JPH0315499B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a new and useful method for forming two-coat metallic coatings, and more particularly, to a method for forming a new and useful two-coat metallic coating, and more particularly, the present invention relates to a method for forming a new and useful two-coat metallic coating, and more particularly, a metallic base coating and a topcoat clear coating using a metal powder, a film-forming polymer, and a hydrated coating, respectively. Using both types of paints containing a degradable silyl group-containing polymer and an alkoxysilane-modified resin as main components, first a metallic base paint is applied to the base resin, and then a clear paint is applied as a top coat on top of the metallic base paint. Apply it, then leave it at room temperature.
Alternatively, it relates to a coating film forming method comprising baking and curing. In recent years, metallic finish coating methods have been widely used for the purpose of beautifully finishing metal surfaces such as automobile bodies, and this method mainly uses metal powder,
The coating is formed by applying a metallic base paint comprising a pigment and a film-forming resin, and then applying a top clear paint to form a transparent film. By the way, the film-forming resin that is the main component of this metallic base paint is alkyd.
Melamine resins, acrylic-melamine resins, cellulose resin-modified acrylic lacquers, pure acrylic lacquers, or acrylic-urethane resins are used.On the other hand, as top clear resins, acrylic-melamine resins are used. resins, alkyd-melamine resins, acrylic-urethane resins, acrylic lacquers, etc. are used. However, clear coatings using these film-forming components are insufficient in terms of weather resistance, and the coating may crack or crack if exposed outdoors for a long period of time. It has a major disadvantage of being inferior in durability, such as yellowing or yellowing. In order to overcome these drawbacks, paints using moisture-curable acrylic resins containing hydrolyzable silyl group-containing copolymers as the main component have been proposed, but such resins are extremely The current situation is that nothing satisfactory has yet been found in terms of providing a coating film with poor flexibility. However, as a result of intensive research in view of the various shortcomings in the prior art as described above, the present inventors have developed a top clearer that uses a hydrolyzable silyl group-containing polymer and an alkoxysilane-modified resin as the main components. By using paint that
The present invention was completed by discovering that a coating film having not only weather resistance but also sufficient hardness and excellent flexibility could be obtained. That is, in the present invention, first, a metallic base paint containing metal powder, a film-forming polymer, a diluting thinner, and, if necessary, a coloring pigment is applied to the surface of the substrate, and then one molecule is coated as a top coat. A compound (a-1) containing at least two or more hydroxyl groups in it, and at least one general formula in one molecule [However, R ¹ , R ² and R ³ in the formula are each an independent linear or branched alkyl group, cycloalkyl group, alkenyl group, alkyl group substituted with a halogen atom or an alkoxyl group, or a phenyl group. or represents a substituted phenyl group. ] The alkoxysilane-modified resin (A) obtained by reacting the compound (a-2) containing a trialkoxysilyl group represented by A clear composition comprising a hydrolyzable silyl group-containing polymer (B) containing at least one hydrolyzable silyl group per molecule at its terminal, a curing catalyst (C), and a solvent (D). Apply and
The object of the present invention is to provide a new method for forming a two-coat metallic coating film having excellent flexibility and weather resistance, which comprises forming a cured coating film by baking or drying at room temperature. First of all, all currently used metallic base paints can be applied, but if we explain each component that makes up the paint, typical metal powders include aluminum powder. , copper powder, zinc powder, etc. Typical film-forming polymers include thermosetting acrylic-melamine type resin, alkyd-melamine type resin, oil-free alkyd-melamine type resin, acrylic-melamine type resin, etc. Moisture-curable hydrolyzable silyl group-containing polymers such as cold-curing (low-temperature curing) polyurethane resins, such as blocked isocyanate-type resins, alkyd-blocked isocyanate-type resins, oil-free alkyd-blocked isocyanate-type resins, or polyurethane-type resins. Systematic resins include room temperature drying type, (low temperature drying type) pure acrylic lacquer, cellulose resin modified acrylic lacquer, etc., and diluting thinners include metal powder and film-forming polymers.
