JPH0959558A - Composition for coating material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a coating composition comprising a hydroxyl group- containing fluorine-containing copolymer, a cross-linking agent, an alkoxysilane, an ultraviolet light absorber and/or a photostabilizer and an organic solvent, excellent in adhesion to a metal base, especially to a stainless steel base. SOLUTION: This composition for a coating material comprises (A) a hydroxyl group-containing fluorine-containing copolymer, (B) a cross-linking agent reactive with a hydroxyl group (e.g. polyisocyanate), (C) an alkoxysilane (preferably an alkyltrialkoxysilane containing a 1-10C alkyl directly bonded to a silicon atom), (D) an ultraviolet light absorber (e.g. 2-hydroxy-4-methoxybenzophenone) and/or a photostabilizer [e.g. bis(2,2,6,6-tetramethyl-4-pyridyl)sebacate] and (E) an organic solvent. The component A comprises preferably 30-60mol% of a fluoroolefin unit, 3-30mol% of a hydroxyl group-containing vinyl monomer and 10-67mol%, of another vinyl monomer unit. The fluoroolefin is preferably chlorotrifluoroethylene.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fluororesin coating composition having good adhesion to a metal substrate (especially stainless steel substrate).

[0002]

2. Description of the Related Art Conventionally, when a fluorine paint is applied to a metal base, the colored paint is usually applied via an epoxy primer. However, when a clear paint or a color clear paint is applied to maintain the metallic appearance, an appropriate primer cannot be used, and therefore the metal must be applied directly. Adhesion of conventional fluororesins to metals, particularly to stainless steel, was not sufficient except when a metal surface was subjected to chemical conversion treatment. Specifically, the water-resistant adhesion is particularly poor, and it was difficult to apply it to materials used in hot and humid places. To solve this problem,
Japanese Unexamined Patent Publication (Kokai) No. 62-174387 proposes a method of applying a small amount of a silane coupling agent to a metal surface before coating with a fluorine coating material. However, the method proposed in the above publication has a problem that it is not easy to uniformly apply a minute amount of the silane coupling agent, and it is difficult to adopt the method in the field construction.

[0003]

DISCLOSURE OF THE INVENTION In the present invention, a composition for a fluororesin coating capable of forming a clear coating film or a color clear coating film having good water-resistant adhesion to a metal whose surface is not subjected to chemical conversion treatment. Aimed to provide.

[0004]

Means for Solving the Problems The present inventors have made intensive studies to solve the above problems, and as a result, have completed the present invention. That is, the present invention provides (a) a fluorine-containing copolymer having a hydroxyl group, (b) a crosslinking agent reactive with a hydroxyl group, (c)
A coating composition comprising an alkoxysilane, (d) an ultraviolet absorber and / or a light stabilizer, and (e) an organic solvent. Hereinafter, the present invention will be described in more detail.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION As the fluorine-containing copolymer (a) having a hydroxyl group in the present invention, a fluoroolefin,
Polymers containing a hydroxyl group-containing vinyl monomer and other vinyl monomers as constituents are preferred. Furthermore, the preferred ratio of the fluoroolefin unit, the hydroxyl group-containing vinyl monomer unit and the other vinyl monomer unit in the fluorocopolymer is based on the total amount of each monomer unit,
Fluoroolefin unit: 30 to 60 mol%, hydroxyl group-containing vinyl monomer unit: 3 to 30 mol%, and other vinyl monomer unit: 10 to 67 mol%.

Specific examples of the fluoroolefin include monofluoroethylene, difluoroethylene, trifluoroethylene, tetrafluoroethylene, chlorotrifluoroethylene, hexafluoropropylene and the like. Chlorotrifluoroethylene is copolymerizable and easy to handle. It is preferable in terms. If the proportion of the fluoroolefin in the fluorinated copolymer is less than 30 mol%, the weather resistance will decrease, and if it exceeds 60 mol%, the solubility in the solvent will decrease. A more preferable amount is 40 to 60 mol%.

