Resin dispersions, paints, can ends and can bodies

Abstract

The present disclosure provides a resin dispersion and coating material that are excellent in stability and can form coating films that are excellent in processability, retort resistance, and openability and are suitable for use as coating films for can bodies, can lids, etc., using a polyester resin that does not contain any structural units derived from bisphenol A, bisphenol F, or bisphenol S and does not contain any sulfo group or salt thereof, as well as a can lid and can body using the coating material. The resin dispersion of the present disclosure contains a polyester resin (A) having an acid value of 16 mgKOH / g or less and a number-average molecular weight of 8,000 or more, a phenol resin (B) having a weight-average molecular weight of 500 to 2,700 and a specific structure, a neutralizing agent, an organic solvent, and water, and contains 30 to 130 parts by mass of the organic solvent per 100 parts by mass of the total of resins (A) and (B).

Description

[Technical Field]

[0001] The present disclosure relates to a resin dispersion, a paint containing the resin dispersion, a can lid formed using the paint, and a can body formed using the paint. [Background technology]

[0002] Epoxy resin-based paints, such as epoxy resin-phenolic resin-based paints, epoxy resin-amino resin-based paints, and epoxy resin-acrylic resin-based paints, are widely used as coating compositions for metal containers such as beverage cans (hereinafter sometimes referred to as can bodies) and metal lids (hereinafter sometimes referred to as can lids or lids). However, because many epoxy resin-based paints are manufactured using bisphenol A (hereinafter sometimes referred to as BPA) and other raw materials, there is a growing demand for paints that do not contain bisphenol A. Against this background, polyester-based water-based paints that do not use bisphenol A and other raw materials have been proposed as paints for coating can lids and can bodies.

[0003] Patent Document 1 describes a method for producing a cellulose acetate copolymer having an acid value of 150 eq / 10 6 Patent Document 2 discloses the use of a polyester resin (A) having an acid value of 2 to 50 mgKOH / g and a polyester resin (B) having an acid value of 0 to 50 mgKOH / g. Patent Document 3 discloses the use of a polyester resin (A) and a polyester resin (B) having an acid value difference of 5 mgKOH / g or more. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-292665 [Patent Document 2] Japanese Patent Application Laid-Open No. 2013-249376 [Patent Document 3] Japanese Patent Application Publication No. 2019-163454 Summary of the Invention [Problem to be solved by the invention]

[0005] Because can bodies and can lids undergo severe processing (e.g., necking, beading, scoring, riveting, etc.) during production, the coating film coating the metal substrate is also required to have high process resistance. Furthermore, depending on the type of contents, after filling the can with the contents, a high-temperature retort treatment may be performed to sterilize the contents. Therefore, the coating film coating the metal substrate is required to have excellent retort resistance. Furthermore, the coating film coating the metal substrate is required to have various properties, such as corrosion resistance (acid resistance and alkali resistance) to prevent corrosion of the metal substrate by the contents after filling, and excellent hygiene with no leaching of paint components. Additionally, in the case of can lids, excellent opening properties are also required.

[0006] However, while conventional paints have excellent retort resistance, they often have issues with stability as water-based paints. Furthermore, even when excellent stability as water-based paints is achieved using resins with sulfo groups or their salts or high-acidity polyesters, the resulting paint film often lacks sufficient retort resistance and processability, creating a need for improvements that can achieve both of these properties. In particular, can lids require extremely high levels of processability, so the coating must be flexible and stiff. However, for ease of opening, the coating must also be hard and snappy, which are the opposite of flexibility and stiffness. The market is demanding paints that can achieve both of these properties.

[0007] An object of the present disclosure is to provide a resin dispersion and paint that are excellent in stability and that can form coating films suitable for coating can bodies, can lids, etc., that have excellent processability, retort resistance, and openability, using a polyester resin that does not have any structural units derived from bisphenol A, bisphenol F, or bisphenol S and that does not have any sulfo group or salt thereof, and also to provide can lids and can bodies using the paint. [Means for solving the problem]

[0008] The present inventors have conducted extensive research and found that the problems of the present disclosure can be solved in the following aspects, leading to the completion of the present disclosure. [1]: A resin dispersion containing a polyester resin (A), a phenolic resin (B), a neutralizing agent, an organic solvent, and water, The polyester resin (A) has an acid value of 16 mgKOH / g or less and a number average molecular weight of 8,000 or more, the phenolic resin (B) has a weight-average molecular weight of 500 to 2,700, and contains 50 mol % or more of structural units derived from meta-cresol out of a total of 100 mol % of structural units derived from phenolic compounds, and contains 0.01 to 0.2 methylol groups, 0.8 to 1.3 butoxymethyl groups, and a total of 0.15 to 0.5 methylene bonds and dimethylene ether bonds per aromatic ring in the phenolic resin (B); A resin dispersion containing 30 to 130 parts by mass of the organic solvent per 100 parts by mass of the polyester resin (A) and the phenolic resin (B) combined. [2]: The resin dispersion according to [1], wherein the mass ratio of the polyester resin (A) to the phenolic resin (B) is polyester resin (A) / phenolic resin (B)=95 / 5 to 70 / 30. [3]: The resin dispersion according to [1] or [2], wherein the phenolic resin (B) has structural units derived from para-cresol in a proportion of 50 mol % or less relative to a total of 100 mol % of structural units derived from phenolic compounds. [4]: The resin dispersion according to any one of [1] to [3], wherein the polyester resin (A) has structural units derived from one or more polycarboxylic acid components selected from the group consisting of terephthalic acid, isophthalic acid, sebacic acid, and trimellitic acid (anhydride), and structural units derived from one or more polyhydric alcohol components selected from the group consisting of 1,2-propanediol, 1,4-cyclohexanedimethanol, 2-methyl-1,3-propanediol, ethylene glycol, 1,4-butanediol, and trimethylolpropane, and wherein, out of 100 mol % of the structural units derived from the polyhydric alcohol components of the polyester resin (A), 20 to 99.9 mol % of structural units derived from one or more polyhydric alcohol components selected from the group consisting of 1,2-propanediol, 1,4-cyclohexanedimethanol, and 2-methyl-1,3-propanediol and 0.1 to 80 mol % of structural units derived from one or more polyhydric alcohol components selected from the group consisting of ethylene glycol, 1,4-butanediol, and trimethylolpropane. [5]: The resin dispersion according to any one of [1] to [4], wherein the water is contained in an amount of 40 to 90 mass % relative to 100 mass % in total of the water and the organic solvent. [6]: A coating material containing the resin dispersion according to any one of [1] to [5]. [7]: A can lid obtained by coating a metal substrate with the coating material according to [6]. [8]: A can body having a metal substrate coated with the coating material according to [6]. [Effects of the Invention]

[0009] The present disclosure has the excellent effect of providing a resin dispersion and paint that are excellent in stability and that can form coating films suitable for coating can bodies, can lids, and the like, which have excellent processability, retort resistance, corrosion resistance, and openability, using a polyester resin that does not have any structural units derived from bisphenol A, bisphenol F, or bisphenol S and does not have any sulfo group or salt thereof, as well as a can lid and can body using the paint. DETAILED DESCRIPTION OF THE INVENTION

[0010] The present disclosure will be described in detail below. Other embodiments are also included within the scope of the present disclosure as long as they are consistent with the spirit of the present disclosure. In this specification, a numerical range specified using "to" includes the numerical values ​​before and after "to" as the lower and upper limits. Unless otherwise noted, the various components in this specification may be used independently, either singly or in combination of two or more types. The numerical values ​​described in this specification refer to values ​​obtained by the methods described in the Examples below, etc.

[0011] The resin dispersion of the present disclosure contains a polyester resin (A), a phenolic resin (B), a neutralizing agent, an organic solvent, and water. Each component will be described below.

[0012] <Polyester resin (A)> The polyester resin (A) is a polymerization product of a polycarboxylic acid or its ester-forming derivative with a polyhydric alcohol, and does not contain any structural units derived from bisphenol A, bisphenol F, or bisphenol S. The polyester resin (A) also does not contain any sulfo group or salt thereof. The polyester resin (A) can be obtained, for example, by dehydration condensation of a carboxy group of a polycarboxylic acid with a hydroxy group of a polyhydric alcohol. Alternatively, the polyester resin (A) can be obtained by dealcoholization of an ester of a polycarboxylic acid with a lower alcohol such as methanol or ethanol with a polyhydric alcohol. The resin dispersion of the present disclosure may contain polyester resins other than those mentioned above, as long as they do not deviate from the spirit and scope of the present disclosure.

