US5708069A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Method for making hydrophobic silica gels under neutral conditions
Assignee: Dow Silicones Corp
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Filing: 1997-02-24
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Granted: 1998-01-13
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Expires: 2017-02-24
Abstract
Abstract The present invention is hydrophobic silica gels and a method for their preparation under neutral conditions. The method comprises two steps, where in the first step the pH of a silica hydrosol is adjusted with a base to within a range of about pH 3 to pH 7 to facilitate formation of a silica hydrogel. In the second step the silica hydrogel is contacted with an organosilicon compound in the presence of a catalytic amount of a strong acid to effect hydrophobing of the silica hydrogel. In a preferred method, in a third step the hydrophobic silica gel is contacted with a sufficient quantity of a water-immiscible organic solvent to convert the hydrophobic silica hydrogel into a hydrophobic silica organogel.
Inventors
- 👤 Gary Thomas Burns
- 👤 Qin Deng
- 👤 James Richard Hahn
- 👤 Clifford Carlton Reese
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 13:31
CPC Classifications
C; C01; C01B; C01B33/00; C01B33/113; C01B33/12; C01B33/16; C08; C08K; C08K9/00; C08K9/04; C08K9/06; Y; Y10; Y10T; Y10T428/00; Y10T428/29; Y10T428/2913; Y10T428/2933; Y10T428/2962; Y10T428/2982; Y10T428/2991; Y10T428/2993; Y10T428/2995
Claims Analysis
Total Claims: 24
Claim 1
Independent Claim
216 words
A method for preparing a hydrophobic silica gel comprising: (A) adjusting the pH of a silica hydrosol comprising about 0.02 to 0.5 g of SiO 2 per milliliter with a base to within a range of about pH 3 to pH 7 at a temperature within a range of about 10° C. to 250° C. to facilitate formation of a silica hydrogel and (B) mixing the silica hydrogel with (1) a catalytic amount of a strong acid and (2) an organosilicon compound selected from the group consisting of organosilanes described by formula R.sup.2.sub.a H.sub.b SiX.sub.4-a-b and organosiloxanes described by formula R.sup.2.sub.n SiO.sub.(4-n)/2, where each R 2 is independently selected from a group consisting of hydrocarbon radicals comprising about 1 to 12 carbon atoms and organofunctional hydrocarbon radicals comprising about 1 to 12 carbon atoms, each X is independently selected from a group consisting of halogen and alkoxy radicals comprising 1 to 12 carbon atoms, a=0, 1, 2, or 3, b=0 or 1, a+b=1, 2, or 3 with the proviso that when b=1 then a+b=2 or 3, n is an integer of from 2 to 3 inclusive to form a hydrophobic silica hydrogel having a surface area within a range of about 100 m 2 /g to 850 m 2 /g as measured in the dry state.
Claim 2
Independent Claim
216 words
A method for preparing a hydrophobic silica gel comprising: (A) adjusting the pH of a silica hydrosol comprising about 0.02 to 0.5 g of SiO 2 per milliliter with a base to within a range of about pH 3 to pH 7 at a temperature within a range of about 10° C. to 250° C. to facilitate formation of a silica hydrogel and (B) mixing the silica hydrogel with (1) a catalytic amount of a strong acid and (2) an organosilicon compound selected from the group consisting of organosilanes described by formula R.sup.2.sub.a H.sub.b SiX.sub.4-a-b and organosiloxanes described by formula R.sup.2.sub.n SiO.sub.(4-n)/2, where each R 2 is independently selected from a group consisting of hydrocarbon radicals comprising about 1 to 12 carbon atoms and organofunctional hydrocarbon radicals comprising about 1 to 12 carbon atoms, each X is independently selected from a group consisting of halogen and alkoxy radicals comprising 1 to 12 carbon atoms, a=0, 1, 2, or 3, b=0 or 1, a+b=1, 2, or 3 with the proviso that when b=1 then a+b=2 or 3, n is an integer of from 2 to 3 inclusive to form a hydrophobic silica hydrogel having a surface area within a range of about 100 m 2 /g to 850 m 2 /g as measured in the dry state.
