JPH044080A - Production of coated film - Google Patents

Abstract

PURPOSE:To form a coated film having excellent weatherability, finish appearance and coating workability without consuming a large quantity of energy and without causing environmental pollution by applying an aq. coating material to the surface of a material to be coated and applying a specific thermosetting powder coating material thereto, then subjecting the coating to curing by heating. CONSTITUTION:The ag. coating material contg. a metallic pigment and/or coloring pigment is first applied as a base coat to the surface of the material to be coated in order to form the coated film by a 2-coat 1-bake treatments. The thermosetting powder coating material contg. the resin components formed by compounding 10 to 50 pts.wt. fluororesin with 100 pts.wt. polyester resin which is solid at ordinary temp. and has a crosslinkable reaction group of 1000 to 30000 number average mol. wt. and a hardener which can form crosslinkage by reacting with the crosslinkable reaction group of the above- mentioned resin components is applied to this coated surface. The coating is then cured by heating to form the coated film.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a novel method for producing a coating film. More specifically, the present invention relates to a method for producing a coating film with excellent weather resistance, finished appearance, and painting workability through a two-coat, one-bake process without consuming a large amount of energy or causing environmental pollution. .

[Conventional technology] Conventionally, for the exterior panels of automobiles, paints containing metallic pigments and coloring pigments such as aluminum pigments and mica pigments (hereinafter referred to as base coats) have been used for cosmetic properties and weather resistance.
A method is used in which a transparent paint (hereinafter referred to as top coat) is applied on top of the transparent paint (hereinafter referred to as top coat) and cured by heating to form a coating film, without painting and baking.

On the other hand, in response to the increasingly serious environmental pollution problem, low-pollution paints with reduced organic solvent emissions are desired.

For this reason, various methods have been tried for forming the paint film, and one of the most effective methods is known, for example, to use a water-based paint for the base coat and a powder paint for the top coat. ing. Various water-based paints have been proposed for use in the base coat (JP-A-56-157358, JP-A-64-24870), and powder paints to be used in the top coat include: For example, thermoplastic fluororesin powder coatings made of ethylene-tetrafluoroethylene copolymer (JP-A-61-181567, JP-A-61
-181571, JP 61-181572), polyester resin-based thermosetting powder coatings using blocked isocyanate compounds, triglycidyl isocyanurate, etc. as curing agents, and glycidyl-based powder coatings using dibasic acids as curing agents. The acrylic resin-based thermosetting powder coating containing the same is disclosed [``Powder and Industry'' February issue, 33rd to
42 pages (1984)].

However, the above-mentioned powder coatings used as top coats are not necessarily fully satisfactory. For example, the former thermoplastic fluororesin powder coating made of ethylene-tetrafluoroethylene copolymer has good weather resistance but poor adhesion to the base coat.
, When painting the fluororesin, it is necessary to heat it to a temperature higher than the melting point of the fluororesin, which leads to poor painting workability.
It has drawbacks such as the inevitable consumption of a large amount of thermal energy.

On the other hand, although polyester resin powder coatings and acrylic resin powder coatings do not have the drawbacks of fluororesin powder coatings as described above, they do have the disadvantage of insufficient weather resistance.

[Problems to be Solved by the Invention] Under these circumstances, the present invention aims to produce a coating film with excellent weather resistance, finished appearance, and painting workability without consuming a large amount of energy or causing environmental pollution. This was done for the purpose of providing a method.

[Means for Solving the Problem] As a result of extensive research to achieve the above object, the present inventors have found that after applying a water-based paint as a base coat to the surface of the object to be painted, a top coat is applied to the painted surface. Applying a specific thermosetting powder coating and then heating and curing2
It was discovered that the objective could be achieved through coat 1 baking treatment, and the present invention was completed based on this knowledge.

That is, in producing a coating film by a two-coat one-bake process, the present invention applies a water-based paint containing a metallic pigment and/or a colored pigment to the surface of the object to be coated, and then applies (A) to this coated surface. (b) 10 parts by weight of a polyester resin having a crosslinkable reactive group and having a number average molecular weight of 1,000 to 30,000 that is solid at room temperature; (b) 10 parts by weight of a fluororesin
Applying a thermosetting powder coating comprising a resin component blended with ~50 parts by weight, and (B) a curing agent capable of reacting with the crosslinking reactive group of the resin component to form a crosslink, The present invention provides a method for producing a coating film, which is characterized in that the coating film is then cured by heating.

