Heat resistant thermal seal film
Multilayer films are disclosed. The multilayer film may include a core layer and a heat seal layer where the heat seal lay comprises a polypropylene copolymer and a polyethylene copolymer. The polypropylene copolymer of the heat seal layer has specific properties such as ethylene content and iCCD elution profile to contribute to the desirable properties of the film. The multilayer film can form effective heat seals, even when in contact with heated contents. The multilayer film can be formed into a bag where the bag is suitable for carrying hot or heated contents.
1 . A multilayer film comprising at least (A) a core layer that comprises a polyolefin polymer and (B) a heat seal layer, wherein the heat seal layer comprises:
a) from 30 to 80 weight percent of a polypropylene copolymer having:
i) a total ethylene content (Et) from 5 to 30 weight percent, based on the total weight of the polypropylene copolymer; and
ii) a density from 0.80 to 0.95 g/cc; and
iii) a melt index at 230° C. of no more than 5 dg/min; and
iv) an iCCD profile where in iCCD elution testing from 25° C. to 150° C., elutes at least 10 weight percent of the polypropylene copolymer from 25° C. to 35° C. and no more than 30 weight percent of the polypropylene copolymer between 35° C. and 100° C.; and
b) from 20 to 70 weight percent of a polyethylene copolymer having a density from 0.895 to 0.925 g/cc and melt index at 190° C. below 3 dg/min.
2 . The multilayer film of claim 1 , wherein the core layer comprises a polyethylene having a density from 0.895 to 0.930 g/cc and a melt index at 190° C. below 3 dg/min.
3 . The multilayer film of claim 1 , wherein the polypropylene copolymer of the heat seal layer has:
a) a total ethylene content (Et) from 8 to 20 weight percent, based on the total weight of the polypropylene copolymer; and
b) a density from 0.895 to 0.910 g/cc; and
c) a melt index (I2) at 230° C. of 1 to 3 dg/min.
4 . The multilayer film of claim 1 , wherein the core layer comprises from 25 to 65 weight percent of the polypropylene copolymer, and from 35 to 75 weight percent of a polyethylene having a density from 0.895 to 0.930 g/cc and a melt index at 190° C. below 3 dg/min.
5 . The multilayer film of claim 1 , wherein the core layer and the heat seal layer comprise polyethylene having a density from 0.905 to 0.922 g/cc and a melt index at 190° C. from 0.1 to 1.0 dg/min.
6 . The multilayer film of claim 1 , wherein the polypropylene copolymer has an iCCD elution profile where in iCCD elution testing from 25° C. to 150° C., from 12 to 18 weight percent of the polypropylene copolymer elutes at temperatures from 25° C. to 35° C.
7 . The multilayer film of claim 1 , wherein the polypropylene copolymer has an iCCD elution profile where in iCCD elution testing from 25° C. to 150° C., from 10 to 20 weight percent of the polypropylene copolymer elutes at temperatures between 35° C. and 100° C.
8 . The multilayer film of claim 1 , wherein the polypropylene copolymer in the heat seal layer is an impact copolymer.
9 . The multilayer film of claim 1 , wherein the polypropylene copolymer in the heat seal layer is an impact copolymer and wherein:
a) in iCCD elution testing from 25° C. to 150° C., from 12 to 18 weight percent of the polypropylene copolymer elutes at temperatures between 25° C. and 35° C.; and
b) in iCCD elution testing from 25° C. to 150° C., from 10 to 20 weight percent of the polypropylene copolymer elutes at temperatures between 35° C. and 100° C.
10 . The multilayer film of claim 1 , wherein the heat seal layer comprises from 35 to 50 weight percent of the polypropylene copolymer.
11 . The multilayer film of claim 1 , wherein the core layer comprises from 25 to 65 weight percent of a polypropylene copolymer, and from 35 to 75 weight percent polyethylene having a density from 0.895 to 0.930 g/cc and a melt index at 190° C. below 3 dg/min, wherein the polypropylene copolymer of the core layer has:
a) a total ethylene content (Et) from 8 to 20 weight percent, based on the total weight of the polypropylene copolymer; and
b) a density from 0.895 to 0.910 g/cc; and
c) a melt index (I2) at 230° C. of 1 to 3 dg/min.
12 . The multilayer film of claim 11 , wherein the core layer and the heat seal layer comprise polyethylene having a density from 0.905 to 0.922 g/cc and a melt index at 190° C. from 0.1 to 1.0 dg/min.
13 . The multilayer film of claim 1 , wherein the heat seal layer comprises:
a) from 35 to 50 weight percent of the polypropylene copolymer, wherein:
i) the total ethylene content (Et) of the polypropylene copolymer is from 8 to 20 weight percent, based on the total weight of the polypropylene copolymer; and
ii) the density of the polypropylene copolymer is from 0.895 to 0.910 g/cc; and
iii) the melt index (I2) at 230° C. of the polypropylene copolymer is 1 to 3 dg/min,
iv) in iCCD elution testing from 25° C. to 150° C., from 12 to 18 weight percent of the polypropylene copolymer elutes at temperatures between 25° C. and 35° C.; and
v) in iCCD elution testing from 25° C. to 150° C., from 10 to 20 weight percent of the polypropylene copolymer elutes at temperatures between 35° C. and 100° C.; and
b) from 50 to 65 weight percent of the polyethylene copolymer having a density from 0.900 to 0.912 g/cc and a melt index from 0.5 to 1.5 dg/min.
14 . A bag comprising the multilayer film from claim 1 .
15 . A process to package heated materials, comprising the steps of:
a) placing materials with a temperature of at least 90° C. in a bag that is open at one end, and
heat sealing the open end of the bag to fully close the bag, wherein the bag comprises the multilayer film from claim 1 .