Study On The Lignin Structure Of Triploid Clone Of Populus Tomentosa Carr.

All kinds of nonwood plant fibers occupy a great proportion in raw material structure in the paper industry of our country. It now has become an obstacle for the further development of paper industry. Increasing wood fibers for paper-making is understood and recognized by all sides related. So cultivating superior trees which suite to plant in pulp forest base is one of the most urgent tasks for now. "Grow fast, quality high and mature early" is the basic requirements for those trees.Triploid clones of populus tomentosa carr. are a series of new tree-types which cultivated by the Research Room of White Polar, BJFU. They grow fast because they have 1 more chromosome than normal clone, and they are excellent trees for pulping. In order to understand the detailed properties of pulping and bleatching about one of triploid clones Populus tomentosa Carr. , we extracted the MWL and LCC from triploid clone Populus tomentosa Carr. and the residual lignins in unbleached pulp by KP and AS-AQ, then the lignin building unit of it was analysed by nitrobenzene oxidation, and the MWL and lignin-carbonhydrate complex (LCC) and the residual lignins were analysed by means of FT-IR and 13C-NMR , The main results are as follows:Lignin is made up by three types of unit, p-hydroxyphenylpropane unit, guaiacylpropane unit and syringylpropane unit. The percent of these units in lignin of triploid clones is 2.22%, 44.16% and 53.62% respectively, There are less p-hydroxyphenylpropane units and syringylpropane units, but more guaiacylpropane units in the lignin structure of triploid clones than normal clone. So the lignin of triploid clones degrades a little more difficult than the normal clone.The carbohydrate in LCC of triploid clone of populus tomentosa carr. is mainly made up of xylan and glucuronic acid, and the content of other monosaccharide is little. The chemical bonds between lignin and carbohydrate are majority bonds of carbohydrate and guaiacyl, among them the chemical bonds produced between cellulose and lignin may make delignification more difficult in the process of pulping and bleaching.The pulp by AS-AQ had less condensed lignin structure , lignin-carbonhydrate complex (LCC) and carboxy group as compared with pulp by KP . we can infer that the bleachability of AS-AQ pulp is better than that of KP pulp.Sum up, the complex lignin structure and LCC of triploid clone of populus tomentosa carr. may be the reason that delignification is difficult in the process of pulping and bleaching. For the means of pulping, the bleachability of unbleached pulp by means of AS-AQ is better than that of pulp by means of KP.