WO2001074915A1

WO2001074915A1 - Ampholytic polymer dispersion composition and method of use

Info

Publication number: WO2001074915A1
Application number: PCT/US2001/008103
Authority: WO
Inventors: Shih-Ruey T. Chen; Nichlolas Vozza; James E. Rak; Randy Loeffler
Original assignee: Calgon Corporation
Priority date: 2000-03-31
Filing date: 2001-03-14
Publication date: 2001-10-11
Also published as: AU4570301A; AR027757A1

Abstract

Disclosed are novel aqueous dispersions of ampholytic polymers. The dispersion pH of 2 to 6 allows the dispersion to contain high levels of the ampholytic polymer and remain pourable where similarly active solutions would be in a non-pourable gel form. The use of the novel aqueous dispersions of ampholytic polymer, in a cosmetically acceptable medium for the treatment of a keratin-containing substrate is also disclosed. The use of the novel aqueous dispersions of ampholytic polymers to thicken aqueous solutions as an additive in the manufacture of paper, as a component in drilling fluid compositions, as a component of cementing compositions and as an agent for waste water treatment is further disclosed.

Description

AMPHOLYTIC POLYMER DISPERSION COMPOSITION AND METHOD OF USE

FIELD OF THE INVENTION

The present invention relates to novel aqueous dispersions of ampholytic polymers and the process for preparing such aqueous dispersions.

The aqueous dispersions of ampholytic polymers are useful in personal care, waste water, paper processing and thickening applications.

BACKGROUND OF THE INVENTION

One of the problems that has confronted industry in the use of high molecular weight water-soluble polymers, or polyelectrolytes, is how to deliver the polymer into water so that it can be utilized for its intended purpose. Early water-soluble polymers were provided as dilute aqueous solutions. As the technology improved, and the molecular weights of the polymers became larger, it became increasingly difficult for manufacturers to ship these polymers in solution form because of the high viscosity of even one-half to one percent solutions of the polymers. Manufacturers accordingly started shipping the polymers in the form of drum dried pulverized solids, which could be dissolved into water using various mechanical means. While solving shipment problems, some mechanical means degraded the polymers through shear, and, incomplete dissolution of water-soluble polymers, the formation of swollen translucent particles or "fish eyes", often resulted. This led to a waste of polymer, and in some cases, detrimental results such as in the case of so called "fish-eye" particles, which, for example, caused defects in the manufacture of paper.

In the early 1970's water-in-oil emulsions of water soluble polymers were introduced. Using the water-in-oil technology, high molecular weight polymers that rapidly dissolved could be produced, and this technology achieved great acceptance in the water soluble polymer industry. A disadvantage of the water-in-oil emulsion polymer technology however is that the emulsions contain substantial quantities of hydrocarbon liquid. The introduction of hydrocarbon liquids into the systems where these water- soluble polymers are used is not always beneficial and, in some cases, not possible at all due to total organic carbon (TOC) restrictions for waste water discharges.

U.S. Pat. No. 4,929,655 and U.S. Pat. No. 5,006,590 issued to Kyoritsu Yuki Co. Ltd. describes and claims a method for the production of dispersions of water-soluble cationic polymers. These polymers were manufactured in an aqueous salt or brine solution in which the polymer was insoluble. The process yielded dispersions of high molecular weight polymers which when added to water would completely dissolve over a relatively short period of time. While an advance to the art, the invention was practical only for dispersions of cationically charged water-soluble polymers containing at least a portion of a hydrophobically modified cationic monomer.

US Patent No. 5,605,970 discloses and claims a method for the manufacture of a particular anionic water-soluble polymer in dispersion form. This disclosure teaches that certain anionic polymers, incorporating hydrophobically modified monomers, can be prepared using dispersion polymer methods. This patent specifically teaches the manufacture of acrylic acid-ethylhexylacrylate polymers. The ethylhexylacrylate monomer adds a hydrophobic character to the polymer, causing the polymer to become insoluble in certain brine solutions. While these polymers, and the methods for their manufacture are useful, the incorporation of a hydrophobic monomer into a water soluble polymer, where water solubility is desirable is not always advantageous in the final use of the polymer.

US Patent No. 5,837,776 discloses aqueous dispersions of water soluble nonionic and anionically charged vinyl and allyl addition polymers which are obtained by polymerizing in the presence of an anionically charged water-soluble polymer stabilizer in a saturated salt solution. While these polymers, and the methods for their manufacture are useful, the incorporation of the anionically charged water-soluble polymer stabilizer into various end uses can have a negative impact on the performance attributes of dispersed polymer leading to less than optimum performance. Also, the presence of so much salt in the resulting polymer solution has a negative effect on solution viscosity as well as polymer performance in some instances.

The polymers outlined above are used in many application areas due to the interaction of polyelectrolyte with substrates that carry a charge. The basic science that explains polymer - surface interactions can be applied to many end use applications, such as paper coating, conditioning hair and skin, waste-water clarification, suspension stabilization, as well as fluid loss control in oil field cementing and drilling operations.

For example; the surface properties of keratin are of interest in cosmetic science, and there has been a long-standing desire to discover ingredients, which will beneficially affect the topical and bulk condition of keratinous substrates, such as hair. The term "keratin" used herein refers to human or animal hair, skin and/or nails. For example, such ingredients must have adequate adherent properties, so that they are not only adsorbed initially, but are also retained on exposure to water. This property is referred to as "substantivity", i.e., the ability of a material to be adsorbed onto keratin, or in the case of hair, resisting removal by water rinse-off.

Hair is composed of keratin, a sulfur-containing fibrous protein. The isoelectric point of keratin, and more specifically of hair, is generally in the pH range of 3.2-4.0. Therefore, at the pH of a typical shampoo, hair carries a net negative charge. Consequently, cationic polymers have long been used as conditioners in shampoo formulations, or as a separate treatment, in order to improve the wet and dry combability of the hair. The substantivity of the cationic polymers for negatively charged hair along with film formation facilitates detangling during wet hair combing and a reduction in static flyaway during dry hair combing. Cationic polymers generally also impart softness and suppleness to hair.

When cationic polymers are added to shampoos (or to skin care products such as cleaning compositions) containing anionic surfactants, formation of highly surface active association complexes generally takes place, which imparts improved foam stability to the shampoo. Maximum surface activity and foam stability, or lather, are achieved at near stoichiometric ratios of anionic surfactant: cationic polymer, where the complex is least water soluble. Generally, cationic conditioners exhibit some incompatibility at these ratios. Compatibility gives a commercially more desirable clear formulation, while incompatibility leads to a haze or precipitation, which is aesthetically less desirable in some formulations.

