Two-component addition-cure thermal control coating

Abstract

A thermal control coating is disclosed and described herein. The thermal control coating is provided by a two-part, addition-cure silicone composition. The composition includes a curable siloxane and titanium dioxide. The composition is fast-curing and, when cured, exhibits low solar absorptance, high solar reflectance, and / or high infrared emissivity. Additionally, the composition, when cured, exhibits good flexibility and can be applied to a surface without the aid of a primer.

Description

[Technical Field]

[0001] This application claims priority to and benefit of U.S. Provisional Application No. 63 / 448,691, filed February 28, 2023, entitled "Two-Component Addition-Cure Thermal Control Coating," the disclosure of which is incorporated herein by reference in its entirety.

[0002] The present invention relates to addition-curable siloxane coatings. In particular, the present invention relates to addition-curable siloxane coatings that exhibit low absorptivity, high infrared emissivity, and relatively fast cure. The coatings may find use in a variety of applications, including where low solar absorptivity and high infrared emissivity are desired. [Background technology]

[0003] Thermal management systems provide a way to maintain thermal properties such as temperature, temperature fluctuations, and humidity. Thermal management can be achieved by active or passive means. Active temperature control may involve mechanical or electrical devices, such as electrical heaters and / or coolers. Passive temperature control does not involve mechanical or electrical devices, but rather involves thermal control coatings or structural designs. For example, aircraft and aeronautical vehicles may contain components that generate significant amounts of heat, which must be dissipated by thermal radiation through the vehicle's exterior surfaces. In addition, radiative surfaces are subject to thermal radiation from incident sunlight, reducing the thermal efficiency of the surfaces. At high altitudes and outside the Earth's atmosphere, where atmospheric pressure is low, there is little or no atmosphere to transfer heat to or from vehicle components. During operation, one side of an article may be directly exposed to the sun, while the other side faces away from the sun. Thus, extreme temperature differences can occur between different components of the vehicle, and extreme temperature changes can occur when the vehicle changes position relative to the sun, causing components of the vehicle to be heated directly by the sun. Radiation can be achieved through the use of thermal control surfaces that can absorb thermal radiation from sunlight and emit thermal radiation. Such surfaces have a desired range of values ​​for solar absorptivity (α) and infrared emissivity (ε). For surfaces such as heat dissipation devices, it is important to absorb as little solar radiation as possible (low α) while simultaneously radiating as much heat as possible (high ε). Summary of the Invention

[0004] The following is a summary of the present disclosure to provide a basic understanding of some embodiments of the present invention. This summary is not intended to identify key or critical elements, nor is it intended to define any limitations on the scope of the embodiments or claims. Moreover, this summary may provide a simplified overview of some embodiments, which may be described in more detail in other parts of the disclosure.

[0005] Provided is a siloxane composition suitable for use as a thermal control coating. The composition exhibits one or more of low solar absorptance, high infrared emissivity, and / or high solar reflectance. In one embodiment, the composition is an addition-curable siloxane. In an embodiment, the composition is provided as a two-part composition.

[0006] In one embodiment, provided is a curable coating composition comprising: an alkenyl-functional siloxane; a hydride-functional siloxane; titanium dioxide particles; an addition cure catalyst; and, optionally, an adhesion promoter.

[0007] In one embodiment, the titanium dioxide is present in an amount of about 20% to about 50% by weight, based on the total weight of the composition.

[0008] In one embodiment according to any of the above embodiments, the titanium dioxide particles have a particle size of about 1 nm to about 500 nm.

[0009] In one embodiment according to any of the above embodiments, the titanium dioxide particles are selected from rutile titanium dioxide, anatase titanium dioxide, or a mixture thereof.

[0010] In one embodiment according to any of the above embodiments, the titanium dioxide particles comprise fumed anatase / rutile titanium dioxide.

[0011] In one embodiment according to any of the above embodiments, the alkenyl-functional siloxane is present in an amount of about 40% to about 80% by weight, based on the total weight of the composition.

[0012] In one embodiment according to any of the above embodiments, the alkenyl-functional siloxane has the formula: M 1 a M 2 b D 1 c D2 d T 1 e T 2 f Q g (I) and wherein the compound is selected from the group consisting of: M 1 =R 1 R 2 R 3 SiO 1 / 2 M 2 =R 4 R 5 R 6 SiO 1 / 2 D 1 =R 7 R 8 SiO 2 / 2 D 2 =R 9 R 10 SiO 2 / 2 T 1 =R 11 SiO 3 / 2 T 2 =R 12 SiO 3 / 2 Q=SiO 4 / 2 where R 1 , R 2 , R 3 , R 7 , R 8 , and R 11 are independently selected from a C1 to C30 hydrocarbon, a C6 to C30 aromatic group, or a C1 to C30 alkoxy group; R 4 , R 5 , R 6 , R 9 , R 10 , and R 12 are independently selected from a C1 to C30 hydrocarbon, a C6 to C30 aromatic group, a C1 to C30 alkoxy group, and a C2 to C30 alkenyl group, with the proviso that R 4 , R 5 , R 6 , R 9 , and / or R 12One or more of the groups are selected from C2-C30 alkenyl groups; The subscripts a, b, c, d, e, f, and g are zero or positive according to the following restrictions: 2 < a + b + c + d + e + f + g < 2000, and b + d + f > 0.

[0013] In one embodiment, the alkenyl-functional siloxane is of the formula M 2 D 1 c M 2 an alkenyl-functional siloxane of, an alkenyl-functional siloxane of the formula M 1 a D 2 d Q g or a combination thereof.

[0014] In one embodiment, the alkenyl-functional siloxane comprises a first alkenyl-functional siloxane having the formula M 2 D 1 c M 2 and a second alkenyl-functional siloxane having the formula M 1 a D 2 d Q g In one embodiment, the first alkenyl-functional siloxane is present in an amount of about 50 wt% to about 80 wt% based on the total weight of the alkenyl-functional siloxane, and the second alkenyl-functional siloxane is present in an amount of about 20 wt% to about 50 wt% based on the total weight of the alkenyl-functional siloxane.

