Aqueous compositions of stabilized aminosilane group containing silica particles

Abstract

The present invention provides aqueous chemical mechanical planarization (CMP) polishing compositions have excellent heat aging and shelf stability in the form of concentrates comprising a mixture of a compound containing two quaternary ammonium groups, such as hexabutyl C.sub.1-C.sub.8 alkanediammonium dihydroxides or salts thereof, preferably N,N,N,N′,N′,N′-hexabutyl-1,4-butanediammonium dihydroxide (HBBAH), and aminosilane group containing silica particles in the amount of from 1 to 30 wt. % or, preferably, from 15 to 22 wt. %, as solids based on the total weight of the composition, the composition having a pH ranging from 3 to 5 or, preferably, from 3.5 to 4.5 wherein the composition is stable against visible precipitation or sedimentation at a 15 wt. % solids content after heat aging at a temperature of 45° C. for at least 6 days.

Claims

1. An aqueous chemical mechanical planarization (CMP) polishing composition comprising a mixture of a compound containing two quaternary ammonium groups, and aminosilane group containing silica particles containing one or more cationic nitrogen atom in the amount of from 1 to 30 wt. % as solids, based on the total weight of the composition, the composition having a pH ranging from 3 to 5, wherein the total amount of cationic nitrogen atoms from the aminosilane on the silica particles and the compound containing two quaternary ammonium groups ranges from 170 to 500 nM/m.sup.2 silica particles in the aqueous CMP polishing composition, and, further wherein, the composition is stable against visible precipitation or sedimentation at a 15 wt. % solids content after heat aging at a temperature of 45° C. for at least 6 days.

2. The aqueous chemical mechanical planarization (CMP) polishing composition as claimed in claim 1, wherein the compound containing two quaternary ammonium groups is chosen from hexabutyl C.sub.1-C.sub.8 alkanediammonium dihydroxides or salts thereof and the composition comprises no oxidizer compound.

3. The aqueous chemical mechanical planarization (CMP) polishing composition as claimed in claim 2, wherein the compound containing two quaternary ammonium groups is N,N,N,N′,N′,N′-hexabutyl-1,4-butanediammonium dihydroxide (HBBAH).

4. The aqueous chemical mechanical planarization (CMP) polishing composition as claimed in claim 1, wherein the aminosilane group containing silica particles comprise an aminosilane containing one or more tertiary amine groups or one or more secondary amine groups.

5. The aqueous chemical mechanical planarization (CMP) polishing composition as claimed in claim 4, wherein the aminosilane group containing silica particles comprise an aminosilane containing one or more tertiary amino group which is N,N-(diethylaminomethyl)triethoxysilane (DEAMS)).

6. The aqueous chemical mechanical planarization (CMP) polishing composition as claimed in claim 1, wherein the amount of aminosilane in nanomoles of cationic nitrogen atoms on the silica particle per square meter of silica particle surface area (nM/m.sup.2 silica) ranges from 70 to 500 nM/m.sup.2 silica in the aqueous CMP polishing composition.

7. The aqueous chemical mechanical planarization (CMP) polishing composition as claimed in claim 6, wherein the amount of aminosilane ranges from 100 to 300 nM/m.sup.2 silica.

8. The aqueous chemical mechanical planarization (CMP) polishing composition as claimed in claim 1, wherein the amount of the compound containing two quaternary ammonium groups ranges from 18 to 100 nM of the compound containing two quaternary ammonium groups per m.sup.2 of the silica particles (nM/m.sup.2 silica) in the aqueous CMP polishing composition.

9. The aqueous chemical mechanical planarization (CMP) polishing composition as claimed in claim 1, further comprising a buffer, which is a carboxylate of a (di)carboxylic acid having a pKa of 3 to 7 in the amount of from 0 to 50 millimoles per kg of the total composition.

10. The aqueous chemical mechanical planarization (CMP) polishing composition as claimed in claim 1, wherein the composition comprises aminosilane group containing silica particles in the amount of from 15 to 22 wt. %, as solids, based on the total weight of the composition.

11. The aqueous chemical mechanical planarization (CMP) polishing composition as claimed in claim 1, wherein the compositions comprise no oxidizer compound.

Description

EXAMPLES

(1) The following examples illustrate the various features of the present invention.

(2) In the Examples that follow, unless otherwise indicated, conditions of temperature and pressure are ambient temperature and standard pressure.

(3) The following materials were used in the Examples that follow:

(4) HBBAH=N,N,N,N′,N′,N′-hexabutyl-1,4-butanediammonium dihydroxide (Sachem, Austin, Tex.).

(5) AEAPS=N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, 98% (Gelest Inc., Morrisville, Pa.);

(6) DEAMS=(N,N-diethylaminomethyl)triethoxysilane, 98%, (Gelest Inc.);

(7) BMIC=1-butyl-3-methylimidazolium chloride, 98%, (Sigma-Aldrich, Milwaukee, Wis.);

(8) BTMAC=Benzyltrimethylammonium chloride, 98% (Sigma-Aldrich).

(9) The various silica particles used in the Examples are listed in Table A, below.

(10) TABLE-US-00001 TABLE A Silica particles Con- Aqueous Nominal centration Z-avg Silica D.sub.#.sup.2 SSA.sup.3 SSA.sup.4 (wt. % PS Slurry Source pH (nm) (m.sup.2/g) (m.sup.2/g) solids) (nm) Slurry A Klebosol ™.sup., 1 7.7 23.6 115 110 30 35.3 1598-B25 Slurry B Klebosol ™.sup., 1 7.7 15.4 177 200 30 28.4 1598-B12 Slurry C Klebosol ™.sup., 1 2.5 59.3 46 50 30 77.0 30H50 .sup.1Merck KgAA, Darmstadt, Germany. All particles are spherical and produced from sodium silicate raw materials. .sup.2Number average mean diameter by DLS. .sup.3Calculated as 2720/D.sub.#. .sup.4Reported specific surface areas from Merck KgAA for each product, not lot specific.

(11) The following abbreviations were used in the Examples that follow:

(12) POU: Point of use; RR: Removal rate; SA: Surface Area; SSA: Specific surface area.

(13) The following test methods were used in the Examples that follow:

(14) Initial pH and Aged pH: The “Initial pH” of compositions tested was that pH measured one time from the indicated concentrate compositions disclosed below at the time they were made; the “Aged pH” was measured one time after the time specified in the examples.

(15) pH at POU: The pH at point of use (pH at POU) was that measured during removal rate testing after dilution of the indicated concentrate compositions with water to the indicated solids content.

