Rutile titanium dioxide microspheres and ordered botryoidal shapes of same

Rutile TiO2 microparticles which comprise generally spherical structures in the range of from 1 to 2 microns in diameter, said spherical structures comprising ordered acicular aggregates of elongated TiO2 crystallites, produced by the process comprising:

• (a) forming an aqueous solution of a soluble titanium compound at a titanium concentration of from 0.5 to 1.0 moles per liter;
• (b) introducing a morphology controlling agent selected from the group consisting of an α-hydroxy carboxylic acid of the formula R—CH(OH)COOH, an α-hydroxy carboxamide of the formula R—CH(OH)CONH2 or an α-amino acid of the formula R—CH(NH2)COOH, wherein R is an alkane, alkene, alkyne, arene, or cycloalkane group having 4 or fewer carbon atoms, into the solution at an acid- or carboxamide-to-titanium molar ratio of from 0.02 to 0.2 while simultaneously heating the solution to a temperature in the range of from 75° C. to 80° C. with constant stirring;
• (c) maintaining the stirred solution at a temperature in the range of from 75° C. to 80° C. for a period of from one to 3 hours;
• (d) elevating the temperature of the stirred solution to a value of from 100° C. to the refluxing temperature and maintaining said temperature for a period of from 2 hours to 4 hours to form a reaction product;
• (e) optionally neutralizing the reaction mixture which results from step (e);
• (f) cooling the reaction mixture to room or ambient temperature;
• and
• (h) separating and drying the reaction product.

A method for preparing rutile TiO2 particles which comprise structures in a botryoidal morphology having a size in the range of from 10 to 20 microns, said structures being aggregates of elongated TiO2 crystallites having a thickness of from 3 nm to 5 nm, said method comprising:

• (a) forming an aqueous solution of a soluble titanium compound at a titanium concentration of from 0.5 to 1.0 moles per liter;
• (b) introducing a morphology controlling agent selected from an α-hydroxy carboxylic acid of the formula R—CH(OH)COOH, an a-hydroxy carboxamide of the formula R—CH(OH)CONH2 or an a-amino acid of the formula R—CH(NH2)COOH, wherein R is an alkane, alkene, alkyne, arene, or cycloalkane group having 4 or fewer carbon atoms, into the solution at an acid- or carboxamide-to-titanium molar ratio of from 0.02 to 0.2 while simultaneously heating the solution to a temperature in the range of from 75° C. to 80° C. with constant stirring;
• (c) introducing TiO2 seeds into the stirred solution at a seed-to-TiO2 molar ratio of from 0.0005 to 0.0015 and maintaining the stirred solution at a temperature in the range of from 75° C. to 80° C. for a period of from one to 3 hours;
• (d) elevating the temperature of the stirred solution to a value of from 100° C. to the refluxing temperature and maintaining said temperature for a period of from 2 hours to 4 hours to form a reaction product;
• (e) optionally neutralizing the reaction mixture resulting from step (d);
• (f) cooling the reaction mixture to room or ambient temperature;
• and
• (g) separating and drying the reaction product.

Rutile TiO2 microparticles comprising structures in a botryoidal morphology having a size in the range of from 10 to 20 microns and formed by the process of:

• (a) forming an aqueous solution of a soluble titanium compound at a titanium concentration of from 0.5 to 1.0 moles per liter;
• (b) introducing a morphology controlling agent selected from an α-hydroxy carboxylic acid of the formula R—CH(OH)COOH, an α-hydroxy carboxamide of the formula R—CH(OH)CONH2 or an α-amino acid of the formula R—CH(NH2)COOH, wherein R is an alkane, alkene, alkyne, arene, or cycloalkane group having 4 or fewer carbon atoms, into the solution at an acid- or carboxamide-to-titanium molar ratio of from 0.02 to 0.2 while simultaneously heating the solution to a temperature in the range of from 70° C. to 80° C. with constant stirring;
• (c) introducing TiO2 seeds into the stirred solution at a seed-to-TiO2 molar ratio of from 0.0005 to 0.0015 and maintaining the stirred solution at a temperature in the range of from 70° C. to 80° C. for a period of from one to 3 hours;
• (d) maintaining the stirred solution at a temperature in the range of from 70° C. to 80° C. for a period of from one to 3 hours;
• (e) elevating the temperature of the stirred solution to a value of from 100° C. to the refluxing temperature and maintaining said temperature for a period of from 2 hours to 4 hours to form a reaction product;
• (f) optionally neutralizing the reaction mixture resulting from step (e);
• (g) cooling the reaction mixture to room or ambient temperature and separating and drying the reaction product.