JPS5840175A - Anticorrosive coating method - Google Patents

Abstract

PURPOSE:To prevent deterioration caused by an alkaline substance over a long time and to enhance the affinity of undercoat paint with topcoat organic paint, by applying chlorine-contg. resin emulsion onto the undercoat paint film of inorganic thick zinc dust paint. CONSTITUTION:Inorganic thick zinc dust paint composition containing alkyl silicate or alkali silicate as a binder and zinc dust as an anticorrosive pigment is applied to a workpiece to be coated such as steel sheet by brushing or spraying. Chlorine-contg. resin emlsion as such at pH in an acid zone is then applied to the paint film. In this way, its reaction with alkaline substance formed from the zinc-rich paint film and its reaction with the surface of the zinc dust in the paint film are accelerated, so that curing the zinc-rich paint can be promoted. The chlorine-contg. resin emulsion also acts as a mistcoat or etching primar to the organic paint to be applied as the topcoat.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an anti-corrosion coating method, and more particularly to an anti-corrosion coating method in which a chlorine-containing resin emulsion is applied on a coating film of an inorganic high-concentration zinc powder paint to improve topcoatability. It is something.

When applying various paints to objects such as steel plates, a high concentration zinc dust paint (zinc linch paint) is used as an undercoat for corrosion prevention purposes, but due to workability and pollution caused by organic solvents, it is Inorganic high-concentration zinc powder paint (inorganic zinc-rich paint) that uses water-soluble alkali silicate as a binder rather than organic zinc-rich paint
is attracting interest. However, when this inorganic zinc-rich paint is used as a single film, it exhibits excellent properties such as water resistance, corrosion resistance, weather resistance, and solvent resistance. I'm having a problem. In other words, since the binder of inorganic zinc rich paint is alkaline, the alkaline content generated from the binder softens the top coat, causing blistering and interlayer peeling. Essentially, the adhesion between inorganic zinc-rich paint and general organic paint is poor. Curing of inorganic zinc clinch paints requires weathering for a relatively long time, generally about 3 to 10 days, and if curing is insufficient, the above interlayer adhesion will be adversely affected. The coating surface of inorganic zinc-rich paint is porous, and when an organic coating is directly overcoated on top of the porous coating, foaming occurs, which impairs the coating performance of the finished surface. Although various efforts have been made to overcome these drawbacks, no sufficiently effective solution has yet been found. For example, as a method of accelerating curing, attempts have been made to apply an acidic aqueous solution such as phosphoric acid on the zinc-rich paint coating, or simply to sprinkle water on it. Although this method is effective to some extent in accelerating curing, it has problems in terms of work hours and wastewater treatment, and does not solve any of the above-mentioned problems other than accelerating curing. Next, apply a 30 to 50% thinner diluted solution of the top coat paint once on the zinc rich paint surface (mist coat) and then top coat, or apply an etch/glue primer (JIS-5633-1 type). Attempts have been made to seal the surface of zinc-rich paint and improve its adhesion with organic paints, such as applying a topcoat after coating. In the case of mist coating, the viscosity of the thinner diluted liquid is low, so it is effective as a sealing treatment for the surface of Zinc Kuributi paint, and foaming during topcoating is considerably suppressed, but it is not effective in accelerating curing or improving interlayer adhesion. It has no effect, and no etching is observed; on the contrary, the phosphoric acid contained in the primer neutralizes the alkaline substances on the surface of the zinc-rich paint and prevents its cohesive failure, which is seen as a temporary alkali neutralization effect. There was something I should have done. However, the polyvinyl butyral resin in the etching primer inherently has poor alkali resistance and water resistance, causing blistering of the paint film and interlayer...
It had serious defects in terms of chestnuts, etc. Furthermore, Japanese Patent Publication No. 56-8674 proposes a method in which a mixed paint of phosphoric acid and/or phosphate and an organic resin emulsion is applied to the surface of the zinc-rich paint film, and then a regular top coat is applied. It was done. This method uses phosphoric acid and/or phosphate salts to neutralize the alkaline content generated from the binder of zinc-rich paint, reduces the influence of alkali, and also aims to achieve adhesion with the top organic paint using organic resin. It was something. However, as in the case of etching primer, since the paint is mixed with phosphoric acid added to neutralize the alkali, depletion of the acid due to neutralization leads to changes in the paint composition and a decrease in effectiveness. Resins having ester bonds, such as alkyd resins and vinyl acetate resins, which are representative examples, have poor alkali resistance, and peeling between layers occurs over time, resulting in problems in terms of adhesion over time. The methods that have been proposed in the past address the propositions of accelerating the curing of zinc-rich paint, preventing foaming during topcoating, and improving glabella adhesion between the surface of the zinc-rich paint film and the surface of the coating applied thereon. Moreover, it is only an improvement method that can provide insufficient effects for each individual, and in the end, the zinc-rich paint, which has excellent corrosion resistance, cannot be fully utilized. This results in the range of use being limited, or in combination with methods such as curing acceleration, sealing treatment, intermediate coating, etc., resulting in an increase in the number of man-hours. In view of this current situation, the present inventors have developed a simple paint that helps accelerate the curing of zinc-rich paint, suppresses alkaline content from the binder, prevents deterioration due to alkaline substances over a long period of time, and has good affinity with organic paints used as top coats. The present invention was achieved as a result of continued research in order to obtain a multi-purpose paint that has the following properties and is useful for sealing the surfaces coated with zinc clinch paint.

