Method for producing aqueous hydrolysates from aminoalkyltrialkoxysilanes

Abstract

The present invention relates to a process for preparing aqueous hydrolysates of aminoalkyltrialkoxysilanes by (a) initially charging water, optionally heating, (b) adding hydrolysable silanes consisting of at least one aminoalkyltrialkoxysilane in an amount which provides a molar ratio of water to total amount of aminoalkyltrialkoxysilane of 10.5 to 20, and (c) distilling off the alkyl alcohol formed in the reaction,
wherein the solids content in an aqueous composition thus prepared is 30% to 55% by weight, based on the composition, and the aqueous solution has a total content of free and bound alkyl alcohol of not more than 1% by weight, based on the composition.

Claims

1. A process for preparing an aqueous hydrolysate of an aminoalkyltrialkoxysilane, comprising: (a) initially charging water, optionally with heating, (b) adding one or more hydrolysable silanes comprising at least one aminoalkyltrialkoxysilane in an amount which provides a molar ratio of water to a total amount of aminoalkyltrialkoxysilane of 10.5 to 20:1, and (c) distilling off an alkyl alcohol formed in the reaction, wherein a solids content in an aqueous composition thus prepared is 30% to 55% by weight, based on the composition, and the aqueous composition has a total content of free and bound alkyl alcohol of not more than 1% by weight, based on the composition.

2. The process of claim 1, wherein the aminoalkyltrialkoxysilane has a formula
HRNR.sup.2Si(OR.sup.3).sub.3 in which R.sup.1 is H or a C.sub.1-C.sub.4-alkyl group; R.sup.2 is a bivalent C.sub.1-C.sub.4-alkyl group; and R.sup.3 is a C.sub.1-C.sub.3-alkyl group.

3. The process of claim 2, wherein R.sup.1 is H.

4. The process of claim 2, wherein R.sup.2 is a bivalent propyl group [(CH.sub.2).sub.3-] and R.sup.3 is selected from the group consisting of methyl and ethyl.

5. The process of claim 1, wherein the aminoalkyltrialkoxysilane is at least one selected from the group consisting of 3-aminopropyltriethoxysilane and 3-aminopropyltrimethoxysilane.

6. The process of claim 1, wherein the solids content in the aqueous composition thus prepared is 40% to 55% by weight, based on the composition.

7. The process of claim 1, wherein the molar ratio of water to the total amount of aminoalkyltrialkoxysilane is 11 to 18:1.

8. The process of claim 1, wherein a duration of the aminoalkyltrialkoxysilane addition in (b) is 20 to 240 minutes.

9. The process of claim 1, wherein an internal reactor temperature on commencement of the addition of the aminoalkyltrialkoxysilane in (b) is 25 C. to 50 C., and the internal reactor temperature at the end of the addition of the aminoalkyltrialkoxysilane in (b) is 50 C. to 80 C.

10. The process of claim 1, wherein the distilling off of the alkyl alcohol is commenced immediately after the addition of the aminoalkyltrialkoxysilane has ended.

11. The process of claim 1, wherein a period of time between the end of the addition of the aminoalkyltrialkoxysilane and commencement of the distilling off of the alkyl alcohol is less than 5 minutes after attainment of distillation conditions.

12. The process of claim 1, wherein the aqueous composition has a total content of free and bound alkyl alcohol of not more than 0.7% by weight, based on the composition, measured after hydrolysis of a sample of the aqueous composition with sulphuric acid and subsequent neutralization with aqueous sodium carbonate solution by gas chromatography.

13. The process of claim 1, wherein the aqueous composition has a turbidity value of 5 FNU or less measured according to ISO 7027.

