WO2014102308A2

WO2014102308A2 - Method for purifying a recycle stream from a system for producing polyarylene ether sulfones

Info

Publication number: WO2014102308A2
Application number: PCT/EP2013/078027
Authority: WO
Inventors: Christoph Sigwart; Jutta VONEND; Cornelis Hendricus DE RUITER; Annette KREINER; Jörg Erbes; Tobias Kortekamp
Original assignee: Basf Se
Priority date: 2012-12-28
Filing date: 2013-12-27
Publication date: 2014-07-03
Also published as: WO2014102308A3

Abstract

Porposed is a method for purifying a recycle stream (1) from a system for producing polyarylene ether sulfones by the polycondensation of aromatic bis-halogen compounds and aromatic bisphenols or salts thereof in the presence of at least one alkali metal- or ammonium carbonate or -hydrogen carbonate in an N-alkyl-2-pyrrolidone as a solvent, containing - 60 to 90% by weight water, -10 to 40% by weight N-alkyl-2-pyrrolidone and, as a specification-detrimental impurity, up to 5000 ppm by weight of the alkyl succinimide corresponding to the N-alkyl-2-pyrrolidone and, in addition, up to 1000 ppm by weight additional high boilers relative to N-alkyl-2-pyrrolidone, in particular inorganic salts, each relative to the total weight of the recycle stream (1), the sum of the components being 100% by weight, to obtain a purified N-alkyl-2-pyrrolidone stream (2) that can be fed back into the system for producing polyarylene ether sulfones by purification by distillation in a purification column (K) which is characterized in that a prepurification step by evaporation in one or more evaporator stages is provided upstream of the purification by distillation in order to reduce the content of inorganic salts, wherein one or more vapor streams (3, 4, 5) are obtained which are fed to the purification column (K) as feed streams, and wherein the bottom stream is discharged from the last evaporator stage and the bottom stream from the purification column (K) is partially or entirely fed to an additional column (ZK) and is divided therein into a bottom stream (11) that is discharged and a top stream (12) that is recycled into the purification column (K).

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

Ultrason ^® 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 processes are known, for example, from US Pat. No. 4,870,153, EP-A 113,112, 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):

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.

From CN 2007 100 39497 a process for the recovery of NMP as a solvent from the polycondensation to para-phenylene terephthalamide is known, after which the polymer washed with deionized water, the washing solution with an alkali or alkaline earth metal carbonate, oxide or hydroxide neutralized, in two thin-layer 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 a Pure distillation is to obtain a pure NMP stream having a purity 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 is.

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. In particular, the residence time in the bottom of the pure column should be reduced in order to minimize side reactions and at the same time to reduce the losses of NAP via the discharge.

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 - 60 to 90% by weight of water,

- From 10 to 40 wt .-% N-alkyl-2-pyrrolidone and as a specification harmful impurity up to 5000 ppm by weight of the N-alkyl-2-pyrrolidone corresponding Alkylsuccinimids and next up to 1000 ppm by weight further high boilers to N Alkyl-2-pyrrolidone, in particular inorganic salts, each based on the total weight of the recycle stream, wherein the sum of the components 100 wt .-% results to give a pure N-alkyl-2-pyrrolidone stream, the the plant for the production of Polyarylenethersulfonen is traceable by pure distillation in one 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 one or more vapor streams are obtained, which are fed as feed streams of the pure column, and wherein the bottom stream the last evaporator stage discharged and the bottom stream from the pure column partially or completely fed to an additional column and is separated into a bottom stream, which is discharged, and a top stream, which is recycled into the clean column. It has been found that it is possible to work up recycle streams from the production of polyarylene ether sulfones in an apparatus-effective and energetically favorable manner to pure NAP by precleaning by evaporation in a classical distillation column a pre-purification by evaporation, in which the content in one or more evaporator stages is reduced in salts in the recycle stream and by the loss of NAP is minimized by the bottom stream from the pure column is further worked up in an additional column.

Preferably, the additional column is operated at a lower pressure compared to the pure column.

The additional column preferably has from five to ten theoretical plates.

The additional column is preferably operated in such a form that the bottom stream from the same still contains 5 to 30% NAS, preferably 10 to 20% NAS, in each case based on the total weight of the bottom stream.

The bottom stream from the pure column is preferably fed completely to the additional column. The top stream from the additional column is preferably recycled to the pure column, in particular below the withdrawal of the pure NAP stream.

Particularly preferably, the bottom stream from the additional column is fed to another use or disposed of properly.

The recycle stream preferably contains 70 to 85% by weight of water,

25 to 30 wt .-% of N-alkylpyrrolidone and as a specification harmful impurity up to 1000 ppm by weight of the corresponding N-alkylsuccinimide and also up to 300 ppm by weight of further high boilers towards N-alkylpyrrolidone, in particular inorganic salts, each based on the total weight of the recycle stream, wherein the sum of the components 100 wt .-% results

The N-alkyl-2-pyrrolidone is in particular N-ethylpyrrolidone or N-methylpyrrolidone, preferably N-methylpyrrolidone.

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 majority of the vapor from the first evaporator stage, which is fed as a feed stream of the pure column, from 70 to 90% of the withdrawn in the recycle stream contained water.

