Ethyl cellulose
Structural formula | |||||||
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![]() Typical excerpt from an ethyl cellulose polymer degree of substitution 2 |
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General | |||||||
Surname | Ethyl cellulose | ||||||
other names |
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CAS number | 9004-57-3 | ||||||
Monomers / partial structures | ethylated cellobiose | ||||||
Brief description |
white granules |
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properties | |||||||
Physical state |
firmly |
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safety instructions | |||||||
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As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions . |
Ethyl cellulose (technical language, standard language: ethyl cellulose ) is a macromolecular substance that is obtained semi- synthetically from naturally occurring cellulose . Chemically, it is a cellulose ether , which occurs in different types, which differ in their degree of polymerization ( molar mass distribution ) and in their degree of etherification. Ethyl cellulose is typically a hydrophobic white powder and is soluble in organic solvents (e.g. ethanol ).
Extraction and presentation
Ethyl cellulose is not found in nature, but is produced synthetically by treating cellulose with a hot, alkaline solution (a lye, for example sodium hydroxide ) and then with ethyl halides - such as ethyl chloride .
Since not all hydroxyl groups react in this reaction, mixtures are formed with different degrees of substitution . The degree of substitution of the individual starch components within a polymer can also vary.
Chemical properties
Chemically, ethyl cellulose is an ethyl ether of cellulose and is produced by replacing hydrogen atoms in the hydroxyl groups with ethyl groups .
Depending on the number of substituted hydroxyl groups, the ethyl celluloses differ. Cellulose is a chain molecule made up of numerous glucose molecules, each glucose unit has three hydroxyl groups. Different ethyl celluloses can be described by their degree of substitution (DS), the average number of etherified hydroxyl groups per glucose unit. The theoretical maximum is 3.0, typical values are in the range from 2.2 to 2.6. The degree of substitution influences the solubility in different solvents. While ethyl cellulose types with low degrees of substitution (0.8-1.3) are soluble in water, an increase in the degree of substitution leads to improved solubility in alcohols and increased hydrophobicity . Most technical grade ethyl celluloses are insoluble in water and soluble in a wide range of organic solvents and their mixtures. Ethyl cellulose is thermoplastic ; the softening point can be lowered by adding plasticizers .
use
Ethyl cellulose is a versatile compound that is used as a thickening agent, binding agent, adhesive, as well as a film-forming agent and water-repellent barrier layer. It is the main component of lightfast cellulose ether coatings , packaging materials, thermoplastics , artificial snow for Christmas trees, cable insulation, protective skins and seals . Ethyl cellulose is also used as an additive to synthetic resins and waxes for painting colored Easter eggs and as an additive for stamping inks in the food industry (stamping eggs or cheese).
Food and luxury foods
Ethyl celluloses (additive number E 462 ) as well as other chemically modified derivatives of cellulose (E 461 and 463 to 469) are approved in the EU as a food additive for various purposes.
pharmacy
Ethyl cellulose is widely used as a pharmaceutical excipient in drug production: for example, to increase the viscosity in liquid drug preparations , as a binder for tablet granules, as a builder and disintegrant for tablets and, in particular, as a film former (e.g. trademarked under Surelease ® ) for coated tablets.
According to the characterization in the European Pharmacopoeia, pharmaceutical grades of ethyl cellulose contain an ethoxy group content of 44.0% to 51.0%.
Individual evidence
- ^ The Merck Index: An Encyclopedia of Chemicals, Drugs, and Biologicals. 9th edition. Merck & Co., Whitehouse Station, NJ, USA 1976, ISBN 0-911910-26-3 , p. 497.
- ↑ a b Data sheet Ethyl cellulose, Ph Eur, viscosity 10 mPa.s from Sigma-Aldrich , accessed on May 14, 2017 ( PDF ).
- ↑ a b Otto-Albrecht Neumüller (Ed.): Römpps Chemie-Lexikon. Volume 2: Cm-G. 8th, revised and expanded edition. Franckh'sche Verlagshandlung, Stuttgart 1981, ISBN 3-440-04512-9 , p. 1203.
- ↑ YES Brydson: Plastics Materials . 6th edition. Butterworth-Heinemann, London 1995.
- ↑ AQUALON ® Ethyl Cellulose (EC) Physical and Chemical Properties. (PDF) (No longer available online.) 2002, archived from the original on May 16, 2011 ; accessed on April 30, 2016 .
- ↑ Dow Cellulosics ETHOCEL Ethyl Cellulose Polymers Technical Handbook. (PDF) (No longer available online.) 2005, archived from the original on February 15, 2016 ; accessed on April 30, 2016 .
- ↑ Zusatzstoffe-online.de: methyl cellulose .
- ↑ Commentary on the European Pharmacopoeia 4.04, ethyl cellulose. Loose-leaf collection, 19th edition 2005, Wissenschaftliche Verlagsgesellschaft Stuttgart.
- ↑ European Pharmacopoeia. 6th edition. Basic work 2008, 6.0 / 0822, pp. 2508-2510.