REMOVAL OF AL-SALTS, HCL, NACL AND ORGANIC BY-PRODUCT FROM STRONG ALKALINE DIOPAT SUSPENSION BY MEANS OF ALKALINE STABLE NANOFILTRATION FOLLOWED BY SEPARATION OF SALTS AND BYPRODUCTS AFTER NEUTRALIZATION OF DIOPAT SOLUTION BY MEANS OF ULTRAFILTRATION

Abstract

The present invention provides an improved process for isolating 2,4-bis-(2,4-dihydroxyphenyl)-6-(4-methoxyphenyl)-1,3,5-triazine (DIOPAT) from an aqueous alkaline mixture M having a pH of 10 or more and comprising the 2,4-bis-(2,4-dihydroxyphenyl)-6-(4-methoxyphenyl)-1,3,5-triazine, 2,4-dihydroxybenzophenone, and aluminum salts, wherein the process comprises a nanofiltration step, a precipitation step, and a further filtration step.

Claims

1.-15. (canceled)

16. A process for isolating 2,4-bis-(2,4-dihydroxyphenyl)-6-(4-methoxyphenyl)-1,3,5-triazine (DIOPAT) from an aqueous alkaline mixture M having a pH of 10 or more and comprising (i) the 2,4-bis-(2,4-dihydroxyphenyl)-6-(4-methoxyphenyl)-1,3,5-triazine; (ii) 2,4-dihydroxybenzophenone; (iii) aluminum salts; wherein the process comprises the steps of a) separating the 2,4-bis-(2,4-dihydroxyphenyl)-6-(4-methoxyphenyl)-1,3,5-triazine from the aluminum salts and the 2,4-dihydroxybenzophenone by nanofiltration of the alkaline mixture M, wherein the 2,4-bis-(2,4-dihydroxyphenyl)-6-(4-methoxyphenyl)-1,3,5-triazine is obtained in the form of an alkaline aqueous solution S as the retentate; b) precipitating the 2,4-bis-(2,4-dihydroxyphenyl)-6-(4-methoxyphenyl)-1,3,5-triazine by modifying the pH of the aqueous solution S to a value of 9.5 or lower; c) separating the precipitated 2,4-bis-(2,4-dihydroxyphenyl)-6-(4-methoxyphenyl)-1,3,5-triazine from the aqueous solution S by filtration, wherein the 2,4-bis-(2,4-dihydroxyphenyl)-6-(4-methoxyphenyl)-1,3,5-triazine is obtained in the form of an aqueous suspension SP as the retentate; wherein the nanofiltration step a) is performed at a pressure of from 10 to 30 bar and at a temperature in the range of from 20 to 60° C.

17. The process of claim 16, wherein the nanofiltration step a) is performed with a nanofiltration membrane having a sodium chloride retention rate of at least 60%.

18. The process of claim 16, wherein the nanofiltration step a) is performed with a polymer-based nanofiltration membrane.

19. The process of claim 18, wherein the polymer-based nanofiltration membrane has a pore size of 2 nm or lower.

20. The process of claim 16, wherein the nanofiltration step a) is performed in a protective gas atmosphere and/or under the exclusion of light.

21. The process of claim 16, wherein the nanofiltration step a) is performed at a pressure of from 15 to 25 bar, and at a temperature in the range of from 50 to 60° C.

22. The process of claim 16, wherein the nanofiltration step a) involves washing of the retentate with water.

23. The process of claim 22, wherein the amount of washing water is at least three times as high as the amount of the alkaline mixture M.

24. The process of claim 16, wherein in the precipitation step b) modifying the pH is performed with hydrogen chloride.

25. The process of claim 24, wherein the in the precipitation step b) modifying the pH is performed by diluting the aqueous solution S with water and then adding the diluted aqueous solution S to an aqueous hydrogen chloride solution.

26. The process of claim 16, wherein the precipitation step b) is performed by modifying the pH of the aqueous solution S to a value of 8 or lower.

27. The process of claim 16, wherein the filtration step c) is performed with a membrane having a pore size in the range of from 20 to 500 nm.

28. The process of claim 16, wherein the filtration step c) is performed with a ceramic membrane, which is a TiO.sub.2, ZrO.sub.2, or Al.sub.2O.sub.3 membrane.

29. The process of claim 28, wherein the ceramic membrane is an α-Al.sub.2O.sub.3 membrane.

30. The process of claim 16, wherein the filtration step c) is performed at a pressure of from 1 to 6 bar, and at a temperature in the range of from 20 to 95° C.

31. The process of claim 16, wherein the filtration step c) involves washing of the retentate with water.

32. The process of claim 31, wherein the amount of washing water is at least two times as high as the amount of the aqueous solution S.

33. The process of claim 16, wherein the filtration step c) provides the aqueous suspension SP with a dry content of 2,4-bis-(2,4-dihydroxyphenyl)-6-(4-methoxyphenyl)-1,3,5-triazine in the range of from 2 to 10% by weight based on the total weight of the aqueous suspension SP.

