CA2350280A1

CA2350280A1 - Low molecular weight hydrogenated nitrile rubber

Info

Publication number: CA2350280A1
Application number: CA002350280A
Authority: CA
Inventors: Frederic Guerin; Sharon X. Guo; Zsolt Szentivanyi
Original assignee: Bayer Inc; Bayer AG
Current assignee: Arlanxeo Canada Inc; Bayer AG
Priority date: 2001-06-12
Filing date: 2001-06-12
Publication date: 2002-12-12
Also published as: US7772328B2; WO2002100941A1; EP1754720A2; US20030088035A1; HK1068362A1; US7951875B2; DE60219011T2; EP1401950B1; BR0210349B1; BR0210349A; US20100240848A1; CN1318493C; JP4753535B2; KR20040027517A; JP4468063B2; EP1401950B2; JP2004529256A; MXPA03011205A; DE60219011T3; US20080090970A1

Abstract

A hydrogenated nitrite rubber having lower molecular weights and narrower molecular weight distributions than those known in the art can be prepared by the claim metathesis of nitrite butadiene rubber, followed by hydrogenation of the resulting metathesised NBR.

Description

JUN-12-01 15:16 From:BAYER SARNIA PATENT DEPT +519-339-1523 T-609 P.04/18 Job-Low 1111olecular Weight Hydrogenated Nitrite Rubber Field of the Inyention.
The present invention relates to hydrogenated nitrite rubbEr polymers having lower molecular weights and narrower molecular weight distributions than those known in the art.
Background of the Inventlan Hydrogenated nitrite rubber (HNBR), prepared by the selective hydrogenation of acrylonitril~-butadiene rubber (nitrite rubber; NSR), is a specialty rubber which has very ~ood heat resistance, excellent ozone and chemical resistance, and excellent oil resistance. Coupled with the high level of mechanical properties of the rubber (in particular the high resistance to abrasion) it is not surprising that HNBR has found widespread use in the automotive (seals, hoses, bearing pads) ail (stators, well head seals, valve plates), electricai (cable sheathing), mechanical engineering (wheeis, rollers) and shipbuilding (pipe seals, couplings) industries, amongst others.
Commercially available HNBR has a Mooney viscosity in the range of from about 55 to about 105, a molecular weight in the range of from about 20x,000 to about 2o b00,b0b, a polydiaporsity greater than 3.0 end a residual double bond (RDB) content in the range of from about 1 to about 18°~ (by IR spectroscopy).
One limitation in processing HNBR is the relatively high Mooney Viscosity. In principle, HNBR having a lower molecular weight and lower Moaney viscosity would have belt~r proeessability. Attempts have been made to reduce the molecular weight of the polymer by mastication (mechanical breaiidowrr)-~rnd b~rz:hetiticr~rrt~arrs-(fQr w--example, using strong acid), but such methods have the disadvantages that they result in the introduction of functional groups (such as carboxylic acid and ester groups) into the polymer, and the altering of the microstructure of the polymer. This results in unacveptabie ~ ;n the ~raperti~ea ~ the poiymar. in additloa. these types ~f approaches, by their very nature, produce polymers having a broad molecular weight distribution.
A hydrogenated nitrite rubber having a low Mooney (~55) and improv~ad processability, but which has the same microstnlcture as those l~Uk~ber5 which are JUN-12-01 15:17 From:BAYER SARNIA PATENT DEPT +519-339-1523 T-809 P.05/18 Job-currently available, is difficult to manufacture using current technologies.
The hydrogenation of NBR to produce HNBR results in an increase in the Mooney viscosity _.. Lt tii~ i~~: N~v. -F:-_._.'f~.-~~y =iivi$~SB ~atlO ~i~inj is ~rriicyieiiji e~uiiiw ~, depending upon the polymer grade, hydrogenation level and nature Qf the feedstock.
~ Furthemlore, limitations associated with the production of NBR itself dictate the low viscosity range for the HNBR f~edstock. Currently, one of the lowest Mooney viscosity products availabl$ is Therban VP KA 8837 (available from Bayer), which has a Moonay viscosity of about 56 (ML 1+4 ~ 104°C) and a RDB of about 18%.
to Kari Ziegler's discovery of the high affeCtiveness of certain metal salts, in combination with main group alkylating agents, to promote olefin polymerization under mild conditions has had a significant impact on chemical research and productir~n to date. It was discovered early on that some "Zisgier-type" catalysts not only promote the proposed coordination-insertion mechanism but also effect an entirely different 1S chemical process, that is the mutual exchange (or metathesis) reaction of alkenes ().
R~ R2 R~ R2 Ca~
R-.--R R R
Fi~4re '!
AGyclic diene metathesls (or ADMET) Is catalyzed by a great variety of transition metal complexes as well as non-metallic systems. Heterogenepus catalyst systems based on metal oxides, sulfides or metal salts were originally used for the metathesia of 20 olefins. However, the limited stability (especially towards hetero-substituenEs) and the lack of Selectivity resulting from the numerous active sites and side reactions are major drawbacks of the heterogeneous systems.
Homogeneous systems have als4 been devised and used to Effect olefin 25 metathesis. These systems after significant activity and control advantages Aver the heterogeneous catalyst systems. For example, certain Rhodium based complexes are effective catalysts far the metathesis of electron-rich olefins.

