Method of making hollow spheres by spray drying

Claim 2

A FIRST AQUEOUS SOLUTION CONSISTING ESSENTIALLY OF SODIUM SILICATE HAVING AN SIO2,NA2O MOLE RATIO OF 1.5:1 TO 4.0:1 AND AN NA2O CONTENT OF 5 TO 20 PERCENT ON A WEIGHT BSSIS, MAINTAINED AT A TEMPERATURE BETWEEN ROOM TEMPERATURE AND THE SOLUTION BOILING POINT, AND

Claim 5

sodium hexametaphosphate, to produce with agitation a homogeneous final aqueous solution having a solids concentration of 5 to 35 percent, a sodium hexametaphosphate concentration of at least 20 percent and a viscosity below 200 cp, maintained at a temperature below said final solution boiling point; B. spraying droplets of said final aqueous solution into a dryer utilizing air having an inlet temperature between 200* C and 500* C while maintaining said droplets entering said dryer at a temperature below said third solution boiling point and recovering a product consisting essentially of a mass of hollow spheres having a water content less than 25 percent; c. subjecting said spray dried product to further drying at a temperature between about 70*- 400* C for a time sufficient to reduce the moisture content below about 7 percent and avoiding intumescence, and D. recovering a mass of generally hollow closed spherical particles having a bulk density of about 2 - 20 lbs./ft.3 and a particle size within the range of 10 - 400 mesh.

Claim 6

sodium hexametaphosphate, to produce with agitation a homogeneous final aqueous solution having a solids concentration of 5 to 35 percent, a sodium hexametaphosphate concentration of at least 20 percent and a viscosity below 200 cp, maintained at a temperature below said final solution boiling point; B. spraying droplets of said final aqueous solution into a dryer utilizing air having an inlet temperature between 200* C and 500* C while maintaining said droplets entering said dryer at a temperature below said third solution boiling point and recovering a product consisting essentially of a mass of hollow spheres having a water content less than 25 percent; c. subjecting said spray dried product to further drying at a temperature between about 70*- 400* C for a time sufficient to reduce the moisture content below about 7 percent and avoiding intumescence, and D. recovering a mass of generally hollow closed spherical particles having a bulk density of about 2 - 20 lbs./ft.3 and a particle size within the range of 10 - 400 mesh.

Claim 7

A method according to claim 1 wherein the aqueous sodium silicate solution has an SiO2:Na2O ratio of between about 1.8:1 and 2.8:1.

Claim 8

a second aqueous solution consisting essentially of 16 to 18 percent sodium pentaborate on a weight basis, maintained at a temperature between room temperature and the solution boiling point, to produce with agitation a homogeneous third aqueous solution having a solids concentration of 5 tO 35 percent, a sodium pentaborate concentration of 6 to 7 percent and a weight ratio of sodium pentaborate to Na2O of 1.1:1 to 1.3:1 maintained at a temperature below said third solution boiling point; B. spraying droplets of said third aqueous solution into a dryer utilizing air having an inlet temperature between 200* C and 500* C while maintaining said droplets entering said dryer at a temperature below said third solution boiling point and recovering a product consisting essentially of a mass of hollow spheres having a water content less than 25 percent; C. subjecting said spray dried product to further drying at a temperature between about 70* - 400* C for a time sufficient to reduce the moisture content below about 7 percent and avoiding intumescence, and D. recovering a mass of generally hollow closed spherical particles having a bulk density of about 2 - 20 lbs./ft.3 and a particle size within the range of 10 - 400 mesh.

Claim 9

a second aqueous solution consisting essentially of 16 to 18 percent sodium pentaborate on a weight basis, maintained at a temperature between room temperature and the solution boiling point, to produce with agitation a homogeneous third aqueous solution having a solids concentration of 5 tO 35 percent, a sodium pentaborate concentration of 6 to 7 percent and a weight ratio of sodium pentaborate to Na2O of 1.1:1 to 1.3:1 maintained at a temperature below said third solution boiling point; B. spraying droplets of said third aqueous solution into a dryer utilizing air having an inlet temperature between 200* C and 500* C while maintaining said droplets entering said dryer at a temperature below said third solution boiling point and recovering a product consisting essentially of a mass of hollow spheres having a water content less than 25 percent; C. subjecting said spray dried product to further drying at a temperature between about 70* - 400* C for a time sufficient to reduce the moisture content below about 7 percent and avoiding intumescence, and D. recovering a mass of generally hollow closed spherical particles having a bulk density of about 2 - 20 lbs./ft.3 and a particle size within the range of 10 - 400 mesh.

