Method for solution-polymerising (meth)acrylic acid

Abstract

The present invention relates to a novel method for preparing a (meth)acrylic acid polymer in an aqueous solution, said polymer having a molecular mass lower than 8000 g/mol, for example using copper carbonate and iron sulphate (or the derivatives thereof).

Claims

1. A process for preparing a (meth)acrylic acid polymer in aqueous solution, the process comprising: continuously and simultaneously introducing: at least one (meth)acrylic acid monomer to be polymerized, and a polymerization initiator into a reactor heated to a temperature temperature of at least 60° C. and comprising an iron salt or a hydrated derivative thereof and at least one of copper acrylate, copper methacrylate or copper maleate, to obtain a (meth)acrylie acid polymer having a molecular mass of less than 8000 mol.

2. The process of claim 1, further comprising preparing said at least one of copper acrylate, copper methacrylate or copper maleate by introducing into the reactor: a1) water, a2) copper carbonate CuCO.sub.3, or a derivative thereof, and a3) at least one of (meth)acrylic acid or maleic acid prior to said continuously and simultaneously introducing said at least one (meth)acrylic acid monomer to be polymerized and said polymerization initiator into said reactor.

3. The process of claim 1, wherein a mass percentage of the at least one of copper acrylate, copper methacrylate or copper maleate relative to the at least one(meth)acrylic acid monomer to be polymerized is between 0.5% and 5%.

4. The process of claim 1, wherein a mass percentage of the iron salt, or hydrated derivative thereof, relative to the at least one (meth)acrylic acid monomer to be polymerized is between 0.01% and 3%.

5. The process of claim 1, wherein no chain-transfer agent is added to the reactor.

6. The process of claim 1, wherein the process does not include any step of removing reaction byproducts after polymerization occurs.

7. The process of claim 1, wherein a degree of conversion of the at least one (meth)acrylic acid monomer to be polymerized is greater than 99%.

8. The process of claim 1, wherein the reactor comprises no nonaqueous solvent.

9. The process of claim 1, wherein the iron salt or hydrated derivative thereof is an iron sulfate or a hydrated derivative thereof.

10. The process of claim 1, wherein the process provides a (meth)acrylic acid polymer having a molecular mass of less than 6000 g/mol.

11. The process of claim 1, wherein the (meth)acrylic is acid polymer has a polydispersity index PI of between 2 and 3.

12. The process of claim 2, further comprising: simultaneously introducing the iron salt, or hydrated derivative thereof, and components a1), and a2) and a a3) into the reactor prior to said continuously and simultaneously introducing said at least one (meth)acrylic acid monomer to be polymerized and said polymerization initiator into said reactor, wherein the iron salt or hydrated derivative thereof is an iron sulfate or a hydrated derivative thereof.

13. The process of claim 12, wherein a mass ratio between the copper carbonate, or derivative thereof, and the iron sulfate, or hydrated derivative thereof, ranges between 1:4 and 10:1.

14. The process of claim 2, wherein the reactor comprises no nonaqueous solvent.

15. The process of claim 2, wherein the copper carbonate derivative is selected from the group consisting of CuCO.sub.3.Cu(OH).sub.2, (Cu.sub.2(OH).sub.2CO.sub.3) and (Cu.sub.3(OH).sub.2(CO.sub.3).sub.2).

16. The process of claim 2, wherein the process provides a (meth)acrylic acid polymer having a molecular mass of less than 6000 g/mol.

17. The process of claim 2, wherein the (meth)acrylic acid polymer has a polydispersity index PI of between 2 and 3.

Description

EXAMPLES

(1) In each of the following examples, the molecular mass of the polymers according to the invention is determined by size exclusion chromatography (SEC) or gel permeation chromatography (GPC).

(2) Such a technique uses a Waters™ brand liquid chromatography machine equipped with a detector. This detector is a Waters™ brand refractometric concentration detector.

