Antioxidant TBX
[CAS# 1879-09-0]

Identification

• Classification: Catalysts and additives >> Antioxidant
• Name: Antioxidant TBX
• Synonyms: 2-(tert-Butyl)-4,6-dimethylphenol; 2,4-Dimethyl-6-tert-butylphenol; Topanol A; Anitoxidant 6BX; Antioxidant LA; Antioxidant AO 30; MMA inhibitor
• Molecular Formula: C₁₂H₁₈O
• Molecular Weight: 178.27
• CAS Registry Number: 1879-09-0
• EC Number: 217-533-1
• SMILES: CC1=CC(=C(C(=C1)C(C)(C)C)O)C

Properties

• Density: 1.0±0.1 g/cm³ Calc.^*
• Melting point: 22 ºC (Expl.)
• Boiling point: 249.0 ºC 760 mmHg (Calc.)^*
• Flash point: 111.7 ºC (Calc.)^*
• Index of refraction: 1.512 (Calc.)^*

^* Calculated using Advanced Chemistry Development (ACD/Labs) Software.

Safety Data

• Hazard Symbols: GHS06;GHS07;GHS08;GHS09 Danger
• Hazard Statements: H301-H302-H310-H315-H319-H373-H411
• Precautionary Statements: P260-P262-P264-P264+P265-P270-P273-P280-P301+P316-P301+P317-P302+P352-P305+P351+P338-P316-P319-P321-P330-P332+P317-P337+P317-P361+P364-P362+P364-P391-P405-P501

Hazard Classification

Hazard	Class	Category Code	Hazard Statement
Skin irritation	Skin Irrit.	2	H315
Eye irritation	Eye Irrit.	2	H319
Acute toxicity	Acute Tox.	4	H302
Chronic hazardous to the aquatic environment	Aquatic Chronic	2	H411
Specific target organ toxicity - repeated exposure	STOT RE	2	H373
Acute toxicity	Acute Tox.	1	H310
Acute hazardous to the aquatic environment	Aquatic Acute	1	H400
Skin sensitization	Skin Sens.	1	H317
Chronic hazardous to the aquatic environment	Aquatic Chronic	1	H410
Acute toxicity	Acute Tox.	3	H311
Acute toxicity	Acute Tox.	3	H331
Skin corrosion	Skin Corr.	1B	H314
Specific target organ toxicity - single exposure	STOT SE	3	H335
Acute toxicity	Acute Tox.	3	H301
Acute toxicity	Acute Tox.	2	H310

Discovory and Applicatios

Antioxidant TBX, chemically known as 2,2'-Methylenebis(6-tert-butyl-4-methylphenol), is a sterically hindered phenolic antioxidant used to protect polymers and organic materials from thermal and oxidative degradation. It belongs to the class of bisphenolic antioxidants, which are widely employed in the stabilization of plastics, rubber, oils, and lubricants due to their effectiveness in interrupting free-radical oxidation pathways.

The structure of Antioxidant TBX features two phenolic rings, each substituted with a methyl group in the para position and a bulky tert-butyl group in the ortho positions, linked through a methylene bridge. This configuration enhances the molecule's stability and its ability to donate hydrogen atoms to neutralize reactive oxygen species and free radicals formed during polymer processing and environmental exposure. The tert-butyl groups provide steric hindrance, preventing rapid oxidation of the phenolic hydroxyl groups, and thereby extend the antioxidant's activity over longer durations.

Antioxidant TBX was developed in response to the need for high-performance antioxidants capable of withstanding elevated temperatures during the extrusion, molding, or compounding of thermoplastic and elastomeric materials. Its primary mode of action is radical scavenging: it inhibits oxidation by donating hydrogen atoms to lipid or polymer radicals, forming relatively stable phenoxyl radicals that do not propagate chain degradation reactions. These features make it particularly useful for thermally sensitive systems, such as polyolefins, polystyrenes, polyamides, and synthetic rubbers.

One of the key advantages of Antioxidant TBX is its low volatility and excellent color retention. It resists sublimation at processing temperatures and does not cause discoloration of the final product, which is essential for applications where appearance is critical. This makes it a preferred additive in light-colored or transparent materials, as well as in applications where long-term weathering or heat exposure is expected, such as in automotive components, building materials, and electrical insulation.

In practice, Antioxidant TBX is often used in combination with other antioxidants, such as phosphite-based secondary antioxidants. These combinations allow for a synergistic effect, where TBX acts as a primary antioxidant to trap radicals, while secondary antioxidants decompose hydroperoxides, regenerating the active phenolic antioxidant in the process. This dual-action system provides enhanced protection during both high-temperature processing and prolonged storage or use.

In terms of safety and regulatory acceptance, Antioxidant TBX has been evaluated for its toxicological profile and is approved for use in specific applications, including some food-contact materials. Its molecular design ensures low migration and extraction, reducing the risk of leaching into surrounding media. This property is critical in applications involving exposure to liquids or foodstuffs.

The industrial synthesis of Antioxidant TBX typically involves the alkylation of cresol derivatives followed by a methylene bridging step to yield the bisphenolic structure. The resulting product is a white to light tan crystalline powder, with good solubility in organic solvents and compatibility with various polymer matrices. It is commercially available and used as a masterbatch additive or directly incorporated into polymer formulations.

As sustainability becomes increasingly important in materials science, there is ongoing research into biodegradable and environmentally benign alternatives to conventional antioxidants. However, Antioxidant TBX continues to serve as a benchmark for thermal and oxidative stability, with well-documented performance and a broad application profile. Its durability, processing safety, and compatibility with a wide range of materials ensure its continued relevance in both legacy and modern polymer systems.

References

2002. Reversed-phase HPLC of polymer additives with multiple on-line spectroscopic analysis (UV, IR, (1)H NMR and MS). Analytical and Bioanalytical Chemistry.
DOI: 10.1007/s00216-002-1249-3

2003. Determination of Phenolic Antioxidants in Spilled Aviation Fuels by Gas Chromatography-Mass Spectrometry. Chromatographia.
DOI: 10.1365/s10337-003-0079-6

2008. About selective methods of synthesis of 6-tert-butyl-2-methylphenol and 6-tert-butyl-2,4-dimethylphenol. Russian Journal of General Chemistry.
DOI: 10.1134/s1070363209060218