[0015] In one embodiment according to any of the above-described embodiments, the composition comprises fumed silica. In one embodiment, the fumed silica is present in an amount of about 0.1 wt% to about 10 wt% based on the total weight of the composition.

[0016] [[ID=四十七]] In one embodiment according to any of the above-described embodiments, the catalyst is a platinum-based catalyst.

[0017] In one embodiment according to any of the above embodiments, the adhesion promoter is selected from cyclosiloxanes containing Si—H functional groups.

[0018] In one embodiment according to any of the above embodiments, the adhesion promoter is present in an amount of about 0 to about 30 wt %, based on the total weight of the composition.

[0019] In one embodiment according to any of the above embodiments, the composition is provided as a two-part composition comprising: a first part comprising an alkenyl-functional siloxane; titanium dioxide, and a catalyst; and a second part comprising an alkenyl-functional siloxane, a hydride-functional siloxane, titanium dioxide, and optionally an adhesion promoter.

[0020] In one embodiment according to any of the above embodiments, a coating formed from the composition at a thickness of about 1.5 mm to about 2 mm has a solar absorptance (α) of 0.35 or less. s )

[0021] In one embodiment according to any of the above embodiments, a coating formed from the composition at a thickness of about 1.5 mm to about 2 mm has a solar absorptance (α) of about 0.1 to 0.35. s )

[0022] In one embodiment according to any of the above embodiments, a coating formed from the composition at a thickness of about 1.5 mm to about 2 mm has an infrared emissivity (ε) of 0.89 or greater.

[0023] In one embodiment according to any of the above embodiments, a coating formed from the composition at a thickness of about 1.5 mm to about 2 mm has a solar absorptance (α) of 0.89 to about 0.98. s )

[0024] In one embodiment according to any of the above embodiments, a coating formed from the composition at a thickness of about 1.5 mm to about 2 mm has a solar reflectance (ρ) of 0.65 or greater. s )

[0025] In one embodiment according to any of the above embodiments, a coating formed from the composition at a thickness of about 1.5 mm to about 2 mm has a solar absorptance (α) of about 0.65 to about 0.9. s )

[0026] In one embodiment according to any of the above embodiments, a coating formed from the composition at a thickness of about 1.5 mm to about 2 mm has a solar absorptance (α s )

[0027] In one embodiment according to any of the above embodiments, a coating formed from the composition at a thickness of about 1.5 mm to about 2 mm has an elongation of about 100% to about 195%.

[0028] In another embodiment, provided is a method of forming a coating on a substrate, comprising curing a composition according to any of the above embodiments.

[0029] In one embodiment, the composition is a two-part composition comprising: (i) a first part comprising an alkenyl-functional siloxane; titanium dioxide, and a catalyst; and (ii) a second part comprising an alkenyl-functional siloxane, a hydride-functional siloxane, titanium dioxide, and optionally an adhesion promoter, and the method comprises combining the first part and the second part and heating at a temperature of from about 80°C to about 150°C.

[0030] In one embodiment according to any of the above embodiments, curing is achieved in about 1 hour.

[0031] In yet another embodiment, provided is a substrate comprising a surface coated with a composition according to any of the above embodiments.

[0032] In one embodiment, the composition is cured to form a coating.

[0033] The following description and drawings disclose various exemplary embodiments. Some improvements and novel aspects may be explicitly identified, while others may be apparent from the description and drawings. [Brief explanation of the drawings]

[0034] The accompanying drawings illustrate various systems, apparatus, devices, and related methods, in which like reference numerals refer to like elements throughout.

[0035] FIG. 1 is a graph showing the total reflection spectrum of the coating film in the example.

[0036] FIG. 2 is a graph showing the total reflection spectrum of the coating film prepared according to Formulation Example 9. DETAILED DESCRIPTION OF THE INVENTION

[0037] Reference will now be made to exemplary embodiments, examples of which are illustrated in the accompanying drawings. As will be understood, other embodiments may be utilized, and structural and functional changes may be made. Furthermore, features of various embodiments may be combined or varied. Thus, the following description is presented by way of example only, and is not intended to limit in any way the various alternatives and modifications that may be made to the illustrated embodiments. In this disclosure, numerous specific details are set forth to provide a thorough understanding of the disclosed subject matter. It should be understood that embodiments of the present disclosure may be embodied in other embodiments that do not necessarily include all aspects set forth herein or elsewhere.

[0038] As used herein, the terms "example" and "exemplary" mean illustrative or illustrative. The terms "example" and "exemplary" do not indicate required or preferred implementations or embodiments. The term "or" is intended to be inclusive rather than exclusive, unless the context indicates otherwise. For example, the phrase "A uses B or C" includes any inclusive permutation (e.g., A uses B; A uses C; or A uses both B and C). As a separate matter, the articles "a" and "an" are generally intended to mean "one or more," unless the context indicates otherwise.

[0039] Viscosity can be measured, for example, using a Brookfield viscometer HATDV-II, spindle 2, at 50 rpm unless otherwise stated.

[0040] Provided are addition-curable siloxane compositions. These compositions may generally be provided as two-part compositions. When cured, these compositions provide materials that exhibit excellent properties suitable for a wide range of applications. These materials are particularly suited for applications where the materials are exposed to extreme temperature changes and / or long-term exposure to sunlight or radiation. Materials formed from these compositions may exhibit one or more of, for example, low solar absorptance, high infrared emissivity, and high solar reflectance.

[0041] The composition comprises: (i) an alkenyl-functional polysiloxane; (ii) a hydride-functional siloxane; (iii) a silicone hydride adhesion promoter; (iv) a titanium dioxide filler; and (v) an addition cure catalyst. The composition may be provided as a two-part composition, as described in more detail below.

