JPH0681819B2 - Water-based adhesive can primer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Field of Industrial Application) The present invention relates to an undercoat agent for an aqueous adhesive can, more specifically, it is applied to a can material and a polyamide adhesive is used in the side seam portion. And a water-based undercoating agent that functions as a primer by utilizing the adhesiveness to a can material.

(Prior Art) A so-called adhesive can is a generic name for a can in a three-piece can, in which the seam of the can body is adhered. In the background that adhesive cans have become more important in metal containers in recent years, tin-free steel such as chrome-plated steel sheets and chromic acid-treated steel sheets, nickel-plated steel sheets, and aluminium-plated sheets have been replaced by tin-plated tin plates. steel sheet,
Various can materials such as aluminum plates are being developed and supplied. That is, since these materials cannot be soldered like tinplate, when making a can body of a three-piece can, it is necessary to use a method of welding the side seams or joining them with an adhesive unlike conventional methods.

When the side seam is bonded with an adhesive, a primer material is usually applied and baked on a tin material such as tin-free steel, and then hot-melt bonding is performed using a polyamide adhesive. Therefore, the property required for the undercoat is a strong adhesion to the can material and the adhesive, and at the same time, various physical properties such as corrosion resistance and workability as the can inner surface coating are required. From this point of view, conventionally, epoxy-phenolic solvent-based paints have been used as the primer for adhesive cans. However, in recent years, with the problem of air pollution due to organic solvents and increasing social concern about resource saving of petroleum resources, no organic solvent is used in the coating industry and container industry, or the content of the organic solvent is reduced as much as possible. The transition to paints that have been made is being actively planned. In particular, the primer for adhesive cans is a paint that is used in large quantities in the production of adhesive cans, and has a great effect on the performance of adhesive cans. The amount of adhesive cans produced is increasing with the increase in the amount of adhesive cans produced, which is why water-based adhesives are strongly desired.

Up to now, epoxy resin-based paints have been mainly studied as water-based can coating materials, and various methods have been proposed as a method for dispersing an epoxy resin in water. For example, as a method of dispersing an epoxy resin using a surfactant, a method of using an anionic or nonionic surfactant is known, but it is inferior in storage stability, hygiene, chemical and mechanical performance. It is not suitable as a paint for use. As a solution to this problem, various self-emulsifying epoxy resins in which an epoxy resin is modified with an acrylic resin and a segment having an emulsifying power is introduced into the molecule have been proposed. Since such a self-emulsifying epoxy resin does not contain a surfactant in the coating film, a strong formed coating film can be obtained by itself. Further, these coatings are blended with a water-soluble amino resin or a phenol resin when a higher curing rate is required. However, with such a conventional technique, when it was used as an undercoat agent for an adhesive can, sufficient adhesive force could not be obtained for the base can material and the polyamide adhesive.

(Problems to be solved by the invention) As a result of intensive studies conducted by the present inventors in view of the above situation, the performance of the conventional epoxy = phenolic solvent-based undercoating agent, that is, the base material and the polyamide-based adhesive agent Succeeds in reducing the amount of organic solvent or substantially freeing organic solvent without sacrificing the function as a protective layer of the underlying material from the contents by guaranteeing the tightness of the can body by maintaining a strong adhesive force to It was done.

[Structure of Invention]

(Means for Solving Problems) That is, the present invention is based on 100 parts by weight (based on an unmodified product) of a bisphenol-type epoxy resin that is potentially self-emulsifying by a carboxyl group introduced into a molecule. ，
A composite resin composition comprising 10 to 60 parts by weight of a phenolic resin having an average of 0.1 to 0.5 methylol groups per phenol ring, the composite resin composition being at least partially neutralized with an amine or ammonia. The present invention relates to an aqueous primer for an adhesive can, which is dispersed in an aqueous medium.

As the phenol used in the phenol resin of the present invention, the phenol conventionally used for producing a phenol resin can be used. That is, bisphenol A, bisphenol B, bisphenol F, 1,1-bis (4-hydroxyphenyl) ethane or the like can be used as the tetrafunctional phenol, and phenol (carbolic acid), m-cresol, m can be used as the trifunctional phenol. -Ethylphenol,
3,5-xylenol, m-methoxyphenol, etc. can be used, and further o-cresol, p-cresol, p-tert-butylphenol, p-ethylphenol, 2,3-xylenol, 2,5-xylenol, p-tertamino Bifunctional phenols such as phenol, p-nonylphenol, p-phenylphenol and p-cyclohexylphenol may be used.

