Drying-/degassing device and also device and method for the direct production of moulded articles from polyester melts

Abstract

The present invention relates to a drying-/degassing device (7) for drying or degassing a polyester granulate, which has a temperature-control zone, a cooling zone, an inlet (6) and an outlet (6) for polyester granulate and also in addition a separate removal possibility (14) for removing hot polyester granulate. In addition, the present invention relates to a device for the direct production of molded articles from polyester melts which comprises the drying-/degassing device according to the invention. In addition, the present invention describes a method for the production of molded articles from polyesters.

Claims

1. A method for the production of moulded articles from polyesters, wherein a) a polyester melt is granulated by means of an underwater granulator, b) the granulate is separated from the cooling water, and also c) is dried/degassed and/or postcondensed, wherein at least a part of the granulate which is dried/degassed and/or postcondensed in step c) is supplied without further cooling to at least one moulding tool and converted into a moulded article.

2. The method according to claim 1, wherein the granulate is maintained, during step c), at a temperature of 100 to 200 C.

3. The method according to claim 1, wherein the temperature of the polyester granulate is maintained, during supply to the moulding tool, at 50 C., relative to the granulate temperature during step c).

4. The method according to claim 1, wherein the part of the polyester granulate, which is not supplied to the moulding tool, is cooled subsequent to step c).

5. The method according to claim 4, wherein the ratio of the granulate supplied to the moulding tool and of the cooled granulate is adjusted between 0.1 and 0.7.

6. The method according to claim 2, wherein the granulate is maintained, during step c), at a temperature of 140 to 190 C.

7. The method according to claim 2, wherein the temperature of the polyester granulate is maintained, during supply to the moulding tool, at 50 C., relative to the granulate temperature during step c).

8. The method according to claim 2, wherein the part of the polyester granulate, which is not supplied to the moulding tool, is cooled subsequent to step c).

9. The method according to claim 1, wherein the temperature of the polyester granulate is maintained, during supply to the moulding tool, at 30 C., relative to the granulate temperature during step c).

10. The method according to claim 2, wherein the temperature of the polyester granulate is maintained, during supply to the moulding tool, at 30 C., relative to the granulate temperature during step c).

11. The method according to claim 3, wherein the temperature of the polyester granulate is maintained, during supply to the moulding tool, at 30 C., relative to the granulate temperature during step c).

12. The method according to claim 1, wherein the temperature of the polyester granulate is maintained, during supply to the moulding tool, at 15 C., relative to the granulate temperature during step c).

13. The method according to claim 2, wherein the temperature of the polyester granulate is maintained, during supply to the moulding tool, at 15 C., relative to the granulate temperature during step c).

14. The method according to claim 3, wherein the temperature of the polyester granulate is maintained, during supply to the moulding tool, at 15 C., relative to the granulate temperature during step c).

15. The method according to claim 5, wherein the ratio of the granulate supplied to the moulding tool and of the cooled granulate is adjusted between 0.3 and 0.5.

16. The method according to claim 2, wherein the granulate is maintained, during step c), at a temperature of 160 to 180 C.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) There are shown in the Figures

(2) FIG. 1 a device according to the invention for the direct production of moulded articles from polyester melts having a drying-/degassing device according to the invention, the removal possibility of which is configured as a spigot above the pellet cooler,

(3) FIG. 2 a device according to the invention for the direct production of moulded articles from polyester melts having a drying-/degassing device according to the invention, in which the removal possibility is configured as a double-walled pipe guided through the pellet cooler,

(4) FIG. 3 a device according to the invention for the direct production of moulded articles from polyester melts having a drying-/degassing device according to the invention, in which the removal possibility is configured as an annular gap in the bottom of the temperature-control zone and is guided outwards partially through the cooler,

(5) FIG. 4 a device according to the invention for the direct production of moulded articles from polyester melts having a drying-/degassing device according to the invention, in which the removal possibility is configured as conveyor screw above the pellet cooler, and also

(6) FIG. 5 a device according to the invention for the direct production of moulded articles from polyester melts having a drying-/degassing device according to the invention which has a two-part configuration and in which the temperature-control zone is separated from the cooler and connected via a connection pipe, the removal possibility being configured in the connection pipe.

