System and method for manufacture of paper, board or the like

Abstract

Drainage and press dewatering system for manufacture of paper, board or the like, comprising (a) amphoteric polyacrylamide, which is a copolymer obtained by polymerizing (meth)acrylamide and 1-80 mol-% of cationic monomers and/or 0.1-70 mol-% of anionic monomers, the polyacrylamide having an intrinsic viscosity in the range of 6-38 dl/g, (b) inorganic microparticles of siliceous material, such as colloidal silica or bentonite, and (c) a high-charged cationic coagulant having a charge density over 5 meq/g and preferably over 6 meq/g determined at pH 6 and selected from aluminium based coagulants, organic polymers and mixtures thereof.

Claims

1. A drainage and a press dewatering system for manufacture of paper, board or the like, comprising: (a) an amphoteric polyacrylamide, which is a copolymer obtained by polymerizing (meth)acrylamide and 1-25 mol-% of cationic monomers and 0.1-24 mol-% of anionic monomers, the polyacrylamide having an intrinsic viscosity in a range of 6-38 dl/g determined in 1 M NaCl at 25 C., (b) inorganic microparticles of siliceous material, selected from colloidal silica or bentonite, and (c) a high-charged cationic coagulant having a charge density over 5 meq/g determined at pH 6 and selected from aluminum based coagulants, organic polymers and mixtures thereof.

2. The system according to claim 1, wherein the amphoteric polyacrylamide has the intrinsic viscosity in a range of 6-20 dl/g, determined in 1 M NaCl at 25 C.

3. The system according to claim 1, wherein the amphoteric polyacrylamide has a cationic net charge, determined by Mtek PCD at pH 2.7.

4. The system according to claim 1, wherein a cationic charge density of the amphoteric polyacrylamide is in a range of 0.2-4 meq/g, determined by Mtek PCD at pH 2.7.

5. The system according to claim 1, wherein the amphoteric polyacrylamide is the copolymer obtained by polymerizing (meth)acrylamide, 4-17 mol-% of cationic monomers and 0.1-15 mol-% of anionic monomers.

6. The system according to claim 1, wherein the amphoteric polyacrylamide is obtained by gel polymerization, where content of non-aqueous solvent during the polymerization is less than 10 weight-%.

7. The system according to claim 6, wherein the polymer content of the amphoteric polyacrylamide is at least 60 weight-%.

8. The system according to claim 1, wherein the amphoteric polyacrylamide comprises <0.01 mol-%, preferably of branching agent or cross-linking agent.

9. The system according to claim 1, wherein the high-charged cationic coagulant is: aluminum based coagulant, which is selected from a group comprising aluminum sulphate, aluminum chloride, polyaluminum chloride (PAC), polyaluminum silicate, polyaluminum sulphate (PAS), polyaluminum silica sulphate, sodium aluminate, alum and any of their mixture, and/or organic polymer, which is selected from polyethylenimine, polyamine, polyDADMAC, polyAPTAC, polyMAPTAC, poly-ADAM-CI and any of their mixture.

10. The system according to claim 1, wherein the system further comprises cationic starch and/or cationic polyacrylamide.

11. The system according to claim 1 used in manufacturing of kraft paper, liner board, test liner, fluting, sack paper, white lined chipboard, core board or folding boxboard.

12. A method for manufacture of paper, board or the like, comprising: obtaining a fibre stock comprising fibres originating from recycled fibre material, unbleached kraft pulping and/or unbleached semichemical pulping, whereby the fibre stock has a conductivity of at least 1 mS/cm; adding to the fibre stock an aqueous solution of a water-soluble amphoteric polyacrylamide, which is a copolymer obtained by polymerizing (meth)acrylamide and 1-25 mol-% of cationic monomers and 0.1-24 mol-% of anionic monomers, the polyacrylamide having an intrinsic viscosity in a range of 6-38 dl/g determined in 1 M NaCl at 25 C.; adding to the fibre stock inorganic microparticles of siliceous material, selected from colloidal silica or bentonite; adding to the fibre stock or to an aqueous flow to be combined with the fibre stock a high-charged cationic coagulant having a charge density over 5 meq/g determined at pH 6 and selected from aluminum based coagulants, organic polymers and mixtures thereof; and forming the fibre stock into a fibrous web.

13. The method according to claim 12, wherein the amphoteric polyacrylamide is added in an amount of 100-1000 g/t dry fibre stock.

