patent literature on catalysts for olefin polymerization...
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Journal of Intellectual Property I~ights
Vol 5 January 2000 pp 1-12
Patent Literature on Catalysts for Olefin Polymerization: [II] Metallocenes
Anand Kumar Kulshreshtha & Santosh Kumar Awasthi
Research Centre, fudian Petrochemicals Corpomtio1'l Uri, Vadodara 391346
Paper chronides the histOlY of patents on olefin polymerization catalysts from E)50s to 1990s. Part I of the paper, published in the September'99 issue of this journal , gives the details of the patents of Ziegle r - NatLa catalysts. This part of the pillll'r reviews tlw recent patent literat un-' on metallocenes (chemical compounds in which metal atoms are 'sandwiched' between relatively planar hydrocarbon ring strudures). I'alent controversies also have not spared the metallocene catalysts. These controwrsies arC' described in the paper. Some important developments in th e fi eld of metallocene patenting are highlighted. Using s tatistical analysis technique , the H&D intensity in this field is explored. The potential that the metallocene technology hilS to offer to tilE' end-user is described.
Review of the Recent Patent Literature on Metallocenes
Nearly 179 patents in metallocene-related topics were granted in th e US in 1995. Some of patents issued in the US in 1995 and 1996 on metallocen e catalysts are shown in Table 1. This list gives an approx imate idea of the research activity in the field [or the said last two years.
These patents can be arbitrarily divided into three categories (not necessarily exclusive):
(i) patents for the synthesis of new polyoletins with already existing or novel metallocene catalysts,
Oi) Patents for supporting techniques for
metallocene catalysts, and
(iii) patents for industrial processes for use
with metallocen e catalysts.
Microstructure control is a c rucial step in
the development of m ctallocene catalysts. It
can be achieved by modifying the nature of
the active centre of ind ividualmetallocenes,
by combining differe nt metallocenes (sol
uble or supported) to produce a polyolefin reactor blend, by supporting the metallo
cene in sllch a way li S to alter its cata lytic
behaviour, or by the use of metallocene cata
lysts with new polymerization processes.
J INTELLEC PIWP I~IGHTS , JANUAIN :W()()
Table I-Recent metallocene catalyst patents (1995-1996)
Company
Albemarle
BAsr
BP Chemicals
DOW
Enichem
Exxon
Patent Number
5,391,529
5,412,131
5,455,333
5,466,647
5,527,930
5,453,475
5,457, 171
5,474,961
5,491. 205
5,496,902
5,514, 760
5,527, 868
5,439,995
5,380,810
5,399,635
5,529,966
5,391 , 629
5,422, 325
5, 427, 991
Title
Siloxy-aluminoxane compositions and catalysts which include such compositions with a metalloccne
Tertiary amino-aluminoxane halides
Preparation of metallocenes
Tertiary amino-aluminoxane halides
Aluminoxanes having in creased catalytic activity
Process for preparing low density ethylene copolymers
Catalyst systems for th e polymerization of C2-C III alken es
Deactivated and reactiv<1tedmctallocene catalyst systems
Preparation of polymer of C2-CIll alk-l-enesusing racemic metallocene complexes as catalysts
Catalyst systems for th e polymerization of C2-CIll alk-I-enes
Soluble catalyst systems [or the preparation of polyalk-1-enes having high mol ecular weights
Catalyst systems [or th e polymeri zation of C2- C III alk-l-enes
Catalyst and prepolymer used for the preparation of polyolefins
Elastic substantiall y lin ear olefin polymers
Process for the preparat ion o[ monocyclopentadieny l metal complex com pounds and method of use
Catalyst and process for (co)polymerizing (X-olefins
Block copolymers from ionic catalysts
Supported polymerization catalysts th eir production an cill se
Polyo nic transition metal catalyst composition
con td
KULSHRESI-ITHA & AWASTHI : PATENTI.ITERATURE ON .. ..
