JP4398080B2 - Paint composition - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
  The present invention relates to a polymer fine powder using supercritical carbon dioxide.BodyThe present invention relates to a coating composition.
[0002]
[Prior art]
Conventionally, as a method for producing polymer fine powder, there is a process in which an unsaturated monomer is solution-polymerized in an organic solvent, the organic solvent is removed from the obtained polymer solution, and drying, pulverization, and the like are performed. It is common. In this process, it is necessary to perform several steps before obtaining a fine powder, and further, the obtained fine powder has a disadvantage that the size of the fine powder is not uniform.
[0003]
Other methods include dispersion polymerization using a dispersion stabilizer in an organic solvent, and JP-A-56-76447 discloses emulsion polymerization in water. Alternatively, a method for removing water is disclosed.
However, when the fine particles obtained by the above method are isolated, there is a problem that the fine particles are fused, resulting in large particles or lumps.
[0004]
On the other hand, a technique using supercritical carbon dioxide has been actively performed recently because it hardly uses an organic solvent and has high extraction efficiency. For example, JP-A-8-104830 discloses a method for producing polymer fine particles for coating by using a polymer reaction solution once polymerized as a raw material, dissolving it in a supercritical phase, and rapidly expanding it. . Japanese Patent Application Laid-Open No. 8-113652 discloses a method for producing polymer fine particles for coating by using a polymer solid once produced as a raw material, dissolving it in a supercritical phase, and rapidly expanding it.
However, these disclosed techniques require a process of obtaining a polymer material once, and thus the process is complicated.
[0005]
As an example of a method for producing a polymer material by carrying out a polymerization reaction in a supercritical fluid, a production method in which a styrene-acrylonitrile copolymer is reacted in supercritical carbon dioxide in the presence of a radical polymerization initiator (special (Kaihei 8-41135), a production method of reacting a styrene-vinyl acetate copolymer in supercritical carbon dioxide in the presence of a radical polymerization initiator (Japanese Patent Laid-Open No. 10-45838) is known. .
However, in these disclosed technologies, the yield is 84% in the former and 12 to 56% in the latter, and the step of recovering unreacted monomers remaining in the system with carbon dioxide Have problems such as having to do. Moreover, in these disclosed methods, the polymer is produced in a supercritical carbon dioxide in a molten state or the like, and further steps such as pulverization are required to obtain a fine powder.
Therefore, in a method for producing a polymer material by carrying out a polymerization reaction in supercritical carbon dioxide, a method for producing a product as a high-quality fine powder with a simple production process and a uniform particle size has been found. The current situation is not.
[0006]
[Problems to be solved by the invention]
  The present inventionThe purpose is goodAn object of the present invention is to provide a coating composition capable of obtaining a simple coating film.
[0007]
[Means for Solving the Problems]
As a result of intensive studies in view of the above problems, the present inventors can polymerize an ethylenically unsaturated monomer having a carboxyl group in supercritical carbon dioxide, and in such a production method. According to this finding, it was found that high-quality polymer fine powder having a uniform particle size can be obtained directly in supercritical carbon dioxide, and the present invention has been completed based on these findings.
[0008]
  That is, according to the present invention, a monomer composition containing an ethylenically unsaturated monomer having a carboxyl group is polymerized in supercritical carbon dioxide.The obtained polymer was reacted with 100 parts by weight of polymer fine powder having a weight average molecular weight of 1,000 to 1,000,000 and an average particle diameter of 0.1 to 50 μm, and a carboxyl group in one molecule. 10 to 300 parts by weight of a crosslinking agent having two or more reactive functional groups capable of forming a chemical bond;A coating composition is provided.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
  The present inventionUsed forIn the method for producing fine powder, the monomer composition is polymerized in supercritical carbon dioxide.
  Supercritical carbon dioxide refers to carbon dioxide at its critical point (critical temperature 31 ° C. or critical pressure 75.2 kg / cm²) Carbon dioxide, which is obtained by heating and pressurizing as described above and becomes a fluid that does not liquefy even when pressurized further, usually having properties of gas and liquid.
