Application of Wesslau, Patent Appeal No. 7447.
| Decision Date | 26 November 1965 |
| Docket Number | Patent Appeal No. 7447. |
| Citation | 353 F.2d 238 |
| Parties | Application of Hermann WESSLAU. |
| Court | U.S. Court of Customs and Patent Appeals (CCPA) |
Arnold Sprung, New York City, Arnold B. Christen, Washington, D. C., for appellant.
Clarence W. Moore, Washington, D. C. (Fred W. Sherling, Washington, D. C., of counsel), for the Commissioner of Patents.
Before WORLEY, Chief Judge, and RICH, MARTIN, SMITH, and ALMOND, Judges.
This appeal is from the decision of the Board of Appeals affirming the rejection of claims 35-431 in appellant's application2 entitled "Process for the Production of Polyethylene With Narrow Distribution of the Molecular Weight." No claims have been allowed.
The invention relates to a process of polymerizing ethylene utilizing a Ziegler-type catalyst system to produce solid polyethylene. Both appellant and the Patent Office have treated the appealed process claims as standing or falling together, and we will do the same. Claim 35, from which the remaining claims depend, is illustrative and reads as follows:
35. In the process of polymerizing ethylene to a solid polymer having a high molecular weight and a narrow molecular weight distribution range, the improvement which comprises polymerizing ethylene in the presence of a polymerization catalyst consisting essentially of a mixture of titanium trichloride, at least one compound of tetravalent titanium Ti(R)4 and at least one organic Aluminum compound soluble in a liquid hydrocarbon and having the general formula R\'Al-(R)2 in which R\' is alkyl and R is selected from the group consisting of halogen, alkoxy and aroxy radicals, wherein between said tetravalent titanium compound and said organic aluminum compound there is present in said mixture at least one halogen atom and at least one member selected from the group consisting of alkoxy and aroxy radicals.
According to appellant's disclosure, polyethylene of high molecular weight may be produced by what has become known in the art as the Ziegler polymerization process. Analysis of the polyethylene so produced has revealed that although the average molecular weight of the polymer is high, a fairly large proportion of the individual polymer chains have a relatively low molecular weight. These low molecular weight fractions are particularly unfavorable for such properties as impact bending strength, rubbing, and fatigue. Appellant has discovered that the proportion of the lower molecular weight chains can be reduced, thereby narrowing the molecular weight distribution, by employing a three-component catalyst system in which either the Ti(R)4 or R'Al(R)2 contains an alkoxide or aroxide moiety.
The references relied on are:
Anderson 2,862,917 December 2, 1958
Muehlbauer 2,905,661 September 22, 1959
Ruhrchemie
(Belgian) 553,694 June 24, 1957
The Ruhrchemie patent relates to a process for producing polyethylene of a desired molecular weight employing certain specified cataylst systems. The pertinent portion of the patent specification reads as follows:
* * * when high molecular weight polyethylene products are to be obtained * * *, the employed mixtures consist of aluminum alkyl compounds and/or halides of aluminum alkyl with quantities of titanium trichloride of at least 0.01 mole * * * and quantities of titanium tetrachloride lower than 0.1 mole * * *; on the other hand, when materials having low molecular weight are to be obtained the employed mixtures consist of aluminum alkyl and/or halide of aluminum alkyl with more than 0.1 mole * * * of titanium tetrachloride per mole of aluminum alkyl and/or halide of aluminum alkyl, and with titanium trichloride at the rate of at least 0.1 mole, preferably 0.3-1 mole approximately per mole of aluminum alkyl and/or halide of aluminum alkyl.
The Anderson patent relates to a process of polymerizing ethylene whereby control over the weight average molecular weight of the polymer and the molecular weight distribution of the polymer is achieved by adhering to process conditions which insure the solubility of the ethylene during polymerization. The process employs coordination catalysts of titanium:
* * * obtained by admixing a trivalent or tetravalent titanium compound of the class consisting of titanium salts and titanium alkoxides with a compound having at least one metal-to-hydrocarbon bond, such as metal alkyls, suitable compounds being lithium aluminum alkyls, aluminum alkyls, Grignard reagents, alkyl aluminum halides, tin alkyls, etc. * * *
Anderson further states:
* * * the steady state compliance an indicia of molecular weight distribution will vary from 3 to 7 when the critical conditions of the process of the present invention are maintained and...
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