NON-IONIC ASSOCIATIVE THICKENING COMPOSITION WITH IMPROVED VISCOSITY RETENTION AFTER TITRATION IN COATING
LATEX ARCHITECTURAL. BACKGROUND OF THE INVENTION 1. Technical Field present invention relates to a water-soluble copolymer composition containing a linear copolymer of aminoplast-ether resin, which has a relatively high content of hydrophobic tristyryl phenol. Such a copolymer contains a unit of the formula:
wherein the divalent R0i contains a divalent alkyleneoxy-containing moiety, Amp is the skeletal moiety of an aminoplast resin, R is hydrogen, alkyl containing from 1 to about 4 carbon atoms or acyl containing from 1 to about 4 carbon atoms , RO is bound to alkylene units of Amp and is a number greater than 1, preferably greater than 2. Amp includes any dimeric and oligomeric component of the aminoplast resin. R02 is tristiryl phenol, which is covalently bound to Amp through a heteroatom, p is a number that is equal to the free valence of Amp minus (2 + q) and q is a positive number. 2. Background Non-ionic thickener associative agents have been used in architectural latex coatings for almost 20 years. These have replaced traditional cellulosic thickening agents, because coatings using non-ionic associative thickeners exhibit improved application properties such as brush drag, flow and equalization and water sensitivity. The term "associative thickener" is recognized in the art to mean a hydrophobically modified, nonionic water soluble polymer capable of interacting in aqueous solution with itself and with other species such as latex particles. Associative thickeners are widely used to increase the performance or effectiveness properties of paints and coatings. The uses of associative thickeners in water-based compositions are described in a number of patents, which include U.S. Patent Nos. 5,574,127, 4,426,485, 4,155,892, 4,079,028; 3,035,004; 2,795,564; 2,875,166 and 3,037,952. One type of associative thickener is described by the two patents of Emmons et al., US Patent No. 4,079,028 and US Patent No. 4,155,892, patented on March 14, 1978 and May 22, 1979, respectively. These patents describe associative polyurethane thickeners containing hydrophobic groups interconnected by hydrophilic polyether groups. Thickening agents are non-ionic. Another type of associative thickener is described in US Pat. Nos. 5,627,232 and 5,629,373 issued May 6, 1997 and May 13, 1997, respectively. These patents describe water-based coating compositions, which contain a linear copolymer of aminoplast-water-soluble ether resin containing interlacing aminoplast segments through ether segments. Aminoplast resins are defined in those patents, and herein, and in the claims, as a kind of stage A thermosetting resin based on the reaction of an amine with an aldehyde and the related acetals containing amines or amides. The structural characteristics and commercial uses of the aminoplast resins are also described in detail in those patents. Figure 1 contains a partial list of aminoplast resins.
Fig l.
The North American Patents. Nos. 5,627,232 and 5,629,337 describe a linear copolymer of aminoplast-ether resin with the formula as described in Fig. 2.
wherein the divalent Roi contains a divalent alkyleneoxy-containing moiety, Amp is the skeletal moiety of an aminoplast resin, R is hydrogen, alkyl containing from 1 to about 4 carbon atoms, or acyl containing from 1 to about 4 carbon atoms, p is a positive number that is equal to the free valence of Amp minus 2, RO is bound to alkylene units of Amp and is a number greater than 1. For the purposes of this invention and the discussion of the prior art, the The skeletal unit of the aminoplast resin is the structure of the aminoplast resin minus the leaving groups RO linked to the alkylene of the alkylol or ether or alkylol ester of the aminoplast resin, without considering whether some of the RO groups are removed from the aminoplast resin. That skeletal unit is referred to herein and in the claims as "Amp". The term "linear", when used herein and in the claims to characterize a polymer, refers to a polymer that is free of crosslinking or branching that makes the polymer solid and cured. A "fully linear" polymer is a polymer that is free of crosslinking and branching. A linear polymer may or may not be a completely linear polymer. The term "acrylic polymer" means any polymer wherein at least 50% by weight is an acrylic or methacrylic acid or ester, including mixtures of such acids and esters individually and together. The term "vinyl acetate polymer" means any polymer that contains at least 50% by weight of vinyl acetate. The symbols and designations used herein are