Degradable urethane and urethane-urea systems
Degradable polymers, including polyurethane and polyurethane-urea compositions, that can be used in aqueous, non-aqueous and dry hot environments as degradable polymers in oil, gas and other applications. Such polymers may be formed from polyurethane-forming compositions, including: (a) an isocyanate component; (b) one or more polyols; (c) a degrading-agent, and (d) optionally, one or more additives. A stoichiometric equivalent of the isocyanate (a) to the polyol (b) may be from about 80 to about 120%.
1 . A polyurethane-forming composition, comprising, based on total weight of the polyurethane-forming composition:
(A) a pre-polymer in a range of from 72 to 84 wt. %, the pre-polymer comprising, in reacted form:
(a) an isocyanate component comprising toluene diisocyanate (TDI) and/or methylene-bis-(phenyl isocyanate) (MDI); and
(b) a polyol, comprising poly (trimethylolpropane/hexamethylene adipate) glycol, having a number average molecular weight in a range of from 50 to 600;
(B) a degrading-agent, comprising hexahydrophthalic anhydride (HHPA) and/or maleic anhydride, in a range of from 9 to 20 wt. %; and
(C) a chain extender, comprising a hydroquinone-bis-hydroxyethyl ether (HQEE), dimethylthio-toluene diamine, 1,4-butanediol, and/or 4,4′-methylenebis(o-chloroaniline) (MOCA), in a range of from 6 to 13 wt. %; and
(D) optionally, an additive,
wherein a stoichiometric equivalent of the isocyanate component (a) to the polyol (b) is in a range of from 80 to 120%,
wherein the prepolymer has a free monomer content in the range of from 0.05 to 5.0 wt %, based on the total prepolymer weight
wherein the pre-polymer (A) has an NCO content in a range of from 3.41 to 9.57 wt. %, and
wherein, the pre-polymer (A), when cured by the chain extender (C), forms a cured urethane network comprising ester groups, and the degrading-agent (B) is mixed in the cured urethane network, and
wherein, in an aqueous environment, the degrading-agent (B) comprising the hexahydrophthalic anhydride (HHPA) and/or the maleic anhydride hydrolyzes to generate an acid that catalyzes a hydrolysis of the ester groups in the cured urethane network, leading to polymer backbone scission, degradation, and generation of soluble fragments.
2 . The composition of claim 1 , wherein the stoichiometric equivalent of the isocyanate component (a) to the polyol (b) is in a range of from 85 to 105%.
3 . The composition of claim 1 , wherein the degrading-agent (B) comprises the maleic anhydride.
4 . The composition of claim 1 , wherein the degrading-agent (B) consists of the hexahydrophthalic anhydride and/or the maleic anhydride.
5 . The composition of claim 1 , wherein the degrading-agent (B) comprises the hexahydrophthalic anhydride.
6 . The composition of claim 1 , wherein the isocyanate component (a) comprises the toluene diisocyanate (TDI).
7 . The composition of claim 1 , wherein the isocyanate component (a) comprises the methylene-bis-(phenyl isocyanate) (MDI).
8 . The composition of claim 1 , wherein the degrading-agent (B) comprises the hexahydrophthalic anhydride (HHPA) and the maleic anhydride.
9 . The composition of claim 1 , wherein the chain extender (C) comprises the hydroquinone-bis-hydroxyethyl ether (HQEE).
10 . The composition of claim 1 , wherein the chain extender (C) comprises the 4,4′-methylenebis(o-chloroaniline) (MOCA).
11 . The composition of claim 1 , wherein the chain extender (C) comprises the dimethylthiotoluene diamine.
12 . The composition of claim 1 , wherein the chain extender (C) comprises the 1,4-butanediol.
13 . A polyurethane composition formed from the polyurethane-forming composition of claim 1 by reacting
(i) a modified prepolymer formed of a mixture of the prepolymer (A) and the degrading-agent (B),
(ii) the chain extender (C), and
optionally (iii) the additive (D).
14 . The polyurethane composition of claim 13 , wherein the polyol (b) and the isocyanate (a) have an NCO:OH ratio in the range of from 2:1 to 20:1.
15 . An article, comprising:
the polyurethane composition of claim 13 .
16 . The article of claim 15 , which is a pumpable tool comprising a plug, a direct connect plug, a bridge plug, a wiper plug, a frac plug, a component of a frac plug, a drill in sand control beaded screen plug, an inflow control device plug, a polymeric plug, a disappearing wiper plug, a cementing plug, a ball, a diverter ball, a shifting and setting ball, a swabbing element protector, a buoyant recorder, a pumpable collet, a float shoe, or a dart.
17 . The article of claim 15 , which is a tool that inhibits flow comprising a seal, a high pressure beaded frac screen plug, a screen basepipe plug, a coating for a balls and a seat, a compression packing element, an expandable packing element, an O-ring, an attached seal, a bullet seal, a sub-surface safety valve seal, a sub-surface safety valve flapper seal, a dynamic seal, a V-ring, a backup ring, a drill bit seal, a liner port plug, an atmospheric disc, an atmospheric chamber disc, a debris barrier, a drill in stim liner plug, an inflow control device plug, a flapper, a seat, a ball seat, a direct connect disk, a drill-in linear disk, a gas lift valve plug, a fluid loss control flapper, an electric submersible pump seal, a shear out plug, a flapper valve, a gaslift valve, or a sleeve.