JPH011767A - Clear paint composition - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a clear coating composition that is particularly suitable for metal substrates and has excellent long-term weather resistance and corrosion resistance.

<Prior Art> It has been widely practiced to coat metal substrates with colored paints in order to give them aesthetic appearance and corrosion resistance.

On the other hand, metal substrates such as stainless steel, aluminum, copper, or brass are widely used without being coated with colored paint in order to take advantage of the metallic luster of the metal substrate itself.

However, such metal substrates are also coated with clear paint to prevent stains such as hand marks from adhering to them and to maintain their metallic luster. However, when a commonly used clear paint such as an acrylic resin or polyester resin paint is applied, there is a problem that, after being left outdoors for several years, the paint film itself develops chalking and its metallic luster deteriorates.

Therefore, it has been considered to apply a fluororesin-based clear paint that has good long-term weather resistance.

<Problems to be solved by the invention> However, fluorine (
Painting with a sealant-based clear paint can maintain a metallic luster for a long period of time, but unexpectedly when exposed outdoors, fluororesin-based clear paint does not cause rust on unpainted metal substrates such as stainless steel. In metal substrates coated with coatings, a phenomenon has occurred in which corrosion spots appear on the surface of the metal substrate under the coating.

Although the cause of this is not certain, it is probably predicted to be as follows. In other words, metal base materials such as stainless steel have a high reflectance of sunlight and other light including ultraviolet rays, while fluororesin-based clear coatings have a higher reflectance than other general acrylic resin-based, polyester-based, etc. clear coatings. , the transmittance of ultraviolet rays is high, and therefore the paint film is greatly affected by sunlight (transmitted light and reflected light) outdoors, and a portion of the fluororesin decomposes, resulting in the production of fluoride and chloride as decomposition products. It is thought that highly active low-molecular-weight compounds such as these act as corrosion factors, corrode the surface of the metal base material, and cause corrosion spots and the like.

As a result of intensive studies in view of the current situation, the inventors of the present invention have developed a method that maintains the metallic luster of the metal base material such as stainless steel for a long period of time, and takes advantage of the long-term weather resistance of the fluororesin clear coating. The inventors have discovered a clear coating composition that can form a coating film that prevents the occurrence of rust, and have thus arrived at the present invention.

Means for Solving the Problems> That is, the present invention provides a coating composition containing as main components a polyol component made of a fluorine-containing copolymer having a hydroxyl group and a curing agent component made of a polyvalent isocyanate compound or an aminoplast compound. relates to a clear coating composition in which an epoxy compound is blended so that the epoxy group concentration is from o, oot to 2.0 mmol per gram of solid content of the mixture of the fluorine-containing copolymer and the epoxy compound. be'.

By applying the clear paint composition of the present invention to a metal substrate, the resulting paint film has good long-term weather resistance without causing paint film defects such as chalking for a long period of time, and therefore retains its metallic luster for a long time. Furthermore, the addition of an epoxy compound to the paint makes it possible to prevent rust from forming.

The present invention will be explained in detail below.

As the fluorine-containing copolymer having a hydroxyl group as a polyol component used in the present invention, any known fluorine-containing copolymer can be used without particular limitation as long as it is soluble in an organic solvent. It dissolves in an organic solvent and can form a coating film even by drying at room temperature or baking at a low temperature, and provides a coating film with excellent weather resistance, durability, and adhesion. Fluorine-containing copolymers described in JP-A-57-34107 are suitable. That is, the fluorine-containing copolymer contains fluoroolefin, cyclohexyl vinyl ether, alkyl vinyl ether, and hydroxyalkyl vinyl ether as essential components, and contains 30 to 70% by weight and 5% by weight, respectively.
It is a copolymer having a number average molecular weight of about 3,000 to 100,000 and containing in proportions of ~60% by weight, 3~50% by weight, and 3~25% by weight.

