Canning and Fish Packaging Technology

Unit 13 - Paper and Board

13.1.3.Methods of producing wood pulp

• Mechanical wood pulp / G sound wood pulp: Pulp is obtained by mechanically grinding the timber. The pulp may be bleached or unbleached.
• Chemical wood pulp: Chipped wood is treated with chemicals at high temperature to remove lignin which leaves behind almost pure cellulose fibres. In this, there are two types (or processes)
• Sulphate pulp (Kraft pulp): This is used when strength is of major importance.
• Sulphite pulp: This gives a fairly strong general purpose material.

Both the above pulps may be bleached white or unbleached.

• Semi chemical pulp: Milder chemical processing combined with mechanical treatment.