JP2002355610A - Coating method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a coating method excellent in the adhesion to a substrate and a primer and capable of obtaining a coating film excellent in weatherability and antistaining properties. SOLUTION: In the method for coating an article or a structure with a topcoat paint directly or through the primer, a composition containing a polymer having a maleimide group is used as the topcoat paint.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for coating an article or structure such as a metal, glass, wood and inorganic substrate with a topcoat comprising a composition containing a polymer having a maleimide group. Articles or structures coated according to the present invention have excellent stain resistance and weather resistance, and can be awarded in these technical fields.

[0002]

[Prior art and its problems] Iron, stainless steel, aluminum,
General buildings, tanks, plants, ships, manufactured from materials such as galvanized steel sheets, concrete and slate
BACKGROUND ART Paints made of various resins are usually applied to waterway works, bridges, electric power facilities, marine structures, heavy vehicles, light vehicles, industrial machines, aircrafts, and the like for the purpose of protection or dressing.
As the paint, polyester resin paint, acrylic urethane resin paint, alkyd resin paint, chlorinated rubber paint, urethane resin paint, silicone alkyd resin paint, polyester melamine resin paint, acrylic melamine resin paint and epoxy resin paint are common. Used in The base material is applied as a top coat through a process of applying and drying a top coat directly or via a primer. Among these, paints having excellent weather resistance, such as acrylic urethane paint, acrylic silicone paint, and fluorine paint, are used as paints for articles or structures requiring weather resistance. However, these highly weather-resistant paints are usually two-pack paints composed of a main agent and a curing agent, and the work of mixing them immediately before painting is required. In addition, there is a one-pack type paint, but some do not involve a cross-linking reaction during drying, so that stain resistance is insufficient or stain resistance and weather resistance are sometimes unsatisfactory. In recent years, as an organic solvent-based coating, a so-called weak solvent-type coating in which a polymer is dissolved in a hydrocarbon-based solvent having little harm to the human body has been studied. However, in weak solvent type acrylic urethane-based paints, to increase the solubility in weak solvents, the hydroxyl groups of the polymer used are reduced, or long-chain monomers, branched monomers, styrene, etc. are used as constituent monomers. However, there is a problem that the weather resistance is insufficient as compared with the strong solvent type paint. Further, in the case of a weak solvent type acrylic silicone-based paint, there is a problem that the curing rate of moisture curing is slower than that in the strong solvent type, since moisture hardly penetrates into the coating film.

[0003]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, by using a composition containing a polymer having a maleimide group as an overcoat, various base materials and It has excellent adhesion to the primer, cures when left outdoors after coating, and can be used to prepare a one-part coating form by using a curing catalyst. The inventors have found that the coating film properties such as stain resistance are excellent and completed the present invention. Hereinafter, the present invention will be described in detail. In this specification, acrylate or methacrylate is represented as (meth) acrylate, and acrylic acid or methacrylic acid is represented as (meth) acrylic acid.

[0004] 1. Polymer Having Maleimide Group In the present invention, a composition containing a polymer having a maleimide group (hereinafter referred to as a maleimide polymer) is used as an overcoat. As the polymer having a maleimide group, those produced by various methods can be used, and in terms of easy production, a single ethylenically unsaturated monomer having a maleimide group (hereinafter referred to as a maleimide monomer) can be used. A polymer or a copolymer of a maleimide monomer and an ethylenically unsaturated monomer copolymerizable therewith (hereinafter simply referred to as an unsaturated monomer) is preferred. Hereinafter, the maleimide monomer will be described.

1-1. Maleimide monomer As the maleimide monomer, a compound having an ethylenically unsaturated group and a cyclic imide group represented by the following formula (1) is preferable.

[0006]

Embedded image

(However, in the formula (1), R ¹ and R ² are each independently a hydrogen atom or an alkyl group, one of them is a hydrogen atom and the other is an alkyl group, or the other is bonded to form a carbon ring. Group to form.)

The ethylenically unsaturated group in the maleimide monomer includes a vinyl group and a (meth) acryloyl group, and a (meth) acryloyl group is preferred.

R ¹ and R ² are each independently an alkyl group or a group formed by bonding to each other in that they are excellent in their own polymerizability or copolymerizability with a monomer containing an ethylenically unsaturated group. Groups forming a carbocycle are preferred. The alkyl group preferably has 4 or less carbon atoms. Furthermore, a group in which each is bonded to form a carbocyclic ring is preferable in that the production of the maleimide monomer is easy, the yield is excellent, and the obtained copolymer is excellent in water resistance. preferably, group -CH ₂ CH ₂ CH ₂ -, or a group -CH ₂ CH ₂ C
H ₂ CH ₂ — is preferred, particularly preferably the group —CH ₂ CH ₂
CH ₂ CH ₂ —.

As the maleimide monomer, a (meth) acrylate containing a maleimide group represented by the following (2) [hereinafter referred to as imide (meth) acrylate] is preferable.

[0011]

Embedded image

However, in the formula (2), R ¹ and R ² are the same groups as described above. R ³ is an alkylene group, R ⁴ is hydrogen or a methyl group, and n is an integer of 1 to 6.

In the formula (2), those in which n is 1 to 2 are preferable, and those in which 1 is more preferable. R ³ preferably has 1 to 6 carbon atoms, and more preferably includes an ethylene group and a propylene group.

