A stripping agent for corrosion-preventive coatings on steel structures and a method for stripping such coatings.

Abstract

Provided is an odorless, high-performance water-soluble release agent that contains no benzyl alcohol, has a high flash point or no flash point, has little impact on the human body and the environment, is easy to handle and is stable. [Solution] The release agent of the present invention consists of a composition that contains the following (a), (b) and (c), and does not contain a substantial amount of benzyl alcohol. (a) 95 to 10% by weight of ethylene, propylene or butylene glycol ether ester represented by the following formula I TIFF2026146998000007.tif29170 (In the above formula, R 1 is independently a C1-C4 alkyl group, R 2 is independently hydrogen, methyl or ethyl, R 3 is independently a C1-C4 alkyl group, and n is 1 to 4) (b) 0 to 30% by weight of an organic protic solvent (c) 5 to 80% by weight of water. The release method is a method in which a release agent is applied to the coating surface of an anticorrosive coating film of a steel structure, and the coating film is swollen and softened to be removed.

Description

[Technical Field]

[0001] The present invention relates to a corrosion-resistant coating remover suitable for repainting steel structures for corrosion prevention purposes, and a method for removing such corrosion-resistant coatings. [Background technology]

[0002] When removing old paint from steel structures for repainting, paint strippers have been used to ensure worker safety and reduce labor. As shown in Non-Patent Documents 1, 2, and 3, these paint strippers are mainly water-based paint strippers with benzyl alcohol as the main component. [Prior art documents] [Non-patent literature]

[0003] [Non-Patent Document 1] https: / / www.sankyo-chem.com / products / repairsolve-s / 「リペアスープブS」 [Non-Patent Document 2] https: / / www.yk-world.com / topics / 877 / 「バントレ」 [Non-Patent Document 3] https: / / www.sansai.com / feature / doro_bridge / index.html "Mud Pack" [Overview of the project] [Problems that the invention aims to solve]

[0004] In addition to the above, many stripping agents containing benzyl alcohol as an active ingredient have been developed in recent years. Stripping agents containing benzyl alcohol contain approximately 50 percent water and are classified as non-hazardous materials under the Fire Service Act. Therefore, although it poses a low risk under the Fire Service Act, it contains a large amount of benzyl alcohol, leading to a high incidence of accidents due to organic solvent poisoning. For this reason, the use of more stringent protective equipment is mandatory compared to paint strippers that do not contain benzyl alcohol. Furthermore, there are concerns that its classification as a non-hazardous material under the Fire Service Act leads workers to be overly concerned with safety, making them more likely to underestimate the risks of organic solvent poisoning and fire. For this reason, there is an urgent need for paint stripping methods that do not use paint strippers with benzyl alcohol as the main ingredient.

[0005] To address the above-mentioned problems, this invention provides an odorless, high-performance, water-soluble stripping agent that does not contain benzyl alcohol, has no high flash point or flash point, has minimal impact on the human body and the environment, is easy to handle, and is stable. [Means for solving the problem]

[0006] The stripping agent of the present invention, which solves the above problems, is characterized by comprising, firstly, the following (a), (b), and (c), and not containing a substantial amount of benzyl alcohol. (a) 95-10 w% of the following ethylene, propylene, butylene glycol ether ester of formula I. [ka] (In the above formula, R 1 R is independently a C1-C4 alkyl group. 2 R is independently hydrogen, methyl, and ethyl. 3 (where n is independently a C1-C4 alkyl group, and n is 1-4) (i) 0-30 w% organic protic solvent (c) 5-80% water

[0007] Secondly, the organic protic solvent is characterized by being an alcohol having 3 to 18 carbon atoms.

[0008] Thirdly, it is characterized by the addition of a thickening agent or gelling agent to improve its applicability and workability.

[0009] Furthermore, a method for peeling an anticorrosive coating of a steel structure according to the present invention firstly comprises, with respect to the coated surface of the anticorrosive coating of the steel structure, a composition that does not contain a substantial amount of benzyl alcohol, (a) 95 to 10% by weight of ethylene, propylene, or butylene glycol ether ester of the following formula I [Chemical Formula] (In the above formula, R 1 is independently a C1-C4 alkyl group, R 2 is independently hydrogen, methyl or ethyl, R 3 is independently a C1-C4 alkyl group, n is 1 to 4), and (b) 0 to 30% by weight of an organic protic solvent, and (c) 5 to 80% by weight of water, the method is characterized by applying the release agent for an anticorrosive coating of a steel structure, swelling and softening the coating, and peeling and removing the coating.

