KEMFORM, POSSIBILITY TO IMPROVE
PRODUCTIVITY OF THE MACHINES FOR
PRINTING AND PACKAGING GRADES
Matti Hietaniemi
Marcus Lillandt
Kemira
Research Scientist
Espoo, Finland
Kemira
Sr Research Scientist
Espoo, Finland
Kimmo Strengell
Kemira Paper
Product Line Manager Retention & Dry Strength
Helsinki, Finland
ABSTRACT
To produce paper and paper board more costefficiently, fiber costs should be reduced. In paper making
this can be achieved using chemistry promoting high filler
loading. In multiply board production target can be
reduction of basis weight from the layers containing
expensive fiber raw materials.
A narrow balance exists in attaining the desired
retention and formation particularly in systems with heavier
ash loads and producing paper with high speed paper
machines. For paper board the challenge is to balance
drainage and formation. Drainage chemistry should also
improve press dryness to improve production rate and
efficiency.
A new generation of both cationic and anionic
micropolymer technologies has been developed. These
water based chemistries are free of volatile organic
compound (VOC), mineral oil aliphatic compounds
(MOAH) and mineral oil saturated hydrocarbon (MOSH).
When these novel micropolymers are applied with linear
poly-acrylamide or in conjunction with inorganic
microparticle technologies, such as colloidal silica,
substantial increases in drainage, fibre retention and ash
retention are observed.
Micropolymers also influenced on paper strength
enabling higher filler content in sheet. A particular note is
the drainage improvement seen with the application of the
cationic micropolymers in unbleached packaging grades.
INTRODUCTION
During paper and board manufacture a narrow
balance exists when achieving the optimal retention in the
process for maximizing runnability, while obtaining the
desired sheet formation. Dispersed colloids deposit onto
fines and fibres to form “flocs” which are retained by
filtration [1]. The adsorption of these small particles
becomes a greater challenge as the furnish is exposed to
increasing hydrodynamic shear stress as machine speed is
increased [2,3]. Further complexity is introduced when ash
containing furnishes are used and the ash constituent is
elevated, intensifying the demand on retention systems.
Main challenge in packaging and board grades is the
drainage and press dewatering improvement without
sacrificing formation.
High molecular weight long chain polymers, polyacrylamides (PAM’s), are efficient for gross retention.
These low charged polymers are generally linear. Although
branched or structured versions are sometimes used, the
linear versions are the most common chemistry applied.
PAM’s generally induce the development of a large flocs via
a bridging mechanism to obtain sufficient retention of fines
and filler. The sheet structure created is often referred to as
“hard flocced” or macro flocculated. In the presence of
filler, PAM’s can agglomerate filler particles.
By
effectively increasing the average particle size of the filler or
pigment, optical efficiency can be compromised. With the
changes in filler distribution within the sheet and particle
size, both opacity and formation can be adversely affected,
as well as other physical properties.
In addition, a substantial level of “bound” water is
present within the floc often hindering the pressing
efficiency of the sheet. Higher dewatering rates may be
observed in the forming section of the paper machine, but
the net water removal after the press section may be lower
[4]. The result can be slower machine speeds or higher
steam demands. Runnability can be also compromised if the
bound water becomes excessive resulting in sheet crushing
and picking. In manufacturing processes that utilize high
efficiency presses such as an extended nip press (ENP), this
loss in pressing efficiency can be very prohibitive.
High charged low molecular weight polymers and
inorganic coagulants allow for fixation or patch retention of
fillers, fines, and detrimental substances. Although they can
improve drainage in some systems through soluble charge
control, they are limited in their ability to maintain retention
because of the lack of floc structure. Moreover, sufficient
application rates to obtain the desired drainage effect, can
lead to an excessive decrease in cationic demand. This can
inhibit retention of other process additives as well as the
principle furnish components.
MATERIALS AND METHODS
Studies were made in laboratory to explore benefits
of micropolymer based retention systems. In addition, a
flocculant, linear cationic polymer and colloidal silica was
used.
Micropolymer
A new generation of micropolymer technology
enables a floc and subsequent sheet structure to be created
that maximizes drainage in the former without
compromising pressing efficiency [5]. This technology is
also very efficient for retention of both calcium carbonates
and kaolins. These polymers are synthesized with either
cationic or anionic charge, which enables this chemistry to
be reactive across the majority of wood and non-wood
containing grades.
The following figure illustrates how the charge and
molar mass of the cationic versions of the micropolymers
relates to the conventional linear cationic PAM’s and short
chain high charge density coagulants.
20
18
Pure PEI
Charge Density (meq/g)
16
14
DMA-Epichlorohydrin
12
Modified PEI
Hydrophobe
10
Figure 3. Schematic of association of hydrophobic monomers.
