WO1992011266A1

WO1992011266A1 - Tetralkoxy silanes, process for their production and their use

Info

Publication number: WO1992011266A1
Application number: PCT/EP1991/002426
Authority: WO
Inventors: Christian Block; Wolfgang Breuer; Helmut Endres; Johannes Hachgenei
Original assignee: Henkel Kommanditgesellschaft Auf Aktien
Priority date: 1990-12-19
Filing date: 1991-12-17
Publication date: 1992-07-09
Also published as: DE4040679A1

Abstract

The description relates to tetralkoxy silanes of Guerbet alcohols, a process for producing bright-coloured tetralkoxy silanes of general formula Si(OR)4 by the transesterification the tetramethoxy or tetraethoxy silane with an alcohol in the presence of catalytic quantities of at least one double-layer hydroxide compound of general formula (I) with the continuous removal of methanol or ethanol and the use of the bright-coloured tetralkoxy silanes as cosmetic constituents, cooling lubricants, hydraulic fluids, heat transfer fluids or anti-foaming agents.

Description

"Tetraalkoxysilanes, a Process for the Production and Their Use"

The invention relates to tetraalkoxysilanes from Guerbet alcohols, a process for the preparation of light-colored tetraalkoxysilanes of the general formula Si (0R _. 4 by transesterification of tetramethoxy or tetraethoxysilane with an alcohol in the presence of catalytic amounts of at least one double-layer hydroxide compound with continuous removal of methanol or ethanol, and the like Use of the light-colored tetraalkoxysilanes as cosmetic ingredients, cooling lubricants, hydraulic fluids, heat transfer fluids or defoamers.

Tetraalkoxysilanes of the general formula Si (0R) 4, which are also referred to as silica tetraesters, are derived from long-chain fatty alcohols and are known, for example, as textile treatment agents. For example, according to German published patent application DE-A-12 69 995, silicic acid esters of unsaturated straight-chain fatty alcohols give textiles a soft feel. Unfortunately, textile materials that have been treated with these silicic acid esters at higher temperatures show a yellowing that is unacceptable for light textiles.

According to German Offenlegungsschrift DE-A-25 10872, silicic acid esters of fatty alcohols from oxo synthesis can also be used as textile treatment agents. Oxo alcohols of this type are essentially saturated and also have 35 to 65% by weight, branched alcohols such as 2-methylundecanol, 2-n-octyldecanol and 2-n-hexyltridecanol. Despite the high proportion of branched alcohols, the hydrolysis stability of their aqueous ones Emulsions are not sufficient if the emulsion is still free

Acid is present. A further disadvantage is that, owing to the production process, the tetraalkoxysilanes can already have their own color or that corrosive hydrochloric acid is produced in the production process.

The tetraalkoxysilanes can be prepared either by direct alcoholysis of tetrachlorosilane or by transesterification of tetramethoxy or tetraethoxysilane with the corresponding alcohols. The transesterification reactions of alkoxysilanes with alcohols have been known in the art for some time (see, for example, in H. Steinmann, G. Tschernko and H. Hamann, Z. Che. Vol. 17, pp. 89-92, 1977). Transesterification catalysts have hitherto generally been used both acids, such as hydrogen chloride, hydrogen fluoride, sulfuric acid, trifluoroacetic acid or p-toluenesulfonic acid, and bases, such as alkali metal hydroxides, methanolates or ethanolates. However, the use of the above-mentioned bases leads to colored tetraalkoxys which, for. B. must be cleaned by an additional distillation step. However, tetraalkoxysilanes can no longer be purified from higher alcohols with a chain length of more than 12 carbon atoms by distillation. In these cases, the basic catalyst must first be neutralized and then the salt formed must be separated off, which means an additional process step.

For this reason, the addition of basic catalysts has been dispensed with in recent developments. For example, a recent publication (Bull. Chem. Soc. Jpn, Vol. 61, pp. 4087-4092, 1988) describes the use of an Amberlyst 15 cation exchanger in the transesterification of tetraethoxysilane with butanol. This Cation exchanger is, however, less effective with higher alcohols and has to be reprocessed after the conversion.

