JPS5942705B2 - Paint composition for cans - Google Patents

Description

[Detailed description of the invention] The present invention relates to epoxy-phenolic coating compositions.

In the production of many can bodies, including fish cans and beverage cans, a method of forming coated steel plates coated with can paint is used in practice.

Among these, coated steel sheets for single cans coated with epoxy-phenol paint are widely used. Epoxy-phenol paints can be used on the circular surface of cans, taking advantage of their excellent resistance to bending and corrosion.
It is sometimes used as a primer for adhesive cans, taking advantage of its adhesive properties to polyamide adhesives. Conventionally, epoxy-phenol paints are resol-type paints obtained by reacting mixed phenols, which are a mixture of two or more phenols with different properties, with formaldehyde in the presence of an alkali catalyst, except in special cases. It was made from phenol formaldehyde resin and bisphenol A epoxy resin.

The durability of such epoxy-phenol paints is largely influenced by the resol type phenol-formaldehyde resin, and depends on the type and composition ratio of the phenol component used, the type and amount of the catalyst, the amount of formaldehyde, the epoxy/phenol ratio, etc. By changing the balance of performance, various epoxy-phenol paints are used depending on the purpose and contents. However, due to recent factors such as diversification of contents and can shapes, there has been a demand for improved performance of epoxyphenol paints. In particular, for general inner surfaces, high processability is required as well as content resistance and corrosion resistance, especially adhesion to the substrate (steel plate) after processing, and for applications as primers for adhesive cans, it is required to withstand high temperature steam sterilization and to be able to withstand high temperature steam sterilization and It is desired to improve the adhesion resistance, content bending resistance, and corrosion resistance. In order to solve this request (1) maintain various functions such as content resistance notes, corrosion resistance notes, adhesive notes for polyamide adhesives, etc. of epoxy phenol paints made of resol type phenol formaldehyde resin and epoxy resin using conventional mixed phenols. At the same time, it is necessary to improve the adhesion curve of coating films and steel sheets, especially during processing.The present inventors have conducted various studies regarding this problem, and as a result, the bifunctional curved phenol layer has been developed using an alkali catalyst. resol type phenol formaldehyde resin (A) obtained by reacting formaldehyde with formaldehyde in the presence of a resol type phenol formaldehyde resin (A) obtained by reacting trifunctional or higher functional phenol with formaldehyde in the presence of an alkali catalyst, bisphenol A type epoxy resin (c
) and an organic solvent.

A painted steel sheet for cans that is painted and baked with an epoxy phenolic paint using a conventional resol-type phenol-based phenol-based epoxy phenol, and a painted steel sheet for cans that is painted and baked with the paint according to the present invention. , are completely different in their coating structure and curve. For example, even if the factors such as the type of phenol, the composition ratio of phenol, the type and amount of catalyst, and the epoxy/phenol ratio are exactly the same for the epoxy phenol paint as a whole, the process, especially the process? The bending between the coating film and the steel plate is much better in the coated steel plate coated with the paint according to the present invention. In addition, regarding content resistance notes and corrosion resistance, the painted steel sheet for cans coated with the paint according to the present invention (approximately equivalent) is The reason why the coated steel sheet for cans coated with the paint according to the present invention and baked has such excellent characteristics will be explained further with respect to the resol type phenol formaldehyde resin, which is the most important part of the present invention. I will explain in detail.Resol type phenol formaldehyde resins used in epoxy phenol paints have conventionally been mixed with one or more difunctional phenols and one or more trifunctional or higher functional phenols, except in special cases. This is used as
Adding flexibility to the resin with difunctional phenols3
This is because the phenols, which are more than sensual, provide content resistance and corrosion resistance. From the structure of the resin, bifunctional phenols and polyfunctional bent phenols are randomly connected with methylene bonds, and the average distance between crosslinking points is adjusted by the bifunctional bent phenols, and by the trifunctional or higher functional phenols, It is thought that the crosslinking density is adjusted. On the other hand, the resol type phenol-formaldehyde resin used in the present invention is synthesized as separate resol type phenol-formaldehyde resins, including mono- and difunctional bent phenols and trifunctional or higher functional phenols. Therefore, in the paint, condensates of linear difunctional curved phenols and condensates of trifunctional or higher functional phenols with a network structure coexist, and in the baked paint film, condensates of linear chains and condensates of trifunctional or higher functional phenols with a network structure coexist. The condensate of
It is conceivable to combine them as if they were one block polymer. Furthermore, in the conventional method, since the reaction rate of difunctional phenol was slower than that of trifunctional or higher functional phenol, there were many low-condensation products, whereas in the present invention, by changing the reaction time of each, It has become possible to freely adjust the degree of condensation between bifunctional phenol and trifunctional or higher functional phenol. Such a difference in the structure of the coating film gives rise to the excellent features of the present invention. As a steel plate on which the paint according to the present invention is painted and baked (1. Tin plated with tin, which has traditionally been used in general cans such as food cans, has been used in recent years as a material in place of tin plate). Chrome plated steel plate, Nickel plated steel plate,
An aluminized steel plate, an aluminum plate, a cold-rolled steel plate, etc. can be used.

