JP2009215474A - Water-based coating material composition and coated material obtained by using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a water-based coating material composition which exhibits excellent processing adhesiveness in the case when it is used as a coating material for cans and excellent corrosion resistance even after severe processing and further, with which a coated film having both hygienic property and flavor property can be formed. <P>SOLUTION: The water-based coating material composition is composed of an acryl-modified phenoxy resin (A) and a phenol resin (D), wherein the phenoxy resin (A) is obtained by grafting at least one radically polymerizable monomer (C) having a composition in which the acid value is adjusted to be 260-520 mgKOH/g to a bisphenol-type phenoxy resin (B) having an epoxy equivalent of 6,000-20,000 g/eq and a number-average molecular weight of 5,000-30,000 under such a condition that the weight ratio of (B) to (C) is 90/10 to 60/40 by using a radical polymerization initiator (E) and then subjecting the resulting resin to an esterification reaction in the presence of a basic compound (F) such as an amine or ammonia. <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 food and beverage packaging container that contains food and drink. More specifically, the present invention relates to an aqueous coating composition suitable for food and beverage packaging containers that require high workability and corrosion resistance, and to-be-coated articles using the same.

  Conventionally, in order to prevent metal materials such as tin, tin-free steel, and aluminum from directly contacting the contents and corroding, metal cans are usually provided with a thin synthetic resin protective coating on the inner surface. The required quality and suitability of the synthetic resin protective coating is becoming higher in the flow of diversification of contents and increase in the number of cans. That is, it has been required to have sufficient processing adhesion and excellent corrosion resistance even after processing, and the quality and flavor retention of the contents have also been required. In addition, bottle-shaped cans that are subjected to severe processing on coated cans are also on the market, and such cans require particularly excellent workability.

  As the coating composition for providing the synthetic resin protective coating, epoxy paints such as epoxy / phenol, epoxy / amino and epoxy / acryl are usually used because of excellent work adhesion, corrosion resistance and flavor properties. . Currently, water-based solutions are being studied from the viewpoints of resource saving, energy saving, occupational hygiene and environmental protection, and various proposals based on aromatic epoxy resins have been made. Aqueous paint compositions mainly composed of aromatic epoxy resins are excellent in process adhesion, corrosion resistance, and physical properties of coating films, and are therefore used as paints for metals, particularly for cans.

  Examples of the aqueous coating composition for inner surface coating include a coating composition in which an acrylic-modified epoxy resin in which an epoxy resin and an acrylic resin are partially bonded and a phenol resin are dissolved or dispersed in an aqueous medium. Are known. It has been proposed that an aqueous coating composition containing an acrylic-modified epoxy resin can be obtained, for example, by the methods shown in the following (1) to (3).

  (1) In Patent Document 1, an ester reaction between a part of a carboxyl group in a carboxyl group-containing acrylic resin and a part of an epoxy group in an aromatic epoxy resin is carried out in the presence of a tertiary amine. After obtaining the acrylic modified epoxy resin (this method is hereinafter referred to as “esterification method”), the excess carboxyl group remaining in the acrylic modified epoxy resin is then neutralized with a basic compound such as ammonia or amines. It is disclosed that a modified epoxy resin can be stably dispersed in an aqueous medium by mixing.

  (2) In Patent Document 2, a radical polymerization initiator such as benzoyl peroxide is used in the presence of an aromatic epoxy resin, and a carboxyl group-containing radical polymerizable monomer such as (meth) acrylic acid and various radical polymerizations. An acrylic modified epoxy resin (this method is hereinafter referred to as “grafting method”) obtained by grafting an acrylic copolymer onto an aromatic epoxy resin by copolymerizing a mixture of functional monomers with ammonia or amines It is disclosed that it can be stably dispersed in an aqueous medium by neutralization with a basic compound such as.

  (3) In Patent Document 3, a part of an epoxy group in an aromatic epoxy resin is reacted with a carboxyl group in a carboxyl group-containing radical polymerizable monomer such as (meth) acrylic acid, and epoxy is contained in one molecule. After obtaining a compound having both a group and a radical polymerizable unsaturated double bond, the compound is copolymerized with a mixture of a carboxyl group-containing radical polymerizable monomer such as (meth) acrylic acid and various radical polymerizable monomers. (This method is hereinafter referred to as “direct polymerization method.”) The resulting copolymer, that is, the carboxyl group in the acrylic-modified epoxy resin is neutralized with a basic compound such as ammonia or amines to modify the modified epoxy resin. It is disclosed that it can be stably dispersed in an aqueous medium.

  While the above method is disclosed, a can containing beverages and foods is formed by winding and joining a can body member and a can lid, and the can body member is bent during the joining. Therefore, cracks and corrosion may occur in the coating film at the tightening portion. In addition, in the case of a bottle-shaped can, particularly severe workability has been required, for example, screw processing is added to the base part. That is, the cured coating film has been required to be improved in terms of endurance to severe processing, corrosion resistance after severe processing, and excellent storage stability, hygiene, and low adsorptivity of flavor aroma components.

  For example, Patent Document 4 proposes an aqueous coating composition that uses a phenoxy resin in addition to an epoxy resin for the purpose of improving the processability of a coating film and contains a combination of both resins and an acrylic resin portion. Yes. Furthermore, Patent Document 5 discloses an aqueous coating composition in which a radically polymerizable monomer is polymerized on a phenoxy resin and then precondensed with a phenol resin as a coating film having excellent storage stability and processability and retortability. Things have been proposed.

However, the aqueous coating composition still has problems to be improved. That is, in the means of Patent Document 4, when the phenoxy resin used in combination for the purpose of improving the processability of the coating film exceeds a specific content, the adhesion with the metal substrate is inferior, whereas, below the specific content The processability of the coating film is insufficient. In addition, with the method of Patent Document 5, the processability is considerably improved, but the pre-condensation with the phenol resin reduces the reaction point, resulting in an increase in the amount of elution from the coating film to the contents. Furthermore, in terms of hygiene, etc., the adhesion of the coating film was lowered, the coating film was floated by heat sterilization treatment, etc., and the quality was not sufficiently satisfied in that the corrosion resistance was lowered. . Furthermore, in general, alcoholic beverages behave differently from beverages that do not contain alcohol, and the flavor aroma components in the beverage are easily adsorbed to the coating film. Improvement of low adsorptivity is particularly desired.
Japanese Patent Publication No.59-37026 Japanese Patent Laid-Open No. 53-1228 JP 58-198513 A JP-A-6-145593 JP-A-10-259228

  The present invention improves various drawbacks of the acrylic-modified epoxy resin, has excellent dispersion stability, excellent processing adhesion when used as an internal paint for cans, and excellent corrosion resistance even after more severe processing. Furthermore, it aims at providing the water-based coating composition which can form the coating film which has hygienic property and flavor property.

  The present invention provides an aqueous coating composition comprising an acrylic-modified phenoxy resin obtained by grafting a radical polymerizable monomer having a specific acid value to a phenoxy resin and then esterifying the phenol resin, and a phenol resin. The present invention has been accomplished by finding that the above problems can be solved.

That is, in the first invention, the acrylic-modified phenoxy resin (A) and the phenol resin (D) are aqueous in a ratio of (A) / (D) = 90/10 to 99.9 / 0.1 (weight ratio). An aqueous coating composition dispersed in a medium,
A radical polymerizable monomer (A) having a composition with an acid value of 260 to 520 mgKOH / g is added to a bisphenol type phenoxy resin (B) having an epoxy equivalent of 6000 to 20000 g / eq and a number average molecular weight of 5000 to 30000. C) is graft polymerized at a ratio of (B) / (C) = 90 / 10-60 / 40 (weight ratio) using the radical polymerization initiator (E), and then the presence of the basic compound (F) The present invention relates to an aqueous coating composition characterized by being esterified below.

The second invention is a resol-type phenol resin in which the phenol resin (D) has a trifunctional phenol as a monomer, and
The present invention relates to the aqueous coating composition according to the first invention, wherein the content of mononuclear benzene ring in the resin is 1% by weight or less and the number average molecular weight is 250 to 1500.

  Moreover, 3rd invention is related with the to-be-coated object formed by coat | covering a base material with the water-based coating composition of 1st or 2nd invention.

  The fourth invention relates to the article to be coated according to the third invention, wherein the base material is any one selected from the group consisting of metal, metal coated with paint, and plastic film-coated metal. .

  Moreover, 5th invention is related with the to-be-coated article of 3rd or 4th invention, wherein a base material is plate shape or bottomed cylindrical shape.

  According to the present invention, it has excellent dispersion stability, and when used as a paint for cans, it has excellent processing adhesion, excellent corrosion resistance even after more severe processing, and also has hygiene and flavor properties. An aqueous coating composition capable of forming a coating film can be provided.

