JP2629793B2 - Painting method - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a method for coating a resin-cured coating film whose coating film surface is not polished, and more particularly, to an acrylic method wherein the coating film surface is not polished. A specific acrylic urethane paint is applied to a cured coating of a thermosetting resin paint or acrylic urethane paint obtained by crosslinking a resin or polyester resin (including an oil-modified type) with an amino resin, and then cured to form the cured coating. The present invention relates to a coating method for forming a cured coating film having extremely excellent adhesion to the film 4.

[Conventional technology]

Conventionally, acrylic urethane paints have been used for a wide range of applications because cured coating films with excellent performance can be obtained even at room temperature or forced drying. However, one of the drawbacks or drawbacks is the adhesion of the thermosetting resin paint, which has not been polished on the surface, to a resin such as acrylic resin or polyester resin (including oil-modified type) crosslinked with amino resin, to the cured coating film. The properties are very unstable and insufficient, for example, the initial curing of the urethane paint, even if it adheres to some extent, the adhesion decreases as the curing progresses, or even at the initial curing stage It is known that many of them do not adhere. Therefore, as one of the methods for improving the adhesion of the urethane paint to the cured coating film, a method of adding a phosphate group-containing compound or copolymerizing has been proposed. However, with such a method, the effect is not sufficient under severe operating conditions such as the type of cured coating film or the cured state of the thermosetting resin paint to be coated, and the effect is not sufficient, or even if it is effective, the pot life Defects, such as shortening of the pigment, selectivity of the pigment in the enamel system (depending on the type of the pigment, reaction with the pigment may cause thickening and gelation of the system), and further, the type of the phosphoric acid group-containing compound (particularly, Depending on the amount of addition, there may be defects such as cissing, craters, and bleeding of the coating over time. At present, it is necessary to rely on a method of polishing the surface of a coating film, which has been used for a long time, as a measure for improving the performance.

Therefore, it is common to provide a polishing process for repair painting, marking coat, two-tone color finish, taping clear finish, etc. in industrial painting lines for automobiles, home appliances, metal products, etc. There is a great difficulty in the operation, and there is an urgent need for an acrylic urethane paint that completely adheres to the cured coating of the uncured thermosetting resin paint.

On the other hand, inorganic building materials such as ALC, cement roof tiles and slate boards, and buildings such as building outer walls, bridges, tanks, etc. have been coated with acrylic urethane paint for a long time. If the cured coating film of acrylic urethane paint that has been exposed for a period of time or deteriorated by that time is in an unpolished state, it will be applied with a newly applied acrylic urethane paint coating film for repair, etc. Poor adhesion, repairing or coloring, etc. requires a polishing process or requires a sealer, which is a major obstacle to the painting process, and this is also a cured coating of unpolished acrylic urethane paint. The emergence of an acrylic urethane paint that completely adheres to the surface is strongly desired.

[Problems to be solved by the invention]

Thus, as long as you follow the conventional technology,
In addition to providing coatings with excellent adhesion to unpolished resin cured coatings (baked coatings) or old acrylic urethane coatings (existing acrylic urethane coatings), in addition to these excellent coatings, It is extremely difficult to use a novel, highly practical, novel coating method.

However, the present inventors can also provide a coating having excellent adhesion to an unpolished resin cured coating or a cured acrylic urethane coating, that is, without going through a polishing step. It is possible to apply such an excellent paint directly on a thermosetting resin paint and a cured coating film of an acrylic urethane paint, and therefore, to streamline or shorten the painting process. In order to provide an extremely practical coating method that can be performed, we have begun intensive research.

Therefore, the problem to be solved by the present invention is, on the one hand, a novel form of paint having remarkably excellent adhesion to a cured coating film of an unpolished thermosetting resin paint or an acrylic urethane paint. An object of the present invention is to provide an extremely practical coating method using

[Means for solving the problem]

Therefore, the present inventors have conducted intensive studies, aiming at the problems to be solved by the invention as described above, in order to solve various problems in the prior art as described above, and as a result, Certain acrylic urethane-based paints
The present invention has been completed by finding that it shows extremely excellent adhesion to a cured coating film of an unpolished thermosetting resin paint or acrylic urethane paint.

"A cured film of a thermosetting resin paint or acrylic urethane paint whose surface is not polished, (A) methyl methacrylate and / or styrene 10 ~
85% by weight Esters of saturated aliphatic monohydric alcohol having 1 to 8 carbon atoms and acrylic acid 10 to 60% by weight Hydroxyl group-containing vinyl monomer 5 to 30% by weight Carboxyl group-containing vinyl monomer and / or phosphoric acid group-containing The solubility parameter (Sp value) obtained by copolymerizing a monomer mixture comprising 0.1 to 10% by weight of a vinyl monomer and optionally 0 to 50% by weight of a vinyl monomer copolymerizable with the above is obtained. And a glass transition point (Tg) of 75 ° C. or less and a number average molecular weight (▲
▼) acrylic polyol 4 in the range of 3000 to 30000
0 to 97% by weight, (B) 3 to 60% by weight of a ketone resin, and (C) 0 to 2% by weight of an acidic phosphoric acid ester (However, the amount of (C) used is the amount of (A) and (B) (A ratio based on the total solid content) and a polyisocyanate [II] in an OH / NCO ratio of 1 / 0.5 to 1 / 1.5 (equivalent ratio). And a method of coating an unpolished resin cured coating film, which is then cured. ”.

