JP2000191979A - Aqueous coating composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an aqueous coating composition excellent in film formability and water resistance, etc., by including a specific hydroxyl-contg. polymer, a polyisocyanate compound, and a pigment or amino resin-based curing agent coated with a compound having a contact angle to water of a specified value or higher. SOLUTION: This aqueous coating composition is obtained by including a hydroxyl-contg. fluorocopolymer composed of polymerization units based on a fluoroolefin, (meth)acrylic hydroxyalkyl ester, and/or the like, or hydroxyl- contg. polymer >=2 mgKOH/g in hydroxyl number such as one containing 0.1-25 mol%, based on the total polymerization units, of polymerization unit based on a hydrophilic site-contg. macromonomer, a self-emulsifiable polyisocyanate compound, and a pigment or amino resin-based curing agent coated with a film of a compound >=65 deg. in contact angle to water such as an acrylic resin or fluororesin.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a composition for water-based paint.

[0002]

2. Description of the Related Art Conventionally, an aqueous coating containing a water-dispersible self-emulsifying polyisocyanate compound and a hydroxyl group-containing acrylic resin, and a copolymer of fluoroolefin, cyclohexyl vinyl ether and other various monomers have been used as water-dispersible resins. The water-based paint contained is a transparent and high-gloss coating film with excellent properties such as high weather resistance, water and oil repellency, stain resistance, non-adhesion, and solvent resistance. It is known to give.

[0003]

However, when a water-dispersible hydroxyl group-containing resin paint is used together with a water-dispersible self-emulsifying polyisocyanate compound, carbon dioxide gas is produced by the reaction between the polyisocyanate compound and water. In some cases, the problem arises that the film is formed and foamed, resulting in poor appearance of the coating film, when the film thickness is large or when drying is fast. This foaming tends to occur when cured at low temperatures. In addition, a hydroxyl group-containing water-soluble resin paint has the same problem. The present invention is a water-based paint composition that is excellent in film-forming properties at low temperatures, and excellent in water resistance, blocking resistance, stain resistance, and chemical resistance, and can provide a coating film that does not lose its appearance due to foaming. The purpose is to provide things.

[0004]

Means for Solving the Problems As a result of diligent studies, the present inventors have found that a "hydroxyl-containing polymer", a "polyisocyanate compound" and a "compound film having a contact angle to water of 65 ° or more" are coated with a compound film. It has been found that the above problems can be solved by adding a pigment or an amino resin-based curing agent, and the present invention has been completed, that is, the present invention provides a "hydroxyl group-containing polymer", a "polyisocyanate compound" and A water-based coating composition comprising: “a pigment or an amino resin-based curing agent covered with a compound film having a contact angle to water of 65 ° or more”. The present invention also provides a composition for an aqueous coating composition, wherein the hydroxyl group-containing polymer has a hydroxyl value of 2 mgKOH / g polymer or more. Further, the present invention provides the above-mentioned composition for water-based paint, wherein the hydroxyl-containing polymer is a hydroxyl-containing fluorine-based copolymer having a polymerized unit based on a fluoroolefin.

Further, the present invention provides a composition for water-based paint, wherein the hydroxyl group-containing polymer has a polymerized unit based on a hydroxyalkyl ester of acrylic acid or methacrylic acid, a hydroxyalkyl vinyl ether or a hydroxyalkyl allyl ether. Provided is a composition for an aqueous coating, which is a fluorine-containing copolymer. Also,
The present invention provides the aqueous coating composition, wherein the hydroxyl group-containing polymer contains 0.1 to 25 mol% of a polymer unit based on a hydrophilic site-containing macromonomer based on all polymer units. I do. The present invention also provides a water-based coating composition, wherein the polyisocyanate compound is a self-emulsifying polyisocyanate compound in the water-based coating composition.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The hydroxyl group-containing polymer used in the present invention may be water-dispersible or water-soluble. The hydroxyl value of the hydroxyl group-containing polymer is 2 mgKOH /
g polymer or more, especially 10 to 60 mg KOH /
g polymers are preferred. Examples of the hydroxyl group-containing polymer include a hydroxyl group-containing non-fluorinated copolymer and a hydroxyl group-containing fluorine-based copolymer, and these copolymers can be used alone or in combination. These copolymers are preferably obtained by emulsion polymerization or seed polymerization. As the hydroxyl group-containing non-fluorinated copolymer, a hydroxyl group-containing acrylic copolymer containing a polymerized unit based on a hydroxyl group-free acrylic monomer and a polymerized unit based on a hydroxyl group-containing acrylic monomer is preferable.

[0007] Suitable hydroxyl-free acrylic monomers include, for example, acrylic acid, methacrylic acid or methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, propyl acrylate, propyl methacrylate, n-butyl acrylate, n-butyl acrylate.
Butyl methacrylate, iso-butyl acrylate,
Examples thereof include alkyl esters of acrylic acid or methacrylic acid having 1 to 12 carbon atoms, such as iso-butyl methacrylate, tert-butyl acrylate, and tert-butyl methacrylate, acrylonitrile, and methacrylonitrile. Examples of the hydroxyl-free acrylic monomer having a crosslinking site other than the hydroxyl group include glycidyl group-containing acrylic monomers such as glycidyl acrylate, glycidyl methacrylate, (β-methyl) glycidyl acrylate, and (β-methyl) glycidyl methacrylate. Body, acrylamide, methacrylamide, dimethylacrylamide, dimethylmethacrylamide, N-te
Examples include carbamoyl group-containing acrylic monomers such as rt-butyl acrylamide, N-tert-butyl methacrylamide, N-octyl methacrylamide, diacetone acrylamide, and diacetone methacrylamide. Hydroxyl-free acrylic monomers can be used alone or in combination of two or more.