The object of the present invention was to provide a new process for the preparation of tetraalkoxysilanes by transesterification of the easily accessible tetramethoxysilane or tetraethoxysilanes with higher alcohols, which, using a suitable catalyst, had the shortest possible reaction times with a high degree of esterification leads to high-purity, light-colored tetraalkoxysilanes. Another object of the present invention was to provide tetraalkoxysilanes which show improved hydrolysis stabilities.

The present invention accordingly relates to a process for the preparation of light-colored tetraalkoxysilanes of the general formula Si (0R) 4, in which R represents a straight-chain and / or branched-chain, saturated and / or unsaturated, aliphatic hydrocarbon radical, by transesterification of Tetramethoxy or tetraethoxysilane with at least one alcohol in the presence of a catalyst, characterized in that the transesterification at temperatures of 80 to 250 ° C in the presence of at least one double-layer hydroxide compound of the general formula

[M (II) ι_ _x M (III) _X (0H) ₂ ] A _a B _b * zH ₂ 0 (I)

in the

M (II) at least for a divalent metal cation,

M (III) at least for a trivalent metal cation,

A for one equivalent of a monoanion of an aliphatic

Monocarboxylic acid with 2 to 34 carbon atoms or for an equivalent a dianion of an al phatic dicarboxylic acid with 4 to 44 C-

Atoms stands,

B represents an equivalent of an inorganic anion, from the group formed by carbonate, hydrogen carbonate, sulfate, nitrate, nitrite, phosphate, hydroxide and halides, and in which the conditions 0.1 _ x _ 0.5, 0 ≤ a ≤ 0.5, 0 _ b _ 0.5, 0 <a + b _ 0.5 and 0 _ z _ 10 are considered to be heterogeneous catalysts and the methanol or ethanol is continuously removed from the reaction mixture.

For the purposes of the invention, the divalent metal cation of the formula (I) is preferably selected from magnesium, calcium, manganese, zinc and copper. The trivalent metal cation of formula (I) is preferably selected from iron and aluminum. If the above - in connection with the explanation of the general formula (I) - is spoken of at least one divalent and trivalent metal cation, this means that in such double-layer hydroxide compounds there may be several divalent or trivalent metal cations next to each other can be present.

Two-dimensional inorganic polycations with intra-crystalline charge balancing by means of movable interlayer anions are also known under the name "double-layer hydroxide compounds" and have been described several times in the literature. Is referred to, for. B. on R. Allmann, "Double-layer structures with brucite-like layered ions", Chimia 24, 99 to 108 (1970). Chemical pose these compounds are mixed hydroxy salts of 2- and 3-valent metal ions and can be characterized by the general formula II:

CM (II) i_χ (III) _x (0H) ₂ ] Bχ ^• z H ₂ 0 (II) where

M (II) for at least one divalent metal ion, M (III) for at least one trivalent metal ion and B for an equivalent of a mono- and / or polybasic inorganic acid and x is a number from 0.2 to 0.4 and z represent a number from 0 to 10.

Some properties of this class of compounds, such as their use as catalyst material, as ion exchangers and some medical applications, have been summarized by W. T. Reichle ("Anionic Clay Minerals", CHEMTECH, Jan. 1986, pp. 58 to 63). Various possibilities for the technical production of these compounds are specified in DE-A-2061 156 and DE-A-20 61 114.

A well-characterized representative of this group of substances is hydrotalcite, which occurs as a mineral in nature. There are also known synthetic hydrotalcites which are described, for example, in DE-C-1 592 126, DE-A-3 346 943, DE-A-3 306 822 and EP-A-207 811. Hydrotalcite is a natural mineral with the ideal formula [Mg6Al ₂ (0H) i5] C03.4H ₂ 0, whose structure is derived from that of brucite (Mg (0H) ₂ ). Brucite crystallizes in a layer structure with the metal ions in octahedral gaps between two layers of densely packed hydroxyl ions, only every second layer of the octahedral gaps being occupied. In hydrotalcite, some magnesium ions are replaced by aluminum ions, which means that the shift package receives a positive charge. This is compensated for by the anions which are located in the intermediate layers together with zeolitic crystal water.

