2. Surface Treatments PPT 110 Chapter 18

3. Why Surface Treatments Provide Resistance to Penetration Enhance Surface Characteristics Improve some physical properties Precoating

4. Surface vs. Internal size Advantages  Optimum control  Less sensitive to changes in wet end  100% retention  Reduction in wet end deposits  Increased press clothing  Improve paper quality Disadvantages  Capital investment for sizing and drying equipment  Energy for drying  Size press problems shut down machine

5. Size Press Configurations Horizontal Vertical Incline Metering

6. Inclined Size Press

7. Puddle Size Press

8. Metering Blade Size Press

9. Principle Effects Absorption –Low solution viscosity –High temperature - ? About rolls –High sheet moisture – wet sponge –Porous sheet –Low internal sizing –Basis weight –Machine speed

10. Principle Effects cont. Pickup/Nip Rejection –Amount of solution –Nip pressure/width/hardness –High sheet roughness – greater film –Separation of sheet/roll –Solids content –Steam usage

11. Size Press Variables

12. Pickup – Effect of Hydraulic vs. Absorption

13. Film Splitting

14. Other Applicators Waterbox – board Tub Sizing - specialty

15. Coating Kitchen

16. Starch Corn, Tapioca, Potato et al –Amylose – linear –Amylopectin – branched Cooked –Batch or continuous –Thick boiling (cooled-setback) –Thin boiling Chemically modified Thermally modified

17. Coating Provide –Gloss –Slickness –Color –Printing detail –Brilliance Fill Void Areas No compensation for poor base

18. Pigment / Binder Pigments –Fine fillers –Plastics Binders –Water soluble –Polymer emulsions Additives

19. Coat – How? On Machine –Massey Print Roll –Air Knife –Metering Bar –Blade Off Machine –Brush –Cast

20. Comparison of Coaters

21. Cast Coater

22. Advantages On Machine Eliminate transport – reduce handling and damage Eliminate intermediate storage of rolls Reduce space requirements Reduce labor requirements Encourages early identification of coating stock quality issues Off Machine Provides greater flexibility Eliminates dependence between other operations Provides superior coating quality

23. Coating Cross Section

24. Factors Affecting Coated Sheets Surface Properties Composition of Coating Method of Coating Method of Drying Extent of Supercalendering

25. Coating ‘Pick’

26. SUPERCALENDERING Alternating Rolls  Filled  Steel High Gloss Amount of Pressure  Hard rolls – smoothness/thinness  Soft rolls – less holes Delicate Nip

27. Supercalender