WO2005049719A2

WO2005049719A2 - Aqueous compositions comprising esters of lactic acid and methods of use

Info

Publication number: WO2005049719A2
Application number: PCT/US2004/037544
Authority: WO
Inventors: Robert T. Sobieski
Original assignee: Omnova Solutions Inc.
Priority date: 2003-11-12
Filing date: 2004-11-10
Publication date: 2005-06-02
Also published as: WO2005049719A3

Abstract

Aqueous polymer compositions comprising a film-forming polymer and a lactate ester are provided. These compositions provide exceptional performance properties, while at the same time being relatively environmentally friendly. These compositions are used as coating compositions and as binders or matrix formation compositions for the formation or articles comprising the film-forming polymer. Methods of use of such compositions, and coating methods wherein the lactate ester is applied separately to the substrate are also provided.

Description

AQUEOUS COMPOSITIONS COMPRISING ESTERS OF LACTIC ACID AND METHODS OF USE

FIELD OF THE INVENTION The present invention relates to aqueous compositions. More specifically, the present invention relates to aqueous compositions comprising film-forming polymers and esters of lactic acid, and methods of use of same. BACKGROUND OF THE INVENTION Protection of various surfaces today is often carried out by applying a coating of polymer material to the surface. Such polymer coatings are beneficial in appearance and in providing certain performance characteristics, such as cleanability, durability or strength. Polymers are also coated on surfaces for other uses as well; for example, polymers having specific characteristics are used as adhesive coatings. Additionally, various materials may be formed using polymer compositions as binders in the manufacturing process, for example paper, composites and nonwoven or woven fabrics. Environmental concerns dictate that such polymer coatings and compositions be used with a minimum of release of unwanted organic materials to the air. Volatile Organic Compounds ("VOCs") contribute to pollution of our planet and otherwise can diminish the quality of life. According to the definition in the European Union VOC-directive, a compound is volatile if the vapor pressure is higher than 0.1 mbar at 20° C. Systems have therefore been developed for application of polymer coatings with a minimum release of VOCs to the atmosphere. One of these systems includes coating and other manufacturing processes where the polymer is delivered from an aqueous composition. Aqueous coating processes present specific challenges in obtaining the desired polymer coating. Adhesion of the polymer to the intended substrate can be challenging. To solve this problem, adhesion promoters are often used to render the substrate receptive to coating by the polymer. One such adhesion promotion system is the use of a strong organic solvent to "swell" the underlying substrate. Such solvents themselves often are VOCs, and additionally often have been found to have deleterious environmental effects and toxicity to humans and/or animals. In addition to adhesion of the polymer coating to the substrate, it can often be challenging to simply get the polymer to coalesce sufficiently to form a film when delivered from an aqueous composition. Coalescing agents are often used to assist in film formation in such circumstances. Coalescing agents are often strong organic solvents that will soften the polymer of the coating, thereby facilitating the formation of a film upon application of the composition to the surface to be coated. One material often used in the industry as both an adhesion promoter and a coalescing agent is n-methyl pyrrolidone ("NMP"). NMP is a listed material on the EPA's SARA & TRI reporting list, as well as California's Proposition 65, which is a law that requires the Governor to publish a list of chemicals known to the state to cause cancer or reproductive toxicity. It is also listed on Executive Order EO13134 as a petroleum-based material. Another class of chemicals often used as adhesion promoters and coalescing agents are the glycols. These chemicals too have reported negative health implications and raise disposal issues. Alkyl lactate esters have been used as degreasers and precision cleaners because of their solvency power for oils, oligomeric and polymeric stains. These materials have been indicated for these uses by PURAC America, Lincolnshire, IL, which offers a line of lactate esters under the brand name PURASOLV^®, listing methyl lactate, ethyl lactate iso-propyl lactate, n-propyl lactate, butyl lactate and 2-ethylhexyl lactate under this brand name. This company further states on its website that "PURASOLV products, with their lower boiling point, are excellent to use when formulating safe solvent systems for high solids coatings. The solubility parameters of the PURASOLV product line offer new opportunities for obtaining high-solids contents with good rheology." Thus, these products are contemplated for use as a solvent in solvent- based coating compositions. SUMMARY OF THE INVENTION It has surprisingly been found that aqueous polymer compositions comprising a film-forming polymer and a lactate ester provide exceptional performance properties, while at the same time being relatively environmentally friendly. These compositions are used as coating compositions and as binders or matrix formation compositions for the formation of articles comprising the film- forming polymer. In one aspect of the present invention, aqueous film-forming polymer compositions are provided wherein the film-forming polymer is present in an amount effective to form a coating layer on a substrate when applied thereto under film formation conditions and the lactate ester is present in an amount effective to act as a coalescing agent for the film-forming polymer. A coalescing agent is effective as such if the film-forming polymer forms a film either more rapidly or at a lower temperature as compared to a like formulation that does not contain the coalescing agent. The film may be continuous or discontinuous. Examples of preferred such coatings include protective coatings, latex paints, water based inks, or adhesive compositions. In another aspect of the present invention, the composition is an article- forming aqueous composition comprising a film-forming polymer and a lactate ester, wherein the film-forming polymer forms a matrix throughout the article. The matrix may be continuous or discontinuous. In another embodiment, the composition is an article-forming aqueous composition comprising a film-forming polymer and a lactate ester, wherein the film-forming polymer acts as an adhesive binder to adhere separate components, such as particles or fibers, to each other to form an article. In another aspect of the present invention, aqueous compositions and methods of use thereof are provided wherein an aqueous composition comprising a film-forming polymer is applied with a lactate ester to a substrate that is swellable by the lactate ester, where the lactate ester is provided in an amount effective to enhance adhesion of the film-forming polymer to the substrate. For purposes of the present invention a coating composition is considered to be "aqueous" if it contains water in an amount sufficient to act as the solvent for a non- water solute in a solution or colloidal dispersion composition, or if there is sufficient water present to act as one of the phases in an emulsion system. In systems wherein water is acting as a solvent (i.e. an solution formulation), preferably, water is present as the majority component of the non-solids portion composition. Most preferably, water is present at an amount of from about 20 to about 80 % of the non-solids portion of the total composition prior to coating on the intended substrate. In emulsion systems, preferably water is the continuous phase of the emulsion. In either the solution formulation or the emulsion formulation, in one embodiment the film-forming polymer preferably is present at a solids content of about 1 to about 15 %. These formulations are particularly advantageous for rapid padding operations (particularly in the textile environment, and find particular benefit in the rapid film-formation properties and potentially enhanced durability to the substrate as afforded to such compositions by incorporation of the lactic ester as described herein. In another embodiment, the film-forming polymer preferably is present at a solids content of about 15 to about 80 %. These formations are particularly advantageous for use in direct coating operations, and find particular benefit in the rapid film-formation properties and potentially enhanced durability to the substrate as afforded to such compositions by incorporation of the lactic ester as described herein. The present invention surprisingly improves the coalescence of film-forming polymer from aqueous compositions. While not being bound by theory, it is believed that the lactate esters enhance coalescence of the film-forming components of the composition by solvating or