GELLING COMPOSITIONS FOR STRIPPING AND CLEANING

Abstract: A chemical composition for stripping and cleaning surfaces of grease, paint and the like. The chemical composition comprising a synthetic water absorbant and swellable polymeric substance for absorbing a solution of a stripping and cleaning agent. The synthetic polymeric substance may be a product marketed in Australia under the trade mark "AGROSOKE", a crosslinked acrylamide or methacrylamide polymer, a crosslinked acrylamide or methacrylamide polymer and a copolymer of acrylamide and acrylic acid, or a crosslinked copolymer of acrylamide or methacrylamide and acrylic acid or methacrylic acid. The stripping and cleaning agent is an aqueous solution of a caustic alkali such as sodium hydroxide which may be optionally enhanced by adding components such as ammonium compounds, compounds containing amine groups and organic solvents at the appropriate time depending upon the intented application.

Description: reri.TNG CX OSITIO S FOR SHIPPING AND CLEANDC Technical Field THIS INVENTION relates to chemical compositions for use as paint, oil or grease removers, cleaning agents, and other related applications. Background Art In many applications where chemicals are used to clean, strip or otherwise act upon a surface, the effectiveness of the action of the chemicals is very much dependent upon contact between the chemicals and the surface. In particular, with paint stripping compositions comprised of chlorinated hydrocarbons or aqueous caustic solutions, the use of these compositions is effective only on substantially horizontal surfaces because of the low viscosity. Additionally, any such solution is effective only for the duration that the solvent component remains unevaporated on the surface being acted upon. When evaporation occurs, a further application of the paint stripping composition is necessary to effectively continue the paint stripping operation. Further, due to the low viscosity of these compositions, it is difficult to confine their action to a particular portion of a surface which is required to be stripped or cleaned. West German Patent Specification Number 3338027 discloses the use of potato flour as a thickening agent for a paint stripping composition. The disadvantage of this type of thickened paint stripping composition, although being an improvement over non thickened aqueous caustic compositions, is that it is still subject to running on substantially vertical surfaces and is still subject to loss of effectiveness due to evaporation of the solvent from the composition, the thickening agent not substantially slowing the rate of evaporation compared with similar aqueous caustic paint strippers which are not thickened. It is an object of the present invention to provide a chemical composition which exhibits improved adhesive and solvent retention properties for use in stripping and cleaning applications. In accordance with one aspect of the present invention there is provided a chemical composition for stripping and cleaning comprising a gel formed by reacting an aqueous alkaline solution with a synthetic polymeric substance. Preferably the polymeric substance has liquid absorbing properties. One suitable polymeric substance is that marketed in Australia under the trade mark AGROSOKE. Suitable synthetic polymeric substances other than AGROSOKE include: a crosslinked acrylamide or methacrylamide polymer. a crosslinked copolymer of acrylamide or methacrylamide and acrylic acid or methacrylic acid. a crosslinked acrylamide or methacrylamide polymer and a copolymer of acrylamide and acrylic acid. The crosslinked polymer and crosslinked copolymer are as substantially described in Canadian Patent Specification Number 1200943. The preferred crosslinking agent of said crosslinked polymers is methylenebisacrylamide which is present in proportion of up to 10% by weight of the other monomer component (s) of the polymer. The crosslinked acrylamide or methacrylamide polymer which further includes a copolymer of acrylamide and acrylic acid, with the weight ratio of acrylamide and acrylic acid in this copolymer preferably being 7:3, is as substantially described in United States Patent Specification Number 4579578. The preferred crosslinking agent of this crosslinked acrylamide or methacrylamide polymer is methylenebisacrylamide which is present in the crosslinked polymer in proportion of up to 10% by weight. Preferably said synthetic polymeric substance is divided into a plurality of particles. Preferably the particle size of- said plurality of particles is between 50 and 200 microns. Preferably the alkaline component of said aqueous alkaline solution is one of sodium hydroxide or potassium hydroxide. Preferably said chemical composition further incorporates a component selected from the following:- - a compound containing an ammonium group - a compound containing an amine group - an organic solvent - a mixture of the above Preferably said organic solvent is one of methylene chloride, acetone or methyl ethyl ketone. Preferably said compound is one of urea or an ammonium compound such as ammonium nitrate. Preferably the quantity of said organic solvent used is up to 20% by volume. Preferably the quantity of said compound used is up to 25% by weight of the weight of said alkaline component. Modes for Carrying Out the Invention The invention will be better understood by reference to the following specific examples: Example 1 Thirty grams of AGROSOKE polymer granules ground to a powder of particle size 100 to 125 microns were slowly added to a hot solution of eighty grams of sodium hydroxide dissolved in one litre of water, whilst stirring. The mixture was stirred thoroughly every ten minutes to ensure that the polymer remained evenly dispersed within the solution. Absorption of the solution was complete in one hour. The resulting chemical composition was found to have the following attributes:- it spread easily on a surface to be stripped or cleaned and exhibited good adhesive properties in so far as that it did not run on or detach from vertical, overhead, or substantially inclined surfaces; it exhibited an initial delayed acting effect which increased the handling safety; it exhibited improved solvent retaining characteristics, when compared with non-polymeric thickened aqueous alkaline stripping and cleaning compositions or solvent based strippers or cleaners, which resulted in an extension of the time that the gel remained effective when in contact with the surface; if the composition dried out due to being employed in extremes of temperature, low humidity or over a long period of time, it was reactivated simply by wetting, whereupon it continued to operate. The chemical composition was found to be particularly suited for use in difficult applications such as the removal of graffiti from porous surfaces. The effectiveness of the composition in difficult applications was improved further by the addition of 20g of a compound containing ammonium or amine groups such as urea or ammonium nitrate. These were added to the composition, prior to application to a surface, in crystaline or aqueous form. It is believed that the resultant reaction with the alkali releases ammonia into the aqueous medium within the gel which improves the effectiveness of the gel. A suitable amount to add was found to be approximately 25% by weight of the weight of the caustic alkali used in the composition. Removal of certain coatings from surfaces, such as polyurethane paints was found to be aided by the addition of an organic solvent such as methylene chloride, acetone, or methyl ethyl ketone to the gel, in amount of up to 20% by volume. Example 2 The second example of the invention is directed toward a chemical composition for stripping paints and grease from surfaces in environments of high relative humidity or of low evapotranspiration. This example is produced in substantially the same manner as the first example except that the thirty grams of AGROSOKE- polymer granules were ground to a smaller powder of a particle size of approximately 50 to 75 microns. The resulting chemical composition was faster acting in its stripping and cleaning properties, but its water retention properties were diminished when compared with the first example; hence its suitability for indoor applications, or high relative humidity applications. In further embodiments, organic solvents such as acetone or methyl ethyl ketone are utilised instead of methylene chloride depending on the application. It should be appreciated that the scope of the present invention is not limited to the particular embodiments described herein, and that the quantities of components of the chemical composition can be varied, and powder size can be varied.

