Patent TW-I411510-B (TW)
Title: Strand pelletization process and device as well as therefrom produced pellets
Inventor: BOCZON JAROSLAW
IPC: B29C48/30
Filed: 2007-11-21
Granted: 2013-10-11
Abstract: The procedure for the production of granulate grain from thermoplastic polyester or copolyester of a polyester melt by a strand granulator, comprises supplying the polyester melt to nozzle (1) of the strand granulator, bringing strands (2) emerging from the nozzle over a discharging line to a granulation device with discharge roller (5), crystallizing the granulate grain in a crystallization chamber by a process gas stream directly on a granulation of the strand in a granulation device (4), and pre-condensing the produced granulate grain. The procedure for the production of granulate grain from thermoplastic polyester or copolyester of a polyester melt by a strand granulator, comprises supplying the polyester melt to nozzle (1) of the strand granulator, bringing strands (2) emerging from the nozzle over a discharging line to a granulation device with discharge roller (5), crystallizing the granulate grain in a crystallization chamber by a process gas stream directly on a granulation of the strand in a granulation device (4), and pre-condensing the produced granulate grain. A strand withdrawal speed (V a b) is adjusted over the discharge roller. The discharge of the strand from the nozzle is carried out with a discharge speed (V a u s) of 110 m/min. The ratio of the discharge speed is adjusted through the surface (f) of the nozzle opening of the respective nozzle (V a u s/f) so that the condition of V a u s/f>= 30 m/(minx mm 2>) prepossesses. The strands emerging from the nozzles are brought directly at the nozzle discharge into a cooling fluid contact over an air gap, whose length is adjusted to 2 mm. The stretching (V = (V a b-V a u s/V a u s) of the resigning strand is adjusted during discharging the strand so that the condition V= 0 prepossesses through adjusting the strand withdrawal speed and/or the discharge speed. The discharge speed is adjusted at 80 m/min to maximum 350 m/min. The surface of the nozzle opening is adjusted to less than 4 mm 2>. The diameter (d) and/or the length (l) of the nozzle opening are adjusted so that the ratio l/d prepossesses the condition l/d=0.3. The nozzle openings are formed so that a strong cross-sectional narrowing takes place directly before the nozzle discharge. The ratio area F at the inlet into the nozzle hole is measured by a place that exists itself around the distance (L) before the discharge of the nozzle opening. The distance (L) is less than 8, which is adjusted through the surface (f) of the nozzle opening so that the condition F/f>= 3 prepossesses. The ratio of F/f prepossesses the condition of F/f>= 20. The distance (L) prepossesses L less than 6. The granulate grain has a strong partly crystalline structure in its mantle surface. The partly crystalline structure has a layer thickness of 10mu m and a crystallization grade of 15%. The cooling fluid has a temperature (T) that lies in the area of T1 to T2, where T1=T g-20[deg] C and T2=Tg+70[deg] C. The glass transition temperature corresponds to the thermoplastic polyester. The polyester melt of the nozzle is brought with a melt temperature of 260[deg] C= T m e l t= 270[deg] C. The nozzle temperature lies greater than 15[deg] C than the melt temperature. The contact time of the polyester melt with the cooling fluid is 1-3 seconds. The crystallization is carried out after separation of the granulate grain from the cooling fluid. The temperature of the process gas at the admission of the crystallization chamber is higher than the temperature of the granulate grain at discharging from the chamber. Independent claims are included for: (1) a granulate grain from thermoplastic polyester or copolyester produced by a strand granulator; and (2) a strand granulator for the production of granulate grain from thermoplastic polyester or copolyester.