JPH0252664B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a water-dispersible thermosetting coating composition that has excellent temporary rust prevention and corrosion resistance, and also satisfies resource saving and low pollution properties. In recent years, in the field of paints and coatings, resource conservation, energy conservation, and environmental issues have been taken up as important themes, and efforts are being made to develop new paints and improve coating methods in these areas. In particular, organic solvents, which are diluents for paints, are emitted into the atmosphere during the drying process of paint films, which poses an extremely serious problem from the standpoint of resource conservation and environmental protection. In order to improve this situation, efforts are being made to reduce the amount of organic solvents in paints.
As a result, we have produced high non-volatile paints called high solids, NAD (non-aqueous dispersion) paints in which high molecular weight polymers are dispersed at high concentrations in non-polar organic solvents (aliphatic hydrocarbons), and NAD (non-aqueous dispersion) paints in which water is used as a diluent. Water-based paints and powder paints that do not use any diluents are already on the market, and are gradually replacing solvent-based paints. Among these, water-based paints are attracting attention as a future type of paint because they use water as a diluent, so there is no risk of fire, etc., conventional painting equipment can be used as is, and the painting environment is comfortable. . Such water-based paints can be classified into emulsion paints, dispersion paints, water-soluble paints, slurry paints, and the like. Although water-based paints have the above-mentioned advantages, they also have many drawbacks, and for this reason they have not been able to replace solvent-based paints today. The main reasons for this are that it is easily affected by the paint environment, especially temperature and humidity, making it difficult to build up a film, that it is easy to cause paint film defects such as wrinkles, sagging, and repellency when the paint film dries, and that it improves its affinity for water. Therefore, introduction of hydrophilic groups into the resin or the combined use of dispersants, surfactants, etc. can lead to poor coating film durability. For this reason, current water-based paints use a considerable amount of organic solvents in order to remove these water-induced defects, and it is difficult to say that they are truly resource-saving and anti-pollution paints. On the other hand, slurry paint is a new type of paint that overcomes the defects of water-based paints, and has already been described in detail in Japanese Patent Publications No. 52851/1983 and Japanese Patent Publication No. 433/1983. To briefly list its characteristics, a slurry paint is a paint in which particulate resin of about 4 to 80 microns is dispersed in water at a solid concentration of 10 to 70% by weight. Therefore, it has many advantages, such as using only water as a medium as a volatile component, and can be applied with a high solids concentration, allowing thick coating, and can be used with conventional solvent-based paint coating equipment. It's an excellent paint. In general, acrylic resins, polyester resins, epoxy resins, alkyd resins, etc. are known as resins used in such slurry paints, but they are particularly important for stability during storage, smoothness of the coating film, and finish. Acrylic resin and polyester resin are said to be preferable from the viewpoint of appearance. In addition, epoxy resin or the like may be used in combination to further enhance anti-corrosion properties. However, if an epoxy resin is used in combination, the weather resistance will be impaired, so it is not preferable to use it as a component of the top coat resin. On the other hand, in order to improve the corrosion resistance of paint films, several examples have been known for a long time of blending phenolcarboxylic acid with various paints. For example, RN
According to Faulkner et al., vegetable oil, fatty acid ester,
Catechol, pyrogallol, gallic acid, or gallic acid ester was introduced into an alkyd resin, a vegetable oil-modified epoxy ester resin, or a vegetable oil-modified polyamide resin using a catalyst such as a metal alkoxide. Solvent-based 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 fields requiring high coating film performance. By the way, when melamine resin is used as a crosslinking agent, if a thick film is applied, foaming will occur during baking, so there is a drawback in terms of painting workability. The need arose. In addition, since slurry paints generally use water, when painted directly onto iron plates such as mild steel plates, similar to conventional water-based paints, phenomena such as temporary rusting that cannot be seen with solvent-based paints occur. There was a problem with this. In order to suppress this phenomenon, temporary rust preventive agents and the like are often used in the same way as with water-based paints, but the use of these agents is not preferable because it has an adverse effect on storage stability. The present invention aims to solve these problems. In other words, it has excellent storage stability,
A water-dispersed heat treatment that has a wide working width, has no defects such as wrinkles during baking, and has excellent coating performance in terms of gloss, smoothness, temporary rust prevention, chemical resistance, and especially secondary adhesion after corrosion resistance tests. A hard coating composition is provided. The gist of the composition of the present invention is to provide excellent performance as a urethane resin in addition to the advantages of polyester resins and acrylic resins made by reacting polyhydric phenol carboxylic acids. In other words, in addition to the excellent water-related properties such as water resistance, humidity resistance, and boiling water resistance of the polyester resin, especially the secondary adhesion after the salt spray test, acrylic resin and urethane resin Excellent coating appearance (gloss, texture, surface smoothness), adhesion, impact resistance,
Chemical resistance etc. can be imparted. Furthermore, it has been found that by crosslinking polyester resin and acrylic resin with an isocyanate compound, a coating film with an appropriate balance between hardness and flexibility can be obtained. In addition to these excellent features, the composition of the present invention has the effect of significantly improving the flowability of the coating film during baking and drying and improving the appearance of the coating film. Furthermore, since the polyester resin contained in the composition of the present invention has higher polarity than acrylic resins, it has an affinity for water and has the effect of improving storage stability in a dispersed state in water. That is, in the present invention, (A)(a) 1 to 15% by weight of polyhydric phenol carboxylic acid
