How to determine the quality of hydroxypropyl methylcellulose (HPMC) is a question that many customers and friends are more concerned about. Today, Xinhe Shanda Cellulose summarizes how to judge the quality of hydroxypropyl methylcellulose (HPMC) Judging the quality of the product:
First of all, we need to understand the production process of hydroxypropyl methylcellulose:
Hydroxypropyl methylcellulose, also known as hypromellose and cellulose hydroxypropyl methyl ether, is made of highly pure cotton cellulose as raw material, which is specially etherified under alkaline conditions.
The synthesis of hydroxypropyl methylcellulose: treat the refined cotton cellulose with lye at 35-40°C for half an hour, press it, crush the cellulose, and age it properly at 35°C to make the average degree of polymerization of the obtained alkali fiber within the desired range. Put the alkali fiber into the etherification kettle, add propylene oxide and methyl chloride in sequence, and etherify at 50-80°C for 5 hours, the maximum pressure is about 1.8MPa. Then add appropriate amount of hydrochloric acid and oxalic acid to the hot water at 90°C to wash the material to expand the volume. Dehydrate in a centrifuge. Wash until neutral, and when the water content in the material is lower than 60%, dry it with a hot air flow at 130°C to a content of less than 5%.
The HPMC produced by the solvent method uses toluene and isopropanol as solvents. If the washing is not good, there will be some faint residual odor. This is a problem with the washing process, and it does not affect the use and there is no problem, but in reality The hydroxypropyl methylcellulose produced by many manufacturers has a particularly strong smell and a pungent smell. The quality of this kind is definitely not up to standard.
Hypromellose is refined cotton impregnated with a rare liquid to obtain alkaline cellulose, then add solvent, etherification agent, toluene, and isopropanol for etherification reaction, and obtain the finished product after neutralization, washing, drying, and crushing. Not good, it will smell, so users can use it with confidence.