JPH0482032B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a coating composition for cans, and more specifically, it has low-temperature curability, retort resistance,
The present invention relates to a can coating composition capable of forming an epoxy-phenol coating film with excellent coating film properties such as corrosion resistance and processability. (Prior Art) Epoxy-phenol paints are widely used as paints for the inner surfaces of cans from the viewpoints of adhesion to metals, corrosion resistance, processability, and the like. Such epoxy-phenol paints are generally baked or cured by being held at a temperature of 190 to 210°C for about 10 minutes. When producing cans for canning, it is often necessary to apply a correction paint to the inner surface of the can. For example, in the case of a can body with an easy-open lid, it is necessary to apply correction paint to the inner surface of the easy-open lid that corresponds to the scored and riveted parts, and it is also necessary to apply correction paint to the inner surface of the easy-open lid that corresponds to the scored and riveted parts. It may be necessary to apply correction paint to the inner surface of the tightening part. To apply this correction paint, spray the paint to the required location,
This is then done by baking. However, when using an adhesive can as a metal can, that is, an adhesive can made by laminating and bonding tain-free steel materials through a polyamide adhesive, the melting point of the polyamide adhesive (for example, nylon 12 (for adhesives) generally 170
Since the temperature ranges from 180°C to 180°C, there is a problem that joints may shift or break under normal correction paint baking conditions. Conventionally, it has already been known to add an acid catalyst to the paint system in order to improve the curing properties of epoxy-phenol paints.
Publication No. 99235 discloses that per 100 parts by weight of a mixture consisting of 30 to 90 parts by weight of an epoxy resin and 70 to 10 parts by weight of a resol type phenol formaldehyde resin (hereinafter abbreviated as phenol resin), an acidic catalyst is added.
Can paints containing 0.1 to 8 parts by weight are shown. (Problems to be Solved by the Invention) However, when an acid catalyst is added to an epoxy-phenol paint, as the amount added increases,
Although the curing rate tends to increase even at relatively low temperatures of around 170°C, the cured coating film formed has problems with hot water resistance. For example, under retort sterilization conditions at 120°C for 90 minutes, A problem arises in that the color becomes white. On the other hand, increasing the concentration of methylol groups in the phenolic resin contained in the paint is expected to promote curability. However, although the acceleration of curing is remarkable at high temperatures of 200℃ or higher,
Baking at a low temperature that does not cause melting of the polyamide adhesive cannot be expected to accelerate curing. Therefore, the present invention eliminates the above-mentioned drawbacks of conventional epoxy-phenol paints, has excellent low-temperature curability, and provides a cured coating film with improved physical properties such as retort resistance, corrosion resistance, and processability. An object of the present invention is to provide a paint composition for cans that is excellent in combination. (Means for Solving the Problems) According to the present invention, in a can composition comprising an epoxy resin, a resol resin, a phenol formaldehyde resin, and an acid catalyst dissolved or dispersed in an organic solvent, the epoxy resin is combined with epichlorohydrin. It is a bisphenol A type epoxy resin derived from bisphenol A, and the resol type phenol formaldehyde resin is a resol type obtained by reacting phenols and formaldehyde in the presence of an alkali metal catalyst or an alkaline earth metal catalyst. It is a phenol-formaldehyde resin, and the number of chemical equivalents of the acid catalyst per 100 parts by weight of paint solid content is X, and the number of methylol groups or etherified methylol groups per benzene ring in the resol type phenol-formaldehyde resin is Y. Then, the above problem can be achieved by setting X and Y within a range that satisfies the following formula: Y≦−25.5X+1.51 Y≧−27.1X+0.46 1.0≧Y≧0.3 0.031≧X≧0.001 I can do it. (Function) The bisphenol type epoxy resin used in the present invention improves the hot water resistance of the final coating film, improves the adhesion to metals and processability, and improves hygiene. It also has excellent physical characteristics. As a phenol resin, by using a resin obtained by reacting phenols and formaldehyde in the presence of an alkali metal catalyst or an alkaline earth metal catalyst, it is possible to impart low-temperature curability. For example, when an ammonia resol resin produced using ammonia as a catalyst is used, low-temperature curability is not observed even if other conditions are the same as in the present invention. In the present invention, the amount of acid catalyst blended in the paint and the concentration of methylol groups or etherified methylol groups in the phenolic resin are determined by the above formula (1),
By satisfying (2), (3) and (4), it is possible to impart low-temperature curability without impairing the above-mentioned physical properties of the coating film. FIG. 1 plots the values of Examples and Comparative Examples described later, with the amount of acid catalyst in the epoxy-phenol paint as the horizontal axis and the concentration of methylol groups or etherified methylol groups as the vertical axis. In the figure, straight line A is the equal sign in formula (1), line B is the equal sign in formula (2), C1 is the equal sign on the left side of formula (3), and C2 is the equal sign in formula (3). In the case of the equal sign on the right side, D1 is the formula (4)
