KR20230073091A - Aqueous coating composition for cans - Google Patents

Abstract

Provided is an aqueous paint composition for cans that is excellent in activity, wear resistance, and processability. The aqueous paint composition for cans includes: an acrylic modified epoxy resin (A); at least one wax (B) selected from a group consisting of three waxes with different melting points; a polyolefin aqueous dispersion (C) having an average particle diameter of 0.1 to 5 μm and a polyolefin penetration degree of 8 or less; and a phenol resin (D) in a specific composition ratio.

Description

Water-based coating composition for cans {AQUEOUS COATING COMPOSITION FOR CANS}

The present invention relates to an aqueous coating composition for cans having excellent activity, wear resistance and processability.

For the metal can, for example, a metal substrate such as aluminum, tin-free steel, or tinplate is used. Coating films are formed on the outer surfaces of cans, can lids, and tabs obtained by processing these metal substrates for the purpose of moldability, designability, and metal surface protection. In particular, since the coating film of the can cover requires resistance to severe processing during molding, an inner wax type paint for cans containing wax in the paint for the purpose of imparting activity has been developed.

For example, Patent Document 1 discloses an aqueous coating composition for the outer surface of a can cover containing a pigment, a pigment dispersion resin and a binder resin, wherein the pigment dispersion resin is an acrylic copolymer having methacrylic acid, styrene and ethyl acrylate as constituent components. An aqueous coating composition for the outer surface of a can cover is disclosed.

Further, in Patent Document 2, a water-soluble acrylic resin (A) containing an animal-based wax (a) having a melting point of 40 to 70° C., a water-based wax dispersion (B) containing an animal-based wax (a), a water-soluble polyester resin (C), and amino A water-based paint composition for the outer surface of a can comprising a resin (D) is disclosed.

Patent Document 1: Japanese Patent Laid-Open No. 2006-176714 Patent Document 2: Japanese Patent Laid-Open No. 2009-191180

However, in the coating compositions described in Patent Literatures 1 and 2, when a large amount of wax is blended to improve coating film activity, the coating film is plasticized and wear resistance is lowered, so it is difficult to achieve both activity and wear resistance at a high level, and processability is insufficient. There were cases where

An object to be solved by the present invention is to provide an aqueous coating composition for a can, which is excellent in activity and wear resistance, and also excellent in processability.

As a result of intensive studies, the present inventors have found that the above problems can be solved by using a coating composition containing an acrylic-modified epoxy resin, a wax, a polyolefin aqueous dispersion, and a phenol resin, and have completed the present invention.

That is, the present invention,

1. A coating composition containing an acrylic-modified epoxy resin (A), a wax (B), a polyolefin aqueous dispersion (C) and a phenol resin (D), wherein the wax (B) is a wax (b1) having a melting point of less than 50°C; containing at least one kind of wax selected from the group consisting of a wax (b2) having a melting point of 50°C or more and less than 100°C and a wax (b3) having a melting point of 100 to 160°C and an average particle diameter of 1 to 15 μm; , the average particle diameter of the polyolefin aqueous dispersion (C) is 0.1 to 5 μm, and the penetration of the polyolefin is 8 or less, based on the total solid content of the acrylic-modified epoxy resin (A), wax ( The total solid content of B) is 0.3 to 10% by mass, the total solid content of the polyolefin aqueous dispersion (C) is 1 to 10% by mass, and the total solid content of the phenol resin (D) is 0.5 to 20% by mass. paint composition.

2. The aqueous coating composition for cans according to item 1, wherein the wax (b1) is at least one selected from the group consisting of lanolin wax, palm oil, and glycerin triesters.

3. The aqueous coating composition for cans according to item 1 or 2, wherein the wax (b2) is at least one selected from the group consisting of microcrystalline wax and carnauba wax.

4. The aqueous coating composition for cans according to any one of items 1 to 3, wherein the wax (b3) is at least one selected from the group consisting of polyethylene wax and polypropylene wax.

5. The solid content of the wax (b1), the wax (b2) and the wax (b3) is 0.1 to 5% by mass of the wax (b1) and the amount of the wax (b2) is based on the total solid content of the acrylic-modified epoxy resin (A). 0.1 to 5% by mass and 0.1 to 5% by mass of wax (b3), the aqueous coating composition for cans according to any one of items 1 to 4 above.

6. The water-based coating composition for cans according to any one of items 1 to 5, which is used for can covers.

7. It is related with the can lid which has the coating film of the water-based can coating composition in any one of 1st item|item to 6th item|item.

The aqueous coating composition for cans of the present invention is excellent in activity and abrasion resistance, and can obtain a coating film excellent in processability.

The present invention is an aqueous coating composition for cans (hereinafter sometimes referred to as the composition of the present invention) characterized by containing an acrylic-modified epoxy resin (A), a wax (B), a polyolefin aqueous dispersion (C) and a phenol resin (D). .)am. Hereinafter, it demonstrates in detail.

<Aqueous coating composition for cans>

<Acrylic Modified Epoxy Resin (A)>

The acrylic modified epoxy resin (A) may be, for example, any one of the following resin (1) and resin (2).

Resin (1): bisphenol type epoxy resin (a1) (hereinafter sometimes abbreviated as “epoxy resin (a1)”) and carboxyl group-containing acrylic resin (a2) (hereinafter abbreviated as “acrylic resin (a2)”) Resin obtained by subjecting ester addition reaction to

The resin (1) can be obtained by easily subjecting the epoxy resin (a1) and the acrylic resin (a2) to an ester addition reaction by heating, for example, in an organic solvent in the presence of an esterification catalyst.

Resin (2): A resin obtained by subjecting an epoxy resin (a1) to graft polymerization of a polymerizable unsaturated monomer component containing a carboxyl group-containing polymerizable unsaturated monomer.

