JP2008231398A - Aqueous coating composition and coated product using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an aqueous coating composition capable of forming a coating film that has excellent water resistance, further has all of sufficient processability, corrosion resistance and slip property, when the composition is used as can coating, particularly lid coating, and can form a coating film having both flavor property and adhesion, when used as an inner surface coating for a can body part. <P>SOLUTION: An epoxy resin (a1), an acrylic resin (a2) of 10 to 135 mg KOH/g acid value, and an acrylic resin (a3) of 180 to 450 mg KOH/g acid value are allowed to react with each other to form an acryl-modified epoxy resin (A1) and the acryl-modified epoxy resin is dispersed in an aqueous medium including a basic compound (a4) to obtain the aqueous resin composition. The acryl-modified epoxy resin (A1) is obtained by allowing the epoxy resin (a1) to react with the acryl resin (a2) in the presence of a basic compound (a4-1) so that the reaction rate of the carboxyl group of the acrylic resin (a2) may become 30 to 95%, then the acrylic resin (a3) is added and they are allowed to react with each other. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an aqueous coating composition and an article to be coated using the same, and more particularly to an aqueous coating composition for covering a beverage packaging container that contains a beverage. More specifically, among the beverage packaging containers, a lid member for a can that requires processability and corrosion resistance, and among them, an aqueous coating composition that is suitable for covering the inner surface of a lid member of a carbonated beverage can that requires particularly high corrosion resistance. About. The water-based coating composition of the present invention is also suitable for coating the inner surface of a can for alcoholic beverages, particularly for the inner surface of the can body part, which requires a high content resistance among beverage packaging containers.

  A coating composition mainly composed of an aromatic epoxy resin is excellent in processability, content resistance and physical properties of a coating film, and is used as a coating for metal, particularly for cans, but the aromatic epoxy resin itself is water-based. Does not dissolve or disperse in the medium.

  On the other hand, water-based undercoats and paints for metals are being studied from the viewpoints of resource saving, energy saving, environmental protection, and various proposals have been made for undercoatings and paints mainly composed of aromatic epoxy resins. ing. For example, a method of dispersing an aromatic epoxy resin in water using a surfactant is known, but the action of the surfactant tends to adversely affect the storage stability of the paint and the physical properties of the coating film.

  Therefore, various so-called self-emulsifying aromatic epoxy resins having a carboxyl group and an epoxy group in one molecule have been proposed as a method for making an aromatic epoxy resin aqueous without using a surfactant. Yes.

  For example, in Patent Document 1 (Japanese Patent Laid-Open No. 53-14963) and Patent Document 2 (Japanese Patent Laid-Open No. 5-9433), a part of the carboxyl group in an acrylic resin having a carboxyl group and an aromatic group are disclosed. A part of the epoxy group in the epoxy resin is ester-reacted in the presence of a tertiary amine to obtain a modified epoxy resin (this method is hereinafter referred to as “esterification method”), and then in the modified epoxy resin It has been shown that a modified epoxy resin can be stably dispersed in an aqueous medium by neutralizing remaining excess carboxyl groups with a basic compound such as ammonia or amines.

  Further, in Patent Document 3 (Japanese Patent Laid-Open No. 57-105418) and Patent Document 4 (Japanese Patent Laid-Open No. 58-198513), some of the epoxy groups in the aromatic epoxy resin are (meth) React with a carboxyl group in a monomer having both a carboxyl group such as acrylic acid and a radically polymerizable unsaturated double bond to obtain a compound having both an epoxy group and a radically polymerizable unsaturated double bond in one molecule. The compound is copolymerized with a mixture of various monomers having a radical polymerizable unsaturated double bond and (meth) acrylic acid (this method is hereinafter referred to as “direct polymerization method”), and the resulting copolymer is obtained. In other words, the modified epoxy resin can be stably dispersed in an aqueous medium by neutralizing the carboxyl group in the modified epoxy resin with a basic compound such as ammonia or amines. It is.

  Furthermore, in Patent Document 5 (Japanese Patent Laid-Open No. 53-1228), a free radical generator such as benzoyl peroxide is used in the presence of an aromatic epoxy resin and a carboxyl group such as (meth) acrylic acid and a radical. An acrylic copolymer is grafted onto an aromatic epoxy resin by copolymerizing a mixture of various monomers having a radically polymerizable unsaturated double bond including a monomer having a polymerizable unsaturated double bond. It has been shown that a modified epoxy resin (this method is hereinafter referred to as “grafting method”) can be stably dispersed in an aqueous medium by neutralization with a basic compound such as ammonia or amines.

  All of the modified epoxy resins obtained by the above methods are self-emulsifying types in which the modified epoxy resin itself has dispersibility in water, and when used as a coating composition, the coating film does not contain a surfactant. Excellent performance and water resistance. However, all of the above self-emulsifying epoxy resins have the disadvantage that the parts derived from the acrylic resin are liable to lose performance such as adhesion to the base inherent in the epoxy resin, corrosion resistance, and good workability. It was.

  In particular, beverage cans filled with carbonated beverages are returned to room temperature after the contents are filled and the lid is attached at a low temperature of about 5 ° C. In this process, carbonic acid volatilizes from the beverage and the pressure inside the can increases, so the lid portion of the can swells outward due to the pressure from inside. After this, there is volatilization from the filling of carbonic acid due to changes in the atmospheric temperature and dissolution in the filling, and the lid repeats unevenness. As a result, the lid is deformed in a state where the contents are filled, and the deformed portion is easily corroded. Therefore, various processes are performed on the lid portion in consideration of such deformation due to internal pressure. Since these various processes are performed after the coating film is provided on both sides of the lid, the coating film has high workability so as not to cause a coating film defect in various processes, so that the coating film is not damaged during processing. High slipperiness and high corrosion resistance are required so that corrosion does not occur even if the lid is uneven after filling the contents.

There are usually two types of methods for imparting slipperiness to the coating film.
1. A slipperiness imparting substance such as wax is added to the paint, and the slipperiness is imparted by orienting the wax or the like on the surface of the coating during the coating formation (hereinafter, this method is referred to as “inner wax”. Is called "inner wax type").
2. The slipperiness imparting substance such as wax is not added to the paint, or only a small amount is added, and the slipperiness is imparted by applying wax after forming the coating film (this method is hereinafter referred to as “outer wax”). .
Recently, an inner wax type paint has been required from the viewpoints of process simplification and productivity.

  Various proposals have been made to improve the processability of a coating film using a self-emulsifying epoxy resin. In Patent Document 6 (Japanese Patent Laid-Open No. 04-283218) and Patent Document 7 (Japanese Patent Laid-Open No. 05-017556), a reaction product of an acrylic resin having an acid value of 0 to 70 and an epoxy resin is further added. It has been proposed to improve the processability of the coating film by reacting a high acid value acrylic resin having an acid value of 100 to 500.

  Patent Document 8 (Japanese Patent Laid-Open No. 2000-73005) discloses an epoxy resin portion, an acid value of less than 50 (mgKOH / g), and a glass transition temperature (hereinafter also referred to as “Tg”) of less than 50 ° C. A modified epoxy resin having a low acid value and a low Tg acrylic resin part, and an aqueous coating agent containing a modified epoxy resin having an epoxy resin part and a high acid value acrylic resin part have been proposed.

