Manufacture Process
Processing Route:
The cellulose is acetylated in a reaction vessel to prepare cellulose triacetate, and then cellulose triacetate is hydrolyzed to form cellulose diacetate. The diacetate cellulose fibre can be obtained by dissolving cellulose diacetate in an acetone solvent and spinning. Fig. 1 shows the schematic diagram of the production process for acetate fiber.
Fig1: Schematic Diagram of the Production Process for Acetate Fiber[6]
Fig2: Outline of the Production Process of Cellulose Acetate[7]
Highly purified wood pulp or cotton linter is used as the raw material cellulose. Cellulose is activated in a pretreatment step. In the subsequent acetylation step, to the cellulose are added acetic anhydride, acetic acid, and sulfuric acid as a catalyst to carry out the esterification reaction.
After the esterification reaction, the acetyl base substituted in each glucose anhydride is slightly less than 3. Then, the hydrolysis process is carried out in the hydrolyzer to reduce the acetic degree of cellulose acetate to the required range of products to produce cellulose diacetate. Finally, the vinegar tablets were separated by water washing.
In the subsequent washing step, the remaining solvent, impurities, and the like are removed. In addition, through a drying step, a cellulose acetate product is obtained. Diluted acetic acid as a byproduct generated in the precipitation and purification steps is concentrated for recycling, or for the raw material for acetic anhydride production.
Another preparation method for cellulose diacetate comprises the following steps[8],
(1), The cellulose, acetic acid, ionic liquid, catalyst-Amberlyst 15, acetylating reagent-acetic anhydride or acetyl chloride are simultaneously added to the reaction device for acetylation reaction, the reaction time is 2 to 12 hours, and the reaction temperature is 60 to 120 degrees Celsius. The ratio of cellulose to ionic liquid is (0.025-0.05) g/ml, the molar ratio of catalyst to cellulose is (0.05-0.1) : 1, and the molar ratio of the acetylating agent to cellulose is (3~). 6) : 1.
(2), After the reaction is completed, the reaction mixture is cooled to room temperature, and solid-liquid separation is carried out to obtain a solid phase catalyst Amberlyst 15 and a product-containing ionic liquid phase, deionized water is added to the ionic liquid phase to precipitate. After separating the solid and liquid, the solid phase containing the product and the ionic liquid phase containing the deionized water phase, the product in ionic liquid phase can be recovered by rotary evaporation to remove the ionized water; the dichloromethane is added to the stationary phase containing the product, and the precipitate is partially dissolved and filtered. The solvent in the filtrate was distilled off, dissolved in acetone, and evaporated to obtain a product.
Manufacture Process
Manufacturing
In the acetic acid fibre industry for cigarettes, the dry spinning method is mainly used to produce a diacetate fibre tow. First, cellulose diacetate is dissolved in an acetone solution. Then, the solution is subjected to multistage compression filtration treatment, the colloid and solid impurities in the spinning solution are removed, and the spinning solution is sprayed from the spinneret at a fixed flow rate to form a tow, and the tow is then curled into the crimper. Finally, it enters the dryer and heats off the residual acetone and water to form a dry tow. The recovery of acetone is for the recovery of acetone evaporating from the tow during the spinning process, thereby preventing explosion due to excessive concentration.