Hindered bisphenol antioxidants

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 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. 

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. 

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

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 ... 

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 versatility of this reaction is extended to a variety of aldehydes. The bisphenol derived from 2,6-di-/ f2 -butylphenol and furfural, (25) where R = furfuryl (13), is also used as an antioxidant. The utility of the 3,5-di-/ f2 -butyl-4-hydroxyben2yl moiety is evident in stabili2ets of all types (14), and its effectiveness has spurred investigations of derivatives of hindered alkylphenols to achieve better stahi1i2ing quaUties. Another example is the Michael addition of 2,6-di-/ f2 -butyl phenol to methyl acrylate. This reaction is carried out under basic conditions and yields methyl... 

Antioxidants. A good antioxidant should be added to CR adhesives to avoid oxidative degradation and acid tendering of substrates. Derivatives of diphenyl amine (octylated diphenyl amine, styrenated diphenyl amine) provide good performance but staining is produced. To avoid staining, hindered phenols or bisphenols can be added. 2 phr antioxidant is sufficient in solvent-borne CR adhesives formulations. 

In an acetone extract from a neoprene/SBR hose compound, Lattimer et al. [92] distinguished dioctylph-thalate (m/z 390), di(r-octyl)diphenylamine (m/z 393), 1,3,5-tris(3,5-di-f-butyl-4-hydroxybenzyl)-isocyanurate m/z 783), hydrocarbon oil and a paraffin wax (numerous molecular ions in the m/z range of 200-500) by means of FD-MS. Since cross-linked rubbers are insoluble, more complex extraction procedures must be carried out (Chapter 2). The method of Dinsmore and Smith [257], or a modification thereof, is normally used. Mass spectrometry (and other analytical techniques) is then used to characterise the various rubber fractions. The mass-spectral identification of numerous antioxidants (hindered phenols and aromatic amines, e.g. phenyl-/ -naphthyl-amine, 6-dodecyl-2,2,4-trimethyl-l,2-dihydroquinoline, butylated bisphenol-A, HPPD, poly-TMDQ, di-(t-octyl)diphenylamine) in rubber extracts by means of direct probe EI-MS with programmed heating, has been reported [252]. The main problem reported consisted of the numerous ions arising from hydrocarbon oil in the recipe. In older work, mass spectrometry has been used to qualitatively identify volatile AOs in sheet samples of SBR and rubber-type vulcanisates after extraction of the polymer with acetone [51,246]. 

Antioxidants. Certain components of heat stabilizers (polyols, phosphites) also serve as antioxidants. The protection against oxidative attack is not as great in PVC as it is in certain ethylenically unsaturated materials. However, PVC compounds may require protection in the high-temperature service as in electrical wire insulation bisphenol A is often incorporated into the plasticizer for this purpose. Impact modifiers containing unsaturation such as acrylonitrile-butadiene-styrene polymers often require antioxidant protection. Hindered phenols such as butylated hydroxytoluene are often used for this purpose, especially when outdoor applications are involved. 

The two major groups among the primary antioxidants are hindered phenolics and aromatic amines. The most widely used antioxidants in plastics are phenolics. The products generally resist staining or discoloration. However, they may form quinoid (colored) structures on oxidation. Phenolic antioxidants include simple phenolics, bisphenolics, polyphenolics, and thiobisphenolics. Hindered phenolics, such as butylated hydroxytoluene (BHT), high-molecular-weight phenolics, and thiobisphenolics, are the most popular of the primary antioxidants. 

In accordance with general experience, nonstaining antioxidants from the class of stearically hindered phenols or bisphenols are less effective. 

Hindered phenolics, because of their nonstaining qualities, are the most preferred type of primary antioxidant for light colored applications such as footwear. This group can be further categorized into simple phenolics (1), bisphenolics (2), polyphenolics (3), and thiobisphenolics (4), as shown on the following page [17]. 

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