WO2014102306A2

WO2014102306A2 - Method for purifying a recycling flow from a plant for producing polyarylene ether sulfones

Info

Publication number: WO2014102306A2
Application number: PCT/EP2013/078025
Authority: WO
Inventors: Jörg Erbes; Cornelis Hendricus DE RUITER; Christoph Sigwart; Gerhard Lange; Jutta VONEND
Original assignee: Basf Se
Priority date: 2012-12-28
Filing date: 2013-12-27
Publication date: 2014-07-03
Also published as: WO2014102306A3

Abstract

The invention relates to a method for purifying a recycling flow (1) from a plant for producing polyarylene ether sulfones by polycondensing aromatic bis-halogen compounds and aromatic bisphenols or salts thereof in the presence of at least one alkali-metal carbonate or hydrogencarbonate or ammonium carbonate or hydrogencarbonate in an N-alkyl-2-pyrrolidone as a solvent, containing 60 to 90 wt% of water, 10 to 40 wt% of N-alkyl-2-pyrrolidone, and, as a specification-impairing contaminant, up to 5000 ppm by weight of the alkyl succinimide corresponding to the N-alkyl-2-pyrrolidone and in addition thereto up to 1000 ppm by weight of additional high boilers in relation to N-alkyl-2-pyrrolidone, in particular inorganic salts, in each case with respect to the total weight of the recycling flow (1), the sum of the components equaling 100 wt%, so as to obtain a pure N-alkyl-2-pyrrolidone flow (2), which can be fed back into the plant for producing polyarylene ether sulfones, by means of purification by distillation in a purification column (K), the method being characterized in that a pre-purification by evaporation in one or more evaporator stages in order to reduce the content of inorganic salts is performed before the purification by distillation, one or more vapor flows (3, 4, 5) being obtained, which are fed to the purification column (K) as feed flows, and the bottom flow from the last evaporator stage being discharged and the bottom flow from the purification column (K) being completely recycled into the last evaporator stage.

Description

Process for the purification of a recycle stream from a plant for the production of polyarylene ether sulfones

The invention relates to a process for the purification of a recycle stream from a plant for the production of polyarylene ether sulfones by polycondensation of aromatic bishalogen compounds and aromatic bisphenols or their salts in the presence of at least one alkali metal or ammonium carbonate or bicarbonate in an N-alkyl-2-pyrrolidone Solvent. Polyarylene ether sulfones are known under the trade name Ultrason ^® of BASF SE, and in particular include polyethersulfones (Ultrason ^® E), polysulfones (Ultrason ^® S) and polyphenylsulfones (Ultrason ^® P).

Ultrason ^® E, Ultrason ^® S and Ultrason ^® P are transparent, high temperature resistant plastics. They are used in many applications in apparatus construction and in the electrical / electronics sector. There are also numerous reasons for use in the food and household sector as glass, metal, ceramic and porcelain substitute: temperature resistance up to 180 ° C or briefly at 220 ° C, good mechanical properties and high resistance to breakage, resistance to superheated steam and a excellent resistance to chemicals.

Ultrason ^® E, S and P are amorphous thermoplastic polymers with the following basic structure:

Ultrason "E

Ultrason * S

Ultrasound * P

Ultrason ^® molded parts are strong, stiff and tough, with high dimensional stability, close to the glass transition temperature.

The most important features of Ultrason ^® are:

temperature-independent properties

very high continuous service temperatures

good dimensional stability

- high rigidity

high mechanical strength

good electrical insulation

favorable dielectric properties

very favorable fire behavior

- extraordinary hydrolysis resistance

As amorphous thermoplastics, the three Ultrason ^® base polymers are transparent. However, due to the high temperatures required in their manufacture and processing, they have a certain inherent color (light golden yellow to ocher), which prevents the theoretically possible transmission values for visible light being achieved. Nevertheless, the qualities available today are suitable for a large number of transparent applications. Ultrason ^® also has high refractive indexes in the visible wavelength range, making it useful in functional optical applications such as lenses for electronic cameras.

Polyarylene ether sulfones are often prepared by polycondensation in the presence of an N-alkyl-2-pyrrolidone, hereinafter referred to as NAP, as a polar aprotic solvent. As N-alkyl-2-pyrrolidones in particular N-methyl or N-ethyl-pyrrolidone, preferably N-methyl-pyrrolidone, are used. Such methods are known, for example, from US Pat. No. 4,870,153, EP-A 1 13 1 12, EP-A 297 363 and EP-A 135 130.

