PROCESS FOR MAKING A SOLID ALKALI METAL SALT OF AN AMINOCARBOXYLATE COMPLEXING AGENT

Abstract

Process for making a solid alkali metal salt (A) of an aminocarboxylate complexing agent, said process comprising the steps of (a) providing a 40 to 80% by weight aqueous solution or slurry comprising salt (A), (b) optionally, heating said slurry or solution to a temperature in the range of from 50 to 150? C., (c) introducing the slurry or solution from step (a) or, if applicable, step (b) into an essentially horizontal cylindrical drying apparatus containing a stirring element that rotates around an essentially horizontal axis and that is charged with solid particles of salt (A), and (d) removing most of the water by evaporation, (e) removing solid salt (A) as granule.

Claims

1. A process for making a solid alkali metal salt (A) of an aminocarboxylate complexing agent, said process comprising the steps of (a) providing a 40 to 80% by weight aqueous solution or slurry comprising a salt (A), (b) optionally, heating said slurry or solution to a temperature in the range of from 50 to 150? C., (c) introducing the slurry or solution from step (a) or, if applicable, step (b) into an essentially horizontal cylindrical drying apparatus comprising a stirring element that rotates around an essentially horizontal axis and that is charged with solid particles of salt (A), wherein the pressure in the cylindrical drying apparatus is in the range from 100 to 600 mbar abs, (d) removing most of the water by evaporation, and (e) removing solid salt (A) as granule.

2. The process according to claim 1, wherein the drying apparatus comprises heating elements at the wall.

3. The process according to claim 1, wherein said aminocarboxylate complexing agent is selected from methylglycine diacetic acid (MGDA) or glutamic acid diacetic acid (GLDA).

4. The process according to claim 1, wherein salt (A) is selected from compounds according to general formula (I)
[CH.sub.3CH(COO)N(CH.sub.2COO).sub.2]M.sub.3-xH.sub.x(I) wherein M is selected from alkali metal cations, same or different, and x in formula is in the range of from zero to 1.0.

5. The process according to claim 1, wherein methylglycine diacetate (MGDA) alkali metal salt (A) is selected from a racemic mixture or mixtures of enantiomers with predominantly the L-enantiomer with an ee value in the range of from 0.1 to 35%.

6. The process according to claim 1, wherein salt (A) removed in step (e) has a moisture content in the range of from 1 to 20% by weight.

7. The process according to claim 1, wherein the solution or slurry provided in step (a) comprises at least one (co)polymer (B) selected from (co)polymers of (meth)acrylic acid and polyethylenimines, non-substituted or substituted with alkoxy groups or CH.sub.2COOH groups that may be neutralized with alkali metal.

8. The process according to claim 1, wherein a sieving step is performed subsequently to step (e).

9. The process according to claim 1, wherein the cylindrical drying apparatus is a continuous fluidization technology dryer.

10. The process according to claim 1, wherein the rotation speed of the stirring element is in the range of from 10 to 300 revolutions per minute.

11. (canceled)

12. (canceled)

13. (canceled)

14. (canceled)

Description

EXAMPLE

I Manufacture of Inventive GranulesGranule Gr. 1

I.1 Manufacture of Solution SL. 1

[0098] Step (a.1): A vessel was charged with 6 kg of an aqueous solution of (A.1) (40% by weight), SL.1.

[0099] Step (b.1): The solution SL. 1 was stirred and heated to 70? C. and then subjected to granulation.

I.2 Granulation of Solution SL. 1

[0100] Step (c.1): Apparatus 1 was charged with 1.5 l of granule MGDA-Na.sub.3, average diameter (D50) 700 ?m (about 1.1 kg), as bed. The granule was stirred with 240 rpm. The walls of Apparatus 1 were heated to a temperature of 140? C. The pressure was adjusted to 300 mbar, abs.

[0101] Step (d.1): A feed of 500 g/hour of SL.1 was introduced into Apparatus and the majority of the water of the feed is evaporated. The bed level Apparatus 1 was adjusted with a weir, additional formed granules diluted and replace the initial bed, and left the dryer over the weir through a ball valve into a sample bottle, which was also evacuated to 300 mbar, abs. After collection of 500 mL granule, the ball valve was closed, vacuum in the sample bottle was broken with air, and the granules were removed from the sample bottle. Then, vacuum of 300 mbar, abs was adjusted again in the sample bottle and the ball valve was opened, to collect new granules.

