Aqueous silica dispersion

Abstract

The present invention relates to a method of producing a dispersion comprising a) mixing an aqueous dispersion of silanized colloidal silica particles with at least one organic compound containing at least two hydroxyl groups to provide an aqueous dispersion of silanized colloidal silica particles and said at least one organic compound, wherein the mixing is performed in the substantial absence of any monofunctional alcohol b) withdrawing water from the formed aqueous dispersion until the remainder of water in the dispersion is below about 10 wt %. The invention also relates to a dispersion obtainable therefrom and the use of the dispersion.

Claims

1. A stable dispersion comprising silanised colloidal silica particles having a weight ratio of silane to silica ranging from about 0.1 to about 1.5, and at least one organic compound containing at least two hydroxyl groups, wherein the silanised colliodal silcia particles is substantially unmodified with respect to monofunctional alcohol such that less than about 10 wt % of the silanised colloidal silica particles are modified by a monofunctional alcohol, wherein the dispersion is substantially free of any monofunctional alcohol, wherein the water content in the dispersion is below about 10 wt %, wherein a viscosity of the dispersion is increased less than 2 times over a period of 2 months, and further wherein the dispersion does not appear in an inhomogeneous form.

2. The dispersion according to claim 1, wherein the water content in the dispersion is below 5 wt %.

3. The dispersion according to claim 1, wherein said at least one organic compound is a polyol.

4. The dispersion according to claim 1, wherein the weight ratio of silica to organic compound ranges from about 1:20 to about 4:1.

5. The dispersion according to claim 3, wherein said polyol has a molecular weight of from about 62 to about 200 g/mole.

6. A method of performing condensation polymerization wherein said polymerization is performed in the presence of the dispersion according to claim 1.

7. A lacquer or coating composition comprising the dispersion according to claim 1.

8. A method of producing a polymeric material comprising reacting a) the dispersion according to claim 1; and b) at least one component selected from an isocyanate, a dicarboxylic acid, an epoxide, a siloxane or a diamine.

9. A method according to claim 8, in which the polymeric material is polyurethane, polyester, epoxy resins, polysiloxane, or a polyamide.

10. The dispersion according to claim 1, wherein the inhomogeneous form is a precipitated form.

11. A stable dispersion comprising (A) silanised colloidal silica particles and (B) at least one organic compound containing at least two hydroxyl groups, said silanised colloidal silica particles being substantially unmodified with respect to monofunctional alcohol, said silanized colloidal silica particles having a weight ratio of silane to silica ranging from about 0.2 to about 1.5, said at least one organic compound having a molecular weight ranging from about 62 to about 200 g/mol, said dispersion being substantially free of any monofunctional alcohol such that less than about 10 wt % of the silica particles are modified by a monofunctional alcohol, said dispersion having a water content below about 10 wt %, wherein the dispersion exhibits a viscosity increase of less than 2 times over a period of 2 months and does not appear in an inhomogeneous form.

12. The dispersion according to claim 11, wherein the inhomogeneous form is a precipitated form.

13. A method of producing a stable dispersion comprising a) mixing an aqueous dispersion of silanised colloidal silica particles having a weight ratio of silane to silica ranging from about 0.1 to about 1.5 with at least one organic compound containing at least two hydroxyl groups to provide an aqueous dispersion of silanised colloidal silica particles and said at least one organic compound, said silanised colliodal silcia particles being substantially unmodified with respect to mono functional alcohol such that less than about 10 wt % of the silica particles are modified by a monofunctional alcohol, wherein the mixing is performed in the substantial absence of any monofunctional alcohol b) withdrawing water from the formed aqueous dispersion until the remainder of water in the dispersion is below about 10 wt %, wherein the produced stable dispersion comprising silanised colloidal silica having a weight ratio of silane to silica from about 0.1 to about 1.5 and at least one organic compound containing at least two hydroxyl groups, wherein the silanised colloidal silica particles are substantially unmodified with respect to monofunctional alcohol such that less than about 10% by weight of the silansied colloidal silica particles are modified by monofunctional alcohol, the stable dispersion is substantially free of any monofunctional alcohol, the water content in the stable dispersion is below about 10 wt %, a viscosity of the stable dispersion is increased less than 2 times over a period of 2 months, and further the stable dispersion does not appear in an inhomogeneous form.

14. A method according to claim 13, wherein said at least one organic compound is a polyol.

15. A method according to claim 14, wherein the polyol has a molecular weight of from about 62 to about 200 g/mole.

16. A method according to claim 14, wherein the weight ratio of silica to organic compound ranges from about 1:20 to about 4:1.

