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EP-3768782-B1 - COATINGS WITH SOLAR REFLECTIVE PROPERTIES

EP3768782B1EP 3768782 B1EP3768782 B1EP 3768782B1EP-3768782-B1

Inventors

  • GREENWOOD, PETER HARRY JOHAN
  • SLEPSKY, Jonathan
  • NORDIN, JAN
  • SANDIN, Olof

Dates

Publication Date
20260506
Application Date
20190319

Claims (13)

  1. A coating composition comprising an organosilane-functionalised colloidal silica and hollow microspheres, wherein the organosilane-functionalised colloidal silica comprises silica particles with one or more organosilane moieties bound to their surface, and wherein the hollow microspheres comprise a thermoplastic polymeric shell.
  2. The coating composition according to claim 1, which is a solar reflective coating composition or cool roof coating composition.
  3. The coating composition according to claim 1 or claim 2, in which one or more of the following conditions apply: a. at least one of the organosilane moieties comprises one or more hydrohilic groups; b. the degree of modification (DM) of the organosilane-functionalised colloidal silica is in the range of from 0.5 to 3; c. the surface area of the silica particles in the organosilane-functionalised colloidal silica is in the range of from 20 to 1500 m 2 g -1 , or is in the range of from 50 to 900 m 2 g -1 ; d. the hollow microspheres are expandable or expanded polymeric microspheres, comprising a polymeric shell enclosing one or more volatile fluids; e. the volume mean diameter of the hollow microspheres is in the range of from 1 to 500 µm; f. the coating composition is aqueous, and comprises no more than 30 wt% organic solvent; g. the coating composition comprises one or more organic binders which contain at least one resin or polymer; h. the coating composition comprises one or more organic binders selected from natural and synthetic latices comprising at least one resin or polymer.
  4. The coating composition according to claim 3, in which one or more of the following conditions apply: a. one or more of the organosilane moieties contain at least one group selected from hydroxyl, thiol, carboxyl, ester, epoxy, acyloxy, ketone, aldehyde, (meth)acryloxy, amino, amido, ureido, isocyanate and isocyanurate; b. the degree of modification (DM) of the organofunctionalised colloidal silica is in the range of from 0.5 to 2; c. the surface area of the silica particles in the organosilane-functionalised colloidal silica is in the range of from 70 to 600 m 2 g -1 , or is in the range of from 150 to 500 m 2 g -1 ; d. the polymeric shell comprises a nitrile-containing monomer; e. the volume mean diameter of the microspheres is in the range of from 3 to 200 µm, or is in the range of from 5 to 100 µm; f. the organic binder comprises an acrylic and/or polyurethane binder; g. the coating composition forms an elastomeric coating when dry; h. the T g of at least one resin or polymer in the organic binder is less than - 20°C, or less than 0°C, or less than -10°C.
  5. The coating composition according to any one of claims 1 to 4, wherein the coating composition is an elastomeric coating composition.
  6. A substrate coated with a coating composition according to any one of claims 1 to 5.
  7. The substrate as claimed in claim 6, in which the coating composition has dried.
  8. Use of an organosilane-functionalised colloidal silica and hollow microspheres for increasing one or more of the storage stability, the reflectance of radiation over the wavelength range 280 to 2500 nm, and the wet adherence of a solar reflective coating composition or a cool roof coating composition, or for improving one or more of the tear resistance, the tensile strength, the dry adherence, the dirt pick-up resistance to hydrophilic and/or hydrophobic materials, and the coating lifetime and ageing characteristics of a solar reflective coating composition or a cool roof coating composition, wherein the organosilane-functionalised colloidal silica comprises silica particles with one or more organosilane moieties bound to their surface, and wherein the hollow microspheres comprise a thermoplastic polymeric shell.
  9. The use according to claim 8 in which the improvement to tensile strength, the reflectance of radiation over the 280 to 2500 nm range, the wet adherence, and the hydrophilic and/or dirt pick-up resistance is still improved after ageing for at least 1000 h according to ISO 16474-2.
  10. The use according to claim 8 or 9, in which the organosilane-functionalised colloidal silica and the hollow microspheres are as defined in claim 3 or claim 4, and/or the solar reflective coating composition or cool roof coating composition additionally comprises an organic binder as defined in claim 3 or claim 4.
  11. The use according to any of claims 8 to 10, in which the solar reflective coating composition or cool roof coating composition is an elastomeric coating composition.
  12. A method of making a coating composition, comprising mixing an organosilane-functionalised colloidal silica, hollow microspheres and optionally one or more organic binders and/or pigments, wherein the coating composition is as defined in claims 1 to 5.
  13. The method of claim 12, in which the organosilane-functionalised colloidal silica is aqueous, and comprises less than 10wt% organic solvent.

