Method for producing polymers on the basis of acryloyldimethyltaurate, neutral monomers, and monomers with carboxylate groups

Abstract

The invention relates to a method for producing water-soluble or water-swellable polymers containing acryloyldimethyltaurate, neutral monomers, and monomers with carboxylate groups. The monomers undergo free radical polymerisation in precipitation in a polar solvent or solvent mixture, providing that an additional polar organic solvent is contained if the polar solvent contains 2-methyl-2-propanol, a ketone or both.

Claims

1. A process for preparing a water-soluble or water-swellable polymer containing a) 5 to 79.99 mol %, of at least one repeat structural unit of the formula (1) ##STR00013## in which R.sup.1, R.sup.2, R.sup.3 is hydrogen, methyl or ethyl, Y is a chemical bond, O, CH.sub.2, C(CH.sub.3)H, C(O)O, C(O), C(O)NR.sup.2, A is a chemical bond, O, arylene, phenylene, linear or branched C.sub.1-C.sub.12-alkylene, a linear monohydroxyalkylene group having 2 to 6 carbon atoms or a linear or branched dihydroxyalkylene group having 3 to 6 carbon atoms, D is S(O), POH, POR.sup.3 or PO.sup.Q.sup.+, Q.sup.+ is H.sup.+, Li.sup.+, Na.sup.+, K.sup.+, Ca.sup.++, Mg.sup.++, Zn.sup.++, Al.sup.+++, Zr.sup.++++ or is mixtures of these ions, b) 20 to 75 mol %, of at least one mutually independent uncharged repeat structural unit, and c) 0.01 to 20 mol %, of at least one further anionic repeat structural unit that have originated from at least one monomer having at least one carboxylate group, wherein the process comprises the step of subjecting monomers from which the structural units a) to c) derive to precipitative free-radical polymerization in a polar solvent or solvent mixture, wherein the polar solvent or solvent mixture comprises water, 2-methylpropan-2-ol and dimethyl ketone, with the proviso that the water content of the solvent does not exceed 10% by weight.

2. The process as claimed in claim 1, wherein the structural unit of the formula (1) are derived from monomers selected from the group consisting of acryloyldimethyltaurate, acryloyl-1,1-dimethyl-2-methyltaurate, acryloyltaurate, acryloyl-N-methyltaurate, vinylsulfonic acid, styrenesulfonic acid, 3-allyloxy-2-hydroxy-1-propanesulfonic acid, vinylphosphonic acid, and 2-acrylamido-2-methylpropanephosphonic acid.

3. The process as claimed in claim 1, wherein the neutralization level of the structural unit of the formula (1) is from 50.0 to 100 mol %.

4. The process as claimed in claim 1, wherein the structural unit b) is at least one monomer selected from the group consisting of N-vinylformamide, N-vinylacetamide, N-methyl-N-vinylformamide, N-methyl-N-vinylacetamide, N-vinyl-2-pyrrolidone, N-vinylcaprolactam, vinyl acetate, N,N-dimethylacrylamide, N-isopropylacrylamide, acrylamide, and methyl acrylate.

5. The process as claimed in claim 1, wherein the structural unit c) derive from monomers of the formula (5) ##STR00014## where R.sup.14, R.sup.15 is hydrogen, methyl or ethyl, C(O)O.sup. Z.sup.+, X, Y.sup.3 is a chemical bond, O, CH.sub.2, C(O)O, OC(O), C(O)NR.sup.15 or NR.sup.15C(O), M is a chemical bond, [C(O)OCH.sub.2CH.sub.2].sub.q, a linear or branched alkylene group having 1 to 6 carbon atoms, a linear or branched, mono- or polyunsaturated alkenylene group having 2 to 6 carbon atoms, a linear monohydroxyalkylene group having 2 to 6 carbon atoms or a linear or branched dihydroxyalkylene group having 3 to 6 carbon atoms, q is an integer from 1-5 and Z+ is H+, Li+, Na+, K+, Zr+, Ca++, Mg++, Zn++, Al+++, Zr++++ or is mixtures of these ions.

6. The process as claimed in claim 1, wherein the structural unit c) is derived from at least one monomer selected from the group consisting of acrylic acid, methacrylic acid, itaconic acid, carboxyethyl acrylate, carboxyethyl acrylate oligomers, 2-propylacrylic acid and 2-ethylacrylic acid and the respective alkali metal or alkaline earth metal salts thereof.

7. The process as claimed in claim 1, wherein the monomers from which the structural units of components a) and c) derive are neutralized prior to the polymerization, or the polymer is neutralized after the polymerization, with a base selected from the group consisting of sodium hydrogencarbonate, sodium carbonate, sodium hydroxide, potassium hydrogencarbonate, potassium carbonate, potassium hydroxide, lithium hydrogencarbonate, lithium carbonate, lithium hydroxide, calcium hydrogencarbonate, and calcium carbonate.

8. The process as claimed in claim 1, wherein the solvent comprises at least one polar organic solvent selected from the group consisting of methanol, ethanol, 1-propanol, 2-propanol, 2-methyl-2-propanol, 1-butanol, 2-butanol, dimethyl ketone, diethyl ketone, tetrahydropyran, tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxane, 1,4-dioxane, and mixtures thereof.

9. The process as claimed in claim 1, wherein the polar solvent comprises 0.5% to 10% by weight of water, 1% to 98.5% by weight of 2-methylpropan-2-ol and 1% to 98.5% by weight of dimethyl ketone.

10. The process as claimed in claim 1, wherein the polar solvent comprises 1% to 5% by weight of water, 7.5% to 91.5% by weight of 2-methylpropan-2-ol and 7.5% to 91.5% by weight of dimethyl ketone.

11. The process as claimed in claim 1, wherein the polar solvent is separated from the product after the polymerization process by a filtration or distillation.

12. A water-soluble or water-swellable polymer prepared by the process as claimed in claim 1, wherein the water-soluble or water-swellable polymer has a k value of 100 to 300.

13. A drilling mud comprising at least one water-soluble or water-swellable polymer as claimed in claim 12.

14. A cement slurry for cementing a deep well, comprising at least one water-soluble or water-swellable polymer as claimed in claim 12.

Description

EXAMPLES

A) Process

(1) In process examples 1 to 20 cited, the polar solvent used which was used to prepare the polymers C was varied. As well as the polar solvent used, further polymers C of the invention were prepared in process examples 1 to 20 by the variation of the monomers. These polymers C and the process example used for the synthesis are compiled in table 1a) to 1c).

Process Example 1

(2) In a 2 liter Quickfit flask with anchor stirrer, reflux condenser with off gas scrubber, combined thermometer/pH meter and a gas inlet tube, 234 g of anhydrous 2-methylpropan-2-ol and 158 g of dimethyl ketone are admixed with 8 g of distilled water.

