A sheet of the type of the present invention is disclosed by German Auslegeschrift 40 18 716. It is manufactured using a rubber-elastic mixture of special Shore A hardness of less than 85 which can be processed thermoplastically, and contains a thermoplastic polyurethane elastomer (TPU) and an ethylene/vinyl acetate copolymer (EVA). The vinyl acetate (VA) content of the EVA is taught to be between 78 and 95% by weight. In the rubber-elastic mixture there should be 50 to 99% by weight of TPU and 1 to 50% by weight of EVA, wherein the sum of the percentages is equal to 100%. The mixture is used to produce molded objects and sheets which are soft and elastic, and are readily processed (that is, without sticking), yet they also have a high strength, a good elongation at break, a high abrasion resistance, and show little swelling in fuels and lubricants.
The VA content of the EVA materials which are presently commercially available is of the order of 40 percent by weight. These materials can be calendered. If such an EVA is used in a thermally-processible mixture in accordance with the information of the German Auslegeschrift 40 18 716, the resulting mixture cannot readily be processed into sheets by calendering because the melt strength is too low. Moreover, calendering of this mixture results in a sheet with unacceptable sticking qualities.
It is therefore an object of the invention to develop an improved thermoplastic material having the desirable properties of the material of German Auslegeschrift 40 18 716, as well as having the capability of being processed into sheets, for example, by calendering.