Suitable hydroxyl-containing acrylic monomers include, for example, 2-hydroxyethyl acrylate and 2-hydroxyethyl acrylate.
Hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, 3-hydroxypropyl acrylate, 3-hydroxypropyl methacrylate, 2-hydroxybutyl acrylate, 2-hydroxybutyl methacrylate,
3-hydroxybutyl acrylate, 3-hydroxybutyl methacrylate, 4-hydroxybutyl acrylate, 4-hydroxybutyl methacrylate, 3-chloro-2-hydroxypropyl acrylate, 3-chloro-
2-hydroxypropyl methacrylate and the like. The hydroxyl group-containing acrylic monomers can be used alone or in combination of two or more. The hydroxyl group-containing acrylic copolymer may contain polymerized units based on other monomers in addition to the above monomers.

Other monomers include styrene, maleic acid, alkanoic acid, vinyl esters, vinylalkoxysilane and the like.

The molecular weight of the hydroxyl group-containing acrylic copolymer is not particularly limited, but is preferably from 500 to 80,000. In addition, an acrylic polymer having a crosslinked site other than a hydroxyl group may be mixed with the hydroxyl group-containing acrylic copolymer, or an acrylic polymer having no crosslinked site may be mixed. The proportion of the acrylic polymer having a crosslinking site other than a hydroxyl group or the acrylic polymer having no crosslinking site is preferably up to 50% by weight based on the acrylic copolymer having a crosslinking site.

As the hydroxyl group-containing fluorine-based copolymer, a copolymer of a fluoroolefin and a monomer other than the fluoroolefin is preferred because of its excellent weather resistance, pigment dispersibility and coating film properties. In addition, the hydroxyl group can be introduced by copolymerizing a hydroxyl group-containing monomer, and among them, a linear, branched or aliphatic chain having sufficient hydrophobicity between the polymerizable functional group and the hydroxyl group. Those having a cyclic hydrocarbon chain are effective in copolymerizability. Furthermore, the hydroxyl group-containing fluorine-based copolymer in the present invention is preferably produced by emulsion polymerization, because it is excellent in stability (mechanical stability and chemical stability) and a uniform dispersion can be obtained. Further, those polymerized in the presence of a hydrophilic site-containing monomer during emulsion polymerization are more excellent in stability and are preferred.

Examples of the hydroxyl group-containing monomer include hydroxyalkyl vinyl ethers, hydroxyalkyl allyl ethers, and hydroxyalkyl esters of acrylic acid or methacrylic acid. Preferred specific examples of the hydroxyl group-containing monomer include a compound represented by the general formula: X-OY-OH
(X is a radically polymerizable unsaturated group, and Y is an alkylene group having 5 or more carbon atoms which may have a cycloalkylene group.)
And specifically the following compounds are exemplified.

(1) CH ₂ = CH〇CH ₂ -cycloC ₆ H ₁₀ -CH ₂ OH (2) CH ₂ = CHCH ₂ OCH ₂ -cycloC ₆ H ₁₀ -CH ₂ OH (3) CH ₂ = CHOC ₉ H ₁₈ OH (4) CH ₂ = CHCH ₂ OC ₉ H ₁₈ OH

Among them, those having a vinyl ether type structure are excellent in alternating copolymerizability with a fluoroolefin,
This is preferable because the weather resistance of the coating film is improved. Here, as the fluoroolefin, a fluoroolefin having about 2 to 4 carbon atoms such as vinylidene fluoride, trifluoroethylene, chlorotrifluoroethylene, tetrafluoroethylene, pentafluoropropylene, and hexafluoropropylene is preferably employed. Particularly, a perhaloolefin is preferable.

Further, it is preferable that the hydroxyl group-containing fluorine-based copolymer obtained by emulsion polymerization has a polymerized unit based on a hydrophilic site-containing monomer. When this polymerized unit is contained as an essential component of the hydroxyl group-containing fluorine-containing copolymer, not only the mechanical and chemical stability of the aqueous dispersion is improved, but also the film forming property and the water resistance of the coating film are improved. And so on. The hydrophilic site of the hydrophilic site-containing monomer may be any of ionic, nonionic, amphoteric, and combinations thereof, but the hydrophilic site is formed only of a unit having an ionic hydrophilic group. In some cases, it is not preferable because there is a problem in the chemical stability of the aqueous dispersion of a hydroxyl group-containing fluorine-based copolymer, and in combination with a site having a nonionic or amphoteric hydrophilic group, or a site having a hydrophilic bond It is desirable to combine with

Further, it is preferable that the monomer containing a hydrophilic site is a macromonomer because the stability is further improved. The macromonomer refers to a low molecular weight polymer or oligomer having a radically polymerizable unsaturated group at one terminal. That is, it is a compound having a radical polymerizable unsaturated group at one end and having at least two repeating units. Although it depends on the type of the repeating unit, one having 100 or less repeating units is usually preferably used from the viewpoints of polymerizability, water resistance and the like. Examples of the hydrophilic portion-containing macromonomer include polyethers having a radically polymerizable unsaturated group at one terminal, such as the following.

