What Is Antioxidant 2246?
Antioxidant 2246, CAS 119-47-1, chemically 2,2′-methylenebis(4-methyl-6-tert-butylphenol), is a hindered phenolic (bis-phenol) antioxidant. It protects rubber, plastics and other organic materials against heat and oxygen ageing – the gradual degradation that makes a polymer harden, crack, discolour or lose strength over time.
Antioxidant 2246 is a non-staining, non-discolouring antioxidant. Because it does not discolour, it is used in light-coloured and bright compounds as well as in general rubber goods, where an amine antioxidant (which is cheaper but stains) could not be used. PolyBlueChem supplies it to a controlled specification with per-batch COA and SDS. This guide covers its chemistry, mechanism, production, specification, properties, applications, comparison with other antioxidants, dosage, safety and supply.
| CAS number | 119-47-1 |
| Chemical name | 2,2′-Methylenebis(4-methyl-6-tert-butylphenol) |
| Synonyms | Antioxidant 2246; 2,2′-methylenebis(6-tert-butyl-4-methylphenol); bis(2-hydroxy-3-tert-butyl-5-methylphenyl)methane; methylene bisphenol |
| Molecular formula | C23H32O2 |
| Molecular weight | 340.5 g/mol |
| Type | Hindered phenolic (bis-phenol) antioxidant |
| Appearance | White or milk white powder |
Chemistry and Structure
Antioxidant 2246 is a bisphenol: two hindered phenol units are joined by a methylene (-CH2-) bridge. Each phenol ring carries a tert-butyl group next to the hydroxyl group and a methyl group para to it. The structure is what gives the product its function:
- The phenolic -OH is the “active” group. It can transfer a hydrogen atom to a peroxy radical (ROO•), stopping the chain reaction of oxidation.
- The bulky tert-butyl group sterically shields the phenolic -OH, which is why the phenol is “hindered” – it reacts with damaging radicals but not with the polymer itself, and it resists side reactions that would discolour the material.
- The methylene bridge raises the molecular weight to about 340, so the molecule is far less volatile than a simple phenol such as BHT. Low volatility means the antioxidant stays in the compound during high-temperature processing and long service.
Because the molecule is entirely hydrocarbon except for the two phenolic hydroxyls, it leaves no colouring or staining groups – hence the “non-staining” reputation that makes it suitable for light-coloured goods.
How It Works as an Antioxidant
Polymers age by an auto-oxidation cycle: heat, light or metal traces start it, and it propagates as peroxy radicals (ROO•) attack the polymer chain, producing more radicals and eventually cross-linking or chain scission. The visible results are hardening, cracking, tackiness or discolouration. Antioxidants break this cycle.
Hindered phenolics such as 2246 act as chain-breaking (radical-scavenging) antioxidants:
- The phenolic -OH donates a hydrogen atom to a peroxy radical, converting it to a stable hydroperoxide and converting the antioxidant into a stable phenoxy radical.
- The phenoxy radical is resonance-stabilised and unreactive, so it does not continue the chain.
- The result is that the oxidation chain is interrupted and the polymer is protected (the induction period before ageing starts is lengthened).
Because hindered phenolics act on radicals rather than being consumed in a single event, their efficiency is measured as the length of protection they give at a given loading. For long-term heat ageing, they are often combined with a secondary (peroxide-decomposing) antioxidant such as a phosphite or thioester, which handles the hydroperoxides that the phenolic leaves behind.
How Antioxidant 2246 Is Produced
Antioxidant 2246 is made by an acid- or base-catalysed condensation: 2-tert-butyl-4-methylphenol (a hindered phenol) is reacted with formaldehyde, which supplies the methylene bridge linking two phenol rings. The reaction is a classic ortho-methylolation and coupling:
- The hindered phenol is methylolated (a -CH2OH group is introduced next to the -OH).
- The methylolated intermediate condenses with a second phenol molecule, forming the -CH2– bridge.
