Sealable Polypropylene Films With Enhanced Stability
A multi-layered sealable film and method of storing and transporting a role of the film without buckling or starring, the film comprising a core layer comprising polypropylene sandwiched between at least a first and (optionally) second tie-layer on either side of the core; a sealable layer with two sides, one side adhered to the first tie-layer; wherein at least the first tie-layer comprising a blend of polypropylene and within the range of from 5 wt % to 40 wt % of a soft polymer additive, preferably a propylene-α-olefin elastomer having within the range of from 10 wt % to 30 wt % α-olefin derived units, wherein the blend is preferably partially or completely immiscible. A roll of the inventive films can be readily stored and transported without loss due to film defects.
1 . A multi-layered sealable film comprising:
(a) a core layer comprising polypropylene sandwiched between at least a first and, optionally, a second tie-layer, on either side of the core;
(b) a sealable layer with two sides, one side adhered to the first tie-layer;
wherein at least the first tie-layer comprises a blend of polypropylene and within the range of from 5 wt % to 40 wt % of a soft polymer additive, by weight of the first tie-layer, wherein the blend of polypropylene and soft polymer additive is a heterogeneous blend characterized in having two glass transition temperatures (Tg) that are within the range of from −60° C. to +30° C.
2 . A multi-layered sealable film of claim 1 , wherein at least the first tie-layer comprises a blend of polypropylene and within the range of from 5 wt % to 40 wt % of a propylene-α-olefin elastomer, by weight of the first tie-layer, having within the range of from 10 wt % to 30 wt % α-olefin derived units.
3 . The film of claim 2 , wherein the film comprises first and second tie-layers on both sides of the core layer which are asymmetric.
4 . The film of claim 3 , wherein the second tie-layer is also adjacent to a metal-accepting skin layer.
5 . The film of claim 4 , wherein the propylene-α-olefin elastomer is substantially absent from the second tie-layer.
6 . The film of claim 2 , wherein the blend of polypropylene with the propylene-α-olefin elastomer in the first tie-layer is heterogeneous.
7 . The film of claim 2 , wherein the amount of propylene-α-olefin elastomer present in the core layer is less than 5 wt % or 3 wt % or 1 wt %, by weight of the core layer;
wherein propylene-α-olefin elastomer is substantially absent from the core layer.
8 . The film of claim 2 , wherein the melting point of the propylene-α-olefin elastomer by DSC is within the range of from 30° C. to 115° C.
9 . The film of claim 2 , wherein the glass transition temperature of the propylene-α-olefin elastomer is within the range of from −50° C. to 0° C.
10 . The film of claim 2 , wherein the crystallinity of the blend of polypropylene and propylene-α-olefin elastomer in the first tie-layer is within the range of from 20% to 36%.
11 . The film of claim 2 , wherein the blend of polypropylene and propylene-α-olefin elastomer in the first tie-layer has one glass transition temperature (Tg) that is within the range of from −50° C. to +20° C.
12 . The film of claim 2 , wherein the blend of polypropylene and propylene-α-olefin elastomer in the first tie-layer has two glass transition temperatures (Tg) that are within the range of from −60° C. to +30° C.
13 . The film of claim 2 , wherein the sealable layer is adjacent to the first tie-layer.
14 . The film of claim 14 , wherein the film has a seal strength (Hayssen) of at least 1100 g/inch at 125° C.
15 . A roll of film comprising the film of claim 2 .
16 . A method of transporting film comprising:
(a) providing a film;
(b) rolling the film onto a spool to form a roll;
(c) loading the roll onto a transport vehicle at a geographic starting point;
(d) transporting the roll to a second geographic point, wherein the temperature change from the starting point to the second point is at least 5° C.;
(e) unloading the roll at the second point having no starring or buckling; and
(f) wherein the film comprises:
1) a core layer comprising polypropylene sandwiched between at least a first and, optionally, a second tie-layer, on either side of the core;
2) a sealable layer with two sides, one side adhered to the first tie-layer;
3) wherein at least the first tie-layer comprises a blend of polypropylene and within the range of from 5 wt % to 40 wt % of a propylene-α-olefin elastomer, by weight of the first tie-layer, and having within the range of from 10 wt % to 30 wt % α-olefin derived units.
17 . The method of claim 17 , wherein the film comprises asymmetric tie-layers on both sides of the core layer.
18 . The film of claim 18 , wherein the second tie-layer is also adjacent to a metal-accepting skin layer.
19 . The film of claim 17 , wherein the blend of polypropylene with the propylene-α-olefin elastomer in the first tie-layer is heterogeneous.
20 . The film of claim 17 , wherein the amount of propylene-α-olefin elastomer present in the core layer is less than 5 wt %, by weight of the core layer; wherein propylene-α-olefin elastomer is substantially absent from the core layer.
21 . The film of claim 17 , wherein the melting point of the propylene-α-olefin elastomer by DSC is within the range of from 30 ° C. to 115 ° C.
22 . The film of claim 17 , wherein the glass transition temperature of the propylene-α-olefin elastomer is within the range of from −50° C. to 0° C.
23 . The film of claim 17 , wherein the crystallinity of the blend of polypropylene and propylene-α-olefin elastomer in the core layer is within the range of from 20% to 36%.
24 . The film of claim 17 , wherein the blend of polypropylene and propylene-α-olefin elastomer in the core layer has one glass transition temperature that is within the range of from −50° C. to +20° C.
25 . The film of claim 17 , wherein the blend of polypropylene and propylene-α-olefin elastomer in the core layer has two glass transition temperatures that are within the range of from −60° C. to +30° C.