Substituting pulp for filler is increasingly attractive for papermakers. Per Svending, Jon Phipps, Ron Lai and Alessandro Martoni FiberLean Technologies Ltd.
Why and how filler should be increased CONFIDENTIAL • Cost drivers • Potential dangers • Impact on PM operation • Impact on optical properties • Alternative filler increase concepts • Papermaking compromises • Practical experience using MFC
Global Pigment Consumption in Paper and Board 16 14,5 Mton Global Paper & Board market 14 Mton 14 estimates range around 450 million ton . Global consumption (M ton) 12 Total pigment consumption is 10 about 28,5 million ton. Other 8 Kaolin Pigment-using segments, P&W, PCC some Specialty Papers, WTL 6 GCC and Boxboard we estimate to about 140 million ton . 4 On this basis, these select 2 grades contain on average about 20% mineral. 0 Filler Coating Source: Omya estimate
The long term view on market pulp price Hawkins Wright Outlook at end 2018: CONFIDENTIAL
A clear majority of P&W paper machines operate with at least 10% market pulp* CONFIDENTIAL Share of production volume / # of PM´s * Market pulp defined as bleached chemical pulp bought in by the mill Source: FisherSolve Q1 2019 5
Low cost of fillers relative to pulp creates a strong driver for increased filler loading Based on 500 USD/ton price difference CONFIDENTIAL 6
Two major hurdles associated with higher filler loading 120 A big drop in strength! Bulk 100 Bulk loss (increased density). 80 Change (%) 60 Example shown is based on, Tensile 40 70 parts Eucalyptus 20 30 parts NBSK Refined to 500 ml CSF 0 GCC filler, 60% <2µm 0 10 20 30 40 Filler content (%)
At constant filler loading, bulk and strength are dependent on level of refining 40 Refining will offer better strength at 35 the expense of bulk. Tensile Index (Nm/g) 30 25 20 Example shown is based on, 15 10 70 parts Eucalyptus 30 parts NBSK 5 Refining from 500-250 ml CSF 0 20% GCC filler, 60% <2µm 1.65 1.7 1.75 1.8 1.85 Bulk (cm 3 /g)
Most important is the impact on PM operating efficiency and on paper quality CONFIDENTIAL • Strength performance stability over time. • Impact on initial wet web strength. • Ability to maintain a constant and high retention. • Impact on formation. • Even distribution of filler in the Z-direction of the sheet. • Impact on drainage and press solids. • Impact on pick-up of surface size. • Impact on coating hold-out. • Surface smoothness before calendering. • Net impact on bulk and stiffness. • Net impact on optical properties. • Net impact on quality of print surface. • Look and feel of the paper. 9
Retention of filler is not the challenge it used to be CONFIDENTIAL This old picture shows the challenge in a clear and simple way. Today´s retention aid systems are however well capable of handling very high loading levels. It is mainly a question of minimizing interference and need for increased dosing. The retention systems can also be of great help in aiding drainage.
Impact of increased filler on initial wet web strength CONFIDENTIAL Moving from 20% to 30% sPCC • TEA Index dropping 24%, at constant 50% press solids. • Press solids increasing 1%, at constant press impulse. • TEA Index drop reduced to 17% as a result of increased press solids at constant press impulse. • Note that the initial wet web TEA is only 1-2% of the dry TEA. Xujun Hua, Tom Owston and Makhlouf Laleg, FP Innovations at PaperCon 2011
The most important effect of MFC for filler increase is the impact on initial wet web strength CONFIDENTIAL Note: This is pilot trial results using 450 ml CSF, 30% Pine / 70% Euca furnish and GCC filler. 12
Increased opacity is a major benefit of higher filler loading 90 Up to 2 units of opacity for +10% filler 89 when starting at normal levels of filler 88 87 Opacity (%) 86 85 Example shown is based on, 84 70 parts Eucalyptus 83 30 parts NBSK 82 Refined to 500 ml CSF 81 GCC filler, 60% <2µm 80 80 g/m 2 paper 0 10 20 30 40 Filler content (%)
Impact of filler particle size Fine and discreet mineral best for scattering CONFIDENTIAL • Fillers, except TiO2, have similar refractive index of around 1,6. • Optical impact is determined by particle size and steepness of size distribution. • Reduction in particle size will increase light scattering but also strength loss. • Flocculating the filler will mimic move to a coarser filler. Jonathan Phipps, Imerys Minerals Ltd at PIRA 2001
Common options for filler increase CONFIDENTIAL Cationic starch is almost universally used. Starch Starch Charge balance limitation. Compatible/complimentary to other system. Reduce de-bonding through agglomerating filler. Pre-flocculation Pre-flocculation Integration with retention aid system required. Complimentary to starch and polymer. Wide range of options with different properties. Polymers Polymers Tend to require integration with retention system. Easy to implement, ”plug and play”. Mainly ”coarse” MFC and Cellulose Filaments. MFC Implementation process more demanding. Strong impact on opacity and initial wet strength.
