JPH03220220A - Production of phenolic resin and can coating agent - Google Patents

Abstract

PURPOSE:To obtain a phenolic resin useful as a curing agent for can coating agents by reacting a phenol component comprising phenol and a bisphenol with formaldehyde in the presence of a catalyst and specifying the content of a free phenol component. CONSTITUTION:A phenol component (a) is obtained by mixing phenol with 0.1-0.5mol, per mol of the phenol, of a bisphenol (e.g. bisphenol A). Component (a) is reacted with 4.0-6.0mol, per mol of component (a), of formaldehyde (b) at 45-50 deg.C for 2-4hr in the presence of 0.5-1.0mol, per mol of the phenol, of a catalyst (c) comprising an alkali metal hydroxide (e.g. NaOH), and the reaction is continued at 60-80 deg.C for 2-5hr. The formed resin is neutralized, washed with water and dewatered to obtain a phenolic resin of a free phenol component content of 0.1% or below based on the resin solids.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for producing a phenol resin used in epoxy-phenol paints and a method for producing can paints containing the same.

More specifically, when used as a curing agent in a water-based paint for cans, a coating film with excellent KMnO4 consumption, adhesion, and curability was obtained! ! The present invention relates to a phenolic resin for use in can paint formulations having a light-colored film and a method for producing the can paint.

[Prior Art] As is well known, the performance of epoxy-phenolic paints is greatly influenced by the properties of the phenolic resin that is the curing agent. In reality, the type and composition ratio of the phenol component used, the type and amount of the catalyst, the amount of formaldehyde, the epoxy/
Various resol-type phenolic resins are used depending on the purpose, with the balance of performance changing depending on the phenol ratio, etc. However, the phenolic resin produced by the conventional method has many remaining free phenol components, and when used as a curing agent for epoxy-phenolic water-based paints, it has drawbacks such as high KM n O4 consumption and poor adhesion. was there.

[Problem to be solved by the invention]

The present inventor has conducted extensive research on phenolic resins for can paint formulations to reduce KMnOa consumption, improve adhesion, and lighten the color of epoxy-phenol water-based paints, which have been traditionally required. It has been found that phenolic resins obtained by reacting specific phenols and formaldehyde in specific ratios with an alkali metal hydroxide as a catalyst are extremely effective.

Its purpose is that when used as a curing agent for epoxy phenolic water-based paints for can paints, K M n
Low Os consumption, excellent adhesion, and good curing properties.
An object of the present invention is to provide a phenol resin capable of imparting properties such as a light color to a paint film, and a can paint using the same.

[Means to solve the problem]

The gist of the present invention is to hydroxylate an alkali metal by mixing 1 mole of phenol and bisphenols in a molar ratio of 1:0.1 to 1:0.5 with 4.0 to 6.0 moles of formaldehyde. This is a method for producing a phenol resin, which is characterized in that the reaction is carried out in the presence of a chemical catalyst, and the free phenol component is reduced to 0.1% or less based on the solid content of the resin.

The bisphenols used in the present invention are bisphenols represented by bisphenol A and bisphenol F.

The mixing ratio of phenol and bisphenols is phenol 1
Preferably, the amount of bisphenols is 0.1 to 0.5 mole per mole, because as the amount of bisphenols increases, the methylolphenol component decreases and the molecular weight increases.
This is not preferable because the compatibility with the aqueous emulsion becomes poor.

In addition, examples of the alkali metal hydroxide used as a catalyst include sodium hydroxide, potassium hydroxide, etc.
The amount of alkali metal hydroxide that should be present in the reaction catalyst is usually 0.5 to 1 per mole of phenol.
．． About 0 mole, preferably 0 per mole of phenol
．． It is about 7 to 0.9 mol. If the molar ratio of the catalyst is less than 0.5, there are few methylol groups in the resin, and when used as a coating material, curing is slow and compatibility and K M n O4 consumption are poor, making it impractical. Conversely, if the molar ratio of the catalyst is 1.
If it is larger than 0 mol, it becomes difficult to control the reaction.

In order to suppress heat generation during addition of the catalyst, it is preferable to add 2/3 of the total amount at the start of the reaction and add the remaining 1/3 after the internal temperature has stabilized.

The reaction conditions include a temperature of 45 to 55°C during the initial reaction;
The time is 2 to 4 hours, and the temperature during the secondary reaction is 60°C.
Preferably, the temperature is 80° C. and the time is 2 to 5 hours.

After the reaction, the resulting resin is preferably neutralized and then washed with water to remove moisture under normal pressure or reduced pressure.

