While the basics of papermaking process has changed very little over the centuries, woodfibre only became the main raw material for mass paper production in the mid-19th century. The key advantage of using woodfibre is that it is a natural renewable resource. Other advantages of using wood include its intrinsic strength, weight per unit length and availability at reasonably low cost.
The manufacture of the first paper is attributed to the Chinese in the 1st century AD. Initially, paper is said to have been made from the fibrous phloem that underlies the bark of the mulberry tree. The idea seems to have evolved from the manufacture of felt. Just as felt was made by compacting animal fibres onto a sheet, so paper was made by compacting plant fibres. Mulberry fibres were mixed with water to form a mash which was then shaken into an even layer on the surface of a fine sieve. After it had drained for a while, the sheet so formed was carefully picked up by the corners, smoothed out and left to dry.
Papermaking secrets were jealously guarded by the Chinese, until the 7th century AD, when Chinese papermakers were among the prisoners of war captured in a battle with an Arab army. The secret was uncovered and papermaking techniques started to spread across the world.
Today, woodfibre arrives at the mill as whole tree trunks, wood chips or paper pulp from other mills. Recycled or waste paper can also be used.
- At the pulp mill, the logs are debarked and are ground to release fibres for mechanical wood pulp or wood chips are processed for chemical pulp.
- The objective of pulping is to break down and dissolve the lignins, the natural ‘glue’ that holds the wood together.
- Paper made mechanical pulp is used for newsprint, speciality papers, tissue, paperboard and wallboard.
- Paper made from chemical pulp and coated to ensure a smooth surface for printing is called coated fine paper (or woodfree paper) and used in the production of calendars, coffee table books, magazines and business reports.
- In the recycled pulping process, newspapers, cardboard boxes and magazines are de-inked at some of Sappi’s mills. End uses for paper made this way include linerboard and fluting for onward conversion into cartons and boxes.
In the recycled pulping process, newspapers, cardboard boxes and magazines are de-inked at some of Sappi’s mills. End-uses for paper made this way include linerboard and fluting for onward conversion into cartons and boxes.
Untreated wood pulp has a brownish colour and is often bleached to make it white. Pulp can be bleached with chlorine or chlorine compounds, as well as with oxygen or hydrogen peroxide. Sappi pioneered the Sapoxal oxygen bleaching process. This world first is now an industry standard.
‘Elemental chlorine free’ (ECF) refers to a bleaching sequence in which no chlorine is used. TCF stands for ‘totally chlorine free’ and refers to bleaching sequences in which no chlorine-containing compounds such as chlorine dioxide are used.
Coated papers contain a layer of coating material on one or both side. The coating materials of pigments and fillers help to improve the printing surface of the paper. Printing and writing papers made from bleached chemical pulp are used for general printing, photocopying and stationery. Referred to as ‘uncoated’, these papers are not coated with a layer of pigment.