(1) CH ₂ = CHO (CH ₂ ) _k [OCH ₂ CH ₂ ] _n O
X (k is an integer of from 1 to 10, n represents an integer of 2 to 20, X is a hydrogen atom or a lower alkyl _{group) (2) CH 2 = CH} (CH 2) j O (CH 2) k -cycloC 6 H ₁₀ (C
H ₂ ) _m [OCH ₂ CH ₂ ] _n OX (j is 0 or 1, k is 0 to 20)
, M is an integer of 0 to 20, n is an integer of 2 to 20, X is a hydrogen atom or a lower alkyl group.) (3) CH ₂ = CHC H ₂ O (CH ₂ ) _k [OCH ₂ CH ₂ ] _n OX (k, n and X are the same as those of the formula (1))

(4) CH ₂ = CHO (CH ₂ ) _k (OC H ₂ CH ₂ )
_{m (OC H 2 CH (CH} 3)) n OX (k is an integer of from 1 to 10, m is from 2 to 20 integer, n represents 0 to 20 integer, X is hydrogen atom or a lower alkyl group, an oxy Ethylene units and oxypropylene units are blocks,
(5) CH ₂ = CHC H ₂ O (CH ₂ ) _k (OC H ₂ CH ₂ ) _m (OC H ₂ C
H (CH ₃ )) _n OX (k, m, n, and X are the same as those of the formula (3), and the oxyethylene unit and the oxypropylene unit may be arranged in any of block and random types. )

Of these, those having a vinyl ether type structure at one end are preferably employed because of their excellent copolymerizability with fluoroolefins. In particular, those having a polyether chain portion composed of an oxyethylene unit or an oxyethylene unit and an oxypropylene unit are preferable because they have excellent hydrophilicity and the like. Further, those having at least two oxyethylene units are preferable because various properties such as stability are achieved. If the number of oxyalkylene units is too large, the water resistance and weather resistance of the coating film are deteriorated, which is not preferable.

The hydrophilic site-containing macromonomer is
It can be produced by a method such as polymerizing formaldehyde with vinyl ether or allyl ether having a hydroxyl group, or subjecting an alkylene oxide or a lactone ring-containing compound to ring-opening polymerization.
Further, as a hydrophilic site-containing macromonomer, a hydrophilic ethylenically unsaturated monomer has a radically polymerized chain,
A macromonomer having a radically polymerizable unsaturated group such as vinyl ether or allyl ether at the terminal may be used.

The hydroxyl group-containing fluorine-based copolymer may contain polymerized units based on monomers copolymerizable with these compounds in addition to polymerized units based on the above compounds. Such monomers include ethylene, olefins such as propylene, ethyl vinyl ether, propyl vinyl ether,
Hydroxyl-free vinyl ethers such as butyl vinyl ether and cyclohexyl vinyl ether; vinyl alkanoates such as vinyl butanoate and vinyl octanoate; vinyl compounds such as aromatic vinyl compounds such as styrene and vinyl toluene; ethyl allyl ether Such as allyl ethers, the above-mentioned hydroxyl-free acrylic monomer, the above-mentioned hydroxyl-containing acrylic monomer,
Examples include isopropenyl ethers and unsaturated fatty acids. In particular, olefins, vinyl ethers, vinyl alkanoates, and allyl ethers are preferably employed.

The olefins here have 2 to 1 carbon atoms.
Those having about 0 are preferred, and those having a linear, branched or alicyclic alkyl group having about 2 to 15 carbon atoms are preferably employed as vinyl ethers, vinyl alkanoates and allyl ethers. In such a monomer, at least a part of hydrogen bonded to carbon may be replaced by fluorine. Hydroxyl group-containing fluorine-based copolymer,
20 to 80 mol% of a polymer unit based on a fluoroolefin, 3 to 40 mol% of a polymer unit based on a hydroxyl group-containing monomer, and 0.1 of a polymer unit based on a hydrophilic site-containing monomer, based on all the polymerized units. Preferably, it is contained at a ratio of ２５25 mol%. If the polymerization unit based on the fluoroolefin is too small, the weather resistance is not sufficiently exhibited, and if it is too large, the water dispersibility becomes extremely poor, which is not preferable. In particular, it is preferably 30 to 70 mol%.

On the other hand, if the number of polymerized units based on the hydroxyl group-containing monomer is small, the degree of crosslinking with the polyisocyanate compound will not be sufficient, and desirable properties in coating properties such as stain resistance, solvent resistance and chemical resistance will be obtained. I can't. On the other hand, if the amount is too large, the hydrophilicity of the polymer is high and the water resistance and boiling water resistance of the coating film deteriorate. Particularly, 5 to 25 mol% is desirable. Further, when the polymerized unit based on the hydrophilic site-containing monomer includes one having a hydroxyl group, the polymerized unit is a polymerized unit based on the hydrophilic site-containing monomer and a polymerized unit based on the hydroxyl group-containing monomer. Is included in both calculations. If the amount of the polymerized unit based on the hydrophilic site-containing monomer is too small, the water dispersibility becomes extremely poor, and if it is too large, the weather resistance and water resistance of the coating film become poor, which is not preferable. In particular, in order to achieve an extremely excellent effect on film forming properties, this polymerized unit is 0.3 to
It is preferably contained at a ratio of 20 mol%. The amount of the polymerized unit other than the polymerized unit based on the fluoroolefin and the polymerized unit based on the hydrophilic site-containing monomer is preferably 0 to 70 mol%. If the number of the polymerized units is too large, the weather resistance becomes poor, which is not preferable.

