POLYELECTROLYTES MODIFIED BY REACTION WITH ANHYDRIDE GROUP CONTAINING COPOLYMERS AND THEIR USE AS FLOCCULENTS

Abstract: The present invention relates to modified polyelectrolytes which are useful as flocculents in separation processes, to processes for preparing the modified polyelectrolytes, flocculent compositions incorporating the modified polyelectrolytes and to separation methods employing the modified polyelectrolytes and modified polyelectrolyte compositions of the invention.

Description: POLYELECTROLYTES MODIFIED BY REACTION WITH ANHYDRIDE GROUP CONTAINING COPOLYMERS AND THEIR USE AS FLOCCULENTS TECHNICAL FIELD The present invention relates to modified polyelectrolytes which are useful as flocculents 1n separation processes, to processes for preparing the modified polyelectrolytes, flocculent compositions Incorporating the modified polyelectrolytes and to separation methods employing the modified polyelectrolytes and modified polyelectrolyte compositions of the invention. The modified polyelectrolytes of the Invention perform better than the prior art polyelectrolytes in that they are capable of achieving the same level of flocculation at lower concentrations and are capable of retaining a higher percentage of super fines. BACKGROUND ART Introduction of synthetic water-soluble polymers to the mining industry in 1951 represented a major development in solid-liquid separation by chemical reagents. They were the first of a wide range of flocculents tailored to meet many needs such as clarification of water (municipal and industrial ) , treatment of municipal sewerage and industrial waste (food processing, oil refining, metal finishing, pulp and ' paper mills etc.), mineral processing (benefication, recycle-water clarification, effluent treatment), and manufacturing processes (paper production, sugar refining, phosphoric acid production etc.). Although there are a large number of commercially available synthetic flocculents the number of significantly different types of chemical structures is relatively limited. In the market place selection of a flocculant depends on optimizing the cost-to-performance ratio, that is, achieving desired performance at minimal cost. Although a systems point of view predominates (including flocculant availability, reproducibil ity, handling, storage, tolerance to fluctuations in treatment-plant loading while meeting output specifications, equip ent-in-place and necessary modification etc), the delivered cost per unit weight of individual flocculants enter as one factor. Consequently, a relatively few monomers suitable for incorporation Into water-soluble polymers and produced on a sufficiently large scale to have low cost, are the major building blocks of commercially important synthetic polymeric flocculants. Practical synthetic organic flocculants are water soluble polymeric substances with weight av-erage molecular weights ranging from about 1000 to greater than 5 million (reported values as high as 20 million). Polyelectrolytes used as flocculants include polymers and copolymers made from a number of monomers including maleic anhydride, maleic add, acrylic acid, acrylamlde, acrylonitrile, methacrylic acid, vinyl sulfonlc acid, p-styrene sulfonic acid, styrene, vinyl methyl ether, metaphosphorlc add, vinylamine, ethyleneimine, vinyl pyridine and 4-vinyl-N- dodecylpyrldinium chloride. DISCLOSURE OF THE INVENTION In a first embodiment of the Invention there is provided a modified polyelectrolyte characterized in that a polyelectrolyte is reacted with a copolymer of at least two ethy enically unsaturated monomers, at least one of which contains anhydride groups. In a second embodiment of the invention there is provided a process for manufacturing a modified polyelectrolyte, which process comprises reacting a polyelectrolyte with a copolymer of at least 2 ethylenically unsaturated monomers, at least one of which contains add anhydride groups. The reaction can be initiated by heat and/or by an inorganic accelarator such as a metallic base. A suitable accelerator is potassium carbonate. The types of known polyelectrolytes suitable for use in this invention are extremely numerous and diversified. No unsuitable commercially available or laboratory synthesized polyelectrolyte has been found. Common trade names defining such polyelectrolytes include: SANY0FL0C; ALFLOC; SUPERFLOC; MACR0FL0C; MAGNAFLOC; MAXFLOC and ZETAG. Other materials designed for the same or similar purposes to those described above may also be used. Generally, the polyelectrolytes which can be modified according to the 4 8 invention have molecular weights in the range 2x10 to 1x10 , especially 5 6 1x10 to 7x10 daltons. The preferred copolymers with which the polyelectrolytes are reacted have molecular weights in the range 1x10 to 1x10 daltons. It is particularly preferred that a known polyelectrolyte flocculant is reacted with a copolymer of methyl vinyl ether and maleic anhydride. A third embodiment of the invention provides a further modified polyelectrolyte characterized in that the modified polymer according to the first