Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
2002-01-18
2004-04-20
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...
C526S348000, C526S142000, C526S123100, C502S103000, C502S113000, C502S115000, C502S120000
Reexamination Certificate
active
06723809
ABSTRACT:
The present invention relates to a bimetal catalyst, the process for its preparation and its use in (co)polymerization processes of &agr;-olefins.
More specifically, the present invention relates to a catalyst for the (co)polymerization of &agr;-olefins of the Ziegler-Natta type, comprising a solid component containing titanium, and a co-catalyst consisting of a hydride or an organometallic compound of groups 1, 2 or 13 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) This catalyst can be obtained by means of an original process set up by the Applicant.
It is known that ethylene, or &agr;-olefins in general, can be polymerized by means of low, medium or high pressure processes on catalysts of the Ziegler-Natta type to give substantially linear polymers with a high molecular weight. These catalysts are generally composed of a compound of elements from group 4 to group 6 of the periodic table in contact with an organometallic compound, or a hydride, of elements of groups 1, 2 or 13 of the same periodic table.
Solid components of Ziegler-Natta catalyst containing a transition metal (generally titanium) a bivalent metal (generally magnesium), a halogen (generally chlorine) and optionally also an electron donor, are known in the art. These solid compounds used in combination with an organometallic compound of aluminum, form catalysts active in (co)polymerization processes of ethylene, in processes carried out at a low temperature and pressure. For example the patent U.S. Pat. No. 3,642,746 describes a solid component of catalyst obtained by contact of a compound of a transition metal with a halide of a bivalent metal treated with an electron donor. According to the patent U.S. Pat. No. 4,421,674 a solid component of catalyst is obtained by contact of a compound of a transition metal with the spray-drying product of a solution of magnesium chloride in ethanol.
According to the patent UK 1,401,708, a solid component of catalyst is obtained by the interaction of a magnesium halide, a non-halogenated compound of a transition metal and an aluminum halide. Patents U.S. Pat. No. 3,901,863 and U.S. Pat. No. 4,292,200 describe solid components of catalyst obtained by putting a non-halogenated compound of magnesium, a non-halogenated compound of a transition metal and an aluminum halide in contact with each other.
The patent U.S. Pat. No. 4,843,049 and European patent application EP-A 243,327 describe a solid component of catalyst which contains titanium, magnesium, aluminum, chiorine and alkoxyl groups, highly active in (co)polymerization processes of ethylene, carried out at low pressure and temperature, with the suspension technique, and at high pressure and temperature, in vessel or tubular reactors, respectively. These solid components are generally obtained by spray-drying an ethanol solution of magnesium chloride to obtain an active carrier, which is interacted in sequence with a titanium tetraalkoxide or with titanium tetrachloride and with an alkyl aluminum chloride, respectively.
All the above catalysts, although relatively active in the processes indicated, are not however completely satisfactory as far as some of the properties of the polymer or copolymer obtained are concerned, with particular reference to the average molecular weight, especially of polyolefins from high temperature processes, which are still unsuitable for certain industrial uses. In addition, there is still room for further improving the activity of the above catalysts.
Attempts have been made to modify the properties of the polymers or copolymers of olefins by using catalysts based on a mixture of transition metals. For example, European patent applications EP-A 177,189 and EP-A 146,507, both describe the preparation and use of catalysts of the Ziegler-Natta type comprising titanium and hafnium in order to obtain polyethylene with a widened (bimodal) molecular weight distribution. The process for the preparation of these catalysts comprises the introduction of titanium and hafnium in two separate steps.
European patent application EP-A 523,785 discloses that the introduction of magnesium-carboxylate and transition metal-carboxylate bonds allow solid components of catalyst to be obtained which are generally improved with respect to those of the known art, in relation to their activity in (co)polymerization processes of ethylene and &agr;-olefins, in processes carried out at low pressure and temperature, at high pressure and temperature and in solution, and in relation to the nature of the polymers thus obtained. The preparation of these catalysts containing metal-carboxylate bonds is carried out by means of a complex process which comprises mixing pre-prepared solutions of magnesium carboxylates and transition metal in an organic hydrocarbon solvent. This method however has the disadvantage of not allowing complete freedom in the selection of the atomic ratios between the metals in the catalyst, for reasons connected to their different solubility in hydrocarbon solvents.
The Applicant has now found that polymers and copolymers of &agr;-olefins having a high molecular weight can be surprisingly obtained, also with processes having a high productivity under high temperature conditions, by using a particular bimetal catalyst of the Ziegler-Natta type supported on magnesium chloride, which has the additional advantage of a particularly simple and convenient preparation process.
In accordance with this, in a first aspect, the present invention relates to a solid component of a catalyst for the (co)polymerization of &agr;-olefins consisting of at least 95% by weight, preferably from 98 to 100% by weight, of titanium, magnesium, at least one metal selected from hafnium and zirconium, aluminum, chlorine and R—COO carboxylate, in the following molar ratios:
M/Ti=0.1-10.0; Mg/Ti=1.0-20.0; Al/Ti=0.01-6.0
Cl/Ti=2.0-70.0; R—COO/Ti=0.1-10.0
wherein: R is an aliphatic, cycloaliphatic or aromatic hydrocarbon radical, containing from 1 to 30 carbon atoms, and
M is a metal selected from hafnium and zirconium or one of their mixtures, and is preferably hafnium,
characterized in that at least 80%, preferably at least 90%, of the titanium is in oxidation state +3, and in addition, at least 1%, preferably from 2 to 10%, of said titanium in oxidation state +3 has a tetrahedral coordination geometry.
The number of carbon atoms of the radical R of said carboxylate is not particularly critical, however it preferably ranges from 6 to 15.
The term “(co)polymerization”, as used in the present description and claims in reference to &agr;-olefins, refers to both the homopolymerization of an &agr;-olefin, for example ethylene to form high density crystalline polyethylene or propylene to form polypropylene, and also to the co-polymerization of an &agr;-olefin with at least one different unsaturated compound copolymerizable therewith (obviously comprising a different &agr;-olefin), for example, the copolymerization of ethylene with ethylidenenorbornene to form a cross-linkable polyethylene, or the copolymerization of ethylene with 1-butene to form linear low density polyethylene.
For the sake of simplicity, the term “mole” and “molar ratio” are used in the present description and claims, both with reference to compounds consisting of molecules and also with reference to atoms and ions, avoiding, for the latter, the use of the terms gram-atom or atomic ratio, even these are more scientifically correct.
According to another aspect, the present invention relates to a process for the preparation of the above solid component of catalyst, comprising the following steps in succession:
(i) preparing a mixture of at least one compound of magnesium a compound of titanium and a compound of a metal M as defined above, in the appropriate proportions, in a medium consisting of an inert organic liquid, in which at least one of said compounds is insoluble;
(ii) preparing a substantially limpid solution by the a
Conti Giuseppe
Menconi Francesco
Moalli Angelo
Zanellato Alberto
Choi Ling-Siu
Polimeri Europa S.r.l.
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