JPH08120217A - Coating composition for can inside - Google Patents

Abstract

PURPOSE: To obtain a coating material for a can inside which is excellent in curability, processability, flavor retention, etc., and very scarcely forms fume when the coating film is backed. CONSTITUTION: A resol type phenolic resin obtained by reacting a phenol resin obtained from a bifunctional phenol A with form-aldehyde with a bisphenol B in a B/A molar ratio of 1/3-4/1 is washed to form a resol type phenolic resin having a hemiformal group content of a specified value or below. This resin is mixed with a bisphenol A type epoxy resin and an organic solvent to obtain a coating composition for a can inside.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a paint for the inner surface of a can, which uses a novel resol type phenol resin which is excellent in curability, processability, flavor and the like, and produces little fumes when baking a coated product.

[0002]

2. Description of the Related Art Inner surfaces of food cans and beverage cans are coated with an inner surface paint to prevent metal elution and corrosion of the cans. Since this coating material comes into contact with food, an epoxy-resole type phenol resin coating material having excellent adhesion to a metal plate, content resistance and water resistance is mainly used. Food cans and beverage cans can be obtained by processing a coated plate obtained by coating and baking this inner surface paint on a metal plate. In recent years, DR cans (Draw a
The diversification of can types and can types such as nd Redraw) and triple neck-in processing is progressing, and more workability than ever has been required. Furthermore, due to the increasing environmental awareness in recent years, fumes generated from paint (when the paint is baked in an oven, low-molecular weight components in the paint and part of the coating film are volatilized by thermal decomposition, and the fumes inside the oven are not discharged. The problem of what has received a heat history in) is highlighted. In the epoxy-resole type phenol resin type coating material, the physical properties of the coating film largely depend on the phenol resin which is a curable resin. In order to improve this processability, for example, in JP-A-2-228314, bisphenol compounds are used. A method of alkoxylating the resol type phenolic resin has been reported. However, in this case, since the methylol group of the phenol resin is alkoxylated with alcohol, when the phenol resin is used as a paint to form a baked coating film, the coating film foams due to dealcoholization. Further, the alkoxylation lowers the reactivity of the low molecular weight component of the phenol resin and increases the generation of fumes in the paint (hereinafter referred to as fumes). Phenolic resins made from bisphenols have excellent adhesion to the substrate, but in order to improve processability while maintaining a balance of various coating performances, phenolic resins consisting only of bisphenols are not sufficient. Is.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to obtain a high-performance paint for the inner surface of a can which is excellent in processability and which satisfies curability, adhesion, hot water resistance, flavor and fumes.

[0004]

Means for Solving the Problems The inventors of the present invention have conducted extensive studies to solve the above problems, and that the method for synthesizing a phenol resin affects the performance as a paint, and that the hemiformal group in the phenol resin is fumes. It was found to be the main cause of. The present invention provides a coating composition for an inner surface of a can, which comprises a resol-type phenol resin, a bisphenol A-type epoxy resin and an organic solvent, wherein the resol-type phenol resin is (1) a bifunctional phenol (A) and formaldehyde. Resol-type phenol obtained by reacting (2) bisphenols (B) at a molar ratio of B / A of 1/3 to 4/1 with a phenol resin obtained by reacting benzene with an alkali catalyst. A coating composition for an inner surface of a can, wherein the resin is a resol-type phenol resin in which a molar ratio of a hemiformal group in the resin to a phenol nucleus is 5% or less by subjecting the resin to a washing treatment (3).

Further, there is provided a coating composition for an inner surface of a can using the resol type phenol resin obtained by subjecting the resol type phenol resin to a hot water washing treatment at a temperature of 60 ° C. to 100 ° C.