embodiment of the invention is further modified by reaction with vinyl pyrrolidone or polyvinyl pyrrolidone followed by further reaction with the copol mer. A fourth embodiment of the invention provides a process for anufacturing a further modified polyelectrolyte which process comprises terminating the process according to the second embodiment of the invention b reducing the temperature, dispersing the reaction mixture with .vinyl pyrrol!idone or polyvinyl pyrrolidone and allowing the reaction to proceed. The further reaction can also be Initiated by heat and/or by an Inorganic accelerator. A fifth embodiment of the invention provides a flocculating composition comprising a modified polyelectrolyte or a further modified polyelectrolyte according to the invention in association with the usual carriers and diluent employed in conventional flocculating compositions. A sixth embodiment of the invention provides a method of flocculation which method comprises adding to a material to be flocculated a modified polyelectrolyte, a further modified electrolyte and/or a flocculating composition according to the invention. BEST MODES OF CARRYING OUT THE INVENTION Polymer solids at an amount of between 0 and 2007., preferably 107. by weight (on the basis of polyelectrolyte solids) may effectively be employed i this invention. Generally, the reaction is carried out by simple mixing or ho ogenization of the polyelectrolyte and copolymer. Reaction times and reaction temperatures will depend on the nature of the polyelectrolyte and th copolymer but generally the reaction can be carried out at temperature of between 0° and 120°C for a time of between 5 minutes to 4 hours. It is preferred that the polyelectrolyte and copolymer be selected such that the reaction can be carried out at a temperature of between 40° and 80 β C for a time of up to 50 minutes. Preferably, he reaction is carried out in solutio In order to further modify the polyelectrolyte, the reaction is stopped preferably by reducing the temperature to below 30 β C, vinyl pyrrol idone or polyvinyl pyrrolidone is added, the mixture is agitated or stirred to dispers the vinyl pyrrolidone or polyvinyl pyrrolidone and the mixture is reheated to restart the reaction. If there is an excess of copolymer, the vinyl pyrrolidone or polyvinyl pyrrolidone reacts with the anhydride moiety of either reacted or unreacted copolymer resulting in a mixture of further modified polyelectrolyte and modified copolymer. It is preferred that the ratio of vinyl pyrrolidone or polyvinyl pyrrolidone to copolymer is in the range 1:1 to 1:10 by weight, more preferably 1:5 by weight. The fol lowing examples i l lustrate preferred embodiments of the invention and shoul d not be construed as l imi ti ng on the scope thereof. EXAMPLE 1 11 polyel ectrolytes were reacted wi th various methyl vi nyl ether/malei c anhydride copolymers . The types of base polymers are set out I n Table 1 . Table 1 Exampl e Type 0 Polyacryl amide 1 Copolymer of Sodium Acrylate and Acryl mide 2 3 4 5 6 7 Terpolymer of Acrylamide, Sodium Acryl te and Maleic Anhydride 8 Terpolymer of Acrylami e, Sodium Acrylate and Vinyl Pyridine 9 Copolymer of Sodium Acrylate and Acyl mide 10 Polysodium Acrylate NOTE: It can be seen that samples 0 to 10 range from nonionic to 1007. anionic. The polymers in Table 1 were reacted with poly methyl vinyl ether/maleic anhydride copolymers of the following molecular weights: ?0,000; 67,000 and 80,000. All reactions were carried out by dispersing the poly methyl vinyl ether/maleic anhydride copolymers in the finished base polymer. This blend was then placed in a water bath at 80 * C and the reaction occurred within 40 minutes. The end point of the reaction could be determined as a visible physical change in the base polymer. The amounts of poly methyl vinyl ether/maleic anhydride) were varied between 0 to 100% of the solids of base polyelectrolytes. The results obtained demonstrated that maximum efficiency (as determined by maximum performance for lowest amount of material) was at 107. polymer solids (based on polyelectrolyte solids) with molecular weight of poly(methyl vinyl ether/maleic anhydride) at 67,000 daltons. Example 2 1s based on the above percentage and molecular weight. The base polymer number refers to Table 1. EXAMPLE 2 The polymers prepared 1n Example 1 were evaluated for efficiency by comparison with the polyelectrolytes from which they were derived. In all cases the performance of the new materials was superior to that of the polyelectrolytes from which they were derived. Comparisons conducted at mine sites were advantageously done by selecting a polyelectrolyte with correct charge density for the materials being separated and comparing these with modified polyelectrolytes comprising the same base polyelectrolyte and possessing the same or similar charge density. Whilst these examples are based on coal flocculatlon, the same and/or similar benefits can be attained wherever polyelectrolyte technology Is in use. The following results were obtained in laboratory scale testing on site at the following