MXPA98009516A - Elimination of ionic contaminants from polymeric cements using a component fund - Google Patents

Abstract

The present invention relates to a process for removing ionic contaminants from a polymeric element containing ionic contaminants comprising: i) Contacting the polymeric cement with a molten component capable of reacting with the ionic contaminants; and ii) separating the component. molten polymer cement asiobten

Description

ELIMINATION OF IONIC CONTAMINANTS FROM CEMENTS POLYMERICOS USING A FUNDED COMPONENT The present invention relates to a process for removing ionic contaminants from polymeric cements. Many of the polymerization operations use a metallic catalyst. On some occasions where productivity is extremely high or where terminal use does not require a pure polymer, the metal can simply be left in the composition. In any case, in many cases the metal must be removed before the polymer can be used. Filtration has been known for a long time as a method for the elimination of insoluble metal contaminants. However, the filtration of viscous polymer solutions is generally slow and expensive. The extraction of the metal with aqueous solutions of acids or chelates is very well known. This approach is often unsatisfactory due to the formation of emulsion, the requirements to prolong the calibration of time, or the saturation of the organic phase in water. Also the polymers, particularly the elastomers have limits such as rough which can be treated without decomposition. The examples of the methods discussed are REF. : 28748 can be found in patents Nos. 2,787,647, 2,999,891 and ,177,391; in British application No. 776,682 and in German application No. 3,520,103. An object of the present invention is to provide a process for the removal of ionic contaminants from polymeric cements. Accordingly, the present invention provides a process for the removal of ionic contaminants from a polymeric cement, containing ionic contaminants comprising: i) contacting the polymeric cement with a molten component such as a metal salt or hydrate capable of reacting with the contaminants ionics; and ii) the separation of the molten component from the polymer cement thus obtained. In this way, the emulsion formation can be advantageously avoided. Figure 1 shows a flow diagram of a polymerization process, which includes the elimination of the initiator followed by a hydrogenation and the recovery of the polymer cement; and Figure 2 shows a flowchart of an alternative embodiment of the present invention wherein the hydrogenated polymer is produced to then remove the metal components.

In accordance with the present invention it has been found that the use of a molten component such as the bisulfate salt for the removal of ionic contaminants as the residue of a lithium catalyst from polymeric solutions prevents the formation of emulsions. This allows another benefit by allowing easy and complete separation after treatment since the molten phase is substantially more dense than the organic phase. In addition, rather than having to accept an intermediate solution in the effectiveness to avoid the introduction of large amounts of water, the melt system has a greater capacity to eliminate contaminants than the one with the aqueous composition. The molten component can be any salt or hydrated salt which is liquid under the conditions used for the removal of the ionic contaminants, which is capable of reacting with the contaminants without significantly damaging the polymer. Acid salts, organic acids, chelating agents and eutectic mixtures of salts; they are adequate. The lithium initiator that catalyzes elastomers is suitable to be brought to a temperature in the range of between 30 to 150 ° C, preferably at a temperature in the range of 50 to 80 ° C, and more preferably at a temperature in the range between 60 to 70 ° C. In this way, sodium bisulfate monohydrate - - which melts at 58.5 ° C is ideally suited for this type of reaction because of its melting point and its ability to provide a source of acidic protons. The salts like monobasic sodium phosphate dihydrate (sodium dihydrogenphosphate dihydrate), sodium orthophosphite pentahydrate, acid sodium phosphite pentahydrate and sodium sulfate decahydrate can also be used, although they are less recommended since they have large amounts of water of hydration. According to the present invention, the undesirable ionic contaminants can be removed from any polymeric cement either an authentic solution or a polymer dispersion of a liquid diluent. Ionic contaminants can be the same type of ionic contaminants or can be different types of ionic contaminants. Generally, the present process is used to remove metal ions from solutions of polymers in organic solvents or in the monomer used in the preparation of the polymer. The removed impurities are usually metal ions of a polymerization catalyst or of a catalyst used for subsequent treatment, such as hydrogenation, although the invention is applicable for the removal of undesirable ions, especially cations, which includes any component such as ammonium ions. . From this way, the metal ions can be removed from the polymeric cement according to the present invention with ions including lithium, nickel and aluminum. In cases, where the metal may be present in metallic form, i.e. with zero valence, the composition may be subject to an oxidation treatment to convert the metal to a metal ion. There must be sufficient contact between the molten component and the ionic contaminant to ensure that the chemical reaction can be carried out. Presumably the removal proceeds by ion exchange as shown in the following exemplary equation where an excess of sodium bisulfate monohydrate and an elastomer solution prepared using a dilithium initiator followed by ethylene oxide to terminate the reaction and introduce an oxygen to each terminal between lithium and the polymer chain. 2NaHS04-H20 (l)? S + Li-0 ~ 0-Li? 2NaLiS04 + HO-OH + xsNaHS04-H20 As noted above in the case of contaminants in the metallic state such as the nickel remaining in a hydrogenation reaction, oxidation may be required before extraction as shown below.

