POLYMERIC STRUCTURE AND ITS USES

Abstract

A polymeric structure, which is obtained by polymerisation of (meth) acrylamide and at least one charged monomer in a polymerisation medium comprising at least a first host polymer, which first host polymer comprises polyvinyl alcohol. The polymeric structure may be used in making of paper, board, tissue or the like as a strength agent, or in dewatering of sludge.

Claims

1. A water-soluble polymeric structure, which is obtained by polymerization of (meth)acrylamide and at least one charged monomer in a polymerisation medium comprising at least a first host polymer, which first host polymer comprises polyvinyl alcohol (PVA) having a degree of hydrolysis at least 70%, and the pH during the polymerization is acidic, preferably pH is in the range of 2-6.

2. The water-soluble polymeric structure according to claim 1, wherein the polymeric structure is obtained by solution polymerisation or gel polymerisation.

3. The water-soluble polymeric structure according to claim 1, wherein polymeric structure has a standard viscosity at most 6 mPas, measured at 0.1 weight-% solids content in an aqueous NaCl solution (1 M), at 25° C., by using Brookfield DVII T viscometer with UL adapter, or a bulk viscosity at most 10 000 mPas, measured at 10 weight-% aqueous solution at pH 3 and 25° C. by using Brookfield DV1 viscometer, equipped with small sample adapter, spindle 31 with maximum rotation speed.

4. The water-soluble polymeric structure according to claim 2, wherein the polymeric structure is obtained by gel polymerisation in a form of a dry particulate product and has a standard viscosity SV of 2-6 mPas, preferably 3.5-4.8 mPas, measured at 0.1 weight-% solids content in an aqueous NaCl solution (1 M), at 25° C., by using Brookfield DVII T viscometer with UL adapter.

5. The water-soluble polymeric structure according to claim 2, wherein the polymeric structure is obtained by solution polymerisation and has a bulk viscosity in the range of 100-15 000 mPas, preferably 500-10 000 mPas, measured at 10 weigh-% aqueous solution at pH 3 and 25° C. by using Brookfield DV1 viscometer, equipped with small sample adapter, spindle 31 with maximum rotation speed.

6. The water-soluble polymeric structure according to claim 1, wherein the polymeric structure comprises at least 1 weight-% and typically 2-50 weight-% and more typically 3-30 weight-% or 5-25 weight-% of polyvinyl alcohol as the first host polymer, calculated from the total polymer content of the composition.

7. The water-soluble polymeric structure according to claim 1, wherein the polyvinyl alcohol has a degree of hydrolysis in the range of 75 — 99%, preferably 85-99%, more preferably 88-99%, and even more preferably the polyvinyl alcohol has a degree of hydrolysis 98% or 99%.

8. The water-soluble polymeric structure according to claim 1, wherein the polyvinyl alcohol has an average molecular weight at least 5000 g/mol, preferably in the range of 5000-1 000 000 g/mol.

9. The water-soluble polymeric structure according to claim 1, wherein the polymeric structure is obtained by polymerisation of (meth)acrylamide and at least 1 mol-% of charged monomer(s), preferably 4-80 mol-%, calculated from total amount of non-ionic monomers, such as (meth)acrylamide and the charged monomer(s).

10. The water-soluble polymeric structure according to claim 1, wherein the at least one charged monomer(s) comprises cationic and/or anionic monomers.

11. The water-soluble polymeric structure according to claim 1, wherein the polymeric structure is obtained by polymerisation of (meth)acrylamide and charged monomer(s), wherein the at least one charged monomer comprises a cationically charged monomer, which is selected from group consisting of 2-(dimethylamino)ethyl acrylate (ADAM), [2-(acryloyloxy)ethyl]trimethylammonium chloride (ADAM-Cl), 2-(dimethylamino)ethyl acrylate benzylchloride, 2-(dimethylamino)ethyl acrylate dimethylsulphate, 2-dimethylaminoethyl methacrylate (MADAM), [2-(methacryloyloxy)ethyl]trimethylammonium chloride (MADAM-Cl), 2-dimethylaminoethyl methacrylate dimethylsulphate, [3-(acryloylamino)propyl]trimethylammonium chloride (APTAC), [3-(methacryloylamino)propyl]trimethylammonium chloride (MAPTAC), and diallyldimethyl-ammonium chloride (DADMAC), and/or an anionically charged monomer, which is selected from unsaturated mono- or dicarboxylic acids, such as acrylic acid, methacrylic acid, maleic acid, itaconic acid, crotonic acid, isocrotonic acid; unsaturated sulfonic acids, such as 2-acrylamido-2-methylpropane sulfonic acid (AMPS), methallylsulfocnic acid; vinyl phosphoric acids, any of their mixtures, and their salts.

