JP2003105251A - Fluororesin powder coating material composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a fluororesin powder coating material composition in which titanium oxide can sufficiently express its functions as white color pigment and a fluororesin has also an excellent weather resistance. SOLUTION: This fluororesin powder coating material composition is characterized by containing a fluorine-containing resin and titanium oxide having catalytic activity of <=3 (mol/kg/min×10).

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a titanium oxide-containing fluororesin powder coating composition having excellent weather resistance.

[0002]

2. Description of the Related Art Fluororesin coating materials have various characteristics which are expressed by the characteristics of fluorine atoms. Among them, C-
The long-term durability resulting from the high stability of the F bond gives the fluororesin extremely excellent weather resistance. Therefore, the fluororesin is widely used in the fields of heavy corrosion resistance, construction, industrial use and the like. However, solvent paints are also a cause of environmental pollution because they release organic solvents into the environment when they are used, and in order to deal with the problem of environmental pollution, which is becoming more serious each year,
Fluororesin powder coatings, which are powders of coatings, are receiving attention. Powder coatings are widely used for general coating on metal surfaces because of their advantages of pollution-free, resource saving and labor saving. Especially, bridges, balustrades, gates, fences, household siding agents with important weather resistance are used. It is also widely used for road construction materials such as car bodies and parts of automobiles, and household products.

By the way, the pigments used in such powder coatings are the same as those used in ordinary solvent-based coatings, and titanium oxide, which is a white pigment, has excellent coloring properties, hiding power, etc., and is inexpensive. Therefore, it is also commonly used in powder coatings. When such a titanium oxide is blended in a powder coating material, for example, an acrylic powder coating material having low weather resistance deteriorates with time from the outermost acrylic resin portion.
On the other hand, in the case of the fluororesin powder coating material, since it has high weather resistance, deterioration is unlikely to occur in the resin portion other than the vicinity of titanium oxide.

[0004]

However, in the area where titanium oxide is present, when ultraviolet rays, oxygen, water, etc. are present, radicals are generated due to the photocatalytic action of the titanium oxide surface, which deteriorates the fluororesin in the vicinity of titanium oxide. There is a problem of causing.

Therefore, an object of the present invention is to provide a titanium oxide-containing fluororesin powder coating composition having excellent weather resistance.

[0006]

DISCLOSURE OF THE INVENTION As a result of intensive studies aimed at achieving the above object, the present inventors have found that a fluororesin powder coating composition containing titanium oxide prepared so that the photocatalytic activity is below a specific value. Then, it is found that titanium oxide can sufficiently exhibit the function as a white pigment, and the weather resistance of the fluororesin powder coating composition will also be excellent,
The present invention has been completed.

That is, the present invention comprises a fluorine-containing resin,
The present invention provides a fluororesin powder coating composition containing titanium oxide having a photocatalytic activity of 3 (mol / kg / min × 10) or less. It is conventionally known that the photocatalytic activity of titanium oxide reduces the weather resistance of the titanium oxide-containing resin. Also, by treating the surface of titanium oxide with silica or alumina,
It is also known that the weather resistance of the titanium oxide-containing resin is improved. However, for example, even if the surface of the resin is treated with the same amount of silica, there is a large difference in the degree of improvement in the weather resistance of the resin depending on the type of the resin, the properties of the silica, the conditions of kneading the resin and silica, and the like. Occurs. Therefore, for the titanium oxide-containing resin, the weather resistance had to be measured each time the resin, silica, kneading conditions, etc. were changed. The present invention can predict the weather resistance of a fluorine-containing resin compounded with titanium oxide simply by measuring the photocatalytic activity of titanium oxide, which is truly surprising.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The fluorine-containing resin used in the fluororesin powder coating composition of the present invention may be either a thermoplastic fluorine-containing resin or a thermosetting fluorine-containing resin, preferably a fluoroolefin unit. A reactive fluorine-containing copolymer containing a crosslinkable reactive group and a curing agent, after coating the powder coating composition on the surface of the article to be coated, when baking,
A thermosetting fluorine-containing resin capable of causing a crosslinking reaction between the crosslinking reactive group of the reactive fluorine-containing copolymer and the curing agent is used. The following description exemplifies a case where a thermosetting fluorine-containing resin containing a combination of a reactive fluorine-containing copolymer and a curing agent is used as the fluorine-containing resin.

