MXPA98005401A - Method of coating and coating composition used in mi - Google Patents

Abstract

The present invention is directed to a method for coating a substrate, under ambient conditions, by conventional single-stage application means, such as simple spray pressure, with a single-pack quick-drying paint, containing a coating composition. of the present invention, which contains a latex binder, an associative thickener and a volatile organic solvent soluble in water. The amounts of the associative thickener and the solvent are such that the paint has a can viscosity, under ambient conditions, in the range of 1,000 cps, and a touch-dry time index, in accordance with ASTM D-1640, less 10 minutes. The method of the present invention and the coating composition used therein, can be used to produce a quick drying coating such as traffic paint for pavement markings or roads, for concrete, asphalt or bituminous roads, pedestrian crossings or parking.

Description

Coating Method and Composition of Reuse Used in the Same Area of the invention. This invention relates to coating compositions which have a low VOC content, which dry quickly and are easy to apply, their preparation and use.

BACKGROUND OF THE INVENTION For a long time, it has been desired to reduce the drying time of the coating compositions, especially for use as paints for traffic, and, for environmental reasons, the content of volatile organic components.

(VOC) in them (in the United States, the allowable amount of VOC that can be released into the air from traffic paints is assumed to be less than 150 grams of VOC per liter of paint). However, these two characteristics are in conflict since when replacing the VOC with water, the drying time usually increases, especially under high ambient humidity conditions, which typically varies within the range of 65 to 90 percent. .

Attempts have been made to improve the drying rate of the aqueous compositions, for example in EP-A 7210003, by adopting a two-stage route where first an aqueous polymer layer is applied, immediately followed by the application of thickener to accelerate its drying . However, this route is uncomfortable and the double package proposal, in two stages, does not comply with the third desired attribute of the coating compositions, ie they can be easy to apply. This invention addresses the problem of reducing the VOC content in coating compositions that are quick to dry and easy to apply in a single stage by conventional single-stage application means, such as air-sprayed, airless spray , spraying without air assisted by air and low pressure spray at high level.

Declaration of the invention. The present invention is directed to a method for coating a substrate, comprising: Applying at ambient conditions, on the surface of said substrate, a layer of a fast-drying paint of a single package containing a water-based coating composition with low VOC content, said composition comprises a latex binder, an associative thickener and a volatile water soluble organic solvent, wherein the amounts of said associative thickener and said solvent are such that said paint has a can viscosity, under environmental, in the range of 1,000 cps to 6,000 cps, and a touch-time index, in accordance with ASTM D-1640, of less than 10 minutes; and evaporating said solvent from said layer, to form said coating on said substrate. The present invention is also directed to a method for improving the drying time of a traffic signal on a pavement or road surface, comprising: applying on said surface a layer of a traffic paint of a single package containing a composition of water-based coating with low VOC content, which comprises a latex binder, an associative thickener in the range of 0.01 percent to 10 percent, and a water-soluble organic volatile solvent in the range of 0.2 percent a 10 percent, all in percentages of volume based on the total volume of the composition, wherein said traffic paint has a can viscosity, under ambient conditions, in the range of 1,000 cps to 6,000 cps, and a time index of touch-dry, in accordance with ASTM D-1640, less than 10 minutes; evaporating said solvent from said layer, to form said traffic signal on said substrate. The present invention is further directed to a water-based, single package, low VOC, and quick-drying coating composition, comprising: a latex binder; an associative thickener at an index of 0.01 percent to 10 percent; and a volatile organic solvent soluble in water in the range of 0.2 percent to 10 percent, all in percentages of volume based on the total volume of the composition, wherein a traffic paint containing said composition has a can viscosity, under environmental conditions, in the range of 1,000 cps to 6,000 cps, and a time index of touch dry, in accordance with ASTM D-1640, less than 10 minutes. One of the advantages of the present invention is that it provides a composition with sufficiently low can viscosity, so that a paint prepared therefrom can be easily sprayed by means of conventional simple pressure traffic paint application devices. Still another advantage is that a layer of a paint containing the composition of the present invention dries at a rate faster than a layer of conventional water-based paints, even under high humidity conditions.

