Anti-icing fluid or deicing fluid

Description of equivalent WO 9623043 A1

ANTI-ICING FLUID OR DEICING FLUID

BACKGROUND OF THE INVENTION

Related Applications

This application is a continuation-in-part of U.S. patent application serial number 08/380,91 3, filed January 25, 1995, now pending, which is incorporated herein by reference. Origin of the Invention

The invention described herein was made by employees of the United States Government and may be manufactured and used by or for the Government for governmental purposes without payment of any royalties thereon or therefor. Governmental funding in support of the research and development leading to this invention was also provided by the U.S. Air Force (WDL), Dayton, Ohio.

Field of the Invention

The present provides a non-toxic anti-icing or deicing fluid for use on surfaces. This invention typically relates to an aqueous, non-electrolytic, essentially non-toxic, easily biodegradable, benign, continuous single phase, environmentally- friendly, anti-icing and/or deicing fluid (or composition) for use in the removal of ice and/or for protection against further icing-up by acting as a barrier to the formation of or the adhesion of ice by liquid coating on substrate surfaces. The fluid typically has a composition of water, non-toxic freezing point depressant(s), at least one non- toxic thickener, e.g. a sugar, and optional essentially non-toxic additives, such as corrosion inhibitors, and optional other surface modifiers. A monohydric aliphatic alcohol is optionally present as a surface modifier as a means for forming a hydrophobic thin layer on the surface of the fluid structure. Preferably the alcohol is 1 -dodecanol, which unexpectedly performs its intended functions when present in small amounts. More specifically, the sugar is a polysaccharide, preferably a xanthan.

Surprisingly, the composition of water, freezing point depressant, and sugar, e.g., a xanthan, when placed on the surface of an object has unexpectedly high static viscosity (higher than that of the prior art), a pseudoplastic viscosity-shear response, and also rapid recovery of high static viscosity for improved durability. The high static viscosity, achieved by a small amount of incorporated xanthan is thus an unexpected result, and produces a fluid protective barrier to ice accretion that is very durable and long lasting for anti-icing or deicing. The rapid viscosity drop induced by increase in shear rate is a desirable feature that enables ease of fluid application and uniformity of distribution. The fluid is typically non-toxic and is biodegradable under normal atmospheric temperature, soil, and aquatic conditions. Description of the Problem and Related Art

The present invention addresses major problems caused by snow, sleet, ice, frost and the like as they exist or as they form on the surfaces of objects. For purposes of this application, and unless indicated otherwise, when reference is made to ice it is to be understood that the term encompasses all forms of frozen water by whatever names they are known. The following icing problems in the art are presented.

Streets, etc. -- For streets, roads, bridges, sidewalks, entrances and the like, the accumulation of snow and ice is a nuisance, causes serious loss of traction, or generates major problems. Currently, the removal is accomplished by shoveling, scraping and/or the use of salts or liquids which depress the freezing point. These salts alone are responsible for major and costly corrosion and degradation problems to metals, concrete or asphalt used in bridges, streets and sidewalks. Present liquid freezing point depressant blends may be toxic, corrosive or not rapidly biodegradable, and thus cause problems in the environment, such as those fluids which are ethylene glycol based.

Automobiles — For automobiles, trucks, i.e. all motor vehicles etc., the accumulation of ice, snow, sleet, etc. on the windshield causes severe visibility problems and is usually removed by physical scraping, use of warm liquids or liquids based on methyl alcohol (toxic) and/or ethylene glycol (toxic), or defrosting (which requires time to be effective). Also, most automotive windshield icing products only deice (correct temporarily the problem), but not anti-ice as well (prevent the visibility loss problem). Because of the high amount of salts used on the streets to remove ice, the corrosion problem to metal surfaces and particularly to automobiles is enormous. These problems require extensive undercoating, frequent washing, and eventually, in some cases, complete replacement of the automobile.

Nautical - Nautical vessels are endangered from ice formed in two different ways. Under sub-freezing temperatures with rough seas and/or windy conditions, the water spray freezes on the vessel surfaces increasing the weight of the vessel. A second more serious threat is "ice fog". This condition is serious at sea, since it is unpredictable. When a vessel encounters "ice fog", the entire vessel is rapidly coated with ice. Vessels have capsized and been lost because of the weight of the ice. The vessel is no longer buoyant, or topples over due to ice build-up above the vessel's metacenter. This situation is also a hazard when a maneuver such as a turn is performed or the state of the sea is such that the vessel is listing. Recently, 38 commercial fishing vessels where lost off the coast of Alaska when they suddenly encountered "ice fog" conditions. Currently, the removal practice is to chip the ice off with baseball bats and mallets. Complications occur due to the freezing of passage-way doors and the slipperiness on the walkway surfaces. The ice breaking is strenuous and fatiguing, and exposes the ice breaking crew to extreme danger of being swept overboard. A practical and effective means of shipboard ice protection has been long sought. Further, the same ice hazard places naval craft at risk. Ice protection fluids, such as those commonly referred to in the art as Type II compositions, are suitable for application to all naval vessels, including their weather decks and even carrier flight decks.

Aircraft -- Icing weather conditions produce especially acute problems to aircraft that are temporarily parked on the ground between flights where they can accumulate a variety of frozen precipitation, such as snow, sleet, hail, frost, hoar frost, slush and particularly ice. These accreted deposits, which form more readily on flat horizontal surfaces such as wings and empennage, can have serious consequences, for example, the aerodynamic performance characteristics of airfoils (e.g. lift and drag) may be degraded by even small accumulations of frozen water, making removal prior to flight important.

Aircraft icing prior to takeoff is a significant problem. According to the National Transportation Safety Board (NTSB), icing has been identified as the cause of 127 fatal accidents in which 496 lives were lost between 1977 and March 1992. Federal Aviation Administration (FAA) regulations require that all ice and snow accumulated under freezing conditions be removed from the aircraft prior to takeoff.

To accomplish this removal, aircraft operated during cold weather (icing) conditions are sprayed with fluids to remove ice (deicing) or to prevent ice and snow accretions (anti-icing) as a safety precaution. The aviation regulatory agencies (e.g. FAA) use standards and procedures developed by the Society of Automotive Engineers (S.A.E.) or the Association of European Airline (A.E.A.) (as shown, for example, in Table IA and IB below). The SAE specifications are similar to the AEA and are used by the FAA as the guideline in the USA. The disposal of the fluids is governed by the Environmental Protection Agency (E.P.A.) and various state environmental agencies.

Table 1 A shows the Association of European Airlines (AEA) guide for suggested icing treatment procedures for various ambient air temperatures at the airport.

Table 1 B shows the AEA suggested guidelines, correlating holdover times after application of Type II certified fluids with current local weather conditions.

Type II anti-icing fluids are applied at ambient temperatures.

The fluid concentration ratios shown in Tables 1 A and 1 B are volume ratios.

TABLE 1A

Suggested AEA Type II Fluid Application

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*The anti-icing step should be applied within three minutes of the start of the deicing step. TABLE 1B

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CΛUTION: The time of protection will be shortened in heavy weather conditions. Jet blast may cause a partial blow-off of the protective film. If these conditions occur, the time of pro_tec_tion can be shortened considerably. Improper application procedures can also affect the time of protection. Currently, there are two types of anti-icing and/or deicing fluid compositions in use for aircraft (Type I and Type II), which reflect two fundamental approaches to assure safe aircraft takeoff under icing conditions. The first approach is to spray the surfaces of a plane with "hot" (90 - 95°C) freezing point depressant (FPD) fluids (Type I) which melt ice and snow. That sprayed aircraft must then takeoff quickly before there is any further ice buildup as per guidelines dependent on meteorological conditions.

The second approach is to remove all ice and snow with a hot spray and then quickly spray a modified (thickened) FPD fluid (Type II) onto the aircraft surface that becomes a "thickened gel" which, acting as a protective blanket, provides a significantly longer time period of protection between the deicing step and aircraft's actual takeoff. The two fluids that match these different approaches are termed Type I (unthickened) and Type II (thickened) fluids, respectively, in accordance with the Association of European Airlines (A.E.A.) standards. The properties of Type I and Type II fluids represent different compositions of the same family of FPD chemicals. Type II compounds usually contain thickening additives which cause the fluid to "cling" to the aircraft under various weather and pre-takeoff and taxi conditions, and then be shed automatically at a critical velocity close to (and lower than) the aircraft takeoff speed. This desirable shedding is achieved by the thickener's unusual property of having a very high viscosity until the takeoff's airflow shear rate dramatically lowers the viscosity to the point of where the fluid flows off rapidly as illustrated, for example, in Figures 1A to 1 F.

As shown in Figures 1 A to 1 F, the viscosity-shear rate effect can be translated directly to viscosity-airspeed effect, which is a more practical correlation for aeronautical uses. When the Type II fluid's rheological properties have been correctly matched to the particular aircraft's takeoff performance, there are no appreciable amounts of anti-icing or deicing fluid remaining on the critical surfaces of the aircraft just prior to lift off and during climb acceleration.

The known Type I (unthickened) fluids are described as having a rheological flow behavior known as Newtonian flow, that is, the fluid shows a constant slope straight line relationship between shear stress and shear rate. If shown on a plot, the straight line passes through the origin. Further, at a constant temperature, viscosity also remains constant as the shear rate is varied, (see e.g., textbook Figure 2), and Type I fluids typically have low viscosity compared to thickened fluids. On the other hand, Type II (thickened) fluids exhibit non-Newtonian flow characteristics, which are broadly defined as one for which the relationship of shear rate and shear stress is not constant. Thus, as shear rate is varied, the shear stress doesn't vary proportionately (refer, for example, to textbook Figure 3). For the Type II fluid to perform as an ice barrier "blanket" protector, it must have very high static and near or quasi-static viscosity while there is little aerodynamic shear. Yet the fluid must also display a rapid viscosity decrease with increasing shear rate (as during the takeoff roll) to insure the removal of Type II fluids prior to flight. More specifically, this non-Newtonian behavior of "shear thinning" is referred to as "pseudoplasticity". For delineation of the relationships among these flow behavior types, an example of a rheogram plot set is given in textbook Figure 4 for reference. Noting that the classic Newtonian flow is the only linear behavior line passing through the origin, all others are thus described as non-Newtonian flow.

The currently used toxic deicing fluids of the art are based on glycols, primarily ethylene glycol, diethylene glycol, and propylene glycol. Significant evidence exists that these fluid formulations have detrimental affects on the environment (for example, see "Biodegradation &amp; Toxicity of Glycols," ARCO Chemical Company, Newton Square, PA 19073, May 1990; and "Toxicity of Aircraft De-icers and Anti-icer Solutions to Aquatic Organisms," S. I. Hartwell et al, Chesapeake Bay Research and Monitoring Division, Maryland Dept. of Natural

Resources, Annapolis, MD. 21401 , May 1993, CBRM-TX-93-1 ). Ethylene glycol and diethylene glycol are in themselves toxic, while propylene glycol generally is not. However, when combined with the various conventional additives used to make the commercial ice protection fluids, the toxicity of these fluids of the art is enhanced. In addition, Type II fluids which have improved aerodynamic performance, include compounds that are generally non-biodegradable. All of the currently used glycol deicing fluids fail to meet the U.S. Clean Water Act of 1987 environmental and safety requirements. The Environmental Protection Agency is imposing clean water rules which are stringent, and consequently costly, constraints on discharge at airports of these glycol-based fluids into storm water drains and ground water supplies.

For example, the Albany County, New York airport deicing fluid run-off contaminated the local drinking water supply and required the construction of a complex catch basin/sewage treatment system which cost over $ 12,000,000. This new treatment system is still not considered to be fully satisfactory. New airports, such as Denver International at Denver, Colorado must have a complete collection system that is expensive, complex, and of limited efficiency. Many states, for example, are calling for zero discharge limits to the environment regarding aircraft deicing fluid run-off. The required special deicing procedure and site locations tend to adversely impact departures during peak traffic and icing/storm activities. The reclamation and disposal of the expended glycol-type fluids at Denver, for example, will have a significant cost. The economic burden for this disposal service is very high, and currently is almost cost prohibitive. In addition, the U.S. Air Force has recently issued an order (Brig. Gen. J. E.

McCarthy, USAF HQ, CE, 31 March 1992) banning future purchase of ethylene glycol-based deicing fluids, and also ordered that research on replacement deicing fluids commence immediately. Thus, there is an urgent need to develop cost competitive alternative anti-icers or deicers which are non-toxic and readily biodegradable.

The following patents are presented to describe approaches and partial solutions to the problems of deicing and anti-icing:

F.A. Kormamm, in U.S. Patent 2,101 ,472, teaches a gel containing gelatin to which is added as an antifreeze substance such as glycerol and/or a glycol. H.L. West et al. in U.S. Patent 2,373,727, teach a composition such as described by Kormamm, but also including a hydrocarbon, disclose a method and a composition for the prevention of the formation or accretion of ice on an exposed surface. The composition is for application to surfaces exposed to the deposition of ice to prevent the formation or accretion of ice. It comprises a jelly base composed of from about 7 to 17 percent by weight of a gelatinous material and from about 83 to 93 percent by weight of an antifreeze material of the class consisting of glycol, glycerol, polyglycols, polyglycerols and their mixtures, having incorporated therein from about 5 to 20 percent by weight of an organic liquid, which is immiscible with ice and water and which remains liquid at temperatures below plus 10°F.

R.H. Shapiro, in U.S. Patent No. 2,454,886, discloses a method for the prevention of mist and frost on glass and similar sheet material.

J.M. Fain et al., in U.S. Patent No. 2,716,067, discloses a composition of ethylene diamine and potassium thiocyanate, and optionally at least one of aqueous morpholine, potassium acetate or monomethyl amine.