Table I- Recent meta1locene catalyst patents (1995-1996)- contd
Company
Fina
Patent Number
5,432,242
5,441,920
5,442,019
5,444,145
5,446,221
5,451,450
5,462,807
5,468,440
5,462,999
5,470,811
5,470,927
5,475,075
5,491,207
5,525,128
5,529,965
5,530,054
5, 387,568
5,393,851
5,395,810
5,416,228
5,449,651
5,476,914
Title
HP catalyst killer
Silicon-bridged tran sition metal compounds
Process for the transitioning between incompatible polymerization catalysts
Ethylene/branched olefin copolymers
Oleaginous compositions containing novel ethylene aolefin polymer viscosity ind ex improver additive
Elastic articles and a process for their production
Heat sealable film s and articles
Process of making orien ted film or structure
Process for polymerizing monomers in fluidized beds
Polymerization catalysts their production and use
Ionic metallocene catalyst composition
Ethylene/longer a-o lefin copolymers
Process of producing high molecular weight ethylene a-olefin elastomers with an indenylmetallocene catalyst system
Fuel oi l additives and co mposition s
Polymerization catalyst systems, their production and use
Elastomeric ethylene copolymers for hot melt adhesives
Preparation of metallocene catalysts for polymerization of olefins
Process for using meLalloccnc catalyst in a conLinuous reactor system
Method of making a homogeneous-heterogeneous catalyst system for olefin polymerization
Process and catalyst for producing isotac tic polyolefins
Metallocene compound for a catalyst component with good catalyst efficiency after aging
Syndiotactic polypropyl ene
contd
J INTELLEe PIWP I{ IGHTS, JANUAI{Y :WOO
Table I-Recent metaIIocene catalyst patent,; (1995-1996)- contd
Company
Hocchst
Mitsubishi
Mitsui
Mobi l
Patent Number
5, 519, 100
5, 391, 789
5,416, 178
5,422,409
5, 455 , 365
5, 455,366
5, 475,060
5, 498, 677
5,504,232
5, 444, 125
5, 468, 781
5, 444, 125
5, 464,905
5,468,781
5,397,757
5, 455, 214
5,461.01 7
5,473,028
5,498,582
Title
Addition of alumin ium alkyl for improved metallocene catalyst
Bridged ch iral metallocenes processes for th eir preparation and their use as catalysts
Process for the preparation of I-olefin polymers
Cycloolefin (co)polymer with a narrow molecular weight distribution and a process for th e preparation thereof
Process [or th e preparati on of an olefin polymer using mctallocencs co ntaining spec ifica ll y substituted ind enyl ligand s
Meta llocenes having bcnzo-fu sed indenyl derivatives as ligands processes [or th ei r preparation and thei r use as catalysts
Cycloolefin block copolymers and a process for their preparation
Process for the preparation an d purification of material of a cycloolefin copolymer
Process for the preparati on of an olefin polymer usin g specific metallocenes
Am in ated olefin polymers
Polypropylene resin expand ed particles
Aminated olefin polymers
Ethylene/a-olefi n co polymer co mposition graft modifi ed ethylene/a-olefin copolymer composition
Polypropylene resin expa nd ed particles
Cocatalysts fo r mclallocene-based olefin polymeriza tion catalyst systems
Meta llocenes supporteci on ion excha nge resin s
Olefin polymerization catalysts
Process and a catalyst fo r preventing reactor foul ing
Supportedmetallocene catalysts for th e production of po lyol efin s
conte! -----------------------------------------------------------------
KU LSI-IR ESI-ITHA & AWASTHI: PATENT I.ITEI~ATUHE ON ....
