Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From silicon reactant having at least one...
Reexamination Certificate
2001-05-18
2002-10-29
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...
C528S029000, C526S065000
Reexamination Certificate
active
06472492
ABSTRACT:
The field of the invention is that of the functionalization of linear or cyclic silicones, in particular polyorganosiloxanes, consisting of M, D, T and optionally Q units.
The POSs to be functionalized, which are more specifically addressed in the context of the invention, are linear or cyclic polyorganohydrosiloxanes. It is the SiH groups of these POSs which serve as attachment points, to functionalities intended to substitute these POSs, in order to give them specific properties, for example anti-adhesion, lubrication, compatibilization, etc., which are all properties that are desired in the diverse and varied applications of silicones.
The present invention relates to the industrial-scale manufacture of multifunctional POSs. In such a context, it is clear that continuous or semi- continuous operating modes are more suited to the industrial requirements of viability and productivity than in the batchwise mode.
The present invention is also directed towards an industrial unit for the manufacture of multifunctional PoSs, in particular according to the process outlined above.
The actual principle of the multi-functionalization of POSs is described in the prior international patent application PCT WO 96/16125. That document discloses the preparation of a POS II containing Si—OEt and Si—H functionality, by dehydrocondensation of polymethylhydrosiloxane &agr;-&ohgr;-Si(Me)
3
containing, for example, 50 MeSiHO
2/2
units. In place of the ethoxy functionality, other alkoxyls are envisaged, such as, e.g. isopropoxy.
The dehydrocondensation is carried out by placing the POS (I) containing SiH in contact with an alcohol which is a precursor of the alkoxy functionality, in the presence of a platinum-based catalyst.
After this dehydrocondensation, a fraction of the starting SiH groups is found to be substituted with an alkoxy residue.
The POS (II) thus obtained is then subjected to hydrosilylation of an olefin, such as octene, by the remaining SiH groups and in the presence of the starting platinum catalyst.
It could thus be observed that the dehydrocondensation of POS (I) containing SiH, with excess alcohol and in the presence of a platinum catalyst, slows down considerably to about a 66% degree of conversion.
Faced with the problem of industrialization of this process for the multi-functionalization of POSs containing SiH groups, the Applicant has had to confront a certain number of technological and technical difficulties, which will be outlined below.
The general specifications sheet for an industrial process for the manufacture of multi-functionalized POSs comprises at least four main requirements: productivity and viability, the quality of the finished products, safety, and the ease of implementation.
As regards the productivity and viability, it is clear, as already indicated above, that a continuous, or even semi-continuous, operating mode must be envisaged.
One of the deciding factors of the quality of the multifunctionalized POSs considered is based on controlling the degree of conversion of the SiH groups by dehydrocondensation (degree of substitution by a first type of functionality). In the case where the alcohol is used as dehydrocondensation reactant, it is important to control the degree of partial alkoxylation in order to ensure its reproducibility. The only close prior art in this respect, namely application PCT WO 96/16125, provides no solution (nor even the start of a solution) since the examples it gives are laboratory tests performed, in a batchwise manner, in 500 ml three-necked round-bottomed flasks.
The industrial safety aspect is also very constraining in this multifunctionalization process, for several reasons. The first is that the release of hydrogen which is a feature of the dehydrocondensation is an obvious menace which should be suppressed. The second arises from the fact that the reaction intermediate POS (II) containing Si—OR and containing Si—H (reactant =alcohol) is an oil which contains a large proportion of SiH, in the presence of platinum catalyst which is still active. This is a potentially dangerous mixture since the possibility of the reaction restarting and thus producing hydrogen in an unexpected and uncontrolled manner cannot be excluded, which represents, under such conditions, a high risk.
There is also an additional technical difficulty associated with the phenomena of intense foaming, induced by the hydrogen produced during the dehydrocondensation.
The examples of the process for the multi-functionalization of POSs containing SiH, as given in the closest prior art WO 96/16125, are batchwise laboratory tests, which do not take account of the industrial preoccupations outlined above.
Given this state of affairs, one of the essential aims of the present invention is to improve the process for the multifunctionalization of POSs described in WO 96/16125 in order to make it into an industrial process for the manufacture of multi-functional POSs which satisfies the requirements of viability and productivity, of quality of finished product, of safety and, lastly, of ease of implementation.
Another essential aim of the present invention is to provide an industrial unit for the manufacture of multifunctional POSs by dehydrocondensation/hydrosilylation, this device needing to be economical, reliable, of good performance and suited to the above-targeted manufacturing process.
These aims, among others, are achieved by the present invention, which relates, firstly, to a process for the continuous or semi-continuous manufacture of multifunctional polyorganosiloxanes (POS) (III) from POS (I) comprising SiH groups and according to a reaction mechanism involving a dehydrocondensation which allows the functionalization of the said POS (I) by the functionality (Fo
1
) and a hydrosilylation of at least one unsaturated compound which is a precursor of a functionality (Fo
2
) on the POS (III),
characterized in that it consists essentially in:
continuously supplying at least one continuous reactor A with:
at least one POS (I) containing SiH groups,
at least one functional reactant (HXR) containing labile hydrogen, preferably an alcohol and/or a thiol (X=O or S), the said
reactant preferably being in excess relative to (I),
and a catalyst comprising a product chosen from transition metals—platinum being particularly preferred,
the said reactor A being the site of a dehydrocondensation leading, in particular:
to a POS (II) comprising residual SiH groups and SiFo
1
groups (Fo
1
=XR),
to reactant HXR,
go and to a gas containing hydrogen and, optionally, gaseous reactant HXR,
allowing the continuous removal and recovery, from the reactor A, of the gas containing hydrogen as it is formed,
optionally collecting the liquid reaction medium provided that this medium contains, in particular, POS II containing SiH/SiFo
1
groups and the catalyst,
transferring the said liquid reaction medium from reactor A to at least a reactor B for hydrosilylation of at least one unsaturated functional compound by the residual SiH groups of the POS (II), so as to obtain the POS (III) containing SiFo
1
and SiFo
2
groups,
allowing the above-targeted hydro- silylation to proceed,
recovering the POS (III) containing SiFo
1
/SiFo
2
groups which is thus formed.
After long and laborious research, the Applicant has, to its credit, been able to demonstrate that the problem of industrialization of a multifunctionalization of POS involved performing a continuous dehydrocondensation, by providing for instantaneous and continuous removal and recovery of the hydrogen as it is formed and, moreover, by evacuating, as early and as quickly as possible, the dangerous POS (II) intermediate towards the other hydrosilylation reactor B in order to neutralize it and make it harmless. In other words, the hydrogen is removed and the reaction intermediate (II) is consumed as it is formed.
These advantageous process modes are guarantees:
of productivity/viability→continuous operation,
of quality→control of the degree of conversion of the POS (I) into POS (II),
of safety→maximu
Priou Christian
Violland Robert
Moore Margaret G.
Rhodia Chimie
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