12. The water-soluble polymeric structure according to claim 1, wherein the polymerisation medium further comprises one or more second host polymer(s), which comprises anionic, cationic and/or amphoteric polymer(s).

13. A method to make paper, board, or tissue, wherein the water-soluble polymeric structure according to claim 1 is added as a strength agent.

14. The method according to claim 13, wherein the water-soluble polymeric structure is added in a fibre stock in amount of 100-4000 g/kg dry pulp.

15. A method to dewater a sludge comprising an aqueous phase and suspended solids, wherein the water-soluble polymeric structure according to claim 1 is added into the sludge.

16. The method according to claim 15, wherein the water-soluble polymeric structure is added into the sludge in amount of 0.5-20 kg/ton dry sludge, preferably 0.75-6 kg/ton dry sludge, preferably 1-4 kg/ton dry sludge and even more preferably 1.5-2.5 kg/ton dry sludge.

17. (canceled)

Description

EXAMPLE 1

Production of Polymeric Structure in Solution Form: Net Cationic Polymeric Structure with PVOH

[0072] An aqueous polymeric structure with polyvinyl alcohol (PVOH) was produced by a two-stage polymerization process. At first “successive second host polymer”, which is an anionic host polymer, is polymerized in the following procedure. De-ionized water 387 g was dosed into a reactor equipped with an agitator and a jacket for heating and cooling. The water is heated to 100° C. Monomer solution is made into a monomer tank by mixing acrylamide (37.5 wt-%) 525 g, sodium hypophosphite 0.5 g, acrylic acid 50 g and diethylenetriamine-penta-acetic acid, penta sodium salt (40%), 0.5 g. The monomer mixture is purged with nitrogen gas for 15 min. Initiator solution is made by dissolving ammonium persulfate 2 g in de-ionized water 34 g. Dosages of the monomer solution and the initiator solution are started at the same time. Dosing time of the monomer solution is 60 min and dosing time of the initiator solution is 105 min. Temperature is kept at 100° C. during dosing. When dosing of the initiator solution is completed, then the mixture is agitated for 30 min at 100° C. Reaction mixture is then cooled to 25° C. Characteristics of the “successive second host polymer” are presented in the Table 1.

TABLE-US-00001 TABLE 1 Characteristics of the successive second host polymer Characteristic Determined values Dry content, % 25.9 Viscosity, mPas 1010 pH 4.2 MWr, g/mol 121 000 MWn, g/mol  14 600 MWp, g/mol 104 000

[0073] The second polymerization stage is to polymerize the second monomer set in an aqueous solution of the two host polymers: the first host polymer, which is PVOH product Mowiol 28-99 (98%) and the above described “successive second host polymer”, which is anionic. PVOH product Mowiol 28-99 (98%) 37 g is dissolved in a reactor, described in production of the host polymer, in 550 g de-ionized water by mixing at 90° C. temperature for 30 min. Successive second host polymer 106 g and citric acid 1 g are dosed into the reactor. pH is adjusted to 3.0 by adding sulfuric acid 50%, 2.1 g. The mixture is purged with nitrogen for 5 min and temperature is adjusted 80° C. by heating. The second monomer mixture is made in a monomer tank by mixing acrylamide (37.5 wt-%) 170 g, acryloyloxyethyltrimethylammonium chloride (80 wt-%) 24 g and diethylenetriamine-penta-acetic acid, penta sodium salt (40%), 0.38 g. pH of the second monomer mixture is adjusted to 3.0 by adding sulfuric acid 50%, 0.35 g. The monomer mixture is purged with nitrogen gas for 15 min. Initiator solution is made by dissolving ammonium persulfate 0.34 g in de-ionized water 34 g. Dosages of the monomer solution and the initiator solution are started at the same time. Dosing time of the monomer solution is 60 min and dosing time of the initiator solution is 90 min. Temperature is kept at 80° C. during dosing by heating and/or cooling. When dosing of the initiator solution is completed, then the mixture is agitated for 30 min at 80° C. Then an aqueous solution of ammonium persulfate 0.5 g and de-ionized water 20 g is dosed into the mixture at 20 min time. The mixture is reacted at 80° C. for 30 min. Reaction mixture is diluted with de-ionized water 56 g and the reaction mixture is then cooled to 25° C. Characteristics of the obtained product, “Polymeric structure”, which is a net cationic polymeric structure with PVOH, are presented in the Table 2.

