SA02220694B1 - CONTINUOUSLY PROCESS FOR PRODUCTION OF POLYESTERS OR COPOLYESTERS - Google Patents

Abstract

Abstract: The present invention relates to a process for the production of polyesters and copolyesters, the process of continuous esterification of dicarboxylic esters and diols or continuous transesterification of dicarboxylic esters with diols is carried out in a number of stages The reaction pressure stages are connected in succession (n) in series, where the pressure in the first reaction pressure stage, which is high, decreases. Compared to the remaining reaction pressure stages, successively from reaction pressure stage to reaction pressure stage, the combined vapor flows of the separate reaction pressure stages are purified in a rectifying column and the obtained diol component is recirculated down the rectifying column to In the first reaction pressure stage at least, and to reduce the technical effort, the last reaction pressure stage should have at least a vacuum, and the pressure in the distillation column is greater than that in the last reaction pressure stage, and the vapors discharged from the last reaction pressure stage condensed to pressure in the distillation column.

Description

B Continuously continuous process for the production of polyesters or copolyesters Full description BACKGROUND The invention relates to a process for the production of polyesters or copolyesters

Contribution of copolyesters by continuous esterification of ester compounds

dicarboxylic esters and diols or continuous transesteification 5 of dicarboxylic esters with compounds

Diols in a number of Jalja reaction pressure stages connected in series first reaction, where the pressure in the first reaction pressure stage decreases 0” (n) in series

“pressure stage which is high compared to other reaction pressure stages; successively from

Reaction pressure stage to pressure stage daa Tay Jeli Combined vapor flows of separate reaction pressure stages to a scrubbing column

dla’ yg rectified —ii rectifying column recirculated component

The diol component on which Joa ta is located down the distillation column to a pressure stage

At least the first interaction.

It is known that the continuous production of polyethylene terfashall

d (PET) polyethylene terephthalate from terephthalic acid (TPA) and ethane-diol

(EG) ethane diol participates in the esterification process in da ya reaction Jd under

Elevated pressure and in another reaction stage under standard pressure

pressure normal and to convert esterification products into oligomers

coligomerize supplies two prepolycondensation stages two v to produce a final reactor sequentially fine vacuum finished polyester melt polyester in final patent description European Alia No. 744 7 for a process of vacuum generation and vapor condensation, including multistage steam jet pumps Jal yall, by means of multistage steam jet pumps ° and preceding spray condenser Each of them has an advanced spray compressor, and the successing direct-contact condensers are operated by a subsequent purified process water vapor column by means of a purified process water vapor (pressure dalle) purification by distillation above the first reaction pressure stage ; It has water vapor and the cooling water is recycled bar? bar (NY wz gl excess pressure plus Ve) from the contact capacitors towards the distillation column. The disadvantages of this cooling water oll organic contamination Cig Bl process are substantially the high percentage and large amount open process circuits In the cycles of the open process, waste water, for each reaction stage, as well as the second reaction stage, Cun (Plan), which is expensive for separate devices. 1 As a result of the high pressure in the diethylene glycol (DEG) pressure stage the first reaction and the bottom of the distillation purification column. General it should be noted that when purifying the original overheated steam stream (Ki

EG of 0 is about weight content original superheated vapor stream materially from steam in terms of matter Tou in the distillation column it loses part to operate the pumps operating steam operational Jo on las energetically shaped and energy the steam jet. The process described above is improved so that the vapors of the first two reaction pressure stages are supplied by distillation and the two vacuum stages of the RS stage and the second stage of the esterification process are combined together into a single-column prepolycondensation stage. Single Yo ava

