JP6696712B2 - Coating composition for cans - Google Patents

Description

  The present invention relates to a coating composition for a can, which has a reduced dynamic coefficient of friction, wear resistance, scratch resistance, workability, wax deposition resistance, and the like, and is excellent in lid-making property.

  For the metal can, for example, a metal base material such as aluminum, tin-free steel, or tin is used. A coating film is formed on the outer surface of the can, the can lid and the tab obtained by processing these metal base materials for the purpose of formability, design and metal surface protection. In particular, the coating film on the can lid is called so-called outer wax, in which wax is applied after the coating film is formed to withstand severe processing during molding, and the influence of the mold during processing on the coating film during molding of the can is reduced. After the wax is applied to the coating, it is processed.

  Although the above outer wax can improve the moldability, the size of the can lid is abnormal due to the wax being deposited and solidified in the mold depending on the conditions of wax application and can lid molding, and the solidified wax. However, the product may slip off the mold and adhere to the can lid, resulting in a decrease in finishability, and improvement has been demanded. In order to improve it, an inner wax type paint for cans in which a wax is contained in the paint in advance has been developed.

  For example, Patent Document 1 discloses a water-based coating composition for an outer surface of a can lid containing a pigment, a pigment-dispersing resin and a binder resin, wherein the pigment-dispersing resin has methacrylic acid, styrene and ethyl acrylate as constituent components. A waterborne coating composition for an outer surface of a can lid is disclosed which is characterized by an acrylic copolymer.

  In addition, Patent Document 2 contains a wax (W1) having a melting point of 50 to 90 ° C., a wax (W2) having a melting point of 100 ° C. or more and an average particle diameter of 1 to 10 μm, and a binder resin. Disclosed is a characteristic water-based coating composition for the outer surface of a can lid.

  However, in the coating composition described in Patent Document 1 or 2, when the total amount of wax is reduced, wax deposition is reduced, but the dynamic friction coefficient is increased and wear resistance and workability are sometimes deteriorated. On the other hand, when the total amount of wax is increased, the dynamic friction coefficient is lowered and the wear resistance and workability are improved, but the abrasion resistance is lowered and the wax is sometimes deposited on the lid making machine.

  From such a background, there has been a demand for a coating composition for a can, which has excellent reduction in dynamic friction coefficient, abrasion resistance, scratch resistance, workability, wax deposition resistance, and the like, and is excellent in lid-making property.

JP, 2006-176714, A JP, 2011-153247, A

  The problem to be solved by the present invention is to reduce the dynamic friction coefficient, wear resistance, scratch resistance and workability, and, while being an inner wax, only the performance imparted to the coating film by the outer wax can be obtained. Another object of the present invention is to provide a coating composition for a can, which is capable of reducing wax deposition on a can lid molding machine, which is a major problem at the time of applying an outer wax, and has excellent lid forming properties.

  As a result of diligent studies, the present inventors have found that a hydroxyl group-containing resin (A), a wax (b1) having a melting point of 35 to less than 50 ° C., a wax (b2) having a melting point of 50 ° C. to less than 100 ° C., and average particles. It was found that the object can be achieved by the coating composition for a can containing at least three kinds of wax (B3) having a diameter of 1 to 15 μm and a melting point of 100 ° C. to 160 ° C. (B3), and to complete the present invention. I arrived.

That is, the present invention is
1. Hydroxyl group-containing resin (A), wax (b1) having a melting point of 35 to less than 50 ° C., wax (b2) having a melting point of 50 ° C. to less than 100 ° C., and an average particle size of 1 to 15 μm and a melting point of 100 ° C. A coating composition for a can containing at least three kinds of wax (B) having a wax (b3) at 160 ° C., wherein the wax (B) is added based on 100 parts by mass of the solid content of the hydroxyl group-containing resin (A). The total amount is 0.3 to 10 parts by mass, and the ratio of the wax (b1), the wax (b2) and the wax (b3) in the wax (B) is 0.1 to 5 parts by mass of the wax (b1) and the wax. (B2) 0.1 to 5 parts by mass and wax (b3) 0.1 to 5 parts by mass, a can coating composition,
2. The coating composition for a can according to item 1, which contains 0.5 to 20 parts by mass of the phenol resin (C) based on 100 parts by mass of the solid content of the hydroxyl group-containing resin (A).
3. 3. The can coating composition according to item 1 or 2, wherein the wax (B) does not contain carnauba wax.
4. The coating composition for a can according to any one of 1 to 3, wherein the wax (b1) is a lanolin wax.
5. The can coating composition according to any one of claims 1 to 4, wherein the wax (b2) is a microcrystalline wax.
6. The coating composition for cans according to any one of 1 to 5, wherein the wax (b3) is polyethylene wax.
7. The coating composition for a can according to any one of 1 to 6, wherein the hydroxyl group-containing resin (A) is a hydroxyl group-containing acrylic modified epoxy resin.
8. The can coating composition according to any one of 1 to 7, which is an aqueous coating composition for a can lid,
9. The coating composition for a can according to any one of 1 to 8, wherein the surface roughness (Sa value) of the coating film is 0.38 μm or more,
10. A can lid obtained by applying the can coating composition according to any one of items 10 to 9.

  The coating composition for a can of the present invention is excellent in reduction of the coefficient of dynamic friction, abrasion resistance, scratch resistance and workability, and the performance of being imparted to the coating film by the outer wax even though it is the inner wax. Therefore, it is possible to reduce wax accumulation on the can lid molding machine, which is a major problem when applying the outer wax. From these things, it is possible to provide a can body having excellent lid-making properties.

