Pigment Volume Concentration

Ultra-Fine Particle Binder Technology for
Low Cost Manufacture of Coated Paper and
Board
Christopher Lewis, Dr Robert Hardy
Kemira Chemicals, Inc., USA
Outline
1. Technology Overview
2. Theory
A. Pigment Volume Concentration
B. Binder Volume Concentration
C. Other Mechanisms
3. Application
4. Pilot Study
A. Coated Board
B. Communication Papers
5. Conclusions
Technology Overview
• Novel Ultra-Fine Particle Size Technology (UFPST)
• Provides a mechanism to significantly reduce total binder
level in the coating color
• Reduction in carbon footprint – mass balance
• The morphology (size) allows for the binder reduction
without compromising surface strength
• Reduction in overall binder level leads to an increase in
the system's Pigment Volume Concentration (PVC)
• PVC increase can be beneficial for enhancing coating properties
Technology Overview
Standard SB Latex
PS, nm
SSA, m2/g
125-150 nm
Equal volume but
8 x more particles
UFPST
PS, nm
SSA, m2/g
60-70 nm
66
125
125
46
Pigment Volume Concentration (PVC)
• Pigment Volume Concentration is defined as the
ratio of the volume of pigment divided by the
total coating volume (pigment + binder)
• PVC = (Pigment Volume/Pigment Volume + Binder
Volume) x 100
• The Critical Pigment Volume Concentration (CPVC)
• Volume of pigment is exactly equal to the volume
of the binder
• Generally occurs around 50%
•
Coating dependent
• Sufficient binder to fill voids between pigment
particles
• Left of CPVC more binder than pigment on a
volumetric basis (paint)
• Right of CPVC more pigment than binder (paper)
PVC and Binder Volume Concentration
• Binder Volume Concentration (BVC) can also
be determined
•
•
•
Pigment Volume = [(parts pigment/total
parts)]/(density pigment)
Binder Volume = [(parts binder/total parts)]/(density
binder)
PVC = [Pigment Volume/(Pigment Volume + Binder
Volume)] x 100
• BVC = (100% - PVC)
• For a 100% Ground Calcium Carbonate system
using 10 parts SB binder per hundred pigment
parts (pph) BVC can be determined
• For a given control volume, the number of
binder particles can be determined knowing
the BVC for that binder/pigment system
Binder System
BVC
10 pph SB
22.13%
10 pph UFPST (1:1)
20.78%
5 pph UFPST (2:1)
11.60%
Binder Volume Concentration
•
•
Control volume of 1 micron3 (reasonable given the pigment is
approximately 0.7 microns
From the particle number and binder size (dp), functional area can be
determined (total binder surface area)
1 micron3
1 micron3
1 micron3
SB Latex (10pph)
dp = 150 nm
N = 126
A = 8.9 micron2
UFPST (5 pph) (2:1)
UFPST (10 pph) (1:1)
dp = 75 nm
N = 941
A = 16.6 micron2
dp = 75 nm
N = 525
A = 9.3 micron2
Pigment Volume Concentration (PVC)
• Ultra-Fine particle size facilitates binder
reduction while maintaining binder surface
area
Replacement of 2 or 3 parts of SB or SA latex
with one part of UFPST is typically observed
• As pigment volume concentration increases, a
sharp break occurs in the coating’s film
properties
• Increased void volume in coating structure
• Increasing pigment volume in any coating
formulation provides opportunity for optical
and printing improvements
•
•
•
•
Opacity
Brightness
Bulk
Ink Set Rates
• UFPS morphology allows for this without
compromising binding strength
Property
•
CPVC
0
100
PVC
8
PVC
• 4.5 parts of SB latex replaced systematically
by UFPST at a replacement ratio of 2:1
• 100% replacement of the SB latex is
achieved with 2.2 parts UFPST
• With increasing PVC of coating, sheet
brightness and opacity increase
• 12 parts of SB replaced systematically by
UFPST at a replacement ratio of 2:1
• 100% replacement of the SB latex is
achieved with 6 parts UFPST
• PVC from 74.7% (PVCi) to 86.5% (PVCf)
• As PVC increases, coating structure
becomes more open
• Decreasing Gurley Porosity values
• Strength not compromised (IGT Dry Pick)
Other Mechanisms
• Toivakka and Bousfield (2003)
and Alam et al. ( 2008 ACFS)
show that a large amount of
binder is not being used to
form joints, just filling up
pore space.
• Black et al. (2010 ACFS) show
that latex not always able to
move to joint.