Incidentally, if the fluoroolefin content is too low, the weather resistance will decrease, and if the fluoroolefin content is too high, it will be difficult to manufacture. Further, if the cyclohexyl 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. Also,
It is particularly important to contain hydroxyalkyl vinyl ether in a proportion within the above range from the viewpoint of improving curability without impairing various useful properties as a paint base. In other words, if the hydroxyalkyl vinyl ether content is too high, not only will the solubility of the copolymer in organic solvents decrease, but also the flexibility of the coating film will decrease, while if the hydroxyalkyl vinyl ether content is too low, the durability and , adhesion deteriorates.

In the fluorine-containing copolymer, the fluoroolefin is preferably perhaloolefin, particularly talolotrifluoroethylene or tetrafluoroethylene.

As the alkyl vinyl ether, those containing a straight or branched alkyl group having 2 to 8 carbon atoms, particularly those in which the alkyl group has 2 to 4 carbon atoms, are preferable. In addition, as a hydroxyalkyl vinyl ether, the number of carbon atoms is 2.
Those containing ~8 hydroxyalkyl groups are preferred.

The fluorine-containing copolymer may contain comonomers other than the four essential components in an amount not exceeding 40% by weight. Typical examples of such comonomers include ethylene, propylene, imbutylene, vinyl chloride, vinylidene chloride, methyl methacrylate, and butyl acetate.

The fluorine-containing copolymer can be produced by causing a copolymerization reaction by allowing a polymerization initiator to act on a monomer mixture in a predetermined proportion in the presence of a polymerization medium. Examples of such fluorine-containing copolymers include Lumiflon LF 10
0.200.210.300.400.502.504
．． 550.552.554.700.800.916
(all brand names manufactured by Asahi Glass Co., Ltd.) etc. are commercially available.

A polyvalent isocyanate compound and/or an aminoplast compound are used as curing agent components in the present invention.

Examples of polyvalent isocyanate compounds include aliphatic or alicyclic diisonanates such as hexamethylene diisocyanate, tetramethylene diisocyanate, inphorone diisocyanate, hydrogenated diphenyl diisocyanate, and hydrogenated xylylene diisocyanate, or their biuret forms, dimers, Typical examples include trimers or reaction products of excess amounts of these isocyanate compounds and low-molecular polyols such as ethylene glycol, glycerin, trimethylolpropane, and pentaerythritol. By mixing these polyvalent isocyanate compounds in a predetermined ratio with the polyol component made of the fluorine-containing copolymer, a two-component coating material that can be cured even at room temperature is obtained.

Further, the polyvalent isocyanate compound may be phenols,
Alcohols, oximes, lactams, amines,
Blocked isocyanate compounds masked with masking agents such as amides can also be used, and in this case, a one-component paint that can be baked can be obtained by mixing with the polyol component in a predetermined ratio.

The mixing ratio of the polyol component and the polyvalent isocyanate compound curing agent component is determined by the equivalent ratio of isocyanate groups of the isocyanate compound to hydroxyl groups of the polyol component (NGOloH).
is (0.15 to 1.5/1), particularly preferably 0.2 to 1.2/1), and within this range it is possible to exhibit the original resin properties. .

If the number of isocyanate groups is too large than the above range, the free isocyanate groups will react with moisture in the air, resulting in a decrease in weather resistance, while if it is too small, satisfactory curability will not be obtained and the crosslinking density will be low, resulting in poor durability. All of these are unfavorable because they reduce solvent resistance, stain resistance, chemical resistance, weather resistance, and the like.

Furthermore, as mentioned above, an aminoplast compound can also be used as a curing agent. The aminoplast compound is a condensation product of an amino compound such as melamine, urea, benzoguanamine, or acetoguanamine and an aldehyde compound, or a compound obtained by further etherifying the condensation product with an alcohol such as butanol. When an aminoplast compound is used, it becomes a one-component paint that can be cured by baking by mixing it with the polyol component in a predetermined ratio.

The mixing ratio (by weight) of the polyol component and the aminoplast compound curing agent component is (95:5 to 60:40), particularly preferably (90:10 to 70:30), and the original resin properties can be maintained within this range. It becomes possible to perform.

