Water-soluble cellulose ethers coatings

Ethyl cellulose (EC) is a water-insoluble cellulose ether. It is produced by reaction of alkali cellulose with ethylene chloride. It has film-forming and thermoplastic properties. As a plastic, it can be processed by extrusion and injections. It is hard, stiff and with good resistance to impact. It is soluble in the molten state with other thermoplastics. As for its film-forming properties, it is used in the formulation of varnishes, inks and glues. It forms removable coatings. 

Cellulose is also commercially modified by acetylation to produce a material suitable for X-ray and cine film. Commercially cellulose ethers are also prepared, such as methylcellulose. This material is water-soluble and gives a highly viscous solution at very low concentrations. Hence it is widely used as a thickener in latex paints and adhesives, in cosmetics and for coating pharmaceutical tablets. 

Examples of aqueous coating solutions include water-soluble low molecular weight cellulose ethers, emulsion polymerization latexes of polymethacrylates, and dispersions of water-insoluble polymers such as ethyl-cellulose in the form of pseudolatex. These solvent-free coating solutions provide a range of different coatings... 

By use of a modification of the well-known Williamson synthesis it is possible to prepare a number of cellulose ethers. Of these materials ethyl cellulose has found a small limited application as a moulding material and somewhat greater use for surface coatings. The now obsolete benzyl cellulose was used prior to World War II as a moulding material whilst methyl cellulose, hyroxyethyl cellulose and sodium carboxymethyl cellulose are useful water-soluble polymers. 

Hydroxypropyl cellulose (HPC) is a non-ionic water-soluble and pH insensitive cellulose ether. It can be used as thickening agent, tablet binder and modified release and film coating polymer. Buccal delivery formulations containing HPC and polyacrylic acid are used for many years and is used for mucoadhesive delivery systems for several drugs. 

Isophorone is a stable, colorless, volatile liquid with a mild odor. It is only slightly soluble in water, but miscible with most lacquer solvents. It is an excellent solvent for many types of cellulose esters, cellulose ethers, oils, fats, gums and resins, both natural and synthetic. It is the most powerful solvent for nitrocellulose and "Vinylite" resins. Isophorone has one of the highest oromatic hydrocarbon dilution ratios for nitrocellulose—5.7 for toluene ond 5.1 for xylene, it will dissolve 30% of "Vinyllte" resin without gelling. At ordinary temperatures solutions can be made of second RS nitrocellulose containing 45% solids. Isophorone is used in the manufacture of coatings, inks, stencil pastes and as a thinner in synthetic resin finishes. 

Hydroxypropylcellulose (HPQ, e.g. Klucel Soluble in water Tablet or pellet coating combined with other cellulosic ethers Powder... 

Hydroxypropylcellulose is a non-ionic, water-soluble, polyhydroxypropy I cellulose ether that is commercially available in a wide range of molecular weights (50000-1,250,000 g mol ). It is widely used in the pharmaceutical industry as a binder for tablets, in film coatings and as a controlled release matrix (255). 

---