[0013] It is important that the polyester resin (A) has an acid value of 16 mgKOH / g or less, preferably 1 to 11 mgKOH / g, more preferably 1 to 8 mgKOH / g, and even more preferably 3 to 8 mgKOH / g. The higher the acid value of the polyester resin (A), the more hydrophilic it becomes, and therefore the water resistance of the coating film deteriorates. By using a polyester resin (A) having an acid value of 16 mgKOH / g or less and a phenolic resin (B) described below, it is possible to achieve both processability, retort resistance, openability, and corrosion resistance.

[0014] The number average molecular weight (hereinafter also referred to as Mn) of the polyester resin (A) is set to be 8,000 or more. There is no upper limit to the Mn, but it is preferably 100,000 or less, and more preferably in the range of 9,000 to 50,000. Within this range, the processability and alkali resistance are further improved, and the solubility of the polyester resin (A) in solvents can be further improved.

[0015] The polyester resin (A) preferably has at least one of the following structures: (i) an alkyl group in the side chain; and (ii) an alicyclic structure in the main chain. This improves the solubility in organic solvents, as described below. It is believed that the improved solubility causes the polyester resin (A) to swell when water is added, and the alkyl group in the side chain and / or the alicyclic structure in the main chain of the polyester resin (A) become compatible with the phenolic resin (B), thereby enabling effective water-based dissolution. It is more preferable that the polyester resin (A) have both of the above structures (i) and (ii).

[0016] Examples of polycarboxylic acids used as monomers for forming the polyester resin (A) include terephthalic acid, isophthalic acid, sebacic acid, adipic acid, and 1,4-cyclohexanedicarboxylic acid. Other polycarboxylic acids that can be used include aromatic dibasic acids, aliphatic dibasic acids, alicyclic dibasic acids, α,β-unsaturated dicarboxylic acids, and anhydrides and alkyl esters thereof. Examples of aromatic dibasic acids include orthophthalic acid, naphthalenedicarboxylic acid, and biphenyldicarboxylic acid. Examples of aliphatic dibasic acids include succinic acid, azelaic acid, dodecanedioic acid, and dimer acid. Examples of alicyclic dibasic acids include 1,3-cyclohexanedicarboxylic acid and 1,2-cyclohexanedicarboxylic acid. Examples of α,β-unsaturated dicarboxylic acids include fumaric acid, maleic acid, itaconic acid, and citraconic acid.

[0017] The polyester resin (A) may have a branched structure. To introduce a branched structure, a trifunctional or higher functional acid may be used in addition to a dibasic acid. Specific examples include trimellitic acid (anhydride) (trimellitic acid and trimellitic acid anhydride are collectively referred to as "trimellitic acid (anhydride)." Hereinafter, "anhydride" will be used.), pyromellitic acid (anhydride), and ethylene glycol bistrimellitate dianhydride are mentioned.

[0018] Among the polycarboxylic acids, terephthalic acid, isophthalic acid, sebacic acid, adipic acid, 1,4-cyclohexanedicarboxylic acid, and trimellitic acid (anhydride) are preferred. The polyester resin (A) preferably contains structural units derived from one or more polycarboxylic acid components selected from the group consisting of terephthalic acid, isophthalic acid, sebacic acid, and trimellitic acid (anhydride). Of 100 mol% of the structural units derived from polycarboxylic acids in the polyester resin (A), it is preferred that the structural units derived from terephthalic acid account for 5 to 100 mol% and that the structural units derived from one or more polycarboxylic acids selected from the group consisting of isophthalic acid, sebacic acid, and trimellitic acid (anhydride) account for 0 to 95 mol% in total. Furthermore, it is preferred that the structural units derived from isophthalic acid account for 0 to 90 mol%, the structural units derived from sebacic acid account for 0 to 45 mol%, and the structural units derived from trimellitic acid (anhydride) account for 0 to 5 mol%.

[0019] The polyester resin (A) may contain a polycarboxylic acid other than the above-mentioned polycarboxylic acids or a monofunctional carboxylic acid. The total amount of structural units derived from the polycarboxylic acid of the polyester resin (A) other than the above-mentioned polycarboxylic acids is preferably 2 mol % or less, based on 100 mol % of the structural units derived from the polycarboxylic acid component of the polyester resin (A). In addition, the structural units derived from monofunctional carboxylic acids preferably account for 2 mol % or less of 100 mol % of the structural units derived from carboxylic acid components in the polyester resin (A).

[0020] The polyhydric alcohol used as a monomer for forming the polyester resin (A) may be, for example, an aliphatic diol having 2 to 10 carbon atoms, an alicyclic diol having 6 to 12 carbon atoms, or a diol containing an ether bond. Examples of aliphatic diols having 2 to 10 carbon atoms include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, neopentyl glycol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, 1,9-nonanediol, 2-methyl-1,3-propanediol, and 2-ethyl-2-butyl-1,3-propanediol. Examples of the alicyclic diol having 6 to 12 carbon atoms include 1,6-cyclohexanedimethanol and 1,4-cyclohexanedimethanol. Examples of diols having an ether bond include diethylene glycol, triethylene glycol, dipropylene glycol, polyethylene glycol, polypropylene glycol, and polytetramethylene glycol.

[0021] Among the polyhydric alcohols, the diol is preferably ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 2-methyl-1,3-propanediol, 1,4-cyclohexanedimethanol, 1,6-cyclohexanedimethanol, or diethylene glycol, and among these, ethylene glycol, 1,2-propanediol, 1,4-butanediol, 2-methyl-1,3-propanediol, or 1,4-cyclohexanedimethanol is more preferred.

[0022] In order to introduce a branched structure into the polyester resin (A), a monomer having three or more hydroxyl groups may be used in addition to the above diols. Specific examples include trimethylolpropane, glycerin, trimethylolethane, mannitol, sorbitol, pentaerythritol, and α-methyl glucoside.

[0023] The polyester resin (A) has structural units derived from one or more polyhydric alcohol components selected from the group consisting of 1,2-propanediol, 1,4-cyclohexanedimethanol, 2-methyl-1,3-propanediol, ethylene glycol, 1,4-butanediol, and trimethylolpropane, and preferably contains, out of 100 mol % of structural units derived from polyhydric alcohol components of the polyester resin (A), 20 to 99.9 mol % of structural units derived from one or more polyhydric alcohol components selected from the group consisting of 1,2-propanediol, 1,4-cyclohexanedimethanol, and 2-methyl-1,3-propanediol and 0.1 to 80 mol % of structural units derived from one or more polyhydric alcohol components selected from the group consisting of ethylene glycol, 1,4-butanediol, and trimethylolpropane. When forming the polyester resin (A), "other" polyhydric alcohols other than the polyhydric alcohols selected from the group consisting of ethylene glycol, 1,2-propanediol, 1,4-butanediol, 2-methyl-1,3-propanediol, 1,4-cyclohexanedimethanol, and trimethylolpropane may be used. However, the total amount of structural units derived from the "other" polyhydric alcohols is preferably 2 mol % or less based on 100 mol % of the structural units derived from the polyhydric alcohol component in the polyester resin (A). Furthermore, if necessary, a small amount of a monofunctional alcohol may be used. For example, the structural units derived from the monofunctional alcohol preferably account for 2 mol % or less of 100 mol % of the structural units derived from the alcohol component.

[0024] The polyester resin (A) may be a commercially available product. Suitable examples include Vylon GK-880 (acid value: 1 mg KOH / g, Mn: 18,000), Vylon GK-640 (acid value: 3 mg KOH / g, Mn: 18,000), Vylon GK-330 (acid value: 1 mg KOH / g, Mn: 17,000), and Vylon GK-360 (acid value: 5 mg KOH / g, Mn: 16,000), all manufactured by Toyobo Co., Ltd., DYNAPOL L490 (acid value: 3 mg KOH / g, Mn: 15,000), manufactured by Evonik Corporation, and UE-9800 (acid value: 3 mg KOH / g, Mn: 13,000), manufactured by Unitika Ltd.

[0025] <Phenol resin (B)> The phenolic resin (B) may be a resin synthesized by an addition condensation reaction between a phenolic compound and an aldehyde such as formaldehyde, etc. The phenolic resin (B) can be synthesized by a known method.

