JPH03146177A - Finishing coat application - Google Patents

Abstract

PURPOSE:To improve appearance and weather-proof properties by applying specific crosslinking clear coating I to the surface of a crosslinking metallic paste applied to the surface of an article for crosslinking effect realization and allowing specific crosslinking clear coating II to be applied under crosslinking effect. CONSTITUTION:Crosslinking clear coating I formulated with polyester resin or a mixture of polyester resin and acrylic resin, and a curing agent is applied for crosslinking effect realization to a surface where crosslinking metallic paste coat containing metal powder and/or coloring pigment is applied to an article. Next, crosslinking clear coating II consisting mainly of a resin compound formulated with a curing agent to a fluoroolefin copolymer is applied to the coat of the coating I to allow crosslinking action. Thus finish coating is completed. The preferable polyester resin used for clear pigment is one with 30 to 300 of hydroxyl and 500 to 5000 of average molecular weight.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a novel and useful topcoating method. More specifically, it consists of using an oil-free alkyd resin as a clear topcoat and a fluorine-containing thread resin as an overcoat clearer, respectively, together with a curing agent, and particularly improves interlayer adhesion, appearance, and weather resistance. The present invention relates to a so-called 3-coat, 2-bake top coating method, such as the top coating of an automobile body, which forms a coating film with excellent properties.

The method of the present invention is particularly useful in the automobile manufacturing industry.

[Conventional technology]

The so-called wet-on-wet method is used as a top coating method for the exterior of automobiles, etc.

That is, a crosslinkable resin paint (base coat) is applied, which is mainly composed of a crosslinkable resin such as a hydroxyl group-containing acrylic resin, a hydroxyl group-containing polyester resin, or a hydroxyl group-containing alkyd resin, and a curing agent, and mixed with metal powder and/or coloring pigment. This is a two-coat, one-bake method in which a clear paint (top coat) containing a crosslinkable resin and a curing agent as main components is immediately applied as a top coat and cured at the same time. The purpose of this clear finish is to improve coating film performance such as durability and chemical resistance, as well as appearance.

In recent years, the demand for weather resistance of automobile top coats has become stronger, and on the other hand, higher quality has been required for the appearance of coated surfaces due to the trend toward higher quality in the market.

As one of the solutions to these problems, for example, adding ultraviolet absorbers or light stabilizers to paints has already been carried out, but this has not reached a sufficient level.

There is also a method of using a hydroxyl group-containing fluoroolefin copolymer as a resin component as a wet-on-wet clear coat paint, but in this case too, the gloss value was too low and the appearance of the painted surface was unfavorable. Furthermore, a method is known in which the wet-on-wet method is applied and cured, and then a new acrylic clear coat paint is applied and cured, but although the appearance of the painted surface is improved, the durability performance is It was still not enough.

[Problems to be Solved by the Invention] However, the various drawbacks of the prior art as described above have been solved, and in particular, the appearance and long-term weather resistance of the coating film have been further improved. In order to find an extremely useful top coating method that has excellent adhesion to the glabella area, we have begun intensive research.

Therefore, the problem to be solved by the present invention is to provide a coating film with excellent long-term weather resistance, excellent appearance, and excellent interlayer adhesion. It is an object of the present invention to provide a so-called 3-coat, 2-bake top coating method that is extremely useful and has excellent durability, and particularly to provide a top coating method.

[Means for Solving the Problems] Therefore, the inventors of the present invention focused on the problems to be solved by the invention as described above, and as a result of intensive studies,
Clear coat paints I and II are a specific cross-linked clear paint I containing an oil-free alkyd resin and a curing agent as main components, and a specific crosslinked clear paint I containing a fluorine-containing thread resin and a curing agent as main components, respectively. Certain cross-linked clear paints,
In other words, the present invention has been completed by discovering an extremely useful top coating method that uses a so-called over'-coat clear paint.

That is, in the present invention, a crosslinkable metallic base coat paint containing metal powder and/or color pigment is applied onto an object to be coated, and then a crosslinkable clear paint I is applied to the coated surface.
(Clear coat I') is applied and crosslinked, and then cross-linked clear coat paint ■ (Clear coat ■
), in which (A) the clear coat paint includes (1) a polyester resin (a-1), or the resin (a-1) and an acrylic resin (a-2); A resin composition containing (2) a curing agent in a blend of (1) a fluoroolefin copolymer and (2) a curing agent is used as the main component. The resin composition formed by blending is used as the main component, and the desired coating film is formed by them, especially,
It can provide a durable coating film that has long-term weather resistance, does not sag in appearance, and has excellent interlayer adhesion.
The present invention aims to provide an extremely useful top coating method.

First, the clear coat paint I described above contains polyester resin (a
-1), or the resin (al) and the acrylic resin (
A resin composition in which a curing agent is blended with a-2) is used, and in particular, a resin composition having a hydroxyl value of 30 to 30 is used.
0 and a number average molecular weight of 500 to 5.000, or together with such a specific polyester resin, a hydroxyl value of 30 to 150 and a number average molecular weight of 1,000 to 20, 000 as a main component of the base resin, and a resin composition composed of the base resin component and a curing agent component is used as the clear coat I.