  In the paints described in Patent Documents 6 and 7, the reaction rate between the epoxy resin and the low acid value acrylic resin exceeds 95%. Since the reaction cannot be carried out, the water dispersibility is lowered, resulting in sag or gelation without water dispersion.

  In general, the processability of the coating film can be improved by lowering the Tg of the film-forming component. Usually, by using a large amount of a monomer having a long alkyl group, the Tg of the acrylic resin can be lowered. However, in order to reduce the Tg of the acrylic resin part which is a constituent part of the self-emulsifying epoxy resin, a large amount of a monomer having a long alkyl group is used, and the compatibility between the epoxy resin part and the acrylic resin part is high. Deteriorate. As a result of the poor compatibility of both parts, the epoxy resin and the unreacted acrylic resin part are separated at the time of coating film formation due to the difference in specific gravity and melt viscosity, and the acrylic resin part is localized on the coating film surface. .

  When a slipperiness imparting substance such as wax is added to the aqueous resin compositions and aqueous coating agents disclosed in Patent Documents 6 to 8 above and used as an inner wax type paint, the Tg of the low acid value acrylic resin is too low. Therefore, the further problem that the slip property of the coating film formed worsens occurred. By constituting the self-emulsifying type epoxy resin with an acrylic resin portion having a Tg that is too low, the acrylic resin portion having a low Tg is oriented on the surface of the coating film. Considered. Although the reason is unknown, when the low Tg acrylic resin portion is formed from a component that essentially requires 2-ethylhexyl acrylate, the slippage is remarkably reduced.

In addition, when the coating film of a beverage can filled with a beverage containing alcohol (hereinafter also referred to as “alcoholic beverage”) is filled with a beverage not containing alcohol (hereinafter also referred to as “non-alcoholic beverage”). Since the behavior is different and the inner surface coating film easily becomes compatible with a beverage containing alcohol, the coating film is likely to deteriorate. Moreover, since the flavor component in alcoholic beverages is more easily adsorbed to the coating film than the flavor component in non-alcoholic beverages, the paint disclosed in the publicly known literature is used for coating the inner surface of cans for containing alcoholic beverages. I couldn't.
Japanese Patent Laid-Open No. 53-14963 JP 55-9433 A JP-A-57-105418 JP 58-198513 A Japanese Patent Laid-Open No. 53-1228 Japanese Patent Laid-Open No. 04-283218 JP 05-017556 A JP 2000-73005 A

  The object of the present invention is to improve various disadvantages of the self-emulsifying type epoxy resin, to be excellent in water resistance, and to have sufficient processability, corrosion resistance and slipperiness when used as a paint for cans, especially as a paint for lids. An object of the present invention is to provide an aqueous resin composition capable of forming a coating film having both flavor and adhesion when used as an inner surface paint of a can body.

  In the present invention, first, an epoxy resin (a1) and a low acid value carboxyl group-containing acrylic resin (a2) are reacted with a carboxyl group reaction rate of the acrylic resin (a2) in the presence of a basic compound (a4-1). Is a water-based resin composition containing an acrylic-modified epoxy resin (A1) obtained by reacting with a high acid value carboxyl group-containing acrylic resin (a3). This has been achieved by finding out that the problem can be solved.

That is, the first invention is an epoxy resin (a1), a carboxyl group-containing acrylic resin (a2) having an acid value of 10 to 135 mgKOH / g, and a carboxyl group-containing acrylic resin (a3) having an acid value of 180 to 450 mgKOH / g. An aqueous resin composition obtained by dispersing an acrylic-modified epoxy resin (A1) obtained by reacting in an aqueous medium containing a basic compound (a4),
In the acrylic-modified epoxy resin (A1), first, the epoxy resin (a1) and the acrylic resin (a2) are reacted in the presence of the basic compound (a4-1) with the carboxyl group reaction rate of the acrylic resin (a2). React to 30-95%, then
The present invention relates to an aqueous resin composition obtained by reacting by adding an acrylic resin (a3).

  The second invention is characterized in that the acrylic-modified epoxy resin (A1) is obtained by adding and reacting the basic compound (a4-2) when adding the acrylic resin (a3). This relates to an aqueous resin composition.

  3rd invention is 0.1-1.5 mol of basic compounds (a4) with respect to 1 mol in total of the carboxyl group which carboxyl group-containing acrylic resin (a2) and carboxyl group-containing acrylic resin (a3) have. It is related with the aqueous resin composition of the 1st or 2nd invention characterized by being.

  4th invention is 0.1-1.5 mol of basic compounds (a4) with respect to a total of 1 mol of the carboxyl group which carboxyl group-containing acrylic resin (a2) and carboxyl group-containing acrylic resin (a3) have. And the molar ratio of the basic compound (a4-1) to the basic compound (a4-2) is (a4-1) / (a4-2) = 0.1-100. The present invention relates to the aqueous resin composition of the second or third invention.

  In a fifth aspect of the invention, the carboxyl group-containing acrylic resin (a2) polymerizes a monomer containing 50% by weight or more of ethyl acrylate, acrylate-2-ethylhexyl, or ethyl acrylate and -2-ethylhexyl acrylate. The aqueous resin composition according to any one of the first to fourth inventions.

6th invention is 100 weight% in total of epoxy resin (a1), carboxyl group-containing acrylic resin (a2), and carboxyl group-containing acrylic resin (a3),
(A1): 30 to 95% by weight,
(A2): 0.1 to 60% by weight,
(A3): 0.5-69.9 wt%
The present invention relates to the aqueous resin composition according to any one of the first to fifth inventions.

The seventh invention reacts the epoxy resin (a1), the carboxyl group-containing acrylic resin (a2) having an acid value of 10 to 135 mgKOH / g, and the carboxyl group-containing acrylic resin (a3) having an acid value of 180 to 450 mgKOH / g. A method for producing an aqueous resin composition containing an acrylic-modified epoxy resin (A1),
First, the epoxy resin (a1) and the acrylic resin (a2) are reacted in the presence of the basic compound (a4-1) so that the reaction rate of the carboxyl group of the acrylic resin (a2) is 30 to 95%. ,
Next, an acrylic resin (a3) is added and reacted, and the resulting acrylic modified epoxy resin (A1) is dispersed in an aqueous medium in the presence of the basic compound (a4). It relates to the manufacturing method.

  8th invention is related with the manufacturing method of the aqueous resin composition of 7th invention characterized by adding basic compound (a4-2) with an acrylic resin (a3).

  A ninth invention relates to an aqueous paint comprising the aqueous resin composition of any one of the first to sixth inventions.

  The tenth invention relates to an article to be coated, which is a base material coated with the water-based paint of the ninth invention.

  An eleventh invention relates to the article to be coated according to the tenth invention, wherein the substrate is any one selected from the group consisting of a metal, a metal coated with a paint, and a plastic film-coated metal.

  The twelfth invention relates to the article to be coated of the tenth or eleventh invention, wherein the substrate is plate-shaped or bottomed cylindrical.

  A thirteenth invention relates to a beverage container using the article to be coated of any of the tenth to twelfth inventions.

