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Application of Nano-Fibrillated Cellulose P S f T t t f I kj tas a Paper Surface Treatment for Inkjet
Printing
Wing T. Luu and Douglas Bousfield, The University of Maine
J h K ttl VTTJohn Kettle, VTT
PaperCon 2011 Page 2234
Motivation
• Nano-fibrillated cellulose (or micro-fibrillated cellulose) should be possible to produce on site at low costspossible to produce on site at low costs.
• By putting this fine material at paper surface, we may be able to improve the print quality of paper.
x 100k 200 nm
PaperCon 2011 Page 2235
Objective
• To explore the potential of nano-fibrillated cellulose (NFC) ti t i l t i i kj t i t(NFC) as a coating material to improve inkjet print quality of woodfree fine papers
PaperCon 2011 Page 2236
Key Questions
• What influence does the combination of NFC and alkyl ketene dimer (AKD) have on absorption and spreading of inkjet inks on uncoated papers
• What influence does NFC have on dye based vs. pigment based inkspigment based inks
PaperCon 2011 Page 2237
Nano-fibrillated Cellulose • NFC suspension – bleached softwood kraft fiber• Initial solids content – about 3.5%%• Prepared by mechanical treatment with pilot-scale
refiner, University of Maine
100 0
1000.0
10000.0
a·s)
3.5% solids
Temp = 25°C
1.0
10.0
100.0
Vis
cosi
ty (P
a
NFC i
x 100k 200 nm0.0
0.1
0 1 100 10000Shear Rate (s-1)
NFC suspension has shear-thinning behavior
Shear Rate (s-1)
FE-SEM image of NFC and its viscosity curve provided by Hamada and Bousfield
PaperCon 2011 Page 2238
Procedure Outline1. Uncoated woodfree fine paper – immerse in 1%
solution of AKD wax in hexane, allow hexane to evaporate, and oven cure at 105°C for 5 minutes.
2. Coat papers with NFC at different coat weights i i d tusing a wire-rod coater. NFC coat wt. ranged from 2 to 5 g/m2
Calender samples at 50°C and nip load of 100 Calender samples at 50°C and nip load of 100 kN/m
3. Print samples using desktop inkjet printer.p g p j p Dye and pigment-based magenta inks
4. Measure print density.p y
PaperCon 2011 Page 2239
Procedure Outline – Coating with NFCInk Layer
• Proposed Mechanism:1. Hydrophobic base paper treated
with AKD limits or prevents fluid penetration into the sheet.
NFC layer
penetration into the sheet. Reduces print-through Ink drops contact on
hydrophobic surface, giving low coverage and low print density
Base sheet treated with AKD
Effect of NFC on Ink Spreading
2. Hydrophilic NFC layer helps ink spread on the AKD-treated paper. Ink drops spread more, giving Effect of NFC on Ink Spreading
Without NFC layer q >> 90°
With NFC layer q < 90°
higher coverage and high print density
NFC layer may also filter pigments on paper surface
Base sheet treated with AKDwith AKD
PaperCon 2011 Page 2240
Results – Effect of AKD only on print litquality
No AKD, dye-based ink With AKD, dye-based • Solid areas printed on base ink paper before and after AKD
treatment• Higher coverage for base
paper without AKDpaper without AKD• Ink drops contract on AKD-
treated paper, giving poor coverage and low print d itNo AKD, pigment-based
inkWith AKD, pigment-based ink
density
PaperCon 2011 Page 2241
Results – Effect of AKD only on print quality
Print density of samples before and after AKD treatment
Sample Dye-based Pigment-based
after AKD treatment
No AKD 0.71 ± 0.01 0.43 ± 0.01
With AKD 0.59 ± 0.02 0.33 ± 0.01
Decrease in PD for both inks after AKD treatmenttreatment
PaperCon 2011 Page 2242
Results – Effect of AKD and NFC on i t lit (D b d i k l )print quality (Dye-based ink only)
AKD, no NFC, calenderedcalendered
Coat AKD base h t ith NFCAKD with 2.0 g/m2,
calendered
NFC layer improves ink
sheet with NFC
NFC layer improves ink spreading and gives higher print density
PaperCon 2011 Page 2243
Results – Effect of AKD and NFC on i t d it ( i t d id )print density (printed side)
1 2 • Dye based ink print
0 76 0.740.83 0.81
1.00
0 8
1.0
1.2
sity
Dye-based ink
Pigment-based ink
• Dye-based ink - print density increased after applying NFC
• Pigment based ink – no 0.76
0.63
0.74
0.420 34 0 36 0 350 4
0.6
0.8
ta P
rint
Den
s change in PD after NFC treatment Possible that pigments are
immobilized or trapped on 0.34 0.36 0.35
0 0
0.2
0.4
Mag
ent pp
the NFC layer
0.0No AKD, no calendering
AKD, no calendering
AKD, with calendering
AKD, NFC - 2 g/m2
AKD, NFC - 5 g/m2
HP Brochure Paper
Additional NFC may not yincrease PD
PaperCon 2011 Page 2244
Results – Effect of AKD and NFC on i t d it ( id )print density (reverse side)
Sample No AKD, no calendering
With AKD, no calendering
With AKD, calendered
With AKD, 2.0g/m2 NFC, calendered
Printed Side 0.76 ± 0.01 0.63 ± 0.02 0.74 ± 0.03 0.83 ± 0.05
Re erse
*Standard deviation of the reverse side PD ranges from ± 0.007 to 0.009
Reverse Side* 0.041 0.019 0.021 0.017
g
Combination of NFC & AKD increases PD
while reducing printwhile reducing print-through
PaperCon 2011 Page 2245
Results – Confocal Laser Scanning Mi (D b d i k)Microscopy (Dye-based ink)
Uncoated woodfree paper(Before AKD treatment)
Uncoated woodfree paper(After AKD treatment)(Before AKD treatment) (After AKD treatment)
47.62 mm
47.62 mm
47.62 mm
47.62 mm
• Sample with no AKD – ink spreads on low contact angle surface, giving a high PD Only with a few areas where the ink did not cover
• Sample with AKD – ink drops contract on hydrophobic surface, giving poor coveragePi t b d i k i il t d b d• Pigment-based inks – similar trends were observed
PaperCon 2011 Page 2246
Concluding Remarks• Combination of AKD and NFC increase print density for
dye-based inkjet inks. No differences observed for pigment inksinks.
• AKD treated fibers limit fluid penetration. Ink drops contract
47.62
AKD treated fibers limit fluid penetration. Ink drops contract on AKD base paper
mm• Both types of inks spread on hydrophilic NFC layer. Give higher print density for dye-based inks.
47.62 mm
PaperCon 2011 Page 2247
The authors would like to thank the industrial sponsors of The Paper Surface Science Program at The University of Maine.
• Armstrong World• Goss International
• VTT (KCL) • SAPPI Fine Paper NA
47.62
• IMERYS• KaMin LLC• OMNOVA S l ti
• SCA • Specialty Minerals Inc.• St Emm• OMNOVA Solutions • Stora-Enso• UPM-Kymmene
47.62 mm
PaperCon 2011 Page 2248
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