DE1955511C - Process for the preparation of Hydroxylgruppe-free hydrogen silsesquioxa - Google Patents

Description

Hydrogen silsesquioxanes are known per se. However, these known products are not exhaustive condensed and contain at least some terminal hydroxyl or alkoxy groups. Because of this With their hydroxyl group content, the known hydrogen silsesquioxanes are susceptible to further condensation and when attempting to remove volatile solvents, like benzene or ether, to evaporate from it, easily an insoluble gel.

This gel formation during the hydrolysis reaction is referred to in US Pat. No. 2,901,460.

Furthermore, the preparation of condensed octameric hydrogen silsesquioxanes is known from a report by Müller and coworkers in Journal für Praktische Chemie (4), Vol. 9, p. 71 (1959). This compound of the formula HSiO ^ j) ₈ was obtained in a yield of less than 1% as an unexpected by-product in the reaction of trichlorosilane and hexamethyldisiloxane in 80% sulfuric acid. The cubic structure of this octamer is described by K. Larsson in Arkiv. Cbem., Vol. 16, p. 215 0960), discussed in detail

The subject of the present invention, however, is a process for the preparation of fully condensed hydrogen silsesquioxanes of fairly high molecular weight in high yields.

These hydroxyl-free polymers of the general formula

(HSiO ₁₁ ) ,,

where η is an even integer with average values of 10 or more are highly cyclized products that are soluble in non-polar solvents such as benzene and hexane. These polymers include volatile types and non-volatile, soluble ones

ίο high molecular weight resins. The polymers, which consist of up to 18 or more hydrogen silsesquioxane compounds, are non-volatile resins that are particularly good coating materials because they are in the form of a solution on the

Substrates can be applied and form a resinous film after evaporation of the solvent. They can be used to make textiles water-repellent and as anti-rust coatings for metal surfaces. Furthermore,

These hydrogen silsesquioxanes act as crosslinkers in Siloxane elastomers are incorporated.

The hydrogen silsesquioxanes which can be prepared according to the invention tend, in contrast to those previously known Species not for further condensation with gel formation.

as The inventive method for production Hydrogen silsesquioxanes free of hydroxyl groups of the general average formula

(HSiO ₃ , ^ ,,

(n = whole even number with an average Value of 10 or more), through hydrolysis and condensation of hydrogen silanes, is thereby marked that one

a) a solution of trichloro- or trimethoxysilanes in a hydrocarbon solvent in a reaction medium consisting of two phases, the concentrated sulfuric acid and

contains an aromatic hydrocarbon, enters and by vigorously mixing the Reaction medium avoids a noticeable gel formation of the reaction product,

b) then washing the reaction mixture with water until it reacts practically neutrally, and

c) then the condensed hydrogen silsesquioxane by evaporation of the solvent and the aromatic hydrocarbon wins.

Trichlorosilane is due to its easy availability So availability is preferred as the starting material

In the process according to the invention, the condensed hydrogen silsesquioxanes are very much obtained high to quantitative yields. The process can be batchwise or continuous

be performed. A preferred embodiment is a continuous reaction separation technique with recovery and recycling of the acidic reaction medium. To achieve virtually quantitative yields of the

Fully condensed polymer are certain factors in carrying out the process of decisive importance: the silane must be introduced into the acidic reaction medium in a fairly dilute solution. Solutions that are about 10

weight percent silane contained in the hydrocarbon solvent are preferred as such Solutions deliver maximum yields with the least amount of solvent possible.

s Hydrocarbon solvents can be any can be used in which the silanes are soluble: Examples are saturated aliphatic ^ hydrocarbons, such as n-pentane, hexane, n-heptane and iso-octane; aromatic and cycloaliphatic hydrocarbons, such as cyclohexane, benzene. Toluene and Xylene: and halogenated, aliphatic and aromatic Hydrocarbons such as trichlorethylene, perchiorethylene. Bromobenzene and chlorobenzene di Ghidiki

wide range: there only needs to be a sufficient Amount of water are formed, which can react with the silanes introduced into the medium. In one embodiment of the invention Procedure, a certain amount of fuming sulfuric acid is introduced into the reaction medium, so that most of the water present in the concentrated sulfuric acid is used up. Arylsulfonic acid can also be added to the reaction medium

di Ph again

must be pretty g g, a mer

Gelbiioung of parts of the product avoided and. The exact rate of addition depends on the Volume of the acidic medium and the degree of vermiculation over the medium. "

