Catalyst components for the polymerization of olefins

Details Catalyst components for the polymerization of olefins Catalyst components for the polymerization of olefins

2002-07-24

2004-03-09

Choi, Ling-Siu (Department: 1713)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

Polymers from only ethylenic monomers or processes of...

C526S943000, C526S904000, C526S158000, C526S348000, C502S103000, C502S109000, C502S152000, C502S159000, C502S402000, C502S439000

Reexamination Certificate

active

06703458

ABSTRACT:

The present invention relates to components of catalysts for the polymerization of olefins and the process for their preparation, the catalysts obtained from them and the use of the said catalysts in the polymerization of olefins. Homogeneous catalysts for the polymerization of olefins obtained from compounds of formula ML
x
in which M is a transition metal especially Ti, Zr, Hf, Cr, Pd and Ni, L is a ligand that is coordinated to the metal, and x is the valence of the metal, are known from the literature. Examples of catalysts of this type with very high activity are those obtained by reacting metallocene compounds Cp
2
ZrCl
2
or Cp
2
TiCl
2
, or their derivatives substituted in the cyclopentadienyl ring, with polyalumoxane compounds containing the —(R)AlO— repeating unit, in which R is preferably methyl (U.S. Pat. No. 4,542,199 and EP-A-129368). Catalysts of the aforementioned type in which the metallocene compound contains two indenyl or tetrahydroindenyl rings with a bridging bond to lower alkylenes or to other divalent radicals are suitable for the preparation of stereoregular polymers of propylene and of other alpha olefins (EP-A-185918).
Stereospecific catalysts are also obtained from dicyclopentadienyl compounds in which the two rings are substituted in various ways with groups with steric hindrance such as to impede the rotation of the rings about the axis with the metal. The substitution of the cyclopentadienyl ring of indenyl or tetrahydroindenyl in suitable positions supplies catalysts that are endowed with very high stereospecificity (EP-A-485823, EP-A-485820, EP-A-519237, U.S. Pat. No. 5,132,262 and U.S. Pat. No. 5,162,278). The catalysts described above supply polymers with very narrow molecular weight distribution (Mw/Mn of about 2).
Furthermore, some of these catalysts have the property of forming copolymers of ethylene with alpha olefins of the LLDPE type or elastomeric ethylene/propylene copolymers with very uniform distribution of the comonomenic units. The LLDPE polyethylene obtained is further characterized by low solubility in solvents such as xylene or n-decane.
The polypropylene obtained with the more stereospecific catalysts mentioned above exhibits greater crystallinity and a higher distortion temperature relative to the polymer obtainable with the conventional heterogeneous Ziegler-Natta catalysts.
Homogeneous catalysts with a different structure are described in international patent application WO 96/23010. These catalysts, comprising a complex between a transition metal and at least one bidentate ligand that has a particular structure, are capable of polymerizing olefins to give a wide range of polymers including copolymers comprising olefins and polar monomers such as carbon monoxide, vinylacetate, (meta)acrylates etc.
Despite their excellent properties in terms of quality of the polymeric products, considerable difficulties are encountered when said homogeneous catalysts are to be used in industrial processes of production of polyolefins that are not carried out in solution. The homogeneous catalysts in fact, are not able to provide polymers with a regular morphology when used in processes such as polymerization in gas-phase. In order to make it possible their use in non-solution polymerization processes, the homogeneous catalysts have to be made heterogeneous by supporting them on suitable supports that are able to endow the catalyst with appropriate morphological properties. Various kinds of supports can be used for this purpose including, among others, metal oxides such as silica, magnesium halides or polymeric supports such as polyethylene, polypropylene and polystyrene. A characteristic that is common to these supports is that they are porous and so enable the metallocene compound to be fixed by being deposited in the pores. The catalytic components thus obtained are therefore in the form of particles of inert material, organic or inorganic, carrying in the surface layer, in correspondence of the pores, the transition metal compound that constitutes one of the components of the catalyst. To achieve efficient support, however, the porosity of the support must be accurately controlled. Moreover, since the extent of supportation depends mainly on the porosity of the support particles, it also proves very difficult to achieve homogeneous distribution of the quantity of compound supported because the individual support particles or fractions have differences in porosity that are sometimes very considerable. In any case, the upper limit of the amount of transition metal compound that can be supported is always determined by the porosity of the support. For example, U.S. Pat. No. 5,106,804 describes catalysts comprising a metallocene compound supported on MgCl
2
in spherical form and partially complexed with an electron-donor compound in which the amount of Zr compound supported on MgCl
2
is relatively low (the Zr/Mg ratio in the catalyst is less than about 0.05). Furthermore, the polymerization yields are not such as to make it possible to obtain polymers containing sufficiently low residues of the catalyst. It is in fact known that supporting tends to lower the activity of homogeneous catalysts considerably. European patent EP 798315 describes a method of preparing homogeneous mixtures consisting of a metallocene, a cocatalyst and a dispersing medium having a oily or waxy consistency that is selected among the non-aromatic long-chain hydrocarbons that have boiling point above 150° C. and viscosity of at least 1 Pa·s at 25° C. According to the inventors these mixtures are endowed with improved stability. Although included in the generic description, the use of a specific hydrocarbon matrix with a melting point above 70° C. as a dispersing medium it is never described specifically. Nor, moreover, is there any specific description of a solid catalytic component in spherical form that comprises a homogeneous catalyst dispersed within a solid hydrocarbon matrix at room temperature. The only use of a solid dispersing medium is reported in Example 3 describing the preparation of solid mass of a paraffinic wax having a melting point between 65 and 70° C. and containing methyl alumoxane in an amount equal to approx. 66 wt. %, which has then been mechanically comminuted to a fine grain powder. In addition to the fact that these mixtures do not possess a suitable morphology, it is also important to observe that according to Table 1 of the said application, the metallocene compound is not present in the formulation of Example 3. As it can be seen from the polymerization data, however, the yields that are obtained using this catalyst are very low even if further alumoxane is added in the reactor. International patent application WO 96/34020 describes a method of preparation of a solid catalyst that comprises supporting a metallocene and an activator on a support, preferably porous, and then coating the said supported catalyst with an inert organic material that is preferably a hydrocarbon component of molecular weight between 200 and 20 000 and is soluble in aromatic solvents at temperatures above 70° C. According to the said patent application, the catalyst thus prepared makes it possible to overcome the problem of reactor fouling, but the polymerization yields (expressed in terms of kg of polymer per g of transition metal) are very low. Surprisingly, it was found that the solid components of catalysts obtained by dispersing a homogeneous catalyst within a hydrocarbon matrix possessing certain characteristics are capable of forming catalysts that have high activity and are able to produce polymers with excellent morphological properties. An object of the present invention therefore comprises spherical catalyst components for the polymerization of formula RCH═CHR, in which R is independently hydrogen or a hydrocarbon group with 1-10 carbon atoms, comprising a homogeneous transition metal compound of formula MP
x
, in which M is a transition metal from Groups 3 to 11 or the lanthanide or actinide Groups of the Periodic Table of the Elements (new IUP

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