JP2002161229A - Primer coating composition for repairing intermediate coated film and method for repairing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a coating material for repairing an intermediate coated film effectively masking defects on the substrate, suitable for excellently finishing and excellent in an adhesion to the substrate and chipping resistance, and to provide a method for the repairing. SOLUTION: This primer for repairing the intermediate coated film comprises an acrylic resin, a polyester resin, a melamine resin, a crosslinkable polymer particulate and a pigment, comprises the crosslinkable polymer particulate in an amount of 1-30 pts.wt. as a solid and the melamine resin in an amount of 22-58 pts.wt. as a solid each based on 100 pts.wt. of the solid part of the acrylic resin, the polyester resin and the melamine resin, has <=540 g/L concentration of volatile organic compounds at the time of coating and >=5,000 cPs viscosity at a brushing speed at the time of applying, comprises the pigment in an amount of 10-68 wt.% based on the solid part of the primer coating composition and has <=24 difference (ΔL=L1-L0) of L value (L0) in the intermediate coated film from L value (L1) in the coated film obtained by baking.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a primer coating composition for intermediate coating repair and a method for repairing an intermediate coating film using the primer coating composition for intermediate coating repair.

[0002]

2. Description of the Related Art Usually, an electrodeposition coating film is formed as an undercoating on an automobile body or parts, and then an intermediate coating film, a base coating film and, if necessary, a clear coating film are sequentially formed.
When it is necessary to remove dust adhering to the intermediate coating film, or when a coating defect such as sagging, pinhole, or dent occurs, the coating must be repaired at that portion.

[0003] The coating repair is usually carried out by grinding a portion of the intermediate coating film requiring repair by sanding or the like, and applying a paint to the ground portion. Conventionally, in this case, there is a problem that the sharpening powder generated by grinding at the time of blank polishing remains, or a sharp trace remains when the sharpening is deep and random, particularly when the base paint is a pale color. . Conventionally, several techniques have been used for the repair procedure.

[0004] For example, rubber and
There is a method of applying a repair-dedicated primer composed of a modified resin composition such as a polyolefin. However, in this method, since the modified resin such as rubber and polyolefin is insoluble in a solvent, a large amount of solvent remains, and defects such as sagging, unevenness, poor appearance, discoloration, and the like due to compatibility with the top coating material are likely to occur. On the other hand, there is a dust part that is applied discontinuously around the repaired part, but this dust part dries easily and becomes insoluble in the solvent, so that the top coating does not blend with the dust part, and has a glossy appearance, poor appearance, Failure is likely to occur. Modified resins such as rubber and polyolefin are originally used for the purpose of preventing rust in the ground part of groundwork, so when used for repairing an intermediate coating film, the workability width is extremely narrow. Had occurred.

[0005] On the other hand, there is a method in which a top coat such as a colored base paint or a colored solid paint is applied in advance to the ground portion of the intermediate coat to conceal the defects of the base, and the top coat of the same color is applied from above. is there. However, the topcoat paint is generally less suitable for concealing defects of the substrate because the viscosity at the time of painting and the solid content at the time of painting are lower than other materials, and a thick film as a wet coating film Since it was necessary, it was easy to cause problems such as sauce and armpits.

[0006]

SUMMARY OF THE INVENTION In view of the above, it is an object of the present invention to effectively mask a defect on a base without causing a defect in repairing a conventional intermediate coating film and to achieve a good finish. An object of the present invention is to provide a coating material for repairing an intermediate coating film and a method for repairing the same, which have excellent adhesion to a base and chipping resistance.

[0007]

The present invention relates to a primer coating composition for repairing an intermediate coating film for repairing an intermediate coating film, wherein the primer coating composition for repairing an intermediate coating film comprises acrylic resin. A resin and a polyester resin, and a melamine resin and a crosslinkable polymer fine particle, which further contain a pigment, wherein the crosslinkable polymer fine particle is a solid content of 100% of the acrylic resin, the polyester resin and the melamine resin. 1 to 30 as a solid content with respect to parts by weight
Per 100 parts by weight of the acrylic resin, the polyester resin, and the melamine resin in terms of a solid content of 22 parts by weight.
-58 parts by weight, the volatile organic compound concentration (VOC) at the time of coating is 540 g / L or less, and the viscosity at the rubbing speed of 10 ^-2 · sec ^-1 at the time of coating is 5000 cps or more. The pigment contains 10 to 68% by weight as a pigment weight concentration (PWC) based on the solid content of the primer coating composition for repairing the intermediate coating film, and the L value (L) of the intermediate coating film ₀ ) and the L value (L ₁ ) of the coating film obtained by applying and baking the primer coating composition for repairing an intermediate coating film (ΔL = L ₁ −).
L ₀ ) is 24 or less, which is a primer coating composition for repairing an intermediate coating film.

[0008] The present invention also provides a method for repairing a part to be repaired of an intermediate coating film formed on a base material, and applying the primer coating composition for repairing the intermediate coating film on the repaired part. , A base coating film and a clear coating film as required. The present invention further provides a substrate having a coating film formed by the above-described coating film forming method. Hereinafter, the present invention will be described in detail.

The primer coating composition for repairing an intermediate coating film according to the present invention is for repairing an intermediate coating film. In the present invention, the intermediate coating film is formed by forming an electrodeposition coating film on a base material, and then applying an intermediate coating material, a base coating material, and, if necessary, a clear coating material in the step of sequentially applying the intermediate coating material. And then bake-hardened.

In the present invention, the repair of the coating film is performed by forming the intermediate coating film and then removing the repaired portion of the coating film by sandpaper or the like. This is performed by applying the primer coating composition for repairing an intermediate coating film of the present invention to a portion having an area that sufficiently covers the above-mentioned removed portion. The part to be repaired may be a part of the intermediate coating film that reaches the electrodeposition coating film or a part of the intermediate coating film, or only the part of the intermediate coating film that reaches the electrodeposition coating film. Rather, it may be a part of the electrodeposition coating film that reaches the base material or a part of the electrodeposition coating halfway.

