MXPA95003357A - Improved latex composition employing specifically defined ethylene oxide/propylene oxide block copolymer surfactant and hydrophobic defoaming agent - Google Patents

Abstract

An improved latex composition is provided that has been found to exhibit a superior ability to form a substantially uniform polymeric film when applied to a substrate. The composition is capable of being handled and applied to a substrate in the absence of excessive foaming. The aqueous composition includes as essential components specified concentrations of a specifically- defined normally liquid predominantly hydrophobic nonionic ethylene oxide/propylene oxide block copolymer surfactant, and a solely hydrophobic defoaming agent (e.g., a hydrocarbon-based mineral oil). It is possible for the composition to be applied even to a hydrophobic (e.g., a polyester filmásubstrate). The compositions of the present invention, following application to a substrate and the volatilization of the water component, form a substantially uniform polymeric film that can serve as a coating or adhesive.

Description

COMPOSITION OF IMPROVED LATEX USING SURGICAL AGENT OF • COPOLYMER OF OXID BLOCK OF ETI-LINE / SPECIFICALLY DEFINED PROPYLENE OXIDE AND HYDROPHOBIC DESPUMENT AGENT INVENTORS: MICHAEL J. ANCHOR, REBECCA P. H0LLIS, and GREC30RY. DRE NO, North Americans, domiciled at 40740 Delta Drive, Northville, Michigan 48167, 7 Broo side Place, Flemington, New Jersey 08822, and at 18237 Valade, Riverview, Michigan 48192, United States-of North America, all assign their rights to BASF CORPORATION , company duly organized and constituted in accordance with the Laws of the State of Delaware, United States of America, with address at 3000 Continental Drive, North, Mount Olive, New Jersey, 07828-1234 United States of America, for the invention that it is described immediately.

Background of the Invention It has been recognized that the spontaneous generation of unwanted foam, detrimental to the handling and application of polymeric latices to form a film on a substrate, leads to imperfections and concomitant lack of uniformity in the resulting coating. Consequently, it has been common practice to also include a defoaming agent in said latices with -frequency in a substantial concentration. However, these defoaming agents have frequently been found to interfere with the wetting and covering of the surface of the substrate by the latex composition and thus interfere with the formation of the desired, continuous and uniform polymeric film on the substrate. once the water component is volatilized. It has also been a common practice to attempt to remedy this deficiency in wetting and surface coverage through the further inclusion in the latex composition of an anionic surfactant. However, it has been found that these anionic surfactants commonly increase the overall propensity for foaming of the latex composition and yet contribute to the lack of uniformity of the resulting film, despite the best intentions of those attempting Apply a highly uniform polymer film. It has been observed that this lack of uniformity of the resulting polymeric film is particularly troublesome when the substrate receiving the latex composition tends to repel water and has a hydrophobic surface. Commonly, polymeric latexes are exposed to agitation or other high cutting conditions at some point during handling and / or during application to a substrate (eg, by spraying or the use of high speed transfer rollers) before of the volatilization of the water component. These conditions can lead to the production of copious amounts of foam which can adversely influence the character of the resulting polymeric film which is applied to a substrate. When foam bubbles are present, the coating of the substrate by the polymeric particles present in the composition Latex tends to be prevented. It is an object of the present invention to provide an improved latex composition for use in final uses of coating or adhesive that exhibits a superior ability to form a uniform film on a substrate. It is an object of the present invention to provide an improved latex composition wherein the polymer particles are present at a relatively high concentration and there is a good resistance to excessive foaming even when agitating or other high shear conditions are encountered. An object of the present invention is to provide an improved latex composition that can be applied to a substrate by spraying, in the absence of excessive foaming. An object of the present invention is to provide an improved latex composition that has the ability to wet and cover the surface of a substrate that will receive a polymer film well, in order to facilitate uniform dispersion in the absence of excessive foaming. An object of the present invention is to provide an improved latex composition which has the ability to wet and cover well the surface of a hydrophobic substrate