present invention is a polyaspartic acid heteropolymer which may be represented by Formula (1): In Formula (1), (i) R, is selected from the group consisting of branched and unbranched alkyl, alkylaryl, and alkenyl groups having from 4 to 30 carbon atoms, and alkyl terminated polymers of ethylene oxide, propylene oxide, and butylene oxide having a molecular weight in the range from about 200 to about 3000; (ii) R2 is selected from the group consisting of hydrogen and branched and unbranched alkyl, alkylaryl, and alkenyl groups having from 1 to 4 carbon atoms; (iii) M+ is a cation; (iv) residues n1, n2, n3, and n4 are present in random order, and the ratio of (ni + n3): (n2 + n4) is from about 1: 99 to about 1: 1; and (v) the molecular weight of the polyaspartic acid heteropolymer is from about 1,000 to about 100,000. The stabilized aqueous emulsion polymerization compositions prepared by the polyaspartic acid heteropolymers of the present invention comprise (a) from about 10% to about 80% by weight of a polymer derived from an emulsion polymerizable ethylenically unsaturated monomer; (b) from about 0.1% to about 10% by weight of a polyaspartic acid heteropolymer; (c) from about 0.01% to about 1% by weight of a free radical polymerization initiating agent;

and (d) the remainder water. The present invention also pertains to a method for making a polymer which comprises emulsifying and stabilizing an aqueous free radical emulsion polymerization reaction of ethylenically unsaturated monomers employing the polyaspartic acid heteropolymers of the present invention.

Background of The Invention The generation of water borne resins by free radical emulsion polymerization is generally carried out in the presence of a surface active agent (surfactant) which emulsifies the hydrophobic discontinuous phase in the aqueous continuous phase and imparts stability to the final polymer phase. The emulsion polymerization composition may be stabilized electrostatically by low molecular weight anionic, cationic, or non-ionic surface active agents, such as sodium dodecyl benzene sulfonate, or by Tn- situ"surface active agents, generated from ionic free radical initiators. The emulsion polymerization composition may also be stabilized sterically by high molecular weight polymeric protective colloids such as polyvinyl alcool.

Surface active agents are integral ingredients in emulsion polymerization reactions which also include, but are not limited to, water, monomer, and a water-soluble free radical initiator. Monomers generally exhibit limited water solubility and surface active agents are required to emulsify water-insoluble monomers to facilitate the reaction between the monomer molecules and the

water-soluble free radicals. The newly formed polymeric discontinuous phase must then be stabilized to coagulation by adsorption and/or grafting of a stabilizing species, which function is also generally carried out by the surface active agent.

Various surface active agents are known in emulsion polymerization.

Matsumoto and Ochi were among the first to describe the generation of surface active agents in situ by using water-soluble anionic free radical initiators (T. Matsumoto and A. Ochi, Kobunushi Kagaku, 22,481 (1965)).

The use of relatively low molecular weight anionic and cationic surface active agents, known to impart stability to polymeric resin dispersions via an electrostatic mechanism, in emulsion polymerization is disclosed in Japanese patent no. 8217809A (Kuraray Co Ltd.), Japanese patent no.

1146786A (Sumitomo Naugatuck KK), and Japanese patent no. 63241084A (Japan Synthetic Rubber Co. Ltd.). Waterborne polymeric resin dispersions generated via the use of these low molecular weight surfactants are generally characterized by relatively small average particles sizes and relatively low viscosity. The use of non-ionic surface active agents, known to impart stability through a steric mechanism, in emulsion polymerization is disclosed in United States patent no. 4,587,290 (S. P. Davies et a/.) and in United Kingdom patent no. 2,124,636A (S. P. Davies et a/.). Relatively high molecular weight protective colloidal stabilizers also provide good emulsification and stabilization in emulsion polymerization. United States

patent no. 5,633,334 (Walker et a/.) discloses the use of a combination of two different types of poly (vinyl alcohol) (PVOH) in the emulsion polymerization of vinyl ester monomers. Specifically, Walker et a/. discloses a polymerization carried out in the presence of 2 to 8% of a protective colloid consisting of a blend of 1 to 3 % of 80% hydrolyzed polyvinyl alcool, 0 to 2 % of 88% hydrolyzed polyvinyl alcool, and 1 to 31% of 96% hydrolyzed polyvinyl alcool. United States patent no. 5,652,289 (Eisenhart et al.'289) discloses the use of a combination of poly (vinyl alcohol) and poly (ethylene oxide) to prepare acrylic emulsion polymers. Specifically, Eisenhart et a/.'289 states that the monomers comprise from about 20 parts by weight to about 70 parts by weight of a vinyl ester monomer; from about 30 parts by weight to about 80 parts by weight of a (Cl-Cl2) alkyl (meth) acrylate monomer; and from about 0.1 parts by weight to about 10 parts by weight of a monoethylenically unsaturated polar monomer. The polymerization is carried out in the presence of about 1.5 parts by weight to about 2.8 parts by weight of a colloidal stabilizer; from about 1.2 parts by weight to about 1.6 parts by weight of a first poly (alkoxiated) alkyi phenol (having about 10 alkoxyl units per molecule); and from about 0.3 parts by weight to about 1.4 parts by weight of a second poly (alkoxylated) alkyl phenol (having about 16 alkoxy units per molecule). United States patent no. 5,652,293 (Eisenhart et al.'293) describes a method for making a polymer from two mixtures.

