JPH0417113B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for forming a coating film with excellent corrosion resistance, weather resistance, etc. In recent years, paints containing scaly metal powder have attracted attention as paints that provide excellent corrosion resistance and a coating appearance, and have come to be widely used for tanks, plants, land steel structures such as bridges, and automobile bodies. . The above paint containing scale-like metal powder generally uses acrylic resin, polyester resin, or
This is a paint containing scaly metal powder that uses epoxy resin or the like. In the conventional painting method, this paint is applied to the surface of the object to be painted, and then a clear paint is applied to form a paint film. However, with conventional paint films containing scaly metal powder, sunlight passes through the top coat and reaches the base coat, so if exposed outdoors for a long period of time, the surface of the base coat deteriorates. , the interlayer adhesion between the undercoat film and the topcoat film decreases, coating film defects such as blistering and cracking are more likely to occur, and gloss retention and long-term durability are poor.As a result, protection and beauty There was a problem that the effectiveness of the armor decreased. Therefore, a method has been adopted in which UV absorbers, light stabilizers, antioxidants, etc. are added to the paint to improve its durability, but even with this method, a paint film with sufficient long-term durability cannot be obtained. That was the reality. In view of the prior art as described above, the present invention aims to provide an excellent method for forming a coating film with excellent gloss retention, long-term durability, corrosion resistance, and weather resistance. . For this purpose, paints containing scale-like metal powders, whose base resin component is a fluorine-containing copolymer containing hydroxyl groups, in which fluorine atoms are bonded to the main chain obtained by using fluoroolefin as an essential component, are used to coat objects. This is achieved by painting the surface and then applying clear paint. According to the method of the present invention, by further improving the weather resistance of the undercoat film, deterioration of interlayer adhesion with the topcoat film is prevented, and the occurrence of blisters, cracks, etc. can be avoided for a long period of time. A coating film with excellent corrosion resistance, weather resistance, gloss retention, and long-term durability can be obtained. The scaly metal powder-containing paint used in the present invention to form the undercoat film has a main chain obtained as an essential component of fluoroolefin so that a cured film can be obtained by crosslinking with a curing agent as a base resin component. Contains a fluorine-containing copolymer containing a hydroxyl group to which a fluorine atom is bonded. As the copolymer, a hydroxyl group-containing fluorine-containing copolymer whose constituent components are fluoroolefin and cycloalkyl vinyl ether is desirable, and in particular, the copolymer described in JP-A-57-34107 is
Not only is it weather resistant, but it also has extremely low oxygen permeability and moisture permeability, so it provides a coating film with excellent corrosion resistance, and has good adhesion with various top coats. Both are possible and can be suitably used. That is, the copolymers that can be suitably used in the present invention include fluoroolefin, cyclohexyl vinyl ether, alkyl vinyl ether, and hydroxyalkyl vinyl ether in amounts of 40 to 60 mol%, 5 to 45 mol%, 5 to 45 mol%, and 3 to 3 mol%, respectively. A proportion of ~15 mol%, preferably 45-55 mol% each,
10-30 mol%, 10-35 mol% and 5-13 mol%
The content is as follows. Too low a fluoroolefin content is not only unfavorable from the viewpoint of weather resistance, but also causes problems in production. Also, those containing too high a fluoroolefin content are also difficult to manufacture. On the other hand, if the cycloalkyl vinyl ether content is too low, the hardness of the coating film will decrease, and if the alkyl vinyl ether content is too low, the flexibility will decrease, so both are not preferred. Furthermore, it is particularly important that the composition contains hydroxyalkyl vinyl ether in a proportion within the above range from the viewpoint of improving curability without impairing various useful properties as a coating paste. In other words, if the hydroxyalkyl vinyl ether content is too high, the solubility of the copolymer will change and it will only dissolve in certain substances such as alcohols, which will only limit its applicability as a solution-type paint base. This is not preferable because it reduces the flexibility of the cured coating film. In addition, if the content is too low, the effect of improving curability will be lost, leading to a decrease in the solvent resistance of the cured coating film, and furthermore, causing disadvantages such as impairing the adhesion with the top coat film. Undesirable. As the fluoroolefin that is the raw material for the fluorine-containing copolymer, it is preferable to use perhaloolefin, particularly chlorotrifluoroethylene or tetrafluoroethylene. Further, as the alkyl vinyl ether, it is preferable to use one containing a linear or branched alkyl group having 2 to 8 carbon atoms, particularly one in which the alkyl group has 2 to 4 carbon atoms. The fluorine-containing copolymer may contain units based on comonomers other than the above four constituent components within a range not exceeding 30 mol%. Such comonomers include olefins such as ethylene, propylene, and isobutylene, haloolefins such as vinyl chloride and vinylidene chloride, unsaturated carboxylic acid esters such as methyl methacrylate, vinyl acetate, n