The reacted polyester resin having a hydroxyl value of 10 to 300...15 to 95% by weight, (b) (i) the phosphoric acid group-containing α,β-monoethylenically unsaturated monomer, and (ii) the above-mentioned Monomers consisting of α,β-monoethylenically unsaturated monomers other than (i) (excluding N-alkoxymethylated monomers of α,β-monoethylenically unsaturated carboxylic acid amides) Phosphoric acid group-containing copolymer resin with a hydroxyl value of 3 to 150 obtained from the mixture
......85 to 5% by weight of a mixture, (B) fine powder thermosetting resin particles consisting of a blocked isocyanate compound, and 0.01 to 5.0% by weight of a surfactant and/or based on the particles. A water-dispersible thermosetting coating composition comprising a thickener and a required amount of water. The polyester resin used in the composition of the present invention undergoes an esterification reaction between a polyhydric phenol carboxylic acid and a polyhydric carboxylic acid, and further, if necessary, a monohydric carboxylic acid other than the polyhydric phenol carboxylic acid, and a polyhydric alcohol. It can be obtained by doing. The weight average molecular weight of the resin is 2,000 to 100,000, preferably 3,000 to 60,000. If the molecular weight is less than this range, it is not only difficult to stably disperse the particles in water at the slurry stage, but also the coating film performance, particularly mechanical performance and chemical performance, deteriorates, which is not preferable. If the molecular weight exceeds this range, not only will it lack compatibility with the acrylic resin or blocked isocyanate compound used in combination, but it may also cause problems in the appearance of the coating film. The hydroxyl value of the polyester resin is 30 to 300 [the number of milligrams of potassium hydroxide (resin solid content value) required to neutralize the carboxyl groups corresponding to the hydroxyl groups present in 1 g of the sample: the same applies below]
It is. A range of 40-200 is preferred. When the hydroxyl value is less than this range, the crosslinking density is low and the coating film cannot exhibit its original performance, and in particular, secondary properties such as water resistance, solvent resistance, and weather resistance deteriorate. If this range is exceeded, the ratio of the curing component of the blocking isocyanate compound to the polyester resin and acrylic resin will increase, and not only will the desired performance of the polyester resin not be exhibited, but the flexibility and adhesion of the coating film will be impaired. . When synthesizing the polyester resin of the present invention, it is essential to use polyhydric phenol carboxylic acid as the carboxylic acid component. This component is reacted in a proportion of 1 to 15% by weight, preferably 2 to 10% by weight, in the polyester resin component. If the content of the component is less than 1% by weight within the above range, after synthesizing the polyester resin, a corrosion resistance test of a coating film formed using a mixture with a phosphoric acid group-containing copolymer resin and a blocked isocyanate compound. The subsequent improvement in secondary adhesion cannot be achieved 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. Polyhydric carboxylic acids and monovalent carboxylic acids other than polyphenolcarboxylic acid include phthalic anhydride, isophthalic acid, terephthalic acid, endomethylenetetrahydrophthalic anhydride, tetrahydrophthalic anhydride, methyltetrahydrophthalic anhydride, methyl Hexahydrophthalic anhydride, hexahydrophthalic anhydride, trimellitic anhydride, succinic acid, adipic acid, azelaic acid, sebacic acid, citric acid, tartaric acid, malic acid, 1,8-naphthalic acid, etc. can be used. Furthermore, benzoic acid, pt-butylbenzoic acid, etc. may also be used as a reaction regulator. These may be used alone or in a mixture of two or more. Next, polyhydric alcohols used in the synthesis of polyester resin include ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, butylene glycol, 1,3-pentanediol,
Neopentyl glycol, 1,6-hexanediol, hydrogenated bisphenol A, 1,4-cyclohexanedimethanol, pentaerythritol,
In addition to glycerin, trimethylolpropane, trimethylolethane, etc., polypropylene glycol,
Higher alcohols such as polyethylene glycol can also be used. These may be used alone or as a mixture of two or more. Further, if necessary, Cardular E (trade name, manufactured by Ciel Chemical Co., Ltd.) may be used in combination. Since the performance of the coating film is significantly affected by the combination of these constituent raw materials, it is necessary to consider the composition of the raw materials that meet the target performance. For example, if the paint film requires water resistance or chemical resistance, use isophthalic acid, neopentyl glycol, etc.; if the paint film requires impact resistance or crack resistance, use adipic acid, sebacic acid, dipropylene, etc. It is already well known that phthalic anhydride, propylene glycol, etc. are used to improve the compatibility of ping glycol and the like with other resins. Furthermore, tetrachlorophthalic anhydride can be used as a raw material to impart special properties, such as flame retardancy, to the coating film. The method for producing polyester resin is a conventional condensation reaction, and the melting method includes an azeotropic method using an azeotropic solvent such as xylene. Things to be careful about are removing condensed water as a by-product from the system as quickly as possible, increasing the capacity of the complete esterification equipment to recover the glycol that comes out azeotropically with high efficiency, and increasing the capacity of the complete esterification equipment. This includes introducing an inert gas to avoid coloring. Further, the acid value of the polyester resin is desirably 50 or less (number of milligrams of potassium hydroxide required to neutralize 1 gram of resin: resin solid content). Next, the phosphoric acid group-containing copolymer resin [component (b) above] used in the present invention is an essential component of the phosphoric acid group-containing α,β-monoethylenically unsaturated monomer [(b)( i)
component] and an α,β-monoethylenically unsaturated monomer other than the above [component (b) (ii)]. By introducing the phosphoric acid group-containing α,β-monoethylenically unsaturated monomer, even when the coating composition of the present invention is applied directly onto an iron plate, it not only suppresses temporary rusting but also makes it easier to store the composition. It is possible to obtain a coating film that improves stability, has even stronger adhesion to metal surfaces, and has significantly superior corrosion resistance and water resistance. The phosphoric acid group-containing α,β-monoethylenically unsaturated monomer is 0.01 to 10.0% by weight in the monomer mixture,
Preferably, it is used in a range of 0.5 to 5.0% by weight.
