Production of mixtures of plastics materials

A process for the production of a pulverulent homogeneous mixture of plastic material which comprises:

• a. extruding a nonhomogeneous mixture of two or more plastic materials through a nozzle means,
• 1. at a temperature between the melting point of the plastic material having the lowest melting point of all components of the mixture and the maximum temperature which may be used without causing a chemical change therein,
• 2. at a nozzle speed of from 1 to 200 m/sec.,
• 3. in an annular flow which tapers to a cone angle of from 5.degree. to 40.degree. which has an annular gap width of from 0.2 to 3 mm and an angle of twist from 0.degree. to 60.degree. to form a molten tube having an internal diameter of from 1 to 30 mm and a wall thickness of from 0.2 to 3 mm;
• b. exposing said extruded nonhomogeneous mixture of plastic materials to a gas or steam shearing medium which is divided into inner and outer streams to create a high shear velocity whereby a homogeneous mixture of plastic material is formed,
• 1. said inner stream of gas or steam shearing medium having a diameter of from 1 to 30 mm and an elevated temperature sufficient to maintain said extruded nonhomogeneous mixture of plastic material in a molten state, said inner stream being so directed that it impinges upon the inner surface of said extruded tube of said nonhomogeneous mixture for a distance of from 2 to 8 mm before reaching the inner edge of the orifice of said product nozzle means,
• 2. said outer stream of gas or steam shearing medium, flowing in an annular space which tapers to a cone angle of from 15.degree. to 70.degree. and having an annular gap width of from 0.3 to 5 mm at an elevated temperature sufficient to maintain said extruded nonhomogeneous mixture in a molten state so that said outer stream being so directed that it impinges upon the outer surface of said extruded tube for a distance of from 1 to 6 mm before exiting from said nozzle means, the volume of said outer stream to said inner stream being 1.2:1;
• c. said extruded nonhomogeneous mixture of plastic materials being subject to high shear velocities of from 10.sup.4 to 10.sup.8 sec.sup.-.sup.1 for from 10.sup.-.sup.4 to 10.sup.-.sup.6 seconds by said inner and outer streams;
• and
• d. spraying the resultant pulverulent homogeneous mixture of plastic material and gas or steam shearing medium from the nozzle means into a cooling and collecting means.