[0042] Alkenyl-functional polysiloxanes

[0043] The composition comprises an alkenyl-functional siloxane, which comprises an alkenyl functional group comprising a C=C bond attached to a silicon atom of the siloxane.

[0044] In one embodiment, the composition has the formula: M 1 a M 2 b D 1 c D 2 d T 1 e T 2 f Q g (I) and alkenyl-functional silicone compounds of the formula: M 1 =R 1 R 2 R 3 SiO 1 / 2 M 2 =R 4 R 5 R 6 SiO 1 / 2 D 1 =R 7 R 8 SiO 2 / 2 D 2 =R 9 R 10 SiO 2 / 2 T 1 =R 11 SiO 3 / 2 T 2 =R 12 SiO 3 / 2 Q=SiO 4 / 2 where R 1 , R 2 , R 3 , R 7 , R 8 , and R 11 are independently selected from a C1 to C30 hydrocarbon, a C6 to C30 aromatic group, or a C1 to C30 alkoxy group; R4 , R 5 , R 6 , R 9 , R 10 , and R 12 is independently selected from C1-C30 hydrocarbons, C6-C30 aromatic groups, C1-C30 alkoxy groups, and C2-C30 alkenyl groups, provided that one or more of R 4 , R 5 , R 6 , R 9 , and / or R 12 groups are selected from C2-C30 alkenyl groups; The subscripts a, b, c, d, e, f, and g are zero or positive according to the following restrictions: 2 < a + b + c + d + e + f + g < 2000, and b + d + f > 0.

[0045] In an embodiment, one or more of R 4 , R 5 , R 6 , R 9 , and / or R 12 are C2-C30 alkenyl groups, C4-C20 alkenyl groups, C6-C15 alkenyl groups, or C8-C10 alkenyl groups. In an embodiment, the alkenyl group is selected from C2-C8 alkenyl groups, C3-C6 alkenyl groups, or C4-C6 alkenyl groups. In one embodiment, the alkenyl group is selected from C2 or C3 alkenyl groups.

[0046] R 1 to R 12 are independently selected from C1-C30 hydrocarbons, C2-C20 hydrocarbons, C3-C15 hydrocarbons, or C4-C10 hydrocarbons; C6-C30 aromatic groups, C8-C20 aromatic groups, or C10-C15 aromatic groups; or C1-C30 alkoxy groups, C2-C20 alkoxy groups, C3-C15 alkoxy groups, or C4-C10 alkoxy groups. In an embodiment, R 1 to R 12is selected from a C1-C4 hydrocarbon, a C1-C3 hydrocarbon, or a C1-C2 hydrocarbon. The aromatic group can be a monocyclic or polycyclic structure. When the aromatic group contains multiple aromatic rings, the rings can be separated by a bond or a spacer group (e.g., an alkylene group), or two or more rings can be fused rings. In embodiments, the aromatic group is selected from a phenyl group. In embodiments, the alkoxy group is selected from a C1-C6 alkoxy, a C1-C4 alkoxy, a C1-C3 alkoxy, or a C1-C2 alkoxy. In embodiments, the alkoxy group is methoxy.

[0047] In one embodiment, the alkenyl-functional silicone contains two or more alkenyl functional groups (i.e., b+d+f>2). In one embodiment, the alkenyl-functional silicone has the formula M 2 D 1 c M 2 In one embodiment, the alkenyl-functional siloxane is of the formula M 1 a D 2 d Q g It is of the type.

[0048] The alkenyl-functional siloxane can be present in an amount of about 40% to about 80% by weight, about 45% to about 75% by weight, or about 50% to about 65% by weight based on the total weight of the composition.

[0049] It is further understood that the composition may contain a mixture of two or more alkenyl-functional silicones. When multiple alkenyl-functional silicones are used, the alkenyl-functional silicones may be of different types (e.g., having different overall configurations in terms of M, D, T, and Q units), different sizes (e.g., having similar M, D, T, and Q structures but different in terms of the number of each unit), and / or different viscosities. The composition may contain a mixture of siloxanes of different types in terms of M, D, T, and Q units. For example, the composition may contain a mixture of two or more MD, MDT, MQ, and / or MDQ type alkenyl-functional resins according to formula (I).

[0050] In one embodiment, the composition has the formula M 2 D 1 c M 2 a first alkenyl-functional silicone having an alkenyl functional group terminal (i.e., end-capped with one or more alkenyl functional groups); and a second alkenyl-functional silicone having an alkenyl functional group pendant to the siloxane chain and having the formula M 1 a D 2 d Q g In one embodiment, the alkenyl-functional siloxane comprises about 50% to about 80% by weight of the alkenyl-functional end-capped siloxane, based on the total weight of the alkenyl-functional siloxane, and about 20% to about 50% by weight of the alkenyl-functional siloxane with pendant alkenyl functional groups, based on the total weight of the alkenyl-functional siloxane.

[0051] It will also be appreciated that the alkenyl-functional siloxane can be provided as a mixture of two or more alkenyl-functional siloxanes of different sizes and / or viscosities. In one embodiment, the composition comprises a first alkenyl-functional siloxane of a first viscosity and a second alkenyl-functional siloxane of a second viscosity. In one embodiment, the first viscosity is relatively low and the second viscosity is higher than the first viscosity. In one embodiment, the composition comprises a first alkenyl-functional siloxane having a viscosity of about 500 cps to about 10,000 cps, about 1,000 cps to about 7,500 cps, about 2,000 cps to about 5,000 cps, or about 3,000 cps to about 4,000 cps, and a second alkenyl-functional siloxane having a viscosity of about 12,000 cps to about 100,000 cps, about 15,000 cps to about 90,000 cps, about 20,000 cps to about 80,000 cps, or about 30,000 cps to about 70,000 cps. When a mixture of alkenyl-functional siloxanes of different viscosities is used, the alkenyl-functional siloxanes can be of the same or different types or formulas. For example, the alkenyl-functional siloxanes can all be of the same type, e.g., MD, MDQ, MDT, MQ, etc., or each can be a mixture of different types of alkenyl-functional siloxanes. In one embodiment, the composition comprises a mixture of alkenyl-functional siloxanes of different viscosities, where the alkenyl-functional siloxanes have the structure M 1 a D 2 d Q g It has.