(16) Removal Rate: Removal rate testing from polishing on the indicated substrate was performed using the indicated polisher, such as a Strasbaugh 6EC 200 mm wafer polisher or “6EC RR” (San Luis Obispo, Calif.) or an Applied Materials Mirra™ 200 mm polishing machine or “Mirra RR” (Applied Materials, Santa Clara, Calif.), as indicated, at the indicated downforce and table and carrier revolution rates (rpm), and with the indicated CMP polishing pad and abrasive slurry at a 200 mL/min abrasive slurry flow rate. A Diagrid™ AD3BG-150855 diamond pad conditioner (Kinik Company, Taiwan) was used to condition the polishing pad. The CMP polishing pad was broken in with the pad conditioner using a down force of 6.35 kg (14.0 lb) for 20 minutes and was then further conditioned prior to polishing using a down force of 4.1 kg (9 lb) for 10 minutes. The CMP polishing pad was further conditioned in situ during polishing at 10 sweeps/min from 4.3 to 23.5 cm from the center of the polishing pad with a down force of 4.1 kg (9 lb). The removal rates were determined by measuring the film thickness before and after polishing using a KLA-Tencor FX200 metrology tool (KLA Tencor, Milpitas, Calif.) using a 49 point spiral scan with a 3 mm edge exclusion.

(17) Z-Average Particle Size: The Z-Average particle size of the indicated composition was measured by Dynamic Light Scattering (DLS) using a Malvern Zetasizer device (Malvern Instruments, Malvern, UK) calibrated per manufacturers recommendations. The z-Avg particle size is the intensity-weighted harmonic mean size, which is a diameter, as calculated by an ISO method. (ISO13321:1996 or its newer pendant ISO22412:2008). Measurements of particle size were done on diluted particle samples at pHs as described in each example.

(18) Zeta Potential: Zeta potential of the indicated compositions was measured by a Malvern Zetasizer instrument in the manner defined above. Measurements of zeta potential were done on compositions diluted to 1% w/w silica with a pH 3.5 solution, the compositions at or near a pH of 3.5.

(19) Formulation Examples: In general, the indicated silica slurry particles diluted in water were adjusted to a pH 4.25 using nitric acid. A 2-4% w/w solution of pre-hydrolyzed aminosilane in water at pH 4.25 was added to the particles to make the resulting slurry composition the indicated millimoles of silane per kg of silica solids (mM/kg silica solids). The pH of the slurry was maintained between 3.5 and 4.25 for 3 hrs, and the content of silica solids at this point was ˜18-24 wt. % of the total wet composition. The compositions were combined with the indicated amount of a compound containing two quaternary ammonium groups and, unless otherwise indicated, were aged at room temperature. Added amounts of quaternary or acid compounds in the tables below are given in units of millimolality (mm) using the total wet weight of the slurry, for example 3 millimoles of a compound in 1 kg of solution is 3 millimolal in compound. Specific formulating methods are detailed, below.

(20) Removal Rate Testing: The slurry concentrates were diluted to 4% w/w in water for removal rate testing with no subsequent pH adjustment. A Strasbaugh 6EC 200 mm wafer polisher was run at 20.7 kPa (3 psi) with a table speed of 93 rpm, and a substrate carrier speed of 87 rpm. To test performance, tetraethoxysilane (TEOS) wafers were polished at a flow rate of 200 mL/min. unless otherwise indicated, an IC1010™ pad from Dow Electronic Materials was used. The 1010™ pad is a urethane pad 80 mils thick with a shore D hardness of 57 (The Dow Chemical Company, Midland, Mich., (Dow)).

Example 1: Effects of Aminosilane Level on Heat Aging Stability

(21) The indicated compositions were allowed to sit for 13 calendar days before heat age testing was begun. Results are shown in Table 1, below.

(22) TABLE-US-00002 TABLE 1 Heat Aging Results at 50° C..sup.1 29 Day (42 Silica total days solids Aminosilane Initial including Example (wt. %) and amount.sup.2 HBBAH RT pH's 4 Day 7 Day 11 Day 14 Day sitting at RT) 1A 24% DEAMS 230 ppm 3.53 OK OK OK hazy Gelled (127) (PS = 118, Zeta = +22) 1B 24% DEAMS 230 ppm 3.55 OK OK OK OK slight Haze (152) (PS = 51, Zeta = +23) .sup.150° C. visual observation; no buffer was used; .sup.2nM/m.sup.2 silica surface area; *denotes comparative Example.

(23) TABLE-US-00003 TABLE 1B Total Cationic Nitrogen Atoms Weight Compound Total average Mono- Containing Two cationic silica amino- Quaternary nitrogen Silica specific silane Ammonium atom.sup.1 (wt. surface (nM/m.sup.2 Groups (nM/m.sup.2 Example %) area (m.sup.2/g) silica) (nM/m.sup.2 silica) silica) 1A* 24 115 127 18.1 145 1B 24 115 152 18.1 170 *-denotes comparative Example; 1. Monoanninosilane, dianninosilane, and diquaternary ammonium contribute 1, 2, and 1 ammoniums for stabilization respectively.

(24) In Example 1A, to form a hydrolyzed aqueous aminosilane, a solution of 3.7% w/w of DEAMS was adjusted to pH 4.25 using nitric acid to yield 4.2 grams of hydrolyzed DEAMS solution. Separately, 29.42 grams of DI water was mixed with 144.3 grams of Slurry A. The pH of the silica slurry was reduced to 4.25 using nitric acid. The hydrolyzed DEAMS solution was then added to the silica solution with mixing. After 30 minutes of reaction between the DEAMS and silica, 2.07 g of a 2% w/w solution of HBBAH (nitrate form) at pH 3.5 was added. The resulting slurry was pH adjusted to 3.5 for heat aging using nitric/KOH as needed. In Example 1B, the amount of hydrolyzed DEAMS added was increased to 5.04 g and the water was decreased correspondingly. After 29 days of aging, the heat aged samples were measured by DLS for zeta potential and particle size by diluting the slurries to 1% solids in a pH 3.5 solution. In order to obtain DLS measurements of Sample 1A, it was first resuspended (although gel did not break) by adding extra pH 3.5 nitric acid solution and sonicating in a water bath.

(25) As shown in Table 1, above, a sufficient level of DEAMS and HBBAH can prevent gelling over 4 weeks of storage at 50° C. at pH 3.5. The Examples 1A and 1B illustrate that raising the DEAMS level in the presence of HBBAH increases stability.

