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
Outline • Background • Commercial uncoated wood-free papers • Pilot paper machine uncoated wood-free papers • Summary and conclusions • Suggested future investigations Océ Software Romania
Océ Software Romania Background
Deinkability of Inkjet Prints Dye-based inks can typically not be flotated, only destroyed by bleaching Typically only uncoated papers create Océ Software Romania a challenge in flotation deinking Source: Océ investigations carried out at independent R&D institutes Laboratory deinking according to INGEDE Method 11 (flotation deinking)
Deinkability of Inkjet Prints Most failures with pigment inks due to filtrate darkening and ink elimination. Océ Software Romania Source: A. Faul, INGEDE, 10 th Research Forum on Recycling 2013 Laboratory deinking according to INGEDE Method 11 (flotation deinking)
Deinking of Commercial Wood-Free Uncoated Papers Océ Software Romania
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 only 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 Océ Software Romania • Ink amount reduced slightly (70-90% of max.) for 7 papers due to ink show-through
Océ Software Romania Flotation Deinking
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 Océ Software Romania
Flotation Deinking of Offset & Inkjet Océ Software Romania 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.
Color Density vs. Deinkability Correlation? 0.74 Density Range Océ Software Romania
Filtrate Darkening vs. Paper Ash Content? Océ Software Romania
Filtrate Darkening vs. Calcium Content? Océ Software Romania
Filtrate Darkening vs. Anionic Demand? Océ Software Romania
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 Océ Software Romania • Papers with a very low cationic demand or anionic demand had a slight tendency to have had lower filtrate darkening
Deinking of Pilot Paper Machine Wood-Free Uncoated Papers Océ Software Romania
Pilot Produced WFU Papers • Fiber composition • 80% Eucalyptus • 20% Softwood • Filler type • GCC, 60% <2 μ m • Filler level • Target of 20% • Sizing agent • 0.06% AKD Pilot Paper Machine • Retention aid Océ Software Romania Munich University of Applied Science • C-PAM • Internal starch • 1% cationic corn starch
Pilot Produced WFU Papers • Trial 1 – only cationic starch surface treatment Trial 2 – 0.2 g/m 2 CaCl 2 + cationic starch surface treatment • Trial 3 – 0.5 g/m 2 CaCl 2 + cationic starch surface treatment • Trial 4 – 0.5 g/m 2 CaCl 2 + 0.2 g/m 2 PolyDADMAC + cationic • starch surface treatment Trial 5 – 0.5 g/m 2 MgSO 4 + cationic starch surface treatment • Océ Software Romania
Pilot Produced WFU Papers • All papers printed with pigment inks • INGEDE 4C test form in duplex used • Maximum ink amounts used for all papers Océ Software Romania
Océ Software Romania Flotation Deinking
Filtrate Darkening vs. Calcium Content? Including PolyDADMAC Océ Software Romania
Pilot Produced WFU Paper Results Trial 4 with 0.5 g/m 2 CaCl 2 + 0.2 g/m 2 PolyDADMAC passed • with fair deinkability Trials 2 & 3 with 0.2 and 0.5 g/m 2 CaCl 2 , respectively, failed • only due to ink elimination • Trial 1 with cationic starch alone and Trial 5 with MgSO 4 failed due to filtrate darkening and ink elimination • MgSO 4 appears to have no positive effect, rather a negative Océ Software Romania effect, on filtrate darkening
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 Océ Software Romania
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 Océ Software Romania • Surface formulation components could prevent entry of individual pigment particle into fiber cell structure • . . .
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 Océ Software Romania
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 Océ Software Romania ● Countless Paper Manufacturers…
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