Methods for improving the water wash resistance of external coating compositions and external coating compositions with improved water wash resistance

Abstract

An external coating composition and a method of coating an external surface with said coating, said composition comprising: an aqueous emulsion of an acrylic polymer and at least one branched cellulose ether, wherein said branched cellulose ether is dissolved in a 1% by weight aqueous solution in 2.55 s... ‑1 The viscosity at 20°C at a shear rate of at least 6000 mPa·s is effective at an addition weight percentage of 0.1% to 2.0% of the external coating composition.

Description

Technical Field

[0001] This disclosure relates to a method for shortening the drying time of an external coating composition, the use of branched cellulose ethers in shortening the drying time of an external coating composition, and coating compositions having shortened drying time and early development of resistance to water washout, such as water washout from rainwater. Background Technology

[0002] Traditional external coatings can be damaged and / or washed off in the event of early rain or other water exposure (e.g., within 24 hours of application). Therefore, applicators can avoid the risk of applying coatings under uncertain weather conditions, which leads to lower productivity and costly delays at the work site. The time before rain resistance begins can also be delayed by incorporating various factors such as high humidity or lower temperatures.

[0003] Cellulose ethers are used as rheology modifiers in various water-based external coating applications to appropriately thicken the coatings. A suitable viscosity of the wet coating formulation is required for successful application to the substrate, and the viscosity can be adjusted to suit any known application method, such as spraying, roller coating, troweling, and brushing. However, cellulose ethers have drawbacks due to their high viscosity; high-viscosity cellulose ethers have viscosity levels exceeding 60,000 mPa·s (as measured by Thermo Haake's Viscotester VT550 from Thermo Fisher Scientific, USA), 2 wt% aqueous solution, 2.55 s -1 Those (at 20°C) are difficult to obtain due to the difficulty in sourcing and processing raw materials (pulp). High-viscosity cellulose ethers also present challenges when formulating coatings because their dissolution rates are too high and exceed the practical limits of preparation, meaning they require excessively long mixing durations for dispersion. Inadequate dissolution of cellulose ether rheology modifiers leads to numerous coating defect problems, such as settling, compaction, or coarse sand, which result in visual defects or can clog nozzles. The modified cellulose ether of the present invention contains chemically bonded polyoxyethylene branches, which enhance the wettability of granular cellulose ether particles. The polyoxyethylene branches promote particle breakage and dissolution of granular rheology modifiers. Compared to conventional linear (unbranched) cellulose ether rheology modifiers, the enhanced wettability of branched cellulose ethers results in formulations that are smoother at different molecular weights and rheological responses. Summary of the Invention

[0004] The embodiments relate to wet coating compositions containing acrylic dispersion binders, methods of manufacturing such compositions, and methods of using said compositions. These end uses may include, but are not limited to, organic plastering for wall coatings, elastomeric roofing coatings (ERC), and / or paint coatings (e.g., external thermal insulation composite systems (ETICS)). The composition can be described as a water-based coating formulation in combination with modified water-soluble cellulose ethers (particularly branched cellulose, such as those described in U.S. Patent 10,150,704B2). Modified cellulose ethers can be prepared by crosslinking with diepoxy polyethers. It has been found that these ethers surprisingly increase the setting time of external coating compositions, which has the benefit of providing earlier water resistance, thereby preventing washout.

[0005] This effect is improved compared to conventional cellulose ethers or other synthetic rheology modifiers. The use of modified cellulose ethers in external coating compositions offers a variety of additional advantages, including reduced rheology modifier requirements and enhanced water washout resistance of the coating.

[0006] In one specific embodiment, branched cellulose ethers containing polyether groups are used as rheology modifiers in external coating formulations. The branched cellulose ethers are cellulose ethers that have been chemically modified using a bis-epoxy polyether crosslinking agent. This modified cellulose ether composition retains sufficient water solubility to act as a rheology modifier (unlike crosslinked cellulose ethers, which are used as water-retaining agents in cement or mortar and do not provide a thickening effect).

[0007] According to the external coating composition and method of using the external coating composition of the present invention, at least one of one or more branched cellulose ethers is a crosslinking reaction product of a crosslinked cellulose ether, which, in the absence of crosslinking, will have a viscosity of 10,000 to 800,000 or preferably 30,000 to 70,000 mPa·s, said viscosity being measured using a rotational rheometer (Thermo Haake, Thermo Fisher Scientific). TM Viscotester™ VT550 at 20°C and a shear rate of 2.55 s⁻¹ -1 The following measurements were taken in the form of a 2% by weight aqueous solution.

[0008] According to the external coating composition and method of using the external coating composition of the present invention, at least one of one or more branched cellulose ethers is selected from unmixed cellulose ethers containing alkyl ether groups, or mixed cellulose ethers containing hydroxyalkyl and alkyl ether groups, such as those selected from alkyl hydroxyethyl cellulose, for example hydroxyalkyl methyl cellulose, and preferably selected from hydroxyethyl methyl cellulose (HEMC), hydroxypropyl methyl cellulose (HPMC), methyl hydroxyethyl hydroxypropyl cellulose (MHEHPC), methyl ethyl hydroxyethyl cellulose (MEHEC) and ethyl hydroxyethyl cellulose (EHEC), or more preferably HEMC.

[0009] The branched cellulose ethers of the present invention used in the external coating compositions and methods of using the external coating compositions have polyether groups having 2 to 100, or preferably 2 to 20, or more preferably 3 to 15 olefin oxide groups.

[0010] According to the external coating composition and method of using the external coating composition of the present invention, the polyether group in at least one of the branched cellulose ethers is a polyoxyethylene selected from polyoxyethylene, polyoxypropylene and combinations thereof, preferably polyoxypropylene.

[0011] The branched cellulose ether in the external coating composition and the method of using the external coating composition of the present invention is hydroxyethyl methyl cellulose containing polyoxypropylene groups, or preferably, hydroxyethyl methyl cellulose containing polyoxypropylene dioxyethylene ether branches or crosslinked branches.

[0012] According to the external coating composition and the method of using the external coating composition, the branched cellulose ether is hydroxyethyl methyl cellulose containing polyoxypropylene groups, or preferably hydroxyethyl methyl cellulose containing polyoxypropylene dioxyethylene ether branches or crosslinked branches.

