Composition comprising cellulose fiber and a water-soluble anionic copolymer as well as method of making said composition

ES 2 336 346 T3

DESCRIPTION

Anionic copolymers prepared in an inverse emulsion matrix and their use in the preparation of cellulosic fiber compositions.

Field of the invention

The present invention relates to water-soluble anionic copolymers obtained by inverse emulsion polymerization and a method of their preparation.

Background of the invention

The manufacture of cellulosic fiber sheets, particularly paper and cardboard, includes the following steps; 1) production of an aqueous suspension of cellulosic fiber, which may also contain spreading agents or inorganic mineral pigments; 2) depositing this suspension on an endless belt or fabric of the mobile paper manufacturing; and 3) forming a sheet from the solid components of the suspension by draining the water.

The foregoing is followed by its pressing and drying of the sheet to further separate the water. Organic and inorganic chemicals are often added to the suspension prior to the sheet forming step to make the papermaking method less expensive, faster and / or to obtain specific properties in the final paper product.

The paper industry continually strives to improve paper quality, increase productivity, and reduce manufacturing costs. Chemicals are often added to the fibrous suspension before it reaches the endless belt or papermaking fabric, to improve the drainage / dewatering method and solids retention; These chemicals are called retention and / or drainage aids.

As far as drainage / dewatering improvement is concerned, drainage or dewatering of the fibrous suspension on the endless belt or papermaking fabric is often the limiting step in achieving faster method speeds. Improved dewatering can also result in a drier sheet in the pressing and drying sections, resulting in reduced water vapor consumption. Furthermore, this is the stage in the papermaking method that determines many of the final properties of the sheet.

With regard to solids retention, retention aids are used in papermaking to increase retention of the fine solids supplied to the reel during the turbulent method of drainage and web forming. Without adequate retention of the fine solids, they are either lost to the factory effluent or accumulate to high levels in the recirculating white water circuit, potentially leading to the accumulation of deposits. Additionally, insufficient retention increases papermaking costs due to losses of additives intended to be adsorbed onto the fiber to provide the respective opacity, strength, or paper sizing properties.

High molecular weight (MW) water soluble polymers with either cationic or anionic charge have traditionally been used as retention and drainage aids. Recent development of inorganic microparticles, known as retention and drainage aids, in combination with high MW water soluble polymers have shown superior drainage and retention efficiency compared to high MW water soluble polymers conventional. US Patents Nos. 4,294,885 and 4,388,150 teach the use of starch polymers with colloidal silicas. US Patent No. 4,753,710 teaches flocculation of the stock supply with a high MW cationic flocculant, inducing shear to the flocculated supply, and then introducing bentonite clay into the supply. US Patents No.^s 5,274,055 and 5,167,766 describe the use of chemically cross-linked organic microparticles or micropolymers as retention and drainage aids in the papermaking process.

US Patent No. 4,339,731 refers to water-in-oil type emulsions containing high concentrations of water-soluble polymers, prepared by incorporating a water-insoluble but soluble polymeric surfactant therein. in oil, prepared from maleic anhydride and a comonomer.

Copolymers are also used to control the deposition of contaminants or organic deposits in papermaking systems. Organic deposits is a term used to describe sticky, water-insoluble materials in the papermaking system that are detrimental to papermaking. Such materials that are obtained from trees during the pulping and papermaking process are called tars or wood tars, while the term adhesions is used to describe the contaminants that are obtained from the adhesives introduced into the papermaking process as a contaminant of recycled fiber. One strategy for the removal of these materials is to agglomerate the organic deposits into larger, non-stick particles that can be separated from the papermaking pulp or that can be incorporated into the sheet without causing deposits in the manufacturing system. of paper or defects on the sheet. Chemicals that are capable of interacting with organic deposits and mitigating their negative impact include

ES 2 336 346 T3 surfactants and polymers. Polymers can be ionic or nonionic, and include materials used as flocculants, coagulants, and dispersants.

The effectiveness of the polymers or copolymers used will vary depending on the type of monomers from which they are composed, the arrangement of the monomers in the polymer matrix, the molecular weight of the synthesized molecule, and the method of preparation. It is the last of these features that is the focus of the present invention.

Specifically, it has been unexpectedly discovered that water soluble anionic copolymers when prepared under certain conditions exhibit unique physical characteristics. Additionally, such copolymers provide unanticipated activity in certain applications including papermaking applications such as retention and drainage aids and contaminant control aids. Although the synthesis methods employed are generally known to those skilled in the art, there is no prior art to suggest that the unique physical characteristics and unanticipated activity observed are obtained.

Summary of the invention

The present invention relates to water soluble anionic copolymers. The invention also relates to a method for the manufacture of the copolymer.

As used in the present invention, the term "copolymer" is understood to be polymer compositions consisting of two or more different monomer units.

In accordance with the present invention, it has been unexpectedly discovered that certain anionic copolymers exhibit unique physical characteristics and provide unanticipated activity when prepared using certain polymerization conditions. The anionic copolymers of the invention are obtained from the reverse emulsion polymerization (water in oil) of one or more water-soluble monomers, in particular of one or more anionic monomers. The anionic copolymers that are obtained are soluble in water.

The anionic copolymers of the invention have the formula:

fB-co-F-} (Formula I) wherein B is a nonionic polymer segment formed from the polymerization of one or more ethylenically unsaturated nonionic monomers; F is an anionic polymer segment formed from the polymerization of one or more ethylenically unsaturated anionic monomers; the mole% ratio of B: F is from 5:95 to 95: 5; and "co" is a designation for a polymer system with an arrangement of two or more monomer components. Furthermore, the preparation is carried out in one way, with the absence of crosslinking agents and via an emulsion process of the water-in-oil type, in such a way that the Huggins constant (k ') determined in 0.01 M NaCl is greater than 0.75 and the storage modulus (G ') for an active polymer solution of 1.5% by weight at 4.6 Hz is greater than 175 Pa.

Detailed description of the invention

The present invention provides water soluble anionic copolymers with unique physical characteristics and methods of preparing the copolymers. The general structure of the water soluble anionic copolymer of the present invention is provided in Formula I.

fB-co-FJ (Formula I)

Nonionic polymer segment B in Formula I is the repeating unit formed after polymerization of one or more ethylenically unsaturated nonionic monomers. Exemplary monomers encompassed by B include, but are not limited to, acrylamide; methacrylamide; N-alkyl acrylamides, such as N-methyl acrylamide; N, N-dialkylacrylamides, such as N, N-dimethyl acrylamide; methyl acrylate; methyl methacrylate; acrylonitrile; N-vinyl methyl acetamide; N-vinyl methyl formamide; vinyl acetate; N-vinyl pyrrolidone, alkyl acrylates, alkyl methacrylates, alkyl acrylamides, alkyl methacrylamides, and alkyloxylated acrylates and methacrylates such as alkyl polyethylene glycol acrylates, alkyl polyethylene glycol methacrylates, and mixtures of any of the foregoing.