[0052] Hydride-functional siloxanes

[0053] The composition includes a hydride-functional siloxane. The hydride-functional siloxane may function as a crosslinker and may be referred to herein as a crosslinker. The hydride-functional siloxane has the formula: M 1 h M 4i D 3 j D 4 k T 3 m T 4 n Q o (II) and wherein the compound is selected from the group consisting of: M 3 =R 13 R 14 R 15 SiO 1 / 2 M 4 =R 16 R 17 R 18 SiO 1 / 2 D 3 =R 19 R 20 SiO 2 / 2 D 4 =R 21 R 22 SiO 2 / 2 T 3 =R 23 SiO 3 / 2 T 4 =R 24 SiO 3 / 2 Q=SiO 4 / 2 where R 13 , R 14 , R 15 , R 19 , R 20 , and R 23 are independently selected from a C1 to C30 hydrocarbon, a C6 to C30 aromatic group, or a C1 to C30 alkoxy group; R 16 , R 17 , R 18 , R 21 , R 22 , and R 24 are independently selected from hydrogen, a C1-C30 hydrocarbon, a C6-C30 aromatic group, a C1-C30 alkoxy group, or a C2-C30 alkenyl group, with the proviso that R 16 , R 17 , R18 , R 21 , R 22 , and / or R 24 is one or more of hydrogen; The subscripts a, b, c, d, e, f, and g are subject to the following restrictions: 1 < h + i + j + k + m + n + o < 100, and i + k + n > 0 and are zero or positive.

[0054] R 13 ~R 24 can be independently selected from C1 - C30 hydrocarbons, C2 - C20 hydrocarbons, C3 - C15 hydrocarbons, or C4 - C10 hydrocarbons; C6 - C30 aromatic groups, C8 - C20 aromatic groups, or C10 - C15 aromatic groups; or C1 - C30 alkoxy groups, C2 - C20 alkoxy groups, C3 - C15 alkoxy groups, or C4 - C10 alkoxy groups. In an embodiment, R 1 ~R 12 is selected from C1 - C4 hydrocarbons, C1 - C3 hydrocarbons, or C1 - C2 hydrocarbons. The aromatic group can be a monocyclic or polycyclic structure. When the aromatic group contains multiple aromatic rings, these rings can be separated by a bond or a spacer group (e.g., an alkylene group), or two or more rings can be fused rings. In an embodiment, the aromatic group is selected from phenyl groups. In an embodiment, the alkoxy group is selected from C1 - C6 alkoxy, C1 - C4 alkoxy, C1 - C3 alkoxy, or C1 - C2 alkoxy. In an embodiment, the alkoxy group is methoxy.

[0055] In one embodiment, the hydridofunctional siloxane is of the type M 3 h D 4 k M 3 h of the kind.

[0056] The hydride-functional silicone (or a mixture of two or more alkenyl-functional silicones) is present in an amount of about 0.01 to about 20 wt. %; about 0.1 to about 5 wt. %; or about 0.1 to about 3 wt. % based on the total weight of the composition.

[0057] Titanium dioxide

[0058] The compositions of the present invention comprise titanium dioxide particles. The titanium dioxide particles can be provided in any suitable shape / form, including rutile, anatase, or a mixture thereof. In one embodiment, the composition comprises rutile titanium dioxide particles. In one embodiment, the composition comprises anatase titanium dioxide particles. In one embodiment, the composition comprises a mixture of rutile and anatase titanium dioxide particles.

[0059] The titanium dioxide particles may have a particle size desired for a particular purpose or intended use. In one embodiment, the titanium dioxide particles may have a particle size between about 1 nm and about 500 nm. In some embodiments, the titanium dioxide particles have a particle size of about 5 nm to about 400 nm, about 10 nm to about 300 nm, about 20 nm to about 250 nm, about 30 nm to about 200 nm, about 40 nm to about 150 nm, or about 50 nm to about 100 nm. In one embodiment, the titanium dioxide particle size is about 50 nm to about 200 nm, about 60 nm to about 75 nm. References to the size of titanium dioxide particles (or crystallites) herein will be understood to refer to the average particle size of the titanium dioxide particles. When a particle size is modified by the term "about," it will be understood to encompass particle sizes somewhat larger or smaller than the stated value to account for experimental error inherent in measurement and variability between different methods for measuring particle size, as will be apparent to those skilled in the art. The diameter may be measured, for example, by transmission electron microscopy (TEM) and X-ray diffraction (XRD).

[0060] Alternatively, the particles may be characterized by their surface area. Typically, titanium dioxide has a surface area of ​​about 20 m, as measured by any suitable method, including the 5-point BET method. 2 / g. More typically, the titanium dioxide particles have a surface area of ​​about 50 m 2 / g or more than 70m 2 In embodiments, the titanium dioxide particles have a surface area of ​​greater than about 100 m 2 / g, or even about 150m 2 / g. In some embodiments, the titanium dioxide photocatalyst has a surface area of ​​greater than about 200 m 2 / g, approximately 250m 2 / g, or even about 300m 2 In embodiments, titanium dioxide has a surface area of ​​greater than about 20 m 2 / g to about 500m 2 / g, approx. 50m 2 / g to about 400m 2 / g, approx. 75m 2 / g to about 300m 2 / g, about 100m 2 / g to about 250m 2 / g, or approximately 150m 2 / g to about 200m 2 / g of surface area.

