Wet runnability of fibre furnish for magazine papers

摘要

Tutkimuksessa selvitettiin mekaanisen massan ja armeeraushavusellun vaikutuksia LWC massojen märkäajettavuusparametreihin. Puristinkuivista ja kuivista paperinäytteistä mitattiin dynaamiset vetolujuus- ja relaksaatio-ominaisuudet suurella vetonopeu-della, joka oli vastaava kuin uudenaikaisilla paperikoneilla. Armeeraussellun lisääminen laski märän paperin jäännöskireyttä kun märkäpuristuk-sen jälkeinen kuiva-ainepitoisuus oli vakio. Armeeraussellun osuutta säätämällä voidaan helpottaa paperikoneen märkäpään ja kuiva-tusosan ajettavuutta. Laboratoriokokeiden tulokset ovat yhtenevät Pilot-koepaperiko-neen tulosten kanssa, jotka on esitetty tässä artikkelissa. Massapohjan alhainen jään-nöskireys oli koepaperikoneella korvattava suuremmalla rataa vakauttavan koneenosan teholla, kun kaikki muut prosessin muuttujat pidettiin muuttumattomina.%The purpose of this study was to examine effects of mechanical pulp types and softwood Kraft pulp as a reinforcement pulp on the web runnability indicators of LWC fibre furnishes. Dynamic tensile strength and relaxation properties of wet and dry paper were investigated with very high speeds corresponding to the draw conditions found on modern paper machine. According the findings, addition of BSK seems to decrease residual tension in wet paper when press dryness between furnishes remains same. Controlling BSK content therefore facilitates the optimization of wet end and dryer section runnability on a paper machine. This finding is in agreement with the laboratory vs. pilot machine results presented in this article. Poor residual tension had to be compensated by greater stabilizing runnability component power when all the other process variables were unchanged. Attempts have been made to determine or improve web runnability using traditional paper testing methods. One of the key items in this paper is the importance of knowing the wet runnability properties of one's basic furnish. The findings show clear differences between wet residual tension (relaxation) and dry tensile strength. This feature is im- portant in the sense that the viscoelastic-plastic behavior of fibres and fibre bonds in a wet fiber network differs based on elastic modulus, strength and residual tension. According the findings, it is possible to optimize the furnish used so that the amount of BSK is optimal for the required dry paper and end user properties (coating process, printing, etc.).