USH1703H - Removal of lithium from polymer cements - Google Patents

Removal of lithium from polymer cements Download PDF

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Publication number
USH1703H
USH1703H US08/652,191 US65219196A USH1703H US H1703 H USH1703 H US H1703H US 65219196 A US65219196 A US 65219196A US H1703 H USH1703 H US H1703H
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United States
Prior art keywords
lithium
acid
alkali metal
polymer
polymer cement
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US08/652,191
Inventor
John David Wilkey
Zaida Diaz
Dale Lee Handlin, Jr.
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Shell USA Inc
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Shell Oil Co
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Priority to US08/652,191 priority Critical patent/USH1703H/en
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Publication of USH1703H publication Critical patent/USH1703H/en
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    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08C—TREATMENT OR CHEMICAL MODIFICATION OF RUBBERS
    • C08C2/00—Treatment of rubber solutions
    • C08C2/02—Purification
    • C08C2/04—Removal of catalyst residues
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F297/00—Macromolecular compounds obtained by successively polymerising different monomer systems using a catalyst of the ionic or coordination type without deactivating the intermediate polymer
    • C08F297/02—Macromolecular compounds obtained by successively polymerising different monomer systems using a catalyst of the ionic or coordination type without deactivating the intermediate polymer using a catalyst of the anionic type
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F6/00—Post-polymerisation treatments
    • C08F6/02—Neutralisation of the polymerisation mass, e.g. killing the catalyst also removal of catalyst residues