[0061] It will be appreciated that the composition can include a mixture of titanium dioxide particles of different particle sizes. For example, the composition can include a mixture of a first population of titanium dioxide particles having a first average particle size and a second population of titanium dioxide particles having a second average particle size, where the first average particle size is different from the second average particle size.

[0062] Titanium dioxide particles with a relatively small average particle size may be used if desired. The use of large particles at high concentrations does not adversely affect the behavior and properties of the composition, but may affect the appearance of the composition when cured on a surface. In particular, the use of large particles may result in a rather matte or textured finish.

[0063] The titanium dioxide can be treated or untreated. In one embodiment, the titanium dioxide particles include a surface treatment. The surface treatment can be a hydrophobic or hydrophilic surface treatment. In one embodiment, the titanium dioxide particles are surface-treated with tetraalkoxysilane. In one embodiment, the titanium dioxide particles are surface-treated with polydimethylsiloxane. In one embodiment, the titanium dioxide particles are treated with alumina. The titanium dioxide particles can also be treated with a polymer selected from carboxymethyl starch, carboxymethyl dextran, carboxymethyl cellulose, polycarboxylic acids, and copolymers containing carboxyl groups. Other suitable surface treatments include, but are not limited to, polycarboxylic acids, such as polyacrylic acid and polymaleic acid, and copolymers such as acrylic acid / maleic acid copolymers and copolymers of acrylic acid / sulfonic acid monomers, etc.

[0064] Titanium dioxide can be present in an amount of about 20% to about 50% by weight, about 25% to about 45% by weight, or about 30% to about 40% by weight, based on the total weight of the composition.

[0065] Filler

[0066] The composition optionally includes one or more fillers other than titanium dioxide. The fillers can be selected as desired for a particular purpose. For example, they may contribute other properties, such as strength, as desired. The optional fillers should not reduce or inhibit the reflectivity, emissivity, or other properties of the composition. Thus, conventional fillers such as carbon black, graphene, graphite, or other dark fillers are less desirable in embodiments and, in embodiments, are excluded from the compositions of the present invention.

[0067] Examples of suitable fillers include, but are not limited to, silicone resins with or without surface modification, silica, nanosilica, fumed silica, particulate forms of cerium, aluminum, zinc, zirconium, and other metal and metalloid oxides; glass fibers, inorganic fillers such as talc, carborundum, mica, boron nitride, inorganic fillers such as clay, kaolin, calcium carbonate, and the like. In one embodiment, the composition comprises a filler selected from silica and / or zinc oxide.

[0068] In one embodiment, the composition includes fumed silica. The fumed silica can be functionalized as desired. In one embodiment, the fumed silica is functionalized with a functionalizing agent such as a halosilane; an organosilane having at least one silanol group and / or an alkoxy, aryloxy, or cycloalkoxy group; an organosilazane, a cyclic organosiloxane, a low-viscosity polyorganosiloxane having silanol groups and / or an alkoxy, aryloxy, or cycloalkoxy group; or a silicone resin having silanol groups and / or an alkoxy, aryloxy, or cycloalkoxy group. Examples of alkoxy groups include alkoxy groups having 1 to 6 carbon atoms, examples of aryloxy groups include groups having 6 to 10 carbon atoms, and examples of cycloalkoxy groups include groups having 6 to 10 carbon atoms. In embodiments, the fumed silica is functionalized with a functionalizing agent selected from the group consisting of silanol-terminated polydimethylsiloxane, octaphenylcyclotetrasiloxane, octamethylcyclotetrasiloxane, and hexamethyldisilazane (HMDZ). Other examples of first organosilicon functionalizing agents include diphenylsilanediol, dimethylsilanediol, methyltriethoxysilane, and phenyltrimethoxysilane. The low-viscosity polyorganosiloxane may contain one or more organic groups selected from the group consisting of methyl, phenyl, vinyl, and 3,3,3-trifluoropropyl groups. Suitable low-viscosity polyorganosiloxanes have viscosities measured at 25°C ranging from about 1 to about 300 centipoise in one embodiment, and from about 5 to about 100 centipoise in another embodiment. Examples of halosilanes include halotrialkylsilanes, such as chlorotrimethylsilane; halotriarylsilanes, such as chlorotriphenylsilane; dichlorodimethylsilane, bis(chlorodimethylsilyl)methane, trichloromethylsilane, bromotrimethylsilane, and others.

[0069] In one embodiment, the composition comprises fumed silica in an amount of about 0.1 wt % to about 10 wt %, about 0.5 wt % to about 7.5 wt %, about 1 wt % to about 5 wt %, or about 2 wt % to about 4 wt %, based on the total weight of the composition.

[0070] In one embodiment of the present invention, the amount of filler is from 0.1% to about 90% by weight of the total composition. In yet another embodiment of the present invention, the amount of filler is from about 5% to about 60% by weight of the total composition. In yet another embodiment of the present invention, the amount of filler is from about 10% to about 40% by weight of the total composition. The filler may be a single type or a mixture of two or more types.

[0071] catalyst

[0072] The composition includes a hydrosilylation catalyst. In one embodiment, the hydrosilylation catalyst may be a platinum-based catalyst. The hydrosilylation catalyst may be, for example, a Speier catalyst or a Karstedt catalyst. Suitable Speier catalysts may include chloroplatinic acid and HPtCl, which are known in the art. Suitable Karstedt catalysts may include Pt{[CH=CH)MeSi]O} catalysts, which are known in the art. In one embodiment, the hydrosilylation catalyst is selected from Karstedt catalysts having the formula Pt{[CH=CH)MeSi]O}, where Me is a methyl group. Karstedt catalysts exhibit better productivity than Speier catalysts for hydrosilylation reactions. Additionally, Karstedt catalysts are commercially available in solution, allowing for control of catalyst concentration, stability, viscosity, and inhibition. If a Karstedt catalyst is used, it is more preferably platinum(0)-1,3-divinyl-1,1,3,3-tetramethyldisiloxane (0.1 M in xylene) and can be used in an amount to provide a platinum metal concentration of about 0.0008 to 0.01 wt %, preferably 0.0001 to 0.005 wt %, and more preferably 0.001 to 0.002 wt %.

