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

A method for forming a water-based coating composition comprising the steps of:

• forming amorphous aluminum orthophosphate by combining phosphoric acid, aluminum sulfate, and sodium hydroxide together for a period of about 30 minutes to form a precipitate and drying the precipitate at a temperature of less than about 130° C. to form amorphous aluminum phosphate particles having one or more closed voids per particle, wherein the powder has a macropore volume substantially less than 0.1 cc/gram, wherein the powder exhibits two endothermic peaks in Differential Scanning Calorimetry between about 90 degrees to about 250 degrees Celsius, wherein the powder has a dispersibility in water of at least 0.025 grams per 1.0 gram of water, and wherein the powder has an average individual particle radius size between 5 and 80 nanometers;
• and
• combining the amorphous aluminum phosphate with a binding polymer useful for forming a latex coating gin composition.

A method of making an opacifying coating composition comprising the steps of:

• Combining phosphoric acid with aluminum sulfate and sodium hydroxide, and reacting the combined materials together for a predetermined time to form amorphous aluminum phosphate;
• drying the amorphous aluminum phosphate at a temperature of about 130° C. or less-wherein when in powder form the dried amorphous aluminum phosphate comprises one or more closed voids per particle and amorphous aluminum phosphate particles are substantially free of open pores;
• and adding the amorphous aluminum phosphate with a binding polymer.