Coating-film piece combustion-inhibiting release agent and method for releasing coating film

Abstract

To provide a coating film peeling agent capable of effectively suppressing the ignition of peeled coating film pieces.SOLUTION: The present invention relates to an aqueous emulsion-based remover for removing a coating film, wherein (1) the remover comprises (1a) an alcohol including an aromatic alcohol, (1b) a paraffin having a melting temperature of 65 °C or less, (1c) at least one of thixotropic agents and low-polarity solvents having a dissolution parameter of 20 or less, and (1d) water, and (2) a water-containing emulsion film formed by the remover is maintained at a temperature of 15 °C for at least 6 hours immediately after application of the remover.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a novel paint stripper that can suppress combustion of peeled paint pieces, and a paint stripping method that uses the paint stripper. [Background technology]

[0002] For example, structures such as bridges, storage tanks, exterior staircases, and floodgates (especially metal structures) are painted to enhance their corrosion resistance (rust prevention) and weather resistance, but when they are repaired, some or all of the paint is repainted.

[0003] When repainting a metal structure, the old paint film (which must be removed) on the surface of the structure must be removed before the new paint can be applied. There are two methods for removing this paint film: physical and chemical.

[0004] Physical methods include, for example, blasting, grinding with a disk sander, etc. These methods are excellent in removal speed, but generate large amounts of dust, which has a negative impact on workers and the surrounding environment.

[0005] One method of chemical removal is to use a paint stripper. Paint strippers can be broadly divided into solvent-based paint strippers and water-based paint strippers. Solvent-based paint strippers are strippers whose main component is an organic solvent, and therefore have the problem of pollution of the working environment due to the evaporation of the organic solvent, as well as the risk of the evaporated organic solvent catching fire. Water-based paint strippers are relatively safe paint strippers because they contain water.

[0006] For this reason, water-based paint strippers have come into widespread use in recent years, and various types of strippers have actually been developed.

[0007] For example, a known paint remover contains (A) a monohydric or dihydric alcohol solvent or its derivative having a boiling point of 100°C or higher, (B) water, and (C) a rheology control agent, where component (C) is a metal soap that is a non-alkali metal salt, and has a viscosity adjusted to 25 Pa s or less (25°C) (Patent Document 1).

[0008] Further, for example, a coating stripping composition is known which has a pH in the range of 5 to 9 and contains water, benzyl alcohol, and at least one cellulose derivative (Patent Document 2). [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Patent Publication No. 2019-131651 [Patent Document 2] International Publication WO2018 / 179925 Summary of the Invention [Problem to be solved by the invention]

[0010] However, even when using a water-based paint stripper, there is a risk of paint chips catching fire after removal. While the cause is unclear, it is thought that when a water-based paint stripper is applied to an old paint film and then stripped, the paint chips are in a flammable state due to the organic components contained in the water-based paint stripper as well as the organic components originally present in the paint chips. If the paint chips are ignited by an ignition source, they will burn. In this case, increasing the water content of the water-based paint stripper is an option, but doing so will not only reduce stripping performance, but may also lead to reduced workability.

[0011] For this reason, there is a strong demand for a stripping agent that can prevent the peeled paint pieces from catching fire, but at present, such a stripping agent has not yet been developed.

[0012] Therefore, a primary object of the present invention is to provide a paint stripper that can effectively suppress the ignition of peeled paint pieces. [Means for solving the problem]

[0013] The present inventors have conducted extensive research in light of the problems of the prior art and have found that the above object can be achieved by using a composition containing specific components as a paint film remover, thereby completing the present invention.