The resin (2) can be obtained, for example, by graft polymerization of a polymerizable unsaturated monomer component to the epoxy resin (a1) in an organic solvent in the presence of a radical generating agent such as benzoyl peroxide.

As the epoxy resin (a1) used in the resin (1) and the resin (2), for example, a resin formed by polycondensation of epichlorohydrin and bisphenol optionally to a high molecular weight in the presence of a catalyst such as an alkali catalyst. , Resin obtained by optionally condensing epichlorohydrin and bisphenol in the presence of a catalyst such as an alkali catalyst to obtain a low molecular weight epoxy resin, and polyaddition reaction of the low molecular weight epoxy resin and bisphenol, and these obtained Any of epoxy ester resins obtained by reacting a dibasic acid with a resin of or the above low molecular weight epoxy resin may be used.

Examples of the bisphenol include bis(4-hydroxyphenyl)methane [bisphenol F], 1,1-bis(4-hydroxyphenyl)ethane, 2,2-bis(4-hydroxyphenyl)propane [bisphenol A], 2, 2-bis (4-hydroxyphenyl) butane [bisphenol B], bis (4-hydroxyphenyl) -1, 1-isobutane, bis (4-hydroxy-tert-butyl-phenyl) -2, 2-propane, p-(4-hydroxyphenyl)phenol, oxybis(4-hydroxyphenyl), sulfonylbis(4-hydroxyphenyl), 4,4'-dihydroxybenzophenol, bis(2 -Hydroxynaphthyl)methane etc. are mentioned, Among these, bisphenol A and bisphenol F can be used suitably. These bisphenols can be used alone or in combination of two or more.

As a dibasic acid used for manufacture of the said epoxy ester resin, the following formula (1)

HOOC―(CH ₂ ) _n ―COOH ㆍEquation (1)

(In the formula, n is an integer of 1 to 12) can be suitably used, and specifically, succinic acid, adipic acid, pimelic acid, azelaic acid, sebacic acid, dodecanedioic acid, hexahydrophthalic acid etc. can be exemplified.

Examples of commercially available epoxy resins (a1) include jER828 (epoxy equivalent: about 190), jER1007 (epoxy equivalent: about 1,700), jER1009 (epoxy equivalent: about 3,500), and jER1010 (epoxy equivalent: about 4,500) manufactured by Mitsubishi Chemical Corporation; Araldite AER6099 (epoxy equivalent: about 3,500) manufactured by Asahi Chiba Co., Ltd.; and Epomic R-309 (epoxy equivalent: about 3,500) manufactured by Mitsui Chemicals Co., Ltd.

As the epoxy resin (a1), among others, a bisphenol type epoxy resin having a number average molecular weight of 2,000 to 35,000, preferably 4,000 to 30,000, and an epoxy equivalent of 1,000 to 12,000, preferably 3,000 to 10,000, is obtained. It can be suitably used from the viewpoint of corrosion resistance.

In addition, the number average molecular weight in the present specification is a value obtained by converting the number average molecular weight measured using a gel permeation chromatography (GPC) based on the molecular weight of standard polystyrene.

Specifically, "HLC8120GPC" (trade name, manufactured by Tosoh Corporation) was used as a gel permeation chromatograph, and "TSKgel G-4000HXL", "TSKgel G-3000HXL", "TSKgel G-2500HXL" and "TSKgel G-2500HXL" were used as columns. 2000HXL” (trade name, both manufactured by Tosoh Corporation) were used, and the measurement was carried out under the conditions of a mobile phase tetrahydrofuran, a measurement temperature of 40° C., a flow rate of 1 mL/min, and a detector (RI).

In the resin (1), during the ester addition reaction, since the carboxyl group in the acrylic resin (a2) undergoes an ester addition reaction with the epoxy group in the epoxy resin (a1), an epoxy group in the epoxy resin (a1) is required, and one molecule of the epoxy resin It is preferable that this epoxy group exists in the range of 0.5-2 on average, and especially 0.5-1.6.

On the other hand, in the resin (2), since the graft reaction occurs by removing hydrogen from the main chain of the epoxy resin and the graft polymerization reaction proceeds, the epoxy group may not substantially exist in the epoxy resin (a1).

The acrylic resin (a2) used in the resin (1) is a copolymer resin containing a carboxyl group-containing polymerizable unsaturated monomer and other polymerizable unsaturated monomers as monomer components.

Examples of the carboxyl group-containing polymerizable unsaturated monomer include monomers such as (meth)acrylic acid, maleic acid, crotonic acid, itaconic acid, and fumaric acid, and these may be used alone or in combination of two or more.

Any other polymerizable unsaturated monomer may be a monomer copolymerizable with the carboxyl group-containing polymerizable unsaturated monomer, and may be appropriately selected and used according to the required performance.

Specifically, for example, aromatic vinyl monomers such as styrene, vinyltoluene, 2-methylstyrene, t-butylstyrene, and chlorostyrene; Methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-, i-, or t-butyl acrylate, hexyl acrylate, 2-ethylhexyl acrylate, n-octyl acrylate, decyl acrylate, lauryl acrylate, cycloacrylate Hexyl, methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-, i-, or t-butyl methacrylate, hexyl methacrylate, 2-ethyl methacrylate alkyl esters or cycloalkyl esters of acrylic acid or methacrylic acid having 1 to 18 carbon atoms, such as hexyl, octyl methacrylate, decyl methacrylate, lauryl methacrylate, and cyclohexyl methacrylate; 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 3-hydroxypropyl acrylate, hydroxybutyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 3- hydroxyalkyl esters having 2 to 8 carbon atoms of acrylic acid or methacrylic acid, such as hydroxypropyl methacrylate and hydroxybutyl methacrylate; N-substituted acrylamides such as N-methylol acrylamide, N-butoxymethyl acrylamide, N-methoxymethyl acrylamide, N-methylol methacrylamide, and N-butoxymethyl methacrylamide, or N- A substituted methacrylatide type monomer etc. are mentioned. These other polymerizable unsaturated monomers can be used singly or in combination of two or more.

