JP2000212502A - Water dispersed composition for coating and its coating - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a water dispersed composition for coating manifesting sufficient adhesion to aged soft and elastic coating, excellent in resistance to cracking and weathering by including specific water dispersion of an acrylic resin, water dispersion of an epoxy resin, a polyhydrazide compound and a polyvalent metal simple body or the like. SOLUTION: The composition includes (A) a water dispersed acrylic resin having keto group and carboxyl group (preferably having glass transition temperature -20-50 deg.C), (B) a water dispersed epoxy resin having epoxy equivalent of 190-270 such as bisphenol-A type epoxy resin or the like, (C) a polyhydrazide compound such as dihydrazide adipate or the like, and (D) a polyvalent metal simple body such as zinc or the like and/or a polyvalent metal compound such as zinc acetate or the like. The preferable compounding ratio of the components A-D, for example, the ratio A/B in solid content is 100/5-10, the component C; 0.01-3.5 equivalent of hydrazide group is used for one equivalent of carboxyl group or epoxy group, the component D; 0.1-1.0 equivalent of metal is used for one equivalent of carboxyl group.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water-dispersible coating composition applied to finishing inside and outside of a building structure and a method of coating the same, and is mainly used as a paint for refurbishment and applied over an old coating film. In particular, the present invention relates to a water-dispersed coating composition and a coating method for forming a coating film having excellent adhesion and durability when the old coating film is a soft elastic coating film, which is excellent in adhesion and durability when overcoated. It is.

[0002]

2. Description of the Related Art A paint for repairing a building structure has suitability for recoating depending on the type of an old paint film, and various kinds of paints are applied from water-based paints to solution-based paints. In particular, when the old coating film is a soft elastic coating film, a method of recoating with a flexible and elastic coating material is applied. When the old coating film is a soft elastic coating film, the elongation of the coating film fluctuates depending on the temperature even after aging. In particular, a multilayer elastic coating film has a high elastic force retention rate. For this reason, in the repair by repainting, it is not possible to use a hard coating film that causes cracking after aging, and there is only a method of repainting with a soft elastic coating material, and in this case, there is a problem of aesthetic contamination. Often occurs.

[0003]

In the renovation of a building structure, especially when the old coating is a soft elastic coating, when the old coating is overcoated with a flexible and elastic coating, the old coating becomes a single-layer coating. In the case of an elastic coating film, the elongation percentage of the coating film is highly temperature-dependent, and the elongation percentage that decreases with time has a large variation depending on the temperature. In the case of a multilayer elastic coating film, the elongation rate does not fluctuate with time because it is protected by the top coating film. For this reason, in the case of repairing by recoating, in any case, only repair with an elastic coating film has been performed. However, since the elastic coating films have a strong film-forming ability and have different moisture and humidity permeability, the problem of peeling between the coating films is likely to occur. The present invention solves these problems upon such renovation, a water-dispersed coating composition which can sufficiently adhere to various soft elastic old coating films and can secure crack resistance and excellent weather resistance over time and the like. The purpose of the present invention is to provide a coating method.

[0004]

The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems. As a result, (A) an aqueous dispersion of an acrylic resin containing a keto group and a carboxyl group (B) an aqueous dispersion of an epoxy resin (C) ) Polyhydrazide compound (D) When a water-dispersed coating composition containing a polyvalent metal alone and / or a polyvalent metal compound is applied on an old coating film, the formed coating film is a polyhydrazide of component (C). Depending on the compound, the acrylic resin of the component (A), the epoxy resin of the component (B), the acrylic resin of the component (A) and the epoxy resin of the component (B) form hydrazide cross-links, respectively. The acrylic resin forms a metal cross-link by a polyvalent metal simple substance and / or a polyvalent metal compound of the component (D), whereby the entire coating film forms a cross-link, and various soft type bullets are formed. To the old coating, sufficiently adhere found that can be secured over time cracking resistance and excellent weather resistance, thereby completing the present invention. That is, the present invention comprises (A) an aqueous dispersion of an acrylic resin containing a keto group and a carboxyl group, (B) an aqueous dispersion of an epoxy resin, (C) a polyhydrazide compound, and (D) a simple polyvalent metal and / or a multivalent metal compound. And a method of applying the water-dispersed coating composition to the inside and outside of a building structure.