¢ A disadvantage of a single pre-polycondensation stage is the size-related limitation of the capacity due to increased gas formation, increased risk of droplets, and a generally undesirable increase in the content of carboxylic groups carboxylic groups in a polyester or polyester 0 copolyester as a result of faster evaporation of BEG during prepolymer condensation without pressure differentiation. The subject of US Patent No. 47700680 is a total process of; stages to produce PET, where in the second reaction stage it provides an esterification process in cold and where it obtains a typical acid conversion ratio of 7951. This conversion appears to be low Tan to release residual gas le in the stage Multi-cued condensation i.e. longer residence times are required to achieve a higher conversion ratio i.e. larger and more expensive reaction devices. In which dla it is necessary to have an additional distillation column with recirculation of BG or another separate condensation system with successive extraction of EG and in the process of vacuum esterification in the reaction phase ABN there are also important reservations regarding the quality of quality and flexibility of the industrial unit plant in relation to the addition of additives, for example, without normal pressure and without stirring the melt, especially in the process of producing Sus PET textile, it is difficult Toa Mixing of agglomerate admixtures without evaporation losses. General description of the invention 7 The objective of the Gy of the present invention is to improve the process described above so that the required amount of hardware and operating costs for water cooling and energy production are JI without impairing the quality of the resulting polyesters or copolyesters and the flexibility of the process. This objective is achieved so that the last reaction pressure stage is operated at least at a vo subatmospheric pressure ranging from 001 to 500 mbar v4

mbar (Tod (absolute) from the process described above. The pressure in the distillation column is greater than in the reaction pressure stage 5A) Ca TAC 25g Goal) drained from the last reaction pressure stage to the pressure in the distillation column. Different esterification or transesterification processes take place in a number of successively connected reaction pressure stages (ifn) and the pressure decreases successively with increasing monomer conversion rates or Jal ya advancing reaction pressure. In the esterification process used to produce polybutylene terepththalate (PBT), it is 5" 5 Jal jo J" reaction pressure exclusively in eld 0, while in the esterification process used to produce PET and polybutylene terepththalate JZ 28 75 (PTT) polytrimethyl terephthalate First reaction pressure stage under plus pressure 70 JD aS Last reaction pressure stage in vacuum. in the process of trans-esterification; and starting with dimethyl terephthalate (0147) and 1; JZ 5875 (BDO) 1,4-butanediol -butanediol The first reaction pressure stage is substantially under ve standard pressure. And for the technical indication of the Gay process of the invention; It is irrelevant if the separate reaction pressure stages are distributed in a single device or separate reaction devices are formed .separate reactors and to perform the operation Gy of the invention; At least two reaction pressure stages are required. and for a particularly useful operation; It is appropriate to use three dal je reaction pressure. It is »| It is possible to use a four-stage process to compress (a TA) the vapors of the last reaction pressure stage to the penultimate reaction pressure stage or pressure in a distillation column. Condensation of the vapors of the last reaction pressure stage is avoided. The latter reaction pressure and therefore; a larger purification column by condensing the vapors to a relatively high pressure.In Ala the process is carried out using la evo reaction pressure; the pressure height in the distillation column varies between the pressure in the ava stage

+ The first reaction pressure and that in the second reaction pressure stage. When more than two reaction pressure stages are used; The pressure in the distillation column does not exceed the pressure in the penultimate reaction pressure stage. Condensation of the vapors may be done by means of a blower compressor or ventilator, but it is particularly useful to perform the condensation of the vapors by means of an AGA gas jet pump using a superheated vapor stream. Reaction pressure stage 1 as a working steam” In view of OY the vapors of the first reaction pressure stage are available at no cost and in sufficient quantity and therefore condensation of vapors using compressors, blowers or ventilators is not taken into consideration except in 01 second stage. Special for the process Gy of the invention Cua The pressure in the distillation column can be adjusted by the exhaustion of residual gas as they are imploded behind the oT placed at the apex of the head of the distillation column Mia by means of a jet pump Liquid jet pump 1 Tso 11” liquid ring pump 1 or by blower as well. In the PET esterification process in particular; Sich is another facet of the Gy process of the invention in controlling the pressure in the esterification stage in vacuum vacuum esterification stage at partial load Tks partial load for pressure drop with lower flow rate e.g. from about YVoo mbar at a flow rate of 7100 to about 17500 mbar at a flow rate of 0 50 with a constant filling level Cull eda in the first reaction pressure stage J Sg low to 0286. As a result of the reduced operating vapor pressure at the gas pump (AE) at partial load; It raises the pressure of the vacuum stage from about 5000 mbar at full load to about mmbar at a flow rate of aly 7896 when the counter-pressure of each is fixed at about 0001 mbar in the distillation column. avq