On the other hand, as the above-mentioned clear coat paint II, a resin composition in which a curing agent is blended with a fluoroolefin copolymer as a main component is used, and in particular, a resin composition having a hydroxyl value of 50 to 200, and , number average molecular weight is 2,000
A resin composition containing a specific fluoroolefin copolymer of 30,000 to 30,000 as the main component of the base resin and comprising such a base resin component and a curing agent component is used as the clear coat II.

When painting an automobile body by the method of the present invention,
Metallic base coat paints, clear coat paints, etc. are rarely applied directly to the object to be coated, but usually go through several processes such as film formation on the object, electrodeposition coating, and/or intermediate coating. However,
It goes without saying that the conventional method up to this point can be applied as is.

Next, as the metallic base coat paint, a paint using a commonly used acrylic resin and an amino resin as a crosslinking agent is used.

In some cases, polyester resins can also be used, and it is also possible to combine these base resin components with cellulose derivatives.

Moreover, isocyanate resin can also be used as a crosslinking agent.

Metallic pigments include commonly used aluminum powder,
Mica or pearl can be applied.

By the way, the polyester resin (a
As mentioned above, for -1), it is desirable to use a so-called hydroxyl-containing polyester resin whose hydroxyl value - the hydroxyl value of the solid content (the same applies hereinafter) - is 30 to 300.
It is desirable to use a hydroxyl group-containing polyester resin having a number average molecular weight (hereinafter the same) in terms of polystyrene according to pc) of 500 to 5,000.

If the hydroxyl value is less than 30, the strength of the coating film will inevitably be poor, while if it exceeds 300, the coating film will inevitably become brittle, which is not preferred.

In addition, if the number average molecular weight is less than 500, the strength and durability of the coating film will inevitably be inferior, while if it is too high, exceeding 5.000,
Either case is undesirable because the appearance of the coating film deteriorates.

As the acid component used in preparing the polyester resin (a-1), in consideration of the weather resistance of the coating film, it is desirable to use so-called alicyclic carboxylic acids having a cyclohexane ring. To exemplify only particularly representative carboxylic acids,
1.1-Cyclohexanedicarboxylic acid, hexahydro (
(anhydrous) phthalic acid, 1,3-cyclohexanedicarboxylic acid, 1,4 cyclohexanedicarboxylic acid, or methylhexahydrophthalic acid (anhydride), and as necessary,
Cyclohexane-based polycarboxylic acids such as 4-tert-butylcyclohexane monocarboxylic acid, hexahydrobenzoic acid or hydrogenated trimellitic acid, as well as their methyl esters can also be used.

Other acid components include (anhydrous) phthalic acid, isophthalic acid, terephthalic acid, benzoic acid, p-tert-butylbenzoic acid or p-methylbenzoic acid, or (anhydrous) trimellitic acid or (anhydrous) pyromellitic acid. Various aromatic carboxylic acids such as acids are used, and furthermore,
Adipic acid, azelaic acid, sebacic acid, tetrahydrophthalic acid, tetrachlorophthalic acid, (
Also used are het acid (anhydride), hymic acid (anhydride), maleic acid (anhydride), fumaric acid or itaconic acid.

Typical examples of polyhydric alcohol components used together with these acid components include ethylene glycol, propylene glycol, 1,3-butylene glycol, 1,6-hexanediol, diethylene glycol, and dipropylene. Glycol, neopentyl glycol, triethylene glycol, cyclohexane dimetatool, hydrogenated bisphenol A1 glycerin, trimethylolethane, trimethylolpropane, pentaerythritol, dipentaerythritol or sorbitol.

An oil component can also be used as part of the acid component in preparing the polyester resin (a-1), that is, within a range where the oil length is less than 30% of the total acid component. However, from the viewpoint of weather resistance, it is preferable to use coconut oil, hydrogenated coconut oil, Cardura EJ (branched aliphatic monocarboxylic acid manufactured by Shell in the Netherlands), octenoic acid, isononanoic acid, etc. Furthermore, if necessary, rice bran oil fatty acid, tall oil fatty acid, soybean oil, castor oil or dehydrated castor oil can also be used as appropriate.

Next, as the above-mentioned acrylic resin (a-2), it is desirable to use a so-called hydroxyl group-containing acrylic resin having a hydroxyl value group of 30-150, and a number average molecular weight of 1,
It is desirable to use a hydroxyl group-containing acrylic resin within the range of 000 to 20,000.

If the hydroxyl value is less than 30, the coating film strength will inevitably be poor; on the other hand, if it exceeds 150, it will be too high (
In both cases, the flexibility of the coating film is inevitably impaired, which is not preferable.

In addition, if the number average molecular weight is less than 1,000, the strength and durability of the coating film will inevitably be inferior.
On the other hand, if it becomes too high, exceeding 20,000, the appearance of the coating film will become poor, so either case is not preferable.

The hydroxyl group-containing acrylic resin used in this clear coat paint (■) includes 2-hydroxyethyl (meth)acrylate, 2-hydroxybutyl (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 or polypropylene glycol or polyethylene glycol mono(meth)acrylate,
[Plaxel FM, FA monomer] [Daicel Chemical (
Co., Ltd., caprolactone addition monomer]
Hydroxyl group-containing polymers such as hydroxyalkyl esters of ethylenically unsaturated carboxylic acids or adducts of these with ε-caprolactone and other unsaturated monomers as described below are mixed in a conventional manner, for example, in a solvent. It is obtained by radical copolymerization using a polymerization initiator such as a peroxide or an AB compound.