^" In many situations, there is a trade off between high cationic charge content, which leads to good substantivity and the ability to formulate clear stable formulations. The need for a highly substantive water-soluble polymer that can be formulated into clear products is needed in the personal care industry.

In certain hair treatment applications, such as permanent waving and coloring hair, the use of common cationic conditioning polymers prior to treatment can lead to less than optimum performance. For example coloring can be uneven or the permanent wave will not hold its shape as desired. There remains a need in the hair treatment industry for an additive that will protect the hair with no adverse consequences.

Polyelectrolytes are also used in the paper-coating end of the papermaking process. Papermaking, as it is conventionally known, is a process of introducing an aqueous slurry of pulp or wood cellulosic fibers

(which have been beaten or refined to achieve a level of fiber hydration and to which a variety of functional additives can be added) onto a screen or similar device in such a manner that the water is removed, thereby forming a sheet of the consolidated fibers, which upon pressing and drying can be processed into dry roll or sheet form.

Paper, used for instance in offset printing, usually requires the additional step of applying a pigmented coating to the surface of the paper. A typical coating compositions for offset printing comprises 100 parts by weight of pigment, from 5 to 25, and preferably from 10 to 20, parts by weight of an adhesive, a water soluble polymer dispersing agent for the pigment, auxiliary agents and water to give a total solids concentration of about 60% by weight.

The adhesive is usually chosen from one or more of a protein derivative, a starch derivative, a cellulose derivative or a latex, and an example of a particular adhesive system would be 10 parts by weight of oxidized starch and 7 parts by weight of styrene-butadiene latex. The pigment would normally have a particle size distribution such that at least 80% by weight, and preferably at least 90% by weight, of its particles have an equivalent spherical diameter smaller than 2 micron in order to provide a coating of good gloss and brightness. The weight mean equivalent spherical diameter range for typical pigments suitable for offset coating compositions is from about 0.3 to about 0.8 micron. The water-soluble polymer dispersing agent for the pigment will typically be present at 0.1 to 2% of the paper coating composition and is required to prevent pigment settling prior to applying the coating to the paper surface. A coating composition intended for use in preparing a coated paper for offset printing generally comprises a hydrophilic polymer material, such as a starch derivative or a cellulose derivative, in order to increase the initial viscosity of the composition and thus inhibit the penetration of the aqueous phase of the composition into the paper web. In the absence of a viscosifying hydrophilic polymer material, as soon as the coating composition contacts the paper web, the aqueous phase tends to be absorbed into the body of the paper, with the result that the local concentration of solids in the composition is increased and the composition becomes so viscous that the shear forces to which it is exposed in the paper coating apparatus render it virtually incapable of passing through the narrow clearance which exists between the applicator device and the moving web. When the hydrophilic polymeric material is present, the surface of the paper web is effectively sealed, thus inhibiting further penetration of the aqueous phase into the paper.

The term "paper, as used herein, includes sheet-like masses and molded products made from natural sources, synthetics such as polyamides, polyesters, rayon and polyacrylic resins as well as from mineral fibers such as asbestos and glass. In addition, paper made from combinations of cellulosic and synthetic materials are applicable herein. Paperboard is also included within the broad term "paper".

In an ink jet recording method, recording is generally carried out by jetting fine drops of ink using a variety of mechanisms so as to form images on a recording paper. Therefore, the recording method of ink jet type has advantages in that it is less noisy, can provide full-color prints with ease and enables high-speed printing, compared with the recording method of dot impact type.

For the paper used in such an ink jet recording method, it is usually required to have properties of (1) ensuring high-speed drying of ink, (2) being free from cissing, feathering and overflowing of ink, (3) providing recorded images of high optical density, and (4) causing no rippling trouble upon absorption of ink.

In addition, ink jet printers have had remarkable development in recent years, so that they have come to ensure considerable colorfulness and vividness in the recorded images. Thus, recording media also have been required to be higher grade merchandise. As matters now stand, it is known that higher grade recorded image which can give such a feeling of higher quality as those provided by photography or high grade printed matter can be obtained by choosing a recording medium having a glossy surface. However, the need for reduction in running cost has also grown in proportion as prices of ink jet printers have declined. Since most of glossy recording media on the market use as their substrates more expensive materials, such as plastic films or laminated papers, they cannot meet the aforesaid need.

In contrast to the recording media on the market in which films or the like are used as substrate, cast-coated paper uses low-priced paper as a substrate and can be prepared in a relatively simple process, so that it has the advantage of a substantially lower cost. Further, as the recording side of cast- coated paper can be rendered glossy, the cast-coated paper is suitable for ink jet recording paper which can give a feeling of high quality and can provide high grade recorded images at a lower price.

High grade ink jet images depend on the formation of "dots" that contrast sharply with the color of the paper. If the ink jet dyes "wick into the paper with the ink vehicle, "fuzzy" dot boundaries result and color intensity is decreased. There remains a need for a material that will substantively bind dye or pigment particles to the surface of ink jet printed paper so that sharply contrasting intense dots are formed.

Another area in which polyelectrolytes provide benefit is in drilling fluids. It is well known that in perforating earthen formations to tap subterranean deposits such as gas or oil, that perforation is accomplished by well drilling tools and a drilling fluid. These rotary drilling systems consist of a drilling bit fitted with appropriate ^'teeth^', then a set of pipes assembled rigidly together end to end, the diameter of which is smaller than that of the drilling bit. This whole rigid piece of equipment, drill bit and drill pipe string, is driven into rotation from a platform situated above the well being drilled. As the drill bit attacks and goes through the geological strata, the crushed mineral materials must be cleared away from the bottom of the hole to enable the drilling operation to continue. Aqueous clay dispersion drilling fluids are recirculated down through the hollow pipe, across the face of the drill bit, and upward through the hole. The drilling fluid serves to cool and lubricate the drill bit, to raise the drilling cuttings to the surface of the ground, and to seal the sides of the well to prevent loss of water and drilling fluids into the formation through which the drill hole is being bored. After each passage through the well, the mud is passed through a settling tank or trough wherein the sand and drill cuttings are separated, with or without screening. The fluid is then again pumped into the drill pipe by a mud pump.