Examples of the difunctional phenol include commonly used phenols such as para-cresol, orthocresol, para-tertiary butylphenol, para-methoxyphenol, and para-nonylphenol.

These bifunctional phenols react alone with formaldehyde in the presence of an alkali catalyst, and can be used as resol type phenol formaldehyde resins or as two or more types of phenols.
Functional Note: A resol-type phenol/formaldehyde resin may be obtained by mixing phenol. Examples of phenols with trifunctional or higher functionality include carbolic acid, metacresol, and reso'
Commonly used phenols such as resin, m-methoxyphenol, and bisphenol A can be mentioned.

These trifunctional or higher functional phenols may be used alone as a resol type phenol formaldehyde resin, or may be mixed with two or more types of trifunctional or higher functional phenols to form a resol type phenol formaldehyde resin. One or more types of resol-type phenol-formaldehyde resins of difunctional phenols and resol-type phenol-formaldehyde resins of trifunctional or higher functional phenols can be used.

As an alkali catalyst (e.g. sodium hydroxide, calcium hydroxide, magnesium hydroxide, base bent metal salts,
Alkaline catalysts such as ammonia, hexamethylenetetramine, trimethylamine, triethylamine, pyridine, etc. can be used.

Further, as formaldehyde, an aqueous solution, one dissolved in an organic solvent, and one dissolved in an aqueous organic solvent system can be used. Resol-type phenol-formaldehyde resin is obtained by heating a phenol and formaldehyde solution in the presence of an alkali catalyst and reacting the evaporated water, formaldehyde, etc. while cooling and refluxing, and decomposing the resulting condensate with water. .

After separating the water, heating may be performed to further advance the condensation. Bisphenol A type epoxy resin is epichlorohydrin and 2,2-bis(4-hydroxyphenyl)
Those obtained by the reaction of propane and having an average molecular weight of 800 or more calculated from the epoxy equivalent can be used, but 2
Those having an average molecular weight of 000 to 4000 are preferred.

Organic solvents used in the present invention include ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, isoborone, benzene, toluene, xylene,
Aromatics such as other alkylbenzenes, cellosolves such as methyl cellosolve, ethyl cellosolve, butyl cellosolve, esters such as methyl cellosolve acetate, butyl cellosolve acetate, ethyl acetate, butyl acetate,
Alcohols such as isopropyl alcohol, butyl alcohol, diacetone alcohol, etc. (or mixed solvents thereof) can be used.

The composition of the phenolic resin component of the epoxy phenol-based paint according to the present invention is 10 to 90 parts by weight of resol type phenol formaldehyde resin (A) and 90 to 10 parts by weight of resol type phenol formaldehyde resin (A). Can be used within a range.

Further, bisphenol A type epoxy resin 0 can be used in a range of 85 to 40 parts by weight for a total of 15 to 60 parts by weight of resol type phenol-formua'redehyde Jugetsu Denpachi and I3). The epoxy phenol paint according to the present invention may contain additives such as coloring agents such as pigments, optical fillers, rust preventives, and various interfacial additives, if necessary.

The epoxy phenol paint according to the present invention is applied to a steel plate by a method such as roller coating or spray coating in an amount of approximately 20 to 70 m9/100 c71 as a dry coating. The baking conditions are approximately 180°C to 220°C, 5
It will be baked in 15 minutes. The contents of the paint according to the present invention have been explained above, but the most important feature of the paint according to the present invention is that the coated steel sheet coated with the paint according to the present invention is coated with the coated steel sheet after being processed. There is an excellent bond between songs. Due to these excellent characteristics, the coating material according to the present invention is very useful both for general can inner surfaces and as a primer for adhesion of adhesive cans. In the case of the inner surface of a general can, the parts to be processed include the putty-folded part of the can body joint (side seam part) and the flange part;
The can lid has a chuck wall radius part and other ring parts, and the can body and can lid have a seam part in common. Among these processed parts, defects in the coating on the putty folding part and the chuck wall radius part cause iron to be leached into the contents, and defective adhesive bending in the seaming part causes the sealing bend of the can to be defective. Therefore, for applications with these strict requirements, paints with good processability have been used that have slightly sacrificed content resistance and corrosion resistance. The present invention is very useful in that it can solve these problems. The adhesive force of the primer in the adhesive can is divided into the adhesive force between the coating film and the adhesive and the adhesive force between the coating film and the steel plate. In normal prone position ('',
The adhesive force between the coating film and the adhesive is usually weaker than the adhesive force between the coating film and the steel plate, and when peeling is performed, peeling occurs at the interface between the coating film and the adhesive. However, if a steel plate-coating film-adhesive structure is subjected to processing strain or immersed in the contents for a long time to accelerate adhesive deterioration, peeling will occur at the interface between the coating film and the steel plate, and the adhesive strength will increase. often deteriorates. As is well known, the bonded portion is subject to processing strain due to seaming and is constantly in contact with the contents. In order to prevent such contact deterioration, it is necessary to increase the adhesive note between the coated steel sheets rather than to strengthen the adhesive note between the coating film and the adhesive. For the reasons mentioned above, the coating of steel sheets with paint according to the present invention is a very useful method for bonding cans, and provides painted steel sheets that have less adhesive deterioration due to processing strain and less deterioration over time due to immersion in the contents. Ru.
The present invention will be specifically explained below using examples.