[0026] Examples of the phenolic resin (B) include resol-type phenolic resins and novolac-type phenolic resins. Resole phenolic resins are phenolic resins obtained using an alkaline catalyst, and novolac phenolic resins are phenolic resins obtained using an acidic catalyst. Examples of phenolic resins include resol-type novolac phenolic resins obtained by further reacting novolac phenolic resins with an alkaline catalyst, and novolac-type resol phenolic resins obtained by further reacting resol phenolic resins with an acidic catalyst. Among these, the phenol resin (B) is preferably a resol type phenol resin from the viewpoint of self-crosslinking or as a curing agent that reacts with the polyester resin (A) and from the viewpoint of dispersibility of the polyester resin (A).

[0027] Examples of the alkali catalyst include hydroxides of alkali metals such as sodium hydroxide, lithium hydroxide, and potassium hydroxide; hydroxides of alkaline earth metals such as magnesium hydroxide and calcium hydroxide; amines such as triethylamine, trimethylamine, and ethanolamine; and ammonia. Alkali metal hydroxides or alkaline earth metal hydroxides are preferred, sodium hydroxide, lithium hydroxide, magnesium hydroxide are more preferred, and sodium hydroxide is most preferred.

[0028] Examples of the acid catalyst include inorganic acids such as hydrochloric acid, sulfuric acid, and phosphoric acid, and organic acids such as formic acid, acetic acid, oxalic acid, succinic acid, maleic acid, fumaric acid, and p-toluenesulfonic acid.

[0029] In phenolic compounds, the ortho and para positions relative to the phenolic hydroxyl group are reactive sites, i.e., aldehydes can be added to the ortho and para carbon atoms. Therefore, a bifunctional phenol is a phenol having a substituent such as an alkyl group or a phenyl group at either the ortho or para position, and has two reactive sites per molecule. Trifunctional phenols are phenols that have no substituents at the ortho and para positions and have three reactive sites per molecule.

[0030] Specific examples of the bifunctional phenol include o-cresol, p-cresol, p-phenylphenol, p-nonylphenol, 2,3-xylenol, and 2,5-xylenol. Specific examples of trifunctional phenols include phenol (carbolic acid), m-cresol, 3,5-xylenol, and resorcinol. Note that "o-" is an alternative spelling of "ortho," "p-" is an alternative spelling of "para," and "m-" is an alternative spelling of "meta."

[0031] It is important that the phenolic resin (B) contains 50 mol % or more of structural units derived from meta-cresol (m-cresol) out of a total of 100 mol % of structural units derived from phenolic compounds, and it is preferable that it further contains structural units derived from para-cresol (p-cresol). In other words, it is desirable to use m-cresol and p-cresol in combination as phenolic compounds. Phenolic resin (B) obtained using m-cresol is highly reactive with polyester resin (A), and its use can achieve high processability, retort resistance, and openability. On the other hand, phenolic resin (B) obtained using p-cresol is less reactive, but imparts good dispersibility to polyester resin (A). This is thought to be because p-cresol only reacts at the ortho position, resulting in a two-dimensional molecular structure of the resulting phenolic resin (B), which is effective as a dispersant for polyester resin (A).

[0032] The phenolic resin (B) preferably contains 10 to 50 mol % of structural units derived from p-cresol, more preferably 20 to 40 mol %, of the total 100 mol % of structural units derived from phenolic compounds. By containing 10 to 50 mol % of structural units derived from p-cresol, the dispersibility of the polyester resin (A) is improved, and structural units derived from m-cresol, which have high reactivity with the polyester resin (A), can be used in combination with the phenolic resin (B).

[0033] Phenol compounds other than m-cresol and p-cresol may be used as the phenolic compound for obtaining the phenolic resin (B). Of the total 100 mol% of structural units derived from phenolic compounds in the phenolic resin (B), the total of structural units derived from phenolic compounds other than m-cresol and p-cresol is preferably 20 mol% or less, more preferably 10 mol% or less, and even more preferably 5 mol% or less. Among phenolic compounds other than m-cresol and p-cresol, o-cresol is preferred from the viewpoint of compatibility with the polyester resin (A).

[0034] For example, a resol-type phenolic resin can be obtained by reacting the above-mentioned phenolic compound with an aldehyde in the presence of an alkali catalyst. The resol-type phenolic resin obtained by this method has alkylol groups at at least some of the ortho- and para-positions, and further has a structure in which the aromatic rings of the phenolic compound are bonded to each other via alkylene groups or dialkylene ether groups.

[0035] Examples of the alkylol group in the resol-type phenolic resin include alkylol groups having 1 to 5 carbon atoms, and among these, methylol, ethylol, and propylene groups are preferred, with methylol groups being more preferred. Furthermore, examples of the alkylene group connecting the aromatic rings of the phenolic compound include alkylene groups having 1 to 5 carbon atoms, and methylene, ethylene, and propylene groups are preferred, with methylene groups being more preferred. The number of carbon atoms in the alkylol and alkylene groups is the same as the number of carbon atoms in the aldehyde used as the raw material. The same applies to the alkylene moiety of the dialkylene ether group connecting the aromatic rings of the phenolic compound. In this embodiment, it is preferable to use formaldehyde as the aldehyde.

[0036] From the viewpoint of curability and dispersibility, it is important that the weight average molecular weight of the phenolic resin (B) is 500 to 2,700, and preferably 600 to 2,500.

[0037] Furthermore, it is desirable that at least a portion of the alkylol groups of the phenolic resin (B) be etherified with an alcohol having 1 to 12 carbon atoms, and more preferably butyl-etherified. If the number of carbon atoms in the ether moiety is too large, compatibility with water will be reduced, and if the number is too small, compatibility with the polyester resin (A) will be reduced. Butyl-etherification improves compatibility with the polyester resin (A), promotes the crosslinking reaction, and further improves dispersibility.

[0038] It is important that the phenolic resin (B) contains 0.01 to 0.2 methylol groups and 0.8 to 1.3 butoxymethyl groups per aromatic ring.

[0039] The phenolic resin (B) contains methylene bonds and dimethylene ether bonds. These bonds are the cross-linking components of the phenolic resin, and the more these bonds there are, the higher the molecular weight or the more three-dimensional cross-linking is thought to occur. Two-dimensional cross-linking is preferred for the phenolic resin (B) to ensure dispersibility. Therefore, it is important that the phenolic resin (B) contains a total of 0.15 to 0.5 methylene bonds and dimethylene ether bonds per aromatic ring.

[0040] <Resin dispersion> The resin dispersion of the present disclosure will be described. The resin dispersion contains a polyester resin (A), a phenolic resin (B), a neutralizing agent, an organic solvent, and water. The resin dispersion can be obtained, for example, as follows. The polyester resin (A) is dissolved in an organic solvent, and after cooling as necessary, the phenolic resin (B) and a neutralizing agent are added, and then water is added to form a liquid dispersion medium made of a mixture of water and the organic solvent, and the polyester resin (A) and the phenolic resin (B) are dispersed in particulate form in the liquid dispersion medium, thereby obtaining the polymerizable composition. Alternatively, the polyester resin (A) can be dissolved in an organic solvent, a neutralizing agent can be added, and then water can be added to form a mixture of water and the organic solvent into a liquid dispersion medium. The polyester resin (A) can then be dispersed in particulate form in the liquid dispersion medium, and the phenolic resin (B) can then be added to obtain a resin dispersion. Alternatively, the polyester resin (A) and the phenolic resin (B) may be kneaded, and then an organic solvent is added to dissolve them, followed by adding a neutralizer and water to form a resin dispersion. Among these, it is preferable to dissolve the polyester resin (A) in an organic solvent, cool it if necessary, add the phenolic resin (B) and a neutralizing agent, and then add water to form a liquid dispersion medium using a mixture of water and the organic solvent, and then disperse the polyester resin (A) and the phenolic resin (B) in particulate form in the liquid dispersion medium.

[0041] The dispersed particles in the resin dispersion preferably have an average particle diameter D50 of 0.1 to 5 μm, more preferably 0.15 to 1 μm, and even more preferably 0.15 to 0.4 μm. A smaller dispersed particle diameter improves the stability of the resin dispersion and the coating material. A larger dispersed particle diameter reduces the affinity between particles when forming a coating film, improving the openability of a coating film formed using a coating material according to the present disclosure, as described below, for example, a coating film covering a metal can lid or can body.

[0042] With this resin dispersion, the combined use of polyester resin (A) and phenolic resin (B) is thought to preferentially crosslink the dispersed particles within them, while preferentially fusing particles between them. This is thought to make it possible to form a coating film that has the normally difficult qualities of flexibility and stiffness, while also achieving the opposing qualities of hardness and sharpness.