Examples of the raw material for the fluoroolefin unit of the reactive fluorine-containing copolymer include tetrafluoroethylene, chlorotrifluoroethylene, trifluoroethylene, vinylidene fluoride, hexafluoropropylene, pentafluoropropylene and the like. Those can be used, and can be appropriately selected depending on the properties required for the coating film, the combination with the copolymer component or the curing agent. Moreover, these fluoroolefins can use 1 type (s) or 2 or more types.

The crosslinkable reactive group of the reactive fluorocopolymer used in the present invention includes a hydroxyl group, a carboxyl group, an amide group, an amino group, a mercapto group, a glycidyl group, bromine,
Examples thereof include active halogen such as iodine and isocyanate group. The method of introducing such a curing reaction site into the copolymer includes a method of copolymerizing a monomer having a crosslinkable reactive group, a method of decomposing a part of the copolymer, and a crosslinkable reaction to a functional group of the copolymer. Means such as a method of reacting a compound giving a group can be mentioned.

The preferred crosslinkable reactive group used in the present invention is a monomer having a hydroxyl group or a group capable of being converted into a hydroxyl group, which has a double bond copolymerizable with a fluoroolefin. Can be used, for example, hydroxyalkyl vinyl ethers such as hydroxyethyl vinyl ether, hydroxypropyl vinyl ether, hydroxybutyl vinyl ether, hydroxyisobutyl vinyl ether, and hydroxycyclohexyl vinyl ether, vinyl hydroxyacetate, vinyl hydroxypropionate, vinyl hydroxybutyrate, and hydroxy Esters of hydroxyalkylcarboxylic acids such as vinyl herbate, vinyl hydroxyisobutyrate and vinyl hydroxycyclohexanecarboxylate with vinyl alcohol, hydroxyethyl ants Hydroxyalkyl allyl ethers such as ether, hydroxypropyl allyl ether, hydroxybutyl allyl ether, hydroxyisobutyl allyl ether, hydroxycyclohexyl allyl ether, hydroxyethyl allyl ester, hydroxypropyl allyl ester, hydroxybutyl allyl ester, hydroxyisobutyl allyl ester, hydroxy Hydroxy allyl esters such as cyclohexyl allyl ester, hydroxy alkyl esters of acrylic acid or methacrylic acid such as 2-hydroxyethyl acrylate, hydroxypropyl acrylate, 2-hydroxyethyl methacrylate, hydroxypropyl methacrylate, and the like, and partial thereof. And compounds substituted with fluorine.

As the raw material for the hydroxyl group-containing unit, one or more of these can be selected and used. Further, it is desirable to use a vinyl-based or allyl-based compound because of its copolymerizability with fluoroolefin.

Examples of the above-mentioned monomer having a carboxyl group used in the present invention include (meth) acrylic acid and carboxyl alkyl allyl ether. Examples of the glycidyl group-containing monomer include glycidyl (meth) acrylate, glycidyl vinyl ether, glycidyl allyl ether, and the like. Examples of the monomer having an amino group include aminoalkyl vinyl ether and aminoalkyl allyl ether. Examples of the amide group-containing monomer include (meth) acrylamide and methylol acrylamide. Examples of the monomer having a nitrile group include (meth) acrylonitrile. As the monomer having an isocyanate group,
Examples thereof include vinyl isocyanate and isocyanate ethyl acrylate. Examples of the monomer having an active halogen group include vinyl chloride and vinylidene chloride.

As a method for decomposing a part of the copolymer, a copolymer having a hydrolyzable ester group-containing monomer is copolymerized and then the copolymer is hydrolyzed to obtain a copolymer. An example is a method of forming a carboxyl group during coalescence. Further, it is also possible to form a cross-linkage by a transesterification reaction in a direct curing reaction without performing ester hydrolysis as described above. As a method of reacting a compound that gives a crosslinkable reactive group to the copolymer, a method of introducing a carboxyl group by reacting a hydroxyl group-containing copolymer with a divalent carboxylic acid anhydride such as succinic anhydride is preferable. Can be adopted.

Further, as the monomer for providing the above-mentioned crosslinkable reaction site, from the viewpoint of copolymerizability with fluoroolefin,
It is preferable to employ a vinyl type or allyl type compound.