Definitions

  • This invention pertains to a process for separating alkali metal compounds from a polymer cement. More specifically, this invention pertains to a process for removing alkali metal compounds from a low-viscosity functionalized polymer cement.
  • terminating agents enable immediate removal of the lithium salt by centrifugation. Removal of the lithium salt has been shown to greatly enhance the hydrogenation process.
  • Preferred terminating agents are those which form lithium salts which are less soluble in the cement than lithium methoxide. Some examples of terminating agents which are particularly effective are 2-ethylhexanoic acid, 12-hydroxy stearic acid, oxalic acid, benzoic acid, and succinic acid.
  • Basic lithium salts such as lithium methoxide retard the hydrogenation of low molecular weight diene polymers. Removal of this salt has had the effect of greatly enhancing the hydrogenation process.
  • the present invention represents an improvement over the prior art in that the salt may be removed immediately after termination, and lithium salts are removed to lower levels than is possible for lithium methoxide. Previously it was found that removing the lithium methoxide by gravity settling or by filtration allowed hydrogenation of the polymers with much lower levels of catalyst. Formation of lithium methoxide precipitate and settling from these cements is very slow and may take weeks. In accordance with the present invention it has been found that judicious choice of polymerization terminating agents enables immediate removal of the lithium salt by centrifugation.
  • Preferred terminating agents are those which form lithium salts which are less soluble in the cement than lithium methoxide.
  • Some examples of terminating agents which are particularly effective are 2-ethylhexanoic acid, 12-hydroxy stearic acid, oxalic acid, benzoic acid, and succinic acid.
  • the polymer may be present in a solvent at a concentration within the range of from about 5 to about 80 weight percent, based on total solution, and the alkali metal compound, such as lithium, may be present at a concentration within the range from about 0.005 to 5 wt % based on the polymer.
  • Contact between the polymer and the terminating agent preferably occurs at a temperature within the range of 20° to 100° C., at a pressure up to 80 psig and at a nominal holding time within the range of 20 minutes to 4 hours.
  • the polymer may be used without a solvent.
  • the method of this invention can be used to separate alkali metal compounds such as lithium compounds from polymers such as low-viscosity functionalized polymer cements (A description of how these polymers can be made follows hereinafter.)
  • the polymer may be hydrogenated or not during the alkali metal separation, but it is preferable to separate lithium compounds prior to hydrogenation.
  • Polymer solvents include but are not limited to hydrocarbons such as paraffins, cycloparaffins, alkyl substituted cycloparaffins, aromatics and alkyl substituted aromatics, such as benzene, toluene, cyclohexane, methyl cyclohexane, n-butane, n-hexane, n-heptane and the like.
  • Ethers such as diethyl ether, tetrahydrofuran, and the like can be used. Mixtures of the foregoing can be removed and another solvent substituted.
  • Centrifugation may be combined with other types of separation, e.g. filtration, settling and decantation.
  • Any alkali metal compound commonly found in a polymer solution when an alkali metal compound is used as the catalyst or initiator can be separated from the polymer.
  • alkali metal hydrides, alkali metal alkoxides and alkali metal hydroxides include alkali metal hydrides, alkali metal alkoxides and alkali metal hydroxides.
