Du Pont of Canada Limited

Baden McDowall Pinney

This invention discloses a self-purging injection valve comprising at least one supply port, at least one purging waste port, an injection port and an injection port barrel, the injection port barrel projecting from the injection port through the valve in communication with said supply port and purging waste port, and a valve stem having an internal passage and being adapted to slide within the injection port barrel between a purging position and an injection position, to seal the injection port, to block the direct flow of materials within the injection port barrel external to the valve stem between the supply port and the purging waste port, but to otherwise permit the flow of purging fluids from the supply port along the internal passage and about the valve stem within the injection port barrel to the purging waste port when said valve stem is in the purging position and to open the injection port and to permit the flow of materials from the supply port within and without the valve stem to the injection port when said valve stem is in the injection position, and a valve stem control means to control the movement of the valve stem, and a purging waste port control means to close the purging waste port in the injection position and to open the purging waste port in the purging position.

Self-purging injection valve

Improved control is provided in a process for the continuous preparation of a polyamide from an aqueous solution of polyamide-forming reactants, e.g., from an aqueous solution of hexamethylene diammonium adipate. The process comprises feeding continuously, the aqueous solution of polyamide-forming reactants or partially polymerized polyamide-forming reactants to an elongated tubular zone having an inlet pressure of at least 60 lb./sq. in. absolute; passing the solution through the elongated zone and gradually reducing the pressure along the zone to progressively flash water into steam while supplying sufficient heat to maintain the temperature of the solution above the melting point of the resultant polyamide; and passing the molten polyamide from the tubular zone into a finishing vessel. The improvement comprises maintaining a substantially constant level in the finishing vessel by controlling the pressure in the tubular zone and thus regulating the flow of molten polyamide from the tubular zone by injecting steam at an intermediate point in the tubular zone.

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Kingston, Canada

Baden McDowall Pinney