[0014] That is, the present invention relates to the following paint piece combustion-suppressing stripping agent and paint film stripping method. 1. An aqueous emulsion paint remover for removing paint films, (1) The release agent is (1a) Alcohols, including aromatic alcohols; (1b) Paraffins having a melting point of 65°C or less; (1c) at least one of a thixotropic agent and a low-polarity solvent having a solubility parameter of 20 or less, and (1d) Water and (2) The water-containing emulsion film formed by the release agent is maintained at a temperature of 15°C for at least 6 hours from immediately after application of the release agent. A paint film combustion-suppressing stripper characterized by: 2. The paint piece combustion retardant stripping agent according to item 1, wherein the content of the paraffins is 0.1 to 5% by weight. 3. The paint piece combustion-retardant stripper according to item 1 or 2, further comprising at least one of a surfactant and a thickener. 4. A method for removing a coating film, comprising: (1) A step of forming a water-containing emulsion film by applying the paint piece combustion-suppressing stripping agent according to any one of items 1 to 3 to the surface of the paint film to be stripped; (2) Aging the emulsion film for a certain period of time after application while maintaining the emulsion film; (3) A process of peeling off the coating film having the water-containing emulsion film. A coating film peeling method comprising: 5. The amount of paint film combustion retardant stripper applied (before drying) is 0.3 to 2 kg / m 2 Item 5. The method according to item 4, [Effects of the Invention]

[0015] According to the present invention, a paint stripper can be provided that can effectively prevent paint chips from igniting after peeling. In particular, the stripper of the present invention uses a combination of paraffins with a melting point of 65°C or less, a thixotropic agent, and at least one low-polarity solvent with a solubility parameter of 20 or less, making it possible to maintain a water-containing emulsion film on the surface of the paint chips after peeling for a relatively long period of time. As a result, paint chips can be prevented from igniting or burning, making it possible to perform paint stripping work more safely. DETAILED DESCRIPTION OF THE INVENTION

[0016] 1. Paint film combustion retardant stripper The paint film piece combustion suppressing stripping agent of the present invention (the stripping agent of the present invention) is an aqueous emulsion paint film stripping agent for stripping paint films, (1) The release agent is (1a) Alcohols, including aromatic alcohols; (1b) Paraffins having a melting point of 65°C or less; (1c) at least one of a thixotropic agent and a low-polarity solvent having a solubility parameter of 20 or less, and (1d) Water and (2) The water-containing emulsion film formed by the release agent is maintained at a temperature of 15°C for at least 6 hours from immediately after application of the release agent. It is characterized by:

[0017] The stripping agent of the present invention is basically in the form of an aqueous emulsion composed of water (aqueous phase) and an oil phase containing organic components, but some of the organic components may be dissolved in water as long as the effects of the present invention are not impaired. By adopting the form of an emulsion composed of two phases, an aqueous phase and an oil phase, when applied to the surface of the old coating film to be stripped (hereinafter also referred to as the "coating film to be stripped"), it becomes possible to more reliably form an aqueous emulsion film by the stripping agent of the present invention on the surface of the coating film to be stripped. As a result, it becomes possible to effectively suppress ignition and combustion of the stripped coating pieces. The reason for this is unclear, but it is thought to be due to the following mechanism of action. After the release agent of the present invention in emulsion form is applied to the coating film to be stripped, the coating film formed by the release agent of the present invention undergoes aging to form a layer structure of "coating film to be stripped / water-rich layer / organic component (especially paraffin)-rich layer." The water in the water-rich layer is trapped by the organic component-rich layer, making it difficult to evaporate. This state is maintained for a long period of time, and as a result, the water-rich layer suppresses ignition of the coating pieces, or even if a temporary ignition does occur, suppresses combustion (spread of fire). In other words, the water-containing emulsion film is still maintained for a certain period of time on the coating pieces after stripping, effectively suppressing ignition and combustion of the coating pieces. The following describes the components that make up the release agent of the present invention.

[0018] (1a) Alcohols including aromatic alcohols The aromatic alcohol mainly functions as a stripping component for stripping the coating film to be stripped.

[0019] The aromatic alcohol itself is not particularly limited, and examples thereof include benzyl alcohol, phenethyl alcohol, hydroxybenzyl alcohol, hydroxyphenethyl alcohol, 4-methylbenzyl alcohol, and 2-ethylbenzyl alcohol. Among these, benzyl alcohol is preferred. These may be used alone or in combination of two or more. These may also be the same release components used in known or commercially available release agents.