JUN-12-01 15:18 From:BAYER SARNIA PATENT DEPT +519-339-1523 T-809 P.O6/18 Job-The discovery that certain metal-alkylidene complexes are capable of catalyzing the metathesis of olefins triggered the development of a new generation of well-defined, highly active, single-site catalysts, Qrx~ongst these, hisr(tricyclohexylphosphir~~x)-benzylidene ruthenium dichloride (commonly know as Grubb's catalyst) has been widely used, due to its remarKable insensitivity to air and moisture and high tolerance towards various functional groups. Unlike the molybdenum-based me~thesls catalysts, this ruthenium carbGne catalyst is stable to acids, alcohola, oldehydca and quaternary amine salts and aan be used in a variety of solvents (CBHe, GH2CI2, TMF, t 6uOH). The mast commonly-used catalysts are based on Mo, W and Ru.
is The use of transition-metal catalyzed alkene metathesis has since enjoyed increasing attention as a synthetic method. Research efforts have been malrtly focused on the synthesis of small molecules, but the application of olefin metathesis to polymer synthesis has allowed the preparation of new polymeric material with unprecedented properties (such as highly stereoregular poly-norbomadiene).
The utilization of olefin metathesis aS a means to produce low molecular w~ight compounds from unsaturated elastomers has received growing interest. The principle for the molecular weight reduction of unsaturated polymers is shown in Figure 2. The 2o use of an appropriat~ catalyst allows the cross-metathesis of the unsaturation of the polymer with the co-olefin. The end result is the cleavage of the polymer chain at the unsaturation sites and the generation of polymer fragments having lower molecular weights. In additiart, another effect of this process is the "homogenizing" of the polymer chain lengths, resulting in a reduction of the polydispersity. From an application arid .25 processing stared point, a narrow molecular weight distribution of the raw polymer results in improved physical properties of the vulcanized rubber, whilst the lower molecular weight provides good processing behavior.

