US2317767A - Cellulose fatty acid esters - Google Patents

Description

' UN rrsD oELLu' osii E 'Rudolt .Hofmann v:and

kusen-I. G.'Werk,. Germany vested; in the gAlic Property Custodian 1 Drawing. Application April 26; 1939; {Serial No'. 270,161; Ihfiermany May .12, 193 8 The-jpresent invention relates to the productlon of fibrous'fatty acid esters of cellulose;

Itis known to produce fibrous esters of'lcelluany particulartpurpose, withinithe .above defl ned limits. The process issuitable' as well'ior the productionffci fibrous cellulose acetate as of lose, for instance cellulose acetate, by reacting cellulosew'ith an es'terifying agent, for instance acetic acidanhydride, in the presenc'e of a.non-.

' solvent for the cellulose ester formed, --for in stance carbon tetrachloride, benzene, ,to1uene,

aliphatic and aromatic ethers and the like, and in the presence'of sulfuric acid as a catalyst. Since esterificationof cellulose in the fibrous form-is still more difficul't than producing cellulose esters in solution, it was necessary 'to'use large amounts oi the sulfuric acid catalyst 7 and/or to subject the cellulose to particular pretreatment processes with water, aqueous sulfuric acid'or lyes in order to carry out the reaction.

I However, cellulose esters prepared in the presence;

of large quantitiesof sulfuric acid are'of' insufficient stability; 'The presence oilarge quantities of water, on the other hand, caused the esterification to proceed very inhomogeneously, and a pre-treatment with sulfuric acid, or lyes causeddegradation of the cellulose, so that the cellulose esters produced according to the said known methods were not of the highest'quality.

We have now found thatfatty'acid esters of 7 1- cellulose in fibrous form can be produced in a verysimple and economical manner by treating cellulose with an esterifying mixture consisting of a fatty acid anhydride, a non-solvent for the cellulose ester formed'and'less than 1% of sul into an acetylating mixture of 350 parts acetic, 1

acid anhydride, 400 parts carbon tetrachloride and 0.7 part concentrated vsulfuric acid. The temperature is raised to 65 C. in the course'of water to the mixture; but this is not absolutely iuric acid. As an example, the concentration may bebetween.0.5-1% of sulfuric acid. The cellulose used in this process may have been pre-treated with'a fatty acid, for instance with glacial acetic acid, but it is not to be pre-treated, as in the previous processes, with water, sulfuric acid or lyes. The reaction is carried out at elevated temperatures, temperatures between and 70 0. being preierredl It .was rather ,un.

expected that in spite of the great difficulties in esterifying cellulose in the fibrous form,: fibrous cellulose esters ofuniform' solubility, highviscosity and excellent mechanical properties could be obtained within normal reaction periods in the presence of such" small quantities ofthe 7 catalyst. It' is especially advantageous-that I 'when preparing fibrous cellulose esters according to our new process no special stabilizing treatment is necessary. q The other reaction conditions Tclearly soluble fibrous cellulose, triacet'ate of nor-,- 5 0.

100 parts cellulose of normal humidity, for

' be dissolved. in glacial acetic acid, The excess of normal humidity havingbeen pre-treated-with I parts glacial acetic acid are introduced into a mixture of 350 parts acetic acid anhydride, 400' course of 3 hours to'60 C..an'd,k ept at that value .Q-until. esterification is coniplete. .After 'about 15" :1 a -d b m Ex lelike'regulationi of the temperature during the reaction, the

relative proportions of and the way of adding the Lever fibrous esters of ,cellulosevwithhigher saturated more fullyillustrated by the 01- weight: Example 1 instance bucked and bleached cotton linters, which have been pre-treated in known .manner with 50v parts glacial acetic acid, are introduced about 3 hours. When the reaction inixturehas I j been kept at that temperature for about 10 hours, esterificationis complete; 'a sample will then clearly dissolve in a mixture of methylene chloride methyl alcohol (9:1). When the v vi s-'- cosity of the-samplecorresponds to the desired value, the sulfuric acid catalyst is neutralized, for instance by adding a basic salt for an organic base to the mixture theneutralizing agent may acetic acid anhydridemaybe destroyed byradding :Ex ampl e 2 c 100. parts'of bucked and bleached cotton :linte'rs parts tolue ne and 0.9 part concentrated sulfuric acid. '-The reaction temperature-is raised in the hours from theintroducingli oi thecellulose a" .mal viscosity hasloeen.formed. is -worked up.

.parts"'bucked' e bieachea calm esteriiying mixture may be varied, as desired for iii of normal humidity having'bejen pre -treated in glinters the usual manner with glacial acetic acid are introduced into a mixture of 350 parts acetic'acid anhydride, 1000 parts carbon tetrachloride and 0.8 part concentrated sulfuric acid. The mixture is heated inthe course of about 3 hours to 70 C.

1. In the production of fibrous fatty acid estersof cellulose from cellulose which has been pretreated with a lower fatty acid,- the modification which comprises reacting the cellulosewith an esterifying mixture consisting of a lower fatty acid anhydride, an organic diluent which is a non-solvent for the cellulose ester formed, and

treated with a lower fatt acid, the modification which comprises reacting the cellulose. with an acetylating mixture consisting of acetic acid anhydride'fan organic diluent which is a"non-.

solvent for the cellulose acetate formed, an amount of sulfuric acid up to 1% based on the weight of the cellulose as a catalyst at a. tem- "perature between and C., theesteriflcation 'being 'carried out until. the cellulose acetate it formed dissolves in a mixture of methylene chloride-methyl alcohol (9:1). 3. ,In the production of fibrous fatty.

"of cellulose; the modification whichl comprises avreacting cellulose which has been pretreated with v glacialacetic acid, with an acetylatingf mixture consisting of acetic acid anhydride, an organic diluent whichis anon-solvent for thecellulose acetate formed, and between 0.5 to 1% sulfuric an amount of sulfuric acid up to 1% based on Q the weight of the cellulose as a catalyst at atemperature between 30 and 70 0., theeste'riflcation being carried out' until the celluloseester formed dissolves in a mixture of methylene chloridemethylene alcohol (9:1); r v a 2. In the production of fibrous fatty acid esters of cellulose from cellulose which hasbeen'preacid based on the weight of the cellulose as a catalyst at a temperature between 30 and 70" C., the esterification being carried out until the ester f dissolves in a mixture of methylene chloride-i ;methyl.alcohol(9:1).

acid esters .nuponn f WILI-IELMV omp; V