Description

Technical Field The present invention relates to compositions that have solar reflective properties, and which can be used, for example, as a "cool roof coating on buildings. The invention also relates to the use of organosilane-modified colloidal silica for improving properties of a solar reflective coating composition. Background Art Reflective coatings are often applied to structures such as buildings to help improve energy efficiency, typically by reducing the load on air conditioning units. A well-known type of coating is the so-called "cool roof" coating, which has high solar reflectance properties that help to reduce heat build-up. Examples of compositions that have solar reflective properties include those described in CN102399483, CN104449171, CN105778689, US6214450, US8287998 and US9540803. Silica and/or microspheres, such as glass or polymeric microspheres, can also be constituents of such coatings. Colloidal silica has also been used as a constituent of coating compositions, including colloidal silica that has been modified with organosilane groups, as described for example in CN107603360, WO2004/035474, WO2008/057029, WO201 1/054774, WO2012/130763 and WO2013/167501. CN 107603360 A describes a coating comprising the following raw materials in parts by weight: 30-40 parts of fluorocarbon emulsion, 18-25 parts of styrene-acrylic emulsion, 7-12 parts of modified silica sol, 6-10 parts of hollow glass beads, 4-6 parts of ceramic microbeads, 1-2 parts of SiO2 aerogel, 0.2-0.3 part of a coalescing agent, 1-2 parts of a preservative, 1-2 parts of a thickening agent, 0.5-1 part of an antifoaming agent and 0.1-0.2 part of a water repellent. CN 104312337 A describes a novel multifunctional high-quality external wall coating which is characterized by being prepared from the following raw materials in parts by weight: 28-33 parts of pure acrylic emulsion, 10-14 parts of nano silica sol, 0.8-1.3 parts of silane coupling agent kh-550, 7-9 parts of nepheline powder, 3-5 parts of lignin, 2-4 parts of hollow glass bead, 2-4 parts of polypropylene fiber, 2-4 parts of tung oil, 1-2 parts of calcium chloride, 6-8 parts of sodium bentonite, 6-8 parts of modified round grain mortar and 25-30 parts of water. EP 1408097 A1 is directed to heat expandable microspheres comprising a polymer shell and an encapsulated blowing agent in which the shell contains an organosilicon compound. US 2010104809 A1 is directed to cool roof covering that includes a protective coating formed from an aqueous coating composition and aggregate embedded in the protective coating, wherein the roof covering has a solar reflectance of at least 70% and a thermal emittance of at least 0.75. KR 101683739 B1 is directed to a water-borne emulsion adhesive composition and a production method thereof, wherein the water-borne emulsion adhesive composition does not contain organic solvents and therefore, can be added when producing a flame-retardant expandable polystyrene foam to secure water resistance and water repellency, and also improves flame retardancy by reducing the rate of heat transfer and enhancing fire resistance. EP 1094091 A1 is directed to liquid silicone rubber composition that is easy to work with in mixing and that upon curing becomes a foamed silicone rubber with a low specific gravity and low thermal conductivity, a method for manufacturing this composition, and a method for manufacturing a foamed silicone rubber. There remains a need for solar reflective compositions that have improved properties. Summary of Invention The invention is directed towards a solar reflective coating composition comprising an organosilane-functionalised colloidal silica and polymeric hollow microspheres. The invention is also directed towards the use of an organosilane-functionalised colloidal silica and/or polymeric hollow microspheres as components of a solar reflective or cool roof coating composition for improving certain properties of the coating. In one aspect, the organosilane-functionalised colloidal silica and/or hollow microspheres can be used for increasing one or more of the following properties: storage stability, the reflectance of radiation over the wavelength range 280 to 2500 nm, and the wet adherence of a solar reflective coating composition or a cool roof coating composition. In another aspect, the organosilane-functionalised colloidal silica and optionally hollow microspheres can be used in a solar reflective coating composition or a cool roof coating composition, for improving one or more of the following properties: tear resistance, the tensile strength, the dry adherence, and the dirt pick-up resistance to hydrophilic and/or hydrophobic materials. In a further aspect, the hollow microspheres and optionally an organosilane- functionalised colloidal silica can be used in a solar reflective coating composition or a cool roof coating composition, for improving the coating lifetime and ageing characteristics. The organosilane-functionalis