamine and 65g of a ketiminized product of diethylenetriamine, reacting at 120 C for 4 hours, and adding 355g of butylcellosolve to obtain a cationic epoxy resin No. 1 having an amine value of 67 mg KOH/g, and a solid content of 80%.
Preparation Example 5 (Preparation of cationic epoxy resin No. 2) A 21-separable flask equipped with a thermometer, reflux condenser and stirrer was charged with 240g of 509 formalin, 55g of phenol, 101g of 98% technical sulfuric acid and 212g of m-xylene, followed by reacting at 84 to 88 C for 4 hours, leaving at rest to separate a resin phase from a sulfuric acid water phase, washing the resin phase with water three times, and stripping unreacted m-xylene under the condition of 20-30 mmHg/120-130 C to obtain 240g of a phenol- modified xylene formaldehyde resin having a viscosity of 1050 centipoise (25 C).
Next, another flask was charged with 1000g of Epikote 828EL (trade name, marketed by Japan Epoxy Resin Co., Ltd., epoxy resin, epoxy equivalent 190, molecular weight 350), 400g of bisphenol A and 0.2g of dimethylbenzylamine, followed by reacting at 130 C so as to be an epoxy equivalent of 750, - 30 adding 300g of xylene formaldehyde resin, 140g of diethanolamine and 65g of a ketiminized product of ethylenetriamine, reacting at 120 C for 4 hours, and adding 420g of butylcellosolve to obtain a cationic epoxy resin No. 2 having an amine value of 52 mg KOH/g, and a resin solid content of 80%.
Preparation Example 6 (Preparation of unsaturated group-modified cationic epoxy resin No. 3) A 21-separable flask equipped with a thermometer, reflex condenser and stirrer was charged with 240g of 50% formalin, 55g of phenol, 101g of 98% technical sulfuric acid and 212g of m-xylene, followed by reacting at 84 to 88 C for 4 hours, leaving at rest to separate a resin phase from a sulfuric acid water phase, washing the resin phase with water three times, and stripping unreacted m-xylene under the condition of 20-30 mmHg/120-130 C to obtain 240g of a phenol- modified xylene formaldehyde resin having a viscosity of 1050 centipoise (25 C).
Next, another flask was charged with 1000g of Epikote 828EL (trade name, marketed by Japan Epoxy Resin Co., Ltd., epoxy resin, epoxy equivalent 190, molecular weight 350), 400g of bisphenol A and 0.2g of dimethylbenzylamine, followed by reacting at 130 C so as to be an epoxy equivalent of 750, adding 300g of the phenol-modified xylene formaldehyde resin, 36g of acrylic acid, 0.lg of hydroquinone, 95g of diethanolamine and 65g of a ketiminized product of - 31 ethylenetriamine, reacting at 120 C for 4 hours, and adding 394g of butylcellosolve to obtain an unsaturated group- modified cationic epoxy resin No. 3 having an amine value of 91 mg KOH/g, an unsaturated group concentration of 0.29 mol/kg and a resin solid content of 80%.
Preparation Example 7 (Preparation of Emulsion No. 1) A mixture of 37.5g (30g as resin solid content) of crosslinking agent No. 1, 87.5g (70g as resin solid content) of cationic epoxy resin No. 1, 3g of Irgacure 184 (Note 2), 5g of Irgacure 819 (Note 3) and 15g of 10% acetic acid was uniformly stirred, followed by dropping 170g of deionized water over about 15 minutes while strongly stirring to obtain an emulsion No. 1 having a solid content of 34%.
Preparation Examples 8-13 (Preparation of Emulsions No. 2 to No. 7) Preparation Example 7 was duplicated except that formulations shown in Table 1 were used respectively to obtain emulsions No. 2 to No. 7. In Table 1, the solid content is parenthesized. - 32
: Z _ --o^ mo _ 0 0 i/) i/) NOT lo _O O _ _ O r N t:4bl_ _ _ _ _ aJ Z a,_rn_ 00 n in us TO pox _ _ _ _ _ c0 v Z in, no up O mmm0 [it- T ELI mu z- m.m to o so m V. no no, o Sol 1 N (7 O O O
Z Z Z _
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U] U1 U]
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o o o o o o Z O O co ao aD _ Z Z a _ _.- X X X (D U 01 O C O O 0 o 3 O
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03 U1 bO D1 O O O O U U o1 u u -- .- .- ,i. .- O O O O O.- (d O O O O O O O E4 E1 U Ul O u) U u) L1 tt) L) u) v] H H _ _ (Note 1) Photomer 3016 (trade name, marketed by Cognis Japan Ltd., epoxyoligomer).
