JP5101747B1 - Two-component aqueous coating composition - Google Patents

Abstract

To provide an environmentally friendly aqueous two-component aqueous coating composition having excellent long-term storage stability and excellent initial water resistance and gloss of a coating film.
A two-component aqueous coating composition comprising: (A) an aqueous acrylic resin having a carboxyl group; and (B) a residue of a polyethylene glycol monoalkyl ether having an ethylene glycol repeating number q of 6 to 40; A carbodiimide compound having a polypropylene glycol monoalkyl ether residue having a polypropylene glycol repeating number r of 4 to 14, wherein the polyethylene glycol monoalkyl ether residue and the polypropylene glycol monoalkyl ether residue are Is a two-component water-based coating composition having a molar ratio of 1: 1 to 1:15.
[Selection figure] None

Description

  The present invention relates to a two-component aqueous coating composition containing a carbodiimide curing agent.

  In the field of paints, there have been many solvent-based paints so far, but from the viewpoint of environmental problems and the like, in recent years, water-based paints with a low content of organic solvents are being replaced. The water-based paint contains a water-soluble or water-dispersible resin, and after coating, forms a coating film by volatilization of a solvent component such as water.

  However, the resin of the water-based paint is provided with a hydrophilic functional group such as a carboxyl group in order to develop water solubility or water dispersibility. For this reason, there is a problem that a large amount of the hydrophilic functional group remains in the formed coating film, resulting in a decrease in water resistance of the coating film.

  Therefore, recently, an attempt has been made to improve the performance such as water resistance of the coating film by incorporating a compound having a carbodiimide group into a water-based paint as a curing agent, and eliminating the carboxyl group by the reaction between the group and the carboxyl group of the resin. (Patent Documents 1 to 4).

JP 2000-007642 A JP 2011-132374 A JP 2000-313825 A JP 2010-260001 A

However, when the water-based paints of Patent Documents 1 to 4 are used outdoors for painting large structures such as outer walls for houses, bridges, and industrial machinery, the initial water resistance after painting may not be sufficiently obtained. There is a new problem that the gloss cannot be sufficiently obtained. For details on the initial water resistance, the water-based paint is apparently dry in the initial stage after painting, but the curing reaction has not yet proceeded sufficiently and the initial water resistance is not sufficient. When exposed to rain shortly after the construction, there was a case where bulges were formed on a part of the coating film. Further, when the temperature is lowered, the elongation rate of the coating film is lowered, so that cracks may occur at the site where the swelling has occurred. Water-based paints that do not provide sufficient gloss have been difficult to use as top coats.
Furthermore, in the field of paints, long-term storage stability of the paints is required. However, there is a problem that when the aqueous paints are used after long-term storage, sufficient film performance cannot be obtained.

  Accordingly, an object of the present invention is to provide an environmentally friendly aqueous two-component coating composition that is excellent in long-term storage stability and excellent in initial water resistance and gloss of a coating film.

  As a result of intensive studies to achieve the above object, the present inventors have obtained a compound comprising a residue of polyethylene glycol monoalkyl ether (PEG part), a residue of polypropylene glycol monoalkyl ether (PPG part) and a carbodiimide part. The number average repeating number of ethylene glycol (EG) units in the PEG part and propylene glycol (PG) units in the PPG part is in a specific range, and the molar ratio of the PEG part to the PPG part in the compound is It has been found that the above object can be achieved by using a carbodiimide compound in a specific range as a curing agent in a two-component aqueous coating composition, and the present invention has been completed.

That is, the present invention is a two-component water-based paint composition,
(A) an aqueous acrylic resin having a carboxyl group;
(B) General formula (1):

｛式中、ｐは１〜５の整数を示し、２つのＲ^１は、独立して、一般式（２）：

{Wherein p represents an integer of 1 to 5 and two R ^{1 s} independently represent the general formula (2):

（式中、数平均繰り返し数ｑが６〜４０の範囲にあり、Ｒ^２は炭素数１〜８のアルキル基またはフェニル基を示す。）で表されるポリエチレングリコールモノアルキルエーテルの残基および／または一般式（３）：

(Wherein the number average repeating number q is in the range of 6 to 40, R ² represents an alkyl group having 1 to 8 carbon atoms or a phenyl group) and / or a residue of polyethylene glycol monoalkyl ether represented by Or general formula (3):

（式中、数平均繰り返し数ｒは４〜１４の範囲にあり、Ｒ^３は炭素数１〜８のアルキル基またはフェニル基を示す。）で表されるポリプロピレングリコールモノアルキルエーテルの残基である。｝で表されるカルボジイミド化合物と、
を含み、ここに、
一般式（１）中のＲ^１において、一般式（２）で表されるポリエチレングリコールモノアルキルエーテルの残基と一般式（３）で表されるポリプロピレングリコールモノアルキルエーテルの残基とのモル比率が、１：１〜１：１５である、２液型水性塗料組成物を提供する。

(Wherein the number average repeating number r is in the range of 4 to 14 and R ³ represents an alkyl group or phenyl group having 1 to 8 carbon atoms), and is a residue of a polypropylene glycol monoalkyl ether represented by . }, A carbodiimide compound represented by
Where
In R ¹ in the general formula (1), the molar ratio between the residue of the polyethylene glycol monoalkyl ether represented by the general formula (2) and the residue of the polypropylene glycol monoalkyl ether represented by the general formula (3) Provides a two-component water-based coating composition having a ratio of 1: 1 to 1:15.

  The two-component aqueous coating composition of the present invention comprises a PEG part, a PPG part, and a carbodiimide part as a curing agent, and the number average repeating number q of the EG unit of the PEG part is in the range of 6 to 40 in the structure. A carbodiimide compound in which the number average repeating number r of the PG units in the PPG part is in the range of 4 to 14 and the molar ratio of the PEG part to the PPG part is in the specific range of 1: 1 to 1:15 is used. Therefore, it is excellent in long-term storage and is excellent in the initial water resistance and gloss of the coating film.

Since the two-component aqueous coating composition of the present invention is also excellent in curing reactivity at low temperatures, a coating film having excellent initial water resistance can be formed in a relatively short time even when the curing temperature is relatively low. . For example, the aqueous coating composition of the present invention can be used and cured in a temperature environment of -10 to 50 ° C., and the curing reaction can proceed effectively within a few hours. An excellent coating film can be formed.
Since the two-component aqueous coating composition of the present invention also relates to an aqueous coating, the content of the organic solvent can be effectively reduced. For this reason, the amount of volatile organic compounds and the amount of environmental pollutants based on the PRTR Law (Act on the Promotion of Improvement in Management and Management of Specific Chemical Substances to the Environment) Compared to this, it can be greatly reduced.

  Hereinafter, the present invention will be described in detail with reference to preferred embodiments thereof.

The two-component aqueous coating composition of the present invention is
(A) an aqueous acrylic resin having a carboxyl group;
(B) General formula (1):

で表されるカルボジイミド化合物と、を含む。

The carbodiimide compound represented by these.

  In the present invention, (A) a water-based acrylic resin having a carboxyl group is preferably used as the coating film-forming resin, and α, β-ethylenically unsaturated monomers having a carboxyl group and other α, β-ethylenically unsaturated monomers are used. It is an acrylic resin obtained by copolymerizing a saturated monomer. (A) As an aqueous acrylic resin having a carboxyl group, an aqueous dispersion acrylic resin having a carboxyl group is more preferably used. One method for obtaining an aqueous dispersion acrylic resin having a carboxyl group is an acrylic emulsion, which can be prepared by carrying out emulsion polymerization in an aqueous medium.

