JPH09215960A - Method for forming double-layered coating film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a practical double-layered coating film with no damage after exposure for a long time by applying a coating wherein a water-based fluorinated resin contg. a fluoroolefin as a constitutional unit and a pigment are essential ingredients as a topcoating. SOLUTION: An undercoating is applied on a base. Then, as a topcoating, a water-based fluorinated resin coating compsn. contg. a water-based fluorinated resin contg. a fluoroolefin as a constitutional unit and a pigment as essential ingredients is applied. Thereafter, drying is performed. A double-layered coating film consisting of the undercoating and the topcoating thus obtd. does not give any damage to the undercoating and provides the topcoating with good adhesiveness and is a coating film with high servicability.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a novel and useful method for forming a multilayer coating film. More specifically, the present invention applies a base coat to a substrate and then
In the method of forming a multilayer coating film by applying a topcoat paint, as the topcoat paint, an aqueous fluororesin paint containing a fluoroolefin as an essential constituent unit and a pigment as an essential component It relates to a method of coating a composition and drying it,
The present invention relates to a novel method for forming a multilayer coating film, which comprises a single coating film obtained from the above aqueous fluororesin coating composition having an ultraviolet transmittance of 20% or less.

[0002]

2. Description of the Related Art In order to secure the adhesion between a coating material and a substrate when the coating material is applied to various substrates, the coating material and the substrate have both been applied so far. It is a general method that an undercoat having adhesiveness has been applied.

Even in the case of coating a fluororesin coating having an ultrahigh weather resistance, which has been developed in recent years, as an overcoat, the adhesion between the substrate and the undercoat, and the undercoat and the fluorine for the overcoat. It is painted in the form of applying an undercoat paint having both adhesiveness with resin paint. Further, it is also common practice to coat a deteriorated old paint film with a fluororesin paint for repair.

In these various applications, even when a fluororesin paint having an ultrahigh weather resistance is applied, the adhesion between the topcoat and the undercoat is impaired after being exposed outdoors for a long period of time. It has been pointed out that the undercoat is first deteriorated, the adhesion between the substrate and the undercoat is impaired, and eventually peeling or blistering (blister) occurs.

Such a phenomenon can be explained as follows. That is, a coating film formed by using a fluororesin coating material as the topcoat, when exposed to light, is less likely to absorb the ultraviolet light in sunlight, especially in the ultraviolet region that generally deteriorates the resin. It has the characteristic of allowing it to pass through.

This is also the reason why it has an extremely high weather resistance as compared with general resin systems, but as a result, the ultraviolet light transmitted through the fluororesin layer is absorbed by the resin layer of the undercoat layer and the undercoat layer is selected. That is, it is the place where it deteriorates, causing the various phenomena described above.

In particular, when a fluororesin clear paint is applied as the top coat, the deterioration of the base coat is remarkable, and various phenomena such as peeling and blistering are recognized within a relatively short period of time. Is.

On the other hand, since the fluororesin coating material is generally more expensive than existing coating materials, it is necessary to design the minimum coating film thickness capable of ensuring ultrahigh weather resistance. There is a strong demand from the industry. Therefore, it is necessary to establish an effective coating system of the undercoat and the fluororesin topcoat that does not transmit ultraviolet rays in sunlight and has the minimum film thickness.

[0009]

As described above, as long as the conventional technique is followed, a multilayer coating film having an extremely high practicality such that no damage is caused even after long-term exposure. Establishing a formation method is absolutely
It was impossible.

However, in view of the existence of various drawbacks in the conventional technique, the present inventors solve the various problems in the conventional technique as described above and, at the same time, meet various demands of the coating industry. Therefore, I earnestly started research.

[0011] Therefore, the problem to be solved by the present invention is to provide a novel coating system when a fluororesin is applied as a top coat, and even after exposure for a long period of time, there is no peeling or peeling. It is to provide an extremely highly practical fluororesin coating system that does not cause blistering.

[0012]

[Means for Solving the Problems]

Therefore, as a result of intensive studies, the inventors of the present invention have focused their attention on the problems to be solved by the invention as described above, and as a result, in such a method for forming a multilayer coating film, as an overcoat, A coating system using a specific water-based fluororesin paint having an ultraviolet transmittance of 20% or less, which is a combination of an undercoat and the above-mentioned water-based fluororesin paint for topcoat, does not cause peeling or peeling even after long-term exposure. To find a target method for forming a multilayer coating film, which is extremely practical, in which the above-mentioned problems of not causing blistering and the like are solved smoothly and brilliantly, Then, the present invention has been completed.

That is, the present invention basically provides a method for forming a multilayer coating film obtained by applying an undercoat on a substrate and then applying an overcoat.

(1) After applying the undercoat,

(2) As a top coat, a water-based fluororesin containing a fluoroolefin as a constituent unit and a pigment are contained as essential components, and a specific water-based fluororesin coating composition is applied and dried. It is intended to provide a novel method for forming a layer coating film.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention relates to a method for forming a multilayer coating film obtained by applying a base coat on a substrate and then applying a top coat.

(1) After applying the undercoat,

(2) As a top coat, an aqueous fluororesin coating composition containing a fluoroolefin as a constituent unit and a pigment as an essential component is applied and dried to obtain a multilayer coating film. They are claiming a forming method.

Further, according to the present invention, as an aqueous fluororesin coating composition, particularly, a coating film formed by the aqueous fluororesin coating composition itself has an ultraviolet transmittance of 20% or less. It is said that it also claims a method for forming a specific multilayer coating film,

The present invention further provides as a basecoat, in particular:
The main component forming the undercoat coating film is that which contains a vinyl-based polymer, and a specific method for forming a multilayer coating film is claimed.

Furthermore, the present invention also claims a specific method for forming a multilayer coating film, in which an alkaline inorganic cured product is used as the substrate.