The resole type phenol resin of the present invention is obtained by the following three steps. A method of synthesizing a linear resol-type phenol from bifunctional phenols and formaldehyde in the first step, adding bisphenols and methylolation in the second step, and removing low molecular weight components by the washing step of the third step. is there. Second
The resol-type phenol resin obtained in the step has a structure in which bisphenols are bound to a linear bifunctional phenol resin, or a structure in which the bifunctional phenol resin and the bisphenols are alternately chained. It is possible to control the cross-linking density of the coating film and improve the coating performance by imparting flexibility and curability with bisphenols and adjusting the ratio of the bifunctional phenols and bisphenols.

Further, the obtained resol type phenol resin is washed as a third step to remove hemiformal body, residual formaldehyde, monomers and the like.
That is, when a conventional can inner surface coating consisting of a resol type phenolic resin and a bisphenol A type epoxy resin is baked in an oven, the hemiformal form in the phenolic resin has a slower crosslinking reaction to polymerize than the methylol form. This is because it volatilizes and causes fumes, and even when the hydroxyl group at the terminal of the hemiformal body in the coating phenol resin reacts to form a coating film, the intermediate ether is easily broken by thermal decomposition and causes fumes.

Hereinafter, the production of the resol type phenol resin will be described in detail, but in this production, the reaction sequence of the bifunctional phenols and the bisphenols is important. When the bifunctional phenols and the bisphenols are reacted at the same time, or when the bisphenols are first reacted and then the bifunctional phenols are reacted, there is no significant difference in the reaction rate. Some or most of the active phenols do not react and remain as monomers,
When it is made into a paint, it not only adversely affects the flavor property and the fume property, but also the resin structure cannot be controlled, and it is not possible to obtain the coating film physical properties that satisfy the required performance.

The bifunctional phenols used in the present invention include p-cresol, o-cresol, p-ethylphenol, p-propylphenol, p-octylphenol, p-methoxyphenol, p-nonylphenol and p-t. -Butylphenol and the like can be mentioned, and these can be used alone or in admixture of two or more. Further, as the formaldehyde supplying substance, formalin, paraformaldehyde, hexamethylenetetramine and the like can be used.

The first step is methylolation of the bifunctional phenols by reacting the bifunctional phenols with formaldehyde in the presence of an alkali catalyst, followed by dehydration condensation. The bifunctional phenol used here is used. It is preferable to react all of the compounds to make them methylol or high molecular weight.

When synthesizing the resol type phenol resin, a conventionally known alkali catalyst may be used. Examples of such alkali catalysts include alkali metal hydroxides such as sodium hydroxide and potassium hydroxide, alkaline earth metal hydroxides such as calcium hydroxide, basic metal salts, trimethylamine and triethylamine. The amines, ammonia, etc. can be used alone or in combination of two or more.

Since the bifunctional phenols are slower in reactivity than the bisphenols and the like, the amount of the alkali catalyst used is 0.05 mol to 1.0 mol per mol of the bifunctional phenols. Is desirable. Further, since formaldehyde is also used in the reaction in the second step, it is necessary to use an excessive amount of formaldehyde, and it is desirable to use formaldehyde in an amount of 2 to 15 mol per 1 mol of the bifunctional phenol.

The reaction conditions for the first step are 50 to 120 ° C. for 1 to 10 hours, preferably 60 to 100 ° C. for 2 to 6 hours, and the water and formaldehyde which evaporate are refluxed for the reaction. In the first step, the important point is to accelerate the condensation reaction of the bifunctional phenols, and for that purpose, the reaction temperature should be as high as possible, but if the reaction temperature exceeds 100 ° C under atmospheric pressure, The water boils and the bubbles become more intense. On the other hand, when the temperature is 60 ° C. or lower, the reaction is slow and the reaction time becomes long. There is no particular limitation on the weight average molecular weight of the phenol resin intermediate at the stage of finishing the first step, but in order to smoothly proceed the resinification reaction in the second step, the weight average molecular weight is preferably 400.
It is preferably between 1 and 1300.

