JP2006169416A - Luster coating composition and method for forming laminated coating film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a luster coating composition containing luster pigment flakes composed of metal pieces obtained by crushing an evaporated metal film and capable of orienting the flakes in a plane in stabilized state and a method for forming a laminated coating film. <P>SOLUTION: The luster coating composition contains (a) an acrylic resin having a glass transition temperature of 0-45°C, a hydroxy value of 20-80 mgKOH/g and a weight-average molecular weight (Mw) of 200,000-1,000,000, (b) a curing agent, (c) a luster pigment composed of metal flakes obtained by crushing an evaporated metal film and (d) a solvent. The ratio of the luster pigment (c) in the composition (c/(a+b+c)) is 0.15-0.5. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a glittering paint composition capable of imparting a coating-like metallic gloss coating appearance and a method for forming a laminated coating film using the same.

  As a method capable of imparting a metallic luster of a plating tone by applying a paint, a method of applying a paint containing a glittering pigment obtained by pulverizing a deposited metal film to form a metal piece is known. In such a method, a method is generally adopted in which after forming an underlayer on an object to be coated such as an automobile wheel, this glittering paint is applied on the underlayer and then a clear paint is applied thereon. (Patent Document 1 and Patent Document 2).

  In such a coating method, the metallic luster of the plating tone is exhibited by orienting the glitter pigment in the glitter coating film in a planar shape. In order to orient the glitter pigment in a planar shape, after coating the foundation layer, the foundation layer is baked and cured, and then the glitter coating is applied, and after coating, the glitter coating is baked and cured. It is painted with clear paint. For this reason, each of the three coating films requires a baking process, and there is a problem that the manufacturing process becomes complicated.

  Patent Document 3 discloses a painting method in which a primer, a color base containing a bright pigment such as an aluminum flake pigment, and a top clear are sequentially coated on an aluminum wheel, and these are simultaneously baked and finished in three coats and one bake. ing. If a laminated coating film can be formed by such a three-coat one-bake method, the baking process is only one process, and the production efficiency can be increased. In Patent Document 4, a primer coating layer, a glitter coating layer, and a clear coating layer are each wet-on-wet using a glitter coating containing a glitter pigment obtained by pulverizing a deposited metal film into a metal piece. And a method of baking and forming a laminated coating film in three coats and one bake is disclosed.

However, in the method disclosed in Patent Document 4, it is difficult to orient the glitter pigment in a planar shape, so that a so-called particle-like sparkling coating film appearance is obtained and a metallic luster of a plating tone cannot be obtained. It was.
Japanese Patent Laid-Open No. 11-80620 JP 2002-263567 A JP 2003-192980 A JP 2004-141710 A

  An object of the present invention is to provide a glittering paint composition capable of obtaining a coating film in which a glittering pigment obtained by pulverizing a vapor-deposited metal film to form a metal piece in a stable state and in a planar state, and a laminate coating using the composition. It is to provide a method for forming a film.

  The glittering paint composition of the present invention comprises an acrylic resin (a) having a glass transition temperature of 0 to 45 ° C., a hydroxyl value of 20 to 80 mgKOH / g, and a weight average molecular weight (Mw) of 200,000 to 1,000,000, It contains the curing agent (b), the glitter pigment (c) obtained by pulverizing the deposited metal film into a metal piece, and the solvent (d), and the content ratio of the glitter pigment (c) [(c) / ( a + b + c)] is 0.15 to 0.5.

  The glittering paint composition of the present invention can stably maintain the orientation state of the glittering pigment even in the state of the coating film before curing. For this reason, even if another paint such as a clear paint is applied thereon by wet-on-wet, the orientation state of the glittering pigment in the coating film can be kept good. Therefore, after orienting the glitter pigment in a planar shape, the planar orientation state can be stably maintained, and a plated metallic luster appearance can be imparted to the object to be coated.

  Hereinafter, each component of the glittering paint composition of the present invention will be described.

<Acrylic resin (a)>
The acrylic resin (a) used in the present invention has a glass transition point of 0 to 45 ° C., a hydroxyl value of 20 to 80 mg KOH / g, and a weight average molecular weight (Mw) of 200,000 to 1,000,000. .

  As described above, the glass transition temperature (Tg) is in the range of 0 to 45 ° C, and preferably in the range of 5 to 35 ° C. If the glass transition temperature is too low, when it is laminated with another coating film by wet-on-wetting, a mixed layer occurs at the interface of the coating film, the orientation of the glitter pigment is lowered, and the hue becomes unfavorable. On the other hand, when the glass transition temperature is too high, film performance such as chipping resistance is lowered.

