WO2000021691A1

WO2000021691A1 - Chemically strippable protective coating and method wherein coating is stripped with alkaline aqueous solution

Info

Publication number: WO2000021691A1
Application number: PCT/US1999/021467
Authority: WO
Inventors: Charles Hawes
Original assignee: Armor All Products Corp
Current assignee: Energizer Auto Inc
Priority date: 1998-10-15
Filing date: 1999-10-15
Publication date: 2000-04-20
Anticipated expiration: 2001-04-15
Also published as: AU1093200A

Abstract

An alkaline strippable coating to protect substrates exposed to environmental conditions such as paint, plastic, rubber and metal. The coating is of a solution acrylic polymer which is not removed by weather conditions. Instead, the coating is chemically strippable by an alkaline aqueous solution such as a high pH cleaning solution. The coating can be applied to large surface areas with a garden hose sprayer. The coating dries to a thin protective film designed to last 1-2 years and add back gloss to surfaces such as vinyl or paint dulled by the effects of weather. The film can minimize oxidation of vinyl or paint by encapsulating the exposed TiO2 which acts as a UV blocker. The film can also add back depth of color to such surfaces and/or minimize the growth of biological soils such as mold/mildew and algae.

Description

CHEMICALLY STRIPPABLE PROTECTIVE COATING AND

METHOD WHEREIN COATING IS STRIPPED

WITH ALKALINE AQUEOUS SOLUTION

Field of the Invention The invention relates to the protection and cleaning of surfaces of articles or structures exposed to environmental conditions such as vinyl, painted or unpainted surfaces, metal and masonry.

Background of the Invention

Various cleaning products are available for purposes of removing undesired material such as dirt, mold, mildew, corrosion, etc. For instance, U.S. Patent Nos. 5,290,470 and 5,376,296 disclose a cleaning product useful for cleaning wood decks, vinyl, etc. and U.S. Patent Nos. 5,605,578; and 5,567,247 disclose cleaning products which can be applied by a hose-end spray gun for cleaning outdoor surfaces such as vinyl siding and painted wood. Examples of hose-end spray guns which can be used for this purpose are disclosed in U.S. Patent No. 5,595,345. Although products of the foregoing type can provide benefits such as ease of application and improved cleaning performance, it would be highly advantageous if the surfaces to be cleaned could also be protected by a strippable protective coating. Protective coatings have been used for years as an active principal agent to extend the life of various surfaces as well as in many cases to add beauty to the surface. Paint used on the exterior of wood frame houses is a well known case in point. Paint of various types extend the life of natural wood primarily by protecting the wood from the effects of weathering, i.e. , rain, UV rays and oxidation. It also is used to beautify the surface as well with various gloss components and colorants. Another case in point is the use of vinyl siding. Vinyl siding is very much like a long lasting paint that doesn't peel or crack and can last many years beyond that of paint.

In the case of paint, depending on the weather, quality of the paint and the nature of the surface it is applied to, i.e. , condition of the previous coating or bare wood peeling and cracking can occur in a few years. Fading of the color and oxidation generally begin noticeably in about two years depending on the weather. Preparation of the surface and repainting can be a laborious and expensive proposition. Vinyl siding is less susceptible to cracking or peeling but does begin to fade and oxidize within one to two years after installation especially on the south side of buildings where there is longer overall sun exposure time. Also, more so than painted surfaces, vinyl siding seems to attract mold/mildew, algae and perhaps other biological soils especially on the north side of the surface which has a shorter overall sun exposure time. U.S. Patent Nos. 2,615,820; 2,680,724; 3,034,915; 3,207,716; 3,625,727 and 3,746,561 disclose strippable coatings which may include a release agent for ease of physically peeling the coating from the object on which it is located. U.S. Patent No. 3,819,394 discloses a coating which can be rinsed from an object by use of a selective solvent such as water or a moderately alkaline aqueous solution in the case of a polyacrylic acid resin coating or an organic solvent in the case of an acrylic acid resin coating. Although such strippable coatings have been suggested for use in protecting goods from damage during shipment, there is an unfilled need for strippable protective coatings for application to surfaces exposed to environmental conditions. Summary of the Invention

The invention provides a chemically strippable coating which can be applied to a substrate exposed to environmental conditions, the coating comprising a dried film of a solution acrylic polymer, the film being chemically removable from the substrate by rinsing the film with an aqueous alkaline solution. The substrate can comprise various materials such as vinyl, plastic, metal, masonry, etc.

