Sealant composition having reduced permeability to gas

A moisture-curable silylated resin-containing composition comprising:

• a) moisture-curable silylated resin, prepared by reacting a hydroxyl-terminated polyurethane prepolymer with and isocyanatosilane, wherein the hydroxyl terminated prepolymer is prepared by reacting a molar excess of a polyol selected from the group consisting of poly(oxyethylene) diols, poly(oxypropylene) diols, poly(oxyethylene-oxypropylene) diols, polyoxyalkylene triols and polytetramethylene glycols, having a number average molecular weight of from 4,000 to 18,000 grams/mole and an end group unsaturation level no greater than 0.04 milliequivalent per gram of polyol with a diisocyanate and wherein the isocyanatosilane is of the formula:
• OCN—R5—Si(R6)y(OR7)3-y
• where R5 is an alkylene group of up to 12 carbon atoms;
• R6 is a alkyl or aryl group of up to 8 carbon atoms;
• R7 is the same or different alkyl group of up to 6 carbon atoms;
• and y is 0, 1 or 2
• which upon curing, provides a cured resin exhibiting permeability to gas;
• b) at least one other polymer having a permeability to gas that is less than the permeability of cured resin (a);
• and,
• c) at least one nanoclay modified with a cationic surfactant-exfoliating agent, wherein the nanoclay particles have a lateral dimension of between 0.01 microns and 5 microns and a vertical dimension of between 0.5 nanometers to 10 nanometers.