Coating stripping composition and coating stripping method

Abstract

To provide a water-based paint-type coating stripping composition and a coating stripping method which can reduce the risk of fire, health hazards, etc. in a coating stripping process and exhibit stripping properties equal to or better than those of solvent-based stripping agents. The coating stripping composition has a pH in the range of 5 to 9 and contains water, benzyl alcohol, and at least one cellulose derivative.

Description

[Technical field]

[0001] The present invention relates to a coating stripping composition and a coating stripping method used in a process for stripping old coatings from steel road bridges, buildings, vehicles, aircraft, and the like. [Background technology]

[0002] Repainting of paint films on bridges and other structures is carried out for the purposes of replacing them with paint films with a longer lifespan in order to reduce the frequency of maintenance, or to remove harmful substances contained in old paint films (hexavalent chromium, lead, PCBs).

[0003] When repainting an old coating film, it is necessary to remove the old coating film. Physical removal methods such as blasting are used to remove the coating film. However, there are concerns that the blasting method will increase the amount of waste and cause damage to workers and the surrounding environment due to dust. In order to solve these problems, a method has been implemented in which a coating film remover containing a chlorine-based solvent such as dichloromethane as the main ingredient (Patent Document 1). However, the use of chlorine-based solvents is restricted due to the impact on the human body and the environment, and currently, non-chlorine-based removers that use various solvents that do not use chlorine-based solvents have been developed.

[0004] Patent Document 2 discloses a method using N-methylpyrrolidone as a non-chlorine based paint stripper.

[0005] Patent Document 3 discloses a W / O type emulsion composition which contains ethyl cellulose, an oil phase containing a solvent capable of swelling ethyl cellulose, and an aqueous phase containing a water-soluble polymer, and which has emulsion stability due to the ethyl cellulose and the water-soluble polymer, but there is no mention of coating film peeling, and the composition is used as a cosmetic. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 5-171076 [Patent Document 2] Japanese Patent Application Publication No. 5-279607 [Patent Document 3] Patent No. 3549995 Summary of the Invention [Problem to be solved by the invention]

[0007] Water-free, non-chlorine-based paint strippers have high stripping performance, but they have problems with fire hazards, complicated cleaning processes after stripping, and worker safety issues due to the large amount of harmful solvents they contain.

[0008] The main object of the present invention is to provide an aqueous paint-type coating stripping composition and a coating stripping method that reduce the risks of fire, health hazards, etc. in the coating stripping process and exhibit stripping properties equal to or greater than those of solvent-based strippers. [Means for solving the problem]

[0009] In order to solve the above problem, the present inventors have attempted to emulsify aromatic alcohol solvents, which are effective for coating film stripping, using surfactants such as polyoxyethylene alkyl ethers, but have found that they do not exhibit sufficient emulsifying properties. However, they have found that the use of cellulose derivatives not only increases viscosity but also exhibits sufficient emulsifying properties. The present invention provides a coating film stripping composition and a coating film stripping method that use cellulose derivatives to improve coating film stripping properties and coating workability while reducing the risk of fire. Item 1. A coating stripping composition having a pH in the range of 5 to 9, comprising water, benzyl alcohol, and at least one cellulose derivative. Item 2. The composition according to item 1, wherein the mass ratio of benzyl alcohol to water (mass of benzyl alcohol / mass of water) is in the range of 0.6 to 4.8. Item 3. The composition according to Item 1 or 2, wherein the cellulose derivative is at least one selected from the group consisting of methyl cellulose, hydroxyethyl cellulose, hydroxypropyl methyl cellulose, butyl cellulose and propyl cellulose. Item 4. The composition according to any one of Items 1 to 3, wherein the content of the cellulose derivative is 0.5 to 3 wt % of the total amount of the composition. Item 5. The composition according to any one of Items 1 to 4, having a viscosity at room temperature in the range of 3,000 to 110,000 mPa s. Item 6. A method for stripping a coating film, comprising applying the coating film stripping composition according to any one of items 1 to 5 to the coating film, and stripping the coating film. Effect of the Invention

[0010] The coating film stripping composition of the present invention contains water, which can greatly reduce the risk of fire. In addition, the cellulose derivative used has not only emulsifying properties but also thickening properties, making it difficult for the composition to drip after application. Furthermore, after the composition penetrates the coating film, it forms a film on the coating film surface, which can suppress the composition from drying, making it useful for shortening the stripping time. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] In the present invention, benzyl alcohol is used as the oil phase of the stripping composition. The mass ratio of water to benzyl alcohol is benzyl alcohol / water=0.6-4.8, preferably 0.8-3.0. If the mass ratio of water to benzyl alcohol is within the above range, it is preferable because it shows excellent emulsion stability and viscosity and does not pose a fire hazard.

