Claims
- 1. A porous, water-insoluble siliceous fiber characterized by having a cross-sectional diameter of 0.001 to 0.5 mm, and a cross-sectional shape in the form of a five to seven-sided polygon in which at least one side is concave, and an essential chemical composition corresponding to the formula
- (SiO.sub.2).sub.3.(H.sub.2 O).sub.x
- in which x is a fractional or whole number from 0 to 6.
- 2. The siliceous fiber of claim 1 which is further characterized by having a surface area of at least 10 m.sup.2 /g, a tensile strength of at least 5,000 lb/in.sup.2, and a density of 1.8 to 2.2 g/cc by flotation.
- 3. The siliceous fiber of claim 1 which is further characterized by having a surface area of at least 500 m.sup.2 /g.
- 4. The siliceous fiber of claim 3 which is further characterized by having a pore volume of at least 0.2 cc/g, an average pore diameter of 10-100 A, and a chemical composition in which x is a fractional or whole number from 0.5 to 6.
- 5. The siliceous fiber of claim 4 characterized by having a surface area of 550 to 1200 m.sup.2 /g.
- 6. The siliceous fiber of claim 5 characterized by having a cross-sectional diameter of 0.01 to 0.2 mm, a tensile strength of at least 5,000 lb/in.sup.2, and a density of 1.8 to 2.2 g/cc by flotation.
- 7. The siliceous fiber of claim 6 characterized by having a surface area of 550 to 1200 m.sup.2 /g, a pore volume of 0.2 to 0.75 cc/g, and an average pore diameter of 10 to 100 A.
- 8. A method of making porous, water-insoluble siliceous fibers which comprises directionally freezing a quiescent body of aqueous polysilicic acid which
- (1) has an SiO.sub.2 content of 0.5 to 20% by weight,
- (2) has a pH of 1 to 7, and
- (3) has polymerized to the point where fibers formed from it by directional freezing are water-insoluble, but has not cross-linked to the extent that it contains substantially less than 1 mole of H.sub.2 O for every three moles of SiO.sub.2,
- by subjecting it to a temperature of -5.degree. to -200.degree. C. whereby a solid-liquid interface advances through the body of polysilicic acid at a rate such that ice grows in a cellular substructure and siliceous fibers form parallel to the direction of advance of the interface; allowing the frozen mass to thaw; and isolating the resulting porous, water-insoluble siliceous fibers.
- 9. The method of claim 8 in which the body of polysilicic acid is subjected to a temperature of -10.degree. to -100.degree. C., and the solid-liquid interface advances through the body of polysilicic acid at the rate of at least 0.2 cm/hr.
- 10. The method of claim 9 in which the aqueous polysilicic acid has an SiO.sub.2 content of 4 to 15% by weight, and a pH of 3 to 6, and the solid-liquid interface advances through the body of polysilicic acid at the rate of at least 2 cm/hr.
- 11. The method of claim 10 in which the aqueous polysilicic acid has a pH of 4.5 to 6.
- 12. The method of claim 11 in which the body of polysilicic acid is in the form of a gel.
- 13. A sheet composed of siliceous fibers in accordance with claim 1.
- 14. The sheet of claim 13 in the form of felt.
- 15. The sheet of claim 13 in the form of paper.
CROSS-REFERENCE TO RELATED APPLICATION
This is a continuation-in-part of copending application Ser. No. 720,848 filed Sep. 7, 1976, now abandoned.
US Referenced Citations (4)
Continuation in Parts (1)
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Number |
Date |
Country |
Parent |
720848 |
Sep 1976 |
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