As the above-mentioned other polymerizable unsaturated monomers, a mixture of styrene and ethyl acrylate is particularly preferred, and the constituent mass ratio of styrene/ethyl acrylate is in the range of 99.9/0.1 to 20/80, particularly 99/1 to 40/60. desirable.

In the acrylic resin (a2), the type and composition ratio of the monomers are not particularly limited, but usually, the carboxyl group-containing polymerizable unsaturated monomer is preferably 15 to 80% by mass, particularly 20 to 60% by mass, and other It is preferable that the polymerizable unsaturated monomer is 85 to 20% by mass, particularly 80 to 40% by mass.

The synthesis of the acrylic resin (a2) can be easily carried out, for example, by subjecting a mixture of the above monomers to a polymerization reaction in an organic solvent in the presence of a polymerization initiator. The acrylic resin (a2) preferably has a resin acid value of 100 to 400 mgKOH/g and a number average molecular weight of 5,000 to 100,000.

The reaction can be carried out by a known method, for example, when an esterification catalyst is blended in a uniform organic solvent solution of the epoxy resin (a1) and the acrylic resin (a2), and substantially all of the epoxy groups are consumed. It can usually be carried out by reacting at a reaction temperature of 60 to 130°C for about 1 to 6 hours. Examples of the esterification catalyst include tertiary amines such as triethylamine and dimethylethanolamine, quaternary salt compounds such as triphenylphosphine, and the like. Among them, tertiary amines can be suitably used. there is.

The solid content concentration in the reaction system of the epoxy resin (a1) and the acrylic resin (a2) is not particularly limited as long as the reaction system is within a viscosity range that does not interfere with the reaction. In addition, when using an esterification catalyst when making an ester addition reaction, it is preferable to use the usage-amount normally in the range of 0.1-1 equivalent with respect to 1 equivalent of epoxy groups in an epoxy resin (a1).

When the acrylic-modified epoxy resin is the resin (2), the polymerizable unsaturated monomer component containing the carboxyl group-containing polymerizable unsaturated monomer graft-polymerized to the epoxy resin (a) is the carboxyl group-containing acrylic resin (a2) in the resin (1). ), and carboxyl group-containing polymerizable unsaturated monomers and other polymerizable unsaturated monomers, which are monomeric components used in the production of ).

The graft polymerization reaction in the resin (2) can be carried out by a known method. For example, a radical generating agent and a polymerizable unsaturated monomer component in an organic solvent solution of the epoxy resin (a1) heated to 80 to 150 ° C. It can be carried out by gradually adding a uniform mixed solution of and maintaining at the same temperature for about 1 to 10 hours. Examples of the radical generating agent include azobisisobutyronitrile, benzoyl peroxide, t-butylperbenzoyloctanoate, and t-butylperoxy-2-ethylhexanoate.

As the organic solvent, it dissolves the epoxy resin (a1), the acrylic resin (a2) or the polymerizable unsaturated monomer component containing the carboxyl group-containing polymerizable unsaturated monomer, and further neutralizes the acrylic modified epoxy resin (A) as a reaction product thereof. Well-known solvents can be used as long as they are organic solvents that do not interfere with the formation of an emulsion during aqueous conversion.

Specific examples of the organic solvent include isopropanol, butyl alcohol, 2-hydroxy-4-methylpentane, 2-ethylhexyl alcohol, cyclohexanol, ethylene glycol, diethylene glycol, 1,3-butylene glycol, and the like. , ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, and the like.

The acrylic-modified epoxy resin as the resin (1) or the resin (2) has a carboxyl group and has a resin acid value within the range of 10 to 160 mgKOH/g, particularly 20 to 100 mgKOH/g for dispersibility, coating performance, etc. It is preferable from the point of view of

The acrylic-modified epoxy resin can be dispersed in an aqueous medium by neutralizing at least a part of the carboxyl groups in the resin with a basic compound.

As said basic compound, amines, ammonia, etc. can be used suitably. Specific examples of the amines include alkylamines such as trimethylamine, triethylamine, and tributylamine; alkanolamines such as dimethylethanolamine, diethanolamine, and aminomethylpropanol; Cyclic amines, such as morpholine, etc. are mentioned. The degree of neutralization of the acrylic-modified epoxy resin is not particularly limited, and is preferably within the range of 0.1 to 2.0 equivalents relative to the carboxyl groups in the resin.

The aqueous medium may be only water, but may be a mixture of water and organic solvent. As the organic solvent, known ones can be used, and those listed as organic solvents that can be used in the production of the acrylic-modified epoxy resin can be suitably used. The amount of the organic solvent in the composition of the present invention is preferably in the range of 20% by mass or less, particularly 10% by mass or less, from the viewpoint of environmental protection and the like with respect to the total amount of resin solid content in the composition of the present invention.

Dispersion of the acrylic-modified epoxy resin into an aqueous medium can be carried out by a conventional method, for example, a method of gradually adding the acrylic-modified epoxy resin to an aqueous medium containing a basic compound as a neutralizing agent under stirring, and the acrylic-modified epoxy resin. After neutralizing with a basic compound, a method of adding an aqueous medium to the neutralized product under stirring, or a method of adding the neutralized product to an aqueous medium, and the like are exemplified.

<wax (B)>

Specific examples of the wax (B) include natural wax, synthetic wax, glycerin and lead, oxides and acid-modified products thereof, and the like can be used singly or in combination of two or more.