intended to be applied consistently, especially as used in formulations and equations, unless specifically stated otherwise. Typical nonionic associative thickeners have only had limited success when used in latex coatings for medium to neutral based formulations based on small particle size acrylics. The problem arises when dyes are added to the formulations. Addition of colorant in the amounts of about 141.7 g (5 oz) or a higher amount results in a substantial reduction in the viscosity of the coating. This reduction in viscosity leads to undesirable coating properties and has been addressed by the manufacturers of architectural coatings in a number of ways. One method that manufacturers have used is to compensate for the decrease in viscosity that occurs after shading. The coating is formulated to have a very high viscosity before the colorant is added. The dye is added hoping that the viscosity of the coating falls to an acceptable level. Another method that manufacturers have used is to incorporate large amounts of surfactants and solvents in the coating to control the decrease in viscosity after shading. Still another method used by the manufacturers is to incorporate other thickening agents such as cellulose thickeners and alkali swelling agents to compensate for the decrease in viscosity. While these methods focus on the problem of viscosity, each of these corrective methods have problems associated with them, which make their use less than ideal. The problem with the formulation of a premature coating with a very high viscosity is that it creates problems in the manufacturing process. The problem with additives such as surfactants and solvents, or cellulosic and alkali-swelling thickeners is that they compromise the application properties of the resulting coating. The additives can also cause problems with the physical properties of the final dried paint film. For example, high levels of surfactants or the use of alkali-swelling thickeners can lead to water sensitivity or poor scrub resistance. What is needed is a non-ionic associative thickener agent that can be used in latex coatings, for medium to neutral based formulations based on small particle size acrylics, which results in a minimum reduction in viscosity when the colorant is added. What is needed is a non-ionic associative thickening agent that can be used in latex coatings of medium to neutral based formulations based on small particle size acrylics, which do not require the addition of surfactants and solvents, or other agents of thickening to achieve a satisfactory viscosity when the colorant is added. What is needed is a non-ionic associative thickening agent that can be used in latex coatings, for medium to neutral based formulations based on small particle size acrylics, which maintains the desirable application properties when the dye is added without compromise the final properties of the film. Brief Summary of the Invention The present invention relates to a water-soluble copolymer composition containing a linear copolymer of aminoplast-ether resin having a relatively high content of hydrophobic tristyryl phenol. Such a copolymer contains a unit of the formula:
wherein the divalent Roi contains a divalent alkylenoxy-containing moiety, Amp is the skeletal residue of an aminoplast resin, R is as defined above, RO is attached to alkylene units of Amp and is a number greater than 1, preferably higher 2. Amp includes any dimeric and oligomeric component of the aminoplast resin. R02 is tristyryl phenol, which is covalently linked to the Amp through a heteroatom, p is a number that is equal to the free valence of the Amp minus (2 + q) and q is a positive number. The relatively high content of the hydrophobe means a copolymer containing more than about 3% tristyryl phenol based on weight. In the preferred embodiment, the copolymer contains about 4% tristyryl phenol to about 10% tristyryl phenol based on weight, when the polymer is produced using polyethylene oxide and a glycoluril compound. In another embodiment of the invention, the invention relates to a novel water-based coating composition containing a linear copolymer of aminoplast-ether resin having terminal groups, characterized by a component of the units constituting the copolymer, or a group monofunctional that covers the end of the copolymer effectively, forming the terminal group. This produces a copolymer of the formula:
where each R0o is the same or different terminal group, such as hydrogen, -R0i-H, attached Amp- (OR) pl, -Amp- (OR) pi, tristyryl phenol, or any other monofunctional organic group, such as alkyl, cycloalkyl, aryl, alkaryl, aralkyl, alkyloxyalkyl, aroxyalkyl, cycloalkoxyalkyl and the like, and pi is a positive number that is equal to the free valency of Amp minus 1. A linear copolymer of aminoplast-ether resin particularly preferred comprises units of the formula :