[0020] The content of aromatic alcohol in the release agent of the present invention can be appropriately set depending on the type and thickness of the coating film to be removed, but is usually about 30 to 80% by weight, and preferably 35 to 70% by weight.

[0021] In the present invention, alcohols other than aromatic alcohols may be contained, for example, monohydric alcohols such as methanol, ethanol, propanol, isopropyl alcohol, and butanol, and polyhydric alcohols such as ethylene glycol, propylene glycol, butylene glycol, diethylene glycol, dipropylene glycol, triethylene glycol, and glycerin.

[0022] The content of alcohols other than aromatic alcohols in the release agent of the present invention can be appropriately set depending on the type and thickness of the coating film to be removed, but is usually about 1 to 20% by weight, and preferably 3 to 10% by weight. (1b) Paraffins with a melting point of 65°C or less (hereinafter simply referred to as "paraffins") Paraffins mainly contribute to the formation of the organic component-rich layer in the water-containing emulsion film.

[0023] The melting point of the paraffins is preferably 65° C. or lower, and particularly preferably 60° C. or lower. If the melting point exceeds 65° C., it may be difficult to form a water-containing emulsion film. The lower limit of the melting point may be, for example, about 40° C., but is not limited to this.

[0024] Suitable examples of such paraffins include, but are not limited to, paraffin wax. Paraffin wax is a wax that is solid at room temperature and is separated and refined from vacuum distillate oil, and is also called "solid wax." Paraffin wax is classified into four types, 120P, 125P, 130P, and 135P, based on their melting points (Japanese Industrial Standards JIS K2235-1991). Any of these types can be used in the present invention, with 135P being particularly preferred. These paraffins can also be commercially available. When using commercially available products, emulsion-type paraffins containing surfactants may be used. Examples of commercially available products include "Paraffin Wax-115" (manufactured by Nippon Seiro Co., Ltd.) and "AQUACER 497" (manufactured by BYK Japan Co., Ltd.).

[0025] The content of paraffins in the release agent of the present invention can be appropriately set depending on the type and thickness of the coating film to be removed, but is usually about 0.1 to 5% by weight, preferably 0.3 to 4% by weight, more preferably 0.5 to 3.5% by weight, and most preferably 0.5 to 2% by weight. Therefore, it can be set to, for example, 1 to 2% by weight.

[0026] (1c) At least one of a thixotropic agent and a low-polarity solvent having a solubility parameter of 20 or less The thixotropic agent and at least one low-polarity solvent having a solubility parameter of 20 or less are components that can mainly contribute to an excellent combustion suppression effect in combination with the paraffins.

[0027] Thixotropic agents are also known as thixotropic agents, and various types such as amide-based, castor oil-based, polyethylene oxide-based, and vegetable oil polymerized oil-based agents can be used. Among these, amide-based thixotropic agents are preferred for use in the present invention. Furthermore, either powder or paste type thixotropic agents can be used. These thixotropic agents can also be commercially available. Examples of commercially available thixotropic agents include "Disparlon F-9030," "Disparlon 6900-20X," "Disparlon A670-20M," and "Disparlon A650-20X" (all manufactured by Kusumoto Chemical Co., Ltd.), "Tallen BA-600," "Tallen M-1020XFS," "Tallen M-1021B," and "Tallen VA750B" (all manufactured by Kyoeisha Chemical Co., Ltd.).

[0028] Low-polarity solvents (hereinafter simply referred to as "low-polarity solvents") having a solubility parameter (SP value) of 20 or less are not particularly limited, but include various organic solvents such as ester solvents such as ethyl acetate (8.6) and butyl acetate (8.5); ketone solvents such as acetone (9.4) and cyclohexanone (9.8); ether solvents such as anisole (19.6), diethyl ether (7.4), tetrahydrofuran (9.1), and propylene glycol monomethyl ether acetate (9.1); aromatic solvents such as toluene (8.9) and xylene (8.8); and petroleum solvents such as naphtha (7.6) and mineral spirits (6.9). Among these, at least one of anisole and naphtha is preferably used. The values ​​in parentheses above are literature values ​​for the SP value.