If the amount of the aminoplast compound is too much than the above range, reactions between the aminoblast compounds tend to occur, reducing the flexibility and chemical resistance of the coating film, and conversely, if the amount is too little, satisfactory curability may not be obtained and crosslinking may occur. Since the density is low, the dissolution resistance, stain resistance, etc. are deteriorated, and both are unfavorable.

In the present invention, an epoxy compound is blended into a coating composition containing these polyol components and a curing agent component as main components in order to prevent the occurrence of rust.

Although the mechanism by which the formation of corrosion spots on the surface of the metal base material under the coating film can be prevented by adding an epoxy compound is not clear, it is possible to prevent the occurrence of corrosion spots on the surface of the metal substrate under the coating film, but it is possible to This is thought to be due to some kind of reaction with the compound to inactivate the corrosion factor.

The epoxy compound referred to in the present invention is a compound having an epoxy group in the molecule, and specifically, the following compounds are representative.

(a) Alkyl esters of acrylic acid or methacrylic acid such as methyl, ethinobebutyl, 2-ethylhexyl,
In acrylic copolymers obtained from mixed monomers of α,β-ethylenically unsaturated monomers such as hydroxyethyl acrylic acid or methacrylic acid, hydroquinepropyl, acrylic acid, methacrylic acid, and styrene, some of the monomers constituting the copolymer An epoxy group-containing acrylic copolymer using an epoxy group-containing comonomer such as glycidyl methacrylate or glycidyl acrylate.

In addition, the concentration of the epoxy group is preferably 5.0 mmol or less (epoxy equivalent equivalent: 200) per gram of solid content of the copolymer from the viewpoint of compatibility with the fluorine-containing copolymer, and particularly 0.
．． 3-3. Omi IJ mole (epoxy equivalent equivalent 3300
~330) is appropriate.

Further, from the viewpoint of compatibility with the fluorine-containing copolymer, the copolymer preferably contains 10 to 70% by weight of an alkyl ester of acrylic acid or methacrylic acid having 3 to 4 carbon atoms.

(1 Near) Molecular weight approximately 300-50 obtained by condensation reaction of bisphenol A and epichlorohydrin
Bisphenol type epoxy resin and phenol novolac type epoxy resin that have an epoxy group at the end of 00.

The epoxy group concentration is 0.2 to 7.0 mmol (500 mmol in terms of epoxy equivalent) per gram of solid content of the epoxy resin.
0 to 142) is appropriate.

(c) Unsaturated fatty acids obtained by esterifying monounsaturated fatty acids such as oleic acid and elaidic acid, di- and tri-unsaturated fatty acids such as linoleic acid, eleostearic acid, and lylunic acid with various alcohols such as methinopethyl, butyl, and octinopearyl. Epoxidized fatty acid ester obtained by epoxidizing ester.

The epoxy group concentration is 0.5 to 6.0% per gram of solid content of the epoxidized fatty acid ester. OmiIJ mol (2000 to 167 in terms of epoxy equivalent) is suitable.

(d) Epoxidized vegetable oils obtained by epoxidizing vegetable oils such as linseed oil, cottonseed oil, safflower oil, and soybean oil.

In addition, the epoxy group concentration is 0.5 to 6.0 mmol (epoxy equivalent equivalent 2
000-167) is suitable.

(e) A glycidyl ether compound obtained by epoxidizing a -valent or divalent or higher polyhydric alcohol.

Specifically, sorbitol polyglycidyl ether, diglycerol polyglycidyl ether, trimethylolpropane polyglycidyl ether, neopentyl glycol diglycidyl ether, 1,6-hexanethiol diglycidyl ether, 1,6-hexanethiol diglycidyl ether, no pairyl glycidibire ether, novelauryl alcohol glycidyl ether, etc. is cited as a representative example.

The epoxy group concentration is suitably 0.5 to 10 mmol (2000 to 100 in terms of epoxy equivalent) per gram of solid content of the glycidyl ether compound.

(f) - A glycidyl ester compound obtained by epoxidizing a basic acid or a polybasic acid.

Specifically, a typical example is diglycidyl adipate esternohephthalate diglycidyl ester.