Example 2: Effect of Quaternary Ammonium on Heat Aging Stability

(26) To make a DEAMS (124 nM/m.sup.2 silica) slurry: 16.8 grams of DI water was mixed with 392 grams of Slurry A. The pH of the solution was reduced to 4.25 using nitric acid. To this mixture was added 11.2 grams of hydrolyzed DEAMS solution which was 3.7% w/w of the DEAMS monomer adjusted to pH 4.25 using nitric acid. After 30 minutes of reaction between the DEAMS and silica, the pH was adjusted to 4.0 using KOH and/or nitric acid. Aliquots of the DEAMS (124 nM/m.sup.2 silica) solution which was 28% w/w silica were then used to prepare solutions of DEAMS (124 nM/m.sup.2 silica) at 24% silica with added millimolal amounts of a quaternary ammonium and/or a carboxylic acid as shown in Table 2, below. The resulting slurries were pH adjusted to ˜4.1 for heat aging using nitric/KOH as needed.

(27) As shown in Table 2, below, HBBAH has the best stabilizing ability for the DEAMS (124 nM/m.sup.2 silica) aminosilane group containing silica particles when stored at pH 4.1. As shown in Table 2B, below, the amount of cationic nitrogen atoms per meter squared of silica is not sufficient to stabilize the compositions after 6 days of heat aging. In Comparative Examples 2G, and 2M, BMIC, containing one imidazolium group gives a composition that performs nearly as well as the inventive HBBAH compound in Comparative Examples 2B, 2K and 2L containing two quaternary ammonium groups, but requires double the loading and gels after 6 days when using sarcosine as a buffer at pH 4.1. It is believed the two succinic acid examples show that maintaining heat stability at pH 4.4 is more difficult than at a pH of 4.1.

(28) TABLE-US-00004 TABLE 2 Heat Aging Results for Various Quaternary Ammonium Compounds.sup.2 Heat EX- Initial aging Heat Heat AM- Buffer.sup.1 RT after 24 aging 2 aging 6 PLE QUAT (mm.sup.3) (mm) pH's hrs Days Days 2A* NONE None 4.30 gelled gelled gelled 2B* HBBAH None 4.06 OK Milky w gelled 0.5 mm slight (230 ppm) viscosity build 2C* Tetramethyl- None 4.06 slight gelled gelled guanidine haze 1 mm 2D* Carnitine None 4.05 slight gelled gelled 1 mm haze 2E* Choline 1 mm None 4.09 haze gelled gelled 2F* Acetyl Choline None 4.09 slight gelled gelled 1 mm haze 2G* BMIC 1 mm None 4.05 OK Milky w gelled slight viscosity build 2H* tetramethyl- None 4.09 OK gelled gelled ammonium 1 mm 2I* BTMAC 1 mm None 4.08 slight gelled gelled haze 2J* Bis(2-hydroxy None 4.1  slight gelled gelled ethyl)dimethyl haze ammonium 1 mm 2K* HBBAH Sarcosine 4.12 OK OK Milky, w 0.5 mm 0.5 mm viscosity build up 2L* HBBAH Succinic 4.4 Milky, but gelled gelled 0.5 mm 0.5 mm OK viscosity 2M* BMIC 1 mm Sarcosine 4.13 OK OK gelled 0.5 mm 2N* BMIC 1 mm Succinic 4.41 milky gelled gelled 0.5 mm .sup.1Sarcosine is n-methyl glycine; .sup.250° C. heat aging with visual observation; .sup.3Millimolal (mm) = Millimoles/kg total wet weight; *Denotes comparative Example.

(29) TABLE-US-00005 TABLE 2B Total Stabilizing Cationic Nitrogen Atoms Weight Total average silica Diamino- Diquaternary cationic specific Monoamino- silane ammonium nitrogen Silica surface area silane (nM/m.sup.2 or Quat atoms.sup.1 Example (wt. %) (m.sup.2/g) (nM/m.sup.2 silica) silica) (nM/m.sup.2 silica) (nM/m.sup.2 silica) 2B* 24 115 124 0 18.1 142 2K* 24 115 124 0 18.1 142 2L* 24 115 124 0 18.1 142 2G*, 24 115 124 0 36.2.sup.2 160 2M*, 2N* *denotes comparative Example; .sup.1Monoaminosilane, diaminosilane, and diquaternary ammonium contribute 1, 2, and 1 cationic nitrogen atoms, respectively; .sup.2Reflects concentration of quat because twice as much is used; quat has one cationic nitrogen atom.

Example 3: Effect of HBBAH Level on Heat Aging

(30) To make a DEAMS (156 nM/m.sup.2 silica) slurries in 3A to 3F: 4.66 grams of DI water was mixed with 130.66 grams of Slurry A. The pH of the solution was reduced to 4.25 using nitric acid. To this mixture was added 4.67 grams of hydrolyzed DEAMS solution which was 3.7% w/w of the DEAMS monomer adjusted to pH 4.25 using nitric acid. After 60 minutes of reaction between the DEAMS and silica, the pH was adjusted to 4.0 using KOH and/or nitric acid. In Comparative Example 3A, the particle size of the DEAMS (156 nM/m.sup.2 silica) solution without undergoing heat aging (storing at room temperature for 6 days) and without extra additives was 36.91 nm (Z-avg), measured at 1% solids and pH 3.5.

(31) For DEAMS (154 nM/m.sup.2 silica) slurries in 3G to 3L: 4.20 grams of DI water was mixed with 104.53 grams of Slurry A and 26.13 g of Slurry B. This gave an 80/20 mixture by weight, which had a weight averaged silica SSA of 127 m.sup.2/g. The pH of the solution was reduced to 4.25 using nitric acid. To this mixture was added 5.13 grams of hydrolyzed DEAMS solution which was 3.7% w/w of the DEAMS monomer adjusted to pH 3.5 using nitric acid. After 20 minutes of reaction, the pH was adjusted to 4.2. After 60 minutes of reaction between the DEAMS and silica, the pH was adjusted to 4.0 using KOH and/or nitric acid.

(32) Aliquots of the DEAMS (156 nM/m.sup.2 silica) or (154 nM/m.sup.2 silica) compositions with 28% w/w silica were then used to prepare slurries at 24 wt. % silica solids with the indicated added millimolal amounts of a quaternary ammonium and/or a carboxylic acid as shown in Table 3. The resulting slurries were pH adjusted to 4.1 for heat aging using nitric/KOH as needed, and aged at 50° C. for 6 days. Visual observations were made, and the solutions which had not significantly thickened were measured for particle size by diluting to 1% solids using pH 3.5 nitric acid solution and measuring at pH 3.5. Measurements of pH (noted with ^) for gelled examples were obtained by adding some water and sonicating to disperse the gel. The gel did not redisperse, but was liquified enough for a pH measurement.