Putch stirrer or other mechanical mixing measures of the reaction timer and de < two-Mdi id i

hylen. Bromine and chlorobenzene. Arylsulfonic acid can also be used in

It is also the speed at which the silanes are entered. When the acidic phase again solution is introduced into the acidic medium, for use or again in the reaction cycle, Achieving high yields is very important. This addition is returned, it was found that the be done fairly slowly so that a noticeable reaction rate is slowed down. This To the disadvantage, the addition of a small amount of water

of the 15 amount to the acid phase during the recycle or balanced before reuse. This creates sulfuric acid and the equilibrium conditions are not affected.

measures of the reaction times and de < two- That when performing the designated

phase acidic medium is a separation of the 20 process obtained reaction product is a Ge phase of the medium avoided and the transport mix of volatile, oligomeric species of the formula of the kite supported in the acid, from which a (HSiO ,,),, < and a non-volatile, resinous, rapid dilution of the silane in the acidic phase polymer.

result.ert. The ratio of volatile olisomers to the

DI-. two-phase reaction medium contains concentrated as non-volatile polymer depends on the reaction lines sulfuric acid and aromatic carbon conditions, such as the hot substance added. Under the term "concentrated" is wedge of the silane and the sulfuric acid concentration. Sulfuric acid with a water content of up to. The reaction conditions also determine the relative 10 ^r . to understand. Large-scale quantities of the individual oligomeric types in the liquid can be volatile fraction of the product in the process according to the invention. ve ™ ends. The formation of octameric hydrogen silsesquioxanes

> .- second component of z \ eiphasigen reaction! Is generally low, it can, for. B. less than tion mediums are aromatic hydrocarbons, I ⁰ Z _{0 of} the total product. Benzene, toluene or xylene are used. Benzene and toluene assume that the octamer, because of their lower boiling points, is less resistant to rearrangement by acid than the others, since they can easily be distilled from the reaction mixture and that after a certain period of time they can graze . in the strongly acidic medium the octamer is higher

Although the exact reaction mechanism in which cyclized species such as (HSiO ₃ J ₁₈ rearranged were not known according to the method of the invention. The ratio of the species

could be the necessary for the hydrolysis of the silanes * o with low molecular weight in the volatile low water concentration from a sulfonation fraction by diluting the sulfuric acid must i d tih Kühltff t glacial acetic acid can be increased. The change in nature

of the product is to the greater effect the condensing silanes and the formation of the 45 sulfuric acid, causing the acid rearrangement of the octamer is reduced.

low water concentration originate from a sulfonation reaction of the aromatic hydrocarbon. according to the following equation:

CH "+ FLSO ₄ ^ C ₆ H ₅ SO ₃ H + H ₂ O.

This could result in partial hydrolysis of some of the silanes with the formation of silanols of the formulas

HSiX ₁ (OH), HSiX (OH) ₄ and HSi (OH) ₃

example 1

A solution of 12.7 g Tnchlorsilan in 150 ml of benzene ₅ o ^ wurd slowly Jn ^ a ^ .sch stirred M -

