Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From silicon reactant having at least one...
Reexamination Certificate
2002-10-02
2004-05-18
Tucker, Philip (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From silicon reactant having at least one...
Reexamination Certificate
active
06737495
ABSTRACT:
The field of the invention is that of the preparation of silicones or polyorganosiloxanes, designated hereinafter POS. The preparation of silicones may be carried out in particular via ring-opening polymerization of cyclic oligosiloxanes (redistribution polymerization) or alternatively by polycondensation of silanol SiOH units carried by silanes, oligoorganosiloxanes or polyorganosiloxanes. The SiOH units involved in the polycondensation may be derived from the hydrolysis of alkoxy SiOR units with R=alkyl.
The polycondensation polymerization reactions which are of interest in the context of the invention are more particularly those which are catalyzed by acidic catalytic systems. Thus, according to another of its aspects, the invention also relates to acidic catalytic systems comprising triflic acid derivatives.
Many methods for producing polydiorgano-siloxane oils or gums, by heterogeneous or homogeneous, acid or base catalysis, from cyclic or acyclic oligomers called oligoorganosiloxanes (OOS) have been known for a long time (see the book by WALTER NOLL, Chemistry and Technology of silicons; Editions 1968 in English ACADEMIC PRESS, pages 209 to 218).
These methods lead to oils or gums which are in particular basic constituents of mono- or bicomponent polydiorganosiloxane compositions which cure into elastomers in the presence of an excessively large amount of catalyst, at high temperature or at room temperature.
The starting materials for these polymerizations may comprise: silanols R
2
Si(OH)
2
or OOSs with silanol ends derived from the hydrolysis of chlorosilanes (R
2
SiCl
2
); hydroxylated silanes or hydroxylated OOSs derived from the hydrolysis of alkoxylated silanes or alkoxylated OOSs; polyorgano-siloxanes with silanol ends; or alternatively cyclosiloxanes which undergo ring opening, followed by redistribution and polymerization.
As regards cyclic monomers, anionic polymerization (base catalysis) has been widely used for the preparation of POS. Even if this anionic polymerization sometimes produces good yields, the cationic polymerization of cyclosiloxanes was found to be more advantageous and was unavoidable. Acid catalysis thus makes it possible to have reactions at room temperature. Furthermore, cationic polymerization may be carried out on cyclosiloxane monomers carrying functional groups, for example SiH or SiCH
2
Cl, which are not compatible with the conditions of anionic methods.
In any case, the ring-opening polymerization of cyclosiloxanes using acidic catalytic systems is very common in laboratories and in industry. It is nevertheless the case that the mechanisms which govern this type of polymerization remain complex and are not always completely controlled.
The literature comprises many studies in which the starting materials or polymerization monomers are hexamethylcyclotrisiloxane (D3) or octamethylcyclo-tetrasiloxane (D4). These polymerizations are initiated by strong protonic acids such as H
2
SO
4
, HClO
4
or by LEWIS acids. Among the latter, trifluoromethane sulfonic acid (or triflic acid, represented by the abbreviation TFOH) has been widely studied.
Accordingly, American U.S. Pat. No. 2,961,245 describes the ring-opening mass polymerization of cyclotrisiloxane containing fluorinated hydrocarbon radicals, in the presence of perfluoroalkanesulfonic acid (for example TFOH or its derivatives), and of linear organosiloxanes with triorganosilyl ends (essentially hexamethyldisiloxane M2) which are used as chain-blocking agents. A fluorinated silicone oil is thus obtained, after devolatilization, whose viscosity is essentially determined by the M2/D
3
ratio. The catalyst is optionally removed by distillation or washing.
In a method for preparing polydiorgano-siloxanes containing silanol ends according to patent EP-B1-0 292 407, a polydimethylsiloxane oligomer with silanol ends, having a viscosity of 100 mPa.s at 25° C., is bulk polycondensed, under reduced pressure, at 110° C. and in the presence of TFOH. The water formed is removed and the addition polycondensation of a polysilazane such as hexamethylcyclotrisilazane is stopped. This product makes it possible to neutralize the effect of the TFOH catalyst.
