JP3229688B2 - Water-based paint - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water-based paint for the outer surface of a can which can form a coating film having excellent workability, retort resistance and adhesion, and which is excellent in wet ink suitability, especially a clear paint for finishing the outer surface of a can. About.

[0002]

2. Description of the Related Art Metal cans have been widely used as containers for packaging various beverages and foods. The outer surfaces of these cans are printed and painted to prevent corrosion of the cans from the external environment, and also for aesthetic purposes and to indicate the contents. For printing and painting on the outer surface of the can, a metal plate is subjected to size coating, then white coating, followed by printing with ink or the like, and a clear paint for finishing is further painted thereon. Size coating and white coating may be omitted. Conventionally, organic solvent solutions such as acrylic / amino resins, polyester / amino resins, and epoxy / amino resins have been widely used as clear paints for finishing.

[0003]

However, since these paints are organic solvent-based paints, they are not preferable in terms of environmental hygiene and fire safety. Therefore, in order to solve these problems, a water-based paint containing no or almost no organic solvent is strongly desired. Japanese Unexamined Patent Publication (Kokai) No. 4-39369 proposes an aqueous acrylic / amino resin. However, although the hardness after retort sterilization is excellent, the workability for severe processing is not yet at a sufficient level.

[0004] In view of the above problems, the present invention provides a water-based paint for the outer surface of a can which can withstand advanced processing, form a coating film having good retort resistance and adhesion, and has excellent wet ink suitability. It is.

[0005]

Means for Solving the Problems The present inventors have established a specific 2
It has been found that the above-mentioned problem can be solved by a water-based paint containing an acrylic resin and an aminoplast resin.

That is, the present invention provides: (A) Weight average molecular weight 6,000 obtained by copolymerizing the following monomers
40 to 60 parts by weight of an acrylic resin having a glass transition temperature of more than 0 ° C. and a methacrylic acid or an alkyl ester of acrylic acid, a glycidyl of methacrylic acid or acrylic acid having an alkyl group having 8 to 20 carbon atoms Esters and 8 to 2 carbon atoms
And at least one monomer selected from adducts of acrylic acid or methacrylic acid and monoepoxy compounds having 8 to 20 carbon atoms.
At least one monomer selected from the group consisting of a ω-hydroxyalkyl ester of methacrylic acid or acrylic acid having a primary hydroxyalkyl group having 4 to 18 carbon atoms and a compound represented by the following formula [1]: %,

[0007]

Embedded image

Wherein R ¹ is H or CH ₃ , R ² is H, CH ₃ or CH ₂ CH ₃ , k is an integer of 2-4, m is an integer of 2-4, n is 1 Represents an integer of 1 to 5. 3 to 10% by weight of an ethylenically unsaturated carboxylic acid; 0 to 10% by weight of a hydroxyalkyl ester of methacrylic acid or acrylic acid having a hydroxyalkyl group having 2 to 3 carbon atoms; An acrylic resin having a weight average molecular weight of 5,000 to 50,000 and a glass transition temperature of 0 ° C. or lower obtained by copolymerizing the following monomers: To 20 parts by weight, having an N-alkoxymethyl group having 1 to 6 carbon atoms, 10 to 40% by weight of N-alkoxymethylmethacrylamide or N-alkoxymethylacrylamide, 3 to 10% by weight of an ethylenically unsaturated carboxylic acid, 0 to 10% by weight of a hydroxyalkyl ester of acrylic acid or methacrylic acid; Possible above-ethylenically unsaturated monomer 40-87 wt% of the non, and (C) a consisting aminoplast resins 20-50 parts by weight of the resin mixture a paint resin component, the resin (A)
And (B) are neutralized with a base, and the resins (A), (B) and (C) are dissolved or dispersed in water.

[0009] The present invention also provides: Item 1 wherein the ethylenically unsaturated monomer in the acrylic resin (A) is at least one monomer selected from an aromatic vinyl monomer and an alkyl ester of methacrylic acid or acrylic acid having an alkyl group having 1 to 4 carbon atoms. The water-based paint described in the above.

[0010] The present invention further provides: Acrylic resin (B)
3. The item 1 or 2 above, wherein the ethylenically unsaturated monomer is at least one monomer selected from an aromatic vinyl monomer and an alkyl ester of methacrylic acid or acrylic acid having an alkyl group having 1 to 4 carbon atoms. Water-based paint.

