Crumbly phase composition of methylglycine N,N diacetic acid

Abstract

The present invention relates to a crumbly phase composition containing on total weight of the composition (i) 70-87 wt % of organic compounds and salts thereof containing 85 to 100 wt % on total organic compounds and salts thereof of MGDA-Na3, wherein at least 60 wt % of the MGDA-Na3 is crystalline, and (ii) 13-30 wt % of water The invention furthermore relates to a process to prepare the above composition and a process to prepare crystals of MGDA-Na3 by drying the above composition.

Claims

1. A crumbly phase composition containing on total weight of the composition (i) 70-87 wt % of organic compounds and salts thereof containing 85 to 100 wt % of MGDA-Na3 on the basis of total organic compounds and salts thereof, wherein at least 60 wt % of the MGDA-Na3 is crystalline wherein the MGDA-Na3 that is crystalline is at least 75% of crystal type I on the basis of total crystalline MGDA-Na3 content, further wherein said crystal type I is a dihydrate crystal, and (ii) 20-30 wt % of water.

2. The crumbly phase composition of claim 1 containing on total weight of the composition (i) 70-80 wt % of organic compounds and salts thereof containing 85 to 100 wt % of MGDA-Na3 on the basis of total organic compounds and salts thereof.

3. The crumbly phase composition of claim 1 containing 75-80 wt % of organic compounds and salts thereof on the basis of the total weight of the composition.

4. The crumbly phase composition of claim 1 wherein the organic compounds and salts thereof contain more than 90 wt % of MGDA-Na3 on the basis of total organic compounds.

5. The crumbly phase composition of claim 1 containing between 50 and 80% of the L enantiomeric form of MGDA and between 20 and 50% of the D enantiomeric form of MGDA.

6. The process to prepare the crumbly phase composition of claim 1 comprising combining an aqueous composition of MGDA-Na3 and solid MGDA-Na3.

7. The process of claim 6 wherein the aqueous composition contains 35-60 wt % of MGDA-Na3.

8. The process to prepare solid crystalline MGDA-Na3 comprising a step of drying the crumbly phase composition of claim 1.

9. The process of claim 8 wherein the solid crystalline MGDA-Na3 contains 90-100% of crystal type I on total crystal content of MGDA-Na3.

10. The process of claim 8 wherein the process involves as a drying step a step selected from the group of an evaporation step, a step of fluid bed drying, a step of spray drying, a step of thin film drying, a step of drum drying, and a spray granulation step.

11. The process of claim 8 wherein in the process a part of the crystalline product as obtained is recycled and mixed with an aqueous composition containing MGDA-Na3 in an amount to prepare additional crumbly phase composition.

12. The process of claim 8 wherein the process is performed continuously.

13. The crumbly phase composition of claim 1 wherein the MGDA-Na.sub.3 that is crystalline is at least 90% of crystal type I on the basis of total crystalline MGDA-Na.sub.3 content.

14. The crumbly phase composition of claim 13 wherein the crystal type I has the following diffraction pattern: TABLE-US-00002 Type I 2 d () 8.2 10.8 10.5 8.4 15.6 5.7 16.5 5.4 17.1 5.2 18.1 4.9 18.8 4.7 21 4.25 21.4 4.15 22.6 3.9 23.7 3.75 24.7 3.6 wherein from 75 to 100 wt % of the MGDA-Na.sub.3 is crystalline, wherein the water is present in an amount of from 22 to 26 wt %; and wherein the organic compounds and salts thereof are present in an amount of from 75 to 78 wt %.

15. The crumbly phase composition of claim 14 wherein 92 to 97% of the MGDA-Na.sub.3 is of crystal type I on the basis of total crystalline MGDA-Na.sub.3 content and 3 to 8% of the MGDA-Na.sub.3 is of crystal type III on the basis of total crystalline MGDA-Na.sub.3 content and has the following diffraction pattern: TABLE-US-00003 Type III 2 d () 5.8 15.2 7.5 11.8 8.1 10.9 9.5 9.3 11.7 7.6 13.9 6.4 15.1 5.9 16.5 5.4 17.3 5.1 18.5 4.8 19.1 4.65 20.1 4.4

16. The crumbly phase composition of claim 15 containing between 50 and 80% of the L enantiomeric form of MGDA and between 20 and 50% of the D enantiomeric form of MGDA.

17. The crumbly phase composition of claim 16 that contains less than 0.01 wt % particulate solid with a pore volume in the range of from 0.25 to 0.75 cm.sup.3/g, determined by nitrogen adsorption in accordance with 66134:1998-02 on total MGDA-Na.sub.3 weight.

