Multi-bore extrusion apparatus
This pressure leakage results in the material in the high pressure zone being at a pressure which is not as great as desired. In some reactions, conducted within a high pressure zone, because of the pressure leakage from the high pressure zone to the low pressure zone, raw material usage is greatly increased to obtain the amount of product which would have been obtained if the pressure in the high pressure zone could have been maintained at a constant higher level.While so doing, this invention also provides a device which may allow for the continuous adjustment of a pressure drop over a flow restricting means in a non-intermeshing, co or counter rotating twin screw extruder and provides a device which can enable the operator to establish a higher pressure drop between adjacent sheet production extruder zones than may be achieved in conventional barrel sections.
One way in which the pressure may be maintained in the reaction section is to have a flow restriction means on each screw between the high pressure zone and a low pressure zone. The material being treated will flow against this restriction means thereby creating substantial back pressure. The magnitude of this back pressure determines the pressure differential between the upstream high pressure zone and the downstream low pressure zone. Unfortunately, because of the channel between the barrel bores, there is considerable pressure leakage between the high pressure zone and the low pressure zone. This leakage diminishes the capacity of the restrictions on the screws to maintain a pressure differential between the high and low pressure zones.
Accordingly this invention provides a multi-bore extrusion apparatus wherein adjacent bores are inter-connected by a longitudinal nip between the bores and wherein screws located within the bores are provided with flow restricting means for delimiting upstream sections of relatively high pressure from downstream sections of relatively low pressure, characterised in that the dimensions of the nip, at least in a part of the length coextensive with the flow restricting means. The problem with which this invention is concerned is the maintenance of a high back pressure in a non-intermeshing parallel or tangential, co or counter rotating twin screw extruder.
In another aspect, this invention contemplates an apparatus for treating material fed therein and comprising a housing having two congruent bores extending through said housing, an inlet extending through said housing and into at least one of said congruent bores, a pair of non-intermeshing parallel or tangential, co or counter rotating single screw extruder, each disposed within one of said bores, means connected operably to said screws for turning said screws, said screws having flow restricting means disposed on each of said screws, said bores having a nip region, said nip region being defined by the ratio of the width between a pair of imaginary parallel lines, said lines being parallel to a plane defined by the center lines of the bores, one of which imaginary lines would touch the top of the nip and the other of which would touch the bottom of the nip.