Oligomeric organosilanepolysufanes, their use in rubber...

Details Oligomeric organosilanepolysufanes, their use in rubber... Oligomeric organosilanepolysufanes, their use in rubber...

1999-06-10

2001-12-18

Dawson, Robert (Department: 1712)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

From silicon reactant having at least one...

C523S213000, C524S492000, C556S427000, C556S431000, C556S435000, C568S021000

Reexamination Certificate

active

06331605

ABSTRACT:

CROSS-REFERENCE TO RELATED APPLICATION
This application is based on German Application DE 198 25 796.1, filed Jun. 10, 1998, which disclosure is incorporated herein by reference.
FIELD OF THE INVENTION
The present invention relates to new oligomeric organosilanepolysulfanes, a process for preparing these and their use in rubber mixtures and for preparing molded articles.
BACKGROUND OF THE INVENTION
It is known that sulfur-containing organosilicon compounds such as 3-mercaptopropyltrimethoxysilane or bis-(3-[triethoxysilyl]-propyl)tetrasulfane can be used as silane bonding agents or reinforcing agents in oxide-filled rubber mixtures, inter alia for the treads and other parts of car tires (DE 2 141 159, DE 2 212 239, U.S. Pat. No. 3,978,103, U.S. Pat. No. 4,048,206).
EP 0 784 072 A1 discloses rubber mixtures based on at least one elastomer with silica as filler and a reinforcing additive, which is prepared by admixing or by producing ‘in situ’ as a reaction product from at least one functional polyorganosiloxane compound, and which contain a functional organosilane as a further constituent. Monomeric building blocks which are used are in particular 3-mercaptopropyltrialkoxysilanes or bis-(trialkoxy-silylpropyl)tetrasulfanes, each of which contain 3 or 6 alkoxy substituents respectively.
Furthermore, it is known that sulfur-containing silane bonding agents, are used during the preparation of scaling compounds, casting molds for casting metal, colorant and protective paints, adhesives, asphalt mixtures and oxide-filled plastics materials.
Finally, possible applications include the fixing of active substances and functional units on inorganic support materials, e.g. when immobilizing homogeneous catalysts and enzymes, when preparing fixed bed catalysts and for liquid chromatography.
When preparing a rubber mixture with organosilanes and a filler, for example a precipitated silica, a chemical reaction takes place during a first mixing process, for example in an internal mixer. This chemical reaction consists of a condensation reaction between the organosilane and the filler, which is associated with the release of considerable amounts of an alcohol. This eliminated alcohol sometimes causes considerable technical problems during further processing of the rubber mixture, such as porosity of the mixture during extrusion or the undesired production of bubbles in the rubber itself. Furthermore, a reduction in the amount of alcohol released during reaction is desirable for health and environmental reasons.
SUMMARY OF THE INVENTION
It has now been found that these disadvantages in the prior art can be largely avoided by the use of oligomeric organosilanepolysulfanes instead of the monomeric sulfur-containing compounds used hitherto.
Accordingly, the present invention provides new oligomeric organosilanepolysulfanes in which the oligomeric organosilanepolysulfane is built up from the three structural units A and/or B and/or C,
in which Y=H, CN, —(CH
2
)
n
SiRR
1
R
2
;
R, R
1
, R
2
and R
3
, independently, represent H, (C
1
-C
4
)alkyl, (C
1
-C
4
)alkoxy, halogen or a OSiR
1
R
2
R
3
group;
x, as a statistical average, is 1-6,
z, as a statistical average, is 2-6, and
n is 1-8 and
o, p and q are each a whole, positive number from 1 to 40 where o+p+q may be ≧2 and <40, with the proviso that at least one structural unit A or B is present in the oligomeric organosilanepolysulfane.
Preferred oligomeric organosilanepolysulfanes of the type described above are built up from the 3 structural units A and/or B and/or C
in which Y, R, R
1
, R
2
, R
3
, x, z and n are defined in the same way as given above and o, p and q are each a whole, positive number between 1 and 20 where o+p+q may be ≧2 and <20, with the proviso that at least one structural unit A or B is present.
