JPH0676470B2 - Method for producing heat-reactive phenolic resin for epoxy resin paint blending - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention provides a coating film having excellent adhesiveness to an object to be coated by blending it with an epoxy resin coating and baking it. The present invention relates to a method for producing a phenol resin for blending a heat-reactive epoxy resin paint, in which the coating film is light in color.

[Prior art]

Epoxy resin paints that have been blended with heat-reactive phenolic resins have been widely used because the coating film after baking has excellent properties such as heat resistance, corrosion resistance, chemical resistance, and content resistance. Has been done. In general, a heat-reactive phenolic resin that is blended with a bisphenol A-type epoxy resin coating obtained by reacting bisphenol A and shrimp chlorohydrin in the presence of caustic soda is 1
One or more phenols and formaldehydes are reacted under alkaline conditions with an alkali catalyst,
Alternatively, two or more phenols having different properties are separately reacted with formaldehyde, and then they are mixed and used. These phenolic resins are known in JP-B-55-45584 and JP-B-59-42705. The catalysts used in the reaction include hydroxides and carbonates of alkali metals such as sodium and potassium, hydroxides and oxides of alkaline earth metals such as calcium, barium and magnesium, ammonia and triethylamine and triethanol. One or more selected from amines such as amines. However, an epoxy resin coating containing a heat-reactive phenolic resin obtained by reacting these phenols and formaldehyde under basic conditions does not have sufficient adhesiveness to a coating object of a baking coating, and Due to its strong yellow coloration, it is required to improve the adhesiveness of the baked coating film to the article to be coated and to lighten it.

[Object of the Invention]

The method for producing a phenolic resin for blending with an epoxy resin coating of the present invention, the epoxy resin coating containing a phenolic resin, which has been conventionally required to be improved, is keen on improving the adhesiveness of a baking coating to an object to be coated and dimming. As a result of research, we found that a heat-reactive phenolic resin obtained by reacting phenols and formaldehydes in the presence of an organic acid metal salt as a catalyst under weak acidity is extremely effective. It has been completed in layers.

In addition, the purpose is to make phenol for epoxy resin paint blending that has excellent adhesiveness of the baked coating to the object to be coated without deteriorating various properties such as flexibility and solvent resistance of the baked coating. It is to provide a method for producing a resin.

[Structure of Invention]

The present invention uses phenols and formaldehydes as catalysts and one or more kinds of organic acid metal salts selected from divalent metal salts of carboxylic acid and naphthenic acid, and has a pH of 3.5.
A method for producing a heat-reactive phenolic resin for compounding an epoxy resin coating, which is obtained by reacting under weak acidity of up to 6.8. Preferred reaction conditions for reacting phenols and formaldehydes with the organic acid metal salt as a catalyst are as follows: the compounding molar ratio of phenols and formaldehydes is 1.0 mol with respect to the phenol nucleus of 1.0 mol.
0 mol or less, the reaction temperature is 80 to 140 ° C, the reaction time is 1 to 10 hours, and the resinification reaction is completed while removing water and unreacted raw materials under normal pressure or reduced pressure. It is to let.

Generally, a resol type phenol resin obtained by reacting a phenol and a formaldehyde with an organic acid metal salt under weak acidity is used for a few applications. This type of resol type phenolic resin has Japanese Patent Publication No. 53-23861 for molding materials, and Japanese Patent Nos. 614946, 726584, and 7538 for self-hardening molding sand.
No. 51, and for self-hardening refractories, see JP-A-57-205
357, JP-A-57-205358 and the like. For molding materials, use only the above-mentioned resol-type phenol resin kneaded with the filler to mold and heat-harden the molding material.For self-hardening molding sand and self-hardening refractory, use the above-mentioned resole-type as a binder. Since the phenol resin is used in combination with polyisocyanate and cured at room temperature, the method is obviously different from the phenol resin obtained by the method for producing the phenol resin for epoxy resin coating composition according to the present invention. The use of this type of phenolic resin as a curing agent or cross-linking agent for epoxy resin coating is a completely new attempt.

Examples of phenols that can be used in the present invention include bifunctional phenols such as orthocresol, paracresol, paraethylphenol, parapropylphenol, paratertiarybutylphenol, paraoctylphenol, paranonylphenol, and trifunctional phenols. The above-mentioned phenols include phenol, meta-cresol, 3,5-xylenol, resorcinol, catechol, bisphenol A, bisphenol F, and one or more selected from these.

The formaldehydes include formaldehyde, paraformaldehyde, trioxane and the like, and they can be used together.