Segment F of the anionic polymer in Formula I is the repeating unit formed after polymerization of one or more ethylenically unsaturated anionic monomers. Exemplary monomers encompassed by F include, but are not limited to, free acids and salts of acrylic acid; methacrylic acid; maleic acid; itaconic acid; acrylamidoglycolic acid; 2-acrylamido-2-methyl-1-propanesulfonic acid, 3-allyloxy-2-hydroxy-1-propane acid

ES 2 336 346 T3 sulfonic, styrene sulfonic acid; vinyl sulfonic acid; vinyl phosphonic acid; 2-acrylamido-2-methyl-propanephosphonic acid and mixtures of any of the foregoing:

The mole percentage of nonionic monomer to anionic monomer B: F can fall within the range of 95: 5 to 5:95, preferably the range is from 75:25 to 25:75 and even more preferably the range is from 65: 35 to about 35:65 and most preferably from 60:40 to 40:60. In this regard, the mole percentages of B and F should add up to 100%. It will be understood that more than one class of nonionic monomer may be present in Formula I. It will also be understood that more than one class of anionic monomer may be present in Formula I.

In a preferred embodiment of the invention the water soluble anionic copolymer is defined by Formula I where B, the nonionic polymer segment, is the repeating unit formed after polymerization of the acrylamide; and F, the anionic polymer segment, is the repeating unit formed after polymerization of an acrylic acid salt. This preferred embodiment can be represented by the following formula:

f-CHz-CH-co-CHrCH-} II

C = oC = o

II

NH₂ O'M '(Formula II) in which M⁺ is the cation of the acrylic acid salt and is preferably Na⁺, K⁺ or NH⁴; and the mole percent ratio of B: F is from 75:25 to 25:75.

In another particularly preferred embodiment of the invention, in formula II, M is Na⁺ and the mole percent ratio of the anionic segment to the nonionic segment is from 60:40 to 40:60.

It is also an aspect of this invention that the water soluble anionic copolymers are prepared in such a way that the resulting polymers exhibit unique physical characteristics and provide unanticipated activity. The resulting water-soluble anionic copolymer is not considered to be a cross-linked polymer since no cross-linking agent is used in the preparation. Small amounts of crosslinking agent are not believed to significantly affect the properties of the polymer of the present invention. The physical characteristics of water soluble anionic copolymers are unique in that their Huggins constant (k ') as determined in 0.01 M NaCl is greater than 0.75 and the storage modulus (G') for a polymer solution active ingredients of 1.5% by weight at 4.6 Hz is greater than 175 Pa, preferably greater than 190 and even more preferably greater than 205. The Huggins constant is greater than 0.75, preferably greater than 0.9 and even more preferably greater than 1.0.

The water soluble anionic copolymers of the present invention are prepared by the technique of reverse emulsion polymerization (water in oil). Such procedures are known to those skilled in the art, for example see US Patent No. 3,284,393, and Reissued US Patent No.^s 28474 and 25,576. The preparation of an aqueous solution of the emulsion polymer can be effected by inversion by adding the emulsion polymer to water, wherein the emulsion or water may also contain an emulsion breaking surfactant. Emulsion breaking surfactants are additional surfactants that are added to an emulsion to promote inversion. The resulting copolymers can also be further separated by precipitation in an organic solvent such as acetone and dried to a powder form. The powder can be easily dissolved in an aqueous medium for use in desired applications.

In general, a reverse emulsion polymerization process is carried out by 1) preparing an aqueous solution of the monomers, 2) adding the aqueous solution to a hydrocarbon liquid containing a suitable surfactant or mixture of surfactants to form an emulsion of monomers reverse, 3) subjecting the monomer emulsion to free radical polymerization, and 4) optionally adding an inversion promoting surfactant to improve inversion of the emulsion when added to water.

The polymerization of the emulsion can be carried out in any manner known to those skilled in the art. Initiation can be effected with a variety of redox and thermal free radical initiators including azo compounds such as azobisisobutyronitrile.

Preferred initiators are oil soluble thermal initiators. Typical examples include, but are not limited to, 2,2'-azobis- (2,4-dimethylpentanenitrile); 2,2'-azobisisobutyronitrile (AIBN); 2,2'-azobis- (2-methylbutanonitrile); 1,1'-azobis- (cyclohexanecarbonitrile), benzoyl peroxide and lauryl peroxide.

Any of the chain transfer agents known to those skilled in the art can be used to control molecular weight. Those include, but are not limited to, lower alkyl alcohols such as isopropanol, amines, mercaptans such as mercaptoethanol, phosphites, thio acids, and allyl alcohol.

The aqueous solution typically comprises an aqueous mixture of nonionic monomer or mixtures of nonionic monomers, and an anionic monomer or mixtures of anionic monomers. The aqueous phase may comprise

ES 2 336 346 T3 also said conventional additives as desired. For example, the mixture may contain chelating agents, pH adjusters, initiators, chain transfer agents as described above, and other conventional additives. For the preparation of the water soluble anionic copolymer materials the pH of the aqueous solution is below 7 and is equal to or greater than 2, and more preferably the pH is 4 to 6.

The hydrocarbon liquid typically comprises straight chain hydrocarbons, branched chain hydrocarbons, saturated cyclic hydrocarbons, aromatic hydrocarbons, or mixtures thereof.

The surfactants or surfactant mixtures used in the invention are generally oil soluble. One or more surfactants can be used. The surfactant or surfactant mixture chosen for the invention includes at least one diblock or triblock surfactant. The choice and amount of the surfactant or surfactant mixture are selected in order to produce a reverse monomer emulsion for polymerization. Such surfactants are known to those skilled in the art, for example see "Hypermer Polymeric Surfactants: Emulsifiers for Inverse Polymerization Processes", ICI Surfactants Product Literature, ICI Americas Inc., 1997. Exemplary surfactants include, but are not limited to, sorbitan monooleate, (eg, Atlas G-946, Uniqema, New Castle, DE), sorbitan sesquioleate, sorbitan trioleate, polyoxyethylene sorbitan monooleate, sulfo- di-2-ethylhexyl succinate, oleamidopropyldimethylamine, and sodium isostearyl-2-lactate. Diblock and triblock polymeric surfactants are used in the present invention. Examples of diblock and triblock polymeric surfactants include, but are not limited to, diblock and triblock copolymers based on polyester derivatives of fatty acids and polyethylene oxide (for example, Hypermer® B246SF and IL-2595, from Uniqema ), diblock and triblock copolymers based on poly [ethylene oxide] and poly [propylene oxide], diblock and triblock copolymers based on polyisobutylene, succinic anhydride and polyethylene oxide and mixtures of any of the foregoing. Preferably the diblock and triblock copolymers are based on polyester derivatives of fatty acids and polyethylene oxide. When using a triblock surfactant, it is preferable that the triblock contains two hydrophobic regions and one hydrophilic region, ie hydrophobic-hydrophilic-hydrophobic. Preferably, one or more surfactants are selected in order to obtain an HLB (hydrophobic-lipophilic balance) value in the range of from 2 to 8, preferably from 3 to 7 and more preferably from 4 to 6.

