Hollow microspheres with organosilicon-silicate surfaces

Claim 2

Hollow microspheres of 5 to 300 microns diameter with shells containing alkali metal silicate and a polysalt, said shells having an organosilicon-silicate surface, said polysalt being an inorganic salt of an alkali metal and/or ammonium cations wherein the anion to cation ratio is reduced when the salt is dissolved and becomes hydrolyzed, said alkali metal silicates having 1.5 to 4.0 moles of Si0 2 per mole of M 2 0 wherein M is sodium or potassium, and said organosilicon being the thermally and hydrolytically stable portion of an initial organosilicon compound having at least one thermally stable and non-hydrolyzable organic group and one or more reactive groups.

Claim 3

The hollow microspheres of claim 1 wherein the ratio of polysalt solids to silicate solids is between 0.02:1 and 3.0:1 and the organosilicon constitutes 0.01 to 4.0% by weight of said microspheres.

Claim 4

The hollow microspheres of claim 2 characterized in that: (a) the ratio of the true density to the bulk density is 1.2 to 1.9 with the true density being 0.05 to 0.90 g/cm and the bulk density being 0.02 to 0.24 g/cm ; (b) the porosity (%P) is 5 to 10% as calculated by the formula wherein ED is the effective density and has a value of 0.05 to 0.90 g/cm 3 and TD is the true density as recited in section 3.(a).

Claim 5

Hollow microspheres of 50 to 300 microns diameter with shells containing alkali metal silicate and a polysalt, said shells having an organosilicon-silicate surface, said microspheres being characterized in that: (a) the ratio of polysalt solids to silicate solids is between 0.02:1 and 3.0:1, said polysalt being an inorganic salt of an alkali metal and/or ammonium cations wherein the anion to cation ratio is reduced when the salt is dissolved and becomes hydrolyzed and said alkali metal silicates having 1.5 to 4.0 moles of Si0 2 per mole of M 2 0 wherein M is sodium or potassium; (b) the organosilicon constitutes 0.01 to 4.0% by weight of the microspheres, said organosilicon being the thermally and hydrolytically stable portion of an initial organosilicon compound having at least one thermally stable and non-hydrolyzable organic group and one or more reactive groups; (c) the ratio of true density to bulk density being between 1.2 and 1.9, the true density being 0.05 to 0.90 g/cm 3 and the bulk density being 0.05 to 0.24 g/cm ; (d) the porosity (%P) of 5 to 10% as calculated by the formula wherein ED is the effective density which has a value of 0.05 to 0.90 g/cm 3 and TD is the true density as recited in section 4.(c);

Claim 6

Hollow microspheres of 50 to 300 microns diameter with shells containing alkali metal silicate and a polysalt, said shells having an organosilicon-silicate surface, said microspheres being characterized in that: (a) the ratio of polysalt solids to silicate solids is between 0.02:1 and 3.0:1, said polysalt being an inorganic salt of an alkali metal and/or ammonium cations wherein the anion to cation ratio is reduced when the salt is dissolved and becomes hydrolyzed and said alkali metal silicates having 1.5 to 4.0 moles of Si0 2 per mole of M 2 0 wherein M is sodium or potassium; (b) the organosilicon constitutes 0.01 to 4.0% by weight of the microspheres, said organosilicon being the thermally and hydrolytically stable portion of an initial organosilicon compound having at least one thermally stable and non-hydrolyzable organic group and one or more reactive groups; (c) the ratio of true density to bulk density being between 1.2 and 1.9, the true density being 0.05 to 0.90 g/cm 3 and the bulk density being 0.05 to 0.24 g/cm ; (d) the porosity (%P) of 5 to 10% as calculated by the formula wherein ED is the effective density which has a value of 0.05 to 0.90 g/cm 3 and TD is the true density as recited in section 4.(c);

Claim 7

The hollow microspheres of either of claims 3 or 4 wherein said polysalt is ammonium pentaborate (APB), the weight ratio of APB solids to silicate solids being between 0.03:1 and 0.5:1; sodium pentaborate (SPB), the weight ratio of SPB solids to silicate solids being between 0.02:1 and 0.3:1; or sodium hexametaphosphate (SHP), the weight ratio of SHP solids to silicate solids being between 1:1 and 3:1.

Claim 8

The hollow microspheres of claim 4 wherein the weight ratio of APB solids to silicate solids is between 0.06:1 and 0.5:1.

Claim 9

The hollow microspheres of either of claims 1 or 4 wherein the initial organosilicon compound is represented by the formula: where n = 1 to 3, X represents Cl, Br, F or OR' and R' is from the family of aliphatic hydrocarbons and provides volatile products upon hydrolysis or thermal decomposition, and where R represents an alkyl, alkenyl or aryl group and their derivatives having varying functionalities but which remain thermally and hydrolytically stable and bound to the silicon.

Claim 10

The hollow microspheres of claim 7 wherein n = 1.

Claim 11

The hollow microspheres of either of claims 1 or 4 wherein the initial organosilicon compound is an organosilane.

Claim 12

The hollow microspheres of claim 9 wherein the organosilane is an alkylalkoxy silane or an arylalkoxy silane.