[0013] Preferably, the external coating composition and the method of using the external coating composition have a crossover point of 1.5 ω or less for a 1.0 wt% solution of at least one of one or more branched ethers, as measured by oscillatory rheology, where the storage modulus (G') and loss modulus (G”) intersect and are the same at the crossover point, wherein G' and G” are measured in Pascals at 20°C using an Anton Paar MCR 302 (Anton Paar of Graz, Austria) equipped with a plate and a cone having a diameter of 50 mm and a cone having a cone angle of 1° and a cone point flatness of 0.05 mm, and an angular frequency (ω) in radians per second varying from 0.1 to 100 ω, with a deformation rate of 0.5%.

[0014] The external coating compositions and methods of using the external coating compositions of the present invention contain a loading of at least one of one or more branched cellulose ethers in a wet coating formulation, providing a formulation with a viscosity of 100 to 75,000, or preferably 2,000 to 15,000, or even more preferably 3,000 to 10,000 mPa·s, said viscosity measured at 25°C using a Brookfield viscometer with a spindle #4 at 60 rpm. The loading of at least one of one or more branched cellulose ethers in the wet coating formulation provides a formulation based on the total weight of the wet coating formulation in the range of 0.1% to 2% by weight and preferably 0.15% to 1.0% by weight. Detailed Implementation

[0015] It has been found that the use of branched cellulose ethers containing polyether groups, preferably cellulose ethers containing alkyl ethers and hydroxyalkyl groups, prepared by reacting with a polyether crosslinking agent, significantly improves the water washability of external coating compositions.

[0016] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. Furthermore, all publications, patent applications, patents, and other references mentioned herein are incorporated herein by reference.

[0017] The numerical ranges disclosed herein encompass all values ​​from the lower limit to the upper limit, and include both the lower and upper limits. For ranges containing exact values ​​(e.g., 1 or 2; or 3 to 5; or 6; or 7), any subranges between any two exact values ​​are included (e.g., 1 to 2; 2 to 6; 5 to 7; 3 to 7; 5 to 6, etc.). Unless otherwise stated, implied by the context, or customary in the art, all parts and percentages are by weight, and all test methods are current methods as of the date of this disclosure.

[0018] As disclosed herein, the terms "composition," "formulation," or "mixture" refer to a physical blend of different components obtained by simply mixing the different components in a physical manner. Based on the total weight of the composition, the sum of the weight percentages of each component in the composition is 100%.

[0019] As used herein, the term "average particle size" refers to the median particle size or particle distribution diameter, as determined, for example, by a Multisizer 3 Coulter Counter (Beckman Coulter, Inc., Fullerton, CA) according to the manufacturer's recommended procedure. The median particle size is defined as the size in which 50% by weight of the particles in the distribution are smaller than the median particle size and 50% by weight of the particles in the distribution are larger than the median particle size. It is the volume-average particle size.

[0020] As disclosed herein, “and / or” means “and, or as an alternative”. Unless otherwise specified, all ranges include end values.

[0021] As used herein, the term "aqueous" means that the continuous phase or medium is water and, based on the weight of the medium, comprises 0% to 10% by weight of the water-miscible compound. Preferably, "aqueous" refers to water.

[0022] As used herein, the term "crossover point" refers to the point where the angular frequency (ω), storage modulus (G'), and loss modulus (G") intersect and are identical, as determined by oscillatory rheometry, where G' and G" are measured in Pascals as a function of angular frequency (ω) at 20°C using an Anton Paar MCR 302 oscillatory rheometer (Anton Paar of Graz, Austria) equipped with a plate and cone with a diameter of 50 mm and a cone shape having a cone angle of 1° and a cone flattening of 0.05 mm, and the angular frequency (ω) varies from 0.1 to 100 radians per second, with a deformation rate of 0.5%. In the rheological assay, the analyte cellulose ether or branched cellulose ether is dissolved in water as follows: 1.0 wt% cellulose ether (on a dry basis) is dispersed in 99.0 wt% water under shear for 1 minute at room temperature with stirring, followed by stirring at 1000 rpm for 10 minutes. The solution is then stored in a tightly sealed round glass container for 24 hours and slowly rotated about its longitudinal axis (horizontal axis) for the entire 24 hours.

[0023] As used herein, the term "DIN EN" refers to the European standard version of the German materials specification published by Beuth Verlag GmbH, Berlin, Germany. Furthermore, as used herein, the term "DIN" refers to the German version of the same materials specification.

[0024] As used herein, the term “DS” is the average number of alkyl-substituted OH- groups per dehydrated glucose unit in a cellulose ether, and the term “MS” is the average number of hydroxyalkyl-substituted OH- groups per dehydrated glucose unit, as determined by the Zeisel method. The term “Ziesel method” refers to the Zeisel cleavage procedure used to determine MS and DS; see G. Bartelmus and R. Ketterer, Fresenius Zeitschrift fuer Analytische Chemie, Vol. 286 (1977, Springer, Berlin, DE), pp. 161–190.

[0025] As used herein, the term branched cellulose ether refers to a cellulose ether modified by a crosslinking reaction with a diepoxy polyether, which, without reacting with the diepoxy polyether, would have a viscosity greater than 10,000, preferably greater than 20,000, and even more preferably 30,000 mPa·s, as measured using a Haake Rotovisko RV 100 rheometer (Thermo Fisher Scientific, Karlsruhe, DE) at 20°C and a shear rate of 2.55 s⁻¹. -1 The following measurements were taken using a 2% by weight aqueous solution.

[0026] As used herein, the term "rinsing" is the likelihood that a coating applied to a surface will be washed away or washed off shortly after application due to exposure to rain or other moisture. Rinsing is quantified as the amount of coating applied to a surface that is reduced compared to its initial coating amount (e.g., 100% coverage).

[0027] As used herein, the term "pigment to binder ratio" or "P / B ratio" is the ratio of the weight of pigment (and filler) to the weight of binder solids in a coating. This is a measure of the ratio of inorganic matter to polymeric binder in a given composition. Pigments can be inorganic particulate materials capable of making a substantial contribution to the opacity or hiding power of a coating. Fillers are inorganic materials such as calcium carbonate, silicates, sand, or alumina trihydrate. If the raw materials added to the coating are known, the pigment to binder ratio can be calculated. Alternatively, when the content is unknown, the pigment to binder ratio can be determined using ash content methods such as ASTM D3723-05 (2017).

[0028] As used herein, the term “effective weight” is the portion of the total weight of additives (e.g., branched cellulose ethers) in a given composition.

