Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
1998-08-27
2001-03-27
Zitomer, Fred (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Polymers from only ethylenic monomers or processes of...
C526S133000, C526S154000, C502S120000, C525S268000, C523S344000
Reexamination Certificate
active
06207775
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a process for preparing a filled polymer composite comprising from about 1 to about 98 percent by weight of interpolymer and from about 2 to 99 percent by weight of filler, the composite obtainable by said process and a shaped article made from such composite.
BACKGROUND OF THE INVENTION
Fillers have been incorporated into interpolymers by melt blending. The preparation of composites by melt blending the polymeric matrix and the filler is a straightforward procedure, but poorly efficient with respect to the properties of the resulting composite. In order to overcome these deficiencies, techniques have been proposed which are based on either the encapsulation of the filler by a polymer coating or the chemical modification of the filler surface. In addition, a polymerization-filling technique has been developed which involves attachment of a Ziegler-Natta-type catalyst onto the surface of an inorganic filler and polymerization of the olefin from the filler surface, (see for example, E. G. Howard et al., Ind. Eng. Chem. Prod. Res. Dev. 20, 421-429 (1981)).
Using this technique, synthesis of polyethylene-based composites by a Al/Ti/Mg catalyst anchored on the surface of kaolin has been reported (International Patent Application WO 96/34900; F. Hindryckx et al., J. Appl. Polym. Sci. 64, 423-438, 439-454 (1997)).
Furthermore, preparation of polymerization-filled composites using a metallocene catalyst has been reported. Kaminsky et al., in German Patent Application DE 3240382, describe the preparation of composites containing polyethylene, or an ethylene butene copolymer, and an inorganic filler using a bis(cyclopentadienyl) zirconocene. Yet, the molar ratios of cocatalyst to catalyst species used in DE 3240382 are very high, ranging from about 32000 to 312500. Synthesis of aluminum- or zinc-containing polyethylene or polypropylene composites has been promoted by a bis(cyclopentadienyl) zirconocene adsorbed on the metal surface (Kaminsky and Zielonka, Polym. Adv. Technol. 4, 415-422 (1993)). Hayashi et al., European Patent Application EP-A-0 374 619, describe polymerization of ethylene in the presence of an organo-aluminum compound and a product obtained by contact treatment of a bis(cyclopentadienyl) zirconocene or a bis(cyclopentadienyl) titanocene catalyst with a filler.
Presently available methods for the preparation of filled composites suffer from various disadvantages. For example, if polymerization does not take place at the filler surface but rather in the homogeneous phase, such as a diluent or solvent, heterogeneous composites are obtained. On the other hand, known methods using polymerization-filling have employed excessive molar ratios of cocatalyst relative to the catalyst species in order to improve polymerization rate and efficiency. A process achieving efficient copolymerization of ethylene or propylene in the presence of a filler with a higher alpha-olefin has not been described yet.
Accordingly, there is a need for an improved process for the preparation of a filled polymer composite, said process eliminating or reducing the disadvantages associated with the known methods and providing a composite with advantageous physico-mechanical properties.
It is the object of the present invention to provide such process.
SUMMARY OF THE INVENTION
The present invention relates to a process for the preparation of a filled polymer composite comprising about 1 to about 98 percent by weight of an interpolymer, and about 2 to about 99 percent by weight of a filler. The process comprises polymerizing ethylene or propylene, and at least one comonomer, in the presence of a cyclopentadienyl-containing transition metal catalyst and a filler, said filler having immobilized thereon a cocatalyst for the cyclopentadienyl-containing transition metal catalyst, under conditions to allow copolymerization of ethylene or propylene and at least one comonomer to form said composite.
In a further aspect, the invention provides a filled composite comprising an ethylene-based or propylene-based interpolymer and a filler, which composite is obtainable by the process of the invention.
In yet another aspect, the invention relates to a shaped article made from such filled polymer composite.
DETAILED DESCRIPTION OF THE INVENTION
All references herein to elements or metals belonging to a certain Group refer to the Periodic Table of the Elements published and copyrighted by CRC Press, Inc., 1989. Also any reference to the Group or Groups shall be to the Group or Groups as reflected in this Periodic Table of the Elements using the IUPAC system for numbering groups. Included within the term “hydrocarbyl” as used herein are C
1-50
straight, branched and cyclic alkyl radicals, C
6-50
aromatic radicals, C
7-50
alkyl-substituted aromatic radicals, and C
7-50
aryl-substituted alkyl radicals. The term hydrocarbyloxy means a hydrocarbyl group having an oxygen link between it and the element to which it is attached.
The filler composition used in the present process contains active polymerization sites on the filler. The active polymerization sites are generated on the filler by immobilizing a suitable cocatalyst to the filler and contacting the cocatalyst-carrying filler with a cyclopentadienyl-containing transition metal catalyst. The term “cyclopentadienyl-containing transition metal catalyst or compound” as used herein means a transition metal compound containing at least one cyclopentadienyl or cyclopentadienyl-derivative ligand. These transition metal compounds are sometimes also referred to as metallocenes. Preferably, such a catalyst having a constrained geometry is used.
The polymerization sites are active in that they are capable of efficiently promoting or catalyzing copolymerization of ethylene or propylene with at least one other monomer on the filler. Substantially all active polymerization sites are associated with the filler under conditions used in the process of the present invention. Thus, a diluent used in the polymerization step is substantially free from active catalyst. The components employed in the process of the present invention are used in a form which allows the reactions to take place at the surface of the filler.
The process of the present invention provides homogeneous-filled composites displaying advantageous properties, such as, for example, good interfacial adhesion between (catalyst treated) filler material and interpolymer matrix, homogeneous dispersion of filler within the polymer matrix, and control of the molecular weight of the interpolymer over a wide range, together with a high level of comonomer incorporation. The composite obtainable according to the process of the present invention can be specifically designed to have desired and advantageous properties, particularly advantageous mechanical properties.
The process according to the invention requires the polymerization being carried out in the presence of a filler having cocatalyst immobilized thereon, and further the transition metal compound. In a preferred aspect, the process involves immobilizing the cocatalyst to the surface of the filler particles, adding of the metallocene catalyst and copolymerizing ethylene or propylene with at least one other olefin. Interpolymerization and composite formation occur simultaneously. As the diluent or solvent around the filler is substantially free from cocatalyst, the interpolymer is formed from the filler surface and not in the solvent or diluent. An interpolymer coating, preferably based on an interpolymer of low or ultra low density, that is, having a relatively high amount of comonomer incorporated therein, is produced at the filler surface, resulting in a homogeneous composite wherein the filler is uniformly dispersed in the interpolymer matrix. The maximum amount of filler which is uniformly dispersible in the interpolymer matrix depends, inter alia, on the particular filler used. If only spots of polymer are produced on the filler particles, the amount of filler is too high.
In a further aspect, the invention prov
Alexandre Michael
Dubois Philippe G.
Hindryckx François J.
Jérô ;me Robert J. E. G.
Marti Miguel Garcia
The Dow Chemical Company
Zalukaeva Tanya
Zitomer Fred
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