According to a preferred embodiment of the invention, the film is a dried film of a water soluble solution acrylic polymer. The solution acrylic polymer preferably has an acid number of at least about 40 and a molecular weight of less than about 100,000. For example, the film can comprises a dried mixture of a solution acrylic polymer, a base, a solvent and water. In one embodiment, the solution acrylic polymer is a thermosetting acrylic resin solution, the base is ammonium hydroxide, and the solvent is glycol ether. One advantageous aspect of the film is that it is not removed from the substrate by exposure of the film to rain water. The substrate can comprise a vinyl surface, a plastic surface, a painted surface, an unpainted metal surface or an unpainted masonry surface.

The invention also provides a method of cleaning a substrate exposed to environmental conditions, the substrate having a chemically strippable coating thereon in the form of a dried film of a solution acrylic polymer having dirt, algae, mold, mildew and/or foreign matter buildup thereon. The method comprises cleaning the substrate by spraying an alkaline aqueous solution onto the film and using the alkaline aqueous solution to chemically strip the film and buildup thereon from the substrate. According to various aspects of the method, a solution acrylic polymer can be sprayed onto the substrate after the cleaning step. For instance, a solution acrylic polymer can be sprayed onto the substrate during the cleaning step such that a new chemically strippable coating is applied to the substrate. The alkaline aqueous solution preferably has a pH of at least about 12. The coating is preferably applied onto the substrate by spraying an aqueous mixture comprising a base and a solution acrylic polymer onto the substrate, the solution acrylic polymer including enough acrylic or metaacrylic acid monomer functionality to provide clear water solubility in the aqueous mixture. The base can comprise an alkaline earth or volatile amine. The aqueous mixture can further include a leveling agent, a fluorocarbon surfactant, a UV absorber, and/or a sun blocking agent. Accordingly, the aqueous mixture can be applied onto a variety of materials such as a vinyl surface, a plastic surface, a painted surface, an unpainted metal surface, or an unpainted masonry surface. If desired, the base can comprise a volatile amine selected from the group consisting of ammonia, methylamine, ethylamine, propylamine, isopropylamine, dimethylamine, cyclohexylamine, trimethylamine, morpholine or combination thereof.

In a preferred method, the aqueous alkaline solution is sprayed onto the substrate by a hand-held hose-end sprayer wherein a concentrated aqueous alkaline solution is diluted with water and the diluted mixture is sprayed onto the film. Likewise, the aqueous mixture can be sprayed onto the substrate by a hand-held hose-end sprayer wherein the solution acrylic polymer is mixed with water supplied to the sprayer by a water hose.

Detailed Description of the Invention The invention provides an alkaline strippable protective coating useful for protecting outdoor surfaces from exposure to damaging environmental conditions such as sun damage, build-up of dirt, growth of algae and mold, etc. The protective coating provides a strippable barrier film which can be removed to expose the protected underlying surface. The protective coating can be periodically replaced by stripping a previously applied protective coating from the surface to be protected and applying a new protective coating. The stripping process removes the protective film and build-up accumulated thereon.

According to one embodiment of the invention, the protective coating is applied to new or cleaned vinyl siding by a consumer or professional service. The protective coating preferably is formulated such that it is not washed off of the vinyl siding by rain or tap water. However, the protective coating is removable by application of an alkaline rinse solution to the coating. For instance, the protective coating along with build-up thereon can be removed by spraying an alkaline cleaning composition onto the coating followed by rinsing the coating from the vinyl siding using a water rinse. For convenience, the cleaning composition and water rinse can be applied using a hand-held, hose end spray gun attached to a water hose. The cleaning composition can be held in a container attached to the spray gun and during application of the cleaning composition to the vinyl siding, the cleaning composition is siphoned from the container as it is mixed with water supplied by the water hose and sprayed from the spray gun. The cleaning composition is diluted as it mixes with the water, the dilution ration ranging from 1 to 50 parts water per 1 part water. Similarly, the protective coating can be applied in the same manner by siphoning the protective coating from a container and spraying a diluted mixture from the spray gun.

The protective coating preferably comprises a film which can be later stripped from an underlying surface by application of an aqueous solution such as an alkaline cleaning solution. It has been found that a protective coating incorporating a solution acrylic polymer can be stripped by an alkaline cleaning solution of the type disclosed in commonly owned U.S. Patent Nos. 5,567,247 and 5,605,578, the disclosures of which are hereby incorporated by reference.