Detailed description of the invention. As used herein: "Weight average molecular weight per CPG" means the molecular weight of a polymer determined by gel permeation chromatography (CPG), using a differential refractometer as a detector. During the analysis typically a set of three CPG columns packed with styrene / divinyl benzene beads having pore sizes in the range of 100 to 10,000 angstroms is used. In general, the solvent used is tetrahydrofuran (THF), flowing at an index of 1.0 ml./min. through CPG columns. The temperature of the columns is usually maintained at 40 ° C. The instrument, such as one supplied by Polymer Laboratories, Amherst, Massachusetts and American Polymer Standars Co., Mentor, Ohio, is first calibrated for molecular weight using standards Reduced distribution of polystyrene or polymethacrylate. The weight average molecular weight of the sample is then determined using the following equation: Weight average molecular weight (Mw) = S (RxM) /? H, where R is the measured detector response over the baseline in a given time and M is the molecular weight at that time, co or is determined from the calibration logarithm. The sum is made for the elution time at the peak start to the elution time at the peak term. This sum is the number reported as the weight average molecular weight. More details regarding gel permeation chromatography (CPG) can be found on page 4, chapter I, of The Characterization of Polymers, published by Rohm and Haas Company, Philadelphia, Pennsylvania in 1976. "glass transition temperature (Tg)" is a reduced temperature index, as measured by conventional differential scanning calorimetry (CED), during which amorphous polymers change from relatively strong brittle crystals to relatively soft viscous rubbers . To measure the Tg by means of this method, the copolymer samples were dried, preheated to 120 ° C, quickly cooled to -100 ° C, and then heated to 150 ° C. at an index of 20 ° C. / minute while the data was collected. The Tg was measured at the midpoint of the inflection using the medium high method. "Latex binder" means "dispersed polymer", "solubilized polymer" (both described below) or a mixture thereof. "Dispersed polymer" means polymer particles, which are dispersed colloidally and stabilized in an aqueous medium. "Solubilized polymer" includes "water soluble polymer", "water reducible polymer" or a mixture thereof. Water soluble polymer means a polymer dissolved in an aqueous medium. Water reducible polymer means a polymer dissolved in water and water miscible solvent. The solubilized polymer results in a polymer solution characterized by having the self-grouping constant (K) of the Mooney equation [1 Inhrel = l / BC -K / 2.5] equal to zero. In contrast, the dispersed polymer has a (K) equal to 1.9. The details of the Mooney equation are revealed in an article entitled "Physical Characterization of Water Dispersed and Soluble Acryl ic Polymers" (Physical characterization of water soluble and dispersed acrylic polymers) by Brendley et al., In "Nonpolluting Coatings and Coating" Processes "(Non-polluting coatings and coating processes) published by Plenum Press, 1973 and edited by Gordon and Prane. "Polymer particle size" means the diameter of the polymer particles measured using a Brookhaven model particle BI-90, supplied by Brookhaven Instruments Corporation, Holtsville, New York, which employs a quasi-elastic light scattering technique for Measure the size of the polymer particles. The intensity of the dispersion is a function of the particle size. The diameter is used based on a heavy intensity average. This technique is described in chapter 3, pages 48 to 61, entitled Uses and Abuses of Photon Correlation Spectroscopy in Particle Sizing (Uses and Abuses of Photon Correlation Spectroscopy in Particle Measurement) by Weiner et al. in 1987, edition of the American Chemical Society Symposium series. "Polymer solids" means the polymer in its dry state. "(Met) acrylate" includes acrylate and methacrylate.

"Viscosity in a can" is the viscosity of a paint at the time of application, for example at the time of spraying the paint on the surface of a substrate. Normally, the presence of an associative thickener in a coating composition tends to increase the can viscosity of a paint containing said composition, at a level where it becomes very difficult to apply the paint by conventional application means. The applicant has unexpectedly discovered that by adjusting the amount of associative thickener and adding a water-soluble volatile organic solvent to the composition, at a certain unexpected level, one can achieve a sufficiently low can viscosity so that the paint can be sprayed by of conventional spray, while drying quickly after application on a substrate. The viscosity of a paint containing the composition of the present invention, as measured at room temperature by means of the Brookfield viscometer model LVT supplied by Brookfield Engineering Laboratories Inc., Stoughton, Massachusetts, (axis # 3 @ 30 RPM), varies in the range from 1,000 to 6,000, preferably from 1,000 to 3,500 centipoise (cps). If the viscosity exceeds the upper limit, it becomes very difficult to spray the paint by conventional single-stage spray application means. If the viscosity falls below the lower limit, the coat of paint will take a long time to dry. It is believed that the associative thickener in the water-based composition increases the viscosity of a water-based coating composition, in part by forming a network of thickener molecules and polymer particles. This network is formed by the association with itself of the hydrophobic thickeners, and with the surface of the polymer particles. Water-soluble organic volatile solvents tend to dissolve these hydrophobic segments, and decrease their tendency to associate, thereby inhibiting the ability of the thickener to increase the viscosity of the coating. When a paint layer containing the composition of the present invention is applied on a substrate surface, the water soluble volatile organic solvent evaporates rapidly, and the hydrophobic segments of the thickener begin to associate causing the viscosity to increase. Thus, if a sufficient amount of thickener is used, the final viscosity will be high enough for the layer to dry and set quickly in a coating.