The above process produces contaminated solvent which must be worked up for economic and environmental reasons and recycled in the process. However, the solvent used in the above process must meet the criteria for a so-called pure NAP, that is, a content of at least 99.0 wt .-% NAP or at least 99.5 wt .-% NAP, or at least 99.8 wt .-% NAP, each based on the total weight of the pure NAP flow, and having as specification-damaging components a maximum of 0.1 wt .-% water and a maximum of 0.01 wt .-% N-alkylsuccinimide, hereinafter abbreviated to NAS, in each case based on the total weight of the pure NAP stream.

Higher contents of NAS in the solvent NAP have an adverse effect on the color of the polyarylene ether sulfone product of value. This is surprising since both NAP itself and NAS, which can be formed by oxidation of NAP with atmospheric oxygen, for example, are colorless substances. For the reasons stated, however, polyarylethersulfones with the lowest possible intrinsic color are in demand on the market. According to previous findings, the polyarylene ether sulfone preparation with NAP as the solvent has a causal relationship between the NAP formed by oxidation of the NAP, for example the N-methyl succinimide (NMS) formed by oxidation of the N-methylpyrrolidone (NMP):

ICJ

and the undesirable inherent color of the final polyarylene ether sulfone product.

It is believed that NAS is a precursor to higher molecular weight colorants that degrade the inherent color of the final polyarylene ether sulfone product.

NAP-containing recycle streams are therefore purified before recycling in the production of polyarylene ether sulfone by purifying in a classical distillation column so far that a pure NAP is obtained, which corresponds to the criteria defined above.

CN 2007 100 39497 discloses a process for recovering NMP as a solvent from polycondensation to para-phenylene terephthalamide, after which the polymer is washed with deionized water, the wash solution is neutralized with an alkali or alkaline earth metal carbonate, oxide or hydroxide , in two Thin-film evaporators, under a pressure of 0.1 to 3.0 bar absolute and a temperature of 90 to 120 ° C a crude distillation and then subjected to a pure distillation, to obtain a pure NMP stream with a purity of greater than 99.5% and a water content of less than 100 ppm, which is suitable for recycling to the plant for polycondensation for the preparation of polymerizable para-phenylene terephthalamides.

In conventional operation, without pre-evaporation, the heat exchanger for the bottom stream of the distillation column for pure NAP sets after a short time by impurities, so that the system must be turned off at short intervals in order to clean the same.

It was accordingly an object of the invention to provide a process for the treatment of recycle streams of polyarylene ether sulfone process by distillation to pure NAP, which is recyclable in the plant for performing polyarylene ether sulfone process, which ensures an increased service life of the distillation column and the moreover, it requires the least possible expenditure on apparatus and energy, and the losses of NAP are as low as possible.

The object is achieved by a process for purifying a recycle stream from a plant for producing polyarylene ether sulfones by polycondensation of aromatic bishalogen compounds and aromatic bisphenols or salts thereof in the presence of at least one alkali metal or ammonium carbonate or bicarbonate in an N-alkyl-2-one. pyrrolidone as solvent containing

From 60 to 90% by weight of water,

From 10 to 40% by weight of N-alkyl-2-pyrrolidone and, as a specification-damaging impurity, up to 5000 ppm by weight of the alkyl succinimide corresponding to N-alkyl-2-pyrrolidone and, in addition, up to 1000 ppm by weight of further high-boiling components N-alkyl-2-pyrrolidone, in particular inorganic salts, in each case based on the total weight of the recycle stream, wherein the sum of the components gives 100 wt .-%, to obtain a pure N-alkyl-2-pyrrolidone stream, the in the plant for the production of polyarylene ether, traceable by pure distillation in a pure column, which is characterized in that the purifying distillation is preceded by a pre-cleaning by evaporation in one or more evaporator stages to reduce the content of inorganic salts, wherein an or a plurality of vapor streams are obtained, which are fed as feed streams of the pure column, and wherein the bottom stream discharged from the last evaporator stage and the bottom stream from the pure column is completely recycled into the last evaporator stage.

It has been found that it is possible to work up recycle streams from the production of polyarylene ether sulfones in an apparatusically and energetically favorable manner to pure NMP, by precleaning by evaporation in a classical distillation column precleaning by evaporation in which the content in one or more evaporator stages is reduced in salts in the recycle stream.

The recycle stream preferably contains from 70 to 85% by weight of water, from 25 to 30% by weight of N-alkyl-2-pyrrolidone and, as a specimen-harmful impurity, up to 1000 ppm by weight of N-alkyl-2-pyrrolidone Alkyl succinimides and in addition up to 300 ppm by weight of further high boilers to N-methyl-pyrrolidone, in particular inorganic salts, each based on the total weight of the recycle stream, wherein the sum of the components 100 wt .-% results. Preferred is a process wherein the N-alkyl-2-pyrrolidone is N-methyl-pyrrolidone and the corresponding succinimide is N-methyl-succinimide.

