Equipment and method for preparing an aldehyde-functionalised polymer

Abstract

Equipment for preparing a polymer solution of a non-ionic, cationic, anionic or amphoteric polymer by reaction between a compound including at least one aldehyde function and at least one base polymer aqueous solution having at least one non-ionic monomer includes a reactor provided with a stirring system, as well as a recirculation loop including between the outlet of the reactor and the inlet of the reactor, a recirculation pump, a pH measuring probe, and a pressure differential in-line measuring device in the form of a calibrated tube configured to measure the pressure difference of the polymer solution between the inlet and the outlet of the calibrated tube, the calibrated tube being branched on the recirculation loop.

Claims

1. Equipment for preparing a polymer solution of a non-ionic, cationic, anionic or amphoteric polymer by reaction between a compound comprising at least one aldehyde function and at least one aqueous solution of a base polymer comprising at least one non-ionic monomer selected from among acrylamide, methacrylamide, N,N-dimethylacrylamide, and acrylonitrile, said equipment comprising a reactor provided with a stirring system; as well as at least: a pipe configured to feed the reactor with water, a pipe equipped with a metering pump configured to feed the reactor with the at least one aqueous solution, a pipe equipped with a metering pump configured to feed the reactor with the compound comprising at least one aldehyde function, a pipe equipped with a metering pump configured to feed the reactor with base, and a pipe equipped with a metering pump configured to feed the reactor with acid, said reactor comprising a recirculation loop configured to make the polymer solution recirculate from a bottom of the reactor towards an upper level of the reactor, characterised in that said recirculation loop comprises between an outlet of the reactor and an inlet of the reactor, a recirculation pump, a pH measuring probe, and a pressure differential in-line measuring device in the form of a calibrated tube configured to measure a pressure difference of the polymer solution between an inlet and an outlet of said calibrated tube, said calibrated tube being positioned in a bypass of the recirculation loop.

2. The equipment according to claim 1, characterised in that the pressure differential in-line measuring device is positioned on either side of the recirculation pump.

3. The equipment according to claim 1, characterised in that the pressure differential in-line measuring device further comprises: a control valve allowing for maintenance of a constant flow rate in the calibrated tube, and a flowmeter allowing for measurement and regulation of a flow rate downstream of the control valve.

4. The equipment according to claim 3, characterised in that the pressure differential in-line measuring device comprises, downstream of the control valve, a duplex filter with meshes between 5 to 50 microns.

5. The equipment according to claim 4, characterised in that the pressure differential in-line measuring device comprises, between the duplex filter and the control valve, a pulsation dampener of the recirculation loop.

6. The equipment according to claim 1, characterised in that the equipment further comprises a turbidimeter directly connected on the recirculation loop of the reactor.

7. A method for preparing a polymer solution of a non-ionic, cationic, anionic or amphoteric polymer derived from a reaction between a compound comprising at least one aldehyde function and at least one aqueous solution of a base polymer comprising at least one non-ionic monomer selected from among acrylamide, methacrylamide, N,N-dimethylacrylamide, and acrylonitrile, by employing the equipment of claim 1, said method comprising the following successive steps: feeding the reactor with water and activating the recirculation pump, feeding the reactor with the at least one aqueous solution of the base polymer and activating the stirring system, feeding the reactor with the compound comprising the at least one aldehyde function, feeding the reactor with base and stopping the addition when the pH measuring probe indicates a pH between 8 and 12, measuring the pressure differential of the polymer solution circulating in the recirculation loop with the pressure differential in-line measuring device, optionally continuously measuring a turbidity of the polymer solution within the reactor, and when a variation of the pressure differential of the polymer solution reaches a value between 100% and 500%, adding acid into the reactor and stopping the addition of the acid when the pH measuring probe indicates a pH between 2.5 and 5.

8. The method for preparing a polymer solution according to claim 7, characterised in that the method further comprises the following steps: transferring the obtained polymer solution with the recirculation pump into a stock tank provided with a sensor for detecting a level of the polymer solution, rinsing all pipes and the reactor with water, and feeding the reactor with water when the detected level of the stock tank is below a threshold level.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The FIGURE is a schematic representation of the equipment of the invention.