As natural waxes, for example, hydrogenated hydrogenated fats and oils obtained by adding beef tallow or lard, beeswax, lanolin wax, spermaceti, hydrogenated spermaceti, carnauba wax, candelilla wax, rice wax, Japan wax, jojoba wax, shellac, etc. animal and vegetable waxes, paraffin wax, microcrystalline wax, montan wax, and mineral waxes such as serine wax.

Examples of the synthetic wax include polyethylene wax, polypropylene wax, polytetrafluoroethylene wax, and silicone wax.

As the wax (B), lanolin wax, olive oil, palm oil, linseed oil, microcrystalline wax, polyethylene wax and the like can be preferably used from the viewpoint of activity and wear resistance.

Commercially available products of the wax (B) include purified lanolin (lanolin wax, trade name, manufactured by CRODA), CERACOL 609N (lanolin wax, trade name, manufactured by BYK), lanolin R (lanolin wax, trade name, manufactured by Nippon Seika Co., Ltd.), outer -Lo- 1 (olive oil, trade name, manufactured by Riken Vitamin Co., Ltd.), refined palm oil (palm oil, trade name, manufactured by Lubrizol Seiyu Co., Ltd.), HI-DISPER 1260 (microcrystalline wax, trade name, manufactured by Gifu Shellac Co., Ltd.), Topco S923 ( Microcrystalline wax, trade name, manufactured by Toyo Petrolite Co., Ltd.), CERAFLOUR 991 (manufactured by BYK, trade name, polyethylene wax, average particle diameter 5 μm, melting point 115° C.), HIGH FLAT2352 (product name, manufactured by Gifu Shellac Manufacturing Co., Ltd., oxidized polyethylene wax, Average particle size: 5 μm, melting point: 138° C.), Lanco 1370LF (Nippon Lubrizol Co., Ltd., trade name, polypropylene wax, average particle size: 9 μm, melting point: 150° C.).

The amount of wax (B) varies depending on the type of wax used, but from the viewpoint of activity and abrasion resistance, based on the total solid content of the acrylic-modified epoxy resin (A) (the total solid amount of the acrylic-modified epoxy resin (A) is 100 In terms of mass%), it is preferably in the range of 0.3 to 10% by mass, preferably 0.3 to 6% by mass, and more preferably 0.5 to 1.5% by mass.

Among the waxes (B), the composition of the present invention comprises a wax (b1) having a melting point of less than 50°C, a wax (b2) having a melting point of 50°C or more and less than 100°C, and a melting point of 100°C to 160°C and having an average particle diameter At least one type of wax selected from the group consisting of wax (b3) having a diameter of 1 to 15 μm is selected and used.

By using at least one kind of wax selected from the group consisting of the above three kinds, the surface roughness of the coating film can be adjusted, and the reduction of the kinetic friction coefficient, activity, wear resistance and workability are excellent, , it is possible to provide a can body excellent in opening properties.

Wax (b1)

The wax (b1) is not particularly limited as long as it is a wax having a melting point of less than 50°C, and from the viewpoint of reducing the coefficient of kinetic friction, improving activity, wear resistance, and processability, lanolin wax, olive oil, palm oil, amine oil, glycerin driesester, etc. can be used suitably.

In addition, commercially available products of the wax (b1) include purified lanolin (lanolin wax, trade name, manufactured by CRODA), outer-Lo-1 (olive oil, trade name, manufactured by Riken Vitamin Co., Ltd.), purified palm oil (palm oil, trade name, Lubrizol Seiyu Co., Ltd.) ) and the like.

Wax (b2)

The wax (b2) is not particularly limited as long as it is a wax having a melting point of 50° C. or more and less than 100° C., preferably 60° C. to 90° C. Lean wax and carnauba wax can be suitably used.

In addition, as commercially available products of wax (b2), HI-DISPER 1260 (microcrystalline wax, trade name, manufactured by Gifu Shellac Co., Ltd.), Dopco S923 (microcrystalline wax, trade name, manufactured by Toyo Petrolite Co., Ltd.), HD-3028 ( Carnauba wax, melting point 82°C, manufactured by Gifu Shellac Manufacturing Co., Ltd.), Hi-Mic-1070 (manufactured by Nippon Seiro Co., Ltd., microcrystalline wax, melting point, 80°C), and the like.

Wax (b3)

Wax (b3) is not particularly limited as long as it has an average particle diameter of 1 to 15 μm, preferably 2 to 11 μm, and a melting point of 100° C. to 160° C., preferably 120° C. to 155° C. Instead, polyethylene wax and polypropylene wax can be suitably used from the viewpoints of reduction of the coefficient of kinetic friction, activity, wear resistance and workability.

Examples of commercially available wax (b3) include CERAFLOUR 991 (manufactured by BYK, trade name, polyethylene wax, average particle diameter: 5 μm, melting point: 115° C.), HIGHFLAT2352 (manufactured by Gifu Shellac Manufacturing Co., Ltd., trade name, oxidized polyethylene wax, Average particle size: 5 μm, melting point: 138° C.), Lanco 1370LF (Nippon Lubrizol Co., Ltd., trade name, polypropylene wax, average particle size: 9 μm, melting point: 150° C.).

In the present invention, the melting point of wax (B) represents the endothermic peak temperature measured by a differential scanning calorimeter (DSC) at a heating rate of 10°C/min. In the case where the wax has a plurality of endothermic peaks, the melting point was taken as the maximum endothermic peak. In addition, the average particle diameter of the wax was measured by the volume average diameter by the laser diffraction/scattering method using a Microtrac UPA (particle size analyzer manufactured by Nikkiso Co., Ltd.).