that is to receive a polymeric film. An object of the present invention is to provide an improved latex composition, wherein a defoaming agent is present in a relatively low concentration, in conjunction with a relatively low concentration of a specifically defined nonionic surfactant, which has been found through of empirical research to provide a highly compatible total composition that makes possible the formation of a substantially uniform film on a substrate. An object in a preferred embodiment of the present invention is to provide an improved latex composition, where the total concentration of surfactant is relatively low and an anionic surfactant is absent. A further object of the present invention is to provide a latex composition that is particularly suitable for forming a transparent, polymeric coating on a paper substrate. A further object of the present invention is to provide a latex composition that well forms a pressure sensitive adhesive layer, when applied to the surface of a hydrophobic polyester film substrate and the water component volatilizes. Another object of the present invention is to provide a process for forming a substantially uniform polymer film on a substrate while using a latex composition in the absence of excessive foaming. These and other objects and advantages of the presently claimed invention will be apparent to those of ordinary experience in the field from a reading of the following detailed description and annexed clauses. Our companion Patent Application Serial No. entitled "Improved Latex Composition Employing - Specifically Defined Alcohol Ethoxylate Surfactant and Hydrophobic Defoaming Agent" is being presented on the same date as this.

Summary of the Invention It has been found that an improved latex composition suitable for end uses of coating or adhesive exhibiting a superior ability to form a substantially uniform film on a substrate in the absence of excessive foaming during handling and during application to a substrate consisting essentially of: (a) an aqueous dispersion medium, (b) about 40 to 60 weight percent of discrete, solid polymer particles present in the aqueous dispersion medium formed by the removal of at least one ethylenically unsaturated monomer, (c) about 0.25 to 1.5 (preferably about 0.75 to 1) percent by weight dissolved in the aqueous medium of an ethylene oxide / nonionic propylene oxide block copolymer surfactant, predominant hydrophobic, norm ^. of the formula: CH, H0- (CH2CH20)? - (CH2C IH0) - (CH2CH20)? -H, having molecular weight of about 3,000 to 6,000) where x is about 5 to 20 (preferably about 6 to 15) and is approximately 40 to 90 (preferably approximately 50 to 70); and (d) about 0.05 to 1 (preferably about 0.25 to 0.5) percent by weight dispersed in the aqueous medium of a single hydrophobic defoaming agent. It has been found that a method for the application in the absence of excessive foaming of a substantially uniform polymeric film to a substrate comprises: (a) applying to a substrate a layer of a latex composition consisting essentially of (i) one gave me aqueous dispersion, (ii) about 40 to 60 weight percent of polymer particles present in the aqueous dispersion medium formed by the polymerization of at least one ethylenically unsaturated monomer, (iii) about 0.25 to 1.5 ( preferably about 0.75 to 1) percent by weight dissolved in the aqueous medium of a predominantly hydrophobic ethylene oxide / non-ionic propylene oxide copolymer surfactant of the formula: H0- (CH2CH20)? - (- (CH2CH20)? - H having a molecular weight of about 1,100 to 9,000 (preferably about 3,000 to 6,000), wherein x is about 5 to 20 (preferably, about 6 to 15) ) ey is about 40 to 90 (preferably about 50 to 70, and (iv) about 0.05 to 1 (preferably about 0.25 to 0.5) percent by weight dispersed in the aqueous medium of a hydrophobic defoaming agent, and ( b) removing the water by volatilization from the latex composition layer present on the substrate to form a polymer film - substantially uniform on the substrate, which is suitable for use as a coating or adhesive.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The improved latex composition of the present composition incorporates about 40 to 60 (preferably 45 to 55) -percent by weight of discrete solid polymer particles formed by the polymerization of at least one monomer. ethylenically unsaturated in an aqueous dispersion medium. These polymer particles are commonly formed by emulsion polymerization, in accordance with known technology. Representative polymeric particles include styrene-butadiene polymers, acrylic polymers, vinyl acetate polymers, vinyl chloride polymers, and mixtures thereof. Particularly good results have been achieved when styrene-butadiene polymer particles are used which are composed of approximately 25 to 45 weight percent styrene. Polymeric particles of boxylated styrene-butadiene polymers can be used. Preferred