JP2001288403A - Water-base coating composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a water-base coating composition that can form a polyester resin film strengthened particularly in hot water resistance and solvent resistance. SOLUTION: The water-base coating composition comprises (A) a polyester resin which has an acid value of 11-40 mgKOH/g, a weight average molecular weight of 14,000 or more, and a degree of dispersion of the molecular-weight distribution of less than 4.0, and (B) a curing agent.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aqueous coating composition which is applied to various substrates to form a coating having excellent hot water resistance and solvent resistance.

[0002]

2. Description of the Related Art A high molecular weight polyester resin composed of a polybasic acid component and a polyhydric alcohol component is used as a film-forming resin as a resin for forming a film, resistance to an organic solvent (solvent resistance), weather resistance, and the like. Because of its excellent adhesiveness to various substrates, it is used in large quantities as a binder component in the fields of paints, inks, adhesives, coatings and the like. Particularly in recent years, the use of organic solvents has tended to be restricted from the standpoint of environmental protection, resource saving, regulation of dangerous substances by the Fire Service Law, etc., and improvement of the workplace environment. Development of an aqueous dispersion of a polyester resin finely dispersed in an aqueous medium has been actively performed.

For example, Japanese Patent Application Laid-Open No. 9-296100 discloses an aqueous polyester resin dispersion in which a polyester resin having an acid value of 10 to 40 mg KOH / g and a weight average molecular weight of 9,000 or more is dispersed in an aqueous medium. It is proposed that a film excellent in processability, water resistance, solvent resistance and the like can be formed by using such an aqueous dispersion.

[0004]

Although the above-mentioned polyester resin aqueous dispersion forms a high-performance film, the film performance, particularly hot water resistance and solvent resistance, are not sufficient depending on the application. There was a case. In such a case, by incorporating a curing agent into the polyester resin aqueous dispersion as described in the above publication, the insufficient performance could be compensated to some extent, but it was not necessarily sufficient, In some cases, the workability of the coating was reduced.

An object of the present invention, which has been made in view of such circumstances, is to provide an aqueous coating composition capable of forming a polyester resin film having particularly enhanced hot water resistance and solvent resistance.

[0006]

Means for Solving the Problems The present inventors have intensively studied to solve such problems, and have used a polyester resin in which the degree of dispersion of the molecular weight distribution is controlled in addition to the acid value and the weight average molecular weight. As a result of examining the combination of this and a curing agent, it was found that the expression of the effect of the addition of the curing agent was influenced by the properties of the polyester resin, particularly the molecular weight distribution, and succeeded in greatly improving the film performance. The present invention has been completed.

That is, the gist of the present invention is that (A) the acid value is 11 to 40 mgKOH / g and the weight average molecular weight is 1
An aqueous coating composition comprising: a polyester resin having a molecular weight distribution of 4,000 or more and a degree of dispersion of less than 4.0; and (B) a curing agent.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
The aqueous coating composition of the present invention has (A) an acid value of 11 to 40 mgKOH / g in an aqueous medium, a weight average molecular weight of 14,000 or more and a molecular weight distribution of 4.
It is a liquid containing a polyester resin less than 0 and a curing agent (B). First, the polyester resin (A) (hereinafter abbreviated as polyester resin A) will be described.

The acid component of the polyester resin A includes aromatic polybasic acids, aliphatic polybasic acids, and alicyclic polybasic acids. Examples of aromatic dicarboxylic acids among the aromatic polybasic acids include terephthalic acid, isophthalic acid, orthophthalic acid,
Examples include naphthalenedicarboxylic acid, biphenyldicarboxylic acid, and the like.Examples of aliphatic dicarboxylic acids among the aliphatic polybasic acids include oxalic acid, succinic acid, succinic anhydride, adipic acid, azelaic acid, sebacic acid, and dodecane diacid. , Saturated dicarboxylic acids such as hydrogenated dimer acid, fumaric acid, maleic acid, maleic anhydride, itaconic acid, itaconic anhydride,
Examples thereof include unsaturated dicarboxylic acids such as citraconic acid, citraconic anhydride, and dimer acid. Examples of alicyclic dicarboxylic acids among alicyclic polybasic acids include 1,4-cyclohexanedicarboxylic acid and 1,3-cyclohexanedicarboxylic acid. Examples thereof include cyclohexanedicarboxylic acid, 1,2-cyclohexanedicarboxylic acid, 2,5-norbornenedicarboxylic acid and its anhydride, and tetrahydrophthalic acid and its anhydride. Also, if necessary, a small amount of 5-
Sodium sulfoisophthalic acid and 5-hydroxyisophthalic acid can also be used as the acid component.

Among the above acid components, aromatic polybasic acids are preferred, and the proportion of the aromatic polybasic acid in the acid component of the polyester resin A is preferably 50 mol% or more, more preferably 60 mol% or more. , 70 mol% or more, more preferably 80 mol% or more. By increasing the proportion of the aromatic polybasic acid, the proportion of the aromatic skeleton in the resin skeleton that is less likely to be hydrolyzed than the aliphatic and alicyclic ester bonds increases, so that the film formed from the coating composition ( This is preferred because the hardness, hot water resistance, and solvent resistance of the resin coating are improved, and the storage stability of the aqueous coating composition is further improved.
Furthermore, among the above-mentioned aromatic polybasic acids, terephthalic acid can be improved in workability, hardness, hot water resistance, solvent resistance, weather resistance, etc. while balancing the various properties of the resin film. Is particularly preferred.

The acid component may be a tribasic or higher polybasic acid such as trimellitic acid, pyromellitic acid, benzophenonetetracarboxylic acid, trimellitic anhydride, pyromellitic anhydride, benzophenonetetracarboxylic anhydride. , Trimesic acid, ethylene glycol bis (anhydrotrimellitate), glycerol tris (anhydrotrimellitate), 1,2,3,4-butanetetracarboxylic acid, and the like. At this time, in terms of maintaining good workability of the resin film, the proportion of the trifunctional or higher polybasic acid in the acid component of the polyester resin A is as follows:
It is preferably at most 10 mol%, more preferably at most 8 mol%, particularly preferably at most 5 mol%.