Some of the most serious problems encountered in producing and maintaining effective clay-based aqueous drilling fluids are caused by the interaction of the mud with the earth formation being drilled. These interactions include contamination of the mud by formation fluids, incorporation into the mud of viscosity producing and inert drilled solids, chemical contamination by drilled solids, or by the infiltration of sea-water and/or fresh water. The conditions of high temperature and pressure inherent with deeper and deeper drilling operations, together with formation interactions, make drilling fluid behavior unreliable and difficult to reproduce.

Characteristics of an ideal drilling fluid would then include the following:

• To have Theological characteristics as desirable as possible to be able to transport the mineral cuttings set in dispersion.

• To allow the separation of cuttings by all known means as soon as the mud flows out of the hole.

• To have such required density as to exert sufficient pressure on the drilled geological formations.

• To retain its fundamental Theological qualities as it is submitted, in very deep drilling, to higher and higher temperatures. Polyelectrolytes are also used in oil field cementing operations. Hydraulic cement compositions are used for carrying out various operations in oil, gas and water wells including, but not limited to construction and completion operations such as primary cementing and remedial operations such as squeeze cementing. Primary cementing involves the placement of a hydraulic cement composition into the annular space between the walls of a well bore and the exterior of a pipe such as casing disposed therein. The cement composition is pumped into the annular space and allowed to set into an annular cement sheath therein whereby the pipe is bonded to the walls of the well bore by the set cement.

As used herein, the term "cement" refers to portland cement, concrete and other mixtures of calcium oxide and sand.

Squeeze cementing techniques usually involve the undesirable movement of oil, gas or water through small holes or cracks in pipe disposed in the well bore; holes, cracks, voids or channels in the annular cement sheath between the pipe and the well bore; annular spaces between the cement sheath and the pipe or the walls of the well bore and permeable zones or fractures in subterranean formations. Such holes, cracks, etc. are plugged by squeezing hydraulic cement compositions therein which harden and form impermeable plugs.

In performing cementing operations in such wells, the cement compositions are often subjected to high temperatures, particularly when the cementing is carried out in deep subterranean zones. The high temperatures can cause premature setting of the cement compositions, i.e., the compositions can not be pumped for long enough times before setting to place them in the zones to be cemented. This requires the use of set retarding additives in the cement compositions which extend the setting times of the compositions so that adequate pumping time is provided in which to place or displace the compositions into desired subterranean zones. In all of the applications outlined above, polymers have been used to improve the properties of the substrate or minimize adverse consequences. For example if the substrate is hair, polymers have been used to improve the detangling and combing of hair after shampooing. Polymers are added to waste-water, as in the case of raw sewage for instance, to coagulate and flocculate solid matter and separate it from the carrier liquid. During paper manufacture, polymers are used to provide faster dewate ng of the sheet, which leads to faster, more economical machine utilization. Polymers are also added during paper manufacture to improve the strength, or resistance to tearing, of the resulting sheet. Polymers are also added to paper coatings to improve the gloss of the sheet and to provide a surface that results in fast drying well defined dots from the ink jet printing process. Polymers are added to drilling fluids and cementing compositions to aid in performance and minimize water loss to the surrounding rock formation. In all of these applications, the polymer must be substantive to the substrate,' meaning that it will adhere or adsorb onto the substrate surface and not be easily removed. Although many polymers are used in the aforementioned applications, there still remains a shortcoming in that high molecular weight polymers are either supplied in a difficult to handle dry from or are dispersed in an undesirable hydrocarbon liquid or saturated salt solution.

SUMMARY OF THE INVENTION

The composition according to the present invention is an aqueous dispersion of an ampholytic polymer that comprises: (A) about 50% to about 99%, by weight water;

(B) about 1% to about 50%, by weight of an ampholytic polymer; and

(C) about 0% to about 0.5% by weight of a preservative; wherein the dispersion has a pH of from about 1 to about 6 and has a bulk viscosity at 25°C of less than 100,000 cps and wherein the ampholytic polymer of (B) comprises: about 1% to about 45%, on a molar basis, of one or more cationic monomers selected from the group consisting of (a) diallyl dialkyl ammonium halides of the general formula:

wherein R¹ is independently an alkyl group from Ci to C₃₆ and X^" is a halide, (b) substituted acrylamides of the general formula:

CH, CR²

C = 0

NH

I

R³

N⁺R¹ ₃ X-

wherein R¹ and X^" are as defined above, R² is H, methyl or ethyl, and R³ is a linear or branched alkyl C₂ to Cι₂ group, and (c) substituted acrylates of the general formula: CH, CR²

R³

N⁺R¹ ₃ X wherein R¹, R², R³, and X^" are as defined above;

(ii) about 1% to about 80%, on a molar basis, of one or more anionic monomers selected from the group consisting of acrylic acid (AA), methacrylic acid (MAA), acrylamidomethyl propane sulfonic acid (AMPSA), methacrylamidomethyl propane sulfonic acid (MAMPSA), crotonic acid (CA), maleic acid (MAH), sodium vinyl sulfonate (SVS), acrylamidoglycolic acid (AGiy), acrylamidomethyl butanoic acid (AMBA) and styrene sulfonic acid (SSA);

(iii) about 0% to about 90%, on a molar basis, of one or more non-ionic monomers selected from the group of acrylamide (Am), methacrylamide (MAm), n-alkyl acrylamide (NAAm), n-alkyl methacrylamide (NAMAm), vinyl pyrrolidone (VP), vinyl acetate (VP), vinyl alcohol (VOH), alkyl esters of acrylic acid and alkyl esters of methacrylic acid.

The method according to the present invention is a method of producing the aqueous dispersion of an ampholytic polymer above and comprises the steps of:

(I) adding the monomers (i), (ii), and any (iii) to water;

(II) assuring that the pH of the mixture above is between 1 and 6 inclusive;

(III) assuring that the mixture is at an appropriate temperature; and

(IV) adding polymerization initiators in the essential absence of oxygen to polymerize the mixture forming a dispersion of polymer in water.

The composition above can be added to various aqueous systems to improve the performance of such systems. These systems comprise keratin treating systems, drilling muds, paper furnishes, cementing compositions, and waste water clarification systems. The above composition can also be added to various aqueous systems as a thickener.

