EFFECT OF PAPERMAKING PARAMETERS ON THROUGH DRYING OF SEMI-PERMEABLE PAPER

Possible extension of industrial practice of through drying from its c urrent use for drying light weight grades etch as tissue papers requir es knowledge of the effect of papermaking parameters. As these effects interact and the variables occur in only limited combinations for mac hine-produced paper, these effects cannot be extracted directly from m easurements with papermachine sheets. Therefore the effects on through drying characteristics of important parameters in commercial papermak ing such as beating, bleaching, wet pressing and formation were examin ed through experiments with handsheets. Bleaching has no significant e ffect on either of the two key aspects of through drying, i.e. momentu m transport and drying rate behavior, while beating as well as wet pre ssing have a strong effect on momentum transport but only a small impa ct on drying rate characteristics. Through drying rate depends sensiti vely on the quality of sheet formation while this parameter has only a small effect on momentum transport. As the increase in drying time fo r paper of poorer formation would have a direct effect an the size of an industrial dryer, this finding is of particular relevance to the ex tension of through drying to heavier grades of paper.