CATIONIC POLYACRYLAMIDES WITH MICRO-BLOCK STRUCTURE

Abstract

Provided is a polymer composition containing a water-soluble cationic copolymer P2 structured in micro-blocks obtained by radical polymerization of at least one non-ionic monomer and at least one cationic monomer, in the presence of a homopolymer P1 having an average molecular weight between 5,000 and 100,000 daltons, the homopolymer P1 having been prepared from 2-acrylamido-2-methylpropane sulphonate in salified form and in the presence of 200 to 20,000 ppm by weight of 2-methyl-2-propenyl-sulphonic acid in salified form. Related methods are also provided.

Claims

1. A polymer composition comprising a water-soluble cationic copolymer P2 structured in micro-blocks obtained by radical polymerization of at least one non-ionic monomer and at least one cationic monomer, in the presence of a homopolymer P1 having an average molecular weight between 5,000 and 100,000 daltons, wherein said homopolymer P1 has been prepared from 2-acrylamido-2-methylpropane sulphonate in salified form and in the presence of 200 to 20,000 ppm by weight of 2-methyl-2-propenyl-sulphonic acid in salified form.

2. The polymer composition according to claim 1, wherein the homopolymer P1 is prepared in the presence of 300 to 10,000 ppm of 2-methyl-2-propenyl-sulfonic acid in salified form.

3. The polymer composition according to claim 1, wherein the homopolymer P1 is prepared in the presence of 300 to 10,000 ppm by weight of 2-methylidene-1,3-propylenedisulfonic acid in salified form.

4. The polymer composition according to claim 1, wherein the salified forms of 2-acrylamido-2-methylpropane sulfonic acid, and of 2-methyl-2-propenyl sulfonic acid are sodium salts.

5. The polymer composition according to claim 1, wherein the water-soluble cationic copolymer P2 is water-soluble and has a weight average molecular weight greater than 100,000 daltons and less than or equal to 40 million daltons.

6. The polymer composition according to claim 1, wherein the cationic monomer of the water-soluble cationic copolymer P2 is chosen from the group consisting of quaternized or salified dimethylaminoethyl acrylate (ADAME), quaternized or salified dimethylaminoethyl methacrylate (MADAME), diallyldimethylammonium chloride (DADMAC), acrylamidopropyltrimethylammonium chloride (APTAC), methacrylamidopropyltrimethylammonium chloride (MAPTAC), and mixtures thereof.

7. The polymer composition according to claim 1, wherein the nonionic monomer of the water-soluble cationic copolymer P2 is chosen from the group consisting of acrylamide, methacrylamide, N-alkylacrylamides, N-alkylmethacrylamides, N,N-dialkylacrylamides, N,N-dialkylmethacrylamides, alkoxylated esters of acrylic acid, alkoxylated esters of methacrylic acid, N-vinylpyridine, N-vinylpyrrolidone, hydroxyalkylacrylates, hydroxyalkylmethacrylates, and mixtures thereof, the alkyl groups being linear and C.sub.1-C.sub.3.

8. The polymer composition according to claim 1, wherein the cationic monomer represents 10 to 90 mol % of the water-soluble cationic copolymer P2, and in that the at least one nonionic monomer represents 10 to 90 mol % of the water-soluble cationic copolymer P2.

9. The polymer composition according to claim 1, wherein the ratio of the moles of cationic monomers in the water-soluble cationic polymer P2 relative to the moles of 2-acrylamido-2-methylpropane sulfonate in salified form in P1 is between 0.2 and 3.

10. The polymer composition according to claim 2, wherein the homopolymer P1 is prepared in the presence of 300 to 10,000 ppm by weight of 2-methylidene-1,3-propylenedisulfonic acid in salified form.

11. The polymer composition according to claim 10, wherein the salified forms of 2-acrylamido-2-methylpropane sulfonic acid, 2-methyl-2-propenyl sulfonic acid, and 2-methylidene-1,3-propylenedisulfonic acid, are sodium salts.

12. The polymer composition according to claim 10, wherein the water-soluble cationic copolymer P2 is water-soluble and has a weight average molecular weight greater than 100,000 daltons and less than or equal to 40 million daltons.

13. The polymer composition according to claim 11, wherein the water-soluble cationic copolymer P2 is water-soluble and has a weight average molecular weight greater than 100,000 daltons and less than or equal to 40 million daltons.