take place with the release of HX. Presumably sulfuric acid (95 to 98 ⁰ Z ₀ H ₁ SO ₄ ) and ^ 4g smoke, the silanes also react first with the acidic phase of sulfuric acid (15 "/, SO ₃ ) about 1. D" with the formation of silyl sulfate, silyl bisulfate and other Süanzugabe to the sa urehaltige η Mdiumdauerte different Silylarykulfonaten. It is believed 55 over 6.5 hours After completion of the Zugbe ™ rde that these compounds m then condensation with a Reak.tionsgem.sch ^ei ^ J ^l ** ™ ^r «£ «^ The SUanols form siloxane bonds under reverse phase and the acid phase is removed. The benzene phase was formed into sulfuric and / or arylsulfonic acid. The washed until it reacted neutrally. ... Dehydrating properties of sulfuric acid During the washing process, there was also vibrating support The prevention of the formation of 60 keiten due to the formation of El ^ IntojReak partial condensates.This mechanism leads to a tion mixture ^ 2g5K ffi complete condensation with formation of the hydro- presumably as surface-active Mitterw ^ gensilsesquioxane and excludes the presence of difficulty has been remedied by eliminating the sol substituents in the polymeric product. Solution with SO ^ ger SchweMsjfcreum ¹ then nut

then evaporated to dryness, and the residue consisted of 4.9 g (97.8% yield) of solid, resinous polymer · (HSiO _{3 2} ) n- This material did not gel during the drying process and was completely soluble in hexane.

Virtually the same results were obtained when this process was carried out continuously, using toluene as an aromatic hydrocarbon in the reaction medium.

Example 2

Several samples of condensed hydrogen silsesquioxane were prepared according to the procedure of Example 1. The volatile oligomeric fraction was 9 to 27% of the total product. The individual volatile components of this fraction were separated by gas chromatography using a chromatographic column of 3:05 m in length, filled with 20% trifluoroprop ¹ Imethylsiloxan on acid-washed filler material, screen mesh size: 80 has been used to 100th A typical distribution of the volatiles was as follows:

Volatile oligomers Molecular
Weight Weight percent of
volatile faction (HSiO ₁₂ ) ,,,
(HSiOj ₂ ) ,,
(HSiO _{3 !!} ), ₄
(HSiO _ai ) " 530
636
742
848 4.2
43.2
36.8
13.5

The molecular weights were determined by mass spectrometry detected. The infrared analysis of the types described above showed 2 = SiH bands at 4.4 and 11.4 microns and a high narrow Si-O-Si band at 8.8 microns, the latter being absorption is characteristic of the cage structure of polycyclic silsesquioxanes. Infrared analysis of the non-volatile content of these soluble resin samples was consistent the above, with an additional weak siloxane band at 9.0 to 9.5 microns, suggesting that the resin was largely polycyclic in structure with some irregular distributed siloxane bonds that cannot be assigned to the cage structure.

Example 3

A mixture of 2260 grams of the sulfuric acid phase recovered from an earlier process of this type and one liter of benzene was placed in a 5 liter flask. The contents of the flask were stirred vigorously while a solution of 136.5 g of trichlorosilane in 1.5 liters of benzene was added. The solution was added using a pressure equalizing dropping funnel under nitrogen. The addition was complete after 10.5 hours.

When the addition was complete, the reaction mixture was placed in a separatory funnel and the acid phase was removed. The benzene phase was then washed with water until it reacted neutrally on acid test paper. The solution was then dried with sodium sulfate and evaporated to dryness in vacuo. The reacted material was then redissolved in hexane and the solution evaporated to dryness in vacuo. 53.9 g of soluble, fully condensed hydrogen silsesquioxane were obtained.

In a sample of the product 15.9% volatiles were detected by sublimation. The distribution of the volatile constituents was determined by gas-liquid chromatography and calculation from the peak area in percent :

(HSiO _{3 2} ) _{! 0}
(HSiO ₃ ,), ·.
(HSiO ₃₂ I ₁₄
(HSiO ₃ ο) _Ι6

Example 4

12.4%

48.8%

35.7%

3.1%

A solution of 10 ml HSiCl ₃ (0.1 mol) in 150 ml benzene was poured into a reaction medium of 260 g concentrated (95 to 98%) H ₂ SO ₄ , 200 g fuming sulfuric acid (15 up to 18% O _s ) and 200 ml of benzene ao entered. After 24 hours, the benzene phase ν urde washed free of acid and evaporated under vacuum to dryness. 4 g (75.5% yield) of hexane soluble material was recovered. Analysis data for (HSiO ₁ J:

^a5 Calculated .... C 0%, H 1.89%, Si 52.8%; found .... C 1.52 ¹ V ₀ , H 1.73%. Si 49.2%.