In the second step, the phenol resin obtained in the first step and the bisphenols are dehydrated and condensed by adding bisphenols to increase the molecular weight. As the bisphenols used in the second step, bisphenol A, bisphenol B, bisphenol F and the like can be used, and these can be used alone or in combination of two or more kinds. The first step and the second step can be carried out in water or an organic solvent, and it is preferable to use water from the viewpoint of cost, and it is also possible to react only water contained in formalin as a reaction medium. is there.

The amount of bisphenols used in the second step is preferably 0.33 to 4.0 moles per 1 mole of the bifunctional phenol used in the first step.
It is more preferably 0.5 mol to 2.0 mol. If the amount of bisphenols is less than 0.33 mol, the curability and adhesion of the coating film using the obtained phenol resin will deteriorate and the water resistance will also deteriorate. Further, if the amount of bisphenols exceeds 4 mols, the workability becomes poor. By changing the amount of bisphenol used in the second step, it is possible to design a phenol resin that meets the required performance.

In the second step, the reaction can be proceeded only by adding bisphenols, or in the second step, the catalyst and formaldehyde can be further added to proceed the reaction. When the catalyst and formaldehyde are further added in the second step, the same one as in the first step can be used. In the second step, heating is carried out under relatively mild conditions at 60 to 120 ° C. for 1 to 6 hours, preferably at 70 to 100 ° C. for 1 to 4 hours, and water and formaldehyde which evaporate are refluxed for reaction.

In the third step, water or warm water is added to the obtained product to wash the product once or several times to remove hemiformal bodies, residual formaldehyde, etc., which have a bad influence on paints and coating films. Remove. It is preferable to wash with warm water at 60 ° C. to 100 ° C. from the viewpoint of cost and washing efficiency.

The molar ratio of the hemiformal group to the phenol nucleus in the resol type phenol resin is ¹³ C-NMR or
Calculated by determining the ratio of the respective integrated values of the carbon C constituting the hemiformal group (indicated by C with an underline in the formula) and the carbon C of the aromatic ring at the base of the phenolic hydroxyl group in the spectrum by ¹ H-NMR measurement. In the present invention, it is essential to use a phenol resin which does not contain a hemi-formal compound or has a particularly limited hemi-formal compound content such that the molar ratio is 5% or less.

[0019]

Embedded image

Next, the bisphenol A type epoxy resin used in the present invention is obtained by the reaction of epichlorohydrin and 2,2-bis (4-hydroxyphenyl) propane, and the one having an average molecular weight of 800 or more calculated from the epoxy equivalent is used. However, those having an average molecular weight of 2000 to 4000 are preferable.

As the organic solvent in the present invention, ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone and isophorone; toluene,
Aromatic hydrocarbons such as xylene and other alkylbenzenes;
Cellosolves such as methyl cellosolve, ethyl cellosolve, and butyl cellosolve; esters such as methyl cellosolve acetate, butyl cellosolve acetate, ethyl acetate, butyl acetate; alcohols such as butyl alcohol and diacetone alcohol, and the like. They can be used alone or in the form of a mixture of two or more kinds. The paint for the inner surface of the can in the present invention has a total amount of 1 to 50 parts by weight of bisphenol A type epoxy resin to 5 to 50 parts by weight of resol type phenol resin.
It can be used as 100 parts by weight.

If desired, other resin components such as phenoxy resin, amino resin, polyvinyl butyral resin, etc. may be used in the paint for the inner surface of the can of the present invention, and coloring agents such as pigments, fillers and various Any auxiliary agent may be used. The paint for the inner surface of the can in the present invention is a dry coating film having a thickness of 40 to 100 mg / 100 cm formed by a method such as roller coating or spray coating on a metal sheet.
Apply with an application amount of about ² . The baking conditions are about 180 to 250 ° C. and 1 to 10 minutes.

