4-MBP (CAS 134-84-9)
| CAS No. | 134-84-9 |
|---|---|
| Alias | Methyl benzophenone |
| Category | Photoinitiators |
| Purity | ≥99.00% |
| Packaging | 20kg/carton |
4-MBP is a general-purpose free radical photoinitiator, often used as an improved version of BP. It offers high initiation efficiency and low odor, and is particularly suited for UV-curable wood coatings and varnishes. Recommended dosage is 3–5% and it can directly replace BP to achieve lower-odor cured products.
Equivalent grades. The same substance is sold by other manufacturers as Omnirad 4MBZ. It is the same CAS number (134-84-9) and the same chemistry, so a formulation written around one of those grades transfers directly.
Introduction
4-MBP is what formulators specify when they want benzophenone behaviour without benzophenone's odour. It is the same Type II mechanism, absorbing at 260 nm and requiring an amine synergist to generate radicals, but the methyl group on the ring changes the volatility and the smell profile of the cured film.
The trade-off is straightforward. In many wood coating and varnish formulations 4-MBP can be substituted for BP directly, and the cured product comes out with less residual odour. What you cannot do is assume the regulatory position follows the chemistry: 4-MBP and benzophenone sit in different places in most of the instruments that matter.
Physical & Chemical Properties
White to pale yellow crystalline powder. Molecular formula C14H12O, molecular weight 196.24, purity ≥99.00%, melting range 55.0–58.0 °C, loss on drying ≤0.50%. Absorption maximum at 260 nm.
Applications
Recommended at 3–5%. Particularly suited to UV-curable wood coatings and varnishes, used with a tertiary amine. It is also an intermediate of interest in organic synthesis.
Regulatory status
4-MBP is listed in Swiss Annex 10 at 0.05 mg/kg, and separately it appears in the sum limit with benzophenone: the combined migration of 4-methylbenzophenone and benzophenone must not exceed 0.6 mg/kg. It has its own entry, number 233, in category V of the German Anlage 14. It has no harmonised classification under CLP. Unlike benzophenone it is not on the EU 10/2011 Annex I positive list.
The 2009 incident that made 4-MBP well known is often retold inaccurately. It concerned muesli, not breakfast cereal generally, and it did not result in an EU-wide ban on 4-MBP. What followed was a Standing Committee conclusion on the benzophenone and 4-methylbenzophenone sum limit, and national legislation in Germany. If a customer cites a ban, that is the history worth correcting.
Handling & Storage
Store sealed in a cool, dry, ventilated area. Consult the SDS.
Packaging
20 kg cartons or drums. COA per batch, SDS in English.
Applications & Industries
Coatings & Paints
Metal driers (cobalt, manganese, zirconium octoate, naphthenates) and photoinitiators for coatings, paints, varnishes and industrial finishes — with COA & MSDS per batch.
UV Curing & Printing Inks
Free radical photoinitiators for UV-curable inks, coatings, adhesives and 3D printing — 1173, 184, 369, 907, ITX, DETX, TPO/TPO-L and liquid blends, QC-tested per batch.
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