The primer coating composition for repairing an intermediate coating film of the present invention has a volatile organic compound concentration (VO) at the time of coating.
C) is 540 g / L or less. If it exceeds 540 g / L, it will be mixed with a base paint or the like to be applied later on wet-on-wet, and the appearance will be reduced due to adaptation, etc. In addition, volatile organic compounds will be volatilized during coating or heat curing. However, it is not preferable from the viewpoint of environmental protection. Preferably, it is 530 g / L or less.

The primer coating composition for repairing an intermediate coating film according to the present invention has a viscosity of 5000 cps or more at a rubbing speed of 10 ^-2 · sec ^-1 during application. When it is less than 5000 cps, problems such as sagging, unevenness, poor appearance, and discoloration due to familiarity with the base paint occur. Preferably, it is 5400 cps or more.

The difference (ΔL = L) between the L value (L ₀ ) of the intermediate coating film and the L value (L ₁ ) of the coating film obtained by applying and baking the primer coating composition for repairing the intermediate coating film. L ₁ -L
₀ ) is 24 or less. If it exceeds 24, the difference in hue between the repaired portion and the portion not to be repaired is increased due to an increase in the brightness difference between the repaired portion and the non-repaired portion. Preferably, it is 21 or less.

When there are a plurality of colors of the intermediate coating film on the same coating line such as an automobile body, the primer coating composition for repairing the intermediate coating film of the present invention has one color for each coating color of the intermediate coating film. It may be designed so as to be one-to-one, or may be designed so as to be unified with a large number of coating colors. From the viewpoint of reducing the number of processes, it is preferable to unify the coating colors with a large number of coatings. Since the primer coating composition for repairing an intermediate coating film of the present invention alone provides a high base concealing property, it is not necessary to make the same color as the base coating film laminated thereon. Color can be appropriately selected according to the conditions.

The primer coating composition for repairing an intermediate coating film according to the present invention contains an acrylic resin and a polyester resin, a melamine resin and fine particles of a crosslinkable polymer, and further contains a pigment. The acrylic resin is not particularly limited, and for example, a conventionally known acrylic resin can be used, and is usually obtained by polymerizing an unsaturated monomer. By containing the acrylic resin, it is possible to improve the physical properties of the coating film, such as increasing the fastness.

As the unsaturated monomer, acrylic acid,
There is no particular limitation as long as it contains methacrylic acid and / or a derivative thereof. The derivative is not particularly limited, and examples thereof include alkyl esters such as ethyl (meth) acrylate; hydroxyalkyl esters such as hydroxyethyl (meth) acrylate; amides such as (meth) acrylamide; and (meth) acrylonitrile and the like. And nitriles. The unsaturated monomer may further include a vinyl compound such as styrene, methylstyrene, and vinyl acetate. The acrylic resin may be a homopolymer or a copolymer using two or more kinds of the unsaturated monomers.

The acrylic resin has a number average molecular weight of 10
It is preferably from 00 to 3500. If it is less than 1000, the properties of the coating film may be inferior. If it exceeds 3500, the smoothness of the coating film becomes insufficient and a good appearance cannot be obtained, and at the same time, the primer coating for repairing the intermediate coating film of the present invention. The viscosity at the time of application of the composition tends to be too high.
More preferably, it is 1200-3000.

The acrylic resin has a hydroxyl value of 40 to 1
It is preferably 60 mgKOH / g (solid content).
If it is less than 40 mgKOH / g, the mixing with the polyester resin becomes insufficient, and the physical properties of the coating film may deteriorate.
If it exceeds 60 mgKOH / g, the water resistance of the coating film may decrease. More preferably, 50 to 150 mg KO
H / g.

The acrylic resin has an acid value of 5 to 50 mg.
It is preferably KOH / g (solid content). 5mgK
If it is less than OH / g, the physical properties of the coating film may be poor, and
If it exceeds 0 mgKOH / g, the water resistance of the coating film tends to recede. More preferably, it is 10 to 45 mgKOH / g.

The acrylic resin is used in the primer coating composition for repairing an intermediate coating film of the present invention in an amount of 5 to 60% in solids.
It is preferable to mix them in a ratio of weight%. If the amount is less than 5% by weight, the film properties may be poor such as a decrease in fastness. If the amount exceeds 60% by weight, the film may be hard and brittle and the film properties such as chipping resistance may be poor. In addition, a large amount of a solvent is required, and the VOC at the time of coating the primer coating composition for repairing an intermediate coating film of the present invention is 540 g / L.
May be exceeded. More preferably, 8 to 56% by weight
It is.

The above polyester resin is generally obtained by polycondensing a polyhydric carboxylic acid and / or an acid anhydride with a polyhydric alcohol. By containing the polyester resin, the coating film can be provided with chipping resistance, base hiding property, surface smoothness, and the like.

The above-mentioned polycarboxylic acid and / or acid anhydride is not particularly restricted but includes, for example, phthalic acid, phthalic anhydride, tetrahydrophthalic acid, tetrahydrophthalic anhydride, hexahydrophthalic acid, hexahydrophthalic anhydride, methyl Tetrahydrophthalic acid, methyltetrahydrophthalic anhydride, hymic anhydride, trimellitic acid, trimellitic anhydride, pyromellitic acid, pyromellitic anhydride, isophthalic acid, terephthalic acid, maleic acid, maleic anhydride, fumaric acid, itaconic acid , Adipic acid, azelaic acid, sebacic acid, succinic acid, succinic anhydride, dodecenyl succinic acid, dodecenyl succinic anhydride and the like.

The polyhydric alcohol is not particularly restricted but includes, for example, ethylene glycol, diethylene glycol, polyethylene glycol, propylene glycol,
Dipropylene glycol, polypropylene glycol,
Neopentyl glycol, 1,2-butanediol,
1,3-butanediol, 1,4-butanediol,
2,3-butanediol, 1,5-pentanediol,
1,6-hexanediol, 1,4-cyclohexanediol, 2,2-dimethyl-3-hydroxypropyl-
2,2-dimethyl-3-hydroxypropionate,
2,2,4-trimethyl-1,3-pentanediol,
Examples include polytetramethylene ether glycol, polycaprolactone polyol, glycerin, sorbitol, annitol, trimethylolethane, trimethylolpropane, trimethylolbutane, hexanetriol, pentaerythritol, dipentaerythritol and the like.

