JPWO2020045361A1 - Coating film peeling composition and coating film peeling method - Google Patents

Abstract

A water-based coating type coating film peeling composition and a coating film peeling method capable of reducing the risk of fire, health problems, etc. in the coating film peeling work process and exhibiting peelability equal to or higher than that of a solvent-based peeling agent. provide.
The present invention comprises water, an alcohol having an aromatic group, an ether having an aromatic group, and at least one cellulose derivative, having a pH of 5 to 9, and having a pH of 5 to 9.
The present invention relates to a coating film peeling composition and the use of the composition, wherein the viscosity, the temperature change rate of the viscosity (5 ° C./25 ° C.) and the thixo ratio satisfy all the conditions (i) to (viii).

Description

The present invention relates to a coating film peeling composition used in a peeling step of an old coating film of a steel structure, a building, a vehicle, an aircraft, etc., and a coating film peeling method.

Steel structures such as steel road bridges are painted for the purpose of aesthetics, design, rust prevention, etc., but repainting work is required due to deterioration over time. Since this repainting work is performed regularly, the cost tends to increase. Therefore, in order to reduce the LCC (life cycle cost) of these steel structures, repainting is being promoted from the conventional general coating system to the heavy anticorrosion coating system, but to apply the heavy anticorrosion coating system It is necessary to completely peel off the old paint film. The general coating system that was applied in the past contains harmful substances such as lead, chromium, and PCB, and the peeling method in the physical construction method such as blasting and power tool processing generates dust containing harmful substances and works. It has become a social problem such as health problems for people and impact on the surrounding environment. On the other hand, in the chemical peeling method using a coating film release agent, the coating film release agent is applied to the coating film to be peeled off to soften and swell the old coating film and can be peeled off in a wet state, so that dust containing harmful substances is generated. It is attracting attention as an effective method without dust.

Similarly, buildings are painted for the purpose of aesthetics, design, and protection of the building. In the past, there were cases where asbestos-containing coating films were used for buildings, and there is concern about the generation of dust containing asbestos during repainting and building demolition. Attention is focused on coating film release agents that can remove old coating films without generating dust.

The coating film release agents are roughly classified into solvent-type coating film release agents using chlorine-based solvents such as dichloromethane (Patent Document 1) and solvent-type coating film release agents using heterocyclic compounds (Patent Document 2). Be done. A solvent-based coating film remover using a chlorine-based solvent has advantages such as high peeling performance and non-ignition, but there is a problem in sustainability of the effect because it volatilizes in a relatively short time. In addition, the use of chlorine-based solvents is restricted due to concerns about health problems, especially the risk of carcinogenesis, and legal regulations. In addition to this solvent, the solvent-type coating film remover, which contains N-methyl-2-pyrrolidone, which is a heterocyclic compound, as the main component and is thickened with a clay mineral thickener, is a dibasic acid ester or fatty acid. A release agent in which an ester, benzyl alcohol, etc. are mixed. Compared with chlorine-based solvents, these solvents have a higher boiling point and a slower volatilization rate, so they can be expected to have a long-lasting effect. However, health risk concerns are also being pointed out for N-methyl-2-pyrrolidone. Further, these solvent-based release agents have a flash point, and from the viewpoint of fire prevention, there is an increasing demand for water-based release agents.

Patent Document 3 discloses a W / O type emulsifying composition containing ethyl cellulose, an oil phase containing a solvent capable of swelling ethyl cellulose, and an aqueous phase containing a water-soluble polymer, and having emulsion stability due to ethyl cellulose and the water-soluble polymer. However, there is no description about peeling of the coating film, and it is used as a cosmetic.

Since Patent Document 4 contains terpenes, aromatic hydrocarbons, and ammonia, there are problems of odor due to evaporation of these and health problems due to inhalation of ammonia. In addition, since it becomes a strongly alkaline solution by blending ammonia, a problem of wastewater treatment arises.

