Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Patent
1985-12-26
1988-12-06
Ivy, C. Warren
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Polymers from only ethylenic monomers or processes of...
526 64, 526 66, 526 67, 526 72, 5261692, 526280, 526348, 5263482, 526918, 526922, 525197, 525240, 525236, 525 52, 525 53, 252 43, C08F 200, C08F 1000
Patent
active
047897147
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to novel copolymers of alpha-olefins. More specifically, it relates to novel copolymers of ethylene with other alpha-olefins which have a polymodal moecular weight distribution wherein individual modes comprising the polymer have narrow molecular weight distributions.
For convenience, certain terms that are repeated throughout the present specification are defined below:
(a) Inter-CD defines compositional variation, in terms of ethylene content, among polymer chains. It is expressed as the minimum deviation (analogous to a standard deviation) in terms of weight percent ethylene from the average ethylene composition for a given copolymer sample needed to include a given weight percent of the total copolymer sample which is obtained by excluding equal weight fractions from both ends of the distribution. The deviation need not be symmetrical. When expressed as a single number, for example, 15% Inter-CD, it shall mean the larger of the positive or negative deviations. For example, for a Gaussian compositional distribution, 95.5% of the polymer is within 20 wt% ethylene of the mean if the standard deviation is 10%. The Inter-CD for 95.5 wt% of the polymer is 20 wt% ethylene for such a sample.
(b) Intra-CD is the compositional variation, in terms of ethylene, within a copolymer chain. It is expressed as the minimum difference in weight (wt) % ethylene that exists between two portions of a single copolymer chain, each portion comprising at least 5 wt% of the chain.
(c) Molecular weight distribution (MWD) is a measure of the range of molecular weights within a given copolymer sample. It is characterized in terms of at least one of the ratios of weight average to number average molecular weight, M.sub.w /M.sub.n, and Z average to weight average molecular weight, M.sub.z /M.sub.w, where: ##EQU1## and Ni is the number of molecules of weight Mi.
Ethylene-propylene copolymers, particularly elastomers, are important commercial products. Two basic types of ethylene-propylene copolymers are commercially available; ethylene propylene copolymers and ethylene propylene terpolymers. Ethylene-propylene copolymers (EPM) are saturated compounds requiring vulcanization with free radical generators such as organic peroxides. Ethylene-propylene terpolymers (EPDM) contain a small amount of non-conjugated diolefin, such as dicyclopentadiene; 1,4-hexadiene or ethylidene norbornene, which provides sufficient unsaturation to permit vulcanization with sulfur. Such ethylene-propylene polymers that include at least two monomers, i.e., EPM and EPDM, will be hereinafter collectively referred to as ethylene-propylene copolymers.
These copolymers have outstanding resistance to weathering, good heat aging properties and the ability to be compounded with large quantities of fillers and plasticizers resulting in low cost compounds which are particularly useful in automotive and industrial mechanical goods applications. Typical automotive uses are tire sidewalls, inner tubes, radiator and heater hose, vacuum tubing, weather stripping, sponge doorseals and Viscosity Index (V.I.) improvers for lubricating oil compositions. Typical mechanical goods uses are for appliance, industrial and garden hoses, both molded and extruded sponge parts, gaskets and seals and conveyor belt covers. These copolymers also find use in adhesives, appliance parts as in hoses and gaskets, wire and cable and plastics blending.
As can be seen from the above, based on their respective properties, EPM and EPDM find many, varied uses. It is known that the properties of such copolymers which make them useful in a particular application are, in turn, determined by their composition and structure. For example, the ultimate properties of an EPM and EPDM copolymer are determined by such factors as composition, compositional distribution, sequence distribution, molecular weight, and molecular weight distribution (MWD).
The efficiency of peroxide curing depends on composition. As the ethylene level increases, it can be shown t
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Cozewith Charles
Ju Shiaw
Verstrate Gary W.
Exxon Research & Engineering Co.
Ivy C. Warren
Walker Alex H.
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