The imide (meth) acrylate can be produced from an acid anhydride, an amino alcohol and (meth) acrylic acid by the methods described in the following documents and patents. -Kiyoshi Kato et al., Journal of Synthetic Organic Chemistry, 30 (10), 89
7, (1972) Javier de Abajo et al., Polymer, vol 33
(5), (1992)-JP-A-56-53119, JP-A-1-2425
No. 69

1-2. Unsaturated Monomer The maleimide polymer of the present invention is preferably a copolymer of a maleimide monomer and an unsaturated monomer in that the resulting composition has a small curing shrinkage. Various monomers can be used as the unsaturated monomer, but alkyl (meth) acrylate is preferable from the viewpoint of excellent physical properties of the coating film and copolymerizability with the maleimide monomer.

As the alkyl (meth) acrylate, various compounds can be used, and any of linear, branched or cyclic alkyl groups can be used. Examples of the (meth) acrylate having a linear alkyl group include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, pentyl (meth) acrylate, and hexyl (meth) acrylate.
Acrylate, octyl (meth) acrylate, nonyl (meth) acrylate, decyl (meth) acrylate,
Examples include lauryl (meth) acrylate, tridecyl (meth) acrylate, cetyl (meth) acrylate, stearyl (meth) acrylate, and behenyl (meth) acrylate. The alkyl group of the monomer may contain an aromatic ring, oxygen, nitrogen, sulfur, halogen and the like. Such (meth) acrylates include benzyl (meth)
Acrylate, phenoxyethyl (meth) acrylate, methoxyethyl (meth) acrylate, ethyl carbitol (meth) acrylate, ethoxy polyethylene glycol (meth) acrylate, aminoethyl (meth)
Acrylate, chloroethyl (meth) acrylate, trifluoroethyl (meth) acrylate, heptadecafluorooctylethyl (meth) acrylate and the like are exemplified.

As the (meth) acrylate having a branched alkyl group, isopropyl (meth) acrylate,
Isobutyl (meth) acrylate, s-butyl (meth)
Acrylate, t-butyl (meth) acrylate, neopentyl (meth) acrylate, ethylhexyl (meth) acrylate, isodecyl (meth) acrylate, and isostearyl (meth) acrylate are exemplified. The alkyl group of the monomer may contain an aromatic ring, oxygen, nitrogen, sulfur, halogen and the like. Examples of such a monomer include 3-methoxybutyl (meth) acrylate, methoxytripropylene glycol (meth) acrylate, and hexafluoropropyl (meth) acrylate.

Examples of the (meth) acrylate having a cyclic alkyl group include cyclohexyl (meth) acrylate,
Examples include isobornyl (meth) acrylate and tricyclodecinyl (meth) acrylate. The alkyl group of the monomer may contain an aromatic ring, oxygen, nitrogen, sulfur, halogen and the like. Examples of such a monomer include tetrahydrofurfuryl (meth) acrylate (meth) acrylate and morpholinoethyl (meth) acrylate.

These alkyl (meth) acrylates are
They can be used alone or in combination.
In the present invention, among these alkyl (meth) acrylates, it is preferable that the alkyl (meth) acrylate has an alkyl group having 1 to 20 carbon atoms from the viewpoint of excellent hardness and weather resistance of the obtained coating film, and an alkyl group having 1 to 8 carbon atoms. It is particularly preferred to have Such monomers include methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, isobutyl (meth) acrylate, t-butyl (meth) acrylate, ethylhexyl (meth) acrylate, and cyclohexyl (meth) Acrylates are exemplified.

As the unsaturated monomer, a functional group-containing monomer can be used. Examples of the functional group include a hydroxyl group, a carboxyl group, an epoxy group, and a hydrolyzable silyl group.

Examples of the hydroxyl group-containing monomer include hydroxyalkyl (meth) acrylates such as hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate and hydroxybutyl (meth) acrylate; 2-hydroxychloropropyl (meth) Acrylates include polyalkylene glycol mono (meth) acrylates such as polyethylene glycol and polypropylene mono (meth) acrylate, lactone-modified hydroxyethyl-modified (meth) acrylate, and hydroxyl group-containing (meth) acrylate oligomer. The lactone-modified hydroxyethyl-modified (meth) acrylate is commercially available, and includes, for example, Placcel F series manufactured by Daicel Chemical Industries, Ltd. Hydroxyl-containing oligomers are commercially available, and are Alonix 5700 (trade name) manufactured by Toagosei Co., Ltd., which is an acrylate oligomer having a hydroxyl group at a terminal, and HE-10, HE-20, and HP-10 manufactured by Nippon Shokubai Chemical Co., Ltd. And HP-20 (both are trade names).

Examples of the carboxyl group-containing monomer include (meth) acrylic acid, itaconic acid, maleic acid, fumaric acid,
Vinyl acetic acid and crotonic acid;

The epoxy group-containing monomer includes (meth)
Glycidyl acrylate, allyl glycidyl ether, glycidyl vinyl ether and the like can be mentioned.

Examples of the hydrolyzable silyl group-containing monomer include:
Examples include trimethoxysilylpropyl (meth) acrylate, triethoxysilylpropyl (meth) acrylate, methyldimethoxysilylpropyl (meth) acrylate, and vinyltrimethoxysilane.

Examples of the unsaturated monomer include α-olefins such as ethylene, propylene and isobutylene; partially halogenated olefins such as vinyl chloride, vinylidene chloride, vinyl fluoride and vinylidene fluoride; And allyl compounds such as allyl butyrate, crotonic esters such as ethyl crotonate and propyl crotonate; vinyl ethers such as ethyl vinyl ether and cyclohexyl vinyl ether; vinyl carboxylate such as vinyl acetate, vinyl propionate and vinyl versatate; styrene, α-methyl Substituted styrenes such as styrene and vinyltoluene; acrylonitrile, acrylamide, and methacrylamide. These monomers may be used in combination of two or more.