The alcohol component of the polyester resin A is preferably an aliphatic glycol having 2 to 10 carbon atoms, an alicyclic glycol having preferably 6 to 12 carbon atoms,
There are glycols containing an ether bond. Examples of such aliphatic glycols include ethylene glycol, 1,
2-propylene glycol, 1,3-propanediol, 1,4-butanediol, 2-methyl-1,3-propanediol, 1,5-pentanediol, neopentyl glycol, 1,6-hexanediol, 3- Methyl-1,5-pentanediol, 1,9-nonanediol, 2-ethyl-2-butylpropanediol and the like, and examples of the alicyclic glycol include 1,4-cyclohexanedimethanol; Examples of the ether bond-containing glycol include diethylene glycol, triethylene glycol, dipropylene glycol and the like. When the ether structure is increased, the hot water resistance of the polyester resin and the weather resistance may be reduced.Therefore, the amount of the ether bond-containing glycol used may be limited to a range where the hot water resistance and the weather resistance of the resin film are not impaired. preferable. Further, bisphenols such as 2,2-bis (4-hydroxyethoxyphenyl) propane can be used.
Glycols obtained by adding one to several moles of ethylene oxide or propylene oxide to each of the two phenolic hydroxyl groups, further, polyethylene glycol,
Polypropylene glycol, polytetramethylene glycol, and the like can be used as an alcohol component if necessary.

Among the above alcohol components, ethylene glycol or neopentyl glycol is particularly preferable. The total ratio of ethylene glycol and neopentyl glycol in the alcohol component of the polyester resin A is preferably 50 mol% or more, and more preferably 60 mol% or more. % Or more, more preferably 70 mol% or more. Ethylene glycol and neopentyl glycol are inexpensive because they are industrially produced in large quantities, and the various properties of the resin film are balanced.Ethylene glycol improves the chemical resistance of the resin film, and neopentyl glycol is Particularly, it is advantageous as an alcohol component of the polyester resin A because it has an advantage of improving the weather resistance of the resin film.

As the alcohol component, a trifunctional or higher functional trihydric or higher polyhydric alcohol, for example, glycerin,
It may contain trimethylolethane, trimethylolpropane, pentaerythritol and the like. At this time,
In terms of maintaining good processability of the resin film, the proportion of the trifunctional or higher polyhydric alcohol in the alcohol component of the polyester resin A is preferably 10 mol% or less,
It is more preferably at most 8 mol%, particularly preferably at most 5 mol%.

The polyester resin A may contain, if necessary, fatty acids such as lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, linoleic acid, linolenic acid, and ester-forming derivatives thereof, benzoic acid, −te
High-boiling monocarboxylic acids such as rt-butylbenzoic acid, cyclohexanoic acid, and 4-hydroxyphenylstearic acid; high-boiling monoalcohols such as stearyl alcohol and 2-phenoxyethanol; ε-caprolactone; lactic acid; β-hydroxybutyric acid; A hydroxycarboxylic acid such as -hydroxybenzoic acid or an ester-forming derivative thereof may be copolymerized.

The acid value of the polyester resin A is 11
４０40 mgKOH / g, and 11 to 30 mgKOH / g.
g is preferable, and 11-25 mgKOH / g is more preferable. When the acid value exceeds 40 mgKOH / g, the hot water resistance and solvent resistance of the resin film become insufficient. On the other hand, when the acid value is 11
If the amount is less than mgKOH / g, it is difficult to disperse the polyester resin in the aqueous medium, and the reactivity with the curing agent is deteriorated. As a result, the hot water resistance and solvent resistance of the resin film are insufficient.

The weight average molecular weight of the polyester resin A is 14,000 or more, preferably 16,000 or more, and more preferably 18,000 or more. When the weight average molecular weight is less than 14,000, the hot water resistance and solvent resistance of the resin film are insufficient, and the workability of the resin film is insufficient. In addition, polyester resin A
The upper limit of the weight-average molecular weight is preferably 45,000 or less, more preferably 40,000 or less, and 35,000 or less, from the viewpoint that a sufficient acid value is easily imparted to the composition and the viscosity of the aqueous coating composition is appropriately maintained. Is particularly preferred.

The degree of dispersion of the molecular weight distribution of the polyester resin A is less than 4.0, preferably 3.8 or less, more preferably 3.6 or less. When the degree of dispersion of the molecular weight distribution exceeds 4.0, the hot water resistance and solvent resistance of the resin film become insufficient. It is considered that the reason for this is that an increase in the degree of dispersion of the molecular weight distribution lowers the uniformity of curing of the polyester resin by the curing agent. The degree of dispersion of the molecular weight distribution is a value obtained by dividing the weight average molecular weight by the number average molecular weight.

The polyester resin A may contain a hydroxyl group as a functional group having reactivity with a curing agent, and the hydroxyl value of the polyester resin A is 30 m.
gKOH / g or less is preferable, 20 mgKOH / g or less is more preferable, and 15 mgKOH / g or less is particularly preferable.

The glass transition temperature (abbreviated as T _g ) of the polyester resin A is not particularly limited, but is preferably 0 to 10 from the viewpoint that the hardness and workability of the resin film are easily balanced. 90 ° C. is preferred, and 30 to 80
C is more preferred.

The polyester resin A can be produced by ordinary polycondensation of one or more of the above-mentioned acid components and one or more of the alcohol components. Examples of known methods that can be used for the production of polyester resin A include: (a) reacting all monomer components and / or low polymers thereof in an inert atmosphere at 180 to 250 ° C. for about 2.5 to 10 hours; A method of obtaining a polyester resin by performing a polycondensation reaction at a temperature of 220 to 280 ° C under a reduced pressure of 130 Pa or less at a temperature of 220 to 280 ° C in the presence of a transesterification catalyst,
(B) terminating the polycondensation reaction at a stage before the target molecular weight is reached, and reacting the reaction product with a chain extender selected from an epoxy compound, an isocyanate compound, a bisoxazoline compound and the like in the next step. A method of increasing the molecular weight by mixing and reacting in a short time, (c) proceeding to the stage where the polycondensation reaction reaches a target molecular weight or more,
A method in which a monomer component is further added, and depolymerization is performed in an inert atmosphere under a normal pressure to a pressurized system to obtain a polyester resin having a target molecular weight can be given.