As the hydroxyl group-containing vinyl monomer, crotonic acid esters such as 2-hydroxyethyl crotonate, 4-hydroxybutyl crotonate and 2-hydroxypropyl crotonate; 2-hydroxyethyl (meth)
(Meth) acrylic acid esters such as acrylate and 4-hydroxybutyl (meth) acrylate; vinyl ethers such as 2-hydroxyethyl vinyl ether and 4-hydroxybutyl vinyl ether; 2-hydroxyethyl allyl ether, 4-hydroxyethyl allyl ether, Allyl ethers such as diethylene glycol monoallyl ether; and (meth) acrylamides such as 2-hydroxyethyl (meth) acrylamide and 4-hydroxyethyl (meth) acrylamide. These hydroxyl group-containing vinyl monomers can be used alone or in combination of two or more. The proportion of the hydroxyl group-containing vinyl monomer in the fluorine-containing copolymer is 3 to 30 mol% as described above.
Is preferred. If the proportion is less than 3 mol%, the reaction points with the curing agent will be insufficient, resulting in insufficient coating film strength.
If it exceeds 0 mol%, the weather resistance and water resistance will deteriorate.

As the other vinyl monomer, carboxylic acid vinyl ester, vinyl ether, norbornadiene compound and unsaturated carboxylic acid or its anhydride can be used. Examples of vinyl carboxylate ethers include vinyl acetate, vinyl propionate, vinyl caproate, vinyl pivalate, Veova-9, Veova-10 (manufactured by Shell Chemical Co.) and the like, aliphatic vinyl carboxylates, vinyl cyclohexanecarboxylate, 4- Examples thereof include vinyl cycloalkanecarboxylates such as t-butylcyclohexanecarboxylate, vinyl benzoate, and aromatic vinylcarboxylates such as pt-butylbenzoic acid. Examples of vinyl ethers include alkyl vinyl ethers such as ethyl vinyl ether and butyl vinyl ether, and cycloalkyl vinyl ethers such as cyclohexyl vinyl ether.
As the unsaturated carboxylic acid, acrylic acid, crotonic acid,
Maleic acid, itaconic acid, vinyl acetic acid and the like can be mentioned.
The amount of unsaturated carboxylic acid in the fluorine-containing copolymer is preferably 5 mol% or less in terms of water resistance.

The number average molecular weight of the fluorine-containing copolymer is 2,000 to 100,000 in terms of polystyrene by gel permeation chromatography from the viewpoint of the strength of the coating film formed and the handleability of the coating material. desirable. The Tg of the fluorinated copolymer is
In order for the formed coating film to exhibit blocking resistance, 1
It is preferably 0 ° C or higher.

Specific examples of the (b) hydroxyl group-reactive crosslinking agent in the present invention include hexamethylene diisocyanate, isophorone diisocyanate and their dimers, trimers, and polyisocyanates such as blocked isocyanate; methylated melamine. , Butylated melamine,
Examples thereof include urea resins and aminoblasts such as benzoguanamine. The amount of the cross-linking agent used is, in the case of the isocyanate-based and block isocyanate-based cross-linking agents, the ratio of the hydroxyl group and the isocyanate in the fluorine-containing copolymer to NCO / O.
H = 1 / 1.2 to 1 / 0.7 is preferable. In the case of an aminoblast resin-based cross-linking agent, it is preferable to mix it with a fluorine-containing copolymer / aminoblast resin = 4/1 to 10/1. Furthermore, when using these crosslinking agents, a curing accelerator such as dibutyltin dilaurate or p-toluenesulfonic acid may be used in combination. If a compound that does not react with hydroxyl groups at room temperature, such as aminoblast resin or blocked isocyanate, is used as the cross-linking agent, it can be mixed at the time of paint production, but if a polyisocyanate that reacts with hydroxyl groups at room temperature is used, just before coating. It is preferable to use it as a mixture with other components.

