WO1999062628A1 - Stabilisation de dispersions de silice - Google Patents

Stabilisation de dispersions de silice Download PDF

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Publication number
WO1999062628A1
WO1999062628A1 PCT/US1999/011849 US9911849W WO9962628A1 WO 1999062628 A1 WO1999062628 A1 WO 1999062628A1 US 9911849 W US9911849 W US 9911849W WO 9962628 A1 WO9962628 A1 WO 9962628A1
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WO
WIPO (PCT)
Prior art keywords
amino
silica
dispersion
silica dispersion
water
Prior art date
Application number
PCT/US1999/011849
Other languages
English (en)
Inventor
Jeffrey P. Chamberlain
Richard J. Strittmatter
Original Assignee
Angus Chemical Company
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Angus Chemical Company filed Critical Angus Chemical Company
Priority to AU42156/99A priority Critical patent/AU4215699A/en
Publication of WO1999062628A1 publication Critical patent/WO1999062628A1/fr

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Classifications

    • CCHEMISTRY; METALLURGY
    • C01INORGANIC CHEMISTRY
    • C01BNON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B33/00Silicon; Compounds thereof
    • C01B33/113Silicon oxides; Hydrates thereof
    • C01B33/12Silica; Hydrates thereof, e.g. lepidoic silicic acid
    • C01B33/14Colloidal silica, e.g. dispersions, gels, sols
    • C01B33/146After-treatment of sols
    • C01B33/148Concentration; Drying; Dehydration; Stabilisation; Purification
    • C01B33/1485Stabilisation, e.g. prevention of gelling; Purification

