SK168388A3 - Method of one-grade elimination of solvent from solution of elastomer polymer - Google Patents

Abstract

Process for removing in a single apparatus the solvent from a solution of elastomeric polymer to at least 20%, consisting in: - introducing into the feed hopper of an endless screw, heated between 150 DEG C and 200 DEG C, at a controlled pressure higher than the boiling pressure of the solvent; - creating a decompression in the feed zone; - removing 80 to 95% of the solvent with the decompression thus created, via the ventilation zone situated at the rear of the feed hopper, while causing the elastomeric polymer solution to travel forward; - heating the polymer solution between 150 DEG C and 200 DEG C; - removing the remainder of the solvent in the ventilation zones situated forward of the feed hopper; - injecting optionally between the various ventilation zones a quantity of water of between 0.5 to 2% by weight of polymer so as to promote the removal of solvent; - introducing the solvent-free elastomeric polymer dough through a die; - cutting the polymer in the granulator situated just behind the die.

Description

Process for single-step removal of solvent from elastomeric polymer solution

Technical field

The invention relates to a process for removing solvent from a polymer solution, in particular to a process for removing solvent from an elastomeric polymer solution having a polymer content of at least 20% by weight.

BACKGROUND OF THE INVENTION AND LONG TIME Besides rubber granulation

Treatment of polymer solutions to remove solvent and obtain polymer granules usually has two steps. In the first step, most of the solvent is removed to form a relatively viscous solution, which is fed to the degassing. equipment containing one or two infinite. a helix and a plurality of openings arranged at the periphery of the helix to escape the evaporated solvent.

The first stage can be carried out either in the reactor or at 1: 0 vij / equally in the final step. In both cases, the problems that arise are associated not only with flow control between the systems used in both stages, but also with the transfer of the polymer solution between the two systems, especially when highly viscous elastomeric polymer solutions are processed.

In two-stage systems, poor thermal stability of the resulting polymer is also observed with respect to many, dead zones that are formed at the screwdriver, the residence time of the polymer in the extruder when the solutions are elastomeric. of polymers of the type treated in conventional underwater installations, rubber crosslinking is observed at the nozzle site. This is due to the high temperature produced by the pressure drop before the nozzle. in granulation of this type.

There is also a requirement to process the solution of the elastomeric polymer so as to obtain / ol as low as possible "volatile compounds, javšak the conventional two-step process i.e. the reduction of the residual content of approximately,,, £ _r Iz .'- / s

0.5% by weight, with respect to the small size of the sXr-uttonine used in the second stage.

Accordingly, it is desirable to find a process for removing the solvent from a solution of elastomeric polymers of rubber or non-rubber nature in one step, to obtain a residual volatile compound content of less than 0.1% by weight.

WITH

According to the invention, the term elastomeric polymer means a polymer of which at least 15% by weight is constituted by an elastomer and the remainder is a thermoplastic .beta.-resin.

SUMMARY OF THE INVENTION

SUMMARY OF THE INVENTION The present invention provides a process for the single-step removal of a solvent from a solution of an elastomeric polymer selected from butadiene and isoprene homopolymers and copolymers of vinyl aromatics and conjugated dienes wherein the conjugated diene fraction is hydrogenated or the like. 20% of this elastomeric polymer, wherein a solution of the elastomeric polymer heated to a temperature between 150 and 200 ° C, a vapor pressure higher than the boiling pressure of the solvent, is fed into the feed hopper of the infinite s-Ŕr-utkovhice, as a result, 80-95% of the solvent is removed, while degassing the solution upstream of the polymer motion, the elastomeric polymer solution is advanced, re-heated to 150-200 ° C, the remainder of the solvent is removed by further degassing

a solution progressing forward, wherein, where appropriate, between different ventilation zones an amount of water ranging between 0.5 and 2% by weight of the polymer X is injected to accelerate the removal of the solvent, and to remove the solvent. Elastomer Paste:

The solvent-free polymer leads to the nozzle and is cut.

The present process is carried out such that the solution of the elastomeric polymer fed to the feed hopper infinite '7 -Mr t ¹ /.

skŕutkovrtice. The yarn is obtained with a content of residual volatile compounds of less than 0.1% by weight.

The elastomeric polymers which are treated according to the invention may be of rubber or thermoplastic nature. To this end, it is possible to process butadiene and isoprene polymers or, in most cases, rubber copolymers consisting of vinylaromatic monomers and conjugated dienes, such as copolymers with a. styrene with butadiene or styrene with isoprene, in which the proportion of conjugated diene monomer is at least 15% by weight. When the process of the invention is applied to elastomeric polymers of thermoplastic nature, these are in most cases block copolymers of conjugated diene having a high styrene content. It is understood that the process of the invention also applies to elastomeric vinylaromate / conjugated diene block copolymers in which the conjugated diene fraction is partially or fully hydrogenated.

