CA2063656A1 - Method of preparing acrylamide/diallyl dimethyl ammonium chloride copolymers - Google Patents

Abstract

ABSTRACT

A process for the production of an improved acrylamide/
diallyl dimethyl ammonium chloride emulsion copolymer utilizing 2,2'-azobis (2,4-dimethylvaleronitrile) as an initiator and adding sodium formate during polymerization.

Description

- - 2n~3~56 METHOD OF PREPARING ACRYLAMIDE/DIALLYL
DIMETHYL AMMONIUM CHLORIDE COPOLYMERS

FIELD OF ~HE INVENTION

The present invention pertains to a method of preparing copolymers for water treatment applications such as for use as flocculants for sludge dewatering, water clarification and reten-tion and drainage aids in paper manufacturing. Particularly, the invention relates to an improved process of making copolymers for such uses by utilizing a water-in-oil emulsion polymerization technique.

Diallyl dimethyl ammonium chloride (DADMAC) is a quater-nary monomer which, when polymerized, yields cationic water soluble polymers.

The copolymerlzation of acrylamide with DADMAC by a water-ln-oil emulslon process is known in the art. For instance, U.S. Pat. No. 3,920,599 discloses the process of preparing the homopolymer of DADMAC and DADMAC/acrylamide copolymers by using 2,2-azo-bis(isobutyronitrlle), benzoyl peroxide, and/or lauroyl peroxide.

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U. S. Patent No. 3,968,037 teaches the use of t-butylper-oxypivalate to polymerize OAOMAC in emulsion.

U. S. Patents No. 4,077,930 and 4,147,681 disclose a process to prepare acrylamide/DADMAC emulsion by using at least 20% by weight, based on the weight of the oil phase, of an emul-sifier having HLB (hydrophile lipophile balance) of at least 7.

U. S. Patent No. 4,439,580 discloses use of free radical initiators such as organic peroxy initiators, redo~ systems, and azo initiators, i.e, 4,4-azobis-4 cyanopentoic acid and 2,2-azobis (isobutyronitrile) ~o polymerize DADMAC in emulsion. The preferred initiator is ammonium persulfate (column 3, lines 24-31~.

U. S. Patent No. 4,864,007 discloses the utilization of a cationic azo initiator (water soluble) and phosphorous acid or a derivative as regulator to polymerize DADMAC.

IS European Patent Application No. O 363 024 relates to a process of preparing acrylamide and DADMAC copolymer in emulsion form v~a a stage addition of acrylamide during the polymerization, and the addition of a chain transfer agent at the conclusion of said copolymerization to prevent branching and cross-linking.

U.S. Patent No. q,307,215 describes a method of preparing acrylamide based polymers by adding sodium formate prior to poly-merization to limit the molecular weight of polymers. The co-monomers are selcted from the group consisting of N-dimethylamino-29~r ethyl methacrylate and acrylic acid. The cationic monomer, DADMAC
and the specific oil soluble initiator used in this invention are not disclosed in the '215 patent.

Furthermore, during testing for the present invention it has been discovered that when the chain transfer agent is added prior to or at the conclusion of copolymerization of acrylamide and DADMAC as suggested by the prior art, the resulting copolymers have undesirable low viscosity (molecular weight) for sludge dewatering applications.

From the above disclosures, it is apparent that none of the prior art has recognized that the copolymsrization of acrylamide with DADMAC in emulsion may be improved by using the specific oil soluble initiator and polymerization conditions as disclosed in this invention. The copolymer obtained by this invention unexpectedly exhibits a more controllable polymerization profile, less gel and higher molecular weight (indicated by solution viscosity) which shows better performance in sludge dewatering applications as compared to the methods disclosed in the prior art. It is accordingly an object of the present invention to produce a high solution viscosity (high molecular weight) acryl-amide/DADMAC emulsion in which the emulsion has improved sludge dewaterlng performance. It is a further object of the invention to improve the process of manufacturing acrylamideJDADMAC emulsion to have a result that is more reproducible, less gel, and more controllable polymerization profile.

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DETAILED DESCRIPTION OF THE INVENTION

In accordance with the invention, it has been surprisingly discovered that by using an oil soluble initiator, i.e., 2,2'-azo-bist2,4-dimethylvaleronitrile) (Du Pont Vazo 52; Wako Y-65) and adding a chain transfer agent during the reaction to polymerize acrylamide and DADMAC in a water-in-oil emulsion process, the resulting copolymer shows unexpectedly more controllable polymerization profile, less gel, higher solution viscosity (high molecular weight) and better performance in sludge dewatering applications as compared to the methods disclosed in the prior art.