The unsaturated monomers mentioned here include aromatic vinyl monomers such as styrene, α-methylstyrene, p-tert-butylstyrene, and vinyltoluene; methyl (meth)acrylate, ethyl (meth)acrylate, and n-propyl (meth)acrylate; ) acrylate, 1so-propyl (meth)acrylate, n-butyl (meth)acrylate, 1
so-butyl (meth)acrylate, tert-butyl (meth)acrylate, 2-ethylhexyl (meth)
(Meth)acrylates such as acrylate, lauryl (meth)acrylate, cyclohexyl acrylate, benzyl (meth)acrylate, dibromopropyl (meth)acrylate or alkoxyalkyl (meth)acrylate; (meth)acrylic acid, crotonic acid, itacon acid, carboxyl group-containing monomers such as maleic acid, fumaric acid, etc. -N-dimethylaminoethyl (meth)acrylamide, N-diethylaminoethyl (meth)acrylamide, N-dimethylaminopropyl (meth)acrylamide or N-diethylaminopropyl (meth)acrylamide ) Amido-based unsaturated monomers containing amino groups such as acrylamide; dialkylaminoalkyl (meth)acrylates such as dimethylaminoethyl (meth)acrylate and diethylaminoethyl (meth)acrylate; or,
L-butylaminoethyl (meth)acrylate, t-butylaminopropyl (meth)acrylate, aziridinylethyl (meth)acrylate, pyrrolidinylethyl (
Basic nitrogen atom-containing monomers such as meth)acrylate or piperidylethyl (meth)acrylate; dialkyl((meth)acryloyloxyalkyl)phosphates or (meth)acryloyloxyalkyl acid phosphates represented by the general formula, general Dialkyl ((meth)acryloyloxyalkyl) phosphites or (meth)acryloyloxyalkyl acid phosphites represented by the formula (R+, Rz and R5 and A are as described above), and Alkylene oxide adducts of the above (meth)acryloyloxyalkyl acid phosphates or acid phosphites, epoxy group-containing vinyl monomers such as glycidyl (meth)acrylate and methylglycidyl (meth)acrylate, and phosphoric acid or phosphorous acid, or Esterified products with these acidic esters, 3-chloro-2-
Phosphorus atom-containing monomers such as acid phosphoxypropyl (meth)acrylate are common; 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate,
2-hydroxybutyl (meth)acrylate, 3-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate-1-13-chloro 2-hydroxypropyl (meth)acrylate, di-2-hydroxyethyl fumarate, mono- α,β-unsaturated carboxylic acid hydroalkyl esters such as 2-hydroxyethyl-monobutyl fumarate or polyethylene glycol mono(meth)acrylate with maleic acid, succinic acid, phthalic acid, hexahydrophthalic acid, tetrahydrophthalic acid, Zentricarboxylic acid, benzenetetracarboxylic acid, "Himic acid" [products of Hitachi Chemical Co., Ltd.], adducts of polycarboxylic acids such as tetrachlorophthalic acid or dodecynylsuccinic acid with anhydrides; vinylethoxysilane,
Silicon monomers such as α-methacryloxypropyltrimethoxysilane; glycidyl (meth)acrylate, (β-methyl)glycidyl (meth)acrylate,
Epoxy group-containing monomers such as (meth)allyl glycidyl ether; acid anhydride group-containing monomers such as vinyl esters of maleic anhydride, itaconic anhydride, and trimellitic anhydride; unsaturated dicarboxylic acids such as fumaric acid or itaconic acid and monohydric alcohols; vinyl esters such as vinyl acetate, vinyl benzoate, and “Heoba” (vinyl varnish chill manufactured by Shell); “Viscoat 88F, 8FM, 17FM, 3F or 3FMJ (
Fluorine-containing acrylic monomer manufactured by Osaka Organic Chemical Co., Ltd.]
, perfluorocyclohexyl (meth)acrylate,
Di-perfluorocyclohexyl fumarate or N-
(per)fluoroalkyl group-containing vinyl esters and vinyl ethers such as 1so-propyl perfluorooctane sulfonamide ethyl (meth)acrylate;
Fluorine-containing polymerizable compounds such as (meth)acrylates or unsaturated polycarboxylic acid esters; or (
There are vinyl monomers that do not have functional groups, such as olefins such as meth)acrylonitrile, vinyl chloride, and vinylidene chloride.

Furthermore, if necessary, as a copolymerizable unsaturated group-containing resin, a so-called alkyd resin modified with an oil or fatty acid having an unsaturated bond copolymerizable with an unsaturated group,
Alternatively, it is also possible to copolymerize polyester resins containing unsaturated groups that have unsaturated bonds that are copolymerizable with unsaturated monomers, or acrylic resins that have unsaturated bonds that are copolymerizable with unsaturated monomers. be.

As mentioned above, as the clear coat paint (2), the polyester resin (a-1
), or a blend of the resin (a-1) and the acrylic resin (a-2) as a base resin component, and a resin composition mainly composed of such a base resin component and a curing agent component is used. However, among the base resin components, this polyester resin (a-1) is essential in terms of the appearance of the paint film and the adhesion with the clear coat paint (■), and it also improves the weather resistance of the paint film. The acrylic resin (a-2) is appropriately blended and used, taking into consideration the physical properties of the coating film.

