Coating Basics - Atrak - pulp and paper industries

Report
Cellulose Fiber Size :
• Soft Wood
• Hard Wood
: Length 3 ~ 4 mm
: Length 0.8 ~ 1.5 mm
Diameter 25 ~ 50 Micron
Diameter 10 ~ 35 Micron
Pores between Fibers : 10 ~ 100 Micron.
Printing Dot Diameter : 25 ~ 50 Micron.
Coating the paper surface with Fine Pigments (Diameter 1~2 Micron)
to cover the fibers and fill the pores.
Printability
 Smoothness
 Uniformity
 Ink Receptivity
Visual Properties
 Brightness
 Opacity
 Gloss
Functionality
 Reduce Ink Consumption
 Glueability
The whole purpose of a coating is to attach uniform
layer of pigment to the base sheet.
A Binder is used to adhere the pigment to the fibers.
There are additional additives in the coating formula to help in
processing or enhance final sheet properties.
Magnification 200x
Magnification 2000x
Magnification 2000x
Natural Pigment: Clay, Calcium Carbonate, Talc.
Synthetic Pigment: PCC, Plastic Pigment, TiO2, Silica, Satin White.
Synthetic Binder: Latex.
Hydrosolubles Binder: Starch, CMC, PVA, Casein.
Additives: Dispersant, Thickener, Cross Linker, OBA, Lubricant, De-Foamer, etc.
Water.
Clay
GCC
TiO2
Interest : paper & ink gloss, rotogravure printability, stiffness.
Draw back : lack of brightness, closed coating.
Interest : brightness, low viscosity, high solid, ink porosity.
Draw back : gloss, low water retention, fiber coverage.
Interest : opacity, brightness, whiteness
Draw back : cost, latex demanding.
Plastic
Pigment
PCC
Silica
Interest : high gloss, brightness, low specific gravity.
Draw back : price, more latex demand.
Interest : brightness, viscosity, low abrasivity.
Draw back : cost, more latex demand.
Interest : brightness, high specific area, opacity.
Draw back : cost, need higher cohesion binder.
Talc
Interest : smoothness, non abrasive, best for gravure.
Draw back : gloss.
Satin
White
Interest : high gloss.
Draw back : work ability.
Magnification 5000x
Brightness : 84 ~ 96 % ISO
Particle Size Distribution : 0.22 ~ 2.00 Micron
Surface Area :
Fine Clay
Standard Clay
Calcined Clay
GCC
20 ~ 25
18 ~ 20
13 ~ 17
8 ~ 13
m2/gram
m2/gram
m2/gram
m2/gram
Angle I
Light Comes
Interface
Substrate
Light Refracted
Angle R
Pigments
Composition
Particle Size
Shape
R.I.
Brightness
Clay
Al2O3.2SiO2.2H2O
0.3 ~ 5.0
Hexagonal Platy
1.56
80 ~ 90
GCC
CaCO3.MgCO3
0.7 ~ 2.0
Cubic Prismatic
Platy
1.65
87 ~ 97
Talc
MgO.4SiO2.H2O
0.3 ~ 5.0
Platy
1.57
85 ~ 90
Gypsum
CaSO4.2H2O
0.2 ~ 2.0
Roundish
1.52
92 ~ 94
Titanium
TiO2
0.2 ~ 0.5
Rod Like
2.55
98 ~ 99
Titanium
TiO2
0.2 ~ 0.5
Roundish
2.70
97 ~ 98
CaCO3
0.1 ~ 1.0
Variable Rod Like
1.59
96 ~ 99
Al2O3.2SiO2
0.7
Aggregated Platy
1.56
93
PCC
Calcined C.
Latex
Hard Latex
: Higher gloss, low binding power, mainly for top coat.
Web Offset Latex : Blistering resistance, low binding power.
Soft Latex
: Lower cost, high binding power, best for pre coat.
Starch
Interest
Draw Back
: Stiffness, price.
: Mottling, low binding power, rheology at high speed.
CMC
Interest
Draw Back
: Water retention, rheology, binding power.
: Handling.
PVA
Interest
Draw Back
: Excellent binding power, gloss, brightness.
: Price, rheology at high level.
Protein
Interest
Draw Back
: Water retention, binding power, bulkier coating layer.
: Handling, rheology at high level, microbiology control.
Pigment
Binder
Pigment
Latex Particles
Pigments Particles
Pigment
Coat Weight
Binder
Solid Content

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