JP2006063106A - Coated film-peeling agent of steel structural material and method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a coated film-peeling agent of a steel structural material, excellent in penetrating property and releasing property against a corrosion proof or highly durable coated film. <P>SOLUTION: This peeling agent is obtained by using a dibasic acid ester as a main component, and blending a solvent having a high boiling point and selected from a heterocyclic ring-based organic compound and an alcohol, and a small amount of an organic acid and surfactant with the ester, wherein the heterocyclic ring-formed organic compound is NMP, DMI or DMSO (N-methyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone and dimethyl sulfoxide). Also as the alcohol, benzyl alcohol can be used. Further, the method for peeling the coated film is provided by applying the coated film-peeling agent obtained by using the dibasic acid ester as the main component, and blending the solvent having the high boiling point and selected from the heterocyclic ring-based organic compound and the alcohol, and the small amount of the organic acid and surfactant with the ester on the coated surface of the steel structural material, penetrating and swelling, and then peeling off the coated film. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention is a coating film for steel structures such as bridges and buildings using structural steel, and particularly a stripping agent suitable for stripping a coating film containing lead, chromium and other environmental pollutants, and a stripping method therefor It is about.

  In general, anticorrosion coating films for steel structures such as steel bridges need to be periodically repainted in order to repair deterioration over time. Usually, rust and deteriorated coating films are peeled off and repainted as a substrate preparation. In this case, the peeling range is small and partial, and is performed by a physical destructive force such as an electric sander as a coating film peeling method.

  In recent years, LCC (Life Cycle Cost) reduction has been demanded, and it is necessary to repaint to highly durable paint system C paint system (organic zinc paint, modified epoxy resin paint, thick film urethane resin paint), etc. Since it is necessary to remove harmful substances such as lead and chromium contained in the anticorrosion coating film, a technique for safely peeling and removing the entire existing coating film is required.

  Electric sanders are suitable for partial removal, but the treatment cost is high for the entire coating film, and because of the physical destructive power, harmful substances contained in the coating film are scattered in the air and rivers. There is a concern of causing pollution.

On the other hand, as disclosed in Japanese Patent Application Laid-Open No. 2004-133867, a wall coating film remover and method proposed by the applicant of the present application is known. By applying a coating film release agent comprising a mixture of either one or both of ethers as a main component and a high-boiling solvent such as NMP, esters, ketones, alcohols and the like and a surfactant in the ether, The coating is softened and peeled off.
Japanese Patent Laid-Open No. 10-279850

  However, since the above-mentioned prior art is intended for coating films of general buildings, A series, B series, which are known as anticorrosion (rust) and high durability coating applied to steel structures such as bridges, The D coating system (which will be described later) has the disadvantage that the permeability to the coating film is poor and the peeling is insufficient.

  In addition, there are some commercially available release agents for general building walls, but none of the anticorrosion coating films for outdoor steel structures can confirm the release performance that can be used practically.

  The release agent of the present invention for solving the above-mentioned problems is primarily composed of a dibasic acid ester as a main component, a high-boiling solvent selected from heterocyclic organic compounds and alcohols, and a small amount. It is characterized by comprising an organic acid and a surfactant.

  Second, the heterocyclic organic compound is NMP, DMI or DMSO.

  Third, the alcohol is benzyl alcohol.

  Fourth, the organic acid is characterized by comprising at least one selected from formic acid, lactic acid, citric acid, and sulfonic acid.

  Fifth, at least one of an inorganic thickener, a nonionic surfactant, or an anionic surfactant is added to increase the viscosity.

  Sixth, the inorganic thickener is bentonite or swellable silica.

  The method of the present invention comprises a coating comprising a dibasic acid ester as a main component, a high boiling point solvent selected from a heterocyclic organic compound and alcohols, a small amount of an organic acid and a surfactant. It is characterized in that the coating film is peeled off by applying a film peeling agent to the painted surface of the steel structure surface and allowing it to penetrate and swell.

  According to the stripping agent of the present invention configured as described above and the stripping method using the same, each coating film of A coating system, B coating system, and D coating system containing harmful substances of steel bridges and steel structures. Can be removed and recovered safely without being scattered in the air.

  There is no generation of coating film dust in the work environment, and worker safety can be secured.

  LCC of steel bridges and steel structures, which are social capital, is superior in terms of cost and safety compared to removal methods performed by physical destructive force such as electric sanders, without the effect of coating performance during repainting. Significantly contributes to reduction.

  Corrosion-resistant coating systems for steel structures subject to the release agent and the release method of the present invention include A coating system (long exposure etching primer, one lead-based rust-preventing paint, long oil phthalate resin paint), B coating system (long exposure etching primer, lead-based anticorrosion paint 1 type, phenol resin MIO coating, chlorinated rubber coating), D coating system (long exposure etching primer, tar epoxy resin coating 1 type).