<< Structure >>

The present invention will be described in more detail below.

Here, first, of course, the above-mentioned undercoat in the present invention is not particularly limited, and various known and commonly used coating agents can be used.

The undercoat is appropriately selected whether it is an aqueous system or an organic solvent system (hereinafter also referred to as a solvent system), a dispersion system or a solution system, or a resin system. Then it can be applied.

If only representative examples of the undercoat coating agent are given, first, as the solvent-based coating agent, an acrylic coating material, an acrylic-urethane coating material, and a (moisture-curing) silicon-containing acrylic material are used. Room temperature drying type paints such as lacquer type paints, alkyd type paints, epoxy / polyamidoamine type paints or moisture curing type polyurethane type paints; and further acrylic / melamine type paints,
Examples include baking type paints represented by acrylic / epoxy type paints, alkyd or polyester / melamine type paints.

Furthermore, in addition to the above-mentioned various organic solvent solution-based paints, various resin-based non-aqueous dispersion-type paints as mentioned above can also be utilized and applied.

Similarly, with respect to the water-based coating agent for the undercoat, acrylic water-soluble paints, alkyd water-soluble paints or fatty acid-modified epoxy water-soluble paints, or these various water-based paints are also used. , Can be used and applied to water-soluble paints in which a cross-linking agent is mixed and mixed.

Alternatively, it may also be used in various aqueous dispersion type paints such as acrylic emulsions or dispersions, alkyd emulsions or dispersions, silicone / acrylic emulsions or dispersions. It can be applied.

These undercoat paints are blended with various additives including pigments according to a conventional method, mixed and made into a paint, and then brushed, spray coated, roll coater or flow coated according to a conventional method. It is applied using various coating methods such as coater, and further dried at room temperature or at an arbitrary temperature from 50 ° C to about 220 ° C for an arbitrary time to form an undercoat film. do it. In some cases, the topcoat of the next step may be applied while the undercoat is still undried.

The substrate to be coated is not limited in any way as long as it can secure the adhesion to the undercoat paint. Since the fluororesin paint used as the top coat is generally mainly used for exterior applications, it is preferably a so-called inorganic base material such as slate, cement and ALC plate, glass and various metals; Alternatively, it can be used with so-called organic base materials such as various organic polymers represented by various plastics, including old coating films existing when repainting wood and buildings. is there.

Among these, the application to alkaline inorganic hardened bodies such as slate or cement or ALC plate, which are particularly frequently used, is an even more desirable embodiment.

Next, the aqueous fluororesin coating composition for topcoating, which contains the aqueous fluororesin containing a fluoroolefin as a constituent unit and a pigment as essential components of the present invention, will be described.

First, the aqueous fluororesin containing a fluoroolefin as a constituent unit used in carrying out the method of the present invention is a resin in the form of being obtained by polymerizing a monomer containing a fluoroolefin as an essential constituent unit. Of these, a fluoroolefin emulsion polymer in the form of being obtained by emulsion polymerization in an aqueous medium is only to be mentioned as a representative example.

Examples of such fluoroolefin emulsion polymers include those exemplified below.

Here, the above-mentioned fluoroolefin has a polymerizable unsaturated double bond in one molecule, and at least one carbon atom forming the polymerizable unsaturated double bond is present. The fluorine atom can be defined as a monomer in a directly bonded form.

As only such representative fluoroolefins, vinyl fluoride,
Such as vinylidene fluoride, tetrafluoroethylene, hexafluoropropylene or chlorotrifluoroethylene.

Above all, it is desirable to use hexafluoropropylene, chlorotrifluoroethylene or vinylidene fluoride. More preferably, chlorotrifluoroethylene is suitable in terms of reaction control during polymerization.

The amount of the fluoroolefin to be contained in the fluoroolefin emulsion polymer used in the present invention is about 10% as a fluorine atom based on the solid content of the fluoroolefin emulsion polymer. The above is appropriate,
Preferably, 15% or more is suitable, and the fluoroolefin may be used in such a range.

When the amount is less than about 10%, the desired fluoroolefin emulsion polymer that exhibits various properties such as weather resistance peculiar to the fluororesin cannot be obtained. Other monomers that can be copolymerized with the above fluoroolefin can be appropriately selected and used in combination with the above fluoroolefin.

Here, if only the representative ones of the other monomers copolymerizable with the fluoroolefin described above are given as examples, the following are generally mentioned.

1. A variety of (fluorine atom-free, halogen-substituted) olefins such as ethylene, vinyl chloride, vinylidene chloride, propylene or butene-1;

2. Vinyl acetate, vinyl propionate,
Vinyl butyrate, vinyl isobutyrate, vinyl pivalate, vinyl caproate, vinyl versatate (vinyl neononanoate or neodecanoate), vinyl laurate, vinyl stearate, vinyl cyclohexanecarboxylate, vinyl p-tert-butylbenzoate or Vinyl esters of various carboxylic acids such as "Beoba" (trade name of vinyl ester, manufactured by Shell in the Netherlands);

3. Trifluoromethyl vinyl ether, 1,1,1-trifluoroethyl vinyl ether,
2,2-difluoroethyl vinyl ether, tetrafluoroethyl vinyl ether, perfluoropropyl vinyl ether, perfluorobutyl vinyl ether, perfluorohexyl vinyl ether, perfluorooctyl vinyl ether, perfluoromethyl vinyl ether, perfluoroethyl vinyl ether, perfluoropropyl vinyl ether, perfluoro Various (per) fluoroalkyl vinyl ethers, such as octyl vinyl ether or perfluorocyclohexyl vinyl ether;

4. Methyl-, ethyl-, n-propyl-, isopropyl-, n-butyl-, isoamyl-, n
Various linear or branched alkyl group-containing alkyl vinyl ethers, such as -hexyl-, n-octyl- or 2-ethylhexyl vinyl ether;