DETAILED DESCRIPTION OF AN EXEMPLARY EMBODIMENT

Example 1

(2) This equipment essentially comprises a reactor (1) provided with a stirring system (2), the reactor being connected to a recirculation loop (3). The recirculation loop (3) is in the form of a duct projecting from the bottom (4) of the reactor (1) also referred to as “outlet” of the recirculation loop and whose opposite end is connected to an upper level (5) of the reactor (1).

(3) The equipment further has pipes intended to feed the reactor with the reactants used to obtain the end product.

(4) These consist of the ducts (7), (8) and (9) feeding the top of the reactor respectively with water, acid and base.

(5) The polymer and the compound comprising at least one aldehyde function are introduced into the recirculation loop (3) via the ducts (10) and (11) respectively.

(6) According to an essential feature of the equipment of the invention, the recirculation loop (3) successively has different elements from the outlet (4) of the reactor up to the inlet (5) in the reactor, namely a recirculation pump (12), a pH probe (13) and finally a pressure differential in-line measuring device (14).

(7) The device (14) comprises, in the flow direction of the polymer, a control valve (15) allowing maintaining a constant flow rate, a flowmeter (16) allowing measuring and regulating the flow rate downstream of the control valve (15), a calibrated tube (17) creating a pressure drop and a pressure differential measuring apparatus (18) positioned between the inlet and the outlet of the calibrated tube, able to measure the pressure drop of the fluid after passage of said fluid in the calibrated tube.

(8) The equipment of the invention further comprises a turbidimeter (19) connected on the recirculation loop (3).

(9) The device (14) is branched on the recirculation loop between a point (20) upstream of the recirculation pump and a point (21) downstream of the inlets (10) and (11) of the reactants.

(10) Finally, the equipment comprises a stock tank (22) provided with a means for detecting a low level of the polymer P2 solution allowing triggering the supply of the reactor (6) with water when the low level of the stock tank is detected.

Example 2

(11) Preparation of a Polymer P1a Solution (AM/DADMAC (95/5 Mol %)): Polymerisation Priming P1a with SPS and Filtered Acrylamide Solution

(12) In a 1-litre reactor equipped with a mechanical stirrer, a thermometer, a refrigerant and a nitrogen gas plunger, 333.8 g of water, 50.1 g of diallyldimethylammonium chloride (DADMAC, 64% by weight in water) are introduced. The pH of the solution is set at 2.5 with sulphuric acid. The medium is heated and maintained at a temperature comprised between 79 and 81° C. thanks to a water bath. Thanks to two continuous castings, are incorporated 535.8 g of a filtered acrylamide solution (solution at 50% by weight) for 90 minutes and a sodium persulfate solution (SPS, 10% by weight in water) for 90 minutes. After 30 minutes of ageing, 0.26 g of sodium bisulphite (solution at 40% by weight) are added to make the possible residual monomers react. A new ageing for 60 minutes is applied before cooling. The obtained polymer P1a solution has a pH of 5.0, a polymer mass concentration of 30.1% and a Brookfield viscosity (LV3 modulus, 12 rpm, 25° C.) of 8,500 centipoises (cps).

(13) Preparation of a Polymer P2a Solution (Reaction Monitored by Turbidimeter)

(14) In a 1-litre reactor equipped with a mechanical stirrer, 46.4 g of the polymer P1a polymer and 748.4 g of water are introduced. The reactor is provided with a pH probe. After 10 minutes of stirring, 5.22 g of glyoxal at 40% (by weight in water) are introduced and then the pH is set at 10.2 with a soda solution at 10% (by weight in water). The temperature is maintained between 20 and 22° C. The progress of the reaction is monitored by turbidity. Once the turbidity variation (Hanna turbidimeter) of the polymer P2a solution is equal to +2 NTU, the reaction is stopped by lowering the pH to less than 3.5 by adding sulphuric acid (92% by weight in water). The Brookfield viscosity (LV1 modulus, 60 rpm, 25° C.) of the polymer P2a solution (weight concentration: 2%) obtained in this manner amounts to 55 cps.

