Production of elastomeric functionalized olefin polymers (Exxonmobil Research And Engineering Company)

CATEGORY: OLEFINS
PATENT
Production of elastomeric functionalized olefin polymers (Exxonmobil Research And Engineering Company)
Publication number
US20120322948 A1
Application number
13/596,567
Publication date
Dec 20, 2012
Inventors
Lisa Saunders Baugh
Enock Berluche
Karla Schall Colle
Original Assignee
Exxonmobil Research And Engineering Company
Abstract
In a process for producing a functionalized polyalkenamer, at least one monomer comprising a monocyclic olefin having at least one pendant alkyl group bonded thereto, wherein the pendant alkyl group has at least two carbon atoms and is substituted with a polar moiety spaced by at least one carbon atom from the monocyclic olefin, is contacted with a polymerization catalyst under conditions effective to effect ring opening polymerization of the monocyclic olefin and produce the functionalized polyalkenamer.
FIELD
This invention relates to a process for producing elastomeric functionalized olefin polymers.
BACKGROUND
Polyolefin-based elastomers having good fluid and heat resistance are a target of great commercial interest since such materials have potential to serve as cost-advantaged competitors to commercial oil-resistant elastomers, such as nitrile rubber (NBR), hydrogenated nitrile rubber (HNBR), and thermoplastic vulcanizates (TPVs), such as Santoprene. In contrast, ethylene-propylene-diene monomer (EPDM) copolymers and other polyolefin-based elastomers do not have sufficient oil resistance to compete in the specialty elastomer market.
The incorporation of functional groups into polyolefins—particularly nitrile groups—is predicted to substantially enhance their fluid resistance. However, the controlled synthesis of nitrile-containing polyolefins through the direct copolymerization (metallocene/Ziegler-Natta, late transition metal, or free-radical) of olefins with acrylonitrile or nitrile-functionalized α-olefins is not currently feasible on a level providing useful catalyst productivities, controlled polymer microstructures, and desirable base polymer properties (see, for example, Padwa, A. Prog. Polym. Sci. 1989, 14, 811-833 and references therein; Mudalige, D. C.; Rempel, G. L. J. Macromol. Sci.—Pure Appl. Chem. 1997, A34, 361-368; Shin, S.-Y. A. et al. Polym. Mat. Sci. Eng. 2004, 91, 100-101; Kochi, T. et al. J. Am. Chem. Soc. 2007, 129, 8948-8949; Marques, M. M. et al. Polym. Int 2001, 50, 579-587; and U.S. Pat. No. 4,698,403. This is due both to orbital mismatch energies between the monomers and/or the tendency of the nitrile group to poison metal catalyst centers through coordination or side reactions. Typically, olefin/acrylonitrile or olefin/nitrile-functionalized α-olefin copolymers are limited to materials containing small amounts of nitrile comonomer (<6 mol %), alternating copolymers with base properties unlike those of polyolefins, materials having low molecular weights (number average molecular weight, Mn, <20,000), systems that require protection/deprotection steps of the nitrite functionality to mitigate catalyst deactivation, systems that place the polar comonomer groups predominantly at chain ends, or systems that provide very low catalyst productivities.
Polyolefins, particularly polyethylene, are commonly modified by the incorporation of C3 or higher alpha-olefin monomers such as 1-butene, 1-hexene, 1-octene, or 1-decene. These comonomers introduce alkyl branch points along the otherwise linear (and/or stereoregular) polymer main chain, reducing crystallinity and improving properties such as toughness and flexibility through the influence of the alkyl side chain groups residing in the amorphous region. The ethylene/α-olefin copolymers known as Linear Low Density Polyethylenes (LLDPEs) are particularly attractive examples of such materials. When sufficient amounts of α-olefin comonomer are introduced to polyolefins, the level of crystallinity of the resultant copolymers may become so low as to enable the production of useful elastomer or plastomer materials. For such reasons, copolymers of ethylene and nitrile-functionalized α-olefin comonomers, especially ω-nitrile-functionalized α-olefin comonomers (which most closely replicate the structures of linear α-olefin comonomers), are of particular desirability. In these materials, the fluid-resistant functional group and the flexible alkyl chain are introduced simultaneously in one desirable structural unit.