5. Vinyl ethers having various (alkyl-substituted) cyclic alkyl groups such as cyclopentyl vinyl ether, cyclohexyl vinyl ether or methylcyclohexyl vinyl ether;

6 Various aralkyl vinyl ethers, such as benzyl vinyl ether or phenethyl vinyl ether;

7. Methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, iso-propyl (meth) acrylate, n-
Butyl (meth) acrylate, iso-butyl (meth)
Acrylate, tert-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate, cyclopentyl (meth) acrylate, cyclohexyl (meth) acrylate or benzyl (meth) acrylate, "Biscoat 8F,
8FM, 3F or 3FM "[trade name of fluorine-containing (meth) acrylic monomer manufactured by Osaka Organic Chemical Co., Ltd.] or perfluorocyclohexyl (meth) acrylate or Ni-propylperfluorooctane sulfone Various (meth) acrylates, such as amidoethyl (meth) acrylate;

8. (Meth) acrylic acid, crotonic acid,
And maleic acid, fumaric acid, itaconic acid or citraconic acid; or maleic anhydride or itaconic anhydride, represented by adducts of various acid anhydride group-containing monomers with glycols. Various unsaturated group-containing hydroxyalkyl ester monocarboxylic acids; various unsaturated dibasic acids such as maleic acid, fumaric acid or itaconic acid, and alkyl alcohols having 1 to 10 carbon atoms as described above. Various carboxyl group-containing monomers and dicarboxylic acids represented by half esters, etc .;

9. Various unsaturated group-containing polyhydroxyalkyl esters represented by di-hydroxyalkyl esters of polyvalent carboxylic acids such as maleic acid or fumaric acid;

10. Various hydroxyalkyl (meth) acrylates such as 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate or 4-hydroxybutyl (meth) acrylate;

11. 2-hydroxyethyl vinyl ether, 4-hydroxybutyl vinyl ether or 6
-Various hydroxyl group-containing vinyl ethers such as hydroxyhexyl vinyl ether;

12. Various hydroxyl group-containing allyl ethers such as 2-hydroxyethoxy allyl ether or 4-hydroxy butoxy allyl ether;

13. Adducts of various hydroxyl group-containing monomers as described above with ε-caprolactone;

14. (Meth) acrylamide, N, N
-Various carboxylic acid amide group-containing monomers represented by dimethyl (meth) acrylamide, N-alkoxymethylated (meth) acrylamide, diacetone acrylamide, N-methylol (meth) acrylamide and the like;

15. p-styrenesulfonamide, N
-Methyl-p-styrenesulfonamide or N, N-
Various sulfonic acid amide group-containing monomers represented by dimethyl-p-styrenesulfonamide and the like;

16. Various N, N-dialkylaminoalkyl (meth) acrylates represented by N, N-dimethylaminoethyl (meth) acrylate; N- [2- (meth) acryloyloxyethyl]
Various (meth) such as piperidine, N- [2- (meth) acryloyloxyethyl] pyrrolidine or N- [2- (meth) acryloyloxyethyl] morpholine
Acrylic ester type monomers; 4- (N, N-dimethylamino) styrene, 4- (N, N-diethylamino)
Various aromatic monomers such as styrene or 4-vinylpyridine; or 2-dimethylaminoethyl vinyl ether, 2-diethylaminoethyl vinyl ether, 4-dimethylaminobutyl vinyl ether, 4-diethylaminobutyl vinyl ether or 6-dimethylamini Various tertiary amino-containing vinyl ethers such as hexyl vinyl ether; or various polyvalent carboxylic acid anhydride group-containing monomers such as maleic anhydride, and active hydrogen groups capable of reacting with these monomers Various tertiary amino group-containing monomers typified by adducts with compounds having both a tertiary amino group and the like;

17. Various cyano group-containing monomers represented by (meth) acrylonitrile and the like;

18. Various phosphate ester group-containing monomers obtained by a condensation reaction between various hydroxyalkyl esters of α, β-ethylenically unsaturated carboxylic acids, such as hydroxyalkyl (meth) acrylates, and phosphate esters. Body;

19. Styrene, α-methylstyrene,
various aromatic vinyl compounds such as p-tert-butyl-styrene or p-methylstyrene, represented by styrene or derivatives thereof;

20. Various crotonic esters, such as methyl crotonate, ethyl crotonate or n-butyl crotonate;

21. Various unsaturated dibasic acid dialkyl esters such as dimethyl malate, dimethyl fumarate, dibutyl fumarate or dimethyl itaconate;

22. Various sulfonic acid group-containing monomers such as 2-acrylamido-2-methylpropanesulfonic acid;

23. CH ₂ = CHCOO (CH ₂ ) ₃
[Si (CH ₃ ) ₂ O] _n Si (CH ₃ ) ₃ , CH ₂ =
_{C (CH 3) COOC 6 H} 4 [Si (CH 3) 2 O] n
Si (CH _{3) 3} or _{CH 2 = C (CH 3)} COO
(CH ₂ ) ₃ [Si (CH ₃ ) ₂ O] _n Si (CH ₃ ) ₃
Or CH ₂ ═C (CH ₃ ) COO (CH ₂ ) ₃ [S
i (CH ₃ ) (C ₆ H ₅ ) O] _n Si (CH ₃ ) ₃ or CH ₂ = C (CH ₃ ) COO (CH ₂ ) ₃ [Si
(C ₆ H ₅ ) ₂ O] _n Si (CH ₃ ) ₃

(However, n in each formula is 0 or 1 to 13)
It is assumed that the integer is 0. )

Various polysiloxane bond-containing monomers represented by the general formula such as:

24. Various polyethers such as polyethylene glycol mono (meth) acrylate, polypropylene glycol mono (meth) acrylate, polytetramethylene glycol mono (meth) acrylate, monoalkoxy polyethylene glycol (meth) acrylate or monoalkoxy polypropylene glycol (meth) acrylate Chain-containing monomers;