The reactive fluorine-containing copolymer used in the present invention has a lower melting point or glass transition temperature of the reactive fluorine-containing copolymer in addition to the above-mentioned two types of units to further improve coating workability. Depending on the purpose of imparting appropriate hardness, flexibility, luster and other physical properties to the coating film, a copolymerizable comonomer with the above two components can be copolymerized.

As such a comonomer, one having an unsaturated group active to the extent that it can be copolymerized with a fluoroolefin and not significantly impairing the weather resistance of the coating film is adopted. Usually, an ethylenically unsaturated compound, For example, alkyl vinyl ethers such as ethyl vinyl ether, propyl vinyl ether, butyl vinyl ether, isobutyl vinyl ether, cyclohexyl vinyl ether, etc., vinyl acetate, vinyl propionate, vinyl butyrate, vinyl isobutyrate, vinyl valerate, vinyl cyclohexanecarboxylate, etc. Esters with alcohols, alkyl allyl ethers such as ethyl allyl ether, propyl allyl ether, butyl allyl ether, isobutyl allyl ether, cyclohexyl allyl ether, ethyl allyl ester, Alkyl allyl esters such as luaryl ester, butyl allyl ester, isobutyl allyl ester, cyclohexyl allyl ester, alkenes such as ethylene, propylene, butylene, isobutylene, acrylic acid, methacrylic acid or ethyl acrylate, propyl acrylate, butyl acrylate, isobutyl Acrylate, 2-ethylhexyl acrylate, ethyl methacrylate, propyl methacrylate,
Butyl methacrylate, isobutyl methacrylate, 2
Examples thereof include esters of acrylic acid or methacrylic acid such as ethylhexyl methacrylate, and partially fluorine-substituted compounds thereof. These monomers may be used alone or in combination of two or more. As these comonomers, vinyl type, allyl type compounds or alkenes having excellent copolymerizability with fluoroolefins are preferably adopted.

When a vinyl-based or allyl-based alkyl ester or alkyl ether is used, the alkyl group is preferably a linear, branched or alicyclic alkyl group having about 2 to 10 carbon atoms. it can.

The reactive fluorine-containing copolymer used in the present invention preferably has a fluorine content of 10% by mass or more. Usually, this fluorine content is related to the constitution ratio of the fluoroolefin unit in the reactive fluorine-containing copolymer.
However, it is also possible to increase or decrease this content by polymer reaction once the copolymer is produced.

When the fluorine content in the reactive fluorine-containing copolymer used in the present invention is less than 10% by mass, it is difficult to obtain a coating film having sufficient weather resistance. The fluorine content in the copolymer is particularly preferably 15 to 72% by mass from the viewpoint of the overall performance balance such as weather resistance and coating workability of the coating film. The reactive fluorine-containing copolymer used in the present invention preferably has a fluorine content of 10% by mass or more and further contains a fluoroolefin unit in the range of 70 to 30 mol%. be able to. That is, when the content of the fluoroolefin unit is 30 mol% or more, the weather resistance is further remarkably improved, and when the content of the fluoroolefin unit is 70 mol% or less, the fluorine-containing copolymer tends to be non-crystalline, that is, the fluorine-containing copolymer. Since the copolymer is less likely to be crystallized, adhesion is good, a coating film having a uniform and smooth surface is easily formed, and high temperature is not required during baking of the coating material, which is particularly preferable.

The reactive fluorine-containing copolymer used in the present invention has a crosslinkable reactive group, and a coating film having toughness and excellent adhesion can be obtained by reaction with a curing agent. The average molecular weight of the copolymer chain per one crosslinkable group present in the copolymer molecule is preferably 250 to 25,000. When the average molecular weight is 25,000 or less, sufficient crosslinking can be achieved and physical properties such as solvent resistance can be kept good, and when it is 250 or more, the crosslinking density will not be too high and the coating film can be coated easily. Good flexibility.
Crosslinking reactive group 1 present in reactive fluorine-containing copolymer molecule
The average molecular weight of the copolymer chain per unit is represented by: [fluorine-containing copolymer molecular weight / number of cross-linking reactive groups in one molecule]. Specifically, this average molecular weight is determined by measuring the crosslinkable reaction group value (mgKOH / g) such as the hydroxyl value, acid value or epoxy group value of the reactive fluorine-containing copolymer by IR spectrum and NMR.
It can be measured by a method such as spectrum or titration and calculated by the following formula. (56.1 / Crosslinkable reactive group value) × 10 ³ [wherein 5
6.1 is the molecular weight of KOH. When the crosslinkable reactive group is an epoxy group, the epoxy equivalent corresponds to this value.

