HYDROPHILIC ICE PHOBIC SUBSTRATES

FIELD OF THE DISCLOSURE

[01] The present disclosure is directed toward a method for removing ice from a substrate in low temperature conditions. The method provides the substrate with a hydrophilic layer that helps to decrease the adhesion of ice on a substrate so that the ice is relatively easy to remove from the substrate.

BACKGROUND OF DISCLOSURE

[02] The formation of ice on substrates, also called icing, is a dangerous condition for many substrates. The formation of ice can negatively affect many different types of structures including airplane wings, airplane bodies, wind turbine blades, wind turbines, power transmission lines, power transmission towers, oil rigs, marine structures, marine vessels, bridges, vehicles, buildings, radio antennas, cell phone towers, and solar panels. The Federal Aviation Administration has set strict guidelines for dealing with ice accumulating of airplanes during the time the vehicle is on the ground and in-flight. Many wind turbines are designed to reduce power or shut of completely if too much ice accumulates on the spinning blades of the turbine.

[03] There is a need for a system or method which would prevent the formation of ice on such structures. If ice formation cannot be completely prevented, then the system should reduce the adhesion of ice to the substrate which in turn would require less energy to remove the ice.

SUMMARY OF THE DISCLOSURE

[04] The current disclosure relates to a method comprising the steps of;

1 ) providing a substrate wherein the substrate comprises a layer of polyalkylene glycol, a polyalkylene glycol derivative or a polymer comprising one or more polyalkylene glycol side chains;

2) allowing ice to form on at least a portion of the substrate; and 3) applying a force to the substrate, to the ice or to a combination thereof that is sufficient to separate the ice from the substrate; wherein the force required to separate the ice from the substrate comprising the polyalkylene glycol layer is less than 1 .76 kg/cm ² when measured according to the following test:

i) the substrate comprising a layer of the polyalkylene glycol or polymer comprising one or more polyalkylene glycol side chains is applied to an aluminum plate;

ii) a cuvette capable of holding at least one cubic centimeter of water is placed onto the applied layer;

iii) one-half of a cubic centimeter of water is placed into the cuvette so that the water contacts the applied layer of polyalkylene glycol and the water is frozen to -10°C to form ice; and

iv) a shear stress is applied to the -10°C ice in a direction that is parallel to the aluminum plate.

[05] The disclosure also relates to a film having a first surface and a second surface, wherein the first surface comprises a layer of polyalkylene glycol covalently bonded to at least a portion of the first surface, and optionally, a layer of an adhesive agent on at least a portion of the second surface of the film.

[06] The disclosure also relates to an article comprising a substrate and the film, and also relates to a kit for applying a layer of polyalkylene glycol to a surface.

DETAILED DESCRIPTION

[07] The features and advantages of the present disclosure will be more readily understood, by those of ordinary skill in the art from reading the following detailed description. It is to be appreciated that certain features of the disclosure, which are, for clarity, described above and below in the context of separate embodiments, may also be provided in combination in a single element. Conversely, various features of the disclosure that are, for brevity, described in the context of a single embodiment, may also be provided separately or in any sub-combination. In addition, references to the singular may also include the plural (for example, "a" and "an" may refer to one or more) unless the context specifically states otherwise. [08] The use of numerical values in the various ranges specified in this application, unless expressly indicated otherwise, are stated as

approximations as though the minimum and maximum values within the stated ranges were both proceeded by the word "about". In this manner, slight variations above and below the stated ranges can be used to achieve substantially the same results as values within the ranges. Also, the disclosure of these ranges is intended as a continuous range including each and every value between the minimum and maximum values.

[09] As used herein:

[10] The phrase "polyalkylene glycol" means a polyether that comprises or consists essentially of repeat units according to (A), (B) or a

combination thereof:

The polyalkylene glycol can be a linear polyalkylene glycol having two terminal groups or it can be a branched copolymer having more than two terminal groups. Each terminal group of the polyalkylene glycol can independently be hydroxyl, -NHR or -OR ¹ , wherein R is H or C1 to C6 alkyl and R ¹ is C1 to C6 alkyl, with the proviso that at least one terminal group is hydroxyl or -NHR. In some embodiments, one of the terminal groups of the polyalkylene glycol is a hydroxyl group and the other terminal group(s) is a methyl or ethyl ether. In some embodiments, R is C1 to C3 alkyl and, in further embodiments, R is methyl or ethyl. In some embodiments, R ¹ is C1 to C3 alkyl and, in further embodiments, R ¹ is methyl or ethyl.

