JPS62257972A - Corrosionproofing aqueous coating - Google Patents

Abstract

PURPOSE:To obtain the titled coating particularly suitable for preventing steel plate from corrosion, by incorporating an aqueous solution of a volatile alkali salt of specific copolymer with a water-soluble complex salt prepared from water-insoluble zinc compound, p-oxybenzoic acid and volatile complexing agent. CONSTITUTION:The objective coating can be obtained by incorporating (A) an aqueous solution or aqueous dispersion of a volatile alkali salt of a copolymer prepared by copolymerization between (i) 0.1-30wt% of an ethylenic unsaturated carboxylic acid (e.g. methacrylic acid) and (ii) 99.9-70wt% of another copolymerizable monomer (e.g. vinyl acetate) with (B) a water-soluble complex salt prepared from (iii) a water-insoluble zinc compound (e.g. zinc oxide), (iv) p-oxybenzoic acid, and (v) a volatile complexing agent (e.g. ethylenediamine).

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a water-based paint composition for preventing corrosion not only on metals with no rust but also on rusted metals from which floating rust has been mechanically removed, particularly steel plates. .

It is known that paints using phenolic carboxylic acids such as U-based tannins, gallic acid, salicylic acid, and anacardic acid derivatives directly chelate iron to improve adhesion, rust prevention, etc.

The present inventors focused on the excellent anticorrosive effect of the water-based emulsion paint containing zinc ammonium carbonate, zinc ammonium phosphate, etc. described in JP-A No. 49-96033, and from the viewpoint of non-polluting polyvalent metals, especially As a result of detailed studies on zinc complex salts, it was found that polyvalent metals, especially zinc white, form water-soluble complex salts with phenolic carboxylic acid and volatile complexing agents.
It was discovered that a paint produced by adding this to a volatile alkali salt aqueous solution or aqueous dispersion of a resin containing a carboxyl group exhibits excellent smooth shaving properties that cannot be compared to the complex salt-free resin. No. 53-40264 describes the zinc ammonium complex salt of gallate, patent application No. 53-40264.
In No. 149970, a patent application was filed for zinc ammonium humate complex salt. Also, after that, the patent application
No. 996, a patent application has been filed for the zinc sorbate ammonium complex salt, which is said to have excellent water resistance.

+11',w As mentioned above, various complex salts are known to be used in water-based anticorrosion paints, but zinc ammonium carbonate, zinc ammonium phosphate, etc. have insufficient anticorrosion effects, and zinc sorbate Ammonium, zinc ammonium gallate, zinc ammonium humate, etc. have excellent anticorrosion effects, but are not fully satisfactory in terms of water resistance.

. The inventors of the present invention further investigated various phenolic carboxylic acids that form water-soluble complex salts.

A water-soluble complex salt formed from paraoxybenzoic acid, a water-insoluble zinc compound, and a volatile complexing agent exhibits an effect equal to or greater than known complex salts in terms of anti-corrosion properties, and has excellent water resistance. The present invention was based on the discovery that this material has significantly superior performance.

That is, 9 the present invention is ethylenically unsaturated carbon raO.

For a volatile alkali salt aqueous solution or aqueous dispersion of a copolymer obtained by copolymerizing 1 to 30% by weight (hereinafter referred to as %) and 99.9 to 70% of another copolymerizable monomer. This is an anticorrosive water-based coating composition obtained by adding a water-insoluble zinc compound, a water-soluble complex salt consisting of paraoxybenzoic acid, and a volatile complexing agent.

Ethylenically unsaturated carboxylic acids used in the present invention include acrylic acid, methacrylic acid, and itaconic acid.

It contains crotonic acid, aconitic acid, maleic acid, etc., and the amount used is 0.1 to 30%, and if it is less than 0.1%, crosslinking with the water-soluble complex salt is insufficient.

Water resistance, solvent resistance, and film-forming properties deteriorate. Moreover, if it exceeds 30%, the water resistance decreases and it is not suitable for practical use.

Preferred amounts range from 1.5 to 5%.

Next, another monomer copolymerized with ethylenically unsaturated carboxylic acid is (meth)acrylic acid ester.

Vinyl acetate, ethylene, isobutylene, styrene.

Butadiene, isoprene, chlorobrene, (meth)acrylonitrile, etc. are used. In addition, acrylamide, hydroxyethyl (meth)acrylate, etc. are also used. These ethylenically unsaturated carboxylic acids and other copolymerizable monomers are copolymerized by conventional solution polymerization or emulsion polymerization using water-soluble solvents such as methanol and isopropanol.

