JP2016113561A - Aqueous coating composition for coating can - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an aqueous coating composition for coating a can having no resin manufactured by using bisphenol A or a raw material containing bisphenol A and excellent in manufacturing stability and storage stability of coating and retort whitening property and corrosion resistance of coating and a coated can by coating the coating composition.SOLUTION: There is provided an aqueous coating composition for coating a can containing a core-shell type acryl resin particle consisting of a shell part manufactured by emulsion polymerization of a polymerizable unsaturated monomer using a nonionic surfactant and a crosslinked core part and a resol type phenol resin (C1) and/or an amino resin (C2).SELECTED DRAWING: None

Description

  The present invention relates to an aqueous coating composition for can coating that can form a coating film having excellent storage stability and excellent water resistance, corrosion resistance, and processability.

  Conventionally, organic solvent-type paints containing bisphenol A type epoxy resins and phenolic resin curing agents have been generally used as paints for the inner surface of cans. However, there is a problem of global environmental pollution caused by organic solvents discharged from these paints. Yes, organic solvent-type paints are being replaced by water-based paints.

  As the water-based paint, for example, a core-shell fine particle-dispersed paint in which core-shell fine particles are uniformly dispersed in the paint is disclosed (Patent Document 1). Patent Document 1 discloses, as a specific example of the coating material, a core-shell type fine particle obtained by an emulsion polymerization method using sodium dodecylbiphenyl ether sulfonate as an emulsifier, and an aqueous solution of a carboxyl group-containing self-emulsifying bisphenol A type epoxy resin. Can coating compositions comprising a dispersion are mentioned. The paragraph [0041] of the specification of Patent Document 1 states that “the content of the core-shell fine particles used in the core-shell fine particle-dispersed coating material of the present invention is 0.5 to 25% by weight in terms of solid content. In the same document, the core-shell fine particle emulsion is added to the aqueous dispersion of the carboxyl group-containing self-emulsifying bisphenol A type epoxy resin so that the solids weight ratio is 10% at maximum. A distributed embodiment is disclosed. Therefore, the can coating composition in the invention of Patent Document 1 substantially contains an aqueous dispersion of a carboxyl group-containing self-emulsifying bisphenol A type epoxy resin as a main component.

  In conventional can coating compositions including the above compositions, epoxy resins manufactured using raw materials containing bisphenol A are generally used to obtain good coating workability and coating film performance. ing. However, from the viewpoint of the influence on the global environment in recent years, a water-based coating for can inner surfaces which does not contain a resin manufactured using a raw material containing bisphenol A is desired. Therefore, in order to reduce the amount of resin produced using a raw material containing bisphenol A, if the content of the core shell fine particles in the can coating composition described in Patent Document 1 is more than 25% by mass. The mechanical properties of the coating film thus obtained were lowered, the workability and adhesion improving effects were lowered, and the flavor property and retort resistance of the coating film were sometimes deteriorated.

  As a coating composition using a resin that does not use bisphenol A as a raw material, for example, a composite obtained by emulsion polymerization of an ethylenically unsaturated monomer using a carboxyl group-containing acrylic copolymer neutralized with a basic compound An aqueous coating composition for coating the inner surface of a can containing a resin emulsion is disclosed (Patent Document 2). However, when the water-based paint contains an organic solvent as a film-forming aid, aggregates resulting from the resin emulsion are likely to be produced during production, production stability is poor, and retort resistance of the obtained coating film is poor. There was a thing.

  Also, an aqueous coating composition using a resin emulsion obtained by coexisting an oxirane functional-containing monomer when an ethylenic monomer is emulsion-polymerized using a carboxyl group-containing acrylic copolymer neutralized with a basic compound Is disclosed (Patent Document 3). However, this paint has a problem that the reaction presumed to be caused by unreacted oxirane groups proceeds during storage and tends to thicken during storage.

  Furthermore, for the inner surface of a can comprising an acrylic-modified polyester resin obtained by graft polymerization of a polymerizable unsaturated monomer containing a carboxyl group-containing polymerizable unsaturated monomer to a polyester having a radical reactive unsaturated group, and a resol type phenolic resin crosslink An aqueous coating composition is disclosed (Patent Document 4). However, the film obtained from the above composition may be inferior in retort whitening resistance.

JP-A-9-67543 JP 2005-179491 A WO2006 / 045017 JP 2002-302039 A

  An object of the present invention is an aqueous coating composition for can coating which does not contain a resin produced using bisphenol A or a raw material containing bisphenol A, and is a production stability and storage stability of a paint, and a coating film resistance. An object of the present invention is to provide an aqueous coating composition for can coating excellent in retort whitening and corrosion resistance, and a coated can formed by coating the coating composition.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have found that the core-shell type acrylic resin particles (A) comprising the shell part and the cross-linked core part, the resol-type phenol resin (C1) and / or amino An aqueous coating composition for can coating comprising a resin (C2), wherein the core-shell type acrylic resin particles (A) are produced by emulsion polymerization of a polymerizable unsaturated monomer using a nonionic surfactant, And the glass transition temperature of the acrylic resin which comprises the said shell part is in the range of 35-105 degreeC, The glass transition temperature of the acrylic resin which comprises the said core part is in the range of -10-25 degreeC, and The total mass of the resol type phenolic resin (C1) and the amino resin (C2) is 0.1 to 10 based on the solid content mass of the core-shell type acrylic resin particles (A). The solid content mass of the core-shell type acrylic resin particles (A) is in the range of 60 to 99.9 mass%, based on the solid content mass of the aqueous coating composition for can coating. The water-based paint composition for can coating characterized by the above has been found to be excellent in production stability and storage stability of the paint, and retort whitening resistance and corrosion resistance of the coating film, thereby completing the present invention.

The present invention provides the following aqueous coating composition for can coating and a coated article obtained by coating the aqueous coating composition for can coating on an object to be coated.
Item 1. Manufactured using raw materials containing bisphenol A or bisphenol A, including core-shell type acrylic resin particles (A) comprising a shell part and a cross-linked core part, and resol type phenol resin (C1) and / or amino resin (C2). An aqueous coating composition for can coating that does not contain a resin, wherein the core-shell type acrylic resin particles (A) are produced by emulsion polymerization of a polymerizable unsaturated monomer using a nonionic surfactant, and The glass transition temperature of the acrylic resin constituting the shell portion is in the range of 35 to 105 ° C., and the glass transition temperature of the acrylic resin constituting the core portion is in the range of −10 to 25 ° C., and the core shell Of resol-type phenolic resin (C1) and amino resin (C2) based on the solid content mass of the acrylic resin particles (A) The solid content mass of the core-shell type acrylic resin particles (A) is 50 to 99.9, based on the solid content mass of the water-based coating composition for can coating, and having a mass in the range of 0.1 to 10 mass%. An aqueous coating composition for can coating, characterized by being in the range of mass%.
Item 2. Item 2. The aqueous coating composition for can coating according to item 1, wherein the mass of the core part in the core-shell type acrylic resin particles (A) is in the range of 10 to 90% by mass based on the total mass of the core part and the shell part.
Item 3. Item 3. The aqueous coating composition for can coating according to Item 1 or 2, wherein the nonionic surfactant has an HLB value in the range of 6 to 20.
Item 4. The nonionic surfactant is at least one selected from the group consisting of polyglycerin fatty acid esters, sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters, sucrose fatty acid esters, and polyoxyethylene fatty acid esters. Item 4. The aqueous coating composition for can coating according to any one of Items 1 to 3.
Item 5. Item 5. The water for can coating according to any one of Items 1 to 4, wherein the nonionic surfactant has a linear or branched, saturated or unsaturated fatty acid ester group having 10 or more carbon atoms. Paint composition.
Item 6. The core-shell type acrylic resin particles (A) are produced by emulsion polymerization of a polymerizable unsaturated monomer using a nonionic surfactant and an anionic surfactant, the nonionic surfactant and an anion Item 6. The aqueous coating composition for can coating according to any one of Items 1 to 5, wherein the mass ratio to the surfactant is in the range of 15/85 to 99/1.
Item 7. The core-shell type acrylic resin particles (A) are produced by emulsion polymerization of a polymerizable unsaturated monomer using a nonionic surfactant and an anionic surfactant, and the core-shell type acrylic resin particles (A) Item 7. The aqueous coating composition for can coating according to Item 6, wherein the mass of the anionic surfactant is within a range of 1.0% by mass or less, based on the solid content mass.
Item 8. The crosslinked core portion in the core-shell type acrylic resin particles (A) reacts with a polymerizable unsaturated monomer having two or more polymerizable unsaturated groups in one molecule and / or complementarily to form a covalent bond. Any one of Items 1 to 7 formed by emulsion polymerization using a polymerizable unsaturated monomer mixture containing a polymerizable unsaturated monomer each having a functional group other than an unsaturated group The aqueous coating composition for can coating according to the description.
Item 9. Any one of Items 1 to 8, wherein the core-shell type acrylic resin particles (A) are obtained by chemically bonding a part of the acrylic resin constituting the core part of the particle and a part of the acrylic resin constituting the shell part. The aqueous coating composition for can coating according to claim 1.
Item 10. Item 10. The aqueous coating composition for can coating according to any one of Items 1 to 9, wherein the core-shell type acrylic resin particles (A) have a crosslinking reactive functional group.
Item 11. Item 11. The aqueous coating composition for can coating according to any one of Items 1 to 10, wherein the aqueous coating composition for can coating is an aqueous coating composition for can inner surface coating.
Item 12. Item 11. The aqueous coating composition for can coating according to any one of Items 1 to 10, wherein the aqueous coating composition for can coating is an aqueous coating composition for outer surface coating of a can.
Item 13. A coated can which is coated with the aqueous coating composition for can coating according to any one of Items 1 to 12.
Item 14. A coated can in which the inner surface of the lid of the can is coated with the aqueous coating composition for can coating according to any one of Items 1 to 11.
Item 15. Item 13. A coated can in which the outer surface of the lid of the can is coated with the aqueous coating composition for can coating according to any one of items 1 to 10.