The copolymers are prepared by a water-in-oil emulsion technique. Such processes have been disclosed in U. S. Patents 3,284,393; Reissue 28,474, and Reissue 28,576, herein incorporated by reference. The general technique used in this invention involves the preparation of an aqueous phase, ranging from about 50% to about 90% by weight of the total emulsion, which aqueous phase is comprised of water, monomers (acrylamide and DADMAC), and chelatlng agents. Ethylenediamine tetraacetic acid or diethylene-triamine pentaacet k acid and their salts are suitable, but not l~miting, chelating agents. Inorganic salts such as sodium sul-fate, sodium chloride, ammonium chloride, sodium nitrate and ammonium sulfate, etc., that are water-soluble and do not interfere wlth the polymerization may be added to the aqueous phase to further reduce the amount of gel, part kularly, if the reaction is conducted in a steel reactor. The amount of salt added will vary widely depending on the specific monomer content, the initiator 2~3~

system, the oil to aqueous phase ratio and the particular salt used, etc. It may vary from about 2 to 6 weight percent based on the aqueous phase. The pH of the aqueous solution is adjusted to 4.0 to 5.5. The total amount of monomers will range from about 30% to about 80%, by weight, based on the total weight of the aqueous phase.

An oil phase is separately prepared, ranging from about 10% to about 50% by weight of the total emulsion, which oil phase is comprised of a liquid organic hydrocarbon, water-in-oil emulsifying agents and oil soluble initiator(s). A preferred group of hydrocarbon liquids include both aromatic and aliphatic compounds. Thus, organic hydrocarbon 7iquids such as benzene, xylene, toluene, mineral oils, kerosenes, naphthas and the like may be used. Oils commonly used for this purpose are the deodorized kerosenes, such as materials commercially available as of Isopar M, LOPS (both from Exxon), Vista LPA (Vista Chemicals) and Soltrol 145 (Philips Petroleum). The water-in-oil emulsifying agent is usually a low HLB surfactant. Typical emulsifiers are mono and digylcerides, sorbitan fatty acid esters and lower N, N-dialkanol substituted fatty amides, and the like, as described in U.S. Patent Reissue 28,576.

The addition of a mixture of emulsifying surfactants, rather than a single emulsifier, is preferred. The concentration of emulsifiers can be from about 3X to about 30% by weight, prefer ably 5% to about 10%, based on the total weight of the oil phase.

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The preferred combined HLB value for the emulsifiers is between 5.0 and 6.5. Polymeric surfactants such as modified polyester surfactants (~ypermer, ICI) and maleic anhydride-sub-stituted ethylene copolymers (PA-l~ or 18, Chevron) may also be added to improve the mechanical stability and increase the solids content of the emulsion.

The preferred initiator in this invention is 2,2'-azobis (2,4-dimethylvaleronitrile). It is available from Du Pont (Vazo 52) and Wako (V-65). The initiator is used in amounts of about 10 to 5,00~ ppm, preferably 50 to 1000 ppm, of the total monomers. It is dissolved in the oil phase as described above or added after homo-gen kation of the water-in-oil emulsion. A portion of the initi-ator may be withheld from the initial emulsion and added, after polymerization has commenced, either continuously or incrementally.

After the aqueous phase and oil phase have been prepared separately, the aqueous phase is then homogenized into the oil phase. Homogenizers, high shear pumps, or high speed agitators that are capable of mixing the two phases into a homogeneous water-in-oil emulsion may be used. Any of the techniques to prepare the 20 inverse emulsions well known to those skilled in the art may be used. The particle size of the resulting emulsion is usually less than 10 um and preferably less than 2 um. After the emulsion is prepared, the system is then sparged with nitrogen to remove all oxygen from the system. The emulsion is under constant agitation 25 or circulation.

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Polymerization is then initiated by heat to induce the decomposition o~ the initiator in the emulsion. The temperature of the reaction medium is maintained at about 40C tG about ~5C, preferably 40C to about 55C.

