JPS629264B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to coating compositions for paints. More specifically, (a) an oil-free alkyd resin containing polyhydric phenol carboxylic acid as one component, and (b)
Coating composition for paint with excellent water resistance and corrosion resistance, consisting of a crosslinkable copolymer resin obtained from a monomer mixture containing an N-alkoxymethylated monomer of α/β-monoethylenically unsaturated carboxylic acid amide relating to things. In recent years, oil-free alkyd resins have been gaining popularity due to their high coating film hardness and flexibility, which is difficult to achieve with oil-modified alkyd resin compositions, as well as their excellent gloss, weather resistance, stain resistance, and chemical resistance. , automobiles, home appliances, machinery, steel furniture, satsushi,
It has come to be widely used as a paint resin for cans, colored galvanized iron, etc. However, in these fields, in addition to the above-mentioned coating film performance, high water resistance, corrosion resistance, etc. are required, so there has been a problem that oil-free alkyd resin alone cannot sufficiently satisfy the required performance. Further, since coating films in such fields are required to have both flexibility and corrosion resistance, the use of epoxy esters and the like has been considered, but the corrosion resistance has not always been sufficient. On the other hand, there is an increasing trend in the use of galvanized steel sheets, aluminum, etc. as materials for the objects to be coated, and accordingly, coatings are required to have considerably high adhesion and corrosion resistance to such materials. In addition, some examples have long been known in which phenolcarboxylic acids and the like have been blended into various paints in order to improve the corrosion resistance of paint films. For example, RN
Solvents in which catechol, pyrogal, gallic acid, or gallic acid esters are introduced into vegetable oils, fatty acid esters, alkyd resins, vegetable oil-modified epoxy ester resins, or vegetable oil-modified polyamide resins using catalysts such as metal alkoxides, as described by Faulkner et al. One-component paints have been developed. (For example, UK Patent No. 1045118, US Patent No.
No. 3304276, No. 3321320, Oil and Color
Journal of the Chemist's Association
Oil and Color Chemist′s Association Volume 50,
See p. 524 (1967), etc. ) However, these resins could not be applied to the above-mentioned industrial paint field, which requires a high level of appearance and film performance. The present invention aims to improve or solve the above problems. Namely, (a) an oil-free alkyd resin containing polyhydric phenol carboxylic acid as one component, and (b) α/β-
It consists of a crosslinkable copolymer resin obtained from a monomer mixture containing an N-alkoxymethylated monomer of monoethylenically unsaturated carboxylic acid amide, and has high hardness and flexibility, Furthermore, the present invention provides a coating composition for paint that provides a coating film having excellent water resistance and corrosion resistance. The present invention provides (a) polyhydric phenol carboxylic acid having a hydroxyl group and a carboxyl group bonded to the same benzene ring.
~15% by weight reacted oil-free alkyd resin with an acid value of 50KOHmg/g or less and a hydroxyl value of 50~250KOHmg/g...5~95% by weight, and (b)(i) N-alkoxymethylated monomer of saturated carboxylic acid amide
5-30% by weight (ii) α/β-monoethylenically unsaturated carboxylic acid
...0.5 to 10% by weight (iii) A monomer mixture consisting of 60 to 90% by weight of a copolymerizable α/β-monoethylenically unsaturated monomer other than the above (i) and (ii) A coating composition for a paint comprising 95 to 10% by weight of a crosslinkable copolymer resin obtained from the following. The oil-free alkyd resin as component (a) used in the present invention contains polyvalent phenol carboxylic acid and polyvalent carboxylic acid, and if necessary, monovalent carboxylic acids other than the polyvalent phenol carboxylic acid and polyvalent carboxylic acid. It is obtained by an esterification reaction with alcohol. The coating film formed from the composition of the present invention containing the resin as one component has high hardness and flexibility, as well as excellent water resistance and corrosion resistance.