In the present invention, an inorganic high-concentration zinc powder paint containing alkyl silicate or alkali silicate as a binder and zinc dust as an anticorrosion pigment is applied to the object to be coated, then a chlorine-containing resin emulsion is applied, and if necessary, a An anti-corrosion coating method is provided, which comprises applying a top coat of paint.

In the present invention, first, an inorganic high-concentration zinc powder paint containing alkyl silicate or alkali silicate as a binder and zinc dust as an anticorrosive pigment is applied onto the object to be coated. The alkyl silicate used here has the general formula 8i (OR)
The alkali silicate is a partially hydrolyzed silicate ester represented by 4 (where R is an alkyl group such as ethyl, butyl, selonrube group, etc.), and the alkali silicate has the general formula % (where M is NaXKXLi, N(CH, 0H)4,
It is a compound represented by N (C, H, OH), etc., where X is a number in the range of 0.5 to 10. These binders are used singly or as a mixture of two or more, and usually a composition consisting of 5 to 40% by weight (in terms of solid content) of one or more of the binders and 95 to 60% by weight of zinc powder is used. Preferably used for the purposes of the present invention. Other pigments, fillers, curing agents, etc. can be added to the coating material as necessary. The blending ratio of the binder and zinc dust is not necessarily critical, but for corrosion prevention purposes it is desirable to blend as much zinc dust as possible, and the above blending ratio is recommended. The anticorrosion effect is greatest when the zinc powder is contained in an amount of 95 to 85% by weight.

The coating composition is applied onto a cleaned object by a conventional method such as brushing, spraying, or air spraying.

The most characteristic feature of the method of the present invention is that a chlorine-containing resin emulsion is applied onto the coating film of the above-mentioned inorganic high-concentration zinc dust paint. This chlorine vinylidene resin system,
Chlorinated rubber emulsions; vinyl chloride/acrylic copolymer, vinyl chloride/vinylidene chloride copolymer emulsions; chloroprene rubber, chlorinated polyolefins such as chlorinated polypropylene, chlorinated polyethylene emulsions; or chlorinated epoxy resin emulsions They can be used alone or in the form of a mixture of two or more. These chlorine-containing resin emulsions can be obtained directly by emulsion polymerization, or by post-emulsifying a resin solution in water with the aid of a surfactant.
When preparing them, p)( is generally in the acidic range of 1 to 7, and acidic ranges have better storage stability. Usually, these are prepared by adjusting I)H with ammonia etc. However, in the present invention, p in the acidic region is used.
Used as I-1. The present inventors discovered that when this acidic resin emulsion was applied onto a zinc-rich paint film, it reacted with alkaline substances generated from the zinc-rich paint film, reacted with the surface of zinc dust in the paint film, and reacted with the iron surface. It has been found that it has the ability to accelerate the curing of zinc-rich paints by promoting reactions such as silicates and self-condensation reactions of silicate. For example, in the case of a zinc-rich paint that uses alkali silicate as a binder, after coating and drying, a chlorine-containing resin emulsion is applied or not, and an epoxy paint is applied as a top coat to prevent adhesion between the eyebrows, etc. As a result of investigating the effect on the curing speed of zinc-rich paint coatings, we found that epoxy paint was applied after applying zinc-rich paint for 3 days, and chlorine-containing resin emulsion was applied 24 hours after applying zinc-rich paint. However, the effect was almost the same as that applied with epoxy paint, confirming that the chlorine-containing resin emulsion is extremely effective in accelerating the curing of zinc clinch paint. It has also been confirmed that for alkyl silicates, the 3-day curing of the zinc-rich paint without applying the chlorine-containing resin emulsion is roughly comparable to the 2-day curing when the resin emulsion is applied, although this is not as pronounced as with the alkali silicate. There is.