(3) The reaction vessel is in a heating bath thermostat. This reaction vessel is blanketed with nitrogen gas and, in a gentle opposing nitrogen stream, 65 g of acryloyldimethyltaurate, 3 g of acrylic acid and 30 g of sodium hydrogencarbonate are introduced. The acryloyldimethyltaurate sodium salt does not dissolve completely in the 2-methylpropan-2-ol/dimethyl ketone/water mixture and is partly in the form of a dispersion of solids. The reaction vessel is blanketed with nitrogen, and 17 g of acrylamide and 15 g of N-vinyl-2-pyrrolidone are introduced. After introduction of the acrylamide and N-vinyl-2-pyrrolidone, the pH is checked once again and corrected if necessary by addition of sodium hydrogencarbonate to pH 7 to 8. A constant nitrogen stream is passed through the solution for at least 1 hour. After this inertization period, the residual oxygen can be monitored by means of an oxygen electrode. Should the measured residual oxygen value in the liquid phase exceed the value of 5 ppm, further inertization may be necessary until this value is attained. Thereafter, the reaction vessel is heated to 40 to 60 C., and 1.0 g of azobis(isobutyronitrile) is added in a gentle nitrogen stream. The initiation of the polymerization becomes apparent from a rise in the internal temperature. After the initiation, the introduction of nitrogen gas is ended. About 5-10 minutes after onset of the polymerization reaction, the temperature maximum has been exceeded and the temperature in the reaction vessel is increased by the heating bath up to the boiling point of the 2-methylpropan-2-ol:dimethyl ketone:water mixture. Under gentle reflux, the now viscous mass is stirred for a further two hours. The reaction product, in the form of a viscous suspension of polymer in the 2-methylpropan-2-ol:dimethyl ketone:water mixture, is isolated by filtration and subsequent drying in a vacuum drying cabinet.

Process Example 2

(4) In a 2 liter Quickfit flask with anchor stirrer, reflux condenser with offgas scrubber, combined thermometer/pH meter and a gas inlet tube, 234 g of anhydrous 2-methylpropan-2-ol and 154 g of dimethyl ketone are admixed with 12 g of distilled water. The reaction vessel is in a heating bath thermostat. The further steps of polymerization process 2 are conducted analogously to polymerization process 1. The changes in the monomer compositions are listed accurately in table 1.

Process Example 3

(5) In a 2 liter Quickfit flask with anchor stirrer, reflux condenser with offgas scrubber, combined thermometer/pH meter and a gas inlet tube, 234 g of anhydrous 2-methylpropan-2-ol and 154 g of dimethyl ketone are admixed with 16 g of distilled water. The reaction vessel is in a heating bath thermostat. The further steps of polymerization process 3 are conducted analogously to polymerization process 1. The changes in the monomer compositions are listed accurately in table 1.

Process Example 4

(6) In a 2 liter Quickfit flask with anchor stirrer, reflux condenser with offgas scrubber, combined thermometer/pH meter and a gas inlet tube, 296 g of anhydrous 2-methylpropan-2-ol and 94 g of dimethyl ketone are admixed with 10 g of distilled water. The reaction vessel is in a heating bath thermostat. The further steps of polymerization process 4 are conducted analogously to polymerization process 1. The changes in the monomer compositions are listed accurately in table 1.

Process Example 5

(7) In a 2 liter Quickfit flask with anchor stirrer, reflux condenser with offgas scrubber, combined thermometer/pH meter and a gas inlet tube, 296 g of anhydrous 2-methylpropan-2-ol and 86 g of dimethyl ketone are admixed with 14 g of distilled water. The reaction vessel is in a heating bath thermostat. The further steps of polymerization process 5 are conducted analogously to polymerization process 1. The changes in the monomer compositions are listed accurately in table 1.

Process Example 6

(8) In a 2 liter Quickfit flask with anchor stirrer, reflux condenser with offgas scrubber, combined thermometer/pH meter and a gas inlet tube, 296 g of anhydrous 2-methylpropan-2-ol and 90 g of dimethyl ketone are admixed with 18 g of distilled water. The reaction vessel is in a heating bath thermostat. The further steps of polymerization process 6 are conducted analogously to polymerization process 1. The changes in the monomer compositions are listed accurately in table 1.

Process Example 7

(9) In a 2 liter Quickfit flask with anchor stirrer, reflux condenser with offgas scrubber, combined thermometer/pH meter and a gas inlet tube, 197 g of anhydrous 2-methylpropan-2-ol and 197 g of dimethyl ketone are admixed with 6 g of distilled water. The reaction vessel is in a heating bath thermostat. The further steps of polymerization process 7 are conducted analogously to polymerization process 1. The changes in the monomer compositions are listed accurately in table 1.

Process Example 8

(10) In a 2 liter Quickfit flask with anchor stirrer, reflux condenser with offgas scrubber, combined thermometer/pH meter and a gas inlet tube, 195 g of anhydrous 2-methylpropan-2-ol and 197 g of dimethyl ketone are admixed with 10 g of distilled water. The reaction vessel is in a heating bath thermostat. The further steps of polymerization process 8 are conducted analogously to polymerization process 1. The changes in the monomer compositions are listed accurately in table 1.

Process Example 9

(11) In a 2 liter Quickfit flask with anchor stirrer, reflux condenser with offgas scrubber, combined thermometer/pH meter and a gas inlet tube, 193 g of anhydrous 2-methylpropan-2-ol and 193 g of dimethyl ketone are admixed with 14 g of distilled water. The reaction vessel is in a heating bath thermostat. The further steps of polymerization process 9 are conducted analogously to polymerization process 1. The changes in the monomer compositions are listed accurately in table 1.

Process Example 10

(12) In a 2 liter Quickfit flask with anchor stirrer, reflux condenser with offgas scrubber, combined thermometer/pH meter and a gas inlet tube, 191 g of anhydrous 2-methylpropan-2-ol and 191 g of dimethyl ketone are admixed with 18 g of distilled water. The reaction vessel is in a heating bath thermostat. The further steps of polymerization process 10 are conducted analogously to polymerization process 1. The changes in the monomer compositions are listed accurately in table 1.

Process Example 11

(13) In a 2 liter Quickfit flask with anchor stirrer, reflux condenser with offgas scrubber, combined thermometer/pH meter and a gas inlet tube, 90 g of anhydrous 2-methylpropan-2-ol and 298 g of dimethyl ketone are admixed with 12 g of distilled water. The reaction vessel is in a heating bath thermostat. The further steps of polymerization process 11 are conducted analogously to polymerization process 1. The changes in the monomer compositions are listed accurately in table 1.

Process Example 12

(14) In a 2 liter Quickfit flask with anchor stirrer, reflux condenser with offgas scrubber, combined thermometer/pH meter and a gas inlet tube, 90 g of anhydrous 2-methylpropan-2-ol and 294 g of dimethyl ketone are admixed with 16 g of distilled water. The reaction vessel is in a heating bath thermostat. The further steps of polymerization process 12 are conducted analogously to polymerization process 1. The changes in the monomer compositions are listed accurately in table 1.