The present invention will be explained in detail below.

In the method of the present invention, a water-based paint is used as the base coat. This water-based paint mainly contains a water-soluble thermosetting resin or a water-dispersible thermosetting resin, a metallic pigment and/or a colored pigment, a water-soluble organic solvent, and deionized water.
Furthermore, extender pigments, viscosity modifiers, coating surface modifiers, etc. are blended as necessary.

The water-soluble or water-dispersible thermosetting resin is, for example, a water-soluble or water-dispersible basic resin selected from alkyd resins, polyester resins, acrylic resins, cellulose resins, etc., and a crosslinking agent. For example, those containing a water-soluble or water-dispersible amino resin obtained by condensation or co-condensation of melamine, benzoguanamine, urea, etc. and formaldehyde, or a water-dispersible block isocyanate resin are used.

As these base resins and crosslinking agents, those already known per se can be used.

There are no particular restrictions on metallic pigments, and metallic pigments that are conventionally used in water-based paints, such as aluminum, copper, brass, bronze, stainless steel, etc., which have undergone surface treatment, or mica-like iron oxide, scaly pigments, etc. Metallic powder, mica flakes coated with titanium oxide or iron oxide, etc. are used.

On the other hand, there are no particular restrictions on coloring pigments, and those commonly used in paints, such as titanium dioxide, red iron,
Inorganic pigments such as yellow iron oxide and carbon black, and organic pigments such as phthalocyanine blue, phthalocyanine green, quinacridone red pigments, and isoindolinone yellow pigments can be used.

In the thermosetting powder coating, the polyester resin of component (A) used as one of the components (A) is as follows:
Solid at room temperature and has a number average molecular weight of 1000 to 300
It is necessary to use one that is in the range of 0.00 and has a crosslinkable reactive group. Examples of the crosslinkable reactive group include a hydroxyl group and a carboxyl group. In the case of polyester resins having hydroxyl groups, the hydroxyl value is 10 to
It is preferable to have a hydroxyl value in the range of 200 mgKOH/9. If the hydroxyl value is less than 10 mgKOH/9, the crosslinking density will be low and there is a risk that sufficient coating film properties will not be obtained. If it exceeds 200 + BKO1l/9, the coating The film tends to be hard and brittle. On the other hand, in the case of polyester resin having carboxyl groups, the acid value is 1
It is preferable to have an acid value in the range of 0 to 200 + BKOH/y; if this acid value is less than 10 m9KO■/9, the crosslinking density will be low, so there is a risk that sufficient physical properties of the coating film cannot be obtained. If it exceeds this, the coating film tends to become hard and brittle.

Furthermore, in the present invention, as the above-mentioned hydroxyl group-containing polyester resin, one that also has a carboxyl group with an acid value of about 5 to 50 mgKOH/9 can be used. Those having a hydroxyl group having a value of about 5 to 50119 KOH/9 can also be used.

As such a polyester resin, for example, a condensate of a polyester-formable carboxylic acid mainly composed of terephthalic acid and a polyhydric alcohol mainly composed of ethylene glycol is preferably used. Examples of the carboxylic acid component include heptalic acid, trimellitic acid, pyromellitic acid and anhydrides thereof, terephthalic acid, isophthalic acid, methylterephthalic acid, adipic acid, sebacic acid,
Examples include succinic acid, hexamaric acid, β-oxydipropionic acid, oxalic acid, and glutaric acid. These carboxylic acids may be used alone or in combination of two or more.

In addition, examples of polyhydric alcohol components include ethylene glycol, propanediol, butanediol, bentanediol, 1,6-hexanediol, neopentyl glycol, 2,2'-diethylpropanediol,
Examples include cyclohexanediol, trimethylolpropane, and pentae IJ l-lit. One type of these polyhydric alcohols may be used, or two or more types may be used in combination.

Examples of such polyester resins include ester resins ER-6640 and ER-6650 as commercially available products.
, ER-6680, ER-8105, ER-8107 [
The above products are manufactured by Nippon Ester Co., Ltd., product name], FINDIC M-8020, M-8075, M-8500, M-
8520, M-8900, A-239-J, A-239
-X [Product name, manufactured by Dainippon Ink & Chemicals Co., Ltd.], Yupica Coat GV-100, GV-150, GV-
230 [manufactured by Nippon Yubika Co., Ltd.], Ularac P-
2065, P-2400, P-3500, P-5000
[The above products are manufactured by DSM, product names], and the like.