British patent GB-A-1 325 654 teaches the polymerization, in the presence of a perfluoroalkane-sulfonic acid (for example TFOH) and silica, of cyclic polysiloxanes D3 and D4, optionally in the form of a mixture with chain-blocking linear diorganopoly-siloxanes of the M2 type. At the end of the reaction, the catalyst may be neutralized with hexamethyldisilazane.
European patent EP-B1-0 133 975 describes the polycondensation, in solvent medium, of linear or branched POSs having silanol functional groups, with a catalytic system comprising triflic acid derivatives.
More recently, catalytic systems based on derivatives of triflic acid or its homologs have been used in the polymerization of cyclosiloxane monomers. The triflic acid derivatives considered are more especially those containing fluorine substituents. By way of example of perfluoroalkanesulfonic acid or known derivative, there may be mentioned: C
n
F
2n+1
SO
3
H, trimethylsilyl ester of triflic acid (CF
3
SO
3
SiMe
3
: TMST), or benzyldimethylsilyl ester of triflic acid (BDMST), combined with a selective proton trap (for example triethylamine, tri-N-butylamine, pyridine) or alternatively a quaternary ammonium salt of triflic acid such as Bu
4
N
+
CF
3
SO
3
−
. The documents JP-A-03/292 329, JP-A-01/000 125, JP-A-62/050 531 and U.S. Pat. No. 4,929,691 relate to catalysts of the C
n
F
2n+1
SO
3
H type.
U.S. Pat. No. 5,696,219 relates to a method for preparing polysiloxanes from cyclosiloxanes, functionalized with fluoroalkyl groups, according to a ring-opening polymerization in the absence of acidic catalytic systems. In this case, the catalytic system comprises silyl esters of triflic acid and, in particular, trimethylsilyl ester of triflic acid CF
3
SO
3
SiMe
3
combined with a LEWIS base, acting as proton trap, 2,6-di-tert-butylpyridine. Without this amine-containing base, the polymerization does not take place. This amine-containing base may be replaced by a triflic acid salt such as tetrabutylammonium triflate.
European application EP-A-0 854 162 and Japanese application JP-A-04/268 333 also relate to the use of trimethylsilyl ester of triflic acid or TMST in the polymerization of cyclosiloxanes.
KAZMIERSKI et al. describe, in Am. Chem. Soc., Div. Poly. Chem., (1998) 439, the use of the silyl ester TMST combined with TFOH for the polymerization of 1,1-diphenyl-3,3,5,5-tetramethyl-cyclotrisiloxane.
In reality, as teaches the article by G. TOSKAS et al. in Macromol. Chem. Phys., 196 (1995) 2715, the role of TMST or of triflic anhydride in the polymerization reactions of cyclosiloxanes is not that of a catalyst but rather that of an inhibitor of parasitic cyclization reaction and of bonding between polymer chains.
The publication by A. TREHAN et al. in TETRAHEDRON LETTERS, Vol. 34, No. 45, pages 7335-7338, 1993 describes a novel catalyst for reactions between acetals and silylated nucleophiles. This novel catalyst is trimethylsilylbis(fluorosulfonyl)imide.
In such a state of the art, one of the essential objectives of the present invention is to significantly improve the homogeneous or heterogeneous catalysis of the industrial polymerization reactions by polycondensation of silanes or of polysiloxanes having SiOH units, as well as by ring-opening polymerization of cyclosiloxanes, for example, of the D3 or D4 type.
The improvement aimed at is an improvement in terms of control, reliability and productivity of industrial methods of production of linear POSs.
Another objective aimed at through the improvement of the catalytic system is to render perfect the quality of the POS products obtained, to optimize safety and to minimize the eco-toxic impacts of the industrial processes.
Another essential objective of the invention is to provide the catalytic system which makes it possible to give the abovementioned method the specifications set out above.
Having set all these ob
Bordone Christian
Desmurs Jean-Roger
Ghosez Leon
Martins Jose
Mignani Gerard
Rhodia Chimie
Tucker Philip
Zimmer Marc S.
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