JPH0558468B2 - - Google Patents

Description

[Detailed description of the invention]

[Objective of the Invention] (Industrial Application Field) The present invention relates to a water-based adhesive can primer, and more specifically, it is applied to a can material, and in the side seam part, the primer coat is applied to a polyamide adhesive and to the can material. It relates to water-based primers that can be used to function as primers. (Prior Art) A so-called bonded can is a general term for three-piece cans in which the seam of the can body is bonded. The reason behind the increasing importance of adhesive cans in metal containers in recent years is that instead of the traditional tin-plated tin, we are using stain-free steel such as chrome-plated steel sheets and chromic acid-treated steel sheets, as well as nickel-plated steel sheets, aluminium-plated steel sheets, and aluminum. Various can materials such as boards have been developed and supplied. In other words, these materials cannot be soldered like tinplate, so when making the can body of a three-piece can, the side seams must be joined by welding or adhesive, unlike conventional methods. When forming side seams with adhesive, a primer is usually applied to the can material such as stain-free steel and baked, and then hot melt bonding is performed using a polyamide adhesive. Therefore, the properties required of the undercoat are strong adhesion to the can material and adhesive, and at the same time, it is also required to have various physical properties such as corrosion resistance and processability as a can inner surface coating. 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, it has become necessary to stop using organic solvents in the coating and container industries.
Alternatively, active efforts are being made to shift to paints that contain as little organic solvent as possible. 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 they have poor storage stability, hygiene, chemical and mechanical performance, and It is unsuitable as a commercial paint. 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. Additionally, water-soluble amino resins and phenolic resins are added to these paints when a faster curing speed is required. but,
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) In view of the above-mentioned circumstances, the present researchers have conducted extensive studies and found that the performance of conventional epoxy-phenol solvent-based primers, that is, the base material and polyamide adhesive. By maintaining strong adhesion to the can, it guarantees the hermeticity of the can body and successfully reduces or virtually eliminates organic solvents without impairing the function of the base material as a protective layer from the contents. This is what I did. [Structure of the Invention] That is, the present invention provides the following (I ), (b), or (c) at least one resol resin 10 to 60
The present invention relates to an aqueous undercoat for adhesive cans, which is obtained by at least partially neutralizing a composite resin composition obtained by mixing or precondensing parts by weight with an amine or ammonia and dispersing it in an aqueous medium. (a) A resol resin having a weight average molecular weight of 800 or more and less than 3,000, which is obtained by reacting a mixed phenol of trifunctional or higher functional phenol and difunctional phenol with formaldehyde in the presence of an alkali catalyst. (b) A resol resin obtained by mixing a resol resin having a weight average molecular weight of 800 or more and less than 3,000, which is obtained by individually reacting a trifunctional or more functional phenol and a bifunctional phenol with formaldehyde in the presence of an alkali catalyst. (c) A weight average molecular weight of 800 obtained by reacting a bifunctional phenol in the presence of a resol resin obtained by reacting a trifunctional or higher functional phenol with formaldehyde in the presence of an alkali catalyst.
Resol resin with a rating of more than 3000 and less than 3000. (Means for solving the problem) As the trifunctional or higher functional phenol used in the resol resin of the present invention, all trifunctional or higher functional phenols conventionally used in the production of resol resins can be used, but for example, trifunctional or higher functional phenols can be used. As the phenol, phenol (carbolic acid), m-gresol, m-ethylphenol, 3,5-xylenol, m-methoxyphenol, etc. can be used.
As the functional phenol, bisphenol A, bisphenol B, bisphenol F, 1,1-bis(4-hydroxyphenyl)ethane, etc. can be used. Furthermore, all of the bifunctional phenols conventionally used in the production of resol resins can be used, such as o-cresol, p-cresol, p-tert-butylphenol, p-ethylphenol, 2, 2 such as 3-xylenol, 2,5-xylenol, p-tert aminophenol, p-nonylphenol, p-phenylphenol, p-cyclohexylphenol, etc.
