Related Background Art Aqueous emulsion polymerization is a process whereby water insoluble or mostly water insoluble monomers are polymerized in dispersed form in an aqueous medium. A surfactant or a surfactant blend is typically used to stabilize the prepared insoluble polymer particles, maintaining particle integrity and preventing phase separation.

Aqueous emulsion polymer systems have been developed in response to continuing environmental and regulatory

pressures to reduce and/or eliminate the use of volatile organic solvents in polymer preparation and delivery systems. While emulsion polymerization has proven to be a highly successful and practical method of preparing commercial industrial polymer products, the performance characteristics of such systems, such as in coatings applications, often do not match the performance obtained from a polymer system delivered from an organic solvent. This is due in part to the existence of the surfactant in the emulsion polymer system. Comprised mostly of highly charged molecules, for example ionic type surfactants such as sodium lauryl sulfate, the surfactant contributes adversely to properties such as water resistance and detergent resistance in coatings applications.

Copolymerizable surfactants, fugitive surfactants, and reactive surfactants have been proposed in the patent and scientific literature as steps toward higher performing emulsion polymer systems. While these approaches have all met with some technical and commercial success, economic considerations often prevent these technologies from displacing conventional surfactants in emulsion polymerization.

An alternative technology is the use of polymeric materials as the stabilizing species in emulsion polymerization systems. These polymeric materials have been referred to in various publications as polymeric surfactants, protective colloids, polymer supports, support resins, polymer seeds, or polymeric stabilizers, and are typically lower molecular weight, between about 400-20,000 Daltons. The polymeric materials'functionality yields a polymer that is either water soluble or soluble on addition of base (known as alkali soluble resin, which contains carboxylic acid or sulfonic acid), or upon addition of acid (known as acid soluble resin, which contains

nitrogen). These"polymeric stabilizers", as referred to herein, serve the same purpose as conventional surfactants in emulsion polymerization, and also provide additional performance characteristics not obtainable from conventional surfactants such as gloss development, flow and leveling control, and dry time control. Polymeric stabilizers are preferably prepared using weaker acids such as carboxylic acids instead of sulfonic acids, and utilize a fugitive amine, for example triethyl amine or ammonia, which results ultimately in a noncharged stabilizing component in the film. As explained below, the presence of large amounts of ionic species in final polymers can detract from performance characteristics such as water resistance. Systems containing polymeric stabilizers exhibit improved resistance properties including water resistance when compared to conventional stabilizers.

Examples of emulsion polymerization systems exist in the patent literature, whereby variations in the monomers, surfactants, addition profiles and processing conditions result in unique compositions and/or unique performance characteristics. U. S. Patent Nos.

4,931,510,5,013,794 and 5,258,466 disclose diisobutylene/maleic anhydride copolymers modified to imide with aminosulfonic acid which are used as resin supports in ranges of 2.5-30% by weight. The resins are used to polymerize such monomers as styrenics, (meth) acrylates, (meth) acrylonitriles and mixtures thereof. The resulting polymers are disclosed as useful as paper surface and fiber sizing agents.

U. S. Patent No. 5,166,272 discloses an alpha olefin (C,, Clou C12) or undecylenic acid/maleic anhydride copolymer which has been modified to incorporate some olefin functionality used in an amount between 5% and 30% by weight to polymerize (meth) acrylics useful in coatings.

U. S. Patent No. 4,775,723 discloses an alpha olefin (C6-

C40)/maleic anhydride copolymer, partially esterified, used in an amount of 2.5% to polymerize ethyl acrylate useful as a lubricant and emulsifying agent.

Japanese Patent No. 6,172,728 discloses an isobutylene/maleic anhydride copolymer modified to imide (commercial Japanese product Isobam 304"') used in an amount of 13.8% by weight to polymerize vinyl acetate monomers which are used in adhesives. The patent discloses use of a co-stabilizer of modified polyvinyl alcohol. U. S. Patent No. 5,298,568 discloses an alpha olefin/maleic anhydride copolymer modified with hydroxy and amino used in an amount of 81% by weight to polymerize acrylate monomers useful in inks and adhesives.

Japanese Patent No. 7,118,312 discloses a chlorinated alpha olefin/maleic anhydride copolymer used in an amount of 50% by weight to polymerize methacrylates useful as a pigment dispersion and in inks. Japanese Patent Nos. 51 001,706, and 83 013,679 disclose a nonpolymeric adduct of alpha olefin/maleic anhydride extended with diamine used in an amount of 20-80% by weight to polymerize (meth) acrylates and (meth) acrylonitriles which are useful as paper sizing agents. Although appearing similar, these adducts are actually non-polymeric emulsifiers and not properly characterized as polymeric stabilizers. Finally, Japanese Patent No. 6,088,052 discloses a diisobutylene/maleic anhydride copolymer, and partial esters thereof, used in an amount of 17% to 95% by weight to polymerize (meth) acrylates useful in ink, overprint and varnishes.

Typically, fairly high levels of resin are used such as 20 or 25% based on monomers and as high as 30% in certain cases depending on the monomer used in the emulsion. This high level can be advantageous in

systems where the performance of the final product is benefitted from high levels of resin, such as when a pigment will be added to the latex or when a printing ink is the final use. However, for some alternative applications of emulsion polymerization, such as industrial coating and high performance thermoset coatings, previously normal levels of support resin such as 20 to 30% are detrimental to the performance of the coating. Water resistance, chemical resistance and resistance to ultraviolet light can be compromised.

Although some of the published art alleges that polymers can be used as stabilizers in emulsion polymerization systems at levels as low as 5% by weight, experience has shown that these polymeric stabilizers are typically useful only at the level of 20 to 30 percent.