DETAILED DESCRIPTION OF THE INVENTION

The aqueous dispersion of an ampholytic polymers of the present invention and compositions containing such polymers are novel and unexpected due to the unique ability for these dispersions to deliver relatively high active polymer from an aqueous carrier which is substantially free of salts and/or hydrocarbon liquids. Specifically, it has been found that the monomers used in making the ampholytic polymers of the invention are soluble in water, however, when the polymerization is performed at a low pH (less than 6), the resulting polymer precipitates and forms an aqueous dispersion without the aid of saturated salt solution or hydrocarbon liquids. This feature unexpectedly permits the preparation of dispersions of such high solid content i.e. as high as 50% based on weight.

In the process of dispersion polymerization, the monomer and the initiator are both soluble in the polymerization medium, but the medium is a poor solvent for the resulting polymer. Accordingly, the reaction mixture is homogeneous at the onset, and the polymerization is initiated in a homogeneous solution. Depending on the solvency of the medium for the resulting oligomers or macroradicals and macromolecules, phase separation occurs at an early stage. This leads to nucleation and the formation of primary particles called "precursors". The particles are believed to be swollen by the polymerization medium and/or the monomer, leading to the formation of spherical particles having a size in the region of about.0.1-10.0 microns.

In any dispersion polymerization, the variables that are usually controlled are the monomer and the initiator, solvency of the dispersion medium, and the reaction temperature. It has been found that these variables can have a significant effect on the particle size, the molecular weight of the final polymer particles, and the kinetics of the polymerization process. For the ampholytic polymer dispersions of this invention, it has surprisingly been found that the pH of the aqueous medium is determining variable for polymer solubility and, therefore, for the dispersion polymerization process.

The pH affects the solvency of the aqueous dispersion medium for the resulting polymer. As the solvency of the dispersion medium increases, (a) the oligomers will grow to a larger MW before they become a precursor nuclei, (b) the anchoring of the stabilizer moiety will probably be reduced and (c) the particle size increases. As the initiator concentration is increased, it has been observed that the final particle size increases. As for the kinetics, it is reported that when the dispersion medium is a non-solvent for the polymer being formed, then the locus of polymerization is largely within the growing particles and the system follows the bulk olymerization kinetics, n (the kinetic chain length)=R_p /R_t, where R_p is the propagation rate and R_t is the termination rate. As the solvency of the dispersion medium for the growing polymer particle is increased, polymer growth proceeds in solution. The polymeric radicals that are formed in solution are then captured by growing particles. Consequently, the locus of the particle polymerization process changes and there is a concomitant change in the kinetics of polymerization. While earlier attempts have attempted to manufacture dispersion polymers of anionic or nonionic monomers through the incorporation of monomers having a hydrophobic character or through the use of saturated salt solutions, we have found that ampholytic water soluble dispersion polymers can be prepared which are stable, of high molecular weight, and which do not necessarily contain monomers having a hydrophobic character or rely on high salt levels in the aqueous medium.

Accordingly, this invention is directed to the manufacture of ampholytic water soluble polymers, in dispersion form, which do not necessarily require the inclusion of a hydrophobically modified monomer or saturated salt solution. This invention is directed to a composition, and method for the manufacture of high molecular weight, ampholytic, water soluble vinyl addition polymers in aqueous dispersion form. The unique aspect of the polymers of this invention is that the polymers are prepared without the inclusion of a monomer which would decrease the water solubility of the resultant polymer material, that is to say that there is no inclusion of a monomer which would have hydrophobic characteristics. As a result of the invention, aqueous dispersions of water soluble ampholytic polymers can be prepared without the inclusion of a hydrophobic monomer component or saturated salt solution component.

The method of producing an aqueous dispersion of an ampholytic polymer according to the present invention comprises the steps of:

(I) adding the monomers (i), (ii), and any (iii) to water;

(II) assuring that the pH of the mixture above is between 1 and 6 inclusive;

(III) assuring that the mixture is at an appropriate temperature; and (IV) adding polymerization initiators in the essential absence of oxygen to polymerize the mixture forming a dispersion of polymer in water.

The method according to the present invention preferably entails a further step of adding a preservative to the dispersion when the temperature is less than about 50° C. The preparation is generally conducted at a pH between about 1 and about 6 but this pH is more preferably between about 2 and about 5, with a pH of about 2 to about 4.5 being most preferred.

The novel aqueous dispersions of ampholytic water-soluble polymers of the present invention comprises:

(A) about 50% to about 99%, preferably about 55% to about 90%, and most preferably about 60% to about 84.99%, by weight water;

(B) about 1 % to about 50%, preferably about 10% to about 45%, and most preferably about 15% to about 40% by weight of an ampholytic polymer; and .

(C) about 0% to about 0.5%, preferably 0% to about 0.4%, and most preferably about 0.01 % to about 0.35% by weight of a preservative.

The dispersion of the present invention preferably has a bulk viscosity at 25°C of less than 100,000 cps, more preferably less than 70,000 cps, and most preferably less than 50,000 cps.

The ampholytic polymer of (B) comprises:

(i) about 1% to about 45%, preferably from about 5% to about 40% (ii) and most preferably from about 15% to about 40%, on a molar basis, of one or more cationic monomers selected from the group consisting of (a) diallyl dialkyl ammonium halides of the general formula:

H₂C CH,

CH, CR²

C = 0

NH

I

R³

N⁺R¹, X-

wherein R¹ and X^' are as defined above, R² is H, methyl or ethyl, and R³ is a linear or branched alkyl C₂ to C₁₂ group, and (c) substituted acrylates of the general formula: CH, CR² c = o

R³

N⁺R¹ ₃ X

wherein R¹, R², R³, and X^" are as defined above;

(iii) about 1 % to about 80%, preferably about 5 to about 70%, and most preferably about 10 to about 65%, on a molar basis, of one or more anionic monomers selected from the group of acrylic acid (AA), methacrylic acid (MAA), acrylamidomethyl propane sulfonic acid (AMPSA), methacrylamidomethyl propane sulfonic acid (MAMPSA), crotonic acid (CA), maleic acid (MAH), sodium vinyl sulfonate (SVS), acrylamidoglycolic acid (AGIy), acrylamidomethyl butanoic acid (AMBA) and styrene sulfonic acid (SSA); (iv)from about 0% to about 90%, preferably from about 5% to about 80%, and most preferably from about 10 to about 75%, on a molar basis, of one or more non-ionic monomers selected from the group of acrylamide (Am), methacrylamide (MAm), n-alkyl acrylamide

(NAAm), n-alkyl methacrylamide (NAMAm), vinyl pyrrolidone (VP), vinyl acetate (VP), vinyl alcohol (VOH), alkyl esters of acrylic acid and alkyl esters of methacrylic acid.