The oligomeric organosilanepolysulfanes according to the invention may be designed to be cyclic, branched or linear via Y.
Compounds according to the invention may be either individual compounds with a defined molecular weight or an oligomeric mixture with a range of molecular weights. For process engineering reasons, oligomeric mixtures are generally simpler to prepare and accept. The compounds have molecular weights between about 800 and 16000 g/mol. Oligomeric organosilanepolysulfanes according to the invention preferably have molecular weights between about 800 and 5000 g/mol.
Oligomeric organosilanepolysulfanes according to the invention are built up in particular from the structural units B and C which are obtained by copolymerization of a suitable polysulfane and an organosilane.
Oligomeric organosilanepolysulfanes according to the invention are prepared by condensation of any two alkoxysilyl structural units. Within the scope of the substitution pattern mentioned above, any sulfur-containing organosilicon compound may be oligomerized with itself or copolymerized with another sulfur-containing or non-sulfur-containing organosilicon compound. In order to prepare oligomeric organosilanepolysulfanes according to the invention, a monomeric compound of the structural type I
in which Y=H, CN, —(CH
2
)
n
SiRR
1
R
2
;
R, R
1
and R
2
, independently, represent H, (C
1
-C
4
)alkyl, (C
1
-C
4
)alkoxy, halogen or a OSiR
1
R
2
R
3
group and x, as a statistical average, may be 1 to 6, optionally in a solvent and/or optionally with the aid of a catalyst, is polymerized with itself at a reaction temperature between 0° C. and 150° C. and with the addition of water or is copolymerized under similar reaction conditions with a compound of the structural type II
RR
1
R
2
R
3
Si  (II)
in which R, R
1
, R
2
and R
3
, independently, represent H, (C
1
-C
4
)alkyl, (C
1
-C
4
)alkoxy, halogen or a OSiR
1
R
2
R
3
group.
The list given below mentions examples of some (sulfur-containing) organosilicon compounds which are suitable for the reaction according to the invention:
bis-(3-[triethoxysilyl]-propyl)tetrasulfane,
3-thiocyanatopropyltriethoxysilane,
3-mercaptopropyltrimethoxysilane,
propyltriethoxysilane, octyltriethoxysilane, hexadecyltriethoxysilane,
dimethyldiethoxysilane,
3-mercaptopropyltriethoxysilane,
bis-3-triethoxysilylpropyldisulfane,
bis-3-triethoxysilylpropyltrisulfane.
The condensation reaction takes place by adding water with the elimination of alcohol and may be performed in bulk or in an inert organic solvent or mixtures thereof such as, for example, in an aromatic solvent such as chlorobenzene, a halogenated hydrocarbon such as chloroform or methylene chloride, an ether such as diisopropyl ether, tert.-butyl methyl ether, tetrahydrofuran or diethyl ether, acetonitrile or a carboxylate, for example ethyl acetate, methyl acetate or isopropyl acetate or an alcohol, for example methanol, ethanol, n-propanol, i-propanol, n-butanol, sec.-butanol or tert.-butanol. Preferred solvents are ethanol or ethyl acetate. The reaction may be catalyzed. The catalyst may then be added in catalytic or stoichiometric amounts. Any type of acidic, basic or nucleophilic catalysts, which are known to a person skilled in the art of the SOLGEL chemistry of alkoxysilanes (see e.g. R. Corriu, D. Leclercq, Angew. Chem. 1996, 108, 1524-1540) are also suitable for oligomerization reactions in the context of the invention. It makes no difference here whether the catalysts are present in the same phase as the reaction solution (homogeneous catalysis) or are present as solids (heterogeneous catalysis) and isolated after completion of the reaction.
Homogeneous catalysis with a Lewis acid such as, for example, tetrabutyl orthotitanate or nucleophilic catalysis with ammonium fluoride or heterogeneous catalysis with aluminum oxide are particularly suitable. Basic catalysis takes place, for example, with an organic base such as triethylamine, tetramethylpiperidine, tributylarnine or pyridine or with an inorganic base such as NaOH, KOH, Ca(OH)
2
, Na
2
CO
3
, K
2
CO
3
, CaCO
3
, CaO, NaHCO
3
, KHCO
3
or alcoholates such as NaOCH
3
or NaOC
2
H
5
. Nucleophilic catalysis may take place using any

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