Aluminum phosphate or polyphosphate particles for use as pigments in paints and method of making same

Abstract

An aluminum phosphate or polyphosphate-based pigment product 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 based product at an elevated temperature, wherein the process is substantially free of an organic acid. The aluminum phosphate or polyphosphate-based pigment is amorphous. The amorphous aluminum phosphate or polyphosphate characterized by a bulk density of less than 2.30 grams per cubic centimeter and a phosphorus to aluminum mole ratio of greater than 0.8. The composition is useful in paints and as a substitute for titanium dioxide.

1 . An amorphous aluminum phosphate or polyphosphate characterized by a bulk density of between 1.95 and 2.30 grams per cubic centimeter and a phosphorus to aluminum mole ratio of greater than 0.8.  
   
   
       2 . An aluminum phosphate or polyphosphate according to  claim 1 , wherein the aluminum phosphate or polyphosphate is in powder form and comprises 1 to 4 voids per particle of amorphous aluminum phosphate or polyphosphate powder.  
   
   
       3 . An aluminum phosphate or polyphosphate according to  claim 1 , wherein the aluminum phosphate or polyphosphate is in dry powder form and further comprises an average individual particle radius size of between 10 and 40 nanometers.  
   
   
       4 . A paint according to  claim 3  where the opacity or whiteness develops during the fabrication or application process of the paint.  
   
   
       5 . An aluminum phosphate or polyphosphate made according to  claim 1  wherein the aluminum phosphate or polyphosphate is an ingredient in a paint.  
   
   
       6 . An aluminum phosphate or polyphosphate made according to  claim 1  wherein the aluminum phosphate or polyphosphate is an ingredient in a varnish, printing ink, or plastic.  
   
   
       7 . An aluminum phosphate or polyphosphate powder made according to  claim 1  wherein the aluminum phosphate or polyphosphate comprises particles containing voids produced during particle drying at temperatures in the range between 15-130° C.  
   
   
       8 . An aluminum phosphate or polyphosphate according to  claim 1 , wherein the aluminum phosphate or polyphosphate is in a powder form and wherein at least 10% of the particles in the powder resist coalescence upon drying.  
   
   
       9 . An amorphous aluminum phosphate or polyphosphate according to  claim 1  wherein the aluminum phosphate or polyphosphate is in slurry form.  
   
   
       10 . An amorphous aluminum phosphate or polyphosphate according to  claim 1  wherein the aluminum phosphate or polyphosphate is in slurry form, and wherein the concentration of solids in the slurry is between 10-55 percent.  
   
   
       11 . An aluminum phosphate or polyphosphate according to  claim 1 , wherein the aluminum phosphate or polyphosphate comprises a slurry capable of drying at temperatures below 130° C. to produce a powder that contains 10-20 water weight percent.  
   
   
       12 . An aluminum phosphate or polyphosphate according to  claim 1 , wherein the aluminum phosphate or polyphosphate comprises an ingredient in a varnish, printing ink or plastic.  
   
   
       13 . An aluminum phosphate or polyphosphate-based pigment product obtainable from 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 based product at an elevated temperature, wherein the process is substantially free of an organic acid, and the aluminum phosphate or polyphosphate-based pigment is amorphous.  
   
   
       14 . The pigment of  claim 13  wherein the phosphoric acid, aluminum sulfate and alkaline solution are added together in a simultaneous manner.  
   
   
       15 . The pigment of  claim 13  wherein the mixture has a pH in the range from about 4.0 to about 4.5.  
   
   
       16 . The pigment made according to  claim 13 , wherein the pigment comprises an ingredient in a varnish, printing ink or plastic.  
   
   
       17 . The pigment made according to  claim 13 , wherein the pigment comprises an ingredient in a paint.  
   
   
       18 . The pigment made according to  claim 13 , wherein the pigment is characterized by a bulk density of less than 2.30 grams per cubic centimeter, and wherein the average particle radius of the individual particles of dry aluminum phosphate or polyphosphate is between 10 and 40 nanometers.  
   
   
       19 . A process of making a white pigment comprising amorphous aluminum phosphate or polyphosphate comprising the following steps: combining phosphoric acid, aluminum sulfate, and sodium hydroxide into a suspension; filtrating and washing said suspension into a cake; dispersion of the washed cake; drying of the cake; polymerization of the dry product; and micronization of the product.  
   
   
       20 . The process of  claim 17  wherein the pigment is added to a mixture comprising titanium dioxide.