Chain transfer agents such as formic acid and its salt, sodium hypophosphite, mercaptoethanol, thioglycolic acid, mercaptoproponic acid and a lower alkyl alcohol having 1 to 4 carbon atoms, etc. can be added during the polymerization to obtain the desired molecular weight (measured by Brookfield viscosity using UL adaptor in a salt solution). The amount of chain transfer agent added can vary between the range of 0.01 to 3.0 weight percent of the total weight of monomers used. The range of 0.02 to 1.5 weight percent is even more desirable.
Sodium formate is the preferred chain transfer agent used in this invention.

After the polymerization is substantially complete, a solution of sodium metabisulfite, sodium bisulfite or S02 gas is further added to stabilize the emulsion and to react with any residual acrylamide.

Inverting surfactants such as those described in U. S.
Patent Re. 28,474 are then added to the emulsion to convert the resulting emulsion to a "self-inverting" emulsion. The typical inverting surfactants include those having rela~ively high HLB
numbers such as ethoxylated octyl and nonyl phenols, ethoxylated 2 ~

nonyl phenol formaldehyde resin, polyethylene oxide esters of fatty acids, and dioctyl esters of sodium sulfosuccinate, etc The inverting surfactants are added in an amount equal to about 0.5 to about 5 percent by weight, preferably 2 to 3 percent, based on the total emulsion. The water-in-oil emulsion thus produced rapidly disperses and dissolves into an aqueous solution upon being added to water. Within minutes, a maximum solution viscosity is obtained.

The entire process of preparing the emulsion in accordance with the invention, is smooth and without difficulty.
Polymers with high molecular weight (judging by the inv~rted UL
viscosity) are obtained. The reaction temperature during poly-merization is controllable. There is no sudden, uncontrollable temperature increase as often occurs with other processes. From the results of C13 NMR, the conversion of DADMAC into polymer is usually higher than 80%, based on the initial amount of DADMAC
monomer charged. Since DADMAC contains the diallyl group and some impurities such as salt and amine, such conversion rate in the copolymer is considered to be excellent.

The residual acryla~ide is undetectable by C-13 NMR. The overall process and results are fairly reproducible. The gel counts are low and the emulsion can be easily filtered through fine screens. Gels are either inverted, coagulated, or non-l~near polymers which are formed during the process. They are undesirable in the use of the polymer due to the tendency to plug the feed line and difficult to dissolve into water. Such 2~3~

g gel formation and removal reduces the effective amount of polymer provided, diminishes available reactor time due to the tedious clean-up procedure involved and increases production costs. Other initiators like 2,2'-azobis(isobutyronitrile)(AIBN), 2,2'- azobis (2-amidinopropane)dihydrochloride (Wako V-50), and t-butylhydro-peroxide/sodium metabisulfite redox pair as disclosed in the prior art, are compared with the present invention. AIBN is a commonly used oil soluble initiator. Y-50 is a water soluble azo initiator as used in the U. S. Patent No. 4,864,007 to polymerize DADMAC.
T-butylhydroperoxide/bisulfite is also a widely used redox system in emulsion polymerization. Similar reaction procedures are used for the polymerization.

As detailed in the experimental section, none of the initiators tried, produce satisfactory results other than the initiator used in the invention. Emulsion polymers initiated by AIBN in the conditions used, contain approximately 10-20 % gel by weight before filtering. Process control and product replication is unacceptable (Comparative Example A). The polymerization has an erratlc temperature profile requiring air quenching to prevent runaway conditions. V-50 produces an excess amount of gel and high residual monomer content after polymerization (Comparative Example B). The redox system, though more controllable, has d~ff~culties to produce as high a molecular weight polymer as the present invention, which is desirable for the use (Comparative Example C). When the chain transfer agent, sodium formate, is added prior to or at the conclusion of polymerization as disclosed ~ 2~3~

by the prior art, the resulting acrylamide/DADMAC copolymers have undesirable low viscosity for sludge dewatering applications (Comparative Examples D and E).

The emulsion polymers prepared above are evaluated for dewatering applications. Sludges from several paper mills are used. ~he results show that the polymers prepared in accordance to the invention, have better overall performanre than those prepared by using methods taught by the prior art.

The following examples are set forth for purposes of illustration only and are not to be construed as limitations on the present invention except as set forth in the appended claims.
All parts and percentages are by weight unless otherwise specified.