  The present invention includes a hydroxyl group-containing resin (A), a wax having a melting point of 35 to less than 50 ° C (b1), a wax having a melting point of 50 ° C to less than 100 ° C (b2), and an average particle size of 1 to 15 µm. Is a coating composition for a can containing at least three types of wax (B3) having a wax (b3) of 100 ° C. to 160 ° C., wherein the wax is based on 100 parts by mass of the solid content of the hydroxyl group-containing resin (A). The total amount of (B) is 0.3 to 10 parts by mass, and the proportion of wax (b1), wax (b2) and wax (b3) in wax (B) is 0.1 to 5 in wax (b1). A coating composition for a can, characterized in that it is 0.1 parts by mass of wax (b2) and 0.1 to 5 parts by mass of wax (b3). The details will be described below.

[Can coating composition]
Hydroxyl group-containing resin (A)
Examples of the hydroxyl group-containing resin (A) include resins having a hydroxyl group, such as polyester resin, acrylic resin, polycarbonate resin, polyurethane resin, epoxy resin, and alkyd resin. These may be used alone or in combination of two or more. Among them, the hydroxyl group-containing resin (A) is preferably a hydroxyl group-containing acrylic modified epoxy resin from the viewpoint of wear resistance, scratch resistance and processability.

Hydroxyl Group-Containing Acrylic Modified Epoxy Resin The hydroxyl group-containing acrylic modified epoxy resin may be any of the following resins (1) and (2). Resin (1): Bisphenol type epoxy resin (a1) (hereinafter may be abbreviated as “epoxy resin (a1)”) and carboxyl group-containing acrylic resin (a2) (hereinafter abbreviated as “acrylic resin (a2)”) And a resin which is obtained by subjecting the resin to an ester addition reaction.

  In the resin (1), the epoxy resin (a1) and the acrylic resin (a2) can be easily subjected to an ester addition reaction by heating them in an organic solvent solution in the presence of an esterification catalyst.

  Resin (2): A resin obtained by graft-polymerizing a polymerizable unsaturated monomer component containing a carboxyl group-containing polymerizable unsaturated monomer onto the epoxy resin (a1). In the resin (2), the polymerizable unsaturated monomer component can be graft-polymerized to the epoxy resin (a1) in the presence of a radical generator such as benzoyl peroxide in an organic solvent.

  As the epoxy resin (a1) used in the resin (1) and the resin (2), for example, epichlorohydrin and bisphenol are polycondensed to a high molecular weight in the presence of a catalyst such as an alkali catalyst, if necessary. Resin, epichlorohydrin and bisphenol are condensed in the presence of a catalyst such as an alkali catalyst, if necessary, to give a low molecular weight epoxy resin, which is obtained by polyaddition reaction of this low molecular weight epoxy resin and bisphenol. The resin may be any of these resins, or an epoxy ester resin obtained by reacting the obtained resin or the above low molecular weight epoxy resin with a dibasic acid.

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 Examples thereof include-(4-hydroxyphenyl) phenol, oxybis (4-hydroxyphenyl), sulfonylbis (4-hydroxyphenyl), 4,4'-dihydroxybenzophenone and bis (2-hydroxynaphthyl) methane. However, bisphenol A and bisphenol F are preferably used. The above bisphenols can be used alone or as a mixture of two or more.

The dibasic acid used in the production of the epoxy ester resin is represented by the following formula (1)
HOOC- _{(CH 2)} n -COOH ··· formula (1)
(In the formula, n is an integer of 1 to 12) is preferably used, and specifically, succinic acid, adipic acid, pimelic acid, azelaic acid, sebacic acid, dodecanedioic acid, and hexa Hydrophthalic acid etc. can be illustrated.

  Examples of commercially available products of the epoxy resin (a1) include jER828 (epoxy equivalent of about 190), jER1007 (epoxy equivalent of about 1,700), jER1009 (epoxy equivalent of about 3,500), jER1010 (epoxy) manufactured by Mitsubishi Chemical Corporation. Equivalent about 4,500); Araldite AER6099 manufactured by Asahi Ciba (epoxy equivalent about 3,500); Epomic R-309 manufactured by Mitsui Chemicals, Inc. (epoxy equivalent about 3,500) and the like.

  The epoxy resin (a1) has 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 A bisphenol type epoxy resin in the range of 10,000 is preferable from the corrosion resistance of the obtained coating film.

  In addition, the number average molecular weight in this specification is the value which converted the number average molecular weight measured using the gel permeation chromatograph (GPC) on the basis of the molecular weight of standard polystyrene.

  Specifically, "HLC8120GPC" (trade name, manufactured by Tosoh Corporation) is used as a gel permeation chromatograph, and "TSKgel G-4000HXL", "TSKgel G-3000HXL", "TSKgel G-2500HXL" and a column are used. Four "TSKgel G-2000HXL" (trade name, all manufactured by Tosoh Corporation) are used, and measurement can be performed under the conditions of mobile phase tetrahydrofuran, measurement temperature of 40 ° C, flow rate of 1 mL / min, and detector RI.

  In the resin (1), the epoxy group in the epoxy resin (a1) undergoes an ester addition reaction with the epoxy group in the epoxy resin (a1) during the ester addition reaction. A group is required, and the average number of epoxy groups per molecule of epoxy resin is 0.5 to 2, preferably 0.5 to 1.6.