(15) Preparation of a Polymer P2b Solution (Reaction Monitored by Pressure Differential Delta P Measurement)

(16) In a 1-litre reactor equipped with a mechanical stirrer, 46.4 g of the polymer P1a polymer and 748.4 g of water are introduced. The reactor is provided with a pH probe. After 10 minutes of stirring, 5.22 g of glyoxal at 40% (by weight in water) are introduced and then the pH is set at 10.2 with a soda solution at 10% (by weight in water). The temperature is maintained between 20 and 22° C. The progress of the reaction is monitored by measuring DeltaP of the polymer P2b solution (pressure differential measuring apparatus: calibrated tube with a diameter: 2 mm and a length: 2.2 m, P2b solution flow rate: 21 mL.Math.min.sup.−1). Once the Delta P has varied by +300%, the reaction is stopped by lowering the pH to less than 3.5 by adding sulphuric acid (92% by weight in water). The Brookfield viscosity (LV1 modulus, 60 rpm, 25° C.) of the polymer P2b solution (weight concentration: 2%) obtained in this manner amounts to 54 cps.

Example 3

(17) Preparation of a polymer P1b solution (AM/DADMAC (95/5 mol %)): polymerisation priming P1b with SPS and non-filtered acrylamide solution

(18) In a 1-litre reactor equipped with a mechanical stirrer, a thermometer, a refrigerant and a nitrogen gas plunger, 333.8 g of water, 50.1 g of diallyldimethylammonium chloride (DADMAC, 64% by weight in water) and 500 ppm of biocatalyst/arylamide are introduced. The pH of the solution is set at 2.5 with sulphuric acid. The medium is heated and maintained at a temperature comprised between 79 and 81° C. thanks to a water bath. Thanks to two continuous castings, are incorporated 535.8 g of a filtered acrylamide solution (solution at 50% by weight) for 90 minutes and a sodium persulfate solution (SPS, 10% by weight in water) for 90 minutes. After 30 minutes of ageing, 0.26 g of sodium bisulphite (solution at 40% by weight) are added to make the possible residual monomers react. A new ageing for 60 minutes is applied before cooling. The obtained polymer P1 b solution has a pH of 4.8, a polymer mass concentration of 29.9% and a Brookfield viscosity (LV3 modulus, 12 rpm, 25° C.) of 8,900 centipoises (cps).

(19) Preparation of a Polymer P2c Solution (Reaction Monitored by Turbidimeter)

(20) In a 1-litre reactor equipped with a mechanical stirrer, 46.4 g of the polymer P1 b polymer and 748.4 g of water are introduced. The reactor is provided with a pH probe. After 10 minutes of stirring, 5.22 g of glyoxal at 40% (by weight in water) are introduced and then the pH is set at 10.2 with a soda solution at 10% (by weight in water). The temperature is maintained between 20 and 22° C. The progress of the reaction is monitored by turbidity. Once the turbidity variation (Hanna turbidimeter) of the polymer P2c solution is equal to +2 NTU, the reaction is stopped by lowering the pH to less than 3.5 by adding sulphuric acid (92% by weight in water). The Brookfield viscosity (LV1 modulus, 60 rpm, 25° C.) of the polymer P2c solution (weight concentration: 2%) obtained in this manner amounts to 15 cps.

(21) Preparation of a Polymer P2d Solution (Reaction Monitored by Pressure Differential Delta P Measurement)

(22) In a 1-litre reactor equipped with a mechanical stirrer, 46.4 g of the polymer P1 b polymer and 748.4 g of water are introduced. The reactor is provided with a pH probe. After 10 minutes of stirring, 5.22 g of glyoxal at 40% (by weight in water) are introduced and then the pH is set at 10.2 with a soda solution at 10% (by weight in water). The temperature is maintained between 20 and 22° C. The progress of the reaction is monitored by measuring DeltaP of the polymer P2d solution (pressure differential measuring apparatus: calibrated tube with a diameter: 2 mm and a length: 2.2 m, P2d solution flow rate: 21 mL.Math.min.sup.−1). Once the Delta P has varied by +300%, the reaction is stopped by lowering the pH to less than 3.5 by adding sulphuric acid (92% by weight in water). The Brookfield viscosity (LV1 modulus, 60 rpm, 25° C.) of the polymer P2d solution (weight concentration: 2%) obtained in this manner amounts to 53 cps.