í 2.í \. ·

These polymers are prepared by solution polymerization of the corresponding parent monomers. The polymers or copolymers are in the form of a solution in a polymeric solvent, in most cases in paraffinic, cycloparaffinic or aromatic hydrocarbons. Examples of suitable solvents are, in particular, cyclohexane, pentane, hexane, cyclopentane (sic), isooctane, benzene, toluene or mixtures of hexane with cyclohexane. The polymer content of the solution is generally between 20 and 60% by weight. . , ₍ "

If the solvent has been removed, it is possible to convert the solvent removal to the residual solvent content tikw (C). ¹ equal to or less than 0,1% when processing is carried out ύ

of a polymer solution in one step.

The propyl ester also found that most of the solvent had to be removed, i. 80 to 95%, through a ventilation opening located behind the rear of the charging hopper.

It has unexpectedly been found that by such a process, not only does the polymer paste continue to move freely with an infinite screw, but the solvent is readily. _{(to be} removed)

2, its passage to the rear of the helix is not at all.

This back ventilation is achieved by preheating the solutions to 150 to 200 ° C and reducing the pressure in the infinite filling zone

2./Ijl/i/W'K, v

-sferutkovh-i-Ge. This pressure reduction is controlled by means of a control valve located in the filling 21 in the pipe of an endless helix.

The effect of this solvent removal is to substantially reduce the temperature of the polymer solution.

The Applicant has found that in order to achieve good solvent removal efficiency in the following ventilation zones, the polymer solution must be reheated to

150 to 200 ° C, the heat input being formed either by heating

7-on-ice skrutkoyn roll - to a temperature of between .180-zi N 250 C, or 7. A'j'Zl b ^b b J '* · -, furniture components -skrutkovnice- /' s-shear ývod zujucimi force, or a combination of different means.

It has been found that if the polymer solution is not reheated to a sufficient temperature, a residual content of the order of 0.1% cannot be achieved.

The residual solvent is gradually removed in

i) OS u, .c.c-1 4 4 individual ventilation zones together with the forward movement

From the polymer paste in the helix.

These zones are usually under a pressure that is lower or z equal to atmospheric pressure. The vacuum rises with the progress of the polymer solution in the helix and varies from atmospheric pressure to about 500 Pa at the end of the helix. These degassing zones are usually 3 to 5 depending on the amount of solvent removed.

Water supplies may be formed between the individual degassing zones to promote solvent removal.

* The amount of water introduced into the polymer paste is usually

0.5 to 2% by weight, based on the polymer.

As mentioned above, there is a different pressure in the degassing zones and that the pressure is reduced. In order to prevent exhaustion, sealing elements are usually used between the degassing zones of the eccentric. They are usually formed by left-hand threads. A component of this type is also located downstream of the water supply points, since at the same time it allows perfect mixing.

¾ i4 ^ *

-Prihlasovate-1 well ¹ 'unexpectedly found · », the granulation conditions are very important. In conventional underwater granulators, the pressure drop is too high and the crosslinking is observed, which is, very unpleasant, 7

Pr-ih-la owl tel-- .zistil that, when, using a granulator of the type that allows the ,, ty-MOUNT was installed right under an endless -skr-ubkovnieou-, it is possible to reduce the dead zone, and _r to reduce the pressure drop So that the temperature of the product remains below the crosslinking temperature of the polymer. Likewise, it is not necessary to cut the polymer under water, which constitutes a clear advantage of the process according to the invention.

-In-hiasovatel- further ^R ?, · found that for good removal of volatile components is necessary that the speed of the Skrut-tkovhice was 100 to 300 ^min-1 (sic). Usually this speed, between 150 and 250 min ^- .

The process according to the invention successfully removes large amounts of solvent from solutions of elastomeric polymers in one step, but does not block or clog the helix.

It will be understood that the invention relates in particular to the treatment of solutions of elastomeric polymers, but can also be applied to any type of polymer that is in the form of a solution in a solvent.

rAaC1.71 -t

- ~ g-gg _ble according to the invention is described in connection with the accompanying drawing which illustrates an extruder -préodstraňovanie solvent from a solution of a polymer containing at least 20% of the polymer.

The polymer solution is fed to a feed hopper 10 of an extruder 12 containing a double infinite

The extruder pressure and feed rate are controlled by a control valve 16.

The extruder comprises a rear ventilation zone 18 to remove most of the solvent. Polymer paste

2.A / 1 / i / th is pushed forward through the infinite-sk-rut-vn-i-ce14. removal ¹ . A plurality of ventilation zones 20 are disposed in the extruder 12. Between the ventilation zones may also be placed means 22 for collecting a liquid, usually water, to facilitate removal of the solvent.

The polymer paste, stripped of solvent in this manner, is passed through the t-bar and is cut into granules in the granulator 26.

The following non-limiting examples are provided to illustrate the invention.

´n kJírfs'y practice); 'q · /, -' k

Example 1

After solution polymerization of butadiene and styrene has been carried out, cyclohexa is obtained ^{from a} new solution containing 38% of the star-z-z. * a styrene-butadiene copolymer containing 40% styrene.

This solution is fed at 170 [deg.] C. at a rate of kg / h to a double hopper-type filling hopper (type WP).

- ZSK-57). The pressure is controlled by a valve located in the feed line. This extruder has one ventilation zone located behind the back of the feed hopper. and three ventilation zones located upstream of the hopper. The nozzle and the infinite granulator are arranged in just 1 hour.

