JP7591815B2 - Paint stripping composition for buildings or structures - Google Patents

Description

The present invention relates to a coating stripping composition for buildings or structures that contains a small amount of benzyl alcohol, has excellent stripping performance, and is stable in low temperature environments.

Usually, the surfaces of buildings and other structures, such as bridges, are painted to provide various functions, such as surface protection, strength maintenance, and aesthetic improvement. When the coating film formed on buildings and structures deteriorates over time due to the effects of ultraviolet rays, etc., the above functions decrease. For this reason, it is necessary to periodically peel off the deteriorated coating film and repaint it.

Methods for removing coatings formed on buildings and structures include physical methods, such as using tools such as disc grinders, electric wire brushes or wire brushes to remove the coating, or spraying and impacting an abrasive material to remove the coating. However, with physical methods, part of the coating is dispersed as fine dust-like coating fragments. If workers inhale these fine coating fragments, they may cause serious health problems. Such health problems are particularly serious when removing coatings that contain harmful substances such as asbestos.

To solve the problem of scattering of the coating film, a method using a coating film stripping composition is known. By applying the coating film stripping composition to soften and swell the coating film, the coating film can be physically stripped using a stripping tool such as a scraper. This method can prevent the generation of fine dust-like coating film particles. Generally, coating film stripping compositions contain a solvent for softening and swelling the coating film. For example, Patent Document 1 discloses a resin remover containing ethylene glycol monoalkyl ether and an inorganic or organic acid. Patent Document 2 describes a coating film stripper containing gamma-butyrolactone, N-methyl-2-pyrrolidone, and bentonite.

Currently, many coating film stripping compositions containing benzyl alcohol are commercially available. For example, Patent Document 3 discloses a coating film stripping agent containing an alcohol-based solvent, water, and a rheology control agent, and exemplifies benzyl alcohol as the alcohol-based solvent. Patent Document 4 discloses a coating film stripping composition containing a solvent and a fatty acid ester, and exemplifies an aromatic hydroxy compound such as benzyl alcohol as the solvent.

Japanese Patent Application Publication No. 9-59546 JP 2013-18887 A JP 2019-131651 A JP 2014-177599 A

In recent years, there have been many poisoning accidents caused by the use of coating film stripping compositions containing benzyl alcohol. A notice from the Ministry of Health, Labor and Welfare, Labor Standards Bureau, Safety and Health Department (partially revised on August 17, 2020, Kianka-hatsu No. 1019, October 19, 2020) states that workers who use gas masks when spraying stripping compositions containing benzyl alcohol have also experienced poisoning symptoms. For this reason, the notice states that workers should use air-supplied masks for the time being. However, the use of air-supplied masks reduces the efficiency of spraying work. On the other hand, Patent Document 4 points out that stripping compositions containing dibasic acid esters and stripping compositions containing ethylene glycol monoalkyl ethers do not have sufficient stripping action. Therefore, there has been a demand for the development of a coating film stripping composition with a low content of benzyl alcohol and excellent stripping performance.

In addition, the work of removing coatings from buildings and structures is usually carried out outdoors. Therefore, coating stripping compositions are sometimes used outdoors in winter. For this reason, coating stripping compositions are required to have stable properties even in low temperature environments, particularly below freezing. For example, the stripping composition is required to maintain fluidity without solidifying even in low temperature environments.

The present invention aims to provide a coating stripping composition for buildings or structures that contains a small amount of benzyl alcohol, has excellent stripping performance, and has stable properties even in low temperature environments.

The coating stripping composition for buildings or structures of the present invention contains a compound of formula (1) (hereinafter referred to as “compound (1)”) and an ester solvent, and has a benzyl alcohol content of less than 1% by weight:
R ₁ -(OCH(R ₂ )-CH(R ₃ )) _n -OH (1)

In formula (1), R ₁ is a C _1-20 alkyl group, a C _2-20 alkenyl or alkynyl group, or a C _5-20 aryl group; R ₂ and R ₃ are each independently a hydrogen atom, a C _1-20 alkyl group, a C _2-20 alkenyl or alkynyl group, or a C _5-20 aryl group; and n is an integer of 1 or greater.

The composition of the present invention has a low content of benzyl alcohol, which prevents poisoning caused by benzyl alcohol and allows spraying without the use of special equipment such as an air mask. In addition, the composition of the present invention has superior stripping performance compared to compositions containing benzyl alcohol. Furthermore, the composition of the present invention has stable properties even in low-temperature environments, making it suitable for use in outdoor paint film stripping operations in winter.

