Treatments of Recycled Pulps from Old Corrugated Containers. Part I. The Effects of Boron Compounds on Optical and Physical Properties

Abstract

Aims: It was aimed to provide understanding of the properties of recycled fibers from Old Corrugated Container (OCC) and to explore boric acid and sodium borohydride effects for improvement of the properties of secondary OCC pulps. Study Design: In order to control past and the stages of the recovered fibers, repeatedly five recycling phases were applied on the same sheets. In each recycling phase, repulped OCC fibers were treated with 5.0% and 10% concentration (w/w) of sodium borohydride and boric acid at least 12 hours (overnight). Methodology: The test sheets were prepared as 120 g/m2. The test papers were dried in conditioned room for one day. Standard paper tests were applied according to Tappi Test Methods. This involves determination of water absorption (Cobb test) (Tappi T-441), color and optical properties (Tappi T-220 and T-525,  ASTM E313, D523 and D1925, CIE L*a*b*) strandard methods, respecitvely. A number of combinations was utilized during recycling procedure of cellulose fibers. Results: It has been found that the bulkiness of paper produced from sodium borohydride treated secondary pulps show higher bulk values than that of the control and boric acid process in the same phase. The highest bulk value of 3.41 cm3/gr was found with 10% sodium borohydride treated pulps at the fifth recycle phase. However, both boron compounds positively effect on Old Corrugated Container (OCC) secondary fibers regarding water absortion properties (Cobb value) of test papers. The highest water absorption value of 135 g/m2, was observed in 10% boric acid treatment conditions at fifth recycling stage that was approximately 8.0% and 26.16% higher than the former recycled papers and control at the same recycling phase, respectively. Conclusion: Test papers treated with both compounds have showed in marginal limits for total color differences (∆E) regardless of chemical treatment and recycling stage.  It was realized that the selected boron compounds used for treatment of OCC secondary fibers did not cause significant changes in the color and optical values. However, need further work to validate reliability.