WO2013129136A1 - 複層塗膜形成方法 - Google Patents
複層塗膜形成方法 Download PDFInfo
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- WO2013129136A1 WO2013129136A1 PCT/JP2013/053658 JP2013053658W WO2013129136A1 WO 2013129136 A1 WO2013129136 A1 WO 2013129136A1 JP 2013053658 W JP2013053658 W JP 2013053658W WO 2013129136 A1 WO2013129136 A1 WO 2013129136A1
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
- B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
- B05D7/00—Processes, other than flocking, specially adapted for applying liquids or other fluent materials to particular surfaces or for applying particular liquids or other fluent materials
- B05D7/50—Multilayers
- B05D7/56—Three layers or more
- B05D7/57—Three layers or more the last layer being a clear coat
- B05D7/572—Three layers or more the last layer being a clear coat all layers being cured or baked together
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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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- 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
- B05D2503/00—Polyurethanes
-
- 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
- B05D2508/00—Polyesters
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
- Y10T428/00—Stock material or miscellaneous articles
- Y10T428/26—Web or sheet containing structurally defined element or component, the element or component having a specified physical dimension
- Y10T428/263—Coating layer not in excess of 5 mils thick or equivalent
Definitions
- the present invention is a three-coat one-bake method in which an aqueous first basecoat paint, an aqueous second basecoat paint, and a clear paint are sequentially applied onto an object to be coated, and the resulting three-layered multi-layer paint film is simultaneously heat-cured.
- the present invention relates to a method capable of forming a multilayer coating film excellent in smoothness, sharpness and chipping resistance by performing preheating (preheating) only once.
- the smoothness and the sharpness of the formed coating film are reduced due to a mixed layer between the water-based first base coat paint and the water-based second base coat paint. Is likely to occur.
- Patent Document 1 discloses an aqueous dispersion of specific acrylic resin particles obtained by emulsion polymerization of an amide group-containing ethylenically unsaturated monomer and another ethylenically unsaturated monomer in a 3-coat 1-bake method.
- a method of controlling the mixed layer by using a water-based intermediate coating material to be contained and forming a multilayer coating film having an excellent appearance is disclosed.
- the coating of the intermediate coating is omitted and the electrodeposition coating is formed on the object to be coated, and then “painting of the base coat paint ⁇ painting of the clear coat paint ⁇ baking curing” An intermediate coating-less method is being studied.
- electrodeposition coatings are excellent in rust prevention
- intermediate coatings are excellent in smoothness and chipping resistance
- base coat coatings and clear coatings are excellent in appearance
- these coatings are laminated.
- the layer coating film can impart excellent rust prevention, smoothness, chipping resistance and appearance to the object to be coated.
- the intermediate coating-less method cannot form an intermediate coating film excellent in smoothness and chipping resistance, the obtained multilayer coating film has a problem that the smoothness and chipping resistance are lowered. is doing.
- Patent Document 2 by using an aqueous base coating composition containing a specific core / shell type acrylic resin emulsion, a specific polyether polyol and an active methylene type block polyisocyanate in an intermediate coating-less system, A multilayer coating film forming method capable of improving the appearance of the coating film while ensuring the chipping resistance and the like of the resulting multilayer coating film is disclosed.
- An object of the present invention is to apply a water-based first base coat paint, and then apply a water-based second base coat paint without pre-heating, pre-heat, and further apply a clear coat paint.
- Excellent smoothness and sharpness in a multi-layer coating film forming method hereinafter, sometimes referred to as “aqueous 1 preheat 3C1B process” in which three layers of an aqueous second base coat film and a clear coat film are simultaneously cured.
- Another object of the present invention is to provide a method capable of forming a multilayer coating film having chipping resistance and hardness.
- the present inventors have determined that a specific aqueous polyester resin, a specific aqueous polyester base coating material is used as the aqueous first base coat paint in the aqueous 1 preheat 3C1B process.
- the present invention has found that a multilayer coating film excellent in smoothness, sharpness, chipping resistance and hardness can be formed by using a paint containing water-based acrylic resin, water-based urethane resin and melamine resin. It came to complete.
- the present invention (1) A step of applying an aqueous first base coat paint (A) on the cured electrodeposition coating film to form a first base coat coating film having a cured film thickness of 20 to 35 ⁇ m; (2) A step of applying the aqueous second base coat paint (B) on the first base coat film without preheating to form a second base coat film having a cured film thickness of 8 to 18 ⁇ m; (3) A step of applying a clear paint (C) on the second base coat film after the preheating to form a clear film having a cured film thickness of 25 to 50 ⁇ m; (4) A coating film forming method including a step of simultaneously heating and curing the first base coat film, the second base coat film and the clear film to form a cured film,
- the aqueous first base coat paint (A) comprises an aqueous polyester resin (a), an aqueous acrylic resin (b), an aqueous urethane resin (c), and a melamine resin (d), and 100 parts by mass of the total resin
- the aqueous polyester resin (a) contains, as a polybasic acid component, a polybasic acid having an aromatic ring and / or an alicyclic ring in a proportion of 55 to 75 mol% based on the total amount of the polybasic acid.
- the water-based acrylic resin (b) is 45 to 80% by mass of a polymerizable unsaturated monomer having an alkyl group having 4 to 8 carbon atoms and 1 to 10% by mass of a hydroxyl group-containing polymerizable unsaturated monomer based on the total mass of monomers.
- a method for forming a layer coating film is provided.
- a multilayer coating film excellent in smoothness, sharpness, chipping resistance and hardness can be formed by using a specific aqueous 1 preheat 3C1B process.
- a cured electrodeposition coating film is first formed by applying an electrodeposition paint on an object to be coated such as a steel plate and curing it by heating.
- a steel plate for automobile bodies for example, an alloyed hot-dip galvanized steel plate, hot-dip galvanized steel plate, electrogalvanized steel plate, cold-rolled steel plate, and the like can be used.
- Surface treatments such as treatment, chromate treatment, and complex oxide treatment may be applied.
- an electrodeposition paint known per se for example, those described in JP-A No. 2003-306796
- a cationic electrodeposition paint is preferably used. Can do.
- Step (1) Next, an aqueous first base coat paint (A) is applied onto the cured electrodeposition coating film to form a first base coat film having a cured film thickness in the range of 20 to 35 ⁇ m.
- the aqueous first base coat paint (A) comprises an aqueous polyester resin (a), an aqueous acrylic resin (b), an aqueous urethane resin (c) and a melamine resin (d) based on 100 parts by mass of the total resin solid content.
- a water-based paint containing 15 to 35 parts by weight of the resin (a), 15 to 30 parts by weight of the resin (b), 15 to 30 parts by weight of the resin (c), and 15 to 35 parts by weight of the resin (d). .
- aqueous polyester resin As the aqueous polyester resin (a), a polybasic acid component containing 55 to 75 mol% of a polybasic acid having an aromatic ring and / or an alicyclic ring based on the total amount of the polybasic acid component is used. A polyester resin having an acid value of 15 to 25 mg KOH / g and a number average molecular weight of 1000 to 5000.
- the aqueous polyester resin (a) can be usually obtained by esterification or transesterification of the polybasic acid component (a-1) and the alcohol component (a-2) described below.
- Polybasic acid component (a-1) As the polybasic acid component (a-1), the mixed layer of the aqueous first base coat paint (A) and the aqueous second base coat paint (B) described later is suppressed, and smoothness, sharpness, chipping resistance and hardness are reduced. From the viewpoint of forming an excellent multilayer coating film, it has an aromatic ring-containing polybasic acid (hereinafter referred to as “aromatic polybasic acid”) (a-1-1) and / or an alicyclic ring. Those containing polybasic acid (hereinafter referred to as “alicyclic polybasic acid”) (a-1-2) are used.
- aromatic polybasic acid hereinafter referred to as “aromatic polybasic acid”
- alicyclic polybasic acid” Those containing polybasic acid (hereinafter referred to as “alicyclic polybasic acid”) (a-1-2) are used.
- the total content of the aromatic polybasic acid (a-1-1) and the alicyclic polybasic acid (a-1-2) in the polybasic acid component (a-1) is the polybasic acid component (a- Based on the total amount of 1), it is generally preferred to be in the range of 55 to 75 mol%, particularly 60 to 70 mol%.
- the aromatic polybasic acid (a-1-1) generally includes an aromatic compound having at least 2, preferably 2 or 3, carboxyl groups in one molecule, an acid anhydride of the aromatic compound, Examples include aromatic esterified products such as phthalic acid, isophthalic acid, terephthalic acid, naphthalenedicarboxylic acid, 4,4′-biphenyldicarboxylic acid, trimellitic acid, pyromellitic acid and the like. An anhydride of the aromatic polycarboxylic acid; a lower alkyl esterified product of the aromatic polycarboxylic acid; and the like.
- the aromatic polybasic acid (a-1-1) can be used alone or in combination of two or more. Of these, phthalic acid, phthalic anhydride, isophthalic acid, trimellitic acid, and trimellitic anhydride are preferably used from the viewpoints of sharpness and chipping resistance of the resulting multilayer coating film.
- the alicyclic polybasic acid (a-1-2) generally has at least one alicyclic structure (mainly a 4-6 membered ring structure) and at least 2, preferably 2 or 3 per molecule.
- An alicyclic polycarboxylic acid such as cyclohexanetricarboxylic acid; an anhydride of the alicyclic polycarboxylic acid; a lower alkyl group of the alicyclic polycarboxylic acid Tel monster, and the like.
- the above alicyclic polybasic acids (a-1-2) can be used alone or in combination of two or more.
- “lower” means that the organic group to which this word is attached has 6 or less carbon atoms, preferably 4 or less.
- the alicyclic polybasic acid (a-1-2) alone or the aromatic polybasic acid (a-1-1) and the alicyclic polybasic acid It is desirable to use (a-1-2) in combination, and the ratio of the two is the molar ratio of aromatic polybasic acid (a-1-1) / alicyclic polybasic acid (a-1-2), Generally, it is preferable to be within the range of 90/10 to 0/100, particularly 50/50 to 0/100, and more particularly 35/65 to 0/100.
