JP2018197303A - Aqueous coating composition - Google Patents

Abstract

To provide an aqueous coating composition excellent in corrosion resistance, retort resistance, and painting workability, and particularly suitable for can inner surface application dispensing with a raw material containing a law-regulated substance such as bisphenol A.SOLUTION: The aqueous coating composition includes: a polyolefin resin aqueous dispersion (A); tannin (B); and an alkali-swelling type viscosity adjustment agent (C) where solid contents of a constituent (B) and a constituent (C) to a total solid content of the polyolefin resin aqueous dispersion (A) consist 0.1-10 mass% of the constituent (B), and 0.1-5 mass% of the constituent (C).SELECTED DRAWING: None

Description

  The present invention relates to a coating composition that is excellent in corrosion resistance, retort resistance, and coating workability, and is particularly suitable for a can inner surface coating.

  Various coating compositions such as epoxy-based, polyvinyl chloride-based, and polyester-based coating materials have been used as coatings for the inner surface of cans from the viewpoints of coating performance such as corrosion resistance and coating workability. In particular, a coating composition containing an epoxy resin produced using a raw material containing bisphenol A or the like as a base resin has been widely used.

  However, a coating composition for the inner surface of a can that does not use a raw material containing bisphenol A (BPA) (including a raw material that can contain a residual level of BPA) is desired from the viewpoint of impact on the environment. A coating composition using a vinyl resin or an acrylic resin described in 2 or 3 as a base resin is disclosed.

  In recent years, laws and regulations that extend and strengthen the scope of regulated substances not only for BPA and the like but also for styrene, formaldehyde, isocyanate and the like are being enacted particularly in Europe and the United States.

  In the present situation where the number of substances subject to regulation increases and the degree of freedom of selection of raw materials that can be used in the coating composition is limited, polyolefin resin is one of the leading substrates for the coating composition for can inner surfaces. .

  Furthermore, water-based paints are being developed from the viewpoint of reducing organic solvents for can inner coatings.

  As a coating composition for a can inner surface using a polyolefin resin as a base resin, Patent Document 4 discloses a coating composition comprising an aqueous dispersion containing polyolefin and a stabilizing solvent composition containing alcohol as constituents. Has been.

  However, the coating composition described in Patent Document 4 is excellent in storage stability, but has insufficient corrosion resistance and painting workability.

JP-A-2005-120306 JP 2005-179491 A Japanese Unexamined Patent Publication No. 2016-113561 JP-T-2006-501291

  The problem to be solved by the present invention is to provide a coating composition that is excellent in corrosion resistance, retort resistance and painting workability, particularly suitable for use on the inner surface of a can, without using a raw material containing a regulated substance such as bisphenol A. Is to provide.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have developed an aqueous coating composition containing a polyolefin resin aqueous dispersion (A), a tannin (B), and an alkali swelling type viscosity modifier (C). According to this, the present inventors have found that the above problems can be solved, and have completed the present invention.

  That is, the present invention relates to the following contents.

1. Containing polyolefin resin water dispersion (A), tannin (B), and alkali swelling viscosity modifier (C),
The solid content of the component (B) and the component (C) is 0.1 to 10% by mass of the component (B) and 0.1% of the component (C) with respect to the total solid content of the polyolefin resin aqueous dispersion (A). A water-based coating composition, characterized in that it is ˜5% by mass.

  2. Item 2. The aqueous coating composition according to Item 1, wherein the solid content of polypropylene is 50% by mass or more of the total solid content of the polyolefin resin aqueous dispersion (A).

  3. Item 3. The aqueous coating composition according to Item 1 or 2, wherein the tannin (B) is tannic acid.

  4). Further, the crosslinking agent (D) having two or more functional groups that react with carboxyl groups in the molecule is contained in an amount of 0.1 to 10% by mass in terms of the solid content based on the total solid content of the polyolefin resin aqueous dispersion (A). Item 4. The aqueous coating composition according to any one of Items 1 to 3, which is characterized by the above.

  The aqueous coating composition of the present invention is excellent in corrosion resistance because it further contains a tannin compound in addition to the polyolefin as the base resin. In addition, since the water-based coating composition of the present invention also contains an alkali swelling type viscosity modifier, it is possible to reduce the occurrence of sagging and brazing, which is a problem in spray coating, etc. Is also excellent.

  As described above, according to the present invention, it is possible to provide an aqueous coating composition that is excellent in both coating film performance and painting workability, particularly for can inner surface applications.

  This invention contains polyolefin resin water dispersion (A), tannin (B), and an alkali swelling type viscosity regulator (C), and it is a component (B with respect to solid content total amount of polyolefin resin water dispersion (A). ) And the component (C) have a solid content of 0.1 to 10% by mass of the component (B) and 0.1 to 5% by mass of the component (C) (hereinafter abbreviated as the present paint). ).

  Hereinafter, the contents of the present invention will be described in detail.

[Water-based paint composition]
Polyolefin resin water dispersion (A)
The aqueous polyolefin resin dispersion (A) in the aqueous coating composition of the present invention is a dispersion in which the polyolefin resin is present in a form dispersed in a medium containing water as a main component.

