SU1155606A1 - Method of obtaining block polycaproamide - Google Patents

Abstract

A METHOD FOR PREPARING LARGE POLYCAPROAMILA by anionic polymerization of caprolactam, which includes mixing the starting components, initiating the reaction by heating the reaction mixture Up to the starting polymerization temperature and carrying out the process in an adiabatic reactor at a temperature below the melting temperature of the polymer, characterized in that eliminating the possibility of cracks and holes and reducing energy consumption, the reaction mixture is preheated to 75-93 C, A (A), the initiation of the reaction is carried out by local impulse heating of a thin layer of the reaction mixture.

Description

And: precaution refers to the volume of the production and processing of polyamides and to be used in the manufacture of polycaproamide products by anionic polymerization of caprolactam by chemical molding.

A method of producing polycaroamide is known by carrying out the anionic polymerization of -caprolactam at a temperature below the melting point of polymer L1J.

According to this method, the reaction mixture, prepared in a mixer at a temperature below the polymerization temperature, is fed into the mold, which is heated to the polymerization temperature, is polymerized and the finished product is cooled. In the process of polymerization and crystallization, the difference between the temperature of the reaction mixture and the environment contributes to the appearance of temperature gradients over the cross section and the occurrence of internal stresses in the products. In addition, the receipt of products requires a large expenditure of electricity to maintain the desired temperature.

There is also known a method of producing block polycaproamide by anionic activated polymerization of f-caprolactam in a reactor, including heating the reaction mixture to the temperature of the start of polymerization and conducting the process consistently throughout the volume at a temperature below the melting point of the polymer. In this method, the polymerization of f-carolam is carried out at 150-220 ° C in a thin layer of the reaction mixture with a pulsed feed of the starting components with layer-by-layer polymer buildup. To carry out the process under isothermal conditions, the upper polymerizing layer of the block is blown with an inert gas 2.

The disadvantage of this method is large energy consumption, since the reactor is constantly heated to 150-220 ° C,

and maintaining thermal equilibrium requires the supply of a large amount of inert gas, which complicates. the process. In addition, if the polymer is layered by layer, the resulting blo may be non-uniform in volume due to redistribution between the layers of the activator and the catalyst.

The closest in technical essence and the achieved effect to the

This is a method for producing block polycaproamide by anionic polymerization of caprolactam, which includes mixing the starting components.

at 80–140 ° C, initiating the reaction by heating the reaction mixture from 80–140 s to the onset temperature of polymerization (150–200 ° C) and conducting the process in an adiabatic reactor at a temperature below the melting point of the polymer. Compared with the known methods, this method allows to increase the quality of polycaproamide by reducing the content of low molecular weight impurities and to somewhat reduce the heterogeneity of the polymer by volume 33.

However, heating the reaction mixture to 150-200 C and maintaining such

temperature in the form during the polymerization leads to a large consumption of electricity; Due to the adiabatic reactor (form) in prices, the temperature of the reaction volume can reach 200–230 0 (at the boundary

with the form of 150-200 C), which leads to the occurrence of heterogeneity of the properties of the polymer, for example, the tensile modulus, by volume; so cad "

the polymer temperature at the end of the process can reach 230 ° C, then the finished polymer has a low degree of crystallinity (0-20%); at the same time, the methods of cooling large-sized polycaproamide products that are currently available in production cannot ensure the complete elimination of residual stresses and the formation of micro- and macro-cracks.

The purpose of the invention is to reduce differences in the modulus of elasticity over the volume of the product, to eliminate the possibility of cracks and cavities and to reduce energy consumption during the production of polycaproamide.

The goal is achieved by the fact that according to the method of obtaining block polycaproamic anionic polymerization of caprolactam, including mixing the starting components, initiating the reaction by heating the reaction mixture to the temperature of the beginning of polymerization (150-220 s) and carrying out the process in adiabatic

the reactor at a temperature below the melting point of the polymer, the reaction mixture is preheated to 75-95 ° C, and the initiating resin pg,

(It is carried out by heating nmggul heating of a thin layer of the mixture to the temperature of the beginning of the reaction.

The process then proceeds in a self-propagation mode.

The drawing shows the scheme of the reactor in which the method is carried out.

The reactor contains an adiabatic casing 1 created by any known method, a flat heater 2, a bottom 3, and a bleed valve A. The upper and lower covers of the reactor are heat insulated to completely eliminate heat exchange with the environment.

The proposed method is carried out in the following manner.

The cylindrical reactor, heated to 75-95 ° C, is filled with a prepared initial reaction mixture with a temperature of 75-95 C. Then the reactor is quickly closed with an upper cap so that the heater surface is completely in contact with the surface of the reaction mixture, while the excess mixture is extracted through bleed valve, after which the latter is closed. Then, a planar heater is placed at the upper end of the reactor to eliminate convection in the reactor bulk. Heated to 150-220 ° C, the heater surface initiates the process in the nearby layer of the reaction mixture, in which the heat gap (due to polymerization and crystallization) initiates the reaction in the subsequent layer and so. to the bottom of the reactor. The total time of the process is determined by the stationary rate of thermal propagation and the rate depends on the composition of the mixture and the initial conditions of the process. The thickness of the initiated layer is about 5 mm. At the end of the process, the reactor is disassembled, the resulting block is removed and cooled in any mode.