The following U. S. and foreign patents are notable regarding the work of others in the art of modified alpha-olefin/maleic anhydride copolymers. U. S. Patent No. 3,039,870 discloses taurine substituted ethylene/maleic anhydride and styrene/maleic anhydride copolymers. British Patent GB 1,246,953 discloses sulfonic acid-substituted polymers of maleic anhydride and copolymers of maleic acid with olefin or vinyl aromatics, esters and ethers. The polymers are said to be useful as additives for cosmetic preparations, hair lacquers, tanning agents, dispersion auxiliaries or textile auxiliaries. U. S. Patents 4,284,517 and 4,317,893 disclose sulfonic acid-substituted copolymers of styrene and maleic anhydride useful as surfactants in waterflooding oil recovery methods. Japanese Patent 57, 42,765 discloses taurine substituted copolymers of alphaolefin/maleic anhydride. U. S. Patent 4,588,786 discloses a process for preparing sulfonic acid- substituted copolymers of isobutylene and maleic anhydride. U. S. Patent 4,618,450 discloses an aqueous

system comprising water and an N-acylated hydrocarbyl sulfonic acid or salt composition having within its structure an imido group or acyl, acylimidoyl or acyloxy group attached directly to the amino nitrogen.

U. S. Patent 4,620,855 discloses N-acylated aminohydrocarbyl sulfonic acids and salt compositions useful as emulsifiers, thickeners, dispersants, fuel additives and lubricants. U. S. Patents 4,931,510, 5,013,794,5,258,466, and 5,356,985 disclose fully sulfonated alpha olefin/maleic anhydride polymers as emulsifiers for emulsion polymerization processes for producing paper sizing polymers.

Therefore an emulsion polymerization stabilizer is desirable which eliminates the need for volatile organic solvents in polymer preparation and delivery systems and is active at reduced levels from those of typical conventional and polymeric stabilizers.

The subject invention provides an polymer resin useful as a stabilizer or support for emulsion polymerization.

The polymers according to this invention are generally amine modified, with taurine preferred as the amine modifier, and contain certain amounts of fully modified, partially modified and unmodified maleic anhydride polymer units. The use of taurine or other alkyl-sulfonic acids is important in that the modified resins are now soluble or dispersible over the entire pH spectrum and thus can be used in more emulsion polymerization systems where prior art styrene/acrylic acid resins are not soluble. By varying the amount of modified, partially modified and unmodified units, the ionic character of the copolymers can be controlled.

This invention also provides a process for producing a polymer by emulsion polymerization which comprises combining in an aqueous solution at least one monomer, a free radical initiator and a polymeric stabilizer

comprising one or more of the copolymer compositions of this invention, wherein the polymeric stabilizer is present in the aqueous solution in an amount greater than 0 and less than 5% by weight. Also, modification of alpha olefin/maleic anhydride copolymers with the appropriate amines renders the resin soluble in a wider pH range. This invention therefore can also provide a process for producing a resin stabilized emulsion polymer which can be prepared at a wider range of pH compared to previous resin stabilized emulsion polymers.

SUMMARY OF THE INVENTION This invention provides a copolymer comprising: (a) from 40 to 95 mole percent maleic anhydride, a portion of which has been modified to the following structure: wherein R is Rl or R2, wherein R1 is H or Cl to Clé linear, branched, or cyclic alkyl, or C1 to Cl8 alkyl substituted with C1 to C4 alkoxy, and R2 is R3- (SO3M) n, wherein R3 is Cl to Cl0 straight or branched alkyl, M is Na, K, Li, NH3, H and n is 1, 2 or 3; such that between 5 to 100% of the maleic anhydride of the copolymer comprises said modified maleic anhydride, and the ratio of R, to R2 in the modified maleic anhydride portion is between 10: 1 and 1: 10; and (b) from 5 to 60 mole percent alpha olefin having the structure:

wherein R4 is a Cs to C30 straight or branched alkyl.

This invention also provides an emulsion polymerization system comprising a polymeric stabilizer, wherein the polymeric stabilizer comprises one or more copolymers as defined above and is present in the emulsion polymerization system in an amount greater than 0 and less than 10% by weight.

The copolymer compositions and the emulsion polymerization system of the invention can be used to prepare stable emulsion polymers at levels of polymeric stabilizer previously believed unattainable by those familiar with polymer stabilized emulsion polymerization. The polymeric stabilizers of this invention provide the benefits realized from prior emulsion polymeric stabilizers. However, because they are used in reduced amounts, and in some instances in amounts less than conventional stabilizers, they avoid the drawbacks of prior art conventional and polymeric stabilizers. In addition, they provide advantageous performance and property attributes. For example, polymers resulting from the claimed emulsion polymerization system exhibit improved properties relating to water, alkali, and chemical resistance.

Thus, this invention also provides a process for producing a polymer by emulsion polymerization which comprises combining in an aqueous solution at least one monomer, a free radical initiator and a polymeric

stabilizer comprising one or more of the copolymer compositions of the invention, wherein the polymeric stabilizer is present in the aqueous solution in an amount greater than 0 and up to 10% by weight.

DETAILED DESCRIPTION OF THE INVENTION This invention provides a copolymer comprising: (a) from 40 to 95 mole percent maleic anhydride, a portion of which has been modified to the following structure: wherein R is Ri or R2, wherein Rl is H or Cl to Cl, linear, branched, or cyclic alkyl, or C1 to cjs alkyl substituted with C1 to C4 alkoxy, and R2 is R3-(SO3M) n,(SO3M) n, wherein R3 is Cl to C10 straight or branched alkyl, M is Na, K, Li, NH3, H and n is 1, 2 or 3; such that between 5 to 100% of the maleic anhydride of the copolymer comprises said modified maleic anhydride, and the ratio of R, to R2 in the modified maleic anhydride portion is between 10: 1 and 1: 10; and (b) from 5 to 60 mole percent alpha olefin having the structure:

wherein R, is a Cs to C30 straight or branched alkyl.