acrylic polymers include copolymers of acrylonitrile, acrylic acid, methacrylic acid, butylacrylic acid, styrene and mixtures thereof. The solid polymeric particles that are dispersed in the aqueous medium commonly have an average particle size number of about 0.05 to 3 microns and, preferably, an average particle size number of about 0.1 to 0. microns. When the latex composition is intended to form a protective or decorative coating on a substrate, the polymer particles are commonly selected to possess the ability to form a firm, relatively non-tacky layer during solidification in accordance with known technology. When the latex composition is intended to form an adhesive layer (e.g., a pressure sensitive adhesive) over a sub-treatment, the polymer particles are commonly selected which are inherently sticky after solidification, or can to do so in accordance with known technology. Representative resins which may optionally be added to influence the tackiness include acrylic hydrocarbon resins, glycerol esters of turpentine resin, resins of castor oil, etc. A predominantly hydrophobic, usually liquid, copolymer surfactant of ethylene oxide / nonionic propylene oxide, usually liquid of the formula indicated below, is dissolved in the aqueous medium of the improved latex composition of the present invention. in a relatively high concentration of about 0.25 to 1.5 percent by weight and, preferably, at a concentration of about 0.75 to 1 percent by weight. This specifically defined nonionic surfactant has a molecular weight of about 1,100 to 9.00 and preferably about 3,000 to 6,000 and of the formula H0- (CH2CH20)? - (C- (CH2CH20)? -H, wherein x is about 5 to 20 and, preferably about 6 to 15 e, and is about 40 to 90, and preferably about 50 to 70 The non-ionic surfactant is predominantly hydrophobic in the sense that more hydrophobic units on a molar basis are always present than the hydrophobic units Usually, said nonionic surfactant includes about 10 to 30 (v. ., 10 to 20) mole percent of recurring hydrophilic oxyethylene units and approximately 70 to 90 (e.g., 80 to 90) mole percent of recurrent hydrophobic oxypropylene units These surfactants are known in the art. and may be formed in accordance with the teachings of U.S. Patent No. 2,674,619 which is incorporated herein by reference.This foraction reaction commonly involves the sequential addition of prpylene oxide and then ethylene oxide to a molecule. that of ethylene glycol. In particularly preferred embodiments, the nonionic surfactant as defined above, possesses (a) a molecular weight of about 3,400, wherein x is about 5 to 6 and is about 50, (b) a mol. about 5,100 where x is about 15 and is about 65 to 70, or (c) a molecular weight of about 5,650, wherein x is about 10 and is about 85. A solely hydrophobic defoaming agent is dispersed in the aqueous medium. of the improved latex composition of the present invention in the relatively low concentration of about 0.05 to 1 percent by weight and, preferably, at a concentration of about 0.25 to 0.5 percent by weight. This defoaming agent has been found to be highly compatible with the previously defined nonionic surfactant and when present in said relatively low concentration, it has been found to facilitate good wetting and covering of a substrate with the latex composition of the present invention. invention, even when said substrate is hydrophobic in nature. The defoaming agent is considered to be solely hydrophobic - in its molecular structure in the sense that it is hydrophobic throughout and for all practical purposes lacks a hydrophilic character in any portion of the molecule. Representative only hydrophobic after agents include hydrocarbon-based mineral oils, organosiloxanes (including emulsions of organ-modified poly isofunctional isoforms), metal soaps, etc. Fatty acids may be present with hydrocarbon-based mineral oils. Also, silica particles having relatively sharp surfaces may optionally be present in conjunction with the only hydrophobic foamed agents. When the silica particles are present with said defoaming agents, they serve mainly to perforate the foam bubbles, rather than to impart a hydrophilicity to the defoamer. In a particularly preferred embodiment, the only hydrophobic defoaming agent is a mineral based oil. of hydrocarbon having a boiling point of about 316 to 4829C. In a preferred embodiment no anionic surfactant is present in the improved latex composition of the present invention. The absence of such anionic surfactant has been found to contribute to the ability of the composition to form a substantially uniform film on a substrate in the absence of excessive foaming, during handling during application to a substrate. Alternatively, other components may optionally be present in the latex composition of the present invention, such as inert fillers in particles, dyes, glycols, thickeners, plasticizers, solvents, auxiliary