The amount of the associative thickener added to the composition is such that a newly applied layer of paint, containing the composition, would have a higher touch-time index, when measured in accordance with ASTM D 1640, of less than 10 minutes , preferably less than 8 minutes and more preferably less than 5 minutes. The ASTM D 1640 test is conducted at an ambient temperature in the range of 20 ° C. at 23 ° C, and 50 ± 2% relative humidity for a 0.305 mm film. (12 mil.) Thickness of wet film. The lowest rate of touch-dry time, according to ASTM D 1640, is 10 seconds. The Applicant has unexpectedly discovered that by adjusting the amount of the associative thickener added to the composition, the above index of touch-dry time of the paint containing the coating composition of the present invention can be obtained by adding associative thickener on a 0.01% scale. to 10%, preferably in the range of 0.05% to 2%. All the percentages are in volume percentages, based on the total volume of the painting. It will be understood that the actual drying time of a paint layer, which contains the coating composition of the present invention, would be different from the drying time index according to ASTM D 1640, since the actual drying time depends on many factors such as ambient temperature and layer thickness. The wet film thickness of the paint layer, depending on the intended use, it usually varies in the range of 0.025 mms. (1 mil.) To 0.75 mms. (30 thousand.). When used as a metallic coating, it can vary in the range of 0.025 mm. (1 mil.) To 0.25 mms. (10 mils.), And when used as a traffic signal can vary in the range of 0.25 mms. (10 mil.) To 0.75 mms. (30 thousand.). The actual drying time of said layer usually varies in the range of 10 seconds to 30 minutes. The associative thickener, sometimes also known as hydrophobic modified water-soluble polymer, used in the present invention, can be any thickener or rheology modifier containing at least two hydrophobic segments separated by hydrophilic segments. A hydrophobic segment is defined as any organic part that, if the additive point (s) of the hydrophilic segments were replaced by bonds for hydrogen atoms, would have a solubility in water at 20 ° C. less than one percent by weight, based on the total weight of the hydrogenated hydrophobic segment. A hydrophilic segment is defined as any organic part that, if the point (s) of addition to the hydrophobic segments were replaced by bonds for hydrogen atoms, would have a solubility in water at 20 ° C, at some pH between 2 and 12 or greater than 5 weight percent, based on the total weight of the hydrogenated hydrophobic segment. Examples of suitable associative thickeners include hydrophobic ethoxylated urethane resins (RUEH thickeners) which are usually the reaction products of polyethylene glycols with diisocyanates. Some of said associative thickeners are described in the co-owned US patent no. 4, 155, 892.