- - Ni0 + H20 + l / 202? Ni2 + + 20H "2NaHSOvH20 + Ni2 + + 20H"? Na2Ni (S04) 2 + 2H20 After the ion exchange or neutralization of the lithium alkoxide with the sodium bisulfate monohydrate or other suitable molten salt, the sodium lithium sulfate can be dissolved in molten sodium hydrogen sulfate monohydrate. The molten salt is denser than in the organic phase allowing a rapid separation of the phase and avoiding emulsion problems that are found if an aqueous extraction system were used. The process can be carried out properly on a continuous or intermittent basis with a short contact time of 1 minute or as much as 24 hours. Preferably, the contact time is in the range of 5 minutes to 5 hours, and more preferably in the range of 10 minutes to 2.5 hours.

The contact can be carried out by stirring or tumbling using static mixers, settling mixers, centrifugal contact or other conventional devices. A continuous process can be used, according to which the two phases are passed current or countercurrent, for example through a column that is equipped with rotating vanes. If a continuous or intermittent process is used in the termination of the reaction, the material is simply left - -asentar what happens quickly since the density of the phase is melted. At this point the two phases can be separated by any conventional method, such as decanting or draining the lower phase in a continuous or intermittent mode. Preferably, the separation is effected by decanting using a level glass or a conductivity probe to detect the interface. The molten component is normally used with a relative excess of that needed to react with the ionic contaminants to provide a denser continuous liquid phase to contain the removed material. In this way, the proportion of the molten component with the impurities can be in the range of 2: 1 to 200: 1 based on equivalents, in the case of sodium hydrogen sulfate monohydrate to remove lithium ions is the same based on moles. Preferably an equivalent ratio can be used in the range of 2: 1 to 100: 1. More preferably an equivalent ratio in the range of 2: 1 to 30: 1. Currently, the upper limit is established only by any economic conditions greater than 200: 1 can offer a small extraction and could be more expensive. Polymers produced by initiating alkali metal polymerizations are usually used without further treatment before recovery of the reaction mixture. Frequently, however, if a polymer with a reduced unsaturated aliphatic is desired, it needs a hydrogenation step. This is preferably carried out before the recovery of the polymer and uses a catalyst that can be added with additional metals to the reaction composition. In some cases it is thought that the removal of alkali metal from a polymer solution generated by an anionic polymerization before hydrogenation is beneficial.,. In accordance with the present invention, lithium ions can be used to remove metal contaminants immediately after polymerization followed by separation of the phase containing the removed ionic contaminants and directly enter the recovery of the polymer or hydrogenation of the polymer before recovery. . Particularly polymerizations with initiator-dilithium where it is desired that the final product is hydrogenated it is advisable to use the present invention to remove the lithium ions prior to hydrogenation. Hydrogenation techniques are for example available in U.S. 3,700,633 and U.S. 4,970,254. Alternatively it is possible to carry out the hydrogenation in the presence of the initiator alkali metal and - henceforth eliminate both the alkali initiator metal and the hydrogenation of the cation catalyst. It is sometimes desirable to incorporate functional groups at the end of polymer chains, particularly elastomeric polymer chains. This can be carried out with dilithium initiators simply by the addition of a terminating agent such as ethylene oxide which gives oxygen-lithium end structures at each end. end of the polymer. However, such polymers tend to form gels. The polymers formed of monolithium initiators can be terminated with ethylene oxide to give an OLi structure at the end, which can be used for the incorporation of a functional group. Recently a technique that has been developed to give a functional group in each end, using what is called a protected functional initiator (PFI). This technique is described in U.S. 5,416,168, and WO 91/12277. These processes use an initiator that has the structure R "0R i where R" is a protecting group, i.e. R3SiOR'Li wherein the R groups are alkyl or a pair of alkyl and hydrogen groups and R 'is an alkylene group. After the polymerization is complete, the termination with ethylene oxide results in a conventional LiO-polymer structure at one end and is not at the other end, as it is protected by the protecting group. According to this the silyl protecting group - -can be removed by a technique called "protection".

It has been found in accordance with the present invention that in protected initiator systems the use of the molten component results in "de-protection" and elimination of the undesirable metallic contaminant. This process as a whole can be exemplified below where the precursor of the protected functional initiator is produced by trimethylsilyl chloride and 3-chloro-2,2-dimethylpropanol.

This product reacts with lithium to give the initiator. The polymer is then formed of a monomer such as 1,3-butadiene and the reaction is terminated with ethylene oxide. A molten component is used according to this invention to "deprotect" in this way the elimination of the organosilyl group from the first end and remove the lithium from the other. This can be clearly seen below: Vulnerability - * H ° -R ^^^ OH - - The polymer present in the polymer cement is suitably produced by polymerizing a monomer selected from the group consisting of said conjugates of monovinylaromatic hydrocarbons or mixtures thereof with a protected functional initiator as described above. The polymeric cement has been tried to dissolve the polymer with a solvent that can be a monomer or another suitable solvent. It is suitable that the polymer is selected from the group consisting of polybutadiene, polyisoprene, isoprene-butadiene copolymers, styrene-butadiene copolymers and isoprene-styrene copolymers. Preferably, the polymer comprises of a copolymer block the composition comprising at least one poly (monovinyl aromatic hydrocarbon) block and at least one poly (conjugated diene) block. In Figure 1 is shown for purposes of illustration, a representation of the present invention where the monomer, the solvent and the catalyst are introduced via feed, line 10 within the area of - reaction formed by a reactor 12. The reaction mixture is stirred by a blade 14 which is rotated by an axis 16. The polymer cement comprises lithium, finished polymer and solvent which are isolated by the first transfer, line 18 and introduced in a lithium removal zone formed by a contact vessel 20, the contents which are mixed by a stirrer 22 which is similar to the agitator 14 and the axis 16. The molten sodium bisulfate monohydrate is transferred from a storage zone which it is formed by a storage container 24 to the contact container 20 via a second line transfer 26. The sodium bisulfate monohydrate is heated to melting conditions in the container 24 by a conventional heating system which is not shown. A heavy phase of sodium bisulfate monohydrate in excess contains sodium lithium sulfate as a result of the removal of lithium from the polymeric cement is isolated from a contact vessel 20 via lithium containing salt, line 28. A portion of the partially exhausted salt is used can be recovered via first recovery, line 30 which is controlled by the valve 31 and until the Ni is eliminated and AC is transferred via third transfer, line 32 to an area of hydrogenation elimination formed by a catalyst removal vessel 34. If it is desired an excess of molten salt can be used to give a salt of high proportion of the polymeric cement in the contact container 20. If this is done, the excess can be removed via line 35 which is controlled by the valve 37 and recirculated to the storage container 24. The contents of this are mixed by the agitator 36 which is similar to axis 16 and blade 14. This removal of the catalyst can be carried out by a conventional treatment with organic and inorganic acids but it is preferable to do so by contact with additional molten material such as that used for the removal of lithium, ie, sodium bisulfate monohydrate fused. The sodium bisulfate monohydrate introduced as shown via line 32 can be reheated if necessary by a conventional heating method that is not shown. The melt passed by excess and the sodium bisulfate monohydrate phase containing lithium sulphates. Nickel and aluminum are isolated via hydrogenation of the salt-containing catalyst removed, line 38 and removal of the finished polymer cement via product recovery, line 40. If desired, the catalyst removal vessel 34 can be operated using an excess of molten salt. , to give a high salt in the proportion of the polymeric cement. This excess is then isolated via line 42 which is controlled by valve 44 and recirculated to storage vessel 24. The remaining part is then - -retained via line 46 which is controlled by the valve 48.

