US 5,178,942 A · Multi-layer opaque film structures tailored to end-use requirements

Abstract

An opaque, biaxially oriented polymeric film structure, produced by orienting the film to a degree which provides low light transmission and improved machinability. The film structure includes a thermoplastic polymer matrix core layer having a first surface and a second surface, within which is located a strata of voids; positioned at least substantially within a substantial number of the voids is at least one spherical void-initiating particle which is phase distinct and incompatible with the matrix material, the void space occupied by the particle being substantially less than the volume of the void; the population of the voids in the core being such as to cause a significant degree of opacity, the core layer including a light absorbing pigment of lamellar morphology; a first non-voided thermoplastic polymer intermediate layer having a first surface and a second surface, the second surface of the first intermediate layer adhering to the first surface of the core layer; and a second non-voided thermoplastic polymer intermediate layer having a first surface and a second surface, the second surface of the second intermediate layer adhering to the second surface of the core layer; wherein the level of light transmission of the film is less than 10% and the degree of orientation is about 8 TDO by less than about 5 MDO.

Claims20

Dependent claims

An opaque, biaxially oriented polymer film structure, produced by orienting the film to a degree which provides low light transmission and improved machinability, comprising:

(a) a thermoplastic polymer matrix core layer having a first surface and a second surface, within which is located a strata of voids;
positioned at least substantially within a substantial number of said voids is at least one spherical void-initiating particle which is phase distinct and incompatible with said matrix material, the void space occupied by 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;
the population of said voids in said core being such as to cause a significant degree of opacity, said core layer including a light absorbing pigment of lamellar morphology;
(b) a first non-voided thermoplastic polymer intermediate layer having a first surface and a second surface, said second surface of said first intermediate layer adhering to said first surface of said core layer;
and
(c) a second non-voided thermoplastic polymer intermediate layer having a first surface and a second surface, said second surface of said second intermediate layer adhering to said second surface of said core layer;
herein the level of light transmission of the film is less than 10% and the degree of orientation is about 8 TDO by less than about 5 MDO.

4 more elements

A process for preparing an opaque, biaxially oriented polymeric film structure of low light transmission and improved machinability, comprising the steps of:

(a) mixing a major proportion of a first thermoplastic polymeric material with a minor proportion of a first material of higher melting point or having a higher glass transition temperature than the first thermoplastic polymeric material to produce a core layer mixture and a minor amount of a light absorbing pigment of lamellar morphology;
(b) heating the core layer mixture produced in step (a) to a temperature of at least above the melting point of the first thermoplastic polymeric material;
(c) dispersing the first material of higher melting point or higher glass transition temperature of the mixture produced in step (a) uniformly throughout the molten first thermoplastic polymeric material in the form of microspheres;
(d) mixing a second thermoplastic polymeric material to produce a first intermediate layer mixture;
(e) heating the intermediate layer mixture produced in step (d) to a temperature of about the melting point of the second thermoplastic polymeric material;
(f) mixing a third thermoplastic polymeric material to produce a second intermediate layer mixture;
(g) heating the second intermediate layer mixture produced in step (f) to a temperature of about the melting point of the second thermoplastic polymeric material;
and
(h) forming a biaxially oriented coextruded film structure from the core layer mixture, the first intermediate layer mixture and the second intermediate layer mixture, said forming step conducted at a temperature and to a degree to form a strata of opacifying voids within the core layer;
wherein the degree of orientation is about 8 TDO by less than about 5 MDO.

7 more elements

Dependencies are inferred from the claim text.

Multi-layer opaque film structures tailored to end-use requirements

Life of this patent

Multi-layer opaque film structures tailored to end-use requirements

Life of this patent

Abstract

Claims20