When the maleimide polymer used in the present invention is a copolymer of a maleimide monomer and an unsaturated monomer, the copolymerization ratio of the monomer is 4 to 40 parts by mass of the maleimide monomer, The amount of the monomer is preferably 96 to 60 parts by mass. When the amount of the maleimide monomer is less than 4 parts by mass, the number of crosslinking points is small, and the curability and the performance of the cured coating film may be deteriorated. Performance may be reduced.

In the top coating composition of the present invention, the maleimide polymer may be in any of a form dissolved in an organic solvent, a form non-aqueous dispersed in an organic solvent, and a form dispersed in water.

The average molecular weight of the maleimide polymer is 1,000 as a number average molecular weight (hereinafter referred to as Mn) in terms of polystyrene determined by gel permeation chromatography.
Preferably it is ~ 1,000,000. When the polymer having a maleimide group is dissolved in an organic solvent and used as an organic solvent-based coating and a non-aqueous dispersion coating, Mn is 3,0.
It is preferably from 100 to 100,000. On the other hand, when the polymer is emulsified and suspended and used as a dispersion in an aqueous medium, Mn is preferably from 10,000 to 500,000.

The glass transition point (hereinafter referred to as T) of the maleimide polymer
g) is preferably in the range of 5 ° C to 80 ° C. If the temperature is lower than 5 ° C., the stain resistance of the coating film may decrease.
If it exceeds 300, the base followability of the coating film will be poor, and cracks may occur.

1-3. Production Method of Maleimide Polymer The maleimide polymer can be produced by copolymerizing the monomers in the presence of a radical polymerization initiator. Examples of the polymerization method include bulk polymerization, suspension polymerization and emulsion polymerization in an aqueous medium, and solution polymerization in an organic solvent. Radical polymerization initiators include peroxides such as diisopropyl peroxydicarbonate, tert-butyl peroxypivalate, benzoyl peroxide and lauroyl peroxide, inorganic peroxides such as ammonium persulfate and potassium persulfate, and azobis Azo compounds such as isobutyronitrile and azobisisovaleronitrile can be used. The amount used is preferably 0.0001 to 10% by weight based on the total amount of the monomers. In any polymerization, a chain transfer agent such as lauryl mercaptan may be added as necessary.

When the maleimide polymer is produced by emulsion polymerization, anionic, nonionic and combinations thereof are preferred as emulsifiers. Examples of anionic emulsifiers include sodium salts of higher alcohol sulfates, and examples of nonionic emulsifiers include polyethylene glycol alkyl ethers. In addition, a reactive emulsifier can also be used, and specifically, latemul (Kao Corporation), eleminol (Sanyo Chemical Co., Ltd.), Aqualon (Daiichi Kogyo Pharmaceutical Co., Ltd.)
Co., Ltd.) and Adecaria Soap (Asahi Denka Kogyo Co., Ltd.). The amount of the emulsifier used is 100
It is preferably in the range of 0.1 to 50 parts by mass with respect to parts by mass. If necessary, potassium carbonate, sodium hydrogencarbonate, hydrotalcite, anion exchange resin and the like may be added as a pH adjuster.

When the maleimide polymer is produced by solution polymerization, the organic solvent to be used includes: cyclic ethers such as tetrahydrofuran and dioxane; hydrocarbons such as n-hexane and cyclohexane; aromatic hydrocarbons such as benzene, toluene and xylene. Compounds; acetates such as ethyl acetate and butyl acetate; ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, methyl amyl ketone and cyclohexanone; alcohols such as ethanol, isopropanol, n-butanol and n-butyl cellosolve; and mineral spirits, carbonized Pegasol 3040 (20% by mass of aromatic component) and Pegasol AN-45 (30% by mass of aromatic component) of a hydrogen-based mixed solvent [all manufactured by ExxonMobil Chemical Co., Ltd.], L
AWS (aromatic content 30% by mass), HAWS (aromatic content 5%)
0% by mass) [all are manufactured by Shell Chemical Co., Ltd.], and hydrocarbon solvents such as Swazole 1000 [made by Maruzen Petroleum Co., Ltd.]. These organic solvents can be used in combination of two or more kinds. The amount of the organic solvent used is preferably in the range of 20 to 200 parts based on 100 parts by mass of the total amount of the monomers.

When a maleimide polymer is produced by non-aqueous dispersion polymerization, the solvent is dissolved in a hydrocarbon-based solvent in the presence of a polymer soluble in the solvent, such as a long-chain alkyl (meth) acrylate copolymer. The above monomer having a composition that becomes insoluble is copolymerized. Examples of the hydrocarbon solvent used in this case include those described above.

The polymerization conditions are not particularly limited.
The preferred polymerization temperature in the preferred reaction is 20-140 ° C
Yes, usually at normal pressure. The preferred polymerization time is 3
~ 40 hours. The monomers used for the polymerization may be initially batch-charged in their entirety, or some of the monomers may be added sequentially as the polymerization proceeds.