A coating stripping composition for buildings or structures according to one embodiment of the present invention (hereinafter simply referred to as "the composition") contains compound (1) and an ester-based solvent, and has a benzyl alcohol content of less than 1% by weight.
R ₁ -(OCH(R ₂ )-CH(R ₃ )) _n -OH (1)

As mentioned above, Patent Document 4 points out that the stripping action of a stripping composition containing ethylene glycol monoalkyl ether is insufficient. Patent Document 1 also discloses that ethylene glycol monoalkyl ether, propylene glycol alkyl ether, and the like are not effective when used alone. Furthermore, as disclosed in Patent Document 4, propylene glycol alkyl ether is only known as a component of a dip-type coating film stripper, and its stripping performance against architectural coating films, particularly architectural coating films (finishing coating materials) made of acrylic resin, was not known. In contrast, it has been newly discovered that the present composition, by using compound (1), has a completely unexpected effect of being superior in stripping performance to the case where benzyl alcohol is used.

This composition contains compound (1). Compound (1) may be used alone or in combination of two or more types.

In formula (1), R ₁ is a C _1-20 alkyl group, a C _2-20 alkenyl group or alkynyl group, or a C _5-20 aryl group. The upper and lower limits of the number of carbon atoms of the C _1-20 alkyl group, the C _2-20 alkenyl group and alkynyl group, and the C _5-20 aryl group can be any integer within the above range. _{R 1} is preferably a C _5-20 aryl group, more preferably a C _5-12 aryl group, and even more preferably a phenyl group. The C _5-20 aryl group may have other substituents on the ring, or may be unsubstituted. For example, R ₁ may be a substituted phenyl group, or may be an unsubstituted phenyl group.

In formula (1), R ₂ and R ₃ are each independently hydrogen, a C _1-20 alkyl group, a C _2-20 alkenyl group or alkynyl group, or a C _5-20 aryl group. The above explanation applies to the C _1-20 alkyl group, the C _2-20 alkenyl group or alkynyl group, and the C _5-20 aryl group. R ₂ and R ₃ may be the same group or atom, or may be different groups or atoms. For example, one of R ₂ and R ₃ may be a hydrogen atom, and the other may be a C _1-20 alkyl group, a C _2-20 alkenyl group or alkynyl group, or a C _5-20 aryl group. In addition, both R ₂ and R ₃ may be hydrogen atoms, or both may be a C _1-20 alkyl group, a C _2-20 alkenyl group or alkynyl group, or a C _5-20 aryl group.

Preferably, one of _R2 and _R3 is a hydrogen atom and the other is a _C1-20 alkyl group, a _C2-20 alkenyl or alkynyl group, or a _C5-20 aryl group. More preferably, one of _R2 and _R3 is a hydrogen atom and the other is a _C1-20 alkyl group, a _C1-10 alkyl group, a _C1-5 alkyl group, or a _C1-3 alkyl group.

In formula (1), n is an integer of 1 or more. The upper and lower limits of n can be appropriately selected from integers of 1 or more as necessary. Preferably, n is an integer of 1 to 100, more preferably, n is an integer of 1 to 50, even more preferably, n is an integer of 1 to 10, and particularly preferably, n is an integer of 1 to 5.

Concerning the combination of R ₁ to R ₃ and n, any combination described above can be specifically selected. As the compound (1), a compound in which R ₁ is a C _5-20 aryl group, one of R ₂ and R ₃ is a hydrogen atom, and the other is a C _1-20 alkyl group, a C _2-20 alkenyl group or alkynyl group, or a C _5-20 aryl group, and n is an integer of 1 to 100 can be mentioned. More preferred examples include a compound in which R ₁ is a C _5-12 aryl group, one of R ₂ and R ₃ is a hydrogen atom, and the other is a C _1-10 alkyl group, and n is an integer of 1 to 10 can be mentioned. Even more preferred examples include a compound in which R ₁ is a substituted or unsubstituted phenyl group, one of R ₂ and R ₃ is a hydrogen atom, and the other is a C _1-5 alkyl group, and n is an integer of 1 to 5 can be mentioned.

Specific examples of compound (1) include diethylene glycol methyl ether, polyethylene glycol methyl ether, propylene glycol phenyl ether, propylene glycol methyl ether, ethylene glycol isopropyl ether, diethylene glycol methyl ether, ethylene glycol benzyl ether, and diethylene glycol hexyl ether.

The content of compound (1) in the composition is not particularly limited and may be within an appropriate range as necessary. The content of compound (1) in the total amount of the composition (100% by weight) is usually 1 to 95% by weight, preferably 1 to 90% by weight, more preferably 3 to 85% by weight, and even more preferably 5 to 80% by weight.

