Two-component addition curing thermal control coating

Abstract

Thermal control coatings are shown and described herein. The thermal control coating is provided from a two component addition cure silicone composition. The composition includes a curable siloxane and titanium dioxide. The compositions are fast curing compositions that exhibit low solar absorptivity, high solar reflectance, and / or high infrared emissivity when cured. In addition, the composition exhibits good flexibility when cured, and can be applied to a surface without the aid of a primer.

Description

[0001] Cross-reference to related applications

[0002] This application claims priority to and the benefit of U.S. Provisional Patent Application No. 63 / 448,691, filed on February 28, 2023, entitled “Two-Part Addition Cure Thermal Control Coating,” the disclosure of which is incorporated herein by reference in its entirety. Technical Field

[0003] The present invention relates to an addition-cured silicone coating. In particular, the present invention relates to an addition-cured silicone coating that exhibits low absorptivity, high infrared emissivity, and relatively fast curing. The coating may find use in a variety of applications, including those where low solar absorptivity and high infrared emissivity are desired. Background Art

[0004] Thermal management systems provide a means of maintaining thermal properties, such as temperature, temperature fluctuations, and humidity. Thermal management can occur through active or passive means. Active temperature control can involve mechanical or electrical devices, such as electric heaters and / or coolers. Passive temperature control involves no mechanical or electrical devices but includes techniques such as thermal control coatings or structural designs. For example, aircraft and aerial vehicles may include components that generate significant amounts of heat, which must be dissipated through thermal radiation from the components' exterior surfaces. Additionally, radiating surfaces are subject to thermal radiation from incident sunlight, which reduces the surface's thermal efficiency. In the lower atmosphere, or even at higher altitudes outside the Earth's atmosphere, there is little or no atmosphere to conduct heat to or from vehicle components. During operation, one side of an object may be directly exposed to the sun, while another side faces away from the sun. Therefore, as the vehicle's position relative to the sun changes and its components are directly heated by the sun, there is the potential for extreme temperature differences and variations between different vehicle components. Radiation can be accomplished through the use of thermal control surfaces that absorb and emit solar radiation. These surfaces have a range of desired values ​​of solar absorptivity (α) and infrared emissivity (ε). For a surface such as a radiator, it is important to absorb as little solar radiation as possible (low α) while radiating as much heat as possible (high ε). Summary of the Invention

[0005] The following is a summary of the present disclosure, which is intended to provide a basic understanding of certain aspects of the present invention. This summary is not intended to identify key or critical elements, nor to define any limitations of the embodiments or claims. Furthermore, this summary may provide a brief overview of certain aspects that may be described in more detail elsewhere in this disclosure.

[0006] Provided are silicone compositions suitable for use as thermal control coatings. The compositions exhibit one or more of low solar absorptivity, high infrared emissivity, and / or high solar reflectivity. In one aspect, the compositions are addition-curable silicones. In embodiments, the compositions are provided as two-component compositions.

[0007] In one aspect, a curable coating composition is provided that includes: an alkenyl-functional siloxane; a hydride-functional siloxane; titanium dioxide particles; an addition cure catalyst; and optionally, an adhesion promoter.

[0008] In one embodiment, titanium dioxide is present in an amount from about 20 wt % to about 50 wt % based on the total weight of the composition.

[0009] In one embodiment according to any of the preceding embodiments, the titanium dioxide particles have a particle size of about 1 nm to about 500 nm.

[0010] In one embodiment according to any of the preceding embodiments, the titanium dioxide particles are selected from rutile titanium dioxide, anatase titanium dioxide, or mixtures thereof.

[0011] In one embodiment according to any of the preceding embodiments, the titanium dioxide particles comprise fumed anatase / rutile titanium dioxide.

[0012] In one embodiment according to any of the preceding embodiments, the alkenyl functional siloxane is present in an amount from about 40 wt % to about 80 wt % based on the total weight of the composition.

[0013] In one embodiment according to any of the preceding embodiments, the alkenyl functional siloxane is selected from compounds of the formula:

[0014] M 1 a M 2 b D 1 c D 2 d T 1 e T 2 f Q g (I)

[0015] in:

[0016] M 1 =R 1 R 2 R 3 SiO 1 / 2

[0017] M 2 =R 4 R 5 R 6 SiO 1 / 2

[0018] D 1 =R 7 R 8 SiO 2 / 2

[0019] D 2 =R 9 R 10 SiO 2 / 2

[0020] T 1 =R 11 SiO 3 / 2

[0021] T 2 =R 12 SiO 3 / 2

[0022] Q = SiO 4 / 2

[0023] Where R 1 , R 2 , R 3 , R 7 , R 8 and R 11 are independently selected from C1-C30 hydrocarbons, C6-C30 aryls or C1-C30 alkoxys;

[0024] R 4 , R 5 , R 6 , R 9 , R<000​​​​​​​​​​​​​​​​​​​​​1 c M2, Formula M 1 a D 2 d Qg or a combination thereof alkenyl functional siloxane.

