Preparation method of hydroxypropyl methylcellulose

Abstract

The invention relates to a preparation method of hydroxypropyl methylcellulose. The preparation method comprises the following production steps: S1, selecting a cellulose raw material with a high polymerization degree and carrying out purification treatment; S2, putting the cellulose raw material into a container and vacuumizing to exhaust air; filling nitrogen gas to protect; S3, adding alkali liquid and carrying out reaction; then squeezing; S4, adding alkaline cellulose into an etherification kettle filled with liquid-state chloromethane and carrying out etherification reaction; S5, washinga material obtained by the etherification reaction through hot water, so as to rapidly expand the volume; S6, selecting a centrifugal machine and dehydrating; S7, drying; S8, crushing and processing;S9, sieving; S10, packaging a finished product. The preparation method of the hydroxypropyl methylcellulose has the advantages of high production efficiency, capability of controlling the viscosity stability very well, energy saving and emission reduction; the requirements of safety of production equipment are reduced and the economic benefits are improved.

Description

technical field [0001] The invention relates to the technical field of cellulose preparation, in particular to a preparation method of hydroxypropyl methylcellulose. Background technique [0002] In the prior art, the preparation process route of hydroxypropyl methyl cellulose is as follows: in a mixed diluent system of a certain proportion, the refined cotton and caustic alkali are subjected to an alkalization reaction, and simultaneously or later in the alkalization reaction material. Methyl chloride and propylene oxide are added to carry out etherification reaction, and then the diluent is recovered, and then the etherification reactant is neutralized, filtered and washed, granulated, wet pulverized, dried, pulverized and mixed to obtain the finished product. There are two specific preparation methods. One method is to carry out alkalization and etherification reaction with a high diluent ratio, that is, to carry out alkalization and etherification reaction under the con...

AI Technical Summary

Problems solved by technology

In this patented method, the mass-volume ratio of refined cotton: methyl chloride = 1:6-25 reaction conditions determines the disadvantages of this hydroxypropyl methylcellulose preparation method: because both the reaction process and the recovery of by-products need to be It is carried out under relatively high pressure, so as stated in the independent claim of the patent, the production must be completed by using an autoclave, that is, the method has high requirements on equipment performance, especially safety, high production cost, and great difficulty in industrial application