JP2003073611A - Water coating composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a water coating composition which is made by selectively using an acrylic monomer as a hydroxylated polymerizable vinyl monomer, of which the pot life can be definitely estimated, and which is excellent in weatherability, or solvent resistance, while suppressing an increase of viscosity of an acrylic emulsion. SOLUTION: This water coating composition comprises a combination of a liquid A comprising an acrylic emulsion with a liquid B comprising essentially a water-dispersible polyisocyanate, wherein the resin component of the liquid A contains a copolymer obtained by polymerizing a monomer mixture containing 5-30 wt.% of a hydroxylated polymerizable unsaturated monomer and 5-90 wt.% of a cycloalkyl polymerizable unsaturated monomer and wherein the ratio of the liquid A to the liquid B is to give an equivalent ratio of the isocyanato groups of the water-dispersible isocyanate to the hydroxyl groups of the hydroxylated polymerizable unsaturated monomer of (0.5 to 2.5):1.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an aqueous coating composition. More specifically, the present invention relates to various paints such as coatings for building exteriors, coatings for building materials, coatings for metals, coatings for plastics, coatings for heavy corrosion protection, coatings for waterproofing roofs and base coats for coating automobiles, woodworking, roofing waterproofing. for,
Various adhesives for floors and heavy vehicles, films,
The present invention relates to an aqueous coating composition that can be used as a coating agent for plastics, glass, paper, fibers, leather, and the like.

[0002]

2. Description of the Related Art Conventionally, various coating materials such as paints for building exteriors and paints for building materials, surface protective agents for structures, water resistance and weather resistance are used because of their advantages of no pollution and good workability during use. A water-based paint containing an aqueous resin dispersion as a main component has been used as a coating agent for a substrate having low property. In such applications, the coating film is exposed to wind and rain or sunlight for a long period of time, and therefore the coating film is required to have weather resistance and water resistance. Therefore, as a water-based paint having weather resistance and water resistance, various cross-linkable paint compositions utilizing a cross-linking reaction have been developed. For example, an example is an aqueous paint in which a polyol is used as a monomer constituting a resin component of an aqueous resin dispersion, and an isocyanate compound is combined with the polyol to cause a crosslinking reaction. However, these have problems that various physical properties of the coating film such as water resistance are not sufficient, and that the pot life is short and thus the working time after mixing them cannot be sufficiently taken during use.

As a solution to these problems, in JP-A-9-71720, a water-dispersed polyisocyanate composition comprising, as an isocyanate compound, a polyisocyanate into which a nonionic hydrophilic group is introduced and an ionic surfactant is used. Is proposed. In this publication, by combining this water-dispersed polyisocyanate composition with an aqueous polyol, the pot life is dramatically extended,
It is said that a coating film having excellent water resistance can be obtained. On the other hand, in JP-A-11-131016, a polyol emulsion having a specific monomer composition containing a hydroxyl group-containing polymerizable vinyl monomer is prepared by adding a nonionic hydrophilic group-introduced polyisocyanate with an ionic surfactant. It has been proposed to combine with a dispersed polyisocyanate composition. According to the publication, this combination makes it possible to prolong the pot life and obtain a coating film excellent in water resistance.

[0004]

However, all of the above-mentioned improved techniques exhibit an excellent prolonging effect in terms of pot life, but in the case of using these crosslinkable coating compositions, pot life is improved. It has a problem that it is very difficult to determine. That is, when the working time is prolonged or when a large amount of coating composition is prepared, etc., even though the crosslinking reaction or the like is already in a state of greatly progressing beyond the pot life, within the range of the pot life. In many cases, it is judged to be used and used, and as a result, the physical properties of the coating film obtained are inferior to those in the usual case.

As described above, in the above-mentioned conventional improved technique, there is a problem that the pot life is unclear so that the pot life is wastefully stored for a long time. Therefore, the problem to be solved by the present invention is to select an acrylic monomer as the hydroxyl group-containing polymerizable vinyl monomer, which can clearly identify the pot life, and also reduce the increase in the viscosity of the acrylic emulsion. It is an object of the present invention to provide a water-based coating composition which is excellent in weather resistance and solvent resistance.

[0006]

In order to solve the above-mentioned problems, the present inventor has conducted diligent studies to facilitate the subsequent pot life when the components contained in the water-based coating composition are actually mixed and used. As the evaluation criteria and means for making the judgment, it was thought that the judgment based on the change in the appearance was the most convenient means, and various assumptions were made, and the experiment was repeated. For example, it is possible to take out a part of the paint at the time of use and determine the pot life by some measuring means. However, if a part of the paint is taken out and measured each time it is used, an extra working time is spent. On the other hand, there is also a method of making a distinction by adding other components to the paint actually used. However, if done in this way, the physical properties of the coating film obtained may be affected.

Therefore, it seems that the simplest and most effective discrimination means is to make a change that can be easily confirmed in appearance as the pot life is exceeded, by devising the constitution of the coating composition itself. I thought that it would be a method that does not adversely affect the physical properties of the coating film. Based on this knowledge,
Regarding the components that can cause the appearance change,
Various studies were conducted to see if it could be included in advance. As a result, in a water-based coating agent composed of a combination of an acrylic emulsion and a water-dispersible polyisocyanate, if a polymerizable unsaturated monomer having a cycloalkyl group is used as a constituent component of the acrylic emulsion, this water-based coating agent can be used. In this case, the pot life can be easily and effectively discriminated by a remarkable increase in viscosity. Furthermore, if the polymerizable unsaturated monomer having the cycloalkyl group is contained, the acrylic emulsion can be obtained. It was also found that it is possible to obtain a product having excellent weather resistance and solvent resistance by reducing the increase in viscosity of No. 1, and it was confirmed that the above problems can be solved at once, and the present invention has been completed.

