JPS6031226B2 - Method for producing acrylic powder coating composition for electrostatic coating - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing an acrylic powder coating composition for electrostatic coating, and more specifically to an electrostatic coating in which a pigment is dispersed in acrylic polymer powder particles. The present invention relates to a method for producing a powder coating composition for use in a vehicle.

As paints, solution-type paints in which paint components are dissolved in organic solvents or emulsion paints in which paint components are dispersed in an aqueous medium have been widely used.

However, the former has a strong risk of causing environmental pollution due to the organic solvents that evaporate, while the latter lacks the physical and chemical properties of the resulting paint film. Paints were introduced, and painting methods using them were developed. This paint is made mainly of resin such as polychlorinated pinyl resin, epoxy resin, polyester resin, or polyamide resin, and pigment, and has a diameter of approximately 30 to 300 mm.
It is a powder consisting of micron particles. This paint is sprayed onto the object to be coated with a flame and melts it to form a coating film.Thermal spraying method involves spraying it onto the object to be coated and then heating it together with the object to melt it to form a coating film. A fluidized bond is fluidized with air, into which a preheated or electrically charged object is charged, adhered to the object, and then heated together with the object to be painted to melt it and form a coating film. method, electrostatic dynamic bonding method, and static dew drying method in which the powder coating is forced to be charged to a high voltage while flowing with air to electrostatically adhere to the object to be coated, and then heated and melted to form a coating consistency. Used in methods such as spray painting. Articles coated in this manner include household appliances, steel furniture, general-purpose pipes, automobile parts, and others. Of these coating methods, the last mentioned static dry spray coating method has recently attracted particular attention and is undergoing significant development.

The acrylic powder coating used as the powder coating for static-dry spray painting was produced by the following method.

Namely, '1 - Melt pulverization method in which the resin is heated and melted, coating film components such as pigments and additives are added, thoroughly kneaded, and then pulverized ■ The resin is powdered in advance, and pigments, additives, etc.
Dry blending method in which coating film constituents such as additives are added and mixed using a high-speed rotating mixer [3] After dissolving the resin in a solvent, coating film constituents such as pigments and additives are added and the mixture is vigorously stirred. This includes the solution deposition method, which adds a non-solvent and precipitates the powder coating.

In any of these methods, secondary processing as described above is applied to the resin obtained by manufacturing in separate steps, so the resulting powder coating has a major drawback of being expensive.

Furthermore, since method '1-- melts and pulverizes the coating film components, the powder coating obtained has particle sizes other than the intended particle size, especially fine particles, which may become unusable. Otherwise, the fine particles must be regenerated by heating and melting to be used again, making them even more expensive.

In addition, the melt-grinding method has the disadvantage that the powder obtained is in the form of non-spherical particles, so the fluidity during coating is poor and the workability is not sufficient. In addition, in the powder coating obtained by method (2), the surface of the resin particles is mainly covered with pigment, so the fusion between the resin particles is not complete, and when this is used, a smooth coating film cannot be obtained. Hard to get.

In order to make the coating smooth, it is necessary to heat the resin to a temperature considerably higher than the melting temperature of the resin itself, so there is a risk that the resin may change in quality. Method (3) requires steps such as dissolving the resin, precipitation of powder coating particles, and recovering the solvent, and is not practical. Powder coatings have not been able to take full advantage of the unique features of acrylic resins.

The present inventors previously invented a method for producing a powder coating that eliminates the drawbacks of conventional acrylic powder coatings, and filed a patent application for this method.

The gist of this is that monomers represented by the general formula (R represents day or CH3 group, R2 represents a hydrocarbon group having 1 to 18 carbon atoms), or a type of copolymerization of these monomers with these monomers. This is a method for producing an acrylic powder coating suitable for powder coating, which is characterized by adding a pigment and, if necessary, other additives to the above monomers and polymerizing them.

(Special Seki 49-96029). In the powder coating obtained by this invention, the pigment is well dispersed in the powder particles, and each particle is approximately spherical.
It has the advantage of being able to considerably lower the baking temperature and simplifying the manufacturing process.

However, even with this method, the resulting powder coating has a small amount of pigment on its particle surface, and when this is used to make the coating stiff, the appearance of the coating surface is not sufficient, and it is difficult to apply electrostatic coating. When used for commercial purposes, there were some problems with workability, and there was room for further improvement.