Specifically, Eisenhart et a/.'293 states that the first mixture is prepared by

adding a first portion of colloidal stabilizer to an aqueous medium. The second mixture is prepared by adding a monomer mixture comprising a monomer charge and a second portion of colloidal stabilizer. The monomer charge consists of from about 40 parts by weight to about 70 parts by weight of a vinyl ester monomer, from about 30 parts by weight to about 60 parts by weight of a (Cl-Cl2) alkyl (meth) acrylate monomer. The combined first and second portions of colloidal stabilizer comprise from about 0.05 parts by weight to about 10 parts by weight colloidal stabilizer. The first portion of colloidal stabilizer comprises from about 1 part by weight to about 60 parts by weight colloidal stabilizer. The first and second portions of colloidal stabilizer are independently selected from the group consisting of poly (vinyl alcool), partially hydrolyzed poly (vinyl alcohol), and fully hydrolyzed poly (vinyl alcohol). United States patent no. 4,911,960 (Mudge et al., 1990) discloses the use of hydroxyethyl cellulose (HEC) and standard emulsion polymerization procedures to produce a polymeric resin which provides superior wet laminating adhesive properties. European patent no.

3,343,534 (Union Carbide Corp.) discloses the use of hydrophobically modified hydroxyethyl cellulose to produce stable aqueous polymer mulsions. Japanese patent no. 57/078404 (Aika Kogyo Co.) discloses the use of polyacrylamide as a protective colloid in the emulsion polymerziation of vinyl acetate. Waterborne polymeric resin dispersions generated via the use of high molecular weight protective colloidal stabilizers are generally

characterized by relatively large average particle sizes and a viscosity which is dependent on the molecular weight and the amount of the protective colloidal stabilizer used.

Poly-amino acid derivatives are known to be useful for preparing oil-in- water and water-in-oil mulsions. United States patent no. 3,846,380 (Fujimoto et a/.) describes both a process for producing poly-amino acid derivatives, which are claimed to be useful surface active agents, and compositions in which the poly-amino acid derivatives are the active ingredient. In particular, Fujimoto et a/. suggests that the poly-amino acids with pendant aliphatic groups are useful as foaming agents, solubilizing agents, dispersing agents, emulsifying agents, rust proofing agents, fiber treating agents, level dyeing agents, and retarding agents. Specific examples cited by Fujimoto et a/. include the use of a poly-amino acid with pendant oleyl groups in a liquid shampoo composition, the use of a poly- amino acid with pendant N-methyl N-lauryl groups in a vanishing cream formulation and the use of a poly-amino acid with pendant palmityl and lauryl groups in a formulation of a tableware detergent. Fujimoto et a/. do not disclose these particular species as useful in free radical emulsion polymerization.

United Kingdom patent GB 2,174,097B (Ceskoslovenska Academie, counterpart of German patent no. DE 3610912) describes the use of poly-a-

amino acid derivatives as emulsion stabilizers in a water-in-oil emulsion.

The poly-a-amino acid derivative is dissolved in dichloroethane followed by dispersion of a water-soluble polymer in the solvent. A cross-linking agent, such as epi-chlorohydrin, is then introduced into the dispersion and allowed to react with the water-soluble polymer. The poly-a-amino acid derivative is said to prevent the aggregation of dispersed particles at the end of the cross-linking reaction. Although Ceskoslovenska Academie claims the stabilizing action of a poly-a-amino acid derivative in a solvent borne cross- linking reaction, it does not describe the use of polyaspartic acid derivatives to generate waterborne resins by free radical emulsion polymerization.

United States patent no. 5,212,235 (Nestaas et a/.) describes the use of hydrophobically modified proteins as oil-in-water emulsifiers and emulsion stabilizers. Nestaas et a/. discloses discloses a C, 2 to C30 alkyl-or alkenyl-succinylated emulsan in which the succinyl group is covalently attached to the protein or polypeptide of the emulsion via an amide linkage.

Nestaas et a/. does not suggest using the hydrophobically modified proteins in free radical emulsion polymerizations.

United States patent no. 5,225,474 (Jon et a/.) describes the use of stabilizing agents with no pendant hydrophobic group. Jon et a/. discloses an emulsion polymerization composition in the form of an aqueous

dispersion which consists of (a) about 1-45% of an emulsion polymerizable monomer which is selected from styrene, butadiene, vinyl acetate, methyl acrylate, ethyl acrylate, butyl acrylate, vinyl chloride, acrylonitrile, acrylamide, and ethylene, and mixtures thereof, and which may include one or more comonomers selected from acrylic acid, itaconic acid, fumaric acid, 2- hydroxyethyl acrylate, and methacrylic acid, (b) about 0.1-5% by weight of an emulsifier and stabilizer component which is a copolymer of (i) a vinyl lactam and (ii) a polymerizable carboxylic acid; (c) about 0.1-2% by weight of a polymerization initiator, and (d) water.

United States patent no. 4,959,428 (Abe et a/.) discloses an emulsion polymerization process employing a water-soluble copolymer as a dispersant. The water-soluble copolymer is obtained by adding an alkali to a carbonyl group containing copolymer which comprises (a) 0.5 to 27% of a carbonyl group containing monomer unit having at least one aldehyde or keto group and a polymerizable double bond per molecule; (b) 2 to 28.5% of a monoolefinically saturated carboxylic acid unit having 3 to 5 carbon atoms; (c) 71 to 97% of a monomer unit which may be an alkyl acrylate, an alkyl moiety of which has 1 to 8 carbon atoms; an alkyl methacrylate. an alkyl moiety of which has 1 to 8 carbon atoms; a vinyl aromatic compound; a vinyl halide; acrylonitrile; methacrylonitrile; or a saturated carboxylic acid vinyl ester; and (d) 0 to 10% of a monomer unit other than those defined in (a) to (c), with the total amount of the monomer units as defined in (a) to (d) being 100% to solubilize the monomers.