Definitions

  • This invention relates generally to aqueous dispersions of fine particles of silica.
  • Such dispersions have many uses, including manufacture of ceramics, coatings, polishes, dentifrices, etc.
  • Silica dispersions characteristically thicken, that is, they are said to be "dilatan ' when subjected to shearing conditions, such as may occur in manufacturing processes. Consequently, it is important in many applications that the viscosity of the dispersion be reduced, and thickening or gelling be prevented.
  • Viscosity is commonly measured with the Brookfield instrument, in which a spindle is rotated at a given speed in the fluid being measured and the resistance correlated to viscosity. While many common liquids are classified as Newtonian, that is, they have a constant viscosity regardless of the shearing conditions applied, silica dispersions tend to become less viscous at first and then to become dilatant. Their viscosity appears to become lower as the shear stress is increased but, at some shear level, they gel and the viscosity increases substantially. This phenomenon is undesirable since gelling can cause problems in handling silica dispersions.
  • U.S. Patent No. 5,246,624 discloses a process for producing a stable dispersion containing more than 40% silica by first adding fumed silica to acidified water and then adding more water and raising the pH to between 7.0 and 12.0 by adding a stabilizer.
  • the patent examples show the use of HC1 to acidify the water and NH 4 OH as a base to raise the pH and stabilize the dispersion.
  • silica in the range of 0-3% AMP, the viscosity of an aqueous dispersion of silica was shown to steeply decline as more AMP was added.
  • pH an indicator of the stability of a silica dispersion.
  • a pH above 7 results when various bases are added to stabilize silica dispersions. Both inorganic and organic bases have been used. Of the organic bases, amines and amino alcohols are known. The art, however, seems to have failed to show how to select amines, or that there are significant differences among them.
  • the present inventor has examined the effect of amines and found that there are differences in their ability to maintain stable silica dispersions under high shear conditions, as will be discussed and demonstrated below.
  • the invention relates generally to the formation of stable aqueous silica dispersions.
  • silica dispersions which are not dilatant. that is, they do not gel even when subjected to high shear stress above about 10 Pa.
  • certain amino alcohols are capable of providing such dispersions.
  • Preferred amino alcohols are those selected from the group consisting of primary, secondary, and tertiary amines in which the nitrogen atom of the amine is bonded to a secondary or tertiary carbon atom.
  • Particularly preferred are amino alcohols defined by the following formula:
  • R 3 where R l5 R 2 and R 3 are independently H, C]-C 10 alkyl, C r C 10 alkanol, C[-C 6 cycloalkyl, C r C 6 cycloalkanol, aryl, or alkylaryl with the proviso that no more than one of R,, R 2 and R 3 is H; and R 4 and R 5 are independently H, C r C 10 alkyl, C r C 10 alkanol,
  • the invention is a stable silica dispersion in which an effective amount of the amino alcohols is used, in particular, in an amount between about 1-10 wt %, based on the amount of silica solids present.
  • an effective amount of the amino alcohols is used, in particular, in an amount between about 1-10 wt %, based on the amount of silica solids present.
  • Especially preferred amino alcohols are
  • the amount of silica present in dispersions according to the invention typically is about 1-30 wt % based on the water present, although greater or lesser amounts are believed to be possible.
  • the silica particles generally will have an effective diameter up to about 10 ⁇ m, typically 1.5 ⁇ m or less, which is within the range typically considered to provide colloidal suspensions.
  • the invention is a method of producing stable aqueous silica dispersions. Predetermined amounts of one or more of the selected amino alcohols are added to the amount of water which is required to provide the desired silica concentration. Then, the predetermined amount of silica particles is added with mixing to produce the stable silica dispersions.
  • the amino alcohols are those defined above.
  • the silica dispersion typically will contain about 1-30 wt % silica particles having an effective diameter up to 10 ⁇ m, typically 1.5 ⁇ m or less and about 1-10 wt % of the amino alcohols based on the amount of silica solids. Other additives, such as biocides, pH modifiers, and dispersants, may be included.
  • a stable silica dispersion is produced which remains non-dilatant even under high shear stress conditions above about 10 Pa. BRIEF DESCRIPTION OF THE DRAWINGS
  • Figure 1 is a graph of the effect of varying the concentration of various bases on the measured Brookfield viscosity.
  • Figure 2 is a bar chart comparing the stability of silica dispersions stabilized by various bases.
