JPH0252665B2 - - 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 properties and coating performance, 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 they are gradually replacing solvent 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 include emulsion paints, dispersion paints, water-soluble paints, and slurries.
It can be classified as paint, etc. 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 painting environment, especially temperature and humidity, and that it is difficult to build up a film, and that the paint film dries under the armpits.
It is easy to cause paint film defects such as sagging and repelling, and the durability of the paint film is poor due to the introduction of hydrophilic groups into the resin and the use of dispersants, surfactants, etc. to improve its affinity for water. Can be mentioned. 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. 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,
To provide a water-dispersed thermosetting coating composition that has a working width, has no defects such as wrinkles during baking, and has excellent coating performance in gloss, smoothness, temporary rust prevention, chemical resistance, corrosion resistance, etc. It is. 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. That is, in addition to the water-related properties of the polyester resin such as water resistance, humidity resistance, and boiling water resistance, corrosion resistance such as salt spray and salt water immersion, weather resistance, and chemical resistance, acrylic resin and urethane resin It can provide excellent coating film appearance (gloss, texture, surface smoothness), adhesion, impact resistance, stain resistance, etc. 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, the present invention provides (A) (a) a polyester resin having a hydroxyl value of 10 to 300 (excluding those using polyhydric phenol carboxylic acid as the acid component);
......15 to 95% by weight, and (b)(i) a phosphate group-containing α,β-monoethylenically unsaturated monomer; and (ii) an α,β-monoethylenically unsaturated monomer other than (i) above. Phosphorus with a hydroxyl value of 3 to 150 obtained from a monomer mixture consisting of unsaturated monomers (excluding N-alkoxymethylated monomers of α, β-monoethylenically unsaturated carboxylic acid amide). Acid group-containing copolymer resin
......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. The polyester resin used in the composition of the present invention is obtained by esterifying a polyvalent carboxylic acid, and if necessary, a monovalent carboxylic acid and a polyhydric alcohol. The weight average molecular weight of the resin is 1000 to 100000, preferably 2000
~60000. 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 polyester resin is 10~
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 hereinafter]. A range of 30 to 200 is preferred. When the hydroxyl value is less than this range, the crosslinking density is low and the original coating film performance cannot be exhibited, 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. . 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, Cardular E (manufactured by Ciel Chemical Co., Ltd., trade name) may be used in combination, if necessary. Polycarboxylic acids and monocarboxylic acids include phthalic anhydride, isophthalic acid, terephthalic acid, endomethylenetetrahydrophthalic anhydride,
Tetrahydrophthalic anhydride, methyltetrahydrophthalic anhydride, methylhexahydrophthalic anhydride, hexahydrophthalic anhydride, trimellitic anhydride, succinic acid, adipic acid, azelaic acid, sebacic acid, citric acid, tartaric acid, malic acid, 1,8
-Naphthalic acid, etc. (excluding polyhydric phenol carboxylic acid) 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. 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 pinglycol and 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 includes a melt method and an azeotropic method using an azeotropic solvent such as xylene. Things to be careful about are removing the by-product condensation water from the system as quickly as possible, increasing the capacity of the complete esterification equipment in order to efficiently recover the glycol produced by azeotropy, and also increasing the capacity of the complete esterification equipment. In order to avoid coloring, inert gas may be introduced. 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)] 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 possible to easily store the composition. It is possible to obtain a coating film that improves stability, has even stronger adhesion to metal surfaces, and has excellent 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 characteristics of the present invention, such as temporary rust prevention effect, storage stability, and high corrosion resistance, could not be sufficiently exhibited, and on the other hand, 10% by weight
If it is used in excess of this amount, it is undesirable because it tends to gel during the copolymerization reaction process. In addition, sufficient effects can be obtained within 10% by weight, so 10% by weight
It is economically undesirable to use more than 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] acidophosphite, etc., and salts and esters thereof, or a mixture of two or more thereof. 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. This is not preferable because the crosslink density becomes too high, which tends to reduce the flexibility, water resistance, etc. of the coating film. 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 components 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, n-octyl (meth)acrylate, lauryl (meth)acrylate, tridecyl (meth)acrylate, Stearyl (meth)
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 alone or in an appropriate 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, inpropyl alcohol, n-propyl alcohol; 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, diethylene glycol monobutyl ether; esters such as methyl acetate, ethyl acetate, butyl acetate; ketones such as methyl ethyl ketone, methyl isobutyl ketone, etc. used. 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,
