JP2006021195A - Method for forming multi-layer coating film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for forming a coating film to be applied to a material having a rough surface texture such as SMC or FRP, or a material having a partially worsened surface texture caused by a molding process or the like, which can simplify prior art processes and improve its finish by enhancing its under layer-masking property. <P>SOLUTION: The method for forming a multi-layer coating film wherein the primer, intermediate, and top coating films are successively applied to a material having a rough surface texture or a material having a partially worsened surface texture caused by a molding process or the like, employes an active energy beam curable paint as a primer paint. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for forming a multilayer coating film. More specifically, the active energy ray-curable coating material is used as a primer coating material for a material having a rough surface or a partially deteriorated surface roughness due to molding or the like. Thus, the present invention relates to a method for forming a multilayer coating film capable of shortening the painting / curing process and improving the finish.

  In a multi-layer coating film forming method in which a primer layer is formed on a surface to which electrodeposition coating has been applied, and then an intermediate coating film and a top coating film are formed in order, improvement of productivity and simplification of equipment Therefore, it is known to use an active energy ray-curable coating material as the primer (see, for example, Patent Document 1).

  In automobile parts and automobile outer plates, weight reduction, energy reduction, painting process shortening, etc. are desired. Among them, as materials for weight reduction, SMC (Sheet Molding Compound), FRP (Fiber Reinforced Plastic, Plastic materials such as those reinforced with carbon fiber or glass fiber, etc., and lightweight metal materials such as high-tensile steel plates and aluminum materials are increasingly used. Is being used.

  However, plastic materials such as SMC and FRP have rough surface shapes and a large number of pinholes. Currently, in order to ensure finish, the primer coating, baking, water polishing, and drying processes are performed twice. Since the process is repeated, there is a drawback that a great deal of labor is required.

  On the other hand, when repairing press scratches and the like, aluminum materials are difficult to take due to the difference in surface roughness between sanded parts and unpolished parts. When a part is bent, the processed surface becomes rough, and therefore, polishing is performed with a great deal of man-hours.

  For example, to reduce the weight of automobiles, aluminum doors (only the door frame may be partially aluminized) are being adopted from high-end cars, but they are made by bending extruded aluminum. Since the surface of the door frame is roughened by bending, it cannot be used as a design surface as it is. Also, a door frame made of an aluminum casting (including die-casting and vacuum die-casting) cannot be used as a design surface because the surface after molding is rough. Therefore, it is necessary to polish the entire design range to smooth the surface. However, the polishing process has a problem that the number of man-hours is large and the cost becomes high. In addition, there is a problem that fine powder generated when polished causes defects in the subsequent coating process.

  In addition, aluminum parts are not easily rusted, so there is no need for electrodeposition coating on the inner plate part. However, at present, electrodeposition coating is performed in the same way as steel plates in order to ensure finish. However, the electrodeposition process requires a long line such as degreasing → surface adjustment → chemical conversion treatment → electrodeposition coating → water washing → drying, and the capital investment is great and the running cost is high. Moreover, in the chemical conversion treatment, chemical conversion sludge of aluminum is generated (chemical conversion sludge twice the iron ratio is generated), and the treatment is also expensive, so it is required to eliminate the electrodeposition process.

  In addition, the magnesium material that has recently been used has a rough substrate surface, and the primer coating → baking → sharpening process is carried out 2-3 times depending on the desired finishing level, and it takes a great deal of man-hours to ensure the appearance quality of the paint. is doing.

In this way, plastic materials and metal materials such as aluminum and magnesium, which are used for weight reduction, generally do not have a good surface condition, and in order to improve the appearance quality of the paint, the number of coatings is increased or sharpened. There is a problem that it is necessary to carry out the polishing finish carefully and requires a lot of man-hours.
JP-A-4-22474

  The object of the present invention is to provide a plastic material such as SMC or FRP, a material with a rough surface shape such as aluminum or magnesium, or an aluminum material whose surface shape partially deteriorates due to molding (for example, bending). In the multilayer coating film forming method for such a material, it is intended to provide a multilayer coating film forming method capable of shortening the current process and improving the base concealing property and obtaining a good finish.

  As a result of diligent research to solve the above problems, the present inventors have made a rough surface shape such as SMC, FRP, and magnesium, or a material whose surface shape has partially deteriorated due to molding processing such as aluminum. By using an active energy ray-curable coating material as a primer coating material for the purpose, it has been found that both the shortening of the coating process and the improvement of the finishing performance can be achieved, and the present invention has been completed.

  Thus, according to the present invention, a primer coating film is formed on a material having a surface roughness Ra value of 0.3 or more when measured with a surface roughness meter under a condition of a cutoff of 0.8 mm. In a multilayer coating film forming method for forming a top coating film after forming an intermediate coating film, the present invention provides a multilayer coating film forming method characterized by using an active energy ray-curable coating as a primer coating. is there.