(Note 2) Irgacure 184 (trade name, marketed by Ciba-Geigy Japan Ltd., photopolymerization initiator).
(Note 3) Irgacure 819 (trade name, marketed by Ciba-Geigy Japan Ltd., photopolymerization initiator).
Preparation Example 14 (Preparation of Pigment-Dispersed Paste) To a mixture of 5.83 parts (solid content 3.5 parts) of 60% solid content quaternary ammonium salt type epoxy resin, parts of titanium white and 2.0 parts of bismuth hydroxide was added 6.3 parts of deionized water, followed by sufficiently stirring to obtain a pigment- dispersed paste having a solid content of 553.
Preparation Example 15 To 318 parts (solid content 108 parts) of Emulsion No. 1 were added 19.1 parts (solid content 10.6 parts) of the pigmentdispersed paste, and 255.4 parts of deionized water to obtain a cationic electrodeposition coating composition No. 1 having a solid content of 20%.
Preparation Examples 16-23 Example 15 was duplicated except that respective formulations shown in Table 2 were used to obtain cationic electrodeposition coating compositions No. 2 to No. 9 having a solid content of 20% respectively. In Table 2, the solid content is parenthesized. - 34 ,E
U N L) U O 0 N0 m
_
V Z ___ NN m i <: Z _ O _ 0 NN 111 1 Z O__ O NN: tD N O __ 0 0 N N:) _ o] Z O __ O N N l= T5A A -...- .-. .-
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c-OOOO OO O O D7eqUlU) UlU] eq -,1-,] u) ,n S4 -1 01Nrr nL0 t 54 u} t.... .. . c: la O O dPO oPO PO op O OPO dP O dP U1 Q, 3 F: (1 P.OZZZZ ZZ Z.,! CO U..-
UC O
Q) o o o o 4o 4 o lO o 4 U N 1 s4 1 -1 r:-,t -1 i:1 '- r: -,1 O u Q o u o U 4 o E O n' 3 [: :' U1 1 -,' dP qS O O O O O O O O -,' n, O o O L) U U U U U W U U U =m U Water Based Intercoat Coating Composition: WP-300T (trade name, marketed by Kansai Paint Co., Ltd., water based intercoat coating composition) was used.
Preparation Example 24 (Preparation of Water Based Topcoat Coating Composition) To a mixture of 70 parts of acrylic resin (hydroxyl value 60 mg KOH/g, acid value 35 mg KOH/g, number average molecular weight 6,000), 30 parts of butyl etherified melamine and dimethylethanolamine as a neutralizing agent was added 60 parts of JR-806 (trade name, marketed by Tayca Corporation, titanium oxide), followed by mixing to obtain a water based topcoat coating composition.
Coating Substrate: A cold-rolled steel plate (70 x 150 x 0.8 mm) chemically treated with Palbond #3020 (trade name, marketed by Nippon Parkerizing Co., Ltd., zinc phosphate treating agent) was used as a coating substrate.
Example and Comparative Example
Example 1
The cationic electrodeposition coating composition No. 1 was coated so as to a film thickness of 20 am, followed by washing with water, preheating at 100 C for 5 minutes, subjecting to irradiation of ultraviolet light from a 120 W/cm metal halide lamp at an irradiation dose of 2000 mj/cm2 for 10 seconds for photocuring, and heating at 140 C for 10 minutes to obtain a cured mono-layer coating film.
Examples 2-6 - 36
Cationic electrodeposition coating compositions No. 2 to No. 6 were used in place of cationic electrodeposition coating composition No. 1 in Example 1, and were subjected to the conditions shown in Table 3 to obtain respective cured mono-layer films.
Example 7
The cationic electrodeposition coating composition No. 1 was coated so as to be a film thickness of 20 am, followed by washing with water, preheating at 100 C for 5 minutes, subjecting to irradiation of ultraviolet light from a 120 W/cm metal halide lamp at an irradiation dose of 2000 mj/cm2 for 10 seconds for photocuring, coating a water based intercoat coating composition, WP-300T (trade name as above mentioned) so as to be a film thickness of 35 m, coating the topcoat coating composition obtained in Preparation Example 24 so as to be a film thickness of 35 m, and heating three coating films simultaneously to obtain a cured multi-layer coating film. Steps of Examples 1-7 are shown in Table 3. - 37
r: ATRIA a a r. _ _ in' e: u a O u O r : 11U 1= 11 O 0 V N O N O U U O _ _ - . . =- r L_ u 3 L) 4 15 Idly up u -c L' -a go]c O c -aft: O u o u al 0 o o o o - r, v u u u U S u v v v v En Comparative Example 1 The cationic electrodeposition coating composition No. 1 was coated so as to be a film thickness of 2Q am, followed by washing with water, and heating at 140 C for 10 minutes without subjecting to irradiation to form a cured mono-layer coating film.