Tandem ring opening metathesis polymerization (ROMP)/hydrogenation techniques have been widely used as an alternate route into functional polyethylene and polyalkenamer structures. To date, these techniques have almost exclusively focused on the synthesis of polymers having functional substituents attached directly to the main chain (constitutionally equivalent to polyolefins produced by the copolymerization of ethylene with a second olefinic monomer having a polar functionality attached directly to one of the polymerizing olefinic carbons). Moreover, these techniques have produced mixed results, with some lower-functionality-tolerant catalysts failing to catalyze polymerization in the presence of the nitrile group. Thus the ROMP of (Z)-cyclooct-4-enecarbonitrile, a functional cyclooolefin monomer that would produce a polymer structure analogous to polyethylene-co-acrylonitrile after tandem ROMP/hydrogenation, was observed to fail when the metathesis catalyst (PCy3)2Cl2Ru═CHCH═CPh2 was used for polymerization (Hillmyer et al. Macromolecules 1995, 28, 6311-6316), but was successfully polymerized with other Ru-based catalysts (PCT International Patent Application WO03/062253A1). The ROMP of nitrile-bearing bicyclo[2.2.1]hept-5-ene-based monomers having one or more methylene spacers between the monomer ring structure and the nitrile functionality has been performed using Ru- and W-based catalysts (for example, see U.S. Pat. Nos. 3,991,139, 3,856,758, and 4,105,608 and WO03/062253A1), in addition to the more common ROMP of the analogous compound with no methylene spacer (5-norbornene-2-carbonitrile). The polymeric ROMP products obtained from the bicyclo[2.2.1]hept-5-ene-based (norbornene-based) monomers, unlike those obtained from monocyclic olefin monomers such as functionalized cyclooctenes, contain intact cyclopentene rings in their backbones.
It has now been found that ROMP of monocyclic olefins having distally pendant polar moieties, especially ω-nitrile-functionalized alkyl substituents, can be used to prepare functionalized polyalkenamers with structures analogous to terpolymers of ethylene, 1,4-enchained butadiene, and an w-nitrile-functionalized α-olefin. Hydrogenation of these functionalized polyalkenamers produces materials equivalent to copolymers of ethylene and w-nitrile-functionalized α-olefins. These materials exhibit improved oil swell resistance as compared to unfunctionalized EPDM copolymers, plus superior thermal stability and low-temperature properties (lower glass transition temperature, Tg) as compared to commercial nitrile rubbers. The materials therefore have potential utility in, for example, the production of gaskets and hoses for automobile applications.
The tandem sequential ROMP/hydrogenation of bi- or multicyclic olefin monomers bearing nitrile substituents directly attached to the ring structure is known (for example, see Jpn. Kokai Tokkyo Koho 63317520A and 60049051A). Unlike the ROMP/hydrogenation of nitrile-substituted monocyclic olefins, these techniques produce materials with intact cycloalkane rings in the polymer backbones, rather than materials analogous to the desired ethylene/nitrile-substituted-α-olefin copolymers. Such materials also bear nitrile substituents that are not separated from the atoms in the polymer main chain by desirable, flexible alkyl groups. For example, Yoshida, Y. et al. J. Appl. Polym. Sci. 1997, 66, 367-375 and references therein and U.S. Pat. No. 6,197,894 disclose the ROMP of nitrile-substituted multicyclic monomers such as 8-cyanotetracyclo[4.4.0.13,5.17,10]-3-dodecene, and the subsequent hydrogenation of the resultant nitrile-functionalized polyalkenamers. The Tgs of the hydrogenated materials, as typical of materials containing backbone rings, were high (>135° C.) and suitable for structural rather than elastomeric purposes.