Most preferred is one or a combination of two or more functional phenols. In addition, the alkaline catalysts used for resol resin production include sodium hydroxide, potassium hydroxide,
Preferred are alkali catalysts such as magnesium hydroxide, basic metal salts, ammonia, hexamethylenetetramine, triethylamine, trimethylamine, pyridine, and the like. Phenol and alkali catalysts such as those mentioned above,
In addition, there are various conditions for producing resol resin using formaldehyde, but in particular, when using it as a component of a water-based adhesive can primer, the following (a), (b), or (c) are applicable. It is important that the product be manufactured under the following conditions. That is, (a) it is a resol resin obtained by reacting a mixed phenol of trifunctional or higher functional phenol and bifunctional phenol with formaldehyde in the presence of an alkali catalyst so that the weight average molecular weight becomes 800 or more and less than 3000; (b) Weight average molecular weight obtained by reacting trifunctional or higher functional phenols and bifunctional phenols individually with formaldehyde in the presence of an alkali catalyst.
800 or more and less than 3000 resol resins; (c) 2.
It must be a resol resin with a weight average molecular weight of 800 or more and less than 3000, obtained by reacting a functional phenol. In such resol resins (a), (b), or (c), it is preferable that the weight ratio of trifunctional or higher-functional phenol to bifunctional phenol is 50-95/50-5. In such a resol resin, trifunctional or higher functional phenols provide content resistance and corrosion resistance, and bifunctional phenols provide flexibility to the resin. Considering the structure of the resin, it is thought that the crosslinking density is adjusted by the trifunctional or higher functional phenol, and the average distance between the crosslinking points is adjusted by the difunctional phenol. and (a), (b) or (c) above.
According to each resol resin manufacturing method, polyfunctional phenols and bifunctional phenols can be connected randomly or in a block shape through methylene bonds. The resol resin obtained in this way has a good balance between processability and adhesion, especially when the weight average molecular weight is 800 or more and less than 3,000. Performance that could never be achieved is created. Here, high performance liquid chromatography was used to measure the weight average molecular weight. Tetrahydrofuran was used as the solvent, and Shodex GPC A- was used as the column.
Two 80M (product name: manufactured by Showa Denko Co., Ltd.) connected together were used. Sample concentration 0.15%, injection volume
Measurement was carried out under the following conditions: 100μ, flow rate 1ml/min, and differential refractometer detector. Styrene monomer and standard polystyrene A-500, A-
1000, A-2500, A-5000, F-1, F-2, F
-4, F-10, F-20, F-40, and F-80 (manufactured by Toyo Soda Kogyo Co., Ltd.), and the weight average molecular weight was determined as a value in terms of polystyrene. By using such a resol resin as one of the components of a water-based primer for adhesive cans, it not only improves the initial adhesive strength but also improves the initial adhesive strength of the base material (steel plate such as stain-free steel) - primer - polyamide adhesive structure. Sufficient adhesive strength is maintained even when subjected to processing strain or subjected to aging tests in hot water, making it possible to obtain a product with excellent properties as an undercoat 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, and commercially available epoxy resins are available. As for Epicoat by Ciel Chemical Co., Ltd.
828, Epicote 1001, Epicote 1004, Epicote 1007, Epicote 1009, Epicote 1010, 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. . The bisphenol type epoxy resin in the present invention, which is potentially a self-emulsifying agent 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 (meth)acryloyl groups per molecule. It can be obtained by polymerizing a phenolic epoxy resin derivative 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, resulting in an average of 0.5 epoxy groups per molecule. It can be obtained as having 0.1 to 1.5 acryloyl groups. The self-emulsifying bisphenol-type epoxy resin in the present invention also contains monobasic carboxylic acid monomer in the presence of the bisphenol-type epoxy resin.
