Back to results
US 4,925,602 AGranted
Method for improving the crimping of polyolefin filter tow
AssigneeFilter Materials Limited
InventorsMichael Hill, Walter A. Nichols
Life of this patent
Estimating the term…
Abstract
A method is provided for heating fibrillated polyolefin film prior to crimping, to improve the crimping, and thus the yield and variability as a filter, of the tow. The fibrillated tow is crimped while still hot from the heating step. The resulting fibers have more uniform crimping at higher levels than those not subject to heating.
Claims19
A method of making polyolefin filter tow, said method comprising, in the listed order, the steps of:
- forming a polyolefin film having a molecular structure;
- orienting said molecular structure by heating said film to just below the melting point of said film and stretching said heated film;
- fibrillating said oriented film to form an interconnected fiber web;
- applying heat to said fibrillated web to raise its temperature above ambient temperature;
- ending the application of heat to said fibrillated web;
- crimping said heated fibrillated web to apply thereto a crimp having a crimp frequency of at least about 40 crimps per inch;
- and
- forming said crimped fibrillated web into filter tow, said filter tow having a maximum yield of at least about 85%.
5 more elements
Dependencies are inferred from the claim text.