resins, etc., as long as they do not modify the character basic composition When a transparent coating is formed, particulate fillers should be omitted as will be evident to the experts in the field. The improved latex composition of the present invention can be applied to a wide variety of substrates. As indicated above, good results can be achieved even when the substrate is hydrophobic in nature. A decorative or protective coating can be easily applied to a substrate. Alternatively, the resulting uniform film is applied to a substrate that can serve as an adhesive (e.g., a pressure sensitive adhesive). The improved latex composition can be applied to a substrate by conventional coating techniques without the need to minimize agitation in an effort to prevent excessive foam formation. In a preferred embodiment, the latex composition is simply applied by spraying to form a uniform layer of the composition on a substrate and, the water component is removed by volatilization to form a substantially uniform polymeric film. Other representative techniques that can be used to form the layer on the substrate include the use of a high-speed transfer roller, the use of a Byrd applicator, a Meyer bar, an air knife, a reverse roller, an engraving Reverse, a die groove, etc. For example, the improved latex composition layer can be applied in a thickness of approximately 20 to 50 microns and dried to form a substantially uniform film having a thickness of approximately 10 to 25 microns. The volatilization can be accelerated through the application of heat, in accordance with techniques known in the art for the specific polymer particles of the latex that are selected. For example, heating may be used for 1 to 10 minutes at about 80 to 105SC. The following examples are presented as specific illustrations of the present invention. It should be understood, however, that the invention is not limited to the specific details set forth in the Examples. In the Examples are presented below various - latex compositions were evaluated for their propensity to form foam, for their dispersibility when applied to a hydrophobic substrate, and for their propensity (or lack thereof) to form a film on a hydrophobic substrate that includes imperfections called "fish eyes". More specifically, the tendency of the composition of latex to foam was evaluated through the use of a conventional test procedure, in which a 300-ml beaker was filled completely with the latex composition, the net weight of the beaker. filling was recorded as "A", the content of the weeping vessel was transferred to a Hobart mixer, the latex composition was stirred for 10 minutes in the Hobart mixer at a selected speed to produce substantial agitation in the absence of spatter, the weeping vessel of 30 ml was filled again - with a portion of the composition obtained from the Hobart mixer and, the net weight of the contents of the weeping vessel including the foam was recorded as "B". The foam percentage was calcjj 16 while the following formula was used: Foam Percent = 1 - "B" / "A" x 100 The dispersion capacity of the latex composition - was determined on the hydrophobic substrate surface which was represented by a polyester film. The latex was introduced by using a pipette into the space under a Byrd applicator in an amount sufficient to cover the entire surface of the substrate and then applied to the substrate. The latex composition was brought to a thickness of approximately 25 microns through the use of the Byrd applicator which was pulled down at a distance of 20.32 centimeters. This dissonance test was carried out in triplicate in each case. After drying, the films that were provided on the substrate f? The drofinoids had a thickness of approximately 12 microns and were evaluated in accordance with their dispersal capacity and the presence or absence of imperfections known as "fishing eyes" as stated above. The dispersion capacity was determined by visual observation with respect to the overall appearance of the resulting dry film. Each film was evaluated (a) by the possible presence of "edge deformation" where the edges of the stretch shrink towards the middle of the test pattern, (b) to detern? "orange mask" where the surface of the film is speckled in a random pattern and, (c) to determine the presence or absence of full coverage. The following classification system was used for this dispersion capacity: 1 = Low, 2 = Regular, 3 = Good, 4 = Very good, and 5 = Excellent The evaluation of "fish eye" of the coating was also well carried out by visual observation, where the film was examined to determine the possible presence of areas -with no observable coverage by the latex polymer particles. These voids can vary from minute spots to large circular holes where there is little or no polymeric covering. The observation of these "fish eye" gaps was classified on the following scale: 1 = Many, 2 = Few, and 3 = None.

