Process for producing prepolymers which cure to improved sealants, and products formed thereby
AssigneeWitco Corporation
InventorsRobert R. Johnston, Patrice Lehmann
Life of this patent
Estimating the term…
Abstract
Silylated polyurethanes exhibiting a superior combination of mechanical properties and which cure in reasonable time to a low-tack sealant, without excessive viscosity, are prepared by reacting a polyol component having terminal unsaturation of less than 0.2 meq/g with a diisocyanate component to form a hydroxyl-terminated prepolymer, and endcapping the prepolymer with an isocyanate silane of the formula OCN--R--Si--(X).sub.m (--OR.sup.1).sub.3-m wherein m is 0, 1 or 2, each R.sup.1 is alkyl containing 1 to 4 carbon atoms, each X is alkyl containing 1 to 4 carbon atoms, and R is a difunctional organic group.
Claims18
A process for preparing a silylated polyurethane, comprising
- (A) reacting (i) a polyol component having terminal unsaturation less than 0.02 milliequivalents per gram of polyol with a molecular weight of 2,000-20,000 daltons, with (ii) a diisocyanate component at a stoichiometric excess of said polyol component to said diisocyanate component, whereby a polyurethane prepolymer is formed which is hydroxyl-terminated;
- and
- (B) reacting said polyurethane prepolymer with one or more isocyanate silanes of the formula (1)
- OCN--R--Si--(X).sub.m (--OR.sup.1).sub.3-m ( 1)
- wherein m is 0, 1 or 2, each R.sup.1 is alkyl containing 1 to 4 carbon atoms, each X is alkyl containing 1 to 4 carbon atoms, and R is a difunctional organic group, to endcap the hydroxyl groups on said prepolymer with said isocyanate silane.
A silylated polyurethane prepared by a process comprising
- (A) reacting (i) a polyol component having terminal unsaturation less than 0.02 milliequivalents per gram of polyol with a molecular weight of 2.000-20.000 daltons, with (ii) a diisocyanate component at a stoichiometric excess of said polyol component to said diisocyanate component, whereby a polyurethane prepolymer is formed which is hydroxyl-terminated;
- and
- (B) reacting said polyurethane prepolymer with one or more isocyanate silanes of the formula (1)
- OCN--R--Si--(X).sub.m (--OR.sup.1).sub.3-m ( 1)
- wherein m is 0, 1 or 2, each R.sup.1 is alkyl containing 1 to 4 carbon atoms, each X is alkyl containing 1 to 4 carbon atoms, and R is a difunctional organic group, to endcap the hydroxyl groups on said prepolymer with said isocyanate silane.
Dependencies are inferred from the claim text.