A process for the processing of an undried particulate polymer or polymer mixture by means of a single- or multiscrew extruder comprising a barrel comprising one or more screws, a feed section intended for the polymer and provided on the barrel and, provided on the barrel, a melting region in which the polymer or polymer mixture melts, where the undried polymer or polymer mixture introduced by way of the feed section into the barrel is devolatilized in at least one vacuum devolatilization region downstream of the feed section and upstream of the melting region in the barrel.

The present disclosure relates to a continuous extrusion process for producing a celluloid article including several steps and a celluloid article prepared by the continuous extrusion process.

The invention is directed to a method for producing an upgraded polymer product from recycled polyvinyl butyral, to a polymer product obtainable by said method, to a construction material comprising such polymer product, and to a use of an extruder vacuum pump. The method of the invention comprises feeding a polymer feed stream to an extruder, wherein said polymer feed stream comprises a recycled polyvinyl butyral; melting said polymer feed stream in the extruder to produce polymer melt and passing said polymer melt through one or more degassing zones connected to a vacuum pump; measuring the melt flow index of the polymer product,
wherein the vacuum pump is operated at a pressure that is controlled by the measured melt flow index of the polymer product.