Table I-Recent metallocene catalyst patents (1995-1996)- contd
Company
Phillips Petroleulll
Solvay
Tosoh
Patent Number Title
5, 399,636 Metallocenes and processes therefor and the rewith
5,401, 817
5,416,179
5,420, 320
5,436, 305
5,451,649
5,459,218
5,466,766
5,473,020
5,492,973
5, 492.974
5,492,975
5,492,978
5,492, 985
5,496,781
5,498,581
5,496,782
5,525,690
5,407, 882
5,434,115
Olefin polymeri zation using silyl-bridged Il1 etallocenes
Catalyst compositions and olefin poloymeriza tion
Method for preparing cyc1opentaclienyl-type ligand s and metallocene compou nds
Organometallic flu orenyl compounds preparation and use
Organometallic fluorenyl compounds preparation and use
Syndiotactic polypropylene prepared using s ilyl bridged metallocenes
Metallocenes and processes therefor an cl therewith
Polymer bound ligands polymer bound metallocen es, catalyst systems
Polymer bound ligands
Process for preparing polymer bound meta llocenes
Polymer bound metallocenes
Process for preparing cata lyst system
Polym erization process
Metallocene catalyst systems, preparation an d use
Method fo r making and using a supported metallocene catalyst system
Cata lyst system, use of this catalyst system fo r the (co) polymerization of olefins, process [or preparing this catalyst system and olefin (co) polymeri zation process
Process for the preparation of a polyolefin and synd iotac tic polypropylene
Olefin polymerization catalyst and olefin polymerization process
Process for producing olefin polymer
5
(j J INTELLEC PROP HIGHTS, JANUARY :,wO()
These trends will be illustrated by analyzing metallocene patents.
Metallocene catalysts with novel active centres that permit the incorporation of bulky comonomers (such as branched and long olefins or evcn macrornonomers) have been discussed recently in several patents. Monocyclopentadienyl compl exes have been uscd to copolymerize ethylene with branched exolefin comonomers to produce copolymers with high content of randomly incorporated branched co mon omer (0 .5 to 10 mole %), narrow copo lymer compositi on distributi on (CCD) , high molecular weigh t (MW) and narrow mol ec ular we ig ht di stributi on (MWD). These polyolefin s are useful for applications wherc high toughn ess is dcsirabl e. A typica l cata lyst system is Me2Si (C5Me4) (NC1 2H~n) TiC I2/NIAO . These monocyclopcntadienyl complexes can also polymerize ethylene and long linear ex-olefins containing 10 to 100 carbon atoms. Monocyclopcntadi enyl com pl exes have been used to produce narrow MWD cth ylene homopolymcr and ethylene/ex-o lefin copolymers containing long chain branches. A typical catalyst SYStCIll is rC5Me4(SiMe2NtBu) lTiMe2/ l ri s (pcn laflll 0 ro ph e n yl) bora lle. Thc Illacromo nomer is produced in situ , apparently clu e to 0-hydrid e elimination reactions. All thesc pal'ents arc based on thc fact that catalytic ccntres with easily accessi ble sites (i. e., not sterica ll y hindered centr es) ca n be des ig n cd (0 favour th e incorporati on of bulky comonomers. Although dicyclopentadienyl catalysts have also becn used for the copolymeriza tion of cthylene and atactic po lypropylene macromonomer, thc macromonomcr reactivity ralios arc much s lTl(l ll er th all the ones ior I11onocyclopcntadienyl complcxes. Th esc patents illu strate quite clearly the flex ibi li ty one has in designing metal loccne cata lysts
to produce polymers with entirely new cha in structures. Block copolymcrs having app lications as phase compati bi lize rs, and useful as disk substrates for magneto-optical storage media have been produced.
A mixed metallocenc/non-mctallocene supported cata lyst is dcsc rib cd in US Pat 5,529,965 and used t.o produce polyol eiins with broad M \VD, with polyclispersity ind ex preferably in the rangc of 4 to 30. In onc example shown in this patcnt, trimcthylaluminiwll and a mixture of (n-BuCp) ;! ZrC I ~
and TiCL, were supported on si lica, in this order. Thc supported ca talyst and tl'i-i sobuty laluminium as cocata lyst were used to polymerize ethylene and I-hexene.
Metallocene catalysts have also been supported on hcterogeneous Zieglcr-Natta ca talysts to produce polyo lefin s with broad MWD. This techniqu e enabl es one to modify th e MWD and CCD of polyolcfin s made with conven tional hetc rogencous ZicglerN atta catalysts and should bc easily ad ;q)ted to already existing manufacturing faci lities. The produccd polymer is claimed to have excel lent powd cr properti es.