EXAMPLE I Latex compositions were formed while 50 weight percent of styrene butadiene polymer particles consisting of about 26 weight percent of recurring units derived from styrene in an aqueous dispersion medium were used. The styrene-butadiene particles were formed by emulsion polymerization and possessed an average particle size number of about 0.30 ml. An ethylenic oxide / nonionic propylene oxide block copolymer surfactant, predominantly hydrophobic, usually liquid, having a molecular weight of about 3.650 of the above formula, wherein x is about methane 8 ey is about 50 , was used in a concentration of about 0.5 weight percent and, a hydrocarbon based mineral oil release agent was present at a concentration of 0.5 weight percent. After volatilization of the aqueous component, a substantially uniform, inherently tacky film was provided on the hydrophobic substrate that was suitable for service as a pressure sensitive adhesive. When evaluated in accordance with the prescribed procedures, the latex composition provided the following test results: Percent Foam: 2.0 (Very low) Dispersion Capacity: 4 (Very good) Fish Eyes: 3 (None).

Comparative Examples For comparative purposes, it was found that when a similar amount of a commonly used anodic sodium dioctyl dulphosuccinate surfactant was replaced by the ethylene oxide / nonionic propylene oxide block copolymer surfactant, predominantly hydrophobic and the mineral oil defoaming agent was omitted from the latex composition, an excessive foaming value of 54.2 percent was observed. This value would indicate excessive foam exposure during handling and during application to a substrate where high cutting conditions were found. Also when a similar amount of the mineral oil defoamer was added to this comparative composition, an excess foaming value of 22.5 percent was still observed which greatly exceeded the value obtained in Example I. 1 Ejanplo II Example I was repeated, with the exception that 1.0-percent by weight of the block copolymer surfactant of ethylene oxide / nonionic propylene oxide, predominantly hydrophobic tertiary was used in the latex composition therein. 0.5 percent by weight was used instead. When evaluated in accordance with the procedures described above, the latex composition provided the following results: Percent Foam: 1.2 (Very low) Dispersion Capacity: 4 to 5 (Very Good to Excelent Fish Eyes: 3 (None ).

EXAMPLE III Example I was repeated, with the exception that the non-ionic, predominantly hydrophobic, ethylene oxide / propylene oxide block copolymer surfactant had a molecular weight of approximately 5.650, x was approximately 1 e and was approximately 85. When evaluated in accordance with the procedures described above, the latex composition provided the following results: Percent of Expuma: 6.4 (Low) Dispersion Capacity: 4 to 5 (Very good to Excelen Fish Eyes 3 (None) EXAMPLE IV Example III was repeated with the exception that the non-ionic, predominantly hydrophobic ethylene oxide / propylene oxide block copolymer surfactant was provided in a concentration greater than 1.0 weight percent and the defoaming agent of mineral oil at a concentration greater than 1.0 weight percent was provided in the latex composition. When evaluated in accordance with the procedures described above, the latex composition provided the following results: Percent Foam: 1.3 (very low) Dispersion Capacity: 5 (Excellent) Fish Eyes: 3 (None) EXAMPLE V Example III was repeated with the exception that the nonionic, predominantly hydrophobic, ethylene oxide / propylene oxide block copolymer surfactant was provided in a concentration greater than 1.0 weight percent and the defoaming agent of mineral oil was provided in the same concentration of only 0.5 weight percent of the latex composition.

When evaluated in accordance with the procedures described above, the latex composition provided the following results: Percent Foam: 4.0 (Low) Dispersion Capacity: 5 (Excellent Fish Eyes: 3 (None).