Comparative Examples 2-5 Respective cured mono-layer coating films were obtained according to the steps shown in Table 4.
Comparative Example 6 The cationic electrodeposition coating composition No. 1 was coated so as to be a film thickness of 20 m, followed by washing with water, preheating at 100 C for 5 minutes, coating the water based intercoat coating composition, WP- 300T (trade name as above mentioned) so as to be a film thickness of 35 m, coating the topcoat coating composition obtained in Preparation Example 24 so as to be a film thickness of 35 m, and heating three coating films simultaneously to obtain a cured multi-layer coating film.
Comparative Example 7 A cured three-layer coating film of Comparative Example 7 was obtained according to the steps shown in Table 4.
Steps of Comparative Examples 1-7 are shown in Table 4 respectively. - 39 q)d
At -do - -- - - - I ' Z O 5 r U b3 U U N
CJ _ _ _ _ _ _ _ _ >- ".
ma al 5 s: 5 A: u u e z r: 5 0 Arc 43-e _ _ _ _ _ _ _ _ Al 5 r 0 0 0 o 5 r: O U li3 U Z 5 C 5 5 5 N h rl _ _ _ _ _ _ _ _ -=N c r 0 JO 0 0 0 U u U Z 5 5 5 _ e _ _ _ _ _ _ _ _ 0 c O o 0 O 0 U 0 ' Z o uo 8 u=-6 u - a, u -v,-= 0= .u E o. o s , U O a, -- o.,,, o -- x o.
U o,- U U g 0 a s 0 s 0 U Q, U U S P4U S -rl U = S
Q N
O = = Q. _ U V) U1 V] U] o: at - - u) l l m Or a) 1 N N l N en Ul l
O X q4 _
so a' u .c U U 4 al JJ U -A -,1 ^ O O h O O O gal kI Up Z Q. o Z o a) z z z a, C - U 54- - Lq 54 - 3 - c I C I 0) , u] - - - - h
O O U O
O
0 {8 - O rl O - E _ U u i: : : : r
U N
UX
t01 t in, in, l
Q
O _.0c -,' .H O q.- O U U1 A - O
_ O O O O O
O Z o Z Z 3 Z
-
Q) I Q _ (Note 4) Gel fraction was measured according to the following steps (1) to (3).
Step (1): a step of measuring a weight O of a test panel.
Step (2): a step of carrying out electrodeposition coating by 20 m, followed by measuring a weight 6) of a cured coating film.
Step (3): a step of dipping respective test panels into acetone at 20 C for 24 hours, followed by drying at room temperature, and measuring a resulting weight By. A gel fraction was determined according to the following formula (1) from respective weights measured in steps (1) to (3).
The higher, the better curing properties is.
Gel fraction = {(-(D)/(-()} x 100 (1) (Note 5) Heating Loss: Heating loss was determined by the method comprising steps (1) to (3): step (1) of measuring a weight 0) of a test panel; step (2) of measuring a weight) of a coating film and the test panel; and step (3) of curing a coating film by mono-layer film-forming methods of Examples 5-7 and Comparative Examples 4-6, followed by measuring a weight of a cured coating film and test panel. That is, the heating loss was determined according to the following formula (2): Heating loss (a) = {(-)/(-)} x 100... (2) Corrosion Resistance: Cross cuts were formed by use of a knife on the surface of a mono-layer electrodeposition reacting film-coated test - 43 panel so as to reach the coating substrate, followed by subjecting to a 840 hours salt water spray test, and evaluating development of rust from the cross cut, and width of blisters as follows.
good: maximum width of rust and blisters less than 3 mm from cut (one side) fair: maximum width of rust and blisters 3 mm or more less than 4 mm from cut (one side) poor: maximum width of rust and blisters 4 mm or more from cut (one side) (Note 7) Specular Reflectance (a): A multi-layer coating film-coated test panel was subjected to a 60 specular gloss measurement in accordance with JIS K-5400.
(Note 8) Water resistance: A multi-layer coating film coated test panel was introduced into a blister box at 50 C, followed by taking out the test panel 240 hours after, drying at room temperature for 2 hours, forming 100 cut squares at an interval of 2 mm, applying a vinyl tape thereonto, strongly peeling off the tape, and examining a number of remaining squares for evaluating as follows.
O: number of remaining squares: 100 it: number of remaining squares: 9099 x number of remaining squares: less than 90 - 44

Claims (11)

  1. Claims 1. A cationic coating composition containing (A) an unsaturated
    group- modified blocked polyisocyanate crosslinking agent obtained by reacting a hydroxyl group- containing unsaturated compound (a), a blocking agent (b) and a polyisocyanate compound (c), (B) a cationic epoxy resin, and (C) a photopolymerization initiator.
  2. 2. A cationic coating composition as claimed in claim 1, wherein an unsaturated group concentration of the unsaturated group-modified blocked polyisocyanate crosslinking agent (A) is in the range of 0.25 to 4.5 moles/kg on the basis of the solid content of the crosslinking agent (A).
  3. 3. A cationic coating composition as claimed in claim 1 or 2, wherein the cationic coating composition further contains a polymerizable unsaturated group-containing compound (D).
  4. 4. A mono-layer coating film-forming method, which comprises subjecting a cationic electrodeposition coating composition as the cationic coating composition as claimed in any one of claims 1 to 3 to an electrodeposition coating to form an electrodeposition coating film, followed by subjecting the electrodeposition coating film to both irradiation and heating to form a cured mono-layer coating film. -
  5. 5. A multi-layer coating film-forming method which comprises the following successive steps (1) to (4): a step (l) of coating the cationic coating composition as claimed in any one of claims 1 to 3 onto a coating substrate to form a cationic coating film, a step (2) of subjecting the cationic coating film formed in the step (1) to irradiation, a step (3) of coating an intercoat coating composition and/or a topcoat coating composition to form an intercoat coating film and/or a topcoat coating film, and a step (4) of simultaneously heating and curing the cationic coating film, and the intercoat coating film and/or the topcoating film.
  6. 6. A multi-layer coating film-forming method as claimed in claim 5, wherein the cationlc coating film formed by the step (1) in claim 5 is preheated at a temperature of 60 to 120 C.
  7. 7. A multi-layer coating film-forming method as claimed in claim 5, wherein the cationic coating composition is a cationic electrodeposition coating composition.
  8. 8. A cationic coating composition substantially as described herein with reference to and as illustrated in
    Examples 1-7.
  9. 9. A mono-layer coating film forming method substantially as described herein with reference to and as illustrated in Examples 1-7. - 46
  10. 10. A multi-layer coating film forming method substantially as described herein with reference to and as illustrated in Examples 1-7.
  11. 11. A coated product obtained by any one of the methods as claimed in claims 4 to 7, 9 or 10. - 47
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US20070023288A1 (en) * 2005-08-01 2007-02-01 Eiji Kuwano Method of forming multi-layered coating film
US20090012235A1 (en) * 2006-02-03 2009-01-08 Basf Corporation Dispersant for use in a fluorocarbon coating composition
US7838582B2 (en) * 2006-02-03 2010-11-23 Ppg Industries Ohio, Inc. Hyperdispersant for use in fluorocarbon coating compositions
US7956144B2 (en) * 2006-02-03 2011-06-07 Ppg Industries Ohio, Inc. Acrylic resin for use in fluorocarbon coating compositions and method of forming the same
US7790011B2 (en) 2006-05-03 2010-09-07 Basf Coatings Gmbh Solid resin-crosslinker mixture for use in aqueous coatings
JP2012530156A (en) * 2009-06-12 2012-11-29 イー・アイ・デュポン・ドウ・ヌムール・アンド・カンパニー Radiation curable coating composition
KR101724709B1 (en) * 2010-10-27 2017-04-07 현대자동차주식회사 Water Based Paint Composition Reducing Volatile Organic Compound
CN102296340A (en) * 2011-09-09 2011-12-28 福清永动力弹簧科技有限公司 Electrophoresis process for spring
RU2684081C2 (en) * 2015-02-10 2019-04-03 Свимк Ллк Novel system for electrodeposition coating
EP3298083B1 (en) * 2015-05-21 2021-01-13 Swimc Llc Antimicrobial agent for coating composition
JP6511599B1 (en) * 2018-09-25 2019-05-15 生春 古田 Cationic electrodeposition coating composition and method of forming a coating film
CN109576742A (en) * 2019-01-26 2019-04-05 宁波市鄞州艾博化工科技有限公司 Novel alkaline non-cyanogen galvanization additive
JP7360986B2 (en) 2020-04-01 2023-10-13 神東アクサルタコーティングシステムズ株式会社 Cationic electrodeposition paint composition

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US20050067284A1 (en) 2005-03-31

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