The content and ratio of hydroxypropoxy and methoxy in HPMC can affect the water retention energy, water solubility, surface activity and gel temperature of the product.
Generally speaking, products with high methoxy content and low hydroxypropoxy content have better water solubility and surface activity, and the gel temperature is relatively low. If the methoxy content is appropriately reduced and the hydroxypropoxy content is increased, The gel temperature of the product can be increased, but if the hydroxypropoxy group exceeds a certain value, the gel temperature will decrease, and its water solubility and surface activity will become worse, but if it is dissolved in an organic solvent, its dissolution effect will be better.
Generally speaking, the methods to control the hydroxypropoxy content and methoxy content mainly include:
① Change the amount of sodium hydroxide used in the entire reaction system. The change in the amount of alkali used in the alkalization of cellulose will directly affect the etherification efficiency of the product and the ratio of the group content. It is generally considered that the alkali A high concentration will increase the methoxy content of the product. On the contrary, under the same conditions, the hydroxypropoxy content can be appropriately increased to a certain extent. It can be understood that the hydroxypropoxy group content is inversely proportional to the concentration of the lye, and the methoxy group is directly proportional to the concentration of the lye.