It has the characteristic that it has excellent adhesion not only to steel plates, but also to materials such as galvanized steel plates, aluminum plates, and stainless steel plates. In order to exhibit the above characteristics, it is essential to use polyhydric phenol carboxylic acid as the carboxylic acid component of the oil-free alkyd of the present invention. The component is 1 to 15 of the oil-free alkyd components.
The reaction is carried out in a proportion by weight, preferably 2 to 10% by weight. In the above range, if the content of this component is less than 1% by weight, the effect of improving the water resistance and corrosion resistance of the coating film formed using the crosslinkable copolymer resin after synthesizing the oil-free alkyd resin will be reduced. I don't get much. On the other hand, if the above-mentioned component is used in an amount exceeding 15% by weight, the resulting cured coating film becomes brittle and a decrease in weather resistance is observed. In addition, since a substantially sufficient effect can be obtained within 15% by weight, it is economically undesirable to use significantly more than 15% by weight. The polyhydric phenol carboxylic acid is 2.3
-dioxybenzoic acid, 2,4-dioxybenzoic acid, 2,5-dioxybenzoic acid, 2,6-dioxybenzoic acid, 3,4-dioxybenzoic acid (protocatechuic acid), 3,5-dioxybenzoic acid, 3・
4,5-trioxybenzoic acid (gallic acid), 2.
Examples include 3,4-trioxybenzoic acid. These may be used alone or in a mixture of two or more. The acid value of the oil-free alkyd resin used in the composition of the present invention is 50 KOHmg/g or less (resin solid content: hereinafter, all acid values in the present invention are expressed in the same way), and the hydroxyl value is 50 to 250 KOHmg/g. (Resin solid content: hereinafter, all hydroxyl values in the present invention are expressed in the same way). Also, the molecular weight is the weight average molecular weight.
A number of about 3,000 to 150,000 is preferable. The weight average molecular weight was measured by gel permeation chromatography (Model A801, manufactured by Toyo Soda Co., Ltd.).
(Hereinafter, the weight average molecular weight in the present invention is measured in the same manner.) The acid value of the oil-free alkyd resin is
If it exceeds 50 KOHmg/g, the alkali resistance etc. of the resulting coating film will be significantly reduced. On the other hand, if the hydroxyl value is less than 50KOHmg/g, there will be less remaining hydroxyl groups available for reaction with the crosslinkable copolymer resin, the crosslinking reaction will be insufficient, and the coating performance will deteriorate. Undesirable. On the other hand, the hydroxyl value
If it exceeds 250 KOHmg/g, it is not preferable because the water resistance of the resulting coating film tends to decrease due to an increase in the number of polar groups. If the weight average molecular weight of the oil-free alkyd resin is lower than 3000, the properties of the oil-free alkyd resin cannot be fully exhibited. Moreover, if it exceeds 150,000, the viscosity of the oil-free alkyd resin solution becomes high, which impairs coating workability, so both are not very preferable. Polyvalent carboxylic acids and monovalent carboxylic acids other than polyvalent phenolcarboxylic acid used in the synthesis of oil-free alkyd resin used in the present invention include, for example, phthalic acid (anhydride), isophthalic acid, and trimellitic acid (anhydride). , pyromellitic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, methyltetrahydrophthalic anhydride, methylhexahydrophthalic anhydride, hymic anhydride, succinic anhydride, adipic acid , sebacic acid, benzoic acid, paratertiary butylbenzoic acid, and the like. These may be used alone or in a mixture of two or more.