When the wax (B) contains the wax (b1), the solid content of the wax (b1) in the wax (B) is 0.1 to 5% by mass based on the total solid content of the acrylic-modified epoxy resin (A); It is preferably within the range of 0.2 to 2% by mass, more preferably 0.2 to 1.0% by mass, from the viewpoints of reduction of the coefficient of kinetic friction, activity, wear resistance and workability. When the wax (B) contains the wax (b2), the solid content of the wax (b2) in the wax (B) is 0.1 to 5% by mass based on the total solid content of the acrylic-modified epoxy resin (A), preferably Preferably, it is within the range of 0.2 to 2% by mass, more preferably 0.2 to 1.0% by mass, from the viewpoint of reducing the coefficient of kinetic friction, activity, wear resistance and workability. When the wax (B) contains the wax (b3), the solid content of the wax (b3) in the wax (B) is 0.1 to 5% by mass based on the total solid content of the acrylic-modified epoxy resin (A); It is preferably within the range of 0.2 to 2% by mass, more preferably 0.2 to 1.0% by mass, from the viewpoints of reduction of the coefficient of kinetic friction, activity, wear resistance and workability. The total solid content of wax (b1), wax (b2), and wax (b3), based on the total solid content of wax (B) (100 mass%), is, for example, 85 mass% or more. 90 mass % or more is preferable, 95 mass % or more is more preferable, and 99 mass % or more is still more preferable.

<Polyolefin aqueous dispersion (C)>

The polyolefin aqueous dispersion (C) may be one processed so as to be dispersible in an aqueous composition such as an aqueous paint, an aqueous dispersion, or an aqueous emulsion, and one obtained by emulsion polymerization or mechanically dispersed polyolefin in an aqueous medium may be used. It can be used alone or in combination of two or more.

In the composition of the present invention, a polyolefin mechanically dispersed in an aqueous medium can be suitably used from the viewpoints of not actively using an emulsifier and water resistance.

The polyolefin of the polyolefin water-based dispersion (C) has an average particle diameter of 0.1 to 5 μm, particularly preferably 0.2 to 4.0 μm, and preferably 0.3 to 3.0 μm, from the viewpoint of the activity and wear resistance and processability of the obtained coating film. do.

In the composition of the present invention, the average particle diameter of the polyolefin aqueous dispersion (C) is a value measured by the Microtrac method.

In the composition of the present invention, the polyolefin of the polyolefin aqueous dispersion (C) preferably has a penetration of 8 or less, particularly 4 or less, and preferably 1 or less from the viewpoint of processability and wear resistance.

In addition, the penetration of the polyolefin constituting the polyolefin aqueous dispersion (C) is standardized in JIS K2207, and a needle of a specified weight is vertically entered into the polyolefin at a temperature of 25 ° C., a load of 100 g, and a penetration time of 5 seconds, It represents the length of penetration, and the value of penetration is 0.1 mm as penetration 1. Therefore, the smaller the penetration is, the harder the polyolefin is, and the larger the penetration is, the softer the polyolefin is. The present invention uses a polyolefin aqueous dispersion obtained by using a polyolefin having a penetration in the above range.

Examples of the type of polyolefin include ionomers such as low-density polyolefins, low-molecular-weight polyolefins, ethylene/methacrylic acid copolymers, and metal salts of ethylene/methacrylic acid copolymers.

Among the above, low-molecular-weight polyolefins, particularly low-molecular-weight polyethylenes, can be preferably used from the viewpoint of water dispersibility.

As the polyolefin aqueous dispersion (C), a commercial item can also be used. Specifically as a commercial item, arrow base by Unitica Co., Ltd., Chemipearl by Mitsui Chemicals Co., Ltd., AB-50 by Gifu Shellac Manufacturing Co., Ltd., etc. are mentioned.

The blending amount of the polyolefin aqueous dispersion (C) may be adjusted according to the desired level of activity, wear resistance and processability, and it is also possible to use two or more types in combination. The total solid content of the polyolefin is in the range of 1.0 to 10.0% by mass, particularly 2.0 to 8.0% by mass, and further 3.0 to 7.0% by mass with respect to the total solid content of the acrylic-modified epoxy resin (A), from the viewpoint of activity, abrasion resistance and workability. preferred in

Phenolic Resin (D)

As the phenolic resin (D), for example, a resol type obtained by condensation reaction of phenols (d1) such as a phenolic compound or bisphenol A and aldehydes (d2) such as formaldehyde in the presence of a reaction catalyst to introduce a methylol group. A phenol resin is mentioned.

Examples of the phenols (d1) include bifunctional phenolic compounds such as o-cresol, p-cresol, p-tert-butylphenol, p-ethylphenol, 2,3-xylenol, and 2,5-xylenol; trifunctional phenolic compounds such as phenolic acid, m-cresol, m-ethylphenol, 3,5-xylenol, and m-methoxyphenol; tetrafunctional phenolic compounds such as bisphenol A and bisphenol F; Phenol compounds, such as these, can be used singly or in combination of two or more.

Examples of the aldehydes (d2) include formaldehyde, paraformaldehyde, trioxane, and the like, and may be used singly or in combination of two or more.

The methylol group of the methylolized phenolic resin may optionally be alkyl-etherified again. As an alcohol used for alkyl etherification, for example, a monohydric alcohol having 1 to 6 carbon atoms, particularly 1 to 4 carbon atoms can be preferably used. Suitable monohydric alcohols include methanol, ethanol, n-propanol, n-butanol, isobutanol and the like.

From the viewpoint of reactivity, the phenolic resin (D) has a number average molecular weight of 200 to 2,000, particularly 300 to 1,200, and an average number of methylol groups per benzene nucleus of 0.3 to 3.0, particularly 0.5 to 3.0. Those within the range of dogs can be suitably used.

