Kraft paper
Kraft paper is the type of paper with the highest strength for the production of e.g. B. paper bags, sandpaper or shopping bags. It consists of almost 100% cellulose fibers , only starch , alum and glue are added to achieve surface effects and increased strength.
Long-fiber softwoods (e.g. spruce , pine ) and especially slow-growing wood from Nordic countries are particularly suitable as raw materials . Straw can also be used on top . The use of waste paper , which contains many damaged fibers, would reduce the strength. Also fillers that z. B. make up a good part of the mass in graphic papers, cannot be used, as this would reduce the porosity and thus prevent the escape of the residual air after the paper sacks have been filled with compressed air.
The extraction of the pulp from the wood by means of the sulfate process gives the highest strengths. In addition, the sulphate process is better suited to utilizing resin-rich types of wood, which in particular enables the use of pine wood.
Another improvement is the milling of the pulp. In the process, so-called fibrils splice off the fiber surface, which interlock with one another and thus ensure crosslinking. The achievable strength increases sharply at the beginning of the grinding, but then flattens out.
Kraft paper is produced up to a basis weight (grammage) of 120 g / m². Paper with a higher grammage is called kraftliner ; it is used as cardboard or as part of corrugated cardboard .
See also
- Papyrolin , a fiber-reinforced paper.
Web links
Individual evidence
- ↑ Otto-Albrecht Neumüller (Ed.): Römpps Chemie-Lexikon. Volume 4: M-Pk. 8th revised and expanded edition. Franckh'sche Verlagshandlung, Stuttgart 1985, ISBN 3-440-04514-5 , pp. 2981-2986.
- ^ Günter Bleisch, Horst Goldhahn, Gerhard Schricker, Helmut Vogt (editors): Lexikon Verpackungstechnik , B. Behr's Verlag, Hamburg, 2003, 1st edition, p. 401, ISBN 978-3-89947-326-1 .