The polyester resin may be composed of a monoepoxide compound such as Cardura E (trade name, glycidyl versatate, manufactured by Shell Chemical Co., Ltd.) or a lactone as a component constituting the ester. . The lactones can form a graft chain by ring-opening addition of a polyhydric carboxylic acid and a polyhydric alcohol to polyesters, for example, β-propiolaclone, dimethylpropiolactone, butyl lactone,
γ-valerolactone, ε-caprolactone, γ-caprolactone, γ-caprylolactone, clotrolactone, δ
-Valerolactone, δ-caprolactone, etc., of which ε-caprolactone is most preferred.

The above-mentioned polycarboxylic acid and / or acid anhydride,
The polyhydric alcohol, the monoepoxide compound, and the lactone can be used alone or in combination of two or more. The polyester resin may further contain a small amount of a monocarboxylic acid, a hydroxycarboxylic acid, or the like as a monomer. It may also contain a drying oil, an anti-drying oil and their fatty acids.

The above polyester resin preferably has a number average molecular weight of 400 to 3,500. If it is less than 400, the curing may be insufficient. If it exceeds 3500, the smoothness of the coating film becomes insufficient and a good appearance cannot be obtained. The viscosity at the time of application of the composition tends to be too high. More preferably, it is 500-2500.

The above polyester resin has a hydroxyl value of 30.
It is preferable that the amount is 250 mgKOH / g (solid content). If it is less than 30 mgKOH / g, poor curing tends to occur, and if it exceeds 250 mgKOH / g, the elasticity of the coating film tends to be low and the chipping resistance tends to be poor. More preferably, it is 50 to 200 mgKOH / g.

The above polyester resin has an acid value of 3 to 60.
It is preferably mgKOH / g (solid content). 3m
If the amount is less than gKOH / g, poor curing is likely to occur.
If it exceeds 0 mgKOH / g, the water resistance of the coating film tends to recede. More preferably, it is 5 to 50 mgKOH / g.

The polyester resin is used in the primer coating composition for repairing an intermediate coating film of the present invention.
It is preferable to mix at a ratio of 60% by weight. 5% by weight
If it is less than 30, the coating film is hard and brittle, and the coating film properties such as chipping resistance may be inferior. If it exceeds 60% by weight,
The concealability of the base may be insufficient. More preferably, it is 8 to 56% by weight.

The amount of the polyester resin is preferably 20 to 80 parts by weight based on 100 parts by weight of the solid content of the acrylic resin and the polyester resin.
When the amount is less than 20 parts by weight, the coating film becomes hard and brittle, and may have poor coating film properties such as chipping resistance. In addition, the VOC at the time of coating the primer coating composition for repairing an intermediate coating film of the present invention is 540 g. / L may be unfavorable from the viewpoint of environmental protection, and when an acrylic resin having a low number average molecular weight is used, the physical properties of the coating film may be reduced. If it exceeds 80 parts by weight, the resin composition of the primer coating composition for repairing an intermediate coating film of the present invention may have poor glass transition temperature, such as too low a glass transition temperature, resulting in poor fastness. More preferably, it is 30 to 70 parts by weight.

The melamine resin is not particularly limited, and for example, those usually used as a curing agent can be used. The melamine resin can be alkyl-etherified into an alkyl-etherified melamine resin, and among them, a melamine resin substituted with a methoxy group and / or a butoxy group is preferable.

The melamine resin substituted with a methoxy group and / or a butoxy group includes those having a methoxy group alone, Cymel 325, Cymel 327, and Cymel 370; Cymel 325, Cymel 327, and Cymel 370; 202, Cymel 204, Cymel 2
32, Cymel 235, Cymel 236, Cymel 23
8, Cymel 254, Cymel 266, Cymel 267
(Both are trade names, manufactured by Mitsui Cytec Co., Ltd.); Mycoat 506 (trade name,
Mitsui Cytec Co., Ltd.), U-Van 20N60, U-Van 20SE (all trade names, manufactured by Mitsui Chemicals, Inc.) and the like. These may be used alone or in combination of two or more. Of these, Cymel 202 and Cymel 25
4 is particularly preferred.

The above-mentioned melamine resin is the above-mentioned acrylic resin,
Solid content 1 of the polyester resin and the melamine resin
22 to 58 parts by weight are added to 00 parts by weight. Even if the amount is smaller or larger than this range, the adhesion between the repair coating film obtained from the primer coating composition for repairing an intermediate coating film of the present invention and the adjacent coating film of the intermediate coating film and / or the base coating film is low. Inconveniences such as lowering and inferior chipping resistance of the coating film occur. Further, when the amount is less than 22 parts by weight, poor curing results. When the amount exceeds 58 parts by weight, the coating film becomes hard and brittle, and the chipping resistance is reduced. Preferably, it is 25 to 55 parts by weight.

As the fine particles of the crosslinkable polymer, those described in JP-A-10-5680 can be used. Specifically, it is insoluble in the organic solvent used in the primer coating composition for repairing the intermediate coating film of the present invention,
It is composed of a polymer crosslinked to some extent, and is preferably microparticles having an average particle size of 0.01 to 10 μm, and has characteristics of being stably dispersed in a coating material. When the average particle size is less than 0.01 μm, difficulty in production equipment is high, and it is difficult to maintain the particle shape. When the average particle size exceeds 10 μm, the stability in the coating material decreases. Preferably, 0.01
１1 μm.