where Roi, R02 and R are as described above, have a value of at least 2, x is O or l, and s + t equal to (i) ^? alonri a 1 ihrp H the nrrion 6
and (ii) 4-x; and the average value of t / s + t is from about 0.01 to about 0.5. In a further preferred embodiment of the invention, the linear copolymer of aminoplast-ether resin used in the coating composition of the invention, comprises a copolymer having terminal groups as illustrated by the following structure:
wherein each R0oi is the same or different terminal group such as hydrogen, -? ½- ?, - (OR) pi, -Amp ° - (OR) pi, tristyryl phenol, or any other monofunctional organic group, such as alkyl, cycloalkyl, aryl, alkaryl, aralkyl, alkyloxyalkyl, aroxyalkyl, cycloalkoxyalkyl and the like, and pi is a positive number which is equal to the free valence of Amp ° minus 1. Amp ° is represented in formula V. The present invention is furthermore refers to a latex coating for medium to neutral based formulations based on small particle size acrylics. The present invention improves this type of latex coatings by reducing the decrease in viscosity, which normally occurs when the colorant is added to the latex coating for medium to neutral based formulations based on small particle size acrylics. The present invention also produces overall improved color acceptance, compared to other competitive compositions and products. Detailed Description of the Invention This invention relates to the use of any aminoplast resin, including those specifically presented in FIG. 1 above, to make the copolymer of the invention. Of these aminoplast resins, associative thickeners of exceptional performance, for use in latex coatings for medium to neutral base formulations based on small particle acrylics, are obtained from the reaction of glycolurils with alkylene oxide glycols to which the tristiryl phenol pendent portions are incorporated. Linear copolymers of aminoplast-ether resin of formula I and subsequent, are manufactured by the novel condensation reaction of a polyfunctional aminoplast resin with a difunctional polyether (alone or with another polyol, as characterized with respect to formulas XII and XIII) in the presence of an acid catalyst. In the prior art, as mentioned above, aminoplast resins are condensed with polyfunctional compounds to produce thermosetting resins or thermo-hardened products (ie, stage C resins). This reaction produces a linear copolymer. Thus, the copolymers of the formulas I, II, III, IV and V are either liquid or thermoplastic solids which are soluble in solvent and soluble or dispersible in water. Linear copolymers of aminoplast-ether resin are manufactured by the copolymerization reaction of a polyfunctional aminoplast resin with an ether containing two terminal active hydrogen groups, in the presence of an acid catalyst, especially a Bronsted-Lowery acid provided in amounts catalytically effective. The reaction is continued until the desired molecular weight is achieved. The desired molecular weight of the copolymer is dependent upon the proposed use of the copolymer. The molecular weight of the copolymer can vary from about 12,000 to about 800,000, preferably from about 20,000 to about 100,000 and much more preferably from about 30,000 to about 80,000. The aminoplast resin is a polymerizable resin of the general formula:
wherein z is a positive number having a value of at least 2. The ether containing two active hydrogen terminal groups comprises a wide variety of compositions. A preferred class is non-ionic. Illustrative of a preferred class of such ethers are polyalkylene oxides of the formula:
H-Oxide of JJ and Jj Alkylene
where "alkylene oxide" is a divalent moiety containing at least two alkylene oxide units in which: 1. the alkylene oxide units form a linear chain and provide a terminal OH, or 2. the oxide units of alkylene are attached to an initiator molecule, such as a diamine, urea, carbamate, phenoxy, amide, bis-imide, and the like, and provide a terminal OH, and / or 3. in which the alkylene oxide is attached to a terminal group having a portion that provides the active hydrogen (-H in formula VII). Further illustrative of such a preferred class are the water soluble or dispersible polyether compounds of the formula:
