Patch repair system for collapsible fuel and water tanks
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.
1. A patch repair system, said system comprising:
a laminate comprised of a layer of a thermoplastic resin and a layer of a coating of a highly crystalline thermoplastic, predominately linear hydroxyl polyurethane (TPU) adhesive, with a crystallization of at least 10 as measured using test DIN 53 240, said adhesive having a latent thermally activated curing component; said adhesive coating providing the laminate with an adhesive surface that when activated forms an adhering patch to a collapsible tank and the like having a damaged area; and
a fugitive solvent selected from the group consisting of a ketone, an aldehyde, an ester, an aromatic hydrocarbon, an ether, a chlorinated alkane and blends thereof applied to the surface of the adhesive, said applied fugitive solvent temporarily activating the adhesive such that until the solvent dissipates, the crystallinity of the TPU adhesive is disrupted making the adhesive tackier with superior wetting, and mobilizing the latent cure component enabling curing of the adhesive.
2. The patch repair system, as claimed in claim 1 , wherein said latent curing component is a blocked isocyanate.
3. The patch repair system, as claimed in claim 2 , wherein said TPU adhesive has pendant hydroxyl groups.
4. The patch repair system, as claimed in claim 2 , wherein said thermoplastic resin is a thermoplastic polyurethane resin.
5. The patch repair system, as claimed in claim 4 , wherein said thermoplastic resin has a medium to a high level of crystallinity.
6. The patch repair system, as claimed in claim 2 , wherein the blocked isocyanate is a dimer of a diisocyanate, a multi-uretdione adduct or a combination thereof.
7. The patch repair system, as claimed in claim 6 , wherein the blocked isocyanate is a uretdione selected from the group consisting of dimers of toluene diisocyanate (TDI), methylene diisocyanate (MDI), xylene diisocyanate (XDI), isophorone diisocyanate (IPDI), hydrogenated methylene diisocyanate (H 12 MDI), and hexamethylene diisocyanate (HMDI).
8. A patch repair system according to claim 1 , wherein said TPU adhesive is further comprised of a cross-linking enhancer.
9. The patch repair system, as claimed in claim 8 , wherein the cross-linking enhancer is a compound with at least two hydroxyl groups.
10. The patch repair system, as claimed in claim 9 , wherein the cross-linking enhancer is selected from the group consisting of: a hydroxyalkylamide, pentaerythritols; mono, di and tri alkanol amines; glycols; abitol; butylene glycol; cyclohexanedimethanol; diethylene glycol; dipentaerythritol; dipropylene glycol; glycerine; hexylene glycol; hydrogenated Bisphenol A; methyl 1,2 propanediol; neopentylglycol; propylene glycol; sorbitol; triethylene glycol; trimethylolpropane; tripentaerythritol, alkoxy and hydroxyl alkoxy cellulose, simple sugars like fructose, sucrose, glucose and starches.
11. A patch repair system according to claim 2 , wherein said TPU adhesive is further comprised of a hydrolytic stabilizer.
12. The patch repair system, as claimed in claim 11 , wherein the hydrolytic stabilizer is selected from the group consisting of carbodiimides, polycarbodiimide, and epoxidized soy bean oil.
13. The patch repair system, as claimed in claim 2 , wherein the thermoplastic resin is compounded to include other additives such as reinforcing fibers, extenders, fillers, antioxidants, UV stabilizers, thermal stabilizers, flame retardants, glass beads, colorants, antimicrobial agents, dyes, pigments, processing aides (i.e., waxes, fluorinated compounds, silicone compounds, surfactants, polymeric processing aides), density modifiers such as phenolic beads, desiccants, buffers, and IR absorbent compounds to facilitate heating (i.e., carbon blacks, graphite, metal oxides).
14. The patch repair system, as claimed in claim 2 , wherein the said TPU adhesive is compounded to include other additives such as reinforcing fibers, extenders, antioxidants, UV stabilizers, thermal stabilizers, flame retardants, fillers, glass beads, colorants, antimicrobial agents, dyes, pigments, processing aides (i.e., waxes, fluorinated compounds, silicone compounds, surfactants, polymeric processing aides), density modifiers such as phenolic beads, desiccants, buffers, and IR absorbent compounds to facilitate heating (i.e., carbon blacks, graphite, metal oxides).
15. The patch repair system, as claimed in claim 1 , wherein the ketone is acetone.
16. The patch repair system, as claimed in claim 1 , wherein the ether is tetrahydrofuran.
17. The patch repair system, as claimed in claim 1 , wherein the ester is ethyl acetate.
18. A patch repair system, according to claim 1 , wherein the laminate is further comprised of a reinforcing fabric.
19. The patch repair system, as claimed in claim 18 , wherein the reinforcing fabric is comprised of fibers formed from polyamide, polyimide, polyester, or glass.
20. A patch repair system, according to claim 1 , wherein the fugitive solvent further comprises a catalyst.
21. A patch repair system, according to claim 1 , wherein the fugitive solvent further comprises an active curing component.
22. The patch repair system, as claimed in claim 20 , wherein said catalyst is selected from the group consisting of amines and organo-metallic agents.
23. The patch repair system, as claimed in claim 21 , wherein said active curing component is selected from the group consisting of isocyanates and transesterification agents.
24. The patch repair system, as claimed in claim 1 , wherein the ketone is methyl ethyl ketone.