As a method for producing the above-mentioned crosslinkable polymer fine particles, an ethylenically unsaturated monomer is emulsion-polymerized with a crosslinkable copolymer monomer in an aqueous medium to form a fine particle copolymer, which is then subjected to solvent substitution. A method of removing water by means of azeotropic, centrifugal separation, filtration and drying; etc .; having an ethylenically unsaturated group in a non-aqueous organic solvent in which monomers such as fatty acid hydrocarbons dissolve but polymers do not dissolve A method of reacting a monomer with a crosslinkable copolymer monomer and dispersing the obtained fine particle copolymer (NA
Various methods such as D method) are known, and in the present invention, any method may be used as long as it has the above characteristics. In the present invention, the former method obtained by emulsion polymerization is preferable, but among them, emulsification of an alkyd resin or a polyester resin synthesized using a monomer having a zwitterionic group in the molecule as one of the polyhydric alcohol components is preferred. Those obtained by subjecting a polymerizable monomer to emulsion polymerization in an aqueous medium in the presence of a functional resin and a polymerization initiator are more preferable.

The above zwitterionic group is represented by -N ⁺ -R-CO
O ^- or -N ⁺ -R-SO ₃ ^- expressed as (wherein, R
Represents a C ₁ -C ₆ linear or branched alkylene group),
As a monomer having this in the molecule, a monomer having two or more hydroxyl groups can be used. As such a monomer, a hydroxyl group-containing aminosulfone-type zwitterionic compound is preferable from the viewpoint of resin synthesis. Specifically, bishydroxyethyl taurine and the like can be mentioned.

As the resin having an emulsifying zwitterionic group in the molecule synthesized using the above monomer, the acid value is 30 to 150 mgKOH / g, preferably 40 to 1 mgKOH / g.
50 mgKOH / g, number average molecular weight of 500 to 500
0, preferably 700-3000 polyester resin can be suitably used. When the ratio exceeds the upper limit, the handleability of the resin decreases. When the ratio falls below the lower limit, the resin having an emulsifying ability is desorbed or the solvent resistance decreases when the coating film is formed.

As the polymerizable monomer to be emulsion-polymerized in the presence of the above resin, it is necessary to include a monomer having two or more radically polymerizable ethylenically unsaturated groups in the molecule. The monomer having two or more radically polymerizable ethylenically unsaturated groups in the molecule is included in 0.1% of all monomers.
It is preferable to contain it in the range of 1 to 70% by weight. The amount is selected to provide sufficient crosslinking to dissolve the particulate polymer in the solvent.

Examples of the monomer having two or more radically polymerizable ethylenically unsaturated groups in the molecule include ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, and trimethylolpropane di ( Examples thereof include (meth) acrylate, trimethylolpropane tri (meth) acrylate, and glycerin di (meth) acrylate.

The amount of the crosslinkable polymer particles obtained as described above is 1 to 30 parts by weight as a solid content with respect to 100 parts by weight of the solid content of the acrylic resin, the polyester resin and the melamine resin. is there. When the amount is less than 1 part by weight, the viscosity at a rubbing speed of 10 ^-2 · sec ^-1 at the time of application may be less than 5000 cps, and the finished appearance is inferior due to compatibility with the base paint and the like. In addition, the smoothness of the coating film tends to be lost, and pinholes are easily generated. More preferably, it is 2 to 20 parts by weight.

The above-mentioned pigments are not particularly limited, and include those used in conventional intermediate coatings, for example, azochelate pigments, insoluble azo pigments, condensed azo pigments,
Organic coloring such as diketopyrrolopyrrole pigment, benzimidazolone pigment, phthalocyanine pigment, indigo pigment, perinone pigment, perylene pigment, dioxane pigment, quinacridone pigment, isoindolinone pigment, metal complex pigment, etc. Pigment: inorganic coloring pigments such as graphite, yellow iron oxide, chromium oxide, red iron oxide, carbon black, titanium dioxide and the like. Further, extenders such as calcium carbonate, barium sulfate, magnesium silicate, clay, talc and calcined kaolin may be used in combination. These may be used alone or in combination of two or more.

As the above pigment, for example, carbon black and titanium dioxide are used as main pigments, and for repairing a standard gray intermediate coating film using these pigments as main pigments, It can also be a primer coating composition. In addition, a primer coating composition for repairing a color intermediate coating film, which is a combination of a set gray having the same brightness or hue as the base coating and various kinds of coloring pigments, can also be used. It is preferable that the above-mentioned pigment contains an extender pigment from the viewpoint of enhancing the base concealing property. The pigment preferably contains titanium dioxide and carbon black, particularly titanium dioxide.

The pigment is used in a concentration of pigment weight (PW) based on the solid content of the primer coating composition for repairing the intermediate coating film.
10) to 68% by weight as C). If the amount is less than 10% by weight, workability is poor, and the finish such as the concealing property of the base and sharpening marks and the discoloration of the sharpness is poor. For example, in the state where the sharpening powder remains, sufficient base concealing property cannot be obtained. 6
If it exceeds 8% by weight, the dispersibility in the coating composition is reduced, the gloss of the coating film is reduced, and the workability, the base concealing property, and the chipping resistance are particularly poor. More preferably, 15
~ 65% by weight. By selecting the kind and content of the above-mentioned pigment, it is possible to easily adjust the above-mentioned ΔL to be 24 or less.

The primer coating composition for repairing an intermediate coating film according to the present invention may further comprise, if necessary, an organic bentonite, a fatty acid polyamide, a polyethylene wax or the like as a thickener; an aromatic hydrocarbon or an aliphatic as an organic solvent. Hydrocarbon-based, ester-based, alcohol-based solvents, etc .; additives include acid catalysts, ultraviolet absorbers, hindered amine light stabilizers, antioxidants, surface conditioners, leveling agents, pigment dispersants, plasticizers, defoamers, etc. May be used. The primer coating composition for repairing an intermediate coating film of the present invention is a conventionally known method for producing a primer coating composition for intermediate coating or repair,
Can be manufactured.

In the primer coating composition for repairing an intermediate coating film thus obtained according to the present invention, the repaired portion of the intermediate coating film formed on the substrate is removed by grinding or the like as described above. Then, it is applied on the above-mentioned repaired site. In the obtained repaired portion, a base coating film and, if necessary, a clear coating film are sequentially formed on the non-repaired portion of the intermediate coating film.