[0027] In one embodiment, the alkenyl functional siloxane comprises a siloxane having the formula M 2 D 1 c The first alkenyl functional siloxane of M2, and the 1 a D 2 d Qg of a second alkenyl functional siloxane. In one embodiment, the first alkenyl functional siloxane is present in an amount from about 50 wt% to about 80 wt%, and the second alkenyl functional siloxane is present in an amount from about 20 wt% to about 50 wt%, based on the total weight of the alkenyl functional siloxane.

[0028] In one embodiment according to any of the preceding 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.

[0029] In one embodiment according to any of the preceding embodiments, the catalyst is a platinum-based catalyst.

[0030] In one embodiment according to any of the preceding embodiments, the adhesion promoter is selected from cyclosiloxanes containing Si-H functional groups.

[0031] In one embodiment according to any of the preceding embodiments, the adhesion promoter may be present in an amount from about 0 wt % to about 30 wt % based on the total weight of the composition.

[0032] In one embodiment according to any of the preceding 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 an optional adhesion promoter.

[0033] In one embodiment according to any of the preceding embodiments, a coating formed from the composition at a thickness of about 1.5 mm to about 2 mm has a solar absorptivity (α s ).

[0034] In one embodiment according to any of the preceding embodiments, a coating formed from the composition at a thickness of about 1.5 mm to about 2 mm has a solar absorptivity (α s ).

[0035] In one embodiment according to any of the preceding 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.

[0036] In one embodiment according to any of the preceding embodiments, a coating formed from the composition at a thickness of about 1.5 mm to about 2 mm has a solar absorptivity (α s ).

[0037] In one embodiment according to any of the preceding 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 ).

[0038] In one embodiment according to any of the preceding embodiments, a coating formed from the composition at a thickness of about 1.5 mm to about 2 mm has a solar absorptivity (α) of about 0.65 to about 0.9. s ).

[0039] In one embodiment according to any of the preceding embodiments, a coating formed from the composition at a thickness of about 1.5 mm to about 2 mm has a solar absorptivity (α s ).

[0040] In one embodiment according to any of the preceding 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%.

[0041] In another aspect, there is provided a method of forming a coating on a substrate comprising curing the composition of any of the previous embodiments.

[0042] In one embodiment, the composition is a two-component composition comprising: (i) a first component comprising an alkenyl-functional siloxane, titanium dioxide, and a catalyst; and (ii) a second component comprising an alkenyl-functional siloxane, a hydride-functional siloxane, titanium dioxide, and an optional adhesion promoter, and the method comprises combining the first component and the second component and heating at a temperature of about 80° C. to about 150° C.

[0043] In one embodiment according to any of the preceding embodiments, curing is complete within about 1 hour.

[0044] In yet another aspect, a substrate is provided, comprising a surface coated with the composition of any of the previous embodiments.

[0045] In one embodiment, the composition is cured to form a coating.

[0046] The following description and drawings disclose various illustrative aspects. Some improvements and novel aspects may be explicitly identified, while other aspects may be apparent from the description and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] The drawings illustrate various systems, devices, apparatus, and associated methods, wherein like reference numerals refer to like parts throughout, and wherein:

[0048] Figure 1 is a graph showing the total reflection spectrum of the film in Example;

[0049] Figure 2 Graph showing the total reflectance spectrum of a film produced via formulation 9. DETAILED DESCRIPTION

[0050] Reference will now be made to the exemplary embodiments and examples shown in the accompanying drawings. It should be understood that other embodiments may be utilized and that structural and functional modifications may be made. In addition, features of the various embodiments may be combined or modified. Therefore, the following description is presented only by way of illustration and should not in any way limit the various replacements and modifications that may be made to the illustrated embodiments. In this disclosure, many specific details are provided to provide a thorough understanding of the subject matter of the present disclosure. It should be understood that aspects of the present disclosure may be practiced through other embodiments, which do not necessarily include all aspects described herein, etc.

[0051] As used herein, the words "embodiment" and "exemplary" mean an example or illustration. Words such as "embodiment" or "exemplary" do not indicate key or preferred aspects or implementations. Unless the context indicates otherwise, the word "or" is intended to be inclusive rather than exclusive. For example, the phrase "A employs B or C" includes any inclusive permutation (e.g., A employs B; A employs C; or A employs both B and C). Furthermore, the articles "a," "an," and "an" generally mean "one or more" unless the context indicates otherwise.

