Butyl cresol

Oxidation inhibitors function by intermpting the hydroperoxide chain reaction. At temperatures up to ca 120°C, di-Z fZ-butyl- -cresol, 2-naphthol,... 

Additives. Compounds are often added to the polymer at the extmder or melt homogenizer. Common additives are antioxidants (qv), thermal stabilizers, sHp agents, antiblock agents, anduv stabilizers. Popular antioxidants are 2,6-di-/-butyl-/)-cresol (BHT), octadecyl... 

Hindered Phenols. Even a simple monophenoHc antioxidant, such as 2,6-di-/ f2 -butyl-/)-cresol [128-37-0] (1), has a complex chemistry in an autooxidizing substrate (Fig. 1). 

Commercially important di- and polyphenoHc stabilizers include 2,2 -methylenebis(6-/ r2 -butyl- -cresol) [85-60-9] (7), l,3,5-trimethyl-2,4,6-tris(3 5 -di-/ /f-butyl-4-hydroxyben2yl)ben2ene [1709-70-2] (8), and tetrakis [methylene(3,5-di- / r2 butyl-4-hydroxyhydrocinnamate)]methane [6683-19-8] (9). 

Stabilization of Fuels and Lubricants. Gasoline and jet engine fuels contain unsaturated compounds that oxidize on storage, darken, and form gums and deposits. Radical scavengers such as 2,4-dimethyl-6-/ f2 butylphenol [1879-09-0] 2,6-di-/ f2 -butyl-/)-cresol (1), 2,6-di-/ f2 -butylphenol [128-39-2], and alkylated paraphenylene diamines ate used in concentrations of about 5—10 ppm as stabilizers. 

Di-rerf-butyl cresol Ionol100 Tinuvin-P Irganox 1076... 

Ionol is a commercial antioxidant, 2,6-di-/cr/-butyl- -cresol, manufactured by Shell Chemical Corp. Inhibitors appear to minimize formation of polymeric side products, although with isoprene the effect is often small. 

Figure 5- Gel permeation chromatogram of butylated -cresol-dicyclopentadiene reaction products.

Di-/ -butyl-4-methylphenol [25377-2/ -i 2,6-Di-/ -butyl-4-methylphenol (di-/ -butyl-/>-cresolDi-/ -butyl- >-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 Food additives). 

Tohienesulfonic Acid. Toluene reacts readily with fuming sulfuric acid to yield toluene-sulfonic acid. By proper control of conditions, p-toluenesulfomc acid is obtained. The pnmaiy use is for conversion, by fusion wilh NaOH, to / -cresol. The resulting high purity -cresol is then alkylated wilh isobutylene to produce 2.6-di-fm-butyl-/ -cresol (BHT), which is used as an antioxidant in foods, gasoline, and rubber. Mixed cresols can be obtained by alkylation of phenol and by isolation from certain petroleum and coal-tar process streams. 

Methylation of phenols and alcohols. Phenols and alcohols are converted into methyl ethers by treatment with sodium hydride methyl iodide in THF at room temperature. The reaction is even applicable to hindered phenols (2,6-di-t-butyl-/>-cresol, 86% yield) and alcohols (triphenylcarbinol, 85% yield). However, acidic phenols (p-nilrophenol) are not methylated by this procedure even at 80°. This behavior contrasts to that of diazomethane, which readily methylates acidic phenols. 

Buttner-Rosin pneumatic dryer, 265 performance, 264 Butyl cresol purification, 547... 

Hindered phenolates have low nucleophilicity and in aprotic solvent may act usefully as EGBs. 2,6-Di-t-butyl-/ -cresol = 16.8) was reduced directly with concomitant hydrogen evolution to give, ex situ, the corresponding tetraethylammonium phenolate [59,60], which was clearly capable of deprotonating aromatic ketones and in the presence of aromatic aldehydes promoted aldol reaction to a, /3-unsaturated ketones which underwent Michael addition. The initial proton transfer from the aromatic ketone ] K = 24.7) is thermodynamically very unfavorable. Even so, aldol reaction took place within a matter of hours upon addition of an aromatic ketone together with an aromatic aldehyde leading to or, /3-unsaturated ketones which subsequently underwent Michael addition with a sec-... 

