MXPA97003785A - Method to produce modified latex polymer with isocian - Google Patents

Abstract

The present invention is directed to a method for producing an aqueous acrylic polymer modified with isocyanate. The method provides for reacting a compound with at least two isocyanate functionality with an isocyanate-reactive polymer to produce the isocyanate-modified acrylic polymer of the present invention with a long shelf life and resistance to solvent

Description

METHOD TO PRODUCE LATEX POLYMER MODIFIED WITH ISOCYANATE The present invention is directed to a method of producing isocyanate-modified acrylic polymer, and in particular a method for producing stable aqueous dispersion for storage of an acrylic-urethane graft copolymer. While there are numerous patents for acrylic-urethane-aqueous graft copolymers, they describe processes that begin with some variant of a normal polyurethane dispersion (PUD) synthesis, followed by an emulsion polymerization. In these processes, an isocyanate-functional prepolymer is manufactured in the absence of water, typically in a flammable and volatile solvent, since the isocyanate functionality, which is highly reactive, reacts with water. The prepolymer is then dispersed in water, after which an acrylic polymer is grafted onto the prepolymer to produce the aqueous acrylic-urethane graft copolymers. To avoid water contamination during this critical step, it is common to use two reaction vessels, one for the synthesis of prepolymer, and a second for the synthesis of emulsion. However, it is difficult to control the stoichiometric balance that is intended, and the molecular weight of the resulting prepolymer when prepared with this process. Due to the accumulation of molecular weight, the resulting prepolymer tends to gel easily, and has a high viscosity. As a result, it is difficult to disperse this prepolymer in water. Since the prepolymer must be dispersed in water in the emulsion vessel, high-power stirring equipment is generally required for the reaction vessels (Progress, in Organic Coatings, 9 (1981), 281-340.) The problems described above are common to both the synthesis of PUD and acrylic-urethane graft copolymers are known in the art, and attempts to improve the situation generally focus on ways to reduce the viscosity of the prepolymer to make the dispersion step easier US Pat. No. 4,888,383 (hereinafter referred to as Patent 383) of Huybrechts discloses a method for preparing a stable dispersion of polyurethane modified polyacrylic The method stipulates adding a polyisocyanate prepolymer chain or polyurethane terminated in isocyanate to a reaction mixture consisting of an aqueous dispersion or polyacrylic emulsion with functional am ina and functional hydroxyl to cause a chain extension of the ingredients. The need for two reaction vessels in this synthesis is generally taken for granted, due to the need to control the isocyanate reaction during the prepolymer synthesis excluding water. Accordingly, there is a need for a process to produce an isocyanate-modified acrylic polymer that is not sensitive to viscosity elevation for chain building reactions, and where it is possible to exercise a considerable degree of control over the rate of the reactivity of the isocyanate, even in the presence of water. The present invention is directed to a novel method for producing an aqueous and isocyanate-modified acrylic polymer comprising: making a reaction with a finished compound in at least two isocyanate functional groups with an isocyanate reactive polymer in an aqueous medium to produce the acrylic polymer modified with aqueous isocyanate. As used herein: "GPC mean molecular weight" means the average molecular weight determined by gel permeation chromatography (GPC) as described on page 4, Chapter I, of The Characterization of Polymers, published by Rohm and Hass Company, Philadelphia, Pennsylvania, USA, in 1976, using polymethyl methacrylate as a standard. The GPC average molecular weight can be estimated by calculating a theoretical weight of the average molecular weight. On systems that contain chain transfer agents, the theoretical average molecular weight is simply the total weight of the polymerizable monomer in grams, divided by the total molar amount of chain transfer agent used during the polymerization. The molecular weight estimation of an emulsion polymer system that does not contain a chain transfer agent is more complex. An imprecise estimate can be obtained by obtaining the total weight of the polymerizable monomer in grams, and dividing that amount by the product of the molar amount of an initiator multiplied by an efficiency factor (in our systems initiated with persulfate, we use a factor of approximately 0.5) . Further information on theoretical molecular weight calculations can be found in Principies of Polymerization, 2nd edition, by George Odian, published by John Wiley and Sons, NY, NY, USA, in 1981, and in Emulsion Polymerization, edited by Irja Pirma, published by Academic Press, NY, NY, USA, in 1982. "The transition temperature of the vitreous state (TG) "is a narrow range of temperature, measured by conventional differential scanning calorimetry (DSC), during which amorphous polymers from relatively hard and brittle glasses are changed to relatively soft viscous gums.To measure the Tg by this method, Copolymer samples were dried, preheated to 120 ° C, rapidly cooled to -100 ° C, and then heated to 150 ° C at a rate of 20 ° C / minute, while the data were collected. measured at the midpoint of inflection using the half-height method Alternatively, the reciprocal of the glass transition temperature of a particular copolymer composition can typically be calculated with a high degree of accuracy when calculating the sum of the respective quotients obtained by dividing each of the weight fractions of the respective monomers, Mi, M2 / -, Mn, from which the copolymer is derived by the Tg value for the homopolymer derived from the monomer respective number, according to an equation of the form: n 1 / Tg (copolymer) =? w (Mi) / Tg (Mi) (1) i = l wherein: Tg (copolymer) is the transition temperature of the calculated vitreous state of the copolymer, expressed in ° Kelvin (° K); (Mi) is the weight fraction of repeating units in the copolymer derived from an i-th monomer; and Tg (Mi) is the transition temperature of the vitreous state, expressed in ° Kelvin (° K), of the homopolymer of an i-th Mi monomer. The transition temperature of the vitreous state of various homopolymers can be found, for example, in "Polymer Handbook", edited by J. Brandrup and E.H. Immergut, Interscience Publishers. "Dispersed polymer" means polymer particles colloidally dispersed and stabilized in an aqueous medium. "Solubilized polymer" includes "Water-soluble polymer", "Water-reducible polymer", or a mixture thereof. Water soluble polymer means a polymer dissolved in an aqueous medium. Water reducible polymer means a polymer dissolved in water and a solvent miscible in water. The solubilized polymer results in a polymer solution characterized by having the self-grouping constant (K) of the Mooney equation [l-ln? Rel = 1 / BC - K / 2.5] equal to zero. In contrast, the dispersed polymer has (K) equal to 1.9. The details of Mooney's equation is revealed in an article entitled "Phisical Characterization of Water Dispersed and Soluble Acrylic Polymers" by Brendley et al., In "Nonpolluting Coatings and Coating Processes", published by Plenum Press, 1973, and edited by Gordon and Prane. "Polymer particle size" means the diameter of polymer particles measured using a Particle Meter BI-90 Brookhaven Model, supplied by Brookhaven Instruments Corporation, Holtsville, New York, USA, which uses a quasi-elastic light scattering technique to measure the size of the polymer particles. The intensity of the scattering is a function of particle size. So uses the diameter based on a heavy average of intensity. This technique is described in Chapter 3, pages 48-61, entitled Uses and Abuses of Photon Correlation Spectroscopy in Partiole Sizing by Weiner et al. in a 1987 edition of the series of American Chemical Society Symposium. "Polymer solids" means polymer in its dry state. The term "(meth) acrylate" includes acrylate and methacrylate. The method of the present invention directed to produce an aqueous isocyanate-modified polymer includes reacting an isocyanate-reactive polymer in an aqueous medium with a finished compound with at least two isocyanate functional groups to produce the aqueous isocyanate-modified polymer. The isocyanate-reactive polymer has a Tg in the range of -56 ° C to 100 ° C, preferably in the range of -40 ° C to 100 ° C and, even more preferably, in the range of -10 ° C to 70 ° C. The isocyanate-reactive polymer is preferably prepared in the aqueous medium by conventional polymerization methods, such as, for example, emulsion polymerization of a monomer mixture, which includes at least one monomer reactive in isocyanate, which is capable of reacting with an isocyanate. It is contemplated that the isocyanate reactive functionality can be incorporated into a polymer, either by adding the isocyanate reactive monomer to the reaction mixture, or by a post-functionalization reaction, which could incorporate the isocyanate-reactive functionality in the polymer, after the polymerization is finished. The amount of isocyanate reactive monomer added to the monomer mixture is adjusted to provide the isocyanate-reactive polymer, at least one isocyanate-reactive half per polymer chain. The range of isocyanate-reactive moieties present in the isocyanate-reactive polymer chain ranges from 1 to 30, preferably 2 to 10, and more preferably from 2 to 4. If the number of isocyanate-reactive moieties present in a polymer chain After 30, the film formation of the aqueous isocyanate-modified polymer will be adversely affected. If the amount of isocyanate-reactive moieties has a polymer chain of less than 1, a coating resulting from this polymer modified with aqueous isocyanate will not have the desired properties, such as hardness; brightness; accession; and resistance to abrasion, solvents and UV. Preferably, the isocyanate-reactive polymer is polymerized by emulsion in the aqueous medium by copolymerizing at least one monomer containing an isocyanate-reactive functionality, including acetoxyethyl (meth) acrylate; N-cyanoacetyl-N-methylaminoethyl (meth) acrylate; monomers of hydroxyalkyl (meth) acrylate, such as hydroxyethyl (meth) acrylate, and hydroxypropyl (meth) acrylate; acrylamide, methacrylamide; alkyl substituted acrylamide, and hydroxybutyl (meth) acrylate isomers. Hydroxyalkyl (meth) acrylate monomers are preferred. Hydroxyethyl (meth) acrylate is even more preferable. The remaining monomers in the monomer mixture suitable for preparing the isocyanate-reactive polymer include alkyl (meth) acrylate monomers, such as (C? -C20) alkyl (meth) acrylate monomers.