That is, the water-based coating composition according to the present invention comprises a combination of liquid A, which is an acrylic emulsion, and liquid B, which essentially contains a water-dispersible polyisocyanate. A copolymer obtained by polymerizing a monomer mixture containing 5 to 30% by weight of a polymerizable unsaturated monomer having a hydroxyl group and 5 to 90 parts by weight of a polymerizable unsaturated monomer having a cycloalkyl group. In addition, the mixing ratio of the liquid A and the liquid B is such that the equivalent ratio of the isocyanate group of the water-dispersible polyisocyanate to the hydroxyl group of the polymerizable unsaturated monomer having the hydroxyl group is 0.5 to 2.5. So that

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The water-based coating composition of the present invention is a combination of liquid A, which is an acrylic emulsion, and liquid B, which essentially contains a water-dispersible polyisocyanate. The liquid B and the liquid B will be described in detail first, and then the combination thereof will be described in detail. [Liquid A that is an acrylic emulsion] Liquid A is a copolymer obtained by polymerizing a monomer mixture containing a polymerizable unsaturated monomer having a hydroxyl group and a polymerizable unsaturated monomer having a cycloalkyl group. Is a water-based emulsion containing as a resin component.

The polymerizable unsaturated monomer having a hydroxyl group is a polymerizable unsaturated monomer having at least one hydroxyl group in the molecule. This hydroxyl group makes it possible to crosslink a polyol obtained by copolymerization using a polymerizable unsaturated monomer mixture with a crosslinking agent. By cross-linking the polyol, it is possible to improve the feel of the coating film, basic properties such as solvent resistance, chemical resistance, and gloss, and weather resistance. Specific examples of the polymerizable unsaturated monomer having a hydroxyl group include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate and 3
-Hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, methyl (α-hydroxymethyl) acrylate, ethyl (α-hydroxymethyl)
Acrylate, butyl (α-hydroxymethyl) acrylate, caprolactone-modified hydroxy (meth) acrylate (trade name: Praxel F series, manufactured by Daicel Chemical Industries, Ltd.), 4-hydroxymethylcyclohexylmethyl (meth) acrylate, ethylene glycol mono (meth) ) Acrylate, diethylene glycol mono (meth) acrylate, tetraethylene glycol mono (meth) acrylate, propylene glycol mono (meth)
Acrylate, dipropylene glycol mono (meth) acrylate, tetrapropylene glycol mono (meth)
Acrylate, 4-methylol cyclohexyl methyl acrylate (manufactured by Hitachi Chemical Co., Ltd., trade name: CHDMM)
Examples thereof include hydroxyl group-containing (meth) acrylates such as A), and among them, 2-hydroxyethyl (meth) acrylate and 2-hydroxypropyl (meth) acrylate are particularly preferable. These can be used alone,
You may use 2 or more types together.

The polymerizable unsaturated monomer having a hydroxyl group is A
It is necessary to contain 5 to 30% by weight, preferably 10 to 25% by weight, and more preferably 10 to 20% by weight of the total amount in the monomer mixture for forming the copolymer that is the resin component of the liquid. It is to contain by weight%. When the content is less than 5% by weight, the crosslink density is insufficient and the physical properties such as solvent resistance, chemical resistance and hardness expected by the crosslink are not improved,
When it exceeds 30% by weight, the amount of the water-soluble monomer is too large to make it difficult to form a high-molecular polymer by emulsion polymerization, and the amount of the water-soluble polymer that affects the decrease in water resistance increases.
In the present invention, the cycloalkyl group structure in the polymerizable unsaturated monomer having a cycloalkyl group specifically includes a cyclobutyl structure, a cyclopentyl structure, a cyclohexyl structure, a cycloheptyl structure, a cyclooctyl structure, a cyclononyl structure. , Cyclodecyl structure, cycloundecyl structure, cyclododecyl structure, cyclotridecyl structure, cyclotetradecyl structure, cyclopentadecyl structure, cyclohexadecyl structure, cycloheptadecyl structure, cyclooctadecyl structure and the like.

Therefore, as the polymerizable unsaturated monomer having a cycloalkyl group, cyclohexyl (meth) acrylate, methylcyclohexyl (meth) acrylate, tert-butylcyclohexyl (meth) acrylate, cyclooctyl (meth) acrylate, cyclo Dodecyl (meth) acrylate, isobornyl methacrylate (manufactured by Kyoeisha Chemical Co., Ltd., product name: light ester IB-
X), isobornyl acrylate (manufactured by Hitachi Chemical Co., Ltd.,
Product name: FA-544A; Kyoeisha Chemical Co., Ltd. product name: Light acrylate IB-XA), Dicyclopentanyl methacrylate (Hitachi Chemical Co., Ltd. product name: FA-51
3M), dicyclopentanyl acrylate (manufactured by Hitachi Chemical Co., Ltd., trade name: FA-513A), 4-methylolcyclohexylmethyl acrylate (manufactured by Hitachi Chemical Co., Ltd.,
Trade names: CHDMMA), 4-methylcyclohexylmethyl (meth) acrylate, cyclohexylmethyl (meth) acrylate and the like, among which, among others,
Cyclohexyl (meth) acrylate, 4-methylcyclohexylmethyl (meth) acrylate and cyclohexylmethyl (meth) acrylate are particularly preferred. These may be used alone or in combination of two or more.

The polymerizable unsaturated monomer having a cycloalkyl group is contained in the monomer mixture for forming the copolymer as the resin component of the liquid A in an amount of 5 to 90% by weight based on the whole amount. It is necessary, and is preferably 10 to 70% by weight, more preferably 30 to 60% by weight. When the content is less than 5% by weight, the viscosity of the emulsion is insufficiently lowered, and when it exceeds 90% by weight, the polymerization stability is lowered and the storage stability of the emulsion becomes poor. The monomer mixture for forming the copolymer, which is the resin component of the acrylic emulsion as the liquid A, contains a polymerizable unsaturated monomer having a glycidyl group, a polymerizable unsaturated monomer having an isocyanate group and an alkoxysilyl group. It may further contain at least one polymerizable unsaturated monomer selected from the group consisting of the polymerizable unsaturated monomers.