In producing the hydroxyl group-containing fluorocopolymer, it is preferable to carry out the emulsion polymerization in the presence of a nonionic emulsifier having an HLB of 12 to 18 and an anionic emulsifier. When the HLB of the nonionic emulsifier is out of this range, the stability at the time of emulsion polymerization is lowered, or the stability of the obtained dispersion is lowered. Particularly preferred HLB is 14-16. In addition, although the anionic emulsifier alone has high stability at the time of emulsion polymerization, the resulting dispersion is liable to agglomerate when an inorganic substance is added, and when formed into a coating film, its high hydrophilicity lowers water resistance. Cheap. On the other hand, with a nonionic emulsifier alone, a very small amount of a viscous substance tends to be generated during emulsion polymerization, and when the aqueous dispersion is stored for a long time or stored at a high temperature, the viscous substance triggers and thickens. And, in some cases, may be transformed into purines. When emulsion polymerization is carried out in the presence of a nonionic emulsifier having an HLB of 12 to 18 and an anionic emulsifier, the stability at the time of compounding the paint is high, the stability at the time of storage is high, and the coating having excellent weather resistance and water resistance is obtained. A fluorinated aqueous dispersion giving a membrane is obtained.

As the lipophilic group of the nonionic emulsifier, one containing no polyfluoroalkyl group is preferred from the viewpoint of forming a dense coating film. Specific examples include alkylphenol ethylene oxide adducts, higher alcohol ethylene oxide adducts, ethylene oxide and propylene oxide block copolymers, and the like. The amount of the emulsifier can be appropriately changed depending on the conditions, but is usually 0.1 to 100 parts by weight per 100 parts by weight of the monomer to be emulsion-polymerized.
About 5 parts by weight is preferably employed. Similarly, the lipophilic group of the anionic emulsifier preferably does not contain a polyfluoroalkyl group. Specific examples thereof include an alkyl benzene sulfonate, an alkyl naphthalene sulfonate, a higher fatty acid salt, an alkyl sulfate, an alkyl ether sulfate, and a phosphate.

The initiation of the emulsion polymerization is carried out by adding a polymerization initiator in the same manner as in the usual initiation of emulsion polymerization. As such a polymerization initiator, a usual radical initiator can be used, but a water-soluble initiator is preferably employed, and specifically, a persulfate such as an ammonium persulfate, hydrogen peroxide or a mixture thereof with sodium hydrogen sulfite is used. , A redox initiator composed of a combination with a reducing agent such as sodium thiosulfate, and an inorganic initiator in which a small amount of iron, ferrous salt, silver sulfate, etc. coexist, or disuccinic peroxide, diglutaric acid Examples include dibasic acid peroxides such as peroxides, azobisisobutylamidine hydrochloride, and organic initiators such as azobisisobutyronitrile. The amount of the polymerization initiator used can be appropriately changed depending on the kind, emulsion polymerization conditions and the like, but is usually preferably about 0.005 to 0.5 part by weight per 100 parts by weight of the monomer to be emulsion-polymerized. Is done. Further, these polymerization initiators may be added all at once, or may be added in portions as needed.

For the purpose of adjusting the pH of the emulsion,
Adjusters may be used. Examples of such a pH adjuster include inorganic bases such as sodium carbonate, potassium carbonate, sodium hydrogen orthophosphate, sodium thiosulfate, and sodium tetraborate, and organic bases such as triethylamine, triethanolamine, dimethylethanolamine, and diethylethanolamine. Is exemplified. The amount of the pH adjuster is usually about 0.05 to 2 parts by weight, preferably about 0.1 to 2 parts by weight, per 100 parts by weight of the emulsion polymerization medium. A higher pH tends to increase the polymerization rate. The optimum value for the emulsion polymerization initiation temperature is appropriately selected according to the type of the polymerization initiator.
C., especially about 10 to 90 C. is preferably employed. The reaction pressure can be appropriately selected, but is usually 1 to 100 kg.
/ cm ² , particularly preferably about ² to 50 kg / cm ² .

In such a production method, an additive such as a monomer, water, an emulsifier, an initiator, etc. may be charged as it is and polymerized as it is. For the purpose of improving various physical properties such as gloss of the coating film, the emulsion may be pre-emulsified using a stirrer such as a homogenizer before the polymerization initiator is added, and then the initiator may be added for polymerization. Further, the monomers may be added in portions or continuously, and in that case, the monomer compositions may be different. The hydroxyl group-containing fluorine-based copolymer can be used alone or in combination of two or more.

