Coating composition

Abstract

An exterior insulation and finish system (EIFS) having a finish layer with high PVC of inorganic fillers and / or pigments is provided, the stain resistance and / or color retention of the exterior insulation and finish system may be improved by adding an alkali metal silanolate to the finish layer in an amount effective to improve stain resistance and / or color retention.

Description

Technical Field

[0001] This application relates to the field of coating compositions. Background Art

[0002] External insulation and finish systems (EIFS) are used on the exterior of buildings to provide good thermal insulation, weather resistance, and appearance at a low cost. EIFS includes at least three layers:

[0003] 1. An insulation layer, which is typically a foam insulation board, such as STYROFOAM TM an insulating material, directly or indirectly attached to a wall substrate by an adhesive or mechanical fasteners;

[0004] 2. A primer layer, which is directly or indirectly attached to the insulation layer, and the primer layer includes a fiber mesh embedded in a coating material; and

[0005] 3. A finish coating layer, which is directly or indirectly attached to the primer layer, and the finish coating contains a coating material that provides weather resistance and the desired appearance.

[0006] Other layers may also be included, such as a water channel below the insulation layer to allow water to escape when water reaches below the EIFS, or a waterproof layer to protect the substrate from water reaching below the EIFS. The EIFS and the layers found therein are described in many published references, such as U.S. Patent Publication 2014 / 0373474 and 2015 / 0159008, and "Application Fast Facts: EIFS" of Publication 832 - 00189 - 01 published by Dow Chemical Company, and can be obtained at dow.com / en-us / market / mkt-building-construction / sub-build-wall-systems-insulation-facade.html.

[0007] The finish coating typically contains inorganic fillers, organic binders, and additives. The fillers generally include sand and other inorganic particles; it may include some materials classified as inorganic pigments, such as titanium dioxide. The binder is typically an emulsion polymer, such as an acrylic polymer. In many cases, the finish layer is designed to have a high solar reflectance in order to minimize the solar heating of the underlying building and reduce the energy and cost required to keep the building cool. In these cases, the filler may contain a high content of white components, such as titanium dioxide and calcium carbonate. Other additives may include known additives for exterior coatings, such as organic pigments, thickeners and flow modifiers, surfactants, antioxidants, and stabilizers.

[0008] Finish coatings are typically applied as aqueous slurries. The slurries generally have a high viscosity such that the finish coatings can be applied with a trowel at a thickness of from 0.1 cm to 2.5 cm when applied vertically. The appearance is generally similar to stucco, and thus the EIFS surface is sometimes referred to as "synthetic stucco".

[0009] EIFS is continuously exposed to the sun and weather. Soiling is a problem for EIFS, especially for light-colored EIFS and EIFS containing a high content of fillers. Light colors show dirt more than dark colors, and soiling can reduce the solar reflectance of light-colored EIFS used in cool building designs. In addition, EIFS containing a high content of fillers is particularly prone to accumulating dirt. Some aromatic compounds are known to improve soil resistance, such as benzophenone and methyl 2-benzoylbenzoate, but they increase the volatile organic compound content of the finish coating.

[0010] Color retention is also a problem for EIFS. Organic colorants are prone to degradation when exposed to sunlight and weather.

[0011] What is needed is a finish coating formulation for EIFS having improved color retention and / or soil resistance. SUMMARY OF THE INVENTION

[0012] We have found that small amounts of alkali metal silanolates in the finish coating can enhance soil resistance and / or color retention. This effect is particularly strong in coatings containing a high content of fillers.

[0013] A first aspect of the invention is an aqueous coating composition comprising:

[0014] a) inorganic fillers at a pigment volume concentration (PVC) of 70 to 90;

[0015] b) an acrylic polymer binder at a concentration effective to bind the fillers and other components of the finish coating to the substrate;

[0016] c) an alkali metal silanolate at a concentration effective to increase the soil resistance or color retention of the resulting coating; and

[0017] d) water in an amount sufficient to completely wet the dry ingredients and provide a slurry.

[0018] A second aspect of the invention is a method of coating a substrate, comprising the steps of: (1) applying an aqueous coating composition to the substrate and (2) drying and hardening the aqueous coating composition, wherein the aqueous coating composition is the aqueous coating composition from the first aspect of the invention. In some embodiments, the substrate comprises an insulating layer and a primer coat of an exterior insulation and finish system, and the aqueous coating composition is applied as a finish coating.

[0019] A third aspect of the present invention is an exterior insulation and finish system attached to the exterior surface of a structure, comprising:

[0020] a) an insulation layer comprising a foamed polymeric insulation material and directly or indirectly attached to a substrate forming the exterior surface of the structure;

[0021] b) a primer coat comprising a fibrous web embedded in a coating material and directly or indirectly attached to the insulation layer; and

[0022] c) a finish coat directly or indirectly attached to the primer coat and comprising:

[0023] i) an inorganic filler at a pigment volume concentration (PVC) of 70 to 90;

[0024] ii) an acrylic polymer binder at a concentration effective to bind the filler and other components of the finish coat to the substrate; and

[0025] iii) an alkali metal silanolate and / or its reaction product at a concentration effective to increase the stain resistance or color retention of the coating. DETAILED DESCRIPTION

[0026] The aqueous coating compositions and resulting coatings of the present invention contain conventional ingredients for finish coats in EIFS: inorganic fillers, organic binders, water, and optional additives. The aqueous coating compositions of the present invention further contain an alkali metal silanolate, and for the finish coat, the content of inorganic fillers and / or pigments is relatively high. A higher content of inorganic fillers and / or pigments generally increases staining and reduces color retention, but in the present invention, staining and color retention can be improved by an alkali metal silanolate and / or its reaction product.

[0027] filler

[0028] The inorganic fillers used in the aqueous coating compositions are water-insoluble powders and granules.

[0029] In some embodiments, the inorganic fillers include oxides, carbonates, and sulfates of silicon, calcium, titanium, and / or aluminum. Examples of commonly used inorganic fillers include silica, titanium dioxide, calcium carbonate, dolomite, kaolin, barium sulfate, wollastonite, mica, talc, feldspar, and glass particles.

[0030] In some embodiments, the fillers may include materials classified as inorganic pigments or pigment extenders. Examples of light-colored inorganic pigments and pigment extenders that may be included in the fillers include titanium dioxide, antimony white, titanium white, zinc white, or barium sulfate, chrome yellow, cobalt yellow, and titanium yellow. The fillers may also include dark inorganic pigments such as oxides of iron and copper and carbon black, but the use of dark or colored inorganic fillers and pigments may reduce the importance of stain resistance and color retention.