Other typical representatives of this group of substances include magaldrate with the ideal formula [gκ) Al5 (0H) 3i] (S04) * nH ₂ 0, pyroaurite with the ideal formula [Mg6Fe ₂ (0H) i6] C03 * 4.5H ₂ 0 and hydrocalumite the ideal formula [Ca Al (0H) 6] N03 * nH ₂ 0.

For the purposes of the present invention, calcined double-layer hydroxide compounds of the general formula (I) can also be used in the process according to the invention. The calcined compounds of the general formula (I) are obtained by heating or calcining by continuously releasing water. In general, the crystal water is completely released at temperatures around 200 ° C. A further increase in temperature leads both to the elimination of water from the hydroxide structure and of carbon dioxide from the carbonate which is usually present as a counter anion.

A prototype of such compounds is the calcined hydrotalcite, of which, for example from DE-A-30 19 632, the anion reuptake is known, with reformation of the layer structure.

In a preferred embodiment of the present invention, the double-layer hydroxide compounds of the general formula (I) used can be the hydrophobic double-layer hydroxide compounds described in the not yet published German patent applications P 40 10 606.3 and P 40 34 305.7 of the applicant. According to the teaching of this unpublished patent application, the hydrophobic double-layer hydroxide compounds are reacted in a low-boiling organic solvent, preferably alcohols with 1 to 6 carbon atoms, open-chain and cyclic ethers and / or ketones, by reacting monocarboxylic acids and / or dicarboxylic acids with double-layer hydroxide. Compounds of the general formula II

[M (II) ι_ _x M (III) _X (0H) ₂ ] B _x * zH ₂ 0 (II)

manufactured. The hydrophobization is particularly preferably carried out in isopropanol, diethyl ether, tetrahydrofuran and / or acetone.

The hydrophobicized double-layer hydroxide compounds of the general formula I can also be obtained by direct reaction of double-layer hydroxide compounds of the general formula II with mono- and / or dicarboxylic acids without the addition of a solvent using any stirring tool, preferably a kneader.

In principle, the compounds of the general formula I can also be analogous to the process known from the teaching of DE-A-3731 919 by reacting double-layer hydroxide compounds with an aqueous suspension of an alkali metal and / or alkaline earth metal salt, preferably sodium salts Produce mono- and / or dicarboxylic acid.

Finally, the hydrophobicized double layer hydroxide compounds can also be obtained from calcined double layer hydroxide compounds by reacting them with the mono- or dicarboxylic acids be preserved; carbonate-free or carbonate-containing products can be obtained with the exclusion of air or COg or in the presence of carbon dioxide.

The stoichiometric water content of the hydrophobic double-layer hydroxide compounds can - depending on the type of production and the drying conditions - be in the range from 0 to 10 molecules; a range from 0 to 4 molecules is preferred, which is generally obtained if the hydrophobic double-layer hydroxide compounds are dried to constant weight at temperatures in the range from 100 to 250 ° C., preferably from 150 to 220 ° C., so that a particularly high catalytic activity can be guaranteed.

In a particularly preferred embodiment of the present invention, compounds derived from hydrotalcite, preferably hydrotalcite, hydrophobized hydrotalcite and / or calcinated hydrotalcite, are used as double-layer hydroxide compounds of the general formula I.

In a general embodiment of the present invention, the reaction mixture containing tetramethoxy or tetraethoxysilane, at least one alcohol and at least one catalyst of the general formula (I) is raised to 80 at a temperature of from 2 to 5 ° C. per minute to 140 ° C, preferably 110 to 130 ° C, heated and then with continuous removal of the methanol or ethanol formed at a reduced temperature heating rate of 0.1 to 2 ° C, preferably 0.3 to 1 ° C, per minute to 150 to 250 ° C, preferably 180 to 200 ° C, heated. In a preferred embodiment of the present invention, the transesterification is carried out in such a way that, based on the amount of methanol or ethanol distilled off, a degree of transesterification of 50 to 99%, preferably 85 to 95%, is achieved. For the purposes of the present invention, the degree of transesterification is understood to mean a percentage which results from the quotient of the amount of alcohol actually distilled off and the amount of alcohol which can theoretically be achieved with quantitative conversion.