In the present invention, if the amount of the methyl methacrylate used in the acrylic polyol (A) is less than 10% by weight (hereinafter abbreviated as%), the hardness, adhesion, gasoline resistance, and solvent resistance are reduced. Is not enough, and if it exceeds 85%, the hardness, gasoline resistance and solvent resistance are sufficient,
It is not preferable because the coating film tends to be brittle and the adhesiveness is rather lowered. Therefore, it is preferable to use 10 to 85%, especially 20 to 70%. When styrene monomer is used, the hardness, adhesion, gasoline resistance and solvent resistance are not sufficient at less than 10%, and the hardness is higher than 85%, but the Sp value is low. When styrene is used alone, 10-40% of gasoline resistance, solvent resistance, and Sp value are considered. It is particularly preferable to keep it in the range of 15 to 30%. When methyl methacrylate and styrene are used in combination, the amount of each used should be within the range of 10 to 85%, taking into account the combination of hardness, adhesion, gasoline resistance, solvent resistance and the above contents. You only have to decide.

Next, if only typical examples of the above-mentioned esters of a saturated aliphatic monohydric alcohol having 1 to 8 carbon atoms and acrylic acid are exemplified, methyl acrylate, ethyl acrylate, n -Propyl acrylate, iso-propyl acrylate, n-butyl acrylate, sec-butyl acrylate, iso-butyl acrylate, tert-butyl acrylate, n-pentyl acrylate, iso-amyl acrylate, n-hexyl acrylate, n-heptyl acrylate, 2 −
Heptyl acrylate, n-octyl acrylate or 2-ethylhexyl acrylate.

These are adhesive with unpolished resin cured coating,
It is an essential component to balance flexibility and chemical resistance, etc. If the amount used is less than 10%, the cured coating film becomes brittle and the adhesiveness decreases, and if it exceeds 60%, the flexibility, Although the adhesion is improved, gasoline resistance, solvent resistance, stain resistance, hardness and the like are reduced, and acrylates having long side chains are more unfavorable since the tendency becomes stronger. Therefore, the amount used is preferably in the range of 10 to 60%, particularly 15 to 55%.

Specific examples of the hydroxyl group-containing vinyl monomer as a component include, for example, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate,
2-hydroxybutyl (meth) acrylate, 3-hydroxybutyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 3-chloro-2-hydroxypropyl (meth) acrylate, di-2-hydroxyethyl fumarate, mono -2-hydroxyethyl-monobutyl fumarate, polypropylene glycol or proethylene glycol mono (meth) acrylate, Praxel FM, FA monomer (Daicel Chemical Co., Ltd.)
Hydroxyalkyl esters of α, β-ethylenically unsaturated carboxylic acids or adducts thereof with ε-caprolactone:
Α, β- such as unsaturated mono- or dicarboxylic acids such as (meth) acrylic acid, crotonic acid, maleic acid, fumaric acid, itaconic acid or citraconic acid, and monoesters of these dicarboxylic acids with monohydric alcohols;
Ethylenically unsaturated carboxylic acids or the α, β-
Unsaturated carboxylic acid hydroxyalkyl esters and maleic acid, succinic acid, phthalic acid, hexahydrophthalic acid,
An adduct with a polycarboxylic acid anhydride such as tetrahydrophthalic acid, benzenetricarboxylic acid, benzenetetracarboxylic acid, "Hymic acid" (a product of Hitachi Chemical Co., Ltd.), tetrachlorophthalic acid or dodecinylsuccinic acid; Cardura E "(glycidyl ester of a branched synthetic fatty acid manufactured by Shell, Netherlands), monoglycidyl ester of monovalent carboxylic acid such as glycidyl ester of coconut oil fatty acid or glycidyl octylate or butyl glycidyl ether, ethylene oxide or propylene oxide Adducts with monoepoxy compounds such as: or adducts thereof with ε-caprolactone:
And hydroxyethyl vinyl ether.

In addition, a polyester resin (including an oil-modified type) having a hydroxyl group and a copolymerizable unsaturated group or an acrylic copolymer can also be used as a component. These are used in the range of about 0.5 to 10% when the obtained acrylic polyol (A) is expected to improve pigment dispersibility at a high level.

The above-mentioned hydroxyl group-containing monomer or resin is used for imparting a function as a cross-linking point to the obtained acrylic polyol (A).
A range of 30%, especially 10-20% is appropriate. 5 used
%, Sufficient cross-linking points cannot be obtained, and sufficient gasoline resistance and solvent resistance cannot be obtained. If it exceeds 30%, the number of cross-linking points becomes too large, resulting in a large strain stress during curing. Become
On the contrary, it is not preferable because the adhesion tends to decrease.