coal washeries: * Indicates the correct charge density on the base polymer m/h Metres/hour R Where a second reaction has been performed on the base polymer. EXAMPLE 3 A Latex polymer of the following characteristics was prepared. Organic solids 32.0% pH(l%) 6.0 Ratio Acrylam1de:Dimethylaminoethyl Methacrylate 60:40 nominal mw 2x10 This polymer was cooled to below 30 β C then further reacted with 1.5% by weight poly(methyl vinyl ether/maleic anhydride) with a mw 80,000 (daltons). The reaction was carried out by dispersing the powder through the latex and placing into a water bath at 50 β C for 50 minutes. On cooling the flocculent latex was packaged. This following results were obtained from testing work on an undigested sewerage sludge obtained ' from a sewerage treatment plant. A. Base Polymer dose 240 ppm Settling Velocity 2.6 m/h Shear resistance pass B. New Polymer dose 240 ppm Settling Velocity 4.7 m/h Shear resistance pass m/h Metres/hour EXAMPLE 4 A solution polymer of the following characteristics was cooked. Organic polymer solids 6% pH(neat) 8.0 Ratio Acrylamide:Acrylic A d 60:100 nominal mw 6x10 This polymer was reacted with 0.5% polymer (methyl vinyl ether/maleic anhydride) with a mw of 67000 daltons(ex GAF). The reaction was carried out by dispersing the powder through the solution and placing into a water bath at 60°C for 4 hours. The resultant mixture was cooled to below 30 β C and 1.0% of polyvinyl pyrollidone was dispersed into the mixture. The mixture was replaced into the water bath for 2 hours. On cooling the flocculent solution was packaged. EXAMPLE 5 A latex polymer of the following characteristics was prepared. Organic solIds 28.5% pH ( l%) 8.0 Ratio Acrylam1de:Acrylic Acid 34:23 nominal mw 12x10 This polymer was cooled to below 30°C then further reacted with 2.5% by weight of poly(methyl vinyl ether/maleic anhydride) mw 67,000 (daltons) dispersed 1n twice Its weight of 1n aromatic solvent. This mixture was coole to below 30 β C and 0.5% of polyvinyl pyrrolidone was dispersed in the mixture. The mixture was replaced Into the water bath for 30 m1n. On cooling the flocculent latex was packaged. EXAMPLE 6 A solution polymer of the following characteristics was prepared. Organic polymer solids 6% pH(neat) 8.0 Ratio of Acrylamide:Acrylic Acid 7:1 nominal mw 5x10 This polymer was reacted with 0.57. poly(methyl vinyl ether/maleic anhydride) with a mw 80,000 daltons. The reaction was carried out by dispersing the powder through the solution and placing Into a water bath at 60°C for 4 hours. The resultant mixture was cooled to below 30°C and 0.1% of polyvinyl pyrrolidone was dispersed in the mixture. The mixture was replaced into the water bath for 2 hours. On cooling the flocculent solution was packaged. EXAMPLE 7 A solution polymer of the following characteristics was prepared. Organic solids 6% pH(neat) 8.0 Ratio of Acrylamide.-Acrylic Acid 50:50 This base polymer was reacted with 0.5% w/w poly(methyl vinyl ether/ maleic anhydride) with a mw of 67,000 daltons. The reaction was carried out by dispersing the powder through the solution and placing into a sealed container in a water bath for 4 hours at 60°C. The resultant mixture was cooled to below 30C and 0.1% of polyvinyl pyrrolidone was dispersed in the mixture. The mixture was replaced into the water bath for.2 hours. On cooling the flocculent solution was packaged. EXAMPLE 8 A solution polymer of the following characteristics was prepared. Organic solids (of acrylic acid) 6% pH(neat) 8.0 This base polymer was reacted with 0.57. poly(methyl vinyl ether/maleic anhydride) with a mw of 67,000 daltons. The reaction was carried out by dispersing the powder through the solution and placing it into a sealed container in a water bath for 4 hours at 60 e C. The resultant mixture was cooled to below 30 β C and 0.1% of polyvinyl pyrrolidone was dispersed in the mixture. The mixture was replaced Into the water bath for 2 hours. On cooling the flocculent solution was packaged. The following results were obtained in laboratory scale testing on site at the following coal washeries: m/h Metres/hour It can be seen from the test data that not only are these compounds a more cost efficient base (on the reaction being done on the compound of ideal charge density in order to coincide with the material being separated), but they also allow for a far greater latitude in charge density whilst maintaining performance. This is of particular importance in the mining industry where frequent (and sometimes dramatic) changes in charge density requirements are experienced throughout the mining process [e.g. change in orebody, change within a coal seam, or changes from coal seam to coal seam, changes in climatic conditions affecting the treatment of sewerage. Many other examples can be quoted]. INDUSTRIAL APPLICATION The present invention provides modified polyelectrolytes which are useful as flocculents and find use in separation processes from fields as diverse as water treatment, oil refining, metal finishing, food processing, paper milling, mineral processing and manufacturing processes.