For the purposes of the present invention, the transesterification of tetramethoxy or tetraethoxysilane with the corresponding alcohol is carried out in a molar ratio of 1: 4 to 1:10, preferably 1: 4.5 to 1: 6. According to the invention, a slight excess of alcohol is therefore preferred, which is either removed together with the methanol or ethanol in the course of the distillative separation or is separated off in a separate distillation step.

In the general embodiment of the present invention, straight and / or branched-chain, saturated and / or unsaturated, aliphatic alcohols having 3 to 32 carbon atoms can be used for the transesterification according to the invention. By way of example only, propanol, butanol, fatty alcohols having 6 to 32 carbon atoms and mixtures of these compounds are to be mentioned here.

In a preferred embodiment, at least one straight-chain or branched-chain, primary or secondary, aliphatic alcohol having 3 to 32 carbon atoms, preferably 2-0ctanol or Guerbet alcohols, is used in the transesterification.

From the multitude of technically producible Guerbet alcohols (see H. Machemer, Angew. Chemie, Volume 64, pages 213-220, 1952 and G. Dieckelmann u. HJ Heinz, "The Basics of Industrial Oleochemistry", pages 145-146, 1988), in particular Guerbet alcohols with 6 to 20 carbon atoms, such as 2-methylpentanol, 2-ethylhexanol, 2-hexyldecanol, 2-0ctyldecanol, 2-Hexyldodecanol and / or 2-octyldodecanol, preferably used.

In principle, however, aromatic alcohols, such as benzyl alcohol, cinnamon alcohol, phenol, dihydroxy- or trihydroxy-benzene derivatives, and cycloaliphatic alcohols having 3 to 20 carbon atoms, such as cyclopropanol, cyclobutanol or cyclodecanol, can also be used according to the invention for the transesterification.

For the purposes of the present invention, the double-layer hydroxide compounds of the general formula I are used in an amount of 1 to 20% by weight, preferably 5 to 15% by weight, based on the respective amount of tetramethoxy or tetraethoxysilane. In principle, smaller amounts of double-layer hydroxide compounds can also be added, although longer reaction times must be expected. According to the invention, the double-layer hydroxide compounds can be used several times for further transesterification even without special work-up.

The present invention furthermore relates to tetraalkoxysilanes of the general formula Si (0R) 4, in which R represents the rest of Guerbet alcohols having 12 to 38 C atoms, preferably R each represents the same radical of a Guerbet alcohol. Suitable examples of Guerbet alcohols are 2-butyloctanol, 2-hexyldecanol, 2-nonyltridecanol, 2-0ctyldodecanol and n-dodecylhexadecanol. Technical Guerbet alcohols are preferred, the technical Guerbet alcohols due to it Manufacturing process can contain up to 20 wt .-% tri- and tetramer Guerbet alcohols. These tetraalkoxysilanes according to the invention can either be prepared by the process according to the invention or by one of the processes known from the prior art. The decisive factor here is whether particularly light-colored tetraalkoxy lanes are desired for the application or not. If the color is not important, the preparation is carried out by the processes known from the prior art, preferably by transesterification of tetramethoxy or tetraethoxysilane in the presence of bases, preferably sodium methoxide, as a catalyst, for example in accordance with the American patents US Pat. No. 2,643,263 or 26 73870. The amounts of tetramethoxy or tetraethoxysilane to be used and the respective Guerbet alcohols correspond to the details of the process according to the invention. After the transesterification, the tetraalkoxysilanes are expediently the

Guerbet alcohols with 12 to 38 carbon atoms are then neutralized in a conventional manner, for example with an acid such as the dilute phosphoric acid. The resulting sodium phosphate is then separated off via the aqueous phase. If light-colored tetraalkoxysilanes according to the invention of Guerbet alcohols are desired, they must be prepared by the process according to the invention.