As the polyester resin or acrylic copolymer having a hydroxyl group and a copolymerizable unsaturated group described above, Japanese Patent Publication No.
No. 22011, No. 46-20502, No. 44-7134, JP-A-48-
No. 78233, 50-58123, etc., as essential, a reducing component having a copolymerizable unsaturated group is essential, and a copolymerizable unsaturated group is contained in a resin skeleton obtained by reacting with other raw material components. Or JP-B-49-47916, 5
First, a saturated polyester having no copolymerizable unsaturated group is obtained as in No. 0-6223, and then a functional group such as a hydroxyl group or a carboxyl group present in the saturated polyester, or further reacted with a diepoxy compound. A compound having a vinyl group and a functional group reactive with these functional groups by utilizing the introduced epoxy group or the like, for example, (meth)
Those having an acid chloride group and a vinyl group such as acrylic acid chloride, those having an epoxy group and a vinyl group such as glycidyl (meth) acrylate, and alkoxysilanol groups such as vinylmethoxysilane and (meth) acryloxyethyltrimethoxysilane Those having an acid anhydride and a vinyl group such as maleic anhydride and tetrahydrophthalic anhydride; fumaric acid;
Vinyl-based monomers such as those having a carboxyl group and a vinyl group such as acrylic acid, molar addition products such as 2-hydroxypropyl (meth) acrylate to hexamethylene diisocyanate, and those having an isocyanate group and a vinyl group such as isoyanate ethyl methacrylate Such as those having a hydroxyl group and copolymerizable unsaturation obtained by adding to a saturated polyester, in advance, a hydroxyl group, a carboxyl group, a copolymerization with a vinyl monomer having a functional group such as an epoxy group as an essential component, Similar to the introduction of the copolymerizable unsaturated group into the saturated polyester described above in the acrylic copolymer having these functional groups, a functional group having reactivity with the functional group contained in the acrylic copolymer is used. Compounds with a vinyl group and a vinyl group, such as (meth) acrylic acid chloride Those having an acid chloride group and a vinyl group, those having an epoxy group and a vinyl group such as glycidyl (meth) acrylate, vinyl silane,
Those having an alkoxysilanol group and a vinyl group such as (meth) acryloxyethyltrimethoxysilane, those having an acid anhydride group and a vinyl group such as maleic anhydride and tetrahydrophthalic anhydride, fumaric acid, (meth) acrylic acid, etc. Having a carboxyl group and a vinyl group,
Hydroxy groups obtained by adding a vinyl monomer such as hydroxypropyl (meth) acrylate to hexamethylene diisocyanate and the like and an isocyanate ethyl methacrylate and the like having a vinyl group and an isocyanate group are not copolymerizable with hydroxyl groups. Those having a saturated group are suitable.

Further, a carboxyl group-containing vinyl monomer and a phosphate group-containing vinyl monomer used as components are
It is used for the purpose of improving the internal catalytic action and the adhesion to the material when the polyisocyanate component (B) is blended.

Examples of those having a carboxyl group include, for example,
Α, β such as unsaturated mono- or dicarboxylic acids such as (meth) acrylic acid, crotonic acid, maleic acid, fumaric acid, itaconic acid or citraconic acid, and monoesters of these dicarboxylic acids with monohydric alcohols; −
Ethylenically unsaturated carboxylic acids; 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 3-hydroxybutyl (meth) Acrylate, 4-
Hydroxybutyl (meth) acrylate, 3-chloro-
2-hydroxypropyl (meth) acrylate, di-2
Α, β-unsaturated carboxylic acid hydroalkyl esters such as -hydroxyethyl fumarate, mono-2-hydroxyethyl-monobutyl fumarate or polyethylene glycol mono (meth) acrylate and maleic acid, succinic acid, phthalic acid, hexa Addition of polycarboxylic acids such as hydrophthalic acid, tetrahydrophthalic acid, benzenetricarboxylic acid, benzenetetracarboxylic acid, "Hymic acid" (product of Hitachi Chemical Co., Ltd.), and polycarboxylic acids such as tetrachlorophthalic acid or dodecinylsuccinic acid There are things.

Examples of those having a phosphate group include the general formula Dialkyl ((meth) acryloyloxyalkyl) phosphates or (meth) acryloyloxyalkyl acid phosphates represented by the general formula (R _{1 to} R ₃ , A: supra), dialkyl [(meth) acryloyloxyalkyl] phosphites or (meth) acryloyloxyalkyl acid phosphites, and further, the above (meth) Acryloyloxyalkyl acid phosphates or alkylene oxide adducts of acid phosphites, epoxy group-containing vinyl monomers such as glycidyl (meth) acrylate and methyl glycidyl (meth) acrylate, and phosphoric acid or phosphorous acid, or acidic esters thereof And 3-chloro-2-acidphosphoxypropyl (meth) acrylate.

If the amount of these materials is less than 0.1%, the effect of use cannot be sufficiently obtained. If the amount exceeds 10%, the pot life is shortened, the viscosity of the resin becomes high, or the one containing a phosphate group becomes cloudy. Is not preferred. Therefore, the amount used is preferably in the range of 0.1 to 10%, particularly 0.3 to 5%.

Examples of the vinyl monomer which can be copolymerized with the above-mentioned components (1) and (2) used as the component include: (1) vinyl monomers having no functional group: (a) α-methylstyrene excluding styrene, p-te
(b): ethyl methacrylate, n-propyl methacrylate, i-propyl methacrylate, excluding methyl methacrylate and the vinyl monomer corresponding to the component;
n-butyl methacrylate, i-butyl methacrylate, t-butyl methacrylate, 2-ethylhexyl methacrylate, lauryl (meth) acrylate, cyclohexyl (meth) acrylate, benzyl (meth) acrylate, dibutomopropyl (meth) acrylate, tribromophenyl ( Various (meth) acrylates, such as alkoxyalkyl (meth) acrylates, such as meth) acrylate or ethoxyethyl (meth) acrylate; and unsaturated monocarboxylic acids, such as maleic acid, fumaric acid or itaconic acid, and monohydric alcohols. Diesters; vinyl acetates, such as vinyl acetate, vinyl benzoate, and "Veoba" (a vinyl ester manufactured by Shell);
"Piscoat 8F, 8FM, 17FM, 3F or 3FM" [fluorinated acrylic monomer manufactured by Osaka Organic Chemical Co., Ltd.], perfluorocyclohexyl (meth) acrylate, di-perfluorocyclohexyl fumarate, or Ni-propyl par (Per) fluoroalkyl group-containing vinyl esters such as fluorooctanesulfonamidoethyl (meth) acrylate, vinyl ethers, fluorine-containing polymerizable compounds such as (meth) acrylates or unsaturated polycarboxylic acid esters; ) There are vinyl monomers having no functional group such as olefins such as acrylonitrile, vinyl chloride, vinylidene chloride, and vinylidene fluoride.