[0031] In the field of EIFS, it is known to select fillers having a particle size suitable for aqueous coating compositions. Some examples of coarse fillers can have a particle size of at least 100 μm, or at least 200 μm, or at least 300 μm, or at least 500 μm, and can have a particle size of at most 3 mm, or at most 2 mm, or at most 1.5 mm, or at most 1 mm, or at most 800 μm, or at most 600 μm. Some examples of fine fillers and pigment extenders can have a smaller particle size, such as at least 1 μm and at most 100 μm.

[0032] Inorganic fillers are generally insoluble in water. Dispersants and wetting agents can help maintain a stable slurry or dispersion. Suitable dispersants and wetting agents are known and commercially available, such as under the following trademarks: TAMOL TM , Calgon, and Dispex. In some embodiments, the dispersant can be a polycarboxylate, a polyphosphate, or a block copolymer having a block that interacts with water and a block that interacts with the filler / pigment. In some embodiments, the wetting agent is a surfactant, such as a fatty acid salt, a poly(ethylene oxide) surfactant, or a silicone-based surfactant.

[0033] The amount of filler in a coating formulation can be described using the pigment volume concentration ("PVC"), which is the percentage of the volume of pigment and filler in the total volume of the solid components in the coating formulation. PVC is calculated by Equation 1:

[0034]

[0035] where V p is the dry volume of the pigment, V e is the dry volume of the filler, and V b dry is the dry volume of the binder.

[0036] The aqueous coating composition of the present invention has a PVC of 70 to 90. In some embodiments, the aqueous coating composition contains at least 73 PVC, or at least 75 PVC, or at least 77 PVC, or at least 79 PVC, or 80 PVC. In some embodiments, the aqueous coating composition contains at most 88 PVC, or at most 86 PVC, or at most 84 PVC, or at most 82 PVC. On the one hand, it can be observed that coatings with a higher PVC are more prone to soiling, and thus in some embodiments, aqueous coating compositions in the lower PVC range may be preferred. On the other hand, some embodiments of the formulations of the present invention are particularly effective in reducing the soiling of high-PVC coatings, and thus in some embodiments, it may be desirable to use the present invention in combination with aqueous coating compositions in the high-PVC range.

[0037] The amount of filler can also be described in weight percentages. In some embodiments, based on the weight of the dry ingredients excluding water, the aqueous coating composition contains at least 70 weight percent, or at least 75 weight percent, or at least 80 weight percent, or at least 83 weight percent, or at least 85 weight percent, or at least 86 weight percent, or at least 87 weight percent of filler. ("Dry ingredients" are inorganic fillers, acrylic polymer binders, alkali metal silanolates, and any other solid additives in the aqueous coating composition.) In some embodiments, based on the weight of the dry ingredients excluding water, the aqueous coating composition contains at most 94 weight percent, or at most 93 weight percent, or at most 92 weight percent, or at most 91 weight percent, or at most 90 weight percent of filler. For example, based on the dry ingredients excluding water, the aqueous coating composition can contain 80 weight percent to 93 weight percent, or 85 weight percent to 92 weight percent, or 87 weight percent to 90 weight percent of filler.

[0038] In some embodiments, based on all ingredients including water, the aqueous coating composition contains at least 65 weight percent, or at least 70 weight percent, or at least 72 weight percent, or at least 74 weight percent, or at least 76 weight percent of filler. In some embodiments, based on all ingredients including water, the aqueous coating composition contains at most 90 weight percent, or at most 88 weight percent, or at most 86 weight percent, or at most 84 weight percent, or at most 82 weight percent, or at most 80 weight percent of filler. For example, based on all ingredients including water, the aqueous coating composition can contain 70 weight percent to 90 weight percent, or 72 weight percent to 84 weight percent, or 74 weight percent to 82 weight percent of filler.

[0039] Binder

[0040] The aqueous coating composition of the present invention comprises an acrylic polymer binder at a concentration effective to bind the filler and other components of the aqueous coating composition to a substrate. Acrylic polymer binders and aqueous dispersions containing acrylic polymer binders are known and are commercially available. They are described in publications such as "Paints" (March 18, 2013) published by the Department of Chemistry, University of York at https: / / www.essentialchemicalindustry.org / materials-and-applications / paints.html.

[0041] An acrylic polymer is a polymer or copolymer containing repeating units derived from acrylic monomers. Acrylic monomers include acrylic acid, methacrylic acid, and their esters. Exemplary esters used in acrylic monomers include alkyl esters, such as alkyl groups containing 1 to 8 carbon atoms or 1 to 4 carbon atoms, or in some cases a methyl group or an ethyl group. Examples of useful acrylic monomers are acrylic acid, methacrylic acid, butyl acrylate, 2-ethylhexyl acrylate, methyl acrylate, ethyl acrylate, methyl methacrylate, and ethyl methacrylate.

[0042] Exemplary acrylic polymer binders can contain at least 70 weight percent, or at least 80 weight percent, or at least 90 weight percent, or at least 95 weight percent of repeating units derived from acrylic monomers. Exemplary acrylic polymer binders can contain up to 100 percent of repeating units derived from acrylic monomers. Some exemplary acrylic polymer binders are copolymers containing units derived from two or more acrylic monomers, such as a copolymer of butyl acrylate with methyl methacrylate and / or methacrylic acid.

[0043] Some exemplary acrylic polymer binders can contain crosslinking acrylic monomers, such as ethyl acetoacetoxyethyl methacrylate (AAEM), which is sold under the trade name: Eastman AAEM. The crosslinking monomer enables the acrylic polymer binder to crosslink upon curing when applied as a coating. In some embodiments, no more than 10 mole percent, or no more than 5 mole percent, or no more than 3 mole percent, or no more than 2 mole percent, or no more than 1 mole percent of the repeating units in the acrylic polymer binder are derived from crosslinking acrylic monomers. In some embodiments, 0 mole percent, or at least 0.1 mole percent, or at least 0.5 mole percent, or at least 1 mole percent of the repeating units in the acrylic polymer binder are derived from crosslinking acrylic monomers. Examples of suitable acrylic polymer binders containing crosslinking acrylic monomers are sold under RHOPLEX TM VSR 1065.