  The polyolefin resin is not particularly limited, and examples thereof include polyethylene, polypropylene, poly-1-butene, poly-3-methyl-1-butene, poly-3-methyl-1-pentene, and poly-4-methyl-1- Ethylene, propylene, 1-butene, 3-methyl-1-butene, 4-methyl-1-, as represented by pentene, ethylene-propylene copolymer, ethylene-1-butene copolymer, and propylene-1-butene copolymer Homopolymers and copolymers (including elastomers) of one or more α-olefins such as pentene, 3-methyl-1-pentene, 1-heptene, 1-hexene, 1-octene, 1-decene, and 1-dodecene, As represented by ethylene-butadiene copolymer and ethylene-ethylidene norbornene copolymer One α-olefin copolymer (including elastomers) having a conjugated or non-conjugated diene, and ethylene-propylene-butadiene copolymer, ethylene-propylene-dicyclopentadiene copolymer, ethylene-propylene-1,5-hexadiene copolymer, and ethylene Polyolefins (including elastomers), such as copolymers of two or more α-olefins with conjugated or nonconjugated dienes, as may be represented by propylene-ethylidene norbornene copolymers, ethylene-vinyl acetate copolymers, ethylene-vinyl alcohol copolymers, Ethylene such as ethylene-vinyl chloride copolymer, ethylene-acrylic acid copolymer, ethylene-methacrylic acid copolymer, and ethylene- (meth) acrylate copolymer Vinyl compounds copolymers and the like.

  In the present specification, “(meth) acrylate” means “acrylate or methacrylate”. “(Meth) acrylamide” means “acrylamide or methacrylamide”.

  Polyolefin resin can be used individually by 1 type or in combination of 2 or more types.

  In this coating material, it is preferable from a corrosion-resistant viewpoint that solid content of a polypropylene is 50 mass% or more among solid content total amount of polyolefin resin water dispersion (A).

  The polyolefin resin may have a functional group such as hydroxyl group, amino group, aldehyde group, epoxy group, ethoxy group, carboxyl group, ester group, and anhydride group, or two or more of these functional groups. .

  The polyolefin resin aqueous dispersion (A) can also contain a stabilizer from the viewpoint of stability (for example, promotion of water dispersion formation).

  Examples of the stabilizer include a surfactant and a polymer. One stabilizer can be used alone, or two or more stabilizers can be used in combination.

  Examples of the surfactant include an anionic surfactant, a cationic surfactant, and a nonionic surfactant.

  Examples of the anionic surfactant include sulfonate, carboxylate, and phosphate.

  Examples of the cationic surfactant include a quaternary amine salt.

  Examples of nonionic surfactants include nonionic group-containing polymers such as polyoxyalkylene and silicone surfactants.

  As the surfactant, a reactive surfactant having reactivity with the polyolefin resin can also be used.

  Examples of the polymer include a polar polymer having a polar group.

  Examples of the polar polymer include those based on resins such as acrylic resin, polyester resin, epoxy resin, polyamide resin, acrylic modified polyester resin, and acrylic modified epoxy resin.

  A polyolefin resin having a polar group can also be used as the polar polymer. Examples of the functional group having polarity include a hydroxyl group, amino group, aldehyde group, epoxy group, ethoxy group, carboxyl group, ester group, and anhydride group.

  In addition, as the stabilizer, for example, a long chain fatty acid having 12 to 60 carbon atoms, a fatty acid salt, a fatty acid alkyl ester, an ethylene-acrylic acid resin, or the like can be used.

  When a stabilizer is used, the solid content of the stabilizer varies depending on the type of the stabilizer, but from the viewpoint of storage stability, it is 5 to 35% by mass, particularly with respect to the total solid content of the polyolefin resin. It is preferably within the range of 10 to 30% by mass.

  The polyolefin resin aqueous dispersion (A) can be obtained by adding a basic compound as a neutralizing agent as necessary and dispersing in water.

  Examples of basic compounds include hydroxides, carbonates, amines, and the like.

  Examples of the hydroxide include ammonium hydroxide, potassium hydroxide, lithium hydroxide, sodium hydroxide and the like.

  Examples of the carbonate include sodium carbonate, sodium hydrogen carbonate, potassium carbonate, calcium carbonate, and the like.

  Examples of the amine include monoethanolamine, diethanolamine, triethanolamine, ammonia, monomethylamine, dimethylamine, trimethylamine, 2-amino-2-methyl-1-propanol, triisopropanolamine, diisopropanolamine, N, N- Dimethylethanolamine, mono-n-propylamine, dimethyl-npropylamine, N-methanolamine, N-aminoethylethanolamine, N-methyldiethanolamine, monoisopropanolamine, N, N-dimethylpropanolamine, 2-amino- 2-methyl-1-propanol, tris (hydroxymethyl) -aminomethane, N, N, N′N′-tetrakis (2-hydroxylpropyl) ethylenediamine, 1.2-diaminopropa 2-amino-2-hydroxymethyl-1,3-propanediol, N, N'-ethylenebis [bis (2-hydroxypropyl) amine] can be mentioned toluene -p- sulfonate and the like.

  The basic compound is preferably an amine from the viewpoint of water resistance.