  The release agent of the present invention mainly comprises a dibasic acid ester such as dimethyl phthalate or dimethyl adipate, and NMP (N-methyl-2-pyrrolidone), DMI (1.3-dimethyl-2-imidazo). A small amount of organic acid and nonion consisting of a heterocyclic organic compound such as lysinone) or DMSO (dimethyl sulfoxide) and a high boiling point solvent selected from alcohols such as benzyl alcohol, formic acid, lactic acid, citric acid, sulfonic acid, etc. A surfactant such as a surfactant and an anionic surfactant is blended.

  In addition to the above, the viscosity can be increased by adding any of inorganic thickeners such as bentonite and swellable silica.

  In developing the release agent of the present invention, screening was performed by applying 6 types of release agents already on the market to the coating systems A, B, D-1, and D-2 shown in the comparative experiments described later. As a result, it was found that the above-mentioned Patent Document 1 has relatively high availability. Based on this result, improvements were made to that of Patent Document 1, and in particular, the results of repeated selection of additives and changes in the amount added to increase the permeability of the release agent to the coating film and promote softening, Examples It became clear that the release agent shown to 1-3 etc. is effective.

  The coating film is peeled off by applying the coating film release agent to the painted surface of a steel bridge or other steel structure and softening and plasticizing the coating film to peel the coating film from the ground (background). By adding a small amount of the above high-boiling solvent and organic acid, the permeation swelling and thus the plasticizing and softening time can be drastically shortened.

More specifically, the above-mentioned release agent is applied to the coated surface of a steel structure composed of an A coating system, a B coating system, a D coating system, or the like at a rate of 1 Kg to 3 Kg per m ² using airless, brush or roller. The active ingredient of the release agent is attached to the coating film, penetrates into the coating film and swells, and remarkably reduces the adhesion to the substrate. Since the film thickness varies depending on the number of times of aging repair work, an appropriate amount is applied within a range of 1 kg to 3 kg per 1 m ² .

  The coating film of the steel structure whose adhesion is significantly reduced can be easily removed with a scraper. As a result, the coating film containing the toxic substance can be separated and recovered without being scattered in the air. In addition, the adhesion of the steel bolts, nuts and indented parts that are difficult to work with the scraper is reduced by the electric disc sander that rotates the wire brush according to the shape of the joining bolts, nuts, and indented parts. Remove the applied film.

  At this time, the electric disc sander that rotates the wire brush is also used on flat surfaces other than the steel plate's joining bolts, nuts, and recesses, so that the remaining long etching primer, residual release agent, and rust are simultaneously removed. This is effective as a base adjustment to ensure the adhesion of newly painted paint. Examples of the coating systems A, B, and D will be described below.

(1) Applicable coating system-A coating system (long-etch etching primer, 1 type lead-based rust-preventing paint, long oil phthalate resin paint)
(2) Release agent formulation Dibasic acid ester 87% by weight
NMP 10% by weight
Formic acid 2% by weight
Nonionic surfactant 1% by weight or less Anionic surfactant 1% by weight or less

(3) Method and Result The product of the present invention was applied to the painted surface in the morning using a roller, and the coating film was peeled off in the morning on the next day (after about 24 hours). The transferability from the roller was good and the coating work was easy and uniform. When observed the next day, the release agent softened and altered the coating and was swollen. The swollen coating film had almost no adhesion to the substrate and could be easily removed with a scraper. Parts that are difficult to work with the scraper, such as the joining bolt, nut, and recess of the steel plate, could be easily removed with an electric disc sander that rotates a wire brush in accordance with the shape of the joining bolt, nut, recess, and the like. After that, the electric disk sander was also applied to the entire plane removed by the scraper, and the C coating system with high durability coating specifications was applied. As for the coating film performance, there was no “blister” or “discoloration” in the subsequent evaluation, and there was sufficient adhesion.

  Compared to the conventional coating film removal technique that is performed only by physical destructive force such as an electric disc sander, the removed coating film can be collected without causing the coating film pieces containing harmful substances to scatter in the air. In addition, although work noise was generated when the last electric disk sander was used, it took less than 1/10 of the time required for the method for the entire coating film.

(1) Applicable coating system-B coating system (long-etch etching primer, phenol resin MIO coating, chlorinated rubber coating)
(2) Stripping agent dibasic acid ester 86% by weight
NMP 10% by weight
Lactic acid 3% by weight
Nonionic surfactant 1% by weight
Anionic surfactant 1% by weight
(3) Method and Result The method and the result are performed in the same manner as in the case of Example 1, and the results are also substantially common.

