Transparent oriented polypropylene film with high moisture vapor and oxygen barrier properties

Abstract

Described are transparent oriented polypropylene films with improved barrier properties and methods of making these films. The films and methods include a core layer comprising polypropylene, hydrocarbon resin, and polyethylene wax to improve moisture vapor barrier properties, an optional barrier layer comprising polar polymers to improve oxygen barrier properties, and optional skin layers to improve heat sealing, winding, printing, and/or adhesion.

What is claimed is: 
     
         1 . A film comprising:
 a core layer comprising high crystalline polypropylene, 2.5-25 wt % hydrocarbon resin, and 0.5-2.0 wt % polyethylene wax.   
     
     
         2 . The film of  claim 1 , wherein the core layer further comprises a fluoropolymer additive. 
     
     
         3 . The film of  claim 1 , wherein the high crystalline polypropylene is a highly isotactic crystalline propylene homopolymer with an isotactic index greater than 95%. 
     
     
         4 . The film of  claim 1 , wherein the hydrocarbon resin is in the range of 5-15 wt % of the core layer. 
     
     
         5 . The film of  claim 1 , wherein the hydrocarbon resin has a glass transition temperature (Tg) from 80 to 90° C. 
     
     
         6 . The film of  claim 5 , wherein the polyethylene wax has a crystallization temperature (Tc) less than the Tg of the hydrocarbon resin of the core layer. 
     
     
         7 . The film of  claim 1 , wherein the hydrocarbon resin has a softening temperature from 135 to 145° C. 
     
     
         8 . The film of  claim 1 , wherein the hydrocarbon resin is a fully hydrogenated water-white hydrocarbon resin. 
     
     
         9 . The film of  claim 1 , wherein the polyethylene wax is 0.75-1.5 wt % of the core layer. 
     
     
         10 . The film of  claim 1 , wherein the polyethylene wax has a melting temperature from 65 to 92° C. 
     
     
         11 . The film of  claim 1 , wherein the polyethylene wax comprises synthetic crystalline polyethylene wax, paraffin wax, Fischer-Tropsch wax, or combinations thereof. 
     
     
         12 . The film of  claim 1 , further comprising a barrier layer comprising polar polymers. 
     
     
         13 . The film of  claim 12 , further comprising a tie-layer between the core layer and the barrier layer. 
     
     
         14 . The film of  claim 1 , further comprising a heat sealable or winding skin layer comprising polyolefin. 
     
     
         15 . The film of  claim 1 , wherein the film has a haze of less than or equal to 5%. 
     
     
         16 . A multi-layer film comprising:
 a core layer comprising high crystalline polypropylene, hydrocarbon resin, and polyethylene wax;   a skin layer comprising polyolefin on a surface of the core layer; and   a barrier layer comprising polar polymers.   
     
     
         17 . The film of  claim 16 , wherein the barrier layer is on a surface of the core layer opposite the skin layer. 
     
     
         18 . The film of  claim 16 , further comprising a tie layer on a surface of the core layer opposite the skin layer between the core layer and the barrier layer. 
     
     
         19 . The film of  claim 18 , wherein the tie layer comprises polyolefin homopolymers, polyolefin copolymers, maleic anhydride grafted or copolymerized polyolefins, or combinations thereof. 
     
     
         20 . The film of  claim 16 , wherein the skin layer comprises polyolefin homopolymers, polyolefin copolymers, polyolefin termpoloymers, maleic anhydride grafted or copolymerized polyolefins, or combinations thereof. 
     
     
         21 . The film of  claim 20 , wherein the skin layer further comprises an antiblocking agent. 
     
     
         22 . The film of  claim 16 , wherein the core layer further comprises a fluoropolymer additive. 
     
     
         23 . The film of  claim 16 , wherein the hydrocarbon resin is in the range of 2.5-25 wt % of the core layer. 
     
     
         24 . The film of  claim 16 , wherein the polyethylene wax is in the range of 0.5-2.0 wt % of the core layer. 
     
     
         25 . The film of  claim 16 , wherein the film has a total thickness in the range of 10-60 μm. 
     
     
         26 . The film of  claim 16 , wherein the film has a moisture vapor transmission rate less than 0.12 g/100 in 2 /day. 
     
     
         27 . The film of  claim 16 , wherein the film has an oxygen gas transmission rate less than 1.5 cc/100 in 2 /day. 
     
     
         28 . The film of  claim 16 , wherein the film has a haze of less than or equal to 5%. 
     
     
         29 . A multilayer film comprising:
 a core layer comprising high crystalline polypropylene, hydrocarbon resin, and polyethylene wax;   a first layer on a surface of the core layer comprising polar polymers; and   a second layer on a surface of the core layer opposite the first layer comprising polar polymers.   
     
     
         30 . The film of  claim 29 , wherein the core layer further comprises a binding promoter. 
     
     
         31 . The film of  claim 29 , wherein the binding promoter comprises maleic anhydride grafted polypropylene. 
     
     
         32 . The film of  claim 29 , comprising a skin layer on a surface of the first or second layer opposite the core layer comprising polyolefin. 
     
     
         33 . A method of making a film comprising:
 coextruding a core layer comprising high crystalline polypropylene, hydrocarbon resin, and polyethylene wax with a skin layer comprising polyolefin.   
     
     
         34 . The method of  claim 33 , further comprising coextruding a barrier layer comprising polar polymers on a surface of the core layer opposite the skin layer. 
     
     
         35 . The method of  claim 33 , further comprising coating a barrier layer comprising polar polymers on a surface of the core layer opposite the skin layer. 
     
     
         36 . The method of  claim 35 , wherein the film is oriented in the machine direction prior to coating of the barrier layer. 
     
     
         37 . The method of  claim 36 , wherein the film is oriented in the transverse direction after coating the film with the barrier layer. 
     
     
         38 . The method of  claim 33 , further comprising coextruding a tie-layer comprising polyolefin on a surface of the core layer opposite the skin layer. 
     
     
         39 . The method of  claim 38 , further comprising inline or offline coating a barrier layer comprising polar polymers on a surface of the tie-layer opposite the core layer. 
     
     
         40 . The method of  claim 38 , further comprising coextruding a barrier layer comprising polar polymers on a surface of the tie-layer opposite the core layer. 
     
     
         41 . The method of  claim 33 , further comprising heat aging the film. 
     
     
         42 . The method of  claim 41 , wherein the aging temperature is lower than a Tg of the hydrocarbon resin and a melting temperature of the polyethylene wax. 
     
     
         43 . The method of  claim 41 , wherein the aging temperature is from 40-70° C. and the aging time is from 12 to 48 hours.