The amount (based on weight percent) of diblock or triblock surfactant depends on the amount of monomer used. The ratio of diblock or triblock surfactant to monomer is at least about 3 to 100. The amount of diblock or triblock surfactant to monomer can be greater than 3 to 100 and is preferably at least 4 to 100 and more preferably 5 to 100 and even more preferably 6 to 100. The diblock or triblock surfactant is the primary surfactant in the emulsification system. A secondary surfactant can be added to facilitate handling and processing and to improve emulsion stability or alter viscosity. Examples of secondary surfactants include but are not limited to sorbitan esters of fatty acids, sorbitan esters of ethoxylated fatty acids, polyethoxylated sorbitan fatty acid, the ethylene oxide and / or propylene oxide adducts of alkyl phenols. , the ethylene oxide and / or propylene oxide adducts of long chain fatty acids or alcohols, mixed ethylene oxide / propylene oxide block copolymers and alkanolamides.

Reverse emulsion polymerization can be performed in any manner known to those skilled in the art, for example see Allcock and Lampe, Contemporary Polymer Chemistry, (Englewood Cliffs, New Jersey, PRENTICE HALL, 1981, chapters 3-5.

The copolymers of the invention can be used in papermaking systems and processes. The copolymers are useful as drainage and retention aids as well as contaminant control aids. In industrial papermaking a suspension of fibers or cellulosic pulp is deposited on an endless belt or fabric of moving papermaking. The suspension may contain other chemicals such as sizing agents, starches, deposit control agents, mineral spreading agents, pigments, fillers, organic or inorganic coagulants, conventional flocculants, or other pulp additives. As the water separates from the deposited suspension, a sheet forms. The sheets are usually then pressed and dried to form paper or cardboard. The copolymers of the invention are added to the suspension before it reaches the endless belt to improve drainage or dewatering and retention of fiber fines and fillers in the suspension.

As a contaminant control aid the polymers of the present invention inhibit tar deposition and adhesions of virgin or recycled pulp feedstock on papermaking equipment. The adjuvant is added to the pulp suspension where it interferes with pitch agglomeration and adhesions that would otherwise adversely affect paper, papermaking equipment or papermaking processes.

Suitable cellulosic fiber pulps include conventional papermaking raw material such as traditional chemical pulp. For example, bleached or unbleached sulfate pulp and sulphite pulp, mechanical pulp such as shredded wood pulp, thermomechanical pulp, chemothermomechanical pulp, can be used, recycled paper pulp such as old corrugated containers, newsprint, office waste, magazine paper, and other waste paper without removing ink, waste paper removed ink, and mixtures thereof.

ES 2 336 346 T3

The copolymer of the invention can be provided to the end use application in a number of physical forms. In addition to the original emulsion form, the copolymer of the invention can also be provided as an aqueous solution, as a dry solid powder, or as a dispersion. The copolymer is typically diluted at the site of application to produce a 0.1 to 1% aqueous solution of active polymer.

This dilute solution of the copolymer of the invention is then added to the papermaking process to affect retention and drainage. The copolymer of the invention can be added to the concentrated raw material or to the dilute raw material, and preferably to the dilute raw material. The copolymer can be added at one feed point, or the feed can be split in such a way that the copolymer is fed simultaneously at two or more separate feed points. Typical feedstock addition points include the feed point (s) before the vent pump, after the vent pump, and before the pressure screen, or after the pressure screen.

The copolymer of the invention is preferably used in a ratio of from 4.5 to 4.5 kg of active polymer per 907 kg of cellulosic pulp, based on the dry weight of the pulp. The copolymer concentration is more preferably from 23 g to 2.3 kg of active polymer per 907 kg of dry cellulosic pulp.

The present invention will be further described with reference to a number of specific examples which are to be considered exclusively illustrative and not restrictive of the scope of the present invention.

Examples

Water soluble anionic copolymers and comparative copolymers

Example 1

Poly (acrylamide / -ammonium acrylate) copolymer reverse emulsion

To a suitable reaction flask equipped with a mechanical overhead stirrer, thermometer, nitrogen sparge tube, and condenser, an oily phase of paraffin oil (135.0 g, Exxol D80 oil, from Exxon, Houston, TX) was charged. and surfactants (4.5 g of Atlas G-946 and 9.0 g of Hypermer® B246SF). The temperature of the oil phase was then adjusted to 37 ° C.

A separate aqueous phase was prepared which is comprised of 53% by weight solution of acrylamide in water (126.5 g), acrylic acid (67.8 g), deionized water (70.0 g), and chelation solution. Versenex 80 (Dow Chemical) (0.7 g). The aqueous phase was then adjusted to pH 5.4 with the addition of ammonium hydroxide solution in water (33.1 g, 29.4% by weight as NH₃). The temperature of the aqueous phase after neutralization was 39 ° C.

The aqueous phase was then charged to the oil phase while simultaneously mixing in a homogenizer to obtain a stable water-in-oil emulsion. This emulsion was then mixed with a 4-blade stirrer while sparging with nitrogen for 60 minutes. During nitrogen sparging the temperature of the emulsion was adjusted to 50 ± 1 ° C. After this, bubbling was stopped and a nitrogen atmosphere was applied.

The polymerization was initiated by feeding a 3% by weight solution of AIBN in toluene (0.213 g) over a period of 2 hours. This corresponds to an initial loading of AIBN as AIBN of 250 ppm on a total monomer basis. During the course of feeding the temperature of the load was allowed to exotherm to 62 ° C (~ 50 minutes), after which the load was held at 62 ± 1 ° C. After feeding the load was kept at 62 ± 1 ° C for 1 hour. Thereafter a 3% by weight solution of AIBN in toluene (0.085 g) was charged in less than one minute. This corresponds to a second loading of AIBN as AIBN of 100 ppm on a total monomer basis. The load was then kept at 62 ± 1 ° C for 2 hours. The batch was then cooled to room temperature and the product was collected.

The preparation of the copolymer of Examples 2-13 and Comparative Examples 1-11 was carried out according to the method of Example 1, except for the changes provided in Table 1 and in the text that follows.

Examples 2-4

Examples 2-4 were prepared as described in Example 1 except that the aqueous phases were adjusted to pH 3.0, 4.0 and 6.0, respectively.

Comparative Examples 1 and 2

Comparative Examples 1 and 2 were prepared as described in Example 1 except that the aqueous phases were adjusted to pH 7.1, and 8.0, respectively. The storage modulus, G ', of these two products was 115 and 36 Pa respectively. Both of these two values ​​were less than the threshold value of 175 Pa for this invention.

ES 2 336 346 T3

Examples 5-6

Examples 5-6 were prepared as described in Example 1 except that the weight ratio of surfactants Atlas G-946 and Hypermer® B246SF was adjusted to 2: 1 and 1: 1, respectively.

Examples 7-9

Examples 7-9 were prepared as described in Example 1 except that the surfactant system was varied as indicated in Table 1.

