JPS63108078A - Water-based undercoating agent for use in making bonded can - Google Patents

Abstract

PURPOSE:To obtain the title undercoating agent which has high adhesiveness to a base material and a polyamide adhesive and consumes less organic solvent, by partially neutralizing a compound resin composition comprising a mixture of a self-emulsifiable bisphenol epoxy resin and a resol resin in a specified ratio, and dispersing the neutralized composition in an aqueous medium. CONSTITUTION:A compound resin composition is formed by mixing 100pts.wt. (on an unmodified resin basis) bisphenol epoxy resin potentially self-emulsifiable due to the carboxyl groups introduced into its molecule with 10-60pts.wt. phenolic resin having an average of 0.15-0.5 methylol groups per phenol ring. This compound resin composition is at least partially neutralized with an amine or ammonia and dispersed in an aqueous medium (a mixture of at least 50wt% water with a hydrophilic organic solvent), thus forming the title undercoating agent.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Field of Application) The present invention relates to a water-based adhesive primer for cans, and more specifically, the present invention relates to a water-based adhesive primer for cans, and more specifically, it is applied to a can material, and a polyamide adhesive is applied to the side seam portion. This invention relates to a water-based primer that functions as a brimer by utilizing its adhesive properties to can materials.

(Conventional technology) A so-called adhesive can is a three-piece can.

A general term for cans whose seams are glued together. The reason behind the increasing importance of adhesive cans in metal containers in recent years is that instead of the traditional tin-plated tin, tin-free steel such as chrome-plated steel sheets and chromic acid-treated steel sheets, as well as nickel-plated steel sheets and aluminium-plated steel sheets are being used. Various can materials such as steel plates and aluminum plates have been developed and supplied. Namely.

These materials cannot be soldered like tin, so
When making the body of a three-piece can, the side seams must be joined by welding or adhesive, which is different from conventional methods.

When making side seams with adhesive 1. Apply a primer to the can material, usually tin-free steel.

Baking is performed, and then real-melt adhesion is performed using polyamide adhesive. Therefore, the characteristics required of the primer are strong adhesion to the can material and adhesive.
At the same time, various physical properties such as corrosion resistance and processability are also required as a paint for the inner surface of a can. From this point of view, epoxy-phenol solvent-based paints have conventionally been used as primer coats for adhesive cans.

However, in recent years, with the problem of air pollution caused by organic solvents and growing social interest in saving petroleum resources, the coating industry and container industry are also trying to eliminate the use of organic solvents, or to reduce the content of organic solvents as much as possible. Efforts are being made to transition to paints with less oxidation. In particular, primer coats for adhesive cans are paints that are used in large quantities in the manufacture of adhesive cans, and have a large effect on the performance of adhesive cans.

As the production volume of adhesive cans increases, the amount used also increases, which is why water-based cans are strongly desired.

Up to now, epoxy resin-based water-based paints have been mainly studied as water-based can paints, and various methods have been proposed for dispersing epoxy resins in water.

For example, methods using anionic and nonionic surfactants are known as methods for dispersing epoxy resins using surfactants, but storage stability is limited.

It is unsuitable as a paint for cans due to its poor hygienic, chemical and mechanical properties. As a solution to this problem, various self-emulsifying epoxy resins have been proposed in which epoxy resins are modified with acrylic resins and segments with emulsifying power are introduced into the molecules. Since such a self-emulsifying epoxy resin does not contain a surfactant in the coating film, a strong coating film can be obtained by itself. In addition, water-soluble amino resins and phenolic resins are added to these paints when a faster curing speed is required.

However, when such prior art is used as an undercoat for adhesive cans, sufficient adhesion to the base can material and polyamide adhesive could not be obtained.

(Problems to be Solved by the Invention) The present researchers have conducted extensive studies in view of the above circumstances, and have found that the performance of conventional epoxy-phenol solvent-based primers, that is, the performance of base materials and polyamide adhesives. Tsu 4 against? It guarantees the sealability of the can by maintaining strong adhesion and functions as a protective layer for the underlying material from the contents, reducing or substantially reducing the amount of organic solvents used. was successfully made free.