[11] The phrase "polyalkylene glycol derivative" means a polyalkylene glycol wherein at least one of the terminal hydroxyl or amine groups has been modified to comprise a functional group that is reactive with a hydroxyl group. The reactive functional group can be an isocyanate functional group, a silanol functional group, a halosilane functional group or a siloxane functional group. In some embodiments, the polyalkylene glycol derivative is a linear polyalkylene glycol consisting of one hydroxyl ternninal group and a siloxane group on the other ternninal end. In another embodiment, the polyalkylene glycol derivative is a linear polyalkylene glycol consisting of a methyl ether terminal group and an isocyanate functional group on the other terminal end. Suitable examples of polyalkylene glycol derivatives can include the structures below, wherein n is an integer in the range of from about 5 to about 70. While each of these three examples show derivatives of polyethylene glycol, the repeat units could be polytrimethylene glycol or a combination of trimethylene ether glycol and ethylene glycol repeat units;

[12] The phrase "polymer comprising one or more polyalkylene glycol side chains" refers to a graft copolymer comprising a backbone polymer that has one or more polyalkylene glycol side chains grafted to the backbone polymer. The backbone polymer is not particularly limited as long as one or more polyalkylene glycol side chains can be grafted thereto. The polyalkylene glycol side chains comprise or consist essentially of the repeat units (A), (B) or a combination thereof. The polyalkylene glycol side chains have one terminal group covalently bonded to the backbone polymer and the other terminal end is hydroxyl, -NHR or -OR ¹ , wherein R and R ¹ are as defined previously. In some

embodiments, the polymer comprising one or more polyalkylene glycol side chains is a polymer comprising or consisting essentially of a polyethylene backbone and polyalkylene glycol side chains. Typically, the polyalkylene glycol side chains are grafted via a portion of the

polyethylene backbone having acrylic acid and/or methacrylic acid repeat units. While other side chains may be present, the concentration and type of side chains must not interfere with the ability of the substrate to have low levels of adhesion to ice, less than 1 .76 kg/cm ² . In some

embodiments, the polymer has side chains that consist of polyalkylene glycol side chains.

[13] The present disclosure relates to a method for separating or removing ice from the substrate. The substrate comprises a layer of polyalkylene glycol, a layer of a polyalkylene glycol derivative or a polymer comprising one or more polyalkylene glycol side chains has an average ice adhesion of less than 1 .76 kg/cm ² . The substrate comprising a layer of polyalkylene glycol or a layer of a polyalkylene glycol derivative means that the substrate has polyalkylene glycol units covalently bonded to at least a portion of the substrate surface. It is believed that a polymer comprising one or more polyalkylene glycol side chains forms a stratified layer wherein the polyalkylene glycol side chains are formed on the surface.

[14] As used herein, the phrase "average ice adhesion" means the force that is required to separate a layer of ice from the substrate and can be determined according to the following procedure:

i) A substrate comprising a layer of a polyalkylene glycol, a layer of a polyalkylene glycol derivative or a polymer comprising one or more polyalkylene glycol side chains is applied to at least a portion of an aluminum plate; ϋ) a cuvette is placed onto the applied layer;

ill) one-half cubic centimeter of water is placed into the cuvette so that the water contacts the applied layer and the water is frozen to -10°C to form ice; and

iv) a shear stress is applied to the cuvette containing the -10°C ice in a direction that is parallel to the aluminum plate; v) determining the applied force necessary to separate the ice from the applied layer;

vi) repeating steps i) through v) at least 3 times and determining an average based on the repetitions.