  The aqueous coating composition for can coating of the present invention is excellent in the production stability and storage stability of the paint, and the retort whitening resistance and corrosion resistance of the coating film.

  The aqueous coating composition for can coating of the present invention (hereinafter sometimes referred to as “coating composition”) comprises core-shell type acrylic resin particles (A) comprising a shell part and a cross-linked core part, and a resol-type phenolic resin ( An aqueous coating composition for can coating comprising C1) and / or amino resin (C2), wherein core-shell acrylic resin particles (A) are produced by emulsion polymerization of a polymerizable unsaturated monomer using a nonionic surfactant And the glass transition temperature of the acrylic resin constituting the shell portion (may be referred to as “shell Tg” in this specification) is in the range of 35 to 105 ° C., and the core portion is The glass transition temperature (may be referred to as “core Tg” in the present specification) of the constituting acrylic resin is in the range of −10 to 25 ° C., and the core-shell acrylic resin The total mass of the resol type phenolic resin (C1) and the amino resin (C2) is in the range of 0.1 to 10% by mass based on the solid content mass of the child (A), and the water-based coating composition for can coating Based on the solid content mass of the product, the solid content mass of the core-shell type acrylic resin particles (A) is in the range of 50 to 99.9% by mass.

Core-shell type acrylic resin particles (A)
The core-shell type acrylic resin particles (A) comprising a shell part and a crosslinked core part can be obtained by conventionally known multistage emulsion polymerization using a polymerizable unsaturated monomer. For example, the core-shell type acrylic resin particles (A) have a polymerizable unsaturated monomer having two or more polymerizable unsaturated groups in one molecule (hereinafter sometimes referred to as “polyvinyl monomer”), and / or. Alternatively, a polymerizable unsaturated monomer mixture (hereinafter referred to as “core monomer mixture (a1)) containing a polymerizable unsaturated monomer each having a functional group other than the unsaturated group capable of reacting in a complementary manner to form a covalent bond In order to form a shell part in the aqueous dispersion after carrying out the first stage emulsion polymerization in the presence of water to obtain an aqueous dispersion of crosslinked core particles. The monomer mixture (a2) of the polymerizable unsaturated monomer (hereinafter referred to as “shell monomer mixture (a2)”. The “core monomer mixture (a1)” has a different monomer composition. Can be in addition, obtained by carrying out the emulsion polymerization of the second stage.

  The polyvinyl monomer can be used in an amount in the range of 0.01 to 10% by mass, preferably 0.05 to 5% by mass, based on the mass of the core monomer mixture (a1).

  Examples of the polymerizable unsaturated monomers each having a functional group that reacts in a complementary manner to form a covalent bond include N-alkoxymethyl (meth) acrylamide and γ- (meth) acryloyloxypropyltrimethoxysilane. The functional groups of the same type can react with each other in a complementary manner to form a covalent bond, or heterogeneous, such as the reaction of a glycidyl group and a carboxylic acid in a combination of (meth) acrylic acid glycidyl ester and (meth) acrylic acid And the like, which can form a covalent bond such as an ester bond by complementary reaction of these two functional groups. The cross-linking reaction in the core particle may be performed, for example, while forming the core particle in the emulsion polymerization in the first stage, or by adding an appropriate catalyst after forming the core particle, or forming a shell part. An appropriate catalyst may be added later.

  Examples of the polymerizable unsaturated monomer include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, and isobutyl (meth) acrylate. , Tert-butyl (meth) acrylate, n-hexyl (meth) acrylate, n-octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, nonyl (meth) acrylate, tridecyl (meth) acrylate, lauryl (meth) acrylate , Stearyl (meth) acrylate, isostearyl (meth) acrylate, cyclohexyl (meth) acrylate, methylcyclohexyl (meth) acrylate, t-butylcyclohexyl (meth) acrylate, cyclod Alkyl or cycloalkyl (meth) acrylate such as sil (meth) acrylate; monomer having an isobornyl group such as isobornyl (meth) acrylate; monomer having an adamantyl group such as adamantyl (meth) acrylate; styrene, α-methylstyrene Vinyl aromatic compounds such as vinyltoluene; vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris (2-methoxyethoxy) silane, γ- (meth) acryloyloxypropyltrimethoxysilane, γ- (meth) acryloyloxypropyltri Monomers having alkoxysilyl groups such as ethoxysilane; perfluoroalkyl (meth) acrylates such as perfluorobutylethyl (meth) acrylate and perfluorooctylethyl (meth) acrylate Monomers having fluorinated alkyl groups such as fluoroolefins; N-substituted maleimides; Vinyl compounds such as N-vinylpyrrolidone, ethylene, butadiene, chloroprene, vinyl propionate, vinyl acetate; (meth) acrylic acid, maleic acid, maleic anhydride Carboxyl group-containing monomers such as acid, fumaric acid, itaconic acid, itaconic anhydride, crotonic acid, β-carboxyethyl (meth) acrylate; (meth) acrylonitrile, (meth) acrylamide, N, N-dimethyl (meth) acrylamide, (Meth) acryloylmorpholine, N-isopropyl (meth) acrylamide, N-hydroxymethyl (meth) acrylamide, N-alkoxymethyl (meth) acrylamide, N, N-dimethylaminoethyl (meth) acrylate, N, N-dimethyl Nitrogen-containing monomers such as adducts of ruaminopropyl (meth) acrylamide, glycidyl (meth) acrylate and amines; 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3- Monoesterified product of (meth) acrylic acid and dihydric alcohol having 2 to 8 carbon atoms such as hydroxypropyl (meth) acrylate and 4-hydroxybutyl (meth) acrylate, (meth) acrylic acid and 2 to 8 carbon atoms Ε-caprolactone modified monoester product with dihydric alcohol, allyl alcohol, hydroxyl group-containing monomer such as (meth) acrylate having a polyoxyethylene chain whose molecular end is a hydroxyl group; glycidyl (meth) acrylate, β-methyl Glycidyl (meth) acrylate, 3,4-epoxycyclohexyl Epoxy group-containing monomers such as methyl (meth) acrylate, 3,4-epoxycyclohexylethyl (meth) acrylate, 3,4-epoxycyclohexylpropyl (meth) acrylate, and allyl glycidyl ether; polyoxyethylene whose molecular terminal is an alkoxy group (Meth) acrylate having a chain; 2- (meth) acrylamide-2-methylpropanesulfonic acid, allylsulfonic acid, styrenesulfonic acid, sulfoethyl (meth) acrylate, and sulfonic acid group-containing monomers such as sodium salt or ammonium salt thereof Monomer having a phosphate group such as 2- (meth) acryloyloxyethyl acid phosphate; acrolein, diacetone (meth) acrylamide, acetoacetoxyethyl (meth) acrylate, 4 to 7 Carbonyl group-containing monomers such as vinyl alkyl ketones having carbon atoms (for example, vinyl methyl ketone, vinyl ethyl ketone, vinyl butyl ketone); allyl (meth) acrylate, ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, Triethylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, 1,3-butylene glycol di (meth) acrylate, 1,4-butanediol di (meth) acrylate, glycerin di (meth) acrylate, glycerin Tri (meth) acrylate, trimethylolpropane di (meth) acrylate, trimethylolpropane tri (meth) acrylate, pentaerythritol di (meth) acrylate, pentaerythritol Lutri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol penta (meth) acrylate, tris (2-hydroxyethyl) isocyanurate tri (meth) acrylate, neopentyl glycol diacrylate, 1,6-hexanediol Di (meth) acrylate, glycerol allyloxy di (meth) acrylate, 1,1,1-tris (hydroxymethyl) ethanedi (meth) acrylate, 1,1,1-tris (hydroxymethyl) ethanetri (meth) acrylate, tri Allyl isocyanurate, triallyl trimellitate, diallyl terephthalate, diallyl phthalate, diallyl isophthalate, pentaerythritol diallyl ether, divinylbenzene, methylene bis (meth) a Riruamido include ethylene bis (meth) polymerizable unsaturated monomer having two or more polymerizable unsaturated groups such as acrylamide per molecule, and combinations thereof.

  In the present specification, “(meth) acrylate” means acrylate or methacrylate, and “(meth) acrylic acid” means acrylic acid or methacrylic acid. “(Meth) acryloyl” means acryloyl or methacryloyl, and “(meth) acrylamide” means acrylamide or methacrylamide.

  In the first stage emulsion polymerization, seed particles are obtained by emulsion polymerization using a small portion of the core monomer mixture (a1), and then the remaining core monomer mixture (a1) is emulsified in the presence of the seed particles. An aqueous dispersion of core particles may be obtained by polymerization.

  The core-shell type acrylic resin particles (A) can be obtained by adding the shell monomer mixture (a2) to the aqueous dispersion of the core particles and performing the second stage emulsion polymerization. At that time, the core-shell type acrylic resin particles (A) having two or more shell portions may be obtained by performing the second stage emulsion polymerization for forming the shell portion in two or more steps. At this time, the blending amount and monomer composition of the shell monomer mixture (a2) may be different at each stage.

  Further, in the production of the core-shell type acrylic resin particles (A), there is no particular limitation on the means for adding the core monomer mixture (a1) or the shell monomer mixture (a2) to the polymerization reaction tank. For example, the first stage of emulsification In the polymerization, the core monomer mixture (a1) may be added all at once, continuously, or intermittently. Similarly, in the second stage emulsion polymerization, the shell monomer mixture (a2) may be added all at once, continuously, or intermittently.

  The core-shell type acrylic resin particles (A) in the present invention have a shell Tg of 35 to 105 ° C, preferably 40 to 100 ° C, more preferably 45 to 90 ° C, and a core Tg of -10 to 25 ° C. Preferably it is in the range of −5 to 20 ° C., more preferably 0 to 15 ° C. When the shell Tg is lower than 35 ° C, the corrosion resistance of the obtained coating film may be inferior, and when the shell Tg is higher than 105 ° C, the workability of the obtained coating film may be inferior. Moreover, when the core Tg is lower than −10 ° C., the corrosion resistance of the obtained coating film may be inferior, and when the core Tg is higher than 25 ° C., the workability of the obtained coating film may be inferior.

