Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From silicon reactant having at least one...
Reexamination Certificate
1996-07-25
2001-02-06
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...
C528S026000, C528S031000, C528S042000
Reexamination Certificate
active
06184329
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to (per)halogenated polyorganosiloxanes (POS) derived from (per)halogenated olefins (e.g. &agr;-olefins) by means of a hydrosilylation reaction, it also being possible to present said reaction as the addition of a hydrogenated silicon compound onto a halogenated reactant having one or more ethylenic or alkynylic units of unsaturation.
It is known in particular that the effects of fluorination, and more precisely of the introduction of perfluorinated units into polymers, are:
to lower the surface energies,
to improve the thermal and chemical stability and
to impart organophobicity and oleophobicity properties.
This type of functionalization by halogenation, and in particular by perfluorination, has been applied to silicone polymers, particularly of the cyclic or non-cyclic polyorganosiloxane type, since the 1970s.
Silicone oils grafted by fluorinated units are thus available which have applications in the textile field as stain or dirt repellents or which can be used as lubricants, as antiadhesives specific for certain adhesives (silicones of high adhesive strength), as grease repellents or else as antifoams. Fluorinated silicone fluids can also be formulated with different thickeners to form mastics or any other sealing and/or jointing materials.
In crosslinked form these fluorinated silicones can be shaped into a variety of engineering parts by molding or extrusion.
For further details on these fluorinated silicones, reference may be made to the article by OGDEN R. PIERCE entitled “Fluorosilicones”—1970—John Wiley & Sons Inc., pages 1 to 15.
A first known strategy for the industrial synthesis of silicones containing perfluorinated units includes “hydrosilylating” a dihalogenohydrogenoorganosilane, such as MeHSiCl
2
(Me=methyl), with an unsaturated compound carrying a perfluorinated unit and having the general formula CH
2
=CH—Rf (Rf=perfluorinated unit). The addition of the silane onto this olefin yields a perfluorinated dihalogenoorganosilane, which can be hydrolyzed to produce a functionalized silicone; this can be a cyclic tetramer, for example. It is possible to subject the latter to a redistribution reaction to give a perfluorinated linear polyorganosiloxane (POS). The hydrosilylation reactions which are involved in this kind of synthesis, and which use various combinations of silicone hybrids and perfluorinated olefins, are known to be catalyzed by selected metal compounds, particularly certain group VIII metals such as platinum. Pt/Sn complexes have thus been employed as hydrosilylation catalysts—cf patent U.S. Pat. No. 4,089,882 (SHINETSU). This synthetic strategy appears to be relatively complex and hence expensive.
With a view to industrial simplification, a second synthetic strategy has been proposed which is based on the direct hydrosilylation of a silicone containing SiH units with an &agr;-fluorinated olefin, e.g. of the type CH
2
=CH—Rf, this perfluorinated unit Rf being attached directly to the olefinic CH by a carbon atom carrying at least one fluorine atom. Here again a variety of group VIII metal catalysts, in particular those based on platinum, are used in this hydrosilylation reaction. It has been found, however, that these catalysts do not afford very high yields. In particular, the conventional industrial hydrosilylation catalysts based on platinum (for example of the KARSTEDT type) are not very efficient. Moreover, it has been observed that substantial amounts of by-product are generated, obviously to the detriment of the perfluorination of the silicones. In these known perfluorinated POS, the radical Rf is joined directly to the Si of the silicone chain. In other words, the linkage in this case corresponds to —CH
2
—CH
2
—(CH
2
)—
m
where m=0.
It is these linkages which are used in U.S. Pat. No. 5,233,071. They originate from the hydrosilylation of a-olefins. However, to overcome the deficiencies of the hydrosilylation catalysts used in the prior art, the process described in said patent involves cobalt-based organometallic complexes [(Co
2
CO
8
, Co
2
CO
6
)(PR
3
)
3
, where R=alkyl, aryl]. Such a technical proposal has appeared unsatisfactory because the reaction times obtained are of the order of a few days and it is essential to use a substantial amount of catalyst (1-2%), which is particularly unfavorable in terms of the economics of the process.