Furthermore, if necessary, any material that can dissolve or stably disperse pigments and other various additive components may be used.If the smoothness of the coating surface and the so-called metal retention of the metal powder are taken into consideration, preferably the boiling point It is appropriate to use diluted thinners consisting of several different solvent components. Further, the metallic base paint can also contain known and commonly used coloring pigments, if necessary. Next, the hydrolyzable silyl group-containing polymer (B) constituting the clear composition described above has the general formula [However, R ⁴ in the formula is a hydrogen atom or an alkyl group,
A monovalent organic group such as an aryl group or an aralkyl group, R ⁵ is a halogen atom or an alkoxyl group,
It represents an acyloxy group, phenoxy group, mercapto group, amino group, iminooxy group or alkenyloxy group, and a is 0, 1 or 2.
Let it be an integer. ] Halosilyl group, alkoxysilyl group represented by
It refers to a polymer containing a functional group that is easily hydrolyzed, such as an acyloxysilyl group, phenoxysilyl group, mercaptosilyl group, aminosilyl group, iminooxysilyl group, or alkenyloxysilyl group, and the above-mentioned alkoxysilane-modified resin Only polymers such as (A) in which an alkoxysilyl group is bonded via an oxygen atom are excluded from the polymer (B). Typical examples of the polymer (B) include vinyl (co)polymers, saturated or unsaturated polyester resins, alkyd resins, urethane resins, and polyether resins. Vinyl-based (common) due to chemical resistance etc.
Polymers are particularly preferred. In addition, as the hydrolyzable silyl group, which can also be called a characteristic group, in the polymer (B), among the various functional silyl groups listed above, alkoxysilyl groups are preferable because they do not produce undesirable volatile components during curing. Most desirable. Therefore, in order to introduce an alkoxysilyl group into the above-mentioned vinyl copolymer, a mixture of a vinyl monomer containing an alkoxysilyl group and another vinyl monomer copolymerizable with the vinyl monomer is used. Copolymerize. A vinyl monomer is radically polymerized using an alkoxysilane containing a mercapto group as a chain transfer agent. A separately prepared vinyl copolymer having an unsaturated group or an epoxy group in its side chain is reacted with aminosilanes, hydrosilanes, and mercaptosilanes containing an alkoxysilyl group. Although well-known methods such as , etc. can be applied, it is most convenient to use only one of these methods, only the method , or a combination of the method and the method. Specific examples of vinyl monomers containing alkoxysilyl groups used when introducing alkoxysilyl groups by the above copolymerization method include γ-
(meth)acryloyloxypropyltrimethoxysilane, γ-(meth)acryloyloxypropyltriethoxysilane, γ-(meth)acryloyloxypropylmethyldimethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltripropoxysilane, vinyl Examples include methyldiethoxysilane, vinyltris(β-methoxyethoxy)silane, and allyltrimethoxysilane. Specific examples of alkoxysilanes containing mercapto groups that are used when introducing alkoxysilyl groups by a method using a chain transfer agent include γ-mercaptopropyltrimethoxysilane and γ-mercaptopropyltriethoxysilane. The alkoxysilyl group-containing monomer and/or mercapto group-containing alkoxysilane are used in an amount such that the amount of alkoxysilyl group introduced per 1000 g of resin solid content is in the range of 0.1 to 3 moles from the viewpoint of curability and cost. It is preferable to do so. In this way, a hydrolyzable silyl group-containing polymer (B) is obtained by copolymerizing the alkoxysilyl group-containing vinyl monomer as described above with a vinyl monomer copolymerizable therewith. It will be done. Typical examples of such copolymerizable vinyl monomers include methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, cyclohexyl (meth)acrylate, (meth)acrylic acid esters such as benzyl (meth)acrylate; hydroxyalkyl esters of (meth)acrylic acid such as 2-hydroxyethyl (meth)acrylate and 2-hydroxypropyl (meth)acrylate; itaconic acid, fumaric acid or monoalkyl or dialkyl esters of dibasic acids such as maleic acid; aromatic vinyl compounds such as styrene, α-methylstyrene, vinyltoluene; and also vinyl acetate, vinyl chloride, (meth)acrylonitrile, N,N-dialkyl aminoalkyl (meth)acrylate,
(meth)acrylic acid, crotonic acid, itaconic acid,