The protective coating is preferably a sprayable aqueous solution. Suitable solution acrylic polymers can be made water soluble by addition of an appropriate base so as to have an acid number above 40 and/or a molecular weight below

100,000. Examples of such solution acrylic polymers can be found in U.S. Patent No. 4,566,962 (see Example 3: 495 parts ethyl acrylate, 355 parts styrene, 150 parts methacrylic acid and acid #70, and Example 8: 290 parts methyl methacrylate, 230 parts ethyl acrylate, 230 parts butylacrylate, 400 parts hydroxyethacrylate, 260 parts methacrylic acid and acid #70), and in U.S. Patent No. 4,591 ,533.

An especially preferred solution acrylic polymer which can be incorporated in the protective coating of the invention is a product called "SYNTHEMUL" available from Reichold Chemical Co. located in Research Triangle Park, North Carolina. This particular solution acrylic polymer has an acid number of 45 ± 5 and a molecular weight of approximately 10,000. The "SYNTHEMUL" can be mixed with other ingredients of a protective coating as follows: 50% "SYNTHEMUL" 40-427, 5% ammonium hydroxide, 10% glycol ether EB, 0.5% Fluorad FC 430 and 34.5% water. When diluted by spraying through a spray gun having a 1: 10 dilution ratio, the protective coating applied to a surface to be protected includes: 5% "SYNTHEMUL" 40-427, 0.5% ammonium hydroxide, 1 % glycol ether EB, 0.05% Fluorad FC 430 and 93.45% water. "SYNTHEMUL" 40-427 is a thermosetting acrylic resin solution supplied in ethylene glycol mono butyl ether and conventional uses include thermosetting enamels, metal coatings and flow coatings where high gloss and superior solvent resistance is needed. Neutralizing with an amine makes SYNTHEMUL 40-427 water-reducible.

According to one embodiment of the invention, the solution acrylic polymer coating formulation is characterized by being low to medium molecular weight and/or enough acrylic or methylacrylic acid monomer functionality in the polymer to give complete clear water solubility when neutralized with an appropriate base. The base can be of the alkaline earth or amine types. However, for the purpose of this invention the base is preferably a volatile amine type. The polymer may also contain other acrylic or methylacrylic esters such as methyl acrylate or methacrylate, ethyl acrylate or methacrylate, propyl (including isopropyl acrylate or methacrylate) and higher similar homologous.

The purpose of the polymeric solution after application of a thin film to a surface is primarily to be a sacrificial surface. That is, once coated onto a precleaned surface such as vinyl or plastic, painted surfaces as well as unpainted surfaces such as metal or masonry, foreign matter such as difficult to remove road film, algae and mold, etc. , deposit onto the thin polymer coating instead of the underlying surface itself. Since the coating is alkaline strippable the coating is removed with an appropriate base taking the built up soil with it leaving a clean surface. In some cases it is also possible to use this polymeric solution containing an excess of volatile amine base in order to strip off the previously applied soiled coating and depositing a new coating simultaneously.

Other attributes found with this coating on vinyl or painted surfaces is the regeneration of gloss and depth of color to the surface lost due to oxidation of the organic surface. Also it is theorized that reduction and perhaps complete elimination of further oxidation is possible. It has also been documented that complete elimination of the growth of unsightly mold/mildew and algae is prevented on the organic surfaces for at least one year or growth season.

A general formula for the solution acrylic polymer is as follows:

Acrylic Acid

CH

CH₂= COOH

Methylacrylic Type

where COOH is an acid group neutralizable with an appropriate base to give complete water solubility, R,, R₂ and R₃ are organic acrylic esters or methacrylic esters to give varying hardness and flexibility. In general, the smaller the R group the harder the dried film and the larger and more branched chains give more flexibility. A-D are the quantities of each monomer in the polymer. At least one of the R groups may contain a hydro xyl group. Also styrene may also be used as one of the monomers.

An appropriate base is a volatile amine type such as ammonia, methylamine, ethylamine, propylamine, isopropylamine, dimethylamine, cyclohexylamine, trimethylamine, moφholine and various combinations thereof. Solution acrylic polymers which can be made water soluble by the addition of an appropriate base are characterized by having an acid number above 40 and a molecular weight below 100,000.

Examples in the patent literature are: U.S. Patent No. 4,566,962 Example 3

495 parts ethyl acrylate 355 parts styrene 150 parts methacrylic acid Acid #70

Example 8

290 parts methyl methacrylate

230 parts ethylacrylate

320 parts butylacrylate

400 parts hydroxyethylacrylate 260 parts methacrylic acid

Acid #70

Other examples can be found in U.S. Patent No. 4,591,533. For the puφose of protecting exterior home surfaces such as vinyl siding, painted wood and aluminum, a preferred solution acrylic polymer is called Synthemul 40427 made by Reichold Chemicals Co. , Research Triangle Park, NC 27709. This solution acrylic polymer has an acid number of 45 ±5 and a molecular weight of approximately 10,000.

