NO324301B1 - Hydrophilic dispersion polymers for paper applications - Google Patents

Abstract

Papermaking involves the formation of an aqueous cellulosic pulp and adding a hydrophilic dispersion polymer to the pulp to increase retention and / or dewatering. The hydrophilic dispersion polymer comprises (a) a cationic monomer and (b) a second monomer of (meth) acrylamide (in an aqueous solution of a polyvalent anionic salt) wherein the polymerization is carried out in the presence of an organic high molecular weight polyvalent cation comprising a water-soluble polymer containing at least one (A) monomer and / or polydiallyldimethylammonium chloride (DADMAC). After the addition of the polymers, the pulp is dewatered to form a sheet which is dried.

Description

The present invention relates to papermaking and more particularly to an improved papermaking process using hydrophilic dispersion polymers as retention and drainage aids.

In the manufacture of paper, an aqueous cellulosic suspension or slurry is formed into a sheet of paper. The cellulose slurry is generally diluted to a consistency (percent dry weight of solids in the slurry) of less than 1% by weight, and often below 0.5%, before the paper machine, while the finished sheet must contain less than 6% by weight of water. Consequently, the dewatering aspects of paper production are very important for the efficiency and costs of production.

The least expensive dewatering method is drainage, and then more expensive methods are used, including vacuum pressing, suction felt and pressing, evaporation and the like and any combination of such methods. Since drainage is both the first dewatering method used and the least expensive, improvement in drainage efficiency will reduce the amount of water that must be removed by other methods and thereby improve the overall efficiency of dewatering and thereby reduce costs.

Another feature of paper production that is very important for the efficiency and costs of production is the retention of the pulp components on and inside the fiber mat that is formed during paper production. A pulp contains particles in the range from 2 - 3 mm for cellulose fibers to fillers measuring only a few microns. Within this area are cellulose fines, mineral fillers (used to increase opacity, lightness and other paper characteristics) and other smaller particles which generally, without the inclusion of one or more retention aids, will pass through the spaces (pores) between the cellulose fibers in the fiber mat that is formed.

A method for improving the retention of cellulose fines, mineral fillers and other pulp components on the fiber mat is the use of a coagulation/flocculation system, added before the paper machine. In such a system, a coagulant is first added to the mass, e.g. a low molecular weight cationic synthetic polymer or a cationic starch, which coagulant reduces the negative surface charge present on the particles in the pulp, especially cellulose fines and the mineral fillers, thereby agglomerating such particles. The coagulant is followed by the addition of a flocculant. The flocculant is generally a high molecular weight cationic or anionic synthetic polymer that bridges the particles and/or agglomerates from one surface to another, binding the particles together into large agglomerates. The presence of such agglomerates in the pulp improves retention. The agglomerates are filtered out of the water onto the fiber web, where non-agglomerated particles would otherwise pass to a large extent.

Although a flocculated agglomerate generally does not affect the drainage of the fiber mat to the extent that would occur if the mass was gelled or contained a quantity of gelatinous material, when such flocs are filtered by the pores of the fiber web, the drainage efficiency will be reduced. Consequently, retention will increase at the expense of reduced drainage.

Another system used to provide an improved combination of retention and dewatering is described in U.S. Patents No. 4,753,710 and No. 4,913,775 to Langleyl et al., issued June 28, 1988 and April 3, 1990, respectively.1 brevity such a method includes addition to the aqueous cellulosic papermaking slurry to first a high molecular weight linear cationic polymer before shearing the slurry, followed by the addition of bentonite after shearing. The shearing is generally provided by one or more of the cleaning, mixing and pumping steps in the papermaking process and the shearing action breaks down the large flocs formed by the high molecular weight polymer into microflocs, and further agglomeration is then ensured by the addition of bentonite clay particles.

Another system uses the combination of cationic starch followed by colloidal silica to increase the amount of material retained in the web by charge neutralization and adsorption of small agglomerates. This system is described in US Patent No. 4,388,150, granted to Sunden et al. 14 June 1983.

US Patent Nos. 5,098,520 and 5,185,062 issued to Begala describe methods for improving dewatering in a papermaking process.