The polymerizable unsaturated monomer having a glycidyl group is not particularly limited, but specifically, for example, glycidyl (meth) acrylate, α-
Methyl glycidyl acrylate, glycidyl allyl ether, oxocyclohexylmethyl (meth) acrylate, 3,4-epoxycyclohexyl methyl acrylate (trade name CYCLOMER A200, manufactured by Daicel Chemical Industries, Ltd.), α-methyl glycidyl methacrylate (trade name M-GMA) , Manufactured by Daicel Chemical Industries, Ltd.,
Examples thereof include polymerizable unsaturated monomers having an epoxy group such as 3,4-epoxycyclohexylmethyl methacrylate (trade name CYCLOMER M100, manufactured by Daicel Chemical Industries, Ltd.).

The polymerizable unsaturated monomer having an isocyanate group is not particularly limited, but specifically, for example, 2-methacryloyloxyethyl isocyanate (trade name Karenz MOI, Showa Denko (Showa Denko) stock)
Made), metacloyl isocyanate (trade name MAI, manufactured by Nippon Paint Co., Ltd.), m-isopropenyl-α, α dimethylbenzyl isocyanate (trade name m-TMI, manufactured by Takeda Pharmaceutical Co., Ltd.) The polymerizable unsaturated monomer which it has can be mentioned. The polymerizable unsaturated monomer having an alkoxysilyl group,
Although not particularly limited, specifically, for example,
Following general formula ^{(1): (R 1)} n -Si- (R 2) 4-n (1) ( In the formula (1), R ¹ represents a radical polymerizable group, R ² represents a halogen hydrogen atom An atom, an alkoxy group, an acyloxy group, a phenoxy group, an aryloxy group, a mercapto group, an amino group, an amide group, an aminooxy group, an iminooxy group and an alkenyloxy group, and n is 1 to 1 It is an integer up to 3.) and a polymerizable unsaturated monomer having an alkoxysilyl group. The radically polymerizable group as R ¹ is not particularly limited, but examples thereof include at least one selected from an allyl group, a vinyl group, an acryloxyalkyl group, a methacryloxyalkyl group and the like.

The polymerizable unsaturated monomer having an alkoxysilyl group represented by the above general formula (1) can be hydrolyzed to form a silanol group, and the hydrolyzable silyl group itself is It can be incorporated as a constituent unit of the resin by directly covalently bonding to a carbon atom or covalently bonding to a carbon atom via a siloxane bond. The polymerizable unsaturated monomer having an alkoxysilyl group represented by the general formula (1) is not particularly limited, but specific examples thereof include γ-methacryloxypropyltrimethoxysilane and γ-methacryl silane. Roxypropyltriethoxysilane, γ-acryloxypropyltriethoxysilane, γ-methacryloxypropylmethyldiethoxysilane, γ-methacryloxypropylmethyldimethoxysilane, vinyltrimethoxysilane,
Vinyltriethoxysilane, vinylisopropoxysilane, vinylmethyldimethoxysilane, 2-trimethoxysilylethyl vinyl ether, 2- (methyldimethoxysilyl) propyl vinyl ether, 3-trimethoxysilylpropyl vinyl ether, 3-triethoxysilylpropyl vinyl ether, etc. Can be mentioned.

Use of a polymerizable unsaturated monomer having a functional group such as a glycidyl group, an isocyanate group and an alkoxysilyl group in the above-mentioned monomer mixture for forming a copolymer which is a resin component of the liquid A. Thus, the crosslinking reaction in the resin component of the aqueous emulsion can be promoted, the gel fraction of the resin component of the aqueous emulsion can be improved, and a coating film having excellent water resistance can be obtained. In the monomer mixture, a polymerizable unsaturated monomer having the glycidyl group, a polymerizable unsaturated monomer having an isocyanate group and a polymerizable unsaturated monomer having an alkoxysilyl group are selected from the group consisting of In the case of using at least one polymerizable unsaturated monomer, the total amount thereof is preferably 0.1 to 10% by weight based on the total amount of the monomer mixture,
It is more preferably 0.3 to 5% by weight, and even more preferably 0.5 to 2% by weight. The above content is 0.1% by weight
If it is less than 10% by weight, no improvement in the gel fraction is observed, and if it exceeds 10% by weight, the coating film becomes too hard.
Cracks and the like will occur during film formation and over time.

The monomer mixture for forming the copolymer which is the resin component of the acrylic emulsion as the liquid A is a UV-stable polymerizable unsaturated monomer and / or a UV-absorbing polymerizable unsaturated monomer. May be further included. Examples of the UV-stable polymerizable unsaturated monomer include 4- (meth) acryloyloxy-2,2,6,6-tetramethylpiperidine, 4- (meth) acryloylamino-2,
2,6,6-Tetramethylpiperidine, 4- (meth) acryloyloxy-1,2,2,6,6-pentamethylpiperidine, 4- (meth) acryloyloxy-1-methoxy-2,2,6 6-tetramethylpiperidine, 4
-Cyano-4- (meth) acryloyloxy-2,2
6,6-Tetramethylpiperidine, 1- (meth) acryloyl-4- (meth) acryloylamino-2,2,2
6,6-Tetramethylpiperidine, 4-crotonoylamino-2,2,6,6-tetramethylpiperidine, 4-
(Meth) acryloylamino-1,2,2,6,6-pentamethylpiperidine, 4-cyano-4- (meth) acryloylamino-2,2,6,6-tetramethylpiperidine, 4-crotonoyloxy- 2,2,6,6-tetramethylpiperidine, 1- (meth) acryloyl-4-
Cyano-4- (meth) acryloylamino-2,2
6,6-Tetramethylpiperidine, 1-crotonoyl-
4-crotonoyloxy-2,2,6,6-tetramethylpiperidine and the like can be mentioned, and among them, 4-
(Meth) acryloyloxy-2,2,6,6-tetramethylpiperidine, 4- (meth) acryloyloxy-
1,2,2,6,6-pentamethylpiperidine is particularly preferred.