AMD/DADMAC COPOLYMER EMULSIONS

Example 1 - Preparation of acrylamide/diallyl dimethyl ammonium chloride copolymers using 2,2'-azobis(2,4-dimethyl-valeronitrile) (DuPont Vazo 52; Wako V-65) as an oil soluble initiator.
Aqueous Phase - AMD (50X) 193.5 DADMAC (6~%) 9.g Dl water 48.5 EDTA (5.6X) 6.7 258.6 parts 2 ~

Oil Phase - Sorbitan monooleate 4.3 Oleic isopropanolamide 3.5 Oil * 100.0 2,2'-Azobis(2,4-dimethyl- 0.01 valeronitrile) 107.81 parts Total Wt. of Emulsion366.41 parts Overall Solids Content28.2X
* Oil: Soltrol 145, Philips Petroleum To a suitable flask were added 48.5 parts deionized water, 193.5 parts acrylamide (50.0% aqueous), and 9.9 parts diallyl dimethyl ammonium chloride (64.0X a~ueous). To this solution was added 6.7 parts of disodium ethylenediamine tetraacetic acid solution (5.6% aqueous). The pH of the agueous monomer phase was then adjusted to pH 4.0-4.5 with dilute sulfuric acid. The oil phase was prepared by dissolving 4.3 parts so~bitan monooleate (Arlacel 80, ICI) and 3.5 parts of oleic isopropanolamide (Witcamide 61, Witco Corp.) in 100.0 parts of oil (Soltrol 145, Phillips Petroleum). ~o this solution was added .01 parts of the oil soluble initiator 2,2'-azobis(2,4-dimethylvaleronitrile) (Vazo 52, DuPont).

The aqueous phase was then added to the oil and homogenized by a conventional homogenizer to obtain a bulk viscosity of 800-1500 cps. The emulsion was charged to a suitable glass reaction vessel and purged with nitrogen gas for 1 hour with stirring. As stirring continued the emulsion was heated to and held at 40 +/- 2C for 3 hours. The temperature was then gradually raised to and held at 45 ~/- 2C for 1 hour.

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A solution of .01 parts of 2,2'-azobis(2,4-dimethylvalero nitrile) in 5.0 parts of oil was prepared and shot fed into the reactor. The temperature was then gradually raised to and held at 50 +/- 2C for I hour. The emulsion was then cooled to 45C
and stabilized by slowly adding 5.4 parts of a 30.0X aqueous solution of sodium metabisulfite. A breaker package was prepared by premixing 8.2 parts of a Cll-CI5 secondary alcohol ethoxylate (Tergitol 15-5-7, Union Carbide) and 1.4 parts of dioctyl ester of sodium sulfosuccinic acid (Aerosol OTS, American Cyanamid). The temperature was maintained at 45C as the entire breaker package was charged to the reactor over I hour. The emulsion was stirred for an additional hour at 45C and was then cooled and filtered to remove any gel. The resulting emulsion had a very low gel content and inverted readily into water to give a viscous polymer solution.
15 A 0.3% solution of the active polymer in 4.0% aqueous NaCl had a viscosity of 24.0 cps. The incorporation of DADMAC was estimated to be 85% of the initial monomer charge by C-13 NMR.

Examples 2-6 were prepared in substantia1 conformity to the procedure described in Example 1. They are characterized in Table 1.

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TABLE I
SUMMARY OF AMD/DADMAC COPOLYMERS
Mole Percent UL Viscosity, cps Example DADMAC (0.3% activ~ DolYmer in 4.0% Nacl) 1 2.2 24.0 2 2.8 21.5 3 2.8 32.0 4 2.8 24.8 2.2 28.0 6 . 1.8 34.2 The following Comparative Examples (A, B and C) are described using other common initiators to prepare acrylamideJdiallyl dimethyl ammonium chloride copolymers.

COMpARAIlyE EXAMPLE A - AMD/DADMAC copolymer using 2,2-azobis (isobutyronitrile) (AIBN: DuPont Vazo 64, Wako V-60) as an oil soluble initiator.

Aqueous Phase - AMD (50%) 193.5 DADMAC (64X) 9.9 DI water 48.5 EDTA (5.6X) 6.7 258.6 parts Oil Phase - Sorbitan Monooleate 4.3 Ole~c isopropanolamide 3.5 Oil g2.8 AIBN 0.01 100.61 parts Total Wt. of Emulsion 359.21 parts Overall Solids Content 28.8%

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The emulsion was prepared in accordance with the procedure described in Example 1. The emulsion was charged to a suitable glass reaction vessel and purged with nitrogen gas for 1 hour with stirring. Stirring continued and the emulsion was heated to and held at 50 +/- 2C for 4 hours. The temperature was then gradually raised to and held at 65 +/- 2C for 1 hour.