The present inventors conducted research aimed at obtaining an acrylic powder coating composition for electrostatic coating and a method for producing the same without the above-mentioned drawbacks, and as a result, they obtained the following knowledge and completed the present invention.

{1} Only when emulsion polymerization is carried out under intense conditions, particles that can be mechanically separated from solid to liquid can be obtained, and particles with a particle size distribution suitable for electrostatic coating and containing pigment inside can be obtained. A spherical powder is obtained.

■ For polymerization, acrylic acid ester, methacrylic acid ester, or a monomer that is liquid at room temperature that can be copolymerized with these, pigments, surfactants, and other additives as necessary are kneaded in advance. The pigment is easily dispersed and contained inside the particles.

{3- The high specific gravity (hardness) of the obtained powder coating composition is preferably 0.2 or more, and if it is less than this value, it is difficult to bake the coated surface to fuse the powder coating particles and form a coating film. , cracks appear in this.

In addition, the volume resistivity value of powder coating particles is 1 to 60.
A powder coating with a resistance value outside this range is unsuitable because the coating film tends to separate from the painted surface. That is, the present invention relates to one or more acrylic monomers represented by the general formula (R is a day or a CH group, R2 is a hydrocarbon group having 1 to 18 carbon atoms), or this acrylic monomer. and one or more monomers copolymerizable with the monomer in an aqueous medium in the presence of a surfactant and a pigment in an amount of 5% by weight or more and less than 2% by weight based on the total monomers, and if necessary, A UV absorber, a stability improver, a molecular weight regulator, a fluidity improver, and a hardening agent are added, and the ratio is 200 to 120 using a strong hawk, that is, a retainer with turbine blade-shaped blades. Emulsion polymerization is carried out under conditions of about pm, diameter 30 to 250 microns, volume specific electrical resistance 1 to 1 and 60, skin, high specific gravity 0.4.
This invention relates to a method for producing an acrylic powder coating composition for electrostatic coating, which comprises obtaining a substantially spherical polymer and then mechanically separating the polymer from an aqueous medium. It is.

The monomers represented by the general formula (R, represents a hydrogen or CH3 group, and R2 represents a hydrocarbon group having 1 to 18 carbon atoms) used in the present invention include methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, lauryl acrylate, stearyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, 2-ethylhexyl methacrylate, lauryl methacrylate, stearyl methacrylate, benzyl acrylate, phenylacrylate, etc. Among these, n-butyl methacrylate,
Particularly preferred is ethyl methacrylate.

When two or more of the above monomers are used, they can be used in any ratio depending on the purpose. Monomers that can be copolymerized with the above monomers include glycidyl acrylate, glycidyl methacrylate, allyl glycidyl ether, hydroxyethyl acrylate, hydroxyethyl methacrylate, and jetylaminoethyl acrylate. , jetylaminoethyl methacrylate, vinylpyridine, acrylic acid,
Methacrylic acid, maleic acid, maleic anhydride, dioctyl maleate, styrene, methylstyrene, pinyltonoleene, N-methylolacrylamide, N-methylolmethacrylamide, acrylamide, methacrylamide, acrylonitrile, methacrylonitrile, butadiene, vinyl chloride, vinyl acetate , vinyl propionate,
Vinyl caprylate, isobutyl vinylenal, vinyl chloride IJ deso, itaconic acid, N-phenylmethacrylamide, 2-vinylnaphthalene, allyl acetate, allyl acrylate, pinyl isocyanate, vinyl urethane, and the like are used.

One or more of these monomers can be arbitrarily selected and used, and the amount used is based on the monomer represented by the above general formula,
Usually 0.05-300% by weight, preferably 0.1-10%
% by weight.

The monomer represented by the above general formula and the monomer copolymerized therewith can be added all at once at the start of polymerization, but depending on the case, they can also be added sequentially as the polymerization progresses.

Pigments used in the present invention include lead cyanamide, yellow lead, zinc yellow, barium chromate, navy blue, silver vermilion, cadmium yellow, antimony sulfide, cadmium red, precipitated barium sulfate, lead sulfate, zinc white, titanium oxide, Benkara, iron black,
Inorganic pigments such as chromium oxide, ultramarine blue, precipitated calcium carbonate, carbon black, lamp black, graphite, clay, cobalt blue, and yellow ±, naphthol green B
, Pigment Green B, Naphthol Yellow S, and other nitro pigments, Permanent Red Station, Brilliant Fast Scarlet, Hansa Yellow 30, Benzidine Yellow, Resole Red, Lake Red C, Lake Red D
, Brilliant Carmine Bait, Permanent Red F Porridge,
pigment scarlet $, azo pigments such as para red, phthalocyanine blue, phthalocyanine green,
Phthalocyanine pigments such as Fast Sky Blue, permanent red BL, isoindorinone pigments,
Organic pigments such as dioxazine violet, aniline black and quinacridone red are used.

