Stock material or miscellaneous articles – Coated or structually defined flake – particle – cell – strand,... – Particulate matter
Patent
1991-07-29
1994-06-07
Teskin, Fred
Stock material or miscellaneous articles
Coated or structually defined flake, particle, cell, strand,...
Particulate matter
428402, 428447, 428523, 526 73, 526116, 526125, 526151, 526159, 526165, 526169, 5261691, 5261692, 526348, 5263486, 525342, 525387, 204 59QM, 204242, B32B 2504, C08F21008
Patent
active
053188497
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a new class of polyolefin rubbers and to a process for their preparation.
There are already known polyolefin rubbers consisting of copolymers of ethylene and of alpha-olefin which have a density of between 0.860 and 0.885. The alpha-olefin chosen for the constitution of these polyolefin rubbers is generally propylene or 1-butene. Various processes for obtaining such polyolefin rubbers are also known. It has already been noted that, owing to its characteristics, each process produces a class of polyolefin rubbers which have a particular macromolecular structure and are particularly suited to being employed efficaciously in some particular application or other.
As is well known to specialists in polyolefin rubbers, the parameters to be taken into consideration in order to define their macromolecular structure completely are:
the polydispersity index Mw/Mn (ratio of the weight-average mass to the number-average mass), analysis),
Thus, a first class of polyolefin rubbers is known, which are marketed by the company Montedison under the trademark Dutral.RTM., consisting of copolymers of 65 to 80 mol % of ethylene and from 20 to 35 mol % of propylene, which have a relative density of 0.850 to 0.870, containing no residual crystallinity and therefore having no crystalline melting point, and which have an average geometric molecular mass of 90 to 100 kg/mole and a polydispersity index of between 2.2 and 2.9. A second class of polyolefin rubbers is also known, which are marketed by the company Mitsui under the trademark Tafmer.RTM., consisting of copolymers of 78 to 92 mol % of ethylene and from 8 to 22 mol % of an alpha-olefin chosen from propylene and 1-butene, which.. have a relative density of 0.860 to 0.890, a residual crystallinity of 1 to 14%, a crystalline melting point J of 75.degree. C. and an average geometric molecular mass of 60 to 120 kg/mole and a polydispersity index of between 2.2 and 2.7.
Furthermore, the utility value of polyolefin rubbers, especially their suitability for being employed in some applications such as especially the insulation and filling of low-voltage to high-voltage electrical cables and the manufacture of flexible products such as tubing or shoe components, is generally measured by the following properties, after crosslinking with a peroxide system:
The problem which the present invention aims to solve consists in improving the property compromise of polyolefin rubbers when compared with the properties of those known at present, especially by improving, at a given density, the elongation at break and the Mattia flexure after crosslinking.
Thus, the first subject of the present invention is a polyolefin rubber consisting of an ethylene/propylene and/or 1-butene copolymer, which has a melt index of approximately between 0.3 and 15 dg/min and a relative density of approximately between 0.860 and 0.885, comprising from 74 to 91 mol % of units derived from ethylene and from 9 to 26 mol % of units derived from propylene and/or 1-butene, characterised by a crystalline melting point J of approximately between 100.degree. and 125.degree. C. Subsidiarily, the polyolefin rubber according to the invention may be characterised by at least one of the following features: approximately between 4 and 8, approximately between 35 and 70 kg/mole, in mol %) of units derived from propylene and from 1-butene, which is expressed by the double equation: described hereinafter) of approximately between 2 and 15%.
As used in the present invention, the crystalline melting point J means the temperature determined at the maximum of the melting curve after crystallisation obtained by subjecting the copolymer sample to the following three-stage process: 150.degree. C., then to 10.degree. C., then again 150.degree. C.
The degree of residual crystallinity according to the present invention is determined by X-ray diffraction, on a copolymer sample which has been subjected to cooling at the rate of 5.degree. C. per hour from 190.degree. C. to room temperature.
The average geometric
REFERENCES:
patent: 3173903 (1965-03-01), Lukach et al.
Breant Patrice
Mehalla Hacene
Morese-Seguela Brigitte
Sofrapo-Commerciale
Teskin Fred
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