US Patent No. 5,334,679 to Yamamoto et al. is directed to a method for producing a water-soluble cationic polymer with a high degree of cationization and a high viscosity in water solution that can be used for flocculants, antistatic agents, and retention agents for paper production. US Patent No. 4,696,962 to Danner et al. is also directed to a cationic polymer composition suitable for use as a flocculant, a retention agent, and a dewatering agent in papermaking. EP 0 308 752 B1 describes a process for awanning paper using a cationic organic polymer, a colloidal silica and a high molecular weight charged acrylamide copolymer. However, none of these references describe the method of the present invention for improving retention and drainage performance in a papermaking process using a hydrophilic dispersion polymer comprised of a cationic monomer of the described formula and a monomer represented by (meth)acrylamide.

The present invention provides a method for improving retention and drainage performance in a papermaking process comprising the steps of: a) forming an aqueous cellulosic papermaking slurry; b) adding an effective amount of a hydrophilic dispersion polymer to the slurry

wherein the hydrophilic dispersion polymer results from the polymerization of

monomers and have an intrinsic viscosity of from 11.9 to 21.2 dl/g, the monomers are selected from the group consisting of:

i. a cationic monomer of formula (I)

wherein R 1 is selected from the group consisting of H and CH 3 ; each of R 2 and R 3 is an alkyl group of 1 to 2 carbon atoms; R 4 is H or an alkyl group of 1 to 2 carbon atoms; A' is selected from the group consisting of an oxygen atom and NH; B' is an alkylene group of 2 to 4 carbon atoms or a hydroxypropylene group; and X" is an anionic mothioine, and ii. a second monomer represented by (meth)acrylamide, in an aqueous solution of a polyvalent anionic salt, wherein the polymerization is carried out in the presence of either a high molecular weight organic multivalent cation comprising a water-soluble polymer containing at least one monomer of formula (I) and/or polydiallyl dimethyl ammonium chloride (DADMAC);

c) draining the slurry to form a sheet; and

d) dry the sheet.

Brief Description of the Drawings

Fig. 1 shows graphical comparison of turbidity reduction between three dispersion polymers and standard latex retention aid. Fig. 2 shows graphical comparison of drainage activity between three dispersion polymers and the standard latex retention aid. Fig. 3 graphically shows retention activity for dispersion copolymers, with higher intrinsic viscosity, containing 10 and 20 mol% DMAEAMCQ. Fig. 4 graphically shows drainage activity for dispersion copolymers, with higher intrinsic viscosity, containing 10 and 20 mol% DMAEAMCQ. Fig. 5 shows a graphical comparison of the retention effect of dispersion latex and dry polymers. Fig. 6 shows a graphical comparison of turbidity reduction for different dispersion polymers with standard flocculants. Fig. 7 shows a graphical comparison of drainage activity for different dispersion polymers with standard flocculants. Fig. 8 shows a graphical comparison of the retention effect of dispersion polymers in relation to the standard latex polymer. Fig. 9 shows a graphical comparison of the drainage effect for dispersion polymers in relation to the standard latex polymer. Fig. 10 shows a graphical comparison of the retention effect of dispersion polymers combined with standard coagulants in relation to dispersion polymers alone. Fig. 11 shows a graphical comparison of the drainage effect of dispersion polymers combined with standard coagulants in relation to dispersion polymers alone.

Description of Preferred Embodiments

The invention includes a papermaking process for improving retention and drainage which comprises forming an aqueous cellulosic papermaking stock and adding a hydrophilic dispersion polymer to the stock. The pulp is then formed into a sheet and dried.

Preferably, the hydrophilic dispersion polymer according to the invention is a copolymer of quaternary dimethylaminoethyl (meth)acrylate methyl chloride (DMAEA MCQ) cationic monomer and (meth)acrylamide (AcAm). It has been found that the described polymer provides advantages when used in the papermaking process. In particular, the hydrophilic dispersion polymers according to the invention exhibit improved retention activity, compared to quaternary dimethylaminoethyl acrylate benzyl chloride

(DMAEABCQ)/acrylamide(AcAm) dispersion copolymer and DMAEA methyl chloride quaternary latex with the same charge. Latex is defined below as an inverse water-in-oil emulsion polymer.

