CS232487B1 - Process for preparing diphenylsilandiol - Google Patents

Abstract

The invention relates to the preparation of diphenylsilandiol in a solvent. According to the invention, said thiophene is obtained by allowing diphenyldichlorosilane to be added to 1 to 100 times by weight of an organic solvent of the general formula RGOX under intensive stirring at a temperature not exceeding 60 ° C, wherein R is hydrogen or alkyl of 1 to 3 carbon atoms and X is alkyl or C 1 to C 5 alkoxy, provided that when R is hydrogen, X is only alkoxy having a designated carbon atom, wherein at least one of R and X contains at least 2 carbon atoms and 1 to 100 times the amount of water; an aromatic hydrocarbon or a mixture of aromatic hydrocarbons having a higher boiling point than the organic solvent used, the organic solvent is distilled off and the diphenylsilandiol is isolated.

Description

The invention relates to a process for preparing diphenylsilandiol from diphenyldichlorosilane.

It is known that in filled organopolysiloxane mixtures their properties change over time. This change towards the rigid nature of the mixture may be undesirable and sometimes it is necessary to re-mix the mixture before repeating.

The addition of diphenylsilandiol used in the preparation of the filled mixture will reduce unwanted solidification or reduce the Saxon and energy requirements for bringing the mixture to a condition suitable for further processing.

For this purpose, it is suitable that the diphenylsilandiol is in a fine form, free of agglomerates and containing as little inorganic substances as possible, which is particularly important for meeting high electrical requirements.

Diphenylsilandiol can also be used as a starting material in the preparation of other compounds. In the preparation of diphenylsilandiol from diphenyldichlorosilane, both the solvent and the diphenylsilandiol can be worked up.

When the preparation is conducted in a solvent (e.g. U.S. Patent 2,646,441), non-alkaline reagents such as alkali metal bicarbonates must be used to neutralize.

However, the reactivity of these compounds in the anhydrous medium is not too high, so that reactions leading to the formation of polycondensates, reducing the yield of monomeric diol, find use.

In the solvent-free processes, the resulting diol is insoluble in the aqueous environment and conditions are created for the closure of the starting materials, neutralization products and polycondensates in the diol particles.

Alkali carbonates, bicarbonates, or mixtures thereof with alkali hydroxides (e.g., German Patent 1,618,403 and German Patent 2,342 3.3) are used for neutralization. Inorganic diol has to be reduced in the isolated diol by washing with water.

But this is lengthy and imperfect. German Patent 2 342 313 discloses a chlorine content of 0.2 g per Kg of product and for the procedure of German Patent 1 6.8 403 even a content of 2 g of chlorine per kg of product and a polycondensate content of 5-1096 wt. wt.

The increased content of polycondensates leads to a requirement for the use of grinding aids in the grinding of the diol. Solvent-free processes also have the disadvantage that if the optimal hydrolysis process fails (for example due to a technical defect), the content of polycondensates and inorganic substances in the diol increases and this reduced quality is irreparable within the technological process used.

Solvent and solvent-free preparation processes can be combined. For example, a diol isolated from an aqueous medium is dissolved in acetone (U.S. Patent 2,899,453), neutralized with bicarbonate, and after removal of the inorganic salts by filtration, the diol is precipitated from the acetone solution with water.

Obviously, solvent-free processes cannot provide a high purity product both in terms of chloride ion content and in terms of polycondensates and impurities derived from starting diphenyldichlorosilane.

It has now been found that diphenylsilandiol in good yield and quality can be prepared by allowing diphenyldichlorosilane, with vigorous stirring and a temperature not exceeding 60 ° C, to be added to a 1 to 100 times the amount of organic solvent RCOX where R is hydrogen or alkyl of 1 to 3 X and X are alkyl or alkoxy of 1 to 5 carbon atoms, provided that when R is hydrogen, X is only alkoxy of a limited number of carbon atoms, wherein at least one of R and X contains at least 2 carbon atoms of 1 to 100 times % by weight of water, after which an aromatic hydrocarbon or a mixture of aromatic hydrocarbons of a higher boiling point than my organic solvent is added to the resulting hydrolyzate solution, the organic solvent is distilled off and the diphenylsilandiol is isolated.

The aromatic hydrocarbon or mixture of aromatic hydrocarbons, or a portion thereof, can be added to the starting components in place of the obtained hydrolyzate.

The hydrolyzate solution can be washed with water, optionally with the addition of an alkaline agent, preferably ammonia water, and filtered.

The process is advantageous in that the hydrolysis of diphenyldichlorosilane proceeds rapidly, without the evolution of by-products of the reaction mixture foaming as in the case of the use of carbonates and bicarbonates.

The resulting solution can be filtered to remove gelled impurities from the starting diphenyldichlorosilane or other mechanical impurities and so further improve the quality of the final product.

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By applying a hydrocarbon of the aromatic group, which has a higher solubility for polycondensates and some impurities from the starting diphenyldichlorosilane than for diphenylsilandiol, the impurity content of the product can be further reduced selectively.

Due to the requirement for the de-distillation of the lower-boiling organic solvent from its mixture 8 by a hydrocarbon, a sufficient difference in their boiling points is desirable and it is preferable not to form an azeotropic mixture with respect to the distilled amount.