[0029] The solubility parameter (SP value) in the present invention may be either a literature value or an actual measurement value; however, if the two values ​​are significantly different, it is preferable to use the actual measurement value. The actual measurement value can be measured according to known methods. For example, a solubility test is conducted to determine whether a sample (usually a polymer) dissolves in 20 different solvents (acetone, methylcyclohexane, methyl ethyl ketone, tetrahydrofuran, meta-xylene hexafluoride, HFE-7100 (hydrofluoroether), dimethyl sulfoxide, diethylene glycol, N-methylpyrrolidone, acetonitrile, 2-propanol, 2-(2-ethoxyethoxy)ethanol, toluene, diiodomethane, acetophenone, benzaldehyde, acetic acid, 2-ethylhexanol, propylene carbonate, and ethanol). An SP sphere (Hansen's solubility sphere) is constructed from the SP values ​​of the solvents that were able to dissolve the sample, and the Hansen SP value can be calculated based on this (by converting units as necessary). The SP values ​​of the monomers that make up the polymer can be determined using commercially available calculation software.

[0030] In the release agent of the present invention, the total amount of the thixotropic agent and at least one low-polarity solvent having a solubility parameter of 20 or less can be appropriately changed depending on, for example, the type of thixotropic agent or low-polarity solvent used, but is usually about 0.5 to 20% by weight, and preferably 0.5 to 15% by weight.

[0031] (1d) Water Water is a component that is primarily responsible for forming a water-containing emulsion film from the release agent of the present invention. From this perspective, the water content of the release agent of the present invention is preferably about 20 to 80% by weight, and more preferably 30 to 70% by weight.

[0032] In particular, in relation to the aromatic alcohol, the weight ratio of aromatic alcohol to water is preferably 1:1 to 1:2, and more preferably 1:1.3 to 1:1.7. By setting such a ratio, better flame retardancy can be obtained.

[0033] (1e) Other ingredients The release agent of the present invention may contain other components as needed, as long as they do not impair the effects of the present invention. Examples include thickeners, surfactants, pH adjusters, preservatives, and rust inhibitors. If an optional component is used, the content of that optional component is included in the content of the essential components. For example, in the case of a surfactant, depending on the surfactant used, it may also function as a thixotropic agent, and the content of that surfactant is included in the content of the thixotropic agent.

[0034] The thickener may be either inorganic or organic. Examples of inorganic thickeners include inorganic powders such as silica, kaolin, serpentine, talc, mica, vermiculite, smectite, bentonite, and sepiolite. Examples of organic thickeners include cellulose derivatives such as sodium alginate, propylene glycol alginate, sodium carboxymethylcellulose, calcium carboxymethylcellulose, sodium starch glycolate, sodium starch phosphate, sodium polyacrylate, and methylcellulose, and synthetic products such as hydroxypropylmethylcellulose. Examples of naturally occurring polysaccharides include guar gum, tara gum, gum arabic, tragacanth gum, alginic acid, carrageenan, xanthan gum, dielangum, peritin, chitin, chitosan, and chitosamine.

[0035] The surfactant may be, for example, an anionic surfactant, a cationic surfactant, an amphoteric surfactant, a nonionic surfactant, etc. Examples of anionic surfactants include fatty acid salts, alkyl sulfate ester salts, alkylbenzene sulfonates, polyoxyethylene alkyl ether sulfates, and dialkyl sulfosuccinates. Examples of cationic surfactants include alkylamine acetates and quaternary ammonium salts. Examples of amphoteric surfactants include alkyldimethylaminoacetic acid betaine and alkyldimethylamine oxide. Examples of nonionic surfactants include glycerin fatty acid esters, propylene glycol fatty acid esters, sorbitan fatty acid esters, polyoxyethylene alkyl ethers, and polyoxyethylene polyoxypropylene ethers.

[0036] Examples of pH adjusters include acid components such as inorganic acids such as hydrochloric acid and phosphoric acid, and organic acids such as acetic acid, oxalic acid, and citric acid. Examples of base components include inorganic alkalis such as sodium hydroxide and potassium hydroxide, and organic alkalis such as monoethanolamine, monoisopropanolamine, diethanolamine, and triethanolamine.