The present composition contains the ester-based solvent. Generally, the freezing point of compound (1) is high; for example, the freezing point of propylene glycol phenyl ether is 11°C. Therefore, a coating film stripping composition containing compound (1) such as propylene glycol phenyl ether may solidify in a low-temperature environment, particularly below freezing at 0°C or below, making it difficult to apply. By containing the ester-based solvent, the present composition can suppress solidification in a low-temperature environment without affecting stripping performance, etc. The ester-based solvent may be used alone or in combination of two or more.

The type of the ester-based solvent is not particularly limited. Examples of the ester-based solvent include dibasic acid esters and fatty acid esters. For example, either a dibasic acid ester or a fatty acid ester may be used as the ester-based solvent, or both may be used in combination. Using a dibasic acid ester and a fatty acid ester as the ester-based solvent is preferable because it increases the viscosity of the composition, particularly the viscosity of a composition containing a thickener, compared to using only one of them.

Examples of the dibasic acid ester include succinic acid ester, glutaric acid ester, and adipic acid ester. Specific examples of the dibasic acid ester include dimethyl succinate, dimethyl glutaric acid, dimethyl adipate, diethyl succinate, diethyl glutaric acid, and diethyl adipate. The dibasic acid ester may be used alone or in combination with two or more kinds. In general, a mixture of two or more kinds is preferred because it is inexpensively available. An example of the mixture of dibasic acid esters is "DBE" manufactured by Sigma-Aldrich.

The fatty acid ester may be a saturated fatty acid ester or an unsaturated fatty acid ester. Examples of the fatty acid ester include esters of fatty acids having 8 to 20 carbon atoms, or esters of fatty acids having 8 to 20 carbon atoms and alcohols having 1 to 6 carbon atoms. Specific examples of the fatty acid ester include methyl caprylate, methyl caprate, methyl laurate, methyl myristate, methyl palmitate, methyl palmitoleate, methyl stearate, methyl oleate, methyl linoleate, methyl linolenate, butyl palmitate, butyl stearate, octyl palmitate, isopropyl myristate, and isopropyl palmitate. The fatty acid ester may be used alone or in combination with two or more types. In general, a mixture of two or more types is preferred because it is inexpensively available. Examples of the fatty acid ester mixture include "TOENOL #2180-70" manufactured by Toei Chemical Co., Ltd.

There is no particular limit to the content of the ester-based solvent, and it can be within an appropriate range as necessary. The content of the ester-based solvent is usually 1 to 97% by weight, preferably 5 to 95% by weight, and more preferably 10 to 90% by weight, of the total amount of the composition (100% by weight). When two or more types of ester-based solvents are used, the total amount of the ester-based solvents can be within the above range.

When a dibasic acid ester and a fatty acid ester are used as the ester solvent, there is no particular limitation on the content and ratio thereof, and they can be set to an appropriate range as necessary. In the total amount of the composition (100% by weight), the content of the dibasic acid ester can be 0.5 to 90% by weight, preferably 2.5 to 80% by weight, more preferably 5 to 70% by weight, and more preferably 5 to 60% by weight, and the content of the fatty acid ester can be 0.5 to 90% by weight, preferably 2.5 to 80% by weight, more preferably 5 to 70% by weight, and more preferably 10 to 60% by weight. The ratio of the dibasic acid ester and the fatty acid ester (dibasic acid ester: fatty acid ester) can be 1: (0.1 to 10), preferably 1: (0.15 to 8), more preferably 1: (0.2 to 6), and more preferably 1: (0.3 to 4) by weight.

In this composition, the content of benzyl alcohol is less than 1% by weight, preferably less than 0.75% by weight, and more preferably less than 0.5% by weight, based on the total weight of the composition (100% by weight). When the content of benzyl alcohol is within the above range, poisoning by benzyl alcohol can be suppressed, and the peeling work can be performed without using special equipment such as an air supply mask when spraying, which is preferable. Note that the statement "The content of benzyl alcohol is less than 0% by weight" in the claims and this document does not mean that benzyl alcohol is contained as an essential component in this composition. Therefore, the lower limit of the content of benzyl alcohol in this composition may be 0% by weight.

In general, coatings are applied not only to horizontal surfaces of structures, but also to vertical surfaces. Increasing the viscosity of the composition is preferable because it allows the composition to be easily applied to vertical surfaces of structures and the coating to be peeled off. The viscosity of the composition (measured with a B-type viscometer using a No. 4 rotor at 30 rpm and a temperature of 20°C) can be in the range of 3 to 50 Pa·s, for example. There are no particular limitations on the method for increasing the viscosity of the composition. Examples of such methods include adding a thickener, as well as adding a resin or a surfactant.