The impact of increased filler loading can be enhanced or compromised by the filler increase system used Filler Pre-flocculation MFC Scattering from good • Opacity distribution of filler, fines and pores in the sheet. Flocculation opening up • Porosity and MFC closing the sheet structure. Some of the press • Press solids solids benefit lost from MFC holding water. Demonstrated ability of • Initial wet strength MFC to enhance initial wet web strength.
Some of the impact will need to be corrected for by changing other inputs. Taking a balanced view on what is most important CONFIDENTIAL Surface area Wet web strength Press solids Retention aids Bonding Pulp refining Sheet closure Pulps used Light scattering HB solids Smoothness Pressing Density Calendering
Increased filler loading will densify paper CONFIDENTIAL Measures need to be taken to mitigate the effect: • Use of BCTMP. • Decreased pulp refining. • Decreased calendering. Cross section image of high-filled sheet. • Decreased press load. Std. copy paper has density of ~0,8 g/cm 3 . Std. fillers have densities of 2,6-2,9 g/cm 3 . • Some compromise in smoothness.
• Retention dropping from 85% to 81% averages. Practical experience of using – Polymer dose increased by 10% MFC for filler increase in UWF. – Alum (added at low level) increased by 40% Mill making 75 g/m 2 paper at about – Cationic starch increased by 0,3 kg/ton. – Microparticle dose decreased by 25%. 700 m/min on a Fourdrinier machine. • Initial drainage slowing down. – Retention aid changes helped recover. Adding 2% MFC and increasing GCC – Closing HB lip opening by 1 mm. filler loading from 25% to 36%. – Refining reduced by 6 kWh/ton. • Improved press solids. Filler increase of 11% replacing Reduction in 3 rd press nip load by 5%.(to aid bulk) – market pulp for substantial savings. – Steam consumption in dryer section reduced by 7%, after reduced press load. • Improved smoothness. – Reduction in calendering nip pressure by 20%. (to aid bulk) – Loss of 30-50 ml Bendtsen smoothness but less two-sided. • Sufficient strength. – Improved initial wet web strength. – Dry burst and tensile dropping by about 10%. – Maintained z-directional and surface strength. Maintained bulk at 1,2 cm 3 g -1 and gaining 2,1 units of opacity. •
Key benefits: Practical experience of using MFC for filler increase in UWF. Mill making 75 g/m 2 paper at about • 11% low cost filler replacing market pulp. 700 m/min on a Fourdrinier machine. • Maintained retention. Adding 2% MFC and increasing GCC filler loading from 25% to 36%. • Improved press solids leading to steam savings. Filler increase of 11% replacing • Strength maintained at sufficient levels. market pulp for substantial savings. • Maintained bulk. • Opacity increase of 2 units.
Images showing how MFC can be made to entangle the mineral particles. CONFIDENTIAL • This MFC has been produced through co-grinding with filler. • The process creates a strong association between MFC and mineral.
Food for thought… CONFIDENTIAL • What if filler increase was not constrained by the current specification? • Would a better printing surface be worth compromising bulk? Grade Mineral content Binder Bulk (cm 3 /g) UWF 21,4% None 1,50 UWF 37,6% 4% MFC 1,31 CWF 49,4% ~4% latex/starch 0,72
Summary and conclusions • Filler increase is a proven way to reduce impact of high pulp cost. • The goal is generally to maintain current product specification. • Compromises are however part of papermaking reality. • Different filler increase systems will lead to different compromises. • Our experience has shown MFC to be an excellent option.
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