One or more of these pigments can be arbitrarily selected and used, and the amount used is preferably 0.1 to 5% by weight based on the total monomers.

In addition, one or more of these pigments can be combined with acrylic acid ester,
in advance with methacrylic acid ester or one or more monomers copolymerized with these, surfactants, or other additives,
Adding the pigment during polymerization after kneading with a three-roll mill, ball mill, etc. is effective for retaining the pigment inside the particles and obtaining particles with a good shape (spherical shape).

In this case, the amount of the monomer that mixes with the pigment is preferably 0.5% by weight or more based on the total monomers.

All of the surfactants used in the emulsion copolymerization reaction of the present invention are known as surfactants, but the concentration used is significantly higher than in conventional cases, and the concentration of surfactants used is significantly higher than in conventional cases. It is necessary to use more than % by weight.

However, it is not economical to add more than 2% by weight. Further, if the amount is less than 5% by weight, it is difficult for the pigment to enter the particles. Particularly suitable surfactants for use in the present invention include anionic surfactants such as sodium dodecylbenzene sulfonate, polyethylene glycol alkyl ether sulfate, sodium dialkyl sulfosuccinate, polyethylene glycol sorbitan alkyl ester, Among nonionic surfactants such as polyethylene glycol alkyl ether, polyethylene glycol alkyl phenyl ether, and polypropylene glycol polyethylene glycol ether, HLB (hydrophilic-lipophilic balance)
is 13 or more, and enteric ionic surfactants such as alkylpicolinium chloride and alkyltrimethylammonium chloride. In the present invention, these surfactants also show very good results when two or more of the above-mentioned pigments are used in combination to prepare a paint exhibiting an intermediate color.
Conventionally, the condition of carrying out vigorous rope worship adopted in the present invention has been rejected as unfavorable in emulsion polymerization reactions.

In the present invention, these conditions have a great influence particularly on the particle size of the polymer.

The particle size of the polymer particles is closely related to the appearance of the coating film, the performance of the coating film, and the workability during electrostatic coating.

That is, in order to obtain a thin coating film, the smaller the particle diameter is, and in order to obtain a thick coating film, the larger the particle diameter is.

However, if the particle size is extremely small, good results cannot be obtained in terms of coating work, such as a poor recovery rate of powder coating during coating.

In the method of the present invention, this particle size can be easily adjusted, and the particle size of the powder is preferably in the range of 30 to 250 microns.

In addition, by adjusting the particle size to a suitable range,
The heat of polymerization generated during polymerization can be easily removed, and the polymerization products can be separated using mechanical separation methods that have rarely been used to separate products obtained by conventional emulsion polymerization methods, such as centrifugation. A method using a sedimentator, a centrifugal filter, especially a decanter-type continuous discharge centrifugal D settler, a basket-type centrifugal D filter, etc. is possible. The produced powder particles are dried by a conventional method,
Namely, flash drying method, fluidized drying method, vacuum drying method,
A tray drying method or a combination of these methods can be used.

Further, the particle size of the powder that becomes lumpy during drying can be adjusted using a suitable pulverizer or the like.

In the present invention, by combining the extremely high concentration of surfactant mentioned above with the harsh rope azalea, the emulsion polymerization reaction can be maintained well, and the acrylic resin can be produced which is especially suitable for dry spray painting. A powder coating composition could be obtained.

This violent swarm refers to the fly swarm conditions that are used in the suspension polymerization method, such as using a rope swarm with a baffle plate and turbine blade-shaped blades to fly at 200 to 120 pm. means. In conventional emulsion polymerization, the rope must be relatively gentle, and when paddle-shaped or anchor-shaped blades are used, the rope-stretching speed of the rope-stripping machine is usually 4.
It is 0-6pm. The dispersion agent, polymerization initiator, polymerization degree regulator, etc. used in the present invention are all conventional ones.