(33) TABLE-US-00006 TABLE 3 Effect of Concentration of Compound Containing Two Quaternary Ammonium Groups and Solids Content Heat Aqueous Silane Initial aging.sup.1 Particle Silica (nM/m.sup.2 QUAT Buffer RT Final (6 size (Z- EXAMPLE Slurry silica) (mm.sup.1) (mm.sup.1) pH's pH Days) avg, nm) 3A* A DEAMS NONE none 4.09 4.41 Hazy 106.00 (156) 3B A DEAMS HBBAH 0.5 none 4.09 4.47 clear 38.95 (156) mm (230 ppm) 3C A DEAMS HBBAH 0.7 none 4.08 4.42 Clear 38.42 (156) mm (323 ppm) 3D A DEAMS HBBAH 0.9 none 4.1 4.44 Clear 38.00 (156) mm (415 ppm) 3E A DEAMS HBBAH 0.7 Sarcosine 4.1 4.4 Clear 40.00 (156) mm (323 5 mm ppm) 3F A DEAMS HBBAH 0.7 Acetic 4.11 4.16 Clear 41.67 (156) mm (323 Acid 5 ppm) mm 3G* A and B DEAMS None None 4.09 4.44 Gelled — (154) 3H* A and B DEAMS HBBAH 0.5 None 4.09 {circumflex over ( )}4.45 Gelled — (154) mm (230 ppm) 3I* A and B DEAMS HBBAH 0.7 None 4.09 {circumflex over ( )}4.42 viscous — (154) mm (323 gelling ppm) 3J A and B DEAMS HBBAH 0.9 None 4.08 {circumflex over ( )}4.43 viscous — (154) mm (415 ppm) 3K A and B DEAMS HBBAH 0.7 Sarcosine 4.07 {circumflex over ( )}4.33 viscous — (154) mm (323 5 mm gelling ppm) 3L* A and B DEAMS HBBAH 0.7 Acetic 4.1 {circumflex over ( )}4.1 Gelled — (154) mm (323 Acid 5 ppm) mm *Denotes comparative Example; .sup.1Millimolal (mm) = Millimoles/kg total wet weight of composition.

(34) TABLE-US-00007 TABLE 3B Total Stabilizing Cationic Nitrogen Atoms Weight Total average silica Diamino- cationic specific Monoamino- silane Diquaternary nitrogen Silica surface area silane (nM/m.sup.2 (nM/m.sup.2 ammonium atoms.sup.1 Example (wt. %) (m.sup.2/g) silica) silica) (nM/m.sup.2 silica) (nM/m.sup.2 silica) 3A* 24% 115 156 0 0 156 3B 24% 115 156 0 18.1 174 3C 24% 115 156 0 25.4 181 3D 24% 115 156 0 32.6 189 3E 24% 115 156 0 25.4 181 3F 24% 115 156 0 25.4 181 3G* 24% 127 154 0 0 154 3H* 24% 127 154 0 16.4 170 3I* 24% 127 154 0 23.0 177 3J 24% 127 154 0 29.5 184 3K 24% 127 154 0 23.0 177 3L* 24% 127 154 0 23.0 177 *denotes comparative Example; .sup.1Monoaminosilane, diaminosilane, and diquaternary ammonium contribute 1, 2, and 1 ammoniums for stabilization respectively.

(35) Tables 3 and 3B, above, show that increasing the level of the compound containing two quaternary ammonium groups at a 24 wt. % loading of aminosilane group containing silica particles provides greater protection against gelling during heat aging for both the Slurry A mixtures and the Slurry A/B mixtures. Tables 3A and 3B also show that the preferred or most effective level of a compound containing two quaternary ammonium groups and aminosilane increases for silica particles, such as those in Slurry B, having a larger surface area. Finally, in Example 3J, the Examples show that addition of an increasing amount of the compound containing two quaternary ammonium groups can improve the heat aging stability. In Comparative Examples 3H, 3I and 3L, a particle solids content of 24% makes stabilization difficult unless there are more than 25 nM/m.sup.2 silica of a compound containing two quaternary ammonium groups, as in Example 3J or an effective buffer is used at a preferred pH, as in Example 3K.

Example 4: Effect of Compound Containing Two Quaternary Ammonium Groups with and without Acetate Buffer

(36) To make the DEAMS (140 nM/m.sup.2 silica) slurry at 28% w/w silica: 12.83 grams of DI water was mixed with 326.66 grams of Slurry A. The pH of the solution was reduced to 4.25 using nitric acid. To this mixture was added 10.50 grams of hydrolyzed DEAMS solution which was 3.7% w/w of the DEAMS monomer adjusted to pH 4.25 using nitric acid. After 30 minutes of reaction between the DEAMS and silica, the pH was adjusted to 4.3 using KOH and/or nitric acid. The particle size of the aminosilane group containing silica particles (140 nM/m.sup.2 silica) in the Examples 4A to 4S after 30 minutes at room temperature and without extra additives was 36.51 nm (Z-avg, done at 1 wt. % solids and pH 3.5). Aliquots of the DEAMS (140 nM/m.sup.2 silica) solution were then used to prepare solutions at 24 wt. % aminosilane group containing silica particle solids with added millimolal amounts of a quaternary ammonium and/or acetic acid as shown in Tables 4A and 4B, below. The resulting slurries were pH adjusted to 4.2-4.3 for heat aging using nitric/KOH, as needed, and aged at 50° C. for 6 days.

(37) TABLE-US-00008 TABLE 4A Heat Aging.sup.1 without a Buffer 6 day Acetic Initial Heat Heat 6 Particle acid RT aging aging day size (Z- EXAMPLE QUAT (mm) (mm.sup.2) pH's (2 day) (6 Day) pH avg, nm) 4A* NONE none 4.33 Gelled gelled 4B HBBAH 0.5 mm none 4.30 OK OK, 4.78 105.9 clear 4C HBBAH 0.9 mm none 4.27 OK OK, 4.73  58.19 clear 4D* N,N,N′,N′- none 4.34 gel gelled tetrannethylguanidine 0.9 mm 4E* Carnitine 0.9 mm none 4.26 thickened gelled 4F* 1-butyl-3- none 4.31 thickened milky, methylimidazoliunn very chloride 0.9 mm viscous 4G* 1-butyl-3- none 4.27 OK OK, 4.71  89.44 methylimidazoliunn clear chloride 2 mm 4H* Tetramethylammonium none 4.35 Gel gelled hydroxide 0.9 mm 4H-1* Benzyltrimethylammonium none 4.34 Gel gelled chloride 0.9 mm .sup.150 = C. visual observation; .sup.2Millimolal (mm) = Millimoles/kg total wet weight; *Denotes comparative Example.

(38) TABLE-US-00009 TABLE 4B Heat Aging.sup.1 with a Buffer Acetic Initial Heat Heat 6 6 day acid RT aging.sup.2 (2 aging.sup.2 (6 day Particle size EXAMPLE QUAT (mm.sup.1) (mm.sup.1) pH's day) Day) pH (Z-avg, nm) 41* NONE 0.4 mm 4.34 gelled gelled 4J HBBAH 0.5 mm 0.4 mm 4.34 OK OK, clear 4.67 89.57 4K HBBAH 0.9 mm 0.4 mm 4.30 OK OK, clear 4.63 53.87 4L* N,N,N′,N′- 0.4 mm 4.34 thickened milky, tetramethylguanidine 0.9 very mm viscous 4M* Carnitine 0.9 mm 0.4 mm 4.30 thickened milky, very viscous 4N* Carnitine 2 mm 0.4 mm 4.20 milky OK, clear 4.38 109.9 4O* 1-butyl-3- 0.4 mm 4.30 milky OK, 4.60 116 methylimidazolium somewhat chloride 0.9 mm clear 4P* 1-butyl-3- 0.4 mm 4.32 OK OK, clear 4.63 83.41 methylimidazolium chloride 2 mm 4Q* Tetramethylammonium 0.4 mm 4.32 gel gelled hydroxide 0.9 mm 4R* Tetramethylammonium 0.4 mm 4.33 thickened milky, hydroxide 2 mm very viscous 4S* Benzyltrimethylammonium 0.4 mm 4.33 thickened milky, chloride 0.9 mm very viscous .sup.1Millinnolal (mm) = Millimoles/kg total wet weight; .sup.250° C. visual observation; *Denotes comparative Example.

(39) TABLE-US-00010 TABLE 4C Total Stabilizing Cationic Nitrogen Atoms Total Weight average Diamino- cationic silica specific Monoamino- silane Diquaternary nitrogen Silica surface area silane (nM/m.sup.2 ammonium atoms.sup.1 Example (wt.%) (m.sup.2/g) (nM/m.sup.2 silica) silica) (nM/m.sup.2 silica) (nM/m.sup.2 silica) 4B 24% 115 140 0 18.1 158 4C 24% 115 140 0 32.6 173 4J 24% 115 140 0 18.1 158 4K 24% 115 140 0 32.6 173 *Denotes comparative Example; .sup.1Monoaminosilane, diaminosilane, and diquaternary ammonium contribute 1, 2, and 1 ammoniums for stabilization, respectively.

(40) As shown in Tables 4A and 4B, above, HBBAH in Examples 4B, 4C, 4J and 4K provides the best results for heat aging at 50° C., including providing the least particle growth relative to other quaternary ammoniums. In Comparative Examples 4G, 4N, 4O and 4P, BMIC can stabilize the compositions when used in unbuffered compositions at more than double the amount of HBBAH used; and, in buffered compositions, only when used at four times the amount as HBBAH (see Ex. 4J), can BMIC stabilize and carnitine nearly stabilize the slurry compositions after 6 days. These Examples, also demonstrate that a small amount of acetic acid as a carboxylate buffer can improve heat aging results somewhat by maintaining a lower z-average particle size.

Example 5: Effect of DEAMS on Aging

(41) To make a DEAMS (181 nM/m.sup.2 silica) slurry Example 5A: 1166.63 grams of DI water was mixed with 5599.94 grams of Slurry A. The pH of the solution was reduced to 4.25 using nitric acid. To this mixture was added 233.43 grams of hydrolyzed DEAMS solution which was 3.7% w/w of the DEAMS monomer adjusted to pH 4.25 using nitric acid. After 180 minutes of reaction between the DEAMS and silica, the pH was adjusted to 4.1 using KOH and/or nitric acid. For DEAMS (181 nM/m.sup.2 silica) Example 5B, the same procedure was used but HBBAH (nitrate form) was added after 180 min to make the slurry 0.7 mm in HBBAH. For DEAMS (181 nM/m.sup.2 silica) Example 5C, the same procedure was used but the monoacetate/mononitrate form of HBBAH was added after 180 min to make the slurry 0.7 mm in HBBAH and 0.7 mm in acetate. The results of heat aging at 45° C. are shown in TABLE 5A, below. Particle size measurements were done by diluting the slurry concentrates to 1% solid solutions with water.

(42) TABLE-US-00011 TABLE 5A Heat Aging at 45° C. Initial Day 7 Day 14 Day 28 HBBAH Initial 14 PS (Z- PS (Z- PS (Z- PS (Z- (nM/m.sup.2 Buffer RT 7 day day 28 day avg, avg, avg, avg, Example silica SA) (mm.sup.2) pH's pH pH pH nm) nm) nm) nm) 5A* NONE* none 4.08 4.51 4.63 gelled.sup.1 39.4 120 380 gelled.sup.1 5B HBBAH none 4.12 4.32 4.48 4.46 38.8 62.6 75.8 156.4 25.4 (323 ppm) 5C HBBAH Acetic 4.15 4.37 4.53 4.56 38.8 65.3 67.8 189.6 25.4 acid (323 ppm) 0.7 mm .sup.1visual observation; .sup.2Millinnolal (mm) = Millimoles/kg total wet weight; *Denotes comparative Example.

(43) TABLE-US-00012 TABLE 5B Polish of SiO2 surface (TEOS) on Strasbauch 6EC Removal Rate Removal Rate of QUAT of SiO.sub.2- no heat SiO.sub.2- 3 weeks aging Example (ppm) aging (Ang/min) at 45 C. (Ang/min) 5A* NONE* 2062 gelled 5B HBBAH (323 ppm) 2116 1984 5C HBBAH (323 ppm) 2109 2011 1. Millinnolal (mm) = Millimoles/kg total wet weight; *-Denotes comparative Example

(44) TABLE-US-00013 TABLE 50 Total Stabilizing Cationic Nitrogen Atoms Total Weight average Diamino- cationic silica specific Monoamino- silane Diquaternary nitrogen Silica surface area silane (nM/m.sup.2 ammonium atoms.sup.1 Example (wt. %) (m.sup.2/g) (nM/m.sup.2 silica) silica) (nM/m.sup.2 silica) (nM/m.sup.2 silica) 5A* 24 115 181 0 0 181 5B 24 115 181 0 25.4 206.4 5C 24 115 181 0 25.4 206.4 *denotes comparative Example; .sup.1Monoaminosilane, diaminosilane, and diquaternary ammonium contribute 1, 2, and 1 ammoniums for stabilization respectively.