[0102] Step (e.1): After collection of 3 kg, a steady state was reached, and the granules so obtained are the inventive granules Gr.1.

II Manufacture of Inventive GranulesGranule Gr.2

II.1 Manufacture of Spray Slurry SL.2

[0103] Step (a.2): A vessel was charged with 4.18 kg of an aqueous solution of (A.1) (40% by weight) and 1.82 kg granules MGDA-Na.sub.3, average diameter, (D50) 700 ?m (81% A.1). An aqueous slurry SL.2 was obtained.

[0104] Step (b.2): The slurry SL.2 was stirred and heated to 70? C. and then subjected to granulation.

II.2 Granulation of Slurry SL.2

[0105] Step (c.2) was like step (c.1).

[0106] Step (d.2) was like (d.1), but with 1000 g/h feed. Inventive granule Gr.2 was obtained.

[0107] Step (e.2): Granule Gr.2 was collected in a way like Gr.1. More granule could be collected per hour.

III Manufacture of Inventive GranulesGranule Gr.3

III. 1 Manufacture of Slurry SL.3

[0108] Steps (a.3) was like (a.2).

[0109] Step (b.3): The slurry SL.3 was stirred and heated to 70? C. and then stirred at 70? C. for 3 hours.

III.2 Granulation of Slurry SL.3

[0110] The protocol of II.2 was followed with SL.3. Granule Gr.3 was obtained.

IV Manufacture of Inventive GranulesGranule Gr.4

IV.1 Manufacture of Slurry SL.4

[0111] Step (a.4): A crystallizer with stirrer and baffles was charged with 5.0 kg of a 40% by weight solution of salt (A.1). The solution was concentrated to 47% by weight by evaporation at 70? C. and 220 mbar.

[0112] Step (b.4): The solution was maintained at 70? C. with stirring at 500 rpm. Then, under stirring, 10 g (0.5% of salt (A.1) in solution) of crystalline MGDA-Na.sub.3, of which 85% was orthorhombic MGDA-Na.sub.3, were added to the solution in the crystallizer. The resultant slurry was stirred for 20 minutes and subsequently was concentrated to 53% by weight by vacuum evaporation at 70? C. and 220 mbar in 4 hours. The resultant slurry was stirred at 70? C. with 500 rpm for 3 hours. Slurry SL.4 was obtained.

IV.2 Granulation of Slurry SL.4

[0113] The protocol of II.2 was followed with SL.4. Granule Gr.4 was obtained.

V. Comparative Example

IV.1 Manufacture of a Comparative Granule by Fluidized Bed Spray Granulation

[0114] The spray granulation was performed in a vertical cylindrical drying apparatus with zig-zag air classifier, commercially available as Glatt Lab Systems with Vario 3 Insert.

[0115] Nm.sup.3: cubic meter at normal conditions-1 atm, 23? C.

[0116] Step (a.5): A vessel was charged with 15 kg of an aqueous solution of (A.1) (40% by weight), SL.5.

[0117] Step (b.5): The solution SL.5 was stirred and heated to 70? C. and then subjected to fluidized bed spray granulation.

[0118] Granulation of spray solution 5 in a fluidized bed spray granulation (Glatt lab systems with Vario 3 insert):

[0119] The vertical cylindrical vessel was charged with 0.9 kg of solid MGDA-Na.sub.3 spherical particles, diameter 350 to 1000 ?m, and 600 g of milled MGDA-Na.sub.3 particles. An amount of 200 Nm.sub.3/h of air with a temperature of 170? C. was blown from the bottom. A fluidized bed of MGDA-Na.sub.3 particles was obtained. The above liquor SL.5 was introduced by spraying 7 kg of SL. 1 (temperature of solution: 70? C.) per hour into the fluidized bed from the bottom through a two-fluid nozzle, absolute gas pressure in the nozzle: 5 bar. Granules were formed, and the bed temperature, which corresponds to the surface temperature of the solids in the fluidized bed, was 98 to 101? C.