wherein X is a functional portion of active hydrogen such as oxy (-0-), sulfhydryl (-S-), amino (-N <), carboxy (-C00-), carboxamido, silyl, phosphoryl, ureido, and similar; R04 and Roe are alkyls of 2 to about 8 carbon atoms; Ros and R07 are one or more alkylene oxide units, for example, such as soluble or water dispersible ethylene oxide, propylene oxide, methylene oxide / mixed 1,2-propylene oxide, methylene oxide / oxide Mixed 1, 3-propylene, mixed ethylene oxide / 1,2-butylene oxide, mixed ethylene oxide / 1,4-butylene oxide and the like; Ro6 is a divalent group such as alkylenoxy, alkylene polyamine, cycloalkylene polyamine, phenoxy, ureido, carbamate, amide and the like; xl and x2 are each equal to the free valence of X; x3, x4, x5, x6 and x7 are each 0 or 1, and one or more of x4 and x6 is 1. Specific illustrations of a preferred class of polyethers included in formula VIII are the polyetherdiols Carbowax® and Pluracol® sold by Union Carbide Chemicals & Plas, Inc. and BASF Performance Chemicals, respectively. There are a variety of functional fluids based on alkylene oxides that are sold by Union Carbide Chemicals & Plas, Inc. and BASF Performance Chemicals that are included in formula VIII. The molecular weight of the polyether reagent can vary from about 106 and lower, to about 35,000, and higher. In the prior art, as mentioned above, the aminoplast resins are condensed with polyfunctional compounds to produce thermosetting resins or thermo-hardened products (ie, stage C resin). The above method produces a linear copolymer. Thus, the copolymers of the formulas I, II, III, IV and V are either liquid or thermopla solids which are soluble in solvent and soluble or dispersible in water. Aminoplast reagents include, but are not restricted to, reaction products of melamine aldehyde, ureas, benzoguanamines, glycolurils and the like, to produce the aminoplast resins arrangement, including, but not limited to, those described in FIG. 1 exposed in the above. While any of these can be used to make associative thickeners, glycolurils, such as those of formula IX
where x is as defined above, they have shown appropriate hydrolytic stability when they are reacted with the polyether compounds, such as those included in formula VIII, to meet commercial criteria, for coating compositions containing a associative thickener agent. However, the reaction products of such aminoplast resins with, for example, thiols and NH groups of amides and carbamates, included in formula VIII are much more hydrolytically stable than the aminoplast-ether resin linkages. The use of such reagents allows the production of copolymers based on aminoplast resin, much more hydrolytically stable. Suitable polyethers include polyalkylene polyethers. Preferred polyethers are soluble in water. The most preferred polyethers are the alkylene polyethers wherein the predominant alkylene groups are ethylene. The most desirable polyethers are polyethylene oxide diols having molecular weights of about 1,000 to about 35,000. Illustrative of the desirable polyethylene oxide diols are those of the formula:
HO - (- CHJOTJO CHJCHÍOH X.
wherein xll has a value of from about 20 to about 800, preferably from about 50 to about 500, and much more preferably from about 100 to about 300. A further desirable embodiment of the invention is the modification of the linear copolymers of aminoplast-ether resin used in the manufacture of the coatings of the invention, by including a minor molar proportion of the following unitary structure in the repeating structure of the copolymer:
-? Pf-R¡5- XI.
wherein R15 is the residue of a diol having a higher hydrophobicity than R0i, to thereby provide a linear copolymer containing the structure
-fAmp- ^ fc Am ~ R "fc XII
where x29 has a value that is greater than x30. Preferably, x30 / x29 is less than about 1, preferably less than about 0.33. Illustrative of such R15 groups are
wherein x31 has a value from about 8 to about 20, x32 has a value from about 8 to about 23, x33 and x34 have values from 0 to about 8. The linear copolymer of formula XII can be modified to possess the terminal groups of formulas II and V, discussed above. The aminoplast-ether linear resin copolymers of this invention contain a hydrophobic pendant group. Acceptable hydrophobic groups include aliphatic phenol to alkylphenol to tristyryl phenol. The most preferred hydrophobic pendant group is tristyryl phenol. The tristyryl phenol is extended from the aminoplast resin component of the linear backbone of the aminoplast-ether resin copolymer. The tristyryl phenol groups are commonly linked to the main chain through the ether or ester groups, as illustrated in formula II. The presence of tristyryl phenol increases the performance of the resultant aminoplast-ether resin copolymer as an associative thickener in architectural