14. The polymer composition according to claim 10, wherein: the cationic monomer of the water-soluble cationic copolymer P2 is chosen from the group consisting of quaternized or salified dimethylaminoethyl acrylate (ADAME), quaternized or salified dimethylaminoethyl methacrylate (MADAME), diallyldimethylammonium chloride (DADMAC), acrylamidopropyltrimethylammonium chloride (APTAC), methacrylamidopropyltrimethylammonium chloride (MAPTAC), and mixtures thereof; and the nonionic monomer of the water-soluble cationic copolymer P2 is chosen from the group consisting of acrylamide, methacrylamide, N-alkylacrylamides, N-alkylmethacrylamides, N,N-dialkylacrylamides, N,N-dialkylmethacrylamides, alkoxylated esters of acrylic acid, alkoxylated esters of methacrylic acid, N-vinylpyridine, N-vinylpyrrolidone, hydroxyalkylacrylates, hydroxyalkylmethacrylates, and mixtures thereof, the alkyl groups being linear and C.sub.1-C.sub.3.

15. The polymer composition according to claim 14, wherein the water-soluble cationic copolymer P2 is water-soluble and has a weight average molecular weight greater than 100,000 daltons and less than or equal to 40 million daltons.

16. The polymer composition according to claim 11, wherein: the cationic monomer of the water-soluble cationic copolymer P2 is chosen from the group consisting of quaternized or salified dimethylaminoethyl acrylate (ADAME), quaternized or salified dimethylaminoethyl methacrylate (MADAME), diallyldimethylammonium chloride (DADMAC), acrylamidopropyltrimethylammonium chloride (APTAC), methacrylamidopropyltrimethylammonium chloride (MAPTAC), and mixtures thereof; and the nonionic monomer of the water-soluble cationic copolymer P2 is chosen from the group consisting of acrylamide, methacrylamide, N-alkylacrylamides, N-alkylmethacrylamides, N,N-dialkylacrylamides, N,N-dialkylmethacrylamides, alkoxylated esters of acrylic acid, alkoxylated esters of methacrylic acid, N-vinylpyridine, N-vinylpyrrolidone, hydroxyalkylacrylates, hydroxyalkylmethacrylates, and mixtures thereof, the alkyl groups being linear and C.sub.1-C.sub.3.

17. The polymer composition according to claim 16, wherein the water-soluble cationic copolymer P2 is water-soluble and has a weight average molecular weight greater than 100,000 daltons and less than or equal to 40 million daltons.

18. The polymer composition according to claim 15, wherein the cationic monomer represents 10 to 90 mol % of the water-soluble cationic copolymer P2, and in that the at least one nonionic monomer represents 10 to 90 mol % of the water-soluble cationic copolymer P2.

19. The polymer composition according to claim 15, wherein the ratio of the moles of cationic monomers in the water-soluble cationic polymer P2 relative to the moles of 2-acrylamido-2-methylpropane sulfonate in salified form in P1 is between 0.2 and 3.

20. A method for treating waste water or improving a papermaking process, said method comprising adding the polymer composition according to claim 1 to an aqueous solution as a flocculant or dry strength agent.

Description

EXEMPLARY EMBODIMENTS OF THE INVENTION

Example 1: Synthesis of Polymers P1a, P1b and P1c

[0056] In a 1-liter jacketed reactor, equipped with a condenser and a stirrer, 190 g of deionized water are added to be heated to 80 C. under a nitrogen atmosphere (nitrogen flow).

[0057] A sodium persulfate solution is prepared in a dropping funnel, by dissolving 17 g of sodium persulfate in 100 g of deionized water. Into a second dropping funnel are charged 690 g of a sodium salt solution of 2-acrylamido-2-methylpropane sulfonic acid at 50% concentration by weight. A high-pressure liquid chromatography analysis indicates an amount of 1556 ppm of 2-methyl-2-propenyl-sulfonic acid in the form of sodium salt and 450 ppm of 2-methylidene-1,3-propylenedisulfonic acid in the form of salt sodium.