These phenols may be used alone or in combination of two or more.

The phenol resin of the present invention in which the methylol groups are adjusted to 0.1 to 0.5 per phenol ring can be obtained by selecting synthesis conditions such as the amount of formaldehyde used, reaction temperature, reaction time, and catalyst. For example, the following phenol resins may be mentioned.

(1) Resol-type phenol resin obtained by adding / condensing 0.3 to 0.8 mol of formaldehyde per phenol ring in the presence of an alkali catalyst (2) Adding 0.5 to 2.0 mol of formaldehyde per phenol ring in the presence of an alkali catalyst Phenolic resin obtained by mixing or condensing a novolac type phenolic resin with a condensed resol type phenolic resin (in this case, the novolac type phenolic resin is 0.5 ~ per phenol ring).
It is a novolac type phenolic resin obtained by addition-condensing 1.5 mol of formaldehyde in the presence of an acidic catalyst. (3) 0.5 to 3.0 mol of formaldehyde per phenol ring is added / condensed in the presence of an alkali catalyst to further add phenol to the resol-type phenol resin, and if necessary, an excess of the above alkali catalyst is used. Phenolic resin that has undergone a condensation reaction with the addition of an acidic catalyst (4) 0.5 to 1.5 mol of formaldehyde per phenol ring is added and condensed in the presence of an acidic catalyst to form a novolac-type phenol resin and formaldehyde and the above acidic catalyst. Phenolic resin to which an excess alkali catalyst was added for addition reaction was carried out. Examples of the alkali catalyst include sodium hydroxide, potassium hydroxide, magnesium hydroxide, basic metal salts, ammonia, hexamethylenetetramine, triethylamine, trimethylamine, pyridine. Alkali catalysts such as

Acid catalysts include hydrochloric acid, sulfuric acid, orthophosphoric acid,
Acidic catalysts such as acids, formic acid and acetic acid are preferred.

The phenolic resin having an average of 0.1 to 0.5 methylol groups per aromatic ring produced as described above has
A crosslink density is suitable. That is, the methylol group is an average of 0.
If more than one is used, the cross-linking density of the coating film formed will decrease, resulting in poor corrosion resistance and processability.
If the number is 5 or more, the crosslink density will be too high and the workability will be poor.
Furthermore, the adhesive strength with hot water is reduced.

Here, the amount of methylol group per aromatic ring is phenol resin
To 0.5 g, add 10 cc of acetylating reagent consisting of pyridine / acetic anhydride (volume ratio 1/1) and heat at 80 ° C for 3 hours, then water 100 cc
Was added and extracted with ethyl ether, 6-N HCl aqueous solution 70
After addition of cc, extraction with ethyl ether and addition of 70 cc of 0.1-N sodium bicarbonate and extraction with ethyl ether were repeated, and then ethyl ether was removed under reduced pressure at room temperature to obtain an acetylated phenol resin, which was dissolved in chloroform and analyzed by H-NMR. 5pp measured
The peaks around m can be quantified to calculate the number of moles of a methylol group added to one phenyl nucleus.

Such a resole resin, that is, a methylol group per phenol ring has an average of 0.1 to 0.5, preferably 0.2 to 0.4.
By using a phenolic resin in the range of 1) as one component of the undercoating agent for water-based adhesive cans, the initial adhesive strength in the structure of the base material (steel plate such as tin-free steel) -undercoating agent-polyamide adhesive is improved. Of course, it is possible to obtain an undercoating agent with excellent properties, which maintains sufficient adhesive strength even when subjected to processing strain or subjected to a aging test in hot water.

In the present invention, the bisphenol type epoxy resin used is an epoxy resin obtained by reacting bisphenols such as bisphenol A, bisphenol B and bisphenol F with epichlorohydrin in the presence of an alkali catalyst. Co., Ltd. Epicote 828, Epicote 1001, Epicote 1004, Epicote
1007, Epicoat 1009, Epicoat 1010, etc. It is also possible to use a modified epoxy resin obtained by reacting the epoxy group or hydroxyl group of the bisphenol type epoxy resin with a vegetable oil fatty acid such as dehydrated castor oil fatty acid, soybean oil fatty acid, coconut oil fatty acid or a modifier such as bisphenol A.