  As an α, β-ethylenically unsaturated monomer having a carboxyl group, acrylic acid, methacrylic acid, acrylic acid dimer, crotonic acid, 2-acryloyloxyethylphthalic acid, 2-acryloyloxyethyl succinic acid, ω-carboxy- Polycaprolactone mono (meth) acrylate, isocrotonic acid, α-hydro-ω-((1-oxo-2-propenyl) oxy) poly (oxy (1-oxo-1,6-hexanediyl)), maleic acid, fumarate An acid, itaconic acid, etc. can be mentioned. Among these, acrylic acid and methacrylic acid are preferable. In this specification, “(meth) acryl” means both acrylic and methacrylic.

  Examples of the other α, β-ethylenically unsaturated monomers include (meth) acrylate esters (for example, methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, (meth) acrylic). N-butyl acid, isobutyl (meth) acrylate, t-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, lauryl methacrylate, phenyl acrylate, isobornyl (meth) acrylate, cyclohexyl methacrylate, ( (Meth) acrylic acid t-butylcyclohexyl, (meth) acrylic acid dicyclopentadienyl, (meth) acrylic acid dihydrodicyclopentadienyl, etc.), polymerizable amide compounds (for example, (meth) acrylamide, N-methylol ( (Meth) acrylamide, N-butoxymethyl (meth) acrylic N, N-dimethyl (meth) acrylamide, N, N-dibutyl (meth) acrylamide, N, N-dioctyl (meth) acrylamide, N-monobutyl (meth) acrylamide, N-monooctyl (meth) acrylamide 2, 4-dihydroxy-4′-vinylbenzophenone, N- (2-hydroxyethyl) acrylamide, N- (2-hydroxyethyl) methacrylamide, etc.), polymerizable aromatic compounds (for example, styrene, α-methylstyrene, vinyl ketone, t-butylstyrene, parachlorostyrene, vinylnaphthalene, etc.), polymerizable nitriles (eg, acrylonitrile, methacrylonitrile, etc.), α-olefins (eg, ethylene, propylene, etc.), vinyl esters (eg, vinyl acetate, propionic acid) Vinyl), dienes (For example, butadiene, isoprene, etc.), polymerizable aromatic compounds, polymerizable nitriles, α-olefins, vinyl esters, and dienes can be mentioned. These can be selected according to the purpose.

  (A) In preparation of the aqueous acrylic resin having a carboxyl group, an α, β-ethylenically unsaturated monomer having a hydroxyl group may be used as necessary. Examples of the α, β-ethylenically unsaturated monomer having a hydroxyl group include hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, hydroxybutyl (meth) acrylate, allyl alcohol, methacryl alcohol, and (meth) acrylic acid. Mention may be made of adducts of hydroxyethyl and ε-caprolactone. Among these, preferred are hydroxyethyl (meth) acrylate, hydroxybutyl (meth) acrylate, and an adduct of hydroxyethyl (meth) acrylate and ε-caprolactone.

  In preparing an acrylic emulsion having a carboxyl group by emulsion polymerization, a crosslinkable monomer can be used as the other α, β-ethylenically unsaturated monomer. The crosslinkable monomer is a compound having two or more radically polymerizable ethylenically unsaturated groups in the molecule. For example, divinylbenzene, ethylene glycol di (meth) acrylate, hexanediol di (meth) acrylate, polyethylene Glycol di (meth) acrylate, allyl (meth) acrylate, 1,4-butanediol di (meth) acrylate, 1,6-hexane di (meth) acrylate, neopentyl glycol di (meth) acrylate, pentaerythritol di (meth) Examples include divinyl compounds such as acrylate, and examples include triallyl cyanurate, pentaerythritol tri (meth) acrylate, trimethylolpropane tri (meth) acrylate, and dipentaerythritol hexa (meth) acrylate. The crosslinkable monomer may be a combination of the above monomers. Allyl (meth) acrylate, ethylene glycol di (meth) acrylate and divinylbenzene, which are relatively easy to handle, are preferred.

  In the preparation of an acrylic emulsion having a carboxyl group, emulsion polymerization in an aqueous medium is performed by, for example, dissolving an emulsifier in an aqueous medium containing water or a hydrophilic organic solvent such as alcohol or glycol as necessary. It can be performed by adding dropwise a mixture of an α, β-ethylenically unsaturated monomer used as a raw material and a polymerization initiator under heating and stirring. What mixed the (alpha), (beta) -ethylenically unsaturated monomer used as a raw material may be previously emulsified using an emulsifier and water.

  Examples of the polymerization initiator that can be suitably used for emulsion polymerization include azo oily compounds (for example, azobisisobutyronitrile, 2,2′-azobis (2-methylbutyronitrile), and 2,2′- Azobis (2,4-dimethylvaleronitrile) and the like, and aqueous compounds (for example, anionic 4,4′-azobis (4-cyanovaleric acid), 2,2-azobis (N- (2-carboxyethyl)) -2-methylpropionamidine and cationic 2,2′-azobis (2-methylpropionamidine)); and redox oily peroxides (eg, benzoyl peroxide, parachlorobenzoyl peroxide, lauroyl peroxide and t-butyl perbenzoate), and aqueous peroxides such as potassium persulfate and persulfate Ammonium and the like).

  As the emulsifier, those usually used by those skilled in the art can be used. As an emulsifier to be used, a reactive emulsifier, for example, Antox MS-60 (manufactured by Nippon Emulsifier Co., Ltd.), Eleminol JS-2 (manufactured by Sanyo Kasei Kogyo Co., Ltd.), Adekari Soap NE-20 (manufactured by Asahi Denka Co., Ltd.) And Aqualon HS-10 (Daiichi Kogyo Seiyaku Co., Ltd.) are particularly preferred. In order to adjust the molecular weight, a mercaptan such as lauryl mercaptan and a chain transfer agent such as α-methylstyrene dimer can be used as necessary.

  The reaction temperature is determined by the initiator, and for example, it is preferably 60 to 90 ° C. for an azo initiator and 30 to 70 ° C. for a redox system. In general, the reaction time is 1 to 8 hours. The amount of the initiator relative to the total amount of the monomer mixture is generally 0.1 to 5% by mass, preferably 0.2 to 2% by mass. The emulsion polymerization can be performed in multiple stages, for example, in two stages. That is, first, a part of the mixture of α, β-ethylenically unsaturated monomers used as the raw material is subjected to emulsion polymerization, and the remainder of the α, β-ethylenically unsaturated monomer mixture is further added to emulsify. Polymerization is performed.

  The acrylic emulsion thus obtained can be suitably used as the above (A) aqueous acrylic resin having a carboxyl group. The volume average particle diameter of the emulsion is preferably in the range of 0.01 to 1.0 μm. When the volume average particle diameter is less than 0.01 μm, workability may be reduced, and when it exceeds 1.0 μm, the appearance of the obtained coating film may be deteriorated. The volume average particle diameter can be adjusted, for example, by adjusting the monomer composition and emulsion polymerization conditions. The volume average particle diameter can be measured by a laser light scattering method.

  The said emulsion can be used by pH 5-10 by neutralizing with a basic compound from a storage-stable viewpoint. The basic compounds are ammonia, methylamine, ethylamine, dimethylamine, diethylamine, trimethylamine, triethylamine, dimethylethanolamine, diethanolamine, diethylaminoethanol, triethanolamine, tetraethylammonium hydroxide, propylamine, dipropylamine, tripropylamine. Butylamine, dibutylamine, tributylamine and the like. The neutralization is preferably performed by adding the basic compound to the system before or after emulsion polymerization.