8
NEW
Micropolymers
(Cationic)
6
4
These associations or interactions build a very highly
structured polymer, creating a three dimensional micronetwork that is estimated to be 50 nanometres (nm) in size
as determined by Zimm analysis. Because the structure is
created without truly cross-linking the polymer constituents,
the charge of the polymer is very accessible, increasing
reactivity. Recent work has shown that this structure is
preferred for retention of clays and carbonates [6]. Data
suggests that there is selectivity for ash. The structure is
illustrated in Figure 4.
p-DADMAC
2
CATIONIC PAM'S
0
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
Molecular Weight (MM)
Figure 1. Charge density versus molecular weight for various
cationic polymers.
The illustration shows the unique combination of molecular
weight and charge density of the cationic micropolymers. In
addition to these properties, they possess a unique structure
and composition. Micropolymers appear as 3 dimensional in
a weak water solution. The structure in weak water solution
enable charges to migrate over longer time in flocculation.
Micropolymer conserve charges over longer time compared
to linear flocculant. This gives certain benefits in a
papermaking retention application.
These polymers are synthesized using a controlled
molecular weight cationic polyacrylamide polymerized
within a coagulant matrix. The end result is a system of
high charge density low molar mass polymers and higher
molecular weight medium cationic polymers. This system is
depicted in the following illustration (figure 2).
Figure 4. Micropolymer structure.
Although the charge is highly accessible, a considerable
portion is buried in the network and requires some shear to
expose it.
This is referred to as the ionic regain.
Consequently, it should be noted that the charge density data
for this chemistry is determined by streaming potential and
does not represent the total charge available within the
micropolymer structure. This combination of charge and
structure allows the polymer to control anionic trash through
fixation while retaining fibres and fillers. The control of
detrimental substances is necessary in many systems in
order to maintain efficiency of process additives such as
starch and sizing agents [7]. The floc structure created is not
only efficient for retention, but it also improves sheet
dewatering through the former and press. Fines and fillers
are flocculated along the long fibres as small discrete flocs,
which minimizes the level of bound water. This structure
reduces the blocking of inter-fibre pores. A greater level of
water can be removed from the former and this dewatering
can continue through the press section. Pictures comparing
the floc structures created with a conventional long chain
linear polymer versus the micropolymer is shown in figure
5.
Figure 2. Characteristics: SEM-cryo picture.
This chemistry can also be produced using an anionic
system of anionic acrylamide, which allows for the
development of anionic charged polymers.
The micropolymers are highly structured polymers
demonstrating very little linearity. This is largely due to the
inclusion of hydrophobic associative groups in the synthesis.
These groups increase the number inter and intra molecular
interactions as shown in the figure 3.
2
Linear polymer
Fennopol K 3500R was used as polymer in the
retention
system.
Fennopol
K3500R
is
linear
polyacrylamide based premium retention polymer that is
delivered as a dry product. It has a 10 mol-% cationic charge
and a medium molecular weight of 7 million g/mol (Figure
7).
(a)
(b)
Figure 5. Light microscopy pictures from flocculated fiber and
filler particles. (a) with linear polymer flocculant. (b) with
micropolymer flocculant.
An additional advantage of the floc structure depicted by
Figure 5b is the improved fines and ash distribution due to
the flocculation along fibre surfaces. This can bring about
increases in strength and improved optical properties.
Kemform® is a retention and drainage system
comprising linear polymers, microparticle silica/bentonite
and micropolymer. Fennosil E TM and Fennosil ESTM product
families have anionic and cationic micropolymers having
charge from -40 to +40 mol-%. The FennosilTM products are
water in water dispersions in salt solution (ES) or in
coagulant solution (E). Finally, this micropolymer
technology is made without oil. They are not emulsions,
and as such, do not contain volatile organic compounds
(VOC’s) or alkyphenol ethoxylate.
The micropolymer selected for the laboratory
experiments is Fennosil ES 325™ - a high molecular weight
cationic micropolymer.
Figure 7. Illustrative picture of cationic polymers like Fennopol
K3500R.
Colloidal silica
Fennosil 515 is microparticle colloidal silica. It’s
particle size is 5 nm and specific surface area 500 m2/g.
Primary use of microparticle silica is to improve drainage at
the wire and especially at the wet pressing. Microparticle
silica retains efficiently starch, fines, internal size AKD or
ASA and fillers – primary (fresh) or secondary filler (with
RCF). Use of microparticle silica typically reduce linting
and improve bonding (Scott Bond) of the paper or board
(Figure 8).