U.S. Patent Application Publication No. 2005/0137369, published Jun. 23, 2005 and the entire contents of which are incorporated herein by to reference, discloses a linear functional polymer comprising randomly repeating units A, B and D, wherein A represents —CH2—; B represents —CH(R1), wherein R1 represents a polar functional group; and D represents —C(═O)—, wherein there are at least four A units separating each B unit, each D unit, and each B and D unit, and further wherein when the total number of B units, y, is an integer greater than or equal to 1; and the total number of D units, h, is an integer greater than or equal to 0, then the total number of A units, x, is an integer sufficient that the molar fraction of the B and D units in the polymer is represented by a value j defined by the equation j=(y+h)/(x+y+h)≦0.032. Thus, the polymer product contains low levels of the polar functional group. The polymer is produced by copolymerizing a first polar substituted monomer, such as cyclooct-4-en-1-ol, with a second non-polar unsubstituted monomer, such as cyclooctene, and is a semicrystalline rather than an elastomeric material.
SUMMARY
In one aspect, the invention resides in a process for producing a functionalized polyalkenamer, the process comprising contacting at least one monomer comprising a monocyclic olefin having at least one pendant alkyl group bonded thereto, said pendant alkyl group having at least two carbon atoms and being substituted with a polar moiety spaced by at least one carbon atom from said monocyclic olefin, with a polymerization catalyst under conditions effective to effect ring opening polymerization of said monocyclic olefin and produce said functionalized polyalkenamer.
Conveniently, said monocyclic olefin has at least five carbon atoms. In one embodiment, said monocyclic olefin comprises a substituted cyclooctene.
Conveniently, said polar moiety is in the ω-position relative to said cyclic olefin along the pendant alkyl group.
Conveniently, said polar moiety is selected from —CN, —CO2R, —C(═O)R, and —S(═O)Ph, where R is an alkyl group having from one to ten carbon atoms or an aryl group having from six to fourteen carbon atoms and Ph is phenyl.
In one embodiment, said monomer comprises (Z)-3-(cyclooct-4-enyl)-propanenitrile.
Conveniently, said monomer is contacted with said polymerization catalyst in the presence of at least one comonomer, such as an unsubstituted monocyclic olefin, for example cyclooctene and/or cyclooctadiene.
Conveniently, said polymerization catalyst comprises a compound of the formula:
wherein L1 and L2 are independently selected from the group consisting of alkyl phosphine, aryl phosphine, 1,3-dimesitylimidazol-2-ylidene, 1,3-di(2,6-diisopropyl-phenylimidazol-2-ylidene, 1,3-diarylimidazol-2-ylidene, 1,3-dimesitylimidazolidin-2-ylidene, 1,3-di(2,6-diisopropylphenyl)imidazolidin-2-ylidene, 1,3-diarylimidazolidin-2-ylidene, 1,3-diphenyltriazine, and pyridine or a halosubstituted pyridine; L3, if present, is pyridine or a halosubtituted pyridine and is identical to L2; and R4 is selected from the group consisting of hydrogen, C1-C20 linear alkyl, C1-C20 branched alkyl, C1-C20 cycloalkyl, C1-C20 alkenyl, aryl and phenyl.
Conveniently, the process further comprises hydrogenating said functionalized polyalkenamer, such as in the presence of a rhodium-based catalyst.
In a further aspect, the invention resides in a functionalized polyalkenamer comprising repeating units of ethylene, butadiene, and a polar group-substituted α-olefin termonomer, said α-olefin termonomer having at least four carbons and having its polar group spaced by at least one carbon from the polymerizing olefin unit.
In yet a further aspect, the invention resides in a functionalized polymer produced by hydrogenating the functionalized polyalkenamer of said further aspect and comprising repeating units of ethylene and a polar group-substituted α-olefin termonomer, said α-olefin termonomer having at least four carbons and having its polar moiety spaced by at least one carbon from the polymerizing olefin unit.
In another aspect, the invention resides in (Z)-3-(cyclooct-4-enyl)-propanenitrile and to a method of its synthesis.
In still another aspect, the invention resides in a functionalized polyalkenamer comprising repeating units of ethylene, butadiene, and 4-pentenenitrile, and the hydrogenated product of said functionalized polyalkenamer comprising repeating units of ethylene and 4-pentenenitrile.
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