As used herein, the term "alkyl (C? -C20)" denotes an alkyl substitution group of 1 to 20 carbon atoms per group. Suitable (C? -C20) alkyl (meth) acrylate monomers include, for example, acrylic and methacrylic ester monomers, including methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, (meth) 2-ethylhexyl acrylate, decyl (meth) acrylate, lauryl (meth) acrylate, cetyl (meth) acrylate, eicosyl (meth) acrylate, isobornyl (meth) acrylate, isodecyl (meth) acrylate, oleyl (meth) acrylate, palmityl (meth) acrylate, stearyl (meth) acrylate, or various mixtures thereof. The vinyl ester monomers, such as, for example, vinyl acetate, vinyl propionate, vinyl neononanoate, vinyl neodecanoate, vinyl-2-ethylhexanoate, vinyl pivalate, vinyl versatate, or a mixture thereof. Suitable vinyl monomers include, for example, vinyl halide, preferably vinyl chloride, vinylidene halide, preferably vinylidene chloride, or various mixtures thereof. Suitable vinyl aromatic monomers include, for example, one or more polymerizable vinyl aromatic compounds and mixtures thereof, and also include styrene, alkyl substituted styrenes, such as α-methylstyrene, α-ethylstyrene, β-methylstyrene and vinyl xylene, halogenated styrenes, such as, chlorostyrene, bromostyrene and dichlorostyrene, other styrenes having one or more non-reactive substitutes in the benzene nucleus, vinyl naphthalene; acrylonitrile or several mixtures of these. The preferred monomer mixture includes (meth) hydroxymethyl acrylate and monoethylenically unsaturated monomers, such as methyl methacrylate, butyl acrylate, butyl methacrylate, ethyl acrylate, ethylhexyl acrylate, styrene, methyl styrene or various mixtures thereof. A more preferred monomer mixture includes at least one or more of the following: 1) butyl acrylate, hydroxyethyl (meth) acrylate and methyl methacrylate, 2) butyl methacrylate, hydroxyethyl (meth) acrylate and methyl methacrylate, 3) butyl acrylate, hydroxyethyl (meth) acrylate and styrene, 4) 2-ethylhexyl acrylate, hydroxyethyl (meth) acrylate and methyl methacrylate, or 5) 2-ethylhexyl acrylate, hydroxyethyl (meth) acrylate and styrene The most preferred monomer includes styrene, hydroxyethyl (meth) acrylate and 2-ethylhexyl acrylate.