[0052] Unless otherwise noted, viscosity can be assessed, for example, using a Brookfield HATDV-II, spindle 2, at 50 rpm.

[0053] An addition-curing silicone composition is provided. The composition can generally be provided as a two-component composition. The composition provides a material that, when cured, exhibits excellent properties suitable for a wide range of applications. The material is particularly suitable for applications where the material will be exposed to extreme changes in temperature and prolonged exposure to sunlight and radiation. The material formed from the composition can exhibit, for example, one or more of low solar absorptivity, high infrared emissivity, high solar reflectivity, and the like.

[0054] The composition comprises: (i) an alkenyl-functional polysiloxane; (ii) a hydride-functional siloxane; (iii) an organosilicone hydride adhesion promoter; (iv) a titanium dioxide filler; and (v) an addition cure catalyst. The composition can be provided as a two-component, as discussed in more detail herein.

[0055] Alkenyl functional polysiloxane

[0056] The composition includes an alkenyl functional siloxane. The alkenyl functional siloxane includes an alkenyl functional group, wherein the alkenyl functional group comprises a C=C bond and is connected to an organosilicon atom of the siloxane.

[0057] In one embodiment, the composition includes an alkenyl functional organosilicon compound of the formula:

[0058] M 1 a M 2 b D 1 c D 2 d T 1 e T 2 f Q g (I)

[0059] in:

[0060] M 1 =R 1 R 2 R 3 SiO 1 / 2

[0061] M 2 =R 4 R 5 R 6 SiO 1 / 2

[0062] D 1 =R 7 R 8 SiO 2 / 2

[0063] D 2 =R 9 R 10 SiO 2 / 2

[0064] T 1 =R 11 SiO 3 / 2

[0065] T 2 =R 12 SiO 3 / 2

[0066] Q = SiO 4 / 2

[0067] where R 1 、R 2 、R 3 、R 7 、R 8 and R 11 are independently selected from C1-C30 hydrocarbons, C6-C30 aryls or C1-C30 alkoxys;

[0068] R 4 、R 5 、R 6 、R 9 、R 10 and R 12 are independently selected from C1-C30 hydrocarbons, C6-C30 aryls, C1-C30 alkoxys and C2-C30 alkenyls, provided that one or more of the R 4 、R<​​​​​​​​​​​​​​​​​​​​​​​​​​​​12 Can be independently selected from C1-C30 hydrocarbons, C2-C20 hydrocarbons, C3-C15 hydrocarbons or C4-C10 hydrocarbons; C6-C30 aryl, C8-C20 aryl or C10-C15 aryl; or C1-C30 alkoxy, C2-C20 alkoxy, C3-C15 alkoxy or C4-C10 alkoxy. In an embodiment, R1-R12 is selected from C1-C4 hydrocarbons, C1-C3 hydrocarbons or C1-C2 hydrocarbons. The aryl group may be a monocyclic or polycyclic structure. In the case where the aryl group comprises multiple aromatic rings, the rings may be separated by a bond or a spacer group (e.g., an alkylene group), or two or more rings may be fused rings. In an embodiment, the aryl group is selected from phenyl. 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 a methoxy group.

[0072] In one embodiment, the alkenyl functional silicone comprises two or more alkenyl functional groups (ie, 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 has the formula M 1 a D 2 d Q g .

[0073] The alkenyl-functional siloxane may be present in an amount from about 40 wt % to about 80 wt %, from about 45 wt % to about 75 wt %, or from about 50 wt % to about 65 wt %, based on the total weight of the composition.

[0074] Further, it will be understood that the composition may include a mixture of two or more alkenyl functional silicones. Where multiple alkenyl functional silicones are used, the alkenyl functional silicones may be of different types (e.g., different overall makeups with respect to M, D, T, and Q units), different sizes (e.g., having similar M, D, T, Q structures but differing in the number of corresponding units), and / or different viscosities. The composition may include a mixture of siloxanes of different types with respect to M, D, T, and Q units. For example, the composition may include a mixture of two or more MD, MDT, MQ, and / or MDQ alkenyl functional resins conforming to formula (I).

[0075] In one embodiment, the composition comprises a first alkenyl functional silicone wherein the terminal alkenyl functional group (ie, terminated by one or more alkenyl functional groups) has the formula M 2 D 1 c M2 ; and having formula M 1 a D 2 d Q g In one embodiment, the alkenyl functional silicone comprises from about 50% to about 80% by weight of an alkenyl functional terminated siloxane and from about 20% to about 50% by weight of an alkenyl functional siloxane having pendant alkenyl functional groups, based on the total weight of the alkenyl functional siloxane.