If the monomer is used less than 0.01% by weight,
The temporary rust prevention effect, storage stability, and high corrosion resistance, which are the characteristics of the present invention, cannot be sufficiently exhibited, and on the other hand, if it is used in an amount exceeding 10% by weight, it tends to gel in the copolymerization reaction process, which is not preferable. Also, 10
Since a sufficient effect can be obtained within 10% by weight, it is economically undesirable to use more than 10% by weight. Specific examples of the monomer include acrylic acid or methacrylic acid containing a hydroxyl group such as acidophosphoxyethyl (meth)acrylate, acidophosphoxypropyl (meth)acrylate, and 3-chloro-2-acidophosphoxypropyl methacrylate. Primary phosphoric acid esters; bis(meth)acryloxyethyl phosphate, acrylic alcohol acid phosphate, vinyl phosphate, mono[2-hydroxyethyl (meth)acrylate] acid phosphite, etc., and their salts and It is one kind or a mixture of two or more kinds such as esters. The above monomer has a hydroxyl group, α, β-
It is produced by reacting a monoethylenically unsaturated monomer with phosphoric anhydride and hydrolyzing the product, but other products such as orthophosphoric acid, metaphosphoric acid, phosphorus oxychloride, phosphorus trichloride, phosphorus pentachloride, etc. It can also be manufactured using The α,β-monoethylenically unsaturated monomers other than the phosphoric acid group-containing α,β-monoethylenically unsaturated monomer used as an essential component in the phosphoric acid group-containing copolymer resin are as described below. , α,β-monoethylenically unsaturated carboxylic acids, hydroxyalkyl esters of said carboxylic acids, alkyl esters of acrylic acid or methacrylic acid, etc. It can be used as a mixture of more than one species. In addition, in order for the above-mentioned phosphoric acid group-containing copolymer resin to undergo a crosslinking reaction with the blocked isocyanate compound,
It is necessary to contain a hydroxyl group in the molecule. Therefore, in order to balance the hydroxyl value of the polyester resin, a necessary amount of hydroxyalkyl ester of α,β-monoethylenically unsaturated carboxylic acid is added as a kind of α,β-monoethylenically unsaturated monomer. It is preferable to use The monomer accounts for 1 to 30% by weight, preferably 2% by weight in the monomer mixture constituting the phosphoric acid group-containing copolymer resin.
Use in the range of ~15% by weight. If the monomer is used in an amount exceeding 30% by weight, it tends to gel during the copolymerization reaction, and the obtained phosphoric acid group-containing copolymer resin has a high viscosity, and moreover, the mixture with the polyester resin and the blocked isocyanate compound tend to gel. If the crosslinking density becomes too high, the flexibility, water resistance, etc. of the coating film tend to decrease, which is undesirable. Specific examples of the monomer include 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-
Hydroxypropyl (meth)acrylate, 2-
Hydroxy-1-phenylethyl (meth)acrylate, polypropylene glycol mono(meth)
Examples include acrylate and glycerin mono(meth)acrylate, and these may be used alone or as a mixture of two or more. It is preferable to use α,β-monoethylenically unsaturated carboxylic acid in an amount of 0.5 to 10% by weight as one component of the phosphoric acid group-containing copolymer resin used in the present invention. The monomer has the effect of improving the compatibility between the phosphoric acid group-containing copolymer resin and the polyester resin and promoting the crosslinking reaction. If the amount is less than 0.5% by weight, the effect will be weakened, and 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. As a raw material for the phosphoric acid group-containing copolymer resin used in the present invention, it is preferable to react with α,β-monoethylenically unsaturated monomers other than those mentioned above in a proportion of 70 to 90% by weight. 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; other N,N'-dimethylaminoethyl (meth)acrylate, glycidyl (meth)acrylate, cyclohexyl (meth)
Acrylate, phenyl methacrylate, benzyl methacrylate, fumaric acid dialkyl esters such as dibutyl fumarate, styrene, vinyltoluene, α-methylstyrene, (meth)acrylonitrile, vinyl acetate, etc. (However, α,
β-monoethylenically unsaturated carboxylic acid amide N
-excluding alkoxymethylated monomers). The above monomers may be used singly or in a suitable combination of two or more depending on the purpose and use of the coating composition. The phosphoric acid group-containing copolymer resin of the present invention is produced by conventional solution polymerization. As the polymerization solvent used in the solution polymerization method,
Water-soluble or water-miscible solvents are used, such as alcohols such as methyl alcohol, ethyl alcohol, isopropyl alcohol, n-propyl alcohol; ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, ethylene glycol monoethyl Ethylene glycol derivatives such as ether acetate; diethylene glycol derivatives such as diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether; esters such as methyl acetate, ethyl acetate, butyl acetate; ketones such as methyl ethyl ketone, methyl isobutyl ketone, etc. are used. be done. These polymerization solvents may be used alone or in an appropriate combination of two or more. In particular, the solubility in water is 10~ at 20℃.
It is preferably about 30% by weight. Examples of the polymerization initiator used include benzoyl peroxide, t-butyl perbenzoate, t-butyl hydroperoxide, cumene hydroperoxide, di-t-butyl peroxide, and t-butyl peroctoate. Examples include organic peroxides and azo compounds such as azobisisobutyronitrile and azodiisobutyric acid nitrile. One or more of these polymerization initiators may be used in combination as appropriate. The polymerization initiator is used in an amount of about 0.1 to 15% by weight based on the nonvolatile content during production of the phosphoric acid group-containing copolymer resin. If necessary, a chain transfer agent to adjust the molecular weight,
For example, dodecyl mercaptan, 2-ethylhexyl thioglycolate, carbon tetrachloride, etc. may be used. The chain transfer agent is preferably used in an amount of about 0 to 5% by weight based on the nonvolatile content during production of the phosphoric acid group-containing copolymer resin. The polymerization temperature during the production of the phosphoric acid group-containing copolymer resin is about 50 to 150°C, the reaction time is about 4 to 12 hours,
The polymerization solvent used in this case is used in such a range that the nonvolatile content during resin production is 10 to 80% by weight, preferably 20 to 70% by weight. In this case, it is better to use a larger amount of the phosphoric acid group-containing α,β-monoethylenically unsaturated monomer and lower the nonvolatile content. The weight average molecular weight of the phosphoric acid group-containing copolymer resin of the present invention is preferably in the range of 8,000 to 70,000, preferably 20,000 to 50,000. Weight average molecular weight
If it does not reach 8000, the coating performance is not sufficient.