If so desired, the isocyanate reactive polymer further includes, in the range of 0.5 percent to 20.0 percent, preferably in the range of 2 percent to 10 percent, of a monomer containing an acid functionality, where all the percentages are expressed as a percentage of weight based on the total weight of the solid polymers. The acid functionality results from including in the monomer mixture one or more of the monoethylenically unsaturated carboxylic acid monomers, such as, for example, acrylic acid, methacrylic acid, itaconic acid, crotonoic acid, aconitic acid, atropic acid, maleic acid maleic anhydride, fumaric acid, vinylbenzoic acid, semi-esters of ethylenically unsaturated dicarboxylic acids, semi-amides of ethylenically unsaturated dicarboxylic acids and various mixtures thereof. Another suitable monomer includes one or more of monomethyl itaconate, monomethyl fumarate, monobutyl fumarate, acrylamidopropane sulfonate, sodium vinyl sulfonate, 2-acrylamido-2-methylpropanesulfonic acid, 2-methacryloxyethyl phosphate and phosphoethyl (meth) acrylate. Monomer containing the monoethylenically unsaturated carboxylic acid is preferred, and acrylic acid, methacrylic acid and mixtures thereof are most preferred.

The polymerization process is typically initiated by conventional free radical initiators, such as, for example, hydrogen peroxide, tertiary butyl hydroperoxide, ammonia and alkali persulfates, typically at a level of 0.05 percent to 3.0 percent by weight, where all weight percentages are based on the weight of the total monomer. Similar levels, Redox systems, can be used using the same primers coupled with a suitable reductive, such as, for example, sodium bisulfite, sodium hydrosulfite and isoscorbic acid. The chain transfer agents can be used in an amount effective to provide the GPC molecular weight. For purposes of regulating the molecular weight of the polymer that is formed, suitable chain transfer agents include known halo-organic compounds, such as, carbon tetrabromide and bromodichloromethane; sulfur-containing compounds, such as, alkylthiols including ethanethiol, butanethiol, tertiary butyl and ethyl mercaptoacetate, as well as aromatic thiols; or various other organic compounds with hydrogen atoms that are easily abstracted by free radicals during polymerization. Additional and suitable chain transfer agents or ingredients include, but are not limited to, butyl mercaptopropionate; isooctylmercaptopropionate; bromoform; bromotrichloromethane; carbon tetrachloride; alkyl mercaptans, such as 1-dodecantiol, tertiary-dodecyl mercaptan, octylmercaptan, tetradecyl mercaptan and hexadecyl mercaptan; alkyl thioglycollates, such as butyl thioglycolate, isooctyl thioglycolate, and dodecyl thioglycolate; thioesters or combinations of these. Mercaptans are the most preferred. When a dispersion of polymer particles is used, the polymer particle size is controlled by the amount of conventional surfactants added during the polymerization process of the emulsion. Conventional surfactants include anionic or nonionic emulsifiers, or combinations thereof. Anionic emulsifiers include salts of fatty rosin and naphthenic acids, condensation products of naphthalene sulphonic acid and low molecular weight formaldehyde, carboxylic polymers and copolymers of the appropriate hydrophilic-lipophilic balance, alkali alkyl or ammonia sulfates, alkyl sulfonic acids , alkyl sulfonic acids, alkyl phosphonic acids, fatty acids, and oxyethylated alkyl phenol sulphates and phosphates. Typical nonionic emulsifiers include alkylphenol ethoxylates, polyvinyl alcohols, polyoxyethylenated alkyl alcohols, polyglycol amine condensates, modified polyethoxyacetyls, long chain carboxylic acid esters, alkylaryl terminated modified ether, and alkylpolyether alcohols. The typical ranges for surfactants are 0.1 to 6 weight percent, based on the total weight of the total monomer. If desired, the isocyanate-reactive polymer can include multi-stage polymer particles with two or more phases of various geometric structures, such as, for example, core / shell particles or core / coating, core / shell particles with envelope phases that encapsulate the nucleus incompletely, core / shell particles with a multiplicity of interpenetrating networks and particles of networks. In all these cases, the majority of the surface area of the particle will be occupied by at least one external phase and the interior of the latex polymer particle will be occupied by at least one internal phase. The external phase weight of the multi-stage polymer particles weighs 5 weight percent to 95 weight percent, based on the total weight of the particle. Frequently it is desirable for each stage of the multistage polymer particles having a different Tg. If so desired, each step of this multistage polymer particles can be provided with different GPC numbers of average molecular weight, such as the multistage polymer particle composition disclosed in U.S. Patent 4,916,171. The multi-stage polymer particles of the isocyanate-reactive polymer are prepared by the conventional emulsion polymerization process, wherein at least two steps differ in composition and are formed sequentially. This process generally results in the formation of at least two polymer compositions. Each of the steps of the