The bisphenol type epoxy resin potentially self-emulsifying by the carboxyl group introduced into the molecule in the present invention has an average of 0.5 or more epoxy groups and an average of 0.1 per molecule.
~ Polymerize bisphenol type epoxy resin derivative having 1.5 (meth) acryloyl groups and copolymerizable monomer containing monobasic carboxylic acid monomer as an essential component in an amount of 10 to 80 parts by weight using a radical polymerization initiator Can be obtained. This epoxy resin derivative is a bisphenol-type epoxy resin with methacrylic acid or acrylic acid in the presence of an alkali catalyst such as sodium hydroxide.
Per molecule by reacting at 0-150 ℃ for 1-6 hours
It can be obtained as having 0.5 epoxy groups and an average of 0.1 to 1.5 acryloyl groups.

The self-emulsifying bisphenol-type epoxy resin of the present invention also comprises a copolymerizable monomer mixture containing 10 to 80% by weight of a monobasic carboxylic acid monomer in the presence of the bisphenol-type epoxy resin, and an organic peroxide such as benzoyl peroxide. It can be obtained by using a relatively large amount of the product and polymerizing it. In this case, a bisphenol type epoxy resin grafted with an acrylic resin is obtained.

The self-emulsifying bisphenol type epoxy resin in the present invention is also an acrylic resin obtained by copolymerizing a copolymerizable monomer mixture containing 12 to 70% by weight of a monobasic carboxylic acid monomer and an average of 1.1 to 1 per molecule. It can be produced by partially binding a bisphenol type epoxy resin having 2.0 epoxy groups.

For the production of the above self-emulsifying bisphenol type epoxy resin, acrylic acid is used as the monobasic carboxylic acid monomer,
Methacrylic acid or the like is used, and as the copolymerizable monomer, methyl acrylate, ethyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, n-amyl acrylate, isoamyl acrylate, n-acrylate -Acrylic acid esters such as hexyl, 2-ethylhexyl acrylate, n-octyl acrylate, decyl acrylate, dodecyl acrylate,
Methyl methacrylate, propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-amyl methacrylate, n-hexyl methacrylate, n-octyl methacrylate, 2-ethylhexyl methacrylate, decyl methacrylate, dodecyl methacrylate, etc. Styrene monomers such as methacrylic acid esters, styrene, vinyltoluene, 2-methylstyrene, t-butylstyrene, chlorostyrene, hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, etc. Hydroxy group-containing monomer, N-methyl roll (meth) acrylamide, N-substituted (meth) acrylic monomers such as N-butoxymethyl (meth) acrylamide, glycidyl acrylate, methacrylic acid Epoxy group-containing monomers such as glycidyl, and one or two acrylonitrile
It can be selected from more than one species.

The copolymerizable monomer mixture containing 12 to 70% by weight of the above-mentioned monobasic carboxylic acid monomer is preferably used in an amount of 10 to 90 parts by weight based on 100 parts by weight of the bisphenol type epoxy resin. If the amount is less than 10 parts by weight, it becomes difficult to impart self-emulsifying property to the epoxy resin, and a stable dispersion cannot be obtained in an aqueous medium. On the other hand, if the amount exceeds 90 parts by weight, hydrophilic carboxyl groups remain in the formed coating film, so that the adhesive strength over time after retort treatment tends to decrease and the corrosion resistance also deteriorates.

In the present invention, the composite resin composition can be obtained by mixing a self-emulsifying bisphenol type epoxy resin and at least one phenol resin, preferably in a hydrophilic solvent. In addition, the composite resin composition of the present invention is prepared by dispersing a self-emulsifying bisphenol A type epoxy resin in an aqueous medium, mixing the phenol resin, and dispersing the bisphenol A type epoxy resin in the aqueous medium. It can also be obtained by incorporating it in particles.

The amount of resol resin in the composite resin composition must be 10 to 60 parts by weight per 100 parts by weight of the self-emulsifying bisphenol type epoxy resin (based on the unmodified product). If it is less than the area, the curability of the coating film will be poor, and sufficient adhesion to the base material and polyamide adhesive will not be obtained. On the other hand, if it exceeds 60 parts by weight, physical properties such as processability of the coating film deteriorate.