Here, the glass transition temperature (Tg) can be calculated using the following formulas (1) and (2).
1 / Tg (° K) = (W1 / T1) + (W2 / T2) + Expression (1)
Tg (° C) = Tg (° K) -273 (2)
In the formula, W1, W2,... Represent the mass% of each monomer used for copolymerization, and T1, T2,... Represent the Tg (° K) of the monomer homopolymer, respectively. T1, T2,... Are values according to Polymer Hand Book (Second Edition, edited by J. Brandup, E. H. Immergut). The glass transition temperature of a homopolymer based on a monomer not described in this handbook is an actual measurement value for a homopolymer having a weight average molecular weight of about 20,000 to 50,000. This measured value is obtained by vacuum suction of a sample taken in a measuring cup to remove volatile components such as a solvent, and then using a differential scanning thermal analysis “DSC-50Q type” (trade name, manufactured by Shimadzu Corporation), The change in the amount of heat in the range of −50 ° C. to + 150 ° C. is measured at a temperature increase rate of 3 ° C./min, and the first baseline change point on the low temperature side is used.

  In addition, in this specification, when the shell part of the core-shell type acrylic resin particles (A) is a multilayer of two or more layers, the shell Tg is based on the composition of all the monomers used in the shell monomer mixture (a2). , Values calculated by the above formulas. Further, when the cross-linked core part is formed using a core monomer mixture (a1) containing a polyvinyl monomer, the core Tg is based on a composition in which the polyvinyl monomer is excluded from the core monomer mixture (a1). It is a value calculated by each of the above formulas.

  The mass of the core part in the core-shell type acrylic resin particles (A) is 10 to 90% by mass, preferably 20 to 70% by mass, more preferably 30 to 60% by mass based on the total mass of the core part and the shell part. Within range. When the mass of the core part is less than 10% by mass, the processability of the obtained coating film may be inferior, and when it is more than 90% by mass, the corrosion resistance of the obtained coating film may be deteriorated.

  The core-shell type acrylic resin particles (A) of the aqueous coating composition of the present invention preferably have an acid group such as a carboxyl group, a phosphoric acid group or a sulfonic acid group from the viewpoint of storage stability. The acid value derived from these acid groups is in the range of 0.5 to 100 mgKOH / g, preferably 20 to 90 mgKOH / g, more preferably 40 to 80 mgKOH / g. When the acid value is larger than 100 mgKOH / g, the water resistance of the resulting coating film may be lowered.

  In addition, the coating obtained is obtained by chemically bonding a part or all of the acrylic resin constituting the core part in the core-shell type acrylic resin particles (A) and a part or all of the acrylic resin constituting the shell part. The retort whitening resistance, corrosion resistance, water resistance, etc. of the film may be improved. Such core-shell type acrylic resin particles (A) include, for example, two polymerizable unsaturated monomers having a functional group capable of reacting in a complementary manner to form a covalent bond [monomer (z1) and monomer ( (1) Method using a monomer [denoted as monomer (z3)] having two or more radical-reactive unsaturated groups having different radical reactivity in one molecule (2) Etc. can be manufactured.

  As the method (1), for example, the first stage emulsion polymerization is performed in the presence of water using the core monomer mixture (a1) containing the monomer (z1) to obtain an aqueous dispersion of core particles. The shell monomer mixture (a2) containing the monomer (z2) is added to the aqueous dispersion, and the second stage emulsion polymerization is carried out to constitute part or all of the acrylic resin constituting the core part and the shell part. Examples thereof include a production method for obtaining core-shell type acrylic resin particles (A) in which a part or all of the acrylic resin to be chemically bonded is obtained.

  Examples of combinations of the monomer (z1) and the monomer (z2) include glycidyl (meth) acrylate, β-methylglycidyl (meth) acrylate, 3,4-epoxycyclohexylmethyl (meth) acrylate, 3 , 4-epoxycyclohexylethyl (meth) acrylate, 3,4-epoxycyclohexylpropyl (meth) acrylate, allyl glycidyl ether and other epoxy group-containing monomers, and (meth) acrylic acid, maleic acid, maleic anhydride as monomer (z2) Examples include combinations with carboxyl group-containing monomers such as acid, fumaric acid, itaconic acid, itaconic anhydride, crotonic acid, and β-carboxyethyl (meth) acrylate. In addition, in the combination of the said epoxy group containing monomer and a carboxyl group containing monomer, the said epoxy group and a carboxyl group react and form an ester bond at the time of manufacture of a core-shell type acrylic resin particle (A).

  As the method (2), for example, the first stage emulsion polymerization is performed in the presence of water using the core monomer mixture (a1) containing the monomer (z3) to obtain an aqueous dispersion of core particles. By adding the shell monomer mixture (a2) to the aqueous dispersion and carrying out the second stage emulsion polymerization, part or all of the acrylic resin constituting the core part and part of the acrylic resin constituting the shell part Or the manufacturing method etc. which obtain the core-shell type acrylic resin particle | grains (A) with which all couple | bonded chemically can be mentioned.

  Examples of the monomer (z3) include vinyl, allyl, butenyl, and pentenyl such as allyl (meth) acrylate, dicyclopentenyl (meth) acrylate, and dicyclopentenyloxyethyl (meth) acrylate. And monomers having an unsaturated group having a different structure from the (meth) acryloyl group such as a group, a cycloalkenyl group, and a cinnamyl group, and a (meth) acryloyl group in one molecule.

  Moreover, when the core-shell type acrylic resin particles (A) have cross-linking reactivity, retort whitening resistance, corrosion resistance, water resistance and the like of the obtained coating film may be improved. The core-shell type acrylic resin particles (A) having crosslinking reactivity can be obtained by emulsion polymerization using a polymerizable unsaturated monomer having a crosslinking reactive functional group. The use amount of the polymerizable unsaturated monomer having a crosslinking reactive functional group is used for the production of the core-shell type acrylic resin particles (A) from the viewpoint of the processability of the obtained coating film, the film resistance at the can lid part, and the like. It is 20 mass% or less with respect to the total amount of a polymerizable unsaturated monomer, Preferably it is 15 mass% or less. The cross-linking reactive functional group can react with the same cross-linking reactive functional group to form a coating film having a cross-linking structure, and the resol type phenolic resin (C1) contained in the aqueous coating composition for can coating of the present invention. And / or those capable of forming a coating film having a crosslinked structure by reaction with amino resin (C2), and having a crosslinked structure by reaction with other crosslinking reactive components contained in the aqueous coating composition for can coating of the present invention. The thing etc. which can form a coating film can be mentioned.

  Examples of the polymerizable unsaturated monomer having a crosslinking reactive functional group include crosslinking reactive (meth) acrylamides such as N-hydroxymethyl (meth) acrylamide and N-alkoxymethyl (meth) acrylamide; glycidyl (meth) Acrylate, β-methylglycidyl (meth) acrylate, 3,4-epoxycyclohexylmethyl (meth) acrylate, 3,4-epoxycyclohexylethyl (meth) acrylate, 3,4-epoxycyclohexylpropyl (meth) acrylate, allyl glycidyl ether Epoxy group-containing monomers such as vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris (2-methoxyethoxy) silane, γ- (meth) acryloyloxypropyltrimethoxysilane, γ- (meth) acrylo Monomers having alkoxysilyl groups such as ruoxypropyltriethoxysilane; (meth) acrylic acid, maleic acid, maleic anhydride, fumaric acid, itaconic acid, itaconic anhydride, crotonic acid, β-carboxyethyl (meth) acrylate, etc. Carboxyl group-containing monomers: 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate and other hydroxyl group-containing monomers Can be mentioned.

  Examples of the radical polymerization initiator that can be used in the emulsion polymerization for obtaining the core-shell type acrylic resin particles (A) include known compounds such as dibenzoyl peroxide, dioctanoyl peroxide, and dilauroyl. Peroxide, distearoyl peroxide, cumene hydroperoxide, tert-butyl hydroperoxide, di-tert-butyl peroxide, tert-butyl peroxylaurate, tert-butyl peroxyisopropyl carbonate, tert-butyl peroxyacetate , Organic peroxides such as diisopropylbenzene hydroperoxide and p-menthane hydroperoxide; azobisisobutyronitrile, azobis (2,4-dimethylvaleronitrile), azobis ( -Methylpropiononitrile), azobis (2-methylbutyronitrile), 4,4'-azobis (4-cyanobutanoic acid), dimethylazobis (2-methylpropionate), 2,2'-azobis [2- (2-imidazolin-2-yl) propane], 2,2′-azobis [2- (2-imidazolin-2-yl) propane] salt (organic acid salt, hydrochloride or sulfate, etc.), 2,2 Salts of '-azobis [2-methylpropionamidine], 2,2'-azobis [2-methylpropionamidine] (organic acid salt, hydrochloride or sulfate, etc.), 2,2'-azobis [N- (2 -Carboxyethyl) -2-methylpropionamidine] hydrate, 2,2'-azobis [N- (2-carboxyethyl) -2-methylpropionamidine] salt (organic acid salt, hydrochloride or sulfuric acid) Etc.), 2,2′-azobis (1-imino-1-pyrrolidino-2-methylpropane), 2,2′-azobis (1-imino-1-pyrrolidino-2-methylpropane) salt (organic acid salt) Azo compounds such as 2,2′-azobis [2-methyl-N- (2-hydroxyethyl) propionamide]; persulfuric acid such as potassium persulfate, ammonium persulfate and sodium persulfate Examples thereof include salts, inorganic peroxides such as hydrogen peroxide, benzoins such as benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, and benzoin isobutyl ether, and combinations thereof. Further, the peroxide-based polymerization initiator may optionally be organic acids such as ascorbic acid, erythorbic acid, tartaric acid, citric acid, salts of these organic acids, tertiary amines, saccharides, mercaptans, pyro-suboxides. Phosphate, phosphite, sodium thiosulfate, sodium sulfite, potassium sulfite, sodium hydrogen sulfite, potassium hydrogen sulfite, sodium bisulfite, sodium metabisulfite, etc., sodium formaldehyde sulfoxylate, ferrous sulfate, chloride One or more known reducing agents such as ferrous iron, Rongalite, and thiourea dioxide may be added and used as a redox initiator.