It is preferable that the carboxyl group contributing to the aqueous conversion of the polyester resin A is unevenly distributed at the terminal of the resin molecular chain rather than in the resin skeleton from the viewpoint of the hot water resistance of the coating. As a method for obtaining such a polyester resin without a side reaction or gelation, a method in which a polybasic acid having three or more functional groups or an ester-forming derivative thereof is added after the start of the polycondensation reaction in the above method (a). Or a method in which an acid anhydride of a polybasic acid is added immediately before the end of the polycondensation reaction. In the above method (b), a low molecular weight polyester resin in which most of the molecular chain ends are carboxyl groups is used as a chain extender. Or a method in which a polybasic acid or an ester-forming derivative thereof is used as a depolymerizing agent in the above method (c).

Next, the curing agent (B) (hereinafter referred to as curing agent B) will be described. The curing agent B is not particularly limited as long as it is a curing agent having reactivity with a functional group of the polyester resin A, for example, a carboxyl group or a hydroxyl group. For example, a phenol resin, an amino resin, a polyfunctional epoxy compound, Polyfunctional isocyanate compounds and their various blocked isocyanate compounds, polyfunctional aziridine compounds, carbodiimide group-containing compounds, oxazoline group-containing polymers, and the like. One of them may be used, or two or more thereof may be used in combination. Good.

Among the above curing agents, oxazoline group-containing polymers and polyfunctional isocyanate compounds are preferred.
Since the oxazoline group-containing polymer and the polyfunctional isocyanate compound can react quickly with the polyester resin A even at a relatively low temperature of less than 150 ° C., when coating the coating composition of the present invention on a substrate having low heat resistance, Particularly preferred.

The oxazoline group-containing polymer preferably used as the curing agent B may be any polymer having an oxazoline group, and is not particularly limited. Here, the oxazoline group is a functional group represented by the following general formula (1).

[0026]

Embedded image (In the formula, R ₁ , R ₂ , R ₃ , and R ₄ each independently represent a hydrogen atom, a halogen atom, an alkyl group, a cycloalkyl group, an aralkyl group, a cycloalkenyl group, an aryl group, or a substituted aryl group.)

The above oxazoline group-containing polymer can be easily obtained by polymerizing a monomer composition containing an oxazoline derivative, as described in, for example, JP-A-9-328656. As such oxazoline derivatives, for example, 2-vinyl-2-oxazoline, 2-vinyl-4-methyl-2-oxazoline, 2-vinyl-2-oxazoline,
Vinyl-5-methyl-2-oxazoline, 2-isopropenyl-2-oxazoline, 2-isopropenyl-4-
Methyl-2-oxazoline, 2-isopropenyl-5-
Methyl-2-oxazoline, 2-isopropenyl-5-
Ethyl-2-oxazoline and the like can be mentioned, and among these oxazoline derivatives, 2-isopropenyl-2-oxazoline is particularly preferable because it is industrially easily available. The monomer other than the oxazoline derivative contained in the monomer composition containing the oxazoline derivative is not particularly limited, as long as it is a compound copolymerized with the oxazoline derivative and is inactive with respect to the oxazoline group. Is, for example, methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, t-butyl (meth) acrylate, (meth) acrylic acid Cyclohexyl,
2-ethylhexyl (meth) acrylate, methoxypolyethylene glycol (meth) acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate,
2-hydroxyethyl (meth) acrylate, (meth)
2-hydroxypropyl acrylate, 4-hydroxybutyl (meth) acrylate, monoesters of (meth) acrylic acid with polypropylene glycol or polyethylene glycol, 2-aminoethyl (meth) acrylate and salts thereof, Caprolactone-modified (meth) acrylic acid, (meth) acrylic acid-2,2,6,6
-Tetramethylpiperidine, (meth) acrylic acid-1,
(Meth) such as 2,2,6,6-pentamethylpiperidine
Acrylic acid esters; sodium (meth) acrylate,
(Meth) acrylates such as potassium (meth) acrylate and ammonium (meth) acrylate; unsaturated nitriles such as acrylonitrile and methacrylonitrile; (meth)
Unsaturated amides such as acrylamide, N-methylol (meth) acrylamide, N- (2-hydroxyethyl) (meth) acrylamide; vinyl esters such as vinyl acetate and vinyl propionate; vinyl ethers such as methyl vinyl ether and ethyl vinyl ether; Α-olefins such as propylene; halogen-containing α, β-unsaturated aliphatic hydrocarbons such as vinyl chloride, vinylidene chloride and vinyl fluoride; α, β-unsaturated hydrocarbons such as styrene, α-methylstyrene and sodium styrenesulfonate. Saturated aromatic hydrocarbons; and the like. In the oxazoline group-containing polymer, the ratio of structural units derived from the oxazoline derivative is preferably 5% by mass or more. When the proportion of the structural unit derived from the oxazoline derivative accounts for 5% by mass or more, the oxazoline group-containing polymer can be sufficiently reacted with the polyester resin A.