Water-soluble oxyamines such as diisopropanolamine, tripropanolamine, and hydroxylamine may also be used singly or as a mixture of two or more thereof. 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 participates in the crosslinking reaction with the polyester resin and the phosphoric acid group-containing copolymer resin, and is characterized in that it provides the excellent weather resistance and chemical resistance that urethane resins have. 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, one of the characteristics of the present invention, such as the flexibility, pigment dispersibility, and excellent coating appearance of the polyester resin, will be impaired. On the other hand, if the polyester resin exceeds 95% by weight, the phosphoric acid group-containing copolymer resin will inevitably decrease, and the temporary rust prevention effect and corrosion resistance, which are the characteristics 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 , and 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, weather resistance, etc. 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 will deteriorate due to the isocyanate groups that have not reacted with the hydroxyl groups in the resin. The softening temperature of the mixed resin particles of the mixture of polyester resin and phosphoric acid group-containing copolymer resin and blocked isocyanate compound used in the present invention is preferably 30 to 100°C. More preferably the temperature is 40 to 80°C. If the softening temperature is lower than 30°C, the storage stability of the paint tends to decrease, and if it is higher than 100°C, the smoothness of the coating film is undesirable. 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 in this case is the same as the polymerization solvent 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 aggregate with each other and the particles tend to foam during heating, resulting in properties similar to those of water-soluble paints. 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 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 thus obtained suppresses temporary rust prevention on the steel plate, and has excellent adhesion to metal surfaces, corrosion resistance, and water resistance. In addition, polyester resin has excellent flexibility, pigment dispersibility, and coating film appearance, phosphoric acid group-containing copolymer resin has excellent corrosion resistance, hardness, and stain resistance, and urethane resin has excellent corrosion resistance, hardness, and stain resistance. It has excellent weather resistance and chemical resistance, and also has excellent coating performance without foaming (flanks) 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". [Method for producing polyester resin solution] [1] Synthesis of polyester resin PX-1 In a reaction vessel equipped with a thermometer, stirrer, sparge gas introduction pipe, temperature control device, partial condenser, etc., 104 parts of phthalic anhydride and adipic acid were added. Mix 190 parts of propylene glycol, 84 parts of propylene glycol, 67 parts of dipropylene glycol, and 67 parts of trimethylolpropane and heat while flowing nitrogen gas.
After raising the temperature to 200-230℃ and heating for 5 hours, when the acid value reached 20, the system was depressurized and the reaction was continued for another 3 hours. As a result, a solid with an acid value of 8, a hydroxyl value of 75, and a weight average molecular weight of 10,500 was obtained. Resin was obtained. This was dissolved in methyl ethyl ketone to obtain a resin solution with a nonvolatile content of 60%. [2] Synthesis of polyester resin PX-2 Isophthalic acid 250
parts, adipic acid 87 parts, benzoic acid 49 parts, neopentyl glycol 84 parts, propylene glycol 61 parts
A solid resin having an acid value of 12, a hydroxyl value of 85, and a weight average molecular weight of 9,800 was obtained by blending 103 parts of trimethylolpropane and 103 parts of trimethylolpropane and reacting in a nitrogen stream for 8 hours.
Dissolve this in methyl ethyl ketone and the nonvolatile content will be 60
% resin solution. [3] Synthesis of polyester resin PX-3 Isophthalic acid 100
parts, adipic acid 204 parts, benzoic acid 24 parts, neopentyl glycol 52 parts, dipropylene glycol 54 parts, trimethylolpropane 52 parts, 1,6 parts
118 parts of hexanediol was blended and reacted in nitrogen gas for 8 hours to obtain a solid resin having an acid value of 15, a hydroxyl value of 110, and a weight average molecular weight of 8,500. 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 added after vacuum drying at 40℃, and vacuum dried for 2 days. (Non-volatile content: 92.6%), methyl ethyl ketone was added thereto to dilute to 60% non-volatile content to obtain NCO-A. Example 1 25 parts of polyester resin solution (PX-1), 33.3 parts of titanium dioxide, 1 part of flow aid (trade name: Modaflow, manufactured by Monsanto), and methyl ethyl ketone.
Add 10 parts of polyester resin solution (PX-1) to the mill base, which was kneaded and dispersed in a sand mill of 10μ or less (measured with a grind gauge: the same applies below).
52.8 parts blocked isocyanate compound (NCO
-A), 33.6 parts of phosphoric acid group-containing copolymer resin solution (PV-1), and 0.7 parts of dibutyltin dilaurate (dissociation catalyst) were added and mixed with stirring to obtain a uniform pigment dispersion. This is heated under high speed stirring at a water temperature of 15
The pigment dispersion was dropped into 3000 parts of water at ℃ to emulsify it, and the solvent was extracted into the water to form resin particles. Thereafter, filtering and washing with water 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%. 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., HLB15.1) 0.5 parts, 10% aqueous solution of alkali salt thickener of acrylic acid copolymer 2
