Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Patent
1998-08-31
2000-08-01
Michl, Paul R.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C08J 932
Patent
active
060968044
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a low-density polymeric composition and its uses, for example as low-voltage electrical insulation, cable jacket material, buoyancy-adjusting filling for a cable or harness, dielectric material between the inner and outer conductors of a coaxial electrical cable, or thermal insulation.
2. Introduction to the Invention
Buoyant cables described in U.S. Pat. No. 4,963,420 and U.S. Pat. No. 4,110,554 use hollow glass micro-spheres to achieve low density combined with crush resistance for use in deep underwater operations. The micro-spheres are either compounded in ethylene or propylene polymers of density between 0.90 and 0.94 g/cc and extrusion-filled into the cable structure, as in U.S. Pat. No. 4,963,420; or are used alone to fill the interstices of the cable structure, thus avoiding difficulties which may occur when compounding the mixture of polymers and micro-spheres, but introducing other problems associated with the loose packing of micro-spheres.
SUMMARY OF THE INVENTION
The present invention relates to polymer/microsphere compositions which, at least in some cases, are surprisingly easy to process and may have advantageous properties for some or all of the aforementioned uses.
The invention accordingly provides a composition comprising, by volume based on the volume of the whole composition, polyolefin elastomer of room temperature density less than 0.9 g/cc and/or thermoplastic olefin/(ester or acid) copolymer elastomer, and density (not bulk density) less than 0.6 g/cc, at least 80%, preferably at least 90%, more preferably at least 95%, by weight, of the micro-balls having a maximum dimension less than 300 micrometers, preferably less than 200 micrometers.
DETAILED DESCRIPTION OF THE INVENTION
In preferred embodiments the composition comprises by volume at least 40%, more preferably at least 50%, or even up to 60%, of the micro-balls. The composition preferably comprises not more than 70% of the micro-balls.
It will be understood that the term "micro-balls" is used herein to avoid any suggestion that the micro-balls must be exactly spherical, since a certain amount of asphericity may be present in commercially available supplies of "micro-spheres" and may be tolerated in practice. It is, however, usually preferable that at least 50%, preferably at least 75%, more preferably substantially all, of the micro-balls are substantially spherical.
Advantageous processing and end-use properties have notably been found to occur when the room-temperature density of the polyolefin elastomer used according to the present invention is significantly less than the 0.9 g/cc minimum of the previously-used low-density polyolefins. It may therefore be advantageous if the density of the said polyolefin elastomer is less than 0.895 g/cc, preferably not more than 0.88 g/cc, more preferably within the range from 0.86-0.88 g/cc. The density will normally be measured by the method according to ISO 1183 (1987 Method A).
In the interests of achieving compositions of desirably low density, it is preferred that the density of the micro-balls is less than 0.5 g/cc, preferably less than 0.4 g/cc. The aforementioned restriction of the maximum dimension of the micro-balls to less than 300 .mu.m means that the preferred substantially spherical micro-balls will have a diameter less than 300 .mu.m. The micro-balls may be formed of any material suitable for the end purposes of the composition in question, but for optimum crush resistance and other properties it is generally preferred that the micro-balls are formed of glassy inorganic material. The balls may be entirely formed of foamed material, or may preferably be hollow with the shell formed of foamed or preferably solid material, provided that sufficiently low density for the present purposes is achieved. Commercially available inorganic micro-spheres marketed under the name of "fly ash", or the glass micro-spheres manufactured and marketed by the companies Emmerson and Cuming, 3M, or Glaverbel
REFERENCES:
patent: 4110554 (1978-08-01), Moore et al.
patent: 4273806 (1981-06-01), Stechler et al.
patent: 4485192 (1984-11-01), Gibbs et al.
patent: 4632948 (1986-12-01), Yamada et al.
patent: 4963420 (1990-10-01), Jarrin et al.
patent: 5196246 (1993-03-01), Kauss
patent: 5246783 (1993-09-01), Spenadel
Search Report dated May 22, 1996, for British Application No. GB 9604411.0.
Search Report mailed Jun. 10, 1997, for International Application No. PCT/GB 97/00463.
Kirkham Stanley
Sawyer Mark
Whiteley Richard Harold
Michl Paul R.
Raychem Limited
LandOfFree
Low-density polymeric composition does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Low-density polymeric composition, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Low-density polymeric composition will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-664634