METHOD FOR PRODUCING ANIONIC POLYMERS AND USE AS RESISTANCE AGENTS IN A PAPER-MAKING METHOD

Abstract

The invention relates to a method for producing anionic polymers that are hydrosoluble in an aqueous solution, comprising at least the following successive steps: b) polymerisation, in an aqueous solution, of anionic monomers containing at least 5 mol % of 2-acrylamido-2-methylpropane sulfonic acid and/or one of the salts thereof and optionally non-ionic monomers up to a mass concentration of polymer A of between 5 and 40%, b) addition of at least one aldehyde into the solution produced in step a), and c) acidification to a pH of between 3 and 4 of the solution produced in step b). The invention also relates to the use thereof in a paper-making method.

Claims

1. Method for producing water-soluble anionic polymers in aqueous solution comprising at least the following successive steps: a) polymerising anionic monomers, in aqueous solution, comprising at least 5 mol % of 2-acrylamido-2-methylpropane sulfonic acid and/or one of the salts thereof and optionally nonionic monomers to a concentration of polymer A of between 5 and 40 weight %; b) adding at least one aldehyde to the solution obtained at step a); c) acidifying the solution obtained at step b) to a pH of between 3 and 4.

2. The method according to claim 1, characterized in that polymer A obtained after step a) contains between 5 and 30 mol % of anionic monomers and between 70 and 95 mol % of at least one nonionic monomer.

3. The method according to claim 1, characterized in that the nonionic monomers are selected from among acrylamide, methacrylamide, N,N dimethylacrylamide and acrylonitrile.

4. The method according to claim 1, characterized in that polymer A is a copolymer of acrylamide and 2-acrylamido-2-methylpropane sulfonic acid and/or the salts thereof.

5. The method according to claim 1, characterized in that for step b) 1 to 30 weight % of aldehyde is added, the aldehyde being selected from the group comprising glyoxal, glutaraldehyde, furan-dialdehyde, 2-hydroxyadipaldehyde, succinaldehyde, dialdehyde starch, 2,2 dimethoxyethanal, diepoxy compounds, and combinations thereof.

6. The method according to claim 1, characterized in that for step b) the aldehyde is glyoxal

7. The method according to claim 1, characterized in that polymer A is branched at step a) in the presence of a radical branching agent selected from the group comprising methylenebisacrylamide (MBA), ethylene glycol diacrylate, polyethylene glycol dimethacrylate, diacrylamide, cyanomethyl acrylate, vinyloxyethyl acrylate or methacrylate, triallylamine.

8. Water-soluble anionic polymer able to be obtained with the method according to claim 1.

9. Method for producing a sheet of paper, cardboard or the like whereby, before or after formation of said sheet, the cellulose material is contacted with at least one additive, characterized in that said additive is a water-soluble anionic polymer obtained with the method according to claim 1.

10. The method according to claim 9, characterized in that the additive is a water-soluble anionic polymer derived from the reaction between a copolymer A comprising at least 5 mol % of 2-acrylamido-2-methylpropane sulfonic acid and/or the salts thereof, and between 70 and 95 mol % of acrylamide, and from 1 to 30 weight % of glyoxal.

11. The method according to claim 9, characterized in that the additive is a water-soluble anionic polymer derived from the reaction between a copolymer A composed of 5 to 30 mol % of 2-acrylamido-2-methylpropane sulfonic acid and/or the salts thereof, and 70 to 95 mol % of acrylamide, and from 1 to 30 weight % of glyoxal.

Description

EXAMPLES OF EMBODIMENT

[0029] Protocol for Synthesis of the Compound of the Invention

[0030] Synthesis of the Base (Co)Polymer (Copolymer A)

[0031] Examples 1 to 3 were performed with a copolymer A of acrylamide and sodium 2-acrylamido-2-methylpropane sulfonate (85:15, mol %). For this purpose, these 2 monomers were placed in a reactor and polymerised in the presence of sodium persulfate and sodium metabisulfite, these catalysts being well known to skilled persons.

[0032] In Example 2, polymer A differs from polymers A in Examples 1 and 3 through its branched structure obtained by adding 500 ppm of methylenebisacrylamide (MBA) to the polymerisation reaction.

[0033] In all the examples, after polymerisation, the weight concentration of copolymer A was 20 in water.

[0034] For the counter-examples (1, 1 bis and 2) the base polymer was a copolymer of acrylamide and sodium acrylate (85:15, mol %).

[0035] Glyoxalation

[0036] End product at 7 weight % in water

[0037] A 1000 mL reactor under agitation was charged with 200 g of copolymer A (20 weight % in water) and 430 g of demineralised water. The reactor was equipped with a pH measuring probe. After an agitation time of 10 minutes, the pH was adjusted to 11.3 with sodium hydroxide solution (30 weight % in water). The temperature was held at between 19 and 26° C.