  • Low viscosity functionalized polymer diols can be made in accordance with the following procedure:
  • B represents polymerized units of one or more conjugated diene hydrocarbons such as butadiene or isoprene.
  • A represents polymerized units of one or more vinyl aromatic compounds such as styrerie.
  • X is the residue of a monolithium initiator such as sec-butyllithium
  • Y is the residue of a dilithium initiator such as the diadduct of sec-butyllithium and m-diisopropenylbenzene.
  • the anionic polymerization of the conjugated diene hydrocarbons is typically controlled with structure modifiers such as diethylether or glyme (1,2-diethoxyethane) to obtain the desired amount of 1,4-addition.
  • structure modifiers such as diethylether or glyme (1,2-diethoxyethane) to obtain the desired amount of 1,4-addition.
  • Dilithium initiation with the diadduct of sec-butyllithium (s-BuLi) and m-diisopropenylbenzene also requires presence of a non-reactive coordinating agent such as diethyl ether, glyme, or triethyl amine, otherwise monolithium initiation is achieved.
  • Ether is typically present during anionic polymerization as discussed above, and the amount of ether typically needed to obtain specific polymeric structures has been sufficient to provide dilithium initiation.
  • anionic polymerization of conjugated dienes may be performed using protected functional initiators (PFI) as described in U.S. Pat. Nos. 5,391,663 and 5,146,168 which are incorporated herein by reference.
  • PFI protected functional initiators
  • Anionic polymerization is often terminated by addition of water to remove the lithium as lithium hydroxide (LiOH) or by addition of an alcohol (ROH) to remove the lithium as a lithium alkoxide (niOR).
  • the living polymer chains are preferably terminated with hydroxyl, carboxyl, phenol, epoxy or amine groups by reaction with ethylene oxide, carbon dioxide, a protected hydroxystyrene monomer, ethylene oxide plus epichlorohydrin, or the amine compounds listed in U.S. Pat. No. 4,791,174, respectively.
  • Hydrogenation of at least 90%, preferably at least 95%, of the unsaturation in low molecular weight butadiene polymers is achieved with nickel catalysts as described in U,S. Pat. Nos. Re. 27,145 and 4,970,254 which are incorporated by reference herein.
  • the preferred catalyst is a mixture of nickel 2-ethylhexanoate and triethylaluminum.
  • the termination step can result in release of fine particles of lithiumbases as described in U.S. Pat. No. 5,166,277 which is incorporated by reference herein.
  • the lithium bases may interfere with hydrogenation of the polymer and preferably are removed, especially if the hydrogenation is to be carried out at high solids.
  • a diol cement containing 1130 ppm Li was synthesized and terminated with methanol. A one gallon aliquot of the solution was allowed to sit undisturbed for 19 days, at which time testing of the supernatant solution indicated a lithium content of 320 ppm Li, for 72% removal efficiency by settling. For the present invention, greater removal efficiencies were achieved in shorter periods of time by a combination of the preferred termination agents and centrifugation.
  • Acids and a diketone were screened to determine successful polymer cement terminating agents. Best results were obtained with oxalic acid, benzoic acid and 12-hydroxystearic acid. These acids are solids so a process is envisioned where the cement is passed through a bed or cartridge of the solid acid to remove lithium.
  • the following table is relevant to lithium (ppm) remaining in a cement (a PFI diol having 20% solids and 4000 molecular weight) after termination with various agents. After the allowed settling time, the supernatants were centrifuged at 5000 g-minutes.

