JPS6157348B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a coating composition, and more particularly to a room temperature curing or low temperature baking type alkyd resin or vinyl polymer coating composition.

The coating composition of the present invention can be applied to substrates (steel, wood).
The present invention provides a coating film that has excellent adhesion to the substrate, high surface hardness, flexibility, and excellent water resistance and chemical resistance.

Conventionally, room-temperature curing or low-temperature baking type coating compositions include oil-modified alkyd resins, amino alkyd resins, epoxy resins typified by glycidyl ether derived from bisphenol A and epichlorohydrin, urethane resins, and urethane-modified resins. Various resins such as acrylic resins are used, but oil-modified alkyd resins have the disadvantage of low coating film hardness, epoxy resins require the addition of amine-based or acid anhydride-based hardeners, and urethane resins With resin, there is a small amount of residual isocyanate, so care must be taken to protect the skin and exhaust air during painting, and the drying temperature is relatively high and the drying time is long.
Each resin has its own disadvantages, such as aminoalkyd resins, which generate formaldehyde which is harmful to the human body and has an irritating odor during baking, which is undesirable from the standpoint of work or environmental hygiene. It does not generate formaldehyde, has low toxicity to the human body, and has excellent water and chemical resistance when baked at room temperature or low temperature for a short time.
Coating compositions having surface hardness and the like are highly desired in the paint and coating industry.

The present inventors have investigated a coating composition that does not generate formaldehyde, which has a harmful and irritating odor as described above, and does not have the odor peculiar to amines, and has sufficiently excellent coating performance. By adding a polyglycidylamine compound having 4 epoxy groups in one molecule to an acid-valued resin,
The present invention has been accomplished by discovering an industrially useful coating composition that can be cured at room temperature or at low temperature without requiring the addition of an amine or acid anhydride curing agent.

The present invention relates to an alkyd resin having a relatively high acid value and having a free carboxyl group in the side chain or terminal of the molecule,
A polyglycidylamine compound having substantially four epoxy groups in one molecule is added to a vinyl copolymer, a mixture thereof, or a modified product as a crosslinking agent.

That is, the present invention involves adding a polyglycidylamine compound having substantially four epoxy groups in one molecule to an alkyd resin and/or vinyl copolymer having an acid value of 20 to 150 and having free carboxyl groups in the molecule. The present invention relates to a coating composition formed by blending.

The alkyd resin having a relatively high acid value in the composition of the present invention has an average molecular weight of 500 to 10,000 and an acid value of 20 to 10,000.
150, preferably 40 to 100 are used.

If the resin acid value is lower than 20, the number of crosslinking points in the coating film will be small, making it impossible to obtain a network structure sufficient to exhibit balanced coating performance, which is undesirable. In addition, if the resin acid value is higher than 150, the corrosiveness of the resin liquid to metal materials will increase.
Furthermore, it is undesirable because its pot life is extremely short and it makes painting work difficult. For the synthesis of such alkyd resins, conventionally known methods for obtaining high acid value type alkyd resins are applied. For example, one or more polyhydric carboxylic acids and one or more polyhydric alcohols, After reacting with an excess of polyhydric alcohol until the acid value becomes 20 or less, a polyfunctional polycarboxylic acid (for example, trimellitic anhydride) is added.
A stepwise reaction method is preferred because it allows the desired high acid value alkyd resin to be easily synthesized.

The polyhydric carboxylic acids and polyhydric alcohols used in the production of the above-mentioned alkyd resins are conventionally used in the production of the alkyd resins, and examples of the polyhydric carboxylic acids include phthalic anhydride, isophthalic acid, terephthalic acid, These lower alkyl esters, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, tetrabromophthalic anhydride, tetrachlorophthalic anhydride, hectic anhydride, maleic anhydride, fumaric acid, itaconic acid, succinic acid, succinic anhydride, adipic acid, Examples include divalent carboxylic acids such as azelaic acid and sebacic acid, trivalent carboxylic acids such as trimellitic anhydride, trimellitic acid, methylcyclohexenetricarboxylic acid, and pyromellitic anhydride.

