JPS583516B2 - Hifukuyofun Matsusoseibutuno Seizouhouhou - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a coating powder composition, more specifically,
This invention relates to a method for producing a novel coating powder composition having a small particle size, uniformity, and true spherical shape by obtaining an aqueous polymer composition consisting essentially only of polymer composition particles and water and then drying this. .

In recent years, pollution due to deterioration of air and water pollution has become a problem, and laws have also been put in place to reduce the amount of inorganic and organic substances released into the air and water from paint, which is thought to be a part of the cause. regulations have been added.

In particular, with solvent-based paints, large amounts of organic solvents, which are volatile components, escape during painting and baking, and there is no way to recover them economically, which poses a fire risk, is unhygienic, and pollutes the atmosphere. It is considered to be one of the sources of pollution.

In order to solve these problems, the paint industry has devised various new paint forms that provide coating without escaping contaminants.

For one thing, there is increasing interest in coating powder compositions that can be coated onto a substrate and heated to flow to form a film on the substrate.

Such a coating powder composition does not contain a solvent, so it can solve the above-mentioned problems of solvent-based paints, and has advantages such as reducing the weight of paint to be transported.

As a method for producing the above-mentioned coating powder composition, a method is generally used in which a bulk polymer is pulverized, or a polymer dispersion obtained by suspension polymerization or precipitation polymerization is dried, melted, and then pulverized.

Since such pulverization is usually performed mechanically using a pulverizer such as a ball mill, air jet, or hammer mill, the resulting powder has an irregular shape and a wide particle size distribution.

Furthermore, when obtaining a powder with a small average particle size or when attempting to pulverize a polymer with high toughness, the pulverization efficiency may be poor or even weak, making it difficult to sufficiently achieve the purpose.

Therefore, even if such powder is used for coating, the particle shape is irregular and the particle size distribution is wide, resulting in poor shielding efficiency and poor filling condition during coating, causing pinholes and see-through of the coating.

Therefore, in order to completely hide the substrate, the film must be sufficiently thick, resulting in the disadvantage that the amount of paint used increases.

At present, there are few methods that improve the shortcomings of production methods that require mechanical pulverization. Methods of obtaining powders of particle size are known.

However, according to this method, although the above-mentioned problems caused by mechanical pulverization can be solved to some extent, since the above-mentioned polymer dispersion is directly subjected to spray drying, the resulting powder contains emulsifiers and amines used during polymerization. If such powder is used for painting, it may reduce the water resistance of the film, cause yellowing of the film due to amines generated during baking, and even cause new problems such as air pollution. arise.

The present inventors have conducted intensive research to solve the problems of the above-mentioned manufacturing method that does not use mechanical pulverization, and to provide powder with a more appropriate particle state. The present inventors have discovered that by producing an aqueous polymer composition containing only water and drying it, a uniform, perfectly spherical powder with a small particle size can be obtained, and the present invention has been completed.

The gist of the present invention is to include a polymer dispersed in water and, if necessary, a dispersant, at least one of which contains a carboxyl group, and the carboxyl group is salted (hereinafter referred to as a carboxylic acid base) with an organic or inorganic base. Aqueous polymer composition starting material, which is stabilized in water by the carboxylic acid groups, is mixed with an acidic substance, thereby converting the carboxylic acid groups into free carboxyl groups, and the resulting low molecular salts are produced. The present invention provides a method for producing a powder composition for coating, which comprises removing the water to obtain an aqueous polymer composition consisting essentially of polymer composition particles and water, and then drying this.

The starting materials for the aqueous polymer composition necessary for producing the desired coating powder composition in the heather invention are specifically the following three systems ((a) to (c) 2). These systems and their production methods will be explained in detail below.

(a) A system in which a polymer having a polymer chain derived from an ethylenically unsaturated group and a carboxylic acid group is stably dispersed in water mainly due to the carboxylic acid group.