Only ead and for Ae lly reasons a constant vacuum is required in the phase of vacuum esterification regardless of the flow rate. Tay for invention; Achieves this pressure stability without large precipitation column dimensions with a controlled drop in the distillation column pressure from +46 to Veo mbar at a flow rate of about 68° and forms the corresponding preform vacuum of the distillation column and is controlled by means of an air exhauster placed behind a” Sa column head condenser and alternatively by means of a liquid jet pump or liquid annulus pump. For the production of the PET esterification product in the form of cual sia, it is preferable to use a three-stage process 0 with the variables indicated in Table 1 for example. Table 1: EG and lea TPA enter in the form of a paste with a molar ratio of less than ¥ and preferably not more than 017 to the first reaction pressure stage (1) operated under excessive pressure; Thus, conversion ratios are obtained for TPA ranging from AA to JAY, and ve switches the second reaction pressure stage (11) under standard pressure Jan Tg at a conversion ratio ranging from about 4 to about 799.4, preferably From about 45.8 to about ALY, the reaction pressure stage (11) is used to mix the additives and to adjust the molar content of 6 in the final product. In the third reaction stage (TI) operated in vacuum, the conversion rate increases from more than 97 to 799 and preferably from 47.4 to JAA0 Y. By means of a jet pump all it evaporates the vapors from the third reaction pressure stage (HD) to the pressure in the distillation purification column.The working steam is withdrawn from the vapors

A

The nominal load vapor pressure rises at the first reaction pressure stage (1) and at nominal load during vapor condensation from the last stage. YLT ranges from −1 by a factor appropriately by the PTT process on continuous production of a two-stage Jan esterification product with the variables shown in Table ¥ for example; using a prepared paste ranging from molar ratio with a molar ratio of TPA and (PDO) 1,3-propanediol of 1 0-propane diol 0

Note to 10.7; Preferably not more than 5 7 Table AAA Lv 0| Introduced molar ratio M 3000 from two phases; Adee enters by PBT and when producing the transesterification product liquid separately to the reaction pressure stage DMT and (BDO) butanediol butane diol to 4,. The process variables are shown in the table () on the first 0.7 in a molar ratio ranging from - for example. Table ?ed [eee | 8000015 Entered molar ratio ava

A brief explanation of the drawings The process according to the invention is represented schematically in the drawings and will be explained later in detail by example. And in the drawings: Figure 1: Lewy shows schematically the process of producing ° esterification / trans-esterification products by two reaction pressure stages for PPT and ¢PBT Ysa: shows a side of the schematic diagram of the process J Sal Gy 1; and vos a: Shows a schematic diagram of the process of producing a PET esterification product by three stages. dicarboxylic acid to the (Y) first reactor via line (1). The product stream drained from the first reactor (Y) is supplied via line (©) to the second reactor (;) The final esterification product is discharged from the second reactor (;) via the line (*). It is supplied to regulate the pressure in the first reaction stage” to (A) heated gas jet pump (Sane) via line (6); and by means of the gas jet pump, the inlet gas stream is condensed through Lal ( ) which consists of the vapors of the second reactor (;) discharged through the line (01) and a ballast stream intended to be used to adjust the pressure in the second reactor (4) and flowing through the line (11); to the pressure in the column Purification by distillation (VY) and the exhaust fumes from the first reactor are fed through the line (1) and the exhaust fumes from the second reactor through the two lines (01 A) to the gas jet pump (A) and in the line (€ 1) the steam stream merges The drain from the gas jet pump (A) by line (VF) with the vapor bypass stream ve supplied by line (7) and fed to the inlet of the scrubber