[0035] 2. Topcoat paint The topcoat paint used in the present invention may be in any form such as an organic solvent type paint, a non-aqueous dispersion type paint and an aqueous paint as long as it has a maleimide polymer. In the case of an organic solvent type paint, the organic solvent used preferably has a boiling point of 60 ° C. or higher. When an organic solvent having a boiling point of less than 60 ° C. is used, when a coating material is used, drying may be too fast and film forming properties may be reduced. Specific examples of the organic solvent include aromatic hydrocarbon-based mixed solvents [commercially available products such as Swazole 1]
000, manufactured by Maruzen Petroleum Co., Ltd.]; ortho acids such as methyl orthoformate and methyl orthoacetate; cellosolve or carbitol solvents such as ethylene glycol monobutyl ether and diethylene glycol monobutyl ether; propylene glycol methyl ether; Alkylene glycol alkyl ethers such as propylene glycol butyl ether; isoprene glycol solvents such as solphite and solphite acetate; terpenes such as mineral spirits, naphtha No. 5, naphtha No. 6, LAWS and HAWS; When the composition of the present invention is a non-aqueous dispersion paint, the organic solvent used may be mineral spirit, naphtha No. 5, naphtha N.
Terpenes such as o6, LAWS and HAWS are preferred. The ratio of the organic solvent is preferably maleimide polymer: organic solvent = 20: 8 to 75:25 (mass ratio).

When the overcoat paint used in the present invention is an aqueous paint, ethanol, ethylene glycol, solfit (3-methoxy-3-methyl-1-butanol [Kuraray Co., Ltd.]), solfit acetate ( 3-methyl-3-methoxybutyl acetate [Kuraray Co., Ltd.]) and Texanol CS12 (2,2,4-trimethyl-
Cellosolve or carbitol solvents such as 1,3-pentanediol monoisobutyrate) [Chisso Corporation]), ethylene glycol monobutyl ether and diethylene glycol monobutyl ether; alkylene glycol alkyls such as propylene glycol methyl ether and propylene glycol butyl ether An organic solvent such as ether may be added. The ratio of the aqueous medium is preferably maleimide polymer: aqueous medium = 30: 70 to 60:40 (mass ratio).

The top coat used in the present invention can be used as a one-part cross-linkable paint because the maleimide group in the polymer participates in the curing reaction. Further, when the maleimide polymer has both hydroxyl groups, it can be used as a two-pack paint using a polyisocyanate as a curing agent, and the maleimide polymer can be used as a hydrolyzable silyl group such as an alkoxysilyl group. Can also be used as a two-pack paint in which a hydrolysis catalyst is blended immediately before painting.

The topcoat paint used in the present invention can be used in any form such as a clear paint, a colored paint colored with a pigment, and a color clear paint containing a small amount of a pigment. In coating, pigments, dispersants, thickeners and solvents are added,
It can be prepared by a usual method. If necessary, additives such as an ultraviolet absorber, a light stabilizer, a leveling agent, an anti-separation agent, a surface conditioner, a silane coupling agent and a thickener may be added. In order to further improve the stain resistance, an alkyl silicate or an alkyl silicate oligomer can be added.

In the case of colored paints, pigments that can be used include, for example, inorganic pigments such as titanium oxide, red iron oxide, calcined pigment, and pearl pigment; organic pigments such as phthalocyanine blue, quinacridone red, isoindolinone, and carbon black; , Volume pigments such as barium sulfate, and metallic pigments such as aluminum flake and stainless flake. Further, as a matting agent, polyethylene wax, polypropylene wax and silica-based matting agent can be added. As an ultraviolet absorber,
Organic ultraviolet absorbers such as benzophenone-based compounds, benzotriazole-based compounds, and oxalic anilide-based compounds, and inorganic ultraviolet absorbers such as ultrafine titanium oxide and cerium oxide can be used. As the silane coupling agent, γ-glycidoxypropyltrimethoxysilane, β
-(3,4 Epoxycyclohexyl) ethyltrimethoxysilane, [gamma] -isocyanatopropyltriethoxysilane, [gamma] -mercaptopropyltrimethoxysilane, and those which can be used as ordinary paint additives can be used.

When the top coat used in the present invention is used as a one-pack type paint which does not use an isocyanate compound, or when the maleimide polymer does not have a hydrolyzable silyl group, ie, the part involved in the curing reaction is a maleimide group. In the case of using only as a coloring paint to which a pigment is added, the curing speed of the maleimide group becomes slow. In that case, it is preferable to use a curing catalyst for the purpose of increasing the curing speed. Examples of the curing catalyst that can be used include a photosensitizer, a photopolymerization initiator, a metal dryer, and a metal chelate.