Japanese Unexamined Patent Publication No. 5-171706 Japanese Unexamined Patent Publication No. 5-279607 Patent No. 3549995 Japanese Unexamined Patent Publication No. 10-330660

Non-chlorine solvent-based coating film remover that does not contain water shows high peeling performance, but since it is composed only of organic solvent, the release agent has a flash point, and it has been pointed out that there is a risk of fire. .. In addition, N-methyl-2-pyrrolidone, which is used as the main solvent, has been pointed out as having a risk of health problems.

A main object of the present invention is a water-based coating film peeling composition capable of reducing the risk of fire, health problems, etc. in the coating film peeling work process and exhibiting peelability equal to or higher than that of a solvent-based peeling agent. And to provide a method for peeling a coating film.

The present invention provides the following coating film peeling composition and coating film peeling method.
Item 1. A coating film containing water, an alcohol having an aromatic group, an ether having an aromatic group, and at least one cellulose derivative, having a pH of 5 to 9, and satisfying all of the following conditions (i) to (viii). Peeling composition
(i) The viscosity η1 at 5 ° C. and a shear rate of 0.1 s ^-1 is in the range of 80,000 to 500,000 mPa · s;
(ii) The viscosity η2 at 5 ° C and a shear rate of 1,000 s ^-1 is in the range of 200 to 1,000 mPa · s;
(iii) The viscosity η3 at 25 ° C. and a shear rate of 0.1 s ^-1 is in the range of 20,000 to 200,000 mPa · s;
(vi) The viscosity η4 at 25 ° C and shear rate of 1,000 s ^-1 is in the range of 200 to 1,000 mPa · s; (v) Temperature change rate at shear rate of 0.1 s ^-1 (5 ° C / 25 ° C) η1 / η3 is in the range of 1.5 to 5.0;
(vi) Temperature change rate (5 ° C / 25 ° C) η2 / η4 at a shear rate of 1,000 s ^-1 is in the range of 0.85 to 2.0;
(vii) The chixo ratio η3 / η4 at 25 ° C is in the range of 50-1,000; and
(viii) The chixo ratio η1 / η2 at 5 ° C is in the range of 100 to 1,000.
Item 2. Item 2. The composition according to Item 1, wherein the sum of the alcohol having an aromatic group and the ether having an aromatic group is 30 to 85% by mass of the entire coating film peeling composition.
Item 3. Item 2. 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. Item 6. The composition according to any one of Items 1 to 3, wherein the content of the cellulose derivative is 0.8 to 3 wt% of the total amount.
Item 5. A method for peeling a coating film, which comprises applying the coating film peeling composition according to any one of Items 1 to 4 to the coating film and peeling the coating film.