Furthermore, monovalent fatty acids and the like can also be used if necessary. Furthermore, polyhydric alcohol components used in oil-free alkyd resin synthesis include ethylene glycol, diethylene glycol, propylene glycol, neopentyl glycol, dipropylene glycol, glycerin, trimethylolethane, trimethylolpropane, pentaerythritol, and dipentaerythritol. , butylene glycol, pentanediol, trimethylpentanediol, hexanediol, 1,4-cyclohexanedimethanol, (hydrogenated) bisphenol A, etc., and these are used alone or as a mixture of two or more. If necessary, a glycidyl ester of tertiary saturated fatty acid (Cardular E: trade name manufactured by Shell Chemical Co., Ltd.) may be used in combination. The oil-free alkyd resin in the present invention is
It can be obtained by esterifying the polyvalent phenol carboxylic acid, polyvalent carboxylic acid, and, if necessary, other monovalent carboxylic acids and polyhydric alcohols by a known method. That is, there is no particular restriction on the reaction method. Generally, at a temperature of about 200 to 250℃ for about 6 to 12 hours,
The reaction may be continued until a predetermined acid value is reached. The oil-free alkyd resin of component (a) thus obtained is mixed with the crosslinkable copolymer resin to obtain the composition of the present invention. When the oil-free alkyd resin of the present invention is solid at room temperature, it can be used after being diluted with an organic solvent. Examples of the organic solvent include methanol, ethanol, n-propanol, isopropanol,
Alcohols such as n-butanol: Ethylene glycol derivatives such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, ethylene glycol monoethyl ether acetate: diethylene glycol monomethyl ether,
Diethylene glycol derivatives such as diethylene glycol monoethyl ether and diethylene glycol monobutyl ether; Esters such as methyl acetate, ethyl acetate, and butyl acetate; Aromatic hydrocarbons such as toluol, xylol, and aromatic petroleum naphtha; acetone, methyl ethyl ketone, methyl isobutyl ketone, etc. Examples include ketones. These organic solvents can be used alone or as a mixture of two or more. Next, in the present invention, a mixture of α and β-monoethylenically unsaturated monomers, which is the component (b) constituting the crosslinkable copolymer resin, is used. As its (i) component, α・
β-monoethylenically unsaturated carboxylic acid amide N
- Using alkoxymethylated monomers as essential components. As mentioned above, component (b) is necessary for the crosslinking reaction with the oil-free alkyd resin. The N-alkoxymethylated monomer of α/β-monoethylenically unsaturated carboxylic acid amide, which is the component (b)(i), is 5 to 30% by weight, preferably 10 to 25% by weight in the crosslinkable copolymer resin. react at a rate of If the content of this component is 5% by weight or less, the crosslinking reaction with the oil-free alkyd resin will be insufficient, resulting in a decrease in solvent resistance. Moreover, if it exceeds 30% by weight, gelation occurs during production of the crosslinkable copolymer resin, which is not preferable. Specific examples of the components include N-methoxymethyl (meth)acrylamide, N-ethoxymethyl (meth)acrylamide, N-n-propoxymethyl (meth)acrylamide, N-isopropoxymethyl (meth)acrylamide, N-n -butoxymethyl(meth)acrylamide, N-sec-
Butoxymethyl (meth)acrylamide, N-t
-butoxymethyl(meth)acrylamide, N-
Examples include N-alkoxymethylated products of α/β-monoethylenically unsaturated carboxylic acid amides such as isobutoxymethyl (meth)acrylamide; or N-methylolated products thereof. These may be used alone or as a mixture of two or more. Further, as a component of the crosslinkable copolymer resin used in the present invention, (b)(ii) α/β-monoethylenically unsaturated carboxylic acid is used in a range of 0.5 to 10% by weight.