The mixture of cresols obtained from coal tar is called cresylic acid, an important technical product used as a disinfectant and in the manufacture of resins and tricresyl phosphate. Cresols are useful as raw materials for various chemical products, disinfectants, and synthetic resins. The isomer o-cresol is a starting material for the herbicides 4,6-dinitro-o-cresol and 2-methyl-4-chlorophenoxyacetic acid. The isomers w-cresol and p-cresol are used in phenol-formaldehyde resins and are converted to tricresyl phosphate (a plasticizer and gasoline additive) and to di-t-butyl cresols (antioxidants called BHT). 

Alkyl phenols as mentioned earlier are phenol derivatives wherein one or more of the benzene ring hydrogens are substituted by an alkyl group. Cresols are monosubstituted methyl phenols, xylenols are dialkyl phenols with two methyl groups. Similarly other alkyl groups such as butyl phenols, butyl cresols are also examples of alkyl phenols. Some of them... 

In the alkylation process, apart from butylated cresols isobu-tylated homopolymers diisobutylene and triisobutylene are also formed. 

Usually di-teAt-butyl cresols are dealkylated at around 200° C in presence of acid catalysts mentioned earlier and produce meto-cresol, para-cresol, and isobutylene. Individual cresols are purified by distillation. Such processes produce 99% + pure individual cresols. As of now, the companies mentioned above produce BHT and m-cresol based on alkylation of m-p-cresols. However, as of now, no company is making pure p-cresol. But theoretically very pure p-cresol can be obtained by dealkylation of BHT. 

Fig. 1. Chemical transformations of 2,6-di- / -butyl- -cresol in an oxidizing medium (10).

Butylated hydroxytoluene (BHT), or 2,6 di-fer -butyl-/ -cresol, was used for many years as an excellent antioxidant in polyether polyols. Owing to its intrinsic volatility, BHT was eliminated as an antioxidant and a new type of polyether called BHT free polyethers has appeared. The low volatility antioxidants give good fogging resistance, such as in interior automotive applications [140]. 

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. ... 

Di-tert-butyl-/>-cresol (2,6-dWert-butyl-4-methylphenol, butylatedhydroxytoluene, BHT or DBPC)... 

Spell and Eddy [3] described infrared (IR) spectroscopic procedures for the determination of up to 500 ppm of various additives in polyethylene (PE) pellets following solvent extraction of the additives at room temperature. They showed lonol (2,6-di-ter -butyl-p-cresol) and Santonox R (4,4 -thio-bis(6-ter -butyl- /-cresol)) are extracted quantitatively from PE pellets by carbon disulfide in 2-3 hours and by isooctane in 50-75 hours. The carbon disulfide extract is suitable for scanning in the IR region between 7.8 and 9.3 (xm, while the isooctane extract is suitable for scanning in the UV region between 250 and 350 nm. 

Low levels of antioxidants, such as 2,6-di-f-butyl-/ -cresol in /xg amounts of PE, have been determined by the first commercial thermal evolution analysis equipment based on the design by Eg-gertsen et al. [906] with flame ionisation detection (Fig. 2.43) [923]. The high sensitivity of FID can also be utilised for vapour pressure measurements... 

The thermal desorption methods discussed in this Chapter are based on heating the material below the decomposition temperature of the polymer, as illustrated by Wampler [1004] in TD-GC of 1 mg PVC/DEHP heated at 300° C. At higher temperatures, less volatile organic additives will be desorbed more readily, but polymer decomposition products (and perhaps additive pyrolysates) will add complexity to the chromatogram, as in case of the analysis of 2,6-di-r-butyl-/ -cresol (BHT) in SBR [784], The obvious lesson here is to heat the polymer only to the temperature necessary to vaporise the materials of interest. The method is also less useful for compounds which are too unstable for GC analysis. Wampler [1010a] has illustrated direct multi-step polymer and additive analysis by sample temperature control on-line with the GC injector for removal of semivolatiles followed by polymer identification by PyGC-MS. 

A study was made of the ozonolysis of butyl rubber and its halogenated derivatives, as well as their model compounds in hexane. The effect of various additives, such as diphenylamine, triisopropyl phosphite, hexylamine and 2,6-di-tert-butyl cresol, on chain scission and rearrangement of bromobutyl rubber, was also evaluated. It was found while the ozonolysis of butyl and chlorobutyl mbbers involved normal cleavage of olefmic double bonds, the mechanism of ozonolysis of bromobutyl mbber was more complicated. 8 refs. 

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