Dry, particulate, inorganic ultrafiltration membranes and the production thereof

Claim 2

A process for the production of a dry, inorganic ultrafiltration membrane comprising: (a) pretreating a microporous membrane support with a volatile liquid medium prior to the coating of said support with a membrane coating material, said liquid medium being non-solvating to said coating material and capable of drawing said coating material into said support and of desolvating said coating material; (b) coating the surface of said pretreated microporous membrane support with said membrane coating material; and (c) exposing the thus-coated membrane to a temperature capable of volatilizing said liquid medium to remove said liquid medium from the microporous membrane support and said membrane coating material, whereby the desolvation of said coating material prior to completion of removal of said liquid medium results in a shrinking of the coating material and the consequent filling, by said coating material, of voids produced as a result of said shrinking, thus avoiding the development of microscopic cracks that otherwise occur upon desolvation of the coated membrane, thereby forming an essentially crack-free mechanically and chemically stable membrane.

Claim 3

The process of claim 1 in which said pretreated membrane support is contacted with a suspension of said membranes coating material, said volatile liquid medium being miscible with said coating suspension.

Claim 4

The process of claim 2 in which said coating suspension comprises an aqueous suspension.

Claim 5

The process of claim 3 in which said support comprises a porous carbon tube and said coating material is coated on the inner surface of said tubing.

Claim 6

The process of claim 2 and including draining excess suspension from the surface of said membrane support, said exposing of the treated membrane to a temperature capable of volatilizing said liquid medium comprising air drying said membrane at a temperature of from about 15° C. to about 100° C.

Claim 7

The process of claim 5 and including firing the thus-treated membrane at a temperature of from about 25° C. to about 1500° C., said firing enhancing the stability of said membrane.

Claim 8

The process of claim 6 in which said firing temperature is from about 60° C. to about 1200° C.

Claim 9

The process of claim 7 in which said firing temperature is from about 400° C. to about 600° C.

Claim 10

The process of claim 7 in which said membrane coating material is taken from the group consisting of the oxides of the metals of Groups III-A, III-B, IV-A, IV-B, V-A, V-B, VI-B, VII-B and VIII, lanthanides and actinides.

Claim 11

The process of claim 9 in which said coating material comprises zirconia.

Claim 12

The process of claim 10 in which said zirconia has a particle size of from bout 5 mμ to about 10μ.

Claim 13

The process of claim 11 in which said particle size is from about 10 mμ to about 1μ.

Claim 14

The process of claim 10 in which said coating suspension comprises an aqueous suspension and said liquid medium comprises acetone.

Claim 15

The process of claim 13 in which said membrane support has a pore size of from about 5 mμ to about 40μ and a pore volume of from about 5% to about 60%.

Claim 16

The process of claim 14 in which said support comprises a porous carbon tube having a pore size of from about 100 mμ to about 2μ and a pore volume of from about 20% to about 40%.

Claim 17

The process of claim 13 in which said support comprises a porous carbon tubing and said coating material is coated on the inner surface of said tube.

Claim 18

The process of claim 2 in which said liquid medium comprises an alcohol or ketone volatile at a temperature of from about 15° C. to about 100° C.

Claim 19

The process of claim 17 in which said liquid medium comprises acetone.

Claim 20

A process for the production of a dry, inorganic ultrafiltration membrane comprising: (a) pretreating a microporous membrane support with a liquid medium comprising an alcohol or ketone volatile at a temperature of from about 15° C. to about 100° C.; (b) coating the surface of said pretreated microporous membrane support with a membrane coating material selected from the group consisting of the oxides of the metals of Groups III-A, III-B, IV-A, IV-B, V-A, V-B, VI-B, VII-B and VIII, lanthamides and actinides;

Claim 21

A process for the production of a dry, inorganic ultrafiltration membrane comprising: (a) pretreating a microporous membrane support with a liquid medium comprising an alcohol or ketone volatile at a temperature of from about 15° C. to about 100° C.; (b) coating the surface of said pretreated microporous membrane support with a membrane coating material selected from the group consisting of the oxides of the metals of Groups III-A, III-B, IV-A, IV-B, V-A, V-B, VI-B, VII-B and VIII, lanthamides and actinides;

Claim 22

(c) exposing the thus-coated membrane to a temperature capable of volatilizing said liquid medium to remove said liquid medium from the microporous membrane support and said membrane coating material, whereby the desolvation of said coating material prior to completion of removal of said liquid medium results in a shrinking of the coating material and the consequent filling, by said coating material, of voids produced as a result of said shrinking, thus avoiding the development of microscopic cracks that otherwise occur upon desolvation of the coated membrane, thereby forming an essentially crack-free mechanically and chemically stable membrane.

Claim 23

(c) exposing the thus-coated membrane to a temperature capable of volatilizing said liquid medium to remove said liquid medium from the microporous membrane support and said membrane coating material, whereby the desolvation of said coating material prior to completion of removal of said liquid medium results in a shrinking of the coating material and the consequent filling, by said coating material, of voids produced as a result of said shrinking, thus avoiding the development of microscopic cracks that otherwise occur upon desolvation of the coated membrane, thereby forming an essentially crack-free mechanically and chemically stable membrane.

Claim 24

A process for the production of a dry, inorganic ultrafiltration membrane comprising: (a) pretreating a porous carbon tube with a liquid medium comprising an alcohol or ketone volatile at a temperature of from about 15° C. to about 100° C., said porous carbon tube having a pore size of from about 100 mμ to about 2μ and a pore volume of from about 20% to about 40%; (b) coating the surface of said pretreated porous carbon tube with a membrane coating material selected from the group consisting of the oxides of the metals of Group III-A, III-B, IV-A, IV-B, V-A, V-B, VI-B, VII-B and VIII, lanthamides and actinides; (c) exposing the thus-coated carbon tube to a temperature capable of volatilizing said liquid medium to remove said liquid medium from the porous carbon tube and said membrane coating material whereby the desolvation of said coating material prior to completion of removal of said liquid medium results in a shrinking of the coating material and the consequent filling, by said coating material, of voids produced as a result of said shrinking, thus avoiding the development of microscopic cracks that otherwise occur upon desolvation of the coated membrane; and (d) firing the thus treated membrane at a temperature of from about 25° C. to about 1500° C., said firing enhancing the stability of said membrane.

Claim 25

A process for the production of a dry, inorganic ultrafiltration membrane comprising: (a) pretreating a porous carbon tube with a liquid medium comprising an alcohol or ketone volatile at a temperature of from about 15° C. to about 100° C., said porous carbon tube having a pore size of from about 100 mμ to about 2μ and a pore volume of from about 20% to about 40%; (b) coating the surface of said pretreated porous carbon tube with a membrane coating material selected from the group consisting of the oxides of the metals of Group III-A, III-B, IV-A, IV-B, V-A, V-B, VI-B, VII-B and VIII, lanthamides and actinides; (c) exposing the thus-coated carbon tube to a temperature capable of volatilizing said liquid medium to remove said liquid medium from the porous carbon tube and said membrane coating material whereby the desolvation of said coating material prior to completion of removal of said liquid medium results in a shrinking of the coating material and the consequent filling, by said coating material, of voids produced as a result of said shrinking, thus avoiding the development of microscopic cracks that otherwise occur upon desolvation of the coated membrane; and (d) firing the thus treated membrane at a temperature of from about 25° C. to about 1500° C., said firing enhancing the stability of said membrane.

Claim 26

A dry inorganic ultrafiltration membrane produced by the process defined in any one of claims 1, 19, 20 and 2 to 18, inclusive.