WO2017115804A1 - 水性塗料組成物および塗膜形成方法 - Google Patents
水性塗料組成物および塗膜形成方法 Download PDFInfo
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- WO2017115804A1 WO2017115804A1 PCT/JP2016/088921 JP2016088921W WO2017115804A1 WO 2017115804 A1 WO2017115804 A1 WO 2017115804A1 JP 2016088921 W JP2016088921 W JP 2016088921W WO 2017115804 A1 WO2017115804 A1 WO 2017115804A1
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- 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
- C09D5/02—Emulsion paints including aerosols
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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
- B05D7/52—Two layers
- B05D7/54—No clear coat specified
- B05D7/542—No clear coat specified the two layers being cured or baked together
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- 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
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- 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
- C09D133/00—Coating compositions based on homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by only one carboxyl radical, or of salts, anhydrides, esters, amides, imides, or nitriles thereof; Coating compositions based on derivatives of such polymers
- C09D133/02—Homopolymers or copolymers of acids; Metal or ammonium salts thereof
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- 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
- C09D133/00—Coating compositions based on homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by only one carboxyl radical, or of salts, anhydrides, esters, amides, imides, or nitriles thereof; Coating compositions based on derivatives of such polymers
- C09D133/04—Homopolymers or copolymers of esters
- C09D133/06—Homopolymers or copolymers of esters of esters containing only carbon, hydrogen and oxygen, the oxygen atom being present only as part of the carboxyl radical
- C09D133/08—Homopolymers or copolymers of acrylic acid esters
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- 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
- C09D133/00—Coating compositions based on homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by only one carboxyl radical, or of salts, anhydrides, esters, amides, imides, or nitriles thereof; Coating compositions based on derivatives of such polymers
- C09D133/04—Homopolymers or copolymers of esters
- C09D133/14—Homopolymers or copolymers of esters of esters containing halogen, nitrogen, sulfur or oxygen atoms in addition to the carboxy oxygen
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- 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
- C09D167/00—Coating compositions based on polyesters obtained by reactions forming a carboxylic ester link in the main chain; Coating compositions based on derivatives of such polymers
- C09D167/02—Polyesters derived from dicarboxylic acids and dihydroxy compounds
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- 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
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- 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
- C09D7/00—Features of coating compositions, not provided for in group C09D5/00; Processes for incorporating ingredients in coating compositions
- C09D7/40—Additives
- C09D7/60—Additives non-macromolecular
- C09D7/63—Additives non-macromolecular organic
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- 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
- C09D7/00—Features of coating compositions, not provided for in group C09D5/00; Processes for incorporating ingredients in coating compositions
- C09D7/40—Additives
- C09D7/65—Additives macromolecular
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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
- B05D2202/00—Metallic substrate
- B05D2202/10—Metallic substrate based on Fe
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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
- B05D2203/00—Other substrates
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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
- B05D2401/00—Form of the coating product, e.g. solution, water dispersion, powders or the like
- B05D2401/20—Aqueous dispersion or solution
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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
- B05D2502/00—Acrylic polymers
- B05D2502/005—Acrylic polymers modified
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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
- B05D2503/00—Polyurethanes
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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
- B05D2505/00—Polyamides
- B05D2505/50—Polyimides
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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
- 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
- B05D3/10—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 other chemical means
- B05D3/102—Pretreatment of metallic substrates
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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
- B05D7/14—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 to metal, e.g. car bodies
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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
- B05D7/52—Two layers
- B05D7/53—Base coat plus clear coat type
- B05D7/532—Base coat plus clear coat type the two layers being cured or baked together, i.e. wet on wet
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
- C08K5/00—Use of organic ingredients
- C08K5/16—Nitrogen-containing compounds
- C08K5/29—Compounds containing one or more carbon-to-nitrogen double bonds
Definitions
- the present invention relates to an aqueous coating composition and a method for forming a coating film using the aqueous coating composition.
- a plurality of coating films having various roles are sequentially formed on the surface of an object such as an automobile body to protect the object to be coated and at the same time impart a beautiful appearance and an excellent design.
- an undercoat film such as an electrodeposition coating film is formed on an object having excellent conductivity, and an intermediate coating film as required, and A method of sequentially forming a top coat film is common.
- the thickness of the first base coating is thinner than the first base coating of the two-coat / one-bake multilayer coating.
- the chipping resistance of the multilayer coating film is reduced, and when the stepping stone collides with the coating film while traveling, the multilayer coating film is destroyed, and the scratch extends to the steel plate or the electrodeposition coating with the steel plate.
- the components of the automobile body include a steel plate and a resin member.
- the resin member has lower heat resistance of the material itself than the steel plate. Therefore, it is necessary to design the curing temperature of the coating composition at a lower temperature than before. On the other hand, by lowering the temperature of the curing step, the crosslinking density of the resulting coating film is lowered, and the performance such as chipping resistance may be inferior.
- Patent Document 1 discloses that an intermediate coating film is formed by coating an aqueous intermediate coating on a substrate having both a steel plate and a plastic substrate. After forming a base coating film by coating a water-based base coating on the film, an organic solvent-type clear coating is applied to form a clear coating, and the three layers of the intermediate coating, the base coating, and the clear coating are formed.
- the water-based base coating material comprises (a) an acrylic resin emulsion, (b) a water-soluble acrylic resin, and (c) a melamine resin, (d) propylene glycol mono It describes about the formation method of the multilayer coating film containing an alkyl ether.
- the multilayer coating film obtained by this forming method is cured at a temperature of 100 ° C. or lower, for example, there is a possibility that sufficient chipping resistance may not be obtained.
- Patent Document 2 JP 2013-133445 A discloses an aqueous coating composition containing (A) an aqueous resin having a hydroxyl group and a carboxyl group, (B) a polyisocyanate compound, and (C) a hydrophilized modified carbodiimide compound. The thing is described.
- evaluation of paint stability, pot life and crosslink density retention is carried out (paragraphs [0132], [0137] and [0138]). From these evaluation items, the aqueous coating composition described in Patent Document 2 is a so-called two-component mixed coating composition in which a part of the curing reaction proceeds by mixing each component. I understand.
- the water-based coating composition of the present invention is different from the two-component mixing type in that it is a so-called one-component coating composition.
- the present invention solves the above-described conventional problems, and an object of the present invention is to provide a one-pack type aqueous coating composition having excellent low-temperature curability.
- an aqueous resin having a hydroxyl group and a carboxyl group (B) a water dispersible block polyisocyanate compound, (C) a hydrophilized modified carbodiimide compound, and (D) an aqueous polyurethane resin,
- An aqueous coating composition comprising: The aqueous resin having a hydroxyl group and a carboxyl group (A) has a hydroxyl value of 80 to 200 mgKOH / g and an acid value of 10 to 40 mgKOH / g in terms of resin solid content.
- the (C) hydrophilized modified carbodiimide compound is represented by the following general formula (I), (II) or (III),
- the (D) aqueous polyurethane resin has a glass transition point (Tg) of ⁇ 50 ° C. or lower,
- Tg glass transition point
- the elongation at break of the cured film of the aqueous polyurethane resin is 400% or more at ⁇ 20 ° C.
- Water-based paint composition [X is a bifunctional organic group containing at least one carbodiimide group, Y is a structure obtained by removing a hydroxyl group from the same or different polyalkylene glycol monoalkyl ether, and Z is a number average molecular weight of 200.
- X is a bifunctional organic group containing at least one carbodiimide group
- Y is a structure obtained by removing a hydroxyl group from the same or different polyalkylene glycol monoalkyl ether
- R 0 is a hydrogen or methyl group.
- R 1 is an alkylene group having 4 or less carbon atoms
- n is 0 or 1
- m is 0-60.
- [X is a bifunctional organic group containing at least one carbodiimide group, and Y has a structure in which a hydroxyl group is removed from the same or different polyalkylene glycol monoalkyl ether.
- [2] The water-based coating composition, wherein the content of the (C) hydrophilized modified carbodiimide compound is 1 to 8% by mass with respect to the resin solid content of the water-based coating composition.
- the water-based coating composition, wherein the (A) water-based resin includes an acrylic emulsion having a number average molecular weight of 10,000 to 80,000.
- the aqueous coating composition whose (C) hydrophilization modified carbodiimide compound represented by the said Formula (III) is the following compound.
- [X is a bifunctional organic group containing at least one carbodiimide group
- Y is the following (i) or (ii): (I) a structure in which a hydroxyl group is removed from polyethylene glycol monoalkyl ether in which an alkyl group having 1 to 3 carbon atoms is ether-bonded to the end of a polyethylene oxide unit having 6 to 20 repeating units; (Ii) A structure in which a hydroxyl group is removed from a polypropylene glycol monoalkyl ether in which an alkyl group having 1 to 8 carbon atoms is ether-bonded to the terminal of a polypropylene oxide unit having 4 to 60 repeats: It is the same or different structure selected from.
- Content of said (D) water-based polyurethane resin is an aqueous coating composition which is 15 mass% or more with respect to the resin solid content of an aqueous coating composition.
- Content of the said (D) water-based polyurethane resin is an aqueous coating composition which is 30 to 40 mass% with respect to the resin solid content of an aqueous coating composition.
- Content of the said (D) water-based polyurethane resin is an aqueous coating composition which is 15 mass% or more and less than 30 mass% with respect to the resin solid content of an aqueous coating composition.
- the content of the (B) water-dispersible block polyisocyanate compound is 10 to 25% by mass with respect to the resin solid content of the aqueous coating composition.
- the content of the (C) hydrophilized modified carbodiimide compound is 1.5 to 7% by mass with respect to the resin solid content of the aqueous coating composition.
- Water-based paint composition Water-based paint composition.
- a method for forming a coating film using an aqueous coating composition A coating process in which the aqueous coating composition is applied to an object to form a coating film; and a curing process in which the obtained coating film is cured at 70 to 100 ° C .; Including Coating film forming method.
- an aqueous coating composition having a content of (D) aqueous polyurethane resin of 30% by mass or more and 40% by mass or less based on the resin solid content of the aqueous coating composition is applied to form a first coating film.
- a water-based paint having a content of (D) a water-based polyurethane resin of 15% by mass or more and less than 30% by mass with respect to the resin solid content of the water-based paint composition on the first coating step to be formed and the first coating film.
- the said to-be-coated article is a coating-film formation method containing a steel plate part and a resin part.
- the water-based coating composition of the present invention has a good curing reaction even under heating conditions under low temperature conditions (for example, heating conditions of 100 ° C. or lower), and a cured coating film having excellent coating film properties is obtained.
- the water-based coating composition of the present invention has, for example, a steel plate part and a resin part that require excellent coating properties (water resistance, chipping resistance, etc.) despite the difficulty of high-temperature heat curing treatment. It can use suitably for the coating of the to-be-coated article which has.
- the aqueous coating composition of the present invention comprises (A) an aqueous resin having a hydroxyl group and a carboxyl group, (B) a water dispersible block polyisocyanate compound, (C) a hydrophilized modified carbodiimide compound, and (D) an aqueous polyurethane resin, including.
- A an aqueous resin having a hydroxyl group and a carboxyl group
- B a water dispersible block polyisocyanate compound
- C a hydrophilized modified carbodiimide compound
- D an aqueous polyurethane resin
- Aqueous resin having a hydroxyl group and a carboxyl group is a binder that undergoes a curing reaction with (B) a water-dispersible block polyisocyanate compound and (C) a hydrophilized modified carbodiimide compound described later. It is an ingredient.
- aqueous resin which has a hydroxyl group and a carboxyl group used in the present invention -The hydroxyl value in terms of resin solids is 80 to 200 mg KOH / g, The acid value in terms of resin solids is 10 to 40 mg KOH / g, Is a requirement.
- the hydroxyl value in terms of resin solid content is more preferably from 80 to 160 mgKOH / g, and the acid value in terms of resin solid content is more preferably from 15 to 35 mgKOH / g.
- the aqueous resin having a hydroxyl group and a carboxyl group used in the present invention has a higher hydroxyl value than the acid value.
- the (A) aqueous resin may be composed of a single resin that satisfies the above requirements for the hydroxyl value and acid value in terms of resin solids, or a plurality that satisfies the above requirements for the hydroxyl value and acid value. You may be comprised from these resin.
- the (A) aqueous resin has two types of functional groups, a hydroxyl group and a carboxyl group, as reactive groups involved in curing.
- (A) the hydroxyl group of the aqueous resin reacts with (B) the polyisocyanate compound, and (A) the carboxyl group of the aqueous resin reacts with (C) the hydrophilized modified carbodiimide compound.
- the type of the (A) aqueous resin is not particularly limited as long as it satisfies the requirements for the hydroxyl group and carboxyl group, but is preferably an acrylic resin and / or a polyester resin because it is easy to produce and obtain. .
- the aqueous coating composition is used as an intermediate coating composition, it is more preferable to use a mixture of an acrylic resin and a polyester resin as the aqueous resin (A).
- the water-based coating composition is used as a topcoat base coating composition, it is more preferable to use an acrylic resin as the (A) water-based resin.
- the acrylic resin that can be suitably used as the (A) aqueous resin includes, for example, a monomer containing an ⁇ , ⁇ -ethylenically unsaturated monomer having a hydroxyl group and an ⁇ , ⁇ -ethylenically unsaturated monomer having a carboxyl group.
- a monomer containing an ⁇ , ⁇ -ethylenically unsaturated monomer having a hydroxyl group and an ⁇ , ⁇ -ethylenically unsaturated monomer having a carboxyl group By subjecting the hydroxyl group and the carboxyl group to acrylic copolymerization in an amount that satisfies the above-mentioned requirements for the hydroxyl value and acid value, the desired resin can be obtained.
- Examples of the ⁇ , ⁇ -ethylenically unsaturated monomer having a hydroxyl group include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, allyl alcohol, methacryl Mention may be made of adducts of alcohol, hydroxyethyl (meth) acrylate and ⁇ -caprolactone. Among these, preferred are 2-hydroxyethyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, and an adduct of 2-hydroxyethyl (meth) acrylate and ⁇ -caprolactone.
- “(meth) acryl” means both acrylic and methacrylic.
- ⁇ , ⁇ -ethylenically unsaturated monomers having a carboxyl group include acrylic acid, methacrylic acid, acrylic acid dimer, crotonic acid, 2-acryloyloxyethylphthalic acid, 2-acryloyloxyethyl succinic acid, ⁇ - Carboxy-polycaprolactone mono (meth) acrylate, maleic acid, fumaric acid, itaconic acid and the like can be mentioned. Among these, acrylic acid and methacrylic acid are preferable.
- acrylic copolymer for obtaining the above (A) aqueous resin other ⁇ , ⁇ -ethylenically unsaturated monomers can be used as necessary.
- the other ⁇ , ⁇ -ethylenically unsaturated monomers include (meth) acrylic acid esters (for example, methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, (meth) acrylic).
- N-butyl acid isobutyl (meth) acrylate, t-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, lauryl methacrylate, phenyl acrylate, isobornyl (meth) acrylate, cyclohexyl methacrylate, ( (Meth) acrylic acid t-butylcyclohexyl, (meth) acrylic acid dicyclopentadienyl, (meth) acrylic acid dihydrodicyclopentadienyl, etc.), polymerizable amide compounds (for example, (meth) acrylamide, N-methylol ( (Meth) acrylamide, N-butoxymethyl (meth) acrylic Amide etc.).
- Examples of the method for obtaining the aqueous resin (A) include a method for obtaining an acrylic resin after performing solution polymerization and a method for obtaining an emulsion by performing emulsion polymerization in an aqueous medium.
- a crosslinkable monomer can be used as the other ⁇ , ⁇ -ethylenically unsaturated monomer.
- the crosslinkable monomer is a compound having two or more radically polymerizable ethylenically unsaturated groups in the molecule, and examples thereof include divinylbenzene, allyl (meth) acrylate, and ethylene glycol di (meth) acrylate. .
- the solution polymerization is generally carried out by stirring under heating conditions while mixing a mixture of ⁇ , ⁇ -ethylenically unsaturated monomers used as raw materials together with a polymerization initiator into a solvent.
- the conditions for solution polymerization are, for example, a polymerization temperature of 60 to 160 ° C. and a dropping time of 0.5 to 10 hours.
- the ⁇ , ⁇ -ethylenically unsaturated monomer used as the raw material can be polymerized in two stages. In this case, it is only necessary that the ⁇ , ⁇ -ethylenically unsaturated monomer used as a raw material satisfies the requirements for the hydroxyl group and the carboxyl group.
- the polymerization initiator is not particularly limited as long as it is used for ordinary polymerization, and examples thereof include azo compounds and peroxides. Generally, the amount of the polymerization initiator with respect to 100 parts by mass of the monomer mixture is 0.1 to 18 parts by mass, preferably 0.3 to 12 parts by mass.
- the solvent that can be used here is not particularly limited as long as it does not adversely affect the reaction, and examples thereof include alcohols, ketones, ethers, and hydrocarbon solvents. Furthermore, in order to adjust the molecular weight, a mercaptan such as lauryl mercaptan and a chain transfer agent such as ⁇ -methylstyrene dimer can be used as necessary.
- the number average molecular weight of the acrylic resin thus obtained by solution polymerization is preferably 4,000 to 20,000.
- the number average molecular weight of the acrylic resin obtained by solution polymerization can be measured by gel permeation chromatography (GPC) using a polystyrene standard sample standard.
- the glass transition point (Tg) of the acrylic resin is preferably in the range of ⁇ 20 to 80 ° C.
- the glass transition point of an acrylic resin can be calculated
- DSC differential scanning calorimeter
- the acrylic resin obtained by the solution polymerization described above (A) aqueous resin can be obtained by removing the solvent as necessary and then adding a basic compound to make it aqueous.
- the basic compound include ammonia, methylamine, ethylamine, dimethylamine, diethylamine, trimethylamine, triethylamine, dimethylethanolamine, diethanolamine, diethylaminoethanol, triethanolamine and the like.
- the amount of the basic compound added is preferably such that the neutralization rate is 60 to 100% with respect to the carboxyl group of the acrylic resin obtained by the solution polymerization. If the neutralization rate is less than 60%, the aqueous solution is not sufficient and the storage stability may be poor.
- the resin solid content of the (A) aqueous resin thus obtained is generally 25 to 55% by mass.
- the acrylic resin thus obtained can be used as an acrylic water dispersion.
- Such an acrylic water dispersion preferably has a volume average particle diameter in the range of 0.01 to 1 ⁇ m.
- the volume average particle diameter is in the above range, there is an advantage that the stability of the aqueous dispersion is improved and the appearance of the obtained coating film is improved.
- the acrylic emulsion described later and the volume average particle diameter can be adjusted by adjusting the monomer composition and / or the emulsion polymerization conditions.
- the emulsifier is dissolved in an aqueous medium containing water or an organic solvent such as alcohol, if necessary, and heated. Under stirring, a mixture of an ⁇ , ⁇ -ethylenically unsaturated monomer used as a raw material and a polymerization initiator can be added dropwise. A mixture of ⁇ , ⁇ -ethylenically unsaturated monomers used as a raw material may be pre-emulsified with an emulsifier and water.
- Polymerization initiators that can be suitably used for emulsion polymerization include azo oily compounds (for example, azobisisobutyronitrile, 2,2′-azobis (2-methylbutyronitrile), and 2,2′- Azobis (2,4-dimethylvaleronitrile) and the like, and aqueous compounds (eg, anionic 4,4′-azobis (4-cyanovaleric acid), 2,2-azobis (N- (2-carboxyethyl)) -2-methylpropionamidine and cationic 2,2′-azobis (2-methylpropionamidine)); and redox oily peroxides (eg, benzoyl peroxide, parachlorobenzoyl peroxide, lauroyl peroxide and t-butyl perbenzoate) and aqueous peroxides (eg potassium persulfate and persulfate) Ammonium and the like).
- azo oily compounds for example, azobisisobutyroni
- emulsifier a general emulsifier usually used by those skilled in the art can be used.
- reactive emulsifiers such as Antox MS-60 (manufactured by Nippon Emulsifier Co., Ltd.), Eleminol JS-2 (manufactured by Sanyo Kasei Kogyo Co., Ltd.), Adekari Soap NE-20 (manufactured by Asahi Denka Co., Ltd.) and Aqualon HS-10 (Daiichi Kogyo Seiyaku Co., Ltd.), Latemul PD-104 (Kao Corp.) and the like are particularly preferred.
- a mercaptan such as lauryl mercaptan and a chain transfer agent such as ⁇ -methylstyrene dimer can be used as necessary.
- the reaction temperature is determined by the initiator. For example, it is preferably 60 to 90 ° C. for an azo initiator or peroxide, and preferably 30 to 70 ° C. for a redox system. In general, the reaction time is 1 to 8 hours. Generally, the amount of the initiator with respect to 100 parts by mass of the monomer mixture is 0.1 to 5% by mass.
- the emulsion polymerization can be performed in multiple stages, for example, in two stages.
- a part of the mixture of ⁇ , ⁇ -ethylenically unsaturated monomers used as the raw material is subjected to emulsion polymerization, and the remainder of the ⁇ , ⁇ -ethylenically unsaturated monomer mixture is further added to emulsify. Polymerization is performed.
- the above emulsion can be used at a pH of 5 to 10 by neutralizing with a basic compound from the viewpoint of storage stability.
- the basic compound may be the same as that used in making the acrylic resin obtained in the previous solution polymerization aqueous.
- the neutralization is preferably performed by adding the basic compound to the system before or after emulsion polymerization.
- the number average molecular weight is preferably 10,000 to 80,000.
- the acrylic emulsion has a hydroxyl value of 80 to 200 mg KOH / g, an acid value of 10 to 40 mg KOH / g, a ratio of the hydroxyl value to the acid value of 3 to 15, and a number average molecular weight of 10 In the range of 8,000 to 80,000, there is an advantage that the crosslink density in the obtained coating film is in a better range while ensuring good coating stability. This is because the number average molecular weight is in a relatively high range of 10,000 to 80,000, and the acrylic emulsion has a large number of hydroxyl groups within the above range. It is considered that the low-temperature curability of the reacting (B) polyisocyanate compound is ensured, whereby the crosslinking density in the resulting coating film is in a better range.
- the number average molecular weight of the acrylic emulsion can be measured by gel permeation chromatography (GPC) using a polystyrene standard sample standard after removing water by drying under reduced pressure or the like.
- the (A) aqueous resin may include a polyester resin.
- a polyester resin that can be used as an aqueous resin is generally prepared by condensing a polyhydric alcohol component and a polybasic acid component so as to satisfy the requirements for the hydroxyl group and carboxyl group. Can do.
- polyhydric alcohol component examples include, for example, ethylene glycol, diethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 2, 2-diethyl-1,3-propanediol, neopentyl glycol, 1,9-nonanediol, 1,4-cyclohexanediol, hydroxypivalic acid neopentyl glycol ester, 2-butyl-2-ethyl-1,3-propane Examples thereof include hydroxycarboxylic acid components such as diol, 3-methyl-1,5-pentanediol, and 2,2,4-trimethylpentanediol.
- polybasic acid component examples include, for example, aromatic polyvalent carboxylic acids and acid anhydrides such as phthalic anhydride, isophthalic acid, terephthalic acid, trimellitic anhydride, tetrachlorophthalic anhydride, pyromellitic anhydride; Hexahydrophthalic anhydride, tetrahydrophthalic anhydride, alicyclic polycarboxylic acids and anhydrides such as 1,4- and 1,3-cyclohexanedicarboxylic acid; maleic anhydride, fumaric acid, succinic anhydride, adipic acid, sebatin
- polybasic acid components such as aliphatic polyvalent carboxylic acids such as acids and anhydrides, and anhydrides thereof. If necessary, a monobasic acid such as benzoic acid or t-butylbenzoic acid may be used in combination.
- mono-epoxide compounds such as monohydric alcohol, Cardura E (trade name: manufactured by Ciel Chemical), and lactones ( ⁇ -propiolactone, dimethylpropiolactone, butyrolactone, ⁇ -valerolactone, ⁇ -caprolactone, ⁇ -caprolactone, etc.) may be used in combination.
- fatty acids such as castor oil and dehydrated castor oil, and an oil component that is one or a mixture of two or more of these fatty acids may be added to the acid component and the alcohol component. It is also possible to graft an acrylic resin or vinyl resin or to react a polyisocyanate compound as long as the above-mentioned requirements for the hydroxyl group and carboxyl group are satisfied.
- the number average molecular weight of the polyester resin thus obtained is preferably 500 to 20,000, and more preferably 1,500 to 10,000. If the number average molecular weight is less than 500, the storage stability when the polyester resin is dispersed in water may be lowered. On the other hand, when the number average molecular weight exceeds 20,000, the viscosity of the polyester resin increases, so that the solid content concentration in the case of coating is lowered, and the coating workability may be lowered.
- the glass transition point of the polyester resin is preferably ⁇ 20 to 80 ° C. When the glass transition point is less than ⁇ 20 ° C., the hardness of the resulting coating film may be lowered, and when it exceeds 80 ° C., the base concealability may be lowered.
- the glass transition point is more preferably 0 to 60 ° C.
- the glass transition point of the polyester resin can be obtained by calculation from the kind and amount of the monomer used for preparing the polyester resin, as in the case of the acrylic resin. Moreover, you may measure the glass transition point of a polyester resin with a differential scanning calorimeter (DSC).
- DSC differential scanning calorimeter
- the polyester resin thus obtained can be neutralized with the basic compounds listed above to obtain (A) an aqueous resin.
- the content of the aqueous resin (A) contained in the aqueous coating composition of the present invention is preferably 20 to 70% by mass, preferably 25 to 60% by mass, based on the resin solid content of the aqueous coating composition. More preferably.
- the aqueous coating composition when used as an intermediate coating composition, (A) when a mixture of an acrylic resin and a polyester resin is used as the aqueous resin, the ratio of the acrylic resin and the polyester resin is acrylic resin /
- the polyester resin is preferably in the range of 5/1 to 1/1.
- the water-dispersible blocked polyisocyanate compound contained in the aqueous coating composition of the present invention comprises malonic acid diester (B-2) in polyisocyanate (B-1). It can be prepared by reacting and then reacting the obtained reactant with the organic amine compound (B-3).
- the polyisocyanate (B-1) is one or more selected from aliphatic polyisocyanates, alicyclic polyisocyanates and aromatic polyisocyanates.
- aliphatic polyisocyanate examples include aliphatic diisocyanate, lysine triisocyanate (hereinafter referred to as LTI), 4-isocyanatomethyl-1,8-octamethylene diisocyanate (trimer triisocyanate: hereinafter referred to as TTI), bis (2 -Isocyanatoethyl) 2-isocyanatoglutarate (glutamate triisocyanate: hereinafter referred to as GTI).
- LTI lysine triisocyanate
- TTI 4-isocyanatomethyl-1,8-octamethylene diisocyanate
- TTI 4-isocyanatomethyl-1,8-octamethylene diisocyanate
- GTI bis (2 -Isocyanatoethyl) 2-isocyanatoglutarate
- aliphatic diisocyanate used in the aliphatic polyisocyanate those having 4 to 30 carbon atoms are preferable.
- HDI is preferred because of its industrial availability.
- the aliphatic diisocyanate only one kind may be used, or two or more kinds may be used in combination.
- the alicyclic polyisocyanate the following alicyclic diisocyanates are mainly used.
- the alicyclic diisocyanate those having 8 to 30 carbon atoms are preferable.
- isophorone diisocyanate hereinafter referred to as IPDI
- 1,3-bis (isocyanatomethyl) -cyclohexane 4,4′-dicyclohexylmethane diisocyanate.
- Norbornene diisocyanate Norbornene diisocyanate
- hydrogenated xylylene diisocyanate and the like.
- IPDI is preferred from the viewpoint of weather resistance and industrial availability. Only 1 type may be used for alicyclic diisocyanate and it may use 2 or more types together.
- aromatic polyisocyanate aromatic diisocyanates shown below are mainly used.
- aromatic diisocyanate examples include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, naphthalene diisocyanate, xylylene diisocyanate, and the like.
- Aromatic diisocyanate may use only 1 type and may use 2 or more types together.
- aliphatic polyisocyanates and / or alicyclic polyisocyanates are preferable because of excellent weather resistance. Furthermore, among the aliphatic polyisocyanates, aliphatic diisocyanates are most preferable.
- polyisocyanates examples include triisocyanates such as LTI, TTI, GTI, or derivatives thereof, biuret bonds, urea bonds, isocyanurate bonds, uretdione bonds, urethane bonds, allophanate bonds, oxadiazine trione bonds, etc. And di-isocyanate di- to 20-mer oligomers produced by forming
- the malonic acid diester (B-2) to be reacted with the polyisocyanate (B-1) is a compound represented by the following general formula.
- W 1 and W 2 are each independently an alkyl group having 1 to 8 carbon atoms, a phenyl group or a benzyl group.
- the phenyl group or benzyl group may have 1 to 3 substituents. Examples of the substituent include an alkyl group having 1 to 6 carbon atoms, a halogen atom such as a fluorine atom or a chlorine atom, an amino group, a sulfonyl group, and a hydroxyl group.
- W 1 and W 2 may be the same or different.
- malonic acid diester examples include dimethyl malonate, diethyl malonate, di-n-propyl malonate, diisopropyl malonate, di-n-butyl malonate, diisobutyl malonate, and di-t-butyl malonate.
- it is dimethyl malonate, diethyl malonate, di-n-propyl malonate, diisopropyl malonate, di-n-butyl malonate, diisobutyl malonate, di-t-butyl malonate, methyl t-butyl malonate. More preferred are dimethyl malonate and diethyl malonate, and most preferred is diethyl malonate.
- the malonic acid diester shown above may be used alone or in combination of two or more.
- the amount of malonic acid diester (B-2) used in the reaction is such that 75 to 150 moles of malonic acid diester (B-2) is used per mole of isocyanate group of polyisocyanate (B-1). preferable.
- This reaction may be performed in the presence of an organic solvent or may be performed without using an organic solvent. When using an organic solvent, it is preferable to use an organic solvent that is inert to the isocyanate group and hardly hydrolyzes.