  The polyolefin resin aqueous dispersion (A) can be produced by a known method. Specifically, it can be produced, for example, by adding at least one polyolefin resin, water, if necessary, a stabilizer, a neutralizing agent (basic compound) and the like, and melt-kneading.

  As a specific production procedure, for example, in the presence of water and one or more neutralizing agents, one or more polyolefin resins, and if necessary, one or more stabilizers are melt-mixed and melt-mixed. An aqueous dispersion can be produced by forming an emulsified mixture and contacting the emulsified mixture with further diluted water while removing heat as necessary to form particles dispersed in water.

  The average particle size of the solid content of the polyolefin resin aqueous dispersion (A) is preferably in the range of 100 to 1000 nm, particularly 110 to 900 nm, more particularly 120 to 800 nm, from the viewpoint of coating workability.

  The average particle size can be measured by a particle size measuring device, for example, Coulter model N4MD (trade name, manufactured by Beckman Coulter, Inc.).

Tannin (B)
Tannin is a term including tannic acid, catechin, gallic acid, etc., and is a general term for water-soluble compounds derived from plants in general, and reacts with metal ions, alkaloids, proteins, etc., hardly soluble salts, complexes, or It is a compound that forms a complex.

  In the aqueous coating composition of the present invention, the tannin can improve the corrosion resistance of the obtained coating film.

  Tannin is a general term for natural polyhydric phenols, which can be roughly classified into hydrolyzable tannin (pyrogallol-type tannin) and condensed tannin (catechol-type tannin).

  Examples of the hydrolyzable tannin include tannic acid such as pentaploid tannin and gallic tannin.

  Examples of the condensed tannin include catechol polymers such as mimosa tannin and salmon tannin.

  Among the above, hydrolyzable tannin is preferable from the viewpoint of corrosion resistance.

  In particular, the crosslinked composition has a higher molecular weight than the raw material tannin and lowers the solubility in water, and therefore, tannic acid having a low molecular weight is preferable.

The tannic acid is not particularly limited, and examples thereof include hameli tannin, oyster tannin, chatannin, pentaploid tannin, gallic tannin, mylobarantannin, dibidi tannin, argarovira tannin, valonia tannin, catechin tannin and the like.
A commercial item can be used as tannic acid. Specifically, for example, “tannic acid extract A”, “B tannic acid”, “N tannic acid”, “industrial tannic acid”, “purified tannic acid”, “Hi tannic acid”, “F tannic acid”, “Local tannic acid” (all manufactured by Dainippon Pharmaceutical Co., Ltd.), “Tannic acid: AL” (manufactured by Fuji Chemical Industry Co., Ltd.) and the like can be mentioned.

  The solid content of the tannin (B) varies depending on the type of tannin, but from the viewpoint of corrosion resistance, the solid content of the tannin (B) is 0.1 to 10% by mass, particularly 0.2%, based on the total solid content of the polyolefin resin aqueous dispersion (A). It is preferable to be within the range of -0.9 mass%.

Alkali swelling viscosity modifier (C)
The alkali swelling type viscosity modifier is generally a vinyl polymer containing an acid group, and is dissolved or swelled in water by being neutralized with an alkaline substance to impart shear thinning and exhibit thickening.

  The vinyl polymer emulsion is a low-viscosity liquid in the acidic region. By neutralizing the vinyl polymer emulsion with ammonia, an amine compound, an inorganic base, or the like, the vinyl polymer emulsion swells and imparts thickening.

  In the aqueous coating composition of the present invention, the alkali swelling viscosity adjusting agent can reduce problems such as sagging and cracking in spray coating, and can improve coating workability.

In the aqueous coating composition of the present invention, an alkali swelling type viscosity modifier is particularly preferably used from the viewpoint of coating workability.
The vinyl polymer may be crosslinked, or may be an uncrosslinked or partially crosslinked polymer.

  Examples of the thickener include Primer ASE-60, Primer ASE-75, Primer ASE-95NP, Primer ASE-108NP, Primer ASE-1000, Primer G-111 (above, Rohm and Haas) (Trade name, acrylic emulsion), Biscarex HV-30, Biscarex HM, Biscarex VS, Biscarex VG2 (above, Hoechst Synthesis Co., Ltd., trade name, acrylic emulsion), SN Sikuner 618, SN Examples include Sikuner 630, SN Sikuner 636, SN Sikuner 650 (manufactured by San Nopco, trade name, acrylic).

  The solid content of the alkali swelling viscosity modifier (C) varies depending on the type of the alkali swelling viscosity modifier, but from the viewpoint of coating workability, the total solid content of the polyolefin resin water dispersion (A) is: It is preferable to be within a range of 0.1 to 5% by mass, particularly 0.2 to 4% by mass, and more particularly 0.3 to 3% by mass.

  As the viscosity adjusting agent, known viscosity adjusting agents other than the alkali swelling type viscosity adjusting agent (C) can be used together as necessary.

