Organic compounds -- part of the class 532-570 series – Organic compounds – Silicon containing
Reexamination Certificate
2000-02-22
2001-10-23
Shaver, Paul F. (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Silicon containing
Reexamination Certificate
active
06307082
ABSTRACT:
RELATED APPLICATIONS
This application claims priority to German application No. 199 07 814.9, filed on Feb. 24, 1999, herein incorporating by reference.
BACKGROUND OF THE INVENTION
The invention relates to a synergistic catalyst system and a process for carrying out hydrosilylation reactions.
Modified siloxanes, in particular organomodified siloxanes, are becoming increasingly important because of their largely definable property profile.
FIELD OF THE INVENTION
A basic synthetic strategy of producing this class of compound employs transition metal-catalyzed addition of SiH-containing silicones onto olefinic compounds (hydrosilylation). Among the many reactions which can be carried out according to this coupling principle, it is possible to distinguish those whose aim is to produce siloxanes having very high degrees of modification, for example derivatives of poly(methylhydrogen)siloxane.
In view of the strongly exothermic nature of SiC-coupling reactions, reactions of poly(methylhydrogen)-siloxanes, particularly in combination with very reactive olefins, represent a considerable hazard potential in large-scale industrial production of organo-modified siloxanes.
The difficulties in the case of these hydrosilylation reactions having a high thermodynamic potential are compounded by a fluctuation in the reaction kinetics caused by partial deactivation of the catalyst used. The partial deactivation of compounds active as homogeneous catalysts can frequently be recognized by the precipitation of dark-colored noble metal derivatives from the hydrosilylation mixtures.
For this reason, sufficiently prompt reaction of the reactants is of key importance for safe industrial implementation. Otherwise, a significantly reduced reaction rate leads to the build-up of undesirable starting material concentrations which subsequently cause operating conditions which are difficult to control when the reaction recommences later (exothermic surge).
Going beyond the safety aspect, the product quality which is achievable in such reactions also depends on the avoidance of uncontrolled accumulation of starting materials, since, for example, the tendency to gel formation is known as an undesirable secondary reaction in the hydrosilylation of hydrogen-rich SiH-siloxanes.
OBJECT OF THE INVENTION
It is therefore an object of the invention to maintain a constantly high catalytic activity over the entire course of the reaction.
SUMMARY OF THE INVENTION
It has now surprisingly been found that specific combination of two or more compounds of platinum metals (e.g.: H
2
PtCl
6
with RuCl
3
×nH
2
O) in-situ generates a catalyst system which ensures safe, prompt reaction of SiH-rich hydrogensiloxanes even in reaction matrices which have been found by experience not to stabilize proven noble metal catalysts sufficiently.
A person skilled in the art could not have foreseen that the combination of two or more noble metal compounds defines a catalytic activity which can be deduced from neither the individual influence of component A nor from the separate influences of each of the components B, C, . . . (see comparative experiments Examples 1 and 2 and 5).
Although hexachloroplatinic acid H
2
PtCl
6
as sole catalyst leads to high final SiH conversions, it tends to cause reactant accumulations which lead to violent spontaneous reactions (Example 1). Ruthenium(III) chloride hydrate is on its own not a convincing catalyst in these reaction systems (Example 2). The activity of rhodium(III) chloride hydrate as catalyst in this reaction is similarly weak (Example 5).
The overproportional catalytic efficiency of a plurality of individual components found here as a result of their combination can therefore be described as a synergistic interaction.
A combination comprising, for example, metal-equivalent proportions of H
2
PtCl
6
and RuCl
3
×nH
2
O allows the course of the reaction in highly concentrated SiH-containing systems to be determined purely by the addition rate of further reactants.
In a modified embodiment of the present invention, it is also possible to introduce the two catalyst components one after the other in a sequential addition reaction (Example 4).
REFERENCES:
patent: 2823218 (1958-02-01), Speier et al.
Dieter Klein Klaus
Knott Wilfried
Windbiel Dagmar
Frommer & Lawrence & Haug LLP
Goldschmidt AG
Shaver Paul F.
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