[0012] Examples of the cellulose derivatives used in the present invention include methyl cellulose, ethyl cellulose, hydroxypropyl cellulose, hydroxyethyl cellulose, hydroxypropyl methyl cellulose, butyl cellulose, and propyl cellulose. The amount of benzyl alcohol used in the present invention is preferably 30 to 90 wt%, more preferably 35 to 85 wt%, even more preferably 40 to 80 wt%, and particularly preferably 45 to 75 wt%, based on 100 wt% of the total amount of the coating stripping composition. The amount of water used in the present invention is preferably 10 to 70 wt%, more preferably 15 to 60 wt%, even more preferably 20 to 50 wt%, and particularly preferably 25 to 40 wt%, based on 100 wt% of the total amount of the coating stripping composition.

[0013] The amount of the cellulose derivative used in the present invention is 0.3 to 5 wt%, preferably 0.4 to 4 wt%, more preferably 0.5 to 3.5 wt%, even more preferably 0.5 to 3 wt%, particularly preferably 1 to 3 wt%, and most preferably 1 to 2 wt%, based on the total amount of the coating stripping composition being 100 wt%. When the amount of the cellulose derivative is within the above range, excellent emulsion stability is exhibited.

[0014] The cellulose derivatives used in the present invention may be used either alone or in combination of two or more.

[0015] The viscosity of the coating film stripping composition of the present invention at room temperature is usually about 3,000 to 110,000 mPa s, preferably about 3,000 to 70,000 mPa s, more preferably about 4,000 to 50,000 mPa s, and even more preferably about 4,000 to 40,000 mPa s. If the viscosity is within the above range, the coating film stripping composition does not drip after application and has excellent application workability. The viscosity can be measured with a B-type viscometer.

[0016] In addition to the above, a pH adjuster (fatty acid such as acetic acid, phosphoric acid, caustic soda, caustic potash, etc.) for making the coating stripping composition acidic or alkaline, a preservative, a chelating agent, etc. may be appropriately added. The pH range in which the cellulose derivative contained in the coating stripping composition of the present invention is not hydrolyzed is about 5 to 9, preferably about 5 to 8, and more preferably about 6 to 8.

[0017] The coating film stripping composition of the present invention is applicable to coating films on the surfaces of steel structures such as steel road bridges, and buildings such as exterior walls, etc. The coating film stripping composition of the present invention is useful for stripping coating films that mainly contain melamine, acrylic, phthalic acid, lacquer, urethane, and epoxy resins.

[0018] The coating amount of the coating film stripping composition of the present invention is preferably 0.5 to 2 kg / m 2 More preferably, 0.5 to 1 kg / m 2 For example, the coating film stripping composition of the present invention can be applied to a coating film, and the coating film can be peeled off using a scraper or the like after 12 to 48 hours, preferably about 24 hours. The coating film stripping composition can be applied to a coating film using a spray, roller, brush, or the like.

[0019] The coating film is peeled off in a floating state from the object to be coated, so it can be easily disposed of by placing it in a disposal bag, etc., and does not scatter harmful substances. EXAMPLES

[0020] The present invention will be described in detail below using examples, but the present invention is not limited to the following examples.