[0029] Suitable cellulose ethers for use in the method of preparing the cellulose ethers containing crosslinked polyether groups of the present invention may include, for example, hydroxyalkyl cellulose or alkyl cellulose, or mixtures of such cellulose ethers. Examples of cellulose ether compounds suitable for use in the present invention include, for example, methylcellulose (MC), ethylcellulose, propylcellulose, butylcellulose, hydroxyethyl methylcellulose (HEMC), hydroxypropyl methylcellulose (HPMC), hydroxyethylcellulose (“HEC”), ethyl hydroxyethylcellulose (EHEC), methyl ethyl hydroxyethylcellulose (MEHEC), hydrophobically modified ethyl hydroxyethylcellulose (hmEHEC), hydrophobically modified hydroxyethylcellulose (hmHEC), sulfoethyl methyl hydroxyethylcellulose (SEMHEC), sulfoethyl methyl hydroxypropylcellulose (SEMHPC), and sulfoethyl hydroxyethylcellulose (SEHEC). Preferably, the cellulose ether is a mixed cellulose ether containing hydroxyalkyl and alkyl ether groups, such as alkyl hydroxyethyl cellulose, such as hydroxyalkyl methyl cellulose, for example hydroxyethyl methyl cellulose (HEMC), hydroxypropyl methyl cellulose (HPMC), methyl hydroxyethyl hydroxypropyl cellulose (MHEHPC), methyl hydroxyethyl cellulose (MEHEC) and ethyl hydroxyethyl cellulose (EHEC).

[0030] In the branched cellulose ethers of the present invention, alkyl substitution is described in cellulose ether chemistry by the term "DS". DS is the average number of substituted OH groups per dehydrated glucose unit. Methyl substitution may be reported, for example, as DS(methyl) or DS(M). Hydroxyalkyl substitution is described by the term "MS". MS is the average number of moles of etherifying agent bound in ether form per mole of dehydrated glucose unit. Etherification with the etherifying agent ethylene oxide is reported, for example, as MS(hydroxyethyl) or MS(HE). Etherification with the etherifying agent propylene oxide is correspondingly reported as MS(hydroxypropyl) or MS(HP). Side groups are determined using the Zeisel method (reference: G. Bartelmus and R. Ketterer, Fresenius Zeitschrift fuer Analytische Chemie 286 (1977), 161-190).

[0031] The branched hydroxyalkyl cellulose ether preferably has a degree of hydroxyalkyl substitution of 1.5 to 4.5 MS(HE), or more preferably, a degree of substitution of 2.0 to 3.0 MS(HE).

[0032] Preferably, the mixed ethers of methylcellulose are used for the crosslinking reaction. In the case of HEMC, the preferred methyl substitution DS(M) value is in the range of 1.2 to 2.1, or more preferably 1.3 to 1.7, or even more preferably 1.35 to 1.65, and the hydroxyalkyl substitution MS(HE) value is in the range of 0.05 to 0.75, or more preferably 0.10 to 0.45, or even more preferably 0.15 to 0.40. In the case of HPMC, the preferred DS(M) value is in the range of 1.2 to 2.1, or more preferably 1.3 to 2.0, and the MS(HP) value is in the range of 0.1 to 1.5, or more preferably 0.15 to 1.2.

[0033] Crosslinking agents suitable for this invention may include compounds having polyoxyethylene or polyalkylene glycol groups and two or more, preferably two, crosslinking groups such as glycidyl or epoxy groups, or olefinically unsaturated groups such as vinyl groups, that form ether bonds with the cellulose ether when crosslinking the cellulose ether. Suitable bifunctional compounds may be selected from, for example, diglycidyl polyalkoxy ethers, diglycidyl phosphonate, and sulfone-containing divinyl polyoxyethylene. Examples of these are diglycidyl polyoxypropylene and glycidyl (poly)oxyalkyl methacrylate, preferably diglycidyl polyalkoxy ethers, such as diglycidyl polyoxypropylene; glycidyl (poly)oxyalkyl methacrylate; diglycidyl phosphonate; or sulfone-containing divinyl polyoxyethylene.

[0034] The amount of crosslinking agent used can be in the range of 0.0001 equivalents to 0.05 equivalents, where the unit "equivalent" represents the molar ratio of the corresponding crosslinking agent to the molar ratio of the dehydrated glucose units (AGU) in the cellulose ether. The preferred amount of crosslinking agent used is 0.0005 equivalents to 0.01 equivalents, or more preferably, 0.001 equivalents to 0.005 equivalents. As used herein, the unit "equivalent" represents the molar ratio of the corresponding crosslinking agent to the molar ratio of the dehydrated glucose units (AGU) in the cellulose ether; and the resulting cellulose ether containing crosslinked polyether groups is granulated and dried.

[0035] The method for branching cellulose ethers to prepare the polyether-containing cellulose ethers of the present invention may include reacting a crosslinking agent with the cellulose ether in a reactor that prepares the cellulose ether itself and in the presence of a caustic alkali or a base. Therefore, the crosslinking reaction is typically carried out in the method for preparing the cellulose ether. Because the method for preparing the cellulose ether involves the stepwise addition of reactants to form alkyl or hydroxyalkyl groups on cellulose, preferably, the branching or crosslinking of the cellulose ether is carried out after: (i) the addition of a haloalkane (e.g., chloromethane) once or multiple times in the presence of a base to form an alkyl ether of cellulose; or (ii) the addition of an epoxide in the presence of a base to form a hydroxyalkyl group on cellulose; or (iii) both of (i) and (ii).

[0036] Any step of gradually adding to form alkyl, hydroxyalkyl, or ether groups on cellulose, whether it occurs before, during, or after the branching or crosslinking of the cellulose ether, can be carried out at a temperature of 40°C to 90°C, preferably 70°C or lower, or more preferably 65°C or lower.

[0037] To prevent the cellulose ether from degrading or decomposing during processing, the branching or crosslinking reaction is carried out in an inert atmosphere at a temperature of room temperature to 90°C or lower, or preferably at the lowest possible temperature; for example, the method is preferably carried out at 60°C to 90°C, or preferably at 70°C or higher.

[0038] After preparing the polyether-containing cellulose ethers of the present invention, they are granulated and dried. If necessary, granulation can be carried out after dehydration or filtration to remove excess water.

[0039] Aqueous emulsions of acrylic polymers

[0040] Aqueous emulsions of acrylic polymers can be prepared by free radical emulsion or suspension polymerization, or by dispersing a pre-formed polymer into an aqueous medium under shear. Monomers suitable for preparing acrylic polymers include, but are not limited to, (meth)acrylic acid and (meth)acrylates, such as alkyl (meth)acrylates. Examples of alkyl (meth)acrylates are, but are not limited to, methyl acrylate, ethyl acrylate, butyl acrylate, glycidyl methacrylate, 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, and 2-ethylhexyl methacrylate, and combinations thereof. Based on the weight of the polymer, the acrylic polymer may contain 0% to 10% by weight, 0.5% to 8% by weight, 0.8% to 5% by weight, or 1% to 3% by weight of (meth)acrylic acid structural units. Based on the weight of the polymer, the acrylic polymer may contain 10% to 100% by weight, 15% to 99% by weight, 20% to 95% by weight, 30% to 80% by weight, or 40% to 75% by weight of alkyl (meth)acrylate structural units.

