สำนักราชบัณฑิตยสภา

241 Somporn Chaiarrekij et al วารสารราชบัณฑิตยสถาน ปีที่ ๓๗ ฉบับที่ ๑ ม.ค.-มี.ค. ๒๕๕๕ Preparation of softwood pulp Commercial softwood pulp was soaked in water overnight. Then, it was beaten using a valley beater until pulp freeness reached the value of 350±50 ml. Preparation of recycle pulp and handsheet making Commercial A4 paper sheets from the same brand were cut into small pieces and soaked in 5% (w/v) sodium hydroxide solution overnight. Then, these paper sheets were re-pulped at 50 ºC for 90 min at the speed of 500 rpm. The pulp was then divided into three portions. The first portion was mixed with kapok pulp with the ratios of kapok pulp: recycled pulp of 0:100, 10:90, 20:80 and 30:70. The second portion was mixed with the softwood pulp of 0:100, 10:90, 20:80 and 30:7. The remaining recycled pulp was then made into handsheets and dried at 90 ºC for 6 min. All these handsheets made from only recycled pulp was then repulped again following the same path as described earlier up to 3 cycles. For each cycle, paper was made from the mixed pulps using the ratio mentioned earlier. Finally, all these handsheets were tested for paper proper- ties like brightness, opacity, density, porosity tensile and tear strengths and so on. The results were then compared as to examine the effects of numbers of recycling cycles. The effects of kapok and softwood pulps on paper properties were also compared. Results and discussion Brightness Figure 1 The Effects of Recycling Cycles, Kapok Pulp and Softwood (SW) Pulp on Brightness (Note: Kapok and SW pulps have brightness values of 19.15% and 84.31%, respectively)