Patent attributes
The invention is a patch system for repairing collapsible fuel tanks, water tanks, inflatable boats, and other articles fabricated from a flexible structural fabric coated with a polymer. The coated structural fabric is made of nylon or polyester synthetic fibers or a blend thereof, which are coated with a thermoplastic elastomer. The structural coated fabric is coated with a thermoplastic elastomer that is a urethane (TPU), or a TPU alloy polymer. Likewise, the patch is a urethane adhesive having a latent cure coated on a TPU film. The patch can also have an integral reinforcing fabric for applications requiring a higher tensile patch. In the invention, the urethane adhesive of the patch is solvent activated by the application of a thin coating of a volatile, substantially low odor, fugitive solvent like acetone or MEK. While in the activated state, the adhesive has much less cyrstallinity and a lot more tack. The solvent activated adhesive has good wetting, and aggressively wets out and adheres to the surface of the TPU coating on the tank. The activated adhesive side of the patch is pressed against the surface of the tank. The solvent will also partially etch the thermoplastic urethane polymer coating on the tank fabric, and rapidly diffuses therein, ultimately evaporating to the surroundings. The cross-linkable urethane adhesive contains a blocked isocyanate and, preferably, an uretdione. The reduced cyrstallinity in the adhesive imparts greater freedom to the blocked isocyanate that can, depending on the equilibrium of the system, begin to cross-link the adhesive. The curing process can be accelerated through the application of heat, albeit will slowly progress to a cured state at ambient conditions.