Specific examples of the photopolymerization initiator and photosensitizer include hydrocarbon sensitizers such as naphthalene and phenanthrene; nitrobenzene derivatives such as nitrobenzene, p-dinitrobenzene and p-nitroaniline; acetophenone and propio Phenone, benzophenone, [4- (methylphenylthio) phenyl] phenylmethane, benzaldehyde, 3-methylacetophenone, 4-methylacetophenone, 3-pentylacetophenone, 4-methoxyacetophenone, 3-bromoacetophenone, 4-allylacetophenone, p-diacetylbenzene, 3-methoxybenzophenone, 4-methylbenzophenone, 4-
Chlorobenzophenone, 4,4′-dimethoxybenzophenone, 1,1′-dimethoxy-1-phenylbenzophenone, 4-chloro-4′-benzylbenzophenone, p, p′-diethylaminobenzophenone, p,
p'-diethylaminobenzophenone, diethoxyacetophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, bis (4-dimethylaminophenyl) ketone, bis (4-diethylaminophenyl) ketone, 2-benzyl- 2-dimethylamino-1- (4-
Benzophenone and acetophenone derivatives such as morpholino ether) butanone-1; benzoin ethers such as isobutyl benzoin ether, isopropyl benzoin ether, benzoin ethyl ether and benzoin methyl ether; 2,2-dimethoxy-1,2-diphenylethane-1 Benzyl ketals such as -one, 1-hydroxycyclohexyl phenyl ketone, and benzyl; 3
-Chloroxanthone, 3,9-dichloroxanthone, 3
-Xanthones such as -chloro-8-nonylxanthone, 2-chlorothioxanthone and 2,4-diethylthioxanthone; bis (2,6-dimethoxybenzoyl) -2,
Acylphosphine oxides such as 4,4-trimethylpentylphosphine oxide and bis (2,4,6-trimethylbenzoyl) phenylphosphine oxide;
Examples include benzoyl, benzoin methyl ether, benzoin butyl ether, benzyl methoxy ketal, and ethyl anthraquinone. Among these, benzphenone derivatives, acetophenone derivatives, xanthones, and acylphosphine oxides are preferred, and xanthones are most preferred. Photopolymerization initiator or photosensitizer,
They may be used alone or in combination of two or more. The amount of the photosensitizer or the photoinitiator is preferably 0.1 to 10 parts by mass per 100 parts by mass of the maleimide polymer,
More preferably, it is 0.5 to 5 parts by mass. When the amount is less than 0.1 part by mass, the curing speed is hardly improved.
If the amount exceeds 0 parts by mass, the discoloration of the coating film becomes large.

As the metal dryer, a metal dryer which is generally used to promote oxidative polymerization of a paint containing an unsaturated fatty acid moiety such as an alkyd paint is preferable. Metals in metal dryers include lead, cobalt, copper,
Examples include tin, zinc, iron, manganese, bismuth, and zirconium. Specifically, lead naphthenate, lead octenoate, cobalt naphthenate, cobalt octenoate, zinc naphthenate, zinc octate, manganese naphthenate, manganese octenoate, copper naphthenate, copper octenoate, iron naphthenate, octene Iron oxide, calcium naphthenate, zirconium naphthenate, zirconium octenoate, bismuth octenoate and the like. Specific examples of the metal chelate compound include aluminum tris (acetylacetonate), titanium tetrakis (acetylacetonate), titanium bis (butoxy) bis (acetylacetonate), titanium bis (isopropoxy) bis (acetylacetonate), Cobalt bis (acetylacetonate), cobalt tris (acetylacetonate), copper bis (acetylacetonate), iron tris (acetylacetonate), manganese bis (acetylacetonate) zirconium tetrakis (acetylacetonate), zirconium bis ( Isopropoxy) bis (acetylacetonate) and the like. Metal dryer,
The metal chelates can be used alone or in combination of two or more. The amount of the metal dryer and the metal chelate is preferably 0.01 to 10 parts by mass, more preferably 0.1 to 10 parts by mass, per 100 parts by mass of the maleimide polymer.
It is 0.5 to 5 parts by mass. When the amount is less than 0.01 part by mass, the curing speed is not so improved, and when the amount is more than 10 parts by mass, the discoloration of the coating film becomes large. As the curing catalyst used in the colored paint, a photoinitiator and a photosensitizer are preferable from the viewpoint of the storage stability of the paint.

[0043] 3. Coating method The present invention is a method for coating a topcoat paint on an article or a structure directly or via a primer, wherein the composition containing the maleimide polymer is used as the topcoat paint. As a method of applying the topcoat, a brush, a spray, a roller, or the like can be used. The viscosity of the top coat may be appropriately set according to the purpose of use. When applying with a brush or a roller, it is preferably 60 seconds or less with an Iwata cup, and when applying with a spray, 20 seconds or less with an Iwata cup. Is preferred.

In the present invention, the base material constituting the article or structure to be coated includes metals such as iron, steel plate, stainless steel, aluminum and zinc steel plate; ABS resin, FRP
Resin, PC resin, hard PVC resin, bakelite resin,
Plastics such as epoxy resin, acrylic resin and polyurethane resin; and cement, concrete skeleton, mortar, cement / asbestos board, wood cement board, A
In addition to alkaline inorganic cured products such as LC, calcium silicate plate and fiber reinforced cement plate, tiles, wood, paper and the like can be mentioned.

In the coating method of the present invention, a top coat may be applied directly to the base material. However, after a primer is applied to the base material in advance, the top coat is applied to the surface of the primer coating film. Is also good. As the primer, a single layer or a plurality of primers may be applied repeatedly according to required performance.

As the primer, it is preferable to use a paint prepared from a resin dissolved or dispersed in a petroleum solvent, that is, a hydrocarbon solvent. Examples of the weak solvent type primer include a weak solvent soluble acrylic urethane paint, a weak solvent dispersed acrylic urethane paint, a weak solvent soluble epoxy paint, a weak solvent dispersed epoxy paint, a weak solvent soluble epoxy paint, and a weak solvent soluble epoxy paint. Solvent-dispersed epoxy paint, weak solvent-soluble epoxy paint using ketimine hardener, weak solvent-dispersed epoxy paint using ketimine hardener, weak solvent-soluble alkyd paint, weak solvent-dispersed urethane paint, etc. Is mentioned. When the top coat is an aqueous dispersion of a maleimide polymer, it is preferable to use an aqueous primer as the primer. Specific examples include an acrylic emulsion paint, a urethane emulsion paint, an acrylic silicone emulsion paint, and an epoxy emulsion paint. When the substrate is an inorganic cured product such as concrete or cement, a silane-based water-absorbing agent can be used as a primer. The silane-based water-absorbing agent is a paint mainly containing an alkoxy group-containing silane compound or a partially hydrolyzed condensate thereof. The paint penetrates into the pores of the substrate to form a water absorption preventing layer by a condensation reaction of an alkoxy group-containing silane monomer and a condensation reaction of the monomer with a hydrophilic group in the substrate. is there. Examples of the silane-based water absorption inhibitor include Aron Water Shut (trade name, manufactured by Toagosei Co., Ltd.) and Aquaproof (trade name, manufactured by Toagosei Co., Ltd.).