  According to the present invention, it is excellent in water resistance, has sufficient processability and corrosion resistance and slipperiness when used as a paint for cans, particularly as a paint for lids, and has a flavor property when used as an internal paint for can bodies. An aqueous resin composition capable of forming a coating film having adhesiveness can be provided.

  The aqueous resin composition of the present invention comprises a low acid value carboxyl group-containing acrylic resin (a2) responsible for processability and corrosion resistance, and a high acid value carboxyl group-containing acrylic resin (a3) and an epoxy resin (a1) responsible for an aqueous function. And an acrylic-modified epoxy resin (A1) obtained by esterification reaction, a basic compound, and an aqueous medium.

  That is, by reacting the carboxyl group-containing acrylic resin (a2) with the epoxy resin (a1) at a specific reaction rate, separation and orientation of the acrylic resin (a2) on the coating film surface can be suppressed / prevented. As a result, a stress relieving function for deformation and processing can be effectively expressed, and a coating film having good workability, corrosion resistance, and slipperiness can be obtained. Furthermore, it has very excellent water dispersibility due to the high acid value acrylic resin part.

  Hereinafter, the epoxy resin (a1), carboxyl group-containing acrylic resin (a2), carboxyl group-containing acrylic resin (a3) and the like used in the present invention will be described.

  Examples of the epoxy resin (a1) used in the present invention include aromatic epoxy resins such as bisphenol type and novolac type, and alicyclic epoxy resins. Of these, bisphenol A-type epoxy resin, bisphenol F-type epoxy resin, and bisphenol B-type epoxy resin are used alone or in combination, or bisphenol A, bisphenol F, and bisphenol B are used in combination from the viewpoint of physical properties of the coating. It is preferable to use an epoxy resin copolymerized with more than one species.

  The carboxyl group-containing acrylic resin (a2) and the carboxyl group-containing acrylic resin (a3) used in the present invention are both copolymers obtained by reacting an α, β-unsaturated carboxylic acid with a monomer copolymerizable therewith. It is.

  Examples of the α, β-unsaturated carboxylic acid include (meth) acrylic acid, maleic acid, itaconic acid, fumaric acid and the like, and (meth) acrylic acid is preferable.

Examples of the copolymerizable monomer that is copolymerized with the α, β-unsaturated carboxylic acid include styrene monomers such as styrene, vinyltoluene, 2-methylstyrene, t-butylstyrene, and chlorostyrene;
Methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, n-isopropyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, (meth ) Tert-butyl acrylate, n-amyl (meth) acrylate, isoamyl (meth) acrylate, n-hexyl (meth) acrylate, cyclohexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, ( (Meth) acrylic acid ester monomers such as n-octyl (meth) acrylate, decyl (meth) acrylate, dodecyl (meth) acrylate, lauryl (meth) acrylate, isobornyl (meth) acrylate;
Hydroxyl group-containing monomers such as 2-hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, and hydroxymethyl (meth) acrylate;
Examples thereof include one or more of N-substituted (meth) acrylic acid monomers such as N-methylol (meth) acrylamide and N-butoxymethyl (meth) acrylamide.

  Of these, styrene and ethyl acrylate are particularly preferred.

  The carboxyl group-containing acrylic resin (a2) and the carboxyl group-containing acrylic resin (a3) can be obtained, for example, by subjecting a mixture of the above monomers to solution polymerization in an organic solvent in the presence of a polymerization initiator.

Carboxyl group-containing acrylic resin (a2) has an acid value X _a is important to be _{10mgKOH / g ≦ X a ≦ 135mgKOH} / g, is preferably _{15mgKOH / g ≦ X a ≦ 120mgKOH} / g. If it is less than 10 mg KOH / g, the reactivity with the epoxy resin (a1) is lowered, and sufficient corrosion resistance of the coating film cannot be obtained and the slipping property is deteriorated. When it is larger than 135 mgKOH / g, the hydrophilicity of the coating film increases and the water resistance deteriorates.

  That is, the carboxyl group-containing acrylic resin (a2) having a specific range of acid values with an acid value not too low is used to esterify the carboxyl group-containing acrylic resin (a2) and the epoxy resin (a1) within a specific reaction rate. By reacting, separation of the epoxy resin (a1) and the carboxyl group-containing acrylic resin (a2) when the coating film is formed can be prevented. By preventing the separation, the carboxyl group-containing acrylic resin (a2) exhibits a sufficient stress relaxation function, improves the workability and corrosion resistance of the resulting coating film, and inhibits the effect of the added wax. In addition, the slipperiness of the coating film is improved.

  Further, the glass transition temperature (Tg) of the carboxyl group-containing acrylic resin (a2) is not particularly limited, but is preferably −20 ° C. ≦ Tg ≦ 20 ° C., and is −18 ° C. ≦ Tg ≦ 10 ° C. More preferably. If it is lower than −20 ° C., the slipperiness of the coating film is deteriorated, and if it is higher than 20 ° C., high workability and corrosion resistance required for a carbonated beverage can may be obtained.

  Furthermore, the weight average molecular weight (Mw) of the carboxyl group-containing acrylic resin (a2) is not particularly limited, but preferably 10,000 ≦ Mw ≦ 200000.

  When the aqueous resin composition of the present invention is used for covering a can lid, the Mw of the carboxyl group-containing acrylic resin (a2) is preferably 30000 ≦ Mw ≦ 200000, and more preferably 40000 ≦ Mw ≦ 160000. preferable. If it is smaller than 30000, the stress relaxation function in the coating film is not sufficient, and the high workability and corrosion resistance required for carbonated beverage cans may not be obtained. On the other hand, if it is larger than 200000, there is a possibility of increasing the viscosity or gelation during the reaction with the epoxy resin (a1).

  In addition, it is extremely difficult to bond the carboxyl group-containing acrylic resin portion having a relatively large Mw to the epoxy resin (a1) by a graft method or a direct polymerization method.

  In the case of the grafting method, the grafting reaction for the epoxy resin (a1) and the polymerization of the acrylic monomer itself compete. In order to increase the molecular weight of the acrylic resin portion bonded to the epoxy resin (a1), it is necessary to reduce the amount of peroxide used as a polymerization initiator and a catalyst for the graft reaction. When the amount of peroxide used is reduced, the graft reaction is less likely to occur, and as a result, the acrylic resin portion is hardly bonded to the epoxy resin (a1), which is close to a simple mixture of the epoxy resin (a1) and the acrylic resin. A composition is obtained. Furthermore, since the substance which inhibits the copolymerization of acrylic monomers, that is, the epoxy resin (a1) is present in a large amount, the molecular weight of the produced acrylic resin becomes small.

  In the case of the direct polymerization method, the molecular weight of the acrylic resin becomes small due to the presence of the epoxy resin (a1) as in the grafting method.

  When the aqueous resin composition of the present invention is used for can lid coating, specifically, the carboxyl group-containing acrylic resin (a2) used in the present invention includes acrylic acid or methacrylic acid, ethyl acrylate and styrene. A copolymer is preferred.

