Study of coatings based on polyisocyanates of moisture cure depending on its resins and water scavengers

Abstract

Hempel Coatings Company have into products assortment a group of paints which is based on isocyanate pre-polymer resins which cure with moisture forming a coating based on polyurea. These paints are called 1 component polyurethanes (1K PU) or moisture curing polyurethanes (MCU). The principal function of these paints is the protection of substrates providing durability to the assets. This project was proposed by Protective Coatings R&D Department due to two reasons: - The resins and water scavengers used for 1K PU are used only for these products so it is really important to have as reduced raw materials stock as possible. In addition these coatings represent a small percentage of the overall Hempel’s Coatings production. - Recently REACH (Regulation on Registration, Evaluation, Authorization and Restriction of Chemicals) has included all the products containing MDI isocyanate monomer/oligomer in the risk sentence R40, limited evidence of a carcinogenic effect, and two 1K PU coatings existing in Hempel contain this isocyanate. Thus this project was thought to study the isocyanate resins and water scavengers available in Hempel’s raw materials stock to reformulate the existing products. When reformulating the existing products the aim is improve 1K PU performance, reduce raw materials stock and, if possible, avoid the use of MDI isocyanates. The project planning consists of the reformulation of all the possible alternatives of the existing standard products using the raw materials available. Afterwards the products formulated must be produced by vacuum dissolver in order to avoid the moisture incorporation. Finally these products have to be applied on the panels for the final testing. The main properties that 1K PU products need to present have been tested and the best combination of isocyanate resins and water scavengers should be found out.