  The multilayer coating film forming method of the present invention is a primer coating film, an intermediate coating film and a top coating film for a material having a rough surface shape or a material whose surface shape is partially deteriorated by molding or the like such as aluminum. In the multilayer coating film forming method of sequentially forming the film, there is an effect that it is possible to achieve both shortening of the coating process and improvement of the finish of the coating film by omitting the water polishing or polishing process.

  The multi-layer coating film forming method of the present invention is particularly suitable for aluminum door frames and aluminum or resin outer lids (for example, roofs, hoods, fenders, doors, backs) that have recently been adopted to reduce the weight of automobiles. It is extremely useful for painting such as doors).

  As mentioned above, aluminum door frames are shaped by bending extruded material, but the surface becomes rough when processed, so it has traditionally been sent to the subsequent process of the automobile production line after the entire design range has been polished. It was. Further, since the door frame made of cast aluminum (including die casting and vacuum die casting) has a rough surface after molding, it is necessary to polish the entire design range in the same manner. In a later process, after a design is applied to the door frame by painting or anodizing, etc., the door is assembled together with the painted door, and assembled to the main body to be a finished vehicle. In addition, since aluminum parts are not easily rusted, it is not necessary to apply electrodeposition coating to the inner plate part. However, in order to ensure the finish of the coating, electrodeposition coating is carried out in the same way as steel plates. is there.

  According to the method for forming a multilayer coating film of the present invention, the active energy ray-curable coating material used as the primer coating material has little shrinkage of the coating film during curing and extremely excellent base concealing property, and the extruded material is bent. Even if an active energy ray-curable coating is applied directly to an aluminum door frame with a rough or cast surface, a primer coating with a smooth surface can be formed. In addition, according to the present invention, it is possible to form a multi-layer coating film excellent in coating finish without subjecting the material to electrodeposition coating in advance. Long production lines such as processing can be replaced with a coating booth for active energy ray-curable paints and a very compact line with only drying. Thus, according to the method of the present invention, it is possible to shorten the automobile production line, greatly reduce the equipment and cost, and provide an environment-friendly automobile production line that eliminates generation of chemical sludge.

  The aluminum door frame can be painted immediately after molding according to the method of the present invention, or when a press-molded aluminum door inner panel or door outer panel is used, it is adapted to the configuration of the door module. The method of the present invention can be applied after the aluminum door frame is assembled to the door inner panel or the door outer panel. In this case, an aluminum phosphorus hose (which may be an electrodeposited iron or Mg phosphorus hose) may be attached.

  Furthermore, when using an aluminum or resin-made outer lid such as a roof, a hood, a fender, a door, or a back door, the method of the present invention can be applied to these parts. The effects of the present invention can be obtained. These parts painted by the method of the present invention are completed by attaching them to a main body painted according to conventional methods.

  Furthermore, by using an aluminum body as the main body and applying the method of the present invention to the main body, the entire automobile production line can be greatly shortened, equipment and costs can be greatly reduced, and environmental protection can be achieved. Can be achieved.

  In the present invention, the active energy ray-curable coating used as a primer coating is free from volume shrinkage due to reaction desorption products because the crosslinking reaction is an addition reaction, and the surface tension of the component itself is high. Since it is a component, it is possible to achieve high solid-state differentiation of the coating material, there is very little volume shrinkage at the time of curing, and it has excellent substrate hiding properties, so it is considered that the above-described effects are exhibited.

  Hereinafter, the multilayer coating film forming method of the present invention will be described in more detail.

Material :
The method of the present invention is effective for coating a material (base material) having a rough surface, in particular, a surface roughness Ra value of 0.3 or more, preferably 0.5 or more. There is no restriction | limiting in particular in the material of such a raw material, For example, a plastic material and a metal material are mentioned. According to the method of the present invention, a plastic material such as SMC or FRP used for an automobile outer plate or an automobile part; a metal material having a rough surface such as magnesium, that is, a large surface roughness Ra value; This is particularly useful for plastics or metal materials whose surface shape deteriorates. The method of the present invention can also be applied to a metal material such as iron.

  Specifically, for example, an aluminum door frame bent from an extruded material or a cast aluminum door, a press-molded aluminum door inner panel or a door outer panel assembled with an aluminum door frame (this includes aluminum (A steel phosphorus hose made of Mg, Mg, or electrodeposited may be attached), aluminum or resin outer lids such as roofs, hoods, fenders, doors, back doors, etc., and molding The method of the present invention can be applied to a manufactured aluminum main body or the like.

  In the present specification, the “surface roughness Ra value” of the material is measured using a stylus type surface roughness measuring instrument described in JIS B 0651 according to the surface roughness standard JIS B 0601-1982, with a cutoff of 0.8 mm. This is the value when measured under conditions.

Primer paint :
In the method for forming a multilayer coating film of the present invention, it is important to use an active energy ray curable coating material having a small weight loss rate upon curing as a primer coating material to be coated on the material as described above. Thereby, the rough unevenness | corrugation of the raw material surface can be efficiently concealed, and the multilayer coating film excellent in finishing property can be formed.

