LU86810A1 - PROCESS FOR REMOVING SOLVENT FROM POLYMER SOLUTION - 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

L-3158

...... ^ f) § ^ Q CtRAND-DUCHÉ DF LUXEMBOURG

'Patent N ° * M. . λί. . f

Minister ♦ of March 16, 1987 of the Economy and the Middle Classes

Intellectual Property Service

πΐΓ £ ωΐνΓΐί - I öS LUXEMBOURG

peman ^ e (I Patent of invention &} · yÎt ^ ·· .............................- -... .................................................. ..: ............................................... ..................... ............................. ................................. (It ♦ I. Request

Labofina SA, 52, rue de.11Industrie, B-1040 ..... Bruxelles, ............. (2i represented ...... by Monsieur Jean Waxweiler, 55 .. ..... rue ..... des. Bruyères, ...

Howald, ........ acting ...... in ...... as agent ....................... .....

.................................................. .................................................. .................................................. ....................................-............. .................................................. ......................................... '......-. ....... (3) deposits! Nt} this sixteenth of March .... mil. nine ..... one hundred and eighty-seven ______________._______________________________ _____ (4i to 15.00 .......... hours, at the Ministry of the Economy and the Middle Classes, in Luxembourg: 1. la this request for obtaining a patent for an invention concerning:

Process for removing the solvent from a polymer solution ^ 5) 2. the description in language .......... r-'u311? 3 -! - ®.® ........ ........................................ of the invention in three copies: 3. ......... 1 ............ drawing boards, in triplicate; 4.1a receipt of taxes paid to the Registration Office in Luxembourg, on 16.0 3 .1.9 87 .............: 5. the delegation of power, dated ..Brussels ... ................................. ...... the .......... .... 12.03.1987; 6. the successor document (authorization); declare (s) assuming responsibility for this declaration, that the inventor (s) is (are): (6)

Jean-Marie Marcelle Guillaume NAVEAU, rue du Paradis 89, B-1400 Nivelles \ claims (nt) for the above patent application the priority of one (s) request (s) from (7) ....... ................................... / .............. ..... ............................................. ............................ filed in (8) ....... / ...... .................................................. .....................................

on (9) ............ / _____________________________________________________________________________________________________-............................... .................................................. .................................................. .................................................. .....

under N ° (10) L .............................. ............ .................................................. .................................................. .................................................. .................................................. .....................................

in the name of (11) J _ _ _____________________________________________________________________________________________________________________________________________________________________________________________________________ elect (elect) domicile for him / her and, if designated, for his / her representative, in Luxembourg ____________________________________________________ 5.5 rue des. ..Bruyèr es..r._BQwald _________________________________________________________________________________________________________________________ (12) request (s) the grant of a patent for the invention for the subject described and represented in the abovementioned appendices, with deferment of this disapproval to ..... ....................... IB- _______________________________________________________________ ___months. (13)

The agent: \ .............................................. .................................................. .................................................. ........ (14) Π. Deposit Minutes

The aforementioned patent application has been filed with the Ministry of the Economy and the Middle Classes.

InteJle Property Service ^ mçôe.JTtttxembourg, dated: l 6.03.19 8 7 A »* '· v / \ _ f î ·'. * / '\ Pr. The Minister of the Economy and Classes Medium,. 15.00. 1 * 5 / î \ a ...........'__________________ hours I, · g »* {pi y \ te -‘ Îif · =? / The head of the intellectual property department,

Af> 8007 y EXPLANATIONS RELATING TO THE DEPOSIT FORM. jf (I l if applicable "Request for certificate of addition to the main patent, to the main patent application No ........... ifiu .......... .. (2) enter the last name, first name, profession aHiPW rin dpinsnrimir InrcnilP "" llti-m "and lin nirtinilier / TU l" c (iinnmirafirtn copiai "form inndinn" aHrKt "rin cieoA civiîl InrcmiB le ·, ηα" mI. _ ("i.

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F-553 LU

* L-3158

DESCRIPTIVE MEMORY FILED IN SUPPORT OF A PATENT INVENTION APPLICATION IN THE GRAND DUCHY OF LUXEMBOURG

LABOFINA S, A.

52 rue de l'Industrie B-1040 Brussels

Process for removing solvent from a solution of polymer F-5 5 3 EB0 £ I2I_ £ PyR-INLiyfB-Lf-S0LyANT_D ^ yNE_SpLyTI0N_DJ.yN_P0LYMERE.