The alkoxysilane in the present invention is a compound in which a hydrolyzable alkoxy group is bonded to a silicon atom, and the number of hydrolyzable alkoxy groups in one molecule is 2 to 2.
Three is preferable, and in that case, as the other substituent bonded to the tetravalent silicon atom, an alkyl group or an alkyl group in which one hydrogen atom is substituted with a functional group is preferable. As the hydrolyzable alkoxy group in the alkoxysilane, a methoxy group and an ethoxy group are preferable, and a methoxy group is suitable particularly when the coating is cured at room temperature to 150 ° C. Specific examples of the alkoxysilane that can be used in the present invention are shown below. ○ Alkyltrialkoxysilane Methyltrimethoxysilane, methyltriethoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, propyltrimethoxysilane, propyltriethoxysilane, butyltrimethoxysilane, butyltriethoxysilane, isobutyltrimethoxysilane, Isobutyltriethoxysilane, amyltrimethoxysilane,
Amyltriethoxysilane, isoamyltrimethoxysilane, isoamyltriethoxysilane, hexyltrimethoxysilane, hexyltriethoxysilane, octyltrimethoxysilane, octyltriethoxysilane, nonyltrimethoxysilane, nonyltriethoxysilane,
Examples include decyltrimethoxysilane and decyltriethoxysilane.

Alkoxysilane having an alkyl group having a functional group bonded to a silicon atom (which is generally called a silane coupling agent, hereinafter referred to as a silane coupling agent) 3- (methoxy) propyl Trimethoxysilane, 3-
(Methoxy) propyltriethoxysilane, ethyl-3
-(Triethoxysilyl) propionate, γ-glycidoxypropyltrimethoxysilane, γ-aminopropyltriethoxysilane, N-β-aminoethylaminopropyltrimethoxysilane, vinyltriethoxysilane, γ-methacryloxypropyltriethoxy Silane,
γ-mercaptopropyltrimethoxysilane and the like can be mentioned. When a silane coupling agent is used, the resulting coating may be colored during long-term storage, and in the present invention, alkyltrialkoxysilane is preferable. A more preferable alkoxysilane is an alkyltrialkoxysilane in which an alkyl group having 1 to 10 carbon atoms is directly bonded to a silicon atom in terms of excellent compatibility with the fluorocopolymer. The preferred amount of alkoxysilane used is
It is 0.02 to 3 parts by weight per 100 parts by weight of the fluorinated copolymer. If the amount of the alkoxysilane used is less than 0.02 part by weight, the effect of water-resistant adhesion is difficult to be exhibited, while if it exceeds 3 parts by weight, the hardness decreases, which is not preferable.

The (d) ultraviolet absorber and / or light stabilizer in the present invention is used for the purpose of suppressing the decomposition of the fluorine-containing copolymer and preventing the formation of rust under the coating film. As the ultraviolet absorber, benzophenone compounds such as 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-ethoxybenzophenone, 2-hydroxy-4-butoxybenzophenone and 2,4-dihydroxybenzophenone; 2- (2 ' -Hydroxyphenyl) benzotriazole, 2- (2'-hydroxy-
5'-methylphenyl) benzotriazole, 2-
(2'-Hydroxy-5'-methylphenyl) -5-carboxylic acid butylbenzotriazole, 2- (2'-hydroxy-5'-methylphenyl) -5,6-dichlorobenzotriazole, 2- (2'- Hydroxy-3 ',
5'-di-t-butylphenyl) benzotriazole and 2- (2'-hydroxy-3'-methyl-5'-t-
A benzotriazole compound such as butylphenyl) -5-chlorobenzotriazole; N- (2-ethoxyphenyl) -N '-(4-isododecylphenyl) ethanediamide, N- (2-ethoxyphenyl) -N'-( 2-
Oxalic acid anilide compounds such as ethylphenyl) ethanediamide and N (2-ethoxy-5-t-butylphenyl-N '-(2-ethylphenyl) ethanediamide; 2-
(2-Hydroxy-4- (2-hydroxy-3-tridecanooxypropyl) phenyl) -4,6-bis (2,4-
Examples thereof include benzotriazine-based compounds such as dimethylphenyl) -1,3,5-triazine. The preferable addition amount of the ultraviolet absorber is 0.1 to 10% by weight based on the total amount of the fluorine-containing copolymer and the crosslinking agent.

