Organic compounds -- part of the class 532-570 series – Organic compounds – Silicon containing
Reexamination Certificate
2001-02-23
2002-08-20
Shaver, Paul F. (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Silicon containing
C556S479000, C528S015000
Reexamination Certificate
active
06437163
ABSTRACT:
The present invention relates to a process for preparing silicones containing (an) arylalkyl function(s) of high purity, by hydrosilylation reaction of a hydrogenopolyorganosiloxane and of a monovinylaromatic compound. The silicones containing (an) arylalkyl function(s) of high purity thus obtained can be used as emollients and/or vehicles in cosmetic compositions, and also as solubilizing agents and emollients in fragrancing compositions.
It is known practice to prepare silicones bearing arylalkyl functions by hydrosilylation reaction of a silicone bearing at least one SiH function with an aromatic compound containing a vinyl unsaturation, especially in the presence of a platinum-based catalyst.
The hydrosilylation of aromatic compounds containing vinyl unsaturation can lead to phenomena of radical-mediated polymerization of the said monovinylaromatic compounds, especially at elevated temperature. The use of radical-mediated-polymerization inhibitors, such as phenols or quinones, is often necessary; however, most of these inhibitors are not sufficiently active under hot conditions and require the presence of oxygen to improve their activity.
The Applicant has found an efficient process for the hydrosilylation of monovinylaromatic compounds, which does not require the presence of a radical-mediated-polymerization reaction inhibitor, while at the same time avoiding the risk of such a polymerization reaction.
According to the invention, it is a process for preparing polyorganosiloxanes containing (an) arylalkyl function(s), of high purity, by hydrosilylation reaction of a hydrogenopolyorganosiloxane, reagent (SiH), with a monovinylaromatic compound, reagent (Vi), in the presence of a hydrosilylation catalyst, the said process being characterized in that
the hydrosilylation operation is carried out
at a temperature from 50° C. to 150° C., preferably from 50° C. to 100° C. and most particularly from 60° C. to 90° C.,
in the presence of a solvent (S), which is inert with respect to the reagents, having a boiling point at atmospheric pressure of less than 200° C., preferably less than 150° C.,
by simultaneous introduction of the two reagents (Vi) and (SiH) into the reaction medium comprising the solvent (S) and the hydrosilylation catalyst, this introduction being carried out such that the respective amounts of the two reagents (Vi) and (SiH) corresponding to a reagent (Vi)/reagent (SiH) molar ratio of more than 0.5 to 1.5, preferably of more than 1 to 1.2, and in that at any moment in the hydrosilylation reaction, the amount of reagent (SiH) present, expressed as the mass of SiH functions (29 g per 1 function), corresponds to less than 2% and preferably less than 1% of the reaction mass, excluding the mass of solvent,
and in that the hydrosilylation operation is followed by an operation for removal of the solvent (S) and any residual reagents (SiH) and (Vi), and/or by a hydrogenation operation, the said hydrogenation operation optionally being followed by an operation for removal (or a new operation for removal) of the products other than the polyorganosiloxanes containing (an) arylalkyl function(s).
In the definition of a mole of hydrogenopolyorganosiloxane, reagent (SiH), the —SiH function will be considered as the elemental species.
In the definition of a mole of monovinylaromatic compound, reagent (Vi), a gram-molecule of monovinylaromatic compound will be considered as the elemental species.
Among the hydrogenopolyorganosiloxanes, reagents (SiH), which may be used to carry out the process of the invention, mention may be made of those corresponding to the formula (1)
(R
1
)(R
2
)(R
3
)Si—O—[Si(R
4
)(H)—O]
n
—[Si(R
5
)(R
6
)—O]
m
—Si(R
7
)(R
8
)(R
9
) (1)
or cyclic homologues thereof, of formula (1) in which
the symbols R
1
and R
9
are identical or different and represent a hydrogen atom or an alkyl radical containing from 1 to 8 carbon atoms, preferably 1 or 2 carbon atoms and most particularly 1 carbon atom,
the symbols R
2
, R
3
, R
4
, R
5
, R
6
, R
7
and R
8
are identical or different and represent an alkyl radical containing from 1 to 8 carbon atoms, preferably 1 or 2 carbon atoms and most particularly 1 carbon atom,
n is an integer or decimal number which may be from 0 to 10, preferably from 0 to 5, at least one of the radicals R
1
and R
9
representing a hydrogen atom when n=0,
m is an integer or decimal number which may be from 0 to 50, preferably from 0 to 10.