The substrate is not particularly restricted but includes, for example, metals, plastics, foams and the like. Of these, metals, particularly castings, are advantageously used. Is particularly preferably used.
The metal product is not particularly limited, for example, iron,
Examples include simple metals such as copper, aluminum, tin, and zinc, and alloys including these simple metals. Specific examples include automobile bodies and parts such as passenger cars, trucks, motorcycles, and buses. It is particularly preferable that the metal product has been subjected to a chemical conversion treatment with a phosphate, a chromate or the like in advance.

The base material may have an electrodeposition coating film formed on the steel sheet subjected to the chemical conversion treatment. As the electrodeposition paint for forming the above electrodeposition coating film, a cationic or anion type electrodeposition coating material can be used, but a cationic type electrodeposition coating material is preferable because it gives a laminated coating film having excellent anticorrosion properties.

The intermediate coating composition for forming the intermediate coating film is not particularly limited, but a gray-based melamine-curable or isocyanate-curable paint containing carbon black and titanium dioxide as main pigments is usually used. As the above-mentioned intermediate coating material, a coating material having the same hue as that of the top coating material or a combination of various coloring pigments can be used.

The base coating material for forming the base coating film is not particularly limited, and examples thereof include those comprising a film-forming resin, a curing agent, a pigment and other additives. In the present invention, the base paint may be any of an aqueous type and a solvent type. The film-forming resin is not particularly limited, and examples thereof include an acrylic resin, a polyester resin, an alkyd resin, an epoxy resin, and a urethane resin. These are combined with a curing agent such as an amino resin and / or a blocked isocyanate resin. Used. The film-forming resin is preferably a combination of an acrylic resin, a polyester resin, and a melamine resin from the viewpoint of pigment dispersibility and workability.

The above-mentioned film-forming resin may contain a different kind of acrylic resin, polyester resin and melamine resin from those used in the primer coating composition for repairing the intermediate coating film of the present invention. In terms of adhesion to a base coating film and good finish, the same type of acrylic resin, polyester resin and melamine resin as those used in the primer coating composition for repairing an intermediate coating film of the present invention are contained. It is preferred that

As the film-forming resin of the base paint,
When the same type and / or a different type of acrylic resin, polyester resin, and melamine resin as those used in the primer coating composition for repairing an intermediate coating film of the present invention are contained, the compounding amounts of these resins are as defined in the present invention. It is not necessary to make it the same as that of the primer coating composition for repairing the intermediate coating film, and the amount can be appropriately selected, and for example, can be the usual amount as the base coating.

The base paint can be used as a metallic base paint by adding a glittering pigment such as aluminum powder or mica powder, or a coloring pigment such as red, blue or black without blending a glittering pigment. It may be used as a solid base paint by blending an extender.

The clear paint for forming the clear coating film is not particularly limited, and examples thereof include those comprising a film-forming resin, a curing agent and other additives. The film-forming resin is not particularly limited, and includes, for example, an acrylic resin, a polyester resin, an epoxy resin, a urethane resin and the like, and these are used in combination with a curing agent such as an amino resin and / or a blocked isocyanate resin. . From the viewpoint of transparency or acid etching resistance, it is preferable to use a combination of an acrylic resin and / or a polyester resin and an amino resin, or an acrylic resin and / or a polyester resin having a carboxylic acid / epoxy curing system. The above electrodeposition paint,
The method for preparing the intermediate coating, the base coating and the clear coating is not particularly limited, and, for example,
A conventionally known method can be used.

The method of applying the intermediate coating, the base coating, and the clear coating is not particularly limited, and may be, for example, an air electrostatic spray commonly called “react gun”; a common name “micro-micro (μμ)”.
It can be performed by using a rotary atomizing type electrostatic coating machine called "bell", "micro (μ) bell", "metabell" or the like. Preferably, a method using a rotary atomization type electrostatic coating machine or the like is used.

When the base paint is applied to an automobile body or the like, in order to enhance design, the base paint is applied by multi-stage painting by air electrostatic spraying, preferably by two stages, or air electrostatic spraying. It is preferable to carry out by a coating method combining the above-mentioned and the above-mentioned rotary atomizing type electrostatic coating machine. The method of applying the primer coating composition for repairing the intermediate coating film of the present invention can be appropriately selected depending on the depth and area of the repaired portion, and is not particularly limited. it can.

The dry film thickness of the primer coating composition for repairing an intermediate coating film depends on the depth of the portion to be repaired and the concealing property of the base, but is usually 1 to 40 μm. The dry thickness of each of the other coating films described above varies depending on the application, but each of the intermediate coating film 5 to 50 μm and the base coating film 5 to 35 μm.
m, the clear coating film is 10 to 80 μm. Exceeding these upper limits may result in poor image clarity or inconveniences such as unevenness and flow during coating. Below the lower limit, the unevenness of the base may not be concealed and the film may break.

In the above coating film forming method, usually, an intermediate coating is applied on the electrodeposition coating film formed by the above method and baked and cured, and then the intermediate coating film is repaired at the portion to be repaired. A method in which a primer coating composition for use, a base coating material and a clear coating material are applied by a wet-on-wet method and then baked and cured at once can be used.

After applying the base paint and before applying the clear paint, the paint is allowed to stand at room temperature for a certain period of time.
A step of preliminarily drying the coating film by heating at a temperature lower than 100 ° C. for 2 to 10 minutes can be performed, and a cured coating film having a high degree of crosslinking can be obtained by performing this step. In particular, when the base paint is used as an aqueous paint, it is preferable to perform the above-mentioned standing or heating and drying step, since a good finished appearance can be obtained.

The baking hardening after the application of the clear paint can be usually performed at 110 to 180 ° C. 1
If the temperature is lower than 10 ° C., the curing is not sufficient. If the temperature exceeds 180 ° C., the coating film becomes hard and brittle. Preferably, 120-
160 ° C. The curing time varies depending on the curing temperature, but is suitably from 120 to 160 ° C. for 10 to 60 minutes.