JUN-12-D1 15:19 Fror~:BAYER SARNIA PATENT DEPT +519-339-1523 T-809 P.OT/1B Job-/ /
// //
Cat .n '~ +
Figure ~ llAetatheslc of Partially Unsaturated Polymer The so-called "depvlymerization" of copolymers of 1,3-butadiene with a variety of co..mon~mors (styrene, propane, divinylbenzene and ethylvinylbenzsne, acrylonitrile, vinyitrimethylsilane and divinyldimethylsilane) in the presence of classics!
Mc~ and W
catalyst system has been investigated. Similarly, the degradation of a nitrite rubber using WCIs and SnMe, ar PhC$CH co-catalyst was reported in 1988. However, the focus of such research was to produce only low molecular fragments which SQUIB
be characterized by conventional chemical means and contains no toaching with respect to the preparation of low molecular weight nitrite rubber polymers.
Furthermore, such praCesees are non-controlled and produce a wide range of products.
The catalytic depolymerization of 1,4~polybutadiene in the presence of substituted olefins or ethylene (as chain transfer agents) in the presence of well-defined C3rubb's or Schrack's catalysts is also possible. The use of Molybdenum or Tungstery compounds of the general structural formula fM(=NR,)(ORZ)3(=CHR); M = Mo, W) to produce low molecular weight polymers or oligomsrs from gelled polymers containing internal unsaturation along the polymer backbone was claimed in U$ 5,446,142.
Again, however, the process disclosed is non-controlled, and there is no teaching with respect to the preparation of low molecular weight nitrite rubber polymers.
Summard of the Invention We have now discovered that hydrogenated nitrite rubber having lower molecular weights and narrower molecular weight distributions than those known in the art can be JUN-12-D1 15:20 From:BAYER SARNIA PATENT DEPT +519-339-1523 T-809 P.OB/1B Job-prepared by the olefin metathesis of nttrile butadiene rubber, followed by hydrogenation of the resulting metathesised NBR.
Thus, one aspect of the disclosed invention is a saturated nitrite rubber having a molecular weight (Mw) in the range of from about 30,000 to about 250,000, a Mooney vlscoslty (ML 1+4 '100) of between about 3 and about 50, and a MIAID (or polydispersity index) of les3 than about 2.~.
Descrir~tion of the Invention As used throughout this 'pac~cation, the term "nitrite polymer" is intended to have a broad meaning and is meant to encompass a copolymer of a conjugated diene and an unsaturated nitrite.
The conjugated diene rnay be a C; C6 conjugated diene. Non-limiting examples of suitable Such conjugated dienes may be selected from the group comprising butadiene, isoprene, piperylene, 2,3-dimethyl i'utadlene and mixtures thereof.
The preferred G~ CB conjugated diene may be selected from the group comprlslng butadiene, isoprene and mixtures thereof. 1"he most preferred Ca C4 conjugated diene is butadiene.
The unsaturated nitrite may be a C3-GS oc,p-unsaturated nitrite. Non-limiting examples of suitable such C3 C6 a,(1-unsaturated n;tnles may -be.selected--from-the-_.. ........... _.
group comprising acrylonitrile, m~thacrylonitrile, ethacrylonitrile and mixtures thereof.
The most preferred C~ C6 a,a-unsaturated nitrite is acrylonitrils.
Preferably, the copolymer comprises from about 40 to about 13b weight percent of the copolymer of bound conjugated diene and from about 15 to about 60 weight percent of the copolymer of bound unsaturated nitrite. More preferably, the copolymer comprises from about 60 to about 75 weight percent of the copolymer of bound conjugated diene and from ab4ut 2a to about 40 weight percent of the copolymer of bound unsaturated nitrite. Most preferably, the copolymer comprises from about fid to about 70 weight percent Of the cOpo!;!??ed: of-bou.~.d. cony~ated-.dime.
and.~r~m. a~QUt.. ._______ 30 to ab4ut 40 weight percent of the copolymer of bound unsaturated nitrite.
S

JUN-12-01 15:21 From:BAYER SARNIA PATENT DEPT +519-339-1523 T-809 P.09/10 Job-Optionally, the copolymer may further comprise a bound unsaturated carboxylic acid. Non-limiting examples of suitable such bound unsaturated car'i»xylic acids may be selected from the group r~mprising fumaric acid, malefic acid, acrylic acid.
methacrylic acid and mixtures thereof. The bound unsaturated carboxylic acid may be present in an amount of from about '! to about 10 weight percent of the copolymer, with this amount displacing a corresponding amount of the conjugated diolefin.
Further, a third monomer rr~ay ba used in production of the nitrile polymer.
Pr~ferably, the third monomer is an unsaturated mono- or di-carboxylic acid or derivative thereof (e.g.. esters. amides and the like).
Step ~: M~tathesls The metathesis reaction can be catalysed by Compounds of formula I, II or 1t1;
as shown below L
>~ R
1~M~C~ , X I~ R
L
Formula I
wherein:
M is Os or Ru;
R and R' are, independently, hydrogen or a hydrocarbon selected from the 2o group confilsting.nf Cg-_C~ alkenyl,_C,~-Cza.alkynyl,..C,-C~ alkyl, anti.
C,-~~, cart~xvlate, _ ~s-Cxo alkoxy, C2 C~ alkenyloxy, CZ C~ alkynyloxy, aryloxy. CZ ~~
alkoxycarbonyl, C, C~ alkylthio, C,-CZO alkylsulfonyl and G,-Czo atkylsulfinyl;
X and X' are independently 9electsd anionic ligands; and L and L' are, independently, ligands selected from the group consisting of ZS phosphines, sulfonated phosphines, tjuorinated phosphines, functionaliaed phosphines having up to three aminoalkyl-, ammoniumalkyl-, alkoxyalkyl-, alkoxylc2~rbonylalkyl-, hydrocyoarbonylalkyl-, hydroxyalkyl- or ketoalkyl- groups, phosphites, phosphinites, phosphonites, phosphinamines. arsinas, stibines, ethers. amines, amides, imtnes, sulfoxides, thioethers and pyridines; optionally, L. and l-' can be linked to one another to JUN-12-O1 15:22 From:BAYER SARNIA PATENT DEPT +519-339-1523 T-809 P.10/1B Job-from a bidentate neutral iigand wherein at (east one of the above-mentioned functional groups is present.
Q