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

Generally, the processing of polymer solutions to remove the solvent and obtain polymer granules comprises two steps. In a first step, a majority of the solvent is removed, so as to have a relatively viscous solution which is introduced into a degassing apparatus comprising one or two worms, and several openings arranged at the periphery of the screw to allow the exhaust of the vaporized solvent.

The first step can be carried out either in a reactor, or also in a fine screw. In both cases, the problems which arise are linked not only to the control of the flow rate between the systems used in the two stages, but also to the transfer of the polymer solution between the two systems, in particular when the solutions are treated. of highly viscous elastomeric polymer.

With two-stage systems, poor thermal stability of the polymer formed is also observed, taking into account the numerous dead zones which are created in the screw or screws and the long residence time of the polymer in the extrusion apparatus.

- 2 -

In addition, when treating solutions of elastomeric polymers of the rubbery type in conventional equipment, with granulation under water, a crosslinking of the rubber is observed at the location of the die. This is due to the high temperature resulting from the pressure drop created upstream of the die with this type of granulation.

It is also asked to treat these solutions of elastomeric polymers so as to obtain a content of residual volatile compounds as low as possible: however, with the usual two-step processes, we are led to limit ourselves to residual contents of approximately 0, 5% by weight, taking into account the reduced size of the screw used in the second step.

It therefore seems desirable to have a process for removing the solvent from solutions of elastomeric polymers, whether rubbery or not, in a single step, until a content of residual volatile compounds is less than 0.1% by weight.

When used in the present invention, the term "elastomeric polymer" means a polymer of which at least about 15% by weight is constituted by an elastomer, the optional residue being constituted by a thermoplastic resin.

The subject of the present invention is a new one-step process for removing the solvent from the solution of elastomeric polymers containing at least 20% of elastomer, and which makes it possible to avoid the drawbacks mentioned above.

The present invention also relates to a new one-step process for removing the solvent from solutions of elastomeric polymers until a residual volatile compound content of less than 0.1% by weight is obtained.

The process of the present invention for removing in a single step the solvent from a solution of polymeric polymer containing at least 20% of elastomeric polymer - 3 - is characterized in that it comprises the following steps: - introducing in the feed hopper of a worm, the elastomeric polymer solution previously heated to a temperature between 150 and 200 ° C, under a controlled pressure higher than the boiling pressure of the solvent; - create a trigger in the feeding area; - Remove, with this expansion thus created, by the ventilation zone located behind the feed hopper, 80 to 95% of the solvent, while advancing the elastomeric polymer solution; - reheating the polymer solution to a temperature of 150 ° C to 200 ° C; - remove, in the ventilation zones located in front of the feed hopper, the rest of the solvent; - optionally injecting between the different ventilation zones, an amount of water between 0.5 and 2% by weight of polymer, so as to promote the evacuation of solvent; - introduce the elastomeric polymer paste, free of solvent, through a die; - cut the polymer in the granulator located just behind the die.

The process of the invention is carried out by introducing the solution of elastomeric polymer into the feed hopper of a worm.

The elastomeric polymers which are treated in the present invention may be of a rubbery or thermoplastic nature. For this purpose, it is possible to treat polymers of butadiene, isoprene or most often copolymers of a rubbery nature consisting of vinylaromatic monomers and conjugated dienes such as, for example, copolymers of styrene and butadiene or styrene and isoprene, in which the proportion of conjugated diene monomer is at least 15% by weight. In the case where the process of the present invention is applied to elastomeric polymers of thermoplastic nature, these are most often block copolymers of styrene and of conjugated diene, having a high styrene content. It is understood that the process of the present invention also applies to elastomeric polymers of the vinyl aromatic block / conjugated diene copolymer type, the conjugated diene fraction of which is partially or completely hydrogenated.

These polymers are obtained by solution polymerization of the corresponding starting monomers. The polymers or copolymers are in the form of a solution in the polymerization solvent, most often paraffinic, cycloparaffinic, aromatic hydrocarbons. Examples of suitable solvents that may be mentioned include cyclohexane, pentane, hexane, cycopentane, isooctane, benzene, toluene, or mixtures of hexane and cyclohexane. The polymer content in the solution is generally between 20 and 60% by weight.

The Applicant has now found that it is possible to carry out the removal of the solvent until a residual solvent content of 0.1% or less is obtained, and this by treating the polymer solution in a single step.

The Applicant has also found that it was necessary to remove most of the solvent, ie from 80 to 95% thereof, by ventilation located behind the feed hopper.