Description

EXAMPLES

(1) The test methods for characterization of the properties of the aqueous solutions which are prepared by the process according to the invention, as specified in the description, the examples and the claims, were conducted as follows:

(2) TABLE-US-00001 Solids [% by weight] The solids content was determined according to DIN 38409-H1-1. SiO.sub.2 [% by weight] The SiO.sub.2 determination was conducted according to the following description: 1 g of a sample was weighed into a 250 ml beaker. One Kjeldahl tablet (Merck No. 15348) and 20 ml of concentrated sulphuric acid were added. The solution was heated gradually until SO.sub.3 vapours formed. After cooling, the solution was cautiously diluted to 200 ml with distilled water. The precipitated silica was filtered through a white-band filter paper. The filter residue was washed with distilled water until the filtrate became neutral (pH > 4). The filter paper was dried and converted to ash in a platinum crucible. The residue was burnt at 800 C. and weighed. After treatment with concentrated hydrofluoric acid, the residue was burnt again at 800 C. and weighed. SiO.sub.2 [% by weight] = 100 m/E m = difference in weight before and after the treatment with hydrofluoric acid in g E = weight of the sample in g. Viscosity (20 C.) [mPas] Determination according to DIN 53015 Density (20 C.) [g/ml] Determination according to DIN 51757 Refractive index (20 C.) DIN 51423 determination Turbidity [FNU] Determination according to ISO 7027 Total alcohol (alcohol, after The total alcohol determination was conducted according to the hydrolysis) [% by weight] following description: 5 g of a sample were weighed into a flask and hydrolysed with 25 ml of sulphuric acid (20%). After addition of 75 ml of distilled water, the solution was neutralized with sodium carbonate solution (20%) and then subjected to a steam distillation. The distillate was collected in a 250 ml flask. According to the expected alcohol content, up to 3 ml of sec- butanol were added and the flask was made up to the mark with distilled water. The alcohols were analysed quantitatively by means of gas chromatography using a capillary column with an FID and appropriate data processing (HP 7820 with OpenLab). Solutions of the expected alcohols and sec-butanol were used for calibration purposes. The sec-butanol served as internal standard. The total alcohol content thus determined in the sample includes the proportion of free alcohol and alcohol bound in the form of hydrolysable alkoxy groups. Free alcohol (ethanol) [% by The determination of the content of free alcohol was conducted weight] according to the following description: 2 g of a sample and 50 mg of 2-butanol as internal standard are dissolved in 10 g of demineralized water. This solution is analysed quantitatively by means of gas chromatography using a capillary column with a TCD and appropriate data processing (HP 7820 with OpenLab). The calibration is effected with a solution of 50 mg of the relevant alcohol and 50 mg of the internal standard used in 10 g of the solvent used.

(3) The space-time yield (STY) reported in the examples was calculated as follows:

(4) $\mathrm{STY}=\frac{\mathrm{Yield}\mathrm{calculated}\mathrm{as}\mathrm{silicon}\left(\mathrm{Si}\right){\mathrm{in}\left[g\right]}^{1)}}{.Math.{\left(\mathrm{volume}\mathrm{of}\mathrm{reactants}\right)\left[l\right]}^{2)}\mathrm{preparation}{\mathrm{time}\left[h\right]}^{3)}}$${}^{1)}\mathrm{Yield}\left(\mathrm{Si}\right)=\mathrm{yield}\left[g\right]w\left(\mathrm{Si}\right)\mathrm{in}\%0.01$$\left(\mathrm{Si}\right)\mathrm{or}w\left(\mathrm{Si}\right)\mathrm{was}\mathrm{calculated}\mathrm{here}\mathrm{on}\mathrm{the}\mathrm{basis}\mathrm{of}\mathrm{the}\mathrm{respective}$${\mathrm{SiO}}_2\mathrm{determination}.{}^{2)}\mathrm{Reactants}\mathrm{refer}\mathrm{to}\mathrm{the}\mathrm{amounts}\mathrm{of}\mathrm{water}\mathrm{and}3\text{-}\mathrm{aminopropyl}\text{-}$$\mathrm{triethoxysilane}\left(\mathrm{AMEO}\right)\mathrm{initially}\mathrm{charged}\mathrm{and}\mathrm{the}\mathrm{amounts}\mathrm{of}\mathrm{AMEO}$$\mathrm{and}\mathrm{water}\mathrm{metered}\mathrm{in}.\mathrm{The}\mathrm{density}\mathrm{for}\mathrm{the}\mathrm{reactants}\mathrm{used}\mathrm{was}\mathrm{assumed}$$\mathrm{simply}\mathrm{to}\mathrm{be}1.0g\text{/}{\mathrm{cm}}^3.\mathrm{This}\mathrm{is}\mathrm{used}\mathrm{to}\mathrm{ca}\mathrm{lculate}\mathrm{the}\mathrm{volume}\mathrm{of}$$\mathrm{reactants}\mathrm{from}\mathrm{the}\mathrm{quotient}\mathrm{of}\left(m_{\mathrm{reactants}}\right)\mathrm{and}\mathrm{the}\mathrm{density}\mathrm{of}$$1.0g\text{/}{\mathrm{cm}}^3.{}^{3)}\mathrm{Preparation}\mathrm{time}=\mathrm{time}\mathrm{from}\mathrm{the}\mathrm{start}\mathrm{of}\mathrm{the}\mathrm{reaction}\left(\mathrm{dropwise}\mathrm{addition}\mathrm{of}\mathrm{AMEO}\mathrm{or}\mathrm{water}\right)\mathrm{to}\mathrm{the}\mathrm{end}\mathrm{of}\mathrm{the}\mathrm{distillation}.$