18. The crumbly phase composition of claim 1 wherein the MGDA-Na.sub.3 that is crystalline is about 100% of crystal type I on the basis of total crystalline MGDA-Na.sub.3 content.

Description

EXAMPLES

Example 1 (Comparative)

(1) A 50 wt % MGDA-Na3 aqueous slurry was prepared by crystallization evaporation, using MGDA-Na3 seeds of the type I variety. The slurry obtained was concentrated further using a laboratory rotary evaporator (temperature 50 C., pressure 200 mbar). At a concentration of 63 wt %, the slurry transformed into a pasty phase, yielding a sticky film on the wall of flask. Further drying yielded a hard film on the wall that could not be harvested efficiently anymore.

Example 2 (Comparative)

(2) 77 kg of a 40.7 wt % MGDA-Na3 aqueous solution was charged to a 80 L Vrieco-Nauta conical screw mixer. The solution was concentrated to 50 wt % MGDA-Na3 (jacket temperature: 50-120 C., pressure 100-200 mbar, screw speed 70 rpm). After adding 300 grams of MGDA-Na3 seeds of the type I variety, the slurry obtained was concentrated further. In the range of 60-65 wt % MGDA-Na3 a thixotropic pasty phase was formed, yielding serious fouling problems. The product eventually obtained was one large spheroidal lump of material that could not be processed further.

Example 3

(3) A crumbly phase composition was prepared by first dosing 17.1 kg of solid MGDA-Na3 (particle size 0.1-1.25 mm), containing solely the type I crystal variety (MGDA-Na3 content 80.8 wt %, crystallinity 75%) to a 50 L Ldige Ploughshare mixer, operated at a rotation speed of 170 rpm, and subsequently dosing 2.9 kg of a 40.7 wt % MGDA-Na3 aqueous solution, during 5 minutes via a dosing pipe. The temperature during mixing was 30-40 C. After dosing, the product (MGDA-Na3 content: 75 wt %) was homogenized for 2 more minutes, before discharging the crumbly phase product.

Example 4

(4) 50 gram of the crumbly phase as obtained in example 3 was dried in petri-dish overnight in an oven at 90 C. The product obtained showing a MGDA-Na3 content of 81.3 wt %, was slightly caked, but could be easily crumbled, by gently tapping on the cake with a spatula, yielding free flowing particles in the range of 0.5-5 mm. The crystallinity of the product was 80%, showing solely the type I variety.

Example 5

(5) 500 gram of the crumbly phase as obtained in example 3 was dried using a laboratory rotary evaporator (temperature 80 C., pressure 500 mbar), during 30 minutes. The product obtained showing an MGDA-Na3 content of 82.1 wt %, was a free-flowing powder containing particles in the range of 0.5-3 mm. The crystallinity of the product was 77%, showing predominantly the type I variety and a small amount of a few percent of the type III variety.

Example 6

(6) 13 kg of the crumbly phase as obtained in example 3 was dried in a 16 L fluid bed drier, during 8 minutes (air temperature 150 C.; product end temperature 90 C.). Subsequently the product was milled using an Alexanderwerk friction sieve.

(7) A free-flowing product was obtained showing an MGDA-Na3 content of 80.1 wt %. The crystallinity of the product was 79%, showing solely the type I variety 73 wt % of the product showed a particle size in between 0.5 and 1.5 mm. The bulk density was 850 Kg/m.sup.3.

(8) Visual inspection using a microscope showed that the majority of the particles had a spheroidal shape (potato-alike).

Example 7

(9) A crumbly phase composition was prepared by first dosing 16 kg of solid MGDA-Na3 (particle size 0.1-1.25 mm), containing solely the type I crystal variety (MGDA-Na3 content 80.3 wt %, crystallinity 79%) to a 50 L Ldige Ploughshare mixer, operated at a rotation speed of 170 rpm, and subsequently dosing 2.55 kg of a 45.1 wt % MGDA-Na3 aqueous solution, during 5 minutes via a dosing pipe. The temperature during mixing was 45-50 C. After dosing, the product (MGDA-Na3 content: 76.1 wt %) was homogenized for 2 more minutes, before discharging the crumbly phase product.

(10) The crumbly phase obtained was subsequently processed as described in example 6, yielding a free-flowing product showing an MGDA-Na3 content of 80.3 wt %. The crystallinity of the product was 78%, showing solely the type I variety. 68 wt % of the product showed a particle size in between 0.5 and 1.5 mm. The bulk density was 840 Kg/m.sup.3.