How can I prepare Trimethylolpropane trimethacrylate (TMPTMA)?
I know that I have to start with Trimethylol propane (TMP) and methacrylic acid (MAA) in 1:3 but I don't know the right condition to get the final product with acid value less than 0.5 mg/KOH without a gelation problem
Hope this will help Botros S Meglaa
https://patents.google.com/patent/JPS5470215A/en
PURPOSE: To obtain the title compound useful as a raw material for synthetic resin, coating compounds, etc. with little discoloration, by extracting a reaction product formed from (meth)acrylic acid and trimethylolpropane with cyclohexane as a solvent.
CONSTITUTION: (Meth)acrylic acid is reacted with trimethylolpropane in the presence of an acid catalyst, and the reaction product is extracted with cyclohexane as a solvent to shift the trimethylolpropane tri(meth)acrylate to the cyclohexane layer. The imperfect ester, e.g. trimethylolpropane diacrylate, etc., unreacted trimethylolpropane, the catalyst, etc. are separated as a residual oil layer. The cyclohexane layer is washed with an alkali and water. After the cyclohexane is distilled away, the residue is treated with active carbon to give the title compound without distillation.
EFFECT: Unreacted raw meterial in the residual oil can be used repeatedly. The color of the product is constant and ≤ APHA20.
Dear Botros S Meglaa many thanks for posting this very interesting technical question on RG. Please note that trimethylolpropane trimethacrylate (TMPTMA) is a commercially available product. Thus in the case that you need only a small amount, it might be a possible option to buy it from a commercial supplier.
A detailed synthetic procedure on a fairly large scale has been published in the following freely accessible link:
https://prepchem.com/trimethylolpropane-triacrylate/
Citation: "2.44 kg of trimethylolpropane, 3.93 kg of acrylic acid, 0.5 kg of an acid ion exchanger (Lewatit 3333 of BAYER AG), 9 g of hydroquinone and 1.5 liters of petroleum ether (boiling range 60° to 70° C) were heated under a water separator, whilst stirring, in a 10 liter three-necked flask equipped with a stirrer, water separator and gas inlet tube. At the same time, a constant stream of air saturated with allyl alcohol was passed through the flask at a rate of 2 liters/hour. In total, 16 ml of allyl alcohol were introduced into the esterification mixture in this way. After 80 hours, the reaction mixture had an acid number of 32 and the boiling point had risen to 72° C. The petroleum ether was distilled off, remnants being removed by applying a vacuum of 0.2 mm Hg at a product temperature of 40° C. The esterification catalyst was separated off by filtration and was kept for further use. The trimethylolpropane triacrylate obtained in practically quantitative yield was pale yellowish and clear. The viscosity corresponded to a time of outflow of 20 seconds measured in a DIN cup 4 at 20° C. The product showed no change even on storage for 4 months at 60° C."
Of course, if you require smaller amounts, you can creduce the amounts of starting materials accordingly. As you can see, an acidic catalyst is required. In this case the authors used an acidic ion exchanger as catalyst. The function of the added hydroquinone is to stabilize the mixture and prevent polymerization. It is not clear to me, however, what the function of the added allyl alcohol is in this reaction. If you run the reaction on a smaller scale, you can perhaps skip the allyl alcohol.
I hope this helps. Good luck with your work and best wishes, Frank Edelmann
Dear, Frank T. Edelmann and Kashif Ameer,
Thank you for your answers. I tried these two formulations before posting the question with no results. Every time, I got high acid value or gel.
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