Coagulant
PAX XL60, a polyalumiunium chloride with 8 %
aluminium and a basicity of 40%, was used as coagulant. Its
structure is illustrated in figure 6. This is a coagulant that
has fast reaction to colloidal particles. It enhances
flocculation when used together with polyacrylamide
flocculants and microparticle colloidal silica in Kemform®
system. Use of PAX XL 60 typically lowers COD, reduce
deposition tendency and improve papermachine cleanliness.
Figure 8. Schematic particle and surface chemistry of
microparticle silica.
Pulp
Studies were conducted on recycled fiber (RCF)
furnish collected from a mill producing coated folding
boxboard (FBB) in Europe. Test pulp was the middle ply
furnish containing RCF and broke. The details of the used
pulp and wire water can be seen in Table 1. The furnish used
in the testing consisted of one part pulp and two parts wire
water. The dilution of the pulp to the consistencies used in
the testing was done with deionized water.
Table 1. The characteristics of used pulp and wire water.
Pulp
Wire water
pH
6,86
6,84
Turbidity
NTU
1978
69
Conductivity of
µS/cm
3170
2410
filtrate
Charge
µekv/l
-216
-258
Zeta potential
mV
-9,6
n.d.
Consistency
g/l
31,4
2,9
Ash content
%
20,4
56,2
Figure 6. PAC structure
3
Retention test
With a very high amount of only Fennopol K3500R
it is also possible to reach good drainage time. The
drawback is though a poor formation of the sheet, which is
due to the large size of the flocks. This was not studied in
this evaluation, but is a known drawback of one polymer
retention systems.
The first pass retention (FPR) of different chemical
systems was determined using Dynamic Drainage Jar (DDJ,
Figure 9). The main part of the equipment is a cylindrical
plastic jar. At the bottom of the jar was a stainless steel
screen type 60M. The papermaking furnish (500ml, 7.7g/l)
was added to the cylindrical plastic jar and agitated at
1000rpm. The chemical components were added to the
furnish and 100ml of the water was taken out through the
wire without stopping the stirrer. PAX XL60 was added 25 s
before the dewatering started, Fennopol K3500R 20 s,
Fennosil 515 10 s and Fennosil ES 352 7 s before
dewatering. Based on the dry solids and the ash content of
the initial furnish and the water taken out through the wire,
the first pass retention and first pass ash retention was
determined.
Figure 10. Improved drainage was seen when Fennosil 515 and
XL60 was combined with K3500R.
By adding the micropolymer Fennosil ES 325 to the
retention system, even better drainage performance was
achieved, Figure 11. This can be seen already at quite small
dosages of Fennosil ES 325 and this system can can
effectively be combined with Fennosil 515.
Figure 9. The Dynamic drainage jar showing the cylindric
plastic jar and stirrer.
Drainage test
The drainage tests were performed with Dynamic Drainage
Analyzer (DDA). The DDA measures drainage under
vacuum. The DDA consists of a cylindrical plastic jar with
stirrer similar to the DDJ and a vacuum system. The pulp
was added to the jar (500ml, 4g/l), stirred at 1000 rpm while
the chemicals were added to the furnish at the same times as
in the retention tests. Thereafter, the stirrer was stopped and
the dewatering started through a steel wire with 0,25 mm
opening. When air starts to flow through the fiber mat, the
vacuum decreases rapidly and this point gives the
dewatering time [8].
Figure 11. The drainage is even further improved when adding
Fennosil ES325 to the retention system.
In this study, clear differences were also found as expected
in first pass ash retention. The relationship between first
pass ash retention and drainage is presented in Figure 12. At
a specific retention level, the linear cationic polymer alone
gives the longest drainage time. By using microparticle
silica (Fennosil 515) and PAX XL60 at a specific retention
level, the dewatering speed was improved with up to 10%
compared to a single component system.
RESULTS AND DISCUSSION
Experimental work is consisting from laboratory tests and
mill cases. In the laboratory tests focus was on dewatering
and retention, while the mill tests focused on production and
cost efficiency verification.
Laboratory results
Drainage and retention performance are crucial for all
retention systems. Fennopol K3500R, which is a cationic
polymer, gives a clear improvement in drainage, see Figure
10. The drainage can also be even further improved by
adding Fennosil 515 and PAX XL60 to the furnish.
4
Table 2. Mill trial conditions for Mill case 1.
Trial basic data
Production: 30 t/h
Grades: 3 ply board
Grammages: 200 - 350 g/m2
Speed 450 m/min
Table 3. Mill trial dosages for Mill case 1.
Chemistry REFERENCE
PVAM (g/t)
Top/ Back 700 - 750
Middle
700 - 750
Figure 12. The drainage was improved also at a specific first
pass ash retention. K3500R added 0g/t (FPAR approx. 5%),
250g/t (FPAR approx. 30%), 500g/t (FPAR approx. 45%) and
750g/t (FPAR approx 55%).
