JPS6025463B2 - High solids coating composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to thermosetting high solids coating compositions.

In recent years, air pollution caused by paint solvents has become a problem.
Various efforts have been made to develop low-pollution coatings that do not use organic solvents at all or use only a small amount of organic solvents, and remarkable progress has been made.

There are various types of low-pollution paints, such as water-soluble, water-dispersible, powder, electron beam-curable, and high-solids paints. Paint is attracting attention. Conventionally, functional group-containing acrylic resins have been used in thermosetting paints in combination with crosslinking agents such as amino resins, but paints made from these resins have a high organic solvent content, and solids content of 40 to 50% by weight for spray coating. (hereinafter expressed in %), and for roll coating, it was 50 to 60%.

Therefore, when the molecular weight of the base acrylic resin is lowered in order to increase the solid content during coating, the physical properties of the resulting coating film are significantly deteriorated, and it can hardly withstand severe conditions such as those used for coil coating. Furthermore, the processability, chemical resistance, corrosion resistance, etc. of the coating film are also reduced due to the lower molecular weight. In view of the above disadvantages, the present inventors have conducted extensive research and found that by using unsaturated oligomers in combination, the solid content during coating can be reduced to 6.
The present invention was developed based on the fact that a coating film with excellent performance can be obtained even with a content of 0% or more.

That is, in the present invention, (1) the number average molecular weight is 1500 to 60;
Acrylic polymer having hydroxyl group and/or carboxyl group in addition to polymerizable unsaturated group in 00 (hereinafter abbreviated as acrylic polymer) 20 to 8% by weight, polyhydric alcohol and (meth)acrylic Oligomer (hereinafter abbreviated as oligomer) which is an ester with an acid and has a polymerizable unsaturated group with a number average molecular weight of 200 to 1000 (hereinafter abbreviated as oligomer) 10 to
The present invention provides a high solids coating composition comprising, as essential components, 10 to 4% by weight of a crosslinking agent consisting of {C] an amino resin and/or a polyisocyanate. This composition has the following characteristics. It is possible to prepare a high solid content paint with a solid content of 70% or more at the time of application, the paint film obtained by heat curing has excellent adhesion to the metal substrate, and the surface hardness of the coating is extremely high. There is no high blocking D distribution, and the coating film has excellent processability. h) The acrylic polymer, which is a component of the filter paper composition, has a hydroxyl group and/or a carboxyl group in addition to the polymerizable unsaturated group, and has a number average molecular weight of 1500 to 60.
0 government is preferably 2000 to 5000.

If the molecular weight is less than 1,500, it will be difficult to obtain a coating film with sufficient processability, and if it exceeds 6,000, it will tend to be difficult to achieve high solidification, which is not preferred. The polymerizable unsaturated group in the acrylic polymer is a functional group that copolymerizes with the polymerizable unsaturated group in the oligomer, and the content thereof is usually preferably 0.1 to 5 per 1000 parts of the acrylic polymer. is 0
．． There are 2 to 3 pieces. Further, the hydroxyl group in the acrylic polymer is a crosslinking functional group when the crosslinking agent is an amino resin and/or a bolysocyanate, and its preferable content is in the range of 10 to 100 KOHmg in terms of hydroxyl value. Furthermore, the carboxyl group is a crosslinking functional group when the crosslinking agent is an amino resin and/or a polyisocyanate, and if necessary, when the binder is an epoxy resin.
In addition, it acts as an internal catalyst for the crosslinking reaction when the crosslinking agent is an amino resin and/or polyisocyanate, and its preferred content is 2 to 80 KOH in terms of acid value. As mentioned above, hydroxyl groups and carboxyl groups coexist because the carboxyl group acts as an internal catalyst for the crosslinking reaction involving the hydroxyl group, and the crosslinking agent participates in both the hydroxyl and carboxyl functions. It is preferable to be there.

In that case, the content of both functional groups is the sum of the hydroxyl value and the acid value, which is 3.
A range of 0 to 12 skin OH bars is preferred. There are various methods to obtain such an acrylic polymer, but the most preferred method is to obtain a backbone polymer having at least one kind of functional group such as a hydroxyl group, a carpoxyl group, an acid hydroxide group, an epoxy group, etc. This is a method in which the functional group is reacted with a polymerizable monomer having mutually reactive functional groups in less than an equivalent amount.

