The Influence of Multivalent Metal Salts in Uncoated Inkjet Papers - - PowerPoint PPT Presentation

The Influence of Multivalent Metal Salts in Uncoated Inkjet Papers on the Deinkability of Production Inkjet Prints

• Dr. David Croll

Océ Printing Systems May 14, 2014

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Outline

• Background
• Commercial uncoated wood-free papers
• Pilot paper machine uncoated wood-free papers
• Summary and conclusions
• Suggested future investigations

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Background

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Deinkability of Inkjet Prints

Source: Océ investigations carried out at independent R&D institutes Laboratory deinking according to INGEDE Method 11 (flotation deinking) Dye-based inks can typically not be flotated, only destroyed by bleaching Typically only uncoated papers create a challenge in flotation deinking

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Deinkability of Inkjet Prints

Source: A. Faul, INGEDE, 10th Research Forum on Recycling 2013 Laboratory deinking according to INGEDE Method 11 (flotation deinking) Most failures with pigment inks due to filtrate darkening and ink elimination.

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Deinking of Commercial Wood-Free Uncoated Papers

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Commercial WFU Papers & Conditions

• 14 Commercial wood-free uncoated papers chosen for the

investigations

• 6 Offset and laser printing papers
• 8 Inkjet optimized papers
• Some papers optimized for both dye and pigment inks
• Some papers optimized only for pigment inks, typically
• nly with mutlivalent salt added to the formulations
• All papers printed with pigment inks
• Print form: INGEDE 4C test form in duplex (2-side printed)
• Maximum ink amounts used for 7 of the papers
• Ink amount reduced slightly (70-90% of max.) for 7 papers

due to ink show-through

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Flotation Deinking

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Commercial WFU Paper Results

• 4 of the 8 inkjet optimized papers passed with fair

deinkability

• 1 inkjet optimized paper failed only due to ink elimination
• 1 inkjet optimized paper failed due to ink specks
• All offset and laser papers and two inkjet optimized papers

failed due to filtrate darkening and ink elimination

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Flotation Deinking of Offset & Inkjet

Both papers are uncoated inkjet treated papers chosen from the list of 14 commercial papers. Color densities in offset printing we adjusted to the same level as the inkjet printed samples.

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Color Density vs. Deinkability Correlation?

0.74 Density Range

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Filtrate Darkening vs. Paper Ash Content?

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Filtrate Darkening vs. Calcium Content?

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Filtrate Darkening vs. Anionic Demand?

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Commercial WFU Paper Results

• No correlation was found between color density and

deinking score or filtrate darkening

• No correlation was found between ash content and deinking

score or filtrate darkening

• Only a very weak correlation between cold water soluble

calcium ion concentration and filtrate darkening could be established, but a certain level of calcium was needed to avoid filtrate darkening

• Papers with a very low cationic demand or anionic demand

had a slight tendency to have had lower filtrate darkening

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Deinking of Pilot Paper Machine Wood-Free Uncoated Papers

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Pilot Produced WFU Papers

• Fiber composition
• 80% Eucalyptus
• 20% Softwood
• Filler type
• GCC, 60% <2 μm
• Filler level
• Target of 20%
• Sizing agent
• 0.06% AKD
• Retention aid
• C-PAM
• Internal starch
• 1% cationic corn starch

Pilot Paper Machine Munich University of Applied Science

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Pilot Produced WFU Papers

• Trial 1 – only cationic starch surface treatment
• Trial 2 – 0.2 g/m2 CaCl2 + cationic starch surface treatment
• Trial 3 – 0.5 g/m2 CaCl2 + cationic starch surface treatment
• Trial 4 – 0.5 g/m2 CaCl2 + 0.2 g/m2 PolyDADMAC + cationic

starch surface treatment

• Trial 5 – 0.5 g/m2 MgSO4 + cationic starch surface treatment

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Pilot Produced WFU Papers

• All papers printed with pigment inks
• INGEDE 4C test form in duplex used
• Maximum ink amounts used for all papers

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Flotation Deinking

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Filtrate Darkening vs. Calcium Content?

Including PolyDADMAC

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Pilot Produced WFU Paper Results

• Trial 4 with 0.5 g/m2 CaCl2 + 0.2 g/m2 PolyDADMAC passed

with fair deinkability

• Trials 2 & 3 with 0.2 and 0.5 g/m2 CaCl2, respectively, failed
• nly due to ink elimination
• Trial 1 with cationic starch alone and Trial 5 with MgSO4

failed due to filtrate darkening and ink elimination

• MgSO4 appears to have no positive effect, rather a negative

effect, on filtrate darkening

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Summary & Conclusions

• The presence of water soluble calcium salt in the

surface of papers has a positive impact on filtrate darkening in the flotation deinking of inkjet prints with pigment inks

• The best deinkability for uncoated papers is achieved

with the combination of a surface formulation containing calcium salt and polymeric cationic additive

• Improvements in the luminosity of deinking accepts

from inkjet prints on uncoated papers are still necessary

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Theories to Explain Positive Deinkability of Inkjet Optimized Uncoated Papers

• Multivalent metal salts in the surface formulation could lead

to an irreversible flocculation of pigment ink particles to a pigment agglomerate size large enough to flotate

• Cationic additives (starch, polymers) in the surface

formulation could lead to an irreversible flocculation of pigment ink particles to an agglomerate size large enough to flotate

• Surface formulation components could prevent entry of

individual pigment particle into the bulk of the paper structure

• Surface formulation components could prevent entry of

individual pigment particle into fiber cell structure

• . . .

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Suggested Further Investigations

• The affect of calcium salt type, amount and location in

the paper structure on deinkability should be further investigated

• The affect of the surface polymer type (starch, PVA,

etc.) and amount on the deinkability should be investigated

• Further investigations are needed to determine

mechanisms to improve the luminosity of deinking accepts from inkjet prints produced with pigment inks

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Special Thanks To…

• Papiertechnische Stiftung: Dr. Elisabeth Hanecker and

Dieter Schulte

• Munich University of Applied Science: Prof. Dr. Stephan

Kleemann, Sandra Röber and Michael Janiczék

• FOGRA: Alexander Schiller
• INGEDE: Andreas Faul and Axel Fischer
• Countless Paper Manufacturers…