SinS - Abstract

Abstract Information :

Resin binders are essential ingredients in ink formulations, where they primarily promote the dispersion of the pigments and the adhesion of the ink to the substrate. Other properties, such as the viscosity, the gloss, and the surface resistance of an ink are determined by the mix of binders employed in the formulation, as well. Based on natural products like gum rosin and tall oil, resin binders can be chemically modified to match the desired properties. Gum rosin, for example, is industrially obtained by heating the pine resin: it is mainly constituted of abietic acid and related resin acids, which are subsequently hydrogenated and esterified to yield the final binder product – esters of hydrogenated rosin, in this case. The analysis of the esters of hydrogenated rosin is crucial for monitoring the consistency of the materials and for matching the chemical properties at molecular level with the macroscopic performances. However, such materials are usually constituted by a large mixture of different chemical species, due to both the sourcing of the natural starting materials and the processes that they undergo, posing significant challenges from an analytical point of view [1]. A chromatographic (uHPLC) method for the separation and the characterisation of the main components of the esters of hydrogenated rosin is presented. Detection is performed by high-resolution mass spectrometry (HRMS) using an Orbitrap® mass analyser, while ionisation of the analytes is obtained using an Atmospheric Pressure Chemical Ionisation (APCI) source. Further investigation expanded the applicability of the same method to another common class of binders based on natural products, namely terpene-phenolic resins. Esters of hydrogenated rosin from different suppliers and characterised by different macroscopic properties have been analysed in terms of their molecular compositions. The uHPLC-HRMS approach allowed us to differentiate between the components and to group them in terms of esterification grade and apparent unsaturation grade of the abietic acid moiety. Comparing these molecular properties across the analysed samples proved to be an effective tool for the evaluation of the raw materials in terms of consistency of the composition and of the macroscopic properties required for the intended application. [1]. Mess, A., Vietzke, J. P., Rapp, C., & Francke, W. (2011). Qualitative analysis of tackifier resins in pressure sensitive adhesives using direct analysis in real time time-of-flight mass spectrometry. Analytical Chemistry, 83(19), 7323–7330. https://doi.org/10.1021/ac2011608