[0010] Secondly, the coating is characterized by being a coating system using a long-term etching primer, a lead-based antirust paint, and a long-oil phthalic acid resin paint.

[0011] Thirdly, the coating is characterized by being a coating system using an organic zinc-rich primer, a modified epoxy resin paint, and a chlorinated rubber-based paint. Effects of the Invention

[0012] According to the release agent for anticorrosive coating of a steel structure and the peeling method of the present invention configured as described above, when peeling the coating of a steel structure such as a railway or road bridge, the release agent does not contain benzyl alcohol that is harmful to the human body, so there is no problem with the use of conventional protective equipment, and the construction efficiency is high, so low cost can be achieved.

[0013] In addition, since the coating can be swollen and softened by applying the release agent and then mechanically peeled and recovered, it will not be dissolved and flowed out into the installation environment of the steel structure, and no load such as environmental pollution will occur. Brief Description of the Drawings

[0014] [Figure 1] (A) and (B) are tables showing the paint and film thickness of each layer constituting the phthalate-based coating and the chlorinated rubber-based coating that are peeled off in the embodiments of the present invention. [Figure 2] This table shows the peeling results after applying the peeling agent according to the present invention (product of the present invention) and existing peeling agents a to f to each of the above coating films, and after 1 day (24 hours) or 2 days (48 hours) have elapsed. [Figure 3] This photograph shows the peeling results when the present invention is applied to a phthalate-based coating. [Figure 4] (A) and (B) are photographs showing the peeling state when a chlorinated rubber coating is peeled off using the product of the present invention. (A) shows the peeling result after 2 days, and (B) shows the peeling result after 1 day. The labels at the bottom of the photographs are the test numbers shown in Figure 2 (these are common to Figures 5 to 10 below). [Figure 5] (A) and (B) are both photographs showing the peeling state after 2 days or 1 day, respectively, of the existing peeling agent a applied to a chlorinated rubber coating. [Figure 6] (A) and (B) are both photographs showing the peeling state after 2 days and 1 day, respectively, of the existing peeling agent b applied to a chlorinated rubber coating. [Figure 7] (A) and (B) are both photographs showing the peeling state after 2 days and 1 day, respectively, of the existing release agent c applied to a chlorinated rubber coating. [Figure 8] (A) and (B) are both photographs showing the peeling state after 2 days or 1 day, respectively, of the existing peeling agent d applied to a chlorinated rubber coating. [Figure 9] (A) and (B) are both photographs showing the peeling state after 2 days or 1 day, respectively, of the existing peeling agent e applied to a chlorinated rubber coating. [Figure 10] (A) and (B) are both photographs showing the peeling state after 2 days or 1 day, respectively, of the existing peeling agent f applied to a chlorinated rubber coating. [Figure 11] (A) and (B) are sample photographs showing the cross-sections of phthalate-based and chlorinated rubber-based coatings applied to the surface of a steel plate, which were then polished in a circular pattern to reveal the circular core of each coating. [Figure 12]It is a comparative table evaluating the safety of conventional release agents a, b, d, f and the product of the present invention. DESCRIPTION OF EMBODIMENTS

[0015] Hereinafter, embodiments of the present invention will be described in detail. The present invention provides a release agent and a release method that are a composition effective for peeling and removing anticorrosive coatings on steel structures such as steel bridges, contain the following (a), (b) and (c), do not contain a substantial amount of benzyl alcohol, have excellent peeling and removal efficiency, and are highly safe in all aspects. (a) 95 to 10% by weight of ethylene, propylene and butylene glycol ether esters represented by the following formula I Chemical Formula (In the above formula, R 1 are each independently a C1-C4 alkyl group, and R 2 are each independently hydrogen, methyl or ethyl, and R 3 are each independently a C1-C4 alkyl group, and n is 1 to 4) (b) 0 to 30% by weight of an organic protic solvent (c) 5 to 80% by weight of water Preferably, the release agent contains an effective amount of ethylene, propylene and butylene glycol ether esters, 10% or more of water is added to make the release agent non-flammable and facilitate the application of an appropriate amount of the solvent, and the release agent is appropriately thickened with a water-soluble thickener, for example, natural polymer derivatives or alkali metal salts or ammonium salts of polyacrylates.