[0037] (2) Water-containing emulsion film formed by the release agent of the present invention In the case of the release agent of the present invention, the water-containing emulsion film formed by the release agent of the present invention is maintained at a temperature of 15°C for at least 6 hours from immediately after application of the release agent.

[0038] The release agent of the present invention is in the form of an aqueous emulsion, and when applied, it forms an aqueous emulsion film. After peeling a coating film having such an aqueous emulsion film on its surface, the aqueous emulsion film remains on the surface of the peeled coating piece for a certain period of time, thereby effectively suppressing the combustion of the peeled coating piece. The reason for this effect is unclear, but it is thought to be due to the following mechanism. Generally, an aqueous emulsion film formed with an aqueous emulsion-type release agent begins to evaporate. With existing release agents, the water evaporates easily, resulting in a dry coating film with a low water content in a relatively short period of time. In contrast, the aqueous emulsion film formed with the release agent of the present invention forms a layer structure of "coating film to be peeled / water-rich layer / organic component-rich layer" as described above. The organic component-rich layer prevents the water from evaporating from the water-rich layer, and this state is maintained for a longer period of time. As a result, the water-rich layer is thought to suppress ignition of the coating piece, or, even if a temporary ignition occurs, to suppress the combustion (spread of fire).

[0039] The environment in which the water-containing emulsion film is maintained is at room temperature and normal humidity for a predetermined period of time, since the release agent of the present invention is usually used outdoors, and the standard for this period in the present invention is a temperature of 15°C (preferably 25°C) for 6 hours or more, preferably 6 hours or more, more preferably 8 hours or more, even more preferably 12 hours or more, more preferably 18 hours or more, and most preferably 24 hours or more. The humidity may be normal humidity, for example, about 10 to 85%, but is not limited to this.

[0040] (3) Production of the release agent of the present invention The release agent of the present invention can be prepared by uniformly mixing and emulsifying these components. In this case, mixing can be carried out using a known or commercially available mixer, kneader, etc. The order in which these components are mixed is not particularly limited as long as a homogeneous aqueous emulsion is obtained, and the components may be mixed simultaneously or sequentially. In this manner, the release agent of the present invention in the form of an aqueous emulsion can be obtained.

[0041] (4) Use of the stripping agent of the present invention The stripping agent of the present invention can be suitably used in accordance with the method described below in "2. Method for stripping coating film."

[0042] 2. How to remove the coating The present invention encompasses a method for removing a coating film using the stripping agent of the present invention. In particular, the present invention provides a method for removing a coating film, comprising the steps of: (1) a step of forming a water-containing emulsion film by applying the release agent of the present invention to the surface of the coating film to be peeled (the coating film to be peeled) (coating step); (2) Aging the emulsion film for a certain period of time after application while maintaining the emulsion film (aging step); (3) A step of peeling off the coating film to be peeled off having the water-containing emulsion film (peeling step) The present invention also encompasses a coating film peeling method comprising the steps of:

[0043] (1) Coating process In the coating step, the release agent of the present invention is applied to the surface of the coating film to be stripped, thereby forming a water-containing emulsion film.

[0044] The coating film to be peeled (the coating film to be removed) is not particularly limited as long as it is a coating film formed on the surface of a structure (particularly a metal structure). The coating film to be peeled may be one coated with a common paint, and the type of paint, the thickness of the coating film to be peeled, etc. are not particularly limited. For example, the method can be applied to a coating film to be peeled that contains at least one of melamine-based resin, acrylic-based resin, phthalic acid-based resin, urethane-based resin, epoxy-based resin, etc.

[0045] Furthermore, the material of the substrate for the coating film to be stripped is not limited, and may be, for example, metal, concrete, wood, etc. In particular, the stripping agent of the present invention is suitable for use with coating films whose substrate is metal (preferably steel). The type of substrate structure is not particularly limited, and the agent can be applied to any structure that requires corrosion resistance and rust prevention, such as bridges, building exterior walls, storage tanks, water gates, garages, etc.

