Patent ID: 9548160
Date: 2017-01-17
CPC Classifications: C08J,H01G

Claim:
1. A capacitor film prepared by biaxially drawing a cast raw sheet, wherein the cast raw sheet is prepared by heating and melting a polypropylene resin and extruding the resin from a T-die, wherein the extruded resin is cooled and solidified on at least one metal drum, the temperature of which is maintained at 90 to 120° C., wherein the polypropylene resin has: a weight average molecular weight, determined by gel permeation chromatography, of 290,000 or more and 370,000 or less; and a molecular weight distribution Mw/Mn of 7.1 to 8.2; wherein the resin comprises; an isotactic component in a proportion of 97.2-97.8% by mass when measured by sequential extraction, and a stereoblock component in a proportion of 0.9% by mass or more and 1.3% by mass or less, when measured by said sequential extraction as the proportion soluble in n-pentane, n-hexane and n-heptane; wherein the cast raw sheet comprises a β-form in a proportion of 9% or more and 17% or less, the proportion being determined by X-ray diffraction intensity; and wherein the film has a thickness of 2.8 μm to 4.0 μm.