  The supercritical carbon dioxide can be obtained by introducing a carbon dioxide gas such as a commercially available one in a cylinder or the like into an apparatus for performing a polymerization reaction to obtain a predetermined temperature and pressure. The carbon dioxide gas to be introduced is preferably carbon dioxide having a purity of 99.9% or more.
[0010]
In the polymerization of the monomer composition, the supercritical carbon dioxide may be further mixed with another additive solvent. As the additive solvent, water, lower alcohols such as methanol and ethanol, acetonitrile and the like can be used. The additive solvent can be added in an amount of about 0.1 to 100 parts by weight with respect to 100 parts by weight of the supercritical carbon dioxide, but it is preferable not to use the additive solvent from the viewpoint of preventing pollution and reducing the environmental load. .
[0011]
  SaidIn the production method, a monomer composition containing an ethylenically unsaturated monomer having a carboxyl group (hereinafter abbreviated as “monomer A”) is used. The monomer A is not particularly limited as long as it has one or more carboxyl groups and ethylenically unsaturated bonds in the molecule. Specifically, for example, methacrylic acid, acrylic acid, crotonic acid, itaconic acid , Mesaconic acid, maleic acid, fumaric acid, half esters thereof, ω-carboxy-polycaprolactone (n = 2) monoacrylate [for example, Aronix M-5300 (trade name, manufactured by Toagosei Co., Ltd.)] or Examples thereof include compounds having an unsaturated bond at the end of a hydrocarbon chain, such as acrylic acid dimer [for example, Aronix M-5600 (trade name, manufactured by Toagosei Chemical Co., Ltd.)], or a mixture thereof. Among these, methacrylic acid and / or acrylic acid is particularly preferable.
[0012]
In addition to monomer A, the monomer composition may further contain an ethylenically unsaturated monomer (hereinafter abbreviated as monomer B) that does not contain a carboxyl group as an optional component.
Although the monomer B is not specifically limited, For example, methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate , Isobutyl (meth) acrylate, sec-butyl (meth) acrylate, cyclohexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, decyl (meth) acrylate, dodecyl (meth) acrylate, hexadecyl (meth) acrylate, etc. ) Acrylic acid alkyl esters; Hydroxyl-containing monomers such as hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, polyethylene glycol (meth) acrylate; Styrenic monomers such as styrene and α-methylstyrene Body; can be mentioned p- vinyltoluene, acrylonitrile and the like; vinyl acetate, vinyl esters such as allyl vinyl; methyl vinyl ether and ethyl vinyl ether. Furthermore, fluorine-containing α, β-ethylenically unsaturated monomers such as 2,2,2-trifluoromethyl acrylate and 2,2,2-trifluoromethyl methacrylate are exemplified. These may be used alone or in combination of two or more.
[0013]
The blending ratio of the monomer A and the monomer B in the monomer composition is such that the monomer A is preferably 1 to 100% by weight, more preferably 10 to 100% by weight. The monomer B is preferably 0 to 99% by weight, more preferably 0 to 90% by weight.
If the monomer A is less than 1% by weight, the resulting polymer may be agglomerated rather than a fine powder, which is not preferable.
[0014]
  SaidThere is no restriction | limiting in particular about the method of superposing | polymerizing a monomer composition, A well-known polymerization method can be used.
  In the polymerization, a dispersion stabilizer having an affinity for carbon dioxide may optionally be used. Examples of the dispersion stabilizer include various surfactants such as hydrocarbons having a fluorine-containing segment and / or a siloxane-containing segment in the molecule.
  The polymerization method is not particularly limited, and for example, any of radical polymerization, cationic polymerization, and anionic polymerization can be used, and radical polymerization is particularly preferable.