[0044] Some exemplary acrylic polymer binders can contain repeating units derived from non-acrylic ethylenically unsaturated comonomers such as ethylene, vinyl esters (such as vinyl acetate), or styrene. Aryl groups can render acrylic polymers susceptible to degradation by ultraviolet light. In some embodiments, monomers containing aryl groups (such as styrene and phenyl esters of acrylic and methacrylic acids) are minimized. In some embodiments, less than 50 mole percent, or less than 30 mole percent, or less than 20 mole percent, or less than 10 mole percent, or less than 5 mole percent, or less than 2 mole percent of the monomers in the acrylic polymer contain aryl groups. In some embodiments, the acrylic polymer is free of detectable levels of aryl-containing monomers, which is essentially 0 percent.

[0045] On the other hand, styrene monomers can impart other useful qualities to the acrylic polymer binder, such as increased hydrophobicity. In some embodiments, the acrylic polymer binder is a styrene-acrylic copolymer, such as UCAR TM DL 424.

[0046] The choice of acrylic monomers and their proportions depends on the intended use of the acrylic polymer as a binder in an exterior coating. Due to variations in outdoor temperature, the coating may undergo thermal expansion and contraction. The acrylic polymer binder can be selected to have a low Tg, such as at most 0 °C, or -10 °C, or -15 °C, or -20 °C, or -30 °C, or -40 °C. There is no minimum desired Tg, but a Tg below -60 °C is rarely necessary.

[0047] The acrylic polymer binder may also need to remain non-molten at the temperatures to which exterior coatings are typically exposed. In some embodiments, the acrylic polymer binder has a melting temperature of at least 60 °C, or at least 75 °C, or at least 80 °C, or at least 95 °C, or at least 110 °C. There is no maximum desired melting temperature, but temperatures above 200 °C are rarely necessary.

[0048] It is known that increasing the content of certain monomers, such as methyl methacrylate, increases the Tg and melting point of the resulting polymer, and it is known that increasing the content of other monomers, such as butyl acrylate, decreases the Tg and melting point of the resulting polymer. In some embodiments, the acrylic polymer binder comprises at least 7 weight percent or at least 10 weight percent or at least 12 weight percent of units derived from methyl methacrylate. In some embodiments, the acrylic polymer binder comprises at most 50 weight percent or at most 45 weight percent or at most 40 weight percent of units derived from methyl methacrylate. In some embodiments, the acrylic polymer binder comprises at least 50 weight percent or at least 55 weight percent or at least 60 weight percent of units derived from butyl acrylate. In some embodiments, the acrylic polymer binder comprises at most 93 weight percent or at most 90 weight percent or at most 88 weight percent of units derived from butyl acrylate.

[0049] In some embodiments, the average diameter of the particles of the acrylic polymer binder is at least 50 nm, or at least 100 nm, or at least 200 nm. In some embodiments, the average diameter of the particles of the acrylic polymer binder is at most 700 nm, or at most 500 nm, or at most 400 nm.

[0050] Binders typically form films under the conditions under which they are applied to the intended substrate. "Forming a film" means that a substance is capable of forming a film when applied to a solid surface. The ability of polymers and their emulsions to form films is known and described in publications such as: P.A. Steward et al., "An Overview of Polymer Latex Film Formation and Properties", 86 Advances in Colloid and Interface Science at 195 - 267 (2000). Generally, the film-forming ability of a polymer increases with lower molecular weight and / or lower Tg and decreases with higher molecular weight and / or higher Tg.

[0051] In an aqueous coating composition, the binder particles are suspended in an aqueous emulsion. This is typically achieved using an emulsifier, which is generally a surfactant. In some embodiments, the emulsifier is an anionic surfactant, and in some embodiments, the emulsifier is a nonionic surfactant. Examples of suitable emulsifiers are sodium dodecylbenzenesulfonate and sodium lauryl sulfate. Examples of suitable emulsifiers can be found under DOWFAX TM , TRITON TM , TERGITOL TM , ECOSURF TMobtained commercially from Polystep and trademark holders.

[0052] Suitable acrylic polymer binders are commercially available from The Dow Chemical Company under the RHOPLEX TM , PRIMAL TM and UCAR TM trademarks. Other acrylic polymer binders can be prepared by emulsion polymerization of suitable monomers in the presence of a suitable emulsifier. Emulsion polymerization methods are well known and are described in many publications such as Emulsion Polymerization ofAcrylicMonomers , published by Rohm and Haas Company (1966) and available at https: / / ia600709.us.archive.org / 35 / items / emulsionpolymeri00rohm / emulsionpoly meri00rohm.pdf ; Lovell et al., Fundamentals of Emulsion Polymerization, 21 Biomacromolecules 4396 - 4441 (2020); and Juaregui, Thesis: Synthesis and Optimization of Emulsion Polymers published by California Polytechnic State University, San Luis Obispo (2016).

[0053] The aqueous coating compositions of the present invention contain a high pigment volume concentration and therefore must contain a low content of binder, but the binder concentration must be high enough to effectively adhere the dry components of the aqueous coating composition to the substrate when the aqueous coating composition cures. In some embodiments, based only on the dry ingredients and excluding water, the aqueous coating composition contains at least 8 volume percent, or at least 10 volume percent, or at least 12 volume percent, or at least 14 volume percent, or at least 16 volume percent, or at least 18 volume percent of binder. In some embodiments, based only on the dry ingredients and excluding water, the aqueous coating composition contains at most 30 volume percent, or at most 27 volume percent, or at most 25 volume percent, or at most 23 volume percent, or at most 21 volume percent of binder.

[0054] In some embodiments, based on the dry ingredients excluding water, the aqueous coating composition contains at least 4 weight percent, or at least 5 weight percent, or at least 6 weight percent, or at least 7 weight percent, or at least 8 weight percent of a binder. In some embodiments, based on the dry ingredients excluding water, the aqueous coating composition contains at most 18 weight percent, or at most 15 weight percent, or at most 12 weight percent, or at most 10 weight percent of a binder. For example, based on the dry ingredients excluding water, the aqueous coating composition can contain from 5 weight percent to 18 weight percent, or from 6 weight percent to 15 weight percent, or from 7 weight percent to 10 weight percent of a binder.

