This application is an application under 35 U.S.C. Section 371 of International Application Number PCT/FR98/02897 filed on Dec. 29, 1998.
The present invention relates to a method for preparing polyorganosiloxanes (silicones) with an ester function (acetoxyalkyl or acetoxyalkenyl) of high purity, primarily free of functions or by-products with an xcex1-olefinic unsaturated bond.
The invention provides a method for producing polyorganosiloxanes with ester functions with formula (I):
R1R2R3SiO(R4R5SiO)p(R6QSiO)qSiR3R2R1xe2x80x83xe2x80x83(I),
where:
symbols R1, R2 are identical or different and represent:
a C1 to C6 alkyl radical or a phenyl radical, preferably methyl;
or a xe2x80x94OR7 radical, where R7 represents a linear or branched C1 to C6 alkyl radical, preferably methyl;
symbols R4, R5 and R6 are identical or different and represent a C1 to C6 alkyl radical or a phenyl radical, preferably methyl;
symbols R3, which may be identical or different, represent:
a linear or branched C1 to C6 alkyl radical or a phenyl radical, preferably methyl;
the symbol Q;
or a xe2x80x94OR7 group, where R7 represents a linear or branched C1 to C6 alkyl radical, preferably methyl;
symbols Q, which may be identical or different, represent an ester function or an alcohol function, respectively with formulae (1) and (2) below:
xe2x80x94Rxe2x80x2OCORxe2x80x3xe2x80x83xe2x80x83(1)
xe2x80x94Rxe2x80x2OHxe2x80x83xe2x80x83(2)
where:
Rxe2x80x2 represents a linear or branched C3-C20 alkylene group, preferably C3-C12, more particularly trimethylene or 2-methyltrimethylene;
Rxe2x80x3 represents a methyl group;
at least one of symbols Q representing an ester function with formula (1);
p represents an average number of 0 or more, preferably more than 5;
q represents an average number of 0 or more, preferably more than 1; at least one of symbols R3 representing the ester symbol Q of formula (1) when q equals 0;
by hydrosilylation between a hydrogeno-polyorganosiloxane with formula II):
R1R2R3SiO(R4R5SiO)p(R6HSiO)qSiR3R2R1xe2x80x83xe2x80x83(II)
where:
symbols R1, R2, R4, R5, R6, p and q have the definitions given above;
symbols R3xe2x80x2, which may be identical or different, represent:
a linear or branched C1 to C6 alkyl radical or a phenyl radical, preferably methyl;
H;
or a xe2x80x94OR7 group, where R7 represents a linear or branched C, to C6 alkyl radical, preferably methyl;
and an xcex1-olefinic alcohol with formula ROH, where R represents an xcex1-olefinic radical from which the divalent radical Rxe2x80x2 derives by opening of the xcex1 double bond and adding hydrogen, preferably an allyl or methallyl radical;
then esterification of the hydroxy-alkylated polyorganosiloxane with formula (III) obtained:
R1R2R3xe2x80x3SiO(R4R5SiO)p(R6Qxe2x80x2SiO)qSiR3xe2x80x3R2R1xe2x80x83xe2x80x83(III)
where:
symbols R1, R2, R4, R5, R6, p and q have the definitions given above;
symbols R3xe2x80x3, which may be identical or different, represent:
a linear or branched C1 to C6 alkyl radical or a phenyl radical, preferably methyl;
the symbol Qxe2x80x2;
or a xe2x80x94OR7 group, where R7 has the definition given above;
symbol Qxe2x80x2 represents the radical Rxe2x80x2OH, where Rxe2x80x2 has the definition given above; with an acyl halide with formula XCORxe2x80x3, where X represents a halogen atom, in particular chlorine, and Rxe2x80x3 has the definition given above, in the absence of an esterification catalyst;
and eliminating the xcex1 olefinic by-products and the hydrohalic acid formed.