Japanese patent specification 7-238503 (Mon et a/.) discloses polyaspartic acid derivatives consisting of the following structural formulas: (A)-NH-C2H3 (CO-) CO-NR,- (CH2) p-SH; where Ri is a hydrogen atom or a C, 4 alkyl group and p is an integer from 1-4; (B)-NH-C2H3 (CO-) CO-NR2 (CH2) q-Y; where R2 is a hydrogen atom or a C, 4 alkyl group, q is an integer from 2-6, and Y is-N (R3) (R4) or-N+ (R3) (R4) (R5) + Z~; where R3 and R4 are C14 alkyl groups (R is not defined) and Z is an anion derived from an organic acid or inorganic acid; and (C)-NH-C2H3 (CO-) COOM ; where M is a hydrogen atom, alkali metal, organic amine, or basic amino acid.

While surface active or emulsifying properties may be common to emulsion polymerization and a variety of detergent, cosmetic, and industrial applications, it is not expected that a material found useful for one application will be suitable for emulsion polymerization. None of the above methods discloses the use of poly-amino acid derivatives as emulsifiers or stabilizers in aqueous free radical emulsion polymerization reactions. Many traditional emulsifiers and stabilizers have been disclosed for performing aqueous free radical emulsion polymerization but all have some limitations in terms of the processes and properties of the final product. The present invention provides an improved method for emulsifying and stabilizing an aqueous free radical emulsion polymerization reaction of ethylenically unsaturated monomers without many of the limitations characteristic of previously known methods.

BRIEF DESCRIPTION OF THE FIGURES Figure 1 illustrates the influence of the level and type of polyaspartic acid heteropolymer (15, OOOMW) emulsifying and stabilizing agent on the final average particle size of the acrylic latex stabilized aqueous emulsion polymerization compositions prepared according to the method of the present invention.

Figure 2 illustrates the influence of the level and type of polyaspartic acid heteropolymer (15, OOOMW) emulsifying and stabilizing agent on the final viscosity of the acrylic latex stabilized aqueous emulsion polymerization compositions prepared according to the method of the present invention.

SUMMARY OF THE INVENTION

This invention relates to the use of derivatives of polyaspartic acid as emulsifiers and stabilizers in aqueous free radical emulsion polymerization reactions. The polyaspartic acid derivatives are useful for stabilizing and emulsifying a wide range of ethylenically unsaturated monomers over a wide range of emulsion polymerization processes and provide stabilized aqueous emulsion latex polymerization compositions having unique properties. The novel stabilized aqueous emulsion polymerization compositions comprise: (a) from about 10% to about 80% by weight of a polymer derived from an emulsion polymerizable ethylenically unsaturated monomer; (b) from about 0.1% to about 10% by weight of a polyaspartic acid heteropolymer; (c) from about 0.01 % to about 1 % by weight of a free radical polymerization initiating agent; and (d) the remainder being water.

The polyaspartic acid heteropolymer in (b) may be represented by Formula (1):

In Formula (1), (i) R, is selected from the group consisting of branched and unbranched alkyl, alkylaryl, and alkenyl groups having from 4 to 30 carbon atoms, and alkyl terminated polymers of ethylene oxide, propylene oxide, and butylene oxide having a molecular weight in the range from about 200 to about 3000; (ii) R2 is selected from the group consisting of hydrogen and branched and unbranched alkyl, alkylaryl, and alkenyl groups having from 1 to 4 carbon atoms; (iii) M+ is a cation; (iv) residues ni, n2, n3, and n4 are present in random order, and the ratio of (n, + n3): (n2 + n4) is from about 1: 99 to about 1: 1; and (v) the molecular weight of the polyaspartic acid heteropolymer is from about 1,000 to about 100,000.

This invention also pertains to a method for making a polymer which comprises comprises polymerizing from about 10% to about 80%, by weight,

of an emulsion polymerizable ethylenically unsaturated monomer in an aqueous medium by free radical initiated polymerization in the presence of: (a) from about 0.1% to about 10% by weight of a polyaspartic acid heteropolymer; and (b) from about 0.01 % to about 1 % by weight of a free radical polymerization initiating agent; to form a stabilized aqueous emulsion polymerization composition, wherein the polyaspartic acid heteropolymer may be represented by Formula (1): wherein Formula (1) is defined above.

This invention also pertains to a stabilized aqueous emulsion polymerization composition prepared by the novel method.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to the use of polyaspartic acid derivatives as emulsifiers and stabilizers in the aqueous free radical emulsion polymerization of ethylenically unsaturated monomers. The polyaspartic acid derivatives are useful for stabilizing and emulsifying a wide range of ethylenically unsaturated monomers over a wide range of emulsion polymerization processes and provide latex polymers having unique properties. The polyaspartic acid derivatives may be utilized by themselves, or may be used in conjunction with anionic, cationic, or non-ionic surfactants, or protective colloidal stabilizers, to stabilize the emulsion polymerization of ethylenically unsaturated monomers. The polymerized resins are prepared by dispersing the ethylenically unsaturated monomer into an aqueous continuous phase containing a polyaspartic acid derivative, followed by slowly adding a free radical initiator and optionally buffer, salts, or functionalized monomers to generate the waterborne polymer. The polyaspartic acid derivatives are highly efficient stabilizers and provide clean, stable resins with viscosities ranging from about 30cps to about 30,000cps at a relatively high solids content and characterized by unexpectedly small average particle sizes. By employing the polyaspartic acid derivatives of the present invention, polymeric resin dispersions can be prepared with the desired rheological properties using a variety of known

emulsion polymerization processes while maintaining other advantageous latex properties including, but not limited to, latent reactive particle surface functionality, low toxicity, biodegradability, and buffer capacity. The general process of emulsion polymerization, which may be enhanced by the use of the polyaspartic acid derivatives of the present invention, has broad utility in terms of the ethylenically unsaturated monomers which may be employed, the polymeric properties which may be achieved, and the range of applications which can be served. Such applications include, but are not limited to adhesives, coatings, binders, fixatives, re-dispersible powders, and sizes for use in glass, paper, and textile applications as well as personal care products. Small amounts of the polyaspartic acid derivative, e. g., 1.4 part per hundred of monomer (pphm), have been found to provide vinyl acetate/di-butyl maleate latex emulsion polymers having a solids content on the order of 42%. Stable vinyl acetate and acrylic based latexes having a solids content on the order of 50%, an average particle size on the order of 0.11lu, and viscosities ranging from 30cps to about 30,000cps have also been prepared. Use of increasing levels of the polyaspartic acid derivatives results in increasing levels in resin viscosity so that the polyaspartic acid derivatives may be used both as a stabilizer and as a thickener.

