Aluminum phosphate, polyphosphate, and metaphosphate particles and their use as pigments in paints and method of making same

Abstract

An aluminum phosphate composition comprising aluminum phosphate, aluminum polyphosphate, aluminum metaphosphate, or a mixture thereof. The composition may be characterized by, when in powder form, having particles wherein some of the particles have at least one or more voids per particle. In addition, the composition is characterized by exhibiting two endothermic peaks in Differential Scanning calorimetry between about 90 degrees to about 250 degrees Celsius. The composition is also characterized by, when in powder form, having a dispersibility of at least 0.025 grams per 1.0 gram of water. The composition is made by a process comprising contacting phosphoric acid with aluminum sulfate and an alkaline solution to produce an aluminum phosphate based product; and optionally calcining the aluminum phosphate, polyphosphate or metaphosphate based product at an elevated temperature. The composition is useful in paints and as a substitute for titanium dioxide.

1 . An aluminum phosphate composition comprising amorphous aluminum phosphate particles, wherein at least some of the particles, when in powder form, have an average of one or more closed voids per particle, and the composition is further characterized by: (a) when in powder form, exhibiting two endothermic peaks in Differential Scanning calorimetry between about 90 degrees to about 250 degrees Celsius; and, (b) when in powder form, having a dispersibility in water of at least 0.025 grams per 1.0 gram of water. 
     
     
         2 . The composition of  claim 1 , wherein said first endothermic peak in Differential Scanning calorimetry occurs between 90 degrees and 120 degrees Celsius, and said second endothermic peak occurs between 150 degrees and 180 degrees Celsius. 
     
     
         3 . The composition of  claim 1  wherein no peak is exhibited between approximately 335 degrees and 345 degrees Celsius in Differential Scanning calorimetry. 
     
     
         4 . The composition of  claim 1  further comprising an ion. 
     
     
         5 . The composition of  claim 1  further comprising sodium. 
     
     
         6 . The composition of  claim 1  further comprising potassium. 
     
     
         7 . The composition of  claim 1  further comprising ammonium. 
     
     
         8 . A coating composition comprising the composition of  claim 1  as an ingredient as combined with a binder polymer. 
     
     
         9 . The composition of  claim 1  wherein the composition, when slurry form has a pH in the range from about 3.0 to about 7.5. 
     
     
         10 . The composition of  claim 1  wherein the composition is obtained from contacting a combination of materials comprising phosphoric acid, aluminum sulfate and alkaline solution. 
     
     
         11 . The composition of  claim 1 , wherein the composition is characterized by a skeletal density of less than 2.40 grams per cubic centimeter, and wherein the average particle radius of the individual particles of dry powder is between 10 and 100 nanometers. 
     
     
         12 . A composition comprising a solvent and an aluminum phosphate composition, comprising amorphous aluminum phosphate particles, wherein at least some of the particles, when in powder form, have an average of one or more closed voids per particle, and the composition is further characterized by: (a) when in powder form, exhibiting two endothermic peaks in Differential Scanning calorimetry between about 90 degrees to about 250 degrees Celsius; and, (b) when in powder form, having a dispersibility in water of at least 0.025 grams per 1.0 gram of water. 
     
     
         13 . The composition of  claim 12 , wherein said composition also comprises titanium dioxide in a reduced amount. 
     
     
         14 . The composition of  claim 12 , wherein in said composition no peak is exhibited between approximately 335 degrees and 345 degrees Celsius in Differential Scanning calorimetry. 
     
     
         15 . The composition of  claim 12 , wherein said paint is substantially free of titanium dioxide. 
     
     
         16 . The composition of  claim 12 , wherein said solvent comprises water. 
     
     
         17 . The composition of  claim 12 , wherein said solvent comprises a polar solvent. 
     
     
         18 . The composition of  claim 12 , wherein said solvent comprises a non-polar solvent. 
     
     
         19 . The composition of  claim 12 , wherein said solvent comprises an organic solvent. 
     
     
         20 .- 51 . (canceled) 
     
     
         52 . A method of making amorphous aluminum phosphate comprising the steps of:
 combining phosphoric acid with aluminum sulfate and sodium hydroxide to react and form a suspension comprising an amorphous aluminum phosphate precipitate;   filtering the suspension to isolate the precipitate; and   drying the precipitate at a temperature less than about 130° C.   
     
     
         53 . The method as recited in  claim 52  wherein the amorphous aluminum phosphate has a bulk density that is less than about 2.1 g/cc. 
     
     
         54 . The method as recited in  claim 52  where the amorphous aluminum phosphate has an average individual particle radius size from about 5 to 80 nanometers. 
     