- the polybasic acid component (a-1) includes, in addition to the aromatic polybasic acid (a-1-1) and the alicyclic polybasic acid (a-1-2), other polybasic acids. Ingredients can also be used, and in particular, aliphatic polybasic acid (a-1-3) can be preferably used.
- the aliphatic polybasic acid (a-1-3) generally includes an aliphatic compound having at least 2, preferably 2 carboxyl groups in one molecule, an acid anhydride of the aliphatic compound, and the aliphatic compound. Esterified products such as succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, brassic acid, octadecanedioic acid, citric acid, etc.
- Aliphatic polyvalent carboxylic acids anhydrides of the aliphatic polyvalent carboxylic acids; and lower alkyl esterified products of the aliphatic polyvalent carboxylic acids.
- the above aliphatic polybasic acids can be used alone or in combination of two or more.
- adipic acid is preferably used from the viewpoint of the smoothness of the resulting multilayer coating film.
- polybasic acid components other than the aromatic polybasic acid (a-1-1), the alicyclic polybasic acid (a-1-2) and the aliphatic polybasic acid (a-1-3), It is not particularly limited, for example, coconut oil fatty acid, cottonseed oil fatty acid, hemp seed oil fatty acid, rice bran oil fatty acid, fish oil fatty acid, tall oil fatty acid, soybean oil fatty acid, linseed oil fatty acid, tung oil fatty acid, rapeseed oil fatty acid, castor oil fatty acid Fatty acids such as dehydrated castor oil fatty acid and safflower oil fatty acid; lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, linoleic acid, linolenic acid, benzoic acid, p-tert-butylbenzoic acid, cyclohexane acid, 10 -Monocarboxylic acids such as phenyloctadecanoic
- the other polybasic acid components can be used alone or in combination of two or more.
- the aromatic polybasic acid (a-1-1) and the alicyclic polybasic acid (a-1-2) are in total 55 to 75 mol% based on the total amount of the polybasic acid components used, In particular, it can be used in the range of 60 to 70 mol%.
- Alcohol component (a-2) As the alcohol component (a-2), a polyhydric alcohol having at least 2, preferably 2 or 3, hydroxyl groups in one molecule can be suitably used.
- the polyhydric alcohol include ethylene glycol, propylene glycol, diethylene glycol, trimethylene glycol, tetraethylene glycol, triethylene glycol, dipropylene glycol, 1,4-butanediol, 1,3-butanediol, 2,3 -Butanediol, 1,2-butanediol, 3-methyl-1,2-butanediol, 2-butyl-2-ethyl-1,3-propanediol, 1,2-pentanediol, 1,5-pentanediol 1,4-pentanediol, 2,4-pentanediol, 2,3-dimethyltrimethylene glycol, tetramethylene glycol, 3-methyl-4,3-pentanediol, 3-methyl
- alcohol component (a-2) In addition to the polyhydric alcohol, other alcohol components can be used as the alcohol component (a-2).
- the other alcohol components include methanol, ethanol, propyl alcohol, butyl alcohol, Monoalcohols such as stearyl alcohol and 2-phenoxyethanol; propylene oxide, butylene oxide, glycidyl esters of synthetic hyperbranched saturated fatty acids (trade name “Cardura E10” HEXION Specialty Chemicals, Inc.), and the like are reacted with an acid. Examples include alcohol compounds obtained.
- the alcohol component (a-2) can be used alone or in combination of two or more. Of these, neopentyl glycol and trimethylolpropane are preferably used from the viewpoints of smoothness and chipping resistance of the resulting multilayer coating film.
- the production of the water-based polyester resin (a) is not particularly limited, and can be performed using a method usually used in the production of a polyester resin.
- the polybasic acid component (a-1) and the alcohol component (a-2) are reacted in an inert gas atmosphere, for example, in a nitrogen stream at a temperature of about 150 to about 250 ° C. for 5 to 10 hours.
- the method of performing esterification reaction or transesterification reaction by this is mentioned.
- the polybasic acid component (a-1) and the alcohol component (a-2) may be added at once, or may be added in several portions.
- the carboxyl group-containing polyester resin is first synthesized, at least a part of the carboxyl groups in the carboxyl group-containing polyester resin can be esterified using the alcohol component (a-2).
- the acid anhydride may be reacted to half-esterify the hydroxyl group-containing polyester resin.
- a catalyst can be used to promote the reaction.
- the catalyst include known catalysts such as dibutyltin oxide, antimony trioxide, zinc acetate, manganese acetate, cobalt acetate, calcium acetate, lead acetate, tetrabutyl titanate, and tetraisopropyl titanate.
- the aqueous polyester resin (a) can be modified with a fatty acid, a monoepoxy compound, a polyisocyanate compound or the like during the preparation of the resin or after the esterification reaction or the transesterification reaction.
- fatty acid examples include coconut oil fatty acid, cottonseed oil fatty acid, hemp seed oil fatty acid, rice bran oil fatty acid, fish oil fatty acid, tall oil fatty acid, soybean oil fatty acid, linseed oil fatty acid, tung oil fatty acid, rapeseed oil fatty acid, castor oil fatty acid, dehydrated castor An oil fatty acid, safflower oil fatty acid, etc. are mentioned.
- a glycidyl ester of a synthetic highly branched saturated fatty acid (trade name “Cardura E10” manufactured by HEXION Specialty Chemicals) can be suitably used.
- polyisocyanate compound examples include aliphatic diisocyanates such as lysine diisocyanate, hexamethylene diisocyanate, and trimethylhexane diisocyanate; hydrogenated xylylene diisocyanate, isophorone diisocyanate, methylcyclohexane-2,4-diisocyanate, methylcyclohexane-2,6 Alicyclic diisocyanates such as diisocyanate, 4,4′-methylenebis (cyclohexyl isocyanate), 1,3- (isocyanatomethyl) cyclohexane; aromatic diisocyanates such as tolylene diisocyanate, xylylene diisocyanate, diphenylmethane diisocyanate; lysine Organic polyisocyanate itself such as triisocyanate or higher polyisocyanate such as triisocyanate, Is an adduct of each of these organic polyisocyanates with
- the aqueous polyester resin (a) is generally a hydroxyl group within the range of 60 to 200 mgKOH / g, particularly 80 to 180 mgKOH / g, more particularly 100 to 150 mgKOH / g, from the viewpoint of water resistance, hardness and the like of the resulting multilayer coating film. It is preferable to have a valence.
- the water-based polyester resin (a) is generally 15 to 25 mg KOH / g, particularly 18 to 23 mg KOH / g, more particularly 19 to 22 mg KOH / g, from the viewpoint of water resistance and sharpness of the resulting multilayer coating film. It is preferable to have an acid value within the range.
- the hydroxyl value and acid value of the aqueous polyester resin (a) can be determined, for example, by adjusting the blending ratio of the polybasic acid component (a-1) and the alcohol component (a-2), in the esterification reaction or transesterification reaction. It can adjust by adjusting reaction temperature or reaction time.
- the water-based polyester resin (a) is generally 1,000 to 5,000, particularly 1,200 to 4, from the viewpoint of smoothness, sharpness, chipping resistance, hardness and the like of the resulting multilayer coating film. Preferably, it has a number average molecular weight in the range of 000, more particularly in the range of 1,250 to 3,000.
- the number average molecular weight of the aqueous polyester resin (a) can be adjusted, for example, by adjusting the reaction temperature or reaction time in the esterification reaction or transesterification reaction.
- the number average molecular weight and the weight average molecular weight are values obtained by converting the number average molecular weight and the weight average molecular weight measured using a gel permeation chromatograph (GPC) based on the molecular weight of standard polystyrene. is there.
- GPC gel permeation chromatograph
- the aqueous polyester resin (a) can be water-soluble or water-dispersed by neutralizing the carboxyl group in the molecule with a basic compound.
- the basic compound include hydroxides of alkali metals or alkaline earth metals such as sodium hydroxide, potassium hydroxide, lithium hydroxide, calcium hydroxide, barium hydroxide; ammonia; ethylamine, propylamine, butylamine , Primary amines such as benzylamine, monoethanolamine, neopentanolamine, 2-aminopropanol, 2-amino-2-methyl-1-propanol, 3-aminopropanol; diethylamine, diethanolamine, di-n-propanol Secondary monoamines such as amine, di-iso-propanolamine, N-methylethanolamine, N-ethylethanolamine; dimethylethanolamine, trimethylamine, triethylamine, triisopropylamine, methyldiethanol Min, 2-
- the amount of the basic compound used is usually in the range of about 0.1 to about 1.5 equivalents relative to the acid groups of the aqueous polyester resin (a) from the viewpoint of water resistance of the resulting multilayer coating film. In the range of about 0.2 to about 1.2 equivalents.
- Aqueous acrylic resin (b) As the water-based acrylic resin (b), a mixed layer of the water-based first base coat paint (A) and the water-based second base coat paint (B) described later is suppressed, and a composite having excellent smoothness, sharpness, chipping resistance, and hardness is used.
- a polymerizable unsaturated monomer (b-1) having an alkyl group having 4 to 8 carbon atoms based on the total mass of monomers, a hydroxyl group-containing polymerizable monomer 1 to 10% by mass of a saturated monomer (b-2), 1 to 10% by mass of a carboxyl group-containing polymerizable unsaturated monomer (b-3) and 0 to 53% by mass of another polymerizable unsaturated monomer (b-4)
- An acrylic emulsion obtained by emulsion polymerization of the monomer component to be contained is used.
- polymerizable unsaturated monomer (b-1) having an alkyl group having 4 to 8 carbon atoms for example, a monoesterified product of (meth) acrylic acid and a monohydric alcohol having an alkyl group having 4 to 8 carbon atoms is used. can do.
- n-butyl (meth) acrylate, iso-butyl (meth) acrylate, tert-butyl (meth) acrylate, pentyl (meth) acrylate, hexyl (meth) acrylate, octyl (meth) acrylate, 2 -Ethylhexyl (meth) acrylate and the like can be mentioned, and these can be used alone or in combination of two or more.
