Preparation method of cellulose acetate particles

Abstract

The invention discloses a preparation method of cellulose acetate particles. The preparation method comprises the following steps: firstly, soaking cellulose in an acetic acid solution containing sulfuric acid for activation, then mixing the activated cellulose with a mixed solution containing catalyst hydrosulfate, acetic acid and acetic anhydride, reacting to obtain a cellulose triacetate solution, then adding an acetic acid aqueous solution for hydrolysis, separating out the reacted cellulose acetate solution in an acetic acid aqueous solution, and carrying out suction filtration, washing and freeze drying to obtain powdery coarse cellulose acetate particles; and dissolving the crude product in an acetone solution, purifying, re-precipitating, carrying out suction filtration, washing, and drying to obtain high-purity cellulose acetate particles. According to the method, the raw material with low cellulose content can be acetylated, the viscosity and molecular weight of the cellulose acetate are not obviously reduced, the cooling acetylation reaction is not required, the solubility of the cellulose acetate is improved, and the influence of the catalyst or the catalyst residue on acetylation, hydrolysis and subsequent processing steps is very small.

Description

technical field [0001] The invention belongs to the field of cellulose acetate preparation, and in particular relates to using sodium bisulfate as a main catalyst to catalyze the acetylation of cellulose and using acetone to purify the crude cellulose acetate product to prepare high-purity cellulose acetate particles. Background technique [0002] The commercially available and industrially produced cellulose acetates reported are almost all produced by using strong acid as the catalyst for the reaction, and a mixture of acetic acid and acetic anhydride as the solvent for the reaction. Compounds that can generally be used as cellulose acetylation catalysts include sulfuric acid, perchloric acid, and sulfonic acids. Of these, sulfuric acid is considered the best catalyst for the commercial production of cellulose acetate, and other catalysts have been ruled out as impractical or dangerous to handle. Currently, the acetic acid homogeneous process using sulfuric acid as a cata...

AI Technical Summary

Problems solved by technology

[0003] However, the cellulose acetate production process using sulfuric acid as a catalyst has many disadvantages: ① High-purity cellulose with a very high cellulose content is required as a raw material

②The acetylation step, especially when catalyzed by sulfuric acid, degrades the cellulose polymer, resulting in a cellulose acetate product with low viscosity (IV) and low molecular weight (MW) ③The acetylation step is highly exothermic, so additional cooling is required device to adjust the reaction, increasing the production cost

④ The large amount of sulfuric acid used in the acetylation and hydrolysis steps not only increases the production cost, but also causes subsequent production difficulties, such as insoluble sulfate clogging the processing line

This method produces cellulose acetate by high-temperature hydrolysis of cellulose triacetate at a hydrolysis temperature of 125°C to 127°C, but the high-temperature method usually makes cellulose acetate products poorly soluble in organic solvents

Patent No. US2923706 discloses a method for acetylation of cellulose using less than 1% cellulose weight sulfuric acid catalyst and at a temperature lower than 50°C, but requires a special pretreatment method