The polyfunctional isocyanate compound preferably used as the curing agent B is a compound having two or more isocyanate groups in one molecule.
2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, diphenylmethane 2,4'- or 4,
4'-diisocyanate, polymethylene polyphenyl diisocyanate, tolidine diisocyanate, 1,4-
Diisocyanatobutane, hexamethylene diisocyanate, 1,5-diisocyanato-2,2-dimethylpentane, 2,2,4- or 2,4,4-trimethyl-1,6-diisocyanatohexane, 1,10- Diisocyanatodecane, 1,3- or 1,4-diisocyanatocyclohexane, 1-isocyanato-3,3,5-trimethyl-5-isocyanatomethyl-cyclohexane, 4,4′-diisocyanatodicyclohexylmethane, Hexahydrotoluene 2,4- or 2,6-diisocyanate, perhydro-
Polyfunctional isocyanate compounds such as 2,4'- or 4,4'-diphenylmethane diisocyanate, naphthalene 1,5-diisocyanate, xylylene diisocyanate, 1,3-bis (isocyanatomethyl) cyclohexane, tetramethyl xylylene diisocyanate, or And their modified products. Here, the modified product is obtained by modifying a diisocyanate of the polyfunctional isocyanate compound by a known method, for example, an allophanate group, a buret group,
Examples thereof include polyfunctional isocyanate compounds having a carbodiimide group, uretonimine group, uretdione group, isocyanurate group and the like, and adduct-type polyfunctional isocyanate compounds modified with a polyfunctional alcohol such as trimethylolpropane. Among these, it is particularly preferable to use a polyfunctional isocyanate compound having an isocyanurate group from the viewpoint of improving the solvent resistance of the resin film. Note that the polyfunctional isocyanate compound may contain monoisocyanate within a range of 20% by mass or less. Among the above-mentioned polyfunctional isocyanate compounds, it is preferable to use a modified product composed of hexamethylene diisocyanate from the viewpoint of improving the solvent resistance of the resin film, and among them, a compound having an isocyanurate group is particularly preferable.

The curing agent B is preferably an aqueous (water-soluble or water-dispersible) curing agent. Specific examples of the preferable aqueous oxazoline group-containing polymer that can be used as the curing agent B in the present invention include, from Nippon Shokubai Co., Ltd., Epocross WS-500, Epocross WS-700, Epocross K1010E, Epocross K1020E, Epocross K1030E, Epocross K2010E, Epocross K2020E, Epocross K
It can be obtained under brands such as 2030E. A preferred aqueous polyfunctional isocyanate compound can be usually obtained by reacting a polyfunctional isocyanate compound with a monovalent or polyvalent nonionic polyalkylene ether alcohol. A commercially available product of such an aqueous polyfunctional isocyanate compound is Bayhydur 310 manufactured by Sumitomo Bayer Urethane Co., Ltd.
0, Bihydur VPLS2150 / 1, SBU Isocyanate L801, Desmodu
r) N3400, Desmodur VPLS2102, Desmodur VPLS2025 / 1, SBU Isocyanate 0772, Desmodur DN, etc., or Takenate WD720, Takenate WD725, Takenate WD730, etc., manufactured by Takeda Pharmaceutical Co., Ltd., and further, Duranate, manufactured by Asahi Kasei Corporation WB40-100, Duranate WB40-80D, Duranate WX-1741
Etc. Above all, Bihidur 3100 and Death Modular DN are particularly preferred.

In the aqueous coating composition of the present invention, the polyester resin A and the curing agent B are dispersed or dissolved in an aqueous medium. Here, the aqueous medium is a medium composed of a liquid containing water as a main component, and may contain a basic compound or an organic solvent described later.

In the aqueous coating composition of the present invention, the total content of the content of the polyester resin A and the content of the curing agent B is defined as the film forming method, the type of the object to be coated, and the desired resin. It can be appropriately selected depending on the thickness and performance of the coating film, and is not particularly limited. However, from the viewpoint of maintaining the viscosity of the coating composition at an appropriate level and exhibiting good film forming ability, 1 to 60% by mass is preferable.
The content is more preferably from 55 to 55% by mass, further preferably from 5 to 50% by mass, and particularly preferably from 10 to 45% by mass.

The mass ratio (A) between the polyester resin A and the curing agent B in the aqueous coating composition of the present invention
/ (B) may be appropriately determined according to the properties of the polyester resin A, the properties of the curing agent B, and the properties of other components to be blended as necessary, and is not particularly limited. In terms of improving the hot water resistance and solvent resistance of the resin film and exhibiting good workability, the range represented by the following formula (2) is preferable, and the range represented by the following formula (3) is more preferable. The range shown by Expression (4) is particularly preferable.

(A) / (B) = 95/5 to 60/40 (2) (A) / (B) = 92/8 to 63/37 (3) (A) / (B) = 90/10 ~ 65/35 (4)

In the aqueous coating composition of the present invention, the carboxyl group of the polyester resin A is preferably neutralized by a basic compound, and aggregation between fine particles is prevented by the electric repulsion between the generated carboxyl anions. And imparts stability to the aqueous coating composition. The basic compound used for such a purpose has a boiling point of 25 because it is easy to volatilize during film formation.
Organic amines at 0 ° C. or lower, more preferably 160 ° C. or lower, or ammonia are preferred. Specific examples of preferably used organic amines include triethylamine, N, N-diethylethanolamine, N, N-dimethylethanolamine, aminoethanolamine, N-methyl-N, N-diethanolamine, isopropylamine, iminobispropylamine , Ethylamine, diethylamine, 3-ethoxypropylamine, 3-diethylaminopropylamine, sec-butylamine, propylamine, methylaminopropylamine, dimethylaminopropylamine, methyliminobispropylamine, 3-methoxypropylamine, monoethanolamine, Examples thereof include diethanolamine, triethanolamine, morpholine, N-methylmorpholine, and N-ethylmorpholine.

The amount of the basic compound to be used is, according to the amount of the carboxyl group contained in the polyester resin A, an amount capable of at least partially neutralizing the carboxyl group, that is,
The equivalent is preferably 0.2 to 1.5 times equivalent to the carboxyl group, more preferably 0.4 to 1.3 times equivalent. When the use amount of the basic compound is 0.2 equivalent or more, dispersion stability can be sufficiently imparted, and when the use amount is 1.5 equivalent or less, the aqueous coating composition is not remarkably thickened.

In dispersing or dissolving the polyester resin A in an aqueous medium (hereinafter referred to as aqueous solution), when water-soluble organic solvent is used in addition to water and the above-mentioned basic compound, the aqueous solution is promptly formed. It is preferred because it is performed. here,
The water-soluble organic solvent refers to an organic solvent having a solubility in water at 20 ° C. of 5 g / L or more, preferably 10 g / L or more. The boiling point of the water-soluble organic solvent is preferably 250 ° C. or lower, more preferably 150 ° C. or lower, since the lower the boiling point, the easier it is to volatilize from the resin film by drying.

