1. Atrak Pulp & Paper Industries Ltd.
Paper & Board Coating

2. Why is Paper Coated ??
Cellulose Fiber Size :
Soft Wood : Length 3 ~ 4 mm Diameter 25 ~ 50 Micron
Hard Wood : Length 0.8 ~ 1.5 mm 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.

3. Why is Paper Coated ?? Printability Smoothness Uniformity
Ink Receptivity
Visual Properties
Brightness
Opacity
Gloss
Functionality
Reduce Ink Consumption
Glueability

4. A Binder is used to adhere the pigment to the fibers.
Coatings Purposes
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.

5. Photo of Un-coated Paper
Magnification 200x

6. Photo of Coated Paper
Magnification 2000x

7. Cross Section of Coated Paper
Magnification 2000x

8. Coating Ingredients 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.

9. Coating Ingredients, Dry Weight %

10. Function of Coating Ingredients
Pigment : Govern optical & printing properties of the paper.
Binders : Give the cohesion of the coating & adhesion of pigments to the base
paper without affecting the properties brought by pigments.
Dispersant : To disperse the pigments.
Cross Linker : Provide wet pick resistant.
OBA : To increase brightness.
Lubricant : Improves flow properties, prevent coating adhesion on to calendar.
Thickener : Modifies the rheology and/or the water retention of the colour.
De-Foamer : Reduces foam.

11. Pigments
Clay
Interest : paper & ink gloss, rotogravure printability, stiffness.
Draw back : lack of brightness, closed coating.
GCC
Interest : brightness, low viscosity, high solid, ink porosity.
Draw back : gloss, low water retention, fiber coverage.
TiO2
Interest : opacity, brightness, whiteness
Draw back : cost, latex demanding.

12. Plastic Pigment PCC Silica
Pigments
Plastic Pigment
Interest : high gloss, brightness, low specific gravity.
Draw back : price, more latex demand.
PCC
Interest : brightness, viscosity, low abrasivity.
Draw back : cost, more latex demand.
Silica
Interest : brightness, high specific area, opacity.
Draw back : cost, need higher cohesion binder.

13. Pigments Talc Satin White
Interest : smoothness, non abrasive, best for gravure.
Draw back : gloss.
Satin White
Interest : high gloss.
Draw back : work ability.

14. Pigment Structure
Magnification 5000x

15. Pigments Properties Brightness : 84 ~ 96 % ISO
Particle Size Distribution : 0.22 ~ 2.00 Micron
Surface Area :
Fine Clay 20 ~ 25 m2/gram
Standard Clay 18 ~ 20 m2/gram
Calcined Clay 13 ~ 17 m2/gram
GCC ~ 13 m2/gram

16. Pigments Properties Refractive Index :
Interface
Substrate
Angle I
Angle R
Light Comes
Light Refracted
R.I. is amount of lights refracted by the pigments.
High R.I. = High Opacity.

17. Pigments Properties 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
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
2.70
97 ~ 98
PCC
CaCO3
0.1 ~ 1.0
Variable Rod Like
1.59
96 ~ 99
Calcined C.
Al2O3.2SiO2
0.7
Aggregated Platy 93

18. Binders
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 : Stiffness, price.
Draw Back : Mottling, low binding power, rheology at high speed.

19. Binders CMC PVA Protein
Interest : Water retention, rheology, binding power.
Draw Back : Handling.
PVA
Interest : Excellent binding power, gloss, brightness.
Draw Back : Price, rheology at high level.
Protein
Interest : Water retention, binding power, bulkier coating layer.
Draw Back : Handling, rheology at high level, microbiology control.

20. What Does Binder Do ? To hold the pigments on the base paper.
To help give good printability.
To give special characteristic.
Pigment
Binder

21. Latex Structure
Latex Particles
Pigments Particles

22. Styrene Butadiene Acrylic. Vinyl Acetate.
Main Binder Types
Styrene Butadiene.
Styrene Acrylic.
Styrene Butadiene Acrylic.
Vinyl Acetate.

23. Dry and Wet Pick Strength. Sheet and Ink Gloss. Printability.
The Influence of Binder
Dry and Wet Pick Strength.
Sheet and Ink Gloss.
Printability.
Blister Resistance.
Ink Drying.
Yellowing.

24. The Influence of Binder
Sheet Gloss
Ink Gloss
Pigment
Coat Weight
Binder
Solid Content

25. Rheology Modifier (Thickener)
Increase low shear viscosity to allow proper application.
Adjust high shear viscosity to provide coat weight control and run-ability.
Increase water retention.
Can enhance optical and printing properties of the finished sheet.

26. Rheology Modifiers Starch Protein Poly - Acrylates  Alco Gum
Sodium Alginate
Urethane Modified Acrylates  Poly Phobe
Cellulosic  Carboxyl Methyl Cellulose (CMC),
Hydroxyl Ethyl Cellulose (HEC)

27. Atrak Pulp & Paper Industries Ltd.
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