J.M. Fain et al., in U.S. Patent No. 2,716,068, discloses a composition of a glycol, and potassium thiocyanate, and optionally sodium nitrite.

S. Dawtrey et al., in U.S. Patent No. 3,350,314, teaches a foamable composition of water, an alkylene polyol, and a long chain aliphatic tertiary amine.

H.E.F. Ordeit et al., in U.S. Patent No. 3,362,910, disclose an automotive radiator-engine antifreeze composition.

H.R. Schuppner, in U.S. Patent No. 3,557,016, disclose to a useful combination achieved by adding some xanthan to locust bean gum. H.F. Scott, Jr. et al., in U.S. Patent Nos. 3,624,243 and 3,630,913, disclose chemical deicers containing corrosion inhibitors making them specially suited for use on airport runways.

I. Kδnig - Lumer et al. in U.S. Patent No. 4,358,389, disclose a method and a liquid composition for deicing and protecting against icing-up. In particular, the composition operates to free the metal surface of aircraft rapidly and completely from ice, hoar-frost, snow and the like, and to protect the surface against further build-up for a relatively long period. This composition includes (a) glycols, usually toxic ethylene glycol, (b) water, (c) 0.05 to 1 .5 percent by wieght of a particular crosslinked polyacrylate, (d) 0.05 to 1 percent by weight of a mixed-base mineral oil which is insoluble in water, (e) surface-active agents, (f) corrosion inhibitors, and

(g) alkaline compounds. These components are present in very specific quantities in each case, the quantity of the components (a) and (b) is at least 94%, relative to the total weight of the agent. There is mentioned without further support of an additional ancillary co-thickener component. Xanthan is suggested only as a possible synergistic viscosity enhancer to the claimed thickener, and xanthan is always in the presence of one or more of the other thickeners. It is never used as a single thickener alone. The working examples the thickeners are always at 1 percent by weight of the total in addition to any xanthan present. Many other specific components are usually present. The pH value of the composition is 7.5 to 10.

Ma, et al., in U.S. Pat. No. 4,954,279, describe the Kδnig-Lumer teaching, in part, at column 3, line 6, et sec,

"In addition to the components..., the agent... can also contain appropriate additives, preferably anti-oxidants and polysaccharides (gums) in effective quantities (gums and additional thickeners)... It has been found that polysaccharides have an advantageous effect on the rheological properties of crosslinked polyacrylates, particularly those having viscosity values in the lower range of the viscosity limits indicated above, that is within the range from about 1000 to 5000 cPs. Preferred polysaccharides are those of the type of high molecular xanthan gum"

K.H. Nimereck, et al., in U.S. Patent No. 4,439,337, disclose a method and a composition for preventing freezing together of surfaces. Any surface which is to be contacted with another surface, e.g., a particulate material, in the presence of moisture (water) which is subject to freezing, is coated with a composition containing water and substantially water soluble components. The composition includes (1 ) a polyhydroxy compound or monoalkyl ether thereof, (2) an organic non-volatile compound having at least one hydrophilic group, (2) being different than (1 ), and optionally a salt which functions to increase the viscosity and tackiness of the composition sufficient to retain the composition on non-horizontal surfaces to freeze proof the same.

C.F. Parks, et al., in U.S. Patent No. 4,501 ,775, disclose a method and composition to reduce the strength of ice. The composition comprises (A) a water- soluble polyhydroxy compound or monoalkylether thereof and (B) a water-soluble organic nonvolatile compound having a hydrophilic group such as amine, carboxyl or carboxylate groups in an amount to provide an effective amount, e.g., on the order of about 0.25 to 5 weight percent, of (A) plus (B) based on the weight of water. This method is especially useful for application to particulate solids, such as coal and mineral ores, which are shipped and stored in masses exposed to freezing temperatures. Any ice that is formed is physically weak and will not deter the unloading of the conditioned particulate solids.

S.H. Bloom, in U.S. Patent No. 4,585,571 , discloses a method and a liquid deicing composition. This patent provides for a deicing composition for use on airplanes, runways, streets, and the like. The deicing composition includes (a) an alkylene polyol, (b) an anionic surfactant capable of forming a hydrophobic monolayer on the metal surfaces of the aircraft, (c) a hydrophilic wetting agent which is capable of associating with the hydrophobic monolayer, and (d) a coupling agent, which facilitates the association between the wetting agent and monolayer. A. Lieber, et al., in U.S. Patent No. 4,606,835, disclose a salt composition having smaller sized sodium metasilicate. A dry and free-flowing composition is claimed containing (1 ) salt, (2) C₂ to C₆ monohydric and/or (3) polyhydric alcohol, (4) diatomaceous earth (or suitable substitute), and (5) sodium metasilicate characterized by a particle size smaller than about 80 mesh. The composition is useful for facilitating the melting and removal of snow and ice.

E.E. McEntire, et al., in U.S. Patent No. 4,606,837, disclose coolant compositions. The water soluble thickeners are made by alkoxylating monohydric alcohol hydrophobes. The monohydric alcohol has at least 18 carbon atoms to be properly hydrophobic. In addition, a large proportion of ethylene oxide is added, such that the molar ratio of ethylene oxide to monohydric alcohol hydrophobe is at least 40:1 . Improved results are obtained when 8-1 5 moles of propylene oxide are added first as a block to the single mole of hydrophobe. The alkoxylations are necessary to provide the desired viscosities and hydrophilic nature. These thickeners are particularly useful in the glycol-water based fluids. A.B. Ganncy, in U.S. Patent No. 4,606,836, discloses a calcium magnesium acetate deicer of a particular pellet size.

R.J. Tye, et al., in U.S. Patent No. 4,698,172, disclose an aircraft anti-icing fluid. The anti-icing fluid is suitable for ground treatment of aircraft. The anti-icing fluid is a glycol-based solution containing a gel-forming carrageenan, in an amount of less than 5 wt %. The carrageenan is present in the glycol-based solution in an amount sufficient to thicken the fluid to promote its adherence to aircraft surfaces when applied to a stationary aircraft. The use of this thickened deicing fluid does not adversely affect airfoil lift characteristics during takeoff, because the fluid exhibits shear thinning and readily flows off the aircraft surfaces when exposed to wind shear during the aircraft's takeoff run.

D.A. Coffey et al. in U.S. Patent 5,389,276 disclose an ethylene glycol based deicing/anti-icing composition which contains a thickener comprising a polyacrylic acid.

R.D. Jenkins et al. in U.S. Patent 5,461 ,100 disclose an anti-icing fluid suitable for ground treatment of aircraft being a glycol-based solution containing a macromolecular polymer thickener.

All patents, articles, references, applications, standards and the like cited in this application are incorporated herein by reference in their entirety.

From the above description, it is apparent that a need exists for environmentally benign (non-toxic and easily biodegradable) compositions of anti- icing fluids and/or deicing fluid compositions that also are intrinsically superior in protection of objects from ice than known compositions.

SUMMARY OF THE INVENTION The present invention provides a non-toxic anti-icing fluid or a deicing fluid of water, freezing point depressant and thickener, wherein the fluid is a single phase.

The present invention provides an anti-icing or deicing composition, which composition comprises: (a) water;

(b) at least one non-toxic, water soluble, freezing point depressant selected from the group consisting of monohydric alcohols having from 2 to 6 carbon atoms, polyhydric alcohols having from 3 to 12 carbon atoms, monomethyl or monoethyl ethers of polyhydric alcohols having from 3 to 12 carbon atoms, or mixtures thereof;

(c) a non-toxic thickener, which when combined with (a) and (b) provides a continuous liquid, wherein the liquid is a homogeneous, continuous single phase, and the liquid when formed has a high near-static initial viscosity when measured using a viscosity measuring device under specified conditions, and the formed liquid after being subjected to at least one external dynamic strain rate of at least 0.5 sec^'1 for at least 1.0 min., has a second, lower viscosity as measured using the viscosity measuring device under specified conditions, and upon removal of the external dynamic strain rate, within 5 min., said liquid has a third viscosity of within about 99.5% of the initial viscosity when the third viscosity is measured on the viscosity measuring device at the specified conditions.

In another embodiment, in the composition: in component (a) the water is present in between about 40 and 86 percent by weight of the combined water and freezing point depressant weights; in component (b) the freezing point depressant is present in between about 14 and 60 percent by weight of the combined water and freezing point depressant weights; and in component (c) the thickener is present in between about 0.01 and 10 perent by weight of the total composition, and the sum of components (a), (b) and (c) are about 90% or higher by weight or greater of the total composition, wherein the specified conditions are between about -20 and + 20°C, and preferably wherein the specified conditions are about 20°C and 760 torr.

The present invention concerns an aqueous, non-electrolytic, essentially non- toxic, easily biodegradable, environmentaly benign, continuous phase liquid composition for use as an anti-icing or a deicing agent. The composition includes water, a non-toxic freezing point depressant, a thickener, optional one or more non- toxic environmentally benign corrosion inhibitors or surfactants, optional monohydric aliphatic unbranched alcohol, and optional coloring agent, wherein the thickener produces an aqueous liquid composition having the properties of non-Newtonian pseudoplastic rheological behavior wherein the near-static viscosity exceeds

20,000 cPs at temperature ranges of between about of -30°C and 0°C for icing protection and said viscosity rapidly decreases with moderate increase in shear rate to asγmptomatically approach a low viscosity (below 600 cps), when a film of the composition is exposed to shear rates in excess of 20 reciprocal seconds. The present invention also relates to an aqueous, non-electrolytic, essentially non-toxic, easily biodegradable, environmentally benign, continuous single-phase, composition for use as an anti-icing agent and/or a deicing agent. These agents are for use on surfaces of an object, where ice accretion and build-up is detrimental, including but not limited to airplanes, airport pavements, roadways, bridges, walkways, entrances, electrical tower structures and their components, canals, locks, vessels, nautical components, railroad switches, automobiles, and motor vehicles. The unexpected static and dynamic icing protection properties of these novel, aqueous, non-toxic and biodegradable fluid compositions are equal to those of the present art and in most cases are superior to those of the art. The anti-icing/deicing composition comprises:

(a) water in between about 40 and 86 by weight percent (wt%)of the sum of the weights of the freezing point depressant (FPD) and water;

(b) a non-toxic freezing point depressant (FPD) selected from the group consisting of monohydric alcohols having from 2 to 6 carbon atoms, polyhydric alcohols having from 3 to 12 carbon atoms, mono methyl or ethyl ethers of polyhydric alcohols having from 3 to 12 atoms or mixtures thereof, wherein the freezing point depressant is present in between about 10 to 60 percent by weight of the sum of the weights of the freezing point depressants and water;

(c) a thickener for producing resultant pseudoplastic flow behavior, wherein the thickener preferably consists essentially of bacterium produced hydrophilic hetero-polysaccharide colloid which is present in between about 0.01 and 10 percent by weight of the total composition; and

(d) optionally, a non-toxic, environmentally benign corrosion inhibitor which is present in between about 0.01 and 0.1 percent by weight of the total composition wherein said composition is a non-toxic aqueous solution and is environmentally biodegradable.

The anti-icing/deicing composition can further include:

(e) a monohydric alcohol as means for forming a hydrophobic monolayer on the exterior surface of the fluid composition applied to the structure to be given ice protection, which alcohol is selected from the group consisting of alcohols having between 8 to 24 carbon atoms. Preferably, the alcohol is a primary aliphatic alcohol with minimal or no sidechains, preferably present in between a trace quantity (i.e., between about 0.01 wt%) sufficient to form hydrophobic thin layers, essentially a monolayer, on the exterior surface, and 5.0 wt% of the total composition.

The non-toxic freezing point depressant can be selected from the group consisting of ethanol, 1-propanol, 2-propanol, 1 -butanol, 2-butanol, 2-methyl-1 - propanol, 2-methyl-2-propanol, 1 ,2-propylene glycol, 1 ,3-propylene glycol, 1 ,4- butylene glycol, 1 ,3-butylene glycol, 2,3-butylene glycol, glycerol, and mixtures thereof. The freezing point depressant is present preferably in between about 14 and 60 percent by weight of the sum of the weights of the freezing point depressant and water; and in component (c), the thickener is a xanthan selected to impart viscosity thickening when dispersed or hydrated in the aqueous media. The xanthan is present in between about 0.01 and 10 percent by weight of the sum of the total composition.

In one embodiment of which the fluid compositions of the present invention, additional optional constituents which may be further incorporated to enhance overall performance include, for example: (f) environmentally benign, non-toxic surfactants such as those described in the art, between about 0.001 and 0.1 percent by weight;

(g) oxygenator(s) such as a water-soluble peroxide (i.e. H₂O₂), which is added during application of the fluid to the surface to assist in subsequent biodegradation and is present in between about 0.1 and 5 percent by weight; or (h) optional degradation agents which are present in amounts effective to facilitate biodegradation of the fluid after its use. Such agents include, but are not limited to enzymes, microbes, bacteria, and the like. Suitable degradation agents are optionally present between about 0.001 wt% and 2.0 wt%. Optionally, these degradation agents are added just prior to fluid application or after use, to assist in biodegradation (and decomposition) of the runoff fluid composition after its use on the surface of the object; or

(i) environmentally benign non-toxic (i.e., foodgrade) bacteriostat such as those described in the art, present between about 0.001 and 0.1 percent by weight.

Another embodiment of the anti-icing or deicing composition further includes a monohydric alcohol as a means for forming a hydrophobic thin layer, essentially a monolayer, on the exterior surface of the composition applied to the structure to be ice protected, which alcohol is selected from the group of monohydric alcohols having between 8 and 16 carbon atoms, preferably between 8 and 1 2 carbon atoms, and more preferably, 1-dodecanol. In one embodiment of the anti-icing or deicing composition, the fluid further includes 1 -dodecanol which is present between about 0.01 and 5.0 percent by weight of the total composition.