[0076] It will also be understood that the alkenyl functional siloxane can be provided as a mixture of two or more alkenyl functional siloxanes of different particle 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 a relatively low viscosity and the second viscosity is a higher viscosity than the first viscosity. In one embodiment, the composition comprises a first alkenyl-functional siloxane having a viscosity of from about 500 cps to about 10,000 cps, from about 1,000 cps to about 7,500 cps, from about 2,000 cps to about 5,000 cps, or from about 3,000 cps to about 4,000 cps, and a second alkenyl-functional siloxane having a viscosity of from about 12,000 cps to about 100,000 cps, from about 15,000 cps to about 90,000 cps, from about 20,000 cps to about 80,000 cps, or from about 30,000 cps to about 70,000 cps. Where a mixture of alkenyl-functional siloxanes of different viscosities is employed, the alkenyl-functional siloxanes may have the same or different base types or formulas. For example, the alkenyl functional siloxanes may all be of the same type, such as MD, MDQ, MDT, MQ, etc., or they may be a mixture of different types. In one embodiment, the composition comprises a mixture of alkenyl functional siloxanes of different viscosities, wherein the alkenyl functional siloxanes have the structure M 1 a D 2 d Q g .

[0077] Hydride-functional siloxanes

[0078] The composition includes a hydride functional siloxane. The hydride functional siloxane can function as a crosslinking agent and may also be referred to herein as a crosslinking agent. The hydride functional siloxane can be selected from compounds of the following formula:

[0079] M 1 h M4 i D 3 j D 4 k T 3 m T 4 n Q o (II)

[0080] in:

[0081] M 3 =R 13 R 14 R 15 SiO 1 / 2

[0082] M 4 =R 16 R 17 R 18 SiO 1 / 2

[0083] D 3 =R 19 R 20 SiO 2 / 2

[0084] D 4 =R 21 R 22 SiO 2 / 2

[0085] T 3 =R 23 SiO 3 / 2

[0086] T 4 =R 24 SiO 3 / 2

[0087] Q=SiO 4 / 2

[0088] where R 13 、R 14 、R 15 、R 19 、R 20 、R 23 and are independently selected from C1-C30 hydrocarbon, C6-C30 aryl or C1-C30 alkoxy;

[0089] R 16 、R 17 、R 18 、R 21 、R 22 and R 24independently selected from hydrogen, C1-C30 hydrocarbons, C6-C30 aryl, C1-C30 alkoxy or C2-C30 alkenyl, provided that R 16 、R 17 、R 18 、R 21 、R 22 and / or R 24 one or more of is hydrogen;

[0090] The subscripts a, b, c, d, e, f, g are zero or positive numbers, subject to the following restrictions: 1 < h + i + j + k + m + n + o < 100, and i + k + n > 0.

[0091] R 13 -R 24 can be independently selected from C1-C30 hydrocarbons, C2-C20 hydrocarbons, C3-C15 hydrocarbons or C4-C10 hydrocarbons; C6-C30 aryl, C8-C20 aryl or C10-C15 aryl; or C1-C30 alkoxy, C2-C20 alkoxy, C3-C15 alkoxy or C4-C10 alkoxy. In an embodiment, R1-R12 are selected from C1-C4 hydrocarbons, C1-C3 hydrocarbons or C1-C2 hydrocarbons. The aryl can be a monocyclic or polycyclic structure. Where the aryl contains multiple aromatic rings, the rings can be separated by a bond or a spacer group (such as an alkylene group), or two or more rings can be fused rings. In an embodiment, the aryl is selected from phenyl. In an embodiment, the alkoxy is selected from C1-C6 alkoxy, C1-C4 alkoxy, C1-C3 alkoxy or C1-C2 alkoxy. In an embodiment, the alkoxy is methoxy.

[0092] In one embodiment, the hydride-functional siloxane is M 3 h D 4 k M 3 h type.

[0093] The hydride-functional organosilicon (or a mixture of two or more alkenyl-functional organosilicons) 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.

[0094] Titanium dioxide

[0095] The present composition includes titanium dioxide particles. The titanium dioxide particles can be provided in any suitable form / morphology, including rutile form, anatase form, or a mixture thereof. In one embodiment, the composition includes rutile titanium dioxide particles. In one embodiment, the composition includes anatase titanium dioxide particles. In one embodiment, the composition includes a mixture of rutile titanium dioxide particles and anatase titanium dioxide particles.