Further, if desired, an acrylic resin having the same crosslinking reactive group may be added to the polyester resin 10.
A mixed resin containing about 20 to 40 parts by weight per 0 parts by weight can also be used. Examples of such mixed resins include A-101 and A-10 as commercially available products.
2, 8-202 [both manufactured by Unitika Co., Ltd., product name]
etc. can be mentioned.

On the other hand, the fluororesin as the (i) component used in combination with the polyester resin as the component (i) has a fluorine content of 10% by weight or more and an intrinsic viscosity of 0.05 to 0.05 as measured at a temperature of 30°C in tetrahydrofuran. 2d1/g
, a fluorine-containing copolymer having a fluoroolefin unit and a crosslinkable reactive group with a glass transition temperature of 30 to 120 °C and a heating loss of 5% or less, or a melting point of 60 to 170 °C,
A thermoplastic fluororesin having a fluorine content of 20% by weight or more is preferably used.

When using the former fluorine-containing copolymer having a crosslinkable reactive group, it is desirable that the crosslinkable reactive group is the same as the crosslinkable reactive group of the polyester resin of component (A) used together, For example, when the crosslinkable reactive group of the polyester resin is a hydroxyl group, it is preferable that the crosslinkable reactive group of the fluorine-containing copolymer is also a hydroxyl group.

This fluorine-containing copolymer is a copolymer containing a fluoroolefin unit and a unit having a crosslinkable reactive group as essential units, and the monomer forming the fluoroolefin unit is, for example, tetrafluoroethylene. , chlorotrifluoroethylene, trifluoroethylene, vinylidene fluoride, hexafluoropropylene, pentafluoropropylene, etc., and may be used as appropriate depending on the properties required for the coating film, the copolymer component, the type of polyester resin used in combination, etc. You can choose. These fluoroolefins may be used alone or in combination of two or more.

Examples of the crosslinkable reactive groups of the fluorine-containing copolymer include hydroxyl groups, carboxyl groups, active halogens such as bromine and iodine, and incyanate groups.

Methods for introducing such a crosslinking reactive group into the copolymer include, for example, a method of copolymerizing a monomer having a crosslinking reactive group, a method of decomposing a part of the copolymer, and a method of decomposing a part of the copolymer. Examples include a method in which a functional group is reacted with a compound that provides a crosslinkable reactive group.

As the monomer having a crosslinkable reactive group, a monomer having a hydroxyl group or a group convertible to a hydroxyl group and a double bond copolymerizable with a fluoroolefin is preferably used. Examples of the monomers having a hydroxyl group or a group that can be converted into a hydroxyl group include hydroxyalkyl vinyl ethers such as hydroxyethyl vinyl ether, hydroquine propyl vinyl ether, hydroxybutyl vinyl ether, hydroxyisobutyl vinyl ether, hydroxycyclohexyl vinyl ether, hydroxyvinyl acetate, hydroxy Esters of hydroxyalkyl carboxylic acids and vinyl alcohol such as vinyl propionate, vinyl hydroxybutyrate, vinyl hydroxyvalerate, vinyl hydroxyisobutyrate, vinyl hydroquine cyclohexanecarboxylate, hydroquine ethyl allyl ether, hydroxypropyl allyl ether, hydroxy Hydroxyalkyl allyl ethers such as butyl allyl ether, hydroxyisobutyl allyl ether, hydroxycyclohexyl allyl ether, hydroxyethyl allyl ester, hydroxypropyl allyl ester, hydroxybutyl allyl ester, hydroxyisobutyl allyl ester, hydroxycyclohexyl allyl ester, etc. hydroxyalkylaryl esters of acrylic acid or methacrylic acid such as 2-hydroxyethyl acrylate, hydroxypropyl acrylate, 2-hydroxyethyl methacrylate, hydroxypropyl methacrylate, and partially fluorinated Among these, vinyl-based and allyl-based compounds are preferred from the viewpoint of copolymerizability with fluoroolefins. Further, these hydroxyl group-containing monomers may be used alone or in combination of two or more. Examples of the monomer having a lopoxyl group include acrylic acid, methacrylic acid, and carboxyalkyl allyl ether, and these may be used alone or in combination of two or more.