Comparative Examples 3 and 4

It should be noted that the surfactant systems used in Comparative Examples 3 and 4 are equivalent to those used in the preparation of the organic microbeads of US Patent Nos.^s 5,167,766 and 5,274,055. For Comparative Example 3, the hydrophilic lipophilic balance of the surfactants used is greater than eight. For Comparative Example 4, it was necessary to adjust the aqueous phase to pH 7.0 to produce a stable emulsion. Clearly, the surfactant and / or initiator packages were not sufficient to produce the desired end product, with a G '> 175 Pa and a K'> 0.75.

Example 10

Example 10 was prepared as described in Example 1 except that the initiator system was varied as indicated in Table 1. In this Example the initial oxidant charge (t-butyl hydroperoxide) was fed in one portion while the Initial reducing charge (sodium metabisulfite) was fed dropwise to the reactor. The time for the addition of the reducing agent was 3.5 hours.

Comparative Examples 5 and 6

For Comparative Example 5 the initial oxidant (cumene hydroperoxide), 25 ppm mol / mol based on total monomers, was charged in less than 5 minutes and the reducing agent (sodium metabisulfite), 25 ppm mol / mol, based on total monomers, it was charged over a period of 3 hours, followed by a retention time of 45 minutes. The second charges of oxidant and reducer, both at 50 ppm mol / mol based on total monomer, were then fed in one portion, after which the charge was held at the reaction temperature of ~ 50 ° C for 2 hours.

For Comparative Example 6, the initial oxidant (potassium bromate) was rapidly charged followed by the charge of the reducer (sodium metabisulfite) over a period of 3 hours, followed by a retention time of 45 minutes. The second charges of oxidant and reducer were then fed in one portion, after which the charge was held at the reaction temperature of ~ 50 ° C for 2 hours.

Comparative Examples 7-10

Comparative Examples 7-10 were prepared as described in Example 1 except that 10, 50, 250, and 2,000 mol / mol ppm of N, N-methylenebisacrylamide (MBA) was added to the aqueous phase, relative to the total monomer charge, respectively. MBA is a crosslinking agent and produces products that are not encompassed by this invention.

Examples 11-12

Examples 11-12 were prepared as described in Example 1 except that the mole ratio of acrylic acid to acrylamide was adjusted to 60:40 and 40:60, respectively.

Example 13

Example 13 was prepared as described in Example 1 except that the initial reaction temperature was 57 ° C for 8 hours, during which the first two initiator additions were charged at 0 and 360 minutes into the retention period. The temperature was then adjusted to 65 ° C and held for 2.5 hours. The third and fourth initiator additions were loaded at 0 and 30 minutes in the second retention period. Aqueous sodium hydroxide also replaced ammonium hydroxide on an equal molar basis.

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TABLE 1. Preparation conditions

<td rowspan="3"></td><td>Grades</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td>

<td>Amount ppm with respect to the total monomer</td><td> 250/100</td><td>s</td><td></td><td></td><td></td><td> -</td><td> =</td><td> -</td><td> =</td><td> =</td><td> =</td><td> =</td><td> =</td><td>in io CN CN</td>

<td>Initiator</td><td>AIBN</td><td> =</td><td> =</td><td> =</td><td> =</td><td> =</td><td>s</td><td></td><td></td><td> =</td><td> =</td><td> =</td><td> =</td><td>t-BHP SMBS</td>

<td rowspan="3">Surfactant Package</td><td>Relationship</td><td> 1 : 2</td><td> -</td><td>s</td><td></td><td>í</td><td> =</td><td> 2 :1</td><td></td><td> 1 :2</td><td> =</td><td>s</td><td> 85 : 15</td><td>OOl</td><td> 1 : 2</td>

<td>Surfactants</td><td>G-946: B246SF</td><td></td><td> -</td><td> =</td><td></td><td> =</td><td> =</td><td></td><td>Sesquioleate:</td><td>G-946: B206</td><td>G-946: IL-2595</td><td>POEHEX: sesquioleate</td><td>G-946</td><td>G-946: B246SF</td>

<td>% in total weight</td><td> 3,0%</td><td></td><td></td><td></td><td> —</td><td> =</td><td> =</td><td></td><td></td><td></td><td> =</td><td></td><td> =</td><td> =</td>

<td rowspan="3">Composition</td><td>pH of the aqueous phase</td><td>Tf lO</td><td>^3,0</td><td> 6,0</td><td>r- '</td><td> 0‘8</td><td>it</td><td> =</td><td></td><td></td><td> =</td><td></td><td> =</td><td>⁷’⁰</td><td></td>

<td>acrylamide</td><td> 50,0%</td><td> =</td><td> =</td><td></td><td></td><td> =</td><td></td><td>í</td><td></td><td> =</td><td> =</td><td> =</td><td></td><td> =</td>

<td>Acrylic acid</td><td> 50,0%</td><td> =</td><td> =</td><td> =</td><td> =</td><td> =</td><td>s</td><td>s</td><td></td><td> =</td><td> =</td><td> =</td><td></td><td> -</td>

<td colspan="2">Example</td><td></td><td>CN</td><td>CO</td><td>Tf</td><td>Example Compare- tive 1</td><td>Example Compare- tive 2</td><td>ID</td><td>CD</td><td>h *</td><td> 00</td><td> 0&gt;</td><td>Example Compare- tive 3</td><td>Example Compare- tive 4</td><td>or</td>

ES 2 336 346 T3

TABLE 1. Preparation conditions (Continuation)

<td rowspan="3"></td><td>Grades</td><td></td><td></td><td>10 ppm MBA</td><td>50 ppm MBA</td><td>250 ppm MBA</td><td>2,000 ppm MBA</td><td></td><td></td><td>4 charges in total</td>

<td>Amount ppm with respect to the total monomer</td><td> 25/25 50/50</td><td> 25/25 50/50</td><td> 250/100</td><td>_s</td><td>s</td><td> =</td><td> =</td><td>s</td><td> 10/10/25/ 100</td>

<td>Initiator</td><td>CHP SMBS</td><td>SSIAIS^εΟ4ΒΜ</td><td>AIBN</td><td> =</td><td></td><td> =</td><td>s</td><td>s</td><td></td>

<td rowspan="3">Surfactant Package</td><td>Relationship</td><td> =</td><td> =</td><td>s</td><td></td><td> =</td><td>s</td><td> =</td><td></td><td> =</td>

<td>Surfactants</td><td></td><td></td><td>_s</td><td>s</td><td> =</td><td> =</td><td></td><td></td><td> =</td>

<td>% in total weight</td><td> -</td><td>⁵</td><td> =</td><td> =</td><td> =</td><td> =</td><td> =</td><td> =</td><td> =</td>

<td rowspan="3">Composition</td><td>pH of the aqueous phase</td><td></td><td></td><td>s</td><td></td><td> =</td><td> =</td><td></td><td> -</td><td> =</td>

<td>acrylamide</td><td> =</td><td> =</td><td> =</td><td> =</td><td>s</td><td></td><td> 40,0%</td><td> 60,0%</td><td> 50,0%</td>

<td>Acrylic acid</td><td> -</td><td>s</td><td></td><td>s</td><td>s</td><td>s</td><td> 60,9%</td><td> 40,0%</td><td> 50,0%</td>

<td colspan="2">Example</td><td>Comparative Example 5</td><td>Comparative Example 6</td><td>Comparative Example 7</td><td>Comparative Example 8</td><td>Comparative Example 9</td><td>Comparative Example 10</td><td></td><td>CM</td><td>CO T</td>

ES 2 336 346 T3

The amount of initiator is ppm in moles with respect to the total monomer charge.