and D2 indicate the case of an equal sign on the right side of equation (4), respectively, and the area surrounded by each of these straight lines is within the range defined by the present invention. Generally, the curing reaction in epoxy-phenolic paints is mainly a reaction between the methylol group in the phenolic resin and the hydroxyl group in the epoxy resin, and a reaction between the phenolic hydroxyl group in the phenolic resin and the terminal oxirane ring in the epoxy resin. (reactions), but the former reaction is dominant in the presence of an acid catalyst. Furthermore, it is recognized that in the curing reaction in the presence of an acid catalyst, a condensation reaction (reaction) between the methylol groups in the phenolic resins, ie, condensation of the phenolic resins, occurs competitively. The present invention is an epoxy
Based on the knowledge that in order to impart low-temperature curing properties to phenolic paints without substantially deteriorating the physical properties of the coating, strict selection and combination of the amount of acid catalyst and the concentration of methylol groups are required. It is something. Again in FIG. 1, in the area below and to the left of straight lines B, C2, and D2, low-temperature curing properties are not imparted, and the extraction resistance, hot water resistance, mechanical strength, etc. of the coating film are insufficient. . The reason for this is thought to be that the above-mentioned reaction does not occur sufficiently in these regions. Furthermore, in the area above and to the right of straight lines A and D1, curing at low temperatures progresses sufficiently;
The cured coating film that is formed begins to whiten under retort conditions. The reason for this is thought to be that in these regions, reactions mainly occur and the rate of reaction is reduced, that is, a heterogeneous reaction occurs. Furthermore, in the region above the straight line C1, the workability of the coating film decreases. This is probably because the reaction mainly occurs and the phenolic resin itself becomes reticulated. (Preferred embodiment of the invention) As the epoxy resin used in the present invention, epihalohydrin and bisphenol A [2,2'-bis(4
-hydroxyphenyl)propane] and has an average molecular weight of 800 to 5,500, particularly preferably 1,400 to 5,500, and is preferably used for the purpose of the present invention. This epoxy resin has the following general formula: In the formula, R is a condensed residue of 2,2'-bis(4-hydroxyphenyl)propane, and n is a number selected such that the average molecular weight of the resin is 800 to 5500. . The molecular weight of the epoxy resin mentioned above is the average molecular weight, and therefore, the epoxy resin for paints with a relatively low degree of polymerization and the linear epoxy resin with a high molecular weight, that is, the phenoxy resin, have an average molecular weight within the above range. There is no problem in using them in combination so that The phenolic resin used in the present invention is a resol resin obtained by reacting phenols with formaldehyde using an alkali metal compound or an alkaline earth metal compound as a catalyst, and has a methylol group or an ether per benzene ring. The number of methylol groups is from 0.3 to 1.0 as mentioned above, especially
It is within the range of 0.35 to 0.85. Various phenols are used as the phenols, but at least a part of the phenols have the following formula: In the formula, R ⁴ is a hydrogen atom or an alkyl group or alkoxy group having 4 or less carbon atoms, and two of the three R ⁴ are hydrogen atoms and one is an alkyl group or an alkoxy group. , R ⁵ is a hydrogen atom or an alkyl group having 4 or less carbon atoms, difunctional phenols represented by, such as O-cresol, p-cresol, p-tertbutylphenol, p-ethylphenol, 2,3-xylenol It is desirable to use one or more difunctional phenols such as , 2,5-xylenol and the like. Further, as the phenols, polycyclic phenols can also be used as at least a part of the phenols. As used herein, polycyclic phenol refers to phenols having a plurality of rings to which phenolic hydroxyl groups are bonded, and representative examples of such polycyclic phenols include the formula In the formula, R represents a direct bond or a divalent bridging group. Divalent phenols represented by the following are known, and such phenols are preferably used for the purpose of the present invention. In the divalent phenol of the formula (), 2
As the valent bridging group R, an alkylidene of the formula -CR ¹ R ² - (in the formula, each of R ¹ and R ² is a hydrogen atom, a halogen atom, an alkyl group having 4 or less carbon atoms, or a perhaloalkyl group) group, -O-, -S-, -SO
-, _-SO2- , ^-NR3- (in the formula, ^R3 is a hydrogen atom or an alkyl group having 4 or less carbon atoms), but alkylidene groups or ether groups are generally preferred. . Suitable examples of such dihydric phenols () are 2,2'-bis(4-hydroxyphenyl)propane (bisphenol A), 2,2'-bis(4-hydroxyphenyl)butane (bisphenol B) 1,1'-bis(4-hydroxyphenyl)ethane, bis(4-hydroxyphenyl)methane (bisphenol F), 4-hydroxyphenyl ether, p-(4-hydroxy)phenol, etc. However, bisphenol A and bisphenol B are most preferred. The above-mentioned difunctional phenols or polycyclic phenols can be used alone or in combination as a mixed phenol.
Of course, these phenols may be substituted with other phenols, such as trifunctional phenols such as phenol (carbolic acid), m-cresol, m-ethylphenol, 3,5-xylenol, m-methoxyphenol; 2,4- Monofunctional phenols such as xylenol and 2,6-xylenol; p-tert
Aluminum phenol, p-nonylphenol, p-
It can also be used in combination with other bifunctional phenols such as phenylphenol and p-cyclohexylphenol. The amount of formaldehyde used is such as to bring about the methylol group concentration mentioned above, and the amount used is related to the functionality and molecular weight of the phenol, but it is generally 0.8 to 4 per mole of phenol.