As the metal sheet to which the paint according to the present invention is applied by baking, a tin-plated tin plate which has been conventionally used for food canning, etc., a chrome-plated steel plate,
Aluminum plated steel plate, aluminum plate, cold rolled steel plate and the like can be used.

[0024]

EXAMPLES Next, examples and comparative examples will be shown and described in more detail. In addition, "parts" and "%" described in Examples and Comparative Examples represent "parts by weight" and "% by weight", respectively.

Synthesis Example 1 30 parts of p-t-butylphenol, 181 parts of 41.5% formalin water and 11 parts of triethylamine were charged into a reaction kettle equipped with a stirrer and a reflux condenser, heated to 80 ° C., and a nitrogen stream was introduced. The reaction was carried out for 2 hours. Then, 182 parts of bisphenol A was added at the same temperature and the reaction was allowed to proceed for 2 hours. Then, 300 parts of water was added thereto, the temperature was raised to 60 ° C., and the mixture was stirred for 3 minutes and then stood still to separate the product from water. After the product is separated from the water by placing it on the ground, vacuum distillation is carried out at 760 mmHg, and the product is dehydrated until no more water comes out and then diluted with n-butanol so that the solid content becomes 60%. A solution P1 was obtained.

Synthesis Example 2 45 parts of pt-butylphenol, 217 parts of 41.5% formalin water and 13 parts of triethylamine were charged into a reaction kettle equipped with a stirrer and a reflux condenser, heated to 80 ° C., and nitrogen stream was passed. The reaction was carried out for 2 hours. Then, 205 parts of bisphenol A was added at the same temperature and the reaction was allowed to proceed for 2 hours. Then, 300 parts of water was added thereto, the temperature was raised to 60 ° C., and the mixture was stirred for 3 minutes and then stood still to separate the product from water. After the product is separated from the water by placing it on the ground, vacuum distillation is carried out at 760 mmHg, and the product is dehydrated until no more water comes out and then diluted with n-butanol so that the solid content becomes 60%. A solution P2 was obtained.

Synthesis Example 3 60 parts of p-t-butylphenol, 217 parts of 41.5% formalin water and 12 parts of triethylamine were charged into a reaction kettle equipped with a stirrer and a reflux condenser, heated to 80 ° C., and nitrogen stream was passed. The reaction was carried out for 2 hours. Then, 182 parts of bisphenol A was added at the same temperature and the reaction was allowed to proceed for 2 hours. Then, 300 parts of water was added thereto, the temperature was raised to 60 ° C., and the mixture was stirred for 3 minutes and then stood still to separate the product from water. After the product is separated from the water by placing it on the ground, vacuum distillation is carried out at 760 mmHg, and the product is dehydrated until no more water comes out and then diluted with n-butanol so that the solid content becomes 60%. A solution P3 was obtained.

Synthesis Example 4 90 parts of p-t-butylphenol, 217 parts of 41.5% formalin water and 11 parts of triethylamine were placed in a reaction kettle equipped with a stirrer and a reflux condenser, heated to 80 ° C., and nitrogen stream was introduced. The reaction was carried out for 2 hours. Then, 137 parts of bisphenol A was added at the same temperature and the reaction was allowed to proceed for 2 hours. Then, 300 parts of water was added thereto, the temperature was raised to 60 ° C., and the mixture was stirred for 3 minutes and then stood still to separate the product from water. After the product is separated from the water by placing it on the ground, vacuum distillation is carried out at 760 mmHg, and the product is dehydrated until no more water comes out and then diluted with n-butanol so that the solid content becomes 60%. A solution P4 was obtained.