swelling the polymer. Additionally, the lactate esters surprisingly enhance adhesion of the resulting coating to a surface when the composition is a coating composition. While not being bound by theory, it is believed that the lactate esters act to lower the surface tension of the coating composition, thereby assisting in adhesion of the polymer coating to the substrate through better wetting. Further, the lactate esters surprisingly act to enhance the adhesion of coatings to polymer substrates. While not being bound by theory, it is believed that the lactate esters swell the polymer substrate, thereby providing an opportunity for the film-forming polymer to at least partially penetrate into the surface of the substrate. Most preferably, the lactate ester acts to swell both the film-forming polymer of the coating and also the polymer of the substrate, thereby both acting as a coalescing agent and an adhesion promoter. Lower alkyl lactates are particularly preferred as the lactate ester to be used in the present invention. Because lower alkyl lactate esters have been recognized to be comparatively environmentally benign, these compounds find particularly advantageous use in applications where typical solvents are prohibited. This is particularly the case in the area of application of coatings to fabrics, which uses large amounts of chemicals and where disposal of effluent material resulting from the use of noxious solvents may be difficult or expensive. Lactate esters in the concentrations as used in the present invention are surprisingly easy to properly dispose of, and in certain cases may be simply disposed by transferring to conventional waste water treatment plants. The present invention is particularly useful in providing stain resistant coatings. The term "hydrophobicity" as used herein means that the coating is water repellent and resists removal by washing. The term "oleophobicity" as used herein means that the coating is resistant to attack and removal by oils. The two terms may be combined herein with reference to the term "repellent." The term "stain resistant" as used herein means that the coating exhibits high stain release. DESCRIPTION OF THE DRAWINGS Fig. 1 provides a non-limiting exemplary schematic of a preferred process for carrying out the present invention. DETAILED DESCRIPTION The incorporation of lactate esters in aqueous film-forming polymer compositions provides many benefits from a performance standpoint. It has surprisingly been found that current film-forming polymer composition formulations wherein lactate esters are substituted for conventional coalescing agents perform as well or better than prior art formulations, in a much more environmentally friendly manner. Thus, performance properties of films formed from aqueous film-forming polymer compositions comprising one or more lactate esters surprisingly may exhibit superior performance properties in one or more aspects that reflect excellent film formation, such as durability, scratch resistance, and tensile strength properties. Additionally, the ability to use an environmentally friendly coalescing agent expands the choice of materials that may be used in a film-forming polymer composition. Thus, because a coalescing agent may now be used, or may be used in a larger quantity than was previously permitted, it is possible to select polymers having a higher glass transition temperature ("Tg") then previously possible for various uses. This in turn affects the properties of the final product, rendering the ultimate article superior in various aspects related to excellent film formation with high Tg polymers, such as in durability, scratch resistance, and tensile strength properties as compared to the properties of like compositions formulated with lower Tg polymers. Surprisingly, lactic esters when added to compositions comprising film- forming polymers will reduce the minimum film-forming temperature of the composition as compared to a like composition not containing a lactic ester. Preferably, lactic esters are added to aqueous film-forming compositions in an amount effective to reduce the minimum film-forming temperature more than 30°C, more preferably more than 50°C, and most preferably more than 80°C. The present invention additionally can provide processing advantages, because coalescence of film-forming polymers can be carried out at faster speeds or at lower ambient temperatures without exceptional heating or expensive lamps. Such processes may be carried out in a more environmentally friendly manner, with superior performance properties of the final product. Preferably, the compositions are formulated so that the coating method or manufacturing method is carried out at a temperature of from about 5° to about 180° C. In one preferred embodiment, the composition is formulated so that the manufacturing or coating method may be carried out at a temperature of typical working conditions in the outdoor environment, e.g. from about 5° to about 50° C. In another preferred embodiment, the composition is formulated so that the manufacturing or coating method may be carried out at a temperature of typical factory line film-formation conditions using relatively low temperature heating equipment, e.g. from about 100° to about 180° C. Compositions of the present invention provide particular advantage in providing superior performance of the final product when components of the product have a relatively low temperature of degradation. For example, coatings to be applied to substrates that are temperature sensitive preferably coalesce at a sufficiently low temperature so that the substrate is not exposed to a temperature above the temperature of degradation of the substrate, to provide a suitable coating layer without damaging the substrate. The present invention allows formulation of coating compositions that utilize higher Tg materials than could conventionally be used on temperature sensitive substrates, because the lactate esters reduce the coalescing temperature of the coating compositions and allow formulations to include materials not before useable in an environmentally friendly fashion on certain substrates without the use of expensive or inconvenient UV lamps or other ways of obtaining coalescence. Examples of substrates that have degradation temperatures that inhibit selection of materials that can be coated thereon particularly include paper, vinyl chloride and polyester. Additionally, film-forming compositions of the present invention surprisingly provide resultant films that have superior strength properties as compared to like compositions not incorporating lactate esters. Such films exhibit superior tensile properties, even without modification of the polymer content of the film itself. Other potential film property benefits from use of lactate esters include improvement in durability, gloss, modulus, elongation, impact strength, and hardness. Improved coating layers may be continuous or discontinuous. In a particularly preferred embodiment, the coating layer is a thin coating, e.g. having a thickness of from about 0.08 mm to about 10 mm. Because such coating layers comprise only a small amount of material on a substrate, the nature of the matrix created in formation of the coating has a disproportionately great effect on the performance of the coating, rendering the present invention particularly advantageous in this embodiment. In a particularly preferred embodiment, coatings of the present invention are formulated to provide protection to the underlying substrate. Such protective coatings are preferably prepared from polymers such as themoplastic polymers such as vinyl polymers (such as acrylate and/or methacrylate (jointly referred to as "(meth)acrylate") copolymers, polyvinyl chloride, polystyrenes, polybutadienes, polyethylene, polypropylene) urethanes polyesters, polyamides, polyethers and certain polycarbonates (e.g. the polycarbonate of bisphenol A), or thermoset polymer such as certain polycarbonates (e.g. crosslinked polycarbonates), epoxies, polydicyclopentadienes, and hybrids and blends of one or more of these polymers. In another particularly preferred embodiment of the present invention, lactate esters are provided as a component in a latex paint composition. Latex paint comprises pigments, binders, liquid carriers including water, and additives (such as surfactants). Paint compositions in general are known in the art, and may be readily formulated by the routineer to incorporate lactate esters by reference to the present disclosure. Preferably, the binder of the latex paint composition comprises styrene- butadiene polymers, vinyl acrylic polymers or acrylic polymers, or combinations thereof as are known in the art. In a particularly preferred embodiment, the paint composition is a zero VOC paint composition, e.g., compositions that meet method 24 of the US Environmental Protection Agency. In another particularly preferred embodiment, the coating composition is a water based ink composition, such as thermal ink jet inks, flexographic inks, gravure inks, lithographic