The monomer has the effect of improving the compatibility between the crosslinkable copolymer resin and the oil-free alkyd resin and promoting the crosslinking reaction. Within the above range, if the amount is less than 0.5% by weight, the effect will be weakened, while if it exceeds 10% by weight, the performance of the cured coating film will deteriorate, which is not preferable. Specific examples of the components include acrylic acid, methacrylic acid, crotonic acid, itaconic acid, maleic acid,
Examples include fumaric acid, and these may be used alone or as a mixture of two or more. Furthermore, as a raw material for the crosslinkable copolymer resin used in the present invention, a copolymerizable (b)(iii) α/β-monoethylenically unsaturated monomer other than the above is used in a proportion of 60 to 90% by weight. Make it react. Specific examples of the component include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate,
Isopropyl (meth)acrylate, n-butyl (meth)acrylate, sec-butyl (meth)acrylate, t-butyl (meth)acrylate, isobutyl (meth)acrylate, n-hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate Acrylate, n-octyl (meth)acrylate, lauryl (meth)acrylate, tridecyl (meth)acrylate, stearyl (meth)acrylate
Alkyl esters of acrylic acid or methacrylic acid such as acrylate; 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3 -Hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 5-hydroxypentyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, neopentyl glycol mono(meth)acrylate, 3-butoxy-2- Hydroxyalkyl esters of α/β-monoethylenically unsaturated carboxylic acids such as hydroxypropyl (meth)acrylate, 2-hydroxy-1-phenylethyl (meth)acrylate, polypropylene glycol mono(meth)acrylate, and glycerin mono(meth)acrylate. Class; Other N・
Fumaric acid dialkyl esters such as N'-dimethylaminoethyl (meth)acrylate, glycidyl (meth)acrylate, cyclohexyl (meth)acrylate, phenyl methacrylate, benzyl methacrylate, dibutyl fumarate, styrene, vinyltoluene , α-methylstyrene, (meth)acrylonitrile, and vinyl acetate. The above-mentioned monomers may be used alone or in an appropriate combination depending on the intended use and application of the coating composition. The crosslinkable copolymer resin which is component (b) of the present invention is produced by conventional solution polymerization. The polymerization solvent used in the solution polymerization method is not particularly limited, but alcohols such as methanol, ethanol, n-propanol, and isopropanol; ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, ethylene glycol mono Ethylene glycol derivatives such as ethyl ether acetate;
Diethylene glycol derivatives such as diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, and diethylene glycol monobutyl ether; aromatic hydrocarbons such as triol, xylol, and aromatic petroleum naphtha; esters such as methyl acetate, ethyl acetate, butyl acetate; methyl ethyl ketone, methyl isobutyl Ketones such as ketones are used. These polymerization solvents may be used alone or in an appropriate combination of two or more. Examples of the polymerization initiator used include benzoyl peroxide, t-butyl perbenzoate, t-butyl peroxide, hydroperoxide, cumene hydroperoxide, di-t-butyl peroxide, and t-butyl peroxide. Examples include organic peroxides such as octoate, and azo compounds such as azobisisobutyronitrile and azodiisobutyric acid nitrile. These polymerization initiators may be used alone or in an appropriate combination of two or more. If necessary, chain transfer agents such as dodecyl mercaptan, 2-ethylhexyl thioglycolate, carbon tetrachloride, etc. may be used to adjust the molecular weight. The weight average molecular weight of the crosslinkable copolymer resin of the present invention is preferably in the range of 10,000 to 100,000, preferably 20,000 to 80,000. Weight average molecular weight
If the weight average molecular weight is less than 10,000, the coating film performance will not be sufficient, while if the weight average molecular weight is more than 100,000, the smoothness will be impaired. In the present invention, the oil-free alkyd resin and the crosslinkable copolymer resin are used in a weight ratio of 5/95 to 90/10. Preferably it is 10/90 to 70/30. If the crosslinkable copolymer resin is less than 10% by weight, the crosslinkability of the coating film will be insufficient, and solvent resistance, chemical resistance, etc. will tend to decrease; on the other hand, if the crosslinkable copolymer resin is less than 95% by weight If the amount is larger, the effect of improving corrosion resistance and water resistance of the oil-free alkyd resin, which is a feature of the present invention, will not be utilized, which is not preferable. The composition comprising the oil-free alkyd resin and crosslinkable copolymer resin of the present invention may further contain curing accelerators, such as mineral acids such as phosphoric acid and hydrochloric acid, p-toluenesulfonic acid, benzenesulfonic acid, etc. One or more organic acids such as aromatic sulfonic acid, phthalic acid monoester, and maleic acid monoester can be used. Also, its uses,
Depending on the purpose, phenolic resin, amino resin, polybutadiene resin, alkyd resin, epoxy resin,
Epoxy ester resin, silicone resin, cellulose resin, etc. can be added and used in combination. Furthermore, if necessary, pigments such as anti-rust pigments, coloring pigments, extender pigments, flow aids, anti-sag agents, etc.
