Impingement mixer

High-Pressure Technique — The components of the formulation are pumped at high pressure (1500 to 3000 pounds/square inch) into an impingement mixer. As the name implies, the mixing is achieved by collisions of the ingredients at high velocity. 

It is different to reaction injection molding (RIM) where it uses a mechanical mixing rather than a high-pressure impingement mixer (Figures. 11.1 and 11.2). The entire shot is mixed in a chamber before injection into the mold, rather than being continuously mixed and injected, as in the RIM process. LIM is used to mold smaller parts that are below the desired capacity of RIM. LIM also allows higher-viscosity materials to be processed. 

Efficient mixing is achieved when flow conditions in the head are turbulent as defined in terms of the Reynolds number (Re) whose value should exceed a critical value (4) of about 50 for an impingement mixer. In its simplest form for flow in a circular orifice, the Reynolds number is given as... 

Impingement Mixers None Continuous 1 < d32 < 50 pm Sparse data work with vendors... 

Other types of equipment such as static (motionless) mixers, rotor-stator mixers, and impingement mixers are used to create dispersions (see Section 9.9). 

The RIM machine, including at least two metering pumps, a selfcleaning impingement mixer, a set of temperature-controlled conditioning tanks, and the piping, hoses, filters and controls required for operation. 

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