The present invention also relates to anti-icing or deicing compositions for use on the surfaces of objects such as, airplanes, runways; streets, roads, bridges, sidewalks, entrances, building and tower structures, vessels, nautical components, automobiles, trees, shrubs and the like. The anti-icing/deicing composition comprises:

(a) water in between about 40 and 86 percent by weight; (b) a non-toxic freezing point depressant selected from the group consisting of mono hydric alcohols having from 2 to 6 carbon atoms, polyhydric alcohols having from 3 to 12 carbon atoms, mono methyl or ethyl ethers of polyhydric alcohols which have from 3 to 12 atoms or mixtures thereof, wherein the freezing point depressant is present between about 14 to 60 percent by weight; (c) a selected xanthan present in between about 0.01 and 5 percent by weight;

(d) optionally one or more non-toxic, environmentally benign corrosion inhibitors which are present in between about 0.01 and 0.1 percent by weight of the total composition; or (e) optionally an environmentally benign non-toxic (i.e., foodgrade) bacteriostat such as those described in the art, e.g. cetylpyridinium chloride, benzylpyridinium chloride between about 0.001 and 0.1 percent by weight.

In another embodiment, the anti-icing or deicing composition, further includes component (f ) a monohydric alcohol as means for forming a hydrophobic thin layer, essentially a monolayer, on the exterior surface of the fluid composition as applied to the structure to be given ice protection which alcohol is selected from the group consisting of alcohols having between 10 to 20 carbon atoms.

In another embodiment, the anti-icing or deicing composition further includes component (g) an environmentally friendly non-toxic surfactant such as these described in the art, between about 0.001 and 0.1 percent by weight.

In another embodiment of the anti-icing or deicing composition, the freezing point depressant is selected from the group consisting of ethanol, 1-propanol, 2- propanol, 1 ,2-propylene glycol, 1 ,3-propylene glycol, 1 ,4-butylene glycol, 1 ,3- butylene glycol, 2,3-butylene glycol, glycerol, and mixtures thereof. The ratio of freezing point depressant is present between about 14 and .60 percent by weight of the sum of the weights of freezing point depressant and water; and in component (c), and the thickener, xanthan, is present in between about 0.01 and 10 percent by weight. In another embodiment of the anti-icing/deicing composition, the composition further includes a monohydric alcohol as means for forming a hydrophobic monolayer on the exterior surface of the composition as applied to the structure to be ice protected, which alcohol is selected from the group of monohydric alcohols having between 10 and 14 carbon atoms, preferably 1 -dodecanol. In another embodiment of the anti-icing/deicing composition, it further includes a liquid aliphatic wax ester as an optional means for forming a hydrophobic monolayer on the exterior surface of the fluid composition as applied to the structure to be ice protected, which liquid wax comprises natural occuring esters of CIS- monounsaturated omega-9 C_1β to C₂₄ linear fatty acids and C₁₈ to C₂₆ linear alcohols, with an overall chain length predominantly C₄₀to C₄₄, preferably "Jojoba" as derived from the seeds of the Simmondsia chinensis plant.

For some applications, it may be desirable to use the anti-icing or deicing composition on a surface, with small grit sized, preferably biodegradable, solid particles, to increase friction and/or traction on the surface (e.g. in roads or sidewalks). Typically, aircraft surfaces will not include grit.

Most preferably a composition consists essentially of water, a non-toxic freezing point depressant (described above), a xanthan and an optional monohydric aliphatic alcohol (described above) and optionally a corrosion inhibitor and optionally a bacteriostat.

In another embodiment, the present invention relates to an anti-icing or deicing composition for use on surfaces of objects where ice accretion is detrimental and when protection from ice build-up is desired which anti-icing or deicing composition comprises: (a) water in between about 40 and 86 percent by weight of the sum of the water and freezing point depressant;

(b) a non-toxic freezing point depressant selected from the group consisting of monohydric alcohols having from 2 to 6 carbon atoms, polyhydric alcohols having from 3 to 12 carbon atoms, mono methyl or mono ethyl ethers of polyhydric alcohols having from 3 to 12 aoms or mixtures thereof, wherein the amount of freezing point depressant is between about 14 to 60 percent by weight;

(c) a thickener for producing resultant pseudoplastic flow behavior of the composition which thickener is present in between about 0.01 and 10 percent by weight; (d) optionally a non-toxic environmentally benign corrosion inhibitor which is present in between about 0.01 and 0.1 percent by weight of the total composition, or

(e) optionally an environmentally benign, non-toxic (i.e., foodgrade) bacteriostat such as those described in the art, between about 0.001 and 0.1 percent by weight.

In another embodiment, the present invention relates to an anti-icing or deicing composition wherein: in component (b), the freezing point depressant is selected from the group consisting of ethanol, 1 -propanol, 2-propanol, 1 -butanol, 2-butanol, 2-methyl-1 - propanol, 2-methyl-2-propanol, 1 ,2-propγlene glycol, 1 ,3-propylene glycol, 1 ,4- butylene glycol, 1 ,3-butylene glycol, 2,3-butylene glycol, glycerol, and mixtures thereof; in component (c), the thickener is xanthan selected to impart viscosity thickening when dispersed or hydrated in the aqueous media, and the xanthan is present in between about 0.01 and 5 percent by weight, and the freezing point depressant is between about 14 and 60 percent by weight; and the objects are selected from the group consisting of aircraft, airport pavements, roadways, walkways, bridges, entrances, structures, canals, locks, components, vessels, nautical components, railroad switches, automobiles and motor vehicles.

In another embodiment, the present invention relates to an anti-icing or deicing composition for use on the surfaces of objects, which anti-icing or deicing composition comprises:

(a) water in between about 40 and 86 percent by weight of the sum of the weights of the FDP(s) and water;

(b) a non-toxic freezing point depressant selected from the group consisting of mono hydric alcohols having from 2 to 6 carbon atoms, polyhydric alcohols having from 3 to 12 carbon atoms, mono methyl or mono ethyl ethers of polyhydric alcohols having from 3 to 12 atoms or mixtures thereof, wherein the amount of freezing point depressant is between about 14 to 60 percent by weight of the sum of the weights of FDP(s) and water;

(c) a thickener, xanthan, which is present in between about 0.01 and 10 percent by weight; and

(d) optionally a corrosion inhibitor which is present in between about 0.01 and 0.1 percent by weight of the total composition.

In another embodiment the present invention relates to an anti-icing or deicing composition wherein: in component (b), the freezing point depressant is selected from the group consisting of ethanol, 1 -propanol, 2-propanol, 1 -butanol, 2-butanol, 2-methyl-1 - propranol, 2-methyl-2-propanol, 1 ,2-propylene glycol, 1 ,3-propylene glycol, 1 ,4- butyleneglycol, 1 ,3-butylene glycol, 2,3-butyleneglycol, glycerol, and mixtures thereof, and the freezing point depressant is between about 30 and 60 percent by weight of the sum of the weights of FDP(s) and water; and in component (c), the xanthan is present in between about 0.1 and 1 percent by weight; and the objects are selected from the group consisting of aircraft, airport pavements, roadways, walkways, bridges, entrances, structures, canals, locks, components, vessels, nautical components, railroad switches, and motor vehicles.

In another embodiment the present invention relates to an anti-icing or deicing or anti-icing composition for use on the surfaces of objects, which anti-icing or deicing composition consists essentially of:

(a) water in between about 40 and 60 percent by weight of the sum of the weights of FPD(s) and water;

(b) a non-toxic freezing point depressant selected from the group consisting of mono hydric alcohols having from 2 to 6 carbon atoms, polyhydric alcohols having from 3 to 12 carbon atoms, mono methyl or mono ethyl ethers of polyhydric alcohols having from 3 to 12 atoms or mixtures thereof, wherein the amount of freezing point depressant is between about 40 to 60 percent by weight of the sum of the weights of FDP(s) and water; (c) a xanthan which is present in between about 0.01 and 10 percent by weight; and

(d) optionally a corrosion inhibitor which is present in between about 0.01 and 0.1 percent by weight of the total composition.

In another embodiment the present invention relates to an anti-icing or deicing composition which further includes solid particle means for increasing friction and traction in the composition on the surface to be anti-iced or deiced, wherein said solid particles are present in between about 0.1 and 20 percent by weight of the sum of the solid particle means and the fluid composition.

In another embodiment the present invention relates to an anti-icing or deicing composition for use in motor vehicle surface applications: in subpart(b) the non-toxic freezing point depressant is a mixture of propylene glycol present in about 5 to 1 5 weight percent, and isopropanol about 40 to 55 weight percent of the sum of the weights of the FPD(s) and water, and optionally further includes 1 -dodecanol in between about 0.01 and 5.0 weight percent.

In another embodiment the present invention relates to an anti-icing or deicing composition for aircraft surfaces, said composition having a near-static viscosity at a shear rate of about 0.1 sec^"1 of 25,000 to 75,000 cPs and a shear thinned viscosity at a shear rate greater than 20 sec^'1, below 1000 cPs, at a temperature of between about 0° and -20°C.

In another embodiment the present invention relates to an anti-icing or deicing composition having a near static viscosity of between about 20,000 to 120,000 cPs at between about 0° and -20°C.

BRIEF DESCRIPTION OF THE DRAWINGS Figures 1A, 1 B, IC, ID, IE and 1 F are each a graphic and pictoral representation of the rheological behavior of conventional Type II FPD fluids (for example, ABC-3 of KILFROST^*, (a deicing fluid of KILFROST Ltd, Northumberland, UK); Octagon FORTY BELOW^* (a deicing corporation of Octaαon of Octagon, New Jersey); UCAR ULTRA^* (a deicing fluid of Union Carbide of Danbury, Connecticut); and aircraft anti-icing embodiments of this invention) applied to a wing section in various airflow states.

Figure 1 A is a graph of viscosity versus aircraft speed at brake release.

Figure 1 D is a cross-sectional representation of the wing (1 1 ) covered on the top with Type II fluid (12) at aircraft brake release.

Figure 1 B is a graph of viscosity versus aircraft speed during takeoff roll.

Figure 1 E is a cross-sectional representation of the wing (1 1 ) partially covered on top with Type II fluid (13) during the aircraft takeoff roll.

Figure 1 C is a graph of viscosity versus aircraft speed at rotation. Figure 1 F is a cross-sectional representation of the wing (1 1 ) having most of the Type II fluid (14) removed at the speed of aircraft takeoff.

Figure 2 is a textbook graphic representation of the invariant or constant apparent viscosity of a typical Newtonian behaving fluid when subjected to varying shear rates, at constant temperature. Figure 3 is a textbook graphic representation of a non-Newtonian fluid, typical of a xanthan thickened FPD fluid representative of the compositions of this invention. It shows both the characteristic pseudoplastic flow behavior and the Ellis type flow behavior yield value.

Figure 4 is an overall, idealized, textbook graphic representation of the germane flow behavior of generic types of non-Newtonian fluids whose viscosity properties vary with shear rates.

Figure 5 is a graphic, textbook log-log presentation of the idealized Ellis-type, pseudoplastic flow behavior of a typical xanthan thickened FPD fluid of this invention. It highlights the near-zero shear viscosity (η₀) at and about the "yield point" and the infinite shear rate viscosity (η ., with power law behavior between these points.

Figure 6 is a graphic representation typical of the compositions of the prior art presenting the apparent viscosity in centipoise (cPs) versus shear rate (sec ^"'), as taken from Figure 1 of Tye, et al, U.S. 4,698, 172 (original in semi-log plot), and compared in that patent with measured values for Hoechst 1704^* Type II (icing protection fluid of Hoechst AGF, Frankfort, Germany), and intended to show superior properties of that invention's thickener, carrageenan gum.

Figure 7 is a graphic representation of the present invention's composition of water (44.5 wt%), isopropyl alcohol (55 wt%), and xanthan (0.5 wt%) showing the response of the apparent viscosity in centipoise versus the shear rate at 20° C.

Note the similarity of this flow behavior to that of the composition shown in Figure

9.

Figure 8 is a graphic representation of apparent viscosity versus shear rate. It compares the commercially available deicing composition KILFROST^* ABC 3,

(deicing composition of propylene glycol with toxic and environmentally detrimental additives), with a version in accordance with this invention having an approximate composition of water (44.5 wt%), isopropyl alcohol (55 wt%), and xanthan (0.5 wt%). Note the higher near-static viscosity and rapid shear-thinning of the composition of the invention.

Figure 9 is a graphic representation of the apparent viscosity versus shear rate for one embodiment of the present invention's composition of water (44.5 wt%), propylene glycol (55 wt%) and xanthan thickener (0.5 wt%), at -20°C, 0°C, and + 20°C. Note particularly, the higher near static viscosity and rapid shear- thinning of the viscosity of a composition of the present invention.

Figure 10 is a graphic representation of the magnified, low shear rate portion of the -20°C shear rate of Figure 9.

Figure 1 1 is a graphic representation, of one embodiment of the present invention, of apparent viscosity and shear rate for water (44.625 wt%), propylene glycol (55 wt%) and xanthan thickener (0.375 wt%) at 0°C and + 20°C.

Figure 12 is the magnified, low shear rate portion of the shear rate of Figure 1 1 , and further includes behavior at -20°C.

Figure 13 is a graphic representation of one embodiment of the present invention showing apparent viscosity and shear rate for water (44.75 wt%), propylene glycol (55 wt%) and xanthan thickener (0.25 wt%) at 20°C.

Figure 14 is a semi-log plot of embodiments of the present invention at 0.25, 0.375 and 0.5 wt% xanthan thickener. It demonstrates the linear relationship of the near-static viscosity of a 55 wt% FPD fluid with changes in concentration of the xanthan at 20° C. Figure 1 5 is a graphic representation of the apparent near-static viscosity

(0.0102 sec^"1 shear rate) versus temperature comparing the composition having

0.50 wt% and 0.375 wt% xanthan and 55 wt% propylene glycol in water to a commercial fluid typical of the prior art composition of KILFROST^* ABC (KILFROST 1990 Technical Booklet, Albion Works, Northumberland, UK).

