KR20130094871A - Coating removal method for steel structure - Google Patents

Abstract

PURPOSE: An exfoliation method of a steel structure is provided to be able to safely remove each coated layer of A paint system, B paint system, and D paint system which include harmful materials of the steel structure without scattering in the air. CONSTITUTION: An exfoliating method of a steel structure comprises s step of coating a paint film exfoliating agent including a solvent with a high boiling point solvent, 2-10 weight% of organic acid, and surfactant, on a coating layer of a coating film with etching resistance and high durability for a steel structure comprising a paint system using any one selected from wet urethane type 1, moisture-curable urethane 3, aqueous acryl, acryl-urethane, thick film epoxy, polyester powder paint, siloxane finishing paint, and fluorine resin finishing paint, expanding the film by penetrating the paint exfoliation agent into the coating film, and exfoliating the coated layer by lowering the adhesiveness and lowering adhesiveness to the background with the plasticizing.

Description

COATING REMOVAL METHOD FOR STEEL STRUCTURE}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for peeling a coating film of a steel structure such as a bridge or a building, and more particularly, to a peeling method suitable for peeling a coating film containing lead, chromium, or other environmental pollutants.

In general, a corrosion resistant coating film of a steel structure such as a bridge requires regular repainting in order to repair deterioration with time, and normally, after ground clearing, rust and deterioration coating film are peeled off and repainted. In this case, the peeling range is small and partial, and is performed by physical destructive force, such as an electric grinder, as a coating film peeling method.

Recently, the life cycle cost (LCC) reduction is required, and the coating film of C-based coating system (organic zinc ridge paint, modified epoxy resin paint, thick film urethane resin paint) of high durability coating system Due to the necessity of replacement, the need to remove harmful substances such as lead or chromium (chromium) contained in the corrosion resistant coating film, a technique for safely peeling off the entire existing coating film is required.

Transmission equipment is a suitable means for partial removal, but in the case of covering the entire coating film, the treatment cost is high and it is carried out by physical destructive force. Therefore, the harmful substances contained in the coating film are splashed in the air or in rivers and everywhere. There is a risk of occurrence.

Accordingly, as a peeling method of the wall coating film, a main component is a mixture of any one or both monoalkyl glycol ethers and dialkyl glycol ethers on the painted surface of a general building wall surface, and NMP, esters, The method of softening and peeling a coating film is proposed by apply | coating the coating film peeling agent which mix | blended high boiling point solvents, such as ketones and alcohols, and surfactant.

However, since the conventional technique is intended for coating films of general buildings, the penetration into the coating film is poor for A-, B- and D-based coating systems known as corrosion resistance and high durability coating applied to steel structures such as bridges. There is a drawback of insufficient peeling.

Japanese Patent Laid-Open No. 10-279850

The present invention is to solve the problems of the prior art described above, the object of the present invention is to safely remove each coating film of A coating system, B coating system, D coating system containing harmful substances of steel structure without scattering in the air. It is possible to provide a method of peeling the film.

In order to solve the above-mentioned problems, the peeling method of this invention uses the high boiling point solvent which consists of benzyl alcohol, the 2-10 weight% organic acid, and the coating film peeling agent which mixes surfactant with the moisture urethane type 1, moisture hardening type. Urethane 3, water-soluble acrylic, acrylic-urethane, thick film type epoxy, polyester powder paint, siloxane finish paint, fluorine resin finish paint It is applied to a coating surface of the film, and penetrates into the coating film, thereby expanding and plasticizing the coating film, thereby lowering the adhesion to the substrate, thereby deteriorating the corrosion resistance and high durability coating film of the steel structure which peels the coating film.

In addition, the organic acid is characterized in that any one of formic acid, lactic acid, citric acid.

Here, the surfactant is characterized in that the nonionic surfactant or anion (ionic) surfactant.

In this case, an inorganic thickener made of bentite or expandable silica is added and thickened.

According to the peeling method of the present invention, it is possible to safely remove and recover the angular film of the A coating system, the B coating system, and the D coating system containing harmful substances of the steel bridge and the steel structure in the air.

In addition, no coating film dust is generated in the working environment, and worker safety can be ensured.

