Joumal of Intellectual Property Rights Vol 4 September 1999 pp 286-292

Patent Literature on Catalysts for Olefin Polymerization: [I] Ziegler-Natta Catalysts

Anand Kumar KuIshreshtha & Santosh Kumar Awasthi

Research Centre, Indian Petrochemicals Corporation Ltd, Vadodara 391 346

Patents can make or break profits resulting from an invention, depending upon an organization's capability to protect its intellectual property rights from litigation by rivals. This paper chronicles the history of patents on olefin polymerization catalysts (rom 1950s to 1990s. Part 1 of the paper discusses in detail the patents ofZiegler-Natta Catalysts. It has been established by patent g ranting agencies that Karl Ziegler was the pioneer in inventing Ziegler catalysts in 1953. Giulio Natta who visited Ziegler's lab and became aware of his research around that time, afterwards became to be known as a co-inventor. Soon after, parallel patent applications were filed in 50 countries. Corporates [ought battles to destroy the patents position of Ziegler but did not succeed.

Ziegler-Natta polyolefin polymerization cata­lysts 1 are actually Ziegler catalysts. On 17 November 1953 Karl Ziegler filed the first patent application in Germany on this sub­ject which was followed by a number of fur­th e r applications in 1954 . These applications were directed to the polymeri­zation of a-olefins at normal or low pressure and a temperature up to 150°C in a hydrocar­bon medium into high-molecular weight, solid and partly or high crystalline polymers.

After the first application in Germany, paral­lel applications in 50 countries were filed . Strong opposition was of course 'faced in industrialized countries like Germany, USA and Japan having sophisticated patent proce­dures. The German chemical companies

BASF, Bayer and Hoechst AG, the British ICI and Shell, and in the US, specifically Du Pont, Phill ips and Montecatini tried with all means available to destroy the patent posi­tion of Ziegler et at..

Standard Oil of Indiana and Phillips P tro­leum independently found in 1950-1952 from research programmes involving alkylating hydrocarbons with ethylene or oligomeriz­ing olefins that solid high polymers as by­products were formed when using certain transition metal oxides on silica-alumina car­riers.

The yields obtained were measured in milli­grams of polymer and efforts to develop fu r­ther the synthesis of these by-products did not proceed at that time. Thirty years later

KULSHRESHTHA&AWASTHI: PATENTLITERARTURE ON CATALYSTS 287

Table I-Early discoveries of low pressure linear polyethylene

Research groups Catalysts Time of initial Early polymer discovery density (g/cm:l)

Alex Zlet Standard Oil of Indiana

Nickel oxide activated Early 1950 0.96 carbon

Molybdenum oxide on alumina

J Paul Hogan and Robert L Banks, Phillips Petroleum Co.

Chromium oxide on silica 1951 0.95-0.97 alumina

Karl Ziegler et at. TiCl4

Max Planck Institute for Coal Research

a court in Wilmington, Delaware, decided that Hogan and Banks of Phillips Petroleum (Table 1) were first party to have these pro­pylene polymers in their hands.

It is pretty clear that the properties of these first propylene polymers are very different from any co mm erc ia ll y produ ced polypropylene products today. Further­more, the catalysts developed by these two American research teams were never used for the co mm erc ial production of polypropylene. Indeed in 1973 both compa­nies took a Ziegler licence.

During the inventive phase in 1953, Italian and American chemists visited the Institute for a period of several months. (From Mon­tecatini/G. Natta, Italy: Paolo Chini, Roberto Magri, Giovanni Crespi; from Hercules Pow­der Co., USA Arthur Glasebrook). The Ital­ian gentlemen were sent to the Institute under an earlier agreement between Monte­catini and Ziegler, covering a research area of pure organo-aluminum chemistry. These visitors could not be kept away from infor­mation concerning the discovery of the new catalysts. At the end of 1953 and January 1954, Ziegler fully infonned a co-worker of

+R1Al Late 1953

Natta and Montecatini of the nature of the new catalysts. Natta et al. used the info rma­tion of Ziegler to polymerize propylene be­fore Ziegler and Martin and filed patents in Italy on the subject all without informing Ziegler, although there was a written agree­ment reserving for Ziegler further research on developing the catalysts and their use for polymerization of olefins. It was a cause of irritation and conflict between the parties.

As expected, Ziegler's and Natta's basic pat­ents very soon became involved in an inter­ference procedure in USA, since both parties claimed the polymerization of propylene us­ing identical catalysts. In 1969 the US Patent Office awarded priority to Ziegler.

Du Pont fought for almost ten years up to 1964, against Ziegler's applications. They took a licence, but tried to trade the price down as far as possible.

Another effort by Du Pont was to get Karl Ziegler to define the term "aluminum trial­kyl" as used in the definition as Ziegler cata­lysts,' so as to award what Du Pont was doing.