The invention furthermore relates to the use of the light-colored tetraalkoxysilanes prepared by the process according to the invention as cosmetic ingredients, cooling lubricants, hydraulic fluids, heat transfer fluids or defoamers. Examples

Example 1 a - d

Reaction of tetramethoxysilane with 2-ethylhexanol / hydrotalcite

38.0 g (0.25 mol) of tetramethoxysilane and 162.5 g (1.25 mol) of 2-ethylhexanol were placed in a distillation apparatus consisting of 250 ml round-bottomed flasks and a 10 cm packed column. 3.8 g of catalyst (10% by weight, based on tetramethoxysilane) were then added, the catalyst consisting of variously modified double-layer hydroxide compounds (see table). The reaction mixture was then heated to 120 ° C. in the course of 20 to 30 minutes. After the start of the reaction, the reaction temperature was increased continuously up to 200 ° C. at a temperature heating rate of 0.5 ° C. per minute while distilling off the methanol formed. At a degree of transesterification of approximately 85 to 95% (determined by the indirect determination of the amount of methanol), the reaction was stopped, the catalyst was filtered off and the product mixture was worked up and analyzed by distillation.

Verσ.e.chsbeispie.e 1 a - c

Reaction of tetramethoxysilane with 2-ethylhexanol / methanolate

38.0 g (0.25 mol) of tetramethoxysilane and 162.5 g (1.25 mol) of ethylhexanol were placed in a distillation apparatus consisting of 250 ml round-bottomed flasks and a 10 cm packed column. Then were

0.66 g (12.5 mmol) sodium methoxide in 9.5 ml methanol (comparative example a), 0.87 g of potassium ethanolate in 10 ml of methanol (comparative example b), 3.8 g of sodium methoxide in 50 ml of methanol (comparative example c) were added.

The reaction mixture was then heated to 80-90 ° C. in the course of 15-20 minutes and, after the reaction had started, the methanol formed as the reaction temperature rose (heating rate approx. 0.5 ° C. per minute, up to 200 ° C. ) separated by distillation. At a degree of transesterification of approximately 85 to 95% (determined by indirectly determining the amount of methanol), the reaction was stopped. After cooling, the crude product was mixed with water in a volume ratio of 1: 1 and dilute phosphoric acid was added until neutralization. The organic phase was separated off and then fractionally distilled (bp at 1 torr: 194 ° C., tetra-2-ethylhexylsilane).

The same procedure was followed for the reaction of tetramethoxysilane with 2-0ctanol (see Table 2) (Example 2).

Table 1: Implementation of tetramethoxysnan with 2-ethylhexanol

¹ [g6 Al ₂ (0H) ₁₆ ] CO3 x 4 H ₂ 0 (from Guilini; type C 300)

2 hydrotalcite (2 kg) hydrophobized with lauric acid (1 kg), kneaded at 80 ° C. for 1 h; Dried in vacuo for 2 h at 200 ° C.

³ Calcination (4 h) of the hydrotalcite at 500 ° C., cooled to 300 ° C. and then stored in a desiccator at room temperature.

⁴ Amount used: see in the text of comparative example 1

It can be seen from Table 1 that after a reaction time of 2 hours, both hydrophobic and caleinated hydrotalcite have the same degree of conversion as the alkali metal alcoholates, which are present as a methanolic solution and are therefore homogeneous catalysts. This is particularly surprising since heterogeneous catalysts are very often less active than homogeneous ones. Furthermore, the use of hydrotalcite leads to colorless products.

Table 2: Implementation of tetramethoxysilane with 2-0ctanol

¹ hydrotalcite (2 kg) hydrophobized with lauric acid (1 kg), kneaded at 80 ° C. for 1 h; Dried in vacuo for 2 h at 200 ° C.