[0015]
The radical polymerization can be performed using a polymerization initiator. The polymerization initiator is not particularly limited, and examples thereof include t-butyl hydroperoxide, cumene hydroperoxide, t-butyl peroxyneodecanate, t-butyl peroxypivalate, and t-hexyl. Organic peroxides such as peroxy-2-ethylhexanoate, methyl ethyl ketone peroxide, acetylcyclohexylsulfonyl peroxide, 2,2′-azobis (2,4-dimethylvaleronitrile), 2,2′-azobis Preferred examples include azo initiators such as (isobutyronitrile) (abbreviated as AIBN) and 2,2′-azobis (2-methylbutyronitrile). AIBN is particularly preferable.
These radical polymerization initiators may be used alone or in combination of two or more.
Moreover, the usage-amount of a radical polymerization initiator is preferably 0.001-30 weight% with respect to 100 weight part of an unsaturated monomer, More preferably, it can be 0.1-10 weight%.
[0016]
Moreover, the reaction temperature at the time of superposition | polymerization can be 31-160 degreeC, Preferably it is 40-150 degreeC, More preferably, it can be 50-100 degreeC. When the reaction temperature is 31 to 160 ° C., the radical polymerization initiator is easily decomposed by heat, and the growth reaction is likely to proceed effectively. The polymerization time depends on the polymerization temperature and other conditions, and cannot be generally defined, but is generally preferably 2 to 48 hours.
[0017]
The polymerization is preferably performed while stirring the reaction system. The stirring conditions are not particularly limited, but it is preferable to use a stirring device and perform the conditions under which the polymer is not precipitated. Specifically, it is preferable to stir at a rotational speed of 50 to 2000 rpm using a stirring device such as a magnetic stirrer.
Specifically, the polymerization is performed, for example, by using 5 to 1500 parts by weight of carbon dioxide with respect to 100 parts by weight of the monomer composition, and a pressure of 30 to 400 kg / cm.², Preferably 60 to 360 kg / cm²At a temperature of 31 to 160 ° C., preferably 40 to 150 ° C.
As the polymerization reaction proceeds, a polymer is produced as a polymer fine powder in supercritical carbon dioxide. After completion of the polymerization reaction, the polymer can be easily taken out from the reaction system as a solid polymer fine powder by lowering the temperature and pressure and discharging carbon dioxide. The extracted polymer fine powder can be directly used as a fine powder product without further crushing steps. In the production method of the present invention, polymer fine powder can be obtained with a reaction rate of 90% or more and a yield of 95% or more.
[0018]
  The present inventionUsed forThe polymer fine powder is a polymer fine powder obtained by the above production method.
  TheThe molecular weight of the polymer fine powder is 1,000 to 1,000,000, preferably 10,000 to 500,000 as a weight average molecular weight. Moreover, the average particle diameter of particle | grains is 0.1-50 micrometers, Preferably it is 0.15-20 micrometers. By having such an average particle diameter, for example, when used as a powder coating, a film having excellent characteristics can be provided. The polymer fine powder of the present invention can be obtained as a high-quality fine powder having a uniform particle diameter by the production method described above.
[0020]
  The coating composition of the present invention comprises:The highContains molecular fine powder.
  The coating composition of the present invention is added to the polymer fine powder.Eh, rackAs a bridging agent, a compound having two or more reactive functional groups capable of reacting with a carboxyl group to form a chemical bond in one molecule.Including.
  The reactive functional group is not particularly limited as long as it can react with a carboxyl group to form a chemical bond, and examples thereof include an epoxy group, an oxazoline group, a silanol group, an alkoxysilane group, a hydroxyl group, an amino group, and an imino group. Preferred examples include groups, isocyanate groups, blocked isocyanate groups, cyclocarbonate groups, vinyl ether groups, aminomethylol groups, acetal groups, and ketal groups. One type of these reactive functional groups may be included, or two or more types may be included in combination.
[0021]
  The content of the crosslinking agent in the coating composition of the present invention is 10 to 300 parts by weight with respect to 100 parts by weight of the polymer fine powder.so,15 to 250 parts by weightPreferGood. When the content of the crosslinking agent is less than 10 parts by weight or more than 300 parts by weight, the strength of the coating film to be formed is lowered, which is not preferable.
