Hydroxyethyl methyl cellulose

Structural formula
Structural formula of hydroxyethylmethyl cellulose R = H, CH 3 , CH 2 CH 2 OH
General
Surname	Hydroxyethyl methyl cellulose
other names	2-hydroxyethyl methyl cellulose 2-hydroxyethyl cellulose methyl ether Methyl hydroxyethyl cellulose Cellulose hydroxyethyl methyl ether HEMC
CAS number	9032-42-2
Monomers / partial structures	Hydroxyethylmethyl glucose
Brief description	colorless to beige solid
Drug information
Drug class	Thickener
properties
Physical state	firmly
solubility	soluble in cold and partly also in hot water (gel formation)
safety instructions
GHS labeling of hazardous substances no GHS pictograms H and P phrases H: no H-phrases P: no P-phrases
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Hydroxyethyl methyl cellulose ( HEMC ) is a collective term for chemical compounds that are produced by the etherification of cellulose . In these, some of the hydroxyl groups of the cellulose are linked as ethers with methyl and with hydroxyethyl groups.

properties

HEMC comes onto the market in various degrees of polymerisation and various degrees of substitution . The size of the macromolecule is usually characterized by its viscosity in 2% aqueous solution, e.g. B. 300 (for approx. 300 mPas), 1000 (for approx. 1,000 mPas) or 40,000 (for approx. 40,000 mPas). It is soluble in both water and organic solvents. The viscosity is greatly increased in aqueous solutions. In contrast to other cellulose ethers , such as hydroxypropyl cellulose , in which the solubility decreases sharply when heated above the critical solution temperature and flocculation can occur, the critical solution temperature with HEMC is significantly higher at up to 110 ° C.

use

Hydroxyethylmethylcellulose is used in construction chemistry for water retention in cementitious wall plasters and in tile adhesives and mortars. In pharmacy it is used as a binding agent and coating for tablets and as a thickener in suspensions and gels.

Manufacturing

Cellulose is swollen with sodium hydroxide solution at 35 ° C in methyl chloride and then reacted with ethylene oxide at 40-55 ° C under pressure. After the reaction has ended, the reaction mixture is neutralized with an organic acid such as formic acid , acetic acid or propionic acid . For isolation, all volatile substances are first distilled off (under reduced pressure), cleaned with a solvent / water mixture and then the solid is dried and ground to a powder.

Trade names

Tylose MH, Walocel MW, Culminal MHEC.

Individual evidence

1. ↑ ^{a b c d} patent US4438264 : Process for the production of hydroxyethyl methyl cellulose. Published on March 20, 1984 , applicant: Bayer Aktiengesellschaft, inventor: Klaus Balser, Helwig Tuebner, Wilhelm Oppermann. ‌
2. ↑ ^{a b c} data sheet methyl 2-hydroxyethyl cellulose from Sigma-Aldrich , accessed on November 19, 2016 ( PDF ).
3. ↑ Amit cellulose - methyl-hydroxyethyl-cellulose. In: amitcellulose.com. Retrieved November 19, 2016 .