  The radical polymerization initiator can be used in an amount in the range of 0.01 to 5% by mass, preferably 0.1 to 1% by mass, based on the total mass of polymerizable unsaturated monomers used for emulsion polymerization. The method for adding the radical polymerization initiator is not particularly limited, and can be appropriately selected depending on the type, mass, etc. For example, it may be added to the monomer mixture or water in advance, and added at the same time during polymerization. Alternatively, it may be dropped.

  The emulsion polymerization for producing the core-shell type acrylic resin particles (A) in the present invention can be performed using a nonionic surfactant. Examples of the nonionic surfactant include the following.

  Polyoxyethylene lauryl ether, polyoxyethylene cetyl ether, polyoxyethylene stearyl ether, polyoxyethylene oleyl ether, polyoxyethylene myristyl ether, polyoxyethylene octyldodecyl ether, polyoxyethylene polyoxypropylene glycol, polyoxyalkylene alkenyl ether Polyoxyalkylene alkyl ethers or polyoxyalkylene alkenyl ethers such as polyoxyethylene tridecyl ether, polyoxyalkylene branched decyl ether, polyoxyethylene isodecyl ether, polyoxyethylene castor oil ether; Examples of commercially available ethers or polyoxyalkylene alkenyl ethers include: “Emulgen 103”, “Emulgen 120”, “Emulgen 220”, “Emulgen 430”, “Emulgen 2025G”, “Emulgen LS-114”, “Latemul PD-430” (above, manufactured by Kao Corporation), etc. Can do.

  Polyoxyethylene phenyl such as polyoxyethylene distyrenated phenyl ether, polyoxyethylene phenyl ether, polyoxyethylene octyl phenyl ether, polyoxyethylene nonyl phenyl ether, polyoxyethylene polycyclic phenyl ether, polyoxyethylene tribenzyl phenyl ether Ethers; Examples of commercially available polyoxyethylene phenyl ethers include “Emulgen A-90” and “Emulgen B-66” (above, manufactured by Kao Corporation).

  Polyoxyethylene monolaurate, polyoxyethylene monopalmitate, polyoxyethylene monostearate, polyoxyethylene monooleate, polyoxyethylene dilaurate, polyoxyethylene dipalmitate, polyoxyethylene distearate, polyoxyethylene geo Polyoxyethylene fatty acid esters such as rate; commercial products of the polyoxyethylene fatty acid esters include, for example, “Emanon 1112”, “Emanon 3299V” (above, manufactured by Kao Corporation) and the like.

  Sorbitan monolaurate, sorbitan dilaurate, sorbitan trilaurate, sorbitan monopalmitate, sorbitan dipalmitate, sorbitan tripalmitate, sorbitan monostearate, sorbitan distearate, sorbitan tristearate, sorbitan monooleate, sorbitan dioleate Sorbitan fatty acid esters such as sorbitan trioleate, sorbitan sesquiolate, sorbitan coconut oil fatty acid esters; commercially available products of the sorbitan fatty acid esters include, for example, “NIKKOL SL-10” (manufactured by Nikko Chemicals) Can be mentioned.

  Polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan dilaurate, polyoxyethylene sorbitan trilaurate, polyoxyethylene sorbitan monopalmitate, polyoxyethylene sorbitan dipalmitate, polyoxyethylene sorbitan tripalmitate, polyoxyethylene sorbitan Monostearate, polyoxyethylene sorbitan distearate, polyoxyethylene sorbitan tristearate, polyoxyethylene sorbitan monooleate, polyoxyethylene sorbitandiolate, polyoxyethylene sorbitan trioleate, polyoxyethylene sorbitan monoisostearate, Polyoxyethylene sorbitan diisostearate, polyoxyethylene sorbitan triisostearate And polyoxyethylene sorbitan fatty acid esters such as polyoxyethylene sorbitan coconut oil fatty acid ester and polyoxyethylene sorbitan monopalmitate; commercial products of the polyoxyethylene sorbitan fatty acid esters include, for example, “NIKKOL TS-10V ”,“ NIKKOL TL-10 ”(manufactured by Nikko Chemicals),“ Leodol TW-O120V ”,“ Leodol TW-P120 ”,“ Leodol TW-L120 ”(manufactured by Kao Corporation), and the like. it can.

  Fatty acid esterified polyoxyethylene sorbitols such as tetraoleic acid polyoxyethylene sorbitol and tetrastearic acid polyoxyethylene sorbite; commercially available products of the above-mentioned polyoxyethylene sorbitol fatty acid esters include, for example, “Leodol 440V”, “Leodol” 460V "(above, manufactured by Kao Corporation).

  Glycerol such as glycerol monostearate, glycerol monooleate, glycerol monolaurate, glycerol monopalmitate, polyoxyethylene glyceryl isostearate, polyoxyethylene glyceryl diisostearate, polyoxyethylene glyceryl triisostearate, polyoxyethylene glyceryl oleate Fatty acid esters; Examples of commercially available glycerin fatty acid esters include “Rheidol MS-165V” (above, manufactured by Kao Corporation) and “NIKKOL MGS-F20V” (above, made by Nikko Chemicals). it can.

  Polyglyceryl fatty acid esters such as polyglyceryl monoisostearate, polyglyceryl monostearate, polyglyceryl monooleate, polyglyceryl monolaurate, polyglyceryl monolaurate, polyglyceryl distearate, polyglyceryl diisostearate, decaglyceryl tristearate, polyglyceryl condensed ricinoleate; Examples of commercially available polyglycerin fatty acid esters include “NIKKOL Hexaglyn PR-15”, “NIKKOL Hexaglyn1-L”, “NIKKOL Hexaglyn1-M”, “NIKKO Decaglyn1-L”, “NIKg Decimlin1-L”, “NIKg NIKKOL Decaglyn1-SV ”,“ NIKKOL Deca lyn1-50SV "," NIKKOL Decaglyn1-ISV "," NIKKOL Decaglyn1-OV "," NIKKOL Decaglyn1-LN "," NIKKOL Decaglyn2-SV "," NIKKOL Decaglyn3-SV "," NIKKOL Decaglyn3-OV "," NIKKOL Decaglyn1 -LVEX "," NIKKOL Decaglyn2-ISV "," NIKKOL Decaglyn7-OV "," NIKKOL Decaglyn1-ISVEX "," NIKKOL Decaglyn1-MVEX "," NIKKOL Decaglyn1-OVEX "," NIKKOL Decaglyn1-PVEX "," NIKKOL Decaglyn1- SVEX "(above, Photochemicals), "Sunsoft M-12J", "Sunsoft Q-12S", "Sunsoft Q-14S", "Sunsoft A-181E", "Sunsoft A-121E" Manufactured by the same company), "MS-5S", "SS-5S", "TS-5S", "MCA-150", "MSW-7S", "ML-500", "MCA-750", "ML-750" (Above Sakamoto Yakuhin Kogyo Co., Ltd.), Poem J-0021 (Riken Vitamin Co., Ltd.), Ryoto Polyglyceride L-10D, Ryoto Polyglyceride M-10D (Mitsubishi Chemical Foods, Inc.) Manufactured).

  Polyoxyethylene glyceryl fatty acid esters such as polyoxyethylene glyceryl monostearate, glyceryl polyoxyethylene oleate, and polyoxyethylene glyceryl triisostearate; commercial products of the polyoxyethylene glycerin fatty acid esters include, for example, “SC -E750 "(manufactured by Sakamoto Yakuhin Kogyo Co., Ltd.)," NIKKOL TMGS-5V "," NIKKOL TMGS-15V "," NIKKOL TMGO-15 "(manufactured by Nikko Chemicals).

  Polyoxyalkylene-modified castor oil such as polyoxyethylene hydrogenated castor oil; commercially available products of the polyoxyethylene hydrogenated castor oil include, for example, “Emernon CH-80” (manufactured by Kao Corporation), “Neugen ES-169D” (Daiichi Kogyo Seiyaku Co., Ltd.).

  Sucrose tristearate, sucrose stearate, sucrose distearate, sucrose polystearate, sucrose pentaerucate, sucrose hexaerucate, sucrose tribehenate, sucrose oleate, sucrose polyoleate, sucrose palmitate, sucrose hexapalmitate, Sucrose fatty acid esters such as sucrose myristate, sucrose laurate, sucrose dilaurate and sucrose polylaurate; commercially available products of the sucrose fatty acid esters include, for example, “S-770”, “S-970”, “ “S-1170”, “S-1570”, “L-1695”, “M-1695”, “O-1570”, “P-1670” (manufactured by Mitsubishi Chemical Foods), “Cosmelike S-160” , " Meraiku O-150 "," Cosmetics like P-160 "(or more, Dai-ichi Kogyo Seiyaku Co., Ltd.) and the like can be given.

  α-hydro-ω- (1- (alkoxy) methyl-2- (2-propenyloxy) ethoxy) -poly (oxy-1,2-ethanediyl), alkoxy polyethylene glycol methacrylate, polyoxyalkylene alkenyl ether, polyoxyethylene Radical-reactive nonionic surfactants such as nonylpropenyl phenyl ether; commercially available products of the above-mentioned radical-reactive nonionic surfactants include, for example, ADEKA rear soap ER-40 (manufactured by ADEKA), Antox LMA series (Japan) Emulsifiers), PD-400 series (Kao Corporation), Aqualon RN series (Daiichi Kogyo Seiyaku Co., Ltd.), and the like.

  Nonionic surfactants other than the above include nitrogen such as polyoxyethylene alkylamine ether, lauric acid myristylic acid diethanolamide, palm kernel oil fatty acid diethanolamide, coconut oil fatty acid diethanolamide, polyoxyethylene coconut oil fatty acid monoethanolamide, etc. You may use polymer type nonionic surfactants, such as a contained nonionic surfactant and a polyoxyethylene polyoxypropylene block polymer.

  The said nonionic surfactant may use together 1 type (s) or 2 or more types.