These include fumaric acid, (anhydrous) maleic acid, N-alkoxymethyl (meth)acrylamide, (meth)acrylamide, N-methylolacrylamide, or (meth)acrylic acid glycidyl ester. The vinyl (co)polymer described above can be prepared by any known method such as solution, bulk, or suspension polymerization, but solution radical polymerization is most preferred. Typical solvents used in this case include hydrocarbons such as toluene, xylene, cyclohexane, n-hexane, and octane; methanol, ethanol, i
- Alcohols such as propanol, n-butanol, i-butanol, sec-butanol, ethylene glycol monoalkyl ether; esters such as ethyl acetate, methyl acetate, butyl acetate, or ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone Alcohol-based solvents may be used, but in order to improve the storage stability of the vinyl (co)polymer solution and the pot life of the composition used in the method of the present invention, alcohol-based solvents may be used in an amount of at least 10% by weight of the total solvent amount. It is preferable to use a solvent containing a solvent. In addition, for the purpose of removing trace amounts of water present in the reaction system, such solvents may contain trialkyl orthoformates such as trimethyl orthoformate or triethyl orthoformate; alkyl tetrasilicate such as tetramethyl silicate or tetraethyl silicate. It is preferable to coexist with esters; and/or self-condensates of the above-mentioned tetrasilicate alkyl esters such as "ethyl silicate 40" (product of Nippon Colcoat Co., Ltd., a mixture of tetramers, pentamers and hexamers of ethyl silicate). Polymerization may be carried out by a conventional method using such a solvent and various polymerization initiators such as an azo type or a peroxide type polymerization initiator. Furthermore, various chain transfer agents such as lauryl mercaptan, 2-mercaptoethanol or α-methylstyrene dimer can also be used in this polymerization. Next, a hydroxyl group-containing compound (a
-1) refers to a compound containing at least two hydroxyl groups in one molecule, and typical examples of such compounds (a-1) include ethylene glycol, diethylene glycol, polyethylene glycol, and propylene glycol. , dipropylene glycol, polypropylene glycol, 1,4-butanediol, 1,3-butanediol, 1,6-hexanediol, cyclohexanedimethanol, neopentyl glycol, glycerin, 3-methylpentane-1,3,5- Polyhydric alcohols such as triol, pentaerythritol, and sorbitol; saturated or unsaturated polyester resins, alkyd resins, vinyl polymers,
Polybutadiene glycol, epoxy resin; and ester compounds containing hydroxyl groups obtained by reacting the above-mentioned polyhydric alcohols or various resins with ε-caprolactone. Among the above-mentioned compounds containing hydroxyl groups, ε-
Particularly preferred are hydroxyl group-containing ester compounds obtained by adding caprolactone. The ε-caprolactone adduct of such a hydroxyl group-containing compound is preferably added in a ratio of about 1 to 20 moles of ε-caprolactone per equivalent of hydroxyl group in the presence of a conventionally known catalyst. As a specific example of a compound (a-2) containing at least one trialkoxysilyl group represented by the above general formula [] per molecule, which is another component used in obtaining the alkoxysilane modified resin (A). is a simple tetra (substituted) alkyl silicate such as tetramethyl silicate, tetraethyl silicate, tetrabutyl silicate, tetra (2-methoxyethyl) silicate or tetra (2-chloroethyl) silicate; tetraphenyl silicate or tetrabenzyl silicate; Substances with the same effect as the above-mentioned tetra(substituted) alkyl silicates (hereinafter abbreviated as the same effect substance) or dimer of tetraethyl silicate, such as
Each of the above-mentioned tetra(substituted) alkyl silicates alone, such as tetra or hexamer, or a condensation product of the same effective alone of said silicates; vinyltrimethoxysilane, vinyltriethoxysilane or glycidoxypropyltrimethoxysilane, γ- Silane coupling agents such as methacryloxypropyltrimethoxysilane or 3-(β-aminoethyl)aminopropyltrimethoxysilane; hydrosilanes such as trimethoxysilane or triethoxysilane; or allyl acetate,