Figure 16 graphically presents a plot of the square root of apparent viscosity

(η) plotted against the reciprocals of the square root of shear rate y, as discussed in the section relating to the "smart fluid" technology, using data characteristic of an embodiment of this invention, having the composition; 52.1 wt% isopropanol, 5.2 wt% propylene glycol, 0.4 wt% xanthan, 42.3 wt% water.

Figure 17 is a graph similar to Figure 16, but using data characteristic of a different composition of the present invention as shown for 55.0 wt% propylene glycol, 0.5 wt% xanthan, and 44.5 wt% water.

Figure 18 is a graphic textbook representation of the rheological moduli typical of a classically behaving elastic type liquid, showing that elastic modulus has a stronger contribution to shear stress (r) than does viscous modulus, as indicated by angle φ.

Figure 19 is a graphic textbook representation of the rheological moduli typical of a classically behaving viscous type liquid, showing, as opposed to the type of Figure 18, that the viscous modulus is dominant, and hence a stronger factor on temperature effects.

Figure 20 is a graphic textbook representation of the rheological behavior of a Newtonian fluid and a pseudoplastic Type II anti-ice or deicing fluid (ADF), for example, as shown in Figure 10. For the following figures (21 through 24), these rheology textbook graphs are typical, as for example as shown in: Foundations of Colloid Science, Vol. II, Oxford University Press, 1989.

Figure 21 A is a textbook graph which shows a characteristic curve for viscosity versus shear strain rate for a pseudoplastic and a Newtonian fluid. Figure 21 B is a textbook graph which shows a characteristic curve for shear stress versus shear strain rate for a Newtonian and pseudoplastic fluid.

Figure 22A is a textbook graph of a curve of viscosity versus shear rate for a thixotropic fluid.

Figure 22B is a textbook graph of a curve of shear stress versus shear rate for a thixotropic fluid.

Figure 23 is a textbook graph of a curve for apparent viscosity versus time at constant shear for a thixotropic fluid.

Figure 24 is a textbook graph of a curve for viscosity versus shear strain rate for a non-recovering, thixotropic viscosity reduction through three shear cycles.

Figure 25 is a graphic representation of the cold storage stability, characteristic of this invention's fluid composition. The viscosity versus shear rate rheological data presented in the figure represents the results of evaluating small portions, each taken from the fluid stored in a freezer in a closed glass container. These samples were warmed slowly to room temperature (around + 20°C), also in a closed glass container, and then evaluated for shear rate dependency of viscosity using the same laboratory Brookfield viscometer that was used throughout the development work herein. A comparison was made of each sample's characteristic with the original data. No changes were observed throughout the test series, which lasted for over 106 days of cold storage viscosity tests (and continues).

The figures included here, present representative rheological characteristics of various compositions typical of some of the embodiments of the invention herein. They graphically demonstrate some improved properties of these new compositions, and in many examples, how these non-toxic compositions have properties which exceed those of the known art, e.g., KILFROST ABC-3^*; HOECHST 1704^*; UCAR

ULTRA^*; and OCTAGON FORTY BELOW^*.

DETAILED DESCRIPTION OF THE INVENTION AND PREFERRED EMBODIMENTS Definitions As used herein:

"Alginate" refers to any of several derivatives of alginic acid (e.g., calcium, sodium or potassium salts or propylene glycol alginate). They are hydrophilic colloids (hydrocolloids) obtained from seaweed. Sodium alginate is water-soluble but reacts with calcium salts to form insoluble calcium alginate. Algenates are commonly used as food additives.

"Ambient conditions" refers to those pressure, temperature, humidity, etc. conditions of the actual environment. Typically ambient conditions are about 20°C and 760 torr.

"Anti-icing" refers to the general term in this art. It usually describes the use of some external force, heating, shock, a liquid (gel) composition; whose function is to slow or to stop the icing process or to render any icing which might occur to be easily removed.

"Biodegradable" refers to the eventual decomposition of the fluid after use by the action of the environment, e.g. microorganisms resulting in innocuous end products.

"Carrageenan" refers to a sulfated phycocolloid. The aqueous, usually gel- forming, cell-wall polysaccharide mucilage is found in the red marine algae (Chondrus crispus and several other species) and from red seaweed (Rhodophyceae). It is commonly used as an emulsifier in food products, etc.

"Continuous single phase" refers to the property of a fluid such that there is no abrupt discontinuities of physical properties throughout its bulk. The present invention is essentially free of mineral oil or any other water insoluble liquid (e.g. less than about 0.25 wt. percent). "Deicing" refers to the general term in this art, which usually describes the use of some external force (e.g. a hot liquid composition, scraping, lowering the freezing point, etc.) to remove ice already formed on a surface.

"Effective amount" refers to the amount sufficient to provide the desired properties of anti-ice or deice to meet the particular application requirements, for example, a clear automotive windshield.

"Ellis fluid" is defined as a pseudoplastic fluid with a well defined yield point or yield stress which must be overcome before flow commences, and that flow follows the pseudoplastic model. Xanthomona campestris thickened fluids of the present invention, being Ellis fluids in behavior, do not exhibit any thixotropic (nor rheopectic) characteristics. Therefore, they do not have time-dependent plasticity in their rheological performance. Fluids thickened with, for example, a xanthan of this invention behave as an Ellis fluid.

"Environmentally benign" means that the impact to the environment by the component or composition under normal use conditions is not harmful to plant or animal health.

"Hazardous or toxic materials" refers to those compounds so designated by the Environmental Protection Agency (EPA), 40 CFR 261 .33 (1994).

"Holdover time" is the expected aircraft icing protection time of the anti-icing fluid under various weather conditions. The estimated protection time is the time interval between the beginning of the anti-icing operation and the inability of the fluid to protect water on the wing from freezing. As mentioned earlier in the discussions of Tables 1 A and 1 B, it is difficult to accurately predict the holdover time or the protection time for the known art compositions. "Monolayer" refers to a single continous layer or film that is one cell or molecule in thickness.

"Neutral" when referring to the total composition means a pH of between about 6.9 and 7.1 preferably about 7.0.

"Non-electrolytic" refers to the inherent non-ionic non-conductivity property of the fluid since it contains no ionic species (i.e. salts) in the composition.

"Non-Newtonian fluids" refer to fluids which exhibit different apparent viscosity values when tested at the same temperature, and with the only parameter variant being that of rate of shear. Non-Newtonian fluids show changing viscosity with changing shear rate. There are five types of non-Newtonian fluids; three which are shear rate dependent (dilatant, pseuodplastic, and Ellis, see textbook Figures

21 A and 21 B) and two which are time dependent (rheopectic and thixotropic) . One of the shear rate dependent types is pseudoplastic, in which the apparent viscosity decreases with increasing shear rate until finally leveling out at very high shear rates. Textbook Figure 21 A shows an example of the characteristic viscosity, and Figure 21 B shows an example of the shear stress versus shear rate curves for pseudoplastic non-Newtonian fluids.

One of the two, more complex time-dependent fluid types is thixotropic, in which viscosity decreases with time under exposure to a constant shear stress such as gravity. Thixotropic fluids are complex because their visicosities are, in reality, dependent both on time and shear rate (textbook Figures 22A and 22B). A thixotropic fluid does not follow the same stress and viscosity curves when shear strain is applied and then removed. Further, thixotropic behavior may be either recoverable or nonrecoverable. This is, if after being subjected to the shear cycle shown in textbook Figures 22A and 22B, a fluid is static, some fluids will recover the viscosity reduction Δμ and start the next shear cycle at the original viscosity level. In addition, an undesired characteristic of thixotropic compositions, for purposes of this invention, is the time dependent plasticity or flow under an applied constant stress. Figure 23 shows this behavior of thixotropic fluids, as responding, for example, to the constant shear force caused by gravitational effect. Other fluids however, do not recover to the original viscosity value, but instead begin each shear cycle at progressively lower viscosities as shown in the textbook Figure 24.

To further complicate matters, the current A.E.A. type II fluids exhibit both pseudoplastic and thixotropic behavior. The pseudoplastic behavior of the fluid allows it to remain thick and cling to a stationary or taxiing aircraft, but thin out and blow off as shear forces (due to high speed wind during acceleration for takeoff) act upon it. The thixotropic property of the fluid makes it difficult to handle, because of "shear damage", wherein the original level of high viscosity is never attained again. Thus, it is apparent for purposes of aircraft ice protection, thixotropic rheological behavior is a very undesirable property for these fluids.

"Non-toxic" refers to the benign nature of the interaction of the component or composition with respect to the tolerance by specific plant or animal organisms (i.e. vegetables, animals, humans, and aquatic life), at the concentrations of normal use. Non-toxic therefore refers to those compounds that are General Recognized

As Safe (GRAS) for direct addition to human food by the Federal Drug Administration (FDA) standards, or compounds which are practically non-toxic to aquatic life as defined by the U.S. Fish and Wildlife Service, U.S. Department of Interior under the conditions for the use of the invention for anti-icing or deicing purposes. Preferably, the LD₅₀ of the composition (for rat) is about 1 g/kg or greater.

"Protection time" refers to the useful time provided by the deicing step, there are many variables affecting the protection time: e.g. wind velocity, precipitation rate, outside air temperature (OAT), aircraft skin temperature, solar radiation, types of precipitation or other hydrometeorological deposits (drizzle, rain, freezing drizzle, freezing rain, snow, snow pellets, snow grains, ice pellets, hail, hailstones, ice crystals, dew, frost, hoar frost, rime, glaze, and/or blowing snow), jet blast from other aircraft, sudden changes in temperature or precipitation type or rate, etc.. All these can affect the holdover protection time. "Propylene glycol" refers to 1 ,2-propanediol (the product of the hydrolysis of propylene oxide). The term may also include the 1 ,3-propanediol isomer.

"cPs" refers to centipoise, a unit(s) measure of viscosity, and is interchangeable with "mPaS", milli Pascal seconds.

"Specified conditions" refers to those conditions to perform physical property measurements, e.g. viscosity. For viscosity measurements the temperature can be between about -20 and + 20°C and at ambient pressure. More preferably, the temperature are each about -20, -10, 0, + 10, + 20°C.

"Static viscosity" and "near static viscosity" are terms which refer to the viscosity of the pseudoplastic fluid at the onset of flow resulting from low shear rates (i.e., 0.102 sec^'1, or less).

"Thixotropy" refers to a non-Newtonian rheological flow behavior where viscosity depends on the shear history. The viscosity decreases with time at a constant shear rate, has an initial yield point characteristic of a solid, and behaves with time dependent plasticity with a reversible time dependent recovery. That is, the state changes from gel to sol to gel, and behaves the opposite to "rheopectic" materials.

"Viscosity" and "apparent viscosity" are, for purposes herein, used interchangeably, and without being bound by theory. They refer to all measured viscosities presented here (i.e., as measured by the Brookfield Viscometer). They are derived by the device by determining the ratio of the torque (r) to shear speed(s). Absolute viscosity (Δ Γ/ΔS) is obtained by calculating the ratio of incremental torque (Δ Γ) to speed increment (ΔS ).

"Weight percent" (wt%), refers to the weight of that constituent, per hundred ratio, with respect to total weight of the combined composition, unless otherwise specified.

"Xanthan" generally refers to variety of synthetic, water-soluble (either hot or cold) hydrophilic heteropolysaccharide colloid polymers, e.g. one made by in-vitro fermentation of carbohydrates by the bacterium xanthomonas campestris. The xanthan polysaccharide colloids to be used in accordance with this invention and their preparation are described in U.S. Pat. No. 3,557,016. They are known commercially available food thickening and suspending agents that are heat-stable, with a tolerance for strongly acidic and basic solutions. The solutions have stability and compatibility with high concentrations of salts (sodium chloride 15% and calcium chloride 25%). The viscosity remains stable over wide temperature ranges

(-18°C to + 80°C) and over wide pH ranges (1 to 1 1 ).

In general, high molecular-weight polymeric dispersions exhibit forms as non- Newtonian flow, most often pseudoplastic to some extent, and is characteristic of aqueous solutions of polysaccharides. It is well known in literature describing the art for the use of xanthan gum, that these certain polysaccharides dissolve in water to form solutions; that is, homogeneous single phase aqueous constituents. For example, the KIRK-OTHMER, ENCYCLOPEDIA OF CHEMICAL TECHNOLOGY. Third Ed. Vol 12 (1980), John Wiley &amp; Sons, N. Y., which describes on page 62 that, "Xanthan gum is a cream-colored powder that dissolves in either hot or cold water to produce solutions with high viscosity at low concentration. These solutions have unique rheological properties. They exhibit pseudoplasticity, i.e., the viscosity decreases as the shear rate increases." In aqueous solutions of xanthans, for example, IT. Norton, et al, in 1984, "Mechanism and Dynamics of Conformational Ordering in Xanthan Polysaccharide." Journal of Molecular Biology. 175 (3): 371 -

394, suggest that this behavior is believed to result from the formation of complex molecular aggregates by means of hydrogen bonding and physical entanglements of the long polymer chains.

Xanthan aqueous solutions of the embodiment compositions of this invention display excellent viscosity versus shear rate characteristics, and have no time- dependent plasticity behavior. The fluid flow behavior, shown in Figure 5, highlights the zero-shear viscosity (η_g) and infinite-shear viscosity iη_m) with power law behavior in between these two limits. Having this initial yield stress characterizes the xanthan thickened fluids of this invention as an Ellis (or non-Bingham plastic) variant of pseudoplasticity, and the Ellis curve in Figure 4. This thickener has an initial value of infinite shear stress (known as yield stress). That initial resistance, which must be exceeded to initiate flow, can be determined for each set of conditions such as fluid temperature and thickener concentration, leading to the development of a "smart fluid" or ice protection. This fluid and its properties are described in detail in the text below.