[0096] The titanium dioxide particles may have a particle size desired for a particular purpose or target application. 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 will 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 particle size of the titanium dioxide particles will be about 50 nm to about 200 nm, about 60 nm to about 75 nm. The size of the titanium dioxide particles (or grains) mentioned herein will be understood to mean the average particle size of the titanium dioxide particulate material. Where the particle size is modified by the term "about", this will be understood to encompass particle sizes that are slightly larger or smaller than the value shown, to account for experimental errors inherent in the measurement and variability between different methods of measuring particle size, which will be apparent to those skilled in the art. The diameter can be measured, for example, by transmission electron microscopy (TEM) and X-ray diffraction (XRD).

[0097] Alternatively, the particles may be characterized by surface area. Typically, titanium dioxide will have a surface area greater than about 20 m² as measured by any suitable method, including the 5-point BET method. 2 More typically, the titanium dioxide particles have a surface area greater than about 50 m 2 / g or above about 70 m 2 In an embodiment, the titanium dioxide particles have a surface area greater than about 100 m 2 / g, and even higher than about 150 m 2 In some embodiments, the titanium dioxide photocatalyst will have a surface area greater than about 200 m 2 / g, above about 250 m 2 / g, or even higher than about 300 m 2 In an embodiment, the titanium dioxide has a surface area of ​​about 20 m 2 / g to about 500 m 2 / g, about 50 m 2 / g to about 400 m2 / g, about 75 m 2 / g to about 300 m 2 / g, about 100 m 2 / g to about 250 m 2 / g or about 150 m 2 / g to about 200 m 2 / g of surface area.

[0098] It will be understood that the composition may comprise a mixture of titanium dioxide particles of different particle sizes. For example, the composition may comprise a first set of titanium dioxide particles having a first average particle size and a second set of titanium dioxide particles having a second average particle size, wherein the first average particle size is different from the second average particle size.

[0099] It may be desirable to employ titanium dioxide particles having a relatively small average particle size. While the use of larger particles in greater concentrations does not negatively affect the performance and properties of the composition, it may affect the appearance of the composition when cured on a surface. In particular, the use of larger particles may provide a more matte or textured finish.

[0100] Titanium dioxide may be treated or untreated. In one embodiment, the titanium dioxide particles include a surface treatment. The surface treatment may 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 aluminum oxide. The titanium dioxide particles may also be treated with a polymer selected from carboxymethyl starch, carboxymethyl dextran, carboxymethyl cellulose, polycarboxylic acid, and a copolymer containing a carboxyl unit. 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 acrylic acid / sulfonic acid monomer copolymers).

[0101] Titanium dioxide can be present in an amount from about 20 wt % to about 50 wt %, from about 25 wt % to about 45 wt %, or from about 30 wt % to about 40 wt %, based on the total weight of the composition.

[0102] filler

[0103] In addition to titanium dioxide, the composition optionally includes one or more fillers. Fillers can be selected according to what is desired for a particular purpose. For example, they can contribute to other desirable properties (such as intensity) of the composition. Optional fillers should not weaken or hinder composition reflectivity, emissivity, etc. Therefore, common fillers such as carbon black, graphene, graphite or other dark fillers can be less desirable in the present composition and are excluded from the present composition in an embodiment.

[0104] Examples of suitable fillers include, but are not limited to, silicone resins, silica, nanosilica, fumed silica, particulate forms of oxides of cerium, aluminum, zinc, zirconium, and other metals and metalloids, with or without surface modification, glass fiber, inorganic fillers (such as talc, silicon carbide, mica, boron nitride), inorganic fillers (such as clay, kaolin, calcium carbonate), etc. In one embodiment, the composition includes a filler selected from silica and / or zinc oxide.

[0105] In one embodiment, the composition comprises fumed silica. The fumed silica can be functionalized as desired. In one embodiment, the fumed silica is functionalized by 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 cycloorganosiloxane, a low viscosity polyorganosiloxane having a silanol group and / or an alkoxy, aryloxy or cycloalkoxy group, or an organosilicon resin having a silanol group and / or an alkoxy, aryloxy or cycloalkoxy group. Examples of alkoxy groups include those 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 one embodiment, the fumed silica is functionalized with a functionalizing agent selected from silanol-blocked polydimethylsiloxane, octaphenylcyclotetrasiloxane, octamethylcyclotetrasiloxane, and hexamethyldisilazane (HMDZ). Other examples of the first organosilicon functionalizing agent include diphenylsilanediol, dimethylsilanediol, methyltriethoxysilane, and phenyltrimethoxysilane. The low-viscosity polyorganosiloxane may contain one or more types of organic groups selected from methyl, phenyl, vinyl, and 3,3,3-trifluoropropyl. Suitable low-viscosity polyorganosiloxanes have a viscosity measured at 25°C in the range of about 1 to about 300 centipoise in one embodiment, and about 5 to about 100 centipoise in another embodiment. Examples of the halogenated silane include halogenated trialkylsilanes such as chlorotrimethylsilane; halogenated triarylsilanes such as chlorotriphenylsilane; dichlorodimethylsilane, bis(chlorodimethylsilyl)methane, trichloromethylsilane, bromotrimethylsilane and the like.