Adducts of compounds having one or more allyl groups per molecule, such as allyl benzoate, diallyl phthalate, diallyl adipate, diallyl succinate or triallyl trimellitate, and the above-mentioned hydrosilanes; Examples include vinyl (co)polymers containing groups, and these may be used alone or in combination of two or more. Among these trialkoxysilyl group-containing compounds (a-2), condensation of tetraalkyl silicates such as tetramethyl silicate, tetraethyl silicate, and tetrabutyl silicate, or tetraalkyl silicates such as dimer, trimer, or tetramer of tetraethyl silicate It is especially desirable from the point of view of price to use In order to prepare the alkoxysilane-modified resin (A) from both the compound (a-1) and the compound (a-2) listed above, it is necessary to prepare These two compounds may be reacted at a temperature of .degree. The reaction method at this time is the compound (a-
There is a method of charging 1), compound (a-2), and catalyst all at once and heating it, or first charging compound (a-2) and catalyst, and then adding compound (a-1) to the mixture. There is also a method of heating while dropping, but in either case, the alcohol produced is distilled under normal pressure or reduced pressure to remove it from the system. However, in the case of the former method, the compound (a-
1) When the content of hydroxyl groups per molecule is high, the risk of gelation increases if the compound is added all at once, so it is particularly preferable to use the dropwise addition method. Catalysts that can be used in this case include titanium compounds such as tetraisopropyl titanate and tetrabutyl titanate; acidic substances such as sulfuric acid, phosphoric acid, alkyl phosphoric acid, and hydrochloric acid; lithium hydroxide, sodium hydroxide, potassium hydroxide, and sodium methylate. Typical examples include alkaline substances such as , triethylamine, and tributylamine, and among these, it is particularly preferable to use titanium compounds. The reaction ratio of compound (a-1) and compound (a-2) during this alkoxysilane modification is as follows: 1 equivalent of hydroxyl group contained in (a-1) to 1 equivalent of trialkoxy group in (a-2) Silyl group is 0.6
-10 equivalents, preferably 0.8-10 equivalents. When the equivalent ratio is less than 0.6, gelation tends to occur during the reaction. Even if the amount exceeds 10 equivalents, there will be no adverse effects on the synthesis or on the properties of the obtained resin, but from a price point of view, it is still
The amount is preferably 10 equivalents or less. In the modification, if the compound (a-1) is liquid at the reaction temperature, there is no need to use a special solvent, but if the compound (a-1) is a solid substance or the compound (a-1) ) and (a-2) do not mix uniformly, it is preferable to use a solvent with a relatively high boiling point that does not react with these two compounds, and a typical example of such a solvent is butyl acetate. , xylene, cellosolve,
Examples include acetate, cyclohexanone, and methyl isobutyl ketone. In addition, in the modification, compound (a-2)
As compound (a-1), the above-mentioned tetra(substituted)alkyl silicates, the same effective simple substances of the silicates, and/or their condensates are used as compound (a-1).
If used in excess of It can be used as it is as the solvent (D) or as a part of the component (D).
The blending ratio with component (B) is 0.5 to 80% by weight of component (A).
A suitable range is 99.5 to 20% by weight of the component (B). Next, as the above-mentioned curing catalyst (C), any known and commonly used catalyst for hydrolysis or condensation of silyl group-containing compounds as mentioned above may be used, and a typical example of such a curing catalyst (C) is butylamine. , dibutylamine, hexylamine, t-butylamine, ethylenediamine, triethylamine, isophoronediamine, imidazole, lithium hydroxide, sodium hydroxide, potassium hydroxide,
Basic compounds such as sodium methylate; tetraisopropyl titanate, tetrabutyl titanate, tin octylate, lead octylate, cobalt octylate, zinc octylate, calcium octylate, lead naphthenate, cobalt naphthenate, dibutyltin diacetate, dibutyltin dioctoate,
Metal-containing compounds such as dibutyltin dilaurate and dibutyltin maleate; phosphoric acid esters of p-toluenesulfonic acid, trichloroacetic acid, phosphoric acid, monoalkyl phosphoric acid, dialkyl phosphoric acid, β-hydroxyethyl acrylate, monoalkyl phosphorous acid, dialkyl phosphorous acid, etc. Among them, tin compounds such as dibutyltin diacetate, dibutyltin dioctoate, dibulltin dilaurate, or dibutyltin maleate are preferred. The amount of curing catalyst (C) used is as follows:
0.001 to total solid content of component (A) and component (B)
A range of 10% by weight, preferably 0.01 to 5% by weight, is suitable. Next, as the above-mentioned solvents (D), each component other than the component (D), that is, the alkoxysilane modified resin.