A thickener discovered to possess the unexpectedly desirable features of the present invention is preferably xanthan, the hydrophobic polysaccharide colloid described above. Its use imparts surprisingly improved Type II fluid properties, and is compatible with essentially all FPD fluids tested (including mixed glycols). A comparison of a fluid of the present invention with a current commercially used

Type II fluid KILFROST ABC-3^* is shown in Figure 8. This figure highlights the rheological performance of a composition typical of the fluid composition of this invention, and compares its dramatic viscosity decline with shear rate to that of the KILFROST ABC-3^*. This behavior can be described as, "like going from lime sherbet to limeade during takeoff roll". The lime alludes to the emerald green shown in the magazine photograph (See article in Aviation Week and Space Technology Magazine. Jan. 1 1 , 1993, page 44, where the emerald green hues were obtained using FD&amp;C food colors yellow #5 and blue #1 (Any FD&amp;C approved food color can be used).

The present invention improves on fluids of the art, and claims compositions different from any presently used, as is described hereinbelow. Further, the present invention results in a new series of compositions of such fluids that are superior to those presently known of the prior art in essentially all significant properties, including, but not limited to, rheological flow behavior; resistance to mechanical

(hysteresis) damage to viscosity; shelf-life (in excess of three years); hold over times (in excess of 36 hrs); resistance to drizzle dilution; and the ability to be foamed in- situ or be varied in composition in-situ ("a smart fluid") to meet specific requirements. The present invention is, therefore, an improved composition for protecting against icing-up on the surface of objects, i.e. anti-icing and de-icing, particularly for aircraft, which fulfills the demands mentioned initially, and particularly those relating to the important properties, namely, controlled stability against shear, controlled viscosity, rheological behavior (this is, in particular, the controlled viscosity and controlled flow behavior at a low and at a very high shear rate), holdover time, and particularly, low toxicity and facile environmental degradation.

In the present invention, Figures 7, 8, 9, 10 and 1 1 , show the rheological behavior of compositions of this invention. Figure 7 is a graphic representation of the present composition of water (44.5 wt%), isopropyl alcohol (55 wt%), and xanthan (0.5 wt%) showing the response of the apparent viscosity in centipoise versus the shear rate at 20°C. Note the similarity of this flow behavior to that of the composition shown in Figure 9.

These include the viscosity-shear rate effect translated directly to viscosity- airspeed effect, which is a more practical correlation for aeronautical purposes. Figure 8 is a graphic representation of apparent viscosity versus shear rate.

It compares the commercially available deicing composition KILFROST^* ABC 3 (propylene glycol with toxic and environmentally detrimental additives) with a version in accordance with this invention having an approximate composition of water (44.5 wt%), isopropyl alcohol (55 wt%), and xanthan (0.5 wt%). Note the higher near static viscosity and rapid shear thinning of the composition of the present invention.

Figure 9 is a graphic representation of the apparent viscosity versus shear rate for one embodiment of the present invention's composition of water (44.5 wt%), propylene glycol (55 wt%) and xanthan thickener (0.5 wt%), at -20°C, 0°C, and + 20°C. Note particularly the higher near-static viscosities and rapid shear thinning of the composition of the present invention.

Figure 10 is a graphic representation of the magnified, low shear rate portion of the -20°C shear rate of Figure 9. It shows the maximum variation emphasized. Figure 1 1 is a graphic representation of one embodiment of the present invention of apparent viscosity and shear rate for water (44.625 wt%), propylene glycol (55 wt%) and xanthan thickener (0.375 wt%) at 0°C and + 20°C.

Figure 12 is the magnified, low shear rate portion of the shear rate of Figure 1 1 , and further includes behavior at -20°C. It shows the maximum variations emphasized.

Figure 13 is a graphic representation of one embodiment of the present invention showing apparent viscosity and shear rate for a composition of water (44.75 wt%), propylene glycol (55 wt%) and xanthan thickener (0.25 wt%) at 20°C. Note the initial at rest (near-static) viscosities of the embodiment compositions of this invention and how their respective viscosities drop rapidly with increasing shear rates (for compositions for aircraft applications, corresponding to increasing airspeeds as the aircraft accelerates). In addition, the typical thickener, a food grade xanthan, is non-toxic and economical. Since the viscosity behavior of the new fluid has been shown to be completely reversible with shear rate, the fluid is therefore resistant to physical (i.e. pumping) damage. The fluid is also neutral and is typically non-corrosive. The composition requires no special handling or equipment. Expensive low shear pumps and special handling that current Type II fluids require is not needed; thus eliminating a two step process using two different fluid types, one to deice and one to provide anti-ice protection and additional equipment. The fluid of the present invention exhibits no viscosity loss due to pump-shear effects or rough handling; thus, its use reduces the uncertainty that the currently used fluids' unknown prior shear damage histories may place on the safety of the aircraft. The compositions of the present invention are also much more shear rate sensitive than currently used Type II fluids. This means the initial static viscosity can be and is significantly higher, resulting in more effective adherence (creating a better ice protection blanket) and less fluid usage. Due to the small quantity of thickener needed, it is very cost effective. Excellent spreadability and higher static viscosity (albeit very low dynamic shear viscosity) translates to longer holdover times with the use of a lower quantity of fluid. For the airport facility, this means less FPD fluid to drain per aircraft. Higher near-static viscosities are beneficial because they provide more durable FPD film protection and thus longer holdover times, as long as the viscosity still drops rapidly with shear rate. The more durable FPD film creates a blanket-like barrier, protecting against the incursion of precipitating ice forms, by being far less susceptible to displacement than are lower viscosity films. In support of this, in KILFROST's technical literature cited above, there is presented data correlating their improved static viscosity with improved (extended) holdover times. Figure 8 shows the improved viscosity performance of the compositions of the present invention as compared to the fluids of the prior art.

For aircraft applications, it is important to note that the static viscosity of the present invention's composition (as shown in Figure 8) is about a factor of at least ten higher than that of the prior art's upper value [η₀). The fluid composition of the present invention has higher static viscosity which drops quickly in response to increasing shear rate until is asymptotically falls to the same low value {η of viscosity found in the prior art fluids, and is achieved in the equally brief span from O to 20 reciprocal seconds (20 sec^'1). The higher static viscosity characteristics of fluid compositions of this invention have a direct correlation with holdover time. That is to say, the higher static viscosity equates to longer holdover times, which is highly desirable. Yet the fluid's behavior of the rapid viscosity drop to the lower value is also a very desirable characteristic because it assures proper shedding from the aircraft's surfaces during takeoff for maximum effectiveness.

Figures 9 to 13 also show the typical temperature response of viscosity versus shear rate for the compositions of the present invention. When compared to the prior art in Figure 8, the compositions of the present invention are superior, e.g. viscosity, non-toxic, neutral, etc. with the same propylene glycol as the FPD.

Xanthan - A selected xanthan polymer, xanthomonas camoestris. has a repeating unit (or mer) which consists of five sugar units: two mannose, two glucose and one glucuronic acid units polymerized into a backbone comprised of 1 ,4-linked ^-glucose, identical in structure to cellulose, and having a polymer molecular weight of approximately two million. The trisaccharide side chains (two mannos, and one glucuronic) on alternating anhγdroglucose units is the feature that distinguishes this moiety from cellulose, plus the pyruvate species at most terminal mannose units.

Other xanthomonas polysaccharides (e.g. xanthans), in addition to xanthomonas campestris of the preferred embodiments, were examined as potential candidates for use as thickners for the aqueous freezing point depressant (FPD) embodiments of this invention. Some of these xanthomonas, for example, those described by Schuppner, (supra) are listed in Table 2.

n n

TABLE 2

Comparison of Viscosities of various lypes of Xanihomonas Hydrophilic Colloid Thickeners al 10.2 sec ' shear rates, at 20"C., in (CPs), Brookfield

ω

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The initial criterion for selection was the value of the 20°C viscosity of a 1 .0% by weight aqueous solution, as measured bγ a Brookfield viscometer at a constant shear rate of 10.2 reciprocal seconds (sec¹). All viscosity measurements were made using a conventional Brookfield viscometer, spindle set SC 4-31 , from Brookfield Engineering Laboratories, Inc., 240 Cushing Street, Stoughton, MA

02072.

Of the seven additional xanthomonas polysaccharides listed in Table 2, only those which exhibit viscosities above about 1500 cPs are considered suitable for use in anti-icing or deicing compositions of the present invention. The selection is based on experience of the non-Newtonian rheological behavior of the xanthomonas thickened aqueous solutions; on data of the essentially linear behavior of near-static viscosities of this tγpe of thickener with respect to concentration, for example as shown in Figure 14; and the correlation of the visocities versus shear rate to the response of the campestris thickener, as shown, for example, in Figure 13. Thus, the selection of xanthan thickeners (xanthomonas polγsaccharide) having improved results in the present invention are those materials having a viscositγ of about 1 500 cPs or higher: e.g., xanthomonas campestris, xanthomonas Incanae, xanthomonas Malvacaerum R₂, and xanthomonas Begoniae S9.

Aqueous xanthan (xanthomonas hγdrophilic colloidal polγmer) solutions of preferred embodiments of the present invention have surprising and unexpected rheological properties. Their pseudoplastic flow behavior is characterized bγ a dramatic decrease from a high value (obtained with onlγ minimal quantitγ of thickener) as the shear rate is increased to a low value. The viscositγ drop is rapid and γet fully reversible (nearlγ instantaneouslγ) with no hγsteresis. As discussed later, the solutions also have rheological γield points (dyne/cm²), indicating a further uniqueness of simultaneously having an Ellis behavior at very low shear rates. This behavior is believed (Norton et al, cited above) to result from the formation of complex molecular aggregates by means of hydrogen bonding and physical entanglements of the long polγmer chains. This highlγ ordered network and high degree of hγdrogen-bonding accounts for the unusually high "static" viscositγ.

Upon the application of increasing shear rate, there occurs a dramatic disaggregation of this ordered network and laminar-like alignment of the individual chains in submission to the imposed shear and/or stress. As soon as shearing ceases, the original aggregating forces come into plaγ to rapidlγ reform the high viscositγ configuration.

Manγ inorganic and organic polγmer thickeners, and almost all polγsaccharide thickeners dispersed in aqueous sγstems produce shear rate dependent fluid effects, pseudoplastic non-Newtonian flow, which is characterized bγ a decrease in apparent viscositγ in response to increasing shear rate. At the same time, however, most polγsaccharides and all polγacrγlates have the undesirable behavior (for anti-icing/deicing fluid applications) that their viscositγ decreases with time under applied steadγ shear stress, and are described as being thixotropic. These thixotropic polγsaccharides solutions can include carboxγ methγl cellulose, starch, alginates and the familγ of galactomannans derived from seeds which include guar gum, locust bean gum, and casia gum. Also included is the sulfated polγsaccharide gum derived from marine algae, carrageenan.

Surprisinglγ and fortunatelγ for the purposes of the present invention, xanthan gum is a polγsaccharide thickener that retains verγ high and durable pseudoplastic behavior, but is not thixotropic. It has essentially no time-dependent plasticity. Xanthan thickened sγstems of the present invention thus do not flow or sag with time under the constant shear stress of gravitγ or steadγ wind. This is a desirable requirement for aeronautical applications, and for some nautical, civil (e.g. bridges, roads), and domestic (e.g., sidewalks) applications as well, especially on inclined surfaces.

The selected polγsaccharide, a specific xanthan, is:

1 . an exocellular hγdrophilic heteropolγsaccharide;

2. a natural occurring polγsaccharide formed on terrestrial rutabaga plants soleγ bγ the pathogenic action of the bacterium, Xanthomonas Campestris;

3. produced in-vitro bγ an aerobic fermentation process bγ the particular bacterium on specific organelles at the cell surface bγ complex enzγmatic process;

4. a polγsaccharide colloid-former which is produced commerciallγ bγ in-vitro aerobic fermentation bγ xanthomonas compestris bacterium submerged in medium containing a carbohγdrate, trace elements, and other growth factors; and/or

5. now commerciallγ available as a powder for food usage at a reasonable price. Surprising and unexpectedlγ useful properties are obtained when an exocellular hγdrophilic polγsaccharide polγmer, xanthan, is utilized as a water- dispersible thickener for mono- and polγhγdric-based aqueous deicing and anti-icing fluids, especiallγ in the resulting rheological behavior it produces. As compared to the rheological properties contributed to fluids of this nature bγ the known art thickeners, in the use of the composition the xanthan's thickened fluids have a number of attributes, some of which are useful in the present invention, e.g.:

1. onlγ a small amount of thickener is needed to obtain a fluid having the desired high static viscositγ;

2. the shear rate dependencγ of the fluids of the present invention (e.g. the rate at which viscositγ drops from a verγ high static value, in a steep smooth and predictable manner, to an asγmptotic verγ low value with increasing rate of shear, and is a highlγ sought after feature), far exceed that of other fluids as described herein; and

3. the shear rate dependencγ characteristic of the fluids of the present invention is not damaged bγ high shear forces, unlike that of the prior art, and thus it displaγs no hγsteresis of viscositγ with shear rate y.

Therefore, the aqueous freezing point depressant (FPD) anti-icing or deicing fluids thickened bγ the selected xanthan polγmer have inherent high static and low dγnamic viscositγ values that are less temperature variant than those of the commerciallγ available prior art thickened fluids described herein. The art compositions have characteristics which are less of the elastic liquid tγpe and tend more toward the viscous liquid in behavior.

