Process for producing wet rubber masterbatch, wet rubber masterbatch, and rubber composition containing wet rubber masterbatch

A method for producing a wet rubber masterbatch obtained using at least a filler, a dispersing solvent and a rubber latex solution as raw materials, wherein the method comprises:

• a coagulation step of mixing a slurry solution containing the filler and the dispersing solvent, and the rubber latex solution with each other to be coagulated, thereby producing a filler-containing rubber coagulate, and
• a heating step of using a single-screw extruder to heat the filler-containing rubber coagulate to 160° C. to 200° C., thereby dehydrating, drying and plasticizing the filler-containing rubber coagulate in a single step,
• wherein the single-screw extruder includes a screw, and an external cylinder in which a slit extended along the length direction of the external cylinder, in the screw-shaft direction, is formed in an internal wall surface of the external cylinder, and
• when the width of the slit is represented by A and the clearance between a crest of the screw and the internal wall surface of the external cylinder is represented by B, the following expression (1) is satisfied:
• 0<AB(Y)/AB(X)<0.9 (1)
• wherein AB (Y) is the product of A and B at a downstream side along the screw-shaft direction of the external cylinder, and AB (X) is the product of A and B at an upstream side along the screw-shaft direction of the external cylinder.