  As described above, the hydroxyl value is in the range of 20 to 80 mgKOH / g, and preferably in the range of 25 to 75 mgKOH / g. When the hydroxyl value is too low, the adhesion as a coating film is lowered. Conversely, when the hydroxyl value is too high, the water resistance is lowered, the solubility of the obtained resin is inferior, and the coating film appearance is lowered.

  The acid value of the acrylic resin (a) is preferably in the range of 10 to 50 mgKOH / g, more preferably in the range of 15 to 35 mgKOH / g. When the acid value is too low, the adhesion as a coating film is lowered. Conversely, when the acid value is too high, the water resistance is lowered.

  As described above, the weight average molecular weight (Mw) of the acrylic resin (a) is in the range of 200,000 to 1,000,000, more preferably in the range of 250,000 to 800,000. If the weight average molecular weight is too low, the effect of the present invention in which the orientation of the glitter pigment is stably maintained in the state of the coating film before curing may not be sufficiently obtained. If the weight average molecular weight is too high, the solubility of the coating composition in a solvent may deteriorate, or the handling property may deteriorate, such as the viscosity of the coating composition becoming too high. The weight average molecular weight can be determined by a GPC method using styrene polymer as a standard.

  Examples of the acrylic resin (a) include a homopolymer or a copolymer obtained by radical polymerization of a radical polymerizable monomer mainly composed of an acrylic ester and / or a methacrylic ester. The polymer molecule preferably has a crosslinkable functional group such as a hydroxyl group or a carboxyl group.

  Examples of the acrylic acid ester and methacrylic acid ester include acrylic acid or monoester of methacrylic acid and a monovalent alcohol having 1 to 20 carbon atoms. Specifically, methyl acrylate, methyl methacrylate, acrylic Examples include ethyl acetate, ethyl methacrylate, propyl acrylate, propyl methacrylate, butyl acrylate, butyl methacrylate, hexyl acrylate, hexyl methacrylate, lauryl acrylate, and lauryl methacrylate.

  Examples of the monomer containing a crosslinkable functional group include hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, caprolactone hydroxyethyl acrylate. , Caprolactone hydroxyethyl methacrylate, acrylic acid, methacrylic acid, maleic acid, fumaric acid and the like. In addition to the above, other monomers capable of radical copolymerization with the above-mentioned monomers, such as acrylonitrile, methacrylonitrile, styrene, vinyl acetate, vinyl methyl ether, vinyl chloride, vinylidene chloride, ethylene, propylene An unsaturated compound having one or more polymerizable double bonds in one molecule can be used.

  The acrylic resin (a) in the present invention has a high average molecular weight as described above. Therefore, it may be difficult to synthesize by solution polymerization, and it can be produced by a polymerization method such as emulsion polymerization (emulsion polymerization), suspension polymerization, NAD (non-aqueous dispersion) polymerization, or bulk polymerization. When manufactured by emulsion polymerization, it can be obtained as an emulsion resin. When the acrylic resin (a) is an emulsion resin, the water during polymerization can be absorbed by adding a glycol solvent as the solvent (d), as described later, and the coating composition is suitably dissolved. Can be prepared.

<Curing agent (b)>
The curing agent (b) in the present invention is a resin or compound for crosslinking and curing the acrylic resin (a).

  As the curing agent (b), for example, one or more selected from amino resins, polyisocyanate compounds, blocked polyisocyanate compounds and polycarboxylic acid compounds are preferably used. The amino resin reacts with the acrylic resin (a) by heating to form a three-dimensional cured coating film. Examples of amino resins include methylolated amino resins obtained by reacting amino components such as melamine, urea, benzoguanamine, acetoguanamine, steroguanamine, spiroguanamine, and dicyandiamide with aldehydes. Examples of aldehydes include formaldehyde, paraformaldehyde, acetaldehyde, and benzaldehyde. In addition, those obtained by etherifying this methylolated amino resin with an appropriate alcohol can be used. Examples of alcohols used for etherification include methyl alcohol, ethyl alcohol, n-propyl alcohol, i-propyl alcohol, and n-butyl alcohol. I-butyl alcohol, 2-ethylbutanol, 2-ethylhexanol and the like. As the amino resin, a melamine resin is preferable, and in particular, a methylolated melamine resin in which at least a part of a methylol group is alkyl etherified is preferable.