[15] In some embodiments, the average ice adhesion of a substrate comprising a layer of the polyalkylene glycol or a layer of a polymer containing polyalkylene glycol side chains is less than 1 .76 kg/cm ² . In other embodiments, the average ice adhesion is less than 1 .41 kg/cm ² (20 psi) or less than 1 .33 kg/cm ² (19 psi) or less than 1 .26 kg/cm ² (18 psi) or less than 1 .20 kg/cm ² (17 psi) or less than 1 .12 kg/cm ² (16 psi) or less than 1 .05 kg/cm ² (15 psi), or less than 0.98 kg/cm ² (14 psi) or less than 0.91 kg/cm ² (13 psi) or less than 0.84 kg/cm ² (12 psi) or less than 0.77 kg/cm ² (1 1 psi) or less than 0.70 kg/cm ² (10 psi) or less than 0.63 kg/cm ² (9 psi) or less than 0.56 kg/cm ² (8 psi) or less than 0.49 kg/cm ² (7 psi) or less than 0.42 kg/cm ² (6 psi) or less than 0.35 kg/cm ² (5 psi).

[16] It has been surprisingly found that a substrate coated with a hydrophilic layer (that is, the polyalkylene glycol layer) can provide the substrate with a very low adhesion to ice. Most ice-phobic substrates provide a low surface energy hydrophobic surface, for example, a fluorinated layer, a siloxane layer or a combination thereof in order to minimize the interaction between the ice and the substrate surface.

[17] To provide a substrate comprising a layer of the polyalkylene glycol, polyalkylene glycol derivative or a polymer comprising one or more polyalkylene glycol side chains, the polyalkylene glycol can be covalently bonded to the substrate or a film of a polymer comprising polyalkylene glycol side chains can be formed and then adhered to the substrate. The polyalkylene glycol comprises or consists essentially of repeat units having the structure denoted by (A), (B) or a combination thereof. If other repeat units are present, it is desired to keep the percentage of the other repeat units below 10 percent by weight based on the total weight of the polyalkylene glycol. If the percentage of the other repeat units is more than 10 percent by weight, then the hydrophilic character of the polymer may change and the average ice adhesion value may increase. In other embodiments, the percentage of other repeat units is less than 5 percent by weight, and, in still further embodiments, the percentage of other repeat units is less than 1 percent by weight. In some embodiments, the polyalkylene glycol is a homopolymer of polyethylene glycol, while in other embodiments the polyalkylene glycol is a homopolymer of

polytrimethylene glycol. In still further embodiments, the polyalkylene glycol is a copolymer of polyethylene glycol and polytrimethylene glycol.

[18] Polyalkylene glycols and the polyalkylene glycol portion of polyalkylene glycol derivatives having a number average molecular weight in the range of from 150 to 3,000 can be used. If the number average molecular weight is too large, then the ice adhesion value increases. In other embodiments, the number average molecular weight can be in the range of from 175 to 2,500, and, in still further embodiments, can be in the range of from 200 to 2,000. The number average molecular weight of a polymer containing one or more polyalkylene glycol side chains can be in the range of from 10,000 to 1 ,000,000 with the proviso that the number average molecular weight of each polyalkylene glycol side chains is independently in the range of from 150 to 3,000, or in the range of from 175 to 2,500 or in the range of from 200 to 2,000.

[19] In order to provide a substrate where ice can be separated from the substrate by a sheer stress of less than 1 .76 kg/cm ² , a layer of the polyalkylene glycol, a layer of the polyalkylene glycol derivative or a layer of the polymer containing one or more polyalkylene glycol side chains must be adhered to the surface of the substrate. In some embodiments, the polyalkylene glycol or polyalkylene glycol derivative can be covalently bonded to the substrate surface. In other embodiments, a layer of the polymer containing one or more polyalkylene glycol side chains can be adhered to the surface of the substrate by one or more known methods, for example, an adhesive agent or double sided tape may be used. The method of covalently bonding the polyalkylene glycol comprises the steps of; a) chemically treating at least a portion of the substrate to provide hydroxyl functional groups on the surface of the substrate, b)

functionalizing the hydroxyl groups with one or more groups that are reactive with a hydroxyl group, and c) contacting the polyalkylene glycol with the oxidized substrate. [20] In another embodiment, the covalently bonded polyalkylene glycol can be produced by a) oxidizing at least a portion of the substrate to provide hydroxyl groups on the surface of the substrate, and b) contacting the oxidized surface with the alkylene glycol derivative; wherein the polyalkylene glycol derivative comprises functional groups that are reactive with the hydroxyl groups of the substrate.

