Method and system for producing a polymer

Abstract

A method for producing a polymer from a first component and a second component using a reactor (50) offers technical advantages, wherein reaction heat produced in the reactor (50) is discharged via a boiling cooler (40) by supplying gaseous vapors produced in the reactor (50) to the boiling cooler (40). A product flow containing condensed vapors is returned to the reactor (50) from the boiling cooler (40) via a separation vessel (60), and an aqueous phase is separated from the product flow in the separation vessel (60). A system is provided for producing a polymer from a first component and a second component, comprising a reactor (50) and a boiling cooler (40) for discharging reaction heat produced in the reactor (50). A separation vessel (60) is arranged between the boiling cooler (40) and the reactor (50) such that a product flow containing condensed vapors is returned to the reactor (50) from the boiling cooler (40) via the separation vessel (60).

Claims

1. A process for producing a (co)polymer from at least one first component and a second component by a reactor, where heat of reaction arising in the reactor is removed by an evaporative cooler, by feeding gaseous vapor formed in the reactor to the evaporative cooler wherein a product stream containing condensed vapor is recirculated from the evaporative cooler via a separator vessel to the reactor, wherein the product stream is cooled in a heat exchanger before entry into the separator vessel, wherein an aqueous phase is separated off from the product stream in the separator vessel and wherein the product stream flows from the separator vessel under the force of gravity into the reactor.

2. The process of claim 1, wherein the first component contains styrene and wherein the second component contains acrylonitrile.

3. The process of claim 1, wherein the second component contains acrylonitrile and wherein the first component contains alpha-methylstyrene.

4. The process of claim 1, wherein the first component contains styrene and wherein the second component contains methyl methacrylate.

5. The process of claim 1, wherein in the separator vessel a separation layer formed above the aqueous phase is separated off from the product stream.

6. The process of claim 1, wherein the first component and/or the second component are introduced at least partly via the evaporative cooler and goes via the separator vessel from the evaporative cooler into the reactor.

7. The process of claim 1, wherein the first component and/or the second component are partly introduced directly to the reactor.

8. The process of claim 6, wherein the first component and/or the second component are fed at least partly in liquid form to the evaporative cooler and/or the reactor.

9. The process of claim 6, wherein solvents and also unreacted monomers of the first component and/or the second component are recirculated from a condensation unit via a return conduit into the evaporative cooler.

10. A system for producing a polymer from at least one first component and a second component, comprising: a reactor and; an evaporative cooler for removing heat of reaction arising in the reactor, wherein a separator vessel is arranged between the evaporative cooler and the reactor in such a way that a product stream containing condensed vapor is conveyed from the evaporative cooler via the separator vessel back into the reactor, wherein a heat exchanger is arranged between the evaporative cooler and the separator vessel in such a way that the product stream is cooled in the heat exchanger before entry into the separator vessel, and wherein the reactor, the evaporative cooler, and the separator vessel are arranged in such a way that the product stream flows from the separator vessel under the force of gravity into the reactor.

11. The system of claim 10, wherein the evaporative cooler has at least one feed opening for introducing the first component and/or the second component.

12. The system of claim 10, wherein the reactor, the evaporative cooler, and the separator vessel are arranged in such a way that vapor formed in the reactor ascends against the force of gravity into the evaporative cooler, and wherein the product stream flows under the force of gravity into the separator vessel.

13. The process of claim 7, wherein the first component and/or the second component are fed at least partly in liquid form to the evaporative cooler and/or the reactor.

14. The process of claim 7, wherein solvents and also unreacted monomers of the first component and/or the second component are recirculated from a condensation unit via a return conduit into the evaporative cooler.

15. The process of claim 8, wherein solvents and also unreacted monomers of the first component and/or the second component are recirculated from a condensation unit via a return conduit into the evaporative cooler.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) In the drawings:

(2) FIG. 1: shows a schematic view of a system for producing a polymer and

(3) FIG. 2: shows a detailed schematic view of a bottom region of the evaporative cooler of the system for producing a polymer from FIG. 1.

(4) A schematic sectional view of a system 10 for producing a polymer from at least one first component and a second component is depicted in FIG. 1.

(5) The system 10 serves, in particular but not exclusively, for producing styrene-acrylonitrile copolymer (SAN), alpha-methylstyrene-acrylonitrile copolymer (AMSAN) and styrene-methyl methacrylate copolymer (SMMA).

(6) The system 10 comprises a reactor 50. In the reactor 50, a polymerization of monomers fed in takes place. A stirrer 52 is arranged within the reactor 50. The stirrer 52 can be driven rotationally by means of an electric motor which is not shown here. Other types of reactors 50 in which a polymerization of monomers fed in can take place can also be used.