In addition, as a method for decomposing a part of the copolymer, for example, after copolymerizing a monomer having an ester group that can be hydrolyzed after polymerization, and then hydrolyzing the copolymer,
Examples include a method of producing carboxyl groups in a copolymer.

Further, in the direct curing reaction without hydrolyzing the ester, a crosslinking bond can be formed by the transesterification reaction.

An example of a method of reacting a functional group of a copolymer with a compound that provides a crosslinkable reactive group is a method of introducing a carboxyl group by reacting a hydroxyl group-containing copolymer with a dihydric carboxylic acid anhydride such as succinic anhydride. Preferred examples include the following.

In addition, as the monomer providing the crosslinking reaction site, vinyl and allyl yarn compounds are particularly suitable because of their copolymerizability with fluoroolefins.

In addition to the above two types of units, this fluorine-containing copolymer also includes a compound that lowers the melting point or glass transition point of the fluorine-containing copolymer.
Monomers that can be copolymerized with the above two components as necessary for the purpose of further improving coating workability or imparting physical properties such as appropriate hardness, flexibility, and gloss to the coating film. may be included.

Such a monomer is preferably one that has an active unsaturated group to the extent that it can be copolymerized with fluoroolefins and does not significantly impair the weather resistance of the coating film, and is usually an ethylenically unsaturated compound such as ethyl Alkyl vinyl ethers such as vinyl ether, propyl vinyl ether, butyl vinyl ether, inbutyl vinyl ether, and cyclohexyl vinyl ether, alkyl carboxylic acids and vinyl alcohols such as vinyl acetate, vinyl propionate, vinyl isobutyrate, vinyl valerate, and vinyl cyclohexane carboxylate. Alkyl allyl ethers such as ethyl allyl ether, propyl allyl ether, butyl allyl ether, butyl allyl ether, cyclohexyl allyl ether, ethyl allyl ester, propyl allyl ester, butyl allyl ester esters, alkyl allyl esters such as cyclohexyl allyl ester, alkenes such as ethylene, propylene, butylene, isobutylene, acrylics, methacrylic acid or ethyl acrylate, propyl acrylate, butyl acrylate isobutyl acrylate, 2-ethylhexyl acrylate, Examples include esters of acrylic acid or methacrylic acid such as ethyl methacrylate, propyl methacrylate, butyl methacrylate, isobutyl methacrylate, and 2-ethylhexyl methacrylate, as well as partially fluorinated compounds of these. Vinyl compounds, allyl compounds, and alkenes that have excellent copolymerizability with olefins are preferred. One type of these comonomers may be used, or two or more types may be used in combination.

In addition, when using a vinyl or allyl alkyl ester or alkyl ether, the alkyl group has 2 carbon atoms.
~10 linear, branched or alicyclic ones are preferred.

The fluorine-containing copolymer used in the thermosetting powder coating of the present invention needs to have a fluorine content of 10% by weight or more. Normally, this fluorine content is determined by the composition ratio of fluoroolefin units in the fluorine-containing copolymer, but it is also possible to increase or decrease this content by polymer reaction after producing the copolymer. .

If the fluorine content is less than 10% by weight, it is difficult to obtain a coating film with sufficient weather resistance. The preferred fluorine content is
The amount is selected in the range of 15 to 72% by weight from the viewpoint of overall performance balance such as weather resistance and painting workability of the coating film.

Further, as the fluorine copolymer used in the present invention, one having a fluorine content of 10% by weight or more and containing fluoroolefin units in a range of 70 to 30 mol% can be particularly preferably used.

This is because when the fluoroolefin unit content is 30 mol% or more, the weather resistance is further significantly improved, and when the fluoroolefin unit content is 70 mol% or less, the fluorine-containing copolymer tends to become amorphous, that is, the fluorine-containing copolymer tends to become non-crystalline. This is because the fluorine copolymer is less likely to form crystals, which makes it easier to form a coating film with good adhesion and a uniform and smooth surface, and also eliminates the need for high temperatures during baking of the coating material.

In the case of a fluorine-containing copolymer having a hydroxyl group as a crosslinkable reactive group, it is desirable that the hydroxyl value thereof be in the range of 1 to 200+uKOH/g, preferably 20 to 1401119KOH/9. If the hydroxyl value is less than 1m9KO■/g, crosslinking may be insufficient and a coating film with desired physical properties may not be obtained;
If it exceeds t, the crosslinking density becomes too high and the flexibility of the coating film decreases.

