Patent ID: 6294119
Filing Date: 2001-09-25
Classification: B29C,B29K,B29L,B60C,Y10S

Abstract:
A method for producing an unvulcanized tread rubber for pneumatic tires, wherein at least one kind of low conductive unvulcanized rubber and at least one kind of high conductive unvulcanized rubber are supplied to respective extruder units on upstream side of a common extrusion head, and thereby caused to flow along respective independent passages in the extrusion head and then merged with each other at a back side of an extrusion orifice in the extrusion head, before they are continuously extruded from the extrusion orifice as an integrated composite body of unvulcanized rubbers corresponding to the unvulcanized tread rubber, wherein:the low conductive unvulcanized rubber is passed through a first passage extending from first extruder unit to the back side of the extrusion orifice, to form at least a cap rubber portion of a tread rubber in a product tire;the high conductive unvulcanized rubber is passed through a second passage extending from a second extruder unit to the back side of the extrusion orifice, to form at least part of the remaining portion of the tread rubber;the high conductive unvulcanized rubber while passing through the second passage is partly introduced into a narrow third passage branched from the second passage, and passed through a slit opening having a cross-sectional shape which is substantially straight in a height direction of the extrusion head and situated in a vicinity of the back side of the extrusion orifice, to form a narrow strip of the high conductive rubber in said composite body unvulcanized rubbers, said narrow strip extending in the low conductive rubber portion of the tread substantially over the entire thickness of the cap rubber portion and circumference thereof, and the high conductive unvulcanized rubber is caused to flow out of the third passage with a speed at the back side of the extrusion orifice which is lower than the speed of the low conductive unvulcanized rubber from the first passage.