(1) Applicable coating system-D coating system (long-etch etching primer, tar epoxy resin paint 1 type)
(2) Release agent formulation Dibasic acid ester 65 wt%
Benzyl alcohol 10% by weight
NMP 20% by weight
Formic acid 4% by weight
Nonionic surfactant 1% by weight
Anionic surfactant 1% by weight
(3) Method and Result By a method common to Example 1, a substantially common result was obtained.

<Comparison experiment>
Next, a comparative experiment result of coating film peeling for each addition amount of the release agent additive and release agent application amount of the present invention will be described.
1. Peeling test period and location (1) Period: November 2003 to January 2004 (2) Location: Yamaichi Chemical Industry Co., Ltd. Nasu Factory Engineering Section Central Laboratory

2. Used release agent The one shown in Example 3 was used. However, the amount of additive was tested with various changes.

3. Used coating test board (painting system) (board size)
A. Coating system for outer surface ・ ・ ・ Phthalic acid paint ・ PA 10cm × 20cm
B. Exterior coating system: Chlorinated rubber coating, CR 10cm x 20cm
D-1. Coating system for inner surface: Modified epoxy paint (white) 7cm x 15cm
D-2. Internal coating system: Tar epoxy paint (black) 7cm x 15cm

4). Test Method and Evaluation Criteria (1) Method A release agent was applied to each coating type test plate A to D-2, allowed to stand for 20 hours, and the degree of softening of the coating film was confirmed using a stainless steel spoon.
Estimated temperature conditions of about 20 ° C during the daytime and 5-10 ° C during the nighttime

(2) Evaluation criteria

5. Test results

  In this example, if the additive is less than 1%, the effect is poor, and if it exceeds 10%, the peelability is not affected, but it has been found that the underlying steel surface may be oxidized. In addition, it is considered desirable for the coating system D-1 to change the number of application of the release agent from 1 to 2 in order to sufficiently perform the peeling.

Since the coating amounts of 500 g / m ² and 1000 g / m ² have almost no difference in peeling performance, it is considered that 500 g / m ² is sufficient in this example. Moreover, it is the result of having applied and peeled twice with respect to the same surface about D-1, and the peelability of the modified epoxy paint was also confirmed.

6). Overall review As it does not contain any chlorinated solvents, it has low skin corrosion, generation of steam, odor, etc., and has little impact on workers, surrounding residents, and the environment, ensuring high safety overall. it can.

  As for workability, since it is a soft paste and slow to dry, the time period for removing the coating film is long (2 to 3 days) after the application of the release agent, and the flexibility of setup is improved and the workability is improved overall.

As described above, the stripping agent and the coating film stripping method of the present invention are applied to the A coating system (long-etch etching primer, lead-based rust-preventing paint, long oil-based phthalate) used for anticorrosion coating of steel bridges and steel structures. Acid resin paint), B coating system (long exposure etching primer, 1 type lead rust prevention paint, phenol resin MIO coating, chlorinated rubber coating), D coating system (long exposure etching primer, 1 type tar epoxy resin coating) On the other hand, glycol ether having plasticizing and softening power penetrates and swells in the coating film using NMP and organic acid as a penetration accelerator. In addition, by using an electric disc sander that rotates the wire brush, the coating performance in repainting can be secured.

  The method of the present invention can be widely used for peeling coating films on steel structures such as steel bridges and steel buildings, regardless of whether they are used for railways, roadways, or sidewalks.

Claims (7)

  Coating remover for steel structure comprising dibasic acid ester as main component, high ester solvent selected from heterocyclic organic compound and alcohol, small amount of organic acid and surfactant. .   The coating film release agent for a steel structure according to claim 1, wherein the heterocyclic organic compound is NMP, DMI or DMSO.   The coating film stripping agent for a steel structure according to claim 1 or 2, wherein the alcohol is benzyl alcohol.   The coating remover for a steel structure according to claim 1, 2 or 3, wherein the organic acid is at least one selected from formic acid, lactic acid, citric acid and sulfonic acid.   The coating film release agent for steel structures according to claim 1, 2 or 3 or 4, wherein at least one of an inorganic thickener, a nonionic surfactant or an anionic surfactant is added to increase the viscosity.   The coating remover for a steel structure according to claim 5, wherein the inorganic thickener is bentonite or swellable silica.   A steel structure is a coating release agent comprising a dibasic acid ester as a main component, a high boiling point solvent selected from heterocyclic organic compounds and alcohols, a small amount of an organic acid and a surfactant. A method for removing a coating film from a steel structure, wherein the coating film is peeled off by being applied to a coated surface of the surface and then penetrating and swelling.