As the dispersed soot, an aqueous medium, ie, water, a mixed solution of water and methanol, etc. can be used, but water is preferable. The amount used is 75 to 100% by weight, preferably 200 to 400%, based on the total amount of monomers. If it is less than this, there will be a problem in removing the heat of polymerization, and if it is more than this, the resulting powder coating composition particles will have a high specific gravity of 0.2 or less, so the shrinkage of the coating film will occur during the baking process described above. Cracks occur and a good coating film cannot be obtained. As the polymerization initiator, a water-soluble polymerization initiator such as hydrogen peroxide, ammonium persulfate, potassium persulfate, or a water-soluble redox catalyst is used. Of course, two or more of these may be used in combination. The addition method may be such that the entire amount is added at the start of polymerization, or it may be added sequentially as the polymerization progresses. The amount used is 0.01~ based on the total amount of monomers.
It is preferably about 3% by weight. In the production method of the present invention, the polymerization reaction system may be acidic or alkaline, and sodium hydrogen carbonate, ammonium carbonate, acetic acid, etc. are used as the pH adjuster. Other additives that may be added as necessary include ultraviolet absorbers, thermal stability improvers, molecular weight regulators, fluidity improvers, and curing agents.

Examples of ultraviolet absorbers and thermal stability improvers include 2-hydroxy-4-methoxybenzophenone, 2,4-dihydroxybenzophenone, 2-(2'-hydroxy-5'-methylphenyl)penzotriazole, phenyl salicylate, and dioctyl sulfate. Ido, 1,3,8 triazor 7,7,9,9-tetramethyl-2,4-dioxy-spiro[4,5]decane, 2-cyanoethyl octyl mercaptan, and the like are used.

One or more of these can be arbitrarily selected and used as needed. Fluidity improvers include phthalate esters such as diptyl phthalate and 2-ethylhexyl phthalate, condensed epoxy resins of epichlorohydrin and 2,2-pis(4-hydroxyphenyl)propane, polyesters, and other coatings. A resin or the like having the ability to improve the fluidity of the membrane is used. One or more of these can be arbitrarily selected and used as necessary, and the amount used is 0.000000000000000000000000000000000000,0000.
A weight percentage of 5 to 3 is preferred. Examples of molecular weight regulators include mercaptans such as ethyl mercaptan, propyl mercaptan, butyl mercaptan, octyl mercaptan, dodecyl mercaptan, 2-mercaptoethanol, thiophenol, and ethyl mercaptoacetate, and those with chain transfer effects such as carbon tetrafluoride. Compounds can be used.

Furthermore, thermosetting acrylic powder coatings can also be produced by the method of the present invention.

As the curing agent, a compound having the effect of reacting with the acrylic resin to cause crosslinking, such as dicyandiamide, boron trifluoride-piveridine, an epoxy compound, and an acid anhydride, is used.

One or more of these can be arbitrarily selected and used as required, and can be added all at once at the start of polymerization, added sequentially as polymerization progresses, or mixed into a suspension or powder after completion of polymerization. According to the present invention, pigments, molecular weight regulators if necessary, and other additives are added at the start of polymerization or during polymerization, so that they are substantially included in the resulting resin particles, A spherical powder coating having a size of 300 microns or a shape close to the spherical shape is obtained.

In the present invention, the disadvantages of the conventional acrylic powder coating manufacturing method,
In other words, problems such as the complexity of the manufacturing process and the deterioration of the resin during manufacturing have been solved.

Further, the powder coating composition obtained by the method of the present invention has great advantages such as being able to be formed into a coating film at a low temperature since the pigment is not substantially present on the surface of the coating particles.

In addition, conventional powder particles whose surfaces are covered with pigments generally have low volume resistivity and are unsuitable for static-dry spray painting, but the composition of the present invention overcomes this drawback. do not have.

The method for producing an acrylic powder coating of the present invention and the coating composition obtained by this method have the following significant industrial effects and advantages.

'1' The powder coating obtained by the present invention has a particle surface substantially composed of a resin component, and the particles can be easily fused together, so compared to the acrylic powder coating obtained by the conventional dry blending method. Baking temperature is lowered by 20~40oo.

■ Since the temperature at dawn can be lowered, there is less deterioration of the resin and less discoloration.

'3} Since spherical particles are obtained, the powder itself has excellent fluidity and the coating thickness can be easily adjusted, making it particularly suitable as a paint for static dry spraying.

