Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
2001-01-31
2003-09-30
Zalukaeva, Tatyana (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Polymers from only ethylenic monomers or processes of...
C526S307000, C526S307100, C526S310000, C526S259000, C526S260000, C526S268000, C526S254000, C507S119000, C524S922000
Reexamination Certificate
active
06627719
ABSTRACT:
TECHNICAL FIELD
This invention concerns polymers for waste water clarification. More particularly, this invention is directed to cationic latex terpolymer flocculants and their use for sludge dewatering.
BACKGROUND OF THE INVENTION
The dewatering of sewage sludges and similar organic suspensions, may be augmented by mixing into them chemical reagents in order to induce a state of coagulation or flocculation which thereby facilitates the process of separation of water. For this purpose, lime or salts of iron or aluminum have been utilized. More recently, synthetic polyelectrolytes, particularly certain cationic copolymers of acrylamide have been found to be useful.
Notwithstanding the variety of commercially available polymers which have been found to be capable of flocculating or coagulating organic sludges, there are various circumstances which tend to limit the usefulness of these reagents. Thus, while for certain sludges economical treatments with these known reagents are feasible, more often sludges require very high and cost-ineffective dosages of reagents in order to treat them successfully. Moreover, variations often occur in sludge from any one source. For example, variations in the supply of material to the sludge making process and/or in the oxidizing conditions that may be involved in the production of the sludge lead to a variety of particle types which must be removed. Furthermore, it is not uncommon to encounter sludges which are, for some reason, not amenable to flocculation by any of the known polymeric flocculating agents. It is therefore an object of the invention to provide to the art a superior method for the dewatering of sludge-containing waste waters.
A cationic water-in-oil emulsion polymer of acrylamide and a cationic monomer incorporating from about 0.1 to 0.75 mole percent of a hydroxyalkyl (meth)acrylate and from about 0.01 to 0.075 weight percent of a chain transfer agent for dewatering sludge is disclosed in U.S. Pat. No. 5,093,413. However, these polymers are relatively inefficient for dewatering sludge under high shear conditions such as centrifuge dewatering. Therefore, another object of this invention is to provide a new class of polymers that provide superior dewatering performance under high shear conditions.
SUMMARY OF THE INVENTION
We have discovered that cationic latex terpolymers incorporating from about 0.9 to about 5 mole percent hydroxyalkyl (meth)acrylate momomer(s) provide superior sludge dewatering performance, particularly under high shear conditions.
Accordingly, in its principal aspect, this invention is directed to a cationic latex terpolymer prepared by polymerizing from about 1 to about 99.1 mole percent of one or more cationic monomers, from about 0.9 to about 5 mole percent of one or more hydroxyalkyl (meth)acrylates and from 0 to about 98.1 mole percent of one or more nonionic monomers.
In another aspect, this invention is directed to a method of dewatering sludge comprising adding to the sludge an effective amount of a a cationic latex terpolymer prepared by polymerizing from about 1 to about 99.1 mole percent of one or more cationic monomers, from about 0.9 to about 5 mole percent of one or more hydroxyalkyl (meth)acrylates and from 0 to about 98.1 mole percent of one or more nonionic monomers.
In another aspect, this invention is directed to a polymer composition comprising a fluorescent tracer compound and a cationic latex terpolymer prepared by polymerizing from about 1 to about 99.1 mole percent of one or more cationic monomers, from about 0.9 to about 5 mole percent of one or more hydroxyalkyl (meth)acrylates and from 0 to about 98.1 mole percent of one or more nonionic monomers.
DETAILED DESCRIPTION OF THE INVENTION
Definitions of Terms
“Alkyl” means a monovalent group derived from a straight or branched chain saturated hydrocarbon by the removal of a single hydrogen atom. Representative alkyl groups include methyl, ethyl, n- and iso-propyl, and the like.
“Alkylene” means a divalent group derived from a straight or branched chain saturated hydrocarbon by the removal of two hydrogen atoms. Representative alkylene groups include methylene, ethylene, propylene, and the like.
“Based on polymer active” and “based on monomer” mean the amount of a reagent added based on the level of vinylic monomer in the formula, or the level of polymer formed after polymerization, assuming 100% conversion.
