During recycling of waste paper from private households different fractions containing plastics and polluted paper fibers are received. Current research at the Institute of Polymer Materials and Plastics Engineering at Clausthal University of Technology showed that the use of waste paper as filler and reinforcement in polypropylene leads to nearly the same mechanical properties as natural fibers like flax, sisal and hemp. The present investigations focus on the chemical cleaning of the paper recyclate to treat the fiber surface and to solve foreign plastics like polystyrene. For this purpose SOXHLET extraction with different solvents is used. The received extracts are examined via infrared spectroscopy, as well as the treated and the untreated fibers. Afterwards, the cleaned paper is incorporated into polypropylene. The received composites are investigated regarding their mechanical properties by tensile testing and CHARPY impact testing.