Description

EXAMPLES

(1) The silica sols used in the examples are shown in Table 1 below:

(2) TABLE-US-00001 TABLE 1 Sol Silica desig- Silica content Surface nation sol (wt %) modification pH Supplier A Bindzil 29 Silane 6-8 Eka Chemicals AB, 30/360 Sweden B Bindzil 30 None 8-11 Eka Chemicals AB, 30/360 Sweden C Bindzil 20 None 2-3 Eka Chemicals AB, 820DI Sweden D Bindzil 50 Yes 2 Eka Chemicals AB, CC301 Sweden E Bindzil 30 Yes 2 Eka Chemicals AB, CC301 Sweden

(3) The polyols used in the examples are shown in Table 2 below:

(4) TABLE-US-00002 TABLE 2 Polyol Brief description Supplier PEG 400 Polyethylene Glycol - Akzo Nobel Surface average molecular weight Chemistry, Sweden 400 PEG 200 Polyethylene Glycol - Fischer Scientific average molecular weight 200 Glycerine Propane-1,2,3-triol Fischer Scientific Ethylene glycol Diethylene Dow (via August Hedinger glycol GmbH) Dipropylene Dow (via August Hedinger glycol GmbH) Dowanol PM, Propylene Glycol Methyl Dow (via August Hedinger Ether GmbH) Dowanol DPM, Dipropylene Glycol Methyl Dow (via August Hedinger Ether GmbH) Dowanol TPM, Tripropylene Glycol Methyl Dow (via August Hedinger Ether GmbH) Arcol 1108 Trifunctional polyether Bayer MaterialScience polyol AG, Leverkusen, Germany Desmophen PU Sucrose-based polyether Bayer MaterialScience 21AP27 polyol AG, Leverkusen, Germany
Dispersions of the silica sols in Table 1 were prepared according to the following general description, with amounts and values for each individual example according to Table 3 below. The respective silica sols were mixed with polyols according to the specifications. In some of the examples the pH of the silica sol was reduced by cation exchange to pH 2 before mixing to the value indicated.

(5) The mixing continued for a period of about 1 minute, whereafter the mixture was subjected to evaporation at a reduced pressure of typically 20-30 mbar, at the temperature indicated, until no more water evaporated. The water content was as indicated in tables 4a and 4b based on the total weight of the evaporated mixture.

(6) The viscosity of the thus evaporated mixtures was determined according to ASTM D1200 using a Ford Viscosity Cup #5 on the date of preparation (table 3), and after aging (table 5 which also contains some initial viscosity data for some of the samples). In table 5, two viscosity measurements were made for some samples after aging. The dates at which viscosity measurements were performed are in the format year-month-day in table 5. In tables 3 and 5, viscosity is measured in seconds using the Ford Viscosity Cup #5 test if not otherwise indicated. For some samples, the viscosity was given in mPas as measured by Brookfield viscometer.

(7) TABLE-US-00003 TABLE 3 SiO.sub.2 (wt %) calculated Visc, Solvent Silica after (seconds) No Solvent (g) Silica sol sol (g) evaporation Ford Cup 5 1 PEG 400 500 CC30, 80 C. 500 21 210 2 PEG 400 1000 CC30, 80 C. 500 12-13 Very viscous but pourable 3 PEG 400 700 CC30, pH 2, 350 12-13 43 80 C. 4 PEG 400 700 CC30, 40 C. 350 12-13 131 5 PEG 400 700 30/360 350 13 (gelled Gel before evaporation) 6 PEG 400 700 30/360, pH 2, 350 13 Gel 80 C. 7 PEG 400 700 CC30, pH 2, 350 12-13 55 80 C. 8 Glycerine 712 CC30, pH 2, 356 12-13 66 80 C. 9 Glycerine 700 CC30, 80 C. 350 12-13 73 10 Glycerine 650 CC30, 80 C. 650 22 103 11 Glycerine 400 CC30, 80 C. 650 31 201 12 Glycerine 200 CC30, 80 C. 650 46 1200 13 Glycerine 400 30/360, pH 2, 650 32 235 80 C. 14 Glycerine 200 30/360, pH 2, 650 48 Gel 80 C. 15 Glycerine 200 30/360, pH 7, 650 45 Gel 80 C. 16 Glycerine 400 30/360, pH 7, 650 32 557 80 C. 17 Glycerine 400 820DI, 80 C. 975 32 433 18 Glycerine 200 820DI, 80 C. 975 47 Gel 19 PEG 400 500 CC30, 40 C. 500 21 24 20 PEG 200 400 CC30, pH 2, 650 28 12 40 C. 21 PEG 200 200 CC30, pH 2, 650 43 31 40 C. 22 PEG 200 200 CC30, 40 C. 650 44 41 23 Arcoll 1108 400 CC30, pH 2, 650 28 126 40 C. 24 PEG 200 200 CC30, pH 2, 1300 53 1926 40 C. 25 PEG 200 400 CC30, pH 2, 1300 45 59 40 C. 26 PEG 200 400 CC30, pH 2, 1300 46 164 60 C. 27 PEG 200 400 CC30, pH 2, 1300 49* 365 80 C. 28 PEG200 (100 g) + B CC30, pH 2, 1300 37 22 (300 g) 60 C. 29 Desmophen 400 CC30, pH 2, 650 17 PU 21AP27 60 C. 30 Desmophen 600 CC30, pH 2, 650 448 PU 21AP27 80 C. 31 Desmophen 400** CC30, pH 2, 650 358 PU 21AP27 80 C. 32 Glycerine 800 CC30, pH 2, 1300 245 80 C. 33 Diethylene 800 CC30, pH 2, 1300 428 mPas glycol 80 C. 34 Ethylene 800 CC30, pH 2, 1300 61 mPas glycol 80 C. 35 Ethylene 400 CC30, pH 2, 1300 181 mPas glycol 80 C. 36 Dowanol 800 CC30, pH 2, 1300 White TPM 50 C. emulsion 35 s/ 1200 mPas 37 Dowanol 800 CC30, pH 2, 1300 White DPM 50 C. emulsion that will be clear solution upon addition of water Viscosity: 25 s 38 Dowanol 800 CC30, pH 2, 1300 8 s/31 mPas PM 50 C. 39 Dipropylene 400 CC30, pH 2, 650 27 s/503 glycol 50 C. mPas 40 Dipropylene 400 30/360 650 Gel after 200 glycol g added 41 Dowanol 400 30/360 650 Gel after 200 TPM g added 42 Dowanol 400 30/360 650 Gel after 200 DPM g added 43 Dowanol 400 30/360 650 Gel after 200 PM g added 44 Dipropylene 400 820DI, 50 C. 975 101 s/>2000 glycol mPas 45 PEG200 800 Bindzil 1300 300 mPas CC301 46 Ethylene 400 Bindzil 1300 790 mPas glycol CC301 CC30: 29% SiO2 30/360: 30% SiO2 *Some silica went over into the condensate Arcoll 1108 only partly water miscible B: Desmophen PU 21AP27 **Addition of 20 g ethanol to the polyol before mixing with silica sols

