JP2003105250A - Fluorine-containing powder coating material composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a fluorine-containing powder coating material composition capable of forming a coating film capable of improving weather resistance of an undercoat film or a substrate and giving the surface having a good appearance. SOLUTION: This fluorine-containing powder coating material composition contains a fluororesin and an ultraviolet-absorbable copolymer obtained by copolymerizing a benzotriazole-based ultraviolet-absorbable vinyl monomer with a copolymerizable monomer.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention can provide a coating film which is excellent in the weather resistance improving property of a lower layer coating film or a base film formed by the fluorine-containing powder coating composition of the present invention and in the appearance of the coating film. It relates to a fluorine-containing powder coating composition.

[0002]

2. Description of the Related Art Fluorine-containing coating compositions have a chemically extremely stable structure when formed into a coating film, so that the fluororesin contained as a resin component is unlikely to be decomposed by light such as ultraviolet rays. Therefore, when a fluorine-containing coating composition is used as a clear coating containing no pigment, it is known that the ultraviolet light transmitted through the obtained clear coating film deteriorates the coating film as the lower layer or the base (subject). ing. As a means for suppressing the transmission of ultraviolet rays, when a fluorine-containing coating composition is used as a solvent-based or water-based clear coating, it has been proposed to add an ultraviolet absorber for the purpose of protecting the lower layer. However, since UV absorbers generally used for paints have low molecular weight, they are volatilized when exposed to high temperatures, and their effect is significantly reduced. for that reason,
When the coating film has to be formed at a high temperature like powder coating, there is a problem that the expected effect cannot be obtained. Further, in the fluororesin powder, there is no ultraviolet absorber that can be uniformly dispersed, and the appearance of the coating film is deteriorated.

[0003]

DISCLOSURE OF THE INVENTION The present invention provides a coating film which is excellent in the weather resistance improving performance and the appearance of the coating film of the lower layer or undercoating film formed by the fluorine-containing powder coating composition of the present invention. An object is to provide a fluorine-containing powder coating composition capable of

[0004]

Means for Solving the Problems As a result of intensive studies to improve the above problems, the present inventors have found that a copolymer obtained by copolymerizing a benzotriazole-based UV absorbing vinyl monomer is The inventors have found that they have excellent ultraviolet absorbing performance and compatibility with fluororesins, and that they do not volatilize from the coating film even when they are heat-cured at high temperatures, and have completed the present invention. That is, the present invention is characterized by containing a fluororesin and a UV-absorbing copolymer obtained by copolymerizing a benzotriazole-based UV-absorbing vinyl monomer and a copolymerizable monomer. A powder coating composition is provided. Further, in the present invention, in the above fluorine-containing powder coating composition, the fluororesin has a hydroxyl value of 10 to 200 mgKOH / g, and an intrinsic viscosity measured in tetrahydrofuran at 30 ° C. of 0.1 to 0.8 dl /.
g, a fluorine-containing powder coating composition having a glass transition temperature of 30 to 80 ° C. by a differential scanning calorimetry (DSC) measurement method.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION The fluororesin in the present invention may be either a thermoplastic fluororesin or a thermosetting fluororesin. The fluororesin preferably has a fluoropolymer unit (p) obtained by polymerizing a fluoromonomer having an ethylenically unsaturated group. As the fluorine-containing monomer having an ethylenically unsaturated group,
For example, tetrafluoroethylene, hexafluoropropylene, perfluorobutene-1, perfluorohexene-1, perfluorononene-1, perfluoro (methyl vinyl ether), perfluoro (ethyl vinyl ether), perfluoro (propyl vinyl ether), Perfluoroolefins such as perfluoro (heptyl vinyl ether); polyfluoroolefins such as chlorotrifluoroethylene, trifluoroethylene, vinylidene fluoride, (perfluoromethyl) ethylene, (perfluorobutyl) ethylene and the like. The fluorine-containing monomer having an ethylenically unsaturated group may be used alone or in combination of two or more.

The fluorine-containing copolymer of the present invention contains at least 20 fluorine-containing polymer units (p) based on all polymer units.
It is preferably an organic polymer having a mol%. When the content of the fluorine-containing polymerized units (p) is less than 20 mol%, sufficient surface stain resistance cannot be exhibited, and stains may become remarkable during long-term use, which is not preferable. In the fluorinated copolymer, the fluorinated polymer units (p) are preferably contained in an amount of 20 to 95 mol%, particularly 30 to 80 mol%, based on all polymer units.