  The polyisocyanate compound may be a free isocyanate compound or a blocked isocyanate compound. Examples of the polyisocyanate compound having a free isocyanate group include aliphatic diisocyanates such as hexamethylene diisocyanate or trimethylhexamethylene diisocyanate, cyclic aliphatic diisocyanates such as xylene diisocyanate or isophorone diisocyanate, tolylene diisocyanate or 4,4 ′. -Organic diisocyanates such as aromatic diisocyanates such as diphenylmethane diisocyanate itself, or adducts of excess amounts of these organic diisocyanates with polyhydric alcohols, low molecular weight polyester resins or water, or the weights of the above organic diisocyanates. Examples thereof include an isocyanate and a biuret body. Examples of such typical commercial products are “Bernock D-750, -800, DN-950, -970 or 15-455” (above, Dainippon Ink and Chemicals, Inc.), “Dismodule L, "N, HL, or N3390" (product of Bayer, West Germany), "Takenate D-102, -202, -110 or -123N" (product of Takeda Pharmaceutical Co., Ltd.), "Coronate EH, L, HL or 203" (Nippon Polyurethane Industry Co., Ltd. product) or "Duranate 24A-90CX" (Asahi Kasei Kogyo Co., Ltd. product).

  Examples of the blocked polyisocyanate compound include those obtained by blocking the above-mentioned polyisocyanate compound having a free isocyanate group with a known blocking agent such as oxime, phenol, alcohol, lactam, malonic ester, mercaptan and the like.

<Brightness pigment (c)>
The glitter pigment (c) used in the present invention is a glitter pigment obtained by pulverizing a deposited metal film into a metal piece. As such bright pigments, bright pigments used in Patent Documents 1, 2, and 4 can be used. Such a glitter pigment uses, for example, a plastic film such as OPP (oriented polypropylene), CPP (crystalline polypropylene), PET (polyethylene terephthalate) as a base film, and a release agent is applied thereon, It can manufacture by performing metal vapor deposition on top, forming a vapor deposition metal film, peeling this vapor deposition metal film from a base film, and grind | pulverizing this. Examples of these commercially available products include METASHEEN 1800 (manufactured by WOLSTHOLME), METALURE L-55700 (manufactured by ECKART WERKE), and the like.

<Solvent (d)>
The solvent (d) can be used without particular limitation as long as it dissolves or disperses the acrylic resin (a) and the curing agent (b) and does not substantially react with them.

  Examples of the organic solvent include hydrocarbon solvents such as heptane, toluene, xylene, octane and mineral spirit, ester solvents such as ethyl acetate, n-butyl acetate, isobutyl acetate, methyl cellosolve acetate and butyl carbitol acetate, and methyl ethyl ketone. , Ketone solvents such as methyl isobutyl ketone and diisobutyl ketone, alcohol solvents such as methanol, ethanol, isopropanol, n-butanol, sec-butanol and isobutanol, n-butyl ether, dioxane, ethylene glycol monomethyl ether, ethylene glycol monoethyl An ether solvent such as ether can be used.

  When an emulsion resin is used as the acrylic resin (a), as described above, it is preferable to use a glycol solvent that can absorb water contained in the polymerization as the solvent (d). Examples of such glycol solvents include propylene glycol monomethyl ether, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether, propylene glycol monoethyl ether acetate, butyl cellosolve, butyl cellosolve acetate, and 3-methyl-3-methoxybutanol. Can be mentioned.

<Coating composition>
In the glittering paint composition of the present invention, the content ratio [(c) / (a + b + c)] of the glittering pigment (c) is in the range of 0.15 to 0.5, and more preferably 0.18 to Within the range of 0.4. This content ratio corresponds to so-called PWC (pigment weight concentration). If the content ratio of the glitter pigment is lowered, the feeling of plating is lowered, so that the hue is not preferable, and conversely, if the content ratio of the glitter pigment (c) is too high, the coating performance such as adhesion and chipping properties is improved. descend.

  In the coating composition of the present invention, the ratio [(a) / (b)] of the acrylic resin (a) and the curing agent (b) is preferably in the range of 95/5 to 70/30, more preferably. Is in the range of 90/10 to 80/20. By setting it within such a range, a coating film with good performance can be obtained.

  In the coating composition of the present invention, the concentration [(a + b) / (a + b + d)] of the acrylic resin (a) and the curing agent (b) in the solvent (d) at the time of spray coating is 0.5 / 100 to 5 It is preferably in the range of 0.0 / 100, more preferably in the range of 1.0 / 100 to 4.0 / 100. If these concentrations are too low, the amount of solvent discharged increases, which is preferable for the environment. Conversely, if these concentrations are too high, the orientation of the glitter pigment tends to decrease, and the hue may be unfavorable.

  In the glittering coating film formed by coating the coating composition of the present invention, the coating film contracts in the thickness direction by evaporating and removing the solvent (d) after coating. At this time, the glitter pigment (c) contained in the coating film is oriented in a planar shape as the coating film shrinks in the thickness direction. That is, the glitter pigment (c) in the state of rising or tilting in the coating film is gradually oriented in the horizontal direction as the coating film contracts in the thickness direction, and is oriented in a planar shape. become. In this way, the glitter pigment (c) is oriented in a planar shape, whereby a plating-like metallic luster can be imparted to the coating film. In the glittering paint composition of the present invention, since the acrylic resin (a) having a high average molecular weight is used as described above, as the solvent (d) evaporates, the acrylic resin (a) inherently has a high viscosity. This makes it possible to control the movement of the glitter pigment (c) in the coating film. For this reason, according to the present invention, the planar alignment state can be stably maintained.