[0016] The present invention further peels and removes the anticorrosive coating on steel structures such as steel bridges from steel materials by applying the composition of the present invention to the anticorrosive coating on steel structures such as steel bridges.

[0017] In this invention, when the ethylene, propylene, and butylene glycol ether ester of formula I is used in combination with the water or water and a water-soluble thickener described above, not only is there no deterioration in permeability due to water or thickener, but it exhibits even greater permeability. Therefore, the penetration swelling time required for the peeling and removal of the anticorrosive coating on steel structures such as steel bridges is shortened compared to when the ethylene and propylene glycol ether ester of formula I are used alone, even when water is added and thickener is used.

[0018] This composition comprises (a) 95 to 10, preferably 90 to 30 weight percent of ethylene, propylene, and butylene glycol ether esters of formula I; (b) 0 to 30, preferably 0 to 20 weight percent of an organic protic solvent; and (c) 5 to 80, preferably 10 to 70 weight percent of water.

[0019] In equation I, R 1 R is independently a C1-C4 alkyl group. 2 R is independently hydrogen, methyl, or ethyl. 3 R is an independent C1C4 alkyl group, and n is 1 to 4. 1 R 3 The alkyl group may be branched or unbranched. Examples of this alkyl group are methyl, ethyl, n-propyl, isopropyl, n-butyl, or isobutyl. Of the propyl and butyl groups, n-propyl and n-butyl are preferred in terms of the balance of osmosis and solubility. The most preferred ethylene, propylene, and butylene glycol ether esters of formula I are R 1 , R 2 R 3 It is a methyl compound.

[0020] R 2 Each is independently hydrogen, methyl, or ethyl. From the viewpoint of toxicity, R is preferred. 2 is methyl. n is 1 to 4, preferably 1 or 2.

[0021] Preferred examples of ether esters of formula I are dipropylene glycol monomethyl ether methyl ester, dipropylene glycol monoethyl ether methyl ester, dipropylene glycol monobutyl ether methyl ester, diblethin glycol monomethyl ether methyl ester, diblethin glycol monoethyl ether methyl ester, and diblethin glycol monobutyl ether methyl ester.

[0022] This composition contains the amount of organoprotic solvent indicated above. Effective organoprotic solvents include, for example, alcohols, saturated open-chain or cyclic alcohols, preferably propanol, e.g., n-propanol or isopropanol; butanol, e.g., n-butanol or i-butanol; hexanol, e.g., n-hexanol or cyclohexanol; heptanol; octanol; decanol; dodecanol, e.g., lauryl alcohol; or octadecanol, e.g., stearyl alcohol; or unsaturated alcohols, preferably allyl or furfuryl alcohol. These alcohols preferably have 3 to 18 carbon atoms. Other effective alcohols include glycols or glycol monoethers, preferably propylene or butylene glycol or glycol monoethers. For example, propylene glycol, dipropylene glycol, butylene glycol, dibutylene glycol, propylene glycol methyl ether, propylene glycol n-butyl ether, dipropylene glycol methyl ether, or dipropylene glycol n-butyl ether. Mixing different organic protic solvents for purposes such as water solubility is also effective, but the total amount should be within the range shown in component (a) of the composition of the present invention.

[0023] The composition of the present invention contains water and, optionally, an organic protic solvent in the amounts indicated above. The composition of the present invention does not necessarily have to contain an organic protic solvent, but the total amount of components (a) and (c) is 5 to 80 percent, preferably 15 to 70 percent, based on the total weight of (a), (b), and (c).

[0024] In this invention, thickeners or gelling agents can be added to improve applicability and workability. For example, organic options include hydroxypropylcellulose, methylcellulose, polyacrylic acid and its alkali metal salts or ammonium salts, or paraffin wax; and inorganic options include kaolin, bentonite, and swellable silica.