Any material that can dissolve or stably disperse (A), the hydrolyzable silyl group-containing polymer (B), and the curing catalyst (C) may be used. Representative examples include toluene, xylene, Various hydrocarbons such as cyclohexane, n-hexane, and octane; various alkyl alcohols such as methanol, ethanol, i-propanol, n-butanol, t-butanol, and ethyl glycol monoalkyl ether; methyl acetate, ethyl acetate, Examples include various ester-based solvents such as butyl acetate; and various ketone-based solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone. Among these, it is particularly preferable to use alcohol-based solvents, and in combination with such alcohol-based solvents, the above-mentioned trialkyl orthoformates, single tetraalkyl silicates, single silicates with the same effect, and/or condensates thereof, etc. The combination with hydrolyzable esters is particularly preferred from the viewpoint of stability. The clear composition for top coat used in the method of the present invention, which is obtained by blending each of the components listed above, includes a known and commonly used flow regulator,
Of course, additive components such as color separation inhibitors, antioxidants, or ultraviolet absorbers may be added. In addition, silicates or silane coupling agents, nitrocellulose or cellulose
Of course, various additive components such as cellulose derivatives such as acetate butyrate can also be added. Here, the above-mentioned silicates or silane coupling agents include γ-aminopropyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, and γ-methacryloxypropyl. Typical examples include trimethoxysilane, vinyltrimethoxysilane, and vinyltriethoxysilane. A clear composition containing each of these components is diluted to a desired viscosity using the solvent (D) as a diluting thinner, and then this diluted paint is applied to the surface of the substrate in advance. metallic
A clear layer may be formed by coating on the base coat layer, and then cured. At this time, after applying the metallic base paint, the base coat layer may be cured by heating in advance, or alternatively, a clear layer may be formed in a so-called wet-on-wet state. The curing method is by baking if the film-forming polymer for the metallic base is a thermosetting type, or by forced drying at a low temperature or by drying at room temperature for approximately
It is sufficient to leave it for about a week, and in this way the desired cured coating film can be obtained. Thus, the coating film forming method of the present invention can be applied to automobiles,
It can be used for woodworking, building materials or even as a coating for plastics. Next, the present invention will be specifically explained with reference to Reference Examples, Examples, and Comparative Examples. In the following, unless otherwise specified, all parts and percentages are based on weight. Reference Example 1 [Example of preparation of hydrolyzable silyl group-containing copolymer for metallic base paint] 400 parts of toluene, n- 294 parts of butanol, 5 parts of methyl orthoformate, and 1 part of tetraethylsilicate were charged and heated to 105°C under a nitrogen atmosphere, and then 300 parts of styrene (St) and 300 parts of methyl methacrylate (MMA) were added. , n-butyl acrylate (n-
BA) 270 parts, γ-methacryloyloxypropyltrimethoxysilane (γ-MPTMS) 130 parts,
Azobisisobutyronitrile (AIBN) 10 parts, t
-Butyl peroxybenzoate (t-BPB)
A mixture of 5 parts of toluene and 300 parts of toluene was added dropwise over 3 hours and kept at the same temperature for 15 hours to obtain a non-volatile content (NV) of 50%, a Gardner color of less than 1, and a number average molecular weight (). A solution of the target polymer with a particle diameter of 15,000 was obtained. Hereinafter, this will be abbreviated as polymer (P-1). Reference Example 2 [Preparation example of hydrolyzable silyl group-containing polymer (B) for clear composition] First, 400 g of toluene was placed in a reactor similar to Reference Example 1.