Two or more mctallocenc catalysts can also be combi ned in such a way as to yield polyolefin s with broad MWD (wh ich favo urs processability) an d relatively na rl'OW CCD.
An un usual way of support ing metallocene catalysts is disc losed in US Pal 5, 498. 581. Melallocenes having ;1 substitu ent wh ich has olefin ic unsatu ration ;m: pre-polymcrized with olcfins in th e presence of an aluminoxanc to form a so lid ll1cta ll oc cnc -containing catalysts syslcm.
KULSHI(ESHTI-IA & AWAS'rl-1I : PATENT L1TEI~ATURE ON .. .. 7
Patent Controversyl on Metallocene Catalysts
In 1984 Exxon deposited EP-A-O 129 368 claiming new catalysts consisting of a large variety of metallocenes and alumoxane.
Exxon claims that they have been th e first one to discover that, by changing substituents on th e cyclopentadienyl rings, it is possible to prepare a large variety of catalysts which result in polymers having different properties.
EP-B-129368 was publish ed on 26 July 1989. An opposition was fil ed by Hoechst and Fina. There have been a lot of patents filed after 1984 which can be co nsid ered to be dominated by the Exxon patent.
Practical application of metallocene - catalysts requires their preadsorption on solid supports such as alumina or si lica gels. Instead of the polymer dust produced by a homogeneously dissolved metallocene catalyst, the solid catalyst particles generate cohe rent polym er grains. As with classical he terogeneous catalysts, these grains appear to be enlarged replicas of the catalyst particles. Metallocene catalysts that are heterogenized, for example, on a silica gel support, can thus be readily used in existing Ziegler-Natta production facilities, for instance in solvent-free slu rIY or gas-phase reaction systems.
In-depth Analysis of Metallocene Patents
EP-A-351392 (Fina, filing date 31 May 1989) di scloses th e so- called "Ewen catalyst" for producing syndiotactic polyolefins. In this case the metallocene itself is new, consequently the claims cover any catalyst containing such a compound. The preparation
of syndiotactic polym ers appears, at this time, fully covered by this patent application.
EP-A-485821 and EP-A-485823 (Hoechst. filing date 1 November 1991) disclose respect ively 2-substituted bridged bis-(4,5.6,7-tetrahydroindenyl) and 2-s llbstituted bridged bis-inclenyl compounds. The substitution of the 2-position provcd to be very effective in increasing the MW of the obtained polypropylene, thus these two patents seem to be of great importance.
After 1984 th ere have been two important developments that do not fall within th e scope of EP-B-129368: the firsL one was th e discovelY that the mcchanism of activation of metallocen e by alumoxan e was the formation of an ionic species. This discovery opened the way to th e preparation of ionic metallocene compounds. In this way it became possible to substitute aillmoxane with an activator and to prepare a catalyst that does not infringe EP-B- 129368. Thus the development of ionic metallocenes represents a clear alternative to the field covered by EP-B-129368. It is thereforc relevant that this time also Exxon was th e first to file two applications (EP-A-277003 and EP-A-277004, filing dil.te 27 J anualY 1988) covering catalysts obtained by reacting a metallocene with an ionizing compound .
The second developm ent was the preparation of the constrained geolllctlY catalysts. In this case the re is a co mpetition between Dow Chemicals and Exxon, since both filed th e priority documents in the USA.
Statistical Aproach to Patents Analysis
Figure 1 shows that Hoechst, Exxo n and Mitsui have been by far thc most active companies in this field. However, Lhe number of applicaLions filed does not say anything
J INTELLEC PIWI' RlGHTS,JANUAHY :W()()
about the relevance of th e patents. A method for estimating th e importance of a patent is by looking at the number of times the patent has been cited in a search report. We have don e this by taking into accoull t the 20 most cited patents and consid ering the applicant.
figure 2 compares th e number of citations received by patents of different companies. from this data it's very cl ear that Exxon is dominating while Hoechst, Fi na and Dow have been able to create a Ii mited but relevant space.