(3) This liquid chromatography apparatus is equipped with a size exclusion column appropriately chosen by a person skilled in the art so as to separate the various molecular weights of the polymers under study.

(4) The liquid elution phase is an aqueous phase adjusted to pH 9.00 with 1 N sodium hydroxide containing 0.05 M of NaHCO.sub.3, 0.1 M of NaNO.sub.3, 0.02 M of triethanolamine and 0.03% of NaN.sub.3.

(5) In detailed manner, according to a first step, the polymerization solution is diluted to 0.9% by dry weight in the SEC dissolution solvent, which corresponds to the SEC liquid elution phase to which is added 0.04% of dimethylformamide which acts as flow marker or internal standard. Next, the solution is filtered through a 0.2 μm filter. 100 μL are then injected into the chromatography machine (eluent: an aqueous phase adjusted to pH 9.00 with 1N sodium hydroxide containing 0.05 M of NaHCO.sub.3, 0.1 M of NaNO.sub.3, 0.02 M of triethanolamine and 0.03% of NaN.sub.3).

(6) The liquid chromatography machine contains an isocratic pump (Waters™ 515) whose flow rate is set at 0.8 ml/min. The chromatography machine also comprises an oven, which itself comprises in series the following column system: a Waters™ Guard Column Ultrahydrogel precolumn 6 cm long and 40 mm in inside diameter, and a Waters™ Ultrahydrogel linear column 30 cm long and 7.8 mm in inside diameter. As regards the detection system, it is composed of an RI Waters™ 410 refractometric detector. The oven is brought to a temperature of 60° C., and the refractometer is brought to a temperature of 45° C.

(7) The chromatography machine is calibrated by means of sodium polyacrylate powder standards of different molecular masses certified by the supplier: Polymer Standard Service or American Polymer Standards Corporation.

(8) The polydispersity index PI of the polymer is the ratio of the mass-average molecular mass Mw to the number-average molecular mass Mn.

(9) The amount of residual monomers is measured according to standard techniques, known to those skilled in the art, for example by high-pressure liquid chromatography (HPLC).

Example 1

(10) The object of this example is to illustrate the preparation of (meth)acrylic acid polymers according to the invention, by using: a dipropionate trithiocarbonate salt (DPTTC) or sodium hypophosphite, iron sulfate heptahydrate, FeSO.sub.4.7H.sub.2O and/or copper carbonate in CuCO.sub.3.Cu(OH).sub.2 form.

(11) Test 1—Prior Art:

(12) This test illustrates a process for preparing a polymer by means of a controlled radical polymerization of RAFT type.

(13) 328 g of water, 94 g of chain-transfer agent 29% DPTTC (i.e. 27 g of 100% DPTTC or 0.092 mol) are placed in a glass synthesis reactor equipped with a mechanical stirrer and heating of oil bath type.

(14) The mixture is heated until it reaches a temperature of 95° C. 328 g of 100% acrylic acid (i.e. 4.558 mol) are added over 2 hours and also, in parallel: 4 g of sodium persulfate Na.sub.2S.sub.2O.sub.8 (i.e. 0.017 mol) dissolved in 76 g of water, and 1.15 g of sodium metabisulfate Na.sub.2S.sub.2O.sub.5 (i.e. 0.006 mol) dissolved in 76 g of water.

(15) The temperature is then maintained for 2 hours, and 3.2 g of 130 V hydrogen peroxide diluted in 46 g of water are then injected.

(16) The mixture is then neutralized by stirring with 381 g of 50% sodium hydroxide diluted in 48 g of water.

(17) The mixture is heated for a further 1 hour at 95° C. and then allowed to cool to room temperature.

(18) Test 2—Outside the Invention:

(19) According to this test, the conditions of test 1 are reproduced, reducing by a factor of 10 the amount of chain-transfer agent DPTTC used.