In the present invention, specific examples of the organic solvent preferably used for making the polyester resin A aqueous include ethanol, n-propanol, isopropanol, n-butanol, isobutanol, sec-butanol, tert-butanol, and the like. alcohols such as n-amyl alcohol, isoamyl alcohol, sec-amyl alcohol, tert-amyl alcohol, 1-ethyl-1-propanol, 2-methyl-1-butanol, n-hexanol, cyclohexanol, methyl ethyl ketone, methyl isobutyl ketone , Ethyl butyl ketone, cyclohexanone, ketones such as isophorone,
Ethers such as tetrahydrofuran and dioxane, ethyl acetate, -n-propyl acetate, isopropyl acetate, -n-butyl acetate, isobutyl acetate, -sec-butyl acetate, -3-methoxybutyl acetate, methyl propionate,
Ester such as ethyl propionate, diethyl carbonate, dimethyl carbonate, ethylene glycol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, ethylene glycol monobutyl ether, ethylene glycol ethyl ether acetate, diethylene glycol, diethylene glycol monomethyl ether Glycol derivatives such as diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, diethylene glycol ethyl ether acetate, propylene glycol, propylene glycol monomethyl ether, propylene glycol monobutyl ether, and propylene glycol methyl ether acetate;
-Methoxy-3-methylbutanol, 3-methoxybutanol, acetonitrile, dimethylformamide, dimethylacetamide, diacetone alcohol, ethyl acetoacetate, and the like.
A mixture of more than one species may be used.

Further, the content of the water-soluble organic solvent in the aqueous coating composition is preferably 30% by mass or less, more preferably 25% by mass or less, and 20% by mass or less.
% By mass or less is more preferable. When the content of the organic solvent is in the above range, the film-forming ability, viscosity, and storage stability of the aqueous coating composition can be favorably maintained.
The content of the water-soluble organic solvent may be adjusted to a desired content by removing the water-soluble organic solvent by azeotropic distillation or the like in the process after the polyester resin A is converted to an aqueous solution. At this time, it is preferable to use a water-soluble organic solvent having a boiling point of 100 ° C. or lower or an azeotrope with water since the organic solvent can be easily removed from the aqueous coating composition.

Further, a compound having a protective colloid action may be added to the aqueous coating composition of the present invention, if necessary. The protective colloid action means that the resin particles are adsorbed on the surface of the resin particles in the aqueous medium, exhibiting the so-called "mixing effect", "osmotic pressure effect", and "volume limiting effect". Refers to the action of preventing. Compounds having such a protective colloid action include polyvinyl alcohol, carboxymethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, modified starch, polyvinylpyrrolidone, polyacrylic acid, acrylic acid and / or vinyl monomer having methacrylic acid as one component. Polymer, polyitaconic acid,
Gelatin, gum arabic, casein, swellable mica and the like can be exemplified.

The aqueous coating composition of the present invention may further contain, if necessary, various agents such as a leveling agent, an antifoaming agent, an anti-peeling agent, a pigment dispersant, an ultraviolet absorber, titanium oxide, zinc oxide, and carbon dioxide. A pigment or dye such as black may be added.

In the present invention, the method for producing the aqueous coating composition is not particularly limited. For example, the polyester resin A and the curing agent B may be collectively charged into an aqueous medium to perform aqueous conversion. Often, the polyester resin A can be made aqueous first, and the curing agent B can be added thereto in two stages.

Hereinafter, a preferred method in the case of performing the above two steps will be described in detail. First, a device is provided which is provided with a tank into which a liquid can be charged and which can appropriately stir a mixture of the aqueous medium and the resin powder or the granular material charged into the tank. As such a device, a device widely known to those skilled in the art as a solid / liquid stirring device or an emulsifying device can be used. Usually, a simple lid is provided and used under normal pressure or slight pressure. However, if necessary, a device capable of applying a pressure of 0.1 MPa or more can be used. An aqueous medium comprising water, a basic compound and a water-soluble organic solvent, and a granular or powdery polyester resin (A) are charged into a tank of this apparatus, and the mixture is preferably stirred and mixed at a temperature of 40 ° C. or lower to obtain a crude mixture. Disperse. At this time, when the shape of the polyester resin is a sheet or a large lump in which coarse dispersion is difficult, the process may be shifted to the following heating step. Next, the temperature in the tank was set to be equal to or higher than Tg of the polyester resin or 40 ° C.
The polyester resin (A) is made sufficiently water-soluble by maintaining stirring at the above temperature, preferably for 15 to 120 minutes, and then cooled preferably to 40 ° C. or lower under stirring.

After this, a jet pulverizing process may be further performed if necessary. The jet crushing process here means that a fluid such as a polyester resin dispersion is ejected from a fine hole such as a nozzle or a slit under high pressure, and resin particles or resin particles collide with a collision plate or the like. This is to further reduce the size of the resin particles by mechanical energy. P. V.
GAULIN's “homogenizer”, Mizuho Industry's “Microfluidizer M-110E / H” and the like. Further, if necessary, the organic solvent added above can be removed by azeotropic distillation or the like. As described above, an aqueous dispersion or solution of the polyester resin A is obtained.

The aqueous coating composition of the present invention is prepared by adding a predetermined amount of a curing agent and, if necessary, other additives while stirring the aqueous dispersion or solution of the polyester resin A. Can be manufactured. In this case, in the stirring and mixing at this time, when it is difficult to uniformly disperse the curing agent B at low speed stirring,
For example, a stirrer such as a homomixer to which a high shear force is applied at a high speed may be used. Further, if necessary, an organic solvent or water can be added for the purpose of lowering the viscosity of the system and improving the dispersibility of the curing agent and the additive.