Examples of polyhydric alcohols include ethylene glycol, propylene glycol, 1.3
- Dihydric alcohols such as butylene glycol, 1,6-hexanediol, diethylene glycol, dipropylene glycol, neopentyl glycol, triethylene glycol, trihydric alcohols such as glycerin, trimethylolethane, trimethylolpropane, pentaerythritol , dipentaerythritol, sorbitol,
Examples include tetrahydric or higher alcohols such as diglycerol.

Additionally, in some cases, the alkyd resin may be made from oils such as linseed oil, tung oil, dehydrated castor oil, soybean oil, safflower oil, coconut oil, castor oil, linseed oil fatty acids, coconut oil fatty acids, tall oil fatty acids, etc. It is also possible to modify the oil using fatty acids. In addition, modified alkyd resins modified with rosin, phenols, vinyl compounds, etc. can also be used.

Furthermore, as described above, the alkyd resin used in the present invention is an alkyd resin with a relatively high acid value of 20 to 150, unlike ordinary alkyd resins, but the alkyd resin has free hydroxyl groups. It is almost impossible to have no hydroxyl groups, that is, to reduce the hydroxyl group to zero, and the alkyd resin used in the present invention preferably has a hydroxyl value of 50 or less, and more preferably 40 or less. is more suitable.

Next, the vinyl copolymer used in the composition of the present invention has a free carboxyl group in its molecule, has an average molecular weight of 3,000 to 100,000, and has an acid value of 20 to 150 as described above. be done.

In this way, vinyl copolymers having free carboxyl groups in the molecule are produced by combining one or more polymerizable or copolymerizable unsaturated carboxylic acids with one or more vinyl monomers in the presence of a polymerization initiator. It can be obtained by copolymerizing the following. This copolymerization is usually carried out by solution polymerization, but other methods include bulk polymerization,
Suspension polymerization or the like can also be used.

Examples of polymerizable or copolymerizable unsaturated carboxylic acids include acrylic acid, methacrylic acid, maleic acid, maleic anhydride, fumaric acid, itaconic acid, and citraconic acid, and one or more of these may be used as the desired acid. It is used as appropriate to have a value.

Examples of vinyl monomers include acrylates such as methyl acrylate, ethyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, 2-ethylhexyl acrylate, lauryl acrylate, methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, 2-
Methacrylates such as ethylhexyl methacrylate and lauryl methacrylate, styrene,
Examples include α-methylstyrene, vinyltoluene, vinyl acetate, acrylonitrile, methacrylonitrile, divinyl ether, and two or more of these vinyl monomers are usually used.

Furthermore, as the polymerization initiator, conventionally known ones are used, such as benzoyl peroxide,
tert-butyl peroxybenzoate, di-tert-
Peroxides such as butyl peroxide, azobisisobutyronitrile, etc. are used.

In addition, conventionally known solvents are used for solution polymerization, such as aromatic hydrocarbons such as toluene and xylene, alcohols such as propanol and butanol, and esters such as ethyl acetate and butyl acetate. , ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, and ethylene glycol monobutyl ether.

The alkyd resin or vinyl copolymer having a relatively high acid value and having a free carboxyl group in the molecule used in the composition of the present invention can be obtained by appropriately using the raw material components as described above. The combination of these raw materials, the proportions of the composition components, etc. are appropriately selected depending on the purpose of the product, the method of use, etc., and in order to provide suitable coating film performance.

Next, examples of the polyglycidylamine compound having substantially four epoxy groups in one molecule, which is another component of the composition of the present invention, include N.
N・N′・N′-tetraglycidylxylylenediamine, N・N・N′・N′-tetraglycidylbisaminomethylcyclohexane, N・N・N′・
N'-tetraglycidyl-3-aminomethyl-
3,5,5-trimethylcyclohexylamine,
Or N.N.N'.N'-tetraglycidyldiaminodiphenylmethane is exemplified. Such polyglycidylamine compounds are conventionally known per se.

The amount of the polyglycidylamine compound blended in the composition of the present invention is 0.8 to 1.2 equivalents, preferably 0.9 to 1.1 equivalents of epoxy groups per equivalent of carboxyl groups in the alkyd resin or vinyl polymer of the present invention. It is. If a polyglycidylamine compound is added in an amount less than 0.8 equivalents as an epoxy group, the crosslinking reaction between the resins will not be sufficiently carried out. When blended, the epoxy group remains unreacted, and in either case, this leads to a decrease in coating film performance, which is undesirable from a practical standpoint.