The phenolic resin obtained in the present invention is mixed with an emulsion containing an epoxy resin as a main component by a conventional method. Preferably, this emulsion is one obtained by addition polymerizing acrylic acid, methacrylic acid, styrene, etc. to an epoxy resin. The ratio of phenolic resin to epoxy resin is
It is usually 2 to IO weight percent in terms of solid content.

〔Example〕

The present invention will be described in detail below with reference to Examples. In the examples, "1 part" indicates "part by weight" and "%" indicates "percent by weight."

rExample zJ 225 parts (2,39 mol) of phenol and 75 parts (0,33 mol) of bisphenol A in 1 part of 37% formalin
Added 292 parts (11,95 mol), 25% as catalyst
200 parts (1.25 mol) of sodium hydroxide aqueous solution is added and reacted at 50°C for 1 hour.

Next, 100 parts of a 25% aqueous sodium hydroxide solution (0.6
25 mol) was added and reacted for another 1.5 hours at 50°C, then heated to 70°C and reacted for 2.5 hours. After the completion of the reaction, 216 parts (0.77 mol) of 35% sulfuric acid was added. The resulting resin was dissolved by adding 450 parts of butanol and 110 parts of ethyl acetate, and washed with water three times at 40°C. After washing with water, water was removed by azeotropic dehydration to obtain the desired phenol resin.

The viscosity of the resin at this time was 120 cps/25 DEG C. The non-volatile content was 41%, and the free phenol component was resin solid.A phenol resin was produced in the same manner as shown in Table 1. The physical properties of the obtained phenol resin are also shown in Table 1.

[Coating film performance test] Using the phenolic resins obtained in Examples 1 to 3 and Comparative Examples 1 to 3 above, water-based paints were prepared as shown below, and the paints were aluminized, applied sparingly, and then baked. ,
Tests were conducted on KMnO, consumption, adhesion, appearance check, etc.

Various test methods are shown below, and the test results are shown in Table 2.

Aqueous emulsion formula ■ Epicote 1009 100. (Part 1■
Butyl cellosolve 100.0 parts ■ Methacrylic acid 50.0 parts ■ Styrene
16.7 parts ■ Benzoyl peroxide 4.67 parts ■ Butyl cellosolve
14.2 parts ■ Dimethylaminoethanol
14.3 parts ■ Ion exchange water 450.
0 parts Put ■■ into a reaction container, and after completely dissolving at 115℃, add the mixture of ■～■ dropwise over 1 hour. Lower the internal temperature to 100℃.

Then, (1) was added and then (2) was added little by little to obtain a milky white aqueous emulsion with a solid content of 23.8% and a viscosity of 85 cps/25°C.

Preparation of water-based paint The above-mentioned water-based emulsion and the phenol resins obtained in Examples and Comparative Examples were mixed so that the solid content weight ratio was 19:1 to obtain a stable water-based paint.

(1) K M n Oa consumption Each of the water-based paints prepared in the above manner was applied to a 5CIX201 aluminum sheet using a bar coater so that the film thickness after baking was 5 to 7 μm.

After baking the test piece at 200℃ for 5 minutes,
The mixture was placed in a 50 (ld) ruby strainer containing 100 ml of chlorine, covered with aluminum foil, and subjected to retort treatment at 130° C. for 30 minutes. The test water thus obtained was measured in accordance with the experimental method described in the Food Sanitation Act (Ministry of Health and Welfare No. 434).

(2) Adhesion The test piece was coated and baked in the same manner as the test piece used for measuring the K M n Oa consumption above, and immersed in water at 100°C for 1 hour. Thereafter, using a cutter knife, 11 vertical and horizontal cuts were made on the coated surface of the test piece, each having a width of about one square. A peeling test was performed using cellophane adhesive tape, and the number of unpeeled pieces was shown in the numerator.

Table 2 [Effects of the Invention] When the phenolic resin produced by the method of the present invention is used as a curing agent for an epoxy-phenolic paint for cans,
A light-colored coating film with low K M n Oa consumption and excellent adhesion can be obtained.

Claims (2)

[Claims] (1) Phenol and bisphenols in a molar ratio of 1:0.
1 mole of phenols mixed at a ratio of 1 to 1:0.5 and 4.0 to 6.0 moles of formaldehyde are reacted in the presence of an alkali metal hydroxide catalyst, and the free phenol components are converted into resin solids. A method for producing a phenolic resin, characterized in that the amount is 0.1% or less. (2) A method for producing a can paint, which comprises blending the phenol resin obtained by the method according to claim 1 into an aqueous emulsion containing an epoxy resin as a main component.