DE632256C - Procedure for determining the amount of catalyst required for the acetylation of a particular type of cellulose - Google Patents

Description

Procedure for determining the for the acetylation of a particular Cellulose Type Required Amount of Catalyst The invention relates to a method to determine the for the acetylation of cellulose with mixtures of acetic anhydride and glacial acetic acid required amount of catalyst. In the known catalytic acetylation of cellulose, which is produced using a wide variety of catalysts, such as sulfuric acid, Perchloric acid, zinc chloride, mixtures of phosphoric acid and perchlorates and the like, is carried out, there was previously no analytical method necessary for acetylation to determine the amount of catalyst required for a particular type of cellulose. Man was rather based on purely empirical attempts to determine the amount of catalyst required reliant. Accordingly, no acetylation process has been found in the literature to date described in which the amount of catalyst required for acetylation is analytical would have been determined using an indicator. Identifying the required However, the amount of catalyst is of great technical importance, because when using excess catalyst the cellulose is strongly acetolytic is degraded while the use of insufficient amounts of catalyst for the formation of incompletely acetylated, technically unusable products leads.

According to the invention, the required amount of catalyst is now determined regardless of the type of catalyst by a preliminary test in which one the mixture of the cellulose to be acetylated, acetic anhydride and glacial acetic acid add a little amethyst violet and then add enough catalyst to make the original The red color of the reaction mixture has turned permanent blue.

The amount of catalyst determined is completely sufficient, to achieve good acetylations, and generally much less than at the acetylation processes previously used in technology.

The invention offers the particular advantage that the required amount of catalyst can be determined quickly and reliably for each technically usable type of cellulose by a simple analytical process. EXAMPLE For the acetylation of technically cleaned cotton linters using superchloric acid as a catalyst, amethyst violet and so much superchloric acid are added to a sample of the acetylation mixture prepared without a catalyst until the color of the amethyst violet has turned into a permanent blue. The experiment shows the consumption of 0.28 % of excess chloric acid, calculated on the weight of the cellulose.

"If you use this amount of catalyst you get after a 24 hour at 35 ° carried out acetylation formed a solid jelly from which a primary acetate with 61% acetic acid is obtained by precipitation with water only 0.140 / 0 superchlaic acid is used as a catalyst, that is, an amount that is insufficient; in order to color amethyst violet permanently blue in the reaction mixture, one obtains from the same starting material after acetylation under the same for 6 days Conditions a product that has not been visibly changed. The acetic acid content was only "r9%.

After acetylation of the mixture using the by the method according to the invention determined amount of catalyst to the formation of a If jelly or solution has taken place, additional amounts of catalyst can be added to the mixture add, thereby accelerating the acetylation process and optionally `also a decrease in the viscosity of the ..-; acetylation mixture, which sometimes is desired, can be achieved without a substantial acetolytic degradation of the Having to fear cellulose acetate.

Claims (1)

PATENT CLAIM Process for the determination of the acetylation of a certain type of cellulose required amount of catalyst, characterized in that that one determines the amount of catalyst in a sample, which in the one with amethyst violet added acetylation mixture causes a permanent blue color.