Example VI Example I may be repeated, with the exception that the latex composition includes 50 weight percent styrene-acrylic polymer particles, instead of styrene-butadiene polymer particles and, applies to a moving paper substrate by spraying. The polymer particles were formed by emulsion polymerization and possess an average particle size number of about 0.30 microns. The latex is handled and applied to the paper substrate in the absence of excessive foaming. After volatilization of the aqueous component, a coating of transparent film of quality, substantially uniform on the paper substrate is provided. Although the invention has been described with preferred embodiments, it will be understood that variations and modifications may be resorted to as will be apparent to those skilled in the art. These variations and modifications must be considered within the scope of the clauses attached hereto.

Claims (6)

1. NOVELTY OF THE INVENTION Having described the invention, it is considered as a -novedad and, therefore, the content of the following clauses is claimed as property. 1. An improved latex composition suitable for use in final coating or adhesive uses exhibiting a superior ability to form a substantially uniform film on a substrate in the absence of excessive foaming during handling and during application to a substrate, which consists essentially of: (a) an aqueous dispersion medium, (b) about 40 to 60 weight percent of solid, discrete polymeric particles present in the aqueous dispersion medium formed by the polymerization of at least one ethylenically active monomer unsaturated, (c) about 0.25 to 1.5 weight percent dissolved in the aqueous medium of a normally liquid, predominantly hydrophobic propylene oxide / copolymer block copolymer surfactant of the formula: CH, H0- (CH2CH20)? - (CH2C IH03) - (CH2CH20)? -H, which has a molecular weight of about 1,100 to 9,000, where x is approximately 5 a-20 e and is about 40 to 90 and, (d) about 0.05 to 1 weight percent dispersed in the aqueous medium of a hydrophobic defoaming agent only.
2. 2. The improved latex composition according to that claimed in clause 1, wherein the discrete solid polymer particles have an average particle size number of about 0.05 to 3 microns.
3. 3. The improved latex composition according to that claimed in clause 1, wherein the discrete solid polymer particles have an average particle size number of about 0.1 to 0.5 microns.
4. 4. An improved latex composition in accordance with that claimed in clause 1, wherein the discrete solid, polymeric particles were formed by emulsion polymerization.
5. 5. An improved latex composition according to claim 1, wherein the solid, discrete, polymeric particles are present in the aqueous dispersion medium in a concentration of about 45 to 55 weight percent.
6. 6. An improved latex composition according to claim 1, wherein the solid, discrete polymer particles are selected from the group consisting of polymers of styrene-butadiene, acrylic polymers, polymers of vinyl acetate, vinyl chloride polymers and mixtures of the above. 1. - An improved latex composition according to claim 1, wherein the solid, discrete, polymeric particles are a styrene-butadiene polymer and have an average particle size number of about 0.1. to 0.5 microns. 8. An improved latex composition in accordance with that claimed in clause 1, wherein the molecular weight is about 3,000 to 6,000, x is about 6 to 15, and is about 50 to 70 in the copolymer surfactant of Ethylene oxide block / nonionic propylene oxide, predominantly hydrophobic. 9. An improved latex composition according to claim 1, wherein the molecular weight is approximately 3,400, x is approximately 5 to 6, and is approximately 50 in the oxide block copolymer surfactant. of ethylene / nonionic propylene oxide, predominantly hydrophobic. 10. An improved latex composition in accordance with that claimed in clause 1, wherein the molecular weight is about t, 100, x is about 15, and is about 65 to about 70 in the oxide block copolymer surfactant of ethylene / nonionic propylene oxide, predominantly hydrophobic. 11. - An improved latex composition in accordance with that claimed in clause 1, wherein the molecular weight is about 5,650, x is about 10, and y is about 85 in the predominantly hydrophobic ethylene oxide / nonionic propylene oxide block copolymer surfactant. 12. An improved latex composition according to claim 1, wherein the predominantly hydrophobic ethylene oxide / propylene oxide nonionic block copolymer surfactant is present in a concentration of about 0.75 to 1 weight percent. 