- Vinyl carboxylates such as vinyl butyrate, unsaturated carboxylic acids such as fumaric acid, maleic acid, acrylic acid, and methacrylic acid. The fluorine-containing copolymer preferably has an intrinsic viscosity of 0.05 to 20 dl/g, particularly 0.07 to 0.8 dl/g, as measured in an uncured state in tetrahydrofuran at 30°C. The above-mentioned fluorine-containing copolymers are produced by polymerization using a polymerization initiator such as a water-soluble initiator or an oil-soluble initiator or ionizing radiation in the presence or absence of a polymerization medium in a monomer mixture of a predetermined ratio. It is produced by causing a copolymerization reaction to occur under the action of an initiating source. Examples of the fluorine-containing copolymers containing hydroxyl groups are commercially available, such as Lumiflon LF100, Lumiflon LF200, Lumiflon LF300, and Lumiflon LF400 (all trade names manufactured by Asahi Glass Co., Ltd.). A paint containing scale-like metal powder using a hydroxyl group-containing fluorine-containing copolymer in which a fluorine atom is bonded to the main chain obtained by using such fluoroolefin as an essential component as a base resin component can be prepared by a known method. You can do it accordingly. That is, in an organic solvent solution of a fluorine-containing copolymer containing a hydroxyl group, a curing agent, a scaly metal powder, and, if necessary, various coloring pigments, additives, modifiers, etc. commonly used for paints are added. By dispersing the scaly metal powder, a paint containing scaly metal powder can be obtained. Examples of the organic solvent include aromatic hydrocarbons such as xylene and toluene, alcohols such as n-butanol, esters such as butyl acetate, ketones such as methyl isobutyl ketone, and glycol ethers such as ethyl cellosolve. In addition, various commercially available thinners can also be used. Further, as the curing agent, in the case of a room temperature curing type, a polyvalent isocyanate having two or more isocyanate groups in one molecule is suitable. The polyvalent isocyanate includes aliphatic or alicyclic diisocyanates such as hexamethylene diisocyanate, tetramethylene diisocyanate, isophorone diisocyanate, hydrogenated diphenylene diisocyanate, hydrogenated xylylene diisocyanate, or biuret forms and dimers thereof.
Typical examples include trimers or reaction products of excess of these isocyanate compounds and low-molecular polyols such as ethylene glycol, glycerin, trimethylolpropane, and pentaerythritol. Needless to say, in the case of a room-temperature curing type, the curing agent becomes a two-component paint, which is mixed with the hydroxyl group-containing fluorine-containing copolymer solution as the main ingredient immediately before coating. In addition, in the case of the bake-hardening type, blocked isocyanate is obtained by masking the polyvalent isocyanate with a masking agent such as phenols, alcohols, oximes, lactams, amines, or amides;
Representative examples include condensation products of amino compounds such as melamine, urea, benzoguanamine, and acetoguanamine with aldehyde compounds, or curing agents such as aminoplast resins in which the condensation products are further etherified with alcohols such as butanol. . Furthermore, as the flaky metal powder used in the above-mentioned flaky metal powder-containing paint, those normally used in flaky metal powder-containing paints can be used, such as flaky aluminum powder, copper powder, bronze powder, iron oxide powder, etc. Examples include powder, mica powder treated with titanium oxide, etc. As for the particle size of the scaly metal powder, it is generally suitable that the average particle size is 3 to 30 microns. In addition, the paint containing scale-like metal powder used in the present invention may further contain various inorganic or organic coloring pigments or anticorrosion pigments such as titanium oxide, carbon black, and phthalocyanine; various additives such as ultraviolet absorbers and surface conditioners; A modifier such as cellulose acetate butyrate can be added as appropriate. The blending ratio of the components constituting these flaky metal powder-containing paints can be varied over a wide range depending on the coating conditions, etc., but usually the total amount of the fluorine-containing copolymer containing hydroxyl groups and the curing agent in the paint is 20 to 20%. 40% by weight, and 1 to 20% by weight of scaly metal powder. Next, as the clear paint used in the present invention, acrylic resin paints, oil-free polyester resin paints, or alkyd resin paints, which are used as top coats for paints containing general flaky metal powder, can be used. . In the case of acrylic resin paints, a vinyl copolymer having hydroxyl groups and/or carboxyl groups is used as the base resin. Specifically, for example, hydroxyethyl (meth)acrylate, (meth)