In the present invention, the organometallic salt used as a catalyst for reacting phenols and formaldehydes is one or two selected from divalent metal salts of carboxylic acid and naphthenic acid. Examples of the type of divalent metal include lead, calcium, manganese, tin, zinc, copper, magnesium and barium, and lead, manganese, zinc and barium are particularly preferable. These catalysts are usually one or more selected from inorganic acids such as hydrochloric acid and sulfuric acid, and organic acids such as benzoic acid, salicylic acid, silicic acid, maleic acid and paratoluenesulfonic acid, which are usually used as acid catalysts. It is also possible to use together.

The amount of catalyst used when reacting phenols and formaldehydes in the presence of an organic acid metal salt as a catalyst under weak acidity is usually 0.0005 to 0.0100 mol per mol of phenols, but depending on the type of catalyst, the amount used may vary. Because they are so different,
It is appropriate to control by the PH of the reaction system. That is, the pH of the reaction system at 25 ° C is 3.5 to 6.8,
Phenols and formaldehydes are preferably reacted with each other using a catalyst so that the amount is preferably 4.5 to 6.0.

Further, in addition to organic acid metal salts as catalysts such that the pH of the reaction system is 3.5 to 6.8, normal alkali metal hydroxides and carbonates, alkaline earth metal hydroxides and oxides ammonia, and 1 out of basic catalysts such as amine compounds
One kind or two or more kinds may be used together in a small amount.

The phenol resin obtained by the method for producing a phenol resin for compounding an epoxy resin coating composition of the present invention is acetylated, and after ¹ H-NMR (proton nuclear magnetic resonance) analysis, the results of dimethylene ether bond, methylene bond and methylol group are shown. The proportion of the number of moles of dimethylene ether bond in the total number of moles is 20% or more, preferably 30% or more. If it is less than 20%, no feature can be found in the adhesiveness of the baked coating film of the epoxy resin paint containing the phenol resin according to the present invention to the article to be coated.

The phenol resin for epoxy resin coating composition according to the present invention, after being acetylated, has a binding molar ratio of formaldehyde to 1 mol of phenol nucleus of preferably 3.0 or less, more preferably 2.4, after analysis by ¹ H-NMR.
It is the following. The number average molecular weight of the phenol resin for blending with the epoxy resin coating material of the present invention is preferably 200 to 900, more preferably 250 to 600 based on the analysis result by GPC (gel permeation chromatography).

The reason why the baked coating film of the epoxy resin coating containing the phenol resin obtained by the method for producing a phenol resin for epoxy resin coating formulation of the present invention has excellent adhesiveness to an object to be coated is that an organic acid metal salt is used as a catalyst. The heat-reactive phenolic resin obtained by reacting under weak acidity contains dibenzyl ether bond compared to the conventional heat-reactive phenolic resin obtained by reacting under basic condition using an alkali catalyst. This is because the ratio is high, in other words, the content ratio of the methylol group is low. That is, in the case of a heat-reactive phenolic resin having a high content of dimethylene ether bonds, the fact that the amount of condensed water generated when it is co-condensed with an epoxy resin and hardened effectively acts to improve the adhesiveness with the article to be coated. it seems to do. Further, the baked coating film of the epoxy resin coating compound containing the phenol resin according to the present invention has a distinctly lighter hue than the baking coating film of the conventional epoxy resin coating compound containing the phenol resin is that the organic acid metal salt is used. The phenolic resin obtained by reacting in a weakly acidic condition with a catalyst is less colored by oxidation than the conventional phenolic resin obtained by reacting under a basic condition using an alkali catalyst, and this effect is due to the epoxy resin. It seems that it also appears in the hue after co-condensation with the resin and curing.

Regarding the phenol resin obtained by the method for producing a phenol resin for epoxy resin coating composition of the present invention, as a solvent that can be used to dissolve into a resin liquid for the purpose of improving the workability of compounding with an epoxy resin, Toluene, aromatics such as xylene, cellosolves such as methyl cellosolve, ethyl cellosolve, butyl cellosolve, cellosolve acetate, butyl cellosolve acetate, esters such as ethyl acetate, butyl acetate, acetone methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, isophorone, etc. One or more selected from alcohols such as ketones, propyl alcohol, butyl alcohol and diacetone alcohol.

〔The invention's effect〕

The epoxy resin coating containing the phenol resin obtained by the method for producing a phenol resin for epoxy resin coating formulation according to the present invention has excellent adhesion of the baked coating to the article to be coated, and the baked coating is extremely pale color. . In addition, since the properties such as heat resistance, corrosion resistance, flexibility, and chemical resistance are also good, the demand for the phenol resin obtained by the method for producing a phenol resin for compounding an epoxy resin coating of the present invention will increase in the future. Expected.

Further, the phenol resin obtained by the method for producing a phenol resin for blending an epoxy resin coating composition of the present invention is used by being blended with various epoxy resins such as bisphenol A type, bisphenol F type, orthocresol novolac type and phenol novolac type. It is possible.