-s kru tko vn i-c ou-.

The following operating conditions are used:

Vacuum in ventilation zones:

rear zone 80 kPa 1st front zone 80 kPa 2nd front zone 8 kPa 3rd front zone 1 kPa rotation speed: 230 min

Prior to the last two ventilation zones, water injection is at a rate of 1% w / w based on the weight of the polymer.

The solvent is obtained in an amount of 92% in the rear zone, 3% in the first and second anterior zones (sic) and 2% in the final zone. The final volatile content is 0.1% by weight.

The pre-granulation pressure is 1.5 MPa and the pre-granulation material temperature is 195 ° C.

The polymer is granulated perfectly without the need to use ··· ..

underwater cutting. s

Example 2 of

After the butadiene-styrene solution polymerization has been carried out, a cyclohexane solution containing 38% of a block of styrene-butadiene copolymer containing 75% of styrene is obtained.

This solution is fed at 165 ° C at a rate of 80 kg / h into the feeding hopper of a twin-screw extruder (type WP ZSK-57). The pressure is controlled by a valve located in the feed line. This extruder has one ventilation zone located behind the rear of the feed hopper and three ventilation zones located upstream of the feed hopper. The trimmer and the granulator are arranged immediately after the "endless sk-ru-weaver-eou-".

The following operating conditions are used:

Vacuum in ventilation zones:

rear zone 80 kPa 1st front zone 80 kPa 2nd front zone 8 kPa 3rd front zone 700 Pa rotation speed: 270 min

Before the last two ventilation zones, water injection is carried out at a ratio of 1% of water by weight.

polymer.

The solvent is obtained in an amount of 89% in the rear zone, 3% and 6% in the first and second front zones, and 2% in the final zone.

The final volatile content is 0.1% by weight.

The pressure before granulation is 1.5 MPa and the temperature of the material before granulation is 192 ° C. The polymer is granular perfectly without the need for underwater cutting.

Example 3

Ι2Λ ^Ζ

After the solution polymerization of isoprene and styrene has been carried out, a cyclohexane solution containing a 38% block of styrene-isoprene copolymer containing 15% styrene is obtained.

This solution is fed at a temperature of 1160 ° C at a rate of 50 ° C / cm J / kg / h to the feeding hopper of a twin-screw extruder (type WP ZSK-57). The pressure is controlled by a valve located in the feed line. This extruder has one ventilation zone located behind the rear of the feed hopper and three ventilation zones located upstream of the hopper. The nozzles and the granulator are arranged immediately after the infinite box.

The following operating conditions are used:

Vacuum in ventilation zones:

rear zone 80 kPa 1st front zone 60 kPa 2nd front zone 6 kPa 3rd front zone 900 Pa rotation speed: 220min "

Before the last two ventilation zone-b is transferred 'p', 9 S * - '·''- Y, R / -; - ⁷ -pomere- injection of water in a 1% water, related to x by weight of the polymer.

The solvent is obtained in an amount of 89% in the rear zone, 4% and 6% in the first and second anterior zone (sic) and 1% in the final zone. The final volatile content is 0.1% by weight.

The pressure before granulation is 800 kPa and the temperature of the material before granulation is 180 ° C.

The polymer is granulated perfectly without the need for underwater cutting. à

Claims (4)

PATENT CLAIMS A process for the one-step removal of a solvent from a Uk2; ^{c) an} elastomeric polymer solution; selected from butadiene-isoprene homopolymers and vinylaromate and conjugated diene copolymers in which the conjugated die fraction is hydrogenated, in particular block copolymers γ / styrene-butadiene and styrene-isoprene, containing at least 20% of this elastomeric polymer, characterized in that A solution of an elastomeric polymer preheated to a temperature between 150 [deg.] C. is fed into the feed hopper of the infinite-hand-screw. And,> 200 ^and C, a pressure higher than the pressure of the boiling point of the solvent, the feed zone is reduced pressure, to thereby remove 80 to 95% of the solvent, wherein the degassed solution upstream / X of movement of the polymer, the solution of the elastomeric polymer is advanced forward - while re-heating to a temperature of 150 to 200 ° C, the remainder of the solvent is removed by further degassing of the forward solution, injecting as much water as possible between different SO 2 ventilation zones. between i / lCu ¢, 0.5% and 2% by weight of the polymer χ to accelerate the solvent removal, wherein the solvent-free elastomeric polymer paste is fed to the die and cut. Method according to claim 1, characterized in that the polymer solution, which is free from 80 to 95% of the solvent, is subjected to repeated heating by heating the -s-Ŕ-orbit-cylinder to a temperature between 180 and 250 ° C and / or introducing the components. * / S> / c c c c c c c c c c c c c c c c Method according to either of Claims 15 and 2, characterized in that the absolute pressure in the helix is gradually reduced from atmospheric pressure up to 500 Pa as the polymer solution progresses. Method according to any one of claims 1 to 3, characterized in that the box is rotated at a speed between ^v η - Ί. 100 to 300 min, preferably between 150 and 2250 min.