Method and apparatus for producing spherical particles from a polymer melt

• Main Authors: RUDOLF GEIER, THEODOR JURGENS
• Format: Patent
• Language: English
• Published: 22.10.2003
• Edition: 7
• Subjects: CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOIDCHEMISTRY; INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS; MAKING GRANULES OR PREFORMS; PERFORMING OPERATIONS; PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL; PREPARATION OR PRETREATMENT OF THE MATERIAL TO BESHAPED; RECOVERY OF PLASTICS OR OTHER CONSTITUENTS OF WASTE MATERIALCONTAINING PLASTICS; THEIR RELEVANT APPARATUS; TRANSPORTING; WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE, IN GENERAL

Molten prepolymer or precondensate is dropped by a nozzle plate (18) into a precipitation tower (20) through which a gas flows in the opposing direction to effect at least part crystallization of the droplets. The nozzle plate and/or the perpolymer may be vibrated. Air is fed to the tower at a temperature (T 1) which is above the glass transition point of the prepolymer. By heat transfer from the droplets the air temperature rises to T 2 which is = 210[deg]C. An independent claim is made for the process plant which includes a vibrator and a nozzle plate (18) with nozzles distributed across the surface. A following precipitation tower(20) is located in an air flow circuit and has a cross-section at least twice as large as the nozzle-containing surface. Preferred Features: Air is fed to the precipitation tower at = 160[deg]C, preferably = 120[deg]C. During production of PET (polyethyleneterephthalate) pellets heat transfer from droplets in the tower raises air temperature to = 160[deg]C. For production of PBT (polybutyleneterephthalate) pellets the temperature rises to = 140[deg]C.