Polyurethane geotextile composite liner with improved water resistance and a process for the production thereof

A process for producing a polyurethane geotextile composite liner comprising:

• (1) impregnating a geotextile with a water-resistant polyurethane which is a reaction product of a mixture comprising:
• a) a liquid polyisocyanate having an isocyanate content of at least 10% by weight,
• b) an isocyanate-reactive component comprising:
• (i) 20 to 90% by weight, based on total weight of b), of castor oil having an OH number of about 160 to about 170, a viscosity of about 500 to about 900 mPa·s at 25° C., and a water content of less than 0.5% by weight, based on total weight of castor oil;
• (ii) 10 to 80% by weight, based on total weight of b), of a polyether polyol having an OH number of from 28 to 700, a functionality of from 2 to 8, a number average molecular weight of from about 240 to about 6,000, and a viscosity of from 50 to 35,000 mPa·s at 25° C., the polyether polyol being the reaction product of an initiator compound with an alkylene oxide in which at least 70% by weight the alkylene oxide is propylene oxide;
• and
• (iii) from 0 to 10% by weight, based on total weight of b) of a low molecular weight diol or triol having an equivalent weight of from 31 to 99;
• c) a urethane catalyst, and optionally,
• d) a filler;
• (2) conforming the polyurethane-impregnated geotextile to a surface to be lined before the polyurethane has fully cured;
• and
• (3) allowing the polyurethane to fully cure,
• wherein said polyurethane geotextile composite liner has improved water resistance, and wherein said improved water resistance comprises a water absorption at 24 hours with a maximum value of about 0.4% or less.