The copolymers of the invention are copolymers of maleic anhydride and alpha olefins, wherein a certain portion of the maleic anhydride in the copolymer has been modified to either the half amide/half acid or to the imide, referred to collectively as the"modified maleic anhydride", by the processes disclosed herein.

As noted, between about 5 mole percent and 100 mole percent of the maleic anhydride of the copolymer of the invention will be modified maleic anhydride. In a preferred embodiment between about 20 mole percent and 80 mole percent of the copolymer of the invention will comprise modified maleic anhydride. In a particularly preferred embodiment between about 60 mole percent and 80 mole percent of the copolymer comprises modified maleic anhydride.

As defined above, the modified maleic anhydride portion of the copolymer of the invention will comprise either the full imide form (I) or the half amid/half acid form (II) depending on the extent to which the process for modifying maleic anhydride is carried out. Thus, it is contemplated that the modified maleic anhydride of the copolymer of the invention will comprise both the half amide/half acid form and the full imide form. In a preferred embodiment, the copolymer of the invention the modified maleic anhydride will be substantially modified to the full imide form, i. e., 95% modified to the full imide form. In a particularly preferred embodiment the modified maleic anhydride will be 99% modified to the full imide form.

As defined above, the modified maleic anhydride portion, whether in the half amide/half acid form or full imide form, will comprise either ammonia, wherein R is Ri and R, is H, or substituted amine, wherein R is

Ri or R2 and Rl is not H. When R is Rl, the substituted amine form comprises alkyl-or alkoxy substituted alkyl-amines. Examples of alkyl substituted amines which are useful to form the modified maleic anhydrides as defined above include, but are not limited to, methylamine, ethylamine, n-propylamine, isopropylamine, n-butylamine, isobutylamine, n-pentylamine, isopentylamine, n-hexylamine, heptylamine, octylamine, nonylamine, decylamine, undecylamine, dodecylamine, tridecylamine, tetradecylamine, stearylamine, 2- ethylhexylamine, laurylamine, cycloheptylamine, cyclohexylamine, cycloctylamine. Examples of alkoxy substituted amines include, but are not limited to, 3- methoxypropylamine, 3-ethoxypropylamine, 3- propoxypropylamine, 3-isopropoxypropylamine, 3- butoxypropylamine, 3-isobutoxypropylamine, as well as poly (ethoxylated) amines and poly (propoxylated) amines, which are sold under the trade name Jeffaminess (Huntsman Chemical).

When R is R2, the substituted amine form comprises taurine modified amine. Taurine is also known as 2- amino ethanesulfonic acid. As used herein, the term "taurine-modified amine"refers to amines modified with C1 to Cl0 straight or branched chain alkysulfonic acids, including ethane sulfonic acid, or their salts to form 2-amino alkylsulfonic acids. The salts include sodium, potassium, lithium, and ammonia salts. Further, as used herein the term"taurine-modified maleic anhydride"refers to modified maleic anhydrides, whether modified to the half amide/half acid form or full imide form, that contain a taurine-modified amine substituent. As defined above, in the modified maleic anhydrides of the copolymers of the invention, the ratio of Ri to R2 is between about 10: 1 and 1: 10. In a preferred embodiment, the ratio is between about 2: 1 and 1: 2.

The copolymer of the invention comprises between about 40 and 95 mole percent maleic anhydride, including modified and unmodified maleic anhydride, and between about 5 and 60 mole percent alpha olefin. In a preferred embodiment, the copolymer comprises between 49 and 95 mole percent maleic anhydride, including modified and unmodified maleic anhydride, and between 5 and 51 mole percent alpha olefin. Separately, the invention contemplates the use of more than one alpha olefin in the copolymer as defined above. Accordingly, the copolymer may comprise 1,2,3,4, etc. unique alpha olefins. As used herein, a"unique alpha olefin" is one in which R4 is distinct from R4 of another alpha olefin in the copolymer. In a preferred embodiment the copolymer of the invention comprises two unique alpha olefins. In a further preferred embodiment, the two unique alpha olefins are present in a ratio of between 10: 1 and 1: 10. In a particularly preferred embodiment, the two unique alpha olefins are present in a ratio of between about 6: 4 and 4: 6.

Copolymers of maleic anhydride and olefin are known.

The olefin/maleic anhydride system is unique in its tendency to form regular alternating copolymers. The olefin/maleic anhydride alternating copolymer has the general structure: Olefin Derived Polymer Segment R H \ H : . I zozo --I Maleic Anhydride Derived Polymer

Segment -Head to Tail Addition -Regular 1: 1 Alternating These polymers are partially disclosed in U. S. Pat. No.

4,358,573 (bulk processing) and U. S. Pat. No. 4,522,992 (solution processing) which patents are expressly incorporated by reference for their disclosure of suitable alpha olefin maleic anhydride polymers as well as in U. S. Pat. No. 4,871,823 likewise incorporated herein by reference.

The anhydride included in the alpha olefin maleic anhydride polymers is most preferably maleic anhydride.

However, other maleic anhydrides can be utilized in this formation of the polymers such as methylmaleic anhydride, dimethylmaleic anhydride, fluoromaleic anhydride, methylethyl maleic anhydride and the like.

Accordingly, as employed herein the term"maleic anhydride"includes such anhydrides in whole or in part. It is preferred that the anhydride be substantially free of acid and the like before polymerization.