■ Compared to the conventional method, the manufacturing process can be simplified, resulting in significant cost reductions.

Next, the embodiments of the present invention will be described with reference to Examples, but the present invention is not limited to the following Examples.

In Examples and Comparative Examples, all parts and % indicate parts by weight and % by weight. Example Titanium oxide 25
1 part, 6 parts of polyethylene glycol nonylphenyl ether of HLB 14, 2 parts of ethyl acrylate, 8 parts of ethyl methacrylate, and 5 parts of styrene were sufficiently kneaded in a high-speed stirrer. Polymerization can with can (can regulation 35 skin can height 78c desk bull margin 3 blades,
After adding 1 part of ammonium persulfate, 0.2 parts of ethyl mercabutane, and 30 parts of water, the lid of the polymerization reactor was closed, and the inside of the polymerization reactor was replaced with nitrogen.

Then, while stirring (rotation speed: 80 pm), the mixture was flooded at 60:00 pm and polymerized at the same temperature for 8 hours. After the polymerization was completed, the obtained product was separated using a centrifuge and dried. As a result,
A powder with a polymerization yield of 95%, a particle size of 60 to 130 microns, and a hard high specific gravity of 0.32 (Powder Tester manufactured by Hosokawa Iron Works → Koyoru) was obtained.

This powder coating is applied to cold rolled steel plates (JIS-G-3141).
When it was electrostatically painted and baked at 200 oo for 5 minutes, a beautiful white coating with a thickness of 100 microns was obtained. Table 1 shows the physical properties of this paint and coating hardness. Example 2 1 part of carbon black and 20 parts of butyl methacrylate were mixed in advance, and 8 parts of sodium dodecylbenzenesulfonate and 18 parts of butyl methacrylate were added to the resulting mixture and thoroughly kneaded with a high-speed stirrer. Example 1
0.2 parts of potassium persulfate, 0.3 parts of thiophenol and 5 parts of water
After adding 0 anchor portions, the inside of the polymerization reactor was purged with nitrogen.

Then, while stirring (rotation speed 100 pm) 6500
The mixture was flooded with water and polymerized at the same temperature for 10 hours. After the polymerization was completed, the obtained product was separated using a centrifuge and dried. As a result, a powder with a polymerization yield of 96%, a particle size of 60 to 140 microns, and a high specific gravity (hardness) of 0.35 was obtained.

This powder contained pigments very well dispersed inside the particles, and its volume resistivity values were 7×1 and 50×1.
This powder coating was electrostatically coated in the same manner as in Example 1, and
After phosphorizing with C for 6 minutes, a beautiful white coating film with a thickness of 50 microns was obtained. Table 1 shows the physical properties of this paint and coating film. As is clear from this table, the coating temperature of the paint of this example is low, and the resulting coating film has chemical resistance, water resistance,
It has excellent weather resistance and has a rough hardness.

Example 3 2 parts of titanium oxide, 3 parts of phthalocyanine, 12 parts of ethyl methacrylate and 3 parts of butyl methacrylate were mixed in advance, and 12 parts of polyethylene glycol solpitan monostearate was added to the resulting mixture, The paste obtained by thoroughly kneading the slurry with a high-speed stirrer was poured into the polymerization reactor equipped with a stirrer as shown in Example 1, and then the persulfate power was added to IJum 0. After adding 0.3 part of ammonium persulfate, 0.1 part of n-butyl mercaptan, and 400 parts of water, the inside of the polymerization reactor was purged with nitrogen.

The mixture was then flooded to 70 qo with stirring (rotation speed: 70 pm) and polymerized at the same temperature for 8 hours. After the polymerization was completed, 2 parts of dioctyl sulfide and 1 part of phenyl salicylate were added, and the mixture was stirred for an additional 3 minutes, and the resulting product was separated using a centrifuge and dried. As a result, the polymerization yield was 93%.
, particle size 30-120 microns, high specific gravity (hardness) 0.3
4 powder was obtained.