[0021] In the present examples and comparative examples, the following cellulose derivatives, polyvinyl alcohol, and polyvinylpyrrolidone were used. Cellulose Derivatives Cellulose derivative 1: Shin-Etsu Chemical Co., Ltd.: Metrose SM-400 Cellulose derivative 2: Shin-Etsu Chemical Co., Ltd.: Metolose 60SH-4000 Cellulose derivative 3: Shin-Etsu Chemical Co., Ltd.: Metrose 65SH-4000 Cellulose derivative 4: Shin-Etsu Chemical Co., Ltd.: Metrose 90SH-4000 Cellulose derivative 5: Shin-Etsu Chemical Co., Ltd.: Metrose SM-4000 Polyvinylpyrrolidone Daiichi Kogyo Co., Ltd.: Pitzkol K-90 Polyvinyl alcohol Kuraray Co., Ltd.: Kuraray Poval PVA105

[0022] Examples 1 to 11 and Comparative Examples 1 to 5 [Emulsion test, viscosity measurement] Metolose SM-400 (2 g) was completely dissolved in 18 g of water. 80 g of benzyl alcohol was added to the solution and stirred for 1 hour to prepare the coating film stripping composition of Example 1. The coating film stripping compositions of Examples 2 to 11 and Comparative Examples 1 to 5 were prepared in the same manner at the ratios shown in Table 1. The liquid state 24 hours after preparation was visually confirmed and the emulsified state was evaluated (emulsification judgment). The evaluation criteria were as follows: ○: Milky white color was maintained ×: Layered The viscosity of the obtained stripping compositions of Examples 1 to 11 was measured using a Brookfield viscometer, and the pH of the obtained stripping compositions of Examples 1 to 11 was measured using pH test paper.

[0023] [Paint film peeling test] The peeling composition prepared in the emulsion test was applied to the following two types of test pieces (coated material 1 and coated material 2), and after a certain time had passed, the test piece surface was scraped with a scraper to test whether the coating could be removed. The evaluation criteria were as follows. ○: The coating was removed ×: The coating could not be removed.

[0024] Coating 1 (super thick epoxy resin paint undercoat for building coating) : A coating material (Eponics H, manufactured by Dai Nippon Toryo Co., Ltd.) consisting of an epoxy resin as the base agent and a modified aliphatic polyamine as the curing agent was applied to a cold-rolled steel plate (SPCC-SD) flat plate (0.8 x 25 x 50 mm) with a brush to a thickness of 230 μm. The coating was then left at room temperature for 3 days to harden. A coating film peeling composition was applied to the resulting coating film with a brush and then allowed to stand for 24 hours, and it was evaluated whether the coating film could be removed (peeling test results (epoxy resin)). The results are shown in Tables 1 to 4. Coating 2 (Phthalic acid-based) : A long oil-based phthalic acid resin paint (Greens Void, manufactured by Dai Nippon Toryo Co., Ltd.) was applied to a cold-rolled steel plate (SPCC-SD) flat plate (0.8 x 25 x 50 mm) with a brush to a thickness of 60 μm. The paint was then left at room temperature for 3 days to completely harden. A paint film stripping composition was applied to the resulting paint film with a brush, and the paint film was then left to stand for 24 hours to evaluate whether the paint film could be removed (peeling test results (phthalic acid resin)). The results are shown in Tables 1 to 4.

[0025] [Table 1]

[0026] [Table 2]

[0027] [Table 3]

[0028] [Table 4]

Claims

1. having a pH in the range of 5 to 9 and comprising water, benzyl alcohol and at least one cellulose derivative; The benzyl alcohol content is 45 to 80 wt % of the total amount, the mass ratio of benzyl alcohol to water (mass of benzyl alcohol:mass of water) is in the range of 60:38.4 to 4.8:1; A coating stripping composition having a cellulose derivative content of 1 to 3.5 wt % of the total amount (excluding those containing hydrogen peroxide, urea peroxide, N-methyl-2-pyrrolidone, ammonia, and substances that decompose to release ammonia).

2. 2. The composition according to claim 1, wherein the cellulose derivative is at least one selected from the group consisting of methyl cellulose, ethyl cellulose, hydroxyethyl cellulose, hydroxypropyl methyl cellulose, butyl cellulose and propyl cellulose.

3. 3. The composition according to claim 1, wherein the content of the cellulose derivative is 1 to 3 wt % of the total amount.

4. The composition according to any one of claims 1 to 3, having a viscosity at room temperature in the range of 3,000 to 110,000 mPa s.

5. A method for stripping a coating film, comprising applying the coating stripping composition according to any one of claims 1 to 4 to the coating film and stripping the coating film.

6. 6. The method for removing a coating film according to claim 5, wherein the coating film comprises a melamine, acrylic, phthalic acid, lacquer, urethane or epoxy type resin.

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