Next, as the vinyl monomer having a functional group, (c): (meth) acrylamide, dimethyl (meth) acrylamide, N-tert-butyl (meth) acrylamide, N-octyl (meth) acrylamide, diacetone acrylamide, dimethyl A methylolated product such as aminopropylacrylamide, N-methylolated (meth) acrylamide obtained by methylolating these with formaldehyde or the like, or a methylolated product such as n-butoxymethyl (meth) acrylamide is C _1-
Amide bond-containing vinyl monomers such as those etherified with monohydric alcohols comprising C _8, (d): dimethylaminoethyl (meth) acrylate,
There are dialkylaminoalkyl (meth) acrylates such as diethylaminoethyl (meth) acrylate.

Among them, the above-mentioned (d) is used for imparting an internal catalyst function to the acrylic polyol (A), for improving the adhesion to materials, compatibility with other resins, pigment dispersibility, etc. These can be used alone or in combination, and the amount of dialkylaminoalkyl (meth) acrylates is
It may be used in the range of 0.05 to 2%.

: Other vinyl monomers having a functional group used as a component include glycidyl (meth) acrylate, (β-methyl) glycidyl (meth) acrylate, (meth) allyl glycidyl ether or α,
β-ethylenically unsaturated carboxylic acids or mono-2-
Various unsaturated carboxylic acids such as equimolar adducts of the hydroxyl group-containing vinyl monomers such as (meth) acryloyloxyethyl phthalate and the above-mentioned polycarboxylic anhydrides can be added to "Epiclone 200, 400, 441, 850 or 1050" [Dainippon Ink Chemical Industry ) Epoxy resin], "Epicoat 828,
1001 or 1004 "(epoxy resin manufactured by Shell)," Araldite 6071 or 6084 "(epoxy resin manufactured by Ciba Geigy, Switzerland)," Chissonox 221 "(epoxy compound manufactured by Chisso Corporation) or" Denacol EX-61 "
Epoxy group-containing polymerizable compound obtained by subjecting various polyepoxy compounds having at least two epoxy groups in one molecule to an addition reaction in an equimolar ratio, such as 1 "(epoxy compound manufactured by Nagase & Co., Ltd.) Or (g): silicon-based monomers such as vinylethoxysilane, α-methacryloxypropyltrimethoxysilane, trimethylsiloxyethyl (meth) acrylate, X-22-5002, and KR-215 (Shin-Etsu Chemical Co., Ltd.) There is.

Various monomers as the above components are combined with the components, SP value, glass transition point, copolymerizability or coating workability, gloss, hardness, flexibility, weather resistance, drying property, solvent resistance The amount of each monomer component and its combination may be determined in the range of 0 to 50% from the viewpoints of compatibility, dilutability, pot life, OH value and the like. In particular, an aromatic vinyl monomer such as α-methylstyrene or vinyl toluene excluding styrene is used in an amount of less than 40%, particularly preferably 35% when weather resistance and yellowing resistance are required.
% Is preferable.

Further, in the case of a silicon-based monomer such as vinylethoxysilane having a hydrolyzable alkoxy group, gelling may occur if used in an excessively large amount. Therefore, when such a monomer is used, the amount used is 10%. It is more preferable to keep the content to less than 5%, particularly preferably less than 5%.

Solubility parameter of acrylic polyol (A) (Sp
Value) is, for example, Journal of Paint Technology 42 (54
1) It can be calculated by the calculation formula described in 76 ('70). If the value is less than 8.95 or more than 9.45, it will not adhere to the unpolished resin cured coating film, This is also not preferable because the tendency of the adhesiveness to decrease with time increases. Therefore, it is preferably in the range of 8.95 to 9.45, particularly 9.00 to 9.40.

Further, the glass transition point (hereinafter, abbreviated as Tg) is calculated by, for example, Fox's formula. If the temperature exceeds 75 ° C., the cured coating film becomes brittle and does not adhere to the unpolished resin cured coating film. Absent. Although the lower limit of Tg is not specified, it is not only the adhesion to the unpolished resin cured film, the hardness, gasoline resistance, solvent resistance, and stain resistance, but also the hardness of the polyisocyanate used as the curing agent. From the point of view, usually, it is better to design at a temperature of about -10 ° C. or more to obtain a preferable result. Therefore, Tg is-
It is preferably in the range from 10 ° C to 75 ° C, especially from -5 to 70 ° C. Next, the number average molecular weight (hereinafter abbreviated as ▲) can be measured by, for example, gel permeation chromatography. If ▲ is less than 3000, the adhesion is relatively good, but the coating film performance is relatively high. For example, gasoline resistance,
Sufficient level of solvent resistance, drying property, etc. could not be obtained.
If it exceeds 30,000, the coating film performance will be at a satisfactory level, but the adhesion will be reduced rather, which is not preferred. Therefore ▲
▼ is preferably in the range of 3,000 to 30,000, particularly 4,000 to 20,000.