Claim 10

A SECOND AQUEOUS SOLUTION CONSISTING ESSENTIALLY OF 16 TO 18 PERCENT SODIUM PENTABORATE ON A WEIGHT BASIS, MAINTAINED AT A TEMPERATURE BETWEEN ROOM TEMPERATURE AND THE SOLUTION BOILING POINT, TO PRODUCE WITH AGITATION A HOMOGENEOUS THIRD AQUEOUS SOLUTION HAVING A SOLIDS CONCENTRATION OF 5 TO 35 PERCENT, A SODIUM PENTABORATE CONCENTRATION OF 6 TO 7 PERCENT AND A WEIGHT RATIO OF SODIUM PENTABORATE CONENTRATION OF 6 TO 7 PER 1.3:1 MAINTAINED AT A TEMPERATURE BELOW SAID THIRD SOLUTION BOILING POINT, B. SPRAYING DROPLETS OF SAID THIRD AQUEOUS SOLUTION INTO A DRYER UTILIZING AIR HAVING AN INLET TEMPERATURE BETWEEN 200*C AND 500*C WHILE MAINTAINING SAID DROPLETS ENTERING SAID DDRYER AT A TEMPERATURE BELOW SAID THIRD SOLUTION BOILING POINT AND RECOVERING A PRODUCT CONSISTING ESSENTIALLY OF A MASS OF HOLOW SPHERES HAVING A WATER CONTENT LESS THAN 25 PERCENT, C. SUBJECTING SAID SPRAY DRIED PRODUCT TO FURTHER DRYING AT A TEMPERATURE BETWEEN ABOUT 70*-400*C FOR A TIME SUFFICIENT TO REDUCE THE MOISTURE CONTENT BELOW ABOUT 7 PERCENT AND AVOIDING INTUMESCENCE, AND D. RECOVERING A MASS OF GENERALLY HOLLOW CLOSED SPHERICAL PARTICCLES HAVING A BULK DENSITY OF ABOUT 2-20 LBS./FT.3 AND A PARTICLE SIZE WITHIN THE RANGE OF 10-400 MESH.

Claim 11

A SECOND AQUEOUS SOLUTION CONSISTING ESSENTIALLY OF 16 TO 18 PERCENT SODIUM PENTABORATE ON A WEIGHT BASIS, MAINTAINED AT A TEMPERATURE BETWEEN ROOM TEMPERATURE AND THE SOLUTION BOILING POINT, TO PRODUCE WITH AGITATION A HOMOGENEOUS THIRD AQUEOUS SOLUTION HAVING A SOLIDS CONCENTRATION OF 5 TO 35 PERCENT, A SODIUM PENTABORATE CONCENTRATION OF 6 TO 7 PERCENT AND A WEIGHT RATIO OF SODIUM PENTABORATE CONENTRATION OF 6 TO 7 PER 1.3:1 MAINTAINED AT A TEMPERATURE BELOW SAID THIRD SOLUTION BOILING POINT, B. SPRAYING DROPLETS OF SAID THIRD AQUEOUS SOLUTION INTO A DRYER UTILIZING AIR HAVING AN INLET TEMPERATURE BETWEEN 200*C AND 500*C WHILE MAINTAINING SAID DROPLETS ENTERING SAID DDRYER AT A TEMPERATURE BELOW SAID THIRD SOLUTION BOILING POINT AND RECOVERING A PRODUCT CONSISTING ESSENTIALLY OF A MASS OF HOLOW SPHERES HAVING A WATER CONTENT LESS THAN 25 PERCENT, C. SUBJECTING SAID SPRAY DRIED PRODUCT TO FURTHER DRYING AT A TEMPERATURE BETWEEN ABOUT 70*-400*C FOR A TIME SUFFICIENT TO REDUCE THE MOISTURE CONTENT BELOW ABOUT 7 PERCENT AND AVOIDING INTUMESCENCE, AND D. RECOVERING A MASS OF GENERALLY HOLLOW CLOSED SPHERICAL PARTICCLES HAVING A BULK DENSITY OF ABOUT 2-20 LBS./FT.3 AND A PARTICLE SIZE WITHIN THE RANGE OF 10-400 MESH.

Claim 12

A method according to claim 1 wherein the aqueous sodium silicate solution has an SiO2:Na2O ratio of between about 2.0:1 and 2.4:1.

Claim 13

A method according to claim 1 wherein said homogeneous third solution has a viscosity of 0.1 to 200 cp.

Claim 14

A method according to claim 1 wherein the spheres recovered in step B. have a water content of less than 20 percent.

Claim 15

A method according to claim 1 wherein the product recovered in step C. has a moisture content below 4 percent.

Claim 16

A method according to claim 1 wherein the drying step C. is carried out in two stages including a first stage maintained at a temperature between 70* and 200* C and a second stage maintained at a temperature between 200* and 400* C.