The polyaspartic acid derivatives are obtained by reacting poly (succinimide) with the desired amount of primary or secondary amine followed by the subsequent hydrolysis of the remaining succinimide groups.

A surprisingly broad range of latex rheology can be directly controlled by the type and amount of amine used to derivatize the polyaspartic acid polymer.

The polyaspartic acid derivatives are characterized by molecular weights in the range about 1,000 to about 100,000 (compared against polyacrylate standards). The polyaspartic acid derivatives are unique polyelectrolytes which impart stabiiization through a complex combination of both electrostatic and steric mechanisms. The polyaspartic acid derivatives provide small final particle sizes, viscosity control, latent reactive functionality potential, large solids content to amount of stabilizer ratio, low toxicity, biodegradability, and buffer capacity.

As set out above, the present invention is directed to a stabilized aqueous emulsion polymerization composition comprising (a) from about 10% to about 80% by weight of a polymer derived from an emulsion polymerizable ethylenically unsaturated monomer; (b) from about 0.1% to about 10% by weight of a polyaspartic acid heteropolymer; (c) from about 0.01 % to about 1 % by weight of a free radical polymerization initiating agent; and (d) the remainder being water.

The stabilized aqueous emulsion polymerization compositions of the present invention are prepared by polymerizing ethylenically unsaturated monomers in aqueous medium, initiated by a free radical initiating agent, in the presence of the novel polyaspartic acid heteropolymer emulsifying and

stabilizing agents according to known aqueous emulsion polymerization techniques. The ethylenically unsaturated monomer, emulsifying and stabilizing agent, and free radical polymerization initiating agent may each be separately introduced into the aqueous medium to form a reaction mixture; or the initiator may be added to the aqueous medium at a controlled rate as the polymerization progresses; or the monomers to be polymerized may be added to the aqueous medium at a controlled rate as the polymerization reaction progresses, or monomer and initiator may be added to the aqueous medium and polymerized to form seed particles to which further amounts of monomer, initiator, and optionally a stabilizing agent may be added at a controlled rate as the polymerization progresses; or to an existing dispersion of stable latex particles, monomer, initiator, and optionally a stabilizing agent may be added at a controlled rate as the polymerization progresses. A buffering agent, such as sodium acetate or ammonium hydroxide, may optionally be included in the emulsion polymerization composition reaction mixture.

Suitable polymerizable ethylenically unsaturated monomers in (a) include vinyl ester monomers such as vinyl acetate, vinyl propionate, vinyl neononanoate, vinyl neodecancate, vinyl 2-ethylhexanoate, vinyl pivalate, vinyl versatate, and mixtures thereof. Other suitable polymerizable ethylenically unsaturated monomers include alkyl (meth) acrylate monomers including methyl acryiate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, lauryl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate,

isodecyl methacrylate, lauryl methacrylate, and mixtures thereof. Other suitable polymerizable ethylenically unsaturated monomers include monoethylenically unsaturated carboxylic acid monomers including acrylic acid, methacrylic acid, itaconic acid, crotonoic acid, fumaric acid, maleic annhydride, and mixtures thereof. Other suitable polymerizable ethylenically unsaturated monomers include styrene, butadiene, acrylonitrile, acrylamide, n-methylolacrylamide, di-butyl maleate, ethylene, vinyl chloride, and mixtures thereof.

Preferred ethylenically unsaturated monomers include styrene, butadiene, vinyl acetate, methyl acrylate, methyl methacrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, vinyl chloride, acrylonitrile, acrylamide, t-octyl acrylamide, n-vinylformamide, n-vinyl acetamide, n-vinyl pyrrolidone, di-butyl maleate, ethylene, and mixtures thereof. More preferred ethylenically unsaturated monomers include methyl methacrylate, butyl acrylate, vinyl acetate, di-butyl maleate, ethylene, and mixtures thereof.

The amount of polymer derived from an emulsion polymerizable ethylenically unsaturated monomer present in the aqueous stabilized emulsion polymerization composition may vary depending upon the particular composition of ethylenically unsaturated monomers employed and the polymerization reaction conditions desired. In general, the amount of polymer derived from an emulsion polymerizable ethylenically unsaturated

monomer employed will be an amount effective to obtain the desired polymerization composition. In a preferred embodiment, the polymer derived from an emulsion polymerizable ethylenically unsaturated monomer in the aqueous stabilized emulsion polymerization composition is present in an amount from about 10% to about 80%, preferably from about 25% to about 75%, and more preferably from about 40% to about 75%, by weight.