[0058] The sodium persulfate solution is added to the reactor over a period of 120 minutes, and the sodium salt solution of 2-acrylamido-2-methylpropane sulfonic acid is added concomitantly over a period of 90 minutes. During the addition of these reagents, and then again for 60 min (counted after addition of the sodium persulfate), the reaction medium is maintained at 80 C. The polymer P1a according to the invention thus obtained has a weight average molecular weight equal to 47,000 daltons (determined from the intrinsic viscosity).

[0059] The synthesis of a P1 b polymer is undertaken by carrying out the same protocol as previously with the only difference that the polymerization temperature is maintained at 100 C. The polymer P1 b according to the invention thus obtained has a weight average molecular weight equal to 24,600 daltons (determined from the intrinsic viscosity).

[0060] The synthesis of a polymer P1c is undertaken by carrying out the same protocol as previously (polymer P1a) with the only difference that the 2-methylpropane sulfonic acid contains an amount of 102 ppm of 2-methyl-2-propenyl-sulfonic acid as the sodium salt and 80 ppm of 2-methylidene-1,3-propylenedisulfonic acid as the sodium salt. The comparative polymer P1c thus obtained has a weight average molecular weight equal to 245,000 daltons (determined from the intrinsic viscosity).

[0061] All the P1 polymers previously described are in the form of an aqueous solution with a concentration of 40% by weight of 2-methylpropane sulfonic acid homopolymer in the sodium salt form in water.

Examples 2: Synthesis of Polymer Compositions Comprising the Polymers P2a and P2b According to the Invention and Comparative Polymers P2c and P2d

[0062] 522 g of deionized water, 202 g of dimethylaminoethyl acrylate quaternized with methyl chloride (80% concentration by weight in water), 276 g of acrylamide (50% concentration by weight in water) and 405 g of polymer P1a (40% concentration by weight in water) are added in a 2000-mL beaker.

[0063] The solution thus obtained is cooled to between 5 and 10 C. then transferred to an adiabatic polymerization reactor. A nitrogen bubbling is then carried out for 30 minutes in order to eliminate all traces of dissolved oxygen.

[0064] Are then added to the reactor: [0065] 0.45 g of 2,2-azobisisobutyronitrile, [0066] 1.5 mL of an aqueous solution at 2.5 g/L of 2,2-Azobis[2-(2-imidazolin-2-yl)propane] dihydrochloride, [0067] 1.5 mL of a 1 g/L aqueous solution of sodium hypophosphite, [0068] 1.5 mL of a 1 g/L aqueous solution of tert-butyl hydroperoxide, [0069] 1.5 mL of an aqueous solution at 1 g/L of ammonium sulphate and iron (II) hexahydrate (Mohr's salt).

[0070] After a few minutes, the nitrogen bubbling is stopped. The polymerization reaction takes place for 4 hours to reach a temperature peak. At the end of this period, the polymer gel obtained is chopped then dried then ground again to obtain a polymer P2a according to the invention in the form of a powder with a weight average molecular weight equal to 8,230,600 daltons (determined from the intrinsic viscosity).

[0071] A polymer P2b is obtained by applying the same protocol with, instead of polymer P1a: polymer P1b. The polymer P2b according to the invention thus obtained in powder form has a weight average molecular weight equal to 8,320,500 daltons (determined from the intrinsic viscosity).

[0072] A polymer P2c is obtained by applying the same protocol with, instead of the P1a polymer: the P1c polymer. The comparative polymer P2c thus obtained in powder form has a weight average molecular weight equal to 8,400,500 daltons (determined from the intrinsic viscosity).

[0073] A polymer P2d is obtained by applying the same protocol but in the absence of polymer P1. The comparative polymer P2d thus obtained in powder form has a weight average molecular weight equal to 8,125,000 daltons (determined from the intrinsic viscosity).

Example 3: Application Performance of Polymer Compositions Comprising Polymers P2a and P2b According to the Invention, and Comparative P2c and P2d in a Papermaking Process

[0074] Retention aids are polymers added to cellulosic fiber slurries prior to paper formation in order to improve the efficiency with which fine particles, including cellulosic fines, are retained in the paper product.

Type of Paper Pulp Used

[0075] Virgin fiber pulp:

[0076] The wet pulp is obtained by disintegrating the dry pulp to obtain a final aqueous concentration of 1% by weight. It is a neutral pH pulp composed of 90% bleached virgin long fiber, 10% bleached virgin short fiber and an additional 30% GCC (ground calcium carbonate) by weight based on fiber weight.