- The product is crystallised, filtered, washed and dried to a white powder.
Reaction control is aimed at maximising the bis-phenol (dimer) and minimising higher oligomers and unreacted phenol, because residual free phenol and oligomers affect melting point, colour and performance. A typical specification therefore fixes the melting point, heating loss, ash and sieve residue rather than only the assay.
Specifications and Quality Control
Antioxidant 2246 is supplied as a white or milk white powder to the following specification:
| Parameter | Specification |
|---|---|
| Appearance | White or milk white powder |
| Melting point | 122 °C min |
| Heating loss | 0.30% max |
| Ash | 0.20% max |
| Sieve residue (150 µm) | 0.5% max |
The parameters each control a different risk:
| Parameter | What it controls |
|---|---|
| Melting point (122 °C min) | Purity and the proportion of the bis-phenol; a low melting point signals free phenol or oligomers |
| Heating loss (0.30% max) | Moisture and volatile content; affects weighing and storage |
| Ash (0.20% max) | Inorganic residues that can affect ageing and colour |
| Sieve residue (150 µm, 0.5% max) | Particle-size / dispersion in the compound |
A specification sheet and a per-batch certificate of analysis (COA) are available on request.
Key Properties
| Property | Behaviour | Practical value |
|---|---|---|
| Function | Chain-breaking antioxidant (radical scavenger) | Protects against heat and oxygen ageing |
| Colour | Non-staining, non-discolouring | Suitable for light-coloured and white compounds |
| Volatility | Low (MW about 340) | Survives high-temperature processing |
| Form | White powder | Easy to weigh and disperse |
| Solubility | Solubility in the polymer is moderate; well dispersed at typical loadings | Effective at low phr |
Applications
Antioxidant 2246 is used wherever a non-staining, heat-ageing-protection is needed.
| Industry | Function |
|---|---|
| Rubber (NR, SBR, BR, NBR) | Anti-ageing protection during processing and service |
| Latex | Protection of natural and synthetic latex compounds |
| Plastics | Thermal-oxidative stabilisation of polyolefins, styrenics and others |
| Adhesives and sealants | Stabilisation against ageing |
| Light-coloured goods | Where a non-staining antioxidant is essential |
| White and coloured rubber | Footwear, white sidewalls, light mechanical goods |
- Tyre and technical rubber – protection of the polymer backbone against heat ageing during cure and service; often combined with an amine antioxidant (6PPD/7PPD) where dynamic-oxidation protection is also needed.
- Light-coloured rubber goods – because it does not stain, it is the antioxidant of choice for white, pastel and bright compounds.
- Plastics – stabilisation of polyolefins and styrenic polymers against processing and service ageing.
- Latex and adhesives – protection of latex film and adhesive layers.
Antioxidant 2246 vs Other Antioxidants
Antioxidant 2246 is often compared with BHT (264), the high-MW hindered phenolics (such as 1010) and the staining amine antioxidants (RD/TMQ, 6PPD/7PPD).
| Antioxidant | CAS | Type | Staining | Typical role |
|---|---|---|---|---|
| Antioxidant 2246 | 119-47-1 | Hindered phenolic (bis-phenol) | Non-staining | Light-coloured rubber and plastics |
| BHT (264) | 128-37-0 | Hindered phenolic (mono-phenol) | Non-staining | Plastics, oils; volatile |
| Antioxidant 1010 | 6683-19-8 | Hindered phenolic (tetrakis) | Non-staining | High-MW plastics; low volatility |
| Antioxidant RD (TMQ) | 26780-96-1 | Amine (quinoline) | Staining | Tyres and dark goods; strong heat/fatigue protection |
| 6PPD / 7PPD | 793-24-8 / 3081-01-4 | Amine (paraphenylenediamine) | Staining | Anti-ozonant / anti-flex for tyres |
Guidance:
- Need non-staining protection? Choose a hindered phenolic – 2246 or BHT/1010.
