Hindered bisphenol

The other class of primary antioxidants are the phenols (hindered phenols, hindered bisphenols, hindered thiobisphenols, polyhydroxy phenols) (Fig. 34). Phenolic antioxidants are generally used when the discolouration of the amine antioxidants cannot be tolerated. Phenols may produce coloured reaction products (yellow, tan or pink) but the discolouration is significantly less than produced with amines. 

Polymer extracts are frequently examined using GC-MS. Pierre and van Bree [257] have identified nonylphenol from the antioxidant TNPP, a hindered bisphenol antioxidant, the plasticiser DOP, and two peroxide catalyst residues (cumol and 2-phenyl-2-propanol) from an ABS terpolymer extract. Tetramethylsuccino-dinitrile (TMSDN) has been determined quantitatively using specific-ion GC-MS in extracts of polymers prepared using azobisisobutyronitrile TMSDN is highly volatile. Peroxides (e.g. benzoyl or lauroylperoxide) produce acids as residues which may be detected by MS by methylation of the evaporated extract prior to GC-MS examination [258]. GC-MS techniques are... 

The most effective antioxidants for light coloured rubber compounds are the hindered bisphenols, but these offer little ozone and flex cracking resistance. 

C4H9)2C6H2(OH)]2CH2. A sterically hindered bisphenol. 

Nonstaining antioxidants This ciass of antioxidants is subdivided into four groups phosphites, hindered phenols, hindered bisphenols, and hydroquinones. Hindered bisphenols such as 4,4 -thiobis(6-r-butyl-m-cresol) are the most persistent of the four classes of material. Because of then-lower molecular weight, hindered phenols tend to be volatile. Phosphites tend to be used as synthetic rubber stabilizers, and hydroquinones such as 2,5-di-re t-amylhydroquinone are used in adhesives ... 

CAS 118-82-1 EINECS/ELINCS 204-279-1 Synonyms Bis (2,6-di-t-butyl-4-hydroxyphenyl) methane Di (4-hydroxy-3,5-di-t-butylphenyl) methane 4,4 -Methylenebis (2,6-bis(1,1-dimethylethyl) phenol) 2,2, 6,6 -Tetra-t-butyl-4,4 -methylenediphenol Classification Sterically hindered bisphenol Empirical C29H44O2 Formula [(C4H9)2C6H2(OH)]2CH2 Properties Lt. yel. powd. insol. in water and 1.0N sodium hydroxide m.w. 424.67 dens. 0.99 (20 C) m.p. 156-158 C b.p. 289 C (40 mm)... 

Hindered bisphenols 2,2 -Methylenebis-(4-methyl-6-t-butylphenol) (Antioxidant 2246) None to slight G-F G-F F-P G P... 

Lattimer and co-workers [25] have applied mass spectrometry (MS) to the determination of antioxidants and antiozonants in rubber vulcanisates. Direct thermal desorption was used with three different ionisation methods [electron impact (El), chemical ionisation (Cl), field ionisation (FI)]. The vulcanisates were also examined by direct fast atom bombardment mass spectrometry (FAB-MS) as a means for surface desorption/ionisation. Rubber extracts were examined directly by these four ionisation methods. Of the various vaporisation/ionisation methods, it appears that field ionisation is the most efficient for identifying organic additives in the rubber vulcanisates. Other ionisation methods may be required, however, for detection of specific types of additives. There was no clear advantage for direct analysis as compared to extract analysis. Antiozonants examined include aromatic amines and a hindered bisphenol. These compounds could be identified quite readily by either extraction or direct analysis and by use of any vaporisation/ionisation method. 

Antioxidants and antiozonants examined include aromatic amines (HPPD, DOPPD, DODPA and poly-TMDQ) and a hindered bisphenol (AO 425). These compounds could be identified quite readily by either extraction or direct analysis and by use of any vaporization/ionization method. 

The hindered bisphenol antioxidants, while useful for minimizing staining, can present problems in some formulations. For example, milled stocks containing some hindered bis-phenols such as Santowhite Crystals (Monsanto) have relatively short bin stability. On aging, for as little as one week at 38 C (100°F), the stock may not make a smooth solution. If the stocks are dissolved within two or three days of milling, no problems are normally encountered. Antioxidant 2246 (American Cyanamid) has been known to create color problems a pink discoloration in latexes, a bluish or blue-green discoloration in some solvent systems, particularly those based on chlorinated solvents. 

Figure 14 Hindered bisphenols used as ligands (Ligand 1, Table 4). Adapted from Tang, L. Wasserman, E. Neithamer, D. etal. Macromolecules 2008, 41, 7306. with permission of the American Chemical Society, USA.

The copolymers are clear tough materials with properties, depending on the a b ratio, ranging from flexible elastomers to tough plastics. Use of the hindered bisphenol (38) in place of bisphenol A gives rise to transparent thermoplasts of exceptionally high and possessing an impressive level of fire-safety performance. " ... 

---