  From the viewpoint of production stability of the core-shell type acrylic resin particles (A), the nonionic surfactant is particularly polyglycerin fatty acid esters, sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters, sucrose fatty acid esters and poly At least one selected from the group consisting of oxyethylene fatty acid esters is preferred.

  The HLB value of the nonionic surfactant is in the range of 6 to 20, preferably 7 to 19, and more preferably 8 to 17 from the viewpoint of storage stability of the aqueous coating composition for can coating of the present invention. When the HLB value is less than 6, the storage stability of the water-coating composition for can coating may be lowered. Two or more types of nonionic surfactants having different HLB values may be used in combination.

Here, the HLB value is an abbreviation for hydrophilic-lipophilic balance, and represents the ratio between hydrophilicity and lipophilicity of an amphiphilic substance as a numerical value between 0 and 20, and the larger the HLB value is, Hydrophilicity increases. As an example of the calculation method of the HLB value, the Griffin formula based on the mass fraction:
HLB value = 20 × (MH / M)
(In the formula, MH represents the molecular weight of the hydrophilic group in the compound that is an amphiphilic substance, and M represents the molecular weight of the compound itself). For example, in a nonionic surfactant of an alkyl ether type, a nonionic surfactant having 80% by mass of a polyoxyethylene group as a hydrophilic group and 20% by mass of an alkyl group as a hydrophobic group in the molecule has an HLB value = Calculated as 20 × 0.8 = 16.

  The HLB value in this specification is the HLB value when the mass% of the hydrophilic raw material in the main raw material of the nonionic surfactant used for the production of the nonionic surfactant for convenience is referred to as P% with reference to the Griffin formula. = A value calculated as 20 × P / 100.

  Further, as the lipophilic group possessed by the nonionic surfactant, those having a linear or branched, saturated or unsaturated fatty acid ester group having 10 or more carbon atoms can be used for the aqueous coating for can coating of the present invention. It is preferable from the viewpoint of the storage stability of the coating composition.

  In the emulsion polymerization for producing the core-shell type acrylic resin particles (A) in the present invention, the nonionic surfactant is used as an essential component, and the total amount of the nonionic surfactant is the polymerizable used in the emulsion polymerization. It is used in the range of 0.05 to 10% by mass, more preferably in the range of 0.1 to 8% by mass based on the total mass of unsaturated monomers, and the resulting coating film has retort whitening resistance and corrosion resistance. This is preferable.

In the emulsion polymerization for producing the core-shell type acrylic resin particles (A) in the present invention, the nonionic surfactant is used as an essential component. In addition to the nonionic surfactant, an anionic surfactant, a cationic surfactant is used. A surfactant, at least one selected from conventionally known surfactants such as zwitterionic surfactants having both anionic and cationic properties, and the nonionic surfactant are used in combination. Also good. As surfactants other than nonionic surfactants, when an anionic surfactant is used in combination, the production stability of the core-shell type acrylic resin particles (A) and the storage stability of the coating composition may be improved. Is preferred.

  Examples of the anionic surfactant include sodium salts and ammonium salts of acid group-containing compounds such as alkylsulfonic acid, alkylbenzenesulfonic acid, and alkylphosphoric acid, an anionic group in one molecule, a polyoxyethylene group, Polyoxyalkylene group-containing anionic surfactant having both a polyoxyalkylene group such as a polyoxypropylene group, reactive anionic surfactant having an anionic group and a polymerizable unsaturated group in one molecule An agent etc. can be mentioned. Examples of the zwitterionic surfactant include dimethylalkyl betaines, dimethylalkyl lauryl betaines, and alkylglycine.

  Examples of the reactive anionic surfactant include sodium salts and ammonium salts of sulfonic acid compounds having a radical reactive unsaturated group such as an allyl group, a (meth) acryloyl group, a propenyl group, and a butenyl group. .

  When the core-shell type acrylic resin particles (A) are produced by emulsion polymerization of a polymerizable unsaturated monomer using the nonionic surfactant and the anionic surfactant, the nonionic surfactant and the anionic surfactant are used. The mass ratio with the agent is in the range of 15/85 to 99/1, preferably 18/82 to 90/10, more preferably 22/78 to 80/20. When the mass ratio of the nonionic surfactant to the anionic surfactant is less than 15/85, the resulting coating film may have poor corrosion resistance and water resistance, and the mass ratio is greater than 99/1. , The effect of using an anionic surfactant together may be reduced.

  The nonionic surfactant and the anionic surfactant are used for the production of the core-shell type acrylic resin particles (A), for example, the emulsion polymerization step of the “core monomer mixture (a1)” and the “shell monomer mixture (a2)”. When the emulsion polymerization is performed in two stages of the emulsion polymerization process, it can be arbitrarily distributed and used in each process. Specifically, for example, the anionic surfactant is used in the emulsion polymerization of the “core monomer mixture (a1)”, and after obtaining an aqueous dispersion of core particles by the first stage emulsion polymerization, the aqueous dispersion monomer is used. The mixture (a2) may be added together with a nonionic surfactant to perform the second stage emulsion polymerization. In the first-stage emulsion polymerization and the second-stage emulsion polymerization, a nonionic surfactant and an anionic surfactant may be mixed from the beginning. In the production of the core-shell type acrylic resin particles (A) in the present invention, how to distribute the nonionic surfactant and the anionic surfactant and how to add them to the polymerization system are freely selected from the viewpoint of production stability and the like. Can be adjusted.

  When an anionic surfactant is used in the production of the core-shell type acrylic resin particles (A), the total amount of the anionic surfactant is 1.0% by mass based on the total mass of the polymerizable unsaturated monomers used in the production. In the following, it is preferable to use within the range of 0.8% by mass or less from the viewpoint of water resistance and corrosion resistance of the resulting coating film.

  The average particle diameter of the core-shell type acrylic resin particles (A) of the aqueous coating composition of the present invention is preferably from 80 to 500 nm, more preferably from 150 to 300 nm, from the viewpoint of storage stability. The average particle size was measured using a submicron particle analyzer N4 (trade name, manufactured by Beckman Coulter, Inc., particle size distribution measuring device) diluted with deionized water to a concentration suitable for measurement. (Measured at about 20 ° C.)

  The emulsion polymerization after the first stage and the second stage can be carried out in the presence of water at a polymerization temperature of 40 ° C. to 98 ° C. for a polymerization time of about 1 to 20 hours.

  In the emulsion polymerization for obtaining the core-shell type acrylic resin particles (A), in addition to the above-mentioned components such as water, a mixture of polymerizable unsaturated monomers, a radical polymerization initiator, a surfactant and the like, if desired, a reducing agent, organic A solvent, a polymer compound, a chain transfer agent, an amine compound, an alkaline metal compound, or the like may be used.

Resol type phenol resin (C1), amino resin (C2)
The aqueous coating composition for can coating of the present invention contains a resol type phenol resin (C1) and / or an amino resin (C2) as a curing agent. The aqueous coating composition for can coating of the present invention can improve the water resistance, corrosion resistance, workability, etc. of the resulting coating film by including the resol type phenol resin (C1) and / or amino resin (C2). Is possible.

  Examples of the resol-type phenolic resin (C1) include a phenolic resin in which a phenolic compound such as phenol or cresol and formaldehyde are subjected to a condensation reaction in the presence of a reaction catalyst to introduce a methylol group; and the methylol introduced above Those in which a part of the group is alkyl etherified with an alcohol having 1 to 6 carbon atoms are included.

  Examples of the phenol compound include bifunctional phenol compounds such as o-cresol, p-cresol, p-tert-butylphenol, p-ethylphenol, 2,3-xylenol, and 2,5-xylenol; coalic acid, m-cresol, Phenol compounds such as trifunctional phenol compounds such as m-ethylphenol, 3,5-xylenol and m-methoxyphenol; can be used alone or in combination of two or more.

  Examples of the formaldehydes include formaldehyde, paraformaldehyde, and trioxane, which can be used alone or in combination of two or more. As the alcohol used for alkyl etherifying a part of the methylol group of the methylolated phenol resin, a monohydric alcohol having 1 to 6 carbon atoms, preferably 1 to 4 carbon atoms, can be suitably used. . Suitable monohydric alcohols include methanol, ethanol, n-propanol, n-butanol, isobutanol and the like.

  The resol type phenol resin (C1) has a number average molecular weight of 200 to 2000, preferably 300 to 1200, and an average number of methylol groups per benzene nucleus of 0.3 to 3.0, Preferably it is in the range of 0.5 to 3.0. In particular, among the resol-type phenol resins, a good corrosion-resistant coating film can be obtained even in a portion where the carboxylic acid formaldehyde resin obtained by condensation reaction of carboxylic acid and formaldehyde has undergone impact processing.

  As amino resin (C2), methylolation obtained by reaction of amino components such as melamine, urea, benzoguanamine, acetoguanamine, steroguanamine, spiroguanamine, dicyandiamide and aldehyde components such as formaldehyde, paraformaldehyde, acetaldehyde, and benzaldehyde. An amino resin is mentioned. Those obtained by etherifying the methylol group of this methylolated amino resin with a lower alcohol having 1 to 6 carbon atoms are also included in the amino resin.

  The amino resin is preferably a lower alkyl etherified melamine resin or a lower alkyl etherified benzoguanamine resin obtained by etherifying some or all of the methylol groups of a methylolated melamine resin or a methylolated benzoguanamine resin with a lower alcohol. The lower alcohol used for the etherification is preferably methyl alcohol, ethyl alcohol, isobutyl alcohol, or n-butyl alcohol. These alcohols can be used for etherification alone or in combination of two or more.