RUEH thickeners are urethane polymers having at least three hydrophobic low molecular weight groups, wherein at least two of them are hydrophobic groups (external) terminals. Many of the polymers also contain one or more internal hydrophobic groups. The hydrophobic groups together contain a total of at least 20 carbon atoms, and are bound through hydrophilic groups (soluble in water). The size range of the hydrophobe varies in the range of 50 to 700 grams per mole, preferably in the range of 100 to 500 grams per mole and more preferably in the range of 200 to 350 grams per mole. The molecular weight of the thickener is such that it can be readily solubilized in water, either by self-solubilization or through interaction with a known solubilizing agent, such as a surfactant or water-miscible alcohol. The molecular weight of the thickener is in the range of 5,000 to 200,000, preferably in the range of 5,000 to 50,000, more preferably in the range of 10,000 to 30,000 and more preferably in the range of 15,000 to 20,000. The RUEH polymers are prepared in non-aqueous media, and are the reaction products of at least reactants (a) and (c) of the following reagents: (a) at least one water-soluble polyether polyol, (b) least one organic polyisocyanate insoluble in water, (c) at least one monofunctional hydrophobic organic compound selected from monofunctional active hydrogen compounds and organic monoisocyanates the, and (d) at least one polyhydric alcohol or polyhydric alcohol ether. The products formed include the following: (1) Reaction products of a reagent (a) containing at least three hydroxyl groups, and the above organic monoisocyanates; (2) Reaction products of reagent (a), reagent (b) which contains two isocyanate groups, and the above compounds containing active hydrogen. Said compounds have an equivalent index of (a) to (b) which is from 0.5: 1 to 1: 1; (3) Reaction products of reagent (a), reagent (b) containing at least three isocyanate groups, and compounds containing active hydrogen; (4) Reaction products of reagent (a), reagent (b) and organic monoisocyanates; and (5) Reaction products of the reactants (a), (b), (d) and the organic monoisocyanates. RUEH thickeners are preferred. One of the advantages of using the RUEH thickener is that a paint prepared therefrom does not have a strong odor, which is typically associated with high pH coating compositions. Associative thickener other includes emulsions which swell / hydrophobized alkali soluble (EHAH thickeners), which are generally copolymers with high levels of (meth) acrylic acid with hydrophobic monomers. Still another type of associative thickener is an acrylamide copolymer thickener, such as that described in commonly assigned US Pat. 4,395,524. Said thickener is an aqueous solution of an addition copolymer anionic vinyl or nonionic, soluble in water, by weight, of at least 50% acrylamide, 0.01 to 50%, an N-substituted acrylamide and, optionally up to 49.99% of other vinyl monomers. The substituent on the nitrogen of the acrylamide is hydrocarbyl, and has 6 or more carbon atoms or is a hydrocarbyl group added to the nitrogen by means of a polyoxyalkylene chain. The weight average molecular weight per CPG of the copolymer is greater than 30,000 but less than two million. The polyacrylamide thickener is preferably a copolymer of acrylamide and one or more N-substituted acrylamides. In other embodiments, it is a copolymer of these amides and other vinyl monomers, preferably hydrophilic, such as hydroxypropyl acrylate, hydroxyethyl methacrylate, hydroxyethyl acrylate, methacrylic acid, acrylic acid and, especially, N-vinylpyrrolidone. Ionic acrylamide copolymers are made by copolymerization with ionizable monomers, preferably methacrylic acid, acrylic acid and itaconic acid. The nonionic copolymers are prepared using N-vinylpyrrolidone or the hydroxyalkyl methacrylates or acrylates or methacrylates and hydroxy-, alkoxy- or polyalkoxyalkyl acrylates, the preferred alkyl groups in these compounds have from 2 to 4 carbon atoms and more preferably 2 or 3, that is, they are ethoxy or propoxy materials. The acrylamide copolymer thickener is a free radical polymerization product, preferably conducted in a substantially oxygen-free atmosphere and employing a free radical initiator at the usual levels, such as between 0.05 and 20 milliequivalents per 100 grams (meq.// lOO gr.) of monomer. A chain transfer agent can be used over a broad concentration index with 0.05 to 20 meq./lOO gr. of dibasic acids, such as middle esters, other alkyl amides and substituted alkyl of acrylic acid, methacrylic acid, maleic acid (mono- and diamides), fumaric acid (mono- and di-amides) and itaconic acid (mono- and di- amides), methacrylamide, diacetone acrylamide, alkyl vinyl ethers, such as butyl vinyl ether, and ureido monomers, including those with cyclic ureido groups. Another variation in the inclusion of the hydrophilic monomer, for example, is when a monomer is included in the polymerization mixture which itself is not hydrophilic, but is altered in the processing or in a subsequent step, e.g. , by hydrolysis, to provide hydrophilicity; examples are monomers containing anhydride and epoxide. Other examples are vinyl alcohol esters such as vinyl formate, vinyl acetate, vinyl propionate, vinyl butyrate and vinyl versatate. The hydrolysis of these monomers produces mer units of vinyl alcohol in the polymer, whose mer units are hydrophilic. The preferred monomer of these is vinyl acetate. As indicated above, the composition of the present invention includes the water soluble volatile organic solvent. The level of water soluble volatile organic solvent is such that a paint containing the composition can be easily sprayed by means of conventional spray techniques, such as air spray, airless spray, airless spray and air spray. low pressure in high volume. As long as the water-soluble volatile organic solvent is evaporated from a paint layer containing the composition of the present invention, the associative thickener present in the layer acts to substantially increase the viscosity, from which the drying rate is accelerated to the touch of the layer. In general, the viscosity, after evaporation of the solvent from the layer, increases at least three times the can viscosity of the paint. The applicant has unexpectedly discovered that when the water-soluble volatile organic solvent is added to the composition, in the range of 0.2% to 10%, preferably in the range of 1% to 10% and more preferably in the range of 1 to 10%. % to 5%, all in volume percentages based on the total paint volume, the unexpected results mentioned above are achieved. The water-soluble volatile organic solvent suitable for use in the present invention includes any organic solvent that is soluble in water at 20 ° C. in at least 5 weight percent of the total weight of the aqueous solution, and having an evaporation index equal to or greater than that of n-butyl alcohol. Examples of suitable solvents include, but are not limited to, acetone, methyl acetate, tetrahydrofuran, ethyl acetate, methyl ethyl ketone, propylene-glycol-methyl ether, ethylene-glycol-methyl ether, methanol, ethanol, isopropanol , n-propanol, sec -butanol, isobutanol, t-butanol, n-butanol, ethyl acetate, propylene acetate-glycol monomethyl ether, ethylene-glycol monomethyl ether acetate, propylene glycol monomethyl ether, ethylene glycol monomethyl ether and mixtures of these. The preferred solvents are acetone and methanol. Acetone is more preferred. The coating composition of the present invention further includes a latex binder, which may be a dispersed polymer having dispersed polymer particles in an aqueous evaporable carrier or it may be a water soluble polymer, a water reducible polymer, a mixture of the water-soluble and water-reducible polymers in the aqueous evaporable carrier