In order to automatically add measured amounts of a catalyst or other substance to a chemical reaction as needed, a signal representing a specific reaction condition is utilized to generate a pulse which has a width representative of the magnitude of said signal. An integrator then adds the pulses and after a predetermined total pulse time triggers an actuating mechanism which performs the operations necessary to add a substance to the chemical reaction.
In a cell culture process, the addition of an additive is only carried out after it has been determined that the previous addition of additive has caused at least a minimum change in metabolic activity of the cells.
A continuous static polymerization reactor unit for the production of liquid polymers, in particular high viscosity organopolysiloxanes, in a predetermined viscosity range comprises a reactor (1) a supply means (10,25) for supplying monomers and/or oligomers to an inlet means (2), and an outlet means (5). The inlet means (2) is adapted for the introduction of a reaction mixture into a reaction chamber (3), and a means for introducing at least one viscosity controlling agent into the supply means is provided to form a reaction mixture with monomers and/or oligomers (11,13,15,12,14,16). The unit is adapted to maintain the values of temperature and flow rate of the resulting reaction mixture/polymer in the reaction chamber (3) substantially constant. A control means (24) is used to detect any variation from a predetermined pressure drop value between the inlet means (2) and the outlet means (5), and should such a variation occur the control means (24) is also used to compute and control a compensating rate of introduction of one or more of the at least one viscosity controlling agents to cause the pressure drop between the inlet means (2) and the outlet means (5) to revert to the predetermined value. A process for making liquid polymers within a predetermined viscosity range is also disclosed.