When a primer is used, the coating interval with the top coat is preferably half a day to one week. It is preferable that the thickness of each of the top coat and the primer is 100 μm or less. In any case, the application of the primer and the top coat may be performed indoors or outdoors. After application of the topcoat paint, it is preferable to dry outdoors in order to promote the curing reaction of the maleimide group. However, a method of evaporating the solvent indoors and then moving outdoors to dry is also possible. Drying outdoors can be used in the shade or on the northern surface because the curing reaction proceeds with reflected light, but it is more preferable to perform it in sunlight.
Topcoat The curing of the topcoat is completed in a few days if it is a clear paint. In the case of a colored paint, the curing reaction proceeds in the depth direction from the surface, so that stain resistance is developed from an early stage.

In the case of a two-pack type paint using a maleimide polymer having a hydroxyl group and a polyisocyanate compound as a curing agent as a top coat, the curing reaction between the hydroxyl group and the isocyanate proceeds when dried indoors, and then the resin is moved outdoors. Then, the curing reaction of the maleimide group proceeds from the surface. When dried outdoors immediately after coating, the curing reaction of the maleimide group and the curing reaction of the hydroxyl group and the isocyanate proceed simultaneously. In the case of a clear coating, since the curing reaction of the maleimide group is faster than the reaction between the hydroxyl group and the isocyanate, it is preferable to dry the coating material outdoors immediately after coating.

When the top coating is a maleimide polymer having a hydrolyzable silyl group, a two-pack coating in which a curing catalyst is added immediately before coating is preferred. In this case, if it is dried indoors after the top coat is applied, only the hydrolysis-condensation reaction of the hydrolyzable silyl group proceeds. Thereafter, when the resin is moved outdoors, the curing reaction of the maleimide group proceeds from the surface. When dried outdoors immediately after coating, the curing reaction of the maleimide group and the hydrolysis-condensation reaction of the hydrolyzable silyl group proceed simultaneously. In general, in the case of a weak solvent-soluble resin, since it has a long-chain alkyl group, it is difficult for moisture to penetrate into the coating film, the rate of the hydrolysis condensation reaction is slow, and it takes time for the stain resistance to develop. However, when a maleimide group curing reaction is involved, crosslinking on the surface proceeds quickly, and therefore it is preferable to dry it outdoors immediately after coating.

The coating film obtained by the above coating method has excellent adhesion to the old coating film, and the weather resistance of the top coating material is excellent, so that the interval between subsequent coating changes is long. Therefore, the cost and man-hour required for repainting can be significantly reduced.

[0051]

The present invention will be described more specifically below with reference to examples and comparative examples. In the following, "%" means% by mass. Abbreviations below have the following meanings. THPI: imide acrylate represented by the following formula (3)

[0052]

(Equation 4)

DMMI: imide acrylate represented by the following formula (4)

[0054]

(Equation 5)

CHA: cyclohexyl acrylate BA: butyl acrylate BMA: butyl methacrylate IBMA: isobutyl methacrylate EHMA: 2-ethylhexyl methacrylate HEMA: 2-hydroxyethyl methacrylate MMA: methyl methacrylate SMA: stearyl methacrylate SA: stearyl acrylate ST: styrene AA: acrylic Acid MAA: methacrylic acid MTRIMS: γ-methacryloxypropyltrimethoxysilane

Preparation of a colored overcoat having only a maleimide group at the cured site. W-1 A copolymer (T-1) produced using a monomer having the type and ratio shown in Table 1 below as a maleimide polymer , Tg:
A 34% solution of HAWS at 34 ° C., Mn: 23000) was used. Using the solution of T1 and each component shown in Table 2, using a high-speed stirrer, each component was stirred and mixed according to a conventional method to prepare a white dispersion (W-1).

-W-2 As a maleimide polymer, a copolymer (T-2, Tg:
A white dispersion (W-2) was prepared in the same manner as for W-1, using a 50% LOWS solution (34 ° C., Mn: 22000) and the components shown in Table 3.

W-3 As a maleimide group-containing copolymer, a non-aqueous dispersion of a copolymer obtained using the monomers shown in Table 2 below (T-3,
A solvent (LAWS, solid content: 50%) was used, and the components shown in Table 3 were used to prepare a white dispersion (W-3) in the same manner as in W-1.

Preparation of paint for comparison W-4 A copolymer (T) obtained by using monomers having the types and ratios shown in Table 1 below as a polymer having no maleimide group
-4, Tg: 31 ° C., Mn: 23000)
Using a 0% solution and the components shown in Table 3, a top coat (W-4) was prepared in the same manner as in W-1.

W-5 Non-aqueous dispersion of a copolymer obtained using monomers shown in Table 2 below as a polymer having no maleimide group (T-
5. A solvent (LAWS, solid content 50%) was used, and the components shown in Table 3 were used to prepare a white dispersion (W-5) in the same manner as in W-1.