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 majority of the vapor from the second evaporator stage, which is fed as a feed stream of the pure column, from 90 to 95% of withdrawn in the recycle stream N-methylpyrrolidone is withdrawn. Advantageously, the second evaporator stage is operated at a pressure in the vapor space in the range of 300 to 400 mbar absolute.

The third evaporator stage is preferably operated 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 fed to the first evaporator stage of the pure column above the vapor stream from the second evaporator stage.

The pure column is preferably designed with 15 to 35, in particular with 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 about 0.5 to 10 wt .-% NAS, especially about 1, 0 to 5 wt .-% NAS contains.

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 of the same, preferably gaseous, withdrawn as a side stream, a bottom stream 7, and a top stream 8, which mainly contains water and is disposed of.

The bottom stream from the clean column K is fed to an additional column ZK and separated therein into a bottom stream 1 1, which is discharged, and a top stream 12, which is recycled into the clean column K. Embodiment:

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

The following distillation conditions were assumed: for the evaporation in the first evaporator stage V1 a pressure of 350 mbar absolute and a temperature of 88 ° C, for the second evaporator stage V2 a pressure of also 350 mbar absolute and a temperature of 145 ° C, for the third evaporator stage V3 a pressure of 150 mbar absolute and a temperature of 146 ° C, for the pure column K a head pressure of 205 mbar absolute and a temperature at the top of 61 ° C, and a pressure of 350 mbar absolute and a temperature of 165 ° C in the bottom, and for the additional column ZK a top pressure of 150 mbar absolute and a temperature at the top of the additional column ZK of 138 ° C, and a pressure of 160 mbar absolute and a temperature of 144 ° C in the bottom of the additional column ZK. The top stream 12 from the additional column ZK is recycled into the bottom of the clean column K.

As can be seen from the table, the NMP loss over the total process is 0.99% (based on the introduced via the recycle stream 1 in the process NMP). The NMS content in the pure NMP stream is 67 ppm by weight.

Pure NMP power

Top stream 8 from bottom stream 6 discharge stream 1 1 2 (side take-off)

Recycle stream 1 of the pure from the third from the swamp of the

column K Evaporator stage V3 Additional column ZK Reinkolonne K

kg / h% kg / h% kg / h% kg / h% kg / h%

H ₂ 0 719.5 71, 9 0.0 0.0 719.5 100 0.0 0.0 0.0 0.0

KCl 0.6 0, 1 0.0 0.0 0.0 0.0 0.6 22.5 0.0 0.0

NMP 279.8 28.0 277.0 100.0 0.0 0.0 2, 1 77.2 0.7 90.0

NMS 0, 100 0.01 0.019 0.0067 0.0 0.0 0.006 0.2350 0.075 10.0

Total 1000 100.0 277, 1 100.0 719.5 100.0 2.7 100.0 0.8 100

NMP 0.99%

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 compared to N-alkyl-2-pyrrolidone. 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 being 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 upstream of a pre-cleaning by evaporation in one or more evaporator stages for reducing 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 Sump stream discharged from the last evaporator stage and the bottom stream from the pure column (K) partially or completely fed to an additional column (ZK) and it is separated into a bottom stream (1 1), which is discharged, and a top stream (12) in the Pure column (K) is recycled.

2. The method according to claim 1, characterized in that the additional column (ZK) is operated at a lower pressure compared to the pure column (K).

3. The method according to claim 1 or 2, characterized in that the bottom stream (1 1) from the additional column (ZK) fed to another use or is burned.

4. The method according to any one of claims 1 to 3, characterized in that the recycle stream (1) From 70 to 85% by weight of water,

25 to 30% by weight of N-alkyl-2-pyrrolidone and, as a specification-damaging impurity, up to 1000 ppm by weight of the alkyl succinimide corresponding to N-alkyl-2-pyrrolidone and, in addition, up to 300 ppm by weight of further high-boiling components compared to N-alkyl-2-pyrrolidone. Methyl pyrrolidone, especially inorganic

Salts, each based on the total weight of the recycle stream (1), wherein the sum of the components gives 100 wt .-%.

5. The method according to any one of claims 1 to 4, characterized in that the N-alkyl-2-pyrrolidone N-ethyl-pyrrolidone or N-methyl-pyrrolidone, preferably N-

Methylpyrrolidone, is.

6. The method according to any one of claims 1 to 5, characterized in that two or three, preferably three evaporator stages (V1, V2, V3) are provided.

7. The method according to claim 6, 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 pure column (K), the predominant fraction, from 70 to 90%, of the water contained in the recycle stream (1) is withdrawn.

8. The method according to claim 7, 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.

9. The method according to any one of claims 6 to 8, 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 fraction, from 90 to 95%, of the recycle stream (1) contained N-methylpyrrolidone is withdrawn.

10. The method according to claim 9, 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.

1 1. Method according to one of claims 6 to 10, 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.

12. The method according to claim 1 1, 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.

13. The method according to any one of claims 6 to 12, characterized in that in the third evaporator stage (V3) as evaporator, a thin-film evaporator is used.

14. The method according to any one of claims 6 to 13, 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.

15. The method according to any one of claims 1 to 14, characterized in that the additional column (ZK) has five to ten theoretical plates.

16. The method according to any one of claims 1 to 15, characterized in that the bottom stream from the pure column (K) is completely supplied to the additional column (ZK).