Clear barrier composites containing polyisobutylene/polyolefin alloy components

DETAILED DESCRIPTION This invention relates to a composite film suitable for use in parenteral drug or blood container applications.
In particular, it relates to a clear, flexible, autoclavable film which when formed into a parenteral drug or blood bag has a high burst strength.
In a preferred embodiment, a 7 mil film has a water vapor transmission rate of less than 2.
5 g/m.
sup.
2 /day.
The composite film of this invention comprises at least one layer of polyolefin and at least one layer of an elastomeric composition.
Preferably, the elastomeric composition is sandwiched between two layers of polyolefin composition.
Since the film must withstand autoclaving at about 121.
degree.
C.
it is preferred that it not shrink when heated in an autoclave.
Shrinkage can result in rupture of the bag formed from the film.
In order to impart thermal stability and eliminate shrinkage, the elastomeric composition is blended with a minor amount of polyolefin, e.
g.
, at least 15 wt %.
The polyolefin resins which are suitable for use in the practice of this invention for blending with the elastomer are those which have a semi-crystalline or crystalline melting point of at least 110.
degree.
C.
Illustrative, non-limiting examples of the polyolefins suitable for use in the practice of this invention are polypropylene (PP), linear low density polyethylene (LLDPE) and polybutylene (PB).
As used in the specification and claims, the term "polypropylene" includes homopolymers of propylene as well as reactor copolymers of polypropylene (RCPP) which can contain about 1 to about 20 wt % ethylene or an alpha olefin comonomer of 4 to 16 carbon atoms.
The polypropylene can be highly crystalline isotactic or syndiotactic polypropylene.
The RCPP can be either a random or block copolymer.
The density of the PP or RCPP can be about 0.
89 to about 0.
91 g/cc.
High density polyethylene (HDPE), useful as the polyolefin resin layer of the multi-layer film of this invention, has a density of about 0.
941 to about 0.
965 g/cc.
High density polyethylene is an established product of commerce and its manufacture and general properties are well known to the art