  As a method of obtaining an aqueous dispersion acrylic resin other than the acrylic emulsion, there is a method of obtaining a resin dispersion (acrylic dispersion) in water after obtaining an acrylic resin by solution polymerization. The acrylic dispersion first comprises an α, β-ethylenically unsaturated monomer having an acid group as described above in the α, β-ethylenically unsaturated monomer mixture, and other α, β-ethylenically unsaturated monomers. An acrylic dispersion can be obtained by performing solution polymerization with a saturated monomer and then neutralizing with a basic compound.

  The solution polymerization is generally a method in which a mixture of the α, β-ethylenically unsaturated monomer used as a raw material is stirred while being dropped into a solvent together with a polymerization initiator under heating conditions. The conditions for solution polymerization are, for example, a polymerization temperature of 60 to 160 ° C. and a dropping time of 0.5 to 10 hours. The α, β-ethylenically unsaturated monomer used as the raw material can be polymerized in two stages. In this case, it is only necessary that the α, β-ethylenically unsaturated monomer used as a raw material satisfies the requirements for the carboxyl group.

  The polymerization initiator is not particularly limited as long as it is used for normal polymerization, and examples thereof include azo compounds and peroxides. Generally, the amount of the polymerization initiator with respect to 100 parts by mass of the monomer mixture is 0.1 to 18 parts by mass, preferably 0.3 to 12 parts by mass.

  Moreover, the solvent which can be used here will not be specifically limited if it does not have a bad influence on reaction, For example, alcohol, a ketone, ether, a hydrocarbon solvent, etc. are mentioned. Further, in order to adjust the molecular weight, a mercaptan such as lauryl mercaptan and a chain transfer agent such as α-methylstyrene dimer can be used as necessary.

  Thus, the number average molecular weight of the acrylic resin obtained by solution polymerization is preferably 4,000 to 20,000. In this specification, the number average molecular weight of the acrylic resin obtained by solution polymerization can be measured by gel permeation chromatography (GPC) using a polystyrene standard sample standard.

  The acrylic resin obtained by the solution polymerization, after removing the solvent as necessary, is neutralized by adding a basic compound to obtain an aqueous acrylic resin having the carboxyl group (A). It is done. Examples of the basic compound include the basic compounds listed above. The amount of the basic compound added is preferably a neutralization rate of 60 to 100% of the carboxyl group of the acrylic resin obtained by the solution polymerization. If the neutralization rate is less than 60%, the aqueous solution is not sufficient and the storage stability may be poor.

  The acrylic resin thus obtained can be used as an aqueous dispersion acrylic resin. Such an aqueous dispersion acrylic resin preferably has a volume average particle diameter in the range of 0.01 to 1 μm. When the volume average particle diameter is in the above range, there is an advantage that the stability of the aqueous dispersion is improved and the appearance of the obtained coating film is improved.

  The aqueous dispersion acrylic resin having a carboxyl group has a resin solid content acid value of preferably 3 to 30 mg / KOH, more preferably 5 to 25 mg / KOH. When the resin solid acid value is larger than 30 mg / KOH, the water resistance of the coating film is lowered, and when it is smaller than 3 mg / KOH, the mechanical stability of the aqueous dispersion of the resin is lowered.

  (A) The aqueous acrylic resin having a carboxyl group may further contain a water-soluble acrylic resin in order to increase gloss. This water-soluble acrylic resin has an α, β-ethylenically unsaturated monomer having an acid group described in the above α, β-ethylenically unsaturated monomer mixture as an essential component, and other α, β-ethylenic monomers. It can be obtained by performing solution polymerization together with an unsaturated monomer.

  The water-soluble acrylic resin is neutralized with a basic compound such as monomethylamine, dimethylamine, trimethylamine, triethylamine, diisopropylamine, monoethanolamine, diethanolamine and dimethylethanolamine and dissolved in water. Can be used.

  In the water-soluble acrylic resin, the acid value of the resin solid content is preferably 35 to 100 mg / KOH, more preferably 40 to 80 mg / KOH. When the resin solid content acid value is larger than 100 mg / KOH, the water resistance of the coating film is lowered, and when it is smaller than 35 mg / KOH, water-solubilization of the resin becomes insufficient. The number average molecular weight is preferably 4,000 to 20,000. When the number average molecular weight is more than 20,000, the viscosity of the coating becomes too high, and when it is less than 4,000, the water resistance of the coating film is lowered.

  The mass ratio (water dispersibility: water solubility) of the resin solid content of the aqueous acrylic resin contained in the paint is preferably 2: 1 to 10: 1 from the viewpoint of further improving the gloss of the coating film.

  In the present invention, (B) general formula (1):

で表されるカルボジイミド化合物として好適に用いることができる化合物は、一般式（４）：

The compound that can be suitably used as the carbodiimide compound represented by the general formula (4):

で表される４,４−ジシクロヘキシルメタンジイソシアネートの脱二酸化炭素を伴う縮合反応により、一般式（５）：

By a condensation reaction involving decarbonization of 4,4-dicyclohexylmethane diisocyanate represented by the general formula (5):

（式中、ｐは１〜５の整数を示す。）で表されるイソシアネート末端ジシクロヘキシルメタンカルボジイミドを合成し、更にこのイソシアネート末端ジシクロヘキシルメタンカルボジイミドと、ポリエチレングリコールモノアルキルエーテルおよびポリプロピレングリコールモノアルキルエーテルとの混合物を反応させることにより製造することができる。

(Wherein p represents an integer of 1 to 5), and an isocyanate-terminated dicyclohexylmethane carbodiimide represented by the following formula is further synthesized with polyethylene glycol monoalkyl ether and polypropylene glycol monoalkyl ether: It can be produced by reacting the mixture.

  The above-mentioned isocyanate-terminated dicyclohexylmethane carbodiimide is basically produced by a conventional carbodiimide production method (US Pat. No. 2,941,956, Japanese Patent Publication No. 47-33279, J. Org. Chem., 28, 2069-2076 (1963), Chemical Review 1981, vol. 81, No. 4, 619-4, 621).

  The condensation reaction involving decarbonization of the dicyclohexylmethane diisocyanate proceeds in the presence of a carbodiimidization catalyst. Examples of the catalyst include 1-phenyl-2-phospholene-1-oxide, 3-methyl- 2-phospholene-1-oxide, 1-ethyl-2-phospholene-1-oxide, 1-ethyl-3-methyl-2-phospholene-1-oxide, 3-methyl-1-phenyl-2-phospholene-1-oxide Alternatively, phospholene oxides such as these 3-phospholene isomers can be used, and in terms of reactivity, the general formula (6):

で表される３−メチル−１−フェニル−２−ホスホレン−１−オキシドが好適である。

3-methyl-1-phenyl-2-phospholene-1-oxide represented by the formula is preferred.

  In addition, the reaction temperature in the condensation reaction is preferably in the range of 80 ° C. to 180 ° C. When the reaction temperature falls below this range, the reaction time becomes extremely long, and when the reaction temperature exceeds the above range, Since the reaction occurs, a high-quality carbodiimide cannot be obtained, which is not preferable in any case.

  Further, the degree of condensation is preferably 1 to 5, and when the degree of condensation exceeds 5, the dispersibility when adding aqueous dicyclohexylmethane carbodiimide to the aqueous resin is lowered, and the aqueous dicyclohexylmethane carbodiimide is previously dispersed in an aqueous solution or water. In the case of a liquid, a good aqueous solution or aqueous dispersion cannot be obtained due to low dispersibility. In order to complete the reaction promptly, the reaction of 4,4'-dicyclohexylmethane diisocyanate is preferably performed under an inert gas stream such as nitrogen.