or a mixture of the dispersed, water-reducible, and water-soluble polymers in the aqueous evaporable carrier. If desired, the latex binder may include a mixture of a dispersed polymer with a water-soluble or a water-reducible polymer. The latex binder in the form of dispersed polymer particles is preferred, wherein the particle size of the dispersed polymer particles varies in the range of 20 to 1000 nanometers, preferably in the range of 30 to 300 nanometers, more preferably in the range of 100 to 250 nanometers. The latex polymer suitable for use in the present invention includes an emulsion polymer of mono- or polyethylenically unsaturated olefinic, vinyl or acrylic monomers, including copolymers and homopolymers of said monomers. Specifically, the dispersed polymer may include poly (vinyl acetate) and vinyl acetate copolymers (preferably at least 50% by weight) with one or more of: vinyl chloride, vinylidene chloride, styrene, vinyltoluene, acrylonitrile, methacrylonitrile, acrylamide, methacrylamide, maleic acid and esters thereof, or one or more of: the acrylic and methacrylic acid esters mentioned in US Pat. 2,795,564 and 3,356,627, whose polymers are well known as the film-forming component of water-based paints; homopolymers of alpha C2-C40 olefins such as ethylene, isobutylene, octane, nonane and styrene; copolymers of one or more of these hydrocarbons with one or more esters, nitriles or amides of acrylic acid or methacrylic acid or with vinyl esters, such as vinyl acetate and vinyl chloride, or with vinylidene chloride; and diene polymers, such as copolymers of butadiene with one or more of: styrene, vinyl toluene, acyl nitrile, methacrylonitrile and esters of acrylic acid or methacrylic acid. It is also very common to include a small amount, such as 0.5 to 2.5% or more, of an acidic monomer in the monomer mixture used to make the aforementioned copolymers by emulsion polymerization. Acids used include acrylic, methacrylic, itaconic, citraconic, crotonic, maleic, fumaric, methacrylic acid dimer. Vinyl acetate copolymers are well known, and include copolymers such as vinyl acetate / butyl acrylate / 2-ethylhexyl acrylate, vinyl acetate / butyl maleate, vinyl acetate / ethylene, vinyl acetate / vinyl chloride / butyl acrylate and vinyl acetate / vinyl chloride / ethylene. Other suitable monomers from which the latex binder can be polymerized include at least one or more of the following monomers: acrylic and methacrylic ester monomers including methyl (meth) acrylate, ethyl (meth) acrylate, ( met) butyl acrylate, 2-ethylhexyl (meth) acrylate, decyl (meth) acrylate, lauryl (meth) acrylate, isobornyl (meth) acrylate, isodecyl (meth) acrylate, oleyl (meth) acrylate, (meth) palmityl acrylate, stearyl (meth) acrylate, hydroxyethyl (meth) acrylate and hydroxypropyl (meth) acrylate; functional acid monomers, such as acrylic acid, methacrylic acid, crotonic acid, itaconic acid, fumaric acid and maleic acid; monomethyl itaconate; monomethyl fumarate; monobutyl fumarate maleic anhydride; acrylamide or substituted acrylamides sodium vinyl sulfonate; phosphoethyl acrylamide propane sulfonate (meth) acrylate; acrylamide of diacetone glycidyl methacrylate; acetoacetyl ethyl methacrylate acrolein and methacrolein; dicyclopentadienyl methacrylate dimethyl-meta-isopropenyl-benzyl isocyanate; isocyanate ethyl methacrylate; styrene or substituted styrenes; butadiene; ethylene; vinyl acetate or other vinyl esters, N-vinyl pyrrolidone; amino monomers, such as, N, N'-dimethylamino and (meth) acrylate. The polymerization techniques used to prepare the latex binder of the present invention are well known in the art. The binder can be prepared by emulsion or solution polymerization, preferably by initiation of free radical. The polymerization can be developed continuously or in series. Both the redox initiation process and the thermal process can be used. The polymerization process is typically initiated by means of conventional free radical initiators, which include hydrogen peroxide; hydroperoxides, such as, t-butyl hydroperoxide; dialkyl peroxides, such as di-t-butyl peroxide; peroxy esters, such as t-butylperoxy pivalate; diacyl peroxides, such as, benzoyl peroxide; azo compounds, such as, 2-2'-azobisisobutyronitrile; and alkali and ammonium persulfates, such as, sodium persulfate, typically at a level of 0.05 percent to 3.0 percent by weight, all percentages by weight based on the total weight of the monomer mixture. Redox systems using the same primers coupled with a suitable reductive such as sodium bisulfite, sodium hydrosulfite, sodium formaldehyde sulfoxylate and ascorbic acid can be used at similar levels. The chain transfer agents can be used in an amount effective to provide the weight average molecular weight per desired CPG. For the purpose of regulating the molecular weight of the latex binder that has been formed, suitable chain transfer agents include well-known halo-organic compounds such as dibromodichloromethane and carbon tetrabromide.; sulfur-containing compounds, such as alkylthiols including ethyl mercaptoacetate, tert-butyl, ethanethiol, butanethiol, as well as aromatic thiols; or several other organic compounds that have hydrogen atoms and that are easily abstracted by free radicals during polymerization. Additional suitable chain transfer ingredients or agents include, but are not limited to, butyl mercaptopropionate; Isooctylmercaptopropionate; bromoform; bromotrichloromethane; carbon tetrachloride; alkyl mercaptans, such as 1-dodecantiol, tertiary-dodecyl-mercaptan, octyl-mercaptan, tetradecyl-mercaptan and hexadecyl-mercaptan; alkyl thioglycollates, such as butyl thioglycolate, isooctyl thioglycolate and dodecyl thioglycolate; thioesters or combinations of these. The mercaptans are preferred. When the latex binder is used in the form of a dispersed polymer, the particle size of the polymer is controlled by the amount of conventional surfactants added during the emulsion polymerization process. Conventional surfactants include anionic, nonionic emulsifiers or combinations thereof. Anionic emulsifiers include salts of fatty rosin and naphthenic acids, condensation products of formaldehyde and low molecular weight naphthalene sulfonic acid, copolymers and carboxylic polymers of the appropriate hydrophilic lipophilic balance, ammonium alkyl sulfates or alkali, alkyl sulfonic acids, alkyl phosphonic acids, fatty acids and phosphates and sulfates of oxyethylated alkylphenol. Typically, nonionic emulsifiers include alkylphenol ethoxylates, polyoxyethylenated alkyl alcohols, amine polyglycol condensates, modified polyethoxy adducts, long chain carboxylic acid esters, modified finished alkylaryl ether, and alkylpolyether alcohols. Typical scales for surfactants are between 0.1 to 6 weight percent, based on the total weight of the monomer mixture. Alternatively, the latex binder may include multi-stage polymer particles, having two or more phases of various geometric structures, such as core / shell or core / shell particles, core / shell particles with shell phases that encapsulate incompletely to the nucleus, core / shell particles with a multiplicity of interpenetrating network particles and nuclei. In all these cases, the majority of the surface area of the particle will be occupied by at least one outer phase, and the interior of the particle will be occupied by at least one interior phase. The outer phase of the multi-stage polymer particles weighs from 5 percent to 95 percent by weight, based on the total weight of the particle. It is usually desired that each stage of the multi-stage polymer particles have a different Tg. If desired, each stage of these multi-stage polymer particles may be provided with a different weight average molecular weight per CPG, such as the multi-stage polymer particle composition disclosed in U.S. Pat. 4,916,171.