The emulsifying and stabilizing agent in (b) is a polyaspartic acid heteropolymerwhich may be represented by Formula (1): In Formula (1), R, is selected from the group consisting of branched and unbranched alkyl, alkylaryl, and alkenyl groups having from 4 to 30 carbon atoms, and alkyl terminated polymers of ethylene oxide, propylene oxide, and butylene oxide having a molecular weight in the range from about 200 to about 3000. Preferred alkyl terminated polymers of ethylene oxide, propylene oxide, and butylene oxide having a molecular weight in the range from about 200 to about 3000 are the ethoxylated amines known as vleffamines@, Huntsman Corporation. Preferably, R, is a branched or

unbranched alkyl, alkylaryl, or alkenyl group having from 8 to 26 carbon atoms, and more preferably R, is a branched or unbranched alkyl, alkylaryl, or alkenyl group having from 8 to 20 carbon atoms. Most preferably, R, is- CBH17,-Cl2H25, or-Cl8H37- R2 is selected from the group consisting of hydrogen and branched and unbranched alkyl and alkenyl groups having from 1 to 4 carbon atoms; Residues ni, n2, ns, and n4 in Formula (1) are present in random order.

The ratio of (n, + n3): (n2 + n4), i. e., the ratio of the hydrophobic moieties to the carboxylic acid moieties, respectively, is from about 1: 99 to about 1: 1, preferably from about 1: 50 to about 1: 4, and more preferably from about 1: 20 to about 1: 8.

The selection of R, and R2 will determine the hydrophilic and hydrophobic character of the polyaspartic acid heteropolymer. Effective emulsion stabilizers are molecules which possess both hydrophilic and hydrophobic character. In general, the hydrophobic moieties tend to associate in solution, whereas the hydrophilic moieties interact strongly with water which facilitates the emulsification of water-insoluble monomers. Hydrophobic moieties tend to adsorb onto the hydrophobic polymer particles thereby anchoring the hydrophilic groups which impart stabilization to the particle.

The amount and type of hydrophobic moieties influences the emulsification

process, the anchoring ability of the stabilizing species, and the final latex viscosity. In general, the preferred amounts and types of hydrophobic moieties are those which provide effective anchoring as well as the desired final latex viscosity. The preferred amounts of hydrophobic moieties incorporated into the backbone of the polyaspartic acid heteropolymer range from about 5% to about 20%, on a mole basis. The preferred types of hydrophobic moieties incorporated into the backbone of the polyaspartic acid heteropolymer include branched and unbranched alkyl, alkylaryl, and alkenyl groups having from 8 to 26 carbon atoms and block copolymers of ethylene oxide and propylene oxide of various molecular weights.

M+ in Formula (1) is a cation to neutralize the carboxlate anion, and may be monovalent or divalent. Nonlimiting examples of suitable cations may be selected from the group consisting of H+, alkali metals, alkaline earth metals, Zn2+, Cu2+, organic amines, and basic amino acids. Suitable alkali metals include lithium, sodium, and potassium. Suitable alkaline earth metals include magnesium and calcium. Preferably, M+ is H+ or Na+.

The molecular weight of the polyaspartic acid heteropolymer in Formula (1) is from about 1,000 to about 100,000., preferably from about 5,000 to about 60,000, and more preferably from about 5,000 to about 30,000.

The amount of polyaspartic acid heteropolymer present in the aqueous stabilized emulsion polymerization composition of ethylenically unsaturated monomers may vary depending upon the particular polyaspartic acid heteropolymer employed, the particular composition of ethylenically unsaturated monomers employed, the polymerization reaction conditions desired as well as the resulting resin control, particle size, and viscosity desired. In general, the amount of polyaspartic acid heteropolymer employed will be an amount effective to emulsify and stabilize the polymerization composition of ethylenically unsaturated monomers. In a preferred embodiment, the polyaspartic acid heteropolymer in the aqueous stabilized emulsion polymerization composition is present in an amount from about 0.1% to about 10%, preferably from about 0.2% to about 5%, and more preferably from about 0.5% to about 5%, by weight.

The polyaspartic acid heteropolymers of the present invention can be prepared by various methods. In general, the desired polyaspartic acid heteropolymers represented by Formula (1) can be prepared by reacting poly (succinimide) with a desired amount of primary or secondary amine and then hydrolyzing the remaining succinimide groups.

The free radical polymerization initiating agent in (c) initiates the free radical emulsion polymerization reaction. Suitable free radical polymerization initiating agents include those well known in the art including,

but not limited to, peroxides, hydroperoxides, persulfates, and azo initiators such as hydrogen peroxide, benzoyl peroxide, tert-butyl hydroperoxide, cumene peroxide, tert-butyl perbenzoate, tert-butyl diperphthalate, methyl ethyl ketone peroxide, ammonium persulfate, sodium persulfate, potassium persulfate, azodiisobutyronitrile, and mixtures thereof, as well as cerium, manganese, and vanadium catalyzed systems and also other systems such as those catalyzed by irradiation. Thermal conditions or redox conditions using a reductant, such as sodium sulphoxylate formaldehyde, isoascorbic acid, or sodium bisulfite, may be used to promote decomposition of the free radical initiating agent. The initiating agent may also be an irradiation source suitable for initiation of free radical polymerization.

The amount of free radical polymerization initiating agent present in the aqueous stabilized emulsion polymerization composition may vary depending upon the particular composition of ethylenically unsaturated monomers employed and the polymerization reaction conditions desired. In general, the amount of free radical polymerization initiating agent will be an amount effective to obtain the desired polymerization composition. In a preferred embodiment, the free radical polymerization initiating agent in the aqueous stabilized emulsion polymerization composition is present in an amount from about 0.01% to about 1%, preferably from about 0.02% to about 0.5%, and more preferably from about 0.05% to about 0.3%, by weight.