14. The method according to claim 12, wherein the amphoteric polyacrylamide is added to thin stock having consistency of 5-20 g/l for improving drainage or thick stock having consistency of >20 g/l for improving paper strength properties.

15. The method according to claim 12, wherein the amphoteric polyacrylamide is added after last shear stage before a headbox of a paper or board machine.

16. The method according to claim 12, wherein the inorganic microparticles of colloidal silica are added in the amount of 100-600 g/t dry fibre stock, or the inorganic microparticles of bentonite are added in an amount of 1-4 kg/t dry fibre stock.

17. The method according to claim 12, wherein the inorganic microparticles are added to thin stock having consistency of 5-20 g/l.

18. The method according to claim 12, wherein the amphoteric polyacrylamide, inorganic microparticles, and high-charged cationic coagulant are added separately from each other.

19. The method according to claim 18, wherein the amphoteric polyacrylamide is added after the addition of the microparticles and the high-charged cationic coagulant.

20. The method according to claim 12, wherein the coagulant is aluminum based coagulant, which is added in an amount of 100-700 g/t dry fibre stock as Al.sup.3, or the coagulant is organic polymer which is added in an amount of 50-1000 g/ton dry pulp.

21. The method according to claim 12, wherein the fibre stock comprises at least 20 weight-% of fibres originating from recycled fibre material.

22. The method according to claim 12, wherein the fibre stock has a conductivity of at least 2 mS/cm.

23. The method according to claim 12, wherein the fibre stock has a starch content of at least 1 weight-%, based on dry total solids.

24. The method according to claim 12, wherein the fibre stock has an ash content of at least 10 weight-%, based on dry total solids.

Description

APPLICATION EXAMPLES

(1) Methods

(2) Pulp and sheet testing devices and standards are given in Table 2. The indexed SCT strength value is the strength divided by basis weight of the paper/board.

(3) TABLE-US-00002 TABLE 2 Pulp and sheet testing devices and standards. Property/Measurement Device/Standard pH Knick Portamess 911 Turbidity (NTU) WTW Turb 555IR Conductivity (mS/cm) Knick Portamess 911 Charge (ekv/l) Mtek PCD 03 Zeta potential (mV) Mtek SZP-06 Consistency (g/l) ISO 4119 Basis weight Mettler Toledo/ISO 536 Ash content, 525 C. ISO 1762 SCT ISO 9895

Application Example 1

(4) Pulp Preparation

(5) European OCC and kraft (unbleached) was used as a raw material. The OCC contains about 16% ash. The original starch of OCC pulp was consumed from the sample during the storage time of 1 week in +5 C. temperature. Pulp and water properties are presented at Table 3. OCC and kraft were mixed in 1:1 ratio based on dry matter. Dilution water was prepared by mixing white water and clear filtrate in 1:1 ratio. Pulp mixture was diluted with the prepared dilution water to 0.7% consistency. Starch content of test pulp was about 2.5%, based on dry total solids.

(6) TABLE-US-00003 TABLE 3 Properties of pulps and waters. White Clear Measurement OCC Kraft water Filtrate pH 6.6 6.9 7.5 7.5 Turbidity, NTU 615 33.1 24.9 31.2 Conductivity, mS/cm 6.8 1.7 3.6 2.8 Charge, ekv/l 738 214 73 83 Zeta potential, mV 4.4 17.0 Consistency, g/l 50.2 30.6

(7) DDA Test

(8) DDA (dynamic drainage analyzer) from Akribi Kemi Konsulter, Sweden was used to measure retention and drainage. 500 ml of pulp was used for each test point. Alum and pulp were added to 500 ml breaker with 100 rpm magnetic stirring for 10 min before drainage. Pulp was poured to DDA 30 s before drainage and DDA stirrer was adjusted to 1000 rpm. Test chemical addition times are indicated as negative time before the drainage starts in Table 4. Stirring was stopped 2 s before drainage. Vacuum was 300 mbar for 30 s after drainage started, and wire opening was 0.25 mm.

(9) Drainage time was recorded and filtrate turbidity was measured immediately. Wet sheet was weighted and wet pressing of the sheets was completed individually immediately after drainage tests by using Lorenz & Wettre (wet press for 1 min at 4 bar pressure, 2 plotter papers both sides of the DDA cake). Pressed sheet was weighted and then sheet from the wire was dried in Lorenz & Wettre hot plate dryer to abs dry for retention calculation. Sheets were weighted after drying. SCT was measured from the DDA sheets.