The total thickness of the intermediate coating film, the base coating film and the clear coating film obtained by the coating film forming method of the present invention is as follows:
It is usually from 30 to 300 μm, preferably from 50 to 250 μm. If it exceeds 300 μm, the physical properties of the film such as a thermal cycle decrease, and if it is less than 30 μm, the strength of the film itself decreases.

The primer coating composition for repairing an intermediate coating film according to the present invention contains a specific amount of the above-mentioned crosslinkable polymer fine particles, and has a viscosity of 500 at a rubbing speed of 10 ⁻² · sec ⁻¹ during coating.
Since it is 0 cps or more, it does not cause compatibility with the base coating film and exhibits a good finished appearance. The coating composition,
In addition, volatile organic compound concentration (VOC) at the time of painting
Is 540 g / L or less, so that a satisfactory finish can be obtained without causing sagging, unevenness, and conformity with the base coating film, and also in terms of environmental protection. The coating composition,
Further, since it has a specific amount of pigment weight concentration (PWC),
In addition to being excellent in base layer concealment, it has good workability and finish.
Further, since the coating composition has a ΔL value of 24 or less, the repaired part has the same hue as the non-repaired part and exhibits good finish. Since the coating composition further contains a specific amount of melamine resin, the coating composition is excellent in adhesion and chipping resistance. A substrate having a coating film formed by the above-mentioned coating film forming method using the primer coating composition for repairing an intermediate coating film has been repaired favorably as described above. It is suitably used as a vehicle body and parts.

[0062]

The present invention will now be described in detail with reference to specific examples.
However, the present invention is limited by the following examples.
Not something. Parts and% mean parts by weight and weight%, respectively.
To taste.Production Example 1 Production of acrylic resin  Nitrogen inlet tube, stirrer, temperature controller, dropping funnel and cooling
Charge 300 parts of xylol into a 2 L reaction vessel equipped with a tube
The temperature was set to 130 ° C. Next, styrene 100
Parts, 400 parts of ethyl acrylate, n-butyl acryle
50 parts, acrylic acid 50 parts, hydroxyl group-containing polymerizable monomer
400 parts of body (Placcel FA-1, manufactured by Daicel Chemical Co., Ltd.)
And t-butyl peroxy-2-hexanoate 130
By mixing the parts, a monomer solution was separately prepared.
The monomer solution is dropped into the reaction vessel over 3 hours while stirring.
After lowering, stirring was continued for 30 minutes, and t-butyl
Oxy-2-hexanoate 10 parts and xylol 10 parts
And the mixture was dropped for 15 minutes and then stirred for 1 hour
And a resin solid content of 70%, a number average molecular weight of 2,000, and hydroxyl
An acrylic resin having a base value of 98 and an acid value of 39 mgKOH / g was used.
Obtained.

[0063]Production Example 2 Production of polyester resin  Synthesis thermometer, stirrer, cooling pipe, nitrogen inlet pipe, water separator,
3-ethoxypropion in a 3 L reaction tank equipped with a rectification column
300 parts of ethyl acid, 500 parts of trimethylolpropane,
250 parts of ε-caprolactone, 0.1 part of dibutyltin oxide
And heated to 150 ° C. and maintained. 2 at 150 ° C
After holding for a while, heat and dissolve
Add 300 parts of tallic acid and keep at 150 ° C for 3 hours
, A number average molecular weight of 2,000 and an acid value of 30 mg KOH /
g (solid content), hydroxyl value 150 mg KOH / g (solid
Varnish with 80% non-volatile content containing polyester resin
I got

[0064]Production Example 3 Production of Crosslinkable Polymer Fine Particles  Stirring heater, thermometer, nitrogen inlet pipe, cooling pipe and decane
Bishydroxyethyl tauri in a reaction vessel equipped with
213 parts by weight, neopentyl glycol 208 parts by weight
Parts, 296 parts by weight of phthalic anhydride, 376 parts of azelaic acid
And 30 parts by weight of xylene and heated to reflux temperature.
Warmed. Here, the water generated by the reaction is
Removed azeotropically. Reaction takes about 3 hours from the start of reflux
Raise the temperature inside the system to 210 ° C and
Until the acid value corresponding to the acid is 135 mg KOH / g
The reaction was carried out with stirring and dehydration.

After cooling the temperature in the reaction system to 140 ° C., 500 parts by weight of “Kajura E10” (trade name, glycidyl versatate) manufactured by Shell Co., Ltd. were added to 30 parts by weight.
Dropped over minutes. Then, after stirring for about 2 hours, the reaction was terminated. Thereby, the acid value of the resin solid content is 55 m
gKOH / g and hydroxyl value of 91 mgKOH / g
And a zwitterionic group-containing polyester resin having a number average molecular weight of 1250 was obtained. 10 parts by weight of the obtained amphoteric group-containing polyester resin, 140 parts by weight of deionized water, 1 part by weight of dimethylethanolamine, 50 parts by weight of styrene and 50 parts by weight of ethylene glycol dimethacrylate are vigorously stirred in a stainless steel beaker. Thereby, a monomer suspension was prepared. Also, an initiator aqueous solution was separately prepared by mixing 0.5 parts by weight of azobiscyanovaleric acid, 40 parts by weight of deionized water, and 0.32 parts by weight of dimethylethanolamine.

A reaction vessel equipped with a stirring and heating device, a thermometer, a nitrogen inlet tube and a cooling tube was charged with 5 parts by weight of an amphoteric group-containing polyester resin, 280 parts by weight of deionized water, and 0.5 part by weight of dimethylethanolamine. To 80 ° C. Here, the previously prepared monomer suspension 251
Parts by weight and 40.82 parts by weight of the aqueous initiator solution at the same time
After the reaction was continued for 60 minutes, the reaction was terminated to obtain a crosslinkable resin particle emulsion.