The monomer for forming the above polymer is one obtained by neutralizing all or part of the carboxyl group of ethylenically unsaturated carboxylic acid with a base (hereinafter referred to as ethylenically unsaturated carboxylate). Can be mentioned.

Ethylenically unsaturated carboxylic acids may be those having one ethylenically unsaturated group and one or more carboxyl groups in the molecule, such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, and fumaric acid. Acids, itaconic acid, monoethyl maleate, monobutyl maleate, mono-2-ethylhexyl maleate, monolauryl maleate, monomethyl icconate, monobutyl itaconate, mono-2-ethylhexyl itaconate, and even 2-human methacrylate. Molar ratio of xyethyl to phthalic anhydride: 1
Examples include reaction products added in a one-to-one ratio.

Examples of the base for converting this ethylenically unsaturated carboxylic acid into its salt include inorganic basic compounds, ammonia, and organic amines.

Examples of inorganic basic compounds include potassium hydroxide, sodium hydroxide, potassium carbonate, etc.; examples of organic amines include monomethylamine, dimethylamine, trimethylamine, monoethylamine, diethylamine, triethylamine, monopropylamine, Monovalent amines such as dimethylpropylamine, monoethanolamine, diethanolamine, triethanolamine,
Water-soluble oxime amines such as N-methylethanolamine, N-aminoethylethanolamine, N-methyldiethanolamine, monoisopropanolamine, diisopropanolamine, triisopropanolamine, and monobutanolamine, and polyvalent amines such as ethylenediamine and diethylenetriamine. Examples include amines.

The above-mentioned ethylenically unsaturated carboxylic acid salt is usually used together with a polymerizable monomer that can be copolymerized with it, and as such a polymerizable monomer, for example, ordinary acrylic acid or methacrylic acid and a carbon number of 14 or less are used. Esters with monoalcohols are most commonly used.

As the above acrylic acid or methacrylic ester,
For example, ethyl acrylate, n-butyl acrylate, 1-butyl acrylate, t-butyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, n-butyl methacrylate, i-butyl methacrylate, t-butyl methacrylate. , lauryl methacrylate, methacrylic acid 2-
Examples include ethylhexyl and cyclohexyl methacrylate.

Furthermore, other copolymerizable monomers may be used as necessary.

Specific examples include the following.

(a) alkenyl aromatic monomers (e.g., styrene α-methylstyrene, chlorostyrene, vinyltoluene, etc.), (b) amides of ethylenically unsaturated carboxylic acids and their substituted amides (e.g., acrylic acid amide, methacrylic acid amide, maleic acid amide, (3) ethylenically unsaturated carboxylic acid nitriles (e.g. acrylonitrile, methacrylonitrile, etc.), (d) ethylenically unsaturated dicarboxylic acid diesters (e.g. dibutyl maleate, diethyl itaconate, etc.), (e) glycidyl acrylate and glycidyl methacrylate, (f) acrylic acid. Addition reaction products of glycidyl or glycidyl methacrylate and fatty acids, addition reaction products of (tri)acrylic acid or methacrylic acid and monoepoxy compounds (for example, Shell Co., Ltd. trade name "Rikiichi Jura E"); Blocked isocyanate group-containing ethylenically unsaturated monomers (for example, blocked vinyl isocyanate or diisocyanate such as tolylene diisocyanate or isophorone diisocyanate) have one incyanate group added to the monomer, which is commonly known as lactam or oxime. compounds in which an ethylenically unsaturated monomer containing an active hydrogen group such as 2-hydroxyethyl methacrylate is added to the remaining isocyanate groups.

When these monomers are used in combination, at least one of the ethylenically unsaturated carboxylates is
-40% by weight, preferably 5-30% by weight, 30-40% by weight of at least one of acrylic acid or methacrylic acid ester
97% by weight, preferably from 50 to 97% by weight, and up to 67% by weight of at least one other copolymerizable monomer.

