Sulfur-functional polyorganosiloxanes

Details Sulfur-functional polyorganosiloxanes Sulfur-functional polyorganosiloxanes

2002-05-13

2004-07-06

Lipman, Bernard (Department: 1713)

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

Synthetic resins

Mixing of two or more solid polymers; mixing of solid...

C525S479000

Reexamination Certificate

active

06759486

ABSTRACT:

INTRODUCTION AND BACKGROUND
The invention relates to new sulfur-functional polyorganosiloxanes, a process for their preparation and their use in rubber mixtures and for the production of mouldings.
The use of sulfur-containing organosilicon compounds such as 3-mercaptopropyltriethoxysilane or bis(3-[triethoxysilyl]propyl)tetrasulfane as silane coupling agents or reinforcing additives in rubber mixtures containing oxide filler for use as treads and other parts of automobile tires is known (DE 2 141 159, DE 2 212 239, U.S. Pat. No. 3,978,103, U.S. Pat. No. 4,048,206).
Furthermore, it is known that sulfur-containing silane coupling agents can be used in the production of sealing compounds, moulds for metal casting, paint coatings and protective coatings, adhesives, asphalt mixtures and for plastics containing oxide filler.
These coupling or bonding agents form bonds both with the filler and with the elastomer and consequently bring about a good interaction between the filler surface and the elastomer. They lower the mixing viscosity and facilitate the dispersion of the filler.
EP 0 784 072 A1 describes the use of a combination of a silane coupling agent and a functionalized polyorganosiloxane having at least one functional siloxyl group which can bond to the silica.
As a coupling agent in rubber mixtures, 3-mercaptopropyltriethoxysilane is able to produce an improved silica/elastomer coupling at a comparatively low dosage (U.S. Pat. No. 3,350,345, FR-A-2 094 859). However, owing to the high reactivity of the SH group and consequently the well-known tendency to form preliminary cross-linking as well as increased mixing viscosity, the workability of the mixtures and their industrial application are limited. It is also known that the addition of a protective additive consisting of a functional polyorganosiloxane having at least one functional siloxyl group decreases the reactivity, lowers the mixing viscosity and thus ensures that such rubber mixtures are workable (EP 0 784 072 A1).
From the economic aspect it is to be regarded as disadvantageous that, in addition to the silane coupling agents described in EP 0 784 072 A1, a siloxyl-functionalized polyorganosiloxane also has to be added to the rubber mixture.
Furthermore, it is known that the use of commercially available silane coupling agents (DE 22 55 577) having three alkoxy substituents on the silicon atom leads to the release of considerable quantities of alcohol during the mixing process.
It is therefore an object of the present invention to avoid problems of the prior art.
SUMMARY OF THE INVENTION
The above and other objects of the invention can be achieved by sulfur-functional polyorganosiloxanes corresponding to the general formula I corresponding to the general formula I
wherein R
1,
R
2
, R
3
, R
4
, independently of one another, denote H, (C
1
-C
4
)alkyl, (C
1
-C
4
)alkoxy, (C
1
-C
4
) haloalkoxy, (C
1
-C
4
) haloalkyl, phenyl, aryl or aralkyl and
W denotes a group which can bond to the silica and preferably can be (C
1
-C
4
) alkoxy
or
(C
1
-C
4
) haloalkoxy and
Y denotes alkyl, haloalkyl, phenyl, aryl or aralkyl and
Z denotes an alkylidene group having 0-6 carbon atoms and
A denotes a group which can bond with at least one elastomer of the rubber mixture:
for q=1 preferably a mercapto group
(SH) and thiocyanate group (SCN) and for q=2 a disulfide (S
2
) and a polysulfide (S
x
) with x=2-10 and H denotes hydrogen and
the sum of k+m+n+p≧3 and also k and n can equal 0.
Preferred polyorganosiloxanes in connection with the invention which may be mentioned first of all are the following, built up from linear statistical, sequential or block polymers, in which R
1
, R
2
, R
3
and R
4
=alkyl, in particular methyl, W=alkoxy, in particular ethoxy, Y=alkyl, in particular n-propyl, Z=alkylidene, in particular CH