The production of the acrylic polyol (A) of the present invention can be carried out using the above-mentioned respective raw materials and components by making full use of a known and commonly used copolymerization reaction method or graft copolymerization reaction method. Butyronitrile (AIB
N), radical-generating polymerization catalysts such as benzoyl peroxide (BPO), t-butyl perbenzoate (TBPB), t-butyl hydroperoxide, di-t-butyl peroxide (DTBPO), cumene hydroperoxide (CHP) Are used alone or as a mixture of several types. Further, at this time, as a solvent to be used, toluene, xylene, Solvesso 100,150 (Shell Petrochemical Co., Ltd.), Swazole 100
Number of aromatic hydrocarbons such as 0.1500 [Maruzen Petrochemical Co., Ltd.], aliphatics such as n-hexane, heptane, octane, mineral spirit, methylcyclohexane, ethylcyclohexane, LAWS (Shell Petrochemical Co., Ltd.) Or alicyclic hydrocarbons, ethyl acetate, butyl acetate, isobutyl acetate, ester solvents such as cellosolve acetate, 3-methoxybutyl acetate, and ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone. used.

Next, the ketone resin used as the component (B) is obtained by adding a ketone such as methyl ethyl ketone, methyl isobutyl ketone, methyl butyl ketone, acetophenone, cyclohexanone, or methylcyclohexanone in the presence of an alkali catalyst.
It can be obtained by reacting with formalin and, if desired, may be further hydrogenated if desired. Industrially, cyclohexanone-based and acetophenone-based products are produced.
80,110H (Honshu Chemical Co., Ltd.), Hiluck 110,111,222
(Hitachi Chemical Co., Ltd.) Alon KR (Toa Gosei Chemical Co., Ltd.) and others are on the market. The ketone resin is used in combination with the component (A) in order to further improve the adhesion to the unpolished resin fat cured coating film, and the proportion of the ketone resin in the mixed system with the component (A) is 3%. %, The adhesiveness to the cured resin film is not stable, and if it exceeds 60%, the solvent resistance of the cured film of the urethane paint, the initial curability, etc. are reduced, so that for the purpose of the present invention. Is not preferred. Accordingly, the proportion occupied by the ketone resin is preferably from 3 to 60%, more preferably from 5 to 50%. (The component (A) is determined according to the amount of the component (B) used). Further, by adding a ketone resin, gloss, chemical resistance, hardness, drying property and the like are also improved.

Next, the acidic phosphoric acid ester used as the component (C) is used together with the component (B) to improve the adhesion to the unpolished resin cured coating film, and comprises (A) an acrylic polyol and (B) a ketone resin. 0 to the total solid content of
What is necessary is just to add in the range of 2%. Although the object of the present invention can be sufficiently achieved without adding such a compound, the addition of the compound further broadens the adhesion and stabilizes it. 2%
Exceeding the above is also undesirable because it also has a catalytic action for the urethane-forming reaction, so that the pot life of the paint system becomes difficult. Examples of the acidic phosphate ester that can be used in the present invention include:
Acidic phosphoric acid methyl ester, ethyl ester, i-
Propyl ester, the butyl ester, the i- butyl ester, the 2-ethylhexyl ester, the octyl ester, the nonyl ester, the decyl ester, include the lauryl esters, monoalcohols these things C ₁ -C ₁₂ And phosphorus pentoxide, etc., and two or more of these can be used alone.

Polyisocyanate [II] used in the present invention
As aromatic diisocyanates such as tolylene diisocyanate and diphenylmethane diisocyanate;
Aliphatic diisocyanates such as hexamethylene diisocyanate and trimethylhexane diisocyanate; isophorone diisocyanate, methylcyclohexane-2,
Alicyclic diisocyanates such as 4 (or 2,6) -diisocyanate, 4,4'-methylenebis (cyclohexylisocyanate), and 1,3- (isocyanatomethyl) cyclohexane; or these diisocyanates and ethylene glycol, polyether polyol ( Polyethylene glycol, polypropylene glycol, etc.), polycaprolactone polyol, trimethylolethane, trimethylolpropane and other polyhydric alcohols and low molecular weight polyester resins (including oil-modified types) having functional groups that react with isocyanate groups and acrylic resins Polymer,
An adduct with water or the like; or a burette, a copolymer (oligomer) of diisocyanates; or a molar adduct of 2-hydroxypropyl (meth) acrylate to hexamethylene diisocyanate, or copolymerizable with an isocyanate group such as isocyanateethyl methacrylate. Copolymers containing a vinyl monomer having an unsaturated group as an essential component;
Those blocked with a known blocking agent such as a polyhydric alcohol, methyl ethyl ketoxime and lactam are suitable.

The combination of the acrylic polyol and the polyisocyanate may be determined according to the glass transition point of the acrylic polyol, the type and hardness of the polyisocyanate, its use, the required coating film performance, etc. In view of the above, it is preferable that OH / NCO = 1 / 0.5 to 1 / 1.5 (equivalent ratio). If the NCO is less than 0.5 equivalent relative to 1 equivalent of OH, the desired coating film properties will not be obtained, and if it exceeds 1.5 equivalents, the coating film properties will be sufficient, but this is not preferable in terms of paint price.