On the other hand, if the weight average molecular weight exceeds 70,000, smoothness will be impaired. Further, the hydroxyl value of the phosphoric acid group-containing copolymer resin of the present invention is in the range of 3 to 150. When the hydroxyl value is less than 3, the crosslinking density becomes low and the solvent resistance of the coating film decreases. On the other hand, if it exceeds 150,
The flexibility and water resistance of the coating film will decrease. Since the phosphoric acid group-containing copolymer resin of the present invention is highly reactive, it tends to increase in viscosity at high temperatures such as in summer. In such cases, in order to further improve storage stability, the acid groups introduced into the phosphoric acid group-containing copolymer resin are neutralized with a basic compound.
A more stable phosphoric acid group-containing copolymer resin can be obtained. Examples of the basic compound include inorganic alkalis such as sodium hydroxide and potassium hydroxide; ammonia, monomethylamine, dimethylamine, trimethylamine, triethylamine, monoethylamine, mono-n-propylamine, dimethyl-n-
Water-soluble amines such as propylamine; monoethanolamine, diethanolamine, triethanolamine, N-methylethanolamine, N-
Aminoethylethanolamine, N-methyldiethanolamine, monoisopropanolamine,
Examples include one or a mixture of two or more water-soluble oxyamines such as diisopropanolamine, tripropanolamine, and hydroxylamine. When neutralizing using such a compound, it includes neutralizing some or all of the acid groups in the phosphoric acid group-containing copolymer resin, and furthermore, it includes neutralizing some or all of the acid groups in the phosphoric acid group-containing copolymer resin. An excessive amount may be added in consideration of the stability of the composition or the performance of the coating film. Next, the blocked isocyanate compound [component (B) above] used in the present invention is an isocyanate compound having two or more isocyanate groups in one molecule, and all of the isocyanate groups are masked with a blocking agent. It is a blocked isocyanate compound. The blocked isocyanate compound is characterized by participating in a crosslinking reaction with the polyester resin and the phosphoric acid group-containing copolymer resin, and imparting the excellent chemical resistance of the urethane resin. The blocking isocyanate compound is a polyisocyanate compound having two or more isocyanate groups in one molecule, such as ethylene diisocyanate, propylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, decamethylene diisocyanate, m
-phenylene diisocyanate, p-phenylene diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 1,5-naphthylene diisocyanate,
4,4',4''-triphenylmethane triisocyanate, 4,4'-diphenylmethane diisocyanate, 3,3'-dimethyl-4,4'-diphenylene diisocyanate, m-xylylene diisocyanate, p-xylylene diisocyanate ,
Polyisocyanates such as isophorone diisocyanate, lysine isocyanate, and excess of the isocyanate compounds, such as ethylene glycol, propylene glycol, 1,3-butylene glycol, neopentyl glycol, 2,2,4
Biuret, a polyisocyanate with two or more functionalities obtained by an addition reaction with a low-molecular polyol such as trimethyl 1,3-pentanediol, hexamethylene glycol, cyclohexanedimethanol, trimethylolpropane, hexanetriol, glycerin, or pentaerythritol. It is an isocyanate compound obtained by blocking a polyisocyanate having a structure such as a polyisocyanate having an allophanate bond with a blocking agent. Examples of the blocking agent include phenols such as phenol and cresol, alcohols such as methanol, benzyl alcohol, and ethylene glycol monoethyl ether, active methylenes such as methyl acetoacetate and dimethyl malonate, acetanilide,
Acid amide type such as acetate amide, other imide type, amine type, imidazole type, urea type, carbamate type, imine type, oxime type, mercaptan type,
There are sulfite-based, lactam-based, etc. In the water-dispersed thermosetting coating composition of the present invention, effective crosslinking occurs when the blocking agent in the blocking isocyanate compound dissociates, so the dissociation temperature of the blocking agent is preferably 100° C. or higher. In the present invention, the polyester resin and the phosphoric acid group-containing copolymer resin are used in a weight ratio of 15/85 to 95/5, preferably 30/70 to 90/10. 15% by weight of polyester resin in the above range
If the amount is less, the effect of improving the secondary adhesion after the corrosion resistance test of the polyester resin, which is one of the characteristics of the present invention, will be diminished, and at the same time, the excellent flexibility, pigment dispersibility, and coating film appearance will be impaired. . On the other hand, if the polyester resin exceeds 95% by weight, the amount of the phosphoric acid group-containing copolymer resin will inevitably decrease, and the temporary antirust effect, which is a feature of the present invention, will decrease. The crosslinking reaction in the composition of the present invention is carried out by the hydroxyl groups in the polyester resin, the hydroxyl groups in the phosphoric acid group-containing copolymer resin, and the isocyanate groups in the blocked isocyanate compound. The ratio of the mixture consisting of a polyester resin and a phosphoric acid group-containing copolymer resin and the blocked isocyanate compound is [(hydroxyl group in the polyester resin) + (hydroxyl group in the phosphoric acid group-containing copolymer resin)]/
(Isocyanate group in blocked isocyanate compound) = 1/0.3 to 1/1.3 (equivalent ratio), preferably 1/0.6 to 1/1.0 (equivalent ratio), and in terms of solid content weight ratio Approximately 20/80~
The ratio is 98.8/1.2. If the amount of the blocked isocyanate compound used is significantly reduced, the effect of improving the chemical resistance of the coating film, which is a feature of the present invention, will be poor. On the other hand, if the amount increases significantly, coating film performance such as water resistance deteriorates due to isocyanate groups that do not react with the hydroxyl groups in the resin. In addition, the polyester resin used in the present invention,
The softening temperature of the resin particles made of a mixture of a phosphoric acid group-containing copolymer resin and a blocked isocyanate compound is preferably 30 to 100°C. More preferably
The temperature is 40-80℃. If the softening temperature is lower than 30℃, the storage stability of the paint tends to decrease, and
If the temperature is higher than 100°C, the smoothness of the coating film will be insufficient, which is not preferable. In addition, in the present invention, known acid catalysts, dissociation catalysts, epoxy resins, cellulose resins, etc. are used as necessary to promote the crosslinking reaction between the mixture of polyester resin and phosphoric acid group-containing copolymer resin and the blocked isocyanate compound. It is also possible to use one or more types of coating film-forming resins such as , amino resins, etc. Next, a method for producing the water-dispersed thermosetting coating composition of the present invention will be explained. The production method includes the production of conventional powder coatings and slurry coatings, etc.