  As such an active energy ray-curable coating material, a known active energy ray-curable coating material comprising a polymerizable unsaturated compound that can be polymerized or crosslinked by irradiation of active energy rays and a photopolymerization initiator may be used. it can. In particular, a coating material having a weight reduction rate upon curing of 15% or less, particularly 10% or less is suitable.

In this specification, the “weight reduction rate at the time of curing” is defined as the coating paint 1 minute after the primer coating is applied to a 20 cm × 20 cm aluminum foil whose tare weight has been measured in advance. The weight (W ₁ ) of the cured coating film (gel fraction 95% or more) after the coating film was substantially completely cured was measured, and the weight (W ₂ ) was measured. It is a value calculated by the following formula.

The polymerizable unsaturated compounds include compounds having 1 or more, preferably 2 to 5 polymerizable unsaturated bonds in one molecule, and specific examples include the compounds exemplified below. These can be used alone or in combination of two or more:
Methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, hexyl (meth) acrylate, octyl (meth) acrylate, lauryl (meth) acrylate, 2-ethylhexyl (meth) acrylate, etc. Esterified product of (meth) acrylic acid and monohydric alcohol having 1 to 22 carbon atoms; mono- or diesterified product of glycol having 2 to 20 carbon atoms such as ethylene glycol, propylene glycol, butylene glycol and (meth) acrylic acid Dicarboxylic acids such as maleic acid, itaconic acid, fumaric acid, mesaconic acid or their anhydrides and half-esterified products or modified products thereof; methoxybutyl (meth) acrylate, methoxyethyl (meth) acrylate, (meth) acrylic C2-C18 alkoxyalkyl ester of (meth) acrylic acid such as ethoxybutyl; aminoethyl (meth) acrylate, N, N-dimethylaminoethyl (meth) acrylate, N, N-diethylaminoethyl (meth) acrylate, Amino acrylic monomers such as Nt-butylaminoethyl (meth) acrylate; (meth) acrylamide, N-methylol (meth) acrylamide, Nn-butoxymethyl (meth) acrylamide, N-methoxymethyl (meta ) Acrylamide monomers such as acrylamide, N-methyl (meth) acrylamide, N-ethyl (meth) acrylamide, N, N-dimethyl (meth) acrylamide; glycidyl group-containing monomers such as glycidyl (meth) acrylate; Styrene, α-methylstyrene Emissions, vinyltoluene, acrylonitrile, vinyl acetate, vinyl compounds such as vinyl chloride; formula _{Ph-O- (C 2 H 4} 0) n -0CHC = CH 2 ( wherein, Ph represents an alkyl group having not more than 15 carbon atoms, optionally A phenyl group which may be substituted with n, and n is an integer of 1 to 6); 2-ethylhexyl carbitol acrylate, N-vinylpyrrolidone, bisphenol A ethylene oxide modified Diacrylate, isocyanuric acid ethylene oxide modified diacrylate, tripropylene glycol diacrylate, pentaerythritol diacrylate monostearate, tetraethylene glycol diacrylate, polyethylene glycol diacrylate, polypropylene glycol Diacrylate, pentaerythritol triacrylate, trimethylolpropane triacrylate, trimethylolpropane propylene oxide modified triacrylate, isocyanuric acid ethylene oxide modified triacrylate, trimethylolpropane ethylene oxide modified triacrylate, dipentaerythritol penta or hexaacrylate, pentaerythritol Tetraacrylate, oligomer having 2 mol of acrylic acid added to both terminal hydroxyl groups of polyurethane, ω-carboxy-polycaprolactone monoacrylate, phthalic acid monohydroxyethyl acrylate, acrylic acid dimer, 2-hydroxy-3-phenoxypropyl acrylate, 2 mol or more of acrylic acid was added to the terminal hydroxyl group of the polyester. Oligomer, the isocyanate group of the polyfunctional isocyanate compound hydroxyl group-containing (meth) compounds prepared by adding an acrylate monomer and the like.

  Such polymerizable unsaturated compounds generally have a number average molecular weight in the range of 50 to 3000, particularly 100 to 2000.

The photopolymerization initiator is for accelerating the polymerization or crosslinking reaction of the polymerizable unsaturated compound by irradiation with active energy rays. For example, benzoin, benzoin methyl ether, benzoin ethyl ether, 2-methylbenzoin, benzyl, benzyldimethyl ketal, diphenyl sulfide, tetramethylthiuram monosulfide, diacetyl, eosin, thionine, mihira-ketone, anthracene, anthraquinone, acetophenone, α-hydroxyisobutylphenone, p-isopropyl α-hydroxyisobutylphenone , Α, α′-dichloro-4-phenoxyacetophenone, 1-hydroxy-1-cyclohexylacetophenone, 2,2-dimethoxy-2-phenylacetophenone, methylbenzoylforme 2-methyl-1- [4- (methylthio) phenyl] -2-morpholino-propene, thioxanthone, benzophenone, 2,2-dimethoxy-1,2-diphenylethane-1-one, 1-hydroxy-cyclohexyl- Phenyl-ketone, 1-hydroxy-cyclohexyl-phenyl-ketone, benzophenone, 2-methyl-1- [4- (methylthio) phenyl] -2-montolinopropanone 1,2-benzyl-2-dimethylamino-1 -(4-morpholinophenyl) -butanone 1,2-hydroxy-2-methyl-1-phenyl-propan-1-one, 2,4,6-trimethylbenzoyldiphenyl-phosphine oxide, 1- [4- ( 2-hydroxyethoxy) -phenyl] -2-hydroxy-2-methyl-1-propane- ON, bis (cyclopentadienyl) -bis (2,6-difluoro-3- (pyr-yl) titanium), 2-hydroxy-2-methyl-1-phenylpropan-1-one, bisacylphosphine oxide , (Η ⁵ -2,4-cyclopentadien-1-yl) [(1,2,3,4,5,6-η)-(1-methylethyl) benzene] -iron (1 +)-hexafluorophos Examples include fate (1-).