- (meth) acrylate means acrylate or methacrylate
- (meth) acrylic acid means acrylic acid or methacrylic acid
- (Meth) acryloyl means acryloyl or methacryloyl
- (meth) acrylamide means acrylamide or methacrylamide.
- n-butyl (meth) is particularly preferable from the viewpoint of the vividness and water resistance of the resulting multilayer coating film. It is preferable to use acrylate, 2-ethylhexyl (meth) acrylate, or the like.
- the hydroxyl group-containing polymerizable unsaturated monomer (b-2) is preferably one having one hydroxyl group and one polymerizable double bond in one molecule, such as 2-hydroxyethyl (meth) acrylate, 2 -(Meth) acrylic acid such as hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate and a dihydric alcohol having 2 to 8 carbon atoms, preferably 2 to 4 carbon atoms Monoesterified product; ⁇ -caprolactone modified product of monoesterified product of (meth) acrylic acid and dihydric alcohol having 2 to 8 carbon atoms; N-hydroxymethyl (meth) acrylamide; allyl alcohol; (Meth) acrylate etc.
- the carboxyl group-containing polymerizable unsaturated monomer (b-3) is preferably one having one carboxyl group and one polymerizable double bond in one molecule, such as (meth) acrylic acid, maleic acid , Crotonic acid, ⁇ -carboxyethyl acrylate and the like, and these can be used alone or in combination of two or more.
- acrylic acid and methacrylic acid are preferably used from the viewpoints of smoothness, sharpness, water resistance, and the like of the resulting multilayer coating film.
- the other polymerizable unsaturated monomer (b-4) is a polymerizable unsaturated monomer other than the polymerizable unsaturated monomers (b-1) to (b-3), and the other polymerizable unsaturated monomer ( As b-4), for example, methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, iso-propyl (meth) acrylate, nonyl (meth) acrylate, dodecyl (meth) acrylate (lauryl) (Meth) acrylate), tridecyl (meth) acrylate, stearyl (meth) acrylate, isostearyl (meth) acrylate, cyclohexyl (meth) acrylate, methylcyclohexyl (meth) acrylate, t-butylcyclohexyl (meth) acrylate, cyclododecyl
- Perfluoroalkyl (meth) acrylate polymerizable unsaturated monomer having a fluorinated alkyl group such as fluoroolefin; polymerizable unsaturated monomer having a photopolymerizable functional group such as maleimide group; N-vinylpyrrolidone, ethylene, butadiene, Vinyl compounds such as chloroprene, vinyl propionate and vinyl acetate; allyl (meth) acrylate, ethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, 1,3-butylene Glycol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, 1,4-butanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, 1,6-hexanediol di (meth) Acrylate,
- the acrylic resin (b) can be produced by copolymerizing the monomer components described above in an aqueous medium by an emulsion polymerization method. Specifically, for example, it can be produced by emulsion polymerization of the monomer component using a polymerization initiator in the presence of a surfactant.
- anionic surfactants and nonionic surfactants are suitable.
- anionic surfactant include sodium salts such as alkyl sulfonic acid, alkyl benzene sulfonic acid, and alkyl phosphoric acid, and ammonium salts.
- Nonionic surfactants include, for example, polyoxyethylene oleyl.
- Ether polyoxyethylene stearyl ether, polyoxyethylene lauryl ether, polyoxyethylene tridecyl ether, polyoxyethylene phenyl ether, polyoxyethylene nonylphenyl ether, polyoxyethylene octylphenyl ether, polyoxyethylene monolaurate, polyoxy Ethylene monostearate, polyoxyethylene monooleate, sorbitan monolaurate, sorbitan monostearate, sorbitan trioleate, polyoxyethyleneso Sorbitan monolaurate, and the like.
- a reactive anionic surfactant having an unsaturated group can also be used.
- the amount of the surfactant used is usually in the range of 0.1 to 15% by mass, particularly 0.5 to 10% by mass, more particularly 1 to 5% by mass, based on the total mass of all monomers used. It is preferable that
- polymerization initiator examples include benzoyl peroxide, octanoyl peroxide, lauroyl peroxide, stearoyl peroxide, cumene hydroperoxide, tert-butyl peroxide, di-tert-amyl peroxide, tert-butyl peroxide.
- Organic peroxides such as laurate, tert-butylperoxyisopropyl carbonate, tert-butylperoxyacetate, diisopropylbenzene hydroperoxide; azobisisobutyronitrile, azobis (2,4-dimethylvaleronitrile), azobis ( 2-methylpropiononitrile), azobis (2-methylbutyronitrile), 4,4′-azobis (4-cyanobutanoic acid), dimethylazobis (2-methylpropionate) Azo compounds such as azobis [2-methyl-N- (2-hydroxyethyl) -propionamide], azobis ⁇ 2-methyl-N- [2- (1-hydroxybutyl)]-propionamide ⁇ ; potassium persulfate And persulfates such as ammonium persulfate and sodium persulfate.
- polymerization initiators can be used alone or in combination of two or more. Moreover, it is good also as a redox initiator by using together with reducing agents, such as saccharide
- reducing agents such as saccharide
- the amount of the polymerization initiator used is generally in the range of 0.05 to 5% by mass, particularly 0.1 to 3% by mass, based on the total mass of all monomers used.
- the method for adding the polymerization initiator is not particularly limited, and can be appropriately selected according to the type and amount thereof. For example, it may be previously contained in the monomer component or the aqueous medium, or may be added all at once during the polymerization, or may be added dropwise.
- the monomer component can contain components such as a chain transfer agent as needed.
- the monomer component can be dropped as it is, but it is desirable to drop the monomer component as a monomer emulsion obtained by dispersing the monomer component in an aqueous medium.
- the particle size of the monomer emulsion is not particularly limited.
- the aqueous acrylic resin (b) thus obtained can generally have an average particle size in the range of about 10 to about 1,000 nm, especially about 15 to about 750 nm, more particularly about 20 to about 500 nm.
- the average particle diameter of the aqueous acrylic resin (b) is a value measured at 20 ° C. after diluting with deionized water by a conventional method using a submicron particle size distribution measuring device.
- a submicron particle size distribution measuring device for example, “COULTER N4 type” (trade name, manufactured by Beckman Coulter, Inc.) can be used.
- a polymerizable unsaturated monomer (b-1) having a C 4-8 alkyl group, a hydroxyl group-containing polymerizable unsaturated monomer (b-2), a carboxyl group-containing polymerizable unsaturated monomer (b-3) ) And other polymerizable unsaturated monomers (b-4) are used to suppress a mixed layer of the aqueous first base coat paint (A) and the aqueous second base coat paint (B) described later, smoothness and sharpness. From the viewpoint of forming a multilayer coating film having excellent chipping resistance and hardness, the following range is preferable based on the total mass of the monomer components.
- the water-based acrylic resin (b) is generally from 4.5 to 50 mgKOH / g, particularly from 9 to 43 mgKOH / g, more particularly from 10 to 40 mgKOH / g, from the viewpoints of storage stability, water resistance of the resulting multilayer coating film, and the like. It preferably has a hydroxyl value within the range.
- the aqueous acrylic resin (b) is generally 7 to 75 mgKOH / g, particularly 7.5 to 60 mgKOH / g, from the viewpoint of smoothness, sharpness, chipping resistance, water resistance and the like of the resulting multilayer coating film. More preferably, the acid value is in the range of 10 to 50 mgKOH / g.
- the water-based acrylic resin (b) is generally from 2,000 to 5,000,000, particularly from 3,000 to 3,000,000, from the viewpoints of smoothness and water resistance of the resulting multilayer coating film. It is particularly preferable to have a weight average molecular weight in the range of 5,000 to 2,000,000.
- the water-based urethane resin (c) means a polyurethane resin that can be dispersed in an aqueous medium containing water as a main solvent or dispersion medium.
- the form in the aqueous medium includes a water-soluble type, a colloidal dispersion type, and an emulsion. Any of a type and a slurry type may be used, but among them, a colloidal dispersion type or an emulsion type is desirable.
- aqueous urethane resin (c) those known per se can be used.
- a polyurethane obtained by reacting a polyol such as polyester polyol, polycarbonate polyol, polyether polyol and polyisocyanate If necessary, those obtained by chain extension in the presence of a chain extender, which is a low molecular weight compound having at least two active hydrogens in one molecule such as diol, diamine, etc., are suitable for aqueous media. It can be used by being stably dispersed or dissolved therein.
- polyester polyol used in the production of the aqueous urethane resin (c) examples include aliphatic diols such as 1,4-butanediol and 1,6-hexanediol, and aliphatic dicarboxylic acids such as adipic acid and sebacic acid.
- polycarbonate polyol include 1,6- Examples include polyether diols obtained by reacting diols such as hexanediol and 3-methyl-1,5-pentanediol with carbonates such as dimethyl carbonate.
- polyether polyols examples include ethylene oxide and propylene. Polyalkylene glycol obtained by ring-opening polymerization of Kisaido the like.
- a carboxyl group-containing diol as a part of the polyol and, if necessary, a carboxyl group neutralizer component.
- carboxyl group-containing diol include dimethylolpropionic acid, dimethylolbutanoic acid, dimethylolbutyric acid, dimethylolvaleric acid, and the like.
- the carboxyl group neutralizer component can be used without particular limitation as long as it is a basic compound that reacts with the carboxyl group of the carboxyl group-containing diol to form a hydrophilic salt.
- triethylamine examples thereof include tertiary amine compounds such as 2- (dimethylamino) ethanol, ammonia and the like.
- a tertiary amine compound is preferably used from the viewpoint of dispersion stability of the obtained aqueous urethane resin (c).
- examples of the polyisocyanate include aliphatic and alicyclic diisocyanates such as hexamethylene diisocyanate, dicyclohexylmethane diisocyanate, isophorone diisocyanate, and hydrogenated xylylene diisocyanate, and isocyanurate cycloadducts thereof.
- examples of the diol as the chain extender include ethylene glycol, 1,4-butanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, cyclohexanediol, and the like.
- examples thereof include ethylenediamine, propylenediamine, xylylenediamine and the like.