In the present invention, a light stabilizer may be used, and specific examples of the light stabilizer include 2- (3,5-
Di-tert-butyl-4-hydroxybenzyl) -2-n-
Butyl malonate bis (1,2,2,6,6-pentamethyl-4-piperidyl) sebacate, bis (2,2,6,
6-tetramethyl-4-piperidyl) sebacate, bis (1,2,2,6,6-pentamethyl-4-piperidyl) sebacate, 8-acetyl-3-dodecyl-7,
7,9,9-Tetramethyl-1,3,8-triazaspiro (4,5) decane-2,4-dione and bis (N-
Examples thereof include amine compounds such as octoxy-2,2,6,6-tetramethyl-4-piperidyl) sebacate.
The amount of the light stabilizer used is preferably 5 wt% or less based on the total amount of the fluorocopolymer and the crosslinking agent.

As the organic solvent for dissolving the fluorine-containing copolymer, those having a boiling point of 60 ° C. or higher are preferable, and specifically, aromatic compounds such as toluene, xylene and solvesso; esters such as ethyl acetate and butyl acetate; Methyl ethyl ketone,
Ketones such as methyl isobutyl ketone, cyclohexanone, methyl amyl ketone and ethyl amyl ketone; alcohols such as n-butanol and i-propanol; cellosolves such as methyl cellosolve, n-butyl cellosolve and n-butyl cellosolve acetate, propylene bricol monomethyl Examples thereof include propylene glycol-based solvents such as ether, propylene bricol monobutyl ether, and propylene glycol monomethyl ether acetate.

The paint composition of the present invention is mainly intended for clear paints, but can also be applied to color clear paints containing a small amount of coloring content. As the coloring pigment used for obtaining the color paint, those commonly used in paints can be used, for example, inorganic pigments such as titanium oxide, red iron oxide, yellow iron oxide, calcined pigment, pearl pigment, etc .; aluminum flakes, stainless flakes. And the like; organic pigments such as phthalocyanine blue, quinacridone red, isoindolinone, carbon black and the like. Further, as the matting agent, polyethylene wax, polypropylene wax, or silica-based matting agent can be added.

When obtaining the paint itself from the paint composition,
In addition to the above pigments, additives such as a leveling agent, a slip agent, an anti-sagging agent, an antifoaming agent, an anti-separation agent, an antioxidant and a heat stabilizer may be added. A pigment oxidizer may be added when the pigment is dispersed in the color clear paint. From the viewpoint of workability, the ratio of the coating film forming component (fluorine-containing polymer + ultraviolet absorber + light stabilizer + crosslinking agent) in the prepared coating composition is 20.
˜70 wt% is preferred. The fluororesin coating thus obtained can be applied by spray coating, roll coater, brush coating or the like. The paint obtained from the coating composition is most suitable for application to metal, but it may be applied to substrates other than metal, for example, plastic, wood, paper, cement-based substrates, It may also be used as a clear top coat on top of other paints.

[0018]

Example 1 The present invention will be described more specifically below with reference to Examples and Comparative Examples. Fluorine-containing copolymer composed of chlorotrifluoroethylene / vinyl propionate / vinyl versatic acid (Veova 9) / 2-hydroxyethyl crotonic acid, and the ratio of each is 49/23/18/10 (mol%) ( Mn = 13000, OH
V = 53, Tg = 28 ° C.) xylene solution (solid content 60)
wt%) was used to prepare a heat-curable clear paint with the following formulation. (Parts by weight) Fluorine-containing copolymer xylene solution (solid content 60%) 100.0 2- (2'-hydroxy-3 ', 5'-di- (1,1-dimethylbenzyl) benzotriazole 2.1 Hexyltriethoxysilane 0.6 0.1% solution of dibutyltin dilaurate 6.0 Coronate 2515 (blocked isocyanate of Nippon Polyurethane Industry Co., Ltd.) 24.3 Solvesso 100 10.0 Cyclohexanone 30.0 Xylene 7.7