M~ C~C~C
Ls R3 Formula II
wherein:
M' is Os or Ru;
R2 and R3 are, independently, hydrogen ar a hydrocarbon selected from the group consisting of GZ C~ alkenyl, Gz C~ alkynyl, C,-G~ alkyl. aryl, C,-G~
carboxylate, C,-C24 alkoxy, Cz C~ alkenylQxy, CZ-C~ alkyryyloxy, aryloxy, G2 Czo alkoxy~--~y'~,;
6;JC
alkylthio. G,-C~ alkylsulfonyl and C,-C2o alkylsulfinyl;
Xx is selected from any anionic ligand; and L2 is a neutral ~r,bonded Iigand, preferably but not limited to arene, substituted arene, hgteroarsne, independent of whether they are mon4- or pQlycyciic;
L3 is a ligand selected from the group consisting of phosphines, sulfonated phoaphines, fluorinated phosphines, functionalized phosphines bearing up to thrPP _._ .._.
aminoalkyl-, ammoniumalkyl-, alkoxyalkyl-, alkoxylcarbonylalkyl-, hydrocycarbonylalkyl-, hydroxyalkyl- or ketoalkyl- groups, phosphltes, phosphlnltes, phosphonites, phosphinamlnes, arsines, stibenes, ethers, amines, amides, imines, sulfoxides, thioethars and pyridines;
Y' is a non-coordinating anion;
n is an iWeger in the range of from 0 to 5;

JUN-12-D1 15.22 From:BAYER SARNIA PATENT DEPT t519-339-1523 T-809 P.11/18 Job-R72 a R
OR7y-"M2 C
I ( Rs N
a R
Formula III
wherein M2 is Mo or W
R', RS are, independently, hydrogen or a hydrocarbon selected from the group consisting of C2-~'~-a!!cep'sy~,-CSC;~_a!kyr~yl,_C;=C~~.alkyl,.arycls.C;~;~.Gafb.Qxyl~te. ~,-Cue, alkoxy, G2 C~ alkenyloxy, C2-C2° alkynyloxy, aryloxy, Ca-Coo alkoxycarbonyl, Ci-C~
alkylthio, C,-C~ alkylsulfonyl and C,-C~ alkylsulfinyl;
RB and R' are independently selected from any unsubstituted or halo-substituted alkyl, aryl, aralkyl groups or silicon-containing 2~nalr~gs thereof.
Catalysts of Formula I are preferred. More preferably, catalysts of Formula I
wherein L and L' are trialkylphosphines, X and X' are chloride ions and M is Ruthenium are preferred.
The amount of catalyst employed in the me~tatllesis reaction will depend upon the nature and activity of the catalyst in question. Typically, the ratio of catalyst to NBR
is in the range of from about 0.005 to about 5, preferably in the range of from about 0.025 to about 1 and, more preferably, in the range of from about 0.1 to about 0.5.
The metathesis reaction is carried out in the presence of a co-olefin which is a Gi to G,g linear or branched olefin such as ethylene, isobutene, styrene or 1-hexane.
Where the co-olefin is a liquid (~sueh as 1-hexane), the amount of co-olefin employed is in the range of from about 1 to about 50 weight %; preferably In the range of ftorn about 10 to about 30 weight %. Where the co-.olefin is a gas (such as ethylene) tfte amount of co-olefin employed is such that it results in a pressure in the reaction vessel in the range of from about 15 to about 150b psi, preferably in the range of from about 75 to about 600 psi.