- melamine resin (d) examples include methylol melamines such as dimethylol melamine, trimethylol melamine, tetramethylol melamine, pentamethylol melamine, and hexamethylol melamine; alkyl etherified products of methylol melamine and alcohol; condensates of methylol melamine; Examples include etherified products with alcohol.
- examples of the alcohol include C 1-10 alkanols such as methyl alcohol, ethyl alcohol, propyl alcohol, isopropyl alcohol, butyl alcohol, isobutyl alcohol, 2-ethylhexyl alcohol, and the like.
- Examples of the melamine resin (d) include a melamine resin having an average of at least three methylol groups methylated per triazine nucleus; an alkyl ether containing a hydrophilic imino group having a weight average molecular weight of about 500 to about 1,000.
- a melamine resin or the like can be preferably used.
- a commercially available product can be used as the melamine resin (d).
- Examples of commercially available products include “Cymel 303”, “Cymel 323”, “Cymel 325”, “Cymel 327”, “Cymel 350”, “ “Cymel 370”, “Cymel 380”, “Cymel 385”, “Cymel 212”, “Cymel 253”, “Cymel 254” (above, trade name, manufactured by Nihon Cytec Industries, Inc.); “RESIMIN 735”, “RESIGIN 740” , “RESIMIN 741”, “RESIMIN 745”, “RESIMIN 746”, “RESIMIN 747”, “(manufactured by Monsanto, trade name);“ SUMIMAL M55 ”,“ SUMIMAR M30W ”,“ SUMIMAR M50W ”(above, Sumitomo Chemical Co., Ltd., trade name); “Uban 20SE” (Mitsui Chemicals, trade name) Can.
- sulfonic acid such as paratoluenesulfonic acid, dodecylbenzenesulfonic acid, dinonylnaphthalenesulfonic acid, etc .
- neutralized salt of the sulfonic acid and amine phosphate ester compound and amine Neutralized salts and the like can be used.
- the blend ratio of the water-based polyester resin (a), water-based acrylic resin (b), water-based urethane resin (c) and melamine resin (d) in the water-based first base coat paint (A) is the smoothness of the resulting multilayer coating film From the viewpoint of sharpness, chipping resistance, hardness, etc., the total resin solid content of 100 parts by mass of the aqueous polyester resin (a), the aqueous acrylic resin (b), the aqueous urethane resin (c) and the melamine resin (d) is As a reference, it is preferable to be within the following range.
- the water-based first base coat paint (A) is a water-based polyester resin (a), water-based acrylic resin (b), water-based urethane resin (c), and melamine resin (d), which are water-based by ordinary coating means. It can be prepared by mixing uniformly in a solvent.
- aqueous solvent deionized water or a mixture of deionized water and a hydrophilic organic solvent can be used.
- hydrophilic organic solvent examples include propylene glycol monomethyl ether.
- the aqueous first base coat paint (A) may further include a pigment, a curing catalyst, a thickener, an organic solvent, a basic neutralizer, an ultraviolet absorber, a light stabilizer, a surface conditioner, and an antioxidant.
- paint additives such as silane coupling agents can be blended.
- the pigment examples include coloring pigments and extender pigments.
- the color pigment include white pigments such as titanium oxide and zinc white; black pigments such as carbon black, acetylene black, lamp black, bone black, graphite, iron black, and aniline black; yellow iron oxide, titanium yellow, and chrome yellow Yellow pigments such as chromium oxide, monoazo yellow, condensed azo yellow, azomethine yellow, bismuth vanadate, benzimidazolone, isoindolinone, isoindoline, quinophthalone, benzidine yellow, permanent yellow; orange pigments such as permanent orange; red oxidation Iron, cadmium red, molybdenum red, naphthol AS azo red, ansanthrone, anthraquinonyl red, perylene maroon, quinacridone red pigment, diketopyrrolopyrrole, watching red, permanent Red pigments such as treads; purple pigments such as cobalt violet, quinacridone violet and dioxa
- extender pigment examples include barium sulfate, barium carbonate, calcium carbonate, aluminum silicate, gypsum, clay, silica, white carbon, diatomaceous earth, talc, magnesium carbonate, alumina white, gloss white, mica powder and the like. be able to.
- the pigments can be used alone or in combination of two or more. Especially, it is preferable to use a titanium oxide, barium sulfate, and a talc from a viewpoint of the chipping resistance of the obtained multilayer coating film.
- the amount of the pigment used varies depending on the type, but the aqueous polyester resin (a), aqueous acrylic resin (b), aqueous urethane resin (c) and melamine resin (d) in the aqueous first base coat paint (A) paint. Usually, it is preferably within the range of about 20 to about 120 parts by mass with respect to 100 parts by mass of the total resin solid content.
- the curing catalyst examples include organometallic compounds, acid compounds, and base compounds.
- organometallic compound examples include tetraisopropyl titanate, tetrabutyl titanate, lithium acetate, acetylacetone iron (III), zinc 2-ethylhexanoate, copper acetate, vanadium trichloride, tin octylate, dibutyltin diacetate, dibutyl Tin dioctoate, dibutyltin dilaurate, dibutyltin dimaleate, tetrabutyltin, dibutyltin oxide, tetra-n-butyl-1,3-diacetyloxydistanoxane, tetra-n-propyl-1,3-diacetyloxydistanoxane, Metal catalysts such as tetra-n-butyl-1,3-dilauryloxydistanoxane, and the like.
- organotin compounds such as tin octylate, dibutyltin diacetate, dibutyltin dilaurate, and distanoxanes are listed. preferable. Furthermore, when low temperature baking is required, dibutyltin diacetate is preferably used.
- the acid compound include p-toluenesulfonic acid, dodecylbenzenesulfonic acid, dinonylnaphthalenesulfonic acid, dinonylnaphthalenedisulfonic acid, butylphosphoric acid, octylphosphoric acid, and the like. A thing etc. are used suitably.
- Examples of the base compound include trimethylamine, triethylamine, dimethylcyclohexylamine, N-tetramethylhexane-1,6-diamine, N-pentamethyldiethylenetriamine, 2-methyl-1,4-diazabicyclo [2,2,2].
- Examples include compounds such as octane.
- the amount of the curing catalyst used varies depending on the type of the water-based polyester resin (a), water-based acrylic resin (b), water-based urethane resin (c) and melamine resin (d) in the water-based first base coat paint (A). Usually, it is preferably within the range of about 0.05 to about 5 parts by mass, based on 100 parts by mass of the total resin solid content.
- the thickener examples include inorganic thickeners such as silicate, metal silicate, montmorillonite, organic montmorillonite and colloidal alumina; polyacrylic acid soda, polyacrylic acid- (meth) acrylic acid ester Polyacrylic acid thickeners such as polymers (commercially available products include, for example, “Primal ASE-60” manufactured by Rohm and Haas, etc.); having urethane bonds and polyether chains in one molecule; In an aqueous medium, a urethane associative thickener that effectively increases the viscosity by associating the urethane bonds with each other (commercially available products such as “UH-814N” and “UH-” manufactured by Asahi Denka Kogyo Co., Ltd.).
- inorganic thickeners such as silicate, metal silicate, montmorillonite, organic montmorillonite and colloidal alumina
- polyacrylic acid soda such as polyacrylic acid- (meth) acrylic acid ester
- Fibrin derivative thickeners such as carboxymethylcellulose, methylcellulose, hydroxyethylcellulose; casein, sodium caseinate, casein Protein thickeners such as ammonium acid; Alginate thickeners such as sodium alginate; Polyvinyl thickeners such as polyvinyl alcohol, polyvinyl pyrrolidone, polyvinyl benzyl ether copolymer; Pluronic polyether, polyether dialkyl ester, poly Polyether thickeners such as ether dialkyl ethers and polyether epoxy modified products; Maleic anhydride copolymer thickeners such as partial esters of vinyl methyl ether-maleic an
- thickeners can be used alone or in combination of two or more.
- the amount used thereof is the water-based polyester resin (a), water-based acrylic resin (b), water-based urethane resin (c) and melamine resin (d) in the water-based first base coat paint (A).
- the total solid content of 100 parts by weight it is usually preferably in the range of 0.1 to 10 parts by weight, particularly 0.5 to 8 parts by weight, and more particularly 1 to 5 parts by weight.
- ultraviolet absorber those known per se can be used, and examples thereof include a benzotriazole-based absorbent, a triazine-based absorbent, a salicylic acid derivative-based absorbent, and a benzophenone-based absorbent.
- a benzotriazole-based absorbent examples thereof include a benzotriazole-based absorbent, a triazine-based absorbent, a salicylic acid derivative-based absorbent, and a benzophenone-based absorbent.
- these ultraviolet absorbers are used, from the viewpoint of weather resistance, yellowing resistance, etc.
- the amount used thereof is the aqueous polyester resin (a) in the aqueous first base coat paint (A), Based on 100 parts by mass of the total resin solid content of the aqueous acrylic resin (b), aqueous urethane resin (c) and melamine resin (d), usually 0.1 to 10 parts by mass, particularly 0.2 to 5 parts by mass, Further, it is particularly preferably in the range of 0.3 to 2 parts by mass.
- the light stabilizer examples thereof include hindered amine light stabilizers.
- the amount used thereof is the water-based polyester resin (a) in the water-based first base coat paint (A), water-based, from the viewpoint of weather resistance, yellowing resistance, etc. of the obtained multilayer coating film.
- the acrylic resin (b), the aqueous urethane resin (c) and the melamine resin (d) Based on 100 parts by mass of the total resin solid content of the acrylic resin (b), the aqueous urethane resin (c) and the melamine resin (d), usually 0.1 to 10 parts by mass, especially 0.2 to 5 parts by mass, Further, it is particularly preferably in the range of 0.3 to 2 parts by mass.
- the aqueous first base coat paint (A) can be applied on the cured electrodeposition coating film by a method known per se, for example, air spray coating, airless spray coating, rotary atomization coating, curtain coat coating, etc. Electrostatic application may be performed during coating. Among these, methods such as air spray coating and rotary atomization coating are particularly preferable.
