THE EFFECT OF SUPERHEATED STEAM DRYING ON THE PROPERTIES OF TMP PAPER

The effect of drying paper made from thermomechanical pulp (TMP) by di rect contact with superheated steam was determined with respect to the physical and optical properties of the sheet. The results were compar ed with those for paper dried by direct contact with hot air. Superhea ted steam drying improved strength properties; burst index, tensile in dex and elastic modulus were increased by 20-30% relative to sheets dr ied in air The increase in strength was attributed to an increase in b onded area caused by the higher sheet temperatures reached in steam dr ying. As a result of the increased bonding but not due to any darkenin g, the brightness of the steam-dried sheets decreased by 5 points. Ste am drying of TMP sheets results in strength and optical properties mor e characteristic of paper made from CTMP.