[0025] Other desired additives include esters of polycarboxylic acids, such as esters of oxalic acid, malonic acid, succinic acid, glutaric acid, or adipic acid.

[0026] The composition of the present invention is effective in removing, for example, the corrosion-preventive coating film on steel structures such as steel bridges from the steel material. This corrosion-preventive coating film consists of various components, such as known chlorinated rubber, phthalic acid resin, or lead-containing rust-preventive paint.

[0027] In using the composition of the present invention for stripping and removing anticorrosive coatings from steel structures such as steel bridges, the composition is applied to the target surface and allowed to come into contact with the surface for a sufficient time to substantially swell and soften the layer to be removed. The composition may be applied to the target surface by conventional methods, such as roller application, brush application, or spray application. The thickness of the applied composition is usually 0.3 to 5 mm, preferably 0.5 to 1 mm. The time the product is left to stand depends on many factors, such as the type of anticorrosive coating and the thickness of the coating due to previous repainting. Typically, at the steel surface temperature and the ambient temperature of the work site, it takes about 24 to 48 hours for the anticorrosive coating to substantially swell and soften.

[0028] After applying this composition to the surface of a corrosion-preventive coating on a steel structure to swell and soften it, the composition and the softened corrosion-preventive coating are removed by known methods, such as hand tools, power tools, or lasers.

[0029] Next, the method and results of an experiment to remove a coating applied to a steel surface using the release agent of the invention are shown below as examples.

[0030] [Examples] Figures 1(A) and 1(B) are tables showing the coating specifications for the phthalate-based coating (Example 1) and chlorinated rubber-based coating (Example 2) applied to the surface of the steel material (not shown) targeted for stripping in Examples 1 and 2, respectively. In both cases, the top column of the table indicates that the coatings are applied sequentially from primer to topcoat, and the right column shows the target film thickness for each layer. Both coatings are corrosion-resistant and durable coatings commonly used on steel structures such as bridges.

[0031] Figure 2 is a table showing the results of evaluating the peelability state due to swelling after a predetermined time (1 day and 2 days) when the release agent according to the present invention and existing release agents indicated by a to f were applied to each coating film of Example 1 and Example 2 described above.

[0032] In Figure 2, A and B correspond to the phthalate-based coating and chlorinated rubber-based coating film in Figure 1 (A) and (B), respectively. Furthermore, the numbers A1, B1, and B2 indicate the number of days elapsed after applying a release agent to the coating film shown in A and B above, either 1 day (24 hours) or 2 days (48 hours).

[0033] Furthermore, a to f represent commercially available release agents that are comparable to the release agent of the present invention ("the product of the present invention"), and their breakdown is as follows. However, a was commercialized through joint research between the applicant and the Public Works Research Institute (an independent administrative agency) and is positioned as the standard product to date, while d to f have benzyl alcohol as their main component. a. InviroOne: Patent numbers 3985966 and 5534233 b. Skeleton AQS: Natco c. Limron Eco: AGUA JAPAN d. RepairSolve S: Sankyo Chemical e. Pantore: Yoshikawa Sangyo f. Mud Pack: Sansai Chemical

[0034] In Figure 2, double circles indicate peeling down to the primer, single circles indicate peeling within the intermediate coat, and black triangles indicate peeling at both the undercoat and intermediate coat. Since all phthalate-based paints peeled down to the primer layer within one day with all stripping agents, the two-day peeling experiment was omitted.

[0035] As shown in Figure 2, for phthalic acid-based coating films, the product of the present invention and existing products a, d to f can be peeled off to the primer layer in one day, except for whether they contain benzyl alcohol. In contrast, for chlorinated rubber-based coating films, only the product of the present invention can be peeled off to the primer layer on the second day.

[0036] Figures 3 to 10 are photographs comparing and showing the peeling results when the product of the present invention and commercially available conventional strippers a to f are applied to phthalic acid-based coating films and chlorinated rubber-based coating films for peeling. The indications [A1-Original] to [B1-f] shown at the bottom of each photograph correspond to the test numbers in the table of Figure 2. Among the test numbers shown in the table of Figure 2, the photographs corresponding to test numbers [A1-a] to [A1-f] of the experiment (Example 1) on phthalic acid-based coating films have the same results as the photograph in Figure 3, so their attachment as drawings is omitted. In addition, the test of leaving for 2 days after coating is also unnecessary, so it is omitted.

