Process for preparing a highly porous sodium perborate

Claim 1

A PROCESS FOR PREPARING HIGHLY POROUS SODIUM PERBORAGE CAPABLE OF TRICKLING, HAVING A PARTICLE SIZE RANGE OF 0.25 TO 1MM. AND HAVING A BULK WEIGHT BETWEEN 0.25 AND 0.45 KG./1., BY REACTION OF A SODIUM METOBORATE SOLUTION WITH HYDROGEN PEROXIDE IN THE ABSENCE OF A STABILIZER, COMPRISING FORMING A REACTION MIXTURE BY ADDING UNDER STIRRING, AT A TEMPERATURE BETWEN 10 AND 15*C., AN AQUEOUS SOLUTION OF SODIUM METABORATE TO AN AQUEOUS SOLUTION OF HYDROGEN PEROXIDE, UNTIL CRYSTALLIZATION OF SODIUM PERBORATE FROM THE REACTION MIXTURE STARTS; THEN FURTHER ADDING SODIUM METABORATE SOLUTION AND ADDING HYDROGEN PEROXIDE SOLUTION TO THE REACTION MIXTURE AND THEREBY MAINTAINING IN THE REACTION MIXTURE AS EXCESS OF HYDROGEN PEROXIDE, CORRESPONDING TO A MOL-RATIO OF HYDROGEN PEROXIDE TO SODIUM METABORATE IN THE RANGE OF 1.1 TO 1.8, AND AFTER THE DESIRED COMPLETION OF PRECIPITATION BY CRYSTALLIZATION, REACTING THE EXCESS OF HYDROGEN PEROXIDE PRESENT WITH AN ADDITIONAL AMOUNT OF SODIUM METABORATE, COOLING THE REACTION MIXTURE UP TO ABOUT 1*C. AND SEPARATING THE PRECIPITATED SODIUM PERBORATE FROM THE MOTHER LIQUOR.