Method for making multilayer polyester film
AssigneeMinnesota Mining and Manufacturing Company
InventorsBrandt K. Carter, Raymond L. Lucking, James A. Klein, Sheldon J. Israel
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Abstract
A multilayer polyester film, and a method for making the same, is provided. The film consists of alternating layers of polyethylene terephthalate and polyethylene naphthalate. Biaxial orientation and subsequent restrained heat setting of these materials results in thin films with tensile moduli in both stretch directions well in excess of the values obtained with monolithic films of either material. In some embodiments, a slippery surface is imparted to the film without the use of conventional slip agents.
Claims41
A method for making a multilayer polyester film, comprising the steps of:
- providing a multilayer film comprising first, second, and third layers, wherein at least one of the first and third layers comprises a naphthalene dicarboxylic acid polyester and wherein the second layer comprises a terephthalic acid polyester;
- and
- orienting the film in at least one direction to a stretch ratio R.sup.6 such that R.sup.6 >k, where k is the maximum stretch ratio obtainable, under the same stretch conditions, for a monolithic film of the naphthalene dicarboxylic acid polyester having the same dimensions.
A method for making a multilayer polyester film, comprising the steps of:
- providing a first resin comprising polyethylene terephthalate;
- providing a second resin comprising polyethylene naphthalate;
- extruding the first and second resin into a multilayer film in which a layer comprising the first resin is disposed between layers comprising the second resin;
- and
- heating the layer comprising the first resin at a sufficient temperature, and for a sufficient amount of time, to induce crystallization in the first resin.
A method for making a multilayer polyester film, comprising the steps of:
- providing a first resin comprising polyethylene terephthalate;
- providing a second resin comprising polyethylene naphthalate;
- extruding the first and second resin into a multilayer film in which a layer comprising the first resin is disposed between layers comprising the second resin;
- stretching the film in at least the transverse direction;
- passing the film through at least one heat zone having a temperature of about 177.degree. C. to about 235.degree. C.;
- and
- relaxing the film in the transverse direction.
A method for improving the modulus of a multilayer film, comprising the steps of:
- providing a multilayer film comprising first, second and third layers, wherein the second layer comprises polyethylene terephthalate and is disposed between the first and third layers, and wherein at least one of the first and third layers comprises polyethylene naphthalate;
- and
- stretching the multilayer film to a stretch ratio of at least about 5.5.
A method for making a multilayer polyester film, comprising the steps of:
- providing a first resin comprising polyethylene terephthalate;
- providing second and third resins;
- extruding the first, second, and third resins into a multilayer film in which at least one layer comprising the first resin is disposed between a layer comprising the second resin and a layer comprising the third resin;
- heating the film to crystallize the first resin;
- and
- stretching the film in at least one direction.
Dependencies are inferred from the claim text.