The amount of the phenol resin (D) is preferably within the range of 0.5 to 20% by mass, particularly 1 to 15% by mass, and further 2 to 10% by mass based on the total solid content of the acrylic-modified epoxy resin (A), from the viewpoint of processability. do.

<Aqueous coating composition for cans>

The water-based paint composition for cans of the present invention is an aqueous paint composition in which acrylic-modified epoxy resin (A) is neutralized and dispersed in an aqueous medium, and in the composition, wax (B), polyolefin aqueous dispersion (C) and phenol resin (D) is contained as an essential component, and optionally, other additives such as surfactants, antifoaming agents, pigments, fragrances and the like may be further contained.

Among the above, a surfactant can be preferably used from the viewpoint of the dispersion stability of the polyolefin (component C) and the external appearance stability of the coating film when a pigment is contained.

As surfactants, for example, alkylbenzenesulfonic acids (and neutralized amines) and the like can be particularly suitably used.

The solid content concentration of the composition of the present invention is not particularly limited, but is preferably in the range of 20 to 45% by mass, preferably 22 to 40% by mass, from the viewpoint of paint stability.

The composition of the present invention can be applied to various substrates, for example, metals such as bleak, aluminum, tin-free steel, iron, zinc, copper, galvanized steel sheet, alloy-coated steel sheet, phosphate treatment of these metals, Chemical conversion-treated metal plates subjected to surface treatment such as chromate treatment, metal plates coated with epoxy resin-based, vinyl resin-based primers, and substrates obtained by processing these metal plates into cans or the like are exemplified.

The composition of the present invention can be used particularly suitably for the inner and outer surfaces of cans, particularly for can covers requiring strict discriminatory properties.

The coating of the composition of the present invention is applied by a known method, for example, a coating method such as roll coater coating or spray coating, so that the dry film thickness is 1 to 20 μm, preferably 2 to 10 μm, and the material is reached. It can be carried out by heating and drying while maintaining a temperature of 120 to 300°C, preferably 200 to 280°C for about 10 seconds to 30 minutes, preferably about 15 seconds to about 15 minutes.

(Example)

Hereinafter, the present invention will be described in more detail by giving Examples and Comparative Examples. The present invention is not limited at all by the following examples. In addition, below, both "part" and "%" are based on a mass standard.

Preparation of acrylic modified epoxy resin (A)

Production Example 1 Production of Epoxy Resin No. 1 Solution

558 parts of jER828 (note 1), 329 parts of bisphenol A, and 0.6 part of tetrabutylammonium bromide were placed in a glass four-necked flask equipped with a thermometer, stirrer, reflux condenser, and nitrogen inlet, and the reaction was carried out at 160 ° C. under a nitrogen stream. . The reaction was tracked by epoxy equivalent, and epoxy resin No. 1 solution was obtained by reacting for about 5 hours. The obtained epoxy resin No. 1 had a number average molecular weight of about 8,000.

(Note 1) jER828: manufactured by Mitsubishi Chemical Corporation, bisphenol A type epoxy resin, epoxy equivalent about 190, number average molecular weight about 380

Production Example 2 Production of Epoxy Resin No. 2 Solution

550 parts of jER828 (Note 1) and 450 parts of bisphenol A were placed in a glass four-necked flask equipped with a thermometer, stirrer, reflux condenser and nitrogen inlet, and the temperature was raised under a nitrogen stream while stirring. When bisphenol A was dissolved and the mixture became transparent (near 100°C), 5.0 parts of tri-n-butylamine was added and the mixture was reacted at 160°C under a nitrogen stream.

The reaction was tracked by epoxy equivalent, and epoxy resin No. 2 solution was obtained by reacting for about 4 hours. The obtained epoxy resin No. 2 had a number average molecular weight of about 4,500.

Preparation Example 3 Preparation of acrylic resin solution

882 parts of n-butanol was put into a glass four-necked flask equipped with a thermometer, stirrer, reflux condenser and nitrogen inlet, and “methacrylic acid 180 parts, styrene 240 parts, ethyl acrylate 180 parts, t-butylperoxy-2- A mixture of 18 parts of ethyl hexanoate was heated to 100 ° C. under a nitrogen stream, and added dropwise after about 3 hours from the dropping funnel, and after dropping, stirring was continued at the same temperature for 2 hours, then cooled to obtain a solid content A 40% acrylic resin solution was obtained. The obtained acrylic resin had a number average molecular weight of about 19,000 and an acid value of 196 mgKOH/g.

Production Example 4 Production of Acrylic Modified Epoxy Resin No. 1 Water Dispersion

In a glass four-necked flask equipped with a thermometer, stirrer, reflux condenser and nitrogen inlet, 80 parts (solid content) of the epoxy resin No. 1 solution obtained in Preparation Example 1 and 20 parts (solid content) of the acrylic resin solution obtained in Production Example 3 were added to ), 33 parts of diethylene glycol monobutyl ether were added, dissolved by heating at 100°C, 2 parts of N,N-dimethylaminoethanol were added, reaction was carried out for about 2 hours, and 3 parts of N,N-dimethylaminoethanol were added. The reaction was continued for 20 minutes. Thereafter, 165 parts of deionized water was added dropwise over 1 hour to obtain an acrylic modified epoxy resin No. 1 water dispersion having an acid value of 34 mgKOH/g and a solid content of 30%.