Specific examples include a method in which an epoxy group-containing skeletal polymer is reacted with a polymerizable polybasic acid (hot water), a method in which a hydroxyl group-containing skeletal polymer is reacted with a polymerizable polybasic acid anhydride, and a method in which a hydroxyl group-containing skeletal polymer is reacted with a polymerizable polybasic acid anhydride. A method of reacting a polymerizable monomer containing a polyhydric hydroxyl group or a polymerizable monomer containing an epoxy group with a skeletal polymer containing (anhydride group); There are methods such as reacting monomers. Examples of (polyvalent) hydroxyl group-containing polymerizable monomers that are raw materials for producing acrylic polymers include 3-hydroxylethyl (meth)acrylate, 8-hydroxypropyl (meth)acrylate, and trimethylolpropane mo/(meth)acrylate. ) acrylate, glycerin mono(meth)acrylate, etc. Examples of polymerizable basic acids include (meth)acrylic acid, itaconic acid monomethyl ester, etc. Examples of polymerizable polybasic acids (anhydrides) include (anhydrous) maleic acid, fumaric acid, (anhydrous) itaconic acid, etc. Examples of epoxy group-containing polymerizable single island bodies include glycidyl (meth)acrylate, (meth)allyl glycidyl ether, etc. Examples of group-containing polymerizable monomers include 8
-Hydroxyethyl (meth)acrylate/toluene diisocyanate adduct, (meth)allyl alcohol/hexamethylene diisocyanate adduct, etc.

Examples of polymerizable monomers that can be used in combination with the functional group-containing polymerizable monomers to form a backbone polymer include methyl (meth)acrylate, ethyl (meth)acrylate, and propyl (meth)acrylate. , diethyl nitagonate, styrene, Q-methylstyrene, etc. The other component, the oligomer, has a polymerizable unsaturated group and has a number average molecular weight of 200 to 200.
It is 1000.

If the molecular weight is less than 20 degrees, it will evaporate during competitive curing and pollute the atmosphere, and if it exceeds 1000, the fluidity of the composition will be poor, making it difficult to achieve a high solid content, and it will also be hard to cure. This is not preferable because the coating film tends to have poor chemical resistance because it does not proceed sufficiently. The amount of polymerizable unsaturated groups is preferably in the range of 2 to 5 per molecule. It is better for the oligomer to contain a functionality that is mutually reactive with the crosslinking agent, but there is no big difference even if it does not. The oligomers include glycerin, trimethylolpropane, bentaerythritol, bentanediol, and 2,2-dimethyl-3-hydride.

Esters of 1 mole of a polyhydric alcohol such as xypropyl-272-dimethyl-3-hydroxypropionate and 2 or more moles of (meth)acrylic acid are suitable, but combinations of such esters with other oligomers such as: It does not prevent For example, 0, hydroxypropyl (meth)acrylate, 8-hydroxybutyl (meth)
It is an ester of a hydroxyl group-containing polymerizable monomer such as acrylate and (meth)acrylic acid. Also, polyhydric carboxylic acids (anhydrides) such as maleic acid (anhydride), itaconic acid (anhydride), phthalic acid (anhydride), trimellitic acid (anhydride), etc.
Ester of 2 moles or more of hydroxyl group-containing polymerizable monomer; hydroxyl group-containing polymerizable monomer, polyhydric carboxylic acid (anhydride), glycidyl (meth)acrylate, (meth)allyl glycidyl ether, etc. Reaction products of epoxy group-containing polymerizable monomers such as: esters of 1 mol of polycarboxylic acid (anhydride) and 2 or more mols of epoxy group-containing polymerizable monomers; polyhydric alcohols, polyhydric carboxylic acids ( reaction product of anhydride) and an epoxy group-containing polymerizable monomer: in addition to a hydroxyl group-containing polymerizable monoisland, active hydrogen-containing polymerizable monomers such as itaconic acid, N-methylol (meth)acrylamide, crotonic acid, etc. and reaction products with polyisocyanates such as toluene diisocyanate, hexamethylene diisocyanate, polyhydric alcohol adducts of these isocyanates;
Ester etc. of carboxyl group-containing polymerizable monomer and epoxy resin are also esters of polyhydric alcohol and (meth) as mentioned above.
The combined use of ester oligomers with acrylic acid is in no way prohibited.

As mentioned above, the crosslinking agent is an amino resin or a polyisocyanate, and each of these can be used alone or in combination.

Furthermore, if necessary, this does not preclude the use of an epoxy resin in combination with both of these crosslinking agents. Typical amino resins include those obtained by reacting one or more of melamine, urea, benzoguanamine, or acetoguanamine with formaldehyde, or by etherifying such reactants with lower alcohols. be.