     
         55 . The method as recited in  claim 52  wherein the amorphous aluminum phosphate consists of sodium aluminum phosphate. 
     
     
         56 . The method as recited in  claim 52  wherein the dried precipitate is substantially free of open pores. 
     
     
         57 . The method as recited in  claim 52  wherein dried precipitate comprises particles having closed voids. 
     
     
         58 . The method as recited in  claim 52  wherein the amorphous aluminum phosphate has a bulk density that is less than about 1.99 g/cc. 
     
     
         59 . The method as recited in  claim 52  wherein the dried precipitate has a macropore volume that is substantially less than 0.1 cc/gram. 
     
     
         60 . The method as recited in  claim 52  wherein during the step of combining, the phosphoric acid, aluminum sulfate, and sodium hydroxide are combined simultaneously. 
     
     
         61 . The method as recited in  claim 52  wherein after the step of combining, adding further sodium hydroxide to the mixture. 
     
     
         62 . The method as recited in  claim 52  further comprising the step of washing the precipitate after the filtering step. 
     
     
         63 . The method as recited in  claim 52  further comprising before the step of drying, adding a dispersant to the precipitate. 
     
     
         64 . The method as recited in  claim 63  wherein the dispersant is sodium tetrapyrophosphate. 
     
     
         65 . A chemical composition comprising the amorphous aluminum phosphate made according to  claim 1  combined and uniformly dispersed within a binding polymer. 
     
     
         66 . The chemical composition as recited in  claim 65  wherein when the chemical composition is dried to form a film has a structure characterized by enmeshed binding polymer and amorphous aluminum phosphate. 
     
     
         67 . A method of making amorphous aluminum phosphate comprising the steps of:
 combining phosphoric acid with aluminum sulfate and sodium hydroxide to form a mixture;   reacting the mixture to form a suspension comprising amorphous aluminum phosphate precipitate;   isolating the precipitate from the suspension;   washing the isolated precipitate; and   drying the precipitate at a temperature less than about 130° C.   
     
     
         68 . The method as recited in  claim 67  wherein the amorphous aluminum phosphate consists of sodium aluminum phosphate. 
     
     
         69 . The method as recited in  claim 67  wherein the amorphous aluminum phosphate has a bulk density that is less than about 2.1 g/cc. 
     
     
         70 . The method as recited in  claim 67  wherein the dried precipitate comprises particles having closed voids. 
     
     
         71 . The method as recited in  claim 67  wherein after the step of drying, the amorphous aluminum phosphate has a macropore volume of substantially less than 0.1 cc/gram. 
     
     
         72 . The method as recited in  claim 67  comprising combining the phosphoric acid, aluminum sulfate, and sodium hydroxide simultaneously. 
     
     
         73 . The method as recited in  claim 67  further comprising before the step of drying, adding a dispersant to the precipitate. 
     
     
         74 . The method as recited in  claim 73  wherein the dispersant is sodium tetrapyrophosphate. 
     
     
         75 . A chemical composition comprising the amorphous aluminum phosphate made according to  claim 67 , wherein the amorphous aluminum phosphate is further combined with a binding polymer to form the chemical composition. 
     
     
         76 . The chemical composition as recited in  claim 75 , wherein the amorphous aluminum phosphate has a bulk density that is less than about 2.1 g/cc, and wherein the chemical composition when dried to form a film has a structure characterized by interpenetrating phases of binding polymer enmeshed with amorphous aluminum phosphate. 
     
     
         77 . A method of making a chemical composition comprising amorphous aluminum phosphate, the method comprising the steps of:
 combining phosphoric acid with aluminum sulfate and sodium hydroxide to form a mixture;   reacting the mixture to form a suspension comprising an amorphous aluminum phosphate precipitate;   filtrating and washing the suspension to isolate the precipitate into a cake;   forming a dispersion of the washed cake;   drying the cake to form amorphous aluminum phosphate particles; and   adding the amorphous aluminum phosphate to a binding polymer to form the chemical composition.   
     
     
         78 . The method as recited in  claim 77  wherein the amorphous aluminum phosphate has a bulk density that is less than about 2.1 g/cc. 
     
     
         79 . The method as recited in  claim 77  wherein during the step of forming a dispersion, a phosphate-based dispersant is used. 
     
     
         80 . The method as recited in  claim 77  wherein when in powder form the amorphous aluminum phosphate has an average individual particle radius size of between 5 and 80 nanometers. 
     
     
         81 . The method as recited in  claim 77  wherein after the step of combining, adding further sodium hydroxide to the mixture.