  Specifically, polyether viscosity modifiers such as pluronic polyethers, polyether dialkyl esters, polyether dialkyl ethers, polyether epoxy modified products; urethane associative viscosity modifiers; montmorillonite, beidellite, nontronite, saponite, Inorganic viscosity modifiers such as hectorite, stevensite, mica, and bentonite; Fibrin derivative viscosity modifiers such as carboxymethylcellulose, methylcellulose, and hydroxyethylcellulose; Protein viscosity modifiers such as casein, sodium caseinate, and ammonium caseinate; Alginate-based viscosity modifiers such as sodium alginate; Polyvinyl-based viscosity modifiers such as polyvinyl alcohol, polyvinylpyrrolidone, and polyvinylbenzyl ether copolymers; Vinylmethyl ether - maleic anhydride copolymer viscosity modifier, such as a partial ester of maleic anhydride copolymer; may be mentioned polyamide-based viscosity modifiers such as polyamide amine salts and the like.

Cross-linking agent (D)
The crosslinking agent (D) is a compound having two or more functional groups that react with carboxyl groups in the molecule. The aqueous coating composition of the present invention can be contained as necessary in order to enhance the curability and improve the coating performance such as corrosion resistance, retort resistance, and water resistance of the resulting coating.

  Examples of the functional group that reacts with a carboxyl group include a hydroxyalkylamide group, an oxazoline group, an aziridine group, an imide group (particularly a carbodiimide group), an epoxy group, a hydroxyl group, and a methylol group.

Of the functional groups, a hydroxyalkylamide group is preferred from the viewpoint of storage stability.
Specific examples of the crosslinking agent include a hydroxyalkylamide crosslinking agent, an oxazoline crosslinking agent, an aziridine crosslinking agent, an imide (particularly carbodiimide group) crosslinking agent, and an epoxy crosslinking agent.

  Examples of the hydroxyalkylamide-based crosslinking agent include bis (N, N′-dihydroxyethyl) adipamide. Specifically, commercial products of EMS-GRILTECH, Switzerland, PRIMID (trademark) XL-522, PRIMID (trademark) SF-4510, and the like can be listed as PRIMID (trademark, trade name of crosslinking agent resin).

  Examples of the oxazoline-based crosslinking agent include 2-vinyl-2-oxazoline, 2-vinyl-4-methyl-2-oxazoline, 2-vinyl-5-methyl-2-oxazoline, 2-isopropenyl-2-oxazoline, A component containing a vinyl monomer containing an oxazoline group such as 2-isopropenyl-4-methyl-2-oxazoline, 2-isopropenyl-5-ethyl-2-oxazoline alone, or a vinyl monomer containing an oxazoline group and others And vinyl resins or acrylic resins copolymerized with the above monomers. Examples of commercially available products include Epocros WS-300, WS-500, WS-700, Epocros K-2010, K-2020, and K-2030 manufactured by Nippon Shokubai Co., Ltd.

  Examples of the aziridine-based crosslinking agent include glycerol-tris (1-aziridinylpropionate), glycerol-tris [2-methyl- (1-aziridinyl)] propionate, glycerol-tris [2-ethyl- ( 1-aziridinyl)] propionate, glycerol-tris [2-butyl- (1-aziridinyl)] propionate), glycerol-tris [2-propyl- (1-aziridinyl)] propionate, glycerol-tris [ 2-pentyl- (1-aziridinyl)] propionate, glycerol-tris [2-hexyl- (1-aziridinyl)] propionate, glycerol-tris [2,3-dimethyl- (1-aziridinyl)] propionate Glycerol-tris [2,3-diethyl- (1-aziridinyl ] Propionate, glycerol-tris [2,3-dibutyl- (1-aziridinyl)] propionate), glycerol-tris [2,3-dipropyl- (1-aziridinyl)] propionate, glycerol-tris [ 2,3-dipentyl- (1-aziridinyl)] propionate, glycerol-tris [2,3-dihexyl- (1-aziridinyl)] propionate, trimethylolpropane-tris (1-aziridinylpropionate) G), trimethylolpropane-tris [2-methyl- (1-aziridinyl)] propionate, trimethylolpropane-tris [2-ethyl- (1-aziridinyl)] propionate, trimethylolpropane-tris [2 -Butyl- (1-aziridinyl)] propionate), trimethylo Propane-tris [2-propyl- (1-aziridinyl)] propionate, trimethylolpropane-tris [2-pentyl- (1-aziridinyl)] propionate, trimethylolpropane-tris [2-hexyl- (1 -Aziridinyl)] propionate, trimethylolpropane-tris [2,3-dimethyl- (1-aziridinyl)] propionate, trimethylolpropane-tris [2,3-diethyl- (1-aziridinyl)] propionate Trimethylolpropane-tris [2,3-dibutyl- (1-aziridinyl)] propionate), trimethylolpropane-tris [2,3-dipropyl- (1-aziridinyl)] propionate, trimethylolpropane -Tris [2,3-dipentyl- (1-aziridinyl Propionate, trimethylolpropane-tris [2,3-dihexyl- (1-aziridinyl)] propionate tetramethylolmethane-tris (1-aziridinylpropionate), tetramethylolmethane-tris [2 -Methyl- (1-aziridinyl)] propionate, tetramethylolmethane-tris [2-ethyl- (1-aziridinyl)] propionate, tetramethylolmethane-tris [2-butyl- (1-aziridinyl)] propione -To), tetramethylolmethane-tris [2-propyl- (1-aziridinyl)] propionate, tetramethylolmethane-tris [2-pentyl- (1-aziridinyl)] propionate, tetramethylolmethane-tris [ 2-hexyl- (1-aziridinyl)] propione -Tetramethylolmethane-tris [2,3-dimethyl- (1-aziridinyl)] propionate, tetramethylolmethane-tris [2,3-diethyl- (1-aziridinyl)] propionate, tetramethylolmethane -Tris [2,3-dibutyl- (1-aziridinyl)] propionate), tetramethylolmethane-tris [2,3-dipropyl- (1-aziridinyl)] propionate, tetramethylolmethane-tris [2, 3-dipentyl- (1-aziridinyl)] propionate, tetramethylolmethane-tris [2,3-dihexyl- (1-aziridinyl)] propionate, pentaerythritol-tetra (1-aziridinylpropionate) ), Pentaerythritol-tetra [2-methyl- (1-aziridinyl) Propionate, pentaerythritol-tetra [2-ethyl- (1-aziridinyl)] propionate, pentaerythritol-tetra [2-butyl- (1-aziridinyl)] propionate), pentaerythritol-tetra [2 -Propyl- (1-aziridinyl)] propionate, pentaerythritol-tetra [2-pentyl- (1-aziridinyl)] propionate, pentaerythritol-tetra [2-hexyl- (1-aziridinyl)] propionate Pentaerythritol-tetra [2,3-dimethyl- (1-aziridinyl)] propionate, pentaerythritol-tetra [2,3-diethyl- (1-aziridinyl)] propionate, pentaerythritol-tetra [2, 3-dibutyl- (1-aziridinyl Propionate), pentaerythritol-tetra [2,3-dipropyl- (1-aziridinyl)] propionate, pentaerythritol-tetra [2,3-dipentyl- (1-aziridinyl)] propionate, pentaerythritol Tetra [2,3-dihexyl- (1-aziridinyl)] propionate, tetraaziridinylmetaxylenediamine, tetraaziridinylmethylparaxylenediamine, tetramethylpropanetetraaziridinylpropionate, neopentyl Glycol di (β-aziridinylpropionate), 4,4′-isopropylidenediphenol di (β-aziridinylpropionate), 4,4′-methylenediphenoldi (β-aziridinini) Lupropionate), 4,4'-bis (ethyleneiminocarbonyl) And amino) diphenylmethane.