A paint composition can be obtained by adding desired amounts of various additives such as color separation preventive agents and surface conditioners, and mixing and kneading using known kneading methods such as sand mills, ball mills, roll mills, paint mixers, etc. I can do it. Various well-known coating methods such as brush coating, dip coating, spray coating, electrostatic coating, and roll coating can be applied to the composition of the present invention thus obtained. As for the objects to be coated, as mentioned above, it is possible to coat not only steel plates but also nonferrous materials such as galvanized plates, tin plated plates, aluminum plates, copper plates, and chemical conversion treated surfaces thereof. Moreover, a normal top coat may be applied on the coating film for aesthetic purposes or other purposes. The heat curing conditions after application of the paint coating composition of the present invention vary depending on the content of crosslinkable functional groups in the composition, the film thickness, the presence or absence of a curing accelerator, etc. usually
A cured coating film can be obtained by heating and drying for 5 to 40 minutes at a suitable temperature in the range of 100 to 200°C. The cured coating film obtained in this way has excellent adhesion to not only steel plates, but also galvanized steel plates, stainless steel plates, and aluminum plates, as well as water resistance, corrosion resistance, and moisture resistance, and has also been tested for salt spray resistance. The secondary adhesion after the moisture resistance test was also extremely excellent. The present invention will be explained below with reference to Examples. still,
"Parts" or "%" represent "parts by weight" or "% by weight." [Method for producing oil-free alkyd resin solution] (1) Oil-free alkyd resin No. 1 (hereinafter abbreviated as PE-1) was placed in a reaction vessel equipped with a stirrer, a thermometer, a cooling tube, and a nitrogen gas introduction tube. 29.0 parts of neopentyl glycol, 15.0 parts of trimethylolethane, 11.0 parts of isophthalic acid, 11.0 parts of phthalic anhydride, and 29.0 parts of adipic acid were charged, heated in a nitrogen gas atmosphere, and after the reaction temperature reached 225°C, the reaction was continued for 4.5 hours. After that, the reaction temperature was lowered to 200℃, then 5 parts of gallic acid was added, and the reaction was further carried out at 200℃ for 2 hours to form an oil-free alkyd with an acid value of 10, a hydroxyl value of 119, and a weight average molecular weight of 20.500. Resin was obtained. This is xylene/butyl cellosolve =
PE-1 was prepared by diluting the non-volatile content to 60% with a 90/10 (parts) mixed solvent. (2) Oil-free alkyd resin No. 2 (hereinafter abbreviated as PE-2) In the same reaction vessel as in (1) above, 28.0 parts of neopentyl glycol and 17.2 parts of trimethylolpropane were added.
1 part, 29.8 parts of isophthalic acid, and 20.0 parts of adipic acid, and heated in a nitrogen gas atmosphere until the reaction temperature reached
After continuing the reaction for 4 hours after reaching 220°C, the reaction temperature was lowered to 190°C, then 5 parts of 3,4-dioxybenzoic acid (protocatechuic acid) was added, and the reaction was further carried out at 190°C for 2.5 hours. acid value
9.5, an oil-free alkyd resin having a hydroxyl value of 135 and a weight average molecular weight of 8,700 was obtained. This was diluted to a non-volatile content of 60% with a mixed solvent of xylene/butyl cellosolve = 90/10 (parts) to give PE-2. (3) Oil-free alkyd resin No. 3 (hereinafter abbreviated as PE-3) In the same reaction vessel as in (1) above, 28.3 parts of neopentyl glycol and 17.2 parts of trimethylolpropane were added.
