WO2002002699A1

WO2002002699A1 - Method for removing paint using a barrier film

Info

Publication number: WO2002002699A1
Application number: PCT/CA2001/000977
Authority: WO
Inventors: Daniel Pageau; Elizabeth Marcu
Original assignee: E.Qu.I.P. International Inc.
Priority date: 2000-07-04
Filing date: 2001-07-03
Publication date: 2002-01-10
Also published as: CA2313375A1; AU2001272247A1

Abstract

A method for efficiently removing a film of paint from a surface which comprises the steps of applying a paint stripper onto the film of paint to be removed; covering the film of paint and paint stripper applied thereto with an impermeable or semi permeable barrier film; allowing the paint striper to act onto the paint at room temperature for a given period of time; and removing the barrier film and cleaning the surface by wiping it and/or washing it with water to remove any paint which has not come off, attached to the barrier film.

Description

METHOD FOR REMOVING PAINT USING A BARRIER FILM

Field of the invention

The present invention relates to a method for facilitating removal of a film of chemically resistant paint by application thereto of a paint stripping agent.

More particularly, the invention relates to a method where a barrier film is used to ensure intimate contact between the paint film and paint stripping agent.

Background of the invention

Chemically resistant paints, such as epoxy, urethanes and others, commonly used on aeroplanes, trains or other types of equipment are very difficult to remove using chemical stripping agents. As a matter of fact, to strip these types of paint off, there are only limited options.

A first option consists of sandblasting the paint to be stripped off with agents such as starch, dry ice or others which will not damage the underlying substrate. This technique is efficient but it results in the production of large amounts of contaminated and/or dangerous sandblasting by-products that are difficult to dispose of, and cannot be used for any other purpose.

A second option consists of using methylene chloride based paint strippers (or those containing CFCs or phenol) because they are very effective. Notwithstanding this effectiveness, the use of methylene chloride has two major drawbacks. Firstly, methylene chloride is not environmentally friendly as it adversely affects the ozone layer and its use is being restricted. Secondly, it cannot effectively remove some paints.

A third option consist of using the GREENSOLV™ products forming the subject matter of US patent Nos. 5,932,530 and 5,952,277 both assigned to the Applicant. These synergistic paint strippers are more environmentally friendly that the methylene chloride based paint strippers, but they are not as effective as desired for removing some high durability paints that are used on some equipments such as airplanes.

Summary of the invention It has now been found that when a paint stripper like those sold by the Applicant under the trademark GREENSOLV is applied (usually by painting) onto a film of paint to be removed and is then covered by a barrier film such as an aluminium foil (or other film such as high density polyethylene), the film of paint is completely removed within 2 hours. If, in contrast, the stripper applied to the film of paint is left exposed to the air with no barrier film, it will still be incompletely removed even after 6 hours.

This is an unexpected result and a similar improvement has been found with other types of strippers, even those containing methylene chloride. In the case of methylene chloride strippers, one could tentatively explain the good result obtained in accordance with the invention by the fact that the barrier film would reduce the evaporation of methylene chloride, which is quite volatile. However, in the case of the GREENSOLV™ strippers, the solvents used therein have an extremely low volatility and at room temperature, the losses due to evaporation would easily be less than 10%. Thus, the enhanced cleaning effect obtained in accordance with the invention is not exclusively due to a prevention of solvent evaporation, although this may account for the improved performance obtained with methylene chloride based strippers. Thus, the main object of the invention is to provide a method for efficiently removing a layer(s) of paint from a surface, which comprises the steps of: ^• applying a paint stripper such as a GREENSOLV™ product, onto the film of paint to be removed; covering the film of paint and the paint stripper applied thereto with an impermeable or semi-permeable barrier film such as an aluminium foil; allowing the paint stripper to act onto the paint at room temperature for a given period of time of typically 2 hours; and removing the barrier film and cleaning the surface by wiping it and/or washing it with water to remove any paint which has not come off attached to the barrier film.

Detailed description of the invention

As aforesaid, the method according to the invention makes use of an impermeable or semi-permeable barrier film to ensure intimate contact between the paint stripping agent and the paint film. The barrier film can be composed of metal (such as aluminium), plastic (such as polyethylene or any other type of plastic material not affected by the solvent system used in the stripping agent), paper (including coated papers) or any other materials. It may also consist of a wax film included in the stripping agent or applied over it. Once the paint film has been removed, the barrier film may be disposed off, recycled of reused. After such a renewal, the surface can be cleaned by wiping and/or washing with water. The chemicals will degrade in less than 16 days and the solids left in water may easily be removed by filtration. After regular treatment, the water used for the washing can be disposed off in a municipal sewer.

Successful tests were carried out by the Applicant using an aluminium foil as barrier film. However, one could also use plastics such as polyethylene or any other type not affected by the solvent system used in the paint stripper. As aforesaid, even plastic coated (or metal film coated) paper could be employed to prevent oxygen/moisture contacts with the paint stripper. The basic idea behind the invention is essentially to limit the contact with air by the use of a barrier film. The actual nature of the film itself does not appear to be critical, other than the fact that it is impermeable or at least semi-impermeable to air and the solvents employed.

As aforesaid, the method according to the invention is particularly effective against chemically resistant paints, such as epoxy and polyurethanes. However, it can also be used on other types of paints with equal effect.

Chemically resistant paints are typically used on equipments such as aeroplanes, boats, trains, cars and other types of equipment. As aforesaid, it has been necessary so far to strip paint using mechanical methods such as blasting with abrasives or non-abrasive materials. The advantages of the present invention can be summarized as follows.

1 . The use of a barrier film improves efficiency of paint removal and, in many cases, it makes it feasible to use chemical stripping method, instead of blasting. 2. The use of a barrier film minimizes the loss of volatile solvents, which lowers VOC emissions and, as a secondary benefit, it ensures that the solvents remain in contact with the paint film, where they can act on it.

3. The use of a barrier film reduces the loss of paint stripper by mechanical means, i.e. it is less likely to drip off of the painted surface, being retained by the barrier film.

4. The use of a barrier film also ensures better, i.e. more intimate, contact between the chemical stripping agent(s) and the paint film. This further improves the stripping action. 5. The use of a barrier film prevents air contact with the stripping composition. In the case of strippers using some classes of gelling agents, exposures to humidity in the air can result destabilization of the gel/solvent matrix, which lowers the efficiency of the stripping agents. By excluding contact with air, the effectiveness of the stripper in increased. 6. The use of an impenetrable barrier film also serves to reduce or eliminate the potential of oxygen to come into contact with the cleaning mixture. Such enhances its cleaning efficiency.

7. Last of all, in some cases, the paint film will adhere to the barrier film. As a result, the use of a barrier film will facilitate removal of the paint when the barrier film is peeled off.

Claims

1 . A method for efficiently removing a film of paint from a surface, which comprises the steps of: applying a paint stripper onto the film of paint to be removed; covering the film of paint and the paint stripper applied thereto with an impermeable or semi-permeable barrier film; allowing the paint stripper to act onto the paint at room temperature for a given period of time; and removing the barrier film and cleaning the surface by wiping 'it and/or washing it with water to remove any paint which has not come off attached to the barrier film.

2. The method of claim 1 , wherein the barrier film is made of a material selected from the group consisting of metals, plastics, papers and wax films including in the paint stripper or applied over said paint stripper.

3. The method of claim 2, wherein the barrier film consists of an aluminium foil.

4. The method of claim 2, wherein the barrier film consists of a polyethylene sheet.

5. The method of any one of claims 1 to 4, wherein said given period of time is of about 2 hours.