Preparation of organic acid esters of cellulose having an improved resistance to delustering

Claim 1

IN A PROCESS FOR MANUFACTURING ORGANIC ACID ESTERS OF CELLULOSE SUITABLE FOR THE PRODUCTION OF FILAMENTS AND FILMS WHEREIN THE CELLULOSE IS ESTERIFIED TO FORM A SOLUTION OF SAID CELLULOSE ESTER AND SAID CELLULOSE ESTER IS PRECIPITATED FROM SAID SOUTION, WASHED AND DRIED, AND IN WHICH SAID PRECIPITATED CELLULOSE ESTER CONTAINS SALTS THAT ARE CAPABLE FOR EXISTING IN TWO DIFFERENT DEGREES OF HYDRATION AND WHICH EXHIBIT A CHANGE IN SPECIFIC VOLUME OF MORE THAN ABOUT 0.6 CUBIC CENTIMETERS PER GRAM IN PASSING FROM ONE DEGREE OF HYDRATION TO THE OTHER DEGREE OF HYDRATION, THE IMPROVEMENT WHICH COMPRISES CARRYING OUT THE WASHING OF SAID PRECIPITATED CELLULOSE ESTER WITH A WATER SOLUTION OF A SALT, SELECTED FROM THE GROUP CONSISTING OF SOLUBLE CALCIUM AND BARIUM SALTS, THAT WILL REACT WITH SAID AFOREMENTIONED SALTS BY METATHESIS TO PRODUCE SALTS WHICH EXHIBIT A CHANGE IN SPECIFIC VOLUME OF LESS THAN ABOUT 0.6 CUBIC CENTIMENTERS PER GRAM IN PASSING FROM ONE DEGREE TO HYDRATION TO ANOTHER DEGREE OF HYDRATION, AT LEAST ONE OF THE SALTS PRODUCED HAVING A LOWER SOLUBILITY THAN THE SALTS PRESENT IN THE ORGANIC ACID ESTERS OF CELLULOSE AND IN THE WASH WATER AND THEN DRYING SAID CELLULOSE ESTER DIRECTLY AFTER SAID WASHING SAID IMPROVEMENT RESULTING IN AN INCREASE IN THE RESISTANCE TO DELUSTERING OF SAID CELLULOSE ESTER WHEN IN THE FORM OF A FILM OR FILAMENT.