Fresh bagasse obtained from the harvest period in a sugar mill from Jalisco, Mexico was depithing to 87/13 ratio fiber/pith, which the cooking trials with furnishes SCB–OCC: 100% SCB, 90/10% SCB–OCC, 80/20%
SCB–OCC, and 70/30% SCB–OCC were carried out in a batch stainless steel rotary digester, electrically heated with temperature control system, and maximum pressure of 8.5 kg cm–2. The white liquor used was prepared from sodium hydroxide (NaOH) at 13% as Na2O based on O.D. weight of pulp with liquor to fiber ratio 10:1, reaction time 30 min, and temperature 170 °C. At the end of pulping (lignin removal), the pulps were washed, disintegrated in a laboratory pulp mixer, and screened.1
1 Additionally, unbleached and bleached SCB soda pulp (100% OLD SCB) prepared in a local Pulp and Paper Mill located in Veracruz Mexico, under conventional industrial conditions: depithing, storing, pulping to conventional soda-based process and bleaching by CEH sequence (chlorination in acidic, alkaline extraction and alkaline hypochlorite bleach) was evaluated.
Table 4.1 The TAPPI test for P&P properties.
Testing
Kappa number of pulp T 236 cm-85
Fiber Length of Pulp by Classification (Bauer-McNett) T-233-cm-82 Forming hand sheets for physical test of pulp T-205-om-88 Standard conditioning and testing atmospheres for
paper, board, pulp hand sheets, and related products
T-402-om-93
Basis weight or grammage T410-om-98
Tensile strength T494 om-96
Bursting strength of paper T-403-om-91
Internal tearing resistance of paper T-414-om-04 Forming hand sheets for reflectance testing of pulp T-218-om-91 Brightness of pulp, paper, and paperboard TAPPI 525-om-98
Opacity T-519-om-96
CED viscosity T-230-om-89
Brightness reversion T-um-200
Folding endurance T-423
Pulp beating T-248-wd-97
Refining level SCAN-m3:65
Drainage time T-205-sp-95
Porosity, air permeability (Gurley method) T-460-om-96
The papermaking potential, pulp properties, and yield of SCB–OCC furnishes and industrial SCB pulp (100% OLD–SCB) were determined according to the Technical Association of the Pulp and Paper Industry (TAPPI) test (Table 4.1).
Pulps were refined at a consistency of 10% to obtain a refining curve, later forming hand sheets, respectively, based on 60 g/m2 for physi- cal tests of strength and drainability properties (Tables 4.2–4.9 and Figures 4.6–4.13).
It was found that the blending of OCC pulp with SCB fiber, since the delig- nification stage, gave well-balanced pulp in strength and drainability proper- ties because the alkali treatment of delignification, increased tear, tensile and
Table 4.2 Pulp-refining degree (Schopper–Riegler °S.R.).
Refining (min)
100%
OLD–SCB
100% FRESH SCB
90/10%
SCB–OCC
80/20%
SCB–OCC
70/30%
SCB–OCC
0 17 14 14 13.5 13.5
4 24 20 21 21 19
8 32 26 27 29 25
12 48 32 34 33 30
16 61 38 36 42 31
20 66 51 42 46 47
Table 4.3 Freeness (mL C.S.F.) Refining
(min)
100%
OLD–SCB
100%
FRESH SCB
90/10%
SCB–OCC
80/20%
SCB–OCC
70/30%
SCB–OCC
0 653 721 721 733 733
4 521 593 574 574 612
8 401 488 472 443 504
12 228 401 375 388 428
16 129 328 351 285 415
20 97 203 285 247 237
Table 4.4 Breaking length (m).
Refining (min)
100%
OLD–SCB
100% FRESH SCB
90/10%
SCB–OCC
80/20%
SCB–OCC
70/30%
SCB–OCC
0 3672 5616 4462 4610 4365
4 4243 7763 8240 7618 7303
8 6643 8939 8744 8280 8198
12 6546 9145 8825 9036 8348
16 6324 9110 8986 9244 8783
20 7687 9256 9302 8885 8421
Table 4.5 Burst index (kPam2/g).
Refining (min)
100%
OLD–SCB
100%
FRESH SCB
90/10%
SCB–OCC
80/20%
SCB–OCC
70/30%
SCB–OCC
0 2.53 3.59 2.92 3.14 3.13
4 3.47 5.56 5.75 5.74 5.68
8 4.72 6.77 6.07 6.35 6.25
12 4.94 7.22 6.15 6.65 6.33
16 5.43 7.32 7.21 7.64 6.53
20 5.61 7.58 6.75 6.80 6.48
Table 4.6 Tear index (mNm2/g).