The polyglycidylamine compound used in the present invention is one having substantially four epoxy groups as described above, but it may contain two to three epoxy groups as long as it does not impede the intended purpose and effect of the present invention. A polyglycidylamine compound having an epoxy group of
It is also possible to use a mixture of ordinary epoxy resins.

When coating a substrate (steel plate, wood) with the composition of the present invention, the viscosity of the coating is adjusted to an appropriate level using a diluting solvent, and then the coating is applied by a known method such as spraying, dipping, or brushing. As this diluting solvent,
For example, aromatic hydrocarbons such as toluene and xylene, esters such as ethyl acetate and butyl acetate, ketones such as methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, etc. glycol ethers,
Examples include alcohols such as isopropyl alcohol and n-butyl alcohol, and one or a mixture of two or more of these may be used.

The composition of the present invention further includes pigments, as desired.
Additives such as fillers, flame retardants, and coating surface improvers can also be added and blended.

Next, the present invention will be specifically explained with reference to Examples and Comparative Examples. In the examples, "parts" refer to parts by weight.
"%" indicates weight %.

Example 1 300 parts of neopentyl glycol, 100 parts of trimethylolpropane, 50 parts of pentaerythritol, 535 parts of isophthalic acid, Charge 143 parts of adipic acid and gradually raise the temperature inside the reactor under a nitrogen gas stream.
After raising the temperature to 240°C, let the reactants react at the same temperature until the acid value of the reactants reaches 20 or less, then lower the temperature inside the container to 180°C or less, and add 44 parts of trimellitic anhydride. After adding trimellitic anhydride, the mixture was reacted at 180°C for about 30 minutes to obtain an oil-free alkyd resin having a resin acid value of 40. The molecular weight of this resin was measured by vapor pressure osmosis method and was found to be 1980.

The resin was diluted to a solid content concentration of 65% using a mixed solvent of xylene and butanol 3:1 (weight ratio) to obtain a varnish with a Gardner implied viscosity of Z ₁ -Z ₂ and a Gardner color number of 1. .

Next, for 93 parts of solid content of the alkyd resin, N.
After adding 7 parts of N・N′・N′-tetraglycidyl metaxylylene diamine (approximately 1 equivalent of epoxy group per 1 equivalent of carboxyl group), xylene, ethylene glycol monobutyl ether,
Diluted with 145 parts of a mixed solvent of isopropyl alcohol and methyl ethyl ketone (weight ratio 70:5:20:5) to a viscosity of 20 seconds in a #4 food cup, non-volatile content: 34
% transparent varnish was obtained. Apply this clear varnish to Bonderite #144 treated steel plate (0.4mm thick).
After spray painting to a thickness of 20 to 30 micrometers, it was baked at 80°C for 20 minutes to obtain a smooth coating with a good appearance. Paint film performance is pencil hardness 2H,
Passed bending test 2mmφ, cross cut 100/100
(Removal of cellophane tape) and extrusion of Erichsen 8 mm, all test results were good.

The varnish was applied to a polyester film and baked under the same conditions as for the steel plate, then the coating was peeled off from the polyester film, and a large excess of acetone was added and boiled for 7 hours for extraction. As a result, the acetone extraction residue (gel fraction) was 90%, indicating that crosslinking was sufficiently performed.

Example 2 1000 parts of a mixed solvent of toluene/butanol = 3/1 (weight ratio) was charged into a reactor equipped with a thermometer, thermocouple, stirring rod, nitrogen gas inlet, and dropping funnel, and the inside of the flask was flushed with nitrogen gas. Replace. After purging with nitrogen gas, raise the temperature until the solvent in the system boils, and add 300 ml of methyl methacrylate, which had been weighed out in advance, to a separate container.
parts, 50 parts of styrene, 50 parts of ethyl methacrylate,
A mixed solution of 400 parts of butyl acrylate, 100 parts of lauryl methacrylate, 100 parts of methacrylic acid, and 10 parts of tert-butyl peroxybenzoate was gradually added dropwise from the dropping funnel over a period of 4 hours. After dropping, react at reflux temperature for 6 hours to reduce non-volatile content to 52%.
Reaction rate 98%, Gardner bubble viscosity _Z3 - _Z4 , Gardner color number 1 or less, acid value 65, average molecular weight by GPC (gel permeation chromatography)
A carboxylic acid-containing acrylic resin solution of 41500 was obtained.