- Preferable organic solvents include, for example, ether solvents such as propylene glycol dimethyl ether, dipropylene glycol dimethyl ether, diethylene glycol dimethyl ether, and diethylene glycol diethyl ether, and ketone solvents such as methyl ethyl ketone and methyl isobutyl ketone.
- ether solvents such as propylene glycol dimethyl ether, dipropylene glycol dimethyl ether, diethylene glycol dimethyl ether, and diethylene glycol diethyl ether
- ketone solvents such as methyl ethyl ketone and methyl isobutyl ketone.
- a reaction catalyst can be used as necessary.
- the reaction catalyst include organic metal salts such as tin, zinc and lead, metal alcoholates, and tertiary amines.
- the above reaction can be generally carried out at ⁇ 20 to 150 ° C., preferably 0 to 100 ° C., more preferably 40 to 80 ° C. By performing the reaction at 150 ° C. or lower, side reactions can be suppressed, and by performing the reaction at ⁇ 20 ° C. or higher, the reaction rate can be kept high.
- Nonionic hydrophilic compounds include polyethylene glycol compounds having at least three consecutive ethylene oxide groups.
- Polyethylene glycol compounds such as monoalkoxy polyethylene glycol, polyethylene glycol or triol, pluronic type polypropylene glycol or triol obtained by addition polymerization of ethylene oxide at the end of polypropylene glycol, polyoxypropylene polyoxyethylene copolymer diol or triol, polyoxypropylene Examples thereof include polyoxyethylene block polymer diol and triol.
- monoalkoxy polyethylene glycol and polyethylene glycol are preferable, and monoalkoxy polyethylene glycol is more preferable.
- Monoalkoxy polyethylene glycol is obtained by adding an alcohol to one end of polyethylene glycol.
- the monoalcohol that can be used in the monoalkoxy polyethylene glycol preferably has 1 to 8 carbon atoms, more preferably 1 to 6 carbon atoms, and still more preferably 1 to 4 carbon atoms. Most preferred are methanol and ethanol. That is, among monoalkoxy polyethylene glycols, monomethoxy polyethylene glycol and monoethoxy polyethylene glycol are preferable, and monomethoxy polyethylene glycol is most preferable.
- polyethylene glycol compounds polyethylene glycol compounds in which a monoalcohol having 1 to 4 carbon atoms is added to one end having a number average molecular weight of 200 to 2000 are particularly preferable.
- a water-dispersible block polyisocyanate compound is prepared.
- the organic amine compound (B-3) include a chain secondary amine compound and a cyclic secondary amine compound containing a nitrogen atom.
- the chain secondary amine compound dialkylamines having two identical or different alkyl groups having 1 to 12 carbon atoms are preferable.
- Preferred examples of the chain secondary amine compound include diisopropylamine, diisobutylamine, di (2-butylamine), di (t-butyl) amine, dicyclohexylamine, Nt-butylcyclohexylamine and the like.
- Cyclic secondary amine compounds containing a nitrogen atom include aziridine, azetidine, pyrrolidine, 2-methylpyrrolidine, piperidine, 2-methylpiperidine, 3-methylpiperidine, 4-methylpiperidine, 4-benzylpiperidine, 2,4-dimethylpiperidine 3,5-dimethylpiperidine, 2,6-dimethylpiperidine, 2,2,6,6-tetramethylpiperidine, 4-piperidinecarboxylic acid methyl ester, 4-piperidinecarboxylic acid ethyl ester, 2,2,6,6 -Tetramethyl-4-piperidone, 4-piperidinopiperidine, piperazine, N-methylpiperazine, N-ethylpiperazine, N-allylpiperazine, N-isobutylpiperazine, N-cyclohexylpiperazine, N-cyclopentylpiperazine, N-phenyl Piperazine, - (2-pyridyl) piperazine, 1- (4-pyrid
- the above reaction may be performed using an organic solvent or may be performed without using an organic solvent.
- an organic solvent it is preferable to use an organic solvent that is inert to the isocyanate group and hardly hydrolyzes.
- organic solvents include, for example, ether solvents such as propylene glycol dimethyl ether, dipropylene glycol dimethyl ether, diethylene glycol dimethyl ether, and diethylene glycol diethyl ether, and ketone solvents such as methyl ethyl ketone and methyl isobutyl ketone.
- the (B) water-dispersible blocked polyisocyanate compound thus obtained can improve storage stability by mixing 10 mol% or more of the basic compound with respect to 1 mol of the blocked isocyanate group of the compound.
- the basic compound include N-allylmorpholine, N-methylmorpholine, N-ethylmorpholine, triethanolamine, 2-methylimidazole and the like.
- a commercially available product may be used as the water-dispersible block polyisocyanate compound.
- Examples of commercially available products include WM44-L70G, which is a block polyisocyanate manufactured by Asahi Kasei Chemical Company.
- the (B) water-dispersible block polyisocyanate compound is maintained in reactivity even under heating conditions of 100 ° C. or lower, and further after being stored in a state of being contained in an aqueous coating composition. And having a high curability retention rate.
- the content of the (B) water-dispersible block polyisocyanate compound contained in the aqueous coating composition of the present invention is preferably 10 to 25% by mass based on the resin solid content of the aqueous coating composition. More preferably, it is ⁇ 22% by mass.
- the curing reaction proceeds well even under heating conditions under low temperature conditions (for example, heating conditions of 100 ° C. or less), and a cured coating film having excellent coating film properties is obtained. There are advantages such as being.
- Hydrophilized modified carbodiimide compound contained in the aqueous coating composition of the present invention contains, -OCONH-X-NHCOOY
- X is a bifunctional organic group containing at least one carbodiimide group
- Y has a structure in which a hydroxyl group is removed from a polyalkylene glycol monoalkyl ether.
- X is a bifunctional organic group containing at least one carbodiimide group
- Y is a structure obtained by removing a hydroxyl group from the same or different polyalkylene glycol monoalkyl ether
- Z is The structure is obtained by removing a hydroxyl group from a bifunctional polyol having a number average molecular weight of 200 to 5,000.
- R 2 is preferably a hydrocarbon group having 6 to 15 carbon atoms.
- Specific examples include a phenylene group, a diphenylenemethyl group, a diphenylene (dimethyl) methyl group, a methylphenylene group, a dimethylphenylene group, a tetramethylxylylene group, a hexylene group, a cyclohexylene group, and a dicyclohexylenemethyl group. be able to. Preference is given to a dicyclohexylenemethyl group.
- the p is 1 to 10.
- p is the number of carbodiimide groups present in the structural unit, preferably 2 or more from the viewpoint of curability, and more preferably 8 or less.
- the number of repetitions is not limited to p, and the number of repetitions is expressed as an average value.
- Y can be represented by the following general formula (b) or (c).
- R 3 is preferably an alkyl group having 1 to 20 carbon atoms. Specific examples include a methyl group, an ethyl group, a butyl group, a hexyl group, an octyl group, a decyl group, a dodecyl group, and a stearyl group.
- R 4 is a hydrogen atom or a methyl group, and is preferably a hydrogen atom. q is 4 to 40. In the general formulas (b) and (c), when R 4 is hydrogen, the general formulas (b) and (c) show the same structure.
- Z is a polymer structure composed of an ether bond, an ester bond, or a carbonate bond, and is difficult to formulate.
- the bifunctional polyol having a number average molecular weight of 200 to 5,000, which will be described later.
- the (C) hydrophilized modified carbodiimide compound having two structural units is a raw material carbodiimide compound containing at least two isocyanate groups in one molecule, a hydroxyl group at the molecular end, and a number average molecular weight of 200 to 5,000.
- a reaction product obtained by reacting the above bifunctional polyol with a molar ratio of the isocyanate group of the raw material carbodiimide compound exceeding the molar amount of the hydroxyl group of the polyol, and further reacting with a polyalkylene glycol monoalkyl ether Can be obtained.
- the raw material carbodiimide compound containing at least two isocyanate groups in the molecule preferably has isocyanate groups at both ends from the viewpoint of reactivity.
- the method for producing a raw material carbodiimide compound having an isocyanate group at both ends is well known by those skilled in the art, and for example, a condensation reaction involving decarbonization of an organic diisocyanate can be used.
- organic diisocyanate examples include aromatic diisocyanates, aliphatic diisocyanates, alicyclic diisocyanates, and mixtures thereof.
- aromatic diisocyanates 4,4- Diphenylmethane diisocyanate, 4,4-diphenyldimethylmethane diisocyanate, 1,3-phenylene diisocyanate, 1,4-phenylene diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 2,4-tolylene diisocyanate
- isophorone diisocyanate dicyclohexylmeta 4,4-diisocyanate, and the like methylcyclohexane diisocyanate
- a carbodiimidization catalyst is usually used.
- the carbodiimidization catalyst include 1-phenyl-2-phospholene-1-oxide, 3-methyl-2-phospholene-1-oxide, 1-ethyl-2-phospholene-1-oxide, 3- Examples thereof include phospholene oxides such as methyl-1-phenyl-2-phospholene-1-oxide and isomers of these 3-phospholenes. From the viewpoint of reactivity, 3-methyl-1-phenyl-2-phospholene-1-oxide is preferred.
- the bifunctional polyol having a hydroxyl group at the molecular end is not particularly limited, but the number average molecular weight is preferably 200 to 5,000 from the viewpoint of reaction efficiency.
- Specific examples of the bifunctional polyol having a hydroxyl group at the molecular terminal include polyether diol, polyester diol, and polycarbonate diol, such as polyethylene glycol, polypropylene glycol, polyethylene propylene glycol, polytetramethylene ether glycol, Polyalkylene glycols such as polyhexamethylene ether glycol and polyoctamethylene ether glycol, polyethylene adipate, polybutylene adipate, polyhexamethylene adipate, polyneopentyl adipate, poly-3-methylpentyl adipate, polyethylene / butylene adipate, polyneopentyl / Polyester diol such as hexyl adipate, polycaprolactone diol, poly-3- Poly
- the reaction between the raw material carbodiimide compound containing at least two isocyanate groups in one molecule and a bifunctional polyol having a hydroxyl group at the molecular end and a number average molecular weight of 200 to 5,000 is the reaction of the raw material carbodiimide compound.
- the reaction is carried out at a ratio in which the molar amount of the isocyanate group exceeds the molar amount of the hydroxyl group of the polyol.
- the reaction of the polyalkylene glycol monoalkyl ether described later cannot be performed sufficiently.
- the ratio between the molar amount of the isocyanate group of the raw material carbodiimide compound and the molar amount of the hydroxyl group of the polyol having a hydroxyl group at the molecular end is from 1.0: 1.1 to 1.0: 2.0 is preferable.
- the degree of polymerization of the raw material carbodiimide compound and the bifunctional polyol having a hydroxyl group at the molecular terminal in the reaction product obtained in this step is preferably 1 to 10 from the viewpoint of reaction efficiency.
- reaction product thus obtained is further reacted with a polyalkylene glycol monoalkyl ether to obtain a (C) hydrophilized modified carbodiimide compound having two structural units.
- a polyalkylene glycol monoalkyl ether those represented by the following general formula (b ′) or (c ′) are used.
- R 3 , R 4 , and q the contents described in the general formulas (b) and (c) are applied as they are to R 3 , R 4 , and q.
- the type and q of R 4 in the above unit are appropriately set within the above ranges in consideration of storage stability, water dispersibility, and reactivity after water volatilizes.
- R 3 in the monoalkoxypolyalkylene glycol is preferably a methyl group and R 4 is preferably a hydrogen atom.
- q is preferably from 4 to 20, more preferably from 6 to 12, from the viewpoint of water dispersibility and reactivity after water volatilizes.
- polyalkylene glycol monoalkyl ether a polyalkylene glycol monoalkyl ether having a number average molecular weight of 200 to 5,000 is preferably used.
- the alkyl group of the polyalkylene glycol monoalkyl ether is preferably an alkyl group having 1 to 20 carbon atoms.
- Specific examples of the polyalkylene glycol monoalkyl ether include, for example, those composed of polyethylene glycol, polypropylene glycol or a mixture thereof having one end blocked with an alkyl group having 1 to 20 carbon atoms.
- polyalkylene glycol monoalkyl ethers include, for example, polyethylene glycol monomethyl ether, polyethylene glycol mono-2-ethylhexyl ether, polyethylene glycol monolauryl ether having a number average molecular weight of 200 to 5,000, Examples thereof include polypropylene glycol monomethyl ether, polypropylene glycol mono-2-ethylhexyl ether, and polypropylene glycol monolauryl ether.
- the reaction product and the polyalkylene glycol monoalkyl ether are reacted at a ratio in which the molar amount of the isocyanate group of the reaction product is the same or higher than the molar amount of the hydroxyl group of the polyalkylene glycol monoalkyl ether.
- the molar amount of the isocyanate group is less than the molar amount of the hydroxyl group, the reaction of the polyalkylene glycol monoalkyl ether with the reaction product cannot be sufficiently performed.
- the molar amount of the isocyanate group of the reaction product may be obtained by direct measurement, or may be a value calculated from the charged composition.
- a catalyst can be used in the reaction between the raw material carbodiimide compound and the bifunctional polyol having a hydroxyl group at the molecular end, and the reaction between the reaction product and the polyalkylene glycol monoalkyl ether.
- the temperature during the reaction is not particularly limited, but is preferably 60 to 120 ° C. from the viewpoint of control of the reaction system and reaction efficiency.
- (C) a hydrophilized modified carbodiimide compound having two structural units can be obtained.
- the (C) hydrophilized modified carbodiimide compound thus produced does not have the structure of the general formula (I) shown above, but various other reaction products derived from the raw materials used. It is a mixture containing. However, in general, it may be regarded as having the structure of the general formula (I).
- R 0 is hydrogen, methyl or ethyl.
- R 1 is an alkylene group having 4 or less carbon atoms, and may be the same or different. Specific examples of the alkylene group include a methylene group, an ethylene group, a propylene group, and a butylene group. n is 0 or 1, and m is 0-60.
- R 0 , R 1 , n and m are determined by the trifunctional polyol used in producing the (C) hydrophilized modified carbodiimide compound.
- the ratio of the hydrophilic part to the hydrophobic part is preferably 2.0 to 6.3.
- the ratio of the hydrophilic part to the hydrophobic part can be determined by dividing the molecular weight of the oxymethylene group or oxyethylene group part present in the carbodiimide compound by the molecular weight of the carbodiimide compound.
- the (C) hydrophilized modified carbodiimide compound having three structural units comprises a raw material carbodiimide compound containing at least two isocyanate groups in one molecule, a polyalkylene glycol monoalkyl ether, and an isocyanate group of the raw material carbodiimide compound.
- the description of the raw material carbodiimide compound of the (C) hydrophilized modified carbodiimide compound having the two structural units is applied as it is.
- the reaction between the raw material carbodiimide compound and the polyalkylene glycol monoalkyl ether is further reacted with a trifunctional polyol after the reaction, so that an isocyanate group needs to remain.
- the equivalent of an isocyanate group needs to exceed the equivalent of a hydroxyl group, Preferably, it is preferable that the equivalent ratio of an isocyanate group and a hydroxyl group is 2/1.
- the reaction can usually be carried out under conditions well known to those skilled in the art, and a tin-based catalyst can be used if necessary.