Example 3

Reaction of tetraethoxysilane with 2-ethylhexanol

52 g (0.25 mol) of tetraethoxysilane and 162.5 g (1.25 mol) of 2-ethylhexanol were placed in a distillation apparatus consisting of 250 ml round bottom flask and a 10 cm packed column. Then 3.8 g of catalyst (7.3% by weight, based on tetraethoxysilane) were added, the catalyst consisting of variously modified double-layer hydroxide compounds. The reaction mixture was then heated to 120 ° C. within 20 to 30 minutes. After the reaction started, the reaction temperature became continuous at a temperature heating rate increased from 0.5 ° C per minute to up to 200 ° C with separation of the ethanol formed. At a degree of transesterification of about 85 to 95% (determined by the indirect determination of the amount of ethanol), the reaction was stopped, the catalyst was filtered off and the product mixture was worked up and analyzed by distillation.

Comparative Example 3

Reaction of tetraethoxysilane with 2-ethylhexanol

52 g (0.25 mol) of tetraethoxysilane and 162.5 g (1.25 mol) of 2-ethylhexanol were placed in a distillation apparatus consisting of 250 ml round bottom flask and a 10 cm packed column. Then were

0.66 g (12.5 mmol) sodium methoxide (1.3% by weight, based on tetraethoxysilane) in 9.5 ml methanol was added

The reaction mixture was then heated to 90-100 ° C. in the course of 15-20 minutes and, after the reaction had started, the resulting ethanol or methanol at an increasing reaction temperature (heating rate approx. 0.5 ° C. per minute, up to 200 ° C) separatively separated. At a degree of transesterification of about 85 to 95% (determined by the indirect determination of the amount of ethanol), the reaction was stopped, after cooling the crude product was mixed with 1: 1 by volume with H2O and dilute phosphoric acid was added until neutralization. The organic phase was separated and fractionally distilled. Table 3: Reaction of tetraethoxysilane with 2-ethylhexanol

- Hydrotalcite (2 kg) hydrophobized with lauric acid (1 kg), kneaded for 1 h at 80 ° C; 2 hours at 200 ° C in a vacuum.

Example 4

Implementation of tetraethoxysilane with 2-0ctyldodecanol

In a distillation apparatus analogous to Example 1, 156 g (0.75 mol) of tetraethoxysilane and 1399.9 g (3.4 mol) of 2-octyldodecanol, 2.7 g of sodium methoxide in the form of a 30% by weight methanoic solution were at 120 ° C warmed. Analogous In Example 1, the reaction temperature was slowly increased to 160 ° C. The reaction was terminated at a degree of transesterification of 95%. After cooling, the mixture was also neutralized with dilute phosphoric acid (see Comparative Example 1) and the organic phase was separated off and dried. A strong yellow product was obtained with a refractive index ΠD ₂ Q = 1.4582.

Example 5

Implementation of tetramethoxysilane with 2-0ctyldodecanol

Analogously to Example 1, 114 g (0.75 mol) of tetramethoxysilane were reacted with 1399 g (3.4 mol) of 2-0ctyldodecanol in the presence of 11.4 g of a hydrophobicized hydrotalcite (1 kg lauric acid to 2 kg hydrotalcite). After the hydrotalcite had been separated off, the excess 2-0ctyldodecanol was distilled off in vacuo. A colorless tetraalkoxysilane was obtained.

Example 6

Reaction of tetraethoxysilane with 2-butyloctanol

Analogously to Example 4, 156 g (0.75 mol) of tetraethoxysilane and 695 g (3.73 mol) of 2-butyloctanol and 5.07 g of sodium ethanolate were reacted as a methanolic solution. Working up was also carried out analogously to Example 4. A yellow product was obtained with the following characteristics: ΠD Q = 1.4482.

Example 7

Reaction of tetraethoxysilane with 2-hexyldecanol Analogously to Example 4, 145.6 g (0.7 mol) of tetraethoxysilane, 762.9 g (3.15 mol) of 2-hexyldecanol and 1.9 g of sodium methoxide (30% by weight solution) were reacted.

A yellow product was obtained with a refractive index of nD ₂ o = 1.4544.