[0055] In some embodiments, based on all ingredients including water, the aqueous coating composition contains at least 4 weight percent, or at least 5 weight percent, or at least 6 weight percent, or at least 7 weight percent of a binder. In some embodiments, based on all ingredients including water, the aqueous coating composition contains at most 15 weight percent, or at most 12 weight percent, or at most 10 weight percent, or at most 9 weight percent of a binder. For example, based on all ingredients including water, the aqueous coating composition can contain from 4 weight percent to 15 weight percent, or from 5 weight percent to 12 weight percent, or from 6 weight percent to 9 weight percent of a binder.

[0056] In some embodiments, an acrylic polymer binder is added to the aqueous coating composition as an aqueous emulsion. In some embodiments, the aqueous emulsion contains at least 30 weight percent or at least 40 weight percent of the acrylic polymer binder and at most 70 weight percent, or at most 60 weight percent, or at most 50 weight percent of the acrylic polymer binder. In some embodiments, the aqueous emulsion contains at least 30 weight percent, or at least 40 weight percent, or at least 50 weight percent of water and at most 70 weight percent or at most 60 weight percent of water. The weight and volume percentages listed above refer to the weight of the acrylic polymer binder, not the weight of the water in the emulsion containing the acrylic polymer binder.

[0057] Alkali metal silicon alkoxide

[0058] The aqueous coating composition contains an alkali metal silanolate in a concentration effective to increase the stain resistance or color retention of the resulting coating. The alkali metal silanolate generally corresponds to Formula 2:

[0059]

[0060] where each M is independently hydrogen or an alkali metal, the alkali metal being selected such that at least one M is an alkali metal, and R is an organic moiety.

[0061] In some embodiments, one M is an alkali metal, in some embodiments two Ms are alkali metals, and in some embodiments all three Ms are alkali metals. In some embodiments, the alkaline metal silanolate comprises a mixture of substances containing different numbers of metal ions. In some embodiments, the mixture of substances contains on average at least 1.0 alkali metal ions, or at least 1.5 alkali metal ions, or at least 2.0 alkali metal ions, or at least 2.5 alkali metal ions per molecule. In some embodiments, the mixture of substances contains on average at most 3.0 alkali metal ions, or at most 2.5 alkali metal ions, or at most 2.0 alkali metal ions, or at most 1.5 alkali metal ions, or at most 1.25 alkali metal ions, or at most 1.0 alkali metal ions per molecule.

[0062] In some embodiments, the alkali metal is lithium. In some embodiments, the alkali metal is sodium. In some embodiments, the alkali metal is potassium. In some embodiments, the alkali metal silanolate contains a mixture of different alkali metals.

[0063] In some embodiments, the organic moiety R contains no more than 12 carbon atoms, or no more than 8 carbon atoms, or no more than 6 carbon atoms, or no more than 4 carbon atoms. In some embodiments, the organic moiety R contains only 1 carbon atom.

[0064] In some embodiments, the organic moiety R is a substituted or unsubstituted aliphatic group, and in some embodiments it is a substituted or unsubstituted alkyl group. In some embodiments, the organic moiety R is unsubstituted. In some embodiments, the organic moiety R contains alcohol, acid or halide substituents.

[0065] In some embodiments, the organic moiety R is an unsubstituted methyl, ethyl, propyl or butyl group.

[0066] Commercially available common alkali metal silanolates include sodium methyl silanolate and potassium methyl silanolate. An aqueous solution (40 weight percent concentration) containing potassium methyl silanolate can be obtained commercially from Dow Chemical Company under the trademark XIAMETER TM OFS-0777. An aqueous solution (40 weight percent concentration) containing sodium methyl silanolate can be obtained commercially from Dow Chemical Company under the trademark XIAMETER TM OFS-0772. Other silanolates can be prepared by known methods, such as by contacting trichloroorganosilane with water and an alkali metal hydroxide. U.S. Patent 4,252,569 describes a method for preparing alkali metal silanolates and also lists many other patents that describe methods for preparing alkali metal silanolates.

[0067] The concentration of the alkali metal silanolate in the aqueous coating composition can effectively increase the stain resistance or color retention of the resulting coating. In some embodiments, based on the dry components and excluding water, the aqueous coating composition contains at least 0.20 wt%, or at least 0.30 wt%, or at least 0.35 wt%, or at least 0.40 wt%, or at least 0.42 wt%, or at least 0.44 wt% of the alkali metal silanolate. In some embodiments, based on the dry components and excluding water, the aqueous coating composition contains at most 3.5 wt%, or at most 3 wt%, or at most 2 wt%, or at most 1.5 wt%, or at most 1.0 wt%, or at most 0.9 wt%, or at most 0.8 wt%, or at most 0.7 wt%, or at most 0.6 wt%, or at most 0.5 wt% of the alkali metal silanolate. For example, based on the dry components and excluding water, the concentration of the alkali metal silanolate in the aqueous coating composition can be from 0.2 wt% to 3.5 wt%, or from 0.3 wt% to 2 wt%, or from 0.3 wt% to 1 wt%, or from 0.4 wt% to 0.8 wt%, or from 0.4 wt% to 0.6 wt%.

[0068] In some embodiments, based on all components including water, the aqueous coating composition contains at least 0.10 wt%, or at least 0.20 wt%, or at least 0.25 wt%, or at least 0.30 wt%, or at least 0.35 wt%, or at least 0.38 wt%, or at least 0.40 wt% of the alkali metal silanolate. In some embodiments, based on all components including water, the aqueous coating composition contains at most 3 wt%, or at most 2 wt%, or at most 1.5 wt%, or at most 1.0 wt%, or at most 0.9 wt%, or at most 0.8 wt%, or at most 0.7 wt%, or at most 0.6 wt%, or at most 0.5 wt% of the alkali metal silanolate. For example, based on all components including water, the concentration of the alkali metal silanolate in the aqueous coating composition can be from 0.1 wt% to 3 wt%, or from 0.2 wt% to 2 wt%, or from 0.3 wt% to 1 wt%, or from 0.35 wt% to 0.8 wt%, or from 0.35 wt% to 0.6 wt%.

[0069] In some embodiments, the weight ratio of the alkali metal silanolate to the acrylic polymer binder in the aqueous coating composition is at least 5 wt%, or at least 8 wt%, or at least 10 wt%, or at least 12 wt%, or at least 15 wt%, or at least 18 wt%, or at least 20 wt%. In some embodiments, the weight ratio of the alkali metal silanolate to the acrylic polymer binder in the aqueous coating composition is at most 50 wt%, or at most 40 wt%, or at most 35 wt%, or at most 30 wt%, or at most 25 wt%.