(20) 328 g of water, 19 g of chain-transfer agent 14% DPTTC (i.e. 2.7 g of 100% DPTTC or 0.0092 mol) are placed in a glass synthesis reactor equipped with a mechanical stirrer and heating of oil bath type.

(21) The mixture is heated until it has reached a temperature of 95° C.

(22) 328 g of 100% acrylic acid (i.e. 4.558 mol) are added over 2 hours and also, in parallel: 4 g of sodium persulfate Na.sub.2S.sub.2O.sub.8 (i.e. 0.017 mol) dissolved in 76 g of water, and 1.15 g of sodium metabisulfite Na.sub.2S.sub.2O.sub.5 (i.e. 0.006 mol) dissolved in 76 g of water.

(23) The temperature is then maintained for 2 hours, and 3.2 g of 130 V hydrogen peroxide diluted in 46 g of water are then injected.

(24) The mixture is then neutralized by stirring with 381 g of 50% sodium hydroxide diluted in 48 g of water.

(25) The mixture is heated for a further 1 hour at 95° C. and then allowed to cool to room temperature.

(26) Test 3—Prior Art:

(27) This test corresponds to test 2 of example 2 of WO 2005/095466 (Coatex).

(28) 150 g of water, 20.31 g of chain-transfer agent 14.4% DPTTC (i.e. 2.92 g of 100% DPTTC) and 50 g of 100% acrylic acid are placed in the synthesis reactor equipped with a mechanical stirrer and heating of oil bath type. The source of free radicals is then added, in the present case 0.4 g of V501. The mixture is heated until it has reached a temperature of 95° C. The temperature is then maintained for 2 hours and the mixture is then allowed to cool to room temperature.

(29) It is then neutralized with 55 g of 50% sodium hydroxide.

(30) Test 4—Prior Art:

(31) This test illustrates a process for preparing a polymer exclusively with sodium hypophosphite monohydrate.

(32) 209 g of water are placed in a synthesis reactor equipped with a mechanical stirrer and heating of oil bath type. 0.1 g of iron sulfate heptahydrate and 0.015 g of copper sulfate pentahydrate are added.

(33) The medium is heated to 90° C. and the following are added simultaneously and continuously over 2 hours: 305 g of acrylic acid and 13 g of water, 19.6 g of 35% H.sub.2O.sub.2 and 25.6 g of NaPO.sub.2H.sub.2.H.sub.2O dissolved in 32 g of water.

(34) The mixture is heated at 90° C. for 1 hour 30 minutes.

(35) It is neutralized with 50% sodium hydroxide until a pH=8 is obtained.

(36) Test 5—Invention:

(37) 245 g of water, 0.28 g of copper carbonate in the form CuCO.sub.3.Cu(OH).sub.2, 5 g of acrylic acid and 0.27 g of iron sulfate heptahydrate are placed in a synthesis reactor equipped with a mechanical stirrer and heating of oil bath type.

(38) The mixture is heated to 94° C., followed by simultaneous and continuous addition over 2 hours of: 35.3 g of 35% H.sub.2O.sub.2 diluted in 9.4 g of water and 274.9 g of acrylic acid.

(39) The mixture is heated at 94° C. for 1 hour 30 minutes.

(40) It is neutralized with 50% sodium hydroxide.

(41) Test 6—Invention:

(42) 245 g of water, 0.28 g of copper carbonate in the form CuCO.sub.3.Cu(OH).sub.2, 5 g of methacrylic acid and 0.31 g of iron sulfate heptahydrate are placed in a synthesis reactor equipped with a mechanical stirrer and heating of oil bath type.

(43) The mixture is heated to 94° C., followed by simultaneous and continuous addition over 2 hours of: 35.3 g of 35% H.sub.2O.sub.2 diluted in 9.4 g of water and 274.9 g of acrylic acid.

(44) The mixture is heated at 94° C. for 1 hour 30 minutes.

(45) It is neutralized with 50% sodium hydroxide.