In another alternative embodiment, the DMAEA MCQ/AcAm hydrophilic dispersion polymers exhibit nearly equal retention and drainage activity compared to commercial standard latex cationic polymers.

The following examples 1-4 indicate methods for producing the copolymer at different ratios between the monomer components. Preferably, the amount of the quaternary dimethylaminoethyl acrylate methyl chloride is present in the copolymer in an amount in the range of 3-20 mol%. The range of the limiting viscosities for the hydrophilic dispersion polymers is preferably 11.9 - 21.2 dl/g. According to a preferred method according to the invention, the dispersion polymer is added in an amount of 0.23 - 2.7 kg of active ingredients per tons of pulp solids.

The present method is believed to be applicable to all grades and types of paper products and further applicable to all types of pulps including chemical pulps, including sulphate and sulphite pulps from both hardwood and softwood and acidic pulps, thermomechanical pulps, mechanical pulps, recycled pulps and wood pulps. Typically, such masses will have a pH in the range 3.0 - 9.0.

The following examples are shown to describe preferred embodiments and applications according to the invention and are not intended to limit this if nothing else is stated in the attached claims.

Example 1 - Procedure for the Preparation of Dispersion Copolymers of Acrylamide and 3 mol% DMAEA MCQ

To a two-liter resin reactor equipped with stirrer, temperature control and water-cooled condenser was added 287.59 g of a 48.1% solution of acrylamide (1.9461 mol), 7.24 g of an 80.6% solution of DMAEAMCQ (0.0301 mol), 250 g of ammonium sulfate, 225.59 g of deionized water, 27 g of glycerol, 56.25 g of a 16% solution of polyDADMAC (polydiallyldimethylammonium chloride) (IV = 1.5 dl/g) , 18 g of a 20% solution of polyDMAEAMCQ (IV=2.0 g/g and 0.3 g of EDTA. The mixture was heated to 48°C and 0.05 g of a 4% solution of 2, 2' azobis(2 amidinopropane)dihydrochloride was added. The resulting solution was flushed with 1 cm<3>/min of nitrogen. After 15 min, polymerization began and the solution became viscous. During the next 4 hours, the temperature was maintained at 48°C and a solution containing 95.86 g (0.6487 mol) of 48.1% acrylamide, 12.07 g (0.0502 mol) of an 80.6% solution of DMAEAMCQ, 9 g glycerol and 0.1 g EDTA was pumped into the reactor using an injection pump mpe. To the resulting polymeric dispersion was added 0.50 g of a 4% solution of 2,2' azobis(2 amidinopropane) dihydrochloride. The dispersion was then further reacted for 2.5 hours at a temperature of 48°C - 55°C. The resulting polymeric dispersion had a Brookfield viscosity of 5,600 eps. 10 g of 99% acetic acid and 20 g of sodium sulfate were added to the above dispersion. The resulting dispersion had a Brookfield viscosity of 1525 eps and contained 20% of a 97/3 copolymer of acrylamide and DMAEAMCQ with an intrinsic viscosity of 12.1 dl/g in a 0.125 molar NaNC>3.

Example 2 - Procedure for the Preparation of Dispersion Copolymers of Acrylamide and 5 mol% DMAEA MCQ.