The alpha olefins generally suitable in the formation of the polymeric stabilizers described herein have from 2 to 60 carbon atoms, preferably between about 2 and 30+ carbon atoms, and include the following: ethylene; propylene; 1-butene; 1-pentene; 1-hexene; 1-heptene; 1-octene; 1-nonene; 1-decene; 1-dodecene; 1-tetradecene; 1-hexadecene; 1-heptadecene; 1-octadecene; 2-methyl-1-butene; 3, 3-dimethyl-l-pentene; 2-methyl-1-heptene; 4, 4-dimethyl-l-heptene; 3,3-dimethyl-1-hexene; 4-methyl-1-pentene; 1-eicosene; 1-docosene; 1-tetracosene; 1-hexacosene; 1-octacosene; 1-triacontene; 1-tetracontene; 1-octatriacontene; 1-tetracontene; 1-octatetracontene; 1-pentacontene; 1-hexacontene; and mixtures thereof. The term"30+"or "cuis used herein in its commonly accepted usage wherein a"C. "1-alkene mixture is a mixture of high boiling 1-alkenes with carbon content between about 30 and 60 carbon atoms per molecule.

Mixtures of the olefins can be combined with anhydrides described above to form terpolymers or higher polymers.

It is preferred to utilize straight chain 1-alkenes having from 6 to 18 carbon atoms, and accordingly, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-heptadecene, 1-octadecene, and mixtures thereof are preferred.

These materials should be substantially free of diolefin as an impurity which causes gel formation and cross-linking. However, small amounts, i. e., less than 2 percent, can be present without causing undue gel formation and cross-linking in the resulting polymers.

Also as noted above, either single materials, i. e., 1-hexene, 1-decene, etc., can be used, or mixtures of these materials may be utilized.

As is well known in the art, polymers containing equimolar ratios of alpha olefin to maleic anhydride

are essentially alternating polymers with maleic anhydride alternating between random comonomers.

Accordingly, the alpha olefin maleic anhydride polymers may contain from about 49 to 95 mole percent of maleic anhydride and more preferably, from 49 to 70 mole percent of maleic anhydride. Under some conditions such as is described in U. S. Patent No. 4,871,823 noted above, it is possible to include an excess of maleic anhydride relative to the comonomer in these polymers.

The amount of alpha olefin will correspondingly vary from about 5 to about 60 mole percent, preferably between about 5 to about 51 mole percent. The optimum alpha olefin maleic anhydride polymers include about 50 mole percent maleic anhydride and about 50 mole percent alpha olefin, but this is dependent upon the alpha olefin selected. This is generally true for C,, and higher carbon content alpha olefins, referred to herein as'C18+ alpha olefins". For polymers containing between about C4 and about Cl0 alpha olefins, it is preferred that greater than an equimolar amount of maleic anhydride be used, up to about 50 mole percent greater.

Generally, it has been found that copolymers of maleic anhydride and a single alpha olefin having no less than 6 and no more than 24 carbon atoms are needed to obtain clear, single phase aqueous compositions, and more preferably, between 6 and 18 carbon atoms alpha olefins maleic anhydride polymers containing higher alpha olefins (i. e., more than 24 carbons per molecule) can be used in the compositions of the present invention in the form of ter-or higher polymers which also contain at least one C2 to Cl9 alpha olefin. Preferably, the ratio of Cl-Cl8 : C,,. alpha olefins is such that the average alpha olefin carbon chain length in the polymer is greater than about 6 and less than about 18 to obtain clear, single phase aqueous compositions.

Alpha olefin/maleic anhydride polymers may be prepared by any of a number of conventional polymerization processes including polymerization processes as set forth in U. S. Reissue Patent No. Re. 28,475 and U. S.

Patent Nos. 3,553,117,3,560,455,3,560,456, 3, 560,457, 573,4,871,823 and 4,859,752. The processes for making polymers disclosed in these patents are all incorporated herein by reference.

The copolymers disclosed herein can be prepared from unmodified alpha-olefin/maleic anhydride co-polymers or by other methods known to those of ordinary skill in the art. Modification of the anhydride functionality on the copolymer can be accomplished with amines by reaction of amines with the polymer in the bulk phase under melt conditions. Alternatively, the reaction can be accomplished in a solvent suitable for the polymer and reactants. In another known method, modification can be achieved in an aqueous medium at elevated temperatures and elevated pressure. A preferred method of modification is the method utilizing an aqueous reaction medium. For example, alpha-olefin/maleic anhydrides can be modified to half-amide/acids or imides by derivitization in water with 2-amino ethanesulfonic acid ("taurine") and ammonia.

The copolymers of the invention are generally low molecular weight materials having a weight average molecular weight of from about 1,000 to about 100,000.

In a preferred embodiment the copolymers have a weight average molecular weight of from about 1,000 to about 10,000. In a particularly preferred embodiment the copolymers have a weight average molecular weight of from about 1,000 to about 5,000.

The present invention also provides an emulsion polymerization system comprising a polymeric stabilizer

which comprises one or more of the copolymers defined above. The term"emulsion polymerization system"as used herein refers to a combination of monomers dispersed in aqueous medium, from which a desired end product polymer precipitates to a stable dispersion.

This system can include further components as discussed hereinafter.

This invention provides for the use of greatly reduced amounts of stabilizers or surfactants in typical emulsion polymerization techniques. The polymeric stabilizers are generally present in the emulsion polymerization system of the invention in as small an amount as necessary to provide emulsion stabilization.

Generally, the polymer stabilizer is present in the emulsion polymer system in an amount greater than 0 and up to 10 percent by weight. In a preferred embodiment the polymer stabilizer is present in the emulsion polymer system in an amount greater than 0 and up to 5 percent by weight. In an equally preferred embodiment the polymer stabilizer is present in the emulsion polymer system in an amount between about 0.5 percent and 4 percent by weight. In an equally preferred embodiment the polymer stabilizer is present in the emulsion polymer system in an amount between about 0.5 percent and 2 percent by weight. In a particularly preferred embodiment the polymer stabilizer is present in an amount between about 0.5 percent and 1 percent by weight.

