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Enhanced Dry and Wet Web Runnability by
Spray Application of Different Polymers –
Laboratory and Pilot Scale Studies
Event: EFPRO-CEPI early stage researchers workshop 2012
VTT: Kristian Salminen, Janne Kataja-aho, Elias Retulainen & Timo Rantanen
Åbo Akademi: Hanna Lindqvist & Anna Sundberg
2 10/8/2012
Background: Wet web properties and paper machine runnability
• Paper machines have reached
their practical maximum width (~11
m). To increase production,
higher speed and less downtime is
required
•Increase of production speed is
often limited by mechanical
properties of wet web
• The fact remains that paper mills
do not typically add chemicals to
improve mechanical properties of
wet web
Pakarinen et al 1995
Hokkanen 1996
3 10/8/2012
Background: Interactions between fibers in the wet state
Hubbe 2006
“ …molecular segments already tend to mix with each other
already at wet state, before the start of drying process. A random
process of molecular motions would be expected to result in
interpenetration and tangling, i.e. a three-dimensional zone of
contact” (Hubbe 2006)
4 10/8/2012
Background: Modification of the fiber surface with polymers
Myllytie 2010
The dispersion of fibrils and interdiffusion between fiber
surfaces can be tailored by adsorbing different polymers onto
fibers Modified from Myllytie 2010
5 10/8/2012
…was to clarify the effects of spraying some
commercial polymers on mechanical
properties of dry and wet paper
The objective of this study…
6 10/8/2012
Methods: Spraying tests at laboratory
CMC
Chitosan
Starch
guar gum
Wet
pressing
50 kPa
350 kPa
Preparation of samples
Measurements
7 10/8/2012
Higher retention of polymers (with no cationic charge)
No effect on formation
To avoid adsorption of polymers mainly to fines fraction
Methods: Why to add polymers by spraying?
8 10/8/2012
Spraying of guar gum increased the wet web tensile strength
significantly, the increase was dependent on MW of guar gum
0.0
0.2
0.4
0.6
0.8
1.0
1.2
45 50 55 60 65
We
t w
eb
te
ns
ile
s
tre
ng
th[
kN
/m ]
Dryness [ % ]
Reference (water spray) Cationic starch 1 g/m2
CMC 1 g/m2 Chitosan 1 g/m2
Guar gum 1 g/m2 Hyd. guar gum 1 g/m2
Reference
ChitosanCMC
Guar gum
Hydrolyzed guar gum
Cationic starch
+130%
Laboratory scale tests: SW kraft pulp
9 10/8/2012
Spraying of guar gum was a significantly more efficient (6
times) way to improve the wet web tensile strength than
addition of guar gum to pulp suspension
0
20
40
60
80
100
120
140
0.0 0.5 1.0 1.5 2.0
Inc
rea
se
in
we
t w
eb
s
tre
ng
th [
% ]
Guar gum addition [ % ]
Spray addition Addition to pulp suspension
Laboratory scale tests: SW kraft pulp
10 10/8/2012
14 3 2
Tasoimulaatikot
1-4
HiVac
3 2 1
Rintapöytä
Kuormitus-
Listat 1-5
MB Imut
1 3 2
MB suction
1 2 3
Forming boardVacuum flatboxes
1-4
Load lists
1-5
Chemicaladdition by
spraying
Pilot trials with CTMP furnish
CTMP furnish for board mid-ply
Running speed 300 m/min
11 10/8/2012
23.8 24.2 24.4 24.0 23.4
0
5
10
15
20
25
We
b d
ryn
es
s a
fte
r fo
rme
r s
ec
tio
n [
% ]
Spraying of guar gum had little effect on dryness after former
or press section
Addition of cationic starch to pulp suspension decreased,
while addition of guar gum increased the wet web tensile
strength at a given dryness level
0.00
0.05
0.10
0.15
0.20
0.25
0.30
35 40 45 50
We
t w
eb
te
ns
ile
s
tre
ng
th [
kN
/m ]
Dryness [ % ]
Starch 10 kg/t Starch 20 kg/tReference Guar Gum 0.1 g/m2Guar Gum 0.3 g/m2
Nip load 500 kN/m
Nip load 1000 kN/m
Pilot trials: CTMP (board mid-ply)
10
kg/t
20
kg/t 1
kg/t
3
kg/t
Ref
12 10/8/2012
88111
127100 109 116
0
20
40
60
80
100
120
140
Inte
rna
l b
on
d
str
en
gth
[ J
/m2
]Addition of 20% guar gum of the corresponding amount of cationic
starch was needed to obtain similar increase in int. bond strength
Pilot trials: CTMP (board mid-ply)
10
kg/t
20
kg/t
1
kg/t
2
kg/t
3
kg/t
Ref
3.1 2.9 2.9 3.1 3.2 3.1
0
0.5
1
1.5
2
2.5
3
3.5
Bu
lk [
cm
3/g
]
13 10/8/2012
Adding cationic starch improved strength properties of dry paper, but had no positive effects on wet web strength
Spraying of non-ionic guar gum appeared to be an interesting possibility to improve strength properties of wet paper
The increase in wet web tensile strength with guar gum was higher for chemical pulp than for chemimechanical pulp
Spraying of guar gum on former section had no effect on dryness after the former or press section
Guar gum spraying improved internal bond strength of CTMP furnish interesting also for board manufacturing
Summary