The composition is the mole% ratio of the monomers.

Atlas G-946 = Sorbitan Monooleate (Uniqema-New Castle, DE)

B246SF = Hypermer® B246SF (Uniqema-New Castle, DE) (triblock polymer based on a polyester derivative of hydroxy-stearic acid and poly [ethylene glycol] of molecular weight (MW) 1500)

Sesquioleate = sorbitan sesquioleate (Aldrich-Milwaukee, WI)

B206 = Hypermer® B206 (Uniqema-New Castle, DE) (triblock polymer based on a polyester derivative of hydroxy-stearic acid and poly [ethylene glycol] of molecular weight (MW) 600)

IL-2595 = Hypermer^® IL-2595 (Uniqema-New Castle, DE) (triblock polymer based on a polyester derivative of hydroxy-stearic acid and poly [ethylene glycol] of molecular weight (MW) 1000)

POEHEX = sorbitol poly (oxyethylene) -hexaoleate (HLB 10.2, Aldrich)

AIBN = 2,2'-azobisisobutyronitrile (Wako-Richmond, VA) t-BHP = t-butyl hydroperoxide (Aldrich-Milwaukee, WI)

SMBS = sodium metabisulfite (Aldrich-Milwaukee, WI)

CHP = cumene hydroperoxide (Aldrich-Milwaukee, WI)

KBrO₃ = potassium bromate (Aldrich-Milwaukee, WI) ppm MBA = ppm in moles of N, N-methylenebisacrylamide (Aldrich-Milwaukee, WI) charged relative to total monomer charge.

Rheological properties of water-soluble copolymers and comparative copolymers

Table 2 is a summary of the rheological characterizations of the examples of water soluble anionic copolymers with respect to a commercial benchmark drainage and retention additive, Polyflex CP.3 (Ciba-Tarrytown, NY). Characterization of four standard anionic polyacrylamides (APAM) (Chemtall-Riceboro, GA) are also provided for comparison purposes: EM 635, AN 956 VLM, AN 956, and AN 956 VHM. The prefix "EM" designates a reverse emulsion product while the prefix "AN" designates a dry powder product. All of these comparative APAM products according to published reports comprise a 50:50 mole% ratio of sodium acrylate and acrylamide. The relative molecular weight of the "AN" series increases as follows: AN 956 VLM &lt;AN 956&gt; AN 956 VHM.

Prior to inverting the water soluble anionic copolymer emulsions for analysis, ~ 2% by weight of an inversion promoting surfactant was added, for example an 80:20 by weight mixture of Tergitol 15-S-9 ( Dow-Midland, MI) and Aerosol-OT-S (Cytec Industries-West Patterson, NJ). The pH of the inverted water-soluble anionic copolymers were then adjusted to a minimum of 7.0 with aqueous sodium hydroxide or ammonium hydroxide, as required.

A discussion of these rheological techniques is provided by Macosko, Reology: Principles, Measurements, and Applications (New York, Wiley, 1994); LH Sperling, Introduction to Polymer Science (New York, Wiley-Interscience, 1992); and J. Ferry, Viscoelastic Properties of Polymers, 3rd edition, (New York, J. Wiley &amp; Sons, 1980). The viscoelastic behavior as discussed in the present invention is a time-dependent response to an applied force, in which at short time intervals or high frequency the material will exhibit hardness or glassy properties, and at long time periods or at low frequency the material can flow and exhibit viscous properties. Viscoelastic properties were determined with 1.5% (w / w) polymer solutions in deionized water, using a Haake RS-75 controlled stress rheometer. A frequency sweep was performed with the rheometer in the dynamic oscillation mode, at a constant effort determined to be within the viscoelastic region, and a frequency range of 0.01 Hz to 10 Hz. The information from this test will define both an elastic component of the material, such as the energy stored per oscillatory cycle, and a viscous component, or the energy lost per cycle. The storage module is defined as:

G '(Pa) = (τ₀ / γο) cosine δ

ES 2 336 346 T3 and the loss modulus (G ”) is defined as:

G ”(Pa) = (to / γ₀) sine δ where τ₀ is the stress amplitude, γ₀ is the maximum amplitude of the strain, and δ is the phase angle shift between the stress and the strain that is obtained.

In the terminal regime (low frequency), the loss modulus is higher than the storage modulus for linear polymers, as long periods of time allow the polymer chains to unravel and exhibit predominantly viscous behavior. As the frequency increases, a rubbery-looking plateau (stabilization) regime occurs in which the time required for the polymer chains to unravel is greater than the time period of the test. In this region, the storage modulus is higher than the loss modulus, and the material appears to be a network composed of permanent entanglements. The modulus is independent of the frequency of the test in this regime. The modulus is a function of the network bond concentration as defined in the theory of rubber elasticity:

G_n = nRT where G_N is the module at the plateau, n is the concentration of the network junctions, R is the gas constant, and T is the temperature.

The modulus at the plateau GN can be considered similar in magnitude to the storage modulus G 'in the plateau regime. As the network junction concentration increases, the modulus will increase. These network junctions can be affected by either chemical or physical crosslinks. As shown in Table 2, the storage modulus G 'of the inventive material at 4.6 Hz is higher than an equivalent linear APAM with EM 635 flocculant, indicating the presence of associative lattice junctions.

The properties of the dilute solution provide a relative indication of the hydrodynamic volume of the polymer (HDV) and the molecular weight. In this experiment, the viscosity of the solvent (n₀) is compared to the viscosity of the polymer solution (η). The specific viscosity (n_sp) is the dimensionless relationship as described by the following equation:

nsp = (n / no) - 1

The reduced specific viscosity (RSV) is the specific viscosity divided by the concentration. The intrinsic viscosity [η], or IV, is the specific viscosity divided by the concentration of the polymer (c) when the concentration is extrapolated to zero concentration.

ínl = [nsp / c] c -&gt; o

Units for IV are deciliter per gram (dL / g) and describe the hydrodynamic volume of a polymer in solution. Thus a higher IV indicates a large hydrodynamic volume in solution, and a higher MW (molecular weight) when comparing conventional polymers of similar composition in a similar solvent. The IV values ​​described in Table 2 were determined in 0.01 M NaCl with dilution concentrations from 0.0025% to 0.025% using a Ubbelohde model "OC" viscometer at 30 ° C.

The dimensionless Huggins constant (k ') is determined from the slope of the IV data according to:

nsp / c = ínl + k '[n]²c wherein the value of c is between 0.0025% by weight and 0.025% by weight.

