Patent TW-201912370-A (TW)
Inventor: MASSOW KLAUS
IPC: B29C48/44
Filed: 2018-07-24
Abstract: Provided herein is a method for concentrating polymer solution in a planetary screw extruder and manufacturing thermally crosslinked polymer simultaneously mixing with a modified liquid, which is characterized in that: (a) the planetary screw extruder comprises a filling zone operating in the atmosphere and the degassing and cooling zones operating under vacuum at the downstream, the filling zone is formed by at least one screw barrel, wherein the length of the filling zone operating under the atmosphere is not more than one-half of the total length of the planetary screw extruder, preferably no more than one-third; (b) the degassing and cooling zone of the planetary screw extruder operating under vacuum consists of at least four, preferably exactly four, screw barrels connected to each other, they each have a vacuum port on the sleeve, the vacuum ports having a cross section of at least 5% of the area of the sleeve that is passed by the planet screw, and the vacuum system is applied through the vacuum ports; (c) all screw barrels are separated from each other by an intermediate ring, the free cross-section of which is selected such that the polymer to be processed can accumulate there, and thus all screw barrels are hermetically separated from each other; (d) at least four screw barrels in the degassing and cooling zone each form a vacuum zone for independent operation, wherein the ratio of the pressure in the first vacuum zone of the first screw barrel with respect to the pressure in the second vacuum zone of the second screw barrel, and the pressure in the second vacuum zone of the second screw barrel with respect to the pressure in the third vacuum zone of the third screw barrel is at least 3:1, preferably at least 5:1; (e) the pressure in the third vacuum zone of the third screw barrel is less than 15 mbar, preferably less than 10 mbar, particularly preferably less than 5 mbar; (f) the pressure in the fourth vacuum zone of the fourth screw barrel is preferably between 100 mbar and 500 mbar; (g) transferring the polymer into a planetary screw extruder in the form of a polymer solution formed by dissolving the polymer in a solvent, wherein the polymer solution is heated to a temperature above the boiling temperature of the same polymer solution at a temperature of at least 60 DEG C, preferably at least 80 DEG C, in particular at least 100 DEG C under a super high pressure of 10 bar before entering the planetary screw extruder; (h) the polymer solution is directly injected into the first screw barrel of the filling zone operated by the atmosphere in the form of superheated liquid through a pressure regulating valve; (i) after evaporating at least part of the solvent in the filling zone operated in the atmosphere, the material flow of the polymer solution fed into the first vacuum zone of the first screw barrel is smaller than 75% of the material flow of the polymer solution that originally delivered to the star screw extruder, preferably less than 65%, particularly less than 55%; (j) the flow temperature of the central screw in the degassing and cooling zone and the screw barrel under vacuum is adjusted so that the polymer to be degassed remains in the plasticized state; (k) the polymer solution is preferably continuously added with the liquid thermally crosslinked agent and optionally the crosslinked accelerator, dye solution or dye dispersion in the range of the fourth vacuum zone of the fourth screw barrel, wherein the feeding port of the material in the first one-third of the length of the barrel in this fourth vacuum zone; (l) the degassing and cooling zone each have a screw barrel, in particular at least two separated circuits for controlling the temperature of the liquid, wherein the polymer solution is cooled in such a manner that no thermally crosslinked agent initiates gelation of the polymer solution in the planetary screw extruder or in the subsequent devices possibly linked to the downstream; (m) the solvent residual amount in the polymer solution behind the third vacuum zone is less than 1% by weight, preferably less than 0.5% by weight, particularly less than 0.1% by weight; (n) transporting the polymer solution discharged from the last screw barrel to a coating device, more preferably, it is an in-line transportation.