The fluorinated copolymer in the present invention may have a polymerized unit (q) other than the polymerized unit (p).
The polymerized units (q) are preferably in a proportion of 0 to 75 mol% with respect to all polymerized units. The polymerized units (q) are preferably polymerized units based on the polymerizable monomer (b) other than the polymerizable monomer (a).

The polymerizable monomer (b) is a polymerizable monomer in which a hydrogen atom directly connected to a carbon atom forming an ethylenically unsaturated group is not substituted with a fluorine atom. As the polymerizable monomer (b), a (meth) acryloyl group,
Examples thereof include a polymerizable monomer having a polymerizable site such as a vinyl group, an allyl group and an isopropenyl group. Specific examples of the polymerizable monomer (b) include vinyl ethers, olefins, allyl ethers, vinyl esters, allyl esters, acrylic acid esters, methacrylic acid esters, isopropenyl ethers, isopropenyl esters, Examples include crotonic acid esters and other polymerizable monomers. Of these, compounds having a linear, branched or alicyclic alkyl group having about 1 to 15 carbon atoms are preferable. Specific compounds include the following.

Vinyl ethers such as methyl vinyl ether, ethyl vinyl ether, butyl vinyl ether, isobutyl vinyl ether, cyclohexyl vinyl ether, chloroethyl vinyl ether, vinyl (perfluoroalkyl) ether, ethylene, propylene, 1-
Olefins such as butene, isobutylene and cyclohexene, styrene monomers such as styrene and α-methylstyrene, allyl ethers such as methyl allyl ether, ethyl allyl ether, butyl allyl ether and cyclohexyl allyl ether, vinyl acetate, vinyl propionate, butyric acid Vinyl, vinyl isobutyrate, vinyl valerate, vinyl hexanoate, vinyl octanoate, Veova 9 and Veova 10 (Shell Chemical Co., carbon number 9 or 10)
(Brand name of vinyl ester of branched fatty acid), vinyl ester of fatty acid such as vinyl versatate, allyl ester such as allyl acetate, methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate , (Meth) acrylic acid esters such as cyclohexyl (meth) acrylate, (meth) acrylic acid amides such as (meth) acrylic acid amide, acrylonitrile, cyano group-containing monomers such as 2,4-dicyanobutene-1 Dienes such as isoprene and butadiene, halogenated olefins such as vinyl chloride and vinylidene chloride, and a polymerizable monomer having a polyoxyalkylene chain with a molecular weight of 100 to 3000 (specifically, a molecular weight of 100 to
3000 polyoxypropylene glycol monoalkyl ether (meth) acrylate) and the like. Of these, polymerizable monomers selected from vinyl ethers, vinyl esters, allyl ethers, allyl esters, isopropenyl ethers and isopropenyl esters are particularly preferable, and vinyl ethers are most preferable. The polymerizable monomer (b) may be used alone,
Alternatively, two or more kinds may be used in combination.

Further, the fluororesin may have a curing reactive site which reacts with the curing agent. The curing reactive site may be present in the polymerized unit (p), but the fluororesin having the curing reactive site is a polymerized unit (r having a curing reactive site other than the polymerized units (p) and (q) (r). Those having) are preferred. Examples of the curing reactive site include a hydroxyl group, a carboxyl group, an amide group, an amino group, a mercapto group, a glycidyl group, a halogen such as bromine and iodine, and a functional group such as an isocyanate group. The polymerized unit (r) is preferably obtained by polymerizing the polymerizable monomer (c) having a curing reactive site. A specific example is shown below.

The hydroxyl group-containing polymerizable monomer (c) includes allyl alcohol; hydroxy vinyl ethers such as (2-hydroxyethyl) vinyl ether, (3-hydroxypropyl) vinyl ether, (4-hydroxybutyl) vinyl ether and hydroxycyclohexyl vinyl ether; (2-hydroxyethyl) allyl ether, (3-hydroxypropyl) allyl ether,
Hydroxyallyl ethers such as (4-hydroxybutyl) allyl ether and hydroxycyclohexyl allyl ether; (2-hydroxyethyl) acrylate,
Hydroxy (meth) acrylates such as (2-hydroxyethyl) methacrylate; vinyl acetate,
Esters of vinyl alcohol with hydroxyalkylcarboxylic acids such as vinyl hydroxypropionate, vinyl hydroxybutyrate, vinyl hydroxyvalerate, vinyl hydroxyisobutyrate and vinyl hydroxycyclohexanecarboxylate; hydroxyethyl allyl ester, hydroxypropyl allyl ester, hydroxybutyl Examples thereof include hydroxyalkyl allyl esters such as allyl ester, hydroxyisobutyl allyl ester and hydroxycyclohexyl allyl ester.

