Abstract: In a process for recycling of gas-containing synthetic plastics material, this material at first is comminuted, molten, degased and filtered. The degased synthetic plastics material is supplied in the same plant before its solidification for gas introduction, and in order to homogenize the gas content, the gas amount introduced into the synthetic plastics material per time unit is controlled in dependence from the synthetic plastics material amount supplied per time unit to the gas introduction, and preferably the pressure of the synthetic plastics material to which gas is to be added, is kept almost constant. The apparatus suitable for performing this process comprises an extruder (12,13) for plasticizing and degasing the synthetic plastics material, the outlet (15) thereof is connected by means of at least one line (16) to a mixer (25), to which also a device (29) for supplying gas is connected.