inks, toners, and the like. Water based inks may be formulated in a manner known in the art, with incorporation of lactate esters as taught herein. In another particularly preferred embodiment, the coating composition is an adhesive. The adhesive may be applied to any desired substrate, such as paper, polymer film, and the like. Adhesives coated in accordance with the present invention on polymer substrates are particularly preferred, because formulations may be prepared that provide exceptional affinity and retention of the adhesive on the polymeric substrate without transfer of the adhesive when the substrate is attached to a surface and subsequently removed therefrom. Most preferably, the adhesive composition is a pressure sensitive adhesive composition. Water based adhesive compositions may be formulated in a manner known in the art, with incorporation of lactate esters as taught herein. In another particularly preferred embodiment of the present invention, lactate esters are used as coalescing agents for aqueous binders in manufacture of non-film products. Such non-film products include nonwoven fabrics, paper and composites made from such materials as wood, inorganic materials, polymers and the like. Examples of composites include fiberboard and other such building materials and shapable materials. Particularly preferred compositions of the present invention are aqueous binders for fabrics, wherein the binder acts to adhere fibers to each other at crossing points in the fabric matrix. Such binder materials are useful both for woven fabrics and for non- woven fabrics. Binder compositions may be formulated in a manner known in the art, with incorporation of lactate esters as taught herein. In a particularly preferred embodiment, lactate esters are incorporated into a plurality of aqueous polymeric coating compositions that are applied sequentially to a surface. While not being bound by theory, it is believed that sequential application of aqueous coating compositions, each comprising one or more lactate esters, results in superior final product properties because the lactate ester component is fully compatible with both layers and facilitates the interaction of the second layer polymer with the first layer polymer. Preferably, at least one of the coating compositions comprises a film-forming polymer. More preferably, the first coating comprises a film-forming polymer. Additional coatings (an preferably subsequent coatings) may optionally comprise a film-forming polymer or comprise only polymers that do not form a film. The present invention is particularly advantageous where the second layer is a fluoropolymer that adheres to the first layer by chemical affinity. The fluoropolymer may be a film-forming polymer or a non-film-forming polymer. A particularly preferred such layer arrangement is described in US Patent Application Serial No. 10/427,740 filed April 30, 2003 in the name of Sobieski, et. al. Particular advantage is observed in the case of systems wherein the second layer polymer (whether fluoropolymer or otherwise) is a non- film-forming polymer, because of the increased affinity of the second layer to the first layer due to the use of the lactate ester in the compositions. Preferably, lactate esters to be used in the present invention are the lactate esters of C1-C10 alkyl alcohols, and more preferably lactate esters of C2-C8 alkyl alcohols. Particularly preferred lactates are the lactate esters of ethanol, isopropanol, n- propanol, butanol and 2-ethyl hexanol. The hydrolysis products of these esters are considered to be benign from an environmental basis, particularly when compared to conventional coalescing agents and adhesion promoters. A particularly preferred ester for use is ethyl lactate, which hydrolyzes to ethanol and lactic acid - both naturally occurring substances. Blends of lactate esters are specifically contemplated. A preferred blend of lactate esters comprises one or more lactate esters of the C2-C4 alkyl alcohol portion in combination with one or more lactate esters having a C5-C10 alkyl alcohol portion. Additionally, blends of lactate esters with conventional coalescing agents or adhesion promoters, such as NMP or the glycols (e.g. ethylene glycol, propylene glycol and the like), are contemplated as providing the benefits of incorporating these conventional components in coating compositions, but at a lesser amount than may otherwise be required. In a preferred embodiment, the composition of the present invention is substantially free of NMP or glycols. In a particularly preferred embodiment, the composition of the present invention comprises no more than about 2% by weight of volatile organic solvents other than lactate esters and their corresponding hydrolysis products. In a more particularly preferred embodiment, the composition of the present invention is substantially free of volatile organic solvents other than lactate esters and their corresponding hydrolysis products. The lactate ester preferably is present at an amount of from about 30 g/1 to about 350 g/1 of the total composition prior to coating on the intended substrate. In some applications, it is contemplated that aqueous compositions comprising a film-forming polymer and lactate may not be applied to a substrate immediately after formulation, and thus may have to be stored for some time prior to use. Certain lactate esters may be subject to hydrolysis in certain aqueous compositions. Preferably, the coating composition is provided in a form where the lactate ester is stabilized against hydrolysis, for example, by addition of a buffer preferably to buffer that composition to neutral pH, such as sodium bicarbonate or of the alcohol corresponding to the alcohol of the lactic acid ester. Compositions used in the present invention may optionally comprise additional components suitable for incorporation in the compositions. A number of such optional additives are commonly employed in the art. These optional additives include wetting agents; curatives; catalysts, which may be employed to facilitate the activation of crosslinking agents and thereby aid in the formation of a layer through partial crosslinking or coalescence of the coating composition; antimicrobials; defoamers; and other additives generally employed in this field. These additives would be present in conventional amounts, chosen so as to not have a negative impact on the properties of the respective final product. The compositions can also include surfactants for the dispersion of the polymers. In the case of coating compositions, surfactants additionally may be incorporated to reduce the surface tension of the coating composition to allow for proper wetting of the substrate. This is particularly desirable when the substrate is a fiber or fabric substrate, in order to enhance penetration around fibers of the substrate on which the coating composition is applied. Examples of preferred surfactants include hydroxyl terminated carboxylic acid dispersants, which are organic compounds that contain one or more carboxyl groups and two or more hydroxyl groups (e.g. 2,2-dimethylol propionic acid). Other useful surfactant compounds include the furnarate polyether glycols described in U.S. Pat. No. 4,460,738. Other useful carboxyl-containing surfactant compounds include aminocarboxylic acids, for example lysine, cystine and 3,5-diaminobenzoic acid. The coating compositions preferably also include a non-rewetting surfactant to facilitate coating of one or more layers. Such non-rewetting surfactants preferably thermally decompose during the drying step after coating of the layer, and therefore are not present in the layer to interfere with the adhesion of subsequently coated layers or in the performance of the coating in place on the substrate. The non-rewetting surfactant additionally is particularly preferred for use in coatings intended to have a repelling activity through hydrophobicity, oleophobicity or both. Traditional surfactants are at least partially hydroscopic, and therefore their presence in repelling coatings is not desired because they would work in opposition to the stain repellant properties of the polymer of the coating. Additionally, traditional surfactants may have a deleterious effect on the cohesive strength of the film of the coating itself. A particularly preferred non-rewetting surfactant is amine oxide, which is preferably provided in amounts from about 5 to about 10 php in each of the coating compositions. Preferably, the amine oxide is included at from about 6 to about 8 php. As used herein, the term "copolymer" encompasses both oligomeric and polymeric materials, and encompasses polymers incorporating two or more monomers. As used herein, the term "monomer" means a relatively low molecular weight material (i.e., generally having a molecular weight less than about 500 Daltons) having one or more polymerizable groups. "Oligomer" means a relatively intermediate sized molecule incorporating two or more monomers and generally having a molecular weight of from about 500 up to about 10,000 Daltons.