Carboxyl group-containing polymerizable monomer (c)
Examples thereof include (meth) acrylic acid and carboxylalkyl allyl ester. Examples of the glycidyl group-containing polymerizable monomer (c) include glycidyl (meth) acrylate, glycidyl vinyl ether, and glycidyl allyl ether. Examples of the amino group-containing polymerizable monomer (c) include aminoalkyl vinyl ether and aminoalkyl allyl ether. Examples of the amide group-containing polymerizable monomer (c) include (meth) acrylamide and methylol acrylamide. As the nitrile group-containing polymerizable monomer (c), for example,
(Meth) acrylonitrile and the like can be mentioned. Examples of the isocyanate group-containing polymerizable monomer (c) include vinyl isocyanate and isocyanate ethyl acrylate. Examples of the halogen group-containing polymerizable monomer (c) include vinyl chloride and vinylidene chloride.

Polymerized unit (r) having a curing reactive site
Can be reacted with a specific compound to give a polymerized unit (r) having another curing reactive site. For example, the hydroxyl group-containing polymerized unit (r) can be converted into a carboxyl group by reacting with a divalent carboxylic acid anhydride such as succinic anhydride.

The hydroxyl value of the fluorine-containing copolymer is 10 to 2
00 mgKOH / g is preferred and 25-200 mgKO
H / g is particularly preferred. If the hydroxyl value of the fluorinated copolymer is smaller than the above range, the impact resistance tends to decrease. On the contrary, if it is larger than the above range, it tends to become brittle. In addition, the fluorine-containing copolymer in tetrahydrofuran 3
The intrinsic viscosity measured at 0 ° C is 0.1 to 2.0 dl / g
Is preferred, 0.1-0.8 dl / g is more preferred,
0.15-0.5 dl / g is especially preferable. If the intrinsic viscosity of the fluorinated copolymer is smaller than the above range, the impact resistance tends to decrease. On the contrary, if it is larger than the above range, it tends to become brittle. Further, the glass transition temperature of the fluorocopolymer by the differential scanning calorimetry (DSC) measurement method is preferably from 30 to 80 ° C, particularly preferably from 35 to 60 ° C. When the glass transition temperature of the fluorinated copolymer is lower than the above range, the transparency and solvent resistance of the coating film tend to be lowered. On the contrary, when it is larger than the above range, the transparency of the coating film tends to decrease.

The fluorine-containing copolymer is polymerized by solution polymerization,
Any of emulsion polymerization, suspension polymerization, and bulk polymerization may be used, and the polymerization is carried out by causing a predetermined amount of the polymerizable monomer to act on a polymerization initiator, an ionizing radiation source, or the like. It is also possible to control the molecular weight in the presence of a suitable chain transfer agent to carry out the polymerization. In the polymerization reaction, 100% of the charged monomers may be converted to a copolymer, or the polymerization reaction may be interrupted halfway to obtain a mixture of an unreacted monomer and a copolymer. Other various conditions can be the same as those used in ordinary solution polymerization, emulsion polymerization, suspension polymerization, bulk polymerization and the like.

When the fluororesin in the powder coating composition of the present invention has a curing reactive site, a curing agent can be used. Examples of the curing agent include polyisocyanate compounds and blocked polyisocyanate compounds. The polyisocyanate compound is preferably a diisocyanate compound. Examples of the diisocyanate compound include an aliphatic diisocyanate compound, an alicyclic diisocyanate compound, and an aromatic diisocyanate compound. Examples of the aliphatic diisocyanate compound include hexamethylene diisocyanate, trimethylene diisocyanate, 1,4
-Tetramethylene diisocyanate, pentamethylene diisocyanate, lysine diisocyanate, 1,3-butylene diisocyanate and the like.

As the alicyclic diisocyanate compound,
Isophorone diisocyanate, 4,4′-methylenebis (cyclohexyl isocyanate), methylcyclohexane-2,4-diisocyanate, methylcyclohexane-2,6-diisocyanate, 1,3-di (isocyanatomethyl) cyclohexane, 1,4-di ( Isocyanatomethyl) cyclohexane, 1,4-cyclohexane diisocyanate, 1,3-cyclopentane diisocyanate, 1,2-cyclohexane diisocyanate and the like can be mentioned. As the aromatic diisocyanate compound,
Examples include tolylene diisocyanate, xylylene diisocyanate, metaxylylene diisocyanate, tetramethyl xylylene diisocyanate, tolylene diisocyanate, 4,4′-diphenylmethane diisocyanate, phenylene diisocyanate and the like. As the diisocyanate compound, an alicyclic diisocyanate compound is preferable, and an isophorone diisocyanate compound is particularly preferable.

