What is the solvent of hydroxypropyl methylcellulose?

Hydroxypropyl methylcellulose (HPMC) is a nonionic cellulose ether commonly used in the construction, pharmaceutical, food and cosmetic industries. It is a high molecular polymer with thickening, emulsification, film-forming, suspension, bonding, lubrication and water retention functions. It is widely used in building mortar, coatings, drug sustained release, food thickeners and other fields.

Solvents for hydroxypropyl methylcellulose

HPMC itself is insoluble in most organic solvents, but is soluble in water and certain specific solvent systems. Its solubility is affected by temperature and pH.

1. Solubility in water

HPMC has unique thermal gel properties. It can be dispersed and dissolved in cold water, but will solidify in hot water. When the water temperature is higher than its gel temperature (usually 60°C-90°C, depending on the degree of substitution and molecular weight), HPMC particles will coagulate and lose solubility; when the temperature drops to a suitable range, it can be dissolved again. Therefore, when preparing HPMC solution, the following methods are usually used:

Hot water dissolution method: first use a small amount of hot water (above 60°C) to wet HPMC to form a protective colloid layer on its surface, and then add cold water to completely dissolve it.

Cold water dispersion method: slowly stir HPMC in cold water to fully disperse it, and form a uniform solution after standing for a certain period of time.

2. Solubility in organic solvents

HPMC is difficult to dissolve directly in many organic solvents, but can be dispersed or dissolved in certain polar solvents or water-organic solvent mixed systems. For example:

Alcohols (such as methanol, ethanol, isopropanol): HPMC is difficult to dissolve in pure alcohol, but can be partially dissolved in a water-alcohol mixed system.

Ketones (such as acetone, methyl ethyl ketone): HPMC is insoluble in a single ketone solvent, but may form a uniform solution in a water-ketone system.

Ethers (such as tetrahydrofuran): HPMC is insoluble in most ether solvents.

Binary solvent system (such as water-ethanol, water-acetone): HPMC can be dissolved or dispersed at a specific ratio of water-organic solvent.

3. Solubility in media with different pH values

HPMC has a wide adaptability to pH values and can maintain good solubility and stability between pH 3-11, but it may degrade in strong acid or strong alkaline environments, affecting its performance.

Factors affecting dissolution

Temperature: The solubility of HPMC is greatly affected by temperature. High temperature will cause gelation and make it lose solubility, while low temperature can increase its solubility.

Agitation: Proper stirring can promote the dispersion and dissolution of HPMC, but excessive stirring may cause foaming, and high-speed stirring should be avoided.

Particle size: Fine powder HPMC is easier to dissolve than granular or coarse powder.

Water quality: The ion concentration and hardness in water may affect the dissolution behavior of HPMC.

The main solvent of hydroxypropyl methylcellulose is water, which is easy to dissolve in cold water and gels in hot water. In addition, it can be dissolved or dispersed in a water-organic solvent mixed system (such as water-ethanol, water-acetone), but its solubility in pure organic solvents is poor. During the dissolution process, the temperature, stirring method and solvent environment need to be controlled to obtain a uniform and stable solution.