  Therefore, even if another paint is applied thereon, it is less affected by this, so that the planar orientation of the glitter pigment can be stably maintained.

  The coating composition of the present invention may contain a resin serving as a binder and other additives as necessary in the coating composition. Examples of the binder resin include a vinyl chloride vinyl acetate copolymer resin, a polyester resin, and a cellulose acetate butyrate resin. Examples of the additive include waxes such as polyethylene wax and polypropylene wax, plasticizers, dispersants, and the like. May be included.

<Formation method of laminated coating film>
The method for forming a laminated coating film of the present invention comprises a step of coating a colored base paint on an article to form a base coating film, and the glitter coating composition of the present invention on the base coating film. Apply a wet-on-wet process so that the dry film thickness is 2 μm or less, and apply a clear paint on the bright paint film by wet-on-wet. It is characterized by comprising a step of forming and a step of heating the base coating film, the glitter coating film and the clear coating film and baking these coating films simultaneously.

  According to the forming method of the present invention, a laminated coating film comprising a base coating film, a glitter coating film, and a clear coating film is formed by a three-coat one-bake method that exhibits a good plating-like metallic luster. can do. This is because, as described above, in the glitter coating film before curing formed using the glitter paint of the present invention, the glitter pigment is oriented in a planar state in a good state, and the clear paint is formed thereon. This is because even when the coating is applied wet-on-wet, the orientation state of the excellent glitter pigment can be stably maintained.

  In the glittering paint of the present invention, the acrylic resin (a) having a high molecular weight is used as described above, and a solvent that hardly dissolves the acrylic resin (a) is used as a solvent for the base paint and the clear paint. Further, the effect of the present invention can be enhanced.

<Base paint>
The base paint in the present invention is a colored base paint, and is preferably a dark-colored base paint in order to give a good plated metallic luster to the laminated coating film. Specifically, it is preferable that the color be black, gray, or navy.

  The base paint can contain a film-forming resin, a curing agent, various organic and inorganic color pigments, and, if necessary, extender pigments.

  As said film forming resin, it is preferable that number average molecular weights are 2000-30000, More preferably, it is 3000-25000. If it is less than 2000, workability and curability are not sufficient, and if it exceeds 30000, the non-volatile content at the time of coating becomes too low, and workability is worsened. In the present specification, the molecular weight is determined by a GPC method using a styrene polymer as a standard.

  Furthermore, it is preferable that the said film-forming resin has a hydroxyl value of 20-180, More preferably, it is 30-160. When the upper limit is exceeded, the water resistance of the coating film decreases, and when the lower limit is exceeded, the curability of the coating film decreases. Moreover, it is preferable that it has an acid value of 10-80 mgKOH / g, More preferably, it is 12-60 mgKOH / g. When the upper limit is exceeded, the water resistance of the coating film decreases, and when the lower limit is exceeded, the curability of the coating film decreases.

  Examples of the film-forming resin include film-forming resins such as acrylic resin, polyester resin, alkyd resin, polyether resin, polyolefin resin, and urethane resin, and one or more of them can be used. It can be used in combination. Furthermore, it is preferable to use an acrylic resin and / or a polyester resin from the viewpoint of coating performance such as weather resistance and water resistance.

  Preferred examples of the curing agent include amino resins, blocked isocyanate resins, epoxy compounds, aziridine compounds, carbodiimide compounds, and oxazoline compounds. A butylated and / or butylated melamine resin and / or a blocked isocyanate resin are generally used in view of various performances and costs of the obtained coating film.

  Content of the said hardening | curing agent is 20 to 50 weight% with respect to the total solid with a film-forming resin. When the content is less than 20% by weight, the curability becomes insufficient, and when the content exceeds 50% by weight, the cured film becomes too hard and brittle.

  Examples of the colored pigment include organic azo chelate pigments, insoluble azo pigments, condensed azo pigments, diketopyrrolopyrrole pigments, benzimidazolone pigments, phthalocyanine pigments, indigo pigments, perinone pigments, and perylene pigments. Pigments, dioxane pigments, quinacridone pigments, isoindolinone pigments, metal complex pigments, and the like. Examples of inorganic pigments include yellow lead, yellow iron oxide, bengara, carbon black, and titanium dioxide. In addition, barium sulfate, clay, talc and the like are used as extender pigments. Further, flat pigments such as aluminum powder and mica powder may be added.