multi-stage polymer particles may contain the same chain transfer agents, surfactants and those disclosed above. The emulsion polymerization techniques used to prepare these multi-stage polymer particles are well known in the art, and are disclosed, for example, in U.S. Patent Nos. 4,325,856; 4,654,397; 4,814,373 and 4,916,171. Once the polymerization is essentially complete, the finished compound with at least two isocyanate functional groups is added to the aqueous medium containing the isocyanate-reactive polymer. The rate at which the compound is added ranges from 0.2 percent to 100 percent of the total isocyanate load per minute, preferably in the range of 1 percent to 10 percent of the total isocyanate load per minute, to allow a controlled and homogeneous dispersion of the compound in the mixture. The aqueous medium containing the isocyanate-reactive polymer is preferably constantly stirred during the addition to improve mixing. Even more preferably, the aqueous medium is stirred to create a vortex, and the compound is preferably added in the center of the vortex funnel shape to improve distributive mixing. It is thought, without relying on this, that the isocyanate-terminated compound reacts with the isocyanate reactive polymer to produce the aqueous isocyanate modified latex polymer of the present invention, and that this gives it a higher storage capacity. When functional-hydroxy polymers are used, it is thought that the urethane linkages are formed by the reaction of hydroxy groups with the isocyanate groups. The isocyanate-terminated compound is added to the aqueous medium at a stoichiometric (SR) ratio formulated below: The isocyanate-terminated compound varies from: The isocyanate reactive polymer 0.1 to 5 The preferred SR varies in the range of 0.5 to 1.5. If the SR exceeds the upper limit, excessive amounts of urea groups are formed by the isocyanate-water reaction. As a result, the desired properties, such as water sensitivity, storage stability, impact resistance, solvent resistance of coatings resulting from the isocyanate-modified polymers are adversely affected. If the SR is below the lower limit, no significant increase in the desired properties is achieved, such as water sensitivity, storage stability, impact resistance, resistance to coating solvents resulting from the isocyanate-modified polymers. The isocyanate compound is preferably supplied with a molecular weight in the range of 200 to 1,000, preferably in the range of 200 to 700, and more preferably in the range of 200 to 500. Some of the desired compounds terminated with at least two isocyanate functionalities include aliphatic, cycloaliphatic or aromatic polyfunctional isocyanates, preferably aliphatic or difunctional cycloaliphatic diisocyanates. Examples of these diisocyanates are hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, bis (4-isocyanatocyclohexyl) -methane, such as, Desmodur® W from Bayer, Pittsburgh, Pennsylvania, USA, xylylene diisocyanate, tetramethylxylene diisocyanate. Examples of aromatic and polyfunctional isocyanates are; toluene diisocyanate, diphenylmethane diisocyanate, Desmodur® N from Bayer (composed of trifunctional Biuret of hexamethylene diisocyanate), Desmodur® N3390 (isocyanurate trimer of hexamethylene diisocyanate), allophanates, Biuret compounds, and uretdiones of diisocyanates or various mixtures of these. Some other compounds suitable for use in the present invention include tetramethylene diisocyanate, 1,4-cyclohexane diisocyanate, 2,4- and 2,6-hexahydrotolylene diisocyanate, 1,4- and 1,3-phenylene diisocyanate. , 4, 4 * -diphenylmethane diisocyanate, 1,5-naphthylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, water dispersible polyisocyanates, such as those described in US 5,185,200, US 5,200,489, EP 516,277, EP 486,881, and in Bock and Petzoldt, Modern Paint and Coatings, February 1996, page 22, and the references noted herein; several mixtures of the above isocyanates are also included. If desired, an acid-reactive crosslinking agent may be added during or after the addition of the isocyanate compound to the aqueous medium containing the isocyanate-reactive polymer supplied with the acid functionality, to interrelate the aqueous isocyanate modified acrylic polymer of the present invention. In this manner, the isocyanate-modified aqueous acrylic polymer can be used in two two-pack thermofixing formulas, which is typically stored in separate containers, and then the user mixes them before application. It is thought, although not relying on this, that the interlacing agent reactive in acid is interrelated with the acid functionality of the isocyanate-reactive polymer. If desired, the aqueous medium may include additives, such as surfactants, pigments and extensions, biocides, pH stabilizers, antifoaming agents, plasticizers, wetting agents and other surface control agents, wet edge additives and drying agents. In general, they should be less than 70 percent, preferably less than 50 percent by weight, based on the total weight of the composition, of the pigment. Suitably, the other additives stipulated above, when present, shall not exceed 10 percent by weight, based on the total weight of the composition, for each additive, and generally only up to 1 or 2 percent of each additive shall be present.