  • Figures 3A-O are graphs showing the effect of increasing shear stress on viscosity for various bases.
  • Figure 4 is a graph showing the maximum obtainable amount of silica solids without gellation of the dispersion.
  • Fine silica particles are used in many applications. Such particles may be made by several known methods, such as the vapor phase hydrolysis of chlorosilanes to produce fumed silica.
  • the particles may vary in size up to about 10 ⁇ m, typically they will be about 0.01-1.5 ⁇ m, in the range of colloidal suspensions.
  • the size of the particles is defined by their average effective diameter, the effective diameter being a known means for defining the size of irregular particles.
  • silica particles are substantially spherical and such particles may also be used in the method of the invention. It is not believed that the source of the silica particles is an important factor in the success of the method of the invention.
  • the amino alcohols of the invention are primary, secondary, or tertiary amines in which the nitrogen atom is bonded to a secondary or tertiary carbon atom.
  • they are defined by the following formula:
  • R,, R 2 and R 3 are independently H, C r C 10 alkyl, C r C 10 alkanol, C C 6 cycloalkyl, C r C 6 cycloalkanol, aryl, or alkylaryl with the proviso that no more than one of R,, R 2 and R 3 is H; and R 4 and R 5 are independently H, C r C 10 alkyl, C r C 10 alkanol, C r C 6 cycloalkyl, C C 6 cycloalkanol, aryl, or alkylaryl.
  • the amino alcohols just defined are superior to other amines and inorganic bases.
  • they are able to better prevent gelling of the silica dispersion under high shear stress conditions, that is, they maintain the silica suspension in a non-dilatant state where other bases fail to do so.
  • they improve the shelf life stability of the dispersions, that is, they maintain the fluidity of the dispersions during storage for longer periods than other bases.
  • 2-amino-2-methyl-propanol AMP
  • 2-amino-2-ethyl- 1,3-propanediol AEPD
  • 2-amino-2 -methyl- 1 ,3-propanediol AMPD
  • 2-amino-2- hydroxymethyl-l,3-propanediol TA
  • 2-amino-l-butanol AB
  • Silica dispersions have generally been made using a base in order to raise the pH and to stabilize a silica- water mixture.
  • Other materials may be added to improve the stability and useful life of the dispersion, such as biocides, pH modifiers, dispersants and the like known in the art.
  • inorganic bases such as KOH and NH 4 OH
  • organic bases such as amines and amino alcohols
  • the choice of base does affect the pH of the dispersion.
  • the pH does not, however, appear to be an indicator of the effectiveness of the base for purposes of this invention.
  • the amino alcohols of the invention provide dispersions with pH values generally lower than are provided by equal dosages of KOH or NH 4 OH.
  • the present inventor has examined the effect on silica dispersions of many bases, both inorganic and organic.
  • the inventor has determined the effect of a range of shear stress values on the viscosity of silica dispersions. He has found that silica dispersions show a decreasing viscosity with increasing amine concentration as measured by the Brookfield instrument, which is consistent with the disclosed performance in the Conley text mentioned above.
  • the inventor has also found, however, that with some bases, gelling occurs when the shear stress is further increased, that is, the silica dispersion becomes dilatant.
  • the amino alcohols of the invention When the amino alcohols of the invention are used to stabilize the silica dispersion, they are non-dilatant under stress conditions where other bases are unable to maintain a low viscosity and gelling occurs. Consequently, the amino alcohols of the invention provide the user with an improved silica suspension which remains fluid under high stress conditions and avoids gelling. It is believed that stress conditions of the Examples are typical of those encountered by silica dispersions in many of their applications. Consequently, it is important that they do not gel while being handled or used. Examples of shear stresses experienced in specific applications are shown in Table 1 (H. A. Barnes, J. F. Hutton and K. Walters, An Introduction To Rheology, Elesiever, Amsterdam, 1989, p. 13).
  • the concentration of dispersed silica particles is not especially limited so far as is currently known, the silica dispersions of the invention typically are those containing about 1-30 wt % silica based on the water present. Larger or smaller concentrations are believed to be feasible. It is believed that higher or lower silica concentrations would also be improved by use of the amino alcohols of the invention.
  • Silica dispersions may be made by first mixing the desired amount of the selected amino alcohol(s) to the amount of water required to yield the desired final concentration of silica in water. Typically, the amount of the amino alcohol(s) used will be in the range of about 1-10 wt % based on the amount of silica solids present. Thereafter, the desired amount of silica particles will be added and mixed with the amine and water to produce the final silica dispersion.