A commonly used mechanical pulverization method can also be applied, but if the softening point is low, the viscosity of the resin particles will be too high and it will be difficult to powder them. Therefore, the water-dispersed thermosetting coating composition of the present invention can be advantageously produced by a special method as described below. First, predetermined amounts of the polyester resin and phosphoric acid group-containing copolymer resin and, if necessary, a basic compound and a blocking isocyanate compound that neutralize some or all of the acid groups in the phosphoric acid group-containing copolymer resin. A mixed resin composition with a curing catalyst, a dissociation catalyst, other coating film-forming resins, etc. as necessary are dissolved in the water-soluble solvent or water-miscible solvent to obtain a resin solution, and if necessary, a pigment is added, Knead and disperse to obtain a pigment dispersion. The solvent used at this time is the same as the polymerization solution used in the solution polymerization method. The amount used is such that the nonvolatile content of the resin solution or pigment dispersion is in the range of 30 to 80% by weight. Next, this resin solution or pigment dispersion is emulsified into fine particles in water in an amount such that all of the water-soluble or water-miscible solvent contained therein is dissolved.
The amount of water used at this time is at least 6 times the amount (weight) of the resin solution or pigment dispersion,
Considering the filtration step after emulsification, it is preferably about 40 times the amount (weight) or less. Furthermore, the emulsification of the resin solution or pigment dispersion is
Methods such as dropping, pouring, or spraying the solution or dispersion into water under vigorous stirring, or mixing water and the solution or dispersion with a line mixer can be used. It is preferable to cool the mixed liquid and maintain the liquid temperature at 30° C. or lower in order to prevent resin particles from coalescing or becoming integrated and becoming coarse due to an increase in temperature and softening of the resin. The stirring or mixing using a line mixer is carried out until the solvent in the emulsion particles is transferred to water and resin particles are formed. In this way, the solvent in the emulsion fine particles is extracted into water, and resin particles are obtained. The resin particles are separated from the water-solvent mixture by filtration or centrifugation, and if necessary, water washing and separation are repeated a necessary number of times to obtain resin particles in the form of a slurry or a water-containing cake. In this way, resin particles preferably having an average particle size of between about 1 and 200 microns are obtained. Furthermore, after adding a surfactant and/or thickener and water to this slurry-like or water-containing cake-like resin particles, a dispersing machine normally used for manufacturing paints is used, such as a sand mill, a ball mill, a disperser, a Sassmeyer mill, a Sentry mill, etc. Finely grind the resin particles with a mill etc. to an average particle size of approximately 1 to 50μ
Adjust between. The thus obtained resin particles of the present invention contain a polyester resin, a phosphoric acid group-containing copolymer resin, and a blocked isocyanate compound in one particle. That is, each particle necessarily contains groups that react with each other when heated, that is, a hydroxyl group and an isocyanate group. Therefore, when the composition of the present invention is heated, a coating film having excellent performance can be obtained through crosslinking in the resin particles and crosslinking reaction between the resin particles. The water-dispersible thermosetting coating composition of the present invention preferably contains the resin particles dispersed in the form of fine particles having an average particle diameter of 1 to 50 μm. If the average particle diameter is smaller than 1 μm, it is not preferable because the particles tend to coagulate among themselves and exhibit properties similar to those of water-soluble paints, such as easy foaming during heating film formation. On the other hand, if it is larger than 50μ, the resin particles tend to settle and coagulate during storage, making it impossible to obtain a smooth coating surface, which is not preferable. In particular, resin particles having an average particle size of 5 to 30 μm are suitable for the present invention because they form a coating material that has excellent storage stability and provides a smooth coating film without foaming. The composition of the present invention may also contain, if necessary, a curing catalyst, organic and inorganic coloring and extender pigments commonly used in paints, temporary rust preventive agents, flow aids, antifoaming agents, anti-settling agents, and anti-mold agents. It can contain additives such as agents, preservatives, and other water-soluble resins, coating film-forming resins such as hydrosols, emulsion resins, and the like. As mentioned above, the softening temperature of the resin particles is preferably 30 to 100°C.