By distillation (VY), where the low-boiling components are separated from the high-boiling diol component, and the drained low-boiling components are detected from the top of the VY column via the line 18) to “(11) condenser a” “Sal.” They carry out the condensate product flowing through Lal (VY) ° reflux stream and product stream through the reflux tank -( VA) reflux tank The reference stream is supplied to the top of the distillation purification column (V7) through the line (V9) and the product stream is withdrawn through the line (71). Often the enriched diol is supplied at the bottom of the purification column By distillation (VY) to the first reactor (Y) through the two lines (YY YY) and only a small part branching through the line (YY) supplies the second reactor (4). feed additives and/or comonomers to the second reactor (;) through the line (YE) and in addition to that; (YY) by line (77a) and used to prepare the paste.If the process diagram represented in Fig. 1 is used for the purpose of transesterification; Diol is fed to the first reactor (7) via line (1) and DMT is fed to the first ae reactor via line (Ye) and to enable the operation of the Gig process according to the scheme represented in the figure 1 also in a vacuum; it provides Gy of Figure 1 a schematic for compression of a residual gas behind the condenser (V1) by means of a (YY) pump to drain the residual gas from the return tank (VA) by means of line (77).The condensate flowing out of the reference tank (VA) is made by means of (YA) bad at »-gauge pressure by dipping tank (79);and then the condensate is removed from the process Through the line (1). In the process diagram, as shown in Figure Jax FF, the EG/TPA paste is sent to the first reactor (YY) via the line (VY), and the said reactor product is fed to the second reactor. (; 3) via line (VY) and the product stream leaving the second reactor (YE) is supplied via line ve (5©) to the third reactor (VT) which discharges the final esterification product die from line path

to

Lage (YY) The vapors discharged from the first reactor (FA) are fed through the line (VY) and are used to adjust the pressure in the reaction stage (V4) of which a small bypass stream flows through the line to the jet pump with heated gas) £0) and via line (7;); the first (FY) flowing through line (7;) is added to the vapors (VE) from the ballast stream of the second reactor vapors of the third reactor sad by Line route (41); to condensate (YT) drained from the third reactor 0 and only (400) to pressure in the distillation purification column by means of the gas jet pump (YY) via line (7;) with (VE) Necessary; fumes from the second reactor are combined in-line (£0) and with the bypass (40) the fumes from the gas jet pump supplied by in-line (794); after confluence through a retention valve The pressure is greater than (YE) (44), so that the pressure in the second reactor pressure maintaining valve is 0 pressure in the distillation column or equal to it, and through the line (£7) fed to the distillation column ( 97;), where the combined vapors separate the high-boiling combined vapors. Y) drained from the top of the distillation column and by line (00) the condensate flows into the reference tank (0) which is re-fed ve and for vacuum operation of the column (OF) part of it to the top of the distillation column (97; ) by line at partial load; The reference tank (0) is connected to a suction pump (£V) that is evaporated by distillation and the condensate drained from the tank (OF) is connected through the line (©) suction pump

Jas (07) in the immersion tank ke ref (01) via line (00) when the bulk of the recirculated ethane is compressed via line (7*) for further processing. x. is recycled from the components High-boiling from the bottom of the JB column containing the amount of ethane diol and the part (09 0A) through the two lines (VY) by distillation (497) to the first reactor through the line (10) Part of the diol (FE) can be withdrawn to the second smaller reactor die diol flowing through line (09) via line (104) and used to prepare the paste.