  The aqueous dicyclohexylmethane carbodiimide of the present invention can be isolated from the reaction system according to a usual method, and the structure represented by the general formula (1) is that an infrared absorption (IR) spectrum and a nuclear magnetic resonance absorption ( NMR) supported by spectra.

Two R ^{1 s in} the general formula (1) of the carbodiimide compound of the present invention independently represent the general formula (2):

（式中、ＥＧ単位の数平均繰り返し数ｑが６〜４０の範囲にあり、Ｒ^２は炭素数１〜８のアルキル基またはフェニル基を示す。）で表されるＰＥＧ部および／または一般式（３）：

(Wherein the number average repeating number q of the EG unit is in the range of 6 to 40, and R ² represents an alkyl group having 1 to 8 carbon atoms or a phenyl group) and / or the general formula (3):

（式中、ＰＧ単位の数平均繰り返し数ｒは４〜１４の範囲にあり、Ｒ^３は炭素数１〜８のアルキル基またはフェニル基を示す。）で表されるＰＰＧ部である。すなわち、本発明のカルボジイミド化合物は、一般式（１）中の２つのＲ^１がそれぞれ一般式（２）および一般式（３）で表される残基である場合や２つのＲ^１がいずれも一般式（２）または一般式（３）で表される残基であるものを含む。具体的には、本発明のカルボジイミド化合物は全体としてＰＥＧ部：ＰＰＧ部が後述する範囲を満たす範囲内で、以下に示すカルボジイミド化合物（１Ａ）〜（１Ｃ）を含む；
（１Ａ）一般式（１）中の２つのＲ^１のうちの一方が一般式（２）で表される残基であり、他方が一般式（３）で表される残基である化合物；
（１Ｂ）一般式（１）中の２つのＲ^１のうちの両方が一般式（２）で表される残基である化合物；および
（１Ｃ）一般式（１）中の２つのＲ^１のうちの両方が一般式（３）で表される残基である化合物。

(Wherein the number average repeating number r of PG units is in the range of 4 to 14, and R ³ represents an alkyl group or phenyl group having 1 to 8 carbon atoms). That is, the carbodiimide compound of the present invention, even the general formula (1) two of R ¹ each formula in (2) and the general formula (3) is a residue or two of R ¹ which is expressed by any What is a residue represented by General formula (2) or General formula (3) is included. Specifically, the carbodiimide compound of the present invention includes the following carbodiimide compounds (1A) to (1C) within the range where the PEG part: PPG part satisfies the range described later;
(1A) a residue Formula (1) one of the two R ¹ in the formula (2), the compound is a residue other is represented by formula (3);
(1B) a compound in which both of two R ^{1 in} the general formula (1) are residues represented by the general formula (2); and (1C) two R ^{1 in} the general formula (1) The compound whose both are residues represented by General formula (3).

  The polyethylene glycol monoalkyl ether that can be used to form the residue represented by the general formula (2), which is the PEG portion of the carbodiimide compound of the present invention, has the general formula (7):

（式中、数平均繰り返し数ｑが６〜４０の範囲にあり、Ｒ^２は炭素数１〜８のアルキル基またはフェニル基を示す。）で表され、具体的にはポリ（エチレングリコール）モノメチルエーテル、ポリ（エチレングリコール）モノエチルエーテル、ポリ（エチレングリコール）モノプロピルエーテル、ポリ（エチレングリコール）モノブチルエーテル、ポリ（エチレングリコール）モノフェニルエーテル、等を挙げることができ、特にポリ（エチレングリコール）モノメチルエーテルが好適である。

(Wherein the number average repeating number q is in the range of 6 to 40, R ² represents an alkyl group having 1 to 8 carbon atoms or a phenyl group), specifically, poly (ethylene glycol) monomethyl Ethers, poly (ethylene glycol) monoethyl ether, poly (ethylene glycol) monopropyl ether, poly (ethylene glycol) monobutyl ether, poly (ethylene glycol) monophenyl ether, and the like, especially poly (ethylene glycol) Monomethyl ether is preferred.

  The number average repeating number q of EG units in the PEG portion is preferably in the range of 6 to 40, and more preferably in the range of 10 to 35. When q is less than 6, hydrophilicity cannot be imparted and water dispersibility is poor. Moreover, when q exceeds 40, it is inferior to water resistance.

  The polypropylene glycol monoalkyl ether that can be used to form the residue represented by the general formula (3), which is the PPG part of the carbodiimide compound of the present invention, has the general formula (8):

（式中、数平均繰り返し数ｒは４〜１４の範囲にあり、Ｒ^３は炭素数１〜８のアルキル基またはフェニル基を示す。）で表され、具体的にはポリ（プロピレングリコール）モノメチルエーテル、ポリ（プロピレングリコール）モノエチルエーテル、ポリ（プロピレングリコール）モノプロピルエーテル、ポリ（プロピレングリコール）モノブチルエーテル、ポリ（プロピレングリコール）モノ２エチルヘキシルエーテル、ポリ（プロピレングリコール）モノフェニルエーテル等を挙げることができ、特にポリ（プロピレングリコール）モノブチルエーテルが好適である。

(Wherein the number average repeating number r is in the range of 4 to 14 and R ³ represents an alkyl group or phenyl group having 1 to 8 carbon atoms), specifically, poly (propylene glycol) monomethyl List ethers, poly (propylene glycol) monoethyl ether, poly (propylene glycol) monopropyl ether, poly (propylene glycol) monobutyl ether, poly (propylene glycol) mono-2-ethylhexyl ether, poly (propylene glycol) monophenyl ether, etc. In particular, poly (propylene glycol) monobutyl ether is suitable.

  The number average repeating number r of the PG units in the PPG part is 4 to 14, preferably 4 to 12, more preferably 4 to 10, and most preferably 4 to 8. The carbodiimide group in the carbodiimide curing agent may react with water during storage to produce a urea group. When the carbodiimide group is reduced by reaction with water, the crosslinking density of the coating film is lowered, and sufficient coating film performance cannot be exhibited. If the number of repetitions r is within the above range, a large amount of highly hydrophobic PPG is present around the carbodiimide group, and the carbodiimide group is protected from water. A high-density coating film is obtained. In addition, since the coating film contains a large amount of highly hydrophobic PPG groups, the coating film is imparted with water repellency and water resistance is improved. When the number of repetitions r is less than 4, since only a small amount of highly hydrophobic PPG is present around the carbodiimide group, the curing rate is slow and a coating film having a high crosslinking density cannot be obtained. Moreover, since sufficient water repellency cannot be provided to a coating film, water resistance falls. When the number of repetitions r exceeds 14, the hydrophobicity of the carbodiimide aqueous dispersion becomes too large, so that the particle size of the aqueous dispersion becomes large and the gloss of the coating film is lowered or the aqueous dispersion is not formed. There is a risk of moisture separation.

  In the carbodiimide compound (B) used in the present invention, the molar ratio of PEG part: PPG part = 1: 1 to 1:15, particularly preferably 1: 2 to 1:15, more preferably 1: 2 to 1: 9, 1: 3 to 1: 8 is more preferable, and 1: 4 to 1: 6 is most preferable. When the molar ratio of the PEG part is large, the water resistance is poor. A small amount of carbodiimide groups in the carbodiimide curing agent react with water to form urea groups. In order to suppress this reaction, it is preferable that the periphery of the carbodiimide group is as hydrophobic as possible and the contact with water molecules is low. If the molar ratio of the PPG part is large, it becomes too hydrophobic, resulting in poor water dispersibility and poor stability. The molar ratio of PEG part: PPG part is based on the blending molar ratio of PEG and PPG used in the production of (B) carbodiimide compound.