The resin particles were finely pulverized by dispersion kneading with a sand mill to obtain a slurry-like paint having an average particle diameter of 14 μm and a pH of 7.7. Example 2 25 parts of polyester resin solution (PX-2), 33.3 parts of titanium dioxide, flow aid (trade name: Modaflow:
Add 1 part of Monsanto Co., Ltd.) and 10 parts of methyl ethyl ketone, knead and disperse in a sand mill to a thickness of 10μ or less, and then add polyester resin solution (PX-2) to the mill base.
7.2 parts, blocked isocyanate compound (NCO-
59.5 parts of A), 75.3 parts of a phosphoric acid group-containing copolymer resin solution (PV-2), and 0.8 parts of dibutyltin dilaurate (dissociation catalyst) were added and mixed with stirring to obtain a uniform pigment dispersion. All of the following operations were carried out in the same manner as in Example 1 to obtain a slurry-like paint having an average resin particle diameter of 17 μm and a pH of 7.8. Example 3 25 parts of polyester resin solution (PX-3), 33.3 parts of titanium dioxide, 1 part of flow aid (trade name: Modaflow, manufactured by Monsanto), and methyl ethyl ketone
Add 10 parts of polyester resin solution (PX
-3) 36.3 parts of a methyl ethyl ketone solution of blocked isocyanate compound (trade name: Kleran U-16109: manufactured by Bayer AG) (adjusted to 50% non-volatile content)
52.8 parts, and phosphoric acid group-containing copolymer resin solution (PV
-2) 61.5 parts and 0.6 parts of dibutyltin dilaurate (dissociation catalyst) were added and mixed with stirring to obtain a uniform pigment dispersion. The water temperature is 20℃ under high speed stirring.
was sprayed into 3000 parts of water to emulsify the pigment dispersion and extract the solvent into the water to form resin particles. Thereafter, filtering and washing with water were repeated to obtain a water-containing cake of resin particles with an average particle diameter of about 120 μm and a water content of about 50%. To 100 parts of this water-containing cake, 0.6 parts of a 40% aqueous solution of a nonionic surfactant (trade name Emulgen 910: HLB12.2 manufactured by Kao Atlas) and 4 parts of a thickener (5% aqueous solution of hydroxyethyl cellulose) were added, and the mixture was milled using a ball mill. The resin particles were dispersed and kneaded, and the resin particles were pulverized to obtain a slurry-like paint having an average particle size of 17 μm and a pH of 7.7. Comparative Example 1 In addition to the kneaded and dispersed mill base of Example 1, 100 parts of a polyester resin solution (PX-1) was added, and a butylated methylolmelamine resin with an average degree of condensation of 2.5, a degree of etherification of 2.5, and a water-soluble component of 1% or less. 41.7 parts of a 60% methyl ethyl ketone solution was added and mixed with stirring to obtain a uniform pigment dispersion. A slurry-like paint having an average particle diameter of 15 μm and a pH of 7.6 was obtained in the same manner as in Example 1. Comparative Example 2 Acidophosphoxyethyl methacrylate, ethyl acrylate and 2-ethylhexyl acrylate were removed from the composition of the resin solution (PV-1) used in Example 1, 2-hydroxyethyl methacrylate was made 105 parts, and other monomer types were added. The reaction was carried out in the same manner as in (1) for the production of a phosphoric acid group-containing copolymer resin solution, except for the same amount as the acid value.
16, a hydroxyl value of 91, a weight average molecular weight of 14,700, and a nonvolatile content of 60.3%. To 25 parts of the resin solution, 33.3 parts of titanium dioxide, 1 part of flow aid (trade name: Modaflow, manufactured by Monsanto), and 10 parts of methyl ethyl ketone were added, and after kneading and dispersing in a ball mill to a size of 10μ or less, further 100 parts of the resin solution and Average degree of condensation 2.5,
41.7 parts of a 60% methyl ethyl ketone solution of a butylated methylolmelamine resin with a degree of etherification of 2.5 and a water-soluble component of 1% or less was added and mixed with stirring to obtain a uniform pigment dispersion. A slurry-like paint having an average particle diameter of 16 μm and a pH of 7.7 was obtained in the same manner as in Example 1. The slurry paint prepared in each of the above examples and comparative examples was spray-painted onto a zinc phosphate chemically treated dull steel plate, set for 5 minutes, preheated at 90°C for 10 minutes, and dried by heating at each predetermined temperature. Film thickness approx.
A coating film of 35μ was formed. Table 1 shows the heating drying conditions and physical property test results for the coating film. (However, for test pieces to observe the appearance of the paint film,
(using polished mild steel plate).

【table】

【table】

[Table] As is clear from the above comparative test results table, the coating film obtained from the composition of the present invention has no temporary rusting property immediately after application and is free from foaming (flanking). Furthermore, the physical properties of the coating film, such as adhesion, impact resistance, flexibility, chemical resistance, weather resistance, cycle test resistance, and secondary adhesion, were also significantly superior to the coating film obtained from the comparative example composition. It was excellent.

Claims (1)

[Claims] 1 (A)(a) Polyester resin with a hydroxyl value of 10 to 300 (excluding those using polyhydric phenol carboxylic acid as the acid component)
………15 to 95% by weight and (b) (i) phosphate group-containing α,β-monoethylenically unsaturated monomer and (ii) α,β-monoethylenically unsaturated other than the above (i) Monomers (excluding N-alkoxymethylated monomers of α, β-monoethylenically unsaturated carboxylic acid amide) containing phosphoric acid groups with a hydroxyl value of 3 to 150 obtained from a monomer mixture consisting of copolymer resin
......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.