(10) Determination of Soluble Starch from DDA Filtrate

(11) Tests use following procedure developed in this project for recycled fiber starch determination:

(12) 25 ml of filtrate was added to 10 ml of 10%-w HCl. Mixture was stirred for 10 min in 50 ml breaker with magnetic stirrer and then mixture was filtrated by gravitation in a funnel with black ribbon filter paper. 1 ml of filtrated mixture was added to 0.5 ml iodine reagent, which consisted 7.5 g KM +5 g/l I2. Absorbance value was measured at 610 nm by Hach Lange DR 900 spectrophotometer 2 min after iodine-solution was added. Zeroing of the spectrophotometer was done with the sample before iodine addition.

(13) C*film 07311 non-ionic degraded starch was used as reference to make calibration equation for starch content. Test pulp starch content was determined by same method than DDA filtrate starch content. Blanc test for HCl-iodine solution absorbance was made to subtract baseline absorbance from the result. Starch retention was calculated as: (pulp starchfiltrate starch)/pulp starch*100%.

(14) Chemicals

(15) Alum: Aluminium sulphate, dry.

(16) Wet end starch: Meribond 155 by Tate&Lyle, cooked at 1% concentration in 97 C. for 30 min.

(17) Surface size starch: C*film 07312 by Cargill, cooked at 1% concentration in 97 C. for 30 min.

(18) EXP 1, amphoteric PAM described in earlier example, dissolved to 0.5% and further diluted to 0.05%.

(19) CPAM1: FennoPol K6340T, high molecular weight dry cationic polyacrylamide retention polymer by Kemira.

(20) Bentonite: Altonite SF by Kemira, retention bentonite.

(21) Test Results

(22) Test program is presented at Table 4. Based on the results (Table 5) compared to test 3, which is typical drainage system for linerboard, the system according to the invention in tests 6-7 achieved simultaneously fast drainage time, low filtrate turbidity, high dryness after forming, high solids content after pressing, retention, SCT strength and ash retention measured by sheet ash. The effect of amphoteric polymer in test 9 was also clear compared to test 8 without amphoteric polymer. Test 11 shows drop in the SCT strength, when high dosage of conventional retention polymer is used.

(23) TABLE-US-00004 TABLE 4 Test points. Time, s 40 40 600 Wet end Surface size 30 20 10 Alum, starch, starch, EXP 1, CPAM 1, bentonite, Test kg/t kg/t kg/t kg/t kg/t kg/t 1 3.9 40 2 3.9 40 3.5 3 3.9 40 0.2 3.5 4 3.9 40 0.4 3.5 5 8 3.9 40 0.2 0.1 3.5 6 8 3.9 40 0.4 0.1 3.5 7 8 3.9 40 0.6 0.1 3.5 8 8 3.9 40 3.5 9 8 3.9 40 0.6 3.5 10 4 3.9 40 0.4 0.1 3.5 11 3.9 40 0.6 3.5

(24) TABLE-US-00005 TABLE 5 Test results. Drainage Filtrate Dryness after Reten- Solids after wet SCT index, Sheet Test time, s turbidity, NTU forming, % tion, % pressing, % Nm/g ash, % 1 5.2 393 16.7 86.9 43.4 23.8 6.4 2 5.5 272 16.7 89.7 42.8 23.2 7.1 3 4.5 212 16.9 92.3 43.9 24.0 7.3 4 3.9 143 17.4 92.8 44.5 22.1 7.6 5 4.8 172 17.4 92.1 44.4 23.5 7.6 6 4.2 137 17.4 93.2 44.0 25.4 7.7 7 3.6 115 17.6 94.8 44.8 24.8 7.7 8 6.1 322 17.0 92.7 43.9 24.3 6.8 9 4.3 133 17.6 95.2 45.1 25.3 7.6 10 4.0 124 17.7 95.4 43.9 25.5 7.6 11 93.7 21.4 7.6

Application Example 2

(25) Pulp Preparation

(26) Central European testliner board was used as a raw-material. The testliner contains about 17% ash and 5% surface size starch, which was enzymatically degraded native corn 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 85 C. The pieces of testliner were wetted for 5 minutes in dilution water at 2% concentration before disintegration. Slurry was disintegrated in Britt jar disintegrator with 30 000 rotations. Pulp was diluted to 0.5% by adding dilution water.