The ethylenically unsaturated carboxylic acid salt is essential to obtain the starting material in the first place and influences the stability of the aqueous polymer composition to be dried and, if necessary, the crosslinkability of the polymer. Therefore, if the amount is too small, it will be difficult to obtain a satisfactory starting material, and if the amount is too large, it will have an undesirable effect on the performance of the polymer coating, such as water resistance and weather resistance.

Too little ester of acrylic acid or methacrylic acid will have an unfavorable effect on the weather resistance and thermal stability of the polymer coating.

The primary purpose of the ethylenically unsaturated carboxylic acid salt is to provide stability to the aqueous polymer composition as described above, but at the same time it is used to stabilize the aqueous polymer composition. When used as a product, it will affect its crosslinking reactivity, so based on this viewpoint,
A part of it may be replaced with a hydroxyl group-containing ethylenically unsaturated monomer.

The range is a range that does not prevent obtaining the desired starting material;
That is, it is about 20% by weight or less of the amount used above.

Examples of such hydroxyl group-containing ethylenically unsaturated monomers include 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, and 1-methyl-acrylate.
2-hydroxyethyl, 2-hydroxyethyl methacrylate, 1-methyl-2-hydroxyethyl methacrylate, polypropylene glycol monomethacrylate, glycerol monomethacrylate, 3-chloro-2 methacrylate
-Hydroxypropyl, allyl alcohol and the like.

In order to obtain a desired starting material from the above monomer structure, polymerization may be carried out under the same conditions as in ordinary emulsion polymerization methods except that no emulsifier is used.

Normally, emulsion polymerization requires the use of an emulsifier, but if the above monomer composition is adopted, the ethylenically unsaturated carboxylic acid salt initially does not exhibit emulsifying action, so the reaction system can be monomerized by discontinuing stirring. It will separate into two layers of Taiyoshi water,
As the polymerization progresses and the ethylenically unsaturated carboxylic acid salt is incorporated into the polymer, this polymer develops an emulsifying effect, and as a result, it is possible to obtain a stable starting material in the same manner as when ordinary emulsion polymerization is carried out. can.

Note that instead of using the ethylenically unsaturated carboxylic acid salt as described above, the desired starting material may be obtained using the ethylenically unsaturated carboxylic acid.

In this case, the ethylenically unsaturated carboxylic acid and the above-mentioned monomers copolymerizable with the same are preferably blended in the above-mentioned proportions, and this is polymerized by a conventional method, and the resulting polymer contains the polymer in water. The carboxylic acid obtained by adding the necessary and sufficient amount of the above base and water for stable dispersion in the polymer and stirring and mixing under heating at a temperature range above the glass transition point of the polymer and below the boiling point of the base used. A starting material stably dispersed in water is obtained by the action of the base.

(b) In the presence of a low-molecular dispersant, a polymer having a polymer chain derived from an ethylenically unsaturated group and preferably having at least one of a carboxyl group, a carboxylic acid group, and a hydroxyl group is mainly contained in the dispersant. A system that is stably dispersed in water using carboxylic acid bases.

As monomers for forming the above polymer, the above-mentioned (
It is most preferable to adopt the same monomer composition as in the case of the system related to a), but since the presence of a low-molecular dispersant is essential for this system, for ethylenically unsaturated carboxylic acid salts, Part or all of it may be replaced with an ethylenically unsaturated carboxylic acid and/or a hydroxyl group-containing ethylenically unsaturated monomer; No carboxylic acid or hydroxyl group-containing ethylenically unsaturated monomer is used, and at least one of the above acrylic acid or methacrylic acid ester and other copolymerizable monomers is used.
There is no problem even if it has a monomeric composition consisting of seeds.

As the low-molecular dispersant used, for example, so-called soaps are used, and specifically, sodium oleate soap, semi-hardened beef tallow soda soap, potassium oleate soap,
Examples include semi-hardened beef tallow potash soap and castor oil potash soap.