  On the other hand, in the above (2), since the graft reaction occurs due to hydrogen abstraction of 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 another polymerizable unsaturated monomer 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, which may be used alone or in combination of two or more. Can be used.

  The other polymerizable unsaturated monomer may be a monomer copolymerizable with the above-mentioned carboxyl group-containing polymerizable unsaturated monomer, and can be appropriately selected and used according to the required performance. And aromatic vinyl monomers such as styrene, vinyltoluene, 2-methylstyrene, t-butylstyrene, 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, cyclohexyl acrylate, methyl methacrylate, ethyl methacrylate, methacryl Acrylic acid such as n-propyl acid, isopropyl methacrylate, n-, i- or t-butyl methacrylate, hexyl methacrylate, 2-ethylhexyl methacrylate, octyl methacrylate, decyl methacrylate, lauryl methacrylate, cyclohexyl methacrylate. Or an alkyl ester or cycloalkyl ester of methacrylic acid having 1 to 18 carbon atoms; 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 3-hydroxypropyl acrylate, hydroxybutyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate , Hydroxyalkyl esters of acrylic acid or methacrylic acid such as 3-hydroxypropyl methacrylate, hydroxybutyl methacrylate, etc. having 2 to 8 carbon atoms; N-methylolacrylamide, N-butoxymethylacrylamide, N-methoxymethylacrylamide, N-methylolmethacrylamide. , N-butoxymethyl methacrylamide, and other N-substituted acrylamide-based or N-substituted methacrylamide-based monomers, and the like, or a mixture of two or more thereof.

  As the other polymerizable unsaturated monomer, a mixture of styrene and ethyl acrylate is particularly preferable, and the constitutional mass ratio of styrene / ethyl acrylate is 99.9 / 0.1-20 / 80, and further 99 / Suitably it is in the range of 1-40 / 60.

  The acrylic resin (a2) is not particularly limited in composition ratio and type of monomer, but is usually 15 to 80% by mass, particularly 20 to 60% by mass of the carboxyl group-containing radically polymerizable unsaturated monomer. %, And the content of the other radically polymerizable unsaturated monomer is preferably 85 to 20% by mass, and particularly preferably 80 to 40% by mass.

  The acrylic resin (a2) can be easily prepared, for example, by subjecting a mixture of the above-mentioned monomers to a solution 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 above reaction can be carried out by a conventionally known method. For example, an esterification catalyst is mixed in a uniform organic solvent solution of an epoxy resin (a1) and an acrylic resin (a2), and substantially all of the epoxy groups are Can be carried out by reacting at a reaction temperature of 60 to 130 ° C. for about 1 to 6 hours until is consumed. Examples of the esterification catalyst include tertiary amines such as triethylamine and dimethylethanolamine, and quaternary salt compounds such as triphenylphosphine. Of these, tertiary amines are preferable. is there.

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 in a viscosity range that does not hinder the reaction. When an esterification catalyst is used in the ester addition reaction, the amount used is usually in the range of 0.1 to 1 equivalent with respect to 1 equivalent of the epoxy group in the epoxy resin (a1). Is good.

  When the hydroxyl group-containing acrylic modified epoxy resin is a resin obtained by the resin (2), the other radical polymerizable unsaturated monomer component containing the carboxyl group-containing polymerizable unsaturated monomer to be graft-polymerized with the epoxy resin (a1) is Examples thereof include a carboxyl group-containing radically polymerizable unsaturated monomer and other polymerizable unsaturated monomers which are monomer components used in the production of the carboxyl group-containing acrylic resin (a2) in the resin (1).

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

  As the organic solvent, an epoxy resin (a1) and an acrylic resin (a2) or a polymerizable unsaturated monomer component containing a carboxyl group-containing polymerizable unsaturated monomer are dissolved, and a reaction product of these is used. Any conventionally known organic solvent can be used as long as it is an organic solvent that does not hinder the formation of an emulsion when a certain acrylic-modified epoxy resin (A) is neutralized and made aqueous.

  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, ethylene glycol monoethyl ether, ethylene. Examples thereof include glycol monobutyl ether and diethylene glycol monomethyl ether.

  The hydroxyl group-containing acrylic modified epoxy resin which is the resin (1) or the resin (2) has a carboxyl group and has a resin acid value of 10 to 160 mgKOH / g, and further 20 to 100 mgKOH / g. It is preferable from the viewpoint of dispersibility and coating film performance.

  The hydroxyl group-containing 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 the basic compound used for the neutralization of the carboxyl group, amines and ammonia are preferably used. Representative examples of the amines include alkylamines such as trimethylamine, triethylamine and tributylamine; alkanolamines such as dimethylethanolamine, diethanolamine and aminomethylpropanol; cyclic amines such as morpholine. The degree of neutralization of the acryl-modified epoxy resin is not particularly limited, but it is usually preferably in the range of 0.1 to 2.0 equivalents with respect to the carboxyl groups in the resin.

  The aqueous medium may be water alone, or may be a mixture of water and an organic solvent. As the organic solvent, any of the conventionally known ones can be used, and those mentioned as the organic solvent that can be used in the production of the hydroxyl group-containing acrylic modified epoxy resin can be preferably used. The amount of the organic solvent in the can coating composition of the present invention is in the range of 20% by mass or less, preferably 10% by mass or less based on the resin solid content of the can coating composition from the viewpoint of environmental protection. Is desirable.