[21] In the embodiments wherein the layer of polyalkylene glycol or derivative thereof is covalently bonded to the surface of the substrate, the substrate surface can be provided functional groups that are reactive with the one or more terminal hydroxyl or amine groups of the polyalkylene glycol. To provide the substrate surface with groups that are reactive with the hydroxyl or amine group of the polyalkylene glycol, the substrate surface can be treated prior to step 1 ) to provide a substrate surface that comprises one or more functional groups that are reactive with the polyalkylene glycol or polyalkylene derivative. In some embodiments, the treatment method is a chemical treatment method. In further

embodiments, the substrate surface can be oxidized to provide a surface comprising hydroxyl functional groups. The hydroxyl functional groups on the substrate surface can then be contacted with one or more of an isocyanato alkyl dialkylhalosilane, a diisocyanate, a triisocyanate or a polyisocyanate thereby providing the substrate surface with one or more groups that are reactive with the hydroxyl or the amine group of the polyalkylene glycol. Contacting the substrate comprising a functional group reactive with hydroxyl or amine groups with the polyalkylene glycol can provide the layer of polyalkylene glycol covalently bonded to the surface of the substrate.

[22] In other embodiments, a polyalkylene glycol derivate can be used wherein the surface of the substrate can be chemically treated to provide reactive functional groups. Subsequently, the treated surface of the substrate can then be contacted with the polyalkylene glycol derivative comprising functional groups that are reactive with the surface of the substrate. In some embodiments, the step of treating the substrate can be an oxidation step. [23] To produce a layer of polyalkylene glycol on the surface of the substrate, either the chemically treated substrate surface can be contacted with one or more of an isocyanatoalkyi dialkylhalosilane, a diisocyanate, a triisocyanate or a polyisocyanate, or the polyalkylene glycol can be contacted with the same, thereby forming a polyalkylene glycol derivative. Suitable isocyanatoalkyi dialkylhalosilanes can include, for example, isocyanatopropyl dimethylchlorosilane, isocyanatopropyl diethyl

chlorosilane, isocyanatoethyl dimethylchlorosilane or a combination thereof. The diisocyanates, can include alkyl diisocyanates and aryl diisocyanates, for example, α,ω-alkyl diisocyanates wherein the alkyl comprises in the range of from 2 to 10 carbon atoms and diisocyanates comprising one or more carbocycles. Specific examples can include, for example, 1 ,6-hexamethylene diisocyanate, 1 ,4-tetramethyl isocyanate, diisocyanatocyclohexane, bis(isocyanatomethyl) cyclohexane, bis

(isocyanatocyclohexyl) methane, isophorone diisocyanate,

diphenylmethane diisocyanate, diisocyanatobenzene, diisocyanato toluene or a combination thereof. Isocyanate functional derivatives of polyisocyanates can also be useful. In some examples, polyisocyanate polymers are useful, for example, polyisocyanates containing allophanate, biuret, isocyanurate or uretdione groups can be used. In other

embodiments, polyisocyanate functional polyurethanes can be used, for example, the reaction products of polyisocyanates with polyols can be used. Suitable polyols can include, for example, alkylene glycols having in the range of from 2 to 6 carbon atoms, trimethylol propane, pentaerythritol, glycerol or a combination thereof.

[24] The surface of the substrate can be chemically treated by contact with an oxidizing agent, for example ozone, potassium permanganate, sodium hypochlorite, hydrogen peroxide, nitric acid, sulfuric acid, or sodium perborate. In some embodiments, after the surface of the substrate has been oxidized, the surface can then be contacted with the polyalkylene glycol derivative. In other embodiments, the oxidized surface of the substrate can be contacted with one or more of the previously mentioned isocyanatoalkyi dialkylhalosilanes, diisocyanates, triisocyanates or polyisocyanates, followed by contact with the polyalkylene glycol. Either embodiment can form a layer of polyalkylene glycol on the surface of the substrate. The amount of polyalkylene glycol covalently bonded to the substrate should be sufficient so that when ice is adhered to a portion of the substrate comprising the layer of polyalkylene glycol, the shear stress required to remove the ice at -10°C is less than 1 .76 kg/cm ² according to the previously mentioned procedure.