In addition, as the curing agent for this clear coat paint I, there may be mentioned those that are reactive with hydroxyl groups, such as aminoaldehyde resins, polyisocyanate compounds, or blocked polyisocyanate compounds. A compound containing an amino group such as melamine, urea, acetoguanamine, benzoguanamine, steroguanamine or spiroguanamine is reacted with an aldehyde compound such as formaldehyde, paraformaldehyde, acetylaldehyde or glyosazar by a conventional method. There are so-called modified products obtained by etherifying the resulting condensation products or each of these condensation products with m alcohols, but in addition to these typical products, there are also Any of them can be applied as long as they are available.

Typical polyisocyanate compounds include aliphatic diisocyanates such as tetramethylene diisocyanate, hexamethylene diisocyanate, or trimethylhexamethylene diisocyanate; isophorone diisocyanate, methylcyclohexane-2,4
- or 2,6-diisocyanate, 4,4'-methylenebis(cyclohexyl isocyanate) or 1
．． Alicyclic diisocyanates such as 3-di(isocyanatomethyl)cyclohexane; or adducts of each of these diisocyanates with polyhydric alcohols or low molecular weight hydroxyl group-containing polymers; diisocyanates such as those listed above; These include a reaction product with water and a biuret-forming agent (biulet form), and a trimer of diisocyanate I (isocyanurate form) as listed above.

Furthermore, as blocked polyisocyanate compounds,
Some of the various polyisocyanates listed above are blocked with known blocking agents such as methyl ketoxime and caprolactam.

The appropriate amount of the curing agent used is 5 to 100 parts by weight based on 100 parts by weight of the hydroxyl group-containing resin. If the amount of curing agent used is less than 5 parts by weight, the coating film is likely to be insufficiently crosslinked, resulting in a decrease in weather resistance and solvent resistance.
If the amount exceeds 0.00 parts by weight, the mechanical properties inevitably deteriorate, which is not preferable in either case.

The clear coat paint I used in the method of the present invention does not normally contain pigments, but may contain metal powder and/or color pigments used in the base coat paint to the extent that the transparency of the paint film is maintained. It is also possible.

This clear coat paint ■ also contains various resins and solvents, as well as fluidity regulators, color separation inhibitors, antioxidants, ultraviolet absorbers, light stabilizers, or silane coupling agents, as necessary. It is a matter of heat theory that various well-known and commonly used additives such as additives can be added.

Typical examples of the various resins include cellulose resins such as nitrocellulose or cellulose acetate butyrate, vinyl chloride/vinyl acetate copolymer resins,
Examples include ketone resin, petroleum resin, or epoxy resin.

The solvents include hydrocarbons such as toluene, xylene, cyclohexane, n-hexane, or octane; esters such as methyl acetate, ethyl acetate, butyl acetate, or ethylene glycol monoethyl ether acetate; acetone, methyl ethyl ketone, and methyl isobutyl. Ketones, such as methyl ethyl ketone or cyclohexanone; amides such as dimethylformamide, dimethylacetamide or N-methylpyrrolidone; or methanol, ethanol, n-propanol, 1so-propanol, n-butanol, 1s
Typical examples include alcoholic solvents such as o-butanol, 5ec-butanol, tert-butanol, or ethylene glycol monoalkyl ether, or mixtures thereof. however,
Among these solvents, when the above-mentioned curing agent component used in the resin composition for clear coat (1) is a polyisocyanate compound or a block polyisocyanate compound, the use of alcoholic solvents should be avoided.

Next, the above-mentioned clear coat paint H will be explained.

As the clear coat paint II, a fluoroolefin copolymer blended with a curing agent as the main component is used, and in particular, a fluoroolefin copolymer with a hydroxyl value of 50 to 200 and a number average molecular weight of 2.000 to 30. It is desirable to use a so-called hydroxyl group-containing fluoroolefin copolymer having a molecular weight of 0.000.

If the hydroxyl value is less than 50, the weather resistance will be poor, while if it exceeds 200, the flexibility will be poor, which is not preferable.

In addition, the number average molecular weight is 2. If it is less than OOO, the durability will inevitably be inferior, and on the other hand, if it is less than 30.0
If it becomes too high, exceeding 00, the coating workability deteriorates, so either case is not preferable.

The hydroxyl group-containing fluoroolefin copolymer is a copolymer containing a fluoroolefin and a hydroxyl group-containing monomer as essential components.

Examples of fluoroolefins include vinyl fluoride, vinylidene fluoride, trifluoroethylene, tetrafluoroethylene, chlorotrifluoroethylene, promotrifluoroethylene, pentafluoropropylene or hexafluoropropylene, or trifluoromethyl trifluorovinyl ether, pentafluoroethylene Perfluoroalkyl perfluorovinyl ethers such as ethyl trifluorovinyl ether or heptafluoropropyl trifluorovinyl ether are typical examples, and among them, tetrafluoroethylene, vinylidene fluoride, chlorotrifluoroethylene, and Preference is given to using hexafluoropropylene. These fluoroolefin monomers may be used alone or in combination of two or more.