At least one dispersant is used in an amount of 1 to 10 parts by weight per 100 parts by weight of the monomer constituent.

A conventional emulsion polymerization method may be employed to obtain a desired starting material from the combination of the above monomer composition and low-molecular dispersant.

Alternatively, the polymerization may be carried out without using this low-molecular-weight dispersant from the beginning, and then the desired starting material may be obtained by adding the dispersant.

In this case, the monomer constituents are polymerized in advance as in the case of (a) above, and the resulting polymer contains a necessary and sufficient amount of low-molecular-weight dispersion for stable dispersion of the polymer in water. A desired starting material can be obtained by adding the agent and water and stirring and mixing while heating at a temperature range equal to or higher than the glass transition point of the polymer.

In the presence of a polymeric dispersant, it has a polymer chain derived from an ethylenically unsaturated group, and preferably has at least one of a carboxyl group, a carboxylic acid group, and a hydroxyl group, with or without bonding to the dispersant. A system in which the polymer is stably dispersed in water mainly due to the carboxylic acid base in the dispersant.

The monomers forming the above polymer may have the same structure as in the case of the system related to (b) above.

That is, preferably at least one of an ethylenically unsaturated carboxylic acid salt, an ethylenically unsaturated carboxylic acid, and a hydroxyl group-containing ethylenically unsaturated monomer is used as a monomer, and if necessary, the above acrylic acid or methacrylic acid is used. The acid ester and/or other copolymerizable monomer may be used in the same proportions as described for the system related to (a) above.

The polymer used as a dispersant has good compatibility with the above polymer and has an acid value of 50 or more.

selected from alkyd resins (oil-modified alkyds or oil-free alkyds) and acrylic resins,
A compound in which at least a portion of the carboxyl groups in the molecule is neutralized with an organic or inorganic base is used.

In addition, this dispersing agent may have a graft active site to which the above-mentioned monomer or its polymer can be chemically bonded.

Groups that may be present in the dispersant molecule as such active sites include, for example, ethylenically unsaturated groups, groups having active hydrogen that can be abstracted by radicals, and mercapto groups.

This polymeric dispersant contains at least one monomer constituent 10
It is used in an amount of 10 to 200 parts by weight relative to 0 parts by weight.

Of course, in addition to this polymeric dispersant, the above-mentioned low-molecular dispersant may be used in combination, and other emulsifiers may also be used in combination if their presence does not pose a problem when forming the system according to (c) into an aqueous polymer composition. You may.

In order to obtain a desired starting material from the combination of the above monomer composition and polymeric dispersant, a conventional emulsion polymerization method may be employed.

In this case, the polymeric dispersant may be previously dispersed in water, or may be added to or dissolved in the monomer constituent and then added to water and subjected to the heavy reaction.

Alternatively, the polymerization may be carried out without using this polymer dispersant from the beginning, and then the dispersant may be added to obtain the desired starting material.

In this case, the desired starting material can be obtained by directly employing the same method as in the case of (b) above.

The aqueous polymer composition starting material in the present invention may be constituted by each of the above-mentioned systems (a), (b) and (c), or in a state in which such systems are mixed. may be configured.

In consideration of the blocking property of the powder obtained by drying the polymeric product, a polymeric product based on a polymer as a starting material or a polymeric product based on a combination of the polymer and a polymeric dispersant has a glass transition property. It is desirable that the temperature is in the range of 30 to 90°C.

When the above-mentioned starting systems (a), (b), and (c) of the present invention are obtained, if the polymerization method employed is emulsion polymerization or a polymerization method similar thereto, the ordinary emulsion polymerization method may be used. It may be implemented accordingly.

That is, about 0.01 to 5% by weight of a polymerization catalyst is added to the monomer constituents, and the reaction temperature is 0 to 100°C, preferably 3% by weight.
Polymerization is carried out at 0-90°C.

In this case, a method in which each component is mixed together at the beginning,
Alternatively, a method of continuously blending can be adopted.