[0070] It is known that alkali metal silanolates react with carbon dioxide to form silicone polymers and / or oligomers. Without intending to be limiting, we assume that at least some of the alkali metal silanolate may react after application of the aqueous coating composition such that the cured coating may contain less or no alkali metal silanolate, but may contain reaction products of the alkali metal silanolate. Examples of reaction products can include silicone polymers and oligomers having organic substituents derived from the alkali metal silanolate. In some embodiments, the combined content of the alkali metal silanolate and the reaction products in the cured coating is within the concentration limits set by the alkali metal silanolate in the aqueous coating composition.

[0071] Other additives

[0072] The aqueous coating composition may optionally contain other additives suitable for finish coatings in EIFS in addition to the filler, binder, alkali metal silanolate, and water. Commercial embodiments of EIFS finish coatings typically contain a variety of additives. Many such components are described in Johan Bieleman (ed.), Additives for Coatings, published by Wiley-VCH Verlag GmbH (2000). Some examples of commonly used additives are listed below. All of the additives listed below are commercially available, along with their usage recommendations.

[0073] The aqueous coating composition may optionally contain an effective amount of organic dyes and pigments to color the resulting coating. Examples of suitable organic dyes and pigments include phthalocyanines (blue / green), quinacridones (red / yellow), quinone derivatives, and azo compounds. The aqueous coating composition of the present invention can be used particularly well with organic dyes and pigments because they can provide improved color retention.

[0074] The aqueous coating composition may optionally contain a thickening agent to make it easier to handle and apply. Examples of thickening agents include inorganic materials (such as certain clays) and polymeric thickening agents such as cellulose ethers, starches, and acrylic polymers).

[0075] For various purposes, the aqueous coating composition may optionally contain surfactants. Some surfactants are emulsifiers, wetting agents, and dispersants that help insoluble components enter and remain in an emulsion or dispersion in an aqueous solvent. Some surfactants are defoamers. Some surfactants promote the adhesion of the aqueous coating composition to the substrate.

[0076] The aqueous coating composition may optionally contain hydrophobic additives to improve the ability of the resulting coating to resist water penetration. Examples of hydrophobic components may include waxes and polymers (such as polypropylene), as well as silicone, silane, or siloxane components.

[0077] The aqueous coating composition may optionally contain leveling agents and coalescing agents. Examples of leveling additives include certain polyacrylate polymers having a low glass transition temperature, such as -20 °C or lower. Coalescing agents promote the interaction of binder molecules when the coating dries on the substrate to form a uniform solid film that is no longer soluble when exposed to fresh water. Examples of coalescing agents include:

[0078] ● Certain branched and cyclic alkanes,

[0079] ● Certain esters, such as 3-hydroxy-2,2,4-trimethylpentyl isobutyrate (TPiB), diesters of adipic acid (ADE), dimethyl phthalate (DMP), 2-hydroxypropyl ethylhexanoate (HPE), and benzyl benzoate, and

[0080] ● Certain ether alcohols, such as ethylene glycol butyl ether, propylene glycol butyl ether, dipropylene glycol butyl ether (DPB), and propylene glycol and ethylene glycol phenyl ethers (PPH and EPH).

[0081] The aqueous coating composition may optionally contain antioxidants. Antioxidants may include primary antioxidants (such as certain amines or sterically hindered phenols) and / or secondary antioxidants (such as certain organophosphates or thioesters).

[0082] The aqueous coating composition may optionally contain light and ultraviolet (UV) stabilizers. Examples of light and ultraviolet (UV) stabilizers may include:

[0083] ● UV absorbers, such as benzotriazoles and other compounds having coordinated double bonds; and

[0084] ● Sterically hindered amines, such as compounds containing 2,2,6,6-tetramethylpiperidine groups.

[0085] The aqueous coating composition may optionally contain other additives in addition to the alkali metal silanolates to further improve the stain resistance (DPUR) of the resulting coating. Examples of DPUR additives include some aromatic compounds (such as benzophenone and methyl 2-benzoylbenzoate), some fluorinated surfactants, some waxes, and some silicones (such as polydimethylsiloxane (PDMS)).

[0086] In some embodiments, based on the dry components excluding water, the amount of additives (excluding alkali metal silanolates) does not exceed 8 weight percent of the aqueous coating composition, or does not exceed 6 weight percent, or does not exceed 5 weight percent, or does not exceed 4 weight percent, or does not exceed 3 weight percent. The amount of additives (excluding alkali metal silanolates) can be 0 weight percent, but in some embodiments, the amount of other additives is at least 0.2 weight percent, or at least 0.5 weight percent, or at least 0.8 weight percent, or at least 1 weight percent, or at least 1.5 weight percent, or at least 2 weight percent. In some embodiments, the amount of additives (excluding alkali metal silanolates) is low enough such that the volume percent, the weight percent excluding water, and the weight percent including water are approximately the same, and thus the previously described concentrations are also applicable to volume percent and weight percent including water. For example, in some embodiments, based on the dry weight of the components and excluding water, the aqueous coating composition contains 0.2 weight percent to 8 weight percent, or 0.5 weight percent to 5 weight percent, or 1 weight percent to 3 weight percent of additives. In some embodiments, based on all components including water, the aqueous coating composition contains 0.2 weight percent to 8 weight percent, or 0.5 weight percent to 5 weight percent, or 1 weight percent to 3 weight percent of additives.

[0087] Water

[0088] The aqueous coating composition contains water. The amount of water is suitable to fully wet the dry components and form a slurry. In some embodiments, the slurry has a low enough viscosity such that it can be applied smoothly and has a high enough viscosity such that it can be applied to a vertical surface and dry without substantially flowing down the surface. In some embodiments, the viscosity of the aqueous coating composition is at least 70 PU, or at least 80 PU, or at least 90 PU. In some embodiments, the viscosity is at most 120 PU, or at most 130 PU, or at most 140 PU.

[0089] In some embodiments, the aqueous coating composition contains at least 5 wt%, or at least 8 wt%, or 9 wt%, or at least 10 wt% water. In some embodiments, the aqueous coating composition contains at most 25 wt%, or at most 20 wt%, or at most 18 wt%, or at most 16 wt% water. For example, in some embodiments, the aqueous coating composition contains 5 wt% to 25 wt%, or 5 wt% to 20 wt%, or 8 wt% to 18 wt%, or 9 wt% to 15 wt% water. Note that in some cases, the acrylic polymer binder, alkali metal silanolate, and / or other additives in the aqueous coating composition can be added as a solution, emulsion, or suspension containing water; in such cases, only a small amount of additional water may be required to achieve the desired water content in the overall aqueous coating composition.