"Polymer" means a relatively large material comprising a substructure formed two or more monomeric, oligomeric, and/or polymeric constituents and generally having a molecular weight greater than about 10,000 Daltons. The Tg of the polymer composition is preferably selected to be above the temperature of use to maximize durability. Incorporation of lactate coalescing agent facilitates film formation at a desired process temperature, while at the same time maximizing durability and/or hardness properties of the resulting coating. Preferably, the polymer of the coating composition has a minimum film-forming temperature above about 30° C, and more preferably above about 40° C. The properties of the coating can also be affected by mixing polymers having a relatively low glass transition temperature ("soft polymers") with polymers of relatively high glass transition temperatures ("hard polymers"). Preferably, the polymer components of the coating are selected to balance the characteristics of the resulting coating, so that the a film is formed under processing conditions while at the same time the final coating is hard enough to be durable under conditions of use. In general, hard polymers are more durable and more stain resistant. Soft polymers generally exhibit more affinity to the substrate due to greater conformation to the surface of the substrate, and tend to readily coalesce under convenient processing conditions to form a film. Preferred soft polymers have a glass transition temperature of below about 30°C, and preferably from about -30°C to about 10°C. Preferred hard polymers have a glass transition temperature of above about 100°C, and more preferably from about 120°C to about 180°C. Preferably, the composition of the coating is a blend of soft and hard polymers comprising about 5% to about 95% of soft polymers and about 95% to about 5% of hard polymers by weight, and more preferably about 10% to about 45% of soft polymers and about 55% to about 90% of hard polymers by weight. Most preferably, the composition of the coating comprises about 20 to about 35% of soft polymers and about 65 to about 80% of hard polymers by weight. In a preferred embodiment of the present invention, the polymers of the coating are predominantly aliphatic in nature. Aromatic functional groups may raise stability and/or discoloration issues in certain environments, and therefore may be less desirable. Polymers are preferably selected from water dispersible thermoplastic polymers, such as vinyl polymers (such as (meth)acrylate copolymers), polyvinyl chloride, polystyrenes, polybutadienes, polyethylene, polypropylene) urethanes polyesters, polyamides, polyethers and certain polycarbonates (e.g. the polycarbonate of bisphenol A), or thermoset polymer such as certain polycarbonates (e.g. crosslinked polycarbonates), epoxies, polydicyclopentadienes, and hybrids and blends of one or more of these polymers. Also contemplated are solutions, dispersions and emulsions comprising components that are reactive to form polymers, including prepolymers. In a preferred embodiment of the present invention, the composition comprises polymer particles in a core/shell configuration, wherein the composition of the core of the particle is different from the composition of the shell of the particle. Such particle configurations allow the incorporation of separated components in highly localized manner, such as taught in US Patent No 6,572,969, or by providing polymers that have different properties, such as high and low Tg. In a particularly preferred embodiment, the composition comprises a plurality of polymers in a core/shell configuration. Preferably, the polymer of the shell of the core/shell polymer particle is swellable or solvatable by the lactate ester of the composition, to assist in film formation of this component of the polymer particle in its intended use. Polymers useful for the present invention may be formed from copolymerized monomers having a combination of monomers that result in a copolymer having characteristic properties. The Tg and other properties of the copolymer may be tailored to the desired properties by incorporation of various selected monomeric compounds during the polymerization process. Thus, soft monomers are preferably incorporated to impart flexibility and toughness to the copolymer, and so that the resulting copolymer exhibits the desired low Tg property. Likewise, hard monomers are incorporated to impart hardness and durability to the copolymer, and so that the resulting copolymer exhibits the desired high Tg property. Monomers may be characterized as "soft" monomers or "hard" monomers by consideration of the Tg of the corresponding homopolymers made from the designated monomer. Thus, for purposes of the present invention, a monomer is considered to be a "soft" monomer if the corresponding homopolymer has a Tg of less than about 25°C. Similarly, a monomer is considered to be a "hard" monomer if the corresponding homopolymer has a Tg of more than about 25°C. Polymers of the coating composition are selected to provide the desired chemical functionalities for providing affinity to a selected substrate and for reactivity to an optionally applied second layer. Examples of preferred functionalities include hydroxyl and/or carboxyl groups. A preferred coating of the present invention comprises a (meth)acrylate copolymer as one of the polymers of the composition. (Meth)acrylate copolymers may be formulated to provide a desired Tg, and also may be provided with useful functionality both for providing affinity to a selected substrate and for reactivity to the optionally applied second layer. The soft monomer is typically a monomeric acrylic or methacrylic acid ester of an alkyl alcohol containing a single hydroxyl, the alcohol being further described as having from 2 to about 14 carbon atoms when the soft monomer is an acrylic acid ester, and about 7 to 18 carbon atoms when the soft monomer is a methacrylic acid ester. Examples of suitable acrylic acid esters for use as the soft monomer include the esters of acrylic acid with non-tertiary alcohols such as ethanol, 1-butanol, 2- butanol, 1-pentanol, 2-pentanol, 3-pentanol, 2-methyl- 1-butanol, 1-hexanol, 2- hexanol, 2-methyl- 1-pentanol, 3 -methyl- 1-pentanol, 2-ethyl-l butanol, 3,5,5- trimethyl- 1-hexanol, 3-heptanol, 1-octanol, 2-octanol, iso-octyl alcohol, 2-ethyl-l- hexanol, 1-decanol, 1-dodecanol, 1-tridecanol, 1-tetradecanol and the like. Examples of suitable methacrylic acid esters for use as the soft monomer include the esters of methacrylic acid with non-tertiary alcohol such as 3-heptanol, 1-octanol, 2-octanol, iso-octyl alcohol, 2-ethyl-l-hexanol, 1-decanol, 1-dodecanol, 1-tridecanol, 1-tetradecanol, 1-octadecanol and the like. Other examples of monomers that can be used for the soft monomer component are monomers having the requisite Tg values including dienes, such as butadiene and isoprene; acrylamides, such as N-octylacrylamide; vinyl ethers, such as butoxyethylene, propoxyethylene and octyloxyethylene; vinyl halides, such as 1,1-dichloroethylene; and vinyl esters such as vinyl versatate, vinyl caprate and vinyl laurate. It is to be understood that the copolymer may comprise a single type of soft monomer or may comprise two or more different soft monomers. A hard monomer of the copolymer is typically a monomeric methacrylic acid ester of an alkyl alcohol containing a single hydroxyl. The alcohol contains from 1 to about 6 carbon atoms, and preferably 1 to about 4 carbon atoms. Examples of suitable monomers for use as the hard monomer include the esters of methacrylic acid with non-tertiary alcohols such as methanol, ethanol, 1-propanol, 2-propanol, 1- butanol, 2-butanol, 1-pentanol, 2-pentanol and 3-pentanol. Other examples of monomers that can be used for the hard monomer component are monomers having the requisite Tg values include methacrylates having a structure other than delineated above, such as benzyl methacrylate, cyclohexyl methacrylate and isobornyl methacrylate; methacrylamides, such as N-t- butylmethacrylamide; acrylates, such as isobornyl acrylate; acrylamides, such as N- butylacrylamide and N-t-butylacrylamide; diesters of unsaturated dicarboxylic acids, such as diethyl itaconate and diethyl fumarate; vinyl nitriles, such as acrylonitrile, and methacrylonitrile; vinyl chloride; vinyl esters, such as vinyl acetate and vinyl propionate; and monomers containing an aromatic ring such as styrene; alpha- methyl styrene and vinyl toluene. It is to be understood that the copolymer may comprise a single type of hard monomer or may comprise two or more different hard monomers. Monomers that may be used to provide hydroxyl functionality for interaction and/or reaction with the fabric or fluoropolymer include the hydroxyalkyl (meth) acrylates, such as 2-hydroxethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4- hydroxybutylacrylate, 6-hydroxyhexylacrylate, p-hydroxycyclohexyl (meth) acrylate, hydroxypolyethylene glycol (meth) acrylates, hydroxypolypropylene glycol (meth) acrylates and alkoxy derivatives, and dipropylene glycol diacrylate. Functional monomers may be incorporated into the copolymer, for example, to facilitate physical interaction with another polymer or material. Examples of such functional monomers include acrylic acid, acrylamide, vinylpyrrolidone or dimethyl aminomethyl methacrylate. The identity of the monomer to be incorporated is determined depending on the optional coupling mechanism to be used to assist in adhering the first coating layer to the substrate, or for bonding the optionally applied second layer to the first layer. Monomers that may be used to provide carboxyl functionality for interaction and/or reaction with the substrate or optionally applied second layer include acrylic acid, methacrylic acid, maleic acid, and itaconic acid. Other acid functionality may be provided by formation of the polymer with monomer containing the desired functionality. Optionally, reactive functionality may be introduced into the polymer during the polymer formation process. For example, acrylate polymers comprising sulfonate functionality may be formed during the polymerization process, wherein the polymerization reaction is initiated using a persulfate, such as sodium or ammonium persulfates. The sulfonate functionality typically is provided as end groups on the acrylate copolymer. As noted hereinabove, the polyurethanes preferably also may be a polymer component of the coating composition. The preparation of polyurethanes generally proceeds in a stepwise manner as by first reacting a hydroxyl terminated polyester or poly ether (reaction of polyols plus hydroxyl terminated carboxylic acid dispersants plus polyisocyanates and sometimes plus a chain extender). Polyurethanes are converted to a polyurethane dispersion through neutralization of the polyurethane reaction usually with an amine (trimethylamine, triethylamine and dimethyl- ethanolamine) in the presence of a carboxylic acid dispersant. The neutralizing agents are preferably at a stoichiometric ratio of 0.9 to about 1.2. Once neutralized, water is added to the reaction mixture. A particularly useful polyurethane is a waterborne aliphatic polycarbonate urethane polymer manufactured by Stahl, Massachusetts, under the trade name WF41-035. The polyisocyanates are prepared at a reaction temperature of about 40°C to 160°C using a catalyst and polyfunctional diisocyanates. Catalysts used include dibutyl tin dilaurate, stannous octoate, diazobicyclo (2,2,2) octane (DABCO), zinc acetyl acetonate (ACAC), and tin octoate. A suitable polyisocyanate is R(NCO)_n, where n is an integer of 2, 3 or 4. Examples of suitable polyisocyanates include hexamethylene diisocyanate, 2,2,4-and/or 2,4,4-trimethyl hexamethylene diisocyanate, p- or m-tetramethyl xylene diisocyanate, methylene bis(4-cyclohexyl isocyanate) (hydrogenated MDI), 4,4-methylene diphenyl isocyanate (MDI), mixtures of MDI with polymeric MDI having an average isocyanate functionality of from about 2 to about 3, 2, p- and m-phenylene diisocyanate, 2,4- and/or 2,6-toluene diisocyanate (TDI) and adducts thereof, and isophorone diisocyanate (IPDI). The polyols can be polyether polyols, polyacetal polyols, a polyolefin polyols, organic polyols (e.g. polycarbonate polyols), or polyester polyols. The number average molecular weight for the polyols are between 400 to 15,000.