Hydroxypropyl acrylate, hydroxybutyl (meth)acrylate, N-methylol (meth)
Ethylene monomers having a hydroxyl group such as acrylamide; Ethylene monomers having a carboxyl group such as (meth)acrylic acid, crotonic acid, itaconic acid, maleic acid, etc.; Aromatics such as styrene, vinyltoluene, benzyl (meth)acrylate, etc. Group vinyl monomer; methyl (meth)acrylate,
(meth)ethyl acrylate, butyl (meth)acrylate, ethylhexyl (meth)acrylate, octyl (meth)acrylate, dimethyl itaconate,
Ester monomers such as dimethyl maleate and dimethyl fumarate; and several other monomers such as (meth)acrylonitrile and vinyl acetate (meth)acrylamide are copolymerized by a conventional solution polymerization method. In addition, in the case of oil-free polyester resin paints, ethylene glycol, propylene glycol, diethylene glycol, butylene glycol, dimethylpropanediol, glycerin, trimethylolethane, trimethylolpropane,
Polyhydric alcohol components such as hexanetriol, pentaerythritol, sorbitol, dipentaerythritol, phthalic anhydride, isophthalic acid, trimellitic anhydride, maleic anhydride, fumaric acid,
The base resin is synthesized with a polybasic acid component such as succinic acid, adipic acid, and sebacic acid by a conventional melt condensation method, azeotropic condensation method, or the like. In the case of alkyd resin paints, castor oil,
The base resin is obtained by modifying the above polyester resin with tung oil, safflower oil, soybean oil, linseed oil, coconut oil, cottonseed oil, tall oil, olive oil, or their fatty acids. The above-mentioned clear paint consists of these base resins and the same organic solvents, curing agents, additives, modifiers, etc. used in the above-mentioned scale-like metal powder-containing paint, and if necessary, a small amount of inorganic or It is also possible to make a color clear by blending organic coloring pigments or organic coloring dyes. Next, the coating film forming method of the present invention can be carried out by a conventional method. In other words, a paint containing scale-like metal powder is applied to the surface of a steel plate, aluminum plate, etc., which has been surface-treated or pre-treated with a primer, surfacer, etc. as necessary, and is diluted with an organic solvent for viscosity of 10 to 30 seconds (as required). Food Cup #4/20
℃) and apply a dry film thickness of approximately 10 to 30μ on the surface of the object to be coated.
Paint it to look like this. Next, the clear paint is diluted with an organic solvent for 15 to 40 seconds (Food Cup #4/20) as necessary.
℃) and apply the coating to a dry film thickness of approximately 10 to 40μ. As for the coating method, ordinary spray coating, electrostatic coating, etc. are used for both the scaly metal powder coating and the clear coating, but there are no particular restrictions on other coating methods. In the present invention, the clear paint can be applied over the flaky metal powder-containing paint film either in an undried state or in a dry state. That is, when the clear paint is applied over and over again when the scaly metal powder-containing paint film is in an undried state, the setting time is about 2 to 20 minutes. In addition, when applying clear paint after the paint film containing flaky metal powder has dried, if the paint containing flaky metal powder is a room temperature curing type, leave it for about 24 hours or more or force dry it. Recoat afterward, or in the case of a bake-curing type, apply multiple coats after baking and curing. In addition, the above fluoroolefin, cycloalkyl vinyl ether,
Paints containing scale-like metal powders whose base resin is fluorine-containing copolymers containing alkyl vinyl ethers and hydroxyalkyl vinyl ethers are
It can be baked and hardened at 130-170℃ for 20-30 minutes. As described above, in the coating film formed by the method of the present invention, the weather resistance of the undercoat film containing the scaly metal powder is very excellent, so that the interlayer adhesion between the undercoat film and the top coat film is not as good as in the conventional case. As a result, the coating film can protect the object to be coated and retain its aesthetic gloss for a long period of time. In addition, after applying a paint containing scale-like metal powder that uses a conventional acrylic resin or polyester resin as a base resin component, a clear paint that uses a hydroxyl group-containing fluorine-containing copolymer as a base resin component is applied. When the resulting paint film is exposed outdoors for a long period of time, sunlight passes through the clear paint film even though the clear paint film has excellent weather resistance, and as a result, paint containing scaly metal powder, which is the undercoat film, Since the surface of the coating film deteriorates, its durability is inferior to that of the coating film obtained by the method of the present invention. The details of the present invention will be explained below with reference to Examples. Note that "parts" and "%" indicate "parts by weight" and "% by weight," respectively. The paints containing scale-like metal powder and the clear paints had the formulations shown in Tables 1 and 2, respectively.