13. An improved coformity latex composition as claimed in clause 1, wherein the hydrophobic defoaming agent is selected from the group consisting of mineral oils based on hydrocarbon, organosiloxanes, metal soaps and mixtures of the previous ones. 14. An improved latex composition according to claim 1, wherein the hydrophobic defoaming agent is a hydrocarbon-based mineral oil having a boiling point of about 316 to 482 0. 15.- A improved latex composition in accordance with that claimed in clause 1, wherein the hydrophobic only defoaming agent is present in a concentration of about 0.25 to 0.5 weight percent. 16. - An improved latex composition in accordance with that claimed in clause 1, wherein an anionic wetting agent is absent. 17. An improved coformity latex composition as claimed in clause 1, wherein a re filled is absent and the composition is suitable for use in the formation of a transparent polymeric coating on a paper substrate after volatilization of the aqueous dispersion medium. 18. An improved latex composition as claimed in clause 1, wherein the composition is suitable for use as a pressure sensitive adhesive when applied to the surface of a hydrophobic polyester film after volatilization of the aqueous dispersion medium. 19. A method for the application, in the absence of excessive foaming, of a substantially uniform polymeric film to a substrate, comprising: (a) applying to a substrate a layer of a latex composition consisting essentially of 9i) a aqueous dispersion medium, (ii) about 40 to 60 weight percent of discrete polymer particles present in the aqueous dispersion medium are formed by the polymerization of at least one ethylenically unsaturated monomer, (iii) about 0.25 to 1.5 percent by weight, dissolved in the aqueous medium, of a surfactant surfactant of ethylene oxide block copolymer of nonionic propylene, predominantly hydrobic phobic, of the formula: H0- (CH2CH20) 2- (CH (CH2CH20)? -H, which has a molecular weight of about 1,100 to 9,000, wherein x is about 5 to -20 and is about 40 to 90, and (iv) approximately 0.05 to 1 weight percent dispersed in the aqueous medium of a lumphophobic defoaming agent only, and (b) removing the water by volatilization from the latex composition layer present on the substrate to form a polymer film - substantially uniform on the substrate, which is suitable for use as a coating or adhesive 20.- A method for the application, in the absence of excessive foaming, of a polymer film substantially uniform to a substrate in accordance with that claimed in the clause 19, wherein the discrete solid polymer particles have an average particle size number of about 0.05 to 3 microns. 21. - A method for the application, in the absence of excessive foaming, of a substantially uniform polymeric film to a substrate, in accordance with that claimed in clause 19, wherein the solid, discrete, polymer particles have an average size number of particle of approximately 0.1 to 0.5 microns. 22. A process for the application, in the absence of excessive foaming, of a polymer film substantially uniform to a substrate, in accordance with that claimed in clause 19, wherein the discrete solid polymer particles were formed by polymerization by emulsion. 23. A process for the application, in the absence of excessive foaming, of a substantially uniform polymeric film to a substrate, in accordance with that claimed - in clause 19, where the solid, discrete polymer particles are present in the aqueous dispersion medium in a concentration of approximately 45 to 55 weight percent. 24. A method for the application, in the absence of excessive foaming, of a polymer film substantially uniform to a substrate, in accordance with that claimed in clause 19, wherein the solid, discrete polymer particles are selected from the group which consists of styrene-butadiene polymers, acrylic polymers, vinyl acetate polymers, vinyl chloride polymers and mixtures of the above. 25. - A procedure for the application, in the absence of foaming? excessive, of a substantially uniform polymeric film to a substrate, in accordance with that claimed in clause 19, wherein the solid, discrete polymeric particles are a styrene-butadiene polymer and have a number-average particle size of approximately 0.1 at 0.5 microns. 26. A method for the application, in the absence of excessive foaming, of a polymer film substantially uniform to a substrate, in accordance with that claimed in clause 19, wherein the molecular weight is approximately 3,000 to 6,000, x is approximately 6 to 15, and is approximately 50 to 70 in the predominantly hydrophobic ethylene oxide / nonionic propylene oxide block copolymer surfactant. 