The hydroxyl group-containing polymer obtained by the seed polymerization includes a core-shell type polymer in which the core is a fluorinated copolymer and the shell is a hydroxyl group-containing acrylic copolymer, and the core is an acrylic copolymer. And a core-shell polymer in which the shell portion is a hydroxyl group-containing fluorine-based copolymer. The monomers constituting these core-shell polymers are obtained from the various monomers described above, for example, hydroxyl-free acrylic monomers, hydroxyl-containing acrylic monomers, fluoroolefins, hydrophilic site-containing monomers, and the like. You can select and use.

The aqueous coating composition of the present invention contains a polyisocyanate compound in addition to the above-mentioned hydroxyl group-containing polymer. Suitable polyisosinate compounds include relatively low-viscosity polyisosinate compounds or self-emulsifying polyisosinate compounds. These are preferable because of their excellent dispersibility in water.

Examples of relatively low-viscosity polyisocyanate compounds include aliphatic polyisocyanate compounds such as hexamethylene diisocyanate. The polyisocyanate compound may be a dimer or a trimer depending on the buret type, isocyanurate ring type and uretdione type.
It may be a monomer. These polyisocyanate compounds are used by being mechanically dispersed in water, and a stable dispersion can be obtained by adding an emulsifier during this dispersion. As the emulsifier used here, known emulsifiers are used without any particular limitation. However, ionic ones, particularly those having an active hydrogen atom, react during dispersion to increase the viscosity or decrease the dispersibility. Not preferred. Nonionic emulsifiers, especially those having polyoxyethylene chains, are preferred.

The self-emulsifiable polyisocyanate compound is a compound which can be emulsified and dispersed in water without an emulsifier. As a specific example, a polyisocyanate compound obtained by reacting a polyoxyalkylene glycol with a polyoxyalkylene glycol is used. Examples thereof include polymers. Here, as the polyoxyalkylene glycol to be subjected to the reaction, those having a molecular weight of 200 to 4,000 are preferably used. Particularly preferably, it is in the range of 300 to 1,500. If the molecular weight is small, the self-emulsifying property is not sufficiently achieved, and if the molecular weight is large, the self-emulsifying property is good, but the stability in water is poor, and the crystallinity is high, so that the low-temperature Storage stability decreases and turbidity occurs. Further, the polyoxyalkylene glycol may be a monoalkyl ether. The polyoxyalkylene glycol in which all or most of the polyoxyalkylene chains are polyoxyethylene chains is preferable from the viewpoint of hydrophilicity.

The reaction between the polyisocyanate compound and the polyoxyalkylene glycol is carried out in the presence of a catalyst such as a tertiary amine, an alkyl-substituted ethyleneimine, a tertiary alkylphosphine, a metal alkylacetonate, or a metal salt of an organic acid. And optionally in the presence of a co-catalyst.
It can be performed at 0 ° C. or lower. In this reaction, it is preferable to adjust the amount of the remaining isocyanate groups to be 10 to 24% by weight. If the amount of the remaining isocyanate groups is small, the hydrophilicity of the water interface layer of the emulsified particles may increase, and the reactivity with the fluorine-based copolymer may decrease, which is not preferable. Further, since a large amount of polyisocyanate compound is required to achieve a sufficient degree of crosslinking, the weather resistance of the coating film may be adversely affected, which is not preferable. If the amount of the residual isocyanate groups is too large, the hydrophilicity of the water interface layer of the emulsified particles is insufficient, and it is difficult to form a stable emulsion. Such a self-emulsifying isocyanate compound is described in JP-B-4-15270.

The content ratio of the hydroxyl group-containing polymer to the polyisocyanate compound is not particularly limited, but the equivalent ratio of NCO group / OH group should be in the range of 0.1 to 2.0. Is preferred. If the corresponding ratio is too large, the isocyanate group may remain in the coating film or react with moisture to form bubbles, which may cause a coating film defect, which is not preferable. On the other hand, if the corresponding ratio is too small, the effect of crosslinking cannot be sufficiently obtained, which is not preferable. In particular, it is preferable that the corresponding ratio be in the range of 0.5 to 1.5.

The amino resin-based curing agent used in the water-based coating composition of the present invention functions as a co-crosslinking agent together with the polyisocyanate compound. At low temperatures, the isocyanate of the polyisocyanate compound is smaller than the hydroxyl group of the hydroxyl group-containing polymer. Reacts easily with groups. As the amino resin curing agent, melamine, urea, benzoguanamine, a compound having an amino group turned into methylol formaldehyde (-CH ₂ OH) in the molecule, such as acetoguanamine, turned into more ether alcohols (-CH ₂ OR) And the like. Specifically, butylated methylol melamine, methylol melamines etherified by lower alcohols such as methylated methylol melamine, epoxy-modified methylol melamine, methylated methylol urea,
Examples include alkylated methylol ureas such as ethylated methylol urea. These may be water-dispersible or water-soluble. The equivalent ratio between the NCO group of the polyisocyanate compound and the hydroxyl group of the amino resin-based curing agent is usually 0.95 to 0.6: 0.05 to 0.4.
It is good if it is between.