【table】

【table】

【table】

[Table] Example 1 A paint containing scale-like metal powder was spray-coated to a dry film thickness of 15μ on a dull steel plate coated with an electrodeposition coating or an alkyd-melamine resin coating, and after setting for 15 minutes, clear paint D was applied. It was spray coated to a dry film thickness of 30μ and left to dry for one day. Comparative Example 1 A coating film was formed in the same manner as in Example 1 except that a paint containing flaky metal powder was used instead of the paint containing flaky metal powder. Example 2 A paint containing flaky metal powder was spray-coated on a chromate-treated aluminum plate to a dry film thickness of 20 μm, and after forced drying at 80°C for 20 minutes, clear paint A was sprayed to a dry film thickness of 30 μm. It was painted and baked at 100℃ for 20 minutes. Example 3 A paint containing flaky metal powder was spray-coated on a chromate-treated aluminum plate to a dry film thickness of 25 μm, and after baking and drying at 150°C for 20 minutes,
Clear paint E was spray-coated to a dry film thickness of 30 μm, and baked at 60° C. for 20 minutes to dry. Comparative Example 2 A coating film was formed in the same manner as in Example 3 except that a paint containing flaky metal powder was used instead of a paint containing flaky metal powder. Example 4 A paint containing flaky metal powder was spray-coated on a chromate-treated aluminum plate to a dry film thickness of 20μ, and after forced drying at 100°C for 5 minutes,
Clear paint C was spray-coated to a dry film thickness of 30 μm, and baked and dried at 150° C. for 20 minutes. Comparative Example 3 A coating film was formed in the same manner as in Example 4 except that a paint containing flaky metal powder was used instead of a paint containing flaky metal powder. Example 5 A coating film was formed in the same manner as in Example 4 except that clear paint B was used instead of clear paint C. Comparative Example 4 A coating film was formed in the same manner as in Example 5, except that a paint containing flaky metal powder was used instead of the paint containing flaky metal powder. Comparative Example 5 Example 1 except that a paint containing flaky metal powder was used instead of the paint containing flaky metal powder, and clear paint F was used instead of clear paint D.
A coating film was formed in the same manner as above. Comparative Example 6 A coating film was formed in the same manner as in Example 1, except that scaly metal powder was used instead of the scaly metal powder-containing paint, and clear paint G was used instead of clear paint E. The test plates obtained in Examples 1 to 5 and Comparative Examples 1 to 6 were examined for coating film appearance, gloss, adhesion, and hot water resistance before being tested using a sunshine weather meter.
Tests were conducted after 2000 hours and after 3000 hours, and the results are shown in Table 3.

【table】

[Table] As is clear from Table 3, the coating film obtained by the method of the present invention has excellent gloss retention, adhesion, hot water resistance, etc. even after the accelerated weathering test, that is, the sunshine weather meter test. It had excellent coating performance. On the other hand, a method for forming a coating film consisting of a combination of a conventional acrylic resin-based and polyester resin-based paint containing scale-like metal powder, a conventional acrylic resin-based and polyester resin-based clear paint, and a combination of an acrylic resin-based and polyester resin-based clear paint The coating films obtained in Comparative Examples 1 to 4 had excellent coating performance at the initial stage, but after the Sunshine Weather-Ometer test, gloss marks, cracks, etc. appeared, and the gloss and adhesion were poor. Coating film performance such as properties deteriorated. Furthermore, the coating films obtained in Comparative Examples 5 and 6 using a combination of a conventional acrylic resin-based coating containing scale-like metal powder and an E clear coating whose base resin component was a fluorine-containing copolymer containing hydroxyl groups had a glossy finish. After the sunshine weather meter test, the gloss did not decrease, but the adhesion was poor.

Claims (1)

[Claims] 1. After coating the surface of the object to be coated with a paint containing scale-like metal powder, the base resin component of which is a fluorine-containing copolymer containing hydroxyl groups, in which fluorine atoms are bonded to the main chain obtained by using fluoroolefin as an essential component, A method for forming a coating film characterized by applying a clear paint.