A device for use with a runner block and a multi-polymer co-injection nozzle having separate rear entrance ports for separate polymer streams, in a multi-coinjection nozzle, multi-polymer injection molding machine, for receiving from the runner block a plurality of separate polymer flow streams and for redirecting them to flow axially out of the forward end of the device into the nozzle rear entrance ports. The device has inlets cut radially into its periphery, each for receiving a polymer flow stream, and has feed channels, each in communication with an inlet and having an inward portion cut toward the device's central axis, and an axial portion communicating with the inward portion, running axially forward and terminating at an exit hole in the device's forward end, the exit holes being in a spaced pattern for feeding the separate polymer flow streams in spaced relation into the nozzle rear entrance ports. In preferred embodiments, the inlets communicate with feed throats, each cut radially into and running about a porton of the circumference of the device and having a terminal end portion which communicates with an axial feed channel, and a receiving chamber, desireably of stepped configuration, is cut axially into the forward end and adapted to receive a co-injection nozzle. Most of the exit holes are radially spaced from each other by an arc of 60.degree.. Isolation means, preferably including a plurality of annular grooves are cut into the periphery of the device between inlets and have an expandable piston ring seated therein to maintain the polymer flow streams isolated from one another.

Apparatus for tri-injecting a plurality of thermoplastic materials to mold an article having a layered wall structure using thermoplastic materials having different optimum processing temperatures including the maintenance of the optimum temperatures in flow paths individual to each material from its source at least to the injection nozzle.

Apparatus for coinjecting a plurality of thermoplastic materials to mold an article having a layered wall structure using thermoplastic material having different optimum processing temperatures including the maintenance of the optimum temperatures in flow paths individual to each material from its source to a mold cavity.

A dosing device for dosing viscous materials has a dosing cylinder for a main material and at least one dosing cylinder for an additive and a common drive for the dosing pistons of said dosing cylinders. In order to permit the simple dosing of the main material and the at least one additive in a time-constant volume ratio, and in order to permit changes to the volume ratio to be made in a simple manner, while permitting the dosing of highly viscous main materials and additives, the dosing cylinders are arranged parallel to one another and their dosing pistons are arranged to be driven with an identical stroke. The dosing piston of the at least one additive dosing cylinder is constructed as a plunger with a smaller cross-section than the cross-section of the associated dosing cylinder. In addition, the plunger is sealingly guided in an interchangeable guide bush of the dosing cylinder. Moveover, the at least one additive dosing cylinder is interchangeably connected as a subassembly to a support frame.

A production method comprising the step of charging prepolymer, a foaming agent and an active hydrogen-containing compound in specified amounts into a tank and foaming/mixing them for a specified time by a mixer, and the subsequent step of pouring the mixture liquid into a metal mold.