288 J INTELLEC PROP RIGHTS, SEPTEMBER 1999

In 1967 Phillips Petroleum opened a com­mercial plant in the US for the production of polypropylene using a catalyst produced from EtzAlCI and a-TiCh.1/3 AlCh. It took six years for an appeal court in Houston to decide that the Ziegler et at. patent involved comes under the definition of a pioneer pat­ent covering a function never before per­formed. As a consequence th e court decided that the catalyst used by Phillips was a Ziegler catalyst and was covered by the Ziegler pioneer patent.

When arguing with the patent examiner in Washington during prosecution over one of the basic Ziegler patents in 1955 the exam­iner took the position that producing the catalyst on one side and using the catalyst producing polyolefins on the other side are two separate inventions, since the catalyst can be used for applications other than po­lymerizing a-olefins. As a consequence he requested division of the application into two parts.

The first part, the catalyst claims, was ac­cepted and the patent issued in 1963, ten years after the invention. The use of this catalyst in a process to polymerize a-olefins was accepted and patented in 1978. Since the American patent law provides a 17 years' protection from the issue of the patent the first patent expired in 1980, but the second patent has expired in 1995.

Ziegler catalysts are wondetiul. A variety of applications are listed in Table 2.

Patents on Conventional Titanium-Aluminum Alkyl Catalysts2

Initially the use of titanium-aluminum alkyl catalysts to 'produce polyethylene grew at a much slower pace than the chromium oxide on silio catalysts. The main difficulty with

the original catalysts was that the yield of polymer per unit of catalysts in low pressure processes was so low that the catalyst residu­als in the polymer had to be extracted. Not only were titanium residuals high but chlo­ride levels were correspondingly high, re­sulting in severe corrosion problems in addition to the colour and stability problems caused by the metal residuals. Since chro­mium oxide catalysts were high in activity (200-600 kg of polymer per gram of Cr metal) and contained no chloride, no catalyst resid­ual removal steps were required. Thus, the cost of operating a titanium-aluminum alkyl process exceeded that of operating a Phillips process. Yet, the market demand for a low molecular weight, narrow WD resin was suf­ficient to spur research.

Here is a good example of how catalyst, process, and market interact. In the early 1970s the Phillips slurry process with Phil­lips catalyst was less costly and easier to operate. However, some products de­manded by the marketplace could not be efficiently produced. So without promise of success, research on the titanium-aluminum alkyl catalysts to improve activities contin­ued at a rapid pace. In the end these efforts were very successful, and the marketplace today is supplied with the sought-after ti ta­nium-aluminum alkyl resin from processes (slurry, solution, and gas phase), which are much more economical than the earlier ver­sions.

Table 2 shows some of the initial work on supported early transition metal catalysts. Although the patented processes repre­sented here did not accomplish the goal of eliminating catalysts removal process steps, they did point the direction and provide the needed incentive to continue the efforts_ It is worth noting how early the supported work began (in 1955). The first supports

KULSHRESHTHA & AWASTHI : PATENTLITERARTURE ON CATALYSTS 289

Table 2 - Polymerization with Ziegler-Catalysts

Polymers Monomers Calalyst

-CH2-CH2- CH2-CH2- (l inear) Ethylene Et2AICI + TiCI4

R R R I I I

- CH2-C-CH2-C-CH2-C-higher et -olefins

AIEt3+ VCI3 I I I Et2AICI + TiCI3 H H H

R = CHJ, C2HS etc_

y H3 H y H3 I -CHcy~CH2-y-CHz-y- Propylene EI2AICI + VCI4

H CH3 H

optically active polym er ,

3-Phenyl-butene-( 1) ElzAICI + TiCIJ

yHJ y H3 EtzAICI + EtAIClz -y-CH2-CH2-CH2-

y- CH2- Ethylene + Propylene

+ VOCIJ H H

Terpolymers Ethylene + Propylene Et2AICI I EtAICI2 I + Diene VOCI3

-(CH2h-CH=CH-CH2- + - CH2-CH-

~ , Vinylcyclopropane Et2AICI + VCI3

-CHz-Q- -CHz-yH-

(yH2lz Biallyl AliBu3 + TiCI4

CH - CH2

-C~2 ,CH2- Et2AICI + CoClz C=C .cis - 1,4 Butadiene EI2AIJ + TiCI4 H H

-C~2 H C= C trans - 1,4 Butadiene AIEtJ + VCI3 H "-CHz-

- CH2-yH-

AIEt3 + Ti(OBu)4

CH 1,2 - Buladiene " AIEI3 + Cr(acb I CH2

- Ctl2 /H2-

C~C cis-l.'l-lsoprene AliBuJ + TiCI4 / H

CHJ

Cyclododecatriene-1,5,9 trans, trans, cis Buladiene EI2AICI + TiCI4

Polypentenamer cis Cyclopentenc AIEIJ + MoCls

Polypentenamer trans Cyclopentenc AIEtJ + WCI6

290 J INTELLEC PROP RIGHTS, SEPTEMBER 1999

were metal oxides (perhaps an imitation of chromium oxide successes), halides, and carbonates.