Example 1

(5) A 2 l four-neck flask with precision glass stirrer, dropping funnel, distillation apparatus, jacketed coil condenser, rotary vane oil pump, bottom thermometer, top thermometer and oil bath with temperature regulation was initially charged with 800.0 g (44.4 mol) of demineralized water under an N.sub.2 blanket, and heated to a bottom temperature of 40.7 C. with the oil bath. After the oil bath had been removed, without further heating, 800.0 g (3.61 mol) of Dynasylan AMEO were added dropwise within 44 min. In the course of this, the bottom temperature rose to 57.5 C. There was minimal turbidity for about 6 min, then the bottoms liquid was colourless and clear. After the dropwise addition has ended, reduced pressure was applied immediately. At a reduced pressure of 304 to 122 mbar, bath temperature 105 C. to 115 C., a bottom temperature of 46.3 C. to 50.7 C., top temperature of 44.4 C. to 49.4 C., 842.7 g of ethanol/water were distilled off within 2.3 h (hydrolysis alcohol+73%). After about 500 g had been distilled off, dropwise addition of 579.2 g of demineralized water was commenced and lasted until the end of the distillation. During the reaction and distillation, there was no precipitation or significant rise in viscosity. After the distillation had ended, the reactor was vented with nitrogen.

(6) The yield was 1320.22 g of clear colourless product.

(7) TABLE-US-00002 The space-time yield was 21.3 [g (Si)/(l h)]. Solids content 30.7% by weight Total alcohol 0.7% by weight

(8) The analysis data of the product obtained are compared once again in summary in Table 1.

Comparative Example 1 (Cf. Example 2 from U.S. Pat. No. 6,512,132)

(9) A 2 l four-neck flask with precision glass stirrer, dropping funnel, distillation apparatus, jacketed coil condenser, rotary vane oil pump, bottom thermometer, top thermometer and oil bath with temperature regulation was initially charged with 800.0 g (3.61 mol) of Dynasylan AMEO under an N.sub.2 blanket, and heated to a bottom temperature of 41.4 C. with the oil bath. After the oil bath had been removed, without further heating, 800.0 g (44.4 mol) of demineralized water were added dropwise within 2 h. In the course of this, the bottom temperature rose to 65.4 C. and significant exothermicity was apparent. Significant precipitation arose over a period of about 8 min, with white flakes, some of which were large. Subsequently, the bottoms liquid was colourless and clear. After the dropwise addition has ended, reduced pressure was applied immediately. At a reduced pressure of 204 to 198 mbar, bath temperature 109 C. to 111 C., a bottom temperature of 46.8 C. to 59.9 C., top temperature of 42.8 C. to 51.3 C., 701.6 g of ethanol/water were distilled off within 2 h (hydrolysis alcohol+40%). After cooling to about 38 C., the reactor was vented with nitrogen and the product was diluted with 435.6 g of demineralized water within about 15 min and hence adjusted to an active content of 60%.

