CS238536B1 - A method for accelerating anionic polymerization of 2-pyrrolidone - Google Patents

Abstract

The invention consists in that the polymerization batch consisting of a monomer and an initiation system, or its part consisting of a monomer and l-caprolactim-6-caprolactam, is tempered in the temperature range of 70 °C to 250 °C, preferably 100 to 150 °C, for 5 minutes to 5 hours, preferably 0.5 to 5 hours, and then allowed to polymerize at a temperature of 15 to 70 °C.

Description

The invention relates to a method for accelerating the anionic polymerization of 2-pyrrolidone (PD) initiated by an alkaline or ammonium salt of PD and accelerated by 1-(1-azacyclohept-1-en-2-yl)-1-aza-2-oxocycloheptanene-6-caprolactam (N-iminolactam) in a block configuration, optionally in the presence of inert liquids that do not dissolve the monomer or polymer.

PD polymerization initiated by alkali or ammonium salts /even at optimal concentrations/ proceeds at a low rate and, although it provides thermally stable poly-(2-pyrrolidone) /PPD/, is economically unusable due to the extreme polymerization times. This so-called unactivated polymerization is characterized by a linear increase in conversion with polymerization time to high degrees of conversion of around 60%. The polymerization is heterogeneous, the resulting polymer is not soluble in the monomer and separates from the reaction mixture.

Acceleration of unactivated polymerization can be achieved in several ways. An order of magnitude increase in speed is achieved by using activators, i.e. substances that have the N-acylamide structure - B CO - N in I

-CO - or allow its formation in the system. The most common activators are N-acyllactams, such as N-benzoyl- or N-acetyl-2-pyrrolidone. Activated polymerization takes place in two kinetically and phase-different stages. In the initial very fast homogeneous phase /max. minutes/, a relatively high conversion of monomer into polymer is achieved, but with a low molar mass. However, even the polymer from the following heterogeneous phase, when the molar mass increases significantly and the conversion increases at a rate similar to unactivated polymerization, cannot be used for pharmaceutical purposes. Its thermal stability is unsatisfactory.

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Acceleration of unactivated polymerization can also be achieved by adding CO2. The polymerization rate increases several times and yet my

238 536 process kinetic character of unactivated polymerization. Isolated polymer can be successfully spun from the melt, but to achieve economic yields it is necessary to conduct the polymerization for tens of hours under optimal conditions.

So far, the most significant acceleration of polymerization can be achieved with N-iminolactams of the type:

N .....-CNC=0 /1/ : x = 3, y = 3 ^/CH ₂ // ^/CH ₂ // /II/: X = 5, y = 3 /111/ : x = 5, y = 5

Under optimal conditions, the time required to reach the limit (maximum) conversion is an order of magnitude lower than in activated polymerization. Surprisingly, the polymerization retains the kinetic character of unactivated polymerization (i.e., linear increase in conversion with polymerization time); the polymerization is heterogeneous from the beginning.

All of the compounds listed have already been used to accelerate polymerization.

2-pyrrolidone used or patented /US pat. 3 040 004, Eur. pat. appl. 033 019/· In the last mentioned case, good thermal stability of the polymer suitable for melt spinning was demonstrated. From the literature data it can be concluded that of the accelerating compounds /1/ to /111/, /111/ is relatively the slowest.

To achieve the limit conversion, it is necessary to polymerize for more than 5 hours.

The above-mentioned disadvantage is eliminated by a method of accelerating polymerization initiated by an alkaline or ammonium salt of 2-pyrrolidone and accelerated by l-caprolactim-6-caprolactam /111/ at a concentration of 0.1 to 10 mol %, which consists in heating the polymerization batch, i.e. a mixture of monomer, alkaline or ammonium salt of 2-pyrrolidone and accelerator /111/ or its part formed by monomer and l-caprolactim-6-caprolactam /111/, first for 5 minutes to 24 hours, preferably 0.5 to 5 hours, in a temperature interval limited by the ceiling temperature of the polymerization process of 70 °C and the melting point of the polymer of 250 °C, preferably in the interval of 100 to 150 °C, and then the polymerization is carried out at a temperature of 15 to 70 °C.

This procedure improves the anionic polymerization method.

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2-pyrrolidone accelerated /111/ and initiated by an alkaline or ammonium salt of 2-pyrrolidone in a block configuration or in the presence of organic solvents that do not dissolve the monomer or polymer according to the invention. Under optimal conditions, i.e. with a suitably selected concentration of the initiation system, time and tempering temperature, the polymerization rate increases at least fivefold compared to polymerization without tempering the batch and therefore the time to achieve maximum conversion is reduced comparably while maintaining a molar mass suitable for spinning the polymer from the melt.

The advantage of the method according to the invention is a significant reduction in the polymerization time while maintaining all important physicochemical parameters of the polymer and therefore improving the economy of the process.

The invention and its purpose are explained in more detail in the following examples.

