Cellulose is a natural polymer and the chief component of wood and plant fibers. Cotton, for example, is almost pure cellulose. Cellulose is a polysaccharide composed of individual anhydroglucose (AHG) units, which are held together by ß-1,4 glycoside linkages that make cellulose a long, rigid molecule. The number of AHG in the polymer chain is defined as the degree of polymerization (DP).
Pure cellulose has large crystalline regions due to hydrogen bonds between the -OH groups on different chains. In manufacturing Bermocoll, purified cellulose is activated in a first step with sodium hydroxide solution. In this alkalization reaction, the structures of the crystalline areas are expanded, allowing the hydroxyl groups to be transformed into alcoholate. This cellulose alcoholate is termed alkali cellulose.
The strong attractive forces between cellulose chains due to interchain hydrogen bonds will be greatly reduced by alkylating the greater portion of the -OH groups, thereby preventing hydrogen bonding. Such chemical modification results in significantly changed characteristics with regard to solubility, surface activity, chemical resistance and enzyme resistance. In this way, it is possible to produce sets of cellulose ethers with carefully calculated performance characteristics.
In Bermocoll, the hydroxyl groups are modified with ethyl and ethylene oxide substituents. The properties of the cellulose ether are determined by the type of substituents, and also by their number and distribution along the molecule chain.