< CA 02350280 2001-06-12 JUN-12-Ol 15:23 From:BAYER SARNIA PATENT DEPT +519-339-1523 T-B09 P.12/18 Job-The metathesls reaction can be carried out in any suitable solv8nt which does not inectiv-ate the-oat~lyst-ar-athepwise -inte:fare ~urith -the -reaction.
.Preferred ~ra~lcar~t,~
include, but are not limited to, dichloromethane, benzene, toluene, tetrahydnafuran, cylcohexane and the like. The most preferred solvent is monochiorobenzene (MCB).
In Certain cases the co-olefin can Itself act as a Solvent (for example, 1-hexane), in wh~h case no ether solvent is nrs~ssary.
The concentration of NBR in the reaction mixture is not critioal but, obviously, 1o should be such that the reaction is not hampered if the mixture is too viscous to be stirred effioiently, for example. Preferably, the concentration of NBR is in the range of from about 1 to about 20%, most preferably in the range of from about fi to about 15%.
The metathesis reaction is carried out at a temperature in the range of from about 2D to about 140°C; preferably in the range of from about 60 to about 1Z0°C.
The reaction time will depend upon a number of factors, including cement concentration, amount of catalyst used and the temperature at which the reaction is performed. The matathssis is oor~tpt~te vvithlr~ the first taro hours under typical 2o conditions. The progress of the metathesis reaction may be monitored by standard analytical techniques. for example using CPC or solution viscosity .
Sfep 2: Hydrrrgenativrr Reduction of the product from the metathesis reaction can ba effected using standard reduction technique kc~nwn. in. tH~ art. For examQle,, homogeneous hydrogenation catalysts known to those of skill in the art, such as Wilkinson's catalyst {(pPh3~3RhGl} and the like can be used.
The hydrogenation rryay b~ performed in sifu i.e. in the same reaction vessel in which the metathesis step is Carried out, without the need to first isolate the metathesised product. The hydrogenation Catalyst is simply added to the vessel, which is then treated with hydrogen to produce the HNB .

JUN-12-O1 15:24 From:BAYER SARNIA PATENT DEPT +519-339-1523 T-B09 P.13/18 Job-Grubb's catalyst, in the presence of hydrogen, is converted to a dihydride complex (PR3)2RuC12Hz, which is itself an olefin hydrogenation catalyst. Thus, in a one-pot reaction. Grubb's catalyst was used to reduce the molecular weight of NBR
in the presence of co-olefin. The reaction mixture was then treated with hydrogen, converting the Grubb's complex to the dihydride speci$s which then hydrogenated the metathesis product to produce the HNBR of the inventJon. The rate of hydrogenation ways lower in this case than In the case where W!lkins8n'a catalyst wax used for the hydragAnation step, but it is clear that such an approach is indeed a viable one.
1o The low MQOney HNBR which forms an object of the invention can be characterized by standard techniques known in the art. For example, the molecular weight distribution of the polymer was determined by gel permeation chromatography (GPC) using a Waters 2690 Separation Module and a Waters 410 Differential Refractometer running Waters Millenium software version 3.05.01. Samples were dissolved in tetrahydrof~ran (THF) stabilis~d with 0.025% BHT. The columns used for the determination were three sequential mixed-B gel column from Polymer l-abs.
Reference Standards used were polystyrene standards from American Polymer Standards Corp.
Tha Mooney viscosity of the n.ibber was determined using ASTM te$t x1646.
For a typical product the Mn is about 27k (compared to 85k for the starting polymer) whilst the ivlw is ain~ut ~4ic-{corr~pared-to-~96k for tho-sts~rtir~g polymet~)...,As._... _ _ _._ expected, the molecular weight distribution falls from about 3.~1 for the starting Perbunan NT 3435 T feedstock to about 2.0 for the metathesiZed product, This is consistent with a more homogeneous range of polymer chain lengths and molecular weights.
A summary of the polymer properties for sclccted samples is shown in JUN-12-O1 15:25 From:BAYER SARNIA PATENT DEPT +519-339-1523 T-B09 P.14/1B Job-(ML 1+4 ~ 100]
Comparative Therba~ ~ ~ -9t3~t30- 3~20000-S45~Od -3.2~ - 73 Starting NBR 8&000 296004 939000 3.64 experiment 73000 188000441000 2.59 43 Experiment B0000 1360402770 2.27 s Experiment 31000 69000 9$000 1.90 3 Experimental Details General Trls(triphenylphosphine)RhQdiNm Chlarida (Wilkinaon's hydrogenation catalyst), 8is(tricyclohexylphosphine)benzylidene ruthenium dichloride (Grubb's metathesis catalyst), 1-hexane, triphenylphocphine (TPP) and monochlorobenzene (MCB) were purchased from JMI, Alfa, Aldrich Chemicals, Elf Atochem and PPG respectively and used as recerv~e~t: -Mefathesfs The metathesis reactions were carded out in a Parr high-pressure reactor under the following conditions:

Cement ConcEntrativn G or 15%

Co-Olefin Ethylene or 1-Hexane Co-Oletln Concentration Variable Agitator Speed 600 rpm Reactor Temperature Variable Catalyst Loading (Grubb's) Variable Solvent Monochlorvbenzene Substrate Perbunan NT 3435 T

Perbunan NT 3429 T

In a typical lab experiment, 200g of rubber was dissolved in 1133~ of MCB
(15°~
solid). The c8ment was then charged to the reactor and degassed 3 times with C2hi,, {100 psi) under full agitation. The react4r was heated to desired temperature and OOmI_ of a monochlt~rabenzene solution containing Grubb's catalyst was add~d to the reactor.

JUN-12-01 15:26 Fro~n:BAYER SARNIA PATENT DEPT +519-339-1523 T-809 P.15/18 Job-The temperature was maintained constant for the duration of the reaction. A
cooling coil connected to a temperature controller and a thermal sensor was used 1Q
regulate the temperature. The progress of the reaction was monitored using solution viscosity measurements for the 6% cements. At higher cement concentration, the reaction was assumed to be complete after 19 hours_ hydrogenation The hydrogenation reactions were carried out in the same reactor as the metathesis under the followir>;g cor~ditior~s:
Cement solid concsntrati~sn 13f Hz(g) pressure 121)0 psi Agitator Speed 600 rpm Reactor Temperature 13$C

Catalyst Loading (Wilkinson's) 0.08 phl' Ti-iphenyiphosphine 1 phr Solvent MonQChlorobenzena In a typical lab experiment, the certyant from the me~tathesis reaction was degassed 3 times with H2 (100 psi) under full agitation. The temperature of the reactor was raised to 130°C and a 60m1.. monochlorobenzene solution containing Wilkinson's catalyst and triphenylphosphine was added to the reactor. The temperature was allowed to increase to 13$°C and maintained constant for the duration of the reaction.
Th$ hydrogenation reaction was monitored by measuring the residual double bond (RDB) level at various intervals using IR spectroscopy.
Alternatively, the Ruthenium metathesis catalyst can be used to hydrogenate the polymer.

Claims

1. A hydrogenated nitrite rubber having a molecular weight (M w) in the range of from about 30,000 to about 250,000 and a polydispersity index of less than about

2.5.
2. A hydrogenated nitrite rubber according to claim 1 wherein the molecular weight (M w) is in the range of from about 40,000 to about 220,000.

3. A hydrogenated nitrite rubber according to claim 2 wherein the molecular weight (Mw) is in the range of from about 55,000 to about 190,000.

4. A hydraggnated nitrite rubber according to claim 1 wherein the polydispersity index is less than about 2.3.

5. A hydrogenated nitrite rubber according to claim 1 wherein the polydispersity index is less than about 2.1.

6. A hydrogenated nitrile rubber according to claim 1 wherein the rubber has a Mooney viscosity (ML 1+4 100) of less than about 55.

7. A hydrogenated nitrite rubber according to claim 6 wherein the rubber has a Mooney viscosity (ML 1 +4 100) of less than about 45.

8. A hydrogenated nitrite rubber according to claim 1 wherein the rubber has a Mooney viscosity (ML 1+4 100) of less than about 35.

9. A hydrogenated nitrite rubber according to claim 1 wherein the rubber has a Mooney viscosity (ML 1+4 100) of less than about 30.

10.A hydrogenated nitrite rubber according to claim 1 wherein the rubber has a Mooney viscosity (ML 1+4 100) of less than about 5.

11.A hydrogenated nitrite rubber having a Mooney viscosity (ML 1+4 100) of less than about 50.

12.A hydrogenated nitrite rubber according to claim 11 having a Mooney viscosity (ML
1+4 100) of less than about 45.

13.A hydrogenated nitrite rubber according to claim 12 having a Mooney viscosity (ML
1+4 100) of less than about 30.

14.A hydrogenated nitrite rubber according to claim 13 having a Mooney viscosity (ML
1+4 100) of less thin about 5.

14. The use of a hydrogenated nitrile rubber according to claim 1 in the manufacture of a seal, hose, bearing pad, stator, well head seal, valve plate, cable sheathing, wheel, roller or pipe seal.