Preparation Of Dissolving Pulp From Bamboo

Dissovling pulp is a kind of refining chemical pulp of highly purified cellulose. It is widely used in producing viscose rayon, nitrocellulose acetate, cellophane and carboxymethyl cellulose etc. Cotton linters and wood pulp have been used as raw materials for producing viscose fiber for a long time; nowadays, the shortage of cotton linters and wood materials is causing severe problems to dissolving pulp factories.As an abundant resource in China and southeast Asia, bamboo can be used as an important raw material for preparing viscose fiber for its unique characteristics, such as long fiber length, high cellulose content closed to wood materials, and short harvest time for just 3-5 years. Consequently, it is meaningful to exploit bamboo to produce dissolving pulp in a reasonable way. This would not only provide a kind of new material to produce dissolving pulp which can lessen the shortage wood resource, but also improve the core competence of bamboo forestry management.In this paper, bamboo from Indonesia was used as raw material to prepare high quality dissolving pulp by prehydrolysis, Kraft pulping and DEDEDH bleaching sequence. The results are shown as follows:1.Appropriate conditions for hot-water prehydrolysis are:liquid ratio 6:1, heating-up time 60 min, highest temperature 170℃, holding time 120 min.2.Appropriate conditions for kraft pulping are:liquor ratio 4:1, time to temperature 60 min, highest temperature 165℃, time at maximum temerature 120 min; alkali content 20%, sulfidity 15% and anthraquinone dosage of 0.1%(based on the dry weight of bamboo chip).3.Appropriate conditions for ECF bleaching are:Do:1.03%(based on the dry weight of bamboo pulp), pH 2.7-3.7, reaction temperature 60℃, pulp consistency 3%, reaction time 60min; D1:1.2%(based on the dry weight of bamboo pulp), pH 4.1-4.6, reaction temperature 80℃, pulp consistency 10%, reaction time 2h; D2:0.4%(based on the dry weight of bamboo pulp), pH 4.1-4.6, reaction temperature 80℃, consistency of 10%, reaction time 2h.4.The experimental results indicated that bamboo dissolving pulp with 97.37% a-cellulose,87.26% ISO brightness, polymerization degree of 1457,0.08% ash content, 21mg/kg iron ion, large dust particles at 1.0 piece/kg, small dust particles at 195 m2/kg, alkali absorption at 609%, could be achieved by the optimizd bleaching process of D0E1D1E2D2. However, the polymerization degree is still too high for the purpose of dissolving pulp use.5.The DP of pulp after ECF can be adjusted to 600-1200 by dosing hypochlorite at 0.2%-1.0% of dry pulp weight in the last H stage bleaching. And the a-cellulose, brightness, alkali absorption can be improved from 96.41%,87.26%, and 610 to 97.68%,88.36%,and 622%, while the iron content and dust particles remain few changes. High quality bamboo dissolving pulp is thereby prepared.