InnoCentive Challenge Name: Materials for Hot Fillable Containers
Doc. Number: (internal use only)
My Solution:
Detailed Description of the Solution
The Solver's proposed polymer material suitable for hot fillable containers is the "High-Transparency Polypropylene (HT-PP)", i.e., Polypropylene (PP) doped with transparency modifiers.
Polypropylene (PP) is a polymer prepared catalytically from propylene by having an isostatic replacement of a hydrogen atom by a methyl group on alternate carbon atoms in the main chain.
A major advantage of Polypropylene (PP) is its higher temperature resistance. Unlike Polyethylene Terephthalate (PET), bottles and containers made of Polypropylene (PP) are suitable for hot filling since the limiting upper-use temperature of this polymer is about 135 C.
Polypropylene (PP) is particularly suitable for items such as trays, funnels, pails, bottles, carboys and instrument jars that have to be sterilised frequently for use in a clinical environment.
In addition, Polypropylene (PP) has excellent mechanical properties, and it has gradually replaced the polyethylenes for many purposes. Polypropylene (PP) is used for making microwave-safe containers due to its high-temperature resistance, non-toxicity and excellent mechanical properties.
Crystallisation behaviour makes conventional Polypropylene (PP) translucent with poor surface gloss and poor transparency. Modification through the addition of transparency modifiers not only retains the advantages of Polypropylene (PP) such as low price, sanitation, high-temperature resistance and convenient processing, but also provides transparency and surface gloss that compare very well with transparent polymers like PET.
Unlike materials such as Polyethylene Naphthalate (PEN) or PEN copolymers, Polypropylene (PP) does not significantly increase material and processing costs.
Each of the Seeker's Technical Requirements is addressed as follows.
The bottles made from High-Transparency Polypropylene (HT-PP):
allow hot filling up to 92 C, even as high as 95 C, as the limiting upper-use temperature of this polymer is about 135 C.
exhibit impact strength = PET at temperature as low as 2 C, as the limiting lower-use temperature of this polymer is about 0 C. The 20 oz. bottle with its contents (weight up to 600 g) should be able to withstand a flat bottom impact of 1.22 m (4 ft) drop without breakage at temperature as low as 2 C.
have no flavour component interaction (i.e., scalping) with the packaged item.
have no leaching interaction with the packaged item.
The bottles made from High-Transparency Polypropylene (HT-PP) allow an injection blow moulding process that can produce bottle with handles as part of the bottles. The photo below shows handles on the Polypropylene (PP) containers (non-transparent).
The bottles made from High-Transparency Polypropylene (HT-PP) maintain transparency when ultraviolet and oxygen barrier additives or oxygen scavenger systems are added. The photo below shows clear Polypropylene (PP) test tubes (no handles).
Material and processing cost of the bottles made from High-Transparency Polypropylene (HT-PP) are comparable to those made from PET.
High-Transparency Polypropylene (HT-PP) should be approved by FDA or an international regulatory body (e.g., European Union) for use in direct contact with foods and should have no detectable odour, as Polypropylene (PP) is widely used by the food industry and by the medical industry in clinical environments.
References and Notes
There is no patent art preventing the use of specific material for their commercial application.
Examples of High-Transparency Polypropylene (HT-PP) include the following:
Total Petrochemicals's PPR 12232 (High-fluidity (MFI 80 g/10 min) random copolymer)