Components such as pigments that do not melt at the heating film forming temperature in the paint are preferably added to the resin particles in an amount of 50% by weight or less. As the surfactant used in the present invention, known surfactants such as nonionic surfactants, anionic surfactants, cationic surfactants, and amphoteric surfactants can be used. For example, sorbitan fatty acid ester, polyoxyethylene sorbitan fatty acid ester, polyoxyethylene sorbitol fatty acid ester, polyoxyethylene fatty acid ester, polyoxyethylene alcohol ether, glycerin fatty acid ester, propylene glycol fatty acid ester, polyoxyethylene castor oil derivative, polyoxyethylene Alkyl phenyl ether, alkyl phosphate ester, polyoxyethylene phosphate ester,
Examples of anionic surfactants include alkyl sulfate salts, polyoxyethylene alkyl ether sulfate salts, alkyl sulfosuccinates, N
-As the acyl sarcosine salt and cationic surfactant, quaternary ammonium salts, pyridinium salts, etc. can be used. Nonionic surfactants are preferred from the viewpoint of dispersion stability of resin particles and coating film performance, especially HLB
is preferably 8 to 18. Further, as the above-mentioned thickener used in place of or in combination with these surfactants, those conventionally used in water-based resin paints can be used. These include, for example, cellulose water-soluble resins such as methyl cellulose, ethyl cellulose, and hydroxyethyl cellulose; polyvinyl alcohol; polyethylene water-soluble resins such as polyethylene glycol ether and polyethylene oxide; methyl vinyl ether maleic anhydride copolymer, and ethylene maleic anhydride copolymer. water-soluble resins based on maleic anhydride copolymers such as styrene and maleic anhydride copolymers; ammonium, amine salts and sodium salts of acrylic acid polymers, bentonite, polyvinylpyrrolidone, alginates, polyacrylamide and their partial hydration Examples include decomposition products, naturally occurring water-soluble resins such as casein and gelatin. The above-mentioned surfactant and/or thickener is added in an amount of 0.01 to 5.0% by weight based on the fine powder resin particles. If the amount added is less than 0.01% by weight, storage stability, coating workability, etc. will deteriorate, and if it is more than 5.0% by weight, the smoothness, water resistance, etc. of the coating film will deteriorate, making it unsuitable for the present invention. . Among the above-mentioned thickeners, amine salts of carboxyl group-containing acrylic copolymers are particularly suitable for the present invention because they become water-insoluble after heating the coating film due to elimination of amines and do not reduce the water resistance of the coating film. be. The mixing ratio of water and fine powder resin particles in the core coating composition of the present invention is preferably 90-30/10-70 by weight. When the composition has fewer resin particles than the above mixing ratio, the solids concentration of the paint is low and the viscosity is low, so when it is applied at a time to a normal coating thickness, for example 20 to 80μ. Phenomena such as sagging occur in the paint film, and to avoid this, several coats are required, causing problems in painting workability. On the other hand, if the amount of resin particles is greater than the above mixing ratio, it will be difficult to make the paint uniform by stirring, kneading, etc. during paint production, and the viscosity characteristics will not be suitable for various painting methods such as spray painting and electrostatic painting. Since it comes off, painting workability tends to be poor and practicality tends to decrease, which is not preferable. The water-dispersed thermosetting coating composition of the present invention can be applied using various well-known coating methods such as brush coating, dip coating, spray coating, electrostatic coating, curtain flow coating, shower coating, and roll coating. I can do it. The conditions for heat curing after coating the coating composition vary depending on the content of crosslinkable functional groups in the composition, film thickness, etc., but are usually at an appropriate temperature in the range of 120 to 200°C for 10 A cured coating film can be obtained by heat treatment for ~40 minutes. The cured coating film obtained in this way suppresses temporary rusting on steel plates, and also improves adhesion to metal surfaces,
Excellent secondary adhesion after corrosion resistance test. In addition, polyester resin has excellent flexibility, pigment dispersibility, and coating film appearance, phosphoric acid group-containing copolymer resin has excellent hardness, and urethane resin has excellent chemical resistance. In addition, it has excellent coating performance with no bubbling that occurs during high-temperature baking. The present invention will be explained below with reference to Examples. In addition, “department”
Or "%" represents "part by weight" or "% by weight". [Production method of polyester resin solution] (1) Synthesis of polyester resin SP-1 In a reaction vessel equipped with a thermometer, stirrer, sparge gas introduction pipe, temperature control device, partial condenser, etc., 394 parts of phthalic anhydride and adipic acid were added. 137 parts of propylene glycol, 96 parts of neopentyl glycol, and 163 parts of trimethylolpropane were mixed together and the reaction temperature was raised to 235°C while flowing nitrogen gas. After continuing the reaction for 7 hours, the reaction temperature was lowered to 190°C. After that, 50 parts of gallic acid was added, and the reaction was further carried out at 190℃ for 1 hour to obtain an acid value.
9.0, a hydroxyl value of 110, and a weight average molecular weight of 9,500. This was dissolved in methyl ethyl ketone to obtain a resin solution with a nonvolatile content of 60%. (2) Synthesis of polyester resin SP-2 Isophthalic acid 215 was synthesized using the same method as in (1) above.
parts, 118 parts of phthalic anhydride, 173 parts of adipic acid, 195 parts of neopentyl glycol, 52 parts of propylene glycol, 92 parts of 1,6-hexanediol,
Blend 95 parts of trimethylolpropane, heat to 235°C in a nitrogen stream, continue the reaction for 6.5 hours, lower the reaction temperature to 190°C, then add 60 parts of 3,4-dioxybenzoic acid (protocatekylic acid). Then, the reaction was further carried out at 190℃ for 2.5 hours, and the acid value was 8.5.
A polyester resin having a hydroxyl value of 123 and a weight average molecular weight of 13,200 was obtained. This was dissolved in methyl ethyl ketone to obtain a resin solution with a nonvolatile content of 60%. (3) Synthesis of polyester resin SP-3 Isophthalic acid 200
163 parts of adipine, 202 parts of phthalic anhydride, 193 parts of neopentyl glycol, 74 parts of propylene glycol, 75 parts of trimethylolpropane, and 63 parts of trimethylolethane were mixed together in nitrogen gas.
After raising the temperature to 235°C and continuing the reaction for 8.5 hours, the reaction temperature was lowered to 195°C, then 30 parts of gallic acid was added, and the reaction was further carried out at 195°C for 1 hour, resulting in an acid value of 9.3.
A polyester resin having a hydroxyl value of 89 and a weight average molecular weight of 11,300 was obtained. This was dissolved in methyl ethyl ketone to obtain a resin solution with a nonvolatile content of 60%. (4) Synthesis of polyester resin SP-4 Using the same method as in (1) above, 164 parts of propylene glycol, 131 parts of dipropylene glycol, 131 parts of trimethylolpropane, and 203 parts of phthalic anhydride were added.
