PP Clarifi ers | packaging
Clarifi ed PP is gaining ground in the packaging market. Now changes in the IP landscape could open up more competition. Pat Toensmeier and Chris Smith report
Clear improvements in PP
Developments in clarifi er technology have opened up new opportunities for polypropylene in the packaging industry, improving optical performance while also enhancing processibility. Using the best of these products, levels of clarity in random PP copolymer grades are claimed to approach that of resins such as PET and PS. Recent changes in the IP landscape mean this could become an increasingly competitive market- place in the future. When PP cools during the moulding process it forms a solid matrix comprised of large crystalline phases – spherulites – which scatter light and give the polymer its typical hazy translucent appearance. Clarifi ers work to accelerate the crystallisation dynamics of the PP resin while also introducing numerous nucleation sites. The result is the creation of a matrix comprised of very many smaller crystalline phases. Provided the crystal dimensions are less than the wavelength of light then scattering is eliminated and the result is a clear PP. Most commercial PP clarifi ers in use today are based on sorbitol chemistry. Many companies offer so-called fi rst and second generation products based on DBS (dibenzylidene sorbitol) and MDBS (methyl- dibenzylidene sorbitol) respectively. While both can provide improved clarity, fi rst generation products provide limited thermal stability while second genera- tion technology cannot meet the organoleptic require- ments of sensitive packaging applications. Third generation clarifi ers such as Milliken’s Millad 3988, based on DMBDS (dimethyldibenzylidene sorbitol), are said to overcome many of the limitations of fi rst and second generation products. Earlier this
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year, a number of patents held by Milliken relating to production and use of DMBDS as clarifi ers expired and Rika International and Roquette have both already announced intentions to step into the market. Rika International is a wholly-owned UK-based subsidiary of New Japan Chemical, which developed and sold a number of sorbitol-based clarifi er patents to Milliken in the 1980s (a move that prevented it market- ing its own DMBDS product until this year). The company (together with its US unit RikAmerica) now plans to begin marketing its own version of the Millad 3988 clarifi er product. The Rika Gel-All DX Series is described as a third
generation powder-form acetal sorbitol-based clarifi er for PP based on 3,4-DMDBS chemistry. The product will join a line-up including fi rst and second generation clarifi ers – Geniset D (DBS) and Geniset MD (MDBS) respectively. Liam Killough, CEO of RiKA Internation- al, says the initial Gel-All DX third generation clarifi er grade will be a “me too” product because that is what the market wants. He claims, however, that the powder will have improved fl ow properties, provide similar clarity to the second generation MDBS chemis- try, and offer a wide processing window. Other benefi ts include high purity, good haze results, low organoleptics, and a low-to-high melt fl ow rate. Typical loadings will be
Main image: The latest PP clarifi er
technology yields results
close to that of PET or PS
Below: Milliken says 200 PP grades now use its NX8000 clarifi er
July/August 2013 | INJECTION WORLD 11
PHOTO: MILLIKEN
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