Device and method for producing a dyed and an undyed plastic melt

A method for producing a dyed and an undyed plastic melt, the method comprising the following method steps:

• providing a multi-shaft screw extruder having a housing, at least two mutually penetrating housing bores configured in the housing a first infeed opening, a second infeed opening and at least two treatment element shafts rotatingly drivable in the at least two mutually penetrating housing bores, the first infeed opening and the second infeed configured to open into the at least two mutually penetrating housing bores, wherein the second infeed opening is disposed upstream of the first infeed opening in a conveying direction;
• providing a first metering installation and a second metering installation, wherein the second metering installation comprises a first metering unit configured to feed a color granulate, and a second metering unit configured to feed a cleaning granulate, said first metering unit and said second metering unit opening into the second infeed opening;
• selecting between a first operating mode for producing the dyed plastic melt and a second operating mode for producing the undyed plastic melt via a control installation, wherein in the first operating mode an undyed plastic material via the first metering installation through the first infeed opening, and the color granulate via the second metering installation through the second infeed opening, are fed into the at least two mutually penetrating housing bores, wherein in the second operating mode the undyed plastic material via the first metering installation is fed through the first infeed opening into the at least two mutually penetrating housing bores, wherein after the production of the dyed plastic melt in the first operating mode the multi-shaft screw extruder is cleaned in a cleaning mode, wherein in the cleaning mode the cleaning granulate is capable of being fed through the second infeed opening into the at least two housing bores via the second metering installation;
• and
• operating the multi-shaft screw extruder, the first metering installation and the second metering installation in a selected operating mode.

A device for producing a dyed plastic melt and an undyed plastic melt, the device comprising:

• a multi-shaft screw extruder configured to provide a plastic melt, the multi-shaft screw extruder comprising a housing with at least two mutually penetrating housing bores configured in the housing, a first infeed opening, a second infeed opening and at least two treatment element shafts disposed so as to be rotatingly drivable in the housing bores, the first infeed opening and the second infeed opening being configured to open into the at least two mutually penetrating housing bores;
• a first metering installation configured to hold a quantity of an undyed plastic material and feed the undyed plastic material through the first infeed opening into the at least two mutually penetrating housing bores;
• a second metering installation configured to selectively feed at least one color granulate and a cleaning granulate through the second infeed opening into the at least two mutually penetrating housing bores, the second metering installation comprising:
• a first metering unit configured to hold a quantity of the color granulate and feed the color granulate;
• and
• a second metering unit configured to hold a quantity of the cleaning granulate and feed the cleaning granulate, said first metering unit and said second metering unit opening into the second infeed opening, wherein the second infeed opening is disposed upstream of the first infeed opening in a conveying direction;
• and
• a control installation configured to select between:
• a first operating mode, including controlling the second metering installation to feed the at least one color granulate with the first metering unit through the second infeed opening into the at least two housing bores via the second metering installation, for producing the dyed plastic melt;
• a second operating mode, including controlling the first metering installation to feed the undyed plastic material through the first infeed opening into the at least two housing bores via the first metering installation, for producing the undyed plastic melt;
• and
• a cleaning mode, including controlling the second metering installation to feed the cleaning granulate with the second metering unit through the second infeed opening into the at least two housing bores via the second metering installation.