CS229401B1 - Method for the cleaning of liquid polymers solution - Google Patents

Description

SUMMARY OF THE INVENTION The present invention relates to a process for the purification of solutions of end group or end group liquid polymers prepared by anionic polymerization of diene and / or vinyl monomers in a hydrocarbon solution in the presence of organometallic initiators from dissolved or suspended deactivated initiator residues containing metal ions.

Liquid polymers, i.e. polymers containing or without end groups at both ends of the polymer chains, are commonly prepared by anionic polymerization in hydrocarbon solutions by the action of organometallic initiators, in particular lithium compounds. The living polymer resulting from such a polymer is allowed to react after the polymerization with various reagents to form end-functional groups, which form a series of moons for the use of these polymers for further chemical reactions, in particular for forming strength polymer structures and block copolymers.

After the functionalization reactions have been carried out, the alkali metal atoms usually remain bound to the non-functional group of the polymer and must be separated from the reaction mixture. If, for the removal of the alkali metal from the polymer functional groups, polyols such as water or an aqueous acid solution, the alkali metal, for example lithium, passes into the phase in the form of hydroxide or salts.

After separation of the aqueous and organic phases, it is then necessary to remove the polymer solution of the initiator residues.

The procedure is such that the gel resulting from the hyphroxylation reaction of a hydrocarbon solution of living polydiene is hydrolyzed from normal temperature by the addition of a mild mono-water;

this produces an alkali metal hydroxide, for example LiOH, which remains in the form of an aqueous solution or, in part, an aqueous dispersion.

After separation of the aqueous phase by centrifugation or sedimentation, a relatively large amount of alkali metal remains in the polymer solution, which must be separated from the polymer. Various methods are known for purifying the polymer from initiator residues. One known method is to first decompose the addition of a small amount of alcohol, ketone or amine to the polymer of the solution, and then precipitate the liquid polymer with a large amount of alcohol, such as methanol or ethanol _.

The heavier liquid polymer is then separated. from a hydrocarbon-alcoholic mixture. Removal of the initiator residues is then accomplished by multiple washes and removal of alcohol residues and solvent by vacuum distillation. (NSR Pat. 11'74 507, NSR Pat. 1186 631,

NSR pat. 1 173 65.8, Franc, Pat. No. 1,413,225, U.S. Pat. 2,708,639).

Another known method first uses the deactivation of the initiator, then k ^ гию! solvents. distillation or steam distillation. The liquid polymer remaining after the reaction, which contains all the deactivated initiator, is then washed with methanol, to which are added inorganic or organic bases or acids, thereby removing the residues of the initiator. The polymer is then dried in a thin film evaporator.

Both processes are not economical because they also work with large quantities of alcohol, the mark of which is lost in the process.

Therefore, the third group of methods uses water to transform. However, PMI usually emits _; which are stable for several hours to several days and can often not be separated, even on high-speed centers to create a sharp and clear interface. The formation of emulsions is prevented by the use of water for washing, in which the ingredients are those which improve the spreading of the emulsion formed (NSR-1 301 521) and can be used for washing. thus scrubbing the initiator residues from the solution. However, this method requires a lot of water and the resulting polymer is not pure enough.

A further group of methods uses contacting the reaction product with absorbent clay and subsequent filtration to remove initiator residues. The clays are effective, but the equipment is costly, especially containing a lot of impurities. (Bit. Pat. 1,004,723).

These disadvantages are possible. using the process of purifying the liquid polymers of the invention.

According to the invention, the purification of solutions of liquid end-capped or non-end-capped polymers prepared by ionic polymerization of diene and / or vinylaromatic compounds in a hydrocarbon solution in the presence of trglottic initiators, from dissolved or suspended initiator residues containing metal ions , preferably strongly acidic cation exchangers,. having a 'meaa * ophthalmic structure.

Sulfonated styrenedivinylbenzene copolymers can be used as the ion exchanger. Since sorption is carried out from the organic solution, the ion exchanger must be swollen with the liquid in which the sorption will take place. Polar liquids soluble in both organic solvent and water can be used to transfer iox from aqueous to organic medium.

Advantages of the method according to the invention:

High levels of metal ion removal from organic polymer solutions can be achieved with a dilution concentration of ppm units when purifying metal ion residues by non-oxides sorption. At the same time, the problems associated with the formation and precipitation of sulfur are eliminated, which greatly reduce the efficiency of extraction of the initiator residues from the polymer solution with alcohol or water. . Losses of polymer that can pass into the wastewater are also eliminated. If the polymer solution contains longer water-soluble initiator residues leachable with water, the process of the invention may be combined with water extraction. In this case, the method according to the invention is used to purify the already partially purified polymer solution by another method, e.g.

water extraction.

t

The purification method of the invention and its advantages are illustrated by the following examples.

i Example 1

A 20% solution of living polybutadiene in toluene prepared by anionic polymerization in the presence of cGr-initiators formed a gel after hydroxylation with propylene oxide. It was decomposed at normal temperature by overlaying with distilled water at 5% by volume per gel volume. After 10 hours. The gel was decomposed and the resulting mixture was separated into two layers. Morrí layer? The turbid solution contained a turbid solution of the polymer and the bottom turbid layer contained both the ID.OH formed in the reaction both dissolved in water and dispersed in the form of a suspension.