The emulsion polymerization system of the present invention is useful for preparing polymers according to known emulsion polymerization techniques. In a typical technique, emulsion polymerization involves polymerizing a mixture of ethylenically unsaturated copolymerizable monomers in an aqueous reaction medium, in the presence of a surfactant and a free radical initiator. The aqueous reaction medium is the liquid

in which the various components are dispersed in an emulsion state by the stabilizer and is substantially composed of water.

In a preferred embodiment of the present invention, the alpha olefin maleic anhydride polymer stabilizer described above is substituted for conventional surfactants. However, the emulsion polymerization system of this invention may comprise the alpha olefin maleic anhydride polymer stabilizer described above and, optionally, one or more conventional surfactants at levels up to 3 percent by weight. Examples of such surfactants include, but not limited to, linear alkyl phenol ethoxylates and primary alcohol ethoxylates such as Triton@ and Tergitol@, respectively (Union Carbide, Danbury, CT).

The free radical initiators useful in the emulsion polymerization system of this invention can be a thermal initiator or a redox initiator. Examples of suitable free radical initiators and components thereof include persulfate initiators, such as sodium persulfate, potassium persulfate, barium persulfate, and ammonium persulfate; alkali metal bisulfites; peroxides such as benzoyl peroxide, and dicumyl peroxide; hydroperoxides such as methyl hydroperoxide and ter-butyl hydroperoxide; acyloins such as benzoin; peracetates such as methyl peracetate and tert-butyl peracetate; perbenzoates such as t-butylperbenzoate; peroxalates such as dimethyl peroxalate and di (tert- butyl) peroxalate; and azo compounds such as azo-bis- isobutyronitrile and dimethyl azo-bis-isobutyrate.

Mixtures of such free radical initiators may also be employed. Typically, the free radical initiator is employed in an amount of at least about 0.1%, preferably from about 0.3% to about 1.0%, by weight based on the total weight of the monomers present and depending on the weight and activity of the initiator.

Suitable monomers that can be polymerized using the emulsion polymerization system of the present invention include monoethylenically unsaturated monomers such as ethylenically unsaturated aromatic monomers, acrylic acid ester monomers, methacrylic acid ester monomers, ethylenically unsaturated acid functional group- containing monomers, and ethylenically unsaturated hydroxy functional group-containing monomers.

Diethylenically unsaturated monomers may also be used if restricted to levels low enough to avoid gelling the polymer.

Examples of ethyleneically unsaturated aromatic monomers include styrene, alpha-methyl styrene, vinyl toluene, para-methylstyrene, and tertbutyl styrene.

Examples of acrylic acid ester monomers are those containing from 1 to 20 carbon atoms in the alkyl group which include methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, n-decyl acrylate, isopropyl acrylate, n-butyl acrylate, n-decyl acrylate, and 2-ethylhexyl acrylate. Examples of methacrylic acid ester monomers are those containing from 1 to 20 carbon atoms in the alkyl group which include methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, n-butyl methacrylate, isopropyl methacrylate, isobutyl methacrylate, n-amyl methacrylate, n-hexyl methacrylate, isoamyl methacrylate, allyl methacrylate, sec-butyl methacrylate, tert-butyl methacrylate, 2-ethylbutyl methacrylate, cinnamyl methacrylate, crotyl methacrylate, cyclohexyl methacrylate, cyclopentyl methacrylate, methallyl methacrylate, n-octyl methacrylate, and 2-ethylhexyl methacrylate. Examples of methacrylates containing aromatic groups include 2-phenylethyl methacrylate and phenyl methacrylate.

Examples of acid functional group-containing ethylenically unsaturated monomers include acrylic

acid, methacrylic acid, crotonic acid, itaconic acid, fumaric acid, maleic acid, citraconic acid, and monoalkyl esters of unsaturated dicarboxylic acids.

Examples of hydroxy functional group-containing ethylenically unsaturated monomers include 2-hydroxyethyl acrylate, 2-hydroxybutyl acrylate, 6-hydroxyhexyl acrylate, 2-hydroxypropyl methacrylate, 6-hydroxyhexyl methacrylate, and 5,6-dihydroxyhexyl methacrylate. Of these, hydroxyethyl-, hydroxypropyl- and hydroxybutyl acrylates are preferred.

The present invention also provides a process for producing a desired polymer by emulsion polymerization which comprises combining in an aqueous solution at least one monomer, a free radical initiator and a polymeric stabilizer comprising one or more alpha olefin/maleic anhydride copolymers defined above, wherein the polymeric stabilizer is present in the aqueous solution in an amount greater than 0 up to 10 percent by weight of the monomers used. In a preferred embodiment the polymeric stabilizer is present in an amount greater than 0 up to 5 percent by weight. In an equally preferred embodiment the polymeric stabilizer is present in an amount between about 0.5 percent and 4 percent by weight. In another preferred embodiment the polymeric stabilizer is present in an amount between 0.5 percent and 2 percent by weight. In a further preferred embodiment the polymeric stabilizer is present in an amount between about 0.5 percent and 1 percent by weight.

The present invention provides an end product polymer having greatly reduced particle size which are produced by the emulsion polymerization process described above.

The end product polymers produced by the methods of this invention have a particle size less than about 100 nanometers. In a preferred embodiment the end product polymers have a particle size between about 40 and

about 90 nanometers. In comparison, typical emulsion polymerization end product polymers have particle sizes in the range of greater than 100 to about 300 nanometers. Due to their small particle size and low levels of stabilizer, end product polymers produced by the emulsion polymerization system of this invention are particularly useful for glossy finishes, ink binders, overprint varnishes, industrial coatings and the like.