  More specifically, a copolymer obtained by copolymerizing a monomer containing 60% by weight or more of ethyl acrylate is preferable, and a copolymer obtained by copolymerizing a monomer containing 65 to 90% by weight of ethyl acrylate is provided. Further preferred. Although the detailed reason is still unclear, even if the Tg of the copolymer itself is about the same, carboxyl-2-ethylhexyl acrylate is used instead of ethyl acrylate as the carboxyl group-containing acrylic resin (a2). When a resin obtained by polymerization is used, the slipperiness of the resulting coating film tends to be lower than that of a resin obtained by copolymerizing ethyl acrylate.

  When the aqueous resin composition of the present invention is used for inner surface coating of cans, particularly inner surfaces of so-called “two-piece cans” in which the can body and bottom are integrally molded, the carboxyl group-containing acrylic resin (a2) The weight average molecular weight (Mw) is preferably 10,000 ≦ Mw ≦ 100,000, and more preferably 10,000 ≦ Mw ≦ 50000. If it is less than 10,000, the stress relaxation function of the coating film is not sufficient, and the processability and corrosion resistance required for a two-piece can for alcoholic beverages cannot be obtained. On the other hand, when it is larger than 100,000, the stress relaxation function of the coating film is too strong, and the adhesion of the coating film of the two-piece can for alcoholic beverages to the substrate is lowered.

  When the aqueous resin composition of the present invention is used to coat the inner surface of a two-piece can, the carboxyl group-containing acrylic resin (a2) is a COOH component selected from the group consisting of acrylic acid and methacrylic acid, methyl methacrylate and styrene. A high Tg component capable of forming a homopolymer having a relatively high glass transition temperature (Tg) selected from the group consisting of: and a relatively low Tg selected from the group consisting of ethyl acrylate and 2-ethylhexyl acrylate A copolymer obtained by copolymerizing a low Tg component capable of forming a homopolymer is preferred. Among them, a copolymer obtained by copolymerizing a monomer containing 50% by weight or more of a low Tg component selected from the group consisting of ethyl acrylate and 2-ethylhexyl acrylate is preferable, and a monomer containing 55 to 90% by weight A copolymer obtained by copolymerizing is more preferable.

  More specifically, a copolymer of acrylic acid or methacrylic acid, ethyl acrylate, and styrene, or a copolymer of acrylic acid or methacrylic acid, methyl methacrylate, and 2-ethylhexyl acrylate is preferable.

Tg in the present invention can be obtained from the following formula described on page 18 of Kyozo Kitaoka, “Introduction to Synthetic Resins for Paints” (Polymer Publishing Society, 1986, 8th edition).
1 / Tg = (W ₁ / Tg ₁ ) + (W ₂ / Tg ₂ )... + (W _n / Tg _n )
Here, the glass transition temperature of the resin Tg is obtained (unit: K), Tg _1, Tg _2, etc. The glass transition temperature of the homopolymer of the respective monomer (unit: K), W _1, W is like ₂ respectively Represents the weight ratio of the monomer (W ₁ + W ₂ +... W _n = 1).

  In the present invention, the weight average molecular weight and number average molecular weight are based on polystyrene in gel permeation chromatography (GPC) measurement.

Next, the carboxyl group-containing acrylic resin (a3) will be described.
It is important that the carboxyl group-containing acrylic resin (a3) has an acid value X _B of 180 mgKOH / g ≦ X _B ≦ 450 mgKOH / g, and preferably 200 mgKOH / g ≦ X _B ≦ 400 mgKOH / g. If it is lower than 180 mgKOH / g, it is difficult to make it water-based, and if it is higher than 450 mgKOH / g, the hydrophilicity of the coating film becomes high and the water resistance is poor.

  The weight average molecular weight is preferably 10,000 to 150,000, and more preferably 15,000 to 100,000. Furthermore, the glass transition temperature is preferably 50 to 120 ° C, and more preferably 55 to 110 ° C.

Such a carboxyl group-containing acrylic resin (a3) can be obtained in the same manner as the carboxyl group-containing acrylic resin (a2).
Specifically, the carboxyl group-containing acrylic resin (a3) used in the present invention is preferably a copolymer of acrylic acid or methacrylic acid, ethyl acrylate and styrene.

The acrylic-modified epoxy resin (A1) uses a basic compound as an esterification catalyst,
(I) the epoxy group of the epoxy resin (a1) and the carboxyl group of the carboxyl group-containing acrylic resin (a2) are reacted at a specific reaction rate;
Then
(II) A carboxyl group-containing acrylic resin (a3) is added, and the carboxyl group of the acrylic resin (a3) is reacted with the epoxy group of the epoxy resin (a1);
Can be obtained.

  In order to obtain the acrylic modified epoxy resin (A1), the reason why the reaction between the epoxy resin (a1) and the carboxyl group-containing acrylic resins (a2) and (a3) is as described above is as follows. The carboxyl group-containing acrylic resin (a2), which has a relatively slow reaction with the group, is preferentially reacted with the epoxy resin (a1) and then has a higher acid value and a relatively quick reaction with the epoxy group ( This is because a3) is reacted with the epoxy resin (a1).

  When the epoxy resin (a1) and the carboxyl group-containing acrylic resins (a2) and (a3) are charged and reacted simultaneously, or the epoxy resin (a1) and the carboxyl group-containing acrylic resin (a3) are reacted first. Since the carboxyl group-containing acrylic resin (a3) having a high acid value and a relatively fast reaction with the epoxy group preferentially reacts with the epoxy resin (a1), the reaction with the epoxy group has a low acid value. The relatively slow carboxyl group-containing acrylic resin (a2) and the epoxy resin (a1) are less likely to occur, and as a result, the stress relaxation function against deformation and processing is less likely to be effectively exhibited, and the workability, corrosion resistance, and slipperiness are reduced. A good coating film cannot be obtained.

  These reactions are usually carried out in an organic solvent. In the reaction step (I), the reaction temperature is 50 to 130 ° C., the reaction time is 10 minutes to 8 hours, and in the reaction step (II) The reaction temperature is 50 to 130 ° C., and the reaction time is 10 minutes to 8 hours.

  In the reaction step (I), that is, the esterification reaction between the epoxy resin (a1) and the carboxyl group-containing acrylic resin (a2), the reaction rate of the carboxyl group of the acrylic resin (a2) is 30 to 95%. It is important that it is 50 to 90%.

  If the reaction rate is less than 30%, the reaction between the acrylic resin (a2) and the epoxy resin (a1) is insufficient, so that sufficient adhesion and corrosion resistance to the substrate cannot be obtained. When the reaction rate exceeds 95%, when the epoxy resin (a1) having a particularly large epoxy equivalent is used, in the reaction (II), the reaction between the acrylic resin (a3) and the epoxy resin (a1). Is difficult to proceed, and the resulting resin composition is insufficiently dispersed in an aqueous medium and aggregates.

  The reaction rate of the carboxyl group can be calculated from the rate of decrease of the acid value of the resin.

  Although it does not specifically limit as an organic solvent used in the reaction process of said (I) and (II), For example, the solvent used for melt | dissolution of epoxy resin (a1), a carboxyl group-containing acrylic resin (a2) And / or the solvent used in the polymerization reaction for obtaining the carboxyl group-containing acrylic resin (a3) may be used as it is. If necessary, it may be added separately.