To a two-liter resin reactor equipped with stirrer, temperature control and water-cooled condenser, 281.68 g of a 48.1% solution of acrylamide (1.9061 mol), 12.07 g of an 80.6% solution were added of DMAEAMCQ (0.05023 mol), 250 g ammonium sulfate, 225.10 g deionized water, 27 g glycerol, 33.75 g of a 16% solution of polyDADMAC (IV=1.5 dl/g), 36 g of a 20 µg solution of polyDMAEAMCQ (IV=2.0 dl/g) and 0.3 g EDTA. The mixture was heated to 48°C and 0.50 g of a 4% solution of 2,2' azobis(2-amidinopropane) dihydrochloride was added. The resulting solution was flushed with lm<3>/min nitrogen. After 15 minutes, polymerization began and the solution became viscous. During the next 4 hours the temperature was maintained at 48°C and a solution containing 93.89 g (0.6354 mol) of 48.1% acrylamide, 20.11 g (0.08368 mol) of an 80.6% 1g solution of DMAEAMCQ, 9 g glycerol and 0.1 g EDTA were pumped into the reactor using a syringe pump. To the resulting polymeric dispersion was added 0.50 g of a 4% solution of 2,2'azobis(2 amidinopropane)dihydrochloride. The dispersion was then reacted for a further 2.5 hours at a temperature of 48-55°C. The resulting polymeric dispersion had a Brookfield viscosity of 1000 eps. 10 g of 99% acetic acid and 20 g of sodium sulfate were added to the above dispersion. The resulting dispersion had a Brookfield viscosity of 2825 eps and contained 20% of a 95/5 copolymer of acrylamide and DMAEAMCQ with an intrinsic viscosity of 14.1 dl/g in 0.125 molar NaNO 3 .

Example 3 - Procedure for the Production of Dispersion Polymers from Acrylamide and 10 mol% DMAEAMCQ.

To a two-liter resin reactor equipped with a stirrer, temperature control and water-cooled condenser was added 239.38 g of a 48.1% solution of acrylamide (1.6199 mol), 21.63 g of an 80.6% solution of DMAEAMCQ (0.09001 mol), 260 g of ammonium sulfate, 258.01 g of deionized water, 18 g of glycerol, 33.75 g of a 16% solution of polyDADMAC (IV=1.5 dl/g), 36 g of a 20% solution of polyDMAEAMCQ (IV=2.0 dl/g) and 0.3 g EDTA. The mixture was heated to 48°C and 0.50 g of a 4% solution of 2,2' azobis(2 amidinopropane) dihydrochloride was added. The resulting solution was flushed with 1 m<3>/min nitrogen. After 15 minutes, polymerization began and the solution became viscous. During the next 4 hours the temperature was maintained at 48°C and a solution containing 79.79 g (0.5399 mol) of 48.1% acrylamide, 36.04 g (0.1500 mol) of an 80.6% solution of DMAEAMCQ, 6 g glycerol and 0.1 g EDTA was pumped into the reactor using a syringe pump. To the resulting polymeric dispersion was added 0.50 g of a 4% solution of 2,2'azobis(2 amidinopropane)dihydrochloride. The dispersion was then further reacted for 2.5 hours at a temperature in the range 48 - 55°C. The resulting polymeric dispersion had a Brookfield viscosity of 7600 eps. 10 g of 99% acetic acid and 20 g of sodium sulfate were added to the above-mentioned dispersion. The resulting dispersion had a Brookfield viscosity of 2100 eps and contained 20% of a 90/10 copolymer of acrylamide and DMAEA MCQ with an intrinsic viscosity of 15.5 dl/g in 0.125 molar NaNO 3 .

Example 4 - Procedure for the Production of Dispersion Copolymers of Acrylamide and 20 mol% DMAEAMCQ.

To a two-liter resin reactor equipped with a stirrer, temperature control and water-cooled condenser was added 136.03 g of a 48.1% solution of acrylamide (0.9205), 37.12 g of an 80.6% solution of DMAEAMCQ (0.1545 mol), 190 g ammonium sulfate, 50 g sodium sulfate, 267.99 g deionized water, 13.2 g glycerol, 33.75 g of a 16% solution of polyDADMAC (IV=1.5 dl /g), 45 g of a 20% solution of polyDMAEAMCQ (IV=2.0 dl/g) and 0.2 g EDTA. The mixture was heated to 48°C and 0.50 g of a 4% solution of 2,2'azobis(2 amidinopropane)dihydrochloride was added. The resulting solution was flushed with 1 m<3>/min nitrogen. After 15 minutes, polymerization began and the solution became viscous. During the next 4 hours the temperature was maintained at 48°C and a solution containing 111.29 g of 48.1% acrylamide, 63.47 g (0.2641 mol) of an 80.6% solution of DMAEA MCQ, 10.8 g glycerol and 0.2 g EDTA were pumped into the reactor using a syringe pump. To the resulting polymeric dispersion was added 0.50 g of a 4% solution of 2,2' azobis(2 amidinopropane) dihydrochloride. The dispersion was then further reacted for 2.5 hours at a temperature in the range 48 - 55°C. The resulting polymeric dispersion had a Brookfield viscosity of 2160 eps. 10 g of 99% adipic acid and 30 g of ammonium sulfate were added to the above-mentioned dispersion. The resulting dispersion had a Brookfield viscosity of 1325 eps and contained 205 of an 80/20 copolymer of acrylamide and