Process Example 13

(15) In a 2 liter Quickfit flask with anchor stirrer, reflux condenser with offgas scrubber, combined thermometer/pH meter and a gas inlet tube, 90 g of anhydrous 2-methylpropan-2-ol and 290 g of dimethyl ketone are admixed with 20 g of distilled water. The reaction vessel is in a heating bath thermostat. The further steps of polymerization process 13 are conducted analogously to polymerization process 1. The changes in the monomer compositions are listed accurately in table 1.

Process Example 14

(16) In a 2 liter Quickfit flask with anchor stirrer, reflux condenser with offgas scrubber, combined thermometer/pH meter and a gas inlet tube, 60 g of anhydrous 2-methylpropan-2-ol and 320 g of dimethyl ketone are admixed with 20 g of distilled water. The reaction vessel is in a heating bath thermostat. The further steps of polymerization process 14 are conducted analogously to polymerization process 1. The changes in the monomer compositions are listed accurately in table 1.

Process Example 15

(17) In a 2 liter Quickfit flask with anchor stirrer, reflux condenser with offgas scrubber, combined thermometer/pH meter and a gas inlet tube, 60 g of anhydrous 2-methylpropan-2-ol and 316 g of dimethyl ketone are admixed with 24 g of distilled water. The reaction vessel is in a heating bath thermostat. The further steps of polymerization process 15 are conducted analogously to polymerization process 1. The changes in the monomer compositions are listed accurately in table 1.

Process Example 16

(18) In a 2 liter Quickfit flask with anchor stirrer, reflux condenser with offgas scrubber, combined thermometer/pH meter and a gas inlet tube, 384 g of tetrahydrofuran are admixed with 16 g of distilled water. The reaction vessel is in a heating bath thermostat. The further steps of polymerization process 16 are conducted analogously to polymerization process 1. The changes in the monomer compositions are listed accurately in table 1.

Process Example 17

(19) In a 2 liter Quickfit flask with anchor stirrer, reflux condenser with offgas scrubber, combined thermometer/pH meter and a gas inlet tube, 394 g of tetrahydrofuran are admixed with 6 g of distilled water. The reaction vessel is in a heating bath thermostat. The further steps of polymerization process 17 are conducted analogously to polymerization process 1. The changes in the monomer compositions are listed accurately in table 1.

Process Example 18

(20) In a 2 liter Quickfit flask with anchor stirrer, reflux condenser with offgas scrubber, combined thermometer/pH meter and a gas inlet tube, 390 g of anhydrous 2-methyltetrahydrofuran are admixed with 10 g of distilled water. The reaction vessel is in a heating bath thermostat. The further steps of polymerization process 18 are conducted analogously to polymerization process 1. The changes in the monomer compositions are listed accurately in table 1.

Process Example 19

(21) In a 2 liter Quickfit flask with anchor stirrer, reflux condenser with offgas scrubber, combined thermometer/pH meter and a gas inlet tube, 300 g of anhydrous 2-methylpropan-2-ol and 86 g of 2-methyltetrahydrofuran are admixed with 14 g of distilled water. The reaction vessel is in a heating bath thermostat. The further steps of polymerization process 19 are conducted analogously to polymerization process 1. The changes in the monomer compositions are listed accurately in table 1.

Process Example 20

(22) In a 2 liter Quickfit flask with anchor stirrer, reflux condenser with offgas scrubber, combined thermometer/pH meter and a gas inlet tube, 90 g of anhydrous 2-methylpropan-2-ol and 300 g of 2-methyltetrahydrofuran are admixed with 5 g of distilled water. The reaction vessel is in a heating bath thermostat. The further steps of polymerization process 20 are conducted analogously to polymerization process 1. The changes in the monomer compositions are listed accurately in table 1.

(23) The polymers C which have been prepared according to inventive process examples 1 to 20 are listed in table 1 below. Changes made, for example the use of another base and the amount used for neutralization of the acryloyldimethyltaurate or the use of another initiator and the amount used, are set out in table 1.