(10) The yield was 1324.4 g of clear colourless product.

(11) TABLE-US-00003 The space-time yield was 11.2 [g (Si)/(l h)]. Solids content 30.8% by weight Total alcohol 1.4% by weight

(12) The analysis data of the product obtained are compared once again in summary in Table 1.

Example 2

(13) A 2 l four-neck flask with precision glass stirrer, dropping funnel, distillation apparatus, jacketed coil condenser, rotary vane oil pump, bottom thermometer, top thermometer and oil bath with temperature regulation was initially charged with 800.0 g (44.4 mol) of demineralized water under an N.sub.2 blanket, and heated to a bottom temperature of 40.2 C. with the oil bath. After the oil bath had been removed, without further heating, 800.0 g (3.61 mol) of Dynasylan AMEO were added dropwise within 40 min. In the course of this, the bottom temperature rose to 58.2 C. Minimal turbidity arose, which disappeared after the end of dropwise addition; the bottoms liquid was colourless and clear. Thereafter, reduced pressure was applied immediately. At a reduced pressure of 326 to 101 mbar, bath temperature 108 C. to 110 C., a bottom temperature of 48.4 C. to 52.9 C., top temperature of 46.7 C. to 49.6 C., 872.0 g of ethanol/water were distilled off within 2.4 h (hydrolysis alcohol+73%). After about 700 g had been distilled off, 46.9 g of demineralized water were added dropwise for dilution within 10 min. Toward the end of the distillation, the bottoms liquid was viscous but still efficiently stirrable. After cooling, the system was vented with nitrogen.

(14) The yield was 762.9 g of clear colourless product.

(15) TABLE-US-00004 The space-time yield was 21.1 [g (Si)/(l h)]. Solids content 52.8% by weight Total alcohol 0.2% by weight

(16) The analysis data of the product obtained are compared once again in summary in Table 1.

Comparative Example 2: (Cf. Example 1 from U.S. Pat. No. 6,512,132)

(17) A 2 l four-neck flask with precision glass stirrer, dropping funnel, distillation apparatus, jacketed coil condenser, rotary vane oil pump, bottom thermometer, top thermometer and oil bath with temperature regulation was initially charged with 1000.0 g (4.52 mol) of Dynasylan AMEO under an N.sub.2 blanket, and heated to a bottom temperature of 40.1 C. with the oil bath. After the oil bath had been removed, without further heating, 500.0 g (27.8 mol) of demineralized water were added dropwise within 1.25 h. In the course of this, the bottom temperature rose to 65.5 C. and significant exothermicity was apparent. Significant precipitation arose over a period of about 18 min, with white flakes, some of which were large. After the dropwise addition had ended, reduced pressure was applied immediately. At a reduced pressure of 216 to 205 mbar, bath temperature 108 C. to 113 C., a bottom temperature of 46.9 C. to 52.9 C., top temperature of 42.6 C. to 48.3 C., 703.4 g of ethanol/water were distilled off within 1.65 h (hydrolysis alcohol+20%). During the distillation, there was a very significant rise in viscosity. At this point, the bottoms were no longer stirrable. The bottoms were solid (active content 125.5%). The system was vented immediately with nitrogen, and 250.4 g of demineralized water were added to the bottoms. In order to get the solids back into solution, the flask was agitated on an RO 10 agitator for 5.25 h. Thereafter, the bottoms were almost completely back in solution. Only on the stirrer paddle was a little solid still present.

(18) The yield was 1037.6 g of clear colourless product.

(19) TABLE-US-00005 The space-time yield is 11.7 g Si/(l h). The space-time yield was 11.7 [g (Si)/(l h)]. Solids content 48.6% by weight Total alcohol 6.5% by weight

(20) The analysis data of the product obtained are compared once again in summary in Table 1.