Examples of hydroxyl group-containing monomers include 2-hydroxyethyl vinyl ether, 3-hydroxypropyl vinyl ether, 2-hydroxypropyl vinyl ether, 4-hydroxybutyl vinyl ether, 3-hydroxybutyl vinyl ether, 2-hydroxy-2-methylpropyl vinyl ether, and 5-hydroxypentyl vinyl ether. Alternatively, there are vinyl ethers containing a hydroxyl group such as 6-hydroxyalkyl vinyl ether, hydroxyalkyl vinyl ether to which ε-caprolactone has been added, or hydroxyalkyl allyl ether to which ε-caprolactone has been added.

Constituent monomers other than the above-mentioned fluoroolefins and hydroxyl group-containing monomers include vinyl 2 monocarboxylic acid vinyl esters having C1 to C18 hydrocarbon groups.
．． 2-dimethylpropanoate, vinyl 2,2-dimethylbutanoate, vinyl 2,2-dimethylpentanoate, vinyl 2,2-dimethylhexanoate, vinyl 2
．． 2-dimethylbutanoate, vinyl 2-ethyl-2-
Methyl butanoate, vinyl 2-ethyl-2-methylpentanoate, vinyl 3-chloro-2,2-dimethylpropanoate, vinyl acetate, vinyl propionate, vinyl butyrate, vinyl isobutyrate, vinyl caproate, capryl vinyl acid, vinyl caprate, vinyl laurate, C9
branched aliphatic vinyl carboxylate, C1° branched aliphatic vinyl carboxylate, CI+ branched aliphatic vinyl carboxylate, or aliphatic carboxylic acid vinyl ester such as vinyl stearate; or vinyl cyclohexane carboxylate, methylcyclohexane carboxylic acid There are carboxylic acid vinyl esters having a cyclic structure such as vinyl, vinyl benzoate, or vinyl p-tert-butylbenzoate.

Other copolymerizable monomers include methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, isopropyl vinyl ether, n-butyl vinyl ether, isobutyl vinyl ether, tert
- Alkyl vinyl ethers or substituted alkyl vinyl ethers such as butyl vinyl ether, n-pentyl vinyl ether, n-hexyl vinyl ether, n-octyl vinyl ether, 2-ethylhexyl vinyl ether, chloromethyl vinyl ether, chloroethyl vinyl ether, benzyl vinyl ether or phenylethyl vinyl ether; cyclopentyl vinyl ether ,
Cycloalkyl vinyl ethers such as cyclohexyl vinyl ether or methyl cyclohexyl vinyl ether; vinyltrimethoxysilane, vinyltriethoxysilane, vinyltripropoxysilane, vinylmethyljethoxysilane, vinyltris(β-methoxyethoxy)silane, allyltrimethoxysilane, Methoxysilylethyl vinyl ether, triethoxysilylethyl vinyl ether, methyldimethoxysilylethyl vinyl ether, trimethoxysilylpropyl vinyl ether, triethoxysilylpropyl vinyl ether, methyldimethoxysilylpropyl vinyl ether, r-(meth)acryloyloxypropyltrimethoxysilane, γ
- Monomers containing hydrolyzable silyl groups such as (meth)acryloyloxypropyltriethoxysilane or T-(meth)acryloyloxypropylmethyldimethoxysilane; ethylene, propylene or butene -
α-olefin necks such as 1; various halogenated olefins, excluding fluoroolefins, such as vinyl chloride or vinylidene chloride; aromatic vinyl compounds such as styrene, α-methylstyrene or vinyltoluene-methyl methacrylate-1 -, methacrylic acid esters such as ethyl methacrylate, butyl methacrylate or cyclohexyl methacrylate; methyl acrylate, ethyl acrylate, butyl acrylate,
Acrylic acid esters such as cyclohexyacrylate are representative.

Furthermore, carboxyl group-containing monomers such as (meth)acrylic acid, crotonic acid, itaconmaleic acid or fumaric acid can also be used.

When preparing the hydroxyl group-containing fluoroolefin copolymer of the present invention from each of the above-mentioned heptamer components, from the viewpoint of weather resistance, the amount of fluoroolefin used is 15 to 70% by weight, preferably 20% by weight based on the total monomers. ~60% by weight
From the viewpoint of the appearance of the coating film, the monocarboxylic acid vinyl ester having a C8 to C+a hydrocarbon group accounts for 5 to 95% by weight, preferably 10 to 80% by weight of the total monomers.
% by weight, and the hydroxyl group-containing vinyl monomer is 3 to 40% by weight, preferably 5% by weight from the viewpoint of weather resistance etc.
~35% by weight is desired.

To prepare a hydroxyl group-containing fluoroolefin copolymer, Japanese Patent Application Laid-open No. 61-275311 and Japanese Patent Publication No. 60-
The method disclosed in Japanese Patent No. 21686 may be used.

As an example of a commercially available product of such a hydroxyl group-containing fluoroolefin copolymer, "
Fluonate K-700 or 7701J, Lumiflon LF-100, LP-200 manufactured by Asahi Glass Co., Ltd.
, LP-300, LP-400 or LP-700J
, or "Cefural Coat" manufactured by Central Glass Co., Ltd.
Examples include.

Further, as the curing agent to be combined with the fluoroolefin copolymer, the same curing agent as that used in the case of the above-mentioned clear coat paint I can be used.