The replacement salt is introduced via line 50. This can be either new salt or recovered salt via line 30 and / or 46 which has been purified. Since it is desirable in lithium-initiated elastomer polymerizations to maintain anhydrous conditions and thus avoid premature termination of the chains and since also the presence of water in the polymeric cement is undesirable due to the potential for emulsion formation, it is preferable to maintain essentially anhydrous conditions through the system. According to the polymeric cement effluent of the lithium elimination zone it can be optionally transferred via fourth transfer line 49 to the drying zone defined by the drying vessel 51 which has an agitator 53. The sodium bisulfate of the zone The retention container defined by the retention vessel 47 is transferred via fifth transfer, line 55 to the drying vessel 51 where the water is absorbed and thus produce sodium bisulfate monohydrate which is transferred via the sixth transfer, line 57 to the storage vessel 24. The polymeric cement either directly from the contact container 20 via line 59, which is controlled by the valve 53 or from the drying vessel 51 is introduced into a hydrogenation zone formed by the hydrogenation vessel 52 via a seventh transfer, line 54 where there is contact with a catalyst of the conventional hydrogenation catalyst type such as for example nickel or aluminum and with hydrogen, which can be introduced via 56 which can be a single line or multiple lines . After conventional contact with the hydrogenation catalyst to effect conventional hydrogenation, thus the hydrogenation of the polymer cement is isolated via separation of hydrogenated polymer, line 58 and introduced into the vessel 34 for removing hydrogenation catalyst. Alternatively, other water removal methods can be employed although it could leave the advantage of recirculating towards the lithium removal stage. In figure 2, it is shown how a polymer cement of the reactor 12 is introduced to the hydrogenation vessel 52 via line 60 which is equivalent to line 54 of figure 1, it is understood that there is no initial stage of elimination of lithium as in figure 1 and generally there is no drying stage since the effluent can be dried in this step. The effluent from the hydrogenation vessel 52 is eliminated via line 58 and introduced into the combined catalyst and protection elimination zone formed by the protection vessel 61.

- The sodium bisulfate monohydrate is introduced from an alternative storage zone defined by an alternative storage vessel 62 via the eighth transfer, line 64, inside a protection vessel 61 where it has contact with the polymeric cement that uses a agitator 66. The heavy phase fused sodium bisulfate monohydrate in excess containing both lithium of the preservation, nickel and aluminum hydrogenation catalyst is isolated via elimination of metal containing salt, line 68 and the polymer cement is isolated by product removal alternative line 70. The protection vessel 61 can be operated with an excess of molten salt if desired, this to give a high salt in proportion of the polymeric cement in the proportion 61 container. This excess is then isolated via line 68 and recirculated to alternative storage vessel 62 via line 72 which is controlled by valve 74. L The partially used salt is removed via line 76 which is controlled by line 78 for recirculation, disposal or purification. According to the embodiment of the present invention, α-α-diol polymers are produced by the use of dilithium initiators or by protected functional initiators. A family of PFIs produces hydroxy functionality in polymer molecules by hydrolysis of a group - silanol protector to produce a terminal alcohol. As shown in Figure 2, this process of this invention makes possible concurrent (1) hydrolysis of the protecting group to produce OH finished polymer; (2) elimination of the metal incorporated during the synthesis of the polymer (Li) and (3) elimination of metals introduced during the optional hydrogenation (Ni and Al). The present invention will now be illustrated by means of the following examples.

