DE1157395B - Process for the preparation of eupolyoxymethylenes - Google Patents

Description

INTERNAT. KL. C 08 g

GERMAN

PATENT OFFICE

D 30477 IVd / 39c

REGISTRATION DATE: 18 A P R I L 1959

NOTICE
THE REGISTRATION
DND ISSUE OF
EDITORIAL NOVEMBER 14, 1963

Eupolyoxymethylene can according to various Process are produced. These processes include, for example, the polymerization of monomeric Formaldehyde in an inert liquid medium in the absence of water and in the presence of dispersants and polymerization catalysts, such as aliphatic or aromatic Amine (US Pat. No. 2,768,994 and H. Staudinger and W. Kern, “Die hochmolekularenorganic Connections, 1932, pp. 280 to 287). Further known catalysts are trialkyl arsines and stibines or phosphines. It is also known to use formaldehyde at low temperatures in solvents Polymerize in the presence of sulfuric acid or boron trichloride. The polymerization can also do so be carried out that before the polymerization of the main part first a small part of the formaldehyde is polymerized, which is then separated off together with any impurities that may be present will.

It is also known from British Patent 748 836 to use formaldehyde in the presence of halogenated hydrocarbons with or without the addition of known catalysts to polyoxymethylene !! to polymerize.

It has also been proposed for the preparation of eupolyoxymethylenes with increased Heat resistance of monomeric formaldehyde in the presence of a sulfur compound, which is the structural element

Method of manufacture
of eupolyoxymethylenes

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has to polymerize. This compound includes, for example, thiuram disulfide, tetramethylthiuram disulfide, 2-mercaptobenzothiazole, etc.

It is also known to eupolyoxymethylenes from formaldehyde in the presence of compounds of the general formula RnM, in which M is a metal, such as Cu or Al, and R is a thiohydrocarbon radical means to manufacture.

It has also already been proposed for the preparation of eupolyoxymethylenes from monomeric Formaldehyde polymerisation with a formaldehyde that has been freed from moisture as much as possible In the presence of sulfur suspended or dissolved in dry gasoline and / or decalin. The average particle size of the suspended sulfur should expediently be smaller here than 200μ. According to this proposal, the applicant can:

German gold and silver refinery

formerly Roessler,
Frankfurt / M., Weißfrauenstr. 9

Dr. Heinrich Hopf! and Dr. Hermann Metzler,

Zurich, Switzerland),

have been named as inventors

Another co-inventor has requested

not to be named

Sulfur in addition to ventilated pure sulfur or finely divided plastic sulfur, especially monoclinic or macromolecular, rubber-insoluble sulfur can be used.

It has now been found that Eupolyoxymethylene can be prepared by polymerization of trioxane using catalysts at temperatures of 50 to 90 ⁰ C by using as catalysts at least one halogenated aliphatic hydrocarbon in amounts of from 0.01 to 10 weight percent, based on the charged trioxane used .

The halogenated hydrocarbons which are used for the process according to the invention can include, for example, carbon tetrachloride, chloroform, methylene chloride, bromoform, dichloroethylene and n-propyl chloride.

The halogenated hydrocarbons are used in amounts of 0.01 to 10% »based on the starting material, used.

The polymerization can be carried out in such a way that the trioxane is admixed with small amounts of the halogenated hydrocarbon and left to stand at an ordinary or slightly elevated temperature until the reaction has ended. Functional but one proceeds in such a way that trioxane heated in a closed vessel with the catalyst at 50 to 9O ⁰ C. It is advantageous to maintain thorough mixing by stirring or rolling the vessel. This is the beginning

309 748/386

clear solution cloudy with precipitation of the polymer and gradually turns into a solid product. By washing with methanol and extracting with dilute sodium hydroxide solution, the low molecular weight Shares are removed. The yields vary between 50 and 90% depending on the catalyst The molecular weights of the polyoxymethylenes obtained vary depending on the reaction conditions between 20,000 and several hundred thousand at a softening point of about 185 ° C.

The eupolyoxymethylenes produced according to the invention can be broken down into those for thermoplastics customary processes to form moldings, for example by injection molding, pressing, etc., or use to cover objects.

Moldings are obtained which are tough and elastic. When heated to 180 ^° C. for one hour, only a slight depolymerization takes place.

Fillers and / or dyes can also be used in a mixture with the eupolyoxymethylenes. This also includes, in particular, glass fibers and slag wool.

It is advantageous to use highly disperse, in particular active, fillers, for example carbon black, preferably alkaline soot, or oxides of metals or metalloids, such as aluminum oxide, Titanium oxide, zirconium oxide or silicon dioxide, which by converting volatile compounds of these substances high temperature in an oxidizing or hydrolyzing medium.

A surprising sudden technical effect of the method according to the invention compared to the Process of British patent 748 836 is to be seen in that in the absence of organic Solvents is worked and thus the regeneration of the solvent is unnecessary.

example 1

40 parts trioxane is melted with 0.4 parts of chloroform in a glass-lined vessel and heated for 24 hours 7O ⁰ C. After this time, the entire product has turned into a solid white mass which, after being crushed, is washed with methanol to remove the unchanged trioxane and treated with dilute sodium hydroxide solution to separate off low molecular weight polyoxymethylenes. After washing out the lye, the product is dried. 23 parts of eupolyoxymethylene with a softening point of 185 ° C. are obtained.

Example 2

10 parts of trioxane are mixed with 0.5 part of carbon tetrachloride according to Example 1 at 70 ° C. for 72 hours heated while the vessel is kept rotating slowly. When working up according to Example 1 8 parts of high molecular weight polyoxymethylene are obtained

An attempt that was carried out without the addition of tetrachlor carbon was carried out gave a yield of only 0.1 to 1% = which can be obtained by moving the The vessel was allowed to increase to 10 to 15%.

Claims (1)

PATENT CLAIM: Process for the preparation of eupolyoxymethylenes by polymerizing trioxane by means of catalysts at temperatures from 50 to 90 ⁰ C ₅ : characterized in that the catalyst used is in at least one aliphatic halogenated hydrocarbon, in amounts of 0.01 to 10 percent by weight, based on the trioxane used ^ used. Considered publications:
British Patent No. 748 836. © 309 748/386 11.63