proach with transition metals attachecl to surface hydroxy species, other group~. were finding that the transition metal did not have to be anchored to the support for high activi­ties. Many of these catalysts (Table 4) con­sisted of magnesium alkoxides reacted with transition metal halides. During the prepara­tion, the original sb-ucture of the magnesium alkoxide is completely desb-oyed and a new species formed, perhaps with an increase in surface area. These catalysts could be fur­ther modified by introduction of additional compounds into the cataly.tic complexes such as complex magnesium alkoxides (e.g., Liz[Mg(OCzHs)4]) or by carryi~g out the reactions in th~ presence of an acid hal-

In the mid-1960s the work on these transi­tion metal supported systems really began to reach fruition . Poss ibly stimulated by Cabot's 1960 patent (BP 969, 761), Solvay, Hoechst, Mitsui, Montecatini, and B.F. Goo­drich came out with a series of patents deal­ing with supporting halotitanium species on hydroxymagnesium halides (Table 3). The degree of dehydration of the support, just as with chromium-silica catalysts, played a sig­nificant rol e in their activities.

While the researchers just mentioned were studying the classic supported catalyst ap-

Patent No.

BP 841,822

US 3, 153 634,

US 2,980,662

US 2,980,662

BP 877,457

BP 969,761

BP 969,767

Table 3- Early supported catalysts

Date

1955

1956

1956

1956

1957

1960

1963

Company Catalyst preparation

British TiCl4 reduced by aluminum alkyls Petrochemicals in the presence of solids such as

MgCO;l.

Sun Oil TiCl4 was adsorbed on Si02 / AlZO;l and reduced

Sun Oil Ti compounds reduced in the presence of solid NaCI, FeCh. AlCh, GaCh

Sun Oil Ti compounds reduced in the presence of sol id , NaCI, FeCh"AlCh, GaCh etc.

Sun Oil TiCl4 reduced in the presence of inorganic compounds.

Cabot Transition metal compounds reduced in the presence of SiOz, AlZO;l, SiOz/ AlZO;l, ZrOz, TiOz, ThO, MgO, etc.

Cabot Transition metal compounds reduced in the presence of Si02, AlZO;l, ZrOz, TiOz: 1110, MgO, etc.

KULSHRESHTHA& AWASTHI : PATENTLITERAIITURE ON CATALYSTS 291

Table 4 - Magnesium hydroxychloride supported catalysts

Patent No. Date Company Catalyst preparation

BP 1,024,336 1963 Solvay Reaction of a transition metal with a hydraxychloride of a bivalent metal, preferably Mg(OH)CI.

JP45-40295 1967 Mitsui TiCI4 reacted with Mg(OH)2 and reduced

US 3,634,384 1968 BFGoodrich TiCI4 reacted with Mg(OH)z and reduced

BE 726,839 1968 Solvay Reaction of magnesium hydroxid e with a transition metal halide

BE 728,002 1968 Montecatini

BE 735,291 1968 Hoechst

Table 5 - Magnesium alkoxide-based catalysts

Patent No. Date Company

US 3,644,318 1968 Hoechst

BE 758,994 1969 Hoechst

BE 743,325 1969 Solvay

BE 780,530 1971 Hoechst

NL216,195 1971 Solvay

ide (e.g., SiCI4 or BCI3). By the end of the 1960s, there was a good deal of interest in this new type of catalyst, which no longer required expensive deashing s teps.

Gradually evolving from all this titanium-alu­minum alkyl catalyst research were even high er activity catalysts. These supported approaches eventually led to the catalyst sys-

Catalyst preparation

TiCI4 reacted with Mg(OR) 2 or a complex magnesium alkoxide

Reaction of magnesium alkoxid e and an acid halide with a tetravalent titanium compound

tems consisting of MgCI2 ball-milled with TiCk

!twas reasonable to try to combine the newly ball-milled MgCIz.Mg(fiCI6» catalyst with alkoxides similar to those used for the Mg(OR) 2. TiCI4 system. The results by the early 1970s were yet another boost in cata­lyst activity, which was at this point high enough to eliminate all deashing steps (Ta­bles 5 and 6).

292 J INTELLEC PROP RIGHTS, SEPTEMBER 1999

Table 6- Magnesium chloride based catalysts

Patent No. Date Company

BP 1,286,867 1968 Montecatini

BE 744,221 1969 Montecatini

BE 747,846 1969 Montecatini

JP 46-34092 1968 Mitsui

U.S. 3,642,746 1968 Mitsui

JP 46-34093 1968 Mitsui

BE 755,185 1969 Hoechst

References

1 Martin H, Ziegler Catalysts (Springer Verlag, New York 1995) .

Cat.alyst preparation

TiCl4 ball-milled with MgCl2

Reaction of MgCl2 with halogenated titanium compounds

TiCl4 reacted with MgCI2. nROH MgC12.nH20 or MgCl2.Lewis base

Reaction of a magnesium dihalide electron donor adduct (e.g., MgCI2. 6C2HsOH) with a titanium compound

2 Welch M B & Hsiech H L, Olefi n po­lymerization catalyst technology, Eur Pat EP 685, 495, 6 Dec 1995.