1 part, 31.0 parts of isophthalic acid, and 20.5 parts of adipic acid, and heated in a nitrogen gas atmosphere until the reaction temperature reached
After continuing the reaction for 5 hours after reaching 230℃, the reaction temperature was lowered to 195℃, then 3 parts of gallic acid was added, and the reaction was further carried out at 195℃ for 1 hour, resulting in an acid value of 8.8, a hydroxyl value of 154, and a weight. Average molecular weight 9500
An oil-free alkyd resin was obtained. This was diluted to a non-volatile content of 60% with a mixed solvent of xylene/butyl cellosolve = 90/10 (parts) to obtain PE-3. (4) Oil-free alkyd resin No. 4 (hereinafter abbreviated as PE-4) In the same reaction vessel as in (1) above, 27.5 parts of neopentyl glycol and 16.5 parts of trimethylolpropane were added.
18.5 parts of adipic acid and 27.5 parts of isophthalic acid were heated in a nitrogen gas atmosphere until the reaction temperature reached
After reaching 240℃, the reaction was continued for 4 hours, the reaction temperature was lowered to 200℃, then 10 parts of gallic acid was added, and the reaction was further carried out at 200℃ for 1.5 hours, resulting in an acid value of 7.2, a hydroxyl value of 141, and a weight. Average molecular weight 7800
An oil-free alkyd resin was obtained. This was diluted to a non-volatile content of 60% with a mixed solvent of xylene/butyl cellosolve = 90/10 (parts) to give PE-4. (5) Oil-free alkyd resin No. 5 (hereinafter abbreviated as PE-5) 27.6 parts of neopentyl glycol and 17.8 parts of trimethylolpropane in the same reaction vessel as in (1) above.
1 part, 32.8 parts of isophthalic acid, and 21.8 parts of adipic acid, and heated in a nitrogen gas atmosphere until the reaction temperature reached
After reaching 230℃, the reaction was carried out for 5.5 hours, and the acid value was
6.8, an oil-free alkyd resin having a hydroxyl value of 145 and a weight average molecular weight of 8,500 was obtained. This was diluted to a non-volatile content of 60% with a mixed solvent of xylene/butyl cellosolve = 90/10 (parts) to give PE-5. (6) Oil-free alkyd resin No. 6 (hereinafter abbreviated as PE-6) In the same reaction vessel as in (1) above, 28.3 parts of neopentyl glycol and 17.2 parts of trimethylolpropane were added.
1 part, 29.5 parts of isophthalic acid, and 20.0 parts of adipic acid, and heated in a nitrogen gas atmosphere until the reaction temperature reached
After reaching 230°C and continuing the reaction for 3.5 hours, the reaction temperature was lowered to 195°C, and then salicylic acid 5
of the mixture was added, and the reaction was further carried out at 195°C for 5.5 hours.
Acid value 9.3, hydroxyl value 142 and weight average molecular weight
8100 oil-free alkyd resin was obtained. Add this to xylene/butyl cellosolve = 90/10 (parts)
Dilute PE-6 to 60% non-volatile content with a mixed solvent of
And so. (7) Oil-free alkyd resin No. 7 (hereinafter abbreviated as PE-7) In the same reaction vessel as in (1) above, 29.0 parts of neopentyl glycol and 16.5 parts of trimethylolpropane were added.
parts, isophthalic acid 12.0 parts, phthalic anhydride 12.0 parts
and 29.0 parts of adipic acid, heated in a nitrogen gas atmosphere, and after the reaction temperature reached 225°C, 4.5 parts of adipic acid was charged.