- polyalkylene glycol monoalkyl ether As the polyalkylene glycol monoalkyl ether, the description of the polyalkylene glycol monoalkyl ether of the (C) hydrophilized modified carbodiimide compound having the above-mentioned two structural units is applied as it is.
- the trifunctional polyol is reacted with the reaction product thus obtained.
- the amount of the trifunctional polyol used in the reaction is preferably such that the hydroxyl equivalent of the reactant is equal to or greater than the isocyanate equivalent, and more preferably the isocyanate equivalent and the hydroxyl equivalent are equal.
- the isocyanate equivalent of the said reaction product can also be calculated
- the reaction can be carried out in the same manner as the reaction between the raw material carbodiimide compound and the polyalkylene glycol monoalkyl ether.
- the trifunctional polyol is preferably trimethylolpropane, glycerin, or an alkylene oxide adduct thereof from the viewpoint of easy availability.
- the alkylene oxide include ethylene oxide and propylene oxide.
- the alkylene oxide adduct of glycerin is commercially available as a GP series from Sanyo Chemical.
- those having a structure in which an alkylene oxide is added to one hydroxyl group are particularly preferred.
- those having such a structure include GP-250 and GP-3000.
- (C) a hydrophilized modified carbodiimide compound having three structural units can be obtained.
- the (C) hydrophilized modified carbodiimide compound thus produced does not have the structure of the general formula (II) as described above, but has the structure of the general formula (II). Can be considered as being.
- X is a bifunctional organic group containing at least one carbodiimide group
- Y has a structure in which a hydroxyl group is removed from the same or different polyalkylene glycol monoalkyl ether.
- X in the general formula (III) is a group that can be represented by the formula (a) in the above general formula (I).
- Y in the general formula (III) has a structure in which a hydroxyl group is removed from the same or different polyalkylene glycol monoalkyl ether. This Y can show the same thing as Y in the above-mentioned general formula (I).
- the (C) hydrophilized modified carbodiimide compound represented by the general formula (III) there is an advantage that the crosslinking density is maintained at a higher level.
- the general formula (I) (II) having a plurality of carbodiimide units has a low reaction efficiency with an acid while the acid value of the aqueous resin is low
- the general formula (III) is a general formula (I) Since it does not have a bulky structure as in (II), it does not hinder the crosslinking of the hydroxyl group and isocyanate of the aqueous resin, so that (C) hydrophilization modification represented by the general formula (III) It is thought that the crosslinking density of the carbodiimide compound has increased.
- Y in the general formula (III) is preferably the following (i) or (ii):
- (ii) a structure having 4 to 60 repeats A structure in which a hydroxyl group is removed from a polypropylene glycol monoalkyl ether in which an alkyl group having 1 to 8 carbon atoms is ether-bonded to the end of a polypropylene oxide unit: More preferably, they are the same or different structures selected from More preferably, the number of repeating (ii) polypropylene oxide units is 15 to 60.
- the (C) hydrophilized modified carbodiimide compound represented by the general formula (III) is a polyalkylene glycol monoalkyl ether which is the same or different from the raw material carbodiimide compound obtained by the above condensation reaction involving decarbonization of organic diisocyanate. Can be prepared by reacting.
- the polyalkylene glycol monoalkyl ether is A polyethylene glycol monoalkyl ether in which an alkyl group having 1 to 3 carbon atoms is ether-bonded to the terminal of a polyethylene oxide unit having 6 to 20 repeats, or A polypropylene glycol monoalkyl ether in which an alkyl group having 1 to 8 carbon atoms is ether-bonded to the end of a polypropylene oxide unit having 4 to 60 repeats, It is more preferable that In the preparation of the (C) hydrophilized modified carbodiimide compound represented by the general formula (III), these polyethylene glycol monoalkyl ethers and polypropylene glycol monoalkyl ethers may be used alone or in combination.
- polyethylene glycol monoalkyl ether examples include polyethylene glycol monomethyl ether, polyethylene glycol monoethyl ether, and polyethylene glycol monopropyl ether, with polyethylene glycol monomethyl ether being particularly preferred.
- polypropylene glycol monoalkyl ether examples include polypropylene glycol monomethyl ether, polypropylene glycol monoethyl ether, polypropylene glycol monobutyl ether, and polypropylene glycol 2-ethylhexyl ether, and polypropylene glycol monobutyl ether is particularly preferable. is there.
- any one Y is (i), the other Y is (ii), and (i) the number of repetitions 6
- the periphery of the carbodiimide group is somewhat hydrophobic in order to improve water resistance when a coating film is formed.
- the periphery of the carbodiimide group is hydrophobic to some extent and the contact with water molecules is kept low.
- the carbodiimide compound represented by the general formula (III) needs to have a certain amount of polyethylene glycol structure in order to maintain hydrophilicity.
- the hydrophilicity of the carbodiimide compound is secured.
- hydrophobicity can be maintained to some extent around the carbodiimide group.
- the content of the (C) hydrophilized modified carbodiimide compound contained in the aqueous coating composition of the present invention is preferably 1 to 8% by mass relative to the resin solid content of the aqueous coating composition, and is preferably 1.5%. It is more preferably from 7 to 7% by mass, and further preferably from 2 to 6% by mass.
- content of a hydrophilic modification carbodiimide compound is less than 1 mass%, there exists a possibility that the water-resistant improvement effect may not be acquired.
- content of the (C) hydrophilization modified carbodiimide compound exceeds 8 mass%, there exists a possibility that water resistance Chijimi property may be inferior.
- the water-based coating composition of the present invention contains both the (B) water-dispersible block polyisocyanate compound and the (C) hydrophilized modified carbodiimide compound, thereby ensuring water resistance of the coating film obtained while ensuring low-temperature curability. The property will be improved.
- the water-based resin has an acid group, and the acid value is in the above range, so that the stability of the paint as a one-component water-based paint composition and the (C) hydrophilicity at the time of curing. Excellent water resistance due to the reaction with the modified carbodiimide compound will be exhibited.
- the aqueous coating composition of the present invention contains (B) a water-dispersible block polyisocyanate compound that reacts with the hydroxyl group of the aqueous resin (A), a coating film having excellent coating film properties is obtained. The coating stability as a one-pack type aqueous coating composition will be excellent.
- the coating stability as a one-pack type aqueous coating composition is achieved.
- the effect of improving the water resistance of the coating film is improved.
- the aqueous coating composition of the present invention contains (D) an aqueous polyurethane resin in addition to the components (A) to (C).
- the aqueous polyurethane resin comprises a polyol compound (D-1), a compound (D-2) having an active hydrogen group and a hydrophilic group in the molecule, an organic polyisocyanate (D-3), and, if necessary, chain extension. It is a polymer obtained by using an agent and a polymerization terminator, and can be prepared by dissolving or dispersing the obtained polymer in water.
- the polyol compound (D-1) is not particularly limited as long as it is a polyol compound having two or more hydroxyl groups.
- the polyol compound (D-1) is, for example, a polyhydric alcohol such as ethylene glycol, propylene glycol, 1,4-butanediol, 1,6-hexanediol, trimethylolpropane, glycerin, polyethylene glycol, polypropylene glycol, polytetra Polyether polyols such as methylene ether glycol; dicarboxylic acids such as adipic acid, sebacic acid, itaconic acid, maleic anhydride, phthalic acid, isophthalic acid, and ethylene glycol, triethylene glycol, propylene glycol, butylene glycol, tripropylene glycol, Polyester polyols obtained from glycols such as neopentyl glycol; polycaprolactone polyols; polybutadiene polyols; polycarbonate
- the compound (D-2) having an active hydrogen group and a hydrophilic group in the molecule includes an active hydrogen and an anion group ⁇ an anion group or an anion-forming group (which reacts with a base to form an anion group.
- Is converted into an anionic group by neutralization with a base before, during or after the urethanization reaction) ⁇ for example, Japanese Patent Publication No. 42-24192 and Japanese Patent Publication No.
- the organic polyisocyanate (D-3) is not particularly limited as long as it has two or more isocyanate groups in the molecule.
- Aliphatic diisocyanates having 2 to 12 carbon atoms such as hexamethylene diisocyanate, 2,2,4-trimethylhexane diisocyanate, lysine diisocyanate;
- Alicyclic diisocyanates having 4 to 18 carbon atoms such as 1,4-cyclohexane diisocyanate, isophorone diisocyanate, 4,4′-dicyclohexylmethane diisocyanate, methylcyclohexylene diisocyanate, isopropylidenecyclohexyl-4,4′-diisocyanate; 2,4-toluylene diisocyanate, 2,6-toluylene diisocyanate, diphenylmethane-4,4′-diisocyanate,
- these polyisocyanate compounds may be used as dimers and trimers (isocyanurate bonds), or may be used as biurets by reacting with amines.
- polyisocyanates having urethane bonds obtained by reacting these polyisocyanate compounds with polyols can also be used. It is more preferable to use an aliphatic diisocyanate as the organic polyisocyanate (D-3). Advantages of preparing a water-based polyurethane resin (D) using an aliphatic diisocyanate can adjust the water permeability of the resulting coating film to an appropriate range, and can obtain good low-temperature initial water resistance. There is.
- the chain extender that can be used as necessary when preparing the aqueous polyurethane resin is not particularly limited as long as it contains two or more active hydrogen groups.
- a low molecular weight number average molecular weight of less than 500
- examples include polyols and polyamines.
- the low molecular polyol include ethylene glycol, propylene glycol, 1,4-butanediol, 3-methylpentanediol, 2-ethyl-1,3-hexanediol, and trimethylolpropane.
- the polyamine include ethylenediamine, hexamethylenediamine, diethylenetriamine, hydrazine, xylylenediamine, and isophoronediamine.
- examples of the polymerization terminator include a compound having one active hydrogen in the molecule, or a monoisocyanate compound.
- Examples of the compound having one active hydrogen in the molecule include monoalcohol (eg, alkyl alcohols such as methanol, butanol and octanol, alkyl alcohol alkylene oxide adducts), or monoamines (eg, butylamine, dibutylamine, etc.) Of the alkylamine).
- monoalcohol eg, alkyl alcohols such as methanol, butanol and octanol, alkyl alcohol alkylene oxide adducts
- monoamines eg, butylamine, dibutylamine, etc.
- Examples of the monoisocyanate compound include methyl isocyanate, ethyl isocyanate, propyl isocyanate, butyl isocyanate, lauryl isocyanate, cyclohexyl isocyanate, phenyl isocyanate, and tolylene isocyanate.
- the reaction method for producing the water-based polyurethane resin is a one-shot method in which each component is reacted at once or a multistage method in which the components are reacted in stages ⁇ part of active hydrogen-containing compound (for example, polymer polyol) and poly Any method of producing an NCO-terminated prepolymer by reacting isocyanate and then reacting the remainder of the active hydrogen-containing compound may be used.
- active hydrogen-containing compound for example, polymer polyol
- the synthetic reaction of the aqueous polyurethane resin is usually carried out at 40 to 140 ° C, preferably 60 to 120 ° C.
- a tin-based catalyst such as dibutyltin laurate or tin octylate used in a normal urethanization reaction or an amine-based catalyst such as triethylenediamine may be used.
- the above reaction may be performed in an organic solvent inert to isocyanate (for example, acetone, toluene, dimethylformamide, etc.), and a solvent may be added during or after the reaction.
- the aqueous polyurethane resin is a known method (in the case of an anion-forming group, a method of neutralizing with a base to form an anion group; in the case of a cation-forming group, a quaternizing agent is used to form a cation group. It can be prepared by dispersing in water after treatment with a method of forming or a method of forming a cationic group by neutralization with an acid.
- the step of dissolving in water is not particularly limited, and may be after the reaction or in the middle of the multistage method.
- an aqueous polyurethane resin can be obtained by dissolving in water while chain-extending with water and / or polyamine.
- the solvent may be removed after dissolving in water.
- the (D) aqueous polyurethane resin in the present invention has a glass transition point (Tg) of ⁇ 50 ° C. or less, and (D) the elongation at break of the cured film of the aqueous polyurethane resin is 400% or more at ⁇ 20 ° C. Condition.
- the glass transition point (Tg) of the above (D) water-based polyurethane resin exceeds ⁇ 50 ° C., the chipping resistance and water resistance of the resulting coating film are inferior.
- the glass transition point (Tg) is more preferably ⁇ 55 ° C. or less, and further preferably ⁇ 58 ° C. or less.
- the glass transition point (Tg) of the aqueous polyurethane resin can be measured by a differential scanning calorimeter.
- the breaking elongation of the cured film of the above (D) water-based polyurethane resin is less than 400% at ⁇ 20 ° C., the chipping resistance and water resistance of the resulting coating film are inferior.
- the breaking elongation is more preferably 500% or more.
- the breaking elongation of the cured film of the above (D) water-based polyurethane resin can be determined according to JIS K7127. Specifically, (D) 95 parts by mass of an aqueous polyurethane resin (resin solid content) and (C) 5 parts by mass of a hydrophilized modified carbodiimide compound (resin solid content) are mixed. The obtained mixture is uniformly coated with a doctor blade so that the dry film thickness becomes 20 ⁇ m. After standing at 20 ° C. for 10 minutes, preheating is performed at 80 ° C. for 3 minutes to volatilize moisture, and baking is performed at 120 ° C. for 30 minutes to prepare a cured film.
- preheating is performed at 80 ° C. for 3 minutes to volatilize moisture
- baking is performed at 120 ° C. for 30 minutes to prepare a cured film.
- the obtained cured film is subjected to a tensile performance test under a test temperature of ⁇ 20 ° C. according to JIS K7127, the elongation at break is measured, and the obtained elongation is defined as the elongation at break.
- (D) aqueous polyurethane resin Commercially available products may be used as the (D) aqueous polyurethane resin.
- Commercially available products include, for example, NeoRez series, which is an aqueous polyurethane resin sold by Enomoto Kasei Co., Ltd., HUX series, which is an aqueous polyurethane resin sold by Adeka, and U-coat series, which is an aqueous polyurethane resin sold by Sanyo Kasei Co., Ltd. , Permarin series, Upren series and so on.
- the content of the (D) water-based polyurethane resin is preferably 15% by mass or more based on the resin solid content of the water-based coating composition.
- the content of the (D) water-based polyurethane resin is 15% by mass or more, there is an advantage that a coating film excellent in chipping resistance, water-resistant adhesion and the like can be obtained.
- the content of the (D) water-based polyurethane resin can be appropriately selected depending on the type of the coating film.
- the content of the (D) aqueous polyurethane resin is 30% by mass or more and 40% by mass or less based on the resin solid content of the aqueous coating composition.
- the content of the (D) aqueous polyurethane resin is 15% by mass to 30% by mass with respect to the resin solid content of the aqueous coating composition. More preferably, it is less than.
- the water-based coating composition of the present invention may contain a resin component (other resin) other than the aqueous resin having the hydroxyl group and carboxyl group (A) as necessary.
- a resin component (other resin) other than the aqueous resin having the hydroxyl group and carboxyl group (A) as necessary.
- the other resin for example, a resin prepared in the same manner as the above (A) aqueous resin having a hydroxyl group and a carboxyl group and having a hydroxyl value of less than 80 mgKOH / g can be mentioned.