DMAEA MCQ with an intrinsic viscosity of 13.7 dl/g in 0.125 molar NaNC>3.

In the following examples, the polymers and the described masses were used.

Polymer p robbers

POLYMER COATING

Dispersions

Other Polymers

IV Provision

The IV determinations of polymer samples were carried out in a 0.125 M NaNC>3 solution. The procedure includes: 1. Prepare a 1% dispersion product (0.2% active polymer) solution by injecting 2 g of the dispersion polymer with a syringe into a vortex of 198 g of deionized water. Continue stirring at 800 rpm for 30 minutes. 2. Prepare a working solution containing 0.045% active polymer from: 3. Fill 2 ml of 0.125 M sodium nitrate solution into a capillary viscometer. Determine the time ts. 4. Remove the sodium nitrate solution and clean the viscometer. Fill 2 ml of the solution containing 0.045% active polymers into the viscometer. Determine the time Ti.

Mass production

Three of the pulps used for polymer activity determination were prepared from thick pulp obtained from a paper mill and diluted to a consistency of approx. 0.5% with drinking water. The fourth pulp was a synthetic alkaline pulp comprising 70% by weight of fiber and 30% by weight of fillers, diluted to a consistency of approx. 0.5% with drinking water. The process water contained 200 ppm calcium hardness (added as CaCk), 152 ppm magnesium hardness (added as MgSC^) and 110 ppm bicarbonate alkalinity (added as NaHCOs).

Awanning and retention trials

Britt CF dynamic drainage jar was used for uniform mixing of polymer and pulp. The mixing speed in the Britt jar was 500 rpm. The dewatering experiment simulates gravity dewatering on a paper machine. The test procedures for dewatering and retention are given below:

1. Measure a 500 ml sample of the thin mass using a measuring cylinder.

2. Add the thin mixture to the Britt jar.

3. Start stirring (500 rpm) and add starch or a coagulant using a syringe (if necessary).

4. After 10 s, add polymer solution to the mass using a syringe.

5. Stop stirring for a total time of 30 s, i.e. 20 s after addition of the polymer.

6. Immediately transfer the treated pulp to the reservoir in the dewatering device.

7. Remove the stopper and collect the filtrate for 5 s.

8. Determine the weight of the filtrate.

9. Determine the turbidity of the filtrate at 450 nm with a DR-2000 spectrometer. The filtrate was diluted (x2) with deionized water.

Awanning and turbidity data were obtained for dispersion and latex polymer using the above mentioned test procedures. In these examples, a measure of the retention is given by the percent reduction in turbidity obtained without any polymer treatment (blank test). Dosing curves for dewatering improvement (%) and turbidity reduction (%) were determined for the investigated polymers. It is well known that the retention and dewatering activities of polymers are dependent on several factors including the type of pulp to be treated. For this reason, masses that were significantly different from each other were chosen. The first was a 100% recycled cardboard pulp. The other was a pulp used for the manufacture of corrugated board products. This pulp was a mixture of old corrugated cardboard (OCC), newspaper pulp and cardboard pulp. Pulps and other additives used for the production of printing paper were collected to produce the third pulp. The fourth pulp was produced in the laboratory and was very similar to alkaline pulp used in the paper industry for the production of fine paper.

Using these test masses described above, dewatering and retention tests as described above were also used to determine the dewatering and retention activities for the dispersions A-H and the polymers A-H in examples 5-9.