  The total pigment concentration (PWC) in the paint including the pigment is 0.1 to 50%, preferably 0.5% to 40%, and more preferably 1.0 to 30. %. When the upper limit is exceeded, the appearance of the coating film deteriorates.

  In addition, a viscosity control agent can be added to the base coating material in order to prevent familiarity with the glittering coating composition and to ensure coating workability. As the viscosity control agent, those generally showing thixotropy can be used, for example, a fatty acid amide swelling dispersion, an amide fatty acid, a polyamide-based one such as a long-chain polyaminoamide phosphate, a colloidal swelling dispersion of polyethylene oxide Polyethylene-based materials, organic acid smectite clays, organic bentonite-based materials such as montmorillonite, inorganic pigments such as aluminum silicate and barium sulfate, flat pigments that develop viscosity depending on the shape of the pigment, cross-linked or non-cross-linked Resin particles and the like can be mentioned as viscosity control agents.

  In addition to the above components, additives usually added to the paint, for example, surface conditioners, antioxidants, antifoaming agents, binder resins such as cellulose acetate butyrate, etc. are blended in the base paint used in the present invention. May be. These compounding amounts are within the range known to those skilled in the art.

  The method for producing the coating composition used in the present invention is not particularly limited, including those described above and below, and a compound such as a pigment is kneaded and dispersed using a sand grind mill, ball mill, roll mill or the like. All methods well known to those skilled in the art can be used.

<Clear paint>
The clear paint used in the present invention is not particularly limited, and a general clear paint can be used.

  The clear paint may be a solvent-type paint, a water-based paint, a water-dispersed paint, or a powder paint. The clear paint may be a colored clear paint.

  The components of the clear coating are not particularly limited, and those containing a film-forming thermosetting resin and a curing agent can be used.

  Preferred examples of the solvent-type clear paint include acrylic resin and / or a combination of a polyester resin and an amino resin, or an acrylic resin having a carboxylic acid / epoxy curing system and / or from the viewpoint of transparency or acid etching resistance. A polyester resin etc. are mentioned.

  Examples of the water-based clear paint include those containing a resin obtained by neutralizing a film-forming resin contained in the solvent-type clear paint described above as an example with a base to make it water-based. be able to. This neutralization can be carried out by adding tertiary amines such as dimethylaminoethanol and triethylamine before or after polymerization.

  On the other hand, as the powder type clear coating material, a normal powder coating material such as thermoplastic and thermosetting powder coating material can be used. A thermosetting powder coating is preferred because a coating film having good physical properties can be obtained. Specific examples of the thermosetting powder coating material include epoxy-based, acrylic-based, and polyester-based powder clear coatings, and acrylic-based powder clear coatings having good weather resistance are particularly preferable.

  As a powder type clear coating used in the present invention, there is no volatile matter at the time of curing, a good appearance is obtained, and since yellowing is small, an epoxy-containing acrylic resin / polycarboxylic acid type powder coating is provided. Particularly preferred.

  Furthermore, it is preferable that a viscosity control agent is added to the clear paint in order to ensure painting workability as in the above base paint. As the viscosity control agent, those generally showing thixotropy can be used. As such a thing, what was mentioned by the description about the above-mentioned base coating material can be used, for example. Moreover, a curing catalyst, a surface conditioner, etc. can be included if necessary.

<Coating of base paint, glitter paint and clear paint>
The method for applying the base paint, the glitter paint, and the clear paint is not particularly limited, and a general painting method can be employed. For example, a base paint, a glitter paint and a clear paint can be formed on an object by wet-on-wet using an air spray coater or an electrostatic coater.

  When applying the base paint, it is preferable to use an electrostatic coating machine in order to improve workability and appearance. As an example of this electrostatic coating machine, for example, an AA electrostatic spray coating called “react gun” or a rotary atomizing electrostatic coating machine can be cited. These include multi-stage coating, preferably 2-3 stage coating, and a coating film can be formed by a coating method combining air electrostatic spray coating and a rotary atomizing electrostatic coating machine. .

  In the present invention, the film thickness of the dry paint film by the base paint varies depending on the desired application, but the dry film thickness of the paint film can be set to 5 to 35 μm, preferably 7 to 25 μm. If the film thickness of the base coating film exceeds 35 μm, the sharpness may be deteriorated, or unevenness or flow may occur in the coating film. Neither of these is preferable because a discontinuous state of the film may occur.

  Further, the glitter paint and the clear paint are applied on the uncured base paint film by wet on wet to form the glitter paint film and the clear paint film.

  In the present invention, the dry film thickness of the coating film formed from the glittering paint varies depending on the desired application, but the dry film thickness of the coating film can be set to 2 μm or less, preferably 0.1 to 1. It is in the range of 0 μm. If the film thickness of the base coating film exceeds 2 μm, the plating feeling may decrease, or unevenness or flow may occur in the coating film, which is not preferable.

