Substituting pulp for filler is increasingly attractive for - - PowerPoint PPT Presentation

Substituting pulp for filler is increasingly attractive for papermakers.

Per Svending, Jon Phipps, Ron Lai and Alessandro Martoni

FiberLean Technologies Ltd.

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Why and how filler should be increased

• 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

2 4 6 8 10 12 14 16 Filler Coating

Global consumption (M ton)

Other Kaolin PCC GCC

14,5 Mton

Source: Omya estimate

Global Paper & Board market estimates range around 450 million ton. Total pigment consumption is about 28,5 million ton. Pigment-using segments, P&W, some Specialty Papers, WTL and Boxboard we estimate to about 140 million ton. On this basis, these select grades contain on average about 20% mineral.

14 Mton

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The long term view on market pulp price

Hawkins Wright Outlook at end 2018:

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A clear majority of P&W paper machines operate with at least 10% market pulp*

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Source: FisherSolve Q1 2019 * Market pulp defined as bleached chemical pulp bought in by the mill

Share of production volume / # of PM´s

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Based on 500 USD/ton price difference

Low cost of fillers relative to pulp creates a strong driver for increased filler loading

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20 40 60 80 100 120 10 20 30 40 Change (%) Filler content (%)

Two major hurdles associated with higher filler loading

A big drop in strength! Bulk loss (increased density). Example shown is based on, 70 parts Eucalyptus 30 parts NBSK Refined to 500 ml CSF GCC filler, 60% <2µm

Bulk Tensile

5 10 15 20 25 30 35 40 1.65 1.7 1.75 1.8 1.85 Tensile Index (Nm/g) Bulk (cm3/g)

At constant filler loading, bulk and strength are dependent on level of refining

Refining will offer better strength at the expense of bulk. Example shown is based on, 70 parts Eucalyptus 30 parts NBSK Refining from 500-250 ml CSF 20% GCC filler, 60% <2µm

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Most important is the impact on PM operating efficiency and on paper quality

• 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.

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Retention of filler is not the challenge it used to be

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.

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Moving from 20% to 30% sPCC

Impact of increased filler on initial wet web strength

• 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

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The most important effect of MFC for filler increase is the impact on initial wet web strength

12 Note: This is pilot trial results using 450 ml CSF, 30% Pine / 70% Euca furnish and GCC filler.

80 81 82 83 84 85 86 87 88 89 90 10 20 30 40 Opacity (%) Filler content (%)

Increased opacity is a major benefit of higher filler loading

Up to 2 units of opacity for +10% filler when starting at normal levels of filler Example shown is based on, 70 parts Eucalyptus 30 parts NBSK Refined to 500 ml CSF GCC filler, 60% <2µm 80 g/m2 paper

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Fine and discreet mineral best for scattering

Impact of filler particle size

• 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

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Common options for filler increase

Cationic starch is almost universally used. Charge balance limitation. Compatible/complimentary to other system.

Starch Starch

Reduce de-bonding through agglomerating filler. Integration with retention aid system required. Complimentary to starch and polymer.

Pre-flocculation Pre-flocculation

Wide range of options with different properties. Tend to require integration with retention system. Easy to implement, ”plug and play”.

Polymers Polymers MFC

Mainly ”coarse” MFC and Cellulose Filaments. 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

• Opacity
• Porosity
• Press solids
• Initial wet strength

Scattering from good distribution of filler, fines and pores in the sheet. Demonstrated ability of MFC to enhance initial wet web strength. Some of the press solids benefit lost from MFC holding water. Flocculation opening up and MFC closing the sheet structure.

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Some of the impact will need to be corrected for by changing other inputs.

Surface area Wet web strength Press solids Bonding Sheet closure Light scattering Smoothness Density Retention aids Pulp refining Pulps used HB solids Pressing Calendering

Taking a balanced view on what is most important

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Increased filler loading will densify paper

Measures need to be taken to mitigate the effect:

• Use of BCTMP.
• Decreased pulp refining.
• Decreased calendering.
• Decreased press load.
• Some compromise in smoothness.

Cross section image of high-filled sheet.

• Std. copy paper has density of ~0,8 g/cm3.
• Std. fillers have densities of 2,6-2,9 g/cm3.

Practical experience of using MFC for filler increase in UWF.

• Retention dropping from 85% to 81% averages.

– Polymer dose increased by 10% – Alum (added at low level) increased by 40% – Cationic starch increased by 0,3 kg/ton. – Microparticle dose decreased by 25%.

• Initial drainage slowing down.

– Retention aid changes helped recover. – Closing HB lip opening by 1 mm. – Refining reduced by 6 kWh/ton.

• Improved press solids.

– Reduction in 3rd press nip load by 5%.(to aid bulk) – 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 cm3g-1 and gaining 2,1 units of opacity.

Mill making 75 g/m2 paper at about 700 m/min on a Fourdrinier machine. Adding 2% MFC and increasing GCC filler loading from 25% to 36%. Filler increase of 11% replacing market pulp for substantial savings.

Practical experience of using MFC for filler increase in UWF. Key benefits:

• 11% low cost filler replacing market pulp.
• Maintained retention.
• Improved press solids leading to steam savings.
• Strength maintained at sufficient levels.
• Maintained bulk.
• Opacity increase of 2 units.

Mill making 75 g/m2 paper at about 700 m/min on a Fourdrinier machine. Adding 2% MFC and increasing GCC filler loading from 25% to 36%. Filler increase of 11% replacing market pulp for substantial savings.

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Images showing how MFC can be made to entangle the mineral particles.

• This MFC has been produced

through co-grinding with filler.

• The process creates a strong

association between MFC and mineral.

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Food for thought…

• 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 (cm3/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.