The weight average molecular weight of said polymer, as measured by viscometry, is preferably from about 1 ,000 to 10,000,000, more preferably from 10,000 to 8,000,000 and most preferably from 50,000 to 7,000,000.

The mole ratio of i):ii) is from 1 :25 to 1 :1 , preferably 1 :10 to 1 :1 , and most preferably 1 :5 to 1 :1.1.

The preservative (C) is selected from the list of methyl paraben, propyl paraben, butyl paraben, , benzoic acid and its corresponding sodium, potassium and ammonium salts, chloromethyl isothiazoiinone and methyl isothiazolinone, DMDM Hydantoin, imidazolidinyl urea, Quaternium 15, diazolinyl urea, bromo nitro propane diol, formaldehyde, sorbic acid and its corresponding sodium, potassium and ammonium salts, and dibromodicyanobutane.

It is also an object of this invention to provide a novel method for the preparation of the aqueous dispersions of ampholytic water-soluble polymers. The water-soluble polymer dispersions may be prepared by conventional solution polymerization techniques, as indicated below. Thus, to prepare the instant polymers the appropriate weights for the desired mol percentages of i), ii), and iii are charged to a glass reactor equipped with a stirring means. The desired amount of water is then added to the reactor with vigorous stirring to give the desired total monomer concentration, which is generally about 5-50% by weight. The monomer mixture may then be adjusted to a pH of about 2.0 to about 6.0 with dilute NaOH, heated to an appropriate initiation temperature, and purged with nitrogen for at least thirty minutes. Polymerization is then initiated by adding a free radical initiator. After the peak exotherm is reached, additional dilution water and sodium bisulfite are added to scavenge any unreacted monomers.

Any free radical initiator may be used, examples include peroxides, azo initiators and redox systems. The polymerization may also be initiated photochemically. The preferred catalysts are sodium persulfate or a mixture of ammonium-persulfate and any azo type initiator, such as 2,2'-azobis-(2,4- dimethyl-4-methoxyvaleronitrile), 2,2'-azobisisobutyronitrile or 4,4'-azobis(4- cyanovaleric acid). The polymerization is characterized by the fact that it begins as a clear, colorless solution and becomes hazy to cloudy as the polymerization progresses and the dispersed polymer phase forms. The final dispersion is milky in appearance and free flowing.

A preferred composition for the ampholytic polymer (B) in the aqueous dispersion of water-soluble ampholytic polymer of the present invention comprises wherein the ampholytic polymer (B) is comprised of monomers of (i) cationic monomers that are selected from the group consisting of (a) diallyl dimethyl ammonium chloride and (b) methacrylamidopropyl trimethyl ammonium chloride; (ii) anionic monomers selected from the group consisting of acrylic acid, methacrylic acid and acrylamidomethylpropane sulfonic acid; and (iii) nonionic monomers selected from the group consisting of acrylamide, methyl acrylate and stearyl methactylate.

A particularly preferred composition for the ampholytic polymer (B) in the aqueous dispersion of water-soluble ampholytic polymer of the present invention is 30 mol % of diallyl dimethyl ammonium chloride as cationic monomer (i), 35 mol % of acrylic acid as anionic monomer (ii), and 35 mol % of acrylamide as nonionic monomer (iii).

Cosmetically Acceptable Media

The aqueous dispersions of water-soluble ampholytic polymers of the present invention are used as compositions for treating hair, skin and nails by incorporating them in a cosmetically acceptable medium in amounts of from 0.1-10% by weight of said terpolymer, and preferably in an amount of from 0.5 to 5% by weight of said water soluble polymer.

These compositions can be presented in various forms, i.e., various cosmetically acceptable media, such as a liquid, cream, emulsion, gel, thickening lotion or powder; they can contain water and also any cosmetically acceptable solvent, in particular monoalcohols, such as alkanols having 1 to 8 carbon atoms, like ethanol, isopropanol, benzyl alcohol and phenylethyl alcohol, polyalcohols, such as alkylene glycols, like glycerins, ethylene glycol and propylene glycol, and glycol ethers, such as mono-, di- and tri-ethylene glycol monoalkyl ethers, for example ethylene glycol monomethyl ether, ethylene glycol monomethyl ether and diethylene glycol monomethyl ether, used singly or in a mixture. These solvents can be present in proportions of up to as much as 70% by weight, relative to the weight of the total composition.

These compositions can also be packaged as an aerosol, in which case they can be applied either in the form of an aerosol spray or in the form of an aerosol foam.

As the propellant gas^{^}for these aerosols, it is possible to use, in particular, dimethyl ether, carbon dioxide, nitrogen, nitrous oxide and volatile hydrocarbons, such as butane, isobutane, propane and, possibly, chlorinated and fluorinated hydrocarbons, although the latter are falling into increasing environmental disfavor.

Preferred compositions can also contain electrolytes, such as aluminum chlorhydrate, alkali metal salts, e.g., sodium, potassium or lithium salts, these salts preferably being halides, such as the chloride or bromide, and the sulphate, or salts with organic acids, such as the acetates or lactates, and also alkaline earth metal salts, preferably the carbonates, silicates, nitrates, acetates, gluconates, pantothenates and lactates of calcium, magnesium and strontium.

These compositions can also be presented in the form of a powder or of lyophilisates to be diluted before use.

The compositions according to the present invention can contain any other ingredient normally used in cosmetics, such as perfumes, dyestuffs which can serve to color the composition itself or the fibres of the hair, preservatives, sequestering agents, thickeners, silicones, softeners, foam synergistic agents, foam stabilisers, sun filters, peptising agents and also anionic, non-ionic, cationic or amphoteric surface-active agents or mixtures thereof.

These compositions can be used, in particular, in the form of a shampoo, a rinsing lotion, a cream or a treatment product which can be applied before or after coloring or bleaching, before or after shampooing, before or after perming or before or after straightening, and can also adopt the form of a coloring product, a setting lotion, a brushing lotion, a bleaching product, a perming product or a straightening product.

A particularly preferred embodiment consists of use in the form of a shampoo for washing the hair.

In this case, these compositions contain anionic, cationic, nonionic or amphoteric surface-active agents typically in an amount from 3 to 50% by weight, preferably 3 to 20%, and their pH is 3 to 10, preferably 4 to 9 and most preferably 4.5 to 8.5.