[0041] The acrylic polymers of this disclosure may comprise structural units of one or more olefinically unsaturated monomers having at least one heterofunctional group. The heterofunctional group may be selected from the group consisting of urea, nitrile, amide, hydroxyl, alkoxysilane (preferably a hydrolyzable alkoxysilane), or phosphorus group. Preferably, the heterofunctional group may be selected from the group consisting of urea, nitrile, and amide. Suitable urea-functionalized monomers include, for example, alkyl (meth)acrylates containing a urea group. Examples of suitable urea-functionalized monomers are shown below:

[0042]

[0043]

[0044] Or mixtures thereof. Representative functional monomers such as Norsocryl 104 are available from Arkema. Suitable alkoxysilane functional monomers include, for example, vinyltrialkoxysilanes, such as vinyltrimethoxysilane; alkylvinyldialkoxysilanes; (meth)acryloyloxyalkyltrialkoxysilanes, such as (meth)acryloyloxyethyltrimethoxysilane and (meth)acryloyloxypropyltrimethoxysilane; their derivatives, and combinations thereof. Preferred alkoxysilane functional monomers are Silquest A-171 available from Momentive. Suitable nitrile functional monomers include, for example, (alkyl)acrylonitrile, such as (meth)acrylonitrile. Suitable amide functional monomers include, for example, (alkyl)acrylamide, such as (meth)acrylamide. Suitable phosphorus functional monomers include, for example, phosphorus-containing (meth)acrylates, such as ethyl (meth)acrylate phosphate, propyl (meth)acrylate phosphate, butyl (meth)acrylate phosphate, their salts, and mixtures thereof; CH2=C(R)-C(O)-O-(R l O) n-P(O)(OH)2, where R = H or CH3, R1 = alkyl, and n = 2-6, such as SIPOMER PAM-100, SIPOMER PAM-200, and SIPOMER PAM-300, are all available from Solvay; phosphoalkoxy esters of (meth)acrylate, such as ethylene glycol (meth)acrylate, diethylene glycol (meth)acrylate, triethylene glycol (meth)acrylate, propylene glycol (meth)acrylate, dipropylene glycol (meth)acrylate, tripropylene glycol (meth)acrylate, their salts, and mixtures thereof. Preferred phosphorus-containing (meth)acrylates are ethylene glycol methacrylate phosphates from manufacturers such as Hangzhou Hairui Chemical Co., Ltd. Suitable hydroxyl-functionalized monomers include, for example, hydroxyethyl (meth)acrylate and hydroxypropyl (meth)acrylate. The alkyl group is preferably a C1-C10 alkyl group, more preferably a C1-C6 alkyl group, or even more preferably a C1-C4 alkyl group.

[0045] Based on the weight of the polymer, the acrylic polymer may contain 0.1 wt% to 20 wt%, 0.5 wt% to 15 wt%, 1 wt% to 12 wt%, or 1.5 wt% to 10 wt%, or 1.5 wt% to 5 wt% of one or more olefinic unsaturated monomer structural units having at least one heterofunctional group.

[0046] The acrylic polymer may also contain structural units of one or more styrene monomers. Styrene monomers may include, for example, styrene, substituted styrene, or mixtures thereof. Substituted styrene may include, for example, benzyl acrylate, 2-phenoxyethyl acrylate, butylstyrene, methylstyrene, p-methoxystyrene, or mixtures thereof. The preferred styrene monomer is styrene. The polymer may contain, by weight, 1% or more, 5% or more, 10% or more, 15% or more, 17% or more, 19% or more, or even 21% or more and simultaneously 40% or less, 35% or less, 30% or less, 28% or less, or even 26% or less of styrene monomer structural units.

[0047] The polymers used in this disclosure can be prepared by free radical polymerization of the monomers described above, preferably by emulsion polymerization. Emulsion polymerization is the preferred method. The total weight concentration of the monomers used to prepare the polymer is equal to 100%. The mixture of monomers can be added purely or in the form of an emulsion in water; or added in one or more forms or continuously, linearly or non-linearly during the reaction time for preparing the polymer. The temperature suitable for the emulsion polymerization method can be below 100°C, in the range of 30 to 95°C, or in the range of 50 to 90°C.

[0048] In one embodiment, the aqueous emulsion of the acrylic polymer may include, but is not limited to: PRIMAL TM EC4642, PRIMAL TM EC 4811, PRIMAL TM EC 2848ER, PRIMAL TM AC261P, PRIMAL TM EC 1791, PRIMAL TM EC1791QS and / or TIANBA TM In 2012, it was available from Dow Chemical Company. Some other non-restricted ERC grades include: PRIMAL. TM EC-5210PU and PRIMAL TM EC-2885ER. Some other non-restrictive ETICS classifications include: UCAR. TM Latex DL 424 and PRIMAL TM WDV-2001. RHOPLEX TM Acrylic emulsion polymers can also be used in other functional compositions.

[0049] The acrylic polymers in this disclosure may have a weight-average molecular weight of 10,000 to 1,000,000, 20,000 to 700,000, or 40,000 to 500,000. The weight-average molecular weight can be measured by gel permeation chromatography (GPC) calibrated with polystyrene standards.

[0050] The Fox Tg of the acrylic polymers used in this disclosure can be -50°C or higher, -40°C or higher, -30°C or higher, -25°C or higher, or even -20°C or higher and simultaneously 30°C or lower, 20°C or lower, 10°C or lower, 0°C or lower, -4°C or lower, or even -5°C or lower. Some preferred embodiments have a Fox Tg in the range of -40°C to 20°C.

[0051] In this disclosure, the aqueous emulsion of the acrylic polymer has a pH not exceeding 11. Typically, one or more volatile or non-volatile bases can be incorporated in effective amounts to maintain the pH of the composition in the range of 7.2 to 11 or 7.5 to 10.5. In some embodiments, one or more volatile or non-volatile bases may be incorporated into the composition at a concentration of 0% to 5.0% by weight. In some embodiments, one or more volatile bases may be incorporated into the composition at a concentration of 0.1% to 2.5% by weight.