The amount may be used in a molar range, particularly in the range of 1 to 3 molar, so as to provide the above-mentioned methylol group concentration. The condensation reaction is carried out in a suitable reaction medium, especially an aqueous medium, in the presence of an alkali metal or alkaline earth metal catalyst. Examples of catalysts include hydroxides and alkaline salts of alkali metals such as caustic soda, caustic potash, and sodium carbonate, as well as magnesium hydroxide, calcium hydroxide, barium hydroxide, calcium oxide, basic magnesium carbonate, basic magnesium chloride, and basic magnesium hydroxide. Hydroxides, oxides, or basic salts of alkaline earth metals such as magnesium acetate are preferably used. These basic catalysts may be present in the reaction medium in catalytic amounts, especially in amounts of 0.01 to 0.5 mol %. The condensation conditions are not particularly limited, and are generally 80 to 130°C and 1 to 10
Heating may be performed for about an hour. The resulting resin can be purified by means known per se, for example by extracting and separating the resin component of the reaction product from the reaction medium using, for example, a ketone, alcohol, hydrocarbon solvent or a mixture thereof, and washing if necessary with water. By removing unreacted substances and further removing water by an azeotropic method or a precipitation method, a phenolic resin that can be mixed with an epoxy resin can be obtained. Of course, it is also possible to react at least a portion of the methylol groups in the resol resin with an alcohol such as butyl alcohol to previously modify the methylol groups into an etherified methylol group. The above-mentioned epoxy resin component (a) and phenolic resin component (b) can be used in combination in any ratio within the range conventionally used in this type of paint, and are not particularly limited. From the viewpoint of retort resistance of the coating film, (a):(b)=95:5 to 50:50, especially
It is desirable to use a paint that combines both in a weight ratio of 90:10 to 60:40. In the present invention, the epoxy resin and phenolic resin can be mixed in a dissolved state in ketones, esters, alcohols, hydrocarbon solvents, or a mixed solvent thereof, and used directly as a paint. Moreover, these mixed resin solutions can be used as a paint after being precondensed at a temperature of 80 to 130° C. for about 1 to 10 hours. Furthermore, epoxy resin and phenolic resin are 2
Instead of using the phenolic resin in the form of a component-based paint, the phenolic resin can first be treated with modifiers known per se, such as fatty acids, polymerized fatty acids, resin acids (or rosins), drying agents, etc., to the extent that the essence of the phenolic resin is not lost. oil,
After being modified with one or more alkyd resins, etc., it is combined with an epoxy resin, or if desired, both resins are modified with a modifier such as vinyl acetal (butyral) resin, amino resin, xylene resin, acrylic resin, etc. Of course, it can also denature. In the present invention, the above-mentioned paint is used in an amount of 1 to 31 chemical equivalents, particularly in an amount of 2 to 25 chemical equivalents, per 100 parts by weight of the solid content of the paint, and
(1) to (4) are blended in a satisfying amount. Examples of acid catalysts include organic acids such as paratoluenesulfonic acid, methanesulfonic acid, citric acid, salicylic acid, lactic acid, acetic acid, and benzoic acid, and inorganic acids such as phosphoric acid, phosphorous acid, sulfuric acid, and hydrochloric acid. . In the present invention, the optimal combination of low-temperature curability and coating physical properties is determined by replacing the aforementioned X and Y with the following formula: Y≦-25.5X+1.51...(1') Y≧-27.1X+0.46...(2 ') 1.0≧Y≧0.3...(3') 0.031≧X≧0.001...(4') The can paint of the present invention is generally used for coating cans or can materials at a resin solids concentration of 10 to 50% by weight, particularly 15 to 40% by weight. The can paint of the present invention is particularly useful as a correction paint for cans, and in this case, it is applied to the areas of the can to be corrected by means such as spray coating. Since the paint of the present invention is low-temperature curable, the baking conditions for the coating film can generally be relatively low, such as 150 to 180°C, and the required baking time is generally 2 to 7 minutes. The range is fine. Of course, this paint is also suitable as a top coat for various cans, and since it can be baked at low temperatures and can reduce baking costs, it can also be used as a paint for TFS can materials, etc. This paint is applied onto the can material by means known per se, such as brush coating, spray coating, dipping, roll coating, doctor coater, electrostatic coating, electrophoretic coating, etc.,
Then, it is baked to form a coating film. (Operations and Effects of the Invention) According to the present invention described above, for can paints, while maintaining the physical properties of the cured coating film, such as retort resistance, corrosion resistance, and processability, at an excellent level,
It has become possible to impart low-temperature curability. Therefore, according to the present invention, when applied as a correction paint or top coat to adhesive cans, especially cans with overlapping joints made of polyamide adhesive, etc., and resin film laminated metal lids and baked. ,
There is a remarkable advantage that displacement or destruction of the bonded or close-contact portion, thermal deterioration of the resin, etc. can be effectively prevented. (Example) Production of phenolic resin In the examples, phenolic resin was produced in the following manner. A predetermined amount of phenols and 37% formalin are placed in a reactor, and a predetermined amount of catalyst is added while heating and stirring at 50°C. Thereafter, the reaction system is raised to a predetermined temperature and reacted for a predetermined time. When an alkali metal compound or alkaline earth metal compound is used as a catalyst, 10% reduction after lowering the liquid temperature to 60℃
