جستجوی مقالات مرتبط با کلیدواژه « خمیر حل شونده » در نشریات گروه « صنایع چوب و کاغذ »

One of the common applications of cellulose is dissolving pulp producing that requires high purity. Different cellulose sources are used to produce dissolving pulp. Due to Deforestation and lack of agricultural land and problems with cultivation, the use of wood and non-wood sources of cellulose is declining. Another source of cellulose is recycled pulp. Chlorine dioxide acts as a completely selective bleaching. Increasing kappa factors is very effective in removing lignin levels. In this research, dissolving pulp from recycled fibers is obtained during soda cooking and bleaching with chlorine dioxide. Then, the effect of changes in kappa factor of the second stage of chlorination on chemical composition (holocellulose and lignin), structural properties (degree of polymerization, alpha-cellulose and degree of brightness) and accessibility (water retention value) are investigated. The results showed that the degradation of holocellulose levels was not severe and did not cause cellulose damage and decreased alpha-cellulose levels as well as the degree of polymerization. The removal of lignin as a hydrophobic component and the presence of hemicellulose as a hydrophilic component increase accessibility (water retention) and decrease brightness degree.

In this study, a bagasse bleached paper-grade pulp from Pars pulp and paper mill was subjected to xylanase (X) treatment and combined with cold caustic extraction (CCE). The positive effect of the enzyme was observed on the removal of hemicelluloses and with increasing the dosage of xylanase treatment (0.01-0.05 g/g pulp), the extraction of hemicelluloses from the pulp increases, but there is still high remaining hemicelluloses in the pulp. The xylanase treatment increased the polydispersity index (8.21-8.46) resulting in a broader molar mass distribution. High molecular weight cellulose fraction (DP>2000) increased by the xylanase treatment and the highest amount was thus observed by 0.05 dosage of the enzyme. The cold caustic extraction compared to the combined treatment results in a significant extraction of hemicelluloses from the pulp. The viscosity and brightness of pulps (82.04 and 454 ml/g, respectively), on the other hand, increase by the cold caustic extraction. Also, a narrow molar mass distribution can be obtained by this treatment which has much potential for targeted production of cellulose. Overall, the results of this study indicate the success of the conversion of paper-grade pulp to dissolving pulp with a cold alkaline treatment.

Acid prehydrolysis aiming to remove hemicelluloses is one the key steps in producing dissolving pulp from wood resources. The objective of the present research is to resolve the necessity of using tis treatment in dissolving pulp production from old corrugated container. Therefore, temperature of 130 C, acid concentration of 1%, time of 30 min and liquor to paper of 7:1 were selected as acid pretreatment and the properties of both samples of with and without prehydrolysis were compared after cooking. The results showed that excluding reactivity, other dissolving pulp required properties including accessibility, degree of polymerization and the alpha cellulose content were diminished. Also, the results of yield and chemical composition indicated the destruction of this step to samples. Finally, regarding the superior properties of samples with no prehydrolysis and their acceptable value of reactivity, not only the acid prehydrolysis necessity was not acknowledged but also its application is not recommended.

Dissolving pulp is used as a raw material to produce numerous cellulosic derivatives like carboxymethyl cellulose, nitrocellulose, viscose, etc. The potential of dissolving pulp production from populus deltoides using alkaline pre-extraction followed by soda-AQ pulping process was investigated across this research. The yield loss of about 15% was achieved in pre-extraction stage through controlling the process parameters, and kappa number of the pulp has been reduced to about 40% with oxygen delignification. The results showed that the alkaline pre-hydrolysis has been affected on increasing the lignin removal rate of fibers. Using alkali catalyst in pre-hydrolysis liquor led to increasing a-cellulose and decreasing brightness level of the dissolving pulp. The a-cellulose and brightness level of dissolving pulp have been upgraded by utilizing higher levels of kappa factor in D0ED1 bleaching. Therefore, the produced dissolving pulp employing 0.45 kappa factor in D0 stage due to its higher a-cellulose, brightness and purity has been more favorable in this research work.

This research was performed to evaluate the potential of acid pre-hydrolysis soda-AQ process for the production of dissolving pulp including high α-cellulose content from Populus deltoides. To achieve the aim, a pre-hydrolysis liquor containing 0.06% acid sulfuric, soda-AQ pulping, and OD0ED1 bleaching sequence were used. The results show that using at least 0.40 kappa factor at D0 stage was necessary to gain access a high quality dissolving pulp including characteristics like having brightness level and α-cellulose content higher than 86% and 98%, respectively. A kappa reduction of 40.3% was achieved by performing a single stage oxygen delignification after soda-AQ pulping to drop kappa number of pulp from 14.1 to 8.4 prior to entrancing the pulp into the final bleaching stage. The results illustrated that producing acid pre-hydrolyzed soda-AQ dissolving pulp including high α-cellulose content and brightness, and even viscosity is completely feasible through controlling and optimizing the acid pre-hydrolysis, pulping, oxygen delignification stages, and D0ED1 bleaching sequence.