  • Dispersions of 10% (by weight) M5 Cab-O-Sil Fumed Silica were prepared by mixing the silica with water containing 2.5%, 5%, or 10% (by weight based on silica solids) of either 2-amino-2-methyl-l-propanol (AMP), 2-amino-2-hydroxymethyl-l,3- propanediol (Tris-Amino or TA), 2-amino-l-butanol (AB), 2-dimethylamino-2-methyl- 1-propanol (DMAMP), monoisopropanolamine (MiPA), dimethylethanolamine (DMEA), monoethanolamine (MEA), or triethanolamine (TEA).
  • the relative viscosity of each sample was then measured using a Brookfield viscometer, using spindle #3 at 60 rpm. The results are shown in Figure 1, which shows that monoethanolamine (MEA),
  • Dispersions of 10% (by weight) M5 Cab-O-Sil Fumed Silica were prepared by mixing the silica with water containing 2.5% (by weight based on silica solids) of either KOH, ammonia, monoethanolamine (MEA), monoisopropanolamine (MiPA), 2-amino- 2-methyl-l-propanol (AMP), 2-amino-l-butanol (AB), 2-dimethylamino-2-methyl-l,3- propanediol (DMAMPD), 2-dimethylamino-l-butanol (DMAB), 2-dimethylamino-2- methyl-1-propanol (DMAMP), diethanolamine (DEA), 2-amino-2-ethyl- 1,3 -propanediol (AEPD), 2-amino-2-hydroxymethyl- 1,3 -propanediol (Tris-Amino or TA), 2- dimethylamino-2-ethyl- 1 ,3-propan
  • EXAMPLE 3 Dispersions of 10% (by weight) M5 Cab-O-Sil Fumed Silica were prepared by mixing the silica with water containing 2.5% (by weight based on silica solids) of either 2-amino-2-methyl- 1 -propanol (AMP), 2-dimethy lamino-2-methy 1- 1 -propanol (DMAMP), monoethanolamine (MEA), triethanolamine (TEA), KOH, or ammonia. The following qualitative test for the stabilizing effects of the amines was then performed. The dispersion samples were stored in jars, undisturbed, on the shelf. Once daily, each jar was shaken rapidly up and down twice by hand, and the dispersions were examined to determine whether gellation had occurred.
  • AMP 2-amino-2-methyl- 1 -propanol
  • DMAMP 2-dimethy lamino-2-methy 1- 1 -propanol
  • MEA monoethanolamine
  • TEA triethanolamine
  • KOH
  • Dispersions of 10% (by weight) M5 Cab-O-Sil Fumed Silica were prepared by mixing the silica with water containing 1.25%, 2.5%, and 5.0% (by weight based on silica solids) of either 2-amino-2-methyl- 1 -propanol (AMP), monoethanolamine (MEA), KOH, ammonia, monoisopropanolamine (MiPA), 2-amino-l-butanol (AB), 2- dimethylamino-2-methyl-l ,3-propanediol (DMAMPD), 2-dimethylamino-l-butanol (DMAB), 2-dimethylamino-2-methyl-l -propanol (DMAMP), diethanolamine (DEA), 2- amino-2-ethy 1- 1 ,3-propanediol ( AEPD), 2-amino-2-hydroxymethyl- 1 ,3-propanediol (Tris-Amino or TA), 2-dimethylamino-2
  • viscosity as a function of shear stress was measured using a research-grade, controlled- stress air-bearing rheometer (TA Instruments ARIOOO).
  • a cone-and-plate geometry was used, wherein a small quantity of dispersion sample was poured onto a plate, and then a cone was lowered onto the sample.
  • the cone used had an angle of 1 :59:00 (degrees: minutes: seconds), and was truncated at the tip by 63 ⁇ m, so that the tip of the cone did not touch the plate, where it would interfere with the viscosity measurement.
  • the dispersion sample filled the gap between the cone and the plate.
  • the cone was then rotated at a controlled shear stress, and the rotational speed (or shear rate) was measured automatically by the rheometer by an optical coder. Viscosity was then calculated, and recorded as a function of shear stress.
  • a dispersion is deemed stable in high shear conditions by the results of the test described here. If the dispersion sample does not show severe shear-thickening effects, or gel, at shear stresses above about 20 Pa, then that dispersion is deemed to be stable in conditions of high shear.
  • viscosity is graphed as a function of shear stress.
  • the slope of a curve in such a graph is negative, the dispersion is shear-thinning.
  • the slope of a curve in such a graph is positive, the dispersion is shear-thickening or dilatant.
  • the viscosity of a dispersion increases at least five-fold as the shear stress is merely tripled (or less), the dispersion is said to have been severely dilatant, or to have gelled.
  • the samples appear to be severely shear-thickening at shear stresses above 10 Pa and then shear-thinning at shear stresses nearing 100 Pa, e.g., 2.5%
  • Fumed Silica were prepared by mixing the silica with water containing 5% (by weight based on silica solids) of either 2-amino-2 -methyl- 1 -propanol (AMP), 2-dimethylamino- 2-methyl-l-propanol (DMAMP), KOH, or ammonia. These dispersions were prepared to determine the maximum silica solid level obtainable by using such additives listed as a stabilizer. The maximum silica concentration was determined as the highest percent silica dispersion that could be prepared without gellation occurring during sample preparation. Notice in Figure 4 that the use of an amino alcohol, as opposed to ammonia or