25. Glycidyl (meth) acrylate, (β-methyl) glycidyl (meth) acrylate,
Contains various epoxy groups such as 3,4-epoxycyclohexyl (meth) acrylate, allyl glycidyl ether, 3,4-epoxyvinylcyclohexane, di (β-methyl) glycidyl malate or di (β-methyl) glycidyl fumarate Monomers;

26. γ- (meth) acryloxypropyltrimethoxysilane, γ- (meth) acryloxypropyltriethoxysilane, γ- (meth) acryloxypropylmethyldimethoxysilane, γ- (meth) acryloxypropylmethyldiethoxysilane, γ -(Meth) acryloyloxypropyltriisopropenyloxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, vinyl (tris-β-methoxyethoxy) silane, vinyltriacetoxysilane, vinyltrichlorosilane or N-β- (N- Vinylbenzylaminoethyl) -γ-aminopropyltrimethoxysilane or a hydrolyzable silyl group-containing vinyl monomer typified by its hydrochloride or the like;

27. Ethylene glycol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, polyethylene glycol di (meth) acrylate,
2 in the molecule, represented by polypropylene glycol di (meth) acrylate, allyl (meth) acrylate, diallyl phthalate, divinylbenzene, hexadiene, octadiene, decadiene, tetradecadiene, 2-methyl-octadiene or decatriene.
Examples thereof include various monomers having one or more polymerizable unsaturated groups having no difference in radical reactivity.

These various monomers are appropriately selected and used in order to adjust the glass transition point of the copolymer finally obtained, the minimum film forming temperature and the like. Of course, these may be used alone or in combination of two or more kinds.

In preparing the fluoroolefin emulsion polymer from the various monomers listed above, only non-functional monomers may be used, but non-functional monomers may be used. It is also possible to use monomers as a main component and, if necessary, use monomers having a functional group in combination.

The fluoroolefin emulsion polymer used in carrying out the method for forming a multilayer coating film according to the present invention may or may not be crosslinked in its particles. However, it is possible to further improve water resistance, weather resistance, and the like, by internal crosslinking.

In order to crosslink the inside of the particles of the fluoroolefin emulsion polymer, various monomers having a hydrolyzable silyl group as described above may be used in combination, or each of them may react with each other. Having a functional group to obtain,
A monomer having two or more functional groups is used in combination, and further, 27. For example, polyfunctional monomers such as the above may be used together.

In the preparation of the fluoroolefin emulsion polymer, it can be said that various known and conventional emulsion polymerization methods are used and applied.

That is, various known non-reactive emulsifiers such as anionic emulsifiers or nonionic emulsifiers, or various known conventional reactive emulsifiers or dispersion stabilizers can be used to obtain known conventional emulsifiers. The polymerization reaction may be carried out by various methods.

As the above-mentioned anionic emulsifiers to be used at that time, only representative ones are exemplified by sulfuric acid ester salts of higher alcohols, alkyl (benzene) sulfonates, alkyl sulfate salts and polyoxys. Of course, ethylene alkylphenol sulfate salt, styrene sulfonate salt or vinyl sulfate salt, and various derivatives thereof may be used alone or in combination of two or more kinds.

Further, as the above-mentioned nonionic emulsifiers, only particularly representative ones will be exemplified. Polyoxyethylene alkyl ether, polyoxyethylene alkylphenyl ether, polyoxyethylene higher fatty acid ester or polyoxyethylene- Of course, these are polyoxypropylene block copolymers and the like, and these may be used alone or in combination of two or more kinds.

In addition to the above, various fluoroalkylcarboxylic acid salts represented by perfluorooctanoate and the like, and various fluorine atom-containing emulsifiers represented by fluoroalkyl sulfate are also used in combination. It means that you can do it.

Further, only specific examples of the reactive emulsifying agent will be exemplified, as described above.
It is possible to use various types of monomers having a so-called salt structure, such as a sulfonate group, a sulfate group, and a phosphate group.

The amounts of these various emulsifiers to be used include
Combine anionic emulsifier and nonionic emulsifier,
Appropriately within the range of about 0.5 to about 10% by weight, based on the total amount of monomers.

Furthermore, in combination with these emulsifiers,
It is said that various water-soluble oligomers selected from the group consisting of polycarboxylic acids and sulfonates, and various so-called water-soluble polymer substances represented by polyvinyl alcohol or hydroxyethyl cellulose are used as protective colloids. You can

The amount of the emulsifier used as described above is
It can also be applied by utilizing a so-called soap-free polymerization method, in which the polymerization reaction is carried out in a form as small as possible or the polymerization reaction is carried out without using it at all.

The polymerization initiator is not particularly limited as long as it is one generally used in emulsion polymerization, but if only typical ones are exemplified, hydrogen peroxide can be used. , Various water-soluble inorganic peroxides; ammonium persulfate, potassium persulfate or sodium persulfate, various persulfates; cumene hydroperoxide, benzoyl peroxide or tert-butyl hydroperoxide, various Or various azo initiators such as azobisisobutyronitrile or azobiscyanovaleric acid, which may be used alone or in combination of two or more. is there.

The amount of the polymerization initiator used is appropriately within the range of about 0.1 to about 2% by weight based on the total amount of the monomers.

It is needless to say that a so-called redox polymerization method in which these polymerization initiators are used in combination with a metal ion and a reducing agent may be used.

If only representative examples of such reducing agents are given, sodium bisulfite,
Sodium metabisulfite, sodium bithiosulfate, sodium hydrosulfate, sodium formaldehyde sulfoxylate or reducing sugar.

Further, if only representative examples of the above-mentioned metal ions are given as examples, it is copper sulfate, ferric chloride, ferric sulfate or silver nitrate.

Further, it goes without saying that various chain transfer agents can also be used.