DETAILED DESCRIPTION OF THE INVENTION

(7) In FIG. 1, an apparatus for the production of moulded articles from polyester melts is represented, which comprises a drying-/degassing device 7 according to the invention. The drying-/degassing device 7 has a removal possibility 14 for removing a partial flow of polyester pellets at high temperature, which is guided via a transfer 17 to the preform machines 18, 18, 18. Removal 14 of the partial flow is effected above the cooler 12 at two or more places on the outer circumference of the drying-/degassing device 7. The removal places 14 open into an outflow pipe 17 which is disposed at an angle to the vertical.

(8) The two or more removal places 14 are combined in a common pipeline 17 which is connected to a conveyor system 17a. The conveyor system 17a transports the polyester pellets at high temperature directly to the preform machines 18, 18, 18. One or more preform machines 18, 18, 18 can be supplied with polyester pellets at high temperature. The polyester pellets are fed, without crystallisation and drying, only with a low dwell time in the receiving container, directly to the preform machines 18, 18, 18.

(9) The number of removal places is fixed according to the ratio between partial flow to the preform machines 18, 18, 18 and the main flow 8 to the pellet cooler.

(10) The drying-/degassing device 7 according to the invention thereby has a one-part configuration, i.e. a cooling device 13 extending vertically downwards is connected directly to the temperature-control zone (also termed conditioning silo). Also the drying-/degassing devices 7 in FIGS. 2 to 4 are configured in this way.

(11) The device according to the invention for the production of moulded articles consists of the following main components which have the same configuration in all of the FIGS. 1 to 5.

(12) (1) Underwater granulation:

(13) A regulated quantity of polyester melt (FC1) is pressed via a suitable number of nozzles into a chamber through which water flows.

(14) (2) Cooling water circulation:

(15) The quantity of granulation water circulating through the circulation pump 2 is regulated in order that the correct dwell time is set in the cooling stretch 4.

(16) (3) Cooling of the granulation water:

(17) In addition to the dwell time in the cooling stretch, the water temperature regulated in the cooler 3 with (TC3) has a strong influence on the remaining residual heat.

(18) (5) Agitated centrifuge->water removal:

(19) In addition to the dwell time and the temperature in the cooling stretch, the remaining contact time between water and granulate grain in the agitated centrifuge 5 remains crucial for the residual heat in the granulate grain. With the regulatable speed of rotation of the rotor (SC5), the contact time of granulate with water can be adjusted optimally in the centrifuge.

(20) (16) Removal by suction:

(21) Fine drops and water vapour are withdrawn by the exhaust fan 16 as rapidly as possible through the sieve of the centrifuge, the water being extensively recovered via the condenser 15. The removal by suction is assisted by hot and dry gas from the thermal treatment 12.

(22) (7) Drying-/degassing device:

(23) The temperature of the thermal treatment is provided by the residual heat in the granulate and the crystallisation heat. The residual heat is controlled with the following process variables (TC1): Granulate weight divided by the melt quantity (FC1) and granulator speed of rotation (SC1), Contact time of water-granulate divided by the water quantity (FC2) and the speed in the cooling stretch 4 and also the speed of rotation of the agitated centrifuge (SC5), Granulation water temperature (TC3), Removal by suction (SC7) with assistance of the gas flows 6 and 12.

(24) With the fan 11, air is conducted from the bottom to the top through the granulate bed which flows from top to bottom in a silo. The gas thereby absorbs highly-volatile by-products, such as water, ethylene glycol, acetaldehyde etc. At a temperature of more than 175 C., this leads to an increase in viscosity and a reduction in the AA content, i.e. to solid-phase postcondensation. With increasing temperature (TC1), both the viscosity increase and the AA reduction per unit of time are greater.

(25) (10) Removal of moisture from the air: In the case of a thermal treatment with ambient air, this should have moisture removed (9).

(26) (8) Further processing:

(27) The granulate can be cooled in a cooler, which is integrated in the silo or connected thereafter for packaging, to the permissible temperature therefor.

(28) (13) Cooler with water circulation for cooling the pellets:

(29) The circulation water is re-cooled with cooling water.

(30) (14) Removal device of the polyester pellets at high temperature above the cooler:

(31) In the case of the configuration of the invention according to FIG. 1, this removal device is configured as a spigot. In the case of the configuration of the invention according to FIGS. 2 to 5, the design of the removal device in the respective portions is described.