The amount of the aminoaldehyde resin, polyisocyanate compound, or blocked polyisocyanate compound used as the curing agent is 5 to 10% by weight per 100% of the hydroxyl group-containing fluoroolefin copolymer.
An appropriate range is 0 parts by weight. If the amount of the curing agent used is less than 5 parts by weight, the coating film is likely to be insufficiently crosslinked, resulting in decreased weather resistance and solvent resistance. If it exceeds 100 parts by weight, the mechanical properties inevitably deteriorate, which is not preferable.

By the way, the clear coat paint obtained in this way has
As in the case of the clear coat paint mentioned above, various resins and solvents such as polyester resin and acrylic resin are added as necessary, as well as fluidity regulators, color separation inhibitors, and oxidation inhibitors. It is a matter of heat theory that various known and commonly used additives such as inhibitors, ultraviolet absorbers, light stabilizers, or silane coupling agents can be added.

Furthermore, since the fluoroolefin copolymer has high light transmittance, it is recommended to add and use an ultraviolet absorber in the clear coat paint to protect the clear coat (I) using the copolymer. This is preferable because it further improves.

In order to form the desired coating film by carrying out the method of the present invention, for example, a base coat paint is applied to the surface of the object to be coated, which has been subjected to surface treatment or, if necessary, a brimer or surfacer. Depending on the situation, dilute with a diluting solvent and apply using a normal method so that the dry film thickness becomes 10 to 50 μm. Next, apply clear coat paint ■ using a normal method (dry film thickness: ~40 μm), and then crosslinked under predetermined conditions. Furthermore, a clear coat paint (2) may be applied thereon (5 to 40 .mu.m) by a normal method and crosslinked under predetermined conditions. The topcoat film obtained in this way is not only highly durable, but also has problems with painting workability such as "flanks" and "sag" compared to the conventional two-coat, one-bake method. Moreover, it has excellent gloss, leveling, and image clarity.

〔Effect of the invention〕

As described above, the coating film obtained by the method of the present invention is particularly highly durable, and has excellent appearance, weather resistance, and even interlayer adhesion. Therefore, the top coating method of the present invention is an extremely useful coating method.

This is achieved for the first time through a novel method of 2-coat, 2-bake painting in which oil-free alkyd resin is first applied to the clear coat, and then fluorine-containing thread resin is applied to the overclear coat. Therefore, it can be said that the method of the present invention is a particularly excellent and greatly improved topcoating method.

〔Example〕

Next, the present invention will be explained by reference examples, examples, and comparative examples.
The layer will be explained in detail. In the following, all parts and percentages are based on weight unless otherwise specified.

Reference Example 1 [Example of Preparation of Polyester Resin (a-1)] 179 parts of trimethylolpropane and 29 parts of neopentyl glycol were placed in a four-way flask equipped with a stirrer, a thermometer, a reflux condenser with a dehydration trap, and a nitrogen gas inlet tube.
Two parts were charged and the temperature was raised to 150°C.

Next, 604.6 parts of hexahydrophthalic acid and 0.85 parts of lithium hydroxide were added and the temperature was raised to 220°C, and further, a dehydration condensation reaction was carried out at this temperature to reduce the acid value of the solid content to 9. This was continued until it reached .8.

After the reaction is complete, cool and add 525 parts of xylene.
The non-volatile content is 65%, the Gardner viscosity at 25°C (the same applies hereinafter) is ■, the acid value and hydroxyl value of the solid content are 6.2 and 100, respectively, and the number average molecular weight is 2.580. A solution of the desired resin was obtained. below,
This is abbreviated as resin (al-1).

Reference Examples 2 to 5 (same as above) Except for changing the raw material preparation as shown in Table 1,
A solution of the target resin was obtained in the same manner as in Reference Example 1.

The respective property values are summarized in the same table.

The abbreviations in the table have the following meanings.

HHPA...Hexahydrophthalic acid IPA...Isophthalic acid AA...Adipic acid TMP...Trimethylolpropane NPC...
Neopentyl glycol 1.6HD...1.6-hexanediol Reference example 6 [
Preparation example of acrylic resin (a-2)) Add 266 parts of "Tsurupez 100" (aromatic hydrocarbon solvent manufactured by Exxon, USA) to a Yotsuro flask equipped with a stirrer, thermometer, condenser, and nitrogen inlet tube. and 6 of n-butanol
7 parts were charged and kept at 120°C.

Next, 150 parts of styrene, 350 parts of n-butyl methacrylate, 80 parts of n-butyl acrylate, 200 parts of 2-hydroxyethyl methacrylate, 2
0 parts acrylic acid, 40 parts tert-butylperoxy 2-ethylhexanoate, 10 parts di-tert
-butyl perbenzoate and 10 parts of azobisisobutyronitrile were added dropwise over a period of 4 hours.

After the dropwise addition, the above temperature was maintained for 6 hours to continue the reaction, resulting in a non-volatile content of 60%, a viscosity of T, an acid value of 9.2, a hydroxyl value of 86, and a number average molecular weight. is 5
, 200 was obtained. Hereinafter, this will be abbreviated as resin (a-21).

Reference Examples 7 to 9 (same as above) Except for changing the raw material preparation as shown in Table 2,
A solution of the target resin was obtained in the same manner as in Reference Example 6.

The respective property values are summarized in the same table.