Refining (min)
100%
OLD–SCB
100%
FRESH SCB
90/10%
SCB–OCC
80/20%
SCB–OCC
70/30%
SCB–OCC
0 9.15 7.85 16.83 21.45 28.67
4 8.87 10.06 11.12 12.09 13.72
8 8.51 11.05 10.46 10.78 12.76
12 8.31 9.80 9.82 10.29 11.76
16 7.85 9.10 9.75 9.20 11.11
20 6.54 8.28 9.70 9.15 11.11
Table 4.7 Folding endurance (double folds).
Refining (min)
100%
OLD–SCB
100%
FRESH SCB
90/10%
SCB–OCC
80/20%
SCB–OCC
70/30%
SCB–OCC
0 30 213 171 158 125
4 84 362 428 688 618
8 156 521 567 871 708
12 172 688 756 973 729
16 206 722 624 657 857
20 220 869 580 525 556
Table 4.8 Porosity (s/100 cm3).
Refining (min)
100%
OLD–SCB
100%
FRESH SCB
90/10%
SCB–OCC
80/20%
SCB–OCC
70/30%
SCB–OCC
0 5 6 2.0 2.0 2.0
4 26 38 34.6 18.7 9.8
8 53 82 37.5 30.7 14.0
12 79 138 59.1 38.7 17.5
16 135 239 92.7 78.4 32.5
20 410 343 93.3 75.8 19.5
Table 4.9 Drainage time of pulp (s).
Refining (min)
100%
OLD–SCB
100%
FRESH SCB
90/10%
SCB–OCC
80/20%
SCB–OCC
70/30%
SCB–OCC
0 4.75 4.55 4.25 4.27 4.29
4 5.93 5.76 5.74 5.31 5.12
8 7.70 6.90 6.46 6.26 5.50
12 9.07 8.05 7.28 6.94 5.86
16 12.08 8.92 8.69 8.29 6.34
20 16.01 11.39 8.19 8.65 6.33
Figure 4.7 Freeness (mL C.S.F.).
0 100 200 300 400 500 600 700 800
0 4 8 12 16 20
Freeness (mL)
Refining time (Minutes)
100 % OLD SCB 100 % FRESH SCB 90/10 SCB-OCC 80/20 SCB-OCC 70/30 SCB-OCC
Figure 4.6 Pulp-refining degree (Schopper–Riegler °S.R.).
0 5 10 15 20 25 30 35 40 45 50 55 60 65 70
0 4 8 12 16 20
Refining time (Minutes)
Pulp-refining degree (Schopper–Riegler °SR)
80/20 SCB-OCC 70/30 SCB-OCC
100 % OLD SCB 100 % FRESH SCB 90/10 SCB-OCC
Figure 4.8 Breaking length (m).
0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000
0 4 8 12 16 20
Breaking Length (m)
Refining time (Minutes)
100 % OLD SCB 100 % FRESH SCB 90/10 SCB-OCC 80/20 SCB-OCC 70/30 SCB-OCC
Figure 4.9 Burst index (kPam2/g).
0.00 1.00 2.00 3.00 4.00 5.00 6.00 7.00 8.00
0 4 8 12 16 20
Burst index (kPam2/g)
Refining time (Minutes)
100 % OLD SCB 100 % FRESH SCB 90/10 SCB-OCC 80/20 SCB-OCC 70/30 SCB-OCC
Figure 4.10 Tear index (mNm2/g).
0.00 3.00 6.00 9.00 12.00 15.00 18.00 21.00 24.00 27.00 30.00
0 4 8 12 16 20
Tear Index(mNm2/g)
Refining time (Minutes)
100 % OLD SCB 100 % FRESH SCB 90/10 SCB-OCC 80/20 SCB-OCC 70/30 SCB-OCC
Figure 4.11 Folding endurance (double folds).
0 150 300 450 600 750 900
0 4 8 12 16 20
Folding endurance (Double folds)
Refining time (Minutes)
100 % OLD SCB 100 % FRESH SCB 90/10 SCB-OCC 80/20 SCB-OCC 70/30 SCB-OCC
Figure 4.13 Drainage time of pulp (s).
