БУТИРАТ АЦЕТАТА ЦЕЛЛЮЛОЗЫ

Химические свойства

white granular crystalline powder

Использование

Contact lens material (hydrophobic).
Cellulose acetate butyrate is the most commonly used organic cel- lulose ester for coating applications.

Определение

Cellulose acetate butyrate (CAB) is a cellulose ester where the hydroxyl groups attached to the glycoside rings in cellulose are partially or fully substituted by acetyl and butyryl groups. The ratio between acetyl and butyryl substitution can be varied in their synthesis, and somewhat different properties can be obtained. The total degree of substitution (DS) is regarded as a maximum of three; however, for a degree of polymerization (DP) of less than 134, a slightly higher DS can occur due to the end-group contribution. Both the DS and the molecular weight of cellulose esters can be altered, and both are reported to lead to a variation in material properties[1].

Подготовка

Cellulose acetate-butyrate (CAB) is prepared in a manner similar to that described previously for cellulose acetate. Esterification is carried out using a mixture of acetic anhydride and butyric anhydride with sulphuric acid as catalyst and then the product is slightly hydrolysed. Depending on the reaction conditions, various products may be obtained; commercial materials generally have about 1-2 butyryl groups per glucose residue.

Промышленное использование

Commonly called butyrate or CAB, it is somewhattougher and has lower moisture absorptionand a higher softening point than acetate.CAB is made by the esterification of cellulosewith acetic acid and butyric acid in the presenseof a catalyst. It is particularly valuedfor coatings, insulating types, varnishes, andlacquers.
Special formulations with good weatheringcharacteristics plus transparency are used foroutdoor applications such as signs, light globes,and lawn sprinklers. Clear sheets of butyrateare available for vacuum-forming applications.Other typical uses include transparent dial covers,television screen shields, tool handles, andtypewriter keys. Extruded pipe is used for electricconduits, pneumatic tubing, and low-pressurewaste lines. Cellulose acetate butyrate alsois used for cable coverings and coatings. It ismore soluble than cellulose acetate and moremiscible with gums. It forms durable and flexiblefilms. A liquid cellulose acetate butyrate isused for glossy lacquers, chemical-resistantfabric coatings, and wire-screen windows. Ittransmits ultraviolet light without yellowing orhazing and is weather-resistant.