Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From silicon reactant having at least one...
Reexamination Certificate
2002-07-03
2004-04-27
Moore, Margaret G. (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From silicon reactant having at least one...
C556S429000, C524S493000, C524S496000, C524S506000
Reexamination Certificate
active
06727339
ABSTRACT:
INTRODUCTION AND BACKGROUND
The present invention relates to oligomeric organosilanes, a process for their production as well as their use.
It is known to use sulfur-containing organosilicon compounds such as 3-mercaptopropyltrimethoxysilane or bis-(3-[triethoxysilyl]-propyl) tetrasulfane as silane coupling agents or reinforcing additives in oxidically filled rubber mixtures, including inter alia for treads and other parts of automobile tires (DE 2 141 159, DE 2 212 239, U.S. Pat. Nos. 3,978,103, 4,048,206).
Rubber mixtures are known from EP 0 784 072 A1 that are based on at least one elastomer with silica as a filler and a reinforcing additive that is produced by mixing, or as an in situ reaction product, at least one functional polyorganosiloxane compound, and that contain a functional organosilane as a further constituent. As monomeric building blocks there are used in particular 3-mercaptopropyltrialkoxysilanes or bis (trialkoxysilylpropyl) tetrasulfanes that in each case carry 3 or 6 alkoxy substituents.
In the production of rubber mixtures 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 involves a condensation between the organosilane and the filler, which is accompanied by a considerable release of alcohol. This eliminated alcohol causes to some extent considerable technical problems during the further processing of the rubber mixtures, such as mixture porosity in the extrusion or undesirable formation of bubbles in the rubber per se. Furthermore a reduction in the release of alcohol during the reaction is desirable for both health and environmental reasons.
It is known that these disadvantages can be largely avoided by the use of oligomeric organosilanepolysulfanes instead of the monomeric sulfur-containing organosilicon compounds that were hitherto used.
Oligomeric organosilanes that are built up from different tructural units A and/or B and/or C
are known from EP 0964021.
A disadvantage of the known oligomeric organosilanes is the poor reinforcing behaviour in rubber mixtures.
An object of the present invention is to produce oligomeric organosilanes that have an improved reinforcing property in rubber mixtures and that on account of the oligomerization lead to a reduced release of ethanol during the mixing process and the subsequent processing steps.
SUMMARY OF THE INVENTION
The above and other objects of the present invention can be achieved by oligomeric organosilanes that are built up from the following 2 structural units A and B according to formula I,
wherein R
1
, R
2
denote a (C
1
-C
4
)alkoxy group, preferably a
methoxy or ethoxy group,
R
3
denotes a straight-chain or branched (C
1
-C
20
)alkyl group, preferably a propyl, octyl or hexadecyl group,
n is equal to 1-8, preferably 3, and
o and p in each case denote a whole positive number from 1-40,
where p/o is equal to 0.2/1 to 6/1.
Where R
3
═C
1
-C
5
then p/o may preferably be 2/1 to 5/1, where R
3
═C
6
-C
8
then p/o may preferably be 0.5/1 to 3/1 and where R
3
═C
9
-C
20
then p/o may preferably be 0.2/1 to 2/1.
The oligomeric organosilanes may be present as an individual compound with a defined molecular weight as well as an oligomeric mixture with a molecular weight distribution.
The oligomeric organosilanes can have molecular weights of 200 to 16000 g/mole. Preferably the oligomeric organosilanes according to the invention can have molecular weights of 400 to 5000 g/mole.
The invention also relates to a process for the production of the oligomeric organosilanes as described herein, which comprises forming a reaction mixture by mixing together the monomeric compounds of the structure types I and II
in which R
1
, R
2
, R
3
and n have the meanings given above and R
4
is a (C
1
-C
4
)alkoxy group, preferably a methoxy or ethoxy group, in which R
4
may be identical or different, and then co-oligomerizing the reaction mixture.
In this connection organosilicon compounds of arbitrary structure and with variously long sequences of the two structural units may be formed within the scope of the structure types I and II given above.
DETAILED DESCRIPTION OF THE INVENTION
According to the invention, the co-oligomerization reaction may be carried out in a solvent and/or optionally with the aid of a catalyst, at a reaction temperature between 0° C. and 150° C.
As the organosilicon compound of the structural unit I there can be used mercaptopropyltriethoxysilane, mercaptopropyl-trimethoxysilane or mercaptopropyl-methyldiethoxysilane.
As the organosilicon compound of the structural unit II there can be used propyltriethoxysilane, propyltrimethoxysilane, propylmethyldiethoxysilane, dimethyldiethoxysilane, octyltriethoxysilane, octyltrimethoxysilane, hexadecyltriethoxysilane or hexadecyltrimethoxysilane.
The co-oligomerization can be carried out with the addition of water and the release of alcohol 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, methylene chloride, an ether such as diisopropyl ether, tert.butyl methyl ether, tetrahydrofuran or diethyl ether, acetonitrile or carboxylic acid esters, for example ethyl acetate, methyl acetate or isopropyl acetate, an alcohol, for example methanol, ethanol, n-propanol, i-propanol, n-butanol, sec. butanol or tert. butanol. Preferred solvents may be ethanol or ethyl acetate.
The reaction according to the present invention may be catalysed. The catalyst can be added in catalytic or stoichiometric amounts. In this connection all types of acidic, basic or neucleophilic catalysts that are known to the person skilled in the art from the SOLGEL chemistry of alkoxysilanes (see for example R. Corriu, D. Leclercq, Angew. Chem. 1996, 108, 1524-1540) are also suitable for the oligomerization within the context of the invention. The catalysts may be present in the same phase as the reaction solution (homogeneous catalysis) or may be present as solids (heterogeneous catalysis) and are separated after the end of the reaction.
An acidic, basic or nucleophilic catalyst can be used in the catalysis.
The basic catalysis can be carried out for example with an organic base such as triethylamine, tetramethylpiperidine, tributylamine 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 can be performed with aluminum oxide or suitable fluorides, for example ammonium fluoride, sodium fluoride, potassium fluoride, or arbitrary tetraalkylammonium fluorides such as tetrabutylammonium fluoride.
Acid catalysis can be carried out with dilute aqueous mineral acids or solutions of Lewis acids in water. Tetrabutyl orthotitanate can for example be used as Lewis acid.
The catalysis is preferably carried out with dilute aqueous NaOH or a solution of ammonium fluoride in water, 1 mole % of catalyst being employed with reference to the amount of water used.
Suitable amounts of methanol can be added for the catalysis.
The reaction conditions, in particular the amount of water added, can be chosen so that the reaction products do not polycondense to form a solid.
After completion of the reaction the readily volatile constituents can be removed and the catalyst can be deactivated in a conventional manner or removed.
The present invention also relates to rubber mixtures which comprise rubber, fillers such as for example precipitated silica, optionally further rubber auxiliary substances, as well as at least one oligomeric organosilane according to the invention.
The oligomeric organosilane according to the invention can be used in amounts of from 0.1 to 15 wt. %, referred to the amount of the rubber used.
The addition of the oligomeric organosilanes according to the invention as well as the addition of the fillers can preferably take place at melt temperatures of 100° to 200° C. The addi
Hasse Andre
Krafczyk Roland
Luginsland Hans-Detlef
Radcziwill Michael
Degussa - AG
Moore Margaret G.
Smith , Gambrell & Russell, LLP
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