If desired, the aqueous medium will also contain cosolvents. Examples of these cosolvents include alcohols, such as methanol, ethanol, isopropanol, glycolyletylene, butanol and 2-ethylhexanol, glycol ethers, such as ethylene glycol monoethylether, diethylene glycol monobutyl ether and propylene glycol methyl ether; ketones, such as acetone and methyl ethyl ketone; solvents, such as N-methylpyrrolidone, dimethylformamide and tetrahydrofuran; partially visible solvents, such as toluene, xylene, heptane, mineral spirits and glycol ether acetates, such as propylene glycol acetate methyl ether. These can be added as grouping solvents, at levels sufficient to reduce the film-forming temperature of the resulting formula to a temperature that is below that required for the particular coating application contemplated. The single package isocyanate-modified aqueous polymer of the present invention provides better storage stability with respect to two pack (two component) acrylic urethane coatings, which typically have an application life ranging from 10 and 35 minutes to a few hours, typically 1 to 4 hours. The polymer of the present invention has a longer shelf life that exceeds at least one month, and typically several years. The coatings resulting from the isocyanate-modified aqueous acrylic polymer of the present invention exhibit hardness; resistance to impact, solvents, abrasion and blockage; Resistance to degradation by ambient and artificial UV light, which results from fluorescent light indoors. As a result, the coatings resulting from the isocyanate-terminated aqueous polymer of the present invention are suitable for use in industrial coating applications, such as in aerosol applications, floor coatings, foam coatings, dip coatings, automotive coatings, architectural coatings for interiors and exteriors, coatings for wood; leather coatings, the coating of polymer substrates, such as acrylonitrile butadiene styrene; protective coatings against scratches, such as those with plastic lenses. Coatings resulting from the isocyanate-terminated aqueous acrylic polymer of the present invention are also suitable for use in adhesives; construction products, such as breasts, mastics; specialized industrial chemical compounds, such as glue used in automotive interior applications, including gloveboxes. The following test procedures were used to evaluate the polymer compositions used in the method of the present invention: The emulsion stability of the isocyanate-modified aqueous compositions was measured by periodically stirring the isocyanate-modified aqueous composition in an aqueous medium contained in an container with a stirring device, such as a rod or stirrer, and then visually examining the agitating device for the presence of gels or coagulated materials, particularly after carefully scraping the bottom and walls of the container containing aqueous medium. The "gelled" compositions (ie, those without stability) typically formed a solid mass in which the agitator device can not essentially be inserted. The compositions with acceptable stability could be easily stirred after a period of one week, even though these compositions could contain a small amount of clots or gel, typically below 2 percent of the total weight, which could be removed by filtration with a coarse filter. , such as a 60 mesh filter. Compositions that are essentially free of clots or gel, are considered as those that have a more than acceptable level of stability. Some of the embodiments of the present invention will be described in detail in the following Examples.