[0038] 16 g of glyoxal (40 weight % in water) were added. pH checking and monitoring of viscosity allowed a product of 70 cps to be obtained (viscosity on completion of the reaction). When this viscosity is reached, the reaction is halted by lowering the pH to below 3.5 through the addition of sulfuric acid (H.sub.2SO.sub.4 92 weight % in water). The final viscosity and pH were recorded.

[0039] The viscometer used was of Brookfield type, with LV1 module and speed of 60 rpm. The pH can be adjusted, after adding glyoxal, with sodium hydroxide solution (10 weight % in water). It is possible to conduct the reaction under controlled pH through continuous addition of 10% sodium hydroxide, but it is also possible to add glyoxal in several fractions.

[0040] The end polymer was stored in a climate chamber at 32° C. to evaluate the stability thereof. Daily monitoring of viscosity was carried out until gelling of the product. The product was then unusable. The viscometer used was of Brookfield type, with LV1 module and speed of 60 rpm.

TABLE-US-00001 Vis- Initial Final cosity viscosity Vis- viscosity Sta- of (after cosity (after bility copol- adding at end of adding at ymer glyoxal) reaction acid) Kinetics 32° C. A (cPs) (cPs) (cPs) (cPs) (min) (days) pH Counter- 1040 29  70 34 27 12 3.1 example 1 Counter- 1040 33 151 70 15  3 3.1 example 1 bis Example 1  910 25  70 69 35 30 3.2 Example 2 1100 30  65 64 29 25 3.1

[0041] To carry out Counter-example 1 bis, the reaction was halted at higher viscosity to obtain a final viscosity equivalent to Example 1, after ascertained drop in viscosity.

[0042] End product at 10 weight % in water

[0043] A 1000 mL reactor under agitation was charged with 355 g of copolymer A (20 weight % in water) and 430 g of demineralised water. The reactor was equipped with a pH measuring probe. After an agitation time of 10 min, the pH was adjusted to 11.3 with sodium hydroxide solution (30 weight % in water). The temperature was held at between 24 and 26° C. 28.5 g of glyoxal (40 weight % in water) were added. pH checking and viscosity monitoring allowed a product to be obtained of 112 cps (viscosity on completion of reaction). When this viscosity is reached, the reaction is halted by lowering the pH to below 3.5 through the addition of sulfuric acid (H.sub.2SO.sub.4 92 weight % in water). The final viscosity and pH were recorded.

[0044] The viscometer used was of Brookfield type, with LV1 module and speed of 60 rpm. The pH can be adjusted, after adding glyoxal, with sodium hydroxide solution (10 weight % in water). It is possible to conduct the reaction at controlled pH via continuous addition of 10% sodium hydroxide, but it is also possible to add glyoxal in several fractions.

TABLE-US-00002 Vis- Initial Final cosity viscosity Vis- viscosity Sta- of after cosity after bility copol- adding at end of adding at ymer A glyoxal reaction acid Kinetics 32° C. (cPs) (cPs) (cPs) (cPs) (min) (days) pH Counter- 1040 50 111  62 35  7 3.4 example 2 Example  910 42 112 110 21 15 3.1 3

[0045] In all the examples (end products obtained with the method of the invention), no drop in viscosity was observed at the time of acidification, contrary to the counter-examples. The stability of the polymers in the counter-examples was also lesser than that of the polymers of the invention.

[0046] Preparation of the Pulp

[0047] The pulp used was composed of virgin fibres. The paper pulp was prepared by disintegrating 60 grams of recycled fibres for 20 minutes in 2 litres of water. The pulp obtained was diluted to a total volume of 9 litres. After accurate measurement of consistency, the required amount of pulp was sampled to obtain a sheet having a grammage of 60 g/m.sup.2. The tests were conducted with the pulp at pH 6.6.

