Compositions – Frost-preventing – ice-thawing – thermostatic – thermophoric,...
Reexamination Certificate
2001-12-12
2004-03-09
Green, Anthony J. (Department: 1755)
Compositions
Frost-preventing, ice-thawing, thermostatic, thermophoric,...
C106S013000, C427S386000, C428S447000
Reexamination Certificate
active
06702953
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an anti-icing composition suitable for use on a variety of substrates, and which is particularly suited for use on substrates related to aircraft environments.
BACKGROUND OF THE INVENTION
Various modes of transportation are at risk of dire consequences due to the build-up of ice during cold or winter conditions. Aircraft that are either parked on the ground or are on the ground between flights can accumulate snow, ice, freezing rain, or frost on the aircraft surfaces and aircraft engine components in cold weather. Such accumulation, particularly on airfoil surfaces, is generally an unsafe airfoil condition in that it hampers and can stop liftoff. Additionally, ice build up during flight can be a problem. The jet engines of airplanes are also at risk of unexpected flame out if ice builds up on certain components of the engine. Additionally, such ice buildup may break off into large chunks which when impacted against components of the engine can cause significant damage. Thus, there is a need for a coating that can effectively reduce the amount of ice build up on surfaces, including those on aircraft, under harsh weather conditions.
SUMMARY OF THE INVENTION
The anti-icing composition of the present invention includes a glassy matrix preferably formed by crosslinking a mixture of a functionally-terminated silicone and an alkoxy-functionalized siloxane to provide an interpenetrating polymer network (“IPN”) of glass and silicone. Grafted to the matrix is a material capable of microphase separation. The material capable of microphase separation is at least two liquid materials, at least one of which is graftable to the matrix. Also included in the material is a freezing point depression agent such as a polyol or salt hydrate. Such a freezing point depression agent may itself be a material capable of microphase separation.
In an alternative embodiment, the present invention provides an anti-icing composition comprising a crosslinked mixture of an epoxy, an alkoxy-functionalized siloxane and a compound (e.g., silane) capable of compatabilizing the epoxy and the alkoxy-functionalized siloxane to provide an epoxy-modified interpenetrating polymer network of glass and epoxy. Grafted to the matrix is the material capable of microphase separation. The composition also includes a freezing point depression agent.
The present invention also provides a substrate such as an airplane wing coated with either the composition including the interpenetrating polymer network of glass and silicone or the composition including the interpenetrating polymer network of glass and epoxy.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The present invention will be more fully understood by reference to the following description and examples. Variations and modifications of the embodiments of the invention can be substituted without departing from the principles of the invention, as will be evident to those skilled in the art.
As previously discussed the present invention provides a glassy matrix preferably formed by crosslinking a mixture of a functionally-terminated silicone and an alkoxy functionalized siloxane to provide an interpenetrating polymer network (“IPN”) of glass and silicone. Grafted to the matrix is a material capable of microphase separation. The material capable of microphase separation is at least two liquid materials, at least one of which is graftable to the matrix. Also included in the material is a freezing point depression agent such as a polyol or salt hydrate. Such a freezing point depression agent may itself be a material capable of microphase separation. Such a glassy matrix is described in U.S. Ser. No. 09/586,378 filed Jun. 2, 2000, the disclosure of which is incorporated by reference herein in its entirety.
Alternatively, the anti-icing composition comprises a crosslinked mixture of an an epoxy, an alkoxy-functionalized siloxane and a silane capable of compatabilizing the epoxy and the alkoxy-functionalized siloxane to provide an epoxy-modified interpenetrating polymer network of glass and epoxy. Grafted to the matrix is the material capable of microphase separation. The composition also includes a freezing point depression agent.
The glassy matrix is crosslinked using a titanium or tin catalyst. Suitable catalysts include titanium, without limitation, alkoxides such as titanium methoxide, titanium ethoxide, titanium isopropoxide, titanium propoxide, titanium butoxide, titanium diisopropoxide (bis 2,4-pentanedionate), titanium diisopropoxide bis(ethylacetoacetao) titanium ethylhexoxide, and organic tin compounds such as dibutyl tin diacetate, dibutyltin laurate, dimethyl tin dineodecanoate, dioctyl dilauryl tin, and dibutyl butoxy chlorotin, as well as mixtures thereof.
The matrix formulation can include a silica gel including propionic or octonoic acid to inhibit the crosslinking reaction so that the anti-icing composition can be applied to the surface to be coated. The glassy matrix can be formed by using a Sol-Gel process such as described in U.S. Ser. No. 09/586,378. Other methods of forming the matrix will be within the skill of one in the art. The matrix formulation may also include fillers such as, without limitation, fumed silica, mica, kaolin, bentonite, talc, zinc oxide, iron oxide, cellulose, pigments, polytetrafluoroethylene powder, ultra high molecular weight polyethylene powder, high, medium and low molecular weight polyethylene powder, or other fillers, as will be readily apparent to those skilled in the art. The glassy matrix formulation may further include carbon black, silicon powder, doped zinc oxide and polyaniline. Such additives can be used to modify the resistive or dielectric or both properties of the anti-icing composition.
The glassy matrix serves to provide a carrier or support material for the material capable of microphase separation. The matrix provides good adhesion to the surface being coated, as well as, toughness, crack resistance, durability, abrasion resistance and stability in the particular environment.
The anti-icing composition of the present invention also includes a material capable of microphase separation. The material comprises at least two liquids, which in addition to its separation aspects, one of which is capable of being grafted into the glassy matrix. A material capable of microphase separation is a material that because of physical or chemical interactions between (among) the liquid materials substantially continuously phase separates or moves.
Suitable functionally-terminated silicones include silanol terminated, vinyl terminated and amino terminated polydimethylsiloxane. Such silicones have low tear strength and can be toughened by incorporating glass (SiO
2
) into the structure. Thus, an alkoxy-functionalized siloxane can be included. Suitable alkoxy-functionalized siloxanes include polydiethoxysiloxane, tetraethoxy silane, tetramethoxy silane, and polydimethoxy siloxane.
One manner of forming the glassy matrix is using a Sol-Gel process employing a catalyst agent such as an organotitanate compound, for example, a titanium alkoxide compound such as, but not limited to, titanium methoxide, titanium ethoxide, titanium isopropoxide, titanium propoxide, titanium butoxide, titanium ethylhexoxide, titanium diisopropoxide (bis 2,4 pentanedionate), titanium diisopropoxide bis(ethylacetoacetate), or any other type of titanium alkoxide compound. These titanium alkoxide compounds can be used separately or in any combination. Although titanium alkoxides are given as examples, other organotitanate compounds can be used. The glassy matrix can also include a carboxylic acid compound. Silica gel is optional to inhibit the crosslinking reaction. Silica gel is used if storage over a long period of time is an issue. This is because it is believed to store moisture. Alternatively, only silica gel can be used in place of the carboxylic acid compound. However, this does not work as well and a lot of silica gel is required.
With respect to the Sol-Gel process, as is well know to those of or
Miller Shawn D.
Simendinger, III William H.
Green Anthony J.
Microphase Coatings Inc.
Myers Bigel & Sibley Sajovec, PA
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