Next, for 90 parts of the solid content of the acrylic resin solution, N・N・N′・N′-tetraglycidyl-1・3-
After adding 10 parts of bisaminomethylcyclohexane (approximately 1 equivalent of epoxy group per 1 equivalent of carboxyl group), 260 parts of the diluting solvent used in Example 1 (mixed solvent of xylene, ethylene glycol monobutyl ether, isopropyl alcohol, and methyl ethyl ketone) was added. A clear varnish with a viscosity of 16 seconds in a #4 food cup and a non-volatile content of 22% was obtained.

The varnish was applied to a steel plate in the same manner as in Example 1, and then baked at 60°C for 20 minutes to form a coating film. The coating film is smooth, has a good appearance, and has a pencil hardness of
3H, bending test 2mmφ passed, cross cut 100/1
00 (cellotape peeling), Erichsen 8 mm extrusion passed. Furthermore, when the baked coating film was immersed in tap water at room temperature for one week, there was no decrease in gloss and no blistering occurred. 5 different baked coatings
% caustic soda solution and gasoline at room temperature for 24 hours, no abnormality was observed in the coating film.

Separately, the varnish was applied to a 0.3 mm plywood board and then baked at 60°C for 20 minutes.The coating had good adhesion to the base material (Crosscut 100/
100, peeled off with cellophane tape).

In addition, when the varnish was applied to a polyester film and baked at 60°C for 20 minutes and 50°C for 30 minutes, and after application, it was left at room temperature for 4 days and 7 days to form a coating film, and the same method as in Example 1 was performed. As a result of acetone extraction, the gel fraction was 91.1% and 91.1%, respectively.
%, 90.6% and 91.6%.

Example 3 Tetraglycidyl-3-aminomethyl-3.5.5-trimethylcyclohexylamine was added to 87 parts (solid content) of the high acid value acrylic resin obtained in Example 2.
After adding 13 parts (approximately 1 equivalent of epoxy group to 1 equivalent of carboxyl group), it was diluted with 265 parts of the same diluting solvent used in Example 1, and the viscosity was 16 seconds in the food cup #4, and the non-volatile content was 21%. We got a transparent varnish.

The varnish was applied to a steel plate in the same manner as in Example 1, and then baked at 60°C for 20 minutes to obtain a smooth coating film with a good appearance. The coating film had a pencil hardness of 2H, passed a bending test of 2 mmφ, passed a crosscut test of 100/100 (removal with Sellotape), and passed an Erichsen extrusion test of 8 mmφ, showing good performance.

Further, as a result of measuring the gel fraction in the same manner as in Example 1, the gel fraction was 90.8%.

Comparative Example 1 82 parts (solid content) of the high acid value acrylic resin obtained in Example 2 was mixed with 18 parts of Epicote #828 (trade name: diglycidyl ether of bisphenol A, manufactured by Ciel Chemical Co., Ltd.) (1 equivalent of carboxyl group). After adding approximately 1 equivalent of epoxy group to the polyester film, a coating film was formed on a polyester film in the same manner as in Example 1, and acetone extraction was performed in the same manner as in Example 1.
The gel fraction was as low as 0.3%, with no crosslinking occurring at all.

Comparative Example 2 After adding 10 parts of diglycidylaniline (approximately 1 equivalent of epoxy group to 1 equivalent of carboxyl group) to 90 parts (solid content) of the high acid value acrylic resin obtained in Example 2, the same procedure as in Example 1 was carried out. Acetone extraction was performed. The gel fraction was only 0.1%, and no crosslinking occurred at all.

Comparative Example 3 After adding 12 parts of triglycidylmethaminophenol (approximately 1 equivalent of epoxy group to 1 equivalent of carboxyl group) to 88 parts (solid content) of the high acid value acrylic resin obtained in Example 2, Example 1 Acetone extraction was performed in the same manner as above. The gel fraction was only 19%, and the degree of crosslinking was extremely low.

Claims (1)

[Claims] 1. A polyglycidylamine compound having substantially 4 epoxy groups in one molecule is blended with an alkyd resin and/or vinyl copolymer with an acid value of 20 to 150 containing free carboxyl groups in the molecule. A coating composition consisting of: