Changes Of Non-lignin Components Of Bambusa Chungii In SCMP Pulping And Its Effect On Yellowing

The high yield bamboo pulp has a good application prospect in China.The development of high yield bamboo pulp is also an important way to solve the shortage of papermaking raw materials.However,the bleaching performance and whiteness stability of bamboo pulp are poor,which severely limits the application of high yield bamboo pulp.This paper mainly studies the changes of non-lignin components,metal elements,lipids,starches and proteins in the SCMP pulping process and its effect on the yellowing,providing a theoretical basis for improving the whiteness and whiteness stability of bamboo pulp.The results are as follows:The content and distribution of non-lignin components in SCMP pulping and bleaching process were studied.It was found that the content of metal elements,lipids,starch and protein decreased by 38.4%,86.5%,93.5%and 70.7%respectively,after process of SCMP pulping.It was also found that some metal elements such as Ca,Mg,Na,lipids,starch and protein remain on the fiber surface of SCMP unbleached and bleached pulp,especially the metal elements Fe,Mn,Cu may be distributed in deeper cell walls.The effect of non-lignin components on the yellowing of SCMP pulp were studied,it was found that lipids were re-deposited on the surface of the fiber after pulping,and the extraction of lipids could expose more structure on fiber surface,the whiteness of the pulp increased by 24.06%,26.12%ISO respectively.In addition,there still more polyphenolic compounds,fatty acids,esters and some substances containing benzene ring structure in lipids after the bleaching.Starch and protein may break or decompose during process of pulping and bleaching,revealing more dichroic groups,and the broken product may agglomerate on the fiber surface.Furthermore,H202 may oxidize some of the hydroxyl groups in starch and amino acids to aldehydes or carboxylic acids,increasing the carbonyl structure..Lipids contained more sterols after light and heat-induced yellowing.Some substances such as small molecular acids,alkanes,alcohols,small molecular aromatics and fatty acids were increased after yellowing,and had formed some substance which contained carbon-carbon double bond and a phenolic hydroxyl structure.In addition,starch and protein have different yellowing properties.Light and heat-induced yellowing could have a greater impact on protein,while starch was more affected by heat-induced yellowing.No new chromophore groups were formed after the process of yellowing both in two components,their effect on the yellowing of the pulp may be derived from the carboxyl or carbonyl groups formed during the bleaching process.