Claim 3
Dependent Claim
31 words
A method according to claim 1, where the pH of the silica hydrosol is adjusted by means of a base to within a range of about pH 3.5 to pH 6.
Claim 4
Dependent Claim
29 words
A method according to claim 1, where the temperature of the silica hydrosol during conduct of step (A) is within a range of about 75° C. to 150° C.
Claim 5
Dependent Claim
29 words
A method according to claim 1, where the temperature of the silica hydrosol during conduct of step (A) is within a range of about 90° C. to 110° C.
Claim 6
Dependent Claim
62 words
A method according to claim 1 further comprising aging the silica hydrogel of step (A) at a pH within a range of about pH 3.5 to pH 8 and a temperature within a range of about 0° C. to 250° C. for a period of time within a range of about 10 minutes to 76 hours prior to conduct of step (B).
Claim 7
Dependent Claim
61 words
A method according to claim 1 further comprising aging the silica hydrogel of step (A) at a pH within a range of about pH 6 to pH 7.5 and a temperature within a range of about 20° C. to 150° C for a period of time within a range of about 1 to 24 hours prior to conduct of step (B).
Claim 8
Dependent Claim
20 words
A method according to claim 1, where the temperature is within a range of about 80° C. to 130° C.
Claim 9
Dependent Claim
21 words
A method according to claim 1 further comprising shearing the silica hydrogel of step (A) prior to conduct of step (B).
Claim 10
Dependent Claim
27 words
A method according to claim 1, where the mixing of step (B) is conducted at a temperature within a range of about 30° C. to 150° C.
Claim 11
Dependent Claim
13 words
A method according to claim 1, where the organosilicon compound is an organosiloxane.
Claim 12
Dependent Claim
10 words
A method according to claim 10, where organosiloxane is hexamethyldisiloxane.
Claim 13
Dependent Claim
13 words
A method according to claim 1, where the organosilicon compound is an organosilane.
Claim 14
Dependent Claim
23 words
A method according to claim 12, where the organosilane is selected from the group consisting of vinylmethyldichlorosilane, vinyldimethylchlorosilane, hexenylmethyldichlorosilane, hexenyldimethylchlorosilane, dimethyldichlorosilane, and bis{3-(triethoxysilyl)propyl}tetrasulfide.
Claim 15
Dependent Claim
24 words
A method according to claim 1, where the organosilicon compound provides at least 0.04 organosilyl units per SiO 2 unit of the silica hydrogel.
Claim 16
Dependent Claim
30 words
A method according to claim 1 further comprising during the mixing of step (B) the presence of a surfactant which facilitates reaction of the organosilicon compound with the silica hydrogel.
Claim 17
Dependent Claim
31 words
A method according to claim 1 further comprising during the mixing of step (B) the presence of a water-miscible solvent which facilitates reaction of the organosilicon compound with the silica hydrogel.
Claim 18
Dependent Claim
34 words
A method according to claim 1 further comprising mixing the silica hydrogel with an effective amount of a heat stabilizing agent selected from the group consisting of water soluble compounds of cerium and iron.
Claim 19
Dependent Claim
26 words
A method according to claim 17, where the water soluble compound is selected from the group consisting of FeCl 3 and CeCl 3 .9H 2 O.
Claim 20
Dependent Claim
58 words
A method according to claim 1 further comprising (C) contacting the hydrophobic silica hydrogel with a sufficient quantity of a water-immiscible organic solvent to convert the hydrophobic silica hydrogel into a hydrophobic silica organogel having a surface area within a range of about 100 m 2 /g to 850 m 2 /g as measured in the dry state.
Claim 21
Dependent Claim
11 words
A hydrophobic silica gel prepared by the method of claim 1.
Claim 22
Dependent Claim
11 words
A hydrophobic silica gel prepared by the method of claim 5.
Claim 23
Dependent Claim
11 words
A hydrophobic silica gel prepared by the method of claim 8.
Claim 24
Dependent Claim
11 words
A hydrophobic silica gel prepared by the method of claim 17.
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