This powder coating did not substantially retain pigment particles on the surface, but had pigment particles dispersed substantially uniformly inside, and was electrostatically coated in the same manner as in Example 1 and baked at 205°C for 5 minutes. A beautiful pale blue coating film with a waist thickness of 40 microns was obtained. Table 1 shows the physical properties of this paint and coating film. As is clear from this table, the dawning temperature of the paint of this example is low, and the resulting paint film has excellent chemical resistance, water resistance, and weather resistance.
Its hardness was 9 days. Example 4 15 parts of quinacridone red, 1 part of polypropylene glycol polyethylene glycol ether, 6 parts of alkylpicolinium chloride, 150 parts of methyl methacrylate, 5 parts of butyl acrylate and 25 parts of 2-ethylhexyl phthalate were heated at high speed. The paste obtained by sufficiently thickening with a stirrer was poured into a polymerization vessel equipped with a stirrer as shown in Example 1, and then 0.5 parts of ammonium persulfate, 0.2 parts of dodecyl mercaptan and 80 parts of water were added. Afterwards, the inside of the polymerization reactor was replaced with nitrogen.

Then, while stirring, the mixture was heated to 70° C. (rotation speed: 120 pm) and polymerized for a short time at the same temperature. After the polymerization was completed, the obtained product was separated using a centrifuge and dried. As a result, a powder with a polymerization yield of 98%, a particle size of 60 to 150 microns, and a high specific gravity (hardness) of 0.25 was obtained.

When this powder was electrostatically coated in the same manner as in Example 1 and baked at 190 qo for 6 hours, a beautiful red coating film with a thickness of 180 microns was obtained. Table 1 shows the physical properties of this paint and coating film. As is clear from this table, the baking temperature of the paint of this example was low, and the resulting paint film had good chemical resistance, water resistance,
It had excellent weather resistance, and its hardness was 2 days. Example 5 15 parts of Hanzaero, 60 parts of ethyl methacrylate, and 4 parts of butyl methacrylate were mixed in advance, and the resulting mixture was stirred at high speed with 3 parts of dodecylbenzene ethoxy sulfate and 4 parts of polyethylene glycol lauryl ether. The paste obtained by thorough kneading in a machine was charged into the polymerization can with stirring device shown in Example 1, and 0.3 ammonium persulfate was added.
parts, n-butylmercabutane 0.05 parts and water 350 parts
After adding 50% of the reactor, the inside of the polymerization reactor was purged with nitrogen.

Then, the mixture was heated to 700C while stirring (rotation speed: 70 pm) and polymerized at the same temperature for 6 hours. After the polymerization was completed, 2 parts of dioctyl sulfide was added and the mixture was stirred for an additional 30 minutes, and the resulting product was separated using a centrifuge and dried. As a result, a powder with a polymerization yield of 93%, a particle size of 50 to 160 microns, and a high specific gravity (hardness) of 0.32 was obtained.

When this powder was electrostatically coated in the same manner as in Example 1 and left to stand for 195:06 minutes, a beautiful yellow coating film with a thickness of 80 microns was obtained. Table 1 shows the physical properties of this paint and coating film. As is clear from this table, the dawning temperature of the paint of this example was low, and the resulting coating film had excellent cold resistance, water resistance, and weather resistance, and its hardness was 9 days. Example 6 In Example 3, 1 part of acrylic acid was added 5 hours after the start of polymerization.

After the polymerization was completed, Epiquat 828 was added and the mixture was stirred for an additional 30 minutes, and the resulting product was separated using a super decanter and dried. As a result, the polymerization yield was 94%, and the particle size was 60%.
A powder of ~120 microns and high specific gravity of 0.35 was obtained. In this powder, the pigment is substantially dispersed within the particles, and Example 1
When electrostatically applied in the same manner as above and baked for 5 minutes at 250 pm, a beautiful pale blue coating with a thickness of 70 microns was obtained. After baking this product for an additional 15 minutes, the coating film was cured and had excellent chemical resistance. Example 7 After the polymerization was completed in Example 2, Epicoat 828 (made by Shell Chemical Co., Ltd.) and 1.1 parts of dicyandiamide were added, and after further stirring for 10 minutes, the obtained product was separated using a centrifuge. , dried.

As a result, a powder with a polymerization yield of 95%, a particle size of 40 to 110 microns, and a high specific gravity (hardness) of 0.35 was obtained.