The present invention also relates to 4. Item 4. The water-based paint according to any one of Items 1 to 3, wherein the aminoplast resin is an alkyl etherified melamine resin, an alkyl etherified benzoguanamine resin, or an alkyl etherified melamine benzoguanamine co-condensation resin.

Further, the present invention provides an aminoplast resin comprising:
Item 5. The aqueous coating composition according to item 4, which is a melamine-benzoguanamine co-condensation resin which is methyletherified, methoxy-ethoxy mixed etherified or methoxy-butoxy mixed etherified.

[0013]

In the paint of the present invention, the acrylic resin (A)
An acrylic resin having a weight-average molecular weight of 6,000 to 15,000 and a glass transition temperature exceeding 0 ° C., and containing the following monomers as components:

The monomer of the formula (1) has a carbon number of 8 to 8 such as n-octyl (meth) acrylate, lauryl (meth) acrylate and 2-ethylhexyl (meth) acrylate.
An alkyl ester of methacrylic acid or acrylic acid having 20 alkyl groups; an adduct of glycidyl (meth) acrylate with a fatty acid having 8 to 20 carbon atoms such as oleic acid, lauric acid, stearic acid; acrylic acid or methacrylic acid; 8 to 8 carbon atoms such as Cardura E10 (Glycidyl ester of branched higher fatty acid, manufactured by Shell Chemical Company)
At least one monomer selected from adducts with 20 monoepoxy compounds;
Octyl (meth) acrylate and 2-ethylhexyl (meth) acrylate are preferred.

The monomer of ω- having 4 to 18 carbon atoms such as 4-hydroxybutyl (meth) acrylate is used.
Ω-hydroxyalkyl (meth) acrylate having a hydroxyalkyl group; for example, in the above formula [1], for example, commercially available products such as Praxel FM2, FM3, and FA2 (all manufactured by Daicel Chemical Industries, Ltd.) It is at least one monomer selected from the compounds represented. The compound represented by the formula [1] is, for example, 2
-Hydroxyalkyl (meth) acrylate such as hydroxyethyl (meth) acrylate and a lactone such as ε-caprolactone. As the monomer (1), 4-hydroxybutyl (meth) acrylate, Praxel FM2, FM3 and FA2 are particularly preferable.

The monomer is an ethylenically unsaturated carboxylic acid such as acrylic acid, methacrylic acid, crotonic acid, (anhydride) maleic acid, (anhydride) itaconic acid, and fumaric acid, and acrylic acid and methacrylic acid are particularly preferable.

The monomer is a hydroxyalkyl (meth) acrylate having a hydroxyalkyl group having 2 to 3 carbon atoms, such as 2-hydroxyethyl (meth) acrylate and hydroxypropyl (meth) acrylate.

The monomer may be any ethylenically unsaturated monomer other than the above-mentioned monomers, and may be, for example, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth). Acrylate, butyl (meth) acrylate,
C1-C6 alkyl ester of acrylic acid or methacrylic acid such as hexyl (meth) acrylate and cyclohexyl (meth) acrylate; for example, styrene, α
Aromatic vinyl monomers such as methylstyrene and vinyltoluene; alkoxyalkyl esters of methacrylic acid or acrylic acid such as methoxybutyl (meth) acrylate; vinyl ethers such as ethyl vinyl ether, butyl vinyl ether, cyclohexyl vinyl ether and phenyl vinyl ether; N-dimethylaminoethyl (meth) acrylate, (meth) acrylamide, N
-Nitrogen-containing monomers such as butoxymethyl (meth) acrylamide, N, N-dimethyl (meth) acrylamide and (meth) acrylonitrile; vinyl esters such as vinyl acetate, vinyl propionate, and isopropenyl acetate; and isopropenyl esters. be able to.
Among them, especially aromatic vinyl monomers such as styrene, α-methylstyrene, vinyltoluene and (meth)
Alkyl (meth) acrylates having an alkyl group having 1 to 4 carbon atoms, such as methyl acrylate, ethyl (meth) acrylate, and butyl (meth) acrylate, are preferred.

The above-mentioned constituents of the acrylic resin (A)
The amount of the monomer is within the following range with respect to the total amount of the monomers. Monomer: 15 to 30% by weight, preferably 15 to 2%
5% by weight of monomer: 10 to 30% by weight, preferably 15 to 3%
0% by weight of monomer: 3 to 10% by weight, preferably 4 to 8% by weight, monomer: 0 to 10% by weight, preferably 5 to 10% by weight, monomer: 20 to 72% by weight, preferably 30% ~ 6
5% by weight.

When the amount of the above monomer is less than 15% by weight, the suitability for wet ink is remarkably poor, and the ink is blurred or bleeds. On the other hand, when the amount exceeds 30% by weight, retort resistance is impaired. The hardness is significantly reduced. When the amount of the monomer is less than 10% by weight, retort resistance is impaired, and particularly, the scratch resistance of the coating film after the retort treatment is significantly reduced. On the other hand, when the amount exceeds 30% by weight, water resistance is reduced. When the amount of the monomer is less than 3% by weight, the stability as a water-based paint is impaired. On the other hand, when the amount exceeds 10% by weight, the viscosity increases, so that the solid content of the water-based paint is reduced. descend.

The above-mentioned monomers are blended as required for the purpose of improving the curability of the coating film, but if the blending amount exceeds 10% by weight, the water resistance is lowered. The above-mentioned monomer is a monomer constituting the balance of the monomer among the constituent monomers of the above, and even if less than 20% by weight, 7
If it exceeds 2% by weight, any of the monomers (1) to (4) will be out of the above range.

A method for obtaining the acrylic resin (A) by copolymerizing the above monomers (1) and (2) may be a known copolymerization method, such as a solution polymerization method or a bulk polymerization method. A solution polymerization method is preferred from the viewpoint of simplicity, and generally, a radical polymerization initiator in an organic solvent, in the presence of a chain transfer agent if necessary, usually at about 90 to 130 ° C. for 5 to 5 minutes.
It can be carried out by heating for about 10 hours to copolymerize.

Typical examples of the organic solvent include hydrocarbon solvents such as xylene and toluene; ketone solvents such as methyl ethyl ketone and methyl isobutyl ketone; ester solvents such as ethyl acetate and butyl acetate; and ethylene glycol monobutyl ether and the like. Ethylene glycol ether solvent: isopropyl alcohol, n-butanol,
Alcohol solvents such as isobutanol and the like,
These solvents can be appropriately selected and used. Representative examples of the radical polymerization initiator include peroxides such as benzoyl peroxide, ketone peroxide, and ammonium persulfate; and azo compounds such as 2,2'-azobisisobutyronitrile and azobisdimethylvaleronitrile. And the like. Representative examples of the chain transfer agent include lauryl mercaptan, octyl mercaptan, and α-methylstyrene dimer.

In the present invention, the acrylic resin (A)
Has a weight average molecular weight of 6,000 to 15,000, preferably 8,000 to 12,000, and a glass transition temperature exceeding 0 ° C, preferably 5 to 50 ° C. When the weight average molecular weight of the resin (A) is less than 6,000, retort resistance and processability are poor, while when it exceeds 15,000, the viscosity increases, so that the solid content of the water-based paint decreases and coating can be performed. Disappears. When the glass transition temperature of the resin (A) is 0 ° C. or lower, the hardness of the coating film decreases.

In the present invention, the weight average molecular weight is a value determined from a calibration curve of polystyrene by gel permeation chromatography, and the glass transition temperature is a value determined by differential scanning calorimetry (DSC).

In the present invention, the acrylic resin (B) is
An acrylic resin having a weight average molecular weight of 5,000 to 50,000 and a glass transition temperature of 0 ° C. or less, and having the following monomers as components:

The monomers are Nn-butoxymethyl (meth) acrylamide, N-ethoxymethyl (meth)
N-alkoxymethyl methacrylamide or N-alkoxymethylacrylamide having an N-alkoxymethyl group having 1 to 6 carbon atoms such as acrylamide and N-methoxymethyl (meth) acrylamide. Among these, particularly Nn-butoxymethylacrylamide,
Nn-butoxymethyl methacrylamide is preferred.
Examples of the monomer include the same monomers as those mentioned as the constituent monomer component of the acrylic resin (A), and acrylic acid and methacrylic acid are particularly preferable.

Examples of the monomer include the same monomers as those described as the constituent monomer component of the acrylic resin (A). May be any ethylenically unsaturated monomer copolymerizable with the above-mentioned monomers and other than the above-mentioned monomers, for example, methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, −
C1-C20 alkyl esters of acrylic acid or methacrylic acid such as ethylhexyl (meth) acrylate, lauryl (meth) acrylate, and stearyl (meth) acrylate; aromatic vinyl monomers such as styrene, α-methylstyrene, and vinyltoluene An alkoxyalkyl ester of methacrylic acid or acrylic acid such as methoxybutyl (meth) acrylate; vinyl ethers such as ethyl vinyl ether, butyl vinyl ether, cyclohexyl vinyl ether, and phenyl vinyl ether; N, N-dimethylaminoethyl (meth) acrylate; ) Nitrogen-containing monomers other than monomers such as acrylamide and N, N-dimethyl (meth) acrylamide; vinyl acetates such as vinyl acetate, vinyl propionate and isopropenyl acetate And the like ester or isopropenyl esters. Of these,
In particular, it has an aromatic vinyl monomer such as styrene, α-methylstyrene and vinyltoluene, and an alkyl group having 1 to 4 carbon atoms such as methyl (meth) acrylate, ethyl (meth) acrylate and butyl (meth) acrylate. Alkyl (meth) acrylates are preferred.

The above-mentioned constituents of the acrylic resin (B)
The amount of the monomer is within the following range with respect to the total amount of the monomers. Monomer: 10 to 40% by weight, preferably 20 to 4%
0% by weight of monomer: 3 to 10% by weight, preferably 4 to 8% by weight, monomer: 0 to 10% by weight, preferably 0 to 5% by weight, monomer: 40 to 87% by weight, preferably 50% ~ 7
5% by weight.

When the amount of the monomer is less than 10% by weight, the processability of the coating film after the retort treatment is remarkably deteriorated. On the other hand, when the amount is more than 40% by weight, the ratio of the amide bond increases and the processability decreases. When the amount of the monomer is less than 3% by weight, the stability as a water-based paint is impaired. On the other hand, when the amount exceeds 10% by weight, the viscosity increases, so that the solid content of the water-based paint is reduced. descend. The above-mentioned monomer is blended as necessary for the purpose of improving the curability of the coating film, but if the blending amount exceeds 10% by weight, water resistance,
Workability decreases. The above-mentioned monomer is a monomer constituting the balance of the monomer among the constituent monomers of, and even if the amount is less than 40% by weight or exceeds 87% by weight, any of the monomers of は ず is out of the above range. Will be.

The method for obtaining the acrylic resin (B) by copolymerizing the above monomers (1) and (2) may be a known copolymerization method, such as a solution polymerization method or a bulk polymerization method. A method similar to the method for manufacturing the above can be used.

In the present invention, the acrylic resin (B)
Has a weight average molecular weight of 5,000 to 50,000, preferably 8,000 to 20,000, and a glass transition temperature of 0C or lower, preferably -30 to -5C. If the weight average molecular weight of the resin (B) is less than 5,000, processability and hardness are inferior. On the other hand, if the weight average molecular weight exceeds 50,000, the viscosity becomes high, so that the solid content of the water-based paint is reduced and coating becomes impossible. When the glass transition temperature of the resin (B) exceeds 0 ° C., workability is impaired.

The aminoplast resin (C) used in the present invention
Examples thereof include partially or completely alkyletherified by alone or by mixing alkyl alcohols having 1 to 4 carbon atoms such as methanol, ethanol, n-propanol, isopropanol, n-butanol and isobutanol, Melamine resins, aminoformaldehyde resins such as benzoguanamine resin and melamine-benzoguanamine co-condensation resin, and more specifically, methyl etherified methylol melamine resin, methyl etherified methylol benzo guanamine resin, methyl etherified melamine-benzo guanamine co-condensation resin, Butyl etherified methylol melamine resin, butyl etherified methylol benzoguanamine resin, methoxy-ethoxy mixed etherified benzoguanamine resin, and the like. Among these, methyl etherification, methoxy-ethoxy mixed etherification, or methoxy-butoxy mixed etherified melamine-benzoguanamine co-condensation resin is particularly preferable in terms of retort resistance and workability.

The paint of the present invention comprises the acrylic resin (A),
A paint comprising a resin mixture comprising an acrylic resin (B) and an aminoplast resin (C) as a resin component, wherein at least a part of the resins (A) and (B) is neutralized by a base, and the resin (A) ), (B) and (C) are water-based paints which are dissolved or dispersed in water.

The mixing ratio of the resins (A), (B) and (C) is such that the total amount of the resins (A), (B) and (C) is 1
The ratio is within the following range with respect to 00 parts by weight. Resin (A): 40 to 60 parts by weight, resin (B): 10 to 20 parts by weight, resin (C): 20 to 50 parts by weight, preferably 30
~ 50 parts by weight. If the amount of the resin (A) is less than 40 parts by weight, the processability of the coating film is reduced, while if it exceeds 60 parts by weight, the retort resistance and the coating film hardness are reduced. If the amount of the resin (B) is less than 10 parts by weight, the processability decreases, while if it exceeds 20 parts by weight, the coating film hardness decreases. When the amount of the resin (C) is less than 20 parts by weight, the curability is reduced, so that the coating film hardness is reduced and the retort resistance is also deteriorated. On the other hand, when the amount of the resin (C) exceeds 50 parts by weight, the processability decreases.

The neutralization of the acrylic resins (A) and (B) can be carried out by using each of the resins (A) and (B), or a mixture of both, and, if necessary, aminoplasts with these resins. It can be performed by mixing a mixture with the resin (C) and other components with a basic compound by a known method. An aqueous solution in the form of an aqueous solution or an aqueous dispersion can be obtained by mixing water during neutralization or by mixing water after neutralization.

As the basic compound used for neutralization,
Hydroxides of alkali metals such as sodium hydroxide; ammonia; primary amines such as ethylamine and monoethanolamine; secondary amines such as diethylamine and diethanolamine; N, N-dimethylaminoethanol;
And tertiary amines such as triethylamine, morpholine, triethanolamine, trimethylamine, triisopropylamine, and methyldiethanolamine. Of these, tertiary amines such as N, N-dimethylaminoethanol, triethylamine, morpholine and triethanolamine are particularly preferred. The amount of the above basic compound used to neutralize the acrylic resin (A) or (B) is such that the basic compound is 0.8 to 1 mol of the carboxyl group in the resin (A) or (B). The range which becomes -1.2 mol is preferable.

The aqueous coating composition of the present invention comprises a neutralized product of an acrylic resin (A) and a neutralized product of an acrylic resin (B) with a basic compound, (Acrylic resin (A), acrylic resin (B), basic compound ), Aminoplast resin (B), water,
If necessary, a curing catalyst, an organic solvent, and a pigment, for example, a paint additive such as a leveling agent, an antifoaming agent, and a lubricant may be contained. Examples of the curing catalyst include p-toluenesulfonic acid, monoalkyl phosphate, amine salts of p-toluenesulfonic acid, and amine salts of alkylbenzenesulfonic acid. The compounding amount of the curing catalyst is usually 5 parts by weight or less based on 100 parts by weight of the resin solid content of the paint.

The solid content of the aqueous coating composition of the present invention is not particularly limited, but is usually in the range of about 35 to 60% by weight. The water-based paint of the present invention can form a coating film having excellent workability, retort resistance, and adhesion, and is excellent in wet ink suitability as a clear paint for finishing on the outer surface of a can.

The water-based paint of the present invention exhibits excellent performance as described above, and is therefore suitable as a white coating for the outer surface of a can. When used as a white coating, a white pigment such as titanium white and, if necessary, talc, calcium carbonate, silica and the like are blended as the pigment component.

The coating process for the outer surface of a can using the water-based paint of the present invention is not particularly limited, but usually, size coating as a primer or directly on a metal material such as tin, aluminum, tin-free steel or the like is performed. The white coating is applied on top. The thickness of the white coating is generally 5 to 15 μm, and the drying conditions are usually at 160 to 220 ° C. for about 30 seconds to 10 minutes.

In general, printing is performed on the above-mentioned metal material directly or on a white coating using an oil-based ink or the like, and a clear paint for finishing is applied thereon. The thickness of the water-based paint of the present invention as a clear paint for finishing is a dry film, generally 5 to 15 μm, and the drying condition is usually 160 to 2 μm.
It is about 30 seconds to 10 minutes at 20 ° C. When applying the clear paint for finishing on the print, it may be applied after the print is dried, but since it has excellent wet ink suitability, it is necessary to apply it in a wet state where the print does not dry This is advantageous because the step can be omitted. The water-based paint of the present invention is white coating, roller coating in any of the clear paint for finishing, a roll coater,
The coating can be performed by a known coating means such as a curtain flow coater, a spray coating, and an electrostatic coating.

[0043]

The water-based paint for external surfaces of cans of the present invention is water-based and is therefore preferable in terms of environmental hygiene and prevention of fire. The obtained coating film has excellent workability, retort resistance and adhesion. Since it has excellent wet ink suitability as a clear paint for finishing the outer surface of a can, it is suitable as a clear paint for finishing the outer surface of a can and a white coating for the outer surface of a can.

[0044]

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples, but the present invention is not limited to these examples. In the following, "part"
All of “%” and “%” are based on weight.

Production of Acrylic Resin (A) Solution Production Example 1 30 parts of ethylene glycol monobutyl ether was charged into a four-necked flask equipped with a thermometer, a stirrer, a reflux condenser, and a nitrogen gas injection tube, and the temperature was raised to 120 ° C. did. In this, 30 parts of styrene, 20 parts of methyl methacrylate,
Mixed solution of 18 parts of 2-ethylhexyl methacrylate, 18 parts of Praxel FM3 (manufactured by Daicel Chemical Industries, Ltd.), 10 parts of hydroxyethyl methacrylate, 4 parts of acrylic acid, and 10 parts of 2,2'-azobisisobutyronitrile as a polymerization initiator Was added dropwise over 3 hours. Thereafter, the mixture was aged at 120 ° C. for 1 hour. Then, a mixture of 1 part of an additional polymerization catalyst 2,2′-azobisisobutyronitrile and 10 parts of ethylene glycol monobutyl ether was added dropwise over 1 hour, and the mixture was further aged for 3 hours. Acrylic resin (A-
1) A solution was obtained. The obtained acrylic resin (A-1)
The acid value was 31, the weight average molecular weight (based on gel permeation chromatography, the same applies hereinafter) of about 9,000, and the glass transition temperature (Tg point) was 42 ° C.

Production Examples 2 to 7 The same procedure as in Production Example 1 was repeated except that the composition of the mixed solution of the monomer and the polymerization initiator to be dropped was as shown in Table 1 below. ~ (A-7)
Was obtained. Production Examples 8 to 13 (for comparison) In Production Example 1, except that the composition of the mixed solution of the monomer and the polymerization initiator to be dropped was as shown in Table 2 below, the same procedure as in Production Example 1 was carried out, and a comparative acrylic resin ( a-1) ~
Each resin solution of (a-6) was obtained.

Production of Acrylic Resin (B) Solution Production Example 14 30 parts of ethylene glycol monobutyl ether was charged into a four-necked flask equipped with a thermometer, a stirrer, a reflux condenser, and a nitrogen gas injection tube, and the temperature was raised to 90 ° C. did. A mixed solution of 35 parts of n-butyl acrylate, 30 parts of 2-ethylhexyl methacrylate, 30 parts of Nn-butoxymethyl methacrylamide, 5 parts of acrylic acid and 6 parts of benzoyl peroxide as a polymerization initiator was added thereto for 3 hours. It dripped over. After that, it is aged at 90 ° C for 5 hours, and the solid content is about 7
A 7% acrylic resin (B-1) solution was obtained. The obtained acrylic resin (B-1) had an acid value of 39, a weight average molecular weight of about 10,000, and a glass transition temperature (Tg point) of -21 ° C.

Production Examples 15 to 17 The acrylic resin (B-2) was prepared in the same manner as in Production Example 14 except that the composition of the mixed solution of the monomer to be dropped and the polymerization initiator was changed as shown in Table 2 below. ~ (B-
Each resin solution of 4) was obtained. Production Examples 18 to 19 (for comparison) In Production Example 14, except that the composition of the mixed solution of the monomer and the polymerization initiator to be dropped was as shown in Table 2 below, the same procedure as in Production Example 14 was carried out, and a comparative acrylic resin ( b-1)
To (b-2) were obtained.

[0049]

[Table 1]

[0050]

[Table 2]

The resin acid value of the acrylic resin obtained in each production example,
The weight average molecular weight and the glass transition temperature (Tg point) were determined according to the following methods. Resin acid value: Determined by dissolving a sample in a mixed solution of ethanol and toluene and performing a neutralization titration with a 0.1 N potassium hydroxide-ethanol solution using a phenolphthalein indicator. Weight average molecular weight: Performed according to JIS K 0124-83, and provided TSK GEL G4000 + G
3000 + G2500 + G2000 (Toyo Soda Co., Ltd.)
At 40 ° C. and a flow rate of 1.0 ml / min.
It was determined from the chromatogram obtained with an R1 refractometer and a calibration curve of polystyrene using tetrahydrofuran for calculation. Glass transition temperature (Tg point): Differential scanning calorimeter DSC-5
Using 0Q (manufactured by Shimadzu Corporation), it was determined from a spectrum obtained by elevating the temperature at a rate of 5 ° C./min.

(Note) in Table 1 is as follows. (Note 1) Monomer G: glycidyl methacrylate 142
Parts and 285 parts of stearic acid, 0.43 parts of tetraethylammonium bromide, 0.071 parts of hydroquinone
The reaction was carried out at 120 ° C. with blowing air in the presence of parts.
The acid value was traced, and when the acid value reached 0.5, the reaction was stopped to obtain an adduct obtained as monomer G. (Note 2) Monomer E: 89 parts of methacrylic acid and AOEX-
24 (manufactured by Daicel Chemical Industries, Ltd., having 15 to 1 carbon atoms)
197 parts of 1,2-epoxyalkane (7) were reacted at 120 ° C. in the presence of 0.28 part of tetraethylammonium bromide and 0.045 part of hydroquinone under air blowing. The acid value was traced, and when the acid value reached 1.0, the reaction was stopped to obtain an adduct obtained as monomer E.

Example 1 The acrylic resin (A-A) having a solid content of about 71% obtained in Production Example 1
1) 70 parts of a solution, 13 parts of an acrylic resin (B-1) solution having a solid content of about 77% obtained in Production Example 14 and 3.1 parts of N, N-dimethylaminoethanol (1 mol of carboxyl groups in the acrylic resin) (Equivalent to 1.0 mol).
Mix uniformly at 50 ° C. and then Nicarac N-6215
50 parts of a methyl etherified methylol melamine-benzoguanamine co-condensation resin having a solid content of 80% (manufactured by Sanwa Chemical Co., Ltd.) and 0.7 parts of Nacure 5225 (manufactured by King Industries, USA, curing catalyst) were added. After thorough mixing at 30 ° C., deionized water was gradually added to prepare an aqueous paint having a solid content of about 40%.

Examples 2 to 11 and Comparative Examples 1 to 9 In Example 1, the types of the acrylic resin solution, the types of the aminoplast resin, and the amounts (solid content) of these resins were as shown in Table 3 below. A water-based paint was prepared in the same manner as in Example 1, except that the amount of N, N-dimethylaminoethanol was adjusted to 1.0 mol per 1 mol of carboxyl groups in the acrylic resin.

(Note) in Table 3 is as follows. (Note 3) Cymel 1123: Mitsui Cyanamid Co., Ltd.
Methoxy-ethoxy mixed etherified benzoguanamine resin, about 99% solids. (Note 4) Cymel 303: Mitsui Cyanamid Co., Ltd.
Made, methyl etherified melamine resin, solid content about 98%.

Preparation of Test Coated Plate A commercially available ink was coated on an aluminum plate having a thickness of 0.3 mm, and the aqueous paints obtained in the above Examples and Comparative Examples were applied thereon by a wet-on-wet method. Of 5 μm, and then baked for 90 seconds under the condition that the maximum temperature at which the material reaches 200 ° C. to obtain a coated plate. The paints of Comparative Examples 2 and 9 had high viscosity and could not be applied. The coated plate obtained as described above was tested for physical properties of a coating film and wet ink suitability. Table 3 shows test results
Shown in The test was performed according to the following method.

Test method Pencil hardness: JIS K-5400 8.4.2 on painted plate
A pencil scratch test specified in (1990) was performed, and evaluation was performed by scratching. Retort resistance: The coated plate was immersed in deionized water and treated in an autoclave at 125 ° C. for 30 minutes to examine the whitening state of the coating film and the pencil hardness of the coating film. The whitening state of the coating film was visually evaluated according to the following criteria. ◎ No whitening, ○: slight whitening, Δ: considerably whitening,
×: Whole surface whitening The pencil hardness of the coating film was determined by raising the treated coated plate from the water, leaving it in 80 ° C. hot water for 3 minutes, and then JIS K-5400 8.4.2 (1990) in 80 ° C. hot water. ), A pencil scratch test was performed, and an evaluation based on scratches was performed.

Workability: JIS K-54 for painted plate
00 8.3.2 (1990) A test was performed under the conditions of a drop weight of 300 g, a tip diameter of a ram 1/2 inch, and a drop weight height of 20 cm according to the DuPont impact resistance test. Cracks of the coating film in the periphery were visually observed. ◎ indicates no cracks, ○ indicates slight cracks, 割 れ indicates considerable cracks in the impact area,
When many cracks were observed also around the impact part, it was indicated as x.

Adhesion: JIS K-5400 8.5.
2 (1990) In accordance with the grid tape method, 1 mm x
One hundred squares of 1 mm were prepared, and an adhesive cellophane tape was stuck on the surface, and the number of cross-cut coatings remaining on the coated surface after abrupt peeling was recorded. 100 indicates that the coating film did not come off at all. Wet ink suitability: The finished appearance of the ink on the coated plate was observed. The case where the ink did not bleed or blur was evaluated as ◎, and the case where the ink bleed or blurred was evaluated as x.

[0060]

[Table 3]

[0061]

[Table 4]

Claims (5)

(57) [Claims] 1. Acrylic resins 40 to 6 having a weight average molecular weight of 6,000 to 15,000 obtained by copolymerizing (A) the following monomers and having a glass transition temperature exceeding 0 ° C.
0 parts by weight, an alkyl ester of methacrylic acid or acrylic acid having an alkyl group having 8 to 20 carbon atoms, a glycidyl ester of methacrylic acid or acrylic acid and 8 to 2 carbon atoms
And at least one monomer selected from adducts of acrylic acid or methacrylic acid and monoepoxy compounds having 8 to 20 carbon atoms.
At least one monomer selected from the group consisting of a ω-hydroxyalkyl ester of methacrylic acid or acrylic acid having a primary hydroxyalkyl group having 4 to 18 carbon atoms and a compound represented by the following formula [1]: %, [Wherein, R ¹ represents H or CH ₃ , R ² represents H, CH ₃ or CH ₂ CH ₃ , k is an integer of 2 to 4, m is 2 to 4
And n represents an integer of 1 to 5, respectively. 3 to 10% by weight of an ethylenically unsaturated carboxylic acid; 0 to 10% by weight of a hydroxyalkyl ester of methacrylic acid or acrylic acid having a hydroxyalkyl group having 2 to 3 carbon atoms; An acrylic resin having a weight average molecular weight of 5,000 to 50,000 and a glass transition temperature of 0 ° C. or lower obtained by copolymerizing the following monomers: To 20 parts by weight, having an N-alkoxymethyl group having 1 to 6 carbon atoms, 10 to 40% by weight of N-alkoxymethylmethacrylamide or N-alkoxymethylacrylamide, 3 to 10% by weight of an ethylenically unsaturated carboxylic acid, 0 to 10% by weight of a hydroxyalkyl ester of acrylic acid or methacrylic acid; Possible above-ethylenically unsaturated monomer 40-87 wt% of the non, and (C) a consisting aminoplast resins 20-50 parts by weight of the resin mixture a paint resin component, the resin (A)
And (B) at least a part of which is neutralized with a base, and wherein the resins (A), (B) and (C) are dissolved or dispersed in water. 2. The ethylenically unsaturated monomer in the acrylic resin (A) is at least one selected from an aromatic vinyl monomer and an alkyl ester of methacrylic acid or acrylic acid having an alkyl group having 1 to 4 carbon atoms.
The water-based paint according to claim 1, which is a kind of monomer. 3. The ethylenically unsaturated monomer in the acrylic resin (B) is at least one selected from an aromatic vinyl monomer and an alkyl ester of methacrylic acid or acrylic acid having an alkyl group having 1 to 4 carbon atoms.
3. The water-based paint according to claim 1, which is a kind of monomer. 4. The aqueous paint according to claim 1, wherein the aminoplast resin is an alkyl etherified melamine resin, an alkyl etherified benzoguanamine resin, or an alkyl etherified melamine-benzoguanamine co-condensation resin. 5. The aqueous coating composition according to claim 4, wherein the aminoplast resin is a methyletherified, methoxy-ethoxy mixed etherified or methoxy-butoxy mixed etherified melamine-benzoguanamine co-condensation resin.