(7) A first feed conduit 31 is connected to the reactor 50. The first feed conduit 31 serves for the introduction of components directly into the reactor 50. The components introduced contain, in particular, monomers. A first return conduit 36 is also connected to the reactor 50. The first return conduit 36 serves for the introduction of a solvent and also of unreacted monomers separated off during degassing. The solvent originates from a condensation unit 71, which will be discussed at a later juncture.

(8) Furthermore, an outlet conduit 34 is connected to the reactor 50. Polymer composition formed in the reactor 50 can be drained from the reactor by means of the outlet conduit 34. A degassing unit 70 is arranged upstream of the reactor 50 and connected to the outlet conduit 34. Polymer composition drained from the reactor 50 via the outlet conduit 34 thus goes into the degassing unit 70 arranged downstream.

(9) The degassing unit 70 serves, in particular, for removing volatile constituents from the polymer composition, in particular solvent and unreacted monomers. An offtake conduit 38 is connected to the degassing unit 70. The polymer produced, which is now at least largely free of unreacted monomers and solvent, can be taken from the system 10 via the offtake conduit 38.

(10) The degassing unit 70 is also connected to the condensation unit 71. Solvent and unreacted monomers which have been removed from the polymer composition in the degassing unit 70 are fed into the condensation unit 71. The solvent and the unreacted monomers condense in the condensation unit 71.

(11) The condensation unit 71 is connected to a collection vessel 80. The condensed solvent and the condensed, unreacted monomers from the condensation unit 71 are fed into the collection vessel 80.

(12) A feed conduit 33 is also connected to the collection vessel 80 and serves for introducing or introducing further amounts of solvent.

(13) The first return conduit 36 which is connected to the reactor 50 and serves for introduction of the solvent and the unreacted monomers into the reactor 50 is also connected to the collection vessel 80. The solvent present in the collection vessel 80 and also the unreacted monomers can thus be partly recirculated via the first return conduit 36 into the reactor 50.

(14) The system 10 further comprises an evaporative cooler 40. The evaporative cooler 40 serves for removing heat of reaction arising in the polymerization in the reactor 50. The evaporative cooler 40 is in the present case configured as shell-and-tube heat exchanger and comprises a plurality of vertical tubes 44. The evaporative cooler 40 is closed, i.e. at the end facing away from the ground, by a cap 42. Furthermore, the evaporative cooler 40 comprises a coolant inlet which is not shown here and a coolant outlet which is likewise not shown here.

(15) The reactor 50 is connected to the evaporative cooler 40 in such a way that the heat of reaction arising during the polymerization in the reactor 50 can be removed by means of the evaporative cooler 40. Gaseous vapor formed in the reactor 50 is fed to the evaporative cooler 40 and condenses in the evaporative cooler 40.

(16) A separator vessel 60 is arranged between the evaporative cooler 40 and the reactor 50. The separator vessel 60 serves to separate off an aqueous phase from a product stream which contains condensed vapor from the evaporative cooler. The evaporative cooler 40 is connected by means of a separator conduit 62 to the separator vessel 60 and the separator vessel 60 is connected by means of a feed conduit 64 to the reactor 50. The separator vessel 60 is arranged in the system 10 in such a way that the product stream flows under the force of gravity from the evaporative cooler 40 through the separator conduit 62 to the separator vessel 60 and further through the feed conduit 64 back into the reactor 50.

(17) The system 10 also comprises a heat exchanger 82 which is arranged in the separator conduit 62 between the evaporative cooler 40 and the separator vessel 60. The product stream exiting from the evaporative cooler 40 flows through the heat exchanger 82 and is cooled in the heat exchanger 82 before entering the separator vessel 60. The heat exchanger 82 here is optional and can also be omitted. In this case, the product stream exiting from the evaporative cooler 40 flows directly into the separator vessel 60.

(18) The feed conduit 64 is connected to an upper region of the separator vessel 60. The separator conduit 62 is connected to a middle region of the separator vessel 60. An outflow 66, which serves to take off the aqueous phase from the separator vessel 60, is connected to a lower region of the separator vessel 60.

(19) Within the evaporative cooler 40, the gaseous vapor formed in the reactor 50 ascends in the vertical tubes 44. A coolant flows around the tubes 44.

(20) The coolant is fed to the evaporative cooler 40 through the coolant inlet, flows around the vertical tubes 44 and exits again from the evaporative cooler 40 through the coolant outlet. In the process, the coolant cools the tubes 44 and also vapor from the reactor 50 which is present therein. As a result, the vapor condenses, and a product stream comprising the condensed vapor flows through the separator conduit 62 into the separator vessel 60.

