Abstract: An apparatus and a method for injecting a liquid dye into a polymer melt, which includes a metering pump with a metering inlet and a metering outlet. The metering inlet connects to a dye tank and the metering outlet connects to a polymer melt carrying component. To add the liquid dye to the polymer melt in the melt carrying component in a quantity that is as uniform and accurate as possible, the invention provides for connecting the metering inlet of the metering pump to a feed outlet of a feed pump, which connects with its feed inlet to the tank. With that, it is possible to generate a feed pressure at the metering inlet of the metering pump, which can be adapted to an injection pressure at the metering outlet of the metering pump.

Abstract: The invention relates to a spin pump for conveying a liquid polymer melt. To drive the conveying means enclosed in the pump housing, a drive shaft is provided, which extends through the pump housing in a bearing bore, and which comprises an external end for connecting to a drive. To seal the outward extending drive shaft, a cooling sleeve is employed which connects in a pressure tight fashion to the pump housing. The cooling sleeve surrounds the drive shaft with a narrow gap therebetween, and the outer surface of the cooling sleeve is cooled by a coolant for increasing the viscosity of the polymer melt which enters the gap between the drive shaft and the cooling sleeve. With an increased viscosity, the melt acts to seal the gap without interfering with the rotation of the drive shaft.