application of nano-fibrillated cellulose as a paper ... · nano-fibrillated cellulose • nfc...

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 235

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


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


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


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


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


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


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


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


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


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


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


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


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


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