Example 1

Potassium salt of 2-pyrrolidone with a concentration of 5.0 mol % was prepared by distilling off methanol and 18 g PD from a mixture of 96.6 g PD and 6.0 g methanolic KOH solution with a concentration of 4.507 mol.kg“ ¹ under an inert argon atmosphere at 85 °C/15 Pa. 5 ml of the batch were introduced with a syringe into one part of the mixing ampoule /ampoule with separate compartments for two solutions/, 5 ml of l-caprolactim-6-caprolactam solution /111/, which was prepared by dissolving 1.2908 g AII/ in 52.2 g PD under an inert argon atmosphere, were introduced into the other part. After sealing under a stream of argon, the ampoule was placed in an oil bath at 45 °C, after 15 minutes of tempering, the contents of the ampoule were mixed and tempered for 1 hour at 90 °C. Then the ampoule was transferred to a bath heated to 45 °C. After 0.5 b, the polymerization was stopped, after extraction of the polymer with methanol 1.4677 g of dry polymer was obtained, i.e. conversion 26.9%, the intrinsic viscosity measured in technical cresol at 25 °C was 100.1 cm^.g”

Under similar conditions, but without tempering at 90 °C, i.e. after mixing at 45 °C the contents of both parts of the ampoule also tempered at 45 °C, the conversion was 2.59% and the intrinsic viscosity = 124 cm\ •g ¹ after 0.5 h of polymerization.

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The polymers showed similar shapes of TGA and DSC curves, TGA determined onset of decomposition 290 °C and 281 °G, respectively, reaching 50% weight loss 304 °C and 294 °C. Measurement conditions: 50 cm^.min”'^ Ar, heating rate 10 ⁰ C.min'” ¹ . The polymers therefore had similar thermal stability suitable for melt spinning.

Example 2

Similar to Example 1, a solution of potassium salt of PD with a concentration of 3.0 mol % and a 1.0 mol % solution of /111/ in PD were prepared and introduced separately into a mixing ampoule, after mixing they were tempered at a temperature of T1 for 1 hour and then polymerized at T£ hours. The results of the polymerizations and comparison with the polymerization without tempering at T1_ are given in the following table:

Sample ^T 1 <1 ^T2 ^2 conversion No. /°c/ /h/ /°c/ /h/ /%/ cm^.g" ¹ 1 45 0 45 0.5 2.59 124.0 2 70 1 45 0.5 9.56 95.5 3 70 2 45 0.5 12.71 81.6 4 70 3 45 0.5 16.14 75.4 5 90 1 45 B,5 26.86 100.1 6 90 2 45 0.5 28.87 84.7 7 150 1 45 0.5 20.38 73.5

Example 3 g 4 mol % Me^NPD /tetramethylammonium-2-pyrrolidone/ and 20 g 1.5 mol % /111/ were mixed at 120 °C and allowed to temper under inert for 0.5 hour. Then the solution was introduced into a stirred reactor and polymerized for 20 minutes at 45 °C at a stirrer speed of 600 min- ¹ . Then 200 ml of dry heptane and 2 g of paraffin /bt 48 °C/ were added. After 3 hours of polymerization, the stirring was stopped, the polymer granules were filtered off and washed with methanol; 30.0 g of polymer was obtained, i.e. the conversion was 75%. The comparative polymerization gave 19.1% conversion.

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Example 4

First, 3 cm? of a solution /111/ in PD with a concentration of 1.0 mol % were prepared, which were tempered for 1 h at 150 °C in an inert Ar atmosphere and then cooled to 45 °C and mixed under an inert Ar atmosphere /see Example 1 for the procedure/ with 3 cm? of a 3.0 mol % solution of the potassium salt of PD in PD, prepared similarly to Example 1. After 1 h of polymerization at 45 °C, the conversion was 74.5 ~ 100 cm^.g ^-1 , whereas in the comparative isothermal polymerization without tempering, the conversion was 6.2 %, [Λ3= 140 cm?.g ^_1 .

Example 5

The heat-treated solution /111/ in PD (alkaline salt absent) can be stored for several days without changing its activity. The solution /111/ in PD of the same concentration as in example 4, tempered for 1 h at 150 °C, was mixed with 3 cm-5 of a fresh solution of the potassium salt of PD in PD after 70 hours of storage at 45 °C /see example 4/. Similar yields of polymer and O2 were achieved as in example 4.

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Claims (1)

SUBJECT OF THE INVENTION Method for accelerating the anionic polymerization of 2-pyrrolidone induced by an initiation system consisting of an alkali or ammonium salt of 2-pyrrolidone at a concentration of 1.5 to 3 mol% and 1-caprolactime-6-caprolactam at a concentration of 0.1 to 10 mol% or in the presence of inert monomer-insoluble liquids or a polymer, characterized in that the polymerization feed consists of the monomer and the initiator system, or a monomer portion thereof and 1-caprolactime-6-caprolactam; tempered in a temperature range of 70 ° C to 250 ° C, preferably 100 and 150 ° C, for 5 minutes to 5 hours, preferably 0.5 to 5 hours, and then allowed to polymerize at a temperature of 15 to 70 ° C. Printed by Moravian printing works, center. 11 100, tr.Lidovy milici 3, Olomouc Price: 2,40 Kčs