[0043] The mass ratio of the polyester resin (A) to the phenol resin (B), polyester resin (A) / phenol resin (B), is preferably from 95 / 5 to 70 / 30, and more preferably from 90 / 10 to 80 / 20.

[0044] <Organic solvents> The resin dispersion contains an organic solvent. An organic solvent is an organic compound used to dissolve and / or disperse substances and is liquid at 25°C and 1 atmosphere. This does not include the phenolic resin (B) contained in the "phenolic resin solution" or the liquid components of the "neutralizing agent" described below. Liquid additives such as Surfynol 420 used in the examples described below are also not included in the organic solvent. Note that liquids used to dissolve and / or disperse solid neutralizing agents are organic solvents. It is important that the resin dispersion contains 30 to 130 parts by mass of organic solvent per 100 parts by mass of the polyester resin (A) and phenolic resin (B) combined, with 35 to 120 parts by mass being preferred, and 40 to 100 parts by mass being more preferred. If the organic solvent content is too low, the polyester resin will not swell, making it impossible to obtain a stable dispersion. If the organic solvent content is too high, the polyester resin will dissolve in the organic solvent even when water is added, preventing the formation of dispersed particles.

[0045] The organic solvent is not particularly limited, but examples thereof include ketone-based solvents, glycol ether-based solvents, alcohol-based solvents, glycol solvents, and acetate-based solvents. Specific examples of ketone solvents include acetone, methyl ethyl ketone, methyl isobutyl ketone, diisobutyl ketone, cyclohexanone, diacetone alcohol, and isophorone. Specific examples of glycol ether solvents include ethylene glycol monomethyl ether, ethylene glycol dimethyl ether, ethylene glycol monoethyl ether, ethylene glycol diethyl ether, ethylene glycol mono(iso)propyl ether, ethylene glycol di(iso)propyl ether, ethylene glycol mono(iso)butyl ether, ethylene glycol di(iso)butyl ether, ethylene glycol mono-tert-butyl ether, ethylene glycol monohexyl ether, 1,3-butylene glycol-3-monomethyl ether, 3-methoxybutanol, 3-methyl-3-methoxybutanol, diethylene glycol monomethyl ether, diethylene glycol dimethyl ether, diethylene glycol monoethyl ether, diethylene glycol diethyl ether, diethylene glycol mono(iso)propyl ether, diethylene glycol di(iso)propyl ether, diethylene glycol mono(iso)butyl ether ... Examples of the propylene glycol diisobutyl ether include ethylene glycol di(iso)butyl ether, diethylene glycol monohexyl ether, diethylene glycol dihexyl ether, triethylene glycol dimethyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol mono(iso)propyl ether, propylene glycol mono(iso)butyl ether, propylene glycol dimethyl ether, propylene glycol diethyl ether, propylene glycol di(iso)propyl ether, propylene glycol di(iso)butyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol mono(iso)propyl ether, dipropylene glycol mono(iso)butyl ether, dipropylene glycol dimethyl ether, dipropylene glycol diethyl ether, diethylene glycol di(iso)propyl ether, and dipropylene glycol di(iso)butyl ether. Specific examples of alcohol-based solvents include ethanol, n-propanol, isopropanol, n-butyl alcohol, isobutyl alcohol, n-amyl alcohol, amyl alcohol, methyl amyl alcohol, octanol, and 2-ethylhexanol. Specific examples of glycol-based solvents include ethylene glycol, diethylene glycol, 1,2-propanediol, dipropylene glycol, and 1,3-butylene glycol. Specific examples of acetate solvents include ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, propylene glycol monomethyl ether acetate, 3-methoxybutyl acetate, ethylene glycol monobutyl ether acetate, and 3-methyl-3-methoxybutyl acetate. Other organic solvents may also be used as appropriate, such as ethyl acetate, butyl acetate, dibasic acid esters, toluene, xylene, aromatic hydrocarbon compounds, aliphatic hydrocarbons, N-methyl-2-pyrrolidone, dimethyl sulfoxide, dimethylformamide, solvent naphtha, etc. Furthermore, organic solvents may be used when producing a coating material, if necessary.

[0046] The organic solvent preferably contains a ketone-based solvent or a glycol ether-based solvent. It is more preferable that the organic solvent contains a total of 60 to 100 mass% of organic solvents selected from the group consisting of ketone-based and glycol ether-based organic solvents, based on 100 mass% of the organic solvent. It is even more preferable that the organic solvent contains both ketone-based and glycol ether-based organic solvents. It is preferable that the organic solvent contains 10 to 60 mass% of ketone-based organic solvents, based on 100 mass% of the organic solvent. As the ketone-based organic solvent, cyclohexanone and methyl ethyl ketone are preferred, and cyclohexanone is more preferred. As the glycol ether organic solvent, ethylene glycol monobutyl ether and diethylene glycol monobutyl ether are preferred, and diethylene glycol monobutyl ether is more preferred.

[0047] <Water> The resin dispersion contains water to make it aqueous. The amount of water is preferably 40 to 90% by mass, with the total of the organic solvent and water being 100% by mass. If the proportion of water is too low, the polyester resin dissolves in the organic solvent, making it difficult to form dispersed particles. On the other hand, if the proportion of water is too high, there will not be enough organic solvent to swell the polyester resin, making it difficult to form particles.

[0048] <Neutralizer> The neutralizing agent is used mainly to neutralize the carboxyl groups in the polyester resin (A) and give the polyester resin (A) water affinity, but some of it also forms bonds with the hydroxyl groups in the phenolic resin (B), imparting ionicity as well as water affinity, and is thought to enhance dispersibility in the polyester resin (A). Examples of the neutralizing agent include dimethylaminoethanol, triethanolamine, ammonia, aminoethanol, sodium hydroxide, sodium carbonate, etc. Among these, dimethylaminoethanol, triethanolamine, ammonia, and aminoethanol are preferred. The amount of the neutralizing agent is preferably 0.3 to 5 molar equivalents, more preferably 0.5 to 3 molar equivalents, relative to the carboxyl groups of (A) in the polyester resin. Among the neutralizing agents, dimethylaminoethanol and the like are not considered to be organic solvents in this specification.

[0049] <Paint> The present resin dispersion is suitable for use in paints. In the paint of the present disclosure (hereinafter also referred to as the present paint), the phenolic resin (B) functions as a curing agent. The present paint preferably contains 30 to 120 parts by mass of an organic solvent per 100 parts by mass of the polyester resin (A) and the phenolic resin (B), and the organic solvent preferably contains a glycol ether-based organic solvent and a ketone-based organic solvent. Furthermore, the present paint preferably contains 40 to 90% by mass of water relative to 100% by mass of the total of water and the organic solvent. The present paint is preferably used to coat beverage cans and the like.

[0050] <Curing agent> The resin dispersion of the present disclosure can be used alone as a coating material, but may also contain various additives and curing agents other than the phenolic resin (B) as needed, as long as the effects of the present disclosure are not impaired.

[0051] Examples of the curing agent include a phenolic resin (Y) other than the phenolic resin (B), an amino resin, a component having an isocyanate group or a derivative thereof, a component having an acid anhydride group, a metal alkoxide compound, a metal chelate compound, and tris(alkoxycarbonylamino)triazine. Among these, the phenolic resin (Y) and the amino resin are preferred. The phenolic resin (Y) and the amino resin can react with the hydroxyl groups of the polyester resin in addition to undergoing a self-crosslinking reaction. The curing agent may be used alone, or two or more of the same type may be used in combination, or two or more of different types may be used in combination.

[0052] The phenolic resin (Y) may be a resin synthesized by an addition condensation reaction between a phenolic compound and an aldehyde such as formaldehyde, etc. The phenolic resin (Y) can be synthesized by a known method. Examples of the phenolic compounds include phenol, o-cresol, p-cresol, m-cresol, p-tert-butylphenol, p-phenylphenol, p-nonylphenol, 2,3-xylenol, 2,5-xylenol, 3,5-xylenol, catechol, resorcinol, and hydroquinone. Among these, phenol, o-cresol, p-cresol, m-cresol, and p-tert-butylphenol are preferred. The phenolic compounds may be used alone or in combination of two or more.

[0053] The phenolic resin (Y) may be a commercially available product. Suitable examples include Phenodur PR285, PR516, PR517, PR519, PR520, PR521, PR827, PR566, PR612, and VPR1785 manufactured by Allnex Corporation; Sumilite Resin PR-55819 manufactured by Sumitomo Bakelite Co., Ltd.; and Shounol BKM-2620, CKM-908, CKS-380A, and CKM-1634 manufactured by Aica Kogyo Co., Ltd.

