Enzymatic hydrolysis performance of hydroxyethyl cellulose
HEC will degrade under the action of enzymes, reducing the viscosity. The resistance to biodegradation was measured by the change of viscosity of HEC solution before and after enzyme attack under certain conditions. Changing the molecular structure of HEC can improve its resistance to enzymatic degradation.
Only when the degree of substitution of HEC is very high and the distribution of substituents is even. It can HEC be protected from the attack of cellulase. Such products are called “biostable”.
The enzyme acts on HEC mainly to break the glycosidic bond between unsubstituted glucose rings. The number of breaks is proportional to the number of unsubstituted glucose ring groups. The resistance of HEC to enzymes was significantly enhanced with the decrease of the number ratio of unsubstituted glucose rings and adjacent diol hydroxyl groups.
The increase of MS reduces the unsubstituted ratio and enhances the anti-enzyme performance. The key to preparing enzyme-resistant HEC is to improve the uniformity of substituent distribution. This reduces the proportion of adjacent unsubstituted glucose rings. Increase the steric hindrance for enzymatic degradation.
If the hydroxyethylation process adopts a two-step method.
HEC can be prepared by properly adjusting the water content in the slurry. The first step is carried out in a higher concentration NaOH solution. And the second step is carried out in a lower concentration NaOH solution.
In addition, when HEC is prepared by the traditional method or the two-step method. The enzyme resistance can be improved by adding a mixed catalyst of LiOH and NaOH. These techniques can increase the accessibility of ethylene oxide to alkali cellulose. Can make the cellulose crystallization region smaller. Improve hydroxyl reactivity. A product with a uniform distribution of substituents was obtained at a lower NaOH concentration.
HEC solution will also be degraded by oxidation, acid hydrolysis, heating and mechanical force. For example, the viscosity reduction in latex paint is due to the degradation of HEC in the presence of oxidizing agents (such as potassium persulfate). Research and technology development to improve the viscosity reduction of HEC caused by non-enzymatic degradation is also important.
LOOK at Landcel’s HEC.