CS238767B1 - Process for controlling the continuous polymerization process - Google Patents

Abstract

A method of controlling the continuous polymerization process of, for example, alkaline polyamide, either manually or automatically. Its essence lies in the fact that the course of the polymerization reaction is regulated by changing the temperature or adjusting the temperature gradient in the reactor according to the instantaneous value of the apparent viscosity of the melt, based on the determined dependence of the apparent viscosity of the melt on temperature.

Description

The invention relates to a process for controlling a continuous polymerization process, for example an alkali polyamide, already having Si ore automatically.

Polymerizations, especially ion-initiated, are usually very rapid exothermic reactions in which the viscosity changes by several orders of magnitude. They are carried out mainly in material reactors with worm agitators and are therefore very difficult to control because of the high inertia of the reactor when it enters its mode. The method of direct control of these processes is not yet known. The only existing regulation is to maintain constant temperatures and flow of input components.

This state affects unfavorable utility properties of the prepared polymers.

The aforementioned disadvantages are overcome by the method of controlling the continuous polymerization process according to the invention, which is based on the fact that the course of the polymerization reaction is controlled by changing the Si temperature by adjusting the temperature gradient in the reactor according to the instantaneous apparent melt viscosity. The empirical dependence of this viscosity on temperature, possibly also on other parameters, such as the concentration of monomer, initiator, etc. must be changed in advance.

The process according to the invention makes it possible to control polymerization reactions in which the control method has not been known to date. This ensures that the polymer obtained still has constant properties which are a decisive measure for its further use.

Two of the possible embodiments of the method according to the invention are schematically shown in the accompanying drawings. Fig. 1 is a process diagram where the polymerization process is controlled manually; 2, the control is then provided automatically. The components J being dosed are a pump, J an imperfectly stirred flow reactor, a radially stirred piston reactor and a microprocessor. The examples are supplemented by graphs expressing the apparent viscosity 1 versus reactor length L (Fig. 31) and the temperature dependence of apparent viscosity 1 versus temperature t (Fig. 4).

Example 1

In the screw reactor 6, the polymerization of the fused 6-caprolactam flowing from the metering pump 6 takes place at 70 ° C. The polymerization is initiated with sodium hydride (0.16 mol%) and activated with a mixture of diethyl carbonate (0.25 mol%) and n-acetylcaprolactam (0.35 mol%). The mixture of components is pre-mixed in the mixing part of the screw and heated to a polymerization initiation temperature of 155 ° C. In this part of the reactor it has a viscosity of 0.6 to 2.8 mPa · s. The premixed mixture proceeds continuously to the polymerization portion of the reactor, where it is heated successively to 170 to 190 ° C, 190 to 210 ° C, and 210 to 230 ° C in three separately heated sections. Expected viscosity profile in individual sections:

section 1 2 3 apparent viscosity 1 to 7 3 to 12 10 to 150 (Pa.s)

The optimum course is given for the desired polymer in Fig. 3, the temperature dependence of the apparent viscosity of the alkali polyamide having a polymerization degree of 150 and a low molecular weight content of 8% by weight. is shown in FIG.

Not by virtue of the instantaneous apparent viscosity value found at location A of reactor 6, the temperature of the most sensitive part of reactor J is manually adjusted. The temperature gradient, if any, at C, D, E and F is also carried out manually. In order to control the response to the intervention, the sections of the polymerization reactor 6 are provided at points C, D, E and F with viscosity measuring sensors, e.g.

Example 2

The procedure as in Example 1, with the process being controlled automatically.

The instantaneous value of the apparent viscosity measured at location A at the end of the reactor 6 (FIG. 2) enters as a basic information into the microprocessor 6 where it is compared with the value required according to the set process conditions and the empirically determined viscosity / temperature dependence. The temperature gradient correction is performed automatically by interfering with the most sensitive point of the reactor. The viscosity control information at points C, D, E and P of the reactor 6 is sent to the microprocessor where it is compared to the expected course after the newly set temperature gradient. If a significant deviation occurs, the trailing control intervenes by adjusting the temperature at the points O, H, J and I according to the known viscosity-temperature dependence.

Claims (1)

SUBJECT OF THE INVENTION Process for controlling a continuous polymerization process, characterized in that the course of the polymerization reaction is controlled by changing the temperature or adjusting the temperature gradient in the reactor according to the instantaneous apparent melt viscosity, based on the empirically determined dependence of the apparent melt viscosity on temperature.