The present invention also includes the following aspects.
Item A. Composition for use in coating film peeling:
A composition containing water, an alcohol having an aromatic group, an ether having an aromatic group, and at least one cellulose derivative, having a pH of 5 to 9, and satisfying all of the following (i) to (viii).
(i) The viscosity η1 at 5 ° C. and shear rate 0.1 s ^-1 is in the range of 80,000 to 500,000 mPa · s;
(ii) The viscosity η2 at 5 ° C and shear rate 1,000 s ^-1 is in the range of 200 to 1,000 mPa · s; (iii) the viscosity η3 at 25 ° C and shear rate 0.1 s ^-1 is 20,000. Within the range of ~ 200,000 mPa · s;
(vi) The viscosity η4 at 25 ° C and shear rate of 1,000 s ^-1 is in the range of 200 to 1,000 mPa · s; (v) Temperature change rate at shear rate of 0.1 s ^-1 (5 ° C / 25 ° C) η1 / η3 is in the range of 1.5 to 5.0;
(vi) Temperature change rate (5 ° C / 25 ° C) η2 / η4 at a shear rate of 1,000 s ^-1 is in the range of 0.85 to 2.0;
(vii) The chixo ratio η3 / η4 at 25 ° C is in the range of 50-1,000; and
(viii) The chixo ratio η1 / η2 at 5 ° C is in the range of 100 to 1,000.
Item B. Use of the following compositions as a coating film remover:
A composition containing water, an alcohol having an aromatic group, an ether having an aromatic group, and at least one cellulose derivative, having a pH of 5 to 9, and satisfying all of the following (i) to (viii).
(i) The viscosity η1 at 5 ° C. and shear rate 0.1 s ^-1 is in the range of 80,000 to 500,000 mPa · s;
(ii) The viscosity η2 at 5 ° C and shear rate 1,000 s ^-1 is in the range of 200 to 1,000 mPa · s; (iii) the viscosity η3 at 25 ° C and shear rate 0.1 s ^-1 is 20,000. Within the range of ~ 200,000 mPa · s;
(vi) The viscosity η4 at 25 ° C and shear rate of 1,000 s ^-1 is in the range of 200 to 1,000 mPa · s; (v) Temperature change rate at shear rate of 0.1 s ^-1 (5 ° C / 25 ° C) η1 / η3 is in the range of 1.5 to 5.0;
(vi) Temperature change rate (5 ° C / 25 ° C) η2 / η4 at a shear rate of 1,000 s ^-1 is in the range of 0.85 to 2.0;
(vii) The chixo ratio η3 / η4 at 25 ° C is in the range of 50-1,000; and
(viii) The chixo ratio η1 / η2 at 5 ° C is in the range of 100 to 1,000.
Item C. Use of the following compositions to produce coating film strippers:
A composition containing water, an alcohol having an aromatic group, an ether having an aromatic group, and at least one cellulose derivative, having a pH of 5 to 9, and satisfying all of the following (i) to (viii).
(i) The viscosity η1 at 5 ° C. and shear rate 0.1 s ^-1 is in the range of 80,000 to 500,000 mPa · s;
(ii) The viscosity η2 at 5 ° C and shear rate 1,000 s ^-1 is in the range of 200 to 1,000 mPa · s; (iii) the viscosity η3 at 25 ° C and shear rate 0.1 s ^-1 is 20,000. Within the range of ~ 200,000 mPa · s;
(vi) The viscosity η4 at 25 ° C and shear rate of 1,000 s ^-1 is in the range of 200 to 1,000 mPa · s; (v) Temperature change rate at shear rate of 0.1 s ^-1 (5 ° C / 25 ° C) η1 / η3 is in the range of 1.5 to 5.0;
(vi) Temperature change rate (5 ° C / 25 ° C) η2 / η4 at a shear rate of 1,000 s ^-1 is in the range of 0.85 to 2.0;
(vii) The chixo ratio η3 / η4 at 25 ° C is in the range of 50-1,000; and
(viii) The chixo ratio η1 / η2 at 5 ° C is in the range of 100 to 1,000.

The coating film peeling composition of the present invention has excellent coating film peeling performance, and the fire risk can be significantly reduced by containing water. In addition, since the cellulose derivative used has not only emulsification but also thickening action, it can be prevented from dripping after application of the composition. Further, after the composition has penetrated into the coating film, a film is formed on the surface of the coating film, and drying of the composition can be suppressed, which is useful for shortening the peeling time.

The coating film peeling composition of the present invention is an emulsified composition, preferably a water-in-oil emulsified composition, and has (i) water, (ii) an alcohol having an aromatic group constituting an oil phase, and an aromatic group. It contains ether and (iii) a cellulose derivative having an emulsifying and thickening action.

In the present invention, various studies have been carried out for improving the peelability of an aqueous coating film remover at a low temperature, and an alcohol having an aromatic group at pH 5 to 9 near neutrality is used as a main solvent, and an aromatic group is added thereto. It has been found that the releasability at low temperature is improved by adding the ether having. Further, instead of these aromatic ether-based solvents, N-methyl-2-pyrrolidone, which is often used in solvent-type coating film removers, a dibasic acid ester mixture, or a ketone-based solvent may be added. In particular, it was found that it does not contribute to the improvement of peelability at low temperatures. It has been found that the coating film release agent composition in the following preferable viscosity range has excellent workability with a brush, a roller, an airless spray, etc., and can hold the chemical without dripping after being applied to a vertical surface. However, since aromatic hydrocarbon solvents and terpenes added to dissolve waxes such as paraffin wax inhibit the increase in viscosity and alkalis such as ammonia hydrolyze cellulose derivatives, a coating film remover composition using these is used. The material will be out of the preferred viscosity range.