Specific examples of the organic solvent used include, for example, alcohols such as n-propanol, isopropyl alcohol, n-butyl alcohol, isobutyl alcohol, n-amyl alcohol, amyl alcohol, and methyl amyl alcohol;
Glycols such as ethylene glycol, diethylene glycol, 1,3-butylene glycol;
Glycol ethers such as ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, methylpropylene glycol, methylpropylene diglycol, propylpropylene glycol, propylpropylene diglycol, butylpropylene glycol;
Acetates such as ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, propylene glycol monomethyl ether acetate, 3-methoxybutyl acetate, ethylene glycol monobutyl ether acetate, 3-methyl-3-methoxybutyl acetate;
Etc.

  The aqueous resin composition of the present invention is a dispersion in which a solid component mainly composed of an acrylic-modified epoxy resin (A1) is dispersed in an aqueous medium in the presence of a basic compound (a4).

  The aqueous medium may be water alone or a mixture of a water-soluble organic solvent having a solubility in water at 20 ° C. of 1% by weight or more in the above organic solvent and water. .

  In the reaction step (I), that is, the reaction between the epoxy resin (a1) and the carboxyl group-containing acrylic resin (a2), the basic compound (a4-1) may be used as the esterification catalyst. is important.

Various basic compounds can be used as the esterification catalyst, but volatile basic compounds are preferred, and specific examples thereof include ammonia, dimethylethanolamine, dimethylbenzylamine, ethanolamine, Examples include diethanolamine and morpholine.
Here, the volatile basic compound means a basic compound that is liquid at 25 ° C. and has a boiling point of less than 200 ° C.

  In the reaction step (II), that is, in the reaction between the epoxy resin (a1) and the carboxyl group-containing acrylic resin (a3), it is preferable to further add a basic compound (a4-2). As the basic compound (a4-2), the same compounds as the basic compound (a4-1) can be used, and among them, a volatile basic compound is preferable.

  In addition, when the acrylic modified epoxy resin (A1) obtained through the reaction step (II) is made aqueous, that is, dispersed in an aqueous medium, the basic compound (a4- 3) may be added. As the basic compound (a4-3), the same compounds as the basic compound (a4-1) can be used, and among them, a volatile basic compound is preferable.

  The basic compound (a4) used in the present invention is composed of the basic compound (a4-1) and the basic compounds (a4-2) and (a4-3) used as necessary. It is.

  The reason why it is preferable to add the basic compound (a4) in each reaction step is that the reaction rate between the epoxy resin (a1) and the carboxyl group-containing acrylic resin (a2) can be easily controlled with good reproducibility. It is.

  Thus, the basic compound (a4) is preferably added separately for each reaction step when the reaction solid content in the reaction step (I) is a higher solid content, specifically 50% by weight or more. This is because the esterification of the epoxy resin (a1) and the carboxyl group-containing acrylic resin (a2) occurs faster when the reaction solid content is higher, and therefore the reaction control is easier when the basic compound (a4) is divided. Depending on the reason. Such esterification reaction at a high solid content has become indispensable as a measure for reducing the amount of organic solvent in recent environmental problems, and also for reducing the amount of solvent removal or cost reduction.

The basic compound (a4) is preferably 0.1 to 1.5 mol with respect to 1 mol in total of the carboxyl groups of the carboxyl group-containing acrylic resin (a2) and the carboxyl group-containing acrylic resin (a3). It is more preferable that it is 0.3-1.0 mol.
When the basic compound (a4-2) is added in the reaction step (II), the molar ratio of the basic compound (a4-1) to the basic compound (a4-2) is (a4-1) /(A4-2)=0.1-100 is preferable, and (a4-1) / (a4-2) = 0.3-100 is more preferable.

When the amount of the basic compound (a4) is less than 0.1 mol, the total amount of the basic compound is insufficient, and a stable aqueous dispersion of an aqueous dispersion may not be obtained.
On the other hand, when the amount of the basic compound (a4) is more than 1.5 mol, the viscosity becomes very high and it may be inappropriate as an aqueous paint.

When (a4-1) / (a4-2) = 0.1 is smaller, the reaction between the epoxy resin (a1) and the carboxyl group-containing acrylic resin (a2) is difficult to proceed. In some cases, the stress relieving function is not effectively exhibited, and a coating film having good workability, corrosion resistance, and slipperiness cannot be obtained.
On the other hand, when (a4-1) / (a4-2) = 100 is exceeded, the reaction between the epoxy resin (a1) and the carboxyl group-containing acrylic resin (a2) proceeds too much. There may be occasional poor dispersion.

  The ratio of the epoxy resin (a1), the carboxyl group-containing acrylic resin (a2), and the carboxyl group-containing acrylic resin (a3), which are components constituting the acrylic-modified epoxy resin (A1), is (a1) + (a2) + When (a3) = 100% by weight, it is preferable that (a1) / (a2) / (a3) = 30 to 95 / 0.1 to 60 / 0.5 to 69.9 (% by weight). (A1) / (a2) / (a3) = 50 to 92/3 to 30/5 to 30 (wt%), more preferably 60 to 85/5 to 20/10 to 25 (wt%) More preferably. If the carboxyl group-containing acrylic resin (a2) is less than 0.1% by weight, the resulting coating film tends to have insufficient corrosion resistance, and if it exceeds 60% by weight, the amount of the epoxy resin is relatively small. There exists a tendency for the adhesiveness of a film | membrane to fall. If the carboxyl group-containing acrylic resin (a3) is less than 0.5% by weight, it tends to be difficult to make it water-based, and if it is more than 69.9% by weight, the water resistance of the coating film tends to decrease.

  Examples of the method for making the acrylic-modified epoxy resin (A1) water-based include the following methods.

  1. The obtained acrylic modified epoxy resin (A1) is added to an aqueous medium to disperse the acrylic modified epoxy resin (A1).

  2. After adding a basic compound (a4-3) to the obtained acrylic modified epoxy resin (A1), this is added in an aqueous medium to disperse the acrylic modified epoxy resin (A1).

  3. The obtained acrylic modified epoxy resin (A1) is added to an aqueous medium containing the basic compound (a4-3) to disperse the acrylic modified epoxy resin (A1).

  4). An aqueous medium is added to the obtained acrylic modified epoxy resin (A1) to disperse the acrylic modified epoxy resin (A1).

  5. After adding a basic compound (a4-3) to the obtained acrylic modified epoxy resin (A1), an aqueous medium is further added to disperse the acrylic modified epoxy resin (A1).

  6). An aqueous medium containing the basic compound (a4-3) is added to the resulting acrylic-modified epoxy resin (A1) to disperse the acrylic-modified epoxy resin (A1).

  By adding a curing agent such as a resol type phenol resin or an amino resin such as a melamine resin or a benzoguanamine resin, a surfactant, an antifoaming agent, a wax, or a pigment to the aqueous resin composition of the present invention as necessary. It can be a water-based paint.

  The water-based paint of the present invention can be applied to various substrates, and an object to be coated covered with the water-based paint can be obtained. As the base material, for example, various kinds of untreated or surface-treated metals such as an aluminum plate, a steel plate, and a tin plate, a metal coated with a primer on these metals, or a polyester film (PET) laminated on these metals. Examples include PET-coated metals.

