5812
Cellulose (2021) 28:5807–5826
(brightness) and ISO 9416 (light scattering coefficient ( s r ), light absorption coefficient ( k r ) and calculated opacity for 65 g/m 2 sheet), with the exception of measured samples (4 test pieces instead of 10).
content (80–85 wt% of all the ‘pass’ fraction samples). Most (84–89 wt%) of the total PCC was found to pass the finest 400 mesh wire. When the cumulative residual was determined, excluding the fraction passing the 400 mesh wire (see Fig. 3), precipitation was found to affect the distribu- tion: the fractions of smaller fiber sizes were empha- sized. This was especially obvious when the fibers were refined. This was associated mainly with the weight of PCC in the finer fiber fractions, which reduced the relative weight of the less PCC-rich fractions (see Fig. 4), and to a lesser degree with the increasing tendency of material to pass the wires. Figure 4 shows the distribution of total ash between the PCC-CTMP fractions and the ash content in each fraction. Most of the total ash that did not pass the 400 mesh wire was found in R100 (0 min refined sample) or R200 (30 and 60 min refined samples), but the ash
Results
Fractionation of CTMP and PCC-CTMP
The different CTMP and PCC-CTMP furnishes were fractionated and characterized as shown in Table 1. With increasing refining, the fines content increased in both CTMP and PCC-CTMP. In the case of the PCC- CTMP, the ‘pass’ fraction corresponded to 40–50 % of the total dry material of the sample, which was significantly greater than for the CTMP. The ‘pass’ fraction was mainly PCC, as indicated by the high ash
Table 1 Proportions of unfractionated pulps and pulp fractions as mean values with 95% confidence intervals. The amount of CaCO 3 was calculated based on the 525 C and 900 C ash content measurements, i.e. the approximate percentage of ash that was CaCO 3 . Values are also given for CTMP, although the samples contained no added CaCO 3
CTMP
PCC-CTMP
0 min
30 min
60 min
0 min
30 min
60 min
Distribution in fractionation (wt%) R30
20.4 ± 2.6 12.2 ± 0.9 7.5 ± 0.4 8.6 ± 1.5 4.9 ± 0.5 3 ± 0.4
R100
50.4 ± 2.3 50.9 ± 2.0 50.8 ± 1.1 30.6 ± 5.6 16.3 ± 2.4 16.3 ± 3.9
R200
17.9 ± 1.3 23.2 ± 2.0 26.9 ± 1.9 14.4 ± 1.4 28.9 ± 2.1 25.7 ± 2.8
R400
4.6 ± 0.2 5.4 ± 0.2 6.3 ± 0.7 4.6 ± 0.2 6.1 ± 0.9 5.7 ± 0.6
Pass
6.7 ± 1.2 8.2 ± 0.8 8.4 ± 0.5 41.8 ± 7.1 43.9 ± 3.3 49.3 ± 1.9
Ash 525 ± 25 C (%) R30
1.2 ± 0.0 1.2 ± 0.2 1.3 ± 0.1 6.4 ± 0.9 8.7 ± 1.1 7.9 ± 2.3
R100
1.1 ± 0.1 1.1 ± 0.0 1.1 ± 0.0 8.1 ± 0.9 8.5 ± 1.5 8.7 ± 3.6
1.3 ± 0.1 1.2 ± 0.1 1.2 ± 0.3 15.0 ± 1.4 11.2 ± 2.1 11.4 ± 4.5
R200
R400
1.8 ± 1.1 1.9 ± 0.4 1.7 ± 0.3 42.2 ± 3 29.4 ± 2.9 29.0 ± 7.7
Pass
89 ± 0.1 86.3 ± 0.4 84.0 ± 0.4
Not fract
1.0 ± 0.0
47.9 ± 0.7 47.3 ± 0.2 48.5 ± 0.6
Ash 900 ± 25 C (%) R30
0.8 ± 0.0 0.8 ± 0.2 0.9 ± 0.1 3.8 ± 0.5 5.1 ± 0.6 4.7 ± 1.2
R100
0.8 ± 0.2 0.8 ± 0.1 0.7 ± 0.0 4.8 ± 0.5 5 ± 0.7
5.1 ± 2.1
R200
0.9 ± 0.0 0.9 ± 0.1 0.8 ± 0.2 8.6 ± 0.9 6.5 ± 1.2 6.6 ± 2.5
R400
1.4 ± 0.9 1.5 ± 0.6 1.3 ± 0.2 24 ± 0.0 17 ± 1.8 16.8 ± 4.3
50.2 ± 0.1 48.7 ± 0.1 47.4 ± 0.2
Pass
CaCO 3 (% of ash) R30 69.9
75.9
68.2
92.3
93.8
91.6
R100
66.5
66.1
70.4
94.0
94.2
92.5
R200
63.8
63.0
62.7
96.7
95.5
96.0
R400
49.3
55.2
60.4
98.1
96.3
96.0
Pass
99.1
99.0
99.3
123
Made with FlippingBook Online newsletter maker