  The water-based coating composition of the present invention contains an acrylic-modified phenoxy resin (A) and a phenol resin (D) at specific ratios. The acrylic-modified phenoxy resin (A) is a resin obtained by grafting a radical polymerizable monomer (C) having a specific acid value to the bisphenol type phenoxy resin (B) and then esterifying it. In the following description, acrylic-modified phenoxy resin (A), bisphenol type phenoxy resin (B), and radical polymerizable monomer (C) are respectively represented by phenoxy resin (A), phenoxy resin (B), and monomer (C). May be abbreviated or simply (A), (B), (C), or the like.

  The present invention is an aqueous coating composition containing an acrylic-modified phenoxy resin (A) obtained by performing an esterification reaction following a so-called graft method. By performing an esterification reaction following the grafting method, the aqueous coating composition has excellent storage stability, and the coated article using the aqueous coating composition has corrosion resistance before and after severe processing, and also hygiene. It has the characteristic that it is excellent regarding The acrylic-modified phenoxy resin (A) is a bisphenol type phenoxy resin (B) having an epoxy equivalent of 6000 to 20000 g / eq and a number average molecular weight of 5,000 to 30,000, and a radical polymerizable monomer (C) having an acid value of 260 to 520 mgKOH / g. ) Using a radical polymerization initiator (E) at a weight ratio (B) / (C) = 90 / 10-60 / 40, and then a basic compound (F) such as amine or ammonia It can be obtained by esterification reaction in the presence of

  First, the bisphenol type phenoxy resin (B), which is a component constituting the acrylic-modified phenoxy resin (A), will be described. Generally, the phenoxy resin (B) refers to a bisphenol-type epoxy resin having a particularly high molecular weight. The phenoxy resin (B) can be industrially produced in the same manner as the bisphenol type epoxy resin. As such a phenoxy resin (B), what is marketed can also be used, for example, JER1256 [Used bisphenol type monomer: Bisphenol A alone, Epoxy equivalent (hereinafter referred to as Eeq) = 8000 g / eq, number average Molecular weight (hereinafter referred to as “Mn”) = 12000, manufactured by Japan Epoxy Resins Co., Ltd.], Phenototo YP-70 [Used bisphenol type monomer: bisphenol A / bisphenol F combined use, Eeq = 13300 g / eq, Mn = 13700, Toto Kasei ( Etc.]. These may be used alone or in combination of two or more. Here, the number average molecular weight of the phenoxy resin (B) and the number average molecular weight of the phenol resin (D) described later are measured by the GPC method (standard polystyrene conversion).

  The present invention is characterized in that the epoxy equivalent of the bisphenol type phenoxy resin (B) is 6000 to 20000 g / eq. Furthermore, the range of 6500 to 15000 is more preferable. Furthermore, the range of 6800-13000 is more preferable. When a phenoxy resin having an epoxy equivalent of less than 6000 g / eq is used, the processability of the coating film is lowered, and the corrosion resistance after processing is inevitably lowered. On the other hand, when the epoxy equivalent exceeds 20000 g / eq, the reactivity of the resulting acrylic-modified phenoxy resin is lowered, and the crosslinking density of the coating film after baking and drying is lowered. As a result, the amount of flavor aroma components adsorbed increases, and the coating film deteriorates significantly, causing problems such as deterioration of the contents.

  The phenoxy resin (B) has a number average molecular weight of 5,000 to 30,000. Furthermore, it is more preferable that it is the range of 6000-20000. When the number average molecular weight is less than 5000 as a phenoxy resin, the processability of the coating film is lowered, and when used as a can body inner coating of a beverage can, the coating film is liable to crack at the tightening portion with the lid. Corrosion is more likely to occur from the tightened portion. On the other hand, if the number average molecular weight exceeds 30000, the viscosity of the resin solution of the acrylic-modified phenoxy resin during the production of the aqueous resin dispersion may become high, making the production difficult. This causes problems such as the inability to obtain a paint resin composition.

  The bisphenol type phenoxy resin (B) is manufactured for industrial use, and is a one-step method in which bis (4-hydroxyphenyl) alkanes and epichlorohydrin are reacted in the presence of a strong alkali, or this one-step method. It is obtained by a two-stage method in which bis (4-hydroxyphenyl) alkanes are further subjected to addition polymerization on the epoxy resin produced by the above method.

  Examples of the bisphenol phenoxy resin (B) include bisphenol A type, bisphenol F type, brominated bisphenol A type, hydrogenated bisphenol A type, and bisphenol S type.

  In the present invention, it is important to use the bisphenol type phenoxy resin (B) in obtaining the acrylic-modified phenoxy resin (A), and it is preferable not to use a low molecular weight epoxy resin. An appropriate amount of a low molecular weight epoxy resin may be used in combination as long as it is not impaired.

  Next, the radically polymerizable monomer (C) that is a component constituting the acrylic-modified phenoxy resin (A) will be described. The radical polymerizable monomer (C) of the present invention is a mixture of a radical polymerizable monomer containing a carboxyl group-containing radical polymerizable monomer as an essential component and copolymerizable therewith.

  Examples of the carboxyl group-containing radical polymerizable monomer include (meth) acrylic acid, maleic acid, itaconic acid, fumaric acid and the like, and (meth) acrylic acid is preferable.

  Examples of the radical polymerizable monomer copolymerizable with the carboxyl group-containing radical polymerizable monomer include styrene monomers such as styrene, vinyltoluene, 2-methylstyrene, t-butylstyrene, chlorostyrene, and methyl (meth) acrylate. , Ethyl (meth) acrylate, n-propyl (meth) acrylate, n-isopropyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, tert-butyl (meth) acrylate , (Meth) acrylic acid n-amyl, (meth) acrylic acid isoamyl, (meth) acrylic acid n-hexyl, (meth) acrylic acid cyclohexyl, (meth) acrylic acid-2-ethylhexyl, (meth) acrylic acid n- Octyl, decyl (meth) acrylate, dodecyl (meth) acrylate, (me ) (Meth) acrylic acid alkyl ester monomers such as lauryl acrylate, isobornyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, hydroxymethyl (meth) acrylate, etc. One type or two or more types of N-substituted (meth) acrylamide monomers such as a hydroxyl group-containing (meth) acrylic acid ester monomer, N-methylol (meth) acrylamide, and N-butoxymethyl (meth) acrylamide may be mentioned. Of these, styrene and ethyl acrylate are particularly preferred. Further, methyl methacrylate is also preferably used for the purpose of adjusting the Tg of the coating film.

  Among the flavor components in alcoholic beverages, particularly in sensory evaluation, the amount of adsorption of the ester compound, which is a component that is easy to perceive flavor change due to its adsorption (low sensory threshold), is reduced. It is important to copolymerize the composition so that the acid value is in the range of 260 to 520 mg KOH / g, which is one of the characteristics of the present invention. Furthermore, it is more preferable that it is the range of 300-460 mgKOH / g.

  When the acid value is lower than 260 mgKOH / g, the dispersion stability of the resulting acrylic-modified phenoxy resin is not sufficient, and problems such as resin settling over time occur. Moreover, the crosslinking density of the coating film is small, the amount of flavor components adsorbed cannot be reduced, and the corrosion resistance is not ensured. On the other hand, when the acid value is higher than 520 mgKOH / g, the copolymerization of the acrylic resin portion becomes non-uniform, the amount of homopolymer of the carboxyl group-containing radical polymerizable monomer increases, and the water resistance is inferior. The graft reaction with the resin (B) and further the subsequent esterification reaction become non-uniform, and gelation during the reaction tends to occur. In addition, the viscosity behavior at the time of making the paint and over time becomes unstable, such as an increase in the viscosity of the paint. From such a viewpoint, it is important that the radical polymerizable monomer (C) has an acid value in the range of 260 to 520 mgKOH / g. In addition, the theoretical value obtained from the carboxyl group-containing radical polymerizable monomer amount contained in the radical polymerizable monomer (C) was used for the acid value in the present invention.

  Here, the present invention is characterized in that the weight ratio of (B) / (C) is 90/10 to 60/40. Furthermore, the range of 85/15 to 65/35 is more preferable. When the radical polymerizable monomer (C) is in excess of the above range as compared with the phenoxy resin (B) which is a hydrophobic resin, it becomes difficult to obtain a stable aqueous resin dispersion. Moreover, even if it can be produced, the hydrophilicity of the resulting acrylic-modified phenoxy resin becomes too high, resulting in problems such as poor water resistance in the coating film performance. On the other hand, when the amount of the radical polymerizable monomer (C) is less than the above range as compared with the phenoxy resin (B), the hydrophilicity of the resulting acrylic-modified phenoxy resin becomes too low and the dispersion becomes stable in water. However, problems such as precipitation of the acrylic-modified phenoxy resin occur over time.