7.5 parts and 371 parts of adipic acid were heated in a nitrogen gas atmosphere until the reaction temperature reached 235°C.
A time reaction was performed to obtain a polyester resin having an acid value of 9.3, a hydroxyl value of 78, and a weight average molecular weight of 9,200. This was dissolved in methyl ethyl ketone to obtain a resin solution with a nonvolatile content of 60%. [Method for producing a phosphoric acid group-containing copolymer resin solution] (1) Put 340 parts of methyl ethyl ketone into a reaction vessel equipped with a stirrer, a thermometer, a dropping funnel, and a cooling tube, raise the temperature to 80°C, and then proceed as follows. of monomer and initiator mixture was added dropwise over 3 hours. 85 parts methyl methacrylate, styrene
160 parts, 50 parts of ethyl acrylate, 25 parts of 2-hydroxyethyl methacrylate, 25 parts of 2-ethylhexyl acrylate, 140 parts of 2-ethylhexyl methacrylate, 5 parts of acidophosphoxyethyl methacrylate, 10 parts of acrylic acid, 10 parts of azobisisobutyronitrile Department. After completion of dripping, azobisisobutyronitrile 1.5
After adding 50% of the reaction temperature to 87°C,
Reaction was carried out for 4 hours, acid value 18.2, hydroxyl value 24,
A resin solution with a weight average molecular weight of 37600 and a non-volatile content of 59.6% was obtained, and the softening temperature of the resin was approximately 72-74
It was warm at ℃. This was designated as PV-1. (2) Put 340 parts of methyl ethyl ketone into a reaction vessel similar to that in which PV-1 was synthesized, and raise the temperature to 80°C.
After raising the temperature to 100 mL, the following monomer and initiator mixture was added dropwise over 3 hours. 110 parts of methyl methacrylate, 110 parts of styrene, 210 parts of ethyl acrylate, 50 parts of 2-hydroxyethyl methacrylate, 5 parts of acidophosphoxyethyl methacrylate, 5 parts of 3-chloro-2-acidophosphoxypropyl methacrylate, 10 parts of acrylic acid, azo 10 parts bisisobutyronitrile. After finishing dropping, azobisisobutyronitrile
After adding 1.5 parts and raising the reaction temperature to 87℃, the reaction was carried out for 4 hours.
48, weight average molecular weight 53500 and non-volatile content 59.8
% resin solution is obtained and the softening temperature of the resin is about 74 ~
It was 76℃. PV-2 was obtained by adding 2/3 mole of triethylamine to the acid value of the resin solution to neutralize it. [Solvent replacement method for blocked isocyanate compound] When a blocked isocyanate compound containing a hydrophobic solvent is used, the solvent in the emulsion fine particles is not extracted into water and remains in the resin particles in the process of forming resin particles. Therefore, the resin particles coalesce or become integrated, which impairs stability, which is not preferable. Therefore, the blocked isocyanate compound was subjected to solvent substitution using the method described below and used in the present invention. Takenate B-820NSU [trade name, manufactured by Takeda Pharmaceutical Co., Ltd.: effective NCO 4.3%, non-volatile content 60% (solvent: Supersol 1500/butyl acetate)] was placed in a vacuum dryer at 40℃ for 2 days under vacuum. After drying (non-volatile content: 92.6%), methyl ethyl ketone was added thereto to dilute to 60% non-volatile content to obtain NCO-A. Example 1 50 parts of polyester resin solution (SP-1), 33.3 parts of titanium dioxide, 10 parts of methyl ethyl ketone, and 1 part of flow aid (trade name: Modaflow, manufactured by Monsanto) were mixed and kneaded in a porcelain pot mill until it became 10μ or less. To the mixed and dispersed mill base, 18.5 parts of polyester resin solution (SP-1), 29.5 parts of phosphoric acid group-containing copolymer resin (PV-1), 68.8 parts of blocked isocyanate compound (NCO-A), and dissociation catalyst were added. (Dibutyltin dilaurate) 0.9 part was mixed and stirred to form a uniform coating solution.
This was dropped into 3,000 parts of water at a water temperature of 15°C under high-speed stirring to emulsify the pigment dispersion and extract the solvent into the water to form resin particles. A water-containing cake of resin particles with a size of about 120μ and a water content of about 50% was obtained. Add 100 parts of this water-containing cake to a 40% aqueous solution of nonionic surfactant (trade name: Emulgen 930, manufactured by Kao Atlas Co., Ltd.).