In this way, chlorine-containing resin emulsions are themselves acidic and are effective in accelerating the curing of inorganic zinc clinch paints.Moreover, unlike organic resin emulsions with phosphoric acid added, the acidic effect is sustained. be done.

Chlorine-containing resin emulsion paints also have excellent alkali resistance, chemical resistance, water resistance, salt water resistance, etc., and are not deteriorated by alkaline substances that are reaction products of zinc in zinc-rich paint coatings. Therefore, this paint stays firmly on the zinc-rich paint film, and the paint is sprayed easily.
Coupled with the zinc-rich paint coating, a sufficient anticorrosion effect can be achieved without causing peeling between the eyebrows.

The emulsion may contain kaolin, clay,
Fillers such as talc, silica powder, alumina, barium sulfate, etc., conventional coloring pigments, antifoaming agents, thickeners, surfactants, etc. can be added, and the paint can be applied by brushing onto the zinc-rich paint film. It is applied by conventional methods such as spray coating, roller coating, etc.

On the coating film of the chlorine-containing resin emulsion paint, if desired, a wide variety of paints can be applied as top coats, from conventional oil-based paints and phthalic acid-based paints to chlorinated rubber-based paints, epoxy-based paints, polyurethane-based paints, and tar-epoxy paints. The chlorine-containing resin emulsion still serves as a mist coat and etching primer, which are conventionally used to seal the surface of the zinc-rich paint coating, and when a top coat is applied, no foaming phenomenon is observed at all. It has also been found that excellent coating performance can be obtained.

As described above, in the present invention, when using an inorganic high-concentration zinc powder paint for corrosion prevention purposes, it is possible to accelerate the curing of the paint, soften the topcoat film due to the alkali content from the binder, prevent blistering of the paint film, and prevent interlayer adhesion. The use of a chlorine-containing resin emulsion solves all problems at once, including a wide selection of topcoats, and the prevention of foaming in the topcoat due to the porosity of the zinc-dusted paint film surface, which is simple and extremely effective. The present invention will be described in detail below with reference to Examples and Comparative Examples.

An inorganic zinc-rich paint coating was obtained as follows.

Blend 1 Sodium silicate aqueous solution (solid content 40%) 20 parts by weight Zinc powder 80 parts by weight Blend 2 Ethyl silicate aqueous solution (solid content 15%) 30 parts by weight Zinc dust 70 parts by weight 150 X 70 X 1.6 WII+1 Mild steel plate (JI
S-G-3141) by sandblasting to remove black skin, rust,
After completely removing the oil, the above formulation 1 or 2 was air-sprayed to a dry film thickness of 75±10μ, and dried at 20°C and 75% RH for 24 hours on the resulting coating film. The emulsion paints, mist coats, or etching primers of the following Examples and Comparative Examples were applied to the surface, and after drying at 20°C and 75RH for 4 hours, the following formulation 3 was applied.
．． Comparative tests were conducted by applying a conventional topcoat No. 4 or No. 5 and drying for 7 days.