(45) As shown in Table 5A, above, there is pH drift as the particle slurry ages. The presence of a small amount of acetate buffer doesn't affect the pH drift in a significant way in this example. However, in Examples 5B and 5C, the addition of HBBAH to the DEAMS-silica particles dramatically slows both particle size growth (z-average) and pH drift. As shown in Table 5B, above, the compositions of the present invention having a small amount of a buffer in Example 5C maintains its removal rate after heat aging for 3 weeks. The composition of Example 5B only lost from 6-7% of its removal rate after heat aging for 3 weeks. No removal rate data are available for the composition of Comparative Example 5A because that composition had gelled after heat aging for 3 weeks.

Example 6: Stabilizing Effect of HBBAH on Mixtures of Two Silica Particles

(46) For DEAMS (199 nM/m.sup.2 silica) slurries in Examples 6A to 6J: 32.66 grams of DI water was mixed with 160 grams of Slurry A. The pH of the solution was reduced to 4.25 using nitric acid. To this mixture was added 7.34 grams of hydrolyzed DEAMS solution which was 3.7% w/w of the DEAMS adjusted to pH 4.25 using nitric acid. After each of 10 and 60 minutes of reaction between the DEAMS and silica of Slurry A, the pH was adjusted to 4.2 using KOH and/or nitric acid. After 18 hours, the particles were adjusted to pH 3.5 using nitric and stored for 7 days.

(47) The slurries in Table 6, below, were prepared by mixing the DEAMS-Slurry A (199 nM/m.sup.2 silica) slurries after storage for 7 days with DI water and Slurry B particles (adjusted to pH 4.3 with glacial acetic acid). The slurries in Table 6 were made to have 18.6% w/w of Slurry A-DEAMS (199 nM/m.sup.2 silica) particles, 1.4% w/w of the pH-adjusted Slurry B particles, and the amounts of extra HBBAH bisacetate salt and acetic acid. The weight average surface area of the Slurry A+B compositions was 119 m.sup.2/g, reducing the mixture to a total of 192 nM DEAMS per m.sup.2 of silica. The final pH of the concentrated particle slurries was set to be ˜4.4 for heat aging studies using acetic acid or KOH to make the final pH adjustment. Heat aging was conducted for 27 days in a 50° C. oven. The starting particle size of the mixed particle system (Slurry A+B) before heat aging and without other additives was measured at 33.29 nm (Z-avg) at pH 4.4 and 1% solids. Particle sizes in Table 6 were measured by DLS at concentrations of 1% solids at pH 4.4. The total amounts of cationic nitrogen atoms are shown in Table 6B, below.

(48) TABLE-US-00014 TABLE 6 Heat Aging1 Of Mixed Aqueous Silica Slurry Heat HBBAH Extra Heat aging.sup.1 Heat EX- bisacetate acetic Initial aging.sup.1 15 Heat 27 day aging AM- (nM/m.sup.2 acid RT day PS.sup.2 aging.sup.1 PS.sup.2 (Z- 27 day PLE silica SA) (mm.sup.3) pH's (Z-avg) 15 day pH avg) pH 6A* 0 0 4.43 56.95 4.60 123.90 4.54 6B 33.6 0 4.44 43.74 4.56 62.00 4.48 (369 Ppm) 6C 33.6 1 4.53 46.05 4.55 65.59 4.45 6D 33.6 2 4.41 44.34 4.52 62.20 4.44 (369 Ppm) 6E 33.6 5 4.40 54.72 4.48 80.40 4.43 6F 39.9 0 4.44 43.22 4.56 57.22 4.51 6G 39.9 2 4.42 47.14 4.52 66.31 4.49 6H 46.2 0 4.45 42.52 4.56 57.92 4.51 6I 68.5 0 4.46 44.38 4.55 58.23 4.49 (751 ppm) 6J 92.4 0 4.46 45.39 4.54 60.90 4.54 .sup.150° C. aging; .sup.2Particle size in nm; .sup.3Millinnolal (mm) = Millimoles/kg total wet weight; *Denotes comparative Example.

(49) TABLE-US-00015 TABLE 6B Total Stabilizing Cationic Nitrogen Atoms Weight average Monoamin Diamino- Total cationic silica specific o-silane silane Diquaternary nitrogen Silica surface area (nM/m.sup.2 (nM/m.sup.2 ammonium atoms.sup.1 (nM/m.sup.2 Example (wt. %) (m.sup.2/g) silica) silica) (nM/m.sup.2 silica) silica) 6A* 20% 119 192 0 0 192 6B 20% 119 192 0 33.6 226 6C 20% 119 192 0 33.6 226 60 20% 119 192 0 33.6 226 6E 20% 119 192 0 33.6 226 6F 20% 119 192 0 39.9 232 6G 20% 119 192 0 39.9 232 6H 20% 119 192 0 46.2 238 6I 20% 119 192 0 68.5 260 6J 20% 119 192 0 92.4 284 *denotes comparative Example; .sup.1Monoanninosilane, diaminosilane, and diquaternary ammonium 1, 2, and 1 ammoniums contribute for stabilization respectively.

(50) The results in TABLE 6 and 6B, above, show that increasing levels of HBBAH increase particle stability up to 1.63 mm or 751 ppm HBBAH as in Example 6I and above, as in Example 6J. In all of Examples 6B to 6J, the inventive HBBAH and aminosilane increased heat aged stability. In Example 6E adding too much acetic acid (which when neutralized is present as either HBBAH acetate or potassium acetate) at 6.6 mm (5 mm added plus 0.8*2 mm on the HBBAH salt) or 400 ppm and increasing the overall ionic strength of the solution leads to a less preferred level of particle stability. When comparing Comparative Examples 3G-3J from Table 3, above, to Examples 6B-6D, the heat aging results also show that increasing the DEAMS level on the particles and reducing the amount of the silica particle wt. % from 24 wt. % to a preferred 20 wt. % can increase stability dramatically as well, even in the presence of a fraction of roughly 7 wt. % of silica particles not containing aminosilane, based on particle solids. Including aqueous silica particles without aminosilane group containing silica particles is not preferred, especially at 4 wt. % or more of the total solids in the composition, and may hamper heat aged stability.