As discussed above, the ability to reduce the level of polymeric surfactant in the emulsion polymer system yields enhancements in performance of surface coating prepared from these emulsion polymers. In addition, the emulsion polymers prepared according to the present invention allows for more flexibility in formulating emulsion polymer systems. For example, typical polymeric stabilized emulsion polymerization systems may contain 30% polymeric resin. Because prior art polymeric support resins are used in amounts approaching 30%, no flexibility is provided in such systems for the addition of other resins to provide other performance characteristics to the finished polymer. In the present invention, however, the lower levels of polymeric stabilizer provide for greater flexibility in formulation. For example, a 1% resin can be used to prepare the emulsion polymer and the additional 29% made up of additional resins post blended in to provide additional performance characteristics. This greatly expands the number of useful compositions that can be prepared using polymeric stabilizer systems.

The polymeric stabilizers of the present invention are typically added as an aqueous solution of polymer and a neutralizing substance. As discussed above, conventional surfactants are comprised of highly charged molecules, for example ionic type surfactants

such as sodium lauryl sulfate. A polymer stabilizer or surfactant, on the other hand, must be neutralized in a solution which provides a counter ion to allow the polymer to mix with the aqueous emulsion. The "neutralizing agent"can be organic or inorganic provided that it allows for solvation of the polymer stabilizer in the aqueous emulsion system.

Examples of organic neutralizing agents include, but are not limited to, volatile organic substances such as ammonia or amines, preferably tri-, di-, or monoalkylamines, for example triethyl amine, morpholine, or alkanolamines, such as 2-amino-1-methyl propanol. The volatile organic substance will perform the neutralizing function and then evaporate upon the formation of the end product polymer. Examples of inorganic neutralizing substances include, but are not limited to, aqueous alkaline solutions containing sodium, potassium, and lithium. Since the inorganic substance is typically not volatile, the counter ion used to perform the neutralizing function will remain in the end product polymer. The prior art shows that the presence of the counter ion detracts from end product polymer performance such as water resistance.

However, the present invention, since it uses greatly reduced amounts of polymer stabilizer, allows for the use of inorganic neutralizing agents which result in levels of counter ion which do not detract from the performance of the polymer end product.

In one embodiment of the emulsion polymerization system, the polymer support is present in a sodium- neutralized solution. In a preferred embodiment of the emulsion polymerization system, the polymer support is present in an ammonium-neutralized solution.

In the present invention, emulsion polymerization can be carried out by any well known free radical addition

aqueous emulsion polymerization process, including batch, semi-batch, multiple stage batch, multiple stage semi-batch, and continuous emulsion polymerization. Preferably, the polymerization according to the present invention is conducted by semi-batch polymerization.

Semi-batch polymerization generally involves initially charging into a polymerization reactor a reaction medium such as water and additional components which facilitate the preparation of a stable dispersion of the polymer in the reaction medium. These components include the surfactants and the bases discussed above.

Other ingredients known in the art such as seed lattices for particle size regulation, monomer precharge for in-situ seed latex preparation, polymer initiators/catalysts/accelerators, chain transfer agents such as butyl mercaptopropionate for molecular weight regulation, and chelators for incidental metal removal may also be added.

The free radical initiator is then added to the initial charge followed by controlled addition, with agitation, of the ethylenically unsaturated copolymerizable monomers over a period of from about 30 minutes to about 4 hours at a temperature typically ranging from about 74°C to about 85°C. Of course, depending upon the free radical initiator employed, higher or lower temperatures and other monomer feed profiles can be employed. When a redox initiator is employed as the free radical initiator, the monomers and the initiator may be simultaneously fed to the initial charge. When the initiator is soluble and suitably stable in the monomers, it can be added to the monomer mixture and thus added to the initial charge along with the monomers. Those of ordinary skill in the art recognize that various initiators exist which operate at various temperatures, including room temperature, and selection of the appropriate initiator will depend upon the methods employed. Upon completion of the controlled

monomer addition, the formed polymer is continuously stirred and maintained at a temperature to facilitate complete consumption of the monomers. Thereafter the polymer is cooled, and additional components such as additional surfactants and bases may be added to further ensure dispersion stabilization. Other well known ingredients including defoamers, wetting agents, thickeners, preservatives, W stabilizers, and water may also be added, as needed. An inert gas such as nitrogen is typically used to purge the polymerization reactor of oxygen and is usually continued throughout the polymerization process.

INDUSTRIALAPPLICABILITY The copolymers and emulsion polymerization systems of the invention provide for the use of greatly reduced levels of resin stabilizer used in emulsion polymerization which results in benefits in performance properties of the resulting polymer, in manufacturing capacity, and in meeting progressive governmental regulatory restrictions with respect to storage, handling and disposal of VOC's. The end use applications of the emulsion polymers of this invention include coating applications such as glossy finishes, ink binders, overprint varnishes, wood lacquers, maintenance and industrial coatings and the like.

EXPERIMENTAL DETAILS The following Examples are provided to illustrate the invention only. They are not intended, and should not be interpreted, to limit the invention defined in claims which follow thereafter.

Example 1 Preparation of Taurine and Ethyl Amine Modified Alpha Olefin Maleic Anhydride Copolymer: 1-Octadecene/Maleic Anhydride Copolymer Modification A two liter 4 necked round bottomed flask equipped with a condenser, thermometer, mechanical agitation and heating mantle was charged with an 1-octadecene/maleic anhydride copolymer (Mw 5947,320 acid number, 174 grams, 496 millimoles anhydride), taurine (99%, 29.4 grams, 232 millimoles), anhydrous sodium hydroxide (9.5 grams, 232 millimoles), 70% aqueous ethyl amine (6.6 grams, 102.7 millimoles) and water (778.5 grams). With agitation, the contents of the reaction vessel were heated to 65 OC. Stirring was continued until the reaction medium was a homogeneous yellow liquid.