For the evaporation, preferably two, more preferably three evaporator stages are provided.

The first evaporator stage is preferably operated at a pressure in the vapor space in the range of 250 mbar absolute to atmospheric pressure, such that the vapor fraction from the first evaporator stage, which is fed as a feed stream to the pure column, the predominant proportion, in particular from 70 to 90%, of the water contained in the recycle stream is withdrawn.

More preferably, the first evaporator stage is operated at a pressure in the vapor space in the range of 300 to 800 mbar absolute. The second evaporator stage is preferably operated at a pressure in the vapor space in the range of 250 to 500 mbar absolute, such that the predominant fraction, in particular from 90 to 95%, is supplied via the vapor stream from the second evaporator stage, which is fed as feed stream to the pure column. of the recycle stream N-alkyl-2-pyrrolidone, especially of N-methyl-pyrrolidone, is taken off.

Advantageously, the second evaporator stage is operated at a pressure in the vapor space in the range of 300 to 400 mbar absolute.

In a preferred embodiment, a third evaporator stage is provided. The third evaporator stage is operated in particular at a pressure in the vapor space in the range of 100 to 400 mbar absolute.

Advantageously, the third evaporator stage is operated at a pressure in the vapor space in the range of 100 to 200 mbar absolute.

It is particularly preferred to use a thin-film evaporator as evaporator in the third evaporator stage. This is less prone to incrustations by deposits.

Advantageously, the vapor stream from the second evaporator stage of the pure column above the vapor stream from the third evaporator stage and the vapor stream from the first evaporator stage of the pure column are fed above the vapor stream from the second evaporator stage.

Preferably, the bottom stream from the pure column is completely recycled to the inlet of the third evaporator stage.

The pure column is preferably designed with 15 to 35, preferably 20 to 30 theoretical plates.

The pure column is preferably operated at a top pressure at which still can be cooled with river water at the top of the column, in particular at a top pressure in the range of 150 to 250 mbar absolute, more preferably at about 200 mbar absolute. The bottom temperature in the pure column is preferably set to about 160 to 170 ° C, so that the bottom stream still contains about 0.5 to 10 wt .-% NMS, in particular still about 1 to 5 wt .-% NMS.

The invention is explained in more detail below with reference to a drawing and an embodiment: The sole FIGURE 1 shows the schematic representation of a preferred system for carrying out the method.

An NMP-containing recycle stream 1 is fed to the first evaporator stage V1, from which a vapor stream 3 containing predominantly water is withdrawn and fed to the pure column K as feed stream. The bottom stream from the first evaporator stage V1 is fed to the second evaporator stage V2; From this, another vapor stream 4 is withdrawn and fed to the pure column K as a further feed stream.

The bottom stream from the second evaporator stage V2 is fed to the third evaporator stage V3. From this, another vapor stream 5 is withdrawn, condensed and fed to the pure column K as a liquid feed stream. From the third evaporator stage V3, a salty bottom stream 6 is discharged. From the pure column K, a pure NMP stream 2 from the stripping section thereof, preferably gaseous, withdrawn as side stream, a bottom stream 7, which is recycled to the third evaporator stage V3, and a top stream 8, which contains predominantly water and is disposed of.

Embodiment:

For a plant corresponding to the schematic illustration in FIG. 1, the Aspen® simulation program from Aspen Technology Inc. simulated a process for processing a recycle stream 1, the values for the composition of the streams shown in the following table being obtained.

The following operating conditions were assumed: For the evaporation of the first evaporator stage V1 a pressure of 350 mbar absolute and a temperature of 80 ° C, for the second evaporator stage V2 a pressure of also 350 mbar absolute and a temperature of 128 ° C, for the third evaporator stage V3 a pressure of 150 mbar absolute and a temperature of 137 ° C, and for the pure column K 23 theoretical plates a head pressure of 197 mbar absolute and a temperature at the top of 60 ° C, and a pressure of 337 mbar absolute and a Temperature of 163 ° C in the swamp. As can be seen from the table, the NMP loss over the overall process is 1.35% (based on the NMP introduced into the process via the recycle stream 1).

The NMS content in the pure NMP stream is 92 ppm by weight.