As described above, the aqueous coating composition of the present invention is obtained by dispersing or dissolving the polyester resin A and the curing agent B in an aqueous medium to prepare a uniform liquid. Here, the term “homogeneous liquid” means that, in appearance, a portion where the solid content concentration is locally different from other portions, such as precipitation, phase separation or skinning, is not found in the aqueous coating composition. Say that. Further, it is preferable that coarse particles are not contained in the aqueous coating composition immediately after preparation. Here, the coarse particles specifically mean that when the aqueous coating composition is subjected to pressure filtration (air pressure 0.2 MPa) using a 300-mesh stainless steel filter (wire diameter 0.035 mm, plain weave), the filter is put on the filter. It is particles that remain, and for the purpose of preventing coarse particles from being mixed into the aqueous coating composition, the above-mentioned filtration or the like may be performed during the production process.

The coating composition of the present invention includes:
A small amount of precipitate or precipitate may occur during storage after preparation. This precipitate or precipitate is a polyester resin A
Is thought to be caused by a partial reaction between the polymer and the curing agent B. Even if these occur, they can be removed by the above-mentioned filtration or the like before use.

Next, the method of using the aqueous coating composition of the present invention will be described. Since the aqueous coating composition of the present invention is excellent in film forming ability, it can be uniformly formed on various substrate surfaces by a known film forming method, for example, a dipping method, a brush coating method, a spray coating method, a curtain flow coating method, or the like. After coating and setting as necessary at around room temperature, a uniform resin film can be formed in close contact with various substrate surfaces by subjecting it to a heat treatment for drying and baking. As a heating device at this time, a normal hot air circulation type oven, an infrared heater, or the like may be used. The heating temperature and the heating time are appropriately selected depending on the type of the curing agent B, the type of the substrate to be coated, and the like. 250 ° C. is preferred, 70 to 230 ° C. is more preferred, 80 to 200 ° C. is particularly preferred, and the heating time is preferably 1 second to 30 minutes, more preferably 5 seconds to 20 minutes, and particularly preferably 10 seconds to 10 minutes. preferable. When the above-mentioned precipitates and precipitates are generated in the coating composition before use, it is preferable to use the coating composition in a state where these are removed.

The thickness of the resin film formed by using the aqueous coating composition of the present invention is appropriately selected depending on the use, but is preferably 0.01 to 100.
μm is preferable, and 0.1 to 50 μm is more preferable.
Particularly preferred is 0.5 to 25 μm. If the film is formed so that the thickness of the resin film is in the above range, a resin film having excellent uniformity can be obtained. In addition, in order to adjust the thickness of the resin film, in addition to appropriately selecting an apparatus to be used for the coating and its use conditions, an aqueous coating composition having a concentration suitable for the intended thickness of the resin film is used. Is preferred. As a method of adjusting the concentration at this time, the concentration may be adjusted to a desired concentration according to the charged composition at the time of preparation, or the aqueous coating composition once prepared may be diluted to a desired concentration.

[0049]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, but it should not be construed that the invention is limited thereto. In addition, various characteristics were measured or evaluated by the following methods.

(1) Composition of polyester resin 1 Determined by ¹ H-NMR analysis (Varian, 300 MHz). In addition, the resin containing the constituent monomer having no peak that can be assigned or determined on the ¹ H-NMR spectrum is subjected to methanol decomposition in a sealed tube at 230 ° C. for 3 hours, and then subjected to gas chromatogram analysis and quantitative analysis. Was done.

(2) Acid Value of Polyester Resin 0.5 g of polyester resin is dissolved in 50 ml of water / dioxane = 10/1 (volume ratio), titrated with KOH using cresol red as an indicator, and consumed for neutralization. KO
The value obtained by converting the mg number of H per 1 g of the polyester resin was determined as the acid value. (3) Hydroxyl value of polyester resin 3 g of the polyester resin was precisely weighed, 0.6 ml of acetic anhydride and 50 ml of pyridine were added, and the mixture was stirred and reacted at room temperature for 48 hours. Subsequently, 5 ml of distilled water was added. 6 more
By continuing stirring for a period of time at room temperature, all acetic anhydride not used in the above reaction was also changed to acetic acid. 50 ml of dioxane is added to this solution, and cresol red
Titration with KOH using thymol blue as an indicator. The amount of KOH consumed for neutralization (W ₁ ) and the amount of acetic anhydride initially charged did not react with the polyester resin. From the amount of KOH required for the sum (calculated value: W ₀ ), the difference (W ₀ -W ₁ ) was determined by the number of mg of KOH, and this value was divided by the number of g of the polyester resin to obtain a hydroxyl value. And

(4) Weight-average molecular weight of polyester resin and degree of dispersion of molecular weight distribution The weight-average molecular weight was determined by GPC analysis (using a liquid sending unit LC-10ADvp type and an ultraviolet-visible spectrophotometer SPD-6AV type manufactured by Shimadzu Corporation). , Detection wavelength: 254 nm, solvent: tetrahydrofuran, converted to polystyrene). Similarly, the number average molecular weight was determined, and the degree of dispersion of the molecular weight distribution was calculated as a value obtained by dividing the weight average molecular weight by the number average molecular weight. (5) Glass transition temperature of polyester resin 10 mg of polyester resin was used as a sample, and a DSC (differential scanning calorimetry) device (DSC manufactured by PerkinElmer) was used.
The measurement is performed under the condition of a heating rate of 10 ° C./min using 7),
The intermediate value of the temperatures at the two bending points derived from the glass transition in the obtained temperature rise curve was determined and defined as the glass transition temperature (T _g ).

(6) Solid Content Concentration of Aqueous Dispersion of Polyester Resin An appropriate amount of the polyester dispersion was weighed and heated at 150 ° C. until the mass of the residue (solid content) reached a constant weight. I asked.

(7) Thickness of resin film Thickness gauge (MICROFIN manufactured by Union Tool Co., Ltd.)
E Σ) using a substrate (PET film in the example)
Is measured in advance, and after forming a resin film on the substrate using the aqueous coating composition, the thickness of the substrate having the resin film is measured in the same manner, the difference is the resin film It was thick.

(8) Hot Water Resistance of Resin Coating The substrate having the resin coating was held in a hot water bath at 90 ° C. for 1 hour, pulled up, air-dried, and visually observed for the state of the resin coating. evaluated. ：: Transparent without any change △: Slight whitening observed X: Clearly whitened XX: Dissolved film (9) Solvent resistance of resin film After dipping in ethyl acetate or toluene) for 30 seconds, the film was pulled up, air-dried, and the state of the resin film was visually observed, and evaluated according to the same criteria as the above hot water resistance.