Example 5

The initial activity studies of the DMAEAMCQ dispersion polymers were performed with 100% recycled linerboard (corrugated linerboard?). This pulp did not contain any added filler and retention was mainly for fines from the fibres. Fig. 1 shows graphically plotted % turbidity reduction against polymer dosage for three of the hydrophilic dispersion polymers and polymer A, namely a standard latex flocculant. The compositions of the dispersions were (1) AcAm/DMAEA MCQ: 97/3, (2) AcAm/DMAEA MCQ: 95/5 and (3) AcAm/DMAEA MCQ: 90/10. Dispersions A, B and C showed increased retention efficiency compared to polymer A. In addition, fig. 1 that turbidity reductions between 60 and 70% were achieved with dispersion polymers at doses of approx. 3.6 kg active ingredient/tonne.

Figure 2 shows the dewatering improvements obtained with the dispersion polymers as described above. Of the dispersions, the copolymer containing 5 mol% DMAEAMCQ showed the best drainage behavior. However, the latex polymer, polymer A, outperformed the dispersions over the entire dosage range investigated. It should be noted that the intrinsic viscosities for the first batches of hydrophilic dispersions were significantly lower than for polymer A.

Example 6

The corrugated coated pulp was a mixture of OCC, newsprint and paperboard pulp. In contrast to recycled "linerboard", this mass contained CaCC>3 as filler. % ash content was found by gravimetric determination to be 7.3%. Preliminary activity testing was carried out with the lower IV (11.9-15.7 dl/g) polymer samples and the data obtained indicated certain important trends in the polymers' behavior. Both retention and dewatering effects of the dispersion polymers increased with increasing mol% DMAEAMCQ. Overall, the 10 mol% DMAEAMCQ copolymer exhibited the best dewatering and retention effect of the investigated dispersions.

The retention effects of the higher IV (17.0 - 21.2 gl/g) dispersion copolymers containing 10 mol% and 20 mol% DMAEAMCQ are shown in fig. 3. Dispersions D, E, F and G containing 10 mol% and 20 mol% DMAEAMCQ showed comparable retention activities to that of polymer A with corrugated coated pulp.

Fig. 4 shows dewatering activities for the higher IV dispersion copolymers containing 10 mol% and 20 mol%

DMAEAMCQ. The results clearly show that in the dose range 0 - 0.68 kg active ingredients/tonne of the hydrophilic dispersion polymers were comparable to the standard flocculant, namely polymer A. When the polymer dose increased to 1.4 kg active ingredients/tonne then 20 mol% continued

The DMAEA MCQ copolymers exhibit dewatering behavior similar to polymer A.

Example 7

The printing paper pulp was a mixture of 90% (softwood, hardwood, wreck with a high ash content, wreck with a low ash content) and 10% (CaCC>3, Ti02, starch, alum). The flocculating agent used in the experiment was polymer D (AcAm/NaAc:70:30). Figure 5 shows the results of Britt jar sieving of the dispersion and dry polymers. On an equal active basis of 0.68 kg/ton, the 10 mol% DMAEAMCQ dispersion (dispersion E) was the best of all polymers including polymer C, polymer D and polymer E, a dry polymer available from Floerger.

Results of the retention and dewatering tests carried out with this mass are shown in figures 6 and 7. Two hydrophilic dispersions containing 10 mol% DMAEAMCQ were compared with polymer A and polymer D. The graphical plot of % turbidity reduction against dosage, figure 6, shows that for low dosages of the flocculants, significant reductions in turbidity (-90%) were obtained for each polymer. In addition, there were no differences in the retention activities between the dispersion and latex polymers.

Figure 7 shows that the dewatering activities of the latex and dispersion polymers were very different. The latex polymer, polymer A, gave the best dewatering effect. Then followed the higher IV dispersion polymer. At doses above 0.45 kg/tonne, the dewatering improvements for the two dispersion polymers were greater than that for polymer D.

Example 8

A synthetic alkaline mass was prepared containing approx. 30% CaC03 as filler and therefore had the highest filler content of the masses produced. In example 8, cationic starch was added to the mass in an amount of approx. 4.54 kg/tonne dry pulp.

