Influence of paper and process conditions on deinking of inkjet prints Minedys Macías, Gregg Lane and Nils Miller: Hewlett-Packard ttp Co. With data collected at PTS-Germany (Dr. Elisabeth Hanecker) and at Stora Enso Research, Germany 211 Hewlett-Packard Development Company, L.P. The information contained herein is subject to change without notice
Agenda 1. Pigmented inkjet ink background 2. Deinking Factors A) Deinking process conditions Pulping shear Process ph Collector type B) Printing materials Paper design Ink I k design 3. Path forward ACS Spring National Meeting 211; Anaheim, California 2
ACS Spring National Meeting 211; Anaheim, California 3
Water resistance and hydrophobicity in pigment based inks - + Aid Acid (H+) or Coagulant M+n from Media or - - - - - Charged pigment Dispersed in H2O bonding agent Un-Charged pigment Not soluble in H2O How do we do it? ph dependent solubility of dispersed pigments Pigments are stable and dispersed at ink ph Media, bonding agent, or environment forces ink to lower ph or causes coagulation At low ph or in presence of coagulant, ink jet pigments are completely l in-soluble in water. ACS Spring National Meeting 211; Anaheim, California 4
Effect of ph on a representative HP pigmented ink Liquid phase behavior 12 1 % Disper rsed Pigmen nt 8 6 4 2 Hydrophobic Hydrophilic Pigment crashes out of suspension at reduced ph, becomes hydrophobic 4 5 6 7 8 9 1 11 12 13 14 ph Ink samples prepared at varying ph, centrifuged Light absorbance measured on supernatant and compared to stable control at alkaline ph ACS Spring National Meeting 211; Anaheim, California 5
Deinking of pigmented inkjet prints Water + chemicals Pulping Shear Heat Flotation Particle size is impacted by: 1) Shear 2) ph 3) Chemistry Successful deinking? Ink film integrity is impacted by: 1) Coagulating agents 2) Dispersant and binder resins 3) Interaction with media ACS Spring National Meeting 211; Anaheim, California 6
Deinking process effects pulping p shear process ph ACS Spring National Meeting 211; Anaheim, California 7
Assessed deinkability is improved when shear and alkalinity are decreased 1 Luminosity (Y) Ink Elimination Filtrate Darkening (ΔY) Yield 1 Key meas sured vatiables (% %) 9 8 7 6 5 4 3 2 1 9 8 7 6 5 4 3 2 1 Yield (%) Web press k ink on Xerox paper with an ink coverage of 7% Method 11 (28) ph ~1 Modified Method 11 (28) Modified Method 11 (28) lo shear lo shear + alkalinity ph ~1 ph 8.2 Lower shear Lower shear & alkalinity Improved deinkability ACS Spring National Meeting 211; Anaheim, California 8
Lower shear during pulping reduces the ink particle fragmentation 74. high shear medium shear low shear 72. Luminosity (Y) 7. 68. 66. 64. higher luminosity 62. 6. 58. Web press k Xerox Web press k + bonding agent Xerox Web press k CL decreasing shear For samples with a constant amount of ink, ink fragmentation will affect luminosity like so: Ink fragmentation = Luminosity ACS Spring National Meeting 211; Anaheim, California 9
Positive impact of collector chemistry Conditions INGEDE Method 11 (28) and common collectors; Data from Stora Enso Research Key measured varia able (%) 1 48%ONP/32%OMG/2%IJ on TMP (b/w) 9 8 7 6 5 4 3 2 1 1% IJ on TMP (b/w) 6 61 59 3 49 16 Method Standard soap Sat'd+Unsat'd 11(28)/oleic acid fatty acid blend 83 68 66 67 66 79 63 7 1 1 2 2 Method 11 (28)/oleic acid Standard soap Sat'd+Unsat'd fatty acid blend Luminosity (Y) Ink Elimination Filtrate Darkening (ΔY) Inkjet print samples web press k INGEDE test file, printed one side, TMP paper Note: threshold applicable to single printed products ACS Spring National Meeting 211; Anaheim, California 1
Paper effects coagulating agents paper composition paper type ACS Spring National Meeting 211; Anaheim, California 11
Paper design and composition have a big effect on deinkability Testing conditions Method 11 (21) 1 Luminosity (Y) Ink Elimination Filtrate Darkening (ΔY) ured variables (% %) Key meas 9 8 7 6 5 4 3 2 1 Large variation on deinking response for the same ink Different papers The print samples are web press k ink with an ink coverage of 7% ACS Spring National Meeting 211; Anaheim, California 12
Coagulating agents in the paper enhance deinkability 1 Luminosity (Y) Ink Elimination Filtrate Darkening (ΔY) Yield 1 9 8 9 8 GOOD DEINKABILITY BY INGEDE STANDARDS Key meas sured vatiables (% %) 7 6 5 4 3 2 1 7 6 5 4 3 2 1 Yield (%) Web press k Xerox paper Baseline performance Testing conditions Method 11 (28) Printed samples have an ink coverage of 7% Web press k CL paper Web press k HP Advanced ACS Spring National Meeting 211; Anaheim, California 13
Deinkability greatly improves when samples are printed on acidic TMP 1 Luminosity (Y) Ink Elimination Filtrate Darkening (ΔY) Yield 1 Key meas sured vatiables (% %) 9 8 7 6 5 4 Why is it that deinking performance 3 is much improved 2 on acidic TMP paper? 1 9 8 7 6 5 4 3 2 1 Yield (%) GOOD DEINKABILITY BY INGEDE STANDARDS Web press k Xerox paper Web press k acidic TMP Test sample is INGEDE test file with an ink coverage is 7% ACS Spring National Meeting 211; Anaheim, California 14