The polyester resins used in Examples and Comparative Examples were obtained as follows. [Polyester resins P-1, P-3, P-4, P-7,
P-8] terephthalic acid 25.10 kg, isophthalic acid 1
A mixture composed of 0.76 kg, 9.38 kg of ethylene glycol, and 13.48 kg of neopentyl glycol was heated in an autoclave at 260 ° C. for 4 hours to carry out an esterification reaction. Next, an ethylene glycol solution containing 1% by mass of antimony trioxide was used as a catalyst at 1.57 k.
g was added, the temperature of the system was raised to 280 ° C., and the pressure of the system was gradually reduced to 13 Pa after 1.5 hours. The polycondensation reaction was further continued under these conditions, and after 2 hours, the system was brought to normal pressure with nitrogen gas, and the temperature of the system was lowered. When the temperature reached 270 ° C, 817 g of trimellitic acid was added, and the mixture was stirred at 250 ° C for 1 hour. Thus, a depolymerization reaction was performed. Thereafter, the resin was discharged in a sheet shape while being pressurized with nitrogen gas. After sufficiently cooling this to room temperature, it was pulverized with a crusher, and a fraction having an opening of 1 to 6 mm was collected using a sieve to obtain a granular polyester resin P-1. In a similar way,
The polyester resins P-3, P-4, and P-4 were made so that the configuration of the acid component and the alcohol component was as shown in Table 1.
-7 and P-8 were obtained. [Polyester resins P-2, P-5] terephthalic acid
85 kg, isophthalic acid 10.65 kg, ethylene glycol 11.18 kg, neopentyl glycol
The mixture consisting of 16 kg was placed in an autoclave at 260
C. for 4 hours to carry out an esterification reaction. Then, 1.56 kg of an ethylene glycol solution containing 1% by mass of antimony trioxide was added as a catalyst, and the temperature of the system was reduced to 28%.
The temperature was raised to 0 ° C., and the pressure of the system was gradually reduced to 13 Pa after 1.5 hours. The polycondensation reaction was further continued under these conditions, and after 2 hours, the system was brought to normal pressure with nitrogen gas, and the temperature of the system was lowered.
And neopentyl glycol 356 g,
For 1 hour to carry out a depolymerization reaction. Thereafter, the resin was discharged in a sheet shape while being pressurized with nitrogen gas. After sufficiently cooling this to room temperature, it was pulverized with a crusher, and a fraction having an opening of 1 to 6 mm was collected using a sieve to obtain a granular polyester resin P-2. In a similar manner, the polyester resin P-5 was obtained so that the configuration of the acid component and the alcohol component was as shown in Table 1. [Polyester resin P-6] terephthalic acid 35.51k
g, 3.32 kg of ethylene glycol and 21.95 kg of 1,2-propanediol were heated in an autoclave at 240 ° C. for 4 hours to carry out an esterification reaction. Next, an ethylene glycol solution containing 1% by mass of tetra-n-butyl titanate as a catalyst was 2.9.
1 kg was added, and the pressure of the system was gradually reduced to 13 Pa after 1.5 hours. The polycondensation reaction was further continued under these conditions, and after 4 hours, the system was brought to normal pressure with nitrogen gas, and the temperature of the system was lowered.
g was added and stirred at 230 ° C. for 2 hours to carry out a depolymerization reaction. Thereafter, the resin was discharged in a sheet shape while being pressurized with nitrogen gas. After sufficiently cooling the mixture to room temperature, it is pulverized with a crusher, and a fraction having an opening of 1 to 6 mm is collected using a sieve, and the granular polyester resin P
-6.

[Polyester resin P-9] Terephthalic acid 2
4.85 kg, isophthalic acid 10.65 kg, ethylene glycol 11.18 kg, neopentyl glycol 1
0.16 kg of the mixture was placed in an autoclave for 2 hours.
The esterification reaction was performed by heating at 60 ° C. for 4 hours. Next, 1.56 kg of an ethylene glycol solution containing 1% by mass of antimony trioxide was added as a catalyst, the temperature of the system was raised to 280 ° C., and the pressure of the system was gradually reduced to 13 Pa after 1.5 hours. The polycondensation reaction was further continued under these conditions, and after 2 hours, the system was brought to normal pressure with nitrogen gas, the temperature of the system was lowered, and when the temperature reached 270 ° C., trimellitic acid was 1.9.
3 kg and 287 g of trimethylolpropane were added, and 2
The mixture was stirred at 50 ° C. for 1 hour to carry out a depolymerization reaction. Thereafter, the resin was discharged in a sheet shape while being pressurized with nitrogen gas. And after cooling it to room temperature,
The mixture was pulverized with a crusher, and a fraction having an opening of 1 to 6 mm was collected using a sieve to obtain a granular polyester resin P-9.

Table 1 shows the results obtained by analyzing or evaluating the type and amount of the depolymerizing agent used in the production and the properties of the obtained polyester resin for each of the polyester resins obtained as described above. Among these polyester resins, the polyester resin A of the present invention
P-1 to P-6 satisfy the requirements as.

[0059]

[Table 1]

Using the above polyester resin, an aqueous dispersion of polyester resin was obtained by the following method. [Aqueous Dispersion of Polyester Resin E-1 to E-9] Using a stirrer (TK Robomix, manufactured by Tokushu Kika Kogyo Co., Ltd.) equipped with a jacketed and sealable 2 liter glass container, 300 g Polyester resin P-1, 1
80 g of isopropyl alcohol, 9.2 g of triethylamine and 511 g of distilled water were charged into a glass container, and the rotation speed of the stirring blade (homodisper) was 7,000.
When the mixture was stirred at rpm, no sedimentation of resin particles was observed at the bottom of the container, and it was confirmed that the container was completely suspended. Then, while maintaining this state, the heated water was passed through the jacket after 10 minutes. And the system temperature is 7
The mixture was kept at 3-75 ° C. and stirred for 30 minutes. afterwards,
Pour cold water into the jacket and rotate at 4,000 rpm
m and cooled to room temperature (about 25 ° C) with stirring.
A milky white uniform polyester resin aqueous dispersion E-1 was obtained. In addition, by performing the same operation with the charged compositions shown in Table 2 below, polyester resin aqueous dispersions E-2 to E-
-9 was obtained. Table 2 below shows the charged composition when the above-mentioned polyester resin aqueous dispersion was obtained, and the solid content concentration measured for the obtained polyester resin aqueous dispersion.

