diene epdm rubber and ethylene propylene epm rubber various grades of which are also commercially available mention should also be made of butyl rubber for bladders and hoses the process of the invention has been developed so as to be capable in principle of use for any rubber solution however it is advantageous for the process that the boiling point of the solvent be very low or at least below the boiling point of water in other cases it will be clear that steam distillation may be used to remove the solvent the carbon blacks which may be used include 30 1000 phr preferably 40 100 phr of any of the industrial carbon blacks these being distinguished by their surface area iodine adsorption of 5 1000 m 2 g to astm d1510 92a and a structure dbp value in the range 50 400 ml 100 g to astm d2414 92 the process also embodies the capability of adding in the process to prepare the product other constituents usually used in a finished rubber mixture examples of these constituents include pale colored fillers e g precipitated silicas or naturally occurring fillers processing aids such as mineral oil plasticizers organosilanes activators antioxidants and cross linking chemicals at the concentrations usually used in such applications the process permits the preparation of fine particle carbon black filled rubber powders based on solution polymers and these remain free flowing even after experiencing mechanical stress such as in conveying and packing the result of the processing detailed above gives fine particle rubber powders which.