Examples of the polymerization catalyst include inorganic peroxides such as potassium persulfate, ammonium persulfate, hydrogen peroxide, and sodium percarbonate; organic peroxides such as benzoyl peroxide, di-t-butyl peroxide, and t-butyl hydroperoxide; 2
, 2'-azobis-2,4-dimethylvaleronitrile, and other azo compounds, and peroxides can be used as redox catalysts in combination with reducing agents such as potassium pyrosulfite, sodium bisulfite, and triethanolamine. You can also do it.

Further, if necessary, chain transfer agents such as mercaptans such as n-octylmercabutane and t-dodecylmercabutane, disulfides such as diisopyrzantogen disulfide, and organic halogen compounds can be used.

In addition, when other polymerization methods are employed, they may be carried out according to ordinary suspension polymerization or bulk polymerization.

An aqueous polymer composition is obtained by treating the above-mentioned starting material with an acidic substance and removing the produced low-molecular salts from the system.

The prevailing idea has been that if hydrogen ions are supplied to an emulsion by an acidic substance, the emulsion will aggregate.

However, even if the starting material having a specific composition was used as described above and the carboxylic acid base was converted to a free carboxyl group by treatment with an acidic substance, the particles dispersed in water did not aggregate. A homogeneous and stable aqueous polymer composition can be obtained because each polymer can exist stably individually.

When treating with an acidic substance, it is desirable to dilute the starting material in advance with water to a nonvolatile content of 60% by weight or less, if necessary.

The above-mentioned acidic substance may be any substance as long as it can dissolve in water and supply hydrogen ions, such as inorganic acids such as sulfuric acid, hydrochloric acid, phosphoric acid, carbonic acid (carbon dioxide gas), formic acid, acetic acid, monochloroacetic acid, dichloroacetic acid, trichloroacetic acid, lactic acid,
Examples include organic acids such as butyric acid and glycolic acetic acid, usually IN
It is recommended to use the following aqueous solutions.

The treatment may be carried out by mixing and stirring the two, but the efficiency of the treatment can be increased by irradiating them with ultrasonic waves.

When the glass transition point of the polymer in the starting material is low, it is desirable to carry out the above treatment in a cooled state.

In the case of carbon dioxide gas, it may be blown directly into the starting material, or if solid carbon dioxide (dry ice) is used,
It is more preferable that the starting material can be cooled at the same time.

It is desirable that the amount of acidic substance used in such a treatment end immediately after the pH value of the starting material to be treated changes.

In order to remove the low-molecular salts that are formed, the starting material that has been treated with an acidic substance can be removed using conventional methods (e.g., centrifugation, ion exchange, diaphragm, reverse osmosis, natural sedimentation, gel precipitation, etc.). If necessary, water (preferably ion-exchanged water) may be added to the resulting precipitate or its hydrate, and the same separation procedure may be repeated to wash the precipitate or its hydrate. Further, if necessary, an arbitrary amount of water (preferably ion-exchanged water) is added to obtain an aqueous polymer composition consisting essentially of polymer composition particles and water.

Note that various fatty acids (e.g., oleic acid and beef tallow) generated from the above-mentioned low-molecular-weight dispersants may coexist with the polymer as they are in the composition, but if necessary, the composition may be mixed with, for example, n-hexane. It can be removed by washing with etc.

Next, the aqueous polymer composition is subjected to a drying treatment.

As the drying method, a usual drying method such as a spray drying method, a fluidized bed drying method, a reduced pressure drying method, etc. is adopted.

It is desirable that the drying temperature be within a range below the glass transition point of the polymer and as high as possible.

Such drying results in a coating powder composition having substantially the same shape and size as the original polymer.

The coating powder composition of the present invention can be coated as it is on a substrate by an electrostatic coating method or a fluidized dip coating method, and then fluidized or hardened by heating to form a good coating.