- Other examples of other resins include, for example, resins having a hydroxyl group, such as polyether diol and polycarbonate diol, and melamine resins having a methylol group.
- Such other resins can be used in any amount, provided that the functions (water resistance, chipping resistance, etc.) of the aqueous coating composition of the present invention are not impaired.
- the aqueous coating composition is a top coating composition, it is a resin prepared in the same manner as the aqueous resin having the hydroxyl group and carboxyl group (A), and the hydroxyl value is less than 80 mgKOH / g. It is preferable that a certain resin is contained in the range of 15 to 45% by mass with respect to the resin solid content of the aqueous coating composition.
- Aqueous paint composition of the present invention comprises: (A) an aqueous resin having a hydroxyl group and a carboxyl group, (B) a water dispersible block polyisocyanate compound, (C) a hydrophilized modified carbodiimide compound, and (D) an aqueous polyurethane resin, Is a water-based coating composition.
- the water-based coating composition of the present invention may contain other resins, pigments, curing catalysts, surface conditioners, antifoaming agents, pigment dispersants, plasticizers as necessary. Further, it may contain a film forming aid, an ultraviolet absorber, an antioxidant and the like.
- the water-based coating composition of the present invention can be prepared by mixing the components constituting the coating composition by commonly used means.
- the resin solid content concentration of the aqueous coating composition of the present invention varies depending on the coating conditions, but is generally preferably set to 15 to 60% by mass.
- the present invention further provides a coating film forming method using the aqueous coating composition.
- This method A coating process for coating the object with the aqueous coating composition to form a coating film, and a curing process for curing the obtained coating film, Is included.
- the aqueous coating composition of the present invention is characterized in that a coating film excellent in coating film properties can be obtained even under low temperature curing conditions. Therefore, the curing conditions in the curing step may be, for example, low temperature curing conditions of 100 ° C. or less, more specifically 70 to 100 ° C., more preferably 70 to 90 ° C.
- an aspect of curing at a temperature of 100 ° C. or higher is not excluded. For example, it can be cured at 100 to 120 ° C. depending on the type and shape of the object to be coated.
- steel sheets such as iron, steel, stainless steel, aluminum, copper, zinc, tin and alloys thereof; polyethylene resins, EVA resins, polyolefin resins (polyethylene resins, polypropylene resins, etc.) ), Vinyl chloride resin, styrene resin, polyester resin (including PET resin, PBT resin, etc.), polycarbonate resin, acrylic resin, acrylonitrile butadiene styrene (ABS) resin, acrylonitrile styrene (AS) resin, polyamide resin, acetal resin, phenol Resin, fluororesin, melamine resin, urethane resin, epoxy resin, polyphenylene oxide (PPO), and the like; and organic-inorganic hybrid materials. These may be in a molded state.
- the steel sheet may be in a state where an electrodeposition coating film is formed after chemical conversion treatment is performed.
- the chemical conversion treatment include zinc phosphate chemical conversion treatment, zirconium chemical conversion treatment, and chromium oxidation chemical conversion treatment.
- the electrodeposition coating film include an electrodeposition coating film obtained by electrodeposition coating using a cationic electrodeposition coating composition or an anion electrodeposition coating composition.
- the above resin may be subjected to steam cleaning using an organic solvent as necessary, or may be cleaned using a neutral detergent. Furthermore, primer coating may be applied as necessary.
- the water-based coating composition of the present invention is characterized in that a coating film having excellent coating film properties can be formed even under low temperature curing conditions. Therefore, as an object to which the method of the present invention can be preferably used, an object to be coated including a steel plate part and a resin part is exemplified.
- the water-based coating composition of the present invention By applying the water-based coating composition of the present invention to such an object to form a coating film, the resin part and the steel plate can be formed without applying heat that causes thermal deformation of the resin part. It becomes possible to form a coating film having good physical properties for both parts.
- different materials such as a resin and a steel plate can be applied using a common coating composition. Thereby, there is an advantage that the hue of the obtained coating film can be matched at a higher level.
- Examples of other coated materials that are suitable as coated materials for applying the aqueous coating composition of the present invention include industrial machinery and construction machinery.
- Industrial machines and construction machines are generally large in size and can withstand strong loads, and therefore have a feature that the constituent base material (steel plate) is thicker than automobile bodies and the like. Therefore, when such an industrial machine or construction machine is an object to be coated, there is a problem that the heat capacity of the object to be coated is large and heat is not sufficiently transferred to the object to be coated in a heating furnace.
- One of the characteristics of the aqueous coating composition of the present invention is that it can be cured at a low temperature and that a coating film having a high crosslinking density can be obtained even when cured at a low temperature.
- the water-based coating composition of the present invention is also suitable for coating with industrial machines and construction machinery to be coated, in which the heat capacity of the object to be coated is large and high-temperature heat curing after coating is difficult. Can be used.
- the aqueous coating composition of the present invention is applied by a coating method usually used by those skilled in the art according to the shape of the coating object, and then, for example, at 70 to 100 ° C. for 10 minutes. A mode in which a cured coating film is formed by heating for ⁇ 2 hours is mentioned.
- the above-mentioned intermediate coating composition and aqueous base coating composition can be applied by a commonly used coating method.
- a commonly used coating method For example, when the intermediate coating composition and the aqueous base coating composition are applied to an automobile body, in order to enhance the appearance of the resulting coating film, multistage coating by air electrostatic spray coating, preferably two stages, is performed. Paint or combine air electrostatic spray painting with a rotary atomizing electrostatic coating machine called “ ⁇ (micro micro) bell”, “ ⁇ (micro) bell” or “metabell” Coating methods can be used.
- the film thickness of the coating film of the water-based intermediate coating composition can be appropriately selected according to the desired application.
- the film thickness is preferably 15 to 35 ⁇ m, for example, and more preferably 15 to 30 ⁇ m.
- the film thickness of the coating film of the aqueous base coating composition can be appropriately selected according to the desired use.
- the film thickness is preferably 10 to 30 ⁇ m, for example.
- a clear coating composition is further applied to form a clear coating film, and then the uncured multilayer coating film is cured.
- Embodiments are also included. This method can omit the baking and drying furnace, and is preferable from the viewpoint of economy and environmental protection.
- a urethane clear coating composition As an example of a clear coating composition that can be suitably used in the above coating process, a urethane clear coating composition can be mentioned.
- the urethane clear coating composition include a clear coating composition containing a hydroxyl group-containing resin and an isocyanate compound curing agent.
- the isocyanate compound as the curing agent is not particularly limited, and examples thereof include aliphatic isocyanates such as trimethylene diisocyanate, tetramethylene diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate (HDI), and trimethylhexamethylene diisocyanate, 1,3-cyclohexane.
- Aliphatic cyclic isocyanates such as pentane diisocyanate, 1,4-cyclohexane diisocyanate, 1,2-cyclohexane diisocyanate, xylylene diisocyanate (XDI), 2,4-tolylene diisocyanate (TDI), 2,6-tolylene diisocyanate, etc.
- Aromatic isocyanates, isophorone diisocyanate (IPDI), norbornane diisocyanate methyl and other alicyclic isocyanates These biuret, etc. multimers and mixtures such as isocyanurate body can be exemplified.
- the hydroxyl value of the hydroxyl group-containing resin is preferably in the range of 20 to 200 mgKOH / g.
- the lower limit is more preferably 30 mgKOH / g
- the upper limit is more preferably 180 mgKOH / g.
- the number average molecular weight of the hydroxyl group-containing resin is preferably in the range of 1000 to 20000. If the number average molecular weight is less than 1000, workability and curability may be insufficient. Moreover, when it exceeds 20000, the non-volatile content at the time of coating will become low, and there exists a possibility that workability
- the lower limit is more preferably 2000, and the upper limit is more preferably 15000.
- the hydroxyl group-containing resin preferably further has an acid value within the range of 2 to 30 mgKOH / g.
- the upper limit is exceeded, the water resistance of the coating film is lowered, and when the lower limit is not reached, the curability of the coating film is lowered.
- the lower limit is more preferably 3 mgKOH / g, and the upper limit is more preferably 25 mgKOH / g.
- the content of the isocyanate compound relative to the hydroxyl group-containing resin can be appropriately selected within the range usually used by those skilled in the art.
- the equivalent ratio (NCO / OH) of isocyanate group (NCO) to hydroxyl group (OH) be used in an amount in the range of 0.5 to 1.7.
- the lower limit is more preferably 0.7, and the upper limit is more preferably 1.5.
- the method for producing the clear coating composition is not particularly limited, and any method known to those skilled in the art can be used. Moreover, a commercial item can also be used as a clear coating composition. Examples of commercially available products include Polyurexel O-1100 Clear, O-1200 Clear (manufactured by Nippon Paint Automotive Coatings Co., Ltd., isocyanate curable clear coating composition).
- the aqueous coating composition of the present invention is applied to form an uncured coating film (an embodiment in which a single coating film is formed, and the first coating film and the second coating film are formed).
- the clear coating composition wet-on-wet and then baking and curing at 70-100 ° C., more preferably 70-90 ° C. for 10-30 minutes.
- a multilayer coating film can be formed.
- a clear coating composition other than the urethane clear coating composition can be used depending on the material of the object to be coated.
- an acid epoxy curable clear coating composition, an acrylic melamine curable clear coating composition, and the like can also be used.
- these clear coating compositions include, for example, “Mac Flow® O-570 Clear” or “Mack”, which is a clear coating composition containing polyepoxide and polyacid, which is sold by Nippon Paint Automotive Coatings Co., Ltd. “Super Lac® O-100 Clear” (trade name) sold by Nippon Paint Automotive Coatings Co., Ltd., which is a clear coating composition containing an acrylic resin and a melamine curing agent. ) And the like.
- the heat curing conditions when these clear coating compositions are used can be appropriately selected according to the composition of each clear coating composition.
- heat curing conditions when these clear coating compositions are used for example, conditions of heating at 120 to 140 ° C. for 10 to 30 minutes can be mentioned.
- the coating method of the clear coating composition the above-mentioned known coating method can be used, and for example, it can be applied by air spray, electrostatic coating or the like.
- the clear coating composition is preferably applied so that the dry film thickness is generally 10 to 80 ⁇ m, preferably 20 to 50 ⁇ m.
- Production Example 1 Production of acrylic emulsion having hydroxyl group and carboxyl group 1,000 parts of deionized water was charged into a reaction vessel equipped with a stirrer, nitrogen introduction tube, temperature controller, condenser, and dropping funnel, and stirred in a nitrogen atmosphere. The temperature was raised to 80 ° C.
- Latemul PD-104 (manufactured by Kao Corporation, 20 A pre-emulsion obtained by adding 100 parts of deionized water to 1,000 parts of deionized water was added dropwise over 2 hours together with an initiator aqueous solution in which 3 parts of ammonium persulfate was dissolved in 300 parts of deionized water. After completion of the dropwise addition, the reaction was further continued at 80 ° C.
- Production Example 2 Production of Acrylic Emulsion Having Hydroxyl Group and Carboxyl Group
- the amount of monomers in the monomer mixture of Production Example 1 is 90 parts by weight of styrene, 249 parts of n-butyl acrylate, 403 parts of n-butyl methacrylate, and 232 parts of hydroxyethyl acrylate. Polymerization was carried out in the same manner except that the content was changed to 3 parts, acrylic acid 26 parts, and dodecyl mercaptan 3 parts, and then 8.2 parts of N, N-dimethylaminoethanol was added to obtain an acrylic emulsion having a resin solid content of 30% by mass. .
- the hydroxyl value in terms of resin solid content of this acrylic emulsion calculated from the monomer composition was 100 mgKOH / g, and the acid value was 20 mgKOH / g.
- the number average molecular weight by GPC measurement after the water removal of the acrylic resin in the obtained acrylic emulsion was 43,000.
- Production Example 4 Production of Polyester Aqueous Dispersion Having Hydroxyl Group and Carboxyl Group
- a reaction vessel equipped with a stirrer, nitrogen introduction tube, temperature controller, condenser and decanter, 250 parts of trimethylolpropane, 824 parts of adipic acid, cyclohexanedicarboxylic acid 635 parts were added, the temperature was raised to 180 ° C., and the condensation reaction was carried out until no water was distilled off. After cooling to 60 ° C., 120 parts of phthalic anhydride was added, the temperature was raised to 140 ° C., and this was maintained for 60 minutes to obtain a polyester resin having a number average molecular weight of 2,000 by GPC measurement.
- PTMG-1000 a polytetramethylene glycol having a number average molecular weight of 1,000 manufactured by Mitsubishi Chemical Corporation, tetramethylene calculated from the number average molecular weight.
- Oxide repeat unit 13.6 95 parts and dibutyltin dilaurate 0.2 part were added and heated to 85 ° C. and held for 2 hours.
- methyl polyglycol 130 polyethylene glycol monomethyl ether manufactured by Nippon Emulsifier Co., Ltd., ethylene oxide repeat number 9 calculated from a hydroxyl value of 130 mgKOH / g
- the reaction was terminated after confirming that the NCO peak had disappeared by IR measurement, and after cooling to 60 ° C., deionized water was added to the hydrophilized modified carbodiimide compound (1) having a resin solid content of 40% by mass. An aqueous dispersion was obtained.
- the resulting hydrophilized modified carbodiimide compound was a compound represented by the above general formula (I).
- Production Example 6 Production of Hydrophilized Modified Carbodiimide Compound (2)
- 43.2 parts and 0.07 part dibutyltin dilaurate were added and kept at 80 ° C. until there was no NCO absorption by IR.
- deionized water was added to obtain an aqueous dispersion of the hydrophilic modified carbodiimide compound (2) having a resin solid content of 25%.
- the resulting hydrophilized modified carbodiimide compound was a compound represented by the above general formula (III).
- a carbodiimide compound which is an isocyanate group and a hydrophilic group was obtained. Furthermore, 300 parts of GP-3000 (a trivalent polyol having a structure in which propylene oxide was added to three hydroxyl groups of glycerin manufactured by Sanyo Chemical Industries, Ltd. on an average of 17 moles each) were added and reacted at 90 ° C. for 6 hours. . It was confirmed by IR measurement that the NCO peak had disappeared, and the reaction was terminated to obtain a hydrophilic modified carbodiimide compound (3).
- GP-3000 a trivalent polyol having a structure in which propylene oxide was added to three hydroxyl groups of glycerin manufactured by Sanyo Chemical Industries, Ltd. on an average of 17 moles each
- hydrophilized modified carbodiimide compound (3) having a resin solid content of 30% by mass.
- the resulting hydrophilized modified carbodiimide compound was a compound represented by the above general formula (II).
- Production Example 8 Production of Colored Pigment Paste After premixing 9.2 parts of a commercially available dispersant “Disperbyk 190” (manufactured by Big Chemie), 17.8 parts of ion-exchanged water, and 73.0 parts of rutile titanium dioxide, a paint conditioner The bead medium was added thereto, and the mixture was dispersed at room temperature until the particle size became 5 ⁇ m or less, and the bead medium was removed by filtration to obtain a colored pigment paste.