  Further, the shape of the substrate may be a plate shape or a bottomed cylindrical shape. Furthermore, after applying the water-based paint of the present invention to these substrates and curing, further deformation processing may be applied. A beverage container can be obtained through various processing steps.

  Various known methods such as roll coater coating, spray coating, dip coating, and electrodeposition coating can be applied as a method of coating the aqueous coating composition of the present invention on the substrate. The thickness of the coating after drying may be appropriately selected depending on the use, but is usually preferably about 1 to 20 μm. As drying conditions for the coated film, it is usually preferably 10 seconds to 30 minutes under the condition that the maximum substrate temperature reaches 120 to 300 ° C.

  Next, the present invention will be specifically described with reference to examples. In the examples, “parts” and “%” are “parts by weight” and “% by weight”, respectively.

Production Example 1: Production of epoxy resin (a1-1) solution (1) Epicoat 4250 (manufactured by Japan Epoxy Resin Co., Ltd., epoxy equivalent 8000, weight average molecular weight 60000) 500 parts (2) Ethylene glycol monobutyl ether 500 parts 4 (1) and (2) were placed in a one-necked flask and stirred at 110 ° C. for 5 hours to obtain an epoxy resin (a1-1) solution having a solid content of 50%.

Production Example 2: Production of Epoxy Resin (a1-2) Solution (1) Epicoat 1010 (manufactured by Japan Epoxy Resin Co., Ltd., epoxy equivalent 4000, weight average molecular weight 12000) 500 parts (2) Ethylene glycol monobutyl ether 500 parts 4 (1) and (2) were placed in a one-necked flask and stirred at 110 ° C. for 3 hours to obtain an epoxy resin (a1-2) solution having a solid content of 50%.

Production Example 3: Production of carboxyl group-containing acrylic resin (a2-1) solution (1) 150 parts of methacrylic acid (2) 150 parts of styrene (3) 700 parts of ethyl acrylate (4) 10 parts of benzoyl peroxide (5) ethylene 90 parts of glycol monobutyl ether (6) 900 parts of ethylene glycol monobutyl ether Charge the above (6) into a four-necked flask and heat and stir to 110 ° C. under a nitrogen stream, and mix the liquid mixture of (1) to (5) to 110 ° C. It was added dropwise over 3 hours. After completion of the dropwise addition, the mixture was stirred at 110 ° C. for 3 hours and cooled to obtain a carboxyl group-containing acrylic resin (a2-1) solution having a solid content of 50%. The acid value of the resin was 98 mgKOH / g, Tg: 8 ° C., and the weight average molecular weight was 74,000.

Production Examples 4 to 17: Production of carboxyl group-containing acrylic resins (a2-2) to (a2-15) solutions According to the formulation shown in Table 1, the carboxyl group-containing acrylic resins (a2-2) to (A2-15) A solution was obtained.

Production Examples 18 to 23: Production of carboxyl group-containing acrylic resins (a3-1) to (a3-6) solutions Carboxy group-containing acrylic resins (a3-1) to (A3-6) A solution was obtained.

Production Example 24: Production of resol type phenolic resin solution A 4-necked flask was charged with 417.7 parts of p-cresol, 580.1 parts of a 40% n-butanol solution of formalin, and 2.2 parts of magnesium hydroxide under a nitrogen stream. And then neutralized with phosphoric acid, and a mixed solvent of xylene / n-butanol / cyclohexanone = 1/1/1 (weight ratio) and a large amount of water were added. The solution was allowed to stand for 5 hours, and the aqueous layer containing the produced salt was separated and removed, followed by azeotropic dehydration to obtain a resol type phenol resin solution having a solid content of 30%.

Example 1
(1) Epoxy resin (a1-1) solution obtained in Production Example 1 462 parts (2-1) Carboxyl group-containing acrylic resin (a2-1) solution obtained in Production Example 3 48 parts (2-2) Dimethylamino Ethanol 10 parts (3-1) Carboxyl group-containing acrylic resin obtained in Production Example 18 (a3-1) solution 112 parts (4) Ion-exchanged water 338 parts (5) Hydisper 3028 [manufactured by Gifu Shellac Factory , Carnauba wax in water dispersion, 10% wax component] 30 parts Charge (1) and (2-1) into a 4-neck flask, heat to 100 ° C, add (2-2), and stir at 100 ° C for 2 hours Continued. The carboxyl group reaction rate of the acrylic resin (a2-1) calculated from the acid value decrease rate was 90%.
Thereafter, (3-1) was charged, and stirring was continued at 100 ° C. for 2 hours, followed by cooling to 70 ° C., and (4) was gradually added over 1 hour. Finally, (5) was added to obtain an aqueous paint having a solid content of 30%.

Example 2
(1) Epoxy resin (a1-1) solution obtained in Production Example 1 462 parts (2-1) Carboxyl group-containing acrylic resin (a2-1) solution obtained in Production Example 3 48 parts (2-2) Dimethylamino Ethanol 5 parts (3-1) Carboxyl group-containing acrylic resin (a3-1) solution obtained in Production Example 18 112 parts (3-2) Dimethylaminoethanol 5 parts (4) Ion-exchanged water 338 parts (5) High Disper 3028 [manufactured by Gifu Shellac Co., Ltd., carnauba wax aqueous dispersion, wax component 10%] 30 parts Charge (1), (2-1) into a 4-neck flask and heat to 100 ° C. (2-2 ) Was added and stirring was continued at 100 ° C. for 2 hours. The reaction rate of the carboxyl group of the acrylic resin (a2-1) calculated from the decreasing rate of the acid value was 80%.
Thereafter, (3-1) and (3-2) were charged, and stirring was continued at 100 ° C. for 2 hours, followed by cooling to 70 ° C., and (4) was gradually added over 1 hour. Finally, (5) was added to obtain an aqueous paint having a solid content of 30%.

Examples 3-18
The epoxy resin solution, the carboxyl group-containing acrylic resin (low acid value) solution, and the carboxyl group-containing acrylic resin (high acid value) solution shown in Table 3 were used in the same amounts as in Example 1, and the same as in Example 1 or Example 2. Thus, a water-based paint having a solid content of 30% was obtained.
(Examples 3 to 17: Procedures similar to Example 2, Example 18: Procedures similar to Example 1.)

Example 19
(1) Epoxy resin (a1-1) solution obtained in Production Example 1 360 parts (2-1) Carboxyl group-containing acrylic resin (a2-1) solution obtained in Production Example 3 120 parts (2-2) Dimethylamino Ethanol 5 parts (3-1) Carboxyl group-containing acrylic resin (a3-1) solution obtained in Production Example 18 150 parts (3-2) Dimethylaminoethanol 5 parts (4) Ion-exchanged water 338 parts (5) High Disper 3028 30 parts (1) and (2-1) were charged into a four-necked flask, heated to 100 ° C., (2-2) was added, and stirring was continued for 2 hours. The reaction rate of the carboxyl group of the acrylic resin (a2-1) calculated from the decreasing rate of the acid value was 80%.
Thereafter, (3-1) and (3-2) were charged, and stirring was continued at 100 ° C. for 2 hours, followed by cooling to 70 ° C., and (4) was gradually added over 1 hour. Finally, (5) was added to obtain an aqueous paint having a solid content of 30%.