  Specific examples of the melamine resin include, for example, Uban 20SE, 225 [above, both are manufactured by Mitsui Toatsu Co., Ltd.], Super Becamine J820-60, L-117-60, L-109-65, Butyl etherified melamine resins such as 47-508-60, L-118-60, G821-60 [all are manufactured by Dainippon Ink and Chemicals, Inc.]; Cymel 300, 303, 325, 327, 350, 730, 736, 738 [all manufactured by Mitsui Cytec Co., Ltd.], Melan 522, 523 [all manufactured by Hitachi Chemical Co., Ltd.], Nicarak MS001, MX430, MX650 [three Sumitomo M-55, M-100, M-40S (Sumitomo Chemical Co., Ltd.), Resimin 740, 747 (both Mon) Methyl etherified melamine resin, etc .; Cymel 232, 266, XV-514, 1130 [all manufactured by Mitsui Cytec Co., Ltd.], Nicalak MX500, MX600, MS95 [all Sanwa Chemical Resinmin 753, 755 [all manufactured by Monsanto Co., Ltd.], Sumimar M-66B (manufactured by Sumitomo Chemical Co., Ltd.), etc., and mixed etherified melamine resins of methyl ether and butyl ether, etc. .

  Specific examples of the benzoguanamine resin include Cymel 1123 (mixed etherified benzoguanamine resin of methyl ether and ethyl ether) and Cymel 1123-10 (mixed etherified benzoguanamine resin of methyl ether and butyl ether) manufactured by Mitsui Cytec Co., Ltd. ), Cymel 1128 (butyl etherified benzoguanamine resin), Mycoat 102 (methyl etherified benzoguanamine resin), and the like.

Aqueous polymer (D)
The aqueous coating composition for can coating of the present invention may further contain a water-soluble or water-dispersible aqueous polymer (D). As the aqueous polymer (D), a known resin which is water-soluble or water-dispersible and does not use bisphenol A as a raw material can be used. For example, acrylic resin, acrylic resin-modified polyester resin, polyester resin , Urethane resins, olefin resins, polyoxyalkylene resins, and resins obtained by modifying each of the above resins by a known method can be used alone or in combination. In the aqueous coating composition for can coating of the present invention, the aqueous polymer (D) can be used in a range of 30% by mass or less in terms of solid content based on the solid content mass of the core-shell type acrylic resin particles (A). From the viewpoint of retort whitening resistance and corrosion resistance of the coating film, it is preferable. By including the aqueous polymer (D) in the aqueous coating composition for can coating of the present invention, it may be possible to adjust the resulting coating film to improve performance such as water resistance, corrosion resistance, and workability. is there.

  The weight average molecular weight of the aqueous polymer (D) is 3000 to 200000, preferably 5000 to 150,000, more preferably from the viewpoint of the storage stability of the aqueous coating composition for can coating of the present invention and the corrosion resistance of the resulting coating film. The thing in the range of 8000-120,000 can be used.

  In the present specification, the weight average molecular weight or number average molecular weight is a value obtained by converting the weight average molecular weight measured with a gel permeation chromatograph (“HLC8120GPC” manufactured by Tosoh Corporation) based on the weight average molecular weight of polystyrene. is there. The columns are “TSKgel G-4000H × L”, “TSKgel G-3000H × L”, “TSKgel G-2500H × L”, “TSKgel G-2000H × L” (both manufactured by Tosoh Corporation, trade name). These were carried out under the conditions of mobile phase: tetrahydrofuran, measurement temperature: 40 ° C., flow rate: 1 ml / min, detector: RI.

  The glass transition temperature of the aqueous polymer (D) is −20 ° C. or higher, preferably −10 to 130 ° C., more preferably 0 to 80 ° C. from the viewpoint of the processability of the resulting coating film. Can be used. In this specification, the glass transition temperature is determined by taking a sample into a measuring cup using a differential scanning thermal analysis “DSC-50Q type” (trade name, manufactured by Shimadzu Corporation) and removing the solvent by vacuum suction. The calorie change is measured in the range of −60 ° C. to + 150 ° C. at a rate of temperature increase of 3 ° C./min, and the first baseline change point on the low temperature side is used.

  From the viewpoint of the storage stability of the aqueous coating composition for can coating of the present invention, the aqueous polymer (D) is preferably a carboxyl group-containing resin. The acid value of the aqueous polymer (D) is 20 to 250 mgKOH / g / g, preferably 50 to 200 mgKOH / g / g, more preferably 80 to 150 mgKOH / g / g, from the viewpoint of water resistance of the resulting coating film. Within range. Some or all of the carboxyl groups of the aqueous polymer (D) may be previously neutralized with a base compound such as an amine before blending the paint, or other paint components containing a base compound such as an amine when blended with the paint. You may neutralize by mixing with.

  When the aqueous polymer (D) is a vinyl polymer (D1), the vinyl polymer (D1) is a resin having substantially no cross-linked structure, and examples thereof include solution polymerization, dispersion polymerization, emulsion polymerization, It can be produced by conventionally known radical polymerization such as bulk polymerization. The unsaturated monomer that can be used for the production of the vinyl polymer (D1) is appropriately selected from those exemplified as the unsaturated monomer that can be used for the production of the core-shell type acrylic resin particles (A). These unsaturated monomers can be selected and used. The radical polymerization initiator that can be used for the production of the vinyl polymer (D1) is appropriately selected from those exemplified as the radical polymerization initiator that can be used for the production of the core-shell type acrylic resin particles (A). Can be used.

  Examples of the solvent that can be used in the solution polymerization, dispersion polymerization, and emulsion polymerization include known organic solvents such as water, toluene, butanol, methyl isobutyl ketone, and butyl cellosolve. Can be used in combination.

  As polymerization conditions in the solution polymerization, the reaction temperature is usually from room temperature to 200 ° C., and the reaction time is from 2 to 10 hours.

  The aqueous polymer (D) preferably has crosslinking reactivity from the viewpoint of water resistance of the resulting coating film. The aqueous polymer (D) includes a crosslinking reaction between the aqueous polymers (D), a crosslinking reaction between the aqueous polymer (D) and the core-shell type acrylic resin particles (A), and the aqueous polymer (D) and the resol type phenol. You may have crosslinking reactivity in any crosslinking reaction, such as a crosslinking reaction with resin (C1) and / or amino resin (C2). When the aqueous polymer (D) is an acrylic resin, the acrylic resin having crosslinking reactivity may be, for example, N-alkoxymethyl (meth) acrylamide, N-hydroxymethyl (meth) acrylamide, hydroxyethyl (meth) acrylate, It can be obtained by copolymerizing a polymerizable unsaturated monomer having a crosslinkable functional group such as hydroxyethyl (meth) acrylate and another polymerizable unsaturated monomer.

Aqueous coating composition for can coating The aqueous coating composition for can coating of the present invention comprises a core-shell type acrylic resin particle (A) comprising a shell part and a cross-linked core part, and a resol type phenol resin (C1) and / or an amino resin. It is the water-based coating composition for can coating | covers which does not contain resin manufactured using the raw material containing (C2) and bisphenol A or bisphenol A.

  The solid content mass of the core-shell type acrylic resin particles (A) is 50 to 99.9% by mass, preferably 70 to 99.5% by mass, based on the solid content mass of the aqueous coating composition for can coating of the present invention. More preferably, it exists in the range of 80-99 mass%. If the solid content mass of the core-shell type acrylic resin particles (A) is less than 50 mass% or more than 99.9 mass%, the retort whitening resistance and corrosion resistance of the resulting coating film may be inferior.

  The total mass of the resol type phenol resin (C1) and the amino resin (C2) is 0.1 to 10% by mass, preferably 0.5 to 9 based on the solid content mass of the core-shell type acrylic resin particles (A). It is in the range of 1% to 7% by mass, more preferably 1% by mass. If the total mass of the resol type phenolic resin (C1) and amino resin (C2) is less than 0.1% by mass, the resulting coating film may be inferior in retort whitening resistance and corrosion resistance, and more than 10% by mass. If it is large, the resulting coating film may be inferior in retort whitening resistance and workability.

  The aqueous coating composition for can coating of the present invention may contain an aqueous polymer (D) or the like as desired. The aqueous polymer (D) can be used within a range of 20% by mass or less based on the solid content mass of the core-shell type acrylic resin particles (A). When the usage-amount of an aqueous polymer (D) is more than 20 mass%, the retort whitening resistance of the coating film obtained may fall.

  The core-shell type acrylic resin particles (A) can be used by neutralizing a part or all of acid groups such as carboxyl groups with a basic compound. Moreover, when an aqueous polymer (D) has acid groups, such as a carboxyl group and a sulfonic acid group, you may neutralize and use a part or all of an acid group with a basic compound.

  As the basic compound that can be used for the neutralization, known inorganic bases and organic bases can be used. For example, inorganic base compounds such as ammonia, sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate; trimethylamine, Examples thereof include alkylamines such as triethylamine and butylamine, alcohol amines such as dimethylaminoethanol, diethanolamine and aminomethylpropanol, polyvalent amines such as ethylenediamine and diethylenetriamine, and organic base compounds such as morpholine. The basic compound is suitable from the viewpoint of the water resistance of the coating film from which ammonia or volatile amines can be obtained.

  The water-based coating composition for can coating of the present invention may be used by appropriately mixing conventionally known raw materials such as organic solvents, antifoaming agents, surfactants, lubricants, waxes, pigments and the like as necessary. Can do.

  Examples of the organic solvent that can be used in the present invention include methanol, ethanol, n-propanol, isopropanol, n-butanol, sec-butanol, tert-butanol, isobutanol, amyl alcohol, n-hexanol, octanol, Alkyl alcohols such as 2-ethylhexyl alcohol; glycol ethers such as methyl cellosolve, ethyl cellosolve, propyl cellosolve, butyl cellosolve, hexyl cellosolve, methyl carbitol, ethyl carbitol, butyl carbitol; or methyl cellosolve acetate, ethyl cellosolve acetate Glycol ether esters such as dioxane, dimethylformamide, tetrahydrofuran, methyl ethyl ketone, methyl isobutyl Ketone, etc. can be mentioned diacetone alcohol, which may be used in combination of two or more.

  Examples of the antifoaming agent include acrylic, vinyl ether, dimethylpolysiloxane, and the like, and two or more of these can be used in combination.

  The water-based coating composition for can coating of the present invention can be applied to various substrates, for example, untreated or surface-treated metal plates such as aluminum plates, steel plates and tin plates, and epoxy to these metal plates. Examples thereof include a metal plate coated with a primer such as a base or vinyl, and those obtained by processing these metal plates into cans.