[0073] inhibitors

[0074] Optionally, the composition can contain an inhibitor to delay or suppress the catalytic activity of platinum catalyst.Suitable examples of inhibitors include, but are not limited to, 1-ethynyl-1-cyclohexanol, 2-methyl-3-butyn-2-ol, 3,5-dimethyl-1-hexyn-3-ol, 3-methyl-1-dodecyn-3-ol, polymethylvinylcyclosiloxanes such as 1,3,5,7-tetravinyltetramethyltetracyclosiloxane, divinyltetramethyldisiloxane, tetravinyldimethyldisiloxane, trialkylthiolate, alkylmaleate, organic sulfoxide, organic amine, diamine, phosphane and phosphite, nitrile, diaziridine, and oxime, acetylene compound, phosphite, maleate, amine or alcohol, which can be used to make targeted adjustments to the process life, onset temperature and crosslinking speed of the composition of the present invention.

[0075] Adhesion promoter

[0076] The composition may optionally contain an adhesion promoter. Suitable adhesion promoters can be selected from alkoxysilanes or aryloxysilanes, including, but not limited to, γ-aminopropyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, bis(trimethoxysilylpropyl) fumarate, or tetracyclosiloxanes modified with acryloxytrimethoxysilyl or methacryloxypropyltrimethoxysilyl functional groups, oligosiloxanes containing alkoxysilyl functional groups, oligosiloxanes containing aryloxysilyl functional groups, polysiloxanes containing alkoxysilyl functional groups, polysiloxanes containing aryloxysilyl functional groups, cyclosiloxanes containing alkoxysilyl functional groups, cyclosiloxanes containing alkoxysilyl and Si—H functional groups, cyclosiloxanes containing aryloxysilyl functional groups, titanates, trialkoxyaluminum, tetraalkoxysilanes, and mixtures thereof.

[0077] The adhesion promoter may be added in an amount of 0 to about 30 wt %, about 0.001 wt % to about 15 wt %, about 0.1 wt % to about 10 wt %, or about 0.5 wt % to about 5 wt %, based on the total weight of the composition.

[0078] UV stabilizers

[0079] The composition may optionally include a UV stabilizer. In embodiments, the UV stabilizer is selected from organic UV stabilizers. The organic UV stabilizer may be selected from the group consisting of, but not limited to, triazines, benzotriazoles, or benzoxazinones. Examples of suitable UV stabilizers include those available from BASF under the trade name Tinuvin®. 登録商標 The triazine 2-(4,6-diphenyl-1,3,5-triazin-2-yl)-5-(hexyl)oxy-phenol (Tinuvin 1600) is commercially available. 登録商標 When 1577) or 2-(2'-hydroxyphenyl)-4,6-bis(4-phenylphenyl) is used, transmittance below 370 nm can be achieved at low UV stabilizer levels while simultaneously achieving higher transmittance at wavelengths above 390 nm.

[0080] Two-component composition

[0081] The compositions of the present invention may generally be provided as two-part compositions. Providing the composition as a two-part composition may prevent premature curing of the composition. In one embodiment, the two-part composition is provided as follows: a first part (Part A) comprising (i) an alkenyl-functional polysiloxane, (ii) a catalyst, (iii) titanium dioxide, (iv) an optional filler, and (v) an optional diluent; and a second part (Part B) comprising (i) an alkenyl-functional siloxane, (ii) a hydride-functional siloxane, (iii) titanium dioxide, (iv) an adhesion promoter, (v) an optional catalyst inhibitor, (vi) an optional filler, and (vii) an optional diluent.

[0082] The components are provided in each part in an amount that results in the desired total concentration of the components when the parts are combined. When a component is provided in each of two parts, the amount of that component in the first part can be approximately equal to the amount of that component in the second part. In one embodiment, the first and second parts are provided to have the same or relatively similar specific gravities. This may facilitate good mixing of the two parts when combined to form the coating. In one embodiment, the first and second parts have specific gravities within about 8%, 5%, 3%, 2%, or 1% or less of each other.

[0083] The first and second parts are stored in separate containers or cartridges prior to use. The first and second parts can be stored at room temperature, for example, from about 18°C ​​to about 25°C.

[0084] Coatings formed from the two-part composition are prepared by mixing the first and second parts, applying the composition to a target surface, and exposing the coating composition to elevated temperatures. In one embodiment, the coating can be cured at room temperature (e.g., from about 18°C ​​to about 25°C). In one embodiment, the coating is exposed to a temperature of from about 80°C to about 150°C. Additionally, curing can occur for about 1 hour.

[0085] The coating can be applied in any suitable manner now known in the art or developed in the future. In embodiments, the coating may be applied by spraying, brushing, rolling, dipping, blade coating, curtain coating, knife coating, or a combination thereof. Spray coating can be used for compositions that further include a solvent, such as a non-volatile solvent. Spraying means also include, but are not limited to, the use of high-flow, low-pressure (HVLP) spray systems, air-assisted / airless spray systems, or electrostatic spray systems. In further or alternative embodiments, the coating is applied in a single application, or in multiple applications.

[0086] The composition of the present invention allows for the use of direct application to a substrate surface. That is, in embodiments, the coating can be applied to a surface and adhere well without the need for a primer. For primerless coating of this composition, the target surface is generally treated before applying the composition. The surface can be treated in any suitable manner, including, but not limited to, solvent washing, flame treatment, corona discharge, and chemical etching. Chemical etching may include etching with an acidic material. In one embodiment, acid etching can be achieved using any protonic acid, such as sulfuric acid, hydrochloric acid, or nitric acid, or an organic acid such as acetic acid, among others. The length of time required for acid etching depends on the acid used, the acid concentration, the substrate material, and the composition of the coating. The exact conditions required for acid etching can be easily determined by one of ordinary skill in the art. Spraying may also allow for the application of a relatively thin coating to the target surface.