34. The process of claim 16, wherein the process further comprises the step of d) concentrating the aqueous suspension SP obtained in step c) by filtration.

35. The process of claim 34, wherein the process further comprises the step of e) drying the concentrate obtained in step d).

Description

EXAMPLE

[0096] Sampling: The sampling and the analysis were the same independent from the process step. After each step, samples of permeate and retentate were taken for:

[0097] Dry content (DC) and NaCl content

[0098] Al content

[0099] Total Organic Carbon (TOC, only permeates)

[0100] DIOPAT content and content of side products (AHRT, 2,4-DHBP, DMPRT)

[0101] DC was measured with DC scales, NaCl was measured by titration, TOC was measured with a TOC analyzer. DIOPAT and side products were determined via HPLC using

[0102] Agilent 1100

[0103] column material: EUROSPH ER 100-C18/5 Knauer

[0104] column length: 25 cm, column diameter: 4 mm

[0105] column temperature: 20° C.

[0106] injection volume: 5 μl

[0107] mobile phase: eluent A: 900 Deionat (2)+100 acetate buffer pH 4.65 (3)+0.2% TBAHS, eluent B: acetonitrile (1)+0.2% TBAHS

[0108] method: flow: 1.0 mL/min, pressure: max. 400 bar, stop time: 30 min

[0109] timetable:

TABLE-US-00001 Time % A % B  5 min 50%   50% 25 min 0% 100% 30 min 0% 100%

[0110] According to the present invention, the Al-salts as well as undesired organic by-products are separated from the DIOPAT by a process comprising a nanofiltration step, a precipitation step, and a further filtration step. Further details in this regard are provided hereinafter.

[0111] An alkaline mixture having a pH in the range of from 12.5 to 13.0 comprising 76 g/L DIOPAT, 6.6 g/L 2,4-DHBP, 121 g/L NaCl, 13.4 g/L Al-salts, 1.1 g/L resorcin, 4.8 g/L benzoic acid, and 77% by weight water was used in the process.

[0112] Nanofiltration:

[0113] The glass parts of the nanofiltration apparatus were covered with aluminum foil, in order to exclude UV light. The feed container was constantly flooded with nitrogen in order to remove oxygen.

[0114] 1 part by volume of the alkaline mixture was diluted with 0.3 parts by volume water and heated to 50° C. in the nanofiltration apparatus. In the first nanofiltration step, the volume of the solution in the retentate is reduced from 1.3 volume parts to 1.0 volume parts. Then, 2 parts by volume of water are added, and the solution is again reduced to 0.7 volume parts by diafiltration. Then, the 0.7 volume parts of the solution are combined with 1.5 parts by volume of water and subjected to diafiltration. [0115] Membrane: Polyether sulfone membrane NTR7470 available from Nitto Denko (2.5 inch spiral wound module with 46 mil spacer) [0116] Operating parameters: [0117] Temperature: 50° C. [0118] Cross flow: to reach DP of around 0.7 bars along the module (about 1.6 m.sup.3/h) [0119] Feed pressure: 30 bars

[0120] Result:

[0121] The density of the solution was reduced from 1.188 g/mL to 1.058 g/mL.

[0122] The ratio of NaCl to DC (dry content) was reduced from 35.4 to 0.1% by weight, i.e. reduction of about 98%.

[0123] The ratio of DIOPAT to DC was increased from 27.9 to 72.7% by weight.

[0124] The Al content in the solution was reduced from 10500 ppm to 660 ppm.

[0125] The 2,4-DHBP content in the solution was reduced by about 50%.

[0126] Neutralization:

[0127] 0.9 parts by volume water and 0.02 parts by volume hydrochloric acid (32% in water) were provided in a mixing tumbler reactor and heated to 60° C. Then, 1 part by volume of the NF concentrate was slowly added within 30 minutes, so that a pH of about 7 was established. The resulting product suspension was then subjected to ultrafiltration.

[0128] Ultrafiltration:

[0129] 1 part by volume of the neutralized product suspension was diluted with 3 parts by volume of water, then diafiltrated, and concentrated to 0.8 parts by volume.

[0130] Membrane:

[0131] Channel element: 6 mm channel, 1 m long

[0132] Membrane material: α-Al.sub.2O.sub.3

[0133] Nominal pore size: 50 nm with 400/200/50 membrane layers

[0134] Operating parameters:

[0135] Temperature: 88° C.

[0136] Cross flow: 3 m/s

[0137] Feed pressure: 2.5 bars

[0138] Process parameters:

[0139] Dilution factor of the start suspension only dead volume of the pump

[0140] Total concentration factor (CF) 1.2

[0141] Total diafiltration factor 3

[0142] Results:

[0143] The ratio of NaCl to DC was reduced from 22 to 1.1% by weight. The NaCl concentration was reduced from 1.4% by weight to 0.08% by weight.

[0144] The ratio of DIOPAT/DC was increased from 68 to 87% by weight.

[0145] The 2,4-DHBP content was reduced by about 50%.