Claim 13

The hollow microspheres of claim 9 wherein the organosilane is selected from the group consisting of methyl-, ethyl-, propyl-, butyl-, vinyl- and phenyltriethoxysilane and methyl-, ethyl-, propyl-, butyl-, vinyl- and phenyl-tripropoxysilane.

Claim 14

The hollow microspheres of claim 9 wherein the organosilane is methyltrimethoxysilane.

Claim 15

The hollow microspheres of either of claims 1 or 4 wherein the initial organosilicon compound is represented by the formulas R 3 SiOSiR 3 , R 3 SINHSiR 3 or R n Si-H 4-n wherein R is an aliphatic hydrocarbon.

Claim 16

The hollow microspheres of claim 13 wherein R is methyl.

Claim 17

The hollow microspheres of any of claims 1, 4, 5, 7, 9 or 13 wherein said microspheres contain 10 to 17% by weight of moisture including chemically bound water.

Claim 18

The hollow microspheres of any of claims 1, 4, 5, 7, 9 or 13 wherein said microspheres contain 5 to 10 % by weight of moisture including chemically bound water.

Claim 19

The process of preparing hollow microspheres of 50 to 300 microns diameter with shells containing alkali metal silicate and a polysalt, said shells having an organosilicon-silicate surface, comprising the steps of: (a) forming a homogeneous solution of 0.02 to 3.0 parts by weight of a polysalt for each part by weight of an alkali metal silicate, said "polysalt" being an inorganic salt of an alkali metal and/or ammonium cations wherein the anipn to cation ratio is reduced when the salt is dissolved and becomes hydrolyzed, said alkali metal silicates having 1.5 to 4.0 moles of SiO 2 per mole of M 2 0, wherein M is sodium or potassium; (b) injecting said homogeneous polysalt-silicate solution into a spray dryer with an inlet temperature of about 150 to 500°C and an outlet temperature of about 100 to 400°C, and simultaneously injecting into said spray dryer a liquid containing an organosilicon compound through a separate injection device in close proximity to the injection point for the homogeneous polysalt-silicate solution, said organosilicon compound having at least one thermally stable and non-hydrolyzable organic group and one or more reactive groups; and (c) recovering the product from the spray dryer.

Claim 20

The process of preparing hollow microspheres of 50 to 300 microns diameter with shells containing alkali metal silicate and a polysalt, said shells having an organosilicon-silicate surface, comprising the steps of: (a) forming a homogeneous solution of 0.02 to 3.0 parts by weight of a polysalt for each part by weight of an alkali metal silicate, said "polysalt" being an inorganic salt of an alkali metal and/or ammonium cations wherein the anipn to cation ratio is reduced when the salt is dissolved and becomes hydrolyzed, said alkali metal silicates having 1.5 to 4.0 moles of SiO 2 per mole of M 2 0, wherein M is sodium or potassium; (b) injecting said homogeneous polysalt-silicate solution into a spray dryer with an inlet temperature of about 150 to 500°C and an outlet temperature of about 100 to 400°C, and simultaneously injecting into said spray dryer a liquid containing an organosilicon compound through a separate injection device in close proximity to the injection point for the homogeneous polysalt-silicate solution, said organosilicon compound having at least one thermally stable and non-hydrolyzable organic group and one or more reactive groups; and (c) recovering the product from the spray dryer.

Claim 21

The process of claim 17 wherein the product recovered from the spray dryer is further dried slowly at temperatures between 70 and 400°C.

Claim 22

The process of either of claims 17 or 18 wherein said polysalt is ammonium pentaborate (APB), the weight ratio of APB solids to silicate solids being between 0.03:1 and 0.5:1; sodium pentaborate (SP B ), the weight ratio of SPB solids to silicate solids being between 0.02:1 and 0.3:1; or sodium hexametaphosphate (SHP), the weight ratio of SHP solids to silicate solids being between 1:1 and 3:1.

Claim 23

The process of claim 19 wherein the initial organosilicon compound is represented by the formula: where n = 1 to 3, X represents Cl, Br, F or OR' and R' is from the family of aliphatic hydrocarbons and provides volatile products upon hydrolysis or thermal decomposition, and where R represents an alkyl, alkenyl or aryl group and their derivatives having varying functionalities but which remain thermally and hydrolytically stable and bound to the silicon.

Claim 24

The process of either of claims 17 or 18 wherein the organosilicon compound is an alkylalkoxysilane or an arylalkoxysilane selected from the group consisting of methyl-, ethyl-, propyl-, butyl-, vinyl- and phenyltriethoxysilane and methyl-, ethyl-, propyl-, butyl-, vinyl- and phenyl-tripropoxysilane.

Claim 25

The process of claim 21 wherein the alkylalkoxysilane is methyltrimethoxysilane.

Claim 26

The process of either of claims 17 or 18 wherein the organosilicon compound is represented by the formulas: or wherein R is an aliphatic hydrocarbon.

Claim 27

The process of claim 23 wherein R is methyl.

Claim 28

The process of either of claims 17 or 18 wherein the organosilicon compound is represented by the formulas: