Hydroxytoluenes

Antioxidants markedly retard the rate of autoxidation throughout the useful life of the polymer. Chain-terminating antioxidants have a reactive —NH or —OH functional group and include compounds such as secondary aryl amines or hindered phenols. They function by transfer of hydrogen to free radicals, principally to peroxy radicals. Butylated hydroxytoluene is a widely used example. 

Antioxidants (qv) have a positive effect on oils when present in the proper concentration. Sterols and tocopherols, which are natural antioxidants, may be analy2ed by gas-Hquid chromatography (glc), high performance Hquid chromatography (hplc), or thin-layer chromatography (tic). Synthetic antioxidants maybe added by processors to improve the performance or shelf life of products. These compounds include butylatedhydroxyanisole (BHA), butylated hydroxytoluene (BHT), / fZ-butyUiydroquinone (TBHQ), and propyl gallate. These materials may likewise be analy2ed by glc, hplc, or tic. Citric acid (qv), which functions as a metal chelator, may also be deterrnined by glc. 

The FCC is to food-additive chemicals what the USP—NF is to dmgs. In fact, many chemicals that are used in dmgs also are food additives (qv) and thus may have monographs in both the USP—NF and in the FCC. Examples of food-additive chemicals are ascorbic acid [50-81-7] (see Vitamins), butylated hydroxytoluene [128-37-0] (BHT) (see Antioxidants), calcium chloride [10043-52-4] (see Calcium compounds), ethyl vanillin [121-32-4] (see Vanillin), ferrous fumarate [7705-12-6] and ferrous sulfate [7720-78-7] (see Iron compounds), niacin [59-67-6] sodium chloride [7647-14-5] sodium hydroxide [1310-73-2] (see lkaliand cm ORiNE products), sodium phosphate dibasic [7558-79-4] (see Phosphoric acids and phosphates), spearmint oil [8008-79-5] (see Oils, essential), tartaric acid [133-37-9] (see Hydroxy dicarboxylic acids), tragacanth [9000-65-1] (see Gums), and vitamin A [11103-57-4]. 

A.ntioxidants. PhenoHc antioxidants, added at about 0.1—0.5 phr, are usually chosen from among butylated hydroxytoluene [128-37-0] (BHT), and Nnonylphenol [104-40-5] for Hquid stabilizer formulations and bisphenol A [80-05-7] (2,2-bis-(/)-hydroxyphenyl)propane) for the soHd systems. Low melting thioesters, dilauryl thiodipropionate [123-28-4] (DLTDP) or distearyl thiodipropionate [693-36-7] (DSTDP) are commonly added along with the phenoHcs to enhance their antioxidant performance. Usually a 3 1 ratio of thiodipropionate to phenoHc antioxidant provides the desired protection. Most mixed metal stabilizer products contain the antioxidant iagredient. 

Solvent extraction followed by gas chromatographic analysis is used to determine paraffin wax antioxidants (qv), ie, butylated hydroxyanisole and butylated hydroxytoluene and other volatile materials. Trace amounts of chlorinated organic compounds, eg, polychlorinated biphenyls, can be deterrnined by using a gas chromatograph with an electron-capture detector (22). 

Several stabilizers are useful in minimizing oxidative degradation during thermoplastic processing or in the bulk soHd. Phenothiazine, hindered phenohc antioxidants such as butylated hydroxytoluene, butylatedhydroxyanisole, and secondary aromatic amines in concentrations of 0.01—0.5% based on the weight of polymer, are effective. 

PTMEG is a polymeric ether susceptible to both thermal and oxidative degradation. It usually contains 300—1000 ppm of an antioxidant such as 2,6-di-/ f2 -butyl-4-hydroxytoluene (BHT) to prevent oxidation under normal storage and handling conditions. Thermal decomposition in an inert atmosphere starts at 210—220°C (410—430°E) with the formation of highly flammable THE. In the presence of acidic impurities, the decomposition temperature can be significantly reduced contact with acids should therefore be avoided, and storage temperatures have to be controlled to prevent decomposition to THF (261). 

