Catalyst – solid sorbent – or support therefor: product or process – Catalyst or precursor therefor – Metal – metal oxide or metal hydroxide
Reexamination Certificate
2000-11-21
2002-06-04
Bell, Mark L. (Department: 1755)
Catalyst, solid sorbent, or support therefor: product or process
Catalyst or precursor therefor
Metal, metal oxide or metal hydroxide
C502S182000, C502S185000, C502S241000, C502S258000, C502S259000, C502S260000, C502S261000, C502S263000, C502S311000, C502S313000, C502S314000, C502S332000
Reexamination Certificate
active
06399538
ABSTRACT:
The present invention is directed to a process for hydrogenating unsaturated polymers.
BACKGROUND OF THE INVENTION
Unsaturated polymers have been previously hydrogenated using a variety of catalysts and conditions. Historically, typical hydrogenation catalysts have low reactivity and require high catalyst to polymer ratios, especially in aromatic polymer hydrogenation. Improvements in catalytic hydrogenation have been achieved using various metals and supports. Group VIII metals of the Periodic Table of the Elements, have been particularly useful in hydrogenating unsaturated polymers, especially aromatic polymers such as described in U.S. Pat. No. 5,612,422. However, these catalysts have been found to have a relatively short life span in that they deactivate upon contact with polar impurities. These polar impurities are associated with the polymerization process and include polar compounds such as terminators, i.e. alcohols. Therefore, in order to obtain a high number of hydrogenation cycles with the catalyst, the polymer must first be purified in a separate purification step.
Accordingly, it remains highly desirable to provide a process of hydrogenating unsaturated polymers using a catalyst which is resistant to deactivation and does not require polymer purification prior to hydrogenation.
SUMMARY OF THE INVENTION
The present invention is a process for hydrogenating an unsaturated polymer comprising contacting the polymer with a hydrogenating agent in the presence of a mixed hydrogenation catalyst, characterized in that the hydrogenation catalyst comprises a Group VIII metal component and at least one component selected from the group consisting of rhenium (Re), molybdenum (Mo), tungsten (W), tantalum (Ta) and niobium (Nb).
Surprisingly, the mixed hydrogenation catalyst is resistant to deactivation upon exposure to impurities within the polymer, thus allowing for a higher number of reuse cycles in the polymer hydrogenation process.
DETAILED DESCRIPTION OF THE INVENTION
The polymers to be hydrogenated by the process of the present invention, include any unsaturated polymer containing olefinic or aromatic unsaturation. Such polymers include any amorphous saturated hydrocarbon thermoplastic. The term saturated refers to the amount of olefinic bonds within the chemical structure. As used herein, saturated refers to a polymer wherein less than 10 percent of the carbon-carbon bonds are olefinic or unsaturated in nature, generally less than 7.5 percent, typically less than 5 percent, advantageously less than 2 percent, more advantageously less than 1.5 percent, preferably less than 1 percent, more preferably less than 0.5 percent and most preferably less than 0.2 percent. These types of polymers include hydrogenated aromatic polymers, hydrogenated cyclic-olefin-(co)polymers and hydrogenated ring opening metathesis polymers. Specific hydrocarbon polymers include those produced from olefinic monomers, such as homopolymers of butadiene or isoprene, copolymers thereof, and aromatic polymers and copolymers. The aromatic polymers useful in the process of the present invention include any polymeric material containing pendant aromatic functionality. Pendant aromatic refers to a structure wherein the aromatic group is a substituent on the polymer backbone and not embedded therein. Preferred aromatic groups are C
6-20
aryl groups, especially phenyl. These polymers may also contain other olefinic groups in addition to aromatic groups. Preferably, the polymer is derived from a monomer of the formula:
wherein R is hydrogen or alkyl, Ar is phenyl, halophenyl, alkylphenyl, alkylhalophenyl, naphthyl, pyridinyl, or anthracenyl, wherein any alkyl group contains 1 to 6 carbon atoms which may be mono- or multisubstituted with functional groups such as halo, nitro, amino, cyano, carbonyl and carboxyl. More preferably Ar is phenyl or alkylphenyl with phenyl being most preferred. Homopolymers may have any stereostructure including syndiotactic, isotactic or atactic; however, atactic polymers are preferred. In addition, copolymers containing these aromatic monomers including random, pseudo random, block and grafted copolymers may be used. For example, copolymers of vinyl aromatic monomers and comonomers selected from nitrites, acrylates, acids, ethylene, propylene, maleic anhydride, maleimides, vinyl acetate, and vinyl chloride may also be used such as styrene-acrylonitrile, styrene-alpha-methylstyrene and styrene-ethylene. Block copolymers of vinyl aromatic monomers may also be used, such as styrene-alpha-methylstyrene block copolymers, styrene-butadiene or styrene-isoprene block copolymers and the like. Examples include styrene-butadiene, styrene-isoprene, styrene-butadiene-styrene and styrene-isoprene-styrene block copolymers. Further examples of block copolymers may be found in U.S. Pat. Nos. 4,845,173, 4,096,203, 4,200,718, 4,201,729, 4,205,016, 3,652,516, 3,734,973, 3,390,207, 3,231,635, and 3,030,346. Blends of polymers including impact modified, grafted rubber containing aromatic polymers may also be used.
