Tertiary phosphite antioxidants

Nawakowski has described a colorimetric method for determining Polygard (trisnonylphenylphosphite) based on hydrolysis to nonyl phenol, followed by coupling with p-nitro benzene-diazonium fluoroborate and colorimetric estimation at 550 nm. 

Various other phenolic antioxidants produced dyes under these conditions, viz. Wingstay S, Agerite Superlite and Nevastain A. 

Brandt has described an alternate method for the determination of Polygard in styrene butadiene latices which utilizes the bathochromic shift in the spectrum of phenols 

The bathochromic shift method has the advantage of being more specific than the diazotization method. Results obtained by this procedure agree well with these based on direct determination of elemental phosphorus (Table 2.3). 

Hilton and Altenau and Hayes and Altenau used mass spectrometry to qualitatively identify volatile antioxidants in sheet samples of synthetic styrene-butadiene rubbers and rubber type vulcanizates. They extracted the polymer with acetone in a Sohxlet apparatus, removed excess solvent and dissolved the residue in benzene. Substances identified and determined by this procedure include N-phenyl-fi-napthylamine, 6-dodecyl-2,2,4-trimethyl 1,2-dihydroquinolines, trisnonyl-phenyl-phosphite, isobutylene - bisphenol A reaction product, 2-mercaptobenzothiazole sulphen-amide (accelerator) N-cyclohexyl-2-benzothiazole sulphenamide, N-tert-butyl-2-benzo-thiazole sulphenamide, 2-(4-morpolinothio) benzothiazole, 2-(2,6-dimethyl-morphal-inothio) benzothiazole, N,N -diisopropyl 2-benzothiazoles, 2-mercaptobenzo-thiazole and N,N -dicyclohexyl-2-benzothiazole sulphamide. 

---

METHOD 15 - DETERMINATION OF DIORGANOSULPHIDE AND TERTIARY PHOSPHITE ANTIOXIDANT IN POLYETHYLENE. M-CHLOROPEROXYBENZOIC ACID OXIDATION METHOD. ... 

Determination of diorganosulphide and tertiary phosphite antioxidants in polyethylene. Chloroperoxybenzoic acid - oxidation method... 

Phosphites. Tertiary phosphites are also commonly used and are particularly effective ia most mixed metal stabilizers at a use level of 0.25—1.0 phr. They can take part ia a number of different reactions duting PVC processing they can react with HCl, displace activated chlorine atoms on the polymer, provide antioxidant functionaHty, and coordinate with the metals to alter the Lewis acidity of the chloride salts. Typical examples of phosphites are triphenyl phosphite [101 -02-0], diphenyl decyl phosphite [3287-06-7], tridecyl phosphite [2929-86-4], and polyphosphites made by reaction of PCl with polyols and capping alcohols. The phosphites are often included in commercial stabilizer packages. 

Kellum [115] has described a class-selective oxidation chemistry procedure for the quantitative determination of secondary antioxidants in extracts of PE and PP with great precision (better than 1 %). Diorgano sulfides and tertiary phosphites can be quantitatively oxidised with /-chloropcroxybenzoic acid to the corresponding sulfones and phosphates with no interference from other stabilisers or additives. Hindered phenols, benzophenones, triazoles, fatty acid amides, and stearate... 

Secondary antioxidants or hydroperoxide decomposers (see Scheme 2.1) are typified by organosulfur species having reducing properties such as sulfides and thioethers. Tertiary phosphites also fall into this category (see Scheme 2.9). 

LI, 2.4 Diorganosulphide (and Tertiary Phosphite) Types of Antioxidants in Polyolefins... 

The method is capable of determining down to 0.05% of diorganosulphide and tertiary phosphite type antioxidants in polyalkenes with an accuracy of 5%. Table 7.8 shows the results obtained by applying the oxidation method to blends of antioxidants in unstabilized polyethylene. The results are in excellent agreement with the theoretical antioxidant content of these polymers. 

HALS exhibit a complex behavior when present in combination with other antioxidants and stabilizers. Effective synergism in both melt and thermal stabilization has been achieved when secondary and tertiary HALS were used in combination with both aromatic and aliphatic phosphites the synergistic optimum depends on the structure of the phosphite. HALS also synergize the action of UV-absorbers, e.g., benzo-triazoles, in different polymers such as polypropylene, polystyrene, and ABS. " ... 

---