This powder substantially contained pigment within the particles, and when it was electrostatically coated in the same manner as in Example 1 and phosphoroused at 180 oo for 5 minutes, a beautiful black coating film was obtained. Table 1 shows the physical properties of this paint and coating film. As is clear from this table, the brazing temperature of the paint of this example was low, and the resulting coating had excellent chemical resistance, water resistance, and weather resistance, and its hardness was 1 day. Example 8 3 parts of carbon black and 50 parts of methyl methacrylate were mixed in advance, and the resulting mixture was mixed with 25 parts of polyethylene glycol sorbitan mo/stearate, 10 parts of methyl methacrylate, 5 parts of lauryl methacrylate, and acrylic acid. 1 part of methyl and 3 parts of 4-vinylpyridine were added, and the resulting paste was thoroughly kneaded using a high-speed stirrer. After adding 0.4 parts of sodium hydrogen and 60 parts of water, the inside of the polymerization reactor was purged with nitrogen.

Then, while stirring (rotation speed: 100 pm) 80oo
and polymerized at the same temperature. 3 hours after the start of polymerization, 4 parts of glycidyl methacrylate was added, and the polymerization was further continued for 2 hours.
did. After the polymerization was completed, 2 parts of dioctyl sulfide was added and the mixture was stirred for an additional 20 minutes.The resulting suspension having a pH of 7.5 was separated using a centrifuge and dried. As a result, a powder with a polymerization yield of 95%, a particle size of 50 to 150 microns, and a bulk density of 0.35 was obtained. This powder coating was used in Example 1.
Electrostatic coating was carried out in the same manner as above, and baking was performed at 20,000 for 15 minutes, resulting in a beautiful black coating film with a thickness of 90 microns. Table 1 shows the physical properties of this paint and coating film. As is clear from this table, the baking temperature of the paint of this example was low, and the resulting coating gap had excellent chemical resistance, water resistance, and weather resistance, and its hardness was 4 days. Example 9 25 parts of titanium oxide, 1 part of polyethylene glycol sorbitan monolaurate, 40 parts of methyl acrylate, 6 parts of butyl methacrylate, 3 parts of acrylic acid, 0.3 parts of ammonium persulfate, 0.1 part of n-butyl mercaptan, water 1
After the 8 anchors were placed in a bag in the polymerization can shown in Example 1, the inside of the polymerization can was purged with nitrogen.

Then, while stirring (rotation speed: 80 pm), the mixture was flooded to 70 qo, and 7 polymers were polymerized at the same temperature. After the polymerization was completed, the obtained product was separated using a centrifuge and dried. As a result,
Polymerization yield 95%, particle size 50-170 microns, bulk specific gravity (
A powder with a hardness of 0.32 was obtained. This powder coating was electrostatically coated in the same manner as in Example 1 and baked at 17,000 for 10 minutes, resulting in a beautiful white coating with a thickness of 120 microns. Table 1 shows the physical properties of this paint and coating film. As is clear from this table, the scaling temperature of the paint of this example was low, and the resulting paint film had excellent chemical resistance, weather resistance, and hardness. Example 10 25 parts of titanium oxide, 5 parts of carbon black, 2 parts of ethyl methacrylate, 8 parts of butyl methacrylate, 6 parts of polyethyglycol sorbitan monolaurate, 0.2 parts of ammonium persulfate, 0.0 parts of n-butyl mercaptan. *country,
35 parts of water was charged into the polymerization reactor shown in Example 1, and after purging with nitrogen, the reactor was flooded to 70 oo of water with stirring (rotation speed: 80 pm) and polymerized at the same temperature for 8 hours.

After the polymerization was completed, the obtained product was separated using a super decanter and dried. As a result, the polymerization yield was 1%, the particle size was 60~
A powder of 150 microns and high specific gravity (hardness) of 0.35 was obtained.

This powder coating was electrostatically coated in the same manner as in Example 1, and
After baking for 5 minutes, a beautiful gray coating film with a thickness of 100 microns was obtained. Table 1 shows the physical properties of this paint and coating film. As is clear from this table, the dawning temperature of the paint of this example was low, and the resulting paint film had excellent chemical resistance and weather resistance, and its hardness was uneven. Comparative Example 1 Polymerization was carried out in the same manner as in Example 1 using 4 parts of sodium dodecylbenzenesulfonate as an emulsifier.

After the polymerization was completed, the obtained product was separated using a centrifuge and dried. As a result, the polymerization yield was 93%, and the particle size was 80-170.
A micron powder was obtained.

In this powder coating, a part of the pigment was present on the particle surface, and when this powder coating was electrostatically coated in the same manner as in Example 1 and baked at 20 and 0 for 5 minutes, the coating was not formed sufficiently. Ko○
When it was left to soak for 15 minutes, decomposition occurred and a satisfactory coating film could not be obtained. Comparative Example 2 In Example 2, the rotation speed was 10
I worshiped the enemy pm and polymerized it.

