Curing of drying oil in wood fibre webs by gamma-irradiation

Laszlo Paszner
A technique is described for improving wood fibre web strength by copolymerization of a hydrocarbon drying oil (CTLA Polymer) within hand-sheets made from pure and admixed forms of high yield chemical (sulfite and sulfate) and groundwood fibres. Oil polymerization can be initiated successfully by prolonged thermal treatment at 145°C, as well as by the novel method of low dosage gamma-ray irradiation. The treatment strengthens inter-fibre bonding. Evidence for copolymerization was sought through
more » ... assessment of tensile and related strength data on variously treated standard handsheets. Effectiveness of the polymerization on pulp types investigated as initiated by heat and low dosage irradiation is strongly related to surface colloidal and basic physical and mechanical properties of the fibres. Maximum strength parameters were obtained with oil saturated sulfite and groundwood handsheets following polymerization by thermal treatment. Copolymerization efficiency by irradiation, on the other hand, is estimated as 73% for sulfite, 65% for groundwood and 50% for kraft handsheets. Effectiveness of oil polymerization by irradiation was found to be proportional to dosages up to 10⁵rad. As anticipated, limit of strength improvement was not set entirely by intrinsic fibre strength, but was also influenced by surface colloidal properties of the fibres. Blends made from chemical-groundwood fibre mixtures behaved more or less proportional to individual pulp strengths and extent of blending. Copolymerized sulfite-groundwood blends at equal proportions approximated the tensile strength of similar kraft papers suggesting better economy with kraft fibres when papers of limited strength are produced. All other strength parameters (elastic modulus, tensile strain and tensile energy absorption) followed similar trends, or if different were of aid in explaining certain phenomena characteristic to treated fibre webs. The presence of graft copolymer could not be conclusively proven, since both the copolymer and oil homopolymer are [...]
doi:10.14288/1.0093641 fatcat:t3s6mss7orgvjemkewubhuy3je