[0061]

[Table 2]

Example 1 As a curing agent, a polyfunctional isocyanate compound having an isocyanurate group based on hexamethylene diisocyanate (manufactured by Sumitomo Bayer Urethane Co., Ltd., Bihydur 3100, isocyanate group content: about 17% by mass, solid content concentration) : 100% by mass). 100 g of the polyester resin aqueous dispersion E-1 was weighed, and while the mixture was stirred with a low-speed stirrer (manufactured by EYELA, MDS-NS), 5.5 g of a curing agent was gradually added, and room temperature (about 25 ° C.)
For 10 minutes. Then add distilled water to this
g was further added and stirred and mixed at room temperature (about 25 ° C.) for about 10 minutes to prepare and obtain an aqueous coating composition. The appearance of the aqueous coating composition was visually observed and found to be uniform without any precipitation or layer separation. Next, the obtained aqueous coating composition was coated on a biaxially stretched PET film (produced by Unitika Ltd., thickness: 12 μm) as a base material, using a table-type coating apparatus (produced by Yasuda Seiki, film applicator No. 542-AB).
After coating using a mold and bar coater)
By heating for 1 minute in an oven set at 30 ° C., a 1 μm-thick resin film was formed on the PET film. The PET film having this resin film was subjected to the evaluation of the characteristics of the resin film.

Example 2 As a curing agent, a polyfunctional isocyanate compound based on hexamethylene diisocyanate, having an isocyanurate group and having a different isocyanate group content from that used in Example 1 (manufactured by Sumitomo Bayer Urethane Co., Ltd.) , Desmodur DN, isocyanate group content: about 22% by mass, solid content concentration: 100% by mass). 300 g of the polyester resin aqueous dispersion E-1 was weighed, and this was stirred at a high speed of 15000 rpm using a composite stirrer (TK Robomix, manufactured by Tokushu Kika Kogyo Co., Ltd.). 60 g was gradually added, followed by stirring and mixing at room temperature (about 25 ° C.) for about 5 minutes. Next, 12.9 g of a curing agent was gradually added, followed by stirring and mixing at room temperature (about 25 ° C.) for about 10 minutes. Then, 240 g of distilled water was added, and the mixture was further stirred and mixed at room temperature (about 25 ° C.) for about 5 minutes to prepare and obtain an aqueous coating composition. The appearance of the aqueous coating composition was visually observed and found to be uniform without any precipitation or layer separation. Next, using the obtained aqueous coating composition, a 1 μm thick
m of resin coating was formed.

Examples 3 to 7 and Comparative Examples 1 to 3 An aqueous coating composition was prepared in the same manner as in Example 1 except that the type of the polyester resin aqueous dispersion was changed, and using the same curing agent as in Example 1. Was prepared and obtained. Visual observation of the appearance of these aqueous coating compositions revealed that all of them were uniform without any precipitation or layer separation. Using the obtained aqueous coating composition, a resin film having a thickness of 1 μm was formed on a PET film by the same operation as in Example 1.

Examples 8 to 12 and Comparative Examples 4 to 6 An aqueous coating composition was prepared in the same manner as in Example 2 except that the type of the aqueous polyester resin dispersion was changed, and using the same curing agent as in Example 2. Was prepared and obtained. Visual observation of the appearance of these aqueous coating compositions revealed that all of them were uniform without any precipitation or layer separation. Using the obtained aqueous coating composition, a resin film having a thickness of 1 μm was formed on a PET film by the same operation as in Example 1. Table 3 below shows the types of the aqueous polyester resin dispersions used in the above Examples and Comparative Examples, and the characteristics of the resin film formed from the obtained aqueous coating composition.

[0066]

[Table 3]

From the above Examples and Comparative Examples, the aqueous coating composition of the present invention can be obtained by coating the polyester resin since the acid value, the weight average molecular weight and the degree of dispersion of the molecular weight distribution are appropriate. It was found that the performance of the resin coating was greatly improved.

[0068]

The aqueous coating composition of the present invention can form a polyester resin film excellent in hot water resistance, solvent resistance and processability, and is required to have hot water resistance and solvent resistance. It is suitable as a binder component in paints and various coating agents, such as anchor coat of various films, inner or outer surface coating of cans, steel plate paint, pre-coated metal paint, adhesive, surface treatment agent, ink, fiber treatment agent, paper coating. They can be used in applications such as agents to improve their performance.

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Sachiko Kokuryo 23 Uji Kozakura, Uji-city, Kyoto Unitika Central Research Laboratory F-term (reference) 4J038 CK022 DA042 DA112 DB002 DD061 DD071 DD191 DG111 DG301 GA06 JB18 JB26 KA03 MA08 MA09 MA10 MA14 NA04 NA14

Claims (5)

[Claims] 1. A polyester resin having (A) an acid value of 11 to 40 mg KOH / g, a weight average molecular weight of 14,000 or more and a molecular weight distribution of less than 4.0, and (B)
An aqueous coating composition comprising a curing agent. 2. The aqueous coating composition according to claim 1, wherein the polyester resin contains at least 50 mol% of an aromatic polybasic acid as a constituent acid component. 3. The aqueous coating composition according to claim 1, wherein the polyester resin is a polyester resin mainly composed of neopentyl glycol and ethylene glycol as constituent alcohol components. 4. The aqueous coating composition according to claim 1, wherein the curing agent is a polyfunctional isocyanate compound. 5. The aqueous coating composition according to claim 4, wherein the polyfunctional isocyanate compound is a modified product comprising hexamethylene diisocyanate.