Heterogeneous Brønsted Catalysis in the Solvent-Free and Multigram-Scale Synthesis of Polyalcohol Acrylates: The Case Study of Trimethylolpropane Triacrylate

This article presents a thorough investigation into the synthesis of trimethylolpropane triacrylate (TMPTA) via the esterification reaction of trimethylolpropane (TMP) with acrylic acid using Amberlite™ 120 IR (H+), Amberlyst® 15, and Dowex™ 50WX8 resins as heterogeneous catalysts. Preliminary comparative tests explored the impact of air flow on water removal during the reaction and different acid-to-alcohol molar ratios (3:1, 6:1, or 9:1 mol:mol). The findings revealed that introducing air significantly enhances TMPTA yield and -OH group conversion, particularly at a 6:1 acid-to-alcohol molar ratio. Based on cost considerations, Amberlite™ 120 IR (H+) was selected as the preferred catalyst for further optimization. This included evaluating the effect of catalyst loading (10%, 5.0%, and 2.5% w/wtot) and assessing the impact of a pre-drying process on resin efficiency. The study concluded that optimal conditions did not necessitate drying, requiring 120 °C, a catalyst loading of 10% w/wtot, a 4 h reaction time, an acid:alcohol ratio of 6:1 mol:mol, the presence of MEHQ (0.1% mol/molAA), and air bubbling at 6 ± 1 Nl/h. Catalyst recycling was effectively implemented with a slight reduction in catalytic activity over consecutive runs. Furthermore, the study explored a scaled-up system with a mechanical stirrer, demonstrating the potential for multi-hundred grams scale-up. Considerations for optimizing the air flow stripping system are also highlighted. In summary, this study provides valuable insights into designing and optimizing the esterification process for TMPTA synthesis, laying the foundation for potential industrial applications.

Presence of 2-hydroxyethyl methacrylate (HEMA) and other (meth)acrylates in nail cosmetics, and compliance with EU legislation: An online market survey

BACKGROUND

During the last 15-20 years, allergic contact dermatitis from acrylates-containing nail cosmetics (acrylic nails, gel nails, gel nail polish) has been increasingly reported. 2-Hydroxyethyl methacrylate (HEMA) is considered to be the major allergenic culprit; few data on its presence in nail cosmetics are available.

OBJECTIVES

To investigate (1) the frequency in which HEMA and di-HEMA trimethylhexyl dicarbamate are present in nail cosmetics; (2) whether nail cosmetics comply with EU regulations; (3) which other (meth)acrylates are present in nail cosmetics and how often.

METHODS

One-line market survey.

RESULTS

HEMA was present in nearly 60% of 394 cosmetic nail products and di-HEMA trimethylhexyl dicarbamate in 34%. Mandatory warnings on the packages of products containing HEMA were absent in 35% ('For professional use only') resp. 55% ('Can cause an allergic reaction'). Forty-five other (meth)acrylates were identified, of which the most frequent were hydroxypropyl methacrylate (25%), isobornyl methacrylate (16%) and trimethylolpropane triacrylate (12%). Some ingredient lists mentioned non-INCI names or non-specific names.

CONCLUSIONS

HEMA was by far the most common ingredient of nail cosmetics, being present in nearly 60% of the products. Violations of EU legislation occurred in >30% (mandatory warnings missing) resp. 10% (mislabelling) of nail cosmetics.