- the coating amount of the aqueous first base coat paint (A) is generally 20 to 35 ⁇ m, particularly 25 to 30 ⁇ m in terms of the cured film thickness from the viewpoint of smoothness, sharpness, chipping resistance, hardness, etc. of the obtained multilayer coating film. It is preferable that the amount be in the range.
- Step (2) On the coating film of the uncured aqueous first base coat paint (A) formed in the step (1), the aqueous second base coat paint (B) is then applied without preheating, and the cured film thickness is 8 A second base coat film in the range of ⁇ 18 ⁇ m is formed.
- the aqueous second base coat paint (B) is a paint generally used for the purpose of imparting an excellent appearance to an object to be coated, and has, for example, an acrylic resin having a crosslinkable functional group such as a carboxyl group and a hydroxyl group.
- a resin component comprising a base resin such as a polyester resin, an alkyd resin, a urethane resin, or an epoxy resin, and a curing agent such as a polyisocyanate compound, a melamine resin, or a urea resin that may be blocked, a pigment, and other additives
- a paint which is dissolved or dispersed in an aqueous medium.
- a color pigment, a glitter pigment, or the like can be used as the pigment.
- coloring pigments include titanium oxide, zinc white, carbon black, molybdenum red, Prussian blue, cobalt blue, azo pigments, phthalocyanine pigments, quinacridone pigments, isoindoline pigments, and selenium (anthraquinone) pigments
- perylene pigments, dioxazine pigments, diketopyrrolopyrrole pigments, and the like may be used alone or in combination of two or more.
- the bright pigment include aluminum (including vapor-deposited aluminum), copper, zinc, brass, nickel, aluminum oxide, mica, aluminum oxide coated with titanium oxide and iron oxide, titanium oxide, and iron oxide.
- the glitter pigment is preferably scaly. Further, as the glitter pigment, those having a longitudinal dimension generally in the range of 1 to 100 ⁇ m, particularly 5 to 40 ⁇ m, and a thickness generally in the range of 0.001 to 5 ⁇ m, particularly 0.01 to 2 ⁇ m are suitable.
- the aqueous second base coat paint (B) may further include a curing catalyst, a thickener, an ultraviolet absorber, a light stabilizer, an antifoaming agent, a plasticizer, an organic solvent, a surface conditioner, an anti-settling agent, and the like.
- Usual paint additives can be contained. These paint additives can be used alone or in combination of two or more.
- the aqueous second base coat paint (B) can be applied on the uncured first base coat film by a method known per se, for example, air spray, airless spray, rotary atomization paint, curtain coat paint, etc. Electrostatic application may be performed during coating. Of these, methods such as air spray coating and rotary atomization coating are preferred.
- the coating amount of the aqueous second base coat paint (B) is such that the cured film thickness is in the range of 8 to 18 ⁇ m, particularly 10 to 15 ⁇ m, from the viewpoint of smoothness and sharpness of the resulting multilayer coating film. Preferably there is.
- the water-based second base coat paint (B) contains a glitter pigment
- the glitter pigment in the second base coat coating film is oriented and glittered if the coating amount is within the above range. It is possible to obtain an appearance having excellent design properties with a sense of brightness and light interference.
- the preheating temperature is usually about 40 to about 100 ° C., particularly about 50 to about 90 ° C., more particularly about 60 to about 80 ° C.
- the preheating time is preferably Usually, it is preferably 30 seconds to 15 minutes, particularly 1 to 10 minutes, more preferably 2 to 5 minutes.
- the aqueous second base coat paint (B) is a two-stage coating from the viewpoint of smoothness, sharpness, design and the like of the multilayer coating film obtained. It is preferable to paint by.
- an automobile painting line is generally divided into an undercoating zone, an intermediate coating zone, a base coat painting zone, and a clear coat painting zone.
- painting is usually divided into two or more times, and setting (stationary) is performed for 30 seconds to 3 minutes between each painting (stage) to prevent sagging of the paint. Measures are taken to obtain high paint quality.
- Each coating in the same zone is called a first stage, a second stage,... In order from the coating performed first.
- Such a coating method is generally called multi-stage coating. For example, when coating in the same zone is performed twice, it is called two-stage coating, and when it is performed three times, it is called three-stage coating.
- step (2) when the aqueous second base coat paint (B) is applied in the base coat coating zone, two stages are used from the viewpoint of the coating film appearance and the coating efficiency. It is preferable to carry out by painting.
- preheating is not performed from the end of the first stage coating to the start of the second stage coating in the above-described two-stage coating, for about 30 seconds to about 3 seconds. It is preferable to leave an interval of minutes.
- the solid content of the aqueous second base coat paint (B) is particularly in the range of 15 to 40% by mass, more particularly 20 to 35% by mass, from the viewpoint of the brightness of the resulting multilayer coating film. It is preferable to be within.
- the preheating temperature is usually about 40 to about 100 ° C., preferably about 50 to about 90 ° C., more particularly about 60 to about 80 ° C.
- the preheating time is usually It is preferably 30 seconds to 15 minutes, particularly 1 to 10 minutes, more preferably 2 to 5 minutes.
- a clear paint (C) is further applied to form a clear film having a cured film thickness in the range of 30 to 50 ⁇ m.
- thermosetting clear coat coating composition As the clear coating (C) used in the method for forming a multilayer coating film of the present invention, any thermosetting clear coat coating composition known per se for coating automobile bodies and the like can be used.
- thermosetting clear coating composition include an organic solvent-type thermosetting coating composition, an aqueous thermosetting coating composition, and a powder thermosetting containing a base resin having a crosslinkable functional group and a crosslinking agent. Can be mentioned.
- Examples of the base resin include an acrylic resin, a polyester resin, an alkyd resin, a urethane resin, an epoxy resin, and a fluorine resin having a crosslinkable functional group
- examples of the curing agent include polyisocyanate.
- examples thereof include a compound, a blocked polyisocyanate compound, a melamine resin, a urea resin, a carboxyl group-containing compound, a carboxyl group-containing resin, an epoxy group-containing resin, and an epoxy group-containing compound.
- Examples of the base resin / curing agent combination in the clear paint (C) include, for example, carboxyl group-containing resin / epoxy group-containing resin, hydroxyl group-containing resin / polyisocyanate compound, hydroxyl group-containing resin / blocked polyisocyanate compound, hydroxyl group-containing resin / A melamine resin etc. are mentioned.
- a combination of a carboxyl group-containing resin / epoxy group-containing resin hereinafter sometimes abbreviated as “acid / epoxy curable clear coating” and a hydroxyl group-containing resin / melamine.
- a combination of resins hereinafter sometimes abbreviated as “melamine curable clear paint” is preferred.
- the clear paint (C) may be a one-component paint or a multi-component paint such as a two-component urethane resin paint. However, from the viewpoint of pot life, a one-component paint is used. It is preferable to do.
- the clear coating (C) may further include a pigment, a curing catalyst, an ultraviolet absorber, a light stabilizer, a surface conditioner, an antioxidant, an antifoaming agent, and a fluidity adjustment as long as the transparency is not impaired.
- An agent or the like can be appropriately blended.
- the clear paint (C) can be applied on the second base coat film by a method known per se, for example, air spray, airless spray, rotary atomization paint, curtain coat paint, etc. Electricity may be applied. Of these, methods such as air spray coating and rotary atomization coating are preferred.
- the coating amount of the clear paint (C) is such that the cured film thickness is in the range of 25 to 50 ⁇ m, preferably 35 to 45 ⁇ m, from the viewpoint of smoothness, sharpness, weather resistance, etc. of the obtained multilayer coating film. Can be.
- an interval of about 1 to 60 minutes can be set at room temperature if necessary.
- Step (4) In the method for forming a multilayer coating film of the present invention, 3 of the uncured first base coat film, the uncured second base coat film and the uncured clear coating film formed in steps (1) to (3).
- the layer coating is heat cured at the same time.
- the curing of the first base coat film, the second base coat film, and the clear film can be performed by a usual baking means of the coating film, for example, hot air heating, infrared heating, high frequency heating and the like.
- the heating temperature is preferably about 80 to about 160 ° C., particularly about 100 to about 140 ° C.
- the heating time is usually 10 to 60 minutes, particularly preferably 15 to 40 minutes.
- Water-based first base coat paint (A): Production of water-based polyester resin (a) Production Example 1 In a reaction vessel equipped with a thermometer, thermostat, stirring device, reflux condenser and water separator, 193 parts of hexahydrophthalic anhydride, 208 parts of isophthalic acid, 183 parts of adipic acid, 376 parts of neopentyl glycol and 122 parts of trimethylolpropane The temperature was raised between 160 ° C. and 230 ° C. over 3 hours. Thereafter, the produced water was distilled off with a water separator and maintained at 230 ° C., and a condensation reaction was carried out until the acid value became 3 mgKOH / g or less.
- trimellitic anhydride was further added, reacted at 170 ° C. for 30 minutes, cooled to 60 ° C. or lower, and 2- (dimethylamino ) Add 0.9 equivalents of ethanol to acid groups, neutralize and then gradually add deionized water to give a hydroxyl value of 125 mg KOH / g, an acid value of 21 mg KOH / g, a number average molecular weight of 1,300, An aqueous polyester resin (a1) having a solid content of 45% and a pH of 7.5 was obtained.
- Production Examples 2-7 The hydroxyl value, acid value, and acid value shown in Table 1 were the same as in Production Example 1 except that the composition of the polybasic acid component (a-1) and the alcohol component (a-2) was as shown in Table 1 below.
- Aqueous polyester resins (a2) to (a7) having a number average molecular weight and having a solid content of 45% and a pH of 7.5 were obtained.
- manufacture of the stable water dispersion was difficult for water-based polyester resin (a6), subsequent evaluation was not implemented.
- Aqueous acrylic resin (b1) which is an acrylic emulsion having a solid content of 45 g / g and a solid content was obtained.
- Monomer emulsion 50 parts of deionized water, 0.9 part of “Aqualon KH-10”, 10 parts of styrene, 20.5 parts of ethyl acrylate, 60 parts of n-butyl acrylate, 8 parts of 2-hydroxyethyl acrylate, and acrylic acid 1 .5 parts were mixed and stirred to obtain a monomer emulsion.