“Based on formula” means the amount of reagent added based on the total formula weight.
“Cationic Monomer” means a monomer as defined herein which possesses a net positive charge. Representative cationic monomers include dialkylaminoalkyl acrylates and methacrylates and their quaternary or acid salts, including, but not limited to, dimethylaminoethyl acrylate methyl chloride quaternary salt, dimethylaminoethyl acrylate methyl sulfate quaternary salt, dimethyaminoethyl acrylate benzyl chloride quaternary salt, dimethylaminoethyl acrylate sulfuric acid salt, dimethylaminoethyl acrylate hydrochloric acid salt, dimethylaminoethyl methacrylate methyl chloride quaternary salt, dimethylaminoethyl methacrylate methyl sulfate quaternary salt, dimethylaminoethyl methacrylate benzyl chloride quaternary salt, dimethylaminoethyl methacrylate sulfuric acid salt, dimethylaminoethyl methacrylate hydrochloric acid salt, dialkylaminoalkylacrylamides or methacrylamides and their quaternary or acid salts such as acrylamidopropyltrimethylammonium chloride, dimethylaminopropylacrylamide methyl sulfate quaternary salt, dimethylaminopropylacrylamide sulfuric acid salt, dimethylaminopropylacrylamide hydrochloric acid salt, methacrylamidopropyltrimethylammonium chloride, dimethylaminopropylmethacrylamide methyl sulfate quaternary salt, dimethylaminopropylmethacrylamide sulfuric acid salt, dimethylaminopropylmethacrylamide hydrochloric acid salt, diethylaminoethyl acrylate, diethylaminoethyl methacrylate, diallyldiethylammonium chloride and diallyldimethyl ammonium chloride. Alkyl groups are generally C
1-4
alkyl. Preferred cationic monomers are dimethylaminoethyl acrylate methyl chloride quaternaryl salt, dimethylaminoethyl methacrylate methyl chloride quaternary salt, acrylamidopropyltrimethylammonium chloride and methacrylamidopropyltrimethylammonium chloride. Dimethylaminoethyl acrylate methyl chloride quaternary salt is more preferred.
“Chain Transfer Agent” means any molecule, used in free-radical polymerization, which will react with a polymer radical forming a dead polymer and a new radical. Representative Chain Transfer Agents are listed by K. C. Berger and G. Brandrup, “
Transfer Constants to Monomer, Polymer, Catalyst, Solvent, and Additive in Free Radical Polymerization
,” Section II, pp. 81-151, in “
Polymer Handbook
,” edited by J. Brandrup and E. H. Immergut, 3d edition, 1989, John Wiley & Sons, New York. Preferred chain transfer agents include sodium formate, 2-mercaptoethanol and isopropanol. Sodium formate is more preferred.
“Hydroxyalkyl (meth)acrylate” means a compound of formula
where R
1
is H or CH
3
and L is C
1
-C
8
, preferably C
1
-C
4
alkylene. Representative hydroxyalkyl (meth)acrylates include hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxybutyl acrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, 6-hydroxyhexyl methacrylate, and the like. 2-Hydroxyethyl methacrylate (HEMA) and 2-hydroxypropyl methacrylate are preferred.
“Latex polymer” means a water-in-oil polymer emulsion comprising a cationic terpolymer according to this invention in the aqueous phase, a hydrocarbon oil for the oil phase and one or more water-in-oil emulsifying agents. Latex polymers are hydrocarbon continuous with the water-soluble polymers dispersed within the hydrocarbon matrix. The latex polymer is “inverted” or activated for use by releasing the polymer from the particles using shear, dilution, and, generally, another surfactant. See U.S. Pat. No. 3,734,873, incorporated herein by reference. Representative preparations of high molecular weight inverse emulsion polymers are described U.S. Pat. Nos. 2,982,749; 3,284,393; and 3,734,873.
Shah Jitendra
Sivakumar Ananthasubramanian
Whipple Wesley L.
Breiningern Thomas M.
Martin Michael B.
Ondeo Nalco Company
Zalukaeva Tatyana
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