coating compositions for medium to neutral based formulations based on small particle size acrylics, where the level of added dye It is in large amounts of approximately 37.5 to 100.9 g / liter (5 to 16 ounces per gallon). This invention relates to the use of any aminoplast resin, including those specifically set forth in Figure 1 above, to make the copolymer of the invention. Of these aminoplast resins, associative thickeners of exceptional performance are obtained from the reaction of glycolurils with alkylene oxide glycols to which portions of tristyryl phenol pending at a relatively high concentration are incorporated. The relatively high concentration of tristyryl phenol means about 3% or more based on weight. In the preferred embodiment, the concentration of tristyryl phenol is at a concentration of about 4% to about 10% based on weight. The production of the aminoplast-ether resin copolymers is done by polymerization in solvent or in the molten state. The typical preparation of an associative thickener agent based on aminoplast resin, such as glycoluril, involves dissolving the aminoplast resin, (eg, glycoluril), a polyether compound within the scope of formula IX (such as a Carbowax® polyether sold by Union Carbide Chemicals &Plastics, Inc. Danbury, Conn.), With or without the addition of one or more hydrophobic polyols within the scope of formula XI, with the addition of ethoxylated tristyryl phenol (such as Soprophor BSU) in a solvent of removal or separation, such as alkylated benzene (e.g., toluene or xylenes). Prior to the combination of these reagents, each can not be dried by azeotropic distillation with toluene, xylenes or a mixture thereof, or by any other drying process. The total concentration of the reactants in the solvent can be maintained from about 10 to about 60% by weight. The temperature of the mixture can be brought to approximately 60 ° -140 ° C, preferably of approximately 80 ° -120 ° C. Then an acid catalyst, such as a sulfonic acid catalyst, is added. The reaction mixture is placed under reduced pressure to lead to a permanent distillation of the toluene / xylenes which makes the alcohol by-product azeotroped, which must be removed in order for the reaction to proceed. Cool solvent is constantly added to maintain a constant level. The reaction is allowed to proceed until a given high viscosity is reached, as measured by the Gardner bubble tubes or until the increase in viscosity is stopped. Such an increase in viscosity indicates an increase in the molecular weight of the copolymer. SPECIFIC ILLUSTRATION OF THE SOLVENT PROCESS The following is an illustration of the sequential steps involved in the preparation of the aminoplast-ether resin copolymer. 1. Polyether polyol, ethoxylated tristyryl phenol and azeotrope-forming solvent (eg toluene) are added to a suitably sized vessel that is equipped with a heater, temperature reading device, a nitrogen inlet and a water trap by Dean Stark and a capacitor. 2. The mixture from step 1 is heated to reflux to dry the mixture by azeotropic distillation. When the water removal is stopped, the mixture is cooled to approximately 100 ° C and the water trap is removed. A distillation column and a receiving vessel are installed in the vessel. 3. Glycoluril (for example Powderlink 1174) is added and allowed to melt. 4. The catalyst is added and is applied empty. The pressure is reduced to a level that causes a permanent or stationary distillation of solvent at approximately 100 ° C. The solvent is continuously replenished from a pressure equalizing addition funnel. 5. As the reaction proceeds, the samples are removed and cooled to room temperature and the viscosity is measured with Gardner bubbles. 6. When the proper viscosity is reached, the heat is removed and the mixture is cooled in a water bath. When the temperature has dropped below 75 ° C, an amine neutralizing agent is added. When the temperature drops below 65 ° C, the. Polymer solution is emptied on trays for air drying. 7. The dried polymer is cut into strips and redissolved in water or water / cosolvent mixture. Polymerization in the molten state involves mixing the same reagents in the absence of a solvent with a heavy duty laboratory mixer (such as a Universal Sigma Blade Mixer, sold by Baker Perkins Guittard SA, Paris, France) at a temperature enough to generate 'leaving groups and remove the reaction condensation products. The removal of volatile by-products by vacuum is necessary in order to shift the reaction to the right and prevent an equilibrium reaction from occurring that prevents the reaction before the desired degree of polymerization is achieved.