TABLE-US-00002 TABLE 2 Characteristics of Polymeric structure Dry solids, % 15.0 Viscosity, mPas 9010 pH 3.0 Charge density at pH 7, meq/g 0.2

EXAMPLE 2

Preparation of Water-Soluble Cationic Polymeric Structures “20PVOH” and “35PVOH” in Solution Form

[0074] A cationic polymeric structure in solution form, which comprises about 17 weight-% PVOH of total polymer content is prepared by polymerizing acrylamide and cationic monomer in polyvinyl alcohol, at pH of about 3.5, in the following procedure: a reactant solution was prepared from 743.1 g PVOH solution, which was achieved by dissolving 19.8 g of polyvinyl alcohol having degree of hydrolysis of 80% and molar mass of about 10 kDa (from Sigma-Aldrich CAS # 9002-89-5) into 723.3 g of de-ionized water at 90° C. for 30 min, and 154.1 g of acrylamide (50 wt-%), 0,942 g of sulfuric acid (93%), 3.1 g of sodium acetate dissolved in 34.7g of de-ionized water, 27.54 g of acryloyloxyethyltrimethylammonium chloride (ADAM-Cl, 80 wt-%), and 0.256 g of penta-Na salt of diethylenetriamine-penta-acetic acid (40%) are dissolved after cooling of PVOH solution. The mixture was purged with nitrogen gas and heated to about 80° C. A system of ammonium persulfate (total 0.625 g, dissolved in de-ionized water) and Na-metabisulfite (1 g, dissolved in de-ionized water) was used for initiating and controlling polymerization. The mixture was reacted at about 80° C. until completion, and then cooled to 25° C. This polymeric structure has bulk viscosity 16300 mPas and dry content 12.54%, The product is labeled as 20PVOH. Another cationic polymeric structure, labeled as 35PVOH, was prepared in same way but using 34.65 g of polyvinyl alcohol, thus containing about 26 w% of PVOH from total polymer content. 35PVOH had bulk viscosity at 13.7% solids content of 35500 mPas. A cationic reference polymer, labeled as PAM, was prepared in same way without using any polyvinyl alcohol, and had bulk viscosity at 11.8% solids content of 8230 mPas, corresponding approx. to Mw of 0.8 MDa. All these polymers contained cationic monomers of about 10 mol-% in the cationic second (last polymerized) polymer network.

EXAMPLE 3

Preparation of Gel Polymerized Polymeric Structures “3SPHOL50” and “DPSrdx” in Dry Form