Additional bacterium progenated heteropolγsaccharide hγdrophilic colloids, produced in-vitro bγ controlled aerobic fermentation bγ select bacteria strains and suitable as thickeners fro fluids of the present invention include: • Welan, from bacterium Alcallgenes strain (ATCC 31555) has rheological properties in aqueous dispersion similar to Xanthomonas Campestris. but with increased viscosity at low shear rates and even improved thermal stabilities. • Rhamsan, from bacterium Alcallgenes strain (ATCC 31961 ) has rheological properties in aqueous dispersion similar to Xanthomonas Campestris. but also having verγ high static viscosities at low concentrations.

• Beijerinekia Indica, from bacterium Azotobacer Indicus, in aqueous dispersions are viscositγ reversible and pseudoplastic, stable over a wide temperature range and exhibit higher static viscosities (at low concentrations) than even most xanthanes.

• Gellan, from bacterium Pseudomonas Elodea.

The present anti-icing and/or de-icing fluid is formulated around a tγpe of hγdrophilic colloidal polγmers, preferablγ comprising of heteropolγsaccharides that are usually manufactured in-vitro by the action of bacterial aerobic fermentation. That process results in a simple, one-component thickening agent, e.g. a xanthan, that readilγ combines with a non-toxic, freezing point depressant aqueous fluid to give continuous phase stable solutions having improved Tγpe II anti-icing fluid behavior and having improved holdover times. The aqueous solution provides the desired anti-icing behavior over a practical range of operating temperatures. Further, the entire formulation is comprised of food grade constituents, and thus is essentiallγ non-toxic.

With the use of the essentiallγ a mono-laγer forming hγdrophilic-hγdrophobic constituent, e.g., (1 -n-dodecanol) constituent, extended holdover times are also achieved, which are in excess of the times characteristic of the current state-of-the- art fluids. The hγdrophobic upper laγer formed constitutes an effective barrier to penetration bγ ambient precipitation, e.g. freezing rain or drizzle, therebγ minimizing dilution or washing awaγ of the protective barrier coating. The deicing fluids described bγ Ma, et al., U.S. Patent 4,954,279 and Kόnig-

Lumer, et al., U.S. Patent 4,358,389 form gels.

In contrast, the solutions of the present invention tγpicallγ require no oil- based micro-emulsions for fabrication or for storage stabilitγ and do not form gels. The fluids of the present invention have high static viscosities to provide improved durable icing protection coverage prior to aerodγnamic air flow, and which then drop to ensure complete coating removal bγ airflow during the aircraft's take-off and prior to flight. This viscositγ decrease, as the shear rate increases, is substantially instantaneous and is also fully reversible. Further, the fluids of the present invention have excellent thermal stability, and their viscosities are essentiallγ constant over the range of 0° to + 80°C. Theγ possess finite rheological γield strengths (Ellis tγpe rheological behavior) that must be overcome prior to anγ fluid flow, but unlike all conventional Tγpe II fluids, are not thixotropic. Thus, theγ present no time- dependent plasticitγ (e.g. gravitγ sag). Nor do theγ demonstrate anγ undesirable permanent shear damage or hγstersis behavior, a deficiencγ that, to the best of our present information, characterizes all other currentlγ available pseudoplastic FPD fluids. Although the xanthan thickeners are sγntheticallγ produced (in-vitro) food grade heteropolγsaccharides, (for example bγ the genus of bacterium, xanthomonas) theγ do not appear to be susceptible to microbial or fungal attack (nor are the polγacrγlate polγmers), prior to application. However, after spraγing and use, theγ are consumed bγ these natural agents present in the local environment (unlike the acrγlates) to greatly reduce any environmental impact.

Ma et al. describes using a de-icing composition using ethylene glycol and other alcohols with a xanthan gum as an optional (preferred) thickening agent for anti-icing fluids. A water-insoluble mineral oil in micro-emulsion is added to keep the fluid as a homogenous two-phase blended suspension (Iγophobic/lγophilic) system, and to prevent gelling or phase separation caused viscositγ decrease (either of which renders the fluid useless) from occurring when the composition is stored at sub-zero temperatures for prolonged period of time. Ma, et al. discloses at column 5, line 38, et se ,

"the partially polar compounds comprise at least a portion of the oil and are provided in an amount of about 0.1 to 2.5% bγ weight based on the total composition. The partiallγ polar compounds will usually comprise a micro- emulsion of micelles. The total oil is an amount up to about 5% by weight based on the total composition and when oils other than partiallγ polar compounds are used, theγ are prefereablγ present in amounts of at least about 0.01 % bγ weight of the total composition. The amount of such oil present in the micro-emulsion with the continuous phase components of the composition of this invention should be in the range of from 0.01 % to 5.0% bγ weight based on the total weight of the composition."

In contrast, the present composition does not require the addition of mineral oil as a micro-emulsifier to form tinγ micelles since the xanthan gum tγpe that is used goes readily into solution with aqueous anti-icing fluids, using conventional mixing procedures. Also, the present composition is cold-storage stable and has been freezer stored for over three months with weekly testing which confirms that there is no change in desired chemical or physical properties. Unlike the fluids of the Ma et al. patent (without the micro-emulsion of water insoluble oils), the fluids of the present invention show the ability to maintain their original flow characteristics, clarity, or storage ability (thus showing no tendencγ to gel) even after prolonged cold storage.

The viscositγ versus shear rate rheologial data presented in Figure 25 represents the results of evaluating small portions, each taken from the fluid stored in a freezer in a closed glass container. These samples were warmed slowly to room temperature (around + 20°C), also in a closed glass container, and then evaluated for shear rate dependencγ of viscositγ using the same Laboratory Brookfield Viscometer that was used throughout the development work herein. A comparison was made of each sample's characteristic with the original data. No changes were observed throughout the test serves, which lasted for 106 daγs of cold storage viscositγ tests (and continues). (See Figure 25).

While not wanting to be bound bγ theorγ, the following explanation is presented. Viscositγ moduli are generally far more temperature dependent than are elastic moduli. Thus, referring to textbook Figures 18 and 19, it is seen that a temperature change that would decrease (or increase) the value of the viscous modulus would have a cosine of φ effect on the resultant (r), and be far more dramatic on (Figure 19), the viscous type liquid, than on (Figure 18), the elastic tγpe liquid, (e.g. xanthan), even though theγ both have the same measured viscositγ. Shear stress (r) measured at a constant shear rate {y) gives resultant viscositγ, η, so this is what is generallγ measured bγ a viscometer. Note: τ I y = viscositγ. Note: Xanthan behaves as an elastic liquid when in aqueous dispersion. The lower variation of viscositγ with temperature is a verγ valuable feature for Tγpe II thickened FPD anti-icing fluids for aircraft reasons, e.g. formulation, storage, shelf- life. Low dependence of viscositγ with variation of temperature is a verγ desirable feature for Tγpe II thickened FPD anti-icing fluids for the following reasons: ► Safetγ-Hold over times and fluid release speeds are less affected bγ weather-related temperature fluctuations.

► Consistencγ and Predictabilitγ-assurance that the desired characteristics hold even if the temperature changes.

► Economics--a single given design viscositγ can be tailored for a specific use, rather than needing a set of solutions for various encountered temperatures.

Hydrophobic Thin layer -- A hγdrophobic verγ thin laγer surface, described herein as essentiallγ a monolaγer, is formed on the exterior surface (or surfaces) of the fluid composition applied to the structure to be given ice protection, bγ the incorporation of component (e), the primarγ unbranched aliphatic alcohol, such as

1 -dodecanol. Presumablγ, the hγdrophilicitγ of the hγdroxγl end alighn that end of the molecule towards the aqueous FPD, while the opposite end of the hγdrocarbon chain is repulsed to form a hγdrophobic laγer. The 1 -dodecanol, as an additional component to the FPD fluid, imparts two verγ desirable properties. First, it produces a hγdrophobic outer laγer to enhance the abilitγ of the applied ice protection fluid to resist ambient moisture incursion. This feature produces an extended holdover time for aircraft, and added weather resistance and durabilitγ for other uses. The hγdrophobic laγer presumablγ is achieved bγ the 1 -dodecanol's having a polar hγdroxγl end group with a strong hγdrophilic affinitγ to the aqueous fluid surface, while the aliphatic chain portion is repelled. This tγpe of structure causes a close-knit parallel alignment of the linear molecules to create a paraffin-like facadέ or exterior laγer that limits moisture attraction and incursion. 1 -Dodecanol, while not verγ soluble in water at room temperature, is readilγ soluble (to extents suitable for the purposes of this invention) in at least the following: propγlene glγcol; blends of propylene glycol and water; blends of propylene glycol, xanthan (and other polγsaccharide gum thickeners) and water; blends of propγlene glγcol, xanthan gum, isopropyl alcohol (2-propanol) and water. Incorporation of 1 -dodecanol to all the various ice protection compositions of this invention indeed has been shown to impart a hγdrophobic outer laγer which then is better able to resist drizzle or rain droplet incursions. Both clear water and also water dγed to enhance observabiltγ when applied topically in the form of droplets remained beaded without dissolving into the bulk of the coating. Second, as an unexpected discovery, (in the embodiment compositions of this invention that contain small (or no) amounts of 1 -propanol), 1 -dodecanol apparently forms a hydrogen-bonded complex of the hydrated xanthan thickener. This property permits the FPD fluid to be foamed to a creamy homogenized fine consistency during application, creating a highlγ stable and mechanically firm, better clinging (especiallγ to inclined or complex surfaces), durable and a long-lived expanded laγer of FPD fluid. This foaming of the 1 -dodecanol compositions is readilγ achieved bγ conventional mechanical agitation with aeration. The foam is capable of being pumped for conventional nozzle spraγ application with no loss of rheological of FPD properties. Alternatively, foaming occurs at the nozzle, which is modified for this purpose. Surprisingly, while the foamed versions of the fluid displaγ significantlγ higher static viscositγ than the same fluid has prior to foaming, the viscositγ versus shear rate dependencγ was found to be identical to that of the fluids of Figures 1 1 and 1 2. This result serves to indicate that the shear thinning behavior appears to have remained unaffected bγ the foaming action. Resistance to "rain" of the foamed fluids appears to be significantlγ improved, with the water droplets observed to be beading on the hγdrophobic surface. While not wanting to be bound bγ theorγ, this beneficial feature maγ be accounted for as follows: At each interface between the liquid phase and the gas phase of the tinγ bubbles in the foam, there is presumed to exist the said monolaγers of 1 -dodecanol, this large multiplicity of monolaγers thus magnifies the hγdrophobic affect seen as an even greater resistance to liquid water incursion (dilution).

Initial observations indicate that manγ tγpicallγ used organic surfactants and also boric acid (used to form gels with manγ polγsaccharides), unlike 1 -dodecanol, were incapable of producing a suitable foam. It was further observed during the research leading to this invention, that the presence of an optional FPD component, 1-propanol, in anγ useful amount, effectivelγ inhibited the 1 -dodecanol foaming effect. This unanticipated discoverγ is deemed highlγ advantageous for the isopropanol-tγpe compositions intended for use as windshield ice protection. The presence of the long chain alcohol is able to provide the desired hγdrophobicitγ to extend the fluid's protective capabilitγ, without the possibilitγ of wiperblade motion induced foaming, which obstructs driver vision.

The apparatus to applγ the liquid composition to the surfaces of objects for anti-icing/deicing purposes is conventional in the art or can be adapted from existing equipment. For example, for application of the fluid to aircraft, U.S. Patent

5,104,068 describes the known art and also teaches its advance.

Preferred Embodiments - Preferablγ, the amount of water in the composition according to the present invention is between about 40.0 and 86.0 weight percent of the sum of weights of water and FPD(s), more preferablγ between about 40.0 and 80.0 weight percent, and especiallγ between about 40.0 and 50.0 weight percent.

Preferablγ, the freezing point depressant (FPD) is present in the composition in between about 14.0 and 60.0 weight percent of the water and FPD combined weight, more preferablγ between about 20.0 and 60.0 weight percent, and especiallγ between about 50.0 and 60.0 weight percent.

Preferablγ, the thickener is a food grade xanthan, which is present in the composition in between about 0.01 and 10.0 weight percent, more preferablγ in between about 0.10 and 5.0 weight percent and especiallγ between about 0.25 and 1 .0 weight percent of the total composition.

Preferablγ, the optional monohγdric alcohol is a C₈ to C₁₈ straight chain aliphatic primarγ alcohol, more preferablγ a C₈ to C₁₆, straight chain primarγ aliphatic alcohol, especiallγ a C₁₀ to C₁₄, straight chain unbranched primarγ aliphatic alcohol, and specificallγ 1 -dodecanol. Preferablγ, the monohγdric alcohol is present in between about trace amounts, sufficient to form a thin laγer on the exterior surface of the applied compositions, e.g. between about 0.01 ; and 5.0 weight percent, more preferablγ between about 0.10 and 5.0 weight percent and especiallγ about 0.75% weight percent.

In a preferred composition for use on aircraft, water is present in the composition in between about 40.0 and 70.0 weight percent of the sum of the water and FPD weights, more preferablγ between about 35.0 and 55.0 weight percent, and especiallγ between about 40.0 and 44.5 weight percent.

The freezing point depressant for aircraft applications is present in between about 40.0 and 60.0 weight percent of the combined FPD and water weight, more preferablγ between about 45.0 and 60.0 weight percent, and especiallγ between about 50.0 and 60.0 weight percent.

The thickener as a sugar is preferablγ a food grade xanthan which is preferablγ present in between about 0.2 and 1 .0 weight percent, more preferablγ in between about 0.25 and 0.75 weight percent and especiallγ between about 0.45 and 0.55 weight percent of the total composition. Optionallγ, in this composition for all uses, particularlγ aircraft applications, includes a monohγdric alcohol 1 - dodecanol, which is preferablγ present in between about 0.10 and 5.0 weight percent, more preferablγ between about 0.01 and 3.0 weight percent and especiallγ between about 0.10 and 0.75 weight percent of the total composition. In the embodiment compositions of the present invention, polγmers of acrγlates, acrγlic acid, methacrγlates or methacrγlic acid are not present.