Patent applications are al so a useful tool for studying th e development of industrial research in a fi eld . figure 3 shows the amount of EP appl ications [1"01111984 to 1993 according to their priori ty date, relat ing to:
- Ziegler-Natta ca talysts in general,
- con ven tional Ziegler-N alta, and
Metallocene catalysts.
f igure 4 shows the % distributi on of metall ocene and con ventional Ziegler catalysts.
from th ese data it is evident that conventional Ziegler-Nalta catalysts ca ll be considered a mature technology an d less research is now dO ll e in this field . However, they still represe nt a very important percentage of til e to tal amoun t, of fil ed patent applications , confirming the opin io n that the decl ine of poly- olcfin s produ ced by co nventi onal Ziegler will be slow and probably not CO I11-plete.
T he seco nd co nclusion is that the amoun t of research in the metall ocene fi eld (and thu s the amou n t of money invested by i nd lI stri es) should be co mparable wi th th e amount of research do ne previously on the conve lltional Ziegler- aUa , since th e amoun t of pa tent applicatio ns filed is compara ble.
Recent Progress on the Advantages of Metallocene Catalysts2
The most remarbble aspect of metall ocenebased cata lyst appears to be that th ey can produce an unprecedented va riety of po lyolefin s. The range of stereo- and regio- regular iti es , mol ec ul ar we ig ht s , ,lIld polydi spersities of copo lymers and cyclopoIymers avai lable with th ese catalys ts excee d s th a t access ibl e with c l assi c~d heLerogenous Ziegle r- Na tt a catalys ts and open .> new possib il ities fo r proclucing ta ilored polyolcfin materi al s.
Types of Metallocene Res ins
As metallocel1 <': calalys is applies to di ffere nt polymerizat ion techniques, <1ml the resul ting resin s can be performance ta ilored, th eir processing characteri stics diffe r by grade, manufacturer, etc. Current cO llll11 ercial llleLallocenes Illay be categorized as fo llows:
0) th e first ca tegory targe ts the commodit y resin market, designed (0 replace trad itional LLDPE wi th a typical densi ty of 0.915 g cm':{, referred to as I1l LLDPEs, where III is llle talloccne c:l talyz\:d.
(ji) th e seco nd and third catego ri es are lower in density (0.865- O . ~ J 5 g cm':') and the resin s can be chssifiecl as plastomers becau se of their clastic be haviour; piastom ers ,Ire dividecl at the 20% C0 1l1 011 0mCr level. the pri ncipal 1110nomer bei ng et hylene: polyalkene (polyo le fi n) pl:1sto lll e r s (POPs) a re 0.895-0.9 15 density and contain :~(J% comonomer; polya lken e (po lyoldin) elastomers (POEs) ar<.: O.98G-0~)~)5 !~
C lll ':~ d e 11 sit y and c () nl a i n 2 () % (~ ;>lllOn01l1(T.
100
80
60
40
20
o
KUI.SI-mESIIT IIA & AWi\STI-II : PATENT L1TEHi\T Ulm () ....
I
Exxon
Hoechst Mitsui
Fina
Montell Idemitsu
Fig 1 - Eli roPCClll pate ll t applicl( iOll s
140
100
60
20
Exxon Fina Cosden
Fig ~ - :\lIlllhn ur c ita tioll s
10 .J INTELLEe PIW P I ~ I G HTS, .J ANUAIN ;woo
250
200
100
100 P;
~
~ ~ ~ II II ~ 1:1
I I I
50
o '84 '85 '86 '87 '88 '89 '90 '91 '92 '93
IZl Total Ziegler EJ Metallocene ill Conventional
Fip; ~~ - Fil i llg (jeEP appl ic<l tiolls
100
80
60
40
20
o '84 '85 '86 '87 '88 '89 '90 '91 '92 '93
m % Metallocene ~ % Conventional
Fig 4- - D istrihu tioll 0 (" fil illgs
KULSf-lRESHTHA&AWASTHI: PATENT L1TE I~ATU lm ON .... 11
(ii i) th e fourth type is mctallocene catalyzed po lypropylene and primaril y a im e d at t h e bi ax iall y o ri e nted polypropylene market.
