1. Field of the Invention
The present invention relates to a new process for the preparation of highly flexible polyurethane plastics, especially polyurethane coatings, which are resistant to chemicals, and to a process for their preparation. The plastics are prepared in the presence of hydroxides or oxides of alkaline earth metals and are based on certain polybutadiene resins containing terminal hydroxyl groups.
2. Description of the Prior Art
The use of hydroxides or oxides of alkaline earth metals in the preparation of non-foamed polyurethane plastics using water-containing reactive systems based on organic polyisocyanates and isocyanate-reactive organic compounds is known. For example, DE-PS 1 170 627 describes the action of calcium oxide as a dehydrating agent in polyurethane systems. GB-PS 1 147 695 describes inter alia the use of calcium hydroxide in water-containing reactive systems for the preparation of non-foamed polyurethane plastics. Hydraulic cements have also been used for foam prevention in water-containing polyurethane systems (see, e.g., DE-OS 2 113 046, DE-OS 2 254 251, DE-OS 2 113 042, DE-OS 2 300 206 or DE-AS 1 924 468). While the resulting products of these prior publications are often very flexible, they do not have adequate water resistance. The water resistance cannot be improved by the addition of bitumen, since the compatibility of these systems with bitumen is inadequate.
To the contrary the coatings prepared in accordance with DE-OS 3 414 807 are very hard, but do not have sufficient flexibility for many applications.
Accordingly, it is an object of the present invention to overcome the deficiencies of the known processes for the preparation of highly flexible plastics, especially highly flexible surface coatings based on polyurethane systems containing water and inorganic fillers. It is an additional object to provide reactive systems which can be used to prepare plastics, especially coatings, which are at least equivalent to those prepared from prior art systems with respect to flexibility and other properties, but also have improved water resistance and, in particular, bitumen compatibility.
This object was achieved in accordance with the present invention as described hereinafter.