  Examples of the imide-based (particularly carbodiimideimide group) crosslinking agent include 1,3-diisopropylcarbodiimide (that is, N, N-diisopropylcarbodiimide), N, N-dicyclohexylcarbodiimide, N-ethyl-N ′-(3-dimethyl). And carbodiimide derivatives such as aminopropyl) -carbodiimide / hydrochloride.

  As a crosslinking agent having a carbodiimide group, for example, carbodilite (trade name) manufactured by Nisshinbo Chemical Co., Ltd. can be used as a commercial product. Examples of carbodilite include water-soluble types “V-02”, “V-02-L2”, “SV-02”, “V-04”, “V-10”, “SW-12G”, etc. ), Emulsion type “E-02”, “E-03A”, “E-05”, etc. (all are product names).

  As the epoxy-based crosslinking agent, any known epoxy resin (compound) having at least two epoxy groups (glycidyl groups) in the molecule can be used without particular limitation, and alicyclic epoxy compounds are particularly suitable. Can be used for

  Commercially available products can be used as the alicyclic epoxy compound, and specific examples include Denacol (trade name) manufactured by Nagase ChemteX Corporation.

  Denacol is a bifunctional type of “EX-211”, “EX-212”, “EX-252”, “EX-810”, “EX-811”, “EX-850”, “EX-851”, “EX-821”, “EX-830”, “EX-832”, “EX-841”, “EX-861”, “EX-911”, “EX-941”, “EX-920”, “EX -931 ", etc. (all are product names), multifunctional types" EX-313 "," EX-314 "," EX-321 "," EX-411 "," EX-421 "," EX-512 " , “EX-521”, “EX-612”, “EX-614”, “EX-614B” and the like (all are product names).

  Examples of the crosslinking agent having a hydroxyl group include aliphatic alcohols such as glycerin, ethylene glycol pentaerythritol, pentaglycerol, and polyvinyl alcohol (hereinafter also referred to as PVA); alicyclic alcohols such as phloroglucitol, quercitol, and inositol. Aromatic sugars such as tris (hydroxy) benzene; sugars such as starch, D-erythrose, L-arabinose, D-mannose, D-galactose, D-fructose, L-rhamnose, saccharose, maltose, lactose; Bifunctional or higher polyhydric alcohols such as sugar alcohols such as L-arabit, adnit, and xylit;

  A crosslinking agent (D) can be used individually by 1 type or in combination of 2 or more types.

  When the cross-linking agent (D) is used, the solid content of the cross-linking agent varies depending on the type of the cross-linking agent, but from the viewpoint of retort resistance, the solid content of the polyolefin resin water dispersion (A) is 0%. 0.1 to 10% by mass, particularly 0.2 to 5% by mass is preferable.

  The aqueous coating composition of the present invention contains a medium containing water as a main component, and the solid content concentration is 10 to 30% by mass, particularly 15 to 25% by mass from the viewpoint of coating workability. Preferably there is.