  To neutralize and disperse the hydroxyl group-containing acrylic modified epoxy resin in the aqueous medium, a conventional method may be used. For example, the hydroxyl group-containing acrylic modified epoxy resin may be stirred in an aqueous medium containing a basic compound as a neutralizing agent. A method of gradually adding a resin, after neutralizing the hydroxyl group-containing acrylic modified epoxy resin with a basic compound, and then adding an aqueous medium to the neutralized product under stirring, or the neutralized product in an aqueous medium. The method of adding may be mentioned.

Wax (B)
As the wax (B) in the can coating composition of the present invention, natural wax or synthetic wax, glyceride and wax, and oxides or acid-modified products thereof can be used.

  Examples of the natural wax include hydrogenated hydrogenated fats and oils of beef tallow or lard, beeswax, lanolin wax, whale wax, hydrogenated whale wax, carnauba wax, candelilla wax, rice wax, wood wax, jojoba wax, shellac. And the like, mineral waxes such as paraffin wax, microcrystalline wax, montan wax, sericin wax and the like.

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

  Other natural waxes such as hydrogenated hydrogenated oils, beeswax, whale wax, hydrogenated whale wax, carnauba wax, candelia wax, rice wax, jojoba wax, shellac, paraffin wax, microcrystalline wax, montan wax, sericin wax, etc. Is mentioned.

  The coating composition for a can of the present invention includes at least one wax (b1) having a melting point of 35 to less than 50 ° C, and a wax having a melting point of 50 ° C to less than 100 ° C ( At least one wax selected from b2) and at least one wax selected from waxes (b3) having an average particle size of 1 to 15 μm and a melting point of 100 ° C. to 160 ° C. are used.

  By using at least three kinds of such specific waxes, the surface roughness of the coating film can be adjusted, the dynamic friction coefficient is reduced, the abrasion resistance, the scratch resistance, the workability and the wax deposition resistance are excellent. It is possible to provide a can body having excellent lid property. Further, it is desirable that these three types of wax (B) do not contain carnauba wax in terms of wax deposition resistance.

Wax (b1)
The wax (b1) is not particularly limited as long as it has a melting point of 35 to less than 50 ° C, preferably 37 to 45 ° C, and has a reduced dynamic friction coefficient, wear resistance, scratch resistance and processing. Lanolin wax, olive oil, palm oil, linseed oil and the like can be preferably used from the viewpoint of improving the properties.

  Commercially available products of wax (b1) include CORONET (lanolin wax, trade name, manufactured by Coronet), purified lanolin (lanolin wax, trade name, manufactured by CRODA), CERACOL 609N (lanolin wax, trade name, BYK Co.). Manufactured), outer Lo-1 (olive oil, trade name, manufactured by Riken Vitamin Co., Ltd.), and refined palm oil (palm oil, trade name, manufactured by Nisshin Oil Co., Ltd.).

Wax (b2)
The wax (b2) is not particularly limited as long as it has a melting point of 50 ° C. or higher and lower than 100 ° C., preferably 60 ° C. to 90 ° C., and has a reduced dynamic friction coefficient, wear resistance, scratch resistance and From the viewpoint of workability, microcrystalline wax can be preferably used.

  As wax (b2) commercially available products, SR-16 (microcrystalline wax, trade name, manufactured by Koyo Chemical Co., Ltd.), HI-DISPER 1260 (microcrystallin wax, trade name, manufactured by Gifu Serratsk Manufacturing Co., Ltd.), Topco S923 (microcrystalline wax, trade name, manufactured by Toyo Petrolite Co., Ltd.) and the like can be mentioned.

Wax (b3)
The wax (b3) is not particularly limited as long as it has an average particle size 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 can be preferably used in terms of reduction of the coefficient of dynamic friction, wear resistance, scratch resistance and workability.

  Examples of commercially available products of wax (b3) include CERAFULUR 991 (manufactured by BYK, trade name, polyethylene wax, average particle diameter 5 μm, melting point 115 ° C.), HIGH FLAT 2352 (manufactured by Gifu Serratsk Manufacturing Co., Ltd., trade name. , Oxidized polyethylene wax, average particle diameter 5 μm, melting point 138 ° C.), Lanco 1370LF (trade name, polypropylene wax manufactured by Nippon Lubrizol Co., average particle diameter 9 μm, melting point 150 ° C.) and the like.

  In the present invention, the melting point of the wax (B) indicates an endothermic peak temperature measured by a differential scanning calorimeter (DSC) at a heating rate of 10 ° C./min. When the wax has a plurality of endothermic peaks, the maximum endothermic peak was taken as the melting point. The average particle diameter of the wax was measured using Microtrac UPA (particle size analyzer manufactured by Nikkiso Co., Ltd.).

  In the present invention, the wax (B) is characterized by using at least three kinds of waxes, that is, the wax (b1), the wax (b2) and the wax (b3), and the total amount thereof is the solid content of the hydroxyl group-containing resin (A). The total amount is in the range of 0.3 to 10 parts by mass, preferably 0.3 to 6 parts by mass, and more preferably 0.5 to 1.5 parts by mass, based on 100 parts by mass.

  Furthermore, the mixing ratio of each of the wax (b1), the wax (b2) and the wax (b3) in the wax (B) is based on 100 parts by mass of the solid content of the hydroxyl group-containing resin (A). 0.1 to 5 parts by mass, preferably 0.2 to 2 parts by mass, more preferably 0.2 to 0.5 parts by mass, wax (b2) 0.1 to 5 parts by mass, preferably 0.2. To 2 parts by mass, more preferably 0.2 to 0.5 parts by mass, 0.1 to 5 parts by mass of the wax (b3), preferably 0.2 to 2 parts by mass, more preferably 0.2 to 0. Within the range of 5 parts by mass, the surface roughness (Sa value) can be adjusted, and it is desirable in terms of reduction of dynamic friction coefficient, wear resistance, scratch resistance, workability, and wax deposition resistance.