The epoxy concentration is suitably 0.5 to 10 mmol (2000 to 100 in terms of epoxy equivalent) per gram of solid content of the glycidyl ester compound.

(g) Alicyclic epoxy compounds obtained by oxidizing a part of the alicyclic ring of an alicyclic ester compound such as dioctyl tetrahydrophthalate.

The epoxy group concentration is suitably 0.5 to 10 mmol (2000 to 100 in terms of epoxy equivalent) per gram of solid content of the alicyclic epoxy compound.

In the present invention, these epoxy compounds are blended in a clear paint such that the epoxy group concentration is 0.001 to 2.0 mmol per gram of solid content of the mixture of the fluorine-containing copolymer and the epoxy compound. If the amount of the epoxy compound added is less than the above range, the corrosion prevention effect will not be sufficiently achieved, and if it is too much, chalking, discoloration, etc. will occur, and weather resistance will deteriorate, which is not preferable.

Further, in the present invention, when an organic tin compound is added in combination with the epoxy compound and about 0.1 to 5 parts by weight based on 100 parts by weight of the total solid content of the polyol component and curing agent component, a further corrosion prevention effect can be obtained. .

As the organic tin compound, for example, a compound represented by the following general formula can be suitably used.

That is, formula -9: % formula % (wherein R,, R2, R3, and R4 are alkyl groups such as methyl and butinobeoctyl, and/or an alkyl group containing an ester bond and having 1 to 10 carbon atoms. ;Y
l, Y2 are fatty acid carboxyl residues, organic carboxyl groups such as maleic acid half ester groups, or organic sulfur derivatives represented by mercapto fatty acid residues such as mercaptoacetic acid and mercaptopropionic acid; X is oxygen, sulfur, or maleic acid, etc. Unsaturated carboxyl group; n is an integer of 0 to 10; when n is 0, monoalkyltin compounds in which R2 is the same substituent as Yl or Y2 are also included. ) is a compound represented by

Specifically, compounds represented by three systems, namely fatty acid salt systems such as dibutyltin dilaurate, dibutyltin distearate, dibutyltin simalate, and tribenzyltin laurate; dibutyltin simalate, dibutyltin laurate, methyl maleate, and dibutyltin Maleins such as dioleyl maleate, dibutyltin methoxymethyl maleate, dibutyltin methyl maleate, dibutyltin dioctyl maleate, monobutyltin trimethyl maleate, monobutyltin trioctyl maleate, tribenzyltin octyl maleate, tribenzyltin trimethyl maleate, etc. Acid salts: Representative examples include sulfur-containing organic tin compounds such as dibutyltin dioctyl thioglycolate, dibutyltin dilauryl mercaptide, dibutyltin mercaptopropanoate, and dibutyltin mercaptopropionate.

Furthermore, organic tin compounds such as tetraphenyltin, tetraoctyltin, and tributyltin acetate may also be mentioned as compounds other than the compounds represented by formula -9.

The clear coating composition of the present invention contains various organic solvents in addition to the above-described components as usual.

Examples of organic solvents include hydrocarbon solvents such as toluene and xylene; ester solvents such as ethyl acetate and butyl acetate; ketone solvents such as methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, and isophorone; methanol,
Typical examples include alcoholic solvents such as eta/-nope butanope.

The clear paint composition of the present invention may further contain various additives such as surface conditioners, ultraviolet absorbers, thickeners, etc., modifiers such as cellulose acetate butyrate, extender pigments, and other additives that do not inhibit metallic luster. It consists of a small amount of colored pigments, dyes, etc.

Next, a coating film forming method using the clear coating composition of the present invention will be explained. The surface of a metal base material such as stainless steel, aluminum, copper or brass may be roughened by etching or otherwise treated with a chelating agent, a coupling agent, etc. in order to improve adhesion as necessary. Clear material: Apply the acid to a dry film thickness of approximately 10 to 100μ by means such as air spray, Airless Spray J7-1 electrostatic spray, Nyawarcoat, dip coating, roll coating, or brush coating, and apply the hardening agent. Depending on the selection, drying at room temperature to 130-170℃,
Low temperature baking for 30 minutes, 200-230℃, 30-200℃
The above-mentioned excellent coating film can be formed by performing high-temperature, short-time baking for seconds.