A portion of Li OH remains dispersed or eventually dissolved in the organic polymer solution. The turbid polymer solution was centrifuged in a laboratory centrifuge for 20 min at 3000 rpm at 1,900 G. After centrifugation, a slightly turbid solution was obtained, which was stabilized by the addition of lonol (2,6-di-tert-butyl-4-methylphenol) entioxidant and concentrated to the laboratory. Vacuum rotary evaporator at 50 ° C pressure 21 kPa.

The concentrated solution was dried in a vacuum oven at 10 to 27 kPa and 50 ° C at a polymer layer thickness of about 1 to 2 cm. In the polymer thus obtained, 560 ppm Li was found by flame photometric determination of residual Li content.

Example 1 a d 2

A portion of the polymer solution treated according to Example 1, after centrifugation in a centrifuge, was washed 3 times with distilled water in an amount of 10% by volume of the polymer solution. The water was mixed into the polymer solution with a glass rod to prevent the formation of a stable emulsion. The rate of washing of LiOH or possibly lithium salts depends to a large extent on the stirring rate. With intensive stirring, emulsions are formed which are very difficult to separate. The solutions after the last centrifugation were turbid. After addition of the entioxidant, they were treated in the same manner as described in Example 1. After evaporation and drying, the polymer contained 210 ppm of residual Li.

Example 3

A 20% solution of living polybutadiene in toluene prepared by anionic polymerization in the presence of organolithic initiators formed a gel after hydroxylation with propylene oxide. After decomposition and removal of the aqueous layer by centrifugation for 20 minutes at 3000 rpm at 1900 G, the upper toluene layer of the polymer was passed at room temperature through a laboratory ion exchange column packed with a strongly acidic cation exchanger of styrene-di-vinyl benzene type * Wofatit KS-10.

The column was ready for operation as follows: the water-swollen ketex, supplied in the non-form, was loaded into an ion exchange column. The H-form was transferred with 7% aqueous HCl. After washing the column with water to neutral, the column was flushed with 1 volume of ethanol per volume of ion exchange resin and then flushed with half volume of toluene. The original turbid toluene polymer solution was strongly alkaline due to LiOH content (560 ppm per polymer). A clear, completely neutral polymer solution flowed out of the column. After evaporation of the solvent and drying, the residual Li content of the polymer was found to be 1 ppm.

Example 4

A 2% solution of living polyisoprene in hexane, prepared by anionic polymerization in the presence of organo-initiators, formed a gel after hydroxylation with totyrolaconone. This was decomposed at normal temperature by coating with distilled water at a volume of 5% by volume per gel volume. After standing for 10 hours, the gel decomposed and the resulting mixture was separated into two layers. The upper layer contained LiOH formed in the reaction both dissolved in water and dispersed as a slurry.

The turbid polymer solution was centrifuged in a laboratory centrifuge for 20 min. at 3000 rpm and 900 G. After centrifugation, a slightly cloudy solution containing 620 ppm Li per polymer was obtained. This solution was passed through a column packed with macroporous cation exchange cation-exchange styrene divinylbenzene copolymer of the trade mark Wofalit KS-10. The column was ready for operation in the same manner as in Example 3, but the column was flushed first with tetrahydrofuran followed by hexane. The effluent polymer solution had a completely neutral reaction and contained 2 ppm residual Li.

Example 5

A 20% solution of living polybutadiene in hexane, prepared by anionic polymerization in the presence of organosodium initiators, was deactivated by adding 5% by volume of methyl alcohol per volume of solution of living polymer. After removal of the methanolic layer by sedimentation, the organic polymer solution was passed through a column unfilled with mneroporous suli-type ketex styrene divinylbenzene copolymer of the trade mark Wofaait KS-10. The column was ready for operation in the same manner as in Example 3, but the column was flushed first with letainolefl and hexane. The effluent polymer solution had a completely neutral reaction and contained less than even ppm residual NO.

Claims (1)

SUBJECT MATTER OF THE INVENTION A process for the purification of solutions of liquid end-capped or non-end-capped polymers prepared by ejonium polymerization of diene and / or vinylerromatic compounds in a hydrocarbon solution in the presence of arganacic initiators The purification is carried out by sorption on ionic amines, preferably on strongly acidic ketexes having a mata ^, opioid structure.