Specifically, the wax (b1) contributes to reduction of the dynamic friction coefficient and improvement of wear resistance. Further, the wax (b2) contributes to the adjustment of the surface roughness (Sa value), the wear resistance and the wax deposition resistance. The wax (b3) is considered to contribute to the adjustment of surface roughness (Sa value), scratch resistance, and wax deposition resistance.
Phenolic resin (C)
The can coating composition of the present invention may contain a phenol resin (C), if necessary. As the above-mentioned phenol resin (C), for example, a phenol compound (c1) such as a phenol compound or bisphenol A and an aldehyde (c2) such as formaldehyde are subjected to a condensation reaction in the presence of a reaction catalyst to introduce a methylol group. The resol type phenolic resin can be mentioned.

  Examples of the phenols (c1) include bifunctional phenol compounds such as o-cresol, p-cresol, p-tert-butylphenol, p-ethylphenol, 2,3-xylenol, and 2,5-xylenol; carboxylic acid, m. -Trifunctional phenol compounds such as cresol, m-ethylphenol, 3,5-xylenol, and m-methoxyphenol; tetrafunctional phenol compounds such as bisphenol A and bisphenol F; and one or two phenol compounds The above can be mixed and used.

  Examples of the aldehydes (c2) include formaldehyde, paraformaldehyde, trioxane and the like, and they can be used alone or in combination of two or more. As the alcohol used for alkyl-etherifying a part of the methylol group of the methylolated phenol resin, a monohydric alcohol having 1 to 6 carbon atoms, preferably 1 to 4 carbon atoms can be preferably used. .. Suitable monohydric alcohols include methanol, ethanol, n-propanol, n-butanol, isobutanol and the like.

  The phenol resin (C) used in the present invention has a number average molecular weight in the range of 200 to 2,000, preferably 300 to 1,200, and an average number of methylol groups per nuclei of benzene of 0. It is suitable that the number is in the range of 3 to 3.0, preferably 0.5 to 3.0.

The phenol resin (C) can improve workability by blending it as needed. When compounded, the compounding ratio is 0.5 to 20 parts by mass, preferably 1 to 16 parts by mass, more preferably 1.2 to 10 parts by mass based on 100 parts by mass of the total solid content of the hydroxyl group-containing resin (A). The amount of 10 parts by mass is suitable from the viewpoint of workability.
Can coating composition A can coating composition of the present invention is an aqueous coating composition in which a hydroxyl group-containing resin (A) is neutralized and dispersed in an aqueous medium, and a wax (b1) is contained in the composition. , At least three kinds of wax (B) including wax (b2) and wax (b3), and if necessary, phenol resin (C) and other additives such as surfactant, defoaming agent, pigment, and fragrance. Can be included. The solid content concentration of the can coating composition of the present invention is not particularly limited, but a range of 20 to 45% by mass, preferably 22 to 40% by mass is suitable from the viewpoint of coating stability.
The coating composition for a can of the present invention can be applied to various substrates, for example, tin, aluminum, tin-free steel, iron, zinc, copper, galvanized steel sheet, metal such as alloy-plated steel sheet, and the like. Chemical conversion treated metal plates that have undergone surface treatment such as phosphate treatment or chromate treatment, metal plates coated with a primer such as epoxy resin type or vinyl resin type on these metal plates, and these metal plates can And the like. Further, the application of the coating composition for a can of the present invention is useful for the inner and outer surfaces of a can, especially for a can lid that requires a strict lid-making property.
The coating composition for a can of the present invention is coated by various known methods, 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. Then, the material reaching temperature is 120 to 300 ° C., preferably the material reaching temperature is 200 to 280 ° C., and heat-dried for about 10 seconds to 30 minutes, preferably about 15 seconds to about 15 minutes to coat the coating film. It is a metal plate.

  The surface roughness (arithmetic mean roughness, Sa value) of the obtained coating film is 0.38 μm or more, preferably 0.38 or more and less than 0.5 μm, which means that the dynamic friction coefficient is reduced and It is desirable to obtain a can body having good wear resistance, scratch resistance, workability, wax deposition resistance, etc. and excellent lid-making properties. The surface roughness (arithmetic mean roughness, Sa value) can be measured by a three-dimensional image processing system (XG series) manufactured by Keyence Corporation. For example, the three-dimensional image-processed image of FIG. 1 shows that the shade is clear and the coating film has large irregularities. By devising such unevenness of the coating film, especially the convex shape of the coating film (contact portion with the lid making machine), reduction of dynamic friction coefficient, wear resistance, scratch resistance, workability and wax deposition resistance It was found that a can body having an excellent lid-making property can be obtained.

Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples. The present invention is not limited to the following examples. In the following, "parts" and "%" are based on mass.
Production of hydroxyl group-containing resin (A) Production Example 1 Epoxy resin solution No. Production of 1 A glass four-necked flask equipped with a thermometer, a stirrer, a reflux condenser and a nitrogen inlet was charged with 558 parts of jER828 (Note 1), 329 parts of bisphenol A, and 0.6 parts of tetrabutylammonium bromide. The reaction was carried out at 160 ° C under a nitrogen stream. The reaction was traced with an epoxy equivalent, and the reaction was performed for about 5 hours to obtain an epoxy resin solution No. Got 1. The obtained epoxy resin No. No. 1 had a number average molecular weight of about 8,000.
(Note 1) jER828: bisphenol A type epoxy resin manufactured by Mitsubishi Chemical Corporation, epoxy equivalent of about 190.