4.004.50 5.005.50 6.006.50 7.007.50 8.008.50 9.009.50 10.00 10.50 11.00 11.50 12.00 12.50 13.00 13.50 14.00 14.50 15.00 15.50 16.00 16.50
0 4 8 12 16 20
Drainage time of pulp (Sec)
Refining time (Minutes)
100 % OLD SCB 100 % FRESH SCB 90/10 SCB-OCC 80/20 SCB-OCC 70/30 SCB-OCC
Figure 4.12 Porosity (s/100 cm3).
0 50 100 150 200 250 300 350 400 450
0 4 8 12 16 20
Gurley Porosity (sec/100cm3)
Refining time (Minutes)
100 % OLD SCB 100 % FRESH SCB 90/10 SCB-OCC 80/20 SCB-OCC 70/30 SCB-OCC
burst strength at different levels of refining in pulps. Besides, the drainage time decreased considerably and porosity of pulps was increased, because the inter-fiber bonding and long fiber proportion were increased with more flex- ible OCC pulps and chemical pulping provided relatively cleaner surfaces, which is consistent with the removal of wax, pectin, lignin, and hemicelluloses
The highest tensile strength, burst, and folding endurance were likely obtained by 80/20, and tear, drainage time of pulp, and porosity by 70/30 and 90/10 were similar to FRESH SCB. In general, SCB serves as a bonding component between long fibers from OCC in the mixture, because strength properties are mainly influenced by fiber length and extend of inter-fiber bonding as a result of delignification process of both fibers, also that elimi- nation of superficial layer was able to increase the contact area because the fibrils became more exposed. This will be very important for pulp washers, runnability in paper machine, press room, and converting machine.
Besides, the SCB pulps were separated in the Bauer-McNett classifier into five fiber length fractions, and the respective mass percentages are rep- resented in Table 4.10.
For SCB–OCC pulps, the largest fraction corresponds to the longest fibers (30 and 50 mesh), but the fines (200 mesh) are the third largest fraction.
The positive increase in the longest fibers (30 and 50 mesh) will have a synergistic effect in strength and drainability properties. They will expand the raw SCB–OCC pulp in different types of paper with several charac- teristics and end use comparable to wood pulp. Nowadays, cellulose from SCB can be applied in many products, for example, composites, chemical derivatives, and others.
In relation to the OLD–SCB pulp, the higher refining values (low free- ness and greater S.R.) in a shorter time, are due to the breaking of cells, higher fines generation, and lower proportion of long fibers that FRESH SCB and SCB–OCC bagasse pulp due to the processes of degradation by depithing and storage. In SCB–OCC pulp, the refining tended toward flex- ibility, swelling and no cutting and fibrillation instead OLD–SCB pulp to
Table 4.10 Pulp classification
Mesh 100%
OLD–SCB
100%
FRESH SCB
90/10%
SCB–OCC
80/20%
SCB–OCC
70/30%
SCB–OCC
30 0.5 18.9 27.7 29.1 32
50 26.9 34.6 22.2 24.9 27.2
100 30.6 26.1 26.5 20.9 11.8
200 19.7 7.9 9.2 10.4 11.9
<200 22.4 12.5 14.4 14.7 17.1
Table 4.11 Bleaching steps.
O Oxygen stage for oxidation of lignin, using molecular oxygen under alkaline conditions at 90–100 °C
A Acid stage to remove transition metals (at 40–60 °C) with sulfuric acid Q Acidic stage (pH 5–6.5) with chelating agents (such as EDTA or DTPA)
for removal of transition metals
D Chlorine dioxide stage using a solution of ClO2 at pH <5 in water for lignin oxidation
P Alkaline bleaching stage with hydrogen peroxide, (pH >10–11, 90 °C) rigidity and thus low mechanical resistance and high drainage resistance to the same degree of refining.
This observation highlights the fact that the major mechanism of strength improvement in SCB–OCC pulps is probably due to increase of inter-fiber bonding as a result of substitution of inactive secondary fibers with active virgin fibers from SCB in blend after alkaline pulping and refin- ing. It is very important to optimize the amount of OCC pulp, as a suit- able reinforcement pulp, to reach enough pulp properties for paper grades without the cost of wood fiber.
The results suggest that it might be worthwhile exploring alternative alkaline pulping of OCC in integrated SCB pulp mills. These findings pro- mote understanding for a more effective formulation of treatment meth- ods for recycled fibers and one possibility that might offer some advantage over current wood pulp as an effectiveness nonwood reinforcement pulp.