Examples of the polyether polyols include polyoxypropylene or polyoxy ethylene diols and triols, poly(oxyethyleneoxypropylene) diols and triols. Examples of the polythioether polyols include glycols, dicarboxylic acids, formaldehyde, aminoalcohols or aminocarboxylic acids. Examples of the polycarbonate polyols include products obtained by reacting monomers such as diols having from 2 to 10 carbon atoms such as 1,3-propanediol, 1,4-butanediol, 1,6- hexanediol, diethylene glycol or te₍traethylene glycol with diaryl carbonates having from 13 to 20 carbon atoms, for example diphenyl carbonate, or with phosgene. A preferred low Tg polymer is a (meth)acrylate copolymer comprising about 70-90 % of one or more soft monomers and 5-30 % of one or more hard monomers, all selected so that the Tg of the copolymer is from about -30 to about 10°C. More preferably, the low Tg polymer comprises about 20-40% butyl acrylate, about 30- 50% ethyl acrylate, and about 5-15 % acrylic acid. Hard polymers are preferably selected for their durability and stain resistant properties. Preferably, the hard polymers are hard enough to withstand conventionally applied forces used for removal of stains from substrates. Additionally, the hard polymer is selected to be hydrolytically stable under conventionally applied cleaning solutions or anticipated staining materials to which the substrates are expected to be exposed in the field of use of the particular substrate to be treated. The hard polymers are preferably hydrolytically stable to prolonged exposure (e.g. 24 hours) to a conventionally applied alkaline cleaning solution, such as Formula 409® cleaner, and to a dilute acid solution such as vinegar having 5% acidity. Preferred hard polymers include selected polyurethane polymers, and particularly polyurethane/poly carbonate polymers. Preferred commercially available polymers include WF 41-035 from Stahl, USA. In particular embodiments of this invention, the coating composition comprises a water-borne urethane polycarbonate having pendent carboxyl groups and a carboxylated acrylic copolymer in amounts of from about 5 to about 95 parts by weight of the urethane polycarbonate with from about 95 parts to about 5 parts by weight of the acrylic copolymer, to total 100 parts by weight of dry solids. More preferably, the composition comprises from about 65 dry to about 75 dry parts by weight of the urethane polycarbonate polymer with from about 35 dry parts to about 25 dry parts by weight of the acrylic copolymer. In a preferred embodiment of the present invention, a durable first layer coating is applied to a substrate, followed by a second layer comprising a fluoropolymer having reactive functional groups that may be bonded to polymers of the first layer. The fluoropolymer typically is not a film-forming polymer, but optionally may be a film-forming polymer. Most preferably, the fluoropolymer is covalently bonded to polymers of the first layer. It has particularly been found that covalent bonds provide superior retention of the fluoropolymer to the first layer, and thus the substrate, under conditions of wear. The second layer may optionally comprise additionally components, and particularly additional polymeric components, provided that the additional components do not deleteriously affect the stain repellant properties of the second layer to a degree to reduce the efficacy of the layers to below acceptable performance of the ultimate coated substrate. Preferably, the second layer comprises no more than about 25% by weight of dry component other than fluoropolymer, and more preferably no more than about 10% of non- fluoropolymer additional components. Generally, any commercially available repellant fluoropolymer may be employed according to this embodiment of the present invention, with the proviso that the fluoropolymer is chosen to have functional sites that can be reacted to functional sites in the first layer. Fluoropolymers that may be used in this application are well known to those of ordinary skill in the art and include all of the fluorochernical textile treating agents. In particular, any of the fiuoropolymer/fluorochemical textile treating agents disclosed in U.S. Pat. Nos. 5,565,265; 5,747,392; 6,024,823; 6,165,920; 6,207,250 and 6,252,210 can be employed, provided that the fluoropolymer has functional sites that can be reacted to functional sites in the first layer. Useful fluoropolymers for practice of this embodiment of the present invention and commercially available include Zonyl 8412 from DuPont, and X-Cape® GFC from OMNOVA Solutions, Inc. In a preferred embodiment of the present invention, the fluoropolymer comprises pendent fluorinated groups linked to the polymer through an ether linkage.

