vtt: kristian salminen, janne kataja-aho, elias retulainen
TRANSCRIPT
The Effects of Certain Polymers on Tensile Strength and Tension Relaxation of Wet WebStrength and Tension Relaxation of Wet Web
VTT: Kristian Salminen, Janne Kataja-aho, Elias Retulainen & Timo RantanenÅbo Akademi: Hanna Lindqvist & Anna Sundberg
PaperCon 2011 Page 833
Table of contents
BackgroundBackgroundObjectives
Methods
Results & Discussion
Summary & Conclusions
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Background (1/3): Wet web strength studies•Lyne & Gallay 1954: The strength of wet web (up to a dryness levelof 25%) originates from surface tension forces and friction betweenfibers. Above this level of dryness, inter-fiber bonding starts to play any g yessential role
•Gierz & Roedland 1979: There is bound water on fiber surfaces.When two fibers with high amount of bound water get close to eachWhen two fibers with high amount of bound water get close to eachother, a high adhesion between these fibers is formed
•Pelton 1993 & 2000 / Hubbe 2006 / Myllytie 2009: Wet fibery ysurface can be considered as a gel-like layer of hydrated cellulosemicrofibrills and polymers. The mixing and orientation of the polymersin the bonding domain affect the strength of dry and wet web
•Tajedo & van de Ven 2008 & 2009: Entanglement friction betweenfibers plays a major role in wet web strength (at dryness 30-55%),whereas surface tension forces have more or less no effect at a givenwhereas surface tension forces have more or less no effect at a givendryness level
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Background (2/3): Wet web properties and paper machine runnability
• Paper machines have reachedtheir practical maximum width(~11 m). To increaseproduction, higher speed andless downtime is required
•Increase of production speed isoften limited by mechanicalproperties of wet web
Pakarinen et al 1995
properties of wet web
• The fact remains that paperThe fact remains that papermills do not typically addchemicals to improvemechanical properties of wetp pweb Hokkanen 1996
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Background (3/3): What should we measure from wet web?
Modified from Kurki et al 2004 & Kurki et al 2000
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Objective of this study…
…was to clarify the effects of some i ll il bl lcommercially available polymers or
combinations of polymers on tensile and relaxation characteristics of wet webrelaxation characteristics of wet web
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Methods (1/2): Spraying tests
Preparation of samples Measurements
Wet ipressing
50 kPa 350 kP
CMC, PVA & CHITOSAN
350 kPa
CHITOSAN CMC + CHITOSAN
CMC + C-PAM C-PAM + A-PAM
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Methods (2/2): Mode of addition testsSpray applicationSpray application
A-PAMC-PAM
Pulp suspension applicationC-PAM
0%Whole pulp
50%
50%
Handsheets
A-PAM50%
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Why to add polymers by spraying?
Higher retention of polymers (with no cationic charge)
No effect on formation
To avoid adsorption of polymers mainly to fines fraction
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Results: Spraying testsResults: Spraying tests
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Reference CMC 1 g/m2
1 2
Reference CMC 1 g/m2CMC 2 g/m2 Chitosan 1 g/m2CMC + Chitosan (1 + 1 g/m2) Pva 1 g/m2CMC + C-PAM (1 + 0.5 g/m2) C-PAM + A-PAM (0.5 + 0.5 g/m2)
1.0
1.2
kN/m
] Dual application trial points
PVA+100%
0.6
0.8
engt
h [ k
ChitosanCMC
+100%
0 2
0.4
nsile
str
e
Reference (Water spray 200 g/m2)
0.0
0.2
45 50 55 60 65
Ten
45 50 55 60 65Dryness [ % ]
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Reference CMC 1 g/m2
1 2
Reference CMC 1 g/m2CMC 2 g/m2 Chitosan 1 g/m2CMC + Chitosan (1 + 1 g/m2) Pva 1 g/m2CMC + C-PAM (1 + 0.5 g/m2) C-PAM + A-PAM (0.5 + 0.5 g/m2)
1.0
1.2
kN/m
] Dual application trial points
PVA+100%