  The reaction temperature of the addition reaction between the isocyanate-terminated dicyclohexylmethane carbodiimide and the mixture of the polyethylene glycol monoalkyl ether and the polypropylene glycol monoalkyl ether is in the range of 60 ° C to 180 ° C, preferably 100 ° C to 160 ° C. Within range. When the reaction temperature falls below this range, the reaction time becomes extremely long. Conversely, when the reaction temperature exceeds the above range, side reactions occur and the carbodiimide compound of the present invention cannot be obtained, which is not preferable in either case.

  In the aqueous coating composition of the present invention, when the mixing ratio of (A) the aqueous acrylic resin having a carboxyl group and (B) the carbodiimide compound represented by the general formula (1) is expressed as a resin solid content ratio, (A) The aqueous acrylic resin is 99 to 60% by mass, preferably 95 to 80% by mass, and (B) the carbodiimide compound is 1 to 40% by mass, preferably 5 to 20% by mass. In terms of molar ratio, (A) the carboxyl group of the aqueous acrylic resin: (B) the carbodiimide group of the carbodiimide compound is 0.8: 1 to 1.2: 1.

  Since the two-component aqueous coating composition of the present invention uses an acrylic resin, it has good weather resistance and can be used as a two-component top coat. In the present invention, the two-component paint means that when the main agent and the curing agent are mixed, the curing reaction proceeds at room temperature and cannot be stored in one solution, and the two components are stored separately and immediately before use. Means a mixture of a main agent and a curing agent.

  The two-component aqueous coating composition of the present invention may contain an organic solvent that dissolves in water. Specific examples of the organic solvent include ethylene glycol, propylene glycol, ethylene glycol monobutyl ether, propylene glycol monobutyl ether, diethylene glycol, dipropylene glycol, diethylene glycol monobutyl ether and the like. From the viewpoint of minimizing the use of VOCs, the amount of organic solvent is preferably as small as possible.

  The two-component aqueous coating composition of the present invention may contain a pigment. Specific examples of the pigment include titanium oxide, yellow iron oxide, red iron oxide, carbon black, phthalocyanine blue, phthalocyanine green, azo red, quinacridone red, benzimidazolone yellow and the like; calcium carbonate, barium sulfate, kaolin, clay And extender pigments such as talc; rust preventive pigments. The concentration of the pigment in the aqueous coating composition is preferably 10 to 50% by mass.

  The two-component aqueous coating composition of the present invention may contain an additive. Specific examples of the additive include a dispersant, a viscosity modifier, a curing catalyst, a surface modifier, an antifoaming agent, a plasticizer, a film-forming aid, an ultraviolet absorber, an antioxidant, and a curing agent.

  The two-component aqueous coating composition of the present invention can be applied to any suitable substrate. Examples of the substrate include metal, wood, plastics, rubber, stone, slate, concrete, mortar, fiber, paper, glass, porcelain, earthenware, film, and composites thereof. For example, when the base material is an inorganic base material such as slate or concrete, a sealer may be applied to the surface in advance. Considering characteristics, it is preferably applied to metals. Examples of the metal include iron, copper, tin, zinc, aluminum, and stainless steel.

  Examples of the object to be coated having metal on the surface (outer surface and inner surface) include, for example, ships, vehicles (for example, railway vehicles, large vehicles), aircraft, bridges, offshore structures, plants, tanks (for example, oil tanks), pipes, Examples include steel pipes and cast iron pipes. In addition to the above, the water-based coating composition can also be applied to buildings and civil engineering structures.

  The coating method typically includes a method in which the aqueous coating composition is applied to an object to be coated (base material) and dried. As a coating method, any appropriate method can be adopted depending on the type of an object (base material) to be coated. For example, application, immersion, etc. with a brush, a roller, air spray, airless spray, a trowel, etc. are mentioned.

  Any appropriate method can be adopted as the drying method. Natural drying or heat drying is preferred. In the case of natural drying, the drying time is preferably 2 hours or longer, more preferably 24 hours or longer.

  The thickness of the coating film formed by applying the aqueous coating composition is preferably 10 to 100 μm, more preferably 20 to 100 μm. When the thickness is thicker than 100 μm, there is a possibility that problems such as sagging occur during coating.

  When the water absorption rate of the coating film obtained by applying and drying at room temperature using the aqueous coating composition of the present invention is too large, the coating film swells due to rain immediately after construction, and the temperature at the time of construction Depending on the case, the coating film may be cracked.

  Before the aqueous coating composition is applied to form a coating film, adhesion and corrosion resistance are improved, so that an undercoat layer with an undercoat paint or an intermediate coat layer with an intermediate paint can be formed on the undercoat layer. it can.

  Any appropriate paint can be adopted as the undercoat paint. For example, an epoxy / Michael curable paint, an epoxy / amine paint, an epoxy dispersion paint, a two-component urethane curable paint, and the like can be given. Further, any appropriate paint can be adopted as the intermediate paint. For example, an epoxy / amine-based paint, a two-component urethane curable paint, and the like can be given.

  A zinc rich layer may be formed by applying an organic or inorganic zinc rich paint before the undercoat paint. By forming the zinc rich layer, the anticorrosion property is excellent, and for example, it is possible to sufficiently cope with a case where a high anticorrosion property such as a bridge, a plant, or a tank is required.

  The undercoat paint, intermediate coat paint and zinc rich paint may contain pigments, additives and the like. Examples of the pigment and additive include the pigments and additives described above. The number, type, and amount of pigments and additives to be added can be appropriately selected according to the purpose.

  Arbitrary appropriate methods can be employ | adopted for the coating method and drying method of the said undercoat, intermediate coating, and zinc rich paint according to the kind of coating material to be used. Examples of the application method and the drying method for the undercoat paint, the intermediate coat paint, and the zinc rich paint include the same methods as the application method and the drying method for the aqueous paint composition described above.

  EXAMPLES Hereinafter, although this invention is demonstrated more concretely based on an Example and a comparative example, this invention is not limited to a following example. In this example, when “%” is simply described, “mass%” is indicated, and when “part” is simply described, “mass part” is indicated.

Production Example 1: Production of a carbodiimide compound having an isocyanate group at both ends Add 25 parts of 3-methyl-1-phenyl-2-phospholene-1-oxide as a carbodiimidization catalyst to 2500 parts of 4,4-dicyclohexylmethane diisocyanate, The reaction was carried out at 170 ° C. until the equivalent amount of isocyanate reached 436 to prepare carbodiimide compound 1 having isocyanate groups at both ends. Carbodiimide compound 1 had 2.8 carbodiimide groups per molecule.

Production Example 2: Manufacture of Aqueous Dispersion of Carbodiimide Compound As shown in Table 1, to 872 parts of carbodiimide compound 1 prepared in Production Example 1, Newpol LB-65 (manufactured by Sanyo Chemical Co., Ltd., polypropylene glycol monobutyl ether) ) 567 parts and MPG-081 (manufactured by Nippon Emulsifier, Polyethylene glycol monomethyl ether, number average repeat number 15) 225 parts were added and reacted at 160 ° C. until there was no absorption derived from isocyanate groups by IR. The mixture was further cooled to 60 ° C., and 2496 parts of deionized water was gradually added and emulsified to obtain a milky white carbodiimide aqueous dispersion 1 having a solid content of 40%.