[0052] Aqueous emulsions of acrylic polymers may have post-addition additives for rapid drying, such as multifunctional amine polymers, such as polyethyleneimine (PEI).

[0053] Based on the total weight of the aqueous emulsion of acrylic polymer, the aqueous emulsion of acrylic polymer can have a solids content of 30%-70%, 40%-65%, or 45-60%.

[0054] Aqueous emulsions of acrylic polymers may have an average particle size in the range of 60 to 800 nm, 80 to 500 nm, or preferably 90 to 300 nm.

[0055] Based on the total weight of the coating composition, the emulsion of the acrylic polymer may be present in amounts of 5% or more, 10% or more, 15% or more, 20% or more, or even 30% or more and simultaneously 80% or less, 70% or less, 60% or less, 50% or less, or 45% or less.

[0056] Branched cellulose ethers

[0057] Typically, methods for producing branched cellulose ethers (BCEs) include an alkalization step and an etherification step. Prior to the alkalization step, a grinding step of the cellulose starting material may be performed, and this is generally desirable; and after the etherification step, a washing step and / or a drying / grinding step of the BCE may be performed. During the alkalization operation of the method, a crosslinking agent is introduced or added to the alkalization operation to provide branching or crosslinking of the cellulose material in subsequent downstream operations of the method, such as during the etherification operation. Preferably, the crosslinking reaction is typically carried out in the method for preparing the cellulose ether.

[0058] In a broad embodiment, the present invention relates to the dosage of a crosslinking agent and the addition of a crosslinking agent to a method for producing a BCE product. In a preferred embodiment, the crosslinking agent is added to or incorporated into an alkalization step or operation of a method in combination with an alkalizing agent in the form of a mixture of the crosslinking agent and the alkalizing agent.

[0059] The low-dose crosslinking agent used in this invention results in ultra-high viscosity products with the same rheological properties as known products (e.g., high viscosity measured in millipascal-seconds [mPa·s] under standard conditions of 25°C and 1 atm pressure), but with higher efficiency of the crosslinking agent. Advantageously, this results in reduced levels of undesirable side reactions and minimal impact on wastewater treatment. Furthermore, in this invention, the dosage of expensive crosslinking agents can be reduced and over-crosslinking can be prevented.

[0060] The advantage of the dosage of the crosslinking agent used in this invention is that the use of alkali / water as the suspension medium (or diluent) for the crosslinking agent makes it easier to achieve a uniform distribution of the dispersion in the cellulose material during the dosing step compared to conventional methods. Furthermore, the use of an alkali / water suspension medium in this invention does not present safety or environmental problems in the manufacturing plant, as is the case with known methods in the art that use organic solvents as diluents for the crosslinking agent. Additional advantages of the method of this invention include, for example, (1) the use of readily available crosslinking agents based on diglycidyl ether chemistry, such as Epilux M 985 or Epilux P13-42, both available from Leuna-Harze GmbH; and (2) the crosslinking agent / alkali / water dispersion is non-toxic. In contrast, known methods use epichlorohydrin (ECH) as the crosslinking agent system; and such known methods have several disadvantages, including, for example, the fact that ECH is known to be toxic, carcinogenic, and has a low boiling point (116°C) and low molecular weight (Mw) (92.53 g-mol⁻¹).

[0061] Such cellulose ethers may include, but are not limited to: WALOCEL TM M 120-01.

[0062] Other additives

[0063] In addition to the components described above, the coating compositions disclosed herein may further comprise any one or a combination of the following additives: pigments, extenders, additional thickeners, defoamers, dispersants, coalescing agents and / or cementitious materials (discussed below).

[0064] Other additives include buffers, neutralizers, humectants, fungicides, biocides, wetting agents, colorants, flow aids, antioxidants, plasticizers, leveling agents, thixotropic agents, adhesion promoters, water-retaining additives, and abrasive carriers. When present, these additives may be present in combinations of 0% to 5% by weight, 0.1% to 3% by weight, or 0.5% to 1.5% by weight, based on the total weight of the coating composition.

[0065] Preferably, the coating composition is selected from external elastomer roof coating compositions, external elastomer wall coating compositions, external coatings, or external plaster coatings.

[0066] pigment

[0067] The coating compositions disclosed herein may also comprise one or more pigments. Pigments may comprise particulate inorganic materials capable of substantially contributing to the opacity or hiding power of the coating. Such materials typically have a refractive index greater than 1.8. Examples of suitable pigments include titanium dioxide (TiO2), zinc oxide, zinc sulfide, iron oxide, barium sulfate, barium carbonate, or mixtures thereof. Based on the total weight of the coating composition, pigments may be present in amounts of zero wt% or more, 0.5 wt% or more, 1 wt% or more, 1.5 wt% or more, or even 2 wt% or more and simultaneously 20 wt% or less, 15 wt% or less, 10 wt% or less, or even 5 wt% or less.

[0068] Incremental agent

[0069] The coating compositions disclosed herein may comprise one or more extenders. Extenders may comprise particulate inorganic materials generally having a refractive index less than or equal to 1.8 and greater than 1.5. Examples of suitable extenders include calcium carbonate, alumina trihydrate, silica, alumina (Al₂O₃), clay, calcium sulfate, aluminosilicates, silicates, zeolites, mica, sand, diatomaceous earth, solid or insulated glass, ceramic beads, and opaque polymers (such as ROPAQUE, available from Dow Chemical Company). TM Ultra E (ROPAQUE is a trademark of Dow Chemical Company), or mixtures thereof. Based on the total weight of the coating composition, the extender may be present in amounts of zero wt% or more, 5 wt% or more, 10 wt% or more, 15 wt% or more, or even 20 wt% or more and simultaneously 80 wt% or less, 70 wt% or less, 60 wt% or less, 50 wt% or less, 40 wt% or less, 30 wt% or less, or even 25 wt% or less.