  These photopolymerization initiators can be used generally in the range of 0.1 to 10 parts by weight, particularly 0.5 to 5 parts by weight, per 100 parts by weight of the polymerizable unsaturated compound.

  Moreover, the active energy ray-curable coating material contains a photosensitizer, a thermal polymerization initiator, a film-forming resin, etc., if necessary, in addition to the polymerizable unsaturated compound and the photopolymerization initiator. be able to.

  The photosensitizer is used in combination with a photopolymerization initiator to promote the photopolymerization reaction. Examples of the photosensitizer that can be used in combination include triethylamine, triethanolamine, methyldiethanolamine, 4-dimethylamino. Tertiary amines such as methyl benzoate, ethyl 4-dimethylaminobenzoate, isoamyl 4-dimethylaminobenzoate, ethyl (2-dimethylamino) benzoate, Michler's ketone, 4,4'-diethylaminobenzophenone, triphenylphosphine, etc. And alkyl phosphine type; thioether type such as β-thiodiglycol.

  These photosensitizers are preferably used in combination within a range of generally 0.01 to 5 parts by weight, particularly 0.01 to 3 parts by weight per 100 parts by weight of the polymerizable unsaturated compound.

  The thermal polymerization initiator is for accelerating the polymerization or crosslinking reaction by heating of the polymerizable unsaturated compound contained in the primer coating of the part where the active energy ray was not irradiated or the part where the irradiation was insufficient. Benzoyl peroxide, di-t-butyl hydroperoxide, t-butyl hydroperoxide, cumyl peroxide, cumene hydroperoxide, diisopropyl benzone hydroperoxide, t-butyl peroxybenzoate, lauryl peroxide, acetyl peroxide, Examples thereof include peroxides such as t-butylperoxy-2-ethylhexanoate; azo compounds such as α, α′-azobisisobutylnitrile, azobisdimethylvaleronitrile, and azobiscyclohexanecarbonitrile.

  These thermal polymerization initiators can be generally blended in the range of 0.1 to 10 parts by weight, particularly 0.5 to 5 parts by weight, per 100 parts by weight of the polymerizable unsaturated compound.

  Examples of the film-forming resin include a base resin having a functional group with a saturated bond as a skeleton, such as a polyester resin, an acrylic resin, and an epoxy resin, a hydroxyl group-containing (meth) acrylic acid ester, (meth) acrylic acid, and methylol. Examples thereof include those in which an ethylenically unsaturated bond is introduced by reacting a vinyl monomer having a functional group that reacts with the functional group in a base resin such as acrylamide or glycidyl (meth) acrylate.

  In addition, if necessary, pigments and other paint additives may be added to the active energy ray-curable coating material used in the present invention to such an extent that the curability by irradiation with active energy rays is not impaired.

  Examples of the pigment include titanium oxide, zinc white, carbon black, cadmium red, molybdenum red, chromium yellow, chromium oxide, Prussian blue, cobalt blue, azo pigment, phthalocyanine pigment, quinacridone pigment, isoindoline pigment, selenium pigment, and perylene. Color pigments such as pigments; extender pigments such as talc, clay, kaolin, barita, barium sulfate, barium carbonate, calcium carbonate, silica, alumina white; metallic pigments such as mica powder coated with aluminum powder, mica powder, titanium oxide, etc. Can give.

  The blending amount of the pigment is generally 1 to 250 parts by weight, particularly 3 to 150 parts by weight per 100 parts by weight of the polymerizable unsaturated compound.

  The active energy ray-curable coating material includes, for example, the above-described polymerizable unsaturated monomer and photopolymerization initiator, and optionally a photosensitizer, a thermal polymerization initiator, and / or a film-forming resin. It can be prepared by mixing and dispersing in organic solvents such as hydrocarbons, esters, ethers, alcohols, and ketones, and in some cases, pigments and / or coating surface conditioners, antioxidants, flow control Additives for paints such as an agent and a pigment dispersant can be appropriately blended.