The type of thickener is not particularly limited. Any thickener commonly used in coating removers can be used as the thickener. Specific examples of the thickener include silica, sepiolite, bentonite, montmorillonite, cellulose-based polysaccharides, acrylic thickeners, and alkylamides. The thickener may be used alone or in combination of two or more types.

There is no particular limit to the content of the thickener, and it can be within an appropriate range as necessary. The content of the thickener is usually 1 to 30% by weight, preferably 2 to 15% by weight, and more preferably 3 to 20% by weight, based on 100% by weight of the total amount of the composition.

The present composition may contain one or more other components known to be used in coating stripping compositions, so long as the effect of the composition is not significantly impaired. Specific examples of such other components include solvents known to be used in stripping compositions (e.g., N-methyl-2-pyrrolidone and γ-butyrolactone), rust inhibitors, cleaning agents, surfactants, acids (e.g., organic acids), and alkalis (e.g., organic amines).

The composition is used to remove coating films formed on buildings or structures. There are no particular limitations on the type of the building or structure. Specific examples of the building include houses (private homes, apartments, condominiums, buildings, etc.), schools, gates, fences, etc. Specific examples of the structure include steel structures such as bridges, pedestrian bridges, water gates, and steel towers.

There is no particular limitation on the part of the building or structure on which the coating film is formed. The coating film may be formed on the outdoor surface or indoor surface of the building or structure. As described above, the composition has stable properties even in low-temperature environments. Therefore, it is preferable that the coating film is formed on the outdoor surface of the building or structure.

There are no particular limitations on the material on which the coating film is formed. Examples of such materials include general materials that are used to construct structures. Specific examples of such materials include metals (steel, etc.), concrete, glass, mortar, and ALC.

Specific examples of the architectural coating film include thin coating material E, waterproof thin coating material E, thick coating material E, multi-layer coating material E, waterproof multi-layer coating material E, and multi-layer coating material RE, as described in JIS A 6909. Specific examples of the coating film for the steel structure include coating system A (long-type etching primer, lead-based rust-preventive paint type 1, long-oil phthalic acid resin paint), coating system B (long-type etching primer, lead-based rust-preventive paint type 1, phenolic resin MIO paint, chlorinated rubber paint), coating system C (epoxy resin paint or modified epoxy resin paint, polyurethane resin paint), etc., as described in the Steel Road Bridge Painting and Corrosion Prevention Handbook (revised edition) published by the Japan Road Association.

There is no particular limitation on the type of coating film. Specific examples of the coating film include coating films mainly composed of acrylic resin, polyester resin, polyurethane resin, epoxy resin, and alkyd melamine resin. Coating films mainly composed of acrylic resin are generally used as architectural coating films, but it is not known that compounds (1) such as propylene glycol phenyl ether are effective in removing coating films mainly composed of acrylic resin. In contrast, the present composition can be suitably used for removing coating films mainly composed of acrylic resin (note that the "main component" means a resin component whose content is 50% by weight or more in 100% by weight of the coating film, or the resin component with the largest content when there are two or more resin components).

The composition is usually applied to a coating film on the surface of a building or structure. If necessary, the composition is left to stand for a certain period of time (usually about 24 hours), and then the coating film is peeled off using a peeling tool such as a scraper. There are no particular limitations on the specific manner of "applying" as long as the composition can be attached to the surface of the building or structure by a method other than immersion. Specific examples of the "applying" include direct application with a brush or the like and spraying with a spray or the like.

There is no particular limitation on the method for preparing the composition. As described above, the composition has a low content of benzyl alcohol, and therefore can suppress poisoning caused by benzyl alcohol, and has superior stripping performance compared to compositions containing benzyl alcohol. Therefore, the composition can be prepared and used, for example, by replacing the benzyl alcohol in a commercially available coating stripper containing benzyl alcohol with compound (1) such as propylene glycol phenyl ether.

The present invention will be specifically explained below with reference to examples. Note that the present invention is not limited to the forms shown in the examples. The embodiment of the present invention can be modified in various ways within the scope of the present invention depending on the purpose, application, etc.