The coating powder composition of the present invention contains a modifying resin such as an alkyd resin, an acrylic resin, an aminoplast resin, a polyfunctional block isocyanate, a polyvalent carboxylic acid, an epoxy resin, etc. inside or outside the particles, or both. curing agents, organic and inorganic pigments, antifoaming agents, surface conditioners, etc. may be included.

Of course, such an agent can be added during or before or after producing the coating powder composition of the present invention, but the addition may be carried out during the production of the starting material, the aqueous polymer composition, and the coating powder composition. This should be done with consideration given to not interfering with the stability and performance of the system being used.

For example, in order to include these agents inside the powder composition particles for coating of the present invention, they may be added and dispersed or dissolved in the composition to be subjected to polymerization or at least one member thereof during the production of the above-mentioned starting material. .

By adopting the method of the present invention consisting of the above configuration,
It is possible to advantageously produce a coating powder composition having a small particle size, uniformity, and true spherical shape, which could not be obtained by conventional methods, and at the time of producing the aqueous polymer composition starting material. The average particle diameter can be adjusted to a range of about 0.1 to 50 μm by appropriately changing the type of monomer structure, the blending amount, and the amount of various dispersants.

Next, the present invention will be specifically explained with reference to Examples.

The present invention will be specifically explained with reference to Examples.

In addition, "parts" in the examples means "parts by weight."

Example 1 In a reaction vessel equipped with a stirrer, thermometer and reflux condenser,
46 parts of methyl methacrylate, 15 parts of styrene, 20 parts of n-butyl acrylate, 15 parts of 2-hydroxyethyl methacrylate, 12 parts of methacrylic acid, 1.5 parts of t-dodecylmercabutane, 15 parts of triethylamine, 2 parts of ammonium persulfate. After charging a mixture consisting of 100 parts of ion-exchanged water and stirring at 65 to 70°C for 2 hours, add 92 parts of methyl methacrylate, 30 parts of styrene,
A mixture consisting of 40 parts of n-butyl acrylate, 30 parts of 2-hydroxyethyl methacrylate, 3 parts of t-dodecylmerbutane, 4 parts of ammonium persulfate, and 200 parts of ion-exchanged water was added at once, and stirred at 65 to 70°C. When the reaction was carried out for 4 hours, a stable aqueous dispersion A having a non-volatile content of 50% by weight was obtained.

50 parts of this aqueous dispersion A was diluted with 200 parts of ion-exchanged water, and while stirring, 2400 parts of a 1/200N sulfuric acid aqueous solution was diluted with 200 parts of ion-exchanged water.
ml, a stable aqueous dispersion A' with substantially no agglomeration was obtained.

Next, the aqueous dispersion A' was centrifuged, the resulting precipitate was washed with water, diluted with ion-exchanged water to a nonvolatile content of 30% by weight, redispersed, and dried in a spray dryer (inlet air temperature: 450°C). When subjected to spray drying at an outlet air temperature of 50°C), there was virtually no agglomeration, and the particles were perfectly spherical and had a particle size of 0.1~
A powder with a uniform particle size distribution of 0.5μ was obtained.

When the above powder was electrostatically coated on an iron plate and baked in a hot air drying oven at 180° C. for 30 minutes, a colorless, transparent, smooth, glossy coating that did not yellow was obtained.

