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New high-clarity PP copolymers.

Two new clarified PP random copolymers for extrusion blow molding are said to offer unprecedented clarity and toughness, plus FDA approval. Himont Inc. in Wilmington, Del., makes Pro-Fax SV-256M using a new clarifying agent (Millad 3940 from Milliken Chemical Co., Spartanburg, S.C.) to achieve haze transmission in the 8-12% range, compared with 12-15% haze for several competing resins made with Milliken's previous food-grade clarifier Millad 3905, which has lower taste and odor. And Rexene Corp., Dallas, makes 23T2A using another new clarifying agent--NC4 from Mitsui Toatsu Chemical (Mitsui & Co., Houston)--to achieve similar haze levels, Rexene says.

Clarity is hard to pin down, though. Test plaques are injection molded, a process which makes far clearer samples than blow molding, because injection mold tools are more highly polished. Processing and machinery differences can also yield different clarity using the same resin.

The toughness of Himont's and Rexene's resins are at least double that of the competition. SV-256M has notched Izod impact of 5.6 ft-lb/in. and 23T2A has a notched Izod of 6, compared with 1.7 for the next closest competitor. This toughness reportedly allows them to be extrusion blow molded without stretch-blow orientation and to achieve thinner walls than other copolymers. Himont's SV-256M also has flex modulus of 150,000 psi and HDT of 187F at 66psi. It reportedly can be hot-filled at up to 200 F.

The Himont resin already has several commercial bottle applictions for syrup, aftershave lotion, household cleaner, and even a coextruded ketchup bottle in Canada. It's being evaluated as an alternative to PET in cough syrup. And Himont sees opportunities in jars for jams, jellies, mayonnaise and tomato sauces and in handleware juices and non-carbonated drink bottles. A version with a higher melt-flow rate (a MFR of 2 is normal for extrusion blow molding grades) is in development for injection stretch-blow molding of pharmaceutical packaging.
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Title Annotation:packaging resins
Author:Schut, Jan H.
Publication:Plastics Technology
Date:Dec 1, 1992
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