The hydroxyl value of the reactive fluorine-containing copolymer having a hydroxyl group as a crosslinkable reactive group is 1 to 200 mgKOH.
/ G, particularly preferably 20 to 140 mgKOH / g. When the hydroxyl value is 1 mgKOH / g or more, crosslinking is sufficient and the coating film has good physical properties. When the hydroxyl group is less than 200 mgKOH / g, the crosslink density does not become too high, and good flexibility can be obtained.

The intrinsic viscosity of the reactive fluorinated copolymer used in the present invention measured at 30 ° C. in tetrahydrofuran is preferably 0.05 to 2 dl / g. When the intrinsic viscosity is 0.05 or more, it becomes solid and can be used as a powder coating composition. When the intrinsic viscosity is 2 or less, the softening point does not become too high and the flowability of the coating film becomes good.

The glass transition temperature of the reactive fluorocopolymer used in the present invention is 30 to 120 ° C., preferably 35.
It is desirable to set the temperature to -100 ° C. Glass transition temperature is 3
If it is 0 ° C. or higher, it becomes solid and easy to use as a powder coating composition. Further, by setting the glass transition temperature to 120 ° C. or less, the softening point does not become too high, and the flowability can be kept good.

When a crystalline polymer is used as the reactive fluorine-containing copolymer, a high temperature is required during baking. When a crystalline polymer is used, it preferably has a melting point of 200 ° C. or lower.

The reactive fluorine-containing copolymer used in the present invention can be synthesized by a conventionally known method. Polymerization can be carried out by allowing a polymerization initiator to act on a monomer mixture in a predetermined ratio in the presence or absence of a catalyst. Further, it can be produced by any method of solution polymerization, emulsion polymerization and suspension polymerization.

In the present invention, the reactive fluorine-containing copolymer is used in the form of powder. The method for obtaining such a powdery fluorine-containing copolymer can be carried out by an appropriate method depending on the polymerization mode. When the copolymer is obtained by emulsion polymerization or suspension polymerization, the dispersion medium is discharged from the polymerization liquid under a reduced pressure of 100 mmHg.
Hereinafter, after being removed by evaporation at 50 to 100 ° C., a willer type,
It can be manufactured by crushing with a crusher such as a vibration mill type or an impact type hammer mill type. When it is obtained by solution polymerization, it can be produced by removing the solvent of the polymerization liquid or by pouring it into a solution in which the polymer is not dissolved to precipitate the fluorine-containing copolymer, removing the solvent and then pulverizing.

The reactive fluorine-containing copolymer used in the present invention is used in the form of powder, and such powder has a residual amount (heating loss) of a solvent (hereinafter, used to include a dispersion medium). It is preferably 5% by mass or less. By setting the residual amount of the solvent in the copolymer to 5% by mass or less, the storage stability of the powder coating material becomes good, and after baking and curing of the powder coating material, foaming, blistering, pinholes, etc. on the coating film occur. Does not occur. In particular, the residual amount of the solvent is preferably 2% by mass or less.

As the curing agent capable of reacting with the crosslinkable reactive group of the above reactive fluorine-containing copolymer, a blocked isocyanate compound such as isophorone diisocyanate, tolylene diisocyanate, xylylene diisocyanate,
Polyisocyanate compounds such as 4,4'-diphenylmethane diisocyanate and hexamethylene diisocyanate, and isocyanate groups such as dimers, trimers and polyisocyanate compounds modified with polyhydric alcohols such as trimethylolpropane Examples thereof include compounds blocked with a blocking agent such as ε-caprolactam, phenol, benzyl alcohol and methylethylketoxime. As the blocked isocyanate compound, a compound that is solid at room temperature can be preferably used.