  The organic solvent used in the reaction step is not particularly limited, but includes alkyl alcohol, ethylene glycol monoalkyl ether, ethylene glycol dialkyl ether, diethylene glycol monoalkyl ether, diethylene glycol dialkyl ether, propylene glycol monoalkyl ether, and the like. An organic solvent can be appropriately used, and may be added separately after the reaction, if necessary.

  In addition, the radical polymerization initiator (E) used for the graft polymerization is not particularly limited, but an azobis-based polymerization initiator, a peroxide-based polymerization initiator, or the like is appropriately used according to a conventional method. Can do. Azobis-based polymerization initiators include azobisisobutyronitrile and azobisisovaleronitrile, and peroxide-based polymerization initiators include benzoyl peroxide, di-tert-butyl peroxide, and tert-butyl. Examples include peroxy-2-ethylhexanoate and cumene hydroperoxide. Among them, organic peroxides are preferable, and benzoyl peroxide is particularly preferable.

  Reaction conditions such as temperature and time at the time of graft polymerization are not special, and can be carried out using conditions known per se. A radical polymerizable monomer (C) is added to the aliphatic skeleton carbon atom of the phenoxy resin (B). Grafts and polymerizes. By using 2 to 10 parts by weight, more preferably 3 to 6 parts by weight of the radical polymerization initiator (E) with respect to 100 parts by weight of the radical polymerizable monomer (C), graft polymerization onto the aliphatic skeleton carbon can be performed. Done preferentially and efficiently.

  By this reaction, a reaction mixture containing a graft polymer, a radical polymer formed associatively but not grafted, and an unreacted phenoxy resin is obtained. In particular, when the molecular weight of the phenoxy resin (B) is high, or when the content of the phenoxy resin (B) is high, the production rate of the graft polymer is low, and the ratio of the unreacted phenoxy resin is high. As a result, problems such as precipitation or separation of the resin component in the aqueous coating composition over time may occur.

  Therefore, as a means for solving the above problems, it is important to perform an esterification reaction following the graft reaction, which is one of the features of the present invention. In this reaction, in the presence of a basic compound (F) used as an esterification catalyst, a carboxyl group possessed by a copolymer of an epoxy group and a radical polymerizable monomer (C) in the unreacted phenoxy resin (B) As a result of the reduction of the unreacted phenoxy resin, the storage stability of the aqueous coating composition is improved. The reaction temperature and time vary depending on the type of resin, the type of solvent, and the like, but generally the reaction temperature is more preferably in the range of 40 ° C to 150 ° C, particularly 60 ° C to 120 ° C.

  Examples of the basic compound (F) used as an esterification catalyst in esterification include alcohol amines such as dimethylethanolamine, ethanolamine, diethanolamine, and aminomethylpropanol; alkylamines such as trimethylamine, triethylamine, and butylamine; Examples include volatile amines such as morpholine and ammonia. The amount of the basic compound (F) required to neutralize 5 to 100 mol%, more preferably 20 to 80 mol%, relative to the carboxyl group in the radical polymerizable monomer (C). Done using.

  After the esterification reaction, the acrylic-modified phenoxy resin (A) can be dispersed in the aqueous medium by neutralizing at least a part of the remaining carboxyl groups with the basic compound (F).

  The aqueous medium in the present invention is a mixture of water and a hydrophilic solvent in which at least 50% by weight, preferably 70% by weight or more is water. Examples of hydrophilic solvents include alcohol solvents such as ethanol, isopropanol, n-propanol, n-butanol, iso-butanol and pentanol, and ethylene glycol alkyl ether solvents such as ethylene glycol monoethyl ether and ethylene glycol monobutyl ether. Diethylene glycol alkyl ether solvents such as diethylene glycol monobutyl ether; propylene glycol alkyl ether solvents such as propylene glycol monomethyl ether and propylene glycol monoethyl ether; and esters of a series of glycol alkyl ether solvents such as ethylene glycol monoethyl ether acetate Although there is a chemical compound, it is not particularly limited.

  The water-based coating composition of the present invention has a phenol resin (D) in a weight ratio of (A) / (D) = 90/10 to 99.9 / 0.1 as a crosslinking agent for the acrylic-modified phenoxy resin (A). It is characterized by containing in the ratio. Furthermore, it is more preferable that it is in the range of 95/5 to 99.8 / 0.2. When the weight ratio of the phenol resin (D) is less than 0.1, it is difficult to obtain a contribution to the curing of the phenol resin (D), the crosslinking density is lowered, and the adsorptivity of flavor aroma components and particularly the corrosion resistance is severe. Corrosion resistance for the alcoholic beverage used is not ensured. On the other hand, when the weight ratio of the phenol resin (D) exceeds 10, the processability of the coating film is deteriorated, and there is a problem that cracks are likely to occur in the processed part such as the above-described lid winding part.

  The phenol resin (D) is a resol type resin formed from a trifunctional phenol monomer such as coalic acid or m-cresol, the benzene ring mononuclear content is 1% by weight or less, and the number average molecular weight is 250. ˜1500 is preferred.

  When the number average molecular weight of the phenol resin is as small as 250 to 1500, generally, the benzene ring mononuclear is contained in an amount of more than 1% by weight. Here, the mononuclear benzene ring is a structure having only one benzene ring in which a trifunctional phenol monomer such as carboxylic acid or m-cresol and a methylol group or an alkoxylated methyl group are bonded to the monomer. The content can be determined by the GPC method. Such a benzene ring mononuclear substance is likely to be eluted from the coating film, and may deteriorate the flavor of the contents of the can for alcoholic beverages. Also, the benzene ring mononuclear has a strong odor and skin irritation and is not desirable from a hygienic viewpoint. The phenol resin (D) preferably used in the present invention has a benzene ring mononuclear content as low as 1% by weight or less although the number average molecular weight is as small as 250 to 1500. Further, the phenol resin (D) inevitably has a low benzene ring dinuclear content, and has a very narrow molecular weight distribution centering on the benzene ring trinuclear to hexanuclear. Such a phenol resin (D) is difficult to be extracted from the coating film and has sufficient reactivity.

  There are various methods for reducing the mononuclear benzene ring contained in the phenol resin (D). One of them is a content of mononuclear benzene ring having a number average molecular weight of 250 to 800 under an acidic catalyst. A novolak-type phenolic resin having an amount of 1% by weight or less is formed, followed by addition of formaldehyde under a basic catalyst, and alkoxylation as necessary.

  The novolak-type phenol resin having a benzene ring mononuclear content of 1% by weight or less can be obtained by removing low molecular weight components typified by a benzene ring mononuclear from the novolac-type phenol resin. Specifically, for example, a technique for removing low molecular weight components under high temperature and reduced pressure, a technique for removing low molecular weight components by steam distillation, and the like can be mentioned. Alternatively, a technique of obtaining a resin having a low content of low molecular components and a narrow molecular weight distribution by using a special acid catalyst such as tartaric acid or citric acid is known. The resulting novolak-type phenolic resin having a benzene ring mononuclear content of 1% by weight or less is added with formaldehyde under a basic catalyst such as sodium hydroxide, magnesium hydroxide, ammonia, triethylamine, etc. A phenolic resin having a benzene ring mononuclear content of 1% by weight or less by further converting the methylol group to an alkoxylated methyl group using an alcohol such as methanol or n-butanol as necessary. ) Can be obtained.

  In order to obtain the phenol resin (D), it is preferable to use trifunctional phenol as the phenol monomer. Examples of the trifunctional phenols include carboxylic acid, m-cresol, m-ethylphenol, m-ethoxyphenol, 3,5-xylenol, and particularly, carboxylic acid and m-cresol are more preferable.

  Phenol monomers other than trifunctional phenols such as monofunctional 2,4-xylenol, 2,6-xylenol; bifunctional p-cresol, p-ter-butylphenol, p-ethylphenol, o-cresol Phenol monomers such as 2,3-xylenol, 2,5-xylenol, and p-nonylphenol can also be used, but when these are used, the functional group concentration is lowered, and the desired reactivity and molecular weight between crosslinks (crosslink (Density) may be difficult to ensure.

  Moreover, it is not preferable to use a tetrafunctional phenol monomer such as bisphenol A and bisphenol F as the phenol monomer because the self-condensation property of the phenol resin becomes too high. In a phenol resin using bisphenol A and bisphenol F as monomers, a self-condensation reaction is likely to occur before the reaction with the acrylic-modified phenoxy resin (A), and it becomes difficult to function as a crosslinking component, making it difficult to form a dense coating film. There is a fear. Furthermore, phenol resin self-condensates generally have hard and brittle properties and tend to degrade the processability of the coating. The deterioration of the workability of the coating film may easily cause a crack in a processed portion such as the above-described lid tightening portion.

  The water-based coating composition of the present invention can be added with a solvent, a surfactant or an antifoaming agent for improving the paintability as required. Further, after forming the coating film, a wax as a lubricant can be added for the purpose of preventing the coating film from being scratched during processing and transportation, and can be preferably used as a paint for the inner surface of cans.