The pigment used in the aqueous coating composition of the present invention is covered with a compound film having a contact angle with water of 65 ° or more. Those covered with a compound film having a contact angle of 70 ° or more with water are preferable, and examples thereof include an acrylic resin and a fluororesin. Specific examples of the compound used for the compound film include a fluorine resin, a chlorinated rubber resin, an epoxy resin, a silicone resin, an acrylic resin, an acrylic silicone resin, and an inorganic paint. Further, the compound used for the compound film may be either a solvent type or an aqueous type. These compounds may or may not have a crosslinking site.

The pigment coated with the compound can be various pigments such as inorganic pigments and organic pigments. Specific examples of the inorganic pigments include titanium oxide, iron oxide, zinc white, and red iron oxide. Specific examples include azo pigments, phthalocyanine pigments, and nitroso pigments. The ratio of the coating compound to the pigment is not particularly limited as long as the surface of the pigment can be coated with the compound, but is usually 0.5 to 10 parts by weight based on 100 parts by weight of the pigment. The content of the compound-coated pigment may be generally 10 to 200 parts by weight, preferably 20 to 120 parts by weight, per 100 parts by weight of the hydroxyl group-containing polymer. Various methods can be applied to coat the pigment with the compound.For example, after dispersing the pigment in a compound solution obtained by dissolving the compound in a solvent, the solvent is skipped and dried, and pulverized as necessary. Method. The water-based coating composition of the present invention contains water. The amount of water may be appropriately selected according to the viscosity of the final composition, coating conditions, applications, and the like, but is usually preferably 50 to 150 parts by weight based on 100 parts by weight of the hydroxyl group-containing polymer. With respect to the method for preparing the aqueous coating composition of the present invention, there are the following methods. First, a method of adding a "polyisocyanate compound" and a "compound-coated pigment or amino resin-based curing agent" to a "hydroxyl group-containing polymer aqueous dispersion" and stirring the mixture. Second, a method of mechanically dispersing a polyisocyanate compound in water and then mixing "a hydroxyl group-containing polymer aqueous dispersion" and "a compound-coated pigment or amino resin-based curing agent". In any of the methods, the dispersing is preferably performed by dissolving the polyisocyanate compound in a suitable organic solvent (eg, methyl ethyl ketone, butyl carbitol acetate) and then mixing with or dispersing in an aqueous fluorocopolymer dispersion or water. Easy,
Further, the particle diameter of the polyisocyanate compound is small, which is preferable. A compound-coated pigment and an amino resin-based curing agent may be used in combination.

The composition for water-based paint of the present invention can be used as it is as a water-based paint, but if necessary, a film-forming aid, a plasticizer, an ultraviolet absorber, a leveling agent, an anti-cissing agent, a skin burr. Additives usually added to aqueous paints, such as inhibitors and pigment dispersants, may be mixed. Examples of the film-forming aid include polyhydric alcohol monoethers such as dipropylene glycol-n-butyl ether, tripropylene glycol-n-butyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monoethyl ether, and diethylene glycol monobutyl ether. Or organic acid esters thereof, 3-ethoxypropionate, and the like. Examples of the plasticizer include conventionally known plasticizers, for example, low molecular weight plasticizers such as dioctyl phthalate, and high molecular weight plasticizers such as vinyl polymer plasticizers and polyester plasticizers.

Further, a coloring agent other than the above-mentioned compound-coated pigment can be mixed with the aqueous coating composition of the present invention. Examples of the coloring agent include dyes, organic pigments, and inorganic pigments.
When the coating film is expected to have excellent weather resistance, it is preferable to use an inorganic pigment. Further, a metallic pigment such as an aluminum paste may be used. As a method for applying the aqueous coating composition of the present invention to an object to be coated, any method such as spray coating, dipping, a roll coater, and a flow coater can be applied. The thickness of the coating film to be formed may be appropriately selected depending on the application, but is usually 20 to 200 μm. The aqueous coating composition of the present invention can form a cured coating film on an object to be coated at a wide range of temperatures from low to high. Curing can be performed while drying. The curing temperature can be arbitrarily selected, for example, between 10 and 280 ° C., and the improvement effect as compared with the prior art is large when curing at a relatively low temperature, and greater when curing at a temperature of 100 ° C. or less. And especially in the case of curing at a temperature of 50 ° C. or lower. The composition of the present invention has good film-forming properties even at room temperature. The curing time may be appropriately selected. Also, the coating film is
Forced drying may be performed at a high temperature.

The aqueous coating composition of the present invention comprises an inorganic base material,
It can be applied to various substrates such as an organic substrate and an inorganic-organic composite substrate. As the inorganic substrate, for example, concrete, natural stone,
Examples include metals such as glass, iron, stainless aluminum, copper, brass, and titanium. In addition, examples of the organic substrate include a coating film, a plastic, a rubber, an adhesive, and wood that have already been formed. Examples of the inorganic-organic composite substrate include fiber-reinforced plastic, resin-reinforced concrete, and fiber-reinforced concrete. Further, specific examples of the coated article to which the aqueous coating composition of the present invention has been applied include automobiles, trains, vehicles, aircraft,
Bridge members, steel towers, tanks, pipes, building exterior panels, building exterior, doors, construction members, window gate members, road median strips, guardrails, road members, waterproof sheets, waterproof layers,
Monuments, poles, telecommunications equipment, electrical and electronic components and the like.