[0075] A cationic polymeric structure “3SPHOL50” in powder form, which comprises about 6 weight-% PVOH of total polymer content is prepared by polymerizing acrylamide and cationic monomer in polyvinyl alcohol, at pH of about 4, in the following procedure: a reactant solution of monomers and polyvinyl alcohol was prepared from 9 g of polyvinyl alcohol having degree of hydrolysis of 80% and molar mass of about 10 kDa (from Sigma-Aldrich CAS # 9002-89-5) in deionized water, 250.6 g of 50% acrylamide solution, 32.9 g of 80% ADAM-Cl, 2.96 g of Na-gluconate, 0.01 g of 40% DTPA Na-salt, 1.88 g of adipic acid, 7.21 g of citric acid, and 4.44 g of dipropylene glycol. The mixture was stirred until solid substances were dissolved, and pH adjusted to around 4 with citric acid. The initiator was 5 ml of 6% 2-hydroxy-2-methylpropiophenone in polyethylene glycol-water (1:1 by weight) solution. After the reactant solution was prepared according to the above description, it was purged with nitrogen flow in order to remove oxygen. The initiator, 2-hydroxy-2-methylpropiophenone in polyethylene glycol-water (1:1 by weight), was added to the reactant solution, and the solution was placed on a tray to form a layer of about 1 cm under UV-light, mainly on the range 350-400 nm (AS1/AS2/AS3=10/5/25). Intensity of the light was increased as the polymerization proceeded to complete the polymerization (from about 550 μW/cm.sup.2 to about 2000 μW/cm.sup.2). The obtained gel was run through an extruder and dried to a moisture content less than 10% at temperature of 60° C. The dried polymer was ground and sieved to particle size 0.5-1.0 mm. The product is labeled as “3SPHOL50”. It had standard viscosity of about 3.4 mPas, corresponding to molecular weight of about 3.5 MDa, and contained cationic monomers of about 7 mol-% in the cationic second (last polymerized) polymer network.

[0076] Another cationic polymeric structure “DPSrdx” with PVOH of higher molar mass in powder form is prepared by polymerizing acrylamide and cationic monomer in polyvinyl alcohol, at pH of about 3-4, in the following procedure: a reactant solution of monomers and polyvinylalcohol was prepared from 17.93 g of polyvinyl alcohol having degree of hydrolysis of about 99.4% and molar mass of about 100 000 g/mol (from Sigma-Aldrich) in deionized water, 405.74 g of 50% acrylamide solution, 77.37 g of 80% ADAM-Cl, 3.87 g of 0.1% Na-hypophosphite, 0.64 ml g of 5% DTPA Na-salt, and 1.66 g of adipic acid. The mixture was stirred until solid substances were dissolved, and pH adjusted to abound 3-4. The initiator system comprised 5 ml of aqueous V50 solution (0.77 g/7 ml) as thermal initiator, and a redox pair of 5 ml of 0.098% ammonium persulfate and 5 ml of 0.053% ferrous ammonium sulphate. After the reactant solution was prepared according to the above description, thermal initiator was added and the reactant solution was degassed at low temperature by nitrogen gas. The redox pair was then injected to the reactant solution to start the polymerization. The obtained gel was run through an extruder and dried to a moisture content less than 10% at temperature of 60° C. The dried polymer was ground and sieved to particle size 0.5-1.0 mm.

[0077] This polymeric structure containing about 6 weight-% of PVOH from total polymer content was labeled as “DPSrdx”. It had standard viscosity of about 3.4 mPas and contained cationic monomers of about 10 mol-% in the cationic second (last polymerized) polymer network.

Application Experiments

[0078] Application experiments 1 and 3 were performed for providing information about the behaviour and effect of the polymeric structures according to the present invention as dry strength compositions. Tables 3 and 4 give methods and standards used for pulp characterisation and sheet testing in the application experiments.

TABLE-US-00003 TABLE 3 Pulp characterization methods Property Device/Standard pH Knick Portamess 911 Turbidity (NTU) WTW Turb 555IR Conductivity (mS/cm) Knick Portamess 911 Charge (μekv/l) Mütek PCD 03 Zeta potential (mV) Mütek SZP-06 Consistency (g/l) ISO 4119

TABLE-US-00004 TABLE 4 Sheet testing devices and standard methods used for produced paper sheets. Measurement Device Standard Basis weight Mettler Toledo ISO 536 Ash content, 525° C. — ISO 1762 Compressive strength SCT Lorentzen & Wettre ISO 9895 Taber, bending stiffness PTA Tappi T 569 Z-directional tensile (ZDT) Lorentzen & Wettre ISO 15754 Tensile strength Lorentzen & Wettre ISO 1924-3

Application Example 1

[0079] This Example simulates preparation of corrugating paper such as testliner or fluting. Central European testliner board was used as raw-material. This testliner contains about 17% ash and 5% surface size starch. Dilution water was made from tap water by adjusting conductivity to 4 mS/cm with salt mixture of calcium acetate 70%, sodium sulfate 20% and sodium bicarbonate 10%. Testliner board was cut to 2×2 cm squares. 2.7 l of dilution water was heated to 70° C. The pieces of testliner were wetted for 10 minutes in dilution water at 2% concentration before disintegration. Slurry was disintegrated in Britt jar disintegrator with 30 000 rotations. Pulp was diluted to 0.6% by adding dilution water.