A list of the surface-active agents, which can be used according to the invention, is given in U.S. Pat. Nos. 4,240,450; 4,445,521 ; and 4,719,099.

Another preferred embodiment consists of use in the form of a rinsing lotion to be applied mainly before or after shampooings. These lotions are typically aqueous or aqueous-alcoholic solutions, emulsions, thickened lotions or gels. If the compositions are presented in the form of an emulsion, they can be nonionic, anionic or cationic. The nonionic emulsions consist mainly of a mixture of an oil and/or a fatty alcohol with a polyoxyethyleneated alcohol, such as polyoxyethyleneated stearyl or cetyl/stearyl alcohol, and cationic surface-active agents can be added to these compositions. The anionic emulsions are formed essentially from soap.

If the compositions are presented in the form of a thickened lotion or a gel, they contain thickeners in the presence or absence of a solvent. The thickeners which can be used are especially carbopol, xanthan gums, sodium alginates, gum arabic and cellulose derivatives, and it is also possible to achieve thickening by means of a mixture of polyethylene glycol stearate or distearate or by means of a mixture of a phosphoric acid ester and an amide. The concentration of thickener is suitably 0.05 to 15% by weight. If the compositions are presented in the form of a styling lotion, shaping lotion or setting lotion, they generally comprise, in aqueous, alcoholic or aqueous- alcoholic solution, the aqueous dispersions of water-soluble ampholytic polymers defined above.

If the compositions of the invention are intended for use in the dyeing of keratin fibres, and in particular human hair, they contain at least one oxidation dyestuff precursor and/or one direct dyestuff, in addition to the aqueous dispersion of water-soluble ampholytic polymers. They can also contain any other adjuvant normally used in this type of composition.

The pH of the dyeing compositions is generally 7 to 11 , and can be adjusted to the desired value by adding an alkalizing agent.

The composition according to the present invention can also be used for waving or straightening the hair. In this case, the composition contains, in addition to the aqueous dispersion of water-soluble ampholytic polymer, one or more reducing agents and, if appropriate, other adjuvants normally used in this type of composition; such compositions are intended for use conjointly with a neutralizing composition.

The composition according to the present invention can also be used for skin care products such as those that are primarily "leave on" formulations such as moisturizing lotions, emulsions and creams and sunscreen formulations. Other skin care products would include "rinse off' formulations such as bar soaps, liquid hand soaps, disinfecting soaps and shower gels. These "rinse off' formulations can be comprised of a variety of surfactants as outlined above, alkali salts of fatty acids (soaps) or combinations of each.

In another embodiment of this invention, a process is provided for in which paper or paperboard having improved properties is made by forming an aqueous cellulosic paper furnish which comprises adding to the furnish an effective amount, based on the dry weight of the solids of the furnish, of aqueous dispersion of an ampholytic polymer, as described above. This amount can typically be from 0.1 to 25 pounds per ton on a dry basis, based on furnish.

The aqueous dispersions of water-soluble ampholytic polymers of the instant invention can generally be successfully added to aqueous cellulosic furnishes over the entire pH range customarily employed in the papermaking process. Preferably, the composition of the instant invention is added to aqueous cellulosic furnishes having a pH from about 3 to 10. Therefore, it will be appreciated by those skilled in the art that the composition of the instant invention may be added to aqueous cellulosic paper furnishes that are acid, alkaline, or neutral in character. It will be understood by those skilled in the art that generally an acid furnish has a pH range from about 3.0 to 5.5, an alkaline furnish has a pH range from about 7.0 to greater than about 10.0, and a neutral furnish has a pH range of from about 5.5 to 7.0.

The instant invention is also directed to a method for drilling a well in a subterranean formation comprising circulating into the well, during drilling an aqueous drilling fluid, the improvement wherein said aqueous drilling fluid comprises: (a) an aqueous clay dispersion; and

(b) the above-described aqueous dispersion polymer.

The clay dispersion may be any finely divided solid which is capable of being dispersed or suspended in an aqueous liquid vehicle. Ordinarily, such material will include hydratable clay or colloidal clay bodies such as Wyoming bentonite, commercial medium-yield drilling clays mined in various parts of the country such as in Texas, Tennessee and Louisiana, and those produced when clay subsurface formations are drilled. Weighting materials added to increase specific gravity such as barites, iron oxide, and the like may also be included.

The aqueous medium may be fresh water such as is obtained from wells or streams; it may be salt water from the sea or from wells; or, it may even include oil-in-water emulsions, i.e., water which has become contaminated in some way with small quantities of oil, or to which such oil has been added to gain some desired advantage. The polymers of the instant invention were found to be particularly effective in salt water and to be stable at high temperature. The drilling mud containing the polymers of the instant invention show both good filtration and rheology properties.

It is contemplated that the drilling muds of the invention may also contain other additives besides the polymers of the invention. Materials such as caustic, quebracho, lime and the like may be added to the drilling mud at the surface while other materials such as gypsum, shale and the like may be encountered in subsurface formations during drilling operations.

When employed in accordance with the invention, the polymer may be added directly to the drilling mud as a dry powder, as a slurry suspended in a suitable liquid, or as a solution in water or some other suitable solvent, and they may be incorporated therein at any convenient point in the mud circulation system. It may be desirable to employ a mixing device such as a cone and jet mixer or the equivalent for incorporating the additive in the mud.

The present invention is also directed to cementing compositions that are useful in oil, gas and water well cementing operations since such compositions have reduced fluid loss to the surrounding formation. Such compositions are used to cement a conduit penetrating a permeable earthen formation via introducing such composition into the space between such conduit and such formation and allowing the composition to harden. These cementing compositions for use in oil, gas and water well cementing operations comprise water, hydraulic cement, and the branched ampholyte polymer of the present invention.

The present invention is also directed to a method for clarifying waste water containing turbidity-causing components which comprises: a) adding to said water an effective turbidity-reducing amount of the aqueous dispersion of water-soluble ampholytic polymers; b) mixing said aqueous dispersion polymer and said water with a mechanical stirring device for sufficient time to allow flocculation of the turbidity-causing components; and then c) separating the flocculated turbidity-causing components from the waste water to obtain clarified water.

The present invention can also be used to thicken aqueous solutions. The thickening action is accomplished by adding the aqueous dispersion of ampholytic polymer composition described above to an aqueous solution and subsequently raising the pH of the aqueous solution above pH 6. The ampholytic polymer will completely solubilize with the higher pH and increase the viscosity of the aqueous solution.