Examples of the UV-absorbing polymerizable unsaturated monomer include 2- [2'-hydroxy-5 '-(methacryloyloxymethyl) phenyl] -2H-benzotriazole and 2- [2-hydroxy-5. -(Methacryloyloxyethyl) phenyl] -2H-1,2,3-benzotriazole, 2- [2'-hydroxy-5 '-(methacryloyloxymethyl) phenyl] -5-t-butyl-
2H-benzotriazole, 2- [2'-hydroxy-
5 '-(meth) acryloyloxyethylphenyl]-
2H-benzotriazole, 2- [2'-hydroxy-
5 '-(meth) acryloyloxypropylphenyl]
-2H-benzotriazole, 2- [2'-hydroxy-5 '-(meth) acryloyloxyhexylphenyl] -2H-benzotriazole, 2- [2'-hydroxy-3'-tert-butyl-5'-( (Meth) acryloyloxyethylphenyl] -2H-benzotriazole, 2- [2'-hydroxy-3'-tert-butyl-5 '-(meth) acryloyloxyethylphenyl] -5-chloro-2H-benzotriazole, 2 −
[2'-hydroxy-5'-tert-butyl-3'-
(Meth) acryloyloxyethylphenyl] -2H-
Benzotriazole, 2- [2'-hydroxy-5'-
(Meth) acryloyloxyethylphenyl] -5-chloro-2H-benzotriazole, 2- [2'-hydroxy-5 '-(meth) acryloyloxyethylphenyl] -5-methoxy-2H-benzotriazole, 2-
[2′-Hydroxy-5 ′-(meth) acryloyloxyethyl] phenyl] -5-cyano-2H-benzotriazole, 2- [2′-hydroxy-5 ′-(meth) acryloyloxyethylphenyl] -5 t-butyl-
2H-benzotriazole, 2- [2'-hydroxy-
5 '-(β-methacryloyloxyethoxy) -3'-
tert-Butylphenyl] -4-tert-butyl-
Benzotriazole-based polymerizable monomers such as 2H-benzotriazole; 2-hydroxy-4-methacryloxybenzophenone, 2-hydroxy-4- (2-hydroxy-3-metalloyloxy) propoxybenzophenone, 2-hydroxy-4- (2-methacryloxy) ethoxybenzophenone, 2-hydroxy-4-vinyloxycarbonylmethoxybenzophenone, 2-hydroxy-4- [3- (meth) acryloyloxy-2-hydroxypropoxy ] Benzophenone-based polymerizable monomers such as benzophenone; and the like, among which, among others,
Benzotriazole-based polymerizable monomers are particularly preferable.

When the UV stable polymerizable unsaturated monomer and / or the UV absorbing polymerizable unsaturated monomer are used in the monomer mixture, the total amount thereof is the above monomer. It is preferably 0.1 to 10% by weight, more preferably 0.2 to 5% by weight, still more preferably 0.5 to 4% by weight, based on the total amount of the mixture. When the content is less than 0.1% by weight, it is difficult to sufficiently exert the effect of improving the weather resistance, and when it exceeds 10% by weight, not only the cost increases but also the polymerization stability tends to decrease. The monomer mixture that forms the copolymer, which is the resin component of the acrylic emulsion as the liquid A, can be copolymerized with the polymerizable unsaturated monomers in addition to the various polymerizable unsaturated monomers. Other polymerizable unsaturated monomers may be included.

The above-mentioned other polymerizable unsaturated monomer is not particularly limited, but specifically, for example, ethyl (meth) acrylate, n-butyl methacrylate, s-butyl methacrylate and t- Of (meth) acrylic acid such as butyl (meth) acrylate such as butyl methacrylate, and 2-ethylhexyl (meth) acrylate, and having 1 to 18 carbon atoms (including aliphatic, alicyclic, and aromatic). (Meth) acrylic acid esters that are alcoholic esters; acrylic acid, methacrylic acid, maleic acid, fumaric acid, crotonic acid, itaconic acid, citraconic acid, maleic anhydride, monomethyl maleate, monobutyl maleate, monomethyl itaconate, Monobutyl itaconate, vinylbenzoic acid, monohydroxyethyl (meth) acrylate oxalate, dimethyl maleate, male Diethyl maleate, dibutyl maleate, dimethyl fumarate, diethyl fumarate, dibutyl fumarate, carboxy-terminated caprolactone modified acrylate (Plaxel FA series, manufactured by Daicel Chemical Industries, Ltd.), carboxyl-terminated caprolactone modified methacrylate (commodity) Famous Praxel FMA series,
Polymerizable unsaturated monomers having a carboxyl group such as manufactured by Daicel Chemical Industries, Ltd .; Polymerizable unsaturated monomer having an aziridinyl group such as acryloylaziridine and 2-aziridinylethyl (meth) acrylate. Polymers; polymerizable unsaturated monomers having an oxazoline group such as 2-isopropenyl-2-oxazoline and 2-vinyl-2-oxazoline;
(Meth) acrylamide, N-monoethyl (meth) acrylamide, N-monomethyl (meth) acrylamide,
Acrylamide derivatives such as N, N-dimethyl (meth) acrylamide, Nn-propyl (meth) acrylamide, N-isopropyl (meth) acrylamide, Nn-butyl (meth) acrylamide; (meth) acrylic acid dimethylamino Basic polymerizable unsaturated monomers such as ethyl, dimethylaminoethyl (meth) acrylamide, vinylpyridine, vinylimidazole, vinylpyrrolidone; cross-linking of N-methylol (meth) acrylamide, N-butoxymethyl (meth) acrylamide, etc. Sex (meta)
Examples thereof include acrylamides; styrene derivatives such as styrene, vinyltoluene, α-methylstyrene, chloromethylstyrene; and polymerizable unsaturated monomers having a cyano group such as (meth) acrylonitrile.