[0090] In some embodiments, the aqueous coating composition further contains an organic solvent miscible with water. Examples of suitable organic solvents include alcohols and diols. In some embodiments, the amount of the organic solvent does not exceed 8 wt%, or does not exceed 6 wt%, or does not exceed 5 wt%, or does not exceed 4 wt%, or does not exceed 3 wt% of the aqueous coating composition (including water). The amount of the organic solvent can be 0 wt%, but in some embodiments, the amount of the organic solvent is at least 0.5 wt%, or at least 1 wt%, or at least 1.5 wt%, or at least 2 wt%. In some embodiments, the amount of the organic solvent is low enough such that there is no substantial difference between volume percentage and weight percentage, and thus the previously described concentrations are also applicable to volume percentage.

[0091] In one embodiment, the aqueous coating composition comprises:

[0092] 1. Inorganic filler with a pigment volume concentration of 1.76 to 86;

[0093] 2. 2.5 wt% to 12 wt% of an acrylic polymer binder;

[0094] 3. 0.3 wt% to 1 wt% of an alkali metal silanolate;

[0095] 4. 0.5 wt% to 5 wt% of other additives; and

[0096] 5. 5 wt% to 20 wt% of water,

[0097] wherein the weight percentages are based on the weight of all components including water.

[0098] Use of aqueous coating compositions and coatings obtained

[0099] Among other uses, the aqueous coating composition can be used to prepare an exterior coating on a substrate, and in particular a finish coating in an exterior EIFS. First, the aqueous composition is applied directly or indirectly to the substrate. Second, the aqueous composition is cured (dried and hardened). Each of these steps is well known.

[0100] In some embodiments, the substrate is a vertical surface, such as a wall, or more specifically the exterior wall of a building. Examples of suitable substrates for walls include any known building surface material, such as wood, gypsum, concrete, or composite panels. In a specific embodiment, the substrate includes an insulating layer and a primer coat of EIFS, and the aqueous coating composition is used to form a finish coating of the EIFS.

[0101] The composition can be applied by known means. For example, depending on the viscosity, it can be troweled and spread, or it can be brushed or roll-coated. If the aqueous coating composition is applied with a trowel, it can also be smooth or textured, and a design can be added. It is known that some weather conditions, such as rain or extremely cold or humid conditions, may not be suitable for applying the aqueous coating composition and can be avoided.

[0102] In some embodiments, the aqueous coating composition is applied with an average thickness of at least 0.05 cm, or at least 0.1 cm, or at least 0.15 cm, or at least 0.2 cm, or at least 0.5 cm. In some embodiments, the aqueous coating composition is applied with an average thickness of at most 5 cm, or at most 3 cm, or at most 2.5 cm, or at most 2 cm, or at most 1.5 cm.

[0103] After its application, the aqueous coating composition is allowed to cure (dry and harden). The time required for the aqueous coating composition to cure can vary widely depending on the water content of the aqueous coating composition and environmental conditions such as temperature and humidity. In some embodiments, the aqueous coating composition dries to the touch in no more than 12 hours, or no more than 6 hours, or no more than 4 hours, or no more than 2 hours, or no more than 1 hour after its application. In some embodiments, the aqueous coating composition dries to the touch in at least 5 minutes, or at least 10 minutes, or at least 15 minutes, or at least 20 minutes, or at least 30 minutes.

[0104] After curing is complete, the aqueous coating composition produces a cured coating that is directly or indirectly attached to the selected substrate. In EIFS, the cured coating can be a finish layer on the EIFS, which includes the insulating layer and the primer coat as described above.

[0105] The cured coating has a content derived from the solids content of the aqueous coating composition. For example, based on the total weight of the dry ingredients, the cured coating may contain:

[0106] 1. Fillers from 1.70 PVC to 90 PVC, as described above;

[0107] 2. An acrylic polymer binder in an amount suitable for attaching the filler to the substrate;

[0108] 3. An alkali metal silanolate and / or its reaction product, the concentration of which can effectively increase the stain resistance or color retention of the resulting coating; and

[0109] 4. Other additives in an amount of 4.0 to 8 weight percent.

[0110] The amounts and descriptions of these components in the cured coating are similar to those of the aqueous coating composition, excluding water. The cured coating typically contains less than 2 weight percent, or less than 1 weight percent, or less than 0.5 weight percent of water.

[0111] As described above, the alkali metal silanolate may have reacted in whole or in part to form reaction products such as organosilicon.

[0112] In some embodiments, when measured according to the test method, the cured coating has a stain resistance of at least 50 percent, or at least 60 percent, or at least 65 percent, or at least 70 percent, or at least 75 percent, or at least 80 percent, or at least 85 percent, or at least 90 percent. There is no maximum desired stain resistance, but in some cases, a stain resistance greater than 98 percent or 85 percent may be unnecessary.

[0113] In some embodiments, when measured according to the test method, the cured coating has a stain resistance that is at least 20 percent, or at least 30 percent, or at least 50 percent, or at least 75 percent, or at least 90 percent, or at least 100 percent greater than a similar cured coating without the alkali metal silanolate. There is no maximum desired improvement in stain resistance, but in some cases, an improvement greater than 300 percent or 200 percent may be unnecessary.

[0114] In some embodiments, when measuring color change according to the test method, the cured coating has a color change (ΔE) of no more than 18, or no more than 15, or no more than 12, or no more than 10, or no more than 8, or no more than 6 after 5000 hours. There is no minimum desired color change, but in some cases, a color change less than 2 or 4 may be unnecessary.

[0115] In some embodiments, when measuring the color change according to the test method, the cured coating has a color change (ΔE) that is at least 1 percentage point less, or at least 2 percentage points less, or at least 4 percentage points less, or at least 6 percentage points less, or at least 8 percentage points less, or at least 10 percentage points less than the color change (ΔE) of a similar cured coating without alkali metal silanolate. There is no maximum desired improvement in terms of color loss, but in some cases, an improvement greater than 20 percentage points or 15 percentage points may be unnecessary. In terms of color loss, but in some cases, an improvement greater than 20 percentage points or 15 percentage points may be unnecessary.