[0106] 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.

[0107] 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 can be a single substance or a mixture of two or more substances.

[0108] catalyst

[0109] The composition includes a hydrosilation catalyst. In one embodiment, the hydrosilation catalyst may be a platinum-based catalyst. For example, the hydrosilation catalyst may be a Speier catalyst or a Karstedt catalyst. Suitable Speier catalysts may include chloroplatinic acid and HPtCl, which are known in the art. 6。 Suitable Karstedt catalysts may include (Pt2{[CH2═CH)Me2Si]2O}3) catalysts known in the art. In one embodiment, the hydrosilation catalyst is selected from a Karstedt catalyst having the formula (Pt2{[CH2═CH)Me2Si]2O}3), wherein Me is a methyl group. The Karstedt catalyst exhibits better productivity for the hydrosilation reaction than the Speier catalyst. In addition, the Karstedt catalyst is commercially available in solution form to control catalyst concentration, stability, viscosity, and inhibition. More preferably, platinum (0)-1,3-divinyl-1,1,3,3-tetramethyldisiloxane (0.1 M in xylene) is used as the Karstedt catalyst. The catalyst may be used in an amount to provide a platinum metal concentration in an amount from about 0.0008 to 0.01 wt %, preferably between 0.0001 and 0.005, and more preferably between 0.001 and 0.002.

[0110] inhibitors

[0111] Optionally, the composition may include an inhibitor to slow down or delay the catalytic activity of the platinum catalyst. Examples of suitable 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, trialkyl cyanurates, alkyl maleates, organic sulfoxides, organic amines, diamines, phosphines and phosphonates (phosiphites), nitriles, diaziridines, and oximes, acetylene compounds, phosphites (esters) (phosiphites), maleates, amines or alcohols, by which the processing life, onset temperature and crosslinking rate of the composition of the present invention can be targeted.

[0112] Adhesion promoter

[0113] The composition may optionally include an adhesion promoter. Suitable adhesion promoters may be selected from alkoxy or aryloxy silanes, such as, but not limited to, γ-aminopropyltrimethoxysilane, 3-glycidyloxypropyltrimethoxysilane, bis(trimethoxysilylpropyl)fumarate, or tetracyclic siloxanes 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 functional groups, cyclosiloxanes containing alkoxysilyl and Si-H functional groups, cyclosiloxanes containing aryloxysilyl functional groups, titanates, trialkoxyaluminum, tetraalkoxysilanes, and mixtures thereof.

[0114] 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.

[0115] UV stabilizers

[0116] The composition optionally includes a UV stabilizer. In an embodiment, the UV stabilizer is selected from an organic UV stabilizer. The organic UV stabilizer can be selected from, but is not limited to, triazines, benzotriazoles, or benzoxazinones. When using triazine 2-(4,6-diphenyl-1,3,5-triazine-2-yl)-5-(hexyl)oxy-phenol (Tinuvin® 1577) or 2-(2'-hydroxyphenyl)-4,6-bis(4-phenylphenyl) (which is sold by BASF under the trade name Tinuvin® 1600), transparency below 370 nm can be achieved at lower UV stabilizer levels, while higher transparency is achieved at wavelengths above 390 nm.

[0117] Two-component composition

[0118] The present composition can generally be provided as a two-component composition. Providing it as a two-component composition can prevent any premature curing of the composition. In one embodiment, the two-component composition is provided as follows: a first component (Component 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 component (Component B) comprising (i) an alkenyl-functional polysiloxane, (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.

[0119] Each component is provided in an amount in each component to provide the desired overall concentration of the component when the components are combined. Where a component is provided in each of the two components, the amount of the component in the first component can be provided in an amount that is roughly equal to the amount of the component in the second component. In one embodiment, the first component and the second component are provided to have the same or relatively similar specific gravity. This can facilitate better mixing of the two components when combined to form a coating. In one embodiment, the first component and the second component have specific gravities that differ from each other by about 8%, 5%, 3%, 2%, or 1% or less.

[0120] The first component and the second component are stored in separate containers or cartridges prior to use.The first component and the second component can be stored at room temperature, for example, from about 18°C ​​to about 25°C.

[0121] A coating formed from a two-component composition is prepared by mixing the first component and the second component, applying the composition to a target surface, and exposing the coating composition to an elevated temperature. In one embodiment, the coating can be cured at room temperature (e.g., about 18° C. to about 25° C.). In one embodiment, the coating is exposed to a temperature of about 80° C. to about 150° C. Furthermore, curing can be achieved within about 1 hour.

