DE1251530B - Process for the production of binary copolymers of Tnoxane - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Int. CL:

C08g

German class: 39 c-19

Number: 1 251 530

File number: F 46374 IV d / 39 c

Filing date: July 19, 1963

Open date: October 5, 1967

It is known that polyoxymethylenes which can be used as plastics either by anionic polymerization of formaldehyde or by cationic polymerization of trioxane, the cyclic trimer of formaldehyde to produce high molecular weight products. Homopolymer Polyoxymethylene contains unstable terminal semi-formal groups and is exposed to thermal stress except for a small percentage after the so-called zipper reaction with the formation of degraded monomeric formaldehyde. In this reaction, a semi-formal molecule is formed when a half-formal molecule is broken down a new unstable semi-formal end group on the macromolecule.

In order to convert polyoxymethylenes with terminal semi-formal groups into technically usable plastics, it is necessary to remove the end groups z. B. to stabilize by esterification. For this purpose, for example, the polymer is dissolved in acetic anhydride at 16O ⁰ C. After the esterification, it is necessary to remove the excess acetic anhydride and the acetic acid that has formed from the polymer again by laborious cleaning operations. In addition, the polymers stabilized in this way are not resistant to alkalis because of the risk of saponification. Despite the actually quite effective stabilization of the products by esterification, there is a risk of a re-establishment of a zipper reaction if such a molecular chain stabilized by end group esterification in the inner part of the chain z. B. breaks under the action of elevated temperatures. This also applies to products whose end groups have been etherified. In addition, in the case of end group etherification, it is difficult to adjust the molecular weight.

Favorable results of the stabilization of polyoxymethylenes are obtained by treating trioxane with saturated cyclic ethers, cyclic carbonates or cyclic formals, such as. B. ethylene oxide or diethylene glycol formal, copolymerized. For the purpose of stabilization, the unstable end groups of the copolymers are broken down by hydrolysis after the polymerization, the zipper reaction only going as far as the comonomer molecules. If the molecular chain is thermally cleaved during processing of the polymer, the chain in question can only be broken down as far as the next comonomer molecules, as a result of which better thermal stability is achieved. Copolyacetals, in particular copolymers with a high content of polyoxymethylene units, of high molecular weight and sufficient stability, are processes for the production of binary
Copolymers of trioxane

Applicant:

Farbwerke Hoechst Aktiengesellschaft

formerly Master Lucius & Brüning, Frankfurt / M.

Named as inventor:

Dipl.-Chem. Dr. Klaus Weissermel,

Frankfurt / M.- Höchst;

Dipl.-Chem. Dr. Edgar Fischer,

Frankfurt / M.- Schwanheim;

Dipl.-Chem. Dr. Claus Schott, Hofheim (Taunus)

already in various fields, including the manufacture of injection-molded and extruded plastic objects, which can also be used at elevated temperatures, have been used with success.

It is also known ternary copolymers of trioxane, cyclic ethers or formals and bifunctional Establish compounds that crosslink during polymerization.

It has now been found that binary copolymers of trioxane can be advantageously prepared by polymerizing from 90 to 99.99 percent by weight of trioxane with 0.01 to 10 weight percent of a bifunctional compound in the presence of cationically active catalysts at temperatures of -50 to +100 ⁰ C if, as bifunctional compounds, comonomers containing firstly a cyclic ether or cyclic acetal group and secondly a cyclic carbonate group, or prepolymers thereof, are used.

In the copolymerization with trioxane at temperatures between -50 and +100 ⁰ C initially participates only the cyclic ether or acetal in the reaction, while the carbonate group remains intact.

The copolymers produced in accordance with the invention can be used to produce foams. In this case, it has proven to be expedient to bring the product obtained by copolymerization in the molten state into the intended shape and then to foam it. It is also possible to use the CO ₂ z. B. in a suitable extruder equipped with a vacuum device.

709 650/399

draw and convert the degassed product into a hard-to-melt hardened substance by ^{tempering for about 1} Z ₂ to 1 hour at 180 to 220 ^{0 C.} Suitable bifunctional compounds for the process according to the invention are comonomers which each contain a cyclic ether group, preferably an epoxy group, or a cyclic acetal group and a cyclic carbonate group, and prepolymers of these compounds. The aliphatic and cycloaliphatic bifunctional compounds are superior to the aromatic compounds, since the aromatic nucleus can lead to low molecular weights as a result of a chain transfer reaction, which is undesirable for some purposes.

Because of their good reactivity and easy accessibility, / ?, y-epoxypropoxy- / 3'-y'-carbonato-propoxyalkanes are of particular interest the general formula

CH ₂ - CH - CH ₂ - O -

_n - O - CH ₂ - CH CH ₂

O - CO - O

in particular those, optionally branched, compounds with η = 1 to 8 are suitable. Furthermore, glycerol-l-glycidyl ether-2,3-carbonate, 2,4,6-trioxa-3-oxobicyclo [3, l, 0] hexane and 3,5,8-trioxa-4-oxobicyclo [5, l, 0] octane or prepolymers of these compounds are extremely effective.

