The effect of recycled fiber and dry strength agent addition on paper properties

In this study, the effect of 10%, 20%, 30%, 40% and 50% recycled fiber addition to suspension of virgin (mixed pine) fibers on strength and optical properties of kraft liner handsheets were to investigated. Also, 0.75% cationic starch (CS) and 0.75% luredur seperately added recycled fiber containing in different ratios and recycled fiber-free fiber suspensions. Thus, effects of dry strength agent type on handsheet properties were determined. In addition, of fiber dimension and viscosity of virgin kraft and recycled pulps were determined. Viscosity of virgin kraft pulp was found to be higher than those of recycled pulp. On the other hand, fiber length of virgin pulp was longer than that of recycled pulp. The tensile index, stretch, TEA, burst index and bulk values of handsheets were decreased with increasing ratio of recyled fiber addition. On the contrary, tear index and brightness of handsheets were increased with increasing ratio of recyled fiber addition. The occurring changes in handsheet opacity with increasing recycled fiber addition were not linear. CS addition to fiber suspension were more efficient than luredur addition with regard to tensile index, stretch, TEA, burst index and brightness of handsheets. On the contrary, the effect of luredur addition on tear index and opacity was more pronounced compared to CS addition. Consequently, the papers in the same strength properies compared to control papers and more recycled fiber containing can be obtained by adding dry strength additives such as CS and luredur to fiber suspension. Key Words Recycled fiber, virgin fiber, CS, luredur, handsheet properties, kraft liner