Alternative materials may include fluorinated oxetane co- or ter- polymers prepared by OMNOVA Solutions, as described in U.S. Pats. No. 5,650,483; 5,668,250; 5668,251 ; and 5,663,289. In a preferred embodiment of the present invention, the fluoropolymer is prepared from monomers or oligomers comprising at least one fluorinated oxetane monomer. Preferably, the fluoropolymer comprises perfluorinated or highly fluorinated functionalities, wherein pendent fluorinated groups have a carbon chain length of equal to or less than four carbons. Such short chain fluorinated moieties have been shown to have low bioaccumulation in living organisms. Perfluorocarbon moieties of up to four carbon atoms in length are thus particularly useful. Alternatively, acrylic, polyether and epoxy based materials can be made utilizing fluorinated moieties based on heptafluorobutyl, perfluoropropyl, and trifluoro ethyl pendant groups that are non-bioacumulative. Due to the present disclosure, those of ordinary skill in the art are now readily able to select an appropriate fluoropolymer based upon the available functional sites of the first layer. Preferred fluoropolymers comprise carboxyl functionalities that may react with functionalities on a polymer of the first layer or with polyfunctional compounds useful as crosslinking agents. A preferred example of such fluoropolymers is X-Cape® GFC, commercially available from OMNOVA. Crosslinking agents may preferably be employed to bond the fluoropolymer to at least one polymer of the first layer, and also may be employed to bond the first layer to the substrate. For purposes of brevity, the use of the crosslinking agent will be illustrated in the context of bonding the fluoropolymer to the first layer, but it will be understood that similar principles apply in bonding the first layer to the substrate or an intermediate layer. When the fluoropolymer and at least one polymer of the first layer contain hydroxyl functionalities, the polyfunctional compounds may be, for example any appropriate crosslinking agent reactive with hydroxyl functionalities. Preferred crosslinking agents include the melamine formaldehyde crosslinking agents, such as Resimene 735 commercially available from Solutia Inc., St. Louis, MO. Alternative preferred crosslinking agents include the urea formaldehyde crosslinking agents, such as GP®2981 commercially available from Georgia-Pacific Corporation, Atlanta, GA. In an alternative embodiment, the first layer and the fluoropolymer can both comprise acid functionalities (such as carboxyl and sulfonyl), and the polyfunctional compounds may be, for example any appropriate crosslinking agent reactive with acid functionalities. Preferred crosslinking agents include the tri-functional aziridines, such as Xama-7 commercially available from Bayer. The crosslinking agent may be provided in the first layer coating composition, in the second layer coating composition, or as a separate composition that is applied before, after or during the coating process of applying each respective layer to the substrate. The crosslinking agent is provided in an amount effective to achieve the desired level of bonding. ' When the crosslinking agent is provided in the respective coating compositions, preferably it is present at up to about 5 php, preferably, from about 0.5 to about 1.5 php (parts per hundred polymer). In a preferred embodiment, the coating is applied to a polymeric substrate that is swellable by the lactate. Such polymeric substrates may be in the form of films, fabrics or articles having a thicker (e.g greater than 1 cm) and optionally a more rigid structure (e.g. a Shore D hardness greater than about 40). Examples of such articles include extruded or formed articles such as pipes, toys, support structures and the like. Examples of polymeric substrate materials include polyvinyl chloride, polyamide, acrylic, polycarbonate, polyester, nylon, and thermoplastic polyolefin ("TPO") (and especially polypropylene). Alternatively, the coatings of the present invention may be applied to porous surfaces, such as wood, paper, drywall and other organic building materials and the like. Additionally, the coatings may be applied to non-swellable surfaces, such as metal, stone, concrete and the like. Coatings may be applied in a plant environment in the manufacture of goods, or on site as a post-installation application. In a particularly preferred embodiment, the coating may be part of a fabric treatment composition to render the fabric more durable and/or water repellant and stain resistant. As used herein, "fabric substrate" relates to woven, knitted and non- woven fabrics of synthetic or natural materials or blends thereof. Fabric substrates of the present invention include woven fabrics as well as non- woven and knitted fabrics. The term "yarn" typically refers to three types of component: monofilaments; multifilament bundles of filaments (including strands or fibers); and groupings of filaments that are twisted together, or so called spun yarns. Yarns may be provided in various physical configurations, such as crinkle shapes and the like. Non-limiting examples of suitable fabric substrates for use according to this invention include synthetic fabrics such as polyesters, nylons, rayons, thermoplastic polyolefins, and the like, and natural fabrics, such as cotton, flax, jute, ramie, and the like. A suitable fabric substrate may also consist of a blend of natural and synthetic fabric materials. In a particularly preferred embodiment of this invention, the fabric substrate is a polyester. Also preferred are fabric substrates comprising blends of polyesters with cotton. In a particularly preferred embodiment of the present invention, a fabric is provided with at least two coatings being applied as separate layers from separate coating compositions. The first layer coating composition includes one or more polymeric components selected according to their affinity with the fabric substrate and ability to form a scrub resistant film. The polymers of the first layer are preferably selected to provide a balance of ease of film-forming under manufacturing conditions, together with durability of the resultant layer and acceptable hand of the final fabric. One or more of these coatings are applied from a composition comprising an alkyl lactate coalescing agent. In a particularly preferred embodiment, a fabric is provided with a first durable coating layer, with a second fluorochemical layer that is bonded to the first layer. One or more of these coatings are applied from a composition comprising an alkyl lactate coalescing agent. One or more additional back coatings may optionally be applied to the fabric substrate to give hydrostatic head and/or protect from bacterial and bacterial by- product migration. This optional back coating is a conventional coating as known in the art, and is applied only to the rear or back face of the fabric. The back coating in particular preferably contains an antimicrobial agent, which serves to preserve the structural integrity of the fabric substrate against deterioration by bacteria, fungus, algae, and other microbial organisms. If this back coating is employed, it is fully dried, as known in the art, before application of the fluoropolymer in a subsequent pass. The composition of the back coating is generally based upon conventional acrylic latices as are well known in the industry. A useful back coating is Performax 3714, a proprietary acrylic formulation supplied by Noveon (Ohio, USA). A formulation for a first layer includes 45 to 50% film-forming acrylic water based emulsion; 22-27% filler, such as calcium carbonate; 10-12% thickener e.g., an alkali swellable material; 1-3% crosslinker, such as an urea formaldehyde; 0.5-1% defoamer; 1-2% surfactant and 1-2% amine. When more than one back coat is used, the coatings may be of the same or different chemical composition. The coating process will now be described in detail with respect to the embodiment wherein two separate layers are applied to a fabric substrate. It will be understood that other coating compositions may be applied with other processes on other substrates, with adaptations that are within the skill of those in the art, taking into account the different materials, substrates and processes as taught herein. Turning now to the exemplary process as presented in schematic form in Fig. 1, the fabric substrate is preferably first cleaned by scouring the fabric to eliminate any residual sizing agents left from fabric production that might cause the fabric to be hydroscopic. The fabric 10 is then let off from a suitable source (not shown) and is passed through a scouring tank 32, containing water and a strong detergent, such as trisodium phosphate, after which it passes through first and second wash tanks 34 and 36; containing water. Once cleaned, the first coating is applied to the fabric substrate. Immediately following washing, the fabric is next fed into a first dip coating tank 38, for application of the first layer coating composition 16. Thus, both sides are coated in one pass, and the fabric carrying the wet base composition is passed between opposed rolls 40, 42, or doctor blades (not shown) to apply pressure to the fabric substrate 10 after wet pick-up of the first layer coating composition and thereby help to ensure that the interstices within the fabric substrate 10 are also coated. The rolls 40, 42 may also help to remove any excess amount of the first layer coating composition picked-up on the fabric 10 during its passage through the bath 16. Next, the wetted fabric 10 is passed through a drying oven 44 where the first layer is dried via removal of water and other volatiles at a temperature and for a residence time sufficient to at least partially cure the first layer. If a back coating is to be employed, it may be applied by a knife blade 46, after drying of the first layer. The substrate carrying the first layer and optional back coating is then passed through the curing stage 48, where additional heat is applied to cure the first layer and the back coating. After drying and curing, the fabric substrate 10, now coated with a first layer 16 and, optionally, a back coating 18 is collected on a take-up roll 50. For the method depicted in Fig. 1, the fabric 10 is first taken up on roll 50 where it is then transported to the next stage, as will be described now. Take-up roll 50 is an optional, non-limiting step in the method, as the fabric 10 could as readily have been continuously directed through subsequent stages of the apparatus. Either way, the fabric 10 is next subjected to additional washings by passing through wash tanks 52 and 54. Immediately following washing, the fabric is next fed into a second dip coating tank 56, for application of the fluoropolymer composition 20. Again, both sides are coated in one pass, and the fabric carrying the wet base composition is passed between opposed rolls 58, 60, or doctor blades (not shown) to apply pressure to the fabric substrate 10 after wet pick-up of the fluoropolymer composition and thereby help to ensure that the interstices within the fabric substrate 10 are also coated. The rolls 58, 60 may also help to remove any excess amount of the fluoropolymer composition picked-up on the fabric 10 during its passage through the bath 20. Next, the wetted fabric 10 is passed through a second drying oven 62 where the fluoropolymer composition is dried via removal of water and other volatiles at a temperature and for a residence time sufficient to at least partially cure the second layer. If a back coating is to be employed, it may be applied by a knife blade 64, after drying of the second layer. The substrate carrying the second layer and optional back coating is then passed through the second curing stage 66, where additional heat is applied to cure the second layer and the back coating. After drying and curing, the fabric substrate 10, now coated with first layer and second layers 16 and 20, and optional back coatings 18 and 22, is collected on a final take-up roll 68. For practice of an alternate method, where only one back coating layer is applied, only one back coating 18 or 22 is applied, with the understanding that the fabric passes from drying to curing of one of the layers without application of the back coating. The present invention also contemplates coated fabrics containing only first and second layers of polymeric materials as described herein, and no back coatings. It is also to be appreciated that although the apparatus and method has been described schematically with reference to tanks and rollers that guide the fabric through the compositions as well as through drying and curing ovens or stages, that alternative equipment could be substituted. Once the fabric 10 containing the first layer and optional back