A formula for a hose end sprayer with a 1 : 10 dilution ratio wherein 1 part solution acrylic polymer coating composition is diluted with 10 parts water is as follows:

50% Synthemul 40427 5 % ammonium hydroxide

10% glycol ether EB 0.5% Fluorad FC 430 34.5% Water

A ready to use formula applied without dilution is as follows: 5% Synthemul 40427

0.5% ammonium hydroxide 1 % glycol ether EB 0.05% Fluorad FC 430 93.45% Water

The foregoing has described the principles, preferred embodiments and modes of operation of the present invention. However, the invention should not be construed as being limited to the particular embodiments discussed. Thus, the above-described embodiments should be regarded as illustrative rather than restrictive, and it should be appreciated that variations may be made in those embodiments by workers skilled in the art without departing from the scope of the present invention as defined by the following claims.

Claims

Claims:

1. A chemically strippable protective coating on a substrate exposed to environmental conditions, the coating comprising a dried film of a solution acrylic polymer, the film being removable from the layer by rinsing the film with an aqueous alkaline solution.

2. The coated substrate of claim 1 , wherein the film is removable from the substrate by rinsing the film with an alkaline cleaning solution.

3. The coated substrate of claim 1, wherein the film is a dried film of a sprayed solution acrylic polymer.

4. The coated substrate of claim 1, wherein the film is a dried film of a water soluble solution acrylic polymer.

5. The coated substrate of claim 1, wherein the solution acrylic polymer has an acid number of at least about 40 and a molecular weight of less than about 100,000.

6. The coated substrate of claim 1, wherein the film comprises a dried solution of a solution acrylic polymer, a base, a solvent and water.

7. The coated substrate of claim 6, wherein the solution acrylic polymer is a thermosetting acrylic resin solution, the base is ammonium hydroxide, and the solvent is glycol ether.

8. The coated substrate of claim 1, wherein the film is not removed from the substrate by exposure of the film to rain water.

9. The coated substrate of claim 1, wherein the substrate comprises a vinyl surface , a plastic surface, a painted surface, an unpainted metal surface or an unpainted masonry surface.

10. A method of cleaning a substrate exposed to environmental conditions, the substrate having a chemically strippable coating thereon, the coating comprising a dried film of a solution acrylic polymer having dirt, algae, mold, mildew and/or foreign matter buildup thereon, the method comprising a step of cleaning the substrate by spraying an alkaline aqueous solution onto the film, the alkaline aqueous solution being effective to chemically strip the film and buildup thereon from the substrate.

11. The method of claim 10, further comprising a step of spraying a solution acrylic polymer onto the substrate after the cleaning step.

12. The method of claim 10, further comprising spraying a solution acrylic polymer onto the substrate during the cleaning step such that a new chemically strippable coating is applied to the substrate.

13. The method of claim 10, wherein the alkaline aqueous solution has a pH of at least about 12.

14. The method of claim 10, further comprising a step of applying the coating to the substrate by spraying an aqueous mixture comprising a base and a solution acrylic polymer onto the substrate, the solution acrylic polymer including enough acrylic or metaacrylic acid monomer functionality to provide clear water solubility in the aqueous mixture.

15. The method of claim 14, wherein the base comprises an alkaline earth or volatile amine.

16. The method of claim 14, wherein the aqueous mixture further includes a leveling agent, a fluorocarbon surfactant, a UV absorber, and/or a sun blocking agent.

17. The method of claim 10, wherein the substrate comprises a vinyl surface, a plastic surface, a painted surface, an unpainted metal surface, or an unpainted masonry surface.

18. The method of claim 14, wherein the base comprises a volatile amine selected from the group consisting of ammonia, methylamine, ethylamine, propylamine, isopropylamine, dimethylamine, cyclohexylamine, trimethylamine, moφholine or combination thereof.

19. The method of claim 10, wherein the aqueous alkaline solution is sprayed onto the substrate by a hand-held hose-end sprayer wherein a concentrated aqueous alkaline solution is diluted with water and the diluted mixture is sprayed onto the film.

20. The method of claim 14, wherein the aqueous mixture is sprayed onto the substrate by a hand-held hose-end sprayer wherein the solution acrylic polymer is mixed with water supplied to the sprayer by a water hose.