When the fluoroolefin emulsion polymer to be used for carrying out the method for forming a multilayer coating film according to the present invention is prepared, in an aqueous medium,
Preferably, in the coexistence of ion-exchanged water and an emulsifier, the monomers, as they are, or in an emulsified state, all at once,
In the presence of the above-mentioned polymerization initiator, the gauge pressure is adjusted to a range of about 1 kg / cm ² to about 100 kg / cm ² , and the temperature is about 50 ° C. The polymerization reaction may be carried out at a reaction temperature of about 150 ° C.

In some cases, there is no problem even if the polymerization reaction is performed under a pressure condition higher than this or under a temperature condition lower than this.

The ratio of total monomers to water is in the range of about 1 to about 60% by weight of the final solid content, preferably 15 to 50% by weight.
It should be set within the range of 55% by weight.

In emulsion polymerization, in order to grow or control the particle size, emulsion particles are preliminarily polymerized in the aqueous phase.
Of course, the so-called seed polymerization method may be used.

As water in the aqueous medium used here, it is basically appropriate to use ion-exchanged water, and the amount thereof is about 70% by weight or more in the aqueous medium. Such a range is appropriate.

The remaining less than about 30% by weight may be used in combination with an organic solvent.

The organic solvent mentioned here is not particularly limited, and any general-purpose organic solvent can be used, but among them, only typical ones are exemplified. Acetone,
Various ketone systems such as methyl ethyl ketone or methyl amyl ketone; various ester systems such as ethyl acetate or butyl acetate; or various aromatic hydrocarbon systems such as benzene, toluene or xylene;

Alternatively, various aliphatic hydrocarbons such as hexane or heptane; various alcohols such as methanol, ethanol, isopropanol or butanol; or freon solvents such as carbon tetrachloride, methylene dichloride or hexafluoroisopropanol. And various halogen-containing organic solvents and the like.

Of these, it is preferable to use an organic solvent of the class that has a high affinity for water and a high ability to dissolve fluoroolefins in an aqueous medium.

That is, to exemplify only particularly representative organic solvents that can be particularly recommended, various so-called hydrophilic solvents such as acetone, methyl ethyl ketone, methanol, ethanol, and isopropanol, and
Examples include various fluorocarbon solvents such as hexafluoroisopropanol.

Here, since carbon tetrachloride, heptane, etc. sometimes act as so-called telogens, it goes without saying that the amount used should be taken into consideration when adjusting the molecular weight. Yes.

The pH during the reaction may be adjusted using various so-called pH buffering agents such as disodium phosphate, borax, sodium hydrogen carbonate or ammonia.

In particular, when a vinyl ether-based monomer is used in the copolymerization reaction, it may be used in a low pH range or at a high pH.
In this case, a side reaction may be caused, so in this case, it should be carried out under the condition that the pH is about 4 to about 10.

The state of the system after the reaction is as follows:
Very few unreacted gaseous monomers remain in the emulsion particles.

Most of these remaining monomers are unreacted fluoroolefins, but it is said that such gaseous monomers are stably removed so as not to destroy the intended emulsion. In order to do so, it is recommended to perform the following operation.

That is, when an acidic group is present in the obtained dispersion, a basic substance is used.
After neutralizing all or part of these acidic groups of the acid group-containing monomers converted to the target polymer, unreacted monomers are removed, or silicon-based and / or mineral oil-based This can be dealt with by various methods such as removing unreacted monomers after adding the compound.

Here, as the above-mentioned silicon-based and / or mineral oil-based compounds, various known and commonly used water-based antifoaming agents may be used and applied.

As a method for removing unreacted monomers, unreacted gaseous monomers are removed under normal pressure or reduced pressure under the condition of heating from room temperature to about 100 ° C. or less. Or, it can be applied by utilizing a steam distillation method or the like. At this time, a so-called inert gas such as nitrogen gas,
By bubbling through the system, removal of such unreacted gaseous monomers can be promoted.

The number average molecular weight of the fluoroolefin emulsion polymer thus prepared is generally 10,000 or more, preferably 50,000.
A value of at least 0, most preferably at least 100,000 is suitable.

The lowest film-forming temperature of the fluoroolefin emulsion polymer is about -10 ° C to about +6.
It is general to design within the range of 0 ° C.

The particle diameter of the fluoroolefin emulsion polymer is not particularly limited, but it is said that the number average particle diameter thereof is within the range of about 30 to about 1,000 nanometers (nm). It is desirable that the emulsion film has a film-forming property.

The above-mentioned aqueous fluororesin coating composition for topcoat, which is used for carrying out the method for forming a multilayer coating film according to the present invention, comprises the above-mentioned aqueous fluororesin,
A pigment is an essential component.

As the pigments, only representative ones are listed, and various inorganic pigments such as carbon black, titanium oxide, calcium carbonate, clay, iron oxide or iron hydroxide are exemplified. Pigments; or various organic pigments represented by phthalocyanine-based, quinacridone-based, azo-based, and the like. These various pigments may be appropriately added depending on the final use.
What is necessary is just to select and use it.

Of these, the use of inorganic pigments is desirable in order not to impair the high degree of weather resistance, which is one of the characteristics of the aqueous fluororesin itself. Compared with the case where inorganic pigments are used, when organic pigments are used, it is inevitably caused by the action of light or heat at the time of exposure, and further by the combined action with water. This is because it is easy to cause deterioration.

However, among the inorganic pigments, in the case of titanium oxide, active radicals are generated on the surface of the titanium oxide by the ultraviolet rays in the presence of water, whereby the titanium oxide particles It is known that the resin layer existing in the vicinity is deteriorated. For that,
When the titanium oxide is selected, it is desirable to use a grade that has been subjected to a treatment for suppressing the above-described action and behavior of the titanium oxide itself.