[0070] Other thickeners

[0071] The coating compositions disclosed herein may contain one or more thickeners (also referred to as "rheology modifiers"). Thickeners may include polyvinyl alcohol (PVA), clay materials, acid derivatives, acid copolymers, urethane associative thickeners (UAT), polyether urea polyurethane (PEUPU), polyether polyurethane (PEPU), or mixtures thereof. Examples of suitable thickeners include alkali-swellable emulsions (ASE), such as sodium or ammonium-neutralized acrylic polymers; hydrophobically modified alkali-swellable emulsions (HASE), such as hydrophobically modified acrylic copolymers; associative thickeners, such as hydrophobically modified ethoxylated urethane (HEUR); and cellulose thickeners, such as methyl cellulose ethers, hydroxymethyl cellulose (HMC), hydroxyethyl cellulose (HEC), hydrophobically modified hydroxyethyl cellulose (HMHEC), sodium carboxymethyl cellulose (SCMC), sodium carboxymethyl 2-hydroxyethyl cellulose, 2-hydroxypropyl methylcellulose, 2-hydroxyethyl methylcellulose, 2-hydroxybutyl methylcellulose, 2-hydroxyethyl ethyl cellulose, and 2-hydroxypropyl cellulose. Preferred thickeners are based on HEUR. Based on the total weight of the coating composition, the thickener may be present in amounts of zero wt% or more, 0.01 wt% or more, or even 0.1 wt% or more and simultaneously 5 wt% or less, 4 wt% or less, or even 3 wt% or less.

[0072] Defoamer

[0073] The coating compositions disclosed herein may contain one or more defoamers. As used herein, "defoamer" refers to a chemical additive that reduces and inhibits foam formation. Defoamers may be silicone-based defoamers, mineral oil-based defoamers, ethylene oxide / propylene oxide defoamers, alkyl polyacrylates, or mixtures thereof. Suitable commercially available defoamers include, for example, TEGO Airex 902W and TEGO Foamex 1488 polyether silicone copolymer emulsions from Evonik, BYK-024 silicone defoamer from BYK, NOPCO NXZ defoamer from San Nopco, or mixtures thereof. Based on the total weight of the coating composition, the defoamer may be present in amounts of zero wt% or more, 0.01 wt% or more, or even 0.1 wt% or more and simultaneously 2 wt% or less, 1.5 wt% or less, or even 1 wt% or less.

[0074] dispersant

[0075] The coating compositions disclosed herein may also contain one or more dispersants. Suitable examples of dispersants include nonionic, anionic, and cationic dispersants, such as polybasic acids having suitable molecular weights, 2-amino-2-methyl-1-propanol (AMP), dimethylaminoethanol (DMAE), potassium tripolyphosphate (KTPP), trisodium polyphosphate (TSPP), citric acid, and other carboxylic acids. Preferred dispersants are polybasic acids, i.e., homopolymers or copolymers of carboxylic acids, hydrophobically or hydrophilically modified polybasic acids, their salts, and any combination thereof. Suitable examples of hydrophobically or hydrophilically modified polybasic acids include polyacrylic acid modified with hydrophilic or hydrophobic monomers such as styrene, acrylates or methacrylates, diisobutylene-modified polyacrylic acid, polymethacrylic acid, and maleic anhydride. Such polybasic acid dispersants have a molecular weight of 400 to 50,000, preferably 500 to 30,000, more preferably 1,000 to 10,000, and most preferably 1,500 to 3,000. Based on the total weight of the coating composition, the dispersant may be present in amounts of zero wt% or more, 0.1 wt% or more, 0.2 wt% or more, or even 0.3 wt% or more and simultaneously 12 wt% or less, 10 wt% or less, 9 wt% or less, 5 wt% or less, or even 2 wt% or less.

[0076] coalescing agent

[0077] The coating compositions disclosed herein may contain one or more coalescing agents. As used herein, "coalescing agent" refers to a slowly evaporating solvent that promotes the diffusion of polymer particles into a continuous film under ambient conditions. Suitable coalescing agents may include, for example, 2-n-butoxyethanol, dipropylene glycol n-butyl ether, propylene glycol n-butyl ether, dipropylene glycol methyl ether, propylene glycol methyl ether, propylene glycol n-propyl ether, diethylene glycol monobutyl ether, ethylene glycol monobutyl ether, ethylene glycol monohexyl ether, triethylene glycol monobutyl ether, dipropylene glycol n-propyl ether, n-butyl ether, or mixtures thereof. Preferred coalescing agents include dipropylene glycol n-butyl ether, ethylene glycol monobutyl ether, diethylene glycol monobutyl ether, n-butyl ether, 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate, or mixtures thereof. Based on the total weight of the coating composition, the coalescing agent may be present in amounts of zero wt% or more, 0.1 wt% or more, or even 1 wt% or more and simultaneously 12 wt% or less, 10 wt% or less, or even 9 wt% or less.

[0078] cement materials

[0079] The coating compositions disclosed herein, particularly two-component cementitious waterproofing coating compositions, may contain one or more cementitious materials, such as cement. Preferably, the cement may be selected from white cement, silicate cement, and composite silicate cement. Based on the total weight of the coating composition, the cementitious material may be present in amounts of zero wt% or more, 5 wt% or more, 10 wt% or more, or even 15 wt% or more and simultaneously 50 wt% or less, 40 wt% or less, 30 wt% or less, or even 25 wt% or less.

[0080] Silicone / Silane Additives

[0081] Silicone / silane additives can be used to increase water vapor permeability, promote adhesion, and increase water contact angle. Examples of such additives include, but are not limited to, DOWSIL. TM IE 6692, DOWSIL TM IE 6683, DOWSIL TM IE 2404 and DOWSIL TM Z 70; DOWSIL TM The product is available from Dow Chemical Company.

[0082] Preparation method

[0083] The coating compositions disclosed herein can be prepared using techniques known in the coatings industry, for example by mixing an aqueous emulsion of an acrylic polymer with the other optional components described above. The components in the coating composition can be mixed in a suitable sequence to provide the coating compositions of this disclosure. Any of the optional components described above can also be added to the composition during or before mixing to form the coating composition. The coating compositions of this disclosure are aqueous coating compositions.

[0084] In some embodiments, the branched cellulose ether is premixed with water and propylene glycol. This mixture is then added to an aqueous emulsion of an acrylic polymer containing the other optional components described above.

[0085] In some embodiments, branched cellulose ethers are premixed with suitable dried formulation components (such as aggregates used in ETICS), and the mixture of dried components is added to the coating composition.

[0086] This disclosure also provides a method for preparing a coating. The method may include: forming a coating composition, applying the coating composition to a substrate, and drying or allowing the applied coating composition to dry to form a coating. The coating composition may be applied to the substrate by existing methods including brushing, dipping, rolling, and spraying. The coating composition is preferably applied by rolling and spraying. Typical rollers and standard rolling techniques are used. Spraying can be performed using standard spraying techniques and equipment, such as air atomization spraying, air spraying, airless spraying, high-volume low-pressure spraying, and electrostatic spraying (e.g., electrostatic spraying), as well as manual or automatic methods. After applying the coating composition to the substrate, the coating composition may be dried or allowed to dry to form a film (i.e., a coating). The method may be carried out at an external ambient temperature of 5°C to 40°C, at room temperature (20°C–25°C), or at elevated temperatures (e.g., 35°C to 60°C). The coating composition provides a coating obtained therefrom (i.e., a film obtained after drying or allowing the coating composition applied to the substrate to dry).