(24) TABLE-US-00001 TABLE 1 Examples of polymers C prepared by the inventive polymerization processes 1 to 20 Neutralizing Ref. Proc. ACDMT/ Comonomer 1 Comonomer 2 Comonomer 3 Comonomer 4 agent Initiator k Polymer ex. mol % Name /mol % Name /mol % Name /mol % Name /mol % Name /g Name /g value C - 1 1 43.7 AA 4.21 AM 33.3 NVP 18.80 NaHCO.sub.3 30 AIBN 1.0 210 C - 2 2 45.0 AA 4.03 AM 32.5 NVP 18.48 NaHCO.sub.3 30 AIBN 1.0 215 C - 3 3 45.0 AA 4.03 AM 32.5 NVP 18.48 NaHCO.sub.3 30 AIBN 1.0 223 C - 4 5 45.0 AA 4.03 AM 32.5 NVP 18.48 NaHCO.sub.3 30 AIBN 1.0 204 C - 5 8 45.0 AA 4.03 AM 32.5 NVP 18.48 NaHCO.sub.3 30 AIBN 1.0 188 C - 6 9 45.0 AA 4.03 AM 32.5 NVP 18.48 NaHCO.sub.3 30 AIBN 1.0 199 C - 7 11 45.0 AA 4.03 AM 32.5 NVP 18.48 NaHCO.sub.3 30 AIBN 1.0 190 C - 8 12 45.0 AA 4.03 AM 32.5 NVP 18.48 NaHCO.sub.3 30 AIBN 1.0 251 C - 9 14 45.0 AA 4.03 AM 32.5 NVP 18.48 NaHCO.sub.3 30 AIBN 1.0 249 C - 10 19 45.0 AA 4.03 AM 32.5 NVP 18.48 NaHCO.sub.3 30 AIBN 1.0 208 C - 21 1 30.9 AA 6.0 AM 63.1 NaHCO.sub.3 54.7 AIBN 2.5 183 C - 22 3 30.9 AA 6.0 AM 63.1 NaHCO.sub.3 54.7 AIBN 2.5 227 C - 23 4 30.9 AA 6.0 AM 63.1 NaHCO.sub.3 54.7 AIBN 2.5 197 C - 24 5 30.9 AA 6.0 AM 63.1 NaHCO.sub.3 54.7 AIBN 2.5 217 C - 25 9 30.9 AA 6.0 AM 63.1 NaHCO.sub.3 54.7 AIBN 2.5 219 C - 26 11 30.9 AA 6.0 AM 63.1 NaHCO.sub.3 54.7 AIBN 2.5 222 C - 27 12 30.9 AA 6.0 AM 63.1 NaHCO.sub.3 54.7 AIBN 2.5 228 C - 28 16 30.9 AA 6.0 AM 63.1 NaHCO.sub.3 54.7 AIBN 2.5 140 C - 29 17 30.9 AA 6.0 AM 63.1 NaHCO.sub.3 54.7 AIBN 2.5 134 C - 30 19 30.9 AA 6.0 AM 63.1 NaHCO.sub.3 54.7 AIBN 2.5 173 C - 31 2 40.1 AA 1.00 VIMA 29.0 AM 29.9 NaHCO.sub.3 40.2 AIBN 1.40 196 C - 32 5 40.1 AA 1.00 VIMA 29.0 AM 29.9 NaHCO.sub.3 40.2 AIBN 1.10 237 C - 33 8 40.1 AA 1.00 VIMA 29.0 AM 29.9 NaHCO.sub.3 40.2 AIBN 1.10 206 C - 34 8 40.1 AA 1.00 VIMA 29.0 AM 29.9 NaHCO.sub.3 40.2 AIBN 1.10 211 C - 35 18 40.1 AA 1.00 VIMA 29.0 AM 29.9 NaHCO.sub.3 40.2 AIBN 1.10 138 C - 36 3 41.1 AA 2.5 AM 56.4 NaHCO.sub.3 27.4 AIBN 1.30 221 C - 37 3 40.1 AA 5.0 AM 54.9 NaHCO.sub.3 29.1 AIBN 1.30 229 C - 38 3 39.0 AA 7.5 AM 53.5 NaHCO.sub.3 30.8 AIBN 1.30 217 C - 39 3 38.0 AA 9.9 AM 52.1 NaHCO.sub.3 32.6 AIBN 1.30 226 C - 40 3 35.8 AA 15.0 AM 49.1 NaHCO.sub.3 36.7 AIBN 1.40 227 C - 46 9 AA 3.99 AM 32.2 NVP 18.30 ACNMT 45.5 NaHCO.sub.3 30.2 AIBN 1.20 225 C - 47 9 AA 4.3 AM 39.1 VIMA 20.72 ACNMT 34.2 NaHCO.sub.3 29.1 AIBN 1.50 228 C - 49 9 VPS 8.5 AM 33.7 MAA 8.13 ACNMT 49.1 NaHCO.sub.3 34.9 AIBN 1.00 217 C - 50 9 VPS 10.1 AM 49.6 MAA 3.78 ACNMT 36.2 NaHCO.sub.3 36.0 AIBN 1.40 223 C - 61 2 29.9 AA 35.01 AM 35.1 NaHCO.sub.3 26.4 AIBN 1.00 207 C - 62 5 29.9 AA 35.01 AM 35.1 NaHCO.sub.3 26.4 AIBN 1.00 196 C - 63 8 29.9 AA 35.01 AM 35.1 NaHCO.sub.3 26.4 AIBN 1.00 204 C - 64 8 29.9 AA 35.01 AM 35.1 NaHCO.sub.3 26.4 DLP 1.00 205 C - 65 18 29.9 AA 35.01 AM 35.1 NaHCO.sub.3 26.4 AIBN 1.00 189 C - 66 2 45.0 AA 4.03 AM 32.5 NVP 18.48 KHCO.sub.3 29.6 AIBN 1.00 207 C - 67 8 45.0 AA 4.03 AM 32.5 NVP 18.48 LiHCO.sub.3 23.9 AIBN 1.00 202 C - 68 9 45.0 AA 4.03 AM 32.5 NVP 18.48 Na.sub.2CO.sub.3 37.3 AIBN 1.00 211 C - 69 11 45.0 AA 4.03 AM 32.5 NVP 18.48 K.sub.2CO.sub.3 37.3 AIBN 1.00 233 C - 70 12 45.0 AA 4.03 AM 32.5 NVP 18.48 Li.sub.2CO.sub.3 26.0 AIBN 1.00 227 C - 74 3 30.9 AA 6.0 AM 63.1 Li.sub.2CO.sub.3 48.1 AIBN 1.00 225 C - 75 5 30.9 AA 6.0 AM 63.1 KOH 36.5 AIBN 1.00 217 C - 76 11 30.9 AA 6.0 AM 63.1 KHCO.sub.3 54.7 AIBN 1.00 213 C - 81 2 29.9 AA 35.01 AM 35.1 KOH 17.6 AIBN 1.00 209 C - 82 5 29.9 AA 35.01 AM 35.1 Na.sub.2CO.sub.3 33.3 AIBN 1.00 213 C - 83 8 29.9 AA 35.01 AM 35.1 NaOH 12.6 AIBN 1.00 217 C - 84 2 40.1 VIMA 29.0 AM 29.9 AA 1.00 K.sub.2CO.sub.3 50.7 AIBN 1.10 209 C - 85 5 40.1 VIMA 29.0 AM 29.9 AA 1.00 KOH 26.8 AIBN 1.10 211 C - 86 8 40.1 VIMA 29.0 AM 29.9 AA 1.00 LiHCO.sub.3 32.5 AIBN 1.10 214 ACDMT = acryloyldimethyltaurate, VPS = vinylphosphonic acid, VSS = vinylsulfonic acid, AMPP = 2-acrylamido-2-methylpropanephosphonic acid, SSS = styrenesulfonic acid, NaSS = sodium styrenesulfonate, ACT = acryloyltaurate, ACNMT = acryloyl-N-methyltaurate, NVP = N-vinyl-2-pyrrolidone, Am = acrylamide, DMAAm = dimethylacrylamide, NVF = N-vinylformamide, VIMA = N-vinyl-N-methylacetamide, AA = acrylic acid, MAA = methacrylic acid, AIBN = azobis(isobutyronitrile)

Comparative Example 1

(25) (noninventive, prepared according to EP 1045869 copolymer prepared in precipitation polymerization 44.5 mol % acryloyldimethyltaurate and 55.5 mol % acrylamide with ammonia gas as neutralizing reagent)

(26) In a 3 liter Quickfit flask with anchor stirrer, reflux condenser with offgas scrubber, combined thermometer/pH meter and a gas inlet tube, 1700 g of anhydrous 2-methylpropan-2-ol are admixed with 50 mL of distilled water. The reaction vessel is in a heating bath thermostat.