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  • Chemical & Material Sciences (AREA)
  • Health & Medical Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Medicinal Chemistry (AREA)
  • Polymers & Plastics (AREA)
  • Organic Chemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Inorganic Chemistry (AREA)
  • Polymerization Catalysts (AREA)
  • Addition Polymer Or Copolymer, Post-Treatments, Or Chemical Modifications (AREA)

Abstract

A process for preparing a polymer cement which is relatively free of alkali metal salt by preparing the polymer cement with a polymerization terminating agent which is an acid which leaves alkali metal salt in the cement which is readily removable by centrifugation.

Description

This application is a nonprovisional filing of United States provisional patent application Ser. No. 60/009,521, filed Dec. 28, 1995.
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention pertains to a process for separating alkali metal compounds from a polymer cement. More specifically, this invention pertains to a process for removing alkali metal compounds from a low-viscosity functionalized polymer cement.
2. Prior Art
Diene polymer cements containing highly basic lithium residues from the initiator (e.g., lithium methoxide) prove to be very difficult to hydrogenate. High levels of nickel/aluminum catalyst are required to thoroughly hydrogenate these materials. Previously it was found that removing the lithium methoxide by gravity settling or by filtration, allowed hydrogenation of the polymers with much lower levels of catalyst. Formation of lithium methoxide precipitate and settling from these cements is very slow, and effective removal may take weeks.
U.S. Pat. No. 5,166,277 to Goodwin and Willis, which is incorporated hereinto by reference, teaches the difficulty encountered in hydrogenating diene polymers in the presence of basic lithium salts. The patent discloses a process of methanol termination and settling.
SUMMARY OF THE INVENTION
It has now been discovered that judicious choice of polymerization terminating agents enables immediate removal of the lithium salt by centrifugation. Removal of the lithium salt has been shown to greatly enhance the hydrogenation process. Preferred terminating agents are those which form lithium salts which are less soluble in the cement than lithium methoxide. Some examples of terminating agents which are particularly effective are 2-ethylhexanoic acid, 12-hydroxy stearic acid, oxalic acid, benzoic acid, and succinic acid.
DESCRIPTION OF PREFERRED EMBODIMENTS
Basic lithium salts such as lithium methoxide retard the hydrogenation of low molecular weight diene polymers. Removal of this salt has had the effect of greatly enhancing the hydrogenation process. The present invention represents an improvement over the prior art in that the salt may be removed immediately after termination, and lithium salts are removed to lower levels than is possible for lithium methoxide. Previously it was found that removing the lithium methoxide by gravity settling or by filtration allowed hydrogenation of the polymers with much lower levels of catalyst. Formation of lithium methoxide precipitate and settling from these cements is very slow and may take weeks. In accordance with the present invention it has been found that judicious choice of polymerization terminating agents enables immediate removal of the lithium salt by centrifugation. Preferred terminating agents are those which form lithium salts which are less soluble in the cement than lithium methoxide. Some examples of terminating agents which are particularly effective are 2-ethylhexanoic acid, 12-hydroxy stearic acid, oxalic acid, benzoic acid, and succinic acid.
During separation of the lithium or other alkali metal compounds, the polymer may be present in a solvent at a concentration within the range of from about 5 to about 80 weight percent, based on total solution, and the alkali metal compound, such as lithium, may be present at a concentration within the range from about 0.005 to 5 wt % based on the polymer. Contact between the polymer and the terminating agent preferably occurs at a temperature within the range of 20° to 100° C., at a pressure up to 80 psig and at a nominal holding time within the range of 20 minutes to 4 hours. Where suitable, where the polymer is liquid, has low viscosity, and low molecular weight, the polymer may be used without a solvent.
The method of this invention can be used to separate alkali metal compounds such as lithium compounds from polymers such as low-viscosity functionalized polymer cements (A description of how these polymers can be made follows hereinafter.) The polymer may be hydrogenated or not during the alkali metal separation, but it is preferable to separate lithium compounds prior to hydrogenation.
Polymer solvents include but are not limited to hydrocarbons such as paraffins, cycloparaffins, alkyl substituted cycloparaffins, aromatics and alkyl substituted aromatics, such as benzene, toluene, cyclohexane, methyl cyclohexane, n-butane, n-hexane, n-heptane and the like. Ethers, such as diethyl ether, tetrahydrofuran, and the like can be used. Mixtures of the foregoing can be removed and another solvent substituted.
Centrifugation may be combined with other types of separation, e.g. filtration, settling and decantation.
Any alkali metal compound commonly found in a polymer solution when an alkali metal compound is used as the catalyst or initiator can be separated from the polymer. These include alkali metal hydrides, alkali metal alkoxides and alkali metal hydroxides.
Low Viscosity Functionalized Polymer Cements
Low viscosity functionalized polymer diols can be made in accordance with the following procedure:
Anionic polymerization of conjugated diene hydrocarbons with lithium initiators is well known as described in U.S. Pat. Nos. 4,039,503 and Re. 27,145 which descriptions are incorporated herein by reference. Polymerization commences with a monolithium, dilithium, or polylithium initiator which builds a living polymer backbone at each lithium site. Typical living polymer structures containing polymerized conjugated diene hydrocarbons are:
X-B-Li
X-A-B-Li
X-A-B-A-Li
Li-B-Y-B-Li
Li-A-B-Y-B-A-Li