[0046] The method for applying the release agent of the present invention is not particularly limited, and can be carried out by known methods such as spraying, roller, brush, etc. The amount of application (before drying) is not limited, but is usually 0.3 to 2 kg / m 2 Approximately 0.5 to 1 kg / m 2 It is preferable to set the following.

[0047] (2) Aging process In the aging step, after the application of the release agent of the present invention, the aqueous emulsion film is maintained and aged for a certain period of time.

[0048] In the aging step, the release agent of the present invention is allowed to penetrate into the coating film to be peeled and the coating film is left to swell for a time sufficient for the aqueous emulsion film to be maintained on the surface of the coating film to be peeled. This time period will vary depending on the working environment and season (temperature, humidity, presence or absence of sunlight), but is generally about 6 to 48 hours, preferably about 10 to 26 hours, after application of the release agent of the present invention.

[0049] The aqueous emulsion film produced by the release agent of the present invention is opaque or translucent due to the emulsification of the release agent, and is therefore formed on the surface of the coating film to be released in an opaque or translucent state. When most of the water in the aqueous emulsion film evaporates, its appearance changes from opaque or translucent to transparent. Therefore, the aging time can be appropriately adjusted within a range in which such a change in appearance is not substantially noticeable visually.

[0050] (3) Peeling process In the peeling step, the coating film to be peeled off having the aqueous emulsion film thereon is peeled off. That is, the coating film to be peeled off is peeled off and removed from the substrate before the aqueous emulsion film has dried and its appearance has not yet changed to transparent.

[0051] The peeling method can be carried out using a known or commercially available peeling tool such as a scraper. The peeled pieces of coating film still contain the aqueous emulsion film on their surface, making them less susceptible to ignition or combustion. By collecting the coating film pieces while they are still in this state, it is possible to more reliably prevent fires caused by the coating film pieces. [Example]

[0052] The features of the present invention will be described in more detail below with reference to examples and comparative examples, but the scope of the present invention is not limited to these examples.

[0053] Examples 1 to 7 and Comparative Examples 1 to 4 A release agent (aqueous emulsion) was prepared by uniformly mixing the components shown in Table 1. The content of each component is expressed in "% by weight."

[0054] [Table 1]

[0055] Details of each product name in Table 1 are as follows: "T-SOL150" - Naphtha manufactured by Ando Parachemie Co., Ltd. "Metolose SM4000" - Cellulose-based thickener manufactured by Shin-Etsu Chemical Co., Ltd. "Metolose 60SH4000" - Cellulose-based thickener manufactured by Shin-Etsu Chemical Co., Ltd. "Metolose 90SH4000" - Cellulose-based thickener manufactured by Shin-Etsu Chemical Co., Ltd. Disparlon F-9030: A fatty acid amide thixotropic agent manufactured by Kusumoto Chemicals Co., Ltd. "Paraffin Wax-115": Paraffin with a melting point of 47°C, manufactured by Nippon Seiro Co., Ltd. AQUACER 497: Manufactured by BYK Japan Co., Ltd., a mixture of 40-50% paraffin, 1-10% stearate, 1-10% fatty acid carboxylic acid ester, and water with a melting point of 60°C. "No. 70-S" Liquid paraffin manufactured by Sanko Chemical Industry Co., Ltd. Docosanol: Higher alcohol, melting point 70°C "Rheodor TW-O320V" - Kao Corporation, a sorbitan fatty acid ester-based nonionic surfactant

[0056] Test Example 1 (Confirmation of water-containing emulsion film) In Examples 1 to 7 and Comparative Examples 1 to 4, the change over time in the appearance of the water-containing emulsion film produced by each release agent was examined. The formation of the water-containing emulsion film was carried out by applying a coating amount (before drying) of 1 kg / m to the surface of the coating film (film thickness 200 μm) of the steel bridge used in the "Test Example 2 (flammability test)" below. 2 The test was carried out by applying the release agents of Examples 1 to 7 and Comparative Examples 1 to 4 with a brush so that the thickness of the release agents was 100 μm. Each release agent was opaque, and a opaque water-containing emulsion film was formed immediately after application. Subsequently, as drying progressed, the appearance of the water-containing emulsion film changed to transparent. During this series of appearance changes, it was measured whether the time from immediately after application at a temperature of 15°C until the water-containing emulsion film became transparent at a visual level was 6 hours or longer. As a result, in Examples 1 to 7, the water-containing emulsion film remained opaque even after 6 hours, and even after 24 hours. On the other hand, in Comparative Examples 1 to 4, the film became transparent within 30 minutes.