Example 4

(23) Preparation of a Polymer Plc Solution (AM/DADMAC (95/5 Mol %)): Polymerisation Priming Plc with V50 and Filtered Acrylamide Solution

(24) In a 1-litre reactor equipped with a mechanical stirrer, a thermometer, a refrigerant and a nitrogen gas plunger, 333.8 g of water, 50.1 g of diallyldimethylammonium chloride (DADMAC, 64% by weight in water) are introduced. The pH of the solution is set at 2.5 with sulphuric acid. The medium is heated and maintained at a temperature comprised between 79 and 81° C. thanks to a water bath. Thanks to two continuous castings, are incorporated 535.8 g of a filtered acrylamide solution (solution at 50% by weight) for 90 minutes and a V50 (2,2′-azobis 2-methylpropionamidine dihydrochloride, 10% by weight in water) solution for 90 minutes. After 30 minutes of ageing, 0.26 g of sodium bisulphite (solution at 40% by weight) are added to make the possible residual monomers react. A new ageing for 60 minutes is applied before cooling. The obtained polymer Plc solution has a pH of 5.0, a polymer mass concentration of 30.1% and a Brookfield viscosity (LV3 modulus, 12 rpm, 25° C.) of 8,420 centipoises (cps).

(25) Preparation of a Polymer P2e Solution (Reaction Monitored by Turbidimeter)

(26) In a 1-litre reactor equipped with a mechanical stirrer, 46.4 g of the polymer P1c polymer and 748.4 g of water are introduced. The reactor is provided with a pH probe. After 10 minutes of stirring, 5.22 g of glyoxal at 40% (by weight in water) are introduced and then the pH is set at 10.2 with a soda solution at 10% (by weight in water). The temperature is maintained between 20 and 22° C. The progress of the reaction is monitored by turbidity. No turbidity variation (Hanna turbidimeter) by n of the polymer P2e solution is observed. The polymer P2e solution gels quickly.

(27) Preparation of a Polymer P2f Solution (Reaction Monitored by Pressure Differential Delta P Measurement)

(28) In a 1-litre reactor equipped with a mechanical stirrer, 46.4 g of the polymer P1c polymer and 748.4 g of water are introduced. The reactor is provided with a pH probe. After 10 minutes of stirring, 5.22 g of glyoxal at 40% (by weight in water) are introduced and then the pH is set at 10.2 with a soda solution at 10% (by weight in water). The temperature is maintained between 20 and 22° C. The progress of the reaction is monitored by measuring DeltaP of the polymer P2f solution (pressure differential measuring apparatus: calibrated tube with a diameter: 2 mm and a length: 2.2 m, P2f solution flow rate: 21 mL.Math.min.sup.−1). Once the Delta P has varied by +300%, the reaction is stopped by lowering the pH to less than 3.5 by adding sulphuric acid (92% by weight in water). The Brookfield viscosity (LV1 modulus, 60 rpm, 25° C.) of the polymer P2f solution (weight concentration: 2%) obtained in this manner amounts to 57 cps.

(29) The results of Examples 1 to 3 are summarized in Table 1

(30) TABLE-US-00001 TABLE 1 Mon- Brook- Acryl- polymer itoring Pa- field amide viscosity tech- ram- viscosity Priming filtering (cps) nology eters (cps) P1a Sodium yes 8,500 P2a Turbidity 2 NTU 55 persulfate P2b Delta P 300% 54 P1b Sodium no 8,900 P2c Turbidity 2 NTU 15 persulfate P2d Delta P 300% 53 P1c Azo V50 yes 8,420 P2e Turbidity 2 NTU gel P2f Delta P 300% 57

(31) The solutions of polymers P1a and P1b differ in that the P1b solution contains a biocatalyst (a common impurity originating from the acrylamide obtained through an enzymatic process). Thus, monitoring of the glyoxalation of these polymers by turbidity leads to polymers with different Brookfield viscosities while when monitoring of the reaction is performed by measuring the pressure differential variation, the obtained polymers have equivalent Brookfield viscosities.