(27) This reaction vessel is blanketed with nitrogen gas, and 245 g of acryloyldimethyltaurate are introduced in a gentle opposing nitrogen stream. The acryloyldimethyltaurate does not dissolve completely in the 2-methylpropan-2-ol/water mixture and is partly in the form of a dispersion of solids. The pH of this mixture is below pH 1. Above the liquid phase, gaseous ammonia is introduced through the gas inlet tube until the pH of the dispersion is between 7 and 8. On attainment of the desired pH range, stirring is continued for another 1 hour and the pH is recorded continuously. The reaction vessel is blanketed with nitrogen, and 105 g of acrylamide are introduced. After the acrylamide has been introduced, the pH is checked again and if necessary corrected to the range of pH 7 to 8. A constant nitrogen stream is passed through the solution for at least 1 hour. After this inertization period, the residual oxygen is checked by means of an oxygen electrode. Should the measured residual oxygen value in the liquid phase exceed the value of 1 ppm, inertization has to be repeated until this value is attained. Thereafter, in a gentle nitrogen stream, 2 g of AIBN are added and the reaction vessel is heated to 60 C. Shortly after attainment of an internal temperature of 60 C., the introduction of nitrogen gas is ended and commencement of the polymerization reaction is observed, which can be determined by an increase in temperature of 10-15 C. About 5-15 minutes after onset of the polymerization reaction, the temperature has been exceeded and the temperature in the reaction vessel is increased by means of the heating bath up to the boiling point of the 2-methylpropan-2-ol/water mixture. Under gentle reflux, the now viscous mass is stirred for a further two hours. The reaction product, in the form of a viscous suspension of polymer in the 2-methylpropan-2-ol/water mixture, is separated off by filtration and subsequent drying in a vacuum drying cabinet.

(28) Yield: 365 g

(29) Dry content (IR dryer at 120 C. for 15 minutes): 96%

(30) K value (0.5% solution in distilled water): 212

Comparative Example 2 According to EP 1033378 Noninventive

(31) A polymerization flask of capacity 2 L, equipped with stirrer, reflux condenser, dropping funnel, gas inlet tube and electrically heated water bath, is initially charged with 600 mL of 2-methylpropan-2-ol, and 77.5 g of acryloyldimethyltaurate are suspended therein while stirring, then 8.5 L of NH.sub.3 gas are introduced and then 7.5 g of acrylamide, 7.5 g of N-vinylformamide and 7.5 g of N-vinylpyrrolidone are added. With introduction of nitrogen, the electrical water bath is used to heat the reaction mixture to 50 C., and 1.0 g of azoisobutyronitrile is added. After an induction time of about 2 hours, polymerization sets in, the reaction temperature rises up to 70 C. and the polymer precipitates out. The mixture is heated at 80 C. for another 2 hours, forming a viscous suspension. The polymer can be isolated by filtration with suction and drying under reduced pressure at 50 C. However, it is also possible to distill the solvent out of the reaction mixture directly under reduced pressure. The polymer is obtained in the form of a white lightweight powder having good solubility in water. K value according to Fikentscher 170.

Comparative Example 3-1 to 3-5 According to US 2012/0095120 Noninventive

(32) A 2 L glass reactor with an internal temperature of 20 C. is initially charged with 344 g of dimethyl ketone, 9.6 g of deionized water and the monomers specified in table 2 and the neutralizing reagent. The contents of the reactor are stirred and inertized with introduction of a strong nitrogen stream for 1 h. The reaction medium is heated to 55 C. and then 0.7 g of DLP (dilauryl peroxide) is added to initiate the polymerization. The reaction mixture is heated to reflux and kept there for 2 h. After cooling to room temperature, the reaction medium is filtered and the polymer residue is dried under reduced pressure.

(33) TABLE-US-00002 TABLE 2 Comparative example 3-1 to 3-8 according to US 2012/0095120 noninventive Neutralizng ACDMT/ Comonomer 1 Comonomer 2 Comonomer 3 agent Initiator Reference mol % Name /mol % Name /mol % Name /mol % Name /g Name /g VGP-3-1 45.0 AA 4.03 AM 32.5 NVP 18.48 NaHCO.sub.3 30 DLP 0.7 VGP-3-2 55.1 VPS 2.44 AM 40.0 NVF 2.5 NaHCO.sub.3 27.5 DLP 0.7 VGP-3-3 30.9 AA 6.0 AM 63.1 NaHCO.sub.3 54.7 DLP 0.7 VGP-3-4 75.4 VPS 2.17 AM 20.2 NVF 2.3 NaHCO.sub.3 44.6 DLP 0.7 VGP-3-5 21.7 VPS 1.13 AM 73.7 NVF 3.4 NaHCO.sub.3 15.8 DLP 0.7 ACDMT = acryloyldimethyltaurate, VPS = vinylphosphonic acid, NVP = N-vinyl-2-pyrrolidone, AM = acrylamide, NVF = N-vinylformamide, DLP = dilauryl peroxide

B) Cement Slurry Application Tests

(34) The testing is effected according to API spec. 10. In an atmospheric consistometer, the cement slurry is stirred/conditioned at the study temperature and then at the same temperature the rheology with the FANN model 35SA viscometer (in the case of high temperature, conditioning is effected at 93 C. and the viscosity is measured). At temperatures >93 C., water loss is measured with a stirring fluid loss apparatus (SFLA).

(35) Table 3 shows the water loss-reducing properties of selected abovementioned examples according to API spec. 10 at 121.1 C. (250 F.) in the stirred filtration test in the FANN HTHP filter press (stirring fluid loss apparatus, SFLA). The test was based on two assessment questions: was ammonia gas emitted during the making-up of the formulation and was it possible to improve the water loss reduction properties of the polymers C? It becomes clear here that no ammonia gas emission occurs any more with the polymers C. Direct comparison of the polymers C against the prior art likewise shows an improvement in the fluid loss properties. The polymer of EP 1045869 had an average fluid loss of 60 mL (mean value from three measurements) in the test conducted. Some of the polymers C were much lower in terms of their fluid loss values. Values of 40 to 45 mL were attained here.

(36) Formulation of the cement slurries for an application at 250 F., about 121 C.:

(37) 600 g of Dyckerhoff Class G cement

(38) 210 g of silica flour

(39) 328.8 g of distilled water

(40) Polymer in the concentration specified in table 1

(41) 1.8 g of dispersant (polynaphthalenesulfonate, PNS)

(42) 1.8 g of retardant (lignosulfonate)

(43) TABLE-US-00003 TABLE 3 (Application test at 250 F. (121 C.)) Rheology after mixing at 80 F. (27 C.), scale divisions at X revolutions per minute Ammonia release in Conc./% Revolutions per minute/rpm API fluid loss Polymer from table 1 formulation by weight 300 200 100 6 3 at 250 F./mL Comparative polymer Yes 0.5 168 117 64 7.5 5.0 60 as per EP1045869 Comparative polymer Yes 0.5 165 118 66 7 5.5 58 as per EP1045869 Comparative polymer Yes 0.5 167 117 64 7.5 5.5 62 as per EP1045869 VGP-3-1 as per US No 0.5 172 114 69 8 5 138 2012/0095120 VGP-3-2 as per US No 0.5 217 145 71 9 4 124 2012/0095120 VGP-3-3 as per US No 0.5 187 126 61 8 6 98 2012/0095120 VGP-3-4 as per US No 0.5 179 120 65 7 4 114 2012/0095120 VGP-3-5 as per US No 0.5 256 163 88 6 3 132 2012/0095120 Polymer C - 2 No 0.5 172 115 67 6.5 4 44 Polymer C - 4 No 0.5 167 114 63 6.5 4 40 Polymer C - 6 No 0.5 166 113 62 7 4.5 44 Polymer C - 7 No 0.5 162 120 63 6.5 3.5 48 Polymer C - 9 No 0.5 167 121 58 7.5 3.5 54 Polymer C - 24 No 0.5 158 107 59 8 5 48 Polymer C - 25 No 0.5 168 114 63 6.5 4 40 Polymer C - 26 No 0.5 164 113 62 7 4.5 44 Polymer C - 61 No 0.5 172 117 65 7 4.5 42 Polymer C - 62 No 0.5 169 117 63 7 4.5 48 Polymer C - 66 No 0.5 174 125 70 8 5 40 Polymer C - 68 No 0.5 176 124 68 7 4 44 Polymer C - 69 No 0.5 168 122 63 6.5 3.5 48 Polymer C - 76 No 0.5 153 116 58 7.5 4 46

