Retort-sterilizable pouch

DETAILED DESCRIPTION OF THE INVENTION There are two basic polymer components in the compositions of the present invention: a propylene-ethylene copolymer and an ethylene-vinyl acetate copolymer.
The propylene-ethylene copolymer (which may be random, block, or any combination thereof) preferably contains between about 1.
0 and about 10 percent by weight ethylene, preferably between about 2.
0 and about 6.
0 percent by weight ethylene.
Typical melt flow values are between about 0.
5 and about 15 grams per 10 minutes, ASTM D1328 condition L, preferably between about 1 and about 10 grams per 10 minutes.
These polypropylene copolymers are preferred over high density polyethylene since they can be retorted or sterilized at 120.
degree.
C.
versus 110.
degree.
C.
for high density polyethylene.
Preferred commercial polymers include Shell 6675 and 7522 copolymers and DN 6009, a developmental Shell grade.
The ethylene-vinyl acetate copolymers which are to be used in the compositions of the invention correspond to the general formula ##STR1## The actual occurrence of the acetate substituents along the hydrocarbon chain is of a random character and thus the letter m denotes the average number of ethylene units per vinyl acetate unit in the molecule rather than the presence of regularly recurrent units having the composition given within the above brackets.
The percent by weight vinyl acetate in the copolymer ranges from about 15% to 30%, preferably from 18% to 28%.
The most useful melt indicies range from about 2 to about 12 grams per 10 minutes.
An excellent copolymer is DuPont's Elvax 360 which has a melt flow of 6.
0, condition E, and contains about 25% w vinyl acetate.
The ethylene-vinyl acetate copolymer (EVA) is essential in order to give impact strength to the compositions.
Accordingly, the compositions preferably contain between about 5 and about 20 percent by weight EVA, more preferably between about 6 and about 15 percent by weight EVA, the remainder consisting of the propylene-ethylene copolymer component