Preparation of end-alkoxylated diorganopolysiloxanes
AssigneeRhone-Poulenc Chimie
InventorRoger Cocco
Life of this patent
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Abstract
Straight-chain diorganopolysiloxanes having alkoxy endgroups, well adapted for formulation into single-component polysiloxane compositions which are stable on storage in the absence of moisture, but which crosslink into elastomeric state in the presence of moisture, are prepared by reacting a dihydroxydiorganopolysiloxane with a polyalkoxysilane, and advantageously also with an alkanol, in the presence of a catalytically effective amount of sodium hydroxide or potassium hydroxide.
Claims14
A process for the preparation of a straight-chain diorganopolysiloxane containing at least one alkoxy group bonded to a silicon atom at each end of its polymer chain, comprising reacting, in the presence of a catalytically effective amount of sodium hydroxide or potassium hydroxide,
- (a) 100 parts by weight of at least one straight-chain diorganopolysiloxane containing a hydroxyl group bonded to a silicon atom at each end of its polymer chain, with
- (b) 0.35 to 6 parts by weight of at least one polyalkoxysilane of the formula:
- (R.sup.4).sub.c (R.sup.1).sub.a Si(OR.sup.2).sub.4-(a+c) ( 1)
- in which a is 0, 1 or 2;
- c is 0, 1 or 2;
- a+c is 0, 1 or 2;
- R.sup.1 is a substituted or unsubstituted, saturated or unsaturated, C.sub.1 to C.sub.13 aliphatic, cycloalkyl or aromatic monovalent hydrocarbon radical, which may comprise an epoxy, primary, secondary or tertiary amine or mercapto group;
- the radicals R.sup.2, which may be identical or different, are each an aliphatic radical having from 1 to 8 carbon atoms, or an aralkyl radical having from 7 to 13 carbon atoms;
- and R.sup.4 is a substituted or unsubstituted, saturated or unsaturated, C.sup.1 to C.sub.13 aliphatic, cycloalkyl or aromatic monovalent hydrocarbon radical, with the proviso that R.sup.4 may be identical to R.sup.1 and with
- (c) 0.5 to 15 parts by weight of at least one alcohol which is added prior to reacting (a) with (b), to yield a straight chain diorganopolysiloxane being viscosity-stable and devoid of silanol groups.
A process for the preparation of a straight-chain diorganopolysiloxane containing at least one alkoxy group bonded to a silicon atom at each end of its polymer chain, comprising reacting, in the presence of a catalytically effective amount of sodium hydroxide or potassium hydroxide, (a) one mole of at least one diorganopolysiloxane containing a hydroxyl group bonded to a silicon atom at each end of its polymer chain, with (b) 2 to 6 moles of at least one polyalkoxysilane of the formula:
- (R.sup.4).sub.c (R.sup.1).sub.a Si(OR.sup.2).sub.4-(a+c) ( 1)
- in which a is 0, 1 or 2;
- c is 0, 1 or 2;
- a+c is 0, 1 or 2;
- R.sup.1 is a substituted or unsubstituted, saturated or unsaturated, C.sub.1 to C.sub.13 aliphatic, cycloalkyl or aromatic monovalent hydrocarbon radical;
- the radicals R.sup.2 which may be identical or different, are each an aliphatic radical having from 1 to 8 carbon atoms, or an aralkyl radical having from 7 to 13 carbon atoms;
- and R.sup.4 is a substituted or unsubstituted, saturated or unsaturated, C.sub.1 to C.sub.13 aliphatic, cycloalkyl or aromatic monovalent hydrocarbon radical, with the proviso that R.sup.4 may be identical to R.sup.1, the mole ratio range of 1:2 to 1:6 being present prior to reacting (a) with (b), to yield a straight chain diorganopolysiloxane being viscosity-stable and devoid of silanol groups.
A process for the preparation of a straight chain diorganopolysiloxane containing at least one alkoxy group bonded to a silicon atom at each end of its polymer chain, by reacting (a) one mole of at least one straight chain diorganopolysiloxane containing a hydroxyl group bonded to a silicon atom at each end of its polymer chain, with (b) 2 to 6 moles of at least one polyalkoxysilane of the formula:
- (R.sup.4).sub.c (R.sup.1).sub.a Si(OR.sup.2).sub.4-(a+c) ( 1)
- in which a is 0, 1 or 2;
- c is 0, 1 or 2;
- a+c is 0, 1 or 2;
- R.sup.1 is a substituted or unsubstituted, saturated or unsaturated, C.sub.1 to C.sub.13 aliphatic, cycloalkyl or aromatic monovalent hydrocarbon radical, which may comprise an epoxy, primary, secondary or tertiary amine or mercapto group;
- the radicals R.sup.2, which may be identical or different, are each an aliphatic radical having from 1 to 8 carbon atoms, or an aralkyl radical having from 7 to 13 carbon atoms;
- and R.sup.4 is a substituted or unsubstituted, saturated or unsaturated, C.sub.1 to C.sub.13 aliphatic, cycloalkyl or aromatic monovalent hydrocarbon radical, with the proviso that R.sup.4 may be identical to R.sup.1,
- wherein the process comprises conducting the reaction in the presence of a catalytically effective amount of a catalyst consisting of sodium hydroxide or potassium hydroxide, and neutralizing the reaction mixture after the desired reaction but prior to the occurrence of polymer rearrangements.
Dependencies are inferred from the claim text.