Production Example 3 Production of Aqueous Dispersion of Carbodiimide Compound As in Production Example 2, a milky white carbodiimide dispersion 2 having a solid content of 40% was obtained using the formulation shown in Table 1.

Production Example 4 Production of Aqueous Dispersion of Carbodiimide Compound As in Production Example 2, a milky white carbodiimide dispersion 3 having a solid content of 40% was obtained using the formulation shown in Table 1.

Comparative Production Example 1 Production of Aqueous Dispersion of Carbodiimide Compound As in Production Example 2, a milky white carbodiimide dispersion 4 having a solid content of 40% was obtained using the formulation shown in Table 1.

Comparative Production Example 2 Production of Aqueous Dispersion of Carbodiimide Compound As in Production Example 2, a milky white carbodiimide dispersion 5 having a solid content of 40% was obtained using the formulation shown in Table 1.

Comparative Production Example 3 Production of Aqueous Dispersion of Carbodiimide Compound As in Production Example 2, a milky white carbodiimide dispersion 6 having a solid content of 40% was obtained using the formulation shown in Table 1.

Comparative Production Example 4 Production of Aqueous Dispersion of Carbodiimide Compound As in Production Example 2, a milky white carbodiimide dispersion 7 having a solid content of 40% was obtained using the formulation shown in Table 1.

Comparative Production Example 5: Production of Aqueous Dispersion of Carbodiimide Compound As shown in Table 1, 648 parts of polypropylene glycol monobutyl ether (number average repeat number 19) 648 parts, and polyethylene glycol, 872 parts of carbodiimide compound 1 prepared in Production Example 1 64 parts of monomethyl ether (number average number of repetitions 15) were added and reacted at 160 ° C. until there was no absorption of NCO by IR. Further, the mixture was cooled to 60 ° C., and deionized water was gradually added, but a uniform aqueous dispersion was not obtained.

Comparative Production Example 6 Production of Aqueous Dispersion of Carbodiimide Compound As in Production Example 2, a milky white carbodiimide dispersion 8 having a solid content of 40% was obtained using the formulation shown in Table 1.

In the table, MPG-081, MPG-041, BFTG, MFTG and BFG are products made by Nippon Emulsifier.
New Pole LB-65 is a product made by Sanyo Kasei.
Uniloop MB-7 and Uniloop MB-11 are products made by NOF.

Production Example A1 Production of Aqueous Dispersion Acrylic Resin (Acrylic Emulsion) Having Carboxyl Group Into a reaction vessel equipped with a stirrer, nitrogen introduction tube, temperature control device, condenser, and dropping funnel, 200.0 parts of deionized water was charged. The temperature was raised to 80 ° C. with stirring in a nitrogen atmosphere.
236.3 parts of 2-ethylhexyl acrylate, 538.0 parts of methyl methacrylate, 200.0 parts of styrene, 25.7 parts of acrylic acid, and Latem PD-104 (made by Kao Corporation, 20% aqueous solution) as an emulsifier 100 parts Was added dropwise over 2 hours together with an aqueous initiator solution in which 3 parts of ammonium persulfate was dissolved in 150 parts of deionized water.
After completion of the dropwise addition, the reaction was further continued at 80 ° C. for 1 hour and then cooled, and 8.2 parts of N, N-dimethylaminoether was added to obtain an acrylic emulsion having a resin solid content of 50 mass%. The resin solid content acid value of this acrylic emulsion calculated from the monomer composition was 20 mgKOH / g, and Tg was 40 ° C.

Production Example A2 Production of Aqueous Dispersion Acrylic Resin (Acrylic Emulsion) Having Carboxyl Group Into a reaction vessel equipped with a stirrer, nitrogen introduction tube, temperature controller, condenser, and dropping funnel, 200.0 parts of deionized water was charged, The temperature was raised to 80 ° C. with stirring in a nitrogen atmosphere.
2-ethylhexyl acrylate 237.0 parts, methyl methacrylate 550.1 parts, styrene 200.0 parts, acrylic acid 12.8 parts, latemul PD-104 (manufactured by Kao Corporation, 20% aqueous solution) as an emulsifier 100 parts Was added dropwise over 2 hours together with an aqueous initiator solution in which 3 parts of ammonium persulfate was dissolved in 150 parts of deionized water.
After completion of the dropwise addition, the reaction was further continued at 80 ° C. for 1 hour and then cooled, and 8.2 parts of N, N-dimethylaminoether was added to obtain an acrylic emulsion having a resin solid content of 50% by mass. The resin solid content acid value of this acrylic emulsion, calculated from the monomer composition, was 10 mg KOH / g, and Tg was 40 ° C.

Production Example A3 Production of Water-Soluble Acrylic Resin Having Carboxyl Group Into a reaction vessel equipped with a stirrer, nitrogen introduction tube, temperature controller, condenser, and dropping funnel, 259.0 parts of 2-methoxy-1-propanol was charged, and nitrogen was added. The temperature was raised to 120 ° C. with stirring under an atmosphere.
Styrene 35.0 parts, methyl methacrylate 19.8 parts, n-butyl acrylate 155.2 parts, ethyl acrylate 19.0 parts, 2-ethylhexyl acrylate 137.2 parts, methacrylic acid 33.8 parts The mixture was mixed with Kaya ester O (tert-butylperoxy-2-ethylhexanate manufactured by Kayaku Akzo Co., Ltd.) for 1 hour together with an initiator solution in which 16.0 parts were dissolved in 25.0 parts of 2-methoxy-1-propanol. And dripped.
After completion of the dropwise addition, the mixture was kept at 120 ° C. for 0.5 hours, and then an initiator solution prepared by dissolving 1.6 parts of Kayaester O in 16.0 parts of 2-methoxy-1-propanol was dropped over 0.5 hours. Furthermore, it stirred at 120 degreeC for 1 hour. Next, after cooling to 60 ° C. and neutralizing with 35.0 parts of N, N-dimethylethanolamine, 287.4 parts of deionized water was added to make it water-soluble, and a water-soluble resin having a resin solid content of 40% by mass was obtained. The resin solid content acid value of this water-soluble acrylic resin calculated from the monomer composition was 55 mgKOH / g, and Tg was −35 ° C.

Production Example A4 Production of Water-Soluble Acrylic Resin Having Carboxyl Group Into a reaction vessel equipped with a stirrer, a nitrogen introduction tube, a temperature controller, a condenser, and a dropping funnel, charged with 259.0 parts of 2-methoxy-1-propanol, nitrogen The temperature was raised to 120 ° C. with stirring under an atmosphere.
Styrene 35.0 parts, methyl methacrylate 8.7 parts, n-butyl acrylate 155.2 parts, ethyl acrylate 19.0 parts, 2-ethylhexyl acrylate 139.1 parts, methacrylic acid 43.0 parts The mixture was mixed with Kaya ester O (tert-butylperoxy-2-ethylhexanate manufactured by Kayaku Akzo Co., Ltd.) for 1 hour together with an initiator solution in which 16.0 parts were dissolved in 25.0 parts of 2-methoxy-1-propanol. And dripped.
After completion of the dropwise addition, the mixture was kept at 120 ° C. for 0.5 hours, and then an initiator solution prepared by dissolving 1.6 parts of Kayaester O in 16.0 parts of 2-methoxy-1-propanol was dropped over 0.5 hours. Furthermore, it stirred at 120 degreeC for 1 hour. Next, after cooling to 60 ° C. and neutralizing with 44.5 parts of N, N-dimethylethanolamine, 277.9 parts of deionized water was added to make it water-soluble to obtain a water-soluble resin having a resin solid content of 40% by mass. The resin solid content acid value of this water-soluble acrylic resin calculated from the monomer composition was 70 mgKOH / g, and Tg was -35 ° C.