Example 20
(1) Epoxy resin (a1-1) solution obtained in Production Example 1 480 parts (2-1) Carboxyl group-containing acrylic resin (a2-1) solution obtained in Production Example 3 30 parts (2-2) Dimethylamino Ethanol 5 parts (3-1) Carboxyl group-containing acrylic resin (a3-1) solution obtained in Production Example 18 110 parts (3-2) Dimethylaminoethanol 3 parts (4) 25% aqueous ammonia 25 parts (5) Ion 317 parts of exchanged water (6) 30 parts of High Disper 3028 (1), (2-1) was charged into a four-necked flask and heated to 100 ° C, (2-2) was added, and stirring was continued at 100 ° C for 2 hours. . The carboxyl group reaction rate of the acrylic resin (a2-1) calculated from the acid value decrease rate was 90%.
Thereafter, (3-1) and (3-2) were charged, and stirring was continued at 100 ° C. for 2 hours, followed by cooling to 70 ° C. (4), and the mixture of (5) was gradually added over 1 hour. Finally, (6) was added to obtain an aqueous paint having a solid content of 30%.

Example 21
(1) 200 parts of water-based paint prepared in Example 1 (2) 3.4 parts of resol type phenolic resin solution prepared in Production Example 24 Add (1) and (2) to a glass bottle and stir for 5 minutes with a Hamilton mixer. An aqueous paint having a solid content of 30% was obtained.

Example 22
(1) Epoxy resin (a1-1) solution obtained in Production Example 1 231 parts (2-1) Carboxyl group-containing acrylic resin (a2-1) solution obtained in Production Example 3 48 parts (2-2) Dimethylamino Ethanol 5 parts (3-1) Carboxyl group-containing acrylic resin (a3-1) solution obtained in Production Example 18 112 parts (3-2) Dimethylaminoethanol 5 parts (4) Epoxy resin (a1) obtained in Production Example 2 -2) Solution 231 parts (5) Ion-exchanged water 338 parts (6) High Disper 3028 30 parts Charge (1) and (2-1) into a four-necked flask and add (2-2) after heating to 100 ° C. And stirring was continued at 100 ° C. for 2 hours. The reaction rate of the carboxyl group of the acrylic resin (a2-1) calculated from the decreasing rate of the acid value was 80%.
Thereafter, (3-1) and (3-2) were added, and stirring was continued at 100 ° C. for 2 hours. Then, (4) was added and stirred at 80 ° C. for 1 hour, and (5) was gradually added over 1 hour. Added. Finally, (6) was added to obtain an aqueous paint having a solid content of 30%.

Comparative Examples 1-5
The epoxy resin solution, the carboxyl group-containing acrylic resin (low acid value) solution, and the carboxyl group-containing acrylic resin (high acid value) solution shown in Table 4 were used in the same amount as in Example 1, and the same as in Example 1 or Example 2. Thus, a water-based paint having a solid content of 30% was obtained.
(Comparative Examples 1 to 4: Procedures similar to Example 1, Comparative Example 5: Procedures similar to Example 2.)

Comparative Example 6
(1) 462 parts of the epoxy resin (a1-1) solution obtained in Production Example 1 (2-1) 48 parts of the carboxyl group-containing acrylic resin (a2-1) solution obtained in Production Example 3
(2-2) Dimethylaminoethanol 10 parts (3-1) Carboxyl group-containing acrylic resin (a3-1) solution obtained in Production Example 18 112 parts (4) Ion-exchanged water 338 parts (5) High Disper 3028 [( Co., Ltd., Gifu Shellac Factory, Carnauba wax aqueous dispersion, wax component 10%] 30 parts Add (1), (2-1) to a 4-neck flask and heat to 100 ° C and add (2-2) And stirring was continued at 100 ° C. for 2 hours. The reaction rate of the carboxyl group of the acrylic resin (a2-1) calculated from the reduction rate of the acid value was 99%.
Thereafter, (3-1) was charged and stirring was continued at 120 ° C. for 4 hours, followed by cooling to 70 ° C., and (4) was gradually added over 1 hour. Finally, (5) was added to obtain an aqueous paint having a solid content of 30%.

Comparative Example 7
(1) Epoxy resin (a1-1) solution obtained in Production Example 1 462 parts (2) Carboxyl group-containing acrylic resin (a3-1) solution obtained in Production Example 18 112 parts (3) Dimethylaminoethanol 10 parts ( 4) 48 parts of the carboxyl group-containing acrylic resin (a2-1) solution obtained in Production Example 3 (5) 338 parts of ion-exchanged water (6) 30 parts of High Disper 3028 Add (1) and (2) to a four-necked flask. (3) is added after the preparation is heated to 80 ° C., stirred at 80 ° C. for 2 hours, (4) is added, and (5) is gradually added over 1 hour to prepare an acrylic modified epoxy resin and a carboxyl group-containing acrylic resin. An aqueous dispersion of a mixture with (a2-1) was obtained, and (6) was further added to obtain an aqueous paint having a solid content of 30%.

Comparative Example 8
(1) Epoxy resin (a1-1) solution obtained in Production Example 1 462 parts (2) Methacrylic acid 3.6 parts (3) Styrene 3.6 parts (4) Ethyl acrylate 16.8 parts (5) Benzoyl Peroxide 1.4 parts (6) Ethylene glycol monobutyl ether 22.6 parts (7) Carboxyl group-containing acrylic resin (a3-1) solution obtained in Production Example 18 112 parts (8) Dimethylaminoethanol 10 parts (9) Ion-exchanged water 338 parts (10) High Disper 3028 30 parts (1) was charged into a four-necked flask and heated to 100 ° C, and then (2) to (6) were added dropwise at 100 ° C over 2 hours. Next, (7) and (8) were added, and the mixture was stirred at 80 ° C. for 3 hours, (9) was added dropwise over 1 hour, and (10) was further added to obtain an aqueous paint having a solid content of 30%.
When the monomers (2) to (6) are polymerized, an acrylic resin having an acid value of 98 mg KOH / g and Tg of 8 ° C. is obtained.

Comparative Example 9
(1) Epoxy resin (a1-1) solution obtained in Production Example 1 462 parts (2) Hydroquinone 0.02 parts (3) 25% aqueous sodium hydroxide solution 0.2 parts (4) Methacrylic acid 1 part (5) Methacrylic acid 2.6 parts (6) Styrene 3.6 parts (7) Ethyl acrylate 16.8 parts (8) Benzoyl peroxide 1.2 parts (9) Ethylene glycol monobutyl ether 22.8 parts (10) Production example 112 parts of the carboxyl group-containing acrylic resin (a3-1) solution obtained in 18 (11) 10 parts of dimethylaminoethanol (12) 336 parts of ion-exchanged water (13) 30 parts of High Disper 3028 30 parts (1) is added to the four-necked flask. Charge (2) to (4) after charging to 100 ° C. and stir at 100 ° C. for 3 hours, methacryloyl group derived from (4) and epoxide derived from (1) To give a compound having a sheet group. Subsequently, the liquid mixture of (5)-(9) was dripped at 100 degreeC over 2 hours, and also it hold | maintained at 100 degreeC for 1 hour. Next, (10) and (11) were added, and after stirring at 80 ° C. for 3 hours, (12) was added dropwise over 1 hour, and (13) was further added to obtain an aqueous paint having a solid content of 30%.
When the monomers (4) to (7) are polymerized, an acrylic resin having an acid value of 98 mg KOH / g and Tg of 8 ° C. is obtained.