[0054] Examples of the amino resin include those obtained by addition reaction of formaldehyde with an amino compound such as urea, melamine, or benzoguanamine. The amino compounds can be used alone or in combination of two or more.

[0055] Commercially available amino resins may be used. Suitable examples include Cymel 301, 303LF, 304, 323, 325, 328, 370, 659, and 1123 manufactured by Allnex; Luwipal 014, 015, 018, 066, 070, 052, and B017 manufactured by BASF; and Amidia P-138, P-196-M, TD-126, ED-126-60S, and 15-159 manufactured by DIC.

[0056] The phenol resin (Y) or amino resin may also be suitably used in which a part or all of the methylol groups formed by addition of formaldehyde are etherified with alcohols having 1 to 12 carbon atoms.

[0057] <Acid catalyst> It is preferable to incorporate a conventionally known curing catalyst into this coating material in order to promote the crosslinking reaction between the polyester resin (A) and the phenolic resin (B). Any known curing catalyst used in coating compositions can be used as the curing catalyst. Suitable examples include acid catalysts such as p-toluenesulfonic acid, dodecylbenzenesulfonic acid, dinonylnaphthalenedisulfonic acid, camphorsulfonic acid, phosphoric acid, and alkylphosphoric acid, as well as amine neutralized products of these acid catalysts. One or more curing catalysts can be used in combination. Among the above acid catalysts, dodecylbenzenesulfonic acid and its neutralized products are preferred as the curing catalyst.

[0058] The content of the curing catalyst is 0.01 to 5.0 parts by mass, preferably 0.02 to 1.0 parts by mass, more preferably 0.03 to 0.5 parts by mass, and even more preferably 0.03 to 0.3 parts by mass, based on 100 parts by mass of the combined solids of the polyester resin (A) and the phenolic resin (B). When an amine-neutralized product of the acid catalyst (e.g., an amine-neutralized product of dodecylbenzenesulfonic acid) is used as the curing catalyst, the content of the acid catalyst excluding the amine should be within the above range. If the amount of the curing catalyst is less than the above range, the curing reaction acceleration effect obtained by adding the curing catalyst cannot be fully achieved. On the other hand, if the amount of the curing catalyst is more than the above range, further effects cannot be expected, and the water resistance of the coating film may be deteriorated.

[0059] <Additives> The coating material of the present disclosure is preferably used to coat beverage cans and the like, and additives such as lubricants such as wax and leveling agents can be blended as needed to prevent scratches on the coating film during the can manufacturing process. Waxes include animal and plant waxes such as carnauba wax, lanolin wax, palm oil, candelilla wax, and rice wax; Petroleum-based waxes such as paraffin wax, microcrystalline wax, and petrolatum; Examples include synthetic waxes such as polyolefin wax and Teflon (registered trademark) wax.

[0060] <Applications of this paint> This paint is preferably used to coat storage containers such as cans for storing beverages, food, etc., and can be used on both the inside and outside of these containers. Because this paint exhibits high levels of processability and corrosion resistance when used for the above purposes, it is particularly suited to coating the inside surfaces of cans, and is particularly suited to use on the inside surfaces of beverage cans and food cans (meaning cans for storing food).

[0061] <Can materials and cans> Cans for storing beverages, food, etc. come in a variety of shapes, but are formed by combining at least two can components. They can be broadly classified into two-piece cans (in a broad sense), which consist of a cylindrical, bottomed member in which the can body and bottom are integrated, and a lid member, and three-piece cans, which consist of a cylindrical can body and lid and bottom members located above and below the can body. Two-piece cans (in a broad sense) also include so-called bottle-shaped cans, which are equipped with a recapable lid member and a bottle member. The drinking spout of the bottle member of a bottle-shaped can is provided with a screw that can be opened and closed using the lid member. The coating material of the present disclosure is suitable for coating can bodies (particularly can bodies of two-piece cans (including bottle cans)) and can lids (excluding bottle can lids).

[0062] The can body of a two-piece can is obtained, for example, by punching out a metal substrate into a flat circular plate for each can, molding the member into a predetermined cup shape with a bottom, spraying a coating composition onto the inner surface of the can, and curing the coating to form an inner coating film. After forming the inner coating film, the open end is subjected to processes such as necking, beading, and scoring. In the case of a bottomed cup-shaped member for a two-piece can, the curing conditions for the coating material are preferably baking at a temperature of 150 to 300°C for 10 seconds to 10 minutes, more preferably 30 seconds to 5 minutes. The thickness (amount of coating) of the coating film after drying on the bottomed cup-shaped member for a can is usually 5 to 150 mg / dm 2 The preferred range is 10 to 100 mg / dm 2 is more preferred.

[0063] Can lids (excluding bottle can lids) are obtained, for example, by applying paint to a metal substrate, curing the paint, forming a coating, punching out a flat circular plate for each can, and then molding the plate to form an opening. Because can lids have complex, highly irregular shapes, their coatings require higher processability than coatings for other components. On the other hand, when opening a can lid, the coating around the opening of the lid must conform to the metal substrate of the lid, ensuring good opening properties (clearness). In cases of poor opening properties, peeling residue of the coating is observed around the opening. In the case of can lids, the curing conditions for the coating are preferably baking at a temperature of 150 to 350°C for 10 seconds to 30 minutes, more preferably 10 seconds to 15 minutes. In the case of can lids, the thickness of the coating film after drying (coating amount) is usually 10 to 200 mg / dm 2 The preferred range is 20 to 180 mg / dm 2 When a rolled long can substrate is used, the curing conditions for the coating material are preferably a temperature of 200 to 350°C and baking for 10 seconds to 3 minutes, more preferably 10 seconds to 1 minute. The thickness of the coating film after drying (coating amount) is usually 10 to 200 mg / dm 2 The preferred range is 20 to 180 mg / dm 2 is more preferred.

[0064] Examples of metal substrates for cans include aluminum, tin-plated steel sheets, chromium-treated steel sheets, and nickel-treated steel sheets, which may further be subjected to surface treatments such as zirconium treatment and phosphate treatment.

[0065] Cans having the can lid or can body of the present disclosure as constituent members are preferably used to store beverages such as drinking water, soft drinks, coffee, tea, beer, chuhai (shochu with carbonated water added), sake, whiskey, and water-based cocktails, as well as foods such as fish, meat, vegetables, fruit, oil, and sauces.

[0066] One embodiment of the beverage can of the present disclosure includes a can lid and a can body member coated with the paint of the present disclosure, and another embodiment of the beverage can of the present disclosure includes a can body member coated with the paint of the present disclosure. [Example]

[0067] The present disclosure will be described in more detail below with reference to examples. In the examples, unless otherwise specified, "parts" means "parts by mass" and "%" means "% by mass." Furthermore, "Mn" means number average molecular weight, and "Mw" means weight average molecular weight.

[0068] (number average molecular weight, weight average molecular weight) The number average molecular weight (Mn) and weight average molecular weight (Mw) were measured using a Tosoh 8020 series high-speed GPC system (tetrahydrofuran solvent, column temperature 40°C, polystyrene standard). Specifically, four columns (Tosoh G1000HXL, G2000HXL, G3000HXL, and G4000HXL) were connected in series, and measurements were performed at a flow rate of 1.0 mL / min.

[0069] (acid number) 0.2 g of polyester resin was precisely weighed and placed in a stoppered Erlenmeyer flask, and 20 mL of THF (tetrahydrofuran) was added to dissolve it. Phenolphthalein test solution was added as an indicator and the solution was left to stand for 30 seconds. The solution was then titrated with 0.1 mol / L alcoholic potassium hydroxide solution until it turned a pale pink color. The acid value was calculated using the following formula. The acid value was the value for the polyester resin in its dry state. Acid value (mgKOH / g)=(a×F×56.1×0.1) / S S: Amount of polyester resin collected × (solid content of acrylic copolymer solution / 100) (g) a: Titration volume (mL) of 0.1 mol / L alcoholic potassium hydroxide solution F: Potency of 0.1 mol / L alcoholic potassium hydroxide solution

[0070] (Polyester Resin Composition) 1 H-NMR analysis (BRUKER ULTRA SHIELD TM 400 PLUS). 1Resins containing constituent monomers for which no assignable or quantifiable peaks were observed in the H-NMR spectrum were subjected to methanol decomposition in a sealed tube at 230°C for 3 hours, followed by gas chromatographic analysis for quantitative analysis.