  The active energy ray-curable coating usually has a viscosity of 15 to 60 seconds / Ford Cup No. Adjust the solid content in the range of 4/20 ° C. and the solid content in the range of 40 to 100% by weight on plastics or metal materials, for example, electrostatic coating, airless spray, air spray, etc. It is preferable to apply by the above method, and the coating film thickness is generally from 10 to 60 μm, particularly preferably from 15 to 40 μm, as a cured coating film.

  The primer coating thus formed is dried at room temperature or at a temperature of 100 ° C. or lower as necessary to evaporate and remove the organic solvent in the coating, and then irradiated with active energy rays to cure the coating. .

  Examples of active energy rays include ultraviolet rays, laser rays, X-rays, electron beams, and ion beam rays. Among these, it is preferable to use ultraviolet rays, and examples of the generator include a mercury lamp, a high-pressure mercury lamp, an ultrahigh-pressure mercury lamp, a xenon lamp, a carbon arc, a metal halide, a gallium lamp, and a chemical lamp.

The irradiation amount of the active energy ray is not particularly limited, but the irradiation amount of the ultraviolet ray is preferably within a range of 10 to 2000 mj / cm ² , and the electron beam may be irradiated at 50 to 300 Kev in an amount of 1 to 20 Mrad. preferable. The irradiation time of these active energy rays is usually 0.5 seconds to 5 minutes. Moreover, the irradiation of an active energy ray can be performed in nitrogen or a carbon dioxide atmosphere as needed.

  The primer coating surface irradiated with the active energy ray thus formed is then optionally coated with an intermediate coating and heated. Thus, the intermediate coating film is cured, and at the same time, the uncured or incompletely cured portion of the primer coating film can be cured.

  In addition, the active energy ray-curable coating material used in the present invention is more advantageous for the base concealing property as the volume shrinkage at the time of curing is smaller, and thus preferably has a solid weight concentration of 80% or more, more preferably 90% or more. It is desirable that

Intermediate coating :
As the intermediate coating, a thermosetting coating containing a base resin, a crosslinking agent, a color pigment and a solvent can be used. Examples of the base resin include a hydroxyl group, a carboxyl group, a silanol group, and an epoxy group. Resins such as acrylic resins, polyester resins, alkyd resins, fluororesins, urethane resins, and silicon-containing resins containing a crosslinkable functional group can be mentioned, and the crosslinker can be a melamine resin that can react with these functional groups. And urea resin, (block) polyisocyanate compound, epoxy compound or resin, carboxyl group-containing compound or resin, acid anhydride, alkoxysilane group-containing compound or resin, and the like.

  Examples of the coloring pigment include titanium oxide, zinc white, carbon black, cadmium red, molybdenum red, chromium yellow, chromium oxide, Prussian blue, cobalt blue, azo pigment, phthalocyanine pigment, quinacridone pigment, isoindoline pigment, selenium pigment, Examples thereof include ordinary paint pigments such as perylene pigments. The blending amount of these color pigments can be arbitrarily selected according to the color tone desired for the coating film. Moreover, as a solvent, normal solvent for coating materials, such as a hydrocarbon type, ester type, ether type, alcohol type, a ketone solvent, and / or water can be used, for example.

  The intermediate coating can be prepared by mixing and dispersing these components. The solid content concentration during coating is about 40 to about 70% by weight, and the viscosity during coating is 15 to 30 seconds / Ford Cup No. A range of 4/20 ° C. is suitable.

  The coating and curing of the intermediate coating film can be performed by a method known per se, and the primer coating film prepared as described above is applied to the primer coating surface, for example, electrostatic coating, airless spray, air spray, etc. In this method, the coating is applied so that the film thickness based on the cured coating is 5 to 50 μm, preferably about 10 to 30 μm, and if necessary, the solvent is evaporated by heating at a temperature of 60 to 80 ° C. for about 10 minutes. Then, an intermediate coating film can be formed by heating at about 120 to about 160 ° C. for about 10 to 40 minutes.

  In order to further improve the base concealing property, it is possible to use an active energy ray curable type as the intermediate coating.

  As the UV curable intermediate coating, the same materials as those mentioned for the primer coating can be used, and the preparation, coating, and curing of the coating are performed in the same manner as described for the primer coating. be able to.

  The primer coating surface or intermediate coating surface thus formed is then coated with a top coating and heated. As a result, the top coat film is cured, and at the same time, the uncured or incompletely cured portions of the intermediate coat film and the primer film can be cured.

Top coat :
As the top coating material, a thermosetting material such as a solid color coating material, a metallic coating material, or a clear coating material can be used, and a top coating film of solid color finishing or metallic finishing can be formed by appropriately combining these. be able to.

  The solid color paint includes a thermosetting paint containing a base resin, a cross-linking agent, a color pigment and a solvent. Examples of the base resin include cross-linkable functional groups such as a hydroxyl group, a carboxyl group, a silanol group, and an epoxy group. Group-containing resins such as acrylic resin, polyester resin, alkyd resin, fluororesin, urethane resin, and silicon-containing resin, and as a crosslinking agent, melamine resin and urea resin that can react with these functional groups , (Block) polyisocyanate compounds, epoxy compounds or resins, carboxyl group-containing compounds or resins, acid anhydrides, alkoxysilane group-containing compounds or resins, etc., and the main components are acid group-containing resins and epoxy group-containing resins. It is also possible to use an acid / epoxy cross-linking coating composition.