[Structure of the invention]

(Means for Solving the Problems) That is, the present invention is based on 100 parts by weight (based on unmodified material) of a bisphenol-type epoxy resin that is made potentially self-emulsifiable by the carboxyl group introduced into the molecule. , the average number of methylol groups per phenol ring is 0.1 to 0.
．． A composite resin composition containing 10 to 60 parts by weight of a phenolic resin having 5 phenolic resins, the composite resin composition being at least partially neutralized with amine or ammonia and dispersed in an aqueous medium. This article relates to an undercoat for adhesive cans.

As the phenol used in the phenolic resin of the present invention, phenol conventionally used in the production of phenolic resins can be used. That is, 4=4- As the functional phenol, bisphenol A, bisphenol B, bisphenol F, 1,1-bis(4-hydroxyphenyl)ethane, etc. can be used.

Also, as a trifunctional phenol, phenol (coal #)
, m-cresol, m-ethylphenol, 3°5-xylenol, m-methoxyphenol, etc. can be used, as well as 0-cresol and p-cresol.

p-tertbutylphenol, p-ethylphenol.

2.3-xylenol, 2.5-xylenol, p-t
ert aminophenol, p-nonylphenol.

Difunctional phenols such as p-phenylphenol and p-cyclohexylphenol may also be used.

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

The methylol group of the present invention is 0.1 to 0 per phenol ring.
．． A phenol resin having five phenol resins can be obtained by selecting the amount of formaldehyde used, the reaction temperature, the reaction time, and the synthesis conditions such as the catalyst. Examples include the following phenolic resins.

(1) Resol type phenol resin obtained by adding and condensing 0.3 to 0.8 moles of formaldehyde per phenol ring in the presence of an alkali catalyst (2) 0.5 to 2.0 moles of formaldehyde per phenol ring groove A phenol resin obtained by mixing or condensing a novolak-type phenol resin with a resol-type phenol resin obtained by adding and condensing the following in the presence of an alkali catalyst. It is a novolac type phenol resin obtained by addition condensation of formaldehyde in the presence of an acidic catalyst.) (3) The phenol ring groove is 0.5 to 3.
Add phenol to the resol type phenol resin obtained by adding and condensing 0 mol of formaldehyde in the presence of an alkali catalyst, and if necessary, add an excess of acidic catalyst to the alkali catalyst to perform the condensation reaction. Phenol resin (4) A novolak type phenol resin obtained by adding and condensing 0.5 to 1.5 moles of formaldehyde per phenol ring groove in the presence of an acidic catalyst, formaldehyde, and the above acidic catalyst. The above alkaline catalysts include sodium hydroxide, potassium hydroxide, magnesium hydroxide, and basic metal salts.

Alkaline catalysts such as ammonia, hexamethylenetetramine, triethylamine, trimethylamine, and pyridine are preferred.

Hydrochloric acid, sulfuric acid, and orthophosphoric acid are examples of acidic catalysts.

Acidic catalysts such as oxalic acid, formic acid, and acetic acid are preferred.

The phenol resin having an average of 0.1 to 0.5 aromatic ring grooves or methylol groups produced as described above has appropriate curability and crosslink density. That is, if the average number of methylol groups is 0.1 or more, the crosslinking density of the resulting coating film decreases, resulting in poor corrosion resistance and processability.

Furthermore, if the average number of methylol groups is 0.5 or more, the crosslinking density becomes too high and processability is poor. Furthermore, the adhesive strength decreases over time in hot water.

Here, the amount of methylol groups per aromatic ring groove was determined by adding 10 cc of an acetylation reagent consisting of pyridine/acetic anhydride (volume ratio 1/1) to 0.5 g of phenol resin at 80°C.

100 cc of pumped water heated for 3 hours was added, further extracted with ethyl ether, and 70 cc of 6-NHCN aqueous solution was added.

After repeating the ethyl ether extraction and the addition of 70 cc of 0.1-N sodium bicarbonate, the ethyl ether was removed under reduced pressure at room temperature to obtain an acetylated phenol resin, which was dissolved in chloroform and measured by II-NMR. By quantifying the peak around 591111, the number of moles of methylol group added to one phenyl nucleus can be calculated.