Neutralize by adding an aqueous phosphoric acid solution, but if ammonia or amines are used as a catalyst, no neutralization is performed. Next, a mixed solvent consisting of 40 parts of methyl isobutyl ketone, 20 parts of toluene, 20 parts of cyclohexanone, and 20 parts of cellosolve acetate is added to extract the resulting resin, and the water and catalyst in the lower layer are separated and removed.
Water remaining in the resin solution was removed by azeotropic dehydration to obtain a phenolic resin solution with a solid content of 30%. The methylol group concentration of these resins was measured by NMR method and expressed as the number of methylol groups or etherified methylol groups per benzene ring. Production of paint Dissolve epoxy resin in a mixed solvent of 50 parts of butyl cellosolve and 50 parts of xylene to prepare a 30% solution.
Mix with 30% phenolic resin solution in the given ratio. After precondensing at 110°C for 2 hours, a predetermined amount of acid catalyst was added and mixed with stirring to prepare a test paint. The amount of acid catalyst added is based on the solid content of the paint unless otherwise specified.
The amount added is expressed per 100g. Evaluation of Paints In the Examples, evaluations of paints were performed in the following manner. Apply paint using a roll coater to metal plates (aluminum plate, electrolytic chromic acid treated steel plate (TFS plate),
After applying the film to a tin-plated steel plate (with a dry coating thickness of approximately 10 micrometers), the coating was baked in a gas oven at 170°C for 5 minutes to harden the coating and form a coated plate. It was submitted for evaluation. (1) Measurement of gel fraction Cut the painted board into 10 cm x 10 cm to prepare a test piece, and measure the initial weight (W ₀ ) of this test piece. These specimens were extracted in methyl ethyl ketone at 75°C for 60 minutes. Take out the test piece, dry it at 150℃ for 30 minutes, and measure its weight (W ₁ ). Next, remove the extraction residue by decomposing it with concentrated sulfuric acid, wash it with water, and measure the weight (W ₂ ) of the dried test piece. do. The gel fraction was determined by the following formula. Gel fraction (%) = (W ₁ − W ₂ )/(W ₀ − W ₂ )×
100 Gel fraction was evaluated using the following criteria. ◎: 90% or more 〇: 75% to 90% △: 50% to 75% ×: 50% or less (2) Retort whitening resistance A coated board was cut into 4 cm x 8 cm to use as a test piece. After immersing the test piece in a beaker containing distilled water and covering the mouth of the beaker with aluminum filtrate,
Subjected to retort treatment at 120°C for 90 minutes. Retort whitening resistance was evaluated based on the following criteria by visually determining the degree of whitening of the coating film after retorting. ◎: No whitening 〇: Slight whitening △: Significant whitening ×: Significant whitening (3) Bending workability The painted plate was cut into 3 cm x 3 cm to prepare test pieces. After pre-folding the test piece so that the coating surface was on the outside and sandwiching two metal plates of the same thickness as the test piece as spacers, a 3 kg iron block was dropped from a height of 40 cm. Processed by bending.
Both ends of this bending test piece were covered with wax and the bending processability was evaluated. The bending processability was evaluated by immersing the bent part of the test piece in 1% saline solution, applying a 7V DC voltage to the test piece as an anode, and measuring the current flowing through the test piece, and evaluating based on the following criteria. did. ◎: 0mA ~ 30mA 〇: 30mA ~ 60mA △: 60mA ~ 100mA ×: 100mA or more (4) Corrosion resistance Single-wound can with aluminum easy-open lid double-sealed on one side of 211 diamond 350ml TFS adhesive can body The test paint was spray painted on the inner surface of the cylinder and baked at 170°C for 5 minutes. 0.4 to this single-rolled can body
% acetic acid aqueous solution and double-seal the lid. These canned goods are retorted at 120°C for 90 minutes and then stored at 50°C for one month. Thereafter, the cans were opened, the inner surface of the can was observed, and the presence or absence of corrosion was evaluated according to the following criteria. ◎: No corrosion 〇: Slight spot corrosion △: Lots of spot corrosion ×: Spot corrosion all over the surface (5) Storage stability Pour the test paint solution into an Erlenmeyer flask, tightly stopper it, and store it at 50℃. The viscosity of the paint solution after storage was measured using a B-type viscometer, and the period until the viscosity reached twice that before the start of storage was investigated. Example 1 Five types of epoxy resins were prepared. Epoxy resins 1, 2 and 3 are bisphenol A type epoxy resins, manufactured and sold by Yuka Ciel Co., Ltd. The epoxy resin 4 is a novolac type epoxy resin manufactured and sold by Ciba Geigy Corporation. Epoxy resin 5 is a bisphenol F type epoxy resin, and was synthesized in the following manner. 1 mol of bisphenol F and 1.4 mol of 10% aqueous sodium hydroxide solution are heated to 45°C, 1.1 mol of epichlorohydrin is added with stirring, and the mixture is heated to 100°C and reacted for 110 minutes. Since the product separates into two layers, the aqueous layer containing sodium chloride and alkalis is removed using a siphon, and 1 mole of methyl isobutyl ketone is added to dissolve the resin. Furthermore, after repeated washing with boiling water until it becomes neutral, 160
The mixture was heated to 0.degree. C. to evaporate methyl isobutyl ketone and cooled to obtain a bisphenol F type epoxy resin. Table 1 shows the number average molecular weights and epoxy equivalents of these epoxy resins.