The present invention is also directed to a method for making a polymer which comprises polymerizing from about 10% to about 80%, by weight, of an emulsion polymerizable ethylenically unsaturated monomer in an aqueous medium by free radical initiated polymerization in the presence of: (a) from about 0.1% to about 10% by weight of a polyaspartic acid heteropolymer; and (b) from about 0.01 % to about 1 % by weight of a free radical polymerization initiating agent; to form a stabilized aqueous emulsion polymerization composition, wherein the polyaspartic acid heteropolymer may be represented by Formula (1): wherein (i) R, is selected from the group consisting of branched and unbranched alkyl, alkylaryl, and alkenyl groups having from 4 to 30 carbon atoms, and alkyl terminated polymers of ethylene oxide, propylene oxide, and butylene oxide having a molecular weight in the range from about 200 to about 3000;

(ii) R2 is selected from the group consisting of hydrogen and branched and unbranched alkyl and alkenyl groups having from 1 to 4 carbon atoms; (iii) M+ is a cation; (iv) residues ni, n2, n3, and n4 are present in random order, and the ratio of (n, + n3): (n2 + n4) is from about 1: 99 to about 1: 1; and (v) the molecular weight of the polyaspartic acid heteropolymer is from about 1,000 to about 100,000.

As set out above, the stabilized aqueous emulsion polymerization compositions are prepared by polymerizing ethylenically unsaturated monomers in aqueous medium, initiated by a free radical initiating agent, in the presence of the novel polyaspartic acid heteropolymer emulsifying and stabilizing agents of the present invention according to known aqueous emulsion polymerization techniques.

The present invention is also directed to a stabilized aqueous emulsion polymerization composition prepared by a method which comprises polymerizing from about 10% to about 80%, by weight, of an emulsion polymerizable ethylenically unsaturated monomer in an aqueous medium by free radical initiated polymerization in the presence of: (a) from about 0.1% to about 10% by weight of a polyaspartic acid heteropolymer; and

(b) from about 0.01 % to about 1 % by weight of a free radical polymerization initiating agent; to form a stabilized aqueous emulsion polymerization composition, wherein the polyaspartic acid heteropolymer may be represented by Formula (1):

wherein (i) R, is selected from the group consisting of branched and unbranched alkyl, alkylaryl, and alkenyl groups having from 4 to 30 carbon atoms, and alkyl terminated polymers of ethylene oxide, propylene oxide, and butylene oxide having a molecular weight in the range from about 200 to about 3000; (ii) R2 is selected from the group consisting of hydrogen and branched and unbranched alkyl and alkenyl groups having from 1 to 4 carbon atoms; (iii) M+ is a cation; (iv) residues nr, n2, n3, and n4 are present in random order, and the ratio of (n, + n3): (n2 + n4) is from about 1: 99 to about 1: 1; and (v) the molecular weight of the polyaspartic acid heteropolymer is from about 1,000 to about 100,000.

Throughout this application, various publications have been referenced.

The disclosures in these publications are incorporated herein by reference in order to more fully describe the state of the art.

The present invention is further illustrated by the following examples which are presented for purposes of demonstrating, but not limiting, the preparation of the compounds and compositions of this invention.

Example 1 Preparation of a Polyaspartic Acid Heteropolymer of the Present Invention Modification of polysuccinimide with 5 mole% dodecylamine This representative example illustrates the preparation of a polysuccinimide derivative in which 5 mole% of the succinimide residues have been condensed with dodecylamine.

A 3 I, four-neck round bottom flask was equipped with a nitrogen inlet- topped reflux condenser, thermometer, stopper, and mechanical stirrer. To this vessel was charged 2250 g of sulfolane and 250 g (2.58 mole succinimide units) of polysuccinimide powder, 30,000 molecular weight. The reaction vessel was placed under a positive pressure of nitrogen and maintained under nitrogen until the reaction was finished. The resulting suspension was brought to 100°C with stirring at which temperature the polysuccinimide slowly dissolved. After the polysuccinimide had completely dissolved, the reaction mixture was cooled to about 60°C. At this point 23.91 g (0.129 mole) dodecylamine was added to the reaction mixture in one portion. The resulting mixture was heated to 140°C with stirring. A clear solution was obtained, and the progress of the reaction was followed by titrating aliquots of the reaction mixture for amine. After 6.5 hr, at least

85% of the starting amine had been consumed. After an addition 24 hours at 140°C during which there was no further decrease in the level of residual amine, the reaction was cooled to room temperature. The cooled, caramel- colored solution was slowly poured into 3 1 of water with vigorous stirring.

The light tan solid that precipitated upon addition of the reaction mixture to water was collecte by vacuum filtration. It was dried in a forced air oven to a constant weight at 80 °C. The yield of product was 300 g. The level of modification with dodecylamine was found to be 5 mole% by proton NMR.

Residual sulfolane in the product was found to be 0.95% by gas chromatography.

Preparation of poly (aspartic acid, sodium salt) modified with 5 mole% dodecylamine.

This representive example illustrates the hydrolysis of polysuccinimide modified with 5 mole% dodecylamine to the corresponding poly (aspartic acid, sodium salt) derivative.

A 31 flask was equipped with a thermometer, reflux condenser, and mechanical stirrer. To the flask was charged, 1005 g of de-ionized water and 292 g of polysuccinimide modified with 5 mole% dodecylamine. The resulting suspension was warmed to 90°C, and a slow addition of 4.2 N NaOH was commenced. The rate of addition was controlled by a Brinkmann

718 STAT Titrino such that the pH of the reaction mixture was maintained at After the addition of 484 ml of 4.2 N NaOH, a clear solution was obtained. The reaction mixture was cooled, and filtered to remove any remaining insoluble particles. The filtrate thus obtained was then extracted with ethyl acetate using a continuous liquid/liquid extractor until the level of residual sulfolane (from the polysuccinimide modification reaction) in the filtrate was less than 50 ppm. Ethyl acetate was distille from the extracted product solution under reduced pressure using a rotary evaporator. The extracted, ethyl acetate-free product solution was then freeze-dried. The yield of tan solid was 314.3 g. The proton NMR of the isolated product was measured and found to be consistent with expectations. The level of residual sulfolane was found to be <60 ppm by gas chromatography.

