Silane-crosslinkable, substantially linear ethylene polymers and

Details Silane-crosslinkable, substantially linear ethylene polymers and Silane-crosslinkable, substantially linear ethylene polymers and

1996-10-03

1998-10-20

Wu, David W.

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

Synthetic resins

Compositions to be polymerized by wave energy wherein said...

525288, C08J 328

Patent

active

058247181

DESCRIPTION:

BRIEF SUMMARY
This invention relates to ethylene polymers. In one aspect, the invention relates to substantially linear ethylene polymers while in another aspect, the invention relates to silane crosslinkable substantially linear ethylene polymers. In yet another aspect, the invention relates to the various uses of these silane crosslinkable polymers, the uses including cable insulation, weatherstripping and fibers.
For many applications, e.g. wire and cable insulation, weatherstripping, fibers, seals, gaskets, foams, footware, tubes, pipes, bellows, tapes, etc., certain selected properties of articles manufactured from polyolefins can be enhanced by introducing chemical linkages between the polymeric molecular chains which constitute the polymer, during, or preferably following, the shaping or molding process. These chemical linkages between different polymeric molecular chains are generally known as "crosslinks". Crosslinks can be introduced between different molecular chains of a polyolefins by a number of mechanisms, one of which is to graft to the individual polymer backbones or chains that constitute the bulk polymer with a chemically reactive compound in such a manner that the grafted compound on one backbone may subsequently react with a similar grafted compound on another backbone to form the crosslink. Exemplary of this method is the "silane crosslinking" method.
Suitable silanes for the silane crosslinking process include those of the general formula ##STR1## in which R' is a hydrogen atom or methyl group; x and y are 0 or 1 with the proviso that when x is 1, y is 1; n is an integer from 1 to 12 inclusive, preferably 1 to 4, and each R independently is a hydrolyzable organic group such as an alkoxy group having from 1 to 12 carbon atoms (e.g. methoxy, ethoxy, butoxy), aryloxy group (e.g. phenoxy), araloxy group (e.g. benzyloxy), aliphatic acyloxy group having from 1 to 12 carbon atoms (e.g. formyloxy, acetyloxy, propanoyloxy), amino or substituted amino groups (alkylamino, arylamino), or a lower alkyl group having 1 to 6 carbon atoms inclusive, with the proviso that not moe than one of the three R groups is an alkyl. Such silanes may be grafted to a suitable polyolefins by the use of a suitable quantity of organic peroxide, either before or during a shaping or molding operation. Additional ingredients such as heat and light stabilizers, pigments, etc., also may be included in the formulation. In any case, the crosslinking reaction takes place following the shaping or molding step by reaction between the grafted silane groups and water, the water permeating into the bulk polymer from the atmosphere or from a water bath or "sauna". The phase of the process during which the crosslinks are created is commonly referred to as the "cure phase" and the process itself is commonly referred to as "curing".
With respect to wire and cable insulation applications, U.S. Pat. No. 4,144,202 by Ashcraft, et al., describes treeing, a phenomenon that is known to occur in olefin-based cable insulation. As here used, "cable" means all forms of electrical conductors specifically including wire and all forms of power cable, that is low, medium and high voltage cable. Ashcraft, et al. teach that treeing is a significant factor in the useful life of cable insulation, and thus in the useful life of the cable itself. As such, cable insulation typically includes a treeing inhibitor which can be either in the form of a crosslinking agent, for example, dicumyl peroxide, or in the form of a noncrosslinking agent, for example, an additive such as one of the organo silanes taught by Ashcraft, et al.
U.S. Pat. No. 5,246,783 to Spenadel, et al., describes a cable insulation comprising a polymer selected from the group consisting of ethylene polymerized with at least one comonomer selected from the group consisting of C.sub.3 to C.sub.20 .alpha.-olefins and C.sub.3 -C.sub.20 polyenes, the polymer having a density in the range of 0.86 g/cm.sup.3 to 0.96 g/cm.sup.3, a melt index in the range of 0.2 dg/min to 100 dg/min, a molecular weight distribu

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Abstract of JP-A-54 005 584.
Ramamurthy, Journal of Rheology, "Wall Slip in Viscous Fluids and Influence of Materials of Construction", 30(2), pp. 337-357, (1986).

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