After continuing the reaction for an hour, the reaction temperature was lowered to 195℃, then 1.5 parts of gallic acid was added, and then the temperature was increased to 195℃.
The reaction was carried out for 1 hour, and the acid value was 9.7, the hydroxyl value was 115,
An oil-free alkyd resin with a weight average molecular weight of 21,800 was obtained. This was diluted to a nonvolatile content of 60% with a mixed solvent of xylene/butyl cellosolve = 90/10 (parts) to obtain PE-7. (8) Oil-free alkyd resin No. 8 (hereinafter abbreviated as PE-8) In the same reaction vessel as in (1) above, add neopentyl glycol, 27.6 parts, and trimethylolpropane.
17.8 parts, isophthalic acid 32.8 parts, adipic acid 21.0 parts
After heating in a nitrogen gas atmosphere and continuing the reaction for 4 hours after the reaction temperature reached 225°C, the reaction temperature was lowered to 195°C, then 0.8 part of gallic acid was added, and the reaction was further heated at 195°C for 50 Reaction was carried out for minutes, acid value 9.5, hydroxyl value 135, weight average molecular weight
10500 oil-free alkyd resin was obtained. This is xylene/butyl cellosolve = 90/10
PE diluted with (part) of mixed solvent to 60% non-volatile content.
-8. [Method for producing a crosslinkable copolymer resin solution] (1) 340 parts of methyl ethyl ketone was placed in a reaction vessel equipped with a stirrer, a thermometer, a dropping funnel, a cooling tube, and a nitrogen gas introduction tube, and the temperature was raised to 80°C. Thereafter, the following monomer and initiator mixture was added dropwise over 3 hours. Methyl methacrylate
50 parts, styrene 150 parts, ethyl acrylate 165
part, N-n-butoxymethylacrylamide
125 parts, 10 parts of acrylic acid, 10 parts of azobisisobutyronitrile. After dropping 1.5 parts of azobisisobutyronitrile was added and the reaction temperature was raised to 87°C, the reaction was carried out for 4 hours, resulting in an acid value of 12.0 and a weight average molecular weight.
38000 and a non-volatile content of 58.4%. This was designated as V-1. Examples 1 to 5 and Comparative Examples 1 to 3 Each oil-free alkyd resin solution PE-1 to PE-8 and crosslinkable copolymer resin V-1 were mixed as shown in the table, and a degreased dull steel plate and a zinc phosphate treated dull steel plate were prepared. Paint with an applicator to a dry film thickness of 20±5 microns on steel plates (Bonderite #144 treatment), galvanized steel plates [Silver Alloy: product name manufactured by Nippon Steel Corporation], and aluminum plates (untreated). After curing by heating for 20 minutes at the baking temperature shown in the table, the film was subjected to a coating performance test. The test results are shown in Table-1.

【table】

[Table] As is clear from the above comparative test results table, the coating film obtained from the composition of the present invention exhibits excellent adhesion to various coated objects, as well as hardness, Erichsen, impact resistance, and moisture resistance. It also showed very excellent performance in terms of secondary adhesion after the salt spray test.

Claims (1)

[Scope of Claims] 1 (a) 1 to 15% by weight of polyhydric phenolcarboxylic acid having a hydroxyl group and a carboxyl group bonded to the same benzene ring, acid value 50KOHmg/
oil-free alkyd resin with a hydroxyl value of 50 to 250 KOHmg/g... 5 to 90% by weight, (b)(i) N-alkoxymethylated monomer of α/β-monoethylenically unsaturated carboxylic acid amide body
...5-30% by weight (ii) α/β-monoethylenically unsaturated carboxylic acid
...0.5 to 10% by weight (iii) A monomer mixture consisting of 60 to 90% by weight of a copolymerizable α/β-monoethylenically unsaturated monomer other than the above (i) and (ii) A coating composition for a paint comprising 95 to 10% by weight of a crosslinkable copolymer resin obtained from.