When the other polymerizable unsaturated monomer is used in the monomer mixture, the total amount thereof is preferably 5 to 90% by weight based on the total amount of the monomer mixture. The acrylic emulsion as the liquid A is preferably neutralized with a neutralizing agent in order to improve emulsion stability and pigment dispersion stability. The above-mentioned neutralizing agent is not particularly limited, and may be a conventionally known neutralizing agent used in neutralizing an acidic group,
Specifically, for example, alkali metal compounds such as sodium hydroxide and potassium hydroxide; alkaline earth metal compounds such as calcium hydroxide and calcium carbonate; ammonia; dimethylaminoethanol, monomethylamine, dimethylamine, trimethylamine, Monoethylamine,
Diethylamine, triethylamine, monopropylamine, dimethylpropylamine, monoethanolamine,
Water-soluble organic amines such as diethanolamine, triethanolamine, ethylenediamine, and diethylenetriamine; and the like. Among these, water resistance of a cured film coating in a paint containing a water-soluble resin dispersion that scatters at room temperature or under heating. Because it can prevent the deterioration of sex
Ammonia and tertiary amines such as dimethylaminoethanol, triethanolamine and trimethylamine are preferred, and low boiling amines such as ammonia, dimethylaminoethanol and trimethylamine are more preferred. These neutralizing agents may be used alone or in combination of two or more.

Regarding the above neutralization, it is preferable that the pH of the acrylic emulsion is 5 to 10, more preferably 6 to 9.5, and even more preferably p.
H is 7 to 9.5. In the above neutralization, when the pH is less than 5, the emulsion stability, pigment dispersibility, and mechanical stability are reduced, and when the pH is more than 10, the water resistance is reduced and the odor is generated. I have a problem. The A
The method for obtaining a liquid acrylic emulsion is not particularly limited, but various conventionally known emulsion polymerization methods in which polymerization is performed in the presence of an emulsifier can be adopted. For example, a method of performing polymerization by adding a polymerization initiator, an aqueous medium and an emulsifier all at once, and a polymerization method such as a so-called monomer dropping method and a pre-emulsion method can be mentioned. Further, for example, multi-stage polymerization such as seed polymerization, core-shell polymerization, power feed polymerization, etc. can be performed to realize the heterophase structure of the emulsion particles.

Examples of the emulsifier include anionic surfactants, nonionic surfactants, cationic surfactants, amphoteric surfactants, polymeric surfactants, and one or more polymerizable carbon-carbon molecules in the molecule. Preferable examples include polymerizable surfactants having an unsaturated bond. These may be used alone or in combination of two or more. The anionic surfactant is not particularly limited, but specifically, alkali metal alkyl sulfates such as sodium dodecyl sulfate and potassium dodecyl sulfate; ammonium alkyl sulfates such as ammonium dodecyl sulfate; sodium dodecyl. Polyglycol ether sulphate, sodium sulphosinoate, alkali metal salts of sulphonated paraffins; alkyl sulphonates such as ammonium salts of sulphonated paraffins; fatty acid salts such as sodium laurate, triethanolamine oleate, triethanolamine abietate, Alkylaryl sulfo such as sodium dodecyl benzene sulfonate, alkali metal sulfate of alkali phenol hydroxyethylene, etc. Over preparative like; higher alkyl naphthalene sulfonate, naphthalenesulfonic acid formalin condensates, dialkyl sulfosuccinate, polyoxyethylene alkyl sulfate salt, and preferably a polyoxyethylene alkylaryl sulfate salts.

The nonionic surfactant is not particularly limited, but specifically, polyoxyethylene alkyl ether, polyoxyethylene alkylaryl ether, sorbitan fatty acid ester, polyoxyethylene sorbitan fatty acid ester, Preferable examples include fatty acid monoglycerides such as glycerol monolaurate, polyoxyethyleneoxypropylene copolymers, condensation products of ethylene oxide with fatty acid amines, amides or acids. The cationic surfactant is not particularly limited, but specific examples thereof include alkylpyridinyl chloride and alkylammonium chloride.

The amphoteric surfactant is not particularly limited, but specifically, lauryl petaine, stearyl petaine, lauryl dimethylamine oxide and the like can be preferably mentioned. The polymer surfactant is not particularly limited, but specifically, polyvinyl alcohol, sodium poly (meth) acrylate, potassium poly (meth) acrylate, ammonium poly (meth) acrylate, Polyhydroxyethyl (meth) acrylate, polyhydroxypropyl (meth) acrylate, a copolymer of two or more kinds of polymerizable monomers that are the constitutional units of these polymers, or a copolymer with other monomers, Preferable examples include phase transfer catalysts of crown ethers.

The above-mentioned polymerizable surfactant is not particularly limited, but specifically, propenyl-2-
Anionic polymerizable surfactants such as sodium ethylhexylbenzene sulfosuccinate, sulfuric acid ester of (meth) acrylic acid polyoxyethylene, ammonium salt of polyoxyethylene alkylpropenyl ether sulfate, and phosphoric acid ester of (meth) acrylic acid polyoxyethylene ester. Preferable examples include nonionic polymerizable surfactants such as polyoxyethylene alkylbenzene ether (meth) acrylic acid ester and polyoxyethylene alkyl ether (meth) acrylic acid ester.

Amount of the above surfactants used (total amount used)
Is not particularly limited, and specifically, it is 0.5 to 0.5 with respect to the total weight of the unsaturated polymerizable monomer used.
It is preferably 10% by weight. The aqueous medium is not particularly limited, but specifically, water is usually used, and a hydrophilic solvent such as a lower alcohol or a ketone can be used in combination if necessary. The amount of the aqueous medium used is not particularly limited and may be appropriately set so that the solid content in the obtained acrylic emulsion becomes a desired content. The polymerization initiator is not particularly limited, but specifically,
For example, 2,2'-azobisisobutyronitrile, 2,
2'-azobis (2-amidinopropane) dihydrochloride,
Water-soluble azo compounds such as 4,4′-azobis (4-cyanopentanoic acid); Persulfates such as potassium persulfate; Peroxides such as hydrogen peroxide, peracetic acid, benzoyl peroxide, and di-t-butyl peroxide Oxide; and the like. These may be used alone or in combination of two or more. The amount of the polymerization initiator used is not particularly limited, but is preferably 0.01 to 1% by weight based on the total weight of the monomers. In order to accelerate the polymerization rate, or
In the case of polymerizing at a low temperature, a reducing agent such as sodium bisulfite, ferrous chloride, ascorbate and Rongalit may be combined.