The blocked isocyanate-based curing agent is obtained by blocking the isocyanate group of the isocyanate-based curing agent with a blocking agent. As the isocyanate-based curing agent, for example, isophorone diisocyanate, tolylene diisocyanate, xylylene diisocyanate,
Examples thereof include polyisocyanate compounds such as 4,4′-diphenylmethane diisocyanate and hexamethylene diisocyanate, and dimers and trimers thereof, and polyisocyanate compounds modified with a polyhydric alcohol. As the polyhydric alcohol, ethanediol,
Propane diol, butane diol, pentane diol, hexane diol, heptane diol, octane diol, cyclohexane diol, cyclohexane dimethanol, and these diols obtained by reacting with a less than stoichiometric amount of dicarboxylic acid or dicarboxylic acid anhydride. Examples thereof include ester group-containing diols, trimethylolpropane, and ester group-containing polyols obtained by reacting trimethylolpropane with a dicarboxylic acid or dicarboxylic acid anhydride in an amount less than the stoichiometric amount. As the isocyanate-based curing agent, a compound having two isocyanate groups is preferable.

Examples of the blocking agent include ε-caprolactam, phenol, benzyl alcohol, methylethylketoxime and the like. Examples of other curing agents include polycarboxylic acids, acid anhydrides, polycyan polyamide compounds, imidazole compounds, amine compounds, melamine resins, glycidyl compounds and polyol compounds. As the polycarboxylic acid, fumaric acid, succinic acid, adipic acid, azelaic acid, sebacic acid, dodecanedioic acid and other aliphatic dibasic acids, an acid value of 10 to 300 mg
Examples thereof include KOH / g, a glass transition temperature of 30 to 120 ° C., and a number average molecular weight of 1000 to 15000 such as polyester resin or acrylic resin. As the acid anhydride,
Examples thereof include phthalic anhydride, trimellitic anhydride, and pyromellitic dianhydride.

Examples of polycyan polyamide compounds include dicyandiamide and dicyandiamide derivatives. Examples of the amine compound include dihydric acid dihydrazide, diaminophenylmethane, and cyclic diamine compounds. Examples of the glycidyl compound include terephthalic acid diglycidyl ester, paraoxybenzoic acid diglycidyl ester, triglycidyl isocyanurate, spiroglycol diglycidyl ether, hydantoin compound, and alicyclic epoxy resin. As the polyol compound, 1,4-bis-2′-hydroxyethoxybenzene, bishydroxyethyl terephthalate, styrene.
Allyl alcohol copolymer, spiroglycol, tris 2-hydroxyethyl isocyanurate, hydroxyl group is 10
-30 mg KOH / g, glass transition temperature 30-120
A polyester resin or an acrylic resin having a number average molecular weight of 1,000 to 15,000 at 0 ° C can be used. The mixing ratio of the fluororesin and the curing agent is 40:60 to 98: by mass.
2 is preferable, and 50:50 to 97: 3 is particularly preferable.

In the powder coating resin composition of the present invention, the ultraviolet absorbing copolymer is obtained by copolymerizing a benzotriazole type ultraviolet absorbing vinyl monomer and a copolymerizable monomer. The benzotriazole-based UV absorbing vinyl monomer has the general formula (1)

[Chemical 1] (In the formula, X represents a hydrogen atom or a chlorine atom. R ¹ represents a hydrogen atom, a methyl group or a tertiary alkyl group having 4 to 8 carbon atoms. R ² represents a linear or branched carbon number. 2-1
The alkylene group of 0 is shown. R ³ represents a hydrogen atom or a methyl group. n represents 0 or 1. ) A monomer represented by the general formula (2)

[0022]

[Chemical 2] (In the formula, R ¹ and R ³ are the same as the above.), A monomer represented by the general formula (3)

[0023]

[Chemical 3]

(In the formula, R ¹ , R ² and R ³ are the same as above. R ⁴ represents an ethylene group or a 2-hydroxypropylene group.) And the like. In the above formula, examples of the tertiary alkyl group having 4 to 8 carbon atoms represented by R ¹ include tert-butyl group, tert-pentyl group, tert-hexyl group, tert-heptyl group, ditert-octyl group and the like. Can be mentioned. Examples of the linear or branched alkylene group having 2 to 10 carbon atoms of R ² include ethylene group, trimethylene group, propylene group,
Examples thereof include a tetramethylene group, 1,1-dimethyltetramethylene group, butylene group, octamethylene group, octylene group, decamethylene group and decylene group.