2
CH
2
CH
2
, m and p=1-100, and k and n=0-50, with the sum of k+m+n+p=10-150, in particular 20-100.
In a preferred embodiment, R
1
, R
2
, R
3
, R
4
can be methyl, W=ethoxy, Y=n-propyl, Z=CH
2
CH
2
CH
2
, A=mercapto (SH), thiocyanate (SCN) for q=1 and A=polysulfide (S
x
) and disulfide (S
2
) for q=2 and k+m+n+p=10-150, in particular 20-100.
The polyorganosiloxanes according to the invention wherein A=S
x
can be cyclic, branched or linear in form.
DETAILED DESCRIPTION OF INVENTION
The compounds according to the invention can exist both as an individual compound having a defined molecular weight, and as a mixture of oligomers having a molecular weight distribution.
The compounds according to the invention corresponding to the general formula I can be easily prepared in two steps, by reacting compounds corresponding to the general formula II
wherein R
1
, R
2
, R
3
and R
4
have the meanings given above and v can be a number between 2 and 150, with compounds corresponding to the general formula III
wherein R
5
H, alkyl and X are fluorine, chlorine, bromine and iodine, preferably chlorine, and w is a number between 0 and 15, preferably w=1 and R
5
=H (allyl chloride) and also R
5
=methyl (methallyl chloride), under catalytic conditions by a mechanism of hydrosilylation using a catalyst from the family of the platinum metals, optionally in a solvent, and optionally at reaction temperatures between 20° C. and 200° C., at pressures between normal pressure or an excess pressure up to 6 bar, to form compounds corresponding to the general formula IV
wherein R
1
, R
2
, R
3
, R
4
, X, Y, Z, m, n and p have the meanings given above.
In the second step, compounds corresponding to the general formula IV can be reacted with MSH, MSCN or M
2
S
x
,
wherein M is a metal ion and x, on statistical average, can be a number between 2 and 10, or with M
2
S and S, wherein M is a metal ion, in an alcohol W-H, wherein W has the meaning given above, optionally at reaction temperatures between 20° C. and 150° C. and optionally under catalytic conditions, at normal pressure, to form the compounds according to the invention corresponding to the general formula I.
The compound corresponding to formula IV can advantageously be prepared as follows: A subequivalent quantity of a mixture consisting of a compound corresponding to formula III, wherein X, R
5
and w have the meanings given above, and a platinum catalyst, preferably of the Karstedt type, are added without solvents, at normal pressure or excess pressure up to 6 bar, preferably at normal pressure, at temperatures between 20° C. and 200° C., particularly preferably 100° C. to 150° C., to a compound corresponding to formula II. The mixture is stirred for 1 h to 8 d, preferably 1 to 4 h, at normal pressure or excess pressure up to 6 bar, preferably at normal pressure, at temperatures between 20° C. and 200° C., particularly preferably 100° C. to 120° C., then the reaction is concluded and the new compounds of type IV remain behind, mostly in the form of viscous liquids.
The reactions can advantageously be carried out under absolute conditions, that is, with the exclusion of moisture.
Various hydrosilylation processes of the type described above are known from U.S. Pat. No. 3,159,601, EP-A-57 459, U.S. Pat. No. 3 419 593, U.S. Pat. No. 3,715,334, U.S. Pat. No. 3,775,452 (Karstedt).
Owing to the differing selectivities of the catalysts, there can be a resulting formation of the fragment corresponding to formula V
wherein R
4
, X, Y and n have the meanings given above.
At a selectivity of 100%, n 0 in compound IV and in fragment V respectively.
In a second step, the compound according to the invention corresponding to formula I can advantageously be prepared as follows: A compound corresponding to formula IV, wherein R
1
, R
2
, R
3
, R
4
, W, X, Y, Z, m, n and p have the meanings given above is added to a suspension of MSH, MSCN or M
2
S and S, or to previously prepared M
2
S
x
, in an alcohol W-H. Hydrogen gas is formed in this process. The reaction is heated for 1 h to 8 d, pr

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