The cationic polymerization can be carried out by methods known per se, in bulk, in solution or in suspension. Aliphatic hydrocarbons, especially hydrocarbons, can be used as solvents with 6 to 18 carbon atoms and aliphatic, preferably chlorine or fluorine-containing halogenated hydrocarbons, in particular those with 1 to 4 carbon atoms or aliphatic ethers with 2 to 4 carbon atoms are used will. The bulk polymerization is particularly smooth.

It is operated at temperatures at which trioxane does not crystallize out, that is, depending on the solvent used at -50 to +100 ⁰ C, _n i the absence of solvents at +20 to + 100 ⁰ C, but preferably at +60 to + 80 ° C.

All substances that trigger a cationic polymerization can be used as catalysts fortune, such as B. inorganic and organic acids, acid halides and in particular Lewis acids (definition of Lewis acids see Kortüm, Textbook of Electrochemistry, Wiesbaden, 1948, pp. 300 and 301). Of the latter, boron trifluoride etherates are very useful. Very suitable are also diazonium fluoroborates. In principle, however, all known, z. B. the one in the Belgian Patent specification 585980 described, cationic catalysts can be used.

The concentration of the catalysts can vary within wide limits. It depends on the Type of catalyst and whether high or low molecular weight copolymers are produced should be. It can be between 0.0001 and 1 percent by weight, based on the total monomer mixture, lie. Generally from 0.001 to 0.1 weight percent catalyst is used.

Since the catalyst tends to degrade the polymer, especially in the presence of moisture, it is advisable to neutralize it immediately after the end of the polymerization, e.g. B. with ammonia or with methanolic or acetone solutions of primary, secondary or tertiary amines, preferably those of aliphatic hydrocarbons with 1 to 4 carbon atoms, as well as mono-, di- or triethanolamine.

The removal of unstable hemiacetal end groups can be carried out in a known manner, as in the case of other copolyacetals. Suitably the slurry of the polymer in aqueous ammonia at temperatures of 100 to 200 ⁰ C, whereby a swelling agent such as methanol or n-propanol, may be present, or dissolving the polymer in an alkaline medium at temperatures above 100 ° C with subsequent re-failure. As solvents are, for. B. benzyl alcohol, ethylene glycol monoethyl ether or a mixture of 60 ° / ₀ methanol and 40 ° / ₀ water as well as ammonia and aliphatic amines as alkalis.

The end group stabilization can, however, also be carried out in a known manner in the absence of solvents in the melt in the presence of stabilizers, expediently at temperatures between 160 and 200 ° C, take place.

The stabilization of the polymer against the influence of heat, light and oxygen can be carried out as in the known trioxane copolymers take place. As heat stabilizers, for. B. polyamides, amides Polybasic carboxylic acids, amidines and urea compounds suitable as oxidation stabilizers Phenols, especially bisphenols and aromatic amines. Λ-Oxybenzophenonderivate are suitable for Light stabilization.

The technical progress of the process according to the invention compared to the known processes is that the copolymers produced according to the invention are produced by heating to 180 to 220 ^° C. as a result of the reaction of the second functional group of the bifunctional compound with elimination of CO ₂ , optionally with the addition of amine or hydroxyl compounds, or they can be branched or crosslinked by tempering and thus converted into poorly fusible to infusible plastic objects and poorly fusible foam bodies, whereas in the known processes crosslinking occurs already during the polymerization.

example 1

96 parts by weight of liquid trioxane and 4 parts by weight of monocarbonate of ethylene glycol diglycidyl ether are placed in a 200 cm ³ screw-type glass. One gives 30 mg of p-Nitrophenyldiazoniumfluorborat to and polymerized at 7O ⁰ C. After the reaction, the block is ground and, boiled with methanol, which contains 1 ° / ₀ triethanolamine. After the homogeneous hydrolysis of the product in the presence of diethylene glycol monoethyl ether in the presence of l ° / ₀ amine at 150 ° C for 1 hour and then boiling the Diäthylenglykolmonoäthyläthers with methanol one obtains a white powder. From-

booty is 50 ° / ₀ , the melt index 1.23 and
= 0.61. In the ultra-red spectrum of the polymer, a carbonyl band occurs at 5.50 μ, which can be assigned to the cyclic carbonate.

Example 2

A mixture of 98 g of liquid trioxane and 2 g of 2,4,6-trioxa-3-oxobicyclo [3, 1, 0] hexane and 30 mg of p-nitrophenyldiazonium fluoroborate is polymerized in a water bath at 70 ° C. and worked up. The polymer yield is 53%> * Ire <i = 0.56.

Claims (1)

Claim: Process for the preparation of binary copolymers of trioxane by polymerizing 90 to 99.99 percent by weight of trioxane with 0.01 to 10 percent by weight of a bifunctional compound in the presence of cationically active catalysts at temperatures from -50 to +100 ⁰ C, characterized in that as bif unfunctional compounds comonomers which firstly contain a cyclic ether or cyclic acetal group and secondly a cyclic carbonate group, or their prepolymers are used. 709 650/399 9.67 © Bundesdruckerei Berlin