Improved electroconductive composition and process of preparation

Claim 2

An electroconductive composition which comprises amorphous silica or a silica-containing material in association with a two-dimensional network of antimony-containing tin oxide crystallites in which the antimony content ranges from 1 to about 30% by weight of the tin oxide.

Claim 3

The composition of Claim 1 in which the composition is a powder comprising shaped particles of amorphous silica, or a silica-containing material, or particles comprising an inert core material having an amorphous silica coating or a silica-containing coating, which are surface-coated with a two-dimensional conducting network of antimony-containing tin oxide crystallites.

Claim 4

The composition of Claim 2 in which the shaped particles have an aspect ratio of at least 2.

Claim 5

The composition of Claim 2 or Claim 3 in which the shaped particles are hollow shells of amorphous silica or a silica-containing material.

Claim 6

The composition of Claims 1, 2, 3 or 4 in which the silica-containing material is a composition selected from metal silicates, silica-containing glass, and material having an extensive co-valent network involving SiO₄ units.

Claim 7

The composition of Claims 1, 2, 3, 4 or 5 in which the silica-containing material is a silica-boria material.

Claim 8

In a polymeric carrier matrix, an elec­troconductive network comprising interconnecting shaped particles, said particles comprising an inert core material having a coating of silica or a silica-containing material and a surface coating of a two-dimensional conducting network of antimony-containing tin oxide crystallites in which the antimony is present in an amount of from 1 to about 30% by weight of the tin oxide.

Claim 9

In a polymeric carrier matrix, an elec­troconductive network comprising interconnecting shaped particles, said particles comprising an inert core material having a coating of silica or a silica-containing material and a surface coating of a two-dimensional conducting network of antimony-containing tin oxide crystallites in which the antimony is present in an amount of from 1 to about 30% by weight of the tin oxide.

Claim 10

In a polymeric carrier matrix, an electroconductive network comprising interconnecting shaped particles, said particles having a structure consisting essentially of a substrate of amorphous silica or a silica-containing material with a surface coating comprising a two-dimensional conducting network of antimony-containing tin oxide crystallites in which the antimony content ranges from 1 to about 30% by weight of the tin oxide.

Claim 11

In a polymeric carrier matrix, an electroconductive network comprising interconnecting shaped particles, said particles having a structure consisting essentially of a substrate of amorphous silica or a silica-containing material with a surface coating comprising a two-dimensional conducting network of antimony-containing tin oxide crystallites in which the antimony content ranges from 1 to about 30% by weight of the tin oxide.

Claim 12

The electroconductive network of Claim 7 or Claim 8 in which the polymeric carrier matrix is a film of paint.

Claim 13

The electroconductive network of Claim 7 or Claim 8 in which the polymeric carrier matrix is a fiber.

Claim 14

The composition of Claim 2 in which the core consists essentially of barium sulfate.

Claim 15

The composition of Claim 2 in which the core consists essentially of titanium dioxide.

Claim 16

An electroconductive composition as in any one of the preceding Claims 1-6 which contains up to about 10% by weight of one or more grain refiners selected from alkali metals, alkaline earth metals, transition metals and rare earth elements.

Claim 17

The composition of Claim 13 in which the grain refiners are selected from Ca, Ba, Sr, and Mg.

Claim 18

A process for preparing an electroconductive composition comprising amorphous silica or a silica-containing material in association with a surface coating comprising a two-dimensional conducting network of antimony-containing tin oxide crystallites which comprises the steps of: (a) providing a substrate of amorphous hydroxylated silica or a silica-containing material; (b) applying a coating layer consisting essentially of hydrous oxides of antimony and tin to the substrate surface; and (c) calcining the coated substrate at a temperature in the range of from 400° to 900°C.

Claim 19

A process for preparing an electroconductive composition comprising amorphous silica or a silica-containing material in association with a surface coating comprising a two-dimensional conducting network of antimony-containing tin oxide crystallites which comprises the steps of: (a) providing a substrate of amorphous hydroxylated silica or a silica-containing material; (b) applying a coating layer consisting essentially of hydrous oxides of antimony and tin to the substrate surface; and (c) calcining the coated substrate at a temperature in the range of from 400° to 900°C.

Claim 20

The process of Claim 15 in which the substrate of amorphous hydroxylated silica is provided by precipitating the silica from solution.

Claim 21

The process of Claim 15 in which the coated substrate is calcined at a temperature in the range of from 400° to 900°C in an oxygen-containing atmosphere.

Claim 22

The process of Claim 15 in which the amorphous hydroxylated silica or silica-containing substrate is provided by coating a finely divided core material with active silica or a silica-containing material.

Claim 23

The process of Claim 18 in which the core material is a carbonate selected from BaCO₃ and CaCO₃.

Claim 24

The process of Claim 18 in which the core material is selected from BaSO₄, CaSO₄ and TiO₂.

Claim 25

The process as in any one of Claims 19, 20 or 21 which includes the additional step of removing the core material.

Claim 26

The process as in any one of Claims 18-21 in which the core material is coated with active silica by: (a) suspending the core material in water and adding a source of active silica while maintaining the pH of the suspension at a value in the range of 8 to 11; and (b) neutralizing alkali contained in the source of silica by adding a dilute mineral acid to the suspension over a predetermined period of time based on the amount of silica present in the suspension.

Claim 27

The process of Claim 22 in which the mineral acid is selected from H₂SO₄, HCl, and HNO₃.

Claim 28

The process of Claim 22, in which the core material is removed by suspending the silica coated particles in water and adding a solvent in which the core material is soluble to the suspension.

Claim 29

A process as in any one of Claims 15-24 in which the coating layer of hydrous oxides of antimony and tin is applied to the silica substrate by: (a) preparing separate aqueous solutions of hydrolyzable tetravalent Sn and trivalent Sb salts; (b) combining the Sn and Sb salt solutions; and (c) adding the combined solution to a slurry of the silica substrate over a predetermined period of time while maintaining the pH of the slurry in the range of 1.5 to 3.5 and the temperature of the slurry in the range of from 25° to 100°C under continuous agitation.

Claim 30

The process of Claim 25 in which the salt solutions are added to a slurry which contains a concentration of up to 3 molar of a grain refiner or mixture of grain refiners selected from alkali metals, alkaline earth metals, transition metals, and rare earth elements.

Claim 31

The process of Claim 26 in which the train refiner is selected from Ca, Ba, Sr, Zn, and Mg.

Claim 32

An electroconductive composition which is a powder comprising shaped particles selected from BaSO₄, SrSO₄, CaSO₄, graphite, carbon, mica, and TiO₂ which are surface-coated with a two-dimensional conducting network of antimony-containing tin oxide crystallites, said particles containing at least about 100 parts per million of a grain refiner or mixture of grain refiners selected from alkali metals, alkaline earth metals, transition metals, or rare earth elements.

Claim 33

An electroconductive composition which is a powder comprising shaped particles selected from BaSO₄, SrSO₄, CaSO₄, graphite, carbon, mica, and TiO₂ which are surface-coated with a two-dimensional conducting network of antimony-containing tin oxide crystallites, said particles containing at least about 100 parts per million of a grain refiner or mixture of grain refiners selected from alkali metals, alkaline earth metals, transition metals, or rare earth elements.

Claim 34

The composition of Claim 28 in which the shaped particle is BaSO₄ and the grain refiner is Ca.

Claim 35

A process for preparing an electroconductive composition comprising shaped particles selected from BaSO₄, SrSO₄, CaSO₄, graphite, carbon, mica, and TiO₂ which are surface-coated with a two-dimensional conducting network of antimony-containing tin oxide crystallites and contain at least about 100 parts per million of a grain refiner or mixtur of grain refiners which comprises the steps of: (a) applying a coating layer to the particles consisting essentially of hydrous oxides of antimony and tin in the presence of a grain refiner, or mixture of grain refiners, selected from alkali metals, alkaline earth metals, transition metals, and rare earth metals; and (b) calcining the coated particles at a temperature of from 400° to 900°C in an oxygen-containing atmosphere.

Claim 36

A process for preparing an electroconductive composition comprising shaped particles selected from BaSO₄, SrSO₄, CaSO₄, graphite, carbon, mica, and TiO₂ which are surface-coated with a two-dimensional conducting network of antimony-containing tin oxide crystallites and contain at least about 100 parts per million of a grain refiner or mixtur of grain refiners which comprises the steps of: (a) applying a coating layer to the particles consisting essentially of hydrous oxides of antimony and tin in the presence of a grain refiner, or mixture of grain refiners, selected from alkali metals, alkaline earth metals, transition metals, and rare earth metals; and (b) calcining the coated particles at a temperature of from 400° to 900°C in an oxygen-containing atmosphere.

Claim 37

The process of Claim 30 in which the coating layer of hydrous oxides of antimony and tin is applied to the particles by: (a) preparing separate aqueous solutions of hydrolyzable tetravalent Sn and trivalent Sb salts; (b) combining the Sn and Sb salt solutions; and (c) adding the combined solution to a slurry of the particles over a predetermined period of time while maintaining the pH of the slurry in the range of 1.5 to 3.5 and the temperature of the slurry in the range of from 25°C to 100°C under continuous agitation.

Claim 38

The composition of Claims 1 or 2 in which the silica-containing material is mica.

Claim 39

The composition of Claim 8 in which the substrate consists essentially of mica.

Claim 40

The composition of Claim 2 in which the coating of amorphous silica or silica-containing coating is less than 20 nm and the conducting network of antimony-containing tin oxide crystallites is less than 20 nm.