JPS61268764A - Aqueous resin dispersion - Google Patents

Abstract

PURPOSE:To obtain the titled dispersion of good adherability and processability, for use in coating on inner surface of cans, by reaction of aromatic epoxy resin with a precondensate from carboxylic acid monomer unit-contg. acrylic resin and specific phenolic resin followed by incorporating the resulting reaction product in an amine-contg. aqueous medium. CONSTITUTION:First, a composite resin composition with an excess of carboxyl group is prepared by, for example, partial reaction of (A) an aromatic epoxy resin containing in one molecular 1.1-2.0 epoxy groups with (B) a precondensate from (i) an acrylic resin containing, as essential component, 12-70wt% of monobasic carboxylic acid monomer unit per molecule and (ii) a phenolic resin containing >=40wt% of a compound of formula (R is H or 1-12C alkyl; X is H or methyl; a and b are each 1 or 2, a+b=3 or 4). The objective resin dispersion can be obtained by dispersing the above composite resin composition in an aqueous medium in the presence of such an amount of ammonia or amine as to be 4-11 in the pH of the system.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to an aqueous resin dispersion, and more specifically, to a water-based resin dispersion useful as a coating composition for metals, particularly as a coating composition for the inner surface of a can. The present invention relates to an aqueous resin dispersion.

(Conventional technology) Paints whose main component is aromatic epoxy resin have poor processability,
Although it is used as a paint for cans because of its excellent content resistance and physical properties of the coating film, the aromatic epoxy resin itself does not dissolve or disperse in an aqueous medium.

On the other hand, water-based paints for cans are being considered from the viewpoint of resource conservation, energy conservation, and environmental pollution.

Various proposals have also been made regarding paints containing aromatic epoxy resins as a main component.

For example, a method is known in which an aromatic epoxy resin is dispersed in water using a surfactant.

The action of surfactants tends to have an adverse effect on the storage stability and physical properties of the paint film.

Various self-emulsifying aromatic epoxy resins have been proposed, which are aromatic epoxy resins modified with acrylic resins having carboxyl groups.

For example, JP-A No. 53-14963 and JP-A No. 5
5-9433 discloses that a partial reactant containing an excess of carboxyl groups obtained by reacting an acrylic resin and an aromatic epoxy resin can be stably dispersed in an aqueous medium in the presence of ammonia or an amine. There is. JP-A-57-1
No. 05418 and Japanese Unexamined Patent Publication No. 198513/1983.

A low-molecular compound having an epoxy group and an acryloyl group in one molecule, which is obtained by partially reacting an aromatic epoxy resin and (meth)acrylic acid, and a monomer mixture containing acrylic acid or methacrylic acid are polymerized to form a basic Aqueous dispersion compositions obtained by neutralization with compounds are disclosed.

Furthermore, JP-A-53-1228 discloses a grafting method obtained by polymerizing a monomer mixture containing a carboxylic acid monomer using a free radical generator such as benzoyl peroxide in the presence of an aromatic epoxy resin. It has been shown that the prepared epoxy resins can be stably dispersed in aqueous media containing bases.

The self-emulsifying aromatic epoxy resin obtained by the above technology does not contain surfactants in the paint, so it can itself provide a strong coating film. Contains a highly water-soluble amino resin. By blending an amino resin, the curing speed of the paint can be improved to a certain extent without deteriorating the physical properties of the paint film, but when used in an amount that is practically satisfactory in terms of curing speed, the adhesion, Processability deteriorates, and especially as a paint for the inner surface of a can, low-molecular-weight compounds originating from the amino resin are eluted into the contents of the can during heat sterilization, resulting in hygiene problems.

It is also known to incorporate a phenolic resin into a self-emulsifying aromatic epoxy resin; however, it was believed that ordinary phenolic resins have a slow curing speed and cannot contribute to improving fast curing properties.

(Problems to be Solved by the Invention) An object of the present invention is to improve the curing speed of a self-emulsifying aromatic epoxy resin coating.

A further object of the present invention is to improve the adhesion and processability of the coating film.

Another object of the present invention is to overcome the sanitary problems associated with the combined use of water-soluble amino resins.

[Structure of the invention]

(Means for Solving the Problems) That is, the present invention provides an acrylic resin (A) containing 12 to 70% by weight of monobasic carboxylic acid monomer units in one molecule as an essential component, and an acrylic resin (A) having the following general formula: 1.1 epoxy groups per molecule are added to the preliminary tank hardware (P) with the phenol resin (C) containing 40% by weight or more of the compound represented by formula (I).
A composite resin composition (D) containing an excess of carboxyl groups obtained by partially reacting an aromatic epoxy resin (B) containing 1 to 2.0 epoxy groups, or a composite resin composition containing 1.1 to 2.0 epoxy groups in one molecule. A precondensate (P') of an aromatic epoxy resin (B) and a phenol resin (C) containing 40% by weight or more of a compound represented by the following formula (I) contains 12% in one molecule. A composite resin composition with an excess of carboxyl groups obtained by partially reacting an acrylic resin (A) containing ~70% by weight of monobasic carboxylic acid monomer units as an essential component (
D') is dispersed in an aqueous medium in the presence of ammonia or amine in an amount such that the pH thereof becomes 4 to 11.

(I) (In formula 2, R is a hydrogen atom or has 1 to 1 carbon atoms.
2 alkyl group, X is a hydrogen atom or methyl group, a, b
are both 1 or 2, and a+b=3 or a+
It is b-4. ) The acrylic resin (A) in the present invention includes acrylic acid,
A monomer mixture consisting of a monobasic carboxylic acid monomer such as methacrylic acid and other copolymerizable monomers is mixed with a common radical polymerization initiator such as azobisisobutyronitrile or benzoyl peroxide in an organic solvent.
It can be obtained by copolymerization at a temperature of 0°C to 150°C.

The copolymerizable monomers include methyl acrylate, ethyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, n-amyl acrylate, isoamyl acrylate, n-hexyl acrylate, and 2-acrylate. Acrylic esters such as ethylhexyl, n-octyl acrylate, decyl acrylate, dodecyl acrylate, methyl methacrylate, propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-amyl methacrylate, n- methacrylate
n-octyl hexyl 2 methacrylate, 2 methacrylate
-Methacrylic acid esters such as ethylhexyl, decyl methacrylate, and dodecyl methacrylate, styrene, and vinyltoluene.

Styrene thread additives such as 2-methylstyrene, t-butylstyrene, and chlorostyrene, hydroxy group-containing monomers such as hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxyethyl methacrylate, and hydroxypropyl methacrylate, N-methylol ( N-substituted (meth)acrylic monomers such as meth)acrylamide and N-butoxymethyl(meth)acrylamide;
It can be selected from one or more of epoxy group-containing monomers such as glycidyl acrylate and glycidyl methacrylate, and acrylonitrile.

The amount of monobasic carboxylic acid monomer used is 12 to 70% by weight based on the total amount of monomers.

If it is less than 12% by weight, the dispersion stability of the resin in an aqueous medium, the adhesion of the painted film to metal, solvent resistance, flavor suitability, etc. will all deteriorate, so it is not preferable. If the amount is too high, the water resistance and boiling resistance of the coating film will deteriorate.

The acrylic resin (A) preferably has a weight average molecular weight in the range of 3000 to 5000.

If the weight average molecular weight is less than 3,000, the crosslinking density of the coating film will increase, which will impede processability.

Also, 40,000. In particular, when the molecular weight exceeds 80,000, gelation tends to occur during reaction with the aromatic epoxy resin (B).

The aromatic epoxy resin (B) in the present invention is preferably one obtained by condensing bisphenol A and shrimp halohydrin in the presence of an alkali catalyst, and has an average of 1.1 to 2.0 epoxy resins in one molecule. having a number average molecular weight of 300 or more, preferably 900 or more. Commercially available products include Epikoat 828° and Epicoat 1001. manufactured by Shell Chemical Co., Ltd. Epicote 1004
．． Epicote 1007. Examples include Epicote 1009.

Furthermore, as the aromatic epoxy resin, a modified epoxy resin is used in which the epoxy group of the bisphenol A type epoxy resin is reacted with a vegetable oil fatty acid such as dehydrated castor oil, soybean oil fatty acid, or coconut oil fatty acid, or a modifier such as bisphenol A. You can also do that.

The phenol resin (C) in the present invention has the following formula (I)
Contains the components represented by.

(However, in formula 2, R is a hydrogen atom or a carbon number of 1 to 1
2 alkyl group, X is a hydrogen atom or a methyl group, a
, b are both 1 or 2, and a+b-3 or +b=4. ) The pheno-7L' tree m (C) containing the compound represented by the general formula (I) contains bisphenols such as bisphenol A or bisphenol F and formaldehyde,
5 formaldehyde for 1 mole of bisphenol A
Using from 1.5 to 10 mol and 1.5 to 4 mol of alkali catalyst, relatively mild reaction conditions are used, i.e. 9 reaction temperature 30 to 70°C for 30 minutes to 4 hours, more preferably 45 to 55°C for 2 to 3 hours. It can be obtained by reacting for a period of time.

In addition, the phenol resin (C) containing the compound represented by the general formula (I) is a trifunctional mononuclear phenol, carbonic acid 9
It can be obtained using m-ethylphenol, 3.5-xylenol, and m-methoxyphenol as raw material phenol. moreover.

The above trifunctional mononuclear phenol and p-Frezy tD.

0-cresol, p-tert-butylphenol.

p-ethylphenol, 2,3-xylenol.

A difunctional phenol such as m-methoxyphenol can also be used in combination. The rIi production of phenolic resin <C> using these mononuclear phenols may be performed under the same reaction conditions as those using bisphenols.

The alkali catalyst used in the synthesis of the phenol resin (C) is preferably a strong base such as sodium hydroxide or potassium hydroxide, but sodium carbonate and the like can also be used alone or in combination.

Formaldehyde can also be used as formalin and paraformaldehyde.

The important point in this synthesis is to suppress the condensation reaction and allow only the addition reaction of formaldehyde to the phenols to occur.For this purpose, the reaction temperature is kept as low as possible (and the alkaline catalyst is used in a number equal to or greater than the number of moles of the phenols, and formaldehyde is Use more than the equivalent number of phenols.

For example, when 1 mole of bisphenol A is used as the phenol, it is suitable to use the alkali catalyst in an amount of about 2 moles and the amount of formaldehyde in an amount of about 8 moles.

The end point of the reaction is determined by GPC measurement.

For reactions such as carbolic acid, the color changes from pale yellow to dark red depending on the degree of condensation.

It can also be determined by managing hue. Furthermore, if the reaction conditions can be controlled sufficiently, it can also be determined by the reaction time.

To separate the phenolic resin (C) containing the compound of general formula (I) from the reaction product, the two reaction mixtures can be acidified with hydrochloric acid, sulfuric acid, etc., and the precipitate can be filtered and washed with water. can.

In the case of reaction products with high solubility in organic solvents, such as bisphenols, the organic solvent and acid can be added simultaneously and extracted into the solvent. The extracted reaction product can be purified by washing with acid, alkali, water, etc., if necessary.

The amount of the compound represented by general formula (I) produced in the phenol resin (C) can be confirmed by GPC measurement. Furthermore, the methylol concentration can be confirmed from nuclear magnetic resonance spectroscopy.

The content of the compound represented by general formula (I) in the phenol resin (C) is 40% by weight or more, preferably 60% by weight or more, more preferably 70% by weight or more. A large amount of the compound represented by the general formula (I) improves fast curing properties, hot water resistance, workability, and adhesion.

The precondensate (P) or (P') in the present invention is
Acrylic resin (A) or epoxy resin (B) and phenol resin (C) are preferably heated in a hydrophilic solvent as described below at 50 to 150°C for 10 minutes to 30 minutes.
It can be obtained by reacting for a period of time. On this occasion,
The phenol resin (C) is used in an amount of 2 to 40% by weight based on the total amount of the resin including the acrylic resin (A) and the aromatic epoxy resin (B). If it is less than 2% by weight, the contribution to the curing speed of the coating film will not be sufficient (and if it is less than 2% by weight,
When the amount exceeds %, physical properties such as processability of the coating film tend to deteriorate.

The composite resin composition (D) or (D) in the present invention is prepared by combining the precondensate (P) and the aromatic epoxy resin (B) or the precondensate (P') and the acrylic resin (A) with ammonia or It can be obtained by reacting at 60° C. to 170° C. for about 10 minutes to 2 hours in the presence of an amine.

The ratio of the acrylic resin (A) to the aromatic epoxy resin (B) is such that the solid content ratio of (A) and (B) is 2:1 to 1:6. Reactions can be measured by oxirane % measurement, viscosity measurement or gel verminion chromatography.
It can be controlled by measuring the molecular weight distribution by (GPC), etc. The final oxirane group content of the partial reactant is 5 to 95%, more preferably 3% as a reduction rate relative to the oxirane content of the aromatic epoxy resin.
0 to 70%. If the reduction rate of oxirane groups is less than 5%, the acrylic resin-aromatic epoxy resin partial reaction product cannot be sufficiently self-emulsified in the aqueous medium and tends to separate during storage, and if it is greater than 95%, the acrylic resin-aromatic epoxy resin partial reaction product tends to separate during storage. The processability of the film tends to deteriorate.

The aqueous dispersion in the present invention is prepared by adding ammonia or amine in an amount such that the final composition has a pH of 4 to 11 and dispersing it in an aqueous medium. urge

The above amine is, for example, trimethylamine.

Alkylamines such as triethylamine and butylamine, alcohol amines such as 2-dimethylaminoethanol, jetanolamine, triethanolamine, and aminomethylpropanol, 1 morpholine, and the like are used. Also ethylenediamine.

Polyvalent amines such as diethylenetriamine can also be used.

In the present invention, the aqueous medium means water alone or a mixture with a hydrophilic organic solvent in which at least 10% by weight is water, and examples of the hydrophilic organic solvent include methanol, ethanol, n-propanol, isopropanol, n-propanol, Alkyl alcohols such as -butanol, 5ec-butanol, tert-butanol, isobutanol, methyl cellosolve, ethyl cellosolve, propyl cellosolve,
Ether alcohols such as butyl cellosolve, methyl calpitol, ethyl calpitol, ether esters such as methyl cellosolve acetate, ethyl cellosolve acetate, other dioxane, dimethyl formamide,
Diamond alcohol, etc. is used.

The aqueous resin dispersion of the present invention can be used as a paint by adding a surfactant, an antifoaming agent, etc. to improve coating properties, if necessary.

Commonly used substrates include metal plates such as untreated steel plates, treated steel plates, galvanized iron plates, and tin plates.As for the coating method, spray painting such as air spray, airless spray, and electrostatic spray is preferred. , dip coating, roll coater coating, electrodeposition coating, etc. are also possible. The baking conditions can be selected from the range of 2 to 30 minutes at a temperature of 150° C. to 230° C. for 9 hours.

The aqueous resin dispersion of the present invention can also be used in rust-preventing primers, printing inks, anti-corrosion paints, etc. by adding appropriate rust preventive agents, pigments, fillers, etc., depending on the purpose.

The present invention will be explained below with reference to examples. In addition.

In the examples, "parts" and "%" are "parts by weight" and "% by weight," respectively.
” is shown.

(Example) [Preparation of acrylic resin solution] Styrene 300 parts Ethyl acrylate 210 methacrylic acid
90 butyl cellosolve
288 Benzoyl peroxide
12 1/4 of the mixture of the above composition was charged into a four-bottle flask purged with nitrogen gas and heated to 80 to 90°C.

While maintaining the temperature, the remaining 3/4 was gradually added dropwise over 2 hours. After one drop was added, the mixture was stirred at that temperature for another 2 hours, then cooled, and the acid value was 93 (in terms of solid content).

(same below), solid content 59.7%, viscosity 4100 cps (
A carboxyl group-containing resin solution was obtained (all viscosities hereinafter refer to measurement results at 25°C).

[Preparation of epoxy resin solution]

Epicote 1007 500 parts Butyl cellosolve 333.3 Pour the entire amount into a 4-hole flask purged with nitrogen gas.

The mixture was gradually heated to raise the internal temperature to 100°C, stirred for 1 hour to completely dissolve, and then cooled to 80°C to obtain an epoxy resin solution with a solid content of 60%.

[Preparation of phenolic resin (C1) solution] Bisphenol A 228 g (1 mol), 37% formalin 649 g (
8 mol), 302 g of 35% sodium hydroxide (2,64
After reacting at 50°C for 2 hours, 25 mol of ethyl
0 g and 250 g of n-butyl alcohol, followed by
Add 401 g (2.2 mol) of 20% hydrochloric acid and stir at 60°C.
After stirring for 0 minutes, the mixture was allowed to stand and was separated into two layers within several minutes. The upper layer was an organic compound layer and the yield was 430 g. Wash the organic layer using water and aqueous ammonia.

Neutralized and 330g of pale purple transparent phenolic resin (C1
)was gotten. Solid content was 30%.

When this solution was analyzed by high performance liquid chromatography and nuclear magnetic resonance absorption spectroscopy, it was confirmed that it contained 75% of a tetramethylol compound of bisphenol A represented by the following chemical formula. The remaining 25% was a mixture of polymethylolated bisphenol A dimers and trimers condensed at the methylol group.

[Preparation of phenolic resin (C2) solution] Bisphenol A 228 g (I mol), 37% formalin 649 g
(8 mol) and 229 g (2 mol) of 35% sodium hydroxide were synthesized and purified in the same manner as in the preparation of phenolic resin (C1), yielding 345 g of a resin solution with a solid content of 30%. . This phenolic resin (C2)
Tetramethylolated bisphenol A halo 3% in solution
Met. The remaining 37% was a mixture of polymethylolated bisphenol A dimers or more.

[Preparation of phenolic resin (C3) solution] 94 g of carbolic acid
(I mol), 405 g (5 mol) of 37% formalin,
211 g (I, 32 mol) of 25% sodium hydroxide was mixed and reacted at 50°C for 2 hours, and then at 70°C for 2 hours to obtain a red transparent solution. Add 100 g of ethyl acetate and 100 g of n-butyl alcohol to this solution.

Subsequently, 200 g (I, 1 mol) of 20% hydrochloric acid was added.

When the mixture was stirred at 60° C. for 10 minutes and allowed to stand, it separated into two layers within a few minutes: the upper layer was a golden yellow organic layer and the lower layer was a pale brown aqueous layer. When the organic layer was washed twice with 150 g of water, the lower layer became an organic layer. The pH of the aqueous layer at this time was 4.2. The yield of the organic layer was 303 g, solid content 26.3%. Remove some of the solvent.

The solid content was 30%. This organic layer was a phenolic resin (C3) containing 55% of a dinuclear polymethylolated mixture of 9-carboxylic acid and 45% of a polynuclear polymethylolated product.

[Preparation of phenolic resin (C4) solution] Bisphenol A 228 g (I mol), 37% formalin 324 g
4 mol), 114 g (I mol) of 35% sodium hydroxide
After reaction at 70℃ for 4 hours, 200g of ethyl acetate
Add 200g of n-butyl alcohol to 20%
151 g (0.83 mol) of hydrochloric acid was added, stirred at 60° C. for 10 minutes, and then allowed to stand, resulting in separation into two layers within a few minutes.

A light brown color with a solid content of 30% was obtained by the same operation as in Example 1.

300 g of a clear solution was obtained. This phenolic resin (C4
) The solution contains 4 tetramethylolated products of bisphenol A.
．． 8%, and the rest was a condensed polynuclear mixture.

Comparative Example 1 ■ 50 parts of the above acrylic resin solution ■ 100 parts of the above epoxy resin solution ■ 2-dimethylaminoethanol 4.8 ■ Ion exchange water
295.2■, ■, and ■ were charged into a reaction vessel, and after reacting at 80° C. for 70 minutes with stirring, ■ was added dropwise over 1 hour without stirring to obtain a milky white resin dispersion.

Example 1 ■ The above acrylic resin solution 50 parts ■ The above phenol resin (C1) solution 60 ■ The above epoxy resin melt 100 ■ 2-dimethylaminoethanol 4.8 ■ Ion exchange water
325.2■ and ■ were charged into a reaction vessel and reacted at 100°C for 1 hour with stirring. GPC before and after reaction
It was confirmed through measurement that a portion of the acrylic resin and phenol resin were bonded. The temperature of the liquid was lowered to 80°C, and ① and ③ were added, reacted for 30 minutes, and then cooled. Furthermore, (2) was added, and while stirring, (2) was added dropwise to obtain a milky white resin dispersion.

Example 2 ■ The above epoxy resin solution 100 parts ■ The above phenol resin (C1) solution 60 ■ The above acrylic resin solution 50 ■ 2-dimethylaminoethanol 4.8 ■ Ion exchange water
325.2■ and ■ were charged into a reaction vessel and reacted at 100°C for 1 hour with stirring. GPC before and after reaction
It was confirmed through measurement that a portion of the epoxy resin and phenol resin were bonded. The temperature of the liquid was lowered to 80°C, and ① and ③ were added, reacted for 30 minutes, and then cooled. Furthermore, (2) was added, and while stirring, (2) was added dropwise to obtain a milky white resin dispersion.

Example 3 ■ The above epoxy resin solution 100 parts ■ The above phenol resin (C1) solution 30 ■ The above acrylic resin solution 50 ■ 2-dimethylaminoethanol 4° 8 ■ Ion exchange water
GPC before and after 0 reaction where 310.2■ and ■ were charged into a reaction vessel and reacted at 100℃ for 1 hour with stirring.
It was confirmed through measurement that a portion of the epoxy resin and phenol resin were bonded. The temperature of the liquid was lowered to 80°C, and ① and ③ were added, reacted for 30 minutes, and then cooled. Furthermore, (2) was added, and while stirring, (2) was added dropwise to obtain a milky white resin dispersion.

Example 4 ■ 100 parts of the above epoxy resin solution ■ 10 parts of the above phenol resin (C1) solution 10 ■ 50 parts of the above acrylic resin solution ■ 2-dimethylaminoethanol 4.80 ion-exchanged water
290.2■ and ■ were charged into a reaction vessel and reacted at 100°C for 1 hour with stirring. GPC before and after reaction
It was confirmed through measurement that a portion of the epoxy resin and phenol resin were bonded. The temperature of the liquid was lowered to 80°C, and ① and ③ were added, reacted for 30 minutes, and then cooled. Furthermore, (2) was added, and while stirring, (2) was added dropwise to obtain a milky white resin dispersion.

Example 5 An aqueous resin dispersion was obtained in the same manner as in Example 1 except that the above phenol)H fat (C2) solution was used in place of the phenol resin (C1) solution.

Example 6 Example 2 except that the above phenol resin (C2) solution was used instead of the phenol resin (C1) solution in Example 2.
An aqueous resin dispersion was obtained in the same manner as above.

Example 7 Example 1 except that the phenol resin (C3) solution was used instead of the phenol resin (C1) solution in Example 1.
An aqueous resin dispersion was obtained in the same manner as above.

Example 8 An aqueous resin dispersion was obtained in the same manner as in Example 2, except that the phenol resin (C3) solution was used instead of the phenol resin (C1) solution.

Comparative Example 2 ■ 50 parts of the above acrylic resin solution ■ 100 parts of the above epoxy resin solution ■ 2-dimethylaminoethanol 4.8 ■ Phenol resin (
C4) Solution 60 ■ Ion exchange water
325.2 ■, ■, ■ were charged into a reaction container and reacted at 80° C. for 70 minutes with stirring. After cooling the reaction solution, ■ was added. After further stirring, (2) was added dropwise to obtain a milky white resin dispersion.

Comparative Example 3 In Example 1, instead of the phenolic resin (C1),
A resin dispersion was obtained in the same manner as in Example 1, except that 22.5 parts of Cymel 325 (water-soluble amino resin manufactured by Mitsui Toatsu ■, solid content 80%) was used.

4. Hexyl cellosolve by replacing the aqueous resin dispersion with solvent.
6% water, 72.4% water, and 23% solids resin dispersion. After that, 25% ammonia water was added little by little until the solid content of all resin dispersions was 21-22.5% and the viscosity was 80%.
It was adjusted to be 0 to 1200 cps. All resin dispersions after this preparation.

After storage at 50°C for 3 months, there was no change in viscosity and no sedimentation was observed, confirming that it was extremely stable. Next,
The prepared resin dispersion was coated on a tin plate to a thickness of 8 to 10 μm, and baked and dried at 165° C. and 200° C. for 5 minutes each to prepare a test panel. Also, the content is 250
The above aqueous dispersion was applied by spraying to the inner surface of a 2-piece m1 tin can, baked at 165° C. and 200° C. for 5 minutes each, and dried to prepare an inner-coated can and tested for various resistances. The test method is as follows.

(I) Adhesion: Approximately 1.5 m using a knife on the coating surface
Make 11 vertical and horizontal cuts in the goban with a width of +w. Adhere with 241-width cellophane adhesive tape.

The number of unpeeled parts of the goblin area when strongly peeled is expressed in the numerator.

(2) Retort resistance = after treatment in water at 125°C for 30 minutes.

The coating film was judged visually and by peeling off with cellophane adhesive tape.

(3) Workability: Using a special folding DuPont impact tester, a sample folded in half was placed at the bottom, and an iron weight with a flat contact surface weighing I kg was dropped from a height of 50 aa. The length of cracks in the paint film that sometimes occur at the bends was measured.

(4) Corrosion resistance: A test piece with x-marked cuts made on the coating surface using a knife was treated in 1% saline solution at 125°C for 30 minutes, and the degree of corrosion near the x-marked area was determined.

(5) Potassium permanganate consumption: Fill a can with internal coating with 250ml of ion-exchanged water and tighten it twice to 60"C-
The samples were treated for 30 minutes and at 100°C for 30 minutes, and then measured according to the test method described in the Food Sanitation Act.

(6) Salt solution storage test: 25% of 1% salt solution in a can with internal coating
After filling with 0+++1 and tightening 9 times, pack it in a cardboard box (15 cans in a 30-can-sized box). Vibrate with a vibrator for 5 hours, collide with 1 loaner, and store at 25℃ for 1 month. did. The above test cans were opened and the amount of iron eluted into the saline solution was measured by atomic absorption spectrometry. (n; average of 15) (7) Flavor retention: 250 m of ion-exchanged water in a can with internal coating
1 was filled and sealed, and after sterilization at 100°C for 30 minutes, the solution in the can was further stored at 50°C for 6 months, and a flavor test was conducted on the solution in the can.

Test Results (I) Adhesion: All samples of Examples and Comparative Examples baked at 165° C. and 200”C were 100/100.

(2) Retort resistance: The judgment results are shown in Table 1. No abnormalities (○): Slight whitening or peeling of the paint film (Δ): Significant whitening or peeling of the paint film (×) Indicated.

(3) Workability: All samples of Examples and Comparative Examples baked at 165°C and 200°C had a crack length of 1
It was 0 mm or less and passed 1.

(4) Corrosion resistance: The judgment results are shown in Table 1.
): Slightly corroded (Δ): Significantly corroded (x).

(5) Potassium permanganate consumption: Table 1 shows numerical values (pp
m).

(6) Salt solution storage test: Table 1 shows the values (ppm).

(7) Flavor preservability: Some changes were observed in the inner-coated can of Comparative Example 3, but no changes were observed in the inner-coated cans of other Examples and Comparative Examples.

〔Effect of the invention〕

The aqueous resin dispersion obtained in the present invention cures in a short time as a gold paint, and the resulting coating film has excellent corrosion resistance. Furthermore, as a paint for one can, it has excellent coating film adhesion, processability, and retort resistance. In addition, the coating film contains unreacted low molecular weight substances, so when used as a paint for the inner surface of a can.

Unreacted low molecular weight substances do not migrate into food contents, and flavor retention is excellent.

(margin)

Claims (1)

[Claims] 1. Acrylic resin (A
), and a compound whose general formula is represented by the following formula (I) is 40
Precondensate with phenolic resin (C) containing at least % by weight (
P) is partially reacted with an aromatic epoxy resin (B) containing 1.1 to 2.0 epoxy groups in one molecule, or a composite resin composition (D) with an excess of carboxyl groups, or one molecule An aromatic epoxy resin (B) containing 1.1 to 2.0 epoxy groups therein and the general formula of the following formula (I)
The precondensate (P') with the phenol resin (C) containing 40% by weight or more of the compound represented by
A composite resin composition (D') with an excess of carboxyl groups obtained by partially reacting an acrylic resin (A) containing 0% by weight of monobasic carboxylic acid monomer units as an essential component is prepared by adjusting the pH
An aqueous resin dispersion, which is dispersed in an aqueous medium in the presence of ammonia or amine in an amount of from 4 to 11. (I) ▲There are mathematical formulas, chemical formulas, tables, etc.▼ (However, in the formula, R is a hydrogen atom or has 1 or 1 carbon atoms.
2 alkyl group, X is a hydrogen atom or methyl group, a, b
are both 1 or 2, and a+b=3 or a+
b=4. ) 2. 60% by weight of a compound whose general formula is represented by formula (I)
The aqueous resin dispersion according to claim 1, which is blended with the phenolic resin (C) containing the above. 3. 70% by weight of a compound whose general formula is represented by formula (I)
The aqueous resin dispersion according to claim 1, which is blended with the phenolic resin (C) containing the above. 4. The aqueous resin dispersion according to claim 1, wherein the weight of the phenolic resin (C) is 2 to 40% by weight based on the total weight of the resin. 5. The weight average molecular weight of the acrylic resin (A) is 3000
80,000 to 80,000. 6. The number average molecular weight of the aromatic epoxy resin (B) is 90
The aqueous resin dispersion according to claim 1, which has a molecular weight of 0 to 6,000. 7. Acrylic resin (A) and aromatic epoxy resin (B)
) The aqueous resin dispersion according to claim 1, having a solid content ratio of 2:1 to 1:6.