The coating film peeling composition of the present invention satisfies all of the following conditions (i) to (viii).
(i) The viscosity η1 at 5 ° C. and a shear rate of 0.1 s ^-1 is 80,000 to 500,000 mPa · s, preferably 100,000 to 400,000 mPa · s, more preferably 150,000 to 300,000 mPa · s;
(ii) When the viscosity η2 at 5 ° C. and shear rate 1,000 s ^-1 is 200 to 1,000 mPa · s, preferably 250 to 700 mPa · s, more preferably 300 to 600 mPa · s;
(iii) The viscosity η3 at 25 ° C. and a shear rate of 0.1 s ^-1 is 20,000 to 200,000 mPa · s, preferably 30,000 to 150,000 mPa · s, more preferably 35,000 to 100,000 mPa · s;
(iv) The viscosity η4 at 25 ° C. and a shear rate of 1,000 s ^-1 is 200 to 1,000 mPa · s, preferably 250 to 700 mPa · s, more preferably 300 to 600 mPa · s;
(v) The rate of change in viscosity (5 ° C / 25 ° C) η1 / η3 when the shear rate is 0.1 s ^-1 is 1.5 to 5.0, preferably 1.5 to 4.0, more preferably 1.7 to 3.5;
(vi) The rate of change in viscosity (5 ° C / 25 ° C) η2 / η4 when the shear rate is 1,000 s ^-1 is 0.85 to 2.0, preferably 0.85 to 1.5, more preferably 0.9 to 1.2;
(vii) The chixo ratio η3 / η4 at 25 ° C. is 50-1,000, preferably 100-700, more preferably 150-500; and
(viii) The chixo ratio η1 / η2 at 5 ° C. is 100 to 1,000, preferably 200 to 800, more preferably 400 to 700.

If the viscosity, the temperature change rate of viscosity (5 ° C / 25 ° C), and the thixo ratio are within the above ranges, the coating film peeling composition may drip after coating in the temperature range to which the coating film stripping agent is applied. It has excellent coating workability. Examples of the temperature range to which the coating film release agent is applied include -5 ° C to 50 ° C, preferably 0 ° C to 40 ° C. The coating film release agent of the present invention can be suitably used in a temperature range from a low temperature range in winter to a high temperature range in summer.

Alcohols having aromatic groups do not contain phenolic hydroxyl groups. Specific examples of the alcohol having an aromatic group include benzyl alcohol, 2-phenylethanol, 1-phenylethanol, 2-phenoxyethanol, and 2-phenoxypropanol. In a preferred embodiment, an alcohol having an aromatic group is the main component of the oil phase. Only one type of alcohol having an aromatic group may be used, or two or more types may be used in combination.

Specific examples of ethers having an aromatic group include alkoxybenzenes such as anisole (methoxybenzene), ethoxybenzene, propoxybenzene and butoxybenzene, 1,2-methylenedioxybenzene, 1,2-ethylenedioxybenzene, and the like. Examples thereof include diphenyl ether and dibenzyl ether. However, the compound corresponding to the alcohol having the above aromatic group is not included. As the ether having an aromatic group, only one kind may be used, or two or more kinds may be used in combination. By blending an ether having an aromatic group, the peelability of the coating film at a low temperature is improved. Ethers having these aromatic groups have a low flash point, but the risk of fire can be reduced by using an aqueous composition.

Examples of the cellulose derivative used in the present invention include alkyl etherified cellulose such as methyl cellulose, ethyl cellulose, butyl cellulose and propyl cellulose, and hydroxyalkyl etherified cellulose such as hydroxypropyl cellulose, hydroxyethyl cellulose and hydroxypropyl methyl cellulose. Examples of the alkyl group in the alkyl etherified cellulose and the hydroxyalkyl etherified cellulose are linear or branched alkyl groups having about 1 to 6 carbon atoms. Only one type of cellulose derivative may be used, or two or more types may be used in combination.

