Suspending agents hydroxypropyl cellulose

Cellulose ethers, more particularly methyl cellulose (MQ, methylhydroxypro-pyl cellulose (MHPC) and hydroxypropyl cellulose (HPC) are used as protective colloids also called primary suspending agents in suspension polymerization for the manufacturing of S-PVC. Their role is maintaining the particle size of the resin. Hydroxyethyl cellulose (HEC) is preferred for manufacturing of vinyl acetate emulsion polymers and as a thickening agent in dispersimi paints. 

Conversions of alkali cellulose with ethylene oxide or propylene oxide, on the other hand, proceed without alkali consumption. The newly formed hydroxyl groups can also add on ethylene oxide or propylene oxide molecules. Commercially produced hydroxypropyl cellulose, with DR = 4, dissolves in water below 38 C. It can be thermoplastically processed and so is used to manufacture water-soluble packaging film, as an adjuvenant in pharmaceutics and confectionery, as a whipped cream stabilizer, as a binder for ceramics, as a suspending agent in emulsion polymerization, etc. 

Mixtures of hydrocoUoidal gelling agents in an aqueous medium have also been employed as water-soluble or water-dispersible additives to provide gels having solids-suspending properties. Such mixtures include a mixture of hydroxypropyl-cellulose and poly(l-alkene-maleic anhydride) as poly(isobutylene-co-maleic anhydride), and a blend of hydroxypropylcellulose and poly(alkyl vinyl ether-co-maleic anhydride) as poly(methyl vinyl ether-co-maleic anhydride) [91]. 

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