[0005]

DETAILED DESCRIPTION OF THE INVENTION The aqueous dispersion (A) of an acrylic resin containing a keto group and a carboxyl group used in the present invention is not particularly limited as long as it is an aqueous dispersion of an acrylic resin containing a keto group and a carboxyl group. For example, acrylic resins include (a1) an ethylenically unsaturated monomer having a keto group, (a2) an ethylenically unsaturated monomer having a carboxyl group, and (a3) copolymerizable with (a1) and (a2). Acrylic acid and / or methacrylic acid derivatives, (a
4) It can be obtained by subjecting a mixture of monomers such as other unsaturated monomers copolymerizable with (a1), (a2) and (a3) to emulsion polymerization in the presence of a dispersion stabilizer by a conventional method. it can. Usually, the acrylic resin refers to a copolymer resin of an acrylic acid and / or methacrylic acid derivative and an unsaturated monomer copolymerizable therewith, and these acrylic monomers include acrylic acid and / or methacrylic acid. The derivative contains a carbonyl group derived from a carboxylic acid and / or an ester group, and also contains a carbonyl group derived from an amide group in an amide compound such as acrylamide, except for acrylonitrile. Therefore, when it is called a normal acrylic resin, it contains a carbonyl group derived from these monomers, but the keto group contained in the acrylic resin according to the present invention is introduced from a ketone compound and / or a formyl compound. A carbonyl group, i.e., a keto group; examples of the monomer (a1) include the number of carbon atoms such as acrolein, diacetone acrylamide, diacetone methacrylamide, formylstyrene, and vinyl methyl ketone, vinyl ethyl ketone, and vinyl butyl ketone; And 4 to 7 vinyl alkyl ketones.

Examples of the monomer (a2) include acrylic acid, methacrylic acid, maleic acid, crotonic acid, vinyl acetic acid, itaconic acid, maleic anhydride, fumaric acid, citraconic acid and the like.

Examples of the monomer (a3) include methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, hexyl acrylate, cyclohexyl acrylate, 2-ethylhexyl acrylate, octyl acrylate, and acrylic acid. Lauryl, stearyl acrylate, methyl methacrylate, ethyl methacrylate,
Propyl methacrylate, isopropyl methacrylate, butyl methacrylate, hexyl methacrylate, cyclohexyl methacrylate, 2-ethylhexyl methacrylate,
C1-C2 of (meth) acrylic acid such as octyl methacrylate, lauryl methacrylate, and stearyl methacrylate
4, alkyl or cycloalkyl esters of methoxybutyl acrylate, methoxybutyl methacrylate, methoxyethyl acrylate, methoxyethyl methacrylate,
C1-C18 alkoxyalkyl esters of (meth) acrylic acid such as ethoxybutyl acrylate and ethoxybutyl methacrylate; C2-C8 of (meth) acrylic acid such as hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate and hydroxypropyl methacrylate Acrylic monomers such as hydroxyalkyl esters, acrylonitrile and methacrylonitrile can be mentioned.

Examples of the monomer (a4) include aromatic unsaturated monomers such as styrene, vinyltoluene, α-methylstyrene, N-vinylpyrrolidone and vinylpyridine; and ethylene, propylene, butylene and pentene. Olefins; diene compounds such as butadiene, isoprene, and chloroprene; and vinyl propionate, vinyl acetate, vinyl pivalate, and beova monomer (a product of Shell Chemical Co., Ltd.). These are used as appropriate according to the desired performance.