Production Example B1: Preparation of white enamel paint (main agent) 61.6 parts of deionized water, 30.0 parts of DISPERBYK-190 (dispersant manufactured by BYK-Chemie), Aqualene 810 (defoamer manufactured by Tego) 1.0 Part and Tipure R-706 (Titanium oxide manufactured by DuPont) were dispersed in a sand mill to obtain a titanium oxide dispersion paste.
378.2 parts of the obtained dispersion paste, 25.4 parts of deionized water, 460.0 parts of the acrylic emulsion obtained in Production Example A1, 123.0 parts of the water-soluble acrylic resin obtained in Production Example A3, CS-12 (manufactured by Chisso Corporation, film-forming aid) 54.0 parts, Adecanol UH-550 (manufactured by Adeka Corporation) 6.6 parts, SN thickener 617 (manufactured by Sannopco Corporation) 4.0 parts 8610ADDITIVE (Dow Corning antifoaming agent) 1.5 parts was added to obtain white enamel paint 1 (main agent).

Production Example B2: Preparation of white enamel paint (main agent) 61.6 parts of deionized water, 30.0 parts of DISPERBYK-190 (dispersant manufactured by BYK-Chemie), Aqualene 810 (defoamer manufactured by Tego) 1.0 Part and Tipure R-706 (Titanium oxide manufactured by DuPont) were dispersed in a sand mill to obtain a titanium oxide dispersion paste.
In addition to 378.2 parts of the obtained dispersion paste, 25.4 parts of deionized water, 559.1 parts of the acrylic emulsion obtained in Production Example A1, CS-12 (made by Chisso Corporation, film-forming aid) 65.6 Parts, Adecanol UH-550 (Adeka thickener) 6.6 parts, SN thickener 617 (San Nopco thickener) 4.0 parts, 8610ADDITIVE (Dow Corning antifoam) 1.5 parts In addition, white enamel paint 2 (main agent) was obtained.

Production Example B3: Preparation of white enamel paint (main agent) 61.6 parts of deionized water, 30.0 parts of DISPERBYK-190 (dispersant manufactured by BYK-Chemie), Aqualene 810 (defoamer manufactured by Tego) 1.0 Part, and PureR-706 (Titanium oxide manufactured by DuPont) were dispersed in a sand mill to obtain a titanium oxide dispersion paste.
To 378.2 parts of the obtained dispersion paste, 25.4 parts of deionized water, 420.0 parts of the acrylic emulsion obtained in Production Example A2, 175.0 parts of the water-soluble acrylic resin obtained in Production Example A4, CS-12 (manufactured by Chisso Corporation, film-forming aid) 54.0 parts, Adecanol UH-550 (manufactured by Adeka Corporation) 6.6 parts, SN thickener 617 (manufactured by Sannopco Corporation) 4.0 parts 8610ADDITIVE (Dow Corning antifoaming agent) 1.5 parts was added to obtain white enamel paint 3 (main agent).

Production Example B4: Preparation of White Enamel Paint (Main Agent) 61.6 parts of deionized water, 30.0 parts of DISPERBYK-190 (dispersant manufactured by BYK-Chemie), Aqualene 810 (defoamer manufactured by Tego) 1.0 Part, and PureR-706 (Titanium oxide manufactured by DuPont) were dispersed in a sand mill to obtain a titanium oxide dispersion paste.
In addition to 378.2 parts of the obtained dispersion paste, 25.4 parts of deionized water, 497.0 parts of the acrylic emulsion obtained in Production Example A1, 77.8 parts of the water-soluble acrylic resin obtained in Production Example A3, CS-12 (manufactured by Chisso Corporation, film-forming aid) 54.0 parts, Adecanol UH-550 (manufactured by Adeka Corporation) 6.6 parts, SN thickener 617 (manufactured by Sannopco Corporation) 4.0 parts , 8610ADDITIVE (an antifoaming agent manufactured by Dow Corning) was added to obtain white enamel paint 4 (main agent).

Examples 1-3
In the ratio shown in Table 2, the white enamel paint 1 obtained in Production Example B1 is used as the main agent, and the aqueous dispersions 1 to 3 of the carbodiimide compounds obtained in Production Examples 2 to 4 are mixed as the curing agent to obtain the paint 1 ~ 3 was obtained.

Example 4
In the proportions shown in Table 2, the white enamel paint 2 obtained in Production Example B2 was used as the main agent, and the aqueous dispersion 1 of the carbodiimide compound obtained in Production Example 2 was mixed as a curing agent to obtain a paint 4.

Example 5
In the ratio shown in Table 2, the white enamel paint 3 obtained in Production Example B3 was used as a main agent, and the aqueous dispersion 1 of the carbodiimide compound obtained in Production Example 2 was mixed as a curing agent to obtain a paint 5.

Example 6
In a ratio shown in Table 2, the white enamel paint 4 obtained in Production Example B4 was used as a main agent, and the aqueous dispersion 1 of the carbodiimide compound obtained in Production Example 2 was mixed as a curing agent to obtain a paint 6.

Comparative Examples 1-5
In the ratio shown in Table 3, the white enamel paint 1 obtained in Production Example B1 is used as the main agent, and the aqueous dispersions 4 to 8 of the carbodiimide compounds obtained in Comparative Production Examples 1 to 4 and 6 are mixed as the curing agent. The paints 7 to 11 were obtained.

  A curing storage stability test of the curing agent, a water resistance test of the coating film, and a gloss measurement of the coating film were performed.

[Curing storage stability test of curing agent]
Immediately after producing the aqueous dispersions 1 to 8 according to the above production examples and comparative production examples, after preparation, after storage at 50 ° C. for 1 month, 2 months and 3 months, paints 1 to 11 were applied according to each example and comparative example. Produced.
Each paint was applied on a glass plate with a 6 mil applicator and allowed to dry at room temperature for 1 week. The prepared coating film was rubbed with acetone, and the number of rubbing until the glass substrate was exposed was recorded with one round trip.

[Water resistance test of coating film]
(1) Water resistance test after 1 hour of drying at 20 ° C. The coating amount of each of the paints 1 to 11 is 120 g / m in a 20 ° C. environment on a steel sheet coated with a solution-type epoxy primer. ^It was painted with a brush so as to be ^2, and dried at 20 ° C. for 1 hour. The prepared coating film was immersed in water at 20 ° C. for 16 hours, and the swelling of the coating film surface was observed immediately after pulling up. Judgment criteria for coating blisters were based on JIS K5600-8-2. The determination results are shown according to the following notation.
“Bulge 0” means that no blister has occurred.
In “bulge j (Sk)”, “j” is a value related to the number (density) of the blisters per unit area generated, and the larger the value, the denser the blisters are generated. “K” is a value relating to the average size (size) of the generated blisters, and the larger the value, the larger the size per blister.

(2) Water resistance test after 1 week of drying at 20 ° C. The coating amount of each of the paints 1 to 11 is 120 g / m ² in a 20 ° C. environment on a steel sheet coated with a solution-type epoxy primer. It was painted with a brush and dried at 20 ° C. for 1 week. The prepared coating film was immersed in water at 20 ° C. for 3 days, and the swelling of the coating film surface was observed immediately after pulling up. Judgment criteria for coating blisters were based on JIS K5600-8-2. The determination result was shown according to the same method as the above-mentioned notation.