wherein B represents polymerized units of one or more conjugated diene hydrocarbons such as butadiene or isoprene. A represents polymerized units of one or more vinyl aromatic compounds such as styrerie. X is the residue of a monolithium initiator such as sec-butyllithium, and Y is the residue of a dilithium initiator such as the diadduct of sec-butyllithium and m-diisopropenylbenzene. Some structures, including those pertaining to polylithium initiators or random units of styrene and a conjugated diene, generally have limited practical utility although known in the art.
The anionic polymerization of the conjugated diene hydrocarbons is typically controlled with structure modifiers such as diethylether or glyme (1,2-diethoxyethane) to obtain the desired amount of 1,4-addition. As described in U.S. Pat. No. Re 27,145 which is incorporated by reference herein, the level of 1,2-addition of a butadiene polymer or copolymer can greatly affect elastomeric properties after hydrogenation.
Dilithium initiation with the diadduct of sec-butyllithium (s-BuLi) and m-diisopropenylbenzene also requires presence of a non-reactive coordinating agent such as diethyl ether, glyme, or triethyl amine, otherwise monolithium initiation is achieved. Ether is typically present during anionic polymerization as discussed above, and the amount of ether typically needed to obtain specific polymeric structures has been sufficient to provide dilithium initiation.
Alternatively, anionic polymerization of conjugated dienes may be performed using protected functional initiators (PFI) as described in U.S. Pat. Nos. 5,391,663 and 5,146,168 which are incorporated herein by reference.
Anionic polymerization is often terminated by addition of water to remove the lithium as lithium hydroxide (LiOH) or by addition of an alcohol (ROH) to remove the lithium as a lithium alkoxide (niOR). For polymers having terminal functional groups, the living polymer chains are preferably terminated with hydroxyl, carboxyl, phenol, epoxy or amine groups by reaction with ethylene oxide, carbon dioxide, a protected hydroxystyrene monomer, ethylene oxide plus epichlorohydrin, or the amine compounds listed in U.S. Pat. No. 4,791,174, respectively.
The termination of living anionic polymers to form functional end groups is described in U.S. Pat. Nos. 4,417,029, 4,518,753 and 4,753,991 which are herein incorporated by reference. Of particular interest for the present invention are terminal hydroxyl, carboxyl, phenol, epoxy and amine groups. Such polymers with number average molecular weights between about 1000 and 20,000 as measured by gel permeation chromatography are low viscosity functionalized polymers.
Hydrogenation of at least 90%, preferably at least 95%, of the unsaturation in low molecular weight butadiene polymers is achieved with nickel catalysts as described in U,S. Pat. Nos. Re. 27,145 and 4,970,254 which are incorporated by reference herein. The preferred catalyst is a mixture of nickel 2-ethylhexanoate and triethylaluminum.
The termination step can result in release of fine particles of lithiumbases as described in U.S. Pat. No. 5,166,277 which is incorporated by reference herein. The lithium bases may interfere with hydrogenation of the polymer and preferably are removed, especially if the hydrogenation is to be carried out at high solids.
EXAMPLES Example 1
For purposes of comparison, a diol cement containing 1130 ppm Li was synthesized and terminated with methanol. A one gallon aliquot of the solution was allowed to sit undisturbed for 19 days, at which time testing of the supernatant solution indicated a lithium content of 320 ppm Li, for 72% removal efficiency by settling. For the present invention, greater removal efficiencies were achieved in shorter periods of time by a combination of the preferred termination agents and centrifugation.
Example 2
Acids and a diketone were screened to determine successful polymer cement terminating agents. Best results were obtained with oxalic acid, benzoic acid and 12-hydroxystearic acid. These acids are solids so a process is envisioned where the cement is passed through a bed or cartridge of the solid acid to remove lithium. The following table is relevant to lithium (ppm) remaining in a cement (a PFI diol having 20% solids and 4000 molecular weight) after termination with various agents. After the allowed settling time, the supernatants were centrifuged at 5000 g-minutes.
              TABLE                                                       
______________________________________                                    
LITHIUM (ppm) REMAINING IN A PFI CEMENT AFTER                             
TERMINATION WITH VARIOUS AGENTS                                           
Contact: 1 hr; Settling temperature: 23° C.                        
                 Termi-                                                   
Initial Termi-   nating                                                   
Li      nating   Agent/Li    Settling                                     
                                   5000                                   
(ppm)   Agent    (m/m)**     (hr)  g-min***                               
______________________________________                                    
478     Acetic   1.7         18    283                                    
        acid                                                              
545     Oxalic   1.5         16    less than 3                            
        acid                                                              
545     Benzoic  1.5         16    less than 3                            
        acid                                                              
545     12 HSA*  1.5         16     7                                     
545     Succinic 1.5         16    160                                    
        acid                                                              
545     diketone 0.7         16    100                                    
______________________________________                                    
 *12-hydroxystearic acid                                                  
 **molar ratio of terminating agent to lithium                            
 ***Parts per million of lithium in the cement after centrifugation