[0080] In hand sheet preparation the used chemicals were added to the test fibre stock in a dynamic drainage jar (DDJ) under mixing, 1000 rpm. Strength chemicals were diluted before dosing to 0.1 weight-% concentration. The polymeric structure according to Example 1 is used as a strength chemical. Reference “Ref pol.” is similar polymer than the polymeric structure of Example 1, but without PVA. The addition amounts of the used strength chemicals are given in Table 5. The strength chemicals are added to the test fibre stock 30 s prior to sheet making. CPAM retention polymer was dosed at dosage of 0.2 kg/t 10 s prior to sheet making. The CPAM dosage was adjusted to get 15% ash content of the handsheet. All chemical amounts are given as kg dry active chemical per ton dry fibre stock.

[0081] Handsheets having basis weight of 110 g/m.sup.2 were formed by using Rapid Köthen sheet former with 4 mS/cm conductivity in backwater, adjusted with salt mixture of calcium acetate 70%, sodium sulfate 20% and sodium bicarbonate 10%, in accordance with ISO 5269-2:2012. The handsheets were dried in vacuum dryers for 6 minutes at 92° C., at 1000 mbar. Before testing the handsheets were pre-conditioned for 24 h at 23° C. in 50% relative humidity, according to ISO 187.

TABLE-US-00005 TABLE 5 Hand sheet tests of application example 1: chemical additions and measured results. Ref pol. Example 1 SCT index Test kg/t dry kg/t dry Nm/g 1 0 19.6 2 3 20.3 3 3 21.0

[0082] The results, presented in Table 5, show that the polymeric structure according to the present invention increase SCT index.

Application Example 2

[0083] Example 1 simulates preparation of corrugating paper such as testliner or fluting. Central European testliner board was used as raw-material. This testliner contains about 17% ash and 5% surface size starch. Dilution water was made from tap water by adjusting Ca.sup.2+ concentration to 520 mg/l by CaCl.sub.2 and by adjusting conductivity to 4 mS/cm by NaCl. Testliner board was cut to 2×2 cm squares. 2.7 l of dilution water was heated to 70° C. The pieces of testliner were wetted for 10 minutes in dilution water at 2% concentration before disintegration. Slurry was disintegrated in Britt jar disintegrator with 30 000 rotations. Pulp was diluted to 0.6% by adding dilution water.

[0084] In hand sheet preparation the used chemicals were added to the test fibre stock in a dynamic drainage jar under mixing, 1000 rpm. Strength chemicals were diluted before dosing to 0.1 weight-% concentration. The used strength chemicals and their addition amounts are given in Table 6. The polymeric structures according to the present invention “20PVOH”, “35PVOH” and “3SPHOL50” are described in Examples 2 and 3. The reference chemical “PAM” was copolymer of ADAM-Cl and acrylamide (cationic charge 10 mol-%, MW=800 000 g/mol). The strength chemicals are added to the test fibre stock 30 s prior to sheet making. In addition to the strength chemicals the retention chemical, CPAM, was dosed at dosage of 0.2 kg/t 10 s prior to sheet making. All chemical amounts are given as kg dry active chemical per ton dry fibre stock.

[0085] Handsheets having basis weight of 80 g/m.sup.2 were formed by using Rapid Köthen sheet former with 4 mS/cm conductivity in backwater, adjusted with CaCl.sub.2 (520mg/l Ca.sup.2+) and NaCl, in accordance with ISO 5269-2:2012. The handsheets were dried in vacuum dryers for 6 minutes at 92° C., at 1000 mbar. Before testing the handsheets were pre-conditioned for 24 h at 23° C. in 50% relative humidity, according to ISO 187.