Such a resol resin, that is, the average number of methylol groups per phenol ring groove is 0.1 to 0.5. Preferably 0
．． By using a phenolic resin in the range of 2 to 0.4 as one component of a water-based adhesive can primer.

In the structure of base material (steel plate such as tin-free steel) - undercoat - polyamide adhesive, it has sufficient adhesive strength not only for the initial adhesive strength but also for processing strain of 31% and aging test in hot water. It is possible to obtain a product with excellent properties as a primer for adhesive cans.

In the present invention, the bisphenol type epoxy resin used is an epoxy resin made by reacting bisphenols such as bisphenol A, bisphenol B, and bisphenol F with epichlorohydrin in the presence of an alkali catalyst. Epicoat 828 from Shell Chemical Co., Ltd. Epicote 1001. Epicote 1004. Epicote 10
07, Epicote 1009. Epicote 101
There are 0, etc. It is also possible to use a modified epoxy resin in which the epoxy group or hydroxyl group of the bisphenol type epoxy resin is reacted 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.

In the present invention, the bisphenol-type epoxy resin that is potentially self-emulsifying due to the carboxyl group introduced into the molecule has an average of 0.5 or more epoxy groups and an average of 0.1 to 1.5 (metal) groups per molecule. ) It can be obtained by polymerizing a bisphenol type epoxy resin derivative having an acryloyl group and a copolymerizable monomer containing 10 to 80 parts by weight of a monobasic carboxylic acid monomer as an essential component using a radical polymerization initiator. . This epoxy resin derivative is produced by reacting a bisphenol type epoxy resin with methacrylic acid or acrylic acid in the presence of an alkali catalyst such as sodium hydroxide at 100 to 150°C for 1 to 6 hours to form 0.5 epoxy groups per molecule. Average 0
．． It can be obtained as having 1 to 1.5 acrylic coil groups.

The self-emulsifying (bisphenol-type epoxy resin) according to the present invention also includes 10 to 80% by weight of monobasic or carboxylic acid monomer in the presence of the bisphenol-type epoxy resin.
Polymerization of a copolymerizable monomer mixture containing
It can be obtained by tightening.

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 also contains 12 to 70 -basic carboxylic acid monomers.
An acrylic resin formed by copolymerizing a copolymerizable child mixture containing 1.1 to 2.0% by weight of an average of 1.1 to 2.0% by weight per molecule.
It can be produced by partially bonding with a bisphenol type epoxy resin having 0 epoxy groups.

In the production of the above self-emulsifying bisphenol epoxy resin, acrylic acid, monobasic carboxylic acid monomer,
Methacrylic acid, etc. are used, and copolymerizable monomers include methyl acrylate, ethyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, n-amyl acrylate, isoamyl acrylate, and 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-methacrylate -Amyl, methacrylic acid esters such as n-hexyl methacrylate, n-octyl methacrylate, 2-ethylhexyl methacrylate, decyl methacrylate, dodecyl methacrylate, styrene, vinyltoluene, 2-methylstyrene, t-methylstyrene.

Styrenic monomers such as chlorstyrene, hydroxy group-containing monomers such as hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, N-methylol (meth)acrylamide, N-butoxymethyl (meth)acrylamide The monomer can be selected from one or more N-substituted (meth)acrylic monomers such as N-substituted (meth)acrylic monomers such as epoxy-I l -- group-containing Motsuma-1 such as glycidyl acrylate and glycidyl methacrylate, and acrylonitrile.

12 to 70 of the basic carboxylic acid monomers shown above
It is preferable to use 10 to 90 parts by weight of the polymerizable monomer mixture based on 100 parts by weight of the bisphenol type epoxy resin. If it is less than 10 parts by weight, it becomes difficult to impart self-emulsifying properties to the epoxy resin,
It cannot be a stable dispersion in aqueous media. Moreover, if the amount exceeds 90 parts by weight, hydrophilic carboxyl groups remain in the formed coating film, which tends to reduce adhesive strength over time after retort treatment and also deteriorates corrosion resistance.