[25] The disclosure also relates to an article comprising a substrate and a layer of polyalkylene glycol on at least a portion of the substrate. In some embodiments, the substrate can include metals, aluminum, iron, steel, steel alloys, glass, polymers, silicone polymers, polyolefins, elastomers, composite materials and wood. In some embodiments, the substrate is an airplane wing, airplane body, wind turbine blade, wind turbine, power transmission line, power transmission tower, oil rig, marine structure, marine vessel, bridge, vehicle, building, radio antenna, cell phone tower, or solar panel.

[26] The disclosure also relates to a film having a first surface and a second surface, wherein the first surface comprises or consists essentially of a layer of polyalkylene glycol covalently bonded to at least a portion of the first surface. The film can optionally have a layer of an adhesive agent applied to at least a portion of the second surface. Suitable films can include, for example, polyolefin, polysiloxane, silicone rubber and elastomeric films. In one embodiment, the substrate can be a silicone rubber film that is treated with ozone to oxidize at least a portion of the first surface of the film. The desired layer of polyalkylene glycol can then be bonded to the oxidized silicone rubber film according to one of the procedures given above. Finally, the silicone rubber film having the layer of polyalkylene glycol adhered thereto can then be adhered to the substrate. The present disclosure also relates to an article comprising the film.

[27] The present disclosure also relates to a kit. The kit comprises or consists essentially of a first component and a second component. The first component comprises or consists of an oxidizing agent and optionally, a liquid carrier. The second component comprises or consists of the polyalkylene glycol derivative in a liquid carrier, wherein the polyalkylene glycol derivative has a structure according to (I);

FG— (X)— OR ²

(I)

wherein FG comprises a functional group that is reactive with a hydroxyl group, X is a polymer having repeat units comprising or consisting of (A) (B) or a combination thereo

R ² is hydrogen or C1 to C6 alkyl. In some embodiments, the FG functional group can include, for example, an isocyanate, a halosilane group, a silanol, or a siloxane group.

[28] The kit allows a user to apply the layer of polyalkylene glycol onto the surface of their choice. The first component can be supplied with one or more of a variety of oxidizing agents depending on the desired substrate to be oxidized. The various oxidizing agent can include, for example, sodium hypochlorite, potassium permanganate, hydrogen peroxide, nitric acid, sulfuric acid, and sodium perborate. In some embodiments, the oxidizing agent can be supplied in a liquid carrier, for example, water. The second component can be the polyalkylene glycol derivative in a liquid carrier, for example, a solvent for the polyalkylene glycol derivative. The kit can also be supplied with instructions for using the kit, personal protective equipment, application devices and materials to clean the substrate prior to application of the materials in the kit and after application of the kit.

[29] Optionally, the substrate surface can be cleaned prior to oxidizing the surface. The first component comprising the oxidizing agent can then be applied to at least a portion of the substrate. The amount of time that that the oxidizing agent contacts the substrate is variable and is

dependent on the strength of the oxidizing agent, the susceptibility of the substrate to oxidation and other factors. One of skill in the art would be able to determine the time with a minimum of experimentation. Any excess of the first component can optionally be removed followed by the application of the second component comprising the polyalkylene glycol derivative. The second component comprising the polyalkylene glycol derivative can then be applied to at least a portion of the oxidized substrate. The amount of time that the polyalkylene glycol derivative contacts the oxidized surface of the substrate is variable and is dependent on the substrate temperature, the amount of oxidized groups on the surface of the substrate and other factors. One of ordinary skill in the art would be able to determine the time with a minimum amount of

experimentation.

[30] Examples

[31] Unless otherwise noted, all ingredients are available from the Sigma Aldrich Company, St. Louis, Missouri.

[32] 3-isocyanatopropyldimethylchlorosilane is available from Gelest Inc., Morrisville, Pennsylvania.

[33] Toluene (99.99%) and dimethylformamide (DMF) are available from EMDMillipore, Billerica, Massachusetts.