  The form of the can to which the aqueous coating composition for can coating of the present invention is applied is a two-piece can composed of two parts, a lid part and a body part integrated with the bottom part, or a lid part, a bottom part, and a body part. 3 piece cans, bottle cans, and the like comprising these three parts can be mentioned, and the water-coating composition for can coating of the present invention can be applied to each of the above parts. Since the film obtained from the aqueous coating composition for can coating according to the present invention is excellent in processability and corrosion resistance, it is suitable for coating a lid portion that repeatedly undergoes uneven changes in the production process of beverage cans and the like.

  Further, the aqueous coating composition for can coating of the present invention may be used for repair coating of the seam portion (joint portion) on the inner surface of the can, and coating of the outer surface of the can such as an outer surface of a can lid or a tab.

  Various known methods such as roll coater coating, spray coating, dip coating, electrodeposition coating, and the like can be applied as a method for coating the base material with the aqueous coating composition for can coating of the present invention. Of these, roll coater coating or spray coating is preferred. The coating thickness may be appropriately selected depending on the intended use, but is usually preferably about 3 to 20 μm in terms of dry film thickness. As the drying conditions of the coated film, it is usually within the range of 10 seconds to 30 minutes, preferably at 200 to 280 ° C. for 15 seconds to 10 minutes under the condition that the maximum material arrival temperature is 120 to 300 ° C. Good.

Next, an Example is given and this invention is demonstrated more concretely. Here, “parts” and “%” mean “parts by mass” and “% by mass”, respectively. In addition, the mass part of the raw material in the following production examples and examples represents the mass part of the active ingredient of the raw material (or may be described as solid content), and the value of the amount of each raw material used in the table is the raw material It represents the mass of the active ingredient (or may be described as solid content).
Manufacture of core-shell type acrylic resin particles (A)
(Production Example 1)
Preparation of emulsion of core monomer mixture (a1-1)
27 parts of deionized water, 0.4 part of “NIKKOL TL-10”, 9.7 parts of styrene, 5 parts of methyl methacrylate, 5 parts of isobutyl methacrylate, 10 parts of ethyl acrylate, 14.9 parts of 2-ethylhexyl acrylate, 2-hydroxy 1 part of ethyl acrylate, 3.9 parts of methacrylic acid, 0.5 part of 1,6-hexanediol diacrylate, and 0.05 part of ammonium persulfate are mixed and stirred to obtain an emulsion of the core monomer mixture (a1-1). Obtained.

Preparation of emulsion of shell monomer mixture (a2-1)
27 parts of deionized water, 0.5 part of “NIKKOL TL-10”, 20 parts of styrene, 10 parts of methyl methacrylate, 5 parts of isobutyl methacrylate, 5 parts of ethyl acrylate, 5.1 parts of 2-ethylhexyl acrylate, 2-hydroxyethyl acrylate 1 part, 3.9 parts of methacrylic acid, and 0.05 part of ammonium persulfate were mixed and stirred to obtain an emulsion of the shell monomer mixture (a2-1).

  A reaction vessel equipped with a heating and cooling device and equipped with a stirrer, a thermometer, a thermostat, a reflux condenser, a nitrogen introduction tube and a dropping device was attached with 95 parts of deionized water and 0.1 ‘NIKKOL TL-10’. The contents were heated to 85 ° C. while stirring and mixing under a nitrogen stream. Next, an amount corresponding to 4% of the total mass of the emulsion of the core monomer mixture (a1-1) and 1 part of a 5% ammonium persulfate aqueous solution were added with stirring, and the mixture was kept at 85 ° C. for 15 minutes. Thereafter, while maintaining the temperature at 85 ° C., the entire remaining amount of the emulsion of the core monomer mixture (a1-1) was dropped over 2 hours and aged for 1 hour.

  Thereafter, while maintaining the temperature of the content at 85 ° C., the emulsion of the shell monomer mixture (a2-1) was added dropwise over 2 hours, and after aging for 2 hours, 2- (dimethylamino) ethanol was added to the content. 5 parts were added. Through the above steps, a dispersion of core-shell acrylic resin particles A-1 neutralized with 2- (dimethylamino) ethanol was obtained.

  The obtained core-shell type acrylic resin particles A-1 are core-shell type acrylic resin particles having a cross-linked core part, and the average particle size is 230 nm (submicron particle size distribution measuring device “COULTER N4 type” (manufactured by Beckman Coulter, Inc.). Used, diluted with deionized water and measured at 20 ° C.), and the solids concentration of the dispersion was 40% by weight. The acid value of the solid content of the core-shell type acrylic resin particles A-1 was 50 mgKOH / g.

(Production Examples 2-33, Comparative Production Examples 1, 5-11)
Except having changed the composition of the emulsion of a core monomer mixture (a1-1) and the emulsion of a shell monomer mixture (a2-1) as shown to Table 1-1 to 1-3, it is the same as that of manufacture example 1. Thus, dispersions of core-shell type acrylic resin particles A-2 to A34 and A-38 to A44 were obtained.

(Comparative Production Example 2)
50 parts of deionized water, 1 part of "L-1695", 20 parts of styrene, 20 parts of methyl methacrylate, 10 parts of isobutyl methacrylate, 30 parts of ethyl acrylate, 10 parts of 2-ethylhexyl acrylate, 2 parts of 2-hydroxyethyl acrylate, methacrylic acid 7.8 parts, 0.2 part of 1,6-hexanediol diacrylate, and 0.05 part of ammonium persulfate were mixed and stirred to obtain an emulsion of the monomer mixture.

  A reaction vessel equipped with a heating and cooling device and equipped with a stirrer, thermometer, thermostat, reflux condenser, nitrogen introduction pipe and dropping device was attached with 95 parts of deionized water and 0.1 part of "L-1695". The contents were heated to 85 ° C. while stirring and mixing under a nitrogen stream. Next, an amount corresponding to 2% of the total mass of the emulsion of the monomer mixture and 1 part of a 5% aqueous ammonium persulfate solution were added with stirring, and the mixture was held at 85 ° C. for 15 minutes. Thereafter, while the temperature was maintained at 85 ° C., the entire remaining amount of the emulsion of the monomer mixture was dropped over 4 hours and aged for 1 hour.

  The obtained single-layer acrylic resin particles A-35 are cross-linked single-layer acrylic resin particles having an average particle size of 200 nm (submicron particle size distribution measuring device “COULTER N4 type” (manufactured by Beckman Coulter, Inc.). The sample was diluted with deionized water and measured at 20 ° C.), and the solid content concentration of the dispersion was 40% by mass. The acid value of the single-layer acrylic resin particles A-35 was 50 mgKOH / g.

(Comparative Production Example 3)
Single-layer acrylic resin particles A-36 were obtained in the same manner as in Comparative Production Example 2 except that the formulation described in Table 1-3 was changed.

(Comparative Production Example 4)
Single-layer acrylic resin particles A-37 were obtained in the same manner as Comparative Production Example 2 except that the formulation was changed to the formulation shown in Table 1-3.

  Resin acid value and particle diameter of core-shell type acrylic resin particles and single-layer type acrylic resin particles obtained in the above production examples and comparative production examples, core Tg of core-shell type acrylic resin particles, shell Tg, core portion and shell portion, The mass ratios are shown in Tables 1-1 to 1-3.

  Moreover, evaluation about the manufacturing stability of each acrylic emulsion particle was also described in Table 1-1 to 1-3. The evaluation criteria are as follows.

  ◯: Abnormalities such as aggregation and blisters are not visually observed in the obtained emulsion, and there is no contamination that becomes a problem in washing the reactor at the contact portion with the emulsion of the reactor after discharging the emulsion.

  ○ △: Abnormalities such as aggregation and irregularities are not visually observed in the obtained emulsion, but the reactor is washed because some agglomerates are seen in the contact portion with the emulsion after discharging the emulsion. The time will be longer. This is an industrially feasible range.

  X: Abnormalities such as aggregation and irregularities are visually observed in the obtained emulsion, and / or aggregates are seen in the contact portion with the emulsion of the reactor after discharging the emulsion, and the washing time of the reactor is long. Become. There is a problem with industrial implementation.

In addition, (Note 1) to (Note 13) in Tables 1-1 to 1-3 are as described below.
(Note 1) NIKKOL TL-10: Polyoxyethylene sorbitan fatty acid ester, HLB value: about 16.9, manufactured by Nikko Chemicals (Note 2) S-770: Sucrose stearate, HLB value: about 7, Mitsubishi Chemical Foods (Note 3) S-970: Sucrose stearate, HLB value: approx. 9, Mitsubishi Chemical Foods (Note 4) L-1695: Sucrose laurate, HLB value: approx. 16, Mitsubishi Chemical Foods Co., Ltd. (Note 5) Poem J-0021: Decaglycerin laurate, HLB value: about 15.5, Riken Vitamin Co., Ltd. (Note 6) Decaglyn 2-SV: Polyglyceryl distearate, HLB value: about 9. 5, manufactured by Nikko Chemicals Co., Ltd. (Note 7) Adeka Soap ER-40: radical reactive nonionic surfactant, HLB value: about 17.2 Manufactured by ADEKA (Note 8) New Coal 714-SF: polyoxyethylene polycyclic phenyl ether sulfate ester salt (anionic surfactant), manufactured by Nippon Emulsifier Co., Ltd. (Note 9) DDBSA ammonium: ammonium dodecylbenzenesulfonate (anion) Surfactant)
(Note 10) Neoperex G-15: Sodium alkylbenzene sulfonate (anionic surfactant), manufactured by Kao Corporation (Note 11) Antox MS-2N: 2-sodium sulfoethyl methacrylate, manufactured by Nippon Emulsifier (Note 12) ) VA-086: 2,2′-azobis [2-methyl-N- (2-hydroxyethyl) propionamide] (water-soluble azo polymerization initiator), interface used for production by Wako Pure Chemical Industries, Ltd. (Note 13) % By weight of nonionic surfactant based on total weight of activator

Production of aqueous polymer (D-1) (Production Example 45)
A reaction vessel equipped with a heating and cooling device, equipped with a stirrer, thermometer, thermostat, reflux condenser, nitrogen inlet tube and dropping device was charged with 130 parts of propylene glycol n-propyl ether and stirred and mixed in a nitrogen stream. While the contents were heated to 100 ° C. Thereafter, a radical polymerizable unsaturated monomer mixture (methyl methacrylate 30 parts, butyl methacrylate 13 parts, styrene 10 parts, ethyl acrylate 17 parts, methacrylic acid 20 parts and N-butoxymethylacrylamide 10 parts) and a polymerization initiator solution (t -A mixture of 2 parts of butyl peroxy-2-ethylhexanoate and 20 parts of propylene glycol npropyl ether) was dropped into the reactor with a metering pump over 4 hours. Aged for 0.5 hours. Subsequently, a polymerization initiator solution (mixed solution of 0.5 part of t-butylperoxy-2-ethylhexanoate and 20 parts of propylene glycol n-propyl ether) was dropped over 0.5 hour, and after completion of the dropping Aged for 2 hours. Thereafter, 13 parts of N, N-dimethylaminoethanol was added and stirred. And it cooled to room temperature and obtained the solution of acrylic-based aqueous resin (D-1) with a solid content of 40 mass%. The acrylic aqueous resin (D-1) had a glass transition temperature of 30 ° C., an acid value of 130 mgKOH / g, and a weight average molecular weight of 30,000.