In the present invention, the aqueous resin dispersion is prepared by adding ammonia or amine to the composite resin composition or the self-emulsifying epoxy resin in an amount such that the final composition has a PH of 4 to 11 and dispersing in an aqueous medium. However, when high boiling point solvents are used in the previous step, it is preferable to remove these solvents under reduced pressure in advance.

As the amine, for example, alkylamines such as trimethylamine, triethylamine and butylamine, alcohol amines such as 2-dimethylaminoethanol, diethanolamine, triethanolamine and aminomethylpropanol, morpholine and the like are used. Also, polyamines such as ethylenediamine and diethylenetriamine can be used. In the present invention, the aqueous medium means a mixture of water and a hydrophilic organic solvent in which at least 50% by weight, preferably 80% by weight or more, more preferably 90% by weight is water, and the hydrophilic organic solvent is methanol. , Ethanol, n
-Propanol, isopropanol, n-butanol, sec
-Alkyl alcohols such as butanol, tert-butanol and isobutanol, ether alcohols such as methyl cellosolve, ethyl cellosolve, propyl cellosolve, butyl cellosolve, methyl carbitol and ethyl carbitol, ether esters such as methyl cellosolve acetate and ethyl cellosolve acetate Dioxane, dimethylformamide, diacetone alcohol, etc. are used.

The aqueous resin dispersion according to the present invention can be used as a paint by adding a surfactant, a defoaming agent or the like for improving the coating property, if necessary.

Applicable can materials include untreated steel plate, treated steel plate, zinc iron plate, tin plate, tin-free steel such as chrome-plated steel plate and chromic acid-treated steel plate, and also metal plate such as nickel-plated steel plate, aluminum-plated steel plate, and aluminum plate. Is suitable, and roll coater coating is the preferred coating method, but spray coating, dip coating, electrodeposition coating, etc. are also possible. The baking conditions can be selected from a temperature of 150 ° C to 230 ° C and a time of 2 to 30 minutes.

Hereinafter, the present invention will be described with reference to examples. In the examples, “part” and “%” represent “part by weight” and “% by weight”, respectively.

(Example) [Preparation of phenol resin solution] Phenol resin A o-cresol 228 parts 37% formaldehyde aqueous solution 85.6 parts 25% ammonia water 28.7 parts The above composition was charged into a nitrogen gas-substituted four-necked flask, and 9
After heating to 5 to 100 ℃ and reacting under reflux for 60 minutes, extract into 350 parts of a mixed solvent of methyl isobutyl ketone (MIBK) 40%, xylene 40%, and cyclohexanone 30%, and wash with water at a temperature of 95 to 110
Heat at ℃ for about 2 hours and separate the water that evaporates. Further dilute with butyl cellosolve to obtain methylol groups per aromatic ring.
0.26 pieces of phenol resin A having a solid content of 30% were obtained.

Phenolic resin B Carboxylic acid 63.5 parts Bisphenol A 154 parts 37% Formaldehyde aqueous solution 115 parts 25% Ammonia water 18.4 parts The above composition was synthesized in the same manner as the phenol resin solution A, 0.33 methylol groups per aromatic ring, solid content 30%. Phenol resin B was obtained.

Phenolic resin C Carboxylic acid 53.5 parts Bisphenol A 130 parts 37% Formaldehyde aqueous solution 208 parts 25% Ammonia water 15.5 parts The above composition was synthesized in the same manner as phenol resin solution A, and 0.64 methylol groups per aromatic ring, solid content 30% Phenol resin C was obtained.

Phenol resin Do-cresol 218 parts 37% formaldehyde aqueous solution 115 parts 25% orthophosphoric acid alcohol solution 23.7 parts The above composition is heated to 95 to 100 ° C and reacted under reflux for 120 minutes, and then the aromatic ring is prepared in the same manner as phenol resin solution A. As a result, a phenol resin D containing 0.05 methylol groups and a solid content of 30% was obtained.

Phenolic resin E 60 parts of phenol resin solution D is mixed with 100 parts of phenol resin solution C, and the reaction is carried out for 60 minutes while dehydrating at 110 ° C. 0.38 methylol groups per aromatic ring, 30% solid content phenol resin I got E.

Preparation of Phenolic Resin F Carbolic acid 36.4 parts Bisphenol A 88.2 parts 37% formaldehyde aqueous solution 141 parts 25% ammonia water 10.5 parts o-cresol 83.4 parts 25% orthophosphoric acid alcohol solution 38.3 parts The above 1 to 4 are charged and heated to 95 to 100 ° C. After reacting under reflux for 30 minutes, add 5 and 6 and then under reflux at 95-100 ° C for 30 minutes.
A minute reaction was performed. Thereafter, in the same manner as in the phenol resin solution A, a phenol resin F having 0.24 methylol groups per aromatic ring and a solid content of 30% was obtained.

