Polypropylene melt-blown sealant films for retort packaging
A polypropylene containing resin composition suitable for use in forming films by the air quenched melt-blown film process for use as a sealing layer in a laminate for retort pouches, The resin composition includes from 80 to 98 percent by weight of a coupled impact propylene copolymer and from 2 to 20 percent by weight of a propylene-ethylene copolymer having from 2 to 10 percent by weight units derived from ethylene, wherein the composition has a melt flow rate of from 0.1 to 2.5 grams/10 minutes.
1. A retort pouch comprising:
a first sheet and an opposing second sheet, each sheet comprising
an outer layer comprising a polyester,
an innermost seal layer consisting of a single layer film comprising a polymeric blend of
(A) from 90 to 98 percent by weight of a coupled impact propylene copolymer comprising from 3 to 11 percent by weight of units derived from ethylene based on the total weight of the impact propylene copolymer and comprising a propylene homopolymer continuous phase and an elastomeric phase comprising an ethylene-propylene copolymer, and
(B) from 2 to 10 percent by weight of a propylene-ethylene copolymer having from 3.5 to 7.0 percent by weight of units derived from ethylene, the blend having a melt flow rate from 0.1 to 2.5 grams/10 minutes as measured in accordance with ASTM D1238 condition L;
a barrier layer located between the outer layer and the seal layer, the barrier layer selected from the group consisting of nylon, polyvinyl chloride, ethylene vinyl alcohol, polyethylene, polypropylene, aluminum foil, metallized nylon, and metallized polyester; and
a heat seal along a common periphery of the first sheet and the second sheet;
wherein the innermost seal layer is bonded directly to the barrier layer by an adhesive layer, and
wherein the retort pouch is wrinkle-free post retort and has an average Ra value less than 0.480 (Gausian, 2.5 mm filter), wherein the retort pouch is retorted at 130° C. for 30 minutes.
2. The retort pouch of claim 1 comprising a first adhesive layer located between the outer layer and the barrier layer, and a second adhesive layer located between the barrier layer and the seal layer.
3. The retort pouch of claim 1 wherein the heat seal is formed at a sealing temperature of 200° C. and a sealing pressure of 275 kPa and the heat seal has a seal strength greater than 40 N/15 mm.
4. The retort pouch of claim 1 wherein the outer layer is polyethylene terephthalate and the barrier layer is aluminum foil.
5. The retort pouch of claim 1 wherein the seal layer is a blown film.