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

  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, 2 Alkyl alcohols such as ethyl hexyl alcohol; methyl cellosolve, ethyl cellosolve, propyl cellosolve, butyl cellosolve, hexyl cellosolve, glycol ethers such as methyl carbitol, ethyl carbitol, butyl carbitol; or methyl cellosolve acetate, ethyl cellosolve acetate Glycol ether esters, etc., dioxane, dimethylformamide, tetrahydrofuran, methyl ethyl ketone, methyl isobutyrate Ketones, mention may be made of diacetone alcohol, and these may be used in combination of two or more.

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

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

  The form of the can to which the water-based coating composition of the present invention is applied includes two-piece cans composed of two parts, a body part integrated with a cover part and a bottom part, and three forms of a cover part, a bottom part, and a body part. Examples thereof include 3-piece cans, bottle cans and the like, and the aqueous coating composition of the present invention can be applied to each of the above-mentioned sites. Since the coating film obtained from the aqueous coating composition of the present invention is excellent in corrosion resistance and retort resistance, it is particularly suitable for coating the inner surface of a can such as a beverage can and a lid portion that repeatedly undergoes uneven changes in the manufacturing process. is there.

  The aqueous coating composition of the present invention can also 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 the outer surface of the can lid or a tab.

  As a method for coating the substrate with the aqueous coating composition of the present invention, various known methods such as roll coater coating, spray coating, dip coating, electrodeposition coating, and the like can be applied. 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 2 to 20 μm in terms of dry film thickness. As drying conditions for the coated film, it is usually preferable that the material reaching maximum temperature is 120 to 300 ° C. for 10 seconds to 30 minutes, particularly 200 to 280 ° C. for 15 seconds to 10 minutes. .

  Hereinafter, the present invention will be described more specifically by way of examples. 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, examples and comparative examples represents the mass part of the solid content (or may be described as an active ingredient) of the raw material, and the value of the amount of each raw material used in Table 1 Represents the mass of the solid content (or may be referred to as an active ingredient) of the raw material. In addition, Notes 1 to 7 in Table 1 are as follows.

Note 1: Purified tannic acid (Dainippon Pharmaceutical Co., Ltd.)
Note 2: Tannic acid for industrial use (Dainippon Pharmaceutical Co., Ltd.)
Note 3: Gallocatechol (chemical name)
Note 4: ASE-60 (alkali swelling type viscosity modifier, ACRYSOL ASE-60, manufactured by Dow)
Note 5: PRIMID XL-522 (hydroxyalkylamide-based crosslinking agent, manufactured by EMS-GRILTECH)
Note 6: Epocross WS-700 (oxazoline-based crosslinking agent, oxazoline group-containing polymer, manufactured by Nippon Shokubai Co., Ltd.)
Note 7: Carbodilite E-02 (imide-based crosslinking agent, carbodiimide resin, manufactured by Nisshinbo Chemical Co., Ltd.)
<Production Example 1 Production of Polyolefin Resin Water Dispersion 1>
Polypropylene (6D43 (trade name), manufactured by Brask America America) added at 212 g / min, PRIMACOR 5980i (trade name, ethylene-acrylic acid copolymer, manufactured by Dow) added at 68 g / min and added at 23 g / min LICOCENE 6452 (trade name, propylene-maleic anhydride graft copolymer, manufactured by Clariant) was supplied to a twin screw extruder heated to 160 ° C. Deionized water was fed to the extruder at 70 g / min and dimethylethanolamine at 30 g / min, and dilution water was fed to two locations in the dilution section of the extruder so that the final solids were 47%. The extruder temperature profile was lowered to a temperature below 100 ° C. by the end of the extruder. Extrusion was carried out while adjusting the back pressure at 1200 rpm to obtain a polyolefin resin aqueous dispersion 1 having a solid content of 47% by mass.

  In addition, the polyolefin resin water dispersion 1 has a solid content of polypropylene of 70% by mass in the total solid content.

<Production Example 2 Production of polyolefin resin aqueous dispersion 2>
Polypropylene added at 150 g / min (6D43 (trade name), manufactured by Brask America America), PRIMACOR 5980i added at 108 g / min, and LICOCENE 6452 added at 45 g / min, twin-screw extrusion heated to 160 ° C. Supplied to the machine. Deionized water was fed to the extruder at 70 g / min and dimethylethanolamine at 30 g / min, and dilution water was fed to two locations in the dilution section of the extruder so that the final solids were 47%. The extruder temperature profile was lowered to a temperature below 100 ° C. by the end of the extruder. Extrusion was carried out while adjusting the back pressure at 1200 rpm to obtain a polyolefin resin aqueous dispersion 2 having a solid content of 47% by mass.

  In addition, the polyolefin resin water dispersion 2 has a solid content of polypropylene of 49.5% by mass in the total solid content.