  The aqueous coating composition of the present invention can be applied to various substrates, and an article to be coated coated with the aqueous coating composition can be obtained. Examples of the base material include various kinds of untreated or surface-treated metals such as an aluminum plate, a steel plate, and a tin plate, a metal obtained by applying a paint such as a primer to these metals, or a polyester film (PET) on these metals. And plastic film-coated metal such as PET-coated metal laminated.

  Further, the shape of the substrate may be a plate shape or a bottomed cylindrical shape. Further, 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.

  As a method of coating the substrate with the aqueous coating composition of the present invention, various known methods, for example, spray coating such as air spray, airless spray, electrostatic spray, etc., dip coating, roll coater coating, electrodeposition coating, etc. Etc. are applicable. The thickness of the coating after drying may be appropriately selected depending on the use, but is usually preferably about 1 to 20 μm. The drying condition of the coated film can be selected from the range of 150 to 300 ° C. and the time of 10 seconds to 30 minutes.

  The present invention will be described more specifically with reference to the following examples. However, the following examples do not limit the scope of rights of the present invention. In the examples, “parts” and “%” represent “parts by weight” and “% by weight”, respectively. In the following phenol resin production examples, the number average molecular weight is a value obtained by the GPC method (standard styrene conversion), and the benzene ring mononuclear content is a value obtained by the GPC method.

Production Example 1 (Production of carboxyl group-containing acrylic copolymer (c6) solution)
A radical polymerizable monomer in which 210 parts of methacrylic acid, 60 parts of styrene and 30 parts of ethyl acrylate are mixed in a four-necked flask substituted with nitrogen gas, and a polymerization initiator solution consisting of 1 part of benzoyl peroxide and 100 parts of butyl cellosolve 1/4 of the mixed solution, 300 parts of butyl cellosolve, and 300 parts of n-butanol were charged. Next, the mixture was heated to 100 ° C. and stirred for 30 minutes, and then 3/4 of a mixed solution composed of a radical polymerizable monomer and a polymerization initiator solution was dropped over 2 hours while maintaining 100 ° C. After completion of dropping, the mixture was further stirred at 2O 0 C for 2 hours, cooled and taken out to obtain a carboxyl group-containing acrylic copolymer (c6) solution having a solid content of 30%. The composition ratio of the radical polymerizable monomer is shown in Table 2.

Production Example 2 [Production of Resol Type Phenolic Resin (d1) Solution]
A 4-necked flask purged with nitrogen gas was charged with (1) 500 parts of coal acid, (2) 237 parts of 37% formalin, and (3) 5 parts of oxalic acid, heated to 95 ° C., and reacted for 3 hours. Next, after reducing the pressure to 60 mmHg and heating to 150 ° C. while dehydrating, further dehydration was continued while blowing nitrogen gas, and the internal temperature was heated to 210 ° C. This state is maintained for 4 hours, and then vacuum dehydration is performed for 1 hour under a reduced pressure of 20 mmHg, thereby obtaining 383 parts of a solid novolak type phenol resin having a benzene ring mononuclear content of 0.1% and a number average molecular weight of 440. It was.

  Next, (4) 200 parts of ion-exchanged water, (5) 200 parts of 20% aqueous sodium hydroxide, and (6) 800 parts of 37% formalin were dissolved in the flask, and the novolak type phenolic resin was dissolved. When reacted for 3 hours, a reddish brown transparent solution was obtained. Next, after cooling to 40 ° C., 190 parts of (7) 20% hydrochloric acid was added to this reddish brown transparent solution and stirred. After about 10 minutes, the upper layer was separated into a colorless and transparent aqueous layer, and the lower layer was separated into a reddish brown organic layer. did. After separating and removing the upper layer by decantation, (8) 490 parts of n-butanol was added, and a resol type phenol resin (d1) having a benzene ring mononuclear content of 0.1% and a number average molecular weight of 680 with a solid content of 50%. ) A solution was obtained.

Production Example 3 [Production of Resol Type Phenolic Resin (d2) Solution]
A 4-necked flask purged with nitrogen gas was charged with (1) 450 parts of m-cresol, (2) 130 parts of 86% paraformaldehyde, and (3) 250 parts of citric acid, heated to 120 ° C., and reacted for 4 hours. It was. After the completion of the reaction, citric acid was removed by washing with (4) 500 parts of ion exchange water. Subsequently, dehydration was performed under reduced pressure of 60 mmHg to obtain 383 parts of a novolak type phenol resin having a benzene ring mononuclear content of 0.4% and a number average molecular weight of 650.

  Next, (5) 220 parts of ion-exchanged water, (6) 180 parts of 20% aqueous sodium hydroxide solution, and (7) 700 parts of 37% formalin were dissolved in a four-necked flask, and after dissolving the above novolac type phenol resin, When the reaction was carried out at 3 ° C. for 3 hours, a reddish brown transparent solution was obtained. Next, after cooling to 40 ° C., 180 parts of (8) 20% hydrochloric acid was added to this reddish brown transparent solution and stirred. After about 10 minutes, the upper layer was separated into a colorless and transparent aqueous layer, and the lower layer was separated into a reddish brown organic layer. did. After separating and removing the upper layer by decantation, (9) 490 parts of n-butanol was added and reacted at 60 ° C. for 3 hours to obtain a benzene ring mononuclear content of 0.1%, a number average molecular weight of 840 solid content of 50%. A resol type phenolic resin (d2) solution was obtained.

Production Example 4 [Production of Resol Type Phenolic Resin (d3) Solution]
In a four-necked flask purged with nitrogen gas, (1) ion-exchanged water 60 parts, (2) 20% aqueous sodium hydroxide 60 parts, (3) bisphenol A 50 parts, (4) bisphenol F 50 parts, (5) 37% When 300 parts of formalin was added and reacted at 60 ° C. for 3 hours, a brown and transparent solution was obtained. Next, after cooling to 40 ° C., 55 parts of (6) 20% hydrochloric acid was added to this brown transparent solution and stirred. After about 10 minutes, the upper layer was separated into a colorless and transparent aqueous layer, and the lower layer was separated into a brown organic layer. did. After separating and removing the upper layer by decantation, (7) 140 parts of n-butanol is added, the content of mononuclear benzene ring is 0.0% (theoretical does not exist), and the solid content is 50 with a number average molecular weight of 320. % Resol type phenol resin (d3) solution was obtained.

Production Example 5 [Production of Resol Type Phenolic Resin (d4) Solution]
A 4-necked flask purged with nitrogen gas was charged with (1) 60 parts of ion-exchanged water, (2) 60 parts of a 20% aqueous sodium hydroxide solution, (3) 100 parts of carboxylic acid, and (4) 200 parts of 37% formalin. When the reaction was carried out at 3 ° C. for 3 hours, a brown and transparent solution was obtained. Then, after cooling to 40 ° C., 55 parts of (5) 20% hydrochloric acid was added to this brown transparent solution and stirred. After about 10 minutes, the upper layer was separated into a colorless and transparent aqueous layer, and the lower layer was separated into a brown organic layer. did. After separating and removing the upper layer by decantation, (6) 140 parts of n-butanol was added, and then reacted at 60 ° C. for 3 hours to obtain a solid content of benzene ring mononuclear content of 4.8% and number average molecular weight of 580. A 50% resol type phenol resin (d4) solution was obtained.

  Table 1 shows the properties of the phenol resins produced in Production Examples 2 to 5.

Example 1 [Production of aqueous coating composition]
164 parts of JER1256 [Eeq = 8000, Mn = 13000, manufactured by Japan Epoxy Resin Co., Ltd.], 70 parts of butyl cellosolve and 78 parts of n-butanol were charged into a four-necked flask purged with nitrogen gas, and the temperature was gradually raised while stirring. The phenoxy resin was completely dissolved at 110 to 120 ° C. With the flask maintained at 115 ± 5 ° C., a polymerization initiator solution consisting of 64 parts of the radically polymerizable monomer (c1) having the composition ratio shown in Table 2, 2 parts of benzoyl peroxide, and 10 parts of butyl cellosolve was added for 1 hour. It was dripped over. After completion of the dropwise addition, the mixture was further maintained at 115 ± 5 ° C. for 2 hours, then cooled to 90 ° C., 10 parts of dimethylaminoethanol was added, and then esterified at 90 ± 3 ° C. for 1 hour. After completion of the reaction, 5 parts of a phenol resin (d1) solution was added, and then 597 parts of ion-exchanged water was added dropwise over 1 hour to obtain an aqueous coating composition having a solid content of 23%.

