Carbodylated cellulose esters

Abstract

A process for preparing a carboxylated cellulose ester from oxidized cellulose is described. The carboxylated cellulose esters have improved solvent solubility and coating resin compatibility when compared to cellulose esters made from regular grade cellulose. The process comprises activating the oxidized cellulose with water. The activated oxidized cellulose is then dehydrated by displacing the water with acetic acid and optionally displacing at least some of the acetic acid with butyric acid or propionic acid. After dehydration the activated cellulose is reacted with an esterifying reagent in the presence of a catalyst at about 0 DEG C. The temperature is gradually increased to a level sufficient to complete reaction and to obtain an intrinsic viscosity ranging from about 0.2 to about 1.6 dl / g. The reacted solution is then hydrolyzed to obtain a hydroxyl content ranging from about 0.05 to about 1.0. The catalyst is neutralized with a neutralizing agent and the solution is optionally filtered and the carboxylated cellulose ester is then precipitated with a precipitating agent. The invention also relates to carboxylated cellulose esters prepared by the process described above as well as high solids coating compositions containing carboxylated cellulose esters made by the above process.

Description

field of invention

[0001] The present invention relates to a process for the preparation of carboxylated cellulose esters from oxidized cellulose. The carboxylated cellulose esters of the present invention can be formulated into coating compositions having very high solids content, ie, greater than 45%. The carboxylated cellulose esters prepared by the process of the present invention exhibit improved compatibility with coating resins and are soluble in a wider range of solvents than conventional cellulose esters. Background of the invention

[0002] Cellulose esters are used in various applications such as filter tows, pharmaceutical coatings, ink compositions, moldings and industrial coatings. Thus, an economical process for their preparation is clearly very desirable. Coating compositions using typical cellulose esters often exhibit low solids content, ie, these compositions require excess solvent, which is detrimental with respect to drying time, solvent evaporation, a...