Contributed by Oleg Figovsky, Director of Research and Development, Hybrid Coating Technologies; and Alexander Leykin, Olga Birukova, Raisa Potashnikova, and Leonid Shapovalov, Polymate Ltd. International Nanotechnology Research Center
Non-isocyanate Hybrid Green Polyurethane™ coatings and foam can be used for many industrial and commercial applications.
Polyurethanes (PUs) are polymers that are widely used in a variety of industrial and consumer applications, including foam and coatings. PUs are now made by reacting two components, one of which has toxic isocyanate groups. Isocyanates are especially hazardous to workers who spray-apply PU paints and foam and also to the environment.
In recent years, intensive research and development has been carried out to prepare isocyanate-free urethanes and polyurethanes [1-3]. Fig. 1 shows the basic reaction “five-membered cyclic carbonate – amine” for producing non-isocyanate polyurethanes (NIPU) with β-hydroxy urethane (HU) functionalities to form the secondary and primary hydroxyl groups:
Hybrid Coating Technologies (HCT) and its strategic partner Polymate INRC are making significant efforts to produce NIPU materials suitable for practical use (coatings, foam, adhesives, sealants, etc.).
The main areas of research and development of HCT – Polymate are the following:
From raw material point of view, great attention has been paid to renewable resources as well as the use of silicon-organic compounds.
Most of the development has focused on oligomer compositions (epoxy, acrylic, etc.) modified by HUs. HU-modifier (HUM) is a product of a reaction between a primary amine (one equivalent of the primary amine groups) and a monocyclic carbonate (one equivalent of the cyclic carbonate groups). HUM is not bound chemically to the main polymer network and is represented by the following formula:
A series of products based on both fossil and renewable raw materials has been developed. Among them, there are HUMs on the base of vegetable oils and products of their processing, organosilanes-based HUMs and so on. With the use of HUMs, a number of isocyanate-free products and perspective formulations have been created: indoor and outdoor paints and flooring; spray and pouring (rigid, semi rigid and flexible) foam for insulation, packing, etc.; and radiation-curable coatings.
A method of synthesis of novel, non-isocyanate polymers with lengthy epoxy-amine chains, pendulous hydroxyurethane units and a controlled number of cross-links was also proposed . A cured hybrid epoxy-amine hydroxyurethane-grafted polymer with a presumably linear structure was prepared, and the testing of these polymers demonstrated increased flexibility. They may be used for various applications, for example, in the manufacturing of synthetic/artificial leather, soft monolithic floorings and flexible foam.
While non-isocyanate foam is still in the research stage, hybrid coatings, comprised epoxy and acrylic matrix modified by NIPU are commercially available. Under the name Green Polyurethane™, an isocyanate-free and phosgene-free alternative to conventional materials has been provided that represents the successful application of HNIPUs in the industry.
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