CS239290B1 - Apparatus for processing of polymers conjugated dienes and/or vinyl aromates,containing reactive groups - Google Patents

Description

The invention relates to a process for the treatment of conjugated member and / or vinylaromate polymers containing reactive groups, in particular carboxyl groups, obtained by functionalizing solutions of corresponding living metal-containing polymers with electrophilic agents, acid digestion by centrifuging and / or extracting the formed metal salts with water; isolation of polymers by solvent evaporation.

Polymers with functional groups are technically important compounds, giving the possibility of a number of other reactions, in particular crosslinked polymer structures and block copolymers can be formed. *

They are prepared in a manner known per se by anionic polymerization in protic or aprotic solvents in the presence of organometallic initiators, in particular lithium compounds, such that the living ends of the polymers formed in the next stage polymerization are functionalized by reaction with suitable functionalizing agents known per se.

After the functionalization reaction, the metal ions are bound to the functional groups of the polymer. In general, two things need to be done to isolate functionally terminated polymers, ie to separate metal ions and solvents: - ·

quantitatively converting primarily formed metal-containing groups into free functional groups, thereby converting the gel-like mass into a low viscosity polymer solution;

- as far as possible completely separate the metallic residues of the initiator and the solvent.

The method used for the isolation depends on the functional group. In the case of functional polymers with OH groups, except for anionic polymers without functional groups, the gel is converted into a low viscosity polymer solution with the addition of hydroxy compounds of either monohydric aliphatic water-soluble alcohols, e.g. methanol, isopropanol or water.

The metal ions are then removed by various methods by extraction with alcohol or water from the polymer solution. Particularly pure polymers are obtained by means of adsorption clays or strongly acidic ion exchangers.

In the case of functionalized polymers with carboxyl groups, the isolation of the polymeric acid from the metal carboxylate takes place first in each case, which leads to the formation of a low-viscosity polymer solution. Hydrogen chloride gas is used for this step.

When the initiator is an organolithium compound, lithium chloride precipitates in solid form from the polymer solution. It can be separated by centrifugation or filtration. However, this does not mean that the polymer solution no longer contains lithium.

Lithium chloride forms hydrates readily due to its low ionic formation and is soluble in many organic, especially polar solvents.

Thus, the known processes for the preparation of functionalized polymers with carboxyl groups are distinguished in the processing phase mainly by different methods of removing excess hydrogen chloride and the remainder of the initiator.

Hydrogen chloride is used in either an almost stoichiometric amount or an excess of 20-25%, preferably 0.5-15 g of water per 100 g of polymer solution can be added.

The acidified polymer solutions are then centrifuged and / or percolated by bleaching. clay or activated charcoal, removing water with anhydrous calcium chloride and salt loss. Electric field flocculation has also been described to improve filtration capability.

It is also known to remove residual dissolved salts, in particular lithium chloride, from a polymer solution by selective extraction, in particular methanol. Maintaining the volume ratios of the polymer solution to methanol and the polymer concentration in the solution is essential, since otherwise the phases are difficult to separate.

Another method of removing salts is to wash the polymer solution with water. However, since an emulsion is formed, this is a difficult operation with an adverse effect on its effectiveness. While slow mixing prevents emulsion formation, it also reduces phase contact, so that the scrubbing effect is insufficient.

Addition of a demulsifier such as propanol can break the emulsion, but in a salt-poor environment, esterifications and affecting the content of COOH- groups occur. This cannot be prevented by the use of detergents as demulsifiers.

These methods have a number of disadvantages. The use of hydrogen chloride as an acidic agent to release the carboxylated polymer requires considerable equipment costs due to aggressiveness. Hydrogen chloride with water is particularly corrosive.

It is necessary to use very expensive special steels and the operator is in danger of gaseous hydrogen chloride. Special safety and health measures are therefore required.

The separation of solid salts from the polymer solution places high demands on the equipment, for example the need for a centrifuge or is time-consuming, for example, for filtration. The adsorbents exhibit irreversible loss of adsorption capacity or need to use a large amount of solvent.

Extraction of polymer solutions with alcohol leads to irreversible dilution and recycling problems. In addition, narrowly defined extraction conditions are difficult to maintain. The esterification reactions cause a decrease in the content of the groups С00Н-.

