Improvement Of The Recyclability Of OCC Pulp By Alkali Soaking Pretreatment

Old corrugated container (OCC) is a very important paper material in nowadays papermaking industry. But the fiber hornification has significant influence on the reuse performance for example the strength of recycled fiber and the efficiency of shattering process, and the recyclability of the recycled fiber has been becoming an important research issues in waste paper recycling field.In this paper, a new modification method of pretreating old corrugated container (OCC) with caustic solution soaking before repulping or adding sodium hydroxide during repulping was studied. The experiment adopted Korea OCC as main raw material and the pieces of OCC material was soaked with NaOH solution before repulping. Inord to be propitious to the actual production, the pre-treated temperature was under the natural temperature:23±2?, and the pulp consistency was 12% so that the pieces of OCC could be submerged fully by the solution. The appropriate conditions of soaked pretreatment were NaOH dosage 2.0%, soaking time 2h, and five different methods of soaking pretreatment was introduced under the optimal pretreatment conditions.The proposed pretreatment has been developed to improve mechanical properties of recycled linerboard made of the OCC, and may improve swellability of recycled fibers, leading to significant increase in tensile, ring crush, and burst index of the recyled sheets, which were increased by 18.99%, 22.29% and 29.75% respectively.Comparing with the control OCC pulp, the shattering process of the OCC soaked with NaOH solution become easier obviously. The shattering rate was increased from 77.63% to 91.49% and the thick slag rate was reduce from 30.36% to 10.62% when the shattering time was 10min, and the shattering time was saved up 30%-50% when the shattering was completed, namely shattering rate was more than 90%. Thus increase the productivity of the repulper. Comparing with the conventional method of post-treating OCC with caustic solution soaking after repulping, the strength properties after caustic soaking pretreatment has some improvement under the same conditions. Such as breaking length, ring crush index and burst index were increased by 6.43%,7.42% and 10.13% respectively. The pulp yield was increased from 56.04% to 80.02% when the shattering time was 10min.Bleaching of pulp from AOCC was conducted and the results show that alkaline soaking pretreatment of OCC and DP bleaching sequence can lead to the whiteness of 60%-65%ISO. Caustic soaking pretreatment of OCC renders the pulp to be more readily bleached. In this way, employment of OCC as a large fibre furnish in bleached paper grades will be possible. In conclusion, OCC could be pretreated efficiently without changing the main recycling process by soaking pretreatment which provides a new method for the recycling of OCC.