Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Patent
1996-12-26
1999-05-11
Smith, Edward J.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Polymers from only ethylenic monomers or processes of...
526127, 526126, 526160, 526282, C08F4/642;210/18
Patent
active
059028670
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a process for the preparation of an elastomeric polymer from ethylene, an .alpha.-olefine and optionally a diene (EA(D)M), according to which these monomers are polymerised under the influence of a metallocene catalyst. More particular this invention relates to the preparation of such a polymer with a high molecular weight. For the scope of this invention `a polymer with a high molecular weight` is understood to be a polymer with a weight average molecular weight M.sub.w, determined in the manner described hereafter, of at least 50,000 kg/kmol.
Such a process is known from EP-A-347,129. In that patent publication use is made of a catalyst that is a bridged bis-radical metallocene catalyst. EADM terpolymers are prepared that have a M.sub.w of at least 110,000 kg/kmol. The terpolymers that are prepared according to EP-A-347,129 have a narrow molecular weight distribution (MWD), as can be inferred from the fact that in the examples the ratio of the weight average molecular weight and the number average molecular weight (M.sub.n ; MWD=M.sub.w /M.sub.n)) is 3.5 or smaller and in particular smaller than 3. In general, polymers with such a narrow molecular weight distribution are obtained when use is made of metallocene catalysts.
The consequence of the narrow molecular weight distribution is that the polymers have good mechanical properties, including a good compression set. The compression set is determined according to ISO 815. A drawback of the narrow molecular weight distribution, however, is that the processability of the polymers is poorer than that of polymers having a wider molecular weight distribution.
The aim of the invention is to provide a process for the preparation of elastomeric polymers with improved processability and unimpaired good mechanical properties.
This aim is achieved according to the invention because in the polymerisation a bimodal elastomeric polymer with a molecular weight distribution (MWD) of more than 3.5 is prepared, using as the metallocene catalyst a 2-indenyl metallocene having the general formula: from groups 14, 15 or 16 of the Periodic System of the Elements, bound to the Ind-group at the 2-position that the amount of water in the polymerisation medium is smaller than 0.5 ppm. According to the invention, elastomeric polymers with improved processability and good mechanical properties are obtained through polymerisation in one reactor with a high catalyst yield.
FIGS. 1, 2 and 3 are SEC chromatograms of the polymers prepared in the Examples.
It has been found that a 2-indenyl metallocene is necessary for obtaining elastomeric polymers with a wide molecular weight distribution, but that the use of this catalyst component does not result in an elastomeric polymer with a wide molecular weight distribution under all reaction conditions. A very important factor is the absence of water in the polymerisation medium. It has been found that a good catalyst activity is observed in the presence of at least 0.5 ppm water, but that a wide molecular weight distribution as well as the bimodality of the polymer are not obtained. The monomers have to be purified more than usual. The polymerisation temperature, the polymerisation time (and, where present, the diene concentration) also affect the width of the molecular weight distribution and the type of bimodality. The above will be explained with reference to examples below.
In the 2-indenyl from formula (1) k is a whole number, coupled to the valency of M in the following manner: k equals the valency of M minus 2, divided by the valency of the Q group. The Ind group and the Cp group are both bound to the metal M. The aforementioned compounds are classed as metallocene compounds (metallocenes). The Cp group may be singly or multiply substituted and may be for example an indenyl group or a fluorenyl group.
In the case of indenyl compounds known per se the R' substituent is bound to the indenyl group at the 1-position of the indenyl ring, the known indenyl compounds hence being 1-indenyl compounds. In the present inv
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Muskens Bernardus J.
Renkema Jacob
DSM NV
Smith Edward J.
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