Examples of the monomer represented by the general formula (1) include 2- [2'-hydroxy-5 '-(methacryloyloxy) phenyl] -2H-benzotriazole and 2-
[2′-Hydroxy-3′-tert-butyl- (methacryloyloxymethyl) phenyl] -2H-benzotriazole, 2- [2′-hydroxy-5 ′-(2-methacryloyloxyethyl) phenyl] -2H-benzo Triazole, 2- [2'-hydroxy-5 '-(2-
Acryloyloxyethyl) phenyl] -2H-benzotriazole, 2- [2'-hydroxy-3'-te
rt-Butyl- (methacryloyloxyethyl) phenyl] -5-chloro-2H-benzotriazole, 2-
[2′-hydroxy-3′-methyl-5 ′-(8-acryloyloxyethyl) phenyl] -2H-benzotriazole and the like can be mentioned.

The monomer represented by the general formula (2) is 2- [2'-hydroxy-5'-tert-butyl-3 '-(methacrylamidomethyl) phenyl] -2H.
-Benzotriazole, 2- [2'-hydroxy-5 '
-Di-tert-octyl-3 '-(methacrylamidomethyl) phenyl] -2H-benzotriazole and the like. Examples of the monomer represented by the general formula (3) include
2- [2'-hydroxy-3'-tert-butyl-
5'-2- (2-methacryloyloxyethoxycarbonyl) ethylphenyl] -2H-benzotriazole, 2- [2'-hydroxy-3'-tert-butyl-5'-2- (3-methacryloyloxy-2-) Hydroxypropoxycarbonyl) ethylphenyl] -2H
-Benzotriazole, 2- [2'-hydroxy-3 '
Examples include -tert-butyl-5'-2- (3-methacryloyloxy-2-propoxycarbonyl) ethylphenyl] -2H-benzotriazole and the like. The benzotriazole-based UV absorbing vinyl monomer may be used alone or in combination of two or more.

Examples of the copolymerizable monomer include, for example,
(Meth) acrylic acid, methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, n-octyl (meth) acrylate, n-lauryl (meth) acrylate and the like (meth ) Acrylic acid and (meth)
Examples thereof include alkyl acrylates, olefins such as 1-hexene, 1-octene and 1-decene, vinyl acetate, styrene, 2-hydroxyethyl methacrylate, acrylamide, vinyl chloride and the like.

The content ratio of the benzotriazole type UV absorbing vinyl monomer in the UV absorbing copolymer is
Usually, 0.1 to 70 mass% is preferable, and 10 to 50 mass%
Is particularly preferable. The weight average molecular weight of the ultraviolet absorbing copolymer is usually preferably 2000 to 100000,
0-50000 is particularly preferable. The mixing ratio of the fluororesin and the ultraviolet absorbing copolymer in the powder coating composition of the present invention is usually 0.2 to 30 parts by mass, preferably 1 to 30 parts by mass of the ultraviolet absorbing copolymer with respect to 100 parts by mass of the fluororesin. ~ 20
Part by weight is especially preferred.

In the powder coating composition of the present invention, if necessary, antioxidants such as antioxidants, ultraviolet absorbers and light stabilizers, fillers, coloring agents such as pigments, leveling agents, surface conditioning agents, etc. Various additives such as an agent, a heat deterioration preventing agent, an antifoaming agent, and storage stability can be arbitrarily added and blended. Known various additives can be used.

As a method for applying the powder coating composition of the present invention, various coating methods such as spray coating, electrostatic powder coating, and fluid immersion coating can be applied. Curing of the coating film after application of the powder coating composition can be carried out at room temperature or under heating. The temperature in the case of heat curing is preferably in the range of 50 to 300 ° C. The thickness of the obtained coating film is not particularly limited, but usually 1
It is 0 to 200 μm. The base material to which the powder coating composition of the present invention is applied is made of various materials such as steel, zinc, aluminum, copper, metal metals such as tin, ceramics, inorganic materials such as concrete, plastics, organic materials such as wood, and the like. The base material may include: The powder coating composition of the present invention may be applied directly to the surface of the base material, or may be applied to the surface of the base material by providing a lower coating film on the surface of the base material. The lower layer coating film may be a single layer or a multilayer of two or more layers. The lower layer coating film can be a coating film made of various coating materials such as urethane resin coating material, polyester resin coating material, acrylic resin coating material, and is preferably a coating film made of urethane resin coating material.