Even if cellosolve or the like is included, there is no problem. Ammonia water or a volatile amine is used to neutralize the ethylenically unsaturated carboxylic acid copolymer. Examples of volatile amines include methylamine, ethylamine, dimethylamine, diethylamine, triethylamine, morpholine, and ethanolamines. The above copolymer may be in the form of an aqueous solution or an aqueous dispersion. In the case of an aqueous solution, it is necessary to introduce an excessive amount of carboxyl groups to make it water-soluble, which is disadvantageous in terms of the water resistance of the dried coating film, but water resistance can also be improved by introducing an appropriate amount of carboxyl groups.

When applied to an aqueous dispersion, conventional emulsion types were considered to have poor spray properties, but by applying the present invention, spray properties can be maintained for over 1000 hours, and the amount of ethylenically unsaturated carboxylic acid introduced can be freely controlled. In addition, the physical properties can be changed easily.

Preferred water-insoluble zinc compounds used in the water-soluble complex salt of the present invention include zinc oxide, zinc hydroxide, and zinc carbonate. Further, as the volatile complexing agent, a volatile base such as ammonia, ethylenediamine, methylamine, ethylamine, dimethylamine, diethylamine, etc. is used. To describe a method for producing zinc paraoxybenzoate ammonia water as a specific example of a water-soluble complex salt, first 5 to 7 g of zinc compound (
5g of zinc oxide, 6g of zinc hydroxide, 7g of zinc carbonate)
, 10 g of water and 25 g of 25% ammonia water are mixed to make a slurry, and while stirring, paraoxybenzoic acid is added little by little until the zinc compound is dissolved transparently. Approximately 8 g of paraoxybenzoic acid is required. Further, the method for producing the ethylenediamine complex salt of zinc paraoxybenzoate is the same as above, but the quantities are 5 to 7 g of the zinc compound, 10 g of water, and 30 g of ethylenediamine.

A proportion of about 10 g of paraoxybenzoic acid is required.

These water-soluble complex salts contain the carboxyl group 1 of the copolymer resin.
Preference is given to using a proportion of 0.1-1 mole per mole.

The coating composition of the present invention contains colored pigments and 9 extender pigments.

It is also possible to mix additives such as antirust pigments.

EXAMPLES The present invention will be described in more detail below with reference to Examples and Comparative Examples. Parts and percentages are by weight.

・Example 1 Cypinol EC-701B (manufactured by Cyden Chemical).

To 100 parts of acrylic copolymer emulsion containing 3% acrylic acid (S degree 45%), 5 parts of butyl cellosolve was added and mixed. A solution containing 2 parts of an aqueous solution of zinc oxide) is applied to a polished steel plate so that the dry film has a thickness of 20 μm. After drying this at room temperature for 7 days, it is subjected to a performance test.

- Example 2 A sample was prepared in the same manner as in Example 1, except that a complex salt using zinc hydroxide as the zinc compound of the zinc ammonium paraoxybenzoate complex salt was used.

- Example 3 A sample was prepared in the same manner as in Example 1, except that a complex salt using zinc carbonate as the zinc compound of the zinc ammonium paraoxybenzoate complex salt was used.

・Example 4 In place of the zinc paraoxybenzoate ammonium complex salt of Example 1, ethylenediamine complex salt of zinc paraoxybenzoate (
A sample was prepared in the same manner as in Example 1, except that a zinc compound (using zinc oxide) was used.

- Comparative Example 1 A sample was prepared in the same manner as in Example 1, except that 2 parts of a water-soluble complex salt solution of zinc ammonium carbonate with a 15% zinc white content was used instead of the zinc ammonium paraoxybenzoate complex salt of Example 1.

Comparative Example 2 5 parts of butyl cellosolve was added to 100 parts of Cypinol EC-710B and applied to a polished steel plate in the same manner as in Example 1 to prepare a sample.

The above samples were subjected to salt water spray and water resistance tests at 35°C, and the results were as follows.

Note: The salt spray test was conducted according to J I 5Z2371.

The water resistance test was conducted according to JI 5K5400.

As is clear from the above description, the anticorrosive water-based paint of the present invention exhibits extremely excellent anticorrosion properties, especially in terms of water resistance as well as smooth shaving properties.

Claims (1)

[Claims] An aqueous solution or dispersion of a volatile alkali salt of a copolymer obtained by copolymerizing 0.1 to 30% by weight of an ethylenically unsaturated carboxylic acid and 99.9 to 70% by weight of another copolymerizable monomer. An anticorrosion water-based coating composition obtained by adding a water-soluble complex salt consisting of a water-insoluble zinc compound, paraoxybenzoic acid, and a volatile complexing agent to a liquid.