The water-based paint composition of the present invention is suitable for painting newly constructed articles such as construction articles, molded articles, installation articles and the like, and already painted articles such as construction articles, molding articles, installation articles and the like. When applying the aqueous coating composition of the present invention to the article to be coated, the surface is polished in advance, sanding,
It is preferable to perform a pretreatment usually used when applying an aqueous paint, such as a sealing treatment, a primer treatment, and application of a primer. An aqueous solution or an aqueous dispersion is preferable as the pore-treating agent, the primer, and the undercoating agent used here,
It may be an organic solvent solution or a non-aqueous dispersion. However, in consideration of the safety of the entire system, it is preferable to use an aqueous solution or an aqueous dispersion. In addition, as the primer or the undercoating agent, there are acrylic type, epoxy type and the like, and epoxy type is preferable because good adhesiveness can be achieved.

[0042]

The present invention will be described in detail with reference to the following synthesis examples and examples, but the present invention is not limited to these examples and the like. The number of parts in the following examples indicates parts by weight unless otherwise specified.

Synthesis Example In a stainless steel autoclave equipped with a stirrer, ethyl vinyl ether (EVE), cyclohexyl vinyl ether (CHVE), and a hydroxyl group-containing monomer (H
CVE, HNVE), macromonomer containing hydrophilic site (EOVE), ion-exchanged water, and potassium carbonate (K
₂ CO ₃ ) 0.22 parts, ammonium persulfate (APS)
0.07 parts, nonionic emulsifier (manufactured by Nippon Emulsifier: N-
1110, HLB value: 14), 3.1 parts, anionic emulsifier (manufactured by Nikko Chemical Co., SLS: 0.1 part) were charged, cooled with ice, and pressurized with nitrogen gas to 3.5 kg / cm ² to remove. I care. After repeating this pressurized degassing twice, degassing to 10 mmHg to remove dissolved air, chlorotrifluoroethylene (CTFE) was charged at a pressure of 3 kg / cm ² , and 12 The reaction was carried out for an hour to obtain a milky white aqueous dispersion of a hydroxyl group-containing copolymer. Table 1 shows the composition and properties of the obtained hydroxyl group-containing fluorocopolymer.

The macromonomer containing a hydrophilic moiety (EO)
The structures of VE) and the hydroxyl group-containing monomer are as follows. EOVE: CH ₂ = CHOCH ₂ -cycloC ₆ H ₁₀ -CH ₂ O (C ₂ H
_{4 O) n} H (average molecular weight _{830) HCVE: CH 2 = CHOC} H 2 -cyclo C 6 H 10 CH 2 OH HNVE: CH 2 = CHOC 9 H 18 OH CHMVOE: ethylene oxide against cyclohexanedimethanol ether 1 mol Compound with 20 moles added

[0045]

[Table 1] Resin liquid 5: Hydroxy group-containing acrylic resin liquid (manufactured by Dainippon Ink and Chemicals, Acridic) was evaporated to dryness, then taken in an emulsifier and dispersed in water (hydroxyl value: 48 mgKOH / g polymer).

Preparation of Compound-Coated Pigment Titanium oxide particles (CR-93, manufactured by Ishihara Sangyo Co., Ltd.) are immersed in a solution prepared by dissolving a compound shown in Table 2 below in a solvent, dried, re-dried, and pulverized. Then, the surfaces of the titanium oxide particles were coated with a compound. The ratio of the pigment to the compound in the compound-coated pigment is such that the compound is
Parts by weight.

[0047]

[Table 2]

Examples 1 to 5 Water-based paint compositions were prepared according to the composition shown in Table 3. In addition, the compounding was performed by first dispersing a self-emulsifying polyisocyanate compound (a compound obtained by adding polyethylene oxide to a trimer of hexamethylene diisocyanate) in water (a mixture of butyl carbitol acetate (BCA) and the self-emulsifying polyisocyanate compound). After that, the mixture was dispersed in water), and then the resulting dispersion was mixed with stirring in an aqueous dispersion of a hydroxyl group-containing fluorocopolymer, and the other additives were added in that order. Finally, 10 parts by weight of a methylolated miramin resin (Cymel 325, manufactured by Mitsui Toatsu Co., Ltd.) was uniformly mixed. Each aqueous paint composition was spray-coated at 20 ° C. on a slate plate coated with an acrylic emulsion undercoat material, dried at 20 ° C. for 8 hours, and cured to obtain a coating film (film thickness: 100 μm). Each of the following tests was performed. The results are shown in Table 4.

(1) Solvent resistance test: The state of the coating film was observed when the coating film was rubbed 200 times with gauze impregnated with methyl ethyl ketone. ○ indicates no change, △ indicates decrease in gloss, and × indicates that the coating film was melted. (2) Weather resistance test: The aqueous coating composition was applied to a slate plate and dried at room temperature for 24 hours. This test piece was subjected to an accelerated weather resistance test for 5000 hours with a sunshine weather o-meter. When the gloss retention after the test was 80% or more, it was evaluated as ○, and when less than 80%, it was evaluated as X. (3) Magic ink removal test: A straight line was drawn on the surface of the coating film with oil-based red magic, and after one hour, the state of the coating film was observed after the magic was wiped off with a gauze soaked with ethanol. ○ indicates no magic mark, Δ indicates slight mark, and X indicates a marked mark. (4) Foaming test: A 2 mm thick paint was poured into a 30 mm diameter petri dish, without wind, at 25 ° C. and 65 ° C. After 24 hours under the standard condition of% RH, the state of the coating film was confirmed, and the presence or absence of foaming was determined. (5) Appearance evaluation test of coating film: The surface condition of the coating film was visually observed.