[Table] On the other hand, using 114 g of bisphenol A, 101 g of 37% formalin and 3 g of magnesium hydroxide,
A reaction was carried out at 90° C. for 1 hour to obtain a phenolic resin (phenolic resin 1). The methylol group concentration of this phenolic resin was 0.51 per benzene ring. Ten types of paints shown in Table 2 were prepared using these epoxy resins and phenolic resins. To these paints, 15 meq. of phosphoric acid was added as an acid catalyst.
These paints were applied to a TFS board with a thickness of 0.22 mm, and after baking and drying, the gel fraction, bending workability, and retort whitening resistance of the dried paint films were examined, and the results are shown in Table 2.
It can be seen that the paint using bisphenol A type epoxy resin, phenol resin, and acid catalyst according to the present invention has well-balanced performance compared to paints using other types of epoxy resins.

[Table] Example 2 Seven types of phenolic resins were prepared under various reaction conditions using 65 g of para-cresol and the amounts of formalin and catalyst shown in Table 3. Table 3 also shows the methylol group concentration of the obtained phenolic resin.

[Table] Using these phenolic resins and epoxy resin 3 of Example 1, seven types of paints were prepared. The blending ratio of epoxy resin and phenolic resin is 80/20,
For each paint, 10 meq. of para-toluenesulfonic acid was added as an acid catalyst. These paints were applied and baked on an aluminum plate with a thickness of 0.35 mm to make a coated plate, and the gel fraction, bending processability, and retort whitening resistance of the dried coating film were examined. The results are shown in Table 4. The paint using bisphenol A type epoxy resin, phenolic resin, and acid catalyst according to the present invention is compared with the paint using phenolic resins (phenolic resins 6, 7, and 8) synthesized using ammonia and amines as catalysts. It can be seen that the coating film has well-balanced performance.

