Compositions: coating or plastic – Coating or plastic compositions – Coating repellent
Reexamination Certificate
2000-03-03
2002-08-13
Brunsman, David (Department: 1755)
Compositions: coating or plastic
Coating or plastic compositions
Coating repellent
C106S213100, C106S270000, C106S271000, C106S272000, C106S287100, C106S287110, C106S287120, C106S287130, C106S287140, C106S287150, C106S287160, C106S010000, C106S003000, C516S123000, C516SDIG001
Reexamination Certificate
active
06432181
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to silicone compositions and a method for treating nonporous surfaces such as glass, porcelain, ceramic, polished or painted metal, plastic, and the like, to render them water, soil and stain repellent. Volatile organic compound (VOC) free cream, paste, powder and solid compositions are provided.
BACKGROUND OF THE INVENTION
There has been extensive research and development involving silicone compositions for rendering nonporous surfaces water repellant. U.S. Pat. No. 2,612,458 (Stedman) discloses the application of substituted polysilicanes to windshields to achieve repellency. U.S. Pat. No. 2,923,653 (Stedman) discloses improved compositions employing alkoxy groups in the polysilicane to improve the repellency. U.S. Pat. No. 2,962,390 (Fain, et al.) describes a paste containing a solid rubbing agent and an alkyl alkoxy silane which when rubbed on a glass surface provides repellency. U.S. Pat. No. 3,244,541 (Fain, et al.) discloses acidic solutions of alkyl alkoxy silane monomers that produce rain repellent films on glass and which are also solvent resistant.
U.S. Pat. No. 3,579,540 (Ohlhausen) discloses water repellent film-forming compositions of alkylpolysiloxanes and acid or alkylpolysiloxanes, acid and solvent which result in durable and effective water repellent films on nonporous substrates. This patent also discloses the importance of adding the acid to the alcohol to form the intermediate half ester and then to add the alkylpolysiloxane in order to solublize the alkylpolysiloxane and eliminate the formation of two or three phases in the mixture. It also discloses that the alkylpolysiloxanes can be employed with solvents, diluents and extenders including colloidal pyrogenic silicas and clays. Isopropyl alcohol solvent was preferred. U.S. Pat. No. 3,817,769 (Fisher) discloses a rapid curing repellent composition by use of dyes, i.e., methylene blue, to give a durable and tough polysiloxane film. However, films prepared in accordance with Fisher's examples gave poor repellency results unless sulfuric acid was also incorporated in the composition. U.S. Pat. No. 3,998,643 (Liddle), discloses the addition of hydrogen fluoride to the Ohlhausen compositions and processes with claimed improved repellency and durability.
U.S. Pat. No. 5,021,089 (Uwata, et al.), discloses a water repellent composition comprising a volatile organic solvent, a silyl phosphate and an organopolysiloxane, thus eliminating the mineral acid required in previously disclosed water repellent compositions. U.S. Pat. No. 5,417,744 (Gasmena) discloses a composition containing a fluorinated polysiloxane, a polysiloxane, a polyester modified polysiloxane, an acid, water and an alcohol to obtain an optically clear coating having hydrophobic properties. U.S. Pat. No. 5,584,917 (Kijima) discloses a water repellent composition comprising an amino group-containing polyorganosiloxane, an organic acid, a surfactant and an aqueous solvent. U.S. Pat. No. 5,697,991 (Frazer) discloses an alkypolysiloxane, mineral acid, solvent and a mild abrasive (0.5-3.0%, preferred 1%) as an improved water repellent treating compound wherein the abrasive serves to enhance dirt and grit removal. U.S. Pat. No. 5,759,618 (Taylor) discloses a strong phosphoric acid, hydrofluoric acid, sulfuric acid cleaning solution for glass surfaces prior to the application of an excess of an alkoxysilane/sulfuric acid solution to the glass surface with timing, temperature and humidity being critical for the removal of the excess in order to achieve an abrasive resistant, water repellent coating on the surface of the glass.
After almost three decades of research and development in water repellent silicone coatings, the dominant technology has involved the use of acidified solvent-based silicone compositions. A multitude of commercial products have been formulated and marketed utilizing some form of alkylsiloxane at about a 10% concentration and a mineral acid at about a 1% concentration and an alcoholic solvent. These alcoholic solutions all yield water repellent coatings on nonporous surfaces, particularly glass surfaces, by application directly onto the surface, usually by rubbing with a paper towel or cloth. Upon evaporation of the alcohol, a hazy film remains which is further polished with a dry wipe material to achieve the desired transparent water repellent coating. During the application process, the odor of the evaporating alcohol can be objectionable, particularly in the confined quarters of a shower or bathroom. OSHA recommends human exposure limits for most alcohols and other solvents to minimize health concerns, i.e., isopropanol (OSHA PEL: TWA 400 ppm, STEL 500 ppm) and ethanol (OSHA PEL: TWA 1000 ppm). These volatile solvents also contribute to air pollution and are considered to be undesirable volatile organic compounds (VOCs) by regulating authorities. These solvents have storage and handling limitations because they are also flammable and could ignite during application or form explosive mixtures if the vapors are confined.
Solvent-based silicone compositions currently have limited industrial application due to their flammability and the toxic vapor exposure to the workers. These solvent-based silicones require additional capital expenditures for explosion proof application equipment, exhaust equipment for vapor removal and scrubbing, and the monitoring of worker exposure to the solvent vapors.
The application of solvent-based silicone compositions utilizes excessive amounts of silicone per square foot of coverage provided due to the evaporation of the solvent and absorption of the silicone by the wipe material. Excessive amounts of the silicone remains in the wipe material and cannot be applied to the surface to be treated. The presence of solvents can also be incompatible with gaskets, paint, etc., associated with the surface being treated. Thus, a need exists for a water repellent composition that eliminates solvents and utilizes the silicone more effectively and economically.
The application of solvent-based silicone compositions also requires time for evaporation of the solvent and results in a hazy water repellent coating which is attributable to the separation of the acid, usually sulfuric acid, from the silicone on evaporation of the solvent. The resulting haze requires a second polishing step and/or dry wipe in order to achieve an optically clear coating. Thus, it is desirable to provide a composition that produces an optically clear water and soil repellent coating without excessive waiting, manpower or additional wiping.
The haze which develops upon application of a solvent based system to a nonporous surface and evaporation of the compatibilizing solvent results from the development of a silicone phase and a strong acid phase. This haze must then be wiped in order to intimately mix the silicone and acid phases onto the surface to remove the excess of the two phases and render it water and soil repellent.
Solvent-based silicone compositions also have storage temperature limitations. For example, alcoholic compositions in closed containers have been reported to “explode” due to the high storage temperatures that can sometimes occur in warehouses or during transport in closed trucks and the like which results in an increase in the internal vapor pressure in the container leading to rupture. Not only does this cause a loss of product and packaging material but it presents a potential hazardous flammable and/or explosive event. There further exists a need for a water repellent silicone composition which is free of volatile organic compounds (VOCs), or VOC compliant, and which is nonhazardous.
Most solvent-based silicone compositions contain the active ingredients at about a 10%/wt level. Thus, almost 90% of the composition is solvent and this requires a large container in order to deliver the product to the customer. The larger container in turn requires more packaging material, larger boxes, more warehouse space, higher shipping costs and more shelf space. It would be very desir
Brunsman David
Resource Development L.L.C.
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