Patent ID: 8734700

Claim:
A process for the production of high tenacity, highly oriented polyolefin sheet having a high heat of fusion comprising: a) feeding a metered amount of a ultra high molecular weight polyethylene (UHMWPE) powder to an apparatus comprising: i) a pair of vertically oriented, counter rotating heated calender rolls defining a nip therebetween and including a top and a bottom heated calender roll, the top heated calender roll having an outer surface and an apex; and ii) a metering mechanism for feeding a metered amount of the polyolefin powder to the apex wherefrom the polyolefin powder softens and agglomerates on the outer surface of the top roll and is drawn on the outer surface of the top roll to the nip by rotation of the top roll from the apex of the top roll surface to the nip; b) rolling the polymer powder through the nip under these conditions until a coherent polyolefin sheet is produced; c) once a coherent polyolefin sheet exits the nip, adjusting the temperature in the nip to a temperature between 12 degrees C. lower to 8 degrees C. greater than the temperature required to initiate the onset of melting for the particular polyolefin powder being processed as determined by differential scanning calorimetry; and d) drawing the coherent polyolefin sheet under controlled tension at a temperature of between 140 and 158° C. to produce a high tenacity, highly oriented polyolefin sheet having a high heat of fusion.