(32) (17) Transport device for polyester pellets at high temperature, consisting of pipeline and feeder.

(33) (18) Preform machine including receiving silo, extruder and injection moulding machine. The number of preform machines is not limited, according to the capacity of the preform machines, between 1 and 20 machines (e.g. 18, 18, 18) can be supplied directly with polyester pellets at high temperature. The number and the size of the removal places 14 from the drying-/degassing device 7 according to the invention and also the capacity of the conveyor system 17 must be adapted to the overall capacity of the preform machines 18, 18, 18.

(34) In FIG. 2, an apparatus for removal 14 of a partial flow of polyester pellets at high temperature from a conditioning silo 7 and transfer to the preform machines 18 is shown. Removal 14 of the partial flow is effected through two or more double-walled pipes which are guided through the cooler. The double-walled pipes can be equipped in addition with an insulating layer which reduces the temperature drop. The double-walled pipes open into a common outflow pipe which is connected to a conveyor system 17.

(35) The conveyor system 17 transports the polyester pellets at high temperature directly to the preform machines 18. One or more 18, 18, 18 preform machines 18 can be supplied with polyester pellets at high temperature. The polyester pellets are fed, without crystallisation and drying, only with a low dwell time in the receiving container, directly to the preform machines 18, 18, 18.

(36) The number of double-walled pipes is fixed according to the ratio between partial flow to the preform machines 18, 18, 18 and the main flow to the pellet cooler.

(37) In FIG. 3, an apparatus for removal of a partial flow of polyester pellets at high temperature from a drying-/degassing device 7 according to the invention and transfer to the preform machines 18 is shown. Removal 14 of the partial flow is effected through a cylindrical annular gap which is connected to the interior of the drying-/degassing device 7 according to the invention by round or slot-shaped openings. The bottom of the annular gap cylinder is disposed at an angle relative to the vertical so that the polyester pellets are collected at one side. At the lowest position of the annular gap cylinder, an outlet pipe which is connected to a conveyor system 17 is disposed. The annular gap cylinder can be equipped in addition with an insulating layer which reduces the temperature drop.

(38) The conveyor system 17 transports the polyester pellets at high temperature directly to the preform machines 18, 18, 18. One or more preform machines can be supplied with polyester pellets at high temperature. The polyester pellets are fed, without crystallisation and drying, only with a low dwell time in the receiving container, directly to the preform machines 18, 18, 18.

(39) The number of openings between inner part and annular gap cylinder is fixed according to the ratio between partial flow to the preform machines 18, 18, 18 and the main flow to the pellet cooler.

(40) In FIG. 4, an apparatus 14 for removal of a partial flow of polyester pellets at high temperature from a drying-/degassing device 7 according to the invention and transfer 17 to the preform machines 18, 18, 18 is shown. Removal of the partial flow is effected by an actuated conveyor screw. The exit of the conveyor screw is connected to the entry of the conveyor system with a pipeline.

(41) The conveyor system 17 transports the polyester pellets at high temperature directly to the preform machines. One or more preform machines can be supplied with polyester pellets at high temperature. The polyester pellets are fed, without crystallisation and drying, only with a low dwell time in the storage container, directly to the preform machines 18, 18, 18.

(42) The size and speed of rotation of the conveyor screw is fixed according to the ratio between partial flow to the preform machines 18, 18, 18 and the main flow to the pellet cooler.

(43) In FIG. 5, an apparatus 14 for removal of a partial flow of polyester pellets at high temperature from a drying-/degassing device 7 and transfer to the preform machines 18, 18, 18 is shown. The drying-/degassing device 7 according to the invention thereby has a two-part configuration, the pellet cooler being present separately from the conditioning silo. Between the cone of the conditioning silo and the pellet cooler, pellets at high temperature are removed via a forked pipe or a T-piece. The polyester pellets are supplied at high temperature to a conveyor system 17.

(44) The conveyor system 17 transports the polyester pellets at high temperature directly to the preform machines 18, 18, 18. One or more preform machines 18, 18, 18 can be supplied with polyester pellets at high temperature. The polyester pellets are fed, without crystallisation and drying, only with a low dwell time in the receiving container, directly to the preform machines 18, 18, 18.

(45) The transport output of the conveyor device determines the ratio between partial flow of the pellets to the preform machines 18, 18, 18 and the main flow to the pellet cooler.