The hydrosilylation step can be carried out in any known manner at a temperature of the order of 20xc2x0 C. to 200xc2x0 C., preferably of the order of 60xc2x0 C. to 120xc2x0 C., in the presence of a hydrosilylation catalyst. Examples which can be cited are those based on platinum such as the platinum complexes described in U.S. Pat. No. 3,159,601, U.S. Pat. No. 3,159,662, U.S. Pat. No. 3,715,334, U.S. Pat. No. 3 ,14,730. A conventional catalyst is the KARSTEDT catalyst used, for example, in an amount of 1 to 300 parts, preferably 5 to 50 parts, by weight of platinum per million parts by weight of reactants.
The relative quantities of hydrogeno-polyorganosiloxane with formula (II) and xcex1-olefinic alcohol ROH generally correspond to an xcex1-olefinic alcohol/hydrogeno-polyorganosiloxane mole ratio more than 1 and less than or equal to 5, preferably more than 1 and less than or equal to 2.
In defining the moles of (xcex1-olefinic alcohol, the elementary entity is considered to be the xcex1-olefinic unsaturated bond; in defining the moles of hydrogeno-polyorganosiloxane, the elementary entity is considered to be the SiH function.
The hydrosilylation operation can be carried out at atmospheric pressure, preferably in bulk; however, it can be carried out in an organic solvent such as toluene, xylene, methylcycyclohexane, heptane, octane, hexamethylsiloxane.
The operation is carried out until the xe2x80x94SiH groups in the reaction mass have disappeared. The operation can be monitored by infrared analysis or volumetric determination.
The excess xcex1-olefinic alcohol can be eliminated by vacuum distillation (for example 13 Pa to 14000 Pa).
The hydrogeno-polyorganosiloxane used in the hydrosilylation step is preferably selected from those with formulae:
Me3SiO(SiMe2O)pxe2x80x2(SiMeHO)qxe2x80x2SiMe3
Me2HSiO(SiMe2O)pxe2x80x2(SiMeHO)qxe2x80x2SiHMe2
Me2HSiO(SiMe2O)pxe2x80x3SiHMe2
where:
Me represents the methyl radical;
pxe2x80x2 represents an average number of the order of 0 to 500, preferably of the order of 5 to 100;
pxe2x80x3 represents an average number of the order of 0 to 100, preferably of the order of 0 to 20;
qxe2x80x2 represents an average number of the order of 1 to 50, preferably of the order of 1 to 30.
The xcex1-olefinic alcohol with formula ROH used in the hydrosilylation step is preferably allyl alcohol or methallyl alcohol.
The esterification operation can be carried out at a temperature of the order of 0xc2x0 C. to 100xc2x0 C., preferably of the order of 15xc2x0 C. to 50xc2x0 C., more particularly of the order of 15xc2x0 C. to 30xc2x0 C.
The relative quantities of hydroxyalkylated polyorganosiloxane and acyl halide with formula XCORxe2x80x3 generally correspond to an acyl halide/hydroxyalkylated polyorganosiloxane mole ratio of the order of 0.1 to 2, preferably of the order of 0.1 to 1.
In defining the moles of hydroxyalkylated polyorganosiloxane, the elementary entity is considered to be the hydroxyalkyl function.
The esterification operation can be carried out at atmospheric pressure, preferably in bulk; however, it can be carried out in an organic solvent such as toluene, xylene, methylcyclohexane, heptane, octane, hexamethylsiloxane.
The acyl halide with formula XCORxe2x80x3 used in the esterification step is preferably acetyl chloride.
The acid halide formed by esterification can be eliminated by entraining it in an inert gas (argon, nitrogen . . . ) then by treatment with a base, such as alkali metal bicarbonates, in particular sodium bicarbonate, in stoichiometric excess over the acyl halide (for example 2 to 3 times the stoichiometry).
After eliminating the by-products by condensing under reduced pressure, the polyorganosiloxane with an ester function can then be recovered by filtering, for example.
xcex1-olefinic siloxane motifs and xcex1-olefinic impurities are those with formulae xe2x95x90Sixe2x80x94Oxe2x80x94R, ROH and Rxe2x80x3COOR, where R represents a linear or branched xcex1-olefinic radical containing 3 to 20 carbon atoms, as defined above (allyl or methallyl, for example), and Rxe2x80x3 is the methyl group.