(46) Test 7—Invention:

(47) Identical to test 5 with 0.345 g of iron sulfate heptahydrate.

(48) Test 8—Invention:

(49) Identical to test 5 with 0.2415 g of iron sulfate heptahydrate.

(50) Test 9—Invention:

(51) Identical to test 5 with 0.414 g of iron sulfate heptahydrate.

(52) Test 10—Invention:

(53) Identical to test 5 with 0.552 g of iron sulfate heptahydrate.

(54) Test 11—Outside the invention:

(55) 245 g of water, 0.28 g of copper carbonate in the form CuCO.sub.3.Cu(OH).sub.2 and 10 g of acrylic acid are placed in a synthesis reactor equipped with a mechanical stirrer and heating of oil bath type.

(56) The mixture is heated to 94° C., followed by simultaneous and continuous addition over 2 hours of: 35.3 g of 35% H.sub.2O.sub.2 diluted in 9.4 g of water and 269.9 g of acrylic acid.

(57) The mixture is heated at 94° C. for 1 hour 30 minutes.

(58) It is neutralized with 50% sodium hydroxide.

(59) Test 12—Invention:

(60) 245 g of water, 0.34 g of copper carbonate in the form CuCO.sub.3.Cu(OH).sub.2, 10 g of acrylic acid and 0.27 g of iron sulfate heptahydrate are placed in a synthesis reactor equipped with a mechanical stirrer and heating of oil bath type.

(61) The medium is heated to 94° C., followed by simultaneous and continuous addition over 2 hours of: 35.3 g of 35% H.sub.2O.sub.2 diluted in 9.4 g of water and 269.9 g of acrylic acid.

(62) The mixture is heated at 94° C. for 1 hour 30 minutes.

(63) It is neutralized with 50% sodium hydroxide.

(64) Test 13—Invention:

(65) Identical to test 12 with 0.229 g of CuCO.sub.3.Cu(OH).sub.2.

(66) Test 14—Outside the invention:

(67) 245 g of water, 0.3 g of iron carbonate FeCO.sub.3, 10 g of acrylic acid and 0.27 g of iron sulfate heptahydrate are placed in a synthesis reactor equipped with a mechanical stirrer and heating of oil bath type.

(68) The medium is heated to 94° C., followed by simultaneous and continuous addition over 2 hours of: 35.3 g of 35% H.sub.2O.sub.2 diluted in 9.4 g of water and 269.9 g of acrylic acid.

(69) The mixture is heated at 94° C. for 1 hour 30 minutes.

(70) It is neutralized with 50% sodium hydroxide.

(71) The results of the measurements taken on the polymers of the above tests are collated in tables 1 to 3 which follow.

(72) TABLE-US-00001 TABLE 1 Mass % Mass % Solids Test DPTTC/ NaPO.sub.2H.sub.2/ Mw content No. monomers monomers (g/mol) PI (%) pH Residual AA (%) 1 PA 8.23 na 5065 1.5 36.6 9 0.13 2 OI 0.82 na 43 400   3.5 36.6 8.5 0.03 3 PA 5.8 na 4947 1.55 36.6 9 0.5 4 PA na 7.0 4780 2.3 40.0 8.0 0.02 na: not applicable PA: prior art OI: outside invention

(73) TABLE-US-00002 TABLE 2 Mass % Mass % Test CuCO.sub.3•Cu(OH).sub.2/ FeSO.sub.4•7H.sub.2O/ CuCO.sub.3•Cu(OH).sub.2/FeSO.sub.4•7H.sub.2O Mw No. monomers monomers ratio (g/mol) PI 5 INV 0.1 0.1 1.04 5770 2.5 6 INV 0.1 0.11 0.91 7030 2.7 7 INV 0.1 0.12 0.83 5575 2.5 8 INV 0.1 0.09 1.18 7020 2.7 9 INV 0.1 0.15 0.69 6075 2.6 10 INV 0.1 0.20 0.52 5730 2.5 11 OI 0.1 0 na 11 105   3.1 na: not applicable INV: invention OI: outside invention