Ink Elimination as a function of Ca content on paper 25 8 m) μg g of Ca /g of pa aper sample (pp 2 15 1 5 7 6 5 4 3 2 1 Ink elimin nation (%) total Ca Ink elimination No correlation can be established ACS Spring National Meeting 211; Anaheim, California 15
Filtrate darkening as a function of Ca content on paper 25 7 Better filtrate t darkening Higher amounts of Ca μg g of Ca /g of pa aper sample (pp m) 2 15 1 5 6 5 4 3 2 1 Filtrate dar kening (%) total Ca ΔY A correlation for basic papers is observed ACS Spring National Meeting 211; Anaheim, California 16
Ink Elimination as a function of Al content on paper 25 8 μg g of Al /g of pa aper sample (ppm m) 2 15 1 5 7 6 5 4 3 2 1 Ink elimin nation (%) total Al Ink elimination No correlation can be established ACS Spring National Meeting 211; Anaheim, California 17
Filtrate darkening as a function of Al content on paper 25 7 Better filtrate t darkening Higher amounts of Al μg g of Al /g of pa aper sample (ppm m) 2 15 1 5 6 5 4 3 2 1 Filtrate dar kening (%) total Al ΔY A correlation for acidic papers is observed ACS Spring National Meeting 211; Anaheim, California 18
Explanation of ERPC score ERPC European recovered paper council 5 parameters are used to asses deinkability Luminosity (Y), Color a*, Dirt particle area (A), Ink elimination (IE) and Filtrate darkening ( Y) Each parameter is given a maximum score Deinkability is rated like so ACS Spring National Meeting 211; Anaheim, California 19
Stora Enso papers printed with HP commercial web ink (pigment based, CMYK, w/o bonding agent) 1 Score for Luminosity Y Score for colour shade a* Score for Dirt Specks Area A5 Score for Dirt Specks Area A25 Score for Ink Elimination IE Score for Filtrate Darkening delta Y 9 8 7 Deinkability Sc core (DIS) 6 5 4 3 2 1-1 -2-3 -4 9,5 9,5 9,4 1 9,6 9,6 9,3 9,2 9,5 9,8 9,9 9,9 9,8 9,7 79 64 92 8 84 92 76 78 65-1 -1 96 96 1 ph aft. pulp. total Score -5 A B B, proto A B A B A B C A B C newsprint SC paper LWC book paper WFU WFC Coated grades show good deinkability (LWC, WFC) Indication of improved deinkability of prototype Deinkability of WFU is challenging (Filtrate darkening + Ink Elimination) ACS Spring National Meeting 211; Anaheim, California 2
A correlation exists between optical density and deinking score Dein nking score (%) 12 1 8 6 4 2 2 y = -26.4x 2 + 111.16x - 18.241 R² =.7193.5 1 1.5 2 2.5 Optical denisity (CMYK) A, WFU C, WFU A, newsprint B, newsprint A, SC B, SC B, WFU LWC C, WFC B, WFC A, WFC A, book B, book Wood free uncoated papers have some of the lowest OD while wood free coated papers have the highest OD ACS Spring National Meeting 211; Anaheim, California 21
The presence of a well defined ink film on papers can be correlated to deinking score < 1μm ~ 1 μm SEM micrograph of Sample WFC-A Optical microscope image of Sample WFU-A Ink film on top of the paper coating Paper coating Ink percolates into the fibers Good deinkability Poor deinkability ACS Spring National Meeting 211; Anaheim, California 22
Conclusions Process parameters such as flotation ph and pulping shear affect the deinking behavior of inkjet inks. Deinking behavior of pigmented inkjet ink is strongly affected by the collector chemistry. Paper design, composition and mfg ph play a role in deinking of inkjet inks. ColorLok papers enhance deinkability Encouraging results from Stora Enso tests on a variety of papers: Coated papers show good deinkability WFU papers are challenging Hypothesis for improved deinkability on coated papers ink film properties such as thickness can affect PS ACS Spring National Meeting 211; Anaheim, California 23
Next Steps Study media effects at HP and in conjunction with paper partners, INGEDE and DPDA Collector chemistry investigation: Hd Hydrophobicity hbiit Different collector systems: surfactant, hybrids, etc. Study ink chemistry factors and impact on deinking. Continue collaborative efforts with paper companies, digital printer manufacturers (DPDA), research organizations and chemical companies in NA and EU. ACS Spring National Meeting 211; Anaheim, California 24
Back up slides
Positive impact of ColorLok technology on pigmented inkjet ink deinkability 1 1 Luminosity (Y) Ink Elimination Filtrate Darkening (ΔY) Yield 9 9 8 8 es Measured variabl 7 6 usable 5 range 4 3 54 66 49 59 71 46 33 48 68 55 52 71 7 6 44 5 4 25 3 2 17 2 1 4 1 NA ColorLok base paper NA ColorLok paper EU ColorLok base paper EU ColorLok paper HP 45 k ink printed with an ink coverage of 7% ACS Spring National Meeting 211; Anaheim, California 26
Ink layer on wood containing uncoated media Basic TMP lo Basic TMP hi ACS Spring National Meeting 211; Anaheim, California 27