EXAMPLES Example 1

Preparation of a water-soluble polyampholyte dispersion Procedure for Preparing Water-Soluble Polyampholyte Dispersion Equipment:

Polymerization/Dilution

2-1 Dewar Flask 2-1 Resin Kettle

Condenser Condenser

Nitrogen with flowmeter Nitrogen with flowmeter

Two-turbine mixer Three turbine mixer

Thermometer Thermometer

Constant Temperature Variac

Materials:

Polymerization Dilution

180 g 50% Aqueous Acrylamide 600 g 20% polymer gel

272.73 g 66% AqueousDMDAAC 190 g Dl Water

90 g Glacial Acrylic Acid 7.5 g Sodium Metabisulfite qs to 1800g Dl Water 1.5 g Methyl Paraben

0.15 g Sodium EDTA 0.3 g Propyl Paraben

1.5 g Salicylic Acid qs to pH 3.1 50% Sodium Hydroxide

0.4 g Sodium Persulfate

0.0076g SMBS

0.00076g CuS0₄

0.76 g Versenex 80 (pH = 6.5) Procedures:

In a 2,000 mL beaker are mixed acrylamide solution, DMDAAC solution, glacial acrylic acid, EDTA, salicylic acid and Dl water. To the reaction mixture a 50% sodium hydroxide is added at ambient temperature until pH of 3.1 is reached. The solution is then heated to 60°C and poured into the 2-I Dewar flask; then a 1.0 SCFM nitrogen purge is begun. After the solution cools to 55°C (about 30 minutes) the Versenex 80, followed by SMBS/CuSO₄ solution and sodium persulfate solution are added. After the solution exotherms to 57°C (about 20 minutes), the agitation is stopped and the nitrogen line lifted to blanket and reduced to 0.1 SCFM. The reaction exotherms at about 92°C. after about 100 minutes. The resulting gel is allowed to set overnight. Then, 600 g of the 20% polymer gel is removed for dilution and charged to a 2-I resin kettle to which Dl water is added, mixed and heated to 80°C.

Nitrogen is blanketed at 0.1 SCFM, and then SMBS is added as a 10% solution and mixed into the diluted gel. Methyl and propyl paraben are dissolved in 100 g of Dl water, dissolved and heated to 80°C. This solution is then added to the diluted polymer gel. This final solution is stirred overnight at 70°C. and decanted to give the final product. The final 15% active solution was milky white in appearance and had a viscosity (25°C) of 8,600 cps.

Example 2

Preparation of a conventional polyampholyte solution

Procedure for Preparing a Polyampholyte Solution Polymer

Equipment: as detailed in Example 1 above. Materials:

Polymerization Dilution

180 g 50% Aqueous Acrylamide 600 g 20% polymer gel

272.73 g 66% AqueousDMDAAC 890 g Dl Water

90 g Glacial Acrylic Acid 7.5 g Sodium Metabisulfite qs to 1800g D I Water 1.5 g Methyl Paraben

0.15 g Sodium EDTA 0.3 g Propyl Paraben

1.5 g Salicylic Acid qs to pH 6.5 50% Sodium Hydroxide

0.4 g Sodium Persulfate

0.0076g SMBS

0.00076g CuS0₄

0.76 g Versenex 80 (pH = 6.5)

Procedures:

In a 2,000 mL beaker are mixed acrylamide solution, DMDAAC solution, glacial acrylic acid, EDTA, salicylic acid and Dl water. To the reaction mixture a 50% sodium hydroxide is added at ambient temperature until pH of 6.5 is reached. The solution is then heated to 60°C and poured into the 2-I Dewar flask; then a 1.0 SCFM nitrogen purge is begun. After the solution cools to 55°C (about 30 minutes) the Versenex 80, followed by SMBS/CuSO₄ solution and sodium persulfate solution are added. After the solution exotherms to 57°C (about 20 minutes), the agitation is stopped and the nitrogen line lifted to blanket and reduced to 0.1 SCFM. The reaction exotherms at about 92°C. after about 100 minutes. The resulting gel is allowed to set overnight. Then, 600 g of the 20% polymer gel is removed for dilution and charged to a 2-I resin kettle to which Dl water is added, mixed and heated to 80°C.

Nitrogen is blanketed at 0.1 SCFM, and then SMBS is added as a 10% solution and mixed into the diluted gel. Methyl and propyl paraben are dissolved in 200 g of Dl water, dissolved and heated to 80°C. This solution is then added to the diluted polymer gel. This final solution is stirred overnight at 70°C. and decanted to give the final product. The final 8% active solution was clear and water white in appearance and had a viscosity (25°C) of 11 ,200 cps. Examples 1 and 2 demonstrate the handling advantage of the dispersion form of the polyampholyte compared with the solution form. The higher solids and lower viscosity make the dispersion form more economical to use and easier to handle.

Example 3 The polymers of Example 1 and 2 were tested in a typical Shampoo.

TABLE 1 Wet Comb

Total Work (mJ)

The lower total work required for the shampoo using the polymer of Example 1 compared with the total work required for the shampoo using the polymer of Example 2 indicates that the polymer of Example 1 performs suprisingly better as a conditioner for hair.

Example 4 An aqueous clay based drilling mud is prepared using the polymer of Example 1 as outlined in Table 2.

Table 2 Clay Based Gypsum Drilling Mud

Ingredient Percent (w/w %)

Water 86.0

Bentonite 3.5

Rev Dust 7.5 Gypsum 1.0

Lignonsulfate 1.0

Polymer of Example 1 0.5

Caustic 0.5

The clay based gypsum drilling mud is aged for 16 hours at 325 °F and then cooled. The resulting API filtrate reading is lower for the formula of the example when compared to a corresponding clay based gypsum drilling mud without polymer.

Example 5 A cementing composition is prepared using the polymer of Example 1 as outlined in Table 3.

Table 3

Cementing Composition

Ingredient Percent (w/w %)

Water 46.0

Class H Cement 43.0

Polymer of Example 1 1.0

The cementing composition is mixed into a slurry. The resulting API filtrate reading (30 minute, 125 °F, 1 ,000 psi) is lower for the formula of the example when compared to a corresponding cementing composition without polymer.

Example 6 This example demostrates the ability of the water-soluble ampholytic polymer dispersion of Example 1 to thicken water. An 11% active solution of the polymer of Example 1 was prepared and pH increased by adding sodium hydroxide solution. The viscosity of the solution was measured at 30°C for each pH.