Emulsion Example 1 An emulsion polymerization process for methyl methacrylate and butyl acrylate in which the sole stabilizer is a 5,000 MW, 10% C12 polyaspartic acid heteropolymer.

This example illustrates the preparation of stabilized aqueous emulsion polymerization compositions prepared according to the method of the present invention employing polyaspartic acid heteropolymers as emulsifying and stabilizing agents. Polymerization was carried out using a semi- batchwise addition of 15 pphm of Methyl Methacrylate/Butyl Acrylate (MMA/BA) and a slow add feed of the remaining monomer, initiator, and buffer.

Ingredient Part per Hundred Monomer Water PolyasparticAcid, 5k, 10%, R=C12* Methyl Methacrylate 43 Butyl Acrylate 57 Ammonium Persulphate 0.4 Ammonium Hydroxide (10% solution) 0.25 Theoretical Solids Content= 36.9% * C12 refers to-C2H25.

This example generated a stabilized aqueous emulsion polymerization composition characterized by a 34.7% solids content;-Brookfield viscosity of 18 cps and average final particle size of 0.0931lm.

Emulsion Example 2 An emulsion polymerization process for methyl methacrylate and butyl acrylate in which the sole stabilizer is a 15,000 MW, 10% C18 polyaspartic acid heteropolymer.

This example illustrates the preparation of stabilized aqueous emulsion polymerization compositions prepared according to the method of the present invention employing polyaspartic acid heteropolymers as emulsifying and stabilizing agents. Polymerization was carried out using a semi- batchwise addition of 15 pphm of Methyl Methacrylate/Butyl Acrylate (MMA/BA) and a slow add feed of the remaining monomer, initiator, and buffer. Polyaspartic Acid Derivative Stabilized Emulsion Co-polymerization of Methyl Methacrylate and Butyl Acrylate

Ingredient Part per Hundred Monomer Water PolyasparticAcid, 10%, R=C, 8* 10 Methyl Methacrylate 43 Butyl Acrylate 57 Ammonium Persulphate 0.4 Ammonium Hydroxide (10% solution) 0.25 Theoretical Solids Content= 38.9% * C18 refers to-C18H37.

This example method generated a stabilized aqueous emulsion polymerization composition characterized by a 38.6% solids content, Brookfield viscosity of 30,000 cps, and average final particle size of 0.141) im.

Emulsion Example 3 An emulsion polymerization process for methyl methacrylate and butyl acrylate in which the sole stabilizer is a 30,000 MW, 5% C12 polyaspartic acid heteropolymer This example illustrates the preparation of stabilized aqueous emulsion polymerization compositions prepared according to the method of the present invention employing polyaspartic acid heteropolymers as emulsifying and stabilizing agents. Polymerization was carried out using a semi- batchwise addition of 15 pphm of Methyl Methacrylate/Butyl Acrylate (MMA/BA) and a slow add feed of the remaining monomer, initiator, and buffer. Ingredient Part per Hundred Monomer Water Polyaspartic Acid, 30k, 5%, R=C12* 2.5 Methyl Methacrylate 43 Butyl Acrylate 57 Ammonium Persulphate 0.4 Ammonium Hydroxide (10% solution) 0.25 Theoretical Solids Content= 35.3% * C12 refers to-C12H25.

This example generated a stabilized aqueous emulsion polymerization composition characterized by a 34.1% solids content, Brookfield viscosity of 20 cps, and average final particle size of 0.141pm.

Emulsion Example 4 An emulsion polymerization process for methyl methacrylate, butyl acrylate, and methacrylic acid in which the sole stabilizer is a 30,000 MW, 10% C12 polyaspartic acid heteropolymer.

This example illustrates the preparation of stabilized aqueous emulsion polymerization compositions prepared according to the method of the present invention employing polyaspartic acid heteropolymers as emulsifying and stabilizing agents. Polymerization was carried out using a slow addition of Methyl Methacrylate/Butyl Acrylate/Methacrylic Acid ( [MMA/BA/MAA- polyAspartate] emulsion. The initiator was also slow added concomitantly.

Ingredient Part per Hundred Monomer Water Polyaspartic Acid, 30k, 10%, R=C12* 4 Methyl Methacrylate 43.5 Butyl Acrylate 43.5 Methacrylic Acid 13 Ammonium Persulphate 0.4 Ammonium Hydroxide (10% solution) 0.25 Theoretical Solids Content= 50.5% * C12 refers to-C12H25.

This example generated a stabilized aqueous emulsion polymerization composition characterized by a 52.8% solids content, Brookfield viscosity of 42 cps, and average final particle size of 0.249pm.

Figure 1 illustrates the influence of the level and type of polyaspartic acid heteropolymer (15,000MW) emulsifying and stabilizing agent on the final average particle size of the acrylic latex stabilized aqueous emulsion polymerization compositions prepared according to the method of the present invention. Figure 2 illustrates the influence of the level and type of polyaspartic acid heteropolymer (15,000MW) emulsifying and stabilizing agent on the final viscosity of the acrylic latex stabilized aqueous emulsion

polymerization compositions prepared according to the method of the present invention. In Figures 1 and 2, C12 refers to-C12H25 and C18 refers to- C18H37. While the average particle size remained in the 0.1 ! 1m to 0.2pm range at all levels of polyaspartic acid heteropolymer, the viscosity of the latexes increased as the level of polyaspartic acid heteropolymer increased.

The ability to control the viscosity of the latex while maintaining a relatively small particle size by adjusting the level of polyaspartic acid heteropolymer is apparent.

