| 摘要 |
Novel processes for preparing a heat shrinkable film by first forming a polyolefinic film on a three-roll calender in which the second and third rolls rotate at about the same speed and the first roll rotates at a slower speed, the top roll is heated to a temperature above the melting point of the polyolefinic material, the middle roll is heated to an elevated temperature below its melting point, and the bottom roll is chilled relative thereto; thereafter subjecting one surface of the resulting film to irradiation from a low energy electron beam at a voltage such that the irradiation dose at the halfdepth of the film is approximately one half the dose at the irradiated surface and at a current to film surface speed ratio such that the surface dose would effect crosslinking sufficient to impart to said film a 100% modulus at 150.degree.C of from about 10 to about 100 pounds per square inch, if the dose at any depth in the film were substantially equal to the surface dose; and then subjecting the opposed surface of the film to irradiation from a low energy beam at a voltage and at a current to speed ratio substantially equal to that in the preceding step, such that the 100% modulus at 150.degree.C of the film as a whole is about 10 to about 100 pounds per square inch and the film is characterized as being substantially uniformly crosslinked throughout its thickness. In the preferred embodiment of this invention a per se known adhesive layer may be applied to provide a heat shrinkable adhesive tape.
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