Table 4 pH Viscosity Appearance

3.5 416cps milky white

4.0 1 ,912cps hazy white

5.5 9,220cps clear

7.3 15,900cps clear

11.4 17,800cps clear

Claims

WHAT IS CLAIMED IS:

1. An aqueous dispersion of an ampholytic polymer comprising:

(A) about 50% to about 99%, by weight water;

(B) about 1% to about 50%, by weight of an ampholytic polymer; and

(C) about 0% to about 0.5% by weight of a preservative; wherein the dispersion has a pH of about 1 to about 6 and a bulk viscosity at 25°C of less than 100,000 cps and wherein the ampholytic polymer of (B) comprises:

(i) about 1% to about 45% of one or more cationic monomers selected from the group consisting of (a) diallyl dialkyl ammonium halides of the general formula:

wherein R¹ is independently an alkyl group from C-i to C₃₆ and X^" is a halide, (b) substituted acrylamides of the general formula:

CH, CR²

C = 0

NH

R³

N⁺R¹ ₃ X-

wherein R and X^" are as defined above, R² is H, methyl or ethyl, and R³ is a linear or branched alkyl C₂ to C₁₂ group, and (c) substituted acrylates of the general formula:

CH₂ CR² c = o

N⁺R¹ ₃ X

wherein R¹ , R², R³, and X^' are as defined above;

(ii) about 1 % to about 80% of one or more anionic monomers selected from the group consisting of acrylic acid (AA), methacrylic acid (MAA), acrylamidomethyl propane sulfonic acid (AMPSA), methacrylamidomethyl propane sulfonic acid (MAMPSA), crotonic acid (CA), maleic acid (MAH), sodium vinyl sulfonate (SVS), acrylamidoglycolic acid (Agly), acrylamidomethyl butanoic acid

(AMBA) and styrene sulfonic acid (SSA); and (iii) about 0% to about 90% of one or more non-ionic monomers selected from the group consisting of acrylamide (Am), methacrylamide (Mam), n-alkyl acrylamide (NAAm), n-alkyl methacrylamide (NAMAm), vinyl pyrrolidone (VP), vinyl acetate

(VP), vinyl alcohol (VOH), alkyl esters of acrylic acid and alkyl esters of methacrylic acid.

2. The aqueous dispersion of an ampholytic polymer according to Claim 1 wherein the preservative (C) is present in a concentration of about 0.01 % to about 0.5% and is selected from the group consisting of methyl paraben, propyl paraben, butyl paraben, benzoic acid and its corresponding sodium, potassium and ammonium salts, chloromethyl isothiazolinone and methyl isothiazolinone, DMDM Hydantoin, imidazolidinyl urea, Quaternium 15, diazolinyl urea, bromo nitro propane diol, formaldehyde, sorbic acid and its corresponding sodium, potassium and ammonium salts, and dibromodicyanobutane.

3. The aqueous dispersion of an ampholytic polymer according to Claim 1 wherein the ampholytic polymer (B) is comprised of monomers of (I) cationic monomers that are selected from the group consisting of (a) diallyl dimethyl ammonium chloride and (b) methacrylamidopropyl trimethyl ammonium chloride; (ii) anionic monomers selected from the group consisting of acrylic acid, methacrylic acid and acrylamidomethylpropane sulfonic acid; and (iii) nonionic monomers selected from the group consisting of acrylamide, methyl acrylate and stearyl methactylate.

4. The aqueous dispersion of an ampholytic polymer according to Claim 1 wherein the ampholytic polymer (B) is present in a concentration of about

10% to about 45% by weight.

5. The aqueous dispersion of an ampholytic polymer according to claim 1 wherein the ampholytic polymer has a weight average molecular weight of about 10,000 to about 10,000,000.

6. A method of producing an aqueous dispersion of an ampholytic polymer according to claim 1 comprising the steps of:

(V) adding the monomers (i), (ii), and any (iii) to water;

(VI) assuring that the pH of the mixture above is between 1 and 6 inclusive;

(VII) assuring that the mixture is at an appropriate temperature; and (VIII) adding polymerization initiators in the essential absence of oxygen to polymerize the mixture forming a dispersion of polymer in water.

7. The method according to claim 6 further comprising adding a preservative to the dispersion when the temperature is less than 50° C.

8. The method according to Claim 6 wherein the polymerization is conducted at a pH of 2.0 to 5.0.

9. A cosmetically acceptable medium comprising about 0.1 to about 20%, based on the weight of said medium, of the aqueous dispersion of the ampholytic polymer of Claim 1.

10. A method for treating a keratin-containing substrate comprising contacting said substrate with an effective amount of a cosmetically acceptable medium comprising from about 0.1 to about 20% by weight of the aqueous dispersion of the ampholytic polymer of Claim 1.

1 1. The method according to Claim 6 wherein said cosmetically acceptable medium is selected from the group consisting of a shampoo, an aftershave, a sunscreen, a hand lotion, a liquid soap, a bar soap, a bath oil bar, a shaving cream, a dishwashing liquid, a conditioner, a hair dye, a permanent wave, a hair relaxer, a hair bleach, a hair setting formulation, a styling gel, and a shower gel.

12. A method for manufacturing paper comprising steps of adding to paper furnish, from 0.1 to 25 pounds per ton on a dry basis, based on furnish of the aqueous dispersion of the aqueous dispersion of an ampholytic polymer of Claim 1.

13. A method for drilling a well in a subterranean formation, comprising circulating into the well, during drilling, an aqueous drilling fluid comprising an aqueous clay dispersion and the aqueous dispersion of an ampholytic polymer composition of Claim 1.

14. A method of cementing a conduit in a borehole penetrating an earthen formation by introducing a cementing composition into the space between said conduit and said formation, wherein said cementing composition comprised water; cement; and from about 0.1% to about 1.5% by weight of cement of aqueous dispersion of an ampholytic polymer composition of Claim

1.

15. A method for clarifying waste-water containing organic turbidity-causing components in water clarification which comprises the step of adding an effective turbidity-reducing amount of the aqueous dispersion of an ampholytic polymer composition of Claim 1 to said water.

16. A method for thickening an aqueous solution comprising the steps of adding the aqueous dispersion of ampholytic polymer composition of Claim 1 to said aqueous solution and subsequently raising the pH of the aqueous solution above pH 6.