Lustrous satin appearing, opaque film compositions and method of preparing same
AssigneeMobil Oil Corporation
InventorsCharles R. Ashcraft, Hee C. Park
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Abstract
The present invention is directed to an opaque, biaxially oriented polymeric film structure of lustrous satin appearance comprising a thermoplastic core matrix having a strata of voids; said voids being created by the inclusion within the matrix material of spherical void-initiating solid particles which are incompatible with the matrix material. The void space occupied by the particle is substantially less than the volume of the void. The polymer matrix material is extruded in the form of a film and positioned on opposite surfaces of the film are void free, transparent thermoplastic skin layers adhering to said surfaces. The structure has excellent opacity and extremely high gloss measurement and a lustrous satin appearance.
Claims32
An opaque, biaxially oriented polymeric film structure of lustrous satin appearance comprising:
- a core thermoplastic polymer matrix material within which is located a strata of voids;
- positioned at least substantially within at least a substantial number of each of said voids, is at least one spherical void-initiating solid 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;
- void-free, transparent, thermoplastic skin layers adhering to the surfaces of said core layer, said skin layers being of a thickness such that the outer surfaces thereof do not, at least substantially, manifest the surface irregularities of said core layer;
- the population of voids in said core being such as to cause a degree of opacity of less than 70% light transmission;
- said structure having a 45.degree. gloss measurement greater than 100%.
A process for preparing a film structure of lustrous satin appearance comprising:
- mixing a major proportion of a first thermoplastic polymeric material with a minor proportion of a second material of a higher melting point or having a higher glass transition temperature than said first material;
- heating the core mixture to a temperature of at least above the melting point of said first material;
- dispersing said second material uniformly throughout the molten first material in the form of microspheres;
- forming a biaxially oriented core layer of said core mixture, said oriented layer having transparent thermoplastic skin films adherent thereto;
- said core layer having been biaxially oriented at a temperature and to a degree to form a strata of opacifying closed cell voids of dimensions X, Y and Z wherein dimensions X and Y are major dimensions and dimension Z is a minor dimension at least generally corresponding to the diameter of said microspheres;
- said skin films being at least substantially void-free and of a thickness which will not manifest surface irregularities of said core layer.
A process for preparing a film structure of lustrous satin appearance comprising:
- mixing a major proportion of polypropylene with a minor proportion of a nylon to form a core mixture;
- heating the mixture to effect melting of both materials;
- uniformly dispersing said nylon throughout the molten polypropylene in the form of microspheres;
- reducing the temperature to below the melting point of the nylon while maintaining the polypropylene molten;
- melting a separate proportion of polypropylene;
- coextruding said core mixture with the melted polypropylene to form a core layer having skin films of polypropylene on both sides thereof;
- biaxially orienting the film structure at a temperature and to a degree to form a strata of opacifying closed cell voids in said core layer, said voids having dimensions X, Y and Z, wherein dimensions X and Y are major dimensions and dimension Z is a minor dimension at least generally corresponding to the diameter of said microspheres;
- said skin films being at least substantially void-free and of a thickness which will not manifest surface irregularities of said core layer.
Dependencies are inferred from the claim text.