The fluorine-containing copolymer is heated at a temperature of 30% in tetrahydro 7 run.
It is necessary that the intrinsic viscosity, measured at °C, be in the range of 0.05 to 2 dn/9. This intrinsic viscosity is 0.05d
If it is less than Δ/g, it is difficult to form a solid and may not be usable as a powder coating, and if it exceeds 2 dl/9, the softening point becomes too high and the flowability of the coating film decreases.

Further, the glass transition temperature of the fluorine-containing copolymer is 30 to 1
It is necessary that the temperature is 20°C, preferably in the range of 35 to 100°C. If the glass transition temperature is less than 30°C, it may not become solid and may not be usable as a thermosetting powder coating; if it exceeds 120°C, the softening point will be too high and the 70- properties of the coating will deteriorate. Deteriorate.

Note that it is not preferable to use a crystalline polymer as the fluorine-containing copolymer because it requires high temperatures during baking, but when using a crystalline polymer, the melting point is 2.
00°C or less is preferable.

The fluorine-containing copolymer can be produced by a conventionally known method. For example, polymerization can be carried out by allowing a polymerization initiator to act on a heptamer mixture at a predetermined ratio in the presence or absence of a catalyst. As for the polymerization method, it can be produced by any of solution polymerization, emulsion polymerization, and suspension polymerization.

In the present invention, the fluorine-containing copolymer is used in powder form. As a method for obtaining such a powdery fluorine-containing copolymer, an appropriate method can be selected depending on the type of polymerization. For example, when a fluorine-containing copolymer is obtained by emulsion polymerization or suspension polymerization, the dispersion medium is usually removed from the polymerization solution at a reduced pressure of 10! It can be produced by distilling off at a temperature of 50 to 100[deg.] C. or less, and then pulverizing the solid content of the residue using a pulverizer such as a Wiley type, vibration mill type, or impact hammer mill type. In addition, when obtained by solution polymerization, the solvent in the polymerization solution is distilled off, or the fluorine-containing copolymer is precipitated by pouring it into a solvent that does not dissolve the polymer, and after the solvent is distilled off, the fluorine-containing copolymer is solidified. It can be manufactured by pulverizing.

The fluorine-containing copolymer used in the thermosetting powder coating in the present invention is used in powdered form, and such powder is
The remaining amount of the solvent (hereinafter used to include the dispersion medium) (
loss on heating) is required to be 5% or less. If a large amount of solvent remains in the fluorine-containing copolymer powder, the storage stability of the powder coating will be poor, and foaming, blistering, pinholes, etc. may occur in the coating after the powder coating is baked and cured. This is not preferable as it makes it easier. In particular, it is preferable that the residual amount of solvent is 2% or less.

On the other hand, when a thermoplastic fluororesin is used for the thermosetting powder coating, the thermoplastic fluororesin has a melting point of 60 to 170°C and a fluorine content of 10% by weight.
The above are used. Examples of commercially available thermoplastic 77 resins include Kynar 500. ADS,
SL (manufactured by Pennwalt, product name), VT-1
00 [manufactured by Daikin Industries, Ltd., product name ko, etc.].

In the thermosetting powder coating, the fluororesin of component (b) is the same as the polyester resin of component (a).
It is necessary to mix it in a ratio of 10 to 50 parts by weight to 0 parts by weight. If the amount is less than 1011 parts by weight, the cured coating film will have poor weather resistance, and if it exceeds 50 parts by weight, the cured coating film will have poor corrosion resistance.