Example 2 [Production of aqueous coating composition]
A 4-necked flask purged with nitrogen gas was charged with 131 parts of phenotote YP-70 [Eeq = 13700, Mn = 13300, manufactured by Tohto Kasei Co., Ltd.], 70 parts of butyl cellosolve and 65 parts of n-butanol, and gradually stirred. The temperature was raised and the phenoxy resin was completely dissolved at 110 to 120 ° C. With the flask maintained at 115 ± 5 ° C., a polymerization initiator solution consisting of 84 parts of the radical polymerizable monomer (c1) having the composition ratio shown in Table 2, 3 parts of benzoyl peroxide, and 10 parts of butyl cellosolve was added for 1 hour. It was dripped over. After completion of the dropwise addition, the mixture was further maintained at 115 ± 5 ° C. for 2 hours, then cooled to 90 ° C., 10 parts of dimethylaminoethanol was added, and then esterified at 90 ± 3 ° C. for 1 hour. After completion of the reaction, 30 parts of a phenol resin (d1) solution was added, and then 597 parts of ion-exchanged water was added dropwise over 1 hour to obtain an aqueous coating composition having a solid content of 23%.

Example 3 [Production of aqueous coating composition]
A four-necked flask purged with nitrogen gas was charged with 148 parts of phenotote YP-70 [Eeq = 13700, Mn = 13300, manufactured by Tohto Kasei Co., Ltd.], 70 parts of butyl cellosolve, 61 parts of n-butanol, and gradually stirred. The temperature was raised and the phenoxy resin was completely dissolved at 110 to 120 ° C. With the flask maintained at 115 ± 5 ° C., a polymerization initiator solution consisting of 63 parts of the radical polymerizable monomer (c1) having the composition ratio shown in Table 2, 3 parts of benzoyl peroxide, and 10 parts of butyl cellosolve was added for 1 hour. It was dripped over. After completion of the dropwise addition, the mixture was further maintained at 115 ± 5 ° C. for 2 hours, then cooled to 90 ° C., 10 parts of dimethylaminoethanol was added, and then esterified at 90 ± 3 ° C. for 1 hour. After completion of the reaction, 38 parts of the phenol resin (d2) solution was added, and then 597 parts of ion exchange water was added dropwise over 1 hour to obtain an aqueous coating composition having a solid content of 23%.

Example 4 [Production of water-based coating composition]
In a four-necked flask purged with nitrogen gas, 22 parts of JER1256 [Eeq = 8000, Mn = 13000, manufactured by Japan Epoxy Resin Co., Ltd.], Phenotote YP-70 [Eeq = 13700, Mn = 13300, manufactured by Tohto Kasei Co., Ltd.] 134 parts, 70 parts of butyl cellosolve and 73 parts of n-butanol were gradually heated while stirring to completely dissolve the phenoxy resin at 110 to 120 ° C. With the flask maintained at 115 ± 5 ° C., a polymerization initiator solution consisting of 67 parts of the radical polymerizable monomer (c1) having the composition ratio shown in Table 2, 2 parts of benzoyl peroxide, and 10 parts of butyl cellosolve was added for 1 hour. It was dripped over. After completion of the dropwise addition, the mixture was further maintained at 115 ± 5 ° C. for 2 hours, then cooled to 90 ° C., 10 parts of dimethylaminoethanol was added, and then esterified at 90 ± 3 ° C. for 1 hour. After completion of the reaction, 13 parts of a phenol resin (d2) solution was added, and then 599 parts of ion-exchanged water was added dropwise over 1 hour to obtain an aqueous coating composition having a solid content of 23%.

Example 5 [Production of aqueous coating composition]
A 4-necked flask purged with nitrogen gas was charged with 166 parts of JER1256 [Eeq = 8000, Mn = 13000, manufactured by Japan Epoxy Resin Co., Ltd.], 70 parts of butyl cellosolve, 71 parts of n-butanol, and gradually heated while stirring. The phenoxy resin was completely dissolved at 110 to 120 ° C. A polymerization initiator solution consisting of 55 parts of a radical polymerizable monomer (c2) having a composition ratio shown in Table 2, 4 parts of benzoyl peroxide, and 10 parts of butyl cellosolve was maintained for 1 hour with the flask maintained at 115 ± 5 ° C. It was dripped over. After completion of the dropwise addition, the mixture was further maintained at 115 ± 5 ° C. for 2 hours, then cooled to 90 ° C., 10 parts of dimethylaminoethanol was added, and then esterified at 90 ± 3 ° C. for 1 hour. After completion of the reaction, 18 parts of the phenol resin (d1) solution was added, and then 596 parts of ion exchange water was added dropwise over 1 hour to obtain an aqueous coating composition having a solid content of 23%.

Example 6 [Production of aqueous coating composition]
In a four-necked flask purged with nitrogen gas, 133 parts of JER1256 [Eeq = 8000, Mn = 13000, manufactured by Japan Epoxy Resin Co., Ltd.], Phenototo YP-70 [Eeq = 13700, Mn = 13300, manufactured by Tohto Kasei Co., Ltd. ] 42 parts, 70 parts of butyl cellosolve and 71 parts of n-butanol were gradually heated while stirring to completely dissolve the phenoxy resin at 110 to 120 ° C. A polymerization initiator solution consisting of 46 parts of a radical polymerizable monomer (c2) having a composition ratio shown in Table 2, 2 parts of benzoyl peroxide, and 10 parts of butyl cellosolve was maintained for 1 hour while the flask was maintained at 115 ± 5 ° C. It was dripped over. After completion of the dropwise addition, the mixture was further maintained at 115 ± 5 ° C. for 2 hours, then cooled to 90 ° C., 5 parts of dimethylaminoethanol was added, and then esterified at 90 ± 3 ° C. for 1 hour. After completion of the reaction, 18 parts of a phenol resin (d1) solution was added, and then 603 parts of ion exchange water was added dropwise over 1 hour to obtain an aqueous coating composition having a solid content of 23%.

Example 7 [Production of water-based coating composition]
A four-necked flask purged with nitrogen gas was charged with 153 parts of JER1256 [Eeq = 8000, Mn = 13000, manufactured by Japan Epoxy Resin Co., Ltd.], 70 parts of butyl cellosolve, 69 parts of n-butanol, and gradually heated while stirring. The phenoxy resin was completely dissolved at 110 to 120 ° C. With the flask maintained at 115 ± 5 ° C., a polymerization initiator solution consisting of 66 parts of the radical polymerizable monomer (c2) having the composition ratio shown in Table 2, 3 parts of benzoyl peroxide, and 10 parts of butyl cellosolve was added for 1 hour. It was dripped over. After completion of the dropwise addition, the mixture was further maintained at 115 ± 5 ° C. for 2 hours, then cooled to 90 ° C., 10 parts of dimethylaminoethanol was added, and then esterified at 90 ± 3 ° C. for 1 hour. After completion of the reaction, 22 parts of the phenol resin (d2) solution was added, and then 597 parts of ion-exchanged water was added dropwise over 1 hour to obtain an aqueous coating composition having a solid content of 23%.

Example 8 [Production of aqueous coating composition]
In a four-necked flask purged with nitrogen gas, 113 parts of JER1256 [Eeq = 8000, Mn = 13000, manufactured by Japan Epoxy Resin Co., Ltd.], Phenotote YP-70 [Eeq = 13700, Mn = 13300, manufactured by Tohto Kasei Co., Ltd.] ] 56 parts, 70 parts of butyl cellosolve and 75 parts of n-butanol were gradually heated while stirring to completely dissolve the phenoxy resin at 110 to 120 ° C. A polymerization initiator solution consisting of 56 parts of a radical polymerizable monomer (c2) having a composition ratio shown in Table 2, 2 parts of benzoyl peroxide, and 10 parts of butyl cellosolve was maintained for 1 hour while the flask was maintained at 115 ± 5 ° C. It was dripped over. After completion of the dropwise addition, the mixture was further maintained at 115 ± 5 ° C. for 2 hours, then cooled to 90 ° C., 10 parts of dimethylaminoethanol was added, and then esterified at 90 ± 3 ° C. for 1 hour. After completion of the reaction, 9 parts of a phenol resin (d2) solution was added, and then 599 parts of ion exchange water was added dropwise over 1 hour to obtain an aqueous coating composition having a solid content of 23%.

Example 9 [Production of water-based coating composition]
A 4-necked flask purged with nitrogen gas was charged with 175 parts of phenotote YP-70 [Eeq = 13700, Mn = 13300, manufactured by Tohto Kasei Co., Ltd.], 70 parts of butyl cellosolve, 63 parts of n-butanol, and gradually stirred. The temperature was raised and the phenoxy resin was completely dissolved at 110 to 120 ° C. With the flask maintained at 115 ± 5 ° C., a polymerization initiator solution consisting of 38 parts of the radical polymerizable monomer (c3) having the composition ratio shown in Table 2, 2 parts of benzoyl peroxide, and 10 parts of butyl cellosolve was added for 1 hour. It was dripped over. After completion of the dropwise addition, the mixture was further maintained at 115 ± 5 ° C. for 2 hours, then cooled to 90 ° C., 10 parts of dimethylaminoethanol was added, and then esterified at 90 ± 3 ° C. for 1 hour. After the completion of the reaction, 34 parts of a phenol resin (d1) solution was added, and then 598 parts of ion-exchanged water was added dropwise over 1 hour to obtain an aqueous coating composition having a solid content of 23%.