A copolymerizable monomer mixture containing 80% by weight can be obtained by polymerizing a relatively large amount of Yuki peroxide such as benzoyl peroxide. In this case, a bisphenol type epoxy resin grafted with an acrylic resin is obtained. The self-emulsifying bisphenol type epoxy resin of the present invention also contains an acrylic resin formed by copolymerizing a copolymerizable monomer mixture containing 12 to 70% by weight of monobasic carboxylic acid monomers, and an average of 1.1 monobasic carboxylic acid monomers per molecule. It can be produced by partially bonding with a bisphenol type epoxy resin having from 2.0 to 2.0 epoxy groups. In the production of the above self-emulsifying bisphenol type epoxy resin, monobasic carboxylic acid monomers such as acrylic acid and methacrylic acid are used, and copolymerizable monomers such as methyl acrylate, ethyl acrylate, and acrylic acid are used. Acrylics such as isopropyl, n-butyl acrylate, isobutyl acrylate, n-amyl acrylate, isoamyl acrylate, n-hexyl acrylate, 2-ethylhexyl acrylate, n-octyl acrylate, decyl acrylate, and dodecyl acrylate. Acid esters, methyl methacrylate, propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-amyl methacrylate, n-hexyl methacrylate, n-octyl methacrylate, 2-ethylhexyl methacrylate, decyl methacrylate, Methacrylic acid esters such as dodecyl methacrylate, styrene, vinyltoluene,
Styrenic monomers such as 2-methylstyrene, t-butylstyrene, and chlorostyrene, hydroxy group-containing monomers such as hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxyethyl methacrylate, and hydroxypropyl methacrylate, N-methylol (meth) Select from one or more of N-substituted (meth)acrylic monomers such as acrylamide and N-butoxymethyl (meth)acrylamide, epoxy group-containing monomers such as glycidyl acrylate and glycidyl methacrylate, and acrylonitrile. I can do it. 12 monobasic carboxylic acid monomers shown above
The copolymerizable monomer mixture containing ~70% by weight is 10~70% by weight per 100 parts by weight of bisphenol type epoxy resin.
Preferably, 90 parts by weight are used. When the amount is less than 10 parts by weight, it becomes difficult to impart self-emulsifying properties to the epoxy resin, and a stable dispersion cannot be obtained in an aqueous medium. Furthermore, if the amount exceeds 9 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 comprises a self-emulsifying bisphenol type epoxy resin and at least one resol resin selected from the above (a), (b), or (c), preferably in a hydrophilic solvent. It can be obtained by mixing. The amount of resol resin in the composite resin composition is determined by the self-emulsifying bisphenol type epoxy resin.
10 for 100 parts by weight (based on unmodified material)
It is necessary that the amount is 60 parts by weight. If it is less than 10 parts by weight, the curing properties of the coating film will be poor, and sufficient adhesive strength to the base material and polyamide adhesive will not be obtained. 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 can be prepared by adding ammonia or amine in an amount such that the final composition has a pH of 4 to 11 and dispersing it in an aqueous medium. When high boiling point solvents are used, it is preferable to remove these solvents in advance under reduced pressure. Examples of the above amines include alkylamines such as trimethylamine, triethylamine, and butylamine; alcohol amines such as 2-dimethylaminoethanol, diethanolamine, triethanolamine, and aminomethylpropanol;
Morpholine etc. are used. Further, polyvalent amines 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, and more preferably 90% by weight is water. Methanol, ethanol, n-propanol, isopropanol, n-butanol, sec-butanol,
Alkyl alcohols such as tert-butanol and isobutanol, methyl cellosolve, ethyl cellosolve, propyl cellosolve, butyl cellosolve,
Ether alcohols such as methyl carbitol and ethyl carbitol, ether esters such as methyl cellosolve acetate and ethyl cellosolve acetate, and 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, an antifoaming agent, etc. to improve coating properties, if necessary. Suitable can materials include untreated steel sheets, treated steel sheets, galvanized iron sheets, tin plates, chromium-plated steel sheets, chromic acid-treated steel sheets, and other stain-free steels, as well as metal sheets such as nickel-plated steel sheets, aluminized steel sheets, and aluminum sheets. As a coating method, roll coater coating is preferred, but spray coating, dipping coating, electrodeposition coating, etc. are also possible. The baking conditions can be selected from the range of temperature 150°C to 230°C and time 2 to 30 minutes. The present invention will be explained below with reference to Examples. In addition,
In the examples, "parts" and "%" indicate "parts by weight" and "% by weight," respectively. (Example) Example 1 [Preparation of resol resin solution] 228 parts of bisphenol A, 108 parts of p-cresol
95 parts, 203 parts of 37% formaldehyde aqueous solution, and 32 parts of 25% sodium hydroxide aqueous solution were charged into a flask.
