At present, hydroxypropyl methylcellulose in the domestic market is mainly divided into hot-dissolving type (also called slow-dissolving type) and instant-dissolving type, and the hot-dissolving type is also the most conventional and the most used type of cellulose.
Hot-melt (slow-melt) hydroxypropyl methylcellulose HPMC has not been treated with glyoxal. If the amount of glyoxal is large, the dispersion will be fast, but the viscosity will increase slowly, and if the amount is small, the opposite will be true. Hydroxypropyl methylcellulose HPMC will clump together when it encounters cold water (but this situation will also dissolve slowly, but it takes a long time.), but it will quickly diffuse in water in hot water until It disappears completely in water, and its viscosity increases slowly when the temperature drops gradually until it becomes a transparent viscous liquid. Its clumping phenomenon is similar to the dissolution of high-viscosity sodium carboxymethyl cellulose. When the cellulose powder outside the water dissolves, it becomes viscous, and then wraps the cellulose inside that has not touched the water, but This situation will also slowly dissolve, but it will take a long time.
Instant-type hydroxypropyl methylcellulose HPMC is surface-treated with glyoxal. It disperses quickly in cold water, but it does not really dissolve. It takes time for its viscosity to rise, because it only diffuses in water in the early stage, which is not of real significance. For the above dissolution, the viscosity reaches the maximum value in about forty minutes. When the viscosity rises, the aqueous solution becomes clear and transparent, which is the real dissolution. Instant-type hydroxypropyl methylcellulose HPMC is used in a specific industry and will not be mixed with dry powder, or when it needs to be dissolved and hot water cannot be used due to equipment conditions and other reasons, instant-type hypromellose Cellulose-based solution to such a difficult problem.