Example 3

(21) An 8 l four-neck jacketed flask with precision glass stirrer, dropping funnel, distillation apparatus, column with 4 Sulzer EX packing elements L=5 cm, W=4 cm (theoretical plates at moderate load 13-20), jacketed coil condenser, rotary vane oil pump, bottom thermometer, top thermometer, thermostat and Prominent Gamma 4 metering pump was initially charged with 3401.8 g (188.8 mol) of demineralized water under an N.sub.2 blanket, and heated to a bottom temperature of 40.0 C. with the thermostat. At this bottom temperature (bath temp. 60 C.), 3400.1 g (15.4 mol) of Dynasylan AMEO were metered in by means of a metering pump within 1 h. In the course of this, the bottom temperature rose to 63.9 C. The bottoms liquid remained colourless and clear. Thereafter, reduced pressure was applied immediately. At a reduced pressure of 106 to 105 mbar, thermostat temperature 96.8 C. to 105 C., a bottom temperature of 37.8 C. to 47.7 C., top temperature of 36.6 C. to 46.9 C., 3719.3 g of ethanol/water were distilled off within 4.75 h (hydrolysis alcohol+75%). After about 1348.71 g had been distilled off, a total of 782.9 g of demineralized water were added dropwise during the distillation for dilution within 2.5 h. The bottoms liquid was colourless, clear and nonviscous during and toward the end of the distillation. There were no precipitates and deposits whatsoever at the edge of the flask. After cooling, the system was vented with nitrogen.

(22) The yield was 3897.2 g of clear colourless product.

(23) TABLE-US-00006 The space-time yield was 12.0 [g(Si)/(l h)]. Solids content 44.7% by weight Total alcohol 0.3% by weight

(24) The analysis data of the product obtained are compared once again in summary in Table 1.

Comparative Example 3

(25) An 8 l four-neck jacketed flask with precision glass stirrer, dropping funnel, distillation apparatus, column with 4 Sulzer EX packing elements L=5 cm, W=4 cm (theoretical plates at moderate load 13-20), jacketed coil condenser, rotary vane oil pump, bottom thermometer, top thermometer, thermostat and Prominent Gamma 4 metering pump was initially charged with 3406.5 g (15.4 mol) of Dynasylan AMEO under an N.sub.2 blanket, and heated to a bottom temperature of 39.9 C. with the thermostat. At this bottom temperature (bath temp. 60 C.), 3400.5 g (188.8 mol) of demineralized water were metered in by means of a metering pump within 2.75 h. In the course of this, the bottom temperature rose to 72.7 C. Very significant exothermicity was apparent. After about 225 ml of demineralized water had been metered in, white flakes and deposits formed at the edge of the flask. The bottoms liquid was milky white. After a further 7 min (300 ml of demineralized water in total), the flakes and turbidity were back in solution; the bottoms liquid remained colourless and clear. After all the demineralized water had been metered in, reduced pressure was applied immediately. At a reduced pressure of 107 to 100 mbar, thermostat temperature 81 C. to 105 C., a bottom temperature of 37.8 C. to 47.7 C., top temperature of 35.2 C. to 50.9 C., 3820.3 g of ethanol/water were distilled off within 5.6 h (receiver+cold trap) (hydrolysis alcohol+80%). After about 1632.4 g had been distilled off, gel-like deposits occurred at the edge of the flask, which accumulated further during the distillation. The bottoms liquid was viscous, colourless and clear after the end of the distillation (viscosity3000 mPa*s, measurement from experiment IL/V180/12-43). After the end of the distillation, the bottoms liquid was diluted to an active content of 88% with 884.45 g of demineralized water within 5 min, and the whole lot was stirred at 48.5 C. to 41.3 C. for about 30 min. The gel from the edge of the flask still had not fully dissolved at this time. After cooling, the system was vented with nitrogen.

(26) The yield was 3761.5 g of clear colourless product.