Production Example 5 Production of Acrylic Modified Epoxy Resin No. 2 Water Dispersion

Put 25 parts of ethylene glycol monobutyl ether and 80 parts (solid content) of the epoxy resin No. 2 solution obtained in Preparation 2 into a glass four-necked flask equipped with a thermometer, stirrer, reflux condenser and nitrogen inlet, and nitrogen stream while stirring. The temperature was raised to 120°C under

After the epoxy resin No.2 solution is completely dissolved, a mixed solution of “4 parts of styrene, 4 parts of methyl methacrylate, 6 parts of n-butyl acrylate, 6 parts of methacrylic acid, and 1 part of benzoyl peroxide” is added at 120°C to 1 part. It was added dropwise over time and held at 120°C for 1 hour after completion of the dropwise addition. Then, it cooled to 90 degreeC, added 6.2 parts of dimethylethanolamine, and mixed-stirred for 15 minutes. Further, 201 parts of deionized water was added dropwise over 1 hour while stirring to obtain an acrylic modified epoxy resin No. 2 aqueous dispersion having an acid value of 44 mgKOH/g and a solid content of 30%.

Preparation of phenolic resin (D)

Preparation Example 6 Preparation of phenol resin No. 1 solution

188 parts of phenol and 324 parts of 37% formaldehyde aqueous solution were placed in a glass four-necked flask equipped with a thermometer, stirrer, reflux condenser and nitrogen inlet, and heated to 50°C to uniformly dissolve the contents. Next, after adding and mixing zinc acetate to adjust the pH in the system to 5.0, it was heated to 90 degreeC and reacted for 5 hours. Then, after cooling to 50°C, adding a 32% calcium hydroxide aqueous dispersion slowly and adjusting the pH to 8.5, reaction was performed at 50°C for 4 hours.

After completion of the reaction, the pH was adjusted to 4.5 with 20% hydrochloric acid, and then the resin component was extracted with a mixed solvent of xylene/n-butanol/cyclohexane = 1/2/1 (mass ratio) to remove the catalyst and neutralized salt. After removal, azeotropic dehydration was then performed under reduced pressure to obtain a solution of phenol resin No. 1 having a solid content of 50%. The number average molecular weight of the resin solid content of phenol resin solution No. 1 was 350, and the average number of methylol groups per benzene nucleus was 1.3.

Preparation Example 7 Preparation of phenol resin No. 2 solution

108 parts of m-cresol, 216 parts of 37% formaldehyde aqueous solution, and 160 parts of 25% aqueous sodium hydroxide solution were placed in a glass four-necked flask equipped with a thermometer, stirrer, reflux condenser and nitrogen inlet, and reacted at 50 ° C. under a nitrogen stream. Then, the temperature was raised to 100 ° C., the reaction was carried out for another hour, and after neutralization with hydrochloric acid, the resin component was extracted with a mixed solvent of xylene / n-butanol = 1/1 (mass ratio), and the catalyst and neutralized salt were removed, Subsequently, azeotropic dehydration was performed under reduced pressure to obtain a solution of phenol resin No. 2 having a solid content of 50%. The number average molecular weight of the resin solid content of the phenol resin No. 2 solution was 350, and the average number of methylol groups per benzene nucleus was 0.7.

Preparation of water-based paint composition for cans

Example 1

In a container, 100 parts (solid content) of acrylic modified epoxy resin No. 1 aqueous dispersion obtained in Production Example 4, 0.3 parts of refined palm oil (Note 2), 1 part of AB-50 (Note 9), and phenol resin No. obtained in Production Example 6 .1 solution 3 parts (solid content) were mixed uniformly, and it adjusted with deionized water, and obtained the water-based coating composition for cans No. 1 of 30 mass % of solid content.

Examples 2 to 84 and Comparative Examples 1 to 65

Water-based coating compositions for cans No. 2 to No. 149 were obtained in the same manner as in Example 1 except for the contents of Table 1. In addition, the results of testing according to the following test method are shown. The composition ratio in Table 1 is the solid content mass ratio.

In addition, water-based coating composition for cans No. 85 to 149 are for comparative examples.

In addition, each note in a table|surface is as follows.

(Note 2) Refined palm oil: manufactured by Nissin Seiyu Co., Ltd., palm oil, melting point 39°C

(Note 3) Refined lanolin: manufactured by CRODA, lanolin wax, melting point 39°C

(Note 4) HD-3028: manufactured by Gifu Shellac Co., Ltd., carnauba wax, melting point 82°C

(Note 5) Hi-Mic-1070: manufactured by Nippon Seiro Co., Ltd., microcrystalline wax, melting point 80°C

(Note 6) Lanco1370LF: manufactured by Nippon Lubrizol Co., Ltd., polypropylene wax, melting point 150°C, average particle diameter 9 μm

(Note 7) CERAFLOUR 991: manufactured by BYK, polyethylene wax, melting point 115°C, average particle diameter 5㎛

(Note 8) CERAFLOUR 913: manufactured by BYK, trade name, polypropylene wax, melting point 160°C, average particle diameter 18㎛

(Note 9) AB-50: manufactured by Gifu Shellac Manufacturing Co., Ltd., average particle diameter 1 μm, penetration 1 to 2

(Note 10) A-375: manufactured by Gifu Shellac Co., Ltd., average particle diameter 2 μm, penetration 1 to 2

(Note 11) A-110: manufactured by Gifu Shellac Manufacturing Co., Ltd., average particle diameter 5 μm, penetration less than 1

(Note 12) Chemipearl W300: manufactured by Mitsui Chemicals Co., Ltd., average particle diameter 3 μm, penetration less than 1

(Note 13) Chemipearl W500: manufactured by Mitsui Chemicals Co., Ltd., average particle diameter 2.5 μm, penetration 10

(Note 14) Chemipearl F640: manufactured by Mitsui Chemicals Co., Ltd., average particle diameter 1 μm, penetration 10

In addition, (Note 9) to (Note 14) are polyolefin dispersions.