In addition, it has no effect on the coating performance during repainting, and is superior in cost and safety compared to the removal method performed according to physical destructive force such as electric grinder, and contributes greatly to reducing LCC of steel bridges and steel structures, which are social capital. do.

As a corrosion-resistant coating system for steel structures which are the object of the peeling method of this invention, A coating system (long and thin form etching primer, lead type antirust agent paint, oil-based phthalic-acid paint), B coating system (long and thin form) Etch primer, lead-based rust preventive paint, phenol resin MIO paint, rubber chloride paint), and D paint system (long and thin form etching primer and tar epoxy resin paint).

The release agent used for this invention has dibasic acid ester, such as dimethyl phthalate and dimethyl adipic acid, as a main component, for example, NMP (N-methyl (methyl) -2-pyrroli). Pyrolidone), a small amount of organic acids, nonionic surfactants and anions consisting of a high boiling point solvent selected from alcohols such as benzyl alcohol, formic acid, lactic acid, citric acid, etc. It is compounding surfactant, such as anion-type surfactant.

In addition to the above, any one of an inorganic thickener made of bentite, expandable silica, or the like may be added and thickened.

In the development of the peeling agent used for this invention, when 6 types of peeling agents which are already commercially applied were applied to the coating systems A, B, D-1, and D-2 shown by the comparative experiment mentioned later, and screening was carried out conventionally, It was found to be relatively more available than technology. On the basis of these results, improvements in the prior art are added, and in particular, the selection of additives for increasing the permeability of the release agent to the coating film and the selection of additives for changing the amount of addition and the change of the amount of addition are repeated. Turned out.

Peeling of a coating film is performed by apply | coating the said coating film peeling agent to the coating surface of a steel bridge and other steel structures, and peeling a coating film from a base by softening and plasticizing a coating film. By adding a small amount of the high boiling point solvent and the organic acid, the penetration expansion as well as the plasticization softening time can be drastically shortened.

More specifically, 1 kg to 3 kg per 1 m 2 of the above-mentioned release agent is applied to the coated surface of the steel structure including A coating system, B coating system, D coating system, etc. using an airless or brush or roller. The active ingredient of the releasing agent is in a state of adhering to the coating film, and permeates and expands in the coating film, thereby significantly lowering the adhesion to the base. Since the film thickness changes in accordance with the frequency | count of implementation of deterioration repair work, application amount is apply | coated appropriate amount within the range of 1 kg-3 kg per 1m <2>.

The coating film of the steel structure in which the adhesive force falls remarkably can be easily removed with a scraper. As a result, the coating film containing the hazardous substance can be separated and recovered without scattering in the air. In addition, the parts which are difficult to work with a scraper such as the joining bolt and nut part of the steel sheet, and the press-fitting mark part may be coated with an electric grinder which rotates a wire brush suitable for the shape of the joining bolt and nut part, the press-fitting mark part, or the like. Remove

At this time, the electric grinder which rotated the wire brush can also be used for the plane other than the joining bolt and nut part of a steel plate, an indentation part, etc., and it can remove a little long thin form etching primer, residual peeling agent, and rust simultaneously. It is effective as a background adjustment for securing the adhesive force of the coating material to apply. Hereinafter, the Example about each coating system of A, B, and D is demonstrated.

Example 1

(1) Target coating system: A coating system (long thin etch primer, lead-based rust preventive paint, oil-based phthalic resin paint)

(2) release agent

87% by weight of dibasic acid ester

NMP 10 wt%

Formic acid 2% by weight

1% by weight or less of nonionic surfactant

Less than 1% by weight of anionic surfactant

(3) Method and result

This invention product was apply | coated to the coating surface using the roller, and the coating film peeling was performed the next day (after about 24 hours). Transferability from a roller was also easy to work, and uniform coating work was possible. As a result of observation on the following day, the release agent softened and deteriorated the coating film and expanded. The expanded coating film had almost no adhesion to the base and could be easily removed with a scraper. Sites that were difficult to work with scrapers such as joining bolts, nuts and press marks on steel sheets could be easily removed by electric grinders in which wire brushes were rotated to fit the shapes of joining bolts, nuts and press marks. Then, the electric grinder was performed also to the whole plane removed with the scraper, and the C coating system of the high durability coating specification was applied. Regarding the coating performance, there was no apparent swelling, discoloration, etc. in the subsequent evaluation, and there was sufficient adhesion.