Claims (1)

VY Claims 1-1 A process for the production of Jil polyesters and copolyesters via Y continuous esterification of dicarboxylic esters ¥ and diols or transitional esterification Continuous transesterification ¢ of dicarboxylic esters with ° diol compounds in a number of Jad ye (n) reaction pressure stages 1) which breaks down all 7 connected series dnseries, where The pressure 7 in the first reaction pressure stage (YY (XY) A which is lel is lower than in Jali (v TYE ) remaining reaction pressure stages 4 » successively from the reaction pressure stage 0 to the pressure stage (Jeli) and the Jal yal combined vapor flows enter 11 individual reaction pressure stages VY to a distillation column (£V VY ) rectifying column rectified 1 and the diol component on which Jia ta is recycled at the bottom of the Rectifying column to the first reaction pressure stage stage yo is at least » characterized by the fact that at least the last reaction pressure stage has a vacuum and the pressure in the rectifying column 1 (for LY) is greater than in the pressure stage reaction pressure with the latter; The vapors discharged from the last Va reaction pressure stage are condensed to the pressure in the taper column. Y. By distillation rectifying column 0 ?- the process according to claim 1; it is characterized by the formation of Yom into; Reaction pressure stages Y (VTLK 77) are connected in series.in series ava A = F 1 The process (Ey) for any of the claims 1 and 1 is characterized in that to produce a PET esterification product Y, it supplies the feed mixture A&W to stage 1 first reaction pressure Y ) first reaction pressure stage 0 to operate at a pressure of 1.1 to 0.0 bar, followed by a second reaction pressure stage J Tad 75 (VE) 5 at a pressure ranging from 4.0 to 1.0 bar and then a pressure stage 1 reaction (1) third reaction pressure stage AG ignites in a vacuum ranging from edd v 1;- process iy for any Of the protection elements 1 and oF, it is distinguished in that for the production of the PTT esterification product Y, it supplies the feed mixture to the Y stage, a first reaction pressure stage that operates at a pressure pressure ¢ ranges from 0.01 to 0.9 bar, followed by a second reaction pressure stage ° operating at pressures ranging from 0.5 to 0.0 bar —o 1 Operation Gy for any of the protection elements 1 and ?; it is characterized as producing a Y product transesterification product (PBT) as it supplies the starting materials ¥ to a reaction pressure stage (Y) reaction pressure stage J Ri 7 at a pressure ranging from 0.8 to 017 bar followed by a J 72d "0 ( ¢ ) second reaction pressure stage at a pressure ranging from 0 to A 1 bar . 01 +- Operation according to any of the protections 1 to 0 is characterized by 1 vapors discharged from the reaction pressure stage ¥ last (4; (V7) by means of a compressor ccompressor ©0100 blower and device "¢ .ventilator 1 "- Operation Gg for any of the protections 1 to ©; Characterized as ca TA vapors discharged from reaction pressure stage J 1 to last ( v Td by ANA A gas jet pump 6 : 06 (.—A 1 process according to claim 7; it is characterized by the use of vapors of the first reaction pressure stage Y (YY “Y) first reaction pressure stage as the operating fluid (Jade) for pump a Ala The gaseous Vv Se A) gas jet pump. \ 4- The process according to any of the protections from 1 to A is characterized by adjusting the pressure ¥ in the EY AY (rectifying column) by draining Gas ¥ residual gas exhaustion supplied behind A ) condenser “a = Call £4 ( ¢ placed at the head of rectifying column -0 1 Operation according to claim 4 is characterized as being discharged Residual gas “oY V) residual gas exhaustion Y ¢ °) by A Alay liquid jet pump 1 liquid ring pump or blower -11. / Operation GE For any of claims 1 to 10; oh esterification products Y or transesterification products are characterized by v being subjected to prepolycondensation and polycondensation. 4v4 \o aliquot & ja casa to 11; It is characterized as 1 for any of the protection elements from Gay process -1 \ to the first reaction pressure stage diol recirculated from recycled diol v Lal via La ( oq (YY ) line via line first reaction pressure stage and paste and used to prepare the dough (fe 9 1 ) $ v4