Continuous two-stage preparation of solvent-free polyacrylate hotmelt PSAs

In a continuous two-stage process for preparing solvent-free polyacrylate hotmelt pressure sensitive adhesives which is gentle on the polymer and redeploys the solvent used in the process the following steps are carried out: polymerizing a self-adhesive pressure sensitive adhesive in solution, the solvent having a low vapor pressure; continuously mixing the polymer solution with antioxidants and preheating the mixture under superatmospheric pressure without boiling it; concentrating the polymer solution to a residual solvent content of less than 0.1% by weight in a concentrating extruder under the effect of reduced pressure and elevated temperatures; condensing, collecting, and re-using the solvent stripped off in the extruder; compounding the abovementioned solvent-freed hotmelt pressure sensitive adhesive with tackifying resins, fillers, stabilizers, crosslinkers or other additives in a second extruder at a moderate melt temperature; transferring the blended solvent-free self-adhesive pressure sensitive adhesive to a downstream coating unit.