TH37778B - A method for the continuous production of expandable plastic resins. - Google Patents

Abstract

Using the DC60, continuous production of expanding plastic pellets (G) is possible, where the molten material (F) is saturated using a fluid expanding agent (B), and the saturated molten material is then pelletized. The process is carried out using a machine which includes the following components: - at least one pressure-generating feeder (10) for the molten material, specifically a volumetric pumping feeder; - a metering machine (9) for the expanding agent; - a contact and homogenization machine (2) for the saturation of the molten material; - at least one cooling machine (3) for the saturated molten material; - an underwater pelletizing machine (6); and - a machine control machine (1). Pelletizing is performed using a liquid, which is used in the pelletizing machine, as a cooling and transport medium for the pellets. Specifically, the liquids are water and brine. The increased pressure is provided by the liquid used during pelletizing, which at least partially suppresses the expansion action of the expanding agent in the unsolidified pellets. Control of the parameters to be set for pelletizing, namely the temperature and pressure of the saturated molten material, is achieved. This will occur at the inlet of the pelletizing machine. In this control, measurements of the aforementioned parameters will be taken, and furthermore, the measured values will be compared to the desired values, and deviations from the desired values due to unit control will be used by the machine controller to affect the heat absorption from the saturated molten material by the cooler. Using this method, expanding plastic pellets (G) can be continuously produced, where the molten material (F) is saturated using a fluid expanding agent (B), and the saturated molten material is pelletized. The procedure is carried out using a machine which includes the following components: - at least one pressure-generating feeder (10) for the molten material, which is, in particular, a volumetric pumping feeder, - a measuring machine (9) for the expanding agent, - a contact and homogenization machine (2) for the saturation of the molten material, - at least one cooler (3) for the saturated molten material, - an underwater pelletizing machine (6), and - a machine controller (1). The pelletizing is performed using a liquid, which is used in the pelletizing machine, as a cooling medium. And for the transport of pellets, especially liquids such as water and brine, the increased pressure is provided by the liquid used during pelletizing. This suppresses, at least partially, the expansion action of the expanding agent in the unsolidified pellets. Control of the parameters to be set for pelletizing, namely the temperature and pressure of the saturated molten material, is performed at the inlet of the pelletizing machine. In this control, the values of the aforementioned parameters are measured, and furthermore, the measured values are compared to the desired values. The deviation from the desired values due to unit control is used by the machine controller to affect the heat absorption from the saturated molten material by the cooler.

Claims (9)

