Polymer blends

Details Polymer blends Polymer blends

2001-02-06

2003-08-19

Nutter, Nathan M. (Department: 1711)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

Mixing of two or more solid polymers; mixing of solid...

C525S222000, C525S238000, C525S240000, C525S241000

Reexamination Certificate

active

06608140

ABSTRACT:

The present invention relates to blends of polymers, particularly blends of polyolefins.
BACKGROUND OF THE INVENTION
The use of certain transition metal compounds to polymerise 1-olefins, for example, ethylene, is well established. The use of Ziegler-Natta catalysts, for example, those catalysts produced by activating titanium halides with organometallic compounds such as triethylaluminium, is fundamental to many commercial processes for manufacturing polyolefins. Over the last twenty or thirty years, advances in the technology have led to the development of Ziegler-Natta catalysts which have such high activities that olefin polymers and copolymers containing very low concentrations of residual catalyst can be produced directly in commercial polymerisation processes. The quantities of residual catalyst remaining in the produced polymer are so small as to render unnecessary their separation and removal for most commercial applications. Such processes can be operated by polymerising the monomers in the gas phase, or in solution or in suspension in a liquid hydrocarbon diluent. Polymerisation of the monomers can be carried out in the gas phase (the “gas phase process”), for example by fluidising under polymerisation conditions a bed comprising the target polyolefin powder and particles of the desired catalyst using a fluidising gas stream comprising the gaseous monomer. In the so-called “solution process” the (co)polymersation is conducted by introducing the monomer into a solution or suspension of the catalyst in a liquid hydrocarbon diluent under conditions of temperature and pressure such that the produced polyolefin forms as a solution in the hydrocarbon diluent. In the “slurry process” the temperature, pressure and choice of diluent are such that the produced polymer forms as a suspension in the liquid hydrocarbon diluent. These processes are generally operated at relatively low pressures (for example 10-50 bar) and low temperature (for example 50 to 150° C.). Commodity polyethylenes are commercially produced in a variety of different types and grades. Homopolymerisation of ethylene with transition metal based catalysts leads to the production of so-called “high density” grades of polyethylene. These polymers have relatively high stiffness and are useful for making articles where inherent rigidity is required. Copolymerisation of ethylene with higher 1-olefins (e.g., butene, hexene or octene) is employed commercially to provide a wide variety of copolymers differing in density and in other important physical properties. Particularly important copolymers made by copolymerising ethylene with higher 1-olefins using transition metal based catalysts are the copolymers having a density in the range of 0.91 to 0.93. These copolymers which are generally referred to in the art as “linear low density polyethylene” are in many respects similar to the so called “low density” polyethylene produced by the high pressure free radical catalysed polymerisation of ethylene. Such polymers and copolymers are used extensively in the manufacture of flexible blown film.
WO 99/12981 discloses that ethylene may be polymerised by contacting it with certain Fe, Co, Mn or Ru complexes of selected 2,6-pyridinecarboxyaldehydebis(imines) and 2,6-diacylpyridinebis(imines); and WO 99/46302 discloses catalysts comprising a mixture of complexes such as those disclosed in WO 99/12981 and other known catalysts for the polymerisation of 1-olefins, such as Phillips (chromium) catalysts, Zeigler catalysts or metallocenes.
SUMMARY OF THE INVENTION
We have discovered that blending two or more polymers, one of which has been made using a catalyst such as the above-mentioned iron catalyst, and another of which has been made using a different catalyst, can result in polymers whose properties are synergistic—ie are more than merely additive.
Thus the present invention provides a 1-olefin polymer comprising a blend of
(1) one or more polymers made using a late transition metal catalyst, and
(2) one or more polyolefins made using a free radical process or polymerised using a Phillips type (chromium oxide) catalyst, a metallocene catalyst, or a Ziegler-Natta catalyst.


REFERENCES:
patent: 6114483 (2000-09-01), Coughlin et al.
patent: WO 99/46302 (1999-09-01), None
S. Mecking, “Reactor blending with early/late transition metal catalyst combinations in ethylene polymerization,” Macromolecular: Repid Communications, vol. 20, No. 3, pp. 139-143, 1999.

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