Process for the continuous polymerization of phosphate compounds for the production of polyphosphate compositions

Abstract

A process for preparing a polyphosphate composition, the process comprising: (a) continuously introducing an aqueous slurry containing from about 5% to about 50% by weight of a phosphate compound into a polymerization vessel; (b1) evaporating water from the aqueous slurry in a first zone of the polymerization vessel; (b2) polymerizing the phosphate compound in a second zone of the polymerization vessel at a temperature in a range of about 250 to about 450°C for a time sufficient to form the polyphosphate composition; and (c) continuously discharging the polyphosphate composition from the polymerization vessel, wherein the polyphosphate composition comprises: at least about 8% by weight of a polyphosphate; and less than or equal to about 35% by weight of the phosphate compound.

Claims

[1] A process for preparing a polyphosphate composition, the process comprising: (a) continuously introducing an aqueous slurry containing from about 5% to about 50% by weight of a phosphate compound into a polymerization vessel; (b1) evaporating water from the aqueous slurry in a first zone of the polymerization vessel; (b2) polymerizing the phosphate compound in a second zone of the polymerization vessel at a temperature in a range of about 250 to about 450°C for a time sufficient to form the polyphosphate composition; and (c) continuously discharging the polyphosphate composition from the polymerization vessel, wherein the polyphosphate composition comprises: at least about 8% by weight of a polyphosphate; and less than or equal to about 35% by weight of the phosphate compound. [2] The method of claim 1, wherein the aqueous slurry contains from about 5 wt% to about 40 wt%, from about 10 wt% to about 40 wt%, or from about 10 wt% to about 30 wt% of the phosphate compound. [3] The process according to claim 1 or 2, wherein the temperature in step (b2) is in a range from about 280°C to about 420°C, from about 300°C to about 400°C, or from about 320°C to about 420°C. [4] A process according to any one of claims 1-3, wherein step (b1) is carried out at an evaporation temperature in a range from about 300°C to about 800°C, from about 400°C to about 700°C, or from about 500°C to about 800°C. [5] The process according to any one of claims 1-4, wherein an average residence time in the polymerization vessel is in a range of from about 1 hour to about 8 hours, from about 2 hours to about 5 hours, or from about 1.5 hours to about 3 hours. [6] The method according to any one of claims 1-5, wherein a ratio of a first average residence time in the first zone to a second average residence time in the second zone (first:second) is in a range from about 1:10 to about 5:1, from about 1:5 to about 3:1, or from about 1:3 to about 1:

1. [7] A method according to any one of claims 1-6, further comprising: (i) determining an amount of the polyphosphate in the polyphosphate composition; and (ii) adjusting the evaporation conditions in step (b1), the temperature in step (b2) and / or the time period in step (b2) based on the amount of polyphosphate in the polyphosphate composition. [8] A method according to any one of claims 1-7, further comprising: (I) determining an amount of the phosphate compound in the polyphosphate composition; and (II) adjusting the evaporation conditions in step (b1), the temperature in step (b2) and / or the time period in step (b2) based on the amount of the phosphate compound in the polyphosphate composition. [9] A process for preparing a polyphosphate composition, the process comprising: (a) continuously introducing a phosphate compound into a polymerization vessel; (b) polymerizing the phosphate compound at a temperature in a range of about 250 to about 450°C for a time sufficient to form the polyphosphate composition; and (c) continuously discharging the polyphosphate composition from the polymerization vessel, wherein the polyphosphate composition comprises: at least about 8% by weight of a polyphosphate; and less than or equal to about 35% by weight of the phosphate compound. [10] The method of claim 9, wherein the phosphate compound contains less than or equal to about 12 wt%, less than or equal to about 10 wt%, less than or equal to about 5 wt%, or less than or equal to about 2 wt% moisture. [11] The process of claim 9 or 10, wherein the temperature in step (b) is in a range from about 280°C to about 420°C, from about 300°C to about 400°C, or from about 320°C to about 420°C. [12] The process according to any one of claims 9-11, wherein an average residence time in the polymerization vessel is in a range from about 30 min to about 300 min, from about 45 min to about 180 min, or from about 60 min to about 120 min. [13] A method according to any one of claims 9-12, further comprising: (i) determining an amount of the polyphosphate in the polyphosphate composition; and (ii) adjusting the temperature and / or the time period in step (b) based on the amount of polyphosphate in the polyphosphate composition. [14] A method according to any one of claims 9-13, further comprising: (I) determining an amount of the phosphate compound in the polyphosphate composition; and (II) adjusting the temperature and / or the time period in step (b) based on the amount of phosphate compound in the polyphosphate composition. [15] A process according to any one of the preceding claims, wherein the polymerization vessel is a rotary kiln, a shaft kiln or a spiral kiln. [16] A process according to any one of the preceding claims, further comprising, after step (c), a step of milling the polyphosphate composition to reduce an average particle size of the polyphosphate composition and / or to reduce agglomeration of the polyphosphate composition. [17] A method according to any one of the preceding claims, wherein the polyphosphate composition comprises from about 15% to about 60%, from about 15% to about 50%, or from about 20% to about 40% by weight of the polyphosphate. [18] A method according to any one of the preceding claims, wherein the polyphosphate composition includes less than or equal to about 25% by weight, less than or equal to about 20% by weight, less than or equal to about 15% by weight, or less than or equal to about 10% by weight of the phosphate compound. [19] A method according to any one of the preceding claims, wherein the polyphosphate composition further comprises from about 35% to about 80%, from about 45% to about 75%, or from about 55% to about 75% by weight of a pyrophosphate compound. [20] A process according to any one of the preceding claims, wherein the phosphate compound comprises: a (metal)(phosphate), a (N-containing cation)(phosphate), a (N-containing cation)(metal)(phosphate) or a combination of these. [21] The method according to claim 20, wherein the N-containing cation is ammonium, arginine, lysine, histidine, melamine or diethanolamine. [22] A method according to claim 21, wherein the metal is zinc, molybdenum, calcium, magnesium, aluminum, copper, barium, tin, tungsten, iron or nickel. [23] A method according to any one of claims 1-19, wherein the phosphate compound comprises ammonium phosphate and the polyphosphate comprises an ammonium polyphosphate. [24] A method according to any one of claims 1-19, wherein the phosphate compound comprises melamine phosphate and the polyphosphate comprises a melamine polyphosphate. [25] A process according to any one of claims 1-19, wherein the phosphate compound comprises melamine magnesium phosphate and the polyphosphate comprises a melamine poly(magnesium phosphate). [26] A method according to any one of claims 1-19, wherein the phosphate compound comprises melamine zinc phosphate and the polyphosphate comprises a melamine poly(zinc phosphate). [27] The process of claim 26, further comprising, prior to step (a), the step of reacting a mixture of water and melamine with a mixture of water, phosphoric acid and zinc oxide to form melamine zinc phosphate. [28] A process according to any one of the preceding claims, wherein the process does not include a drying step. [29] A process according to any one of the preceding claims, wherein the polyphosphate composition has a decomposition onset temperature on a TGA curve (TGA = thermogravimetric analysis) of from about 290°C to about 360°C, from about 300°C to about 350°C, or from about 310°C to about 340°C (or characterized by is). [30] A process according to any one of the preceding claims, wherein the polyphosphate composition has a temperature at a weight loss of 2% on a TGA curve and / or a temperature at a weight loss of 5% on a TGA curve of from about 290°C to about 360°C, from about 300°C to about 350°C or from about 310°C to about 340°C (or characterized by is).