Sulfanylsilanes

Details Sulfanylsilanes Sulfanylsilanes

1999-09-29

2001-05-08

Shaver, Paul F. (Department: 1621)

Organic compounds -- part of the class 532-570 series

Organic compounds

Silicon containing

C556S427000, C556S415000, C152S151000, C523S209000, C523S213000, C523S215000, C523S216000, C524S155000, C524S262000, C524S265000, C525S102000, C525S342000, C525S351000, C525S352000

Reexamination Certificate

active

06229036

ABSTRACT:

INTRODUCTION AND BACKGROUND
The present invention relates to sulfanylsilanes, a process for the preparation thereof and their use.
It is known that sulfur-containing organosilicon compounds such as 3-mercaptopropyltrimethoxysilane or bis-(3-[triethoxysilyl]-propyl)tetrasulfane are used as silane coupling agents or reinforcing additives in oxidically filled rubber mixtures, inter alia for tire treads and other parts of car tires (DE 21 41 159, DE 22 12 239, U.S. Pat. No. 3,978,103, U.S. Pat. No. 4,048,206).
Furthermore, it is known that sulfur-containing silane coupling agents are used during the preparation of sealing compounds, casting moulds for metal goods, coloured and protective paints, adhesives, asphalt mixtures and oxidically filled plastics.
Other possible applications are for the fixing of active substances and functional units to inorganic support materials, for example for the immobilization of homogeneous catalysts and enzymes, for the production of fixed bed catalysts and for liquid chromatography.
The use of mercaptosilanes in rubber mixtures for tire treads is disclosed in the patent FR-A-2.094.859. Known mercaptosilanes and in particular 3-mercaptopropyltrimethoxysilane and 3-mercaptopropyltriethoxysilane are able to produce improved properties with regard to silica/elastomer coupling. The industrial use of these is not possible due to the high reactivity of the SH groups, because, during the production of the mixture, they lead to very rapid pre-vulcanization, also known as pre-scorch, with greatly increased Mooney plasticity and ultimately to mixtures which are almost impossible to process and use in an industrial situation.
For other applications such as, for example, industrial rubber items which are processed in a different way, mercaptosilanes may be used as reinforcing additives. However, in the case of almost all organic mercaptans, their intrinsic, extremely unpleasant and penetrating odor has proven to be a problem which can be only slightly reduced by mechanical means.
As a result of the pre-scorch phenomenon mentioned above, polysulfidic organosilanes, including bis-3triethoxysilyl-propyltetrasulfane or bis-3-triethoxysilylpropyldisulfane (DE 25 42 534, DE 24 05 758, DE 195 41 404, DE 197 34 295) are mostly used as coupling agents for tire treads, these seeming to be the best compromise for silica-filled vulcanizates with regard to reliability of vulcanization, simplicity of production and reinforcing power. However, these coupling reagents have to be used in relatively large amounts. Approximately 2 to 3 times as much as the amount of 3-mercaptopropyltrimethoxysilane are required to produce an equivalent level of coupling properties.
This disadvantage led to a few attempts to get round the processing difficulties by using better, in the sense of reinforcing properties, mercaptosilanes. An attempt of this kind is described in the U.S. Pat. No. 4,474,908. But this method did not produce satisfactory results with regard to scorching and processing problems and in addition is costly. Furthermore, patent EP 0 784 072 A1 describes the use of functional polyorganosiloxanes in addition to a mercaptosilane, which enabled, for the first time, the processing of mercaptosilanes as reinforcing agents in rubber mixtures for tire treads.
SUMMARY OF THE INVENTION
The invention provides sulfanylsilanes, which are characterized in that they are represented by the formula I
X
1
X
2
X
3
Si—A—S—SiR
1
R
2
R
3
  (I)
wherein
X
1
, X
2
, X
3
independently, represent H, (C
1
-C
8
)alkyl, (C
1
-C
8
)alkoxy, (C
1
-C
4
)haloalkyl, aryl, (C
7
-C
16
)aralkyl, halogen, —A—S—SiR
1
R
2
R
3
R
1
, R
2
, R
3
independently, represent H,(C
1
-C
6
)alkyl, (C
1
-C
16
)alkoxy, (C
1
-C
16
)haloalkyl, aryl, (C
7
-C
16
) aralkyl, halogen, X
1
X
2
X
3