coating leaves the first curing oven 48; these layers are not removed in the second stage washing tanks 52 and 54, prior to application of the fluoropolymer layer. Second stage washings merely remove excess surfactants, if any. The focus in applying the first layer is on the dry pick-up of the first layer onto the fabric substrate. As those of ordinary skill in the art will readily appreciate, the weight percent of bath solids may vary to a large degree. For instance, if the bath contains a high percentage of solids, a lower wet pick-up is required to realize a dry pick-up that is satisfactory for forming the scrub resistant first layer, while, if the bath contains a lower percentage of solids, a higher wet pick-up is required to realize a satisfactory dry pick-up. While it should be appreciated that the dry pick-up on the fabric substrate may vary according to the desired properties for the resultant coated fabric, the dry weight of the first layer picked up in this pass may range from about 1 to about 10 percent of the weight of the fabric substrate. Preferably, the dry weight ranges from about 4 to 6 percent of the fabric weight. Generally, when considering the dry pick-up on the fabric, for abrasive and stain resistant properties, a larger dry pick-up is desired. However, it will be appreciated that aesthetics will be negatively affected as the amount of dry pick-up increases. The greatest amount of practical dry pick-up, with the highest level of stain and non-abrasive polymer constituent, can be arrived at experimentally with the principles described herein. In a particular embodiment of this invention, the fabric substrate is a polyester, and the first layer coating composition is a carboxylated acrylic copolymer and polycarbonate urethane polymer blend. More particularly, the acrylic copolymer is Hycar T-138 (Noveon, Ohio, U.S.A.), and has carboxyl and sulfonate groups that make it possible to crosslink with itself or other polymer systems such as acrylics, urethanes, and/or fluoropolymers sharing the same type of functionality. This acrylic copolymer has a low glass transition temperature (Tg) of about -20°C, which permits the blending of this acrylic copolymer with a relatively hard polymer, while maintaining the hand and feel of the fabric being coated. Thus, this acrylic copolymer, in the preferred embodiment, is blended with a urethane latex, namely WF41-035 (Stahl, Massachusetts, U.S.A.), which contains pendant carboxyl groups and has a Sward hardness of about 50. The first layer coating composition bath is made up of WF41-035 and HycarT-138, blended at from 10 to 50%_dry acrylic polymer to from 90 to 50%_dry urethane. The bath also contains a small concentration, up to about 5 php, of trifunctional aziridine, a crosslinking agent, and from about 2 to about 6 php of amine oxide, a non-re-wetter. The polyester fabric of this preferred embodiment is passed through this bath to achieve a wet pick-up of from about 40 to about 50%, correlating to a dry pick-up in the area of about 2%. The acrylic copolymer and urethane blend that forms the major portion of the first layer coating composition is caused to partially crosslink through the aziridine crosslinking agent, which forms a minor portion of the first layer bath. Notably, when crosslinking is employed to form the first layer, the composition is only partially reacted so that available functional sites are still present for binding with a fluoropolymer that is subsequently applied to the fabric substrate as described hereinbelow. The fluoropolymer of this embodiment is X-Cape® GFC (OMNOVA Solutions, Inc., Ohio, USA.), which is a fluorinated acrylate having active hydrogen (carboxyl) groups within the polymer matrix. These groups allow the fluoropolymer to be bound to the blend of acrylic copolymer and urethane polymer that makes up the first layer due to the fact that the first layer, as mentioned above, contains active carboxyl groups. The fluoropolymer is the major solid component while aziridine is present at from about 0.5 to about 1.5 php, and amine oxide is present from about 6 to about 8 php. The polyester fabric of this preferred embodiment is passed through the fluoropolymer composition bath to achieve a dry pick-up of from about 0.25 to about 15 percent by weight. The back coating material of acrylic material is applied twice, as two coatings, once after the first layer is applied and partially cured and once after the 10 second layer is applied and partially cured. The composition is based on a soft water based emulsion, containing filler, thickener, a urea-formaldehyde crosslinker, defoamer and wetting agent. Affinity of the first layer may be evaluated by appropriate testing protocols designed to evaluate the retention of the second layer of the coating system on the fabric under wear conditions. Preferably, the wear testing is selected to model situations that would be predictive of the wear of the fabric under the anticipated conditions of use of that fabric. Such tests are apparent to one of ordinary skill in the art, and include abrasion resistance tests, tape peel tests, flex tests, and the like. The presence of the second layer may be evaluated visibly by the unaided eye, or more preferably through the use of photomicroscopy to closely examine the filaments of the fabric to determine the presence or absence of a coating. Additional evaluation tests may include contact angle evaluations, which will identify the presence or absence of a coating that is wetted or not wetted by the liquid used in the evaluation. Evaluation of oleophobicity is preferably performed in accordance with a test comprising evaluation of the surface tension of the fabric using a selected series of liquid hydrocarbons having varied surface tensions. Oil repellency is graded by identifying the highest numbered test liquid that does not wet the fabric surface. A preferred test for evaluating oleophobicity is AATCC test 11897, or ISO 14419 test method. Similarly, hydrophobicity is preferably evaluated using a selected series of aqueous liquids having varied surface tensions. In a preferred evaluation technique, surface tension of water is modified by incorporating increasing amounts of a miscible surface tension reducing liquid, such as isopropyl alcohol. Water repellency is graded by identifying the highest numbered test liquid that does not wet the fabric surface. Other tests, such as use of a functionalized dye or similar marker to assist in indicating either the presence or absence of a coating, may be used as will be apparent to the skilled artisan. A coating is considered to reinforce the substrate if the substrate has greater structural integrity under conditions of wear as compared to a like substrate without the stain resistant layer. Under this evaluation, samples are exposed to wear conditions in a controlled manner and compared to determine the relative condition of the substrate. Procedures to impart wear forces to the substrate and for evaluation of the relative condition of the substrate may be carried out by protocols that will be apparent to one of ordinary skill of the art. Preferably, standardized wear protocols, such as the Wyzenbeek abrasion protocol for use on fabrics, are used. Such protocols are to be carried out with sufficient force and duration as to cause at least one set of samples to exhibit visible wear, such as damage to or displacement of fabric filaments. The wear may be evaluated visibly by the unaided eye, or more preferably through the use of photomicroscopy. The use of photomicroscope images is particularly useful because such images can be overlaid with a grid and compared to identify deviations from the original construction of the fabric, or closely examined to identify damage to fabric filaments. A layer is considered to be stain resistant if when a staining material wets onto the surface of a substrate, the staining material is more easily removed from the substrate by conventional cleaning techniques than from a like substrate without the stain resistant layer. Such stain removal evaluation tests are, for example, common in the fabric industry; and may include controlled application of cleaning substances, optionally in a predetermined sequential format, to evaluate the ease of removing certain staining materials, such as mustard, blood, and so forth. Aqueous coating compositions may be made by appropriate techniques now apparent to the skilled artisan. For example, the polymer may be prepared in water, or prepared in a solvent with subsequent solvent exchange with water to prepare the ultimate aqueous coating composition. The lactate may be present in the water when the polymer is introduced or during the polymerization to form the polymer, or may be subsequently added to the composition. Generally, the longer the alkyl chain of the alcohol portion of the lactate, the less soluble the lactate is in water. For certain lactates, a surfactant is desired to facilitate solvating the lactate in the coating composition. Preferably, a non-rewetting surfactant is used to assist in solvating the lactate for reasons discussed above. In one embodiment of the present invention, the lactate is added to the coating composition just prior to applying the coating composition to the substrate. This embodiment provides significant advantage in that the lactate is not stored in an aqueous environment that will lead to hydrolysis. The lactate may be added to the coating composition in any appropriate manner, such as by addition in a mixing vessel just upstream from the application device, or by simultaneous application, such as by commingling spray, onto the substrate. In another embodiment of the present invention, lactate is applied directly to the substrate prior to application of the coating composition to the substrate so that the lactate is present and mixed with the coating composition on application of the coating composition to the substrate. This is a particularly preferred technique for facilitating enhancement of adhesion of the coating to the substrate by swelling the substrate. In another embodiment of the present invention, lactate is added to the coating composition prior to storage. In this embodiment, preferably the coating composition is stabilized with respect to the lactate component to retard or prevent hydrolysis of the lactate under conditions of storage as discussed above. Coating compositions as described herein may be applied by any appropriate technique, such as dip coating, spraying, or casting by various techniques, such as using a doctor blade, extrusion die cast or other method of application. Coatings may be applied in any appropriate thickness, depending on the intended use of the coated substrate. Preferably, the coating method is carried out at a temperature of from about 5° to about 180° C. In a particularly preferred embodiment of the present invention, the coating composition is a latex paint. Thus, the present invention provides a composition that provides a durable coating that may be easily applied with a brush, roller, sprayer or other paint delivery device, with an environmentally friendly and benign coalescing agent. Optionally, formation of the film may be assisted by imparting energy to the coating after application to the substrate. For example, the coating composition can be exposed to energy such as a hot air stream or radiant energy. Preferred forms of radiant energy comprise heat supplied by heat lights, including lights at visible, XJV and infrared wavelengths. In products wherein the coating is applied as part of a continuous web process, the coating applicator is preferably installed in line with the web manufacturing equipment and the heating elements are preferably installed downweb from the coating equipment, so that energy is applied shortly after coating. Alternatively, the coating may be applied to a web as a separate application step after complete manufacture of the web. In another aspect of the present invention, an article comprising a polymer matrix is formed by providing an aqueous polymer binder composition comprising a film-forming polymer and one or more lactate esters. Optional components to be bound together, such as fibers or particles, are mixed with the polymer binder composition, and a polymer matrix is formed from the aqueous polymer binder composition. The formation of the matrix may be carried out by any approach suitable for the article to be formed. Typical such processes include a step of allowing water to escape from the system, thereby facilitating the formation of a polymer matrix. Water preferably is driven out of the system by application of heat in a conventional manner, such a passing the article through a heating oven and the like. The invention will be further illustrated by the following non-limiting examples.