In carrying out the method for forming a multilayer coating film according to the present invention, it should be particularly noted that the single coating film formed from the aqueous fluororesin coating composition for top coating has an ultraviolet transmittance of 20%. The pigment concentration must be as follows, or the UV transmittance is 20
It means that the film thickness must be less than or equal to%.

The term "single coating film" as used herein does not mean a coating film applied on a substrate or a coating film applied on an undercoat, but is formed on a so-called smooth substrate such as glass. The term "film-like coating film" refers to a film-formed film and then isolated.

The above-mentioned ultraviolet transmittance is about 30.
It means the average value of the light transmittance in the ultraviolet region in the range of 0 to about 400 nm, and the average value of such a form must be about 20% or less. It is absolutely necessary that the average value is 15% or less and the maximum transmittance in such a section is 30% or less.

The pigment concentration that can satisfy such conditions is a pigment volume concentration (PVC) of about 0.5 to about 4.
A suitable range is 0%, and a suitable pigment weight concentration (PWC) range is about 0.5 to about 50%.

When the pigment is used in a concentration of less than this, no matter what kind of pigment is used, even if the coating film formed from the aqueous fluororesin coating composition for top coating is thickened, It is very difficult and difficult to suppress the permeation of the light within the above range.

In addition, when the amount of the pigment used exceeds the above range, the absolute amount of the pigment volume occupied in the coating film is inevitably increased, and as a result, the weather resistance is maintained. This is because the continuous layer of the resin derived from the fluoroolefin emulsion polymer is relatively small, and the entire coating film cannot exhibit the expected weather resistance.

The film thickness of the coating film formed from the above aqueous fluororesin coating composition for topcoating is generally about 40 μm (μm) or less, and preferably,
It can be designed to be 3 μm or less.

The above-mentioned aqueous fluororesin coating composition for top coating, which is used for carrying out the method for forming a multilayer coating film according to the present invention, is exemplified below in addition to the essential components as already described. It is also possible to add various known and commonly used additives as described above to form a coating material.

Of these, only typical ones are exemplified by 2-ethylhexanol and 2-ethylhexanol.
Various ethylene glycol derivatives represented by propoxy ethanol, 2-n-butoxy ethanol, 2-n-butoxy ethyl acetate and the like;

2-n-propoxypropanol, 3-n
-Various propylene glycol derivatives such as typified by propoxypropanol, 2-n-butoxypropanol or 3-n-butoxypropanol; Diethylene glycol-based derivatives typified by diethylene glycol monobutyl ether or diethylene glycol dibutyl ether Or N-methylpyrrolidone or a derivative thereof;

Furthermore, 2,2,4-trimethyl-1,
3-pentanediol, 2,2,4-trimethyl-1,
3-pentanediol monobutyrate or 2,2,4
-Various alkyl-substituted aliphatic polyhydric alcohol derivatives represented by trimethyl-1,3-pentanediol dibutyrate and the like;

Various polybasic acid esters represented by dibutyl phthalate or butylbenzyl phthalate ester; or an aliphatic organic solvent,
Various film forming aids such as various ones represented by aromatic organic solvents, ketone organic solvents, ester organic solvents, alcohol organic solvents and the like.

Furthermore, fillers other than the above-mentioned pigments; pigment dispersants; pH adjusters; leveling agents; thickeners; water repellents; defoamers; plasticizers; antioxidants; ultraviolet rays. Absorbents; anti-repellent agents; anti-skin agents (anti-skin burrs); anti-freezing agents; or various well-known and commonly used additives such as coupling agents, are appropriately added and used. Of course, it can be done.

Of these, the addition of the ultraviolet absorber can be expected to further reduce the ultraviolet transmittance of the coating film formed from the composition for a water-based fluororesin coating composition for top coating in the present invention. Therefore, its use is as far as desired.

In carrying out the method for forming a multilayer coating film according to the present invention, a base coat as described above is first coated with an undercoat paint, and then an aqueous fluororesin paint composition for top coat is applied. It can be painted.

In this case, this top coating is also applied in accordance with a conventional method by making use of various known and commonly used coating methods such as brush coating, spray coating, roll coater or flow coater, Further, it may be dried at room temperature or may be dried at any temperature from about 50 ° C. to about 220 ° C. for any time to form the top coat film. In some cases, the topcoat may be applied while the undercoat is still undried.

Thus, the multilayer coating film formed by carrying out the method of the present invention can be used especially for construction, building materials, or for repairing an old coating film of a building, and also for roof tiles, glass or Aluminum, stainless steel for various plastic products, woodworking, or automobile repair
It can be widely used for various kinds of substrates to be coated such as steel, chrome plating, various kinds of metals represented by galvanized sheet or tin plate.

[0133]

Next, the present invention will be described more specifically with reference examples, examples and comparative examples. However, the present invention is in no way limited to only these illustrative examples. is not. In the following, all parts and% are based on weight unless otherwise specified.

Reference Example 1 (Preparation Example of Fluoroolefin Emulsion Polymer for Top Coat) System of 2 liter stainless steel pressure resistant reaction vessel (autoclave) equipped with a stirrer, a nitrogen inlet tube, a thermometer and a temperature controller. The inside was thoroughly replaced with nitrogen gas.

Then, 800 parts of ion-exchanged water, 20 parts of sodium dodecylbenzenesulfonate and 20 parts of polyoxyethylene nonylphenyl ether, and
10 parts of borax as a pH buffer was added and dissolved.

Then, vinyl neodecanoate 415
Parts and 15 parts of crotonic acid, and 500 parts of chlorotrifluoroethylene liquefied and collected were charged, and then ethylene gas was forced into the autoclave to an internal temperature of 80 ° C. until the pressure reached 15 kg / cm ^2. The temperature was raised until. The ethylene gas was adjusted so that the system pressure at this time was about 30 kg / cm ² .