The alcohol having an aromatic group is preferably contained in an amount of 20 to 70% by mass, more preferably 30 to 60% by mass, based on the total amount of the coating film peeling composition.

The ether having an aromatic group is preferably contained in an amount of 5 to 30% by mass, more preferably 5 to 20% by mass, based on the total amount of the coating film peeling composition.

The total mass of the alcohol having an aromatic group and the ether having an aromatic group is preferably 35 to 80% by mass, more preferably 40 to 70% by mass of the entire coating film peeling composition.

The mass ratio (a) / (b) of the alcohol (a) having an aromatic group and the ether (b) having an aromatic group is preferably 20 to 1, more preferably 10 to 3.

The cellulose derivative is preferably contained in an amount of 0.8 to 2.5% by mass, more preferably 1.0 to 2.0% by mass, based on the entire coating film peeling composition. When the blending amount of the cellulose derivative is within the above range, excellent emulsion stability and viscosity are exhibited.

Water is preferably contained in an amount of 10 to 60% by mass, more preferably 25 to 55% by mass, based on the entire coating film peeling composition.

As the cellulose derivative used in the present invention, only one type may be used, or two or more types may be used in combination. The viscosity at each temperature and each shear rate can be measured with a rheometer. The chixo ratio and the rate of change in viscosity can be calculated from the viscosities measured at each temperature and shear rate.

The pH range in which the cellulose derivative contained in the coating film peeling 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. Therefore, it is not desirable to add amines such as ammonia, basic compounds such as alkali metal hydroxides, and acidic compounds such as organic acids and inorganic acids to the coating film peeling composition of the present invention.

A preservative such as thiazolin, an evaporation inhibitor such as solid paraffin, a chelating agent such as ethylenediaminetetraacetic acid, a rheology control agent such as fatty acid amide, and the like may be appropriately added to the coating film peeling composition of the present invention.

The application target of the coating film peeling composition of the present invention is a coating film on the surface of a steel structure such as a steel road bridge or a building such as an outer wall. The coating film peeling composition of the present invention is useful for peeling a coating film containing a resin such as melamine, acrylic, phthalic acid, lacquer, rubber chloride, urethane, epoxy, and fluorine.

The coating amount of the coating film peeling composition of the present invention is preferably about 0.5 to 2 kg / m ² , and more preferably about 0.5 to 1 kg / m ² . For example, the coating film peeling composition of the present invention can be applied to a coating film, and the coating film can be peeled off after 12 to 48 hours, preferably 16 to 24 hours, using a hand tool such as a scraper. The coating film peeling composition can be applied to the coating film by using a spray, a roller, a brush or the like. The temperature in the step of applying the coating film peeling composition to the coating film and peeling the coating film after a lapse of a predetermined time can be, for example, -5 ° C to 50 ° C, preferably 0 ° C to 40 ° C. It is preferable to maintain the temperature and apply the coating film peeling composition to the coating film and peel the coating film.

Since the coating film is peeled off from the object to be coated in a floating state, it can be easily disposed of by storing it in a disposal bag or the like, and harmful substances are not scattered.

Hereinafter, the present invention will be described in detail with reference to Examples, but the present invention is not limited to the following Examples.

In this example and comparative example, the following cellulose derivatives were used. Cellulose Derivatives Metrose 60SH-4000: Hydroxypropyl Methyl Cellulose manufactured by Shin-Etsu Chemical Co., Ltd. Metrose 90SH-4000: Hydroxypropyl Methyl Cellulose manufactured by Shin-Etsu Chemical Co., Ltd.

Examples 1 to 7 and Comparative Examples 1 to 5
[Emulsification test, viscosity measurement]
With respect to the coating film peeling compositions of Examples 1 to 7 and Comparative Examples 1 to 5, coating film stripping agent compositions were prepared at the ratios shown in Table 3. The liquid state 24 hours after the preparation was visually confirmed, and the emulsified state was evaluated (emulsification judgment). The evaluation criteria are as follows.

A: Milky white was maintained C: Layered, colorless and transparent.