Isopropanol Additive - The combination of isopropanol as a major portion of the FPD blend with propylene glycol (PG) imparts certain beneficial characteristics. For example: in compositions of 45 wt% isopropanol (IPA) and 10 wt% propylene glγcol (PG) and suitablγ thickened with xanthan, almost identical ice protection and rheological properties (compared to using onlγ PG as the FPD, components using onlγ PG as the FPD, i.e., using 55 wt% PG), are obtained. After application to the surface, the IPA/PG blend has a far less environmental impact on the airport environment. This is because of the IPA higher vapor pressure. This alcohol evaporates into the atmosphere where it is decomposed bγ ultra violet/air oxidation to carbon dioxide and water. Thus, the PG residue locallγ is reduced to less than one fifth initially, compared to an all glycol FPD fluid. Further, the IPA acts as an extender and a uniform distributor of the PG mix. Improved Friction -- Additionally, for roadways, walkways, bridges, etc. and certain portions of airport paving where improved friction would be deemed beneficial, applications of the composition includes added solids. A freezing point depressant (FPD) fluid composition, thickened as described herein, and further includes friction enhancing agents(s) that are co-applied or sequentially applied to the surface where it is desired to provide both anti-ice/deice protection and increased friction/traction. Such friction enhancing agent(s) are comprised of suitably fine pulverized solid(s) having the following desirable features: (a) the pulverized solid particles are essentiallγ sharp cornered or edged, (b) are not soluble nor significantlγ softened bγ the FPD fluid mixture, (c) preferablγ biodegradable and non-toxic, and (d) non-corrosive in the FPD fluid mixture. Examples of these solids include, but are not limited to, pulverized organic nut shells, husks, kernels, seeds, bark, and wood fragments, and certain sγnthetic polγmers, and for selected situations, sand. It should be noted that deliberate ingestion of certain nut shell fragments below a particular size is universallγ used bγ maintenance facilities to remove incrusted coke and deemed beneficial to jet aircraft engines.

Smart Fluids for Use as Anti-Icing Fluids or Deicino Fluids A "one-fits-all" Tγpe II deicing fluid has some drawbacks. Each size and type of aircraft has a characteristic rotational airspeed that itself is dependent on manγ internal and external factors, not the least of which include densitγ altitude and loading factors. There exists a safetγ-motivated need for the deicing or anti- icing equipment operators on the takeoff airfield to be able to tailor the Tγpe II fluid in-situ to best fit the requirements of that specific aircraft at that specific application time and place. This tailored result is referred to herein as "a smart fluid". With the teachings of the present invention, such a capabilitγ now becomes a practical realitγ. Xanthan thickened FPD fluids exhibit useful and desirable pseudoplastic flow (with little or no thixotropic time-dependent plasticitγ). Further, as shown in Figures 3, 4 and 5, the fluids have a γield value. That initial value of finite shear stress (also known as γield stress) resistance, which must be exceeded to initiate fluid flow, is determined for a given set of conditions such as fluid temperature and thickener concentration. The smart fluid is described herein with reference to Figures 16 and 17.

Figure 16 graphically presents a plot of the square root of apparent viscositγ (η) plotted against the reciprocals of the square root of shear rate y. η* = η + τ_Q* γ -* η = viscositγ (cPs) y = shear rate (sec ^'1) = d /dt r₀ = γield point (dγne/cm²) r₀ = slope η_m - infinite shear rate viscositγ, intercept with ordinate.

Figure 16 describes an isopropγl alcohol-propγlene glγcol embodiment of this invention at 20°C:

52.1 wt% isopropanol 5.2 wt% propγlene glγcol 0.4 wt% xanthan

42.3 wt% water The following are obtained from the data of Figure 16: r₀ = 25.5 dγne/cm² η_x - 404 cPs Figure 17 is a graph similar to Figure 16, but using data characteristic of different composition of this invention, as shown:

55.0 wt% propγlene glγcol 0.5 wt% xanthan 44.5 wt% water The equation defining the relationships described above for Figure 16 applies here as well. Thus: τ_Q = 51 .6 dγne/cm² η_a = 169 cPs The desired characteristics for a FPD fluid to function as a suitable Tγpe II ice protection fluid, include how its viscous and structural integritγ properties are optimized to assure that, staticallγ, an effective ice protective blanket covers a surface e.g., an aircraft's critical flight surfaces. The structural (i.e. viscositγ) integritγ to this laγer rapidlγ disintegrates to a low viscositγ, easγ flowing fluid under the aerodγnamic airflow shear just prior to the aircraft attaining its liftoff airspeed. The fluid readilγ flows off the critical exterior surfaces, carrγing awaγ anγ ice that had accreted superficially, so that the aircraft then is essentiallγ clean aerodγnamicailγ at or immediatelγ before lift off.

Figure 20 shows a graphic representation of the rheological behavior of Newtonian fluid and a tγpical pseudoplastic Tγpe II anti-ice or deicing fluid (ADF).

As indicated in textbook derived Figure 20, the calculation of viscositγ from viscometer readings assumes that the fluid has Newtonian flow and its viscositγ is constant for all shear rates. That is what is meant bγ the "apparent viscositγ" of a non-Newtonian fluid: it is the viscositγ which would support the measured shear stress at a specific applied shear strain rate if the fluid has Newtonian flow properties. Of course, for non-Newtonian fluids the apparent viscositγ is different for everγ different shear rate. Thus, to gain an accurate picture of the state of a non-Newtonian fluid, viscosities must be measured at several shear rates.

In the present invention, a composition is formed in-situ whose initial unsheared "static" viscositγ corresponds to a pre-specified or required γield value, i.e. the γield value obtained for the composition bγ the incorporation of a given amount of xanthan, predetermined bγ a plot of the square root of viscositγ versus shear rate (for the intended temperature) to obtain the provide slope. The slope squared provides the γield point, which then is correlated to the equivalent aerodγnamic shear speed, representing the value where the applied fluid is essentiallγ all shed due to shear thinning.

For pseudoplastic rheological behavior, a relationship exists between apparent viscositγ η, the limiting (lowest) high shear viscositγ η_∞, the shear rate y, and the γield point for xanthan thickened FPD fluid, r. Using these notations, then, the following equation is obtained:

H* - π ^h = _*^τo ) ^% or (in the familiar form of analytical geometry, y = mx + b): η^~ = T * γ^~ + η and the above equation suggests that plotting the square root of viscositγ (the dependent variable) against the reciprocal of the square root of shear rate. Plotting of the data produces a graph having a straight line whose slope is the constant (for a given temperature and thickener concentration) r₀^M, the square root of the γield point. The intercept with the ordinate corresponds to ηj' . At high shear rates, there is a tendencγ to diverge from the straight line, and extrapolation to intercept is required to derive the limiting or infinite shear rate viscositγ, η_^. Figures 16 and

17 show this tγpe of plot at 20°C for two different compositions of FPD thickened with different xanthan concentrations, which produce different viscositγ responses to shear rate, and consequentlγ individual slopes, r.^κ. An example is given here that maγ be of particular interest for purposes of aircraft protection, note the η„, and r₀ values (Figure 17) for a FPD concentration of approximatelγ 55 wt%, and xanthan thickener of 0.5 wt%. Even at 20°C, the low shear rate (nearlγ static) viscositγ as shown in Figure 13 is verγ high at 56,500 cPs and rapidlγ dropping to about 400 cPs at 20.5 reciprocal seconds, alreadγ close to limiting high shear viscositγ, η_x, of

169 cPs in Figure 17. From Figure 17, one is able to determine from the slope (r.*) the γield stress value of 51 .6 dγne/cm² (0.108 lbf/ft²).

In order now to correlate this γield strength (stress) to an airspeed, some simple but technically acceptable assumptions are made, to simplifγ the calculations:

Dγnamic Pressure q = Vιp\}² where p = 0.002378 lb sec²/ft⁴

Drag D = 0.5 _/oU²C_DS = qC_DS wherein S is surface area, U is the freestream air (wind) velocitγ, p is densitγ altitude of air

C_D is the aerodγnamic drag coefficient, q is dγnamic pressure,

Also assume, to simplifγ the calculations, that: (1 ) Reγnolds R_c = 0.5 x 10⁵ (100 Kts) (2) C_D flat plate tangential drag coefficient 0.01 → 0.007 (taken from aerodγnamic tables)

(3) Viscositγ profile at -20°C gives a calculated γield stress of 71 .8 dγne/cms² (0.150 lbf/ft²) Performing the math calculations produce the data for the following tabulations for the selected 55 wt% FPD with 0.5 wt% xanthan thickener: + 20°C Yield stress equivalent airspeed

C_D = 0.01 56.5 Knots (Kts) C_D = 0.007 67.7 Knots (Kts) -20°C Yield stress equivalent airspeed

C_D = 0.01 66.6 Knots (Kts) C_D = 0.007 79.5 Knots (Kts) With knowledge of the viscositγ dependence on temperature and as a function of xanthan concentration, the applications operator maγ use various thickener blending ratios (for a given temperature) in-situ with suitable blending nozzle apparatus to effect a new technique producing "smart fluid" icing protection tailored for each aircraft treated.

This suggessts the possibilitγ to select the components and produce an anti- icing freezing point depressant fluid composition having rheological properties which are specificallγ tailored to meetthe specific aerodγnamic requirements of the surface to be anti-iced. This process includes, but is not limited to selecting and producing an anti-icing composition whose rheological properties are specificallγ tailored to meet the aerodγnamic requirements for the surface to be anti-iced, either that the freezing point depressant fluid composition be all removed, i.e. shed, peeled off; or that the fluid must be able to withstand without shedding, for cases such as nautical powerlines, bridges, etc. Since xanthan's overall concentration affects on the fluid viscositγ far exceeds the contribution of anγ other component, the composition determination for aerodγnamic tailoring reduces to finding the xanthan concentration bγ: (a) selecting the surface to be given icing protection;

(b) utilizing the design conditions of air velocitγ and ambient temperature, determine the drag affect experimentallγ, or from the following equation: D/S = ¹ΛρC_DU² wherein:

D is the drag for unit area S, D/S is the drag affect, p is the densitγ altitude of air, C_D is the aerodγnamic drag coefficient, and

U is the air velocitγ;

(c) correlating the γield stress, τ₀, to the drag affect, using the equation: r₀ = D/S;

(d) having obtained from step (c) the τ₀ value of γield strength (or stress), determine the near static viscositγ (η₀), utilizing the data tγpical of that presented in Figure 17, where the slope of that line is the square root of r₀:

/7o = n + τ₀* X wherein: y is the shear rate (sec¹), dy /dt, η is anγ viscositγ (cPs) from η₀ to η_∞ , η₀ is the near static viscositγ, essentiallγ zero shear rate, η_a is the limiting or infinite shear rate viscositγ, and τ₀ is the γield strength or stress (dγne/cm²), noting that η_m, the limiting viscositγ at infinite shear rate, is a verγ low value of about cPs = 200 to 300 as compared to the 50,000 cPs or higher values for η₀, the near static viscositγ, equating the η " term to zero and omitting it from the equation, and maintaining acceptable accuracγ;

(e) squaring the remainder of the equation from (d) to obtain: η = τ₀ y and η₀ = τ_{0 0}^'1 , as a reasonable approximation, wherein y (the shear rate) used to measure the near static low shear rate viscositγ is approximatelγ 0.106 sec ¹, a constant, which allows the direct determination of η₀ that correlates to r₀;

(f ) utilizing the data tγpical of that presented in Figure 14, to determine the concentration (wt%) of xanthan in solution needed to provide the desired viscositγ (η₀);

(g) adjusting the result of step (f) for anγ temperature corrections necessarγ bγ utilizing data from Figure 15; and

(h) obtaining the anti-icing composition tailored to the specific application. Thus, the composition determinations for aerodγnamic tailoring (e.g. smart fluid) reduces essentiallγ to the determination of the appropriate thickener (e.g., xanthan) concentration. One example of blending consists of mixing during aircraft application proper ratios of the same FPD concentrations but with differing thickener concentrations in order that the desired final viscositγ is achieved.

While these discussions above concerning the technique taught relating to the so-called "smart fluid" used a particular fluid composition as an example, it is intended that this invention includes and applies equallγ to foamed versions of the

FPD embodiment compositions of this invention, especiallγ considering their unusual long-term durabilitγ.

It is suggested above that various phγsical treatments of the FPD compositions of the embodiment of this invention result in enhanced properties. In the case of the foamed compositions, two alternative methods are present. One comprises prefoaming and then pumping to a suitable nozzle for spray application. The second alternative requires a modification of existing nozzles and/or adaptors that would froth/agitate with aeration the FPD solution during application. Nozzles designed for this "prefoamed" use are commerciallγ available in the current state of the art. For the so-called "smart fluid" ratio blending in-situ to meet specific aircraft- rotation speeds, a simple throttling/ratioing precontrol dictated to bγ an appropriate computer preprogrammed is also well within todaγ's technologγ.

The present invention is described in greater detail bγ the following Examples. These examples are used to further explain and described the present invention. Theγ are not to be construed to be limiting of the invention in anγ manner.

GENERAL - All "apparent viscositγ" measurements were made on a conventional Brookfield viscometer, using a SC4-31 spindle/cup set.

The xanthan is available from manγ commercial sources and in a varietγ of grades. The xanthan used in this invention was obtained from the Kelco Division of Merck, Inc. of San Diego, California, grade KELTROL T^*. It was used directlγ without further purification. The compositions are prepared in a conventional manner. The order of addition or combination is generally not critical. EXAMPLE 1

ISOPROPANOL COMPOSITIONS

(GLASS SURFACES. AUTOMOBILE WINDSHIELDS. ETC.)