Example 7: Examples with Secondary Amine Group Containing Silane

(51) For AEAPS (43.5 nM/m.sup.2 silica) slurries: 18.81 grams of DI water was mixed with 80 grams of Slurry A. The pH of the solution was reduced to 4.25 using nitric acid. To this mixture was added 1.19 grams of hydrolyzed AEAPS solution which was 2.22% w/w of the AEAPS monomer adjusted to pH 4.25 using nitric acid. After 10 minutes of reaction between the AEAPS and silica, the pH was adjusted to 4.2 using KOH and/or nitric acid and stored at room temperature. The particles were used the next day to make aging formulations.

(52) For the AEAPS (58 nM/m.sup.2 silica) slurries: 18.41 grams of DI water was mixed with 80 grams of Slurry A and 1.59 grams of hydrolyzed AEAPS solution using the procedure above.

(53) The slurries listed in TABLE 7A, below, were prepared by mixing the AEAPS (43.5 nM/m.sup.2 silica) or (58 nM/m.sup.2 silica) solutions with DI water and optionally Slurry B particles (30 wt. %, adjusted to pH 4.0 with nitric acid). Only Slurry A contained aminosilane group containing silica particles. When Slurry A and Slurry B were mixed as in Table 7A, the resulting weight-averaged specific surface area was 118 m.sup.2/g. The final pH of the concentrated particle slurries was set to be ˜4.0 for heat aging studies using nitric acid or KOH to make the final pH adjustment. Heat aging was conducted for up to 12 days in a 50° C. oven. Particle sizes were measured at pH 4 using samples diluted to 1% solids with pH 4 nitric acid solution.

(54) TABLE-US-00016 TABLE 7A Secondary Amine Group Containing aminosilane group containing silica particle Formulations and Heat Aging at 50° C. AEAPS (nM/m.sup.2 silica SA) Heat Heat and Slurry aging 12 aging Slurry A B HBBAH Heat 53 hrs 12 day 12 days Particle particle (nM/m.sup.2 Initial aging PS.sup.1 (Z- day Heat PS.sup.1 (Z-avg) EXAMPLE (wt. %) wt % silica SA) RT pH's 53 hrs avg) pH aging avg) 7A* AEAPS   0% None 4.00 gel (43.5) 23% 7B* AEAPS 1.15% None 4.02 gel (43.5) 21.85% 7C AEAPS   0% HBBAH 4.04 slight 59.39 4.03 haze 90.47 (43.5) bisacetate haze 23% 98 7D* AEAPS 1.15% HBBAH 4.04 slight 84.06 gel (43.5) bisacetate haze 21.85% 95.8 7E* AEAPS 1.15% HBBAH 4.00 slight 71.45 gel (43.5) bisnitrate haze 21.85% 95.8 7F* AEAPS   0% None 4.06 haze 133.50 gel (58) 23% 7G* AEAPS 1.15% None 4.05 gel (58) 21.85% 7H AEAPS   0% HBBAH 4.06 slight 42.93 4.06 slight 47.77 (58) 23% bisacetate haze haze 98 7I AEAPS 1.15% HBBAH 4.05 slight 49.96 4.08 slight 73.43 (58) bisacetate haze haze 21.85% 95.8 *denotes comparative Example; .sup.1Particle size in nm.

(55) TABLE-US-00017 TABLE 7B Total Stabilizing Cationic Nitrogen Atoms Weight Total average silica Diamino- cationic specific Monoamino- silane Diquaternary nitrogen Silica surface area silane (nM/m.sup.2 (nM/m.sup.2 ammonium atoms.sup.1 Example (wt. %) (m.sup.2/g) silica) silica) (nM/m.sup.2 silica) (nM/m.sup.2 silica) 7A* 23% 115 0 43.5 0 87 7B* 23% 118 0 42.4 0 84.8 7C 23% 115 0 43.5 98 185 7D* 23% 118 0 42.4 95.8 180.6 7E* 23% 118 0 42.4 95.8 180.6 7F* 23% 115 0 58 0 116 7G* 23% 118 0 56.5 0 113 7H 23% 115 0 58 98 214 7I 23% 118 0 56.5 95.8 208.8 *denotes comparative Example; .sup.1Monoanninosilane, dianninosilane, and diquaternary ammonium contribute 1, 2, and 1 ammoniums for stabilization, respectively.

(56) As shown in Table 7A, above, Examples 7C, 7H and 7I exhibit improved stability effects from including a compound containing two quaternary ammonium groups, HBBAH (compare Comparative Examples 7A, 7B, 7F and 7G). Increasing the level of aminosilane for formulations using AEAPS, a secondary amine group containing silane can help heat age stability (compare Comparative Examples 7D and 7E with inventive Examples 7H and 7I). In combination with the buffer or salt, the preferred amount of the tested aminosilane containing a secondary amine group and having two cationic nitrogen atoms is that amount which provides more than 100 nM cationic nitrogen atoms per m.sup.2 of silica. Including aqueous silica Slurry B without aminosilane group containing silica particles in the amount of 4 wt. % or more of total solids, as in Comparative 7D and 7E, is not preferred and may hamper heat aged stability.

Example 8: Heat Aging with Compositions of Silica Mixtures

(57) The quantities of reagents are listed in TABLE 8A. DI water was mixed with Slurry A. The pH of the solution was reduced to 4.25 using nitric acid. To this mixture was added hydrolyzed DEAMS solution which was 3.7% w/w of the DEAMS monomer adjusted to pH 4.25 using nitric acid. After 30 minutes of reaction between the DEAMS and silica, the pH was readjusted to 4.25 using KOH and/or nitric acid. Then a 10% w/w solution of Slurry B pH-adjusted to 4.25, or as received Slurry C, was optionally added. A second addition of DEAMS solution was optionally performed. After another 30 min, HBBAH bisacetate (from a stock solution at pH 4.4) was added and the pH was readjusted to 4.4. The final solutions were heat aged in a convection oven at 50° C. for 28 days.

(58) The formulations of 8D-1, 8E-1 and 8F-1 were adjusted to a pH of 3.5 using nitric acid. The formulations 8D-1, 8E-1 and 8F-1 were measured for particle size by diluting with pH 3.5 nitric to 1% solids. All other formulations in Example 8 were measured for particle size by diluting with pH 4.4 nitric acid solution to 1% solids.