  As the color pigment, those exemplified for the primer paint can be used. These blending amounts can be arbitrarily selected according to the color tone desired for the coating film. Moreover, as a solvent, normal solvent for coating materials, such as a hydrocarbon type, ester type, ether type, alcohol type, a ketone solvent, and / or water can be used, for example.

  The solid color paint can be prepared by mixing and dispersing the above-mentioned components. The solid content concentration during coating is about 40 to about 70% by weight, and the viscosity during coating is 15 to 30 seconds / Ford Cup No. . A range of 4/20 ° C. is suitable.

  The metallic paint includes a thermosetting paint containing a base resin, a cross-linking agent, a color pigment, a metallic pigment and a solvent. Of these, the base resin, the cross-linking agent, the color pigment and the solvent are exemplified for a solid color paint. Things can be used. Examples of the metallic pigment include flake-like aluminum, mica, mica whose surface is coated with a metal oxide, and mica-like iron oxide. The solid content concentration of the metallic paint is about 15 to about 40% by weight, and the viscosity is 12 to 25 seconds / Ford Cup No. It is preferable that it exists in the range of 4/20 degreeC.

  The clear paint contains the same base resin, cross-linking agent and solvent as described for the solid color paint, and further contains a color pigment and a metallic pigment as necessary so as not to impair the transparency of the coating film. A curable paint can be used. When the clear paint is applied, the solid content concentration is about 40 to about 70% by weight, and the viscosity is 15 to 40 seconds / Ford Cup No. It is preferable that it exists in the range of 4/20 degreeC.

  Specific examples of the method for forming a top coat film using a solid color paint, a metallic paint, and a clear paint include the following methods.

  a) After applying a solid color paint and, if necessary, a clear paint on the surface of the primer coating or intermediate coating, it is heated to cure the top coating to form a multilayer coating. Method.

  b) A method in which a metallic coating and a clear coating are applied to the primer coating surface or the intermediate coating surface, and then heated to cure these top coating films to form a multilayer coating film.

  In method a), a solid color coating is applied to the primer coating surface or intermediate coating surface by electrostatic coating, airless spraying, air spraying, etc., and the film thickness based on the cured coating film is 5 to 50 μm, preferably 10 Apply to about 30 μm, and if necessary, heat for about 10 minutes at a temperature of 60 to 80 ° C. to volatilize the solvent. After coating the film so that the film thickness is 10 to 80 μm, preferably about 20 to 50 μm, if necessary, the film is heated at 60 to 80 ° C. for about 10 minutes to volatilize the solvent, and then about 120 to about 160 ° C. Is heated for about 10 to about 40 minutes to cure the coating film to form a multilayer coating film.

  In the method b), the primer coating or intermediate coating surface is coated with a metallic paint by a method such as electrostatic coating, airless spraying, air spraying, etc., and the film thickness based on the cured coating is 10 to 50 μm, preferably 15 to After coating to a thickness of about 35 μm and, if necessary, heating for about 10 minutes at a temperature of 60 to 80 ° C. to volatilize the solvent, the clear coating is then similarly applied to a film thickness of 10 to 10 After coating to 80 μm, preferably about 20 to 50 μm, and if necessary, the solvent is stripped by heating at a temperature of 60 to 80 ° C. for about 10 minutes, and about 10 to about 10 to about 120 to about 160 ° C. A multilayer coating film is formed by heating for 40 minutes to cure the coating film.

  Further, in order to further improve the base concealing property, it is also possible to use an active energy ray curable type as the top coating.

  As the active energy ray curable top coating, the same materials as described in the primer coating can be used. In the case of a solid color coating, a coloring pigment is used. In the case of a metallic color coating, a metallic pigment is an essential component. As a blend.

  In this case, the coating material can be prepared in the same manner as described in the primer coating material, and the coating and curing can be performed by the active energy ray irradiation method shown in the primer coating material. The method can be carried out in the same manner as the method a) and the method b) described above for the top coat.

  In the method for forming a multilayer coating film of the present invention, an overtop clear coating film can be further formed on the surface of the top coating film for the purpose of further improving the finish.

Overtop clear paint :
It is preferable to use an active energy ray curable type as the overtop clear coating, and it contains a polymerizable unsaturated compound and a photopolymerization initiator that can be polymerized by irradiation with active energy rays described in the primer coating. Similar ones can be used. Further, if necessary, a color pigment or a metallic pigment can be blended to such an extent that the transparency is not hindered.

  The preparation of the paint, the painting and the curing of the coating film can be carried out in the same manner as described for the primer paint.

  Thus, according to the present invention, a coating film of an active energy ray-curable coating material, and in some cases, a multilayer coating film comprising an intermediate coating film and a top coating film can be formed on the material surface. When the method of the present invention is applied to a relatively inexpensive automobile body such as a popular car, the intermediate coating step and / or the top coating step can be omitted.

  Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. All parts and percentages are by weight. The film thickness is based on the cured film thickness. In addition, this invention is not limited to a following example.

1. Sample preparation 1) Material:
SMC (Sheet Molding Compound, plastic material) having a size of length × width × thickness of 200 mm × 300 mm × 5 mm and an aluminum material having a size of length × width × thickness of 300 mm × 100 mm × 2 mm were used as coating objects. For SMC, air blown and degreased with isopropyl alcohol were used, and for aluminum materials, alkali degreased and zinc phosphate treated were used.

2) Primer paint Primer paint (B-1): 100 parts of pentaerythritol triacrylate (trade name Aronix M-305, manufactured by Toagosei Co., Ltd.), 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -Mixing and dispersing 3 parts of butanone-1 (photopolymerization initiator), 60 parts of titanium oxide and 0.2 part of carbon black in an equal weight mixed solvent of xylene and swazol 1500 (trade name, hydrocarbon solvent manufactured by Cosmo Oil) Viscosity 30 seconds / Ford Cup No. It adjusted to 4/20 degreeC and solid content concentration 85%, and the primer coating material (B-1) was obtained.

  Primer paint (B-2): Oligomer (number average molecular weight) obtained by adding a hydroxyl group-containing acrylic monomer (FA-2; manufactured by Daicel Chemical Industries) to a trifunctional isocyanate compound (N-3300; nurate-type isocyanate compound, manufactured by Sumitomo Bayer) 1455, 30 parts having 3 polymerizable double bonds per molecule), 70 parts pentaerythritol triacrylate, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butanone-1 (photopolymerization) 3 parts of initiator, 60 parts of titanium oxide and 0.2 part of carbon black were mixed and dispersed in an equal weight mixed solvent of xylene and swazole 1500, viscosity 30 seconds / Ford Cup No. It adjusted to 4/20 degreeC and solid content concentration 85%, and the primer coating material (B-2) was obtained.

  Primer paint (B-3): trade name Soflex No. 5301 light gray primer, manufactured by Kansai Paint Co., Ltd., acrylic resin / isocyanate resin thermosetting paint.

  Primer paint (B-4): Brand name Electron 9600 gray, manufactured by Kansai Paint Co., Ltd., thermosetting epoxy resin cationic electrodeposition paint.

3) Mid-coat paint Mid-coat paint (C-1): Brand name Amirac TP-65-2 gray, manufactured by Kansai Paint Co., Ltd., polyester resin / melamine resin thermosetting intermediate coat.

Intermediate coating (C-2): Polyester oligomer obtained by adding acrylic acid to hydroxyl group-containing polyester resin (number average molecular weight 15)
00, 2 parts of polymerizable double bond per molecule), 40 parts of pentaerythritol triacrylate, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butanone-1 (photopolymerization) 3 parts of initiator), 5 parts of t-butyl peroxy-2-ethylhexanoate (thermal polymerization initiator), 60 parts of titanium white pigment and 0.5 part of carbon black, xylene and swazol 1500 (product of Cosmo Oil, product) (Name, hydrocarbon solvent) and mixed in an equal weight mixed solvent, and adjusted to a viscosity of 20 seconds / Ford Cup # 4/20 ° C. and a solid content of 85% to obtain an intermediate coating (C-2). .

4) Topcoat paint Topcoat paint (D-1): Trade name US300 black, manufactured by Kansai Paint Co., Ltd., acrylic resin / melamine resin-based thermosetting topcoat solid color paint.

  Top coat (D-2): 30 parts of pentaerythritol triacrylate (trade name Aronix M-305, manufactured by Toagosei Co., Ltd.), 70 parts of modified polyether acrylate (trade name “LR8985”, molecular weight 700, manufactured by BASF), 2 -3 parts of benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butanone-1 (photopolymerization initiator) and 3 parts of carbon black were mixed with xylene and swazole 1500 (manufactured by Cosmo Oil, trade name, hydrocarbon type) Solvent) is mixed in an equal weight mixed solvent, and the viscosity is 40 seconds / Ford Cup No. It adjusted to 4/20 degreeC and 90% of solid content rate, and the top coat (D-2) was obtained.

  Top coating (D-3): Trade name TB-510 Silver, manufactured by Kansai Paint Co., Ltd., acrylic resin / melamine resin thermosetting top coating.

  Top coating (D-4): Trade name TC-71, manufactured by Kansai Paint Co., Ltd., acrylic resin / melamine resin thermosetting top clear coating.

2. Examples and Comparative Examples Example 1
Primer paint (B-1) is applied to the entire surface of the SMC material that has been pretreated by air spraying to a thickness of 25 μm, left at room temperature for 5 minutes, and then the surface of the primer is coated with 2000 mj of ultraviolet light using a metal halide lamp. Irradiation was performed for 30 seconds so as to be / cm ² . Furthermore, this primer coating surface was air-sprayed with an intermediate coating (C-1) to a thickness of 25 μm and cured by heating at 140 ° C. for 30 minutes. Further, this intermediate coating surface was coated so that the top coating material (D-1) was 40 μm, and then heated and cured at 140 ° C. for 30 minutes to obtain a test plate.

