Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
2002-06-12
2004-08-24
Rabago, Roberto (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Polymers from only ethylenic monomers or processes of...
C526S172000, C526S134000, C526S169100, C502S103000, C502S117000, C502S155000, C502S167000, C556S033000, C556S034000, C556S137000, C556S138000
Reexamination Certificate
active
06780947
ABSTRACT:
The present invention relates to new metal complexes and their use in the preparation of catalytic compositions capable of polymerizing &agr;-olefins.
More specifically, the present invention relates to a particular organometallic complex of a transition metal or of the group of lanthanides, a catalytic composition comprising it and at least one organometallic activator, as well as a process for the (co)polymerization of &agr;-olefins within a wide range of temperatures and pressures, in the presence of said catalytic composition.
It is generally known in the art that ethylene, or &agr;-olefins in general, can be polymerized or copolymerized by means of low, medium or high pressure processes with heterogeneous catalysts based on a transition metal of groups 4 to 6 of the periodic table of elements (in the form approved of by IUPAC and published by “CRC Press Inc.” in 1989, to which reference will be made hereafter with the term “periodic table”), generally known as Ziegler-Natta type catalysts. A more recent group of catalysts active in the polymerization of &agr;-olefins consists of the combination of an oligomeric organo-oxygenated derivative of aluminum (in particular methylaluminoxane or MAO) with an &eegr;
5
-cy-clopentadienyl compound (metallocene) of a transition metal of the same groups 4 to 6 of the periodic table, and especially group 4. These latter catalysts are substantially soluble in hydrocarbon solvents and for this reason are often defined as “homogeneous”, even if used at times in heterogeneous form by means of supporting on an inert solid material. The characteristics of polymerization processes based on this type of catalytic systems can substantially differ from those of processes using heterogeneous catalysts of the Ziegler-Natta type, to such an extent that new olefinic polymers can be obtained, in certain cases, which could not be prepared with the traditional systems. Among the numerous publications available in literature on the matter, reference is made, for example, to the publications “Progress in Polymer Science”, vol. 20 (1995), pages 309-367, and “Journal of Molecular Catalysis A: Chemical”, vol. 128 (1998), pages 1-331, for a wide range of applications of the above techniques and results obtained.
In the continuous attempt to improve the state of the art, new catalysis methods have been recently proposed for the polymerization of &agr;-olefins based on complexes of “heavy” transition metals, i.e. of groups 8 to 10 of the periodic table.
Oligomerization processes of olefins in the presence of nickel complexes have already been known for some time but it has rarely been possible to obtain high olefinic polymers with a catalysis based on this metal, as described, for example, in European patent 558,143.
Subsequently, international patent application WO 96/23010 described complexes of Pd(+2) or Ni(+2) with 1,4-N,N-1,4-diphenylbutadiene (DAB), or other ligands deriving therefrom, having the following characteristic structure (I):
wherein each Ar group is a phenyl group optionally substituted with hydrocarbyl radicals, which, combined with typical activators of metallocene complexes, such as MAO mentioned above, or ionic activators more recently developed, based on boranes, are capable of homo-polymerizing ethylene to surprisingly give a branched product, or co-polymerizing ethylene with other &agr;-olefins, with non-conjugated dienes and with &agr;,&bgr;-unsaturated polar organic compounds such as acrylates. In spite of a significant improvement with respect to the prior known art, the molecular weights obtained are still unsatisfactory. It has been observed, however, that with this group of catalysts, the molecular weight of the polyethylene produced increases with an increase in the steric hindrance of the substituents on the two aromatic groups bound to the nitrogen atoms.
Polymerization catalysts have also been proposed, according to international patent application WO 98/27124, comprising iron and cobalt complexes with nitrogenated tridentate chelating agents (TRI) having the following general formula (II):
wherein each R—N generally consists of a derivative of aniline of the following type:
wherein the groups R
1
and R
5
groups are alkyl groups with a high steric hindrance, such as for example, iso-propyl, tert-butyl, etc., whereas R
2
, R
3
and R
4
can be indifferently selected from hydrogen, alkyl, substituted alkyl, aryl. For example, the following two structures are provided for the preparation of cobalt or iron complexes suitable for the polymerization of ethylene:
wherein: R′=H or CH
3
.
These ligands can form catalysts having a certain polymerization activity also in situ, i.e. if charged into the polymerization reactor as such, in the presence of suitable Fe or Co metal salts. For example, it is described that by charging Co(acac)
2
+(IV)+MAO (or MMAO) into a reactor in the presence of ethylene, the formation of polyethylene is observed even though there is a modest catalytic activity with respect to cobalt.
The molecular weight control of the polymer obtained with said catalysts critically depends on the steric hindrance of the R
1
and R
5
groups of each phenylimine group. Higher molecular weights are obtained with substituents with a greater hindrance. However, compared with those obtained with traditional catalytic systems, the olefinic polymers produced, under comparative conditions, with the above catalytic systems, still show decisively low, polydispersed molecular weights, which are such that the mechanical and process qualities required for typical market uses such as the production of films or plates, cannot be reached.
Another example is the publication “Collect. Czech. Chem. Commun.” (vol. 63, no.3, 1998, pages 371-377) disclosing lanthanide complexes bearing an acyclic open-chain ligand obtained by condensation of 2 molecules of 2,6-diacetylpyridine with one molecule of 1,3-phenylenediamine, said ligand being therefore characterised by the presence of 2 imine functions together with 2 acyl functions.
Contrary to the current opinion that the presence of two phenylimine groups substituted with radicals having a high steric hindrance, is critical in the above ligands to obtain polymeric materials of &agr;-olefins with a satisfactory molecular weight, the Applicant has surprisingly found that this requisite is not necessary for complexes with particular imine ligands defined and claimed hereunder. These complexes can also be obtained with simpler and more rapid methods than the complexes according to the above international patent application WO 98/27124, and are consequently more economic and available.
A first object of the present invention therefore relates to a complex of a metal M selected from transition metals and lanthanides in an oxidation state different from zero, comprising a neutral ligand coordinated to the metal M consisting of a mono-imine of 2,6-diacylpyridine (abbreviated IAP) having the following general formula (V):
wherein: R′ and R″ can be independently hydrogen or a hydrocarbon radical, preferably aliphatic, having from 1 to 10 carbon atoms, optionally halogenated, more preferably methyl,
each R
i
(i=1-8) is independently hydrogen, halogen or C
1
-C
10
alkyl, or C
6
-C
15
aryl, optionally halogenated, on the condition that at least one of the R
1
or R
5
groups, preferably both, is a hydrocarbon radical.
Said complex as defined in accordance with the present invention comprises any physical form thereof, such as for example, its isolated solid form, the form dissolved in a suitable solvent, or supported on appropriate organic or inorganic solids, preferably having a granular or powder physical form. In general, it can be represented, in the terms specified above, by the following formula (VI):
(IAP)M(X)
n
(VI)
wherein: (IAP) represents the above ligand having formula (V),
M is a metal selected, in its more general sense, from transition metals, i.e. metals of groups 3 to 12 of the periodic table, and from lanthanides, which i
Corso Gianni
Masi Francesco
Mestroni Giovanni
Milani Barbara
Proto Antonio
Enichem S.p.A.
Rabago Roberto
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