[0037] As shown in the above photographs, in Example 1, for phthalic acid-based coating films, a sufficient peeling effect due to swelling and softening is recognized one day after coating (this point is the same as existing strippers a to f). In addition, as shown in Figure 4 (A) and (B), in Example 2 for chlorinated rubber-based coating films, although peeling could not be achieved after 1 day, sufficient peeling up to the primer layer was recognized after 2 days.

[0038] In contrast, as shown in Figure 5 (A), (B) to Figure 10 (A), (B), conventional coating strippers a to f could not achieve sufficient peeling up to the primer layer on both the first day and the second day, whereas the difference in peeling superiority achieved by the product of the present invention was confirmed.

[0039] In addition, Figure 11 (A) and (B) show the coating surfaces of phthalic acid-based and chlorinated rubber-based, which are scraped into a circular shape with sandpaper, and ground deeper at the center and sequentially shallower toward the outer periphery. It shows that the center is the primer layer, and cross sections of the top coat layer are sequentially exposed toward the outer periphery. Each coating layer on the steel plate in Figure 11 (A) and (B) corresponds to the five coating layers in Figure 1 (A) and (B).

[0040] Figure 12 is a table comparing the safety of the conventional stripping agents a, b, d, and f with the product of the present invention, showing a comparison of hazard (safety) evaluations based on the components contained in each stripping agent according to the GHS classification (Globally Harmonized System of Classification and Labelling of Chemicals).

[0041] As shown in the figure, while stripping agents a to f are required to display many hazardous material indications under GHS categories 1 to 4 in various systems or fields related to the human body, the present invention has no obligation to display hazardous material indications except for being classified as category 2B for damage to or irritation to the eyes.

[0042] Furthermore, regarding the disclosure requirements under domestic laws and regulations shown in the lower section of the comparison table in Figure 12, there are no mandatory restrictions except for the requirement to notify if the crystalline silica content is 0.1 wt% or more, and in this respect as well, its high level of safety is highly regarded.

Claims

1. A stripping agent for corrosion-preventive coatings on steel structures, comprising a composition containing (a), (b), and (c) below, and not containing substantially any amount of benzyl alcohol. (a) 95-10 wt% of the following ethylene, propylene, butylene glycol ether ester of formula I. 【Chemistry 1】 (In the above formula, R 1 C 1 ~C 4 R is an alkyl group 2 R is independently hydrogen, methyl, and ethyl. 3 C 1 ~C 4 (It is an alkyl group, and n is between 1 and 4.) (i) 0-30 w% organic protic solvent (c) 5-80 wt water

2. The corrosion-preventive coating stripper for steel structures according to claim 1, wherein the organic protic solvent is an alcohol having 3 to 18 carbon atoms.

3. A stripping agent for corrosion-preventive coatings on steel structures according to claim 1, wherein a thickening agent or gelling agent is added to improve the applicability and workability.

4. The composition consists of a coating that does not contain a substantial amount of benzyl alcohol on the surface of the corrosion-preventive coating of steel structures. (a) 95-10 wt% of the following ethylene, propylene, butylene glycol ether ester of formula I. 【Chemistry 2】 (In the above formula, R 1 is independently C 1 to C 4 alkyl group, R 2 is independently hydrogen, methyl or ethyl, and R 3 is independently C 1 to C 4 alkyl group, n is 1 to 4), and (i) 0-30 w% organic protic solvent, (c) A method for removing corrosion-preventive coatings from steel structures, comprising applying a coating remover for steel structures containing 5-80 wt% water, thereby swelling and softening the coating and allowing it to peel off.

5. A method for removing a corrosion-preventive coating from a steel structure according to claim 4, wherein the coating system comprises a long-exposure etching primer, a lead-based rust-preventive paint, and a long-oil phthalic resin paint.

6. A method for removing a corrosion-preventive coating from a steel structure according to claim 4, wherein the coating system comprises an organic zinc-rich primer, a modified epoxy resin coating, and a chlorinated rubber coating.

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