[0061]

[Table 1]

[0062]

[Table 2]

[0063]

[Table 3]

Preparation of a clear top coat having only a maleimide group as a curing site. C-1 A monomer having the type and ratio shown in Table 4 below as a maleimide polymer, and a reactive emulsifier Aqualon HS10 [ Daiichi Kogyo Seiyaku Co., Ltd.], and an aqueous dispersion (solid content: 45%) of a copolymer (T-6) produced by emulsion polymerization was used. The components shown in Table 5 were stirred and mixed to prepare a clear paint (C-1).

C-2 As a polymer having no maleimide group, a monomer having the kind and ratio shown in Table 4 below, and as an emulsifier, a reactive emulsifier Aqualon HS10 [Daiichi Kogyo Seiyaku Co., Ltd.] An aqueous dispersion (solid content: 45%) of a copolymer (T-7) produced by emulsion polymerization was used. The components shown in Table 5 were stirred and mixed to prepare a white dispersion (C-2).

[0066]

[Table 4]

[0067]

[Table 5]

Preparation of Colored Topcoat Coating Using Maleimide Group and Hydroxyl Group Copolymer (T-8) was prepared using monomers of the type and ratio shown in Table 6 below as a maleimide polymer. , Tg:
33 ° C., OHV: 52 mg KOH / g · resin, Mn: 1
6000) was used. A solution of T-8 and each component shown in Table 8 were prepared in the same manner as in W-1 to prepare a main component (W-6) of a white topcoat paint. W-
To 100 g of No. 6, 15.4 g of a 50% HAWS solution of duranate TSS100 (manufactured by Asahi Kasei Corporation) as a polyisocyanate-based curing agent was added to prepare a test paint.

W-7 As a maleimide group-containing copolymer, a non-aqueous dispersion of a copolymer obtained using the monomers shown in Table 7 below (T-9,
The solvent used was LAWS, and the solid content was 50%. Using the components shown in Table 8, a white dispersion (W-7) was prepared in the same manner as in W-1. Duranate TSS, a polyisocyanate-based curing agent, for 100 g of W-7
100% HAWS 50% solution (manufactured by Asahi Kasei Corporation)
7.4 g was added to obtain a test paint.

Preparation of Comparative Coating Material Copolymer (T-8) obtained by using monomers having the types and ratios shown in Table 6 below as polymers having no W-8 maleimide group
−10, Tg: 32 ° C., OHV: 52 mgKOH / g
Using a 50% HAWS solution of a resin (Mn: 17000) and using the components shown in Table 8, a main agent (W-8) of a white overcoat was prepared in the same manner as in W-1. W-
To 100 g of No. 8, 15.4 g of a 50% HAWS solution of duranate TSS100 (manufactured by Asahi Kasei Corporation), which is a polyisocyanate-based curing agent, was added to prepare a test paint.

[0071]

[Table 6]

[0072]

[Table 7]

[0073]

[Table 8]

Preparation of Colored Topcoat Using Maleimide Group and Alkoxysilyl Group in Combination Copolymer (T) prepared using W-9 maleimide polymer using monomers of the types and ratios shown in Table 9 below -11, T
g: 32 ° C., Mn: 15000). A solution of T-11 and each component shown in Table 10 were
In the same manner as W-1, the base material (W
-9) was prepared. For 100 g of W-9, dibutyltin diacetate (toluene 0.2
% Solution) was added to obtain a test paint.

W-10 Copolymers (T-12, T-12) prepared by using monomers having the types and ratios shown in Table 9 below as maleimide polymers
g: 33 ° C., Mn: 16000). A solution of T-12 and each component shown in Table 10 were
In the same manner as W-1, the base material (W
-10) was prepared. To 100 g of W-10, 14.0 g of dibutyltin diacetate (a 0.2% solution in toluene) was added as a curing catalyst to prepare a test paint.

Preparation of paint for comparison: W-11 As a polymer having no maleimide group, a copolymer (T) obtained using monomers of the types and ratios shown in Table 9 below
-13, Tg: 32 ° C., Mn: 17000)
Using a 50% solution, using the components shown in Table 10, W-
In the same manner as in Example 1, the base material (W-1)
1) was prepared. For 100 g of W-11, dibutyltin diacetate (toluene 0.2
% Solution) was added to obtain a test paint.

W-12 As a polymer having no maleimide group, a copolymer (T) obtained by using monomers of the types and ratios shown in Table 9 below
−14, Tg: 34 ° C., Mn: 15000) using a 50% xylene solution, using the components shown in Table 10,
In the same manner as in Example 1, the base material (W-1)
2) was prepared. For 100 g of W-12, dibutyltin diacetate (toluene 0.2
% Solution) was added to obtain a test paint.

[0078]

[Table 9]

[0079]

[Table 10]

Coating Example Coating Example 1 A cold-rolled steel plate (SPCC) was degreased with toluene, and Esco NB Mild, a weak solvent type epoxy primer manufactured by Kansai Paint Co., Ltd., was applied indoors by spraying. After standing at room temperature for one day, the top coating material W-1 was roller-coated indoors (dry film thickness: about 30 μm). One hour after coating, the coated plate was moved outdoors and dried for 2 weeks.

Coating Examples 2 and 3 Using W-2 and W-3 as top coats,
Coating was carried out in the same manner as described above.

Comparative coating examples 1 and 2 W-4 and W-5 were used as the topcoat paints.
Coating was carried out in the same manner as described above.