- Dispersant “Disperbyk 190” manufactured by Big Chemie
- ion-exchanged water 17.8 parts
- rutile titanium dioxide a paint conditioner
- ⁇ , ⁇ -ethylenically unsaturated monomer mixture in the second stage at 80 ° C. 24.5 parts of ethyl acrylate, 2.5 parts of 2-hydroxyethyl acrylate, 3.1 parts of methacrylic acid, Aqualon HS
- a 10% by weight aqueous dimethylaminoethanol solution was added to adjust the pH to 7 to obtain an emulsion resin having an average particle size of 110 nm, a solid content of 24% by weight, a solid content acid value of 20 and a hydroxyl value of 40. It was 0 degreeC when the glass transition point was computed based on all the monomer compositions.
- Example 1 Preparation of intermediate coating composition
- a hydroxyl group-containing acrylic resin emulsion prepared in Production Example 1 resin solid content 30%
- a hydroxyl group-containing polyester resin prepared in Production Example 2 was prepared.
- aqueous base coating composition In a container having an agitator, 100 parts of the hydroxyl group-containing acrylic resin emulsion obtained in Production Example 1 (resin solid content 25%) and 125 parts of the acrylic emulsion resin obtained in Production Example 9 (Resin solid content: 24%) Stir-mix, 21.2 parts of WM44-L70G (solid content concentration: 70.7%, manufactured by Asahi Kasei Chemical) as a water-dispersible block polyisocyanate, and a hydrophilized modified carbodiimide compound prepared in Production Example 5 12.5 parts (resin solid content 40%), aqueous polyurethane resin 66.7 parts (resin solid content 30%), and 21 parts (solid content 65%) of Alpaste MH8801 (aluminum pigment manufactured by Asahi Kasei Co., Ltd.) as a bright pigment.
- WM44-L70G solid content concentration: 70.7%, manufactured by Asahi Kasei Chemical
- Examples 2 to 17 In the preparation of the intermediate coating composition and the aqueous base coating composition, the intermediate coating composition and the aqueous base coating composition were prepared in the same manner as in Example 1 except that the components and blending amounts shown in the following table were changed. Was prepared. A multilayer coating film was formed in the same manner as in Example 1 using the obtained coating composition. In addition, the compounding quantity shown in the following table
- Example 18 Using the intermediate coating composition and the aqueous base coating composition prepared in Example 1, a multilayer coating film was formed by the following procedure.
- WB-3110CB (trade name, manufactured by Nippon Paint Automotive Coatings Co., Ltd., a non-chlorinated polyolefin-containing conductive paint) is dried on a resin member (polypropylene) as a water-based primer for adhesion using a rotary atomizing electrostatic coating device.
- the aqueous intermediate coating composition was coated with a rotary atomizing electrostatic coating apparatus so that the dry film thickness was 25 ⁇ m, and then the water-based base coating was coated with a rotary fog.
- the film was coated with a chemical electrostatic coating apparatus so that the dry film thickness was 15 ⁇ m, and preheated at 80 ° C. for 3 minutes. Note that a 6-minute interval was provided between the coating of the aqueous intermediate coating composition and the aqueous base coating composition. Furthermore, Polyurexel O-1200 (trade name, manufactured by Nippon Paint Automotive Coatings Co., Ltd., polyisocyanate compound-containing two-component acrylic urethane-based organic solvent-type clear paint) is used as a clear paint on the coated plate. After coating with a coating apparatus so that the dry film thickness was 35 ⁇ m, heat curing was performed at 80 ° C. for 20 minutes to obtain a test piece on which a multilayer coating film was formed.
- a chemical electrostatic coating apparatus so that the dry film thickness was 15 ⁇ m, and preheated at 80 ° C. for 3 minutes. Note that a 6-minute interval was provided between the coating of the aqueous intermediate coating composition and the aqueous base coating composition.
- Comparative Examples 1-7 In the preparation of the intermediate coating composition and the aqueous base coating composition, the intermediate coating composition and the aqueous base coating composition were prepared in the same manner as in Example 1 except that the components and blending amounts shown in the following table were changed. Was prepared. A multilayer coating film was formed in the same manner as in Example 1 using the obtained coating composition.
- the obtained cured film was subjected to a tensile performance test under a test temperature of ⁇ 20 ° C. according to JIS K7127, and the elongation at break (breaking elongation) was measured. The measurement was performed 20 times, and the average value of 18 times excluding the maximum value and the minimum value was defined as the elongation at break of the sample.
- the test plate having the multilayer coating film obtained in each Example and Comparative Example was subjected to a stepping stone test using the Gralove Tester KSS-1 (manufactured by Suga Test Instruments Co., Ltd.) under the following conditions. . ⁇ Test conditions> Stone size: 6-8mm The amount of stone: 0.7-0.8g / piece distance: 35cm Shot pressure: 0.6 kg / cm 2 Shot angle: 45 ° Test temperature: -20 ° C
- the test plate after the stepping stone test was visually evaluated according to the following criteria. In the following criteria, 4 points or more are judged to be acceptable and usable. 5: Peeling is hardly seen.
- the test plate of the above-mentioned multilayer coating film was exposed to an atmosphere at 40 ° C. with a humidity of 99% or more and 50 ° C. for 240 hours. After completion of the exposure, the film was dried at 20 ° C. for 24 hours, and then the multilayer coating film of the test plate was cut into a lattice shape with a cutter so as to reach the substrate, and 100 goblets having a size of 2 mm ⁇ 2 mm were prepared. Subsequently, an adhesive cellophane tape (trademark) was attached to the surface, and the remaining number of Gobang eyes coatings after the tape was rapidly peeled off at 20 ° C. was measured. The superiority or inferiority of the coating film can be determined by the number of peeling of the grid. If even one piece of the grid is peeled off, it is judged that practical use is difficult.
- aqueous polyurethane resins described in the above table are as follows.
- the multilayer coating film formed using the aqueous coating composition of the example is baked and cured under a low temperature condition of 80 ° C., all have excellent water resistance, moisture resistance and chipping resistance. It was confirmed that it has sex. On the other hand, it was confirmed that the multilayer coating film formed using the water-based coating composition of the comparative example was inferior in one or more performances among water resistance, moisture resistance and chipping resistance.
- the water-based coating composition of the present invention has a good curing reaction even under heating conditions under low temperature conditions (for example, heating conditions of 100 ° C. or lower), and a cured coating film having excellent coating film properties is obtained.
- a coating film having excellent coating properties water resistance, chipping resistance, etc.
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Abstract
Description
[1]
(A)水酸基およびカルボキシル基を有する水性樹脂、
(B)水分散性ブロックポリイソシアネート化合物、
(C)親水化変性カルボジイミド化合物、および
(D)水性ポリウレタン樹脂、
を含む水性塗料組成物であって、
上記(A)水酸基およびカルボキシル基を有する水性樹脂は、樹脂固形分換算で、80~200mgKOH/gの水酸基価、および、10~40mgKOH/gの酸価を有し、
上記(C)親水化変性カルボジイミド化合物が、下記一般式(I)、(II)または(III)で表されるものであり、
上記(D)水性ポリウレタン樹脂は、ガラス転移点(Tg)が-50℃以下であり、
上記(D)水性ポリウレタン樹脂の硬化膜の破断伸度が-20℃において400%以上である、
水性塗料組成物。
[2]
上記(C)親水化変性カルボジイミド化合物の含有量は、水性塗料組成物の樹脂固形分に対して1~8質量%である、水性塗料組成物。
[3]
上記(A)水性樹脂は、数平均分子量が10,000~80,000であるアクリルエマルションを含む、水性塗料組成物。
[4]
上記式(III)で表される(C)親水化変性カルボジイミド化合物が、下記化合物である、水性塗料組成物。