[0022]
The coating composition of the present invention may contain a pigment as necessary. Examples of the pigment include inorganic pigments such as titanium dioxide, red pepper, yellow iron oxide, and carbon black, organic pigments such as phthalocyanine blue, phthalocyanine green, quinacridone red pigment, and isoindolinone yellow pigment, aluminum powder, and copper powder. Examples thereof include metal powders such as talc, barium sulfate, silica, calcium carbonate, alumina white, extender pigments such as clay, and mica powder. The coating composition containing such a pigment can be used as a colored powder coating or the like. Alternatively, the coating composition of the present invention can be constituted without containing a pigment and used as a clear powder coating or the like.
The coating composition of the present invention can contain a thermoplastic resin such as a fluororesin, a vinyl copolymer resin, a polyethylene resin, a polypropylene resin, or a polyester, if necessary. These thermoplastic resins can be blended particularly preferably when the coating composition of the present invention is used as a powder coating.
The content ratio of the pigment and / or thermoplastic resin in the coating composition of the present invention is preferably less than 40 parts by weight with respect to 100 parts by weight of the polymer fine powder. When the content ratio exceeds 40 parts by weight, the corrosion resistance of the coating film is lowered, which is not preferable.
[0023]
The coating composition of the present invention can contain other components such as a solvent such as an aqueous solvent, if necessary. Moreover, it can also be set as the composition for coating materials which does not contain a solvent, and can be used as a powder coating material. The coating composition of the present invention is particularly suitable for use as a powder coating because the polymer fine powder can have a fine particle size.
The coating composition of the present invention may contain additives such as a leveling agent, a pigment dispersant, an ultraviolet absorber, a light stabilizer, a heat stabilizer, and an antifoaming agent as necessary.
The coating composition of the present invention can be used for coating arbitrary articles. For example, it is applied to a metal plate such as an iron plate, a galvanized plate, an aluminum plate, and a stainless plate having a thickness of about 0.2 to 2 mm. Can do. Moreover, it is preferable that the article coated with the coating composition of the present invention prepared as a powder coating can withstand the baking conditions described below.
[0024]
The method for coating the coating composition of the present invention is not particularly limited. In the case of powder coating, the coating or powdering using a commercially available electrostatic coating machine (applied voltage −50 to −90 kV) is described in the above description. After uniform coating by a body coating method, etc., baking is performed at 150 to 300 ° C., preferably 160 to 250 ° C. for 20 seconds to 60 minutes, preferably 30 seconds to 30 minutes in a hot air baking furnace, infrared furnace, induction heating furnace or the like. Then, it can be carried out by forming a coating film having a coating thickness of 20 to 200 μm, preferably 30 to 100 μm. By performing such coating, a coating film excellent in smoothness can be obtained.
[0025]
A coated product having a coating film formed by coating the coating composition of the present invention is excellent in smoothness, so that it can be used for automobile bodies and parts; home appliances such as refrigerators and air conditioners; poles, soundproof walls, guardrails, etc. Building materials; building materials such as building interior and exterior walls, pole rolls, roofs, partition plates; telecommunications equipment such as telephones; pipes, joints, metal machinery, trash cans, accessory cases, steel furniture, steel desks, beverage cans, etc. Metal products such as iron, galvanized steel, stainless steel, and aluminum; fibers and heat-resistant paper made from glass, wood, gypsum board, glass fiber, etc .; preferably plastics having heat resistance of 150 ° C. or higher; It can be used as a colored product.
[0026]
【The invention's effect】
  The present inventionCoatingThe composition for the ingredients isThe highSince it contains molecular fine powder, a smooth painted surface can be formed.
[0027]
【Example】
Next, the present invention will be described more specifically with reference to examples. In addition, this invention is not limited at all by these examples.
The measurement methods used in the examples are as follows.
1. Measurement of weight average molecular weight;
Gel permeation chromatography (GPC);
Model: manufactured by Tosoh Corporation, GPC-8020,
Conditions: Column: Tosoh Corporation TSKgel-G3000PW_XL, TSKgel-G6000PW_XL2 in series, column temperature: 45 ° C., flow rate: 1 ml / min, eluent: phosphate buffer (pH 7.4, 20 mM), standard sample; polyethylene glycol, detector; UV (Tosoh Corporation UV) -8020), and RI (Tosoh Corporation RI-8020)
2. Particle size measurement of powder;
Model: Scanning electron microscope (Hitachi S-80)
Measurement conditions: Measured at an acceleration voltage of 15 KV and 20 KV.