(44) As shown by the comparison of the inventive examples in table 3 with the comparative examples VGP-2, VGP-3-1 to VGP-3-5, the process of the invention that utilizes a solvent mixture gives a product which differs from products that have been obtained with just one solvent according to the prior art. The products obtained by the process of the invention show lower water loss when they are used as additive in cement slurries and drilling mud.

C) Drilling Mud Application Tests

(45) In the examples which follow, the polymers C are compared with comparative polymer 2 from EP 10033378, known from the prior art, in a barite-weighted seawater drilling mud with 3% KCl and a specific weight of 2.1 kg/L. Prior to use, a drilling mud is adjusted with sodium hydroxide to a pH of 9-11. The amount used in each case was 2.5% by weight.

(46) The quality of the mud and hence the efficacy of the additives is assessed by the following criteria: a) Fluid loss after 30 minutes in an HTHP filter press at 150 C. and a pressure of 500 psi (35 bar) after dynamic ageing of the mud in a roller oven at 130, 150, 170, 185 and 200 C. for 16 h or 66 h. b) Rheology (plastic viscosity [PV], yield point [YP], gel strengths [Gel st.] after 10 seconds [10 ] and 10 minutes [10]), measured in a Fann-35 rotary viscometer after makeup, and also dynamic ageing in a roller oven at 130, 150, 170, 185 and 200 C. for 16 h or 66 h.

(47) The following additives were used for the studies:

(48) a) comparative polymer 2

(49) b) VGP-3-1 (from table 2)

(50) c) VGP-3-2 (from table 2)

(51) d) VGP-3-3 (from table 2)

(52) e) polymer C-31 (from table 1)

(53) g) polymer C-62 (from table 1)

(54) h) polymer C-5 (from table 1)

(55) j) polymer C-21 (from table 1)

(56) TABLE-US-00004 TABLE 4 Ageing/h before 16 16 16 66 16 Temperature/ C. Polymer 130 150 170 170 200 Comparative Fluid loss/mL 44 46 22 19 27 polymer 2 PV (cp) 76 85 74 83 74 56 as per EP1045869 YP/lb/100 ft.sup.2 27 31 34 22 8 6 10 gel st. 5 8 9 7 3.5 5 10 gel st. 12 14 12 10 6 5 VGP-3-1 as per Fluid loss/mL 77 80 75 103 105 US 2012/0095120 PV (cp) 97 109 102 89 74 71 YP/lb/100 ft.sup.2 21 14 15 10 5 8 10 gel st. 11 18 18 13 9 7 10 gel st. 18 25 27 24 19 17 VGP-3-2 as per Fluid loss/mL 58 34 38 43 41 US 2012/0095120 PV (cp) 63 71 90 82 69 49 YP/lb/100 ft.sup.2 21 28 42 29 9 8 10 gel st. 12 11 13 11 5 4 10 gel st. 14 15 17 17 6 6 VGP-3-3 as per Fluid loss/mL 66 69 64 92 94 US 2012/0095120 PV (cp) 103 93 89 78 64 71 YP/lb/100 ft.sup.2 20 15 14 9 6 8 10 gel st. 10 15 15 11 7 5 10 gel st. 15 22 20 14 9 5 Polymer C-5 Fluid loss/mL 42 43 20 21 24 PV (cp) 83 87 79 80 76 58 YP/lb/100 ft.sup.2 25 33 31 26 9 6.5 10 gel st. 7 8 9 8 3.5 6 10 gel st. 12 13 13 11 6 5.5 Polymer C-21 Fluid loss/mL 41 48 29 31 34 PV (cp) 75 84 79 84 73 61 YP/lb/100 ft.sup.2 27 29 31 26 9 6.5 10 gel st. 8 7 9 7 4.5 6 10 gel st. 14 16 15 13 7 6 Polymer C-31 Fluid loss/mL 20 16 17 18 19 PV (cp) 68 75 73 77 63 51 YP/lb/100 ft.sup.2 23 26 22 19 18 16 10 gel st. 7 8 8 8 5 5 10 gel st. 12 15 15 13 7 6 Polymer C-62 Fluid loss/mL 27 19 23 23 25 PV (cp) 65 64 71 64 59 48 YP/lb/100 ft.sup.2 27 32 27 24 14 16 10 gel st. 9 8 9 13 5 5 10 gel st. 12 11 13 17 6.5 6

(57) The test results show comparable values to comparative example 2, with regard to the uniform rheological properties of the drilling mud after makeup and after ageing over the temperature range from 130 to 200 C. The polymers C have a broad temperature range with regard to their efficacy as a fluid loss additive.

(58) As shown by the comparison of the inventive examples in table 4 with the comparative examples VGP-2, VGP-3-1 to VGP-3-4, the process of the invention that utilizes a solvent mixture gives a product which differs from products which have been obtained with just one solvent according to the prior art. The products obtained by the process of the invention show a lower water loss when used as additive in cement slurries and drilling mud.

D) Comparison to WO 2010/108634

(59) A comparison of the copolymers of the invention with those from examples 4 and 6 from WO 2010/108634 was conducted.