Production Example 2 Epoxy resin solution No. 2 manufacturing
A glass four-necked flask equipped with a thermometer, a stirrer, a reflux condenser and a nitrogen inlet was charged with 550 parts of jER828 (Note 1) and 450 parts of bisphenol A and heated under a nitrogen stream while stirring. When bisphenol A was dissolved and the mixture became transparent (around 100 ° C), 5.0 parts of tri-n-butylamine was charged, and the reaction was carried out at 160 ° C under a nitrogen stream.
The reaction was traced with an epoxy equivalent, and the reaction was performed for about 4 hours to obtain an epoxy resin solution No. Got 2. The obtained epoxy resin No. No. 2 had a number average molecular weight of about 4,500.

Production Example 3 Production of Acrylic Resin Solution A glass four-necked flask equipped with a thermometer, a stirrer, a reflux condenser and a nitrogen inlet was charged with 882 parts of n-butanol, and "180 parts of methacrylic acid, 240 parts of styrene, acrylic A mixture of 180 parts of ethyl acidate and 18 parts of t-butylperoxy-2-ethylhexanoate "was heated to 100 ° C. under a nitrogen stream and added dropwise from the dropping funnel over about 3 hours. Stirring was continued for 2 hours at temperature and then cooled to obtain an acrylic resin solution having a solid content of 40%. 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 Hydroxyl group-containing acrylic modified epoxy resin solution No. Production of No. 1 The epoxy resin No. 1 obtained in Production Example 1 was placed in a glass four-necked flask equipped with a thermometer, a stirrer, a reflux condenser and a nitrogen inlet. 80 parts (solid content) of 1 solution, 20 parts (solid content) of the acrylic resin solution obtained in Production Example 3, and 33 parts of diethylene glycol monobutyl ether were added and heated to 100 ° C. to dissolve them, and then N, N- After 2 parts of dimethylaminoethanol was added and the reaction was carried out for about 2 hours, 3 parts of N, N-dimethylaminoethanol was added and the reaction was continued for 20 minutes. Then, 165 parts of deionized water was added dropwise over 1 hour to obtain a hydroxyl group-containing acrylic modified epoxy resin solution No. having an acid value of 34 mgKOH / g and a solid content of 30%. Got 1.

Production Example 5 Hydroxyl group-containing acrylic modified epoxy resin solution No. 2 manufacturing
In a glass four-necked flask equipped with a thermometer, a stirrer, a reflux condenser and a nitrogen inlet, 25 parts of ethylene glycol monobutyl ether, the epoxy resin solution No. 80 parts (solid content) of 2 was added, and the temperature was raised to 120 ° C. under a nitrogen stream while stirring.
Epoxy resin solution No. After 2 was 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” was added at 120 ° C. for 1 hour. After the dropping, and after finishing the dropping, the temperature was maintained at 120 ° C. for 1 hour, and the hydroxyl group-containing acrylic modified epoxy resin solution No. Got 2. Then, a hydroxyl group-containing acrylic modified epoxy resin solution No. 2 was cooled to 90 ° C., 6.2 parts of dimethylethanolamine was added, and the mixture was stirred for 15 minutes. Further, 201 parts of deionized water was added dropwise over 1 hour with stirring to give a hydroxyl group-containing acrylic modified epoxy resin solution No. having an acid value of 44 mgKOH / g and a solid content of 30%. Got 2.

Production Example 6 of Phenol Resin (C) Phenol Resin Solution No. Preparation of 1 A glass four-necked flask equipped with a thermometer, a stirrer, a reflux condenser and a nitrogen inlet was charged with 188 parts of phenol and 324 parts of 37% aqueous formaldehyde solution, and heated to 50 ° C to uniformly dissolve the contents. did. Next, after adding and mixing zinc acetate to adjust the pH in the system to 5.0, the mixture was heated to 90 ° C. and reacted for 5 hours. Then, the mixture was cooled to 50 ° C., 32% calcium hydroxide aqueous dispersion was slowly added to adjust the pH to 8.5, and then the reaction was carried out at 50 ° C. for 4 hours.

  After the reaction was completed, 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 neutralize the catalyst. The salt was removed, and then azeotropic dehydration was performed under reduced pressure to obtain a phenol resin solution No. Got 1. Phenol resin solution No. The resin solid content of No. 1 had a number average molecular weight of 350, and the average number of methylol groups per benzene nucleus was 1.3.

Production Example 7 Phenol resin solution No. Preparation of 2 A glass four-necked flask equipped with a thermometer, a stirrer, a reflux condenser and a nitrogen inlet was charged with 108 parts of m-cresol, 216 parts of 37% aqueous formaldehyde solution and 160 parts of 25% aqueous sodium hydroxide solution, After reacting at 50 ° C under a nitrogen stream, the temperature was raised to 100 ° C and the reaction was continued for 1 hour. After neutralization with hydrochloric acid, the resin component was mixed with a mixed solvent of xylene / n-butanol = 1/1 (mass ratio). Is extracted to remove the catalyst and neutralized salt, and then azeotropically dehydrated under reduced pressure to obtain a phenol resin solution No. Got 2. Phenol resin solution No. The resin solid content of No. 2 had a number average molecular weight of 350 and an average number of methylol groups per benzene nucleus was 0.7.