【table】

[Table] Example 3 Seven types of phenolic resins having different methylol group concentrations were synthesized. Phenol raw material, formalin amount,
Details of the synthesis conditions such as the amount of catalyst are shown in Table 5. Magnesium hydroxide was used as a synthesis catalyst, and the amount added is shown in the table.

[Table] Using these phenolic resins and epoxy resin 3 of Example 1, paints with eight basic formulations were prepared by blending the epoxy resin and phenolic resin at a ratio of 80/20. To each of these basic formulations, 11 levels of phosphoric acid were added as an acid catalyst to form 88 test coatings. Furthermore, 8 types of test paints were prepared by adding 10 meq. of para-toluenesulfonic acid to the 8 types of paints with the basic formulations described above. These 96 types of paints were applied and baked onto a 0.23 mm thick tin-plated steel plate to produce a coated plate, and the performance of the coated plate was evaluated. The results are summarized in Table 6. In addition, the relationship between the methylol group concentration of the phenolic resin used in these 96 types of paints and the amount of acid catalyst added to the paints is shown in Figure 1 along with the evaluation results of paint film performance. As for the evaluation in the figure, a comprehensive evaluation of gel fraction, bending workability, and retort whitening resistance was performed, and the criteria were as follows. ◎: Excellent in all performances 〇: Slightly inferior in either performance △: Significantly inferior in either performance ×: Significantly inferior in either performance Methylol group concentration of phenolic resin and acid catalyst In the paint according to the present invention, in which the combination of the concentration of methylol group and the amount of acid catalyst added is within an appropriate range, the coating film formed exhibits balanced performance. It can be seen that there are some defects in the performance of the paint or coating film.

【table】

[Table] Example 4 Eight types of paints were made using epoxy resin 3 of Example 1, phenolic resins 4, 6, and 8 of Example 2, and phenolic resins 10, 11, 13, 15, and 16 of Example 3. Prepared. The blending ratio of epoxy resin and phenolic resin is 75/25, and
15 meq. of para-toluenesulfonic acid was added. The corrosion resistance and storage stability of these paints were evaluated and the results are shown in Table 7. The paints according to the present invention (paints 1, 4, 5, 6, and 7) are all excellent in both corrosion resistance and storage stability, but the comparative paints (paints 2, 3, and 8) have poor corrosion resistance and storage stability. The performance of one or both is inferior.

【table】 [Brief explanation of the drawing]

FIG. 1 is a graph plotting the values of Examples and Comparative Examples, with the horizontal axis representing the amount of acid catalyst in the epoxy-phenol paint and the vertical axis representing the concentration of methylol groups or etherified methylol groups.

Claims (1)

[Scope of Claims] 1. A can composition comprising an epoxy resin, a resol type phenol formaldehyde resin, and an acid catalyst dissolved or dispersed in an organic solvent, wherein the epoxy resin contains epichlorohydrin and bisphenol A.
It is a bisphenol A type epoxy resin derived from resol type phenol formaldehyde resin obtained by reacting phenols and formaldehyde in the presence of an alkali metal catalyst or an alkaline earth metal catalyst. It is a resin, and the number of chemical equivalents of the acid catalyst per 100 parts by weight of paint solid content is X, and the number of methylol groups to etherified methylol groups per benzene ring in the resol type phenol formaldehyde resin is Y, A paint composition for cans, wherein X and Y are within a range satisfying the following formula: Y≦−25.5X+1.51 Y≧−27.1X+0.46 1.0≧Y≧0.3 0.031≧X≧0.001.