[34] Ice adhesion measurements

[35] The ice adhesion of the various polyalkylene glycol compositions was tested using the following procedure. The compositions were adhered to an aluminum plate mounted onto a cold stage (TE Technology Inc., Model #CP200TT) according to the procedures given below. Eight 1 cm ² cuvettes were placed randomly on the composition and 0.5 cubic centimeters of deionized water was added to the cuvettes so that the water contacted the applied layer of composition. The cold stage was then programmed to -10°C at 1 .5°C/minute from room temperature. The circular head of a force gauge (Mark 10 Inc., Series 3) mounted on a syringe pump (Harvard Inc., Model #33) was placed close to, but not touching one of the cuvettes and within about 1 millimeter from the bottom of the cuvette. The syringe pump was turned on so that the force gauge moved toward the cuvette at about 0.029 millimeters/second. The ice adhesion was calculated by the reading on the force gauge divided by the cross sectional area of the ice in contact with the layer of composition. The process was repeated for the remaining cuvettes and the average ice adhesion value was calculated.

[36] Preparation of polyethylene glycol modified silicone rubber

[37] Silicone rubber sheets, available from MSC Industrial Supply Company, Melville, New York, as product #85988004, were cleaned by washing with acetone and then dried in a 1 10°C vacuum oven for 1 hour. The dried silicone pieces were then treated with ozone using a UVO cleaner model number 42 for 30 minutes. In a dry box, a solution of 3- isocyanatopropyldimethylchlorosilane, 7 ml and toluene (99.99%) was heated to 25°C. The ozone treated silicone rubber pieces were then transferred to the dry box and placed in contact with the solution of the 3- isocyanatopropyldimethylchlorosilane in toluene. After contacting the solution for 36 hours, the silicone rubber pieces were removed and allowed to dry. In the dry box, solutions of 7ml polyethylene glycol of various molecular weights in 14 ml of DMF were prepared by stirring the two ingredients and holding them at 70°C. The dried samples of NCO treated silicone rubber were then placed in contact with the polyethylene glycol solutions and allowed to soak for 18 hours. The silicone rubber pieces were then removed from the solutions rinsed with DMF, followed by toluene, then ethanol.

[38] The polyethylene glycol treated silicone rubber pieces were then tested for ice adhesion according to the procedure given above. Table 1 shows the results of the testing.

TABLE 1

[39] The results of Table 1 show that the polyethylene glycol substrates provide surfaces that have low adhesions to ice when compared to a sample of the silicone rubber without the polyalkylene glycol layer.

[40] Ice adhesion of a polymer containing one or more polyalkylene glycol side chains.

[41] A 6 millimeter thick film of a polymer having a polyethylene backbone and polyethylene glycol side chains (PE/PEO) was adhered to an aluminum plate using double sided tape. A second sample consisting of a 40 micrometer thick film of a polymer having a polyethylene backbone with polyalkylene glycol side chains was adhered to an aluminum plate using double sided tape. The polyethylene/polyethylene oxide films are available from E.I. du Pont de Nemours and Company, Wilmington, Delaware. The 2 films were subjected to ice adhesion testing using the previously presented method with one exception. Rather than determining the ice adhesion at one temperature, -10°C, each sample was subjected to testing at a several temperatures. The temperatures and the average ice adhesion values are shown in Table 2.

TABLE 2

[42] The results from Table 2 indicate that the average ice adhesion values of the PE/PEO films increases with decreasing temperatures. The results also indicate that the thicker the film layer, the lower the ice adhesion value.

[43] In order to show that the polyalkylene glycol containing substrates are able to provide low ice adhesion surfaces over several repetitions of ice build-up and removal, the following procedure was used. The average ice adhesion value of silicone rubber/PEO sample #4 was determined according to the above procedure as cycle #1 . For cycle #2, cuvettes were placed onto silicone rubber/PEO #4 at the same spots as they were for cycle #1 or as close as possible to those spots. The ice adhesion test measurements were then repeated and the average ice adhesion value was determined for cycle #2. This process was repeated 10 times and the results are reported in TABLE 3.

TABLE 3

[44] The results in Table 3 show that the composition is able to retain low levels of ice adhesion after many cycles of ice accumulation and removal.