The acrylic urethane-based paint used in the method of the present invention is one containing the above components, but if desired, an acrylic resin, an epoxy resin, an amino resin, a vinyl chloride-vinyl acetate copolymer, and other resins such as a polyester resin. Compatible additives and various commonly used paint additives such as pigment dispersants, leveling agents, UV absorbers, light stabilizers, antioxidants, and curing accelerators suitable for each crosslinking system Can also be blended. Further, after the coating material of the present invention is applied to an unpolished cured coating film and cured, an overcoating can be further performed with another coating material. Painting is spray painting,
The coating can be performed by a known and commonly used method such as roller coating, brush coating, and electrostatic coating. The acrylic urethane paint used in the method of the present invention can be cured by heating at room temperature or at 30 ° C. to 180 ° C. for 1 minute to 60 minutes depending on the use, the coating process, the material to be coated, and the curing conditions.

Needless to say, the paint used in carrying out the coating method of the present invention can be used as an enamel paint using a pigment, or can be used as a clear paint without using a pigment.

〔Example〕

Next, the present invention will be described more specifically with reference to Production Examples, Examples and Comparative Examples.
As long as it does not depart from its purpose and technical idea, or does not impair the effects of the present invention,
It is by no means limited to the following examples only.

In the following, all parts and percentages are by weight unless otherwise specified.

Production Example 1 (Synthesis of Acrylic Polyol) 300 parts of toluene and n-butyl acetate (hereinafter abbreviated as butyl acetate) were placed in a four-necked flask equipped with a stirrer, a reflux condenser, a thermometer, and an N ₂ gas inlet tube. 500 parts), heated to 115 ° C, and heated to 115 ° C with methyl methacrylate 718.
Parts, 153 parts of methyl acrylate, 124 parts of 2-hydroxyethyl acrylate, 5 parts of methacrylic acid, 200 parts of toluene
, 30 parts of t-butyl peroctoate and 5 parts of t-butyl perbenzoate were added dropwise over 4 hours, and the mixture was kept at 115 ° C. for about 15 hours to obtain a nonvolatile content of 50.1%.
Viscosity U, acid value 2.0 OH value 30 ▲ ▼ 10000, Sp value 9.40, Tg67 ° C
Acrylic polyol was obtained.

Production Example 2 (Synthesis of Acrylic Polyol) 300 parts of toluene and 500 parts of isobutyl acetate were charged into the same four-necked flask as used in Production Example 1, and the temperature was raised to 110 ° C .; , 275 parts of ethyl acrylate, 2-hydroxyethyl methacrylate 1
16 parts, methacryloyloxyethyl acid phosphate 2 parts, toluene 200 parts, t-butyl peroctoate 30
Parts, 5 parts of t-butyl perbenzoate and 4 parts of azobisisobutyronitrile were added dropwise over 4 hours, and the mixture was kept at 110 ° C. for about 15 hours to obtain a nonvolatile content of 49.9%.
Viscosity S, acid value 1.4, OH value 25, ▲ ▼ 8000, Sp value 9.20, T
An acrylic polyol having a g of 53 ° C. was obtained.

Production Example 3 (Synthesis of Acrylic Polyol) 200 parts of toluene, 300 parts of methyl isobutyl ketone, and butyl acetate were placed in the same four-necked flask as used in Production Example 1.
Charge 200 parts and 4 parts of fumaric acid, raise the temperature to 115 ° C,
458 parts of methyl methacrylate, 347 of butyl acrylate
Parts, 2-hydroxyethyl acrylate 34 parts, 2-hydroxyethyl methacrylate 55 parts, methacryloyloxyethyl acid phosphate 2 parts, ethyl methacrylate 100 parts, toluene 300 parts, t-butyl peroctoate
A mixture of 50 parts, 8 parts of t-butyl perbenzoate, and 6 parts of azobisisobutyronitrile was added dropwise over 4 hours, and the mixture was kept at 115 ° C. for about 15 hours to obtain a nonvolatile content of 50.0%.
%, Viscosity N, acid value 3.4, OH value 20, ▲ 4000, Sp value 9.0
5. An acrylic polyol having a Tg of 19 ° C. was obtained.

Production Example 4 (Synthesis of Acrylic Polyol) In Production Example 1, the vinyl monomer to be dropped was 539 parts of methyl methacrylate, 216 parts of ethyl acrylate, 100 parts of butyl acrylate, 83 parts of 2-hydroxyethyl acrylate, and Plaxel monomer FM. -2 (manufactured by Daicel Chemical Industries, Ltd.) 50 parts, methacrylic acid 10 parts, and mono-2-methacryloyloxyethyl phthalate 2 parts, except that the nonvolatile content was 50.1%, the viscosity was UV, the acid was 5%. Price 2.
5. An acryl polyol having an OH value of 20, an A value of 10,000, a Sp value of 9.15, and a Tg of 31 ° C. was obtained.

Production Example 5 (Synthesis of Acrylic Polyol) The vinyl monomer dropped in Production Example 1 was 383 parts of methyl methacrylate and 2-ethylhexyl acrylate 2
Using 37 parts, 210 parts of 2-hydroxyethyl acrylate, 20 parts of acrylic acid, and 150 parts of n-butyl methacrylate,
Except that the dropping time was set to 7 hours, the same procedure as in Production Example 1 was carried out except that the nonvolatile content was 49.8%, the viscosity V, the acid value was 7.8, the OH value was 50, and
Acrylic polyol having 0, Sp value of 9.05 and Tg of 8 ° C. was obtained.