Synthesis Example 5 120 parts of pt-butylphenol, 347 parts of 41.5% formalin water and 10 parts of triethylamine were charged into a reaction kettle equipped with a stirrer and a reflux condenser, heated to 80 ° C., and nitrogen stream was passed. The reaction was carried out for 2 hours. Then, 91 parts of bisphenol A was added at the same temperature to proceed the reaction for 2 hours. After that, 300 parts of water was added, the temperature was raised to 60 ° C., the mixture was stirred for 3 minutes, and then allowed to stand to separate the product from water. After standing to separate the product from water, vacuum distillation is carried out at 760 mmHg, dehydration is carried out until water disappears, and the product is diluted with n-butanol to a solid content of 60%. A solution P5 was obtained.

Synthesis Example 6 135 parts of p-t-butylphenol, 347 parts of 41.5% formalin water and 9 parts of triethylamine were charged into a reaction kettle equipped with a stirrer and a reflux condenser, heated to 80 ° C., and nitrogen stream was introduced. The reaction was carried out for 2 hours. Then, 68 parts of bisphenol A was added at the same temperature to proceed the reaction for 2 hours. Then, 300 parts of water was added thereto, the temperature was raised to 60 ° C., and the mixture was stirred for 3 minutes and then stood still to separate the product from water. After standing to separate the product and water,
It was distilled under reduced pressure at 760 mmHg, dehydrated until no water came out, and then diluted with n-butanol so that the solid content was 60% to obtain a phenol resin solution P6 of the present invention.

Synthesis Example 7 30 parts of pt-butylphenol, 258 parts of 41.5% formalin water, and 13 parts of triethylamine were charged into a reaction kettle equipped with a stirrer and a reflux condenser, heated to 80 ° C., and nitrogen stream was passed. The reaction was carried out for 2 hours. Then, 228 parts of bisphenol A was added at the same temperature to proceed the reaction for 2 hours. Then, 300 parts of water was added thereto, the temperature was raised to 60 ° C., and the mixture was stirred for 3 minutes and then stood still to separate the product from water. After separating the product and water by placing it in place, the product was distilled under reduced pressure at 760 mmHg, dehydrated until water disappeared, and then diluted with n-butanol to a solid content of 60%. Resin solution P
Got 7.

Synthesis Example 8 150 parts of pt-butylphenol, 347 parts of 41.5% formalin water and 8 parts of triethylamine were charged into a reaction kettle equipped with a stirrer and a reflux condenser, heated to 80 ° C., and nitrogen stream was passed. The reaction was carried out for 2 hours. Then, 46 parts of bisphenol A was added at the same temperature to proceed the reaction for 2 hours. Then, 300 parts of water was added thereto, the temperature was raised to 60 ° C., and the mixture was stirred for 3 minutes and then stood still to separate the product from water. After standing to separate the product and water,
After performing vacuum distillation at 760 mmHg and dehydration until no water came out, it was diluted with n-butanol so that the solid content was 60%, and the phenol resin solution P8 for Comparative Example was used.
I got

Synthesis Example 9 60 parts of pt-butylphenol, bisphenol A1
82 parts, 217 parts of 41.5% formalin water and 12 parts of triethylamine were charged into a reaction vessel equipped with a stirrer and a reflux condenser, heated to 80 ° C., and reacted in a nitrogen stream for 2 hours. Then, 300 parts of water was added thereto, the temperature was raised to 60 ° C., and the mixture was stirred for 3 minutes and then stood still to separate the product from water. After standing to separate the product and water, vacuum distillation was performed at 760 mmHg, and dehydration was performed until water disappeared, followed by diluting with n-butanol so that the solid content was 60%. Phenol resin solution P9 was obtained.

Synthesis Example 10 182 parts of bisphenol A, 41.5% formalin water 2
17 parts and 12 parts of triethylamine were charged into a reaction kettle equipped with a stirrer and a reflux condenser, heated to 80 ° C., and reacted in a nitrogen stream for 2 hours. Then, 60 parts of pt-butylphenol was added at the same temperature and the reaction was allowed to proceed for 2 hours. Then, 300 parts of water was added thereto, the temperature was raised to 60 ° C., and the mixture was stirred for 3 minutes and then stood still to separate the product from water. After standing to separate the product and water, vacuum distillation was performed at 760 mmHg, and dehydration was performed until water disappeared, followed by diluting with n-butanol so that the solid content was 60%. Phenol resin solution P10 was obtained.

