Process for preparing improved ethylene vinyl acetate compositions and films

Abstract

The present invention relates to film-forming compositions containing ethylene vinyl acetate copolymers with a vinyl acetate percentage that causes film-forming problems and processability problems and an alkylene bisoleamide which is used to enhance the film forming capabilities of these high VA content resins. The invention also relates to films prepared from these compositions and to coating compositions.

What is claimed is:  
     
         1 . A process for producing blown film comprising the steps: 
 (i) blending (a) an ethylene copolymer in pellet form, wherein the copolymer is obtained from copolymerization of ethylene and a monomer selected from an ester containing moiety; and 
 (b) an alkylene bisoleamide of the formula: R—C(O)—NHC 2 H 4 NHC(O)—R wherein R is selected from a C 4 -C 25  saturated or unsaturated hydrocarbon wherein the monomer, absent component (b), provides sticking properties to the film composition to preclude film formation or processability, wherein component (b) is not included as part of the pellet composition of (a) prior to pelletization;  
   (ii) extruding said composition through an extruder at 130° C.-260° C. to form a molten polymeric blend;    (iii) cooling the polymeric blend through a cooling or nip roll to form the blown film wherein the bisoleamide additive modifies the surface of the blown film to permit separation of the film from the cooling or nip roll and slitting of the film.    
     
     
         2 . The process according to  claim 2  wherein the blown film comprises at least one layer comprising ethylene vinyl acetate having a VA content of between 10 and 40 wt. %, N,N′-ethylene bisoleamide and an optional additional excipient selected from a polyethylene or ethylene copolymer ionomer.  
     
     
         3 . The process according to  claim 2  wherein additional layers are laminated, coated or coextruded with the blown film to produce a multilayer structure and said additional layers are selected from barrier layers or adhesive layers.  
     
     
         4 . The process according to  claim 3  wherein the barrier layer is selected from EVOH.  
     
     
         5 . A process for producing an extrusion coating comprising the steps: 
 (i) making a polymer composition comprising: 
 (a) an ethylene copolymer wherein the copolymer has ethylene and a monomer selected from an ester containing moiety; and  
 (b) an alkylene bisoleamide of the formula: R—C(O)—NHC 2 H 4 NHC(O)—R wherein R is selected from a C 4 -C 25  saturated or unsaturated hydrocarbon wherein the monomer, absent component (b), provides sticking properties to the film composition to preclude film formation or processability;  
   (ii) melting and extruding the polymer composition into a coating die;    (iii) distributing the molten polymer composition to a straight slit opening; and,    (iv) coating a substrate with the molten polymer composition from the slit opening.