TABLE-US-00006 TABLE 6 Hand sheet tests of application example 2: chemical additions and measured results. SCT Burst PAM 20PVOH 35PVOH 3SPHOL50 index index Test kg/t dry kg/t dry kg/t dry kg/t dry Nm/g kPam.sup.2/g 1 0 21.8 1.6 2 1 22.3 1.8 3 1 23.1 1.8 4 3 23.6 1.8 5 1 22.7 1.8 6 3 23.6 1.9 7 1 22.8 1.8

[0086] The results, presented in Table 6, show that the polymeric structures according to the present invention increase SCT index and burst index.

Application Example 3

[0087] The effect of addition of the polymeric structure “DPSrdx” of cationic polyacrylamide (CPAM) and polyvinylalcohol (PVOH) in the multi-component strength system on the z-directional tensile strength (ZDT) was studied with folding box board furnish containing CTMP pulp (80%) and coated broke (20%). The polymeric structure “DPSrdx” was prepared with gel polymerization as presented in Example 3. 150 g/m.sup.2 sheets were formed with dynamic sheet former (DSF) as follows: Test fibre stock was diluted to 0.6% consistency with deionized water, and pH was adjusted to 7 and conductivity to 1.5 mS/cm. The obtained pulp mixture was added to DSF. Chemical additions were made to mixing tank of DSF. Water was drained out after all the pulp was sprayed. Drum was operated with 1250 rpm, mixer for pulp 450 rpm, pulp pump 950 rpm/min, number of sweeps 100 and scoop time was 60 s. Sheet was removed from drum between wire and 1 blotting paper on the other side of the sheet. Wetted blotting paper and wire were removed. Sheets were wet pressed at Techpap nip press with 5 bar pressure with 2 passes having new blotting paper each side of the sheet before each pass. Dry content was determined from the pressed sheet by weighting part of the sheet and drying the part in oven for 4 hours at 110° C. Sheets were dried in restrained condition in drum dryer. Drum temperature was adjusted to 92° C. and passing time to 1 min. Four passes were made. First two passes with between blotting papers and 2 passes without. Before testing in the laboratory sheets were pre-conditioned for 24 h at 23° C. in 50% relative humidity, according to the standard ISO 187.

[0088] Strength additives used in the experiments were cationic starch (8kg/t) and a mixture of cationic waxy starch and the polymeric structure “DPSrdx” (addition levels of 1.5 and 2.5 kg/t) and anionic polymer strength additive (2,4 kg/t). All chemical amounts were kg dry chemical per ton dry fibre stock. The polymeric structure “DPSrdx” was a dry polymer and in said polymeric structure the CPAM had a substitution degree of 10 mol-% and proportion of PVOH was 6 wt-%. All points included retention aids (CPAM 200 g/t and APAM 200 g/t).

[0089] Results, presented in Table 7, show that the polymeric structure “DPSrdx” according to the present invention increases substantially Z-directional strength without decreasing bulk in a multicomponent strength system.

TABLE-US-00007 TABLE 7 Effect different strength systems on board properties ZDT Tensile index Bulk [kPa] [Nm/g] [cm.sup.3/g] No strength additives 102 10.1 2.78 Starch 8 kg/t + 2.4 kg/t 177 15.0 2.64 anionic strength additive Starch 8 kg/t + 1.5 kg/t 219 14.6 2.68 mixture of DPSrdx and waxy starch + 2.4 kg/t anionic strength additive Starch 8 kg/t + 2.5 kg/t 233 15.2 2.70 mixture of DPSrdx and waxy starch + 2.4 kg/t anionic strength additive

Application Example 4

[0090] Application example 4 was performed for providing information about the behaviour and effect of the polymeric structures according to the present invention in sludge dewatering.

[0091] Polymeric structure of cationic polyacrylamide and polyvinyl alcohol (PVOH) comprises PVOH as a first host polymer and the second polymer, which is polymerized in a polymerization medium comprising the first host polymer, is a copolymer of acrylamide and 30 mol-% [2-(acryloyloxy)ethyl]trimethyl ammonium chloride (ADAM-Cl). The amounts of PVOH are 6 and 9 weight-% in polymerization medium. PVOH used is varied in molar masses and degree of hydrolysis. The properties of PVOH used in this study are shown in Table 8. The final dry polymer composition comprises both polymers, cationic polyacrylamide and PVOH.