The average particle size of the crosslinkable resin particle emulsion was 55 nm as measured by a dynamic light scattering method. Xylene was added to this crosslinkable resin particle emulsion, and azeotropic distillation was performed under reduced pressure to remove water and replace the medium with xylene. Thus, a xylene solution of crosslinkable resin particles having a resin solid content of 20% by weight, which can function as a structural viscosity imparting agent, was obtained. The obtained crosslinkable polymer fine particles had an average particle size of 100 nm.

[0068]Production Example 4 Primer coating for repair of intermediate coating film
Of the composition  Acrylic resin obtained in Production Example 1, Polyes obtained in Production Example 2
Teru resin, surface conditioner (Dispalon KS-281, Kusunoki
Hon Kasei Co., Ltd.), titanium oxide (Taipec CR-97, stone
Hara Sangyo Co., Ltd.), carbon black (MA-100, Mitsubishi)
Precipitated barium sulfate as an extender, carbonized
Hydrogen solvents (Solvesso-100, Exxon Chemical Co., Ltd.)
), Xylol and toluene in the amounts shown in Table 1.
After mixing and pre-mixing, paint conditioner
At room temperature for 1 hour to obtain a pigment-dispersed paste
Was. Add methyl / butyl mixed alcohol to the above pigment dispersion paste.
Cymel 202 (non-melted ether melamine resin)
Volatile content 80%) and Cymel 254 (non-volatile content 80%)
(Both trade names, manufactured by Mitsui Cytec Co., Ltd.)
, The crosslinkable polymer fine particles obtained in Production Example 3 were added, and 10 minutes
Disperser agitated, primer coating for repair of intermediate coating film
Compositions 1 to 9 were obtained. The amount of the resins in Table 1 is
Expressed as solids.

[0069]Preparation example Preparation of base  Treat with 30cm x 40cm x 0.8mm zinc phosphate
Dal steel sheet with cationic electrodeposition paint (Power Top U-5)
0, manufactured by Nippon Paint Co., Ltd.)
And baked at 170 ° C. for 30 minutes. L value
(L₀ ) Was 75. On top of this, an intermediate coating (ol
Gas P-2, manufactured by Nippon Paint Co., Ltd.
/ Xylene = 1/4 (weight ratio)) for 23 seconds / 20 ° C (#
4 Ford Cup) diluted and air sprayed
It was applied with a gun so that the dry film thickness was about 40 μm.
After setting for 7 to 10 minutes, bake at 140 ° C for 30 minutes
The ground was obtained.

[0070]Examples 1 to 5, Comparative Examples 3 to 6 Intermediate coating film
Repair of  10cm x 10cm coating film of the base obtained in Preparation Example
Sandpaper (WATER PROOF PA)
PER (Aluminum Oxide; AA-800)
-CW), manufactured by SANKYO) and obtained in Production Example 4.
Blown primer coating compositions 1 to 9
Using a spray gun so that the dry film thickness becomes 15 μm
Applied. The primer coating composition for repairing the intermediate coating film
L value of object 1 (L₁ ) Was 95. Then the base coat
Xylene, toluene and butyl acetate
20: 30/20 with a solvent consisting of 30:30:40
℃ (# 4 Ford Cup) diluted Silva
-Metallic paint (Super Rack M-1300, Japan
(Made by Paint Co., Ltd.) so that the dry film thickness becomes 15 μm.
Applied voltage -60kV, rotation using additive "metabell"
Several 25000 rpm, shaving air pressure 3.5 kg
/ Cm^Two , Two-stage painting with a discharge rate of 120 cc / min
Was. 1.5 minute interval between two applications
Was. After the second application, setting was performed for 3 minutes.
On the obtained base painted surface, butyl acetate / xylene = 1 /
30 seconds / 20 ° C (# 4 Fordka)
Acid-epoxy curable solvent cream diluted to
Paint (Macflow O-1300 Clear, Nippon Paint)
Int Co.) with an air spray gun and a dry film thickness of about 4
Coating was performed so as to be 0 μm. Set for 7 minutes
Thereafter, baking was performed at 140 ° C. for 30 minutes to obtain a laminated coating film.

For each of the above-mentioned primer coating compositions for repairing the intermediate coating film, the nonvolatile content (% by weight), the pigment weight concentration (PWC) with respect to the solid content of the primer coating composition for repairing the intermediate coating film (PWC) (% by weight), Volatile organic compound concentration (VOC) at the time of coating (g / L), viscosity at the time of coating (cps)
/ 10 ^-2 · sec ^-1 ), the difference between the L value of the base (L ₀ ) and the L value (L ₁ ) of the coating film obtained by applying and baking the primer coating composition for repairing the intermediate coating film. (ΔL = L ₁ −
L ₀ ) was measured and calculated. Table 1 shows the results. The measurement of the L value and the viscosity at the time of coating was performed as follows.

(Measurement of L value) The L value was measured using Minolta CR-300 (manufactured by Minolta). (Measurement of Viscosity at the Time of Coating) Each primer coating composition for repairing the intermediate coating film was applied to a 400 mm × 300 mm tin plate using a hand spray gun so as to have a dry film thickness of 15 μm. The wet coating was collected in a closed container. About 5 mL of this sample was collected, and the viscosity was measured with an LSV (Low Shear Viscometer PN-IV, manufactured by Tokyo Keiki Co., Ltd.). Rubbing speed (sec)
^-1 ) was plotted in the form of viscosity (cps), and the viscosity (cps) at the rubbing speed (10 ^-2 sec ^-1 ) was read from this graph.

[0073]

[Table 1]

(Evaluation) The obtained laminated coating film was evaluated as follows. Table 2 shows the results. 1. Repairability (sharp discoloration) Sharp discoloration was visually observed and evaluated according to the following criteria. ○ I can't see it at all. ○ △ You can see it when you look closely. △ Seen from a certain angle. △ × Somewhat easy to see. × Clearly visible from everywhere.

