Paper manufacture
The manufacture of paper depends on many different parameters. Grammage, the desired sheet properties as well as the production capacity are only some of them. In order to make the topic understandable we in the following want to show you a simplified production process.
Stock preparation and head box
All raw material components as cellulose, pulp wood or waste paper are fed into stock preparation. There dyestuffs and auxiliary substances are added according to production recipe. This mixture is diluted and cleaned of small air bubbles. The head box spreads the flow evenly and uniformly the entire width of the machine. On the wire the fibres precipitate in layers and at the same time the water is sucked off towards below. After this procedure the paper still contains about 80% of water.
Wire section
During this phase the structure of the wire is pressed into the fibrous web. In order that the structure shall be the same on both sides there are double wire machines. There might be differences in the properties between the wire side and the surface which might lead to an asymmetric construction of the paper. An egotteur (wire-covered roll) can counter-act and presses the fibre flocks into the sheet.
Press section
During the press section the rolls further dehydrate the wet fibre fleece. The machine consists of several roll systems, whereupon the pressure put on the fibre fleece is growing permanently. The press procedure leads to a compression of the paper structure and thus to a higher consistency. At the end of this section the paper has a maximum solids content of 50 to 55%.
Drying section
Since paper is a shrinking material the final density can be determined only when there is a rest wetness of 6-10%.The air serves as transport medium for the vapour released by the heat. Depending on which drying procedure is used we make a difference between contact, convection and the novel infra-red drying.
Glazing
After drying the paper is glazed in glazing rollers. Of late there often is a soft calendar (a roll covered with a soft plastic cover). The glazing achieved here is much more effective and better than the one by two metal rolls.
Reel
Quality control is made by a hole detector in order to discover possible faults. On the reel cutter paper rolls are cut to the widths ordered by the customer and the format cutter chops the paper to sheet format.
Surface refinement
In order to improve properties the paper is refined afterwards. Thus, among others the desired smoothness and brilliance as well as the ability for recycling of the paper.