The reaction was carried out at ℃ for 60 minutes. The resulting condensation product was extracted into a mixed solvent consisting of 30 parts of methyl isobutyl ketone (MIBK), 30 parts of cyclohexanone, and 40 parts of xylene, and dehydrated by heating and refluxing for 120 minutes, resulting in a solid product with a weight average molecular weight of 1410. A 30% resol resin solution was obtained. The weight average molecular weight of the resol resin was measured using high performance liquid chromatography. The column is Syodex GPCA-80M (manufactured by Showa Denko K.K.)
Two of them were used in series, and the moving bed was tetrahydrofuran. The sample was diluted with tetrahydrofuran to make the solid content 0.15%, injection volume 100 μ, mobile phase flow rate 1 ml/
The detector was a differential refractometer. The weight average molecular weight was determined by dividing the chart obtained above into minute portions and using the following formula. Here, Hi: magnitude of response of i category _o Σ Hi: total of all responses Mi: molecular weight of i category The calibration curve used to determine the molecular weight of each i category is the standard polystyrene equivalent value manufactured by Toyo Soda Kogyo Co., Ltd. It is. [Preparation of self-emulsifying bisphenol epoxy resin] 200 parts of Epicote 1007 and 70 parts of butyl cellosolve were placed in a flask and dissolved, and then 0.15 part of a 25% aqueous potassium hydroxide solution was added and the temperature was raised to 120°C. 7.5 parts of acrylic acid was added dropwise to this over 120 minutes while maintaining the liquid temperature in the flask at 120°C. After dropping, cool and take out, acid value 0.3, average 1
A compound having one epoxy group and one acryloyl group in the molecule was obtained. Styrene to 100 parts of this compound
35 parts, methacrylic acid 15 parts, methyl methacrylate 20 parts
1 part, 0.4 part of azobisisobutyronitrile, and 80 parts of n-butanol were added and mixed uniformly. 50 parts of this mixed solution was placed in a flask and heated to 90°C.
The remaining mixture was added dropwise over 120 minutes while maintaining the liquid temperature in the flask at 90°C, and after the dropwise addition was completed, the reaction was continued for an additional 180 minutes. In this way, a potentially self-emulsifying bisphenol type epoxy resin was obtained due to the carboxyl group introduced into the molecule. [Preparation of aqueous dispersion] 348 parts of the above self-emulsifying epoxy resin solution (100 parts of unmodified epoxy resin) and 174 parts of the above resol resin solution (52.2 parts of resin) were placed in a flask and mixed with 2-dimethyl while stirring. Neutralization was performed by adding 13 parts of aminoethanol. Thereafter, the temperature was raised to 80°C, reacted for 30 minutes, and then cooled. After cooling, 730 parts of ion-exchanged water was gradually added while stirring to obtain a milky white dispersion with a solid content of 20% and a viscosity of 430 cps. The obtained dispersion was stored at 50°C for 3 months, but no abnormality was observed. Example 2 [Preparation of resol resin solution] 242 parts of bisphenol B, 203 parts of 37% formaldehyde aqueous solution, and 14 parts of 25% aqueous ammonia were placed in a flask and reacted at 65°C for 180 minutes. Subsequently, 54 parts of o-cresol was added and reacted at 95°C for 30 minutes. The resulting condensation product was extracted into a mixed solvent consisting of 30 parts of MIBK, 30 parts of cyclohexanone, and 40 parts of xylene, and dehydrated by heating and refluxing for 120 minutes to obtain a resol resin with a weight average molecular weight of 1350 and a solid content of 30%. A solution was obtained. [Preparation of aqueous dispersion] 348 parts of the self-emulsifying epoxy resin of Example 1 (unmodified epoxy resin content: 100 parts) and 174 parts of the above resol resin solution (resin content: 52.2 parts) were charged into a flask and mixed with stirring. - Neutralization was carried out by adding 13 parts of dimethylaminoethanol. Thereafter, the temperature was raised to 80°C, reacted for 30 minutes, and then cooled. After cooling, 730 parts of ion-exchanged water was gradually added while stirring to obtain a milky white dispersion with a solid content of 20% and a viscosity of 290 cps. The obtained dispersion was stored at 50°C for 3 months, but no abnormality was observed. Example 3 [Preparation of resol resin solution] 72 parts of carbolic acid, 157 parts of 37% formaldehyde aqueous solution
10.6 parts of 25% ammonia water into a flask.