The catalysts usable for carrying out the copolymerization reaction include the standard Broonsted-Lowery acid catalysts, typically used for the condensation of aminoplast resins. Such acid catalysts include mineral acids, (for example HC1, H2SO4 / H3PO4, and the like) aryl sulphonic and aryl alkylsulphonic acids, such as benzenesulfonic acid, p-toluenesulfonic acid, 1-naphthalenesulfonic acid, 2-naphthalenesulfonic acid, acid Naphthalene-1, 5-disulfonic acid, naphthalene-2,7-disulfonic acid, 1,3,6-naphthalenetrisulfonic acid, naphtholsulfonic acid, dinonylnaphthalenesulfonic acid, dodecylbenzenesulfonic acid, oxalic acid, maleic acid, hexamic acid, alkyl phosphate ester, phthalic acid, and copolymerized acrylic acid. Of these catalysts, the sulfonic acid catalysts are the most effective and efficient for making the copolymers of the invention and. Dodecylbenzenesulfonic acid is the most preferred sulfonic acid catalyst. The glycolurils are marketed by Cytec Industries as Cymel 1170, 1171, 1175 and Powderlink 1174. The Cymel versions are either mixed methylolated species and typically contain a relatively high dimeric or oligomeric content of about 20 weight percent. The Powderlink 1174 is a purer form that is only the methyl ester of the formula:
with about 3-5 weight percent of a dimer-oligomer of the monomeric form. The purer the monomeric form of the aminoplast resin, the better the formation of the copolymers of the invention. At about 5-7 weight percent Powderlink 1174, x is 0 and such a monomeric form is trifunctional. The dimer-oligomer forms provide larger amounts of methoxy per molecule. For example, the dimer contains 6 functional groups of methoxide. Such tri-and hexa-functionality does not alter this invention. The glycoluryl ether bond is much more resistant to hydrolysis than other aminoplast-ether resin bonds. The higher dimer-oligomer content of the less pure glycolurils is not as favored as the minor dimer-oligomer content of Powderlink 1174. Further reduction of the oligomers can be effected by recrystallization. Powderlink 1174 is called a "resin" and "crosslinking agent" by Cytec, and has been sold under the name Cymel® (ie Cymel 1174). Its empirical structure is C12H22 4O6. Its chemical name is Imidazo [4, 5-DJ imidazol-2, 5 (1H, 3H) -dione, tetrahydro-1, 3, 4, 6-tetrakis (methoxymethyl) -. CAS 17464-88-9. It is also known by the following names: (i) Glycoluril, 1,3,4,6 tetrakis methoxymethyl, (ii) Glycoluril, tetrakis methoxymethyl, (iii) Glycoluril,?,?,?,? tetrakis methoxymethyl, (iv) Glioxal diurien, tetrakis methoxymethyl and (v) Tetramethoxytetramethyl acetylene diurea. The favored name is (i) and such a skeletal structure is called glycoluril. The ratio of the aminoplast resin to the difunctional polyether is not critical. Typically, either the aminoplast resin or the difunctional polyether can be used in molar excess or stoichiometrically equivalent amounts in the manufacture of the copolymer. linear of the invention. In the characterization stoichiometry of the aminoplast resin, the resin is treated as being difunctional, since the linearity, according to the invention, is achieved when the aminoplast resin functions as a difunctional monomer although the resin has the functionality of more high, for example, tri- and tetrafunctionality, as may be the case. Thus, more than one mole of polyether diol to one mole of, for example, a glycoluril such as Powderlink 1174, represents a stoichiometric excess of the polyether to the glycoluril. Using this characterization, 1-2 moles of one reactive to one mole of the other can be used. Either the polyether or the aminoplast resin may be in excess. Nevertheless, it is more common to use a mole amount of a reagent of about 1-1.75 to 1 of the other reagent. Commonly, a molar excess of the aminoplast resin is employed because more hydrophobicity can be incorporated into the copolymer in this manner. This is especially the case when the copolymer is dimeric to oligomeric (for example, having less than about 15 repeating units). When more superior polymer structures are manufactured, a higher reaction ratio of the polyether reagent is used, up to a mol ratio of 1 or 2.1. In general, it is desirable to use a molar excess of aminoplast resin of about 100-1.0 moles to 1 mole of the difunctional polyether. The amount of ethoxylated tristyryl phenol should not exceed about 2.0 moles, not be less than about 0.4 moles per mole of aminoplast resin reacted in the copolymer of the invention. Usually, the amount of ethoxylated tristyryl phenol ranges from about 0.7 mole to about 1.5 mole per mole of reacted aminoplast resin. Waterborne coatings can be defined as coatings containing water as the main volatile component and use water to dilute the coating to the application consistency. These coatings consist mainly of resinous binders, pigments, water and organic solvent. The type of pigmentation and the pigment incorporation method vary widely. Waterborne coatings can be manufactured by dispersing, emulsifying or emulsifying the resinous binder by the use of added surfactants. This technique leads to opaque liquids. Because some hard resins are difficult or impossible to disperse directly in the water, the resin can sometimes be dissolved in a solvent immiscible with water, and the resulting solution dispersed by the use of added surfactants. In this case, the solvent aids in the coalescence of