- Production Examples 9-14 a water-based acrylic emulsion having a solid content of 45% having the hydroxyl value and acid value shown in Table 2 is the same as Production Example 8 except that the monomer composition is as shown in Table 2 below. Acrylic resins (b2) to (b7) were obtained.
- Production Example 15 In a reaction vessel equipped with a thermometer, thermostat, stirring device, reflux condenser, nitrogen inlet tube and dropping device, 50 parts of propylene glycol monoethyl ether was charged, stirred and mixed in a nitrogen stream, and heated to 85 ° C. Next, 100 parts of the monomer mixture described in Table 2 below and 2 parts of 2,2′-azobis (2,4-dimethylvaleronitrile) were dissolved, and this mixture was dropped into the reaction vessel over 3 hours. After completion of the dropping, aging was performed at 85 ° C. for 1 hour.
- Production of water-based first base coat paint (A) Production Example 16 28.9 parts of the aqueous polyester (a1) solution obtained in Production Example 1 (13 parts of resin solid content), 90 parts of “JR-806” (trade name, manufactured by Teica, rutile titanium dioxide), “Carbon MA— 100 ”(trade name, manufactured by Mitsubishi Chemical Co., Ltd., carbon black) and 42.4 parts of deionized water were mixed, the pH was adjusted to 8.0 with 2- (dimethylamino) ethanol, and then 30 with a paint shaker. A pigment dispersion paste was obtained by dispersing for a minute.
- ASE-60 trade name, manufactured by Rohm and Haas, thickener
- 2- (dimethylamino) ethanol and deionized water were added to the resulting mixture, pH 8.2, paint solids 47 %, Ford Cup No. 20 at 20 ° C.
- An aqueous first base coat paint (A-1) having a viscosity according to 4 of 30 seconds was obtained.
- Production Examples 17 to 42 aqueous first base coat paints (A-2) to (A-27) were obtained in the same manner as in Production Example 16, except that the composition of each resin was as shown in Table 3 below.
- Example 1 The aqueous first base coat paint (A-1) obtained in Production Example 16 was electrostatically applied to the above test object so as to have a cured film thickness of 27 ⁇ m and left for 6 minutes. Next, electrostatic coating is performed on the uncured first base coat film with an aqueous second base coat paint (B-1) shown below (Note 3) so that the cured film thickness becomes 7 ⁇ m (first stage). ), After an interval of 1.5 minutes, electrostatic coating was applied so that the cured film thickness became 7 ⁇ m (second stage), and after standing for 2 minutes, preheating was performed at 80 ° C. for 5 minutes.
- B-1 aqueous second base coat paint
- the clear coating (C-1) shown in the following (Note 4) was electrostatically coated so as to have a cured film thickness of 40 ⁇ m, and left for 7 minutes.
- a test plate was prepared by heating at 30 ° C. for 30 minutes to simultaneously cure the three-layer coating film. All electrostatic coatings were performed using a rotary atomizing electrostatic coating machine.
- Examples 2 to 13 and Comparative Examples 1 to 18 Examples 2 to 13 and Comparative Example 1 were carried out in the same manner as in Example 1, except that the aqueous first base coat paint (A-1) in Example 1 was changed to the aqueous first base coat paint shown in Table 4 below. ⁇ 18 test plates were prepared.
- Test method Smoothness: The smoothness of each test plate was evaluated based on the LW value measured by “Wave Scan” (trade name, manufactured by BYK Gardner). It shows that the smoothness of a coating surface is so high that LW value is small.
- a test plate was placed on a specimen holder of a stepping stone testing machine JA-400 type (trade name, chipping test device) manufactured by Suga Test Instruments Co., Ltd., at -20 ° C., from a distance of 55 cm to 0.2 MPa (2.0 kgf / 50 g of No. 7 crushed stone was made to collide with the test plate at an angle of 90 degrees with compressed air of cm 2 ). Thereafter, the obtained test plate was washed with water, dried, a cloth adhesive tape (manufactured by Nichiban Co., Ltd.) was attached to the coated surface, and after peeling it, the degree of occurrence of scratches on the coating film was visually observed, Evaluation was made according to the following criteria.
- Pencil hardness In accordance with JIS K 5600-5-4, a pencil lead is applied at an angle of about 45 ° to the test coating plate surface, and pressed firmly against the test coating plate surface to the extent that the core does not break. I moved it. The hardness symbol of the hardest pencil that did not tear the coating film was defined as pencil hardness.
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Abstract
Description
(1) 硬化電着塗膜上に、水性第1ベースコート塗料(A)を塗装し、硬化膜厚で20~35μmの第1ベースコート塗膜を形成せしめる工程;
(2) 第1ベースコート塗膜上に、予備加熱することなく、水性第2ベースコート塗料(B)を塗装し、硬化膜厚で8~18μmの第2ベースコート塗膜を形成せしめる工程;
(3) 予備加熱後、第2ベースコート塗膜上に、クリヤー塗料(C)を塗装し、硬化膜厚で25~50μmのクリヤー塗膜を形成せしめる工程;並びに、
(4) 第1ベースコート塗膜、第2ベースコート塗膜及びクリヤー塗膜を同時に加熱硬化させて、硬化塗膜を形成せしめる工程
を含む塗膜形成方法であって、
水性第1ベースコート塗料(A)は、水性ポリエステル樹脂(a)、水性アクリル樹脂(b)、水性ウレタン樹脂(c)及びメラミン樹脂(d)を、これらの樹脂の合計樹脂固形分100質量部を基準にして、樹脂(a)を15~35質量部、樹脂(b)を15~30質量部、樹脂(c)を15~30質量部及び樹脂(d)を15~35部含み、