After the polymerization was completed, the resulting product was centrifuged, and most of the particles escaped through the filter cloth. This shows that it is difficult to obtain a powder with suitable particles unless the pseudo-azusa is strong. As a result of drying some of the particles collected in the bottle with a filter cloth, a powder with a particle size of 15 to 45 microns was obtained at a yield of 10%.
When this powder was electrostatically coated in the same manner as in Example 1 and baked at 185 oo for 5 minutes, a coating film of 80 microns was obtained. Table 1 shows the physical properties of this paint and coating film. Comparative Example 3 Polymerization was carried out in Example 9 by rotating the rope at a rotational speed of 200 pm.

As a result of drying the product obtained after the completion of polymerization, the polymerization yield was 9.
3%, particle size 100-250 mic. A powder with pigment attached to the surface was obtained. This powder was coated in the same manner as in Example 1,
When baked at 180 qo for 5 minutes, the coating did not thicken, so when it was further baked at 200°C for 10 minutes, decomposition was severe and a satisfactory coating consistency could not be obtained. Table 1 shows the physical properties of this paint and coating film.

Comparative Example 4 8 parts of butyl methacrylate, 2 parts of ethyl methacrylate, 5 parts of polyethylene glycol sorbitan mo/stearate, 0.0 parts of potassium persulfate. Starting from $, put 500 parts of water and 0.2 parts of n-butyl mercaptan into a polymerization can,
While stirring (rotation speed: 10 pm), the mixture was heated to 6000 ml and polymerized at the same temperature for 6 hours.

Since the polymer could not be separated by mechanical separation, the resulting milk sap was salted out, dried and crushed to a particle size of 10 to 2.
A 5 micron powder was obtained. To 100 parts of this powder were added 15 parts of titanium oxide and 1 $ part of 2-ethylhexyl phthalate, and the mixture was stirred at high speed and fished on a rocky shore for 30 minutes. The obtained powder coating was a powder with a particle size of 50 to 150 microns, and this was coated in the same manner as in Example 1, and was brazed at 20,000 for 5 minutes, but it did not form a film, and it was further coated at 220 o for 1 pip. When I tested it for a while, it decomposed and a satisfactory coating film could not be obtained. The properties of this paint and coating are shown in Table 1.

Table 1 Powder properties Various properties of paint films Table 1 Test methods and evaluation methods Test items Test method Flowability index
Using a powder tester manufactured by Hosokawa Iron Works Co., Ltd.,
This is an index determined using the method of Mr. Carr of the United States, and the closer this index is to 100, the better the fluidity of the powder is.

Bulk specific gravity Based on the same powder tester as above
Value based on the method of measuring "Hard High Specific Gravity".

Volume resistivity (Q arc) Value measured at 500 V DC for 1 minute using an ultra-high resistance measuring device manufactured by Takeda Riken.

Chemical Resistance Each test piece was separately immersed in a 10% caustic soda solution and a 10% sulfuric acid solution for one week, and then comprehensively evaluated based on the degree of discoloration and blistering of both test pieces.

Weather resistance Evaluate changes after 1 year of outdoor exposure.

Water resistance A test piece was immersed in distilled water and changes after one week were evaluated.

Evaluation display method ◎ is particularly excellent.

0 is good.

△ is inferior. × is particularly poor.

Claims (1)

[Claims] 1 General formula ▲ Numerical formula, chemical formula, table, etc. ▼ (R_1 is H or CH_3 group, R_2 has 1 to 1 carbon atoms
8) or one or more monomers copolymerizable with this acrylic monomer, in an aqueous medium to all monomers. In the presence of a surfactant and a pigment in an amount of 5% by weight or more and less than 20% by weight, an ultraviolet absorber, a stability improver, a molecular weight regulator, a fluidity improver, and a curing agent are further added as necessary. , under vigorous stirring, i.e. 200-1200 rpm using a stirrer with turbine blade type impellers.
Emulsion polymerization is carried out under stirring of approximately
Micron, volume specific electrical resistance 10^9~10^1^6Ω
・An acrylic powder coating for electrostatic coating, which is characterized by obtaining a substantially spherical polymer with a bulk specific gravity of 0.2 cm or more, and then mechanically separating and obtaining this polymer from an aqueous medium. Method of manufacturing the composition.