Elimination of contaminants in wet natural rubber

A method for preparation of decontaminated natural rubber, characterized in that it comprises a decontamination step in which wet natural rubber coagulum with a humidity level greater than 12% by weight passes through a system comprising an extruder and a filter installed at the extruder outlet,

• the extruder comprising a grooved sheath, a screw arranged in the sheath and comprising a hub and a thread which extends radially outwardly relative to the hub,
• a grooved sheath having an axially symmetrical structure comprising in its thickness grooves opening on the inner surface of the sheath,
• each groove comprising
• a bottom face delimited by two bottom ridges,
• two side faces extending towards the inside from the bottom face, each being delimited by a bottom ridge and a ridge intersecting the inner surface of the sheath,
• and characterized in that the sheath is such that, in any plane perpendicular to the axis of the sheath, R expressed in mm being the distance between the sheath center and the inner surface of the sheath:
• a. the ratio (total length of groove openings expressed in mm)/(2πR), designated A, is at least equal to 0.25 and at most equal to 0.9;
• b. the ratio (number of grooves/2R), designated B, is greater than or equal to 0.1;
• c. the ratio (depth of grooves expressed in mm)/(2R), designated C, is greater than 0.02, and
• d. the plane passing through the two bottom ridges forming, with each plane passing through a bottom ridge and an intersection ridge delimiting a side face, an angle d at least equal to 60° and at most equal to 90°.