5. • Process of removing bark from wood log
• Converting these wood log into chips
6. RMP sandwiches wood chips
between two revolving disks. Heat
due to friction softens the lignin
and allows greater separation of
the cellulose fibres, while
contributing less fibres damage
• Thermomechanical pulping ( TMP) – 110°C to
150 °C
• Chemithernomechanical pulping(CTMP) – pre-
trearment with sodium suplhite
7. 1. Alkaline
• Soda process
• Kraft process (sulfate process)
• Sulfite process
2. semi-chemical process
• Neutral-sulfite semichemical (NSSC) process
8. • Bleaching is a chemical process applied to chemical and mechanical pulps, primarily to increase their
brightness but it also improves the cleanliness of pulp through removing extractives and other contaminants.
9. Inter-fibre bonding can be increased by
mechanical refining, in which the surface
structure of the fibre is modified by swelling the
fibre in water and increasing the surface area.
Hydrapulper
10. Additives such as alum or synthetic
resins are used to increase the water
repellancy of the fibres. Wet strength
resins can be added to increase the
strength of the product when
saturated with water. Fluorescent
whitening agents (FWAs), also known
as optical brightening agents (OBAs),
can be added at this stage to increase
whiteness and brightness.
11. • The fibre in water suspension, roughly 2% fibre and 98% water, is formed in an even layer.
• This is achieved by depositing the suspension of fibre at a constant rate onto a moving plastic mesh, known as the
wire. On some machines, forming is carried out on a wire mesh covered cylinder.
• Forming results in a layer of entangled fibres from which water is then removed by drainage, which may be assisted
by vacuum.
• Dewatering involves pressing, drying .
12. • White pigmented coatings are applied to one or both sides of many types of paper and board on-machine.
• The coatings comprise mineral pigments, such as china clay and calcium carbonate, and synthetic binders
(adhesives), dispersed in water.
• Excess coating is usually applied, it is smoothed.
13. • In many applications, the surface of the sheet needs
improvement so that any characters imposed on the sheet
are legible.
• This is achieved by calendering, a process that reorients the
surface fibers in the base sheet of paper (or the coating
applied to the surface) through the use of pressure.
• This serves to smooth the surface, control surface texture
and develop a glossy finish. Such papers are known as
machine finished (MF).