<Manufacture of the manufacture example 3 alkali swelling type viscosity modifier 1>
A four-necked flask equipped with a reflux tube, a thermometer, a dropping funnel, and a stirrer was charged with 882 parts of n-butanol and heated to 100 ° C. under a nitrogen stream, “240 parts of methacrylic acid, 240 parts of methyl methacrylate, acrylic acid A mixture of a monomer of 120 parts of ethyl and 18 parts of t-butylperoxy-2-ethylhexanoate and a polymerization initiator was added dropwise from the dropping funnel in about 3 hours, and after the addition, at the same temperature. Stirring was continued for 2 hours, followed by cooling to obtain an acrylic resin solution (alkali swelling type viscosity modifier 1) having a solid content of 40% by mass. The obtained resin (solid content) had an acid value of 261 mg KOH / g and a number average molecular weight of about 19,000.

<Production of Example 1 Aqueous Coating Composition 1>
The raw materials shown in Table 1 were mixed at the composition ratio (mass solid content ratio) shown in Table 1, and ethylene glycol monobutyl ether was added to 7% by mass while diluting with deionized water, and pH was adjusted with dimethylethanolamine. Was adjusted to 8.0 to obtain an aqueous coating composition 1 having a solid content concentration of 20% by mass.

<Examples 2 to 16 and Comparative Examples 1 to 4 Production of aqueous coating compositions 2 to 20>
In the same manner as in Example 1, water-based paint compositions 2 to 20 were produced. The aqueous coating compositions 17 to 20 are coatings for comparative examples.

<Comparative Example 5 Production of Aqueous Coating Composition 21 (Epoxy Coating Composition)>
Epicoat 828EL (manufactured by Japan Epoxy Resin, bisphenol A type epoxy resin, epoxy equivalent of about 190, molecular weight of about 350) 558 parts by mass on a four-necked flask equipped with a reflux tube, a thermometer and a stirrer, Tetrabutylammonium bromide 0.6 mass part was prepared, and the polymerization reaction was performed at 160 degreeC under nitrogen stream. The reaction was monitored by epoxy equivalent, and was allowed to react for about 5 hours to obtain a bisphenol A type epoxy resin having a number average molecular weight of about 11,000 and an epoxy equivalent of about 8000.

  A four-necked flask equipped with a reflux tube, a thermometer, a dropping funnel, and a stirrer was charged with 882 parts by mass of n-butanol and heated to 100 ° C. under a nitrogen stream, “180 parts by mass of methacrylic acid, 240 parts by mass of styrene, A mixture of 180 parts by weight of ethyl acrylate and 18 parts by weight of t-butylperoxy-2-ethylhexanoate and a polymerization initiator was dropped from the dropping funnel in about 3 hours, and after the dropping, Stirring was continued at the same temperature for 2 hours and then cooled to obtain an acrylic resin solution having a solid content of 40% by mass. The obtained resin (solid content) had a resin acid value of 196 mg KOH / g and a number average molecular weight of about 19000.

  In a four-necked flask equipped with a reflux tube, a thermometer, and a stirrer, 80 parts by mass (solid content) of the bisphenol A type epoxy resin obtained above, 50 parts by mass (solid content) of the 40% by mass acrylic resin solution obtained above 20 parts by mass), 33 parts by mass of diethylene glycol monobutyl ether were added and heated to 100 ° C. to dissolve, and then 2 parts by mass of N, N-dimethylaminoethanol was added and reacted for about 2 hours. Thereafter, 3 parts by mass of N, N-dimethylaminoethanol was added and the reaction was continued for 20 minutes. Thereafter, 165 parts by mass of deionized water was added dropwise over 1 hour to disperse in water to obtain an aqueous coating composition 21 (acryl-modified epoxy coating composition) having an acid value of 34 mg KOH / g and a solid content concentration of 30% by mass. .

<Manufacture of the comparative example 6 water-based coating composition 22 (polyester type coating composition 1)>
A 10L autoclave was charged with 2660 parts of terephthalic acid, 15.5 parts of trimellitic acid, 2450 parts of propylene glycol, 350 parts of 1,4-cyclohexanedimethanol, and 1.8 parts of titanium tetrabutoxide, and 3.5 kg / cm · G The temperature was gradually raised to 235 ° C. over 3 hours under nitrogen pressurization to carry out an esterification reaction. Subsequently, the pressure was reduced to 10 mmHg over 1 hour and the polymerization was carried out under reduced pressure, the temperature was raised to 250 ° C., and the latter polymerization reaction was carried out at 1 mmHg or less for 90 minutes to obtain a polyester resin.

  The obtained polyester resin was added with a mixed solvent of cyclohexanone / solvesso 150 (trade name, petroleum-based aromatic solvent) (mass ratio 1/1) to a solid content concentration of 40% by mass to form an aqueous coating composition 22 (polyester coating). Composition 1) was obtained.

<Comparative Example 7 Production of Aqueous Coating Composition 23 (Polyester Coating Composition 2)>
To a four-necked flask equipped with a reflux tube, a thermometer, and a stirrer, 100 parts of m-cresol, 180 parts of a 37% aqueous formaldehyde solution, and 1 part of sodium hydroxide were added and reacted at 60 ° C. for 3 hours. Dehydrated at 50 ° C. for 1 hour. Subsequently, 100 parts of n-butanol and 6 parts of phosphoric acid were added and reacted at 110 to 120 ° C. for 2 hours. After completion of the reaction, the obtained solution was filtered, and n-butanol was added to obtain a resol type phenol resin solution having a solid content of 40% by mass.