[0116] Test Method

[0117] The parameters described in this application can be measured using the following measurement methods:

[0118]

[0119] Pigment volume concentration : The pigment volume concentration (PVC) is calculated by the following formula:

[0120]

[0121] where V p is the volume of the pigment, V e is the volume of the filler, and V b dry is the dry volume of the binder.

[0122] Stain resistance: Use the following materials and equipment

[0123]

[0124]

[0125]

[0126]

[0127] Color retention :

[0128] Add the Colortrend 888 - 7214 blue dye colorant at 2 wt% to each finish. Apply the sample to the substrate and cure as described for soil resistance in Step 1.

[0129] According to ASTM G - 155b, using 102 minutes of drying / 18 minutes of wetting, 100% light, and 0.35 W / m 2The cycle of irradiance, weathering tests on cured samples were carried out in an Atlas Ci5000 Weather-o-meter. Colors were measured before weathering and after 3000 and 5000 hours of exposure according to ASTM2244. According to the change in CIE L*a*b* color scale units, the color change value represented by ΔE was calculated according to the following equation:

[0130] ΔE = [(L* 测量值 – L* 初始值 ) 2 + (a* 测量值 – a* 初始值 ) 2 + (b* 测量值 – b* 初始值 ) 2 ) 0.5

[0131] Example

[0132] The following examples illustrate some embodiments of the present invention, but do not limit the full scope of the present invention.

[0133] Eight finish coating compositions containing the components listed in Tables 1 to 3 were prepared. The PVC of each formulation is listed in the table.

[0134] Table 1

[0135]

[0136] Table 2

[0137]

[0138]

[0139] Table 3

[0140]

[0141]

[0142] Dirt resistance (DPUR) test

[0143] Finish 1 and Finish 2 were blended with an aqueous solution of potassium methylsilanolate (XIAMETER TM OFS-0777, 40% to 45% solids) in the proportions listed in Table 4 to prepare Examples 1 to 6 of the present invention. Finish 1 and Finish 2 were also blended with the following other additives in the proportions listed in Table 4 to prepare Comparative Examples 1 to 8.

[0144] ·DOWSIL TM Z70 Silicone Polymer Emulsion (60% solids)

[0145] ·DOWSIL TM Q1-3563 Silicone Fluid

[0146] ·SP 1: A stabilizer package containing 2 parts of Tinuvin 1130 hydroxyphenyl benzotriazole UV absorber and 1 part of Tinuvin 292 hindered amine stabilizer.

[0147] For clarity, in Examples IE1, IE2, and CE2 to CE4, the DPUR additive (potassium methyl silanolate solution or alternative additive) was added to the fully formulated finish 1 or finish 2. In Examples IE3 to IE6 and CE6 to CE8, the DPUR additive was added to the binder before mixing the DPUR additive with the other components to form finish 1 or finish 2.

[0148] The sample finishes were applied to the boards and the stain resistance was tested as described in the test method. The results are listed in Table 4.

[0149] Table 4

[0150]

[0151]

[0152] 1 - Y Reflectance retention %. The higher the value, the less dirt is retained and the better the DPUR.

[0153] 2–XIAMETER TM OFS-0777 contains approximately 40 weight percent solids in water. The measured amount refers to the solution, not the solids.

[0154] Color retention

[0155] Finishes 1 and 2 were blended with XIAMETER TM OFS-0777 aqueous potassium methyl silanolate solution (40% to 45% solids) in the proportions listed in Table 5 to prepare Examples 7 to 8 of the present invention. Finishes 1 and 2 were also blended with the other additives listed previously in the proportions listed in Table 5 to prepare Comparative Examples 9 to 16. Colortrend 888-7214 blue dye colorant was added to each finish at 2 weight percent. The finishes were applied to the boards and the color loss was tested as described in the test method, i.e., the color after drying was tested, followed by accelerated light aging for 5045 hours, and then the color was measured again. The results are listed in Table 5.

[0156] Table 5

[0157] Example Finishing agent DPUR Additives Additive Wt.% <![CDATA[Color loss 2 > IE7 1 <![CDATA[XIAMETER TM OFS-0777]]> 1 6.7 IE8 2 <![CDATA[XIAMETER TM OFS-0777]]> 1 15.6 CE9 1 none 0 9.9 CE10 1 <![CDATA[DOWSIL TM Z70]]> 1.5 7.2 CE11 1 <![CDATA[DOWSIL TM Q1-3563]]> 2 9 CE12 1 SP1 0.25 5.7 CE13 2 none 0 21.2 CE14 2 <![CDATA[DOWSIL TM Z70]]> 1.5 7.7 CE15 2 <![CDATA[DOWSIL TM Q1-3563]]> 2 8.1 CE16 2 SP1 0.25 15.7

[0158] 2 - ΔE. The smaller the value, the less color loss and the better the color retention.

[0159] The color retention test was repeated for finishing agents 3 to 8 using 3000 - hour and 5000 - hour light aging. The results are listed in Table 6.

[0160] Table 6

[0161]

[0162] Formula with high TiO2 and benzophenone

[0163] Finishing agent 2 was repeated, except that the finishing agent contained 6 weight percent TiO₂ and 0.3 weight percent benzophenone was added. The finishing agent sample was blended with additional soiling (DPUR) additives shown in Table 7. The sample was applied to a board and the soil resistance was tested according to the test method. The results are listed in Table 7. The example named IE is an example of the present invention, and the example named CE is a comparative example.

[0164] Table 7

[0165] Example No. DPUR Additives <![CDATA[DPUR 1 > Internet Explorer 15 <![CDATA[1% XIAMETER TM OFS-0777 Silanol Solution]]> 66 Internet Explorer 16 <![CDATA[1% XIAMETER TM OFS-0772 Silanol Solution]]> 57 CE 41 none 47 CE 42 <![CDATA[1% DOWSIL TM Z-70 silicone emulsion]]> 44 CE 43 <![CDATA[1% DOWSIL TM Silicone fluid Q1-3563]]> 36

[0166] 1 - Y reflectance retention %. The higher the value, the less dirt is retained and the better the DPUR.

[0167] Formulated with high TiO2 and styrene acrylic binder

[0168] Finishing agent 2 was repeated, except that the finishing agent contained 6 weight percent TiO₂ and UCAR TM DL 424 (styrene - acrylic binder) was used instead of PRIMAL TM WDV - 2001 binder. The finishing agent sample was blended with additional DPUR additives shown in Table 8. The sample was applied to a board and the soil resistance was tested according to the test method. The results are listed in Table 8. The example named IE is an example of the present invention, and the example named CE is a comparative example.

