Method and device for granulating plastics and/or polymers
First Claim
1. A method for the pelletization of plastics and/or polymers, comprising the steps of:
- supplying a melt having a specific viscosity coming from a melt generator via a diverter valve having a bypass position and a plurality of different operating positions to a plurality of pelletizing heads through which the melt is pelletized, said plurality of pelletizing heads having different throughput capacities;
during start-up of a pelletizing process, first directing said melt through said diverter valve in said bypass position;
controlling the melt generator such that a melt flow volume of said melt provided by the melt generator is continuously increased during said start-up and determining a temperature of the melt in a region of the diverter valve;
said step of first directing said melt through said diverter valve continuing until the melt flow volume reaches a lower capacity of a first pelletizing head having a first throughput capacity and the determined melt temperature in the diverter valve region reaches a predetermined minimum temperature;
thereafter, when said first throughput capacity of said first pelletizing head and said predetermined minimum temperature in the diverter valve region have been reached during said start-up of the pelletizing process, diverting the melt from said bypass position to said first pelletizing head having said first throughput capacity;
while still in said startup of said pelletizing process, increasing the melt flow volume of said melt by controlling the melt generator until a lower capacity limit of a second pelletizing head having a larger throughput capacity than the throughput capacity of said first head is reached; and
subsequently while still in said startup, switching over the diverter valve to divert the melt to said second pelletizing head after the melt flow volume provided by the melt generator has reached the lower throughput capacity of said second pelletizing head and at least one additional parameter of said pelletizing process has reached a predetermined reference value.
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Accused Products
Abstract
A method and apparatus for the pelletization of plastics and/or polymers, in which a melt coming from a melt generator is supplied via a diverter valve having different operating positions to a plurality of pelletizing heads through which the melt is pelletized. The plurality of pelletizing heads have different throughput capacities and are used sequentially for the start-up of the pelletizing process, with the melt first being supplied to a first pelletizing head having a smaller throughput capacity and then the melt volume flow being increased and the diverter valve being switched over such that the melt is diverted by the diverter valve to a second pelletizing head having a larger throughput capacity.
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Citations
14 Claims
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1. A method for the pelletization of plastics and/or polymers, comprising the steps of:
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supplying a melt having a specific viscosity coming from a melt generator via a diverter valve having a bypass position and a plurality of different operating positions to a plurality of pelletizing heads through which the melt is pelletized, said plurality of pelletizing heads having different throughput capacities; during start-up of a pelletizing process, first directing said melt through said diverter valve in said bypass position; controlling the melt generator such that a melt flow volume of said melt provided by the melt generator is continuously increased during said start-up and determining a temperature of the melt in a region of the diverter valve; said step of first directing said melt through said diverter valve continuing until the melt flow volume reaches a lower capacity of a first pelletizing head having a first throughput capacity and the determined melt temperature in the diverter valve region reaches a predetermined minimum temperature; thereafter, when said first throughput capacity of said first pelletizing head and said predetermined minimum temperature in the diverter valve region have been reached during said start-up of the pelletizing process, diverting the melt from said bypass position to said first pelletizing head having said first throughput capacity; while still in said startup of said pelletizing process, increasing the melt flow volume of said melt by controlling the melt generator until a lower capacity limit of a second pelletizing head having a larger throughput capacity than the throughput capacity of said first head is reached; and subsequently while still in said startup, switching over the diverter valve to divert the melt to said second pelletizing head after the melt flow volume provided by the melt generator has reached the lower throughput capacity of said second pelletizing head and at least one additional parameter of said pelletizing process has reached a predetermined reference value. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A method for the pelletization of plastics and/or polymers using a pelletizing apparatus including a diverter valve having at least one melt generator connection, a bypass position, at least two pelletizer connections and a valve gate for the connection of the melt generator connection selectively to at least one of the pelletizer connections, a respective pelletizing head being connected to the at least two pelletizer connections, each of said at least two pelletizing heads having different throughput capacities, a melt generator for generating a melt having a variable melt volume flow being connected to the melt generator connection, and a control apparatus configured to switch the connection of the melt generator connection of the diverter valve amongst said bypass position and said pelletizing heads, said method comprising the steps during start up of a pelletizing process of:
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supplying a melt having a specific viscosity from a melt generator; directing the specific viscosity melt through the bypass position of said diverter valve; increasing a melt flow volume of said specific viscosity melt until said melt flow volume reaches at least a lower capacity of a first pelletizing head having a first throughput capacity and a temperature of said melt in a region of the diverter valve reaches a predetermined minimum temperature; thereafter using said control apparatus to switch said valve gate of said diverter valve from said bypass position to supply said melt to said first pelletizing head; further increasing the melt flow volume of said specific viscosity melt until said melt flow volume reaches at least a lower throughput capacity of a second pelletizing head, said lower throughput capacity of said second pelletizing head being greater than the lower throughput capacity of said first pelletizing head; and subsequently using said control apparatus to switch said valve gate of said diverter valve from said first pelletizing head to divert the specific viscosity melt to said second pelletizing head in response to said further increase in said melt flow volume. - View Dependent Claims (11, 12, 13, 14)
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Specification