Dissolution method and synthesis method of hydroxypropyl methylcellulose
Hydroxypropyl methylcellulose is a non-ionic cellulose ether made from natural polymer material cellulose through a series of chemical processing. They are a white powder that swells in cold water to a clear or slightly hazy colloidal solution. It has thickening, binding, dispersing, emulsifying, film-forming, suspending, adsorption, gel, surface activity, moisture retention and protective colloid, etc.
1. All models can be added to the material by dry mixing;
2. When it needs to be directly added to the normal temperature aqueous solution, it is best to use the cold water dispersion type. After adding, it usually takes 10-90 minutes to thicken;
3. Ordinary models can be dissolved by stirring and dispersing with hot water first, then adding cold water, stirring and cooling;
4. If there is agglomeration and wrapping during dissolving, it is because the stirring is not sufficient or the ordinary model is directly added to the cold water. At this time, it should be stirred quickly.
5. If bubbles are generated during dissolution, it can be left for 2-12 hours (the specific time is determined by the consistency of the solution) or removed by vacuuming, pressurizing, etc., or adding an appropriate amount of defoaming agent.
Synthesis method 1. Treat the refined cotton cellulose with alkali solution at 35-40°C for half an hour, press, pulverize the cellulose, and properly age at 35°C, so that the average degree of polymerization of the obtained alkali fiber is within the required range. Put the alkali fiber into the etherification kettle, add propylene oxide and methyl chloride in turn, and etherify at 50-80℃ for 5h, the maximum pressure is about 1.8MPa. Then add an appropriate amount of hydrochloric acid and oxalic acid to the hot water at 90 ° C to wash the material to expand the volume. Dehydrate with a centrifuge. Wash until neutral, when the water content in the material is less than 60%, dry it with a hot air flow at 130°C to less than 5%.