(Note 15) Nacure 5225: manufactured by King Industries, USA, trade name, amine neutralization solution of dodecylbenzenesulfonic acid

(Note 16) Nacure 2500: manufactured by King Industries, USA, trade name, amine neutralization solution of p-toluenesulfonic acid

[Table 1]

[Table 2]

[Table 3]

[Table 4]

[Table 5]

[Table 6]

[Table 7]

[Table 8]

[Table 9]

Creation of trial version

An aluminum plate with a thickness of 0.26 mm was coated with a bar coater so that the dry film weight was 40 mg / 100 cm 2 for each aqueous coating composition for cans No. It baked for 17 seconds under conditions of an atmospheric temperature of 315°C and a wind speed of 30 m/min so that the temperature was 270°C, and corresponding test plates were obtained.

About each obtained test plate, the following evaluation items were tested and evaluated. Table 1 shows the evaluation results together.

Coating film appearance: About each test plate, the external appearance was evaluated visually. Appearance was evaluated according to the following criteria for smoothness, convexity and concavity of the surface of the coating film:

◎: The painted surface is smooth, and convexities and concavities of 1 mm or more in diameter are not recognized.

○: Very slight convexities and/or concavities with a diameter of 1 mm or more, and extremely slight irregularities were observed.

△: convexity and/or concavity with a diameter of 1 mm or more is recognized

×: Convexity and/or concavity with a diameter of 1 mm or more is remarkably recognized.

Workability: After cutting the test plate 5 cm in the rolling direction and 4 cm in the vertical direction, the lower part was folded in two parallel to the short side. In a room at 20°C, two aluminum plates with a thickness of 0.26 mm were sandwiched between the folded portions of the test piece, and set in a special folding type Dupont impact tester. After dropping an iron weight of 1kg with a flat contact surface from a height of 50cm to give an impact to the folding part, energize the folding tip with an applied voltage of 6.5V for 6 seconds, and then apply a current value of 20mm width to the folding tip. (mA) was measured and evaluated according to the following criteria:

◎ is less than 10mA

○ is 10 mA or more and less than 20 mA

Δ is greater than or equal to 20 mA and less than 40 mA

× is more than 40mA

Coefficient of kinetic friction: A mass of 1 kg supported by three steel balls was placed on a test plate adjusted to a size of 15 cm × 30 cm, and pulled at a speed of 150 cm / min. ) was obtained. The smaller the kinetic friction coefficient (μ value), the better the activity:

◎ indicates that the μ value is less than 0.06

In ○, the μ value is 0.06 or more and less than 0.1

Δ has a μ value of 0.1 or more and less than 0.15

× is a μ value of 0.15 or more

Scratch resistance: For a test plate adjusted to a size of 10 cm × 20 cm, a tribo gear (manufactured by Shinto Scientific Co., Ltd., trade name, HEIDON-22H, test needle 150 μm, scratch speed 60 mm / min) was used, and the test needle The scratch resistance was evaluated by the load reached on the aluminum plate:

◎ indicates that the load that the test needle reached on the aluminum plate is 300 g or more

○ indicates that the load reached by the test needle on the aluminum plate is 200 g or more and less than 300 g

△ indicates that the load the test needle reached on the aluminum plate was 150 g or more and less than 200 g

× is less than 150g when the test needle reaches the aluminum plate

Abrasion resistance: For a test plate adjusted to a size of 1.5 cm × 16 cm, Bowden abrasion tester (manufactured by Shinko Joki Co., Ltd., slip tester with soda type, friction ball indenter 3/16 inch steel ball, load 4 kgf, friction speed 7 reciprocations / min. ), a friction test was performed, and the number of times of friction until scratches occurred on the coating film was measured, and evaluated according to the following criteria.

◎ shows no scratches on the coating film after 50 rubbing cycles

○ indicates that the coating film is scratched when the number of rubbing is 30 or more and 49 or less.

△ indicates that the coating film is scratched when the number of rubbing is 10 or more and 29 or less.

× indicates scratches on the coating film when the number of rubbing is 9 or less.

A can body having a coating film excellent in activity, wear resistance and workability can be provided.

Claims (7)

A coating composition containing an acrylic modified epoxy resin (A), a wax (B), a polyolefin aqueous dispersion (C) and a phenol resin (D),
The wax (B) is a wax (b1) with a melting point of less than 50°C, a wax (b2) with a melting point of 50°C or more and less than 100°C, and a wax (b3) with a melting point of 100 to 160°C and an average particle diameter of 1 to 15 μm (b3). ) contains at least one wax selected from the group consisting of
The average particle diameter of the polyolefin aqueous dispersion (C) is 0.1 to 5 μm, and the polyolefin penetration is 8 or less,
Based on the total solid content of the acrylic-modified epoxy resin (A), the total solid content of the wax (B) is 0.3 to 10% by mass, the total solid content of the polyolefin aqueous dispersion (C) is 1 to 10% by mass, the phenol resin (D ), characterized in that the total amount of solid content is 0.5 to 20% by mass
A water-based paint composition for cans;
According to claim 1,
Wax (b1) is at least one selected from the group consisting of lanolin wax, palm oil and glycerin triesters.
A water-based paint composition for cans;
According to claim 1 or 2,
wax (b2) is at least one selected from the group consisting of microcrystalline wax and carnauba wax;
A water-based paint composition for cans;
According to claim 1 or 2,
wax (b3) is at least one selected from the group consisting of polyethylene wax and polypropylene wax;
An aqueous coating composition for cans.
According to claim 1 or 2,
The solid content of wax (b1), wax (b2) and wax (b3) is 0.1 to 5% by mass of wax (b1) and 0.1 to 5% by mass of wax (b2) based on the total solid content of acrylic-modified epoxy resin (A). 5% by mass, and 0.1 to 5% by mass of wax (b3)
A water-based paint composition for cans;
According to claim 1 or 2,
for can lids
A water-based paint composition for cans;
having a coating film of the aqueous coating composition for a can according to claim 1 or 2;
can cover.