Assessment of Total Retention and Ash Retention

[0077] For all the following tests, the polymer solutions are prepared at 0.5% by weight. After 45 minutes of preparation, the polymer solutions are diluted 10 times before injection.

[0078] The various results are obtained using a Britt Jar type device with a stirring speed of 1000 rpm.

[0079] The process sequence is as follows: [0080] T=0 s: Stirring of 500 mL of paper pulp at a concentration of 0.5% by weight. [0081] T=10 s: Addition of the retention agent (300 g of dry polymer P2/ton of dry pulp). [0082] T=20 s: Sampling of the first 20 mL corresponding to the dead volume under the cloth, then recovery of 100 mL of white water.

[0083] The percentage of First Pass Retention (% FPR), corresponding to the total retention, is calculated according to the following formula: % FPR=(CHBCWW)/CHB*100

[0084] where: [0085] CHB: Headbox consistency; and [0086] CWW: White water consistency.

[0087] The First Pass Ash Retention percentage (% FPAR), corresponding to the total retention, is calculated according to the following formula: % FPAR=(AHBAWW)/AHB*100

[0088] where: [0089] AHB: Headbox ash consistency; and [0090] AWW: White water ash consistency.

[0091] For each of these analyses, the highest values correspond to the best performance.

[0092] The results are summarized in Table 1.

Gravity Drainage Performance Evaluation using the Canadian Standard Freeness (CSF)

[0093] In a beaker, the pulp is processed at a stirring speed of 1000 rpm.

[0094] The process sequence is as follows: [0095] T=0 s: Stirring of 500 mL of pulp at a concentration of 0.6% by weight. [0096] T=10 s: Addition of the retention agent (300 g of dry polymer P2/ton of dry pulp). [0097] T=20 s: Stirring stopped and addition of the amount of water necessary to obtain 1 liter.

[0098] This liter of pulp is transferred to the Canadian Standard Freeness Tester and the TAPPI T227om-99 procedure is applied.

[0099] The volume, expressed in mL, recovered by the side arm, gives a measure of the gravity drainage. The higher the value, the better the gravity drainage.

[0100] This performance may also be expressed by calculating the percent improvement over blank (% CSF).

[0101] Higher values correspond to better performance. The results in Table 1 show that the polymer compositions comprising the P2 polymers according to the invention (P2a and P2b) make it possible to improve the drainage performance and the total retention compared to the comparative polymers P2c and P2d.

TABLE-US-00001 TABLE 1 Polymer % FPAR % FPR % CSF P2a 32.4 71.23 7.5 P2b 33.3 74.4 11.3 P2c 20.3 64.5 1.7 P2d 19.1 61.8 1.5

Example 4: Flocculation Test of the Polymer Compositions Comprising the Polymers P2a and P2b According to the Invention, and Comparative P2c and P2d

[0102] The polymers are dissolved in tap water to obtain aqueous solutions with a concentration of 0.4% by weight of polymer relative to the total weight of the solution. The solutions are mechanically stirred at 500 rpm until complete solubilization of the polymers and obtaining clear and homogeneous solutions.

[0103] A series of flocculation tests are carried out on a mining effluent from a coal mine having a solids content of 17.4% by weight.

[0104] An amount of each solution, corresponding to a polymer dosage of 280 g of polymer per ton of dry matter from the mining effluent, is added to 200 g of mining effluent. Thorough mixing is done manually until optimal flocculation and water release are observed.

[0105] The result is expressed by Net Water Release (NWR) which corresponds to the total amount of water recovered 1 hour after the flocculation test, minus the amount of water unduly added during the incorporation of the aqueous polymer solution in the suspension. The same NWR is calculated after 24 hours, which gives a good indication of the maximum water release.

[0106] At the end of these 24 hours, the turbidity of the water supernatant thus released is also measured.

[0107] The results in Table 2 demonstrate that the polymer compositions comprising the polymers P2a and P2b according to the invention make it possible to improve the NWR and the turbidity of the supernatant (compared to the comparative polymers P2c and P2d).

TABLE-US-00002 TABLE 2 Polymer 1 hour NWR 24 hour NWR Turbidity (NTU) P2a 87 90 12 P2b 89 93 9 P2c 74 76 25 P2d 72 73 44