[0057] Test example 2 (flammability test) The amount of coating (before drying) on ​​the surface of the coating film (film thickness approximately 200 μm) of a steel bridge is 1 kg / m 2 The release agents of Examples 1 to 7 and Comparative Examples 1 to 4 were applied with a brush so that the coating film was coated with the release agent. 24 hours after application was completed, the coating film coated with the release agent was scraped with a scraper to remove the coating film. After removal, a piece of the coating film (approximately 3 cm x 3 cm in size) was placed on a brick block, and a lighter flame was brought close to the coating film piece. After holding the piece close for 15 seconds, it was visually confirmed whether the coating film piece had burned. The results are shown in Table 1. Cases where there was no ignition or combustion were marked with "○", and cases where there was ignition were marked with "×".

[0058] Examples 8 to 11 and Comparative Examples 5 to 11 A release agent (aqueous emulsion) was prepared by uniformly mixing the components shown in Table 2. The components in Table 2 are the same as those described above for Table 1. The content of each component is expressed in "% by weight."

[0059] Test Example 3 (Confirmation of water-containing emulsion film) In Examples 8 to 11 and Comparative Examples 5 to 11, the change over time in the appearance of the water-containing emulsion film produced by each release agent was examined. The formation of the water-containing emulsion film was carried out by applying a coating amount (before drying) of 1 kg / m to the coating surface of the test piece prepared in "(1) (Preparation of coating film test piece)" of "Test Example 4 (Removability test)" below. 2 The test was carried out by applying the release agents of Examples 8 to 11 and Comparative Examples 5 to 11 with a brush so that the thickness of the release agents was 100 μm. Each release agent was opaque, and a opaque water-containing emulsion film was formed immediately after application. Subsequently, as drying progressed, the appearance of the water-containing emulsion film changed to transparent. During this series of appearance changes, it was measured whether the time from immediately after application at a temperature of 25°C until the water-containing emulsion film became transparent at a visual level was 8 hours or longer. As a result, in Examples 8 to 11, the water-containing emulsion film remained opaque even after 8 hours, and also after 24 hours. On the other hand, in Comparative Examples 5 to 11, the water-containing emulsion film became transparent within 8 hours.

[0060] Test Example 4 (peelability test) (1) Preparation of coating test specimens A blast-treated SS400 (Japan Industrial Standard) steel plate conforming to ISO Sa 2 1 / 2 was painted with a long-form etching primer (Vinylex 120 Active Primer Eco (color: dark green) by Nippon Paint Co., Ltd.). Two coats of lead- and chromium-free rust-preventive paint (Lasgon Safety (color: red rust, gray) by Kansai Paint Co., Ltd.) were then applied on top of that, followed by a long-oil phthalate resin paint undercoat (SD Marine Safety Undercoat (color: white) by Kansai Paint Co., Ltd.) and a long-oil phthalate resin paint topcoat (SD Marine Safety Topcoat (color: yellow) by Kansai Paint Co., Ltd.). The painted steel plate was baked at 60°C for one week to prepare coating specimens with a coating thickness of approximately 200 μm. (2) Peel test The coating amount on the coating surface of the coating test piece prepared above was 1 kg / m 2 Each release agent of Examples 8 to 11 and Comparative Examples 5 to 11 was applied with a brush so that the coating film was peeled off after 24 hours in an environment of 25°C temperature and 50% humidity. If the entire coating film could be peeled off, it was marked "Good", and if part or all of the coating film could not be peeled off, it was marked "Poor". The results are shown in Table 2.

