Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
2002-06-26
2004-08-10
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...
C526S126000, C526S153000, C526S161000, C526S201000, C526S904000, C526S943000
Reexamination Certificate
active
06774194
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a supported catalyst for the polymerization of olefins, to the process for the preparation thereof and to the use of said supported catalyst in processes for the polymerization of olefins.
2. Description of the Prior Art
Homogeneous catalytic systems for the polymerization of olefins based on coordination complexes of a transition metal such as titanium, zirconium or hafnium with ligands of the cyclopentadienyl type are known. Generally, these catalytic system comprise a soluble cocatalyst, such as the methylalumoxane (MAO).
These homogeneous catalytic systems show many advantages in comparison with traditional heterogeneous catalysts of the Ziegler-Natta type. In particular, they allow a careful control of the stereoregularity degree and type, the molecular weight distribution and comonomer distribution, besides making easier the use of higher alpha-olefins, diolefins and dienes as comonomers. Thus, new polymers or polymers endowed with remarkably improved properties can be obtained.
However, being soluble in the reaction system, these catalytic systems can not easily be utilized in polymerization processes which are not carried out in solution. Furthermore, the polymers obtained by processes using the above mentioned catalysts, are generally not endowed with satisfactory morphological characteristics.
In order to avoid these drawbacks, systems have been suggested based on supporting at least one component of the above mentioned catalysts on insoluble solid supports. In most cases these solid supports consist of inorganic oxides and, in particular, of silica or alumina.
In the prior art, cases are found wherein the opportunity of using supports of the polymeric type is foreseen.
In European patent applications EP-279 863 and EP-295 312 supported homogeneous catalysts comprising methylalumoxane and bis(cyclopentadienyl)zirconium dichloride are described. Besides silica inorganic supports, organic supports consisting of polyethylene or polystyrene have been used. In the preparation of the supported catalysts, use has been made of n-decane, which has the function of precipitating the methylalumoxane. These supported catalysts, after a prepolymerization treatment with ethylene in n-decane, have been used in the polymerization reaction of ethylene in gas-phase. To attain acceptable results, high amounts of methylalumoxane for each gram of solid support have been used.
In European patent application EP-518 092 catalysts of the type metallocene/alumoxane supported on polypropylene are described. These catalysts have been used in the polymerization reaction of propylene carried out in liquid monomer or in gas phase. Nothing is said about the bulk density of the polymers obtained.
Although these types of catalytic systems supported on polymeric materials are useable in processes carried out in suspension or in gas phase with acceptable yields, however they do not allow polymers endowed with good morphological characteristics to be obtained.
SUMMARY OF THE INVENTION
It has now been found by the Applicant that metallocene/alumoxane catalytic systems can be advantageously made heterogeneous by supporting them on functionalised porous organic supports. By this way it is possible to obtain catalysts in form of spherical particles, endowed with acceptable activities, able to produce polymers which duplicate the shape of the catalyst and therefore are endowed with controlled morphology and high bulk density.
Therefore, an object of the present invention is a supported catalyst for the polymerization of olefins comprising:
(A) a porous organic support functionalised with groups having active hydrogen atoms;
(B) at least one organo-metallic compound of aluminium containing at least one heteroatom selected from oxygen, nitrogen and sulphur; and
(C) at least one compound of a transition metal selected from those of groups IVb, Vb or VIb of the Periodic Table of the Elements, containing at least one ligand of the cyclopentadienyl type.
Another object of the present invention is a process for the preparation of a supported catalyst according to the present invention, which process comprises the step of contacting, in an inert solvent, the components (A), (B) and (C) among themselves.
Still another object of the present invention is a supported and pre-polymerized catalyst for the polymerization of olefins obtainable by subjecting a supported catalyst according to the present invention to a pre-polymerization treatment with at least one olefinic monomer.
A further object of the present invention is a process for the homo- or co-polymerization of olefins comprising the polymerization reaction of one or more olefinic monomers in the presence of a supported catalyst according to the present invention.
Still a further object of the present invention is a process for the homo- or co-polymerization of olefins comprising the polymerization reaction of one or more olefinic monomers in the presence of a supported and pre-polymerized catalyst according to the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The porosity (B.E.T.) of the organic support is generally higher than 0.2 cc/g, preferably higher than 0.5 cc/g, more preferably higher than 1 cc/g. In particular, supports suitably useable have a porosity comprised between 1 and 3 cc/g.
The surface area (B.E.T.) of the organic support is generally higher than 30 n/g, preferably higher than 50 m
2
/g, more preferably higher than 100 m
2
/g. In particular, the surface area can reach values of about 500 m
2
/g and over.
The organic support is preferably in form of particles having controlled morphology, in particular microspheroidal morphology with a diameter comprised between about 5 and 1000 &mgr;m, preferably between 10 and 500 &mgr;m, more preferably between 20 and 200 &mgr;m.
Supports which can be used in the catalysts according to the present invention are those polymers, endowed with the above mentioned characteristics regarding the porosity and surface area, which show functional groups having active hydrogen atoms.
Examples of suitable functional groups are hydroxyl groups, primary and secondary amino groups, sulphonic groups, carboxylic groups, amido groups, N-monosubstituted amido groups, sulphonamido groups, N-monosubstituted sulphonamido groups, sulphydril groups, imido groups and hydrazido groups.
The amount of functional groups contained in the supports is generally higher than 0.2 milliequivalents (meq) for each gram of solid support, preferably higher than 0.5 meq for each gram of solid support, more preferably is comprised between 1 and 6 meq for each gram of solid support.
A class of supports particulary suitable for use in the catalysts of the present invention can be obtained from partially cross-linked porous styrenic polymers. These supports can be prepared by copolymerization of styrenic monomers, such as styrene, ethylvinylbenzene, vinyltoluene, methylstyrene and mixtures thereof, with comonomers able to be cross-linked, such as divinylbenzene, divinyltoluene and mixtures thereof. Preferred styrenic polymers are partially cross-linked styrene/divinylbenzene copolymers. Methods for the preparation of these copolymers are described, for example, in U.S. Pat. No. 4,224,415, the content of which is incorporated in the present description.
Porous polymers of this type can be functionalised by means of known methods. The most common methods to functionalise polystyrene resins are reported in “Comprehensive Pol. Sci., Pergamon Press, pages 82-85 (1989)”.
A method for the preparation of alpha-hydroxyalkylated resins is described by I. Fujita et al. in “Separation Science and Technology, 26, 1395-1402, (1991)”.
Functionalized porous styrenic polymers useable as supports according to the present invention are, moreover, those which can be directly obtained from the copolymerization of styrenic monomers with comonomers functionalized with groups containing active hydrogens or their precursors. Examples of these polymers are the styrenic copolymer
Albizzati Enrico
Dall'Occo Tiziano
Piemontesi Fabrizio
Resconi Luigi
Basell Technology Company BV
Bryan Cave LLP
Rabago Roberto
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