水性ポリエステル樹脂(a)は、多塩基酸成分として、芳香族環及び/又は脂環族環を有する多塩基酸を、多塩基酸総量を基準にして、55~75モル%の割合で含有するものを用いて得られるものであって、酸価が15~25mgKOH/gであり且つ数平均分子量が1000~5000であり、
水性アクリル樹脂(b)は、モノマーの合計質量を基準にして、炭素数4~8のアルキル基を有する重合性不飽和モノマー45~80質量%、水酸基含有重合性不飽和モノマー1~10質量%、カルボキシル基含有重合性不飽和モノマー1~10質量%及びその他の重合性不飽和モノマー0~53質量%を含有するモノマー成分を乳化重合することにより得られるアクリルエマルションである
ことを特徴とする複層塗膜形成方法を提供するものである。
前記硬化電着塗膜上には、次いで、水性第1ベースコート塗料(A)が塗装され、硬化膜厚が20~35μmの範囲内の第1ベースコート塗膜が形成せしめられる。
水性第1ベースコート塗料(A)は、水性ポリエステル樹脂(a)、水性アクリル樹脂(b)、水性ウレタン樹脂(c)及びメラミン樹脂(d)を、これらの合計樹脂固形分100質量部に基いて、樹脂(a)を15~35質量部、樹脂(b)を15~30質量部、樹脂(c)を15~30質量部および樹脂(d)を15~35質量部含有する水性塗料である。
水性ポリエステル樹脂(a)は、多塩基酸成分として、芳香族環及び/又は脂環族環を有する多塩基酸を、多塩基酸成分の総量に基いて55~75モル%含有するものを用いて得られる、酸価が15~25mgKOH/gであり且つ数平均分子量が1000~5000であるポリエステル樹脂である。
多塩基酸成分(a-1)としては、水性第1ベースコート塗料(A)及び後述する水性第2ベースコート塗料(B)の混層を抑制し、平滑性、鮮映性、耐チッピング性及び硬度に優れた複層塗膜を形成せしめるという観点から、芳香族環を有する多塩基酸(以下、「芳香族多塩基酸」と称す)(a-1-1)及び/又は脂環族環を有する多塩基酸(以下、「脂環族多塩基酸」と称す)(a-1-2)を含有するものが使用される。多塩基酸成分(a-1)中の芳香族多塩基酸(a-1-1)及び脂環族多塩基酸(a-1-2)の合計含有量は、多塩基酸成分(a-1)の総量を基準として、一般に55~75モル%、特に60~70モル%の範囲内が好適である。
なお、本明細書において、「低級」とは、この語が付された有機基の炭素数が6個以下、好ましくは4個以下であることを意味する。
芳香族多塩基酸(a-1-1)及び脂環族多塩基酸(a-1-2)は、合計で、使用する多塩基酸成分の総量を基準にして、55~75モル%、特に60~70モル%の範囲内で使用することができる。
アルコール成分(a-2)としては、1分子中に少なくとも2個、好ましくは2もしくは3個の水酸基を有する多価アルコールを好適に使用することができる。該多価アルコールとしては、例えば、エチレングリコール、プロピレングリコール、ジエチレングリコール、トリメチレングリコール、テトラエチレングリコール、トリエチレングリコール、ジプロピレングリコール、1,4-ブタンジオール、1,3-ブタンジオール、2,3-ブタンジオール、1,2-ブタンジオール、3-メチル-1,2-ブタンジオール、2-ブチル-2-エチル-1,3-プロパンジオール、1,2-ペンタンジオール、1,5-ペンタンジオール、1,4-ペンタンジオール、2,4-ペンタンジオール、2,3-ジメチルトリメチレングリコール、テトラメチレングリコール、3-メチル-4,3-ペンタンジオール、3-メチル-1,5-ペンタンジオール、2,2,4-トリメチル-1,3-ペンタンジオール、1,6-ヘキサンジオール、1,5-ヘキサンジオール、1,4-ヘキサンジオール、2,5-ヘキサンジオール、ネオペンチルグリコール、1,4-シクロヘキサンジメタノール、トリシクロデカンジメタノール、水添ビスフェノールA、水添ビスフェノールF等の2価アルコール;これらの2価アルコールにε-カプロラクトン等のラクトン類を付加したポリラクトンジオール;ビス(ヒドロキシエチル)テレフタレート等のエステルジオール類;ビスフェノールAのアルキレンオキサイド付加物、ポリエチレングリコール、ポリプロピレングリコール、ポリブチレングリコール等のポリエーテルジオール類;グリセリン、トリメチロールエタン、トリメチロールプロパン、ジグリセリン、トリグリセリン、1,2,6-ヘキサントリオール、ペンタエリスリトール、ジペンタエリスリトール、ソルビトール、マンニット等の3価以上のアルコール;これらの3価以上のアルコールにε-カプロラクトン等のラクトン類を付加させたポリラクトンポリオール類等が挙げられる。
水性アクリル樹脂(b)としては、水性第1ベースコート塗料(A)及び後述する水性第2ベースコート塗料(B)の混層を抑制し、平滑性、鮮映性、耐チッピング性、硬度に優れた複層塗膜を形成せしめるという観点から、モノマーの合計質量を基準にして、炭素数4~8のアルキル基を有する重合性不飽和モノマー(b-1)45~80質量%、水酸基含有重合性不飽和モノマー(b-2)1~10質量%、カルボキシル基含有重合性不飽和モノマー(b-3)1~10質量%及びその他の重合性不飽和モノマー(b-4)0~53質量%を含有するモノマー成分を乳化重合することにより得られるアクリルエマルションが使用される。
水酸基含有重合性不飽和モノマー(b-2):1~10質量%、好ましくは2~9質量%、さらに好ましくは4~8質量%、
カルボキシル基含有重合性不飽和モノマー(b-3):1~10質量%、好ましくは1~8質量%、さらに好ましくは1~6質量%、
その他の重合性不飽和モノマー(b-4):0~53質量%、好ましくは8~47質量%、さらに好ましくは10~46質量%。
水性ウレタン樹脂(c)は、水を主たる溶媒もしくは分散媒とする水性媒体中に分散することができるポリウレタン樹脂を意味し、水性媒体中における形態としては、水溶性タイプ、コロイダルディスパーションタイプ、エマルションタイプ及びスラリータイプのいずれであってもよいが、なかでも、コロイダルディスパーションタイプ又はエマルションタイプであることが望ましい。
メラミン樹脂(d)としては、例えば、ジメチロールメラミン、トリメチロールメラミン、テトラメチロールメラミン、ペンタメチロールメラミン、ヘキサメチロールメラミン等のメチロールメラミン;メチロールメラミンとアルコールとのアルキルエーテル化物;メチロールメラミンの縮合物とアルコールとのエーテル化物等を挙げることができる。ここで、該アルコールとしては、例えば、メチルアルコール、エチルアルコール、プロピルアルコール、イソプロピルアルコール、ブチルアルコール、イソブチルアルコール、2-エチルヘキシルアルコール等のC1~10アルカノールが挙げられる。
水性ポリエステル樹脂(a):15~35部、好ましくは20~30部、
水性アクリル樹脂(b) :15~30部、好ましくは20~25部、
水性ウレタン樹脂(c) :15~30部、好ましくは20~25部、
メラミン樹脂(d) :15~35部、好ましくは20~30部。
工程(1)で形成される未硬化の水性第1ベースコート塗料(A)の塗膜上には、予備加熱することなく、次いで水性第2ベースコート塗料(B)が塗装され、硬化膜厚が8~18μmの範囲内の第2ベースコート塗膜が形成せしめられる。
水性第2ベースコート塗料(B)は、一般に被塗物に優れた外観を付与することを目的として使用される塗料であって、例えば、カルボキシル基、水酸基等の架橋性官能基を有する、アクリル樹脂、ポリエステル樹脂、アルキド樹脂、ウレタン樹脂、エポキシ樹脂等の基体樹脂と、ブロックされていてもよいポリイソシアネート化合物、メラミン樹脂、尿素樹脂等の硬化剤とからなる樹脂成分を、顔料、その他の添加剤と共に、水性媒体中に溶解ないし分散させて塗料化したものを使用することができる。
工程(2)で形成される未硬化の第2ベースコート塗膜上には、さらに、クリヤー塗料(C)が塗装され、硬化膜厚が30~50μmの範囲内のクリヤー塗膜が形成せしめられる。
本発明の複層塗膜形成方法において使用されるクリヤー塗料(C)としては、自動車車体等の塗装用としてそれ自体既知の熱硬化性クリヤーコート塗料組成物をいずれも使用することができる。該熱硬化性クリヤー塗料組成物としては、例えば、架橋性官能基を有する基体樹脂及び架橋剤を含有する、有機溶剤型熱硬化性塗料組成物、水性熱硬化性塗料組成物、粉体熱硬化性塗料組成物等を挙げることができる。
本発明の複層塗膜形成方法においては、工程(1)~(3)で形成される未硬化の第1ベースコート塗膜、未硬化の第2ベースコート塗膜及び未硬化のクリヤー塗膜の3層塗膜が同時に加熱硬化せしめられる。
水性ポリエステル樹脂(a)の製造
製造例1
温度計、サーモスタット、攪拌装置、還流冷却器及び水分離器を備えた反応容器に、ヘキサヒドロ無水フタル酸193部、イソフタル酸208部、アジピン酸183部、ネオペンチルグリコール376部及びトリメチロールプロパン122部を仕込み、160℃~230℃の間を3時間かけて昇温させた。その後、生成した水分を水分離器で留去しながら230℃に保持し、酸価が3mgKOH/g以下となるまで縮合反応させた。次いで、得られた縮合反応生成物にカルボキシル基を付加するために、さらに無水トリメリット酸30部を加え、170℃で30分間反応させた後、60℃以下に冷却し、2-(ジメチルアミノ)エタノールを酸基に対して0.9当量添加し、中和してから脱イオン水を徐々に添加することにより、水酸基価125mgKOH/g、酸価21mgKOH/g、数平均分子量1,300、固形分45%及びpH7.5の水性ポリエステル樹脂(a1)を得た。
多塩基酸成分(a-1)及びアルコール成分(a-2)の配合組成を下記表1に示すとおりとする以外は、製造例1と同様にして、表1に示す水酸基価、酸価及び数平均分子量を有する、固形分45%、pH7.5の水性ポリエステル樹脂(a2)~(a7)を得た。なお、水性ポリエステル樹脂(a6)は、安定な水分散体の製造が困難であったため、その後の評価は実施していない。
製造例8
温度計、サーモスタット、撹拌装置、還流冷却器、窒素導入管及び滴下装置を備えた反応容器に、脱イオン水60部及び「アクアロンKH-10」(商品名、第一工業製薬株式会社製、ポリオキシエチレンアルキルエーテル硫酸塩エステルアンモニウム塩、有効成分:97%)0.52部を仕込み、窒素気流中で撹拌混合し、80℃に昇温した。次いで、下記モノマー乳化物のうちの全量の1%及び3%過硫酸アンモニウム水溶液5部を反応容器内に導入し、80℃で15分間保持した。その後、残りのモノマー乳化物を3時間かけて、同温度に保持した反応容器内に滴下し、滴下終了後1時間熟成を行なった。その後、5% 2-(ジメチルアミノ)エタノール水溶液40部を反応容器内に徐々に加えながら30℃まで冷却し、100メッシュのナイロンクロスで濾過しながら排出し、水酸基価39mgKOH/g、酸価12mgKOH/g及び固形分45%のアクリルエマルションである水性アクリル樹脂(b1)を得た。
製造例8において、モノマーの配合組成を下記表2に示すとおりとする以外は、製造例8と同様にして、表2に示す水酸基価及び酸価を有する固形分45%のアクリルエマルションである水性アクリル樹脂(b2)~(b7)を得た。