Hypothesis – small binder can end up
near pigment contact points. Better use
of binder:
Pigment
2 microns
Pigment
2 microns
Other Mechanisms
Hypothesis 2: Fine binder may lead to a more
open pore space
• Fine binder is pulled to particle
contacts, not sitting in open space
Rheology
• Stable rheology
• Typically lower Brookfield
viscosities and high shear
viscosity (Hercules)
• Lower elastic and viscous
modulus observed
• Lower viscoelastic
response
• Lower blade/rod loads
often observed
• Viscous effect consistent
with Brookfield and
Hercules data
Divalent Cation Stability
• Divalent cations acts as a
“fixative” for the inks in
pigment based ink jet ink
• Calcium chloride
• 1% of calcium ion (Ca2+) on a
volumetric basis was
introduced to each binder
system via a 10% calcium
chloride solution
• No destabilization with UFPST
High SSA SB Latex
UFPST
Pilot Evaluation – Bleached Board
•
•
•
Coated Bleached Board - 2C1S
The focus of the study was on the top coat
The pre-coat was applied at the mill site with a jet applicator
blade coater (13 g/m2)
•
•
•
Top coat applied at the pilot facility with a jet applicator blade
•
•
•
•
•
•
100 parts GCC
Constant for all the top coat conditions
500 meters/minute (m/min)
Top coat target weight was 13 g/m2
Top coat pigment system 50% GCC and 50% kaolin
Held constant for all conditions
The control formulation contained 16 parts of Styrene
Acrylate (SA)
SA systematically replaced at 2:1 replacement with UFPST
Conditions – Bleached Board Evaluation
Control
1
2
3
4
Fine Particle High
Glossing Clay
50
50
50
50
50
UFGCC
50
50
50
50
50
UFPST
0
2
4
6
8
16
12
8
4
0
65.5
65.5
65.5
65.5
65.5
Latex
Target solids (%)
Results – Bleached Board Evaluation
• The PVC of the
control was 71.3%
and that of
condition #4 was
82.8%
• There was an
increase in gloss
of about 5 units
• Slight increase in
brightness
• About ½ point
Results – Bleached Board Evaluation
• Increased porosity –
Controllable
• No Loss in Glueability
• Faster ink set rates
observed (at equal pick)
• Similar (NPA) slopes
• Very Good Printing Results
Print Rating
Description
5-8
Very Good
9 - 12
Average
>13
Poor
Pilot Evaluation – Communication Papers
•
•
Communication Grade
C1 = Control 1 =
clay/carbonate
– Two binder system
•
C2 = Control 2 = 100%
carbonate
– Single binder system
•
UFPST to replace the
portion/all of the binder
system of control 2
Objective:
1. Sheet gloss development
by replacement of Binder
2
2. Increase solids due to
friendlier rheology to
further enhance gloss
development
Pigment System
Solids
C1
C2
A
B
C
D
GCC/C
lay
GCC
GCC
GCC
GCC
GCC
65% 65% 69% 70% 70% 69%
Binder 1
3
0
0
0
0
0
Binder 2
3
7
3
1.5
1
0
UFPST
0
0
1.5
1.8
2
2.5
Starch
7
4
4
3
4
5
Results Gloss – Communication Papers
Gloss
• Increase in gloss of 4
– 7 points
depending on level
of substitution
• Able to match and
exceed the gloss of
the clay containing
formulation with a
100% carbonate
pigment system
Results Porosity – Communication Papers
Porosity
• Able to open the
coating structure
• Achieved similar
porosity to the clay
containing sheet ,
or increased it
• Controllable
response
Results Brightness – Communication Papers
Brightness
• Brightness increased
• Two mechanisms
impacting
1.
Moving to brighter
pigment system (C1 to
C2) with higher
carbonate
2.
Increasing PVC
improves the light
scatter with lower total
binder use with the
UFPST (C2 to D)
Conclusions
• UFPST binder allows for significant reductions in binder level
without loss in surface strength
• Binder replacement ratios of 2:1 and higher are typical, giving
opportunity for meaningful reductions in coating costs
• Reduction in overall binder levels lead to an increase in the
systems Pigment Volume Concentration (PVC)
• Increased PVC yields significant enhancements in optical
properties, more open coating structure, and faster ink set rates
• Ink set rates have been increased without the detrimental effect
of picking or piling
• The UFPST provides consistent rheology and coating color
stability with and without the presence of divalent cations such
as calcium
Contacts
Nilton Almeida - Bus&Dev Applications, Paper, South America
Tel. +55 11 2189-4900 | Mobile +55 19 99664-4359
[email protected]
Talita Dultra Application Specialist, Paper Brazil
Mobile +55 11 97127-2936
[email protected]
Christopher Lewis Regional Applications Manager, North America
Tel. +1 360 901 7428
[email protected]

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