Coating Example 4 A cold-rolled steel plate (SPCC) was degreased with toluene, and Eton 2100HB primer [Epoxy primer manufactured by Kawakami Paint Co., Ltd.] was spray-coated indoors (dry film thickness: about 4).
0μ). After being left at room temperature for one day, W-6 was applied as a top-coat paint indoors with a roller (dry film thickness: about 30 μm). Painting 1
After an hour, the painted board was moved to the outdoor south side and dried for 2 weeks.

Coating Example 5 Using W-7 as a top coat, coating was performed in the same manner as in Coating Example 4.

Comparative Coating Example 3 Coating was performed in the same manner as in Coating Example 4, except that W-8 was used as the top coat.

Test Examples 1 to 8 The following tests were performed on the coated plates of the coating examples 1 to 5 and the comparative coating examples 1 to 3. Table 11 shows the results.

Adhesion The coated plate is immersed in tap water at room temperature for 24 hours. take out,
After air drying for 2 hours, a cross-cut peeling test is performed according to JIS K5400, and the residual ratio is measured.

-Stain resistance In the industrial zone in the southern part of Nagoya City, a test piece was placed outdoors on the south side 6
It was fixed at an angle of 0 degrees and exposed for 5 months. The change (ΔL) in the L value before and after the test was measured. The larger the -ΔL value is, the more dirty it is.

Weather resistance The coated plate was measured for glossiness 60 degrees before and after the sunshine weather meter was tested for 1000 hours, and the retention (%) was calculated.

[0090]

[Table 11]

Coating Example 6 An aqueous acrylic paint (white) was spray-painted indoors on an asbestos slate plate. One day after the application, the top coat C-1 was applied in a room by painting (dry film thickness: 20 µm). Three hours after the coating, it was moved to the south side outdoors and dried for one week.

Comparative Coating Example 4 A coated plate was prepared in the same manner as in Coating Example 6, except that C-2 was used as the top coat.

The coated sheets prepared in Coating Example 6 and Comparative Coating Example 4 were tested for adhesion, stain resistance and weather resistance in the same manner as described above. In the adhesion test,
The grid was 25 squares. Table 12 shows the obtained results.

[0094]

[Table 12]

Coating Example 7 An aluminum plate was coated with a top coat W-9 indoors using a roller (dry film thickness 30 μm). Two hours after the application, it was dried outdoors (shade).

Coating Example 8 A coated plate was produced in the same manner as in Coating Example 7, except that W-10 was used as the top coat.

Comparative Coating Examples 5 and 6 W-11 and W-12 were used as overcoat paints, and coated plates were produced in the same manner as in Coating Example 7.

Test Examples 11 to 14 Using the coated plates of Coating Examples 7 and 8 and Comparative Coating Examples 5 and 6,
The following tests were performed. The results are shown in Table 13.・ Gloss value The glossiness of the coating film after 2 weeks of drying was determined according to JIS K5400
It measured according to. Curing time One drop of xylene was applied to the coating film that was being dried outdoors, and the number of days from the coating required for eliminating the insoluble portion when rubbing with a finger was determined. -Adhesion The coated plate is immersed in tap water at room temperature for 24 hours. take out,
After air drying for 2 hours, a cross-cut peeling test is performed according to JIS K5400, and the residual ratio is measured. The square is 1
It was performed on 00 cells. -Weather resistance Gloss 60 degrees before and after the coated plate was tested for 1000 hours with a sunshine weather meter was measured, and the retention (%) was calculated.

[0099]

[Table 13]

[0100]

According to the coating method of the present invention, the adhesion to the substrate and the primer is excellent, and the coating film obtained is excellent in weather resistance and stain resistance.

Continued on the front page F term (reference) 4D075 AE03 CA13 CA32 CA34 CB06 DA06 DA23 DB02 DB04 DB05 DB07 DB12 DB18 DB21 DB35 DB37 DB38 DB43 DB46 DB47 DB48 DB50 DB61 DC01 DC05 EA06 EA07 EA13 EA23 EA41 EA43 EB13 EB19 EB17 EB17 EB20 EB37 EB38 EB43 EB45 4J038 CB001 CC001 CD001 CE001 CF001 CG011 CG061 CG141 CG161 CG171 CH011 CH071 CH081 CH111 CH201 CH231 CJ131 CL001 GA08 HA156 JA02 KA06 NA03 NA05 PA12 PB05 PB06 PB07 PC01 PC02 PC03 PC06

Claims (6)

[Claims] 1. A method for applying a top coat to an article or a structure directly or via a primer, wherein a composition containing a polymer having a maleimide group is used as the top coat. 2. The coating method according to claim 1, wherein the maleimide group of the polymer is represented by the following formula (1). Embedded image [However, in the formula (1), R ¹ and R ² are each independently a hydrogen atom or an alkyl group, one of them is a hydrogen atom and the other is an alkyl group, or a group which forms a carbon ring by bonding each other. It is. ] 3. The coating method according to claim 1, wherein the primer is a composition containing water or an aliphatic hydrocarbon-based solvent as a main component and a solvent. 4. The coating method according to claim 1, wherein the top coat is a composition containing water or an aliphatic hydrocarbon-based solvent as a main component and a solvent. 5. The method according to claim 1, wherein the top coating is a one-pack type coating.
The coating method according to claim 4. 6. A coating composition according to claim 1, wherein the top coating composition is a clear coating composition.
The coating method according to claim 5.