Example 10 [Production of aqueous coating composition]
In a four-necked flask purged with nitrogen gas, 103 parts of JER1256 [Eeq = 8000, Mn = 13000, manufactured by Japan Epoxy Resin Co., Ltd.], Phenototo YP-70 [Eeq = 13700, Mn = 13300, manufactured by Tohto Kasei Co., Ltd.] ] 92 parts, 70 parts of butyl cellosolve and 79 parts of n-butanol were gradually heated while stirring to completely dissolve the phenoxy resin at 110 to 120 ° C. With the flask maintained at 115 ± 5 ° C., a polymerization initiator solution consisting of 34 parts of the radical polymerizable monomer (c3) having the composition ratio shown in Table 2, 3 parts of benzoyl peroxide, and 10 parts of butyl cellosolve was added for 1 hour. It was dripped over. After completion of the dropwise addition, the mixture was further maintained at 115 ± 5 ° C. for 2 hours, then cooled to 90 ° C., 10 parts of dimethylaminoethanol was added, and then esterified at 90 ± 3 ° C. for 1 hour. After completion of the reaction, 2 parts of the phenol resin (d1) solution was added, and then 597 parts of ion-exchanged water was added dropwise over 1 hour to obtain an aqueous coating composition having a solid content of 23%.

Example 11 [Production of aqueous coating composition]
A 4-necked flask purged with nitrogen gas was charged with 186 parts of JER1256 [Eeq = 8000, Mn = 13000, manufactured by Japan Epoxy Resin Co., Ltd.], 70 parts of butyl cellosolve and 69 parts of n-butanol, and gradually heated while stirring. The phenoxy resin was completely dissolved at 110 to 120 ° C. With the flask maintained at 115 ± 5 ° C., a polymerization initiator solution consisting of 33 parts of the radical polymerizable monomer (c3) having the composition ratio shown in Table 2, 2 parts of benzoyl peroxide, and 10 parts of butyl cellosolve was added for 1 hour. It was dripped over. After completion of the dropwise addition, the mixture was further maintained at 115 ± 5 ° C. for 2 hours, then cooled to 90 ° C., 5 parts of dimethylaminoethanol was added, and then esterified at 90 ± 3 ° C. for 1 hour. After completion of the reaction, 22 parts of the phenol resin (d2) solution was added, followed by dropwise addition of 603 parts of ion-exchanged water over 1 hour to obtain an aqueous coating composition having a solid content of 23%.

Example 12 [Production of aqueous coating composition]
A 4-necked flask purged with nitrogen gas was charged with 177 parts of phenotote YP-70 [Eeq = 13700, Mn = 13300, manufactured by Tohto Kasei Co., Ltd.], 70 parts of butyl cellosolve, 71 parts of n-butanol, and gradually stirred. The temperature was raised and the phenoxy resin was completely dissolved at 110 to 120 ° C. With the flask maintained at 115 ± 5 ° C., a polymerization initiator solution consisting of 44 parts of radically polymerizable monomer (c3) having the composition ratio shown in Table 2, 3 parts of benzoyl peroxide, and 10 parts of butyl cellosolve was added for 1 hour. It was dripped over. After completion of the dropwise addition, the mixture was further maintained at 115 ± 5 ° C. for 2 hours, then cooled to 90 ° C., 10 parts of dimethylaminoethanol was added, and then esterified at 90 ± 3 ° C. for 1 hour. After completion of the reaction, 18 parts of a phenol resin (d2) solution was added, and then 597 parts of ion exchange water was added dropwise over 1 hour to obtain an aqueous coating composition having a solid content of 23%.

Example 13 [Production of aqueous coating composition]
A four-necked flask purged with nitrogen gas was charged with 169 parts of JER1256 [Eeq = 8000, Mn = 13000, manufactured by Japan Epoxy Resin Co., Ltd.], 70 parts of butyl cellosolve, and 75 parts of n-butanol, and gradually heated while stirring. The phenoxy resin was completely dissolved at 110 to 120 ° C. A polymerization initiator solution consisting of 56 parts of a radical polymerizable monomer (c2) having a composition ratio shown in Table 2, 2 parts of benzoyl peroxide, and 10 parts of butyl cellosolve was maintained for 1 hour while the flask was maintained at 115 ± 5 ° C. It was dripped over. After completion of the dropwise addition, the mixture was further maintained at 115 ± 5 ° C. for 2 hours, then cooled to 90 ° C., 10 parts of dimethylaminoethanol was added, and then esterified at 90 ± 3 ° C. for 1 hour. After completion of the reaction, 9 parts of a phenol resin (d3) solution was added, and then 599 parts of ion-exchanged water was added dropwise over 1 hour to obtain an aqueous coating composition having a solid content of 23%.

Example 14 [Production of aqueous coating composition]
A four-necked flask purged with nitrogen gas was charged with 148 parts of phenotote YP-70 [Eeq = 13700, Mn = 13300, manufactured by Tohto Kasei Co., Ltd.], 70 parts of butyl cellosolve, 61 parts of n-butanol, and gradually stirred. The temperature was raised and the phenoxy resin was completely dissolved at 110 to 120 ° C. With the flask maintained at 115 ± 5 ° C., a polymerization initiator solution consisting of 63 parts of the radical polymerizable monomer (c1) having the composition ratio shown in Table 2, 3 parts of benzoyl peroxide, and 10 parts of butyl cellosolve was added for 1 hour. It was dripped over. After completion of the dropwise addition, the mixture was further maintained at 115 ± 5 ° C. for 2 hours, then cooled to 90 ° C., 10 parts of dimethylaminoethanol was added, and then esterified at 90 ± 3 ° C. for 1 hour. After completion of the reaction, 38 parts of a phenol resin (d4) solution was added, and then 597 parts of ion-exchanged water was added dropwise over 1 hour to obtain an aqueous coating composition having a solid content of 23%.

Comparative Example 1 [Production of water-based coating composition]
A four-necked flask purged with nitrogen gas was charged with 164 parts of phenotote YP-50S [Eeq = 36000, Mn = 16000, manufactured by Tohto Kasei Co., Ltd.], 70 parts of butyl cellosolve, and 78 parts of n-butanol and gradually stirred. The temperature was raised and the phenoxy resin was completely dissolved at 110 to 120 ° C. With the flask maintained at 115 ± 5 ° C., a polymerization initiator solution consisting of 64 parts of the radically polymerizable monomer (c1) having the composition ratio shown in Table 2, 2 parts of benzoyl peroxide, and 10 parts of butyl cellosolve was added for 1 hour. It was dripped over. After completion of the dropwise addition, the mixture was further maintained at 115 ± 5 ° C. for 2 hours, then cooled to 90 ° C., 10 parts of dimethylaminoethanol was added, and then esterified at 90 ± 3 ° C. for 1 hour. After completion of the reaction, 5 parts of a phenol resin (d1) solution was added, and then 597 parts of ion-exchanged water was added dropwise over 1 hour to obtain an aqueous coating composition having a solid content of 23%.

Comparative Example 2 [Production of aqueous coating composition]
A 4-necked flask purged with nitrogen gas was charged with 166 parts of JER1009 [Eeq = 3000, Mn = 2900, manufactured by Japan Epoxy Resin Co., Ltd.], 70 parts of butyl cellosolve and 71 parts of n-butanol, and gradually heated while stirring. The epoxy resin was completely dissolved at 110 to 120 ° C. A polymerization initiator solution consisting of 55 parts of a radical polymerizable monomer (c3) having a composition ratio shown in Table 2, 2 parts of benzoyl peroxide, and 10 parts of butyl cellosolve was maintained for 1 hour while the flask was maintained at 115 ± 5 ° C. It was dripped over. After completion of the dropwise addition, the mixture was further maintained at 115 ± 5 ° C. for 2 hours, then cooled to 90 ° C., 10 parts of dimethylaminoethanol was added, and then esterified at 90 ± 3 ° C. for 1 hour. After completion of the reaction, 18 parts of a phenol resin (d1) solution was added, and then 598 parts of ion-exchanged water was added dropwise over 1 hour to obtain an aqueous coating composition having a solid content of 23%.