- Light-coloured, high-temperature processing? 2246 (higher MW than BHT, so less volatile).
- Strong dynamic / fatigue protection in dark goods? An amine antioxidant (RD, 6PPD) is more effective but stains.
- Multi-purpose blends – 2246 is often used with a phosphite or thioester to cover both radical and hydroperoxide routes.
Dosage and Use
Antioxidant levels are set by the compound and the required service life, and must be confirmed by ageing tests. The figures below are orientation only.
| Application | Starting-point guidance |
|---|---|
| General rubber | A few phr, adjusted for the polymer, cure system and expected service temperature |
| Light-coloured rubber goods | Set for the required colour stability and heat-ageing life |
| Plastics | Low percentages of the polymer weight |
| Combined systems | Used with a secondary antioxidant (phosphite/thioester) for full protection |
2246 disperses well as a powder. Because it works on radicals, over-loading does not simply “add more protection” – the level is optimised against cost, bloom and the specific ageing mechanism.
Interaction with Vulcanisation and Other Additives
An antioxidant is one part of a compound, and it interacts with the other parts. Two interactions matter in practice.
- With the cure system – antioxidants can influence cure kinetics, and some (especially amines) can affect the scorch and cure rate. Phenolic antioxidants such as 2246 are generally benign in this respect, which makes them easy to use alongside sulfenamide, thiazole and guanidine accelerators. The level is still confirmed by cure testing (rheometer) on the finished compound.
- With other protective agents – for full protection a compound may combine a hindered phenolic (heat/oxygen ageing) with an amine antiozonant/antiflex agent (such as 6PPD/7PPD), plus a secondary antioxidant. The phenolic provides the non-staining part of the package; the amine covers dynamic and ozone attack in dark goods.
| Additive in the compound | Typical interaction with 2246 |
|---|---|
| Sulfenamide / thiazole / guanidine accelerators | Largely independent; confirm cure rate by test |
| Amine antiozonant (6PPD/7PPD) | Complementary – phenolic for heat ageing, amine for dynamic/ozone |
| Secondary antioxidant (phosphite/thioester) | Synergistic – handles hydroperoxides |
| Fillers, oils and plasticisers | No direct reaction; dispersion and solubility govern performance |
The practical rule is to treat the antioxidant as part of a system: choose the type and level together with the cure system, the service conditions and the colour requirement, and confirm the ageing life by heat-ageing tests on the finished article.
Safety, Handling and Storage
- Low hazard – hindered phenolic antioxidants are of low acute toxicity and are widely used in rubber and plastics.
- Dust – use dust control where large amounts are handled; avoid breathing the powder.
- Hygiene – good industrial hygiene practice; wash after contact.
- Storage – keep sealed, cool and dry; the powder should stay free-flowing and white.
Regulatory and Food-Contact Notes
| Use | Status (as commonly cited) |
|---|---|
| Rubber and plastics (industrial) | Governed by the buyer’s specification and by the relevant article/contact regulations |
| Food-contact applications | Only where the material is permitted for the specific contact use; confirm the applicable regulation for your market |
For any food-contact or potable-water application, confirm that the grade and the specific use are permitted in your market before ordering; a technical grade is supplied here.
Packaging, Logistics and Supply
| Item | Standard options |
|---|---|
| Packaging | 25 kg PP/PE bags or fibre drums |
| Documentation | Per-batch COA and SDS |
| Incoterms | FOB and CIF |
| Storage | Sealed, cool and dry |
As a specialty rubber chemical, price depends on the feedstock phenol, formaldehyde and the finishing quality. Buying on committed tonnage gives the best terms. For buying guidance see the rubber-additives cluster overview.