Example 1 Can coating material No. 1
In a container, the acrylic modified epoxy resin solution No. 1 obtained in Production Example 4 was used. 100 parts (solid content), 0.5 parts of H-645 wax (Note 2), 0.5 parts of SR-16 (Note 5), and 0.5 parts of CERAFLOUR 991 (Note 9) were uniformly mixed and the mixture was removed. Can paint No. 1 having a solid content of 30% by mass adjusted with ionized water. Got 1.

Examples 2 to 21 Can paint No. 2 to No. 21
Can coating No. 1 was obtained in the same manner as in Example 1 except that the content of the formulation in Table 1 was used. 2 to No. I got 21. In addition, the result of the test according to the following test method is shown.

Comparative Example 1 Can coating material No. 22
In the container, the hydroxyl group-containing acrylic modified epoxy resin No. 1 obtained in Production Example 4 was used. 100 parts (solid content), HD-3028 (* 6) 1 part, and CERAFLOUR 991 (* 9) 1 part were uniformly mixed and adjusted with deionized water to prepare a paint for can No. having a solid content of 30% by mass. ． I got 22.

Comparative Examples 2 to 18 Can No. 23-No. 39
Can coating No. 1 was obtained in the same manner as in Comparative Example 1 except that the formulation contents in Table 2 were used. 23-No. I got 39. The result of the test according to the following test method is shown.

(Note 2) H-645 wax: manufactured by Chukyo Yushi Co., Ltd., lanolin, melting point 40 ° C.
(Note 3) Refined palm oil: manufactured by Nisshin Oil Co., Ltd., palm oil, melting point 39 ° C.
(Note 4) Purified lanolin: manufactured by CRODA, lanolin wax, melting point 39 ° C.
(Note 5) SR-16: Koyo Chemical Co., Ltd., microcrystalline wax, melting point 83 ° C.
(Note 6) HD-3028: Gifu Serratku Seisakusho Co., Ltd., carnauba wax, melting point 82 ° C. (Note 7) Super Heart Run: CRODA, lanolin alcohol, melting point 65 ° C.
(Note 8) Lanco 1370LF: manufactured by Nippon Lubrizol, polypropylene wax, melting point 150 ° C., average particle diameter 9 μm.
(Note 9) CERAFLOUR 991: BYK, polyethylene wax, melting point 115 ° C., average particle size 5 μm
(Note 10) Synfluo 178XF: manufactured by MICRO POWDERS, microcrystalline wax, melting point 106 ° C., average particle diameter 4 μm
(Note 11) CERAFLOUR 913: manufactured by BYK, trade name, polypropylene wax, melting point 160 ° C., average particle diameter 18 μm.

Preparation of test plate The water-based coating composition obtained in each example was coated on a 0.26 mm thick aluminum plate with a bar coater so that the dry coating film weight was 40 mg / 100 cm ^2, and the maximum temperature reached by the dryer was reached. Of 270 ° C. and an air temperature of 315 ° C. and a wind speed of 30 m / min for 17 seconds to obtain a test plate.

(Note 12) Surface roughness:
The surface roughness (arithmetic mean roughness, Sa value) of the test plate was measured using an optical interference microscope (XG series manufactured by Keyence Corporation, trade name, three-dimensional image processing system), and the average of the test plates (5 sheets) The value was evaluated according to the following criteria. In addition, the test plate whose appearance was visually inferior and whose appearance was remarkably defective was excluded from the measurement of the surface roughness.
⊚ indicates that the surface roughness (arithmetic mean roughness, Sa value) is 0.38 or more and less than 0.5. .. The three-dimensional image is illustrated in FIG. 1. A surface roughness (arithmetic mean roughness, Sa value) is 0.3 or more and less than 0.38. ··· The three-dimensional image is illustrated in FIG. 2. Δ indicates that the surface roughness (arithmetic mean roughness, Sa value) is 0.19 or more and less than 0.3. .. The three-dimensional image is illustrated in FIG. 3. X indicates that the surface roughness (arithmetic mean roughness, Sa value) is less than 0.19. .. The three-dimensional image is illustrated in FIG.

(Note 13) Dynamic friction coefficient:
A mass of 1 kg supported by three steel balls was placed on a test plate and pulled at a speed of 150 cm / min to obtain a dynamic friction coefficient (μ value). The smaller the dynamic friction coefficient (μ value), the better the sliding property.
◎, μ value is less than 0.06
◯: μ value is 0.06 or more and less than 0.1 Δ: μ value is 0.1 or more and less than 0.15
X has a μ value of 0.15 or more.

(Note 14) Wear resistance:
The test plate is subjected to a friction test with a Bowden abrasion tester (manufactured by Shinko Machinery Co., Ltd., Soda adhesion tester, friction ball indenter 3/16 inch steel ball, load 4 kgf, friction speed 7 reciprocations / min). The number of times of friction until scratches were generated on the coating film was measured and evaluated according to the following criteria.

⊚ indicates that the number of times of rubbing is 50 times and no scratches are found on the coating film. ◯ indicates that the number of times of rubbing is 30 times or more and scratches on the coating layer is 49 times or less. Δ indicates that the number of rubbing times is 10 times or more. Also, the coating film has scratches after 29 times or less. In the case of ×, the coating film has scratches after the number of times of friction is 9 times or less.