Example 2 Into a reaction vessel similar to Example 1, 100 parts of ion-exchanged water was charged, and while stirring at 65 to 70°C, 46 parts of methyl methacrylate, 20 parts of styrene, 15 parts of n-butyl acrylate, and 2 parts of methacrylic acid were added. - a mixture of 15 parts of hydroxyethyl, 12 parts of methacrylic acid, 1.5 parts of t-dodecylmerbutane and 14 parts of triethylamine and a mixture of 2 parts of ammonium persulfate and 50 parts of ion-exchanged water were separately prepared simultaneously for 1 hour. After stirring for 1 hour after the dropwise addition, 150 parts of ion-exchanged water was added and while maintaining the temperature at 65 to 70°C, 92 parts of methyl methacrylate and 4 parts of styrene were added.
0 parts, 30 parts of 2-hydroxyethyl methacrylate, t-
A mixture consisting of 3 parts of dodecylmercabutane and 30 parts of N-butoxymethylol acrylamide and a mixture consisting of 4 parts of ammonium persulfate and 100 parts of ion-exchanged water were separately and simultaneously dropped over 2 hours, and the mixture was stirred for 2 hours after the completion of the dropwise addition. As a result, a stable aqueous dispersion with a nonvolatile content of 40% by weight was obtained.

50 parts of this water dispersion was diluted with 2000 parts of ion-exchanged water, and 120 ml of 1/10N sulfuric acid was gradually added dropwise to this while stirring, and then centrifuged to obtain a precipitate (non-volatile content: 60% by weight). After washing with ion-exchanged water and drying in a fluidized bath dryer (air temperature 50°C), a uniform powder with substantially no agglomeration and a perfect spherical shape with a particle size of 0.1 to 0.5μ was obtained. .

When the above powder was electrostatically coated and baked under the same conditions as in Example 1, a colorless, transparent, smooth and glossy film was obtained.

Example 3 Into a reaction vessel similar to Example 1, 500 parts of a 5% by weight polyacrylic acid aqueous solution was charged, and 31 parts of dimethylaminoethanol was added thereto. While stirring, 13 parts of 2-hydroxyethyl acrylate and methacrylic acid were added. Methyl 36 parts, styrene 45 parts, acrylic acid n-butyl 8 parts, methacrylic acid n
A mixture consisting of 18 parts of -butyl, 4 parts of t-dodecylmerkabutane, and 6 parts of 2,2'-azobis-2,4-dimethylvaleronitrile was added at once and stirred at 65 to 70°C for 5 hours, resulting in a non-volatile content of 19 A stable aqueous dispersion with a particle size of several microns in weight percent was obtained.

While stirring this aqueous dispersion, add 1/10N-sulfuric acid 3400
ml was gradually added dropwise, followed by filtration and water washing, and the resulting residue was directly subjected to spray drying (artificial air temperature 150℃, outlet air temperature 50℃). A uniform powder with a diameter of several μm was obtained.

When the above powder was electrostatically coated and baked under the same conditions as in Example 1, a colorless, transparent, smooth and glossy film was obtained.

Example 4 In a reaction vessel similar to Example 1, 46 methyl methacrylate was added.
15 parts of styrene, 20 parts of n-butyl acrylate, 15 parts of 2-hydroxyethyl methacrylate, 24 parts of methacrylic acid, 1.5 parts of t-dodecylbutane, 7.4 parts of sodium hydroxide, ammonium persulfate. 2 parts and 150 parts of ion-exchanged water and heated at 65 to 70°C with stirring.
After reacting for an hour, 92 parts of methyl methacrylate was added to this,
A mixture of 30 parts of styrene, 40 parts of n-butyl acrylate, 30 parts of 2-hydroxyethyl meccrylate, and 3 parts of t-dodecylbutane and a mixture of 4 parts of ammonium persulfate and 200 parts of ion-exchanged water were separately prepared. They were simultaneously added dropwise over a period of 2 hours, and stirring was continued for 2 hours after the completion of the addition to obtain a stable aqueous dispersion with a non-volatile content of 47% by weight.

Dilute 50 parts of this water dispersion with 200 parts of ion-exchanged water,
While stirring this, 1/200N-sulfuric acid aqueous solution 4520ml
The precipitate obtained was washed with water, diluted with ion-exchanged water to a nonvolatile content of 30% by weight, redispersed, and spray-dried (inlet air temperature 150°C, When the powder was exposed to an outlet air temperature of 50° C., a uniform powder with substantially no agglomeration, perfectly spherical shape, and a particle size of 0.1 to 0.5 μm was obtained.

