Patent No. U.S. 7,820,757 B2
BASF has been awarded a patent for a process for producing a polyamide with titanium dioxide pigments comprised of dispersing the titanium dioxide pigments in a mixture containing water and caprolactam with an apparatus. The apparatus is comprised of a dispersing chamber, a disk-shaped rotor disposed in the dispersing chamber, a stator which has radial openings and is disposed in conjunction with the rotor in a dispersing zone of the dispersing chamber, a product inlet on each side of the rotor, such that a confluence of two product streams from each of the product inlets is disposed in an outer peripheral region of the disk-shaped rotor, and a product outlet at the outer periphery of the dispersing zone of the dispersing chamber, by feeding the titanium dioxide pigments through one of the product inlets and the mixture, containing water and caprolactam, through the other  product inlet to the dispersing chamber, and obtaining a product mixture, containing water, caprolactam and the titanium dioxide pigment from the product outlet, and polymerizing the product mixture to form the polyamide containing titanium dioxide pigments and wherein water is removed from the product mixture before or during the polymerization, blending the product mixture with additional caprolactam followed by polymerizing the additional caprolactam to form a masterbatch and filtering the masterbatch in a melt through a filter, wherein an average mean pressure build-up of the polymerized masterbatch, determined as a difference between a final pressure and an initial pressure upstream of the filter, divided by an amount put through, is approximately 7 bar/kg.