/ Reference Example 10 (Example of Preparation of Fluoroolefin Copolymer) In a 21 stainless steel autoclave which was sufficiently purged with nitrogen, 390% of vinyl P tert-butylbenzoate was added.
parts, 100 parts of "Beover 9" (vinyl ester of branched aliphatic monocarboxylic acid, C1, manufactured by the aforementioned company), 4
-110 parts of hydroxybutyl vinyl ether, acetic acid n
-430 parts of butyl, 20 parts of 2,2-azobis(2,4-dimethylvaleronitrile and
3 parts of 765J (amine compound manufactured by Sankyo Co., Ltd.) were charged. Next, 400 parts of liquefied chlorotrifluoroethylene was introduced under pressure, and the mixture was heated at 60°C for 1 hour with stirring.
The reaction was carried out for 5 hours, and when the non-volatile content reached 67%, it was cooled to room temperature and 175 parts of xylene was added to obtain a solution of the desired copolymer with a non-volatile content of 60%. Hereinafter, this will be abbreviated as copolymer (b-1-1), and the solid content of this product had a hydroxyl value of 53 and a number average molecular weight of 25,000.

Reference Example 11 (same as above) The composition ratio of the monomers to be used was changed to 110 parts of vinyl benzoate, 300 parts of 4-hydroxyethyl vinyl ether, 190 parts of cyclohexyl vinyl ether, 400 parts of chlorotrifluoroethylene, and n-butyl acetate was replaced. The reaction was carried out in the same manner as in Reference Example 1O, except that 670 parts of xylene was used, and the nonvolatile content was 60 parts.
% of the desired copolymer solution was obtained.

Hereinafter, this will be abbreviated as copolymer (b-1-2), and the solid content of this product had a hydroxyl value of 145 and a number average molecular weight of 7,000.

Reference Example 12 (Example of Preparation of Base Coat Paint) According to the composition ratio shown below, a paint prepared by a normal paint preparation method was mixed with a diluting solvent to form Ford Cup N01.
The desired paint was obtained by adjusting the viscosity to 11 to 12 seconds.

"Super Beckamin L-117-60" 33 "
Al Paste 1860YLJ 23
Total: 177 Total: 218 Hereinafter, this will be abbreviated as paint (BC-2).

Reference Example 14 (same as above) The desired coating material was obtained in the same manner as Reference Example 12, except that the composition ratio was changed to the one shown below.

Hereinafter, this will be abbreviated as paint (B(,-1)).

Reference Example 13 (same as above) Same as Reference Example 12, except that the composition ratio was changed as shown below, and the adjusted viscosity was changed to 13 to 14 seconds for Ford Cup No. 4. The desired paint was obtained.

``Tie Bake CR-93J (rutile type titanium oxide manufactured by Ishihara Sangyo Co., Ltd.) 60 Hereinafter, this will be abbreviated as paint (BC-3).

Reference Example 15 (Example of Preparation of Clear Coat Paint ■) According to the composition ratio shown below, a compound prepared by a normal paint preparation method was mixed with Ford Cup N using a diluting solvent.
The viscosity was adjusted to 25 seconds in step 4 to obtain the desired paint. Hereinafter, this will be abbreviated as paint (CC-1).

Resin (a-1-1) 108 parts [Super Beckamine L-117-60J 50
Reference Examples 16 to 28 (same as above) Target paints were obtained in the same manner as Reference Example 15, except that the composition ratios were changed to those shown in Table 3.

The general description of the commercial products listed in the same table is as follows.

Reference Example 29 (Example of Preparation of Clear Coat Paint ■) According to the composition ratio shown below, a compound prepared by a normal paint preparation method was mixed with a diluting solvent to form Ford Cup N.
The desired coating material was obtained by adjusting the viscosity so that it would take 23 seconds at step 4. Hereinafter, this will be abbreviated as paint (CC-14).

Resin (c-1-1) 117 parts "Sumimar M-100CJ 30s"
Nacure 5225J
2 “Tinuvin 900 J
1 Sanol LS-765, 1# Reference Examples 30 to 34 (same as above) The desired paint was prepared in the same manner as Reference Example 29, except that the composition ratio was changed to that shown in Table 4. Obtained.

The general description of the commercial products listed in the same table is as follows.

Reference Example 35 (Example of Preparation of Comparative Clear Coat Paint) According to the composition ratio shown below, a compound prepared by a conventional method was mixed with a diluting solvent to form Ford Cup No. 4.
The viscosity was adjusted to 23 seconds to obtain a control clear coat paint.

Hereinafter, this will be abbreviated as paint (CC'-1).

Resin (a-2-1) 117 parts “Super Hekkamin L-117-60J 50
"Tinuvin 900" 1 [Sanol LS-765J 1 Reference example 3
6 to 41 (same as above) A control clear coat paint was obtained in the same manner as Reference Example 35, except that the composition ratio was changed as shown in Table 5.

481- Examples 1 to 18 Base coat paints obtained in Reference Examples 12 to 14, clear coat paints ■ obtained in Reference Examples 15 to 28, and clear coat paints ■ obtained in Reference Examples 29 to 34. on a coated plate obtained by applying an automotive electrodeposited primer and an intermediate coat Surfacer to a mild steel plate that has been subjected to phosphorization treatment using
First, the dry film thickness is 15-20μm by air spraying.
After applying the base coat paint, let it set for 3 minutes, then apply the clear coat paint I wet-on-wet to a dry film thickness of 25 to 30 μm, leave it for 20 minutes, and then heat it with electric hot air. Drying was performed in a dryer under predetermined conditions.

