Catalyst – solid sorbent – or support therefor: product or process – Catalyst or precursor therefor – Plural component system comprising a - group i to iv metal...
Reexamination Certificate
1996-10-22
2001-08-14
Wu, David W. (Department: 1713)
Catalyst, solid sorbent, or support therefor: product or process
Catalyst or precursor therefor
Plural component system comprising a - group i to iv metal...
C502S104000, C502S118000, C502S120000, C502S121000, C502S122000, C502S123000, C502S128000, C502S152000, C502S155000, C526S943000
Reexamination Certificate
active
06274529
ABSTRACT:
The present invention relates to an activated catalytic system for the (co)polymerization of alpha-olefins.
More specifically, the present invention relates to a catalytic system comprising a metallocene complex of a transition metal, active in homo- and co-polymerization processes of alpha-olefins, and particularly ethylene.
It is generally known in the art that alpha-olefins can be polymerized by means of low, medium or high pressure processes with catalysts based on a transition metal, generally known as Ziegler-Natta type catalysts.
A particular group of these catalysts, generally having very high polymerization activities, consists of the combination of an organo-oxygenated derivative of aluminium (commonly called aluminoxane) with a &eegr;
5
-cyclopentadienyl derivative of a transition metal, also commonly called metallocene, which can be defined in its most general form with the following formula (I):
wherein M represents a metal of group 4 of the periodical table of elements, formally in the oxidation state of +4, and is preferably titanium or zirconium; R
1
and R
2
each independently represent a group having an anionic nature such as, for example, a hydride, a halide, a phosphonated or sulfonated anion, an alkyl or alkoxy group, an aryl or aryloxy group, an amide group, a silyl group, etc; Cp independently represents a ligand of the &eegr;
5
-cyclopentadienyl type and is generally selected from &eegr;
5
-cyclopentadienyl, &eegr;
5
-indenyl, &eegr;
5
-fluorenyl and their variously substituted derivatives; R
3
can, independently of the nature of the other substitutes, have one of the definitions of the ligand Cp, or R
1
or R
2
groups. “Bridged” metallocenes are also of particular interest in the known art, wherein the Cp and R
3
groups, the same or different, are linked by a covalent bridge which normally also comprises other carbon atoms or heteroatoms. For a known technique for the preparation of the above compounds, reference should be made, as an example, to the publication of H. Sinn, W. Kaminsky, in Adv. Organomet. Chem., vol. 18 (1980), page 99 and U.S. Pat. No. 4.542.199.
Catalytic systems based on metallocenes normally allow high polymerization activities to be reached in the presence of an aluminoxane in great molar excess with respect to the metal M, with an atomic ratio Al/M usually between 500 and 5000. This creates the presence of a relatively high quantity of aluminium in the polyolefins thus obtained, consequently making them unsuitable for numerous applications in which the presence of metal ions is not tolerable, such as, for example, when insulating properties or food compatibility are required.
In addition, aluminoxanes and particularly methylalumoxane which is the activator normally used, necessitate relatively complicated synthetic methods and conservation which make their use in various applications inconvenient with respect to the less costly traditional catalytic systems based on titanium or vanadium chlorides and aluminiumalkyls.
More recently catalysts of the metallocene type have been developed, which are capable of polymerizing olefins also without aluminium compounds and particularly aluminoxanes. These systems are commonly based on the formation of a catalytic species of a cationic nature, obtained by the contact of a suitable metallocene with strong Lewis acids. Various cationic systems of this type are described for example, in the publications of R. R. Jordan in “Advances in Organometallic Chemistry”, vol. 32 (1990), pages 325-387, and X. Yang et al. in “Journal of the American Chemical Society”, vol. 116 (1994), page 10015, which provide, as well as a detailed description of the field, numerous patent references on the subject.
The activity of cationic metallocene catalytic systems is generally lower, however, than the high activity of systems using methylalumoxane in prejudice of a wider diffusion of the former.
A small increase in the activity of catalysts comprising metallocenes of transition metals, particularly Ti and Zr, has been observed in oligo- and poly-merization processes of alpha-olefins carried out in polar solvents. F. S. Duiachkovskii et al, in “Journal of Polymer Science, Part C”, vol. 16 (1967) pages 1333-1339, describes an increase in the oligomerization constant of 1-decene in the presence of a catalytic system obtained by the combination of cyclopentadienyltitanium methylchloride with aluminiummethyldichloride, when the solvent medium varies from benzene to dichloroethane. The same reference also describes a polymerization experiment of ethylene in dichloroethane using the same catalytic system in the presence of an electric field. In each case the productivities observed were low. A polymerization process of olefins carried out in a solvent such as dichloroethane is also industrially unrealistic owing to the great purification difficulties of the polymer obtained with this process and for the high operating costs of the process itself
German patent 4.426.122 (Nippon Oil) discloses the use of an organic compound containing at least one fluorine-carbon bond to increase the activity of a catalytic system comprising a metallocene of a metal of group 4 of the periodic table and methylaluminoxane (MAO). Also in this case, however, a relatively small increase in activity is observed, which is obtained, in addition, in the presence of MAO, with the relative disadvantages mentioned above.
European patent application pub. No. 648,786 relates to a polymerization catalyst comprising an ionic metallocene and a Lewis base. Although increased polymerization activities are shown at high temperature with diisobutylphthalate, the strong Lewis bases disclosed in this reference are known to have a poisoning effect on olefin polymerization catalyst which make their use unsuitable for many processes at low to medium temperature.
The demand for metallocene catalysts with a high activity excluding the use of aluminoxanes as activators therefore remains unanswered.
The Applicant has now surprisingly found that the activity of metallocene catalysts not comprising aluminoxanes is considerably increased in the presence of particular organic substances not containing metals.
A first object of the present invention therefore relates to an improved catalyst for the (co)polymerization of alpha-olefins comprising the following components in contact with each other:
(A) a metallocene derivative of a metal selected from the group consisting of transition metals and lanthanides, capable in itself of promoting the polymerization of olefins without organo-oxygenated compounds of metals of groups 13 or 14 of the periodic table of elements,
(B) a substance not containing metal atoms, characterized in that this substance (B) consists of an aprotic polar compound having a weak co-ordinating capacity.
A second object of the present invention relates to an improved process for the (co)polymerization of alpha-olefins characterized in that it is carried out in the presence of the above improved catalyst.
The term “(co)polymerization of alpha-olefins” as used hereafter in the text and claims refers both to the homopolymerization and copolymerization of alpha-olefins with each other or with another ethylenically unsaturated polymerizable compound.
The metallocene derivative (A) of the present invention is an organometallic compound of a transition metal or lanthanide, preferably a metal selected from Ti, Zr and Hf, characterized by the presence of at least one &eegr;
5
-cyclopentadienyl group co-ordinated to the metal, and by the capacity of promoting the polymerization of alpha-olefins also without an organo-oxygenated compound of a metal of groups 13 or 14 of the periodic table. These organo-oxygenated compounds are monomeric or polymeric organometallic derivatives containing at least one oxygen atom linked to a metal of group 13 or 14 of the periodic table, such as, for example, aluminoxanes, especially methylaluminoxane, galloxanes or stannoxanes, which are widely used as co-catalysts of many catalytic systems based on metallocenes.
The element
Fusco Roberto
Gila Liliana
Guglielmetti Gianfranco
Longo Luca
Proto Antonio
Enichem S.p.A.
Lu Caixia
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Wu David W.
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