[0061] Test Example 5 (Flame Retardancy Test) The coating film that peeled off in Test Example 4 (peelability test) was placed on a brick block, and a flame was brought close to it with a lighter, and it was visually confirmed whether the coating film had burned. If the coating film did not ignite even after being held close to the fire for 5 seconds, it was marked "○", if the coating film ignited within 5 seconds of being held close to the brick block but immediately went out, it was marked "△", and if the coating film ignited within 5 seconds of being held close to the brick block but did not go out until the coating film had burned out, it was marked "×". The results are shown in Table 2.

[0062] [Table 2]

[0063] As is clear from the results in Table 2, Examples 8 to 10, in which 0.5 wt % or more of solid paraffin was added as an evaporation inhibitor, had good flame retardancy, whereas Comparative Examples 5 and 6, in which no evaporation inhibitor was added, had poor flame retardancy. Comparative Examples 7 and 8, in which liquid paraffin and higher alcohol were added as evaporation inhibitors, also had poor flame retardancy.

[0064] From the above, it can be said that it is desirable for the evaporation inhibitor to be solid at room temperature, to have no hydrophilic groups such as hydroxyl groups, and that the amount of the evaporation inhibitor to be blended is desirably 0.5% by weight or more.

[0065] Furthermore, in Examples 8 and 9, in which the benzyl alcohol content was 40% by weight and the same solid paraffin was used but the blending amounts were different, Example 9 had better flame retardancy, and when the benzyl alcohol content was 40% by weight, it was particularly desirable that the blending amount of solid paraffin be 1% by weight or more.

[0066] In Examples 8 and 11 and Comparative Examples 9 and 10, 0.5 wt% solid paraffin was added, and the ratio of benzyl alcohol to water was varied. The blending amounts were adjusted so that the viscosities were similar. Examples 8 to 11, which contained 0.5 wt% or more solid paraffin and had a water weight ratio to benzyl alcohol weight (i.e., [(water content) / (benzyl alcohol content)]) of 1 or more, exhibited good flame retardancy. In contrast, Comparative Examples 9 to 11, which contained 0.5 wt% or more solid paraffin but had a water weight ratio to benzyl alcohol weight of less than 1, exhibited poor flame retardancy. It is believed that by increasing the ratio of water weight to benzyl alcohol weight to 1 or more, more water is retained in the release agent, and the cooling effect of the contained water improves flame retardancy. [Industrial Applicability]

[0067] The stripping agent of the present invention is effective in safely stripping paint films applied to structures such as bridges, storage tanks, exterior staircases, and water gates.

Claims

1. A method for forming a water-containing emulsion film by applying an aqueous emulsion-based coating film remover to the surface of a coating film to be removed, comprising the steps of: The aqueous emulsion-based paint film remover is (1) The release agent is (1a) alcohols including aromatic alcohols; (1b) Paraffins having a melting point of 65°C or less; (1c) at least one of a thixotropic agent and a low-polarity solvent having a solubility parameter of 20 or less, and (1d) water A method for forming a water-containing emulsion film, comprising:

2. The method according to claim 1, wherein the aqueous emulsion film formed by the release agent is maintained at a temperature of 15°C for at least 6 hours from immediately after application of the release agent.

3. The method according to claim 1 , wherein the coating film to be peeled contains at least one of a melamine-based resin, an acrylic-based resin, a phthalic acid-based resin, a urethane-based resin, and an epoxy-based resin.

4. 2. The method of claim 1, wherein the weight ratio of aromatic alcohol to water is from 1:1 to 1:

2.

5. 2. The method according to claim 1, wherein the release agent contains 30 to 70 wt % of an aromatic alcohol, 0.1 to 5 wt % of a paraffin having a melting point of 65° C. or less, and 0.5 to 20 wt % of at least one of a thixotropic agent and a low-polarity solvent having a solubility parameter of 20 or less.

6. The amount of the release agent applied (before drying) is 0.3 to 2 kg / m ２ The method of claim 1 , wherein

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