[0071] (Composition of phenolic resin) 13 The values ​​were determined by C-NMR analysis (JNM-ECX400 manufactured by JEOL Ltd.). The phenolic resin was applied to a glass plate as a thin film, vacuum dried at 40°C for 12 hours, then dissolved in deuterated chloroform and measured with a pulse interval of 25 seconds and an accumulation count of 7,000. For the analysis, the center of the triple line of deuterated chloroform was set to 77.0 ppm. The integral value from 150 to 160 ppm was set to 1, which is considered to be a structural unit derived from the phenolic compound, and the integral value was calculated as follows: Butoxymethyl group: 29.5 to 32.5 ppm Methylol group: 61.5 to 64.5 ppm Methylene bonds: 34.0 to 38.0 ppm Dimethylene ether bond: 65.0 to 67.0 ppm (since there are two carbon atoms, the number of bonds is divided by 2)

[0072] <Production example of polyester resin>

[0073] [Manufacturing example A-1] In a reaction vessel, 93.1 parts of terephthalic acid (19.8 mol% of 100 mol% polycarboxylic acid components), 372.5 parts of isophthalic acid (79.2 mol% of 100 mol% polycarboxylic acid components), 189.3 parts of 2-methyl-1,3-propanediol (67.6 mol% of 100 mol% polyhydric alcohol components), 141.9 parts of 1,4-cyclohexanedimethanol (31.5 mol% of 100 mol% polyhydric alcohol components), 3.76 parts of trimethylolpropane (0.9 mol% of 100 mol% polyhydric alcohol components), titanium butoxide 0.05 parts were charged into a polymerization reactor, and the temperature was gradually increased to 250 ° C. under a nitrogen atmosphere, and an esterification reaction was carried out over 6 hours. Next, after cooling to 230 ° C. under a nitrogen stream, the pressure was reduced to 5 mmHg or less over 30 minutes, and the polymerization reaction was carried out for 2 hours in that state. The resin was then cooled to 200°C under a nitrogen stream, and 5.35 parts of trimellitic anhydride (1.0 mol% of 100 mol% of the polycarboxylic acid component) was added and reacted for 2 hours to obtain polyester resin A-1. The analytical results of the obtained polyester resin A-1 are shown in Table 1.

[0074] [Manufacturing example A-3] ~ [Manufacturing example A-31], [Manufacturing example A-101], [Manufacturing example A-102] Polyester resins A-3 to A-31 and A-101 to A-102 were obtained in the same manner as in Production Example A-1, except that the types and amounts of the polycarboxylic acid component and polyhydric alcohol component were changed, and analyzed in the same manner. Note that in the examples and comparative examples in which trimellitic acid (TMA) was not added, the step corresponding to "cooling the resin to 200°C under a nitrogen stream, adding 5.35 parts of trimellitic anhydride (1.0 mol % of 100 mol % of the polycarboxylic acid component), and allowing to react for 2 hours" described in Production Example A-1 was not performed.

[0075] [Table 1]

[0076] The abbreviations in Table 1 are as follows: TPA: Terephthalic acid IPA: Isophthalic acid SEA: Sebacic acid TMA: Trimellitic acid EG: Ethylene glycol PG: 1,2-propanediol MPO: 2-methyl-1,3-propanediol CHDM: 1,4-cyclohexanedimethanol 1,4-BD: 1,4-butanediol TMP: Trimethylolpropane

[0077] <Phenol resin manufacturing example>

[0078] [Manufacturing example B-1] A four-neck flask was charged with 75.6 g (0.7 mol) of m-cresol, 32.4 g (0.3 mol) of p-cresol, 324.3 g of 37% formalin (4.0 mol as formaldehyde), and 16.0 g of 25% sodium hydroxide (0.1 mol as sodium hydroxide). The mixture was reacted at 40°C for 8 hours, followed by 3 hours at 70°C. After the reaction was complete, 18.2 g of 20% aqueous hydrochloric acid was slowly added while cooling to neutralize the mixture. The separated and precipitated resin was washed four times with water. The water was then removed by vacuum dehydration. This water washing and vacuum dehydration process was repeated three times for purification, and the resulting resin was then dehydrated under reduced pressure until its moisture content was less than 1%. After the dehydration treatment, 400 parts of n-butanol was added to 100 parts of the resin, and the internal temperature was raised until reflux began at normal pressure. The alkoxylation reaction was carried out at 115-123°C for 10 hours. To complete the reaction, the water generated during the reaction was constantly removed. After this, excess unreacted n-butanol was removed under reduced pressure, and the solids concentration was adjusted to 50% by mass, yielding phenolic resin solution B-1. Table 2 shows the analytical results of the resulting phenolic resin.

[0079] [Manufacturing example B-2] 100 parts of butyl cellosolve was added to 100 parts of phenol resin solution 1, and the mixture was heated at 115 to 123°C. After removing the n-butanol, butyl cellosolve was added so that the solid concentration became 50%, thereby obtaining phenol resin solution B-2.

[0080] [Manufacturing examples B-3~B-8] [Manufacturing examples B-1001~B-1007] Phenol resin solutions B-3 to B-8 and B-1001 to B-1007 were obtained in the same manner as in Production Example 1, except that the types and quantitative ratios of the monomer components were changed as shown in Table 2, and the amounts of 37% formalin and n-butanol, as well as the reaction temperature and reaction time, were changed appropriately.

[0081] [Table 2]

[0082] [Example 1] 149 parts of polyester resin A-1 and 82 parts of diethylene glycol monobutyl ether were placed in a reaction vessel and heated. Once the temperature reached 120°C, stirring was initiated. After 3 hours, it was confirmed that the resin had dissolved, and the mixture was cooled to 80°C while stirring. Subsequently, 52.5 parts of phenolic resin solution B-1 and 1.18 parts of dimethylaminoethanol were added, and 215.3 parts of ion-exchanged water were added dropwise over 30 minutes while maintaining the temperature at 80°C. Resin dispersion 1 was obtained, and its stability was evaluated and its average particle size was measured.

[0083] The abbreviations in Tables 3 to 7 are as follows: S1: Diethylene glycol monobutyl ether S2: Butyl cellosolve S3: Cyclohexanone S4: Methyl ethyl ketone S5: Isopropanol

[0084] <Dispersion stability> Resin Dispersion 1 placed in a container with a lid was placed in a thermostatic chamber at 25°C, and the state was checked every week and evaluated according to the following evaluation criteria. 5: No separation even after 6 months or more (very good) 4: Separation between 3 and 6 months (good) 3: Separation within 1 month to 3 months (practical) 2: Separation takes between one week and one month (practical depending on conditions) 1: Separation in less than a week (not practical) If the coating separated within one week, it was not evaluated as a coating material, as described below.

[0085] <Average particle size> The average particle size here refers to the particle size (D50) at which the cumulative frequency is 50% in volume terms. The average particle size is the D50 value measured using a dynamic light scattering distribution measurement device (Microtrac MT3300EXII manufactured by Nikkiso Co., Ltd.). Water was poured into the device, and resin dispersion 1 was added so that the TR was 0.95 to 0.8, and measurements were performed. The measurement conditions were particle conditions: transmittance: transparent, refractive index: 1.52, shape: aspherical, and solvent conditions: refractive index: 1.333. The measurement time was 20 seconds, and the number of measurements was 2. Note that if sedimentation occurred immediately after dispersion preparation, it was marked as "unmeasurable."

[0086] [Examples 2 to 67] [Comparative Examples 1001 to 1016] According to the formulations shown in Tables 3 to 7, resin dispersions 2 to 67 and 1001 to 1016 were obtained in accordance with Example 1 and evaluated in the same manner. For convenience, Example 1 is shown as Example 45 in Table 5 and Example 56 in Table 6, and Example 32 is shown as Example 39 in Table 5.

[0087] [Example 68] To 100 parts of Resin Dispersion 1014, 12.35 parts of Phenol Resin Solution B-1 was added with stirring to obtain Resin Dispersion 68. The stability of Resin Dispersion 68 was evaluated, and the average particle size was measured. The stability was 4, and the average particle size was 0.25 μm.

[0088] [Table 3]

[0089] [Table 4]

[0090] [Table 5]

[0091] [Table 6]

[0092] [Table 7]

[0093] The abbreviations in Tables 3 to 7 are as follows: DMAE: Dimethylaminoethanol TEA: Triethanolamine

[0094] In Comparative Examples 1001 to 1003, which contained polyester resin (A) but no phenolic resin (B), the stability of the dispersion was not practical, whereas the resin dispersions of Examples 1 to 67 according to the present disclosure were confirmed to exhibit excellent stability.

