New antioxidant has improved properties A new phosphite antioxidant for polyolefin, olefin copolymer, polycarbonate, and polyamide resins has been introduced by Ciba's additives division in Hawthorne, N.Y. Called CGA 12 and priced at $9.89 per lb, the compound is intended as a secondary antioxidant to complement the protective effects of hindered phenol primary antioxidants during melt processing of these resins. Compared with competing phosphites, the new additive has greater resistance to hydrolysis, and its use leads to less unsightly yellowing caused by degradation of hindered phenols. The company expects Food & Drug Administration approval of the compound for use in plastics for food and drug packaging in the first quarter of 1995. During melt processing, the heat generated induces oxidative degradation of plastics: Carbon-hydrogen bonds are cleaved to form carbon free radicals, R-, along the polymer chain. These free radicals react with oxygen to form peroxide radicals, ROO-, which in turn abstract protons from the polymer chain, producing hydroperoxides (ROOH) and additional carbon free radicals. Hindered phenol primary antioxidants neutralize peroxide radicals, preventing them from doing further damage. Hydroperoxides produced by surviving peroxide radicals are destroyed by phosphite ester secondary antioxidants. But in destroying polymer peroxides, many hindered phenols are oxidized to highly conjugated yellow quinones. And some other commercial triaryl phosphites are susceptible to hydrolysis to phenols,
which may cause discoloration and off odors and tastes. The new compound is intended to take some load off hindered phenols by taking care of the antioxidant function in a different part of the cycle. Resistance to hydrolysis may come from the polycyclic structure of the phosphite ester. And an aminotriester feature of the structure may lead to the additive's properties as a metal deactivator. In the antioxidant, two of the three hydroxyl groups of phosphorous acid are
esterified with 2,2,-bis(2,4-di-ferf-butylphenol). Three such hydrogen phosphite ester molecules are esterified with triethanolamine. The three phosphite and one amino group form a pocket that may complex transition-metal ions and prevent them from catalyzing damage to resins. Such metal ions come into play when the polyolefin resin has been produced with a metallocene catalyst or when the resin is used as insulation for copper wire. Stephen Stinson
With over 150 years of experience manufacturing organic chemicals, you can trust Miles Inc. and Bayer A< (Germany) as your global suppliers of custom, fine and organic intermediates. For more information on our synthesizing and manufacturing capabilities, call (800) 662-2927 or write Miles Inc. Fiber, Organics & Rubber Division Mobay Road Pittsburgh, PA 15205
Additive resists hydrolysis and suppresses yellowing /(CH3)3C^^.C(CH3)3
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MILES
p—OCH2CH2-LN
^^C(CH3)3 CGA 12
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A Responsible Care® Company
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CIRCLE 8 7 ON READER SERVICE CARD
SEPTEMBER 19,1994 C&EN
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