The reaction was carried out at 95°C for 60 minutes. The resulting condensation product
MIBK 45 parts, cyclohexanone 45 parts, xylene 60 parts
The weight-average molecular weight was extracted into a mixed solvent consisting of
1820, a resol resin solution (a) with a solid content of 30% was obtained. 150 parts of p-tert-butylphenol, 195 parts of 37% formaldehyde aqueous solution, 25% aqueous ammonia
13.6 parts were charged into a flask and reacted at 95°C for 60 minutes. The resulting condensation product was extracted into a mixed solvent consisting of 30 parts of MIBK, 30 parts of cyclohexanone, and 40 parts of xylene, and dehydrated for 120 minutes by heating and refluxing to obtain a resol resin with a weight average molecular weight of 2050 and a solid content of 30%. Solution (b) was obtained. The resol resin solution (a) and the resol resin solution (b) were mixed at a weight ratio of 1:1 to obtain a mixed resol resin solution. [Preparation of aqueous dispersion] 348 parts of the self-emulsifying epoxy resin solution of Example 1 (unmodified epoxy resin content: 100 parts) and 100 parts of the above resol resin solution (resin content: 30 parts) were charged into a flask and mixed with stirring. - Neutralization was carried out by adding 13 parts of dimethylaminoethanol. Thereafter, the temperature was raised to 80°C, reacted for 30 minutes, and then cooled. When 730 parts of ion-exchanged water was added dropwise while cooling,
A milky white dispersion with a solids content of 20% and a viscosity of 520 cps was obtained. The obtained dispersion was stored at 50°C for 3 months, but no abnormality was observed. Example 4 [Preparation of aqueous resin dispersion] 100 parts of Epicote 1009 and 67 parts of ethyl cellosolve were charged into a flask and dissolved, and then the liquid temperature was raised to 115°C while stirring. Benzoyl peroxide 3.0
After dissolving 30 parts of methacrylic acid, 20 parts of styrene, and 10 parts of ethyl acrylate in a mixed solution, the entire amount was added dropwise over 60 minutes while maintaining the liquid temperature at 110 to 120°C. After further reacting at 115°C for 120 minutes, it was cooled and 83 parts of the resol resin solution of Example 1 (50.1 parts as resin content) and 4.8 parts of 2-dimethylaminoethanol were added at 80°C. After stirring thoroughly,
600 parts of ion-exchanged water was gradually added to obtain a stable aqueous dispersion. Comparative Example 1 [Preparation of resol resin solution] 228 parts of bisphenol A, 108 parts of p-cresol
1 part, 203 parts of 37% formaldehyde aqueous solution, and 14 parts of 25% ammonia water were charged into a flask and reacted at 95°C for 35 minutes. The resulting condensation product was extracted into a mixed solvent consisting of 30 parts of MIBK, 30 parts of cyclohexanone, and 40 parts of xylene, and dehydrated by heating and refluxing for 80 minutes to obtain a resol resin with a weight average molecular weight of 710 and a solid content of 30%. A solution was obtained. [Preparation of aqueous resin dispersion] 348 parts of the self-emulsifying epoxy resin solution of Example 1 (unmodified epoxy resin content: 100 parts) and 174 parts of the above resol resin solution (resin content: 52.2 parts) were charged into a flask and stirred. 2-dimethylaminoethanol
Neutralization was performed by adding 7.5 parts. Thereafter, the temperature was raised to 80°C, reacted for 30 minutes, and then cooled. When 660 parts of ion-exchanged water was gradually added while cooling,
A milky white dispersion with a solids content of 23% and a viscosity of 380 cps was obtained. The obtained dispersion was stored at 50°C for 3 months, but no abnormality was observed. Comparative Example 2 [Preparation of resol resin solution] 150 parts of p-tert-butylphenol, 108 parts of o-cresol, 130 parts of 37% formaldehyde, 25%
A resol resin solution having a molecular weight of 1180 and a solid content of 30% was obtained in the same manner as in Example 1 using 14 parts of aqueous ammonia. [Preparation of aqueous resin dispersion] Using the self-emulsifying epoxy resin of Example 1 and the above-mentioned resol resin, the same procedure as in Example 1 was carried out to obtain a milky white dispersion with a solid content of 20% and a viscosity of 390 cps. Comparative Example 3 [Preparation of aqueous resin dispersion] 348 of the self-emulsifying epoxy resin solution of Example 1
(100 parts of unmodified epoxy resin) and 26 parts of the resol resin solution of Example 1 (7.8 parts of resin).