[Preparation of self-emulsifying bisphenol type epoxy resin I] Epicoat 1007 300 parts Butyl cellosolve 162 parts 10% potassium hydroxide solution 0.5 parts Methacrylic acid 2.8 parts Hydroquinone 0.01 parts Methacrylic acid 120 parts Styrene 120 parts Ethyl acrylate 60 parts Azobisbutyi Ronitrile 15 parts n-Butanol 150 parts The above was charged into a 4-necked flask filled with nitrogen.
After melting at ℃, add and
After reacting at 0 ° C for 5 hours and cooling as an epoxy resin derivative, add after adding well, stirring well and ⅔ of the total amount.
Took out. Reheat the flask to 90 ° C and remove it 3
(2) was added dropwise over 2 hours, and the reaction was continued for 2 hours. Then, the solid content was adjusted to 60% to obtain a self-emulsifying bisphenol type epoxy resin I.

[Preparation of self-emulsifying bisphenol type epoxy resin II] Epicoat 1007 300 parts Butyl cellosolve 300 parts Methacrylic acid 150 parts Styrene 100 parts Ethyl acrylate 50 parts Benzoyl peroxide 21 parts Charge the above to a four-necked flask with nitrogen substitution 115
After melting at ℃, the mixture from was added dropwise over 1 hour,
After reacting at 115 ° C for another 2 hours, the mixture is cooled and the solid content is reduced to 6
Adjusted to 0%, self-emulsifying bisphenol type epoxy resin I
Got I.

Example 1 Self-emulsifying epoxy resin I 333 parts (unmodified epoxy resin 100 parts) Phenol resin A 100 parts (resin content 30 parts) 25% ammonia water 12.7 parts Ion-exchanged water 704 parts The above was charged into a flask and stirred. Was added to neutralize. After that, the temperature was raised to 80 ° C., reacted for 30 minutes, and then cooled. After cooling, the mixture was gradually added with stirring to obtain a milky white dispersion having a solid content of 20% and a viscosity of 520 cps.

Example 2 A phenol white resin having a solid content of 20% and a viscosity of 460 cps was obtained in the same manner as in Example 1 except that the phenol resin A of Example 1 was changed to the phenol resin B.

Example 3 The same procedure as in Example 1 was carried out except that the phenol resin A in Example 1 was changed to the phenol resin E to obtain a milky white dispersion having a solid content of 20% and a viscosity of 670 cps.

Example 4 A phenolic resin A was used instead of the phenolic resin A of Example 1, and a milky white dispersion having a solid content of 20% and a viscosity of 710 cps was obtained in the same manner as in Example 1.

Example 5 Self-emulsifying epoxy resin II 333 parts (100 parts as unmodified epoxy resin) Phenolic resin B 100 parts (resin content 30 parts) 2-Dimethylaminoethanol 20.7 parts Ion-exchanged water 696 parts Solid content 20%, viscosity 520c
A milky white dispersion of ps was obtained.

Example 6 A milky white dispersion having a solid content of 20% and a viscosity of 830 cps was obtained in the same manner as in Example 5 except that the phenol resin B was changed to the phenol resin F.

Example 7 Self-emulsifying epoxy resin I 333 parts (100 parts as unmodified epoxy resin) Phenolic resin B 170 parts (resin content 51 parts) 25% ammonia water 12.7 parts Ion-exchanged water 739 parts Similarly, solid content 20%, viscosity 910c
A milky white dispersion of ps was obtained.

Example 8 Self-emulsifying epoxy resin I 333 parts (100 parts as unmodified epoxy resin) Phenol resin B 100 parts (30 parts as resin content) 25% ammonia water 12 parts Ion-exchanged water 700 parts The above was charged into a flask and stirred. While adding it, it neutralized. When added with further stirring, a milky white dispersion was obtained. To this dispersion was added with stirring. A dispersion having a solid content of 22% and a viscosity of 410 cps was obtained.

Comparative Example 1 The same procedure as in Example 1 was carried out except that the phenol resin A of Example 1 was changed to the phenol resin C to obtain a milky white dispersion having a solid content of 20% and a viscosity of 390 cps.