In the present invention, the composite resin composition can be obtained by mixing a self-emulsifying bisphenol-type epoxy tree 1i7 and at least one phenolic resin, preferably in a hydrophilic solvent. In addition, 1 the composite resin composition of the present invention is prepared by dispersing a self-emulsifying bisphenol A type epoxy resin in an aqueous medium, and then mixing a phenol resin therein. It can also be obtained by incorporating it into particles of epoxy resin.

The amount of resol resin in the composite resin composition is 100 parts by weight of self-emulsifying bisphenol epoxy resin (
If the amount is less than 10 parts by weight, the curing properties of the coating film will be poor and the adhesion to the base material and polyamide adhesive will not be sufficient. I can't get the value. Moreover, if it exceeds 60 parts by weight, physical properties such as processability of the coating film will deteriorate.

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

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.

Polyvalent amines such as ethylenediamine and diethylenetriamine can also be used. In the present invention, the aqueous medium is at least 50% by weight, preferably 80% by weight or more,
More preferably, it means a mixture of water and a hydrophilic organic solvent, which is 90% by weight water.

Methanol and ethanol are hydrophilic organic solvents.

Al:1-rual:l-ols such as n-propatool, isopropatool, n-butanol, 5ec-butanol, tert-butanol, isobutanol, methyl cellosolve, ethyl-1! n-solve, propyl cellosolve.

Ether alcohols such as butyl cellosolve, methyl carbitol, ethyl carpitol, ether esters such as methyl cellosolve acetate, ethyl cellosolve acetate, other dioxane, dimethyl formamide,
Diacetone alcohol etc. are used.

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

Applicable can materials include untreated steel sheets and treated steel sheets.

Tin-free steel such as galvanized iron plate, tin plate, chromium-plated steel plate, and chromic acid-treated steel plate, as well as metal plates such as nickel-plated steel plate, aluminium-plated steel plate, and aluminum plate, are suitable. Roll coater painting is the coating method. Although preferred, spray painting, dip painting, electrodeposition painting, etc. are also possible. Also, what are the baking conditions?

The temperature of 150°C to 230°C for 2 hours can be selected from the range of 2 to 30 minutes.

The present invention will be explained below with reference to examples. Note that in one example, "part" and "%" indicate "part by weight" and "1% by weight", respectively.

(Example) [Preparation of phenolic resin solution] Phenol resin A ■0-cresol 228 parts■3
7% formaldehyde aqueous solution 85.6 parts■2
5% ammonia water 28.7 parts
Put the binary composition into a four-hole flask with nitrogen gas replacement,
After heating to 95-100°C and reacting under reflux for 60 minutes, 40% of 5-methyl isobutyl ketone (MIBK) was added.

Mixed solvent 3 of 40% xylene and 30% cyclohexanone
After extraction and water washing, the mixture was heated at a temperature of 95 to 110° C. for about 2 hours to separate the evaporated water. The mixture was further diluted with butyl cellosolve to obtain a phenolic resin containing 0.26 methylol groups per aromatic ring and a solid content of 30%.

Phenol resin B ■Carbolic acid 63.5 parts ■Bisphenol A I 54 parts■
37% formaldehyde water? 8'l & 115
Part ■ 25% ammonia water 18.
4 parts The above composition was similarly synthesized into a phenol resin solution, with 0.33 methylol groups per aromatic ring and 30% solid content.
Phenol resin B was obtained.

Phenol resin C ■Carbolic acid 53.5 parts■Bisphenol A 130 parts■
37% formaldehyde■25% ammonia water 15.5
The above composition was similarly synthesized into a phenol resin solution to obtain a phenol resin C having 0.64 methylol groups per aromatic ring and a solid content of 30%.

Phenol resin D ■O-cresol 218 parts 03
7% formaldehyde aqueous solution 115 parts■25%
Orthophosphoric acid alcohol solution 23.7 parts The above composition was heated to 95-100°C. After reacting under reflux for 120 minutes, the same procedure as for phenol resin solution A was carried out to obtain 0.05 methylol groups per aromatic ring. A phenolic resin resin with a solid content of 30% was obtained.

Phenol resin E Mix 60 parts of phenol resin solution to 100 parts of phenol resin solution, and add 60 parts while dehydrating at 110°C.
The reaction was carried out for 0 minutes to obtain a phenolic resin E having 0.38 methylol groups per aromatic ring and a solid content of 30%.