  The aqueous coating composition 20 obtained in Comparative Example 6 and the resol type phenol resin solution were mixed at 7: 3 (mass ratio), and 0.1 part of dodecylbenzenesulfonic acid was further added to 100 parts of the solid content of the mixture. Was added and mixed to obtain an aqueous coating composition 23 (polyester coating composition 2) having a solid concentration of 40% by mass.

<Comparative Example 8 Production of Aqueous Coating Composition 24 (Acrylic Coating Composition)>
Preparation of emulsion of core monomer mixture 27 parts of deionized water, “NIKKOL TL-10” (trade name, PEG-20 sorbitan cocoate (emulsifier), Nikko Chemicals) 0.4 part, 9.7 parts of styrene, methyl 5 parts of methacrylate, 5 parts of isobutyl methacrylate, 10 parts of ethyl acrylate, 14.9 parts of 2-ethylhexyl acrylate, 1 part of 2-hydroxyethyl acrylate, 3.9 parts of methacrylic acid, 0.5 part of 1,6-hexanediol diacrylate And 0.05 part of ammonium persulfate (polymerization initiator) were mixed and stirred to obtain an emulsion of the core part monomer mixture.

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

  A reaction vessel equipped with a heating and cooling device and equipped with a stirrer, thermometer, thermostat, reflux condenser, nitrogen introduction tube and dropping device was added to 95 parts of deionized water and 0.1 part of “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 and 1 part of a 5% aqueous ammonium persulfate solution were added with stirring and held 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 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 was dropped over 2 hours, and after aging for 2 hours, 2- (dimethylamino) ethanol (neutralizing agent) was added to the content. By adding 5 parts, a dispersion of core-shell type acrylic resin particles was obtained.

  After adding 1 part of the above-mentioned resol type phenol resin solution to the obtained dispersion of core-shell type acrylic resin particles, it is diluted with deionized water to form an aqueous coating composition 24 (acrylic coating composition) having a solid content concentration of 20% by mass. )

<Preparation of test paint plate>
Each water-based coating composition obtained in the examples and comparative examples was applied to a # 0.251 aluminum plate having a thickness of 0.25 mm which was subjected to a zirconium-based surface treatment, and was coated with a bar coater so that the dry coating thickness was 5 μm. Each test plate was obtained by curing by heating at 200 ° C. for 1 minute.

  In addition, as a test plate for coating workability, a can inner surface coated can which was coated on the inner surface of a two-piece can with airless spray and cured in a conveyor oven at a temperature of 200 ° C. for 1 minute. Was subjected to a performance test.

  The following performance tests were performed using the obtained test coating plates.

  In the evaluation of each performance test, ◎ and ○ are acceptable (practical) levels, and Δ and x are unacceptable (unusable) levels.

[Corrosion resistance]
The test coating plate was immersed in the following aqueous test solution at 45 ° C. for 4 weeks, and then the coated surface state was visually observed and evaluated according to the following criteria.

◎: Glossy, no corrosion is observed ○: Glossy, but no corrosion is observed △: Slight corrosion is observed ×: Corrosion is remarkable Test aqueous solution 1: 3% by mass of citric acid and sodium chloride each Aqueous solution dissolved to a concentration Aqueous solution for test 2: Aqueous solution in which citric acid and sodium chloride are dissolved in a concentration of 3% and ethanol in a concentration of 7% each [Coating workability]
The can inner surface coated can obtained above was cut open with gold scissors, and the state in which the paint sagged on the bottom of the can and the boiling state were evaluated according to the following criteria.

○: Sagging is low and boiling is not observed △: Sagging and boiling are slightly observed ×: Sagging and boiling are remarkable [Retort resistance]
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.

◎: No whitening is observed at all ○: Partial whitening is slightly observed △: Slight whitening is observed as a whole ×: Remarkably whitening is observed Further, as evaluation items, “BPA, St, formaldehyde” In the column “Presence or absence”, the presence or absence in the paint of any of bisphenol A (BPA), St (styrene), or formaldehyde, which are legally regulated substances, is indicated as “Yes” or “No”.

  A coating can excellent in corrosion resistance and retort resistance can be provided, and an aqueous coating composition that does not contain a legally regulated substance such as bisphenol A excellent in coating workability can be provided.

Claims (4)

Containing polyolefin resin water dispersion (A), tannin (B), and alkali swelling viscosity modifier (C),
The solid content of the component (B) and the component (C) is 0.1 to 10% by mass of the component (B) and 0.1% of the component (C) with respect to the total solid content of the polyolefin resin aqueous dispersion (A). A water-based coating composition, characterized in that it is ˜5% by mass. The aqueous coating composition according to claim 1, wherein the solid content of polypropylene is 50% by mass or more of the total solid content of the polyolefin resin aqueous dispersion (A). The aqueous coating composition according to claim 1 or 2, wherein the tannin (B) is tannic acid. Further, the crosslinking agent (D) having two or more functional groups that react with carboxyl groups in the molecule is contained in an amount of 0.1 to 10% by mass in terms of the solid content based on the total solid content of the polyolefin resin aqueous dispersion (A). The water-based coating composition according to any one of claims 1 to 3, wherein