To obtain the acrylic emulsion as the above-mentioned liquid A, if necessary, chain transfer of t-dodecyl mercaptan, n-octyl mercaptan, n-dodecyl mercaptan, mercaptoacetic acid, mercaptopropionic acid, 2-mercaptoethanol, etc. Agents can be used. In obtaining the acrylic emulsion as the liquid A, the polymerization temperature and the polymerization time are not particularly limited, but the polymerization temperature is preferably 0 to 100 ° C, more preferably 50 to 90 ° C, and the polymerization time is preferably 1 to 15 hours. . [Liquid B Indispensable for Water-Dispersible Polyisocyanate] As the water-dispersible polyisocyanate, a water-dispersible polyisocyanate having water solubility imparted by a polyethylene oxide chain is dispersed with an anionic or nonionic dispersant. The polyisocyanate of aliphatic or alicyclic type and a part of the isocyanate group of its derivative are represented by the following general formula (2): RO (CH ₂ CH ₂ O) _m —H (2) (In the formula (2), R is an alkyl group having 1 to 4 carbon atoms, and m is an integer of 2 to 20) and reacted with polyethylene oxide monoalkyl ether to give water. Those having dispersibility are preferable.

Examples of the aliphatic or alicyclic polyisocyanate include hexamethylene diisocyanate containing isocyanurate group, uretdione group, urethane group, allophanate group, biuret group and / or oxadiazine group or isophorone diisocyanate. More specifically, AQUANATE 100 (trade name) and AQUANATE 110 manufactured by Nippon Polyurethane Industry Co., Ltd.
(Trade name), Aquanate 200 (trade name) and Aquanate 210 (trade name), Sumitomo Bayer Urethane Co., Ltd. Vivijour TPLS-2032 (trade name), Sumitomo Bayer Urethane Co., Ltd. SUB-isocyanate-L801 (Trade name), Takenate WD-720 (trade name) and Takenate WD manufactured by Takeda Pharmaceutical Co., Ltd.
Examples include -725 (trade name), Staphyroid WD-220 (trade name) manufactured by Takeda Pharmaceutical Co., Ltd., and Resamine D-56 (trade name) manufactured by Dainichiseika Co., Ltd., and the like. These can be used alone or in combination.

The term "water dispersion" as used in the present invention means a state in which polyisocyanate is dispersed in water so as to be an O / W type,
It is prepared by adding polyisocyanate to water and mechanically stirring it with a stick or a hand mixer. The water-dispersible polyisocyanate used in the present invention can be used after adding an organic solvent. Polyisocyanate mixed with an organic solvent has a low viscosity, which improves water dispersibility,
Further, it has a feature that the residual rate of the isocyanate group at the time of water dispersion becomes high and the pot life becomes long.
In this case, the organic solvent needs to have no functional group that reacts with the isocyanate group. Further, the organic solvent needs to be compatible with the polyisocyanate of the present invention. [Water-Based Coating Composition] The water-based coating composition according to the present invention is a combination of the above-mentioned acrylic solution A and solution B, which essentially contains a water-dispersible polyisocyanate, in the following blending ratios.

The mixing ratio of liquid A and liquid B is such that the equivalent ratio of "isocyanate group in water-dispersed polyisocyanate" to "hydroxyl group of polymerizable unsaturated monomer having hydroxyl group contained in acrylic emulsion" is 0. It is necessary to be 0.5 to 2.5, preferably 0.8 to 2,
More preferably, it is 1.2 to 1.8. When the above blending ratio is such that the equivalent ratio is less than 0.5, the crosslink density is insufficient, and the expected physical properties such as solvent resistance, water resistance, and hardness become insufficient, so that it exceeds 2.5. When the above-mentioned mixing ratio, the isocyanate group becomes excessive more than necessary,
Reaction products other than the cross-linking reaction with the liquid A (reactions with water, for example) increase, which causes deterioration of physical properties.

When the solution A and the solution B are mixed and stirred to form an aqueous coating composition, the solution B produces polyisocyanate oil droplets. When this is applied, the oil droplets are destroyed by the energy of aggregation of the aqueous acrylic emulsion particles, the polyisocyanate penetrates between the aqueous emulsion particles and into the particles, and the isocyanate groups of the polyisocyanate and the surface of the aqueous acrylic emulsion particles and the inside of the particles. The hydroxyl groups of are reacted, the crosslinking reaction between particles and in the particles proceeds, and a tough coating film excellent in water resistance can be formed. The water-based coating composition according to the present invention contains, if necessary, a pigment, a dispersion stabilizer, a viscosity modifier, a leveling agent, a light stabilizer, an antioxidant, an ultraviolet absorber, a filler, a plasticizer, a lubricant, and a curing agent. Accelerating catalysts and the like can be added. The addition amount of these may be appropriately set within a range that does not impair the properties of the water-based coating agent of the present invention, and is not particularly limited. [Use and Use of Water-Based Coating Composition] The water-based coating composition according to the present invention is a combination of the liquid A and liquid B, but the form of the combination is not particularly limited. However, it is usually a two-liquid type in which both are mixed at the time of use.

The means for mixing the liquid A and the liquid B is not particularly limited, but a stirring means, a shaking means and the like which are usually used can be used, so long as they can be mixed uniformly. Good. For example, stirring means for mechanically stirring using a stirring rod, stirring means using a stirrer equipped with an impeller, stirring means using a magnetic stirrer, shaking means using a mechanical shaker, and the like can be mentioned. The use of the water-based coating composition according to the present invention is not particularly limited, but in addition to the coating composition, a coating composition in which a solvent-based polyurethane coating composition is used, particularly a coating composition for exterior repainting of buildings. Alternatively, automobile repair paints and plastic paints can be made water-based. Furthermore, sealing agents, adhesives, inks,
It can be applied to a wide range of fields such as coating materials, casting materials, elastomers, raw materials for foams and plastics, and fiber treatment agents.