Furthermore, 10 hours later, a clear coat paint (2) was applied so that the dry film thickness was 25 to 30 μm, and after being left for 10 minutes, it was dried in an electric hot air dryer under predetermined conditions.

The performance of each 3-coat, 2-bake topcoat film thus obtained was evaluated. Those results are
All are shown in the same table.

Comparative Examples 1 to 10 The base coat paints obtained in Reference Examples 12 to 14 and the clear coat paints obtained in Reference Examples 35 to 41 or the clear coat paint I obtained in Reference Example 15 were used, and According to the conditions shown in Table 7, an electrodeposition primer for automobiles and an intermediate coating surfacer were applied to a mild steel plate that had been subjected to a phosphorization treatment, and then a dry film thickness of 15 to 15 mm was first applied by air spraying. After applying the base coat paint to a dry film thickness of 20 μm, leave it for 3 minutes, then apply the clear coat paint until the dry film thickness is 30 μm.
The coating was applied wet-on-wet to a thickness of ~35 μm, left for 20 minutes, and then dried under predetermined conditions in an electric hot air dryer.

The performance of each two-coat 1-baked topcoat film thus obtained was evaluated. Those results are
All are shown in the same table.

However, in Comparative Example 10, -
After applying the base coat paint, painting and drying the clear coat paint, apply the clear coat paint ■ obtained in Reference Example 30, that is, CC-15, to a dry film thickness of 35
It was coated to a thickness of ~40 μm, left for 10 minutes, and then dried under predetermined conditions in an electric hot air dryer.

Similar performance evaluations were also performed on the control 3-coat, 2-bake coating film thus obtained.

The results are shown together.

/ As is clear from Tables 6 and 7, the three-coat, two-bake topcoat film obtained by the method of the present invention has excellent appearance, weather resistance, and interlayer adhesion. Therefore, the method of the present invention is known to be extremely useful.

teenager Reason Man

Claims (1)

[Scope of Claims] 1. A cross-linkable metallic base coat paint containing metal powder and/or colored pigment is applied to the object to be coated, and then a cross-linkable clear paint I (Clear Coat I) is applied to the coated surface. After coating and crosslinking, in the top coating method in which a crosslinked clear paint II (clear coat II) is further applied and crosslinked, (A) as the above clear coat paint I, (1) polyester resin (a-1), Alternatively, a resin composition comprising a blend of the resin (a-1) and the acrylic resin (a-2) mixed with (2) a curing agent is used as a main component, and (B) the above clear coat paint
As II, (1) fluoroolefin copolymer (2)
A top coating method characterized by forming a coating film using a resin composition containing a curing agent as a main component. 2. Claim 1, wherein the polyester resin used as the clear coat paint has a hydroxyl value within the range of 30 to 300 and a number average molecular weight within the range of 500 to 5,000. The top coating method described in . 3. The acrylic resin (a-2) used as the above clear coat paint I has a hydroxyl value within the range of 30 to 150 and a number average molecular weight within the range of 1,000 to 20,000. The top coating method according to claim 1, which comprises: 4. The fluoroolefin copolymer used as the above-mentioned clear coat paint II has a hydroxyl value within the range of 50 to 200 and a number average molecular weight within the range of 2,000 to 30,000. Claim 1
The top coating method described in . 5. The fluoroolefin copolymer used as the clear coat paint II mentioned above is one of the fluoroolefins.
5 to 70% by weight, 5 to 95% by weight of monocarboxylic acid vinyl ester having a hydrocarbon group having 1 to 18 carbon atoms,
The top coating method according to claim 1 or 4, wherein the monomer composition is comprised of 3 to 40% by weight of the hydroxyl group-containing monomer and 0 to 77% by weight of other copolymerizable monomers. 6. The fluoroolefin copolymer used as the above-mentioned clear coat paint II is one of the fluoroolefins.
5 to 70% by weight, essential aromatic monocarboxylic acid monovinyl ester having a hydrocarbon group having 1 to 18 carbon atoms, and optionally aliphatic and/or monovinyl ester having a hydrocarbon group having 1 to 18 carbon atoms. or a monocarboxylic acid vinyl ester having a hydrocarbon group having 1 to 18 carbon atoms, which also includes an alicyclic monocarboxylic acid monovinyl ester.
5. The top coating method according to claim 1, wherein the monomer composition is 95% by weight, 3 to 40% by weight of the hydroxyl group-containing monomer, and 0 to 77% by weight of other copolymerizable monomers. 7. The fluoroolefin copolymer used as the clear coat paint II mentioned above is one of the fluoroolefins.
5 to 70% by weight, and 5 to 95% by weight of vinyl benzoate and/or vinyl p-tert-butylbenzoate, a monocarboxylic acid vinyl ester having a hydrocarbon group having 1 to 18 carbon atoms; The top coating method according to claim 1 or 4, wherein the monomer composition is comprised of 3 to 40% by weight of the hydroxyl group-containing monomer and 0 to 77% by weight of other copolymerizable monomers.