Claims: THE CLAIMS defining the invention are as follows:- 1. A chemical composition for stripping and cleaning comprising a gel formed by reacting an aqueous alkaline solution with a synthetic polymeric substance, wherein said synthetic polymeric substance has liquid absorbing properties. 2. A chemical composition as claimed in claim 1, where suitable synthetic polymeric substances include one of: a product marketed in Australia under the trade mark AGROSOKE a crosslinked polymer of acrylamide or methacrylamide a crosslinked copolymer of acrylamide or methacrylamide and acrylic acid or methacrylic acid a crosslinked polymer of acrylamide or methacrylamide and a copolymer of acrylamide and acrylic acid 3. A chemical composition as claimed in claim 2 where the crosslinking agent of said crosslinked polymers is methylenebisacrylamide. 4. A chemical composition as claimed in claim 3 where the quantity of said crosslinking agent of said cross¬ linked polymers is 10% by weight or less. 5. A chemical composition as claimed in claim 2 where the acrylamide monomer, which forms said copolymer of acrylamide and acrylic acid, is present in proportion 70% by weight, and the acrylic acid monomer which forms said copolymer of acrylamide and acrylic acid, is present in proportion 30% by weight. 6. A chemical composition as claimed in any of the preceding claims wherein said polymeric substance is divided into a plurality of particles. 7. A chemical composition as claimed in any of the preceding claims where the particle size of said plurality of particles of said polymeric substance is between 50 and 200 microns. 8. A chemical composition as claimed in any of the preceding claims wherein the alkaline component of said aqueous alkaline solution is one of sodium hydroxide or potassium hydroxide. 9. A chemical composition as claimed in any of the preceding claims which further includes a compound containing ammonium or amine groups. 10. A chemical composition as claimed in claim 9 wherein said compound is one or urea or ammonium nitrate. 11. A chemical composition as claimed in claims 9 or 10 wherein the quantity of said compound used is up to 25% by weight of the weight of said alkaline component. 12. A chemical composition as claimed in any of the preceding claims which further includes an organic solvent. 13. A chemical composition as claimed in claim 12 where said organic solvent is one of methylene chloride, propanone or butanone. 14. A chemical composition as claimed in claims 12 or 13 wherein the quantity of said organic solvent used is up to 20% by volume. 15. A chemical composition as claimed in any of the preceding claims wherein said chemical composition is a paint stripper, graffiti remover, grease stripper, and an industrial cleaner. 16. A chemical composition for stripping and cleaning substantially as herein described.

Inventors: BROUGH THOMAS, DAVIES GREGORY DONALD, BROUGH, THOMAS, DAVIES, GREGORY, DONALD
Applicants: BROUGH THOMAS, DAVIES GREGORY DONALD, LONCAR ANTHONY MATHEW, BROUGH, THOMAS, DAVIES, GREGORY, DONALD, LONCAR, ANTHONY, MATHEW
Application year: 1989
Main classification: C09D9
IPC codes: C08F220, C09D9, C11D3, C11D7, C11D17