Comparative Example 2 The same procedure as in Example 1 was carried out except that the phenol resin A of Example 1 was changed to the phenol resin D to obtain a milky white dispersion having a solid content of 20% and a viscosity of 850 cps.

Comparative Example 3 A milky white dispersion having a solid content of 20% and a viscosity of 640 cps was obtained in the same manner as in Example 5 except that the phenol resin B of Example 5 was changed to the phenol resin C.

Comparative Example 4 333 parts of self-emulsifying epoxy resin I (100 parts as unmodified epoxy resin) 333 parts of phenol resin B (100 parts as resin content) 25% ammonia water 12.7 parts Ion-exchanged water 821 parts Similarly, solid content 20%, viscosity 790c
A milky white dispersion of ps was obtained.

Using the aqueous resin dispersions obtained in each Example and Comparative Example as an undercoat on a chrome-treated steel sheet having a thickness of 0.22 mm, 2.5 to
After roller coating to a dry film thickness of 3μ, 10 at 210 ℃
It was baked and dried for 1 minute. A 1,2-aminolauric acid polymer was sandwiched between the coated plates, and the sample was cut into an adhesive width of 5 mm after pressure bonding with a hot press at 200 ° C for 10 seconds and cooling.
This was subjected to a T-shaped peeling test with a Shopper type tensile strength tester at an ambient temperature of 25 ° C. Also this adhesive sample
After soaking in hot water at 90 ℃ (hot water aging test), cooling and drying 25
A T-shaped peel test was performed at ℃.

Furthermore, the water-based resin dispersion of each example was applied to a tin plate (0.23 mm thick, #
50 / 50ET) roller coating and baking at 200 ℃ for 10 minutes,
A coated plate having a dry coating of 4.5 to 5 was obtained.

A flat No. 2 can was formed from the above-mentioned coated plate, and the contents of a commercially available salmon boiled can were repacked in this flat No. 2 can and subjected to retort treatment at 117 ° C for 4 hours, then opened and the inner surface was sulfided. The degree of blackening was observed.

Next, using a special goby folding DuPont tester, place the folded sample at the bottom, and touch the flat surface of the contact with an iron weight of 1 kg to drop the height of 50 cm from the coating film of the bent part. The length of the crack was measured and the crack length was indicated by 0 to 10 mm ・ ・ ・ ・ ○ 10 to 20 mm ・ ・ ・ ・ △ 20 mm or more ・ ・ ・ ×.

The above test results are shown in Table 1.

According to these results, the undercoating agent according to the present invention shows good adhesiveness both before treatment and after aging with hot water. On the other hand, in Comparative Example 2, the adhesiveness when untreated was insufficient, and in Comparative Examples 1 and 3, a significant decrease in the adhesiveness after hot water aging could be recognized, and the present invention The undercoating agent according to (1) has excellent performance as a can inner surface coating in terms of its corrosion resistance and workability.

〔The invention's effect〕

The undercoating agent for adhesive cans of the present invention can obtain a stable resin dispersion even in an aqueous medium in which the proportion of water in the coating solvent is 90% by weight or more, and is excellent in adhesiveness. Since it uses a resole resin, it has extremely high adhesion to the base material and the polyamide adhesive.

Continuation of front page (56) Reference JP 62-201970 (JP, A) JP 57-87470 (JP, A) JP 57-126859 (JP, A) JP 60-215016 (JP , A) JP-A-61-97371 (JP, A)

Claims (3)

[Claims] 1. A bisphenol type epoxy resin that is potentially self-emulsifying by a carboxyl group introduced into the molecule.
A composite resin composition in which 10 to 60 parts by weight of a phenolic resin having an average of 0.1 to 0.5 methylol groups per phenol ring is mixed with 100 parts by weight (based on an unmodified product). An aqueous primer for an adhesive can, wherein the composition is at least partially neutralized with an amine or ammonia and dispersed in an aqueous medium. 2. The self-emulsifying bisphenol type epoxy resin and the phenol resin are mixed or pre-condensed in an organic solvent, and then at least partially neutralized and dispersed in an aqueous medium. An aqueous undercoat agent for adhesive cans according to item 1. 3. An aqueous primer for an adhesive can according to claim 1, wherein the methylol group of the phenol resin is 0.2 to 0.4 on average per phenol ring.