In addition, the coating composition suitable for use in the present invention may include standard formulation additives, such as coalescents, pigments, extenders, defoamers, surfactants, wetting agents, dispersants, waxes, slip aids and crosslinkers. As used herein, coalescents are those film-forming agents that are evaporated from an applied layer, substantially after the evaporation of the water and water-soluble volatile organic solvent present in the applied layer. The coating composition of the present invention is generally provided with a solids content in the range of 50 percent to 85 percent, all in volume percentages based on the total volume of the composition. The paint containing the coating composition of the present invention is generally provided with a pigment volume concentration in the range of 40 percent to 70 percent, all in percentages of volume based on the total volume of the paint. If desired, the method of the present invention may include casting glass beads onto the layer of a traffic paint containing the coating composition of the present invention, before the layer is dried to ensure adhesion of the beads of glass to the layer applied on a road surface. The glass beads arranged facially on the traffic signs act as light reflectors. If glass beads are not used, traffic signals will be difficult to see at night and under bad weather conditions. Thus, almost all traffic signals are usually pearly, ie the glass beads are dispersed and fixed on the surface of the coatings manually at the rate of 0.72 to 2.9 kilograms or more per liter of paint, for visibility at night and under rainy conditions. The glass beads are cast by methods known in the art, such as by spraying the glass beads driven and transported by an air jet and expelled on the surface or by spreading the glass beads at a desired rate from a storage hopper. placed on the layer of traffic paint. The glass beads are applied on the layer, while the layer is still in its "wet" state, that is, before the layer dries to form the traffic paint signal. The amount of glass beads scattered on the layer depends on the size, the refractory index and the surface treatment of the glass beads. The typical glass beads specified for traffic signs are described in accordance with the AASHTO Designation M 247-81 (1993) developed by the American Association of State Highway and Transportation Officials, Washington, DC Optionally, glass beads can be previously mixed with traffic paint before it is applied to road surfaces. The method of the present invention can be used to produce a fast-drying coating useful as a traffic paint for marking roads or pavement, for concrete, asphalt or bituminous roads, pedestrian walkways or parking lots, a metal protection coating, a mastic for ceilings or other building components, and a covering for masonry, wood, plastics, fibers and woven and non-woven fabrics, glass, leather or paper.