[0035]

EXAMPLES The present invention will be described in more detail below with reference to examples, but the present invention is not limited thereto. In the following, "parts by weight" may be simply referred to as "parts" for convenience. First, the measuring methods used in the following examples and comparative examples are shown below. (Measurement of non-volatile content) About 1 g of sample is weighed and dried with a hot air dryer to obtain 10
After 5 ° C. × 1 hour, the remaining dry amount was regarded as the nonvolatile content, and the ratio to the weight before drying was expressed in wt%. (Emulsion viscosity) The viscosity was measured at 30 min ^-1 and 25 ° C with a BM type viscometer (manufactured by TOKIMEC). When measuring the viscosity, the rotor was selected according to the viscosity.

(Measurement of pH) The value at 25 ° C. was measured with a pH meter (F-23, manufactured by Horiba, Ltd.). -Example 1- (Preparation of acrylic emulsion) A dropping funnel, a stirrer,
A flask equipped with a nitrogen gas introduction tube, a thermometer and a reflux condenser was charged with 593 parts of water, and the temperature was raised to 70 ° C. with stirring while slowly blowing nitrogen gas. On the other hand, in a polymerizable monomer mixture consisting of 520 parts of cyclohexyl methacrylate, 310 parts of 2-ethylhexyl acrylate, 20 parts of acrylic acid, and 150 parts of hydroxyethyl methacrylate, 15% of Hitenol N-08 (Daiichi Kogyo Seiyaku Co., Ltd.) was added. 67 parts of an aqueous solution, 80 parts of a 25% aqueous solution of Nonipol 200 (manufactured by Sanyo Kasei Co., Ltd.), and 233 parts of water were added to prepare a pre-emulsion mixture. 5% by weight of this pre-emulsion mixture was added to the above flask and, after sufficiently replacing the atmosphere with nitrogen, 8.0 parts of a 5% aqueous solution of ammonium persulfate was added to initiate polymerization. After maintaining the inside of the reaction system at 70 ° C. for 10 minutes, the remaining pre-emulsion mixture and 72 parts of a 5% aqueous solution of ammonium persulfate were uniformly added dropwise over 180 minutes. During the dropping, the inside of the reaction system was maintained at 70 ° C., and after the dropping was completed, the mixture was aged at 70 ° C. for 60 minutes with stirring to complete the polymerization. Then, the reaction system was cooled, and at 60 ° C. or lower, 15 parts of 25% ammonia water as a neutralizing agent was added to give a nonvolatile content of 50% by weight, pH 8.2, and an emulsion viscosity of 600 mPa · s.
Of acrylic emulsion was prepared.

Nonvolatile content, pH of acrylic emulsion
The emulsion viscosity is shown in Table 3. (Water-dispersible polyisocyanate) 100% Bayhidur 3100 (manufactured by Sumitomo Bayer Urethane Co., Ltd.) was mixed with water in a weight ratio of 1/1, and stirred with a disper at 1000 rpm for 3 minutes to prepare 50% water. A dispersible polyisocyanate was prepared. (Preparation of coating composition) First, 150 parts by weight of the acrylic emulsion obtained as described above, 71.1 parts by weight of a dispersion paste (details will be described later), and CS-12 as a film forming aid.
(Cisso brand name) 9.8 parts by weight, Defoamer Nopco 8034L (San Nopco brand name) 0.8 parts by weight, Thickener 5% ADECANOL UH-420 (Asahi Denka Kogyo KK) Trade name) 4.0 parts by weight, deionized water 0.8
Parts by weight were mixed to form an acrylic emulsion mixture.

Next, the equivalent ratio (hereinafter sometimes simply referred to as "OH / NCO") of the hydroxyl group (-OH) in the acrylic emulsion and the isocyanate group (-NCO) in the water-dispersible polyisocyanate is 1. /1.5
The acrylic emulsion mixture and the 50% water-dispersible polyisocyanate were mixed so that Specifically, 157.7 parts by weight of the acrylic emulsion mixture and 43.2 parts by weight of the 50% water-dispersible polyisocyanate were mixed and stirred. In the following, the mixing amount of both is the acrylic emulsion mixture (parts by weight) / 50% water-dispersible polyisocyanate (parts by weight).
= A / B.

Thus, the coating composition of Example 1 (hereinafter referred to as coating (1)) was obtained. As the dispersion paste, 72.0 parts by weight of Demol EP (trade name of Kao Co.) as a dispersant, DISCOTE N-14 (trade name of Daiichi Kogyo Seiyaku Co., Ltd.) as a dispersant 60. 0 parts by weight, Emulge 909 (trade name of Kao Corporation) as a wetting agent, 12.0 parts by weight, ethylene glycol (manufactured by Nippon Shokubai Co., Ltd.) as a wetting agent, 72.0 parts by weight, Nopco 8034L ( Sannopco's trade name) 12.0 parts by weight, titanium oxide Taipek CR-95 (Ishihara Sangyo's trade name) 1200.0 parts by weight, deionized water 25
2 parts by weight of a mixture of 3000 parts by homodisper
The mixture was stirred at rpm for 60 minutes, and after stirring, the product obtained by further filtering with a 100-mesh wire net was used.

-Examples 2 to 8-Acrylic emulsions were prepared with the monomers, neutralizing agents and blending amounts shown in Table 1 and Table 2, and further OH /
The same operation as in Example 1 was carried out except that the coating composition was prepared by setting NCO and A / B as shown in the same table, and the coating compositions of Examples 2 to 8 (hereinafter, referred to as coating (2) ~ (8)
Called). The nonvolatile content, pH and emulsion viscosity of the acrylic emulsion are shown in Tables 3 and 4. -Comparative Examples 1-5-Acrylic emulsions were prepared with the monomers, neutralizing agents and blending amounts as shown in Table 5, and OH / NCO and A / B were shown in the same table to prepare coating compositions. The same operations as in Example 1 were carried out except that they were prepared, and Comparative Examples 1 to 5
The coating composition (hereinafter, referred to as comparative paints (1) to (5)) was obtained.

Table 6 shows the nonvolatile content, pH and emulsion viscosity of the acrylic emulsion.