List of recent metallocene catalyst pa tents (1995-96) 4 is given in Tabl e 1.
Patentability of Metallocene Technology
One of the major fac tors inlluencing th e development of PE ca talyst and product technology over the past few years has been the spi ralling costs associated with research an d development. This has promoteci the [o rm;1-tion of tech nology joint ventures of the type ;1nnounced by BP Chemica ls - Dow amI UCC-Exxo n as well as many others with more restricted scope.
The cost of maintaining and protec ti ng a comprehensive pate nt porUolio is also incre;1sing and the cost to th e industry as a whole can be exemplified by the num bcr of patents associated with th e polymerization of ethylene with metallocene catalysts that have been filed ovcr the past 14 years (sec Table 1). Add itionally, it is perceived that thc standard s of patentability req uireci by Pate ll t OJfices are declining and that they are increasingly prone to allow the Courts to rcsolve issues of va lidity and scope. This is an ex pe ns ive, resource co ns uming , a nci lengthy process and does not bcnefit thc end user, because co mmcrcia li zation of ncw developments can be substantiall y retard cd. Th is is a key reaso n fo r th e dclay in the commercializa tio n of metallocenc catalysed polyethylenes.
At one tim e it was relatively easy to determine the scopc of a p;lrticular patent, alld how long it would be in forcc. However th is is no longcr truc.
With high and increasing resea rch and development costs, it is evident why technology licensing is used as a means of recovery of company costs. Licensing can be lucrative as shown below, based on data provided by Chem Systems:
(i) Profitability (at 10% re turn) on a 200,000 tonnes pcr ann um plant buil t at a cost of $ 100 x lOG would be
c $12.5xlO ) per annu lll.
(i i) The licensing of a 200,000 tonnes per c annum plant provid es $25 X 10 ) net
income.
(i ii) Hence one PE plant licence provides the eq ui valent or two years profi t fro Ill production.
These figures do not include the licensing support costs and th e costs associated with developi ng techn ology in order to be in a leadership position. Such costs are subsla ntial , and even th e largest companies are now joining fo rces to ensure lhat til ey remain al the forefront. Over th e past 10 years, the Innovene and U nipol processes have equally accounted fo r GO% of new PE capacity, and it is expected that a similar percen tage will be captu red by the gas phase fluid bed process ill future. Despite this success, both BP Chemicals and UCC have decided to fo rm current opt imum metallocene cata lysl technologies. It is bel ieved that this sets th e pattern fo r th e futu re, in which these two alliances will be the major licensors of new technology co llaborat ion agreements with other compa nies who have skill s and/or parti cular technologies that will enhance th e capabiliti es oJ lhe partn erships. There will obviously continue to be opport unistic licenso rs in thc othe r, relatively minor, segment-s of the market, bllt th e vasllll;tjority of producers will become licell 'ees.
12 J INTELLEC PImp RIGHTS.JANUAI~Y 2()()O
Intellectual Property Estates
The patent s ituation is another reason why companies are forming joint ventures to ex
ploit metallocene catalysts [or licensing. says Holand Hingmann, a research scientist
at BASF (Ludwigshafen, Germa ny). "There have been so many unpubli shed [m etallo
cene 1 patents that commerciali zation is at ri sk," he says, although he expects th ere to be a "natural shakeout" of the market, in
time.
References
1. Serravalle M SPO'96, Metallocenc '96.
2 Brintizinger H H ct aI, Allgew Chelll Jut Engl Ed, 34, 1995, 1143-70.
3 Soares J B P & Hamielec A E, Molec lI
lar Struc ture of Mctallocene Polyol c
fins, hog Polym Sci, 21 (4) 1996, 651-706.
4 Williams K, Plast RuM & Compos Proc & AjJplicants, 27(1) 1998,30-34.