On the other hand, typical polyisocyanates include various diisocyanates such as tolylene diisocyanate, xylyresodiisocyanate, diphenylmethane diisocyanate, and hexamethylene diisocyanate; polyhydric alcohol adducts of the diisocyanates (
For example, “Desmodule L” manufactured by Bayer in West Germany
J; or a polymer of the diisocyanate without a burette (for example, "Desmodur N" manufactured by the same company)
) etc.

Furthermore, representative examples of the above epoxy resins that can be used in combination with amino/resins and polyisocyanates include "Epicort 828, 1001 or 1004" (a product of Shell, Netherlands) or "Epicron 83li 850 or 1050" Bisphenol A/Epichlorohydrin type such as Nippon Ink Kagaku Kogyo (product name); or polyhydric alcohol/Epichlorohydrin type such as glycerin diglycidyl ether, neobentyl glycol glycidyl ether or trimethylolpropane triglycidyl ether.

The composition of the present invention consists of: (1) 20 to 80% acrylic polymer, preferably 40 to 60%, 'B' 10% to 4 oligomer;
0%, ni} It is composed of 10 to 40% of the firewood and groove agent.

This composition is crosslinked and cured by heating, usually to 130-270° C., in the presence of a polymerization catalyst and, if necessary, other catalysts. Examples of the polymerization catalyst include cumene hydroperoxide, ditertiary butyl peroxide, and azobisisobutyronitrile. Examples of other catalysts that may be used as necessary include hydrochloric acid, sulfuric acid, para-toluenesulfonic acid, etc. for amino resins, and triethylamine, tributylamine, etc. for epoxy resins and polyisocyanates. The present invention will be explained below according to examples.

Parts in the text indicate parts by weight. Reference Example 1 48 parts of butyl acrylate, 2 parts of acrylic acid, 1 part of n-dodecylmercaptan, 14 parts of azopisisobutyronitrile and 200 parts of ethyl acetate were heated to 80 qo for 15 hours.

Next, after removing 175 parts of ethyl acetate, 1 part of triethylamine, 0.5 parts of hydroquinone and 28 parts of glycidyl methacrylate were added and heated to 9 Pc for 3 hours to give a molecular weight of 4500 and an unsaturated group content of 0. 3 seal/1
000 g, acrylic polymer solution 1 having a hydroxyl value of 20.6 and an acid value of 21.5 was obtained. Reference example 2 Butyl acrylate, 13 parts of 8-hydroxyethyl methacrylate, 1 part of n-dodecyl mercaptan, 15 parts of azobisisobutyronitrile, 5 parts of penzoyl peroxide, and 200 parts of ethyl acetate in 80 oo It was heated for 1 hour.

Next, after removing 1700 parts of ethyl acetate, 49.5 parts of maleic anhydride was added and heated to 80 qo for 1 hour, resulting in a molecular weight of 4000 and an unsaturated group content of 0.75 pieces/100.
A female solution 2 of an acrylic polymer having a hydroxyl value of 42 and a hydrophilic acid value of 425 was obtained. Reference Example 3 48 parts of butyl acrylate, 13 parts of P-hydroxyethyl methacrylate, 1 part of n-dodecylmercabutane, 16 parts of azobisisobutyronitrile, 5 parts of pensol peroxide, and 200 parts of ethyl acetate. 80o
The mixture was heated for 1 hour at a temperature of

Next, 1,680 parts of ethyl acetate was removed by distillation, and then 49.5 parts of maleic anhydride was added, and the mixture was heated to 80°C for 1 hour, and then 0.5 parts of hydroquinone, 1 part of triethylamine, and 6 parts of glycidyl methacrylate were added, and 95q.
o for 3 hours to give a molecular weight of 4500 and an unsaturated group content of 1.
．． A solution 3 of an acrylic polymer having a solidity of 3/100, a hydroxyl value of 71.8, and an acid value of 6.1 was obtained. Example 1 100 parts of Solution 1 obtained in Reference Example 1, 4 parts of trimethylolpropane trimethacrylate, 3 parts of hexamethoxymethylmelamine, and 9 parts of titanium oxide were kneaded in a ball mill, and then diluted with xylol. A white paint with a solid content of 73% was obtained.