Production Example 6 (Synthesis of Acrylic Polyol) (1) 513 parts of isophthalic acid was placed in a four-necked flask equipped with a stirrer, a thermometer, a reaction water removing device, and an N ₂ gas inlet tube.
19 parts of maleic anhydride, 106 parts of adipic acid, 391 parts of neopentyl glycol, 83 parts of trimethylolpropane, 30 parts of pentaerythritol, and 0.005 part of an antifoaming agent were charged to 180 ° C.
Temperature, hold at the same temperature for 2 hours, and then take 3 hours
The temperature was raised to 220 ° C and maintained at the same temperature under an N ₂ gas atmosphere until the acid value became 9 or less, and then toluene / butyl acetate = 50/50 (weight ratio) so that the nonvolatile content became about 50%. ) To obtain an unsaturated group-containing polyester resin having a nonvolatile content of 50.0%, a viscosity of 0, an acid value of 4.2 and an OH value of 67.

(2) The same four-necked flask as used in Production Example 1 was charged with 280 parts of toluene, 500 parts of butyl acetate, and 40 parts of the unsaturated polyester solution synthesized in the previous step (1). At 400 ° C., 400 parts of methyl methacrylate, 100 parts of methyl acrylate, 141 parts of ethyl acrylate, 133 parts of 2-hydroxyethyl methacrylate, 4 parts of methacrylic acid,
Methacryloyloxyethyl acid phosphate 2 parts,
Styrene 100 parts, ethyl methacrylate 50 parts, 2-ethylhexyl methacrylate 50 parts, toluene 200 parts, t-
A mixture of 20 parts of butyl peroctoate, 5 parts of t-butyl perbenzoate and 3 parts of azobisisobutyronitrile was added dropwise over 5 hours.
Non-volatile content 50.1%, viscosity X, acid value 2.3, OH value 3
Acrylic polyol having 0, 15,000, Sp value of 9.25, and Tg of 52 ° C was obtained.

Production Example 7 (Synthesis of Acrylic Polyol) 450 parts of toluene and 300 parts of methyl isobutyl ketone were placed in the same four-necked flask as used in Production Example 1, and the unsaturated polyester solution 100 synthesized in the former stage (1) of Production Example 6 The temperature was raised to 90 ° C, and at 90 ° C, methyl methacrylate 27 was added.
6 parts, ethyl acrylate 50 parts, butyl acrylate 107
Parts, 2-hydroxyethyl acrylate 107 parts, 2-hydroxyethyl methacrylate 50 parts, methacrylic acid 8
A mixture consisting of 2 parts of dimethylaminoethyl methacrylate, 200 parts of styrene, 100 parts of isobutyl methacrylate, 50 parts of dibutyl fumarate, 200 parts of toluene, 5 parts of t-butyl peroctoate and 15 parts of azobisisobutyronitrile. Add dropwise over time, and when the addition is complete,
Non-volatile content 49.8%, viscosity Z, acid value 3.0, OH value 4
Acrylic polyol having 0, 18,000, Sp value of 9.37, and Tg of 38 ° C was obtained.

Production Example 8 (Synthesis of Acrylic Polyol) Production Example 2 except that the monomer mixture was changed to 350 parts of styrene, 505 parts of n-butyl acrylate, 140 parts of 2-hydroxyethyl methacrylate, and 5 parts of methacrylic acid in Production Example 2.
50.0% of non-volatile content, viscosity M, acid value 1.6, OH value 3
Acrylic polyol having 0, ▲ ▼ 8000, Sp value of 9.10 and Tg of −2 ° C. was obtained.

Production Example 9 (Synthesis of acrylic polyol) Same as Production Example 1 except that the monomer mixture was changed to 52 parts of methyl methacrylate, 819 parts of methyl acrylate, 124 parts of 2-hydroxyethyl acrylate, and 5 parts of methacrylic acid in Production Example 1. To obtain a nonvolatile content of 50.2%, viscosity R, acid value
An acrylic polyol having 2.0, an OH value of 30, an A of 10,000, a Sp value of 9.5, and a Tg of 7 ° C was obtained.

Preparation Example 10 (Synthesis of acrylic polyol) In Preparation Example 2, the monomer mixture was prepared by adding 406 parts of methyl methacrylate, 470 parts of 2-ethylhexyl acrylate,
Except for using 119 parts of hydroxyethyl methacrylate and 5 parts of methacrylic acid, a nonvolatile content was 50.0% in the same manner as in Production Example 2,
Viscosity 0, acid value L.9, OH value 25, ▲ 8000, Sp value 8.69, T
An acrylic polyol having a g of 7 ° C. was obtained.

Production Example 11 (Synthesis of Acrylic Polyol) In Production Example 6, 292 parts of styrene, 62 parts of methyl methacrylate, 487 parts of 2-ethylhexyl acrylate, 133 parts of 2-hydroxyethyl methacrylate were used.
Part, methacrylic acid 4 parts, methacryloyloxyethyl acid phosphate 2 parts, except that the nonvolatile content was 49.8%, viscosity S, acid value 2.0, OH value 30, ▲ ▼ 1.
An acrylic polyol having a 5000, an Sp value of 8.76 and a Tg of −11 ° C. was obtained.