温度計、サーモスタット、撹拌装置、還流冷却器、窒素導入管及び滴下装置を備えた反応容器に、プロピレングリコールモノエチルエーテル50部を仕込み、窒素気流中で撹拌混合し、85℃に昇温した。次いで、下記表2に記載のモノマー混合物100部と2,2’-アゾビス(2,4-ジメチルバレロニトリル)2部とを溶解し、この混合物を3時間かけて反応容器内に滴下した。滴下終了後、85℃で1時間熟成を行った。その後さらに2,2’-アゾビス(2,4-ジメチルバレロニトリル)0.5部及びプロピレングリコールモノメチルエーテル10部を溶解した溶解液を1時間かけて反応容器内に滴下した。滴下終了後1時間熟成を行った後、30℃まで冷却し、プロピレングリコールモノメチルエーテル10部を加え、100メッシュのナイロンクロスで濾過しながら排出し、水酸基価39mgKOH/g、酸価60mgKOH/g及び固形分60%の水性アクリル樹脂(b8)を得た。
製造例16
製造例1で得た水性ポリエステル(a1)の溶液28.9部(樹脂固形分13部)、「JR-806」(商品名、テイカ社製、ルチル型二酸化チタン)90部、「カーボンMA-100」(商品名、三菱化学社製、カーボンブラック)1部及び脱イオン水42.4部を混合し、2-(ジメチルアミノ)エタノールでpHを8.0に調整した後、ペイントシェーカーで30分間分散させて顔料分散ペーストを得た。次に、撹拌混合容器内において、得られた顔料分散ペースト162.3部(水性ポリエステル樹脂固形分13部)、製造例1で得た水性ポリエステル樹脂(a1)26.7部(樹脂固形分12部)、製造例8で得た水性アクリル樹脂(b1)55.6部(樹脂固形分25部)、「ユーコートUX-8100」(商品名、三洋化成工業社製、水性ウレタン樹脂、固形分35%)67.6部(樹脂固形分25部)、「サイメル325」(商品名、日本サイテックインダストリーズ社製、メラミン樹脂)31.3部(樹脂固形分25部)及び脱イオン水65部を均一に混合した。得られた混合物に「プライマルASE-60」(商品名、ロームアンドハース社製、増粘剤)、2-(ジメチルアミノ)エタノール及び脱イオン水を添加して、pH8.2、塗料固形分47%、20℃におけるフォードカップNo.4による粘度が30秒である水性第1ベースコート塗料(A-1)を得た。
製造例16において、各樹脂の配合組成を下記表3に示すとおりとする以外は、製造例16と同様にして水性第1ベースコート塗料(A-2)~(A-27)を得た。
(注2):「サイメル325」(商品名、日本サイテックインダストリーズ社製、メラミン樹脂)
合金化溶融亜鉛めっき鋼板に、「エレクロンHG-350E」(商品名、関西ペイント社製、熱硬化型エポキシ樹脂系カチオン電着塗料)を硬化膜厚で20μmになるように電着塗装し、170℃で30分間加熱して硬化させて試験用被塗物とした。
上記試験用被塗物に、製造例16で得た水性第1ベースコート塗料(A-1)を、硬化膜厚で27μmとなるように静電塗装し、6分間放置した。次いで、該未硬化の第1ベースコート塗膜上に、下記(注3)に示す水性第2ベースコート塗料(B-1)を、硬化膜厚で7μmとなるように静電塗装し(第1ステージ)、1.5分間のインターバルをおいた後、硬化膜厚で7μmとなるように静電塗装し(第2ステージ)、2分間放置後、80℃で5分間予備加熱を行なった。次いで、該未硬化の第2ベースコート塗膜上に、下記(注4)に示すクリヤー塗料(C-1)を硬化膜厚で40μmとなるように静電塗装し、7分間放置した後、140℃で30分間加熱して3層の塗膜を同時に硬化させることにより試験板を作製した。静電塗装は全て回転霧化型の静電塗装機を用いて行った。
(注4)クリヤー塗料(C-1): 「ルーガベークHK-4」(商品名、関西ペイント社製、メラミン硬化型クリヤー塗料、基体樹脂/硬化剤の組み合わせ:水酸基含有樹脂/メラミン樹脂)。
実施例1における水性第1ベースコート塗料(A-1)を下記表4に示す水性第1ベースコート塗料に変更した以外は、実施例1と同様に操作して、実施例2~13及び比較例1~18の試験板を作製した。
上記実施例1~13及び比較例1~18で得られた各試験板について、下記の試験方法により評価を行なった。その結果を下記表4に示す。
平滑性:
各試験板について、「Wave Scan」(商品名、BYK Gardner社製)によって測定されるLW値に基づいて、平滑性を評価した。LW値が小さいほど塗面の平滑性が高いことを示す。
各試験板について、上記「Wave Scan」によって測定されるSW値を用いて評価した。SW値が小さいほど塗面の鮮映性が高いことを示す。
スガ試験機社製の飛石試験機JA-400型(商品名、チッピング試験装置)の試片保持台に試験板を設置し、-20℃において、55cmの距離から0.2MPa(2.0kgf/cm2)の圧縮空気により、7号砕石50gを試験板に90度の角度で衝突させた。その後、得られた試験板を水洗し、乾燥し、塗面に布粘着テープ(ニチバン社製)を貼着し、それを剥離した後、塗膜のキズの発生程度等を目視で観察し、下記の基準により評価した。
1点:キズの大きさが極めて小さく、電着面や素地の鋼板が露出していない
1.5点:キズの大きさが小さく、電着面や素地の鋼板が露出していない
2点:キズの大きさは小さいが、電着面や素地の鋼板が露出している
2.5点:キズの大きさは大きく、素地の鋼板も大きく露出している
3点:キズの大きさはかなり大きく、素地の鋼板も大きく露出している
JIS K 5600-5-4に準じて、試験塗板面に対し約45°の角度に鉛筆の芯を当て、芯が折れない程度に強く試験塗板面に押し付けながら前方に均一な速さで約10mm動かした。塗膜が破れなかった最も硬い鉛筆の硬度記号を鉛筆硬度とした。
Claims (15)
- (1) 硬化電着塗膜上に、水性第1ベースコート塗料(A)を塗装し、硬化膜厚で20~35μmの第1ベースコート塗膜を形成せしめる工程;
(2) 第1ベースコート塗膜上に、予備加熱することなく、水性第2ベースコート塗料(B)を塗装し、硬化膜厚で8~18μmの第2ベースコート塗膜を形成せしめる工程;
(3) 予備加熱後、第2ベースコート塗膜上に、クリヤー塗料(C)を塗装し、硬化膜厚で25~50μmのクリヤー塗膜を形成せしめる工程;並びに、
(4) 第1ベースコート塗膜、第2ベースコート塗膜及びクリヤー塗膜を同時に加熱硬化させて、硬化塗膜を形成せしめる工程
を含む塗膜形成方法であって、
水性第1ベースコート塗料(A)は、水性ポリエステル樹脂(a)、水性アクリル樹脂(b)、水性ウレタン樹脂(c)及びメラミン樹脂(d)を、これらの樹脂の合計樹脂固形分100質量部を基準にして、樹脂(a)を15~35質量部、樹脂(b)を15~30質量部、樹脂(c)を15~30質量部及び樹脂(d)を15~35部含み、
水性ポリエステル樹脂(a)は、多塩基酸成分として、芳香族環及び/又は脂環族環を有する多塩基酸を、多塩基酸総量を基準にして、55~75モル%の割合で含有するものを用いて得られるものであって、酸価が15~25mgKOH/gであり且つ数平均分子量が1,000~5,000であり、
水性アクリル樹脂(b)は、モノマーの合計質量を基準にして、炭素数4~8のアルキル基を有する重合性不飽和モノマー45~80質量%、水酸基含有重合性不飽和モノマー1~10質量%、カルボキシル基含有重合性不飽和モノマー1~10質量%及びその他の重合性不飽和モノマー0~53質量%を含有するモノマー成分を乳化重合することにより得られるアクリルエマルションである
ことを特徴とする複層塗膜形成方法。 - 芳香族環を有する多塩基酸(a-1-1)がフタル酸、無水フタル酸、イソフタル酸、トリメリット酸及び無水トリメリット酸よりなる群から選ばれ、そして脂環族環を有する多塩基酸(a-1-2)が1,2-シクロヘキサンジカルボン酸、1,2-シクロヘキサンジカルボン酸無水物、1,3-シクロヘキサンジカルボン酸、1,4-シクロヘキサンジカルボン酸、4-シクロヘキセン-1,2-ジカルボン酸及び4-シクロヘキセン-1,2-ジカルボン酸無水物よりなる群から選ばれる請求項1に記載の複層塗膜形成方法。
- 芳香族環を有する多塩基酸(a-1-1)及び脂環族環を有する多塩基酸(a-1-2)を、(a-1-1)/(a-1-2)のモル比が35/65~0/100となる割合で使用する請求項1又は2に記載の複層塗膜形成方法。
- 水性ポリエステル樹脂(a)が18~23mgKOH/gの酸価又は1,200~4,000の数平均分子量を有する請求項1に記載の複層塗膜形成方法。
- 炭素数4~8のアルキル基を有する重合性不飽和モノマーがn-ブチル(メタ)アクリレート及び2-エチルヘキシル(メタ)アクリレートよりなる群から選ばれる請求項1に記載の複層塗膜形成方法。
- 水酸基含有重合性不飽和モノマーが2-ヒドロキシエチル(メタ)アクリレート、2-ヒドロキシプロピル(メタ)アクリレート、3-ヒドロキシプロピル(メタ)アクリレート及び4-ヒドロキシブチル(メタ)アクリレートよりなる群から選ばれる請求項1に記載の複層塗膜形成方法。
- カルボキシル基含有重合性不飽和モノマーがアクリル酸及びメタクリル酸よりなる群から選ばれる請求項1に記載の複層塗膜形成方法。
- 水性アクリル樹脂(b)が、モノマーの合計質量を基準にして、炭素数4~8のアルキル基を有する重合性不飽和モノマー50~75質量%、水酸基含有重合性不飽和モノマー2~9質量%、カルボキシル基含有重合性不飽和モノマー1~8質量%及びその他の重合性不飽和モノマー8~47質量%を含有するモノマー成分を乳化重合することにより得られるアクリルエマルションである請求項1に記載の複層塗膜形成方法。
- 水性アクリル樹脂(b)が4.5~50mgKOH/gの水酸基価、7~75mgKOH/gの酸価及び2,000~5,000,000の重量平均分子量を有する請求項1に記載の複層塗膜形成方法。
- 水性ウレタン樹脂(c)がコロイダルディスパーションタイプ又はエマルションタイプのウレタン樹脂である請求項1に記載の複層塗膜形成方法。
- 水性第1ベースコート塗料(A)が、水性ポリエステル樹脂(a)、水性アクリル樹脂(b)、水性ウレタン樹脂(c)及びメラミン樹脂(d)を、これらの樹脂の合計樹脂固形分100質量部を基準にして、樹脂(a)を20~30質量部、樹脂(b)を20~25質量部、樹脂(c)を20~25質量部及び樹脂(d)を20~30部含む請求項1に記載の複層塗膜形成方法。
- 工程(2)において、水性第2ベースコート塗料(B)を2ステージ塗装によって塗装する請求項1に記載の複層塗膜形成方法。
- クリヤー塗料(C)がメラミン硬化型クリヤー塗料又は酸/エポキシ硬化型クリヤー塗料である請求項1に記載の複層塗膜形成方法。
- 請求項1~14のいずれか1項に記載の方法により複層塗膜が形成された物品。
- 水性ポリエステル樹脂(a)、水性アクリル樹脂(b)、水性ウレタン樹脂(c)及びメラミン樹脂(d)を、これらの樹脂の合計樹脂固形分100質量部を基準にして、樹脂(a)を15~35質量部、樹脂(b)を15~30質量部、樹脂(c)を15~30質量部及び樹脂(d)を15~35部含み、
水性ポリエステル樹脂(a)は、多塩基酸成分として、芳香族環及び/又は脂環族環を有する多塩基酸を、多塩基酸総量を基準にして、55~75モル%の割合で含有するものを用いて得られるものであって、酸価が15~25mgKOH/gであり且つ数平均分子量が1,000~5,000であり、
水性アクリル樹脂(b)は、モノマーの合計質量を基準にして、炭素数4~8のアルキル基を有する重合性不飽和モノマー45~80質量%、水酸基含有重合性不飽和モノマー1~10質量%、カルボキシル基含有重合性不飽和モノマー1~10質量%及びその他の重合性不飽和モノマー0~53質量%を含有するモノマー成分を乳化重合することにより得られるアクリルエマルションである
水性第1ベースコート塗料。
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