Further, fumaric acid, succinic acid, adipic acid,
Aliphatic dibasic acids such as azelaic acid, sebacic acid, dodecanedioic acid, acid anhydrides such as phthalic anhydride, trimellitic anhydride, pyromellitic dianhydride, acid value 10-300 mgK
OH / g, glass transition temperature of 30 to 120 ° C., number average molecular weight of 1000 to 15,000 polyester resin, acrylic resin, dicyandiamide and dicyandiamide derivative, imidazole and imidazole derivative, dibasic acid dihydrazide, diaminophenylmethane, cyclic Amine compounds such as amidine compounds, melamine resin, terephthalic acid diglycidyl ester, paraoxybenzoic acid diglycidyl ester, triglycidyl isocyanate, spiroglycol diglycidyl ether, hydantoin compound, alicyclic epoxy resin and other glycidyl compounds, 1,4- Bis2'-hydroxyethoxybenzene, bishydroxyethyl terephthalate, styrene / allyl alcohol copolymer, spiroglycol, tris2-hydroxyethyl Isocyanurate, hydroxyl value 10
~ 300 mgKOH / g, glass transition temperature 30 ~ 12
Examples thereof include a polyester resin having a number average molecular weight of 1000 to 15000 at 0 ° C., and a hydroxyl compound such as an acrylic resin. As the curing agent, a compound that is solid at room temperature can be preferably used.

The amount of the curing agent blended is 3 to 40 parts by mass, preferably 5 parts by mass, relative to 100 parts by mass of the reactive fluorine-containing copolymer.
˜20 parts by mass. The amount of the curing agent blended is copolymer 10
By setting the content in the range of 3 to 40 parts by mass with respect to 0 parts by mass, a coating film having excellent physical properties such as surface gloss, stain resistance, impact resistance, and weather resistance can be formed.

The titanium oxide used in the present invention has a photocatalytic activity of 3 (mol / kg / min × 10) or less, preferably 1.
0 to 2.5 (mol / kg / min × 10).
Usually, titanium oxide has a photocatalytic activity of 3 (mol / kg /
Min. × 10), the photocatalytic activity is 3 (mol / k)
Titanium oxide having g / min × 10) or less is required to reduce the photocatalytic activity of titanium oxide as a raw material.
When the photocatalytic activity is 4 (mol / kg / min × 10) or more, the radical deterioration of the fluororesin becomes remarkable. The titanium oxide as a raw material is not particularly limited as long as it can be used as a pigment. For example, anatase 1 class, 2 class, rutile 1 class, 2 class, 3 classified according to JIS K5116.
It may be any of Class 4 and Class 4. Among these, those whose main applications are high weather resistance applications and super weather resistance applications are preferable. Specifically, for example, CR80, R830, CR-9 manufactured by Ishihara Sangyo
7, CR-90, CR-93, CR95, J manufactured by Teika
R-602, JR-602S, JR-701, JR-6
03, JR-805 and the like. There is no particular limitation on the average particle size or particle size distribution of titanium oxide as a raw material.

The method for lowering the photocatalytic activity is not particularly limited, and examples thereof include a method of adding a different metal and a method of surface treatment with silica or the like. This will be described below.

The rutile type titanium oxide has a slower deterioration rate of the coating film when blended with a resin than the anatase type, but pure rutile is also a semiconductor and has a photochemical activity of causing a photocatalytic reaction. . Rutile type titanium oxide crystals of industrial products contain a small amount of impurity elements in the crystal,
The pentavalent or higher metal element acts as a donor of the rutile semiconductor. Before forming rutile type crystals, Al ³⁺ , Zn ²⁺ , Mg
^By adding ²⁺ , Sb ³⁺ or the like as a conditioner and substituting Ti ⁴⁺ in the crystal, high weather resistance can be obtained.

The surface of titanium oxide is coated with silica, alumina, titania, zirconia, zinc white, antimony oxide or the like. The reason why the weather resistance is improved by the surface treatment with silica or the like is presumed as follows.
OH radicals and HO ₂ radicals generated on the surface of titanium oxide upon irradiation with ultraviolet rays have strong oxidizing power, but are unstable and have a short life, and decompose as follows. 2 · OH → H ₂
O + O ₂ . Therefore, it is presumed that while the free radicals pass through the surface-coated metal hydrous oxide layer, the above-mentioned decomposition proceeds due to the catalytic action of the hydrous oxide layer, and the free radicals involved in the oxidative decomposition of the resin decrease.