<Effects of the Invention> By applying the clear coating composition of the present invention to a metal substrate, the resulting coating film can last for a long period of time without causing coating defects such as chalking, and the metal substrate under the coating film can be coated with the clear coating composition of the present invention. The metal base material can maintain its metallic luster in good condition for a long period of time without causing corrosion spots on the surface.

The present invention will be explained in more detail below. In the examples, "parts" and "%" are expressed on a weight basis.

[Fluorine-containing copolymer solution A]

52 parts of chlorotrifluoroethylene, 4-hydroxy-
A fluorine-containing copolymer (number average molecular weight: 6,800,
A 60% quijirole solution with a hydroxyl value of 100) was obtained. (Hereinafter referred to as fluorine-containing copolymer solution A) [Fluorine-containing copolymer solution B] 54 parts of chlorotrifluoroethylene, 4-hydroxy-
A fluorine-containing copolymer (number average molecular weight: 23,000
, a 60% quijirole solution with a hydroxyl value of 52) was obtained. (Hereinafter referred to as fluorine-containing copolymer solution B) [Fluorine-containing copolymer solution C] 30 parts of chlorotrifluoroethylene, 25 parts of tetrafluoroethylene, 10 parts of 4-hydroxy-n-butyl vinyl ether, 18 parts of cyclohexyl vinyl ether, A monomer consisting of 17 parts of ethyl vinyl ether was
4 of the fluorine-containing copolymer (number average molecular weight 45,000, hydroxyl value 52) according to the method described in Publication No. 7-34107.
A 0% cyclohexanone solution was obtained. (Hereinafter referred to as fluorine-containing copolymer solution C) [Acrylic resin solution] 30 parts of methyl methacrylate, 2 parts of butyl methacrylate
0 parts, 37 parts of 2-ethylhexyl acrylate, 1 part of methacrylic acid, 12 parts of 2-hydroxyethyl methacrylate
A solution of acrylic resin (number average molecular weight 15,000, hydroxyl value 50) (non-volatile content 60%) was obtained by solution polymerizing the monomer consisting of
I got it.

(hereinafter referred to as acrylic resin solution) [Curing agent A] 55.5 parts of a polyisocyanate having a cyanurate ring, which is a trimer of hexamethylene diisocyanate, was dissolved in 20 parts of methyl ethyl ketone, 24.5 B of methyl ethyl ketone oxime was added thereto, and the mixture was reacted. Blocked isocyanate compound solution (NGO equivalent: 360, non-volatile content: 8
0%) was obtained.

(Hereinafter referred to as curing agent A) [Curing agent port] A polyisocyanate compound having a cyanurate ring which is a trimer of hexamethylene diisocyanate (NGO equivalent weight 199, non-volatile content 100%) (Hereinafter referred to as curing agent port) [Curing agent C] A solution of butyl etherified melamine resin dissolved in a mixed solvent consisting of Kizilol and butanol (non-volatile content 60±
2%). (Hereinafter referred to as curing agent C) [Epoxy compound A] Consists of 10 parts of glycidyl methacrylate, 20 parts of methyl methacrylate, 20 parts of butyl methacrylate, 37 parts of 2-ethylhexyl acrylate, 1 part of methacrylic acid, and 12 parts of 2-hydroxyethyl methacrylate. The monomer was solution polymerized in a mixed solvent consisting of quijirole and butyl acetate, and an acrylic resin (epoxy group concentration O 1,704 mm) was prepared.
j2/g: number average molecule ff115000; hydroxyl value 50) solution (non-volatile content 60%) was obtained. (Hereinafter referred to as epoxy compound A) [Epoxy compound port] Bisphenol A type epoxy resin [Epoxy group concentration 5.
05 mmof/g; r Epicote 802 (trade name manufactured by Yuka Shell Epoxy Co., Ltd.)] (hereinafter referred to as epoxy compound) [Epoxy compound C] 9, lO-Epoxy butyl stearate [Epoxy group concentration 2.31 mmoβ/g Nioxirane oxygen 3.7%]
(hereinafter referred to as epoxy compound C) Coepoxy compound II] Epoxidized soybean oil obtained by epoxidizing refined soybean oil [Epoxy group concentration 4.37 mmo! ! /g: Epoxidation rate of about 90%] (hereinafter referred to as epoxy compound 2) [Epoxy compound 2] 2-ethylhexyl glycidyl ether [Epoxy group concentration 5.10 mmof/g; rBuna:L-LE EX-
12J, (trade name manufactured by Nagase Chemical Industries, Ltd.)] (hereinafter referred to as epoxy compound E) [To the epoxy compound] Adipic acid diglycidyl ether [Epoxy group concentration 6.
80 mmof/g; rDenacol EX-701J
(Product name manufactured by Nagase Kasei Kogyo Co., Ltd.)] (hereinafter referred to as epoxy compound) [Epoxy compound T] 4.5-epoxyhexahydrophthalate dioctyl [epoxy group concentration 2.45 mmoβ/g] (hereinafter referred to as epoxy compound T) ) Examples 1 to 12 and Comparative Examples 1 to 3 Paints were prepared by stirring and mixing the components shown in Table 1. In Example 3, a hardening agent (b) was mixed before coating to prepare a clear paint.