In order to reduce the dispersion of the particle size of diphenylsilandiol, it is suitable to carry out the distillation of the organic solvent with good mixing of the mixture.

Due to the condensation properties of the silanol, distillation at lower temperatures is appropriate, which is made possible by the selection of a suitable hydrocarbon and by distillation under reduced pressure.

The choice of the relatively low boiling hydrocarbon facilitates its later removal from its mixture with diphenylsilandiol.

The examples below illustrate an embodiment of the process of the invention without limiting it.

ř k '1 and d 1.

600 g of water, 400 g of toluene, 700 g of ethyl acetate were introduced into the flask and 100 g of technical diphenyldichlorosilane having a purity of 98.55% by weight were added over 13 minutes with vigorous stirring of the mixture.

After the lower layer was evaporated, the solvent layer was washed 6 times with 100 g of water, filtered and the lower boiling portions were distilled off under stirring and reduced pressure. The distillation residue was cooled, filtered, and the filter cake was washed 3 times with 75 g of toluene and degassed with toluene by suction of air.

232 * 67

81 g of the product were obtained as tiny needles and contained 1.4 ppm Cl. The yield was 96.2% of the theory of diphenylsilandiol.

Example 2

1,500 g of water, 1,000 g of toluene, 1,750 g of ethyl acetate were introduced into the flask and 250 g of diphenyldichlorosilane of the same quality as in Example t were added over 30 minutes under the same conditions as in Example 1. except that portions of 250 g of water were washed through, and to the second wash water was added 5 ml of ammonia water and an NH4 concentration of 25% by weight. and the filter cake was washed 3 times with 125 g of toluene. 204 g of product were obtained, representing 96.9% of the theory of diphenylsilandiol. 01 content was 0.3 PPW ·

Example 3

600 g of water, 600 g of ethyl acetate were added to the flask, and 100 g of diphenyldichlorosilane of the same quality as in Example 1 was admitted from the vigorous stirring over 10 minutes with cooling at 15-20 ° C.

The procedure was the same as in Example 1 except that it was washed 4 times, and to the first wash water was added 1.2 ml of ammonia water, 400 g of toluene was added before distillation, and the filter cake was washed 3 times with 100 g of toluene.

81.2 g of product (96.2% of theory) were obtained with a content of 1 ppm Cl.

Example 4

To the present mixture of 500 g of water, 350 g of ethyl acetate and 300 g of toluene, 50 g of diphenyldichlorosilane of purity according to Example 1 were added over a period of 10 minutes at 14-6 ° C. The upper layer was not washed and was treated analogously to Example 1. 40.1 g of product (95.3% of theory) were obtained with a content of 1.5 ppm Cl.

Example 5 '

The procedure was similar to that in Example 3. 50 g of water and 350 g of methyl isobutyl ketone were used. 50 g of diphenyldichlorosilane were allowed to flow in the course of 10 minutes at 14-16 ° C. It was washed 6 times with 25 g of water with the addition of 0.2 ml of ammonia water.

Before distillation, 350 g of xylene was added instead of toluene. 40.5 g of product (96.2% of theory) were obtained with a content of 1.5 ppm Cl.

Example 1 a d 6

To the present mixture of 150 g of water, 350 g of ethyl formate and 200 g of toluene, 50 g of diphenyldichlorosilane of the same quality as in Example 1 were admixed at 0-6 ° C at 0-6 minutes.

Washed 6 times with 25 g of water with the addition of ammonia water. After distillation of the solvent, filtration, washing the filter cake 3 times with 50 g of toluene and drying, 32 g of product (75% of theory) were obtained with a content of 11 ppm Cl.

Example 1 a d 7

The procedure was similar to Example 3. Methyl ethyl ketone was used instead of ethyl acetate. 61 g of product (72.5% of theory) were obtained with a content of 2 ppm Cl.

Example 8

The procedure was similar to Example 3. 150 g of water, 350 g of butyl acetate were charged and 50 g of diphenyldichlorosilane were allowed. The hydrolyzate solution was washed 6 times with 25 g of water, 350 g of xylene was added prior to distillation, and the filter cake was washed 3 times with 50 g of xylene. 39.1 g of product (92.9% of theory) were obtained with a content of 11 ppm Cl.

Claims (3)

Process for the preparation of diphenylsilandiol, characterized in that, with vigorous stirring, at a temperature not exceeding 60 ° C, diphenyldichlorosilane is admixed with from 1 to 100 times by weight of an organic solvent of the formula RCOX, wherein R is hydrogen or C 1 -C 3 alkyl; alkyl or alkoxy of 1 to 5 carbon atoms, provided that when R is hydrogen, X is only alkoxy of a limited number of carbon atoms, wherein at least one of R and X contains at least 2 carbon atoms and 1 to 100 times by weight of water, an aromatic hydrocarbon or a mixture of aromatic hydrocarbons of a higher boiling point than the organic solvent used is added to the resulting hydrolyzate solution, the organic solvent is distilled off and the diphenylsilandiol is isolated. 2. A process according to claim 1, wherein all or part of the hydrocarbon or a mixture of hydrocarbons or part thereof is added to the starting components. 3. The process according to claim 1, wherein the hydrolyzate solution is washed with water, optionally with the addition of an alkaline reagent, preferably ammonia water, and optionally filtered.