| Résumé : |
Tertiary amine catalysts used for manufacturing polyurethanes and polyisocyanurates are known to degrade over time, producing products such as aldehydes that can directly contribute to emissions of organic compounds. To remain within the tolerable exposure limits, an analytical method with sufficient accuracy is needed to ensure that no or low concentrations of aldehydes are present in the catalyst samples.
Recently, a systematic analytical approach was reported for the accurate determination of aldehydes present in amine catalysts or amines by liquid chromatography using ultraviolet (UV) detection of their 2,4-dinitrophenylhydrazone derivatives.1 Based on various factors controlling the derivatization of aldehydes, optimum conditions were selected for the accurate determination of aldehydes. In addition, probable reaction mechanisms in both acidic and basic conditions were highlighted.
Since amine catalyst solutions in water are basic, it is important to have a clear understanding of the derivatization of aldehydes present in these materials, specifically, by looking at the effects of solution pH, derivatization reaction time and the number of active nitrogen atoms in amines. It was found that only a small fraction of aldehydes present in the amine can be derivatized in a basic environment. It appeared that most of the reaction steps in the near neutral and basic environments are kinetically slow and equilibrium limited. Ideally, the derivatization using 2,4-dinitrophenyl-hydrazine (DNPH) can be completed in an acidic environment, specifically, at pH around 2 with an excess amount of DNPH.
In this work, aldehyde data for four amine catalyst samples containing 1-3 nitrogen atoms have been obtained. The structures and chemical names of these amine catalyst samples are provided in Figure 1. This article intends to address issues related to the formation and accurate determination of aldehydes in amine catalysts used in the polyurethane industry. |
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Ajouter le résultat dans votre panier Affiner la rechercheFormation and determination of aldehydes in amine catalysts in ADHESIVES & SEALANTS INDUSTRY (ASI), Vol. 22, N° 4 (04/2015)
