Antioxidants phosphite-based

U626 is a rather complex molecule. Very interestingly the phosphite moieties in U626 can have also an important role in the stabilization. Phosphites are well-known stabilizers and they are called secondary antioxidants, while hindered phenol-based stabilizers are known as primary antioxidants. Phosphites have the ability to react with hydroperoxides to yield phosphates according to scheme 5.[20,38] U626 combines primary and secondary stabilizers in the same molecule. 

Benzofuranones are similar to hydroxylamines in that on an equivalent weight basis, they are more powerful than conventional phenolic antioxidants or phosphite-based melt-processing stabilizers. Once again it should be noted... 

Introduction of additives is a well-known method for the mechanism of the chemical reaction investigation. The experience has shown effectiveness of triple stabilizing formulations (Cu-containing compound + phenolic antioxidant + phosphite) for aryl-aliphatic polyamides, polyphthtalamides and other thermally stable polymers. The conception of such formulation is based on the mechanisms of the stabilizing action of the components ... 

Here we have to distinguish between transparent and non-transparent polyamides. In the former, the known phenolic antioxidants soluble in polyamides may be used, and perhaps compatible UV-stabilizers based on benzotriazole. For the latter, all stabilizers or stabilizer systems suitable for polyamides can be used, such as phenolic antioxidants, phosphites, and inorganic systems [502]. 

Cost bilizers. In most cases the alkyl tin stabilizets ate particularly efficient heat stabilizers for PVC without the addition of costabilizers. Many of the traditional coadditives, such as antioxidants, epoxy compounds, and phosphites, used with the mixed metal stabilizer systems, afford only minimal benefits when used with the alkyl tin mercaptides. Mercaptans are quite effective costabilizets for some of the alkyl tin mercaptides, particularly those based on mercaptoethyl ester technology (23). Combinations of mercaptan and alkyl tin mercaptide ate currendy the most efficient stabilizers for PVC extmsion processes. The level of tin metal in the stabilizer composition can be reduced by up to 50% while maintaining equivalent performance. Figure 2 shows the two-roU mill performance of some methyl tin stabilizers in a PVC pipe formulation as a function of the tin content and the mercaptide groups at 200°C. 

Oxidation of LLDPE starts at temperatures above 150°C. This reaction produces hydroxyl and carboxyl groups in polymer molecules as well as low molecular weight compounds such as water, aldehydes, ketones, and alcohols. Oxidation reactions can occur during LLDPE pelletization and processing to protect molten resins from oxygen attack during these operations, antioxidants (radical inhibitors) must be used. These antioxidants (qv) are added to LLDPE resins in concentrations of 0.1—0.5 wt %, and maybe naphthyl amines or phenylenediamines, substituted phenols, quinones, and alkyl phosphites (4), although inhibitors based on hindered phenols are preferred. 

Organophosphoms compounds, primarily phosphonic acids, are used as sequestrants, scale inhibitors, deflocculants, or ion-control agents in oil wells, cooling-tower waters, and boiler-feed waters. Organophosphates are also used as plasticizers and flame retardants in plastics and elastomers, which accounted for 22% of PCl consumed. Phosphites, in conjunction with Hquid mixed metals, such as calcium—zinc and barium—cadmium heat stabilizers, function as antioxidants and stabilizer adjutants. In 1992, such phosphoms-based chemicals amounted to slightly more than 6% of all such plastic additives and represented 8500 t of phosphoms. Because PVC production is expected to increase, the use of phosphoms additive should increase 3% aimually through 1999. 

Synergism based on the mixture of a chain-breaking antioxidant (sterically hindered phenol) and a hydroperoxide decomposer (organic sulfides or phosphites). 

The patent describing this development discloses that a mixture of a thermally stable phenolic antioxidant and a sterically hindered phosphite was used in a hydrotreated base stock. However, the heterosynergism between the radical scavenger (phenolic antioxidant) and the hydroperoxide decomposer (phosphite) was not shown in solvent-refined base stocks. An additional benefit of this technology is energy saving, due to extremely good control of viscosity. 

Recyclostab , containing antioxidants and costabilizers, viz. Recyclostab 411 or 421, based on phenol, phosphite antioxidants and suitable co-stabilizer, designed for PO or PET recycling. Recyclostab 451 has been successfully used for recycling PP battery cases by injection molding. 

There is also a new solid phosphite antioxidant developed by GE Specialty Chemicals, based on butyl ethyl propane diol chemistry, which has EDA approval for food contact applications. 

For aliphatic PAs, the short-term thermal stability needed for most processing can be realized by incorporating a hindered phenolic antioxidant such as di-ferf-butyl cresol. Primary antioxidants based on secondary aromatic amines are efficient stabilizers of the oxidation reactions of PA6. The efficiency can be further increased by a combination with a phosphite antioxidant. In contrast, primary antioxidants based on phenol are ineffective in the oxidation of PA6. ... 

Worldwide production of APEs is about 390,000 tons, and about 80% of it is used to produce octyl- or nonylphenol ethoxylate (NPE) nonionic surfactants. About 10% of it is used in manufacturing phosphite antioxidants (tris(4-nonyl-phenyl) phosphite used in rubber and plastics compounds. The stabilizers and plasticizers based on NP are also used in plastics intended for food-contact applications. They are not highly persistent chemicals and once discharged into the environment, APEs rapidly hydrolyze into alkylphenols that are subsequently slowly biodegraded by microorganisms. The USEPA criteria concentrations for freshwater NP exposure is CMC = 28 acute-pg/1 and CCC = 6.6 chronic-pg/l aquatic community might be exposed to >CMC concentration only briefly and [Pg.209]

A new phosphite secondary antioxidant, based on butyl ethyl propane diol, reputedly yields high activity, solubility, and hydrolytic stability in a range of polymers. This would allow the producer to use lower levels of additives to achieve similar results. 

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