Claims: CLAIMS 1. A modified polyelectrolyte characterized in that a polyelectrolyte is reacted with a copolymer of at least two ethylenically unsaturated monomers, at least one of which contains anhydride groups. 2. A process for the manufacture of a modified polyelectrolyte, which process comprises reacting a polyelectrolyte with a copolymer of at least 2 ethylenically unsaturated monomers, at least one of which contains acid anhydride groups. 3. A process according to claim 2 wherein the polyelectrolyte has a 4 8 molecular weight In the range 2x10 to 1x10 daltons. 4. A process according to claim 3 wherein the polyelectrolyte has a molecular weight In the range 1x10 5 to 7x106 daltons. 5. A process according to any one of claims 2 to 4 wherein the polyelectrolyte is present at an amount of from 0 to 200% on the basis of polyelectrolyte solids. 6. A process according to claim 5 wherein the polyelectrolyte is present at an amount of 10% on the basis of polyelectrolyte solids. 7. A process according to any one of claims 2 to 6 wherein the copolymer 4 6 has a molecular weight in the range 1x10 to 1x10 daltons. 8. A process according to any one of claims 2 to 7 wherein the copolymer is a copolymer of methyl vinyl ether and maleic anhydride. 9. A process according to any one of claims 2 to 8 wherein the polyelectrolyte is reacted with the copolymer at a temperature of between 0° and 120 β C for a time of between 5 minutes and 4 hours. 10. A process according to claim 9 wherein the reaction is carried out at a temperature of between 40° and 80°C for a time of up to 50 minutes. 11. A process according to any one of claims 2 to 10 wherein the polyelectrolyte and copolymer are reacted in solution. 12. A modified polyelectrolyte as defined in claim 1 manufactured according to a process as defined in any one of claims 2 to 11. 13. A further modified polyelectrolyte characterized in.that the modified polyelectrolyte according to claim 1 is further modified by reaction with vinyl pyrrolidone or polyvinyl pyrrolidone followed by further reaction with the copolymer. 14. A process for the manufacture of a further modified polyelectrolyte which process comprises terminating the process according to claim 2 by reducing the temperature, dispersing the reaction mixture with vinyl pyrrolidone or polyvinyl pyrrolidone and allowing the reaction to proceed. 15. A process according to claim 14 wherein the temperature is reduced to -li¬ below 30°C, the mixture is agitated or stirred to disperse the vinyl pyrrolidone or polyvinyl pyrrolidone and the mixture is reheated to restart the reaction. 16. A process according to claim 14 or claim 15 wherein the ratio of vinyl pyrrolidone or polyvinyl pyrrolidone to copolymer is in the range 1:1 to 1:10 by weight. 17. A process according to claim 16 wherein the ratio of vinyl pyrollidone or polyvinyl pyrollidone to copolymer is 1:5 by weight. 18. A further modified polyelectrolyte as defined in claim 13 manufactured according to a process as defined in any one of claims 14 to 17. 19. A flocculating composition comprising a modified polyelectrolyte as defined in claim 1 or claim 12 or a further modified polyelectrolyte as defined in claim 13 or claim 18 in association with the usual carriers and diluents employed in conventional flocculating compositions. 20. A method of flocculation which method comprises adding to a material to be flocculated a modified polyelectrolyte as defined in claim 1 or claim 12, a further modifed polyelectrolyte as defined in claim 13 or claim 18 and/or a flocculating composition as defined in claim 19. SUBSTITUTE SHEET

Inventors: WATSON MARK RAEY, WATSON, MARK, RAEY
Applicants: WATSON MARK RAEY, WATSON, MARK, RAEY
Application year: 1989
Main classification: C08G81
IPC codes: B01D21, C02F1, C08G81