Films of radiation resistant heat sealable polymer blends having a surface adhesion layer grafted thereto

#This invention relates to polymer blends of compatible polymers resistant to the effects of sterilization irradiation, methods for preparing such polymer blends, and articles, such as fibers, films, and nonwoven fabrics incorporating such polymer blends. More particularly, this invention relates to polymer blends of non-crystalline mesomorphous polypropylene and polymers compatible with such polypropylene. Films of such blends may be used as heat sealable packaging for medical articles requiring sterilized storage, heat sealable backings for transdermal delivery medical packaging, or as heat sealable components for use as ostomy pouches also possibly requiring sterilized storage.

#Polypropylene is often a material of choice for medical articles due to its various properties such as non-toxicity, chemical resistance and inertness to drugs and liquid media used with drugs, as well as its low cost and ease of processing by means of extrusion, molding, and the like.

#However, a disadvantage of crystalline polypropylene is its inherent inability to be heat sealed against another material. Medical articles or packaging for medical articles often require heat sealing in the manufacturing process to assemble the components of the article or the packaging process to protect the active ingredient or medical article in the packaging from undesired exposure.

#FIG. 1 is a graph comparing percent elongation at break values for Examples 1-5 with hypothetical linear values for Examples 1-5.

#FIG. 2 is the x-ray diffraction pattern of crystalline polybutylene of Example 1.

#FIG. 3 is the x-ray diffraction pattern of the polymer blend of Example 2.

#The polymer blends of compatible polymers of the present invention substantially maintain their structural integrity for a useful period after irradiation. The blends are produced from non-crystalline mesomorphous polypropylene blended with a polymer compatible with such polypropylene.

#As described above, compatibility of a polymer with non-crystalline mesomorphous polypropylene is determined by a comparison of the percent elongation at break of a weight fraction of a blend with the hypothetical value of percent elongation at break at that weight fraction as determined by the respective blended polymers in their proportionate weight fraction.

#Graphically, the determination of a blend of a "compatible polymer" and non-crystalline mesomorphous polypropylene is apparent from an examination of FIG. 1, depicting the unirradiated, zero duration results from Table I below. The percent elongation at break of each example of the blend is greater than the hypothetical value of the percent elongation at break for that blend in that weight fraction. Therefore, each of the weight fractions of the blends is a mixture of non-crystalline mesomorphous polypropylene and a "polymer compatible with said polypropylene".