Then, at the same temperature, an aqueous catalyst solution prepared by dissolving 5 parts of potassium persulfate in 200 parts of ion-exchanged water was added.
It was pressed into the reaction vessel for 3 hours. Even after the addition of this aqueous catalyst solution, the polymerization reaction was allowed to proceed at the same temperature and the same system internal pressure for 10 hours. The pH during the reaction proceeded at 3.5. During the reaction, the pressure in the system decreases as the monomer is consumed, and the pressure of the reaction system is reduced to 30 kg / cm 3 by introducing ethylene each time.
Hold on to ² .

After completion of the reaction, the reaction mixture was cooled to room temperature and
% Ammonia water was added until the pH reached approximately 7.5, and 1% of a 5% aqueous dispersion of "Nopco 8034L" [trade name of silicone antifoam agent manufactured by San Nopco Co., Ltd.] was added. 0.0 part was added and stirred well. Next, unreacted gas was gradually removed from the system, and the pressure in the system was returned to normal pressure. Then, the pressure was reduced, and the unreacted gas dissolved in the dispersion was distilled off under reduced pressure.

The dispersions thus obtained each had a nonvolatile content of 48.5%, a pH of 7.2, a minimum film-forming temperature of 30 ° C., and an average particle diameter of 0.08.
It was a white aqueous dispersion having a size of μm. Hereinafter, this is abbreviated as (A-1).

According to the composition (A-1), elemental analysis, ion chromatography analysis, infrared absorption spectrum and composition analysis by thermal decomposition gas chromatography revealed that ethylene was 7.4% by weight and fluoroolefin was 4% by weight, respectively.
7.3% by weight, and the vinyl ester monomer is 43.7.
It was confirmed that the composition was such that the content of the acid group-containing monomer was 1.6% by weight and the content of the acid group-containing monomer was 1.6% by weight.

Reference Example 2 (Preparation Example of Aqueous Silicon / Acrylic Resin for Undercoat Paint) A reaction vessel equipped with a stirrer, thermometer, condenser and nitrogen gas inlet was charged with 660 parts of ethylene glycol monoisopropyl ether and charged with nitrogen. In the atmosphere, 8
The temperature was raised to 0 ° C.

Next, 100 parts of styrene, 250 parts of methyl methacrylate and 4 parts of n-butyl methacrylate were used.
A mixture of 80 parts, 70 parts of ethyl acrylate and 100 parts of dimethylaminoethyl methacrylate, 8 parts of azobisisobutyronitrile and 5 parts of tert-butyl peroxy octoate (TBPO) in 4 hours. It was dripped over.

Even after the completion of dropping, by keeping the same temperature for 10 hours, the nonvolatile content is 60%, and
A desired solution of the tertiary amino group-containing vinyl polymer (I) having a number average molecular weight of 9,500 was obtained.

Subsequently, at room temperature, 1.0 part of an 88% aqueous solution of formic acid was added to 100 parts of the solution of the polymer (I), and stirring was continued. The neutralization rate at this time is 50%
Met. Next, 49 parts of water was added thereto, and stirring was continued until the contents became uniform.
The desired aqueous product was obtained. Hereinafter, this is abbreviated as aqueous compound (WB-1).

Reference Example 3 (Preparation Example of Pigment Paste for Emulsion Paint) 200.8 parts of "Taipaque CR-97" (trade name of zirconium surface-treated rutile type titanium oxide manufactured by Ishihara Sangyo Co., Ltd.) 5.6 parts of "Orotan SG-1" (trade name of pigment dispersant manufactured by Rohm and Haas Company, USA), 3.9 parts of 10% aqueous solution of sodium tripolyphosphate salt, "Neugen EA-" 120 "[trade name of polyoxyethylene nonylphenyl ether emulsifier manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.] 1.8 parts, ethylene glycol 14.5 parts and" Best Side FX "[Dainippon Ink and Chemicals Incorporated] Brand name of preservatives manufactured by Co., Ltd.] 0.8
And 0.6 parts of "SN Deformer 121" [trade name of defoamer manufactured by San Nopco Co., Ltd.] and 5 parts of water
9.1 parts and 0.4 part of 28% aqueous ammonia were mixed and sufficiently stirred at room temperature using a disper.
The paste thus obtained is hereinafter referred to as a pigment paste (P
aster).

Reference Example 4 [Preparation Example of Pigment Paste Red for Emulsion Paint] Instead of “Taipaque CR-97”, acid value iron Fe _{2 was used.}
"TR-420" as O ₃ [manufactured by Toda Kogyo Co., Ltd.,
A red pigment paste was obtained in the same manner as in Reference Example 3, except that [trade name of α-Fe ₂ O ₃ ] was used.

Examples 1 to 6 and Comparative Examples 1 to 3 Various undercoat paints and topcoat paints were prepared with the compounding ratios shown in Table 1. A topcoat paint was also prepared as a control paint. Then, using a Stormer viscometer, each paint is adjusted to 85 KU,
Diluted with water.

Then, each coating material was applied onto a substrate as shown in the same table and dried. After a while
Each of the test plates thus obtained was subjected to so-called outdoor exposure in the suburbs of Miyazaki city for 3 years, and then the gloss retention was evaluated. In addition, the adhesion of the test piece exposed outdoors was also evaluated and judged. The results are shown in the same table.

As an accelerated test, a sunshine weatherometer was used for 3,000 hours.
After performing accelerated weather resistance, gloss retention and adhesion were evaluated. Further, the film thickness and ultraviolet transmittance of the dried coating film, polypropylene plate, after applying the aqueous fluororesin paint for topcoat, after drying, thus obtained, each dried coating film, from the substrate, Let me isolate
The film thickness and the ultraviolet transmittance were measured.