(27) DDA Test

(28) DDA (dynamic drainage analyzer) from Akribi Kemi Konsulter, Sweden was used to measure retention and drainage. 500 ml of pulp was used for each test point. Polyaluminium chloride (PAC) and pulp were added to 500 ml breaker with 100 rpm magnetic stirring for 10 min before drainage. Other test chemical addition times are indicated as negative time before the drainage starts in Table 6. Pulp was poured to DDA 30 s before drainage and DDA stirrer was adjusted to 1000 rpm. Stirring was stopped 2 s before drainage. Vacuum was 300 mbar for 30 s after drainage started, and wire opening was 0.25 mm.

(29) Drainage time was recorded and filtrate turbidity was measured immediately. Wet sheet was weighted. Wet pressing of the sheets was completed individually immediately after drainage tests in Lorenz & Wettre wet press for 1 min at 4 bar pressure, 2 plotter papers both sides of the DDA cake. Pressed sheet was weighted. Sheet from the wire was dried in Lorenz & Wettre hot plate dryer to abs dry for retention calculation, and sheets were weighted after drying.

(30) Determination of Soluble Starch from DDA Filtrate

(31) The determination of soluble starch was carried out as previous application example.

(32) Chemicals

(33) PAC 3: Polyaluminium chloride, 5.2% Al and 70% basicity.

(34) Silica: structured colloidal silica, S-value: 34, surface area 750, pH: 10.6, water solution diluted to 0.5%.

(35) EXP 1, amphoteric PAM described in earlier example, dissolved to 0.5% and further diluted to 0.05%.

(36) EXP 2, amphoteric PAM described in earlier example, dissolved to 0.5% and further diluted to 0.05%.

(37) EXP 3, amphoteric PAM described in earlier example, dissolved to 0.5% and further diluted to 0.05%.

(38) APAM: FennoPol A8050 R, high molecular weight dry anionic polyacrylamide retention polymer by Kemira.

(39) Test Results

(40) Test plan and results are presented at Tables 6-7. Conventional drainage system with APAM (test 4-5) uses dosages of 0.1-0.2 kg/t, because higher dosage is not contributing to retention or drainage. The systems according to the invention (tests 6-11) are improving drainage time, filtrate turbidity, filtrate starch reduction and retention. EXP 1, net cationic amphoteric polymer is performing better than neutral or anionic amphoteric polymer.

(41) TABLE-US-00006 TABLE 6 Test plan, dosinq time and dosage amounts. Time, s 600 15 10 10 10 10 PAC 3. kg/t as Silica, APAM, EXP3, EXP2, EXP1, Test product kg/t kg/t kg/t kg/t kg/t 1 2 10 3 10 0.45 4 10 0.45 0.1 5 10 0.45 0.2 6 10 0.45 0.4 7 10 0.45 0.8 8 10 0.45 0.4 9 10 0.45 0.8 10 10 0.45 0.4 11 10 0.45 0.8

(42) TABLE-US-00007 TABLE 7 Test results. Filtrate Filtrate Filtrate Drainage turbidity, starch starch Retention, Test time, s NTU absorbancy reduction, % % 1 11.2 707 0.649 0 90.6 2 7.27 557 0.589 9 90.4 3 15.15 538 0.564 13 91.0 4 10.02 176 0.551 15 92.5 5 8.15 102 0.527 19 92.3 6 7.85 103 0.541 17 92.7 7 5.85 96 0.528 19 93.6 8 9.15 86 0.517 20 92.8 9 8.41 95 0.532 18 93.9 10 7.34 102 0.508 22 94.0 11 6.28 75 0.509 22 92.4

Application Example 3

(43) Pulp preparation, DDA test and starch determination as in previous example, but testliner was from Eastern Europe, having about 16% ash and about 5 starch.

(44) Chemicals

(45) PAC 1: Polyaluminium chloride, 7.5% Al and 40% basicity.

(46) PAC 3: Polyaluminium chloride, 5.2% Al and 70% basicity.

(47) Silica: structured colloidal silica, S-value: 34, surface area 750, pH: 10.6, water solution diluted to 0.5%.

(48) EXP 2, amphoteric PAM described in earlier example, dissolved to 0.5% and further diluted to 0.05%.