All claims which will not appear on the advertisement page: 1. A method for the continuous production of expanded plastic pellets (G) by saturating the plastic melt (F) using a fluid-type expanding agent (B) and pelletizing the saturated melt using a machine which includes at least one pressure-generating feeder (1) for the melt, specifically a volumetric pump feeder, a metering machine (9) for the expanding agent, a contact and homogenizing machine (2) for the saturation of the melt, at least one cooling machine (3) for the saturated melt, an underwater pelletizer (6) and a control machine (1), where pelletizing is carried out using a liquid used in the pelletizer as a cooling and transport medium for the pellets, which is characterized by the liquid used during pelletizing being introduced into the aforementioned pelletizer (6) through a pump (60) under increasing pressure, on the basis that the expansion action of the expanding agent in the unsolidified pellets is at least partially suppressed and that the parameters to be determined for pelletizing are controlled, where the parameters are temperature. The pressure of the saturated molten material at the inlet of the pelletizing machine, and the pressure and temperature thereof, are measured by the machine controller to obtain the measured values. However, the measured values are compared to the desired values, and the deviation between the measured values and the desired values is used by the machine controller to control and affect the heat absorption from the saturated molten material by the cooler. 2. The method under claim 1, which is characterized by the fact that the liquid is water. 3. The method under claim 1, which is characterized by the liquid being saline solution. 4. The method under claim 1, which is characterized by the stationary mixer being used as the instrument for contact and homogenization (2) and/or similarly the cooling instrument (3), is the stationary mixer. 5. The method under claim 4, which is characterized as a stationary mixer consisting of mixing parts. 6. The method under claim 5, which is specified as follows: the mixing components shall be specially designed as heat exchanger tubes. 7. Any of the methods under claims 1 through 6, which are characterized as the feeder (10) for the melt is a gear pump or extruder, the feed force of which can be affected by the control device (1) in relation to the variable supply of the melt (F) to be saturated, whereby the measured feed of the expanding agent (B) is controlled. 8. One of the methods under claims 1 through 7 is characterized that the expanding agent (B) is dispersed in the molten material (F) in the first stage of the contact and homogenization machine (2), by applying a large shear action in a stationary mixer (2a), and that the mixture obtained in this manner is fed to a second stage (2b) where the mixture is dynamically maintained within a predetermined pressure range and for a period of time held within a predetermined time interval. 9. One of the methods under Reputation 1 through 8, which is characterized as polystyrene, styrene-copolymer, polyolefin or a mixture of the materials mentioned, shall be used as plastic (F); and that water (H2O), carbon dioxide (CO2), nitrogen (N2), low-boiling hydrocarbons, or a mixture of the materials mentioned shall be used as expanding agents (B). 1. One of the methods under Reputation 9, which is characterized as polyolefin being polyethylene. 1. One of the methods under Reputation 9, which is characterized as polyolefin being polypropylene. 1. One of the methods under Reputation 9, which is characterized as low-boiling hydrocarbons being pentane. 1. One of the methods under Reputation 1 through 12, which is characterized as an additive. At least one of the following compounds shall be mixed in before, during and/or after saturation: 1 Method under one of the claims 1 to 13, which is characterized that one of the different pellet forms shall be produced; 1 Method under the claim 14, which is characterized that pellets (G) shall be produced in the form of "pellets"; 1 Method under the claim 14, which is characterized that pellets (G) shall be produced in the form of "spheres"; 1 Method under the claim 14, which is characterized that pellets (G) shall be produced in the form of partially expanded pellets; 1 Machine for the production of expanded plastic pellets (G) under one of the claims 1 to 17, which is characterized that it shall include the following components arranged in series: First gear pump (10) or extruder (10) for the melt to be saturated; A stationary mixer (2) with a channel connection to the metering pump (9) for the expanding agent (B); a cooler (3) or a set of coolers, whose heat exchanger is designed as a part of the stationary mixer; a second gear pump, which is arranged within the set of coolers; an additional stationary mixer (5); an underwater pelletizer (6); and an electronic control unit (1), which is provided for the control of the parameters to be set for pelletizing and for this purpose has signaling connections (110, 13, 16, 19) to the pump or extruder (9, 10), to the cooler or to a number of coolers and to the pelletizer as well. 1. A unit for the production of expanding plastic pellets (G) in accordance with any of the claims 1 to 17, which are characterized as to include the following components arranged in series: the first gear pump (10) or extruder (10) for the saturating agent; A stationary mixer (2) with a channel connection to the metering pump (9) for expansion assistance (B); a cooler (3) or a set of coolers whose heat exchanger is designed as a stationary mixing unit; a second gear pump which is arranged after the cooler, an additional stationary mixer (5); an underwater pelletizer (6); and an electronic control unit (1) which is provided for the control of parameters to be set for pelletizing and for this purpose shall have signaling connections (110, 13, 16, 19) to the pump or extruder (9,10), to the cooler or to a number of coolers and to the pelletizer as well as 2 units according to claim 18 or 19, which is characterized that the stationary mixer (2) which follows the first gear pump shall be the first stationary mixer (2a) which is followed by the second stationary mixer (2b), in which the mixing unit In one stationary mixer, a greater shear force is generated than in a second mixer, resulting in the second stationary mixer having a larger flow cross-section than the corresponding cross-section of the first stationary mixer.