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1. “Organic phosphites are well-known and are commonly used as secondary antioxidants in polymer compositions including, for example, polyolefins, polyvinyl chloride, and elastomers. Examples of such phosphites are disclosed in H. Zweifel (Ed) Plastics Additives Handbook, 5th edition, Hanser Publishers, Munich 2000. Phosphite stabilizers, both liquid and solid, are known in the art.

Solid organic phosphite stabilizers are widely used as secondary antioxidants in polymer compositions. One commercially available antioxidant is tris(2,4-di-t-butylphenyl) phosphite, shown below, a solid antioxidant commonly known as Alkanox.TM. 240 (Chemtura Corporation, Middlebury, Conn., USA), Irgafos.TM. 168 (Ciba Specialty Chemicals Corp., Tarrytown, N.Y., USA) and Doverphos.TM. S-480 (Dover Chemical Corp., Dover, Ohio, USA). U.S. Pat. No. 5,254,709, the entirety of which is incorporated herein by reference, describes the synthesis of tris(2,4-di-t-butylphenyl) phosphite by reacting 2,4-di-t-butyl phenol with phosphorus trichloride in the presence of catalyst. The isolated phosphite is described as a white crystalline solid having a melting point of C.-1”

[Gelbi, Power and Hill, US Patent 8,178,005 (5/15/2012)]

2. “Organic alkylphenolic phosphites in general, are good secondary antioxidants, but there is a perceived problem that has developed in the scientific community that a number of commonly used compounds, including nonylphenol, may exhibit estrogenic activity, See Jobling, S., et al., "Detergent Components in Sewage Effluent are Weakly Estrogenic to Fish: An In-Vitro Study Using Rainbow Trout Hepatocytes," Aquatic Toxicology, Vol. 27 (1993) pp. 361-372 and Soto, A. M. et al., "p-Nonylphenol: An Estrogenic Xenobiotic Released from Modified Polystyrene," Env. Health Perspectives, Vol. 92 (1991) pp. 167-173. There is even concern with other traditionally used alkylphenols such as 2,4-dibutylphenol. See The Ministry of Heath, Labour and Welfare, Japan 2001, Chemical Substance Toxicity Test Report, 2,4 Di-tert-butylphenol, Vol 8 (1) 363-395.

Therefore, it is desirable to provide phosphites with lower contents of nonylphenol and which are not based on lower alkylphenols, especially 2,4-di-t-butylphenol. In the prior art, tris(nonylphenyl)phosphite has been made more hydrolytically stable by the addition of amines such as tris(isopropanol) amine ("TiPA"). Both tris(nonylphenyl)phosphite and tris(isopropanol) amine are FDA sanctioned for use in many polymer applications. U.S. Pat. Nos. 7,199,170 and 7,468,410 disclose phosphites that can replace TNPP but are either based on 2,4-di-t-butylphenol or lower alkylphenols. Any new phosphites which are to be considered as TNPP replacements need to be a liquid at room temperature and meet or exceed all the performance properties of TNPP. Important performance properties required include: good polymer compatibility, low odor in the polymer during processing, good melt flow and color stability in multi extrusion test, and good color stability in gas fade aging.

[Jakupca, US Patent 8,258,215 (9/4/2012)]


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Roger D. Corneliussen

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Copyright 2012 by Roger D. Corneliussen.
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* Date of latest addition; date of first entry is 5/24/2012.