(i)繰り返し数6~20のポリエチレンオキサイドユニットの末端に、炭素数1~3のアルキル基がエーテル結合した、ポリエチレングリコールモノアルキルエーテルから、水酸基を除いた構造、
(ii)繰り返し数4~60のポリプロピレンオキサイドユニットの末端に、炭素数1~8のアルキル基がエーテル結合した、ポリプロピレングリコールモノアルキルエーテルから、水酸基を除いた構造:
から選択される、同一または異種の構造である。]
[5]
上記式(III)で表される(C)親水化変性カルボジイミド化合物において、何れか一方のYが(i)であって他方のYが(ii)であり、および、
上記構造(i)および(ii)の比率が、(i):(ii)=1:0.7~1:8の範囲内である、
水性塗料組成物。
[6]
上記(D)水性ポリウレタン樹脂の含有量は、水性塗料組成物の樹脂固形分に対して15質量%以上である、水性塗料組成物。
[7]
上記(D)水性ポリウレタン樹脂の含有量は、水性塗料組成物の樹脂固形分に対して30質量%以上40質量%以下である、水性塗料組成物。
[8]
上記(D)水性ポリウレタン樹脂の含有量は、水性塗料組成物の樹脂固形分に対して15質量%以上30質量%未満である、水性塗料組成物。
[9]
上記(B)水分散性ブロックポリイソシアネート化合物の含有量は、水性塗料組成物の樹脂固形分に対して10~25質量%であり、
上記(C)親水化変性カルボジイミド化合物の含有量は、水性塗料組成物の樹脂固形分に対して1.5~7質量%である、
水性塗料組成物。
[10]
水性塗料組成物の樹脂固形分に対する、上記(B)水分散性ブロックポリイソシアネート化合物および(C)親水化変性カルボジイミド化合物の含有量の質量比は、(B):(C)=25:1~1.25:1である、
水性塗料組成物。
[11]
水性塗料組成物を用いる塗膜形成方法であって、
上記水性塗料組成物を被塗物に塗装して塗膜を形成する、塗装工程、および
得られた塗膜を、70~100℃で硬化する、硬化工程、
を包含する、
塗膜形成方法。
[12]
上記塗装工程は、
被塗物上に、(D)水性ポリウレタン樹脂の含有量が水性塗料組成物の樹脂固形分に対して30質量%以上40質量%以下である水性塗料組成物を塗装して第1塗膜を形成する、第1塗装工程、および
上記第1塗膜上に、(D)水性ポリウレタン樹脂の含有量が水性塗料組成物の樹脂固形分に対して15質量%以上30質量%未満である水性塗料組成物を塗装して第2塗膜を形成する、第2塗装工程、
を包含する、
塗膜形成方法。
[13]
上記被塗物は、鋼板部および樹脂部を含む、塗膜形成方法。
(A)水酸基およびカルボキシル基を有する水性樹脂、
(B)水分散性ブロックポリイソシアネート化合物、
(C)親水化変性カルボジイミド化合物、および
(D)水性ポリウレタン樹脂、
を含む。以下、各成分(A)~(D)およびこれらの特徴について詳述する。
(A)水酸基およびカルボキシル基を有する水性樹脂は、後述する(B)水分散性ブロックポリイソシアネート化合物および(C)親水化変性カルボジイミド化合物と硬化反応するバインダー成分である。そして本発明において用いられる(A)水酸基およびカルボキシル基を有する水性樹脂は、
・樹脂固形分換算での水酸基価が80~200mgKOH/gであり、
・樹脂固形分換算での酸価が10~40mgKOH/gである、
ことを要件とする。
樹脂固形分換算での水酸基価は80~160mgKOH/gがより好ましく、樹脂固形分換算での酸価は15~35mgKOH/gがより好ましい。
本発明の水性塗料組成物に含まれる(B)水分散性ブロックポリイソシアネート化合物は、ポリイソシアネート(B-1)に、マロン酸ジエステル(B-2)を反応させ、次いで得られた反応物と有機アミン化合物(B-3)とを反応させることによって調製することができる。
本発明の水性塗料組成物に含まれる(C)親水化変性カルボジイミド化合物は、分子内に、
-OCONH-X-NHCOOY
[Xは少なくとも1個のカルボジイミド基を含有する2官能性有機基であり、Yはポリアルキレングリコールモノアルキルエーテルから水酸基を除いた構造である。]
で表される構造単位を1個または複数個有している。上記構造単位を有することで、優れた水分散性および優れた硬化性の両方の性能が得られると考えられる。
上記構造単位を2個有するものとしては、下記一般式(I)で表されるものがある。
(i)繰り返し数6~20のポリエチレンオキサイドユニットの末端に、炭素数1~3のアルキル基がエーテル結合した、ポリエチレングリコールモノアルキルエーテルから、水酸基を除いた構造
(ii)繰り返し数4~60のポリプロピレンオキサイドユニットの末端に、炭素数1~8のアルキル基がエーテル結合した、ポリプロピレングリコールモノアルキルエーテルから、水酸基を除いた構造:
から選択される、同一または異種の構造であるのがより好ましい。
さらに好ましくは、前記(ii)のポリプロピレンオキサイドユニットの繰り返し数が15~60である。
上記(i)および(ii)を有する、一般式(III)で示される(C)親水化変性カルボジイミド化合物を用いることによって、水分散性に優れ、安定性が向上し、さらに架橋密度がより高いレベルで保持されるという利点がある。
・繰り返し数6~20のポリエチレンオキサイドユニットの末端に、炭素数1~3のアルキル基がエーテル結合した、ポリエチレングリコールモノアルキルエーテル、または、
・繰り返し数4~60のポリプロピレンオキサイドユニットの末端に、炭素数1~8のアルキル基がエーテル結合した、ポリプロピレングリコールモノアルキルエーテル、
であるのがより好ましい。一般式(III)で示される(C)親水化変性カルボジイミド化合物の調製において、これらのポリエチレングリコールモノアルキルエーテルおよびポリプロピレングリコールモノアルキルエーテルは、単独で用いてもよく、併用してもよい。
上記ポリプロピレングリコールモノアルキルエーテルとしては、具体的にはポリプロピレングリコールモノメチルエーテル、ポリプロピレングリコールモノエチルエーテル、ポリプロピレングリコールモノブチルエーテル、ポリプロピレングリコール2-エチルヘキシルエーテル等を挙げることができ、特にポリプロピレングリコールモノブチルエーテルが好適である。
一般式(III)で示される(C)親水化変性カルボジイミド化合物において、塗膜が形成したときに耐水性を向上させるため、カルボジイミド基の周辺がある程度疎水性となっていることが好ましい。また、水によるカルボジイミドの失活を抑止し、安定性を保持するため、カルボジイミド基の周辺がある程度疎水性となっており、水分子との接触が低い状態に保たれているのが好ましい。その一方で、一般式(III)で示されるカルボジイミド化合物において、親水性を維持するためには、ポリエチレングリコール構造を一定量有することが必要となる。ここで、上記(i)および(ii)の構造が、(i):(ii)=1:0.7~1:8の範囲内で存在する場合において、カルボジイミド化合物の親水性を確保しつつ、一方でカルボジイミド基の周辺においてある程度疎水性を保つことができる。これにより、低温硬化性により優れ、かつ、塗料安定性にもより優れた水性塗料組成物が得られるという利点がある。なお、上記比率(i):(ii)は、(i):(ii)=1:0.7~1:1.5の範囲内であるのがさらに好ましい。
本発明においては、80~200mgKOH/gの水酸基価、および、10~40mgKOH/gの酸価を有する、(A)水酸基およびカルボキシル基を有する水性樹脂と共に、上記(B)水分散性ブロックポリイソシアネート化合物および(C)親水化変性カルボジイミド化合物を併用することによって、水分散性および水分散安定性に優れており、かつ、低温硬化性に優れる、1液型の水性塗料組成物を調製することが可能となった。本発明においては、(A)水性樹脂が、酸基を有する一方で、酸価が上記範囲であることによって、1液型の水性塗料組成物としての塗料安定性と共に、硬化時に(C)親水化変性カルボジイミド化合物との反応による優れた耐水性が発揮されることとなる。また、本発明の水性塗料組成物が、上記(A)水性樹脂の水酸基と反応する(B)水分散性ブロックポリイソシアネート化合物を含むことによって、塗膜物性に優れた塗膜が得られると共に、1液型の水性塗料組成物としての塗料安定性が優れることとなる。ここで、上記(B)水分散性ブロックポリイソシアネート化合物および(C)親水化変性カルボジイミド化合物の含有量の質量比が上記範囲であることによって、1液型の水性塗料組成物としての塗料安定性が向上し、かつ、塗膜耐水性などの効果が向上するなどの利点がある。
本発明の水性塗料組成物は、上記成分(A)~(C)に加えて(D)水性ポリウレタン樹脂を含む。(D)水性ポリウレタン樹脂は、ポリオール化合物(D-1)と、分子内に活性水素基と親水基を有する化合物(D-2)と、有機ポリイソシアネート(D-3)と、必要により鎖伸長剤及び重合停止剤を用いて得られるポリマーであって、得られたポリマーを水中に溶解または分散することによって、調製することができる。
ヘキサメチレンジイソシアネート、2,2,4-トリメチルヘキサンジイソシアネート、リジンジイソシアネ-トなどの、炭素数2~12の脂肪族ジイソシアネート;
1,4-シクロヘキサンジイソシアネート、イソホロンジイソシアネート、4,4’-ジシクロヘキシルメタンジイソシアネート、メチルシクロヘキシレンジイソシアネート、イソプロピリデンシクロヘキシル-4,4’-ジイソシアネートなどの、炭素数4~18の脂環族ジイソシアネート;
2,4-トルイレンジイソシアネート、2,6-トルイレンジイソシアネート、ジフェニルメタン-4,4’-ジイソシアネート、1,5’-ナフテンジイソシアネート、トリジンジイソシアネート、ジフェニルメチルメタンジイソシアネート、テトラアルキルジフェニルメタンジイソシアネート、キシリレンジイソシアネート、テトラメチルキシリレンジイソシアネート、4,4’-ジベンジルジイソシアネート、1,3-フェニレンジイソシアネート等の芳香族ジイソシアネート;
リジンエステルトリイソシアネート、トリフェニルメタントリイソシアネート、1,6,11-ウンデカントリイソシアネート、1,8-ジイソシアネート-4,4-イソシアネートメチルオクタン、1,3,6-ヘキサメチレントリイソシアネート、ビシクロヘプタントリイソシアネート等のトリイソシアネート類;
などが挙げられる。
また、これらのポリイソシアネート化合物の、ダイマー、トリマー(イソシアヌレート結合)で用いられてもよく、また、アミンと反応させてビウレットとして用いてもよい。更に、これらのポリイソシアネート化合物と、ポリオールを反応させたウレタン結合を有するポリイソシアネートも用いることができる。
有機ポリイソシアネート(D-3)として、脂肪族ジイソシアネートを用いるのがより好ましい。脂肪族ジイソシアネートを用いて(D)水性ポリウレタン樹脂を調製することによって、得られる塗膜の透水性を適切な範囲に調節することができ、また良好な低温初期耐水性を得ることができるという利点がある。
本発明の水性塗料組成物は、必要に応じて、上記(A)水酸基およびカルボキシル基を有する水性樹脂以外の樹脂成分(その他の樹脂)を含んでもよい。その他の樹脂の1例として、例えば、上記(A)水酸基およびカルボキシル基を有する水性樹脂と同様に調製される樹脂であって、水酸基価が80mgKOH/g未満である樹脂が挙げられる。その他の樹脂の他の1例として、例えば、ポリエーテルジオール、ポリカーボネートジオールなどの、水酸基を有する樹脂、および、メチロール基を有するメラミン樹脂、などが挙げられる。
また、例えば、上記水性塗料組成物が上塗り塗料組成物である場合は、上記(A)水酸基およびカルボキシル基を有する水性樹脂と同様に調製される樹脂であって、水酸基価が80mgKOH/g未満である樹脂を、水性塗料組成物の樹脂固形分に対して15~45質量%の範囲内で含むのが好ましい。
本発明の水性塗料組成物は、
(A)水酸基およびカルボキシル基を有する水性樹脂、
(B)水分散性ブロックポリイソシアネート化合物、
(C)親水化変性カルボジイミド化合物、および
(D)水性ポリウレタン樹脂、
を含む水性塗料組成物である。本発明の水性塗料組成物は、上記成分(A)~(D)以外に、必要に応じて、上記その他の樹脂、顔料、硬化触媒、表面調整剤、消泡剤、顔料分散剤、可塑剤、造膜助剤、紫外線吸収剤、酸化防止剤などを含んでもよい。本発明の水性塗料組成物は、塗料組成物を構成する各成分を、通常用いられる手段によって混合することによって、調製することができる。
本発明はさらに、上記水性塗料組成物を用いた塗膜形成方法も提供する。この方法は、
上記水性塗料組成物を被塗物に塗装して塗膜を形成する、塗装工程、および
得られた塗膜を硬化させる、硬化工程、
を包含する。
本発明の水性塗料組成物は、低温硬化条件であっても、塗膜物性に優れた塗膜を得ることができることを特徴とする。そのため、上記硬化工程における硬化条件は、例えば100℃以下の低温硬化条件であってよく、より具体的には70~100℃、さらに好ましくは70~90℃といった硬化条件であってよい。
一方で、本発明の水性塗料組成物においては、100℃以上の温度で硬化させる態様を排除するものではない。例えば、被塗物の種類および形状などに応じて、100~120℃で硬化させることもできる。
上記方法における被塗物として、鉄、鋼、ステンレス、アルミニウム、銅、亜鉛、スズなどの金属およびこれらの合金などの鋼板;ポリエチレン樹脂、EVA樹脂、ポリオレフィン樹脂(ポリエチレン樹脂、ポリプロピレン樹脂など)、塩化ビニル樹脂、スチロール樹脂、ポリエステル樹脂(PET樹脂、PBT樹脂などを含む)、ポリカーボネート樹脂、アクリル樹脂、アクリロニトリルブタジエンスチレン(ABS)樹脂、アクリロニトリルスチレン(AS)樹脂、ポリアミド樹脂、アセタール樹脂、フェノール樹脂、フッ素樹脂、メラミン樹脂、ウレタン樹脂、エポキシ樹脂、ポリフェニレンオキサイド(PPO)などの樹脂;および、有機-無機ハイブリッド材などが挙げられる。これらは成形された状態であってもよい。
被塗物上に、上記中塗り塗料組成物を塗装して第1塗膜を形成する、第1塗装工程、および
前記第1塗膜上に、上記水性ベース塗料組成物を塗装して第2塗膜を形成する、第2塗装工程、
を包含する態様が挙げられる。
撹拌機、窒素導入管、温度制御装置、コンデンサー、滴下ロートを備えた反応容器に、脱イオン水1,000部を仕込み、窒素雰囲気下で攪拌しながら80℃に昇温した。
スチレン103部、メタクリル酸n-ブチル290部、アクリル酸n-ブチル280部、アクリル酸ヒドロキシエチル302部、アクリル酸26部、ドデシルメルカプタン3部および乳化剤としてのラテムルPD-104(花王社製、20%水溶液)100部を脱イオン水1,000部に加えて乳化したプレエマルションを、過硫酸アンモニウム3部を脱イオン水300部に溶解した開始剤水溶液とともに2時間かけて滴下した。
滴下終了後、さらに80℃ で1時間反応を継続した後冷却し、N、N-ジメチルアミノエタール8.2部を加え樹脂固形分30質量%のアクリルエマルションを得た。モノマー組成から計算される、このアクリルエマルションの樹脂固形分換算での水酸基価は130mgKOH/g、酸価は20mgKOH/gであった。また、得られたアクリルエマルションにおけるアクリル樹脂の、水分除去後のGPC測定による数平均分子量は、45,000であった。
製造例1のモノマー混合物におけるモノマーの量を、スチレン90部、アクリル酸n-ブチル249部、メタクリル酸n-ブチル403部、アクリル酸ヒドロキシエチル232部、アクリル酸26部、ドデシルメルカプタン3部にそれぞれ変更する以外は同様にして重合した後、N、N-ジメチルアミノエタノール8.2部を添加し樹脂固形分30質量%のアクリルエマルションを得た。モノマー組成から計算される、このアクリルエマルションの樹脂固形分換算での水酸基価は100mgKOH/g、酸価は20mgKOH/gであった。また、得られたアクリルエマルションにおけるアクリル樹脂の、水分除去後のGPC測定による数平均分子量は、43,000であった。
撹拌機、窒素導入管、温度制御装置、コンデンサー、滴下ロートを備えた反応容器に、2-メトキシ-1-プロパノール712部を仕込み、窒素雰囲気下で攪拌しながら120℃に昇温した。
スチレン50部、アクリル酸2-エチルヘキシル20部、メタクリル酸2-エチルヘキシル122部、メタクリル酸n-ブチル426部、メタクリル酸ヒドロキシエチル182部のモノマー混合物を、カヤエステルO(化薬アクゾ社製のtert-ブチルペルオキシ-2-エチルヘキサネート)24部を2-メトキシ-1-プロパノール160部に溶解した開始剤溶液とともに1.5時間かけて滴下した。
滴下終了後、120℃で1時間保ち、次いで、メタクリル酸n-ブチル50部、メタクリル酸ヒドロキシエチル119部、アクリル酸31部のモノマー混合物を、カヤエステルO 6部を2-メトキシ-1-プロパノール40部に溶解した開始剤溶液とともに1時間かけて滴下した。
滴下終了後、120℃で0.5時間保った後、後ショットとして、さらにカヤエステルO 3部を2-メトキシ-1-プロパノール55部に溶解した開始剤溶液を0.5時間かけて滴下し、さらに120℃で1時間攪拌して、樹脂固形分50質量%、GPC測定による数平均分子量6,000のアクリル樹脂を得た。
減圧加熱して溶剤を留去した後、N、N-ジメチルアミノエタノール39部を添加した後、さらに脱イオン水1206部を投入、攪拌することによって、樹脂固形分45質量%のアクリル樹脂水分散体を得た。モノマー組成から計算される、このアクリル水分散体の樹脂固形分換算での水酸基価は130mgKOH/g、酸価は24mgKOH/gであった。
撹拌機、窒素導入管、温度制御装置、コンデンサー、デカンターを備えた反応容器に、トリメチロールプロパン250部、アジピン酸824部、シクロヘキサンジカルボン酸635部を加え、180℃に昇温して、水が留出しなくなるまで縮合反応を行った。60℃まで冷却した後、無水フタル酸120部を加え、140℃まで昇温して、これを60分間保ち、GPC測定による数平均分子量2,000のポリエステル樹脂を得た。ジメチルアミノエタノール59部(樹脂が有する酸価の80%相当(中和率80%))を80℃で加え、さらに脱イオン水1920部を投入、攪拌することによって、樹脂固形分45質量%のポリエステル水分散体を得た。このポリエステル水分散体の樹脂固形分換算での水酸基価は90mgKOH/g、酸価は35mgKOH/gであった。