Preferentially, n is equal to 1 and m is equal to 0; in this case, the said reagent (SiH) is a hydrogenoheptaorganotrisiloxane (abbreviated as MD′M), most particularly hydrogenoheptamethyltrisiloxane.
Among the monovinylaromatic compounds, reagents (Vi), which may be used to carry out the process of the invention, mention may be made of those with a boiling point of less than 200° C., preferably less than 150° C., at atmospheric pressure and corresponding to formula (2)
CH
2
═C(R)—&PHgr;(R′
1
)(R′
2
)(R′
3
)(R′
4
)(R′
5
) (2)
in which formula
the symbol &PHgr; represents an aromatic nucleus containing 6 carbon atoms,
the symbol R represents H or CH
3
,
the symbols R′
1
, R′
2
, R′
3
, R′
4
and R′
5
are identical or different and represent H, CH
3
, F, Cl or Br.
Styrene, &agr;-methylstyrene, &agr;-methylstyrene dimer and pentafluorobenzene may be mentioned preferentially.
Among the solvents (S), inert with respect to the reagents, which may be used to carry out the process of the invention, mention may be made of organic solvents such as toluene, xylene, methylcyclohexane, heptane, octane, etc. and most particularly polyorganosiloxane solvents such as hexamethyldisiloxane.
The hydrosilylation operation is carried out in the presence of a hydrosilylation catalyst; this catalyst is chosen in particular from those based on platinum (0) or on a platinum (0) derivative, such as the platinum complexes described in U.S. Pat. Nos. 3,159,601, 3,159,662, 3,715,334, 3,814,730, etc. A preferred catalyst is the Karstedt catalyst, used for example in a proportion from 1 to 300 parts, preferably from 5 to 100 parts, by mass of platinum per million parts by mass of reagents (SiH) and (Vi) used.
The hydrosilylation operation is preferably carried out at atmospheric pressure.
The introduction of the reagents (SiH) and (Vi) is preferably carried out by simultaneously and continuously adding the two reagents to the reaction mass comprising the solvent and the catalyst.
The addition time is adjusted so as to consume the reagent (Vi) by hydrosilylation gradually as it is introduced. The amount of reagent (Vi) in the medium is thus always low, which limits the risks of a radical-mediated polymerization.
Similarly, the simultaneous introduction of the two reagents and their simultaneous consumption avoids the accumulation of free —(SiH) functions in the medium; the potential exothermicity of the reaction is thus limited.
The use of a radical-mediated polymerization inhibitor is thus unnecessary.
The solvent (S) and the unreacted reagents can then be removed. Their removal can be carried out by distillation under vacuum or reduced pressure (for example from about 1.013 Pa to 101 300 Pa).
This distillation operation can optionally be followed by a hydrogenation operation, so as to remove the remaining unsaturations due to a dehydrogenocondensation reaction. The proportion of compounds whose presence is due to this dehydrogenocondensation reaction increases as the temperature increases. Such compounds are undesirable in applications such as cosmetology or perfumery in particular.
The hydrogenation operation can be carried out at a temperature from about 25° C. to 200° C., preferably from about 50° C. to 150° C., at a hydrogen pressure from about 0 bar to 50 bar, preferably from about 5 bar to 25 bar, in the presence of an effective amount of hydrogenation catalyst.
Among the hydrogenation catalysts which may be mentioned most particularly are platinum and palladium; they can be used in a proportion from 0.01% to 5
Branlard Paul
Mignani Gerard
Olier Philippe
Willemin Claudie
Burns Doane Swecker & Mathis L.L.P.
Rhodia Chimie
Shaver Paul F.
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