The reaction medium was then transferred to a 2 liter stainless steel pressure reactor equipped with mechanical agitation, electronic band heating, water and air cooling and thermal regulation. The reactor was sealed and the temperature was raised to 175 °C, whereupon the pressure of the reactor was observed to be 140 psi. The reaction was held at this temperature for an additional 2 hours. It was then cooled and decanted, whereupon an additional quantity of water (50 grams) and 28% aqueous ammonia (2.2 grams, 36.2 millimoles) were added. The final solution was semi-translucent with a pH of 6.4 and a solids level of 16.0%.

Example 2 Preparation of Taurine and Ethyl Amine Modified Alpha Olefin Maleic Anhydride Copolymer: 1-Decene/Maleic Anhydride (Excess Maleic) Copolymer Modification A three liter 4 necked round bottomed flask equipped with a condenser, thermometer, mechanical agitation and heating mantle was charged with an 1-decene/maleic

anhydride copolymer (Mw 3337,586 acid number, 461 grams, 2407 millimoles anhydride), taurine (99%, 60.9 grams, 482 millimoles), 70% aqueous ethyl amine (101 grams, 1571 millimoles) and water (1877 grams). With agitation, the contents of the reaction vessel were heated to 60 °C. Stirring was continued until the reaction medium was a homogeneous yellow liquid.

A portion of this reaction solution (1100 grams) was then transferred to a 2 liter stainless steel pressure reactor equipped with mechanical agitation, electronic band heating, water and air cooling and thermal regulation. The reactor was sealed and the temperature was raised to 175 °C, whereupon the pressure of the reactor was observed to be 140 psi. The reaction was held at this temperature for an additional 2 hours. It was then cooled and decanted, whereupon an additional quantity of water (50 grams) was added. The final solution was semi-translucent with a pH of 3.6 and a solids level of 20.0%.

Example 3 Emulsion Polymerization Using Modified Alpha Olefin Maleic Anhydride Copolymers: Stabilizer Efficiency with Hydrophobic Monomers Emulsion polymerization systems requiring hydrophobic monomers such as 2-ethylhexyl acrylate and styrene typically require high levels of resin stabilizer to achieve a stable dispersion of fine particle size. The following series of emulsion polymer exemplifies the utility of the polymeric stabilizers of the present invention to prepare stable emulsion polymers with reduced levels of stabilizer.

EmulsionPommer A glass 1 liter 4 necked round bottomed flask equipped with mechanical agitation, thermometer with thermoregulator (Thermowatchs Instruments for Research and Industry, Inc., Cheltenham, PA), condenser, nitrogen purge line, mechanical feed pump, and heating mantle, was charged with deionized water and an aqueous modified resin solution as prepared in Example 1 above.

The solution was raised to 82 °C. A 10% solution of ammonium persulfate initiator in deionized water was added to the reactor, and a mixture of methyl methacrylate, 2-ethylhexyl acrylate, and styrene was fed into the reactor over a 60 minute time period.

Nitrogen was used as an inert gas purge throughout the reaction, and the temperature was maintained at 82 °C.

The monomer addition period was followed by a one hour hold period, whereupon the reaction was cooled, and filtered through 100 micron screening to a storage container. In all cases the resultant emulsion polymers were stable and contained little or no grit or settlement. Particle sizes as measured by hydrodynamic chromatography were all ranged from 50 to 60 nm in diameter, illustrating the small particle size polymer systems attainable with the present invention.

Table 1 shows the various levels of emulsion polymerization reactants A through G used to prepare this series of copolymers. Table 2 outlines some of the physical properties of the resulting polymers.

Table 1. Polymerization Scheme for Example 3 A-G Emulsion A B C D E F G % Stabilizer 10 10 10 10 10 10 10 CHARGE: Deionized Water (g) 137.4 137.4 137.4 137.4 137.4 137.4 137.4 Resin Solution from 100 100 100 100 100 100 100 ExampleI UQITIATOR Ammonium 1.15 1.15 1.15 1.15 1.15 1.15 1.15 CHARGE: Persulfate (g) Deionized Water (g) 10 10 10 10 10 10 10 FEED: Methyl Methacrylate 72 43.2 43.2 57.6 43.2 57.6 57.6 (g) 2-Ethylhexyl 43.2 28.8 72 32.4 50.4 54 43.2 Acrylate (g) Styrene (g) 28.8 72 28.8 54 50.4 32.4 43.2 Monomer Ratio 50/30/20 30/20/50 30/50/20 40/22/38 30/35/35 40/38/22 40/30/30 (MMA/EHA/Sty) FLUSH : Deionized Water (g) 10 10 10 10 10 10 10

Table 2. Physical Properties of Resin Stabilized Emulsion Polymer Example 3 A-G A B E F G % Stabilizer 10 10 10 10 10 10 10 % Solids 40. 4 40.2 40.2 38.4 39.6 40.0 40.3 pH 6.7 7.1 7.2 6.6 6.8 7.2 7.2 Viscosity 67 75 17 38 51 77 73 (Centipoise) Particle Size 57 48 48 50 48 48 49 (diameter in nm) Appearance a a a a a a- m@@@@@@@, @@settlement<BR> b Milky, settlement

Example 4 Modified Alpha Olefin/Maleic Anhydride Copolymer Stabilizer at Reduced Levels in Emulsion Polymerization To further illustrate the highly efficient nature of the modified polymers of the present invention as stabilizers in emulsion polymerization, a series of emulsion polymers were prepared with successively reduced levels of stabilizer level.