—A—S
A represents a (C
1
-C
16
)alkyl group, each of which may be linear or branched, saturated or unsaturated and may optionally be substituted with (C
1
-C
4
)alkyl, (C
1
-C
4
)alkoxy, halogen, nitrile, (C
1
-C
4
)haloalkyl, NO
2
, (C
1
-C
4
)thioalkyl, NR
1
R
2
, —A—S—SiR
1
R
2
R
3
or X
1
X
2
X
3
—A—, aryl or (C
7
-C
16
) aralkyl.
A preferred group of sulfanylsilanes according to the invention are characterized in that
X
1
, X
2
, X
3
independently, represent (C
1
-C
4
)alkyl, (C
1
-C
4
)alkoxy, halogen
R
1
, R
2
, R
3
independently, represent (C
1
-C
4
)alkyl, (C
1
-C
4
)alkoxy, halogen or X
1
X
2
X
3
Si—A—S and
A represents (C
1
-C
4
)alkyl.
A further preferred groups of sulfanylsilanes according to the invention are characterized in that
X
1
, X
2
, X
3
independently, represent methoxy or ethoxy,
R
1
, R
2
, R
3
independently, represent methyl or X
1
X
2
X
3
Si—A—S
and
A represents propyl.
The expression “alkyl” is understood to cover both “straight-chain” and also “branched” alkyl groups. The expression “straight-chain alkyl group” is understood to cover, for example, groups such as methyl, ethyl, n-propyl, n-butyl, n-pentyl, n-hexyl, “branched alkyl group” is understood to cover groups such as, for example, isopropyl or tert.-butyl. The expression halogen stands for fluorine, chlorine, bromine or iodine. The expression “alkoxy” represents groups such as, for example, methoxy, ethoxy, propoxy, butoxy, isopropoxy, isobutoxy or pentoxy.
“Aryl” is understood, in the context of the invention, to cover phenyls, biphenyls or other benzenoid compounds which are optionally substituted with (C
1
-C
3
)alkyl, (C
1
-C
3
)alkoxy, halogen, hydroxyl or heteroatoms such as NR
1
R
2
OR
1
, PR
1
R
2
R
3
or SR
1
. “Aralkyl” is understood to mean that the “aryl ” groups mentioned above are bonded to the corresponding silicon atom or sulfur atom or with both via a (C
1
-C
6
)alkyl chain, which for its part may be substituted with (C
1
-C
3
)alkyl, (C
1
-C
3
)alkoxy or a halogen. If the “aryl” group has a heteroatom available, such as O or S, then the (C
1
-C
6
)alkyl chain may also form a bond with the silicon atom and/or sulfur atom via the heteroatom.
In the data given for substituents, such as e.g. (C
1
-C
4
)alkoxy, the number in the subscript gives the total number of carbon atoms in the group.
Examples of sulfanylsilanes according to the invention in accordance with formula (I) are:
(EtO)
3
—Si—(CH
2
)
3
—S—Si(CH
3
)
3
[(EtO)
3
—Si—(CH
2
)
3
—S]
2
Si (CH
3
)
2
[(EtO)
3
—Si—(CH
2
)
3
—S]
3
Si (CH
3
)
[(EtO)
3
—Si—(CH
2
)
3
—S]
2
Si (OEt)
2
[(EtO)
3
—Si—(CH
2
)
3
—S]
4
Si
(EtO)
3
—Si—(CH
2
)
3
—S—Si(OEt)
3
(MeO)
3
—Si—(CH
2
)
3
—S—Si(C
2
H
5
)
3
[(MeO)
3
—Si—(CH
2
)
3
—S]
2
Si(C
2
H
5
)
2
[(MeO)
3
—Si—(CH
2
)
3
—S]
3
Si(CH
3
)
[(MeO)
3
—Si—(CH
2
)
3
—S]
2
Si(OMe)
2
[(MeO)
3
—Si—(CH
2
)
3
—S]
4
Si
(MeO)
3
—Si—(CH
2
)
3
—S—Si(OMe)
3
(EtO)
3
—Si—(CH
2
)
2
—CH(CH
3
)—S—Si(CH
3
)
3
(EtO)
3
—Si—(CH
2
)
2
—CH (CH
3
)—S—Si(C
2
H
5
)
3
(EtO)
3
—Si—(CH
2
)
2
—CH (CH
3
)—S—Si(C
6
H
5
)
3
(EtO)
3
—Si—(CH
2
)
2
—(p—C
6
H
4
)—S—Si(CH
3
)
3
The invention also provides a process for preparing sulfanylsilanes of the general formula X
1
X
2
X
3
Si—A—S—SiR
1
R
2
R
3
, which is characterized in that the corresponding mercaptosilane X
1
X
2
X
3
Si—Alkyl—SH is reacted with chlorosilanes Cl—SiR
1
R
2
R
3
in the presence of a base in an organic solvent, the mixture is heated to boiling point to complete the reaction, the solvent is distilled off and solid hydrochloride produced from the base is then filtered off. As an organic solvent could be used alkanes. As a base could be used triethylamine or other amines.
The corresponding sulfanylsilanes are generally so clean that possible purification by distillation is not required.
DETAILED DESCRIPTION OF INVENTION
The expression “alkyl” is understood to cover both “straight-chain” and also “branched” alkyl groups. The expression “straight-chain alkyl group” is understood to cover, for example, groups such as methyl, ethyl, n-propyl, n-butyl, n-pentyl, n-hexyl, “branched alkyl group” is understood to cover groups such as, for example, isopropyl or tert.-butyl. The expression “halogen” stands for fluorine, chlori

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