Compared with the conventional film removal technique performed only by physical destructive force such as an electric grinder, the removal coating film can be recovered without scattering the debris containing the harmful substances in the air. In addition, the working noise is generated when the last electric grinder is used, but it ends in less than 1/10 of the time compared to the method of covering the entire coating film.

[Example 2]

(1) Target coating system-B coating system (long and thin etching primer, lead-based rust preventive paint, phenol resin MIO paint, chlorinated rubber paint)

(2) release agent

Dibasic acid ester 82% by weight

NMP 10 wt%

Lactic acid 3% by weight

3% by weight of nonionic surfactant

3% by weight of anionic surfactant

(3) Method and result

It carried out by the method similar to the case of Example 1, and obtained substantially common results.

[Example 3]

(1) Target coating system -D coating system (long thin form etching primer, tar epoxy resin coating one kind)

(2) release agent

67% by weight of dibasic acid ester

Benzyl alcohol 10% by weight

NMP 18 wt%

Formic acid 4% by weight

1% by weight of nonionic surfactant

1% by weight of anionic surfactant

(3) Method and result

By a method common to Example 1, substantially common results were obtained.

Next, the comparative experiment result of coating film peeling for every addition amount of the additive of the releasing agent of this invention, and releasing agent application quantity is shown.

1.Release test conduct period and conduct place

(1) Implementation period: 2011 10. ~ 2012. 02

(2) Implementation place: Korea Expressway Corporation structure center laboratory

2.used release agent

What was shown in Example 3 was used. However, the amount of the additive was changed and tested, respectively.

3. Used paint test

A. Moisture hardening type Urentan 1

B. Moisture-curable Urentan 3

C. Water Soluble Acrylic

D. Acryl Urethane

E. Thick Film Epoxy

F. Polyester Powder Coating

G.siloxane Urethane Finish

H.siloxane Finish

I. Fluorine Resin Finish

4.Test Methods and Evaluation Criteria

(1) Method

The release agent was applied to the test plates A to I of the respective coating systems and, after standing for 20 hours, the degree of softening of the coating film was confirmed.

Temperature condition: estimated at around 20 ℃ during the day, 5-10 ℃ at night

5.Test result

In this test example, when the additive was less than 1%, the effect was insufficient, and when it was more than 10%, the peelability was not affected, but it was found that the possibility of oxidizing the base steel surface occurred.

Since the coating amounts of 500 g / m 2 and 1000 g / m 2 have almost no difference in peeling performance, in this example, 500 g / m 2 is considered to be sufficient.

6.General comment

Regarding safety, it does not contain any chlorine-based solvents, so that it is low in corrosion of skin, generation of vapor, odor, and the like.

In terms of workability, since drying is slow in a soft paste form, the time taken for removing the coating film after the release of the release agent is long (2 to 3 days), the flexibility of the procedure is improved and the workability is comprehensively improved.

Claims (4)

The coating film release agent which mix | blends the high boiling point solvent which consists of benzyl alcohol, 2-10 weight% organic acid, and surfactant, is moisture urethane type 1, moisture hardening type urethane 3, water-soluble acrylic, acryl- urethane type, thick film type epoxy type, It is applied to the coating surface of the corrosion-resistant and high-durability coating film for steel structures made of a coating system using any one selected from the group consisting of polyester powder coating, siloxane finish coating, and fluororesin finishing paint, and infiltrate the coating film to expand the coating film. The coating film peeling method of the steel structure characterized by plasticizing and peeling a coating film by reducing the adhesive force to a base.
The method of claim 1, wherein the organic acid is any one of formic acid, lactic acid, and citric acid.
The method of claim 1 or 2, wherein the surfactant is a nonionic surfactant or an anionic surfactant.
The coating film peeling method of a steel structure according to any one of claims 1 to 3, wherein an inorganic thickener made of bentite or expandable silica is added and thickened.