Organic, Natural Pigments as Paper Coatings. Jaakko Raukola Web Surface Modification 5.2

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1 Organic, Natural Pigments as Paper Coatings Jaakko Raukola Web Surface Modification 5.2

2 Background: Biodegradable Fillers and Pigments for Paper Making Mineral fillers give paper opacity, brightness and better printability. When 1000 kg of paper is recycled, kg of inorganic de-inking sludge is formed. In Europe 86.5 million tons of paper was consumed and 46.8 million tons were recycled, 22 million tons of paper ended up for final disposal (landfill, combustion) after primary use and 6.4 million tons to other recovery options (Incineration, composting, other treatments) (CEPI statistics, year 2004) Assuming that fillers and pigments were organic and they could be combusted, these could replace 8 million tons of fuel oil in energy production. Paper x.y Speakers name 2

3 Background High brightness and opacity are qualities needed for good fillers and pigments. The properties are based on effective light scattering of the material. Optimum size of a single round solid filler particle for ultimate light scattering is a half of the wave length of visible light (around 200 nm). The objective was to manufacture nanoscale pigments or stabilized porous filler structures of renewable materials, to be used in paper production instead of mineral materials. Manufacturing techniques for stabilized microcapsule filler foams and pigment particles of optimum particle size (Ø= 250 nm) with narrow particle size distribution was developed. Product properties were optimised by means of modelling. Paper x.y Speakers name 3

4 Surface Topography of Coated Papers Uncalendered CLC-6000 samples; AP = Starch pigment AP + GCC AP + Clay AP AP + Clay + GCC Paper x.y Speakers name 4

5 Surface Topography of Coated Samples Calendered CLC-6000 AP (100pph) coating Paper x.y Speakers name 5

6 ISO-brightness,gloss and opacity values, calendered CLC coated papers 90,0 ISO% Gloss Opacity 85,0 76,0 80,0 75,0 75,5 75,0 74,5 70,0 65,0 74,0 73,5 73,0 60,0 55,0 72,5 72,0 71,5 50,0 AP-Clay AP-HC AP-HC-Clay AP Clay HC 71,0 AP-Clay AP-HC AP-HC-Clay AP Clay HC Starch based pigment (AP) improves brightness and it increases gloss when used together with mineral pigments adds opacity when used together with clay and mineral pigment mixture (HC = GCC = Carbonate) Paper x.y Speakers name 6

7 Roughness of Coated Papers Roughness ml/min Gloss % Clay75/AP kn/m Clay100/AP0 325 kn/m Clay75/AP kn/m Clay100/AP0 440kN/m mixture of pigment AP and clay improves gloss and smooths roughness with lower calandering pressures than pure clay Paper x.y Speakers name 7

8 45,0 40,0 35,0 PRINT GLOSS HSWO Clay75/AP kn/m Clay75/AP kn/m Print Gloss 60º Clay100/AP0 325 kn/m Clay100/AP0 440kN/m 30,0 % 25,0 20,0 15,0 10,0 5,0 0,0 Cyan 100% Black 100% Magenta 100% Yellow 100% improves printed gloss for all sub-colours with AP pigment improved color strength with lower amount of printing colour Paper x.y Speakers name 8

9 Surface Strength Initial Pick Velocity m/s Clay75/AP kn/m Clay100/AP0 325 kn/m Clay75/AP kn/m Clay100/AP0 440kN/m better pick resistance, better surface strength even with low calendering pressures with AP addition Paper x.y Speakers name 9

10 Adhesion Promotion Clay 100 % 75 % Clay 25 % AP - improved surface properties (gloss, smoothness, brightness) - improved surface strength - improved offset printability (print gloss and density) adhesion promotion as coated surface in extrusion coating Paper x.y Speakers name 10

11 Conclusion Products Nanoparticles or nanoporous structures or foams based on acetylated starch with varying molecular weight and substitution degree. Preparation in pilot scale. Properties - Mathematical models show that optimum light scattering with spherical starch pigment morphology particles is obtained with particle diameters between nm. - Low packaging density (0,35) gives better light scattering than high (0,6). - Non-mineral spherical pigments in coating give good: - improved surface properties (gloss, smoothness, brightness, surface strength) - improved offset printability (print gloss and density) - adhesion promotion as coated surface in extrusion coating 1000 nm 1000 nm 2000 nm Paper x.y Speakers name 11

12 Acknowledges VTT - Technical Research Centre of Finland Juha Saari, Kirsi Kataja, Pia Qvintus-Leino, Lauri Kuutti, Soili Peltonen, Hannu Mikkonen Western Michigan University Margaret Joyce University of Helsinki Prof. Kari Lumme and Dr. Antti Penttilä University of Joensuu Prof. Raimo Silvennoinen, Petri Karvonen and Antti Oksman Geological Survey of Finland Dr. Saija Luukkanen, Mauno Miettinen Funding: Tekes M Real Oyj Stora Enso Oyj VTT Ciba Specialty Chemicals Oy Metso Paper Oyj Paper x.y Speakers name 12