(32) When priming for the obtainment of the polymers changes (P1a and P1c), this has an effect on monitoring of the glyoxalation reaction of these polymers by turbidity. The obtained polymers are different: a solution (P2a) and a gel (P2e).

(33) However, when monitoring of the glyoxalation reaction is performed by measuring the pressure differential variation, the obtained polymers have equivalent Brookfield viscosities.

Example 5: Application Testing of the Polymers P2

(34) For these examples, pulps of recycled fibres are used.

(35) The wet pulp is obtained by dry pulp disintegration in order to obtain a final aqueous concentration of 1% by weight. It consists of a pulp with a neutral pH composed by 100% of fibres of recycled cardboard.

(36) Metering of each polymer P2 amounts to 2.5 dry kg/ton of paper.

(37) Assessment of Drainage (DDA) Performances

(38) The DDA (Dynamic Drainage Analyser) allows automatically determining the time (in seconds) necessary to drain a fibrous suspension under vacuum. The polymers are added to the wet pulp (0.6 litre of pulp at 1.0% by weight) into the cylinder of the DDA under stirring at 1,000 rpm:

(39) T=0 s: start of pulp stirring

(40) T=10 s: addition of the polymer P2

(41) T=30 s: stop of stirring and drainage under vacuum at 200 mBar for 60 s

(42) The pressure under the fabric is recorded over time. Once all of the water is evacuated off the fibrous mattress, air passes through the latter thereby revealing a slope breaking point in the curve representing the pressure under the fabric over time. The time, expressed in seconds, reported at this slope breaking point corresponds to the drainage time. Hence, the shorter the time, the better the vacuum drainage is.

(43) Performances in DSR (Dry Strength) Application, Grammage at 80 g.Math.m−2

(44) The necessary amount of pulp is sampled so as to ultimately obtain a sheet having a grammage of 80 g.Math.m−2.

(45) The wet pulp is introduced into the vat of the dynamic sheet former and is kept under stirring. The different components of the system are injected into this pulp according to the predefined sequence. In general, a contact time from 30 to 45 seconds between each polymer addition is met.

(46) Paper sheet formers are made with an automatic sheet former: a blotter and the forming fabric are placed in the bowl of the dynamic sheet former before starting the rotation of the bowl at 1,000 rpm and building the water wall. The processed pulp is distributed over the water wall to form the fibrous mattress over the forming fabric.

(47) Once water has been drained, the fibrous mattress is recovered, pressed under a press outputting 4 bars, and then dried at 117° C. The obtained sheet is conditioned for one night in a room with controlled humidity and temperature (50% of relative humidity and 23° C.). The dry strength properties of all sheets obtained through this procedure are then measured.

(48) Bursting is measured with a Messmer Buchel M 405 burst tester according to the standard TAPPI T403 om-02. The result is expressed in kPa. The burst index is determined, expressed in kPa.Math.m.sup.2/g, by dividing this value by the grammage of the tested sheet.

(49) The dry breaking length is measured in the machine direction with a tensile apparatus Testometric AX according to the standard TAPPI T494 om-01. The result is expressed in km.

(50) The results of the application testing of the polymers P2 obtained in Examples 1 to 3 are summarised in Table 2 (% increase with respect to a control).

(51) TABLE-US-00002 TABLE 2 % Burst % DBL % Polymer index MD drainage P2a 21.4 16.2 34.8 P2c 15.8 10.6 19.4 P2b 21.4 16.2 34.8 P2d 21.9 16.2 34.2 P2f 21.9 16.5 35.1

(52) The polymer P2c, which contains an impurity (biocatalyst) for which the glyoxalation reaction has been monitored by turbidimetry, has lower performances in terms of burst, dry strength and vacuum drainage in comparison with the polymers obtained in an identical manner (P2d) but with a monitoring of the glyoxalation reaction by measuring the pressure differential.

(53) In addition, the polymers P2b and P2f, respectively obtained by glyoxalation of polymers P1a and P1c the priming thereof during the polymerisation thereof was different (V50/SPS), have equivalent performances in terms of dry strength of the paper and vacuum drainage when monitoring of the glyoxalation reaction has been performed by measuring the pressure differential.