(1) Preparation of coating film stripping composition The components and ratios of the coating film stripping compositions of the examples and comparative examples are shown in Tables 1 and 2. The content of each component in Tables 1 and 2 is in weight percent. The coating film stripping compositions of the examples and comparative examples were prepared by stirring and mixing each component with a propeller blade. The details of the components in Tables 1 and 2 are as follows.
Propylene glycol phenyl ether ("Dowanol PPH" manufactured by The Dow Chemical Company)
Dibasic acid ester: "DBE" manufactured by Sigma-Aldrich
Viscosifier: Organically modified bentonite

(2) Peel test 1 (for buildings)
Each of the coating film stripping compositions of the Examples and Comparative Examples was applied to the multi-layer coating material E (sprayed tile) ^at 0.5 kg/m2 and left in a thermostatic chamber at 20°C for 24 hours. The coating film was then peeled off with a scraper. The peeling state was evaluated based on the following criteria. The results are shown in Table 1.
◎: Easily removable 〇: Removable △: Difficult to remove ×: Very difficult to remove

(3) Peel test 2 (for structures)
Each of the coating film stripping compositions of the Examples and Comparative Examples was applied at 1.0 kg/ ^m2 to the A coating system (phthalic acid system) and left in a thermostatic chamber at 20°C for 24 hours. The coating film was then peeled off with a scraper. The peeling state was evaluated based on the same criteria as in the peeling test 1. The results are shown in Table 2.

(4) Coagulation Test Mixtures were prepared in the proportions (wt%) shown in Table 3 using the propylene glycol phenyl ether, dibasic acid ester, and methyl oleate used in the preparation of the coating stripping compositions of the Examples. These mixtures were placed in a freezer at -5°C, and after 24 hours, the presence or absence of coagulation was visually confirmed. The results are shown in Table 3. In addition, the presence or absence of coagulation was visually confirmed for the solvent compositions of Examples 1 to 4 and the Comparative Example (propylene glycol phenyl ether, dibasic acid ester, and methyl oleate) by the same method as above. The results are shown in Table 4. In Tables 3 and 4, "◯" means that coagulation did not occur, and "×" means that coagulation occurred.

As can be seen from Tables 1 and 2, the coating film stripping compositions of the examples show excellent stripping performance in both the multi-layer coating material E and A coating systems. These results show that the coating film stripping compositions of the examples can be suitably used to strip coatings from both buildings and structures.

From Table 1, it can be seen that the coating film stripping compositions of the examples containing propylene glycol phenyl ether have superior coating film stripping performance compared to Comparative Examples 2 to 9, which used solvents other than benzyl alcohol. In addition, when comparing Comparative Example 1, which used benzyl alcohol as the solvent, with Comparative Examples 2 to 9, which used a solvent other than propylene glycol phenyl ether instead of benzyl alcohol, Comparative Examples 2 to 9 have inferior stripping performance compared to Comparative Example 1. In contrast, Example 2, which used propylene glycol phenyl ether instead of benzyl alcohol, has superior coating film stripping performance compared to Comparative Example 1. This result shows that the use of propylene glycol phenyl ether instead of benzyl alcohol improves stripping performance compared to the use of other solvents.

From Table 3, it was confirmed that propylene glycol phenyl ether alone solidified at -5°C. On the other hand, from Tables 3 and 4, a mixture containing propylene glycol phenyl ether and an ester solvent (dibasic acid ester and/or oleic acid methyl ester) did not solidify even at -5°C. From these results, the coating film stripping composition of this example is stable in properties even under conditions below freezing point and can be applied. Furthermore, from Table 4, since solidification is suppressed even when propylene glycol phenyl ether is used instead of benzyl alcohol, the coating film stripping composition of this example does not lose its stability in properties in low temperature environments even when propylene glycol phenyl ether is used instead of benzyl alcohol.

Claims (4)

A coating stripping composition for buildings or structures, comprising a compound of formula (1) and an ester solvent, the content of the ester solvent being 40 to 90% by weight, and the content of benzyl alcohol being less than 1% by weight:

R ₁ -(OCH(R ₂ )-CH(R ₃ )) _n -OH (1)

In the formula,
R ₁ is a C _2-20 alkenyl or alkynyl group, or a C _5-20 aryl group;
R ₂ and R ₃ are each independently a hydrogen atom, a C _1-20 alkyl group, a C _2-20 alkenyl or alkynyl group, or a C _5-20 aryl group;
n is an integer of 1 or more. 2. The coating stripping composition according to claim 1, wherein R ₁ is a C _5-20 aryl group, one of R ₂ and R ₃ is a hydrogen atom and the other is a C _1-20 alkyl group, and n is an integer from 1 to 10. The coating stripping composition according to claim 1 or 2, wherein the ester-based solvent comprises either or both of a dibasic acid ester and a fatty acid ester. A method for removing a coating film from a building or structure, comprising applying the coating film-removing composition according to any one of claims 1 to 3 to a coating film on a surface of the building or structure, and then removing the coating film using a removing tool.