[0048] Polymer Property Testing

[0049] Performance Under DSR Application (Dry Strength), Grammage of 60 g/m2

[0050] 1/Sheet Formation

[0051] Paper handsheets were produced using an automatic dynamic handsheet former. The pulp is placed in the dynamic former tank, diluted to a consistency of 0.32 weight % and left under moderate mechanical agitation to homogenise the fibrous suspension. In manual mode, the pulp is pumped as far as the nozzle to prime the circuit. A blotter and the forming fabric are placed in the bowl of the dynamic former before setting the bowl in rotation at 1000 m/min and building the water wall. A polymer of PAE type (polyaminopolyamide-epichlorhydrin) was added at a metering rate of 3 kg/t sec. After 45 seconds, the polymer of Examples 1 to 3 or the counter-example was added to the fibrous suspension under agitation with a contact time of 45 seconds before adding a retention agent (FO 4190 PG10) in an amount of 150 g/t. The sheet was then produced (in automatic mode) via 22 nozzle sweeps, spraying the pulp into the water wall. After draining the water and completion of the automatic sequence, the forming fabric with the formed network of fibres was removed from the bowl of the dynamic former and placed on a table. A dry blotter was deposited on the side of the wet fibre mattress and pressed once with a roller. The assembly was turned over and the fabric gently separated from the fibrous mattress. A second dry blotter was deposited and the sheet (between the two blotters) was pressed once under a press applying 4 bars, then dried on a drying plate for 9 min at 107° C. Both blotters were then removed and the sheet stored overnight in a room under controlled humidity and temperature (50% relative humidity and 23° C.). The dry strength properties of all the sheets obtained with this procedure were evaluated.

[0052] 2/Burst Test

[0053] The Burst index was measured with a Messmer Buchel M 405 testing machine (mean of 14 measurements). The test was conducted in accordance with TAPPI standard T403 om-91.

[0054] 3/Dry Tensile Test

[0055] Breaking length was measured with AXM250 dynamometer testing system. The test was conducted in accordance with TAPPI standard 494 om-88.

[0056] 4/Wet Tensile Test

[0057] Breaking length was measured with AXM250 dynamometer testing system. The test was conducted in accordance with TAPPI standard 456 om-87

[0058] Application Test 1

[0059] In the following example, the sheets of paper were produced according to the above procedure by adding the polymer in a proportion of 1.0 and 2.0 kg/T (dry polymer/dry fibre).

TABLE-US-00003 Counter- Counter- Counter- Counter- example 1 example 1 Example Example example 1 example 1 bis bis Ref. 1 (1 kg) 1 (2 kg) (1 kg) (2 kg) (1 kg) (2 kg) Grammage 62.7 61.7 61.7 61.9 58.6 62.6 61.1 Burst index 3.13 3.68 4.21 3.64 3.98 3.70 3.90 Improvement % 18% 34% 16% 27% 18% 25% Dry tensile test (km) 5.00 5.90 6.24 5.80 6.09 5.70 6.45 Improvement % 18% 25% 16% 22% 14% 29% Wet tensile test (km) 1.80 2.42 2.62 2.39 2.57 2.34 2.57 Improvement 34% 46% 33% 43% 30% 43%

[0060] The above table shows improved performance of physical properties when the polymer of the invention is used. The polymers containing acrylic acid (Counter-examples 1, 1 bis and 2) exhibit lower performance.

[0061] Application Test 2

[0062] In the following example, the polymers of Examples 1 and 2 were compared with anionic polymers well-known to persons skilled in the art: carboxymethylcellulose (CMC) and anionic polyacrylamide (anionic PAM). The sheets of paper were produced according to the procedure already-cited. The PAE-type polymer was added in a proportion of 2 kg/t for each test.

TABLE-US-00004 Anionic Example Example CMC PAM 1 2 Ref. 1 kg/t 1 kg/t 1 kg/t 1 kg/t Grammage 63.03 62.29 61.58 60.53 62.26 Burst index 2.568 3.104 2.842 3.317 3.368 Improvement % 20.88% 10.68% 29.17% 31.16% Dry tensile test 4.423 5.043 4.809 5.309 5.396 (km) Improvement % 14.02% 8.73% 20.03% 22.00% Wet tensile test 1.728 2.058 1.829 2.320 2.247 (km)

[0063] In this table, a distinct improvement can be seen when the polymer obtained with the method of the invention is used, compared with the polymers known to skilled persons.

[0064] Application Test 3

[0065] In the following example, the cationic polymer used for all the sheets was a glyoxalated cationic polymer in a proportion of 2 kg/t (this polymer replaced the PAE in Application test 2).

TABLE-US-00005 PAM contre- CMC Anionique Exemple 1 Exemple 2 exemple 1 Ref. 1 kg/t 1 kg/t 1 kg/t 1 kg/t 1 kg/t Grammage 64.16 64.4 64.8 63.72 63.11 63.99 Burst index 2.498 2.980 3.040 3.345 3.413 3.222 Improvement % 19.31% 21.72% 33.94% 36.66% 28.99% Dry tensile test (km) 4.459 5.006 4.985 5.271 5.513 4.585 Improvement % 12.27% 11.80% 18.21% 23.64% 2.83% Wet tensile test (km) 0.703 1.020 1.244 1.376 1.494 1.227

[0066] In this table a distinct improvement can be seen when the polymer obtained with the method of the invention is used, even though the cationic polymer is of different type (glyoxalated cationic polymer/PAE).