In the thermosetting powder coating of the present invention, the curing agent used as component (B) has the crosslinking properties of the component (A), that is, the resin component consisting of a combination of (a) polyester resin and (b) fluororesin. It is necessary that it be capable of reacting with a reactive group to form a crosslink. Examples of such curing agents include blocked isocyanate compounds, specifically polyisocyanate compounds such as isophorone diisocyanate, tolylene diisocyanate, xylylene diisocyanate, 4,4'-diphenylmethane diisocyanate, and hexamethylene diisocyanate, and dimeric compounds thereof. Compounds in which the isocyanate groups of isocyanate compounds such as polyisocyanate compounds modified with polyhydric alcohols such as dimers and trimethylolpropane are blocked with blocking agents such as ε-caprolactam, phenol, benzyl alcohol, and methyl ethyl ketoxime; are aliphatic dibasic acids such as fumaric acid, succinic acid, adipic acid, azelaic acid, sebacic acid, and dodecanoic acid, acid anhydrides such as phthalic anhydride, trimellitic anhydride, and pyromellitic anhydride, melamine resin, and terephthalic acid. Diglycidyl ester, paraoxybenzoic acid diglycidyl ester, triglycidyl isocyanurate, spiroglycol diglycidyl ether, hydantoin compound, alicyclic epoxy resin, number average molecular weight 500-60
Glycidyl compounds such as acrylic resin containing 00 glycidyl group or β-methylglycidyl group, 1,4-bis-2'-hydroxyethoxybenzene, bishydroxyethyl terephthalate, styrene-allyl alcohol copolymer, spirotaglycol, Examples include tris-2-hydroxyethyl isocyanurate, and among these, compounds that are solid at room temperature are preferred.

If desired, the thermosetting powder coating material of the present invention may contain additives normally used in thermosetting powder coatings, small amounts of inorganic pigments, organic pigments, etc. as a third component. Examples of such additives include coating surface conditioners, ultraviolet absorbers, heat deterioration inhibitors, foaming inhibitors, and the like. One type of these additives, small amounts of inorganic pigments, and organic pigments may be used, or two or more types may be used in combination.

Furthermore, in the thermosetting powder coating, the third component, which is used as desired, may be blended in advance with the resin component (A) and/or the curing agent (B).

There are no particular limitations on the method for preparing the thermosetting powder coating used in the present invention, and methods conventionally used in the production of thermosetting powder coatings can be used. The thermosetting powder coating obtained in this way is usually 400 p.
It has a particle size of less than m.

In the method of the present invention, first, the water-based paint is applied to the surface of the object to be painted. It is desirable to apply the coating at a temperature of 20 to 30°C. After painting, leave it for 5 to 10 minutes at the above humidity and temperature, pre-dry it for about 3 to 20 minutes at a normal temperature of 50 to 80°C, cool it to room temperature, and then apply the thermosetting powder to the painted surface. The body paint is usually applied using an electrostatic powder coating machine to a dry film thickness of about 40 to 100 μm, and then heated in a hot air oven or infrared oven at a temperature of 140 to 190°C for 15 to 40 minutes. The desired coating film is formed by heating and curing in a dielectric heating furnace or the like.

[Example] Next, the present invention will be explained in more detail with reference to Examples.
The present invention is not limited in any way by these examples.

The coating film performance was determined as follows.

(1) Weather resistance Evaluated using a sunshine carbon weather meter as an accelerated weather resistance test method in accordance with JIS D-02057, 6 (after 1000 hours).

Very good: Hardly any change observed (gloss retention rate 85 or higher) Good: Slight change observed (gloss retention rate 65 or higher but less than 85) Poor: Severe change observed (gloss retention rate lower than 65) ) (2) Water resistance test piece was immersed in warm water at 40°C for 240 hours to check for swelling of the coating film,
The presence or absence of appearance abnormalities such as wrinkles was examined.

(3) Add 40% by weight sulfuric acid 0.2taQ to the acid resistance test piece at 50℃ for 15 minutes.
The paint was spotted for minutes to check for abnormalities in appearance, such as stains, blisters, and wrinkles.

(4) Adhesion Determined by the cross-cut test method in accordance with JIS D-02028, 12. (5) Flexibility The coating was bent to 2T and evaluated for cracking or peeling of the coating.

(6) Paint film appearance The coated board was illuminated with a fluorescent light and judged based on the unevenness of the paint film.

Good: Little unevenness Poor: Severe unevenness Production Example 1 Production of acrylic resin aqueous dispersion (a-1) for water-based paint In a flask equipped with a stirrer, reflux condenser, and thermometer,
113 parts by weight of deionized water, 30% by weight Newco170
7F [Anionic surfactant, manufactured by Nippon Nyukazai Co., Ltd.
Add 15 parts by weight of the product name and 0.25 parts by weight of ammonium persulfate, and heat and stir at 70°C. Next, the following 7-mer mixture was added dropwise over 3 hours, and then kept at 70°C for an additional 3 hours until the heating residue was 44.5% by weight, pH 2,
An acrylic resin dispersion (a-1) of No. 3 was obtained.

