Flexible film composition for heat seals and container with same
The present disclosure is directed to compositions and film structures suitable for heat seal production. The heat sealable flexible film structure includes: a layer (A) comprising a propylene-based plastomer or elastomer (“PBPE”) and a low density polyethylene; a layer (B), adjacent to layer (A), comprising at least 50 percent by weight of the layer (B) of an ethylene-based polymer; and an outermost layer (C) comprising a material having a melting point greater than 140° C. Weight percents are based on the total weight of the respective layer. The heat sealable flexible film structure is used to make a flexible container ( 10 ) having one or more heat seals ( 12 ). The heat seal ( 12 ) can be a frangible heat seal, a hard heat seal, or a combination thereof.
1. A flexible container comprising:
a first film and a second film, each film comprising a heat sealable flexible film structure comprising:
a seal layer (A) consisting of (i) from 35 to 80 percent by weight of the layer (A) of a propylene based plastomer or elastomer (“PBPE”) and (ii) from 20 to 65 percent by weight of layer (A) of a low density polyethylene having a melt index from 0.2 g/10 min to 50 g/10 min and a density in the range of from 0.915 g/cm 3 to 0.935 g/cm 3 ;
a base layer (B) comprising an ethylene-based polymer selected from the group consisting of high density polyethylene (HDPE), linear low density polyethylene, (LLDPE), low density polyethylene (LDPE) and combinations thereof; and
an outermost layer (C) comprising a material having a melting point greater than 140° C.;
wherein the films are arranged such that the layer (A) of each film is in contact with each other and the second film is superimposed on the first film to form a common peripheral edge; and
a heat seal is located along at least a portion of the common peripheral edge;
a hard seal wherein opposing layers (B) are in contact with each other; and
a frangible seal wherein opposing layers (A) are in contact with each other.
2. The flexible container of claim 1 wherein the seal layer (A) has a thickness less than 30 microns.
3. The flexible container of claim 1 wherein the seal layer (A) comprises from 50 wt % to 80 wt % propylene/ethylene copolymer and from 50 wt % to 20 wt % low density polyethylene.
4. The flexible container of claim 1 wherein the base layer (B) comprises a high density polyethylene having a density from 0.940 g/cc to 0.965 g/cc and a melt index less than 5.0 g/10 min.
5. The flexible container of claim 1 wherein the outermost layer (C) is a material selected from the group consisting of poly(ethylene terephthalate) (PET), polyamide, propylene homopolymer, and combinations thereof.
6. The flexible container of claim 1 further comprising an inner layer (D) disposed between layer (B) and the outermost layer (C).
7. The flexible container of claim 6 wherein the inner layer (D) comprises a polymer selected from the group consisting of a high density polyethylene, a linear low density polyethylene, a low density polyethylene, ethylene vinyl alcohol copolymer, maleic anhydride-modified polyethylene, polyamide, cyclic olefin copolymer, ethylene vinyl acetate, propylene homopolymer, vinylidene chloride polymer, and combinations thereof.
8. The flexible container of claim 6 wherein the inner layer (D) comprises a high density polyethylene having a density from 0.940 g/cc to 0.965 g/cc and a melt index less than 5.0 g/10 min.
9. The flexible container of claim 1 wherein the film structure is processed via a cast extrusion process or a blown film extrusion process.
10. The flexible container of claim 1 wherein one or more of the layers is foamed.
11. The flexible container of claim 1 wherein the hard seal is located along at least one peripheral edge and wherein the frangible seal is located in an area other than the peripheral edge.
12. The flexible container of claim 1 wherein the first film and the second film are components of a single flexible sheet, the single flexible sheet folded to superimpose the second film on the first film.
13. The flexible container of claim 1 wherein the peripheral heat seal defines a container interior, the frangible seal traverses the container interior and defining two compartments.
14. The flexible container of claim 1 wherein the base layer (B) of the first film is melted and fused to base layer (B) of the second film to form the hard seal.
15. The flexible container of claim 1 wherein the flexible container is a member selected from the group consisting of a pouch, a sachet, and a stand-up pouch.
16. The flexible container of claim 15 wherein the heat seal along at least a portion of the common peripheral edge is a combination of a hard seal and a frangible seal.
17. The flexible container of claim 1 wherein the PBPE is a propylene/ethylene copolymer having greater than 0.85 substantially isotactic sequences and a crystallinity from 1% to 30%.
18. The flexible container of claim 17 wherein the layer (A) consists of a blend of 75 wt % PBPE and 25 wt % low density polyethylene, based on total weight of layer (A); and
the blend has a density from 0.89 g/cc to 0.90 g/cc, and a melt index from 3.0 g/10 min to 4.0 g/10.
19. The flexible container of claim 17 wherein the layer (A) consists of a blend of 50 wt % PBPE and 50 wt % low density polyethylene, based on total weight of layer (A); and
the blend has a density from 0.90 g/cc to 0.91 g/cc, and a melt index from 1.0 g/10 min to 2.0 g/10 min.