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  Making Pulp from Wood

Combination Pulps

Thermo-Mechanical-Pulp (TMP) and Chemi-Thermo-Mechanical-Pulp (CTMP) are a combination of the mechanical and chemical processes. De-barked logs are chipped in both, then heated to extreme temperatures to soften them before passing through grindstones for mechanical reduction to fibres. The difference is that chemicals are sprayed onto the chips in the CTMP process to reduce the undesirable effects of the retained natural wood substances. The main disadvantage of this form of pulping is the high energy demand.

The consumer often requires high quality papers which retain strength, do not discolour during storage or go yellow when exposed to light. One of the most effective ways of achieving all three is bleaching which has the added advantages of improving absorption capacity and getting rid of small residues of bark or wood, as well as giving a high level of purity, particularly important when the paper is being used for hygiene, medical or certain food packaging purposes.

For many years chlorine was used because of its efficiency. In recent years however it has been discovered that alternative bleaches such as chlorine dioxide or oxygen have a lower impact on the environment and they are now increasingly being used throughout the industry.

© 2003 design by Ahmed Abdel-Rahman