To this paint, 1% ditertiary butyl peroxide and 1% paratoluene sulfonic acid were added and applied to a metal plate with a 6 mil applicator and applied at 150 oo for 30 minutes.
Example 2 100 parts of solution 2 obtained in Reference Example 2, 4 parts of neobentyl glycol dimethacrylate, 3 parts of hexamethoxymethylmelamine, and 9 parts of titanium acetate were milled in a ball mill, and then A white paint with a solids content of 76% was obtained by diluting with xylol.

The same procedure as in Example 1 was carried out by adding 1% of cumene hydroperoxide and 1% of para-toluenesulfonic acid to this paint. Example 3 Obtained from 100 parts of solution 3 obtained in Reference Example 3, 1 mole of 2,2-dimethyl-3-hydroxypropyl-2,2-dimethyl-3-hydroxypropionate and 2 moles of acrylic acid. The three base parts of polyester oligomer and the nine anchor parts of titanium oxide are milled in a ball mill, and then
Add 40 parts of "Desmodur N" [biuret form of hexamethylene diisocyanate (water adduct of hexamethylene diisocyanate) manufactured by Bayer AG, West Germany],
It was then diluted with xylene to obtain a white paint with a solids content of 70%.

Ditertiary butyl peroxide was then added to this paint at a rate of 1% and applied to a metal plate with a 6 mil applicator and then baked at 14,000 for 20 minutes.

Comparative Example 1 130 parts of Solution 3 obtained in Reference Example 3, 5 parts of the polyester oligomer used in Example 3, and 9 parts of titanium oxide were kneaded in a ball mill, and then diluted with xylene to obtain a mixture with a solid content of 70%. A white paint was obtained.

Using this paint, the same procedure as in Example 3 was carried out. Example 4 100 parts of solution 1 obtained in Reference Example 1, 3 parts of trimethylolpropane trimethacrylate, 1 part of neobentylglycol dimethacrylate, 3 parts of hexamethoxymethylmelamine, and 9 parts of titanium oxide. After kneading Ikarito in a ball mill, it was diluted with xylene to obtain a white paint with a solid content of 82%.

Apply this paint to a galvanized iron plate with a percoater,
0 for 1 minute. Example 5 100 parts of Solution 2 obtained in Reference Example 2, 3 parts of bentaerythritol tetramethacrylate, 1 part of neobentyl glycol dimethacrylate, 3 parts of hexamethoxymelamine, and 90 parts of titanium oxide. After kneading the mixture in a Pall mill, the mixture was diluted with xylene to obtain a white paint with a solid content of 85%.

Using this paint, the same procedure as in Example 4 was carried out. Example 6 100 parts of Solution 3 obtained in Reference Example 3, 2 parts of the polyester oligomer used in Example 3, 3 parts of trimethylolproban trimethacrylate, 2 parts of hexamethoxymethylmelamine, and Nine titanium oxide particles were mixed in a ball mill and diluted with xylene to obtain a white paint with a solid content of 84%.

Using this paint, the same procedure as in Example 4 was carried out. Example 7 100 parts of solution 2 obtained in Reference Example 2, 4 parts of trimethylolpropane triacrylate, 15 parts of glycerin diglycidyl ether, 3 parts of hexamethoxymethylmelamine, and 100 parts of titanium oxide. The mixture was milled in a ball mill and diluted with xylene to obtain a white paint with a solid content of 78%.

This paint contains 1% cumene hydroperoxide and 2-
0.1% methylimidazole was added and applied to a metal plate with a 6 mil applicator and baked at 150°C for 30 minutes.
Comparative Example 2 130 parts of Solution 3 obtained in Reference Example 3, 3 parts of the polyester oligomer used in Example 3, 4 parts of trimethylolpropane trimethacrylate, and 9 parts of titanium oxide were blended and kneaded in a ball mill. A white paint with a solids content of 80% was obtained by diluting with xylol.

Using this paint, the same procedure as in Example 4 was carried out. Tables 1 and 2 show the performance of the coating obtained in each of the above examples. 1st
table

Claims (1)

[Claims] 1 (A) 20 to 80% by weight of an acrylic polymer having a number average molecular weight of 1,500 to 6,000 and having hydroxyl and/or carboxyl groups in addition to polymerizable unsaturated groups, (B) polyhydric alcohol and (meth)acrylic acid 10 to 40% by weight of an oligomer having a polymerizable unsaturated group having a number average molecular weight of 200 to 1000, and (C) an amino resin and/or a polyisocyanate crosslinking agent of 10 to 40% by weight. A high solids coating composition comprising as an ingredient.