Film and sheet for folding packaging containers

Abstract

A film of biodegradable polylactic acid polymers (PLA) and copolymers are produced by biaxially orienting single and multilayer extrusions. The film and sheets are stiff, have excellent optical properties and show excellent retained folding and creasing properties making them especially desirable for the production of folded box like containers. The surface layer(s) of the film and sheet may be heat sealable or modified with a particle to give improved coefficient of friction (COF), blocking resistance, reduced static generation, improved winding and improved package formation on packaging machines.

What is claimed is: 
     
         1 . A high clarity container produced from a bi-axially oriented heat stable composite film of from 4 to 30 mils thickness which has been stretched in both the machine direction and transverse direction by a ratio of 2 to 6 times consisting essentially of, an inner layer of polylactic acid with a first and second surface and attached to one or both of said first and second inner layer surfaces one or more additional skin layers of the same or different polylactic acid resins as the inner layer, at least one of the skin layers containing spherical particles for the purpose of reducing the coefficient of friction (COF) of the composite film, the container produced by folding or creasing combined with sealing or gluing along at least one edge or between two surfaces to create a sealed container. 
     
     
         2 . A high clarity container produced from film according to  claim 1 , by folding or creasing and sealing or gluing along an edge with a folding and reclosable flap on at least one surface of the container for the purpose of gaining access to the interior of the package. 
     
     
         3 . A folding thermoformed high clarity container from a bi-axially oriented heat stable composite film of from 4 to 30 mils thickness which has been stretched in both the machine direction and transverse direction by a ratio of 2 to 6 times consisting essentially of, an inner layer of polylactic acid with a first and second surface and attached to one or both of said first and second inner layer surfaces one or more additional skin layers of the same or different polylactic acid resins as the inner layer, the skin layers containing spherical particles for the purpose of reducing the coefficient of friction (COF) of the composite film, with a hinged fold for repetitive opening and closing of the container in conjunction with a means for sealing or holding the container in a closed configuration. 
     
     
         4 . The high clarity container of  claim 1  wherein the polylactic acid skin layers are of the same polymer as the inner layer. 
     
     
         5 . The high clarity container of  claim 1  wherein the skin layers are of a lower melting polylactic acid composition than the inner layer. 
     
     
         6 . The high clarity container of  claim 1  wherein the skin layers are of a lower crystallinity than the inner layer. 
     
     
         7 . The high clarity container of  claim 1  wherein one skin layer is of a different polylactic acid composition than the other skin layers. 
     
     
         8 . The high clarity container of  claim 1  wherein one skin layer does not contain the spherical particles. 
     
     
         9 . The high clarity container of  claim 1  wherein the spherical particles are a crosslinked polymethylsilsesquioxane particles. 
     
     
         10 . The high clarity container of  claim 1  wherein the spherical particles are a crosslinked acrylic resin particles. 
     
     
         11 . The high clarity container of  claim 1  wherein the spherical particles are composed of a polymeric substance. 
     
     
         12 . The high clarity container of  claim 1  wherein the spherical particles are present in a range of from 0.01% to 0.5% (100 to 5000 ppm) by weight of the polylactic acid of the skin layer. 
     
     
         13 . The high clarity container of  claim 1  wherein one or both first and second inner layer surfaces are subjected to corona, flame or plasma treatment. 
     
     
         14 . The high clarity container of  claim 1  wherein at least one intermediate skin layer is added between the inner layer and outer skin layers. 
     
     
         15 . The high clarity container of  claim 1  wherein intermediate skin layers are attached to the first surface and second surface of the inner layer and located between the inner layer and outer skin layers. 
     
     
         16 . The high clarity container of  claim 15  wherein at least one of the intermediate skin layers are colored with a transparent dye. 
     
     
         17 . The high clarity container of  claim 1  wherein the inner layer is colored with a transparent dye. 
     
     
         18 . The high clarity container of  claim 1  wherein at least one of the skin layers are colored with a transparent dye.