3. Evaluation of painted surface
The appearance of the coating film was evaluated according to the method of JIS K 5400 7.1 (1999), and the specular gloss of the coating film was evaluated according to the method of JIS K 5400 7.6 (1999).
[0028]
  ManufacturingExample 1
  A metal high-pressure polymerization vessel with a capacity of 54 ml having a stirrer and a temperature measuring device is heated to 31 ° C. or higher, and 2.7 g of methacrylic acid, 2.7 g of methyl methacrylate, 2,2′-azobis (isobutyrate) (Ronitrile) 21.6 mg was added, and then carbon dioxide was injected. The temperature in the polymerization vessel was quickly 65 ° C., and the pressure was 300 kg / cm.²It heated and pressurized so that it might become. After reaching the predetermined temperature and pressure, the monomer was polymerized for 24 hours while stirring at 700 rpm. After completion of the polymerization, the temperature and pressure in the polymerization vessel were lowered, and then carbon dioxide was discharged. White polymer fine powder was obtained in the polymerization vessel, and the yield was 5.3 g (yield 98.1%).
  When the molecular weight of the polymer fine powder was measured by GPC, the Mw (weight average molecular weight) was 180,000. Moreover, when this polymer fine powder was observed using a scanning electron microscope, it was confirmed that the fine powder had a particle size of 2.5 μm. FIG. 1 shows a photograph of the results of observation by a scanning electron microscope.
[0029]
  ManufacturingExample 2
  A metal high-pressure polymerization vessel with a capacity of 54 ml having a stirrer and a temperature measuring device was heated to 31 ° C. or higher, and 2.7 g of acrylic acid, 2.7 g of n-butyl acrylate, 2,2′-azobis ( 21.6 mg of isobutyronitrile) was added, and then carbon dioxide was injected, and the temperature in the polymerization vessel was quickly 60 ° C. and the pressure was 280 kg / cm.²It heated and pressurized so that it might become. After reaching the predetermined temperature and pressure, the monomer was polymerized for 12 hours while stirring at 1000 rpm. After completion of the polymerization, the temperature and pressure in the polymerization vessel were lowered, and then carbon dioxide was discharged. White polymer fine powder was obtained in the polymerization vessel, and the yield was 5.2 g (yield 96.2%).
  When the molecular weight of the polymer fine powder was measured by GPC, Mw was 160,000. The polymer fine powder was confirmed to be a fine powder having an average particle size of 3.0 μm by scanning electron microscope measurement.
[0030]
  ManufacturingExample 3
  A metal high-pressure polymerization vessel with a capacity of 54 ml having a stirrer and a temperature measuring device was heated to 31 ° C. or higher, and 4.1 g of acrylic acid, 1.3 g of methyl methacrylate, 2,2′-azobis (isobutyrate) were added to the polymerization vessel. (Nitrile) 43.2 mg was added, and then carbon dioxide was injected, and the temperature in the polymerization vessel was quickly 70 ° C. and the pressure was 360 kg / cm.²It heated and pressurized so that it might become. After reaching the predetermined temperature and pressure, the monomer was polymerized for 24 hours while stirring at 400 rpm. After completion of the polymerization, the temperature and pressure in the polymerization vessel were lowered, and then carbon dioxide was discharged.
  White polymer fine powder was obtained in the polymerization vessel, and the yield was 5.3 g (yield 98.1%). The molecular weight Mw of the polymer fine powder was 120,000 from the GPC measurement. Further, it was confirmed that the polymer fine powder was a fine powder having a uniform particle size of 2.0 μm by scanning electron microscope measurement.