Example 2
After the intermediate coating was applied and cured in exactly the same way as in Example 1, the top coating (D-3) was 15 μm and the top coating (D-4) was 35 μm on the intermediate coating surface. After coating with wet-on-wet as described above, these coating films were simultaneously cured by heating at 140 ° C. for 30 minutes to obtain test plates.

Example 3
A test plate was obtained in the same manner as in Example 1, except that the primer paint (B-2) was used instead of the primer paint (B-1).

Example 4
In Example 1, a test plate was obtained in exactly the same manner as in Example 1 except that the aluminum material was used instead of the SMC material.

Example 5
Primer paint (B-1) is applied to the entire surface of the SMC material that has been pretreated by air spraying to a thickness of 25 μm, left at room temperature for 5 minutes, and then the surface of the primer is coated with 2000 mj of ultraviolet light using a metal halide lamp. Irradiation was performed for 30 seconds so as to be / cm ² . Next, the primer coating surface was air spray-coated with an intermediate coating (C-2) to a thickness of 25 μm and allowed to stand at room temperature for 5 minutes, and then ultraviolet rays were applied to the intermediate coating surface with a metal halide lamp at 2000 mj / cm ^2. Irradiation was performed for 30 seconds. Furthermore, the top coat (D-2) is applied to the intermediate coating surface so as to have a thickness of 40 μm, and is allowed to stand at room temperature for 5 minutes, and then the ultraviolet light is applied to the top coating surface with a metal halide lamp to 2000 mj / cm ^2. Was irradiated for 30 seconds to obtain a test plate.

Comparative Example 1
Example 1 is the same as Example 1 except that primer paint (B-3) is used instead of primer paint (B-1), and the curing condition of the primer coating is changed to heating at 140 ° C. for 30 minutes. A test plate was obtained.

Comparative Example 2
In the step of painting and curing the primer paint (B-3) of Comparative Example 1, the same procedure as in Comparative Example 1 is applied except that the step of primer coating ⇒ 140 ° C x 30 minutes heating ⇒ water research is repeated twice. A test plate was obtained.

Comparative Example 3
Primer paint (B-4; electrodeposition paint) was electrodeposited to a thickness of 25 μm on the entire surface of the pretreated aluminum material and cured by heating at 170 ° C. for 30 minutes. Next, an intermediate coating (C-1) was applied by air spray to the electrodeposition coated surface to a thickness of 25 μm and cured by heating at 140 ° C. for 30 minutes. Further, the top coat (D-1) was applied to the intermediate coating surface so as to have a thickness of 40 μm, and then heated and cured at 140 ° C. for 30 minutes to obtain a test plate.

3. Coating Film Performance Test Results Table 1 shows the performance test results of the multilayer coating films obtained in Examples 1 to 5 and Comparative Examples 1 to 3.

  The test method of the performance test in Table 1 is as follows.

Final finish visual inspection : The result of visual evaluation of the presence or absence of unevenness (including pinholes) due to the material with the final coating after top coating, ○ is not recognized at all, Δ is slightly uneven, X indicates that irregularities are clearly and frequently recognized.

Ra value : Primer measured with a surface rough clock (manufactured by Tokyo Seimitsu Co., Ltd., surface roughness shape measuring instrument “Surfcom 570A”) under the conditions of a cutoff of 0.8 mm (scanning speed 0.3 mm / sec, magnification 5000 times). Ra values of the coated surface and the top coated surface (the smaller the value, the smoother and better the surface state of the coating film is).

Number of coatings : Total number of coatings (number of coating layers) of primer layer, intermediate coating layer and top coating layer.

Claims (9)

  A primer coating film is formed on a material having a surface roughness Ra value of 0.3 or more when measured with a surface roughness meter under a condition of a cutoff of 0.8 mm, and then an intermediate coating film is formed as necessary. Then, in the multilayer coating film forming method for forming a top coating film, an active energy ray curable coating material is used as the primer coating material.   The method for forming a multilayer coating film according to claim 1, wherein the weight loss rate during curing of the active energy ray-curable coating material is 15% or less.   The method for forming a multilayer coating film according to claim 1 or 2, wherein the material is a plastic material or a metal material.   The method for forming a multilayer coating film according to claim 3, wherein the plastic material is FRP or SMC.   The method for forming a multilayer coating film according to claim 3, wherein the metal material is aluminum, magnesium or iron.   The method for forming a multilayer coating film according to any one of claims 1 to 5, wherein the primer coating film is cured by using both active energy ray irradiation and heating.   The multilayer coating film forming method according to any one of claims 1 to 6, wherein an active energy ray-curable coating is used as the intermediate coating.   The multilayer coating film forming method according to any one of claims 1 to 7, wherein an active energy ray-curable coating material is used as the top coating material.   The multilayer coating film forming method according to claim 1, wherein the active energy ray-curable coating material as the primer coating material has a weight solid content concentration of 80% or more.