The burnout and breaker addition steps were the same as outlined in Example 1. The final emulsion contained approximately 10-20% gel (by weight) before filtering. Also, the reaction was somewhat exothermic using this initiator. Extensive cooling and air quenching was required in order to control the reaction rate.
A 0.3% solution of the active polymer in 4.0% aqueous NaCl had a viscosity of 26.1 cps.

COMPARATIYE EXAMBLE B - AMD/DADMAC copolymer using 2,2'-azobis-(2-amidinopropane)dihydrochloride (Wako V-50) as a water soluble initiator.
Aqueous Phase - AMD (50X) 193.5 DADMAO (64%) 9.9 DI water 48.5 EDTA (5.6%) 6.7 V-50 0.01 258.61 parts Oil Phase - Sorbitan Monooleate 4.3 Oleic isopropanolamide 3.5 Oil 100.0 107.8 parts Total Wt. of Emulsion 366.41 parts Overall Solids Content 28.2%

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This copolymer was prepared in accordance with the procedure described in Example 1. The final emulsion contained approximately 10-20% gel (by weight) before filtering. During the burnout step, a significant exotherm was observed indicating the presence of a large amount of unreacted monomer.

A 0.3% solution of the active polymer in 4.0% aqueous NaCl had a viscosity of 22.0 cps.

COMPARATTVE EXAMPLE C - AMD/DADMAC copolymer was prepared using t-butylhydroperoxide (t-BHP) and sodium metabisulfite as a redox initiator.

Aqueous Phase - AMD (50%~ 193.8 DADMAC (64%) 9.3 Dl water 47,4 EDTA (5.6%) 6.9 t-BHP (1.4%) 0.4 257.8 parts Oil Phase - Sorbitan Monooleate 7.8 ojl 92.6 100.4 parts Total Wt. of Emulsion 358.2 parts Overall Solids Content 28.8X

The emulsion was prepared in accordance with the procedure described in Example 1. The emulsion was charged to a suitable glass reaction vessel and purged with nitrogen gas for 1 hour with stirring. A solution of 0.50X aqueous sodium metabisulfite was prepared and sparged with nitrogen for I hour. 3.9 parts of this 2~3~$~

solution was then added to the reactor at such a rate as to maintain the resulting exotherm 45-50C. This addition was completed in 3-4 hours. The burnout and breaker addition steps utilized the charges and procedure outlined in Example 1. The S final emulsion had a low gel content and inverted readily into water to give a viscous polymer solution. A 0.3X solution of the active polymer in 4.0% aqueous NaCl had a viscosity of 21.9 cps.

ExamDles 7~2 AMD/DADMAC copolymer using 2,2'-azobis(2,4-dimethyl valero-nitrile) as the initiator and adding sodium formate during the polymerization.

A similar procedure to that described in Example I was used, except the initiator was added at 40C and the polymeri-zation temperature was held at 50C for 5 hours before being cooled down and an aqueous solution of sodium formate was added to the emulsion approximately 90 minutes after the start of the poly-merization. After polymerization, sodium bisulfite solution and a trace amount of t-BHP were added to further react with residual acrylamide in the emulsion. A similar breaker package was also added to the emulsion. The amount of gel formed in these runs was neg1igible. The surfaces on the steel reaGtor wall (inside) and agitator were relatively clean. The formulation is as follows:
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Aqueous Phase - AMD (53.0%) 385.3 parts DADMAC (64.0%) 14.0 Water 127.5 Ammonium chloride 22.0 t-BHP (1.4%) 14.3 Oil Phase - Sorbitan Monooleate 11.2 Oleic isopropanolamide 6.3 Oil 188.3 Vazo 52 3.015 Oil 8.0 Sodium formate 0.77 Water 1.4 tBHP (1.0%) 1.5 SMBS (33.0%) 11.8 Tergitol 15-S-7 17.8 Aerosol OTOS 3.1 Oil: LOPS, Exxon Vazo 52: 2,2'-azob~s(2,4-dimethylvalero-nitrile), Du Pont A sample of the emu1sion was taken from the reactor prior to adding the formate solution. This sample was analyzed for the conversion of the acrylamide monomer by a titration method. The sample was also inverted into a 4.0X aqueous NaCl solution to prepare a 0.3% active solution based on the initial monomer charges. The results and the final copolymer viscosity are shown in Table Il.