The use of water as an extraction agent is disadvantageous because it leads to the formation of an emulsion that is difficult to disrupt. Further manufacturing operations are required. After extraction, the water is saturated with organic substances, which must be recovered at a high energy cost, in order to avoid loss and pollution of the environment.

These disadvantages are overcome by a process for the treatment of conjugated diene polymers and / or vinylaromates containing reactive groups, in particular carboxyl groups, obtained by functionalizing solutions of the corresponding living metal-containing polymers with electrophilic agents, acid digestion by centrifugation and / or extraction of the formed metal salts with water, solvents, characterized in that the acids have a dissociation constant of less than 10 ⁴ , that the molar ratio of acid to metal ion is 1: 1 to 2: 1 and optionally by introducing an organic phase with a pK value greater than 4 before evaporating the solvent by contact with strongly acidic cation exchangers having a macroporous structure, preferably sulfonated styrene-divinylbenzene copolymers.

In particular, monohydric organic acids having 2 to 3 carbon atoms, preferably acetic acid or phosphoric acid, in particular orthophosphoric acid, can be used as acids.

The molar ratio of acid anion to metal ion may preferably be 1.05: 1 to 1.6: 1.

The acid can advantageously be used in concentrated form or as water-dilute solutions.

Acetic acid can be used in a concentration range of 90 to 20, preferably 60 to 40 wt. orthophosphoric acid, especially at a concentration of 84 to 40 wt. %, but the acid concentration is not critical.

All of the polymers having neutral to weakly acidic groups can be prepared by using said acids. These polymers can be prepared in a known manner by polymerizing a C 4 -C 12 conjugated diene such as 1,3-butadiene, asoprene or 2,3-dimethyl-1,3-butadiene, or a vinylaromate such as styrene or styrene derivatives such as alpha-methylstyrene or p-methoxystyrene, optionally by copolymerization of conjugated dienes with vinylaromates.

In this case, it is used as a catalyst for organometallic, in particular organolithium compounds, and is worked in a solvent or the metal is metallized with an organometallic, especially organolithium compound.

Electrophilic agents such as carbon dioxide gas or lactone are used to terminate living centers. It has been found that the weakly acidic polymer solution remaining after addition of said acids and separation of the resulting salts or saline solutions can be freed from the remaining metal ions by sorption on strongly acidic ion exchangers up to a content below 10 ppm based on the final product.

Suitable ion exchangers are strongly acidic cation exchangers with a macroporous structure, for example sulfonated styrene-divinylbenzene copolymers. If the polymer solution contains other undesirable substances which can be washed with water, extraction with water can also take place before the ion exchangers.

Given the specific quality requirements for the end product, it is not always necessary to finely clean the polymer solution with the ion exchangers. For this purpose, water scrubbing according to any of the above procedures is sufficient and / or even further refinement can be abandoned.

Phosphoric acids and their salts are practically insoluble in hydrocarbon solvents. When processing hydrocarbon solutions of functionalized polymers with phosphoric acid, it is therefore not necessarily necessary to carry out a fine refining with ion exchangers.

Importantly, when using weak acids of the invention, such as acetic or phosphoric acid, for the treatment of functionalized polymers, the use of fine-ion exchangers is in any case possible, allowing the preparation of very pure polymers, even those having carboxyl groups.

Of course, functional group-free polymers obtained by terminating living metal-grouped polymers with acidic hydrogen compounds, such as aliphatic alcohols, primary or secondary amines or water, can of course be processed by the process of the invention, but water washing is generally sufficient.

A decisive advantage of the process according to the invention is that aggressive hydrogen chloride is eliminated from the process in each direction.

A further advantage is that after addition of weak acids to the polymeric metal compounds, irrespective of the method of addition, no emulsions are formed and sharply bounded layers are formed and that residual metal ions of the initiator are deposited on the ion exchanger so that the polymer solution is optically clarified.

Furthermore, it is an advantage, for polymers with carboxyl groups, that there is no danger of esterification as in the action of hydrogen chloride, so that there is no significant reduction in the COOH functionality.

Example 1

1.35 L of a bleached live polybutadiene solution containing 24 wt. % in toluene / tetrahydrofuran was reacted with carbon dioxide gas.

Pblybutadlene had a kinetic molecular weight of 2000. This amount of solution contained 288 mmol of lithium. The reaction resulted in a gel-like polymeric lithium carboxylate. The total amount of gel was 1200 g.

This amount was divided into three equal portions and further treated alternatively with hydrochloric acid, acetic acid and orthophosphoric acid for comparison.

a) Hydrochloric acid treatment (comparative example) 400 g of polymer gel was placed in an open container and 2.6 l of hydrogen chloride gas was slowly fed into the bottom of the container through a glass tube.

This corresponds to an excess of 1.2 mol relative to 96 mmol of lithium in the gel. After 16.h, the gel turned to an almost clear solution with a white deposit on the bottom which was lithium chloride. A lithium chloride is aspirated from the clear weakly acidified polymer solution by means of a 2000 g centrifuge.

This solution had a titration content of 231 ppm lithium based on the polymer. Then, the polymer solution was washed four times with 20 vol% water at 333 K to remove excess hydrogen chloride and reduce the lithium content.

Washing with water is carried out in a bottom-mixer to suppress emulsion formation under laminar flow and the mixing time is always 30 seconds. The aqueous phase is drained through a valve in the bottom of the vessel.

At the end of the fourth wash, the remaining water is removed by centrifugation. After addition of an antioxidant / 0.5 wt. % of irganox 565, based on the expected amount of polymer, which was 96 g / s, was removed on a rotary evaporator at 333 K and at a pressure of 2 to 5 kPa.

76 g of polybutadiene with carboxylic end groups remained in the vial and had the appearance of a clear, yellowish, viscous liquid. It had an average molecular weight of 1,960 and a COOH content of 0.919 mmol / g, corresponding to a functionality of 1.82. The residual lithium content of the polymer was determined to be 189 ppm by flame photometry.

b / Treatment with acetic acid

400 g of polymer gel was put into a flask along with 6.1 g of pure acetic acid and the mixture was allowed to stand covered for 40 h. A grayish-white solution was formed which was lithium acetate.

The upper half of the solution was clear, the lower half to the interface was liquid to solid, increasingly cloudy. Lithium acetate was separated from the polymer solution with a 2000 g centrifuge.

A clear solution remained having a polymer content of 23.6 wt. % and lithium content, determined by potentiometric titration with 0.1 n HCl based on polymer, of 0.68 mmol / g, which is about 4,720 ppm lithium.

As in alternative a), the polymer solution was washed twice with water and a second time. washing the residual water was removed by centrifugation. The slightly turbid solution after centrifugation has a polymer content of 24.2 wt. % and the polymer content of lithium was 1420 ppm.

Then this polymer solution was passed through a cation exchange layer based on sulfonated polystyrene-divinylbenzene (Wofatit KS-LO), which was pretreated as follows:

The cation exchanger in the form of Na swollen with water is filled into a layer and converted to form H with a 7% solution of HCl in water. It is then washed with water until it is almost neutral. It is then flushed with the same volume of ethanol as that of the cation exchanger and then with half the volume of toluene.

For the cation exchanger layers drains clear polymer solution with a pH value less than 4. After the stabilization and solvent evaporation, which is carried out in the same way as the ^one described above to give 87 g of polybutadiene having terminal carboxyl groups, which formed a clear, slightly yellowish, viscous liquid with an average molecular weight 1,940 and with a COOH group content of 0.985 mmol / g. This corresponds to 1.91 functionality. The content of lithium was determined to be 1 ppm by flame photometry.

92 239290 * 6, с / processing with orthophosphoric acid

400 g of polymer gel was placed in a flask together with 20 ml of concentrated phosphoric acid (84.5%). The mixture was allowed to stand for 12 hours with occasional stirring. The molar ratio of Li to phosphoric acid was 1: 1.05.

The resulting polymer solution was treated as in alternative b) by centrifugation, washed twice with water and passed through a cation exchange layer. After removal of the solvent on a vacuum rotary evaporator, 90 g of polybutadiene having a terminal molecular weight of 1,950 and a carboxyl group content of 0.969 mmol / g of polymer were obtained, corresponding to a functionality of 1.90. .

The lithium content after centrifugation was 136 ppm, after washing with water 42 ppm and after cation exchange 2 ppm.