TABLE-US-00008 TABLE 8 Polyvinyl alcohol properties. Polyvinyl alcohol Molar Degree of Degree of names mass hydrolysis polymerization PVOH-80  9 500 80 n/a PVOH 15-99 100 000 99.4 n/a PVOH 56-98 195 000 98 2400

[0092] All polyvinyl alcohol products are dry. For making the aqueous solution of PVOH, the polymers are dissolved in water at high temperature (about 95° C.) for the required time to make a clear and transparent aqueous solution (about 1 hour) under vigorous stirring. A round flask is used equipped with a mechanical stirrer and a refrigerant. The flask is immersed in an oil bath. The PVOH aqueous solution is cold down and used to make the cationic polyacrylamide reaction in it. Reaction characteristics and polymer properties of polymers made with PVOH are shown in Table 9. The polymerisations of the polymeric structures were prepared as essentially as the polymeric structure “DPSrdx” presented in Example 3.

[0093] The commercial dry cationic polyacrylamide is used as a reference, which is commonly formed by a polymerization reaction using acrylamide and 30 mol-% of [2-(acryloyloxy)ethyl]trimethyl ammonium chloride (ADAM-Cl).

TABLE-US-00009 TABLE 9 Standard viscosity SV, Insolubles, Reaction PVOH mPas wt-% time Max T Polymers wt-% (QCTM 20) (QCTM 37) h:min ° C. Reference 0 4.09 <0.01 0:32 87.2 cPAM-PVOH-6 6 3.64 <0.01 0:34 87.9 (PVA-80) cPAM-PVOH-9 9 3.7 <0.01 0:52 97.32 (PVA-80) cPAM-PVOH-6 6 3.56 0.2 0:18 89.8 (15-99) cPAM-PVOH-6 6 4.11 <0.01 0:28 94.21 (56-98)

[0094] Sludge conditioning and mechanical dewatering by Minipress were studied as follows. A beaker is provided with 220 g sludge. The sludge is subjected to rapid mixing of about 300 rpm. A calculated amount of ferric chloride is added, and followed by mixing for 2 min. Then the conditioned sludge is flocculated by addition of 2 kg/t polymer. The sludge is once again subjected to rapid mixing for about 2-5 seconds. Once flocs are formed, the mixing is stopped. All the conditioned sludge in the beaker is transferred to a Minipress for dewatering. After the Minipress testing is completed, the obtained the sludge cake is retrieved and measurement of the cake dryness (i.e. solids contents) is made by using heating in an oven over night at 105° C.

[0095] The sludge is mainly undigested sludge from a wastewater treatment plant mainly treating municipal wastewater. The incoming sludge has pH of 6.2-7.0 and a solids content of about 3.17-5.0 weight-%.

[0096] Table 10 shows dryness after the sludge is conditioned by ferric chloride and polymeric structure comprising PVOH-80. Table 11 shows dryness after the sludge is conditioned by ferric chloride and polymeric structure comprising PVOH 15-99 or PVOH 56-98.

[0097] In the results can be observed an increase in sludge dryness with polymeric structure according to the invention compared to the reference samples.

TABLE-US-00010 TABLE 10 Sludge dryness after dewatering Test (%) 1 Reference 31.5% cPAM-PVOH-6(PVOH-80) 33.6% (   2.1%) 2 Reference 27.0% cPAM-PVOH-6(PVOH-80) 28.2% (   1.2%) 3 Reference 25.6% cPAM-PVOH-6(PVOH-80) 26.0% (   0.4%) 4 Reference 24.1% cPAM-PVOH-6(PVOH-80) 24.3% (   0.2%) cPAM-PVOH-9-(PVOH-80) 25.6% (   1.5%) cPAM-PVOH-12(PVOH-80) 25.7% (   1.6%)

TABLE-US-00011 TABLE 11 Sludge dryness after dewatering Test (%) 1 Reference 31.5% cPAM-PVOH-6(15-99) 34.9% (   3.4%) 2 Reference 27.0% cPAM-PVOH-6(15-99) 28.2% (   2.1%) 4 Reference 24.1% cPAM-PVOH-6(56-98) 25.1% (   1.0%)