Antioxidant 2246 in Plastics, Adhesives and Coatings
Although it is best known as a rubber antioxidant, 2246 is also used to stabilise plastics and related materials. In each case the job is the same – to break the oxidation chain before the polymer is damaged – but the processing conditions change how the antioxidant must behave.
| Material | Why 2246 helps |
|---|---|
| Polyolefins (PE, PP) | Protects against thermal oxidation during extrusion and long-term service |
| Styrenic polymers (ABS, SBR-based) | Non-staining stabilisation without discolouring the polymer |
| Adhesives and sealants | Prevents ageing-induced tack loss or hardening |
| Coatings and films | Protects the binder against heat and light ageing |
In plastics, the non-staining character and the relatively low volatility of 2246 matter during compounding and forming: a volatile antioxidant (such as BHT) can be lost at high melt temperatures, while 2246 stays in the polymer and keeps its protection.
Heat Ageing, Bloom and Compatibility
Three practical effects decide how an antioxidant behaves in a real compound.
- Heat ageing – the antioxidant lengthens the induction period before oxidation starts. The higher the service temperature and the longer the life required, the more important a low-volatility, high-molecular-weight antioxidant such as 2246 becomes.
- Bloom – if an antioxidant is added above its solubility limit in the polymer, it can migrate to the surface (bloom), which wastes the addition and can spoil the appearance. For non-staining goods this matters as much as the colour of the antioxidant itself.
- Compatibility and dispersion – a finely divided powder that disperses evenly gives more reliable protection than the same weight poorly dispersed. Particle size (sieve residue on the COA) is a useful proxy for dispersion behaviour.
Because 2246 is non-discolouring and disperses cleanly, it is a common choice where a compound must stay white or bright through its whole ageing life.
Combining with Secondary Antioxidants
Chain-breaking antioxidants handle peroxy radicals but leave hydroperoxides behind, and these can still decompose to start new oxidation. A secondary (peroxide-decomposing) antioxidant removes them. Using the two together is standard practice because the combination is more effective than either alone (synergism).
| Component | Role | Examples |
|---|---|---|
| Primary (chain-breaking) | Scavenges peroxy radicals | Hindered phenolics such as 2246, BHT, 1010; amines such as RD |
| Secondary (hydroperoxide-decomposing) | Removes hydroperoxides | Phosphites; thioesters (thiodipropionates) |
A typical stabiliser package therefore pairs a phenolic (or amine) with a phosphite or thioester. 2246 is often the phenolic partner, giving non-staining radical protection while the secondary antioxidant handles hydroperoxides.
Frequently Asked Questions about Antioxidant 2246
What is Antioxidant 2246 used for?
It is a non-staining hindered phenolic antioxidant used to protect rubber, latex and plastics against heat and oxygen ageing, including light-coloured compounds.
What is the CAS number?
119-47-1.
Is it the same as BHT?
No. BHT (264, CAS 128-37-0) is a single-ring hindered phenol; 2246 is a bisphenol with a higher molecular weight and lower volatility.
Does it stain or discolour rubber?
No – it is non-staining and non-discolouring, which is why it suits white and light-coloured goods.
Can it replace an amine antioxidant like RD?
Only partly. Hindered phenolics protect against heat/oxygen ageing; amine antioxidants give stronger fatigue protection but stain. In tyres the two are often combined.
What is a typical addition level?
A few phr in rubber, set by the ageing test; confirm on your own compound.
How should it be stored?
Sealed, cool and dry, away from moisture and strong odours.
Related reading
- Antioxidant 2246 in rubber and plastics
- Rubber antioxidants and accelerators: selection guide
- Butylated hydroxytoluene (BHT): properties and applications
- Antioxidant RD (TMQ): properties and applications
- Antioxidant 2246 (CAS 119-47-1) – product page
PolyBlueChem supplies Antioxidant 2246 (CAS 119-47-1) to a controlled specification, with per-batch COA and SDS, competitive pricing on bulk volumes and FOB/CIF delivery. Contact us with your application, tonnage and delivery port.