As reviewed by Mark et al., Compilers, Encyclopedia of Polymer Science and Engineering (New York, J. Wiley &amp; Sons, 1988), Volume 1, pages 26-27, typical values ​​of k 'for linear polymers are of the order about 0.25-0.50. An increase in k 'value is indicative of an increase in polymer "structure", and can be attributed to a number of factors including the association of a crosslinked polymer structure. The k 'values ​​in Table 2 for linear APAMs are all from 0.3 to 0.4, while values ​​greater than 0.75 are obtained for the preferred water-soluble anionic copolymer of the present invention, further supporting the presence of non-linear species.

The average molecular weight determined from the viscosity M_v It is determined from the values ​​of the specific viscosity reduced to 0.025% of polymer in 1 M NaCl, which also contains 0.1% of a Surfonic® N-95 surfactant (Chevron Texaco, San Francisco). The M_v It is determined from a reduced specific viscosity / Mv calibration curve established for conventional APAMs of known molecular weight. The Mv in the Table should be interpreted as the Mv of a linear APAM with the same reduced specific viscosity as the polymer sample. Actual Mv values ​​are probably higher than those listed since associations are not destroyed at 0.1% concentration of Surfonic N-95 surfactant.

ES 2 336 346 T3

TABLE 2

<td>Example</td><td>G 'at 4.6 Hz Pa</td><td>Viscosity Intrinsic dL / g</td><td>Constant of Huggins k '</td><td>M_vg / mol</td>

<td> 1</td><td> 260</td><td> 41</td><td> 2,2</td><td> 8,0</td>

<td> 2</td><td> 237</td><td> 32</td><td> 2,0</td><td> 3,1</td>

<td> 3</td><td> 236</td><td> 32</td><td> 2,5</td><td> 3,0</td>

<td> 4</td><td> 205</td><td> 43</td><td> 1,9</td><td> 7,6</td>

<td>Comparative Example 1</td><td> 115</td><td> 68</td><td> 0,7</td><td> 13,5</td>

<td>Comparative Example 2</td><td> 36</td><td> 47</td><td> 1,5</td><td> 4,2</td>

<td> 5</td><td> 312</td><td> 29</td><td> 2,2</td><td> 6,2</td>

<td> 6</td><td> 369</td><td> 37</td><td> 2,3</td><td> 4,6</td>

<td> 7</td><td> 310</td><td> 38</td><td> 1,8</td><td> 5,6</td>

<td> 8</td><td> 315</td><td> 30</td><td> 1,7</td><td> 3,3</td>

<td> 9</td><td> 290</td><td> 39</td><td> 2,2</td><td> 6,6</td>

<td>Comparative Example 3</td><td> 130</td><td> 82</td><td> 0,6</td><td> 16,7</td>

<td>Comparative Example 4</td><td> 136</td><td> 88</td><td> 0,2</td><td> 20,7</td>

<td> 10</td><td> 189</td><td> 50</td><td> 1,1</td><td> 12,9</td>

<td>Comparative Example 5</td><td> 133</td><td> 50</td><td> 1,0</td><td> 8,0</td>

<td>Comparative Example 6</td><td> 154</td><td> 50</td><td> 1,0</td><td> 9,8</td>

<td>Comparative Example 7</td><td> 745</td><td> 15</td><td> 12,0</td><td> 1,5</td>

<td>Comparative Example 8</td><td> 1.869</td><td> 10</td><td> 3,3</td><td> 0,6</td>

<td>Comparative Example 9</td><td> 4.230</td><td> 2</td><td> 28,0</td><td> 0,2</td>

<td>Comparative Example 10</td><td> 6.539</td><td> 1</td><td>N / A</td><td>N / A</td>

<td> 11</td><td> 328</td><td> 42</td><td> 2,3</td><td> 6,6</td>

<td> 12</td><td> 237</td><td> 41</td><td> 1,1</td><td> 7,6</td>

<td> 13</td><td> 198</td><td> 46</td><td> 1,9</td><td> 5,6</td>

<td>Polyflex CP.3</td><td> 383</td><td> 32</td><td> 1,0</td><td>N / A</td>

<td>AN 956 VLM</td><td> 31</td><td> 20</td><td> 0,3</td><td> 3,8</td>

<td>AN 956</td><td> 75</td><td> 60</td><td> 0,4</td><td> 12,0</td>

<td>AN 956 VHM</td><td> 87</td><td> 80</td><td> 0,4</td><td> 17,0</td>

<td>EM 635</td><td> 130</td><td> 90</td><td> 0,3</td><td> 23,0</td>

Storage modulus (Pa) = 1.5% (w / w) of polymer at 4.6 Hz at 25 ° C.

Intrinsic Viscosity IV (dL / g): 0.01 M NaCl using a Ubbelohde Model “OC” Viscometer at 30 ° C.

ES 2 336 346 T3 k '= the Huggins constant measure was determined from the IV data.

M_v = Average molecular weight determined from the viscosity determined from the reduced specific viscosity / M calibration_v from a linear APAM of known molecular weight (MW).

For Examples 7-10 the k 'calculated for these samples is suspect due to the low IV resulting from the presence of the crosslinking agent.

Behavioral tests

The technique of sheet forming and retention chemistry are well known in the art. For example see Handbook for Pulp and Paper Techlogist, compiler GA Smook, (Atlanta GA, TAPPI Press, 1989), and Pulp and Paper, Chemistry and Chemical Technology, 3^to edition, compiler JP Casey, (New York, Wiley Interscience, 1981).

To evaluate the behavior of the examples of water-soluble anionic copolymers of the present invention, a series of retention tests in Britt tank and drainage of the Canadian Standard Freeness (CSF) were carried out in comparison with Polyflex CP.3 (Ciba), an organic drainage aid commonly referred to in the industry as a "micropolymer". Four conventional anionic polyamides (Chemtall) were also evaluated for comparison purposes: EM 635, AN 956 VLM, AN 956, and AN 956 VHM. Unless stated otherwise, all percentages, parts, etc., are by weight.

For each of these examples the copolymers were mixed with a cationic set point polyacrylamide and tested. In a similar manner, the example copolymers were blended with a benchmark anionic polyacrylamide / sodium acrylate. The copolymers of the examples were added to 907 kg of supplied solids (181 g) of active component. Thus, the efficacy of the copolymers of the invention and that of the comparative copolymers were compared with these cationic and anionic retention / drainage formulations without adding the copolymers of the invention. The following is a description of the test procedures.

The raw material used in this series of tests is a synthetic alkaline raw material. This raw material is prepared from dried hardwood (hardwood) and softwood abrasive stone pastes, and from water and additional materials. First market dried hardwood (hardwood) and softwood abrasive stone paste are refined separately in a Valley Beater laboratory (Voith, Appleton, WI). These pastes are then added to an aqueous medium.

The aqueous medium used in the preparation of the raw material is composed of a mixture of hard local water and deionized water until obtaining a representative hardness. Inorganic salts are added in such amounts as to provide this medium with representative alkalinity and conductivity of the total solution.

To prepare the raw material, hardwood (hardwood) and softwood are dispersed in the aqueous medium in the typical hardwood (hardwood) and softwood ratios. Precipitated calcium carbonate (PCC) is introduced into the raw material in an amount of 25 percent by weight, based on the combined weight of the pastes, in such a way as to provide a total raw material that is composed of 80% of fiber and 20% PCC load.