One appreciable disadvantage of these cobalt-based complexes is that they catalyze reactions other than hydrosilylation. In particular, they are capable of taking part in polymerization processes involving the rupture of epoxy rings. This lack of specificity is particularly troublesome. Moreover, these are not industrial catalysts.
U.S. Pat. No. 5,348,769 discloses linear or cyclic polyorganosiloxanes comprising siloxy units D substituted by a first perfluorinated functional unit of the formula —R
3
ZRf, and other siloxy units D carrying a second functional unit of the ether-hydroxyl or alkyl-hydroxyl type. The linkage or bridge joining Si to Rf in the first perfluorinated functional unit consists especially of —(CH
2
)
x
Z, where x=2, 3 or 4 and Z=NHCO, NHSO
2
, O
2
C, O
3
S, OCH
2
CH
3
, NHCH
2
CH
2
or CH
2
CHOHCH
2
. The catalyst used is preferably chloroplatinic acid. This is not one of the simplest techniques as it requires the prior preparation of the perfluoroalkylated olefinic reactant. This considerably lengthens the synthesis times and hence increases the cost of the process.
Apart from these linkages whose precursors are perfluoroalkylated &agr;-olefins of the formula CH
2
=CH—Rf, the technical literature of the prior art also describes bridges whose olefinic precursors are of the type CH
2
=CH)—{circle around (L)}—Rf, the chemical bond between {circle around (L)} and Rf being an ester bond. The latter results from the reaction of a carboxyl group with a perhalogenated alcohol, preferably perfluorinated alcohol, and said carboxyl group is generally the hydrolysis product of an acid anhydride.
Thus PCT patent application WO 94/12561 discloses POS grafted by fluorinated units only in the &agr; and &ohgr; positions at the ends of the silicone chains. These POS &agr;,&ohgr;-perfluorinated on alkyl ester groups do not exhibit optimum properties in respect of surface tension lowering or oleophobicity and hydrophobicity.
European patent application No. 0 640 644 describes perfluorinated (Rf) silicone derivatives which can be used in cosmetic formulations. These perfluorinated silicone derivatives are characterized by siloxy units D carrying three different types of perfluorinated grafts, namely:
where R
2
, R
3
=alkyl, e.g. CH
3
;
2≦i≦16, e.g. i=3; 1≦m,n≦6; ≦p≦200; 0≦r≦50;
the number of siloxy units D grafted in this way is between 1 and 200; and
X, Y=single bond, —CO— or C
1
—C
6
-alkylene.
A common feature of these perfluorinated grafts (1) to (3) is the presence of ether bonds within the linkage joining the perfluorinated radical Rf to the silicon. Each of these ether bonds represents a possible point of rupture by chemical attack, under certain conditions.
This is a major disadvantage of these known perfluorinated POS because the labile character of the perfluorinated groups is clearly unacceptable in certain applications.
This review of the prior art shows that there are no chemically stable, halogenated—preferably (per)fluorinated—POS which comprise on the one hand fluorinated lateral grafts resulting from the hydrosilylation of perfluorinated olefins with SiH units and having alkyl and/or alkyl ester linkages but not ether linkages, and on the other hand other, non-perfluorinated functional units capable of giving them diverse and varied physical and chemical properties and opening up avenues in numerous applications.
Furthermore, the prior art contains even fewer disclosures of such POS which can be obtained in a simple, economic and hence perfectly industrial manner.
SUMMARY OF THE INVENTION
Under these circumstanc
Jost Philippe
Karrer Philippe
Mignani Gerard
Olier Philippe
Burns Doane Swecker & Mathis L.L.P.
Moore Margaret G.
Rhone-Poulenc Chimie
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