Pure NMP stream sump stream 6

Recycle2 (side draw) top stream 8 from the third stream 1 from the pure column K evaporator stage

Pure column K V3 kg / h% kg / h% kg / h% kg / h%

H ₂ 0 742.2 74.2 0.01 0.0 742.16 100 0.00 0.1

KCl 0.0 0.0 0.00 0.0 0.00 0.0 0.01 0.3

NMP 257.5 25.8 254.14 100.0 0.00 0.0 3.48 97.5

NMS 0.1 0.0 0.03 0.0 0.00 0.0 0.07 2.1

Total 1000.0 100.0 254.18 100.0 742.16 100.0 3.57 100.0

NMP-1, 35%

loss

Claims

claims

1 . Process for the purification of a recycle stream (1) from a plant for the preparation of polyarylene ether sulfones by polycondensation of aromatic bishalogen compounds and aromatic bisphenols or their salts in the presence of at least one alkali metal or ammonium carbonate or bicarbonate in an N-alkyl-2-pyrrolidone solvent containing - 60 to 90% by weight of water,

From 10 to 40% by weight of N-alkyl-2-pyrrolidone and, as a specification-damaging impurity, up to 5000 ppm by weight of the alkyl succinimide corresponding to N-alkyl-2-pyrrolidone and, in addition, up to 1000 ppm by weight of further high-boiling components N-alkyl-2-pyrrolidone, in particular inorganic salts, in each case based on the total weight of the recycle stream (1), the sum of the components resulting in 100% by weight, giving a pure N-alkyl-2-pyrrolidone Stream (2), which is traceable to the plant for the preparation of polyarylene ether sulfones, by purifying in a pure column (K), characterized in that the purifying distillation is preceded by a pre-cleaning by evaporation in one or more evaporator stages to reduce the content of inorganic salts, wherein one or more vapor streams (3, 4, 5) are obtained, which are fed as feed streams of the pure column (K), and wherein the bottom stream discharged from the last evaporator stage and the Sumpfstr om from the pure column (K) is completely recycled to the last stage of the evaporator.

2. The method according to claim 1, characterized in that the recycle stream (1) - 70 to 85 wt .-% water,

- 25 to 30 wt .-% N-alkyl-2-pyrrolidone and as spezifikationsschädliche

Contamination up to 1000 ppm by weight of the alkyl succinimide corresponding to the N-alkyl-2-pyrrolidone and, in addition, up to 300 ppm by weight of further high boilers relative to N-methylpyrrolidone, in particular inorganic salts, in each case based on the total weight of the recycle Streams (1), the sum of the components being 100% by weight,

contains.

3. The method according to any one of claims 1 or 2, characterized in that the N-alkyl-2-pyrrolidone N-ethyl-pyrrolidone or N-methyl-pyrrolidone, preferably N-methyl-pyrrolidone, is.

4. The method according to any one of claims 1 to 3, characterized in that two or three, preferably three evaporator stages (V1, V2, V3) are provided.

5. The method according to claim 4, characterized in that the first evaporator stage (V1) is operated at a pressure in the vapor space in the range of 250 mbar absolute to atmospheric pressure, such that on the vapor stream (3) from the first evaporator stage (V1), which is fed as feed stream to the clean column (K), the predominant fraction, in particular from 70 to 90%, of the water contained in the recycle stream (1) is withdrawn.

6. The method according to claim 5, characterized in that the first evaporator stage (V1) is operated at a pressure in the vapor space in the range of 300 to 800 mbar absolute.

7. The method according to any one of claims 4 to 6, characterized in that the second evaporator stage (V2) is operated at a pressure in the vapor space in the range of 250 to 500 mbar absolute, such that on the vapor stream (4) from the second evaporator stage (V2), which is fed as feed stream to the pure column (K), the predominant portion, from 90 to 95%, of the recycle stream (1) contained N-alkyl-2-pyrrolidone, especially N-methylpyrrolidone is withdrawn.

8. The method according to claim 7, characterized in that the second evaporator stage (V2) is operated at a pressure in the vapor space in the range of 300 to 400 mbar absolute.

9. The method according to any one of claims 1 to 8, characterized in that the third evaporator stage (V3) is operated at a pressure in the vapor space in the range of 100 to 400 mbar absolute.

10. The method according to claim 9, characterized in that the third evaporator stage (V3) is operated at a pressure in the vapor space in the range of 100 to 200 mbar absolute.

1 1. Method according to one of claims 1 to 10, characterized in that in the third evaporator stage (V3) as evaporator, a thin-film evaporator is used.

12. The method according to any one of claims 1 to 1 1, characterized in that the vapor stream (4) from the second evaporator stage (V2) of the pure column (K) above the vapor stream (5) from the third evaporator stage (V3) and the vapor stream ( 3) from the first evaporator stage (V1) of the pure column (K) above the vapor stream (4) from the second evaporator stage (V2) is supplied.

13. The method according to claim 12, characterized in that the bottom stream (7) from the pure column (K) is completely recycled to the inlet of the third evaporator stage (V3).