PULP GRADES

Pulp grades are classified according to their production process.

They are classified by original species: softwood or hardwood and by the production process used: chemical or mechanical and bleached or unbleached

Mechanical Pulp
Semi-Chemical Pulp
Chemical Pulp
De-inked Pulp

Photo of pulp

MECHANICAL PULP

Stone Groundwood pulp: by grinding wood into relatively short fibres. This pulp is used mainly in newsprint and wood-containing papers, like LWC (lightweight coated) and SC (super-calendered) papers

Thermo-mechanical pulp (TMP): produced in a thermo-mechanical process where wood particles are softened by steam before entering a pressurised refiner. TMP has mainly the same end-uses as stone groundwood pulp. Variants of the above two processes are pressurised stone groundwood pulp and refiner mechanical pulp.

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SEMI-CHEMICAL PULPS

Semi-chemical pulp: produced in a similar way to TMP (thermo-mechanical pulp), but the wood particles are chemically treated before entering the refiner. This pulp has properties suited to tissue manufacture. Some chemi-thermo mechanical pulp (CTMP) pulp is used in printing and writing grades. CTMP pulp is classified under semi-chemical pulps in the Harmonised System of the Customs Cooperation Council. In the Food and Agricultural Organisation (FAO) of the United Nations, as well as other industry statistics, such chemi-thermo mechanical pulps are grouped with mechanical pulp.

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CHEMICAL PULPS

Sulphite pulp: produced by cooking wood chips in a pressure vessel in the presence of bisulphite liquor. End-uses range from newsprint, printing and writing papers, tissue and sanitary papers. The sulphite can be either bleached or unbleached.

Sulphate (or kraft) pulp: pulp produced by cooking wood chips in pressure vessels in the presence of a sodium hydroxide (soda) liquor. The pulp may be unbleached or bleached. End-uses are widespread, with bleached pulp particularly used for graphic papers, tissue and carton board, wrappings, sack and bag papers, envelopes and other unbleached speciality papers.

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DE-INKED PULPS:

Pulp made from recovered paper from which inks and other contaminants have been removed.

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For further information on pulp see the section on Pulp Production