Procedure for the Preparation of Polymer 1 To a 5 liter stirred reactor containing 1383.0 grams of deionized water (DI water) and 48.2 grams of sodium dodecylbenzene sulfonate aqueous solution (active ingredient by 23%) which was heated to 85 ° C, 43.4 grams of Monomer Mixture 1 (MM # 1) was added as shown in the Table below. The container used to store MM # 1 was then rinsed with 15 grams of DI water, and the rinse was added to the reactor. Then a solution of 2.08 grams of ammonia persulfate in 15.0 grams of DI water, and a solution of 2.08 grams of sodium carbonate in 45 grams of DI water were added. Ten minutes after the first addition of MM # 1, with the temperature of the reaction mixture maintained at 85 ° C, the remainder of MM # 1 and the 2.08 gram solution of ammonia persulfate in 150.0 grams of water were uniformly added. DI to the reaction mixture for a period of 180 minutes. The final reaction mixture was neutralized to a pH of 7.5 with 29% aqueous ammonia.

The same procedure described herein was used to prepare polymers 2, 3 and Comparative Polymer A, using the appropriate monomer mixtures shown in the Tables below: Mixture of Monomers 1 for Polymer 1 Mixture of Monomers for Polymer 2 Mixture of Monomers for Polymer 3 Mixture of Monomers 1 for the Comparative Polymer A Preparation Procedure for Polymer 4 To a stirred reactor of 5 liters, which contained 1383.0 grams of deionized water (DI), and 3.0 grams of aqueous solution of sodium dodecylbenzene sulfonate (active ingredient 23%) that was heated to 85 ° C, 43.4 grams of Monomer Emulsion # 1 (ME # 1) was added as shown in the Tables below. The container used to store ME # 1 was then rinsed with 15 grams of DI water, and the rinse was added to the reactor. Then a solution of 2.08 grams of ammonia persulfate in 15.0 grams of DI water, and a solution of 2.08 grams of sodium carbonate in 45 grams of DI water were added. Ten minutes after the first addition of Me # l, with the temperature of the reaction mixture maintained at 85 ° C, the remainder of ME # 1 and a solution of 1.04 grams of ammonia persulfate in 75.0 grams were added to the reaction. of water DI to the reaction mixture at a uniform rate for a period of 90 minutes. Thirty minutes later, with the temperature of the reaction still maintained at 85 ° C, Monomer Emulsion # 2 (ME # 2) and a solution of 1.04 grams of ammonia persulfate in 75.0 grams of DI water were added to the mixture. reaction at a uniform rate for a period of 90 minutes. The final reaction mixture was neutralized to a pH of 7.5 with 29% aqueous ammonia. The same procedure as described herein was used to prepare Polymer 5, by using the appropriate Monomer Emulsions that appear in the following Tables: Emulsion of Monomers No. 1 for Polymer 4 Emulsion of Monomer No. 2 for Polymer 4 Emulsion of Monomers No. 1 for Polymer 5 Emulsion of Monomers No. 2 for Polymer 5 Preparation of Latex Polymers Modified with Isocyanate Examples 1 to 8 of the isocyanate-modified polymers of the present invention, which are shown in the following Table 1, were prepared with the following procedure. A round 4-necked flask, equipped with a condenser, a stirrer and a thermometer was charged with the polymer shown in Table 1 below. The isocyanate compound, which appears in Table 1 below, was then added to the charge. Additional DI water, shown in Table 1 below, was added to the reaction mixture to adjust the final solids of the resulting isocyanate-modified polymer, which was stirred overnight at room temperature under nitrogen. The reaction mixture was then neutralized to pH = 7.0 with aqueous ammonia hydroxide (28%).