Add 0.5 parts of HLB15.1) and 2 parts of a 10% aqueous solution of an alkali salt thickener of an acrylic acid copolymer, disperse and knead with a sand mill to finely grind the resin particles, and have an average particle size of 16 μm and a pH of 7.6. A slurry paint was obtained. Example 2 50 parts of polyester resin solution (SP-2), 33.3 parts of titanium dioxide, 10 parts of methyl ethyl ketone, and 1 part of flow aid (trade name: Modaflow, manufactured by Monsanto) were mixed and kneaded in a porcelain pot mill until the mixture had a particle size of 10μ or less. In addition, 5.6 parts of polyester resin solution (SP-2), 55.7 parts of phosphoric acid group-containing copolymer resin (PV-2), and methyl ethyl ketone of a blocked isocyanate compound (trade name: Kleran U-16109, manufactured by Bayer AG) were added to the dispersed mill base. Solution (non-volatile content 50%
66.8 parts of (adjusted to) and 0.9 parts of a dissociation catalyst (dibutyltin dilaurate) were added and mixed with stirring to form a uniform coating solution. This was dropped into approximately 3,000 parts of water at a temperature of 15° C. under high-speed stirring to emulsify the pigment dispersion and extract the solvent into the water to form resin particles. Thereafter, filtration and water washing were repeated to obtain a water-containing cake of resin particles with an average particle diameter of about 100 μm and a water content of about 50%. To 100 parts of this water-containing cake were added 0.6 parts of a 40% aqueous solution of nonionic surfactant (trade name Emulgen 910 HLB12.2 manufactured by Kao Atlas) and 4 parts of a thickener (5% aqueous solution of hydroxyethyl cellulose), and dispersed in a ball mill. The resin particles were combined and finely pulverized to obtain a slurry-like paint having an average particle size of 17 μm and a pH of 7.5. Example 3 45 parts of a polyester resin solution (SP-3), 33.3 parts of titanium dioxide, 10 parts of methyl ethyl ketone, and 1 part of a flow aid (trade name: Modaflow, manufactured by Monsanto) were blended and kneaded and dispersed in a pot mill until it became 10μ or less. Further, 68 parts of a phosphoric acid group-containing copolymer resin (VP-2), 53.3 parts of a blocked isocyanate compound (NCO-A), and 0.7 parts of a dissociation catalyst (dibutyltin dilaurate) were added to the mill base, and after stirring and mixing, this was mixed. was made into a uniform paint solution. The average particle diameter of the resin particles was determined in the same manner as in Example 1 below.
A slurry paint of 14μ and PH7.9 was obtained. Comparative Example 1 50 parts of polyester resin solution (SP-4) was added as a substitute for 50 parts of polyester resin solution (SP-1) from the mill base formulation of Example 1, and the polyester resin solution (SP-4) was added to the mill base, which was kneaded and dispersed. 4), 75 parts of melamine resin (average degree of condensation
41.7 parts of a 60% methyl ethyl ketone solution of a butylated methylol melamine resin with a degree of etherification of 2.5, a degree of etherification of 2.5, and a water-soluble component of 1% or less were added to form a uniform coating solution. This was made into a slurry using the same method as in Example 1 to obtain a slurry-like paint having an average particle size of 16 μm and a pH of 7.9. Comparative Example 2 As a substitute for 5 parts of acidophosphoxyethyl methacrylate and 5 parts of 3-chloro-2-acidophosphoxypropyl methacrylate from the monomer formulation of the phosphoric acid group-containing copolymer resin (PV-2), 2
- Acrylic copolymer resin solution obtained by blending 10 parts of hydroxyethyl methacrylate (hydroxyl value
52) 50 parts, 33.3 parts of titanium dioxide, 10 parts of methyl ethyl ketone, and 1 part of a flow aid (trade name: Modaflow, manufactured by Monsanto) were mixed and dispersed in a porcelain pot mill until the thickness was 10μ or less, and then the acrylic copolymer was added to the mill base. A uniform coating solution was prepared by adding 66.7 parts of the polymer resin solution, 50.0 parts of a blocked isocyanate compound (NCO-A), and 0.7 parts of a dissociation catalyst (dibutyltin dilaurate). This was made into a slurry using the same method as in Example 1 to obtain a slurry paint having an average particle size of 17μ and a pH of 7.6. The slurry paint prepared in each of the above Examples and Comparative Examples was spray-painted onto a dull steel plate treated with zinc phosphate, and after setting for 5 minutes, the paint was heated to 90°C.
Preheated for 10 minutes. Thereafter, it was heated and dried at each predetermined temperature to form a coating film with a thickness of 35 μm. Table 1 shows the heating drying conditions and physical property test results for the coating film. (However, a polished mild steel plate was used as the test piece for observing the appearance of the paint film).

【table】

[Table] As is clear from the above comparative test results table, the coating film obtained from the composition of the present invention shows no temporary rusting immediately after coating, and also does not foam when heated and dried. Furthermore, it has superior adhesion, flexibility, impact resistance, and chemical resistance compared to the coating film obtained from the comparative example composition, as well as water resistance, secondary adhesion after moisture resistance tests, and salt spray resistance. The secondary adhesion after the test was particularly excellent.

Claims (1)

[Scope of Claims] 1 (A)(i) A polyester resin having a hydroxyl value of 10 to 300, which is reacted with 1 to 15% by weight of polyhydric phenol carboxylic acid, and (b)(i) ) a phosphate group-containing α, β-monoethylenically unsaturated monomer; (ii) an α, β-monoethylenically unsaturated monomer other than (i) above (however, α, β-monoethylenically unsaturated monomers A phosphoric acid group-containing copolymer resin having a hydroxyl value of 3 to 150 obtained from a monomer mixture consisting of
...85 to 5% by weight of a mixture, and (B) fine powder thermosetting resin particles consisting of a blocked isocyanate compound, 0.01 to 5.0% by weight of a surfactant and/or additive to the particles. A water-dispersible thermosetting coating composition comprising: a sticky agent; and a required amount of water. 2 The mixing ratio of the above (A) and the above (B) is [hydroxyl group in the mixture consisting of the above (A) (a) and (A) (b)] / [isocyanate group in the above (B)] = 1 /0.3 to 1/1.3 (equivalent ratio)
The water-dispersible thermosetting coating composition described in 1. 3 The monomer mixture constituting the phosphoric acid group-containing copolymer resin includes (i) phosphoric acid group-containing α,β-monoethylenically unsaturated monomer ……0.01 to 10% by weight (ii) α, β-monoethylenically unsaturated carboxylic acid
………0.5-10% by weight (iii) Hydroxy alkyl ester of α,β-monoethylenically unsaturated carboxylic acid
......1 to 30% by weight (iv) Copolymerizable α, β other than the above (i), (ii) and (iii)
−
Monoethylenically unsaturated monomer (however, α, β-
N- of monoethylenically unsaturated carboxylic acid amide
(excluding alkoxymethylated monomers)
. . 70 to 90% by weight of the water-dispersed thermosetting coating composition according to claim 1.