Recycling makes very responsible use of raw materials for cardboard
The use of raw materials in paperboard production depends on the type of paperboard. We distinguish between wood board (made from wood pulp) or gray board (made from waste paper).
We refer to recycled waste paper as secondary raw material. The simpler the end product, the more of this secondary raw material it contains and the more environmentally friendly it is. Solid board is made from up to 100% recovered paper.
Primary fiber pulps, on the other hand, are components recycled from wood, i.e. mechanical pulp, waste from sawmills, pulp from thinned wood or semi-chemical pulp. Pulp is produced in a closed cycle from bark chips, resin and lignin – a type of binder that holds the wood fibers together. This produces a brown, fibrous sulfate pulp of high strength. Since almost all the energy for pulp production is obtained from the combustion process, this production process can also be said to be environmentally friendly.
The latter more valuable components are used in paperboards, the use of which must meet special requirements. For these higher-quality products, additives such as starch, sizing agents, and colors are also used. Finally, during surface finishing at the end of production, binders, mineral pigments and waxes can also be used to give the board the finish appropriate to its use.
The production process of cardboard
Waste paper and pulp are first prepared for production. This means that the waste paper is cleaned of foreign bodies and dirt and ground up. After chemical decolorization (deinking), the recycled material prepared in this way is mixed with water and additives to form an aqueous solution. The pulp, after being broken down into its fibers and ground to a pulp, is combined with the prepared waste paper.
The further production steps depend on whether the board is wound board or fourdrinier board.
For the production of “wound board”, the highly diluted fiber suspension is pumped onto several circular screens, where the so-called sheet formation takes place and the material is dewatered for the first time by pressing. The fiber fleece obtained in this way is then wound wet onto a so-called forming roll until the desired layer thickness is achieved. By cutting the cardboard cylinder, a sheet is created that passes through a three-level dryer and is then cut to the desired size by longitudinal and cross cutters.
For the production of Fourdrinier board, the pulp is applied to a wire section consisting of a bottom wire and a top wire. A headbox mounted at right angles to the running direction ensures uniform distribution of the stock. The fiber suspension is dewatered between the two screens, creating a continuous fiber layer that is removed at the end of the screen and fed into a press area where the wet paperboard web is pressed out through felts. The residual moisture is then evaporated in the drying machine, and the cardboard web is then smoothed and rolled out or cut directly into sheets.
“Machine board” is usually made up of plies of different compositions, with the top plies usually made of the higher quality material. Machine board is produced by pressing together several fiber webs produced simultaneously on cylinder mold and/or Fourdrinier machines. (Handmade paperboard).