It has been unexpectedly found that, in doing so, not only does the polymer paste continue to advance without hindrance with the worm, but the solvent is easily removed since there is no hindrance as it passes towards the back of the screw.

This rear ventilation is carried out by preheating - 5 -

Solutions at 150-200 ° C and creating a relaxation in the feed zone of the worm. This expansion is adjusted by means of the control valve located on the feed line of the worm.

This removal of the solvent has the effect of considerably reducing the temperature of the polymer solution.

The Applicant has found that, in order to obtain a good yield of solvent removal in the upper ventilation zones, the polymer solution had to be reheated to a temperature between 150 ° C. and 200 ° C. calories being achieved either by heating the barrel of the screw to a temperature between 180 ° C and 250 ° C, or by providing in the screw elements introducing shear forces, or by combining the various means;

It has been found that if the polymer solution is not heated to a sufficient temperature, it does not succeed in reaching levels of residual contents of the order of 0.1%.

As the polymer paste advances in the screw, the residual solvent is gradually eliminated through the various ventilation zones.

These areas are generally under a pressure less than or equal to atmospheric pressure. The vacuum increases as the polymer solution progresses in the screw, and goes from atmospheric pressure to about 5 mbar at the end of the screw. These degassing zones are generally 3 to 5 in number depending on the amount of solvent to be removed.

Between each of the degassing zones, water supplies can be provided to promote the elimination of the solvent. Generally, the amount of water introduced into the polymer dough is between 0.5 and 2% by weight based on the polymer.

- 6 -

As has just been specified above, the degassing zones are at different pressures, and in order to avoid the phenomena of suction, it is customary to introduce sealing elements into the screw between the zones of degassing. These are generally made up of left-hand screw elements. This type of element is also placed after the places where water is introduced, because it also makes it possible to obtain an intimate mixture.

The Applicant has also unexpectedly found that the granulation conditions are very important. Thus, in the usual granulators under water, the pressure drop is too great and there is a reticulation of the polymer, which is very annoying.

The Applicant has found that by using a type of granulator allowing the die to be installed just downstream of the worm, it has been possible to reduce the dead zones and reduce the pressure drop, so that the temperature of the product remains limited below the polymer crosslinking temperature. It is also no longer necessary to cut the polymer under water, which represents a certain advantage of the process of the invention.

The Applicant has also found that it was necessary to operate the screw at a speed of 100 to 300 RPM to obtain good disclosure. Generally, this speed is between 150 and 250 RPM.

According to the method of the invention, it is possible to remove in a single step large quantities of solvent out of solutions of elastomeric polymers, without creating a problem of blockage or clogging of the screw.

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

- 7 -

The process of the present invention is however described with the aid of the appended figure which represents an extruder for removing the solvent from a polymer solution containing at least 20% of polymer.

The polymer solution is introduced into the feed hopper (10) of an extruder (12) comprising a double worm screw (14).

The pressure in the extruder and the feed rate are controlled by means of the control valve (16).

The extruder has a rear ventilation zone (18) through which most of the solvent will be removed. The polymer paste is drawn forward using the worm screws (14). To remove the rest of the solvent, several ventilation zones (20) were placed on the extruder (12). Between the ventilation zones, means have also been provided (22) for introducing a fluid, generally water, to promote the elimination of the solvent.

The polymer paste thus freed from its solvent crosses the die (24) and is cut into granules by means of the granulator (26).

The following examples are given to better illustrate the present invention, but without limiting its scope.

- 8 -

Exemgle_1

After carrying out the solution polymerization of butadiene and styrene, a 38% solution in cyclohexane of a styrene-butadiene radial copolymer containing 40% of styrene is recovered.

This solution is introduced at a temperature of 170 ° C. into the feed hopper of a twin screw extruder (type ZSK-57 WP) at a flow rate of 75 kg / hour. The pressure is adjusted by means of the valve located on the supply line. This extruder has a ventilation zone located at the rear of the feed hopper and three zones located in front of this hopper. The die and the granulator were placed just downstream of the worm.

The following operating conditions were applied: Vacuum in the ventilation zones: - rear zone 800 mbar 1st zone before 800 mbar 2nd zone before 80 mbar 3rd zone before 10 mbar

rotation speed: 230 RPM

Water injections were made before the last two ventilation zones, at a rate of 1% water based on the weight of the polymer.

The solvent was recovered at a rate of 92% in the rear zone, 3% in the 1st and 2nd front zone, and 2% in the last zone. The final volatile content was 0.1% by weight.