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  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Dispersion Chemistry (AREA)
  • Inorganic Chemistry (AREA)
  • Colloid Chemistry (AREA)
  • Silicon Compounds (AREA)

Abstract

L'invention concerne des dispersions de silice stables aqueuses, que l'on peut produire en ajouter des quantités efficaces de certains amino-alcools primaires, secondaires, et tertiaires tels que définis dans cette invention. Ces dispersions se ne dilatent pas, même lorsqu'elles sont soumises à une contrainte élevée.
PCT/US1999/011849 1998-06-04 1999-05-28 Stabilisation de dispersions de silice WO1999062628A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU42156/99A AU4215699A (en) 1998-06-04 1999-05-28 Stabilization of silica dispersions

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US8792898P 1998-06-04 1998-06-04
US60/087,928 1998-06-04

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WO1999062628A1 true WO1999062628A1 (fr) 1999-12-09

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6612911B2 (en) 2001-01-16 2003-09-02 Cabot Microelectronics Corporation Alkali metal-containing polishing system and method
CN1305765C (zh) * 2001-01-09 2007-03-21 Az电子材料美国公司 具有中性pH的阴离子胶态二氧化硅含水悬浮液的制备方法和其应用
US7238618B2 (en) 2000-04-11 2007-07-03 Cabot Microelectronics Corporation System for the preferential removal of silicon oxide

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2601352A (en) * 1950-01-16 1952-06-24 Du Pont Silica sols and method of making same
US2799658A (en) * 1952-05-02 1957-07-16 Monsanto Chemicals Colloidal silica compositions
US2984629A (en) * 1957-11-04 1961-05-16 Cabot Corp Aqueous dispersions of pyrogenic silica
US3630954A (en) * 1969-05-08 1971-12-28 Du Pont Organic amine-strong base stabilized high surface area silica sols and method for preparing same
US5176752A (en) * 1991-07-31 1993-01-05 W. R. Grace & Co.-Conn. Stabilized microsilica slurries and cement compositions containing the same
US5221497A (en) * 1988-03-16 1993-06-22 Nissan Chemical Industries, Ltd. Elongated-shaped silica sol and method for preparing the same

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2601352A (en) * 1950-01-16 1952-06-24 Du Pont Silica sols and method of making same
US2799658A (en) * 1952-05-02 1957-07-16 Monsanto Chemicals Colloidal silica compositions
US2984629A (en) * 1957-11-04 1961-05-16 Cabot Corp Aqueous dispersions of pyrogenic silica
US3630954A (en) * 1969-05-08 1971-12-28 Du Pont Organic amine-strong base stabilized high surface area silica sols and method for preparing same
US5221497A (en) * 1988-03-16 1993-06-22 Nissan Chemical Industries, Ltd. Elongated-shaped silica sol and method for preparing the same
US5176752A (en) * 1991-07-31 1993-01-05 W. R. Grace & Co.-Conn. Stabilized microsilica slurries and cement compositions containing the same

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US7238618B2 (en) 2000-04-11 2007-07-03 Cabot Microelectronics Corporation System for the preferential removal of silicon oxide
US7365013B2 (en) 2000-04-11 2008-04-29 Cabot Microelectronics Corporation System for the preferential removal of silicon oxide
CN1305765C (zh) * 2001-01-09 2007-03-21 Az电子材料美国公司 具有中性pH的阴离子胶态二氧化硅含水悬浮液的制备方法和其应用
US6612911B2 (en) 2001-01-16 2003-09-02 Cabot Microelectronics Corporation Alkali metal-containing polishing system and method

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Publication number Publication date
AU4215699A (en) 1999-12-20

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