(27) TABLE-US-00007 The space-time yield was 6.3 [g (Si)/(l h)]. Solids content 45.0% by weight Total alcohol 0.1% by weight

(28) The analysis data of the product obtained are compared once again in summary in Table 1.

Comparative Example 4: (Cf. Example 1 from EP1031593A2)

(29) A 4 l four-neck flask with precision glass stirrer, dropping funnel, distillation apparatus, jacketed coil condenser, rotary vane oil pump, bottom thermometer, top thermometer and oil bath with temperature regulation was initially charged with 1250.0 g (69.4 mol) of demineralized water under an N.sub.2 blanket. Separately, within 35 minutes, a mixture of 480.0 g (2.17 mol) of Dynasylan AMEO and 120.0 g (0.46 mol) of AMEO high boilers was added dropwise by means of the metering device (AMEO high boilers is a mixture of Dynasylan AMEO and about 20% bis-AMEO). In the course of this, the bottom temperature rises from room temperature to 50 C. The mixture was stirred at 50 C. for 3 h. At an absolute pressure of 130 mbar to 100 bar, 450 g of ethanol/water mixture are distilled off at a bottom temperature of 39 C. to 41 C. within about 1.3 h. At the end, the end product is adjusted to a weight of 1500 g with water.

(30) The yield was 1500.0 g of colourless, slightly cloudy product.

(31) TABLE-US-00008 The space-time yield was 7.2 [g (Si)/(l h)]. Solids content 20.1% by weight Total alcohol not determined

(32) The analysis data of the product obtained are compared once again in summary in Table 1.

(33) TABLE-US-00009 TABLE 1 Comparison of the analysis data of the products obtained from the examples E 1 CE 1 E 2 CE 2 E 3 CE 3 CE 4 Molar ratio of the feedstocks: 12.3:1 12.3:1 12.3:1 6.2:1 12.2:1 12.3:1 26.4:1 water to silane component Solids content in the product 30.7 30.8 52.8 48.6 44.7 45.0 20.1 [% by wt.] SiO.sub.2 content in the product 16.4 16.4 28.6 26.2 21.3 21.8 9.3 [% by wt.] Viscosity (20 C.) 10.6 11.0 550 267 80.3 92 n.d. [mPas] Turbidity [FNU] 0.74 0.9 1.9 0.5 0.3 1.3 4 Total ethanol (after 0.7 1.4 0.2 6.5 0.3 0.1 n.d. hydrolysis) [% by wt.] Free ethanol in the product 0.7 1.4 0.2 5.9 0.3 0.1 n.d. [% by wt.] Colour number <5 <5 <5 <5 <5 <5 n.d. [mg PtCo/l] Space-time yield 21.3 11.2 21.1 11.7 12.0 6.3 7.2 [g (Si)/(l h)]
Comparison of the Results from the Experiments:

(34) Examples E1, CE1, B2 and CE2 (cf. Table 1) were conducted under comparable apparatus conditions. In the case of the procedure according to the invention, the STY and hence the economic viability were much higher compared to U.S. Pat. No. 6,512,132. Moreover, in CE2, a product with a much higher total ethanol content is obtained.

(35) Examples E3 and CE3 can also serve for a comparison of the STYs with regard to the apparatus prerequisites. Thus, Example 3 conducted in accordance with the invention has much better economic viability compared to Comparative Example 3, as demonstrated by the STY. The turbidity value in the product from CE3 is also well above that from E3.

(36) Comparative Example 4 (CE4) corresponds to the teaching according to Example 1 on EP 1031593 A2, except that only a solids content of 20% by weight is achieved therein.

(37) In addition, the metering and/or stirring times in CE1, CE2, CE3 or CE4 are much longer than in the inventive examples E1, E2 and E3.

(38) Furthermore, products according to the invention from E1, E2 and E3 have a high solids content and environmentally advantageous low VOC content (in the form of total ethanol), which constitutes a measure of the completeness of the hydrolysis reaction and hence not leastaside from the exceptional economic viability of the process according to the inventionalso a measure of its quality.