| Larix Kaempferi is a kind of tree which the forest experts draw attention to since it was introduced into China at the end of 19 century. And now it's someproperties ,such as fast-growing, wide-adaptive, less plant diseases and insect pests, agamic, have been known widely. After inheritance modification about 40 years, it already became an important kind of trees in the Changjiang River valley and some north areas, with tremendous ecological benefit. There are more than 200,000 hectares L.K. plantation in Liaoning, Jilin and Heilongjiang provinces so on. It expressed fast-expanding trend when it was introduced into south china. At present, there are more than 30,000 hectares Larch planted in our country annually.This paper is a subtask of national "fifteen" item which is named "the technology of breed selection and plantation of Larch" and have performed a systemic studies of the properties of material and papermaking of L.K., with high value of practicable application and theory.The first section of this paper is to analyze the properties of chemical compositions and fiber shape of L.K., through systemic studies on its chemical compositions, saccharide compositions and fiber shape in different age (12,15 and 23 years) and in different vertical location within a stem. As a result, the chemical compositions of L.K. in different age have certain difference: With the growing of L.K. trees, the total carbohydrate decreases, water extractives including cold water extractives and hot water extractives increase, and !%NaOH extractives also increase; glucosan and xylan decrease, however, galactosan increases, crystallinity index reduces. Taking chemical compositions and fiber shape into account, 12-year and 15-year Larix kaempferi have some advantages over those older than 20 years in papermaking. As compared with native Larches, its water extractives, 1%NaOH extractives and galactosan are less, however, glucosan is more. So L.K. is better than native Larch in papermaking.We have investigated the KP and AS-AQ pulping properties of L.K. in the second section of this paper. After investigating the influence of alkali charge , sulfidity and time at max. tempereture on L.K. kraft pulping, we find the optimal technical conditions of pulping are that alkali charge(to Na2O) is 21%, sulfidity is 25%, the max temperature is 170 C and time at max. temperature is 2.5h, liquor ratio is 1:4; Under this pulping condition, we can get a pulp with about 23 kappa number and 42%-44% yield of pulp. At the same time, in the three sections of L.K.stem, the middle section is easier to cooking; The difference among individual plants in klaft pulping is very little.After investigating the influence of the AS-AQ pulping parameters, we find the optimal technical conditions of AS-AQ pulping are that alkali charge(to NaOH) is 32%, ratio of sulfite is 0.7, the max temperature is 175 C, time at max. temperature is 6h, AQ charge is 0.15% and liquor ratio is 1:4; Under this pulping condition, we can get a pulp with about 35 kappa number and above 47% yield of pulp.Furthermore, with the growing of L.K., the trees become harder to cooking, alkali consumption and kappa number of pulp increase; 12-years L.K. has some advantages over those older than 20 years in papermaking.In the third section, we perform the study of the bleaching properties of the L.K. pulp with KP and AS-AQ pulp.According to the experiment results, after the bleaching of CEH, L.K. kraft pulp can get 71%ISO, AS-AQ pulp can get 73%ISO; bleaching by the procedure of CDEHD, D/CE1D1E2D2 and DE1D1E2D2, the pulp can reach above 80%ISO; with the assist of H2O2 in oxygen bleaching, the pulp can get 50%ISO; after the subsequent bleaching with H2O2 , it can reach 76%ISO.The degree of polymerization of AS-AQ pulp, either unbleached pulp or bleached pulp, is higher than that of KP pulp.The fourth section of this paper is to analyze the physical properties of L.K. pulp. As a result, the physical properties of KP unbleached pulp are close to B grade national standard of unbleached s... |
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