Table 1 The following abbreviations were used in Table 1 above: Ex. Means Example.

Compound means isocyanate compound. IC No. 1 means Desmodur® XP-7063 water dispersible polyisocyanate supplied by Bayer, Pittsburgh, Pennsylvania, USA. IC No. 2 means bis (4-isocyanatocyclohexyl) -methane Desmodur® W supplied by Bayer, Pittsburgh, Pennsylvania, USA. X means that no gel or clot was observed after a period of one week, which is an indication of a level of stability above acceptable. The observation was discontinued thereafter. And it means clot or filterable gel that was observed after a period of one week, which is an indication of an acceptable level of stability. The observation was discontinued after this. Z means gelled, which is an indication of a composition that is not stable. From Table 1 it can be seen that the isocyanate-modified aqueous acrylic polymers of the present invention, made from emulsion polymers containing isocyanate-reactive functional groups (Examples 1-5, 7 and 8) are more stable than those which do not have these functionalities (Comparative Example 6).

Claims (10)

1. A method for producing an isocyanate modified aqueous acrylic polymer comprising: reacting a finished compound with at least two isocyanate functional groups with an isocyanate reactive polymer in an aqueous medium to produce the isocyanate-modified aqueous acrylic polymer.

2. The method of claim 1, further comprising providing the isocyanate-reactive polymer with an acid function. The method of claim 2, which comprises adding an inter-linking agent to the aqueous medium to cause the acid functionality to react in the polymer with the cross-linking agent. 4. The method of claim 1, wherein the compound has a molecular weight in the range of 200 to 1,000. The method of claim 1, wherein the stoichiometric ratio of the reactive groups, for the finished compound in at least two isocyanate functional groups with the isocyanate reactive polymer vary in the range of 0.5 to 5. 6. The method of Claim 1, wherein the isocyanate reactive polymer is supplied with from 1 to 30 reactive isocyanate functionalities per polymer chain. The method of claim 6, wherein the isocyanate reactive functionalities result from an isocyanate reactive monomer selected from the group consisting of acetoxyethyl (meth) acrylate, N-cyanoacetyl-N-methylaminoethyl (meth) acrylate, ( meth) hydroxyethyl acrylate, hydroxypropyl (meth) acrylate, acrylamine, methacrylamide, alkyl substituted acrylamide, isomers of hydroxybutyl (meth) acrylate and various mixtures thereof. The method of claim 1, wherein the compound selected from the group consisting of hexamethylene diisocyanate, bis (4-isocyanatocyclohexyl) methane, toluene diisocyanate, Biuret compound of hexamethylene diisocyanate functional, isocyanurate trimer of hexamethylene diisocyanate, 4,4'-diphenylmethane diisocyanate, isophorone diisocyanate, water dispersible polyisocyanates and various mixtures thereof. 9. A method for producing an aqueous isocyanate-modified acrylic polymer comprising: emulsion polymerizing a mixture of monomers in an aqueous medium to produce an isocyanate-reactive polymer, wherein the mixture contains at least one isocyanate-reactive monomer, and at least an acrylic monomer with an acid functional; adding a finished compound with at least two isocyanate functional groups to the aqueous medium in a stoichiometric ratio of the isocyanate-reactive monomer against the isocyanate-terminated compound ranging from 0.5 to 5, wherein the compound has a molecular weight that varies by the range of 200 to 1,000; making a reaction of the isocyanate-reactive polymer with the compound to produce the isocyanate modified latex polymer with a longer storage stability. 10. An isocyanate-modified acrylic polymer produced in accordance with claims 1 or 9.