Construction HPMC-Talking about the process of etherification in HPMC production
The raw material of hydroxypropyl methylcellulose can be refined cotton or cotton pulp. It is necessary to pulverize it before or during the alkalization process. Pulverization is to destroy the aggregated structure of the cellulose raw material through mechanical energy. , in order to reduce the crystallinity and the degree of polymerization, increase its surface area, thereby improving the accessibility and chemical reaction ability of the reaction reagent to the three hydroxyl groups on the glucose ring group of the cellulose macromolecule.
According to the analysis of hydroxypropyl methylcellulose manufacturers, the surface-treated hydroxypropyl methylcellulose particles can be dispersed in neutral water without agglomeration, but the product viscosity will not be immediately. After the hydroxypropyl methylcellulose is soaked for a certain period of time, the chemical structure of the surface treatment is destroyed, and the water can dissolve the HPMC particles. At this time, the product particles have been fully dispersed and absorbed enough water, so the product does not agglomerate after dissolving. , unite.
The dispersion speed and dissolution speed of hydroxypropyl methylcellulose HPMC depend on the degree of surface treatment. The surface treatment is slight, the dispersion speed is relatively slow, and the sticking speed is faster; while the product with deeper surface treatment has a faster dispersion speed, The sticking speed is slow. If this series of products are to be dissolved rapidly in this state, a small amount of alkaline substances can be added dropwise when they are dissolved alone. The current market is usually called slow-dissolving products.
The complexity of the synthesis principle of hydroxypropyl methylcellulose is not very high. Centrifugal separation, raw material pulverization, causticization, etherification, solvent recovery, washing and drying involve a large number of technical keys and rich knowledge connotations. For different varieties of products, each environment has the closest control conditions, such as temperature, time, pressure and material flow control. Auxiliary equipment and control instruments are the guarantee of stable product quality and reliable production system.