Claims (9)

We claim:
1. A process for removing alkali metal compounds from a polymer cement comprising:
preparing polymer cement of conjugated dienes with a polymerization terminating agent which is an acid selected from 2-ethylhexanoic acid, 12-hydroxyl stearic acid, oxalic acid, benzoic acid, and succinic acid and which leaves alkali metal salt in the cement; and
removing the alkali metal salt from the polymer cement.
2. The process of claim 1 wherein the alkali metal is lithium.
3. The process of claim 1 wherein the polymer cement is a functionalized mono-ol or diol having a number average molecular weight between 1000 and 20,000.
4. The process of claim 1 wherein the terminating agent is oxalic acid.
5. The process of claim 1 wherein the terminating agent is benzoic acid.
6. The process of claim 1 wherein the terminating agent is 12-hydroxy stearic acid.
7. The process of claim 1 wherein the terminating agent is succinic acid.
8. The process of claim 1 wherein the alkali metal salt is removed from the polymer cement by centrifugation.
9. The process of claim 1 wherein the alkali metal salt is removed from the polymer cement by filtration.
US08/652,191 1995-12-28 1996-05-23 Removal of lithium from polymer cements Abandoned USH1703H (en)

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Citations (18)

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US3270079A (en) * 1962-09-10 1966-08-30 Exxon Research Engineering Co Removal of alkali metal from liquid hydrocarbon polymers
US3867295A (en) * 1973-08-13 1975-02-18 Mobil Oil Corp Block copolymers and lubricant compositions containing the same
US3954915A (en) * 1973-08-13 1976-05-04 Mobil Oil Corporation Block copolymers of hydrogenated diene-styrene with polymerized alkylene oxide and alkylene sulfide
US4083895A (en) * 1976-06-14 1978-04-11 Mobil Oil Corporation Modified block copolymers and process of preparing the same
US4169115A (en) * 1977-03-30 1979-09-25 The Dow Chemical Company Preparation of block copolymers and products therefrom
US4587330A (en) * 1985-02-22 1986-05-06 Atlantic Richfield Company Purification of polymer solutions
US4595749A (en) * 1984-11-23 1986-06-17 Shell Oil Company Direct removal of NI catalysts
EP0186918A2 (en) * 1984-11-23 1986-07-09 Shell Internationale Researchmaatschappij B.V. Separating heavy metals from polymers
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US4963608A (en) * 1987-12-29 1990-10-16 Nippon Gohsei Kagaku Kogyo Kabushiki Halogen-containing thermoplastic resin composition
US5051462A (en) * 1987-08-14 1991-09-24 Nippon Gohsei Kagaku Kogyo Kabushiki Kaisha Halogen-containing thermoplastic resin composition
US5166277A (en) * 1991-10-31 1992-11-24 Shell Oil Company Hydrogenation of unsaturation in low molecular weight diene polymers
US5177297A (en) * 1991-10-30 1993-01-05 Shell Oil Company Method of removing a polymerization catalyst
US5231143A (en) * 1989-12-14 1993-07-27 The B. F. Goodrich Company High-temperature oil-resistant elastomers
USH1303H (en) * 1990-05-24 1994-04-05 Shell Oil Company Removal of nickel catalyst from polymer solutions by water addition and centrifugation

Patent Citations (20)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE149073C (en) *
DE252293C (en) *
DE153695C (en) *
US3270079A (en) * 1962-09-10 1966-08-30 Exxon Research Engineering Co Removal of alkali metal from liquid hydrocarbon polymers
US3867295A (en) * 1973-08-13 1975-02-18 Mobil Oil Corp Block copolymers and lubricant compositions containing the same
US3954915A (en) * 1973-08-13 1976-05-04 Mobil Oil Corporation Block copolymers of hydrogenated diene-styrene with polymerized alkylene oxide and alkylene sulfide
US4083895A (en) * 1976-06-14 1978-04-11 Mobil Oil Corporation Modified block copolymers and process of preparing the same
US4169115A (en) * 1977-03-30 1979-09-25 The Dow Chemical Company Preparation of block copolymers and products therefrom
EP0186918A2 (en) * 1984-11-23 1986-07-09 Shell Internationale Researchmaatschappij B.V. Separating heavy metals from polymers
US4595749A (en) * 1984-11-23 1986-06-17 Shell Oil Company Direct removal of NI catalysts
EP0358283A2 (en) * 1984-11-23 1990-03-14 Shell Internationale Researchmaatschappij B.V. Separating heavy metals from polymers
US4587330A (en) * 1985-02-22 1986-05-06 Atlantic Richfield Company Purification of polymer solutions
DE3520103A1 (en) * 1985-06-05 1986-12-11 Basf Ag, 6700 Ludwigshafen Process for the treatment of catalysts and/or residues of initiator-containing polymers or solutions thereof
US5051462A (en) * 1987-08-14 1991-09-24 Nippon Gohsei Kagaku Kogyo Kabushiki Kaisha Halogen-containing thermoplastic resin composition
US5071893A (en) * 1987-08-14 1991-12-10 Nippon Gohsei Kagaku Kogyo Kabushiki Kaisha Halogen-containing thermoplastic resin composition
US4963608A (en) * 1987-12-29 1990-10-16 Nippon Gohsei Kagaku Kogyo Kabushiki Halogen-containing thermoplastic resin composition
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USH1303H (en) * 1990-05-24 1994-04-05 Shell Oil Company Removal of nickel catalyst from polymer solutions by water addition and centrifugation
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GB9626719D0 (en) 1997-02-12

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