[0122] The coating can be applied in any suitable manner currently known in the art or later developed. In an embodiment, the coating can be applied via spraying, brushing, rolling, dipping, scraping, curtain coating, skiving or a combination thereof. By further comprising a composition of a solvent (such as a non-volatile solvent), a spray coating can be adopted. Further, the spraying method includes but is not limited to using a high flow low pressure (HVLP) spray system, an air-assisted / airless spray system or an electrostatic spray system. In a further or alternative embodiment, the coating can be applied in a single application or in multiple applications.

[0123] The composition of the present invention allows the use of direct coating of substrate surface. That is, in an embodiment, coating can be applied to and fully adhere to the surface without primer. For the primer-free coating of composition, generally before the coating composition, the target surface is processed. The surface can be processed in any suitable manner, such as but not limited to solvent cleaning, flame treatment, corona discharge (corona discharge), chemical etching. Chemical etching can include etching by acidic materials. In one embodiment, acid etching can be completed using any protonic acid (such as, for example, sulfuric acid, hydrochloric acid or nitric acid) or organic acid (such as acetic acid). The duration required for acid etching depends on the acid, acid concentration, substrate material and coating composition used. Those skilled in the art can easily determine the precise conditions required for acid etching. Spraying also allows relatively thin coatings to be applied to the target surface.

[0124] Furthermore, the composition was found to allow for the coating of curved surfaces. In particular, the flexibility and properties of the composition allow for easier coating of curved surfaces and provide good surface coverage.

[0125] In another embodiment, the surface can be pre-treated with a primer to enhance the adhesion of the coating. Examples of suitable primer materials include, but are not limited to, tetra-n-butyl titanate and ethyl orthosilicate in a mineral spirit solvent. Such primers are commercially available from Momentive Performance Materials under the name SS4155 primer.

[0126] The coating can be provided at a thickness desired for a particular purpose or intended application. In one embodiment, the coating is provided at a wet thickness of about 50 microns or more. At this level, excellent solar absorptivity is observed in the coating according to the present technology. If desired, thicker coatings can be used, which can reduce solar absorptivity. In one embodiment, the coating, after curing, can have a thickness of about 5 mils or more, about 7 mils or more, or about 10 mils or more.

[0127] The coating can be used on a variety of substrates, including but not limited to metal substrates and plastic substrates. In one embodiment, the substrate is selected from aluminum substrates, magnesium substrates, titanium substrates, etc. Examples of aluminum substrates include but are not limited to bare aluminum, cast aluminum, aluminum alloys, etc.

[0128] Coatings formed from the compositions of the present invention exhibit a wide range of properties that allow the coatings to be used in a variety of applications, including the application of coatings produced from the compositions. s ), high infrared emissivity (ε) and high solar reflectivity (ρ s ) One or more of the following. Using ASTM E903-20, a UV-visible spectrophotometer with an integrating sphere is used to measure the solar absorptivity at T0 (initial absorptivity after curing) and after 1000 hours at 150°C; and using ASTM E903-20, a UV-visible spectrophotometer with an integrating sphere is used to measure the solar reflectivity at T0 and after 1000 hours at 150°C. Emissivity can 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:

[0129] - Solar absorptivity (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; about 0.17 to about 0.20 s ); and / or

[0130] - 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

[0131] - a solar reflectance (ρ) of 0.65 or more, 0.75 or more, 0.8 or more, or 0.85 or more to about 0.65 to about 0.9, about 0.7 to about 0.88, about 0.75 to about 0.85, or about 0.8 to about 0.83 s ).

[0132] The coatings of the present technology also exhibit good flexibility. In 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%.

[0133] Example

[0134] Two-component coating compositions were prepared according to the formulations described in Tables 1 and 2. The coating compositions were prepared by mixing components A and B of the corresponding formulations, applying the composition to a surface, and exposing the composition to a temperature of 80°C for about 1 hour. The solar absorptivity at T0 (initial absorptivity after curing) and after 1000 hours at 150°C were measured using a UV-visible spectrophotometer with an integrating sphere using ASTM E903-20; and the solar reflectivity at T0 and after 1000 hours at 150°C was measured using a UV-visible spectrophotometer with an integrating sphere using ASTM E903-20. These results are shown in Table 3. Table 4 shows the reflectometer data for Formulations 1-8, showing the total absorptivity, total reflectivity, and emissivity after exposure to a temperature of 150°C for 1000 hours.

[0135] Table 1

[0136]

[0137] Table 2

[0138]

[0139] Table 3

[0140]

[0141] Table 4

[0142]

[0143] Figure 1 Total reflectance spectra of films prepared from Formulations 1-8 are shown. Figure 2 The total reflectance spectrum of the film from Formulation 9 is shown.