The obtained coating material was applied to a SUS304 (No3 finish) plate, size 0.6 × 200 × 300 mm, using a bar coater so that the dry film thickness was 20 μm.
Then, the coated plate was obtained by curing with a hot-air dryer under curing and curing conditions of 200 ° C. for 3 minutes. A pencil hardness test was performed on the obtained coated plate. Furthermore, regarding the initial coated plate and the coated plate immersed in boiling water for 5 hours, cross-cut adhesion and 5
A cross-cut adhesion test was performed after performing Erichsen of mm. In addition, after the paint was stored at 40 ° C. for one month, it was checked whether the paint was colored. The results are shown in Table 1.

[0020]

Example 2 Using the same fluorine-containing copolymer as in Example 1,
A room temperature curable paint was prepared with the following composition. (Parts by weight) Fluorine-containing copolymer xylene solution (solid content 60%) 100.0 2- (2'-hydroxy-3 ', 5'-di- (1,1-dimethylbenzyl) benzotriazole 2.1 γ-methacryloxypropyltrimethoxysilane 0.6 0.1% solution of dibutyltin dilaurate 6.0 Duranate TPA (Asahi Kasei's hexamethylene diisocyanate isocyanurate type trimer) 10.8 Xylene 2.9 Toluene 26. 8 Methyl isobutyl ketone 13.4 The obtained coating material was applied to a SUS304 plate in the same manner as in Example 1 and then cured at room temperature for 1 week to obtain a coated plate. A similar test was performed, and 40 for the formulation without crosslinker.
A storage test was carried out at 1 ° C. for 1 month, and the presence or absence of coloration was observed.

[0021]

Example 3 A room temperature curable coating material was prepared in the same composition as in Example 2 except that the alkoxysilane in Example 2 was changed to γ-aminopropyltriethoxysilane. The conditions for preparing the coated plate and the evaluation of the coated plate were performed in the same manner as in Example 2.
The results are shown in Table 1.

[0022]

Comparative Example 1 A coating material was prepared in the same composition as in Example 1 except that the alkoxysilane was not used in Example 1. The coating method, curing conditions, and test method were the same as in Example 1.

Comparative Example 2 The physical properties of a coating film obtained in the same manner as in Example 2 except that the alkoxysilane was not used were evaluated.

[0023]

[Comparative Example 3] Using the same fluorine-containing copolymer as in Example 1, a coating material was produced with the following formulation. (Parts by weight) Fluorine-containing copolymer xylene solution (solid content 60%) 100.0 2- (2'-hydroxy-3 ', 5'-di- (1,1-dimethylbenzyl) benzotriazole 2.1 Hexyltriethoxysilane 3.2 Dibutyltin dilaurate 0.1% solution 6.0 Coronate 2515 (blocked isocyanate of Nippon Polyurethane Industry Co., Ltd.) 24.3 Solvesso 100 10.0 Cyclohexanone 30.0 Xylene 5.7 or less, coating, drying The coated plate was evaluated in the same manner as in Example 1.

[0024]

[Table 1]

[0025]

According to the present invention, it is possible to obtain a fluororesin coating material having good adhesion even to a metal which has not been subjected to chemical conversion treatment.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Etsuzo Marumoto 1 in Funami-cho, Minato-ku, Nagoya-shi, Aichi

Claims (1)

[Claims] 1. A fluorine-containing copolymer having (a) a hydroxyl group, (b) a crosslinking agent reactive with a hydroxyl group, (c) an alkoxysilane, (d) an ultraviolet absorber and / or a light stabilizer, and (e). A coating composition comprising an organic solvent.