  In the coating method of the present invention, the clear coating film that is applied after the formation of the glitter coating film smoothes unevenness caused by the glitter coating film, flickering that occurs when the glitter pigment is included, and plating. Form to create a feeling. Specifically, as a coating method, it is preferable to form a coating film using a rotary atomizing electrostatic coating machine such as a bell or μμ bell.

  The dry film thickness of the clear coating film formed by the clear coating is generally preferably about 10 to 80 μm, more preferably about 20 to 60 μm. If the upper limit is exceeded, defects such as cracks or sagging may occur during coating, and if the lower limit is not reached, the underlying irregularities cannot be concealed.

  After applying the base paint, the glitter paint and the clear paint, it is preferable to leave it for a predetermined time and set it. It is preferable to evaporate at least a part of the solvent (d) contained in the coating film by such setting. The setting time is preferably about 2 to 20 minutes.

  In order to promote evaporation of the solvent (d), preheating is preferably performed as necessary. In particular, it is preferable to preheat as necessary after applying the glittering paint composition of the present invention. By preheating, evaporation of the solvent (d) contained in the paint can be promoted, and maintenance of the orientation state of the glitter pigment in the coating film can be further enhanced. The preheating temperature is preferably about 30 to 80 ° C., and the preheating time is preferably about 1 to 5 minutes.

<Coating material>
The object to be coated in the present invention is not particularly limited, and a metal substrate, a plastic substrate, or the like can be used as the object to be coated. Examples of the metal substrate include automobile wheels such as aluminum wheels.

  Since the aluminum wheel is an aluminum casting, there are large irregularities on its surface. If such a large unevenness exists, it may be difficult to form a metallic luster of a plating tone. If such a large unevenness exists on the substrate, a primer is applied on the object to be coated. It is preferable to smooth the surface. As the primer, it is preferable to use a powder paint capable of forming a thick coating film. Therefore, in such a case, it is preferable to apply the base paint after applying the powder paint on the object to be coated and baking it.

<Baking of laminated coating film>
According to the method of the present invention, the base coating film, the glitter coating film, and the clear coating film are applied wet-on-wet to form these multilayer coating films, and then the multilayer coating films are heated and baked at the same time. The baking temperature is appropriately selected depending on the kind of the film-forming resin in each paint, but it is generally preferable to heat to a temperature in the range of 80 to 160 ° C. When the object to be coated is a plastic substrate, it may not be heated to a high temperature, so it is preferable to bake by heating to a temperature in the range of 80 to 100 ° C. In this case, the coating film-forming resin in the base paint, the glitter paint, and the clear paint is preferably a two-component mixed type isocyanate curable resin. By using such a resin, baking at a low temperature as described above is possible.

<Article of the present invention>
The article of the present invention is characterized in that a multilayer coating film is formed on an article to be coated by the method for forming a multilayer coating film of the present invention.

  That is, the article of the present invention is formed from the colored base coating film formed on the article to be coated and the glitter coating composition of the present invention, and has a dry film thickness of 2 μm or less on the base coating film. And a laminated coating film comprising a glitter coating film provided on the surface and a clear coating film formed on the glitter coating film.

  By using the glittering paint composition of the present invention, a glittering coating film having a glittery surface orientation can be easily formed, and a plating-like metallic luster can be imparted to an object to be coated.

  According to the method for forming a laminated coating film of the present invention, for example, even when a laminated coating film is formed by a 3-coat 1-bake method, a good plating-like metallic luster can be imparted to an object.

  Hereinafter, the present invention will be described with reference to specific examples, but the present invention is not limited to the following examples.

[Preparation of resin solution of acrylic resin (a)]
Using the monomer composition, initiator, solvent, and water shown in Table 1 and Table 2 and polymerizing the monomer at the predetermined temperature and time shown in Table 1 and Table 2, the resin solution of the acrylic resin (a) Prepared. Resin solution A to resin solution K were prepared by emulsion polymerization. The resin solution L was prepared by solution polymerization.