[0042]

[Table 1]

[0043]

[Table 2]

[0044]

[Table 3]

[0045]

[Table 4]

[0046]

[Table 5]

[0047]

[Table 6]

The abbreviations in the table are as follows. HEMA: hydroxyethylmethacrylate AA: acrylic acid CHMA: cyclohexylmethacrylate GMA: glycidylmethacrylate mTMA: m-isopropenyl-α, α'-dimethylbenzylisocyanate A-174: γ-methacryloxypropyltrimethoxysilane LA-87: 2 2,4,4-Tetramethylpipedinyl methacrylate RUVA-93: 2- (2'-hydroxy-5'-methacryloxyethylphenyl) -2H-benzotriazole MMA: methyl methacrylate ST: styrene 2EHA: 2-ethylhexyl acrylate BA: butyl acrylate DMAE: dimethylaminoethanol With respect to the coating materials (1) to (8) and the comparative coating materials (1) to (5) thus obtained, coating film viscosity, coating appearance, solvent resistance, water resistance For and weather resistance were measured and evaluated by the following criteria. The results are shown in Tables 7-9.
(Note that in the following, paint preparation means, as described above,
It means that a coating composition is obtained by mixing and stirring an acrylic emulsion mixture and 50% water-dispersible polyisocyanate. (Paint viscosity) The paint was put in a 250 ml polypropylene container and the KU viscometer (manufactured by Brookfield, product name:
MODEL KU-1 VISCOMETER)
EBS UNIT was measured. Measurements were made 1 hour, 7 hours, and 24 hours after the paint was prepared.

(Coating appearance) The container was tilted to evaluate the fluidity. Evaluation was made 7 hours after the paint was prepared. No change: The same fluidity as in the initial stage of paint preparation is observed. Thickening: The fluidity is slightly lower than in the initial stage. High viscosity: A state in which the fluidity is greatly reduced compared to the initial stage. Gelation: There is no fluidity at all. (Solvent resistance) A coating was applied to an aluminum plate having a size of 7 cm x 15 cm with a 4 mil applicator at 1 hour and 7 hours after the coating was prepared, and then cured for 7 days to obtain a test plate. The state of the coating film after rubbing the test plate by hand with absorbent cotton impregnated with xylene 200 times (rubbed with xylene) was evaluated.

◯: No change X: There is a change in the coating film such as scratches and dissolution. (Water resistance) An aluminum plate having a size of 7 × 15 cm was coated with a 4 mil applicator at 1 hour and 7 hours after the coating was prepared, and then cured for 7 days to obtain a test plate. The test plate was subjected to a submersion test, and the swelling of the coating film after one day was observed. ○: No change. Δ: There is a little prestar.

X: There is swelling on the entire surface. (Weather resistance) The coating material was applied on a flexible board coated with a solvent-based sealer so that the dry film thickness was about 120 μm. After application, it was dried at 25 ° C. for 7 days, and this was used as a test piece. Using this test piece, Sunshine Weather Ometer (manufactured by Suga Test Instruments Co., Ltd., model:
The accelerated weather resistance test was performed by WEL-SUN-HCB), the gloss retention rate of the coating film after 2000 hours was calculated, and the change in the coating film was evaluated according to the following criteria.

[0052] ◯: Gloss maintenance rate is 80% or more. X: 80% or less of gloss maintenance rate.

[0053]

[Table 7]

[0054]

[Table 8]

[0055]

[Table 9]

[0056]

EFFECTS OF THE INVENTION According to the present invention, a water-based coating composition capable of clearly identifying the pot life, reducing the increase in the viscosity of the acrylic emulsion, and further excellent in weather resistance and solvent resistance is provided. can do.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Satoshi Shiraishi             5-8 Nishiomitabicho, Suita City, Osaka Prefecture             Within Nippon Shokubai F-term (reference) 4J038 CC061 CC062 CG141 CG142                       CG151 CG152 CG171 CG172                       CH031 CH032 CH041 CH042                       CH051 CH052 CH071 CH072                       CH081 CH082 CH121 CH122                       CH201 CH202 CJ031 CJ032                       CK021 CK022 DG131 DG132                       DG261 DG262 GA07 GA11                       GA15 JB02 JB09 LA02 NA03                       NA04 NA24 PB05 PC02 PC03                       PC06 PC08 PC10

Claims (5)

[Claims] 1. A combination of a liquid A which is an acrylic emulsion and a liquid B which essentially contains a water-dispersible polyisocyanate, wherein the liquid component A is a polymerizable unsaturated monomer having a hydroxyl group. 5 to 30% by weight, and a copolymer obtained by polymerizing a monomer mixture each containing 5 to 90 parts by weight of a polymerizable unsaturated monomer having a cycloalkyl group, and the solution A and B The mixing ratio of the liquid is such that the equivalent ratio of the isocyanate group of the water-dispersible polyisocyanate to the hydroxyl group of the polymerizable unsaturated monomer having a hydroxyl group is 0.5 to 2.
A water-based coating composition having the composition of No. 5. 2. The monomer mixture, wherein the polymerizable unsaturated monomer having a glycidyl group, the polymerizable unsaturated monomer having an isocyanate group and the following general formula (1): (R ¹ ) _n —Si -(R ² ) _4-n (1) (In the formula (1), R ¹ represents a radically polymerizable group, R ² represents a hydrogen atom halogen atom, an alkoxy group, an acyloxy group, a phenoxy group, an aryloxy group. , At least one selected from the group consisting of a mercapto group, an amino group, an amide group, an aminooxy group, an iminooxy group and an alkenyloxy group, and n is an integer from 1 to 3.). At least one selected from the group consisting of polymerizable unsaturated monomers having an alkoxysilyl group
The water-based coating composition according to claim 1, which is a mixture further containing one. 3. The monomer mixture according to claim 1, wherein the monomer mixture is a mixture further containing an ultraviolet stable polymerizable unsaturated monomer and / or an ultraviolet absorbing polymerizable unsaturated monomer. The water-based coating composition described. 4. The solution A is neutralized to pH 5 to 10 with ammonia and / or a tertiary amine compound,
The water-based coating composition according to any one of claims 1 to 3. 5. The water-based coating composition according to any one of claims 1 to 4, which is a coating composition.