Comparative Example 3 [Production of aqueous coating composition]
A four-necked flask purged with nitrogen gas was charged with 177 parts of ZX-1451 [Eeq = 3200, Mn = 5800, manufactured by Tohto Kasei Co., Ltd.], 70 parts of butyl cellosolve and 71 parts of n-butanol, and gradually heated while stirring. The epoxy resin was completely dissolved at 110 to 120 ° C. A polymerization initiator solution consisting of 44 parts of a radical polymerizable monomer (c2) having a composition ratio shown in Table 2, 2 parts of benzoyl peroxide, and 10 parts of butyl cellosolve was maintained for 1 hour with the flask maintained at 115 ± 5 ° C. It was dripped over. After completion of the dropwise addition, the mixture was further maintained at 115 ± 5 ° C. for 2 hours, then cooled to 90 ° C., 10 parts of dimethylaminoethanol was added, and then esterified at 90 ± 3 ° C. for 1 hour. After completion of the reaction, 18 parts of a phenol resin (d2) solution was added, and then 598 parts of ion-exchanged water was added dropwise over 1 hour to obtain an aqueous coating composition having a solid content of 23%.

Comparative Example 4 [Production of aqueous coating composition]
A four-necked flask purged with nitrogen gas was charged with 153 parts of JER1256 [Eeq = 8000, Mn = 13000, manufactured by Japan Epoxy Resin Co., Ltd.], 70 parts of butyl cellosolve, 69 parts of n-butanol, and gradually heated while stirring. The phenoxy resin was completely dissolved at 110 to 120 ° C. A polymerization initiator solution consisting of 66 parts of a radical polymerizable monomer (c4) having a composition ratio shown in Table 2, 2 parts of benzoyl peroxide, and 10 parts of butyl cellosolve was maintained for 1 hour with the flask maintained at 115 ± 5 ° C. It was dripped over. After completion of the dropwise addition, the mixture was further maintained at 115 ± 5 ° C. for 2 hours, cooled to 90 ° C., 15 parts of dimethylaminoethanol was added, and then esterified at 90 ± 3 ° C. for 1 hour. After completion of the reaction, 22 parts of the phenol resin (d2) solution was added, and then 593 parts of ion exchange water was added dropwise over 1 hour to obtain an aqueous coating composition having a solid content of 23%.

Comparative Example 5 [Production of aqueous coating composition]
A four-necked flask purged with raw gas was charged with 177 parts of phenotote YP-70 [Eeq = 13700, Mn = 13300, manufactured by Tohto Kasei Co., Ltd.], 70 parts of butyl cellosolve, 71 parts of n-butanol, and gradually stirred. The temperature was raised and the phenoxy resin was completely dissolved at 110 to 120 ° C. With the flask maintained at 115 ± 5 ° C., a polymerization initiator solution consisting of 44 parts of radically polymerizable monomer (c5) having the composition ratio shown in Table 2, 2 parts of benzoyl peroxide, and 10 parts of butyl cellosolve was added for 1 hour. It was dripped over. After completion of the dropwise addition, the mixture was further maintained at 115 ± 5 ° C. for 2 hours, then cooled to 90 ° C., 5 parts of dimethylaminoethanol was added, and then esterified at 90 ± 3 ° C. for 1 hour. After completion of the reaction, 18 parts of a phenol resin (d1) solution was added, and then 603 parts of ion exchange water was added dropwise over 1 hour to obtain an aqueous coating composition having a solid content of 23%.

Comparative Example 6 [Production of aqueous coating composition]
179 parts of JER1256 [Eeq = 8000, Mn = 13000, manufactured by Japan Epoxy Resin Co., Ltd.] in a four-necked flask purged with nitrogen gas, the carboxyl group-containing acrylic copolymer (c6) solution 106 prepared in Production Example 1 Part, 38 parts of butyl cellosolve and 29 parts of n-butanol were gradually heated while stirring to completely dissolve the phenoxy resin at 110 to 120 ° C. Thereafter, the mixture was cooled to 90 ° C. and 10 parts of dimethylaminoethanol was added, followed by esterification at 90 ± 3 ° C. for 1 hour. After completion of the reaction, 38 parts of the phenol resin (d1) solution was added, and then 596 parts of ion-exchanged water was added dropwise over 1 hour, but the viscosity of the resin solution was high and a stable aqueous dispersion could not be obtained. .

Comparative Example 7 [Production of aqueous coating composition]
A 4-necked flask purged with nitrogen gas was charged with 179 parts of JER1256 [Eeq = 8000, Mn = 13000, manufactured by Japan Epoxy Resin Co., Ltd.], 70 parts of butyl cellosolve, 61 parts of n-butanol, and gradually heated while stirring. The phenoxy resin was completely dissolved at 110 to 120 ° C. With the flask maintained at 115 ± 5 ° C., a polymerization initiator solution consisting of 32 parts of the radically polymerizable monomer (c1) having the composition ratio shown in Table 2, 2 parts of benzoyl peroxide, and 10 parts of butyl cellosolve was added for 1 hour. It was dripped over. After the completion of dropping, the temperature was further maintained at 115 ± 5 ° C. for 2 hours, and then cooled to 90 ° C. After adding 38 parts of the phenol resin (d1) solution, an aqueous solution comprising 5 parts of dimethylaminoethanol and 603 parts of ion-exchanged water was added dropwise over 1 hour to obtain an aqueous coating composition having a solid content of 23%.

Comparative Example 8 [Production of aqueous coating composition]
200 parts of JER1256 [Eeq = 8000, Mn = 13000, manufactured by Japan Epoxy Resin Co., Ltd.], 70 parts of butyl cellosolve and 61 parts of n-butanol were charged into a four-necked flask purged with nitrogen gas, and gradually heated while stirring. The phenoxy resin was completely dissolved at 110 to 120 ° C. With the flask maintained at 115 ± 5 ° C., a polymerization initiator solution consisting of 11 parts of the radically polymerizable monomer (c1) having the composition ratio shown in Table 2, 1 part of benzoyl peroxide, and 10 parts of butyl cellosolve was added for 1 hour. It was dripped over. After completion of the dropwise addition, the mixture was further maintained at 115 ± 5 ° C. for 2 hours, then cooled to 90 ° C., 2 parts of dimethylaminoethanol was added, and then esterified at 90 ± 3 ° C. for 1 hour. After the completion of the reaction, 38 parts of the phenol resin (d1) solution was added, and then 607 parts of ion exchange water was added dropwise over 1 hour to obtain an aqueous coating composition having a solid content of 23%.

Comparative Example 9 [Production of water-based coating composition]
A 4-necked flask purged with nitrogen gas was charged with 110 parts of JER1256 [Eeq = 8000, Mn = 13000, manufactured by Japan Epoxy Resin Co., Ltd.], 70 parts of butyl cellosolve, 69 parts of n-butanol, and gradually heated while stirring. The phenoxy resin was completely dissolved at 110 to 120 ° C. With the flask maintained at 115 ± 5 ° C., a polymerization initiator solution consisting of 110 parts of the radically polymerizable monomer (c3) having the composition ratio shown in Table 2, 3 parts of benzoyl peroxide, and 10 parts of butyl cellosolve was added for 1 hour. It was dripped over. After completion of the dropwise addition, the mixture was further maintained at 115 ± 5 ° C. for 2 hours, cooled to 90 ° C., 20 parts of dimethylaminoethanol was added, and then esterified at 90 ± 3 ° C. for 1 hour. After completion of the reaction, 22 parts of the phenol resin (d1) solution was added, followed by dropwise addition of 586 parts of ion-exchanged water over 1 hour to obtain an aqueous coating composition having a solid content of 23%.

Comparative Example 10 [Production of water-based coating composition]
A four-necked flask purged with nitrogen gas was charged with 184 parts of phenotote YP-70 [Eeq = 13700, Mn = 13300, manufactured by Tohto Kasei Co., Ltd.], 70 parts of butyl cellosolve, and 80 parts of n-butanol, and gradually stirred. The temperature was raised and the phenoxy resin was completely dissolved at 110 to 120 ° C. A polymerization initiator solution comprising 46 parts of a radically polymerizable monomer (c2) having a composition ratio shown in Table 2, 2.8 parts of benzoyl peroxide, and 10 parts of butyl cellosolve while maintaining the inside of the flask at 115 ± 5 ° C. The solution was added dropwise over 1 hour. After completion of the dropwise addition, the mixture was further maintained at 115 ± 5 ° C. for 2 hours, then cooled to 90 ° C., 10 parts of dimethylaminoethanol was added, and then esterified at 90 ± 3 ° C. for 1 hour. After completion of the reaction, 0.2 part of the phenol resin (d1) solution was added, and then 597 parts of ion-exchanged water was added dropwise over 1 hour to obtain an aqueous coating composition having a solid content of 23%.