TRIAL
Fennosil ES 325+ Fennosil 515 (g/t)
600 + 1250
300+ 500
Mill case 2. White top kraftliner
By using a cationic micropolymer (Fennosil ES325), we got
excellent dewatering at high first pass ash retention, Figure
13. Once again, the Fennosil 515 can also be used to
improve the retention system even further.
Mill is producing white top krafliner board with a
production rate of 310 000 ton/a. Currently board market for
packaging grades is very good and the key thing is to
increase output with same fixed costs.
Mill runs the retention system based on cationic
PAM + bentonite -system with fair amount of cationic
starch. Kemira implemented Kemform® trials on this
machine with very impressive results:
 Production rate at 38 t/h against budgeted 36 t/h
 Improved runnability and board characteristics
 Improved retention and more clean wire part and
short loop
Mill case 3. Specialty fine paper
Mill producing uncoated fine paper from hardwood and
softwood bleached kraft together with PCC had ambition to
increase filler content in paper because mill is limited with
fiber supply in the pulp plant. Increasing filler in paper
improve profit.
Kemira’s Kemform system was trimmed with
Fennosil 515 microparticle technology. Anionic linear
Fennopol was added as a co-mix with Fennosil 515 and
anionic micropolymer Fennosil ES 210 through a mixing
device after the pressure screens.
Figure 13. Best drainage at a specific first pass ash retention
can be achieved with a combination of Fennopol K3500R,
Fennosil 515 and Fennosil ES325
Mill case 1. Folding boxboard (FBB)
Mill is producing coated folding boxboard with a
production rate of 250 000 ton/a. Mill wanted to improve
production output and they also suffer from quality
problems such as delamination. Trial set-up is expressed in
tables 2-3.
Mill runs polyvinylamine (PVAM) chemistry in
retention. Kemira implemented Kemform® trials on this
machine with solid results:
 Overall equipment efficiency (OEE) % was
reported being 2% units higher on monthly basis
after Kemira system was onstream
 Delamination problems disappeared. Key success
factor was the realized higher dry content after the
wet press
Results:
 Response of the retention system improved in such
a way that it was able to increase 2% filler in the
sheet with similar dusting propensity than with
standard filler content in paper.
 Reduced usage of bleached kraft pulp provided
great savings for the mill!
Mill case 4. Fine paper
Mill producing specialty bulky uncoated fine paper from
hardwood bleached kraft and BCTMP together with PCC
had target to increase filler content and improve formation
in paper. Increasing filler in paper improve gross margin %
of paper production. Good formation for a specialty
producer is a necessity.
5
Kemira’s Kemform® system was applied on the
machine
with significant machine and quality
improvements. Results outlook was following:
 It was able to increase 2% filler in the sheet
 Formation improved visually and by Beta
measurement by 10%
 Bulk is maintained despite increased filler content
in paper
CONCLUSIONS
Kemform® comprises a retention system that
consist a micropolymer, Fennosil 515 microparticle silica
and traditional retention polymer.
Micropolymers are polymerized in a salt solution.
Micropolymers are structurated polymers in a weak water
solution and therefore provide differentiated performance
profile compared to traditional retention polymers
In the experimental part was tested for folding box
board with recycled pulp furnish. Fennosil 515 improves
drainage. Drainage can further be improved by adding PAX
XL 60 (PAC) and cationic micropolymer Fennosil ES 325 to
the system.
Reference case histories proof that in industrial
scale production Kemform® can improve productivity. Dry
content after wet pressing was improved which enables
savings in dryer section steam consumption and enables
higher production speed.
On printing and writing grades Kemform can
support to increase filler content in paper with similar
strength and optical properties than earlier.
REFERENCES
1. Klass, C.P., Sharp, A.J. and Urick, J.M., Tappi C.A.
Report No. 57(55) (1975)
2. Hubbe, M.A., Tappi J. 69(8): 116-117 (1986)
3. Tam Doo, P.A., Kerekes, R.J., and Pelton, R.H., J. Pulp
Paper Sci. 10(4): J80-88
4. Henderson, K., Lewis, C., Tappi 2000 Annual Meeting
Proceedings, P.125
5. Lewis, C., Polverari M., Paptac 2007 Proceedings
6. Polverari, M., Lagos, D., Lewis, C., 2006 Mineral PIRA
Proceedings
7. Auhorn J.W. and Melzer J, Tappi 1979 Annual Meeting
Proceedings, p.49.
8. AB Akribi Kemikonsulter. www.dda.se/dda_manual.pdf
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