The cationic potato starch used is Stalok 400 (AE Staley, Decatur, IL), and the alum is aluminum sulfate octadecahydrate available as a 50% solution (Delta Chemical Corporation, Baltimore, MD).

The cationic flocculant used in the benchmark cationic polyacrylamide treatment program (referred to as CPAM) is a 90/10 mol% acrylamide / acryloxytrimethylammonium chloride mixture (Perform PC 8138, ex Hercules); The anionic flocculant used in the benchmark anionic polyacrylamide treatment program (referred to as APAM) is a 70/30 mol% blend of acrylamide / sodium acrylate copolymer (Perform PA 8137, ex Hercules); flocculants are commercially available as self-inverting water-in-oil emulsions. The water soluble anionic copolymers and the Comparative Copolymers were added in an amount of 0.2 kg / t to a baseline treatment formulation for the "CPAM No. 0.4" data consisting of 5 kg / t of Sta-Lok 400, 2.5 kg / t of alum, and 0.2 kg / t of Perform pC 8138.

The baseline treatment for the data from (APAM No. 0.2) consisted of 5 kg / t of Sta-Lok 400, 2.5 kg / t of alum, and 0.1 kg / t of Perform PA 8137 .

The Britt vat retention test (Paper Research Materials, Inc., Gig Harbor, WA) is known in the art. In the Britt tank retention test a specific volume of raw material is mixed under dynamic conditions and an aliquot of the raw material is drained through the sieve at the bottom of the tank, so that the level of materials can be quantified. fines that are retained. The Britt tank used for the present tests is equipped with 3 openings on the cylinder walls to induce a turbulent mixing, and with a 76 pm sieve on the bottom plate.

ES 2 336 346 T3

Britt vat retention tests were performed with ~ 500 ml of the synthetic feedstock, which has a total solids concentration of 0.5%. The test is carried out at 1200 rpm with the sequential addition of starch, followed by alum, followed by polymeric flocculant, and followed by drainage aid; the materials are all mixed during specified time intervals. After the drainage aid has been introduced and mixed, the filtrate is collected.

The calculated retention values ​​are the retention of fines in which the content of fines in the raw material is first determined by washing ~ 500 ml of raw material with 10 liters of water under mixing conditions to separate all particles of fine, defined as particles smaller than the 76 pm sieve of the Britt well. The retention of fines is then determined for each treatment by draining 100 ml of filtrate after the described addition sequence, then the filtrate is filtered through a 1.5 µm filter paper previously weighed. The retention of fines is calculated according to the following equation:

% retention of fines = (weight of filtrate - weight of fines) / weight of filtrate.

wherein the weight of the filtrate and that of the fines are both normalized to 100 ml. The retention values ​​obtained represent the average of two replicated operations.

The Britt vat retention test was run with the water-soluble anionic copolymer examples and the Comparative Examples with 0.2 kg / t pulp and 0.2 kg / t CPAM / t pulp.

The CSF device (Lorentzen &amp; Wettre, Code 30, Stockholm, Sweden) is used to determine the relative drainage rate or dewatering rate also known in the art (TAPPI Test Procedure T-227). The CSF device consists of a drainage chamber and a velocity measuring funnel both mounted on a suitable support. The drainage chamber is cylindrical, equipped with a perforated sieve plate and a hinged plate at the bottom, and with a hinged vacuum-tight lid at the top. The velocity measuring funnel is equipped with a hole in the bottom and a side overflow hole.

The CSF drainage tests were carried out with 1 liter of raw material with a solid consistency of 30%. The feedstock is prepared for the externally described treatment from the CSF device, using equivalent mixing speeds and times as described for the Britt vat tests, in a square beaker to provide a turbulent mixing. Upon completion of the additive addition and mixing sequence, the treated raw material is poured into a drain chamber, the top lid is closed, and the bottom plate is then immediately opened. The water is allowed to drain freely into the funnel that measures velocity; water flow in excess of that determined by the bottom hole will overflow through the side hole and is collected in a graduated cylinder. The values ​​generated are expressed in milliliters (ml) of filtrate; higher quantitative values ​​represent higher levels of drainage or dehydration.

The Britt vat retention and CSF drainage values ​​shown in Table 3 are the difference in the retention and refinement values ​​for the example compounds relative to a base treatment with CPAM or APAM. In both the Britt vat retention and CSF drainage tests, higher enhancement values ​​indicate higher activity and more desired response.

(Table goes to next page)

ES 2 336 346 T3

TABLE 3

<td>Example</td><td>CPAM N ° 0.4 Cuba Britt % retention of fines</td><td>CPAM N ° 0.4 CSF ml of increment</td><td>APAM N ° 0.2 CSF ml of increment to</td>

<td> 1</td><td> 30,0</td><td> 200</td><td> 155</td>

<td> 2</td><td> 28,0</td><td> 190</td><td> 150</td>

<td> 3</td><td> 27,5</td><td> 180</td><td> 140</td>

<td> 4</td><td> 31,5</td><td> 205</td><td> 160</td>

<td>Comparative Example 1</td><td> 23,9</td><td> 165</td><td> 120</td>

<td>Comparative Example 2</td><td> 5,6</td><td> 145</td><td> 105</td>

<td> 5</td><td> 27,0</td><td> 180</td><td> 135</td>

<td> 6</td><td> 30,0</td><td> 200</td><td> 150</td>

<td> 7</td><td> 31,5</td><td> 210</td><td> 160</td>

<td> 8</td><td> 19,7</td><td> 120</td><td> 95</td>

<td> 9</td><td> 30,0</td><td> 175</td><td> 135</td>

<td>Comparative Example 3</td><td> 28,0</td><td> 200</td><td> 165</td>

<td>Comparative Example 4</td><td> 27,0</td><td> 205</td><td> 165</td>

<td> 10</td><td> 27,3</td><td> 195</td><td> 155</td>

<td>Comparative Example 5</td><td> 25,9</td><td> 200</td><td> 150</td>

<td>Comparative Example 6</td><td> 27,9</td><td> 200</td><td> 150</td>

<td>Comparative Example 7</td><td> 20,1</td><td> 160</td><td> 130</td>

<td>Comparative Example 8</td><td> 22,3</td><td> 140</td><td> 100</td>

<td>Comparative Example 9</td><td> 8,4</td><td> 95</td><td> 60</td>

<td>Comparative Example 10</td><td> -20,0</td><td> 60</td><td> - 10</td>

<td> 11</td><td> 29,5</td><td> 200</td><td> 150</td>

<td> 12</td><td> 32,9</td><td> 200</td><td> 155</td>

<td> 13</td><td> 30,0</td><td> 205</td><td> 155</td>

<td>Polyflex CP.3</td><td> 30,0</td><td> 200</td><td> 150</td>

<td>AN 956 VLM</td><td> 0,0</td><td> 120</td><td> 70</td>

<td>AN 956</td><td> 15,0</td><td> 160</td><td> 120</td>

<td>AN 956 VHM</td><td> 18,0</td><td> 185</td><td> 130</td>

<td>EM 635</td><td> 20,0</td><td> 190</td><td> 135</td>

The data shown in Table 3 illustrate the retention / drainage (R / D) activity of the water-soluble anionic copolymers of the invention compared to the results obtained with Polyflex CP.3, the polyacrylates.