[0031]

EXAMPLES The present invention will be described in more detail with reference to Examples below, but the present invention is not limited thereto. The intrinsic viscosity shown below was measured in tetrahydrofuran at 30 ° C. Further, the glass transition temperature is determined by differential scanning calorimetry (DS
It was measured by C).

Synthesis Example 1 54 parts by weight of methyl methacrylate, 13 parts by weight of n-butyl methacrylate, 3 parts by weight of 2-hydroxyethyl methacrylate, 2- [2'-hydroxy-3'-tert-butyl-5. '-2- (3-methacryloyloxy-2-hydroxypropoxycarbonyl) ethylphenyl] -2H-benzotriazole 30
A mixture of 100 parts by mass of azoisobutyronitrile and 2.8 parts by mass of azoisobutyronitrile was gradually added dropwise to 100 parts by mass of butyl acetate heated to 120 ° C., and then maintained at 120 ° C. for 4 hours. Next, the solvent was volatilized from the obtained reaction product under reduced pressure of 50 torr at 160 ° C. to obtain a weight average molecular weight of 1
0000 UV absorbing copolymers were obtained.

(Synthesis Example 2) According to the method described in JP-B-60-21686, a monomer composition of chlorotrifluoroethylene / cyclohexyl vinyl ether / hydroxybutyl vinyl ether of 50/39/11 mol% was copolymerized and contained. A fluorocopolymer was synthesized. The obtained fluorine-containing copolymer has a hydroxyl value of 50 mgKOH /
g, intrinsic viscosity 0.24 dl / g, glass transition temperature 57
The heating loss was 2% by mass or less.

(Synthesis Example 3) Ion-exchanged water 860 was placed in a stainless steel autoclave equipped with a stirrer and having an internal volume of 2.5 L.
g, 10-undecenoic acid 35 g, fluorine-based anionic emulsifier (Sumitomo 3M, trade name "FC-143") 4.
75 g, 2.2 g of nonionic emulsifier (Nippon Emulsifier, trade name "N-1110"), and t-butanol 4
6.6 g was charged, and deaeration with a vacuum pump and pressurization with nitrogen gas were repeated to remove air. Next, tetrafluoroethylene / propylene / ethylene (85/5/1
0 mol%) of the mixed monomer was introduced until the pressure in the autoclave reached 2.4 MPa. Then, 2 mL of a 25 mass% aqueous solution of ammonium persulfate was added to start the reaction. A mixed monomer gas 55 of tetrafluoroethylene / propylene / ethylene (54/26/20 mol%) while pressurizing and maintaining the pressure as the pressure decreases
0.5 g was added continuously to continue the reaction. During the progress of the reaction, an aqueous solution of 25% by mass of ammonium persulfate 30m
L was added continuously. After 18 hours, supply of the mixed monomer gas was stopped, the autoclave was cooled with water to reach room temperature, unreacted monomers were purged, and the autoclave was opened to obtain an aqueous dispersion having a solid content concentration of 40.1% by mass. It was The glass transition temperature of this fluororesin was 20 ° C.

(Synthesis Example 4) 70 g of the aqueous dispersion obtained in Synthesis Example 3 was placed in a glass flask having an internal volume of 200 mL equipped with a thermometer, a stirrer, and a reflux condenser, and heated to 80 ° C. . When the temperature reached 80 ° C, methacrylic acid t
-Butyl 4.2 g, n-butyl methacrylate 2.2 g,
An aqueous dispersion obtained by emulsifying 4.2 g of methyl methacrylate, 1.0 g of 2-hydroxyethyl methacrylate and 0.02 g of an anionic emulsifier (sodium lauryl sulfate) in a 50% by mass aqueous solution was added dropwise over 1 hour. After dispersing with stirring for 18 hours, the mixture was heated to 60 ° C. 60 ° C
When the temperature reached, 1 mL of a 0.5 mass% aqueous solution of ammonium persulfate was added to start the reaction. Reaction time 4.5
After the elapse of time, the mass ratio of the fluorocopolymer and the methacrylic acid ester polymer was 77:23, and the solid content concentration was 50.8 mass%.
An aqueous dispersion of was obtained. Next, while stirring this aqueous dispersion, a 10% by mass aqueous solution of potassium chloride was added to coagulate /
Allowed to settle. After filtering with a glass filter, washing and filtering with ion-exchanged water were repeated, and the resulting granular polymer was washed with 3 times.
It was dried in an oven at 0 ° C. for 12 hours to obtain a fluorine-containing copolymer powder. The obtained fluorocopolymer had a glass transition temperature of 50 ° C. and a heating loss of 2% by mass or less.