(49) Test Results

(50) Tests are comparing PAC coagulants (Table 8-9) and dosage levels of components. Both PAC1 and PAC3 performed well. Best result was obtained with test 8, which has highest dosage of components. Test 2 indicated PAC dosage (0.375 kg/t as Al) that was too low to achieve best performance. It is beneficial to keep certain dosage ratio range for system components with different charges. Tests 5-6 are on same level than tests 3-4. This indicates that added Al-content is critical, and basicity range of 40-70% is good for this application.

(51) TABLE-US-00008 TABLE 8 Test plan, dosing time and dosage amounts. 600 600 15 10 Time, s PAC 1, kg/t PAC 3, kg/t Silica, EXP2, Test as product as product kg/t kg/t 1 0 2 5 0.38 0.5 3 10 0.38 0.5 4 20 0.38 0.5 5 7.5 0.38 0.5 6 15 0.38 0.5 7 20 0.38 1 8 20 0.75 1 9 10 0.75 0.5 10 10 0.75 1

(52) TABLE-US-00009 TABLE 9 Test results Drainage Retention, Turbidity, Filtrate starch, Test time, s % NTU ppm 1 11.6 96.5 721 298 2 8.7 98.9 157 283 3 7.6 100.0 115 249 4 7.5 99.7 113 224 5 7.5 99.0 105 252 6 7.1 99.3 105 228 7 6.0 99.0 76 227 8 5.3 98.8 94 209 9 7.3 99.4 122 241 10 6.0 98.8 120 239

Application Example 4

(53) Pulp preparation, DDA test and starch determination as in previous example, but Eastern European testliner was disintegrated to clear filtrate and 250 ml of white water was added to 250 ml of 1% consistency pulp at 30 s in DDA test. Water properties are expressed in Table 10.

(54) TABLE-US-00010 TABLE 10 Water properties for test furnish manufacturing. clear filtrate wire water pH 6.8 6.7 Turbidity, NTU 158 73.6 Conductivity, mS/cm 1.79 2.23 Charge, ekv/l 21.4 22.76 Consistency, g/l 0.34 2.76 Ash content, % 50.26 49.35 Ca mg/l 460 Suspended solids, g/l 4.11

(55) Chemicals

(56) PAC 3: Polyaluminium chloride, 5.2% Al and 70% basicity.

(57) EXP 1, amphoteric PAM described in earlier example, dissolved to 0.5% and further diluted to 0.05%.

(58) CPAM 2: FennoPol K3500 P, medium molecular weight dry cationic polyacrylamide retention polymer by Kemira.

(59) Bentonite: Altonite SF by Kemira, retention bentonite.

(60) Test Results

(61) Experiments of this example (Table 11-12) indicate that drainage time, solids after forming and solids after pressing can be improved simultaneously with inventive system in test 5-7 compared to system without amphoteric polymer. Very good filtrate turbidity was achieved in tests 6-7, where amphoteric polymer dosage was 0.5-0.7 kg/t. Amphoteric polymer performs also alone (tests 2-3), but the superior drainage time and starch retention improvements are obtained only using all three components.

(62) TABLE-US-00011 TABLE 11 Test plan, dosing time and dosage amounts 600 40 15 10 Time, s PAC 3, EXP1, CPAM2, bentonite, Test kg/t as product kg/t kg/t kg/t 1 0 2 0.3 3 0.5 4 8 0.12 2 5 8 0.3 0.12 2 6 8 0.5 0.12 2 7 8 0.7 0.12 2

(63) TABLE-US-00012 TABLE 12 Test results Drainage Filtrate Starch Starch Solids after wet Solids after Reten- Test time, s turbidity, NTU Absorbancy retention, % pressing, % forming, % tion, % 1 9.44 1870 46.8 22.7 93.8 2 8.16 998 1.17 2.5 49.5 25.4 99.6 3 7.55 751 1.07 11.3 50.2 25.2 97.8 4 9.12 1165 0.97 20.6 49.2 25.3 97.0 5 7.02 751 0.99 19.0 50.1 25.7 98.2 6 6.17 583 0.98 19.4 49.7 25.3 97.3 7 4.59 508 0.99 19.1 50.9 25.3 96.2

(64) Even if the invention was described with reference to what at present seems to be the most practical and preferred embodiments, it is appreciated that the invention shall not be limited to the embodiments described above, but the invention is intended to cover also different modifications and equivalent technical solutions within the scope of the enclosed claims.