Developments in Use of MFC in Packaging Specialties

Specialty Papers Europe 2018
Cologne, April 23-25
Per Svending, VP Marketing

We make composites of MFC and mineral

FiberLean^® MFC, Microfibrillated Cellulose, is a composite produced by co-grinding cellulose fibers with minerals, such as GCC, PCC or kaolin, based on a proprietary patented process.

Higher filler loading in uncoated woodfree papers through use of MFC-mineral composites

Full scale UWF results with 1 and 2% MFC addition

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

Improved base paper to make better coated papers through use of MFC-mineral composites

Full scale results with 1.5% MFC addition

For today´s standard papers it is all about cost

As from the previous example:

• 7,5% pulp replaced by filler
• 1,5% pulp transformed to MFC

Today´s cost differential between pulp and filler is often €500 per dry ton or more.

Adding 7,5% more filler creates €37,50 per ton of paper in gross value.

To create net value the cost of transforming pulp to MFC must be below €2 500 per ton.

MFC in Packaging: Folding boxboard is a superior stiffness board grade

Publically available stiffness specifications

Folding Boxboard can be made even better

• Folding Boxboard mid ply bulk can be increased by reducing mechanical pulp refining energy.
• The limitation to this is set by the med ply strength, typically the Z-directional strength.
• MFC can help overcome this limitation.

MFC in Packaging: Strength from MFC can be successfully traded for better bulk/stiffness and higher productivity

Results from full scale trial

MFC in Packaging: Folding Boxboard application, full scale results

Filler increase and basis weight reduction in Top/Back

• 2.25% MFC in each
• +10% filler in each, 4 g/m² of top layer and 3 g/m² of bottom replaced by middle layer
• Conditions chosen to maintain stiffness
• Machine speed, filler retention and runnability maintained

Specification maintained at reduced cost

•  Bending stiffness and brightness unchanged
• Significantly improved smoothness

White Top Liner application, full scale results

Filler increase and basis weight reduction

• 2.5% MFC in white layer
• +9% filler in the white layer
• 10 g/m² of top layer replaced by brown layer
• Conditions chosen to maintain brightness
• Machine speed, filler retention and runnability maintained

Specification maintained at reduced cost

• Minor changes in strength properties
• Large reduction in air permeability
• 40% increase in Scott Bond
• Potential for higher filler increase and brightness

Two approaches to using MFC-mineral composite to make white top liner

Much less bleached fiber needed to make printable surface

Wet-end coating on top of the wire section

• MFC-mineral composite applied as a low solids slurry on top of the still consolidating base layer.
• The composite has the ability to stay on the surface without penetrating into the base.
• The top layer is drained using existing foils and vacuum boxes.
• Pressing and drying as normal for the combined coating and base board.
• The top layer is strong and has good adhesion while offering coverage, low porosity, smoothness and excellent printabilty.

High growth print methods are challenging the substrates ability to manage large amounts of water

Mercury porisometry measurements on conventionally and MFC-mineral wet-end coated White Top Liner

MFC-mineral coating yields larger pores and more pore volume

Print properties as a function of pore structure

Coated WTTL and MFC-mineral composite coated linerboard

MFC in Packaging:

MFC-mineral composite coating offers great printability for inkjet and flexo, ideal for printed white boxes

Images of print scanned from pilot made WT linerboard

Surprise, surprise. No smearing!

The MFC-mineral composite coating is good at accepting moisture from water based inkjet printing.

Our inkjet printing development partner is Screen GP IJC in Cambridge, UK

Our goal is attractive and well defined

The challenge is to make it work at high speed

• Being able to feed a highly viscous suspension through an applicator.
• Applying the coating without damaging the still unconsolidated sheet below.
• Create good formation to get the surface coverage needed.
• Rapid water removal using existing drainage elements.
• Ensure good runnability through press section.

How to make a composite gel structure like this work in a coating application?

10 000 PA s viscosity @ 0.01 s^-1 shear rate for a composite at a total solids of 10%.

Dilution is obviously a possibility but will naturally result in more water to drain, through the base sheet.

Optimizing solids, viscosity and drainage is a key consideration for successful high speed operation of this coating method.

The MFC-mineral composites are shear-thinning

Alternative application principles evaluated

Pilot trial application of 30 g/m² dry MFC-mineral composite at 500 m/min on top of 70 g/m² base

Several alternatives have been evaluated on high speed pilot machines.

Under the right conditions high-speed application works!

Couch and press solids are dependent on keeping application solids high

Couch solids:

Press solids:

Wet-end coating as a pre-coat

For barrier coatings or for hold out of other costly coatings

An unbleached longfiber kraft pulp makes a pretty open sheet.

Application of 30 g/m² is sufficient to increase the Gurley number from about 10 sec to 250 sec.

It is interesting to think of this as a pre-coat for specialty coated papers.

For paper machines with only one conventional coating step, in film press or similar, this could represent entirely new possibilities.

Making lighter paper with more filler without sacrificing tensile strength or opacity

If bulk and stiffness are not important, there is an opportunity

Summary: Addition of MFC offers several possibilities