Mixing Kneader and Process for Preparing Poly(Meth)Acrylates Using the Mixing Kneader

A mixing kneader comprising at least two shafts (2, 3) on whose surfaces are disposed kneading bars (4) on elements (5) and which are enclosed by a casing (6), in which at least one orifice (10) above the shafts and at least one orifice (11) for product removal are formed, the shafts (2, 3) being mounted so as to be rotatable at the same or different rates and in the same or opposite sense at both ends and being driven at at least one end, wherein at least one of the following features is ensured:

• (a) the shafts are designed in such a way that flexural resonant frequencies of the shaft have a separation of at least 5% from the excitation frequencies,
• (b) at least one shaft is configured as a hollow shaft and is flowed through by a temperature-control medium, an inlet (12) being disposed on one side and an outlet (13) on the other side of the shaft,
• (c) the at least one orifice is closed above the shafts by a displacer (23) whose side facing the shafts is configured such that a gap is present between the displacer (23) and the kneading bars of the shafts and has a maximum gap width which corresponds to the available gap width between kneading bars and casing.