[0095] On the other hand, in Comparative Examples 1006 to 1011, which did not use the phenolic resin (B) specified in the present disclosure, it was confirmed that the stability of the resin dispersion was not practically acceptable. Furthermore, when the amount of organic solvent exceeds 130 parts by mass relative to 100 parts by mass of the total of polyester resin (A) and phenolic resin (B), it was confirmed that the stability of the resin dispersion was poor, as shown in Comparative Example 1005. Furthermore, when the amount of the organic solvent is less than 30 parts by mass, it was confirmed that the stability of the resin dispersion was poor, as shown in Comparative Example 1004.

[0096] Furthermore, considering that resin dispersion 68 (Example 68), which was prepared by preparing resin dispersion 1014 that did not contain phenolic resin (B) and then adding phenolic resin (B), had improved stability and a smaller average particle diameter than resin dispersion 1014, it is believed that adding phenolic resin (B) after preparing a polyester resin dispersion also has the effect of improving the stability of the dispersion.

[0097] <Lid paint> [Example 101] As shown in Table 8, 1,000 parts by mass of resin dispersion 1 (containing 298 parts by mass of polyester resin and 52.5 parts by mass of phenolic resin) obtained in Example 1 was placed in a container, and while stirring, 1.00 part by mass of Surfynol 420 (an acetylene glycol-based nonionic surfactant, manufactured by Nissin Chemical Industry Co., Ltd.) as an additive and 2.10 parts by mass of Nacure 5925 (a dodecylbenzenesulfonic acid-based acid catalyst, 25% active ingredient, isopropanol solution) as a catalyst were added to obtain paint 101. Various evaluations were performed using the methods described below.

[0098] [Examples 102 to 162] According to the formulations shown in Tables 8 to 12, paints 102 to 162 were obtained and evaluated in the same manner as in Example 101. For convenience, Example 101 is described as Examples 139 and 145 in Table 10.

[0099] [Comparative Example 2001-2005] As shown in Table 10, Resin Dispersions 1012 to 1016 were used instead of Resin Dispersion 1, and paints 2001 to 2005 were obtained in the same manner as in Example 101, and evaluated in the same manner.

[0100] [Comparative Example 2006] A container was charged with 193.4 parts of polyester resin A-1, 145 parts of Flexisolv DBE esters (Invista) as an organic solvent, and 145 parts of xylene, and heated. Once the temperature reached 120°C, the mixture was stirred. After two hours, the resin was confirmed to be dissolved, and the mixture was cooled to room temperature. Then, while stirring, 68.2 parts of phenolic resin solution 1, 153.4 parts of Flexisolv DBE esters (Invista), 191.1 parts of xylene, 52 parts of butyl cellosolve, and 76.8 parts of cyclohexanone were added and mixed. 1.6 parts of Nacure 5925 were added as a catalyst to obtain water-free paint 2006.

[0101] <Evaluation of paint properties> The resulting paint was used to evaluate the following physical properties. [Paint stability] As in the evaluation of the stability of the resin dispersion, each of the resulting paints was placed in a thermostatic chamber at 30°C, and the condition was checked every week and evaluated according to the following criteria. 5: No separation even after 6 months or more (very good) 4: Separation between 3 and 6 months (good) 3: Separation within 1 month to 3 months (practical) 2: Separation takes between one week and one month (practical depending on conditions) 1: Separation in less than a week (not practical)

[0102] <Average particle size> The average particle size was measured in the same manner as in the measurement of the average particle size of the resin dispersion.

[0103] [Preparation of lid test panel] Each paint was applied to an aluminum plate with a thickness of 0.26 mm, with a dry mass of 110 mg / dm 2 The panels were then dried and cured by passing them through a double conveyor oven in 24 seconds, with the first zone having a temperature of 286°C and the second zone having a temperature of 326°C, to prepare test panels for lids with a coating. The resulting test panels for lids were evaluated as follows.

[0104] <Adhesion strength evaluation> The test panel was cut into a length of 100 mm and a width of 5 mm to serve as a test plate for measuring adhesion. A 25 mm section was removed from the tip of the long piece of the test plate for measuring adhesion, and two test plates were stacked with the coated surfaces facing inward. Nylon tape was sandwiched between the test plates, and the nylon tape was used as a hot-melt adhesive to perform heat fusion at 200°C for 30 seconds. After spreading out the unbonded portion, the T-peel strength between the cured coating and the aluminum plate was measured using a tensile tester (Tensilon) at a pulling rate of 200 mm / min, and rated according to the following criteria. 5: T-peel strength is 3kgf or more (very good) 4: T-peel strength is less than 3 kgf, 2 kgf or more (good) 3: T-peel strength is less than 2kgf, 1kgf or more (practical) 2: T-peel strength is less than 1 kgf, 0.4 kgf or more (practical depending on conditions) 1: Less than 0.4 kgf (not practical)

[0105] <Bending workability test> <<Initial>> The test panel was cut into a size of 30 mm wide x 50 mm long to prepare test plates for evaluating bending processability. Next, at room temperature (25°C), a 3 mm diameter round bar was attached to the test plate at a position 30 mm long with the coating facing outward. The test plate was then folded in half along the round bar to prepare a test specimen. Two 0.26 mm thick aluminum plates were sandwiched between the folded test specimens, and a 1 kg rectangular weight measuring 15 cm wide x 5 cm high x 5 cm deep was dropped from a height of 40 cm onto the bent portion of the test specimen to completely fold it. The aluminum plate was then removed, and the folded portion of the test piece was immersed in 1% saline solution. A current of 6.0 V was then applied for 6 seconds between the metal part of the flat portion of the test piece that was not immersed in the saline solution and the saline solution, and the current value was measured. If the coating film has poor workability, the coating film at the bent portion will crack, exposing the underlying metal plate and increasing the conductivity, resulting in a high current value. Evaluation was made according to the following evaluation criteria. 5: Less than 5mA (very good) 4: 5mA or more and less than 10mA (good) 3: 10mA or more but less than 20mA (practical) 2: 20mA or more but less than 50mA (practical depending on conditions) 1: 50mA or more (not practical)

[0106] <<After time has passed>> A new test plate for evaluating bending processability was prepared, and left to stand in a thermostatic chamber at 37°C for 60 days, then returned to room temperature (25°C), and bent at room temperature in the same manner as in the bending processability test described above, and the current value was measured. Next, the current value after standing in the thermostatic chamber at 37°C for 60 days was subtracted from the initial current value to determine the current value, and the value was evaluated according to the following criteria. 5: Less than 1mA (very good) 4: 1mA or more and less than 5mA (good) 3: 5mA or more but less than 10mA (practical) 2: 10mA or more but less than 15mA (practical depending on conditions) 1: 15mA or more (not practical)

[0107] <Opening test> <<Before retort processing>> The test panel was cut into a size of 50 mm x 50 mm, and a press was used to create an irregularity on the painted surface of the test panel in the shape of a typical stay-on tab opening on a beverage can to prepare an evaluation sample. Next, an aluminum plate was peeled off from the unpainted side of the test panel along the shape of the opening, and the resulting opening was magnified under a microscope and visually evaluated. Poor openability means that the coating film tends to remain around the opening, resulting in a large protrusion into the opening. Good openability means that the coating film does not protrude into the opening at all, or if it does protrude, the protrusion is very small. Specifically, the width of the protruding coating film was measured and evaluated according to the following criteria. 5: The maximum width of the protruding coating is less than 100 μm (very good). 4: The maximum width of the protruding coating is 100 μm or more and less than 200 μm (good). 3: The maximum width of the protruding coating is 200 μm or more and less than 500 μm (practical). 2: The maximum width of the protruding coating is 500 μm or more and less than 800 μm (practical depending on the conditions). 1: The maximum width of the protruding coating is 800 μm or more (not practical).

[0108] <<After retort processing>> A newly prepared evaluation sample was immersed in water and retorted in a retort oven at 125°C for 30 minutes, and then tested and evaluated in the same manner as in the above-mentioned openability test.

[0109] <Retort resistance test> The test panels were immersed in water, an aqueous solution containing 2% by mass of citric acid at a pH of approximately 2, and an aqueous solution adjusted to pH 12 using sodium hydroxide, and then retorted in a retort oven at 125°C for 30 minutes.The appearance of the coating was then visually evaluated according to the following criteria. 5: No change at all (very good). 4: There is some change, but there is almost no whitening (good). 3: Very slight whitening (usable). 2: Light whitening (practical depending on conditions). 1: Significant whitening (not practical).