Example 1 100 parts by mass of the fluororesin obtained in Synthesis Example 2 was added to 7 parts by mass of the ultraviolet absorbing copolymer obtained in Synthesis Example 1 and a curing agent (trade name "adduct manufactured by Hüls"). B-1530 ", 25 parts by mass of ε-caprolactam-blocked isophorone diisocyanate-based polyisocyanate compound, and mixed for about 1 minute by a dry blender (trade name" Henschel mixer "manufactured by Mitsui Kakoki Co., Ltd.), and Extrusion kneader under the temperature condition of 90 to 130 ° C.
-46 ") was used for melt kneading. Next, after cooling to 20 ° C., crushing with an impact hammer mill, sieving with a 180-mesh wire mesh to remove coarsely crushed material, collecting powders that have passed through the wire mesh and collecting thermosetting fluorine-containing powder coating composition I got a thing.

Example 2 Chlorotrifluoroethylene / cyclohexyl vinyl ether / isobutyl vinyl ether / hydroxybutyl vinyl ether (50/15)
Fluorine resin (hydroxyl value 120 mgKOH / g, intrinsic viscosity 0.21 dl / g, glass transition temperature 45 ° C., heating loss 2 mass% or less) obtained by copolymerizing 100% by mass) Was blended with 7 parts by mass of the ultraviolet absorbing copolymer obtained in Synthesis Example 1 and 60 parts by mass of a curing agent (manufactured by Huls, trade name “Adduct B-1530”), and a dry blender (manufactured by Mitsui Chemicals, Inc. , Henschel Mixer)) for about 1 minute, then 9
The mixture was melt-kneaded under a temperature condition of 0 to 130 ° C. using an extrusion kneader (manufactured by Pus Co., Ltd., trade name “Pusconider PR-46”). Next, after cooling to 20 ° C., crushing with an impact hammer mill, sieving with a 180-mesh wire mesh to remove coarsely crushed material, collecting powders that have passed through the wire mesh and collecting thermosetting fluorine-containing powder coating composition I got a thing.

(Example 3) 100 parts by mass of the fluororesin obtained in Synthesis Example 4 was mixed with 7 parts by mass of the UV-absorbing copolymer obtained in Synthesis Example 1, and a dry blender (manufactured by Mitsui Kakoki Co., Ltd.) was used. , A trade name "Henschel mixer") for about 1 minute, and then an extrusion kneader under the temperature condition of 90 to 130 ° C (manufactured by Puss, trade name "Pusconider PR-46").
Was melt-kneaded. Next, after cooling to 10 ° C., crushing with an impact hammer mill, sieving with a 180-mesh wire mesh to remove coarsely crushed material, and collecting powders passing through the wire mesh to obtain a thermoplastic fluorine-containing powder coating composition Got

Comparative Example 1 100 parts by mass of the fluororesin obtained in Synthesis Example 2 was added to a benzotriazole-based ultraviolet absorber (trade name "Tinuvin 900", manufactured by Ciba Specialty Chemicals, 2- [2-hydroxy-]. 3,5-di (1,1-dimethylbenzyl) phenyl] -2H-benzotriazole) 7 parts by mass and a curing agent (manufactured by Huls, trade name "Adduct B-1530") 25 parts by mass were compounded, and dry blender (Mitsui Kakoki Co., Ltd., trade name "Henschel Mixer") for about 1 minute, then 9
The mixture was melt-kneaded under a temperature condition of 0 to 130 ° C. using an extrusion kneader (manufactured by Pus Co., Ltd., trade name “Pusconider PR-46”). Next, after cooling to 20 ° C., crushing with an impact hammer mill, sieving with a 180-mesh wire mesh to remove coarsely crushed material, collecting powders that have passed through the wire mesh and collecting thermosetting fluorine-containing powder coating composition I got a thing.

(Comparative Example 2) 100 parts by mass of a polyester powder coating (manufactured by Unitika Ltd., trade name "ER-8150") was added to a benzotriazole type ultraviolet absorber (manufactured by Ciba Specialty Chemicals, trade name "Tinuvin"). 90
0 ") 7 parts by mass and a curing agent (triglycidyl isocyanate) 25 parts by mass, and mixed with a dry blender (manufactured by Mitsui Kakoki Co., Ltd., trade name" Henschel Mixer ") for about 1 minute, and then at 90 to 130 ° C. Extrusion kneader under temperature conditions (Pus Co., trade name "Pusconider PR-4
6 ”) was used for melt kneading. Next, after cooling to 20 ° C., it is ground with an impact hammer mill, sieved with a 180-mesh wire net to remove coarsely ground material, and the powder that has passed through the wire net is collected to form a thermoplastic polyester powder coating composition. Obtained.