27. A method for the application, in the absence of excessive foaming, of a substantial polymeric film uniformly to a substrate, in accordance with that claimed in clause 19, wherein the molecular weight is approximately 3,400, x is approximately 5. at 6, ey is about 50 in the predominantly hydrophobic ethylene-non-ionic propylene oxide copolymer surfactant. 28.- A procedure for the application, in the absence of excessive foaming, of a substantially uniform polymeric film to a substrate, in accordance with that claimed in clause 19, where the molecular weight is approximately 5,100, x is approximately 15. and, and is approximately 65 to 70 - in the predominantly hydrophobic ethylene oxide / nonionic propylene oxide copolymer surfactant. 29. A method for the application, in the absence of excessive foaming, of a polymer film substantially uniform to a substrate, in accordance with that claimed in clause 19, wherein the molecular weight is approximately 5,600, x is approximately 10 e , and is about 85 in the predominantly hydrophobic ethylene oxide / nonionic propylene oxide copolymer surfactant agent. 30. A method for the application, in the absence of excessive foaming, of a substantially uniform polymeric film to a substumulus, as claimed in clause 19, wherein the oxide block copolymer surfactant of ethylene / nonionic propylene oxide, predominantly hydrophobic, is present in a concentration of about 0.75 to 1 weight percent. 31.- A procedure for the application, in the absence of excessive foaming, of a substantially uniform polymeric film to a substrate, in accordance with that claimed in clause 19, wherein the hydrophobic only defoaming agent is selected from the group that It consists of mineral oils based on hydrocarbons, organosi loxians, metal soaps and mixtures of the above. 32. - A method for the application, in the absence of excessive foaming, of a substantially uniform polymeric film to a substrate, in accordance with that claimed in clause 19, wherein the hydrophobic defoaming agent alone is a mineral oil based on hydrocarbon that It has a boiling point of approximately 316 to 482eC. 33.- A method for the application, in the absence of excessive foaming, of a substantially uniform polymeric film to a substrate, in accordance with that claimed in clause 19, wherein the hydrophobic only defoaming agent is present in a concentration of about 0.25 to 0.5 percent by weight. 34.- A procedure for the application, in the absence of excessive foaming, of a substantially uniform polymeric film to a substrate, in accordance with that claimed in clause 19, wherein the anionic wetting agent is present. 35.- A procedure for the application, in the absence of excessive foaming, of a substantially uniform polymeric film to a substrate, in accordance with that claimed in clause 19, where the substrate is paper, a -filling in the The latex composition and the latex composition form a transparent polymeric coating on the paper substrate after volatilization in the aqueous dispersion medium. 36. - A method for the application, in the absence of excessive foaming, of a polymer film substantially uniform to a substrate, in accordance with that claimed in clause 19, wherein the substrate is a hydrophobic polyester film and the composition of The latex forms a pressure sensitive adhesive when applied to the surface of the hydrophobic polyester film after volatilization of the aqueous dispersion medium. SUMMARY OF THE INVENTION An improved latex composition that has been found to exhibit a superior ability to form a substantially uniform polymer film when applied to a substrate is provided. The composition is capable of being handled and applied to a substrate in the absence of excessive foaming. The aqueous composition includes as essential components, specific concentrations of a copolymer surfactant of ethylene oxide / nonionic propylene oxide, predominantly hydrophobic, usually liquid, and a hydrophobic, defoaming agent (e.g., an oil). hydrocarbon-based mineral). It is possible that the composition is still applied to a hydrophobic substrate (e.g., a polyester film substrate). The compositions of the present invention, after application to a substrate and volatilization of the water component, form a substantially uniform polymeric film which can serve as a coating or adhesive. In testimony of which, I have signed the above description and novelty of the appointment as agent of BASF CORPORATION, in Mexico City, Federal District, today, 4 OF AC30ST0 OF 1995. p.p.de BASF CORPORATION. JÓSE HIN0J0SA CUELLAR