Example 2

A solution of dilithium polybutadiene with a kinetic molecular weight of 2500 in methyl tert-butyl ether was reacted with CO 2. A solid white gel was formed in an amount of 900 g containing 0.32 moles of lithium. The whole gel content was mixed with 77 g of a 40% solution of acetic acid in water and left to stand for 16 h.

A gel-free solution was formed consisting of an upper clear organic layer and a lower water layer with a sharp phase interface. The organic layer containing the functionalized polymer was separated on a laboratory centrifuge at 3000 rpm and 1900 g _n from the aqueous acetic layer eluted with lithium acetate.

The polymer solution had a solids content of 44.2 wt. % and 53 mmol of lithium per liter. After stabilizing the polymer solution 0.5 wt. % Of Irganox 565 based on polymer and solvent evaporation in vacuo left 390 g of polybutadiene with carboxyl groups in the form of a yellow viscous liquid with an average molecular weight of 2,450, a COOH content of 0.787 mmol / g and a functionality of 1.93 having an IIthium content of 910 ppm.

Example 3

A solution of di-Na-alpha-methylstyrene getramer in tetrahydrofuran was allowed to react^with plyⁿn^ým oxide u^hličand^tým^, p^Řwhere the formation ^⁵20 May^G colorless^Ehim^Gelvi. T^Ento gel is nec^hand^l reago 70 µl of a 60% aqueous solution of iodoic acid was added and then allowed to stand for 16 hours.

It contained 0.5 moles of Na. A gel-free upper organic phase and a lower aqueous phase were formed. The organic phase, which contained tetrahydrofuran and dissolved tetrameric alpha-methylstyrene dicarboxylic acid, was separated from the lower excess acetic acid and the sodium acetate and water dissolved therein by. centrifugation.

The solids content of the oligomer solution thus isolated was 22.7 wt. %, the content of Na relative to the oligomer was 320 ppm. The fine purification of the oligomer solution was then carried out according to Example 1, alternative ad b), using a strongly acidic cation exchanger.

Evaporation of the tetrahydrofuran on a rotary evaporator and drying of the concentrated solution at 323 K in a vacuum dryer at 10 to 20 kPa gave 115 g of a colorless powdery tetrameric alphamethylstyrene dicarboxylic acid, with a Na content of 3 ppm.

Example 4

0.55 l of a solution of live trilithium polybutadiene with a mean kinetic molecular weight of 3 500 in benzene at a concentration of 20% by weight. %, containing 86 mmol of lithium, was reacted with ethylene oxide.

A solid polybutadiene trialcoholate formed which was reacted with 22 g of a 50% aqueous orthophosphoric acid solution _f corresponding to a molar ratio of lithium to phosphoric acid of 1: 1.3.

The mixture was stirred until the alcoholate turned into a liquid polymer solution. This solution is centrifuged at 3,000 rpm and 1,900 g in a centrifuge and the aqueous phases are separated. The benzene solution had a lithium content of 76 ppm.

The solution was washed twice with 10 vol% water, then the polymer was isolated from the solution by evaporation of the solvent on a vacuum rotary evaporator. The polymer had an average molecular weight of 3,440, a hydroxyl group content of 0.849 mmol / g polymer, resulting in a functionality of 2.92 and a lithium content of 34 ppm.

Claims (4)

SUBJECT OF THE INVENTION Process for the treatment of polymers of conjugated dienes and / or vinylaromates containing reactive groups, in particular carboxyl groups, obtained by functionalization of solutions of corresponding living metal-containing polymers with electrophilic agents, acid digestion by centrifugation and / or extraction of formed metal salts with water; -4-solvents, characterized in that the acids have a dissociation constant of less than 10, that the molar ratio of acid to metal ion is 1: 1 to 2: 1 and optionally by introducing an organic phase having a pK value greater than 4 before evaporating the solvent by contact with strongly acidic cation exchangers having a macroporous structure, preferably with sulfonated styrene-divinylbenzene copolymers. Process according to claim 1, characterized in that the acid used is a monohydric organic acid having 2 to 3 carbon atoms, preferably acetic acid or phosphoric acid, in particular orthophosphoric acid. 3. The process of claim 1 wherein the molar ratio of acid anion to metal ion is from 1.05: 1 to 1.6: 1. 4. Process according to claim 1, characterized in that the acids are used in concentrated form or as water-dilute solutions.