[0150]

[Table 1]

[0151]

[Table 2]

[0152]

[Table 3]

[0153]

[Table 4]

[0154]

[Table 5]

[0155]

[Table 6]

<< Footnote in Table 1 >>

Type of undercoat paint

A ... "Boncoat EC-880" [trade name of aqueous acrylic emulsion manufactured by Dainippon Ink and Chemicals, Inc .; nonvolatile content = 50%, Brookfield viscosity at 25 ° C (the same applies below) = 700 cps) , P
H = 8, minimum film-forming temperature = 29 ° C.], and by mixing the Paste obtained in Reference Example 3,
A white paint with a PVC content of 20% was used.

In the case of such a coating, a minimum film-forming temperature of 5 ° C. and a stomacher can be obtained by appropriately blending a thickener, a film-forming auxiliary and the like according to a conventional method. It was a paint with a viscosity of 85 KU.

The undercoat paints were applied by brushing.

B ... Aqueous product obtained in Reference Example 2 (WB-
1) is used, which is titanium oxide "Taipec CR-9.
7 "was blended so that the PWC would be 35%, and then kneaded with a sand mill.

Immediately before coating, the curing agent γ-glycidoxypropyltrimethoxysilane was used in the same manner as the tertiary amino group in the aqueous product (WB-1) obtained in Reference Example 2. The ingredients were blended to give an equivalent amount, stirred, and then spray-painted.

C ... "Bernock DM-678" [trade name of moisture-curing urethane resin manufactured by Dainippon Ink and Chemicals; non-volatile content = 35%, Gardner viscosity at 25 ° C. (the same applies hereinafter) = A ₂ Below, the isocyanate value is 4
%] Was used for spray coating as it was without blending the pigment.

D ... "Epiclon 1050-70X"
[Trade name of epoxy resin manufactured by Dainippon Ink and Chemicals, Inc .; non-volatile content = 70%, viscosity = Y, epoxy equivalent = 4
75 (solid content value)] and rouge (iron oxide Fe ₂ O ₃ ) were mixed and kneaded, and then the curing agent “Lackamide TD-973” [Dainippon Ink and Chemicals, Inc.]
Non-volatile content = 60%, viscosity = Y, amine value = 170] made of polyamide resin blended so that the epoxy groups in the epoxy resin and the amino groups in the curing agent are equivalent. Thus, a room temperature curing type epoxy resin coating material was obtained.

This paint was applied by brushing.

E: "Acridic BZ-1161" as a solvent-based silicone / acrylic resin (manufactured by the same company,
Trade name of toluene / isobutanol solution of acrylic resin; non-volatile content = 44%, viscosity = Z ₁ , acid value = 2) and “Acridic BZ-1163” as a curing agent (manufactured by the same company, curing agent A trade name of ethyl cellosolve solution; active ingredient = 80%, viscosity ... <A) was only blended, and no pigment was blended, and spray coating was performed as it was.

Drying conditions (same as undercoat and topcoat)

RT * 7: Meaning of drying for 7 days at room temperature

RT * 3: Meaning of drying for 3 days at room temperature

Topcoat paint types

FEM: Meaning of water-based paint using fluoroolefin emulsion polymer

Pigment Species and PWC and PVC

Types of pigments contained in the water-based fluororesin paint and their concentrations

TiO ₂ ............ Pa obtained in Reference Example 3
It means a compounded form using ste to have a predetermined concentration.

Fe ₂ O ₃ ..... means a form in which the red pigment paste obtained in Reference Example 4 was blended so as to have a predetermined concentration.

Carbon ... Carbon black
It means a dispersed pigment dispersed in water with polyoxyethylene nonylphenyl ether.

The top coating composition was prepared by blending a fluoroolefin emulsion polymer and a pigment, respectively, and further used as a thickener, "Primal TT-93".
5 "(trade name of emulsion containing carboxylic acid group, manufactured by Rohm and Haas Co., Ltd.) is used to increase the viscosity of" Texanol "(product of Eastman Chemical Co., USA) as a film forming aid. I made it a paint by mixing it.

Ultraviolet Transmittance: Using an "UV-Vis spectrophotometer" manufactured by JASCO Corporation, the ultraviolet transmittance of 300-400 nm was measured,
The average value was displayed.

Type of substrate

Slate: A flexible plate manufactured by Nozawa Co., Ltd. is used.

Old coating ……………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………… I did it.

Mild steel plate ……………… Untreated mild steel plate, dull

Aluminum: Chromated aluminum plate

Gloss retention rate: Remaining rate of gloss value after exposure to initial value gloss value before exposure.

The expression "peeling" means that the coating film has peeled off and measurement cannot be performed.

Adhesion: A so-called cross-cut adhesion test was conducted.

In the case of "whole surface peeling", it is described as "zero (0)", and conversely, in the case of not peeling at all, "100".
When it is in between, it is described according to the number of remaining stitches.

[0188]

As described in detail above, the method for forming a multilayer coating film according to the present invention is a highly practical multilayer film which is excellent not only in weather resistance but also in adhesion to a base. A coating film is provided, and in particular, according to the method of the present invention, by optimizing the pigment concentration, it becomes possible to further reduce the film thickness conventionally required, The invention can be said to be a novel method.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display area C09D 127/12 PFH C09D 127/12 PFH // C09D 5/00 PPF 5/00 PPF

Claims (4)

[Claims] 1. A method for forming a multilayer coating film obtained by applying a base coat on a substrate and then applying a top coat,
(1) After applying the undercoat, (2) applying an aqueous fluororesin coating composition containing a fluoroolefin as a constituent unit and a pigment as essential components as an overcoat, and then drying. A method for forming a multilayer coating film, which is characterized. 2. The above-mentioned aqueous fluororesin coating composition,
The UV transmittance of the coating film formed by itself is 20%
The method of claim 1, wherein: 3. The method according to claim 1, wherein the undercoat contains a vinyl polymer as a main component forming a coating film of the undercoat. 4. The method according to claim 1, wherein the substrate is a cured inorganic inorganic material.