[0144] As shown in the tables and graphs, films formed from compositions according to the present technology exhibit high solar reflectance, high emissivity, and low solar absorptivity. These properties are observed over extended periods of time. This is particularly true when compared to Formulation 5, which does not include titanium dioxide, and Formulation 9, which has a relatively low concentration of titanium dioxide.

[0145] The above description includes examples of this specification. Of course, for the purpose of describing this specification, it is impossible to describe all conceivable combinations of components or methods, but those skilled in the art will recognize that many further combinations and permutations of this specification are possible. Therefore, this specification is intended to cover all such substitutions, modifications and variations, as long as they are within the spirit and scope of the appended claims. In addition, to the extent that the term "comprising" is used in the detailed description or claims, such term is intended to be inclusive and is used in a manner similar to the term "comprises", as "comprising" will be interpreted as inclusive when used as a transition word in a claim.

[0146] The foregoing description identifies various non-limiting embodiments of thermal control coatings. Modifications may be made by those skilled in the art and those who can make and use the present invention. The disclosed embodiments are for illustrative purposes only and are not intended to limit the scope of the invention or the subject matter set forth in the claims.

Claims

1. A curable coating composition comprising: an alkenyl-functional siloxane; a hydride-functional siloxane; titanium dioxide particles; an addition-curing catalyst; and an optional tackifier.

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

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

4. The curable composition according to any one of claims 1 to 3, wherein the titanium dioxide particles are selected from rutile titanium dioxide, anatase titanium dioxide or a mixture thereof.

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

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

7. The curable composition according to any one of claims 1 to 5, wherein the alkenyl-functional siloxane is selected from compounds of the following formula: M 1 a M 2 b D 1 c D 2 d T 1 e T 2 f Q g (I) wherein: 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 Independently selected from C1-C30 hydrocarbon, C6-C30 aryl or C1-C30 alkoxy; R 4 、R 5 、R 6 、R 9 、R 10 and R 12 are independently selected from C1-C30 hydrocarbons, C6-C30 aryls, C1-C30 alkoxys, and C2-C30 alkenyls, provided that R 4 、R 5 、R 6 、R 9 and / or R 12 One or more of the groups are selected from C2-C30 alkenyl groups; the subscripts a, b, c, d, e, f, g are zero or positive numbers, satisfying the following restrictions: 2 < a + b + c + d + e + f + g < 2000, and b + d + f > 0.

8. The curable composition according to claim 7, wherein the alkenyl functional siloxane is selected from the group consisting of: 2 D 1 c M2, Formula M 1 a D 2 d Q g or combinations thereof.

9. The curable composition of claim 8, wherein the alkenyl functional siloxane comprises a siloxane having the formula M 2 D 1 c The first alkenyl functional siloxane of M2, and the 1 a D 2 d Q g A second alkenyl functional siloxane.

10. The curable composition according to claim 9, wherein the first alkenyl-functional siloxane is present in an amount of about 50 wt% to about 80 wt%, 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 siloxanes.

11. The curable composition according to any one of claims 1 to 10, comprising fumed silica.

12. The curable composition according to 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. The curable composition according to any one of claims 1 to 12, wherein the catalyst is a platinum-based catalyst.

14. The curable composition according to any one of claims 1 to 13, wherein the tackifier is selected from cyclic siloxanes containing Si-H functional groups.

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

16. The composition according to any one of claims 1 to 15, wherein the composition is provided as a two-component composition, comprising: a first component comprising an alkenyl-functional siloxane, titanium dioxide and a catalyst; and a second component comprising an alkenyl-functional siloxane, a hydride-functional siloxane, titanium dioxide and an optional tackifier.

17. The composition of any one of claims 1 to 16, wherein a coating formed from the composition at a thickness of about 1.5 mm to about 2 mm has a solar absorptivity (α s ).

18. The composition of any one of claims 1 to 16, wherein a coating formed from the composition at a thickness of about 1.5 mm to about 2 mm has a solar absorptivity (α s ).

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

20. The composition of any one of claims 1 to 18, wherein a coating formed from the composition at a thickness of from about 1.5 mm to about 2 mm has a solar absorptivity (α s ).

21. The composition of any one of claims 1 to 20, wherein a coating formed from the composition at a thickness of from about 1.5 mm to about 2 mm has a solar reflectance (SR) of 0.65 or greater. s ).

22. The composition of any one of claims 1 to 20, wherein a coating formed from the composition at a thickness of from about 1.5 mm to about 2 mm has a solar absorptivity (α s ).

23. The composition of any one 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 a solar absorptivity (α s ).

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

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

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

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

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

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