Blend 3 (chlorinated rubber resin paint) Chlorinated rubber resin 30 parts by weight plasticizer
6 Titanium white 20 7 Lika 3 Anti-flow agent
1 Solvent 40 Formulation 4 (Epoxy resin paint) (Paint liquid) Solid epoxy resin 40 parts by weight (epoxy equivalent 450-500) Titanium white 28 Anti-settling agent
2 Solvent 30 Total 100 (Curing agent) Polyamide resin (amine value 250) 100 parts by weight Needle 100 (Mixing ratio)
Paint liquid/curing agent = 85/15 (weight ratio) combination 5 (
alkyd resin paint), alkyd resin 30 parts by weight titanium white
25 Heavy carbon 5 Dryer 1.0 Anti-skinning agent
1.0 Specialty 38.0 Example 1 Vinyl chloride/acrylic copolymer emulsion paint Bengara,
After dispersing the pigment components of talc and precipitated baryta in water, a vinyl chloride/acrylic copolymer emulsion (manufactured by BF Gutdrich, trade name Zeon 460 x 25, resin solid content 45 cm) was added and dispersed uniformly. In addition, a thickener (
ethyl cellulose) and antifoaming agent (N0PCO-NXZ
, manufactured by San Nopco Co., Ltd.) to obtain an emulsion paint (resin content: 45%, total solid content: 60%). p)l was 6.5.

This emulsion paint was applied onto the inorganic zinc-rich paint film of formulation 1 or 2, and heated at 20°C and 75°C.
After drying at RH for 4 hours, top coats of formulations 3 to 5 were applied. The resulting coating film was subjected to a comparative test.

Example 2 Vinyl chloride/vinylidene chloride copolymer emulsicon (1
, C, made by I company, ... Roflex 202) Surfactant (Emulgen PP-290 chemical soap, K.

After dispersion in water, add the above copolymer emulsion (resin solid content 60%) and make it uniform, then add a thickener (ethyl cellulose) and an antifoaming agent (NOPCO-NXZ, manufactured by San Nopco). , an emulsion paint was obtained. p
H was 4.5.

Coated on quality zinc rich paint film, 20℃, 75℃
After drying at RH for 4 hours, top coats of formulations 3 to '5 were applied. The resulting coating film was subjected to a comparative test.

Comparative Example 1 On top of the inorganic zinc rich paint film of Formula 1 or 2, the top coat of Formula 4 was diluted with thinner and applied once with 40% thinner solution and radish as a mist coat.
After drying at 0° C. and 75° RH for 4 hours, a top coat of formulation 4 was applied again for a comparative test.

・□Comparative Example 2 Etching primer (JIS K5633-1 type) was applied on the inorganic zinc rich paint film of formulation 1 or 2, and after drying at 20°C and 75% RH for 4 hours, a top coat of formulation 4 or 5 was applied. The paint was applied over and over again and subjected to a comparative test.

Comparative Example 3 A mixed paint mixture of 98 parts by weight of vinyl acetate emulsion (manufactured by Sekisui Kagaku Co., Ltd., trade name Nisudine 5520) and 2 parts by weight of 85% ornophosphoric acid was applied onto the inorganic zinc-rich paint film of formulation 1, and dried. A top coat of Post Formulation 4 was applied again and subjected to a comparative test.

The test results are shown in Table 1.

Table 1 Example 2 〃 〃 Blend 4 〃 Example 2 Blend 3 〃 Blend 4 〃 Blend 5 〃 Sickrich coating film and〃 Comparative example 2 Blend 4 Severe foaming Full-surface blistering Etched fryer / 47 squares V 7A/Arno r/+iL, 1st above
It is clear from the table that when a chlorine-containing resin emulsion is applied on a zinc-rich paint film according to the method of the present invention and a top coat is further applied, no foaming of the top coat is observed due to the pore-sealing effect of the chlorine-containing resin emulsion. , because it accelerates the curing of the zinc-rich paint, suppresses the alkaline content, and is not susceptible to deterioration due to alkaline substances, there is no blistering of the paint film, and no cohesive failure or adhesion failure between layers of the zinc-rich paint film is observed. Furthermore, it can be seen that various top coats can be applied safely.

Claims (1)

[Claims] An inorganic high-concentration zinc powder paint containing alkyl silicate or alkali silicate as a binder and zinc dust as an anticorrosion pigment is applied to the object to be coated, then a chlorine-containing resin emulsion is applied, and if necessary, a regular paint is applied. An anticorrosion coating method characterized by topcoating.