The monomers (a1), (a2) and (a)
3) The proportion of (a4) in the entire monomer component varies depending on desired properties, for example, glass transition temperature, coating film performance, etc., but monomer (a1) 0.2 to 10% by weight monomer (A2) 0.1 to 10% by weight Monomer (a3) 5 to 90% by weight Monomer (a4) 0 to 50% by weight is preferred. In the present invention, the glass transition temperature of the acrylic resin of the component (A) is preferably from -20 ° C to 50 ° C,
If it is less than 50 ° C, the overcoat will have large elongation and crack the top coat, and if it exceeds 50 ° C, the elongation of the coating will be small and it will not be able to follow the old coating and will eventually crack. Are not preferred. (B) used in the present invention
The epoxy resin aqueous dispersion mainly enhances the adhesion of the coating film. For example, a self-emulsifying epoxy resin of bisphenol A type having an epoxy equivalent of 190 to 270 or
Bisphenol A type having an epoxy equivalent of 170 to 200,
Or bisphenol AD type, or bisphenol F
Aqueous dispersion obtained by forcibly emulsifying a liquid epoxy resin of a mold and a mixture of the aqueous dispersion, or an epoxy equivalent of 450 to
An aqueous dispersion obtained by forcibly emulsifying 3,300 bisphenol A type solid epoxy resin, an aqueous dispersion of a mixture of a forced emulsion of a liquid epoxy resin and a forced emulsion of a solid epoxy resin, and the like are used.

The content ratio of the aqueous dispersion of the epoxy resin (B) varies depending on the desired coating film performance, but the weight ratio of the acrylic resin (A) / epoxy resin (B) is 100% by solid content. A ratio of / 5 to 10 is preferred. When the content of the component (B) is less than 5, the desired adhesion is hardly obtained, and when it exceeds 10, the softening of the coating film becomes remarkable, which is not preferable. The polyhydrazide compound (c) used in the present invention reacts with the carbonyl group of the acrylic resin (A) and the epoxy group of the epoxy resin (B) to form an acrylic resin, an epoxy resin, and an acrylic resin and an epoxy resin. A crosslinking agent which forms a complex crosslink with a resin by hydrazide crosslinking and metal crosslinking by the component (D) described later. For example, adipic dihydrazide, succinic dihydrazide, glutaric dihydrazide, etc. can be used. Are preferred. Also,
(C) The content ratio of the polyhydrazide compound is such that the amount of the hydrazide group is 0.01 to 3.5 equivalents to 1 equivalent of the carbonyl group of the acrylic resin of the component (A) and 1 equivalent of the epoxy group of the epoxy resin of the component (B). Is preferable.

The polyvalent metal simple substance and / or polyvalent metal compound (D) used in the present invention is metal-crosslinked with the acrylic resin of the component (A) to form a composite crosslink together with the hydrazide crosslink by the component (C). A crosslinking agent, for example,
Metal oxides such as zinc oxide containing divalent and trivalent metals,
Metal salts such as zinc phosphate and zinc acetate, hydroxides such as aluminum hydroxide, and metals such as free calcium can be preferably used. The content ratio of (D) a simple polyvalent metal and / or a polyvalent metal compound is such that the amount of the metal is 0.1 to 1.0 equivalent per 1 equivalent of the carboxyl group of the acrylic resin of the component (A). Is preferred. The water-dispersed coating composition of the present invention is prepared by uniformly mixing and dispersing the components (A) to (D), and the component (A) and the component (C) are preliminarily mixed, and (B) The component (D) may be mixed, the component (B) and the component (C) may be mixed in advance, and the components (A) and (D) may be mixed.
It can also be prepared by mixing the components (D) simultaneously. The water-dispersed coating composition of the present invention is obtained by mixing and dispersing pigments such as titanium oxide, calcium carbonate, clays, talcs, and mica in addition to the above-mentioned components (A) to (D), and increasing if necessary. A one-part water-dispersed paint is prepared by adding a tackifier, an antifoaming agent, a film-forming aid, a surfactant and the like. The water-dispersed coating composition of the present invention thus prepared is diluted with fresh water, applied on various old coatings inside and outside the building structure by a brush, a roller, a spray, etc., and dried and cured at room temperature. .

