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.