[0087] The coating compositions disclosed herein can be applied and adhered to a wide variety of substrates. Examples of suitable substrates include concrete, cementitious substrates, wood, metal, stone, elastomeric substrates, glass, or fabric. The coating compositions are suitable for a wide range of coating applications, such as waterproofing coatings, architectural coatings, marine and protective coatings, automotive coatings, wood coatings (including furniture coatings, joinery coatings, and floor coatings), coil coatings, road marking paints, and civil engineering coatings. The coating compositions can be used alone or in combination with other coatings to form multilayer coatings.

[0088] It should be noted that the effective weight percentage of a given composition (e.g., a topcoat or ERC) is a portion of the total weight of the composition as an additive (e.g., a branched cellulose ether).

[0089] Example

[0090] Preparation of gel-like cross-linked cellulose ethers :

[0091] Branched cellulose ether 1 (BCE-1) is a diglycidyl ether modified from 70% hydroxyethyl methyl cellulose and 30% cotton linters. DS (methyl) = 1.57; MS (hydroxyethyl) = 0.28; product viscosity 12690 mPa·s; 1% (w / w) aqueous solution shear rate 2.55 s⁻¹. -1 , 20℃ (Thermo Haake Viscotester VT550); COV = 0.5 rad / s (Anton Paar MCR 302). Cross value COV = 0.5 rad / s (1 wt%, Anton Paar MCR 302, 20℃).

[0092] Cross-linked cellulose ether synthesis :

[0093] The branched HEMC cellulose ether was based on 70 wt% wood pulp and 30 wt% cotton lint, and was prepared in the same manner as described in the experimental section of Hild et al. (WO2020223040A1, Hild Reference) using 0.0013 mmol branching agent / mol AGU (dehydrated glucose unit), as disclosed in Innovative Example 1 of Hild Reference.

[0094] Test coating composition :

[0095] To test the exterior coating composition and method disclosed in this invention, an extruded polystyrene (XPS) board representing an exterior surface (e.g., a wall, roof, etc.) was coated with a primer and then with a topcoat. The topcoat mixture was spread evenly on the primer using a trowel, and then rubbed with a wetted XPS sheet to homogenize the surface. The resistance of this coating to early water exposure was then tested.

[0096] The compositions disclosed in this invention were also tested as elastomeric roofing coatings (ERCs), wherein the ERCs were applied directly to XPS panels without a primer. The resistance of this coating to early water exposure was then tested.

[0097] I.) Preparations tested

[0098] Table 1A - Chemicals Used in Preparations

[0099]

[0100]

[0101] Table 1B - Cellulose Ether Viscosity

[0102] NATROSOL 250MBR 4500–6500 mPa·s 2％ <![CDATA[WALOCEL TM MW 15000PFV]]> 16000mPa·s 2％ <![CDATA[WALOCEL TM 40000PFV]]> 35000–45000 mPa·s 2％ Branched cellulose ether (BCE-1) 120000mPa·s 2％ <![CDATA[Walocel TM MKX 45000PF 20L]]> 40000-50000 mPa·s 2％

[0103] Note: The above data is from Ashland Natrosol 20 TDS NR 4739-1. Tested under standard conditions using Brookfield, spindle #4, and 60 rpm.

[0104] Table 2 - Primer Mixtures

[0105]

[0106] Table 3A - Comparative Topcoat Compositions

[0107]

[0108] Table 3B - Topcoat Compositions of the Invention

[0109]

[0110] Table 4 - ERC Preparations

[0111]

[0112]

[0113] II.) Experimental Procedure

[0114] Preparation of XPS boards with primer

[0115] The cement primer was prepared according to DIN EN 12004-2, comprising the components listed in Table 2. The primer was then applied to the XPS board (28×23×2cm) to a thickness of 3mm using a trowel. Plastic spacers (280×8×3mm) were fixed at the long edges of the XPS board to define the thickness. The primer was then allowed to dry at 23°C and 50% relative humidity for at least 48 hours.

[0116] Topcoat preparation

[0117] The topcoat (organic primer) is prepared by adding the different components listed in Table 3 in the order shown in Table 3. Components 1-5 are added to a container (0.8-1.3L) placed directly on a balance, with brief manual stirring between each component. The mixture is then mixed at 800 rpm using a Dispermat F105 mixer. The container radius should be at least twice the radius of the mixer blades to ensure proper mixing. Components 6-10 are then added while stirring for 5-10 minutes. The mixture is then stirred at 800 rpm for another 10 minutes. The speed is then reduced to 400 rpm, after which the acrylic binder (component 11) is slowly added. After mixing for 5 minutes, the intervening mixture of component 12 is added, and mixing continues for another 5-10 minutes, depending on the thickener added. The premix of component 12 is prepared by adding all the dry components to a container and blending them using a Turbula Unit T2C dry mixer. This is crucial for the uniform addition of the cellulose ether thickener and for preventing agglomeration. The pigment-to-binder ratio for the topcoat is 16.3:1.

[0118] ERC coating preparation

[0119] Prepare the ERC formulation according to the formula in Table 4. Prepare the abrasive in a stainless steel grinding jar. Combine the ingredients in the listed order and mix at high speed for 20 minutes. Reduce the mixing speed to maintain a vortex and add the diluent ingredients in the listed order. Combine the premixed ingredients in a separate container and add them to the grinding jar. Continue mixing for 10 minutes with thorough stirring to maintain a vortex. The pigment to binder ratio of the ERC coating is 1.4:1.

[0120] ERC coating application

[0121] The coating was applied directly to the unprimed XPS board substrate. Application was performed using a Zehntner gap applicator with a 1mm gap size. The width of the coating was 12cm. Prior to early water testing, the coated board was cured for 3 hours at 23°C and 50% humidity.

[0122] Early water testing of ERC coating

[0123] After conditioning, place the sample in a water spray nozzle ( A stainless steel nozzle (17CA, 1.1L / Min) was placed 30cm in front of the plate. Water was sprayed at a controlled pressure of 2 bar for 3 minutes. The plate was then dried at 23°C and 50% relative humidity before photographing.