Methyl acrylate 40 parts by weight Styrene
10 parts by weight butyl acrylate
30 parts by weight 2-hydroxyethyl methacrylate 15 parts by weight Methacrylic acid 5 parts by weight Production Example 2 Production of acrylic resin aqueous solution (a-2) for water-based paint In a flask equipped with a stirrer, reflux condenser, and thermometer,
Add 80 parts by weight of butyl cellosolve, and stir and heat to 140°C. Next, the following seven-mer mixture was added dropwise over 3 hours.

Methyl methacrylate 45 parts by weight Butyl acrylate 25 parts by weight Styrene
10 parts by weight 2-hydroxyethyl methacrylate 10 parts by weight acrylic acid 10 parts by weight t-butyl peroxybenzoate 1 part by weight Next, 0.5 part by weight of t-butyl peroxybenzoate was added, and the reaction was further continued at 140°C for 2 hours. Solid content 55.2% by weight, acid value 43, number average molecular weight 4600
A resin solution was obtained. This material was neutralized in an equivalent amount with dimethylaminoethanol, and further deionized water was added to make an acrylic resin aqueous solution (a-2
) was obtained.

Production Example 3 Production of water-based paint Add dimethylaminoethanol to the aqueous acrylic resin dispersion (a-1) obtained in Production Example 1, neutralize it to pH 7.5, and add the solution obtained in Production Example 2 to 100 parts by weight. 50 parts by weight of acrylic resin aqueous solution (a-2), aluminum paste AW
-500B (manufactured by Asahi Kasei Metals Co., Ltd., trade name) 6 parts by weight,
A mixture of 10 parts by weight of deionized water and 10 parts by weight of butyl cellosolve was added, and a mixture of melamine resin [Cynol 3] was added.
50: 325 parts by weight of a product manufactured by Mitsui Cyanamid Co., Ltd. was added and mixed well. This was diluted with deionized water in a #4 Ford cup for 20 seconds/20°C to obtain a water-based paint.

Production Example 4 Production of fluorine-containing copolymer (A-1) for thermosetting powder coatings In a pressure-resistant reactor made of stainless steel with an internal volume of 300 cc and equipped with a stirrer, 157 g of t-butanol, 16 g of cyclohexyl vinyl ether (c-HxVE), 9 g of isobutyl vinyl ether (isoBVE), 259 g of hydroxybutyl vinyl ether (HBVE), 1 g of potassium carbonate and 0.07 g of azobisisobutyronitrile (AI BN)
y was charged, and dissolved air was removed by solidification and degassing with liquid nitrogen.

Next, chlorotrifluoroethylene (CTFE) sog was introduced and the temperature was gradually raised to 65°C.
The reaction was continued under stirring while maintaining the temperature, and after 10 hours, the reaction vessel was cooled with water to stop the reaction, and after cooling to room temperature,
Unreacted monomers were extracted and the reactor was opened.

Next, it was heated to 60°C and the dispersion medium was removed under a reduced pressure of 1 mmHg for 24 hours, and the solid residue was pulverized with an impact hammer mill to obtain a fluorine-containing copolymer (A-1). .

The obtained fluorine-containing copolymer (A-1) had a hydroxyl value of 12
0 m+5IKOR/g, glass transition temperature 45°C
1 Loss on heating 2% or less, temperature 30 in tetrahydrofuran
The intrinsic viscosity [η] measured at °C was 0.21 di/g.

Moreover, as a result of the analysis, the copolymer composition almost matched the seven-mer composition.

Example 1 Fluorine-containing copolymer for thermosetting powder coating (A-1) 8.6
Parts by weight, ester resin ER-6650 [manufactured by Nippon Ester Co., Ltd., trade name, hydroxyl value 30, number average molecular weight 400]
0.7g 61℃! , solid content 100%] 75.6 parts by weight,
Adduct B-1530 (curing agent brand name, manufactured by Hüls)
ε-caprolactam blocked isocyanate, solid content 1
00%) 15.3 parts by weight and 0.5 parts by weight of Modaflow (coating surface preparation agent, trade name, leveling agent manufactured by Monsanto) were mixed with a dry blender [manufactured by Sai Kakoki Co., Ltd., trade name Henschel Mixer] to approx. Mix evenly for 1 minute, then 9 minutes.
The mixture was melt-kneaded using an extrusion kneader (manufactured by Bus Co., Ltd., trade name Busco Kneader PR-46) at a temperature of 0 to 130°C. Next, after cooling to 10°C, it was finely pulverized using a hammer type impact pulverizer, and then filtered through a 180-mesh wire mesh to obtain a thermosetting powder coating.