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TABLE II
Viscositv Results of AMD!DADMAC Copolv~ers Example 7 ExamDle 8 Example 9 Solution viscosity prior 13.5 cps 11.8 cps 13.7 cps to formate addition % AMD conversion by titration prior to formate addition 65.1% 48.5% 61.8%
Solution viscosity of 26.4 cps 27.3 cps 31.2 cps final product * Solution viscosity: 0.3% active in 4% NaCl solution, as measured - with an UL adaptor COMPARATIVE EXAMPLE D - AMDIDADMAC copolymer using 2,2'-azobis(2,4-dimethylvaleronitrile) as the initiator and adding sodium formate to the aqueous phase prior to polymerization.

This emulsion was prepared according to the procedure and formulatlon as described ln Example 7 except that sodium formate was added to the aqueous phase before polymerization as disclosed in U.S. Patent No. 4,307,215.

The final emulsion contained approximately 3.0% gel (by weight) before filterlng. The copolymer had a low viscosity of 7.8 cps (0.3% of the active polymer in 4.0 X NaCl solution). It is undestrable to be used for sludge dewatering applications.

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COMPARATIVE EXAMPlE E - AMD/DADMAC copolymer using 2,2' azobis (N,N'-dimethylisobutyramidine)dihydrochloride/persulfate as the initiator and adding sodium hypophosphite at the conclusion of copolymerization.

The emulsion was prepared in substantial conformity to the procedure of Example 1 in EP 0363 024 Al in which part of the acrylamide was charged to the emulsion during the reaction and a chain transfer agent, sodium hypophosphite, was added at the conclusion of the copolymerization. The resulting copolymer had a Yiscosity of 8 cps (0.3% active in 4% NaCl solution) which was considerably lower than the copolymer prepared by the process of this invention.

EFFICACY TESTING

Comparative Examples A and B were deemed unacceptable due lS to the high amount of gel formed during the polymerizations.
Comparative Examples D and E had such low viscosities that they were undesirable for sludge dewatering applications. Example 2 and Comparative Example C produced copolymers with equivalent UL
viscosities. These two samples were then subjected to efficacy testing to determine if any difference in performance existed. A
Buchner Funnel Test was used to evaluate the dewatering activity of each polymer. A mixture of primary and secondary sludge from a ` \ paper mill was used as the test substrate. Results are shown in Table Ill. (See Figures 1, 2 and 3).

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TABLE III
SUMMARY OF BUCH~R FUNNEl TESTS
Filtrate Collected (m~) @ Time Indicated (sec) Dosage Example (DDm3 5 10 15 20 30 2 550 78 108 122 13~ 138 Example 2 and Comparative Example C were alsn evaluated at a different paper mill using a substrate of mixed primary and secondary sludge. Results are shown in Table IV.

TABEE IV
SUMMARY OF BUCHNER FUNNEL TESTS
Filtrate Collected (~ Ttme Indicated ~sec~
Dosage E~a~mQle (Dpm) 5 10 15 20 30 2~3~5~

The results of the drainage tests show that the polymer prepared in accordance w1th the present invention performed better than Comparative Example C.

The copolymers prepared in Examples 3, 4, and 6 were also evaluated for dewatering activity using a Buchner Funnel Test, the results. of which are shown in Table V. The test substrate was a mixture of prjmary and secondary sludge taken from a sludge holding tank at a paper mill. The total sludge solids were 2.17X.

TABEE Y
10 SUMMARY OF ~U0HNER FUNNEL TESTS
Filtrate Collected tml) @ Time Indicated (sec) Dosage ExamDle(DDmI 5 10 15 20 30 40 So 2~ 3 300 116 146 158 168 174 180 184 6 300 11~ 144 160 172 182 190 Ig4 Polymers prepared by the process of Examples 7-9 were evaluated us1ng a Buchner ~unnel Test in secondary sludge from a paper mlll. The results are shown in Table YI.

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TABLE Vl SUMMARY OF BUCHNER FUNNEL TEST
Polymer Dosage Filtrate Collected (ml) (DDm) in 2 minutes The polymers performed well on the filter press. They retained their efficacy even when the sludge had a relatively high pH of 10 - 11.