[0124] Early water test of topcoat

[0125] The topcoat mixture was evenly spread over the primer using a trowel, and then rubbed with a damp XPS sheet to homogenize the surface. The thickness of the topcoat was limited by the size of the large aggregates formed. The boards were then dried under controlled conditions and for a given time (see Results section). The Voetsch climate chamber was used to dry the boards in a challenging environment (e.g., at least 75% relative humidity and 7°C for 7 hours).

[0126] After the defined drying time, the sample was placed 30 cm in front of a water spray nozzle (stainless steel nozzle 17CA, 1.1 L / min). Water was sprayed at a controlled pressure of 2 bar for 15 minutes. The plate was then dried at 23°C and 50% relative humidity, and then photographed (180 dpi, Canon PowerShot SX200 IS, RGB).

[0127] Image processing

[0128] The images of the plates were analyzed using GIMP 2.10.22 software. Uncovered areas were manually marked as white, and covered areas as red. After merging the red and white layers into a new image, the percentage of coverage was extracted based on the binary histogram (pixel resolution) of that image for each plate.

[0129] III.) Results

[0130] Tables 5 and 6 below show the percentage of area of ​​primer and topcoat aggregates retained on a given XPS board after early water testing. A higher percentage of coverage indicates that the formulation exhibits better early water resistance. As shown in Table 5, the curing conditions for the given coatings are challenging and are intended to represent application in high humidity / rainy environments. The samples shown in Table 5 were cured at 7°C, 76% relative humidity, and a 7-hour drying time. The samples shown in Table 6 were cured at 23°C, 50% relative humidity, and a 3-hour drying time.

[0131] The comparative samples in Tables 5 and 6 are characterized by the use of conventional CE rheology modifiers and synthetic rheology modifiers added at the same effective level. The compositions disclosed in this invention are compared at the same or reduced effective concentrations in the formulations.

[0132] Table 5 - Performance of primer / topcoat under high humidity

[0133]

[0134] Table 6 - Performance of primer / topcoat under environmental conditions

[0135]

[0136] Table 7 shows the percentage of area of ​​ERC retained on a given XPS board after the initial water test. The ERC formulation was applied to an unprimed XPS board and cured at 23°C, 50% relative humidity, and a drying time of 3 hours. The coated and dried XPS board was then washed with water for 3 minutes at approximately 29 PSI (2 bar). Tables 8-10 show the various physical properties of the tested and comparative ERCs.

[0137] Table 7 - ERC formulation results

[0138]

[0139] Table 8 - Water Absorption Rate Results of ERC Preparations

[0140]

[0141] Table 9 - Results of Elongation at Break for ERC Preparations

[0142]

[0143] Table 10 - Maximum Tensile Strength of ERC Preparations

[0144]

[0145] IV.) Analysis .

[0146] The results showed that the branched cellulose ether exhibited significantly improved early water resistance compared to synthetic or conventional CE. Under challenging conditions (Table 5), the coverage area remained above 90%, while conventional CE gave approximately 70%. The synthetic thickener performed even worse, with a coverage area of ​​only 30%. This significant improvement was also achieved after drying under ambient conditions for only 3 hours (Table 6).

[0147] The ERC prepared using branched cellulose ethers also showed a significant improvement. As shown in Table 7, the remaining coverage area after the early water test was more than twice (nearly three times) that observed with conventional CE and synthetic thickeners. The percentage of water absorption of the embodiments of the present invention tested were also superior to that of conventional CE and synthetic thickeners (Table 8). Tables 9 and 10 show that the ERC produced using branched cellulose ethers also exhibited similar elongation and tensile strength as conventional ERC.

Claims

1. An external coating composition, said external coating composition comprising: a) Aqueous emulsions of acrylic polymers, and b) At least one branched cellulose ether containing chemically bonded polyoxyethylene branches, wherein the at least one branched cellulose ether is dissolved in a 1% by weight aqueous solution at 2.55 s. -1 The viscosity at 20°C at a shear rate of at least 6000 mPa·s, and the effective addition weight percentage of the external coating composition is 0.1% to 2.0%, wherein the at least one branched cellulose ether has a crossover point of 1.5 radians / second or less for a 1.0 wt% solution of the at least one branched ether as measured by oscillatory rheology, the storage modulus G' and loss modulus G” intersect and are the same at the crossover point, wherein G' and G” are measured in Pascals at 20°C using an Anton Paar MCR 302 equipped with a plate and cone having a diameter of 50 mm, the cone having a cone angle of 1° and a cone point flattening of 0.05 mm, and the angular frequency ω varying in the range of 0.1 to 100 radians / second, and the deformation rate is 0.5%.

2. The composition according to claim 1, wherein the branched cellulose ether is dissolved in a 1% by weight aqueous solution in 2.55 s -1 The viscosity at 20°C at the given shear rate is at least 10,000 mPa·s.

3. The composition according to claim 1, wherein the composition further comprises one or more pigments.

4. The composition according to claim 3, wherein the ratio of pigment to binder is 16.3 to 1.

5. The composition according to claim 3, wherein the ratio of pigment to binder is 1.4 to 1.

6. The composition according to claim 1, wherein the effective addition weight percentage of the at least one branched cellulose ether is 0.13% to 0.5% of the external coating composition.

7. An exterior coating formed from the composition of claim 1, wherein the composition is applied to a substrate.

8. A method for coating an outer surface, the method comprising: a) Apply a primer to the outer surface and allow the primer to dry for at least 48 hours, and b) Apply a topcoat evenly over the primer, wherein the topcoat comprises an aqueous emulsion of an acrylic polymer and at least one branched cellulose ether containing chemically bonded polyoxyethylene branches, wherein the at least one branched cellulose ether is dissolved in a 1% by weight aqueous solution at 2.55 s. -1 The viscosity at 20°C at a shear rate of at least 6000 mPa·s, and the effective addition weight percentage of the topcoat is 0.1% to 2.0%, wherein the at least one branched cellulose ether has a crossover point of 1.5 radians / second or less for a 1.0 wt% solution of the at least one branched ether as measured by oscillatory rheology, the storage modulus G' and loss modulus G” intersect and are the same at the crossover point, wherein G' and G” are measured in Pascals at 20°C using an Anton Paar MCR 302 equipped with a plate and cone having a diameter of 50 mm, the cone having a cone angle of 1° and a cone point flattening of 0.05 mm, and the angular frequency varying in the range of 0.1 to 100 radians / second, and the deformation rate of 0.5%.

9. The method of claim 8, wherein the topcoat is applied at a temperature of 7°C to 25°C and a relative humidity of at least 75%.

10. The method of claim 8, wherein the effective weight percentage of the at least one branched cellulose ether added is 0.13% to 0.2% of the topcoat.

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