[0110] <Acetic acid resistance> A test panel measuring 60 x 40 mm was prepared. It was immersed in a 4% acetic acid solution and sealed. After 10 days at 50°C, the state of the coating was observed. Evaluation was made according to the following criteria. 5: No change at all (very good). 4: Some blistering (good). 3: Small blisters are visible all over the surface (usable). 2: Large blister present (may be usable depending on conditions). 1: The entire coating has peeled off (not suitable for practical use).

[0111] <Overall rating> The average value of each evaluation result was calculated by rounding up or down, and the result was evaluated on a five-point scale: 5 (best), 4 (excellent), 3 (good), 2 (acceptable), and 1 (unacceptable). However, if there was even one evaluation of 1 (unsuitable for practical use) in each evaluation, it was marked as 1 (unacceptable).

[0112] [Table 8]

[0113] [Table 9]

[0114] [Table 10]

[0115] [Table 11]

[0116] [Table 12]

[0117] The abbreviations in Tables 8 to 12 are as follows: Surfynol 420: Acetylene glycol-based nonionic surfactant, manufactured by Nissin Chemical Industry Co., Ltd. Nacure 5925: Dodecylbenzenesulfonic acid catalyst, 25% active ingredient, isopropyl alcohol solution

[0118] As shown in Tables 8 to 12, Examples 101 to 163, which used resin dispersions according to the present disclosure, exhibited good performance. In particular, they exhibited significant effects in terms of opening properties compared to the comparative examples. The polyester resin (A) in the present disclosure is not uniformly dissolved in the coating material, but is dispersed as particles. The polyester resin (A) particles fuse together during drying when forming a coating film, and then react with the curing agent to form a cured coating film. It is presumed that the remnants of the interface between the original polyester resin (A) and phenolic resin (B) particles allowed the formation of a cured coating film with excellent opening properties. The use of low-polarity resins is thought to be advantageous for performance involving water. However, low-polarity resins have poor adhesion to substrates such as metals, and when the coating film is subjected to stress such as bending, slight gaps tend to form between the substrate and the resin. By using phenolic resin (B), which functions as both a curing agent and a dispersant, it is possible to use low-polarity polyester resins, which are normally not usable as aqueous dispersions, as aqueous dispersions, while achieving high water resistance, adhesion, and bendability. Furthermore, it is thought that phenolic resin (B) surrounds polyester resin (A), with the functional groups derived from phenolic resin (B) facing outward from the particles. As a result, it is thought that adhesion to substrates and bendability have been improved.

[0119] <Evaluation of paints on the inside of can bodies> [Example 201] 1000 parts by mass of the resin dispersion 60 obtained in Example 60 was placed in a container, and 750 parts by mass of water, 1.0 part by mass of Surfynol 420, and 2.1 parts by mass of Nacure 5925 were added while stirring to obtain paint 201, which was then subjected to various evaluations using the methods described below.

[0120] <Evaluation of paint properties> [Paint stability] The same tests were carried out as for the lid coating, and the evaluation was carried out according to the same criteria.

[0121] [Preparation of test panels for can body inner surface] The obtained paint 201 was applied to an aluminum plate having a thickness of 0.26 mm so that the dry mass of the coating film was 45 mg / dm 2 The coating was applied using a bar coater so that the coating was as follows: and the coating was baked in a gas oven at an atmospheric temperature of 200°C for 2 minutes to prepare a test panel for the inner surface of a can body. The obtained test panels for can body inner surfaces were evaluated in the same manner as the test panels for lids, including adhesive strength, bending processability (initial, 37°C, after 60 days of standing), and retort resistance (water, acidic citric acid (pH 2), alkaline NaOH (pH 12)). Furthermore, the acetic acid resistance before and after denting was evaluated as described below. The results are shown in Table 13.

[0122] <Acetic acid resistance> <<Before dent processing (untreated)>> As in the case of the lid test panel, the can body inner surface test panel was immersed in a 4% acetic acid solution and sealed. After 10 days at 50°C, the state of the coating film was observed and evaluated according to the following evaluation criteria. <<After dent processing>> A test panel for the inner surface of a can body was cut to 5 cm x 5 cm and processed in a DuPont testing machine under conditions of 1 / 4 inch, a load of 300 g, and a height of 25 cm so that the painted surface was convex. The panel was then immersed in a 4% acetic acid solution and sealed. After 10 days at 37°C, the condition of the coating film in the processed area was observed. Evaluation was based on the following criteria. 5: No change at all (very good). 4: Some blistering (good). 3: Small blisters are visible all over the surface (usable). 2: Large blister present (may be usable depending on conditions). 1: The entire coating has peeled off (not practical).

[0123] [Examples 202 to 208] [Comparative Examples 3001 to 3003] As shown in Table 13, paints 202 to 208 and 3001 to 3003 were obtained in the same manner as in Example 201, except that the type of resin dispersion was changed, and were similarly evaluated.

[0124] [Comparative Example 3003] As shown in Table 13, evaluation was carried out in the same manner as in Example 201, except that paint 2005, which does not contain water, was used instead of paint 201.

[0125] [Table 13]

[0126] As shown in Table 13, Examples 201 to 208, which used the resin dispersion according to the present disclosure, showed good performance. [Industrial Applicability]

[0127] This paint is suitable for use in coating containers such as cans for storing beverages, food, etc. It is particularly suitable for coating the inner surface of the can body and the can lid. It is also suitable for coating the outer surface. It can also be used in containers for purposes other than food, such as engine oil. It can also be used to coat materials other than metals, such as plastics.

[0128] This application claims priority based on Japanese Patent Application No. 2024-098044, filed June 18, 2024, the disclosure of which is incorporated herein in its entirety.

Claims

1. The composition comprises a polyester resin (A), a phenolic resin (B), a neutralizing agent, an organic solvent selected from a ketone-based solvent, a glycol ether-based solvent, an alcohol-based solvent, a glycol solvent, and an acetate-based solvent, and water; The polyester resin (A) has an acid value of 16 mg KOH / g or less and a number average molecular weight of 8,000 or more, the phenolic resin (B) has a weight average molecular weight of 500 to 2,700, contains 50 mol % or more of structural units derived from meta-cresol out of a total of 100 mol % of structural units derived from phenolic compounds, and contains, per aromatic ring in the phenolic resin (B), 0.01 to 0.2 methylol groups, 0.8 to 1.3 butoxymethyl groups, and a total of 0.15 to 0.5 methylene bonds and dimethylene ether bonds; The organic solvent is contained in an amount of 30 to 130 parts by mass per 100 parts by mass of the total of the polyester resin (A) and the phenolic resin (B), The resin dispersion contains 40 to 90% by mass of the water, with the total of the water and the organic solvent being 100% by mass.

2. 2. The resin dispersion according to claim 1, wherein the mass ratio of the polyester resin (A) to the phenolic resin (B) is polyester resin (A) / phenolic resin (B)=95 / 5 to 70 / 30.

3. 2. The resin dispersion according to claim 1, wherein the phenolic resin (B) contains structural units derived from para-cresol in a proportion of 50 mol % or less based on a total of 100 mol % of structural units derived from phenolic compounds.

4. The polyester resin (A) has structural units derived from one or more polycarboxylic acid components selected from the group consisting of terephthalic acid, isophthalic acid, sebacic acid, and (anhydrous) trimellitic acid, as well as structural units derived from one or more polyhydric alcohol components selected from the group consisting of 1,2-propanediol, 1,4-cyclohexanedimethanol, 2-methyl-1,3-propanediol, ethylene glycol, 1,4-butanediol, and trimethylolpropane. The polyester resin (A) contains, out of 100 mol% of the structural units derived from the polyhydric alcohol components, 20 to 99.9 mol% of structural units derived from one or more polyhydric alcohol components selected from the group consisting of 1,2-propanediol, 1,4-cyclohexanedimethanol, and 2-methyl-1,3-propanediol, and 0.1 to 80 mol% of structural units derived from one or more polyhydric alcohol components selected from the group consisting of ethylene glycol, 1,4-butanediol, and trimethylolpropane. The resin dispersion according to claim 1,

5. A paint comprising the resin dispersion according to any one of claims 1 to 4.

6. A can lid comprising a metal substrate coated with the coating material according to claim 5.

7. A can body having a metal substrate coated with the paint according to claim 5.

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