(59) TABLE-US-00018 TABLE 8A Formulations Slurry A First Second particle DEAMS Slurry Slurry DEAMS HBBAH Example wt % add (mm.sup.1) B C add(mm.sup.1) mm.sup.1 (ppm) 8A 18.6% 4.6 1.4% 0.00 0.00 0.80  (369) 8B 18.6% 4.6 1.4% 0.00 0.30 0.80 8C 18.6% 5.5 1.4% 0.00 0.30 0.80  (369) 8D 18.6% 1.9 1.4% 0.00 0.30 2.60 (1198) 8E 20.0% 1.9 0.0% 4.0% 0.00 2.60 8F 20.0% 1.9 0.0% 4.0% 0.30 2.60 .sup.1Millinnolal (mm) = Millimoles/kg total wet weight

(60) TABLE-US-00019 TABLE 8B Heat Aging at 50° C. Results and Effect of pH 28 0 day 2 day 14 day PS day Ex- 0 PS 2 PS (Z- 14 PS (Z- 19 (Z- 28 PS (Z- am- day (Z-avg, day avg, day avg, day avg, day avg, ple pH nm) pH nm) pH nm) pH nm) pH nm) 8A 4.41 35.74 4.52 35.97 4.61 38.18 4.66 44.85 4.68 57.33 8B 4.41 34.88 4.51 35.04 4.59 36.35 4.65 40.05 4.68 48.52 8C 4.41 34.80 4.51 35.24 4.61 34.67 4.66 36.44 4.69 39.08 8D* 4.25 37.29 4.30 47.48 4.28 107.50 Gel 8E* 4.26 58.74 4.31 95.10 Gel Gel Gel 8F* 4.25 55.84 4.30 67.22 4.26 viscous Gel 8D-1 3.50 3.64 37.80 3.72 39.11 3.73 41.04 3.74 42.97 8E-1 3.50 3.63 59.02 3.71 62.85 3.72 66.05 3.69 71.04 8F-1 3.50 3.59 54.87 3.66 56.08 3.67 58.51 3.68 58.41 *denotes comparative Example.

(61) TABLE-US-00020 TABLE 8B Total Stabilizing Ammonium Weight Total average silica Diamino- cationic specific Monoamino- silane Diquaternary nitrogen Silica surface area silane (nM/m.sup.2 ammonium atoms.sup.1 Example (wt. %) (m.sup.2/g) (nM/m.sup.2 silica) silica) (nM/m.sup.2 silica) (nM/m.sup.2 silica) 8A 20% 119 193 0 34 227 8B 20% 119 206 0 34 240 8C 20% 119 244 0 34 278 8D* 20% 119 92 0 109 201 8E* 24% 104 76 0 104 180 8F* 24% 104 88 0 104 192 8D-1 20% 119 92 0 109 201 8E-1 24% 104 76 0 104 180 8F-1 24% 104 88 0 104 192 *denotes comparative Example; .sup.1Monoanninosilane, dianninosilane, and diquaternary ammonium contribute 1, 2, and 1 ammoniums for stabilization respectively.

(62) As shown in Table 8B, above, in the heat aging results for Examples 8A, 8B, 8C, a combination of the aminosilane DEAMS and HBBAH provides slurries which show little particle growth after heat aging at 50° C. for 28 days at a pH of 4.4 to 4.6. As shown in Comparative Examples 8D, 8E and 8F, compositions having less than the preferred 140 nM/m.sup.2 of aminosilane do not pass the stability test at a less preferred pH of 4.5 even though the total cationic nitrogens/m.sup.2 are 180 or more. However, in Examples 8D-1, 8E-1 and 8F-1, at a pH of 3.5 addition of more than 1000 ppm HBBAH even in compositions having less than 100 nM of cationic nitrogen atoms per m.sup.2 silica of aminosilane enables heat aging stability for aqueous silica slurry compositions having particles as small as Slurry B (25 nm) and as large as Slurry C (75 nm).

Example 9: Effect of pH on Stability

(63) Aqueous silica slurry formulations after mixing are listed in Table 9A, below. DI water was mixed with Slurry A. The pH of the solution was reduced to 4.25 using nitric acid. To this mixture was added hydrolyzed DEAMS solution which was 3.7% w/w of the DEAMS monomer adjusted to pH 4.25 using nitric acid. After 30 minutes of reaction between the DEAMS and silica, the pH was readjusted to 4.25 using KOH and/or nitric acid. Then, as indicated in Table 9A, below, a 24% w/w solution of Slurry B pH-adjusted to 4.25, or as received Slurry C, was added. A second addition of DEAMS solution was optionally performed. After another 30 min, HBBAH bisacetate (from a stock solution at pH 4.4) was added and the pH was adjusted as listed in Table 9A, below, with nitric acid. The final solutions were heat aged in a convection oven at 45 C for 28 days.

(64) TABLE-US-00021 TABLE 9A Formulations Ex- Slurry First Slurry Slurry Second HBBAH am- A DEAMS B C DEAMS (mm) Final ple (wt. %) add (mm) (wt. %) (wt. %) add (mm) (ppm) pH 9A 18.6% 4.6 1.4% 0.sup.   0.9 0.8 4.40 (369)  9B 18.6% 5.5 1.4% 0.sup.   0.3 0.8 4.40 9C   20% 1.9 .sup.  0 4% 0.9 2.6 3.56 (1198) 9D   20% 1.9 .sup.  0 4% 0.3 2.6 3.54

(65) TABLE-US-00022 TABLE 9B Heat Aging at 45° C. Results 14 0 day 7 day day 28 day PS (Z- PS (Z- 14 PS (Z- 28 PS (Z- 0 day avg, 7 day avg, day avg, day avg, Example pH nm) pH nm) pH nm) pH nm) 9A 4.37 32.1 4.43 32.12 4.51 32.32 4.53 32.67 9B 4.36 32.155 4.42 31.935 4.52 32.08 4.87 32.575 9C 3.42 58.99 3.48 58.08 3.50 58.33 3.52 58.815 9D 3.41 59.045 3.47 57.915 3.51 58.075 3.51 58.65 *denotes comparative Example

(66) TABLE-US-00023 TABLE 8C Total Stabilizing Ammonium Weight average silica Diamino- Total cationic specific Monoamino- silane Diquaternary nitrogen Silica surface area silane (nM/m.sup.2 ammonium atoms.sup.1 Example (wt. %) (m.sup.2/g) (nM/m.sup.2 silica) silica) (nM/m.sup.2 silica) (nM/m.sup.2 silica) 9A 20% 119 231 0 34 265 9B 20% 119 244 0 34 278 9C 24% 104 112 0 104 216 9D 24% 104 88 0 104 192 *denotes comparative Example; .sup.1Monoanninosilane, dianninosilane, and diquaternary ammonium contribute 1, 2, and 1 ammoniums for stabilization respectively.

(67) As shown in Table 9B, above, the inventive compositions remain stable at a range of pHs from 3 to 5.