Preferably the number average molecular weight (Mn) of the polymer to be hydrogenated is from 10,000 to 3,000,000, more preferably from 30,000 to 400,000, and most preferably from 50,000 to 300,000, as measured by gel permeation chromatography.
Cyclic-olefin-copolymers suitable for hydrogenation are copolymers of cycloolefin monomers with any other monomer containing aromatic and/or olefinic unsaturation. Cyclic-olefin copolymers include norbornene-type polymers as described in U.S. Pat. Nos. 5,115,041, 5,142,007, 5,143,979, all of which are incorporated herein by reference. The cycloolefin moiety may be substituted or unsubstituted. Suitable cycloolefin monomers include substituted and unsubstituted norbornenes, dicyclopentadienes, dihydrodicyclopentadienes, trimers of cyclopentadiene, tetracyclododecenes, hexacycloheptadecenes, ethylidenyl norbornenes and vinylnorbornenes. Substituents on the cycloolefin monomers include hydrogen, alkyl alkenyl, and aryl groups of 1 to 20 carbon atoms and saturated and unsaturated cyclic groups of 3 to 12 carbon atoms which can be formed with one or more, preferably two, ring carbon atoms. Generally speaking, the substituents on the cycloolefin monomers can be any which do not poison or deactivate the polymerization catalyst. Examples of preferred monomers include but are not limited to dicyclopentadiene, methyltetracyclododecene, 2-norbornene, and other norbornene monomers such as 5-methyl-2-norbornene, 5,6-dimethyl-2-norbornene, 5-ethyl-2-norbornene, 5-ethylidenyl-2-norbornene, 5-butyl-2-norbornene, 5-hexyl-2-norbornene, 5-octyl-2-norbornene, 5-phenyl-2-norbornene, 5-dodecyl-2-norbornene, 5-isobutyl-2-norbornene, 5-octadecyl-2-norbornene, 5-isopropyl-2-norbornene, 5-p-toluyl-2-norbornene, 5-&agr;-naphthyl-2-norbornene, 5-cyclohexyl-2-norbornene, 5-isopropenyl-2-norbornene, 5-vinyl-2-norbornene, 5,5-dimethyl-2-norbornene, tricyclopentadiene (or cyclopentadiene trimer), tetracyclopentadiene (or cyclopentadiene tetramer), dihydrodicyclopentadiene (or cyclopentene-cyclopentadiene co-dimer), methyl-cyclopentadiene dimer, ethyl-cyclopentadiene dimer, tetracyclododecene 9-methyl-tetracyclo[6,2,1,13,6O2,7]dodecene-4, (or methyl-tetracyclododecene), 9-ethyl-tetracyclo[6,2,1,13,6O2,7]dodecene-4, (or ethyl-tetracyclododecene), 9-hexyl-tetracyclo[6,2,1,13,6O2,7]-dodecene-4, 9-decyl-tetracyclo[6,2,1,13,6O2,7]dodecene-4, 9-decyl-tetracyclo[6,2,1,13,6O2,7]dodecene-4, 9,10-dimethyl-tetracyclo-[6,2,1,13,6O2,7]dodecene-4, 9-methyl-10-ethyl-tetracyclo[6,2,1,13,6O2,7]-dodecene-4, 9-cyclohexyl-tetracyclo[6,2,1,13,6O2,7]dodecene-4, 9-chloro-tetracyclo[6,2,1,13,6O2,7]dodecene-4, 9-bromo-tetracyclo[6,2,1,13,6O2,7]-dodecene-4, 9-fluoro-tetracyclo[6,2,1,13,6O2,7]dodecene-4, 9-isobutyl-tetracyclo[6,2,1,13,6O2,7]dodecene-4, and 9,10-dichloro tetracyclo-[6,2,1,13,6O2,7]dodecene-4.
Polymers comprising two or more different types of monomeric units are also
Bell Mark L.
Hailey Patricia L.
The Dow Chemical Company
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