4,4-ジシクロヘキシルメタンジイソシアネート700部および3-メチル-1-フェニル-2-ホスホレン-1-オキシド7部を170℃で7時間反応させ、上記一般式(a)で表される構造の、1分子にカルボジイミド基を3個有し、両末端にイソシアネート基を有するカルボジイミド化合物を得た。
次に、製造したイソシアネート末端を有する4,4-ジシクロヘキシルメタンカルボジイミド180部に、PTMG-1000(三菱化学社製の数平均分子量1,000のポリテトラメチレングリコール、数平均分子量から計算されるテトラメチレンオキサイドの繰り返し単位13.6)95部およびジブチル錫ジラウレート0.2部を加えて、85℃に加熱し、これを2時間保った。
次いで、メチルポリグリコール130(日本乳化剤社製のポリエチレングリコールモノメチルエーテル、水酸基価130mgKOH/gから計算されるエチレンオキサイドの繰り返し数9)86.4部を加え、85℃で3時間保った。IR測定によりNCOのピークが消失していることを確認して反応を終了し、60℃に冷却した後、脱イオン水を加えて、樹脂固形分40質量%の親水化変性カルボジイミド化合物(1)の水分散体を得た。得られた親水化変性カルボジイミド化合物は、上記一般式(I)で表される化合物であった。
製造例5において製造したイソシアネート末端を有する4,4-ジシクロヘキシルメタンカルボジイミド90部に、繰り返し数が平均19のポリプロピレングリコールモノブチルエーテル120部、メチルポリグリコール130 43.2部およびジブチル錫ジラウレート0.07部を加え、IRでNCOの吸収がなくなるまで80℃で保った。60℃に冷却した後、脱イオン水を加えて樹脂固形分25%の親水化変性カルボジイミド化合物(2)の水分散体を得た。得られた親水化変性カルボジイミド化合物は、上記一般式(III)で表される化合物であった。
また、得られた親水化変性カルボジイミド化合物における、(i)ポリエチレングリコールモノアルキルエーテルから水酸基を除いた構造、および(ii)ポリプロピレングリコールモノアルキルエーテルから水酸基を除いた構造の比率は、(i):(ii)=1.0:1.0であった。
4,4-ジシクロヘキシルメタンジイソシアネート393部および3-メチル-1―フェニル-2-ホスホレン-1-オキシド8 部を180℃で16時間反応させ、下記式で表される構造の、1分子にカルボジイミド基を4個有し、両末端にイソシアネート基を有するカルボジイミド化合物を得た。ここに、オキシエチレン基の繰り返し数が9であるポリエチレングリコールモノメチルエーテル130部およびジブチル錫ジラウレート0.2部を加え、90℃で2時間加熱して、下記式で表される構造の、末端がイソシアネート基および親水性基であるカルボジイミド化合物を得た。さらに、GP-3000(三洋化成工業社製のグリセリンの3つの水酸基に、プロピレンオキサイドを平均で17モルずつ付加した構造を有する3価のポリオール)300部を加え、90℃で6時間反応させた。IR測定によりNCOのピークが消失していることを確認して反応を終了し、親水化変性カルボジイミド化合物(3)を得た。ここに脱イオン水を加えて撹拌し、樹脂固形分30質量%の親水化変性カルボジイミド化合物(3)の水分散体を得た。得られた親水化変性カルボジイミド化合物は、上記一般式(II)で表される化合物であった。
市販の分散剤「Disperbyk 190」(ビックケミー社製)9.2部、イオン交換水17.8部、ルチル型二酸化チタン73.0部を予備混合した後、ペイントコンディショナー中でビーズ媒体を加え、室温で粒度5μm以下となるまで混合分散し、ビーズ媒体を濾過にて取り除いて着色顔料ペーストを得た。
イオン交換水194.1部を仕込んだ反応容器に、アデカリアソープNE-20(旭電化社製α-[1-[(アリルオキシ)メチル]-2-(ノニルフェノキシ)エチル]-ω-ヒドロキシオキシエチレン、固形分80重量%水溶液)0.2部と、アクアロンHS-10(第一工業製薬社製ポリオキシエチレンアルキルプロペニルフェニルエーテル硫酸エステル)0.2部とを加え、窒素気流中で混合攪拌しながら80℃に昇温した。次いで、第1段目のα,β-エチレン性不飽和モノマー混合物として、アクリル酸メチル18.5部、アクリル酸エチル31.7部、アクリル酸2-ヒドロキシエチル5.8部、スチレン10.0部、アクリルアミド4.0部、アデカリアソープNE-20を0.3部、アクアロンHS-10を0.2部、およびイオン交換水70部からなるモノマー混合物と、過硫酸アンモニウム0.2部、およびイオン交換水7部からなる開始剤溶液とを2時間にわたり並行して反応容器に滴下した。滴下終了後、1時間同温度で熟成を行った。
さらに、80℃で第2段目のα,β-エチレン性不飽和モノマー混合物として、アクリル酸エチル24.5部、アクリル酸2-ヒドロキシエチル2.5部、メタクリル酸3.1部、アクアロンHS-10を0.3部、およびイオン交換水30部からなるモノマー混合物と、過硫酸アンモニウム0.1部、およびイオン交換水3部からなる開始剤溶液とを0.5時間にわたり並行して反応容器に滴下した。滴下終了後、2時間同温度で熟成を行った。
次いで、40℃まで冷却し、400メッシュフィルターで濾過した。さらに10重量%ジメチルアミノエタノール水溶液を加えpH7に調整し、平均粒子径110nm、固形分24重量%、固形分酸価20、水酸基価40のエマルション樹脂を得た。全モノマー組成に基づきガラス転移点を算出したところ、0℃であった。
中塗り塗料組成物の調製
撹拌機を有する容器に、製造例1で調製した水酸基含有アクリル樹脂エマルション 119.67部(樹脂固形分30%)を配合し、製造例2で調製した水酸基含有ポリエステル樹脂を25.78部(樹脂固形分45%)、水分散性ブロックポリイソシアネートとしてWM44-L70G(旭化成ケミカル製 固形分濃度 70.7%)を 24.19部、製造例5で調整した親水化変性カルボジイミド化合物を 13.5部(樹脂固形分40%)、水性ポリウレタン樹脂を100部(樹脂固形分30%)、製造例8で調製した顔料分散ペースト部 122.11部、イオン交換水を68部、ジメチルエタノールアミン(キシダ化学社製)0.01部でPHを8.0に調整し、アデカノールUH-814N(ウレタン会合型粘性剤、有効成分30%、旭電化工業社製、商品名)1.0部を混合攪拌し、水性中塗り塗料組成物を得た。
撹拌機を有する容器に、製造例1で得られた水酸基含有アクリル樹脂エマルションを100部(樹脂固形分25%)および製造例9で得られたアクリルエマルション樹脂を125部(樹脂固形分24%)撹拌混合し、水分散性ブロックポリイソシアネートとしてWM44-L70G(旭化成ケミカル製 固形分濃度 70.7%)を 21.2部、製造例5で調製した親水化変性カルボジイミド化合物を 12.5部(樹脂固形分40%)、水性ポリウレタン樹脂を66.7部(樹脂固形分30%)、光輝性顔料としてアルペーストMH8801(旭化成社製アルミニウム顔料)21部(固形分65%、PWC12%)、リン酸基含有アクリル樹脂5部、ラウリルアシッドフォスフェート0.3部を添加し、さらに、2-エチルヘキサノール30部、アデカノールUH-814N3.3部(ADEKA社製増粘剤、固形分30%)、ジメチルエタノールアミン(キシダ化学社製)0.01部、そしてイオン交換水 150部を均一分散することにより水性ベース塗料組成物を得た。
リン酸亜鉛処理したダル鋼板に、パワーニクス150(商品名、日本ペイント・オートモーティブコーティングス株式会社製カチオン電着塗料)を、乾燥塗膜が20μmとなるように電着塗装し、160℃で30分間の加熱硬化後冷却して、鋼板基板を準備した。
得られた基板に、上記水性中塗り塗料組成物を回転霧化式静電塗装装置にて乾燥膜厚が25μmとなるように塗装し、ついで上記水性ベース塗料を回転霧化式静電塗装装置にて乾燥膜厚が15μmとなるように塗装し、80℃で3分間プレヒートを行った。なお、水性中塗り塗料組成物と水性ベース塗料組成物との塗装の間に6分間のインターバルを置いた。さらに、その塗板にクリヤー塗料として、ポリウレエクセル O-1200 (商品名、日本ペイント・オートモーティブコーティングス株式会社製、ポリイソシアネート化合物含有2液アクリルウレタン系有機溶剤型クリヤー塗料)を回転霧化式静電塗装装置にて乾燥膜厚が35μmとなるように塗装した後、80℃で20分間の加熱硬化を行い、複層塗膜の形成された試験片を得た。
中塗り塗料組成物および水性ベース塗料組成物の調製において、下記表に示した成分および配合量に変更したこと以外は、実施例1と同様にして、中塗り塗料組成物および水性ベース塗料組成物を調製した。得られた塗料組成物を用いて、実施例1と同様にして複層塗膜を形成した。なお、下記表中に示される配合量は樹脂固形分量である。
実施例1で調製した中塗り塗料組成物および水性ベース塗料組成物を用いて、以下の手順により、複層塗膜を形成した。
樹脂部材(ポリプロピレン)に、密着用水性プライマーとして、WB-3110CB (商品名、日本ペイント・オートモーティブコーティングス株式会社製、非塩素化ポリオレフィン含有導電塗料)を回転霧化式静電塗装装置にて乾燥膜厚が15μmとなるように塗装し、ついで上記水性中塗り塗料組成物を回転霧化式静電塗装装置にて乾燥膜厚が25μmとなるように塗装し、ついで上記水性ベース塗料を回転霧化式静電塗装装置にて乾燥膜厚が15μmとなるように塗装し、80℃で3分間プレヒートを行った。なお、水性中塗り塗料組成物と水性ベース塗料組成物との塗装の間に6分間のインターバルを置いた。さらに、その塗板にクリヤー塗料として、ポリウレエクセル O-1200 (商品名、日本ペイント・オートモーティブコーティングス株式会社製、ポリイソシアネート化合物含有2液アクリルウレタン系有機溶剤型クリヤー塗料)を回転霧化式静電塗装装置にて乾燥膜厚が35μmとなるように塗装した後、80℃で20分間の加熱硬化を行い、複層塗膜の形成された試験片を得た。
中塗り塗料組成物および水性ベース塗料組成物の調製において、下記表に示した成分および配合量に変更したこと以外は、実施例1と同様にして、中塗り塗料組成物および水性ベース塗料組成物を調製した。得られた塗料組成物を用いて、実施例1と同様にして複層塗膜を形成した。
(D)水性ポリウレタン樹脂95質量部(樹脂固形分量)および製造例5に記載の(C)親水化変性カルボジイミド化合物5質量部(樹脂固形分量)を、2つの樹脂固形分が合計で100質量部となるように混合した。埃、ダストなどがかからないような清浄な環境において、出来上がった混合液を、平坦なポリプロピレン板の上に、乾燥膜厚が20μmとなるように、ドクターブレードで均一に塗装した。20℃で10分間静置した後、80℃で3分間プレヒートを行い、水分を揮発させた後に、120℃で30分間焼き付けて、硬化膜を調製した。得られた硬化膜を、JIS K7127に従い、試験時温度-20℃の条件下で引張性能試験を行い、破断時の伸び率(破断伸度)を測定した。測定は20回行い、最大値と最低値を除いた18回の平均値をそのサンプルの破断伸度とした。
各実施例および比較例で得られた複層塗膜を有する試験板を、グラロベ試験機KSS-1(スガ試験機社製)を用い、以下の条件下で飛石試験を行った。
<試験条件>
石の大きさ:6~8mm
石の量:0.7~0.8g/個
距離:35cm
ショット圧:0.6kg/cm2
ショット角度:45°
試験温度:-20℃
飛石試験後の試験板を、下記基準により目視評価した。下記基準において、4点以上を、実用上の使用が可能であり合格と判断する。
5:剥離がほとんど見られない。
4:剥離面積は小さいが、電着塗膜と中塗塗膜との界面での剥離は殆ど見られない。
3:剥離面積がやや大きく、電着塗膜と中塗塗膜との界面で剥離が見られる。
2:剥離面積が大きく、電着塗膜と中塗塗膜との界面で剥離が見られる。
1:剥離面積が大きく、電着塗膜が破壊している。
上記複層塗膜の試験板を、40℃の温水に240時間浸漬し、引き上げ、20℃で24時間乾燥した後、試験板の複層塗膜を素地に達するようにカッターで格子状に切り込み、大きさ2mm×2mmのゴバン目を100個作成した。続いて、その表面に粘着セロハンテープ(商標)を貼着し、20℃においてそのテープを急激に剥離した後のゴバン目塗膜の残存枚数を計測した。
碁盤目の剥がれ枚数で塗膜の優劣を判定することができる。碁盤目の剥がれが一枚でも生じた場合は、実用上の使用は困難と判断する。
上記複層塗膜の試験板を40℃の温水に240時間浸漬し、引き上げ、20℃で24時間乾燥した後、試験板を目視で視認し、試験前後での外観の変化を観察した。下記基準において○、および○△評価で実用性があると判断できる。
○:艶、平滑性にほとんど差が見られない。
○△:艶、平滑性にわずかに変化が見られる。
△:艶、平滑性に変化がみられる。
△×:艶、平滑性とも変化がみられるが、特に艶の変化が顕著である。
×:艶、平滑性ともに顕著な差が確認できる。
上記複層塗膜の試験板を40℃の湿度99%以上でかつ50℃の雰囲気に240時間曝露した。曝露終了後に、20℃で24時間乾燥した後、試験板の複層塗膜を素地に達するようにカッターで格子状に切り込み、大きさ2mm×2mmのゴバン目を100個作成した。続いて、その表面に粘着セロハンテープ(商標)を貼着し、20℃においてそのテープを急激に剥離した後のゴバン目塗膜の残存枚数を計測した。
碁盤目の剥がれ枚数で塗膜の優劣を判定することができる。碁盤目の剥がれが一枚でも生じた場合は、実用上の使用は困難と判断する。
塗料組成物を調製した後、40℃で3日間放置し、塗料液中に流動性のない塊ができるかまたは塗料液全体が流動性をなくしたものを不合格(×)とし、そうでないものを合格(○)とした。
A:N9603(楠本化成社製)、固形分濃度:34%、Tg:-10℃、破断伸度:12%
B:HUX-232(ADEKA社製)、固形分濃度:30%、Tg:-18℃、破断伸度:130%
C:N800(三洋化成社製)、固形分濃度:38%、Tg:-60℃、破断伸度:312%
D:パーマリンU150(三洋化成社製)、固形分濃度:30%、Tg:-60℃、破断伸度:610%
一方で、比較例の水性塗料組成物を用いて形成された複層塗膜は、耐水性、耐湿性および耐チッピング性のうち1つまたは複数の性能が劣っていることが確認された。
Claims (13)
- (A)水酸基およびカルボキシル基を有する水性樹脂、
(B)水分散性ブロックポリイソシアネート化合物、
(C)親水化変性カルボジイミド化合物、および
(D)水性ポリウレタン樹脂、
を含む水性塗料組成物であって、
前記(A)水酸基およびカルボキシル基を有する水性樹脂は、樹脂固形分換算で、80~200mgKOH/gの水酸基価、および、10~40mgKOH/gの酸価を有し、
前記(C)親水化変性カルボジイミド化合物が、下記一般式(I)、(II)または(III)で表されるものであり、
前記(D)水性ポリウレタン樹脂は、ガラス転移点(Tg)が-50℃以下であり、
前記(D)水性ポリウレタン樹脂の硬化膜の破断伸度が-20℃において400%以上である、
水性塗料組成物。
- 前記(C)親水化変性カルボジイミド化合物の含有量は、水性塗料組成物の樹脂固形分に対して1~8質量%である、請求項1記載の水性塗料組成物。
- 前記(A)水性樹脂は、数平均分子量が10,000~80,000であるアクリルエマルションを含む、請求項1または2記載の水性塗料組成物。
- 前記式(III)で表される(C)親水化変性カルボジイミド化合物が、下記化合物である、請求項1~3いずれかに記載の水性塗料組成物。
(i)繰り返し数6~20のポリエチレンオキサイドユニットの末端に、炭素数1~3のアルキル基がエーテル結合した、ポリエチレングリコールモノアルキルエーテルから、水酸基を除いた構造、
(ii)繰り返し数4~60のポリプロピレンオキサイドユニットの末端に、炭素数1~8のアルキル基がエーテル結合した、ポリプロピレングリコールモノアルキルエーテルから、水酸基を除いた構造:
から選択される、同一または異種の構造である。] - 前記式(III)で表される(C)親水化変性カルボジイミド化合物において、何れか一方のYが(i)であって他方のYが(ii)であり、および、
前記構造(i)および(ii)の比率が、(i):(ii)=1:0.7~1:8の範囲内である、
請求項4記載の水性塗料組成物。 - 前記(D)水性ポリウレタン樹脂の含有量は、水性塗料組成物の樹脂固形分に対して15質量%以上である、請求項1~5いずれかに記載の水性塗料組成物。
- 前記(D)水性ポリウレタン樹脂の含有量は、水性塗料組成物の樹脂固形分に対して30質量%以上40質量%以下である、請求項1~5いずれかに記載の水性塗料組成物。
- 前記(D)水性ポリウレタン樹脂の含有量は、水性塗料組成物の樹脂固形分に対して15質量%以上30質量%未満である、請求項1~5いずれかに記載の水性塗料組成物。
- 前記(B)水分散性ブロックポリイソシアネート化合物の含有量は、水性塗料組成物の樹脂固形分に対して10~25質量%であり、
前記(C)親水化変性カルボジイミド化合物の含有量は、水性塗料組成物の樹脂固形分に対して1.5~7質量%である、
請求項1~8いずれかに記載の水性塗料組成物。 - 水性塗料組成物の樹脂固形分に対する、前記(B)水分散性ブロックポリイソシアネート化合物および(C)親水化変性カルボジイミド化合物の含有量の質量比は、(B):(C)=25:1~1.25:1である、
請求項1~9いずれかに記載の水性塗料組成物。 - 水性塗料組成物を用いる塗膜形成方法であって、
前記方法は、
請求項1~10いずれかに記載の水性塗料組成物を被塗物に塗装して塗膜を形成する、塗装工程、および
得られた塗膜を、70~100℃で硬化する、硬化工程、
を包含する、
塗膜形成方法。 - 前記塗装工程は、
被塗物上に、請求項7記載の水性塗料組成物を塗装して第1塗膜を形成する、第1塗装工程、および
前記第1塗膜上に、請求項8記載の水性塗料組成物を塗装して第2塗膜を形成する、第2塗装工程、
を包含する、
請求項11記載の塗膜形成方法。 - 前記被塗物は、鋼板部および樹脂部を含む、請求項11または12記載の塗膜形成方法。
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