6 by weight of the skin layer and preferably from 0 1 to 0 3 by weight of the skin layer the relative thicknesses of the core and surface layers are chosen such that the final surface skin layer thickness after stretching may vary from 1 to 68 microns and preferably from 3 to 25 microns regardless of the final film thickness the multilayer film may be produced by sequential or simultaneous orientation with a tenter frame process common to the industry and well known in the art in the particular case of a sequential orientation the following steps are outlined the individual layers of the film are produced by melting the polymers individually in separate extruders adding the particles to the polymer feed to the extruder and mixing and dispersing in the polymer during the melting of the polymer the individual layers are filtered to insure melt cleanliness without removing the added particles and combined in a multicavity die it should be understood by those skilled in the art that the multilayer melt combination can also be done with a coextrusion feedblock or combined in a coextrusion feedblock and a multicavity die in combination as the multilayer melt is extruded from the die it is cast directly against a chilled chromed casting roll or alternatively it may be forced against a chilled chromed casting roll with the use of a pinning mechanism well known in the art such as electrostatic pinning an air knife a vacuum box an additional nip cooling roll or a combination of methods such as an air knife and electrostatic edge pinning however it is formed the cast film is cooled by the casting roll to set the.