Production Example 12 (Synthesis of Acrylic Polyol) In Production Example 8, 450 parts of styrene was added to the monomer mixture.
Except for using 400 parts of 2-ethylhexyl acrylate, 140 parts of 2-hydroxyethyl methacrylate, and 5 parts of methacrylic acid, a nonvolatile content of 50.0%, a viscosity L, and
Acid value 1.8, OH value 30, ▲ ▼ 8000, Sp value 8.80, Tg-1 ° C
Acrylic polyol was obtained.

Examples 1 to 8 and Comparative Examples 1 to 4 Adhesion of cured thermosetting resin coatings to cured coatings using acrylic urethane-based coatings having the coating compositions shown in Table 1 and without polishing the coating surface ( (Primary and secondary adhesion) were evaluated. The evaluation results are summarized in Table 1, and the evaluation method is as follows.

Evaluation I “Melamine resin-acrylic resin paint” [“Acridec 52-765” (manufactured by Dainippon Ink and Chemicals, Inc.) /
"Super Beckamine J-820-60" (same as above) = 70/30
(Solid content ratio), PWC = 40% ("Taipeku CR-93" (manufactured by Ishihara Sangyo Co., Ltd.)), "melamine resin-polyester resin paint"["BeccoliteM-6003-60" (Dainippon) Ink Chemical Industry Co., Ltd.
/ Super Beckamine J-820-60 = 70/30
(Solid content ratio), PWC = 40% ("Taipe CR-9
3))], and “Melamine resin-alkyd resin paint” (“Peccosol J-524iM-60” (manufactured by Dainippon Ink and Chemicals, Inc.) / “Super Beckamine J-820”).
−60 ”= 70/30 (solid content ratio), PWC = 40% (“ Taipec
Each of the thermosetting resin coatings of CR-93 ")) was made into a coating by a conventional method, then spray-coated on a Ponde # 144 treated steel plate, and baked at 150 ° for 30 minutes.

“Acrylic urethane paint” [“Acridic A-
801-P "(manufactured by Dainippon Ink and Chemicals, Inc.) /" Barnock DN-950, PWC = 40% ("Taipec CR-93"). Spray-painted on treated steel sheet, 1 group 12 at 100 ℃
After baking for another hour, the other group was baked at 80 ℃ for 2 hours,
It was stored at room temperature for one month and baked outdoors for one year.

Each of the obtained cured resin coatings is not polished, and an acrylic urethane-based coating having a coating composition as shown in Table 1 is spray-coated thereon, baked at 60 ° C. for 40 minutes, and then subjected to primary adhesion and secondary adhesion. Was evaluated.

(Primary Adhesion) For a sample left at room temperature for 7 days, a peeling test using a cellophane tape was performed.

(Secondary Adhesion) After leaving in a blister box of 50 ° C. × 98% RH for 7 days, it was taken out, and two hours later, a peeling test using a cellophane tape was performed.

Evaluation II In the same manner as in Evaluation I described above, each thermosetting resin of “melamine resin-acrylic resin paint”, “melamine resin-polyester resin paint” and “melamine resin-alkyd resin paint” was applied to Bonde # 144 treated steel sheet. After coating and baking a paint and an acrylic urethane paint, an acrylic urethane paint having a paint composition shown in Table 1 is applied and baked without polishing the cured coating film. Next, "Acridic DU-589" (NV55%, OH value: 44, manufactured by Dainippon Ink and Chemicals, Inc.) / "Bernock DN-950" (NV75) was further applied as a top coating on the acrylic urethane-based cured coating film. %, N
Acrylic urethane clear paint consisting of 12.5% CO, HMDI to adduct of trimethylolpropane, manufactured by Dainippon Ink and Chemicals, Inc. = 100/27 (solution ratio) is spray-coated and baked at 60 ° C for 40 minutes Was.

Primary adhesion and secondary adhesion were evaluated in the same manner as in Evaluation I.

(Effect of the Invention) The coating method of the present invention can provide a coating film having excellent adhesion to a cured coating film of an unpolished thermosetting resin paint and an acrylic urethane paint, that is, without passing through a polishing step. Since the coating of the present invention can be applied directly from the cured coating of a thermosetting resin coating and an acrylic urethane coating, the coating process can be streamlined, and the effect is very large.

Claims (1)

(57) [Claims] 1. A cured film of a thermosetting resin paint or an acrylic urethane paint, whose surface is not polished, comprising: (A) methyl methacrylate and / or styrene 10 to
85% by weight Esters of saturated aliphatic monohydric alcohol having 1 to 8 carbon atoms and acrylic acid 10 to 60% by weight Hydroxyl group-containing vinyl monomer 5 to 30% by weight Carboxyl group-containing vinyl monomer and / or phosphoric acid group-containing The solubility parameter obtained by copolymerizing a monomer mixture comprising 0.1 to 10% by weight of a vinyl monomer and, if necessary, 0 to 50% by weight of a vinyl monomer copolymerizable with the above, is in the range of 8.95 to 9.45. Acrylic polyol having a glass transition point of 75 ° C. or less and a number average molecular weight in the range of 3,000 to 30,000, (B) a ketone resin 3 to 60% by weight, and (C) an acidic phosphoric acid Ester 0 to 2% by weight (however, the amount of (C) used is a ratio to the total solid content of (A) and (B)) and a mixture of polyisocyanate [II] and OH / NCO = 1 / 0.5 ~ 1 / A method for coating an unpolished resin-cured coating film, characterized in that an acrylic urethane-based coating compounded in a ratio of 1.5 (equivalent ratio) is applied and then cured.