(Evaluation method) 100 parts by mass of the powder coating composition obtained in the examples or comparative examples was used as tetrahydrofuran 2
After dissolving in 100 parts by mass, it was applied on a glass plate having a thickness of 100 μm so that the dry film thickness was 15 μm, and dried at room temperature for 24 hours. Next, in order to examine the stability of the ultraviolet absorber contained in the dried coating film during thermosetting, the glass plate on which the coating film was formed was baked for 30 minutes in a heating furnace at 180 ° C. After drying at room temperature and after baking, the absorbance at an absorption wavelength of 280 to 380 nm was measured using a spectral light transmittance measuring device (manufactured by Shimadzu Corporation, trade name "UV-3100"). Table 1 shows the retention rate after baking when the value after drying at room temperature was set to 100. A coating film obtained by spray-coating a urethane-based white paint (manufactured by Dainippon Paint Co., Ltd., trade name "V Shine") on a zinc phosphate-treated steel sheet to a dry film thickness of 15 µm and curing it. The powder coating composition obtained in Example or Comparative Example was electrostatically coated on the surface and cured in an oven at 180 ° C. for 20 minutes to obtain a coating film having a dry film thickness of 65 μm combined with an undercoat layer. It was The obtained coating film was exposed for 2000 hours by an accelerated weather resistance tester (manufactured by Daipla Wintes Co., Ltd., trade name “Dipla Metal Weather”).
Exposure test conditions: irradiation (63 ° C., 40% RH × 4 hours, shower 5 seconds / 15 minutes) and condensation (30 ° C., 98% RH)
X 4 hours) were alternately repeated. The 60 ° gloss value of the coating film before and after the acceleration test was measured to determine the gloss retention rate (%).
Furthermore, the state of the interface between the upper coating layer and the lower coating layer was observed. The results are shown in Table 2.

[0042]

[Table 1]

From Table 1, it can be seen that the comparative example 1 containing the conventionally used low molecular weight ultraviolet absorber in the coating film volatilizes during the heat curing treatment, while the ultraviolet absorbing copolymer It can be seen that in Examples 1 and 2 in which the coalesced compound was blended, the ultraviolet absorbing ability was retained without volatilizing even during the heat curing treatment.

[0044]

[Table 2]

As can be seen from Table 2, since Example 1, Example 2 and Comparative Example 1 are made of fluororesin, there is almost no decrease in gloss due to deterioration of the overcoat layer, but the low molecular weight ultraviolet absorber of Comparative Example 1 is used. For the one blended in the coating film, since the ultraviolet absorber volatilized during the heat curing treatment, ultraviolet rays penetrated the topcoat layer and deteriorated the undercoat layer, causing partial peeling at the interface. Since Comparative Example 2 is a polyester resin, the glossiness was lowered due to deterioration of the topcoat layer itself, but no abnormality was observed between the undercoat layer and the interlayer because the ultraviolet absorbing copolymer was blended. It was

[0046]

EFFECTS OF THE INVENTION The fluorine-containing powder coating composition of the present invention is capable of improving the weather resistance of a lower coating film or an underlayer, and particularly preventing interfacial peeling between the lower coating film and the coating film formed by the fluorine-containing powder coating composition. A coating film having excellent properties and coating appearance can be provided.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Masao Unoki             Asahi Glass Co., Ltd. 10 Goi Coast, Ichihara City, Chiba Prefecture             In the company F-term (reference) 4J038 CD091 CD111 CD121 CD131                       CG142 CH192 CJ012 CJ022                       CJ062 CJ102 CJ132 CJ142                       DA132 DA162 DG262 DG302                       GA03 GA06 GA07 GA09 GA11                       GA12 GA13 JA35 JB01 KA03                       MA13 MA14 PA02 PC02 PC03                       PC06 PC08

Claims (2)

[Claims] 1. A fluorine-containing powder comprising a fluororesin and an ultraviolet-absorbing copolymer obtained by copolymerizing a benzotriazole-based ultraviolet-absorbing vinyl monomer and a copolymerizable monomer. Body coating composition. 2. A fluororesin having a hydroxyl value of 10 to 200 mg.
The KOH / g, the intrinsic viscosity measured at 30 ° C. in tetrahydrofuran at 0.1 to 0.8 dl / g, and the glass transition temperature of 30 to 80 ° C. by a differential scanning calorimetry (DSC) measurement method. Fluorine powder coating composition.