(21) One or more feed openings 46 are arranged in the cap 42 of the evaporative cooler 40. The feed openings 46 in the cap 42 of the evaporative cooler 40 serve for introducing components into the evaporative cooler 40. Furthermore, a plurality of nozzles 48 can be provided in the cap 42 of the evaporative cooler 40. The nozzles 48 are connected to the feed openings 46. Components which are introduced into the cap 42 of the evaporative cooler 40 through the feed openings 46 thus go to the nozzles 48 in the cap 42 of the evaporative cooler 40.

(22) The nozzles 48 are arranged in the cap 42 of the evaporative cooler 40 in such a way that components which are introduced through the feed openings 46 into the evaporative cooler 40 are distributed from above over all vertical tubes 44 of the evaporative cooler 40. The components introduced through the feed openings 46 into the evaporative cooler 40 thus drop under the force of gravity into the vertical tubes 44 of the evaporative cooler 40 in which the vapor from the reactor 50 condenses.

(23) A second feed conduit 32 is connected to the cap 42 of the evaporative cooler 40. The second feed conduit 32 serves for introduction of components into the evaporative cooler 40. The components fed in contain in particular monomers. The second feed conduit 32 is connected to the feed openings 46 in the cap 42 of the evaporative cooler 40.

(24) Components introduced via the second feed conduit 32 thus go via the feed openings 46 to the nozzles 48 in the cap 42 of the evaporative cooler 40 and from there into the vertical tubes 44.

(25) A second return conduit 35 opens into the second feed conduit 32. The second return conduit 35 is, like the first return conduit 36, connected to the collection vessel 80. Thus, the solvent present in the collection vessel 80 and also the unreacted monomers can be fed in their entirety or partly into the second feed conduit 32 via the second return conduit 35. The second return conduit 35 thus serves for introduction of a solvent and of the unreacted monomers into the evaporative cooler 40.

(26) Furthermore, an offgas conduit 49 is connected to an upper side of the cap 42 of the evaporative cooler 40. Offgases from the evaporative cooler 40 can exit via the offgas conduit 49.

(27) FIG. 2 shows a detailed schematic depiction of a lower region of the evaporative cooler 40 of the system 10 for producing a polymer shown in FIG. 1. Here, in particular, the lower region of the evaporative cooler 40, which is located below the tubes 44 and to which the separator conduit 62 and the reactor 50 are connected, is shown.

(28) The lower region of the evaporative cooler 40 has an approximately funnel shape. A riser tube 67 extends from the reactor 50 into the funnel-shaped lower region of the evaporative cooler 40. A cover 68 is arranged above the riser tube 67 and below the tubes 44. The cover 68 is configured in such a way that vapor flowing downward under the force of gravity from the tubes 44 and also monomers impinge on the cover 68 and are diverted laterally to an interior wall of the funnel-shaped lower region. The cover 68 thus prevents vapor flowing downward under the force of gravity from the tubes 44 and also monomers from falling into the riser tube 67 and flowing into the reactor 50.

(29) A discharge port 63 is installed at an outer wall of the funnel-shaped lower region of the evaporative cooler 40. The separator conduit 62 is connected to the discharge port 63. The vapor flowing downward under the force of gravity from the tubes 44 and also monomers flow through the discharge port 63 as product stream into the separator conduit 62 and further to the separator vessel 60.

(30) In the reactor 50, a polymerization of the monomers takes place while stirring by means of the stirrer 52. Heat of reaction arises in the polymerization. The heat of reaction results in gaseous vapor ascending from the reactor 50 into the evaporative cooler 40. The gaseous vapor formed in the reactor 50 ascends in the vertical tubes 44 of the evaporative cooler 40 and is cooled there. As a result, the vapor condenses, and the product stream comprising the condensed vapor flows to the separator vessel 60.

(31) The polymer composition formed in the polymerization has a solids content of about 50%-80%, preferably 60%-70%. The polymer composition is then fed via the outlet conduit 34 to the degassing unit 70. In the degassing unit 70, the volatile constituents, in particular solvent and unreacted monomers, are removed from the polymer composition. The polymer produced, which is now largely free of volatile constituents, is taken off from the system 10 via the offtake conduit 38.

(32) The solvent removed from the polymer composition and also the unreacted monomers are conveyed through the condensation unit 71 and the collection vessel 80 and possibly partly recirculated via the first return conduit 36 back into the reactor 50 or recirculated in their entirety or partly via the second return conduit 35 back into the evaporative cooler 40.

(33) The components are present in liquid form. The components are introduced through the feed openings 46 in the cap 42 of the evaporative cooler 40 into the evaporative cooler 40. The components are distributed into the vertical tubes 44 of the evaporative cooler 40 via the nozzles 48 in the cap 42 of the evaporative cooler 40. Here, the components drop from above under the force of gravity into the vertical tubes 44 of the evaporative cooler 40.