  Storage stability was evaluated for the water-based paints obtained in Examples 1 to 22 and Comparative Examples 1 to 9, and various physical properties of the coating film were evaluated for test panels prepared under the following conditions. The results are shown in Table 5. Various test methods are as follows.

(1) Storage stability: Each paint was stored in a thermostat at 50 ° C., and appearance properties were periodically evaluated over 3 months.
○ ··· Good storage stability × ··· Abnormalities such as gelation, sedimentation and separation occurred during storage.

    <Test panel preparation conditions> Each water-based paint was applied by a bar coater on an aluminum plate having a thickness of 0.30 mm so that the coating thickness when dried was 10 μm, and baked and dried at 200 ° C. for 3 minutes. Was made.

(2) Workability The test panel is cut into a size of 30 mm × 50 mm, folded in half so that the width of the test site is 30 mm with the coating film on the outside, and the thickness between the two folded test pieces A 0.30 mm aluminum plate was sandwiched, and a load of 3 kg was dropped on the bent portion from a height of 45 cm.
Thereafter, a sponge soaked with 1% saline is pressed outside the bent portion. The other side of the sponge is in contact with a metal plate as an electrode, and a current of 6 V × 10 seconds is applied between the metal plate and the tip of the bent coating plate, and the metal plate and the bent portion after 10 seconds are energized. The current value was measured.
Less than 3mA
3-7mA …… △
Over 7mA ...

(3) Corrosion resistance test The test panel was cut into a size of 30 mm x 50 mm and immersed in a carbonated beverage at 5 ° C for 10 days. The paint panel is taken out in an atmosphere of 5 ° C., and in a wet state, the coating film is immediately turned outward and folded in half so that the width of the test site is 30 mm, and the thickness is 0.30 mm between the folded test pieces. A 3 kg load was dropped onto the bent part from a height of 45 cm. Subsequently, it was immersed in a carbonated beverage at 40 ° C. for one month, and the degree of corrosion of the bent portion was visually determined.
No corrosion ...
Some corrosion ...
Corrosion throughout ...

(4) Water resistance The test panel was retorted at 125 ° C. for 40 minutes, and the coating film surface state was visually evaluated according to the following criteria.
○: No abnormality is observed.
Δ: Some whitening is observed.
X: Remarkably whitening is observed.

(5) Sliding property A weight of 1 kg with three steel balls attached to the coating surface of the test panel was placed so that the steel balls were in contact with the coating surface, and this weight was applied at a speed of 150 mm / min. Then, the dynamic friction coefficient at this time was measured. The smaller the dynamic friction coefficient, the better the slipperiness.

(6) Flavor property The test panel was subjected to a retort treatment at 125 ° C. for 30 minutes in a beverage containing alcohol, and the treated liquid after the retort was evaluated by a sensory test using a panel.
In addition, the drink which was not used for the retort was made into the blank.
○: Equivalent to blank △: Slightly different from blank ×: Significant difference from blank

(7) Adhesion The test panel is subjected to a retort treatment at 125 ° C. for 30 minutes in a beverage containing alcohol, the coating surface is cut into a grid pattern with a cutter knife, and a peel test is performed with a cellophane tape. The state was evaluated visually.
○: No peeling Δ: Peeling less than 50% of the cut part ×: Peeling of 50% or more of the cut part occurred

Claims (13)

An acrylic modified epoxy obtained by reacting an epoxy resin (a1), a carboxyl group-containing acrylic resin (a2) having an acid value of 10 to 135 mgKOH / g, and a carboxyl group-containing acrylic resin (a3) having an acid value of 180 to 450 mgKOH / g An aqueous resin composition in which the resin (A1) is dispersed in an aqueous medium containing the basic compound (a4),
In the acrylic-modified epoxy resin (A1), first, the epoxy resin (a1) and the acrylic resin (a2) are reacted in the presence of the basic compound (a4-1) with the carboxyl group reaction rate of the acrylic resin (a2). React to 30-95%, then
An aqueous resin composition comprising an acrylic resin (a3) and a reaction.   2. The aqueous resin composition according to claim 1, wherein the acrylic-modified epoxy resin (A1) is prepared by adding the basic compound (a4-2) to the reaction when the acrylic resin (a3) is added.   The basic compound (a4) is 0.1 to 1.5 mol with respect to 1 mol in total of the carboxyl groups of the carboxyl group-containing acrylic resin (a2) and the carboxyl group-containing acrylic resin (a3). The aqueous resin composition according to claim 1 or 2.   The basic compound (a4) is 0.1 to 1.5 mol with respect to a total of 1 mol of the carboxyl groups of the carboxyl group-containing acrylic resin (a2) and the carboxyl group-containing acrylic resin (a3), and a base The molar ratio of the basic compound (a4-1) to the functional compound (a4-2) is (a4-1) / (a4-2) = 0.1-100. The aqueous resin composition as described.   The carboxyl group-containing acrylic resin (a2) is obtained by polymerizing ethyl acrylate, 2-ethylhexyl acrylate, or a monomer containing 50% by weight or more of ethyl acrylate and 2-ethylhexyl acrylate. The aqueous resin composition according to any one of claims 1 to 4. In a total of 100% by weight of the epoxy resin (a1), the carboxyl group-containing acrylic resin (a2), and the carboxyl group-containing acrylic resin (a3),
(A1): 30 to 95% by weight,
(A2): 0.1 to 60% by weight,
(A3): 0.5-69.9 wt%
The aqueous resin composition according to any one of claims 1 to 5, wherein An acrylic-modified epoxy obtained by reacting an epoxy resin (a1), a carboxyl group-containing acrylic resin (a2) having an acid value of 10 to 135 mgKOH / g, and a carboxyl group-containing acrylic resin (a3) having an acid value of 180 to 450 mgKOH / g A method for producing an aqueous resin composition containing a resin (A1),
First, the epoxy resin (a1) and the acrylic resin (a2) are reacted in the presence of the basic compound (a4-1) so that the reaction rate of the carboxyl group of the acrylic resin (a2) is 30 to 95%. ,
Next, an acrylic resin (a3) is added and reacted, and the resulting acrylic modified epoxy resin (A1) is dispersed in an aqueous medium in the presence of the basic compound (a4). Manufacturing method.   The method for producing an aqueous resin composition according to claim 7, wherein the basic compound (a4-2) is added together with the acrylic resin (a3).   An aqueous paint comprising the aqueous resin composition according to claim 1.   An article to be coated, wherein the substrate is coated with the water-based paint according to claim 9.   11. The article to be coated according to claim 10, wherein the substrate is selected from the group consisting of a metal, a metal coated with a paint, and a plastic film-coated metal.   The article to be coated according to claim 10 or 11, wherein the substrate is in the form of a plate or a bottomed cylinder. A beverage container comprising the article to be coated according to claim 10.