[0120] Particles which are large (heavy) enough fell through the zigzag air classifier into a sample bottle. The smaller (lighter) granules were blown through the recycle back into the fluidized bed by the air classifier. The particles in the sample bottle were classified by a 1000 ?m screen. The granules below 1000 ?m are the value fraction. The granules over 1000 ?m are the overs (oversized particles). The overs and if necessary, some granules of the value fraction, are milled down using a Kinematica Polymix PX-MFL 90D at 4000 rpm, 2 mm mesh. The milled granules were introduced into the fluidized bed through the milled product recycle and served as seeds for new granules.

[0121] After 90 minutes of spray granulating a steady state was reached. Then, the granule C-Gr.5 was collected.

VI. Evaluation of Gr.1 to Gr.4 and C-Gr.5

Percarbonate Stability:

[0122] An amount of 10 g of granule (inventive or comparative) was mixed with 5 g of sodium percarbonate Na.sub.2CO.sub.3.Math.1.5 H.sub.2O.sub.2, commercially available from Evonik (tradename Q30). The mixture so obtained was filled into a cell culture flask (or tissue culture flask) closed with a ventilated closure (German: Schraubverschlu?kappe mit Membran) and stored under air at 35? C. and 70% humidity. Before storing as well as after 12 days, after 19 days and after 26 days, the diffuse reflection was determined as remission and measured with a spectrometer for determining the whiteness, manufacturer: Konica Minolta Spectrophotometer CM-2600d, measuring b-value at wavelength of 360 nm-740 nm. A high diffusion reflection corresponds to a high yellowing of the sample. The diffuse reflection values obtained are summarized in table below:

[0123] The results are summarized in Table 1:

TABLE-US-00002 TABLE 1 Yellowing results of granules made according to the inventive process and a comparative granule b value Gr. 1 Gr. 2 Gr. 3 Gr. 4 C-Gr. 5 b-value before storage 3.09 2.48 1.72 1.86 4.31 ? b after 12 days 2.19 2.35 1.76 1.62 13.57 ? b after 19 days 12.79 3.69 5.12 3.86 4.42 ? b after 26 days 5.57 3.76 2.49 1.30 5.00 b-value total yellowing 23.64 12.28 11.09 8.64 27.30

[0124] The values of ? b refer to the respective previous measurements.

Flowability Tests:

[0125] An amount of 5 g of respective granule was stored in a petri dish under air at 35? C. and 70% humidity for 168 hours.

[0126] After 24 h, after 48 hours and after 168 hours the flowability was visual determined. The petri dish was smoothly shaken manually.

[0127] The rating was determined visually by flowability grades e.g.: from 0=good flowability up to 4=granule is dissolved in water.

TABLE-US-00003 TABLE 2 Flowability test results of inventive granules and a comparative granule grade Gr. 1 Gr. 2 Gr. 3 Gr. 4 C-Gr. 5 after 24 hours 2.0 0 0 0 2.0 after 48 hours 2.0 0 0.5 0.5 2.0 after 168 hours 2.0 0 0.5 0.5 3.0

VII. Powder X-Ray Diffraction Analysis of Gr.4

[0128] A powder X-ray analysis was performed on Gr.4. Data were collected at the Material Science beamline at the Swiss Light Source (SLS) using a wavelength of 0.7 ?. A share of 48% by weight was Form IV.

[0129] The ee value was 21%.

[0130] The following reflections were obtained

TABLE-US-00004 d [?] Relative intensity I [%] 10.79 100 3.79 21 2.81 17 11.00 17 3.67 16 3.87 16 5.55 13 7.74 10 5.26 9 4.18 9

[0131] d: lattice spacing. ?: ?ngstrom. The relative intensity refers to the largest peak at 10.79 ?. The ten reflections with the highest intensity are characteristic for Form IV obtained from granule Gr.4.

[0132] Further reflections were found as follows:

TABLE-US-00005 d [?] Relative intensity I [%] 6.83 8 4.61 8 5.40 8 3.30 8 4.05 8 4.35 7 3.97 7 4.18 6

[0133] The respective X-ray powder diffraction pattern was indexed using a monoclinic space group P2.sub.1 of the following lattice parameters: [0134] ?: 129.635 (1?) lattice parameter a: 21.876(8) ? [0135] lattice parameter b: 8.709(3) ? [0136] lattice parameter c: 14.286(5) ?

[0137] The diffraction diagram is shown in FIG. 1.