DE522054C - Process for the production of cellulose ethers - Google Patents

Description

Process for the manufacture of cellulose ethers During manufacture of cellulose: it has been shown that those ethers which i1 / 2 to z1 / 2 Moles of alkyl per mole of cellulose, for technical purposes are most suitable as they have by far the best mechanical properties. In addition, however, they have the great disadvantage that they, in front of the ethers of the Initial members of the aliphatic series, against water, especially at low temperatures, are rather volatile, which makes them usable for a great many purposes is excluded.

If, on the other hand, ethers are produced by further alkylation, whose degree of alkylation is above 21/2 mol. per mol. of cellulose, products are obtained which are resistant to water, but considerably in their strength Ethers with less than a1 '! 2 moles of alkyl per mole of cellulose are inferior.

It has now been found that alkyl celluloses with about i1 / .2 to z1 / 2 mol. of alkyl per mol. of cellulose while maintaining the particularly favorable mechanical Properties of this class of ether can be made completely waterproof if one is at the production of cellulose ethers from metal compounds of cellulose and haloalkyl to 10 to 30 moles of alkyl halide up to 2 moles of aralkyl halide. , The Action of this mixture on a suitable alkali cellulose or other metal compound the cellulose can take place both in the liquid and in the gas phase.

The etherification takes place at such temperatures and if necessary such pressures that saponification of the excess alkylating agent used is avoided. The saponification temperatures of the various alkylating agents under different pressures depending on the type of alkylating agent used from each other. Some of them are described in the literature, e.g. B. those of the haloalkyls, in some cases, they are easy to determine through simple preliminary tests.

The cellulose alkyl ethers produced by the process described above are in contrast to the previously known cellulose alkyl ethers of a medium all: ylation stage, which otherwise have good mechanical properties, but a certain sensitivity show to water, largely insensitive to water and also have also good mechanical properties. E.g. a film made of ethyl cellulose which has been prepared according to the invention with the addition of benzyl chloride, Water sensitivity in shape the elongation of the water in a very insignificant way Dimensions in the appearance .. When immersed in water of 0 ° C, the film remains complete unchanged and inclined not the slightest effort to dissolve or change. That the elimination of water sensitivity by introducing small amounts of Aralkyl groups could not be foreseen.

In the literature, so-called mixed ethers of cellulose, i.e. H. such ethers, which z. B. contain benzyl groups in addition to ethyl groups, described, however, these have mixed ethers in which approximately the same number of molecules Ethyl and benzyl or even significant amounts of benzyl are not present the good mechanical properties identified above.

In contrast, the products of the present process are not considered to be mixed To designate ether in the usual sense, since here the aralkyl halide is only completely is used to a lesser extent and, surprisingly, the water instability nonetheless the cellulose ether with about 1/2 "to 21/2 mol. alkyl per mol. cellulose completely eliminated without reducing the excellent mechanical properties of these products will. Example 96o parts by weight of wood pulp in cardboard form are 2 hours soaked in 50 ° Joiger sodium hydroxide solution at 30 °, then to a content of 3 to 6 mol. Alkali (calculated on 1 mole of cellulose) squeezed, shredded and = short time of Left to ripen at 20 °. The sodium cellulose obtained is placed in a pressure vessel with a mixture of 5,460 parts of chloroethyl and 76z parts of benzyl chloride (i.e. on 1 mole of cellulose i q Mbl. of chloroethyl and 1 mole of benzyl chloride) at one temperature from 10 to 10 ° and the vapor pressure of the alkylating agent mixture corresponding to these temperatures Heated for 6 to 7 hours. After removing the excess chloroethyl, the Reaction product by washing with water from excess alkali and common salt and by suitable organic solvents of any excess present Liberated benzyl chloride and then dried.

The product obtained is in a mixture of alcohol and benzene completely clearly soluble in the ratio of i: i and is against water, even ice water, perfectly consistent.

Claims (1)

PATENT CLAIM A process for the preparation of ethers of cellulose by the action of alkylating agents on metal compounds of cellulose using an excess of the alkylating agent, characterized in that up to 2 mol of aralkyl halide is added to the alkylating agent used for every 10 to 30 mol and carrying out the alkylation at temperatures and optionally pressures at which saponification of the excess alkylating agent used to form free acid is avoided.