Synthesis Example 11 60 parts of p-t-butylphenol, 217 parts of 41.5% formalin water, and 12 parts of triethylamine were placed in a reaction kettle equipped with a stirrer and a reflux condenser, heated to 80 ° C., and nitrogen stream was passed. The reaction was carried out for 2 hours. Then, 182 parts of bisphenol A was added at the same temperature and the reaction was allowed to proceed for 2 hours. Sulfuric acid was added to neutralize excess triethylamine, pH = 6
It was set to ~ 7. It was distilled under reduced pressure at 760 mmHg, dehydrated until no water came out, and then diluted with n-butanol so that the solid content became 60% to obtain a phenol resin solution P11 for a comparative example.

Synthesis Example 12 45 parts of p-t-butylphenol, 217 parts of 41.5% formalin water and 13 parts of triethylamine were placed in a reaction kettle equipped with a stirrer and a reflux condenser, heated to 80 ° C., and nitrogen stream was passed. The reaction was carried out for 2 hours. Then, 205 parts of bisphenol A was added at the same temperature and the reaction was allowed to proceed for 2 hours. Sulfuric acid was added to neutralize excess triethylamine and the pH was adjusted to 6-
I set it to 7. It was distilled under reduced pressure at 760 mmHg, dehydrated until no water came out, and then diluted with n-butanol so that the solid content was 60% to obtain a phenol resin solution P12 for a comparative example.

Evaluation of paints The phenol resin solutions obtained in the above Synthesis Examples 1 to 12 and Epoxy resin Epicoat 10 manufactured by Yuka Shell Epoxy Co., Ltd.
09 and epoxy resin / phenolic resin in solid content ratio 8
The paint was prepared so that it would be / 2. Each paint is diluted with a 1: 1 mixed solvent of butyl cellosolve and xylene to give a solid content of 3
It was set to 0%. Each paint was paint-baked and the coating film performance was evaluated.

The paint was applied on a chrome-plated steel sheet with a bar coater so as to have a concentration of 60 mg / 100 cm ² , and 205
A coated plate A was prepared by baking at 10 ° C for 10 minutes and subjected to the coating film performance test described below. Also, this paint was applied to one side of the aluminum foil using a bar coater so as to be 60 mg / 100 cm ² and dried at 150 ° C. for 1 minute to remove the solvent,
Further, the above coating material was applied to the back surface thereof so as to have a concentration of 60 mg / 100 cm ² and baked at 205 ° C. for 10 minutes to prepare a water extract liquid flavor test test panel B.

The respective evaluation methods are shown below, and the evaluation results are shown in Tables 1 and 2.

(1) Curability The coated plate A is placed in a flask equipped with a reflux condenser and immersed in methyl ethyl ketone. After heating and extraction with methyl ethyl ketone for 1 hour from the start of reflux, the amount of extraction from the coating film is calculated in percentage. The following criteria were used to evaluate the methyl ethyl ketone extraction rate.

◯: Extraction rate 10% or less, Δ: Extraction rate 10
-20%, x: extraction rate of 20% or more

(2) Workability The coated plate A was cut into a piece of 5 cm × 4 cm, pre-bent so that the coated surface was on the outside, and two metal plates of the same thickness were sandwiched between the two middle plates to make 1 kg of iron. 50cm weight
A test piece was obtained by dropping it from the height of and bending it. The processed part of the test piece was immersed in 1% saline, and the amount of electricity passed after 3 seconds at 6 V was measured using the test piece as an anode, and evaluated according to the following criteria.

