CHEMICAL TREATMENT OF RECYCLED PULP FIBRES FOR PROPERTY DEVELOPMENT: PART 3. EFFECTS ON OCC PULPS

Chemical treatment with sodium hydroxide, formamide and ethyl acetate is shown to affect certain properties of paper made from recovered fibres. Sodium hydroxide treatment improves the brightness of sheets by approx. 0.12-17.2% under similar recycling conditions. All chemical treatments usually improve the tensile and burst strengths of sheets to some degree. The highest tensile and burst strength values of 42.09 Nm/g and 2.60 kPa m(2)/g were obtained at the first recycling stage with 10% ethyl acetate treatment (O10Et(1)), and these represent approximately 142.2% and 100% improvement of tensile and burst strength respectively. In contrast, although the results revealed that certain chemical treatments markedly improved both tensile and burst strengths, there is some variation observed for tear strengths. The largest improvement in tear strength (72.9%) was found at the third recycling stage with 5.0% formamide treatment (O5Fa(3)), followed by O10Et(3) (33.9%) and O10Na(3) (29.2%). It is important to note that the highest tear strength value of 9.09 Nm(2)/g was found at the second recycling stage of the control samples. The results clearly show that the tensile and burst strengths of sheets can be improved by certain chemical treatments, but there is no correlation with tear strengths.