(74) TABLE-US-00003 TABLE 3 Mass % Mass % Test CuCO.sub.3•Cu(OH).sub.2/ FeSO.sub.4•7H.sub.2O/ CuCO.sub.3•Cu(OH).sub.2/FeSO.sub.4•7H.sub.2O Mw No. monomers monomers ratio (g/mol) PI 12 INV 1.12 0.1 1.24 7165 2.5 13 INV 0.08 0.1 0.83 7310 2.5 14 OI 0 + 0.1 na 30 440   5.7 0.1% FeCO.sub.3 na: not applicable INV: invention OI: outside invention

(75) For all of the tests according to the invention, it is noted that the degree of conversion of the monomers to be polymerized is greater than 99.7% and that the content of residual monomers is largely less than 3000 ppm relative to the dry polymer.

Example 2

(76) The object of this example is to illustrate the contents of carbon sulfide, of hydrogen sulfide and of phosphate ions of various samples using polymer solutions of the prior art or polymer solutions according to the present invention.

(77) The analyses of the various samples are performed using an Agilent G1530 gas chromatograph coupled to an Agilent G2577A mass spectrometer as detector. Injection is performed using an Agilent G1888 headspace. An Agilent HP5 30 m×0.25 mm×1 μm column is used (5% phenyl and 95% methylsiloxane phase) which allows elution of the analyses.

(78) The analysis is performed using 2 grams of the samples in native form. The quantification is performed by the dosed addition method.

(79) The analyses of the various samples are also performed using a Metrohm 761 Compact IC ion chromatograph equipped with a conductimetric detector, a chemical suppressor and a CO.sub.2 suppressor. A Metrohm Asupp5 250 anion-exchange column and two precolumns (Metrohm Asupp5 and RP) are used in order to elute the anions including HPO.sub.4.sup.2−.

(80) The analysis is performed using 0.1 g of sample diluted in 60 g of distilled water.

(81) The quantification is performed using external calibration.

(82) Three syntheses are performed: a polyacrylic acid prepared by means of a controlled radical polymerization process of RAFT type, according to test 1 of example 1 above, a polyacrylic acid prepared by means of a polymerization process according to test 4 of example 1 above, a solution of polyacrylic acid polymer prepared by means of a process according to the present invention, according to test 5 of example 1 above.

(83) Samples 1, 2 and 3 are obtained, respectively. All three samples are brought to a solids content of 36% by weight.

(84) The results of analyses on these samples are collated in table 4 below.

(85) TABLE-US-00004 TABLE 4 Content of Content of INVention HPO.sub.4.sup.2− SO.sub.4.sup.2− Content of Content of Samples Prior Art (ppm) (ppm) H.sub.2S (ppm) CS.sub.2 (ppm) 1 PA - RAFT nd 7758 200 1000 2 PA - hypo 5032 128 nd nd 3 INV <50 257 nd nd nd: not detectable

(86) The analysis of sample 1, i.e. a polyacrylic acid obtained by means of a RAFT process, indicates large contents of sulfur-based byproducts SO.sub.4.sup.2−, H.sub.2S and CS.sub.2, which is a major drawback due to their toxicity.

(87) The analysis of sample 2, i.e. a polyacrylic acid prepared by means of a process of the prior art with a high content of NaPO.sub.2H.sub.2, indicates a high content of residual HPO.sub.4.sup.2−ions (5032 ppm).

(88) The analysis of sample 3, namely a solution of polyacrylic acid polymer prepared by means of a process according to the present invention, shows that the contents of H.sub.2S and CS.sub.2 are not detectable. The content of phosphate ions is markedly less than that of sample 2.

(89) The polymer obtained by means of the process of the invention offers a good compromise in terms of purity relative to the polymers obtained with RAFT or sodium hypophosphite processes.