Figure 8 shows the dose retention curves for the two hydrophilic dispersions containing 10 mol% and 20 mol% DMAEAMCQ (dispersion E, G) compared to polymer B and polymer C.

Polymer B (IV=19.1 dl/g) is a material with a higher molecular weight than polymer A (IV=17.7 dl/g). The results indicate that the hydrophilic dispersion polymers containing 10 mol% and 20 mol% DMAEAMCQ are also very effective retention aids for fine paper applications.

Dewatering data for the investigated polymers with standard alkaline mass are shown in Figure 9. The hydrophilic dispersion containing 20 mol% DMAEAMCQ showed better dewatering than polymer C and the 10 mol% DMAEA MCQ dispersion polymer. The evaporation effect was comparable to that of polymer B.

The previous results showed that hydrophilic dispersion polymers are effective retention and dewatering aids for a wide range of pulps. The activities of the new dispersion polymers in one polymer program were comparable or at times better than the inverse emulsion polymer, polymer A.

Example 9

Coagulant efficiencies for the retention and dewatering activities of two DMAEAMCQ dispersion polymers (10 mol% and 20 mol% DMAEAMCQ) were evaluated in a two-polymer program and are shown in Figures 10 and 11. The corrugated pulp was selected for this investigation. Coagulants including polymer F, (Epi/DMA), polymer G (poly-DADMAC, IV=0.55) and polymer H (polyDADMAC, IV=1.9) were used. Figure 10 shows an increase of approx. 30% in retention effect for dispersion F, namely 20 mol% DMAEAMCQ polymer with an addition of 0.91 kg/ton of high IV polyDADMAC. There was also a measurable increase in retention with polymer F and polymer G. There were no significant changes in retention activities for the 10 mol% DMAEA MCQ (dispersion D) polymer with the addition of coagulants. The coagulants showed a less favorable effect on the dewatering activities of the two DMAEAMCQ dispersion polymers (Figure 11).

Claims (5)

1. A method of improving retention and drainage performance in a papermaking process comprising the steps of: a) forming an aqueous cellulosic papermaking slurry; b) adding an effective amount of a hydrophilic dispersion polymer to the slurry wherein the hydrophilic dispersion polymer results from the polymerization of monomers and has an intrinsic viscosity of from 11.9 to 21.2 dl/g, the monomers being selected from the group consisting of: i. a cationic monomer of formula (I) wherein R 1 is selected from the group consisting of H and CH 3 ; each of R 2 and R 3 is an alkyl group of 1 to 2 carbon atoms; R 4 is H or an alkyl group of 1 to 2 carbon atoms; A' is selected from the group consisting of an oxygen atom and NH; B' is an alkylene group of 2 to 4 carbon atoms or a hydroxypropylene group; and X" is an anionic mothioine, and ii. a second monomer represented by (meth)acrylamide, in an aqueous solution of a polyvalent anionic salt, wherein the polymerization is carried out in the presence of either a high molecular weight organic multivalent cation comprising a water-soluble polymer containing at least one monomer of formula (I) and/or polydiallyl dimethyl ammonium chloride; c) draining the slurry to form a sheet; and d) drying the sheet. 2. Method according to claim 2, characterized in that the hydrophilic dispersion polymer is a copolymer of quaternary dimethylaminoethyl acrylate methyl chloride and acrylamide, and wherein the amount of quaternary dimethylaminoethyl acrylate methyl chloride present in the copolymer is in the range 3 - 20 mol%. 3. Method according to claim 1, characterized in that the dispersion polymer is added in an amount of from 0.36 - 0.91 kg of active ingredient/tonne of dry mass. 4. Method according to claim 1, characterized in that it further comprises the step of adding a coagulant before the addition of the hydrophilic dispersion polymer, where the coagulant is selected from the group consisting of Epi/DMA and polymeric diallyldimethylammonium chloride. 5. Method according to claim 4, characterized in that it further comprises adding a cationic starch to the mass in an amount of approx. 4.54 kg/tonne calculated on dry mass.