HPMC can be divided into quick-dissolving (surface treated) and hot-dissolving (non-surface treated) types.
The quick-dissolving product quickly disperses in cold water and disappears into the water. At this time, the liquid is not viscous, because HPMC is only dispersed in water, not really dissolved. About 2 minutes, the viscosity of the liquid gradually increases and forms a transparent viscous gel.
For hot soluble type, it clumps in cold water, but in hot water, it disperses rapidly and disappears in hot water until the temperature drops to a certain temperature, then it slowly appears viscous until it forms a transparent viscous colloid. The reason for cold water caking is that the outer layer of cellulose powder encounters cold water and immediately starts to be viscous and thickens into a transparent colloid, while the cellulose inside does not come into contact with water and is surrounded by colloid, or is in powder form but slowly dissolves.
In practice, hot water is not needed to dissolve hot-melt products, since putty powder or mortar is in powder form. After dry mixing, the cellulose separates from the other materials. It becomes immediately viscous in contact with water and does not clump. Hot soluble type can only be used in putty powder and mortar. In liquid glues and paints, it will clump. It can be used in instant (surface treatment), putty powders and mortars as well as liquid glues and paints in a wide range of applications. There are no contraindications. However, for quick-dissolving (surface treatment), its water retention and stability cannot be compared to hot-soluble (non-surface treatment).
If hot-soluble (non-surface treated) HPMC is added directly to water, clumping will occur before dissolution. However, dissolution in this manner is very slow and difficult. Here we recommend three dissolution methods for users depending on the application.
Since HPMC is insoluble in hot water, the initial HPMC can be evenly dispersed in hot water and quickly dissolved after cooling. Two typical methods are as follows.
Add hot water (85°C) to the container. Gradually add hydroxypropyl methylcellulose under slow stirring, HPMC floats on the water surface and gradually forms a slurry, cooling the slurry while stirring.
Add 1/3 or 2/3 of the required amount of hot water (85°C) to the container and gradually add HPMC to the hot water with constant stirring. Cold or ice water is then added to the hot water slurry to reach the desired level. Continue stirring to cool the mixture.
Mix the HPMC powder with a large amount of other powders, mix well with a blender, and then add water to dissolve. At this point HPMC can be dissolved without clumping because there is only a little bit of HPMC in each tiny little corner. the powder will dissolve immediately upon contact with water. This method is used by putty powder and mortar manufacturers.
HPMC is easily dissolved by pre-dispersing or wetting with organic solvents such as ethanol, ethylene glycol or oil, and then adding water to dissolve.
Surface-treated powders are developed specifically to prevent caking in wet-mix applications (e.g., paint and emulsion applications). To prepare a solution from the surface-treated powder, the powder is placed directly in cold water. Over time, a fully developed solution with the appropriate viscosity is prepared by continuously stirring the solution.
For rapid dissolution, the fast dissolving (surface treated) HPMC will dissolve rapidly after adding ammonia or alkaline water to adjust the pH value to 8-10 to form a solution.
In conclusion, the correct method for different types of products can be dissolved adequately. If lumps appear when dissolving, it is caused by insufficient stirring or direct addition to cold water. In this case, stir quickly. In addition, if bubbles are generated when dissolving, leave it or add defoamer.
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