In the present invention, of the above,
It is preferable to use the above method. Of these, titanium oxide is preferably surface-treated with a powder containing at least silica. In addition to silica, alumina, titania, etc. may be used together. In such a method, the weather resistance effect of the resin changes depending on the properties of silica and the like, the type of resin, the kneading conditions and the like. For example, even if the resin is surface-treated with the same amount of silica, the effect of improving the weather resistance is small in the porous silica treatment for emulsion coating, and the effect of improving the weather resistance is observed in the dense silica treatment. Thus, the amount of titanium oxide surface coating such as silica does not necessarily have a high correlation with the improvement of the weather resistance of the titanium oxide-containing resin. The present invention makes it possible to improve the weather resistance of a fluororesin simply by adjusting the photocatalytic activity of titanium oxide.

The surface treatment of titanium oxide with silica etc.
For example, it can be carried out by dispersing titanium oxide in a solvent and adjusting the pH, then adding silica or the like, and stirring, filtering, washing, drying, baking and the like.

In the present invention, the photocatalytic activity is defined by R. B.
The acetone production rate is measured according to the method described in Cundall, JOCCA, Vol. 61, page 351 (1978). That is, using the reactor shown in FIG. 1, 0.2 g of titanium oxide was suspended and injected in 20 mL of isopropanol, and the medium pressure mercury lamp arc lamp 250 W was irradiated in an oxygen stream while stirring to change the acetone production rate. It can be measured by measuring. This is because isopropanol does not undergo auto-oxidation due to UV irradiation and heating, and free radicals · OH and HO ₂ · that are generated from adsorbed hydroxy groups and oxygen by light irradiation on the titanium oxide surface.
However, it utilizes the property of oxidizing isopropanol to change to acetone.

The content of titanium oxide having a photocatalytic activity of 3 (mol / kg / min × 10) or less in the fluororesin powder coating composition of the present invention is 20% by mass or more, particularly 40 to 40% by mass relative to the fluororesin. 100 mass% is preferable. When it is 20% by mass or more, the function as a pigment of titanium oxide is effectively exhibited, and the weather resistance of the fluororesin powder coating composition is not deteriorated. In the present invention, the average photocatalytic activity of titanium oxide in the fluororesin powder coating composition may be 3 (mol / kg / min × 10) or less, and the photocatalyst is not partially surface-treated with silica or the like. Activity is 3 (m
ol / kg / min × 10) may be contained in the fluororesin powder coating composition injection, but the total titanium oxide in the fluororesin powder coating composition is 3 (mol / k).
It is more preferable to have a photocatalytic activity of g / min × 10) or less.

The fluororesin powder coating composition of the present invention comprises
Additives normally used in coating compositions can be included as the third component. That is, coloring pigments other than titanium oxide (for example, red iron oxide, yellow iron oxide, inorganic pigments such as carbon black and phthalocyanine blue, phthalocyanine green, quinacridone red pigment, organic pigments such as isoindolinone yellow pigment), talc, carbonic acid. Add one or more kinds of additives such as extender pigments such as calcium, metal powders such as aluminum powder and stainless steel powder, mica powders and leveling agents, ultraviolet absorbers, heat deterioration inhibitors, antifoaming agents, etc., if desired. You can In the present invention, the above-mentioned third component optionally blended may be blended in advance with at least one of a fluorine-containing resin and titanium oxide having a photocatalytic activity of 3 (mol / kg / min × 10) or less. The fluororesin powder coating composition of the present invention can be prepared by kneading a fluorine-containing resin and titanium oxide having a photocatalytic activity of 3 (mol / kg / min × 10) or less and then pulverizing. The kneading is performed, for example, by a roll type kneader such as a two-roll or three-roll type, a vertical kneader, a pressure kneader, a blade type kneader such as a planetary mixer, a ball type rotary mill, a sand mill, an attritor, or the like. Machine, ultrasonic disperser, nanomizer, etc. can be used. The kneading temperature is, for example, 100 to 180 ° C., particularly 120 to 16
0 ° C is preferred. The kneading time is, for example, preferably 3 to 30 minutes, particularly preferably 5 to 15 minutes.

The fluororesin powder coating composition produced as described above is applied to iron, aluminum, copper, zinc or a mixture thereof such as stainless steel and brass.
For example, by uniformly coating with a commercially available electrostatic powder coating machine, fluidized dipping device, etc., and then baking in a hot air oven, infrared oven, dielectric heating oven, etc., it is excellent in coloring property due to titanium oxide and has weather resistance. A good coating film can be formed.