No silanol content was detected by infrared analysis. The minor carbon content (1.52%) indicated the presence of traces of benzene in the product.

Example 5

A solution of 12.9 g of HSi (OCH _{3) 3} (0.106 mol) in 150 ml of benzene was added dropwise over 5 hours in a mixture of 80.2 g of concentrated (95 to 98%) sulfuric acid, 59.8 g of fuming sulfuric acid ( 15 to 18% SO ₈ ) and 200 ml of benzene added with stirring. After 72 hours the benzene phase was washed until it reacted neutrally, filtered and evaporated to dryness in vacuo. 3.6 g (68% yield) of hydrogen silsesquioxane soluble in hexane were obtained.

Example 6

A solution of 10 ml of HSiQ, (0.1 mol) in 150 ml of benzene was added dropwise over the course of 3.75 hours to a mixture of 170 g of concentrated sulfuric acid (95 to 98%), 35 g of benzenesulfonic acid and 200 ml of benzene with stirring . The benzene phase was washed until neutral and evaporated to dryness under vacuum. 4.0 g (75.5% yield) of soluble hydrogen silsesquioran were obtained.

Example 7

For comparison, a solution of 10 ml of HSiCl ₄ in 150 ml of benzene was introduced into a mixture of 177 g of concentrated sulfuric acid (95 to 98%) and 200 ml of benzene within 5.5 hours with stirring. The reaction mixture contained neither fuming sulfuric acid nor benzenesulfonic acid. After washing and evaporating the benzene in vacuo, 1.8 g (34% yield) of soluble hydrogen silsesquioxane was obtained.

This example shows that the process can be performed without the addition of fuming sulfuric acid or arylsulfonic acid in a two-phase reaction medium

liur dui be ·.

eh ler

can be carried out. However, it also shows that greater yields are achieved by adding these components.

. Examples

A solution of 10 ml (0.1 mol) of HSiCl in 150 ml of benzene was poured into a reaction medium of 80 g of concentrated (95 to 98 ° / _e ) sulfuric acid, 60 g of fuming sulfuric acid (15 ° / ₀ SO ₃ ), 200 ml of glacial acetic acid and 200 ml of benzene added with stirring. The addition of the silane reactant to the reaction medium was made after the medium was cooled to room temperature.

Analysis of the product (HSiO ,,,) by gas-liquid chromatography showed three volatiles: (HSiO ₃₁₁ ) J, (HSiO ₃ Zt) ₁₀ and (HSiOaIt) _n , which are present in a peak area ratio of 2: 2: 1 was.. ·

This example shows the effect of glacial acetic acid, which increases the content of low molecular weight oligomers in the volatile components of the reaction product.

g he oil se

309635/326

Claims (3)

Patent claims: 1. Process for the preparation of hydroxyl-free hydrogen silsesquioxanes of the general Average formula 0; - whole even number with an average Value of 10 or more) by hydrolysis and condensation of hydrogen silanes. through this marked that one a) a solution of trichloro- or trimethoxysilanes in a hydrocarbon solution mine in a reaction medium consisting of two phases, which contains concentrated sulfuric acid and an aromatic hydrocarbon, enters and avoids a noticeable gel formation of the reaction product by vigorous mixing of the reaction medium, b) then the reaction mixture washes with water until it reacts practically neutral, and c) then the condensed hydrogen silsesquioxane by evaporation of the solvent and the aromatic hydrocarbon wins. 2. The method according to claim 1, characterized in that there is used as the aromatic hydrocarbon for the two-phase The reaction medium used is benzene or toluene. 3. Modification of the method according to claim 1, characterized in that one additionally fuming sulfuric acid or an arylsulfonic acid are used in addition to the concentrated sulfuric acid.