Synthesis of bio-based non-isocyanate polyurethanes and their modification towards industrial application

Descripción del proyecto

Síntesis de poliuretanos sostenibles de origen biológico sin isocianatos

Los poliuretanos sin isocianatos (NIPU, por sus siglas en inglés) son alternativas ecológicas y no tóxicas a los poliuretanos utilizados en productos sanitarios, recubrimientos, aislantes y adhesivos. Sin embargo, su uso en la industrialización plantea retos debido a su bajo peso molecular, su escasa capacidad de reacción y su elevada hidrofilia, lo que degrada su rendimiento termomecánico. Con el apoyo de las Acciones Marie Skłodowska-Curie, el equipo del proyecto SPRUT tiene como objetivo sintetizar los NIPU sostenibles a partir de materiales de origen biológico y modificarlos para aplicaciones industriales. En primer lugar, creará un catalizador eficaz a base de heteroscorpionato de aluminio para la conversión de bisepóxidos de origen biológico en bicarbonatos cíclicos de cinco miembros mediante la fijación de CO2. Se utilizarán diversos métodos para aumentar el peso molecular de los biocompuestos de bicarbonato resultantes, que servirán de materia prima para los NIPU. Por último, se llevarán a cabo modificaciones químicas para reducir la hidrofilia.

Objetivo

This project is devoted to synthesis of non-isocyanate polyurethanes (NIPU) from bio-based sources and their post-modification towards industrial application. The use of bio-based monomers for NIPU synthesis allows to overcome the dependence on fossil resources and to reduce the CO2 emissions. However there are several possible drawbacks for industry such as high prices for bio-based monomers and demand for arable land to ensure large scale production.
NIPU were introduced in 1990s as the alternative to conventional polyurethanes because they allow to avoid usage of toxic isocyanates. However, they were not industrialised due to their insufficient molecular weights limited by reaction ability of monomers and increased hydrophilicity that facilitates hydrolysis during processing.
The SPRUT project will simultaneously deal with several NIPU related issues.
At first, the effective catalyst based on Al heteroscorpionate complexes for converting bio-based bisepoxides to 5-membered cyclic bicarbonates via CO2 addition will be developed. The obtained bicarbonate bio-compounds will be used as feedstock for production of NIPU applying various approaches to increase their MW above 20000 Da: synthesis in bulk, copolymerization of two different bicarbonates and the use of ionic liquids.
In the 2nd stage of the project, the unique method for post-synthetic modification of NIPU that was never used for these polymers will be introduced to increase their mechanical properties and processability. The basic click reaction of bio-based aldehydes (heptaldehyde and benzaldehyde) with adjacent hydroxyl groups in the NIPU backbone enables the reduction of intermolecular hydrogen bonding leading to better processability. The resulting aldehyde modified NIPUs containing non-polar side chains are supposed to be much more hydrophobic and possess increased physico-mechanical properties compared to previously developed NIPU and even some conventional PUs.