parts, n-butanol 294 parts, methyl orthoformate 5 parts
The temperature was raised to 105°C under a nitrogen atmosphere, and then at the same temperature 300 parts of St, 400 parts of MMA, 85 parts of n-BA, 15 parts of mono-n-butyl maleate, and γ-
A mixture consisting of 200 parts of MPTMS, 6 parts of AIBN, 30 parts of t-butylperoxyoctoate (t-BPO) and 300 parts of toluene was added dropwise over 4 hours, and the temperature was further maintained for 15 hours to produce Gardner color at 50% NV. A solution of the desired polymer (B) of 1 or less was obtained. Hereinafter, this will be abbreviated as polymer (B-1). Reference Example 3 [Preparation example of alkoxysilane-modified resin (A)] In a reactor equipped with a stirring device, a thermometer, a nitrogen introduction tube, and a cooling tube, 62 parts (1 mol) of ethyl glycol and 342 parts (342 parts of ε-caprolactone) were added. mol) and 0.02 part of tetrabutyl titanate were charged, the temperature was raised to 180°C under a nitrogen atmosphere, and the temperature was maintained at the same temperature for 6 hours to obtain an adduct with a molar ratio of ethyl glycol and ε-caprolactone of 1:3. Ta. Next, the temperature was lowered to 90°C, and then 624 parts of tetraethyl silicate and 1 part of tetrabutyl titanate were added, that is, the equivalent ratio of the tetraethyl silicate to the hydroxyl group in the adduct of ethylene glycol and ε-caprolactone was 1.5. In addition, the temperature was raised to 110°C under a nitrogen atmosphere, but during this time, when the temperature reached 100°C or higher, ethyl alcohol began to distill out. Thereafter, the target resin (A) was obtained by maintaining the temperature at 110 to 120°C until no more ethyl alcohol was distilled out. Hereinafter, this will be abbreviated as resin (A-1). Reference Example 4 (Same as above) In a reactor similar to Reference Example 3, 134 parts (1 mol) of trimethylolpropane and 684 parts of ε-caprolactone were added.
part (6 mol) and tetrabutyl titanate 0.04
The temperature was raised to 80° C. over 6 hours under a nitrogen atmosphere to obtain an adduct of trimethylolpropane and ε-caprolactone in a molar ratio of 1:6. Next, after lowering the temperature to 90°C, 936 parts of tetraethyl silicate and 5.3 parts of tetrabutyl titanate were added.
parts were added so that the equivalent ratio of this tetraethyl silicate and the adduct of trimethylolpropane and ε-caprolactone was 1.5, and
Until the distillation of ethyl alcohol stops at 120℃.
The reaction was carried out for about 3 hours to obtain the target resin (A). Hereinafter, this will be abbreviated as resin (A-2). Reference Example 5 (Same as above) 818 parts of the adduct of trimethylolpropane and ε-caprolactone in a 1:6 (molar ratio) obtained in Reference Example 4, 2230 parts of "ethyl silicate 40" and tetrabutyl titanate. A mixture of 9.2 parts of
The produced ethyl alcohol was distilled off to obtain a resin (A) modified with a tetraethylsilicate self-condensate. Hereinafter, this will be abbreviated as resin (A-1). Examples 1 to 8 First, a metallic base paint was prepared by using the polymer (P-1) obtained in Reference Example 1 and "Alpaste 1109MA" as a metal powder [aluminum powder manufactured by Toyo Aluminum Co., Ltd.]. ;NV=65%] and
Dibutyltin diacetate as a curing catalyst is mixed in the proportions shown below, and then toluene/
This was carried out by diluting a composition of n-butanol/methyl orthoformate/tetraethyl silicate = 60/36/3/1 (weight ratio) with a diluting thinner so that the viscosity was 14 seconds with a food cup #4. Ivy. The metal powder concentration of the metallic base paint obtained here was 10%. Hereinafter, this will be abbreviated as base paint (i). Polymer (P-1) 100 parts "Alpaste 1109MA" 8.5〃 Dibutyltin diacetate 0.2〃 Next, to prepare a clear composition for top coat, first, the polymer (B-1) obtained in Reference Example 2 was prepared. ,
Resins (A-1) to (A-
3) and dibutyltin diacetate in the proportions shown in Table 1, and then toluene/xylene/n-butanol/methyl isobutyl ketone/cellosolve acetate/methyl orthoformate/
Tetraethyl silicate 18/30/29/10/10/
This was done by diluting with a diluted thinner of 2/(weight ratio) so that the viscosity measured by #4 food cup was 27 seconds. However, the same table also includes clear paint (v) for comparison. After that, first apply base paint (i) on a 0.8 mm thick Bonderite treated steel plate (Dull #144 treated steel plate).
Spray paint to a dry film thickness of 35 to 45 μm, then let it set for 5 minutes,
Various clear paints (i) to (iv)) were applied separately to form a film with a dry film thickness of 35 to 45 μm. Each coated plate obtained here was dried at room temperature for one week at 23°C to form a cured coated plate for testing. Comparative Examples 1 and 2 First, the following procedures were carried out, except that the formulation was as follows, and a mixed solvent of toluene/xylene/ethyl acetate = 30/40/30 (weight ratio) was used as the diluting thinner. Acrylic-urethane metallic base paints were prepared in the same manner as in Examples 1-8. Hereinafter, this will be abbreviated as base paint (ii). "Acrylic 44-127" [Acrylic polyol manufactured by Dainippon Ink and Chemicals Co., Ltd.; NV = 50%,
OHV=32.5〃 100 parts “Burnock DN-950” (polyisocyanate resin manufactured by the same company; NV=75%, isocyanate group content = 12.5%) 19.5〃 “Alpaste 1109MA” 11〃 Next, metallic base paint as,
Just as the base paint (ii) is used in addition to the base paint (i), the clear paint is formulated without any alkoxysilane-modified resin (A), as shown in Table 1. A film was formed in the same manner as in Examples 1 to 8, except that the prepared control clear paint (v) was used, and the film was dried at room temperature to produce a control cured coating plate. Various coating properties tests were conducted on each metallic coating film obtained in each Example and Comparative Example. The results are summarized in Table 2, and the coating film obtained by the method of the present invention has good weather resistance.
Moreover, it is known to have sufficient hardness and good flexibility.

【table】

【table】

Claims (1)

[Claims] 1. First, a base paint comprising a metal powder, a film-forming polymer, a diluting thinner, and, if necessary, a coloring pigment is applied to the surface of the substrate, and then As a top coat (A) a compound (a-1) containing at least two hydroxyl groups in one molecule and at least one general formula in one molecule; [However, R ¹ , R ² and R ³ in the formula are each an independent linear or branched alkyl group, cycloalkyl group, alkeni group, alkyl group substituted with a halogen atom or an alkoxyl group, or a phenyl group. or represents a substituted phenyl group. ] An alkoxysilane-modified resin obtained by reacting the compound (a-2) containing a trialkoxysilyl group represented by (B) with the side chain and/or main chain other than the above resin (A). A clear composition comprising a hydrolyzable silyl group-containing polymer containing at least one hydrolyzable silyl group per molecule at the terminal end of the clear polymer, (C) a curing catalyst, and (D) a solvent. A new method for forming a two-coat metallic coating film having excellent flexibility and weather resistance, which method comprises coating the coating and then baking or drying it at room temperature to form a cured coating film. 2. The film-forming polymer is substantially an acrylic-melamine type resin, an alkydo-melamine type resin, an acrylic-urethane type resin, a Lutzker type resin, or a hydrolyzable silyl group-containing polymer. A method according to claim 1. 3. The method according to claim 1 or 2, wherein the hydrolyzable silyl group-containing polymer (B) is substantially a hydrolyzable silyl group-containing vinyl polymer. Method. 4. The alkoxysilane-modified resin (A) is a resin obtained by substantially using an addition reaction product of a polyhydroxy compound and ε-caprolactone as the hydroxyl group-containing compound (a-1), A method according to claim 1. 5 The alkoxysilane modified resin (A) is a trialkoxysilyl group-containing compound (a-2),
The method according to claim 1, characterized in that the resin is obtained using substantially a single tetra(substituted) silicate, an equivalent single unit of the silicate, and/or a condensate thereof. . 6. The method according to claim 1, wherein the solvent D contains an alkyl alcohol and/or a hydrolyzable ester as an essential solvent. 7. The method according to claim 1, wherein the clear composition contains an ultraviolet absorber.