  In resin production by emulsion polymerization, 126.95 parts of ion-exchanged water was added to a reaction vessel, and the temperature was raised to a predetermined temperature while mixing and stirring in a nitrogen stream. Next, 5 parts of styrene monomer, 28.46 parts of methyl methacrylate, 39.12 parts of ethyl acrylate, 7.42 parts of 2-hydroxyethyl methacrylate, 0.5 part of Aqualon HS-20, Adekalya soap NE-20 0 A monomer emulsion consisting of .5 parts and 80 parts of ion-exchanged water and an initiator solution consisting of 0.24 parts of ammonium persulfate and 10 parts of ion-exchanged water were dropped into the reaction vessel in parallel over 2 hours. After completion of dropping, the mixture was aged at the same temperature for 1 hour. Further, a monomer emulsion comprising 15.07 parts of ethyl acrylate, 1.86 parts of 2-hydroxyethyl methacrylate, 3.07 parts of methacrylic acid, 0.2 part of Aqualon HS-20 and 10 parts of ion-exchanged water at the same temperature. And an initiator solution consisting of 0.06 part of ammonium persulfate and 10 parts of ion-exchanged water were dropped into the reaction vessel in parallel over 0.5 hours. After completion of dropping, the mixture was aged at the same temperature for 2 hours. Subsequently, after cooling to 40 degreeC and filtering with a 400 mesh filter, 0.16 part of dimethylaminoethanol was added and the resin solution A was obtained. Resin solution B to resin solution K were also produced in the same manner.

  In addition, Adekaria soap NE-20 and Aqualon HS-10 shown in Table 1 and Table 2 have the following contents.

Adekaria soap NE-20: manufactured by Asahi Denka Co., Ltd., oxyethylene emulsifier, 80 wt% aqueous solution ・ Aqualon HS-10: manufactured by Daiichi Kogyo Seiyaku Co., Ltd., phenyl ether emulsifier Resin component in resin solution, glass transition temperature The hydroxyl value (OH value), acid value, and weight average molecular weight were measured and shown in Tables 1 and 2.

  Resin solutions A to F shown in Table 1 were used in the following examples. Moreover, the resin solutions GL shown in Table 2 were used in each comparative example shown below. Resin solutions G and H have glass transition temperatures that are out of the scope of the present invention. Further, the resins of the resin solutions I and J have an OH value outside the scope of the present invention. In addition, the resins of the resin solutions K and L are out of the scope of the present invention in weight average molecular weight.

(Preparation of glitter paint composition)
Using the resin solutions A to L prepared as described above, the glittering paint compositions of Examples 1 to 7 and Comparative Examples 1 to 6 were prepared with the formulations shown in Tables 3 and 4.

  The symbols shown in Tables 3 and 4 are as follows.

METASHEEN 1800: Aluminum pigment paste obtained by pulverizing an aluminum vapor-deposited film, manufactured by WOLSTENHOLME, aluminum content of 10% by weight
・ Uban 20N60: Melamine resin varnish, manufactured by Mitsui Chemicals, solid content 20% by weight
Modaflow: manufactured by Monsanto Co., Ltd., acrylic resin surface conditioner Tables 3 and 4 show the ratio of acrylic resin / melamine resin and pigment weight concentration (PWC) in each coating composition.

[Formation of laminated coating film]
Chromic acid-treated aluminum steel plate (AC4C) with a thickness of 10 mm, length of 7 cm and width of 15 cm, acrylic powder coating (trade name “Powdax A400 Clear” manufactured by Nippon Paint Co., Ltd.), After electrostatic coating to 100 μm, baking was performed at 160 ° C. for 30 minutes.

Next, an acrylic resin black base paint (manufactured by Nippon Paint Co., Ltd., trade name “Super Lac M100 Black”) was applied on the coating film formed of the powder paint so that the dry film thickness was 15 μm. After setting for 5 minutes, the glittering paint compositions of Examples 1 to 7 and Comparative Examples 1 to 6 were sprayed with a spray gun (trade name “Wider 61”, manufactured by Iwata Co., Ltd.) with an air pressure of 2 kg / cm ^2. Then, the coating was applied so that the dry film thickness was 0.5 μm. After leaving for 10 minutes to set, acrylic clear paint (trade name “Super Rack 5000 AW-10 Clear” manufactured by Nippon Paint Co., Ltd.) was applied with a spray gun similar to the above to a dry film thickness of 35 μm, After setting for 8 minutes, baking was performed at 140 ° C. for 30 minutes.

  A laminated coating film was formed as described above, and the coating film appearance, metallic luster, and chipping resistance were evaluated for each coating film as follows.

<Appearance of coating film>
The appearance of the coating film was evaluated by the naked eye according to the following criteria.

  5: Smooth and quite glossy.

  4: There is a glossiness.

  3: Normal feeling.

  2: I feel blurred.

  1: No glossiness.

<Metallic luster>
The metallic luster of each coating film was evaluated with the naked eye according to the following criteria.

  5: There is a metallic luster of a considerable plating tone.

  4: There is a metallic luster of plating.

  3: Normal feeling.

  2: I feel blurred.

  1: No metallic luster.

<Chipping resistance>
A stepping stone testing machine according to ASTM D3170 was used as a test apparatus, and the chipping resistance was measured as follows.