Example 1 1 mol of p-Tert-buty'lefueno-1 was dissolved in 2.4 mol of 37% formaldehyde aqueous solution, 0.2 mol of 25% aqueous ammonia was added, and the mixture was reacted at 95 DEG C. for 3 hours.

The resulting condensation product was mixed with parts by weight of MIBK3O, 30 parts by weight of cyclohexanone, and 40 parts by weight of xylene.
Extract with agent (S) and wash with water? The mixture was allowed to stand for one day and the aqueous layer was separated to obtain resol lip liquid (4) with a solid content of 30%. 1 mol of bisphenol A was added to a 37% aqueous formamide solution2.
Dissolve it to 4 mol, add 2 mol of 25% ammonia water and add 9
The reaction was carried out at 5°C for 1 hour.

The obtained condensation product was extracted into a mixed solvent (S) consisting of MIBK3O parts by weight, 30 parts by weight of cyclohexanone, and 40 parts by weight of xylene, washed with water, left standing for 1 day and night, and the aqueous layer was separated.
A resol liquid with a solid content of 0% (referred to as Bl) was also dissolved in the above mixed solvent (S) and Epicoat 1007 (an epoxy resin manufactured by Shinil Co., Ltd.) to make an epoxy resin lip liquid with a solid content of 40% (referred to as Q). .Resol solution (4), Resol solution (4), Resol solution (
B) Epoxy Jugetskutsu 0 to solid liquid ratio 22.5:22.
The mixture was mixed at a ratio of 5:55 to form an epoxyphenol paint.

Next, after coating a tin plate (0.23 mm thick, #50/50ET) with the top paint using a roller, baking was performed for 200' ClO to obtain a coated plate (D) with a coating thickness of 50 m9/Dm2.The above coated plate Form a No. 2 can from D, and use a commercially available can of boiled salmon.
Repack into the above-mentioned No. 2 can and seal the lid to 1.05 kg/C.
Did you perform steam treatment for 90 minutes at TIL pressure? ,50℃
After being stored for two weeks, the can was opened and the black sulfide discoloration on the inner surface was observed.

(Sulfide black discoloration resistance) As a result, sulfide black discoloration was hardly observed and the product was in good condition. 30m in diameter from the painted board (D)
77! When a cap with a height of 30 mm was punched out using a press, no peeling of the paint film was observed, and the punching process was good.Also, when the above cap was subjected to a peel test using commercially available cellophane tape, it was found that the cap did not peel off. The paint film peeled off in a width of about 5 mm from the edge.Did you scratch the painted board (D) with a sharp knife?
1,05k9/? in the prone state immersed in 1% saline solution. When steam treatment was carried out for 90 minutes at a pressure of

Example 2 A coating material was prepared in the same manner as in Example 1 by varying the resol solution in Example 1, a coated board was prepared, and seven tests were conducted in the same manner as in Example 1.

The results are shown in Table 1. Example 3 Resol solution (4) in Example 1, resol solution (
), epoxy resin solution (O solid content ratio 12.5:1
They were mixed in a ratio of 2.5:75 to prepare an epoxy phenol paint.

Apply this paint to a 0217mm thick hightop (manufactured by Toyo Kohan Co., Ltd.)
After coating with a roller, it was baked and dried at 20°C for 10 minutes.

The coating amount was 50m/Dm2. 1,2-aminolauric acid polymer (relative viscosity 2.3) between the above painted plates
After sandwiching the film and pressing it with a hot press at 200° C. for 10 seconds and cooling, the adhesive sample (D) was cut into an adhesive width of 5 mm.

When this was subjected to a peeling test using a Sietsupa type tensile strength tester at ambient temperatures of 25°C and 12°C, the peeling strength was 5, 2k9/5m71L, and 2.2k9, respectively.
/5mm. Also, the adhesive sample (E) was immersed in hot water at 95°C for 15 hours and 24 hours? , cool and dry;
A peel test was conducted at 25°C. Peel strength is 5,
0k9/5mm and 3.5kg/5mm, and there was little deterioration in adhesive strength. Next, after bending the adhesive sample (0) in 1/8 inch, a peel test was performed.The result was 4.5 kg/5 mT1L at the bent part.Example 4Resol solution in Example 3 The paint was adjusted by changing various things.

Claims (1)

[Claims] 1. Resol type phenol formaldehyde resin (A) obtained by reacting a bifunctional phenol with formaldehyde in the presence of an alkali catalyst, resol type phenol obtained by reacting a trifunctional or higher functional phenol with formaldehyde in the presence of an alkali catalyst. A can coating composition comprising a formaldehyde resin (B), a bisphenol A type epoxy resin (C), and an organic solvent (D).