(60) General polymerization method for preparation of the polymers by the precipitation process in tert-butanol according to WO 2010/108634

(61) A 1 liter Quickfit flask with reflux condenser, gas inlet, internal thermometer and stirrer is initially charged with 400 g of tert-butanol, and the calculated amount of 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS, Lubrizol) is added. Subsequently, the addition of the equimolar amount of sodium hydroxide or sodium carbonate is neutralized (target pH 6-7) and the calculated amount of 2-carboxyethyl acrylate or 2-carboxyethyl acrylate oligomer mixture (Bimax Chemicals Ltd.) and the calculated amount of crosslinker are added to the reaction mixture. Should the pH of the reaction mixture have drifted into the acidic range after the addition of comonomer, it is neutralized again by further addition of sodium hydroxide or sodium carbonate (target pH 6-7). After the mixture has been inertized with N.sub.2 or argon, at an internal temperature of 60 C., dimethyl 2,2-azobisisobutyrate (V-601) is added as initiator and the polymerization reaction is initiated. After a few minutes, there is precipitation of the finished polymer. The mixture is heated to reflux for two hours and the polymer is then freed of the solvent by means of a suction filter and dried under reduced pressure. This method is generally applicable to all polymerization reactions described hereinafter in table 1. Examples 1 to 6 from WO 2010/108634 were prepared with the aid of this method. The results obtained were as follows:

(62) TABLE-US-00005 TABLE 5 Comparative examples 4 to 6 according to WO 2010/108634 Neutralizing ACDMT/ Comonomer 1 Comonomer 2 Comonomer 3 agent Initiator k Reference mol % Name /mol % Name /mol % Name /mol % Name /g Name /g value Comparison D2 -1 85.5 CEA-oligo 10 DMAAm 4 PEAS 0.5 NaOH 19.4 V601 1.1 106 Comparison D2 -2 85.5 CEA-oligo 10 DMAAm 4 PEAS 0.5 Na.sub.2CO.sub.3 25.7 V601 1.1 118 Comparison D2 -3 44.5 CEA 15 DMAAm 40 TMPTA 0.5 NaOH 18.4 DLP 1.7 134 Comparison D2 -4 44.5 CEA 15 DMAAm 40 TMPTA 0.5 Na.sub.2CO.sub.3 24.4 DLP 1.7 137 Comparison D2 -5 79.5 CEA-oligo 10 DMAAm 10 PEAS 0.5 NaOH 12.7 V601 1.3 116 Comparison D2 -6 79.5 CEA-oligo 10 DMAAm 10 PEAS 0.5 Na.sub.2CO.sub.3 28.8 V601 1.3 125 ACDMT = acryloyldimethyltaurate, CEA-oligo = carboxyethyl acrylate oligomer mixture, CEA = carboxyethyl acrylate, DMAAm = Dimethylacrylamide, TMPTA = trimethylolpropane triacrylate, PEAS = pentaerythritol diacrylate monostearate, V601 = dimethyl 2,2-azobisisobutyrate, DLP = dilauryl peroxide
Cement Slurry Application Tests

(63) The testing is effected according to API spec. 10. In an atmospheric consistometer, the cement slurry is stirred/conditioned at the study temperature and then at the same temperature the rheology with the FANN model 35SA viscometer (in the case of high temperature, conditioning is effected at 93 C. and the viscosity is measured). At temperatures >93 C., water loss is measured with a stirring fluid loss apparatus (SFLA).

(64) Table 6 shows the water loss-reducing properties of selected abovementioned examples according to API spec. 10 at 121.1 C. (250 F.) in the stirred filtration test in the Fann HTHP filter press (stirring fluid loss apparatus, SFLA). Formulation of the cement slurries for an application at 250 F., about 121 C.:

(65) 100 g of Dyckerhoff Class G cement

(66) g of silica flour

(67) 54.8 g of distilled water

(68) Polymer in the in Table 5a) to 5c) in the Specified Concentration

(69) 0.3 g of dispersant (polynaphthalenesulfonate, PNS)

(70) 0.5 g of retardant (lignosulfonate)

(71) TABLE-US-00006 TABLE 6 (Application test at 250 F. (121 C.)) Rheology after mixing at 80 F. (27 C.), scale divisions at X revolutions per minute Polymer from Concentration/ Revolutions per minute/rpm API fluid loss table 5a) to 5c) % by weight 300 200 100 6 3 at 250 F./mL Comparison D2 -1 0.5 171 128 62 7 4.5 93 Comparison D2 -2 0.5 195 133 64 7.5 3.5 87 Comparison D2 -3 0.5 183 116 57 6.5 3.5 >100 Comparison D2 -4 0.5 201 139 69 7 4 >100 Comparison D2 -5 0.5 177 118 63 7 4 >100 Comparison D2 -6 0.5 182 124 58 6.5 3.5 >100
Then a polymer of the same composition was produced according to the inventive process example 2.

(72) TABLE-US-00007 TABLE 7 Comparative examples 4 to 6 according to WO 2010/108634 synthesized by the inventive process example 2 Neutralizing ACDMT/ Comonomer 1 Comonomer 2 Comonomer 3 agent Initiator k Reference mol % Name /mol % Name /mol % Name /mol % Name /g Name /g value Polymer C - 77 85.5 CEA-oligo 10 DMAAm 4 PEAS 0.5 NaHCO.sub.3 41 V601 1.1 216 Polymer C - 78 44.5 CEA 15 DMAAm 40 TMPTA 0.5 NaHCO.sub.3 39 DLP 1.7 240 Polymer C - 79 79.5 CEA-oligo 10 DMAAm 10 PEAS 0.5 NaHCO.sub.3 41 V601 1.3 238 ACDMT = acryloyldimethyltaurate, CEA-oligo = carboxyethyl acrylate oligomer mixture, CEA = carboxyethyl acrylate, DMAAm = dimethylacrylamide, TMPTA = trimethylolpropane triacrylate, PEAS = pentaerythritol diacrylate monostearate, V601 = dimethyl 2,2-azobisisobutyrate, DLP = dilauryl peroxide

(73) TABLE-US-00008 TABLE 8 (Application test at 250 F. (121 C.)) Rheology after mixing at 80 F. (27 C.), scale divisions at X revolutions per minute Polymer from Concentration/ Revolutions per minute/rpm API fluid loss table 5a) to 5c) % by weight 300 200 100 6 3 at 250 F./mL Polymer C - 77 0.5 159 115 69 7 4. 64 Polymer C - 78 0.5 172 122 84 8 5 70 Polymer C - 79 0.5 153 111 53 6.5 4.5 88

(74) Comparative examples D2-1 to D2-6 also showed a much lower K value than the polymers having the identical composition according to inventive process example 2 (polymer C-77 to C-79). This suggests incomplete polymerization, since the sodium salt was only of limited to zero solubility in the solvent mixture of the process described in WO2010/108634 and hence was not available for the polymerization. For testing of the polymers obtained, these were used as water loss reducers in cement slurries. The use of sodium hydroxide and sodium carbonate did not result in any release of ammonia, but comparative examples D2-1 to D2-6, by contrast with the polymers (polymer C-77 to C-79) of the process of the invention, also showed a much poorer API fluid loss at 250 F.. This shows clearly that, by the described process according to WO2010/108634, polymers of sodium salts of acryloyldimethyltaurate are obtainable, but comparative examples D2-1 to D2-6 showed that these polymers are not suitable water loss reducers.

(75) Application Tests

E) Comparison to EP 1059316

(76) A comparison of the copolymers of the invention with those of polymer examples 4 to 6 from EP 1059316 was conducted.