The pressure before granulation was 15 bars and the temperature of the material before granulation was 195 ° C.

The polymer was perfectly granulated, without having to cut under water.

Exemgle_2

After carrying out the solution polymerization of butadiene and styrene, a 38% solution in cyclohexane of the styrene-butadiene block copolymer containing 75% styrene is recovered.

This solution is introduced at a temperature of 165 ° C. into the feed hopper of a twin screw extruder (type ZSK-57 WP) at a flow rate of 80 kg / hour. The pressure is adjusted by means of the valve located on the supply line. This extruder has a ventilation zone located at the rear of the feed hopper and three zones located in front of this hopper. The die and the granulator were placed just downstream of the worm.

The following operating conditions were applied: Vacuum in the ventilation zones: - rear zone 800 mbar 1st zone before 800 mbar 2nd zone before 80 mbar 3rd zone before 7 mbar

rotation speed: 270 RPM

Water injections were made before the last two ventilation zones, at a rate of 1% water based on the weight of the polymer.

The solvent was recovered at a rate of 89% in the rear zone, 3% and 6% in the 1st and 2nd front zones, and 2% in the last zone. The final volatile content was 0.1% by weight.

The pressure before granulation was 15 bars and the temperature of the material before granulation was 192 ° C.

The polymer was perfectly granulated, without having to cut under water.

Exemg_l e_3

After having carried out the solution polymerization of isoprene and styrene, a 38% solution in cyclohexane of a styrene-isoprene block copolymer containing styrene is recovered.

This solution is introduced at a temperature of 160 ° C. into the feed hopper of a twin screw extruder (type ZSK-57 WP) at a flow rate of 50 kg / hour. The pressure is adjusted by means of the valve located on the supply line. This extruder has a ventilation zone located at the rear of the feed hopper and three zones located in front of this hopper. The die and the granulator were placed just downstream of the worm.

The following operating conditions were applied: Vacuum in the ventilation zones: - rear zone 800 mbar 1st zone before 600 mbar 2nd zone before 60 mbar 3rd zone before 9 mbar

rotation speed: 220 RPM

Water injections were made before the last two ventilation zones, at the rate of 1 Z of water based on the weight of polymer.

The solvent was recovered at a rate of 89% in the rear zone, 4% and 6 Z in the 1st and 2nd front zone, and 1 Z in the last zone. The final volatile content was 0.1% by weight.

The pressure before granulation was 8 bar and the temperature of the material before granulation was 180 ° C.

The polymer was perfectly granulated, without having to cut under water.

Claims (6)

1. Method of the present invention for removing in one step the solvent from an elastomeric polymer solution containing at least 20% of elastomeric polymer characterized in that it comprises the following steps: - introducing into the feed hopper an endless screw, the elastomeric polymer solution previously heated to a temperature between 150 and 200 ° C, under a controlled pressure higher than the boiling pressure of the solvent; - create relaxation in the feeding area; - remove, with the trigger thus created, by the ventilation zone located behind the feed hopper, 80 to 95% of the solvent, while advancing the elastomeric polymer solution; - reheating the polymer solution to a temperature of 150 ° C to 200 ° C; - remove, in the ventilation zones located in front of the feed hopper, the rest of the solvent; - optionally injecting between the different ventilation zones, an amount of water between 0.5 and 2% by weight of polymer, so as to promote the evacuation of solvent; - Introducing the elastomeric polymer paste, free of solvent, through a die; - cut the polymer in the granulator located just behind the die. 2. Method according to claim 1, characterized in that the solvent is removed from solutions of elastomeric polymers chosen from butadiene, isoprene homopolymers and vinyl aromatic copolymers% Λ - 12 - and conjugated dienes, of which La Conjugated diene fraction is hydrogenated or not, in particular styrene-butadiene and styrene-isoprene block copolymers. 3. Method according to any one of claims 1 and 2, characterized in that the polymer solution which has lost 80 to 95% of its solvent is heated by bringing the sleeve of the screw to a temperature between 180 ° C and 250 ° C, and / or by introducing elements into the screw creating shear forces. 4. Method according to any one of claims 1 to 3, characterized in that the absolute pressure in the screw is reduced from atmospheric pressure to 5 mbar as the progress of the polymer solution in the screw. 5. Method according to any one of claims 1 to 4, characterized in that the screw comprises from 3 to 5 degassing zones. 6. Method according to any one of claims 1 to 4, characterized in that the screw is rotated at a speed of rotation between 100 and 300 RPM, and preferably between 150 and 250 RPM.