Nanjing GIANT Machinery Co.,Ltd.

A polymer single screw extruder having heating means which is thermostatically controlled for regulated heating of the extruder barrel and, hence, the material being extruded. In preferred embodiments the extruder barrel is fitted with two longitudinally spaced-apart electric heating elements, each of which is independently controlled with separate thermostats attached to the barrel in the vicinity of the element which it controls. The first heating element is located near the feed inlet of the extruder, and the second near the extrusion orifice. The first element provides high heat input for rapid softening of the polymeric feed. The other element provides additional heat input for extrusion of the polymeric material at a constant, preselected temperature.

While the twin screw extruder described in application Ser. No. 94,810 has proven satisfactory for the intended purpose, certain problems have arisen which are associated with regulation of the barrel temperature and its coincident effect upon the polymeric material being extruded. If an elastomeric sealant composition is subjected to excessive temperature during extrusion, the elastomer therein will be degraded and/or certain other materials, such as rubber compounding oil, will be boiled off. If, on the other hand, the heating temperature is too low, the composition is difficult to convey through the extruder and expel from the extrusion orifice, and if the resulting tape is not hot enough it will not have the desired viscosity and bonding characteristics for filling and sealing of the structural joint.

Elastomeric sealant tapes can be formed by means of an sheet production extruder having a heated barrel. An elastomeric sealant composition is fed into one end of the barrel and is extruded out the other end through a suitably shaped orifice. Heating causes the previously-stiff sealant composition to soften, thereby improving the extrudability thereof and enhancing bondability of the resulting tape to substrates on either side of a structural joint being sealed.

During extrusion, therefore, heat input to the barrel must be high enough to sufficiently soften the sealant and permit extrusion at the desired temperature. However, when extrusion is interrupted for some reason, heat input must be reduced lest sealant which remains in the single screw extruder barrel become overheated. Otherwise, the barrel must be emptied of sealant. Alternatively, the heat to the barrel can be turned down, but in such a case the extruder must be reheated again before the extrusion operation is resumed.