Adjustment of phenolic resin F■Carbolic acid 36.4 parts■Bisphenol A 8 8.
2 parts ■ 37% formaldehyde aqueous solution 141
Part ■ 25% ammonia water 10.
5 parts■0-cresol 83.
4 parts 25% orthophosphoric acid alcohol solution 38.
Add 3 parts of 1 to 4 above and heat to 95 to 100°C. After reacting for 30 minutes under reflux, 5 and 6 were added and further 95~
The reaction was carried out at 100° C. for 30 minutes under reflux. Thereafter, the mixture was added to a phenol resin solution in a manner similar to 11j1 to obtain a phenol resin F having 0.24 methylol groups per aromatic ring groove and a solid content of 30%.

[Preparation of self-emulsifying bisphenol type Evo-Toshi resin r] ■ Epicor 1-1007 300
Part■Butyl cellosolve 162
■10% potassium hydroxide? 8 liquid O,
S part■Methacrylic acid
2.8 parts ■Hydroquinone
0.01 part ■Methacrylic acid
120 parts■Styrene 1
20 parts ■ Ethyl acrylate 60
Part■Azobisbutyronitrile 15 parts@
In-butanol 150 parts Add the above ① and ② to a fourth flask that has been replaced with nitrogen and heat at 100°C.
After dissolving in , then dissolve ■ in ■ and add 13
After the reaction was carried out at 0° C. for 5 hours to form an epoxy resin derivative and the mixture was cooled, [phase] was added from ①, and two-thirds of the total amount was taken out by stirring well. The flask was reheated to 90° C., two-thirds of the removed solution was added dropwise over 2 hours, and after further reaction for 2 hours, the same content was adjusted to 60% to obtain a self-emulsifying bisphenol type epoxy resin I.

[Preparation of self-emulsifying bisphenol-type epoxy resin ■]
■ 300 parts of Epicote 1007 ■ 300 parts of butyl cellosolp ■ 150 parts of methacrylic acid ■ 100 parts of styrene ■ 50 parts of ethyl acrylate ■ 21 parts of benzoyl peroxide After charging the above ■ and ■ into a four-bottle flask purged with nitrogen and melting at 115°C,
Add the mixture from ■ to ■ dropwise over 1 hour, and then add
After reacting at 5°C, cool and adjust the solid content to 60%.
A self-emulsifying bisphenol type epoxy resin ■ was obtained.

Example 1 ■ Self-emulsifying epoxy resin ■ 333 parts (100 parts of unmodified epoxy resin) ■ Contains phenolic resin 100 parts (
30 parts as resin content) 025% ammonia water 12.7
Part-19 = (1) 704 parts of ion-exchanged water The above (1) and (2) were charged into a flask and stirred, and then (2) was added to neutralize. Thereafter, the mixture was heated to 80° C., reacted for 30 minutes, and then cooled. After cooling, the mixture was stirred (1 piece of shinokara (2) was gradually added to obtain a milky white dispersion with a solid content of 20% and a viscosity of 520 cps.

Example 2 The phenol resin in Example 1 was replaced with phenol resin B, and the other conditions were the same as in Example 1, with a solid content of 20%.

A milky white dispersion with a viscosity of 4.60 cps was obtained.

Example 3 The phenol resin in Example I was replaced with phenol resin E, and the other conditions were the same as in Example 1, with a solid content of 20%.

A milky white dispersion with a viscosity of 670 cps was obtained.

Example 4 The phenol resin in Example 1 was replaced with phenol resin F, and the other conditions were the same as in Example 1, with a solid content of 20%.

119 milky white particles with a viscosity of 710 cps were obtained.

Example 5 ■Self-emulsifying resin J--Si resin IT 333
parts (100 parts as unmodified epoxy resin) ■ Phenol resin 8 100 parts (30 parts as resin) ■ 2-dimethylaminoethanol 20.7 parts ■ Ion exchange water 696 parts The above composition was the same as in Example 1. Mold content 20%, viscosity 520
A milky white dispersion of cps 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 phenol resin B was replaced with phenol resin F.

Example 7 ■ Self-emulsifying epoxy resin 1 333 parts (100 parts as unmodified epoxy resin) ■ Phenol resin 8
170 parts (51 parts as resin) 025% ammonia water 12.7
Part ■ Ion exchange water 739 parts The above composition was the same as in Example 1, solid content 20%, viscosity 91
A milky white dispersion of 0 cps was obtained.

Example 8 ■ Self-emulsifying epoxy resin r 333 parts (
100 parts as unmodified epoxy resin) 100 parts of phenolic resin B (30 parts as resin)
part) 025% ammonia water 12 parts ■Ion exchange water 700 parts'' Binary■
was placed in a flask, stirred, and then added to neutralize. After further stirring, (2) was added to obtain a milky white dispersion. To this dispersion was added an IW-based material (2). A dispersion with a solid content of 22% and a viscosity of 410 cpS was obtained.

Comparative Example I The phenol resin in Example 1 was replaced with phenol resin C, and the other conditions were the same as in Example 1, with a solid content of 20%.

119 milky white particles with a viscosity of 390 cps were obtained.

Comparative Example 2 The phenol resin in Example 1 was replaced with phenol resin, and the other conditions were the same as in Example 1, with a solid content of 20%.

A milky white dispersion with a viscosity of 850 cps was obtained.

Comparative Example 3 Phenol resin B in Example 5 was replaced with phenol resin C, and the other conditions were the same as in Example 5, with a solid content of 20%.

A milky white dispersion with a viscosity of 640 cps was obtained.

Comparative Example 4 ■ Self-emulsifying epoxy resin 1 333 parts (100 parts as unmodified epoxy resin) ■ Phenol resin B
333 parts (100 parts as resin content) 025% ammonia water 12.7
821 parts of ion-exchanged water
Same binary composition as Example 1, solid content 20%, viscosity 7
A milky white dispersion of 90 cps was obtained.

The aqueous resin dispersion obtained in each Example and Comparative Example was used as an undercoat to perform roller coating on a 0.22 inch thick chromium-treated steel plate to a dry film thickness of 2.5 to 3 μm, and then Baking drying was performed at ℃ for 10 minutes.

A 1,2-aminolauric acid polymer was sandwiched between the coated plates, and after being pressed with a hot press at 200° C. for 10 seconds and cooled, the sample pieces were cut into 511 pieces while being bonded.

This was subjected to a T-shaped peel test using a Schopper tensile strength tester at an ambient temperature of 25°C. Further, this adhesive sample was immersed in hot water at 90°C (hot water aging test), and after cooling and drying, a T-shaped peel test was conducted at 25°C.

Furthermore, the body is placed on a tin plate (0,23
1 thickness, #5015017. Roller painting place &2 on T)
Baking was performed at 00° C. for 10 minutes to obtain a coated board with a dry coating of 4.5 to 5.

A No. 2 can was formed from the above-mentioned coated plate, and the contents of a commercially available boiled salmon can were soaked in this No. 2 can at 117°C.

After 4 hours of retort treatment, the can was opened and the degree of sulfide blackening on the inner surface was observed.

Next, using a special folding DuPont tester, a sample folded in half was placed at the bottom, and a 1 kg iron weight with a flat contact surface was dropped from a height of 5 Qcm. Cracks in the paint film at the folded part occurred. The length of the crack was measured, and the crack length was expressed as 0-10 mm...0 10-20 fins...Δ 201 m or more...×.

The above test results are shown in Table 1.

According to the results, the undercoat according to the present invention exhibits good adhesion both in the untreated state and after aging in hot water. On the other hand, in Comparative Example 2, the adhesion was insufficient when untreated, and in Comparative Example 1 and Comparative Example 3, a significant decrease in adhesion after aging in hot water was observed, and the present invention This primer has excellent corrosion resistance and processability as a paint for the inside of cans.

〔Effect of the invention〕

The adhesive can primer of the present invention can provide a stable resin dispersion even in an aqueous medium in which the proportion of water in the paint solvent is 90% by weight or more, and has excellent adhesive properties. Since it uses resol resin, it has extremely high adhesion to the base material and polyamide adhesive.

Claims (1)

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