Comparative Examples 1 and 2 In the same manner as in the examples, aqueous coating compositions were prepared according to the composition shown in Table 3. Instead of the compound-coated pigment in the examples, titanium oxide (CR-93, manufactured by Ishihara Sangyo Co., Pigment No .: 7) was used in Comparative Example 1, and titanium oxide (CR-93, manufactured by Ishihara Sangyo) was used in Comparative Example 2. -97, Pigment No .:
8) was used. Using the obtained aqueous coating composition, a coating film was obtained in the same manner as in the examples, and various tests were performed in the same manner as in the examples. Table 4 shows the test results.

[0051]

[Table 3]

Polyisocyanate compound 1: Self-emulsifying polyisocyanate compound (DC Nippon Polyurethane Co., Ltd.)
-3901 (NCO content: 12% by weight)) Polyisocyanate compound 2: Self-emulsifying polyisocyanate compound (DC-3900 manufactured by Nippon Polyurethane Co., Ltd.)
(NCO content 17% by weight)).

[0053]

[Table 4]

Examples 6 to 10 Water-based paint compositions were prepared according to the composition shown in Table 5. In addition, the compounding was performed by first dispersing a self-emulsifying polyisocyanate compound (a compound obtained by adding polyethylene oxide to a trimer of hexamethylene diisocyanate) in water (a mixture of butyl carbitol acetate (BCA) and the self-emulsifying polyisocyanate compound). After that, the mixture was dispersed in water), and then mixed with the aqueous dispersion of the fluorine-containing copolymer while stirring, and the other additives were added in this order. Finally, 4 parts by weight of a methylolated miramin resin (Cymel 325, manufactured by Mitsui Toatsu Co., Ltd.) was uniformly mixed. Each aqueous coating composition was spray-coated at 20 ° C on a slate plate coated with an acrylic emulsion undercoating material, cured at 40 ° C for 8 hours, and then dried at 90 ° C for 40 minutes to obtain a coating. Each of the above tests was performed on the film (film thickness: 100 μm). Table 6 shows the results.

Comparative Examples 3 and 4 In the same manner as in Examples, compositions for water-based paints were prepared according to the composition shown in Table 5. Comparative Example 1 and Comparative Example 2
Did not contain a melamine resin. Using the obtained aqueous coating composition, a coating film was obtained in the same manner as in the examples, and various tests were performed in the same manner as in the examples. Table 6 shows the test results.

[0056]

[Table 5]

Methylol melamine 1: manufactured by Mitsui Toatsu Co., Ltd., Cymel 325 methylol melamine 2: manufactured by Sanwa Chemical Co., Ltd., Niclac MX45 polyisocyanate compound 1: self-emulsifying polyisocyanate compound (manufactured by Nippon Polyurethane Co., DC-3901)
(NCO content: 12% by weight)) Polyisocyanate compound 2: Self-emulsifying polyisocyanate compound (DC-3900 manufactured by Nippon Polyurethane Co., Ltd.)
(NCO content 17% by weight)).

[0058]

[Table 6]

[0059]

The composition for water-based paints of the present invention is excellent in safety, excellent in film formation at a relatively low temperature, and has water resistance, blocking resistance, stain resistance, and chemical resistance. And a coating film whose appearance is not impaired by foaming can be provided.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4J034 DA01 DF11 DG02 DG03 DJ05 DP15 DP17 DP18 HA07 HB08 HC03 HC34 HC35 JA03 KB04 LA33 QA02 QC05 RA07 4J038 CD091 CE052 CG141 CH121 DA142 DA162 DA172 DG262 EA011 GA03 KA15 MA08 MA08

Claims (6)

[Claims] 1. An aqueous solution comprising a “hydroxyl group-containing polymer”, a “polyisocyanate compound”, and a “pigment or amino resin-based curing agent covered with a compound film having a contact angle to water of 65 ° or more”. Compositions for paints. 2. A polymer having a hydroxyl value of 2 mgK.
The aqueous coating composition according to claim 1, which is at least OH / g polymer. 3. The aqueous coating composition according to claim 1, wherein the hydroxyl group-containing polymer is a hydroxyl group-containing fluorine-based copolymer having a polymerization unit based on a fluoroolefin. 4. The hydroxyl group-containing polymer is a hydroxyl group-containing fluorine-containing copolymer having a polymerization unit based on a hydroxyalkyl ester of acrylic acid or methacrylic acid, a hydroxyalkyl vinyl ether or a hydroxyalkyl allyl ether. 4. The composition for a water-based paint according to any one of 3. 5. A polymer having a hydroxyl group-containing polymer having a polymerization unit based on a hydrophilic site-containing macromonomer in an amount of 0.1 to all polymerized units.
The aqueous coating composition according to any one of claims 1 to 4, which contains 1 to 25 mol%. 6. The polyisocyanate compound according to claim 1, wherein the polyisocyanate compound has a self-emulsifying property.
The composition for an aqueous paint according to any one of the above.