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US 2020/0262933 A1Published application
Cellulose acetate and method for producing cellulose acetate
AssigneeDaicel Corporation
InventorsNaohiro OYAMADA, Akihiro HIGUCHI
Life of this patent
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Abstract
Provided is cellulose acetate with which a hollow fiber membrane having excellent salt rejection and water permeability can be produced. The cellulose acetate, in which a total content of calcium and magnesium is 2.8 to 3.5 μmol/g; a 6 percent viscosity is 40 to 80 mPa⋅s; a degree of filtration Kw is 35 g−1 or less; a molecular weight distribution Mw/Mn is 3.00 or less; and a degree of acetylation is 61.3 to 62.3%.
Claims7
A cellulose acetate, wherein:
- a total content of calcium and magnesium is 2.8 to 3.5 μmol/g;
- a 6 percent viscosity is 40 to 80 mPa⋅s;
- a degree of filtration Kw is 35 g−1 or less;
- a molecular weight distribution Mw/Mn is 3.00 or less;
- and
- a degree of acetylation is 61.3 to 62.3%.
3 more elements
A method for producing cellulose acetate, comprising the steps of:
- crushing a pulp having a carboxyl group content of 1.0 meq/100 g or more;
- pretreating the crushed pulp by bringing the pulp into contact with acetic acid or a sulfur-containing acetic acid;
- bringing the pretreated pulp into contact with a mixed solution of acetic acid and acetic anhydride to esterify the pulp with acetic anhydride;
- adding a neutralizing agent to hydrolyze the cellulose acetate obtained by the esterification;
- precipitating the cellulose acetate whose degree of acetyl substitution is adjusted by the hydrolysis;
- and
- adding a stabilizer to the precipitated cellulose acetate,
- wherein the mixed solution is in a state between 10° C. below freezing and 3° C. below freezing, and
- in the esterification step, a temperature of a reaction system reaches a peak temperature between 48° C. and 55° C. by less than 50 minutes after the pretreated pulp is brought into contact with the mixed solution of acetic acid and acetic anhydride, and the temperature of the reaction system drops by 5° C. from the peak temperature by less than 70 minutes from the above contact point.
6 more elements
Dependencies are inferred from the claim text.