[0012]

EXAMPLES The water-dispersed coating compositions of Examples 1 to 3 and Comparative Examples 1 to 3 were prepared by uniformly mixing and dispersing the respective coating compositions shown in Table 1 in accordance with the usual method of coating production. Numerical values are given in parts by weight.

[0013]

[Table 1]

(Note 1-1) 30 parts of methyl methacrylate,
An aqueous acrylic resin dispersion having a Tg of 0 ° C. obtained by copolymerizing 52 parts of butyl acrylate, 4 parts of diacetone acrylamide, 4 parts of acrylic acid, 10 parts of styrene, and 100 parts of water. (Note 1-2) 21 parts of methyl methacrylate, 64 parts of butyl acrylate, 1.5 parts of diacetone acrylamide, 0.5 part of acrylic acid, 10 parts of styrene, 3 parts of polyethylene glycol monomethacrylate, and 100 parts of water are copolymerized. Acrylic resin aqueous dispersion at Tg-16 ° C. (Note 2) An aqueous epoxy resin dispersion comprising 60 parts of a bisphenol AD epoxy resin, 6 parts of a mixture of three types of an alkylene oxide adduct of bisphenol A and an alkylene oxide adduct of a higher alcohol, and 34 parts of water. (Note 3) Zinc acetate (Note 4) A mixture of 5 parts of titanium oxide and 138 parts of calcium carbonate. (Note 5) A mixture of a polycarboxylic acid type polymer surfactant and a polyoxyethylene phenyl ether surfactant. (Note 6) A mixture of hydroxymethyl cellulose and hydroxyethyl cellulose. (Note 7) An acetylene-containing polysiloxane emulsion-based antifoaming agent. (Note 8) 2.2.4-Trimethyl-1.3-pentadiol monoisobutyrate

As a result of coating each paint on an old paint film composed of a single-layer elastic (Ac / St type) system which was subjected to outdoor backlash for one year with a roller, the results shown in Table 2 were obtained. In Examples 1, 2 and 3, although there was a difference in adhesion strength and elongation, a good coating state after aging was obtained. As in Comparative Example 1, when the epoxy resin is excluded, the adhesive force is reduced, the coating film tends to be blistered, the behavior balance of the old coating film is lost, and finally the coating film is peeled off. Comparative Example 2
However, since the cross-linking reactivity of the epoxy resin cannot be expected, a plastic effect is obtained, and the elongation percentage increases, but the tensile strength decreases. For this reason, long-term physical strength of the coating film cannot be expected, and a problem remains in terms of durability. In Comparative Example 3, since the crosslink density of the acrylic resin decreases, the water resistance and the tensile strength of the coating film decrease. Since the long-term physical strength of the coating film is weak, the overall durability is reduced. As described above, the paint of the present invention has a composite cross-linking structure combined with a combination of a composite resin, so that it is possible to repeatedly apply the coating to an expected elastic finish surface.

[0016]

[Table 2]

(Note 9) JIS A 6909 bond strength test Standard time (Note 10) JIS A 6909 test method (Note 11) JIS A 6909 test method (Note 12) JIS A 6909 and JIS A 6
021 test method (Note 13) One year after the outdoor southern surface at 30 ° in the Kanto area

[0018]

According to the present invention, there can be provided a water-dispersed coating composition which can be sufficiently adhered to various soft elastic old coating films, and which can secure crack resistance and excellent weather resistance over time, and a coating method thereof. .

Claims (2)

[Claims] 1. An aqueous dispersion of an acrylic resin containing (A) a keto group and a carboxyl group, (B) an aqueous dispersion of an epoxy resin, (C) a polyhydrazide compound, and (D) a simple polyvalent metal and / or a polyvalent metal compound. A water-dispersed coating composition, comprising: 2. An aqueous dispersion of an acrylic resin containing (A) a keto group and a carboxyl group, (B) an aqueous dispersion of an epoxy resin, (C) a polyhydrazide compound, and (D) a simple polyvalent metal and / or a polyvalent metal compound. A method of applying the water-dispersed coating composition to inside and outside of a building structure.