ES 2 336 346 T3 conventional anionic licks and Comparative Examples. In general, for the G-946 / B246SF surfactant plus AIBN initiator system, the overall R / D activity was optimal for an aqueous phase pH of 5-6 (Examples 1, 4, 5, and 6) and increasing the content of B246SF in the surfactant package (Examples 1, 5 and 6). For the other initiator and / or surfactant systems the R / D activity was comparable to that of Polyflex CP.3 and conventional anionic polyacrylamides, except for Example 8 which exhibited increased R / D activity, but lowest globally.

A series of retention and drainage tests were also performed using a vacuum drainage test developed to differentiate the activity between microparticle technology and conventional linear flocculants. The results of this trial show the ability of the VDT trial to differentiate drainage aids in both CPAM and APAM programs by magnitude of drainage time.

The set-up of the device is similar to that of the Buchner funnel test as described in various reference books on filtration, for example, Perry's Chemical Engineers' Handbook, 7^to addendum, (McGraw-Hill, New York, 1999), pages 18-78. The VDT consists of a 300 ml magnetic Gelman filter funnel, a 250 ml graduated cylinder, a quick disconnect, a water trap, and a vacuum pump with a vacuum gauge and regulator. The VDT test is performed by first setting the vacuum to the desired level, typically 33.9 kPa, and placing the funnel appropriately on the cylinder. Next, 250 g of 0.5% by weight paper pulp is loaded into a beaker and then the required additives are added according to the treatment program (for example, starch, alum and the flocculants from the test) to the pulp under agitation provided by an overhead mixer. The pulp is then poured into the filter funnel and the vacuum pump is started while simultaneously starting a timer. Drainage efficiency is expressed as the time required to obtain a 230 ml filtrate.

The principle of VDT is based on the theory of filtration with cake formation, for reference see L. Svarovsky, compiler, Solid-Liquid Separation, 3rd edition (London, Butterworths, 1990), Chapter 9. Initially, the solids in the suspension is deposited on a relatively fine filter medium that serves to support the filter cake. The successive deposits of layers of solids form the filter cake or mat. The speed of the filtrate passing through the filter cake (or mat) depends on the density of the flocs, the size distribution of the flocs in the filter cake, and the levels of residual polymeric materials present in the phase. watery. A flocculant that forms dense, uniformly sized flocs and has a low residual level of water (ie good formation characteristics) will show good drainage in the VDT test, and vice versa.

The data in Table 4 illustrates the activity of the water soluble anionic copolymers of the invention for a series of VDT assay evaluations in an APAM program identical to the formulation used in the CSF assays. The levels of starch, alum, and associated anionic flocculant from the base treatment are as described in Table 3. The experimental and comparison examples were evaluated at a concentration of 0.2 kg / t as active compounds. A difference in drain time greater than 1.0 seconds between the samples is considered statistically significant.

(Table goes to next page)

ES 2 336 346 T3

TABLE 4

<td>Example</td><td>0.2 kg / t VDT (s)</td>

<td> 1</td><td> 21,3</td>

<td> 2</td><td> 22,1</td>

<td> 3</td><td> 22,5</td>

<td> 4</td><td> 21,2</td>

<td>Comparative Example 1</td><td> 23,7</td>

<td>Comparative Example 2</td><td> 27,0</td>

<td> 5</td><td> 22,0</td>

<td> 6</td><td> 20,6</td>

<td> 7</td><td> 20,5</td>

<td> 8</td><td> 24,9</td>

<td> 9</td><td> 27,5</td>

<td>Comparative Example 3</td><td> 22,4</td>

<td>Comparative Example 4</td><td> 23,6</td>

<td> 10</td><td> 21,9</td>

<td>Comparative Example 5</td><td> 23,6</td>

<td>Comparative Example 6</td><td> 22,2</td>

<td>Comparative Example 7</td><td> 23,0</td>

<td>Comparative Example 8</td><td> 24,2</td>

<td>Comparative Example 9</td><td> 27,0</td>

<td>Comparative Example 10</td><td> 33,0</td>

<td> 11</td><td> 21,0</td>

<td> 12</td><td> 20,3</td>

<td> 13</td><td> 20,6</td>

<td>Polyflex CP.3</td><td> 20,0</td>

<td>AN 956 VLM</td><td> 28,6</td>

<td>AN 956</td><td> 25,0</td>

<td>AN 956 VHM</td><td> 26,2</td>

<td>EM 635</td><td> 25,6</td>

<td>Control test No drainage control agent</td><td> 32,0</td>

ES 2 336 346 T3

The data in Table 4 shows a difference in the magnitude of the drain time between the water soluble anionic copolymers of the present invention, Polyflex CP.3 and the conventional anionic polyacrylamide flocculants. Polyflex CP.3 exhibits a fast drainage rate, whereas conventional anionic polyacrylamide flocculants were characterized by a slower drainage rate. In general, for the water soluble anionic copolymers prepared using the G-946 / B246SF surfactant combination plus the AIBN initiator combination, the performance trends were comparable to those of Polyflex CP.3 for the examples exhibited in the Table 3 an optimized DR activity. The VDT response for the Comparative Examples was observed to decrease dramatically with increasing pH of the aqueous phase above 6, and with increasing addition of MBA. Comparative Examples of polymers prepared with alternative surfactant systems (Comparative Examples 3 and 4) and initiator systems (Comparative Examples 5 and 6) exhibit a poor VDT drainage response, similar to that of conventional polyacrylamides.

Taken together, the use of certain combinations of emulsifying surfactants, initiator systems, and aqueous phase pH produces water-soluble anionic copolymers characterized by a k 'greater than 0.75, and a G' greater than 175 Pa, which unexpectedly exhibit training and R / D activity comparable to organic microparticle technology, such as Polyflex Cp.3.

The preferred water-soluble anionic copolymers of the present invention are prepared via a reverse emulsion polymerization technique employing an emulsifying surfactant consisting of an AB or A_B_A polymeric surfactant, an aqueous phase pH of 2 to 7, and an oil soluble free radical initiator.

Particularly preferred water-soluble anionic copolymers are prepared via a reverse emulsion polymerization technique employing Hypermer.^® B246SF or IL-2595 with sorbitan monooleate as the emulsifying surfactant package, an aqueous phase pH of 3 to 6, and the use of 2,2'-azobisisobutyronitrile (AIBN) as the free radical initiator.

It is noted that the foregoing examples have been provided merely for the purpose of explanation and should not be construed as limiting the present invention in any way.

The water-soluble anionic copolymers of the present invention may also exhibit unique activity in other applications such as coagulants and / or flocculants in wastewater treatment applications, or as rheology modifiers in drilling and / or water treatment applications. cement.