0.6
0.8
engt
h [ k
ChitosanCMC
+100%
0 2
0.4
nsile
str
e
Reference (Water spray 200 g/m2)
GGM (1 / 2)
0.0
0.2
45 50 55 60 65
Ten
Cationic starch / Xylan (1 g/m2)GGM (1 g/m2)
45 50 55 60 65Dryness [ % ]
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Adding different polymers had no clear effect on elastic modulus(tensile stiffness) and residual tension (the tension remaining(tensile stiffness) and residual tension (the tension remainingafter 0.475 s of relaxation) of wet web
Reference CMC 1 g/m2 Reference CMC 1 g/m2
30
40
s [ k
N/m
]
Reference CMC 1 g/m2CMC 2 g/m2 Chitosan 1 g/m2CMC + Chitosan (1 + 1 g/m2) PVA 1 g/m2CMC + C-PAM (1 + 0.5 g/m2) C-PAM + A-PAM (0.5 + 0.5 g/m2)
506070
n [ N
/m ]
Reference CMC 1 g/m2CMC 2 g/m2 Chitosan 1 g/m2CMC + Chitosan (1 + 1 g/m2) PVA 1 g/m2CMC + C-PAM (1 + 0.5 g/m2) C-PAM + A-PAM (0.5 + 0.5 g/m2)
10
20
last
ic m
odul
us
10203040
esid
ual t
ensi
o
045 50 55 60 65
Drynness [ % ]
El 045 50 55 60 65
Dryness [ % ]
Re
It seems likely that different polymers increasedstrength of fiber-fiber contacts, but had only minor if anyeffect on the readiness of fiber segments to carry load
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Adding different polymers by spraying increased drypaper tensile index, but had no effect on density.p p , y
Bond strength increases
50607080
[ Nm
/g ]
400500600700
[kg/
m3 ]
01020304050
e 2 2 2 2) 2 2) 2)
Tens
ile in
dex
0100200300400
rence
g/m2)
g/m2)
g/m2)
g/m2)
g/m2)
g/m2)
g/m2)
Den
sity
[
Referen
ceCMC 1
g/m2
CMC 2 g/m
2Chito
san 1
g/m2
CMC + Chito
san (1
+ 1 g/m
2)PVA 1
g/m2
CMC + C-P
AM (1 +
0.5 g/m
2)
CPAM +
A-PAM (0
.5 + 0
.5 g/m
2)
Refere
CMC (1 g/
CMC (2 g/
Chitosa
n (1 g/
CMC + Chito
san (1
+ 1 g/
PVA (1 g/
CMC + C-P
AM (1 +
0.5 g/
C-PAM +
A-PAM (0
.5 + 0
.5 g/
C-P
Biggest increase in dry paper tensile strength was obtained with sequential addition of CMC and chitosan
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Results: Mode of addition testsResults: Mode of addition tests
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Sequential addition of oppositely charged polymersimproved dry and wet web strength, while adding of thesame polymers on separately to different part of pulpsuspensions (50/50) only minor effects were seen70
0.8
1.0
h [ k
N/m
]
Reference C-PAM + A-PAM by sprayingC-PAM + A-PAM to pulp
40
50
60
70
ex [
Nm
/g ]
0 0
0.2
0.4
0.6
ensi
le s
tren
gth
0
10
20
30
Tens
ile in
de
0.045 50 55 60 65
Dryness [ % ]
T0Reference C-PAM + A-PAM
by sprayingC-PAM + A-PAM
to pulp
Adding polymers to pulp suspension resulted as loweradsorption of polymers and impaired formation of thep p y psheets (compared to spray application trial point)
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• S i f l t b i t ti ibilit t
Summary / Conclusions• Spraying of polymers seems to be an interesting possibility to
improve dry and wet web strength• It could enable higher retention of different polymers and thus
d th t f l ill it ld kreduce the cost of polymers on paper mill or it could makepossible the usage of polymers having no cationic charge
• The effect of polymers on strength of dry and wet web wash t i ti f h lcharacteristic for each polymer
• Polymers improved the strength of the wet web significantlymore (relatively) than dry paper
• Highest increase in wet web strength was obtained withsequential spray addition of oppositely charged polymers andwith a hydrophilic polymer having high molar mass
• Spraying of anionic polymers to the outermost layer of papermight also reduce adhesion problems at (anionic) center roll
• It seems also likely that electrostatic interactions play anIt seems also likely that electrostatic interactions play anessential role in wet web strength
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Th kThank you ffor your
attention!!!The support of Kemira, Metso Paper, Stora Enso, UPM and
TEKES to this study is gratefully acknowledged
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