Comparative Example D1-1

(77) General polymerization method for preparation of polymers 4 to 5 by the polymerization process in aqueous solution according to EP 1059316

(78) A polymerization flask of capacity 2 L, equipped with stirrer, reflux condenser, dropping funnel, gas inlet tube and electrically heated water bath, is initially charged with 121.4 mL of deionized water and 1.6 g of 65% vinylphosphonic acid, and purged with nitrogen, and aqueous 22% ammonia solution is added until a pH of 7-7.5 has been attained. This solution is then heated to 60 C.

(79) A monomer/initiator solution consisting of 290 g of deionized water, 72.6 g of ACDMT, 29.1 g of 50% acrylamide, 10.4 g of N-vinylformamide, 5.2 of 60% DADMAC, 2.1 g of acrylic acid, 0.5 mL of isopropanol, 0.51 g=2,2-azobis(2-methylpropionamidine) dihydrochloride and the amount of aqueous 22% ammonia solution required to establish a pH of 7.0 to 7.5 is prepared. 10% (about 45 mL) of the monomer/initiator solution is introduced into the polymerization flask. The mixture is stirred at 60 C. until polymerization sets in (about 30 min). Then the residual monomer/initiator solution is metered in at constant metering rate over a period of 2.5 hours. Heating is continued at 80 C. for another 2 hours. A clear solution of high viscosity is obtained, which can be sent directly to use as a drilling mud additive or as an additive to cement slurries.

(80) This method is generally applicable to all polymerization reactions described hereinafter in table 9. Examples 4 to 6 from EP 1059316 were prepared with the aid of this method. The results obtained were as follows:

(81) TABLE-US-00009 TABLE 9 Comparative examples 4 to 6 according to EP 1059316 Comparative ACDMT/ VPS/ AM/ AA/ NVF/ Comonomer Initiator polymer mol % mol % mol % mol % mol % Name /mol % Name /g D1-1 41.3 1.1 24.1 12.4 17.2 DADMAC 3.9 AAPH 0.51 D1-2 42.4 1.2 24.2 12.8 17.7 AMPT 1.7 AAPH 0.51 D1-3 53.2 1.3 7.8 15.9 19.3 DADMAC 2.5 AAPH 0.51 ACDMT = acryloyldimethyltaurate, VPS = vinylphosphonic acid, AM = acrylamide, NVF = N-vinylformamide, AA = acrylic acid, DADMAC = diallyldimethylammonium chloride, AMPT = 3-acrylamidopropyltrimethylammonium chloride, AAPH = 2,2-azobis(2-methylpropionamidine) dihydrochloride

(82) Note relating to the continuous aqueous polymerization process described in EP 1059316:

(83) The continuous aqueous polymerization process described in EP 1059316 initially charges a monomer (vinylphosphonic acid) in a polymerization flask and subsequently meters in a monomer/initiator solution. Proceeding from the copolymerization parameters for vinylphosphonic acid with the individual monomers in the monomer/initiator solution, it is clearly apparent to the person skilled in the art that, at the start of the polymerization, polymers with a higher vinylphosphonic acid content will arise than at the end of the polymerization. It can even be assumed that the polymers synthesized at the end of the polymerization will now contain virtually no vinylphosphonic acid. Instead, a mixture of copolymers with different compositions is obtained, and so the molar ratios reported in table 7 relate solely to the monomer ratios used. These polymers are not comparable with the polymers from the process of the invention.

(84) Cement Slurry Application Tests

(85) The testing is effected according to API spec. 10. In an atmospheric consistometer, the cement slurry is stirred/conditioned at the study temperature and then at the same temperature the rheology with the FANN model 35SA viscometer (in the case of high temperature, conditioning is effected at 93 C. and the viscosity is measured). At temperatures >93 C., water loss is measured with a stirring fluid loss apparatus (SFLA).

(86) Table 10 shows the water loss-reducing properties of selected abovementioned examples according to API spec. 10 at 121.1 C. (250 F.) in the stirred filtration test in the Fann HTHP filter press (stirring fluid loss apparatus, SFLA). Formulation of the cement slurries for an application at 250 F., about 121 C.:

(87) 100 g of Dyckerhoff Class G Cement

(88) g of silica flour

(89) 54.8 g of distilled water

(90) Polymers D1-1 to D1-3 in the Concentration Specified

(91) 0.3 g of dispersant (polynaphthalenesulfonate, PNS)

(92) 0.5 g of retardant (lignosulfonate)

(93) TABLE-US-00010 TABLE 10 (Application test at 250 F. (121 C.)) Rheology after mixing at 80 F. (27 C.), Ammonia scale divisions at X revolutions per minute Polymer from release in Concentration/ Revolutions per minute/rpm API fluid loss table 9 formulation % by weight 300 200 100 6 3 at 250 F./mL D1-1 Yes 0.5 104 68 31 4-5 3 >100 D1-2 Yes 0.5 112 74 29 4-5 3 >100 D1-3 Yes 0.5 98 75 34 4-5 3.5 >100
Then polymers of the same composition were prepared by the inventive process example 7.

(94) TABLE-US-00011 TABLE 11 Comparative examples 4 to 6 according to WO 2010/108634, synthesized according to inventive process example 7 Neutralizing ACDMT/ VPS/ AM/ AA/ NVF/ Comonomer agent Initiator k Reference mol % mol % mol % mol % mol % Name /mol % Name /g Name /g value Polymer C - 80 41.3 1.1 24.1 12.4 17.2 DADMAC 3.9 NaHCO.sub.3 39.1 AIBN 1.1 211 Polymer C - 81 42.4 1.2 24.2 12.8 17.7 AMPT 1.7 NaHCO.sub.3 39.2 AIBN 1.0 219 Polymer C - 82 53.2 1.3 7.8 15.9 19.3 DADMAC 2.5 NaHCO.sub.3 39.1 AIBN 1.0 204

(95) TABLE-US-00012 TABLE 12 (Application test at 250 F. (121 C.)) Rheology after mixing at 80 F. (27 C.), scale divisions at X revolutions per minute Polymer from Concentration/ Revolutions per minute/rpm API fluid loss table 11 % by weight 300 200 100 6 3 at 250 F./mL Polymer C - 80 0.5 184 125 81 8 4.5 74 Polymer C - 81 0.5 169 119 63 7 4 88 Polymer C - 82 0.5 175 132 74 8 4.5 76

(96) The use of the aqueous ammonia solution during the synthesis of comparative examples D1-1 to D1-3, as a result of the alkaline composition of the cement formulation, leads to release of ammonia gas during the addition of the polymer solutions. Direct comparison of comparative examples D1-1 to D1-3 with the polymers of identical composition according to inventive process example 7 (Polymer C-80 to C-82) shows a much poorer API fluid loss at 250 F. for the comparative polymers. The comparisons show very clearly that the polymers according to the continuous aqueous polymerization process described in EP 1059316 do have the same composition as in the process of the invention, but the polymers of the process of the invention feature much better performance.