Test procedures The following test procedures were used to generate the data reported in the examples below: Dry to touch test This test was developed according to the ASTM D 1640 method. A layer with a wet film thickness of 0.305 mm was placed on an aluminum panel. (12 mil.) Of a test sample prepared according to the present invention or a comparative paint. Then periodically the layer was touched lightly with the finger. The drying time to the touch was recorded when the layer no longer adhered to the finger.

Canned Paint Viscosity Measurement The viscosity of canned paint was measured by means of a Brookfield viscometer model LVT supplied by Brookfield Engineering Laboratories, Inc., Stoughton, Massachusetts, using a # 3 @ 30 RPM shaft.

Examples The examples of the associative thickeners (Tx and T2), which are shown in table 1 below, were made by means of the following standard procedure: A round bottom flask, with three necks, with a capacity of 100 ml. , was adapted with a reflux condenser connected to a drying tube filled with CaS04, a gas inlet tube, a serious capsule and a magnetic stirrer. The solid components (marked with * in Table 1 below) were placed in the flask, the system was leveled with dry nitrogen, the agitator was turned on and then the flask was heated until the solid components melted. The liquid components were then injected into the flask through the capsule in the order listed in table 1 below, then the mixture was heated under reflux for five hours. Right away, 10 gr. of ethanol were added to the flask, and the reflux continued for one more hour. The resulting solutions were emptied into open glass containers, and placed in a 160 ° F oven. for four days until the volatiles had been removed. The resulting solids were then dissolved in methanol to make 33.3 weight percent solutions, based on the total weight of the solution.

Table 1 Thickener # Ti t2 Poly (ethylene glycol) 1 20.00 gr. Mn = 4600 * Poly (ethylene glycol) 2 20.00 gr.

Mn = 8000 * Octanol 0.57 gr. 0.33 gr.

Ethylene glycol 0.14 gr. 0.08 gr.

Methyl ethyl ketone 4.00 gr. 4.00 gr.

Isophorone diisocyanate 1.94 gr. 1.12 gr.

T-12 (1% solution in 0.07 gr 0.07 gr.

Propylene glycol-methyl-ether-acetate methyl ethyl ketone 8.00 gr. 8.00 gr. 1 = supplied by Aldrich Chemical Company, Milwaukee, Wisconsin 2 = supplied by Aldrich Chemical Company, Milwaukee, Wisconsin Mn means number average molecular weight * these were solid components.

Preparation of paint The following main series were prepared mixing together the ingredients listed below in Table 2, in the order shown: Table 2 Main series # B2 Bi Emulsion polymer1 302 .2 gr. 3802.5 gr.

Water 56. í 3 gr. 568.5 gr.

Dispersant2 7.2 gr. 72.0 gr.

Defoamer3 2.0 gr. 20.0 gr.

Pigment4 100 .0 gr. 1000.0 gr.

Alargante5 760 • 6 gr. 7606.0 gr.

Coalescing agent * 6 230.0 gr.

Water * 230.0 gr.

Surfactant agent * 7 1.0 gr. 1 = Rhoplex® TP-257 emulsion polymer supplied by Rohm and Haas Company, Philadelphia, Pennsylvania. 2 = Tamol® 901 Dispersant @ 30 percent based on solids, supplied by Rohm and Haas Company, Philadelphia, Pennsylvania. 3 = Drewplus® L-493 defoamer supplied by Drew Chemical Company, Boonton, New Jersey. = titanium dioxide white pigment TiPure® R-900, supplied by E.l. duPont de Nemours & Company, Wilmington, Delaware. 5 = powdered natural calcium carbonate 0myacarb®-5, evaluated in accordance with ASTM D 1199, type GC, grade II, having an average particle size of 5.5 microns with maximum oil absorption no. 10, supplied by O ya, Inc., Proctor, Vermont. 6 = Texanol ® ester alcohol, supplied by Eastman Chemicals, Kingsport, Tennessee. 7 = Octyl-phenoxy-polyethoxyethanol surfactant agent Triton® X-405, supplied by Union Carbide Chemicals, Inc., Danbury, connecticut @ 70 weight percent solids * these ingredients were premixed.

The following paintings test? > 1 to P4 and P5, and the comparative test paints CP1 to CP5 were prepared by mixing together the ingredients listed below, in the order shown. The amount of thickener added was adjusted to achieve the viscosity that is listed in Table 4 below.

Table 3 Main series Solvent * Water * ßslider l 654.8 gr. (BJ 5.55 gr.1 14.54 gr.i p2 730.8 gr. (Bj 12.40 gr.1 1.01 gr. I p3 705.3 gr. (BJ 5.98 gr.1 15.65 gr.t2 P4 685.8 gr. (BJ 11.63 gr.1 9.40 gr. t2 CPi 676.0 gr. (BJ 11.47 gr.2 9.26 gr. p5 200.0 gr. (BJ 6.0 gr.1 7.0 gr.t2 CP2 200.0 gr. (BJ 6.0 gr.1 7.0 gr.

CP3 200.0 gr. (BJ 6.0 gr.3 7.0 gr.t2 CP4 200.0 gr. (BJ 13.0 gr.t2 CP5 200.0 gr. (BJ 6.0 gr.1 7.0 gr. Non-associative thickener5 1 = acetone 2 = diethylene glycol butyl ether 3 = ethylene glycol butyl ether 4 = associative thickener Acrysol® RM-825, supplied by Rohm and Haas Company, Philadelphia, Pennsylvania. 5 = Non-associative thickener Acrysol® ASE-60, supplied by Rohm and Haas Company, Philadelphia, Pennsylvania. * These ingredients were previously mixed.

The highest amount of VOC in the paints tested was in P2 at 86 grams per liter of paint, and the lowest amount was in P5 at 80 grams per liter of paint. Thus, all the test paints were well within the proposed upper limit for VOCs in the paint. In appropriate comparison, the comparative paints also had VOCs in similar amounts.