[0031]
  ManufacturingExample 4
  A metal high-pressure polymerization vessel with a capacity of 54 ml having a stirrer and a temperature measuring device was heated to 31 ° C. or higher, and 1.1 g of methacrylic acid, 4.3 g of 2-ethylhexyl methacrylate, 2,2′-azobis ( (Isobutyronitrile) 21.6 mg was added, and then carbon dioxide was injected. The temperature in the polymerization vessel was quickly 65 ° C., and the pressure was 300 kg / cm.²It heated and pressurized so that it might become. After reaching the predetermined temperature and pressure, the monomer was polymerized for 24 hours while stirring at 500 rpm. After completion of the polymerization, the temperature and pressure in the polymerization vessel were lowered, and then carbon dioxide was discharged.
  White polymer fine powder was obtained in the polymerization vessel, and the yield was 5.3 g (yield 98.1%). The molecular weight of this polymer fine powder was Mw of 180,000 from GPC titration. Further, this polymer fine powder was confirmed to be a fine powder having a particle size of 8.0 μm by scanning electron microscope measurement.
[0032]
  ManufacturingExample 5
  A metal high-pressure polymerization vessel with a capacity of 54 ml having a stirrer and a temperature measuring device was heated to 31 ° C. or higher, and 2.7 g of methacrylic acid, 2.7 g of methyl methacrylate, 2,2′-azobis (isobutyrate) were added to the polymerization vessel. (Ronitrile) 21.6 mg was added, and then carbon dioxide was injected. The temperature in the polymerization vessel was quickly 65 ° C., and the pressure was 60 kg / cm.²It heated and pressurized so that it might become. After reaching the predetermined temperature and pressure, the monomer was polymerized for 15 hours while stirring at 700 rpm. After completion of the polymerization, the temperature and pressure in the polymerization vessel were lowered, and then carbon dioxide was discharged.
  White polymer fine powder was obtained in the polymerization vessel, and the yield was 5.3 g (yield 98.1%). The molecular weight of this polymer fine powder was 160,000 Mw from GPC measurement. Further, when the polymer fine powder was observed using a scanning electron microscope, it was confirmed that the polymer fine powder had a uniform particle size of 15 μm.
[0033]
  ManufacturingExample 6
  A metal high-pressure polymerization vessel with a capacity of 54 ml having a stirrer and a temperature measuring device was heated to 31 ° C. or higher, and 5.4 g of methacrylic acid and 21.6 mg of 2,2′-azobis (isobutyronitrile) were added to the polymerization vessel. After that, carbon dioxide is injected, and the temperature in the polymerization vessel is 65 ° C. and the pressure is 200 kg / cm²It heated and pressurized so that it might become. After reaching the predetermined temperature and pressure, the monomer was polymerized for 6 hours while stirring at 1500 rpm. After completion of the polymerization, the temperature and pressure in the polymerization vessel were lowered, and then carbon dioxide was discharged.
  White polymer fine powder was obtained in the polymerization vessel, and the yield was 5.2 g (yield 96.2%). The molecular weight of the polymer fine powder was 150,000 as Mw (weight average molecular weight) as measured by GPC. Further, this polymer fine powder was confirmed to be a fine powder having an average particle size of 12 μm by scanning electron microscope measurement.
[0034]
  ManufacturingExample 7
  A metal high-pressure polymerization vessel with a capacity of 54 ml having a stirrer and a temperature measuring device was heated to 31 ° C. or higher, and 5.4 g of methacrylic acid, 2.16 g of n-butyl methacrylate, 2,2′-azobis ( (Isobutyronitrile) 21.6 mg was added, and then carbon dioxide was injected. The temperature in the polymerization vessel was quickly 60 ° C., and the pressure was 300 kg / cm.²It heated and pressurized so that it might become. After reaching the predetermined temperature and pressure, the monomer was polymerized for 24 hours while stirring at 1000 rpm. After completion of the polymerization, the temperature and pressure in the polymerization vessel were lowered, and then carbon dioxide was discharged.