As can be seen from the examples and comparative examples, the use of catalytic amounts of double-layer hydroxide compounds surprisingly leads to colorless tetraalkoxysilanes with a similar reaction time and degree of conversion compared to base catalysis.

Claims

Patent claims

1. Process for the preparation of light-colored tetraalkoxysilanes of the general formula Si (0R) 4, in which R represents a straight-chain and / or branched-chain, saturated and / or unsaturated, aliphatic hydrocarbon radical, by transesterification of tetramethoxy or tetraethoxysilane with at least one alcohol in the presence of a catalyst, characterized in that the transesterification at temperatures of 80 to 250 ° C in the presence of at least one double-face hydroxide compound of the general formula

[M (II) ι_ _x M (III) _X (0H) ₂ ] A _a B _b * zH ₂ 0 (I)

in the

M (II) at least for a divalent metal cation,

M (III) at least for a trivalent metal cation,

A for one equivalent of a monoanion of an aliphatic

Monocarboxylic acid with 2 to 34 carbon atoms or for an equivalent of a dianion of an aliphatic dicarboxylic acid with 4 to 44

Carbon atoms,

B for an equivalent of an inorganic anion, from which of

Carbonate, bicarbonate, sulfate, nitrate, nitrite, phosphate,

Hydroxide and halides formed group, and in which the conditions

0.1 _ x _ 0.5,

0 _ a _ 0.5,

0 _ b _ 0.5, 0 <a + b _ 0.5 and

0 _ z _ 10 are considered to be heterogeneous catalyst and the methanol or

Ethanol continuously removed from the reaction mixture.

2. The method according to claim 1, characterized in that the double-layer hydroxide compound of the general formula I derived from hydrotalcite compounds, preferably hydrotalcite, hydrophobized hydrotalcite and / or calcined hydrotalcite.

3. The method according to claim 1 and 2, characterized in that the reaction mixture containing tetramethoxy or Te¬ traethoxysilane, at least one alcohol and at least one catalyst of the general formula I, with a Temperatur¬ heating rate of 2 to 5 ° C per minute heated to 80 to 140 ° C, preferably 110 to 130 ° C, and then with continuous removal of the methanol or ethanol formed at a reduced temperature heating rate of 0.1 to 2 ° C per minute, preferably 0.3 to 1 ° C per minute , heated to 150 to 250 ° C, preferably 180 to 200 ° C.

4. Process according to claims 1 to 3, characterized gekennzeich¬ net that one carries out the transesterification with a degree of transesterification - based on the amount of methanol or ethanol distilled off - from 50 to 99%, preferably 85 to 95%.

5. The method according to claims 1 to 4, characterized gekennzeich¬ net that the transesterification of tetramethoxy or Tetra¬ ethoxysilane with the corresponding alcohol in one mol Ratio of 1: 4 to 1:10, preferably 1: 4.5 to 1: 6.

6. The method according to claims 1 to 5, characterized gekennzeich¬ net that for the transesterification of tetramethoxy or tetraethoxysilane at least one straight or branched chain, primary and / or secondary alcohol having 2 to 32 carbon atoms, preferably 2-0ctanol or Guerbet alcohols.

7. The method according to claim 6, characterized in that one uses Guerbet alcohols having 6 to 20 C atoms, preferably 2-methylpentanol, 2-ethylhexanol, 2-hexyldecanol, 2-octyldecanol, 2-hexyldodecanol and / or 2-0ctyldodecanol.

8. The method according to claims 1 to 7, characterized gekennzeich¬ net that the double-layer hydroxide compounds of the general formula I in an amount of 1 to 20 wt .-%, preferably 5 to 15 wt .- - based to the respective amount of tetramethoxy or tetraethoxysilane.

9. Use of the light-colored tetraalkoxysilanes according to claims 1 to 8 as cosmetic ingredients, cooling lubricants, hydraulic fluids, heat transfer fluids or defoamers.

10. Tetraalkoxysilanes of the general formula Si (0R) 4, in which R represents the rest of Guerbet alcohols with 12 to 38 carbon atoms.