Test results Table 4 Paint # Solvent level Thickener Viscosity Time (% on solids (cps) dried to resin) touch (min.) P2 101 tx 2840 2.25 p3 51 t2 2520 6 p4 101 t2 2320 2 CPi 102 thickener 2400 11 associative3 101 t2 1500 3.5 CP2 101 without thickener 1230 22 CP3 102 t2 1400 12.5 CP4 siri solvent t2 1460 14 CP5 101 thickener no 1660 14 Associative4 1 = solvent with high volatility 2 = solvent with low volatility 3 = associative thickener Acrysol® RM-825 , supplied by Rohm and Haas Company, Philadelphia, Pennsylvania. 4 = non-associative thickener Acrysol® ASE-60, supplied by Rohm and Haas Company, Philadelphia, Pennsylvania.

Table 4 above shows the touch drying times in minutes obtained from various compositions having substantially the same viscosity (the first set of Px-P4 and CPX, and the second set of P5, CP2-CP5). From the test results shown in Table 4, it can be seen that while the amount of solvent added to the paint is increased (Px versus P2 and P3 versus P4) the drying time to the touch substantially reduces. However, due to the environmental limitation, there is a limit on how much solvent should be added to the composition. In addition, Table 4 also shows that when an associative thickener (P5) is replaced with a non-associative thickener (CP in the composition, there is a substantial increase in the time of touch drying. associative (CP2) or when a solvent of low volatility (CP3) was used or when no solvent was used (CP, the time of drying to the touch was significantly greater than that of the paint that contained the associative thickener, and to which was added water soluble organic solvent with high volatility in the amounts noted above (P. Thus, it is noted that the applicant has unexpectedly discovered that including a certain desired level of associative thickener and high volatile water soluble organic solvent in the coating composition, a paint was obtained with low amounts of VOC from a single package, which can be easily applied by conventional means, such as by pressure sprayer, and has fast drying characteristics.

Claims (10)

1. Claims 1. A method for coating a substrate, comprising: applying under ambient conditions, on the surface of said substrate, a layer of a fast-drying paint of a single package, containing a water-based coating composition with low VOC amounts, said composition comprises a latex binder, an associative thickener and a water soluble organic volatile solvent, wherein the amounts of said associative thickener and said solvent are such that said paint has a can viscosity, under ambient conditions, in the range of 1,000 cps to 6,000 cps, and a touch-time index, in accordance with ASTM D-1640, of less than 10 minutes; and evaporating said solvent from said layer to form said coating on said substrate. The method according to claim 1, wherein a concentration in pigment volume of said paint is in the range of 40 percent to 70 percent, all in volume percentages based on the total volume of the paint. 3. The method according to claim 1 or 2, wherein said composition has a solids content in the range of 50 percent to 85 percent, all in volume percentages based on the total volume of the composition. 4. The method according to claims 1, 2 or 3, wherein said thickener is selected from the group consisting of RUEH, EHAH, acrylamide copolymer and mixtures thereof. The method according to claims 1, 2, 3 or 4, wherein said solvent is selected from the group consisting of acetone, methyl acetate, tetrahydrofuran, ethyl acetate, methyl ethyl ketone, propylene glycol ether, methyl, ethylene-glycol-methyl ether, methanol, ethanol, isopropanol, n-propanol, sec-butanol, isobutanol, n-butanol and mixtures thereof. 6. A coating produced according to the method of claims 1, 2, 3, 4 or 5. 7. A method for improving the drying time of a traffic signal on a road or pavement surface, comprising: in said surface a layer of a traffic paint of a single package containing a water-based coating composition with low amounts of VOC, comprising a latex binder, an associative thickener in the range of 0.01 percent to 10 percent , and a water-soluble organic volatile solvent in the range of 0.2 percent to 10 percent, all in volume percentages based on the total volume of the composition, wherein said traffic paint has a can viscosity, under ambient conditions, in the range of 1,000 cps to 6,000 cps, and the touch-time index, in accordance with ASTM D-1640, is less than 10 minutes; evaporating said solvent from said layer, to form said traffic signal on said substrate. The method according to claim 7, wherein said solvent of said layer is evaporated at an index of 10 seconds to 30 minutes under high humidity conditions. 9. A water-based, single-pack coating composition with low amounts of VOC and fast drying, comprising: a latex binder; an associative thickener; and a water-soluble organic volatile solvent, wherein the amounts of said associative thickener and said solvent are such that a fast-drying, single-pack paint, containing said composition, has a can viscosity, under ambient conditions, in the range from 1,000 cps to 6,000 cps, and a touch-dry time index, in accordance with ASTM D-1640, of less than 10 minutes. 10. A water-based, single-pack coating composition with low amounts of VOC and fast drying, comprising: a latex binder; an associative thickener in the range of 0.01 percent to 10 percent; and a water-soluble organic volatile solvent in the range of 0.2 percent to 10 percent, all in volume percentages based on the total volume of the composition, wherein a traffic paint containing said composition has a low can viscosity. environmental conditions, in the range of 1,000 cps to 6,000 cps, and a touch-time index, in accordance with ASTM D-1640, less than 10 minutes.