[0087] Additionally, the composition has been found to allow for the coating of curved surfaces, particularly the flexibility and properties of the composition allow it to be applied to curved surfaces more easily and have the ability to provide good surface coverage.

[0088] In another embodiment, the surface may be pretreated with a primer to improve adhesion of the coating. Examples of suitable primers include, but are not limited to, ethyl orthosilicate and tetra-n-butyl titanate in mineral spirits. Such a primer is commercially available from Momentive Performance Materials, Inc. under the designation SS4155 Primer.

[0089] The coating can be provided at any thickness desired for a particular purpose or intended use. In one embodiment, the coating is provided at a wet film thickness of about 50 micrometers or greater. At this level, excellent solar absorptance is observed for coatings according to the present invention. Thicker coatings can be used, if desired, which may reduce solar absorptance. In one embodiment, the coating, after curing, can have a thickness of about 5 mils or greater, about 7 mils or greater, or about 10 mils or greater.

[0090] The coatings can be used on a variety of substrates, including, but not limited to, metal substrates and plastic substrates. In one embodiment, the substrate is an aluminum substrate, a magnesium substrate, a titanium substrate, etc. Examples of aluminum substrates include, but are not limited to, untreated aluminum, cast aluminum, aluminum alloys, and others.

[0091] Coatings formed from the compositions of the present invention exhibit a wide range of properties, allowing the coatings to be used in a variety of applications, including applications such as: s ), high infrared emissivity (ε), and high solar reflectance (ρ s) Solar absorptance at TO (initial absorptance after cure) and after 1000 hours at 150°C was measured using ASTM E903-20 with a UV-Visible spectrophotometer equipped with an integrating sphere, and solar reflectance at TO and after 1000 hours at 150°C was measured using ASTM E903-20 with a UV-Visible spectrophotometer equipped with an integrating sphere. Emissivity may be measured according to ASTM E408. In one embodiment, the coating has one or more of the following properties at a coating thickness of about 1.5 mm to about 2 mm: a solar absorptance (α) of 0.35 or less; 0.25 or less; 0.2 or less; 0.15 or less; about 0.1 to 0.35; about 0.12 to about 0.30; about 0.15 to about 0.25; or about 0.17 to about 0.20 s ); and / or an infrared emissivity (ε) of 0.89 or greater, 0.9 or greater, 0.92 or greater, 0.95 or greater, or 0.98 or greater; 0.89 to about 0.98, about 0.9 to about 0.95, 0.89 to about 0.92, or about 0.9 to about 0.92; and / or a solar reflectance (ρ) of 0.65 or greater, 0.75 or greater, 0.8 or greater, or 0.85 or greater; from about 0.65 to about 0.9, from about 0.7 to about 0.88, from about 0.75 to about 0.85, or from about 0.8 to about 0.83 s ).

[0092] The coatings of the present technology also exhibit good flexibility, hi one embodiment, the coating has an elongation of about 100% to about 195%, about 110% to about 185%, about 120% to about 175%, about 130% to about 160%, or about 140% to about 150%.

[0093] Example

[0094] Two-part compositions were prepared according to the formulations shown in Tables 1 and 2. Coating compositions were prepared by mixing Part A and Part B of each formulation, applying the compositions to a surface, and exposing the compositions to a temperature of 80°C for approximately 1 hour. Solar absorptance at TO (initial absorptance after cure) and after 1000 hours at 150°C was measured using a UV-Vis spectrophotometer equipped with an integrating sphere according to ASTM E903-20. Solar reflectance at TO and after 1000 hours at 150°C was measured using a UV-Vis spectrophotometer equipped with an integrating sphere according to ASTM E903-20. The results are shown in Table 3. Table 4 shows spectrophotometer data for Formulations 1-8, showing total absorptance, total reflectance, and emissivity after 1000 hours of exposure at 150°C. [Table 1] [Table 2] [Table 3] [Table 4]

[0095] Figure 1 shows the total reflectance spectra for the coatings prepared from Formulations 1 to 8. Figure 2 shows the total reflectance for the coating from Formulation 9.

[0096] As shown in the tables and figures, coatings formed from compositions according to the present technology exhibit high solar reflectance, high emissivity, and low solar absorptance. These properties are observed over extended periods of time, especially when compared to Formulation 5, which contains no titanium dioxide, and Formulation 9, which contains a relatively low concentration of titanium dioxide.

[0097] The foregoing description includes examples of the present specification. Of course, for purposes of describing the present specification, it is not possible to describe every conceivable combination of components or methodologies, but one of ordinary skill in the art may recognize that many additional combinations and permutations of the present specification are possible. Accordingly, the present specification is intended to embrace all such changes, modifications, and variations that fall within the spirit and scope of the appended claims. Furthermore, to the extent the term "comprising" is used in the detailed description or the claims, it is intended to be inclusive in the same manner as "including," but in the same manner as "comprising" is interpreted when used as a transitional term in the claims.

[0098] The foregoing description reveals various non-limiting embodiments of the thermal control coating. Modifications will occur to those skilled in the art and to those who make and use the invention. The disclosed embodiments are for illustrative purposes only and are not intended to limit the scope of the invention or subject matter set forth in the claims.

Claims

1. 1. A curable coating composition comprising: alkenyl-functional siloxanes; hydride-functional siloxanes; titanium dioxide particles; an addition cure catalyst; and A curable coating composition optionally comprising an adhesion promoter.

2. 10. The curable coating composition of claim 1, wherein the titanium dioxide is present in an amount of about 20% to about 50% by weight based on the total weight of the composition.

3. 3. The curable composition of claim 1 or 2, wherein the titanium dioxide particles have a particle size of about 1 nm to about 500 nm.

4. 4. The curable composition of claim 1, wherein the titanium dioxide particles are selected from rutile titanium dioxide, anatase titanium dioxide, or mixtures thereof.

5. 5. The curable composition of claim 4, wherein the titanium dioxide particles comprise fumed anatase / rutile titanium dioxide.

6. 6. The curable composition of any of claims 1 to 5, wherein the alkenyl-functional siloxane can be present in an amount of about 40% to about 80% by weight, based on the total weight of the composition.

7. The alkenyl-functional siloxane has the formula: M １ ａ M ２ ｂ D １ ｃ D ２ ｄ T １ ｅ T ２ ｆ Q ｇ (I) and wherein the compound is selected from the group consisting of: M １ =R １ R ２ R ３ SiO １／２ M ２ =R ４ R ５ R ６ SiO １／２ D １ =R ７ R ８ SiO ２／２ D ２ =R ９ R １０ SiO ２／２ T １ =R １１ SiO ３／２ T ２ =R １２ SiO ３／２ Q=SiO ４／２ where R １ , R ２ , R ３ , R ７ , R ８ , and R １１ is independently selected from a C1 to C30 hydrocarbon, a C6 to C30 aromatic group, or a C1 to C30 alkoxy group; R ４ , R ５ , R ６ , R ９ , R １０ , and R １２ are independently selected from a C1 to C30 hydrocarbon, a C6 to C30 aromatic group, a C1 to C30 alkoxy group, and a C2 to C30 alkenyl group, with the proviso that R ４ , R ５ , R ６ , R ９ , and / or R １２ one or more of the groups are selected from C2 to C30 alkenyl groups; 6. The curable composition of any of claims 1 to 5, wherein the subscripts a, b, c, d, e, f, and g are zero or positive subject to the following constraints: 2<a+b+c+d+e+f+g<2000, and b+d+f>0.

8. The alkenyl-functional siloxane has the formula M ２ D １ ｃ M ２ , formula M １ ａ D ２ ｄ Q ｇ 8. The curable composition of claim 7, wherein the alkenyl-functional siloxane is selected from the group consisting of:

9. The alkenyl-functional siloxane has the formula M ２ D １ ｃ M ２ a first alkenyl-functional siloxane having the formula: １ ａ D ２ ｄ Q ｇ 9. The curable composition of claim 8, comprising a second alkenyl-functional siloxane having the formula:

10. 10. The curable composition of claim 9, wherein the first alkenyl-functional siloxane is present in an amount of about 50% to about 80% by weight and the second alkenyl-functional siloxane is present in an amount of about 20% to about 50% by weight, based on the total weight of the alkenyl-functional siloxanes.

11. 11. The curable composition of claim 1, comprising fumed silica.

12. 12. The curable composition of claim 11, wherein the fumed silica is present in an amount of about 0.1 wt% to about 10 wt%, based on the total weight of the composition.

13. 13. The curable composition of claim 1, wherein the catalyst is a platinum-based catalyst.

14. The curable composition of any of claims 1 to 13, wherein the adhesion promoter is selected from cyclosiloxanes containing Si-H functional groups.

15. 15. The composition of any of claims 1 to 14, wherein the adhesion promoter is present in an amount of from about 0 to about 30 wt%, based on the total weight of the composition.

16. The composition may be provided as a two-part composition: a first part comprising an alkenyl-functional siloxane; titanium dioxide, and a catalyst; and 16. The composition of any of claims 1 to 15, comprising a second part comprising an alkenyl-functional siloxane, a hydride-functional siloxane, titanium dioxide, and optionally an adhesion promoter.

17. Coatings formed from the compositions at thicknesses of about 1.5 mm to about 2 mm have solar absorptances (α) of 0.35 or less. ｓ 17. The composition of claim 1, wherein

18. A coating formed from the composition at a thickness of about 1.5 mm to about 2 mm has a solar absorptance (α) of about 0.1 to 0.

35. ｓ 17. The composition of claim 1, wherein

19. 19. The composition of any of claims 1 to 18, wherein a coating formed from the composition at a thickness of about 1.5 mm to about 2 mm has an infrared emissivity (ε) of 0.89 or greater.

20. A coating formed from the composition at a thickness of about 1.5 mm to about 2 mm has a solar absorptance (α) of 0.89 to about 0.

98. ｓ 19. The composition of claim 1, wherein

21. Coatings formed from the compositions at thicknesses of about 1.5 mm to about 2 mm have a solar reflectance (ρ) of 0.65 or greater. ｓ 21. The composition of claim 1, wherein

22. A coating formed from the composition at a thickness of about 1.5 mm to about 2 mm has a solar absorptance (α) of about 0.65 to about 0.

9. ｓ 21. The composition of claim 1, wherein

23. A coating formed from the composition at a thickness of about 1.5 mm to about 2 mm has a solar absorptance (α ｓ 23. The composition of any of claims 1 to 22, wherein

24. 23. The composition of any of claims 1 to 22, wherein a coating formed from the composition at a thickness of about 1.5 mm to about 2 mm has an elongation of about 100% to about 195%.

25. 25. A method of forming a coating on a substrate comprising curing the composition of any of claims 1 to 24.

26. 26. The method of claim 25, wherein the composition is a two-part composition comprising: (i) a first part comprising an alkenyl-functional siloxane; titanium dioxide, and a catalyst; and (ii) a second part comprising an alkenyl-functional siloxane, a hydride-functional siloxane, titanium dioxide, and optionally an adhesion promoter, and the method comprises combining the first part and the second part and heating at a temperature of from about 80°C to about 150°C.

27. 27. The method of claim 25 or 26, wherein curing is achieved in about 1 hour.

28. 25. A substrate comprising a surface coated with the composition of any of claims 1 to 24.

29. 30. The substrate of claim 28, wherein the composition is cured to form a coating.

Images