(Note 15) Scratch resistance:
Tribogear (Shinto Kagaku Co., Ltd., trade name, HEIDON-22H, test needle 150 μm, scratching speed 60 mm / min) is used for the test plate, and the test needle reaches the aluminum plate, and the scratch resistance is obtained. Was evaluated.
◎ indicates that the load when the test needle reaches the aluminum plate is 300 g or more. ○ indicates that the load that the test needle reaches the aluminum plate is 200 g or more and less than 300 g. △ indicates that the load that the test needle reaches the aluminum plate is 150 g or more. And less than 200 g x, the load at which the test needle reached the aluminum plate was less than 150 g.

(Note 16) Workability:
After the test coated plate was cut in the rolling direction by 5 cm and in the vertical direction by 4 cm, the lower part was folded in two in parallel with the short side. Two aluminum plates having a thickness of 0.26 mm were sandwiched between the bent portions of the test pieces of this test coated plate in a room at 20 ° C. and set in a special goby folding DuPont impact tester. After dropping a weight of iron having a flat contact surface and a weight of 1 kg from a height of 50 cm to give an impact to the bent portion, the bent tip is energized with an applied voltage of 6.5 V for 6 seconds, The current value (mA) of the 20 mm width of the bent tip was measured and evaluated according to the following criteria.
⊚ is less than 10 mA. ◯ is 10 mA or more and less than 20 mA. Δ is 20 mA or more and less than 40 mA. × is 40 mA or more.

(Note 17) Wax accumulation resistance:
Nine test plates are used, and eight SUS plates are alternately sandwiched between the nine test plates to form a layer, which is then pressed by a pressure bonding machine. After performing the press 5 times, all the test plates were exchanged again, and 8 SUS plates similar to those used in the previous 5 presses were alternately sandwiched between 9 test plates, and the press was repeated 5 times (total). 10 times). The mass increase of the SUS plate before and after pressing was measured and evaluated according to the following criteria.
⊚ indicates that the mass increase of the SUS plate is less than 1.0 mg. ○ indicates that the mass increase of the SUS plate is 1.0 mg or more and less than 3.0 mg. Δ indicates that the mass increase of the SUS plate is 3. 0 mg or more and less than 10.0 mg × indicates that the mass increase of the SUS plate is 10.0 mg or more.

(Note 18) Overall evaluation:
Comprehensive evaluation was performed based on the following criteria. In addition, it is desirable that the abrasion resistance, the scratch resistance, the workability, the wax deposition resistance, and the like are good and the lid-making property is excellent.
In the evaluation of dynamic friction coefficient, abrasion resistance, scratch resistance, workability, and wax deposition resistance, ⊚ indicates that the total of ⊚ is 3 or more and does not include the evaluation of Δ or less.
◯ indicates that the evaluation of dynamic friction coefficient, wear resistance, scratch resistance, workability and wax deposition resistance has a total of 2 or less, and does not include the evaluation of Δ or less.
In the evaluation of dynamic friction coefficient, wear resistance, scratch resistance, workability, and wax deposition resistance, Δ is 2 or less in total, and includes evaluation of Δ or less, but there is no x.
The symbol "x" indicates that the coefficient of dynamic friction, wear resistance, scratch resistance, workability, or wax deposition resistance is evaluated.

   It is possible to provide a can body having a good dynamic friction coefficient, wear resistance, scratch resistance, workability, wax deposition resistance, etc., and excellent lid-making properties.

It is a three-dimensional image processed image by an optical interference microscope where the unevenness of the coating film is "◎" level. It is a three-dimensional image processing image by the optical interference microscope with the unevenness of the coating film being a level of "○". It is a three-dimensional image processing image by the optical interference microscope with the unevenness of the coating film at the level of "△" It is a three-dimensional image processing image by the optical interference microscope of the unevenness of the coating film is "x" level.

Claims (9)

Hydroxyl group-containing resin (A), wax (b1) having a melting point of 35 to less than 50 ° C. , microcrystalline wax (b2) having a melting point of 60 ° C. to less than 90 ° C., and an average particle size of 1 to 15 μm and a melting point of 100. A coating composition for a can containing at least three kinds of waxes (B3) having a wax (b3) of 100 to 160 ° C., the wax (B) being based on 100 parts by mass of the solid content of the hydroxyl group-containing resin (A). ) Is 0.3 to 10 parts by mass, and the proportion of wax (b1), wax (b2) and wax (b3) in wax (B) is 0.1 to 5 parts by mass of wax (b1). And 0.1 to 5 parts by mass of the wax (b2) and 0.1 to 5 parts by mass of the wax (b3). The can coating composition according to claim 1, which contains 0.5 to 20 parts by mass of the phenol resin (C) based on 100 parts by mass of the solid content of the hydroxyl group-containing resin (A). The coating composition for cans according to claim 1 or 2, wherein the wax (B) does not contain carnauba wax. The can coating composition according to any one of claims 1 to 3, wherein the wax (b1) is a lanolin wax. Wax (b3) is, for cans coating composition according to any one of claims 1 to 4 which is a polyethylene wax. Hydroxyl group-containing resin (A), coating composition for cans according to any one of claims 1 to 5 is a hydroxyl group-containing acrylic-modified epoxy resin. Coating composition for cans according to any one of claims 1 to 6, which is a water-based coating compositions for can lids. Coating composition for cans according to any one of claims 1 to 7 the surface roughness of the coating film (Sa value) is not less than 0.38 .mu.m. A can lid obtained by coating the can coating composition according to any one of claims 1 to 8 .

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