The viscosities of the obtained coating film peeling compositions of Examples 1 to 7 and Comparative Examples 1 to 5 were measured using a rheometer. Specifically, the viscosity was measured using a rheometer MCR302 manufactured by Antonio Par, in accordance with JIS Z8803: 2011.

The pH of the obtained coating film peeling compositions of Examples 1 to 7 and Comparative Examples 1 to 5 was measured using pH test paper, and as a result, pH = 7 in each case.

[Coating film peeling test]
The peeling composition prepared in the emulsification test is applied to the following two types of test pieces (A coating film system and B coating film system), allowed to stand at a specified temperature, and after a predetermined time elapses, the surface of the test piece is scraped. It was rubbed and tested whether the coating film could be removed. The specified temperature was 5 ° C. and the predetermined time was 24 hours. The evaluation criteria are as follows.

"A coating film system" refers to "general exterior surface / general environment use" among the uses described in "Steel Road Bridge Painting / Anticorrosion Handbook". "B coating film system" refers to "general outer surface / for a slightly severe corrosive environment" among the uses described in "Steel Road Bridge Painting / Anticorrosion Handbook".

A: The coating film could be easily removed. B: The coating film could be removed by applying a strong force.
C: The coating film could not be removed

The A coating system and B coating system are shown below. All paints are manufactured by Kansai Paint Co., Ltd.

Test pieces of A coating system and B coating system were prepared by sequentially applying the coating materials shown in Table 1 or Table 2 above to a rolled steel sheet for general structure (SS400) flat plate (0.3 × 210 × 300 mm). The coating film peeling composition was applied to the obtained coating film with a brush and then allowed to stand in a constant temperature bath at 5 ° C. for 24 hours to evaluate whether the coating film could be removed. The results are shown in Table 3. In addition, the viscosities of Examples 1-7 and Comparative Example 1-5 at 5 ° C. and a shear rate of 0.1 s ^-1 were η 1,5 ° C., and the viscosities at a shear rate of 1,000 s ^-1 were η 2, 25 ° C. Viscosity η3 at s ^-1 , 25 ° C, shear rate 1,000 s ^-1 Viscosity η4, shear rate 1,000 s ^-1 temperature change rate η1 / η3, shear rate 1,000 s ^-1 temperature Table 4 shows the rate of change η2 / η4, the viscosity ratio η3 / η4 at 25 ° C, and the viscosity ratio η1 / η2 at 5 ° C.

Claims (5)

A coating film peeling composition containing water, an alcohol having an aromatic group, an ether having an aromatic group, and at least one cellulose derivative, having a pH of 5 to 9, and satisfying all of the following (i) to (viii). object
(i) The viscosity η1 at 5 ° C. and a shear rate of 0.1 s ^-1 is in the range of 80,000 to 500,000 mPa · s;
(ii) The viscosity η2 at 5 ° C and a shear rate of 1,000 s ^-1 is in the range of 200 to 1,000 mPa · s;
(iii) The viscosity η3 at 25 ° C. and a shear rate of 0.1 s ^-1 is in the range of 20,000 to 200,000 mPa · s;
(vi) The viscosity η4 at 25 ° C and a shear rate of 1,000 s ^-1 is in the range of 200 to 1,000 mPa · s; (v) The temperature change rate η1 / η3 at a shear rate of 0.1 s ^-1 In the range of 1.5-5.0;
(vi) The temperature change rate η2 / η4 at a shear rate of 1,000 s ^-1 is in the range of 0.85 to 2.0;
(vii) The chixo ratio η3 / η4 at 25 ° C is in the range of 50-1,000; and
(viii) The chixo ratio η1 / η2 at 5 ° C is in the range of 100 to 1,000. The composition according to claim 1, wherein the sum of the alcohol having an aromatic group and the ether having an aromatic group is 30 to 85% by mass of the entire coating film peeling composition. The composition according to claim 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. The composition according to any one of claims 1 to 3, wherein the content of the cellulose derivative is 0.8 to 3% by mass of the total amount. A method for peeling a coating film, which comprises applying the coating film peeling composition according to any one of claims 1 to 4 to the coating film and peeling the coating film.