The vitamin D resin is stabilized against oxidation by the addition of < 1 wt% butylated hydroxyanisole or butylated hydroxytoluene. 

Oligomeric hindered amine light stabilizers are effective thermal antioxidants for polypropylene. Thus 0.1% of A[,Af-bis(2,2,6,6-tetramethyl-4-piperadinyl)-l,6-hexanediamine polymer, with 2,4,6-trichloro-l,3,5-triazine and 2,4,4-trimethyl-2-pentaneainine [70624-18-9] (35) (Fig. 5), protects polypropylene multifilaments against oxidation when exposed at 120°C in a forced-air oven (22) for 47 days. 3,5-Di-/ l -butyl-4-hydroxytoluene [128-37-0] (0.1%) affords protection for only 14 days. 

Stabilization of Elastomers. Polyunsaturated elastomers are sensitive to oxidation. Stabili2ers are added to the elastomers prior to vulcani2ation to protect the mbber during drying and storage. Nonstaining antioxidants such as butylated hydroxytoluene (1),... 

Di-/ l -butyl-4-methylphenol /2j5 i77-2/-i72,6-Di-/ l -butyl-4-methylphenol (di-/ l -butyl-/)-cresolDi-/ l -butyl-j )-cresol or butylated hydroxytoluene (BHT)) is most commonly used as an antioxidant in plastics and mbber. Use in food is decreasing because of legislation and it is being replaced by butylated hydroxy anisole (BHA) (see Antioxidants Eood additives). 

ButylatedHydroxyAnisole (BHA). This material is an oxidation inhibitor and has been accepted for use in foods where the use of butylated hydroxytoluene (BHT) is restricted (see Food additives). It is manufactured by the alkylation of 4-hydroxyanisole [150-76-5] with isobutylene that yields a mixture of 2- and S-Z fZ-butyl isomers as products (124). 

To obtain maximum lifetime, the oxidants must not be lost during service. A major potential source of loss is the evaporation of the antioxidant. Evaporation is often observed with BHT (butylated hydroxytoluene), a monomeric phenol, and to avoid evaporation less volatile, higher molecular weight antioxidants are used (i.e. bisphenols). 

Antioxidants. Antioxidants are rarely needed because of the highly saturated nature of the polymer chains. If protection against severe environmental ageing conditions is needed, typical antioxidants (Ethanox 702, Irganox 1010) can be added. In some cases, zinc dibutyldithiocarbamate (0.05-0.2 wt%) or butylated hydroxytoluene (BHT) can be used as stabilizers. 

Chemical Designations - Synonyms Benzenecarbinol, alpha-Hydroxytoluene Phenylcarbinol Phenylmethanol Phenylmethyl Alcohol Chemical Formula C HjCHjOH. 

Chemical Designations - Synonyms Cresylic Acids Hydroxytoluenes Methylphenols Oxytoluenes Tar Acids Chemical Formula CH3C3 H4OH. 

Dipping solution II Dissolve 24 ml tetraethylene pentamine and 60 mg butyl-hydroxytoluene in 36 ml dichloromethane. 

Inhibited THF is problematic for semipreparative separations. Because small quantities of polymer are being collected along with larger volumes of solvent, more inhibitor, usually butylated hydroxytoluene (BHT), than sample is often collected in each fraction. Thus, one must carefully consider if the BHT will cause a problem in the subsequent analysis of the isolated fractions. If it does, uninhibited THF or other alternate solvents should be used. It must be remember that if uninhibited THF is used, the analyst must pay careful attention to the inevitable peroxide formation in the solvent/fractions. 

Phenol is a radical scavenger . Other radical scavengers include 3,5-di-tert-butyl-4-hydroxytoluene (butylated hydroxytoluene or BHT) and vitamin E. 

B. m-Phenylene-diisocyanate, toluenediisocyanate. xylenediisocya-nate, butylated hydroxytoluene, 5-chlorotoluenediisocyanate, and methylene-bis-(4-cyclohexylisocyanate)... 

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