(8) TABLE-US-00004 TABLE 4a H.sub.20 wt- SiO.sub.2 wt-% by % (Karl No XRF Fisher) Visc. Ford Cup 5 25 41.2 5.0% 92 s (8 weeks old sample) 26 43.8 2.0% 228 s (3 weeks old sample) 26a 41.2 5.0% 78 s 27 44.1 0.93% 453 s (3 weeks old sample) 27a 41.2 5.0% 86 s aDiluted sample with DI-water and PEG 200 in order to have the same water and silica content as No 25.

(9) TABLE-US-00005 TABLE 4b SiO.sub.2 wt-% by H.sub.20-wt % (Karl No XRF Fisher) 28 34.8 28.0% 29 22.1 30.0% 30 25.5 8.4% 31 23.1 3.2% 32 29.5 1.2% 33 28.4 1.1% 34 28.8 1.3% 35 42.6 1.6%

(10) TABLE-US-00006 TABLE 5 Visc. (sec.) Ford Cup 5 (aged) measured on 2008- Sample 12-22 if not otherwise No preparation date indicated 1 2008-04-11 912 2 2008-04-11 10 3 2008-04-11 100 4 2008-04-11 gel 7 2008-04-16 very viscous but pourable 8 2008-04-16 93 9 2008-04-16 95 10 2008-04-16 150 11 2008-04-17 282 12 2008-04-17 2556 13 2008-04-17 459 16 2008-04-17 Gel 17 2008-04-18 885 19 2008-04-21 15 20 2008-05-16 12 21 2008-05-16 31 22 2008-05-16 41 23 2008-08-14 126 24 2008-08-15 3208 25 2008-08-15 59 26 2008-09-23 241 27 2008-09-23 428 28 2008-11-18 19 29 2008-11-18 16 30 2008-11-20 418 31 2008-11-20 very viscous but pourable 32 Visc. After 78 days 242 s 33 Visc. After 25 days 150 mPas

(11) As can be seen in Table 5, the storage stability of the dispersions according to the invention is excellent, whereas the comparative dispersions 5-6 and 13-18 (comprising non-silanised silica particles) either become unstable and gel, or become much more viscous than dispersions based on silanised silica particles prepared under comparable conditions, i.e. with equal or similar amounts of silica, polyol, mixing temperature etc.

Heat Stability

(12) In order to evaluate temperature stability and to have an indication whether the silica is freely dispersed in the polyol or react with the polyol as well as being stable enough in the polyol to be used under temperatures relevant for resins, e.g. alkyd polymerization. About 50 g (volume about 30 ml) of silica sol No 13 and No 33 were autoclaved in a 50 ml autoclave at 220 C. for 5 hours.

(13) After autoclaving:

(14) Non-silanised silica sol No 13 was fully polymerized into a hard solid material.

(15) Silanised silica sol No 33 on the other hand had low viscosity at high temperature and liquid (though viscous) at room temperature.