[0169] Table 8

[0170] Example No. DPUR Additives <![CDATA[DPUR 1 > IE 17 <![CDATA[1% XIAMETER TM OFS-0777 Silanol Solution]]> 48 IE 18 <![CDATA[1% XIAMETER TM OFS-0772 Silanol Solution]]> 42 CE 44 none 36 CE 45 <![CDATA[1% DOWSIL TM Z-70 silicone emulsion]]> 35

[0171] 1 - Y reflectance retention %. The higher the value, the less dirt is retained and the better the DPUR

[0172] Formulated with high TiO2, cross-linking binder and benzophenone

[0173] Repeat finish 2, except that the finish contains 6 weight percent TiO2 and uses the crosslinked acrylic binder RHOPLEX TM VSR-1065 in place of PRIMAL TM WDV-2001 binder and add 0.3 weight percent benzophenone. Blend the finish samples with the additional DPUR additives shown in Table 9. Apply the samples to panels and test for stain resistance according to the test method. The results are listed in Table 9. The examples designated IE are examples of the present invention, and the examples designated CE are comparative examples.

[0174] Table 9

[0175] Example No. DPUR Additives <![CDATA[DPUR 1 > IE 19 <![CDATA[1% XIAMETER TM OFS-0777 Silanol Solution]]> 97 CE 46 none 59 CE 47 <![CDATA[1% DOWSIL TM Q1-3563 silicone fluid]]> 35

[0176] 1-Y reflectance retention %. The higher the value, the less dirt is retained and the better the DPUR.

[0177] Formulations with alternative stain resistance additives

[0178] Blend the samples prepared with finish 2 with the DPUR additives shown in Table 10. Apply the samples to panels and test for stain resistance according to the test method. The results are listed in Table 10. The examples designated IE are examples of the present invention, and the examples designated CE are comparative examples.

[0179] Table 10

[0180]

[0181] 1-Y reflectance retention %. The higher the value, the less dirt is retained and the better the DPUR. Measured for the exposed portion of the panel.

Claims

1. An aqueous coating composition, the aqueous coating composition comprising: a) an inorganic filler at a pigment volume concentration of 70 to 90; and b) an acrylic polymer binder at a concentration effective to bind the filler and other components of the aqueous coating composition to a substrate; and c) an alkali metal silanol salt, the concentration of which can effectively increase the stain resistance or color retention of the resulting coating; and d) water in an amount sufficient to completely wet the dry components and provide a slurry.

2. The aqueous coating composition according to claim 1, wherein the pigment volume concentration of the inorganic filler is at least 75, the concentration of the acrylic polymer binder is 5 wt% to 18 wt%, and the concentration of the alkali metal silanolate is 0.2 wt% to 3.5 wt%, wherein the wt% is based on the total weight of the dry components excluding water, and the "dry components" are the filler, the acrylic polymer binder, the alkali metal silanolate, and any other solid additives in the aqueous coating composition.

3. The aqueous coating composition according to claim 2, wherein the pigment volume concentration of the inorganic filler is 78 to 86.

4. The aqueous coating composition according to claim 2, wherein the amount of the alkali metal silanolate is 0.3 wt% to 2 wt% based on the total weight of the dry components excluding water.

5. The aqueous coating composition according to claim 2, wherein the alkali metal silanolate comprises sodium methyl silanolate or potassium methyl silanolate.

6. The aqueous coating composition according to claim 2, the aqueous coating composition having a viscosity of 70 PU to 140 PU.

7. The aqueous coating composition according to claim 2, wherein the amount of water is 5 wt% to 20 wt% of the entire aqueous coating composition.

8. The aqueous coating composition according to claim 2, the aqueous coating composition further comprising 0.2 wt% to 8 wt% of other additives other than components (a), (b), (c), and (d), the additives selected from the group consisting of organic dyes and pigments, thickeners, surfactants, hydrophobic additives, leveling agents and coalescing agents, antioxidants, light and ultraviolet light stabilizers, and additional soil-release additives other than the alkali metal silanolate, wherein the wt% is based on the total weight of the dry components excluding water.

9. The aqueous coating composition according to claim 8, wherein the other additives include additional soil-release additives other than the alkali metal silanolate.

10. The aqueous coating composition according to claim 2, wherein the acrylic polymer binder contains repeating units derived from a crosslinking monomer.

11. The aqueous coating composition according to claim 1, the aqueous coating composition comprising: a) an inorganic filler at a pigment volume concentration of 76 to 86; b) an acrylic polymer binder at 5 to 12 weight percent; c) an alkali metal silanolate at 0.3 to 1 weight percent; d) other additives at 0.5 to 5 weight percent; and e) water at 5 to 20 weight percent, wherein all weight percents are based on the weight of all components including water.

12. An exterior insulation and finish system known as EIFS, attached to the exterior surface of a structure, the EIFS comprising: a) an insulating layer comprising a foamed polymeric insulating material and directly or indirectly attached to a substrate forming the outer surface of the structure; b) a primer coat comprising a fibrous web embedded in a coating material and directly or indirectly attached to the insulating layer; and c) a finish coat directly or indirectly attached to the primer coat and comprising: i) inorganic fillers and / or inorganic pigments at a pigment volume concentration of 70 to 90; ii) an acrylic polymer binder, the concentration of which can effectively bond the fillers and other components of the finish coat to the substrate; and iii) an alkali metal silanol salt and / or its reaction product, the concentration of which can effectively increase the stain resistance or color retention of the finish coat.

13. The exterior insulation and finish and insulation system according to claim 12, wherein the finish coat comprises: a) an inorganic filler and / or inorganic pigment at a pigment volume concentration of 76 to 86; b) an acrylic polymer binder at 6 to 15 weight percent; c) an alkali metal silanolate at 0.3 to 1 weight percent; d) other additives at 0.2 to 8 weight percent; and e) water at less than 2 weight percent, wherein all weight percents are based on the weight of components (a) to (d).

14. The exterior insulation and finish system according to claim 12, wherein when tested according to the test method, the finish coat has a stain resistance of at least 50 percent.

15. The exterior insulation and finish system according to claim 12, wherein when tested according to the test method, the finish coat has a color change (ΔE) of no more than 12 after 5000 hours.

Images