[0042]

EXAMPLES Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples.

Synthesis Example 1 In a pressure vessel with a stirrer (pressure resistance 5.0 MPa) made of stainless steel having an internal capacity of 300 mL, 157 g of xylene, 16 g of cyclohexyl vinyl ether (CHVE), 9 g of isobutyl vinyl ether (iBVE), 25 g of hydroxybutyl vinyl ether (HBVE), 1 g of potassium carbonate and 0.07 g of perbutyl perpivalate (PBPV) were charged, and dissolved oxygen was removed by solidification degassing with liquid nitrogen. After that, chlorotrifluoroethylene (CTF
E) 50 g was introduced and the temperature was gradually raised. The reaction was continued under stirring while maintaining the temperature at 65 ° C., and after 10 hours, the reactor was water-cooled to stop the reaction. After cooling to room temperature, unreacted monomer was removed and the reactor was opened. The obtained reaction liquid was filtered through diatomaceous earth to remove solids, and thus a fluorocopolymer solution A-1 was obtained. Table 1 shows the blending ratio of the used monomers, the solid content concentration of the fluorinated copolymer solution A-1, and the presence or absence of acrylic modification. Then, this was dried under vacuum and the solvent was distilled off to obtain a fluororesin solid polymer A.

[0044]

[Table 1]

Synthesis Example 2 A fluorine-containing copolymer solution B-1 was obtained in the same manner as in Synthesis Example 1, except that the composition of the monomer in Synthesis Example 1 was changed to that shown in Table 1. Table 1 shows the blending ratio of the used monomers, the solid content concentration of the fluorine-containing copolymer solution B-1, and the presence or absence of acrylic modification. Then, a fluororesin solid polymer B was obtained in the same manner as in Synthesis Example 1.

Synthesis Example 3 In a stainless steel autoclave with an internal volume of 2.5 L equipped with a stirrer, 860 g of ion-exchanged water, 35 g of allyl glycidyl ether, 46.6 g of t-butanol and 2 parts of potassium carbonate were added.
6.2 g was charged, and deaeration with a vacuum pump and pressurization with nitrogen gas were repeated to remove air. Next, 72 g of tetrafluoroethylene, 1.1 g of propylene and 1.4 g of ethylene were introduced into the autoclave. When the temperature inside the autoclave reached 70 ° C, the pressure was 1.34M.
Pa was shown. Thereafter, 2 mL of a 25% aqueous solution of ammonium persulfate was added to start the reaction. As the pressure decreases, pressurizing and maintaining the pressure, tetrafluoroethylene 50 mol%, propylene 25 mol%, ethylene 25
The reaction was continued by continuously adding 250.5 g of a mixed gas of mol%. During the reaction, ammonium persulfate 2
30 mL of 5% aqueous solution was continuously added. After 8 hours, the supply of the mixed gas was stopped, the autoclave was water-cooled to reach room temperature, unreacted monomers were removed, and the autoclave was opened to obtain an aqueous dispersion C-1. Next, to this dispersion C-1, a mixed solution of 78 g of methyl methacrylate, 12 g of glycidyl methacrylate, 90 g of ion-exchanged water, 0.09 g of sodium lauryl sulfate, and 2 g of nonionic emulsifier (Nippon Emulsifier, trade name Newcol 1120) is added. Then, under a nitrogen gas atmosphere, ammonium persulfate 0.2
g was added, and the mixture was heated and stirred at 65 ° C. for 5 hours to carry out acrylic modification. Table 1 shows the blending ratio of the used monomers, the solid content concentration of the aqueous dispersion C-1, and the presence or absence of acrylic modification. Next, 1N hydrochloric acid was added thereto until the pH reached 3, and the mixture was aggregated, washed repeatedly with ion-exchanged water, and then dried at 60 ° C. to obtain a powdery polymer C.