(34) Due to the heat of reaction which arises as a result of the polymerization in the reactor 50, gaseous vapor also ascends against the force of gravity from the reactor 50 into the vertical tubes 44 of the evaporative cooler 40. There, the vapor is cooled and condenses. In the process, mixing of the condensed vapor with the components which are introduced from above under the force of gravity via the second feed conduit 32 into the vertical tubes 44 of the evaporative cooler 40, and with substances introduced via the second return conduit 35 takes place.

(35) The condensed vapor subsequently flow together with the components introduced via the second feed conduit 32 into the evaporative cooler 40 and together with the substances fed via the second return conduit 35 as product stream under the force of gravity from the evaporative cooler 40 to the separator vessel 60.

(36) In the separator vessel 60, an aqueous phase settles at the bottom, and a separation layer is formed directly above the aqueous phase. The aqueous phase is, optionally together with the separation layer, drained through the outflow 66 from the separator vessel 60. The aqueous phase and the separation layer are thus separated off from the product stream which contains the condensed vapor and the components introduced into the evaporative cooler 40.

(37) A product stream which contains virtually exclusively condensed vapor, components introduced into the evaporative cooler 40, i.e. monomers, and also solvent is fed via the feed conduit 64 under the force of gravity to the reactor 50. The feed conduit 64 here is attached to the separator vessel 60 above the aqueous phase. The product stream thus leaves the separator vessel 60 from above the aqueous phase.

(38) The process described here for producing a polymer is based on a continuous procedure. The components are introduced continuously in their entirety or at least partly via the second feed conduit 32 into the evaporative cooler 40, or not more than partly introduced via the first feed conduit 31 into the reactor 50. Monomers which are introduced via the first feed conduit 31 into the reactor 50 or via the second feed conduit 32 into the evaporative cooler 40 and which are not recirculated via the degassing unit 70 and the condensation unit 71 are also referred to as fresh monomers.

(39) The polymer produced is likewise taken off continuously via the offtake conduit 38. The solvent is circulated in the system 10. The solvent is at most partly conveyed from the condensation unit 71 via the first return conduit 36 into the reactor 50 or via the second return conduit 35 in its entirety or partly into the evaporative cooler 40.

(40) The invention is explained in more detail by the examples, figures and claims.

(41) In a process known from the prior art for producing a polymer (SAN), the vapor condensed in the evaporative cooler 40 was recirculated together with solvent and unreacted monomers directly into the reactor 50.

(42) The polymer produced was taken off continuously and subsequently processed further to produce pellets. After about six months, surface defects were observed on workpieces which had been produced from the pellets produced by injection molding. Subsequent inspection of the reactor revealed deposits and foulings on the shaft of the stirrer 52 and also on parts of the wall of the reactor 50. Operation was continued without cleaning.

(43) After a further about 3 to 6 months, red particles were also found in the pellets. Subsequent inspection of the reactor 50 showed not only a further increase in the abovementioned deposits and foulings but also proportions of reddish material within the deposits and foulings. To eliminate these undesirable constituents, the reactor 50 had to be cleaned.

(44) In an experiment for producing a polymer (SAN) by means of the process of the invention in a system 10 according to the invention, the product stream was recirculated from the evaporative cooler 40 via the separator vessel 60 into the reactor 50. The polymer produced was taken off continuously and subsequently processed further to produce pellets.

(45) In the present case, it took about two years before surface defects were observed on workpieces which had been produced from the pellets produced by injection molding. Red particles were not found in the pellets within two years. After about two years, an inspection of the reactor 50 was likewise carried out. Here, only small amounts of foulings and deposits of polymer were found on the shaft of the stirrer 52 and on the walls of the reactor 50.

LIST OF REFERENCE NUMERALS

(46) 10 System

(47) 31 First feed conduit

(48) 32 Second feed conduit

(49) 33 Feed conduit

(50) 34 Outlet conduit

(51) 35 Second return conduit

(52) 36 First return conduit

(53) 38 Offtake conduit

(54) 40 Evaporative cooler

(55) 42 Cap

(56) 44 Tube

(57) 46 Feed opening

(58) 48 Nozzle

(59) 49 Exhaust gas conduit

(60) 50 Reactor

(61) 52 Stirrer

(62) 60 Separator vessel

(63) 62 Separator conduit

(64) 63 Discharge port

(65) 64 Feed conduit

(66) 66 Outflow

(67) 67 Riser tube

(68) 68 Cover

(69) 70 Degassing unit

(70) 71 Condensation unit

(71) 80 Collection vessel

(72) 82 Heat exchanger