  White polymer fine powder was obtained in the polymerization vessel, and the yield was 5.2 g (yield 96.2%). The molecular weight of this polymer fine powder was 160,000 as Mw (weight average molecular weight) from GPC measurement. The polymer fine powder was confirmed to be a fine powder having an average particle size of 3.0 μm by scanning electron microscope measurement.
[0035]
  Reference manufacturingExample
  A metal high-pressure polymerization vessel with a capacity of 54 ml having a stirrer and a temperature measuring device was heated to 31 ° C. or higher, and 5.4 g of methyl methacrylate and 21.6 mg of 2,2′-azobis (isobutyronitrile) were placed in the polymerization vessel. Then, carbon dioxide is injected, and the temperature in the polymerization vessel is quickly 60 ° C. and the pressure is 300 kg / cm.²It heated and pressurized so that it might become. After reaching the predetermined temperature and pressure, the monomer was polymerized for 24 hours while stirring at 1500 rpm. After completion of the polymerization, the temperature and pressure in the polymerization vessel were lowered, and then carbon dioxide was discharged.
  In the polymerization vessel, 2.5 g of a colorless and transparent plate-like polymer was obtained (yield 46.3%). In addition, 2.9 g of unreacted methyl methacrylate was recovered.
[0036]
  ComparisonProduction example
  In a four-necked flask having a stirrer, a thermometer, a reflux condenser and a dropping funnel, 50 parts by weight of deionized water, Eleminol ES-12 (trade name, manufactured by Daiichi Kogyo Seiyaku Co., Ltd., anionic surfactant) 2 parts by weight and 0.1 part by weight of sodium bicarbonate were charged, heated and maintained at 80 ° C. A mixture of 20 parts by weight of methacrylic acid, 20 parts by weight of methyl methacrylate, and 0.5 parts by weight of ammonium persulfate was dropped from the dropping funnel over 2 hours. After completion of the dropwise addition, the liquid temperature was kept at 80 ° C. for 2 hours. Thereafter, the polymerization was terminated by cooling to room temperature. The particle diameter of the polymer fine particles in the obtained solution was 0.1 μm.
  Water was removed using an evaporator, and polymer fine particles were isolated from the polymer fine particle solution. Due to the fusion of the particles at that time, the average particle size of the isolated polymer fine particles became 100 μm. The yield of the polymer fine particles was 30 g (yield 75%).
[0037]
  Example1
  For steel test panels of 0.8 × 100 × 300mm with electrodeposition and intermediate coatingManufacturingA clear coating film was formed by electrostatically applying a paint prepared by mixing 10 g of the polymer fine powder prepared in Example 7 and 2.7 g of polyglycidyl methacrylate as a crosslinking agent, followed by baking at 150 ° C. for 25 minutes. When the appearance and specular gloss of this coating film were observed, a smooth coating film surface was observed, and the 60 ° C. specular glossiness was 91.
[0038]
  Comparative example1
  Compared to 0.8 x 100 x 300 mm steel test panel with electrodeposition and intermediate coatingProduction exampleA coating film in which 10 g of the polymer fine powder prepared in the above and 2.7 g of polyglycidyl methacrylate as a crosslinking agent were mixed was electrostatically applied, and then baked at 150 ° C. for 25 minutes to form a clear coating film. When the appearance and specular glossiness of this coating film were observed, the coating surface was not smooth and was not glossy, and the specular glossiness at 60 ° C. was 55.
[Brief description of the drawings]
[FIG. 1] FIG.Manufacturing3 is a scanning microscope photograph of the polymer fine powder obtained in Example 1 (magnification × 8,000).

Claims (2)

A monomer composition containing an ethylenically unsaturated monomer having a carboxyl group was polymerized in supercritical carbon dioxide, and had a weight average molecular weight of 1,000 to 1,000,000, Cross-linking agent 10-300 having 100 parts by weight of polymer fine powder having an average particle size of 0.1-50 μm and two or more reactive functional groups capable of forming a chemical bond by reacting with a carboxyl group in one molecule. A coating composition comprising parts by weight . 2. The coating composition according to claim 1, wherein the ethylenically unsaturated monomer having a carboxyl group is (meth) acrylic acid.

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