RU2000934C1 - Method for granulation of polymeric materials - Google Patents

Abstract

Usage: in chemical engineering and can be used in the processing of wet polymeric materials and screw drying machine. SUMMARY OF THE INVENTION: The polymeric material is fed into a screw dryer. Extrude his worm com through a die. The material flow is granulated by applying a jet of liquid to the swearing. A granulation liquid jet is formed as a layer of superheated liquid before the polymer material enters the die. They create pressure fluctuations in the material at the exit of the worm, the minimum values of which are lower than the saturation pressure of the moisture vapor in the polymer material, and the maximum values exceed this pressure. The granules are then separated from the stream. The loading of the worm machine is carried out in separate portions with materials with a moisture content of 12-17%. A supercoating liquid is additionally supplied to the superheated liquid layer in the zone of material exit from the worm channel. 2 s of f-ly, 1 tab. 4 ill.

Description

The invention relates to chemical engineering and can be used in the processing of wet polymeric materials in a screw dryer.

A method is known for granulating polymeric materials, in which the polymeric material is fed into the screw machine, it is extracted with the screw through the die and granulation of the material flow is carried out by applying a fluid under pressure to the material and the granules are separated from the rod. The disadvantage of this method is that it does not take into account the possibility of self-regulation of the material in case of moisture in it.

Another method for granulating polymeric materials is known, in which the polymeric material is fed into a screw dryer, it is processed with a screw through a die and granulation of the material flow is performed by feeding a liquid stream to the material and separating the granules from the stream.

The disadvantage of this method is that at the exit from the die, the material will be wetted and moisture will need to be re-separated from the polymer. The ego will necessitate the use of additional energy costs.

An object of the invention is to reduce the energy costs of granulation.

The problem is solved due to the fact that the liquid stream for granulating the material flow is formed in the form of a layer of superheated liquid before the polymer material enters the die and the pressure fluctuates at the material exit from the worm, the minimum values of which are lower than the saturation pressure of the vapor in the polymer material, and maximum values exceed this pressure. The loading of the worm machine is carried out with individual gyurcini material with a moisture content of 12-17%. An easily boiling liquid is additionally supplied to the superheated liquid layer in the zone E1 of the material exit from the worm channel.

In FIG. 1 shows a longitudinal section of a worm machine; in FIG. 2-4 frequency characteristics of the lengths of acridags obtained by processing a thermoplastic elastomer in a worm machine.

The method of granulating polymeric materials during dehydration in a screw dryer is carried out as follows.

The wet polymer is fed into the cavity of the housing 1 of the screw dryer through a loading funnel (not shown conventionally in Fig.), It is captured by screw spirals of the screw 2 and transported in the direction of the die 3. During transportation by the screw 2, the polymer is machined and heated. During machining

material, the part of the moisture contained in the polymer is removed from it and transported together with it in the form of separate nests to the die 3. When the material enters the die 3 due to the significant

5, the differences in the viscosities of the polymer and the moisture contained in the nests cause the squeezed moisture materials to be displaced into the layer A adjacent to the entrance to the die 3. When layer A is filled with moisture, it is periodically expelled from the cavity of the housing 1 through the die 3 in the form of a liquid wall layer which leads to a drop in pressure in the material located immediately before the entrance to the die 3, and boiling

5 of moisture contained in the polymer, as well as the moisture that formed layer A. Boiling of the moisture leads to the fact that at the entrance to the die 3 there is a discontinuity in the material and individual particles of material begin to slip through the die 3, i.e. spontaneous polymer granulation occurs.

For the regular process of spontaneous granulation of wet

5 of the polymer, it is necessary that the pressure in the material in front of the die 3 created by means of the screw 2 does not lead to stationary suppression of the process of moisture boiling in the material and

0 layer A Therefore, the loading of the worm machine with a wet polymer is carried out in separate portions, and during the operation of the machine, such a loading capacity of the polymer is selected in which spontaneous granulation is visually observed. Loading in separate portions, i.e. loading the bus in the fast-food mode not only allows lowering the pressure level in the material at the exit from the worm 2. but also allows the polymer to be transported at a speed of 2. in which mechanical moisture extraction from the polymer is actively proceeding with the formation of moisture nests 5, filling the supply of layer A, located before the exit to the die 3. In addition, the operation of the machine in this mode leads to significant pulsations of the pressure in the material at the exit of the worm 2 and allows reaching conditions at which the minimum values the pressures are lower than the vapor saturation pressure of the moisture contained in the polymer, and the maximum values exceed this pressure. The frequency of pressure fluctuations is further controlled by the rotational speed of the worm 2. Thus, the process of spontaneous granulation of the wet polymer during dehydration in a screw dryer is achieved.

The regularity of the process of spontaneous granulation of the wet polymer contributes to an increase in the humidity of the material loaded into the machine. The process of spontaneous granulation is carried out in the range of polymer moisture from 12 to 17%. High humidity of the material is undesirable due to the difficulty of mechanically heating the polymer, since the adhesion of the material to the machine body 1 is greatly reduced. The hole 4 in the machine body 1 allows, if necessary, to supply a low boiling liquid to the layer A when the pressure is reduced. The supply of such liquid to the BA layer through the opening 4 allows loading into

machine material with moderate humidity, for example in the range of 8-10%.

PRI me R. In FIG. 2-4 show particular characteristics of extrudate lengths

(N is the number of extrudates of a certain length C taken from the total number of samples obtained) obtained for divinyl styrene thermoplastic elastomer when it is dried in a screw machine. Table 1

material processing modes corresponding to FIG. 2-4.

From FIG. 2-4 it follows that the size of the particles obtained as a result of spontaneous granulation can be adjusted by

use of dies of appropriate length. As the length of the die decreases, shorter extrudates form. The proximity of the length of the extrudate to the length of the die used allows a rational approach to the selection of the dimensions of the forming tool of the worm machine.

(56) Copyright certificate of the USSR N: 1653992, cl. B 29 B 9 / U6, 1990. USSR Patent No. 379077

class B 29 B 9/06, 1973.

Claims (3)

1. METHOD OF GRANULATING POLYMERIC MATERIALS, in which the polymer material is fed into a screw dryer, it is extruded with a screw through a die and granulation of the material flow is carried out by supplying a liquid stream to the material and separating the granules from the flow, characterized in that, for the purpose of, To reduce the energy costs of granulation, a liquid stream to granulate the material flow is formed as a layer of superheated liquid before the polymer material enters the die and pressure fluctuations in the material exit a worm, the minimum values of which are lower than the saturation pressure of the moisture vapor in the polymer material, and the maximum values exceed this pressure. 2. The method according to claim 1, characterized in that the worm machine is loaded in separate batches of material with a moisture content of 12-17%. 3. The method according to claim 1, characterized in that a low-boiling liquid is additionally supplied to the superheated liquid layer in the zone of exit of the material from the worm channel. tollй8 6 f , v H (- | 1) It11 6 8 Yu ft K b e (pl) Fig. I 1f-Yunm dq - 1mn twenty fifty yf 15 im 1530 bf (nm) Fig.Z F -2.5mm 60 L3 (mp)