http://www.diva-portal.org
Postprint
This is the accepted version of a paper presented at Fundamental Mechanical Pulp Research Seminar, FMPRS2019, Norrköping Sweden.
Citation for the original published paper:
Engstrand, P., Ferritsius, R., Rundlöf, M., Paulsson, M. (2019) Decrease in strengthalong a process line for SC paper
In: Fundamental Mechanical Pulp Research Seminar, FMPRS2019, Norrköping, SwedenArranged by Mid Sweden University in cooperatrion with Holmen AB, Valmet AB, AF AB and Treesearch.
N.B. When citing this work, cite the original published paper.
Permanent link to this version:
http://urn.kb.se/resolve?urn=urn:nbn:se:miun:diva-38045
Decrease in strength
along a process line for SC paper
Per Engstrand Miun
Rita Ferritsius Miun, Stora Enso Mats Rundlöf Capisco
Magnus Paulsson Miun
HC
Bleaching
7
Conditions
• Spruce TMP and wood meal
• NaOH as alkali source
• 15% pulp consistency, 60°C, 120 min.
• SCAN sheet forming, white water recirculation
Main findings
• Sheet density, WRV, and –COOH increases at a pH value above ~11
• The sheet density is closely related to the –COOH content
• The tensile index is not linearly related to sheet density and –COOH content
Hypotheses
• Introduction of –COOH fi inceased swelling fi increased fiber flexibility fi facilitates formation of interfiber bonds fi increased strength
• Concentration of –COOH groups on the surfaces more important than the total charge for strength properties
• The counterions influences the swelling fi influences the physical properties
Engstrand et al.
The Significance of carboxylic groups for the physical properties of mechanical pulps
6th Int. Symp. Wood Pulp. Chem. Melbourne, Australia, April 29 - May 3, 1991, vol. 1., 75
NaOH
AkzoNobel BC Application RD&I | Strength, HP bleaching
7
Conditions
• Spruce TMP and wood meal
• NaOH as alkali source
• 15% pulp consistency, 60°C, 120 min.
• SCAN sheet forming, white water recirculation
Main findings
• Sheet density, WRV, and –COOH increases at a pH value above ~11
• The sheet density is closely related to the –COOH content
• The tensile index is not linearly related to sheet density and –COOH content
Hypotheses
• Introduction of –COOH fi inceased swelling fi increased fiber flexibility fi facilitates formation of interfiber bonds fi increased strength
• Concentration of –COOH groups on the surfaces more important than the total charge for strength properties
• The counterions influences the swelling fi influences the physical properties
Engstrand et al.
The Significance of carboxylic groups for the physical properties of mechanical pulps
6th Int. Symp. Wood Pulp. Chem. Melbourne, Australia, April 29 - May 3, 1991, vol. 1., 75
NaOH
AkzoNobel BC Application RD&I | Strength, HP bleaching
Engstrand et al.
The Significance of carboxylic groups for the physical properties of mechanical pulps 6th Int. Symp. Wood Pulp. Chem. Melbourne, Australia, April 29 - May 3, 1991, vol. 1., 75
This is true in a clean system (lab).
Na base and thus high initial pH
Rundlöf M., Htun M., Höglund H. Wågberg L. IMPC 1995 Ottawa, JPPS 2000 26(9) p314 Fresh fines in dist. water
Fines from press effluent, more or less DCS
Fresh fines + DCS from press
Rundlöf M., Htun M., Höglund H., Wågberg, L.
1995 IMPC, Ottawa 2000 JPPS 26 (9) p314
Clearly, surface properties were affected
0 15 20 25 30 35 40
0 10 20 30 40 50 60
Fibre fraction
BDDJ Acetone extracted BMcN Fresh fines
Tensile index (kNm/kg)
Fines content (%)
White water fines:
Rundlöf M., Htun M., Höglund H., Wågberg, L.
1995 IMPC, Ottawa 2000 JPPS 26 (9)
The decrease in tensile index at the first dilution after refining shows no clear relation to specific energy or if high or low bleaching was run at the time.
Effect of first dilution simulated in the lab.
Strength decrease over bleach tower
5 samples x 4 during 24hrs:
48 50 52 54 56 58
60 Tensile index kNm/kg)
Mix from 3 refiners
48 50 52 54 56 58
60 Tensile index kNm/kg)
55,0 57,0 59,0 61,0 63,0 65,0 67,0 69,0 71,0 73,0
75,0 Contact angle 0.1s (°)
0,00 0,05 0,10 0,15 0,20 0,25 0,30 0,35 0,40
0,45 Ethanol extractable subst. (%-wt)
Surface composition, atom-%
ESCA – Electron Spectroscopy Chemical Analysis (XPS – X- ray --), max depth 100Å
Estimated surface coverage of extractives:
Extracted Dirt
Sample
C
O C
O C
O
! "
$ #
%
&
−
! +
"
$ #
%
&
! =
"
$ #
%
& ( 1 )
"
"
φ
φ
Surface composition, atom-%
ESCA (XPS), max depth 100Å
Estimated surface coverage of extractives:
Extracted Dirt
Sample
C
O C
O C
O
! "
$ #
%
&
−
! +
"
$ #
%
&
! =
"
$ #
%
& ( 1 )
"
"
φ φ
from C-C,
[O/C] gives the same pattern