2. Underlayer concealing property The undercolor and defects of the underlayer were visually observed and evaluated according to the above-mentioned criteria. 3. Workability The workability was evaluated according to the following criteria, focusing on the presence of defects such as sagging and armpits. ○ No problems such as sagging and armpits. ○ △ Some defects such as sauce and armpit occur. △ Defects such as sauce and armpit slightly decreased. △ × Defects such as sauce and armpit are considerably reduced. × Impossible.

4. Finishability The finish appearance was visually observed and evaluated according to the following criteria. ○ Very good. ○ △ Good. △ Slight decrease. △ × considerably reduced. × Impossible.

5. Color Tone Identity (Scaling) Hue differences were visually observed between the repaired part and the non-repaired part, and the color tone identity (scaling) was evaluated in accordance with the above-described criteria.

6. Adhesion Regarding the adhesion between the base and base coatings and the repair coatings, 10 × 10 = 100 squares were cut into squares of 1 mm × 1 mm with a cutter knife, and Nichiban cellophane tape was applied. It was measured by attaching it on a surface and peeling it off in the direction of 90 °, and evaluated according to the following criteria. ○ Very good. ○ △ Good. △ Slight decrease. △ × considerably reduced. × Significant reduction.

7. Chipping resistance Sample holder for stepping stone tester (manufactured by Suga Test Instruments Co., Ltd.)
A coated plate cooled to 0 ° C. was attached so that the angle of entry of the stone was 90 °, and 100 g of No. 7 crushed stone was jetted at an air pressure of 3 kg / cm ² to cause the crushed stone to collide with the coated plate. From the degree (number, size, breaking place) of peeling at that time, evaluation was made according to the criteria of the above 6.

[0080]Comparative Example 1  Primer coating composition for repairing intermediate coating film obtained in Production Example 4
Instead of the repair primer (CR-kai, PPG
Examples 1 to 5, Comparative Example 3
6 and a laminated coating film was formed and evaluated.

[0081]Comparative Example 2  Primer coating composition for repairing intermediate coating film obtained in Production Example 4
Instead of silver metallic that has the same color as the base
Paint (Super Rack M-1300, L value 75, Nippon Paint
Examples 1-5,
A laminated coating film was formed and evaluated in the same manner as in Comparative Examples 3 to 6.
Was.

[0082]Comparative Example 7  Primer coating composition for repairing intermediate coating film obtained in Production Example 4
Examples 1 to 5, Comparative Examples 3 to
In the same manner as in 6, a laminated coating film was formed and evaluated.

[0083]

[Table 2]

From Table 2, it can be seen that Comparative Example 7 using no repair primer, Comparative Example 1 using a conventional repair primer, Comparative Example 2 using a base paint of the same color as the base, and no crosslinkable polymer fine particles were included. Not only Comparative Example 6 using the repair primer having a small amount of the melamine resin but also any one of those using the repair primer composed of the same kind of components as the primer coating composition for repairing the intermediate coating film of the present invention is In Comparative Examples 3 to 5, which were not within the scope of the invention, it was found that any of the evaluation items was inferior. On the other hand, in each of the examples using the primer coating composition for repairing an intermediate coating film of the present invention, favorable results were obtained in any of the evaluation items.

[0085]

As described above, the primer coating composition for repairing an intermediate coating film of the present invention has the above-mentioned constitution, and thus has problems such as sharpening discoloration, poor appearance such as sagging, unevenness, shine, spots, and waki. Since not only a good finish can be obtained without occurrence, but also excellent in base concealing property, adhesion to the base, and chipping resistance, it can be suitably used for repairing an intermediate coating film.

Continuation of the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) C09D 7/12 C09D 7/12 161/28 161/28 167/00 167/00 201/00 201/00 F-term (reference) ) 4D075 AE03 BB03X BB20X CA04 CA13 CA47 CB07 DA06 DA23 DA25 DA27 DB02 DB05 DB06 DB07 DB08 DB31 DC12 DC13 EA07 EA41 EA43 EB14 EB19 EB22 EB32 EB33 EB35 EB36 EB38 EB45 EB52 EB56 CG52 EC1 CH041 CH042 CH121 CH122 CJ031 CJ032 CJ071 CJ072 DA161 DA162 DD051 DD052 DD121 DD122 KA08 MA09 MA10 MA12 MA14 MA15 NA01 NA11 NA12 PA19 PB07 PB12 PC08

Claims (5)

[Claims] A primer coating composition for repairing an intermediate coating film for repairing an intermediate coating film, wherein the primer coating composition for repairing an intermediate coating film comprises an acrylic resin, a polyester resin, and melamine. It contains a resin and crosslinkable polymer fine particles, and further contains a pigment, wherein the crosslinkable polymer fine particles, the solid content of the acrylic resin, the polyester resin and the melamine resin 100 parts by weight, the solid content And the melamine resin contains 22 to 58 parts by weight as a solid content based on 100 parts by weight of the solid content of the acrylic resin, the polyester resin and the melamine resin. Yes, volatile organic compound concentration (VO
C) is 540 g / L or less, and the rubbing speed at the time of coating is 1
The viscosity at 0 ^-2 · sec ⁻¹ is 5000 cps or more, and the pigment contains 10 to 68% by weight as a pigment weight concentration (PWC) based on the solid content of the primer coating composition for repairing the intermediate coating film. And the difference (ΔL) between the L value (L ₀ ) of the intermediate coating film and the L value (L ₁ ) of the coating film obtained by applying and baking the primer coating composition for repairing the intermediate coating film. = L ₁ -L ₀ ) is 24 or less. 2. The primer coating composition for repairing an intermediate coating film according to claim 1, wherein the pigment contains titanium dioxide as a pigment. 3. The repaired portion of the intermediate coating film formed on the base material is ground, and the primer coating composition for repairing the intermediate coating film according to claim 1 or 2 is applied on the repaired portion. And subsequently forming a base coating film and, if necessary, a clear coating film. 4. The method according to claim 3, wherein the base coating film contains an acrylic resin, a polyester resin, and a melamine resin. 5. A substrate having a coating film formed by the coating film forming method according to claim 3.