EmulsionPolymer A glass 1 liter 4 necked round bottomed flask equipped with mechanical agitation, thermometer with thermoregulator (Thermowatchs Instruments for Research and Industry, Inc., Cheltenham, PA), condenser, nitrogen purge line, mechanical feed pump, and heating mantle, was charged with deionized water and an aqueous modified resin solution as prepared in Example 1 above.

The solution was raised to 82 °C. A 10% solution of ammonium persulfate initiator in deionized water was added to the reactor, and a mixture of methyl methacrylate, 2-ethylhexyl acrylate, and styrene (weight percent ratio of 50MMA/30EHA/20S) was fed into the reactor over a 60 minute time period. Nitrogen was used as an inert gas purge throughout the reaction, and the temperature was maintained at 82 °C. The monomer addition period was followed by a one-hour hold period, whereupon the reaction was cooled, and filtered through 100 micron screening to a storage container. In all cases the resultant emulsion polymers were stable and contained little or no grit or settlement. Particle sizes as measured by hydrodynamic chromatography were all ranged from 50 to 65 nm in diameter.

Table 3 shows the various levels of emulsion polymerization reactants A through G used to prepare this series of copolymers. Table 4 outlines some of the physical properties of the resulting polymers.

Table 3. Polymerization Scheme for Example 4 A-E<BR> . Emulsion A B C D E % Stabilizer 10 8 6 4 2 CHARGE: Deionized Water (g) 137.4 149 216 233.5 249 Resin Solution from 100 79.4 75.9 49.7 24.3 Example1 INITIATOR Ammonium 1.15 1.15 1.5 1.5 1.5 CHARGE: Persulfate (g) Deionized Water (g) 10 10 10 10 10 FEED: Methyl Methacrylate 72 72 94 94 94 (g) 2-Ethylhexyl 43.2 43.2 56.4 56.4 56.4 Acrylate (g) Styrene (g) 28.8 28.8 37.6 37.6 37.6 Monomer Ratio 50/30/20 50/30/20 50/30/20 50/30/20 50/30/20 (MMA/EHA/Sty) FLUSH: Deionized Water (g) 10 10 10 10 10

Table 4. Physical Properties of Resin Stabilized Emulsion Polymer Example 4 A-E C D E % Stabilizer 10 8 6 4 2 % Solids 40.4 40.4 40.5 40.0 40.0 pH 6.7 6.6 6.6 6.6 4.0 Viscosity 67 75 17 38 51 (Centipoise) Particle Size57 54 59 62 65 (diameter in nm) _ Appearance a a a a a <BR> a Translucent, no settlement<BR> b Milky, settlement

Example 4 illustrates the small particle size polymer systems attainable with the present invention, even at very low levels of stabilizing resin. In addition, the Example illustrates the ability to prepare resin stabilized emulsion polymers at lowered pH's.

Example 5 Shear Stability of Modified Alpha Olefin/Maleic Anhydride Copolymer Stabilized Emulsion Polymers Polymer stabilized emulsion polymer systems are typically favored over systems using conventional surfactants for stabilization when shear stability is a significant consideration. Example 5 demonstrates that shear stability of the emulsion polymers prepared from the present invention retain the shear stability, even at the reduced levels of resin stabilizer.

Emulsion polymers from Example 1 A-G were subjected to shear stability testing. A laboratory blender with a 120 g capacity was charged with 100.0 grams of emulsion polymer. The cover was placed on the blender and the emulsion polymer was agitated rigorously on the highest setting of the blender for a designated time of 5 minutes. A shear stable material typically will remain fluid for the 5 minute interval. Instability is illustrated in viscosity rise, gelation and/or flocculation of the emulsion polymer.

Table 5 summarizes the shear stability testing. In all cases the shear stability of the resin stabilized emulsion polymers of the present invention surpassed the control polymer prepared with conventional surfactants.

Table 5. Shear Stability of Resin Stabilized Emulsion Polymer Example 5 A-H A B C D E F G H* % Stabilizer 10 10 10 10 10 10 10 3 % Solids 40.4 40.2 40.2 38.4 39.6 40.0 40.3 40.0 Shear Pass Pass Fail after Pass Fail after 3 Fail after Pass Fai ! after Stability 3 minutes minutes 3 minutes 20 seconds Test *Control Polymer, utilizing sodium lauryl sulfate stabilizer as conventional surfactant.

Example 6 Electrolyte Stability of Modified Alpha Olefin/Maleic Anhydride Copolymer Stabilized Emulsion Polymers Multivalent ions such as calcium, magnesium and manganese typically impart instability when introduced into typical resin stabilized emulsion polymer systems.

Multivalent ion stability is a desirable property.

Example 6 illustrates the capability of designing multivalent ion stability into the polymer systems of the present invention.

200 grams of deionized water is charged to a glass jar.

Emulsion polymers that were prepared using emulsion stabilizer from Example 2 were charged (. 52 grams of polymer solids), and 4.9 grams of a 5.7% solution of manganese sulfate was added with stirring.

Observations were made regarding flocculation/precipitation, clouding and settlement.

Table 6 summarizes the electrolyte stability testing.

Table 6. Electrolyte Stability of Resin Stabilized Emulsion Polymer Example 6 A-G Emulsion A B C D E F G % Stabilizer 10 ID 10 10 10 10 10 Monomer Ratio 50/30/20 30/20/50 30/50/20 40/22/38 30/35/35 40/38/22 40/30/30 MMA/EHA/Sty Electrolyte Translucent, Hazy No Translucent, Translucent, Translucent, Stability solution, Data no no no no settlement no settlement settlement settlement settlement settlement

In all cases, emulsion polymers prepared with conventional surfactant or unmodified alpha olefin/maleic anhydride copolymer stabilizers yielded immediate precipitation of polymer.

Other variations and modifications of this invention will be obvious to those skilled in this art. The present invention is not to be limited except as set forth in the following claims.