EXAMPLES EXAMPLE 1 Removal of lithium from polymer cement before hydrogenation. A jacketed reaction vessel was charged first with 613 g of a 20% solution of a butadiene-based monopolymer, initiated with sec-butyllithium in cyclohexane and 68.7 g of sodium bisulfate monohydrate. The mixture was then stirred at 500 rpm with a blade stirrer and heated to 65 ° C where the hydrated salt is melted. The mixture is stirred in this manner for two hours and then allowed to cool. The lithium content of the organic phase was reduced by 35 ppm to 7 ppm, and was easily hydrogenated to remove the 97% unsaturation.

EXAMPLE 2 Removal of lithium nickel and aluminum from the polymer cement; with the simultaneous production of hydroxide functionality by hydrolysis of a silanol protecting group.

In a similar manner, 410 g of a 20% cydohexane solution of a polymer produced by the polymerization of butadiene with a silicon-base protected functional initiator was placed in a jacketed vessel with 46.5 g of sodium bisulfate monohydrate. The mixture was heated to 64 ° C whereby the salt was melted and agitated by bubbling a gaseous mixture at 5% oxygen into nitrogen through the solution. The levels of residual metals in the solution were reduced as shown: Pre-treatment Pos-treatment Li 169 ppm 5 ppm Ni 59 ppm < 2 ppm At 62 ppm < 2 ppm Simultaneously the silicon-based protecting group has been completely hydrolyzed as determined by the proton NMR and HPLC.

- - EXAMPLE 3 Removal of Li, Ni and Al from a polymeric cement using dehydrogenated sodium dihydrate phosphate. 600 g of a 20% solution of a polymer produced by butadiene polymerized with a protected functional initiator based on silicon was contacted with 60 g of sodium phosphate dihydrate and heated to 73 ° C and where the salt is molten and agitated for 6 hr. The treatment with the phosphate salt produced substantial reductions in the level of residual metals as shown below.

Pre-treatment Pos-treatment Li 390 ppm 61 ppm Ni 181 ppm 96 ppm Al 165 ppm 86 ppm It is clear that from the above and according to the present invention the ionic contaminants can be attractively removed from the polymeric cements.

Claims (8)

- - CLAIMS

1. A process for removing ionic contaminants from a polymeric cement, the content of ionic contaminants comprises: i) contacting the polymeric cement with a molten component capable of being a metal salt or hydrate to react with the ionic contaminant; and ii) separating the molten component from the polymer cement thus obtained.

2. A process according to claim 1, characterized in that the ionic contaminants comprise the lithium, nickel and aluminum ions.

3. A process according to claim 1 or 2 characterized in that the polymer is selected from the group comprising polybutadiene, polyisoprene butadiene-isoprene copolymers, butadiene-styrene copolymers and isoprene-styrene copolymers.

4. A process according to any of claims 1 to 3, characterized in that the molten component is present in an amount to give a mol equivalent proportion of the molten component to the ionic contaminant in the range of 5: 1 to 100: 1.

5. A process according to any of claims 1-4, characterized in that the cement polymer is contacted with the molten component at a temperature between 50 to 80 ° C.

6. A process according to claims 1-5, characterized in that the molten component is sodium bisulfate monohydrate, the ionic contaminant is lithium and wherein the proportion of mol equivalent of sodium bisulfate monohydrate is in the range of 10. : 1 to 30: 1.

7. A process according to any of the re-indications 1-7, characterized in that the contact is carried out for a period of time between 5 minutes to 5 hours.

8. A process according to any of claims 1-8, characterized in that the polymeric cement comprises a polymer initiated with lithium in a solution of cyclohexane which is in contact with molten sodium bisulfate monohydrate for a period of time of 10 days. minutes to 2.5 hours. At a temperature between 50 to 80 ° C, where after a liquid-liquid separation, an upper polymer which has a reduced lithium content is obtained as a result of an ion exchange with molten sodium bisulfate monohydrate.