The polymer prepared by the process of the present invention also exhiblts efficacy in paper retention applications.

The initiator and polymerization conditions in accordance with the present invention can be used to copolymerize acrylamide w1th monomers other than DADMAC. The monomers may comprtse cationtc monomers such as dimethylaminoethyl acrylate, diethytaminoethylacrylate, dimethylaminoethylmethacrylate, dtethylamtnoethylmethacrylate and methyl chloride or dimethyl sulfate quaternary salts of the above compounds. As shown in Table Vll, acrylamtde copolymers of Examples 10-14 were prepared in a procedure stmtlar to the one described in Examples I and 2. The resultlng emulston polymers had a substantially lower gel content.

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TABLE VII
SUMMARY OF CATIONIC ACRYLAMIDE COPOLYMERS

Cation~c Mole Percent UL Viscosity, cps ExamDle Monomer Cat. Monomer(0.3% active Dolvmer in 4.0% N3cl) IO AETAC 2.0 41.9 II AE~AC 5.0 44.8 I2 METAC 2.0 25.5 I3 METAC 2.0 30.9 14 DEAS I.5 34.0 IO AETAC = dimethylaminoethylatrylate/methyl chloride METAC - dimethylam1noethylmethasrylate/methyl chloride DEAS - diethylam1noethylacrylate/dimethyl sulfate Other typical an10n1c comonomers copolymerized with acrylam1de can be selected from acryl1c ac1d, methacrylic acid, I5 male1c acid, 1taconic ac1d, and the like, and water-soluble salts thereof. These salts can include, but are not limited to, the sodium, potass~um, and am~on1u~ salts thereof. The mole percent of the comonomers ~n the polymers may vary within certain limits, prov1ded that the total adds up to 100%.

Wh~le the invent10n has been descrtbed with respect to particular embodiments thereof, it is apparent that numerous other forms and mod~ficat~ons of th1s 1nvention w~ll be obvious to those skilled ln the art. The appended cla1ms and this 1nvention generally should be construed to cover all such obvious forms and modifications Z5 wh1ch are within the true spirit and scope of the present invention.

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Claims (11)

1. A process for the production of a stable water-in-oil emulsion copolymer having repeat units of acrylamide and diallyl dimethyl ammonium chloride monomers the improvement which comprises blending a sufficient amount of said acrylamide with said diallyl dimethyl ammonium chloride in an aqueous medium to create an aqueous phase, homogenizing said aqueous phase into an oil phase containing about 5 to 10% by weight of at least one emulsifier in a reaction vessel, polymerizing said monomers at a temperature of about 40° -65°C in the presence of 2,2'-azobis(2,4-dimethylvaleronitrile) and, during polymerization, adding a sufficient amount of a chain transfer agent selected from the group consisting of formic acid and its salt, sodium hydrophosphite mercaptoethanol, thioglycolic acid, mercapto-propionic acid and a lower alkyl alcohol having from 1 to 4 carbon atoms resulting in said emulsion copolymer being substantially free of gel.

2. A process according to claim 1 wherein said emulsifier has a combined HLB of approximately 5.0 to 6.5.

3. A process according to claim 1 further comprising poly-merizing said copolymer in the presence of a chelant.

4. A process according to claim 1 wherein the polymeri-zation temperature is about 40° - 55°C.

5. A process according to claim 1 wherein the amount of said acrylamide and said diallyl dimethyl ammonium chloride is about 30% to about 80% by weight, based on the total weight of the aqueous phase.

6. A process according to claim 1 wherein the amount of 2,2'-azobis(2,4-dimethylvaleronitrile) is from about 10 to 5,000 ppm based on the total of said monomers.

7. A process according to claim 6 wherein the amount of 2,2'-azobis (2,4-dimethylvaleronitrile) is from about 50 to 1000 ppm based on the total of said monomers.

8. A process according to claim 1 wherein said aqueous phase is adjusted to a pH of about 4.0 to 5.5;

9. A process according to claim 1 wherein said chain transfer agent is added in an amount of between 0.01 and 3.0 weight percent based on the total weight of the monomers.

10. A process according to claim 9 wherein said claim transfer agent is added in an amount of between 0.02 and 1.5 weight percent based on the total weight of the monomers.

11. A process according to claim 1 wherein said chain transfer agent is formic acid or salt thereof.