the subsequent film. Surface activity or water dispersibility can also be introduced into the resin molecules by chemical modification of the resin, by introducing functional polar groups such as the carboxyl group. Some very finely dispersed resins appear as clear or slightly cloudy liquids; they are often described as soluble dispersions, solubilized, colloidal, microemulsions, hydrosols, etc. These resins contain incorporated functional groups that confer "solubility" in the water to the resin and, normally, no added external surfactants are used. Water-bearing resin binders can be classified as anionic, cationic or non-ionic. The anionic dispersions are characterized by negative charges on the resin or by negative charges on the surfactant associated with the resin. The cationic dispersions have a positive charge on the resin or on the surfactant associated with the resin. Nonionic dispersions are those that have been dispersed by the addition of nonionic surfactants or that contain an incorporated hydrophilic segment such as polyethylene oxide that is part of the main chain of a relatively hydrophobic resin molecule. The coating compositions can be of thermoplastic or thermoplastic varieties. The resin used in the formation of the coating can be insoluble in water and the conversion of such resin into a water carrying system typically involves converting the resin into an emulsion or dispersion. In the context of this invention, the water-bearing composition contains the aminoplast-ether resin copolymer associative thickener of the invention. Aqu polymer dispersions can be prepared according to well-known emulsion polymerization processes, using one or more emulsifiers of an anionic, cationic or non-ionic type. Mixtures of two or more non-neutralizing emulsifiers can be used without considering the type. The amount of emulsifier can vary from about 0.1 to 10% by weight or can sometimes be even higher, based on the weight of the total monomer charge. In general, the molecular weight of these emulsion polymers is high, for example, a number average molecular weight of about 100,000 to 10,000,000, more commonly above 500,000. The water-insoluble resin can be any of those known in the art, and can be a conventional natural or synthetic polymeric latex, emulsified with one of a non-ionic, cationic or anionic surfactant. The primary resins are based on copolymerized homopolymerized olefinic monomers such as vinyl acetate; vinyl chloride; styrene; butadiene; vinylidene chloride; acrylonitrile; methacrylonitrile; acrylic acid; methacrylic acid; alkyl acrylates; alkyl methacrylates; acrylamide; methacrylamide; hydroxyethyl methacrylate ("HEMA"); glycidyl methacrylate; dihydroxypropyl methacrylate; homopolymers of alpha-olefins of 2 to 40 carbon atoms such as ethylene, isobutylene, octene, nonene and styrene and the like; copolymers of one or more of these hydrocarbons with one or more esters, nitriles or amides of acrylic acid or methacrylic acid or with vinyl esters, such as vinyl acetate and vinyl chloride, or with vinylidene chloride; and diene polymers, such as copolymers of butadiene with one or more of styrene, vinyl toluene, acrylonitrile, methacrylonitrile, and esters of acrylic acid or methacrylic acid and the like. It is also very common to include a small amount, such as 0.1 to 5% or more, of an acidic monomer in the monomer mixture used to make the aforementioned copolymers by emulsion polymerization. Acids used include acrylic, methacrylic, itaconic, crotonic, maleic, fumaric, and the like. Vinyl acetate copolymers are well known and include copolymers such as vinyl acetate / butyl acrylate / 2-ethylhexyl acrylate, vinyl acetate / butyl maleate, vinyl acetate / ethylene, vinyl acetate / vinyl chloride / butyl acrylate and vinyl acetate / vinyl chloride / ethylene. Other systems carrying water involve reactive copolymers that are crosslinked by the presence of complementary functional groups in the system. For example, an acrylic ester / glycidyl methacrylate copolymer can be emulsified and cross-linked by the presence of a melamine-formaldehyde resin similarly emulsified in the system. In another system, a HEMA and other acrylate copolymer, hydroxyl terminated polyesters, polyethers or polyurethanes can be emulsified and crosslinked by the presence of either an aminoplast resin, a blocked polyisocyanate or polyisocyanate. The term "acrylic polymer" means any polymer wherein at least 50% by weight is an acrylic and methacrylic acid or ester, which includes mixtures of such acids and esters individually and together. The term "vinyl acetate polymer" means any polymer that contains at least 50% vinyl acetate. The acrylic of small particle size
(about 0.1-0.15 microns) and other latexes are effectively thickened, and improved flow and level of equalization, by the thickening agents of this invention. The use of this invention to produce architectural coatings for medium to neutral base formulations, based on small-particle size acrylics, where the level of added colorant is in large quantities from about 37.45 to 119.84 grams per liter (5 to 16) ounces per gallon) eliminates the need to incorporate other thickener systems, such as cellulosic and alkali swelling agents or large amounts of surfactants. The amount of the aminoplast resin copolymer-ether described herein, which is employed in the coating composition of the invention, is not critical.
