|
Acetate versatile materials used for the high cellulose content of cotton pulp or senior softwood pulp, and currently still has to import wood pulp. Research and development of wood pulp, acetate fiber industry has become China's ability to achieve sustainable development of the key issues, eucalyptus as an important fast-growing hardwood species, such as can be used in the production of high purity cellulose acetate pulp, right of acetate fiber industry is of great significance. Eucalyptus urophylla thesis as raw material, the pulping, bleaching, xylanase treatment and alkaline refining process, to obtain a pulp to meet the requirements of cellulose acetate, and then activated, acetic acid, hydrolysis and other processing, and its reaction mechanism was discussed. The main experimental results are as follows: (a) eucalyptus pulp KP AQ method were used, conditions are: alkali charge 17% (Na 2 O meter), sulfidity 16%, AQ 0.05%, liquid ratio of 1:4, idling 30 min, 90 min heating to 130 ℃; heating up again 90 min to 170 ℃, heat 60 min. (2) In order to obtain high brightness pulp, without causing environmental pollution, D 1 ED 2 Conventional bleaching conditions were discussed, D 1 section with a chlorine content must be controlled at 3.6% or less; alkali treatment conditions need to be more strongly to remove hemicellulose, to improve the α-cellulose content of the pulp and the average degree of polymerization. But want to use by increasing the amount of the base to a substantial increase in α-cellulose content is not feasible. Eucalyptus wood cellulose acetate pulp bleaching conditions: D 1 segment with chlorine 3.6%, 70 ℃, 90 min, pulp consistency 10%, pH 3.5; E segment NaOH 2.0%, 75 ℃ , 60 min, pulp consistency 10%; D 2 segment with chlorine 0.9%, 70 ℃, 90 min, pulp consistency 10%, pH 3.5; P segment of NaOH and H 2 < / sub> O 2 usage agreement was 2.5%, 70 ℃, 90 min, 10% pulp consistency. (3) optimum xylanase treatment conditions are: enzyme dosage of 120 IU / g, 60 ℃, time 2h, pulp consistency of 3%, pH6.0; alkali refining, NaOH addition to remove part of the hemicellulose, and can some short-chain cellulose dissolved away, when the alkali concentration of 4%, the average degree of polymerization to 1163, whiteness increased 90.0%, α-fibrous content of 96.78%, reaching acetate pulp international standards. (4) after the xylanase treatment of pulp for infrared scanning. Chromophore and Auxochrome such as C = O stretching vibration (1058cm -1 ), lignin - alkyl ether group COC stretching vibration (1164cm -1 ) , aryl - alkyl ether bond (1240cm -1 ), lignin carbonyl stretching vibration of C = O (1637cm -1 ), wood Sufang ring vibration (1430 cm -1 ) absorption peak in the xylanase treatment, the strength has weakened, this may be the xylanase treated pulp whiteness reasons for the increase. (5) Activation of eucalyptus pulp optimum conditions: the activation time of 3.0 h, the activation temperature 50 ℃, the amount of 500% acetic acid; acetic optimum conditions of: the amount of 400% acetic anhydride, sulfuric acid catalyst, the amount of 7.5%, temperature 60 ℃, time 2h; optimum hydrolysis conditions: acetic acid content of 80%, hydrolysis temperature was 60 ℃, cellulose acetate obtained degree of substitution of 2.51. (6) of the pulp after activation for X-ray diffraction scan and combining infrared spectra. Activation process is simply a process of physical swelling, does change the crystalline structure of cellulose, and the area makes it possible to increase, with more hydroxyl groups and vinegar acidifier may, in favor of the reaction acetic acid, with acetic acid to pulp The activation process is ill-prepared acetification, there is no significant other chemical reactions take place. (7) for cellulose acetate infrared scanning. 1752cm -1 of the stretching vibration of C = O, 3348 cm -1 is-OH stretching vibration, its intensity decreased significantly, indicating that the pulp of the product acetic acid is the main component cellulose acetate; acetate fiber X-ray diffraction scans of the cellulose acetate hydrogen weakened, while the introduction of the cellulose acetate structure is subjected to a crystallization degree of damage, resulting in reduction of the crystallinity of cellulose.
|