EXAMPLE 1 A study was conducted using methyl, ethyl, n-propyl, butyl, and 2- ethylhexyl lactates as a polymeric coalescent as compared to conventional glycol ether based materials. This study entailed purchasing a commercial zero VOC paint from Sherwin Williams, Harmony 6403 36095 Interior Flat lot# 0123 OK0933CJB, and post adding the lactate esters at a level consistent with solvent content of typical VOC-containing paints of 150 grams/Liter. Controls were also prepared, one being the commercial paint without added solvent, and a second being the commercial paint with a post addition of diethylene glycol monobutyl ether ("Butyl Carbitol") and propylene glycol phenyl ether ("Dowanol PPH") in a 1 : 1 ratio. The samples are set forth in Table 1.

Table 1

observations indicated that the higher Mw, hydrophobic, linear lactate esters swelled the latex particles and were not entirely compatible with this paint system. To increase the compatibility, the higher Mw, hydrophobic, linear lactate esters were blended with lower Mw, hydrophilic lactate esters at a ratio of 1:1. The branched high Mw lactate ester, 2-ethylhexyl lactate, was found to be compatible in this paint system.

Once the samples were prepared, several films were cast on lacquered Lenetta cards and HDPE release films at a 10 mil dry film thickness. The samples were allowed to set at room temperature and ambient relative humidity for seven days. The coatings cast on the lacquered Lenetta cards were then tested for abrasion resistance via the Taber instrument with a #10 grind wheel. Results are reported in Table 2. The film abrasion resistance properties are reported as mass of coating loss/1000 rotational cycles. Additionally, tensile strength of the films cast onto HDPE (including load, % strain at maximum load, as well as tensile energy absorption) are reported in Table 2.

The performance results observed show that abrasion, resistance is improved over the commercially available 0 VOC paint when lactate esters are added. Abrasion resistance is comparable or markedly superior to the control sample where environmentally undesirable glycol ester coalescing agents are added. Similarly, observed load and strain properties at maximum load are also improved over the commercially available 0 VOC paint when lactate esters are added. Percent strain at maximum load is comparable or markedly superior to the control sample where environmentally undesirable glycol ester coalescing agents are added. It is particularly noted that the above test merely comprises post addition of lactate esters to a commercially available paint formulation, wherein the exact components of the formulation are not known. It is envisioned that significantly superior results would be obtained through optimized formulation with known latex binders, emulsifiers, rheology additives, and surfactants.

EXAMPLE 2 Comparative Example 2A A first coating composition bath was prepared having the following chemical make-up:

The first layer coating composition bath had a 4 percent total solids concentration, inclusive of the small concentration of trifunctional aziridine (a crosslinker) and amine oxide (a non-rewetter). A fabrics as described below were coated in a conventional coating operation, with a wet pick-up in this first layer pass of about 50 percent, yielding a theoretical dry pick-up of about 2 percent. A first layer on the fabric was formed by passing the coated fabric through heating ovens at 300°F to cure the composition. The fabric was then passed through a fluoropolymer composition bath so that the fluoropolymer could be incorporated on to the first layer that was formed in the first pass. The fluoropolymer composition bath was made up as follows:

The wet pick-up of the fluoropolymer was about 50 percent, corresponding to a theoretical dry pick-up of about 1.5 percent. A second layer on the fabric was formed by passing the coated fabric through heating ovens at 300°F to cure the composition. The treated fabric was then back coated twice with a conventional acrylic latex at a wet pick-up of about 47 percent and dry pick-up of about 22 percent, and was thereafter completely dried and cured in an oven at 300°F.

Example 2B Coating layers were applied as described in Comparative Example 2 A above, except that the first coating composition bath had the following chemical make-up:

and the fluoropolymer composition bath was made up as follows:

Results of this test are reported in Table 3. Table 3

The samples used in this study consisted of 100% polyester jacquards. The variation from pattern to pattern can be attributed to the differences in weave constructions. As may be observed, back coating compositions exhibit significantly improved hydrostatic resistance when the composition comprises a lactate ester. While not being bound by theory, it is believed that the lactate ester further coalesces the topical treatment, and additionally migrates to the back coating application to build film strength, thus increasing hydrostatic resistance. Conventional coalescent components, such as the glycol ethers, are not a viable alternative in fabric coating applications due to environmental and handling issues. All percentages and ratios used herein are weight percentages and ratios unless otherwise indicated. All publications, patents and patent documents cited are fully incorporated by reference herein, as though individually incorporated by reference. Numerous characteristics and advantages of the invention meant to be described by this document have been set forth in the foregoing description. It is to be understood, however, that while particular fonns or embodiments of the invention have been illustrated, various modifications, including modifications to shape, and arrangement of parts, and the like, can be made without departing from the spirit and scope of the invention.

Claims

CLAIMS: I . An aqueous composition comprising a film-forming polymer and a lactate ester. 2. The composition of claim 1 , wherein the film-forming polymer is present in an amount effective to form a coating layer on a substrate when applied thereto under film formation conditions and the lactate ester is present in an amount effective to act as a coalescing agent for the film-forming polymer. 3. The composition of claim 2, wherein the composition is a protective coating composition. 4. The composition of claim 2, wherein the composition is an adhesive composition. 5. The composition of claim 2, wherein the composition is a water based ink composition. 6. The composition of claim 1, wherein the composition is an aqueous binder for manufacture of non-film products. 7. The composition of claim 6, wherein the non-film products are selected from nonwoven fabrics, paper and composites. 8. The composition of claim 1, wherein the film-forming polymer is selected from vinyl polymers, urethanes, polyesters, polyamides, polyethers, thermoplastic polycarbonates and hybrids and blends of one or more of these polymers. 9. The composition of claim 1, wherein the film-forming polymer is selected from thermoset polycarbonates, epoxies, polydicyclopentadienes, and hybrids and blends of one or more of these polymers. 10. The composition of claim 1, wherein the composition is an aqueous solution. I I. The composition of claim 1, wherein the composition is an emulsion. 12. The composition of claim 1, wherein the composition comprises from about 30 g/1 to about 350 g/1 lactate ester by weight. 13. A method of coating a substrate, comprising a) providing an aqueous polymer coating composition comprising a film- forming polymer, and b) coating the substrate with the coating composition; wherein one or more lactate esters is added to the coating composition prior to film formation. 14. The method of claim 13, wherein the coating method is carried out at a temperature of from about 5° to about 180° C. 15. The method of claim 13, wherein the coating method is carried out at a temperature of from about 5° to about 50° C. 16. The method of claim 13, wherein the coating method is carried out at a temperature of from about 100° to about 180° C. 17. The method of claim 13, wherein the substrate is a fabric. 18. The method of claim 13, additionally comprising coating the coated composition with a second aqueous polymer coating composition comprising a polymer and one or more lactate esters. 19. The composition of any of claims 1-12 or the method of any of claims 13-18, wherein the polymer coating composition is a latex paint. 20. A method of coating a substrate swellable by a lactate ester, comprising a) providing an aqueous polymer coating composition comprising a film- forming polymer; b) coating the substrate with one or more lactate esters in an amount effective to at least partially swell the substrate; and c) coating the substrate with the aqueous polymer coating composition while the substrate is at least partially swollen. 21. A method of forming an article comprising a polymer matrix comprising a) providing an aqueous polymer binder composition comprising a film- forming polymer and one or more lactate esters, and b) forming a polymer matrix from the aqueous polymer binder composition. 22. The composition of any of claims 1-12 and 19 or the method of any of claims 13-21, wherein the lactate ester is selected from one or more lactate esters of C1-C10 alkyl alcohols.

23. The composition of any of claims 1-12 and 19 or the method of any of claims 13-21, wherein the lactate ester is selected from one or more lactate esters of C2-C8 alkyl alcohols. 24. The composition of any of claims 1-12 and 19 or the method of any of claims 13-21, wherein the lactate ester is selected from the group consisting of ethyl lactate, isopropyl lactate, n-propyl lactate, butyl lactate and mixtures thereof. 25. The composition of any of claims 1-12 and 19 or the method of any of claims 13-21, wherein the lactate ester comprises ethyl lactate. 26. The composition of any of claims 1-12 and 19 or the method of any of claims 13-21, wherein the lactate ester is a mixture of ethyl lactate and an additional lactate selected from the group consisting of isopropyl lactate, n-propyl lactate, butyl lactate, pentyl lactate, hexyl lactate, heptyl lactate, octyl lactate, 2-ethyl hexyl lactate and mixtures thereof.