That amount will vary based on the resin system used, the concentration of water, the amount of fillers and the selection of the fillers, the presence or absence of thixotropic agents and the like. In that regard, the amount of the aminoplast-ether resin copolymer in the composition is sufficient to express the composition. However, in general, the amount of the copolymer ranges from about 0.1 weight percent to about 15 weight percent, preferably from about 0.5 weight percent to about 10 weight percent, and far more preferably about 1 weight percent to about 8 weight percent, of the weight of the coating composition, exclusive of fillers, pigments and similar additives. The following is an illustrative formulation for an architectural coating based on acrylic of small particle size. Optiflo H600 is the aminoplast-ether resin copolymer described above. Example DAgua, propylene glycol, Tamol 731, foamaster VL, Kathon LX are added to a high speed dispersing tank equipped with a high speed stirring hood blade. Agitation is started followed by the addition of the dry Ti02 pigment R900. The mixture is ground at high speed (~ 2,000 rpm) for 20 to 30 minutes or until the Ti02 is well dispersed (usually determined using a hegman milling calibrator greater than 6). 2) Once the grinding is complete, the speed or shear is reduced and the ground pulp is transferred to another tank equipped with a mixing blade (usually a slow speed blade blade). The SG-10M and OP62 are added and mixed for approximately 10 minutes. The remaining ingredients can be added (water, Optiflo L100 and Optiflo H600). Usually a defoamer (Foamaster VL) is added to remove any retained air. 3) Quality control checks usually consist of viscosity (Stormer &ICI), pH, weight per gallon (WPG), hiding power and color acceptance. SEMI-BRILLO SG-10M MOLLING KG (LBS) LITERS (GALLONS)
WATER 5.05 (11.13) 5.07 (1.34) PROPYLENE GLYCOL 29.51 (65.00) 28.43 (7.51) TAMOL 731 5.85 (12.88) 5.30 (1.40) FOAMASTER VL 0.45 (1.00) 0.49 (0.13)
KATHON LX 0.82 (1.80) 0.83 (0.22) TI-PURE R-900 114.86 (253.00) 28.77 (7.60) MILLING OF Ti02 @ 1300 rpm FOR 30 MINUTES MAXIMUM TEMPERATURE RECORD OF MILLING: DECREASE CUBE OF 18.92 LITERS (5 GALLONS) - 3F KNIFE
MOLLING KG (LBS) LITERS (GALLONS)
WATER 39.95 (88) 39.97 (10.56)
RHOPLEX SG-|10 211.34 (465.5) 199.77 (52.78)
ROPAQUE OP-62 12.70 (27.96) 12.30 (3.25)
TEXANOL 11.04 (24.32) 11.62 (3.07)
SUBTOTAL 431.58 (950.62) 332.59 (87.87) HIGH-SPEED MIXING FOR 30 MINUTES WPG RECORD: 10.82 pH RECORD: PREMEZCLA: KG (LIBRAS) LITERS (GALLONS)
WATER 32.78 (72.20) 32.82 (8.67)
L100 12.87 (28.35) 12.41 (3.28)
H600 0.23 (0.50) 0.23 (0.06)
FOAMASTER VL 0.45 (1.00) 0.49 (0.13)
TOTAL 497.92 (1, 052, 67) 378.50 (100.00)% PVC: 27.26% VS: 34:10
Examples of Paint Evaluation in a Neutral Base Latex Paint Formulation:
The 17.5% solution of Example 1 was evaluated in a semi-gloss neutral base formulation containing Rhopex SG-10M acrylic latex. The paints were colored with 340.2 grams (12 ounces) of Dye F (red iron oxide) from CreaNova (888). Stormer Stormer load after initial nuanced U (pounds (KU) (Kü) dry / lOOgal) Example 1 0.525 108 98 10
Acrysol 0.525 102 82 20
RM825
Evaluation in an intense Base Latex Paint Formulation: The 17.5% solution of Example 1 was evaluated in a semi-gloss neutral base formulation containing Rhopex SG-20M acrylic latex. The paints were tinted with 226.8 grams (8 ounces) of Dye F (red iron oxide) from CreaNova (888). Stormer Stormer load after initial nuanced KU (pounds (KU) (KU) dry / lOOgal) Example 1 0.44 111 91
Acrysol 0.44 110 64
R 825