What is Hydroxypropyl Methylcellulose (HPMC)?

Hydroxypropyl methylcellulose (HPMC), also known as hydroxypropyl methylcellulose, is a cellulose ether produced from refined cotton cellulose through an etherification reaction under alkaline conditions. It appears as a white powder, tasteless, odorless, and non-toxic, soluble in cold water to form a colorless, transparent, viscous solution. This product possesses excellent water retention, thickening, film-forming, binding, emulsifying, and dispersing properties, and exhibits good acid and alkali resistance, enzyme resistance, and chemical stability. It is widely used in various industrial fields such as building materials, coatings, pharmaceuticals, food, and daily chemicals.

In building materials, HPMC primarily functions as a water retainer and thickener. Its water retention is crucial for the full hydration and curing of hydraulic materials such as cement and gypsum. The viscosity range is typically selected based on the application; putty products commonly use a viscosity of approximately 100,000 mPa·s, while mortar applications often use higher viscosities (such as 150,000 mPa·s and above) to enhance workability and anti-sagging properties.

HPMC is primarily produced using a solvent method. Raw materials include refined cotton, chloromethane, and propylene oxide, supplemented with solvents such as alkalis, acids, toluene, and isopropanol. If solvent residue is not completely removed during post-processing, the finished product may have a slight odor.

Regarding common construction problems, the following two points should be clarified:

Putty powdering: This is mainly related to the quality and composition ratio of lime, with HPMC having a relatively small impact. Ensuring the water retention properties of HPMC helps the material to fully hydrate, which can indirectly improve strength, but it is not the main cause of powdering.

Surface efflorescence: This phenomenon originates from soluble salts and alkalis in the base material (such as concrete) migrating to the surface and crystallizing with moisture, and is not directly related to HPMC itself. It can be prevented by controlling the alkali content of the base material, using an alkali-resistant primer, or reducing the amount of water used during construction.

Main application areas include:

Building materials: Used in cement mortar, tile adhesive, thermal insulation mortar, gypsum-based grout, plastering slurry, etc., to improve workability, water retention, and adhesion.

Chemical Industry: Used as a suspension stabilizer in the polymerization of vinyl chloride and other polymers, and as a thickener and stabilizing component in pesticides, latexes, and adhesives.

Cosmetics and Detergents: Used to adjust the rheological properties and foam stability of products such as shampoos and toothpastes.

Pharmaceutical Industry: Used as a matrix for tablet coatings, sustained-release formulations, eye drop lubricants, and topical gels, playing roles in thickening, water retention, and film formation.

In summary, hydroxypropyl methylcellulose is a multifunctional polymeric excipient. Its properties can be controlled by key indicators such as hydroxypropyl content and viscosity. Proper selection can significantly improve the process adaptability and quality stability of the final product.