Abstract There are disclosed opaque, biaxially oriented polymeric film structures each comprising a thermoplastic polymer matrix material, e.g., polypropylene, within which is located a stratum of voids, and positioned within each of at least a substantial number of the voids is at least one spherical void-initiating solid particle (i.e., a cavitating agent) of cross-linked polystyrene (CLPS) which is phase-distinct and incompatible with the matrix material, the volume of the particle being substantially less than the volume of the void, with one generally cross-sectional dimension of the particle at least approximating a corresponding cross-sectional dimension of the void. Also disclosed is a method of preparing the foregoing film structure by extruding into a film a combination of the matrix material and CLPS particles dispersed therein, and biaxially orienting the film either simultaneously or sequentially.
An opaque, biaxially oriented polymeric film structure comprising a thermoplastic polymer matrix material within which is located a stratum of voids, and positioned within at least a substantial number of each of said voids is at least one spherical void-initiating solid particle of cross-linked polystyrene which is phase-distinct and incompatible with said matrix material, the volume of said particle being substantially less than the volume of said void, with one generally cross-sectional dimension of said particle at least approximating a corresponding cross-sectional dimension of said void.
Claim 2
Dependent Claim
86 words
An opaque, biaxially oriented polymeric film structure comprising a thermoplastic polymer matrix material within which is located a stratum of voids, and positioned within at least a substantial number of each of said voids is at least one spherical void-initiating solid particle of cross-linked polystyrene which is phase-distinct and incompatible with said matrix material, the volume of said particle being substantially less than the volume of said void, with one generally cross-sectional dimension of said particle at least approximating a corresponding cross-sectional dimension of said void.
Claim 3
Dependent Claim
13 words
The film structure of claim 1 wherein said polymeric matrix material is polypropylene.
Claim 4
Dependent Claim
18 words
The film structure of claim 2 wherein said particle is from 0.1 to about 10 microns in size.
Claim 5
Dependent Claim
14 words
The film structure of claim 3 wherein said cross-linked polystyrene is cross-linked with divinylbenzene.
Claim 6
Dependent Claim
18 words
The film structure of claim 1 having on at least one surface thereof a void-free thermoplastic skin layer.
Claim 7
Dependent Claim
11 words
The film of claim 5 wherein said skin layer is transparent.