The use of the epoxy resin paint containing the phenol resin obtained by the method for producing a phenol resin for epoxy resin paint blending according to the present invention is as a primer for an adhesive for a food can inner surface, a chemical can inner surface, a drum can lining, and an adhesive can. For coating, the inner and outer surfaces of crown caps, and high-grade primers for tableware, food instruments, etc.

Hereinafter, the present invention will be described in detail with reference to examples, but the present invention is not limited to the examples. In addition, all "parts" and "%" described in the examples and comparative examples mean "parts by weight" and "% by weight".

Example 1 A resin reactor equipped with a stirrer, a reflux condenser and a thermometer was charged with 150 parts of phenol, 850 parts of paracresol and 583 parts of 80% paraformaldehyde, and manganese acetate was added to adjust the pH of the reaction system to 6.2. After that, the temperature was gradually raised. After the temperature reached 110 ° C, the mixture was reacted for 5 hours under reflux under normal pressure,
Furthermore, dehydration reaction was performed under reduced pressure of 35 to 60 Torr. 40To
When the internal temperature reached 122 ° C. in rr, the dehydration reaction was terminated to obtain a heat-reactive phenol resin for epoxy resin paint blending.
After that, in order to improve the workability of mixing with the epoxy resin,
Methyl ethyl ketone was added to and mixed with a phenol resin for epoxy resin paint formulation to obtain a resin liquid having a non-volatile content (according to JIS K6909) of 33% at a Gardner color number of 1,125 ° C. After acetylating the phenolic resin for epoxy resin paint formulation, the results of ¹ H-NMR analysis showed that 100 g of the 33% resin solution described above contained a methylol group and an active methylene group generated upon thermal decomposition of a dimethylene ether bond. 0.35
It contained mol.

Example 2 Bisphenol A1000 was added to a resin reactor of the same type as in Example 1.
, 80% paraformaldehyde (370 parts) and ethyl cellosolve (300 parts) were added, and 24% lead naphthenate was added to adjust the pH of the reaction system to 5.6, and then the temperature was gradually raised. The reaction was carried out under reflux under normal pressure for 4.5 hours, and the dehydration reaction was further carried out under normal pressure to finish when the internal temperature reached 125 ° C. to obtain a heat-reactive type phenol resin for epoxy resin paint blending. After that, ethyl cellosolve was added and mixed, and the Gardner color number was 1,125.
A resin liquid having a nonvolatile content at 33 ° C. of 33% was obtained. According to ¹ H-NMR analysis, 100 g of the 33% resin liquid contained 0.28 mol of active methylene groups generated upon thermal decomposition of methylol groups and dimethylene ether bonds.

Example 3 Paracresol 1000 was added to a resin reactor of the same type as in Example 1.
Part, 88% paraformaldehyde 400 parts, 37% formalin 5
50 parts and 300 parts of cellosolve acetate were charged, zinc acetate was added to adjust the pH of the reaction system to 5.1, and then the temperature was gradually raised. The reaction was carried out under reflux under normal pressure for 3.5 hours, and the dehydration reaction was further carried out under normal pressure to finish when the internal temperature reached 125 ° C. to obtain a heat-reactive phenol resin for epoxy resin paint blending. Thereafter, cellosolve acetate was added and mixed to obtain a resin liquid having a non-volatile content of 33% at Gardner color number of 1,125 ° C. According to ¹ H-NMR analysis, the above 33% resin solution 1
00g contained 0.41 mol of a methylol group and an active methylene group generated upon thermal decomposition of a dimethylene ether bond.

Example 4 1000 parts of para-tertiary butylphenol and 85% paraformaldehyde 520 were added to a resin reactor of the same type as in Example 1.
And 250 parts of xylene were charged, barium acetate was added to adjust the pH of the reaction system to 4.9, and then the temperature was gradually raised. After reacting under reflux under normal pressure for 5.0 hours, dehydration reaction was further carried out under normal pressure to reach an internal temperature of 123 ° C, then kept under a reduced pressure of 30 Torr, and a thermal reaction ended when the internal temperature reached 127 ° C. A type of phenolic resin for epoxy resin paint formulation was obtained. Thereafter, a mixed solvent having a weight ratio of xylene and butanol of 80:20 was added to obtain a resin liquid having a nonvolatile content of 33% at Gardner color number of 1,125 ° C. According to ¹ H-NMR analysis, the above 33
% Resin liquid contained 0.33 mol of an active methylene group generated upon thermal decomposition of a methylol group and a dimethylene ether bond.