Comparative Example 11 [Production of water-based coating composition]
A 4-necked flask purged with nitrogen gas was charged with 160 parts of JER1256 [Eeq = 8000, Mn = 13000, manufactured by Japan Epoxy Resin Co., Ltd.], 70 parts of butyl cellosolve, and 50 parts of n-butanol, and gradually heated while stirring. The phenoxy resin was completely dissolved at 110 to 120 ° C. With the flask maintained at 115 ± 5 ° C., a polymerization initiator solution consisting of 40 parts of radically polymerizable monomer (c2) having the composition ratio shown in Table 2, 2 parts of benzoyl peroxide, and 10 parts of butyl cellosolve was added for 1 hour. It was dripped over. After completion of the dropwise addition, the mixture was further maintained at 115 ± 5 ° C. for 2 hours, then cooled to 90 ° C., 5 parts of dimethylaminoethanol was added, and then esterified at 90 ± 3 ° C. for 1 hour. After completion of the reaction, 60 parts of a phenol resin (d2) solution was added, followed by dropwise addition of 604 parts of ion-exchanged water over 1 hour to obtain an aqueous coating composition having a solid content of 23%.

Comparative Example 12 [Production of aqueous coating composition]
148 parts of JER1256 [Eeq = 8000, Mn = 13000, manufactured by Japan Epoxy Resin Co., Ltd.], 148 parts of butyl cellosolve, and 69 parts of n-butanol were charged into a four-necked flask purged with nitrogen gas, and gradually heated while stirring. The phenoxy resin was completely dissolved at 110 to 120 ° C. A polymerization initiator solution comprising 63 parts of a radically polymerizable monomer (c2) solution having a composition ratio shown in Table 2, 3 parts of benzoyl peroxide, and 10 parts of butyl cellosolve while maintaining the inside of the flask at 115 ± 5 ° C. It was added dropwise over time. After completion of the dropping, the mixture was further maintained at 115 ± 5 ° C. for 2 hours, and then 21 parts of a phenol resin (d2) solution was added and reacted at 115 ± 5 ° C. for 2 hours to precondense the phenol resin. After completion of the reaction, an aqueous solution composed of 10 parts of dimethylaminoethanol and 606 parts of ion-exchanged water was added dropwise over 1 hour to obtain an aqueous coating composition having a solid content of 23%.

  Table 3 shows the properties of the phenoxy resin and epoxy resin used in Examples and Comparative Examples.

  About the aqueous coating compositions obtained in Examples 1 to 14, Comparative Examples 1 to 5 and Comparative Examples 7 to 12, (1) Storage stability was evaluated, and various coating films were applied to test panels prepared under the following conditions. Physical properties were evaluated. The results are shown in Tables 4 and 5. Various test methods are as follows.

(Coating performance test panel production)
The aqueous paint compositions obtained in Examples 1 to 14, Comparative Examples 1 to 5 and Comparative Examples 7 to 12 were placed on an aluminum plate having a thickness of 0.1 mm so that the coating thickness after baking and drying was 5 μm. It was painted and baked and dried at 200 ° C. for 1 minute (peak temperature holding time) to prepare a test panel. Using each test panel, the following coating film performance evaluations (2) to (7) were performed, and the test results are shown in Tables 4 and 5.

(1) Storage stability: Each paint was stored in a thermostat at 50 ° C., and the appearance properties were periodically evaluated over 3 months.
A: “Good storage stability”
○: “No abnormality after 2 months, and abnormalities such as gelation, sedimentation and separation occurred after 3 months”
Δ: “No abnormality after 1 month, and abnormalities such as gelation, sedimentation and separation occurred after 2 months”
X: “Anomalies such as gelation, sedimentation and separation occurred within one month.”

(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 Three aluminum plates of 0.30 mm were sandwiched and a 3 kg load was dropped from the height of 45 cm onto the bent part. 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 folded painted plate, and the current between the metal plate and the bent portion after 10 seconds. The value was measured.
A: “Less than 2 mA”
○: “2 mA or more and less than 4 mA”
Δ: “4 mA or more and less than 7 mA”
×: “Over 7 mA”

(3) 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.
A: “No whitening is observed”
○: “Slightly whitening is observed.”
Δ: “Slight whitening is observed.”
×: “Remarkably whitening is observed”

(4) Adhesion The test panel was retorted at 125 ° C. for 40 minutes, the coating surface was cut into a grid pattern with a cutter knife, a peel test was performed with a cellophane tape, and the surface state was evaluated visually.
A: “No peeling”
○: “Peeling occurs at less than 10% of the cut part”
Δ: “Peeling occurs at 10% or more and less than 50% of the cut part”
X: “Peeling occurs at 50% or more of the cut part.”

(5) Corrosion resistance test The test panel was cut into a size of 30 mm x 50 mm and immersed in a beverage containing alcohol 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 a thickness of 0.30 mm is provided between the folded test pieces. Three aluminum plates were sandwiched, and a load of 3 kg was dropped onto the bent portion from a height of 45 cm. Subsequently, it was immersed in a beverage containing alcohol at 40 ° C. for 1 month, and the degree of corrosion of the bent portion was visually determined.
A: “No corrosion at all”
○: “Very little corrosion is recognized.”
Δ: “Slight corrosion is observed.”
×: “Significant corrosion is observed”

(6) Flavor component adsorption rate As flavor standard substances, ethyl acetate, ethyl caproate, ethyl caprylate, isoamyl acetate, and 2-acetate, which are considered to be important due to their large content and low sensory threshold Limonene, which is known as a typical component of orange flavor, was added to phenylethyl and used. It can be said that the lower the standard material adsorption rate, the better the flavor retention. Each test panel 500 cm ² was immersed in 500 cc of 5% ethanol aqueous solution containing 5 ppm each of various flavor standard substances (6 types of ethyl acetate, ethyl caproate, ethyl caprylate, isoamyl acetate, 2-phenylethyl acetate and limonene) After sealing, 30 days passed at 37 ° C. Each test panel after 30 days was taken out and washed with distilled water, and then the coating film was re-immersed in 100 cc of diethyl ether to extract each flavor standard substance adsorbed on the test panel, and the amount of adsorption was quantified by gas chromatography. . Each flavor substance was contained in the immersion liquid (500 cc) in an amount of 0.0025 g, and with this amount taken as 100%, the adsorption rate of each flavor component was calculated from the amount adsorbed on the coating film and evaluated according to the following criteria.
A: “Adsorption rate average of 6 flavor substances is less than 3.0%.”
○: “Average value of adsorption rate of 6 kinds of flavor substances is 3.0% or more and less than 5.0%”
Δ: “Adsorption rate average value of 6 flavor substances is 5.0% or more and less than 10%.”
×: “Adsorption rate average value of 6 kinds of flavor substances is 10% or more.”

(7) Potassium permanganate consumption Potassium permanganate consumption is a test method equivalent to COD (chemical oxygen demand), which is a general water quality test. The lower the measured value, the better the hygiene. It can be said that. Each test panel 500 cm ² was immersed in 500 cc of distilled water, sealed, and then retorted at 125 ° C. for 40 minutes. The consumption of potassium permanganate for each treated water was measured and evaluated according to the following criteria.
A: “Potassium permanganate consumption is less than 1.0 ppm.”
○: “Potassium permanganate consumption is 1.0 ppm or more and less than 3.0 ppm.”
Δ: “Potassium permanganate consumption is 3.0 ppm or more and less than 5.0 ppm.”
X: “Potassium permanganate consumption is 5.0 ppm or more.”

  The aqueous coating compositions of Examples 1 to 14 are composed of an acrylic-modified phenoxy resin obtained by grafting a radical polymerizable monomer having a specific acid value composition to a phenoxy resin and then esterifying the phenol resin. Water-based paint composition that improves various drawbacks of acrylic-modified epoxy resins, has excellent dispersion stability, and has excellent processing adhesion when used as a paint for cans. It was found that a coating film exhibiting high corrosion resistance and having both hygiene and flavor properties can be formed.

Claims (5)

An aqueous solution obtained by dispersing an acrylic-modified phenoxy resin (A) and a phenol resin (D) in an aqueous medium at a ratio of (A) / (D) = 90/10 to 99.9 / 0.1 (weight ratio). A coating composition comprising:
A radical polymerizable monomer (A) having a composition with an acid value of 260 to 520 mgKOH / g is added to a bisphenol type phenoxy resin (B) having an epoxy equivalent of 6000 to 20000 g / eq and a number average molecular weight of 5000 to 30000. C) is graft polymerized at a ratio of (B) / (C) = 90 / 10-60 / 40 (weight ratio) using the radical polymerization initiator (E), and then the presence of the basic compound (F) An aqueous coating composition characterized by being esterified below. The phenol resin (D) is a resol type phenol resin having a trifunctional phenol as a monomer, and
The aqueous coating composition according to claim 1, wherein the content of mononuclear benzene ring in the resin is 1% by weight or less and the number average molecular weight is 250 to 1500.   An article to be coated, which is obtained by coating a substrate with the aqueous coating composition according to claim 1.   4. The article to be coated according to claim 3, wherein the substrate is selected from the group consisting of a metal, a metal coated with a paint, and a plastic film-coated metal.   5. The article to be coated according to claim 3, wherein the substrate is plate-shaped or bottomed cylindrical.