Preparation Example 1 Commercially available titanium oxide (CR-95 manufactured by Ishihara Sangyo Co., Ltd .: alumina treatment amount (titanium oxide; hereinafter the same) 2 to 4%, silica treatment amount 3 to 5%, titania treatment amount 0 to 1) %) 90 g
Was mixed with 1 L of ethanol to prepare a dispersion liquid. This dispersion was heated to 45 ° C., 28% aqueous ammonia was added to adjust the pH to 9.5 or higher, and while maintaining this condition,
Tetraethoxysilane as SiO ₂ and 110 g of 2
8% aqueous ammonia was added. After the addition was completed, the mixture was further stirred for 2 hours, filtered, washed, dried at 110 ° C., and then calcined at 600 ° C. to prepare a silica-coated titanium oxide white pigment. Here, the amount of tetraethoxysilane is the photocatalytic activity of the silica-coated titanium oxide white pigment,
10 (mol / kg / min × 10) (A), 4.0 (mo
1 / kg / min × 10) (B), 3.0 (mol / kg /
Min × 10) (C), 2.5 (mol / kg / min × 10)
(D) and 2.2 (mol / kg / min × 10) (E), four types of preliminary tests were conducted in advance, and the total amount of titanium oxide and silica was 50 to 70%.

Examples 1 to 6 and Comparative Examples 1 to 2 Polymers A to C obtained above and the curing agents shown in Table 2,
Silica-treated titanium oxide was uniformly mixed with a dry blender (Mitsui Kakoki Co., Ltd., trade name Henschel Mixer) for about 1 minute, and then an extrusion kneader (Bus Co., trade name Busconieder PR-46) was used. Mixed at 140 ° C,
The mixture was kneaded, then cooled to 10 ° C. or lower, pulverized by a hammer-type impact pulverizer, and then passed through a 150-mesh wire net to obtain a titanium oxide-containing fluororesin powder coating material. The obtained powder coating is electrostatically coated on a zinc phosphate-treated steel plate,
It was heated in an oven at 0 ° C. for 20 minutes to obtain a coating film having an average film thickness of 50 μm. The physical properties of the obtained paint and coating film were measured by the following methods. The results are shown in Table 3.

[0049]

[Table 2]

[0050]

[Table 3]

A weather resistance sunshine weather meter (manufactured by Suga Test Instruments Co., Ltd.) was used to measure the gloss retention at 60 ° after exposure for 5000 hours. 60 ° gloss is JIS K5400
It was measured according to 7.6.

As is clear from Table 3, the photocatalytic activity is 3
The fluororesin powder coating using titanium oxide of (mol / kg / min × 10) or less had no abnormal appearance of the coating film and had a high gloss retention rate. On the other hand, the photocatalytic activity is 3 (mo
The fluororesin powder coating composition using titanium oxide exceeding 1 / kg / min × 10) had some glossiness and low gloss retention.

[0053]

The fluororesin powder coating composition of the present invention comprises:
Titanium oxide is capable of sufficiently exhibiting the function as a white pigment, and is also excellent in weather resistance of the fluororesin powder coating composition.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an apparatus for measuring photocatalytic activity.

[Explanation of symbols]

1: Stirrer 2: Oxygen injection tube 3: Aluminum block 4: Light irradiation window 5: Temperature measurement point

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Yu Yamauchi             Asahi Glass Co., Ltd. 10 Goi Coast, Ichihara City, Chiba Prefecture             In the company F term (reference) 4J037 AA22 CA12 CA24 EE03 EE28                       EE35 EE43 EE48 FF22                 4J038 CB031 CB091 CB131 CC032                       CD091 CD111 CD121 CD131                       CE051 CF051 CF091 CG031                       CG141 CH031 CH041 CH251                       DA092 DB042 DB112 DD002                       DG302 GA03 HA166 JA75                       JB07 JB32 KA03 LA02 MA02                       MA13 MA14 NA03 NA27 PA02                       PA19 PB02 PB05 PB07

Claims (3)

[Claims] 1. A fluorine-containing resin and a photocatalytic activity of 3 (m)
Fluorine resin powder coating composition containing titanium oxide having an ol / kg / min × 10) or less. 2. A photocatalytic activity of 3 (mol / kg / min × 1
The fluororesin powder coating composition according to claim 1, wherein the titanium oxide of 0) or less is treated with a powder containing at least silica. 3. The photocatalytic activity is 3 (mol / kg / min × 1
The fluororesin powder coating composition according to claim 1 or 2, wherein the titanium oxide content, which is 0) or less, is 20% by mass or more based on the fluororesin.