Solid content 20%, viscosity 610 cps using the same method as Example 1
A milky white dispersion was obtained. Comparative Example 4 [Preparation of aqueous resin dispersion] Using 348 parts of the self-emulsifying epoxy resin solution of Example 1 (100 parts of unmodified epoxy resin) and 350 parts of the resol resin solution of Example 2 (105 parts of resin), A dispersion having a solid content of 20% and a viscosity of 350 cps was obtained in the same manner as in Example 1. The aqueous resin dispersions obtained in Examples 1 to 4 and Comparative Examples 2 to 4 were mixed into a 0.17 mm thick high top (manufactured by Toyo Kohan Co., Ltd.).
After coating with a roll coater, the film was baked and dried at 200°C for 10 minutes. The coating amount was 50 mg/dm. A 1,2-aminolauric acid polymer (relative viscosity 2.3) film was sandwiched between the above-mentioned coated plates and heated to 200°C.
After crimping with a heat press for 10 seconds and cooling, the adhesive width is 5
A try-on sample was obtained which was cut into mm. This is heated to 25℃ and
A T-peel test was carried out using a Schopper tensile strength tester at an ambient temperature of 120°C. The results are shown in the table below.

[Table] Next, the aqueous resin dispersion of each example was placed on a tin plate (0.23 mm
After coating with a roller to a #50/50ET (thickness, #50/50ET), baking was performed at 200°C for 10 minutes to obtain a coated plate with a dry coating film of 4.5 to 5 μm. A No. 2 can is formed from the above-mentioned painted board, and the contents of a commercially available boiled salmon can are repacked into this No. 2 can.
After performing retort treatment at ℃ for 4 hours, the can was opened and the degree of sulfide blackening on the inner surface was observed. The results are shown in the table below.

〔Effect of the invention〕

The adhesive can primer of the present invention can obtain a stable resin dispersion 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. The following (a), ( A composite resin composition obtained by mixing or precondensing 10 to 60 parts by weight of at least one resol resin selected from (b) or (c) is at least partially neutralized with an amine or ammonia and placed in an aqueous medium. A water-based primer for adhesive cans that is dispersed in (a) A resol resin having a weight average molecular weight of 800 or more and less than 3,000, which is obtained by reacting a mixed phenol of trifunctional or higher functional phenol and difunctional phenol with formaldehyde in the presence of an alkali catalyst. (b) A resol resin obtained by mixing a resol resin having a weight average molecular weight of 800 or more and less than 3,000, which is obtained by individually reacting a trifunctional or more functional phenol and a bifunctional phenol with formaldehyde in the presence of an alkali catalyst. (c) A weight average molecular weight of 800 obtained by reacting a bifunctional phenol in the presence of a resol resin obtained by reacting a trifunctional or higher functional phenol with formaldehyde in the presence of an alkali catalyst.
Resol resin with a rating of more than 3000 and less than 3000. 2 In resol resin (a), (b) or (c), 3
2. The water-based undercoat for adhesive cans according to claim 1, wherein the weight ratio of the functional or higher functional phenol to the bifunctional phenol is 50-95/50-5.