(3) Coating water absorption measurement test after 1 hour of drying at 20 ° C. Each of paints 1 to 11 is applied to a polypropylene plate with a brush so that the coating amount is 120 g / m ² in a 20 ° C. environment. And dried at 20 ° C. for 1 hour. After drying, the coating film is peeled off and its weight is measured. After the weight measurement, the coating film was immersed in water at 20 ° C. for 16 hours, and immediately after lifting, the moisture on the coating film surface was lightly wiped, and then the weight was measured. From these measured values, the coating film water absorption was determined by the following equation.
Water absorption (%) = (weight of coating film after immersion) / (weight of coating film before immersion) × 100-100

(4) Water resistance test after 3 hours of drying at 5 ° C. Each of paints 1 to 11 is applied to a steel sheet coated with a solution-type epoxy primer so that the coating amount is 120 g / m ² in a 5 ° C. environment. Painted with a brush and dried at 5 ° C. for 3 hours. The prepared coating film was immersed in water at 5 ° C. for 16 hours, and the coating surface was observed for cracking immediately after being pulled up. The judgment criteria for coating film coating were determined based on JISK5600-8-4. The determination results are shown according to the following notation.
“Crack 0” means that no crack has occurred.
In “crack j (Sk) l”, “j” is a value related to the number (density) of unit cracks per unit area, and the larger the value, the denser the cracks are generated. “K” is a value related to the average size (size) of the generated cracks, and the larger the value, the larger the size per one crack. "L" is a grade (ac) related to the depth of cracks that occurred, a is a surface crack that does not penetrate the top coat, b is a top coat that penetrates, but the coating under it has no cracks, c represents the crack which has penetrated all the coating-film layers.

(5) Coating film water absorption measurement test after 3 hours of drying at 5 ° C. Each of paints 1 to 11 is applied to a polypropylene plate in a 5 ° C. environment so that the coating amount (at the time of drying) is 120 g / m ^2. It was painted with a brush and dried at 5 ° C. for 3 hours. After drying, the coating film is peeled off and its weight is measured. After the weight measurement, the coating film was immersed in water at 5 ° C. for 16 hours, and immediately after pulling up, the moisture on the coating film surface was lightly wiped, and then the weight was measured. From these measured values, the coating film water absorption was determined by the following equation.
Water absorption (%) = (weight of coating film after immersion) / (weight of coating film before immersion) × 100-100

[Glossiness measurement of coating film]
Paints 1-11 were applied on a glass plate with a 6 mil applicator and allowed to dry at room temperature for 1 week. The surface of the prepared coating film was measured for 60-degree gloss with a gloss meter (Micro Trigloss manufactured by BYK-Gardner). A gloss value of 80 or more is a practically acceptable range, and a gloss value of 85 or more is preferable.

[Explanation of results]
(1) Curing storage stability Examples 1 to 6 were good results, even when a curing agent stored at 50 ° C. for 3 months from the production was used and the substrate was not transparent after 50 rubbing treatments. On the other hand, in Comparative Examples 1 to 4, when a hardener that was stored for one or two months was used, the substrate was transparent before the rubbing treatment was performed 50 times. It was found that there was a difference in the stability of the curing agent itself depending on the number average repeating number of PG units of the carbodiimide curing agent and the ratio of PEG / PPG.

(2) Water resistance after 1 hour of drying at 20 ° C. Examples 1 to 6 were good results with no blistering in the initial water resistance test of the coating film. On the other hand, in Comparative Examples 1 to 4, blisters occurred in part or all. In addition, the water absorption rate of the coating film was about 10 to 25% higher in Comparative Examples 1 to 4 than in Examples 1 to 6. It was found that there was a difference in initial water resistance depending on the number average repeating number of PG units of the carbodiimide curing agent and the ratio of PEG / PPG.

(3) Water resistance after 3 hours of drying at 5 ° C. Examples 1 to 6 were satisfactory in the initial water resistance test of the coating film, and were good results. On the other hand, cracks occurred in some or all of Comparative Examples 1 to 4. In addition, the water absorption rate of the coating film was about 10 to 30% higher in Comparative Examples 1 to 4 than in Examples 1 to 6. It was found that there was a difference in initial water resistance depending on the number average repeating number of PG units of the carbodiimide curing agent and the ratio of PEG / PPG at 5 ° C. as well as at 20 ° C.

(4) About gloss of coating film The gloss value of the coating film of Examples 1-6 was 80 or more, and was favorable. Further, when an aqueous dispersion acrylic resin having a resin solid content acid value of 3 to 30 mg / KOH and a water-soluble acrylic resin having a resin solid content acid value of 35 to 100 mg / KOH are used, the gloss value of the coating film is 85 or more. And the best results were obtained (Examples 1 to 3 and 5 to 6).

[Measuring method]
(1) Hydroxyl value The hydroxyl value was measured based on JIS K1557-1 (Plastics-Polyurethane raw material polyol test method-Part 1: Determination of hydroxyl value).

(2) Number average repetition number q and r
The number average repeating number q of ethylene glycol of polyethylene glycol monoalkyl ether and the number average repeating number r of propylene glycol of polypropylene glycol monoalkyl ether are polyalkylene glycol monoalkyl represented by the following general formula (10): This corresponds to the number average repeating number s of the alkylene glycol of ether. The number average repeating number s (= q, r) was determined based on the following formula from the molecular weight and hydroxyl value of the polymer.

In the formula, the unit molecular weight of the ether part = 12 m + 2 m + 16 = 14 m + 16
Sum of alkyls at both ends / hydrogen molecular weight = 12n + 2n + 1 + 16 + 1 = 14n + 18

  Since the two-component water-based coating composition of the present invention uses a carbodiimide compound having a specific structure as a curing agent, it is excellent in initial curing characteristics and in storage stability. Therefore, it can be used in various fields of room temperature drying and baking drying.

Claims (4)

A two-component aqueous coating composition comprising:
(A) an aqueous acrylic resin having a carboxyl group;
(B) General formula (1):

{Wherein p represents an integer of 1 to 5 and two R ^{1 s} independently represent the general formula (2):

(Wherein the number average repeating number q is in the range of 6 to 40, R ² represents an alkyl group having 1 to 8 carbon atoms or a phenyl group) and / or a residue of polyethylene glycol monoalkyl ether represented by Or general formula (3):

(Wherein the number average repeating number r is in the range of 4 to 14, and R ³ represents an alkyl group or phenyl group having 1 to 8 carbon atoms). . }, A carbodiimide compound represented by
Where
In R ¹ in the general formula (1), the molar ratio between the residue of the polyethylene glycol monoalkyl ether represented by the general formula (2) and the residue of the polypropylene glycol monoalkyl ether represented by the general formula (3) Is a two-component water-based coating composition having a ratio of 1: 1 to 1:15.   2. The two-component aqueous coating composition according to claim 1, wherein the aqueous acrylic resin (A) contains an aqueous dispersion acrylic resin having a resin solid content acid value of 3 to 30 mg / KOH.   The aqueous acrylic resin (A) includes an aqueous dispersion acrylic resin having a resin solid content acid value of 3 to 30 mg / KOH and a water-soluble acrylic resin having a resin solid content acid value of 35 to 100 mg / KOH. The two-component water-based coating composition according to claim 1, which is contained at a mass ratio of 2: 1 to 10: 1.   The two-component aqueous coating composition according to any one of claims 1 to 3, wherein the molar ratio of the residue of polyethylene glycol monoalkyl ether to the residue of polypropylene glycol monoalkyl ether is 1: 2 to 1:15. .