The choice of the heating temperature of the initial mixture (75-95 0) is determined by two factors: at this temperature the monomer becomes liquid, which makes it possible to obtain a uniform distribution of the activator and catalysis in the reaction mixture, and the reaction under these CONDITIONS practically does not proceed. The latter is necessary for

the implementation of the process F mode r.hgp wave propagation.

The temperature of the heat pump should be higher than the mixture temperature at 75125 ° C (i.e. 150-220 ° C, which was determined experimentally. The heater operation time depends on the initial temperature of the mixture and its composition and is determined experimentally. We offer The heater temperature range does not affect polymer properties and process characteristics.

The method provides a significant reduction in energy consumption due to the fact that the initial temperature of the reaction mass is set to 75-95 ° C, which is 75-120 ° lower than the known methods, and local heating (150-220 ° C) of the upper layers is maintained only for 30 to 50 minutes . During this time, the front of polymerization is established and the temperature rises by self-heating due to the exothermic combination of the processes of polymerization; ii and crystallization. The temperature of the finished polymer at the end of the HO-IBO C process, the degree of crystallinity of the polymer is TO-50%; there is no need to select the optimal polymer cooling mode. The resulting block has no micro or macrocracks and cavities.

Since the front of the polymer is evenly distributed and uniformly distributed during the process, the mass transfer and heat exchange are excluded, the polymer has the same properties throughout the volume.

Example 1. A mixture of 200 g of f caprolactam and 1.97 g of sodium caprolac tallic sodium, and a mixture of 200 g are prepared in two containers at 85 ±. ° C.

6-caprolactam containing 1.54 g of 2,4-toluene diisocyanzta (102 T) as an activator. Maybe any other activator with a small induction period can be used. With stirring, the reaction mixture from both tanks is poured into a cylindrical reactor made of a fluoroplastic 200 mm long, 45 mm in diameter and heated to 85 + 2 ° C. To prevent heat exchange with the environment, the reactor is placed in a Dewar vessel. The reactor is closed with a lid equipped with a flat heater ich non-steel. After equalizing the temperature throughout the volume, voltage is applied to the heater spirals and its temperature is raised to 185 ° C for 30 seconds, after which polymerization begins in the reactor. The temperature in the reactor is recorded by thermocouples located along the length of the reactor. To prevent the formation of gaps in the block due to the force of gravity (separation of the liquid from the reduced volume of solid polymer), the bottom plate is designed as a rod displaced by a spring. The spring elasticity is selected empirically. The heater is turned off after 30 minutes. The total process time is 3 hours. The end time of the process is recorded with thermocouples. After completion of the process, the reactor is disassembled and the block is subjected to cooling. Example 2. A mixture containing 330 g of caprolactam containing 0.42 g of metam is prepared in a container at 82 ± + 2 C, and after dissolving the salt with thorough stirring, 2.60 g of 2,4-toluene bis-caprolactam are introduced. the mixture is poured into a cylindrical reactor of fluoroplastic 240 mm long and internal diameter of 50 mm. The bottom plate is made in the form of a rod displacing by means of a spring. The reactor is closed with a lid equipped with a flat heater and placed in an air thermostat with a temperature of 6; tour 82 ± 2 ° C. After equalizing the temperature throughout the volume, voltage is supplied to the heater coil and the temperature of the heater is raised to 200 ° C for 15–20 s. The heater is turned off after 25–30 min. The total reaction time is 4 hours. At the end of the process, the reactor with the block is cooled at a rate of 0.5 / min. PRI me R 3. The polymer was prepared as described in Example 1. The initial temperature of the reaction mixture was 95 ± 2 ° C. The reactor was also heated to 95 ± 2 ° C. The temperature of the heater was 220 ° C. The sequence of operations was the same as in Example 1. The heater was turned off after 25 minutes. The process time is 2.6 hours. EXAMPLE 4 A polymer is prepared as described in Example 1. The mixture temperature is 75 ± 2 ° C, the temperature of the reactor is also 75 ± 2 ° C, the temperature of the heater is 150 ° C. The heater is turned off after 45 minutes. The total process time is 4 hours. EXAMPLE 5. A polymer is prepared as in Example 1. A mixture temperature of 75+ + 2 ° C, a temperature of 75 ± 2 ° C, and a heater of 200c. Heater is turned off after 45 hours. The total process time is 4 hours. The results of the analysis of the material obtained by the known and proposed method are shown in the table.

Polycaproamide, obtained by example

one

2 3 4

 . 5 Prototype

.18010 + 1000 18000 t 1000 18000 ± 1000 18000 t 1000 18000 ± 1000 18000 ± 1000

Claims (1)

METHOD FOR PRODUCING BLOCK POLYCAPROAMIDE by caprolactam anionic polymerization, which includes mixing the starting components, initiating the reaction by heating the reaction mixture to the polymerization start temperature and carrying out the process in an adiabatic reactor at a temperature below the polymer melting temperature, characterized in that, in order to increase polymer uniformity in volume products, eliminating the possibility of cracking and sinks and reducing energy consumption, the reaction mixture was pre-heated to 75-95 ° C, and tsiirovanie reaction is carried local pulsed heating of a thin layer of the reaction mixture. > 1 1 5 5606