Comparative Example 1 A resin reactor of the same type as in Example 1 was charged with 150 parts of phenol, 850 parts of paracresol, and 1260 parts of 37% formalin, and 2
After 80 parts of a 5% aqueous sodium hydroxide solution was added to make the reaction system basic, the temperature was gradually raised and the reaction was carried out at 100 ° C. for 1 hour.
The mixture was neutralized with acetic acid, allowed to stand at room temperature, and the aqueous layer was separated and removed. Then, 500 parts of n-butanol and 500 parts of xylene were charged, and the temperature was adjusted.
A resol type phenol resin was obtained by reacting at 120 ° C. for 3 hours while removing water. After that, a mixed solvent of the same weight of n-butanol and xylene was added to make Gardner color number 3,
A resin solution having a nonvolatile content of 33% at 125 ° C. was obtained. ¹ H-NMR
According to the analysis, 100 g of the 33% resin liquid contained 0.30 mol of a methylol group and an active methylene group generated upon thermal decomposition of a dimethylene ether bond.

Comparative Example 2 Bisphenol A1000 was added to a resin reactor of the same type as in Example 1.
25 parts, 37% formalin 800 parts, xylene 300 parts, 25
% 100 parts of a caustic soda aqueous solution was added to make the reaction system basic, the temperature was raised, and the reaction was carried out at 100 ° C. for 1.5 hours. The mixture was neutralized with sulfuric acid, allowed to stand at room temperature, and the aqueous layer was separated and removed. Then 50 ~
The operation of adding 1000 parts of warm water at 60 ° C., stirring and allowing to stand and separating and removing the aqueous layer was repeated 3 times to complete washing with warm water. continue
A dehydration reaction was performed under a reduced pressure of 25 to 80 Torr to obtain a heat-reactive phenolic resin. Then, xylene was added to obtain a resin liquid having a Gardner color number of 2,125 ° C. and a nonvolatile content of 33%. According to ¹ H-NMR analysis, 100 g of the 33% resin liquid contained 0.28 mol of active methylene groups generated upon thermal decomposition of methylol groups and dimethylene ether bonds.

Comparative Example 3 In a resin reactor of the same type as in Example 1, 1000 parts of paratertiary butylphenol, 1195 parts of 37% formalin, xylene.
Charge 250 parts, add 25 parts of 25% caustic soda aqueous solution and 30 parts of 25% ammonia water to make the reaction system basic, and then add 80 parts.
The reaction was carried out at 0 ° C for 2 hours. After neutralizing with hydrochloric acid, the same treatment as in Comparative Example 2 was performed to obtain a heat-reactive phenolic resin. After that, xylene was added to make Gardner color number 2,125.
A resin liquid having a nonvolatile content at 33 ° C. of 33% was obtained. According to ¹ H-NMR analysis, 100 g of the 33% resin solution contained 0.33 mol of a methylol group and an active methylene group generated upon thermal decomposition of a dimethylene ether bond.

[Adjustment of epoxy resin paint]

Epoxy equivalent 1900 Bisphenol A type epoxy resin 70
In a solution obtained by dissolving 0 g of the same weight mixed solvent of butyl cellosolve and xylene in 1400 g, a 33% resin solution of the phenol resin for epoxy resin coating formulation obtained in Examples 1 to 4 or obtained in Comparative Examples 1 to 3 was obtained. 33% of phenolic resin
An epoxy resin paint was prepared by adding the resin solution in a quantity corresponding to 3.0 mol of active methylene groups generated by thermal decomposition of methylol groups and dimethylene ether bonds, and further adding and mixing 2 g of 75% phosphoric acid.

[Epoxy resin paint test results]

Apply the above adjustment paint to a 0.25 mm thick tin plate using a roll coater so that the thickness of the baked coating film is 5 μ,
A test piece was prepared by baking at 210 ° C. for 10 minutes.

Regarding the coating film characteristics of the test piece, the coating film appearance, coating film adhesion, flex resistance and solvent resistance were tested, and the results are shown in Table 1.

The epoxy resin paints containing the resin liquids shown in Test Nos. 1 to 5 have better coating adhesion than the epoxy resin paints containing the resin liquids shown in Tests No. 6 to 9 and the appearance of the coating film. The hue was obviously pale. In addition, the flex resistance and solvent resistance were comparable. Therefore, the baked coating film of the epoxy resin paint using the phenol resin obtained by the method for producing a phenol resin for compounding an epoxy resin paint according to the present invention was extremely excellent in adhesiveness to an object to be coated and was a light color.

Claims (1)

[Claims] 1. A pH of 3.5 using phenols and formaldehydes as catalysts using one or more kinds of organic acid metal salts selected from divalent metal salts of carboxylic acids and naphthenic acids.
A method for producing a heat-reactive phenolic resin for compounding an epoxy resin coating, which is obtained by reacting under weak acidity of 6.8.