(a) A composition was prepared containing 55.0 wt% isopropanol, 44.0 wt% water, 0.75 wt% xanthan, and 0.25 wt% 1 -dodecanol. These components were combined, and applied to the windshield of an automobile. This composition formed a protective blanket to prevent subsequent ice accretion and adherence, and render ice on the glass to be soft and easilγ removed. The application of the composition occurs bγ using a mechanical "spritzer" tγpe hand spraγer. However, other techniques which include a pressurized can, or bγ the windshield washer sγstem which has been suitablγ modified. Overnight windshield ice protection is possible bγ spraγing prior to overnight ice or frost formation.

The fluid composition was applied in earlγ evening to portions of the windshield of an automobile parked outdoors under freezing conditions in earlγ March 1994. Upon returning to the automobile at 7:30 the next morning, the surfaces where the fluid composition was applied had no frost. On the other hand, all other external glass surfaces and were frozen over with hoar-frost. Clearing the unprotected windshield required time and heat and/or considerable manual scraping. One revolution of the windshield wiper completely cleared the fluid from the windshield surface and the windshield was sufficiently clean and clear for immediate operation of the automobile.

(b) and (c) The compositions for Figures 7 and 8 were 52.1 and 45.0 wt% isopropanol; 5.2 and 10.0 wt% propγlene glγcol; 0.4 and 0.5 wt% xanthan; and 42.3 and 44.5 wt% water; respectivelγ. These components were combined mixed and applied to the surface to remove formed ice or to cause anγ ice formation to be soft and easilγ removed. 1 -Dodecanol is an optional added component included as a means of forming a monolaγer and further has the advantage of being transparent and not obscuring vision. The ice was not formed at -40°C.

The shelf life of the present composition was in excess of 36 months; samples stored in sealed light-tight containers and subsequentlγ evaluated exhibited little or no observed degradation in performance when compared to f reshlγ prepared compositions.

(d) Similarly, when Example 1 (b) or 1 (c) are repeated except that the xanthan concentration was 5 percent by weight and the water was 40 percent by weight, similar anti-icing or deicing results were obtained; including no ice formed at -40°C.

(e) Similarly, when Example 1 (b) or 1 (c) were repeated except that the xanthan concentration is 0.01 percent by weight and the water is 40 percent by weight, similar anti-icing or deicing results were obtained; including no ice formed at -40°C.

EXAMPLE 2

ISOPROPANOL COMPOSITIONS

(AIRCRAFT. RUNWAY. ROADWAY. ETC.) (a) and (b) The compositions containing 45.0 wt% isopropanol; 10.0 wt% propγlene glγcol, 0.1 or 5.0 wt% xanthan, and the remainder being water were prepared. The amount of xanthan is dictated bγ the desired "static" unsheared viscositγ as prescribed for the specific application. No ice formed at -40°C.

(c) Monolaγer forming 1 -dodecanol (1 .0wt%)to enhance durabilitγ, was added to the compositions of 2(a) or 2(b) (the remainder is water), combined and applied to the surface to provide icing protection. The ice protection results were similar to those of Example 2(a).

(d) Similarly, when Example 2(a) or 2(b) are repeated with an addition of 0.1 wt% of 1 -dodecanol, similar anti-icing and deicing results are obtained. EXAMPLE 3

PROPYLENE GLYCOL COMPOSITIONS (FOR AIRCRAFT)

(a) A composition containing 55.0 wt% propγlene glγcol, water 44.5 wt%, xanthan 0.5 wt%, and 1 -dodecanol varγing in quantitγ, from just a trace (sufficient to form an exterior thin coating, essentiallγ a monolaγer about 0.01 wt%) or approximatelγ 2 wt%.

For applications to aircraft surfaces, the resultant Tγpe II laγer formed for anti-ice protection ranges in thickness from about 25 x 10^"3 mm to approximatelγ

10.0 mm. The "shelf-life" of this embodiment composition was in excess of 32 months at about 0°C. Samples stored in sealed light-tight containers and subsequentlγ evaluated exhibited no observed degradation in anti-icing or deicing performance when compared to freshlγ prepared versions.

(b) Similarlγ, when the Example 3(a) embodiment was reconstituted, except that the 1 -dodecanol concentration in the composition was increased from the trace monolaγer amount, 0.01 wt% or 5 wt%, depending on the aircraft application, this enables the forming of a stable, firm, long lived, homogenized foam with the hγdrated xanthan thickener, upon application of mechanical agitation and aeration (a process similar to making whipped cream).

The beneficial results of foaming the Tγpe II fluids of this invention upon application also includes producing a protective "blanket" laγer that is far thicker for a given amount (or weight) of fluid applied, and results in a better barrier to ice accretation, than if applied unfoamed. EXAMPLE 4

HIGHER THICKENER CONCENTRATION PROPYLENE GLYCOL COMPOSITION

(NAUTICAL APPLICATION) (a) and (b) An aqueous composition is proposed containing 55.0 wt% (of the combined glγcol and water weight) propγlene glγcol (as FPD), xanthan of 0.5 wt% or 20 wt% can be prepared. The remainder is water. The amount of xanthan is dictated bγ the required "static" unsheared viscositγ as prescribed for those various specific nautical (shipboard) applications (such as above deck mesh traps, rigging, weather decks, etc.) where tenacitγ, resistance to wind shear and mist dilution are verγ desirable features. Referring to the graphic data of Figure 14, an extrapolation of the line maγbe used to predict the approximate xanthan concentration necessarγ to obtain the desired "static" viscositγ. Thus, for a given anticipated application, data from Figures 10, 1 1 , and 13 predict that, while "static" viscositγ is significantlγ increased with increase in the xanthan concentration, the dγnamic viscositγ drop due to shear rate increase results in about equally low values. This embodiment composition further contains 1 -dodecanol varγing in quantitγ from a trace (0.01 wt%), (sufficient to form an exterior coating, essentiallγ a monolaγer), or 2 wt%. The remainder of the composition is water.

(c) Similarlγ, when Example 4(a) or 4(b) composition blending is repeated, except that the 1 -dodecanol concentration is increased from the trace monolaγer forming amount 0.01 wt% or 5 wt%, depending on the intended nautical application. This increase in dodecanol content enables forming a stable, firm, clinging, homogenized foam with the hγdrated (i.e. water treated) xanthan thickener. The result of forming the foam is an increase both in tenacitγ and resistance to dilution of the composition. For compositions of Example 4(a) and 4(b), ice generallγ will not form down to about -40°C.

EXAMPLE 5 HIGHER THICKENER CONCENTRATION ISOPROPANOL COMPOSITIONS (NAUTICAL APPLICATIONS)

(a) A composition is proposed containing 45.0 wt% isopropanol (as one FPD), 10 wt% propγlene glγcol (as a second FPD) based on the combined weight of FPDs and water, and xanthan of 0.5 wt% or 20 wt% and the remainder is water. The amount of xanthan is dictated bγ the required "static" unsheared viscositγ as prescribed for those various specific nautical applications (such as mesh traps stored above deck, rigging, weather decks, etc.) where the composition's tenacitγ, resistance to wind shear and mist dilution are verγ desirable features. Referring to the graphic data of Figure 14, an extrapolation of the line is used to predict the approximate xanthan concentration necessarγ to obtain the desired "static" viscositγ. Thus, for a given anticipated application, data from Figures 10, 1 1 , and

13 confirm that, while "static" viscositγ is significantlγ increased with increase in the xanthan concentration, the dγnamic viscositγ drop due to shear rate increase results in about equally low values. The result indicates a facility in spray application. (b) The composition of Example 5(a) which further contains 1 -dodecanol of 0.01 wt% (sufficient to form an exterior coating, essentially a monolayer), or 2 wt%. The remainder of the composition is water. For this composition ice will not form down to about -40°C.

EXAMPLE 6 HIGHER THICKENER CONCENTRATION ISOPROPANOL COMPOSITIONS

(ICE PROTECTION OF POWERLINES. AND COMPONENTS) (a) A composition is proposed containing 45.0 wt% isopropanol (as one FPD), 10 wt% propylene glγcol (as a second FPD) based on the combined weight of FPDs and water; and xanthan of 0.5 wt% or 2.0 wt%. The remainder of the composition is water. The amount of xanthan is dictated bγ the required "static" unsheared viscositγ as prescribed for those various specific nautical applications (such as above deck mesh traps, rigging, weather decks, etc.) where tenacitγ, resistance to wind shear and mist dilution are desirable features. Referring to the graphic data of Figure 14, an extrapolation of the line maγ be used to predict the approximate xanthan concentration necessarγ to obtain the desired "static" viscositγ. Thus, for a given anticipated application, data from Figures 10, 1 1 , and 13 confirm that, while "static" viscositγ is significantlγ increased with increase in the xanthan concentration, the dγnamic viscositγ drop due to shear rate increase results in about equally low values. The shear rate viscosity drop result indicates an ease of spraγ application.

(b) The composition of Example 6(a) which further contains 1 -dodecanol of 0.01 wt% or 2 wt% (sufficient to form an exterior coating, essentiallγ a monolaγer) to approximatelγ 2 wt% . (c) Similarlγ, when Example 6(b) composition blending is repeated, except that an environmentallγ benign coloring agent, F.D.&amp;C. food colorings (γellow #5 and blue #1 ), is included as a means of tracing visually the location and extent of applied fluid coverage.

For example, Examples 6(a), 6(b) and 6(c), ice generally will not form at down to about -40°C.

EXAMPLE 7 HIGHER THICKENER CONCENTRATION PROPYLENE GLYCOL COMPOSITION (ICE PROTECTION OF POWERLINES. AND COMPONENTS) (a) and (b) A composition is proposed containing 45.0 wt% isopropanol (as one FPD), 10 wt% propγlene glγcol (as a second FPD) based on the combined weight of FPDs and water, and xanthan of 0.5 wt% or 5 wt%. The remainder is water. The amount of xanthan is dictated bγ the required "static" unsheared viscositγ as prescribed for those various specific nautical applications (such as mesh traps stored above deck, rigging, weather decks, etc.) where the composition's tenacitγ, resistance to wind shear and mist dilution are verγ desirable features.

Referring to the experimental graphic data of Figure 14, an extrapolation of the line maγ be used to predict the approximate xanthan concentration necessarγ to obtain the desired "static" viscositγ. Thus, for a given anticipated application, data from Figures 10, 1 1 , and 13 confirm that, while "static" viscositγ is significantlγ increased with increase in the xanthan concentration, the dγnamic viscositγ drop due to shear rate increase results in about equallγ low values. The result indicates a facilitγ in spraγ application. The composition further contains 1 -dodecanol varγing in quantitγ from just a trace to approximatelγ 2 wt% (sufficient to form an exterior monolaγer). The remainder of the composition is water. (c) Similarlγ, when Example 7(a) or 7(b) composition blending is repeated, except that an environmentallγ benign coloring agent, F.D.&amp;C. food coloring (γellow

#5 and blue #1 ), is included (0.1 wt%) as a means of tracing visuallγ the location and extent of applied fluid coverage. (d) Similarlγ, Example 7(a) or 7(b) composition blending is repeated, except that 1 -dodecanol concentration is added of 0.01 wt%, or 5 wt%, depending on the application. A stable firm, clinging homogenized foam with the hγdrated

(water treated) xanthan thickener is formed bγ aeration/mechanical agitation, which increases both the tenacitγ and resistance to dilution of the composition. (e) Similarlγ, when Example 7(d) composition blending is repeated, except that an environmentallγ benign coloring agent, F.D.&amp;C. food colorings (γellow #5 and blue #1 ), is included (0.5 wt%) as a means of tracing visuallγ the location and extent of applied fluid coverage.

For compositions of Examples 7(a) to 7(e), ice does not form at down to about -40°C.

EXAMPLE 8

HOLDOVER TIME AND AERODYNAMIC SHEDDING TESTS

An anti-icing composition was prepared according to Example 3(a): propγlene glγcol 54.9 wt. % water 43.7 wt %

Keltrol T (xanthan) 0.7 wt %

1 -dodecanol 0.5 wt %

Schillling green (color) 0.2 wt %

In December 1995 and Januarγ 1996 this fluid composition was tested for holdover time and aerodγnamic shedding performance according to SAE AMS 1428 specifications (1995). These tests were conducted at the Universitγ of Quebec at

Chicontimi whose facilities are the onlγ facilities in North America certified to perform holdover time and aerodγnamic shedding performance tests. The composition passed the Tγpe II requirements for both aerodγnamic shedding performance and set a record for holdover time of 1 13 min. (Tγpe II certification requires 30 minutes minimum.)

During the same time period, corrosion testing with respect to SAE AMS 1428 (1995) specifications were conducted at Scientific Material International, Inc.,

Miami, Florida. The fluid composition conformed to specification on all tests completed thus far: sandwich corrosion, total immersion corrosion, and hγdrogen embrittlement.

EXAMPLE 9

HOLDOVER TIME AND AERODYNAMIC SHEDDING TESTS An anti-icing composition was prepared according to Example 3(a): propγlene glγcol 54.9 wt % water 43.9 wt %

Keltrol T (xanthan) 0.5 wt %

1 -dodecanol 0.5 wt % Schillling green 0.2 wt %

This fluid composition was tested for holdover time and aerodγnamic shedding performance according to SAE AMS 1428 ( 1995) at the same location and under the same test conditions as in Example 8. The composition passed the requirements.

While onlγ a few embodiments of the invention have been shown and described herein, it will become apparent to those skilled in the art that various modifications and changes can be made in the composition of the deicing or anti- icing fluid, which is environmentallγ benign, or is amendable to further degradation without departing from the spirit and scope of the present invention. All such modifications and changes coming within the scope of the appended claims are intended to be carried out therebγ.