Emulsion Example 5 An emulsion polymerization process for vinyl acetate in which the sole stabilizer is a 15,000 MW, 5% C12 polyaspartic acid heteropolymer.

This example illustrates the preparation of stabilized aqueous emulsion polymerization compositions prepared according to the method of the present invention employing polyaspartic acid heteropolymers as emulsifying and stabilizing agents. Polymerization was carried out using a semi- batchwise addition of 15 pphm monomer and a slow add feed of the remaining monomer, oxidizing, and reducing agents.

Polyaspartic Acid Derivative Stabilized Emulsion Polymerization of Vinyl Acetate

Ingredient Part per Hundred Monomer Water Polyaspartic Acid, 5% R=C12* 4.0 Vinyl Acetate 100 Ammonium Persulphate 0.2 Sodium Formaldehyde Sulfoxylate 0.15 Theoretical Solids Content = 50. 1 % * C12 refers to-C,2H25.

This example generated a stabilized aqueous emulsion polymerization composition characterized by a 50.8% solids content, Brookfield viscosity of 339 cps, average final particle size of 0.160Fm, and a vinyl acetate residual monomer content of 5867ppm.

Emulsion Example 6 An emulsion polymerization process for vinyl acetate and di-butyl maleate in which the sole stabilizer is a 5,000 MW, 5% C18 polyaspartic acid heteropolymer.

This example illustrates the preparation of stabilized aqueous emulsion polymerization compositions prepared according to the method of the present invention employing polyaspartic acid heteropolymers as emulsifying and stabilizing agents. Polymerization was carried out using a batchwise addition of monomer and slow add feed of oxidizing and reducing agents. Polyaspartic Acid Derivative Stabilized Emulsion Co-polymerization of Vinyl Acetate and Di-butyl Maleate

Ingredient Part per Hundred Monomer Water Polyaspartic Acid, 5k, 5% R=C, B* 5 Vinyl Acetate 79.5 Di-Butyl Maleate 20.5 t-Butyl Hydroperoxide 0.26 Sodium Formaldehyde Sulfoxylate 0.45 Sodium Acetate 0.05 Theoretical Solids Content = 45.5% * C18 refers to-C18H37.

This example generated a stabilized aqueous emulsion polymerization composition characterized by a 45.4% solids content, Brookfield viscosity of 4200 cps, average final particle size of 0.086pm, and a vinyl acetate residual monomer content of 727 ppm.

Emulsion Example 7 An emulsion polymerization process for vinyl acetate and di-butyl maleate in which the sole stabilizer is a 15,000 MW, 5% C18 polyaspartic acid heteropolymer.

This example illustrates the preparation of stabilized aqueous emulsion polymerization compositions prepared according to the method of the present invention employing polyaspartic acid heteropolymers as emulsifying and stabilizing agents. Polymerization was carried out using a batchwise addition of monomer and slow add feed of oxidizing and reducing agents. Ingredient Part per Hundred Monomer Water Polyaspartic Acid, 5% R=C18* 1.4 Vinyl Acetate 79.5 Di-Butyl Maleate 20.5 t-Butyl Hydroperoxide 0.26 Sodium Formaldehyde Sulfoxylate 0.45 Sodium Acetate 0.05 Theoretical Solids Content = 44.2% * C, 8 refers to-C18H37.

This example generated a stabilized aqueous emulsion polymerization composition characterized by a 42.2% solids content, Brookfield viscosity of 26 cps, average final particle size of 0.135 lim, and a vinyl acetate residual monomer content of 730ppm.

Emulsion Example 8 An emulsion polymerization process for vinyl acetate and di-butyl maleate in which the sole stabilizer is a 30,000 MW, 5% C12 polyaspartic acid heteropolymer.

This example illustrates the preparation of stabilized aqueous emulsion polymerization compositions prepared according to the method of the present invention employing polyaspartic acid heteropolymers as emulsifying and stabilizing agents. Polymerization was carried out using a batchwise addition of monomer and slow add feed of oxidizing and reducing agents.

Ingredient Part per Hundred Monomer Water Polyaspartic Acid, 30k, 5% R=C12* 5 Vinyl Acetate 79.5 Di-Butyl Maleate 20.5 t-Butyl Hydroperoxide 0.26 Sodium Formaldehyde Sulfoxylate 0.45 Sodium Acetate 0.05 Theoretical Solids Content = 45. 1% * C12 refers to-C12H25.

This example generated a stabilized aqueous emulsion polymerization composition characterized by a 44.6% solids content, Brookfield viscosity of 2560 cps, average final particle size of 0.134pm, and a vinyl acetate residual monomer content of 165 ppm.

This viscosity effect was also observed for latexes of vinyl-acetate/di- butyl maleate. Table 1 summarizes the influence of type and level of polyaspartic acid heteropolymer on average particle size and Brookfield viscosity.

Table 1 Influence of the Level and Type of Polyaspartic acid Heteropolymer on the final Viscosity and Average Particle Size of Vinyl Acetate/Di-butyl Maleate Latexes

PolyAspartate PolyAspartate Average Particle Brookfield Solid Type Level Size (pm) Viscosity Content (% of M) (cps) (% w/w) 5% C18* 1. 4 0. 135 26 42 5% C18* 4. 0 0. 093 105 42 <BR> <BR> 10% C18* 1. 4 0. 125 39 42<BR> 10% C18* 4. 0 0. 096 1370 44 * C, 8 refers to-C18H37.

While a number of embodiments of this invention have been represented, it is apparent that the basic construction can be altered to provide other embodiments which utilize the invention without departing from the spirit and scope of the invention. All such modifications and variations are intended to be included within the scope of the invention as defined in the appended claims rather than the specific embodiments which have been presented by way of example.