Next, the steel plate was treated with zinc phosphate [manufactured by Nippon Parriki Rising Co., Ltd., trade name, Bonderite #3004].
Cationic storage paint [Nippon Oil & Fats Co., Ltd., product name: Aqua #
4100] to a dry film thickness of 20 μm.17
After baking at 5℃ for 30 minutes, apply an intermediate coating [NOF
Co., Ltd., product name, Hiepico N01] with a dry film thickness of 30μ
Paint it so that it becomes m and bake it for 30 minutes at 140°C.
Create a test board and do it again.

The water-based paint obtained in Production Example 3 was applied to the surface of this test plate.
Spray paint so that the dry film thickness is 15 μm, and
After drying at °C for 3 minutes, the thermosetting powder coating was electrostatically sprayed to a dry film thickness of 50 μm.
A test piece was prepared by baking at 170°C for 30 minutes.

Table 1 shows the test results of the coating film performance of this test piece.

Example 2.3 and Comparative Examples 1 to 4 Using a water-based paint obtained in Production Example 3 and a thermosetting powder paint prepared in the same manner as in Example 1 based on the formulation shown in Table 1, A test piece was prepared in the same manner as in Example 1, and its coating film performance was determined. The results are shown in Table 1.

Example 4.5 Using Aquabase Silver [manufactured by ICI, trade name] as the water-based paint, and with the formulation shown in Table 1, Example 1
A test piece was prepared in the same manner as in Example 1 using a thermosetting powder coating prepared in the same manner as in Example 1, and the coating film performance thereof was evaluated. The results are shown in Table 1.

(The following is a blank space) As shown in Examples 1 to 5, according to the present invention, a coating film with excellent weather resistance, water resistance, acid resistance, adhesion, flexibility, and coating film appearance is formed. As shown in Example 1.4, when the polyester resin/fluororesin ratio is less than 100/10, weather resistance is poor. Furthermore, as shown in Comparative Example 2.3, when the polyester resin/fluororesin ratio exceeds lOO150, water resistance, adhesion, flexibility, and coating film appearance are poor.

[Effects of the Invention] According to the present invention, a coating film with excellent weather resistance, finished appearance, and painting workability can be efficiently produced without consuming a large amount of energy or causing environmental pollution.

November 1990

Claims (1)

[Scope of Claims] 1. When producing a coating film by a two-coat one-bake process, a water-based paint containing a metallic pigment and/or a colored pigment is applied to the surface of the object to be coated, and then on this coated surface,
(A) (B) Number average molecular weight of solid at room temperature 1000-30
Polyester resin 100 having 000 crosslinkable reactive groups
Contains (b) a resin component containing 10 to 50 parts by weight of a fluororesin, and (B) a curing agent that can react with the crosslinkable reactive group of the resin component to form a crosslink, based on the weight part. A method for producing a coating film, which comprises applying a thermosetting powder coating consisting of the following: and then curing it by heating. 2. The method for producing a coating film according to claim 1, wherein the polyester resin having a crosslinkable reactive group is a hydroxyl group-containing polyester resin having a hydroxyl value of 10 to 200 mgKOH/g. 3 Polyester resin having a crosslinkable reactive group has an acid value of 10
2. The method for producing a coating film according to claim 1, wherein the polyester resin has a carboxyl group content of 200 mg KOH/g. 4. The fluororesin has a fluorine content of 10% by weight or more and an intrinsic viscosity of 0.0 as measured in tetrahydrofuran at a temperature of 30°C.
The coating film according to claim 1, 2 or 3, which is a fluorine-containing copolymer having a fluoroolefin unit and a crosslinkable reactive group with a glass transition temperature of 30 to 120°C and a heating loss of 5% or less. Method. 5. The method for producing a coating film according to claim 1, 2 or 3, wherein the fluororesin is a thermoplastic fluororesin having a melting point of 60 to 170°C and a fluorine content of 10% by weight or more.