摘要:
A process for continuously preparing a polyolefin composition made from or containing a bimodal or multimodal polyolefin and one or more additives in an extruder device equipped with at least one hopper. The process includes the steps of supplying a bimodal or multimodal polyolefin in form of a polyolefin powder to the hopper; (a) measuring the flow rate of the polyolefin powder or (b) measuring the flow rate of the prepared polyolefin pellets; supplying one or more additives to the hopper; adjusting the flow rates of the additives supplied to the hopper in response to the measured flow rate of the polyolefin powder or adjusting the flow rate of the polyolefin powder in response to the measured flow rate of the polyolefin pellets; melting and homogenizing the polyolefin powder and additives within the extruder device; and pelletizing the molten polyolefin composition into the polyolefin pellets.
摘要:
In a method and an apparatus for increasing the intrinsic viscosity of a polycondensate melt at negative pressure, the melt enters a chamber (25), in which a negative pressure of less than 20 mbar prevails, through a perforated plate or a screen (16) having a plurality of openings (26) with a diameter of less than 0.5 mm. The melt passes through this chamber (25) in free fall in thin threads and remains in a reservoir (19) beneath the chamber (25) for at least one minute. The melt is moved constantly in the reservoir (19), and discharged from the reservoir (19), by a helical mixing and discharge part (27).
摘要:
A method and system for melt processing a thermoplastic composition that contains a starch and plasticizer is provided. The composition is melt blended and extruded through a die to form an extrudate, which is thereafter cooled using a multi-stage system of the present invention that includes at least one water-cooling stage and at least one air-cooling stage. More particularly, the extrudate is initially contacted with water for a certain period time so that it becomes partially cooled and solidified on its surface. After the water-cooling stage(s), the extrudate is also subjected to at least one air-cooling stage in which a stream of air is placed into contact with the extrudate.
摘要:
The present invention relates to an improved process of purging an extrusion apparatus. The purging process is improved by adjusting the type of polymer material used to purge the extrusion apparatus and by adjusting the purging flow rate. The purging flow rate is lower than the extrusion flow rate, and the rotation speed of the screw (24) during purging is done by means of an auxilary motor (8).
摘要:
A cleaning device for a low-pressure mixing chamber particularly for polyurethane, comprising a conical mixing screw (11), which is actuated rotationally by motorization means (12) rigidly coupled to a slider (13), which moves on an advancement guide (14); the slider (13) is associated with means (15) for positioning the screw (11) inside a mixing chamber (16) between a retracted mixing position and an advanced cleaning position. Means (17) for measuring the axial thrust of the screw (11) on the residues of reacted material that are present in the chamber (16) and/or means (24) for measuring the torque generated by the motorization means (12) are associated with the positioning means (15). Means (19) are also provided for detecting the position of the screw (11) in the point where the axial thrust of the screw (11) and/or the torque generated by the motorization means (12) are/is highest; the position detection means (19), the axial thrust measuring means (17) and the torque measuring means (24) are interfaced with means (20) for comparing the measured values of position, axial thrust and/or torque of the motorization means (12) with the preset limit values of position, axial thrust and/or torque. There are also control and feedback means (21a), which manage the retraction of the positioning means (15) if the limit values of axial thrust or torque are exceeded, so as to return the slider (13) to a position in which the axial thrust of the screw (11) and the torque generated by the motorization means (12) are lower than the respective preset limit values.
摘要:
A system (Fig. 16) for metering and dispensing component liquids and solids has a microprocessor-based control system and progressive cavity pumps which provide accurate control of component ratios, shot sizes, flow rates and dispense durations. The system has feedback components (58, 66, 60, 68) for controlling the pressure, flow rates, fluid levels and amounts of fluids dispensed. The pressure in the flow system is used to control the pumps (34, 36) rather than a valved nozzle (49). The system may be used as a sprayer with compressed air added. Back and forth movement of the pump provides compensation for pressure changes. A mold charging system uses pressure to control the pumps which are cycled on and off to avoid overpressurizing the mold. The rate of pressure increase is used to control the rate of flow from the pumps as the mold approaches completion of the charge to avoid overpressurizing the mold.
摘要:
Bei einem Verfahren zum Aufschmelzen und Homogenisieren von multimodalen der bimodalen Polyolefinen wird ein mehrwellig ausgebildeter erster Extruder (1) und ein diesem in Förderrichtung (17) nachgeordneter zweiter Extruder (2) eingesetzt. Der zweite Extruder (2) ist ebenfalls mehrwellig ausgebildet. Der Außendurchmesser der Schnecken-Wellen (14, 15) des ersten Extruders (1) ist kleiner als der Außendurchmesser der zweiten Schnecken-Wellen (29, 30) des zweiten Extruders (2). Der erste Extruder (1) wird mit einer höheren Drehzahl angetrieben als der zweite Extruder (2). Die Schergeschwindigkeit ist im ersten Extruder (1) höher als im zweiten Extruder (2).
摘要:
A polymer feed device for feeding a thermoplastic polymer to a screw extruder or the like, the feed device includes a shaft (22) and an auger (24) rotatable about the shaft (22), the auger (24) having a clearance from the shaft (22) such that when rotated about the shaft (22) it wipes polymer therefrom and feeds the polymer to the extruder or the like. Extruder systems and polymer recycling systems including such devices are also described. Variable density polymer waste can be recycled using such systems. Such systems also provide greater flexibility when processing virgin polymer granules.
摘要:
A two-component mixing and dispensing system for mixing and dispensing two-component polymeric materials which react chemically with one another when combined to form a mixture includes a controller for adjusting the pressure at which at least one of the components is supplied to a dispenser dependent upon variations in the parameters which affect the cure time of the mixture.