The clear paints obtained in Examples 1 to 12 and Comparative Examples 1 to 3 were coated as follows, and the resulting coated plates were subjected to an accelerated weather resistance test (Du Cycle Uniday Meter Test 500).
time) and an outdoor exposure test (2 years in Okinawa).

<Test 1> Example 1.2.6.7.8.11.12 and Comparative Example 1.
The clear paint obtained in 2.3 was coated with a plate thickness of 0.5
It was spray-painted on a degreased stainless steel plate (SUS304 hairline finish) of 1.0 mm in diameter and baked at 160° C. for 20 minutes to obtain a cured coating (30 μm thick), which was used for testing. The test results are shown in Table 2.

<Test 2> The clear paint obtained in Example 4.5.9 was applied in the same manner as in Test 1, and baked at 160°C for 30 minutes to obtain a cured film (20μ thick), which was used for the test.

The test results are shown in Table 2.

<Test 3> The clear paint obtained in Example 10 was applied to the stainless steel plate using a barcoder, and baked in a drying oven at 300°C for 1 minute to obtain a cured film (20μ thick), which was used for testing. The test results were as shown in Table 2.

<Test 4> The clear paint obtained in Example 3 was coated with a plate thickness of 0.8 + nm.
It was spray-painted on a chromate-treated aluminum plate and dried at room temperature for two weeks to obtain a cured coating (30μ thick).
I gave up on the exam. The test results are shown in Table 3.

Table 3 As is clear from the test results in Tables 2 and 3, it was confirmed that the clear paint of the present invention prevented the occurrence of rust in the weather resistance test, and was also able to maintain its metallic luster for a long period of time. there were.

On the other hand, the clear paint to which no epoxy compound was added (Comparative Example 1) could not prevent the occurrence of rust, and conversely, the clear paint to which an excessive amount of epoxy compound was added (Comparative Example 2) caused chalking.

In addition, conventional acrylic resin clear paint (Comparative Example 3)
Chalking occurred and some parts of the paint film peeled off.

Claims (2)

[Claims] (1) In a coating composition whose main components are a polyol component made of a fluorine-containing copolymer having hydroxyl groups and a curing agent component made of a polyvalent isocyanate compound or an aminoplast compound, Per gram of solid content of the mixture of copolymer and epoxy compound,
A clear paint composition characterized in that the amount is blended to be 0.001 to 2.0 mmol. (2) The fluorine-containing copolymer is fluoroolefin 30
~70% by weight, cyclohexyl vinyl ether 5-60
Claim No. 1, characterized in that it is a copolymer consisting of 3 to 50% by weight of alkyl vinyl ether, 3 to 25% by weight of hydroxyalkyl vinyl ether, and 0 to 40% by weight of other comonomers. ) The clear paint composition described in item 1.