Patent GB-468880-A (GB)
Title: Process for the stabilisation of cellulose esters
IPC: C08B3/28
Filed: 1936-10-09
Abstract: The process described in the parent Specification for removing the retained catalyst residues from simple or mixed cellulose esters prepared by esterifying cellulose in presence of a sulphurcontaining catalyst is modified by treating the cellulose ester in the non-dissolved state with a hydrolytically inactive stabilizing agent consisting of one or more compounds of the general formula R<1> (OR<11>)n (COOR<111>)m in which the groups but not the linkages are indicated.  R<1>, R<11>, R<111> are hydrocarbon radicals substituted if desired by halogen, nitrogen, or other group, or if desired R<1> or R<111> may be hydrogen or R<1> may be absent. The letters n and m are integral numbers, n being equal to or greater than zero, and m being equal to or greater than 1.  The stabilizing-agent may be a polybasic organic acid or ester, an oxy-acid etherified in the oxy-group or an ester thereof, an acid-ether or ester thereof, or an ester of a polyhydric alcohol. The lower fatty acids and esters thereof with monohydric alcohols are excluded except when used in conjunction with other substances of the above general formula.  The stabilizing agent may be diluted or suspended by an indifferent liquid.  Stabilization may be carried out on the cellulose ester freed from the esterification bath by a combination of treatments at room temperature and raised temperature, and it may be followed by rinsing.  Some of the stabilizing agents may be used as non-solvents during the esterification process.  After use, the stabilizing liquid may be treated for re-use, by neutralizing or adsorbing impurities with carbonates, lime, or basic silicates, or by esterification of acid impurities with alcohol. Stabilization may be accelerated by the presence of hydrochloric acid, or perchloric acid.  In the case of stabilizing agents insoluble in water, the treatment may be carried out in presence of water.  The fibrous cellulose ester may be washed with stabilizing liquid, and then after removal of most of the liquid, treated with warm water.  The catalyst eliminated passes into the aqueous phase.  In an example, linters are pretreated with acetic acid and a small amount of sulphuric acid, acetylated with a mixture of acetic anhydride, ethylglycol acetate and sulphuric acid in a hydro-extractor with initial cooling, and then stabilized.  The acetylation liquid is removed by centrifuging and the fibres are treated several times cold and then at 100 DEG  C. with ethyl glycol acetate.  In another example, stabilization is effected by treatment at low temperature with ethyl glycol acetate, and then with boiling ethyl acetate in a Soxhlet apparatus.  In another example, butylglycol acetate is used as non-solvent in the esterification, and ethyl glycol acetate is used as stabilizing liquid.  Other stabilizing liquids specified are trimethylene glycol diacetate, di- and tri-ethylene glycol diacetate, diethyl glycerol acetate, propyloxyacetic acid or its ethyl ester, acetoxyacetic acid or its ethyl ester, ethyl oxalate, adipic acid or its ethyl ester, furfuryl acetate, cyclohexyl acetate, phthalic esters, m-nitrophenyl acetic ester, and b -chlorethyl glycol acetate.  Triacetin or methyl glycol acetate when used should be diluted with indifferent liquids to reduce the solvent action on the cellulose ester.  Cellulose propionate, or butyrate may be treated similarly to cellulose acetate.