DE740985C - Process for the production of cellulose esters - Google Patents

Description

Process for the preparation of cellulose esters It is known that to achieve the highest possible quality products, such as rayon, films, etc., various measures when Aci.dylieren of cellulose, z. B. in the form of cotton linters or wood pulp, a crucial one in the presence of zinc chloride as a catalyst Attributes influx. As such come z. B. consider the civilian composition of the acidylation mixture, the type of temperature control, the measurement of the reaction time etc.

A known measure is to use zinc chloride as a catalyst and of mineral acid salts, e.g. B. sodium sulfate, to acetylierei ,, which however the solubility of the acetyl cellulose and the filterability of the solutions are not in the favorable sense influences `-erden. By special pretreatment in the presence of basic Agents such as pyridine or sodium acetate can also be used to partially cellulose first esterify and then by known methods in the presence of acidic compounds, such as hydrochloric acid, sulfuric acid, zinc chloride, halogen compounds of oxygen acids and the like, acidylate completely. However, this is time consuming and costly because one must work in two stages.

It has been found that there are considerable improvements in accordance with the invention can be achieved, which can be used both in the production, for. B. in terms of uniformity, the viscosity, the filterability and the clarity of the solutions, as well as the finished goods, e.g. B. films, threads, etc., especially with regard to the mechanical Properties, e.g. B. the tear strength, flexibility. etc., have a beneficial effect.

The method according to the invention for the preparation of cellulose esters .by treating unesterified cellulose with a mixture of fatty acid anhydride, Solvents with zinc chloride as a catalyst is that the esterification with the addition of fatty acid salts oI of compounds with the fatty acids present in the reaction mixture form salts, is carried out.

You can use the compounds or the salts individually or mixed instead Add your acidylation mixture to the catalyst as well. Such connections can e.g. B. hydroxides, carbonates or fatty acid salts of alkali metals and des Ammonium, also compounds of metals such as magnesium, zinc, manganese, aluminum, z. B. their oxides, hydroxides, carbonates or fatty acid salts; than organic salt-forming compound is suitable for. B. pyridine.

The method according to the invention makes it possible to avoid the degradation of the cellulose and to achieve clear, filterable, uniform solutions in one operation. This enables the production of high quality products, e.g. B. of films, threads, etc., with favorable mechanical properties. EXAMPLE 100 kg of cotton linters, which have been pretreated by one of the known processes in which esterification of the cellulose does not occur, are acidylated with the following mixture: 2.50 kg of acetic anhydride, 130 kg of glacial acetic acid, 130 kg of zinc chloride, 0.3 kg of zinc oxide .

After 311 hours at a temperature of 5 °, a cellulose triacetate with an acetic acid content of 61.5 to 62.2 ° 10 is obtained. A 10% solution in Methylenchloridinetlianol 9: i gives a viscosity according to the falling ball method z. B. from 150 seconds. Without the addition of zinc oxide, the viscosity is 30 seconds. Example e A batch according to Example i, the cellulose having been pretreated by one of the known processes in which esterification does not occur, instead of 0.3 kg of zinc oxide, contains ten times the amount.

After 1. to; An hour at a temperature of> 6 to 6o 'becomes a Cell silose triacetate obtained with an acetic acid content of 61.5 to 62.2 ° 1o. One 10% solution in methylene chloride methanol gives a fall time of 100 seconds. Without the addition of zinc oxide, the VISCOSITY is 20 to 3o sectand.

EXAMPLE 3 100 kg of spruce wood pulp are acidylated with the following mixture after a customary pretreatment in which, however, no chemical change in the cellulose occurs: 130 kg of zinc chloride, 130 kg of glacial acetic acid, 250 kg of acetic acid anhydride, 100 kg of butyric acid, 0.75 kg of magnesium acetate .

After .1 hours a cellulose mixed ester is obtained at a temperature of 56 °, in which a substantial part of the acid residue is made up of butyric acid.

Claims (1)

PATENT CLAIM: Process for the production of cellulose esters by treating unesterified cellulose with a mixture of fatty acid anhydride, solvents and zinc chloride as catalyst, characterized in that the esterification is carried out with the addition of fatty acid salts or of compounds which form salts with the fatty acids present in the reaction mixture . To distinguish the subject of the application from the state of the art, the following publications were taken into account in the granting procedure: German patents .... \? R. 22d.330, 56o 037; French patent specification 60o 08o.