Powder and granule, process for making such powder and granule, and use thereof

Abstract

The present invention is directed towards a process for making a powder or granule containing (A) at least one chelating agent selected from methyl glycine diacetic acid (MGDA) and glutamic acid diacetate (GLDA) and iminodisuccinic acid (IDS) and their respective alkali metal salts, (B) at least one homo- or copolymer of (meth)acrylic acid, partially or fully neutralized with alkali,
said process comprising the steps of (a) mixing the at least one chelating agent (A) and the at least one homo- or copolymer (B) in the presence of water, (b) removing most of said water by spray-drying or spray granulation using a gas with an inlet temperature of at least 125° C.

Claims

1. A process for making a powder or granule comprising (A) in the range of from 80 to 99% by weight of methyl glycine diacetic acid (MGDA) or an alkali metal salt thereof, (B) in the range of from 1 to 20% by weight of a polymer selected from (i) polyacrylic acid, (ii) copolymers of (meth)acrylic acid and a comonomer having at least one sulfonic acid group, and (iii) salts thereof, wherein the polymer has an average molecular weight Mw in the range of from 1,200 to 30,000 g/mol, determined by gel permeation chromatography and referring to the respective free acid, percentages referring to the solids content of said powder or granule, the process comprising; (a) mixing (A) and (B) in the presence of water thereby forming a solution; and (b) removing most of said water from the solution by spray-drying or spray granulation using a gas with an inlet temperature of at least 125° C. to form the powder or granule.

2. The process according to claim 1, wherein (B) is a per-sodium salt of polyacrylic acid.

3. The process of claim 1, wherein the water is removed from the solution by spray-drying to form the powder in which (A) and (B) are in molecularly disperse form.

4. The process of claim 3, wherein all f the particles of the powder contain both (A) and (B).

5. The process of claim 1, wherein the inlet temperature during the spray-drying or spray granulation is from 150° C. to 220° C.

6. The process of claim 1, wherein (A) is a trisodium salt of methylglycine diacetic acid, and (B) is a polyacrylic acid that is at least 25% neutralized and has a Mw of 4,000-30,000 g/mol, determined by GPC and referring to the free acid.

7. The process of claim 1, wherein the water is removed from the solution by spray granulation to form a fluidized bed of particles.

Description

EXAMPLE I: MANUFACTURE OF INVENTIVE GRANULES

I.1 Manufacture of Spray Solution SL.1

(1) A vessel was charged with 6.37 kg of an aqueous solution of (A.1) (40% by weight) and 630 g of a 45% by weight aqueous solution of polymer (B.1). The solution SL.1 so obtained was stirred and then subjected to spray granulation.

I.2 Spray Granulation of Spray Solution SL.1

(2) A cylindrical vessel with a perforated plate at the bottom, diameter of the cylinder: 148 mm, top lateral area 0.017 m.sup.2, height: 40 cm, with a cone-shaped cartridge, inner lateral area of 0.00785 m.sup.2, was charged with 1 kg of solid MGDA-Na.sub.3 spherical particles, diameter 350 to 1,250 μm. An amount of 42 Nm.sup.3/h of nitrogen with a temperature of 150° C. was blown from the bottom. A fluidized bed of MGDA-Na.sub.3 particles was obtained. The above solution SL.1 was introduced by spraying 1.9 kg of SL.1 (20° C.) per hour into the fluidized from the bottom through a two-fluid nozzle, parameters: 4.5 Nm.sup.3/h nitrogen, absolute pressure in the nozzle: 3.4 bar. Granules were formed, and the bed temperature, which corresponds to the surface temperature of the solids in the fluidized bed, was 100° C.

(3) After every 30 minutes portions of solids were removed with an in-line discharge screw attached to the cylindrical vessel directly above the perforated plate. After such removal, an amount of 1 kg of granule remained in the fluidized bed. The solids removed were subjected to two sieving steps. Three fractions were obtained: coarse particles (diameter>1.25 mm), fines (diameter<0.355 mm), middle fraction (0.355 mm<diameter<1.25 mm). The coarse particles were milled using a hammer mill (Kinetatica Polymix PX-MFL 90D) at 4000 rpm (rounds per minute), 2 mm mesh. The powder so obtained was mixed with the fines and then altogether returned into the fluidized bed.

(4) After 2 hours of spray granulating a steady state was reached. The middle fraction was collected as inventive granule Gr.1. The residual moisture of Gr.1 was determined to be 10.5 to 11.0%, referring to the total solids content of the granule.

(5) In the above example, hot nitrogen of 150° C. can be replaced by hot air having a temperature of 150° C.

II. Manufacture of Further Spray Solutions and Spray Granulation Thereof

II.1 Manufacture of Spray Solution SL.2 and Spray Granulation

(6) A vessel was charged with 6.685 kg of an aqueous solution of (A.1) (40% by weight) and 315 g of a 45% by weight aqueous solution of polymer (B.1). The solution SL.2 so obtained was stirred and then subjected to spray granulation.

(7) For spray granulation, the protocol according to I.2 was followed but with spraying of SL.2 instead of SL.1. Inventive granule Gr.2 was obtained.

II.2 Manufacture of Spray Solution SL.3 and Spray Granulation

(8) A vessel was charged with 6.055 kg of an aqueous solution of (A.1) (40% by weight) and 945 g of a 45% by weight aqueous solution of polymer (B.1). The solution SL.3 so obtained was stirred and then subjected to spray granulation.

(9) For spray granulation, the protocol according to I.2 was followed but with spraying of SL.3 instead of SL.1. Inventive granule Gr.3 was obtained.

(10) All inventive granules Gr.1, Gr.2, and Gr.3 contain (A.1) and polymer (B.1) in molecularly disperse form.

II.3: Comparative Example: Manufacture of a Comparative Spray Solution and Spray Granulation Thereof

(11) A vessel was charged with 7 kg of an aqueous solution of (A.1) (40% by weight) but no polymer (B.1). The solution C-SL.4 so obtained was then subjected to spray granulation.

(12) For spray granulation, the protocol according to I.2 was followed but with spraying of C-SL.4 instead of SL.1. Inventive granule C-Gr.4 was obtained.

III. Storage Tests

(13) An amount of 10 g of inventive granule Gr.1 or Gr.2 or Gr.3 or of comparative granule C-Gr.4 was mixed with 5 g of sodium percarbonate 2Na.sub.2CO.sub.3.3H.sub.2O commercially available from Reckitt Benckiser. The mixture so obtained was filled into a glass container and stored under air at 35° C. and 70% humidity. 5 minutes after start of the storage test, and after each 11 days, after 18 days, and after 25, the diffuse reflection was determined as remission and measured with a spectrophotometer for determining the whiteness, manufacturer: Elrepho from Data Color SF450 aperture LAV 30, measuring b-value at a wavelength of 360-700 nm. Further parameters: average daylight D65/10°, optical geometry D0. A high the diffuse reflection corresponds with a high yellowing of the sample. The diffuse reflection values obtained are summarized in table 1.

(14) TABLE-US-00001 TABLE 1 Yellowing behavior of inventive granules and of comparative granule Diffuse reflection after Gr.1 Gr.2 Gr.3 C-Gr.4  5 minutes 7.5 8.54 8.82 6.44 11 days n.d. n.d. n.d. 10.42 18 days 9.65 11.06 9.77 17.75 25 days 15.72 n.d. 19.31 25.06 n.d.: not determined

(15) The yellowing/diffuse reflection is determined as B value.