Water-based paint composition (E-1 to 53)
Example 1
The dispersion of core-shell type acrylic resin particles A-1 having a solid content of 40% by mass obtained in Production Example 1 was 250 parts (solid content 100 parts) and “CKS-3898” having a solid content of 50% by mass (trade name, Showa) 10 parts (represented as “5” of solid content 5 parts in Table 2-1) and 15 parts of butyl cellosolv are mixed while stirring with a disper. The solid content was adjusted by adding deionized water to obtain an aqueous coating composition E-1 having a solid content of 20% by mass.

(Examples 2 to 40, Comparative Examples 1 to 13)
In the same manner as in Example 1, each component and butyl cellosolve were mixed with stirring according to the respective formulations shown in Tables 2-1 to 2-4 below, and deionized water was added to the mixed mixture to adjust the solid content. Then, aqueous coating compositions E-2 to E53 having a solid content of 20% by mass were produced. In addition, the compounding quantity of each component in a table | surface is based on the amount of solid content or the amount of active ingredients. The curing agent “Cymel 303” in the table is a methyl etherified melamine resin manufactured by Mitsui Chemicals.

  (Note 14) in the table is “71ADDITIVE” (product name, polyether-modified silicone-based antifoaming agent, manufactured by Toray Dow Corning).

Preparation of test coating plate Each water-based coating composition obtained in the above examples and comparative examples was dried on a # 5021 aluminum plate having a thickness of 0.25 mm and subjected to phosphoric acid chromate treatment, resulting in a dry coating thickness of 5 μm. Thus, the bar coater was applied and cured by baking at 200 ° C. for 1 minute to obtain a test coating plate. The performance test was performed according to the following test method. The evaluation of the test results is shown in Tables 2-1 to 2-4. In the evaluation, those in the range of ◎, ○, ○ △ were judged to be practical, and those in the range of Δ, × were judged to be rejected.

[Storage stability]
The paint conditions after the water-based paints of Examples and Comparative Examples were stored at 45 ° C. for 2 months were evaluated according to the following criteria.
A: No abnormality
○: Slight oil droplets are observed by observation with a transmission microscope of 100 times magnification
Δ: Oil droplets are visually observed
×: Oil droplets are significantly generated [T-bend bending workability]
The test coating plate was cut 5 cm in the rolling direction and 4 cm in the vertical direction, and then the lower part was folded in parallel with the short side. Two aluminum plates having a thickness of 0.26 mm were sandwiched between bent portions of the test piece of the test coating plate in a room at 20 ° C., and set in a special goby folding type DuPont impact tester. After dropping a weight of 1 kg of iron with a flat contact surface from a height of 50 cm and giving an impact to the bent portion, the bent tip portion was energized at an applied voltage of 6.5 V for 6 seconds, A current value (mA) of 20 mm width at the bent tip was measured and evaluated according to the following criteria.
: Less than 10 mA
○: 10 mA or more and less than 20 mA
○ △: 20 mA or more and less than 40 mA
Δ: 40 mA or more and less than 80 mA
×: 80 mA or more [Retort whitening resistance (may be referred to as “water resistance” in this specification)]
The test coating plate was immersed in water and treated in an autoclave at 125 ° C. for 30 minutes, and then the whitening state of the coating film was visually observed and evaluated according to the following criteria.

A: No whitening is observed
○: Partial whitening is slightly observed
○ △: Slight whitening is observed overall
Δ: Fair whitening is observed
×: Remarkably whitening is observed [corrosion resistance]
The test plate is immersed in a mixed aqueous solution in which 3% each of citric acid, malic acid and sodium chloride are dissolved and stored at 45 ° C. for 4 weeks. The coated surface is visually observed and evaluated according to the following criteria. did.
◎: No gloss or corrosion
○: There is gloss, but no corrosion is observed
○ △: Slight corrosion is observed
Δ: Corrosion is considerably observed
×: Corrosion is remarkable [feathering resistance (film remaining resistance)]
The test coating plate was made into a lid using a lid-making press to produce a can lid having a coating surface on the inner surface side. The prepared can lid is immersed in boiling water at 100 ° C. for 10 minutes, and then the opening piece (tab) provided on the top surface of the can lid is pulled upward with the coating film surface facing downward. The part was opened. And the peeling width of the coating film from the opening edge part of the opening part was measured, and the following reference | standard evaluated. In addition, evaluation of (double-circle) (triangle | delta) is a practical range.
A: Maximum peel width of the coating film is less than 0.2 mm,
○: The maximum peel width of the coating film is 0.2 mm or more and less than 0.4 mm,
○ △: The maximum peel width of the coating film is 0.4 mm or more and less than 0.5 mm,
Δ: The maximum peel width of the coating film is 0.5 mm or more and less than 1.0 mm,
X: The maximum peeling width of the coating film is 1.0 mm or more

Claims (15)

Manufactured using raw materials containing bisphenol A or bisphenol A, including core-shell type acrylic resin particles (A) comprising a shell part and a cross-linked core part, and resol type phenol resin (C1) and / or amino resin (C2). An aqueous coating composition for can coating that does not contain a resin, wherein the core-shell type acrylic resin particles (A) are produced by emulsion polymerization of a polymerizable unsaturated monomer using a nonionic surfactant, and The glass transition temperature of the acrylic resin constituting the shell portion is in the range of 35 to 105 ° C., and the glass transition temperature of the acrylic resin constituting the core portion is in the range of −10 to 25 ° C., and the core shell Of resol-type phenolic resin (C1) and amino resin (C2) based on the solid content mass of the acrylic resin particles (A) The solid content mass of the core-shell type acrylic resin particles (A) is 50 to 99.9, based on the solid content mass of the water-based coating composition for can coating, and having a mass in the range of 0.1 to 10 mass%. An aqueous coating composition for can coating, characterized by being in the range of mass%. The aqueous coating composition for can coating according to claim 1, wherein the mass of the core part in the core-shell type acrylic resin particles (A) is in the range of 10 to 90% by mass based on the total mass of the core part and the shell part. . The aqueous coating composition for can coating according to claim 1 or 2, wherein the nonionic surfactant has an HLB value in the range of 6 to 20. The nonionic surfactant is at least one selected from the group consisting of polyglycerin fatty acid esters, sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters, sucrose fatty acid esters, and polyoxyethylene fatty acid esters. The aqueous coating composition for can coating according to any one of claims 1 to 3. The can coating according to any one of claims 1 to 4, wherein the nonionic surfactant has a linear or branched, saturated or unsaturated fatty acid ester group having 10 or more carbon atoms. Water-based paint composition. The core-shell type acrylic resin particles (A) are produced by emulsion polymerization of a polymerizable unsaturated monomer using a nonionic surfactant and an anionic surfactant, the nonionic surfactant and an anion The water-based coating composition for can coating according to any one of claims 1 to 5, wherein a mass ratio with the surfactant is in a range of 15/85 to 99/1. The core-shell type acrylic resin particles (A) are produced by emulsion polymerization of a polymerizable unsaturated monomer using a nonionic surfactant and an anionic surfactant, and the core-shell type acrylic resin particles (A) The aqueous coating composition for can coating according to claim 6, wherein the mass of the anionic surfactant is within a range of 1.0% by mass or less based on the solid content mass of the can. The crosslinked core portion in the core-shell type acrylic resin particles (A) reacts with a polymerizable unsaturated monomer having two or more polymerizable unsaturated groups in one molecule and / or complementarily to form a covalent bond. It is formed by emulsion polymerization using a polymerizable unsaturated monomer mixture containing a polymerizable unsaturated monomer each having a functional group other than an unsaturated group. A water-based coating composition for can coating as described in 1. The core-shell type acrylic resin particles (A) are obtained by chemically bonding a part of the acrylic resin constituting the core part of the particle and a part of the acrylic resin constituting the shell part. The aqueous coating composition for can coating according to any one of the above. The water-based paint composition for can coating according to any one of claims 1 to 9, wherein the core-shell type acrylic resin particles (A) have a crosslinking reactive functional group. The aqueous coating composition for can coating according to any one of claims 1 to 10, wherein the aqueous coating composition for can coating is an aqueous coating composition for can inner surface coating. The aqueous coating composition for can coating according to any one of claims 1 to 10, wherein the aqueous coating composition for can coating is an aqueous coating composition for can outer surface coating. A coated can which is coated with the aqueous coating composition for can coating according to any one of claims 1 to 12. A coated can, wherein the inner surface of the lid of the can is coated with the aqueous coating composition for can coating according to any one of claims 1 to 11. A coated can in which the outer surface of the lid of the can is coated with the aqueous coating composition for can coating according to any one of claims 1 to 10 and 12.