◯: 10 mA or less, Δ: 10 to 20 m
A, x: 20 mA or more

(3) Adhesion Two pieces of the coated plate A were cut into 0.5 cm × 7 cm pieces, and the nylon tape was sandwiched between the coated surfaces, and the temperature was kept at 200 ° C. for 1 hour.
A test piece was obtained by thermocompression bonding at 6 kg / cm ² for 1 minute. The test piece was opened in a T-shape and set in a tensile tester, and the T-shape was peeled at a pulling speed of 200 mm / min, and the peel strength was measured and evaluated according to the following criteria.

◯: 3 kg / 5 mm or more, Δ: 3 to 2 kg
/ 5 mm, x: 2 kg / 5 mm or less

(4) Retort resistance The coated plate A was cut into 5 cm × 10 cm to prepare a test piece.
Put in a beaker, immerse in distilled water, and retort at 125 ° C. for 30 minutes. The test piece was taken out, and the degree of whitening of the coating film was visually judged and evaluated according to the following criteria.

◯: No whitening, Δ: Slight whitening,
×: considerably whitened

(5) Flavoring A coated plate B coated on both sides of an aluminum foil is put in a heat-resistant bottle,
Immerse in distilled water. At this time, 1 ml of distilled water is applied to 1 cm ² of the coating area of the aluminum foil coating plate. Cover the heat-resistant bottle, retort at 125 ° C for 30 minutes, and flavor test the internal solution (taste test by the taste of the tongue).
Was performed and evaluated according to the following criteria.

◯: No change, Δ: Slight change,
×: There is considerable change

(6) Fume property A paint is applied on a TFS plate so that the coating amount is 100 mg / 100 cm ² , and dried at 150 ° C. for 20 minutes to remove the solvent. The coated surface is placed on a hot plate kept at 220 ° C., a stainless steel frame having a height of 1 cm and an aluminum foil are immediately placed on the hot plate, and the aluminum foil is water-cooled. The heated volatiles generated from the coated plate are attached to the aluminum foil for 5 minutes, and the attached weight is measured. The amount of heated volatiles per unit coating film weight was calculated and evaluated according to the following criteria.

◯: 0.1% or less, Δ: 0.1 to 0.5
%, X: 0.5% or more

[0052]

[Table 1]

(*) The integrated value of the carbon peak of hemiformal (85 to 95 ppm) and the peak of the carbon bonded to the hydroxyl group of the phenol nucleus (1) by ¹³ C-NMR.
The molar ratio of hemiformal to the phenol nucleus was calculated from the ratio of integrated values of 50 to 160 ppm).

[0054]

[Table 2]

[0055]

[Table 3]

[0056]

[Table 4]

[0057]

EFFECT OF THE INVENTION When a paint for the inner surface of a can obtained by combining the resol-type phenol resin obtained by the present invention with an epoxy resin is applied to a can metal sheet and baked, the amount of fumes generated in the oven is higher than that of the conventional product. Since it is extremely low, the coating workability is good, and the workability, adhesion, hot water resistance, flavor and the like of the cured coating film are excellent, so that it has a high practical value as a paint for the inner surface of a can.

Claims (2)

[Claims] 1. A coating composition for an inner surface of a can, which comprises a resol-type phenol resin, a bisphenol A-type epoxy resin and an organic solvent, wherein the resol-type phenol resin is:
(1) Bifunctional phenols (A) and formaldehyde are reacted in the presence of an alkali catalyst to a phenol resin, and (2) bisphenols (B) at a molar ratio B / A of 1/3 to. The resol type phenolic resin obtained by reacting at a ratio of 4/1 is a resol type phenolic resin in which the molar ratio of the hemiformal group in the resin to the phenol nucleus is 5% or less by (3) washing treatment. A coating composition for the inner surface of a can characterized by: 2. The resol-type phenol resin has a temperature of 6
The coating composition for an inner surface of a can according to claim 1, which is a resol-type phenol resin obtained by performing a warm water washing treatment at 0 ° C to 100 ° C.