  Fix the coated plate to the surface where the stepping stone hits. Using 500 g of basalt with a diameter of 4.8 to 8 mm as a stepping stone, this is gradually put into a hopper over about 10 minutes, and the stone is blown from a nozzle with an injection pressure of 0.4 MPa and applied to the coating surface of the coating plate. The temperature of the coated plate was room temperature (23 ° C.), and the distance between the nozzle and the coating surface was 35 cm.

  After the stone is applied, the surface of the paint film surface is wiped clean, and a Nichiban industrial gum tape is pressure-bonded onto the paint film surface so as not to contain bubbles. After crimping, hold one end of this industrial gummed tape and remove the tape from the coating surface. Thereby, the coating-film part which is not closely_contact | adhering peels from a coating plate. The diameter and number of peeled portions of this coating film were measured, and the results are shown in Tables 5 and 6 as “chipping resistance”.

  As can be seen from the results shown in Tables 5 and 6, Examples 1 to 7 according to the present invention are superior to Comparative Examples 1 to 6 in coating film appearance and metallic luster.

  In Comparative Example 2, a resin having a glass transition temperature higher than the range of the present invention is used, but it can be seen that chipping resistance is lowered when such a resin is used. Further, when a resin having a glass transition temperature lower than the range of the present invention is used as in Comparative Example 1, or when a resin having a hydroxyl value outside the range of the present invention is used as in Comparative Examples 3 and 4, and It can be seen that when a resin having a weight average molecular weight lower than the range of the present invention is used as in Comparative Example 6, the appearance of the coating film is deteriorated and good metallic luster cannot be obtained. In addition, as in Comparative Example 5, when a resin having a weight average molecular weight higher than the range of the present invention is used, it is understood that the resin cannot be dissolved in a solvent and cannot be made into a paint.

Claims (13)

  Acrylic resin (a) having a glass transition temperature of 0 to 45 ° C., a hydroxyl value of 20 to 80 mg KOH / g, and a weight average molecular weight (Mw) of 200,000 to 1,000,000, a curing agent (b), and a deposited metal film The pigment (c), which was crushed into a metal piece, and the solvent (d), and the content ratio [(c) / (a + b + c)] of the glitter pigment (c) is 0.15 to 0.4. A glittering paint composition characterized by being 5.   2. The glittering paint composition according to claim 1, wherein the ratio [(a) / (b)] of the acrylic resin (a) and the curing agent (b) is 95/5 to 70/30.   The glitter coating composition according to claim 1 or 2, wherein the curing agent (b) is a melamine resin.   The concentration [(a + b) / (a + b + d)] in the solvent (d) of the acrylic resin (a) and the curing agent (b) during spray coating is 0.5 / 100 to 5.0 / 100, The glitter paint composition according to any one of claims 1 to 3.   The glittering paint composition according to any one of claims 1 to 4, wherein the acrylic resin (a) is an emulsion resin. Painting a colored base paint on the object to be coated to form a base coating film;
On the said base coating film, the glitter paint composition of any one of Claims 1-5 is applied by wet on wet so that a dry film thickness may be 2 micrometers or less, and a glitter coating film is formed. And a process of
On the glitter coating film, a clear paint is applied wet-on-wet to form a clear coating film,
A method of forming a multilayer coating film, comprising: heating the base coating film, the glitter coating film, and the clear coating film, and baking these coating films simultaneously.   The method for forming a laminated coating film according to claim 6, wherein the object to be coated is an automobile wheel.   The method for forming a laminated coating film according to claim 7, wherein the automobile wheel is an aluminum wheel.   The method for forming a multilayer coating film according to any one of claims 6 to 8, wherein the base coating material is applied after a powder coating material is applied onto the object to be coated and baked. .   The base coating film, the glitter coating film, and the clear coating film are heated to a temperature in the range of 80 to 160 ° C., and these coating films are baked at the same time. The method for forming a laminated coating film according to claim 1.   The method for forming a laminated coating film according to claim 10, wherein the coating film forming resin in the base coating film, the glitter coating film, and the clear coating film is an isocyanate curable resin.   The article | item characterized by forming the laminated coating film on the to-be-coated article by the method of any one of Claims 6-11. A colored base coating film formed on an object to be coated;
Acrylic resin (a) having a glass transition temperature of 0 to 45 ° C., a hydroxyl value of 20 to 80 mg KOH / g, and a weight average molecular weight (Mw) of 200,000 to 1,000,000, a curing agent (b), and a deposited metal film The pigment (c), which was crushed into a metal piece, and the solvent (d), and the content ratio [(c) / (a + b + c)] of the glitter pigment (c) is 0.15 to 0.4. A glittering coating film formed from the glittering coating composition of No. 5, and provided on the base coating film so that the dry film thickness is 2 μm or less;
An article comprising a laminated coating film comprising a clear coating film formed on the glitter coating film.