When electrostatic coating and baking were performed using the Joki powder under the same conditions as in Example 1, a colorless, transparent, smooth, non-yellowing, glossy film was obtained.

Example 5 In a reaction vessel similar to Example 1, 46 methyl meccrylate was added.
15 parts of styrene, 20 parts of n-butyl acrylate, 15 parts of 2-hydroxyethyl methacrylate, 8 parts of sodium oleate soap, 1.5 parts of t-dodecylmercabutane,
After charging 2 parts of ammonium persulfate and 150 parts of ion-exchanged water and reacting at 65 to 70°C for 2 hours with stirring,
To this was added a mixture consisting of 92 parts of methyl meccrylate, 30 parts of styrene, 40 parts of n-butyl acrylate, 30 parts of 2-hydroxyethyl methacrylate, and 30 parts of t-dodecylbutane, 4 parts of ammonium persulfate, and 200 parts of ion-exchanged water. A mixture consisting of 1.5% and 1.0% was simultaneously added dropwise over a period of 2 hours, and stirring was continued for 2 hours after the completion of the addition, to obtain a stable aqueous dispersion with a nonvolatile content of 45% by weight.

Dilute 50 parts of this water dispersion with 200 parts of ion-exchanged water,
While stirring this, 4500 m of 1/200N-sulfuric acid aqueous solution was added.
The precipitate obtained was washed with water, diluted with ion-exchanged water to a nonvolatile content of 30% by weight, redispersed, and spray-dried (inlet air temperature 150°C, When the powder was exposed to an outlet air temperature of 50° C., a uniform powder with substantially no agglomeration, perfectly spherical shape, and a particle size of about 0.2 μm was obtained.

When the above powder was electrostatically coated and baked under the same conditions as in Example 1, a colorless, transparent, smooth and glossy film was obtained.

Example 6 In a reaction vessel similar to Example 1, 400 parts of a 10% by weight polyacrylic acid aqueous solution and 5 parts of dimethylaminoethanol were added.
To this were added 160 parts of the mixture (A) shown below, 80 parts of titanium oxide (trade name "Ti-PureR-900" by DuPont) and the above mixture (A) while stirring and maintaining the temperature at 70°C. A mixture consisting of 50 parts of copolymer, 2 parts of ammonium persulfate and 5 parts of ion-exchanged water.
A mixture consisting of 0 parts was added separately and simultaneously over a period of 3 hours, and stirring was continued for 2 hours after the completion of the addition, to obtain a stable aqueous dispersion with a non-volatile content of 48% by weight.

Mixture (A) A monomer mixture with the following composition is used:

Hydroxypropyl acrylate 30 parts Methyl methacrylate 9 parts Styrene
110 parts n-butyl acrylate
21 parts n-butyl methacrylate 32 parts Next, 50 parts of the above dispersion was diluted with 1950 parts of ion-exchanged water, and while stirring, 35 parts of an IN-sulfuric acid aqueous solution was gradually added dropwise, and then centrifuged. The obtained precipitate was diluted with an arbitrary amount of ion-exchanged water, redispersed, and spray-dried (inlet air temperature 150°C, outlet air temperature 50°C).
When subjected to this process, a perfectly spherical powder with a particle size of several microns was obtained with virtually no agglomeration.

When electrostatic coating and baking were performed using the above powder under the same conditions as in Example 1, a smooth and glossy film was obtained.

Claims (1)

[Claims] 1 Contains a polymer dispersed in water and a dispersant if necessary, at least one of them contains a carboxyl group, the carboxyl group is converted into a salt (carboxylic acid base) with an organic or inorganic base, and the carboxylic acid base The aqueous polymer composition starting material, which has been stabilized in water, is mixed with an acidic substance, thereby converting the carboxylic acid groups into free carboxyl groups, removing the resulting low molecular weight salts, and then drying. A method for producing a characteristic coating powder composition.